Bio

Clinical Focus


  • Pulmonology (Lung) and Critical Care
  • Pulmonary Disease

Academic Appointments


Professional Education


  • Medical Education:Columbia University College of Physicians and Surgeons (1988) NJ
  • Fellowship:Stanford University School of Medicine (1992) CA
  • Residency:Stanford University School of Medicine (1990) CA
  • Internship:Stanford University School of Medicine (1989) CA
  • Board Certification: Pulmonary Disease, American Board of Internal Medicine (1994)
  • Board Certification: Critical Care Medicine, American Board of Internal Medicine (1995)
  • A.B.-A.M., Harvard University, Chemistry and Physics (1979)
  • Ph.D., Columbia University, Biochemistry (1986)
  • M.D., Columbia University P&S, Medicine (1988)

Research & Scholarship

Current Research and Scholarly Interests


RESEARCH INTERESTS:
Our research program has several active projects:
1.) Pulmonary Vascular Disease – We are studying experimental hypertensive pulmonary vascular disease, aiming to determine the pathophysiologic mechanisms of disease progression, and to identify and develop novel antiproliferative strategies for prevention and treatment. Our group is the first to show that hydrophobic statins such as simvastatin, effectively prevent fatal pulmonary hypertension in rats, and reverse established pulmonary hypertension with neointimal vascular occlusion. The mechanisms of simvastatin’s efficacy involve inhibition of proliferation and induction of apoptosis of vascular smooth muscle cells. A translational effort to human clinical trials has been initiated at Stanford. Colleague Dr. John Faul (Assistant Professor, PCCM) is directing a randomized, placebo-controlled clinical trial of simvastatin for treatment of Primary Pulmonary Hypertension in the Stanford University Chest Clinic.
2.) Lung Inflammation and Regeneration – We are funded by the NIH to study the regulation of cytokine gene expression in bronchial epithelial cells. Inflammatory cytokines contribute to host defenses against pathogens introduced through the airways. Excessive host inflammation in the airways contributes to airway diseases such as asthma and COPD, and inappropriate host inflammatory responses contribute to bronchiectasis in cystic fibrosis and in nontuberculous mycobacterial disease. Together with colleague Dr. Stephen Ruoss (Associate Professor, PCCM), we are characterizing the role of cystic fibrosis gene mutations in susceptibility to nontuberculous mycobacterial pulmonary infections.
We are characterizing lung stem cells capable of self-renewal and of promoting lung regeneration after injury. For this project, we are collaborating with Dr. Judy Shizuru (Associate Professor, Bone Marrow Transplantation, Stanford), and Dr. Chris Contag, expert in imaging (Associate Professor, Pediatrics and Microbiology, Stanford). We are using transgenic donor mice, marked with reporter genes, to identify and enriching stem cells capable of homing to and repopulating lung endothelium and epithelium. This project is funded by the Beckman Center (Stanford).
3. Lung surfactant rheology and cellular oxidative stress - We are studying the biophysical properties of lung surfactant in collaboration with Dr. Gerry Fuller, Professor of Chemical Engineering (Stanford). Dr. Fuller’s group has a unique instrument capable of measuring the dynamic viscosity of surfactants. Our aims in this collaboration are to establish how hydrophobic surfactant proteins B and C contribute to lowering the surface tension and viscosity of lung surfactant in health and disease. These studies are relevant for the pathogenesis of interstitial lung diseases and pulmonary fibrosis. The studies are funded by the Bio-X Committee at Stanford.
4.) Novel Gene Regulators NF45 and NF90 – We are funded by the NIH to continue studies of two novel transcription factors cloned by Dr. Peter Kao in 1994. These proteins were isolated based on the regulation of the IL-2 gene in T-lymphocytes. They are widely distributed and are now recognized to regulate transcription, mRNA splicing, nuclear export, and protein translation. In order to further characterize their biologic functions, our group is the first to generate mice with targeted disruptions (knockouts) of NF45 and NF90. Currently we are characterizing the phenotypes of these mice, focusing on changes in patterns of gene regulation.

Teaching

2013-14 Courses


Graduate and Fellowship Programs


Publications

Journal Articles


  • NF90 regulates inducible IL-2 gene expression in T cells JOURNAL OF EXPERIMENTAL MEDICINE Shi, L., Godfrey, W. R., Lin, J., Zhao, G., Kao, P. N. 2007; 204 (5): 971-977

    Abstract

    Activation of T cells induces the production of T cell growth and survival factor interleukin (IL) 2. Regulatory T cells intrinsically fail to induce IL-2 expression upon activation and can suppress IL-2 production in conventional T cells. Thus, the control of IL-2 expression is critically important to T cell immune responses, yet the mechanisms remain incompletely understood. Nuclear factor (NF) 90 is a zinc-finger DNA- and double-stranded RNA-binding protein subunit that binds specifically to the antigen receptor response element (ARRE)/NF of activated T cells target sequence in the IL-2 proximal promoter. Inducible binding of NF90 to the IL-2 promoter in vivo is shown by chromatin immunoprecipitation. NF90 gene-targeted mice exhibit perinatal lethality. Compared with newborn NF90(+/+) mice, newborn NF90(-/-) mice demonstrate severe impairment of IL-2 expression. Compared with wild-type cells, T cells deficient in NF90 are impaired in ARRE and IL-2 transcriptional activation and IL-2 mRNA stabilization. Fetal liver cells from NF90 gene-targeted mice were transplanted into irradiated adult recombination activating gene (RAG)-2(-/-) and IL-2Rgamma(-/-) mice deficient in T cells, B cells, and natural killer cells. NF90(+/+)- and NF90(-/-)-RAG chimeric mice showed grossly normal repopulation of the thymus and spleen, but only NF90(-/-) T cells were severely impaired in IL-2 gene expression. Compared with littermates, NF90(-/-) RAG chimeric mice exhibited profound T cell lymphocytopenia in the peripheral circulation. Thus, NF90 regulates inducible IL-2 transcription, mRNA stability, and gene expression in T cells and represents a novel therapeutic target for the modulation of T cell immune responses.

    View details for DOI 10.1084/jem.20052078

    View details for Web of Science ID 000246467600002

    View details for PubMedID 17470640

  • Dynamic binding of Ku80, Ku70 and NF90 to the IL-2 promoter in vivo in activated T-cells NUCLEIC ACIDS RESEARCH Shi, L., Qiu, D., Zhao, G., Corthesy, B., Lees-Miller, S., Reeves, W. H., Kao, P. N. 2007; 35 (7): 2302-2310

    Abstract

    IL-2 gene expression in activated T-cells is initiated by chromatin remodeling at the IL-2 proximal promoter and conversion of a transcriptional repressor into a potent transcriptional activator. A purine-box regulator complex was purified from activated Jurkat T-cell nuclei based on sequence-specific DNA binding to the antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target DNA sequence in the proximal IL-2 promoter. ARRE DNA-binding subunits were identified as NF90, NF45 and systemic lupus erythematosis autoantigens, Ku80 and Ku70. Monoclonal antibodies to Ku80, Ku70 and NF90 specifically inhibit constitutive and inducible ARRE DNA-binding activity in Jurkat T-cells. Ku80, Ku70 and NF90 bind specifically to the IL-2 gene promoter in vivo, as demonstrated by chromatin immunoprecipitation. Activation of Jurkat T-cells and mouse primary spleen cells induces binding of Ku80 and NF90 to the IL-2 promoter in vivo, and decreases binding of Ku70 to the IL-2 promoter in vivo, and these dynamic changes are inhibited by immunosuppressants cyclosporin A and triptolide. Dynamic changes in binding of Ku80, Ku70 and NF90 to the IL-2 proximal promoter in vivo correlate with chromatin remodeling and transcriptional initiation in activated T-cells.

    View details for DOI 10.1093/nar/gkm117

    View details for Web of Science ID 000246294700027

    View details for PubMedID 17389650

  • Thrombin-activatable procarboxypeptidase B regulates activated complement C5a in vivo BLOOD Nishimura, T., Myles, T., Piliposky, A. M., Kao, P. N., Berry, G. J., Leung, L. L. 2007; 109 (5): 1992-1997

    Abstract

    Plasma procarboxypeptidase B (proCPB) is activated by the endothelial thrombin-thrombomodulin [corrected] complex. Activated proCPB [corrected] (CPB) functions as a fibrinolysis inhibitor, but it may play a broader role by inactivating inflammatory mediators. To test this hypothesis, C5a-induced alveolitis was studied in wild-type (WT) and proCPB-deficient mice (proCPB-/-). C5a-induced alveolitis, as measured by cell counts and total protein contents in bronchoalveolar lavage fluids, was markedly enhanced in the proCPB-/- mice. E229K thrombin, a thrombin mutant with minimal clotting activity but retaining its ability to activate protein C and proCPB, attenuated C5a-induced alveolitis in WT but not in proCPB-/- mice, indicating that its beneficial effect is mediated primarily by its activation of proCPB. Lung tissue histology confirmed these cellular inflammatory responses. Delayed administration of E229K thrombin after the C5a instillation was ineffective in reducing alveolitis in WT mice, suggesting that the beneficial effect of E229K thrombin is due to the direct inhibition of C5a by CPB. Our studies show that thrombin-activatable proCPB, in addition to its role in fibrinolysis, has intrinsic anti-inflammatory functions. Its activation, along with protein C, by the endothelial thrombin-TM complex represents a homeostatic response to counteract the inflammatory mediators generated at the site of vascular injury.

