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Antioxidants Modulate Oral Fibroblasts Response to Reactive Oxygen Species Inducing Agents
alter progression of ALD is still poorly understood. The objective of this research was to define the mechanisms involved in ω-3/ω6 PUFA mediated prevention/exacerbation of ALD and study the role of endogenous PUFA derived free radicals. Using a voluntary oral ethanol intake rat model, we administered diets supplemented with 1) fish oil (FO, rich in ω-3 Eicosapentaenoic and Docosahexaenoic acids) and 2) safflower oil (SO, rich in ω-6 Linoleic acid) with or without ethanol for 8 weeks. Liver histology and serology results showed development of severe liver injury in rats fed SO with ethanol while no liver injury was observed in rats fed FO with ethanol. Hepatic m-RNA expression of proinflammatory/ pro-fibrotic cytokines TNF-α, TGF-β and protein level of lipid peroxidation enzyme COX-2 were found to be significantly upregulated in rats fed SO with ethanol while their downregulation was observed in rats fed FO with ethanol compared to rats fed SO and FO without ethanol respectively. In addition, using our novel technique combining LC/ESR, LC/MS and spin trapping with spin trap α-[4-pyridyl-1-oxide]-N-tert-butyl nitrone (POBN), endogenous free radicals generated via peroxidation of arachidonic acid were tentatively identified as 4hydroxynonenal type (POBN/•C9H16O2, m/z 351), PGF2-type • (POBN/ C20H33O5, m/z 548), and GSH conjugated free radicals formed from the COX peroxidation pathway, in bile of rats fed SO. However, mainly the GSH conjugated radicals were observed in bile of rats fed FO. This data suggests that exacerbation of COX2 mediated lipid peroxidation in rats fed SO contributes in disease progression by generation of ω-6 PUFA-derived free radicals and upregulation of inflammatory cytokines such as TNF-α. However, in rats fed FO, downregulation of COX-2 mediated free radical generation, downregulation of TNF-α, along with GSH mediated free radical conjugation/ detoxification may prevent the development of ALD. Supported by NIEHS Grant ES-012978. doi: 10.1016/j.freeradbiomed.2010.10.264
258 Basic Amino Acid Residues Within (aa105125) eNOS Region are Responsible for the “Flexible Arm” Movement and the Inhibition of ZnS4 Mutants Ruslan Rafikov1, Fabio V Fonseca1, Sanjiv Kumar1, Shawn Elms1, David Fulton1, and Stephen M Black1 1 Medical College of Georgia Oxidation of cysteine residues in the zinc-tetrathiolate cluster (ZnS4) of eNOS results in dimer disruption and loss of activity. ZnS4 is located adjacent to an unstructured region of eNOS that lies beneath the substrate entrance. We have termed this region the flexible arm (aa105-125). Molecular dynamic simulation experiments indicated that ZnS4 disruption alters the conformation of the flexible arm resulting in closure of the substrate channel subsequently limiting access to the heme. To test this model we initially utilized ZnS4 disrupted eNOS mutant proteins (C94A, C99A and C94A/C99A). Our data demonstrated a decrease in both NO and superoxide production in the ZnS4 cluster mutants and that these changes correlated with decreased heme accessibility. Further molecular dynamic simulations suggested that the closed conformation of the “flexible arm” is stabilized by the formation of salt bridges between positively charged residues within the “flexible arm” and negatively charged residues located in the substrate channel. Mutation of these basic amino residues within the flexible arm to alanine (R107A/K108A/R112A) restored heme access on the background of a disrupted ZnS4 cluster (C94A/C99A). Further, the dimer fraction in this mutant protein was significantly increased and this correlated with enhanced NO production. However, there was also a two-fold increase in superoxide generation that resulted in eNOS self-nitration. Togetehr our data suggest a new mechanism of redox regulation of eNOS where disruption of ZnS4 reduces access to the substrate channel limiting eNOS uncoupling. doi: 10.1016/j.freeradbiomed.2010.10.265
