Huang Lab Publications

Associate Professor (Research) of Neurology (Adult Neurology)

Publications

  • Reduced Hippocampal Neuronal Activity and Impaired Cognitive Function in a Mouse Model of Chronic Kidney Disease. FASEB journal : official publication of the Federation of American Societies for Experimental Biology Suzaki, A., Sul, J., Day, H., Goba, L., Huang, T. 2022; 36 Suppl 1

    Abstract

    Chronic kidney disease (CKD) is characterized by a progressive loss of renal function that leads to an accumulation of uremic toxins in the circulation, despite regular dialysis. In CKD, uremic toxins can cross the blood-brain barrier and cause neuroinflammation. Consequently, patients with CKD experience various symptoms, including fatigue and impaired cognitive function. A significant barrier to investigation of uremic toxicity and its impact on cognitive function has been the difficulty of performing studies in humans, due in part to the lack of access to relevant tissues. To examine the pathogenic mechanism of uremic toxicity in the development of cognitive impairments, a partial nephrectomy (PNx) mouse model was used as the experimental system. Sham and PNx mice were maintained for 12-14 weeks after 5/6 nephrectomy and then assessed for motor function, cognitive function, and neuronal activity. Kidney function, as measured by glomerular filtration rate, was reduced by 40% in PNx mice, which corresponded to a 65% reduction in kidney mass. Blood urea nitrogen levels were 2.3 times higher in PNx mice, but no significant changes in plasma creatinine levels were observed. Despite reduced kidney function, PNx mice performed at the same level as sham controls in ambulatory activity, working spatial memory, and object recognition. There was also no evidence of increased anxiety. However, in the Puzzle Box paradigm, in which mice were tested for problem solving skills over multiple days with increasingly difficult tasks, PNx mice on average took three times longer to overcome the obstacle in the final two tasks. Ex vivo examination of neuronal activity following exposure to a novel environment revealed a 30% reduction in c-Fos positive neurons in the hippocampal dentate gyrus in PNx mice. Similarly, the population of fast-spiking parvalbumin positive interneurons, which are essential for coordinating neuronal activities, were also reduced in PNx mice. Collectively, the data support a correlation between reduced neuronal activity and impaired cognitive performance in PNx mice. These impairments are likely a consequence of exposure to elevated levels of uremic toxins in the brain due to reduced kidney function.

    View details for DOI 10.1096/fasebj.2022.36.S1.R4204

    View details for PubMedID 35555038

  • Exposure to Gulf War Illness-related agents leads to the development of chronic pain and fatigue. Life sciences Nguyen, H., Sahbaie, P., Goba, L., Sul, J., Suzaki, A., Clark, J. D., Huang, T. 2021: 119867

    Abstract

    AIMS: A substantial contingent of veterans from the first Gulf War continues to suffer from a number of Gulf War-related illnesses (GWI) affecting the neurological and musculoskeletal systems; the most common symptoms include chronic pain and fatigue. Although animal models have recapitulated several aspects of cognitive impairments in GWI, the pain and fatigue symptoms have not been well documented to allow examination of potential pathogenic mechanisms.MAIN METHODS: We used a mouse model of GWI by exposing mice repeatedly to a combination of Gulf War chemicals (pyridostigmine bromide, permethrin, DEET, and chlorpyrifos) and mild immobilization stress, followed by investigating their pain susceptibilities and fatigue symptoms. To assess whether enhanced antioxidant capacity can counter the effects of GW agents, transgenic mice overexpressing extracellular superoxide dismutase (SOD3OE) were also examined.KEY FINDINGS: The mouse model recapitulated several aspects of the human illness, including hyperalgesia, impaired descending inhibition of pain, and increased tonic pain. There is a close association between chronic pain and fatigue in GWI patients. Consistent with this observation, the mouse model showed a significant reduction in physical endurance on the treadmill. Examination of skeletal muscles suggested reduction in mitochondrial functions may have contributed to the fatigue symptoms. Furthermore, the negative impacts of GW agents in pain susceptibilities were largely diminished in SOD3OE mice, suggesting that increased oxidative stress was associated with the emergence of these Gulf War symptoms.SIGNIFICANCE: the mouse model will be suitable for delineating specific defects in the pain pathways and mechanisms of fatigue in GWI.

    View details for DOI 10.1016/j.lfs.2021.119867

    View details for PubMedID 34358550

  • Fear Deficits in Hypomyelinated Tppp Knockout Mice. eNeuro Nguyen, H., Meservey, L. M., Ishiko-Silveria, N., Zhou, M., Huang, T., Fu, M. 2020

    Abstract

    Oligodendrocytes in the central nervous system (CNS) produce myelin sheaths that insulate axons to facilitate efficient electrical conduction. These myelin sheaths contain lamellar microtubules that enable vesicular transport into the inner sheath. Mechanistically, oligodendrocytes rely on Golgi outpost organelles and the associated protein tubulin polymerization promoting protein (TPPP) to nucleate or form new microtubules outside of the cell body. Consequently, elongation of lamellar microtubules is defective in Tppp knockout (KO) mice, which have thinner and shorter myelin sheaths. We now explore the behavioral phenotypes of Tppp KO mice using a number of different assays. In open-field assays, Tppp KO mice display similar activity levels and movement patterns as wildtype mice, indicating that they do not display anxiety behavior. However, Tppp KO mice lack fear responses by two types of assays, traditional fear-conditioning assays and looming fear assays, which test for innate fear responses. Deficits in fear-conditioning, which is a memory dependent task, as well as in spatial memory tests support possible short-term memory defects in Tppp KO mice. Together, our experiments indicate a connection between CNS myelination and behavioral deficits.SIGNIFICANCE STATEMENT Oligodendrocytes are cells in the brain that make myelin sheaths, which wrap concentrically around axons to provide insulation that facilitates electrical conduction. Fear responses have historically been attributed to neuronal activity. However, emerging literature indicates that mouse models with defective myelination display long-term fear deficits. Here, we look at a specific mouse model that lacks an oligodendrocyte-specific protein that is important for building the cellular structure of microtubules, which allow for transport to and along the myelin sheath. These mice display deficits in both memory-dependent fear as well as innate fear responses. Thus, our work indicates that myelin structure is important for fear response.

