Ruidong Ye

Neuroprotective effects of ginsenoside Rd against oxygen-glucose deprivation in cultured hippocampal neurons

We previously found that ginsenoside Rd (GSRd), one of the main active ingredients in Panax Ginseng, attenuates H(2)O(2)-induced oxidative injury in PC12 cells. Mounting evidence suggests that the oxidative stress is crucially involved in the pathophysiologic process of ischemia. In the present study, we examined the protective role of GSRd to attenuate ischemic neuronal injury in vitro. Cultured hippocampal neurons were exposed to oxygen-glucose deprivation (OGD) for 2h followed by a 24-h reoxygenation. GSRd exhibited remarkable neuroprotection when presented during OGD and reoxygenation, which may be ascribed to its antioxidative properties by reducing the intracellular reactive oxygen species and malondialdehyde production; increasing glutathione content; and enhancing the antioxidant enzymatic activities of catalase, superoxide dismutase and glutathione peroxidase. Additionally, GSRd could stabilize the mitochondrial membrane potential and attenuate apoptotic death of hippocampal neurons after OGD exposure. These findings suggested that GSRd may be a potential neuroprotective agent for cerebral ischemic injury and should encourage further in vivo studies on stroke to explore the potential neuroprotective efficacy of GSRd.

Ginsenoside Rd attenuates early oxidative damage and sequential inflammatory response after transient focal ischemia in rats

We previously found that ginsenoside Rd (Rd), one of the main active ingredients in Panax ginseng, attenuates neuronal oxidative damage in vitro induced by hydrogen peroxide and oxygen-glucose deprivation. In this study, we sought to investigate the potential protective effects and associated mechanisms of Rd in a rat model of focal cerebral ischemia. Rats administered with Rd (0.1-200mg/kg) or vehicle was subjected to transient middle cerebral artery occlusion. Rd at the dose of 10-50mg/kg significantly reduced the infarct volume and improved the long-term neurological outcome up to 6 weeks after ischemia. To evaluate the underlying mechanisms, in vivo free radical generation was monitored using microdialysis, oxidative DNA damage was identified by 8-hydroxy-deoxyguanosine immunostaining, oxidative protein damage was identified by the assessment of protein carbonyl and advanced glycosylation end products, and lipid peroxidation was estimated by determining the malondialdehyde and 4-hydroxynonenal formations. Microdialysis results displayed a prominent inhibitory effect of Rd on the hydroxy radical formation trapped as 2,3- and 2,5-DHBA. Early accumulations of DNA, protein and lipid peroxidation products were also suppressed by Rd treatment. Although Rd partly preserved endogenous antioxidant activities in the ischemic penumbra, in sham rats without stroke, endogenous antioxidant activities were not affected by Rd. Furthermore, we assayed sequential inflammatory response in a later phase after ischemia. Rd significantly eliminated inflammatory injury as indicated by the suppression of microglial activation, inducible nitric oxide synthase and cyclooxygenase-2 expression. Collectively, these findings demonstrated that Rd exerts neuroprotection in transient focal ischemia, which may involve early free radicals scavenging pathway and a late anti-inflammatory effect.

Ginsenoside Rd attenuates mitochondrial dysfunction and sequential apoptosis after transient focal ischemia

We previously found that ginsenoside Rd (Rd), one of the major active ingredients in Panax ginseng, protects neuronal cells from hydrogen peroxide and oxygen-glucose deprivation, an in vitro model of cerebral ischemia. In this study, we examined the protective effects of Rd in an animal model of focal cerebral ischemia. Rats administered with Rd or vehicle were subjected to transient middle cerebral artery occlusion (MCAO). Rd (50 mg/kg) significantly reduced the infarct volume by 52.8%. This reduction of injury volume was associated with an improvement in neurological function and was sustained for at least 2 weeks after the induction of ischemia. To evaluate the underlying mechanisms of Rd against stroke, brain tissues were assayed for mitochondrial enzyme activities, mitochondrial membrane potential (MMP), production of reactive oxygen species (ROS), energy metabolites, and apoptosis. Rd markedly protected mitochondria as indicated by preserved respiratory chain complex activities and aconitase activity, lowered mitochondrial hydrogen peroxide production, and hyperpolarized MMP. Microdialysis results illustrated that Rd significantly decreased the accumulation of lactate, the end product of anaerobic glycolysis, and increased pyruvate, the end product of aerobic glycolysis, hence inducing a lower lactate/pyruvate ratio. Additionally, in vitro studies further exhibited that Rd protected isolated mitochondria from calcium-induced damage by attenuating mitochondrial swelling, preserving MMP and decreasing ROS production. Moreover, Rd treatment reduced mitochondrial release of cytochrome c (CytoC) and apoptosis-inducing factor (AIF), thereby minimizing mitochondria-mediated apoptosis following ischemia. In conclusion, these findings demonstrated that Rd exerts neuroprotective effects in transient focal ischemia, which may involve an integrated process of the mitochondrial protection, energy restoration and inhibition of apoptosis.

