Study Of The Role Of5-Lipoxygenase In The Mechanism Of Protection To Brain Induced By Isoflurane Preconditioning

The Ischemic Cerebrovascular Disease （ICVD） has been one of common andfrequently diseases which threaten human health.It is one of the central nervous systemdiseases with the characteristics of blood circulation disorder in brain. The inflammatoryresponse pariocipated in the cerebral ischemia-reperfusion injury and the inflammatoryresponse was one of most studied mechanisms in the cerebral ischemia-reperfusion injury.5-LOX is one of most Inflammatory cytokines in the cerebral ischemia-reperfusion injury andplay a key role in the inflammatory response.At the same time，lots of experiment haveproved that5-LOX pariocipated in the pathophysiology of cerebral ischemia-reperfusioninjury.Previous studies have shown that the inflammatory response mediated by Toll-like recepter（TLRs） involved in the injury after the cerebral ischemia-reperfusion injury.TLR4can actived NF-κB through MyD88singaling pathway， which induced inflammatorycascade.The MyD88is the set point for every TLRs signal. Early studies by our group hasshown that isoflurane preconditioning can reduce the inflammatory reaction and the damageto the focal cerebral ischemia reperfusion model in rats by inhibiting the expression ofTLR4and MyD88. Therefore what is the role of5-LOX in the signaling pathway ofsynthetic of NF-κB dependented on the MyD88in the cerebral? And whetherpreconditioning with the isofluran can protect the brain by inhibiting the expression of5-LOX. This study is aim to investigate that the role of5-LOX in the signaling pathway ofMyD88-NF-kB and the mechanism of protection by isoflurane preconditioningPart1The impact of5-LOX to the MyD88dependented synthesis ofNF-kB after cerebral ischemia-reperfusion.Objective:To inverstigate the impact of5-LOX to the synthetic of NF-κB in the centralnervous system.Methods:Thirty male adult Sprague-Dawley rats （(body weighing250-280g) wererandomly divided into three groups（n=10each）：sham operation group（group S）：stripvessel without insert thread into right Internal carotid artery；Focal cerebral I/R group（I/Rgroup）：the focal cerebral I/R modal was induced by nylon mono filamen-t. Pulling outthe line for reperfusion after blocking for120min；Inhibitor treated group（B group）：Injecting the BW-B70C which is the inhibitor of5-LOX by2mg/kg through cervicalvessels. Induced MCAO model following methods of gourp I/R group after30mins ofinhibitor injection.. Western blot and RT-PCR were used to analyse the protein and mRNAexpression level of5-LOX, Myd88and NF-κB in the brain after reperfusion for24h.Results:Compared to group S,the level mRNA and protein of5-LOX, Myd88and NF-κBwere significantly increased（P<0.05）in group I/R and B；compared to I/R group，themRNA and protein level of5-LOX,Myd88and NF-κB were significantly declined（P<0.05）in group B.Conclusion:The5-LOX participates in the ynthetic of NF-κB dependented on the MyD88 after the cerebral ischemia-reperfusion.Part2The role of5-LOX in the protective mechanism to brain byisoflurane preconditioningObjective:To investigate the role of5-LOX in the protective mechanism to brain byisoflurane preconditioning to the modal MCAO.Methods:Thirty nine male adult Sprague-Dawley rats between250-280g were picked，anddivided into three group（n=13each） randomly：sham operation group（group S）：stripvessel without insert thread into right Internal carotid artery；Focal cerebral I/R group（I/Rgroup）：the focal cerebral I/R modal was induced by nylon mono filamen-t. Pull out theline for reperfusion after blocking for120min. Isoflurane preconditioning group（I group）administered with2%isoflurane for2h，Induced MCAO model following methods ofgourp I/R group after24h. At the next24h after the reperfusion, the neurological deficitscores were evaluated,and infarct size were measured. Western blot and RT-PCR wereused to analyse mRNA and protein expression level of5-LOX, Myd88and NF-κB in thebrain after reperfusion for24h.Results:Compared to group S, in group I/R, groupI, the neurological deficit scoresincreased，the infarct size increased，and the mRNA and protein level of5-LOX,Myd88and NF-κB were significantly increased. Compared to group I/R, the neurological deficitscores，the infarct size，and the mRNA and protein level of5-LOX,Myd88and NF-κBwere significantly declined in group I（P<0.05）.Conclusion:Isoflurane preconditioning can reduce focal cerebral I/R injury bydown-regulating the expression of5-LOX and inhibiting MyD88/NF-κB signalingpathway in rats.