    View details for DOI 10.1182/blood-2006-03-012567

    View details for Web of Science ID 000244641100036

    View details for PubMedID 17105819

  • Aerosolized amikacin for treatment of pulmonary Mycobacterium avium infections: an observational case series. BMC pulmonary medicine Davis, K. K., Kao, P. N., Jacobs, S. S., Ruoss, S. J. 2007; 7: 2-?

    Abstract

    Current systemic therapy for nontuberculous mycobacterial pulmonary infection is limited by poor clinical response rates, drug toxicities and side effects. The addition of aerosolized amikacin to standard oral therapy for nontuberculous mycobacterial pulmonary infection may improve treatment efficacy without producing systemic toxicity. This study was undertaken to assess the safety, tolerability and preliminary clinical benefits of the addition of aerosolized amikacin to a standard macrolide-based oral treatment regimen.Six HIV-negative patients with Mycobacterium avium intracellulare pulmonary infections who had failed standard therapy were administered aerosolized amikacin at 15 mg/kg daily in addition to standard multi-drug macrolide-based oral therapy. Patients were monitored clinically and serial sputum cultures were obtained to assess response to therapy. Symptomatic improvement with radiographic stabilization and eradication of mycobacterium from sputum were considered markers of success. Of the six patients treated with daily aerosolized amikacin, five responded to therapy. All of the responders achieved symptomatic improvement and four were sputum culture negative after 6 months of therapy. Two patients became re-infected with Mycobacterium avium intracellulare after 7 and 21 months of treatment. One of the responders who was initially diagnosed with Mycobacterium avium intracellulare became sputum culture positive for Mycobacterium chelonae resistant to amikacin after being on intermittent therapy for 4 years. One patient had progressive respiratory failure and died despite additional therapy. There was no evidence of nephrotoxicity or ototoxicity associated with therapy.Aerosolized delivery of amikacin is a promising adjunct to standard therapy for pulmonary nontuberculous mycobacterial infections. Larger prospective trials are needed to define its optimal role in therapy of this disease.

    View details for PubMedID 17319962

  • Prospective analysis of cystic fibrosis transmembrane regulator mutations in adults with bronchiectasis or pulmonary nontuberculous mycobacterial infection CHEST Ziedalski, T. M., Kao, P. N., Henig, N. R., Jacobs, S. S., Ruoss, S. J. 2006; 130 (4): 995-1002

    Abstract

    Bronchiectasis and pulmonary infection with nontuberculous mycobacteria (NTM) may be associated with disease-causing mutations in the cystic fibrosis transmembrane regulator (CFTR).Fifty adult patients at Stanford University Medical Center with a diagnosis of bronchiectasis and/or pulmonary NTM infection were prospectively characterized by sweat chloride measurement, comprehensive mutational analysis of CFTR, and sputum culture results.A de novo diagnosis of cystic fibrosis (CF) was established in 10 patients (20%). Patients with CF were more likely than those without CF to have mucus plugging seen on chest high-resolution CT, and women with a CF diagnosis were thinner, with a significantly lower mean body mass index than the non-CF subjects. Thirty CFTR mutations were identified in 24 patients (50% prevalence). Sweat chloride concentration was elevated > 60 mEq/dL (diagnostic of CF) in seven patients (14%), and from 40 to 60 mEq/dL in eight patients (16%). The frequency of CFTR mutations was elevated above that expected in the general population: heterozygous DeltaF508 (12% vs 3%), R75Q (14% vs 1%), and intron 8 5T (17% vs 5 to 10%). Other known CFTR mutations identified were V456A, G542X, R668C, I1027T, D1152, R1162L, W1282X, and L183I. Three novel CFTR mutations were identified: A394V, F650L, and C1344S.Mutations in CFTR that alter RNA splicing and/or functional chloride conductance are common in this population, and are likely to contribute to the susceptibility and pathogenesis of adult bronchiectasis and pulmonary NTM infection. Careful clinical evaluation for disease cause should be undertaken in this clinical context.

    View details for DOI 10.1378/chest.130.4.995

    View details for Web of Science ID 000241265700014

    View details for PubMedID 17035430

  • Simvastatin enhances bone morphogenetic protein receptor type II expression BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Hu, H., Sung, A., Zhao, G. H., Shi, L. F., Qiu, D. M., Nishmura, T., Kao, P. N. 2006; 339 (1): 59-64

    Abstract

    Statins confer therapeutic benefits in systemic and pulmonary vascular diseases. Bone morphogenetic protein (BMP) receptors serve essential signaling functions in cardiovascular development and skeletal morphogenesis. Mutations in BMP receptor type II (BMPR2) are associated with human familial and idiopathic pulmonary arterial hypertension, and pathologic neointimal proliferation of vascular endothelial and smooth muscle cells within small pulmonary arteries. In severe experimental pulmonary hypertension, simvastatin reversed disease and conferred a 100% survival advantage. Here, modulation of BMPR2 gene expression by simvastatin is characterized in human embryonic kidney (HEK) 293T, pulmonary artery smooth muscle, and lung microvascular endothelial cells (HLMVECs). A 1.4kb BMPR2 promoter containing Egr-1 binding sites confers reporter gene activation in 293T cells which is partially inhibited by simvastatin. Simvastatin enhances steady-state BMPR2 mRNA and protein expression in HLMVEC, through posttranscriptional mRNA stabilization. Simvastatin induction of BMPR2 expression may improve BMP-BMPR2 signaling thereby enhancing endothelial differentiation and function.

    View details for DOI 10.1016/j.bbrc.2005.10.187

    View details for Web of Science ID 000233944500010

    View details for PubMedID 16297860

  • Lung surfactant gelation induced by epithelial cells exposed to air pollution or oxidative stress AMERICAN JOURNAL OF RESPIRATORY CELL AND MOLECULAR BIOLOGY Anseth, J. W., Goffin, A. J., Fuller, G. G., Ghio, A. J., Kao, P. N., Upadhyay, D. 2005; 33 (2): 161-168

    Abstract

    Lung surfactant lowers surface tension and adjusts interfacial rheology to facilitate breathing. A novel instrument, the interfacial stress rheometer (ISR), uses an oscillating magnetic needle to measure the shear viscosity and elasticity of a surfactant monolayer at the air-water interface. The ISR reveals that calf lung surfactant, Infasurf, exhibits remarkable fluidity, even when exposed to air pollution residual oil fly ash (ROFA), hydrogen peroxide (H2O2), or conditioned media from resting A549 alveolar epithelial cells (AEC). However, when Infasurf is exposed to a subphase of the soluble fraction of ROFA- or H2O2-treated AEC conditioned media, there is a prominent increase in surfactant elasticity and viscosity, representing two-dimensional gelation. Surfactant gelation is decreased when ROFA-AEC are pretreated with inhibitors of cellular reactive oxygen species (ROS), or with a mitochondrial anion channel inhibitor, as well as when A549-rho0 cells that lack mitochondrial DNA and functional electron transport are investigated. These results implicate both mitochondrial and nonmitochondrial ROS generation in ROFA-AEC-induced surfactant gelation. A549 cells treated with H2O2 demonstrate a dose-dependent increase in lung surfactant gelation. The ISR is a unique and sensitive instrument to characterize surfactant gelation induced by oxidatively stressed AEC.

    View details for DOI 10.1165/rcmb.2004-0365OC

    View details for Web of Science ID 000230864800007

    View details for PubMedID 15860796

  • Granzyme B is dispensable for immunologic tolerance to self in a murine model of systemic lupus erythematosus ARTHRITIS AND RHEUMATISM Graham, K. L., Thibault, D. L., Steinman, J. B., Okeke, L., Kao, P. N., Utz, P. J. 2005; 52 (6): 1684-1693

    Abstract

    Proteolytic autoantigen cleavage by the serine protease granzyme B has been implicated in the development of systemic autoimmune disease; however, there has been no conclusive demonstration of a pathogenic role for granzyme B in autoimmunity. In this study, we evaluated the role of granzyme B in a murine model of autoimmunity.To identify potential novel granzyme B substrates, complementary DNAs encoding nuclear factor 45 (NF45) and NF90 were used to generate (35)S-methionine-labeled proteins by coupled in vitro transcription/translation. Radiolabeled proteins were then incubated with purified recombinant granzyme B or caspases, and the cleavage products were analyzed by autoradiography. We also immunized granzyme B-deficient and granzyme B-intact mice with the mineral oil pristane. Production of autoantibodies directed against granzyme B substrates in response to pristane was evaluated by Western blotting, immunoprecipitation, and enzyme-linked immunosorbent assay.The double-stranded RNA-binding protein NF90 was identified as a novel substrate for caspases and granzyme B, both in vitro and in vivo. NF90 is uniquely cleaved by granzyme B in vitro; however, pristane immunization still induced anti-NF90 antibodies in granzyme B-deficient mice. Pristane-treated granzyme B-deficient mice also produced antibodies directed against the U1-70-kd antigen, a previously identified granzyme B substrate. Last, antibodies directed against U1-70 kd arose spontaneously in granzyme B-deficient mice.These results demonstrate that granzyme B is not required for the production of autoantibodies directed against antigens that are granzyme B substrates in vitro. The data also suggest a protective role for this proapoptotic protease in systemic autoimmunity.

