JNK Inhibitor SP600125 Attenuates Rat Brain Ischemia-reperfusion Injury By Downregulating MMP-9 Expression

Acute ischemic stroke is caused by cerebral artery occlusion,accounting for more than80% of all strokes.Ischemic stroke is one of the leading causes of adult death and acquired disability worldwide.The c-Jun N-terminal kinase is a critical pathway in the mitogenactivated protein kinase pathway.Studies have shown that during cerebral ischemiareperfusion,the JNK signaling pathway is highly activated,promoting the transcription of ischemia-related genes,ultimately leading to neuronal pathology and dysfunction.Previous studies have shown that inhibition of JNK has protective effects on cerebral ischemiareperfusion injury,and its specific mechanism is still unclear.Matrix metalloproteinase-9 is also a key regulator in ischemic reperfusion brain injury,which can disrupt the integrity of the blood-brain barrier.An inflammatory reaction occurs after the BBB is destroyed,and cerebral edema and brain tissue structure are destroyed,which exacerbates neuronal death or apoptosis.Objective: To investigate the relationship between JNK and MMP-9 after cerebral ischemia/reperfusion in rats,and to investigate whether JNK inhibitor(SP600125)has protective effects on cerebral ischemia/reperfusion injury by inhibiting the expression of MMP-9.Methods: A 1h reperfusion model of middle cerebral artery occlusion(MCAO)in Sprague-Dawley rats was made by suture.A total of 100 SD male rats were randomly divided into sham operation group,ischemia group and SP600125 group.After MCAO1 h,the expression of p-JNK/JNK and MMP-9 protein in rat cerebral cortex was detected at different time points of reperfusion for 3h,6h,24 h and 48 h.The neurological deficit score(18-point system)was evaluated at 48 hours after MCAO reperfusion.The volume of cerebral infarction was measured by TTC staining,and the degree of cerebral edema was measured by dry and wet weight method.JNK inhibitor SP600125(dissolved in 10% DMSO,final concentration20mmol/L)was injected into the lateral ventricle 30 min before cerebral ischemia/reperfusion,and the neurological deficit score was reevaluated in MCAO for 48 h reperfusion.Volume,degree of cerebral edema,and expression levels of p-JNK/JNK,MMP-9 protein in rat brain.Results: At 48 h after 1 hour of brain cerebral ischemia and reperfusion,the neurological score was significantly lower in the ischemic group than in the sham operation group(8.6 vs18,P(27)0.001),and the volume of cerebral infarction was increased(65.024 vs 0,P(27)0.001),the degree of cerebral edema was aggravated(1.325 vs 1.017,P(27)0.001);At 24 h after 1 hour of MCAO,the protein expression of p-JNK/JNK in the cerebral cortex of rats began to increase(P(27)0.05),while the protein expression level of MMP-9 was also higher than that of sham operation group(P(27)0.01,P(27)0.05).Compared with the ischemic group,the neurological deficit of SP600125 group was improved(8.6 vs 14.5,P(27)0.001),the volume of cerebral infarction decreased(65.024 vs 30.828,P(27)0.001),the degree of cerebral edema decreased(1.325 vs 1.254,P(27)0.01),and the protein expression levels of p-JNK/JNK and MMP-9 in SP600125 group were also higher than ischemic group(P < 0.01).Conclusion: 1.Both JNK and MMP-9 increased at 1h and 48 h after cerebral ischemia,accompanied by cerebral edema,cerebral infarction and neurological damage.JNK and MMP-9 may be involved in brain damage after reperfusion in rat MCAO.2.JNK inhibitor SP600125 may down-regulate the expression of MMP-9,reduce brain edema and cerebral infarction after ischemia-reperfusion,thereby playing a protective role in the brain.