Multi Organ Transplant Program, Department of Surgery, University of Toronto, Toronto General Hospital, Toronto, Canada.
J Hepatol. 2012 Jan;56(1):153-9. doi: 10.1016/j.jhep.2011.05.033. Epub 2011 Jul 12.
BACKGROUND & AIMS: Sinusoidal endothelial cell (SEC) and hepatocyte death are early, TNF-α mediated events in ischemia and reperfusion of the liver (I/Rp). We previously reported that TNF-α induced liver injury is dependent on Fibrinogen like protein 2 (FGL2/Fibroleukin) and showed that FGL2 binding to its receptor, FcγRIIB, results in lymphocyte apoptosis. In this study we examine whether I/Rp is induced by specific binding of FGL2 to FcγRIIB expressed on SEC.
Hepatic ischemia and reperfusion was induced in wild type (WT) mice and in mice with deletion or inhibition of FGL2 and FcRIIB. Liver injury was determined by AST release, necrosis and animal death. Apoptosis was evaluated with caspase 3 and TUNEL staining.
FGL2 deletion or inhibition resulted in decreased liver injury as determined by a marked reduction in both levels of AST and ALT and hepatocyte necrosis. Caspase 3 staining of SEC (12% vs. 75%) and hepatocytes (12% vs. 45%) as well as TUNEL staining of SEC (13% vs. 60%, p=0.02) and hepatocytes (18% vs. 70%, p=0.03), markers of apoptosis, were lower in Fgl2(-/-) compared to WT mice. In vitro incubation of SEC with FGL2 induced apoptosis of SEC from WT mice, but not FcγRIIB(-/-) mice. Deletion of FcγRIIB fully protected mice against SEC and hepatocyte death in vivo. Survival of mice deficient in either Fgl2(-/-) (80%) or FcγRIIB(-/-) (100%) was markedly increased compared to WT mice (10%) which were subjected to 75min of total hepatic ischemia (p=0.001).
FGL2 binding to the FcγRIIB receptor expressed on SEC is a critical event in the initiation of the hepatic reperfusion injury cascade through induction of SEC and hepatocyte death.
在肝脏的缺血再灌注（I/Rp）过程中，窦状内皮细胞（SEC）和肝细胞死亡是早期的 TNF-α 介导事件。我们之前报道过，TNF-α 诱导的肝损伤依赖于纤维蛋白原样蛋白 2（FGL2/Fibroleukin），并表明 FGL2 与其受体 FcγRIIB 结合导致淋巴细胞凋亡。在这项研究中，我们研究了 I/Rp 是否是由 FGL2 与 SEC 上表达的 FcγRIIB 的特异性结合引起的。
在野生型（WT）小鼠和 FGL2 缺失或抑制以及 FcRIIB 缺失或抑制的小鼠中诱导肝缺血再灌注。通过 AST 释放、坏死和动物死亡来确定肝损伤。通过 caspase 3 和 TUNEL 染色评估细胞凋亡。
FGL2 缺失或抑制导致肝损伤明显减少，AST 和 ALT 水平以及肝细胞坏死均显著降低。SEC（12%比 75%）和肝细胞（12%比 45%）的 caspase 3 染色以及 SEC（13%比 60%，p=0.02）和肝细胞（18%比 70%，p=0.03）的 TUNEL 染色，凋亡标志物，在 Fgl2(-/-)小鼠中均低于 WT 小鼠。SEC 与 FGL2 体外孵育诱导 WT 小鼠 SEC 的凋亡，但不诱导 FcγRIIB(-/-)小鼠的凋亡。FcγRIIB 的缺失完全保护小鼠体内 SEC 和肝细胞死亡。缺乏 Fgl2(-/-)（80%）或 FcγRIIB(-/-)（100%）的小鼠的存活率明显高于 WT 小鼠（10%），后者经历了 75 分钟的全肝缺血（p=0.001）。
FGL2 与 SEC 上表达的 FcγRIIB 受体结合是启动肝再灌注损伤级联反应的关键事件，通过诱导 SEC 和肝细胞死亡。
