POSSIBLE MOLECULAR MECHANISMS FOR PORTAL HYPERTENSION AND THE IMPLICATIONS ON ITS TREATMENT

门静脉高压的可能分子机制及其治疗的意义

基本信息

批准号：
14571204
负责人：
TOMIKAWA Morimasa
金额：
$ 1.79万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14571204/
关键词：
portal hypertension hyperdynamic circulation intrahepatic vascular resistance endothelial nitric oxide synthase (eNOS)hepatic stellate cell (HSC)nitric oxide (NO)Rho kinase Akt シグナルトランスダクション ROCK RHOkinase阻害剤肝線維化肝硬変治療

项目摘要

Portal hypertension is characterized by the hyperdynamic circulation in the splanchnic organs as well as by the increased intrahepatic vascular resistance. Excessive nitric oxide production by endothelial nitric oxide synthase (eNOS) and elevated tumor necrosis factor-α (TNF-α) are implicated in the development of the systemic hyperdynamic circulation and portal hypertensive (PHT) gastropathy. The increased intrahepatic vascular resistance is associated with a contraction of hepatic stellate cells (HSCs) and a reduction of nitric oxide (NO) production in sinusoidal endothelial cells. HSCs also plays a major role in hepatic fibrogenesis, leading to portal hypertension. However, the molecular mechanisms for these phenomena remain to be elucidated. The aims of our studies are to determine the molecular basis for the hyperdynamic circulation of splanchnic organs and the intrahepatic microcirculatory disturbance.Our present study demonstrates for the first time that : (1)eNOS activation in … More PHT gastric mucosa is due to : (a)increased phosphorylation of eNOS at serine 1177 ; (b)activation of the PI 3-kinase/Akt signaling pathway ; (c)enhanced binding of Akt to eNOS ; and, (2)TNF-α neutralizing antibody reduces phosphorylation of eNOS and activation of the PI 3-kinase/Akt signaling pathway in PHT gastric mucosa to the normal levels. In PHT gastric mucosa elevated TNF-α induces phosphorylation of eNOS at serine 1177 (required for its activation) via activation of the PI 3-kinase/Akt signaling pathway.PHT gastric mucosa is highly susceptible to injury caused by alcohol, aspirin and other noxious factors, but the mechanism is not fully understood. Since such mucosal injury is initially mediated by oxygen free radicals, and since MAP kinase (ERK2) protects against cellular stress and induces cell proliferation, we postulated that oxidative stress-induced ERK2 activation is defective in PHT gastric mucosa. Here we demonstrated that in PHT gastric mucosa, ERK2 activation by oxidative stress is impaired. This impairment is mediated by overexpression of MAP kinase phosphatase-1 (MKP-1), which results from an underlying oxidative state, and is ameliorated by inhibiting MKP-1. Supplementing vitamin E, a free radical scavenger, normalizes MKP-1 expression in PHT gastric mucosa and completely reverses the increased susceptibility to alcohol injury. Our findings provide the molecular mechanism for the pathophysiology of PHT gastropathy and should expedite developing effective non-invasive therapy.In the rat model of liver fibrosis induced by dimethlnitrosamine(DMN), fasudil (a novel specific inhibitor of Rho kinase) conceptation orally reduced fibrosis of the liver in 3 weeks. HSCs activation induced by liver injuary, as shown by the decreased the number of activated HSCs (_-SMA positive cells) and the protein expression_-SMA was also reduced in 3weeks. Moreover, oral administration of fasudil significantly reduced portal pressure of DMN rats at both 1 and 3 weeks, compared to DMN alone. This study indicates that oral administration of fasudil reduce extracellular matrix deposition and portal hypertension in vivo. In vitro experiments showed 1_M fasudil induced HSC apoptosis. The reduction of liver fibrosis and portal hypertension is likely to be induced by inhibition of HSC activation and apoptosis. These points will impact on the new therapiutic drug for cirrhotic patients.The present study demonstrates in cirrhotic rats by the bile duct ligation that (1)Rho kinase signaling and its dawnstream _-SMA protein is upregulated; and (2)the long-term inhibition of Rho kinase with fasudil leads to the reduced contraction of HSCs and the upregulation of eNOS phosphorylation and prevents the microcirculatory disturbance, finally improving the portal hypertension in liver cirrhosis. Less

门脉高压的特征是内脏器官的高动力循环以及肝内血管阻力增加，内皮一氧化氮合酶（eNOS）产生过多的一氧化氮和肿瘤坏死因子-α（TNF-α）升高与门静脉高压有关。全身高动力循环和门静脉高压（PHT）胃病的发展肝内血管阻力增加与肝脏收缩有关。星状细胞（HSC）和肝窦内皮细胞一氧化氮（NO）生成的减少也在肝纤维化中发挥着重要作用，导致门静脉高压。然而，这些现象的分子机制仍有待阐明。我们研究的目的是确定内脏器官高动力循环和肝内微循环障碍的分子基础。我们目前的研究首次证明： (1) PHT 胃粘膜中 eNOS 激活是由于：(a) eNOS 丝氨酸 1177 磷酸化增加；(b) PI 3-激酶/Akt 信号通路激活；(c) Akt 与 eNOS 结合增强； (2)TNF-α 中和抗体可减少 eNOS 的磷酸化和 PI 3-激酶/Akt 信号通路的激活在 PHT 胃粘膜中，升高的 TNF-α 通过激活 PI 3-激酶/Akt 信号通路诱导 eNOS 在丝氨酸 1177 处磷酸化（其激活所需）。PHT 胃粘膜对这种情况高度敏感。酒精、阿司匹林和其他有害因素引起的损伤，但其机制尚不完全清楚，因为这种粘膜损伤最初是由无氧介导的。由于 MAP 激酶 (ERK2) 可以防止细胞应激并诱导细胞增殖，因此我们推测 PHT 胃粘膜中氧化应激诱导的 ERK2 激活存在缺陷。在此，我们证明，在 PHT 胃粘膜中，氧化应激引起的 ERK2 激活受损。这种损伤是由 MAP 激酶磷酸酶-1 (MKP-1) 过度表达介导的，这是由潜在的氧化状态引起的，并且通过抑制 MKP-1（一种自由基清除剂）可改善 PHT 胃粘膜中 MKP-1 的表达，并完全逆转对酒精损伤的敏感性增加。我们的研究结果为 PHT 胃病的病理生理学提供了分子机制。加快开发有效的非侵入性治疗方法。在二甲基亚硝胺（DMN）诱导的大鼠肝纤维化模型中，法舒地尔（一种新型特异性抑制剂） Rho激酶）口服可在3周内减少肝损伤引起的HSC活化，如活化的HSC（_-SMA阳性细胞）数量减少以及蛋白表达_-SMA在3周内也减少所示。此外，与单独使用 DMN 相比，口服法舒地尔在第 1 周和第 3 周均显着降低了 DMN 大鼠的门静脉压力。这项研究表明，口服法舒地尔可减少细胞外基质沉积和门静脉高压。体外实验表明，1_M fasudil 诱导 HSC 凋亡的作用很可能是通过抑制 HSC 活化和凋亡而引起的。目前的研究。通过胆管结扎在肝硬化大鼠中证明 (1) Rho 激酶信号及其 Dawnstream _-SMA 蛋白上调，以及 (2) 对 Rho 激酶的长期抑制；法舒地尔导致HSC收缩减少，eNOS磷酸化上调，防止微循环障碍，最终改善肝硬化门脉高压。