Effect of riluzole on Ca2+ movement and cytotoxicity in Madin-Darby canine kidney cells

Abstract

Riluzole is a drug used in the treatment of amyotrophic lateral sclerosis; however, its in vitro action is unclear. In this study, the effect of riluzole on intracellular Ca2+ concentration ([Ca2+]i) in Madin-Darby canine kidney (MDCK) cells was investigated using the Ca 2+-sensitive fluorescent dye, fura-2. Riluzole (100-500 μM) caused a rapid and sustained increase of [Ca2+]i in a concentration-dependent manner (EC50 = 150 μM). Some 40 and 50% of this [Ca2+]i increase was prevented by the removal of extracellular Ca2+ and the addition of La3+, respectively, but was unchanged by dihydropyridines, verapamil and diltiazem. In Ca 2+-free medium, thapsigargin - an inhibitor of the endoplasmic reticulum (ER) Ca2+-ATPase - caused a monophasic [Ca 2+]i increase, after which the increasing effect of riluzole on [Ca2+]i was attenuated by 70%; in addition, pre-treatment with riluzole abolished thapsigargin-induced [Ca 2+]i increases. U73122, an inhibitor of phospholipase C (PLC), abolished ATP (but not riluzole)-induced [Ca2+]i increases. At concentrations of 250 and 500 μM, riluzole killed 40 and 95% cells, respectively. The cytotoxic effect of riluzole (250 μM) was unaltered by pre-chelating cytosolic Ca2+ with BAPTA. Collectively, in MDCK cells, riluzole rapidly increased [Ca2+]i by stimulating extracellular Ca2+ influx via an La3+-sensitive pathway and intracellular Ca2+ release from the ER via, as yet, unidentified mechanisms. Furthermore, riluzole caused Ca2+-unrelated cytotoxicity in a concentration-dependent manner. © 2006 SAGE Publications.