The preventive effects of natural plant compound carvacrol against combined UVA and UVB-induced endoplasmic reticulum stress in skin damage of rats

The skin is constantly exposed to a variety of environmental stressors, including ultraviolet (UV) radiation. Exposure of the skin to UV radiation causes a number of detrimental biological damages such as endoplasmic reticulum (ER) stress. The ER stress response is a cytoprotective mechanism that maintains homeostasis of the ER by increasing the capacity of the ER against the accumulation of unfolded proteins in the ER. Carvacrol (CRV) is a monoterpenoid phenol found in essential oils with antimicrobial and anti-inflammatory activities. We investigated for the first time in the literature the potential protective role of CRV against combined UVA and UVB-induced skin damage by targeting the ER stress pathway in a rat model. For this purpose, expressions of Grp78, Perk, Atf6, Ire-1, Chop, Xbp1, Casp12, elF2α, and Traf2 genes related to ER stress were analyzed by RT-PCR and protein expression levels of GRP78, ATF6, CHOP, and XBP1 were determined by ELISA assay in tissue sections taken from the back of the rats. As a result of analysis, it was seen that the expression levels of aforementioned ER stress genes increased significantly in the UVA + UVB irradiated group compared to the control group, while their expression levels decreased markedly by supplementation of CRV in UVA + UVB + CRV group. With regard to expressions of foregoing proteins, their levels escalated notably with UVA + UVB application and decreased markedly by CRV supplementation. In conclusion, present study revealed that CRV ameliorates UVA + UVB-induced ER stress via reducing the expression of mRNA as well as proteins involved in the unfolded protein response (UPR) pathway and inducing apoptosis as evidenced from high Caspase12 level.