Bio

Academic Appointments


Professional Education


  • B.S., Taipei Medical College, Medical Technology (1981)
  • M.S., University of Oklahoma HSC, Microbiol. and Immunol. (1985)
  • Ph.D., University of Oklahoma HSC, Microbial Genetics (1988)

Research & Scholarship

Current Research and Scholarly Interests


We study the role of oxygen free radicals in oxidative tissue damage and degeneration. Our research tools include transgenic and knockout mice and tissue culture cells for in vitro gene expression.

Teaching

2013-14 Courses


Graduate and Fellowship Programs


Publications

Journal Articles


  • Extracellular superoxide dismutase is important for hippocampal neurogenesis and preservation of cognitive functions after irradiation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Zou, Y., Corniola, R., Leu, D., Khan, A., Sahbaie, P., Chakraborti, A., Clark, D. J., Fike, J. R., Huang, T. 2012; 109 (52): 21522-21527

    Abstract

    Cranial irradiation is widely used in cancer therapy, but it often causes cognitive defects in cancer survivors. Oxidative stress is considered a major cause of tissue injury from irradiation. However, in an earlier study mice deficient in the antioxidant enzyme extracellular superoxide dismutase (EC-SOD KO) showed reduced sensitivity to radiation-induced defects in hippocampal functions. To further dissect the role of EC-SOD in neurogenesis and in response to irradiation, we generated a bigenic EC-SOD mouse model (OE mice) that expressed high levels of EC-SOD in mature neurons in an otherwise EC-SOD-deficient environment. EC-SOD deficiency was associated with reduced progenitor cell proliferation in the subgranular zone of dentate gyrus in KO and OE mice. However, high levels of EC-SOD in the granule cell layer supported normal maturation of newborn neurons in OE mice. Following irradiation, wild-type mice showed reduced hippocampal neurogenesis, reduced dendritic spine densities, and defects in cognitive functions. OE and KO mice, on the other hand, were largely unaffected, and the mice performed normally in neurocognitive tests. Although the resulting hippocampal-related functions were similar in OE and KO mice following cranial irradiation, molecular analyses suggested that they may be governed by different mechanisms: whereas neurotrophic factors may influence radiation responses in OE mice, dendritic maintenance may be important in the KO environment. Taken together, our data suggest that EC-SOD plays an important role in all stages of hippocampal neurogenesis and its associated cognitive functions, and that high-level EC-SOD may provide protection against irradiation-related defects in hippocampal functions.

    View details for DOI 10.1073/pnas.1216913110

    View details for Web of Science ID 000313627700077

    View details for PubMedID 23236175

  • Paradoxical Relationship between Mn Superoxide Dismutase Deficiency and Radiation-Induced Cognitive Defects PLOS ONE Corniola, R., Zou, Y., Leu, D., Fike, J. R., Huang, T. 2012; 7 (11)

    Abstract

    Radiation therapy of the CNS, even at low doses, can lead to deficits in neurocognitive functions. Reduction in hippocampal neurogenesis is usually, but not always, associated with cognitive deficits resulting from radiation therapy. Generation of reactive oxygen species is considered the main cause of radiation-induced tissue injuries, and elevated levels of oxidative stress persist long after the initial cranial irradiation. Consequently, mutant mice with reduced levels of the mitochondrial antioxidant enzyme, Mn superoxide dismutase (MnSOD or Sod2), are expected to be more sensitive to radiation-induced changes in hippocampal neurogenesis and the related functions. In this study, we showed that MnSOD deficiency led to reduced generation of immature neurons in Sod2-/+ mice even though progenitor cell proliferation was not affected. Compared to irradiated Sod2+/+ mice, which showed cognitive defects and reduced differentiation of newborn cells towards the neuronal lineage, irradiated Sod2-/+ mice showed normal hippocampal-dependent cognitive functions and normal differentiation pattern for newborn neurons and astroglia. However, we also observed a disproportional decrease in newborn neurons in irradiated Sod2-/+ following behavioral studies, suggesting that MnSOD deficiency may render newborn neurons more sensitive to stress from behavioral trainings following cranial irradiation. A positive correlation between normal cognitive functions and normal dendritic spine densities in dentate granule cells was observed. The data suggest that maintenance of synaptic connections, via maintenance of dendritic spines, may be important for normal cognitive functions following cranial irradiation.

    View details for DOI 10.1371/journal.pone.0049367

    View details for Web of Science ID 000312269500104

    View details for PubMedID 23145165

  • Oxidative stress and adult neurogenesis-Effects of radiation and superoxide dismutase deficiency SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY Huang, T., Zou, Y., Corniola, R. 2012; 23 (7): 738-744

