Section of Digestive Diseases, Yale University, New Haven, Connecticut.
Section of Digestive Diseases, Yale University, New Haven, Connecticut; Section of Digestive Diseases, Department of Veterans Affairs Connecticut Healthcare, West Haven, Connecticut.
Gastroenterology. 2014 Jun;146(7):1763-74. doi: 10.1053/j.gastro.2014.03.014. Epub 2014 Mar 20.
BACKGROUND & AIMS: The NACHT, LRR, and pyrin domain-containing protein 3 (NLRP3) inflammasome induces inflammation in response to organ injury, but little is known about its regulation. Toll-like receptors (TLRs) provide the first signal required for activation of the inflammasome and stimulate aerobic glycolysis to generate lactate. We examined whether lactate and the lactate receptor, Gi-protein-coupled receptor 81 (GPR81), regulate TLR induction of signal 1 and limit inflammasome activation and organ injury.
Primary mouse macrophages and human monocytes were incubated with TLR4 agonists and lactate and assayed for levels of pro-interleukin (IL)1β, NLRP3, and caspase-1 (CASP1); release of IL1β; and activation of nuclear factor-κB (NF-κB) and caspase-1. Small interfering RNAs were used to reduce levels of GPR81 and arrestin β-2 (ARRB2), and an NF-κB luciferase reporter transgene was transfected in RAW 264.7 cells. Cell lysates were analyzed by immunoprecipitation with an antibody against GPR81. Acute hepatitis was induced in C56BL/6N mice by administration of lipopolysaccharide and D-galactosamine. Acute pancreatitis was induced by administration of lipopolysaccharide and cerulein. Some mice were given intraperitoneal injections of sodium lactate or small interfering RNA against Gpr81. Activation of NF-κB in tissue macrophages was assessed in mice that expressed a reporter transgene.
In macrophages and monocytes, increasing concentrations of lactate reduced TLR4-mediated induction of Il1B, Nlrp3, and Casp1; activation of NF-κB; release of IL1β; and cleavage of CASP1. GPR81 and ARRB2 physically interacted and were required for these effects. The administration of lactate reduced inflammation and organ injury in mice with immune hepatitis; this reduction required Gpr81 dependence in vivo. Lactate also prevented activation of NF-κB in macrophages of mice, and, when given after injury, reduced the severity of acute pancreatitis and acute liver injury.
Lactate negatively regulates TLR induction of the NLRP3 inflammasome and production of IL1β, via ARRB2 and GPR81. Lactate could be a promising immunomodulatory therapy for patients with acute organ injury.
NACHT、LRR 和富含pyrin 结构域的蛋白 3（NLRP3）炎症小体可响应器官损伤引发炎症，但目前对其调控机制知之甚少。Toll 样受体（TLR）提供激活炎症小体所需的第一信号，并刺激有氧糖酵解以产生乳酸。我们研究了乳酸及其受体，G 蛋白偶联受体 81（GPR81）是否调节 TLR 诱导的信号 1 并限制炎症小体激活和器官损伤。
原代小鼠巨噬细胞和人单核细胞与 TLR4 激动剂和乳酸孵育，并检测白细胞介素（IL）1β、NLRP3 和半胱天冬酶-1（CASP1）前体水平、IL1β 释放以及核因子-κB（NF-κB）和 CASP1 的激活情况。用 GPR81 和 arrestin β-2（ARRB2）的小干扰 RNA 降低其水平，并在 RAW 264.7 细胞中转染 NF-κB 荧光素酶报告基因。用针对 GPR81 的抗体进行免疫沉淀分析细胞裂解物。用脂多糖和 D-半乳糖胺诱导 C56BL/6N 小鼠急性肝炎，用脂多糖和 cerulein 诱导急性胰腺炎。一些小鼠给予腹腔注射乳酸钠或针对 Gpr81 的小干扰 RNA。用表达报告基因的小鼠评估组织巨噬细胞中 NF-κB 的激活情况。
在巨噬细胞和单核细胞中，增加浓度的乳酸可降低 TLR4 介导的 Il1B、Nlrp3 和 Casp1 诱导、NF-κB 激活、IL1β 释放和 CASP1 切割。GPR81 和 ARRB2 相互作用，并需要在体内发挥这些作用。给予乳酸可减少免疫性肝炎小鼠的炎症和器官损伤，这种减少需要体内的 Gpr81 依赖性。乳酸还可防止 NF-κB 在小鼠巨噬细胞中的激活，且在损伤后给予可减轻急性胰腺炎和急性肝损伤的严重程度。
乳酸通过 ARRB2 和 GPR81 负调节 TLR 诱导的 NLRP3 炎症小体和 IL1β 的产生。乳酸可能是急性器官损伤患者有前途的免疫调节治疗方法。
