title: A role for Bach1 and HO-2 in suppression of basal and UVA-induced HO-1 expression in human keratinocytes.
abstract: Ultraviolet A (UVA) radiation is an oxidizing agent that strongly induces the heme oxygenase 1 (HO-1) gene and expression of the protein in cultured human skin fibroblasts but weakly induces it in skin keratinocytes. Lower basal levels of HO-1 and much higher basal levels of HO-2 protein are observed in keratinocytes compared with fibroblasts. Using both overexpression and knockdown approaches, we demonstrate that HO-2 modulates basal and UVA-induced HO-1 protein levels, whereas HO-1 levels do not affect HO-2 levels in skin fibroblasts and keratinocytes. Silencing of Bach1 strongly increases HO-1 levels in transformed HaCaT keratinocytes and these HO-1 levels are not further increased by either UVA irradiation or silencing of HO-2. This is consistent with the conclusion that high constitutive levels of HO-2 expression in keratinocytes are responsible for the resistance of these cells to HO-1 induction by UVA radiation and that Bach1 plays a predominant role in influencing the lack of HO-1 expression in keratinocytes. Bach1 inhibition leading to HO-1 induction reduced UVA-irradiation-induced damage as monitored both by the extent of LDH release and by nuclear condensation, so that Bach1 inhibition seems to protect against UVA-irradiation-induced damage in keratinocytes.
authors.affiliation: Department of Pharmacy and Pharmacology, University of Bath, Bath BA2 7AY, UK.
authors.forename: Julia Li
authors.initials: JL
authors.lastname: Zhong
authors.forename: Chintan
authors.initials: C
authors.lastname: Raval
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Edwards
authors.forename: Rex M
authors.initials: RM
authors.lastname: Tyrrell
mesh_terms: D050976:Basic-Leucine Zipper Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051856:Fanconi Anemia Complementation Group Proteins / Q000235:genetics / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D006367:HeLa Cells; D006419:Heme Oxygenase (Decyclizing) / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism; D018384:Oxidative Stress / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D011836:Radiation Tolerance / Q000235:genetics; D012867:Skin / Q000473:pathology; D014162:Transfection; D014466:Ultraviolet Rays
chemical_list: C102108:BACH1 protein, human; D050976:Basic-Leucine Zipper Transcription Factors; D051856:Fanconi Anemia Complementation Group Proteins; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D034741:RNA, Small Interfering; C496541:HMOX1 protein, human; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C105245:heme oxygenase-2