    Abstract

    Hippocampus plays an important role in learning and memory and in spatial navigation. Production of new neurons that are functionally integrated into the hippocampal neuronal network is important for the maintenance of functional plasticity. In adults, production of new neurons in the hippocampus takes place in the subgranular zone (SGZ) of dentate gyrus. Neural progenitor/stem cells go through processes of proliferation, differentiation, migration, and maturation. This process is exquisitely sensitive to oxidative stress, and perturbation in the redox balance in the neurogenic microenvironment can lead to reduced neurogenesis. Cranial irradiation is an effective treatment for primary and secondary brain tumors. However, even low doses of irradiation can lead to persistent elevation of oxidative stress and sustained suppression of hippocampal neurogenesis. Superoxide dismutases (SODs) are major antioxidant enzymes for the removal of superoxide radicals in different subcellular compartments. To identify the subcellular location where reactive oxygen species (ROS) are continuously generated after cranial irradiation, different SOD deficient mice have been used to determine the effects of irradiation on hippocampal neurogenesis. The study results suggest that, regardless of the subcellular location, SOD deficiency leads to a significant reduction in the production of new neurons in the SGZ of hippocampal dentate gyrus. In exchange, the generation of new glial cells was significantly increased. The SOD deficient condition, however, altered the tissue response to irradiation, and SOD deficient mice were able to maintain a similar level of neurogenesis after irradiation while wild type mice showed a significant reduction in the production of new neurons.

    View details for DOI 10.1016/j.semcdb.2012.04.003

    View details for Web of Science ID 000309264300004

    View details for PubMedID 22521481

  • Persistent Expression of Hepatitis C Virus Non-Structural Proteins Leads to Increased Autophagy and Mitochondrial Injury in Human Hepatoma Cells PLOS ONE Chu, V. C., Bhattacharya, S., Nomoto, A., Lin, J., Zaidi, S. K., Oberley, T. D., Weinman, S. a., Azhar, S., Huang, T. 2011; 6 (12)

    Abstract

    HCV infection is a major cause of chronic liver disease and liver cancer in the United States. To address the pathogenesis caused by HCV infection, recent studies have focused on the direct cytopathic effects of individual HCV proteins, with the objective of identifying their specific roles in the overall pathogenesis. However, this approach precludes examination of the possible interactions between different HCV proteins and organelles. To obtain a better understanding of the various cytopathic effects of and cellular responses to HCV proteins, we used human hepatoma cells constitutively replicating HCV RNA encoding either the full-length polyprotein or the non-structural proteins, or cells constitutively expressing the structural protein core, to model the state of persistent HCV infection and examined the combination of various HCV proteins in cellular pathogenesis. Increased reactive oxygen species (ROS) generation in the mitochondria, mitochondrial injury and degeneration, and increased lipid accumulation were common among all HCV protein-expressing cells regardless of whether they expressed the structural or non-structural proteins. Expression of the non-structural proteins also led to increased oxidative stress in the cytosol, membrane blebbing in the endoplasmic reticulum, and accumulation of autophagocytic vacuoles. Alterations of cellular redox state, on the other hand, significantly changed the level of autophagy, suggesting a direct link between oxidative stress and HCV-mediated activation of autophagy. With the wide-spread cytopathic effects, cells with the full-length HCV polyprotein showed a modest antioxidant response and exhibited a significant increase in population doubling time and a concomitant decrease in cyclin D1. In contrast, cells expressing the non-structural proteins were able to launch a vigorous antioxidant response with up-regulation of antioxidant enzymes. The population doubling time and cyclin D1 level were also comparable to that of control cells. Finally, the cytopathic effects of core protein appeared to focus on the mitochondria without remarkable disturbances in the cytosol.

    View details for DOI 10.1371/journal.pone.0028551

    View details for Web of Science ID 000298171400106

    View details for PubMedID 22164304

  • Irradiation Enhances Hippocampus-Dependent Cognition in Mice Deficient in Extracellular Superoxide Dismutase HIPPOCAMPUS Raber, J., Villasana, L., Rosenberg, J., Zou, Y., Huang, T. T., Fike, J. R. 2011; 21 (1): 72-80

    Abstract

    The effects of ionizing irradiation on the brain are associated with oxidative stress. While oxidative stress following irradiation is generally viewed as detrimental for hippocampal function, it might have beneficial effects as part of an adaptive or preconditioning response to a subsequent challenge. Here we show that in contrast to what is seen in wild-type mice, irradiation enhances hippocampus- dependent cognitive measures in mice lacking extracellular superoxide dismutase. These outcomes were associated with genotype-dependent effects on measures of oxidative stress. When cortices and hippocampi were analyzed for nitrotyrosine formation as an index of oxidative stress, the levels were chronically elevated in mice lacking extracellular superoxide dismutase. However, irradiation caused a greater increase in nitrotyrosine levels in wild-type mice than mice lacking extracellular superoxide dismutase. These paradoxical genotype-dependent effects of irradiation on measures of oxidative stress and cognitive function underscore potential beneficial effects associated with chronic oxidative stress if it exists prior to a secondary insult such as irradiation.

