Minocycline modulation of alpha-MSH production by keratinocytes in vitro

The anti-inflammatory mechanisms of minocycline, an antibiotic used in the treatment of the inflammatory component of acne, are only partially understood. In addition to inflammation due to cytokines (IL-1, IL-6, TNF-alpha, etc.), recent studies have shown that neuropeptide-mediated neurogenic inflammation may play an important role in cutaneous inflammation. The purpose of this study was to investigate minocycline-induced modulation of cutaneous production of alpha-melanocyte-stimulating hormone (alpha-MSH), a neuropeptide with known anti-inflammatory activity. Two different skin models were used: explants of inflammatory skin and reconstituted skin, both incubated with minocycline at different concentrations and for different time periods. Epidermal production of alpha-MSH, as evaluated by immunofluorescence and immunoperoxidase techniques, showed increased expression in both models. This neuropeptide, which has an anti-inflammatory activity (notably through production of IL-10, antagonism of IL-1 and inhibition of the chemotaxis of polymorphonuclear leukocytes), thus plays a role in the anti-inflammatory action of minocycline.