α-Melanocyte-stimulating hormone alleviates pathological cardiac remodeling via melanocortin 5 receptor.

α-Melanocyte-stimulating hormone (α-MSH) regulates diverse physiological functions by activating melanocortin receptors (MC-R). However, the role of α-MSH and its possible target receptors in the heart remain completely unknown. Here we investigate whether α-MSH could be involved in pathological cardiac remodeling. We found that α-MSH was highly expressed in the mouse heart with reduced ventricular levels after transverse aortic constriction (TAC). Administration of a stable α-MSH analog protected mice against TAC-induced cardiac hypertrophy and systolic dysfunction. In vitro experiments revealed that MC5-R in cardiomyocytes mediates the anti-hypertrophic signaling of α-MSH. Silencing of MC5-R in cardiomyocytes induced hypertrophy and fibrosis markers in vitro and aggravated TAC-induced cardiac hypertrophy and fibrosis in vivo. Conversely, pharmacological activation of MC5-R improved systolic function and reduced cardiac fibrosis in TAC-operated mice. In conclusion, α-MSH is expressed in the heart and protects against pathological cardiac remodeling by activating MC5-R in cardiomyocytes. These results suggest that analogs of naturally occurring α-MSH, that have been recently approved for clinical use and have agonistic activity at MC5-R, may be of benefit in treating heart failure.