736 UVA-induced photoaging inhibits autophagic degradation by impairing lysosomal function and cathepsins expression in dermal fibroblasts

Abstract

Radiation induced bystander effects(RIBE) refer to the reactions appearing in nonirradiated cells which triggered by the intercellular communication between directly irradiated cells and non-radiated cells. Ultraviolet radiation induced bystander effects(UV-RIBE) are a part of RIBE short of researches. Recent researches imply that exosome-mediated miRNAs play a role in RIBE. The exosomes were isolated from the culture medium of human skin fibroblasts(HSFs) by differential centrifugation. Three biology targets relevant to photo damage were used to measure the UV-RIBE, including cell proliferation capacity, degree of oxidative damage and apoptosis rate. The miR-4655-3p binding sites of E2F2 mRNA 3'UTR were forecasted by TargetScan and verified by dual luciferase reporter assay. The expression of miR-4655-3p were increased in HSFs exposed to UV radiation(20J/cm 2 single UVA radiation or 60mJ/cm 2 single UVB radiation ) and exosomes secreted from these cells. Exosomes from UV-irradiated HSFs induced UV-RIBE, including decreased cell proliferation capacity, increased oxidative damage and increased apoptosis rate of bystander cells. Up-or down-regulating the expression of miR-4655-3p in exosomes respectively enhanced or weakened UV-RIBE to some extent. miR-4655-3p down-regulated E2F2 mRNA expression by directly targeting its 3'UTR. Our outcomes prove that UV radiation ( including UVA and UVB ) could increase the miR-4655-3p expression in directly irradiated HSFs and miR-4655-3p addition promote their packaging into exosomes. Exosomal miR-4655-3p could contribute to UV-RIBE by directly repressing the expression of E2F2 mRNA.