| Background and objective:The focal zone consists of ischemia central zone and ischemia penumbra after ischemia brain damage. Currently considered, in central zone of ischemic neuronal, the death of nerve cells in the form of necrosis, the death of nerve cells is irreversible; in ischemic penumbra, the main forms of neuronal death is apoptosis, under certain conditions, nerve cell death is reversible, Therefore, the key to treat ischemic brain injury is to save the dying neurons in ischemic penumbra. Hypoxia inducible factor-la (HIF-lα) is a transcription factor. In anoxic conditions, it widespread in the human body and mammalian.In recent years, more and more evidence show that, in cerebral ischemia-reperfusion injury HIF-la has a protective effect. This effect of HIF-1αis through its regulation the expression of corresponding target gene. Erythropoietin (EPO) is regulated by hypoxia glycoprotein hormone, it a downstream target gene of HIF-1 a. EPO plays a role in brain protection through by upregulating bcl-2, bcl-x1 gene expression, inhibition the expression of caspase-3, inhibition the excessive of NO synthesis, against glutamate excitotoxicity, inhibiting the release of cytochrome c and other ways. Presently, it was reported that Chinese medicine polygonum multiflorum thunb and its active pharmaceutical ingredients tetrahydroxystilbene glucoside (TSG) had protective effects on cerebral ischemia, but the mechanism was not fully understood. In this study, we observed the protein expression of HIF-lαand EPO and the effect of TSG. Using TUNEL detect the apoptotic cell. The impairment of brain tissue and apoptotic cells were detected to investigate the mechanism of neuroprotective.The results may provide the experimental bases for the new drug development and therapeutic strategy on cerebral ischemia.Methods:The healthy male sprague-dawley rats weighting 400～500g were randomly divided into three groups:sham operation group (n=24), NS control group (n=24), TSG treatment group (60mg/kg/d, n=24). After 7 days intragastric (ig) administration of TSG (treatment groups) or natural saline (NS control group). Transient focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). Then, neurological behavior evaluation was performed by the method of Longa's scoring. The pathologic changes were observed by hematoxylin and eosin (HE) staining at 6h,12h,24h and 7d.The protein expression of HIF-la and EPO were measured by methods of immunohistochemistry, the expression of apoptotic cells were detected by terminal deoxynucleotide transferase-mediated nick end labeling (TUNEL) technique..Results:1.Compared with I/R group, treatment with TSG could decrease the grade of the rat neurological defects except at 6h after reperfusion.2. Typical neural necrosis could be observed in I/R group and TSG group by HE staining at 24h after reperfusion.3. The protein expression of HIF-1αand EPO were detected few in control group. The protein expression of HIF-la and EPO increased at 6h after cerebral reperfusion, the protein expression of HIF-1αreached maximum at 24h, reduced at 48h and maintained much at 7d in NS control group and TSG groups. The protein expression of EPO reached maximum at 48h, and maintained much at 7d in NS control group and TSG group. Compared with model group, treated with TSG could significantly increase the protein expression of HIF-1α,EPO and reduce apoptotic cells'numbers after reperfusion.4. Few apoptotic cells were detected in control group. Apoptotic cells'numbers increased significantly at 6 h after reperfusion in I/R group and TSG group compared with in control group. The peak of apoptotic cells'numbers appeared at 24 h after reperfusion, and lasted to 48 h and 7 d after reperfusion. Compared with I/R group, treated with TSG could reduce apoptotic cells'numbers.Conclusions:Tetrahydroxystilbene glucoside probably through inducing the increase of HIF-la in rats suffered ischemia-reperfusion injury to raise the expression of EPO, and then reduce the number of apoptotic cell.
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