Effects Of PrP~c On The Expression Of NLRP3 And Its Downstream Factors In Cerebral Ischemia/Reperfusion Injury

Background:Ischemic stroke is the most common type of stroke in the world.At present,the most effective treatment for ischemic stroke is acute reperfusion and recanalization,but the reperfusion of blood flow in the ischemic area will lead to ischemia/reperfusion injury and aggravate the brain tissue damage.Intracellular prion protein PrP^cis mainly expressed in the central nervous system.PrP^c can stimulate neurite growth,inhibit oxidative stress-dependent cell death,and promote anti-apoptotic signaling,which has a protective effect on cerebral ischemia in mice.NLRP3 inflammasomes mediates the inflammatory response and cell death by releasing the inflammatory cytokines IL-1βand IL-18 after a series of aggregation and activation steps.And the NLRP3 inflammasome is upregulated in cerebral ischemia/reperfusion injury.Oxidative stress is not only a factor of PrP^c in cerebral ischemia/reperfusion injury,but also a major stimulator of NLRP3 inflammasome activation.It is suggested that the effect of PrP^c on cerebral ischemia/reperfusion injury may be related to NLRP3 inflammasome,but there is no relevant study on the relationship between the two in cerebral ischemia/reperfusion injury.This is exactly the question that this study intends to explore.Methods:Male mice of Wild Type（WT）and PRNP knockout Type(PRNP.KO,PRNP^-/-)aged from 6 to 8 weeks were randomly divided into control,sham and middle cerebral artery occlusion（MCAO）group,with 6 mice in each group.MCAO group was modulated with monofilament nylon suture-occluded method,and the monofilament was removed after 90minutes of ischemia.Compared with the MCAO group,the sham-operation group only separated and ligated the blood vessels without inserting the monofilament nylon suture.After 24 h of ischemia,the neurobehavioral score was performed,and the failure of modeling and death of mice were excluded,ensuring that 6 mice in each group were enrolled in the follow-up experiments.The infarct area was calculated by triphenyltetrazolium chloride（TTC）staining.The expression levels of NLRP3 inflammasome and its downstream factors caspase-1 and IL-1βin the cerebral tissues of the infarct side and the contralateral side were detected by Real-time PCR.The relationship between different PrP^cexpression levels and NLRP3 inflammasome and its downstream factors in the infarcted side and contralateral side were observed.Results:1.The behavioral scores of both WT and PRNP.KO mice after MCAO were significantly higher than those of control group and sham group（P<0.05）,but there was no significant difference between sham group and control group.The behavioral score of PRNP.KO mice was significantly higher than that of WT mice（P<0.05）.2.The infarct volume in the MCAO group of WT and PRNP.KO was significantly larger than that in the control group and sham group with the same genotype（P<0.05）,and the infarct volume in the PRNP.KO group was significantly larger than that in the WT group（P<0.05）.3.In both WT and PRNP.KO mice,the expression level of NLRP3 inflammasome in the left brain tissue（infarct side）of MCAO group was significantly higher than that of control group and sham group,and the expression level of NLRP3 inflammasome in the left brain tissue of MCAO of PRNP.KO mice was significantly higher than that in the right brain tissue of MCAO（P<0.05）.In both WT and PRNP.KO mice,The expression level of Caspase-1 in the left brain tissue（infarct side）of MCAO group was significantly higher than that of control group,and in the left brain tissue of PRNP.KO MCAO group was significantly higher than that of sham group（P<0.05）.The expression level of IL-1βin left brain tissue of WT and PRNP.KO MCAO group was significantly higher than that of control group,sham group and right brain tissue of MCAO（P<0.05）.4.The expression of NLRP3 inflammasome and IL-1βin the infarct side of PRNP.KO MCAO mice was significantly higher than that in WT MCAO mice（P<0.05）,while the level of caspase-1 in PRNP.KO MCAO was slightly higher than that in WT MCAO group,but there was no statistical significance（P>0.05）.Conclusion:1.PrP^c played a protective role in cerebral ischemia/reperfusion injury.2.NLRP3 inflammasome/caspase-1/IL-1βis involved in the occurrence and development of cerebral ischemia/reperfusion injury.3.PrP^c had a protective effect on cerebral ischemia/reperfusion injury possibly by inhibiting the expression of NLRP3 inflammasome and IL-1β.