    View details for DOI 10.1002/art.21092

    View details for Web of Science ID 000229721700012

    View details for PubMedID 15934098

  • NF90 regulates cell cycle exit and terminal myogenic differentiation by direct binding to the 3 '-untranslated region of MyoD and p21(WAF1/CIP1) mRNAs JOURNAL OF BIOLOGICAL CHEMISTRY Shi, L. F., Zhao, G. H., Qiu, D. M., Godfrey, W. R., Vogel, H., Rando, T. A., Hu, H., Kao, P. N. 2005; 280 (19): 18981-18989

    Abstract

    NF90 and splice variant NF110/ILF3/NFAR are double-stranded RNA-binding proteins that regulate gene expression. Mice with targeted disruption of NF90 were engineered. NF90(-/-) mice were born small and weak and succumbed to perinatal death within 12 h because of neuromuscular respiratory failure. Lung inflation and morphology were normal in NF90(-/-) mice. The diaphragm and other skeletal muscles in NF90(-/-) mice demonstrated disorganized arrangement and paucity of myofibers, evidence of myocyte degeneration and increased apoptosis. The expression of myogenic regulators, MyoD, myogenin, and p21WAF1/CIP1, was severely decreased in NF90(-/-) mice. These myogenic transcription factors and cell cycle inhibitors are regulated in part through post-transcriptional mRNA stabilization. Northwestern blotting revealed that NF90 is the principal and specific p21WAF1/CIP1 and MyoD 3'-untranslated region RNA-binding protein in developing skeletal muscles. NF90 regulates transcription factors and a cell cycle inhibitor essential for skeletal muscle differentiation and for survival.

    View details for DOI 10.1074/jbc.M411034200

    View details for Web of Science ID 000228932300052

    View details for PubMedID 15746098

  • NF45/ILF2 tissue expression, promoter analysis, and interleukin-2 transactivating function EXPERIMENTAL CELL RESEARCH Zhao, G. H., Shi, L. F., Qiu, D. M., Hu, H., Kao, P. N. 2005; 305 (2): 312-323

    Abstract

    NF45/ILF2 associates with NF90/ILF3 in the nucleus and regulates IL-2 gene transcription at the antigen receptor response element (ARRE)/NF-AT DNA target sequence (P.N. Kao, L. Chen, G. Brock, J. Ng, A.J. Smith, B. Corthesy, J. Biol. Chem. 269 (1994) 20691-20699). NF45 is widely expressed in normal tissues, especially testis, brain, and kidney, with a predominantly nuclear distribution. NF45 mRNA expression is increased in lymphoma and leukemia cell lines. The human and murine NF45 proteins differ only by substitution of valine by isoleucine at amino acid 142. Fluorescence in situ hybridization localized the human NF45 gene to chromosome 1q21.3, and mouse NF45 gene to chromosome 3F1. Promoter analysis of 2.5 kB of the murine NF45 gene reveals that significant activation is conferred by factors, possible including NF-Y, that bind to the CCAAT-box sequence. The function of human NF45 in regulating IL-2 gene expression was characterized in Jurkat T-cells stably transfected with plasmids directing expression of NF45 cDNA in sense or antisense orientations. NF45 sense expression increased IL-2 luciferase reporter gene activity 120-fold, and IL-2 protein expression 2-fold compared to control cells. NF45 is a highly conserved, regulated transcriptional activator, and one target gene is IL-2.

    View details for DOI 10.1016/j.yexer.2004.12.030

    View details for Web of Science ID 000228409100008

    View details for PubMedID 15817156

  • Simvastatin treatment of pulmonary hypertension - An observational case series CHEST Kao, P. N. 2005; 127 (4): 1446-1452

    Abstract

    Statins confer cardiovascular benefits beyond the reduction of serum cholesterol through antiproliferative and antiinflammatory mechanisms and induction of endothelial nitric oxide expression. In pneumonectomized rats injected with monocrotaline, simvastatin reversed established pulmonary hypertension and conferred a 100% survival advantage.To evaluate the safety and efficacy of simvastatin for treatment of patients with pulmonary arterial hypertension (PAH).Open-label observational study performed at Stanford University Medical Center. Sixteen patients with primary and secondary causes of PAH, World Health Organization (WHO) classes I (n = 2), II (n = 4), III (n = 3), IV (n = 7), are described. Simvastatin was prescribed at 20 to 80 mg/d and continued in the absence of adverse effects.Serial measurements of 6-min walk (6MW) performance, hemodynamics, and echocardiographic estimates of right ventricular systolic pressures (RVSPs) were recorded on each patient. Simvastatin treatment was not associated with hepatic dysfunction, muscle necrosis, or other adverse events. Individual patients demonstrated improvements in 6MW performance, improvements in cardiac output, or decreases in RVSP that may be attributable to simvastatin treatment. Overall, the rate of disease progression appeared to be attenuated, and WHO class IV patients demonstrated improved survival.Simvastatin treatment appears safe in patients with PAH.

    View details for Web of Science ID 000228349900058

    View details for PubMedID 15821229

  • Longitudinal transcriptional analysis of developing neointimal vascular occlusion and pulmonary hypertension in rats PHYSIOLOGICAL GENOMICS Vaszar, L. T., Nishimura, T., Storey, J. D., Zhao, G. H., Qiu, D. M., Faul, J. L., Pearl, R. G., Kao, P. N. 2004; 17 (2): 150-156

    Abstract

    Pneumonectomized rats injected with the alkaloid toxin, monocrotaline, develop progressive neointimal pulmonary vascular obliteration and pulmonary hypertension resulting in right ventricular failure and death. The antiproliferative immunosuppressant, triptolide, attenuates neointimal formation and pulmonary hypertension in this disease model (Faul JL, Nishimura T, Berry GJ, Benson GV, Pearl RG, and Kao PN. Am J Respir Crit Care Med 162: 2252-2258, 2000). Pneumonectomized rats, injected with monocrotaline on day 7, were killed at days 14, 21, 28, and 35 for measurements of physiology and gene expression patterns. These data were compared with pneumonectomized, monocrotaline-injected animals that received triptolide from day 5 to day 35. The hypothesis was tested that a group of functionally related genes would be significantly coexpressed during the development of disease and downregulated in response to treatment. Transcriptional analysis using total lung RNA was performed on replicate animals for each experimental time point with exploratory data analysis followed by statistical significance analysis. Marked, statistically significant increases in proteases (particularly derived from mast cells) were noted that parallel the development of vascular obliteration and pulmonary hypertension. Mast-cell-derived proteases may play a role in regulating the development of neointimal pulmonary vascular occlusion and pulmonary hypertension in response to injury.

    View details for DOI 10.1152/physiolgenomics.00198.2003

    View details for Web of Science ID 000222088800009

    View details for PubMedID 15082832

  • Members of the NF90/NFAR protein group are involved in the life cycle of a positive-strand RNA virus EMBO JOURNAL Isken, O., Grassmann, C. W., Sarisky, R. T., Kann, M., Zhang, S., Grosse, F., Kao, P. N., Behrens, S. E. 2003; 22 (21): 5655-5665

    Abstract

    A major issue of current virology concerns the characterization of cellular proteins that operate as functional components of the viral multiplication process. Here we describe a group of host factors designated as 'NFAR proteins' that are recruited by the replication machinery of bovine viral diarrhea virus, a close relative of the human pathogen hepatitis C virus. The NFAR proteins associate specifically with both the termini of the viral RNA genome involving regulatory elements in the 5' and 3' non-translated regions. Modification of the protein interaction sites in the 3' non-translated region yielded viral RNAs that were replication deficient. Viral replication was also inhibited by RNAi approaches that reduced the concentration of RNA helicase A, a member of the NFAR group, in the host cell's cytoplasm. Further experimental data suggest that NFAR proteins mediate a circular conformation of the viral genome that may be important for the coordination of translation and replication. Because NFAR proteins are presumed components of the antiviral response, we suspect that viral recruitment may also serve to weaken cellular defense mechanisms.

    View details for Web of Science ID 000186448300001

    View details for PubMedID 14592965

  • Simvastatin rescues rats from fatal pulmonary hypertension by inducing apoptosis of neointimal smooth muscle cells CIRCULATION Nishimura, T., Vaszar, L. T., Faul, J. L., Zhao, G. H., Berry, G. J., Shi, L. F., Qiu, D. M., Benson, G., Pearl, R. G., Kao, P. N. 2003; 108 (13): 1640-1645

    Abstract

    Pulmonary vascular injury by toxins can induce neointimal formation, pulmonary arterial hypertension (PAH), right ventricular failure, and death. We showed previously that simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in pneumonectomized rats injected with the alkaloid toxin monocrotaline. The present study was undertaken to investigate the efficacy of simvastatin and its mechanism of reversing established neointimal vascular occlusion and pulmonary hypertension.Pneumonectomized rats injected with monocrotaline at 4 weeks demonstrated severe PAH at 11 weeks (mean pulmonary artery pressure [mPAP]=42 versus 17 mm Hg in normal rats) and death by 15 weeks. When rats with severe PAH received simvastatin (2 mg x kg(-1) x d(-1) by gavage) from week 11, there was 100% survival and reversal of PAH after 2 weeks (mPAP=36 mm Hg) and 6 weeks (mPAP=24 mm Hg) of therapy. Simvastatin treatment reduced right ventricular hypertrophy and reduced proliferation and increased apoptosis of pathological smooth muscle cells in the neointima and medial walls of pulmonary arteries. Longitudinal transcriptional profiling revealed that simvastatin downregulated the inflammatory genes fos, jun, and tumor necrosis factor-alpha and upregulated the cell cycle inhibitor p27Kip1, endothelial nitric oxide synthase, and bone morphogenetic protein receptor type 1a.Simvastatin reverses pulmonary arterial neointimal formation and PAH after toxic injury.

