Abdullah Shafique Ahmad

Neuroprotective effects of Withania somnifera on 6-hydroxydopamine induced Parkinsonism in rats

6-Hydroxydopamine (6-OHDA) is one of the most widely used rat models for Parkinsons disease. There is ample evidence in the literature that 6-OHDA elicits its toxic manifestations through oxidant stress. In the present study, we evaluated the anti-parkinsonian effects of Withania somnifera extract, which has been reported to have potent anti-oxidant, anti-peroxidative and free radical quenching properties in various diseased conditions. Rats were pretreated with 100, 200 and 300 mg/kg b.w. of the W. somnifera extract orally for 3 weeks. On day 21, 2 mL of 6-OHDA (10 mg in 0.1% in ascorbic acidsaline) was infused into the right striatum while sham operated group received 2 mL of the vehicle. Three weeks after 6-OHDA injections, rats were tested for neurobehavioral activity and were killed 5 weeks after lesioning for the estimation of lipidperoxidation, reduced glutathione content, activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase and catalase, catecholamine content, dopaminergic D2 receptor binding and tyrosine hydroxylase expression. W. somnifera extract was found to reverse all the parameters significantly in a dose-dependent manner. Thus, the study demonstrates that the extract of W. somnifera may be helpful in protecting the neuronal injury in Parkinsons disease.

The Flavanol (−)-Epicatechin Prevents Stroke Damage through the Nrf2/HO1 Pathway

Epidemiologic studies have shown that foods rich in polyphenols, such as flavanols, can lower the risk of ischemic heart disease; however, the mechanism of protection has not been clearly established. In this study, we investigated whether epicatechin (EC), a flavanol in cocoa and tea, is protective against brain ischemic damage in mice. Wild-type mice pretreated orally with 5, 15, or 30 mg/kg EC before middle cerebral artery occlusion (MCAO) had significantly smaller brain infarcts and decreased neurologic deficit scores (NDS) than did the vehicle-treated group. Mice that were posttreated with 30 mg/kg of EC at 3.5 hours after MCAO also had significantly smaller brain infarcts and decreased NDS. Similarly, WT mice pretreated with 30 mg/kg of EC and subjected to N-methyl-D-aspartate (NMDA)-induced excitotoxicity had significantly smaller lesion volumes. Cell viability assays with neuronal cultures further confirmed that EC could protect neurons against oxidative insults. Interestingly, the EC-associated neuroprotection was mostly abolished in mice lacking the enzyme heme oxygenase 1 (HO1) or the transcriptional factor Nrf2, and in neurons derived from these knockout mice. These results suggest that EC exerts part of its beneficial effect through activation of Nrf2 and an increase in the neuroprotective HO1 enzyme.

Neuroprotection by crocetin in a hemi-parkinsonian rat model

Reactive oxygen species (ROS) are implicated as the leading biochemical cause of neuronal death in various neurologic disorders, including Parkinsons disease. In the present study, neuromodulatory effects of crocetin (active constituent of Crocus sativus) in a 6-hydroxydopamine (6-OHDA) model of rat Parkinsonism were investigated. Male Wistar rats were pre-treated with crocetin (25, 50 and 75 microg/kg body weight) for 7 days and subjected to unilateral intrastriatal injection of 10 microg 6-OHDA on day 8. Locomotion and rotation were observed on day 23 post-injection, and after 4 weeks, striatum and substantia nigra were dissected out by decapitation. Activity of antioxidant enzymes and content of dopamine (DA) and its metabolites were estimated in striatum, whereas glutathione (GSH) content and thiobarbituric acid reactive substance (TBARS) were evaluated in substantia nigra. Levels of GSH and dopamine were protected, while TBARS content was attenuated in crocetin-treated groups. The activity of antioxidant enzymes was decreased in the lesion group, but protected in the crocetin-treated groups. These findings were supported by the histopathologic findings in the substantia nigra that showed that crocetin protects neurons from deleterious effects of 6-OHDA. This study revealed that crocetin, which is an important ingredient of diet in India and also used in various systems of indigenous medicine, is helpful in preventing Parkinsonism and has therapeutic potential in combating this devastating neurologic disorder.

