Abstract 19957: Angiotensin II Type 2 Receptor Potentiates Skeletal Muscle Stem Cell Differentiation via GSK-3β/β-catenin Signaling Pathway: Implications for Treatment of Cachexia and Skeletal Muscle Wasting
Patients with advanced congestive heart failure (CHF) or chronic kidney disease (CKD) often have increased angiotensin II (Ang II) levels and cachexia. We previously demonstrated that Ang II infusion in rodents causes skeletal muscle wasting and decreases muscle regenerative potential via Ang II type 1 receptor (AT1R) signaling, likely contributing to cachexia in CHF and CKD. We also found that Ang II type 2 receptor (AT2R) potentiates skeletal muscle stem cell (MuSC) differentiation and muscle regenerative capacity. However, mechanisms whereby AT2R regulates MuSC differentiation and its potential involvement in cachexia development remain unknown. To understand the signaling pathways downstream of AT2R in MuSC, we screened for phosphoprotein changes using microarray, on which 1318 unique antibodies against various phosphoproteins are spotted. We found that 20 phosphoproteins were upregulated (>1.4 fold change) and 28 were downregulated (<0.7 fold change) after AT2R knockdown by siRNA in primary MuSCs. Based on this screening, we found that GSK-3β activity is significantly suppressed (i.e. increased inhibitory Ser9 phosphorylation) during MuSC differentiation. AT2R knockdown prevented GSK-3β activation, and suppressed MuSC differentiation both in vitro and in vivo. The increase in GSK-3β activity after AT2R knockdown was associated with inhibition of downstream β-catenin activity, measured by TCF/LEF reporter assay both in vitro and in vivo. Treatment with GSK-3β inhibitor BIO and Wnt3A inhibited GSK-3β activity after AT2R knockdown and restored MuSC differentiation in vitro and skeletal muscle regeneration in vivo. Importatnly, we found that skeletal muscle regeneration was reduced (decreased regenerating myofiber size and myogenin/desmin expression) in a mouse myocardial infarction model of CHF, concomitantly with markedly blunted AT2R expression and with an increase of GSK-3β activity. In these mice, hindlimb injection of BIO inhibited GSK-3β activity and restored muscle regenerative capacity. These data indicate that AT2R/GSK-3β/β-catenin pathway plays a critical role in regulating MuSC differentiation and muscle regeneration, and could be a novel therapeutic target in wasting disorders such as CHF and CKD.
Author Disclosures: T. Yoshida: None. P. Delafontaine: None.
- © 2016 by American Heart Association, Inc.