MC3R activation does not attenuate pro‐inflammatory macrophage‐induced reductions in myoblast proliferation

Abstract

BackgroundActivation of the melanocortin‐3‐receptor (MC3R) has potent anti‐inflammatory effect on macrophages. Acute muscle injury (AMI) is followed by an invasion of pro‐inflammatory macrophages (MΦ1).ObjectiveThe objective of this experiment was to determine whether 1) MΦ1would affect myoblast proliferation, a key step in recovering from AMI and 2) whether MC3R activation would alleviate the effects of MΦ1 on myoblast proliferation.Methods and ResultsRAW 264.7 MΦ (2.0 × 106 in a 10‐cm dish) were treated with 10 ng/ml for 24 hours. Conditioned media was added to 0.5 × 106 C2C12 myoblasts in a 24‐well plate for 48 hours, then proliferation of the myoblasts was measured via the MTT assay. Proliferation of myoblasts treated with MΦ1‐conditioned media was significantly lower than controls from non‐activated MΦ1. Alternatively, the MΦ1were scraped, and 5,000 MΦ1were co‐cultured with 0.5 × 106 C2C12 myoblasts in a 24‐well plate for 48 hours. Myoblasts in the presence of MΦ1also had significantly decreased proliferation, providing additional evidence that MΦ1 reduce myoblast proliferation. Pre‐treatment of the MΦ for 24 hours with 100 nM MT‐II, a MC3R agonist, did not attenuate the decreased proliferation. Current experiments are examining the possibility of a dose‐response relationship.Supported by Winston‐Salem State University Department of Life Sciences.