Exploring the effect of total flavonoids of patriniae radix on neuronal apoptosis in neonatal rats with hypoxic⁃ischemic encephalopathy based on PKC/ERK pathway
Objective：This study aims to explore the effect and mechanism of total flavonoids of patriniae radix on hippocampal neuron apoptosis in neonatal rats with hypoxic-ischemic encephalopathy（HIE）. Methods：Seventy-two neonatal rats were divided into sham operation group，model group，chelerythrine group（5 mg/kg），and total flavonoids of patriniae radix low -（50 mg/kg）and high-（100 mg/kg）dose groups，total flavonoids of patriniae radix + chelerythrine group（100 mg/kg total flavonoids of patriniae radix+5 mg/kg chelerythrine），with 12 rats in each group. The HIE model was constructed by ligating the right common carotid artery and hypoxic treatment for 2.5 h. Rats in the chelerythrine group were intraperitoneally injected with chelerythrine，and the total flavonoids of patriniae radix groups were given the corresponding doses of total flavonoids of patriniae radix by gavage. Rats in the total flavonoids of patriniae radix + chelerythrine group were injected intraperitoneally with chelerythrine while giving total flavonoids of patriniae radix by gavage，once daily for 7 consecutive days. The neurological deficit score was used to detect the nerve function of rats. Hematoxylin- eosin（HE）staining was used to observe the pathological changes in the hippocampus of brain tissue. TdT -mediated dUTP nick end labeling（TUNEL）/neuronal nuclei antigen（NeuN）fluorescent double staining was used to observe the apoptosis of hippocampal neurons. Western blot was used to detect the expression of protein kinase C（PKC）/extracellular signal-regulated kinase（ERK） pathway and apoptosis-related proteins in brain tissue. Oxygen-glucose deprivation/reperfusion（OGD/R）was used to construct a cell model. CCK -8 and lactate dehydrogenase（LDH）assays were performed to analyze the neuronal effect of total flavonoids of patriniae radix on primary hippocampal neurons. Cell apoptosis was analyzed by flow cytometry，and Western blot was used to detect the expression of apoptosis-related proteins. Results：In the in vivo study，compared with the sham operation group，the rats in the model group showed different degrees of neurological deficits，and the neurological deficit score，the numbers of NeuN+ TUNEL+ cells，the expression of Bax and Caspase-3 in brain tissue increased significantly，while the expression of Bcl-2，the ratios of p-PKC/PKC and p -ERK1/2/ERK1/2 reduced significantly（P < 0.05）. The neurons in the CA1 area of the hippocampus were swollen and decreased in number. Compared with the model group，the neurological function of the total flavonoids of patriniae radix low -dose and high -dose group improved，and the neurological deficit score，the numbers of NeuN+ TUNEL+ cells，the expression of Bax and Caspase-3 in brain tissue reduced significantly，while the expression of Bcl-2，the ratios of p-PKC/PKC and p-ERK1/2/ERK1/2 increased significantly（P < 0.05）. The neurons in the CA1 area of the hippocampus were increased in density. And on the basis of the intervention of total flavonoids of patriniae radix，combined with chelerythrine can significantly reduce the inhibitory effect of total flavonoids of patriniae radix on hippocampal neuronal apoptosis after HIE. In an in vitro study，total flavonoids of patriniae radix increased cell viability after OGD/R injury，reversed neuronal damage and reduced hippocampal neuronal apoptosis，while increasing hippocampal neuronal p-PKC/ PKC and p-ERK1/2 /ERK1/2 ratio（P < 0.05），verified the activation of PKC/ERK pathway by total flavonoids of patriniae radix in OGD/R- induced primary hippocampal neurons. Conclusion：Total flavonoids of patriniae radix can inhibit hippocampal neuron apoptosis in neonatal rats with HIE，and its mechanism may be related to the activation of PKC/ERK pathway.
