Block nucleotide-binding oligomerization domain-like receptor protein 3 inflammasome to alleviate non-alcoholic steatohepatitis and liver fibrosis / 中华消化杂志

ABSTRACT

Objective:To explore the role of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in non-alcoholic steatohepatitis (NASH).Methods:The liver tissue samples of 24 patients admitted the Second Affiliated Hospital of Fujian Medical University were selected, including 12 NASH samples from liver biopsy and 12 normal liver tissues from the margin of hepatic hemangioma. The expression of NLRP3, apoptosis-associated speck-like protein (ASC), caspase-1, interleukin (IL)-1β and the content of triglyceride (TG) were detected. Wild-type and NLRP3 -/- C57BL/6 mice were fed with normal diet or methionine-choline deficient diet (MCD) for 8 weeks. The wild-type mice were divided into MCC950 NASH, 0.9% sodium chloride (NaCl) NASH, MCC950 and 0.9% NaCl group, 8 mice in each group, and were fed with MCD diet and treated with MCC950, fed with MCD diet and treated with 0.9% NaCl, fed with normal diet and treated with MCC950, and fed with normal diet and treated with 0.9% NaCl respectively for eight weeks. After eight weeks, the pathologic changes of liver tissues were observed with hematoxylin-eosin staining and immunohistochemistry. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), free fatty acid (FFA), IL-1β and TG in serum were determined by enzyme linked immunosorbent assay. The expression levels of NLRP3, ASC, caspase-1 and IL-1β in liver tissues were examined by Western blotting and real-time quantitative polymerase chain reaction. Primary Kupffer cells were isolated and cultured from the livers of wild-type and NLRP3 -/- mice and divided into control group and palmitic acid group. The expression levels of related proteins in the supernatant of cells culture were detected by Western blotting. Independent sample t test and one-way ANOVA were used for statistical analysis. Results:The expression levels of NLRP3, ASC, caspase-1, IL-1β and the content of TG of the liver tissues of the NASH patients were all higher than those of healthy control group (all P<0.05). The formation of steatohepatitis in hepatocyte of MCD-fed mice was more obvious than that of nomal diet-fed mice, with more hepatocyte ballooning and inflammatory cell infiltration. The expression of NLRP3, ASC, caspase-1, IL-1β, caspase-1 activity and the content of TG in liver tissue of NASH mice were all higher than those of normal diet-fed group (all P<0.05); and serum levels of ALT, AST, IL-1β, and the content of FAA were all higher than those of normal diet-fed group (all P<0.05). The serum levels of ALT, AST, IL-1β and IL-18 of NLRP3 -/- NASH mice were all lower than those of wild-type NASH mice (all P<0.05). The serum level of ALT, the expression of ASC, caspase-1 and IL-1β in liver tissues, and the degrees of liver fibrosis of wild-type MCC950 NASH group were all lower than those of 0.9% NaCl NASH group (all P<0.05). The expression of NLRP3, ASC, caspase-1, caspase-1 activity, and secretion of IL-1β and IL-18 in Kupffer cells from wild-type mouse treated with palmitic acid were all higher than those of the negative control group (all P<0.05). However, the changes of the above indicators in Kupffer cells from NLRP3 -/- mouse were not affected by palmitic acid treatment. Conclusion:NLRP3 blockade can significantly alleviate the liver injury and fibrosis in NASH mice and prevent the development of NASH.