    View details for DOI 10.1523/ENEURO.0170-20.2020

    View details for PubMedID 32878961

  • Over-expression of miR-34c leads to early-life visceral fat accumulation and insulin resistance. Scientific reports Jones, P. H., Deng, B., Winkler, J., Zirnheld, A. L., Ehringer, S., Shetty, V., Cox, M., Nguyen, H., Shen, W., Huang, T., Wang, E. 2019; 9 (1): 13844

    Abstract

    Overweight children and adolescents are at high risk for adult and late life obesity. This report investigates some underlying mechanisms contributing to obesity during early life in an animal model. We generated a strain of transgenic mice, cU2, overexpressing human microRNA 34c, a microRNA functionally implicated in adipogenesis. Male and female cU2 mice exhibit significant weight gain, accompanied by marked increase in abdominal fat mass and metabolic abnormalities, including reduction of both glucose clearance rate and insulin sensitivity, as early as two months of age. Adipogenesis derailment at this early age is suggested by decreased expression of adiponectin, the fat mass and obesity-associated gene, and the adiponectin receptor R1, coupled with a reduction of the brown fat biomarker PAT2 and the adipogenesis inhibitor SIRT1. Notably, adiponectin is an important adipokine and an essential regulator of glucose and fatty acid homeostasis. cU2 mice may provide a crucial animal model for investigating the role of miR-34c in early onset insulin resistance and visceral fat mass increase, contributing to accelerated body weight gain and metabolic disorders. Intervention in this dysregulation may open a new preventive strategy to control early-life weight gain and abnormal insulin resistance, and thus prevalent adult and late life obesity.

    View details for DOI 10.1038/s41598-019-50191-3

    View details for PubMedID 31554925

  • CNS bioavailability and radiation protection of normal hippocampal neurogenesis by a lipophilic Mn porphyrin-based superoxide dismutase mimic, MnTnBuOE-2-PyP5 Redox Biology Leu, D., Spasojevic, I., Nguyen, H., Deng, B., Tovmasyan, A., Weitner, T., Sampaio, R. S., Batinic-Haberle, I., Huang, T. 2017; 12: 864-871
  • Cognitive impairments following cranial irradiation can be mitigated by treatment with a tropomyosin receptor kinase B agonist EXPERIMENTAL NEUROLOGY Yang, P., Leu, D., Ye, K., Srinivasan, C., Fike, J. R., Huang, T. 2016; 279: 178-186

    Abstract

    Brain radiotherapy is frequently used successfully to treat brain tumors. However, radiotherapy is often associated with declines in short-term and long-term memory, learning ability, and verbal fluency. We previously identified a downregulation of the brain-derived neurotrophic factor (BDNF) following cranial irradiation in experimental animals. In the present study, we investigated whether targeting the BDNF high affinity receptor, tropomysin receptor kinase B (TrkB), could mitigate radiation-induced cognitive deficits. After irradiation, chronic treatment with a small molecule TrkB agonist, 7,8-dihydroxyflavone (DHF) in mice led to enhanced activation of TrkB and its downstream targets ERK and AKT, both important factors in neuronal development. DHF treatment significantly restored spatial, contextual, and working memory, and the positive effects persisted for at least 3months after completion of the treatment. Consistent with preservation of cognitive functions, chronic DHF treatment mitigated radiation-induced suppression of hippocampal neurogenesis. Spine density and major components of the excitatory synapses, including glutamate receptors and postsynaptic density protein 95 (PSD-95), were also maintained at normal levels by DHF treatment after irradiation. Taken together, our results show that chronic treatment with DHF after irradiation significantly mitigates radiation-induced cognitive defects. This is achieved most likely by preservation of hippocampal neurogenesis and synaptic plasticity.

    View details for DOI 10.1016/j.expneurol.2016.02.021

    View details for PubMedID 26946222

  • 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

    View details for PubMedCentralID PMC3535634

  • SOD2 deficiency-induced oxidative stress attenuates steroidogenesis in mouse ovarian granulosa cells. Molecular and cellular endocrinology Zaidi, S. K., Shen, W. J., Cortez, Y. n., Bittner, S. n., Bittner, A. n., Arshad, S. n., Huang, T. T., Kraemer, F. B., Azhar, S. n. 2020: 110888

    Abstract

    This study investigated the effects of SOD2 (MnSOD)-deficiency-induced excessive oxidative stress on ovarian steroidogenesis in vivo and isolated and cultured granulosa cells using WT and Sod2 ± mice. Basal and 48 h eCG-stimulated plasma progesterone levels were decreased ∼50% in female Sod2 ± mice, whereas plasma progesterone levels were decreased ∼70% in Sod2 ± mice after sequential stimulation with eCG followed by hCG. Sod2 ± deficiency caused about 50% reduction in SOD2 activity in granulosa cells. SOD2-deficiency also caused a marked reduction in progestins and estradiol in isolated granulosa cells. qRT-PCR measurements indicated that the mRNA expression levels of StAR protein and steroidogenic enzymes are decreased in the ovaries of Sod2 ± mice. Further studies showed a defect in the movement of mobilized cytosolic cholesterol to mitochondria. The ovarian membrane from Sod2 ± mice showed higher susceptibility to lipid peroxidation. These data indicates that SOD2-deficiency induced oxidative stress inhibits ovarian granulosa cell steroidogenesis primarily by interfering with cholesterol transport to mitochondria and attenuating the expression of Star protein gene and key steroidogenic enzyme genes.