Ginsenoside Rd attenuates redox imbalance and improves stroke outcome after focal cerebral ischemia in aged mice

We previously found that ginsenoside Rd (Rd), one of the main active ingredients in Panax ginseng, protects against ischemic brain damage induced by oxygen-glucose deprivation in vitro and middle cerebral artery occlusion (MCAO) in vivo. Considering stroke happens frequently in aged individuals, we herein sought to further define the protective effects of Rd in the aged mice. 16-18-month-old mice administered with Rd (0.1-200 mg/kg) or vehicle were subjected to transient MCAO. Rd at the doses of 10-50 mg/kg significantly reduced both cortical and striatal infarct volume. This protection was associated with an improvement in neurological function and was sustained for at least 2 weeks after the insult. Importantly, Rd was effective even when administered up to 4 h after recirculation. To evaluate the underlying mechanisms, oxidative DNA damage was identified by 8-hydroxy-deoxyguanosine immunostaining, oxidative protein damage was identified by the assessment of protein carbonyl, and lipid peroxidation was estimated by determining the malondialdehyde formation. Rd significantly suppressed the accumulations of DNA, protein and lipid peroxidation products at 24 h post-ischemia. Rd also protected mitochondria at 4 and 24 h after reperfusion as indicated by preserved respiratory chain complex activities and aconitase activity, lowered mitochondrial hydrogen peroxide production, and hyperpolarized mitochondrial membrane potential. Furthermore, Rd partly enhanced endogenous antioxidant activities following MCAO. Collectively, these findings demonstrated that Rd exerts neuroprotection against transient focal ischemia in the aged brain, which may be associated with the attenuation of redox imbalance.

Sevoflurane preconditioning induces neuroprotection through reactive oxygen species-mediated up-regulation of antioxidant enzymes in rats.

BACKGROUND:It has been reported that sevoflurane preconditioning can induce neuroprotection, the mechanisms of which, however, are poorly elucidated. We designed the present study to examine the hypothesis that sevoflurane preconditioning could reduce cerebral ischemia– reperfusion injury through up-regulating antioxidant enzyme activities before ischemic injury by generating reactive oxygen species (ROS). METHODS:In preconditioning groups, adult male Sprague–Dawley rats were pretreated with 1 hour sevoflurane exposure at a dose of 1%, 2%, or 4% for 5 consecutive days. At 24 hours after the last exposure, all rats were subjected to focal brain ischemia induced by middle cerebral artery occlusion for 120 minutes followed by 72-hour reperfusion. The role of ROS in ischemic tolerance was assessed by administration of the free radical scavenger dimethylthiourea and antioxidant N-acetylcysteine before each preconditioning. Brain ischemic injury was evaluated by neurologic behavior scores and brain infarct volume calculation. Antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase [GSH-px]) of brain tissue and blood serum were tested at 24 hours after the last sevoflurane preconditioning. RESULTS:Sevoflurane preconditioning reduced infarct size and improved neurobehavioral outcome in a dose-dependent manner. The neuroprotective effects of sevoflurane preconditioning were abolished by dimethylthiourea and N-acetylcysteine. The activities of catalase and glutathione peroxidase (GSH-px) in the brain tissue were elevated by sevoflurane preconditioning before ischemic injury. The up-regulated activity of GSH-px in serum negatively correlated with brain infarct volume percentage. CONCLUSION:Sevoflurane preconditioning induces cerebral ischemic tolerance in a dose– response manner through ROS release and consequent up-regulation of antioxidant enzyme activity before ischemic injury in rats. Serum GSH-px activity could be developed as a marker to assess the effectiveness of sevoflurane preconditioning before ischemia.

Sevoflurane preconditioning improves mitochondrial function and long-term neurologic sequelae after transient cerebral ischemia: role of mitochondrial permeability transition.

