Effects Of Mild Hypothermia Combined With Salidroside On Blood-brain Barrier In Rats With Global Cerebral Ischemia-reperfusion

Objective: To explore the protective effects and mechanisms of mild hypothermia combined with salidroside on the blood brain barrier in rats with global cerebral ischemia reperfusion,and to provide experimental basis for its clinical application.Methods: 90 male SD rats were randomly divided into 5 groups according to the random digital table method(n=18):(1)Sham operation group(Sham group): rats were subjected to exposure of bilateral pterygoid holes as well as bilateral common carotid artery and intraperitoneal injection with 0.9% sodium chloride solution;(2)Global cerebral ischemia reperfusion group(GCI/R group): GCI/R model was modified from Pulsinelli’s 4-VO method and blood reperfusion was performed at 10 minutes following cerebral ischemia.Before reperfusion,rats were subjected to intraperitoneal injection with 0.9% sodium chloride solution;(3)Mild hypothermia treatment group(MH group): rats suffered from global cerebral ischemia and before reperfusion,they were subjected to intraperitoneal injection with 0.9% sodium chloride solution and mild hypothermia therapy.Mild hypothermia was sustained for 3h by ice bags and heat lamp;(4)Salidroside treatment group(Sal group): rats suffered from global cerebral ischemia and before reperfusion,they were subjected to salidroside therapy(20mg/kg).(5)Mild hypothermia combined with salidroside treatment group(MH+Sal group): rats suffered from global cerebral ischemia and before reperfusion,they were subjected to mild hypothermia and salidroside therapy(20mg/kg).Mild hypothermia was maintained for 3h.The 0.9% sodium chloride solution injected in Sham,GCI/R and MH groups was the same volume as the salidroside solution injected in Sal and MH+Sal groups.Rats were subjected to injection every 24 h after first intraperitoneal injection of 0.9% sodium chloride solution or salidroside until 72 h after reperfusion.The neurological function deficiency was evaluated according to the Geocadin’s neurologic deficit scale(NDS)at 72 h after cerebral ischemia reperfusion.The morphological changes of brain tissue cells were evaluated by HE staining method.The brain water content was measured by wet-dry weights method.The permeability of blood brain barrier was measured by Evans blue method.The activity of SOD was measured by WST-8 method.The content of MDA was measured by barbituric acid method and the content of ROS was detected by DHE staining.The expression of MMP9、claudin5 and occludin were measured by western blot method.Results:(1)Compared with Sham group,the NDS of rats in GCI/R group was obviously decreased(P<0.001),significant pathological changes of brain tissue cells were observed under microscope,the brain water content was significantly increased(P<0.001),the permeability of blood brain barrier was increased(P<0.001),the activity of SOD was reduced,the expression of ROS and MDA was increased(P<0.001),the expression of MMP9 was up-regulated and the expression of claudin5 and occludin was decreased(P<0.001);(2)The NDS of the treatment groups increased to varying degrees compared with the GCI/R group and the pathological changes of brain tissue cells were improved.The brain water content and blood brain barrier permeability were decreased,the activity of SOD was increased,the content of ROS and MDA was decreased,the expression of MMP9 was decreased and the expression of claudin5 as well as occludin was increased.Among above treatment group,changes in MH+Sal group were most significant.Conclusion: Mild hypothermia combined with salidroside significantly attenuated blood brain barrier damage caused by global cerebral ischemia reperfusion and ameliorated brain edema,tissue pathological changes and neurological dysfunction caused by blood brain barrier disruption.This may be related to its inhibition of oxidative stress,reduction of ROS,MMP9 and degradation of claudin5 as well as occludin.