    View details for DOI 10.1016/j.mce.2020.110888

    View details for PubMedID 32717420

  • Accumulation of Uremic Solutes in the Cerebrospinal Fluid in Experimental Acute Renal Failure. American journal of physiology. Renal physiology Mair, R. D., Nguyen, H., Huang, T., Plummer, N. S., Sirich, T. L., Meyer, T. W. 2019

    Abstract

    The accumulation of uremic solutes in kidney failure may impair mental function. This study profiled the accumulation of uremic solutes in the cerebrospinal fluid (CSF) in acute renal failure. CSF and plasma ultrafiltrate were obtained from rats at 48 hours after sham operation (control, n=10) or bilateral nephrectomy (nephrectomy, n=10) and analyzed using an established metabolomic platform. 248 solutes were identified as uremic based on their accumulation in plasma ultrafiltrate of nephrectomized compared to control rats. CSF levels of 124 of these solutes were sufficient to allow calculation of CSF/plasma ultrafiltrate concentration ratios. Levels of many of the uremic solutes were normally lower in the CSF than in the plasma ultrafiltrate indicating exclusion of these solutes from the brain. CSF levels of the great majority of the uremic solutes increased in renal failure. The increase in the CSF was however relatively less than in the plasma ultrafiltrate for most solutes. In particular, for the 31 uremic solutes with CSF to plasma ultrafiltrate ratios less than 0.25 in control rats, the average CSF to plasma ultrafiltrate ratio decreased from 0.13 ± 0.07 in control rats to 0.09 ± 0.06 in nephrectomized rats revealing sustained ability to exclude these solutes from the brain. In summary, levels of many uremic solutes are normally kept lower in the CSF than in the plasma ultrafiltrate by the action of the blood-brain and blood-CSF barriers. These barriers remain functional but cannot prevent accumulation of uremic solutes in the CSF when the kidneys fail.

    View details for DOI 10.1152/ajprenal.00100.2019

    View details for PubMedID 31141401

  • The Golgi Outpost Protein TPPP Nucleates Microtubules and Is Critical for Myelination. Cell Fu, M. M., McAlear, T. S., Nguyen, H. n., Oses-Prieto, J. A., Valenzuela, A. n., Shi, R. D., Perrino, J. J., Huang, T. T., Burlingame, A. L., Bechstedt, S. n., Barres, B. A. 2019

    Abstract

    Oligodendrocytes extend elaborate microtubule arbors that contact up to 50 axon segments per cell, then spiral around myelin sheaths, penetrating from outer to inner layers. However, how they establish this complex cytoarchitecture is unclear. Here, we show that oligodendrocytes contain Golgi outposts, an organelle that can function as an acentrosomal microtubule-organizing center (MTOC). We identify a specific marker for Golgi outposts-TPPP (tubulin polymerization promoting protein)-that we use to purify this organelle and characterize its proteome. In in vitro cell-free assays, recombinant TPPP nucleates microtubules. Primary oligodendrocytes from Tppp knockout (KO) mice have aberrant microtubule branching, mixed microtubule polarity, and shorter myelin sheaths when cultured on 3-dimensional (3D) microfibers. Tppp KO mice exhibit hypomyelination with shorter, thinner myelin sheaths and motor coordination deficits. Together, our data demonstrate that microtubule nucleation outside the cell body at Golgi outposts by TPPP is critical for elongation of the myelin sheath.

    View details for DOI 10.1016/j.cell.2019.08.025

    View details for PubMedID 31522887

  • Oxidative Stress Contributes to Fracture/Cast-Induced Inflammation and Pain in a Rat Model of Complex Regional Pain Syndrome JOURNAL OF PAIN Guo, T., Wei, T., Huang, T., Kingery, W. S., Clark, J. 2018; 19 (10): 1147–56

    Abstract

    Clinical evidence suggests that vitamin C (Vit C) may protect against the development of complex regional pain syndrome (CRPS) after fracture or surgery. Tibia fracture followed by 4 weeks of cast immobilization (fracture/cast) in rats results in nociceptive, vascular, and bone changes resembling clinical CRPS. In this study, fracture/cast rats were treated with the oxidative stress inhibitors Vit C, N-acetyl cysteine, or 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl to examine their effects on CRPS-related nociceptive and vascular changes. Administration of these agents significantly reduced fracture/cast-induced cutaneous allodynia by 64 to 78%, muscle hyperalgesia by 34 to 40%, and hind limb unweighting by 48 to 89%. Treatments with Vit C and N-acetyl cysteine reduced the oxidative stress markers malondialdehyde in the skin, muscle, and sciatic nerve, and lactate in the gastrocnemius muscle of the fracture/cast limb. Furthermore, Vit C treatment inhibited the post-fracture upregulation of substance P and calcitonin gene-related peptide in the sciatic nerve and the increased expression of the pain-related inflammatory mediators, including interleukin (IL)-6, and nerve growth factor in the skin and IL-1β, and IL-6 in the muscle of the post-fracture/cast limb. These data suggest that oxidative stress may contribute to the nociceptive features of the rat CRPS model.Vit C reduced the CRPS-like signs, oxidative stress, and the upregulation of neuropeptide production and inflammatory mediators observed after tibia fracture and casting in rats. Limiting oxidative stress by use of Vit C or alternative strategies could reduce the risk of developing CRPS after surgery or other forms of trauma.

