腺苷酸活化蛋白激酶异常激活促进肝细胞凋亡：内毒素诱导肝损伤发病新机制及干预新靶点

Endotoxin-induced liver injury is a pivotal step in the development of liver dysfunction in several clinical disorders. AMP activated protein kinase (AMPK) is an important metabolism regulating enzyme which is closely associated with inflammation and tumor. We have recently found that hepatic AMPK was aberrantly activated in mice with endotoxin-induced liver injury. Inhibition of AMPK by pharmacological reagents attenuated hepatocyte apoptosis and liver injury. These effects were accompanied with decreased phosphorylation of c-Jun N-terminal kinase (JNK), a typical member of mitogen-activated protein kinases (MAPK). It was reported that JNK was a downstream target of AMPK and JNK pathway was crucial for the induction of hepatocyte apoptosis. Therefore, the enhancement of JNK activation and the promotion of hepatocyte apoptosis by AMPK might be a novel mechanism underlying the progression of endotoxin-induced liver injury. To confirm our hypothesis, the causal connection among AMPK activation, JNK activation and hepatocyte apoptosis will be investigated in mice with endotoxin-induced liver injury at the first step. And then, the mechanisms through which AMPK promotes hepatocyte apoptosis will be investigated by determination of the downstream pro-apoptotic and anti-apoptotic factors of JNK. Finally, our hypothesis will be further confirmed by molecular intervention in cultured hepatocyte in vitro. The aim of this research project is to reveal that AMPK would promote heptocyte apoptosis via activating JNK, which might be a novel mechanism responsible for the hepatocyte damage in endotoxin-induced liver injury. The expected data from this project would suggest new strategy for the prevention and treatment of endotoxin-induced liver injury.

内毒素诱导的肝损伤是多种疾病并发肝功能障碍的关键环节。腺苷酸活化蛋白激酶（AMPK）是重要代谢调节酶，与炎症、肿瘤关系密切。我们近期在内毒素诱导的肝损伤小鼠发现AMPK被异常激活；抑制AMPK可减轻肝细胞凋亡及肝组织损伤，这伴随丝裂原活化蛋白激酶（MAPK）家族成员JNK磷酸化受抑。由于JNK是AMPK的下游底物且JNK可促进肝细胞凋亡，AMPK激活JNK、促进肝细胞凋亡可能是内毒素诱导肝损伤的发病新机制。为此，本课题拟首先在动物模型中探明AMPK激活、JNK活化及肝细胞凋亡之间的因果联系；随后通过检测JNK下游关键促凋亡及抗凋亡因子的磷酸化等方面揭示AMPK促凋亡的分子机制；最后在体外培养的肝细胞上采用分子生物学手段进一步证实AMPK通过JNK促进肝细胞凋亡并揭示相关下游分子机制。本项目旨在揭示AMPK通过JNK促进肝细胞凋亡这一内毒素诱导肝损伤的发病新机制并为其防治提供新思路。

本研究探讨了腺苷酸活化蛋白激酶在内毒素诱导肝损伤发病中的作用机制，结果发现腺苷酸活化蛋白激酶在内毒素诱导肝损伤中异常激活，并通过JNK活化促进肝细胞凋亡，结果表明AMPK 是内毒素诱导的肝损伤中重要致病因子，揭示了内毒素诱导肝损伤的发病新机制并为其防治提供新思路。