| Background and objective: Recombinant tissue-type plasminogen activator is the first recommended intravenous thrombolytic agent for acute ischemic stroke(AIS).However,the application of which is hampered by its narrow therapeutic time-window of 4.5 hours and potential hemorrhagic complication.Remote ischemic preconditioning(RIPC)refers to the short-term ischemic/reperfusion treatment of peripheral distal organs to make the distant organs or tissues resistant to long-term injury,and it has been proved to be an additive therapy to improve clinical outcomes in patients with acute ischemic stroke.So this study characterized the beneficial effect of RIPC about the permeability of BBB,risk of HT after thrombolysis,infarct volume and neurological deficits on delayed rt PA thrombolysis in a rat model of thromboembolic stroke and also its potential mechanism.Methods: A total of 432 Male SD rats weighing 300-350 g were randomly divided into the group RIPC+rt PA and group rt PA.Rats of group RIPC+rt PA received a 7-day RIPC treatment(once in the morning and once in the evening),rats of group rt PA received anesthetization-only and then subjected to stroke.In the first part of our study,rats both of group RIPC+rt PA and group rt PA were subjected to thromboembolic middle cerebral artery occlusion at the eighth day,and only 240 rats with successful occlusion received thrombolytic therapy with rt PA at 3 hours,5 hours and 7 hours after the surgery.The specific mechanism of the neuroprotective function of RIPC was explored in the second part of our study.At the eighth days,rats in both groups were injected protein PDGF-C with intravenously or lateral ventricular injection,normal saline was also injected as a control group right before the surgery.Then 120 rats with successful occlusion received thrombolytic therapy with rt PA at 5 hours after surgery.This part contained 5 groups,namely group NS,group PDGF-C(iv.),group RIPC+NS,group RIPC+PDGF-C(iv.)and also group RIPC+PDGF-C(icv.).Meanwhile,24 rats were randomly divided into 4 groups,the sham group did not receive any treatment,the rt PA group received intravenous rt PA at the time point of 7d+12h,the RIPC group received 7d RIPC treatment,and the RIPC+rt PA group received intravenous rt PA at 12 h after 7d RIPC treatment,and blood was collected and analyzed at 24 h after 1d,7d and 24 h after 7d.Longa scoring test,horizontal ladder behavioral test and forelimb function test were used to evaluate the neurological deficits after stroke.TTC staining was used to calculate the infarct volume in ischemic rats.The expression of Claudind5、Occludin、ZO-1、Laminin、PDGF-CC、PDGFRα and also p-PDGFRα were analyzed by Western blot.Intracerebral hemorrhage was measured by hemoglobin level and BBB permeability level was determined by measuring the extravasation of Evans blue dye.The content of PDGF-CC protein in peripheral blood was measured by Rat Platelet-derived growth factor CC Elisa Kit.Results: 1、Compared with group rt PA,cerebral infarct volume of rats in group RIPC+rt PA with thrombolysis therapy at 3 hours,5 hours and 7 hours were decreased by 6.1%(P<0.001),4.2%(P<0.05)and 8.3%(P<0.001).The neurological deficits of rats in group RIPC+rt PA was significantly improved compared with the group rt PA(P<0.05)in both 3 time points of thrombolysis.2、Compared with group rt PA,Evan’s blue permeability decreased in rats of group RIPC+rt PA in 3 hours’ thrombolysis(P<0.05),and also decreased in group RIPC+rt PA in 5 and 7 hours’ thrombolysis(P<0.01).In the meanwhile,hemoglobin content in ischemic hemisphere of group RIPC+rt PA decreased compared that with group rt PA,and the hemoglobin content of the 5h group showed statistically significant difference(P<0.05).Compared with group rt PA,the expression levels of Claudin5,Occludin,Laminin and zo-1 protein were decreased in group RIPC+rt PA.3、After receiving RIPC treatment for 7 days,the content of PDGF-CC in the peripheral blood of group RIPC+rt PA was significantly lower than that of group rt PA(P<0.01).The expression level of p-PDGFRα protein in ischemic hemisphere of group RIPC+rt PA was significantly decreased compared with that in group rt PA of 3 hours’ thrombolysis(P<0.01),and reduced compared with that in group rt PA of 5 hours’ thrombolysis(P<0.05),and showed no significant difference statistically in 7 hour group(P>0.05).4、Compared with group RIPC+NS,Evan’s blue permeability and hemoglobin content in ischemic brain tissue of group RIPC+PDGF-C(iv.)increased(P<0.05),and significantly higher in group RIPC+PDGF-C(icv.)(P<0.001).Compared with group NS,Evan’s blue permeability and hemoglobin content in ischemic brain tissue of group PDGF-C(iv.)significantly increased(P<0.05).5、Compared with group RIPC+NS,the expression of p-PDGFRα level in group RIPC+PDGF-C(icv.)and group RIPC+PDGF-C(iv.)were increased(P<0.05);Compared with group NS,the expression of p-PDGFRα level in group RIPC +PDGF-C(icv.)was increased(P<0.05),and decreased in RIPC+NS group(P< 0.05).6、In normal rats without cerebral ischemia model,the content of PDGF-CC in peripheral blood showed a decreasing trend after 1 day(once in the morning and once in the evening)of RIPC treatment(P<0.05)without time dependence.Compared with sham group,p-PDGFRα protein in brain tissues of RIPC group showed a decreasing trend,but the difference was not statistically significant.Compared with the rt PA group,p-PDGFRα protein in the brain tissue of the RIPC+rt PA group was significantly reduced(P<0.001).Conclusion: 1、RIPC treatment could improve the neurological deficits and BBB function in thrombotic stroke rats with thrombolysis within or beyond therapeutic time window.2、The PDGF-CC content in the blood of normal rats decreased after RIPC treatment,and it was not time dependent.3、The mechanism by which RIPC improves the blood-brain barrier function in thrombotic stroke rats with thrombolysis may be implemented by inhibiting the PDGF-CC /PDGFRα signaling pathway. |
PDF Full Text Request