    View details for DOI 10.1161/01.CIR.0000087592.47401.37

    View details for Web of Science ID 000185624500032

    View details for PubMedID 12963647

  • Selective regulation of gene expression by nuclear factor 110, a member of the NF90 family of double-stranded RNA-binding proteins JOURNAL OF MOLECULAR BIOLOGY Reichman, T. W., Parrott, A. M., Fierro-Monti, I., Caron, D. J., Kao, P. N., Lee, C. G., Li, H., Mathews, M. B. 2003; 332 (1): 85-98

    Abstract

    Members of the nuclear factor 90 (NF90) family of double-stranded RNA (dsRNA)-binding proteins have been implicated in several biological processes including the regulation of gene expression. cDNA sequences predict that the proteins have a functional nuclear localization signal and two dsRNA-binding motifs (dsRBMs), and are identical at their N termini. Isoforms are predicted to diverge at their C termini as well as by the insertion of four amino acid residues (NVKQ) between the two dsRBMs. In this study, we verified the expression of four of the isoforms by cDNA cloning and mass spectrometric analysis of proteins isolated from human cells. Cell fractionation studies showed that NF90 and its heteromeric partner, NF45, are predominantly nuclear and largely chromatin-associated. The C-terminally extended NF90 species, NF110, are almost exclusively chromatin-bound. Both NF110 isoforms are more active than NF90 isoforms in stimulating transcription from the proliferating cell nuclear antigen reporter in a transient expression system. NF110b, which carries the NVKQ insert, was identified as the strongest activator. It stimulated transcription of some, but not all, promoters in a fashion that suggested that it functions in concert with other transcription factors. Finally, we demonstrate that NF110b associates with the dsRBM-containing transcriptional co-activator, RNA helicase A, independently of RNA binding.

    View details for DOI 10.1016/S0022-2836(03)00885-4

    View details for Web of Science ID 000185034400009

    View details for PubMedID 12946349

  • Effect of a surgical aortocaval fistula on mono crotaline-induced pulmonary hypertension CRITICAL CARE MEDICINE Nishimura, T., Faul, J. L., Berry, G. J., Kao, P. N., Pearl, R. G. 2003; 31 (4): 1213-1218

    Abstract

    Increased pulmonary blood flow is believed to contribute to the development of pulmonary hypertension. We investigated the effect of overcirculation via an aortocaval fistula, on the development of monocrotaline-induced pulmonary hypertension in rats. Monocrotaline was administered 1 wk after the creation of an aortocaval fistula.Randomized, controlled study.Research laboratory of an academic institution.Male Sprague-Dawley rats.Overcirculation was induced by pneumonectomy and by surgical creation of aortocaval fistula. Pulmonary artery hypertension was induced by administration of monocrotaline.Aortic blood flow, Pao(2), and pulmonary arterial pressure were measured 4 wks later. A blinded investigator quantified pulmonary arterial neointimal formation in small pulmonary arteries. Compared with animals that received monocrotaline and/or underwent pneumonectomy but did not undergo aortocaval fistula, the presence of a surgical aortocaval fistula was associated with increased aortic blood flow (p <.001), increased Pao(2) (p <.001), and lower mean pulmonary arterial pressure (p <.001). In addition, rats with aortocaval fistula had less pulmonary arterial neointimal formation than matched animals without an aortocaval fistula (p =.034).The presence of a surgical aortocaval fistula attenuates, rather than worsens, the development of monocrotaline-induced pulmonary hypertension in rats.

    View details for DOI 10.1097/01.CCM.0000059440.44597.07

    View details for Web of Science ID 000182411900033

    View details for PubMedID 12682495

  • Immunosuppressive and anti-inflammatory mechanisms of triptolide, the principal active diterpenoid from the Chinese medicinal herb Tripterygium wilfordii Hook. f. Drugs in R&D Qiu, D., Kao, P. N. 2003; 4 (1): 1-18

    Abstract

    Extracts of Tripterygium wilfordii hook. f. (leigong teng, Thundergod vine) are effective in traditional Chinese medicine for treatment of immune inflammatory diseases including rheumatoid arthritis, systemic lupus erythematosus, nephritis and asthma. Characterisation of the terpenoids present in extracts of Tripterygium identified triptolide, a diterpenoid triepoxide, as responsible for most of the immunosuppressive, anti-inflammatory and antiproliferative effects observed in vitro. Triptolide inhibits lymphocyte activation and T-cell expression of interleukin-2 at the level of transcription. In all cell types examined, triptolide inhibits nuclear factor-kappaB transcriptional activation at a unique step in the nucleus after binding to DNA. Further characterisation of the molecular mechanisms of triptolide action will serve to elucidate pathways of immune system regulation.

    View details for PubMedID 12568630

  • Simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in rats AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Nishimura, T., Faul, J. L., Berry, G. J., Vaszar, L. T., Qiu, D. M., Pearl, R. G., Kao, P. N. 2002; 166 (10): 1403-1408

    Abstract

    Hypertensive pulmonary vascular disease is characterized by abnormal proliferation of vascular endothelial and smooth muscle cells, leading to occlusion of pulmonary arterioles, pulmonary hypertension, right ventricular failure, and death. Compounds with antiproliferative effects on vascular endothelial and smooth muscle cells, such as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, may prevent the development of experimental hypertensive pulmonary vascular disease. Pneumonectomized rats injected with monocrotaline at 7 days develop severe hypertensive pulmonary vascular disease with neointimal formation. Rats were randomized to receive either vehicle or treatment with the HMG-CoA reductase inhibitor simvastatin (2 mg/kg per day). By Day 35, rats that received vehicle had higher mean pulmonary arterial pressures (53 +/- 2 mm Hg) and right ventricular hypertrophy (right ventricle/[left ventricle plus septum] [RV/LV+S] = 0.78 +/- 0.09) than rats in Group PMS5-35 that received simvastatin from Day 5 to 35 (mean pulmonary arterial pressure = 27 +/- 3 mm Hg, RV/LV+S = 0.34 +/- 0.08; p < or = 0.001). Pulmonary vascular remodeling with neointimal formation consisting of vascular smooth muscle cells was more severe in vehicle-treated rats (vascular occlusion score, 1.98 +/- 0.02) than in Group PMS5-35 (vascular occlusion score, 0.59 +/- 0.46; p < 0.001). In addition, lung endothelial nitric oxide synthase gene expression was decreased in vehicle-treated animals but was restored toward normal levels in simvastatin-treated animals. Simvastatin attenuates monocrotaline-induced pulmonary vascular remodeling with neointimal formation, pulmonary arterial hypertension, and right ventricular hypertrophy in rats.

    View details for DOI 10.1164/rccm.200203-268OC

    View details for Web of Science ID 000179116500019

    View details for PubMedID 12406854

  • High prevalence of autoimmune thyroid disease in pulmonary arterial hypertension CHEST Chu, J. W., Kao, P. N., Faul, J. L., Doyle, R. L. 2002; 122 (5): 1668-1673

    Abstract

    An association between thyroid disease and pulmonary arterial hypertension (PAH) has been reported, yet the pathogenetic relationship between these conditions remains unclear. Because immune system dysfunction may underlie this association, we sought to determine the prevalence of autoimmune thyroid disease (AITD) in patients with PAH.Prospective observational study at a single academic institution.Sixty-three consecutive adults with PAH (ie, sustained pulmonary artery systolic pressure, > 25 mm Hg) were evaluated for clinical, biochemical, and serologic features of AITD.Thyroid gland dysfunction was determined by clinical examination for goiter, and by biochemical measurements of thyrotropin and free thyroxine. Immune system dysfunction was determined by serologic measurements of antibodies to thyroglobulin and thyroid peroxidase. First-degree family history of AITD also was ascertained in order to investigate for genetic clustering of autoimmunity.Thirty-one patients (49%; 95% confidence interval [CI], 37 to 62%) received diagnoses of AITD. Eighteen patients were newly diagnosed, and 9 patients required the initiation of pharmacologic treatment. There was no chronologic relationship between the diagnosis or treatment of PAH and that of AITD. Sixteen patients (25%; 95% CI, 15 to 36%) had 24 first-degree family members with AITD.Approximately half of the patients with PAH have concomitant AITD. These two conditions may be linked by a common immunogenetic susceptibility, and the elucidation of this association may advance the understanding of the pathophysiology and treatment of PAH. Systematic surveillance for occult thyroid dysfunction in patients with PAH may prevent the hemodynamic exacerbation of right heart failure.