    View details for PubMedID 29715519

  • The hippocampal extracellular matrix regulates pain and memory after injury. Molecular psychiatry Tajerian, M., Hung, V., Nguyen, H., Lee, G., Joubert, L., Malkovskiy, A. V., Zou, B., Xie, S., Huang, T., Clark, J. D. 2018

    Abstract

    Chronic pain poses a heavy burden for the individual and society, comprising personal suffering, comorbid psychiatric symptoms, cognitive decline, and disability. Treatment options are poor due in large part to pain centralization, where an initial injury can result in lasting CNS maladaptations. Hippocampal cellular plasticity in chronic pain has become a focus of study due to its roles in cognition, memory, and the experience of pain itself. However, the extracellular alterations that parallel and facilitate changes in hippocampal function have not been addressed to date. Here we show structural and biochemical plasticity in the hippocampal extracellular matrix (ECM) that is linked to behavioral, cellular, and synaptic changes in a mouse model of chronic pain. Specifically, we report deficits in working location memory that are associated with decreased hippocampal dendritic complexity, altered ECM microarchitecture, decreased ECM rigidity, and changes in the levels of key ECM components and enzymes, including increased levels of MMP8. We also report aberrations in long-term potentiation (LTP) and a loss of inhibitory interneuron perineuronal ECM nets, potentially accounting for the aberrations in LTP. Finally, we demonstrate that MMP8 is upregulated after injury and that its genetic downregulation normalizes the behavioral, electrophysiological, and extracellular alterations. By linking specific extracellular changes to the chronic pain phenotype, we provide a novel mechanistic understanding of pain centralization that provides new targets for the treatment of chronic pain.

    View details for PubMedID 30254235

  • Nociceptive and Cognitive Changes in a Murine Model of Polytrauma. The journal of pain : official journal of the American Pain Society Sahbaie, P., Tajerian, M., Yang, P., Irvine, K. A., Huang, T., Luo, J., Wyss-Coray, T., Clark, J. D. 2018

    Abstract

    POLYTRAUMA COMMONLY INVOLVES CONCUSSION (MILD TRAUMATIC BRAIN INJURY: mTBI) and peripheral trauma including limb fractures. Interactions between mTBI and peripheral injuries are poorly understood, both leading to chronic pain and neurobehavioral impairments. To elucidate these interactions, a murine polytrauma model was developed. mTBI alone resulted in similar increased mechanical allodynia in males and females. Female fracture and polytrauma groups displayed greater increases in hindpaw tactile hypersensitivity for weeks after injury than respective male groups. Capsaicin evoked spontaneous pain behaviors were greater in fracture and polytrauma females compared to males. The mTBI and polytrauma males displayed significant deficits in spatial working memory. All fracture, mTBI or polytrauma groups had deficits in object recognition memory. Only male mTBI or polytrauma mice showed greater agitation and increased risk taking behavior in open field testing as well as zero maze tests. Additionally, impaired diffuse noxious inhibitory control was observed in all mTBI and polytrauma mice. The model presented offers clinically relevant features useful for studying persistent pain, cognitive and other behavioral changes after TBI including polytrauma. A better understanding of nervous system dysfunction after TBI and polytrauma might help prevent or reduce persistent pain and disability in these patients.PERSPECTIVE: The polytrauma model presented has relevant features of chronic pain and neurobehavioral impairments useful for studying mechanisms involved in their development. This model may have special value in understanding altered descending pain modulation after TBI and polytrauma.

    View details for PubMedID 29964216

  • MicroRNA-Mediated Therapy Modulating Blood-Brain Barrier Disruption Improves Vascular Cognitive Impairment. Arteriosclerosis, thrombosis, and vascular biology Toyama, K., Spin, J. M., Deng, A. C., Huang, T., Wei, K., Wagenhauser, M. U., Yoshino, T., Nguyen, H., Mulorz, J., Kundu, S., Raaz, U., Adam, M., Schellinger, I. N., Jagger, A., Tsao, P. S. 2018

    Abstract

    OBJECTIVE: There are currently no effective treatments for the prevention of dementia associated with vascular cognitive impairment. MicroRNAs regulate gene expression at the post-transcriptional level and play key roles in vascular disorders. TNFalpha (tumor necrosis factor-alpha) regulates blood-brain barrier breakdown through modification of cerebral tight junctions. Here, we sought key TNFalpha-responsive microRNAs that might influence blood-brain barrier breakdown via cerebral tight junction disruption in vascular cognitive impairment.APPROACH AND RESULTS: Using a mouse model of vascular cognitive impairment, chronic cerebral hypoperfusion within the white matter was induced with bilateral common carotid artery stenosis (BCAS) surgery. TNFalpha gene expression was increased in white matter post-BCAS surgery, and TNFalpha stimulation decreased claudin-5, ZO-1 (tight-junction protein 1), and occludin gene expression in murine brain endothelial cells. In silico analysis predicted 8 candidate microRNAs as regulators of claudin-5, ZO-1, and occludin gene expression. Of these, only miR-501-3p was upregulated by TNFalpha in vitro and was upregulated in the white matter after BCAS surgery. Further, miR-501-3p directly bound to the 3'-untranslated region of human ZO-1 and downregulated transendothelial electric resistance. In vivo administration of a locked nucleic acid -modified antisense oligonucleotide versus miR-501-3p suppressed BCAS-induced reduction of ZO-1 gene expression and blood-brain barrier disruption within the white matter and significantly ameliorated working memory deficits after BCAS surgery.CONCLUSIONS: We here provide the first evidence that the TNFalpha-miR-501-3p-ZO-1 axis plays an important role in the pathogenesis of cerebral hypoperfusion-induced working memory deficits and white matter lesions, as a result of blood-brain barrier breakdown via tight junction disruption. Therapeutic manipulation of miR-501-3p holds promise for limiting vascular cognitive impairment progression.