    View details for DOI 10.1002/hipo.20724

    View details for Web of Science ID 000286489100007

    View details for PubMedID 20020436

  • Genetic modifier of mitochondrial superoxide dismutase-deficient mice delays heart failure and prolongs survival MAMMALIAN GENOME Kim, A., Chen, C., Ursell, P., Huang, T. 2010; 21 (11-12): 534-542

    Abstract

    Mn superoxide dismutase (MnSOD)-deficient mice (Sod2-/-) suffer from mitochondrial damage and have various survival times and phenotypic presentations that are dependent on the genetic background of the mutant mice. The mitochondrial NADPH transhydrogenase (NNT) was identified as a putative genetic modifier based on a genome-wide quantitative trait association study on the molecular defect of the protein in more severely affected Sod2-/- mice and on the biological function of NNT. Hence, Sod2-/- mice on the C57BL/6J (B6J) background have the shortest survival time, and the mice are homozygous for the truncated Nnt allele (Nnt ( T )). On the other hand, genetic backgrounds that support longer survival of Sod2-/- mice all have at least one normal copy of Nnt (Nnt ( W )). To confirm the role of NNT in the phenotypic modification of Sod2-/- mice, we introduced a normal copy of Nnt allele from a C57BL/6 substrain into B6J-Sod2-/- mice and analyzed survival time, cardiac functions, and histopathology of the heart. The study results show that the presence of a normal Nnt allele preserves cardiac function, delays the onset of heart failure, and extends the survival of B6J-Sod2-/- mice to the end of gestation. Postnatal survival, however, is not supported. Consequently, the majority of B6J-Sod2-/- mice died within a few hours after birth and only a few survived for 5-6 days. The study results suggest that NNT is important for normal development and function of fetal hearts and that there may be other genetic modifier(s) important for postnatal survival of Sod2-/- mice.

    View details for DOI 10.1007/s00335-010-9299-x

    View details for Web of Science ID 000285364600002

    View details for PubMedID 21069343

  • Age-related Defects in Sensorimotor Activity, Spatial Learning, and Memory in C57BL/6 Mice JOURNAL OF NEUROSURGICAL ANESTHESIOLOGY Barreto, G., Huang, T., Giffard, R. G. 2010; 22 (3): 214-219

    Abstract

    Impaired locomotor activity and spatial memory are common features in the natural aging process, and aging is an important risk factor for neurodegenerative disease and postoperative cognitive dysfunction. To characterize age-related changes in psychomotor performance, we assessed sensorimotor activity, spatial learning, and memory in C57BL/6 mice using the Rotarod, foot fault, and Barnes Maze tests. Old mice exhibit significant deficits in locomotor activity and spatial memory relative to young mice, but improve with training. These tests will be useful to assess outcome in neurodegenerative disease and postoperative cognitive dysfunction models carried out in aged mice.

    View details for DOI 10.1097/ANA.0b013e3181d56c98

    View details for Web of Science ID 000278709200006

    View details for PubMedID 20479674

  • Enhanced expression of mitochondrial superoxide dismutase leads to prolonged in vivo cell cycle progression and up-regulation of mitochondrial thioredoxin FREE RADICAL BIOLOGY AND MEDICINE Kim, A., Joseph, S., Khan, A., Epstein, C. J., Sobel, R., Huang, T. 2010; 48 (11): 1501-1512

    Abstract

    Mn superoxide dismutase (MnSOD) is an important mitochondrial antioxidant enzyme, and elevated MnSOD levels have been shown to reduce tumor growth in part by suppressing cell proliferation. Studies with fibroblasts have shown that increased MnSOD expression prolongs cell cycle transition time in G1/S and favors entrance into the quiescent state. To determine if the same effect occurs during tissue regeneration in vivo, we used a transgenic mouse system with liver-specific MnSOD expression and a partial hepatectomy paradigm to induce synchronized in vivo cell proliferation during liver regeneration. We show in this experimental system that a 2.6-fold increase in MnSOD activity leads to delayed entry into S phase, as measured by reduction in bromodeoxyuridine (BrdU) incorporation and decreased expression of proliferative cell nuclear antigen (PCNA). Thus, compared to control mice with baseline MnSOD levels, transgenic mice with increased MnSOD expression in the liver have 23% fewer BrdU-positive cells and a marked attenuation of PCNA expression. The increase in MnSOD activity also leads to an increase in the mitochondrial form of thioredoxin (thioredoxin 2), but not in several other peroxidases examined, suggesting the importance of thioredoxin 2 in maintaining redox balance in mitochondria with elevated levels of MnSOD.

    View details for DOI 10.1016/j.freeradbiomed.2010.02.028

    View details for Web of Science ID 000277822400006

    View details for PubMedID 20188820

  • Radiation-induced reductions in neurogenesis are ameliorated in mice deficient in CuZnSOD or MnSOD FREE RADICAL BIOLOGY AND MEDICINE Fishman, K., Baure, J., Zou, Y., Huang, T., Andres-Mach, M., Rola, R., Suarez, T., Acharya, M., Limoli, C. L., Lamborn, K. R., Fike, J. R. 2009; 47 (10): 1459-1467

    Abstract

    Ionizing irradiation significantly affects hippocampal neurogenesis and is associated with cognitive impairments; these effects may be influenced by an altered microenvironment. Oxidative stress is a factor that has been shown to affect neurogenesis, and one of the protective pathways that deal with such stress involves the antioxidant enzyme superoxide dismutase (SOD). This study addressed what impact a deficiency in cytoplasmic (SOD1) or mitochondrial (SOD2) SOD has on radiation effects on hippocampal neurogenesis. Wild-type (WT) and SOD1 and SOD2 knockout (KO) mice received a single X-ray dose of 5 Gy, and quantification of the survival and phenotypic fate of newly generated cells in the dentate subgranular zone was performed 2 months later. Radiation exposure reduced neurogenesis in WT mice but had no apparent effect in KO mice, although baseline levels of neurogenesis were reduced in both SOD KO strains before irradiation. Additionally, there were marked and significant differences between WT and both KO strains in how irradiation affected newly generated astrocytes and activated microglia. The mechanism(s) responsible for these effects is not yet known, but a pilot in vitro study suggests a "protective" effect of elevated levels of superoxide. Overall, these data suggest that under conditions of SOD deficiency, there is a common pathway dictating how neurogenesis is affected by ionizing irradiation.

