Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning
Role of phosphatidylinositol 3-kinase in the development of hepatocyte preconditioning
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DOI：
10.1053/j.gastro.2004.06.018
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发表时间：
2004-09-01
期刊：
影响因子：
29.4
通讯作者：
Albano, E
中科院分区：
文献类型：
--
作者：
Carini, R;De Cesaris, MG;Albano, E
背景与目的：缺血预处理已被证明可有效减少肝脏手术期间的缺血/再灌注损伤。然而，所涉及的机制仍然知之甚少。在这里，我们研究了磷脂酰肌醇 3-激酶 (PI3K) 在导致肝脏预处理的信号通路中的作用。方法：在经过 10 分钟缺氧和 10 分钟复氧预处理的离体大鼠肝细胞中评估 PI3K 活化。结果：低氧预处理刺激了 3,4,5-三磷酸磷脂酰肌醇的产生以及 PI3K 下游靶标 PKB/Akt 的磷酸化。相反，渥曼青霉素或LY294002抑制PI3K会消除肝细胞对预处理引起的缺氧损伤的耐受性。预处理肝细胞中的 PI3K 激活需要刺激腺苷 A(2A) 受体，并可通过腺苷 A(2A) 受体激动剂 CGS21680 进行模拟。在用 CGS21680 处理的细胞中，通过分别用 2,5-二脱氧腺苷和 H89 抑制腺苷酸环化酶和 PKA 或分别用百日咳毒素和 PP2 阻断 Galphai 蛋白和 Src 酪氨酸激酶来阻止 PI3K 激活。 H89 还消除了腺苷 A(2A) 受体的磷酸化。然而，毛喉素直接激活 PKA 并不能刺激 PI3K。这表明 PKA 磷酸化腺苷 A(2A) 受体可能通过 Src 与 Galphai 蛋白偶联来激活 PI3K。我们还观察到，通过损害 PI3K 介导的磷酸酶 Cgamma (PLCgamma) 激活，渥曼青霉素和 LY294002 阻断了通过蛋白激酶 C (PKC) delta/e 同工酶进行的预处理信号的下游转导。结论：肝细胞缺氧预处理后，腺苷 A(2A) 受体、PKA、Galphai 蛋白和 Src 联合刺激，PI3K 被激活。通过调节 PKC-ε/δ 依赖性信号，PI3K 在肝脏对缺氧/再灌注的耐受性的发展中发挥关键作用。
Background & Aims: Ischemic preconditioning has been proved effective in reducing ischemia/reperfusion injury during liver surgery. However, the mechanisms involved are still poorly understood. Here, we have investigated the role of phosphatidylinositol 3-kinase (PI3K) in the signal pathway leading to hepatic preconditioning. Methods: PI3K activation was evaluated in isolated rat hepatocytes preconditioned by 10-minute hypoxia followed by 10-minute reoxygenation. Results: Hypoxic preconditioning stimulated phosphatidylinositol-3,4,5-triphosphate production and the phosphorylation of PKB/Akt, a downstream target of PI3K. Conversely, PI3K inhibition by wortmannin or LY294002 abolished hepatocyte tolerance against hypoxic damage induced by preconditioning. PI3K activation in preconditioned hepatocytes required the stimulation of adenosine A(2A) receptors and was mimicked by adenosine A(2A) receptors agonist CGS21680. In the cells treated with CGS21680, PI3K activation was prevented either by inhibiting adenylate cyclase and PKA with, respectively, 2,5-dideoxyadenosine and H89 or by blocking Galphai-protein and Src tyrosine kinase with, respectively, pertussis toxin and PP2. H89 also abolished the phosphorylation of adenosine A(2A) receptors. However, the direct PKA activation by forskolin failed to stimulate PI3K. This suggested that PKA-phosphorylated adenosine A(2A) receptors may activate PI3K by coupling it with Galphai-protein through Src. We also observed that, by impairing PI3K-mediated activation of phospholypase Cgamma (PLCgamma), wortmannin and LY294002 blocked the downstream transduction of preconditioning signals via protein kinase C (PKC) delta/e isozymes. Conclusions: PI3K is activated following hepatocyte hypoxic preconditioning by the combined stimulation of adenosine A(2A) receptors, PKA, Galphai protein, and Src. By regulating PKC-epsilon/delta-dependent signals, PI3K can play a key role in the development of hepatic tolerance to hypoxia/reperfusion.