    View details for PubMedID 29650692

  • Radiation-Mediated Tumor Growth Inhibition Is Significantly Enhanced with Redox-Active Compounds That Cycle with Ascorbate ANTIOXIDANTS & REDOX SIGNALING Tovmasyan, A., Bueno-Janice, J. C., Jaramillo, M. C., Sampaio, R. S., Reboucas, J. S., Kyui, N., Benov, L., Deng, B., Huang, T., Tome, M. E., Spasojevic, I., Batinic-Haberle, I. 2018

    Abstract

    We aim here to demonstrate that radiation (RT) enhances tumor sensitization by only those Mn complexes that are redox active and cycle with ascorbate (Asc), thereby producing H2O2 and utilizing it subsequently in protein S-glutathionylation in a glutathione peroxidase (GPx)-like manner. In turn, such compounds affect cellular redox environment, described by glutathione disulfide (GSSG)/glutathione (GSH) ratio, and tumor growth. To achieve our goal, we tested several Mn complexes of different chemical and physical properties in cellular and animal flank models of 4T1 breast cancer cell. Four other cancer cell lines were used to substantiate key findings.Joint administration of cationic Mn porphyrin (MnP)-based redox active compounds, MnTE-2-PyP5+ or MnTnBuOE-2-PyP5+ with RT and Asc contributes to high H2O2 production in cancer cells and tumor, which along with high MnP accumulation in cancer cells and tumor induces the largest suppression of cell viability and tumor growth, while increasing GSSG/GSH ratio and levels of total S-glutathionylated proteins. Redox-inert MnP, MnTBAP3- and two other different types of redox-active Mn complexes (EUK-8 and M40403) were neither efficacious in the cellular nor in the animal model. Such outcome is in accordance with their inability to catalyze Asc oxidation and mimic GPx.We provided here the first evidence how structure-activity relationship between the catalytic potency and the redox properties of Mn complexes controls their ability to impact cellular redox environment and thus enhance the radiation and ascorbate-mediated tumor suppression.The interplay between the accumulation of cationic MnPs and their potency as catalysts for oxidation of Asc, protein cysteines, and GSH controls the magnitude of their anticancer therapeutic effects. Antioxid. Redox Signal. 00, 000-000.

    View details for PubMedID 29390861

  • SOD1 Lysine 123 Acetylation in the Adult Central Nervous System FRONTIERS IN CELLULAR NEUROSCIENCE Kaliszewski, M., Kennedy, A. K., Blaes, S. L., Shaffer, R. S., Knott, A. B., Song, W., Hauser, H. A., Bossy, B., Huang, T., Bossy-Wetzel, E. 2016; 10

    Abstract

    Superoxide dismutase 1 (SOD1) knockout (Sod1(-/-)) mice exhibit an accelerated aging phenotype. In humans, SOD1 mutations are linked to familial amyotrophic lateral sclerosis (ALS), and post-translational modification (PTM) of wild-type SOD1 has been associated with sporadic ALS. Reversible acetylation regulates many enzymes and proteomic studies have identified SOD1 acetylation at lysine 123 (K123). The function and distribution of K123-acetylated SOD1 (Ac-K123 SOD1) in the nervous system is unknown. Here, we generated polyclonal rabbit antibodies against Ac-K123 SOD1. Sod1 deletion in Sod1(-/-) mice, K123 mutation or preabsorption with Ac-K123 peptide all abolished antibody binding. Using immunohistochemistry, we assessed Ac-K123 SOD1 distribution in the normal adult mouse nervous system. In the cerebellum, Ac-K123 SOD1 staining was prominent in cell bodies of the granular cell layer (GCL) and Purkinje cell dendrites and interneurons of the molecular cell layer. In the hippocampus, Ac-K123 SOD1 staining was strong in the fimbria, subiculum, pyramidal cells and Schaffer collateral fibers of the cornus ammonis field 1 (CA1) region and granule and neuronal progenitor cells of the dentate gyrus. In addition, labeling was observed in the choroid plexus (CP) and the ependyma of the brain ventricles and central canal of the spinal cord. In the olfactory bulb, Ac-K123 SOD1 staining was prominent in axons of sensory neurons, in cell bodies of interneurons and neurites of the mitral and tufted cells. In the retina, labeling was strong in the retinal ganglion cell layer (RGCL) and axons of retinal ganglion cells (RGCs), the inner nuclear layer (INL) and cone photoreceptors of the outer nuclear layer (ONL). In summary, our findings describe Ac-K123 SOD1 distribution to distinct regions and cell types of the normal nervous system.

    View details for DOI 10.3389/fncel.2016.00287

    View details for Web of Science ID 000390161400001

    View details for PubMedID 28066183

    View details for PubMedCentralID PMC5167747

  • Differential Efficacy of Ketamine in the Acute versus Chronic Stages of Complex Regional Pain Syndrome in Mice ANESTHESIOLOGY Tajerian, M., Leu, D., Yang, P., Huang, T. T., Kingery, W. S., Clark, J. D. 2015; 123 (6): 1435-1447