    View details for DOI 10.1016/j.freeradbiomed.2009.08.016

    View details for Web of Science ID 000271934400017

    View details for PubMedID 19703553

  • A New Mouse Model for Temporal- and Tissue-Specific Control of Extracellular Superoxide Dismutase GENESIS Zou, Y., Chen, C., Fike, J. R., Huang, T. 2009; 47 (3): 142-154

    Abstract

    The extracellular isoform of superoxide dismutase (EC-SOD, Sod3) plays a protective role against various diseases and injuries mediated by oxidative stress. To investigate the pathophysiological roles of EC-SOD, we generated tetracycline-inducible Sod3 transgenic mice and directed the tissue-specific expression of transgenes by crossing Sod3 transgenic mice with tissue-specific transactivator transgenics. Double transgenic mice with liver-specific expression of Sod3 showed increased EC-SOD levels predominantly in the plasma as the circulating form, whereas double transgenic mice with neuronal-specific expression expressed higher levels of EC-SOD in hippocampus and cortex with intact EC-SOD as the dominant form. EC-SOD protein levels also correlated well with increased SOD activities in double transgenic mice. In addition to enabling tissue-specific expression, the transgene expression can be quickly turned on and off by doxycycline supplementation in the mouse chow. This mouse model, thus, provides the flexibility for on-off control of transgene expression in multiple target tissues.

    View details for DOI 10.1002/dvg.20470

    View details for Web of Science ID 000264655500002

    View details for PubMedID 19165829

  • Identification of biomarkers associated with the development of hepatocellular carcinoma in CuZn superoxide dismutase deficient mice PROTEOMICS Elchuri, S., Naeemuddin, M., Sharpe, O., Robinson, W. H., Huang, T. 2007; 7 (12): 2121-2129

    Abstract

    To identify biomarkers associated with the development of hepatocellular carcinoma (HCC) in CuZn superoxide dismutase (CuZnSOD, Sod1) deficient mice, 2-DE followed by MS analysis was carried out with liver samples obtained from 18-month-old Sod1-/- and +/+ mice. The intracellular Ca binding protein, regucalcin (RGN), showed a divergent alteration in Sod1-/- samples. Whereas elevated RGN levels were observed in -/- samples with no obvious neoplastic changes, marked reduction in RGN was observed in -/- samples with fully developed HCC. GST mu1 (GSTM1), on the other hand, showed a significant increase only in the neoplastic regions obtained from Sod1-/- livers. No change in GSTM1 was observed in the surrounding normal tissues. Marked reduction was observed in two intracellular lipid transporters, fatty acid binding protein 1 (FABP1) and major urinary protein 11 and 8 (MUP 11&8), in Sod1-/- samples. Analysis of additional samples at 18-22 months of age showed a three-fold increase in enolase activities in Sod1-/- livers. Consistent with previous findings, carbonic anhydrase 3 (CAIII) levels were significantly reduced in Sod1-/- samples, and immunohistochemical analysis revealed that the reduction was not homogenous throughout the lobular structure in the liver.

    View details for DOI 10.1002/pmic.200601011

    View details for Web of Science ID 000247642100016

    View details for PubMedID 17514684

  • Lack of extracellular superoxide dismutase (EC-SOD) in the microenvironment impacts radiation-induced changes in neurogenesis FREE RADICAL BIOLOGY AND MEDICINE Rola, R., Zou, Y., Huang, T., Fishman, K., Baure, J., Rosi, S., Milliken, H., Limoli, C. L., Fike, J. R. 2007; 42 (8): 1133-1145

    Abstract

    Ionizing irradiation results in significant alterations in hippocampal neurogenesis that are associated with cognitive impairments. Such effects are influenced, in part, by alterations in the microenvironment within which the neurogenic cells exist. One important factor that may affect neurogenesis is oxidative stress, and this study was done to determine if and how the extracellular isoform of superoxide dismutase (SOD3, EC-SOD) mediated radiation-induced alterations in neurogenic cells. Wild-type (WT) and EC-SOD knockout (KO) mice were irradiated with 5 Gy and acute (8-48 h) cellular changes and long-term changes in neurogenesis were quantified. Acute radiation responses were not different between genotypes, suggesting that the absence of EC-SOD did not influence mechanisms responsible for acute cell death after irradiation. On the other hand, the extent of neurogenesis was decreased by 39% in nonirradiated KO mice relative to WT controls. In contrast, while neurogenesis was decreased by nearly 85% in WT mice after irradiation, virtually no reduction in neurogenesis was observed in KO mice. These findings show that after irradiation, an environment lacking EC-SOD is much more permissive in the context of hippocampal neurogenesis. This finding may have a major impact in developing strategies to reduce cognitive impairment after cranial irradiation.

