Cell surface expression of melanocortin-1 receptor on HaCaT keratinocytes and alpha-melanocortin stimulation do not affect the formation and repair of UVB-induced DNA photoproducts

摘要

Ultraviolet (UV) exposure induces an up-regulation of melanocortin-1 receptor (MC1R) expression in human skin and the alpha-melanocyte-stimulating hormone (a-MSH) may reduce UVB-induced DNA damage in normal human melanocytes.Using high-performance liquid chromatography coupled to tandem mass spectrometry,we investigated the formation and repair of DNA lesions in UVB-irradiated HaCaT cells stably transfected with the wild type MC1R gene (HaCaT-MClR).Similar levels of 8 bipyrimidine photoproducts including cyclobutane pyrimidine dimers (CPDs) (ToT,ToC,CoT),(6-4) photoproducts ((6-4)PPs) (TT-(6-4)PPs,TC-(6-4)PPs) and their Dewar valence isomers together with 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) were found to be generated in both non-transfected and HaCaT-MClR cells after UVB exposure.Time-course studies of DNA photoproduct yields indicated that the DNA repair ability depended upon radiation doses.It was shown that (6-4)PPs were removed from the DNA of UVB-irradiated cells much more efficiently than CPDs.The repair efficiency of 8-oxodGuo,CPDs and (6-4)PPs was relatively similar in both cell lines and was not modified by stimulation with a-MSH before UVB-exposure.In conclusion,cell surface-enforced expression of MClRs on HaCaT keratinocytes and alpha-MSH stimulation do not affect the formation of UVB-induced DNA photoproducts and their subsequent repair.