    Abstract

    Complex regional pain syndrome (CRPS) is a painful, disabling, and often chronic condition, where many patients transition from an acute phase with prominent peripheral neurogenic inflammation to a chronic phase with evident central nervous system changes. Ketamine is a centrally acting agent believed to work through blockade of N-methyl-D- aspartate receptors and is being increasingly used for the treatment of refractory CRPS, although the basis for the drug's effects and efficacy at different stages of the syndrome remains unclear.The authors used a mouse model of CRPS (n = 8 to 12/group) involving tibia fracture/cast immobilization to test the efficacy of ketamine (2 mg kg day; 7 days) or vehicle infusion during acute (3 weeks after fracture) and chronic (7 weeks after fracture) stages.Acute-phase fracture mice displayed increased limb temperature, edema, and nociceptive sensitization that were not reduced by ketamine. Fracture mice treated with ketamine during the chronic phase showed reduced nociceptive sensitization that persisted beyond completion of the infusion. During this chronic phase, ketamine also reduced latent nociceptive sensitization and improved motor function at 18 weeks after fracture. No side effects of the infusions were identified. These behavioral changes were associated with altered spinal astrocyte activation and expression of pain-related proteins including N-methyl-D-aspartate receptor 2b, Ca/calmodulin-dependent protein kinase II, and brain-derived neurotrophic factor.Collectively, these results demonstrate that ketamine is efficacious in the chronic, but not acute, stage of CRPS, suggesting that the centrally acting drug is relatively ineffective in early CRPS when peripheral mechanisms are more critical for supporting nociceptive sensitization.

    View details for DOI 10.1097/ALN.0000000000000889

    View details for PubMedID 26492479

  • Sex differences in a Murine Model of Complex Regional Pain Syndrome NEUROBIOLOGY OF LEARNING AND MEMORY Tajerian, M., Sahbaie, P., Sun, Y., Leu, D., Yang, H. Y., Li, W., Huang, T. T., Kingery, W., Clark, J. D. 2015; 123: 100-109

    Abstract

    Complex Regional Pain Syndrome (CRPS) is a major cause of chronic pain after surgery or trauma to the limbs. Despite evidence showing that the prevalence and severity of many forms of chronic pain, including CRPS, differ between males and females, laboratory studies on sex-related differences in animal models of CRPS are not available, and the impact of sex on the transition from acute to chronic CRPS pain and disability are unexplored. Here we make use of a tibia fracture/cast mouse model that recapitulates the nociceptive, functional, vascular, trophic, inflammatory and immune aspects of CRPS. Our aim is to describe the chronic time course of nociceptive, motor and memory changes associated with fracture/cast in male and female mice, in addition to exploring their underlying spinal mechanisms. Our behavioral data shows that, compared to males, female mice display lower nociceptive thresholds following fracture in the absence of any differences in ongoing or spontaneous pain. Furthermore, female mice show exaggerated signs of motor dysfunction, deficits in fear memory, and latent sensitization that manifests long after the normalization of nociceptive thresholds. Our biochemical data show differences in the spinal cord levels of the glutamate receptor NR2b, suggesting sex differences in mechanisms of central sensitization that could account for differences in duration and severity of CRPS symptoms between the two groups.

    View details for DOI 10.1016/j.nlm.2015.06.004

    View details for Web of Science ID 000359510900013

    View details for PubMedID 26070658

    View details for PubMedCentralID PMC4530062

  • Oxidative stress and redox regulation on hippocampal-dependent cognitive functions ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS Huang, T., Leu, D., Zou, Y. 2015; 576: 2-7
  • Delayed Administration of Alpha-Difluoromethylornithine Prevents Hippocampus-Dependent Cognitive Impairment after Single and Combined Injury in Mice RADIATION RESEARCH Allen, A. R., Eilertson, K., Sharma, S., Baure, J., Allen, B., Leu, D., Rosi, S., Raber, J., Huang, T., Fike, J. R. 2014; 182 (5): 489-498

    View details for DOI 10.1667/RR13753.1

    View details for Web of Science ID 000345604200003

  • Brain Neuroplastic Changes Accompany Anxiety and Memory Deficits in a Model of Complex Regional Pain Syndrome ANESTHESIOLOGY Tajerian, M., Leu, D., Zou, Y., Sahbaie, P., Li, W., Khan, H., Hsu, V., Kingery, W., Huang, T. T., Becerra, L., Clark, J. D. 2014; 121 (4): 852-865

    Abstract

    Complex regional pain syndrome (CRPS) is a painful condition with approximately 50,000 annual new cases in the United States. It is a major cause of work-related disability, chronic pain after limb fractures, and persistent pain after extremity surgery. Additionally, CRPS patients often experience cognitive changes, anxiety, and depression. The supraspinal mechanisms linked to these CRPS-related comorbidities remain poorly understood.The authors used a previously characterized mouse model of tibia fracture/cast immobilization showing the principal stigmata of CRPS (n = 8 to 20 per group) observed in humans. The central hypothesis was that fracture/cast mice manifest changes in measures of thigmotaxis (indicative of anxiety) and working memory reflected in neuroplastic changes in amygdala, perirhinal cortex, and hippocampus.The authors demonstrate that nociceptive sensitization in these mice is accompanied by altered thigmotactic behaviors in the zero maze but not open field assay, and working memory dysfunction in novel object recognition and social memory but not in novel location recognition. Furthermore, the authors found evidence of structural changes and synaptic plasticity including changes in dendritic architecture and decreased levels of synaptophysin and brain-derived neurotrophic factor in specific brain regions.The study findings provide novel observations regarding behavioral changes and brain plasticity in a mouse model of CRPS. In addition to elucidating some of the supraspinal correlates of the syndrome, this work supports the potential use of therapeutic interventions that not only directly target sensory input and other peripheral mechanisms, but also attempt to ameliorate the broader pain experience by modifying its associated cognitive and emotional comorbidities.