259 The Degree of Oxidative Stress Induced by Bioactivationdependent Hepatotoxins Presage the Mediation of Caspaseactivated DNAse (CAD) dependent DNA Fragmentation and Cyt c Release to Propel Apoptotic and Necrotic Cell Deaths in the Liver in vivo Sidhartha D Ray1,2, Sonia D Pravasi1, and Shruti Desai1 1 2 AMS College of Pharmacy & Health Sciences, Creighton University College of Pharmacy Most bioactivation-dependent hepatotoxins, such as acetaminophen, furosemide, CCl4 and thioacetamide (TAM) produce BRIs to orchestrate cell demise using oxidative stress (lipid peroxidation), genomic injury and mitochondria-centric massive perturbations. During this crisis, liver cells in particular, are faced with incessant burden of detoxification of BRIs to stall lethal consequences. However, it is not known how these events organize their sequence to propel apoptosis and necrosis in vivo. Since, pre-necrotic events cannot be separated from preapoptotic events in vivo, we hypothesized that intensity of BRIsmediated oxidative stress preceding the generation of oligonucleosome-length DNA fragmentation and cyt c release would suggest a predominance of apoptosis in the presence of necrosis. In order to test this hypothesis, adult mice (ICR; 12 weeks or older; 12h starved) were administered a hepatotoxic dose of TAM (50 mg/kg) and sacrificed at 0, 6, 12, 18 and 24 hours later. Blood was collected for serum chemistry and the livers for genomic analysis and molecular biology. Serum chemistry revealed dramatic increases in lipid peroxidation (%↑ at 0h: 100±12; 6h: 195±18; 12h: 275±34; 18h: 345±41; 24h: 412±48) as reflected in ALT activity (U/L at 0h: 24±4; 6h: 4112±421; 12h: 7889±812; 18h: 9890±1108; 24h: 11,980±1498). This scenario followed massive quantitative DNA fragmentation. Qualitative analysis of genomic injury by agarose gel electrophoresis revealed successful mediation of Caspase-Acivetd-DNAsedependent DNA laddering, timely cyt c release, and suppression of bcl-Xl expression. Heavy presence of apoptotic nuclei in PASstained liver sections suggested predominance of apoptosis supporting our notion that the intensity of oxidative stress played an instrumental role in triggering apoptosis. Therefore, prevalence of numerous cells with necrotic features very late in the liver injury process may not accurately reflect % apoptosis, and therefore, should not be confused with the conclusion that bioactivationdependent hepatotoxins favor necrosis over apoptosis. doi: 10.1016/j.freeradbiomed.2010.10.266
260 Antioxidants Modulate Oral Fibroblasts Response to Reactive Oxygen Species Inducing Agents Symone San Miguel1, Lynne Opperman1, Edward Allen1, Jan Zielinski2, and Kathy Svoboda1 1 2 TAMHSC Baylor College of Dentistry, Dallas, Texas, Zielinski Research, Vista, California Oxidative damage of soft oral tissues has many causes. It may result from exposure to chemicals or biochemicals, for example by teeth whitening products, alcohol, or even from the body's own processes. Our working hypothesis is that oral fibroblasts are susceptible to damage from hydrogen peroxide (H2O2), ethanol and nicotine. These agents elevate reaction oxygen species (ROS), which must be eliminated from the cells by a variety of antioxidant defense mechanisms. In this study, we investigated specific antioxidant (AO) combinations that counteract the effects of H2O2, ethanol and nicotine on cultured oral fibroblast proliferation and oxidative damage. Oral fibroblasts obtained from human gingival (HGF) tissues were seeded into96-well plates. After achieving 70% confluence,the cells were pre-treated with
SFRBM/SFRRI 2010
S101
