Invariant NKT cells promote alcohol-induced steatohepatitis through interleukin-1β in mice

Background & Aims It was reported that alcohol consumption activated the NLRP3 inflammasome in Kupffer cells, leading to mature interleukin (IL)-1β release in alcoholic liver injury; however, how IL-1β promotes liver injury remains unclear. Methods We investigated the role of IL-1β in alcoholic steatohepatitis by using a chronic plus single-binge ethanol consumption mouse model. Results Here, liver steatosis was accompanied by notably increased invariant natural killer T (iNKT) cell numbers and activation, and iNKT-deficient Jα18−/− mice developed less alcohol-induced steatosis, with reduced liver inflammation and neutrophil infiltration. Kupffer cells and IL-1β were required for the hepatic iNKT accumulation, as either blocking IL-1β signaling with a recombinant IL-1 receptor antagonist (IL-1Ra), depleting Kupffer cells by clodronate liposomes, or specifically silencing IL-1β in Kupffer cells by nanoparticle-encapsulated siRNA, resulted in inhibited hepatic iNKT cell accumulation and activation, as well as amelioration of alcoholic fatty liver. In addition, IL-1β overexpression in hepatocytes was sufficient to compensate for Kupffer cell depletion. Increased gene and protein expression of mature IL-1β correlated with elevated expression of the NLRP3 inflammasome components NLRP3, ASC, and cleaved caspase-1 in Kupffer cells from ethanol–exposed wild-type mice. NLRP3 deficiency led to the attenuation of alcoholic steatosis, similarly as Kupffer cell depletion, almost without hepatic NKT cells. Conclusions After alcohol–exposure Kupffer cell-derived IL-1β triggered by NLRP3 activation, recruits and activates hepatic iNKT cells, subsequently promoting liver inflammation and neutrophil infiltration, and inducing alcoholic liver injury. It was reported that alcohol consumption activated the NLRP3 inflammasome in Kupffer cells, leading to mature interleukin (IL)-1β release in alcoholic liver injury; however, how IL-1β promotes liver injury remains unclear. We investigated the role of IL-1β in alcoholic steatohepatitis by using a chronic plus single-binge ethanol consumption mouse model. Here, liver steatosis was accompanied by notably increased invariant natural killer T (iNKT) cell numbers and activation, and iNKT-deficient Jα18−/− mice developed less alcohol-induced steatosis, with reduced liver inflammation and neutrophil infiltration. Kupffer cells and IL-1β were required for the hepatic iNKT accumulation, as either blocking IL-1β signaling with a recombinant IL-1 receptor antagonist (IL-1Ra), depleting Kupffer cells by clodronate liposomes, or specifically silencing IL-1β in Kupffer cells by nanoparticle-encapsulated siRNA, resulted in inhibited hepatic iNKT cell accumulation and activation, as well as amelioration of alcoholic fatty liver. In addition, IL-1β overexpression in hepatocytes was sufficient to compensate for Kupffer cell depletion. Increased gene and protein expression of mature IL-1β correlated with elevated expression of the NLRP3 inflammasome components NLRP3, ASC, and cleaved caspase-1 in Kupffer cells from ethanol–exposed wild-type mice. NLRP3 deficiency led to the attenuation of alcoholic steatosis, similarly as Kupffer cell depletion, almost without hepatic NKT cells. After alcohol–exposure Kupffer cell-derived IL-1β triggered by NLRP3 activation, recruits and activates hepatic iNKT cells, subsequently promoting liver inflammation and neutrophil infiltration, and inducing alcoholic liver injury.