    View details for Web of Science ID 000179376600031

    View details for PubMedID 12426269

  • 40-O-(2-hydroxyethyl)-rapamycin attenuates pulmonary arterial hypertension and neointimal formation in rats AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Nishimura, T., Faul, J. L., Berry, G. I., Veve, I., Pearl, R. G., Kao, P. N. 2001; 163 (2): 498-502

    Abstract

    Pneumonectomized rats develop pulmonary hypertension (PH) and pulmonary vascular neointimal formation 4 wk after monocrotaline (MCT) administration. Male Sprague-Dawley rats were injected with MCT (60 mg/kg) on Day 7 after left pneumonectomy. Three groups (n = 5) received 40-O-(2-hydroxyethyl)-rapamycin (RAD, 2.5 mg/kg/d, by gavage): Group PMR(5-35) from Day 5 to Day 35, Group PMR5-14 from Day 5 to Day 14, and Group PMR15-35 from Day 15 to Day 35. By Day 35, rats that received vehicle had higher mean pulmonary arterial pressures (Ppa = 41 +/- 3 mm Hg) (p < 0.001), right ventricular systolic pressures (Prv,s = 45 +/- 2 mm Hg) (p < 0.01), and right ventricle/(left ventricle plus septum) (0.55 +/- 0.05) (p = 0.028) than rats in Groups PMR5-35 (Ppa = 25 +/- 3 mm Hg, Prv,s = 32 +/- 7 mm Hg, RV/LV&S = 0.42 +/- 0.06) and PMR5-14 (Ppa = 29 +/- 4 mm Hg, Prv,s = 30 +/- 5 mm Hg, RV/LV&S = 0.43 +/- 0.07). Pulmonary arterial neointimal formation (quantified by a vascular occlusion score) was more severe in vehicle-treated rats (1.93 +/- 0.03) than in Groups PMR5-14 (1.56 +/- 0.27) and PMR(5-35) (1.57 +/- 0.1) (p < 0.01). RAD attenuates the development of MCT-induced pulmonary arterial hypertension in the pneumonectomized rat.

    View details for Web of Science ID 000167050900038

    View details for PubMedID 11179130

  • Triptolide attenuates pulmonary arterial hypertension and neointimal formation in rats AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Faul, J. L., Nishimura, T., Berry, G. J., BENSON, G. V., Pearl, R. G., Kao, P. N. 2000; 162 (6): 2252-2258

    Abstract

    This paper reports the effect of triptolide (a diterpenoid triepoxide) on the development of monocrotaline (MCT)-induced pulmonary hypertension in pneumonectomized rats. Male Sprague- Dawley rats were injected with MCT (60 mg/kg) on Day 7 after left pneumonectomy. Rats received therapy from Day 5 to 35 with triptolide (0.25 mg/kg intraperitoneally, every other day, n = 10), or vehicle (0.1 ml of ethanol/cremophor intraperitoneally, every other day, n = 10). By Day 35, triptolide-treated rats demonstrated lower mean pulmonary arterial pressure (mPAP) than vehicle-treated rats (mPAP 21 +/- 3 versus 42 +/- 5 mm Hg, p < 0.001). Triptolide-treated rats also had significantly less right ventricular hypertrophy (RVH) and pulmonary arterial neointimal formation. In a rescue experiment, rats initiated therapy on Day 21. At Day 35, vehicle-treated rats (n = 4) had higher mPAP (40 +/- 9 mm Hg), greater RVH, and more severe pulmonary arterial neointimal formation than rats that received triptolide (0.25 mg/kg every other day, n = 7, mPAP 30 +/- 4 mm Hg) and rats that received triptolide (0.2 mg/kg daily, n = 7, mPAP 25 +/- 5 mm Hg, p < 0.01). In pneumonectomized rats that receive MCT, triptolide attenuates the development of pulmonary hypertension and RVH, and promotes regression of pulmonary arterial neointimal formation.

    View details for Web of Science ID 000165794700050

    View details for PubMedID 11112148

  • Anti-inflammatory effects of triptolide in human bronchial epithelial cells AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY Zhao, G. H., Vaszar, L. T., Qiu, D. M., Shi, L. F., Kao, P. N. 2000; 279 (5): L958-L966

    Abstract

    Triptolide (PG490, 97% pure) is a diterpenoid triepoxide with potent anti-inflammatory and immunosuppressive effects in transformed human bronchial epithelial cells and T cells (Qiu D, Zhao G, Aoki Y, Shi L, Uyei A, Nazarian S, Ng JC-H, and Kao PN. J Biol Chem 274: 13443-13450, 1999). Triptolide, with an IC(50) of approximately 20-50 ng/ml, inhibits normal and transformed human bronchial epithelial cell expression of interleukin (IL)-6 and IL-8 stimulated by phorbol 12-myristate 13-acetate (PMA), tumor necrosis factor-alpha, or IL-1 beta. Nuclear runoff and luciferase reporter gene assays demonstrate that triptolide inhibits IL-8 transcription. Triptolide also inhibits the transcriptional activation, but not the DNA binding, of nuclear factor-kappa B. A cDNA array and clustering algorithm analysis reveals that triptolide inhibits expression of the PMA-induced genes tumor necrosis factor-alpha, IL-8, macrophage inflammatory protein-2 alpha, intercellular adhesion molecule-1, integrin beta(6), vascular endothelial growth factor, granulocyte-macrophage colony-stimulating factor, GATA-3, fra-1, and NF45. Triptolide also inhibits constitutively expressed cell cycle regulators and survival genes cyclins D1, B1, and A1, cdc-25, bcl-x, and c-jun. Thus anti-inflammatory, antiproliferative, and proapoptotic properties of triptolide are associated with inhibition of nuclear factor-kappa B signaling and inhibition of genes known to regulate cell cycle progression and survival.

    View details for Web of Science ID 000090056200023

    View details for PubMedID 11053033

  • Protein-arginine methyltransferase I, the predominant protein-arginine methyltransferase in cells, interacts with and is regulated by interleukin enhancer-binding factor 3 JOURNAL OF BIOLOGICAL CHEMISTRY Tang, J., Kao, P. N., Herschman, H. R. 2000; 275 (26): 19866-19876

    Abstract

    Arginine methylation is a common post-translation modification found in many proteins. Protein-arginine methyltransferase I (PRMT1) contributes >90% of type I protein-arginine methyltransferase activity in cells and tissues. To expand our knowledge on the regulation and role of PRMT1 in cells, we used the yeast two-hybrid system to identify proteins that interact with PRMT1. One of the interacting proteins we cloned is interleukin enhancer-binding factor 3 (ILF3), also known as M phase phosphoprotein 4. ILF3 is closely related to nuclear factor 90 (NF90). Using an immunofluorescence analysis, we determined that ILF3 and PRMT1 co-localize in the nucleus. Moreover, PRMT1 and ILF3 co-precipitate in immunoprecipitation assays and can be isolated together in "pull-down" experiments using recombinant fusion proteins. ILF3 is a robust substrate for methylation by PRMT1 and can modulate PRMT1 activity in in vitro methylation assays. Deletion studies demonstrated that the COOH-terminal region of ILF3, which is rich in arginine, glycine, and serine, is responsible for the strong interaction between PRMT1 and ILF3 and is the site of ILF3 methylation by PRMT1. Although ILF3 and NF90 are highly similar, they differ in their carboxyl-terminal regions. Because of this difference, NF90 does not interact with PRMT1, is a much poorer substrate than ILF3 for PRMT1-dependent methylation, and does not modulate PRMT1 enzyme activity.

    View details for Web of Science ID 000087941300060

    View details for PubMedID 10749851

  • Autoantibodies define a family of proteins with conserved double-stranded RNA-binding domains as well as DNA binding activity JOURNAL OF BIOLOGICAL CHEMISTRY Satoh, M., Shaheen, V. M., Kao, P. N., Okano, T., Shaw, M., Yoshida, H., Richards, H. B., Reeves, W. H. 1999; 274 (49): 34598-34604

    Abstract

    Cellular responses to viral infection are signaled by double-stranded (ds) RNA, which is not found in substantial amounts in uninfected cells. Although cellular dsRNA-binding proteins have been described, their characterization is incomplete. We show that dsRNA-binding proteins are prominent autoantigens. Sera from B6 and B10.S mice with pristane-induced lupus and human autoimmune sera immunoprecipitated a novel set of 130-, 110-, 90-, 80-, and 45-kDa proteins. The proteins were all major cellular poly(IC)-binding factors. N-terminal amino acid sequences of p110 and p90 were identical and matched nuclear factor (NF) 90 and M phase phosphoprotein 4. p45 and p90 were identified as the NF45.NF90 complex, which binds the interleukin-2 promoter as well as certain highly structured viral RNAs. NF90.NF45 and M phase phosphoprotein 4 belong to a large group of proteins with conserved dsRNA-binding motifs. Besides binding dsRNA, NF90.NF45, p110, and p130 had single-stranded and dsDNA binding activity. Some sera contained autoantibodies whose binding was inhibited by poly(IC) but not single-stranded DNA or vice versa, suggesting that the DNA- and RNA-binding sites are different. These autoantibodies will be useful probes of the function of dsRNA-binding proteins. Their interaction with dsRNA, an immunological adjuvant, also could promote autoimmunity.

    View details for Web of Science ID 000083979600017

    View details for PubMedID 10574923

  • Erythromycin inhibits transcriptional activation of NF-kappa B, but not NFAT, through calcineurin-independent signaling in T cells ANTIMICROBIAL AGENTS AND CHEMOTHERAPY Aoki, Y., Kao, P. N. 1999; 43 (11): 2678-2684

    Abstract

    The molecular mechanism of the anti-inflammatory effect of erythromycin (EM) was investigated at the level of transcriptional regulation of cytokine gene expression in T cells. EM (>10(-6) M) significantly inhibited interleukin-8 (IL-8) expression but not IL-2 expression from T cells induced with 20 ng of phorbol 12-myristate 13-acetate (PMA) per ml plus 2 microM calcium ionophore (P-I). In electrophoretic mobility shift assays EM at 10(-7) to 10(-5) M concentrations inhibited nuclear factor kappa B (NF-kappaB) DNA-binding activities induced by P-I. Reporter gene assays also showed that EM (10(-5) M) inhibited IL-8 NF-kappaB transcription by 37%. The inhibitory effects of EM on transcriptional activation of IL-2 and DNA-binding activity of nuclear factor of activated T cells (NFAT) were not seen in T cells. On the other hand, FK506, which is also a macrolide derivative, inhibited transcriptional activation of both NF-kappaB and NFAT more strongly than EM did. The mechanism of EM inhibition of transactivation of NF-kappaB was further investigated in transiently transfected T cells that express calcineurin A and B subunits. Expression of calcineurin did not render transactivation of NF-kappaB in T cells more resistant to EM, while the inhibitory effect of FK506 on transactivation of NF-kappaB was attenuated. These findings indicate that EM is capable of inhibiting expression of the IL-8 gene in T cells through transcriptional inhibition and that this inhibition is mediated through a non-calcineurin-dependent signaling event in T lymphocytes.

