CS affects keratinocytes SRB1 expression and localizazion via the production of H202 and formation 4HNE protein adducts

Scavenger Receptor B1 (SRB1), also known as HDL receptor, is involved in cellular cholesterol uptake. Stratum corneoum (SC), the outermost layer of the skin, is composed for more than 25% by cholesterol. Several reports support the view that alteration of SC lipids composition may be the cause of impaired barrier function which gives rise to several skin diseases. For this reason the regulation of the genes involved in cholesterol uptake is of extreme significance for skin health. Being the first shield against the outdoor insults, the skin is exposed to several noxious substances and among these is cigarette smoke (CS) which has been recently associated to various skin pathologies. Using immunoblotting, immunoprecipitation, RT-PCR, and confocal microscopy we have demonstrated that the translocation and the consecutive lost of SRB1 in human keratinocytes after CS exposure is driven by hydrogen peroxide (H2O2) which derives not only from the CS gas phase but mainly from the activation of cellular NADPH oxidase (NOX). This effect was reversed when the cells were pretreated with NOX inhibitors, catalase, or superoxide dismutase (SOD) inhibitor. Furthermore, CS caused the formation of SRB1-aldheydes adducts (Acrolein and 4-Hydroxynonenal) and the increased of its ubiquitination which is the cause of SRB1 lost. In conclusion, exposure to CS, through the production of H2O2, induced post-translational modifications of SRB1 with the consequence lost of the receptor and this may contribute to the skin physiology alteration.