Coenzyme Q10 modulates cognitive impairment against intracerebroventricular injection of streptozotocin in rats

Coenzyme Q10 (CoQ10), a peculiar lipophilic antioxidant, is an essential component of the mitochondrial electron-transport chain. It is involved in the manufacturing of adenosine triphosphate (ATP) and has been linked with improving cognitive functions. The present study shows the neuroprotective effect of CoQ10 on cognitive impairments and oxidative damage in hippocampus and cerebral cortex of intracerebroventricular-streptozotocin (ICV-STZ) infused rats. Male Wistar rats (1-year old) were infused bilaterally with an ICV injection of STZ (1.5 mg/kg b.wt., in normal saline), while sham group received vehicle only. After 24 h, the rats were supplemented with CoQ10 (10 mg/kg b.wt. i.p.) for 3 weeks. The learning and memory tests were monitored 2 weeks after the lesioning. STZ-infused rats showed the loss of cognitive performance in Morris water maze and passive avoidance tests. Three weeks after the lesioning, the rats were sacrificed for estimating the contents of thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), protein carbonyl (PC), ATP and the activities of glutathione peroxidase (GPx), glutathione reductase (GR), cholineacetyltransferase (ChAT) and acetylcholinesterase (AChE). Significant alteration in the markers of oxidative damage (TBARS, GSH, PC, GPx and GR) and a decline in the level of ATP were observed in the hippocampus and cerebral cortex of ICV-STZ rat. A significant decrease in ChAT activity and a concomitant increase in AChE activity were observed in the hippocampus. However, supplementation with CoQ10 in STZ-infused rats reversed all the parameters significantly. Thus, the study demonstrates that CoQ10 may have a therapeutic importance in the treatment of Alzheimers type dementia.

GOSPEL: A Neuroprotective Protein that Binds to GAPDH upon S-Nitrosylation

We recently reported a cell death cascade whereby cellular stressors activate nitric oxide formation leading to S-nitrosylation of GAPDH that binds to Siah and translocates to the nucleus. The nuclear GAPDH/Siah complex augments p300/CBP-associated acetylation of nuclear proteins, including p53, which mediate cell death. We report a 52 kDa cytosolic protein, GOSPEL, which physiologically binds GAPDH, in competition with Siah, retaining GAPDH in the cytosol and preventing its nuclear translocation. GOSPEL is neuroprotective, as its overexpression prevents NMDA-glutamate excitotoxicity while its depletion enhances death in primary neuron cultures. S-nitrosylation of GOSPEL at cysteine 47 enhances GAPDH-GOSPEL binding and the neuroprotective actions of GOSPEL. In intact mice, virally delivered GOSPEL selectively diminishes NMDA neurotoxicity. Thus, GOSPEL may physiologically regulate the viability of neurons and other cells.

Ginkgo biloba affords dose‐dependent protection against 6‐hydroxydopamine‐induced parkinsonism in rats: neurobehavioural, neurochemical and immunohistochemical evidences

Ginkgo biloba extract (EGb), a potent antioxidant and monoamine oxidase B (MAO‐B) inhibitor, was evaluated for its anti‐parkinsonian effects in a 6‐hydroxydopamine (6‐OHDA) rat model of the disease. Rats were treated with 50, 100, and 150 mg/kg EGb for 3 weeks. On day 21, 2 µL 6‐OHDA (10 µg in 0.1% ascorbic acid saline) was injected into the right striatum, while the sham‐operated group received 2 µL of vehicle. Three weeks after 6‐OHDA injection, rats were tested for rotational behaviour, locomotor activity, and muscular coordination. After 6 weeks, they were killed to estimate the generation of thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH) content, to measure activities of glutathione‐S‐transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), catalase, and superoxide dismutase (SOD), and to quantify catecholamines, dopamine (DA) D2 receptor binding, and tyrosine hydroxylase‐immunoreactive (TH‐IR) fibre density. The increase in drug‐induced rotations and deficits in locomotor activity and muscular coordination due to 6‐OHDA injections were significantly and dose‐dependently restored by EGb. The lesion was followed by an increased generation of TBARS and significant depletion of GSH content in substantia nigra, which was gradually restored with EGb treatment. EGb also dose‐dependently restored the activities of glutathione‐dependent enzymes, catalase, and SOD in striatum, which had reduced significantly by lesioning. A significant decrease in the level of DA and its metabolites and an increase in the number of dopaminergic D2 receptors in striatum were observed after 6‐OHDA injection, both of which were significantly recovered following EGb treatment. Finally, all of these results were exhibited by an increase in the density of TH‐IR fibers in the ipsilateral substantia nigra of the lesioned group following treatment with EGb; the lesioning had induced almost a complete loss of TH‐IR fibers. Considering our behavioural studies, biochemical analysis, and immunohistochemical observation, we conclude that EGb can be used as a therapeutic approach to check the neuronal loss following parkinsonism.

