Format

Send to

Choose Destination
J Hepatol. 2015 Feb;62(2):412-20. doi: 10.1016/j.jhep.2014.09.015. Epub 2014 Sep 16.

Arginase 2 deficiency results in spontaneous steatohepatitis: a novel link between innate immune activation and hepatic de novo lipogenesis.

Author information

1
Children's Hospital of Pittsburgh, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.
2
Department of Pediatrics, University of California San Diego (UCSD), CA, USA.
3
Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
4
Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA.
5
Department of Pathology, University of California San Diego, La Jolla, CA, USA.
6
Department of Pediatrics, University of California San Diego (UCSD), CA, USA. Electronic address: afeldstein@ucsd.edu.

Abstract

BACKGROUND & AIMS:

Innate immune activation has been postulated as a central mechanism for disease progression from hepatic steatosis to steatohepatitis in obesity-related fatty liver disease. Arginase 2 competes with inducible nitric oxide synthase (iNOS) for its substrate and the balance between these two enzymes plays a crucial role in regulating immune responses and macrophage activation. Our aim was to test the hypothesis that arginase 2 deficiency in mice favours progression from isolated hepatic steatosis, induced by high fat feeding, to steatohepatitis.

METHODS:

Arginase 2-knockout (Arg2(-/-)) mice were studied for changes in liver histology and metabolic phenotype at baseline and after a short term course (7 week) feeding with a high fat (HFAT) diet. In additional experiments, Arg2(-/-) mice received tail vein injections of liposome-encapsulated clodronate (CLOD) over a three-week period to selectively deplete liver macrophages.

RESULTS:

Unexpectedly, Arg2(-/-) mice showed profound changes in their livers at baseline, characterized by significant steatosis as demonstrated with histological and biochemical analysis. These changes were independent of systemic metabolic parameters and associated with marked mRNA level increases of genes involved in hepatic de novo lipogenesis. Liver injury and inflammation were present with elevated serum ALT, marked infiltration of F4/80 positive cells, and increased mRNA levels of inflammatory genes. HFAT feeding exacerbated these changes. Macrophage depletion after CLOD injection significantly attenuated lipid deposition and normalized lipogenic mRNA profile of livers from Arg2(-/-) mice.

CONCLUSIONS:

This study identifies arginase 2 as a novel link between innate immune responses, hepatic lipid deposition, and liver injury.

KEYWORDS:

Arginase 2; Inflammation; Innate immunity; Liver fibrosis; Macrophage activation; Non-alcoholic fatty liver disease; Steatohepatitis

PMID:
25234945
PMCID:
PMC4736721
DOI:
10.1016/j.jhep.2014.09.015
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center