title: Ultraviolet light (UVB and UVA) induces the damage-responsive transcription factor CHOP/gadd153 in murine and human epidermis: evidence for a mechanism specific to intact skin.
abstract: C/EBP-homologous protein (CHOP)/gadd153 (or CHOP) is a transcription factor induced by endoplasmic reticulum (ER) stress. Forcible overexpression of CHOP causes apoptosis in keratinocytes in culture. Here, we asked whether CHOP might be increased in the skin after UVB (280-320 nm) exposure, thus implicating CHOP in sunburn cell (SBC) formation. SKH-1 hairless mice were exposed to a ultraviolet (UV) source (80 mJ per cm2; approximately 74% UVB, approximately 16% UVA), and skin biopsies examined by immunohistology and immunoprecipitation. Compared with non-irradiated epidermis, CHOP expression was significantly increased at 30 min, and reached maximal levels by 24 h. Similar increases in CHOP following UVB exposure were observed in human buttock skin. The time course of CHOP expression preceded SBC formation and another marker of apoptosis, caspase-3 cleavage. Intracellular CHOP accumulated mainly in cytoplasmic and perinuclear locations, with little remaining in the nucleus. To examine mechanisms, cultured keratinocytes were irradiated in vitro and examined by western blotting. Under conditions that eliminated ER stress because of cell handling, CHOP did not accumulate (and was in fact decreased) in the cells. Thus, induction of CHOP in keratinocytes requires factors present only in the native skin. Overall, the data suggest that CHOP participates in adaptive responses of the epidermis following UVB/UVA exposure in vivo.
authors.affiliation: Department of Biomedical Engineering, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Anand
authors.forename: Enakshi
authors.initials: E
authors.lastname: Chakrabarti
authors.forename: Hiroko
authors.initials: H
authors.lastname: Kawamura
authors.forename: Charles R
authors.initials: CR
authors.lastname: Taylor
authors.forename: Edward V
authors.initials: EV
authors.lastname: Maytin
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D000078404:Epidermal Cells; D004817:Epidermis / Q000378:metabolism* / Q000528:radiation effects*; D005260:Female; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000378:metabolism*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C497249:DDIT3 protein, human; C497250:Ddit3 protein, mouse; D014157:Transcription Factors; D051742:Transcription Factor CHOP