Calcium-dependent nitric oxide production is involved in arsenite-induced micronuclei.
Arsenic, a human carcinogen is known to induce sister-chromatid exchanges, chromosome aberrations and micronuclei (MN), but its mechanisms remain unknown. Recently, independent studies have suggested that intracellular calcium and reactive oxygen species are involved in arsenite-induced MN, and nitric oxide (NO) is involved in arsenite-induced poly(ADP-ribosylation). The aim of this research is to investigate the involvement of these molecules in arsenite-induced MN. The intracellular oxidant level and calcium level were monitored with a flow cytometer by using dichlorofluorescein diacetate and fluo3-AM, respectively. The NO production was estimated from the nitrite in cell culture medium with a spectrophotometer by using diaminonaphthalene. The results show that a 4-h treatment with arsenite above 5 microM, caused a dose-dependent increase of oxidant, NO, as well as intracellular calcium level. The arsenite-increased intracellular oxidant level was inhibited by NO synthase inhibitors, S-methyl-l-thiocitrulline and Nomega-nitro-l-arginine methyl ester and calcium chelators, ethylene glycol-bis (beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, and 2-[(2-bis-[carboxymethyl]-amino-5-methylphenoxy)-methyl]-6-methoxy-8- bis[carboxy-methyl]aminoquinoline, but not by catalase inhibitor, 3-aminotriazole. The arsenite-increased NO could also be suppressed by NO synthase inhibitors and calcium chelator. However, the arsenite-increased intracellular calcium level was inhibited by calcium chelators, but not by NO synthase inhibitors. A 4-h treatment with arsenite above 10 microM, also induced MN dose-dependently. The arsenite-increased MN could be reduced by NO synthase inhibitors, calcium chelators, as well as superoxide dismutase and uric acid. These results suggest the involvement of peroxynitrite in arsenite-induced MN. We surmise that the disturbance of NO production may cause cardio/peripheral vascular disorders, and the peroxynitrite-mediated DNA damages may cause genetic instability and, hence, cancers in arsenic-exposed humans.
Gurr
J R
JR
Institute of Radiation Biology, National Tsing-Hua University, Hsinchu 30043, Taiwan.
Liu
F
F
Lynn
S
S
Jan
K Y
KY
D000818:Animals; D018053:Arsenites / Q000633:toxicity*; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism*; D002374:Catalase / Q000037:antagonists & inhibitors / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D006224:Cricetinae; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D048629:Micronuclei, Chromosome-Defective / Q000187:drug effects* / Q000502:physiology; D015162:Micronucleus Tests; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D016877:Oxidants / Q000378:metabolism
D018053:Arsenites; D002614:Chelating Agents; D004791:Enzyme Inhibitors; D016877:Oxidants; D009569:Nitric Oxide; D004533:Egtazic Acid; D006861:Hydrogen Peroxide; D002374:Catalase; D019001:Nitric Oxide Synthase; C015001:arsenite; D002118:Calcium; D019331:NG-Nitroarginine Methyl Ester