Mitochondrial accumulation under oxidative stress is due to defects in autophagy

• Published in: Journal of cellular biochemistry 2013-01, Vol.114 (1), p.212-219
• Main Authors: Luo, Cheng, Li, Yan, Wang, Hui, Feng, Zhihui, Li, Yuan, Long, Jiangang, Liu, Jiankang
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Animals; Apoptosis Regulatory Proteins - genetics; Apoptosis Regulatory Proteins - metabolism; AUTOPHAGY; Autophagy - drug effects; Autophagy - genetics; Beclin-1; Cell Line; DNA, Mitochondrial - biosynthesis; DNA, Mitochondrial - genetics; Gene Expression - drug effects; Microtubule-Associated Proteins - genetics; Microtubule-Associated Proteins - metabolism; Mitochondria, Heart - drug effects; Mitochondria, Heart - metabolism; MITOCHONDRIAL BIOGENESIS; MITOCHONDRIAL DNA (mtDNA); MITOCHONDRIAL MASS; Mitochondrial Turnover - drug effects; Myoblasts, Cardiac - cytology; Myoblasts, Cardiac - drug effects; Myoblasts, Cardiac - metabolism; OXIDATIVE STRESS; Oxidative Stress - drug effects; Protein Isoforms - genetics; Protein Isoforms - metabolism; Rats; Signal Transduction - drug effects; Small Ubiquitin-Related Modifier Proteins - genetics; Small Ubiquitin-Related Modifier Proteins - metabolism; TERT-BUTYL HYDROPEROXIDE (tBHP); tert-Butylhydroperoxide - pharmacology
• ISSN: 0730-2312; 1097-4644
• DOI: 10.1002/jcb.24356

Mitochondrial dynamics maintains normal mitochondrial function by degrading damaged mitochondria and generating newborn mitochondria. The accumulation of damaged mitochondria influences the intracellular environment by promoting mitochondrial dysfunction, and thus initiating a vicious cycle. Oxidative stress induces mitochondrial malfunction, which is involved in many cardiovascular diseases. However, the mechanism of mitochondrial accumulation in cardiac myoblasts remains unclear. We observed mitochondrial dysfunction and an increase in mitochondrial mass under the oxidative conditions produced by tert‐butyl hydroperoxide (tBHP) in cardiac myoblast H9c2 cells. However, in contrast to the increase in mitochondrial mass, mitochondrial DNA (mtDNA) decreased, suggesting that enhanced mitochondrial biogenesis may be not the primary cause of the mitochondrial accumulation. Therefore, we investigated changes in a number of proteins involved in autophagy. Beclin1, Atg12–Atg5 conjugate, Atg7 contents decreased but LC3‐II accumulated in tBHP‐treated H9c2 cells. Moreover, the capacity for acid hydrolysis decreased in H9c2 cells. We also demonstrated a decrease in DJ‐1 protein under the oxidative conditions that deregulate mitochondrial dynamics. These results reveal that autophagy became defective under oxidative stress. We therefore suggest that defects in autophagy mediate mitochondrial accumulation under these conditions. J. Cell. Biochem. 114: 212–219, 2012. © 2012 Wiley Periodicals, Inc.