    View details for Web of Science ID 000342741000020

  • Hepatitis C and Alcohol Exacerbate Liver Injury by Suppression of FOXO3 AMERICAN JOURNAL OF PATHOLOGY Tumurbaatar, B., Tikhanovich, I., Li, Z., Ren, J., Ralston, R., Kuravi, S., Campbell, R., Chaturvedi, G., Huang, T., Zhao, J., Hao, J., O'Neil, M., Weinman, S. A. 2013; 183 (6): 1803-1814

    Abstract

    Hepatitis C virus (HCV) infection exacerbates alcoholic liver injury by mechanisms that include enhanced oxidative stress. The forkhead box transcription factor FOXO3 is an important component of the antioxidant stress response that can be altered by HCV. To test whether FOXO3 is protective for alcoholic liver injury, we fed alcohol to FOXO3(-/-) mice. After 3 weeks, one third of these mice developed severe hepatic steatosis, neutrophilic infiltration, and >10-fold alanine aminotransferase (ALT) elevations. In cell culture, either alcohol or HCV infection alone increased FOXO3 transcriptional activity and expression of target genes, but the combination of HCV and alcohol together caused loss of nuclear FOXO3 and decreased its transcriptional activity. This was accompanied by increased phosphorylation of FOXO3. Mice expressing HCV structural proteins on a background of reduced expression of superoxide dismutase 2 (SOD2; Sod2(+/-)) also had increased liver sensitivity to alcohol, with elevated ALT, steatosis, and lobular inflammation. Elevated ALT was associated with an alcohol-induced decrease in SOD2 and redistribution of FOXO3 to the cytosol. These results demonstrate that FOXO3 functions as a protective factor preventing alcoholic liver injury. The combination of HCV and alcohol, but not either condition alone, inactivates FOXO3, causing a decrease in expression of its target genes and an increase in liver injury. Modulation of the FOXO3 pathway is a potential therapeutic approach for HCV-alcohol-induced liver injury.

    View details for DOI 10.1016/j.ajpath.2013.08.013

    View details for Web of Science ID 000327829000012

    View details for PubMedID 24225087

  • Effects of Altered Levels of Extracellular Superoxide Dismutase and Irradiation on Hippocampal Neurogenesis in Female Mice INTERNATIONAL JOURNAL OF RADIATION ONCOLOGY BIOLOGY PHYSICS Zou, Y., Leu, D., Chui, J., Fike, J. R., Huang, T. 2013; 87 (4): 777-784

    Abstract

    Altered levels of extracellular superoxide dismutase (EC-SOD) and cranial irradiation have been shown to affect hippocampal neurogenesis. However, previous studies were only conducted in male mice, and it was not clear if there was a difference between males and females. Therefore, female mice were studied and the results compared with those generated in male mice from an earlier study.Female wild-type, EC-SOD-null (KO), and EC-SOD bigenic mice with neuronal-specific expression of EC-SOD (OE) were subjected to a single dose of 5-Gy gamma rays to the head at 8 weeks of age. Progenitor cell proliferation, differentiation, and long-term survival of newborn neurons were determined.Similar to results from male mice, EC-SOD deficiency and irradiation both resulted in significant reductions in mature newborn neurons in female mice. EC-SOD deficiency reduced long-term survival of newborn neurons whereas irradiation reduced progenitor cell proliferation. Overexpression of EC-SOD corrected the negative impacts from EC-SOD deficiency and irradiation and normalized the production of newborn neurons in OE mice. Expression of neurotrophic factors brain-derived neurotrophic factor and neurotrophin-3 were significantly reduced by irradiation in wild-type mice, but the levels were not changed in KO and OE mice even though both cohorts started out with a lower baseline level.In terms of hippocampal neurogenesis, EC-SOD deficiency and irradiation have the same overall effects in males and females at the age the studies were conducted.

    View details for DOI 10.1016/j.ijrobp.2013.08.002

    View details for Web of Science ID 000325763300031

    View details for PubMedID 24064316

  • 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

    View details for PubMedCentralID PMC3493523

  • 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

    View details for PubMedCentralID PMC3410958

  • Redox balance- and radiation-mediated alteration in hippocampal neurogenesis FREE RADICAL RESEARCH Huang, T. 2012; 46 (8): 951-958

    Abstract

    Changes in the intracellular and extracellular redox balance have been correlated with cell fate decisions in terms of proliferation versus differentiation, entering versus existing cell cycle and survival versus cell death. Adult hippocampal neurogenesis has been correlated with neuronal plasticity of learning and memory; however, the process is exquisitely sensitive to changes in redox balance. Cranial irradiation is an effective modality in treating brain tumours but often leads to deficits in hippocampus-related learning and memory, which is most likely due to sustained elevation of oxygen free radical production and suppression of hippocampal neurogenesis. The subcellular redox environment affecting hippocampal neurogenesis is largely unknown. Using mutant mice deficient in each one of the three superoxide dismutase (SOD, EC 1.15.1.1) isoforms, we have begun to determine the consequences of SOD deficiency in hippocampal neurogenesis and the related functions of learning and memory under normal condition and following cranial irradiation.

