Neuroprotective efficiency of NMDA receptor blockade in the striatum and CA3 hippocampus after various durations of cerebral ischemia in gerbils

Post-stroke effects of IC87201 on neurobehavioral function and brain injuries: A stereological study

Objectives

Stroke is the second leading cause of global death and is characterized by excitotoxic neuronal death caused by NMDA (N-Methyl-D-Aspartate) receptor overactivation. The present study was conducted to investigate the therapeutic potential of IC87201, a novel small molecule interfering with the NMDA receptor intracellular signaling pathway, in reducing the extent of ischemic stroke-induced brain damage.

Materials and Methods

Cerebral ischemia was induced by the middle cerebral artery occlusion (MCAO) method in 24 anesthetized adult male rats for one hour. The animals were randomized into sham, MCAO, MCAO+ DXM (Dextromethorphan hydrobromide monohydrate) as an NMDA antagonist, and MCAO+ IC87201 groups which in the last two groups, DXM (50 mg/kg) and IC87201 (10 mg/kg) were injected intraperitoneally after ischemia. The neurobehavioral scores were appraised for 7 days and after that, brain tissue was appropriately prepared to perform the stereological evaluations.

Results

The administration of IC87201 significantly recovered post-ischemia damages, including neurobehavioral function, reduction of volume of the total hemisphere, cortex, and striatum in rat brain, and the percentage of infarcted areas. Additionally, in the striatum region, IC87201 caused an increase in the total number of neuronal and non-neuronal cells as well as a decrease in the total number of dead cells. Some of these parameters were improved by DXM, but in general, IC87201 outperformed that.

Conclusions

IC87201 was successful in minimizing ischemia-induced damage, especially in the striatal region. In addition, IC87201, as a molecule that acts on the intracellular signaling cascade of the NMDA receptor, performed better than DXM, as an antagonist of this receptor.

Functional and pharmacological analysis of agmatine administration in different cerebral ischemia animal models

Agmatine (AgM, 100 mg/kg i.p.) effect was tested in parallel at two animal models of cerebral ischemia - rat MCAO model (60'/24 h, 60'/48 h, 90'/24 h, 90'/48 h) and gerbil global ischemia (10') model, administrated 5 min after reperfusion. Aim was to evaluate AgM effect on functional outcome 24 and 48 h after MCAO on neurological and sensor-motor function, and coordination in rats. AgM administration significantly reduced infarct volume, improved neurological score and improved post-ischemic oxidative status. Results of behavioral tests (cylinder test, beam walking test, and adhesive removal test) have shown very effective functional recovery after AgM administration. Efficiency of AgM administration in gerbils was observed in forebrain cortex, striatum, hippocampus, and cerebellum at the level of each examined oxidative stress parameter (nitric oxide level, superoxide production, superoxide dismutase activity, and index of lipid peroxidation) measured in four different time points starting at 3 h up to 48 h after reperfusion. The highest levels were obtained 6 h after the insult. The most sensitive oxidative stress parameter to AgM was nitric oxide. Additionally, we performed pharmacological analysis of AgM on rat isolated common carotid arteries. The findings imply that mixed population of potassium channels located on the smooth muscle cells was involved in common carotid artery response to AgM, with predominance of inward rectifying K⁺ channels. In our comparative experimental approach, judged by behavioral, biochemical, as well as pharmacological data, the AgM administration showed an effective reduction of ischemic neurological damage and oxidative stress, hence indicating a direction towards improving post-stroke recovery.

Ischemic postconditioning protects against ischemic brain injury by up-regulation of acid-sensing ion channel 2a

Ischemic postconditioning renders brain tissue tolerant to brain ischemia, thereby alleviating ischemic brain injury. However, the exact mechanism of action is still unclear. In this study, a rat model of global brain ischemia was subjected to ischemic postconditioning treatment using the vessel occlusion method. After 2 hours of ischemia, the bilateral common carotid arteries were blocked immediately for 10 seconds and then perfused for 10 seconds. This procedure was repeated six times. Ischemic postconditioning was found to mitigate hippocampal CA1 neuronal damage in rats with brain ischemia, and up-regulate acid-sensing ion channel 2a expression at the mRNA and protein level. These findings suggest that ischemic postconditioning up-regulates acid-sensing ion channel 2a expression in the rat hippocampus after global brain ischemia, which promotes neuronal tolerance to ischemic brain injury.

