Arisawa Sakiko, Ishida Kumiki, Kameyama Natsumi, Ueyama Jun, Hattori Ai, Tatsumi Yasuaki, Hayashi Hisao, Yano Motoyoshi, Hayashi Kazuhiko, Katano Yoshiaki, Goto Hidemi, Takagi Kenji, Wakusawa Shinya
Department of Medical Technology, Nagoya University School of Health Sciences, Nagoya, Japan.
Biochem Pharmacol. 2009 Mar 1;77(5):858-66. doi: 10.1016/j.bcp.2008.11.012. Epub 2008 Nov 25.
Ursodeoxycholic acid (UDCA) is widely recognized as an effective compound in the treatment of chronic hepatitis and is known to modulate the redox state of the liver accompanied by an increase of GSH. In the present study, to access the antioxidative effect of UDCA and to clarify the molecular basis of the action on GSH level, we evaluated its effects in HepG2 cells exposed to excessive iron. UDCA inhibited both a decrease in the GSH level and an increase in the reactive oxygen species caused by excessive iron in the cells. UDCA increased the gene expression of the catalytic- and modifier-units of glutamine-cysteine ligase (GCL), which is a key enzyme in GSH synthesis. We further investigated the effect of UDCA on the phosphatidylinositol 3-kinase (PI3K)/Akt pathway, and obtained results showing that UDCA-induced increase in the GSH level was prevented by LY294002, a PI3K inhibitor. In addition, Western blot analysis of Akt showed that, while the total Akt level remained unchanged, the phosphorylated Akt level was increased by UDCA, and this increase was also prevented by LY294002. Moreover, UDCA promoted the translocation of a transcription factor, nuclear factor-E2-related factor-2 (Nrf2), into the nucleus, and this action was inhibited by LY294002. From these results, it was indicated that UDCA increased the GSH synthesis through an activation of the PI3K/Akt/Nrf2 pathway. This may be a primary mechanism of antioxidative action of UDCA concerned with its therapeutic effectiveness in chronic hepatitis.
熊去氧胆酸（UDCA）被广泛认为是治疗慢性肝炎的有效化合物，已知其可调节肝脏的氧化还原状态，并伴随谷胱甘肽（GSH）水平升高。在本研究中，为了探究UDCA的抗氧化作用并阐明其对GSH水平作用的分子基础，我们评估了其在暴露于过量铁的HepG2细胞中的作用。UDCA抑制了细胞中过量铁引起的GSH水平降低和活性氧的增加。UDCA增加了谷氨酰胺 - 半胱氨酸连接酶（GCL）催化亚基和调节亚基的基因表达，GCL是GSH合成中的关键酶。我们进一步研究了UDCA对磷脂酰肌醇3 - 激酶（PI3K）/Akt信号通路的影响，结果表明，PI3K抑制剂LY294002可阻止UDCA诱导的GSH水平升高。此外，对Akt的蛋白质印迹分析表明，虽然总Akt水平保持不变，但UDCA使磷酸化Akt水平升高，而LY294002也可阻止这种升高。此外，UDCA促进转录因子核因子E2相关因子2（Nrf2）易位至细胞核，而LY294002可抑制这一作用。从这些结果表明，UDCA通过激活PI3K/Akt/Nrf2信号通路增加了GSH的合成。这可能是UDCA抗氧化作用的主要机制，与其在慢性肝炎中的治疗效果相关。