    View details for DOI 10.3109/10715762.2012.664770

    View details for Web of Science ID 000306427200004

    View details for PubMedID 22315982

  • Endogenous mitochondrial oxidative stress in MnSOD-deficient mouse embryonic fibroblasts promotes mitochondrial DNA glycation FREE RADICAL BIOLOGY AND MEDICINE Breyer, V., Weigel, I., Huang, T., Pischetsrieder, M. 2012; 52 (9): 1744-1749

    Abstract

    The accumulation of somatic mutations in mitochondrial DNA (mtDNA) induced by reactive oxygen species (ROS) is regarded as a major contributor to aging and age-related degenerative diseases. ROS have also been shown to facilitate the formation of certain advanced glycation end-products (AGEs) in proteins and DNA and N(2)-carboxyethyl-2'-deoxyguanosine (CEdG) has been identified as a major DNA-bound AGE. Therefore, the influence of mitochondrial ROS on the glycation of mtDNA was investigated in primary embryonic fibroblasts derived from mutant mice (Sod2(-/+)) deficient in the mitochondrial antioxidant enzyme manganese superoxide dismutase. In Sod2(-/+) fibroblasts vs wild-type fibroblasts, the CEdG content of mtDNA was increased from 1.90 ± 1.39 to 17.14 ± 6.60 pg/μg DNA (p<0.001). On the other hand, the CEdG content of nuclear DNA did not differ between Sod2(+/+) and Sod2(-/+) cells. Similarly, cytosolic proteins did not show any difference in advanced glycation end-products or protein carbonyl contents between Sod2(+/+) and Sod2(-/+). Taken together, the data suggest that mitochondrial oxidative stress specifically promotes glycation of mtDNA and does not affect nuclear DNA or cytosolic proteins. Because DNA glycation can change DNA integrity and gene functions, glycation of mtDNA may play an important role in the decline of mitochondrial functions.

    View details for DOI 10.1016/j.freeradbiomed.2012.02.021

    View details for Web of Science ID 000304177500026

    View details for PubMedID 22370091

  • Mitochondrial oxidative stress and epilepsy in SOD2 deficient mice: Attenuation by a lipophilic metalloporphyrin NEUROBIOLOGY OF DISEASE Liang, L., Waldbaum, S., Rowley, S., Huang, T., Day, B. J., Patel, M. 2012; 45 (3): 1068-1076

    Abstract

    Epileptic seizures are a common feature associated with inherited mitochondrial diseases. This study investigated the role of mitochondrial oxidative stress in epilepsy resulting from mitochondrial dysfunction using cross-bred mutant mice lacking mitochondrial manganese superoxide dismutase (MnSOD or SOD2) and a lipophilic metalloporphyrin catalytic antioxidant. Video-EEG monitoring revealed that in the second to third week of postnatal life (P14-P21) B6D2F2 Sod2(-/-) mice exhibited frequent spontaneous motor seizures providing evidence that oxidative stress-induced mitochondrial dysfunction may contribute to epileptic seizures. To confirm the role of mitochondrial oxidative stress in epilepsy a newly developed lipophilic metalloporphyrin, AEOL 11207, with high potency for catalytic removal of endogenously generated reactive oxygen species was utilized. AEOL 11207-treated Sod2(-/-) mice showed a significant decrease in both the frequency and duration of spontaneous seizures but no effect on seizure severity. A significant increase in the average lifespan of AEOL 11207-treated Sod2(-/-) mice compared to vehicle-treated Sod2(-/-) mice was also observed. Indices of mitochondrial oxidative stress and damage (aconitase inactivation, 3-nitrotyrosine formation, and depletion of reduced coenzyme A) and ATP levels affecting neuronal excitability were significantly attenuated in the brains of AEOL 11207-treated Sod2(-/-) mice compared to vehicle-treated Sod2(-/-) mice. The occurrence of epileptic seizures in Sod2(-/-) mice and the ability of catalytic antioxidant therapy to attenuate seizure activity, mitochondrial dysfunction, and ATP levels suggest that ongoing mitochondrial oxidative stress can contribute to epilepsy associated with mitochondrial dysfunction and disease.

    View details for DOI 10.1016/j.nbd.2011.12.025

    View details for Web of Science ID 000300519600024

    View details for PubMedID 22200564

    View details for PubMedCentralID PMC3418969

  • 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

    View details for PubMedCentralID PMC3229600

  • Enhancing Mitochondrial Respiration Suppresses Tumor Promoter TPA-Induced PKM2 Expression and Cell Transformation in Skin Epidermal JB6 Cells CANCER PREVENTION RESEARCH Wittwer, J. A., Robbins, D., Wang, F., Codarin, S., Shen, X., Kevil, C. G., Huang, T., Van Remmen, H., Richardson, A., Zhao, Y. 2011; 4 (9): 1476-1484

    Abstract

    Differentiated cells primarily metabolize glucose for energy via the tricarboxylic acid cycle and oxidative phosphorylation, but cancer cells thrive on a different mechanism to produce energy, characterized as the Warburg effect, which describes the increased dependence on aerobic glycolysis. The M2 isoform of pyruvate kinase (PKM2), which is responsible for catalyzing the final step of aerobic glycolysis, is highly expressed in cancer cells and may contribute to the Warburg effect. However, whether PKM2 plays a contributing role during early cancer development is unclear. In our studies, we have made an attempt to elucidate the effects of varying mitochondrial respiration substrates on skin cell transformation and expression of PKM2. Tumorigenicity in murine skin epidermal JB6 P+ (promotable) cells was measured in a soft agar assay using 12-O-tetradecanoylphorbol-13-acetate (TPA) as a tumor promoter. We observed a significant reduction in cell transformation upon pretreatment with the mitochondrial respiration substrate succinate or malate/pyruvate. We observed that increased expression and activity of PKM2 in TPA-treated JB6 P+ cells and pretreatment with succinate or malate/pyruvate suppressed the effects. In addition, TPA treatment also induced PKM2 whereas PKM1 expression was suppressed in mouse skin epidermal tissues in vivo. In comparison with JB6 P+ cells, the nonpromotable JB6 P- cells showed no increase in PKM2 expression or activity upon TPA treatment. Knockdown of PKM2 using a siRNA approach significantly reduced skin cell transformation. Thus, our results suggest that PKM2 activation could be an early event and play a contributing role in skin tumorigenesis.

    View details for DOI 10.1158/1940-6207.CAPR-11-0028

    View details for Web of Science ID 000294490100019

    View details for PubMedID 21673231