title: Effect of methoxychlor on Ca2+ handling and viability in OC2 human oral cancer cells.
abstract: The effect of the insecticide methoxychlor on the physiology of oral cells is unknown. This study aimed to explore the effect of methoxychlor on cytosolic Ca(2+) concentrations ([Ca(2+)](i)) in human oral cancer cells (OC2) by using the Ca(2+)-sensitive fluorescent dye fura-2. Methoxychlor at 5-20 μM increased [Ca(2+)](i) in a concentration-dependent manner. The signal was reduced by 70% by removing extracellular Ca(2+). Methoxychlor-induced Ca(2+) entry was not affected by nifedipine, econazole, SK&F96365 and protein kinase C modulators but was inhibited by the phospholipase A2 inhibitor aristolochic acid. In Ca(2+)-free medium, treatment with the endoplasmic reticulum Ca(2+) pump inhibitor thapsigargin or 2,5-di-tert-butylhydroquinone (BHQ) inhibited or abolished methoxychlor-induced [Ca(2+)](i) rise. Incubation with methoxychlor also inhibited thapsigargin- or BHQ-induced [Ca(2+)](i) rise. Inhibition of phospholipase C with U73122 did not alter methoxychlor-induced [Ca(2+)](i) rise. At 5-20 μM, methoxychlor killed cells in a concentration-dependent manner. The cytotoxic effect of methoxychlor was not reversed by chelating cytosolic Ca(2+) with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid/AM (BAPTA/AM). Annexin V-FITC data suggest that methoxychlor (10 and 20 μM) evoked apoptosis in a concentration-dependent manner. Together, in human OC2, methoxychlor induced a [Ca(2+)](i) rise probably by inducing phospholipase C-independent Ca(2+) release from the endoplasmic reticulum and Ca(2+) entry via phospholipase A(2)-sensitive channels. Methoxychlor induced cell death that may involve apoptosis.
authors.affiliation: Department of Dentistry, Kaohsiung Veterans General Hospital, Taiwan.
authors.forename: Li-Ling
authors.initials: LL
authors.lastname: Tseng
authors.forename: Su-Shung
authors.initials: SS
authors.lastname: Shu
authors.forename: Chun-Chi
authors.initials: CC
authors.lastname: Kuo
authors.forename: Chiang-Ting
authors.initials: CT
authors.lastname: Chou
authors.forename: Yao-Dung
authors.initials: YD
authors.lastname: Hsieh
authors.forename: Sau-Tung
authors.initials: ST
authors.lastname: Chu
authors.forename: Chao-Chuan
authors.initials: CC
authors.lastname: Chi
authors.forename: Wei-Zhe
authors.initials: WZ
authors.lastname: Liang
authors.forename: Chin-Man
authors.initials: CM
authors.lastname: Ho
authors.forename: Chung-Ren
authors.initials: CR
authors.lastname: Jan
mesh_terms: D000704:Analysis of Variance; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D016923:Cell Death; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects*; D003600:Cytosol / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000473:pathology; D004963:Estrenes / Q000378:metabolism; D016257:Fura-2; D006801:Humans; D006873:Hydroquinones / Q000378:metabolism; D007306:Insecticides / Q000494:pharmacology*; D008731:Methoxychlor / Q000494:pharmacology*; D009062:Mouth Neoplasms / Q000473:pathology*; D009543:Nifedipine / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D011760:Pyrrolidinones / Q000378:metabolism; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
chemical_list: D004963:Estrenes; D006873:Hydroquinones; D007306:Insecticides; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C019359:2,5-di-tert-butylhydroquinone; D004533:Egtazic Acid; D011493:Protein Kinase C; D010738:Type C Phospholipases; D009543:Nifedipine; C025603:1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid; D008731:Methoxychlor; D002118:Calcium; D016257:Fura-2