Effect of the neuroprotective agent riluzole on intracellular Ca 2+ levels in IMR32 neuroblastoma cells

Abstract

Riluzole is an effective neuroprotective drug. Its effect on intracellular free Ca2+ levels ([Ca2+]i) has not been explored. This study examined the effect of riluzole on [Ca2+]i in IMR32 neuroblastoma cells using fura-2 as a Ca2+ probe. Riluzole 0.1-1 mM increased [Ca2+]i in a concentration-dependent manner. Removal of extracellular Ca2+ inhibited the response by 52 +/- 5%. The [Ca2+]i increase induced by 0.2 mM riluzole was unaltered by 0.1 mM La3+ or 10 microM verapamil, but was inhibited by 51 +/- 4% by 10 microM nifedipine. In Ca2+-free medium, pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) reduced the 0.2 mM riluzole-induced Ca2+ release by 44 +/- 3%; this reduction was augmented to 66 +/- 5% by additionally depleting the Ca2+ stores in the Golgi complex with 50 microM brefeldin A. Inhibition of inositol 1,4,5-trisphosphate formation by 2 microM U73122, a phospholipase C inhibitor, did not affect Ca2+ release induced by 0.2 microM riluzole. It was concluded that the neuroprotective agent riluzole increased [Ca2+]i in IMR32 neuroblastoma cells concentration-dependently by releasing Ca2+ from multiple stores in an inositol 1,4,5-trisphosphate-independent manner and also by inducing nifedipine-sensitive Ca2+ influx.

Effect of Riluzole on Cytosolic Ca²⁺ Increase in Human Osteosarcoma Cells

“…It seems that IP 3 is not involved in riluzoleinduced Ca 2+ release because suppressing PLC-coupled IP 3 formation did not affect riluzole-induced Ca 2+ release, consistent with the data found in neuroblastoma cells [30]. [42,43].…”

“…Our data from the previous [30] and present studies showing that riluzole can induce [Ca 2+ ] i increases in both excitable (neuroblastoma) and nonexcitable (osteoblastoma) cells suggest that riluzole has multiple effects on Ca 2+ movement. Riluzole induced immediate and sustained [Ca 2+ ] i increases at concentrations normally used by researchers to examine its effect on other cellular processes.…”

“…It was found that riluzole induced Ca 2+ entry through a dihydropyridinesensitive pathway that was insensitive to La 3+ or verapamil. Capacitative Ca 2+ entry has been shown to play a major role in Ca 2+ influx in MG63 cells [30][31][32][33]. This indicates that MG63 cells may possess another Ca 2+ influx pathway other than capacitative Ca 2+ entry since the latter is insensitive to dihydropyridines but is blocked by La 3+ .…”

“…Recently, it has been shown that riluzole caused an increase in [Ca 2+ ] i in neuroblastoma cells [30]. This is against the conventional notion that riluzole acts as an inhibitory agent in signal transduction.…”

The Neuroprotection Exerted by Memantine, Minocycline and Lithium, against Neurotoxicity of CSF from Patients with Amyotrophic Lateral Sclerosis, Is Antagonized by Riluzole

“…For instance, riluzole has been shown to distort the intracellular Ca 2+ homeostasis [50,51,52]; this may be linked to its reported apoptotic and cytotoxic effects in human prostate cancer cells [53] and in Madin-Darby canine kidney cells [52]. On the opposite side are the findings that riluzole regulates the expression of neurotrophic factor genes in C6 glioma cells [54], stimulates the synthesis of nerve growth factor and brain-derived neurotrophic factor in cultured mouse astrocytes [55], and augments brain-derived neurotrophic factor production with consequent proliferation of granule precursor cells in the rat hippocampus [56] and promotion of survival of rat MCNs through stimulation of trophic activity produced by spinal astrocyte monolayers [45].…”