The effects of dantrolene alone or in combination with nimodipine in glutamate-induced neurotoxicity in cerebellar granular cell cultures of rat pups

Time-dependent effects of dantrolene on motor evoked potentials in experimental spinal cord injuries

Objectives:Traumatic spinal cord injury (SCI) is a significant clinical problem with numerous secondary complications and perpetual deficits. No potent treatment is currently available to fully repair motor and other neurological functions. We studied the effects of dantrolene (DNT) at different time points, on the motor-evoked potentials (MEPs) and the apoptosis response in spinal cord injury. Methods:The study was conducted on a total of 38 rabbits divided into five main groups.These were group 1 (sham): only laminectomy (n = 6), group 2 (SCI): laminectomy and traumatic SCI (n = 8), group 3 (DNT 0h): just after the SCI, DNT 10 mg/kg I.P. (n = 8), group 4 (DNT 1h): 1 h after the SCI, DNT 10 mg/kg I.P. (n = 8), and group 5 (DNT 4h): 4 h after the SCI, DNT 10 mg/kg I.P. (n = 8). Results: DNT, which was administered as the treatment, had a therapeutic effect on the motor function. This effect was observed by recording neural transmission obtained via the Tarlov test and a transcranial magnetic stimulator by using the values of the MEPs. A significant decrease was histopathologically observed in the apoptotic cell count. Discussion: The electrophysiological efficacy of our model of trauma as SCI has been complemented with the significant differences between the control group and the SCI group. This creates a need for electrophysiological studies to be conducted in the future because effects, even at a minimum level, may play an important role in finding an applicable medicine for SCI.

Dantrolene exerts protective activity in double and triple combination with nimodipine, ruthenium red and basilene blue in bilirubin-induced neurotoxicity in cell culture of rats

In the present study, dantrolene, nimodipine, basilen blue, and ruthenium red were tested in experimental bilirubin toxicity in cortical cell culture of rats. Neurotoxicity was induced by 10(-4) M bilirubin. Basilen blue in the highest concentration of 10(-4) M was determined as the most protective agent when applied alone. Dantrolene alone was found surprisingly ineffective in all doses tested. But it was found very protective both in double and triple combinations. Nimodipine, basilen blue, and ruthenim red neuroprotective potentials were enhanced by adding dantrolene into the media. Best double combination was determined as dantrolene plus ruthenium red. On the other hand, most useful triple combination was found as dantrolene plus nimodipine plus basilen blue. As a result, dantrolene wasn't found to be effective alone, while it seems most potential compound in combined application in bilirubin-induced neurotoxicity. The importance of calcium intrusion was confirmed in bilirubin-induced neurotoxicity.

The effects of dantrolene on hypoxic-ischemic injury in the neonatal rat brain

BACKGROUND

The pathophysiology of brain damage from hypoxia or ischemia has been ascribed to various mechanisms and cascades. Intracellular calcium overload and a calcium excitotoxic cascade have been implicated. It has been suggested that disturbances of endoplasmic reticulum calcium homeostasis are involved in the induction of neuronal cell injury. Two types of intracellular Ca2+-release channels, involving the ryanodyne receptor and the inositol (1,4,5)-triphosphate receptor, are essential for Ca2+ signaling in cells. Dantrolene, which is used for the treatment of malignant hyperthermia syndrome, has been reported to inhibit Ca2+ release through ryanodyne receptors from the endoplasmic reticulum into the cytosol. We designed this study to investigate the neuroprotective effects of dantrolene on hypoxic-ischemic brain damage in the neonatal rat brain.

METHODS

Seven-day-old Sprague-Dawley rats were assigned into two groups; control group (n = 69) and dantrolene group (n = 60). Dimethyl sulfoxide was administered intracerebroventricularly in the control group, and dantrolene in dimethyl sulfoxide was similarly administered to the dantrolene group, before hypoxic-ischemic brain injury (HII). HII was induced by the ligation of the common carotid artery under isoflurane anesthesia, followed by exposure to about 2.5 h of hypoxia (oxygen concentration was maintained at 7%-8%). 1H magnetic resonance spectroscopy was performed 1 day after HII. This noninvasive method evaluated apoptotic processes in the brain after HII. Morphologic score analyses and the calculated percentage of infarct areas after 2,3,5-triphenyltetrazolium chloride staining 14 days after HII were also used to evaluate the effects of dantrolene on HII. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining was performed 1 day after HII using 24 more rats.

