| Objectives: Cerebral ischemia endangers the health and life of human being seriously. It has become a hot and difficult topic to study the pathophysiologic mechanism of ischemic stroke and search for efficient way to cure it. Following the study carrying out, some people have pointed out that oxidative stress and inflammatory response are two important pathophysiologic mechanisms of ischemic stroke, and they are also the primary reasons on aggravating the degree of illness. Inflammation and oxidative stress-related genes are dramatically up-regulated in neurons after ischemia which providing a new promising treatment strategy. Recently It has been reported that sonic hedgehog(Shh)signaling pathway, nuclear factor erythroid 2-related factor 2(Nrf2)/antioxidant response element(ARE)and nuclear factor kappa B(NF-κB)signaling pathway are focused on cerebral ischemia research. Shh pathway and Nrf2/ARE pathway are very important intracellular anti-oxidative and cytotoxic defense mechanism. Up-regulation of these signaling pathway can induce a variety of antioxidant and detoxification enzymes, and exert an protective effect via increasing the Superoxide dismutase 1 ( SOD1 ) activity and Glutathione peroxidase(GSH-PX)activity. The activated signaling pathway of NF-κB plays an important role in the death of nerve cells. Abundant of pharmacology and clinical research find that polydatin has anti-inflammatory, anti-oxidant, anti-apoptosis, anti-tumor and anti-viral effects. However, little is known regarding the effect of polydatin in the acute phase of ischemic stroke. This study is to evaluate the time course expression of glioma-associated oncogene homolog 1( Gli1 ) , Patched-1 ( Ptch1 ) , Nrf2, SOD1 and NF-κB and the neuroprotective effect of polydatin in the acute phase of cerebral ischemia in rats.Methods: Male and healthy Sprague-Dawley rats were subjected to modified permanent middle cerebral artery occlusion ( MCAO ) , as described by Longa previously. Experiment 1 was used to evaluate the time course expression of Gli1, Ptch1 and SOD1 after cerebral ischemia, including normal control group, 3 h, 6 h, 12 h, 24 h, 48 h and 72 h six time points. Experiment 2 was used to detect polydatin's neuroprotection in the acute phase of cerebral ischemia. Rats were randomly assigned to four groups: Sham operated group(Sham), Vehicle group, Polydatin-L group(MCAO + polydatin 12.5 mg/kg)and Polydatin-H group(MCAO + polydatin 50 mg/kg). Polydatin was administered immediately after MCAO and then continued with daily injections for 2 days. At 24 h and 72 h after ischemia neurological deficit was evaluated using a modified six point scale, brain water content was measured by wet-dry method, infarct size was analyzed with 2,3,5-triphenyltetrazolium chloride ( TTC ) staining. Immunohis-tochemistry, reverse transcription-polymerase chain reaction(RT-PCR), western blotting and confocal microscope were used to analyze the expression of Gli1, Ptch1, Nrf2, SOD1 and NF-κB. Experiment 3 was used to detect polydatin's influence on blood-brain barrier(BBB). In this part rats were assigned to four groups as the same way of experiment 2. Western blotting and RT-PCR were used to detect the expression of claudin-5.Results:1 After cerebral ischemia the expression of Gli1, Ptch1 and SOD1 were up-regulated at 6 h, reached the peak at 24 h, and decreased at 72 h.2 Rats in Vehicle group, Polydatin-L group and Polydatin-H group performed a right palsy. Neurological deficit score in Polydatin-H group was decreased compared with Vehicle group(Polydatin-H vs. Vehicle 24 h: 2.6±0.3 vs. 4.1±0.2;72 h: 2.1±0.3 vs. 4.2±0.2,P < 0.05). There was no significant difference in the neurological deficit score between Polydatin-L group and Vehicle group(Polydatin-L vs. Vehicle 24 h: 3.40±0.4 vs. 4.1±0.2;72 h: 3.7±0.21 vs. 4.2±0.2,P > 0.05).3 High dose polydatin reduced the brain water content of ipsilateral hemispheres significantly(Polydatin-H vs. Vehicle 24 h: 80.00%±1.60% vs. 84.37%±0.98%;72 h: 78.53%±1.9% vs. 85.07%±1.81%,P < 0.05)at 24 h and 72 h after cerebral ischemia. In Polydatin-L group the brain water content reduced significantly compared with Vehicle group(Polydatin-L vs. Vehicle: 82.45%±1.25% vs. 85.07%±1.81%,P < 0.05)at 72 h, but not with Polydatin-L treatment at 24 h.4 Extensive lesion was developed in both striatum and lateral cortex in Vehicle group. High dose of polydatin significantly reduced the infarct volume after MCAO(Polydatin-H vs. Vehicle 24 h: 37.38%±2.62% vs. 42.58%±1.82%;72 h: 36.30%±2.79% vs. 42.98%±2.19%,P < 0.05). However, there was no significant difference in infarct volume between Vehicle group and Polydatin-L group.5 High dose of polydatin promoted the expression of Gli1, Ptch1, Nrf2 and SOD1 after MCAO(P < 0.05)at 24 h and 72 h. However, this result is not in Polydatin-L group. In contrary, NF-κB′s expression was decreased both in Polydatin-H and Polydatin-L groups at 24 h and 72 h(P < 0.05).6 Compared with Sham group, MCAO induced sharply reduction of claudin-5(P < 0.05). After treatment with high dose of polydatin, claudin-5′s expression was increased in Polydatin-H(P < 0.05)at 24 h and 72 h. However, the up-regulation of claudin-5 was not observed in Polydatin-L group(P > 0.05).Conclusions: This work shows that the regularity of the time course expression of Gli1, Ptch1 and SOD1 are up-regulated in the early stage of cerebral ischemia. Systemic administration of polydatin is effective which can ameliorate the neurological deficit, decrease the infarct size and improve the brain edema caused by MCAO. Those effects may be through up-regulation of Gli1, Ptch1, Nrf2 and claudin-5 and down-regulation NF-κB expression.
|
PDF Full Text Request