State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, PR China.
Laboratory of Anti-inflammation, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, PR China.
Metabolism. 2021 Jul;120:154797. doi: 10.1016/j.metabol.2021.154797. Epub 2021 May 10.
Obeticholic acid (OCA) has been proved to play potential therapeutic effect on nonalcoholic steatohepatitis (NASH). Up to now, the study of OCA on NLRP3 inflammasome activation in macrophage is still blank and merits great attention. Here, we aimed to better characterize the role and mechanism of OCA on NASH treatment focusing on NLRP3 inflammasome activation in macrophages.
The effects of OCA on inflammasome activation were investigated in BMDM, Kupffer cell, BMDC and LX2 cell. Preconditioned media from BMDM culture was used to treat primary hepatocytes to explore the effects of macrophage NLRP3 inflammasome activation on the function of hepatocytes. In vivo, high fat diet plus CCl (DIO + CCl) induced murine NASH model and choline-deficient and amino acid-defined (CDA) diet-induced NASH mice were used to verify the inhibitory effect of OCA on inflammasome activation in liver macrophages and recapitulate its protective role on NASH progressing. To clear up the effect of OCA on macrophage is FXR dependent or not, FXR siRNA was introduced into BMDMs.
OCA blockaded NLRP3 inflammasome in BMDMs by impacting on the activation stage and disrupting ASC oligomerization. Preconditioned supernatant from LPS + ATP treated BMDMs increased mRNA expression of lipogenic enzymes and lipid content, whereas preconditioned supernatant from OCA treated BMDM blocked these effects in both normal and the FXR knockdown hepatocytes. In DIO + CCl mice, the population of inflammatory myeloid lineage cells in livers was decreased upon OCA treatment. Accordingly, the level of IL-1β and IL-18 in liver, the hepatic expression of ASC, pro-caspase-1 and active caspase-1, the expression of caspase 1 p20 in liver macrophages were also reduced. Similar results were obtained in CDA diet-fed mice. Furthermore, OCA maintained the inhibition on NLRP3 inflammasome activation in FXR knockdown BMDMs, suggesting FXR could be dispensable in this effect.
This finding brings up a new mechanism of OCA on NASH treatment, suggested by direct inhibition on NLRP3 inflammasome activation in macrophage, further suppression on inflammasome activation-elicited hepatic lipid accumulation, and contributing to the amelioration of NASH.
奥贝胆酸（OCA）已被证明对非酒精性脂肪性肝炎（NASH）具有潜在的治疗作用。迄今为止，关于 OCA 对巨噬细胞中 NLRP3 炎性小体激活的研究仍是空白，值得高度关注。在这里，我们旨在通过更好地描述 OCA 对 NASH 治疗的作用和机制，重点关注巨噬细胞中 NLRP3 炎性小体的激活。
在 BMDM、Kupffer 细胞、BMDC 和 LX2 细胞中研究了 OCA 对炎性小体激活的影响。使用 BMDM 培养的预条件培养基处理原代肝细胞，以探讨巨噬细胞 NLRP3 炎性小体激活对肝细胞功能的影响。在体内，使用高脂肪饮食加 CCl（DIO+CCl）诱导的小鼠 NASH 模型和胆碱缺乏和氨基酸定义（CDA）饮食诱导的 NASH 小鼠验证 OCA 对肝巨噬细胞中炎性小体激活的抑制作用，并再现其对 NASH 进展的保护作用。为了明确 OCA 对巨噬细胞的作用是否依赖于 FXR，我们将 FXR siRNA 导入 BMDM。
OCA 通过影响激活阶段和破坏 ASC 寡聚化来阻断 BMDM 中的 NLRP3 炎性小体。用 LPS+ATP 预处理的 BMDM 的预条件上清液增加了脂肪生成酶的 mRNA 表达和脂质含量，而用 OCA 预处理的 BMDM 的预条件上清液则阻断了正常和 FXR 敲低的肝细胞中的这些作用。在 DIO+CCl 小鼠中，OCA 处理后肝脏中炎性髓系细胞的数量减少。相应地，肝内 IL-1β和 IL-18 水平、肝 ASC、前胱天蛋白酶-1 和活性胱天蛋白酶-1、肝巨噬细胞中 caspase 1 p20 的表达也降低。在 CDA 饮食喂养的小鼠中也得到了类似的结果。此外，OCA 在 FXR 敲低的 BMDM 中维持对 NLRP3 炎性小体激活的抑制作用，表明 FXR 在这种作用中可能是可有可无的。
这项发现提出了 OCA 治疗 NASH 的一种新机制，即直接抑制巨噬细胞中的 NLRP3 炎性小体激活，进一步抑制炎性小体激活引起的肝内脂质积累，有助于改善 NASH。