    View details for Web of Science ID 000083445300015

    View details for PubMedID 10543746

  • Tick-borne pulmonary disease - Update on diagnosis and management CHEST Faul, J. L., Doyle, R. L., Kao, P. N., Ruoss, S. J. 1999; 116 (1): 222-230

    Abstract

    Ticks are capable of transmitting viruses, bacteria, protozoa, and rickettsiae to man. Several of these tick-borne pathogens can lead to pulmonary disease. Characteristic clinical features, such as erythema migrans in Lyme disease, or spotted rash in a spotted fever group disease, may serve as important diagnostic clues. Successful management of tick-borne diseases depends on a high index of suspicion and recognition of their clinical features. Patients at risk for tick bites may be coinfected with two or more tick-borne pathogens. A Lyme vaccine has recently become available for use in the United States. Disease prevention depends on the avoidance of tick bites. When patients present with respiratory symptoms and a history of a recent tick bite or a characteristic skin rash, a differential diagnosis of a tick-borne pulmonary disease should be considered. Early diagnosis and appropriate antibiotic therapy for these disorders lead to greatly improved outcomes.

    View details for Web of Science ID 000081513200037

    View details for PubMedID 10424529

  • Nuclear factor-90 of activated T-cells: A double-stranded RNA-binding protein and substrate for the double-stranded RNA-dependent protein kinase, PKR BIOCHEMISTRY Langland, J. O., Kao, P. N., Jacobs, B. L. 1999; 38 (19): 6361-6368

    Abstract

    NFAT transcription factors play a central role in initiating T-cell activation through the induction of immediate-early T-cell specific genes including interleukin-2 (IL-2). NFAT transcription factors bind to a sequence in the IL-2 enhancer known as the antigen receptor response element 2 (ARRE-2). Multiple proteins exhibiting ARRE-2 binding activity have been isolated, including a heterodimer from stimulated T-cell nuclear extracts consisting of Mr = 90 000 (NF90) and Mr = 45 000 (NF45) subunits. The subunits of this heterodimer have been cloned, and NF90 was found to encode a protein containing two domains that are predicted to form motifs capable of binding to double-stranded RNA. Using in vitro translated polypeptides, we have demonstrated that NF90 specifically binds to double-stranded RNA. Furthermore, NF90 was phosphorylated in a double-stranded RNA-dependent manner likely by the interferon-induced, double-stranded RNA-dependent protein kinase, PKR. The NF90 protein was found to be expressed not only in T-cells, but also in nonimmune HeLa cells. In HeLa cells, the protein was almost exclusively localized to the ribosome salt wash fraction of cell lysates.

    View details for Web of Science ID 000080500300047

    View details for PubMedID 10320367

  • PG490 (triptolide) cooperates with tumor necrosis factor-alpha to induce apoptosis in tumor cells JOURNAL OF BIOLOGICAL CHEMISTRY Lee, K. Y., Chang, W. T., Qiu, D. M., Kao, P. N., Rosen, G. D. 1999; 274 (19): 13451-13455

    Abstract

    Progress in the treatment of solid tumors has been slow and sporadic. The efficacy of conventional chemotherapy in solid tumors is limited because tumors frequently have mutations in the p53 gene. Also, chemotherapy only kills rapidly dividing cells. Members of the tumor necrosis factor (TNF) family, however, induce apoptosis regardless of the p53 phenotype. Unfortunately, the cytotoxicity of TNF-alpha is limited by its activation of NF-kappaB and activation of NF-kappaB is proinflammatory. We have identified a compound called PG490, that is composed of purified triptolide, which induces apoptosis in tumor cells and sensitizes tumor cells to TNF-alpha-induced apoptosis. PG490 potently inhibited TNF-alpha-induced activation of NF-kappaB. PG490 also blocked TNF-alpha-mediated induction of c-IAP2 (hiap-1) and c-IAP1 (hiap-2), members of the inhibitor of apoptosis (IAP) family. Interestingly, PG490 did not block DNA binding of NF-kappaB, but it blocked transactivation of NF-kappaB. Our identification of a compound that blocks TNF-alpha-induced activation of NF-kappaB may enhance the cytotoxicity of TNF-alpha on tumors in vivo and limit its proinflammatory effects.

    View details for Web of Science ID 000080200400072

    View details for PubMedID 10224110

  • Immunosuppressant PG490 (triptolide) inhibits T-cell interleukin-2 expression at the level of purine-box/nuclear factor of activated T-cells and NF-kappa B transcriptional activation JOURNAL OF BIOLOGICAL CHEMISTRY Qiu, D. M., Zhao, G. H., Aoki, Y., Shi, L. F., Uyei, A., Nazarian, S., Ng, J. C., Kao, P. N. 1999; 274 (19): 13443-13450

    Abstract

    PG490 (triptolide) is a diterpene triepoxide with potent immunosuppressive and antiinflammatory properties. PG490 inhibits interleukin(IL)-2 expression by normal human peripheral blood lymphocytes stimulated with phorbol 12-myristate 13-acetate (PMA) and antibody to CD3 (IC50 of 10 ng/ml), and with PMA and ionomycin (Iono, IC50 of 40 ng/ml). In Jurkat T-cells, PG490 inhibits PMA/Iono-stimulated IL-2 transcription. PG490 inhibits the induction of DNA binding activity at the purine-box/antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target sequence but not at the NF-kappaB site. PG490 can completely inhibit transcriptional activation at the purine-box/ARRE/NF-AT and NF-kappaB target DNA sequences triggered by all stimuli examined (PMA, PMA/Iono, tumor necrosis factor-alpha). PG490 also inhibits PMA-stimulated activation of a chimeric transcription factor in which the C-terminal TA1 transactivation domain of NF-kappaB p65 is fused to the DNA binding domain of GAL4. In 16HBE human bronchial epithelial cells, IL-8 expression is regulated predominantly by NF-kappaB, and PG490 but not cyclosporin A can completely inhibit expression of IL-8. The mechanism of PG490 inhibition of cytokine gene expression differs from cyclosporin A and involves nuclear inhibition of transcriptional activation of NF-kappaB and the purine-box regulator operating at the ARRE/NF-AT site at a step after specific DNA binding.

    View details for Web of Science ID 000080200400071

    View details for PubMedID 10224109

  • Mycobacterium avium-intracellulare pulmonary infection in HIV-negative patients without preexisting lung disease - Diagnostic and management limitations CHEST Huang, J. H., Kao, P. N., Adi, V., Ruoss, S. J. 1999; 115 (4): 1033-1040

    Abstract

    To review the experience of an outpatient pulmonary clinic with Mycobacterium avium-intracellulare (MAI) pulmonary disease in the HIV-negative population without preexisting lung disease.Retrospective clinical series.University medical center.The clinic charts of all patients who fulfilled the current American Thoracic Society criteria for MAI pulmonary infection and who had no preexisting lung disease or immunosuppression were reviewed.Of 31 patients identified, 94% were female, 90% were white, and the median age at diagnosis was 63 years. The median time interval from symptom onset to diagnosis was 10 months. Bronchiectasis or small nodules without predilection for any lobe was found in 93%. Bronchoscopy or open lung biopsy for diagnosis was required in 45% because of nondiagnostic sputum cultures. At > or = 12 months, 50% failed therapy, 86% continued to be symptomatic, and 58% did not tolerate their initial multidrug regimen.These results emphasize the observed chronic nature of MAI pulmonary disease in this population, both before diagnosis and despite therapy. The sensitivity of sputum culture in this population is low, so an aggressive diagnostic approach, including bronchoscopy, should be considered if sputum cultures are negative. Current treatments are suboptimal because of poor drug tolerance and significant failure rates. Last, the preponderance of disease in older white women argues for a genetic or acquired immune deficiency to explain disease susceptibility.

    View details for Web of Science ID 000079655900026

    View details for PubMedID 10208205

  • Diaphragmatic paralysis due to Lyme disease EUROPEAN RESPIRATORY JOURNAL Faul, J. L., Ruoss, S., Doyle, R. L., Kao, P. N. 1999; 13 (3): 700-702

    Abstract

    Lyme disease is a tick-borne spirochaete infection which, in a proportion of patients, can lead to neuropathy. This article describes a case of diaphragmatic paralysis due to Lyme disease. A 39-yr-old male presented to the hospital because of an acute left facial palsy. Six weeks prior to admission he had developed a circular rash on his left flank during a camping holiday. He also complained of shortness of breath and arthralgia for 1 week. His chest radiograph demonstrated a raised right hemi-diaphragm. Diaphragmatic paralysis was confirmed by fluoroscopy (a positive sniff test). Serology revealed evidence of recent infection by Borrelia burgdorferi. On the basis of the patient's clinical presentation, a recent history of erythema migrans, and positive Lyme serology, a diagnosis of neuroborreliosis was made. He received oral doxycycline therapy (200 mg x day(-1)) for three weeks. Facial and diaphragmatic palsies resolved within eight weeks. On the basis of this case, a diagnosis of Lyme disease should be considered in patients from endemic regions with otherwise unexplained phrenic nerve palsy.

