Chinese Academy of Medical Sciences, China.
J Cell Biochem. 2011 Jan;112(1):299-306. doi: 10.1002/jcb.22919.
Accelerated glucose metabolism leads to oxidative stress and DNA damage in cells; these effects are related to glucose toxicity. The precise mechanisms of glucose toxicity are still unclear. The aim of this work was to investigate the mechanism of poly(ADP-ribose) polymerase 1 (PARP1), which is a DNA repair enzyme activated by high-glucose-induced oxidative stress, and its effect on glucose toxicity in HepG2 hepatocytes. HepG2 cells were cultured under normal (5.5 mM) or high (30 mM) glucose conditions for 4 days. PJ34, which is an inhibitor of PARP1, was used to determine the downstream effects of PARP1 activation. PARP1 activity in 30 mM-glucose-treated cells was more than that in 5.5 mM-glucose-treated cells, and the activity correlated with the increase in ROS generation and DNA damage. PJ34 suppressed PARP1 activation and prevented the high-glucose-induced suppression of SIRT1 and AMP-activated protein kinase (AMPK) activity, which was similar to its effect on the restoration of intracellular nicotinamide adenine dinucleotide (NAD) content. Further, the phosphorylation of insulin receptor was attenuated in response to insulin stimulation under high glucose conditions, and PJ34 could reverse this effect. The results of transfection of HepG2 cells with PARP1 small interfering RNA were similar to those obtained by treatment of the cells with PARP1 inhibitor PJ34. These data suggest that high-glucose-induced PARP1 activation might play a role in glucose toxicity by down-regulating SIRT1 and AMPK activity through NAD depletion and resulting in insulin insensitivity.
葡萄糖代谢加速会导致细胞内的氧化应激和 DNA 损伤；这些影响与葡萄糖毒性有关。葡萄糖毒性的确切机制仍不清楚。本工作旨在研究聚（ADP-核糖）聚合酶 1（PARP1）的机制，PARP1 是一种由高葡萄糖诱导的氧化应激激活的 DNA 修复酶，及其对 HepG2 肝细胞中葡萄糖毒性的影响。将 HepG2 细胞在正常（5.5mM）或高（30mM）葡萄糖条件下培养 4 天。使用 PARP1 抑制剂 PJ34 来确定 PARP1 激活的下游效应。在 30mM 葡萄糖处理的细胞中，PARP1 的活性高于在 5.5mM 葡萄糖处理的细胞中，并且该活性与 ROS 生成和 DNA 损伤的增加相关。PJ34 抑制 PARP1 的激活，并防止高葡萄糖诱导的 SIRT1 和 AMP 激活蛋白激酶（AMPK）活性的抑制，这与它对细胞内烟酰胺腺嘌呤二核苷酸（NAD）含量恢复的作用相似。此外，在高葡萄糖条件下，胰岛素刺激时胰岛素受体的磷酸化作用减弱，而 PJ34 可逆转这种作用。用 PARP1 小干扰 RNA 转染 HepG2 细胞的结果与用 PARP1 抑制剂 PJ34 处理细胞的结果相似。这些数据表明，高葡萄糖诱导的 PARP1 激活可能通过 NAD 耗竭下调 SIRT1 和 AMPK 活性从而导致胰岛素不敏感，从而在葡萄糖毒性中发挥作用。
