Section of Digestive Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
Am J Pathol. 2013 Mar;182(3):786-95. doi: 10.1016/j.ajpath.2012.11.032. Epub 2013 Jan 9.
Nogo-B (reticulon 4B) accentuates hepatic fibrosis and cirrhosis, but the mechanism remains unclear. The aim of this study was to identify the role of Nogo-B in hepatic stellate cell (HSC) apoptosis in cirrhotic livers. Cirrhosis was generated by carbon tetrachloride inhalation in wild-type (WT) and Nogo-A/B knockout (Nogo-B KO) mice. HSCs were isolated from WT and Nogo-B KO mice and cultured for activation and transformation to myofibroblasts (MF-HSCs). Human hepatic stellate cells (LX2 cells) were used to assess apoptotic responses of activated HSCs after silencing or overexpressing Nogo-B. Livers from cirrhotic Nogo-B KO mice showed significantly reduced fibrosis (P < 0.05) compared with WT mice. Apoptotic cells were more prominent in fibrotic areas of cirrhotic Nogo-B KO livers. Nogo-B KO MF-HSCs showed significantly increased levels of apoptotic markers, cleaved poly (ADP-ribose) polymerase, and caspase-3 and -8 (P < 0.05) compared with WT MF-HSCs in response to staurosporine. Treatment with tunicamycin, an endoplasmic reticulum stress inducer, increased cleaved caspase-3 and -8 levels in Nogo-B KO MF-HSCs compared with WT MF-HSCs (P < 0.01). In LX2 cells, Nogo-B knockdown enhanced apoptosis in response to staurosporine, whereas Nogo-B overexpression inhibited apoptosis. The absence of Nogo-B enhances apoptosis of HSCs in experimental cirrhosis. Selective blockade of Nogo-B in HSCs may represent a potential therapeutic strategy to mitigate liver fibrosis.
Nogo-B(网抑素 4B)加重肝纤维化和肝硬化,但机制尚不清楚。本研究旨在确定 Nogo-B 在肝星状细胞(HSC)凋亡在肝硬化中的作用。采用四氯化碳吸入法在野生型(WT)和 Nogo-A/B 敲除(Nogo-B KO)小鼠中诱导肝硬化。从 WT 和 Nogo-B KO 小鼠中分离 HSCs 并进行培养,以激活和转化为肌成纤维细胞(MF-HSCs)。使用人肝星状细胞(LX2 细胞)评估沉默或过表达 Nogo-B 后活化的 HSC 的凋亡反应。与 WT 小鼠相比,肝硬化 Nogo-B KO 小鼠的肝脏纤维化明显减少(P < 0.05)。在肝硬化 Nogo-B KO 肝脏的纤维化区域中,凋亡细胞更为明显。与 WT MF-HSCs 相比,Nogo-B KO MF-HSCs 在受到 staurosporine 刺激时,凋亡标志物 cleaved poly (ADP-ribose) polymerase 和 caspase-3 和 -8 的水平明显升高(P < 0.05)。用内质网应激诱导剂 tunicamycin 处理后,与 WT MF-HSCs 相比,Nogo-B KO MF-HSCs 中的 cleaved caspase-3 和 -8 水平升高(P < 0.01)。在 LX2 细胞中,Nogo-B 敲低增强了对 staurosporine 的凋亡反应,而 Nogo-B 过表达抑制了凋亡。实验性肝硬化中 HSC 中 Nogo-B 的缺失增强了凋亡。选择性阻断 HSCs 中的 Nogo-B 可能代表减轻肝纤维化的潜在治疗策略。