title: The antidepressant mirtazapine-induced cytosolic Ca2+ elevation and cytotoxicity in human osteosarcoma cells.
abstract: The effect of the antidepressant mirtazapine on cytosolic free Ca2+ concentration ([Ca2+]i) and viability has not been explored in any cell type. This study examined whether mirtazapine alters Ca2+ levels and causes cell death in osteoblast-like cells using MG63 human osteosarcoma cells as a model. [Ca2+]i and cell viability were measured using the fluorescent dyes fura-2 and WST-1, respectively. Mirtazapine at concentrations above 250 microM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 60% by removing extracellular Ca2+. The mirtazapine-induced Ca2+ influx was sensitive to blockade of nifedipine and verapamil. In Ca(2+)-free medium, after pretreatment with 1.5 mM mirtazapine, 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor), 2 microM CCCP (a mitochondrial uncoupler), and 1 microM ionomycin failed to release more stored Ca2+; conversely, pretreatment with thapsigargin, CCCP and ionomycin abolished mirtazapine-induced Ca2+ release. Inhibition of phospholipase C with 2 microM U73122 did not change mirtazapine-induced [Ca2+]i, increase. Seal of Ca2+ movement across the plasma membrane with 50 microM extracellular La3+ enhanced 1 microM thapsigargin-induced [Ca2+]i increase, suggesting that Ca2+ efflux played a role in lowering thapsigargin-induced [Ca2+]i increase; however, the same La3+ treatment did not alter mirtazapine-induced [Ca2+]i increase. At concentrations of 500 microM and 1000 microM, mirtazapine killed 30% and 60% cells, respectively. The cytotoxicity was not reversed by chelating cytosolic Ca2+ with BAPTA. Collectively, in MG63 cells, mirtazapine induced a [Ca2+]i increase by causing Ca2+ release from stores and Ca2+ influx from extracellular space. Furthermore, mirtazapine caused cytotoxicity at higher concentrations in a Ca(2+)-dissociated manner.
authors.affiliation: Department of Psychiatry, Kaohsiung Veterans General Hospital, Kaohsiung 813, ROC.
authors.forename: Chin-Chuan
authors.initials: CC
authors.lastname: Pan
authors.forename: He-Hsiung
authors.initials: HH
authors.lastname: Cheng
authors.forename: Chun-Jen
authors.initials: CJ
authors.lastname: Huang
authors.forename: Yih-Chau
authors.initials: YC
authors.lastname: Lu
authors.forename: I-Shu
authors.initials: IS
authors.lastname: Chen
authors.forename: Shiuh-Inn
authors.initials: SI
authors.lastname: Liu
authors.forename: Shu-Shong
authors.initials: SS
authors.lastname: Hsu
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
authors.forename: Jong-Khing
authors.initials: JK
authors.lastname: Huang
authors.forename: Jin-Shyr
authors.initials: JS
authors.lastname: Chen
authors.forename: Chung-Ren
authors.initials: CR
authors.lastname: Jan
mesh_terms: D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology*; D001859:Bone Neoplasms / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism*; D016257:Fura-2; D006801:Humans; D008803:Mianserin / Q000031:analogs & derivatives* / Q000494:pharmacology; D000078785:Mirtazapine; D012516:Osteosarcoma / Q000378:metabolism; D013997:Time Factors; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D000929:Antidepressive Agents, Tricyclic; D008803:Mianserin; D000078785:Mirtazapine; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2