Dantrolene Is Cytoprotective in Two Models of Neuronal Cell Death

Abstract

The neuroprotective effects of dantrolene, an inhibitor of calcium release from intracellular stores, were investigated in a model of cell death induced by calcium release from endoplasmic reticulum in vitro. Thapsigargin (50 nM), a selective inhibitor of endoplasmic reticular Ca2+‐ATPase, significantly increased the cytosolic Ca2+ concentration to 230% over basal levels, induced DNA fragmentation, and reduced cell viability from 94% in control cells to 41% after a 24‐h treatment in GT1‐7 hypothalamic neurosecretory cells. Pretreatment with dantrolene for 30 min significantly inhibited elevation of cytosolic Ca2+ levels, DNA fragmentation, and GT1‐7 cell death induced by thapsigargin in a dose‐dependent manner. To determine if dantrolene would also be protective in an in vivo model of neurodegeneration, it was administered intravenously immediately following a 5‐min global cerebral ischemia in gerbils, and the number of intact hippocampal CA1 pyramidal neurons was counted 7 days later. The effects of dantrolene on brain and rectal temperature were monitored in a separate experiment. Dantrolene significantly increased the number of intact CA1 pyramidal neurons from 40% (untreated ischemic animals) to 67 (10 mg/kg), 78 (25 mg/kg), or 83% (50 mg/kg) of values in sham controls (all p < 0.001). No significant changes in brain or rectal temperature were detected for 4 h following 50 mg/kg dantrolene. These results suggest that abnormal Ca2+ release from intracellular stores can induce neuronal death and that such a mechanism may contribute to delayed hippocampal neuronal death after cerebral ischemia. Dantrolene may be a potentially useful drug for neuroprotection after cerebral ischemia.

Ischemia Enhances Activation by Ca2+and Redox Modification of Ryanodine Receptor Channels from Rat Brain Cortex

“…The importance of our results resides in the fact that, at the concentrations of Mg 2ϩ and ATP present in the cytoplasm, only high activity channels, such as those that preferentially emerged during ischemia, are sufficiently activated by Ca 2ϩ to sustain CICR (Bull et al, 2007). Previous experiments, showing that RyR inhibition with dantrolene reduces the sustained [Ca 2ϩ ] increase and the subsequent neuronal death in animal models of ischemia, support the hypothesis that RyR channels mediate CICR during ischemia (Frandsen and Schousboe, 1991;Zhang et al, 1993;Wei and Perry, 1996;Yano et al, 2001;Clodfelter et al, 2002;Nakayama et al, 2002;Li et al, 2005). We propose that local production of reactive species caused by ischemia initially increases markedly the high activity response of RyR channels by S-glutathionylation of RyR2 and thus facilitates RyR-mediated CICR in brain cortex and steadily amplifies the cytoplasmic [Ca 2ϩ ] increase produced by ischemia-enhanced Ca 2ϩ entry.…”

Effects of Azumolene on Ca2+Sparks in Skeletal Muscle Fibers

“…These two isoforms of RyR are expressed at about the same level in frog skeletal muscle. Dantrolene was found to decrease Ca 2ϩ release from intracellular stores in central neurons (Wei and Perry, 1996;Pelletier et al, 1999;Mattson et al, 2000), which express predominantly RyR3. Heterologously expressed RyR3 was also significantly inhibited by dantrolene and azumolene, and this inhibition was comparable with the dantrolene inhibition of RyR1 (Zhao et al, 2001).…”

Protracted lithium treatment protects against the ER stress elicited by thapsigargin in rat PC12 cells: roles of intracellular calcium, GRP78 and Bcl-2

“…The role of excessive Ca 2 þ depletion from the ER in thapsigargin cytotoxicity is supported by the observation that blocking ryanodine receptors with dantrolene suppresses cell apoptosis induced by thapsigargin. 52 Since inhibition of thapsigargin-induced Ca 2 þ loss from the ER would prevent both elevation of cytoplasmic Ca 2 þ and depletion of ER Ca 2 þ , treatments that inhibit ER Ca Figure 6 Lithium treatment increases Bcl-2 protein levels and blocks the Bcl-2 proteins loss induced by thapsigargin in PC12 cells. Cells were teated with 2 mM LiCl for 7 days, before being exposed to 100 nM thapsigargin for 12 h. Cells in control experiments received no treatment.…”