Abstract 16116: Genetic Deficiency of the H2S Producing Enzyme, Cystathionine Gamma-Lyase (CSE) Results in Impaired Cardiac Mitochondrial Function, Increased Oxidative Stress, and Exacerbated Myocardial Reperfusion Injury
Introduction: H2S is formed from cysteine by enzymes in the mammalian heart via cystathionine γ-lyase (CSE). H2S is a critical gaseous signaling molecule that upregulates antioxidants and promotes cell survival. We investigated the effects of loss of endogenous H2S production in the heart using CSE knockout (KO) mice.
Methods: Basal cardiac mitochondrial respiration (State 3 and State 4) was measured using an oxygraph electrode in CSE KO (n = 8) and wild-type (WT) mice (n = 11). Cardiac levels of the nuclear transcription factor Nrf2 and its inhibitory protein, Keap1 were also performed (n=5) and myocardial levels of antioxidant proteins were also measured. The respiratory control ratio (RCR) was calculated by taking the ratio of State 3/State 4.
Results: Mitochondrial State 3 respiration was significantly (p < 0.05) lower in the CSE KO mice compared to WT. However, there was no difference in State 4 respiration. Moreover, the RCR was significantly lower (p < 0.001) in CSE KO compared to WT. Western blotting analysis revealed a significant increase (p < 0.05) in myocardial Nrf2 and Keap1 protein levels in the cytosol of CSE KO mice compared to WT suggesting an impairment in this antioxidant signaling pathway. We failed to observe a significant difference in myocardial levels of thioredoxin, superoxide dismutase, and hemeoxygnease-1 in CSE KO mice vs. WT. Mice (n = 12-13) were subjected to 45 min of myocardial ischemia (MI) and 24 h reperfusion (R). Both groups displayed similar area-at-risk (AAR) per left ventricle (LV). The CSE KO mice displayed a significant increase in infarct size (INF) per AAR compared to WT (62 ± 2% vs. 42 ± 3%, respectively, p < 0.001). This exacerbation of MI/R injury was attenuated by 50% with Na2S therapy at reperfusion (29 ± 4% INF/AAR, p < 0.001 vs. CSE KO).
Conclusion: These data demonstrate the critical role of endogenous H2S on cardiac mitochondrial function and protection of the heart against MI/R injury.
- © 2011 by American Heart Association, Inc.