Inhibition of Soluble Epoxide Hydrolase by t‐TUCB Ameliorated Liver Injury in a Chronic‐Binge Ethanol Administration Mouse Model

Abstract

IntroductionCytochrome P450 epoxygenases are important enzymes involved in the conversion of polyunsaturated fatty acids (PUFAs) into epoxides, which have been shown to have beneficial effects in a number of inflammation‐related diseases. However, the in vivo half‐lives of these epoxides is short, due to the action of soluble epoxide hydrolase (sEH), an enzyme responsible for converting epoxides into their bioactive dihydroxy metabolites. sEH inhibitors, such as trans‐4‐{4‐[3‐(4‐trifluoromethoxyphenyl)‐ureido] cyclohexyloxy} benzoic acid (t‐TUCB), are being explored as a therapy for inflammation‐related diseases. Alcoholic liver disease (ALD) is one such disease, characterized by hepatic steatosis, inflammation and injury. Alcoholic hepatitis (AH) is a life threatening condition with a one‐year survival rate of less than 50%, highlighting the urgent need for improved therapies.HypothesisInhibition of sEH by t‐TUCB will attenuate chronic‐binge ethanol (EtOH)‐induced liver injury in a mouse model of AH.Materials and MethodsC57BL/6 male mice were fed all liquid diets containing 5% ethanol (n=13), 5% EtOH plus 5 μg/ml t‐TUCB (n=15), or pair‐fed with isocaloric maltodextrin (n=15) for 10 days, followed by a single oral EtOH gavage (5 g/kg). Mice were euthanized 9h later and blood and liver tissue were collected. Plasma alanine aminotransferase (ALT) levels were measured as a marker of liver injury. Formalin‐fixed, paraffin‐embedded liver sections were prepared and stained with haemotoxylin and eosin, terminal deoxynucelotidyl transferase dUTP nick end labeling (TUNEL), and chloroacetate esterase (CAE) for histological evaluation of liver damage, hepatic apoptosis and neutrophil accumulation, respectively. Liver RNA was isolated for determination of gene expression changes related to pro‐inflammatory and ER stress pathways.ResultsCompared to control animals, chronic‐binge EtOH administration resulted in liver injury, which was significantly attenuated by inhibition of sEH. Plasma ALT levels were significantly lower in the EtOH+t‐TUCB group compared to the EtOH‐administered group (102+27 vs 355+114, U/L, respectively, p < 0.05). In addition, a significant decrease in hepatocyte apoptosis (TUNEL‐positive cells) was observed in the EtOH+t‐TUCB group compared to EtOH group. Hepatic steatosis and inflammation (CAE‐positive cells) were similar in EtOH and EtOH+t‐TUCB treated animals. t‐TUCB treatment did not affect expression of genes related to ER stress (Chop and Xbp1) or inflammation (Pai1), suggesting that other ER stress or inflammation‐related genes or other pathways are necessary for the beneficial effect of sEH inhibition in ALD.ConclusionsThese data demonstrate the ability of sEH inhibition to attenuate chronic‐binge‐EtOH induced liver injury (as shown by decreased plasma ALT activity) in a mouse model mimicking human AH. The molecular mechanisms underlying this effect need further investigation.Support or Funding InformationSupported by grants from NIH and Veterans AdministrationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.