RESULTS

The lipid/creatine ratios in the right hemispheres in the dantrolene group 1 day after HII were significantly lower than those of the control group (P < 0.05). There was no significant difference between the two groups in the N-acetylaspartate/creatine ratios. The gross morphologic scores were lower in the dantrolene group than in the control group (P < 0.05), and infarct area (%) after 2,3,5-triphenyltetrazolium chloride staining was less in the dantrolene group than in the control group (P < 0.05) 14 days after HII. Further work with 24 rats showed no significant difference, however, in the number of TUNEL positive cells on the two groups.

CONCLUSIONS

Our results show that dantrolene, administered intracerebroventricularly before HII, had a neuroprotective effect in HII model of the neonatal rat brain.

Dantrolene: mechanisms of neuroprotection and possible clinical applications in the neurointensive care unit

Calcium plays a central role in neuronal function and injury. Dantrolene, an inhibitor of the ryanodine receptor, inhibits intracellular calcium release from the sarco-endoplasmic reticulum. We review the available data of dantrolene as a potential neuroprotective agent and briefly summarize its other pharmacologic effects that may have potential applications for patients in the neurointensive care unit (NICU). Areas with the need for continued research are identified.

Disruption of endoplasmic reticulum calcium stores is involved in neuronal death induced by glycolysis inhibition in cultured hippocampal neurons

Disturbances in neuronal calcium homeostasis have been implicated in a variety of neuropathological conditions, including cerebral ischemia, hypoglycemia, and epilepsy, and possibly constitute part of the cell death process associated with chronic neurodegenerative disorders. We investigated if endoplasmic reticulum (ER) calcium stores participate in neuronal death triggered by moderate glycolysis inhibition induced by iodoacetate, an inhibitor of glyceraldehyde-3-phosphate dehydrogenase, in cultured hippocampal neurons. Results show that exposure to iodoacetate leads to a slow partial decrease in cell survival, which is significantly prevented in the absence of Ca(2+) or in the presence of the calcium chelator BAPTA-AM. Treatment with caffeine and a low (1 microM) concentration of ryanodine, which activates the ryanodine receptor (RyR), exacerbates neuronal death, whereas dantrolene and 25 microM ryanodine, which antagonizes RyR, prevents damage. Xestospongin C (XeC), an antagonist of the inositol-3-phosphate (IP(3)) receptor (IP(3)R) also prevents neuronal damage. Inhibitors of the ER calcium ATPase (sarcoendoplasmic reticulum Ca(2+) ATPase; SERCA) have no effect. The decrease in ATP levels induced by iodoacetate is potentiated by caffeine and prevented by dantrolene. Although only a slight increase in glutamate extracellular levels is observed 3.5 hr after iodoacetate exposure, the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, MK-801, efficiently prevents neuronal damage. Taken together, the data suggest that neuronal death induced during moderate glycolysis inhibition involves calcium influx through NMDA receptors and calcium release from intracellular ER stores. These results might be relevant to the understanding the mechanisms involved in neuronal damage related to aging and chronic neurodegenerative diseases, which have been associated with decreased glucose metabolism.

Prevention of acute adriamycin cardiotoxicity by dantrolene in rats

Possible preventive effect of dantrolene against the peroxidative damage in rat heart which was induced by the administration of an acute dose of adriamycin (ADR, 20 mg/kg, i.p.) has been examined. Forty-eight hours after ADR administration, biochemical changes including the activities of serum creatine kinase isoenzyme (CK-MB), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) and the levels of malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in heart tissue were measured. Pretreatment of rats with dantrolene, given i.p. 30 min prior to ADR injection, substantially reduced the peroxidative damage in the myocardium, and markedly lowered the serum CK-MB, LDH and AST. The protective effects obtained by dantrolene administration, however, were not complete and did not reach those of the control group. Dantrolene, at 5 mg/kg, was useful to obtain significant protective effects, while the protector effect of higher dantrolene dosing level (10 mg/kg) was weak or absent. These results suggest that, at least in part, due to antioxidative properties, dantrolene may provide a significant protective effect against acute ADR-induced cardiotoxicity.

