BackgroundPrimary biliary cholangitis (PBC) is characterized by increased biliary damage, inflammation and liver fibrosis. Early stage PBC is marked by biliary proliferation, whereas late stage PBC shows ductopenia. We have shown that dominant‐negative transforming growth factor b receptor II (dnTGFβRII) mice at 12 wk of age mimic early stage PBC. We have found that melatonin therapy or prolonged exposure to complete darkness reduces biliary hyperplasia and liver fibrosis in models of cholestasis. However, the impact of melatonin or dark therapy on PBC‐related injury is unknown. The aim of our study was to evaluate the effects of melatonin or dark therapy in a mouse model of early stage PBC.MethodsWe used background‐matched, male wild‐type (WT) and dnTGFβRII at 12 wk of age that were given drinking water containing melatonin (0.03%) or placed in complete darkness for 1 wk along with the related controls. Liver damage was evaluated by H&E. Intrahepatic bile duct mass (IBDM) was measured by CK‐19 staining. Biliary senescence was evaluated by staining for p16 and p21, and SA‐β‐galactosidase activity. Biliary and liver inflammation were determined by IL‐6 and F4/80 (Kupffer cell marker) staining. Liver fibrosis was determined by Sirius Red staining and immunofluorescence for collagen type‐1a. Hepatic stellate cell (HSC) activation was shown by SYP‐9 and α‐SMA staining. Human control and early stage PBC serum samples were obtained, and serum melatonin levels were measured by EIA.ResultsdnTGFβRII at 12 wk of age (early stage PBC mouse model) treated with melatonin or complete darkness had decreased (i) IBDM, (ii) biliary senescence, (iii) liver fibrosis, (iv) biliary and liver inflammation, and (v) HSC activation/liver fibrosis. Human early stage PBC samples had decreased serum melatonin levels.ConclusionInhibition of melatonin signaling perpetuates biliary damage associated with PBC. Restoration of melatonin‐dependent signaling via melatonin treatment or dark therapy may be therapeutic for patients with early stage PBC.Support or Funding InformationNIH NIDDK R01, VA MeritThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Objective Conflicting microbiota data exist for primary sclerosing cholangitis (PSC) and experimental models. Goal: Define complex interactions between resident microbes and their association in PSC patients by studying antibiotic-treated specific pathogen-free (SPF) and germ-free (GF) multi-drug-resistant 2 deficient ( mdr2 -/- ) mice. Design We measured weights, liver enzymes, RNA expression, histological, immunohistochemical and fibrotic biochemical parameters, fecal 16s rRNA gene profiling, and metabolomic endpoints in gnotobiotic and antibiotic-treated SPF mdr2 -/- mice and targeted metagenomic analysis in PSC patients. Results GF mdr2 -/- mice had exaggerated hepatic inflammation and fibrosis with 100% mortality by 8 weeks; early SPF autologous stool transplantation rescued liver-related mortality. Broad-spectrum antibiotics and vancomycin alone accelerated disease in weanling SPF mdr2 -/- mice, indicating that vancomycin-sensitive resident microbiota protect against hepatobiliary disease. Vancomycin treatment selectively decreased Lachnospiraceae and short-chain fatty acids (SCFAs) but expanded Enterococcus and Enterobacteriaceae. Antibiotics increased cytolysin-expressing E. faecalis and E. coli liver translocation; colonization of gnotobiotic mdr2 -/- mice with translocated E. faecalis and E. coli strains accelerated liver inflammation and mortality. Lachnospiraceae colonization of antibiotic pre-treated mdr2 -/- mice reduced liver fibrosis, inflammation and translocation of pathobionts, while Lachnospiraceae-produced SCFA decreased fibrosis. Fecal E. faecalis / Enterobacteriaceae was positively and Lachnospiraceae was negatively associated with PSC patients’ clinical severity Mayo risk scores. Conclusions We identified specific functionally protective and detrimental resident bacterial species in mdr2 -/- mice and PSC patients with associated clinical outcomes. These insights may guide personalized targeted therapeutic interventions in PSC patients.