Department of Pediatric Surgery and Department of Teaching & Research, Pu-Li Christian Hospital, Nantou, Taiwan; Department of Applied Chemistry, National Chi-Nan University, Nantou, Taiwan.
Department of Surgery, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine, Kaohsiung, Taiwan.
Int Immunopharmacol. 2018 Mar;56:310-319. doi: 10.1016/j.intimp.2018.01.047. Epub 2018 Feb 20.
The role of transforming growth factor-β activated kinase 1 (TAK1) in modulating the function of Kupffer cells (KCs) within cholestatic livers remains unclear. This study examined the immunopharmacological action of dexamethasone (DEX) in modulating hepatic TAK1 expression and related signaling activity in a rat model of bile duct ligation-mimicked obstructive jaundice. The in vitro effects of DEX on porcine biliary extract (PBE)-modulated gene expression and phagocytosis of KCs were examined using a rat alveolar macrophage cell line (NR8383 cells). Although DEX therapy did not restore the downregulated TAK1 expression and phosphorylation, it significantly attenuated the upregulation of high-mobility group box 1 expression and caspase-3 activation in whole liver extracts of cholestatic rats, possibly via enhancing extracellular signal-regulated kinase-mediated signaling. Dual immunofluorescence staining of cholestatic livers and western detection on primary KCs isolated from cholestatic livers identified that DEX treatment indeed increased both the expression and phosphorylation levels of TAK1 in the KCs of cholestatic livers. In vitro studies using alveolar NR8383 macrophages with KC-characteristic gene expression further demonstrated that DEX not only repressed the pro-inflammatory cytokine production including with respect to interleukin (IL)-1β and IL-6, but also enhanced gene expression of TAK1 and a phagocytic marker, natural-resistance-associated macrophage protein 1, under PBE-mimicked cholestatic conditions. However, WST-1 assay showed that DEX did not protect NR8383 macrophages against the PBE-induced cytotoxicity. Immunofluorescence visualization of cellular F-actin by phalloidin suggested that DEX sustained the PBE-induced phagocytosis morphology of NR8383 macrophages. In conclusion, DEX treatment may pharmacologically restore the expression and activity of TAK1 in KCs, and sustain the phagocytic phenotype of KCs in cholestatic livers.
转化生长因子-β激活激酶 1（TAK1）在调节胆汁淤积性肝脏中枯否细胞（KCs）功能中的作用尚不清楚。本研究在胆管结扎模拟的梗阻性黄疸大鼠模型中，研究了地塞米松（DEX）在调节肝 TAK1 表达和相关信号活性方面的免疫药理学作用。使用大鼠肺泡巨噬细胞系（NR8383 细胞）研究了 DEX 对猪胆液提取物（PBE）调节的基因表达和 KCs 吞噬作用的体外作用。尽管 DEX 治疗并未恢复下调的 TAK1 表达和磷酸化，但它显著减弱了整个胆汁淤积大鼠肝脏提取物中高迁移率族蛋白 1 表达和半胱天冬酶-3 激活的上调，可能是通过增强细胞外信号调节激酶介导的信号。对胆汁淤积性肝脏的双重免疫荧光染色和从胆汁淤积性肝脏分离的原代 KCs 的 Western 检测鉴定，DEX 处理确实增加了胆汁淤积性肝脏中 KCs 的 TAK1 的表达和磷酸化水平。使用具有 KC 特征基因表达的肺泡 NR8383 巨噬细胞进行的体外研究进一步表明，DEX 不仅抑制了包括白细胞介素（IL）-1β和 IL-6 在内的促炎细胞因子的产生，而且在 PBE 模拟的胆汁淤积条件下增强了 TAK1 和吞噬标记物天然抗性相关巨噬细胞蛋白 1 的基因表达。然而，WST-1 测定表明 DEX 不能保护 NR8383 巨噬细胞免受 PBE 诱导的细胞毒性。鬼笔环肽对细胞 F-肌动蛋白的免疫荧光可视化表明，DEX 维持了 PBE 诱导的 NR8383 巨噬细胞的吞噬形态。总之，DEX 治疗可能在药理学上恢复 KCs 中 TAK1 的表达和活性，并维持胆汁淤积性肝脏中 KCs 的吞噬表型。
