IL-6反式信号途径在肝切除术后肝衰中的作用及其机制研究

Liver surgery remains the treatment of choice for most hepatobiliary malignancies. The mechanism of post-hepatectomy liver failure (PHLF), as a major surgical concern, has yet to be elucidated. IL-6 plays an important role in both liver regeneration and inflammatory response following liver resection, which works in two fashions: classic- and trans-signaling. In classic signaling, IL-6 binds to the membrane-bound IL-6R conjugating with gp130 dimer (e.g. hepatocyte) and stimulates the intracellular JNK/STAT3 pathways. In trans-signaling, IL-6 can pre-bind to a soluble form of IL-6R (sIL-6R) and stimulate a cell without membrane-bound IL-6R (e.g. hepatic sinusoidal endothelial cell) via the isolated gp130 dimer. Pharmaceutical blockade of IL-6 trans-signaling has been reported to attenuate the IL-6-induced over-inflammation in a number of autoimmune diseases. However, the role of IL-6 trans-signaling effect in PHLF and its mechanism remain to be elusive. Our preliminary study showed that the serum IL-6 level of PHLF mice was dramatically higher than that of the survival control at early postoperative phase (6h), followed by a peak of serum sIL-6Rα at postoperative 24h. Administering IL-6 neutralizing antibody at postoperative 3h significantly improved animal survival. In contrast, administering hyper-IL-6 (a IL-6/sIL-6R fusion protein) but not the recombinant IL-6 increased the mortality of PHLF, indicating that an enhanced IL-6 trans-signaling effect might be the culprit of PHLF. In the next step, based on our modified animal model and a novel non-invasive scoring system for PHLF, IL-6 trans-signaling will be blocked using sgp130Fc (a IL-6/sIL-6R neutralizer) to determine its role in PHLF. The key factors and effector cells along its pathway will be studied to fill the mechanistic gaps therein. This might unravel new prognostic markers and therapeutic strategies of PHLF.

肝切除术后肝衰（PHLF）复杂难治。IL-6是重要炎性因子，具有经典和反式两条信号途径。经典途径中，IL-6直接结合膜表面受体mIL-6R，刺激肝再生与细胞急相反应；反式途径中，IL-6结合游离受体sIL-6R，可识别跨膜蛋白gp130作用于膜表面不表达mIL-6R的细胞，扩大作用范围与促炎效应。选择性干预IL-6反式途径已在自身免疫性疾病中取得显著疗效。然而IL-6反式途径在肝衰中的作用及其机制尚未阐明。申请人前期实验提示肝衰动物术后极早期出现IL-6过度分泌，IL-6中和抗体可改善预后；术后早期sIL-6Rα水平显著增高，给予hyper-IL-6活化其反式信号途径加剧PHLF发生。因此我们推测IL-6反式信号途径活化与PHLF显著相关。基于前期工作基础，课题组展开IL-6反式信号途径关键因子、效应细胞及其作用机制的系统研究，有助于发现PHLF新的早期监测指标和治疗策略。

肝切除术后肝衰（PHLF）复杂难治。白细胞介素-6（IL-6）是重要炎性因子，具有经典（classic signaling）和反式（trans-signaling）两条信号途径 。经典信号途径中，IL-6直接结合肝细胞膜表面受体mIL-6R，刺激肝再生与细胞急相反应；反式信号途径中， IL-6结合游离受体sIL-6R，可识别跨膜蛋白gp130而作用于某些细胞膜表面并不表达mIL-6R的细胞，从而扩大效应范围并促进炎症效应。采用药物选择性干预IL-6反式信号途径已证实有助于抑制某些自身免疫性疾病，使我们有理由推测在大范围肝切除条件下，选择性干预IL-6反式信号途径可能在不影响其经典信号途径启动肝再生及细胞保护性反应的前提下，调控过度炎症反应所致器官功能不全甚至衰竭。目前IL-6 反式信号途径在肝衰中的调控作用及其机制尚未阐明。基于前期工作基础，课题组展开IL-6反式信号途径关键因子、效应细胞及其作用机制的系统研究。首先，建立并优化小鼠极量肝切除模型，标准化手术技术和围术期处理，为后期机制性研究提供可靠模型；建立并发表小鼠PHLF早期预判评分体系（BCS评分），并实验证实其准确性；监测发现，PHLF动物术后极早期（6h）出现IL-6过度分泌，肝细胞特征性脂肪积累，肝窦受压，SEC形态不显著，肝再生水平下降；术后3h给予固定剂量anti-IL-6抗体，出现相应组织学和血清学改善，PHLF发生率下降，生存率提高；术后早期sIL-6Rα水平显著增高，给予hyper-IL-6（IL-6/sIL-6R融合蛋白）而非单纯重组IL-6，活化其反式信号途径加剧PHLF发生，生存率下降。术后3h给予固定剂量sgp130Fc阻断IL-6反式信号途径，PHLF发生率减少，生存率提高；术后即早给予sIL-6R剪切酶ADAM17活化剂PMA干预显示PHLF发生率提高，提示ADAM17与sIL-6R及反式信号途径激活相关性。肝组织RNA-seq基因芯片分析亦得到部分线索性发现。综上结果，IL-6是PHLF新的早期监测指标，术后极早期给予anti-IL-6抗体或sIL-6R融合蛋白，有助减轻IL-6反式信号途径导致的过度炎症反应，减少组织病理损伤、PHLF发生和动物死亡，IL-6反式信号途径有助成为临床PHLF治疗的新靶标。