α-Melanocyte-stimulating hormone (α-MSH) is an endogenous peptide hormone and neuropeptide of the melanocortin family, with a tridecapeptide structure and the amino acid sequence Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. It is the most important of the melanocyte-stimulating hormones (MSHs) (also known as melanotropins) in stimulating melanogenesis, a process that in mammals (including humans) is responsible for pigmentation primarily of the hair and skin. It also plays a role in feeding behavior, energy homeostasis, sexual activity, and protection against ischemia and reperfusion injury.

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The alpha-melanocyte stimulating hormone (α-MSH) is a neuropeptide belonging to the melanocortin family. It is well known for its anti-inflammatory and antipyretic effects and shares several characteristics with antimicrobial peptides (AMPs). There have been some recent reports about the direct antimicrobial activity of α-MSH against various microbes belonging to both fungal and bacterial pathogens. Similar to α-MSH's anti-inflammatory properties, its C-terminal residues also exhibit antimicrobial activity parallel to that of the entire peptide. This review is focused on the current findings regarding the direct antimicrobial potential and immunomodulatory mechanism of α-MSH and its C-terminal fragments, with particular emphasis on the prospects of α-MSH based peptides as a strong anti-infective agent.

Singh, M., & Mukhopadhyay, K. (2014). Alpha-melanocyte stimulating hormone: an emerging anti-inflammatory antimicrobial peptide. BioMed research international, 2014.

Although melanocyte stimulating hormone (MSH) peptides are known to stimulate pigmentation in man, previous reports suggest that human melanocytes are relatively unresponsive to these peptides in vitro. This may be related to the conditions under which the melanocytes were cultured. Thus, we have re-investigated the in vitro effects of MSH peptides using human melanocytes cultured in the absence of artificial mitogens. Human melanocytes were incubated with alpha-MSH or its potent analogue Nle4Dphe7 alpha-MSH for 3 days. After 18 hours, melanocyte morphology had evolved from mainly bipolar to dendritic in approximately 66% of cultures.

Hunt, G., Todd, C., Cresswell, J. E., & Thody, A. J. (1994). Alpha-melanocyte stimulating hormone and its analogue Nle4DPhe7 alpha-MSH affect morphology, tyrosinase activity and melanogenesis in cultured human melanocytes. Journal of Cell Science, 107(1), 205-211.

Melanocortins are known to affect feeding and probably insulin activity through the central nervous system. It was also recently shown that peripheral alpha-melanocyte-stimulating hormone (alpha-MSH) administration can reduce weight gain in both genetic and diet-induced obese mice. As obesity is often associated with disregulation of glucose and insulin, we investigated the nature of glucose homeostasis in the obese pro-opiomelanocortin (POMC) knockout mouse. Here we report that though they are obese, mice deficient in POMC (and, thereby, deficient in alpha-MSH) are euglycemic throughout their lives.

Brennan, M. B., Costa, J. L., Forbes, S., Reed, P., Bui, S., & Hochgeschwender, U. (2003). α-Melanocyte-Stimulating Hormone Is a Peripheral, Integrative Regulator of Glucose and Fat Metabolism. Annals of the New York Academy of Sciences, 994(1), 282-287.