Induction of Ca2+ signaling and cytotoxic responses of human lung fibroblasts upon an antihistamine drug oxatomide treatment and evaluating the protective effects of Ca2+ chelating.

Background Objectives Methods Results Conclusion Oxatomide, an antihistamine drug of the diphenylmethylpiperazine family, has anti‐inflammatory effects in airway disease. Because oxatomide was shown to cause diverse physiological responses in several cell models, the impact of oxatomide on Ca2+ signaling and its related physiological effects has not been explored in IMR‐90 human fetal lung fibroblasts.This study assessed the effect of oxatomide on cell viability and intracellular free Ca2+ concentrations ([Ca2+]i) and examined whether oxatomide‐induced cytotoxicity through Ca2+ signaling in IMR‐90 cells.Cell viability was measured by the cell proliferation reagent (WST‐1). [Ca2+]i was measured by the Ca2+‐sensitive fluorescent dye fura‐2.Oxatomide (10–40 μM) concentration dependently reduced cell viability and induced [Ca2+]i rises in IMR‐90 cells. This cytotoxic effect was reversed by chelation of cytosolic Ca2+ with BAPTA‐AM. In terms of Ca2+ signaling, oxatomide‐caused Ca2+ entry was inhibited by modulators of store‐operated Ca2+ channels (2‐APB and SKF96365) and protein kinase C (PKC) inhibitor (GF109203X). Furthermore, oxatomide‐induced Ca2+ influx was confirmed by Mn2+‐induced quench of fura‐2 fluorescence. In a Ca2+‐free medium, preincubation with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin inhibited oxatomide‐evoked [Ca2+]i rises. Conversely, treatment with oxatomide abolished thapsigargin‐induced [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 also inhibited oxatomide‐caused [Ca2+]i rises.In IMR‐90 cells, oxatomide‐induced cytotoxicity by preceding [Ca2+]i rises involving PKC‐sensitive store‐operated Ca2+ entry and PLC‐dependent Ca2+ release from the endoplasmic reticulum. BAPTA‐AM, with its Ca2+ chelating effects, may be a potential compound for preventing oxatomide‐induced cytotoxicity. [ABSTRACT FROM AUTHOR]