Effect of Usnic Acid on Neuronal Necroptosis in Rats with Cerebral Infarction by Regulating the RIPK1/RIPK3/MLKL Signaling Pathway / 中药新药与临床药理

ABSTRACT

Objective To investigate the impact of usnic acid on neuronal necroptosis in rats with cerebral infarction by regulating the receptor-interacting protein kinase 1(RIPK1)/receptor-interacting protein kinase 3(RIPK3)/mixed lineage kinase domain-like protein(MLKL)signaling pathway.Methods The rat model of cerebral infarction was established by middle cerebral artery occlusion and reperfusion(MCAO/R).The successfully modeled rats were divided into model group,NEC-1(RIP1 inhibitor)group,low-,medium-,and high-dose of usnic acid groups,with 20 rats in each group.Another 20 rats were selected as a sham-operation group.After 3 days of drug intervention,the modified Neurological Severity Scale(mNSS)was applied to evaluate the degree of neurological damage of rats in each group.TTC staining was applied to detect the volume of cerebral infarction.HE staining was selected to observe pathological damage in brain tissue.PI/NeuN staining was selected to observe neuronal necrosis.RT-qPCR was used to detect mRNA levels of RIPK1,RIPK3 and MLKL in rat ischemic brain tissue.Western Blot was used to determine the expressions of RIPK1/RIPK3/MLKL signaling pathway related proteins in rat ischemic brain tissue.Results Compared with the sham-operation group,the neural cells in the model group showed structural damage,cell disrupted,deformation,and nuclear pyknosis,furthermore,the mNSS score,the cerebral infarction volume,proportion of PI-positive neurons were significantly increased(P＜0.05).The mRNA levels of RIPK1,RIPK3,MLKL in brain tissue,ratio of p-RIPK1/RIPK1,and the levels of RIPK3 and MLKL proteins were obviously increased(P＜0.05).Compared with the model group,the damage degree of neurocyte morphology in the low-,medium-,and high-dose of usnic acid groups was gradually alleviated,the nuclear membrane was gradually became clear,and the cell body was gradually returned to normal.The neurocyte morphology in the NEC-1 group was basically intact,and the nuclear membrane was basically clear.The mNSS score,cerebral infarction volume and proportion of PI-positive neurons in NEC-1 group and usnic acid groups were significantly decreased(P＜0.05).The mRNA levels of RIPK1,RIPK3,MLKL,ratio of p-RIPK1/RIPK1,and levels of RIPK3 and MLKL proteins in brain tissue were obviously reduced in usnic acid groups and NEC-1 group.Also,there was dose-dependent decrease in usnic acid groups(P＜0.05).No statistically obvious difference was found between the high-dose usnic acid group and the NEC-1 group(P＞0.05).Conclusion Usnic acid inhibits neuronal necroptosis in rats with cerebral infarction by inhibiting the RIPK1/RIPK3/MLKL signaling pathway,thereby alleviating brain injury in rats with cerebral infarction.