Objective To investigate the effect of total alkaloids of Rhizoma Corydalis(TAC)on the expression of silencing information regulator 1(Sirt1)/tumor suppressor P53 protein signaling pathway-related proteins in the hippocampus of rats with chronic cerebral ischemia(CCH),and to explore its mechanism.Methods The rats were randomly divided into Sham operation group,model group,TAC high-dose group(14 mg/kg)and TAC low-dose group(7 mg/kg),with 6 rats in each group.A modified bilateral common carotid artery permanent occlusion method(BCCAO)was used to establish a rat model of CCH,and only bilateral common carotid arteries were separated in the Sham group.After the modeling was completed,each group was given the corresponding drug or isotonic saline by gavage,once a day,and the treatment lasted for 14 days.Hematoxycin-eosin staining was used to observe the pathological changes in the hippocampus of rats,in situ terminal deoxynucleotidyl transferase-mediated deoxyuridinetriphate-biotin nick end labeling assay(TUNEL)was used to detect neuronal apoptosis,and Western blotting and immunohistochemistry were used to detect expression of Sirt1,P53,P53 positive apoptosis regulator(PUMA),B-cell lymphocytoma-2(Bcl-2)protein,Bcl-2-related X protein(BAX),respectively in the hippocampus of rats.Results(1)There were significant differences in the number of apoptotic cells and apoptosis rate among the four groups(F-values were 71.417 and 76.835,respectively,both P＜0.01).There were statistically significant differences in the mean integral optical density values of Sirt1,P53,PUMA,BAX and Bcl-2 protein positive expression areas among the four groups(F-values were 1 178.390,42.465,867.413,110.656 and 131.801,all P＜0.01).There were significant differences in the relative expression levels of Sirt1,P53,PUMA,BAX and Bcl-2 among the four groups(F-values were 9.497,11.863,58.552,186.855 and 12.466,all P＜0.01).(2)Compared with the Sham operation group,the neuronal arrangement of brain tissue in the hippocampus of the model group was disordered,the nuclear consolidation increased,and the glial cells and inflammatory cells increased significantly,and the number and apoptosis rate of neurons in the hippocampus of the model group increased significantly(respectively[10.8±1.5]cells vs.[2.0±0.9]cells and[35.5±4.5]％vs.[6.2±2.6]％;both P＜0.05),and the average integral optical density values of the positive expression areas of Sirt1 and Bcl-2 proteins decreased significantly(84.6±6.6 vs.244.6±4.9,138.5±6.7 vs.210.9±10.0;both P＜0.05),the average integral optical density values of P53,PUMA and BAX proteins were significantly increased(156.8±11.6 vs.93.5±11.6,151.3±3.3 vs.38.0±4.0,87.0±5.0 vs.38.4±5.5;all P＜0.05),the relative expression levels of Sirt1 and Bcl-2 proteins were significantly decreased(0.51±0.07 vs.0.74±0.07,0.36±0.03 vs.0.53±0.05;both P＜0.05),and the relative expression levels of P53,PUMA and BAX proteins were significantly increased(0.37±0.06 vs.0.21±0.02,0.62±0.06 vs.0.23±0.02,1.08±0.06 vs.0.45±0.03;all P＜0.05).(3)Compared with the model group,the hippocampal tissue structure of the high-dose and low-dose TAC groups was relatively compact and uniform,the neurons were neatly arranged,and the cell structure was relatively clear and complete,while the number of neuronal apoptotic cells and the apoptosis rate decreased significantly(respectively[3.8±0.7]cells vs.[6.2±1.2]cells,[12.4±2.8]％vs.[20.2±3.9]％;both P＜0.05),and the average integrated optical density values of the positive expression areas of Sirt1 and Bcl-2 proteins(the high-dose and low-dose TAC groups:Sirt1 150.0±4.8,131.3±1.3,and Bcl-2 207.1±7.4,169.5±3.9,respectively)were significantly increased(both P＜0.05),the average integral optical density values of P53,PUMA and BAX proteins were significantly decreased(the high-dose and low-dose TAC groups:P53 105.9±8.8,115.5±9.0,and PUMA56.8±5.1,74.4±3.9,and BAX40.5±5.6,48.4±5.0,respectively,all P＜0.05),the relative expression levels of Bcl-2 protein(the high-dose and low-dose TAC groups:0.53±0.05,0.47±0.02,respectively)were significantly increased(P＜0.05),the relative expression levels of P53(the high-dose and low-dose TAC groups:0.21±0.02,0.24±0.04,respectively),PUMA(the high-dose and low-dose TAC groups:0.36±0.02,0.28±0.04,respectively)and BAX proteins(the high-dose and low-dose TAC groups:0.52±0.02,0.54±0.03,respectively)were significantly decreased(all P＜0.05),the relative expression level of Sirt1 protein in the TAC high-dose group was significantly decreased(0.71±0.05,P＜0.05),and the relative expression level of Sirt1 protein in the TAC low-dose group was not statistically significant(0.52±0.08,P＞0.05).Conclusion TAC can alleviate neuronal damage and reduce the apoptosis rate of neurons in the hippocampus of CCH rats,and the mechanism may be related to the activation of Sirt1/P53 pathway,inhibition of P53 protein activity,and thus the expression level of apoptosis-related proteins in the downstream of TAC.