Nimodipine and TMB-8 potentiate the AMPA-induced lesion in the basal ganglia

Acute injection of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) into the rat globus pallidus leads to calcium precipitation, neuronal death and gliosis. In order to determine whether L-type calcium channels and/or release of Ca(2+) from intracellular stores contribute to the effects of AMPA, nimodipine and 8-(N,N-diethylamino) octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) were administered in combination with AMPA. Nimodipine, but not TMB-8, tended to exacerbate the calcification process initiated by AMPA; the AMPA/nimodipine/TMB-8 combination produced much more calcium deposition than AMPA (+62%, P<0.05). AMPA alone induced a slight but not significant astroglial reaction. Nimodipine slightly enhanced the astroglial reaction triggered by AMPA, whereas TMB-8 doubled it (P<0.001 versus AMPA). These data suggest that blockade of L-type calcium channels by nimodipine enhances calcium imbalance triggered by AMPA, and the calcium release from the endoplasmic reticulum does not participate in the AMPA-induced calcification.

In Vitro and in Vivo Effects of Dantrolene on Carbonic Anhydrase Enzyme Activities

The effects of dantrolene were investigated on carbonic anhydrase (CA) enzyme activities in in vitro human and in in vivo Sprague-Dawley rat erythrocytes. For in vitro study, human carbonic anhydrase-I (HCA-I) and -II (HCA-II) were purified by Sepharose 4B-L-tyrosine-sulfanylamide affinity chromatography, rats were used for in vivo study. In vivo and in vitro CA enzyme activity was determined colorimetrically using the CO(2)-hydration method of Wilbur and Anderson. Dantrolene (1.64 x 10(-5)-6.56 x 10(-5) M) showed in vitro inhibitory effects on HCA-I and HCA-II hydratase activity, when determined using the CO(2)-hydratase method. 50% inhibitory concentration (IC(50)) was 4.09 x 10(-5) M for HCA-I and 3.24 x 10(-5) M for HCA-II. Rat erythrocyte CA activity was significantly inhibited by 10 mg/kg dantrolene for up to 3 h (p<0.001) following intraperitoneal administration. In conclusion, Dantrolene inhibited the carbonic anhydrase enzyme activity under in vitro and in vivo conditions.

Ultrastructural clues for glutamate-induced necrosis in parietal and cerebellar neurons

Glutamate excitotoxicity has been postulated to underlie the neuronal death that occurs after ischemia. The most sensitive tissues to ischemic injury are hippocampus and cerebellum, whereas cerebrum is more resistant. We studied the glutamate-induced ultrastructural alterations in rat parietal and cerebellar neurons comparatively. We observed that glutamate (45 min, 10-7 m) causes considerable nuclear, mitochondrial and cytoplasmic changes in both the neuron types. Mitochondrial and nuclear changes were particularly more severe in cerebellar granular, than the ones in parietal neurons. It has been concluded that glutamate induces necrotic changes in both parietal and cerebellar neurons. But cerebellar cortex was found to be more sensitive to glutamate excitotoxicity than cerebral cortex. We suggest that mitochondrial damage is, probably, an important factor in neuron necrosis, which is mediated by glutamate excitotoxicity.

Dantrolene protects erythrocytes against oxidative stress during whole-body irradiation in rats

In our study, we examined the radioprotective effects of dantrolene against gamma irradiation-induced damage of blood cells after total body irradiation of rats. Rats were divided into three groups of eight rats each. The first group was the control group receiving no dantrolene or irradiation, the second group received total body irradiation (RT) with 5 Gy of gamma irradiation only, and the third group received dantrolene at a dose of 5 mg x kg(-1) plus RT. Dantrolene was given intraperitoneally 30 min before RT. All groups were sacrificed 2 h after RT, and blood samples were taken. Leukocyte, and thrombocyte counts and hemoglobin levels were measured. Furthermore, malondialdehyde (MDA) levels in plasma and erythrocytes and superoxide dismutase (SOD) and glutathione peroxidase activities (GSH-Px) in erythrocytes were determined. It was found that pretreatment with dantrolene at a dose of 5 mg x kg(-1) significantly reduced the MDA levels and increased the antioxidant SOD and GSH-Px activities, and prevented the decrease in leukocyte and thrombocyte counts. We conclude that dantrolene has clear antioxidant properties when given prior to radiation exposure and the protective effect of dantrolene against damage inflicted by radiation, depends, at least in part, on the decrease in lipid peroxidation and increase in the activity of antioxidant enzymes SOD and GSH-Px.