    View details for DOI 10.1016/j.freeradbiomed.2007.01.020

    View details for Web of Science ID 000245514000002

    View details for PubMedID 17382195

  • Genetic modifiers of the phenotype of mice deficient in mitochondrial superoxide dismutase HUMAN MOLECULAR GENETICS Huang, T. T., Naeemuddin, M., Elchuri, S., Yamaguchi, M., Kozy, H. M., Carlson, E. J., Epstein, C. J. 2006; 15 (7): 1187-1194

    Abstract

    Sod2-/- mice, which are deficient in the mitochondrial form of superoxide dismutase (MnSOD), have a short survival time that is strongly affected by genetic background. This suggests the existence of genetic modifiers that are capable of modulating the degree of mitochondrial oxidative damage caused by the MnSOD deficiency, thereby altering longevity. To identify these modifier(s), we generated recombinant congenic mice with quantitative trait loci (QTL) containing the putative genetic modifiers on the short-lived C57BL/6J genetic background. MnSOD deficient C57BL/6J mice with a QTL from the distal region of chromosome 13 from DBA/2J were able to survive for as long as those generated on the long-lived DBA/2J background. Within this region, the gene encoding nicotinamide nucleotide transhydrogenase (Nnt) was found to be defective in C57BL/6J mice, and no mature NNT protein could be detected. The forward reaction of NNT, a nuclear-encoded mitochondrial inner membrane protein, couples the generation of NADPH to proton transport and provides NADPH for the regeneration of two important antioxidant compounds, glutathione and thioredoxin, in the mitochondria. This action of NNT could explain its putative protective role in MnSOD-deficient mice.

    View details for DOI 10.1093/hmg/ddl034

    View details for Web of Science ID 000236105800014

    View details for PubMedID 16497723

  • Selective neuronal vulnerability and inadequate stress response in superoxide dismutase mutant mice FREE RADICAL BIOLOGY AND MEDICINE Lynn, S., Huang, E. J., Elchuri, S., Naeemuddin, M., Nishinaka, Y., Yodoi, J., Ferriero, D. M., Epstein, C. J., Huang, T. T. 2005; 38 (6): 817-828

    Abstract

    To understand the role of oxidative stress and mitochondrial defects in the development of neurodegeneration, we examined the age-related pathological changes and corresponding gene expression profiles in homozygous mutant mice deficient in the mitochondrial form of superoxide dismutase (MnSOD, SOD2). These Sod2-/- mice, generated on a B6D2F1 background, developed ataxia at Postnatal Day (P) 11 and progressively deteriorated with frequent seizures by P14. Histopathological examination revealed neurodegenerative changes consistent with the neurological signs. Vacuolar degeneration was observed in neurons and neuropil throughout the brainstem and rostral cortex. The motor trigeminal nucleus in brainstem and the deeper layers of the motor cortex were the earliest regions to degenerate, with the thalamus and hippocampus affected at later stages. Oligonucleotide microarrays were used to compare gene expression profiles in the brainstem and thalamus of Sod2+/+ and -/- mice from birth to P18. Notably, a large set of heat-shock protein genes was transcriptionally down regulated, and this was most likely due to a reduction in the heat-shock transcription factor 1 (HSF1). Other major classes of differentially expressed genes include lipid biosynthesis and ROS metabolism.

    View details for DOI 10.1016/j.freeradbiomed.2004.12.020

    View details for Web of Science ID 000227502500014

    View details for PubMedID 15721992

  • CuZnSOD deficiency leads to persistent and widespread oxidative damage and hepatocarcinogenesis later in life ONCOGENE Elchuri, S., Oberley, T. D., Qi, W. B., Eisenstein, R. S., Roberts, L. J., Van Remmen, H., Jepstein, C. J., Huang, T. T. 2005; 24 (3): 367-380

    Abstract

    Mice deficient in CuZn superoxide dismutase (CuZnSOD) showed no overt abnormalities during development and early adulthood, but had a reduced lifespan and increased incidence of neoplastic changes in the liver. Greater than 70% of Sod1-/- mice developed liver nodules that were either nodular hyperplasia or hepatocellular carcinoma (HCC). Cross-sectional studies with livers collected from Sod1-/- and age-matched +/+ controls revealed extensive oxidative damage in the cytoplasm and, to a lesser extent, in the nucleus and mitochondria from as early as 3 months of age. A marked reduction in cytosolic aconitase, increased levels of 8-oxo dG and F2-isoprostanes, and a moderate reduction in glutathione peroxidase activities and porin levels were observed in all age groups of Sod1-/- mice examined. There were also age-related reductions in Mn superoxide dismutase activities and carbonic anhydrase III. Parallel to the biochemical changes, there were progressive increases in the DNA repair enzyme APEX1, the cell cycle control proteins cyclin D1 and D3, and the hepatocyte growth factor receptor Met. Increased cell proliferation in the presence of persistent oxidative damage to macromolecules likely contributes to hepatocarcinogenesis later in life.