Prostaglandin EP4 receptor agonist protects against acute neurotoxicity

Under various abnormal physiologic conditions, overactivation of glutamate-gated ion channel receptor family members, including NMDA receptors, causes increase in COX-2 expression and generation of prostaglandins. PGE(2) exerts its physiologic actions mainly through its PGE(2) prostanoid (EP) receptors. In the present study, the role of the EP4 receptor against NMDA-induced excitotoxicity was investigated. Using the EP4 receptor agonist ONO-AE1-329, which has relative selectivity toward murine EP receptors on the order of EP1:EP2:EP3:EP4 of >1000:210:120:1, respectively, we questioned whether activation of the EP4 receptors has the potential to attenuate injury in brain. Mice were pretreated by intracerebroventricular injection with different doses of ONO-AE1-329 (0.1, 1, and 10 nmol; n = 9/group) and, after 20 min, by a single unilateral intrastriatal injection of NMDA (15 nmol, n = 12). NMDA injection produced a significant lesion in the ipsilateral striatum. This lesion volume was significantly reduced in groups that were pretreated with ONO-AE1-329, with maximum protection of more than 32% at 10 nmol. This is the first study revealing the protective effect of ONO-AE1-329 in an acute model of excitotoxicity in brain, and it suggests that preferential stimulation of EP4 receptors attenuates excitotoxic brain injury.

Protective effect of Nardostachys jatamansi in rat cerebral ischemia.

The protective effect of Nardostachys jatamansi (NJ) on neurobehavioral activities, thiobarbituric acid reactive substance (TBARS), reduced glutathione (GSH), thiol group, catalase and sodium-potassium ATPase activities was studied in middle cerebral artery (MCA) occlusion model of acute cerebral ischemia in rats. The right MCA of male Wistar rats was occluded for 2 h using intraluminal 4-0 monofilament and reperfusion was allowed for 22 h. MCA occlusion caused significant depletion in the contents of glutathione and thiol group and a significant elevation in the level of TBARS. The activities of Na(+)K(+) ATPase and catalase were decreased significantly by MCA occlusion. The neurobehavioral activities (spontaneous motor activity and motor coordination) were also decreased significantly in MCA occlusion group. All the alternations induced by ischemia were significantly attenuated by 15 days pretreatment of NJ (250 mg/kg po) and correlated well with histopathology by decreasing the neuronal cell death following MCA occlusion and reperfusion. The study provides first evidence of effectiveness of NJ in focal ischemia most probably by virtue of its antioxidant property.

Serine Racemase Deletion Protects Against Cerebral Ischemia And Excitotoxicity

d-Serine, formed from l-serine by serine racemase (SR), is a physiologic coagonist at NMDA receptors. Using mice with targeted deletion of SR, we demonstrate a role for d-serine in NMDA receptor-mediated neurotoxicity and stroke. Brain cultures of SR-deleted mice display markedly diminished nitric oxide (NO) formation and neurotoxicity. In intact SR knock-out mice, NO formation and nitrosylation of NO targets are substantially reduced. Infarct volume following middle cerebral artery occlusion is dramatically diminished in several regions of the brains of SR mutant mice despite evidence of increased NMDA receptor number and sensitivity.

Heme oxygenase-1 protects brain from acute excitotoxicity.

Heme oxygenase is a rate-limiting enzyme that degrades heme, a pro-oxidant, into carbon monoxide, iron, and bilirubin. Heme oxygenase has two active isoforms: heme oxygenase-1 and heme oxygenase-2. Heme oxygenase-1 can be induced by various insults. Several investigators have postulated that it has cytoprotective activities, although its role in the nervous system is not fully understood, especially considering that normally heme oxygenase-2 accounts for the vast majority of heme oxygenase activity in the brain. Here, the basal effect of heme oxygenase-1 was investigated in acute glutamatergic excitotoxicity to test the hypothesis that N-methyl-D-aspartate-induced acute toxicity in brain is attenuated by heme oxygenase-1. N-methyl-D-aspartate was unilaterally injected into the striatum of wildtype and heme oxygenase-1 knockout mice. After 48 h, brains were harvested, sectioned, and stained with Cresyl Violet to measure the lesion size. Lesion volume was significantly (P<0.05) greater in brains of heme oxygenase-1 knockout mice (15.2+/-3.1 mm(3); n=10) than in those of wildtype mice (6.2+/-1.5 mm(3); n=11). In addition, Western blot analysis indicated no detectable differences between wildtype and heme oxygenase-1 knockout mouse brains in the levels of the glutamate or N-methyl-D-aspartate receptors studied. To test whether heme oxygenase-1 could specifically protect neurons, mouse primary neuronal cell cultures of wildtype and heme oxygenase-1 knockout mice were treated with or without N-methyl-D-aspartate. Cell viability of the heme oxygenase-1 knockout neurons was significantly less than that of wildtype neurons at each of the N-methyl-D-aspartate concentrations tested (12.8+/-1.3%, 16.0+/-1.4%, and 18.4+/-1.8% at 30, 100, and 300 microM N-methyl-D-aspartate, respectively). These results indicate that heme oxygenase-1 provides neuroprotection against acute excitotoxicity and suggest that potential intervention that can increase heme oxygenase-1 activity within the brain should be considered as a therapeutic target in acute and potentially chronic neurological disorders.