| Stroke is one of the main causes of death worldwide,The largest number of strokes in China,87% of them are ischemic stroke.Because of its narrow treatment window,high fatality rate and poor prognosis,there is a threat to the survival of mankind.There is no clinically effective drug for the curing of stroke.but researches have shown delta opioid receptor(DOR)drugs have a benefit effect on ischemic stroke.delta opioid receptor is GPCRs.These few years,many studies have demonstrated that DOR agonists can reduce cerebral ischemic damage,but the specific mechanism of action is still unclear.The G protein-coupled receptor family and the receptor tyrosine kinase(RTKs)family are two important receptor families,which mediate a variety of signals in the body,and there is a signal dialogue.Studies have shown that the activation of GPCR by agonists will cause the activation of MMP on the cell membrane,the precursor of HB-EGF(pro-HB-EGF)is cleaved into active HB-EGF,which is released in free form and interacts with RTKs such as EGFR.Combines to activate downstream signals.This process is called transactivation.In the downstream signaling pathway,the MAPK pathway,downstream of which is ERK and Akt pathways that protect cells against ischemia-reperfusion injury.Oxygen-ischemia has important physiological significance for promoting cell survival.In previous studies,the molecular mechanism of transactivation was studied at the cellular level,but there are few studies in the body model.And whether the transactivation pathway is involved in the process of ischemia-reperfusion injury in the brain has not been reported yet.Therefore,in this topic,we use the rat middle cerebral artery occlusion/reperfusion model to simulate ischemic stroke.Pretreatment with DOR agonist DADLE was injected into the lateral ventricle,and the neurological behavior score results showed that DADLE can significantly improve the motor and sensory function of rats after MCAO/Reperfusion,TTC assay founds that DADLE can significantly reduce the area of ischemic infarction.The use of EGFR blocker AG1478 and metalloproteinase inhibitor GM6001 can block the protective effect of DADLE on cerebral ischemia in rats.The key proteins of the pathway were analyzed by western blotting,and it was found that DADLE activated EGFR,Akt and ERK1/2 in the hippocampus over time,and increased the protein expression level of EGFR.Among them,protein phosphorylation and peak expression changes appeared at 24 hours.AG1478 and GM6001 can suppress the above phenomenon.The results of ELISA and q PCR showed that DADLE activated DOR to increase the free HB-EGF in the cerebrospinal fluid,but the amount of HB-EGF in the tissue decreased at the level of m RNA and protein.In addition,the TUNEL method to detect the level of apoptosis also indicates that the protective effect of DOR on cerebral ischemia is also related to the reduction of hippocampal cells Related to apoptosis.In summary,these results illustrate that the EGFR transactivation pathway caused by MMP-mediated release of HB-EGF is involved in the process of the DOR agonist DADLE in reducing cerebral ischemia-reperfusion injury.At the same time,these results suggest that the molecular mechanism of the neuroprotective effect of DOR also provides new ideas for reducing and preventing ischemic stroke injury. |
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