Studies on the regulation of inducible nitric oxide synthase (iNOS) induction with statins in liver injury

研究表明，他汀类药物（HMG-CoA还原酶抑制剂）对心脏和肝脏疾病的保护作用与其对内皮型一氧化氮合酶（eNOS）或诱导型一氧化氮合酶（iNOS）的调节有关。据报道，他汀类药物可增强肝硬化患者的肝脏NO生成，降低血管张力。然而，目前还不清楚哪些NOS有助于增加NO的产生。我们假设他汀类药物参与炎症肝脏中iNOS的上调，导致肝脏阻力降低。在存在或不存在匹伐他汀的情况下，用促炎细胞因子白细胞介素（IL）-1β处理原代培养的大鼠肝细胞。用匹伐他汀预处理细胞导致IL-1β上调iNOS诱导，随后增加NO产生。匹伐他汀对Iκ B的降解和NF-κB的活化无影响。然而，匹伐他汀超诱导I型IL-1受体（IL-1 RI）的上调，这是除了Iκ B/NF-κB途径外诱导iNOS所必需的。甲羟戊酸和香叶基香叶基焦磷酸可阻断匹伐他汀对iNOS和IL-1 RI诱导的刺激作用。转染实验表明，匹伐他汀增加了iNOS mRNA的稳定性，而不是其启动子的反式激活。为了支持这一观察结果，匹伐他汀增加了对应于iNOS mRNA的3 'UTR的反义转录物，其通过与3' UTR和RNA结合蛋白相互作用来稳定iNOS mRNA。这些结果表明，匹伐他汀上调iNOS的稳定其mRNA，可能是通过超诱导IL-1 RI和反义转录。他汀类药物可能有助于一种新的强化治疗肝损伤，包括肝硬化。

Studies have indicated that protective effects of statins (HMG-CoA reductase inhibitor) are associated with the regulation of endothelial nitric oxide synthase (eNOS) or inducible NOS (iNOS) in heart and liver diseases. Statins have been reported to enhance hepatic NO production and decrease the vascular tone in patients with cirrhosis. However, it is unclear which NOS contributes to the increased NO production. We hypothesized that statins are involved in the up-regulation of iNOS in inflammatory liver, resulting in decreased hepatic resistance. Primary cultured rat hepatocytes were treated with pro-inflammatory cytokine interleukin (IL)-1β in the presence or absence of pitavastatin. Pretreatment of cells with pitavastatin resulted in up-regulation of iNOS induction by IL-1β, followed by increased NO production. Pitavastatin had no effects on the degradation of Iκ B or activation of NF-κB. However, pitavastatin super-induced the up-regulation of type I IL-1 receptor (IL-1 RI), which is essential for iNOS induction in addition to the Iκ B/NF-κB pathway. Mevalonate and geranylgeranylpyrophosphate blocked the stimulatory effects of pitavastatin on iNOS and IL-1 RI induction. Transfection experiments revealed that pitavastatin increased the stability of iNOS mRNA rather than its promoter transactivation. In support of this observation, pitavastatin increased the antisense-transcript corresponding to the 3'UTR of iNOS mRNA, which stabilizes iNOS mRNA by interacting with the 3'UTR and RNA-binding proteins. These findings demonstrate that pitavastatin up-regulates iNOS by the stabilization of its mRNA, presumably through the super-induction of IL-1 RI and antisense-transcript. Statins may contribute to a novel potentiated treatment in liver injuries including cirrhosis.