The effects of aqueous extract of Lavandula angustifolia flowers in glutamate-induced neurotoxicity of cerebellar granular cell culture of rat pups

In the present study, neuroprotective effect of Lavandula angustifolia flower aqueous extract in glutamate-induced neurotoxicity in rat pups cerebellar granular cell culture was investigated. The extract at doses of 10 microg ml(-1), 100 microg ml(-1), 1 mg ml(-1) and 10 mg ml(-1) was applied to culture flasks. The extract at doses of 100 microg ml(-1) and 1 mg ml(-1) significantly blocked glutamate-induced neurotoxicity, with the most effective dose being 1 mg ml(-1). On the other hand, 10 mg ml(-1) dose of extract increased the dead cell with respect to glutamate group, despite being found insignificant statistically. As a result, L. angustifolia protected the neurons against glutamate toxicity.

Effects of immunosuppressants, calcineurin inhibition, and blockade of endoplasmic reticulum calcium channels on free fatty acid efflux from the ischemic/reperfused rat cerebral cortex

Elevated levels of free fatty acids (FFA) have been implicated in the pathogenesis of neuronal injury and death induced by cerebral ischemia. This study evaluated the effects of immunosuppressants agents, calcineurin inhibitors and blockade of endoplasmic reticulum (ER) calcium channels on free fatty acid formation and efflux in the ischemic/reperfused (I/R) rat brain. Changes in the extracellular levels of arachidonic, docosahexaenoic, linoleic, myristic, oleic and palmitic acids in cerebral cortical superfusates during four-vessel occlusion-elicited global cerebral ischemia were examined using a cortical cup technique. A 20-min period of ischemia elicited large increases in the efflux of all six FFAs, which were sustained during the 40 min of reperfusion. Cyclosporin A (CsA) and trifluoperazine, which reportedly inhibit the I/R elicited opening of a mitochondrial permeability transition (MPT) pore, were very effective in suppressing ischemia/reperfusion evoked release of all six FFAs. FK506, an immunosuppressant which does not directly affect the MPT, but is a calcineurin inhibitor, also suppressed the I/R-evoked efflux of FFAs, but less effectively than CsA. Rapamycin, a derivative of FK506 which does not inhibit calcineurin, did not suppress I/R-evoked FFA efflux. Gossypol, a structurally unrelated inhibitor of calcineurin, was also effective, significantly reducing the efflux of docosahexaenoic, arachidonic and oleic acids. As previous experiments had implicated elevated Ca(2+) levels in the activation of phospholipases with FFA formation, agents affecting endoplasmic reticulum stores were also evaluated. Dantrolene, which blocks the ryanodine receptor (RyR) channel of the ER, significantly inhibited I/R-evoked release of docosahexaenoic, arachidonic, linoleic and oleic acids. Ryanodine, which can either accentuate or block Ca(2+) release, significantly enhanced ischemia/reperfusion-elicited efflux of linoleic acid, with non-significant increases in the efflux of myristic, arachidonic, palmitic and oleic acids. Xestospongin C, an inhibitor of the inositol triphosphate (IP(3)R) channel, failed to affect I/R-evoked FFA efflux. Thapsigargin, an inhibitor of the Ca(2+)-ATPase ER uptake pump, elicited significant elevations in the efflux of myristic, arachidonic and linoleic acids, in the absence of ischemia. Collectively, the data suggest an involvement of both ER and mitochondrial Ca(2+) stores in the chain of events which lead to PLA(2) activation and FFA formation.

Nitric oxide donor sodium nitroprusside induces neurotoxicity in cerebellar granular cell culture in rats by an independent mechanism from L-type or dantrolene-sensitive calcium channels

The effects of sodium nitroprusside (SNP) in rat cerebellar granular cell culture were investigated in the present study. All doses of the SNP (10, 25, 50, 100, 250, 500 microM) were able to induce cell death compared with control values (p < 0.001 for all groups tested). Interestingly enough, a nonlinear dose-response curve was obtained for SNP-induced neurotoxicity. We also investigated the possible neuroprotective effects of nimodipine and dantrolene, alone or in combination. Both drugs failed to prevent neuronal cell death at the doses tested, either alone or in combination. Despite the fact that the most effective dose was a dantrolene concentration of 10 microM with SNP 500 microM and a concentration of 1 microM with SNP 50 microM, the differences were insignificant statistically. According to our results, SNP-induced cerebellar toxicity appears to be an independent reaction from L-type or endoplasmic reticulum calcium currents.

