A Possible Role of a Stress Hormone in Acne : Toll-like Receptor 2 Expression Is Enhanced by Glucocorticoids in Human Keratinocytes

Abstract

A link between psychosocial stress and acne has long been postulated, but its mechanism is not yet clear. Cortisol, the main glucocorticoid (GC) in humans, is considered a stress hormone. It is well known that GC treatment provokes an acneiform reaction. Toll-like receptor 2 (TLR2) activation by Propionibacterium acnes (P. acnes) may induce skin inflammation via induction of various proinflammatory molecules. In this study, we examined the effects of GC on TLR2 expression in cultured human keratinocytes (HK) to elucidate a relationship between stress and acne. The addition of GC to HK markedly enhanced their TLR2 gene expression, which was further stimulated by P. acnes, TNF-α or IL-1α. Moreover, Melia azadirachta extract had potent inhibitory activity against TLR2 expression induced by GC and TNF-α. These findings suggest that GC-enhanced TLR2 expression plays an important role in the exacerbation of acne. Moreover, Melia azadirachta extract may be useful to prevent inflammation of stress-induced acne.