Activation of the NLRP3 inflammasome by CCl4 exacerbates hepatopathogenic diet-induced experimental NASH

Abstract

Introduction and objectives: Administration of carbon tetrachloride (CCl₄), along with an hepatopathogenic diet, is widely employed as a chemical inducer to replicate human nonalcoholic steatohepatitis (NASH) in rodents; however, the role of the nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome in this model remains unclear. We aimed to determine the relevance of NLRP3 inflammasome activation in the development of NASH induced by CCl₄ along with an hepatopathogenic diet in male Wistar rats.

Materials and methods: Animals were fed either a high fat, sucrose, and cholesterol diet (HFSCD) or a HFSCD plus intraperitoneal injections of low doses of CCl₄ (400 mg/kg) once a week for 15 weeks. Liver steatosis, inflammation, fibrosis, and NLRP3 inflammasome activation were evaluated using biochemical, histological, ultrastructural, and immunofluorescence analyses, western blotting, and immunohistochemistry.

Results: Our experimental model reproduced several aspects of the human NASH pathophysiology. NLRP3 inflammasome activation was induced by the combined effect of HFSCD plus CCl₄ and significantly increased levels of both proinflammatory and profibrogenic cytokines and collagen deposition in the liver; thus, NASH severity was higher in the HFSCD+CCl₄ group than that in the HFSCD group, to which CCl₄ was not administered. Hepatic stellate cells, the most profibrogenic cells, were activated by HFSCD plus CCl₄, as indicated by elevated levels of α-smooth muscle actin. Thus, activation of the NLRP3 inflammasome, triggered by low doses of CCl₄, exacerbates the severity of NASH.

Conclusions: Our results indicate that NLRP3 inflammasome activation plays a key role and may be an important therapeutic target for NASH treatment.

Keywords: CCl(4); Fibrosis; Inflammation; NASH; NLRP3 inflammasome; Nonalcoholic steatohepatitis.