桔梗皂苷D通过Bax/Bcl-2/Caspase-3信号通路抑制细胞凋亡保护急性肺损伤的机制研究＊

目的 探讨桔梗皂苷D对脂多糖诱导的大鼠急性肺损伤的保护机制。方法 35只雄性SPF级SD大鼠,随机分为假手术组、桔梗皂苷D对照组、模型组、桔梗皂苷D给药组和地塞米松组,每组7只。除假手术组和桔梗皂苷D对照组外,其余各组采用脂多糖诱导大鼠急性肺损伤模型。造模24 h后,牺牲大鼠并称体重及两肺重量,计算肺指数;脱氧核糖核苷酸末端转移酶介导的缺口末端标记（TUNEL）法检测肺组织细胞凋亡并计算凋亡指数（Apoptosis Index,AI）;透射电镜下观察大鼠肺组织超微结构的改变;蛋白免疫印迹法（Western blot）检测肺组织凋亡相关蛋白B细胞淋巴瘤/白血病-2（Bcl-2）,Bcl-2相关X蛋白（Bax）,半胱氨酸天冬氨酸蛋白酶-3（Caspase-3）,多聚腺苷二磷酸核糖聚合酶1（PARP1）蛋白及活化的天冬氨酸蛋白水解酶-3（Cleaved Caspase-3）,Cleaved PARP1的表达水平。结果 与假手术组比较,模型组大鼠肺指数显著升高（P < 0.01）,肺组织细胞凋亡指数（AI）显著升高（P < 0.01）,肺组织Bcl-2及Bcl-2/Bax蛋白表达显著下调（P < 0.01）,Bax,Cleaved Caspase-3/Caspase-3,Cleaved PARP1/PARP1蛋白表达均显著升高（P < 0.01）;透射电镜下可见到凋亡小体,影响并改变了肺组织细胞超微结构;与模型组比较,桔梗皂苷D给药组及地塞米松组肺指数明显降低（P < 0.01）,肺组织AI明显降低（P < 0.01）,肺组织中Bcl-2及Bcl-2/Bax蛋白表达显著上调（P < 0.01）,Bax,Cleaved Caspase-3/Caspase-3,Cleaved PARP1/PARP1蛋白表达均显著降低（P < 0.01）;透射电镜下,桔梗皂苷D给药组和地塞米松组肺组织细胞超微结构状态较好。结论 桔梗皂苷D对脂多糖诱导的大鼠急性肺损伤具有保护作用,其作用机制与抑制Bax/Bcl-2/Caspase-3信号通路,减轻肺组织细胞凋亡密切相关。

Studies on Mechanism of Platycodin D Inhibiting Apoptosis and Protecting Acute Lung Injury Via Bax/bcl-2/caspase-3 Signaling Pathway

Objective To investigate the protective effect and mechanism of platycodin D (PLD) on lipopolysaccharide (LPS)-induced acute lung injury (LPS-ALI) in rats and its mechanism.Methods Thirty-five male SPF SD rats were randomly divided into 5 groups (n = 7): sham group, PLD control group, model group, PLD treatment group and dexamethasone group. Except sham group and PLD control group, the other groups were given LPS to induce the rat ALI model. After LPS instillation for 24 h, rats were sacrificed and weighed. Meanwhile, both lungs were removed and weighed. And then, the lung index was calculated. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL) was used to detect apoptosis of lung cells and apoptosis index (AI) was calculated. Western blot was used to detect the expression levels of apoptosis-related protein b-lymphocytoma-2 (Bcl-2), Bcl-2-related X protein (Bax), cysteine protease-3 (Caspase-3), Poly-ADP-ribosomal Polymerase1 (PARP1), Cleaved Caspase-3, Cleaved PARP1.Results Compared with sham group, in model group, the lung index was significantly increased (P < 0.01), and the apoptosis index (AI) of lung tissue was significantly increased (P < 0.01). The lung expression of Bcl-2 and Bcl-2/Bax protein were significantly decreased (P < 0.01), and Bax, Cleaved Caspase-3/Caspase-3, Cleaved PARP1/PARP1 protein were significantly increased (P < 0.01). Apoptotic bodies were observed under transmission electron microscope and the ultrastructure of lung tissue cells was changed. Compared with model group, in PLD treatment group and dexamethasone group, the lung index was significantly decreased (P < 0.01), and the apoptosis index (AI) of lung tissue was significantly decreased (P < 0.01). The lung expression of Bcl-2 and Bcl-2/Bax protein were significantly increased (P < 0.01), and Bax, Cleaved Caspase-3/Caspase-3, Cleaved PARP1/PARP1 protein were significantly decreased (P < 0.01). Under transmission electron microscope, the ultrastructure of lung tissue cells was in good condition in PLD treatment group and dexamethasone group.Conclusion Platycodin D can protect LPS-ALI rats, and its mechanism is related to the inhibition of Bax/Bcl-2/caspase-3 signaling pathway and the reduction of apoptosis in lung tissue.