Hepatopancreatobiliary Service, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
Hepatology. 2010 Feb;51(2):621-32. doi: 10.1002/hep.23365.
Endogenous ligands such as high-mobility group box 1 (HMGB1) and nucleic acids are released by dying cells and bind Toll-like receptors (TLRs). Because TLR9 sits at the interface of microbial and sterile inflammation by detecting both bacterial and endogenous DNA, we investigated its role in a model of segmental liver ischemia-reperfusion (I/R) injury. Mice were subjected to 1 hour of ischemia and 12 hours of reperfusion before assessment of liver injury, cytokines, and reactive oxygen species (ROS). Wild-type (WT) mice treated with an inhibitory cytosine-guanosine dinucleotide (iCpG) sequence and TLR9(-/-) mice had markedly reduced serum alanine aminotransferase (ALT) and inflammatory cytokines after liver I/R. Liver damage was mediated by bone marrow-derived cells because WT mice transplanted with TLR9(-/-) bone marrow were protected from hepatic I/R injury. Injury in WT mice partly depended on TLR9 signaling in neutrophils, which enhanced production of ROS, interleukin-6 (IL-6), and tumor necrosis factor (TNF). In vitro, DNA released from necrotic hepatocytes increased liver nonparenchymal cell (NPC) and neutrophil cytokine secretion through a TLR9-dependent mechanism. Inhibition of both TLR9 and HMGB1 caused maximal inflammatory cytokine suppression in neutrophil cultures and conferred even greater protection from I/R injury in vivo.
TLR9 serves as an endogenous sensor of tissue necrosis that exacerbates the innate immune response during liver I/R. Combined blockade of TLR9 and HMGB1 represents a clinically relevant, novel approach to limiting I/R injury.
死亡细胞释放的内源性配体，如高迁移率族蛋白 B1（HMGB1）和核酸，与 Toll 样受体（TLR）结合。由于 TLR9 通过检测细菌和内源性 DNA 位于微生物和无菌性炎症的交界处，我们研究了其在节段性肝缺血再灌注（I/R）损伤模型中的作用。在评估肝损伤、细胞因子和活性氧（ROS）之前，将小鼠进行 1 小时缺血和 12 小时再灌注。用抑制胞嘧啶鸟嘌呤二核苷酸（iCpG）序列处理野生型（WT）小鼠和 TLR9（-/-）小鼠后，肝 I/R 后血清丙氨酸氨基转移酶（ALT）和炎症细胞因子明显减少。肝损伤是由骨髓来源的细胞介导的，因为 WT 小鼠接受 TLR9（-/-）骨髓移植后可免受肝 I/R 损伤。WT 小鼠的损伤部分依赖于中性粒细胞中的 TLR9 信号，该信号增强了 ROS、白细胞介素 6（IL-6）和肿瘤坏死因子（TNF）的产生。在体外，坏死肝细胞释放的 DNA 通过 TLR9 依赖的机制增加了肝非实质细胞（NPC）和中性粒细胞的细胞因子分泌。TLR9 和 HMGB1 的联合抑制可最大程度地抑制中性粒细胞培养物中的炎症细胞因子，并在体内提供对 I/R 损伤的更大保护。
TLR9 是组织坏死的内源性传感器，可加剧肝 I/R 期间的固有免疫反应。TLR9 和 HMGB1 的联合阻断代表了一种有临床意义的、新颖的方法来限制 I/R 损伤。
