Heat promotes melanogenesis by increasing the paracrine effects in keratinocytes via the TRPV3/Ca2+/Hh signaling pathway

Global warming and rising temperature significantly increase the incidence of heat stress, which is known to affect the process of inflammation and aging. However, the effect of heat stress on skin melanogenesis is not fully known. We found that healthy foreskin tissues underwent significant pigmentation when exposed to 41℃. Furthermore, heat stress promoted melanogenesis in pigment cells by increasing the paracrine effects of keratinocytes. High-throughput RNA sequencing showed that heat stress activates the Hedgehog (Hh) signaling pathway in keratinocytes. The agonists of Hh signaling promote the paracrine effect of keratinocytes on melanogenesis. In addition, TRPV3 agonists activate the Hh signaling in keratinocytes and augment its paracrine effect on melanogenesis. The heat-induced activation of Hh signaling is dependent on TRPV3-mediated Ca2+ influx. Heat exposure promotes melanogenesis by increasing the paracrine effects in keratinocytes via the TRPV3/Ca2+/Hh signaling pathway. Our findings provide insights into the mechanisms of heat-induced skin pigmentation. The experiment was divided into two groups, with a control group of three samples and an experimental group of three samples. The control group treated HaCaT cells at 37℃ for 3 days, 1 hour per day, while the experimental group treated HaCaT cells at 41℃ for 3 days, 1 hour per day.