Sustained Ca2+-induced Ca2+-release underlies the post-glutamate lethal Ca2+ plateau in older cultured hippocampal neurons

Several studies have shown that a prolonged Ca(2+) elevation follows a glutamate-mediated excitotoxic insult in cultured neurons, and may be associated with impending cell death. Recently, we showed that the prolonged Ca(2+) elevation that emerges as neurons age in culture is specifically linked to an age-related increase in excitotoxic vulnerability. However, the multiple sources of Ca(2+) that contribute to Ca(2+) elevation during and after glutamate exposure are not well understood. Here, we examined the Ca(2+) sources of the age-related prolonged Ca(2+) elevation in cultured hippocampal neurons. Studies with caffeine showed that the ryanodine receptor-dependent releasable pool of Ca(2+) from intracellular stores was similar in older and younger neurons. Thapsigargin, which inhibits intracellular store refilling, did not mimic the age-related prolonged Ca(2+) elevation and, in fact, partially reduced it. Ryanodine, which blocks Ca(2+)-induced Ca(2+)-release (CICR) from stores, completely blocked the age-related prolonged Ca(2+) elevation following glutamate exposure but did not alter maximal Ca(2+) elevation during the glutamate exposure. Thus, we conclude that sustained CICR plays a selective and key role in generating the lethal, age-related, prolonged Ca(2+) elevation, and is the likely mechanism underlying age-related, enhanced vulnerability to excitotoxicity in neurons.

Anti-inflammatory and antinociceptive properties of dantrolene sodium in rats and mice

Our study aimed at examining the possible anti-inflammatory and antinociceptive effects of dantrolene sodium in rats and mice. The anti-inflammatory effect of dantrolene sodium (2.5, 5 and 10 mg kg (-1)) was investigated and compared with diclofenac sodium (5 mg kg (-1)) using the formalin-, histamine-, and carrageenan-induced paw oedema and cotton pellet granuloma tests. Analgesic effects of dantrolene sodium were evaluated and compared with metamizol (200 mg kg (-1)) in acetic acid-induced writhing and formalin-induced paw licking tests. It was found that dantrolene sodium significantly diminished the nociceptive response in mice, showing at the same time considerable anti-inflammatory properties in rats.

Mechanism of the beneficial effects of dantrolene sodium on ethanol-induced acute gastric mucosal injury in rats

In our study, we examined anti-ulcerogen and antioxidant effects of dantrolene sodium on ethanol-induced gastric lesions in rats. Dantrolene sodium was administered intraperitoneally (i.p.) in several doses, and famotidine was used at a dose of 20 mg kg (-1). It was found that pretreatment with dantrolene sodium at doses of 1, 5 and 10 mg kg(-1) significantly reduced ethanol-induced gastric damage and malondialdehyde levels, and significantly increased antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. We conclude that dantrolene sodium clearly has antioxidant properties and that the protective effect of dantrolene sodium against ethanol-induced gastric mucosal lesion, at least in part, depends upon the reduction in the lipid peroxidation and an increase in the activity of antioxidant enzymes SOD and GSH-Px.

In vitro antioxidant properties of dantrolene sodium

Dantrolene sodium is a skeletal muscle relaxant, which inhibits intracellular Ca2+ release from the sarcoplasmic reticulum. The aim of this study is to examine possible in vitro antioxidant effects of dantrolene sodium. For this reason, the in vitro antioxidant effects of dantrolene sodium were studied using thiocyanate methods. Additionally, the reducing power and free radical scavenging activity were determined. Dantrolene sodium showed strong antioxidant activity in the linoleic acid emulsion system. The antioxidant activity increased with an increasing amount of dantrolene sodium (50, 100, 250 microg). The 50, 100 and 250 microg samples of dantrolene sodium showed 55%, 70% and 82% inhibition on peroxidation of linoleic acid, respectively. On the other hand, the 250 microg sample of alpha-tocopherol showed 62% inhibition of peroxidation of linoleic acid. Like antioxidant activity, the reducing power of dantrolene sodium increased in a dose-dependent manner. The reducing power of dantrolene was statistically significant vs control, but lower than butylated hydroxytoluene (BHT) and quercetin. Although dantrolene sodium had free radical scavenging activity this was not statistically significant. In contrast to dantrolene sodium, quercetin and butylated hydroxyanisole (BHA) had highly potent free radical scavenging activities and those were statistically significant. According to the these results, it may be said that antioxidant effect of dantrolene sodium is more related to its antioxidant activity in linoleic acid emulsion and reducing power, than to its free radical scavenging activity. These properties may be major reasons for the inhibition of lipid peroxidation.