The exploration of effect of terfenadine on Ca2+ signaling in renal tubular cells.

Terfenadine, an antihistamine used for the treatment of allergic conditions, affected Ca2+-related physiological responses in various models. However, the effect of terfenadine on cytosolic free Ca2+ levels ([Ca2+]i) and its related physiology in renal tubular cells is unknown. This study examined whether terfenadine altered Ca2+ signaling and caused cytotoxicity in Madin-Darby canine kidney (MDCK) renal tubular cells. The Ca2+-sensitive fluorescent dye fura-2 was used to measure [Ca2+]i. Cell viability was measured by the fluorescent reagent 4-[3-[4-lodophenyl]-2-4(4-nitrophenyl)-2H-5-tetrazolio-1,3-benzene disulfonate] water soluble tetrazolium-1 (WST-1) assay. Terfenadine at concentrations of 100-1000 µM induced [Ca2+]i rises concentration dependently. The response was reduced by approximately 35% by removing extracellular Ca2+. In Ca2+-free medium, treatment with the endoplasmic reticulum Ca2+ pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) partly inhibited terfenadine-evoked [Ca2+]i rises. Conversely, treatment with terfenadine abolished BHQ-evoked [Ca2+]i rises. Inhibition of phospholipase C (PLC) with U73122 inhibited 95% of terfenadine-induced Ca2+ release. Terfenadine-induced Ca2+ entry was supported by Mn2+-caused quenching of fura-2 fluorescence. Terfenadine-induced Ca2+ entry was partly inhibited by an activator of protein kinase C (PKC), phorbol 12-myristate 13 acetate (PMA) and by three modulators of store-operated Ca2+ channels (nifedipine, econazole, and SKF96365). Terfenadine at 200-300 µM decreased cell viability, which was not reversed by pretreatment with the Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in MDCK cells, terfenadine induced [Ca2+]i rises by evoking PLC-dependent Ca2+ release from the endoplasmic reticulum and Ca2+ entry via PKC-sensitive store-operated Ca2+ entry. Furthermore, terfenadine caused cell death that was not triggered by preceding [Ca2+]i rises.