H2O2, ethanol and nicotine for 30 and 60 minutes. Thereafter, -5 cells were exposed to 10 M of the bioactive AO mixtures; resveratrol (R), ferulic acid (F) phloretin (P) and tetrahydrocurcuminoids (T); (RFT, PFR, PFT) for 24 hours. Cell viability was monitored by MTS assay. The fluorescence response of dichlorodihydrofluorescein diacetate to various ROS was measured. Incubation of HGF cells in the presence of H2O2, ethanol and nicotine resulted in a dose-dependent decrease of viable cells at 30 and 60 minutes.AO compounds increased recovery or survival of cells exposed to 10% or 15 % ethanol, 6 mM nicotine, and 0.00075% but not 0.001% H2O2. In summary, H2O2, ethanol and nicotine increased ROS. AO treatment decreased ROS in the presence of H2O2, ethanol or nicotine. The triple combinations of RFT, PFR or PFT are effective modulators in the presence of all insulting substances tested. These data indicate that pure AOs counteracted the detrimental effects of H2O2, ethanol, and nicotine in oral fibroblasts. In addition, the AOs decrease ROS activity by protecting the cells against free radical formation doi: 10.1016/j.freeradbiomed.2010.10.267
261 Coffee Induced Protective Redoxsignalling in Oxidative Stressassociated Diseases Tanja Sauer1, and Gerald Muench1 1 University of Erlangen Increased levels of reactive oxygen species (ROS) are believed to be the most critical factor involved in shortening life span. Indeed, oxidative stress plays a pivotal role in the pathogenesis of severe diseases associated with aging such as Alzheimer’s, Parkinson, cancer, type 2 diabetes mellitus and cardiovascular diseases. Epidemiological studies postulate that habitual consumption of certain foods such as coffee reduces the risk of oxidative stressassociated diseases. However, the protective mechanism of coffee still remains unclear. Since the redox-sensitive transcription factor NRF2 regulates genes encoding antioxidant proteins, the effect of coffee on NRF2 was investigated. Briefly, after coffee stimulation of macrophages, NRF2 activation was detected immunochemically as nuclear translocation. In addition, hydrogen peroxide levels (H2O2) were measured by the FOXPCA-Assay. Coffee significantly up-regulated nuclear NRF2 levels (20-folds). Given that raw coffee did not induce a significant NRF2 activation, it was suggested that the roasting products act as a trigger. Many mechanisms for NRF2 regulation were predicted including an increased intracellular ROS level. In fact, compared to nonstimulated cells the ROS level was amplified 4-fold by a mixture of roasting products. Instead of increasing with time, the ROS level plateaued after 4 h and decreased slightly to 24 h. This effect was associated with the NRF2-dependent up-regulation of the antioxidant defence. Imhoff et al. suggested that the level of intracellular ROS produced in the mitochondria, was promoted by the extracellular redox-status, especially by oxidizing conditions. Indeed, coffee generated up to 275 µM H2O2. Interestingly, NRF2 activation was only slightly decreased by catalase co-treatment. Consequently, H2O2 could be excluded as the unique trigger. Thus, the roasting products were highlighted as further active compounds in NRF2 activation. The data reported herein postulate a NRF2-dependent mechanism for the protective effect of coffee against oxidative stress-associated diseases via redox signalling pathways triggered by roasting products. doi: 10.1016/j.freeradbiomed.2010.10.268
S102
