The intestinal mucus layer protects the epithelium from noxious agents, viruses, and pathogenic bacteria present in the gastrointestinal tract. It is composed of mucins, predominantly mucin-2 (Muc2), secreted by goblet cells of the intestine. Experimental alcoholic liver disease requires translocation of bacterial products across the intestinal barrier into the systemic circulation, which induces an inflammatory response in the liver and contributes to steatohepatitis. We investigated the roles of the intestinal mucus layer, and in particular Muc2, in development of experimental alcohol-associated liver disease in mice. We studied experimental alcohol-induced liver disease, induced by the Tsukamoto-French method (which involves continuous intragastric feeding of an isocaloric diet or alcohol) in wild-type and Muc2−/− mice. Muc2−/− mice showed less alcohol-induced liver injury and steatosis that developed in wild-type mice. Most notably, Muc2−/− mice had significantly lower plasma levels of lipopolysaccharide than wild-type mice after alcohol feeding. In contrast to wild-type mice, Muc2−/− mice were protected from alcohol-associated microbiome changes that are dependent on intestinal mucins. The anti-microbial proteins Reg3b and Reg3g were expressed at significantly higher levels in the jejunum of Muc2−/− mice fed the isocaloric diet or alcohol, compared with wild-type mice. Consequently, Muc2−/− mice showed increased killing of commensal bacteria and prevented intestinal bacterial overgrowth. Conclusion: Muc2−/− mice are protected from intestinal bacterial overgrowth and dysbiosis in response to alcohol feeding. Subsequently, lower amounts of bacterial products such as endotoxin translocate into the systemic circulation, decreasing liver disease.

Chronic liver disease is rising in western countries and liver cirrhosis is the 12th leading cause of death worldwide. Simultaneously, use of gastric acid suppressive medications is increasing. Here, we show that proton pump inhibitors promote progression of alcoholic liver disease, non-alcoholic fatty liver disease, and non-alcoholic steatohepatitis in mice by increasing numbers of intestinal Enterococcus spp. Translocating enterococci lead to hepatic inflammation and hepatocyte death. Expansion of intestinal Enterococcus faecalis is sufficient to exacerbate ethanol-induced liver disease in mice. Proton pump inhibitor use increases the risk of developing alcoholic liver disease among alcohol-dependent patients. Reduction of gastric acid secretion therefore appears to promote overgrowth of intestinal Enterococcus, which promotes liver disease, based on data from mouse models and humans. Recent increases in the use of gastric acid-suppressive medications might contribute to the increasing incidence of chronic liver disease.

Mutations in the RYR1 gene cause severe myopathies. Mice with an I4895T mutation in the type 1 ryanodine receptor/Ca2+ release channel (RyR1) display muscle weakness and atrophy, but the underlying mechanisms are unclear. Here we show that the I4895T mutation in RyR1 decreases the amplitude of the sarcoplasmic reticulum (SR) Ca2+ transient, resting cytosolic Ca2+ levels, muscle triadin content and calsequestrin (CSQ) localization to the junctional SR, and increases endoplasmic reticulum (ER) stress/unfolded protein response (UPR) and mitochondrial ROS production. Treatment of mice carrying the I4895T mutation with a chemical chaperone, sodium 4-phenylbutyrate (4PBA), reduces ER stress/UPR and improves muscle function, but does not restore SR Ca2+ transients in I4895T fibres to wild type levels, suggesting that decreased SR Ca2+ release is not the major driver of the myopathy. These findings suggest that 4PBA, an FDA-approved drug, has potential as a therapeutic intervention for RyR1 myopathies that are associated with ER stress.

BackgroundReceptor-interacting protein 3 (RIP3), a member of RIP family proteins, has been shown to participate in programmed necrosis or necroptosis in cell biology studies. Evidence suggests that necroptosis may be a mode of neuronal death in the retina.ResultsIn the present study we determined the expression of RIP3 in normal rat retina and its changes following acute high intraocular pressure (aHIOP). RIP3 immunoreactivity (IR) was largely present in the inner retinal layers, localized to subsets of cells expressing neuron-specific nuclear antigen (NeuN), parvalbumin and calbindin in the ganglion cell layer (GCL) and inner nuclear layer (INL). No double labeling was detected for RIP3 with PKC-α or rhodopsin. RIP3 immunoreactivity was increased in the GCL at 6 hr and 12 hr, but reduced at 24 hr in the retina, without apparent alteration in laminar or cellular distribution pattern. Western blot analysis confirmed the above time-dependent alteration in RIP3 protein expression. RIP3 expressing cells frequently co-localized with propidium iodide (PI). A few co-localized cells were observed between RIP3 and Bax or cleaved caspase-3 in the GCL in 12 hr following aHIOP.ConclusionsThe results indicate that RIP3 is expressed differentially in retinal neurons in adult rats, including subsets of ganglion cells, amacrine and horizontal cells. RIP3 protein levels are elevated rapidly following aHIOP. RIP3 labeling co-localized with PI, Bax or cleaved caspase-3 among cells in the ganglion cell layer following aHIOP, which suggest its involvement of RIP3 in neuronal responses to acute ischemic insults.

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