title: Contributions of reactive oxygen species and mitogen-activated protein kinase signaling in arsenite-stimulated hemeoxygenase-1 production.
abstract: Hemeoxygenase-1 (HO-1) is an oxidative stress responsive gene upregulated by various physiological and exogenous stimuli. HO-1 has cytoprotective activities and arsenite is a potent inducer of HO-1 in many cell types and tissues, including epidermal keratinocytes. We investigated the potential contributions of reactive oxygen species (ROS) generation and mitogen-activated protein kinase (MAPK) activation to arsenite-dependent regulation of HO-1 in HaCaT cells, an immortalized human keratinocyte line. Both epidermal growth factor (EGF) and arsenite stimulated ROS production was detected by dihydroethidium (DHE) staining and fluorescence microscopy. Arsenite induced HO-1 in a time- and concentration-dependent manner, while HO-1 expression in response to EGF was modest and evident at extended time points (48-72 h). Inhibition of EGF receptor, MEK I/II or Src decreased arsenite-stimulated HO-1 expression by 20-30%. In contrast, addition of a superoxide scavenger or inhibition of p38 activity decreased the arsenite-dependent response by 80-90% suggesting that ROS and p38 are required for HO-1 induction. However, ROS generation alone was insufficient for the observed arsenite-dependent response as use of a xanthine/xanthine oxidase system to generate ROS did not produce an equivalent upregulation of HO-1. Cooperation between ERK signaling and ROS generation was demonstrated by synergistic induction of HO-1 in cells co-treated with EGF and xanthine/xanthine oxidase resulting in a response nearly equivalent to that observed with arsenite. These findings suggest that the ERK/MAPK activation is necessary but not sufficient for optimal arsenite-stimulated HO-1 induction. The robust and persistent upregulation of HO-1 may have a role in cellular adaptation to chronic arsenic exposure.
authors.affiliation: MSC09 5360, 1 University of New Mexico Health Sciences Center, Program in Toxicology, College of Pharmacy, Albuquerque, NM 87131, USA.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Cooper
authors.forename: Ke Jian
authors.initials: KJ
authors.lastname: Liu
authors.forename: Laurie G
authors.initials: LG
authors.lastname: Hudson
mesh_terms: D018053:Arsenites / Q000494:pharmacology*; D002460:Cell Line; D004815:Epidermal Growth Factor / Q000494:pharmacology; D051547:Heme Oxygenase-1 / Q000096:biosynthesis*; D006801:Humans; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D034741:RNA, Small Interfering / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013268:Stimulation, Chemical; D014969:Xanthine Oxidase / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000096:biosynthesis
chemical_list: D018053:Arsenites; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D004815:Epidermal Growth Factor; D051547:Heme Oxygenase-1; D014969:Xanthine Oxidase; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C015001:arsenite