262 Regulation of Human ALDH2 Activity by Electrophiles – Implications for Organic Nitrate Induced Tolerance, Oxidative Stress and Reactive Fatty Acid Metabolites in MI Richard Schell1, Matthias Oelze1, Maike Knorr1, Sebastian Steven1, Tjebo Heeren1, Jens Kamuf1, Andrea Pautz2, Julia Art2, Philip Wenzel1, Thomas Münzel1, Hartmut Kleinert2, and Andreas Daiber1 12 Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Germany Objective: In a recent Science publication, Chen et al. have shown that mitochondrial aldehyde dehydrogenase (ALDH-2) reduces ischemic damage in an experimental MI model. These authors showed that pharmacologic (glyceryl trinitrate [GTN], cyanamide) or genetic (protein kinase Cε knockout) inhibition of ALDH-2 results in increased infarct area and impaired cardiac function in response to MI. We here compared effects of various electrophiles (organic nitrates, reactive fatty acid metabolites or oxidants) on the activity of ALDH-2 with special emphasis on organic nitrate-induced inactivation of the enzyme – the clinical correlate of nitrate tolerance. Methods: Recombinant human ALDH-2 was over-expressed in E. coli using a plasmid (kindly provided by K.K. Ho and H. Weiner, Purdue University, West Lafayette, USA). ALDH-2 activity was determined with an HPLC-based assay. Results: The organic nitrate GTN caused a severe concentrationdependent decrease in enzyme activity whereas incubation with pentaerithrityl tetranitrate (PETN) had only minor effects. 4hydroxynonenal, an oxidized prostaglandin J2 and 9- or 10nitrooleate caused a significant inhibition of ALDH-2 activity. Hydrogen peroxide and NO generation caused only minor inhibition of ALDH-2 activity whereas peroxynitrite generation or bolus additions lead to severe impairment of the enzymatic activity. Conclusions: Electrophiles of different nature potently regulate the enzymatic activity of ALDH-2 and thereby may influence the resistance to ischemic damage in response to MI. These data are in good accordance with our previous observations that ALDH-2 is an important antioxidant enzyme and contributes to protection from doxorubicin- or age-induced vascular dysfunction. The here observed beneficial profile of PETN is in accordance with previous reports on the lack of nitrate tolerance and vascular oxidative stress under chronic PETN therapy. In contrast, GTN may contribute to ischemic MI damage by inhibition of ALDH-2 and induction of oxidative stress. doi: 10.1016/j.freeradbiomed.2010.10.269
263 Inhibition of EGFR Signaling Induces Metabolic Oxidative Stress in Human Head and Neck Cancer Cells Andrean L. Simons1, Kevin P. Orcutt1, Arlene D. Parsons1, Zita A. Sibenaller1, Peter M. Scarbrough1, Arya Sobhakumari1, Yueming Zhu1, Werner W. Wilke1, Amanda L. Kalen1, Francis J. Miller2, Prabhat Goswami1,3, and Douglas R. Spitz1,3 1 Free Radical and Radiation Biology Program, Department of 2 3 Radiation Oncology, Department of Internal Medicine, Holden Comprehensive Cancer Center, The University of Iowa Redox regulation of epidermal growth factor (EGFR) signaling plays a major role in the protection of cancer cells against oxidative stress. In this work we test the hypothesis that the EGFR tyrosine kinase inhibitor, Erlotinib (ERL), induces cytotoxicity via oxidative stress in human head and neck cancer (HNSCC) cells. ERL induced cytotoxicity in vitro and in vivo, and increased oxidative stress parameters such as percentage glutathione disulfide (%GSSG) and CDCFH2 oxidation, which
SFRBM/SFRRI 2010
258 Basic Amino Acid Residues Within (aa105125) eNOS Region are Responsible for the “Flexible Arm” Movement and the Inhibition of ZnS4 Mutants Ruslan Rafikov1, Fabio V Fonseca1, Sanjiv Kumar1, Shawn Elms1, David Fulton1, and Stephen M Black1 1 Medical College of Georgia Oxidation of cysteine residues in the zinc-tetrathiolate cluster (ZnS4) of eNOS results in dimer disruption and loss of activity. ZnS4 is located adjacent to an unstructured region of eNOS that lies beneath the substrate entrance. We have termed this region the flexible arm (aa105-125). Molecular dynamic simulation experiments indicated that ZnS4 disruption alters the conformation of the flexible arm resulting in closure of the substrate channel subsequently limiting access to the heme. To test this model we initially utilized ZnS4 disrupted eNOS mutant proteins (C94A, C99A and C94A/C99A). Our