    View details for DOI 10.1038/sj.onc.1208207

    View details for Web of Science ID 000226279700008

    View details for PubMedID 15531919

  • Life-long reduction in MnSOD activity results in increased DNA damage and higher incidence of cancer but does not accelerate aging PHYSIOLOGICAL GENOMICS Van Remmen, H., IKENO, Y., Hamilton, M., Pahlavani, M., Wolf, N., Thorpe, S. R., Alderson, N. L., Baynes, J. W., Epstein, C. J., Huang, T. T., Nelson, J., Strong, R., Richardson, A. 2003; 16 (1): 29-37

    Abstract

    Mice heterozygous for the Sod2 gene (Sod2+/- mice) have been used to study the phenotype of life-long reduced Mn-superoxide dismutase (MnSOD) activity. The Sod2+/- mice have reduced MnSOD activity (50%) in all tissues throughout life. The Sod2+/- mice have increased oxidative damage as demonstrated by significantly elevated levels of 8-oxo-2-deoxyguanosine (8oxodG) in nuclear DNA in all tissues of Sod2+/- mice studied. The levels of 8oxodG in nuclear DNA increased with age in all tissues of Sod2+/- and wild-type (WT) mice, and at 26 mo of age, the levels of 8oxodG in nuclear DNA were significantly higher (from 15% in heart to over 60% in liver) in the Sod2+/- mice compared with WT mice. The level of 8oxodG was also higher in mitochondrial DNA isolated from liver and brain in Sod2+/- mice compared with WT mice. The increased oxidative damage to DNA in the Sod2+/- mice is associated with a 100% increase in tumor incidence (the number of mice with tumors) in old Sod2+/- mice compared with the old WT mice. However, the life spans (mean and maximum survival) of the Sod2+/- and WT mice were identical. In addition, biomarkers of aging, such as cataract formation, immune response, and formation of glycoxidation products carboxymethyl lysine and pentosidine in skin collagen changed with age to the same extent in both WT and Sod2+/- mice. Thus life-long reduction of MnSOD activity leads to increased levels of oxidative damage to DNA and increased cancer incidence but does not appear to affect aging.

    View details for DOI 10.1152/physiolgenomics.00122.2003

    View details for Web of Science ID 000187327300005

    View details for PubMedID 14679299

  • Forkhead transcription factor FOXO3a protects quiescent cells from oxidative stress NATURE Kops, G. J., Dansen, T. B., Polderman, P. E., Saarloos, I., Wirtz, K. W., Coffer, P. J., Huang, T. T., Bos, J. L., Medema, R. H., Burgering, B. M. 2002; 419 (6904): 316-321

    Abstract

    Reactive oxygen species are required for cell proliferation but can also induce apoptosis. In proliferating cells this paradox is solved by the activation of protein kinase B (PKB; also known as c-Akt), which protects cells from apoptosis. By contrast, it is unknown how quiescent cells that lack PKB activity are protected against cell death induced by reactive oxygen species. Here we show that the PKB-regulated Forkhead transcription factor FOXO3a (also known as FKHR-L1) protects quiescent cells from oxidative stress by directly increasing their quantities of manganese superoxide dismutase (MnSOD) messenger RNA and protein. This increase in protection from reactive oxygen species antagonizes apoptosis caused by glucose deprivation. In quiescent cells that lack the protective mechanism of PKB-mediated signalling, an alternative mechanism is induced as a consequence of PKB inactivity. This mechanism entails the activation of Forkhead transcription factors, the transcriptional activation of MnSOD and the subsequent reduction of reactive oxygen species. Increased resistance to oxidative stress is associated with longevity. The model of Forkhead involvement in regulating longevity stems from genetic analysis in Caenorhabditis elegans, and we conclude that this model also extends to mammalian systems.

    View details for Web of Science ID 000178056300050

    View details for PubMedID 12239572

  • Increased sensitivity of homozygous SOD2 mutant mice to oxygen toxicity FREE RADICAL BIOLOGY AND MEDICINE Asikainen, T. M., Huang, T. T., Taskinen, E., Levonen, A. L., Carlson, E., Lapatto, R., Epstein, C. J., Raivio, K. O. 2002; 32 (2): 175-186

    Abstract

    Induction or overexpression of pulmonary manganese superoxide dismutase (MnSOD) has been shown to protect against oxygen (O2) toxicity. Genetic inactivation of MnSOD (Sod2) results in multiple organ failure and early neonatal death. However, lungs or O2-tolerance of Sod2 knockout mice have not been investigated. We evaluated survival, lung histopathology, and other pulmonary antioxidants (glutathione cycle) of homozygous (-/-) and heterozygous (+/-) Sod2 mutant mice compared with wild-type controls (Sod2+/+) following 48 h exposure to either room air or to O2. The ability of antioxidant N-acetylcysteine to compensate for the loss of MnSOD was explored. Mortality of Sod2-/- mice increased from 0% in room air to 18 and 83% in 50 and 80% O2, respectively. N-acetylcysteine did not alter mortality of Sod2-/- mice. Histopathological analysis revealed abnormalities in saccules of Sod2-/- mice exposed either to room air or to 50% O2 suggestive of delayed postnatal lung development. In 50% O2, activities of glutamate-cysteine ligase (GCL) (previously known as gamma-glutamylcysteine synthetase, gamma-GCS) and glutathione peroxidase increased in Sod2-/- (35 and 70%, respectively) and Sod2+/- (12 and 70%, respectively) mice, but glutathione levels remained unaltered. We conclude that MnSOD is required for normal O2 tolerance and that in the absence of MnSOD there is a compensatory increase in pulmonary glutathione-dependent antioxidant defense in hyperoxia.

