Tsai Ming-Shian, Lin Yu-Chun, Sun Cheuk-Kwan, Huang Shih-Che, Lee Po-Huang, Kao Ying-Hsien
Department of Surgery, E-DA Hospital, Kaohsiung, Taiwan; The School of Medicine for Post-Baccalaureate, I-Shou University, Kaohsiung, Taiwan.
Department of Medical Research, E-DA Hospital, Kaohsiung, Taiwan.
PLoS One. 2014 Nov 14;9(11):e112113. doi: 10.1371/journal.pone.0112113. eCollection 2014.
The role of nerve growth factor (NGF) in liver injury induced by bile duct ligation (BDL) remains elusive. This study aimed to investigate the relationship between inflammation and hepatic NGF expression, to explore the possible upstream molecules up-regulating NGF, and to determine whether NGF could protect hepatocytes from oxidative liver injury. Biochemical and molecular detection showed that NGF was up-regulated in cholestatic livers and plasma, and well correlated with systemic and hepatic inflammation. Conversely, systemic immunosuppression reduced serum NGF levels and resulted in higher mortality in BDL-treated mice. Immunohistochemistry showed that the up-regulated NGF was mainly localized in parenchymal hepatocytes. In vitro mechanistic study further demonstrated that TGF-β1 up-regulated NGF expression in clone-9 and primary rat hepatocytes. Exogenous NGF supplementation and endogenous NGF overexpression effectively protected hepatocytes against TGF-β1- and oxidative stress-induced cell death in vitro, along with reduced formation of oxidative adducted proteins modified by 4-HNE and 8-OHdG. TUNEL staining confirmed the involvement of anti-apoptosis in the NGF-exhibited hepatoprotection. Moreover, NGF potently induced Akt phosphorylation and increased Bcl-2 to Bax ratios, whereas these molecular alterations by NGF were only seen in the H2O2-, but not TGF-β1-treated hepatocytes. In conclusion, NGF exhibits anti-oxidative and hepatoprotective effects and is suggested to be therapeutically applicable in treating cholestatic liver diseases.
神经生长因子（NGF）在胆管结扎（BDL）诱导的肝损伤中的作用仍不清楚。本研究旨在探讨炎症与肝脏NGF表达之间的关系，探索上调NGF的可能上游分子，并确定NGF是否能保护肝细胞免受氧化性肝损伤。生化和分子检测表明，NGF在胆汁淤积性肝脏和血浆中上调，且与全身及肝脏炎症密切相关。相反，全身免疫抑制降低了血清NGF水平，并导致BDL处理小鼠的死亡率更高。免疫组织化学显示，上调的NGF主要定位于实质肝细胞。体外机制研究进一步表明，TGF-β1上调了克隆-9细胞和原代大鼠肝细胞中的NGF表达。外源性补充NGF和内源性过表达NGF在体外有效保护肝细胞免受TGF-β1和氧化应激诱导的细胞死亡，同时减少了由4-HNE和8-OHdG修饰的氧化加合物蛋白的形成。TUNEL染色证实抗凋亡参与了NGF所表现出的肝保护作用。此外，NGF有力地诱导Akt磷酸化并增加Bcl-2与Bax的比率，而NGF引起的这些分子改变仅在H2O2处理而非TGF-β1处理的肝细胞中可见。总之，NGF具有抗氧化和肝保护作用，提示其在治疗胆汁淤积性肝病方面具有治疗应用价值。