    View details for Web of Science ID 000079849000041

    View details for PubMedID 10232450

  • CsA-sensitive purine-box transcriptional regulator in bronchial epithelial cells contains NF45, NF90, and Ku AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY Aoki, Y., Zhao, G. H., Qiu, D. M., Shi, L. F., Kao, P. N. 1998; 275 (6): L1164-L1172

    Abstract

    Human bronchial epithelial (HBE) cells express interleukin (IL)-2 [Y. Aoki, D. Qiu, A. Uyei, and P. N. Kao. Am. J. Physiol. 272 (Lung Cell. Mol. Physiol. 16): L276-L286, 1997]. 16HBE-transformed cells contain constitutive and inducible nuclear DNA-binding activity for the purine-box/nuclear factor (NF) of activated T cell (NFAT) target DNA sequence in the human IL-2 enhancer. Transcriptional activation through the purine-box DNA sequence requires stimulation with phorbol 12-myristate 13-acetate + ionomycin, and this activation is inhibited by cyclosporin A. Immunohistochemical staining of 16HBE cells demonstrates nuclear expression of the purine-box DNA-binding proteins NF45 and NF90 and no expression of NFATp or NFATc. NF90 and NF45 associate with the DNA-dependent protein kinase catalytic subunit and the DNA-targeting subunits Ku80 and Ku70 (N. S. Ting, P. N. Kao, D. W. Chan, L. G. Lintott, and S. P. Lees-Miller. J. Biol. Chem. 273: 2136-2145, 1998). Antibodies to Ku potently inhibit the purine-box DNA-binding complex. The purine-box transcriptional regulator in 16HBE cells likely comprises NF45, NF90, Ku80, Ku70, and the DNA-dependent protein kinase catalytic subunit.

    View details for Web of Science ID 000077747100018

    View details for PubMedID 9843854

  • Leukotriene B-4 mediates histamine induction of NF-kappa B and IL-8 in human bronchial epithelial cells AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY Aoki, Y., Qiu, D. M., Zhao, G. H., Kao, P. N. 1998; 274 (6): L1030-L1039

    Abstract

    In 16HBE transformed human bronchial epithelial cells, histamine stimulated interleukin (IL)-8 mRNA and protein secretion, and this histamine stimulation was inhibited by the H1-receptor antagonist diphenhydramine (DPH), by the inhibitor of 5-lipoxygenase-activating protein (FLAP) MK-886, by the 5-lipoxygenase inhibitor Zileuton, and by dexamethasone. Histamine stimulated bronchial epithelial cell production of leukotriene B4 (LTB4), and this production was inhibited by FLAP inhibitors MK-886 and L-655,238 and Zileuton. Histamine stimulated IL-8 luciferase reporter gene activity that was inhibited with DPH, dexamethasone, MK-886 and L-655,238, and Zileuton. The inhibition of IL-8 transcription and protein secretion by FLAP inhibitors and Zileuton was reversed with exogenous LTB4. There was increased IL-8 nuclear factor-kappaB (NF-kappaB) DNA-binding activity after histamine stimulation, and this was inhibited by DPH and MK-886. Cytoplasmic phospholipase A2 mRNA levels were also potently induced by histamine. Thus histamine stimulation of bronchial epithelial cells involves binding at H1 receptors, production of LTB4, activation of NF-kappaB and increased expression of IL-8.

    View details for Web of Science ID 000073905400019

    View details for PubMedID 9609743

  • Analyses of the NRAMP1 and IFN-gamma R1 genes in women with Mycobacterium avium-intracellulare pulmonary disease AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE Huang, J. H., Oefner, P. J., Adi, V., Ratnam, K., Ruoss, S. J., Trako, E., Kao, P. N. 1998; 157 (2): 377-381

    Abstract

    Mycobacterium avium-intracellulare (MAI) pulmonary disease causes substantial morbidity in a population of older, HIV-negative women without preexisting lung disease. The cause for disease susceptibility in these patients is unknown, although their relative phenotypic homogeneity suggests the existence of a common, subtle immune deficiency. An investigation was undertaken to determine if these patients have a defect in their natural resistance-associated macrophage protein (NRAMP1) or interferon gamma receptor 1 (IFN-gammaR1) genes. A point mutation in murine nramp, an autosomal recessive gene controlling resistance to intracellular organisms, correlates with overwhelming Mycobacterium bovis infection in mice. The corresponding region in human NRAMP1, two coding polymorphisms and one promoter NRAMP1 polymorphism, as well as two IFN-gammaR1 polymorphisms, were analyzed to determine if an allele was present to correlate with disease. Genomic DNA was purified from eight women with MAI pulmonary disease and four controls. Regions of interest were amplified by PCR; three sites were analyzed by restriction fragment length polymorphisms, and three were analyzed using denaturing high-performance liquid chromatography. The NRAMP1 promoter polymorphism of 18 additional random controls was analyzed by microsatellite sizing. No allelism was found in NRAMP1 corresponding to the murine mutation, or in the two coding regions. In the NRAMP1 promoter microsatellite, 3 of 8 patients were heterozygous for a dinucleotide sequence insertion, as were 10 of 22 controls. None of the patients had either of the two known IFN-gammaR1 mutations. In conclusion, in women with MAI pulmonary disease, there is no evidence for a genetic defect in NRAMP1 or IFN-gammaR1 to correlate with disease.

    View details for Web of Science ID 000071907200004

    View details for PubMedID 9476846

  • DNA-dependent protein kinase interacts with antigen receptor response element binding proteins NF90 and NF45 JOURNAL OF BIOLOGICAL CHEMISTRY Ting, N. S., Kao, P. N., Chan, D. W., Lintott, L. G., Lees-Miller, S. P. 1998; 273 (4): 2136-2145

    Abstract

    The DNA-dependent protein kinase (DNA-PK) is composed of a large catalytic subunit of approximately 470 kDa (DNA-PKcs) and the DNA-binding protein, Ku. Absence of DNA-PK activity confers sensitivity to x-rays and defects in both DNA double-strand break repair and V(D)J recombination. However the precise function of DNA-PK in DNA double-strand break repair is not known. Here we show, using electrophoretic mobility shift assays, that polypeptides in a fraction purified from human cells interact with DNA-PK and stabilize the formation of a complex containing DNA-PKcs-Ku and DNA. Five polypeptides in this fraction have been identified by amino-terminal sequence analysis and/or immunoblotting. These proteins are NF90 and NF45, which are the 90- and 45-kDa subunits of a protein known to bind specifically to the antigen receptor response element of the interleukin 2 promoter, and the alpha, beta, and gamma subunits of eukaryotic translation initiation factor eIF-2. We also show that NF90, NF45, and eIF-2 beta are substrates for DNA-PK in vitro. In addition, recombinant NF90 promotes formation of a complex between DNA-PKcs, Ku, and DNA, and antibodies to recombinant NF90 or recombinant NF45 immunoprecipitate DNA-PKcs in vitro. Together, our data suggest that NF90, in complex with NF45, interacts with DNA-PKcs and Ku on DNA and that NF90 and NF45 may be important for the function of DNA-PK.

    View details for Web of Science ID 000071595200043

    View details for PubMedID 9442054

  • Cyclosporin A-sensitive calcium signaling represses NF kappa B activation in human bronchial epithelial cells and enhances NF kappa B activation in Jurkat T-cells BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Aoki, Y., Kao, P. N. 1997; 234 (2): 424-431

    Abstract

    Activation of the NFkappaB transcription factor in 16HBE human bronchial epithelial cells was compared with activation of NFkappaB in Jurkat T-cells. An NFkappaB-luciferase reporter gene was activated by phorbol myristyl acetate (PMA) in both cell types. Ionomycin added to PMA (P/I) inhibited NFkappaB activation in epithelial cells and enhanced PMA activation in T-cells. Cyclosporin A (CsA) inhibited calcium signaling in both cell types. Nuclear NFkappaB DNA-binding stimulated with PMA was inhibited with ionomycin in epithelial cells and was enhanced with ionomycin in T-cells; CsA reversed both effects of ionomycin. Cytosolic IkappaB-alpha was regulated identically in both cell types. Thus, calcium activated opposing nuclear signaling pathways in epithelial cells and T-cells. Calcium-mediated repression of NFkappaB in epithelial cells was derepressed by CsA, and this establishes a mechanism through which CsA may exert proinflammatory effects in nonlymphoid cells.

