Abstract 11822: Inhibition of Protease Oxidation Preserves Protein Turnover of Mitochondrial Electron Transport Complex and Improves Respiration Capacity in Pressure Overload Heart Failure
Background: Mitochondrial dysfunction is a prominent feature of heart failure. Our preliminary examinations on mitochondrial remodeling in heart failure using microarray and mitochondrial iTRAQ proteome revealed that mitochondrial electron transport chain (ETC) proteins increased even with a decrease of mRNA expression in murine pressure overload heart failure. We investigated the underlying mechanism and pathological involvement with focus on the protein quality control.
Methods and results: Pressure overload heart failure was introduced with the transverse aortic constriction and samples were obtained at 8 weeks. We confirmed the accumulation of complexes I, III, and IV protein by blue native PAGE of isolated mitochondria from failing heart. Isolated mitochondria were incubated with 10mM ATP at 37°C for 6 hr followed by immunoblot for NADH dehydrogenase 1 alpha subcomplex subunit 9 (Ndufa9) and COX5a, prominently up-regulated proteins in iTRAQ analysis. These proteins degradation was attenuated in isolated mitochondria from failing heart. Moreover, FITC-casein assay indicated that decreased protease activity contributed to impaired ETC protein degradation. Immunoblot for DNPH-reactive products of oxidation showed that failing heart had remarkable oxidation in mitochondrial protein including ATP dependent Lon protease. Oxidative stress condition caused by H2O2 impaired ATP-dependent protein degradation of isolated mitochondria from sham operated heart. Short-term, 1 week of antioxidant treatment with tempol (1 mM in drinking water) ameliorated protease activity and protein degradation of isolated mitochondria from failing heart, which resulted in the improvement of respiration capacity assessed by mitochondrial oxygen consumption. Long-term, 6 weeks treatment prevented the progression of heart failure.
Conclusions: Present study suggested that oxidative stress impaired ATP dependent protease activity followed by abnormal protein turnover and respiration deficiency in pressure overload heart failure. Antioxidant therapy inhibited the development of cardiac dysfunction by preserving the protein quality control system.
- © 2012 by American Heart Association, Inc.