The Zinc Ion Chelating Agent TPEN Attenuates Neuronal Death/apoptosis Caused by Hypoxia/ischemia Via Mediating the Pathophysiological Cascade Including Excitotoxicity, Oxidative Stress, and Inflammation

AIMS

We aim to determine the significant effect of TPEN, a Zn(2+) chelator, in mediating the pathophysiological cascade in neuron death/apoptosis induced by hypoxia/ischemia.

METHODS

We conducted both in vivo and in vitro experiments in this study. PC12 cells were used to establish hypoxia/ischemia model by applying oxygen-glucose deprivation (OGD). SHR-SP rats were used to establish an acute ischemic model by electrocoagulating middle cerebral artery occlusion. The effect of TPEN on neuron death/apoptosis was evaluated. In addition, the relative biomarks of excitotoxicity, oxidative stress, and inflammation reactions in hypoxia/ischemia PC12 cell model as well as in SHR-SP rat hypoxia/ischemia model were also assessed.

RESULTS

TPEN significantly attenuates the neurological deficit, reduced the cerebral infarction area and the ratio of apoptotic neurons, and increased the expression of GluR2 in the rat hypoxia/ischemia brain. TPEN also increased blood SOD activity, decreased blood NOS activity and blood MDA and IL-6 contents in rats under hypoxia/ischemia. In addition, TPEN significantly inhibited the death and apoptosis of cells and attenuated the alteration of GluR2 and NR2 expression caused by OGD or OGD plus high Zn(2+) treatments.

CONCLUSIONS

Zn(2+) is involved in neural cell apoptosis and/or death caused by hypoxia/ischemia via mediating excitotoxicity, oxidative stress, and inflammation.

Protective effects of guanosine against sepsis-induced damage in rat brain and cognitive impairment

The development of cognitive impairment in sepsis is associated with neurotoxic effects caused by oxidative stress. We have assessed the effects of acute and extended administration of guanosine (GUA) on brain oxidative stress parameters and cognitive impairment in rats submitted to sepsis by cecal ligation and perforation (CLP). To achieve this goal, male Wistar rats underwent either sham operation or CLP with GUA. Rats subjected to CLP were treated with intraperitoneal injection of GUA (8 mg/kg after CLP) or vehicle. Twelve and 24 h after CLP, the rats were sacrificed, and samples from brain (hippocampus, striatum, cerebellum, prefrontal cortex and cortex) were obtained and assayed for thiobarbituric acid reactive species (TBARS) formation and protein carbonyls. On the 10th day, another group of rats was submitted to the behavioral tasks. GUA administration reduced TBARS and carbonyl levels in some brain regions between 12 and 24 h after CLP, and ameliorated cognitive impairment evaluated 10 days after CLP. Our data provide the first experimental demonstration that GUA was able to reduce the consequences of CLP-induced sepsis in rats, by decreasing oxidative stress parameters in the brain and recovering the memory impairment.

C-Phycocyanin is neuroprotective against global cerebral ischemia/reperfusion injury in gerbils

Although the huge economic and social impact and the predicted incidence increase, neuroprotection for ischemic stroke remains as a therapeutically empty niche. In the present study, we investigated the rationale of the C-Phycocyanin (C-PC) treatment on global cerebral ischemia/reperfusion (I/R) injury in gerbils. We demonstrated that C-PC given either prophylactically or therapeutically was able to significantly reduce the infarct volume as assessed by triphenyltetrazolium chloride (TTC) staining and the neurological deficit score 24h post-stroke. In addition, C-PC exhibited a protective effect against hippocampus neuronal cell death, and significantly improved the functional outcome (locomotor behavior) and gerbil survival after 7 days of reperfusion. Malondialdehyde (MDA), peroxidation potential (PP) and ferric reducing ability of plasma (FRAP) were assayed in serum and brain homogenates to evaluate the redox status 24h post-stroke. The treatment with C-PC prevented the lipid peroxidation and the increase of FRAP in both tissue compartments. These results suggest that the protective effects of C-PC are most likely due to its antioxidant activity, although its anti-inflammatory and immuno-modulatory properties reported elsewhere could also contribute to neuroprotection. To our knowledge, this is the first report of the neuroprotective effect of C-PC in an experimental model of global cerebral I/R damage, and strongly indicates that C-PC may represent a potential preventive and acute disease modifying pharmacological agent for stroke therapy.