    View details for Web of Science ID A1997XB33100028

    View details for PubMedID 9177287

  • Human airway epithelial cells express interleukin-2 in vitro AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY Aoki, Y., Diu, D. M., Uyei, A., Kao, P. N. 1997; 272 (2): L276-L286

    Abstract

    Human airway epithelial cells (AEC) produce the T cell growth factor interleukin (IL)-2 that likely modulates the T cell lung inflammatory response. IL-2 mRNA from cultured AEC and from Jurkat T cells was analyzed by reverse transcription-polymerase chain reaction and Northern hybridization. IL-2 mRNA is present constitutively in AEC and is enhanced twofold after stimulation with phorbol 12-myristate 13-acetate (PMA; 20 ng/ml) + histamine (2 mM). Normal human AEC secrete IL-2 at rest (7 pg/ml), and IL-2 secretion is increased threefold after stimulation with PMA + histamine; this increase is inhibited by dexamethasone and diphenhydramine. Transcriptional regulation of IL-2 was investigated with a transgenic human AEC line, 16HBE/IL-2 luciferase; there is constitutive IL-2 transcription at rest, and IL-2 transcription is enhanced 8-fold by PMA and 25-fold by PMA + histamine. IL-2 regulation differs fundamentally between AEC and Jurkat T cells. AEC IL-2 likely promotes local proliferation of T cells and may contribute to pathological airway inflammation in asthma.

    View details for Web of Science ID A1997WJ52400014

    View details for PubMedID 9124379

  • PURIFICATION BY DNA AFFINITY-CHROMATOGRAPHY OF 2 POLYPEPTIDES THAT CONTACT THE NF-AT DNA-BINDING SITE IN THE INTERLEUKIN-2 PROMOTER JOURNAL OF BIOLOGICAL CHEMISTRY Corthesy, B., Kao, P. N. 1994; 269 (32): 20682-20690

    Abstract

    NF-AT is a lymphoid-specific transcription factor that is though to be largely responsible for determining the cell type-specific expression of the interleukin 2 (IL2) gene. Using two different purification schemes, we found that the NF-AT binding site present in the IL2 promoter is the target for two distinct polypeptides with a relative molecular weight of 45,000 and 90,000. Direct extraction of NF-AT binding activity from highly purified nuclei confirms that p45 and p90 are components of the NF-AT complex. UV-induced covalent cross-linking of p45 and p90 to the NF-AT sequence indicates that both polypeptides interact with DNA. We demonstrate using in vitro transcription that antibodies to subunits p45 and p90 strongly reduce activation of an artificial promoter carrying three NF-AT recognition sites. The complex we have purified has the potential to interact with cis-acting elements identified in the promoter of genes expressed early during T cell activation and to the HIV long terminal repeat. We also show that phosphorylation modulates interaction of NF-AT to its cognate binding site. All together, our data suggest that p45 and p90 form the constitutively expressed nuclear factor(s) proposed by Yaseen et al. (Yaseen, N.R., Maizel, A. L., Wang, F., and Sharma, S. (1993) J. Biol. Chem. 268, 14285-14293).

    View details for Web of Science ID A1994PB31700073

    View details for PubMedID 8051169

  • CLONING AND EXPRESSION OF CYCLOSPORINE-A-SENSITIVE AND FK506-SENSITIVE NUCLEAR FACTOR OF ACTIVATED T-CELLS - NF45 AND NF90 JOURNAL OF BIOLOGICAL CHEMISTRY Kao, P. N., Chen, L., Brock, G., Ng, J., Kenny, J., SMITH, A. J., Corthesy, B. 1994; 269 (32): 20691-20699

    Abstract

    Nuclear Factor of Activated T-cells (NF-AT) is a crucial transcription factor required for T-cell expression of interleukin 2. Purified NF-AT contains 45-kDa and 90-kDa subunits (Corthésy, B., and Kao, P. N. (1994) J. Biol. Chem. 269, 20682-20690). Partial internal amino acid sequences derived from each subunit indicate that these proteins are novel. The amino acid sequences were used to clone the cDNAs encoding each subunit. The cDNAs predict proteins of novel structures: NF45 has limited similarity to prokaryotic transcription factor sigma-54 and to human DNA topoisomerase II; NF90 has limited similarity to Drosophila Staufen in a domain predicted to bind double-stranded RNA. RNA encoding NF45 and NF90 exists in nonstimulated Jurkat T-cells and in all other cell types examined (HeLa, HepG2, K562). Immunofluorescence microscopy was used to demonstrate that both proteins are located in the nucleus of Jurkat T-cells. Clones NF45 and NF90 with a polyhistidine fusion tag were transiently expressed and processed in the native environment of Jurkat T-cells. Histidine-tagged NF45 and NF90 proteins, affinity-purified on nickel chelate columns, encode a NF-AT DNA-binding activity that is enhanced following T-cell stimulation, and this enhancement is blocked when T-cells are stimulated in the presence of cyclosporin A or FK506.

    View details for Web of Science ID A1994PB31700074

    View details for PubMedID 7519613

  • ACETYLCHOLINE-RECEPTOR BINDING-SITE CONTAINS A DISULFIDE CROSS-LINK BETWEEN ADJACENT HALF-CYSTINYL RESIDUES JOURNAL OF BIOLOGICAL CHEMISTRY Kao, P. N., Karlin, A. 1986; 261 (18): 8085-8088

    Abstract

    A conserved feature of all nicotinic receptors is the presence of a readily reducible disulfide bond adjacent to the acetylcholine binding site. Previously we showed that in intact receptor from Torpedo californica electric tissue reduction of this disulfide followed by affinity alkylation with 4-(N-maleimido)benzyltri[3H] methylammonium iodide specifically and uniquely labels the alpha subunit residues Cys-192 and Cys-193. To identify all of the half-cystinyl residues contributing to the binding site disulfide(s), we have now reduced receptor under mild conditions and alkylated with a mixture of 4-(N-maleimido)benzyltri[3H]methylammonium iodide and N-[1-14C]ethylmaleimide and find that Cys-192 and Cys-193 are labeled exclusively. Furthermore, from unreduced receptor we have isolated two cyanogen bromide peptides of alpha, one containing Cys-192 and Cys-193, and the other containing Cys-128 and Cys-142 (which are the other potential contributors to the binding site disulfide(s]. These isolated peptides incorporate iodo[1-14C]acetamide only following reduction by dithiothreitol. Our results demonstrate that: 1) the binding site disulfide is between Cys-192 and Cys-193; 2) Cys-128 is disulfide-cross-linked to Cys-142; and 3) under conditions that reduce Cys-192 and Cys-193 completely, Cys-128 and Cys-142 remain cross-linked. At the acetylcholine binding site, agonists induce a local conformational change that stabilizes the binding site disulfide against reduction. We suggest that a transition between two stable conformations of the vicinal disulfide, both involving a nonplanar cis peptide bond between Cys-192 and Cys-193, is associated with receptor activation by agonists.

    View details for Web of Science ID A1986C866000003

    View details for PubMedID 3722144

  • Identification of the alpha subunit half-cystine specifically labeled by an affinity reagent for the acetylcholine receptor binding site. journal of biological chemistry Kao, P. N., Dwork, A. J., KALDANY, R. R., SILVER, M. L., Wideman, J., Stein, S., Karlin, A. 1984; 259 (19): 11662-11665

    Abstract

    Nicotinic acetylcholine receptors contain a readily reducible disulfide bond at the periphery of the acetylcholine binding site. Following reduction of this disulfide, the binding site is susceptible to affinity labeling by electrophilic reagents with quaternary ammonium moieties. We reduced purified receptor from Torpedo californica electric tissue and affinity alkylated it with 4-(N-maleimido)benzyltri[3H]methylammonium iodide. The label was incorporated solely into the alpha subunit of the receptor. Isolated, labeled alpha subunit was cleaved with CNBr, and the fragments were separated by reverse-phase high-performance liquid chromatography. A uniquely labeled CNBr fragment was isolated, and its partial sequence was determined by automated Edman degradation. This CNBr fragment was cleaved at tryptophan residues, the subfragments were separated, and the labeled subfragments were partially sequenced. From our protein sequence information, we identify the labeled CNBr fragment as residues 179 to 207 of the sequence of alpha predicted from the cDNA sequence (Noda, M., Takahashi, H., Tanabe, T., Toyosato, M., Furutani, Y., Hirose, T., Asai, M., Inayama, S., Miyata, T., and Numa, S. (1982) Nature (Lond.) 299, 793-797). From the cycle of the Edman degradation in which radioactive residues are released, we conclude that Cys 192 and, possibly in addition, Cys 193 are the residues specifically labeled by 4-(N-maleimido)benzyltri[3H]methylammonium iodide. They are, therefore, close to the acetylcholine binding site.

    View details for PubMedID 6480577

  • THE ACTIVE GUANIDINIUM GROUP OF SAXITOXIN AND NEOSAXITOXIN IDENTIFIED BY THE EFFECTS OF PH ON THEIR ACTIVITIES ON SQUID AXON PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY Kao, P. N., JAMESKRACKE, M. R., Kao, C. Y. 1983; 398 (3): 199-203

    Abstract

    The relative potencies of saxitoxin at pH 7.25 and 8.25 have been determined on the squid giant axon under voltage-clamp conditions or by Vmax of the propagated action potential. Of the two guanidinium groups in saxitoxin, the 7, 8, 9 group has been identified as the biologically active group. The evidence lies in the demonstration of a quantitative agreement between the relative abundance of the protonated, positively charged form of that group at pH's 7.25 and 8.25 (ratio 1.80) with the relative potencies (ratio 1.79) of the toxin. The 1, 2, 3 group is excluded by the lack of agreement between the relative abundance of the protonated form (ratio 1.00) and the relative potencies at these pH's. The 1, 2, 3 group is further excluded by the observation that neosaxitoxin is equally potent at pH 6.50 and 7.25, in spite of a difference of 6-fold in the abundance of a deprotonated hydroxyl group on N-1 which should have influenced the potency.

    View details for Web of Science ID A1983RG12600003

    View details for PubMedID 6314239

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