The Effect Of MicroRNA-155 On Cerebral Ischemia-Reperfusion Injury Through Regulation Of Notch

Objective: To investigate the the molecular mechanism of mi R-155 in the regulation of cerebral ischemia/reperfusion(I/R)injury with middle cerebral artery occlusion(MCAO)in mice.Methods: A total of 120 male C57BL/6 mice were randomly divided into the following six groups(n=20 in each): sham group,Pre-IR group,mi R-155-/-sham group,mi R-155-/-Pre-IR group,mi R-155+/+sham group,mi R-155+/+Pre-IR group.The MCAO model was established in mice.The effect of cerebral I-R injury on the neural function of mice was evaluated by triphenyltetrazole chloride(TTC)staining and nerve function scoring.The real-time quantitative polymerase chain reaction(RT-q PCR)technique was used to test the expression of mi R-155.By using hematoxylin-eosin(HE)staining the effect of mi R-155 on brain histopathology was assessed.The effect of mi R-155 on the permeability of blood brain barrier was evaluated by measuring evans blue(EB)and water content in brain tissue.The effect of mi R-155 on endothelial function was estimated by measuring nitric oxide(NO)content and expression of endothelial nitric oxide synthase(e NOS).Immunoblotting was employed to check the expressions of Notch1,Notch1 intracellular domain(NICD)and Hesl,and RT-q PCR was adopted to check Notch1 and Hesl m RNA levels in order to clarify the role of mi R-155 in Notch signaling pathway.The experimental data were expressed by mean±standard(?x ±s).Independent sample t test / Student-Newman-Keuls test and one-way ANOVA were used to analyze the differences between groups.Results: Compared with the sham operation group,the mice showed significant neurological damage after MCAO modeling(P<0.001).TTC staining showed large pale areas in the left hemisphere of the mouse,suggesting cerebral infarction.The expression of mi R-155 was significantly increased after MCAO in the brain of mice(P <0.001).HE stainingresults showed that mi R-155 deletion can reduce cerebral cortical edema and neuronal damage.Western blot showed that compared with the Pre-IR group,the expression of Notch1,NICD and Hes1 in the mi R-155-/-Pre-IR group increased(P<0.05).Compared with the Pre-IR group,the apoptosis detection and RT-q PCR results showed that the deletion of mi R-155 decreased the percentage of TUNEL staining positive cells(P<0.001)and caspase-3 levels(P<0.01).Compared with the Pre-IR group,inhibition of mi R-155 expression increased NO production and e NOS expression(P<0.001),leading to downregulation of the brain water content and EB level(P<0.01).However,Overexpression of mi R-155 restored all these changes to similar levels in the Pre-IR group.The expression of Notch1,NICD and Hesl could improve the cerebral I-R injury status.Conclusion: In mouse I-R injury,inhibition of mi R-155 expression have protective effects on I-R injured brain tissue.The results of this study indicate that mi R-155 can block normal NO production and e NOS expression through the Notch signaling pathway.This regulatory mechanism may be one of the potential targets for the treatment of ischemic stroke in the future.