We investigated the migration of intestinal immune cells to the liver and their contribution to alcoholic liver disease. In mice fed ethanol, we found that an increased number of invariant natural killer T (iNKT) cells, which respond to the antigen presented by CD1d, migrated from mesenteric lymph nodes to the liver. iNKT cells react to lipid antigens, so we studied their activities in mice with intestinal epithelial cell-specific deletion of Pparg (PpargΔIEC) as a model for altering intestinal lipidomic profiles. Levels of CD1d increased in intestines of ethanol-fed PpargΔIEC mice, and in cell-tracking experiments, more iNKT cells migrated to the liver, compared with mice without disruption of Pparg. Livers of PpargΔIEC mice had increased markers of apoptosis and liver injury after ethanol feeding. iNKT cells isolated from livers of ethanol-fed PpargΔIEC mice induced apoptosis of cultured hepatocytes. An inhibitor of iNKT cells reduced ethanol-induced liver injury in PpargΔIEC mice. Duodenal tissues from patients with alcohol-use disorder have been found to have increased levels of CD1d compared with tissues from patients without alcohol overuse. Ethanol use, therefore, activates iNKT cells in the intestine to migrate to liver, where they-along with the resident hepatic iNKT cells-contribute to hepatocyte death and injury. NEW & NOTEWORTHY In this article, we studied migration of intestinal immune cells into the liver in response to ethanol-induced liver disease. We found that chronic ethanol feeding induces expression of CD1d by enterocytes, which activate invariant natural killer T (iNKT) cells in mesenteric lymph nodes; activation is further increased with loss of peroxisome proliferator-activated receptor gamma gene and altered lipid profiles. The activated iNKT cells migrate into the liver, where they promote hepatocyte apoptosis. Patients with alcohol use disorder have increased expression of CD1d in the small intestine. Strategies to block these processes might be developed to treat alcoholic liver disease.
Keywords: ALD model; Kaede transgenic mice; immune regulation; invariant natural killer T; liver damage.