UVB Upregulates Inflammatory Cytokines in Rosacea Cell Model by Promoting the Expression of TRPVs and TLR2

The expression of transient receptor potential vanilloid (TRPV) and Toll-like receptor 2 (TLR2) in the lesion sites of patients with rosacea is increased. Ultraviolet B (UVB) radiation can induce inflammation of keratinocytes in patients with rosacea, but the relationships between UVB and TRPVs/TLR2 in rosacea remain unclear.

RT-qPCR and Western Blot were applied to determine the expression levels of TRPV1, TRPV2, TRPV3, TRPV4 and TLR2 in the rosacea keratinocyte model after ultraviolet irradiation (n=3). After treating the rosacea cell model with TRPV1, TRPV4 and TLR2 inhibitors, ELISA was used to detect the expressions of rosacea-associated inflammatory cytokines in rosacea cells exposed to UVB, including IL-1β, IL-6, IL-8 and TNF-α (n=6). The changes in DNA methylation levels of TRPV1, TRPV4 and TLR2 promoters were detected by MeDIP, and the levels of histone modifications H3K4me3, H3K9me3 and H3K27me3 were determined by ChIP (n=3).

UVB exposure increases the secretion levels of rosacea-associated inflammatory cytokines in HaCaT cells and LL-37-induced rosacea keratinocyte models, and promotes the expression of TRPV1, TRPV4 and TLR2 at mRNA and protein levels (P < 0.05). In the LL-37-induced HaCaT cell model, TRPV1 and TLR2 antagonists reduced the secretion levels of IL-1β and IL-8, and TRPV4 antagonists reduced IL-6 secretion level (P < 0.05). Under UVB exposure, TRPV4 and TLR2 antagonists respectively reduced the concentrations of IL-1β and TNF-α in the HaCaT cells stimulated by LL-37 (P < 0.05). In addition, UVB exposure increased the H3K4me3 level of the TRPV1 promoter region in HaCaT cells treated by LL-37 (P < 0.05).

Our results indicate that UVB induces inflammatory cytokines in rosacea keratinocyte models through upregulation of TRPV1, TRPV4, and TLR2 expression, potentially mediated by epigenetic mechanisms.