Multiple research groups have demonstrated that the outcome of patients receiving liver grafts from brain death donors (DBD) is poorer when compared with patients receiving grafts from living donors. This might be due to an increased hepatocyte apoptosis induced after brain death (BD). In this work, we found that the activity of PP2A-Akt pathway is significantly increased in clinical donor ex vivo hepatocytes after BD by iTRAQ protein quantification analysis. The same results were confirmed in animal models. A time-dependent promotion of apoptosis was also found in DBD rabbit liver, as demonstrated by the increased levels of cleaved Caspase 3 and the decreased of Bcl-2. To further investigate the roles of PP2A and Akt in regulating apoptosis of hepatocytes after BD, we cultivated human liver cell line L02 with serum deprivation and hypoxia, to simulate the ischemic and hypoxic conditions of hepatocytes in DBD. Increased apoptosis and decreased viability were observed during the time in this model. Meanwhile PP2A activity and Akt activity were respectively increased and decreased. Notably, the proportion of Akt phosphorylation at Ser473 decreased, while other known targets of PP2A (p38, JNK and ERK) were not affected in terms of protein levels or phosphorylation. These results suggested that PP2A is involved in apoptotic induction of hepatocytes after brain death by specific suppression of Akt. This discovery was further confirmed with pharmaceutical and genetic methods. Our work implied potential targets for reducing liver cell apoptosis and improving organ donor quality after BD.

中文翻译：

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PP2Ac上调脑死亡后肝脏供体中的PI3K-Akt信号传导并诱导肝细胞凋亡。

多个研究小组证明，与从活体供体接受移植的患者相比，从脑死亡供体（DBD）接受肝移植的患者的预后较差。这可能是由于脑死亡（BD）后诱导的肝细胞凋亡增加所致。在这项工作中，我们发现通过iTRAQ蛋白定量分析，BD后临床供体离体肝细胞中PP2A-Akt途径的活性显着增加。在动物模型中证实了相同的结果。在DBD兔肝脏中还发现了凋亡的时间依赖性促进，这由裂解的Caspase 3的水平升高和Bcl-2的降低所证实。为了进一步研究PP2A和Akt在调节BD后肝细胞凋亡中的作用，我们培养了具有血清剥夺和缺氧状态的人肝细胞L02，模拟DBD中肝细胞的缺血和缺氧状况。在此模型期间，观察到凋亡增加和生存力降低。同时，PP2A活性和Akt活性分别升高和降低。值得注意的是，Ser473的Akt磷酸化比例降低，而其他已知的PP2A靶标（p38，JNK和ERK）在蛋白质水平或磷酸化方面均不受影响。这些结果表明PP2A通过特异性抑制Akt参与脑死亡后肝细胞的凋亡诱导。药物和遗传方法进一步证实了这一发现。我们的工作暗示了减少BD后肝细胞凋亡和改善器官供体质量的潜在目标。在此模型期间，观察到凋亡增加和生存力降低。同时，PP2A活性和Akt活性分别升高和降低。值得注意的是，Ser473的Akt磷酸化比例降低，而其他已知的PP2A靶标（p38，JNK和ERK）在蛋白质水平或磷酸化方面均不受影响。这些结果表明，PP2A通过特异性抑制Akt参与脑死亡后肝细胞的凋亡诱导。药物和遗传方法进一步证实了这一发现。我们的工作暗示了减少BD后肝细胞凋亡和改善器官供体质量的潜在目标。在此模型期间，观察到凋亡增加和生存力降低。同时，PP2A活性和Akt活性分别升高和降低。值得注意的是，Ser473的Akt磷酸化比例降低，而其他已知的PP2A靶标（p38，JNK和ERK）在蛋白质水平或磷酸化方面均不受影响。这些结果表明PP2A通过特异性抑制Akt参与脑死亡后肝细胞的凋亡诱导。药物和遗传方法进一步证实了这一发现。我们的工作暗示了减少BD后肝细胞凋亡和改善器官供体质量的潜在目标。Ser473处Akt磷酸化的比例降低，而其他已知的PP2A靶标（p38，JNK和ERK）在蛋白质水平或磷酸化方面均不受影响。这些结果表明PP2A通过特异性抑制Akt参与脑死亡后肝细胞的凋亡诱导。药物和遗传方法进一步证实了这一发现。我们的工作暗示了减少BD后肝细胞凋亡和改善器官供体质量的潜在目标。Ser473处Akt磷酸化的比例降低，而其他已知的PP2A靶标（p38，JNK和ERK）在蛋白质水平或磷酸化方面均不受影响。这些结果表明PP2A通过特异性抑制Akt参与脑死亡后肝细胞的凋亡诱导。药物和遗传方法进一步证实了这一发现。我们的工作暗示了减少BD后肝细胞凋亡和改善器官供体质量的潜在目标。