Therapeutic time window of picroside on cerebral ischemia reperfusion injury in rats

BACKGROUNG: Cerebral schemia may result in cerebral edema and neuronal injury by activating some endogenous mechanisms. It has been confirmed that picrosideⅡ could protect neuronal damage in vitro an ex vitro. OBJECTIVE: The aim of the present study is to explore the neuroprotective effects and the perfect treatment window of picrosideⅡ on brain insult in rats following middle cerebral artery occlusion and reperfusion (MCAO/R). DESIGN, TIME AND SETTING: A randomized, controlled animal experiment was performed at Institute of Cerebrovascular Diseases, Qingdao University Medical College from September 2008 to May 2009. MATERIALS AND METHODS: One hundred and sixty-five adult healthy male Wistar rats were randomly divided into a sham-operation group (n=15), a control group (n=75) and a treatment group (n=75). Rats in the control group and the treatment group were experimented surgery operation of MCAO/R with an intraluminal monofilament suture from left external-internal carotid artery. Those in the treatment group were injected 1.0％ picrosideⅡat a single dosage of 10mg/kg from the tail vein. We evaluated neurological function score by Longa’s method, cerebral infarction volume with tetrazolium chloride (TTC) stain. Then we compared cell apoptosis by terminal deoxynucleotidyl transference-mediated biotinylated deoxyuridine triphosphate nick end labeling technique (TUNEL), and determined the expression alternation of aquaporin-4 (AQP-4) via fluorescence labeling analysis and RT-PCR technique. RESULTS: After MCAO/R, neurological function scores were decreased, and a small infarction focus could be detected in ischemic cortex in the control group at ischemic 0.5h, along with the increased number of positive-apotosis cells and the elevated expression of AQP-4 mRNA and its protein. With the duration of ischemia, neurological scores and infarction sizes obviously increased in the control group during ischemic 1.0h-2.0h. A great deal of positive-apoptotic cells were widespread in the cortex and the striatum in the ischemic ipsilateral. Simultaneously, the expression of AQP-4 mRNA and its protein increased to some extent. PicrosideⅡ treatment significantly improved the loss of neurological function, decreased the infarction volume, and elevated the expression levels of AQP-4 mRNA and its protein compared with those in the control group. The therapeutic effect of picrosideⅡ was notable, especially in the ischemic 1.0h subsection. CONCLUSION: These results demonstrate that picrosideⅡ played a neuroprotective effect on cerebral ischemic reperfusion by inhibiting apoptosis and regulating the expression of AQP-4 mRNA and its protein. The best therapeutic window is at ischemic 1h after MCAO.

Therapeutic time window of picroside on cerebral ischemia reperfusion injury in rats