Objective:Anesthetic preconditioning appears to be a viable strategy to treat ischemic cerebral injury. Here we investigated 1) whether the protection conferred by sevoflurane preconditioning sustains in time; 2) whether sevoflurane preconditioning diminishes mitochondrial dysfunction following cerebral ischemia; and 3) whether mitochondrial permeability transition pore plays a crucial role in the sevoflurane preconditioning. Design:Laboratory investigation. Setting:University research laboratory. Subjects:Sprague-Dawley rats. Interventions:Rats underwent 2 hrs of focal cerebral ischemia induced by middle cerebral artery occlusion. Preconditioning was elicited with sevoflurane (2.3%) for 60 mins at 24 hrs before ischemia. The involvement of mitochondrial permeability transition pore was determined with a mitochondrial permeability transition pore opener atractyloside and a specific mitochondrial permeability transition pore inhibitor cyclosporin A. In vitro study was performed on acutely isolated mitochondria subjected to calcium overload. Measurements and Main Results:Sevoflurane preconditioning significantly decreased the infarct size by 35.9% (95% confidence interval 6.5–28.4, p < .001). This reduction of injury volume was associated with a long-term improvement of neurological function according to modified neurological severity score (F = 13.6, p = .001) and sticky-tape test (F = 29.1, p < .001) for 42 days after ischemia. Furthermore, sevoflurane preconditioning markedly protected mitochondria, as indicated by preserved respiratory chain complex activities and membrane potential, lowered mitochondrial hydrogen-peroxide production, and attenuated mitochondrial permeability transition pore opening. Isolated mitochondria also demonstrated a reduced sensitivity to Ca2+-induced mitochondrial permeability transition pore opening after pre-exposure to sevoflurane in vitro (95% confidence interval 24.2–196.5,p = .006). Inhibiting mitochondrial permeability transition pore using cyclosporin A resulted in protective effects similar to those seen with sevoflurane preconditioning, whereas pharmacologically opening the mitochondrial permeability transition pore with atractyloside abrogated all the positive effects of sevoflurane preconditioning and cyclosporin A, including suppression of mitochondrial permeability transition pore opening, counteraction of mitochondria-dependent apoptotic pathway, and subsequent histological and behavioral improvements. Conclusions:Sevoflurane preconditioning protects mitochondria from cerebral ischemia/reperfusion injury and ameliorates long-term neurological deficits. Inhibition of mitochondrial permeability transition pore opening is a crucial step in mediating the neuroprotection of sevoflurane preconditioning.

Ginsenoside Rd Protects Neurons Against Glutamate-Induced Excitotoxicity by Inhibiting Ca 2+ Influx

Our previous studies have demonstrated that ginsenoside Rd (GSRd), one of the principal ingredients of Pana notoginseng, has neuroprotective effects against ischemic stroke. However, the possible mechanism(s) underlying the neuroprotection of GSRd is/are still largely unknown. In this study, we treated glutamate-injured cultured rat hippocampal neurons with different concentrations of GSRd, and then examined the changes in neuronal apoptosis and intracellular free Ca2+ concentration. Our MTT assay showed that GSRd significantly increased the survival of neurons injured by glutamate in a dose-dependent manner. Consistently, TUNEL and Caspase-3 staining showed that GSRd attenuated glutamate-induced cell death. Furthermore, calcium imaging assay revealed that GSRd significantly attenuated the glutamate-induced increase of intracellular free Ca2+ and also inhibited NMDA-triggered Ca2+ influx. Thus, the present study demonstrates that GSRd protects the cultured hippocampal neurons against glutamate-induced excitotoxicity, and that this neuroprotective effect may result from the inhibitory effects of GSRd on Ca2+ influx.

Age-related differences in experimental stroke: possible involvement of mitochondrial dysfunction and oxidative damage.

Age is the single most important risk factor for cerebral stroke. Unfortunately, the effect of age on ischemic brain damage is less clear. In this study, we sought to examine the potential influence of aging on the histologic and functional outcomes after ischemia. Juvenile (4 weeks of age), young adult (4 months of age), mid-aged (11-12 months of age), and aged (18-19 months of age) mice were subjected to transient middle cerebral artery occlusion. There was no remarkable difference of infarct volume on postoperative days 1 and 3. However, on postoperative day 7, aged mice exhibited significantly worsened infarct volume compared with juvenile and young mice. Intriguingly, the increase of infarct volume was most prominent in the striatal area rather than in cortex. Accordingly, aged mice displayed a slower and incomplete functional recovery after stroke. We further evaluated the effects of aging on the oxidative damage and mitochondrial dysfunction following ischemia. Brain tissues were assayed for lipid, DNA, and protein peroxidation products, mitochondrial enzyme activities, mitochondrial membrane potential, production of reactive oxygen species, and antioxidant activities. Aging was associated with declined mitochondrial function and antioxidant detoxification following ischemia, thereby inducing a deteriorated oxidative damage. Regional subanalyses demonstrated that, in accordance with infarct area, the pro-oxidant/antioxidant imbalance occurred more prominently in subcortical areas. Collectively, these findings suggest mitochondria-mediated oxidative damage may be involved in the age-related aggravated injury in subcortical areas. Mitochondrial protection could be a promising target for neuroprotective therapy, especially in the aged population.

N-methyl-D-aspartate receptor antagonists for migraine: A potential therapeutic approach

Migraine is one of the most common neurological disorders and still remains incurable. New targets for potential pharmacological intervention should be explored and evaluated for effective long-term management of patients with migraine. N-methyl-D-aspartate receptors (NMDARs) are glutamate-gated ion channels widely expressed in the central nervous system. NMDAR activation has been suggested to be implicated in trigeminovascular system and cortical spreading depression, which are involved in the mechanisms of migraine. Thus, it is reasonable to infer that NMDAR antagonists may provide a potentially novel therapeutic approach to the treatment of migraine. So far, no controlled clinical trial has been published that examines the efficacy of NMDAR antagonist for migraine prophylaxis. It is to be hoped that further studies of NMDAR antagonists, especially NR2B-selective and low-affinity antagonists, will enable the potential of these drugs to be fully tested.