Gpbar-1/cAMP/PKA signaling mitigates macrophage-mediated acute cholestatic liver injury via antagonizing NLRP3-ASC inflammasome

Biochim Biophys Acta Mol Basis Dis. 2024 Aug;1870(6):167266. doi: 10.1016/j.bbadis.2024.167266. Epub 2024 May 26.

Abstract

Acute cholestatic liver injury (ACLI) is a disease associated with bile duct obstruction that causes liver inflammation and apoptosis. Although G protein-coupled bile acid receptor1 (Gpbar-1) has diverse metabolic roles, its involvement in ACLI-associated immune activation remains unclear. Liver tissues and blood samples from 20 patients with ACLI and 20 healthy individuals were analyzed using biochemical tests, H&E staining, western blotting, and immunohistochemistry to verify liver damage and expression of Gpbar-1. The expression of Gpbar-1, cAMP/PKA signaling, and the NLRP3 inflammasome was tested in wild-type (WT) and Gpbar-1 knockdown (si-Gpbar-1) mice with ACLI induced by bile duct ligation (BDL) and in primary Kupffer cells (KCs) with or without Gpbar-1-siRNA. The results showed that total bile acids and Gpbar-1 expressions were elevated in patients with ACLI. Gpbar-1 knockdown significantly worsened BDL-induced acute hepatic damage, inflammation, and liver apoptosis in vivo. Knockdown of Gpbar-1 heightened KC sensitivity to lipopolysaccharide (LPS) stimulation. Gpbar-1 activation inhibited LPS-induced pro-inflammatory responses in normal KCs but not in Gpbar-1-knockdown KCs. Notably, NLRP3-ASC inflammasome expression was effectively enhanced by Gpbar-1 deficiency. Additionally, Gpbar-1 directly increased intracellular cAMP levels and PKA phosphorylation, thus disrupting the NLRP3-ASC inflammasome. The pro-inflammatory characteristic of Gpbar-1 deficiency was almost neutralized by the NLRP3 inhibitor CY-09. In vitro, M1 polarization was accelerated in LPS-stimulated Gpbar-1-knockdown KCs. Therapeutically, Gpbar-1 deficiency exacerbated BDL-induced ACLI, which could be rescued by inhibition of the NLRP3-ASC inflammasome. Our study reveal that Gpbar-1 may act as a novel immune-mediated regulator of ACLI by inhibiting the NLRP3-ASC inflammasome.

Keywords: Acute cholestatic liver injury; G protein-coupled bile acid receptor 1; Inflammation response; Macrophage; NLRP3-ASC inflammasome.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Animals
  • Cholestasis* / metabolism
  • Cholestasis* / pathology
  • Cyclic AMP* / metabolism
  • Cyclic AMP-Dependent Protein Kinases* / metabolism
  • Female
  • Humans
  • Inflammasomes* / metabolism
  • Kupffer Cells / metabolism
  • Lipopolysaccharides / toxicity
  • Liver / injuries
  • Liver / metabolism
  • Liver / pathology
  • Macrophages / immunology
  • Macrophages / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Middle Aged
  • NLR Family, Pyrin Domain-Containing 3 Protein* / genetics
  • NLR Family, Pyrin Domain-Containing 3 Protein* / metabolism
  • Receptors, G-Protein-Coupled* / genetics
  • Receptors, G-Protein-Coupled* / metabolism
  • Signal Transduction*

Substances

  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Inflammasomes
  • Cyclic AMP-Dependent Protein Kinases
  • Cyclic AMP
  • Receptors, G-Protein-Coupled
  • GPBAR1 protein, human
  • Gpbar1 protein, mouse
  • Nlrp3 protein, mouse
  • NLRP3 protein, human
  • Lipopolysaccharides