Remote Ischemic Conditioning Attenuates Prognosis Of Intravenous Thrombolytic MCAO Rat Model By Inhibition Of Caspase-1/IL-1β Signaling Pathway

Background and Objective:Ischemic stroke is the most common type of stroke and is one of the leading causes of death and disability worldwide.At present,Recombinant tissue Plasminogen Activator（rt PA）is the most widely used thrombolytic therapy for AIS,but more than50% of patients still have poor prognosis after receiving intravenous thrombolytic therapy with rt PA.How to improve the efficacy of intravenous thrombolysis is a key problem in clinical treatment.Remote ischemic treatment（RIC）is an effective neuroprotective measure that can improve the tolerance of Remote organs to ischemia by temporarily and intermittently treating limbs.The mechanism of RIC’s neuroprotective effect is still unclear,and previous studies have suggested that RIC may be related to inflammation and immune regulation.In this study,MCAO rat model treated wih the rt PA thrombolytic therapy was used to explore whether RIC can play a neuroprotective role in intravenous thrombolytic therapy for cerebral infarction,and further explore its related mechanism.Methods:Ninety two SD rats were randomly divided into 4 groups: Sham、MCAO+rt PA、MCAO+rt PA+early RIC treatment、MCAO+rt PA+late RIC treatment.The MCAO rat model was established by the thread-occlusion method.After 120 minutes of occlusion,reperfusion was performed,and then intravenous thrombolysis was performed immediately with rt PA by caudal vein injection.Rats in RIC treatment groups were treated with RIC within 40 min after infarction and 40 min before reperfusion,respectively.In this study,Zea-Longa Scale was used to evaluate the neurological deficits after stroke.TTC staining was used to detect the infarct area in each group.Evan’s Blue and hemoglobin detection were used to evaluate the BBB damage and hemorrhage transformation after thrombolytic therapy.Western Blot was used to detect the expression of caspase-1 and IL-1β in the cerebral cortex,and HE staining was used to evaluate the damage of neurons.Result:1.Security:24h after reperfusion,Evan’s Blue content and hemoglobin content of MCAO+rt PA+ early RIC group and MCAO+rt PA+ late RIC group showed a decreasing trend compared with MCAO+rt PA group（0.059 vs.0.061 vs.0.062 ug/g,0.226 vs.0.241 vs.0.254mg/dl）,and MCAO+rt PA+ early RIC group decreased more significantly,but there was no statistical difference between the groups.2.Effectiveness:（1）Behavioral scores of MCAO rats in 1d,3d,and 7d after reperfusion showed that the behavioral scores of MCAO+rt PA+ early RIC and MCAO+rt PA+ late RIC groups were significantly lower than those of MCAO+rt PA group,with statistically significant differences（P<0.05）.There was no statistical difference in behavioral scores between the two RIC groups at each time point（P>0.05）.（2）72h after reperfusion,the infarct area of MCAO+rt PA+ early RIC and MCAO+rt PA+ late RIC groups was significantly smaller than that of MCAO+rt PA group,with statistical difference（P<0.05）,and there was no statistical difference between early RIC and late RIC groups（P>0.05）.（3）24h and 7d after reperfusion,HE staining of brain tissue in MCAO+rt PA+ early RIC group and MCAO+rt PA+ late RIC group showed less damage and higher neuron survival ratio compared with MCAO+rt PA group.（4）24h and 7d after reperfusion,caspase-1 and IL-1β expressions in MCAO+rt PA+early RIC and MCAO+rt PA+ late RIC treatment groups were significantly lower than those in MCAO+rt PA group.There were no significant differences in caspase-1 and IL-1β expression at 24 h and 7d after reperfusion between the two RIC groups.Conclusions:1.RIC therapy is safe for MCAO rats receiving intravenous thrombolytic therapy with rt PA,and does not increase the risk of BBB destruction and hemorrhage transformation.2.RIC therapy is effective for MCAO rats receiving intravenous thrombolytic therapy with rt PA,which can effectively reduce the volume of cerebral infarction,reduce neuronal injury,and improve the symptoms of neurological impairment.3.The mechanism of RIC improving the prognosis of intravenous thrombolytic MCAO rats may be related to the down-regulation of caspase-1/IL-1β inflammatory pathway.