ObjectiveAntimicrobial C-type lectin regenerating islet-derived 3 gamma (REG3G) is suppressed in the small intestine during chronic ethanol feeding. Our aim was to determine the mechanism that underlies REG3G suppression during experimental alcoholic liver disease.DesignInterleukin 22 (IL-22) regulates expression of REG3G. Therefore, we investigated the role of IL-22 in mice subjected to chronic-binge ethanol feeding (NIAAA model).ResultsIn a mouse model of alcoholic liver disease, we found that type 3 innate lymphoid cells produce lower levels of IL-22. Reduced IL-22 production was the result of ethanol-induced dysbiosis and lower intestinal levels of indole-3-acetic acid (IAA), a microbiota-derived ligand of the aryl hydrocarbon receptor (AHR), which regulates expression of IL-22. Importantly, faecal levels of IAA were also found to be lower in patients with alcoholic hepatitis compared with healthy controls. Supplementation to restore intestinal levels of IAA protected mice from ethanol-induced steatohepatitis by inducing intestinal expression of IL-22 and REG3G, which prevented translocation of bacteria to liver. We engineered Lactobacillus reuteri to produce IL-22 (L. reuteri/IL-22) and fed them to mice along with the ethanol diet; these mice had reduced liver damage, inflammation and bacterial translocation to the liver compared with mice fed an isogenic control strain and upregulated expression of REG3G in intestine. However, L. reuteri/IL-22 did not reduce ethanol-induced liver disease in Reg3g–/– mice.ConclusionEthanol-associated dysbiosis reduces levels of IAA and activation of the AHR to decrease expression of IL-22 in the intestine, leading to reduced expression of REG3G; this results in bacterial translocation to the liver and steatohepatitis. Bacteria engineered to produce IL-22 induce expression of REG3G to reduce ethanol-induced steatohepatitis.

Background & AimsNon-alcoholic steatohepatitis (NASH) involves steatosis combined with inflammation, which can progress into fibrosis and cirrhosis. Exploring the molecular mechanisms of NASH is highly dependent on the availability of animal models. Currently, the most commonly used animal models for NASH imitate particularly late stages of human disease. Thus, there is a need for an animal model that can be used for investigating the factors that potentiate the inflammatory response within NASH. We have previously shown that 7-day high-fat-high-cholesterol (HFC) feeding induces steatosis and inflammation in both APOE2ki and Ldlr−/− mice. However, it is not known whether the early inflammatory response observed in these mice will sustain over time and lead to liver damage. We hypothesized that the inflammatory response in both models is sufficient to induce liver damage over time.Methods APOE2ki and Ldlr−/− mice were fed a chow or HFC diet for 3 months. C57Bl6/J mice were used as control.ResultsSurprisingly, hepatic inflammation was abolished in APOE2ki mice, while it was sustained in Ldlr−/− mice. In addition, increased apoptosis and hepatic fibrosis was only demonstrated in Ldlr−/− mice. Finally, bone-marrow-derived-macrophages of Ldlr−/− mice showed an increased inflammatory response after oxidized LDL (oxLDL) loading compared to APOE2ki mice.Conclusion Ldlr−/− mice, but not APOE2ki mice, developed sustained hepatic inflammation and liver damage upon long term HFC feeding due to increased sensitivity for oxLDL uptake. Therefore, the Ldlr−/− mice are a promising physiological model particularly vulnerable for investigating the onset of hepatic inflammation in non-alcoholic steatohepatitis.

The symbiotic gut microbiota play pivotal roles in host physiology and the development of cardiovascular diseases, but the microbiota-triggered pattern recognition signaling mechanisms that impact thrombosis are poorly defined. In this article, we show that germ-free (GF) and Toll-like receptor-2 ()-deficient mice have reduced thrombus growth after carotid artery injury relative to conventionally raised controls. GF and wild-type (WT) mice were indistinguishable, but colonization with microbiota restored a significant difference in thrombus growth between the genotypes. We identify reduced plasma levels of von Willebrand factor (VWF) and reduced VWF synthesis, specifically in hepatic endothelial cells, as a critical factor that is regulated by gut microbiota and determines thrombus growth in mice. Static platelet aggregate formation on extracellular matrix was similarly reduced in GF WT, , and heterozygous mice that are all characterized by a modest reduction in plasma VWF levels. Defective platelet matrix interaction can be restored by exposure to WT plasma or to purified VWF depending on the VWF integrin binding site. Moreover, administration of VWF rescues defective thrombus growth in mice in vivo. These experiments delineate an unexpected pathway in which microbiota-triggered TLR2 signaling alters the synthesis of proadhesive VWF by the liver endothelium and favors platelet integrin-dependent thrombus growth.