title: Heavy metal chelator TPEN attenuates fura-2 fluorescence changes induced by cadmium, mercury and methylmercury.
abstract: Stimulation with heavy metals is known to induce calcium (Ca(2+)) mobilization in many cell types. Interference with the measurement of intracellular Ca(2+) concentration by the heavy metals in cells loaded with Ca(2+) indicator fura-2 is an ongoing problem. In this study, we analyzed the effect of heavy metals on the fura-2 fluorescence ratio in human SH-SY5Y neuroblastoma cells by using TPEN, a specific cell-permeable heavy metal chelator. Manganese chloride (30-300 µM) did not cause significant changes in the fura-2 fluorescence ratio. A high concentration (300 µM) of lead acetate induced a slight elevation in the fura-2 fluorescence ratio. In contrast, stimulation with cadmium chloride, mercury chloride or MeHg (3-30 µM) elicited an apparent elevation of the fura-2 fluorescence ratio in a dose-dependent manner. In cells stimulated with 10 or 30 µM cadmium chloride, the addition of TPEN decreased the elevated fura-2 fluorescence ratio to basal levels. In cells stimulated with mercury or MeHg, the addition of TPEN significantly decreased the elevation of the fura-2 fluorescence ratio induced by lower concentrations (10 µM) of mercury or MeHg, but not by higher concentrations (30 µM). Pretreatment with Ca(2+) channel blockers, such as verapamil, 2-APB or lanthanum chloride, resulted in different effects on the fura-2 fluorescence ratio. Our study provides a characterization of the effects of several heavy metals on the mobilization of divalent cations and the toxicity of heavy metals to neuronal cells.
authors.affiliation: Department of Veterinary Pharmacology, Joint Faculty of Veterinary Medicine, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Ohkubo
authors.forename: Atsushi
authors.initials: A
authors.lastname: Miyamoto
authors.forename: Mitsuya
authors.initials: M
authors.lastname: Shiraishi
mesh_terms: D001896:Boron Compounds / Q000494:pharmacology; D002105:Cadmium Poisoning / Q000188:drug therapy*; D002118:Calcium / Q000032:analysis; D002121:Calcium Channel Blockers / Q000494:pharmacology; D045744:Cell Line, Tumor; D002614:Chelating Agents / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005029:Ethylenediamines / Q000494:pharmacology*; D005453:Fluorescence; D016257:Fura-2 / Q000378:metabolism*; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D008630:Mercury Poisoning / Q000188:drug therapy*; D008767:Methylmercury Compounds / Q000506:poisoning*; D009447:Neuroblastoma / Q000737:chemistry / Q000378:metabolism; D014700:Verapamil / Q000494:pharmacology
chemical_list: D001896:Boron Compounds; D002121:Calcium Channel Blockers; D002614:Chelating Agents; D005029:Ethylenediamines; D008767:Methylmercury Compounds; C028521:lanthanum chloride; D007811:Lanthanum; D014700:Verapamil; C109986:2-aminoethoxydiphenyl borate; C044387:N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine; D002118:Calcium; D016257:Fura-2