Abstract 13433: Angiotensin II Type 2 Receptor Regulates Skeletal Myoblast Differentiation: 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. However, the potential role of Ang II type 2 receptor (AT2R) signaling in skeletal muscle physiology remains unknown. We found that AT2R expression was robustly increased in mouse skeletal myoblasts during differentiation, suggesting that the AT2R plays an important role in skeletal muscle regeneration. To test this hypothesis, we infused mice with AT2R antagonist PD123319 (PD, 30 mg/kg/d) or agonist CGP123319 (CGP, 1 μg/kg/min) during cardiotoxin (CTX)-induced muscle injury and regeneration. PD reduced the size of regenerating myofibers (727.5±54.6 and 516.0±37.0 μm2 in sham and PD, respectively, p<0.05) and expression of the myoblast differentiation markers myogenin and eMyHC (56.9% and 40.2% decrease in PD, respectively. p<0.01), whereas CGP had the opposite effects. siRNA mediated AT2R knockdown in mouse primary myoblasts suppressed the increase of myogenin and desmin, resulting in lowered differentiation. We analyzed changes in phosphoprotein levels in myoblasts after AT2R knockdown by phosphoprotein array and identified multiple changes, including increased phospho-ERK1/2 levels. Importantly, inhibition of ERK1/2 restored normal myoblast differentiation in the setting of AT2R knockdown, suggesting the AT2R positively regulates myoblast differentiation by reducing ERK1/2 activity. Furthermore, 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 increase of AT2R expression, strongly suggesting that the AT2R plays an important role in the reduction of skeletal muscle function in CHF. These data indicate that AT2R signaling positively regulates myoblast differentiation and potentiates skeletal muscle regeneration, providing a new therapeutic target in wasting disorders such as CHF and CKD.
- Angiotensin II
- Muscle, skeletal
- Stem/progenitor cells
- Receptor-mediated signaling
- Regenerative medicine stem cells
Author Disclosures: T. Yoshida: None. P. Delafontaine: None.
- © 2014 by American Heart Association, Inc.