NLRP3 Deletion Inhibits the Non-alcoholic Steatohepatitis Development and Inflammation in Kupffer Cells Induced by Palmitic Acid

The cleavage and secretion of pro-inflammatory cytokines IL-1 beta and IL-18 is regulated by NLRP3 (NACHT, LRR, and PYD domain-containing protein 3) inflammasome activation. Kupffer cells (KCs) are implicated in the pathogenesis of various liver diseases, such as non-alcoholic fatty liver disease (NAFLD), alcoholic liver disease, and liver fibrosis. However, the role of NLRP3 played in the non-alcoholic steatohepatitis (NASH) has yet to be evaluated. In the present study, methionine-choline-deficient (MCD) diet was used to establish the mice NASH model. The expression levels of F4/80 and NLRP3 in liver tissues were evaluated, and the IL-1 beta and IL-18 in serum were also evaluated. KCs were isolated from wild-type (WT) mice and NLRP3 knockout (NLRP3(-/-)) mice and then randomly divided into two groups: the control and palmitic acid (PA) groups. The expression levels of NLRP3, ASC, and caspase-1 in KCs were determined by RT-PCR, western blotting, and immunofluorescence. The levels of IL-1 beta and IL-18 in the supernatant (SN) of KCs were evaluated by enzyme-linked immunosorbent assay (ELISA). We found that KCs and NLRP3 play pro-inflammatory roles in the progression of NASH, probably through secretions of IL-1 beta and IL-18 by KCs induced by PA. PA could act as a kind of damage-associated molecular patterns to elevate the messenger RNA and protein expression levels of NLRP3, ASC, and caspase-1 in KCs from WT mice. In the contrast, NLRP3 deletion could inhibit the NLRP3 inflammasome upregulation and activation in KCs induced by PA. Furthermore, the levels of pro-inflammatory cytokines IL-1 beta and IL-18 in the SN of KCs from WT mice were all elevated with the stimulation of PA, and the increase of these cytokines in the SN was blocked by NLRP3 deletion. In conclusion, our novel findings demonstrate that NLRP3 plays a pivotal role in NASH development and pro-inflammatory cytokines IL-1 beta and IL-18 secretion induced by PA stimulation, and NLRP3 might be an effective potential target for the treatment of liver inflammatory diseases associated with NLRP3 inflammasome activation.