title: L-arginine increases UVA cytotoxicity in irradiated human keratinocyte cell line: potential role of nitric oxide.
abstract: Human fibroblasts and keratinocytes possess nitric oxide synthases (NOS), which metabolize L-arginine (L-Arg) for producing nitric oxide (NO*). This report delineates the relations between NO* and UVA in the human keratinocyte cell line HaCaT. NOS activity was stimulated by exposure of cells to L-Arg just after irradiation. L-Arg (5 mM) supply led to an increase in UVA (25.3 J/cm(2)) cytotoxicity (% of viability 18 +/- 3%) whereas neither L-Arg itself nor UVA irradiation induced cell death at the doses used in this study. Cells were also treated either with L-thiocitrulline (L-Thio), an irreversible inhibitor of NOS, or with exogenous superoxide dismutase (SOD) and catalase. L-Thio and SOD prevented L-Arg-mediated deleterious effects in irradiated cells, whereas catalase was ineffective. Intracellular antioxidant enzyme activities were also determined. UVA/L-Arg stress altered catalase (66% decrease) and glutathione peroxidase (83% decrease). DNA damage was evaluated using the 'comet assay' and quantified using the 'tail moment'. UVA alone was genotoxic (mean tail moment: 25.43 +/- 1.23, P<0.001 compared control cells). The addition of L-Arg potentiated DNA damage (mean tail moment: 41.05+/-3.9) whereas L-Thio prevented them (mean tail moment 9.86 +/- 0.98). We attempted to assess the effect of poly(ADP-ribose) polymerase (PARP) inhibition on cell death. Using the PARP inhibitor 3-aminobenzamide, we established that PARP determines both cell lysis and DNA damage induced by UVA and/or L-Arg. Our findings demonstrated that L-Arg was able to increase UVA-mediated deleterious effects in keratinocytes (both DNA damage and cytotoxicity) and that the ratio NO*/O2*- plays a key role in these processes.
authors.affiliation: LBSO/LCR7 No. 8-Université Joseph Fourier, F-38043 Grenoble Cedex 03, France.
authors.forename: C
authors.initials: C
authors.lastname: Didier
authors.forename: N
authors.initials: N
authors.lastname: Emonet-Piccardi
authors.forename: J C
authors.initials: JC
authors.lastname: Béani
authors.forename: J
authors.initials: J
authors.lastname: Cadet
authors.forename: M J
authors.initials: MJ
authors.lastname: Richard
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D001120:Arginine / Q000633:toxicity*; D002374:Catalase / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival; D002956:Citrulline / Q000031:analogs & derivatives / Q000494:pharmacology; D004249:DNA Damage; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000201:enzymology / Q000528:radiation effects*; D008667:Metalloproteins / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000378:metabolism; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D026423:S-Nitroso-N-Acetylpenicillamine; D013482:Superoxide Dismutase / Q000378:metabolism; D013890:Thiourea / Q000031:analogs & derivatives / Q000494:pharmacology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D000975:Antioxidants; D008667:Metalloproteins; D020030:Nitric Oxide Donors; C086715:thiocitrulline; D002956:Citrulline; D009569:Nitric Oxide; D026423:S-Nitroso-N-Acetylpenicillamine; D001120:Arginine; D002374:Catalase; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D011065:Poly(ADP-ribose) Polymerases; D010396:Penicillamine; D013890:Thiourea