Characterization of neutrophil-derived proteinase 3 in animal model of nonalcoholic steatohepatitis

Abstract

Nonalcoholic steatohepatitis (NASH)characterized by co-existence of hepatic steatosis, inflammation and varying degrees of fibrosis is the advanced stage of nonalcoholic fatty liver disease (NAFLD), which is one of most common liver diseases worldwide. Although both clinical and animal evidences consistently demonstrated increased neutrophil infiltration in liver as one of key pathological features of NASH, the functional consequence of hepatic neutrophil recruitment remains elusive. The current study aims to investigate the expression profiles of neutrophil-derived granule protein, proteinase 3 (PR3), in high fat high cholesterol (HFHC) diet-induced NASH, and to generate a mice model for studying NASH. I observed that PR3 levels in blood were significantly elevated in HFHC diet-induced NASH group compared with those in chow control group. In addition, PR3 levels in liver tissues were markedly enhanced at both mRNA and protein levels in NASH group relative to standard chow group. Western immunoblotting analysis further demonstrated that augmented PR3 levels predominantly occurredin neutrophils. Furthermore, expression of PR3 predominantly located in the non-parenchymal cells within the liver. In order to investigate the functional role of PR3 in NASH pathogenesis in a suitable animal model, AppE-null C57 BL/6J mice with wildtype and mutant PR3 genotypes were generated. It was done by backcrossing PR3 global KO mice in Institute for Cancer Research (ICR) background toC57 ApoE KO mice, which possess increased susceptibility to diet-induced liver inflammation, for at least 10 generations. In conclusion, PR3 levels in both circulation and the liver are significantly increased in diet-induced animal model of NASH, indicating that PR3 might be actively involved in the pathogenesis of NASH.