    View details for Web of Science ID 000173416100010

    View details for PubMedID 11796207

  • Transgenic and mutant mice for oxygen free radical studies SUPEROXIDE DISMUTASE Huang, T. T., Raineri, I., Eggerding, F., Epstein, C. J. 2002; 349: 191-213

    View details for Web of Science ID 000174887000020

    View details for PubMedID 11912909

  • Regional vulnerability after traumatic brain injury: Gender differences in mice that overexpress human copper, zinc superoxide dismutase EXPERIMENTAL NEUROLOGY Igarashi, T., Huang, T. T., Noble, L. J. 2001; 172 (2): 332-341

    Abstract

    Neuronal loss was quantified in both cortical and subcortical brain regions after traumatic brain injury in male and female nontransgenic (nTg) and transgenic (Tg) mice that overexpress human copper, zinc superoxide dismutase. Mice were euthanized at 7 days after a controlled cortical impact injury. Sections of brain were processed for immunolocalization of NeuN, a neuronal nuclear antigen, and the complement type 3 receptor, a marker of microglia/macrophages, and stained for iron. Cortical lesion volume and neuronal loss in the medial and/or lateral ventroposterior thalamic nuclei were significantly less in the nTg female compared to the nTg male (P = 0.0373 and P = 0.0023, respectively). In contrast, in CA3 of the hippocampus and laterodorsal thalamic nucleus (LD), there were no gender differences in neuronal loss between these nTg groups. Cortical lesion volume was significantly reduced in Tg males compared to nTg males (P = 0.0137) and was unchanged in the Tg females compared to the nTg females. Neuronal loss was attenuated in the CA3 and LD in the Tg females compared to the nTg females (P = 0.0252 and P = 0.0244, respectively). A similar protection was not observed in the Tg males. Microglial activation paralleled the pattern of neuronal loss and was most consistently aligned with iron deposition in the cortex and hippocampus. No overt differences were found in the pattern of microglial activation or iron staining between nTg and Tg mice nor between genders. Our findings demonstrate that neuroprotection, afforded by overexpression of copper, zinc superoxide dismutase, exhibits both regional and gender specificity.

    View details for DOI 10.1006/exnr.2001.7820

    View details for Web of Science ID 000173218600008

    View details for PubMedID 11716557

  • Genetic modification of prenatal lethality and dilated cardiomyopathy in Mn superoxide dismutase mutant mice FREE RADICAL BIOLOGY AND MEDICINE Huang, T. T., Carlson, E. J., Kozy, H. M., Mantha, S., Goodman, S. I., Ursell, P. C., Epstein, C. J. 2001; 31 (9): 1101-1110

    Abstract

    Mn superoxide dismutase (MnSOD), a mitochondrial antioxidant enzyme, has been shown to be essential for animal survival. MnSOD mutant mice (Sod2-/- mice) on the CD1 background develop severe dilated cardiomyopathy and usually die within 10 d after birth. To characterize better the phenotype and understand the mechanism of superoxide-mediated tissue damage in Sod2-/- mice, congenic Sod2-/- mice on inbred backgrounds were generated to ensure genetic homogeneity. When generated on a C57BL/6J background (B6), more than half of the fetuses develop severe dilated cardiomyopathy by embryonic day 15 and die in the uterus. Those that survive to term usually die within 24 h. In contrast, Sod2-/- mice on DBA/2J (D2) and B6D2F1 (B6D2F1) backgrounds develop normally throughout gestation and do not develop dilated cardiomyopathy. However, the D2 mice do develop a severe metabolic acidosis and survive for only up to 12 d after birth. B6D2F1) mice have a milder form of metabolic acidosis and can survive for up to 3 weeks. The marked difference in lifespans and the development of dilated cardiomyopathy in the B6 but not the D2 or B6D2F1 backgrounds indicate the possible existence of genetic modifiers that provide protection to the developing hearts in the absence of MnSOD.

    View details for Web of Science ID 000171962400009

    View details for PubMedID 11677043

  • Ubiquitous overexpression of CuZn superoxide dismutase does not extend life span in mice JOURNALS OF GERONTOLOGY SERIES A-BIOLOGICAL SCIENCES AND MEDICAL SCIENCES Huang, T. T., Carlson, E. J., Gillespie, A. M., Shi, Y. P., Epstein, C. J. 2000; 55 (1): B5-B9

    Abstract

    Oxidative damage has been implicated in the aging process and in a number of degenerative diseases. To investigate the role of oxygen radicals in the aging process in mammals, the life spans of transgenic mice on a CD-1 background expressing increased levels of CuZn superoxide dismutase (CuZnSOD), the enzyme that metabolizes superoxide radicals, were determined. Homozygous transgenic mice with a two- to five-fold elevation of CuZnSOD in various tissues showed a slight reduction of life span, whereas hemizygous mice with a 15- to 3-fold increase of CuZnSOD showed no difference in life span from that of the nontransgenic littermate controls. The results suggest that constitutive and ubiquitous overexpression of CuZnSOD alone is not sufficient to extend the life spans of transgenic mice.

