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

Terfenadine, an antihistamine used for the treatment of allergic conditions, affected Ca-related physiological responses in various models. However, the effect of terfenadine on cytosolic free Ca levels ([Ca]) and its related physiology in renal tubular cells is unknown. This study examined whether terfenadine altered Ca signaling and caused cytotoxicity in Madin-Darby canine kidney (MDCK) renal tubular cells. The Ca-sensitive fluorescent dye fura-2 was used to measure [Ca]. 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 [Ca] rises concentration dependently. The response was reduced by approximately 35% by removing extracellular Ca. In Ca-free medium, treatment with the endoplasmic reticulum Ca pump inhibitor 2,5-di-tert-butylhydroquinone (BHQ) partly inhibited terfenadine-evoked [Ca] rises. Conversely, treatment with terfenadine abolished BHQ-evoked [Ca] rises. Inhibition of phospholipase C (PLC) with U73122 inhibited 95% of terfenadine-induced Ca release. Terfenadine-induced Ca entry was supported by Mn-caused quenching of fura-2 fluorescence. Terfenadine-induced Ca 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 Ca channels (nifedipine, econazole, and SKF96365). Terfenadine at 200-300 μM decreased cell viability, which was not reversed by pretreatment with the Ca chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester (BAPTA/AM). Together, in MDCK cells, terfenadine induced [Ca] rises by evoking PLC-dependent Ca release from the endoplasmic reticulum and Ca entry PKC-sensitive store-operated Ca entry. Furthermore, terfenadine caused cell death that was not triggered by preceding [Ca] rises.