Abstract 15468: Inhibition of NAD(P)H Oxidase 4 Ameliorates Angiotensin II-Induced Protein Degradation via Improving Mitochondrial Dysfunction in Skeletal Myocytes
Background: Skeletal muscle atrophy is a debilitating phenotype that is associated with a variety conditions, including chronic kidney disease and heart failure. We have previously demonstrated that angiotensin II (Ang II), a key mediator of the renin-angiotensin system, which directly induced skeletal muscle atrophy in mice. In this study, we hypothesized that the activation of NAD(P)H oxidase 4 by Ang II induces protein degradation via mitochondrial dysfunction in skeletal myocytes.
Methods: Mouse skeletal myocytes (C2C12) were cultured. They were transfected by electroporation with Nox4 small interference RNA (siRNA) or scrambled control siRNA. The cells were treated with or without Ang II (10–6-10–8 mol/L) and collected 24 h after treatment.
Results: Ang II treatment showed a dose-dependent increase of NAD(P)H oxidase activity in C2C12 myocytes. It also showed an increase of Nox4 gene expression levels (266%). Gene expression levels of muscle RING finger-1 (MuRF-1) and atrogin-1/MAFbx (Atrogin-1), which are key molecules in protein degradation, were significantly increased (385%; 149%, respectively, compared with control). However, protein expression levels of phosphorylated Akt (Ser473), a key molecule in protein synthesis, were significantly decreased in Ang II-treated myocytes compared with those in controls (–28.4%). Moreover, gene expression levels of mitochondrial transcription factor A (mtTFA) and peroxisome proliferator activator receptor gamma coactivator-1alpha (PGC-1α), which are key factors in mitochondrial function, were significantly decreased in Ang II treated myocytes (–48%; –67%, respectively, compared with control). Nox4 knockdown by siRNA treatment significantly inhibited Ang II-induced upregulation of MuRF-1 and Atrogin-1 (–56%; –60%, respectively, compared with Ang II). By this mean, mtTFA and PGC-1α were improved in Nox4 siRNA treated myocytes (125%; 280%, respectively, compared with Ang II).
Conclusion: The inhibition of Nox4 ameliorated protein degradation and decreased protein synthesis by Ang II via improving mitochondrial dysfunction. This result suggests that Nox4 plays an important role in the development of skeletal muscle atrophy.
Author Disclosures: T. Kadoguchi: None. K. Shimada: None. T. Shiozawa: None. S. Takahashi: None. H. Al Shahi: None. T. Aikawa: None. S. Ouchi: None. Y. Sugita: None. T. Miyazaki: None. K. Akita: None. K. Isoda: None. H. Daida: None.
- © 2016 by American Heart Association, Inc.