title: Opening of chloride channels by 1α,25-dihydroxyvitamin D3 contributes to photoprotection against UVR-induced thymine dimers in keratinocytes.
abstract: UVR produces vitamin D in skin, which is hydroxylated locally to 1α,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)). 1,25(OH)(2)D(3) protects skin cells against UVR-induced DNA damage, including thymine dimers, but the mechanism is unknown. As DNA repair is inhibited by nitric oxide (NO) products but facilitated by p53, we examined whether 1,25(OH)(2)D(3) altered the expression of nitrotyrosine, a product of NO, or p53 after UVR in human keratinocytes. 1,25(OH)(2)D(3) and the nongenomic agonist 1α,25-dihydroxylumisterol(3) reduced nitrotyrosine 16 hours after UVR, detected by a sensitive whole-cell ELISA. p53 was enhanced after UVR, and this was further augmented in the presence of 1,25(OH)(2)D(3). DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid), a chloride channel blocker previously shown to prevent 1,25(OH)(2)D(3)-induced chloride currents in osteoblasts, had no effect on thymine dimers on its own but prevented the 1,25(OH)(2)D(3)-induced protection against thymine dimers. Independent treatment with DIDS, at concentrations that had no effect on thymine dimers, blocked UVR-induced upregulation of p53. In contrast, reduction of nitrotyrosine remained in keratinocytes treated with 1,25(OH)(2)D(3) and DIDS at concentrations shown to block decreases in post-UVR thymine dimers. These results suggest that 1,25(OH)(2)D(3)-induced chloride currents help protect from UVR-induced thymine dimers, but further increases in p53 or reductions of nitrotyrosine by 1,25(OH)(2)D(3) are unlikely to contribute substantially to this protection.
authors.affiliation: Department of Physiology, Bosch Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Vanessa B
authors.initials: VB
authors.lastname: Sequeira
authors.affiliation: Department of Physiology, Bosch Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Rybchyn
authors.affiliation: Department of Physiology, Bosch Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Clare
authors.initials: C
authors.lastname: Gordon-Thomson
authors.affiliation: Department of Physiology, Bosch Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Wannit
authors.initials: W
authors.lastname: Tongkao-On
authors.affiliation: Department of Biochemistry, University of California, Riverside, Riverside, California, USA.
authors.forename: Mathew T
authors.initials: MT
authors.lastname: Mizwicki
authors.affiliation: Department of Biochemistry, University of California, Riverside, Riverside, California, USA.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: Norman
authors.affiliation: Faculty of Veterinary Science, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Vivienne E
authors.initials: VE
authors.lastname: Reeve
authors.affiliation: Department of Dermatology (Medicine), Bosch Institute, University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Gary M
authors.initials: GM
authors.lastname: Halliday
authors.affiliation: Department of Physiology, Bosch Institute, University of Sydney, Sydney, New South Wales, Australia. Electronic address: rebeccam@physiol.usyd.edu.au.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Mason
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D002478:Cells, Cultured; D018118:Chloride Channels / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000502:physiology; D004249:DNA Damage / Q000502:physiology / Q000528:radiation effects*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects*; D008297:Male; D011740:Pyrimidine Dimers / Q000378:metabolism / Q000528:radiation effects*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects*; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D018118:Chloride Channels; D011740:Pyrimidine Dimers; D016159:Tumor Suppressor Protein p53; C118756:dihydroxy-vitamin D3; D014807:Vitamin D; C002744:3-nitrotyrosine; D014443:Tyrosine; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid