Increased expression of TRPV1 channel in intrinsically aged and photoaged human skin in vivo.

Transient receptor potential vanilloid type 1 (TRPV1) is activated by various stimuli including capsaicin, heat and acid. While TRPV1 has been localized in the epidermis, little is known about the physiological role of TRPV1 in the skin, especially in skin ageing. In this study, we investigated the effect of acute UV irradiation on TRPV1 expression in human skin and the changes in TRPV1 mRNA and protein in intrinsic ageing and photoageing using human sun-protected (upper inner arm) and sun-exposed (forearm) skin of young and elderly subjects. Western blot analysis of UV-irradiated young buttock skin revealed that the expression of TRPV1 protein was increased at 24 h (2.3-fold) and 48 h (2.4-fold) after UV irradiation. Real-time PCR analysis also showed that the mRNA level of TRPV1 was augmented by 2.4-fold at 4 h after UV irradiation. TRPV1 protein was expressed at higher levels by 2.6-fold in the sun-protected skin of the elderly subjects than in that of young people according to western blotting, real-time PCR analysis and immunohistochemical staining. In addition, the photoaged skin of elderly showed increased expression of TRPV1 mRNA and protein compared with that of the sun-protected skin of the same individuals. Also, we found increased expression of TRPV1 in nerve fibres of elderly persons using double staining of TRPV1 and nerve fibres. Based on the above results, our data suggest that the expression of TRPV1 is affected by both the intrinsic ageing and photoageing processes.