data demonstrated a decrease in both NO and superoxide production in the ZnS4 cluster mutants and that these changes correlated with decreased heme accessibility. Further molecular dynamic simulations suggested that the closed conformation of the “flexible arm” is stabilized by the formation of salt bridges between positively charged residues within the “flexible arm” and negatively charged residues located in the substrate channel. Mutation of these basic amino residues within the flexible arm to alanine (R107A/K108A/R112A) restored heme access on the background of a disrupted ZnS4 cluster (C94A/C99A). Further, the dimer fraction in this mutant protein was significantly increased and this correlated with enhanced NO production. However, there was also a two-fold increase in superoxide generation that resulted in eNOS self-nitration. Togetehr our data suggest a new mechanism of redox regulation of eNOS where disruption of ZnS4 reduces access to the substrate channel limiting eNOS uncoupling. doi: 10.1016/j.freeradbiomed.2010.10.265
259 The Degree of Oxidative Stress Induced by Bioactivationdependent Hepatotoxins Presage the Mediation of Caspaseactivated DNAse (CAD) dependent DNA Fragmentation and Cyt c Release to Propel Apoptotic and Necrotic Cell Deaths in the Liver in vivo Sidhartha D Ray1,2, Sonia D Pravasi1, and Shruti Desai1 1 2 AMS College of Pharmacy & Health Sciences, Creighton University College of Pharmacy Most bioactivation-dependent hepatotoxins, such as acetaminophen, furosemide, CCl4 and thioacetamide (TAM) produce BRIs to orchestrate cell demise using oxidative stress (lipid peroxidation), genomic injury and mitochondria-centric massive perturbations. During this crisis, liver cells in particular, are faced with incessant burden of detoxification of BRIs to stall lethal consequences. However, it is not known how these events organize their sequence to propel apoptosis and necrosis in vivo. Since, pre-necrotic events cannot be separated from preapoptotic events in vivo, we hypothesized that intensity of BRIsmediated oxidative stress preceding the generation of oligonucleosome-length DNA fragmentation and cyt c release would suggest a predominance of apoptosis in the presence of necrosis. In order to test this hypothesis, adult mice (ICR; 12 weeks or older; 12h starved) were administered a hepatotoxic dose of TAM (50 mg/kg) and sacrificed at 0, 6, 12, 18 and 24 hours later. Blood was collected for serum chemistry and the livers for genomic analysis and molecular biology. Serum chemistry revealed dramatic increases in lipid peroxidation (%↑ at 0h: 100±12; 6h: 195±18; 12h: 275±34; 18h: 345±41; 24h: 412±48) as reflected in ALT activity (U/L at 0h: 24±4; 6h: 4112±421; 12h: 7889±812; 18h: 9890±1108; 24h: 11,980±1498). This scenario followed massive quantitative DNA fragmentation. Qualitative analysis of genomic injury by agarose gel electrophoresis revealed successful mediation of Caspase-Acivetd-DNAsedependent DNA laddering, timely cyt c release, and suppression of bcl-Xl expression. Heavy presence of apoptotic nuclei in PASstained liver sections suggested predominance of apoptosis supporting our notion that the intensity of oxidative stress played an instrumental role in triggering apoptosis. Therefore, prevalence of numerous cells with necrotic features very late in the liver injury process may not accurately reflect % apoptosis, and therefore, should not be confused with the conclusion that bioactivationdependent hepatotoxins favor necrosis over apoptosis. doi: 10.1016/j.freeradbiomed.2010.10.266