    View details for Web of Science ID 000088044100001

    View details for PubMedID 10719757

  • Ts1Cje, a partial trisomy 16 mouse model for Down syndrome, exhibits learning and behavioral abnormalities PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Sago, H., Carlson, E. J., SMITH, D. J., Kilbridge, J., Rubin, E. M., Mobley, W. C., Epstein, C. J., Huang, T. T. 1998; 95 (11): 6256-6261

    Abstract

    A mouse model for Down syndrome, Ts1Cje, has been developed. This model has made possible a step in the genetic dissection of the learning, behavioral, and neurological abnormalities associated with segmental trisomy for the region of mouse chromosome 16 homologous with the so-called "Down syndrome region" of human chromosome segment 21q22. Tests of learning in the Morris water maze and assessment of spontaneous locomotor activity reveal distinct learning and behavioral abnormalities, some of which are indicative of hippocampal dysfunction. The triplicated region in Ts1Cje, from Sod1 to Mx1, is smaller than that in Ts65Dn, another segmental trisomy 16 mouse, and the learning deficits in Ts1Cje are less severe than those in Ts65Dn. In addition, degeneration of basal forebrain cholinergic neurons, which was observed in Ts65Dn, was absent in Ts1Cje.

    View details for Web of Science ID 000073852600073

    View details for PubMedID 9600952

  • DILATED CARDIOMYOPATHY AND NEONATAL LETHALITY IN MUTANT MICE LACKING MANGANESE SUPEROXIDE-DISMUTASE NATURE GENETICS Li, Y. B., Huang, T. T., Carlson, E. J., Melov, S., Ursell, P. C., Olson, T. L., Noble, L. J., YOSHIMURA, M. P., Berger, C., Chan, P. H., Wallace, D. C., Epstein, C. J. 1995; 11 (4): 376-381

    Abstract

    The Sod2 gene for Mn-superoxide dismutase (MnSOD), an intramitochondrial free radical scavenging enzyme that is the first line of defense against superoxide produced as a byproduct of oxidative phosphorylation, was inactivated by homologous recombination. Homozygous mutant mice die within the first 10 days of life with a dilated cardiomyopathy, accumulation of lipid in liver and skeletal muscle, and metabolic acidosis. Cytochemical analysis revealed a severe reduction in succinate dehydrogenase (complex II) and aconitase (a TCA cycle enzyme) activities in the heart and, to a lesser extent, in other organs. These findings indicate that MnSOD is required for normal biological function of tissues by maintaining the integrity of mitochondrial enzymes susceptible to direct inactivation by superoxide.

    View details for Web of Science ID A1995TH62900013

    View details for PubMedID 7493016

Conference Proceedings


  • The use of transgenic and mutant mice to study oxygen free radical metabolism Huang, T. T., Carlson, E. J., Raineri, M., Gillespie, A. M., Kozy, H., Epstein, C. J. NEW YORK ACAD SCIENCES. 1999: 95-112

    Abstract

    To distinguish the role of Mn superoxide dismutase (MnSOD) from that of cytoplasmic CuZn superoxide dismutase (CuZnSOD), the mouse MnSOD gene (Sod2) was inactivated by homologous recombination. Sod2 -/- mice on a CD1 (outbred) genetic background die within the first 10 days of life (mean, 5.4 days) with a complex phenotype that includes dilated cardiomyopathy, accumulation of lipid in liver and skeletal muscle, metabolic acidosis and ketosis, and a severe reduction in succinate dehydrogenase (complex II) and aconitase (a TCA cycle enzyme) activities in the heart and, to a lesser extent, in other organs. These findings indicate that MnSOD is required to maintain the integrity of mitochondrial enzymes susceptible to direct inactivation by superoxide. On the other hand, Lebovitz et al. reported an independently derived MnSod null mouse (Sod2tmlLeb) on a mixed C57BL/6 and 129Sv background with a different phenotype. Because a difference in genetic background is the most likely explanation for the phenotypic differences, the two mutant lines were crossed into different genetic backgrounds for further analyses. To study the phenotype of Sod2tmlLeb mice CD1 background, the Sod2tmlLeb mice were crossed to CD1 for two generations before the -/+ mice were intercrossed to generate -/- mice. The life span distribution of CD1 < Sod2-/- > Leb was shifted to the left, indicating a shortened life span on the CD1 background. Furthermore, the CD1 < Sod2-/- > Leb mice develop metabolic acidosis at an early stage as was observed with CD1 < Sod2-/- > Cje. When Sod2tmlCje was placed on C57BL/6J (B6) background, the -/- mice were found to die either during midgestation or within the first 4 days after birth. However, when the B6 < Sod2 -/+ > Cje were crossed with DBA/2J (D2) for the generation of B6D2F2 < Sod2-/- > Cje mice, an entirely different phenotype, similar to that described by Lebovitz et al., was observed. The F2 Sod -/- mice were able to survive up to 18 days, and the animals that lived for more than 15 days displayed neurological abnormalities including ataxia and seizures. Their hearts were not as severely affected as were those of the CD1 mice, and neurological degeneration rather than heart defect appears to be the cause of death.

    View details for Web of Science ID 000085330600009

    View details for PubMedID 10672232

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