TRPA1 as a Key Regulator of Keratinocyte Homeostasis and Inflammation in Human Skin.

The Transient Receptor Potential Ankyrin 1 (TRPA1) channel is a non-selective cation channel activated by a range of physical and chemical stimuli. While primarily studied in neuronal tissues, TRPA1 is also expressed in human keratinocytes, where its role remains poorly understood. Here, we investigated TRPA1 expression and function in keratinocytes and examined the effects of its activation on cellular proliferation, immune activation, and neuropeptide release under both basal and inflammatory stimuli. TRPA1 expression was detected in basal keratinocytes and was upregulated by pro-inflammatory cytokines. Stimulation with the TRPA1 agonist allyl isothiocyanate (AITC) induced a rapid calcium influx, confirming functional channel activity. AITC at 5 µM did not induce cytotoxicity but significantly reduced keratinocyte proliferation and caused cell cycle arrest. Under stimulation with TNF-α and IFN-γ, TRPA1 activation decreased the surface expression of HLA-DR and ICAM-1, and downregulated mRNA levels of CXCL10, CXCL8, CCL5, and CCL20, while IL-6 expression remained unchanged. Furthermore, AITC treatment reduced the secretion of Substance P, but not CGRP. These findings indicate that TRPA1 functions as a cytokine-inducible, immunomodulatory receptor in human keratinocytes, capable of attenuating proliferation and inflammatory activation without compromising cell viability, thereby suggesting a potential role in maintaining skin homeostasis and modulating cutaneous inflammation.