260 Antioxidants Modulate Oral Fibroblasts Response to Reactive Oxygen Species Inducing Agents Symone San Miguel1, Lynne Opperman1, Edward Allen1, Jan Zielinski2, and Kathy Svoboda1 1 2 TAMHSC Baylor College of Dentistry, Dallas, Texas, Zielinski Research, Vista, California Oxidative damage of soft oral tissues has many causes. It may result from exposure to chemicals or biochemicals, for example by teeth whitening products, alcohol, or even from the body's own processes. Our working hypothesis is that oral fibroblasts are susceptible to damage from hydrogen peroxide (H2O2), ethanol and nicotine. These agents elevate reaction oxygen species (ROS), which must be eliminated from the cells by a variety of antioxidant defense mechanisms. In this study, we investigated specific antioxidant (AO) combinations that counteract the effects of H2O2, ethanol and nicotine on cultured oral fibroblast proliferation and oxidative damage. Oral fibroblasts obtained from human gingival (HGF) tissues were seeded into96-well plates. After achieving 70% confluence,the cells were pre-treated with
SFRBM/SFRRI 2010
S101
H2O2, ethanol and nicotine for 30 and 60 minutes. Thereafter, -5 cells were exposed to 10 M of the bioactive AO mixtures; resveratrol (R), ferulic acid (F) phloretin (P) and tetrahydrocurcuminoids (T); (RFT, PFR, PFT) for 24 hours. Cell viability was monitored by MTS assay. The fluorescence response of dichlorodihydrofluorescein diacetate to various ROS was measured. Incubation of HGF cells in the presence of H2O2, ethanol and nicotine resulted in a dose-dependent decrease of viable cells at 30 and 60 minutes.AO compounds increased recovery or survival of cells exposed to 10% or 15 % ethanol, 6 mM nicotine, and 0.00075% but not 0.001% H2O2. In summary, H2O2, ethanol and nicotine increased ROS. AO treatment decreased ROS in the presence of H2O2, ethanol or nicotine. The triple combinations of RFT, PFR or PFT are effective modulators in the presence of all insulting substances tested. These data indicate that pure AOs counteracted the detrimental effects of H2O2, ethanol, and nicotine in oral fibroblasts. In addition, the AOs decrease ROS activity by protecting the cells against free radical formation doi: 10.1016/j.freeradbiomed.2010.10.267
261 Coffee Induced Protective Redoxsignalling in Oxidative Stressassociated Diseases Tanja Sauer1, and Gerald Muench1 1 University of Erlangen Increased levels of reactive oxygen species (ROS) are believed to be the most critical factor involved in shortening life span. Indeed, oxidative stress plays a pivotal role in the pathogenesis of severe diseases associated with aging such as Alzheimer’s, Parkinson, cancer, type 2 diabetes mellitus and cardiovascular diseases. Epidemiological studies postulate that habitual consumption of certain foods such as coffee reduces the risk of oxidative stressassociated diseases. However, the protective mechanism of coffee still remains unclear. Since the redox-sensitive transcription factor NRF2 regulates genes encoding antioxidant proteins, the effect of coffee on NRF2 was investigated. Briefly, after coffee stimulation of macrophages, NRF2 activation was detected immunochemically as nuclear translocation. In addition, hydrogen peroxide levels (H2O2) were measured by the FOXPCA-Assay. Coffee significantly up-regulated nuclear NRF2 levels (20-folds). Given that raw coffee did not induce a significant NRF2 activation, it was suggested that the roasting products act as a trigger. Many mechanisms for NRF2 regulation were predicted including an increased intracellular ROS level. In fact, compared to nonstimulated cells the ROS level was amplified 4-fold by a mixture of roasting products. Instead of increasing with time, the ROS level plateaued after 4 h and decreased slightly to 24 h. This effect was associated with the NRF2-dependent up-regulation of the antioxidant defence. Imhoff et al. suggested that the level of intracellular ROS produced in the mitochondria, was promoted by the extracellular redox-status, especially by oxidizing conditions. Indeed, coffee generated up to 275 µM H2O2. Interestingly, NRF2 activation was only slightly decreased by catalase co-treatment. Consequently, H2O2 could be excluded as the unique trigger. Thus, the roasting products were highlighted as further active compounds in NRF2 activation. The data reported herein postulate a NRF2-dependent mechanism for the protective effect of coffee against oxidative stress-associated diseases via redox signalling pathways triggered by roasting products. doi: 10.1016/j.freeradbiomed.2010.10.268
