Adiponectin alleviates inflammatory response in metabolic dysfunction-associated steatohepatitis by inhibiting NLRP3 inflammasome-mediated hepatocyte pyroptosis.

BACKGROUND: Activation of NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasomes induced by pyroptosis is crucial in metabolic dysfunction-associated steatohepatitis (MASH) progression. Adiponectin possesses an anti-inflammatory role in various liver diseases. This study aimed to evaluate the effects of adiponectin on MASH.

METHODS: Adiponectin-mediated anti-inflammatory mechanisms, effects on pyroptosis-related proteins, and activation of NLRP3 inflammasomes were investigated using methionine-choline-deficient (MCD)-induced MASH murine model and in vitro models. The degree of MASH inflammation in liver tissue of C57BL/6J mice was assessed using histopathology. Enzyme-linked immunosorbent assay was performed to measure levels of inflammatory factors [interleukin-18 (IL-18), IL-1β, and tumor necrosis factor-α (TNF-α)] in mice serum and culture medium. Western blot and quantitative polymerase chain reaction were performed to analyze the expression of pyroptosis-related genes and proteins in liver tissues of mouse model and in vitro models. Macrophage recruitment in vitro was evaluated using co-culture of upper and lower chambers.

RESULTS: MASH developed in MCD diet mice [metabolic dysfunction-associated steatotic liver disease (MASLD) activity score = 6] but not in methionine-choline-sufficient (MCS) diet mice (MASLD activity score = 3). Compared to MCS-fed mice, MCD-fed mice showed increased serum levels of aspartate aminotransferase, IL-18, IL-1β, and TNF-α and higher MASLD activity score (P < 0.001). Adiponectin inhibited these increases (P < 0.05) and suppressed mRNA and protein levels of NLRP3, gasdermin-D (GSDMD), and GSDMD-N in liver tissues (P < 0.05). In vitro, lipopolysaccharide (LPS)/palmitic acid (PA) increased the levels of IL-18, IL-1β, and TNF-α, mRNA expressions of CASP1 and GSDMD, and production of CASP1, NLRP3, GSDMD, and GSDMD-N (P < 0.01). Adiponectin reduced the levels of these inflammatory factors and downregulated the mRNA expression and protein generation of pyroptosis-related markers (P < 0.05). HepG2 cells pretreated with LPS/PA recruited more J774A.1 cells (P < 0.001) and increased inflammatory factor secretion by J774A.1 cells (P < 0.001). Adiponectin inhibited this recruitment and reduced inflammatory factor secretion (P < 0.001).

CONCLUSIONS: Adiponectin inhibits hepatocyte pyroptosis by reducing the production and activation of NLRP3 inflammasomes, CASP1, and GSDMD, thus improving the inflammatory response in MASH and possibly delaying or reversing MASLD progression.