S102
262 Regulation of Human ALDH2 Activity by Electrophiles – Implications for Organic Nitrate Induced Tolerance, Oxidative Stress and Reactive Fatty Acid Metabolites in MI Richard Schell1, Matthias Oelze1, Maike Knorr1, Sebastian Steven1, Tjebo Heeren1, Jens Kamuf1, Andrea Pautz2, Julia Art2, Philip Wenzel1, Thomas Münzel1, Hartmut Kleinert2, and Andreas Daiber1 12 Universitätsmedizin der Johannes Gutenberg-Universität Mainz, Germany Objective: In a recent Science publication, Chen et al. have shown that mitochondrial aldehyde dehydrogenase (ALDH-2) reduces ischemic damage in an experimental MI model. These authors showed that pharmacologic (glyceryl trinitrate [GTN], cyanamide) or genetic (protein kinase Cε knockout) inhibition of ALDH-2 results in increased infarct area and impaired cardiac function in response to MI. We here compared effects of various electrophiles (organic nitrates, reactive fatty acid metabolites or oxidants) on the activity of ALDH-2 with special emphasis on organic nitrate-induced inactivation of the enzyme – the clinical correlate of nitrate tolerance. Methods: Recombinant human ALDH-2 was over-expressed in E. coli using a plasmid (kindly provided by K.K. Ho and H. Weiner, Purdue University, West Lafayette, USA). ALDH-2 activity was determined with an HPLC-based assay. Results: The organic nitrate GTN caused a severe concentrationdependent decrease in enzyme activity whereas incubation with pentaerithrityl tetranitrate (PETN) had only minor effects. 4hydroxynonenal, an oxidized prostaglandin J2 and 9- or 10nitrooleate caused a significant inhibition of ALDH-2 activity. Hydrogen peroxide and NO generation caused only minor inhibition of ALDH-2 activity whereas peroxynitrite generation or bolus additions lead to severe impairment of the enzymatic activity. Conclusions: Electrophiles of different nature potently regulate the enzymatic activity of ALDH-2 and thereby may influence the resistance to ischemic damage in response to MI. These data are in good accordance with our previous observations that ALDH-2 is an important antioxidant enzyme and contributes to protection from doxorubicin- or age-induced vascular dysfunction. The here observed beneficial profile of PETN is in accordance with previous reports on the lack of nitrate tolerance and vascular oxidative stress under chronic PETN therapy. In contrast, GTN may contribute to ischemic MI damage by inhibition of ALDH-2 and induction of oxidative stress. doi: 10.1016/j.freeradbiomed.2010.10.269
263 Inhibition of EGFR Signaling Induces Metabolic Oxidative Stress in Human Head and Neck Cancer Cells Andrean L. Simons1, Kevin P. Orcutt1, Arlene D. Parsons1, Zita A. Sibenaller1, Peter M. Scarbrough1, Arya Sobhakumari1, Yueming Zhu1, Werner W. Wilke1, Amanda L. Kalen1, Francis J. Miller2, Prabhat Goswami1,3, and Douglas R. Spitz1,3 1 Free Radical and Radiation Biology Program, Department of 2 3 Radiation Oncology, Department of Internal Medicine, Holden Comprehensive Cancer Center, The University of Iowa Redox regulation of epidermal growth factor (EGFR) signaling plays a major role in the protection of cancer cells against oxidative stress. In this work we test the hypothesis that the EGFR tyrosine kinase inhibitor, Erlotinib (ERL), induces cytotoxicity via oxidative stress in human head and neck cancer (HNSCC) cells. ERL induced cytotoxicity in vitro and in vivo, and increased oxidative stress parameters such as percentage glutathione disulfide (%GSSG) and CDCFH2 oxidation, which
SFRBM/SFRRI 2010