Vascular adhesion protein-1 promotes liver inflammation and drives hepatic fibrosis
Chris J. Weston, … , Christopher P. Day, David H. Adams
Chris J. Weston, … , Christopher P. Day, David H. Adams
Published December 22, 2014
Citation Information: J Clin Invest. 2015;125(2):501-520. https://doi.org/10.1172/JCI73722.
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Research Article Hepatology

Vascular adhesion protein-1 promotes liver inflammation and drives hepatic fibrosis

Abstract

Nonalcoholic fatty liver disease (NAFLD) encompasses a range of manifestations, including steatosis and cirrhosis. Progressive disease is characterized by hepatic leukocyte accumulation in the form of steatohepatitis. The adhesion molecule vascular adhesion protein-1 (VAP-1) is a membrane-bound amine oxidase that promotes leukocyte recruitment to the liver, and the soluble form (sVAP-1) accounts for most circulating monoamine oxidase activity, has insulin-like effects, and can initiate oxidative stress. Here, we determined that hepatic VAP-1 expression is increased in patients with chronic liver disease and that serum sVAP-1 levels are elevated in patients with NAFLD compared with those in control individuals. In 4 murine hepatic injury models, an absence or blockade of functional VAP-1 reduced inflammatory cell recruitment to the liver and attenuated fibrosis. Moreover, disease was reduced in animals expressing a catalytically inactive form of VAP-1, implicating enzyme activity in the disease pathogenesis. Within the liver, hepatic stromal cells expressed functional VAP-1, and evaluation of cultured cells revealed that sVAP-1 promotes leukocyte migration through catalytic generation of ROS, which depended on VAP-1 enzyme activity. VAP-1 enhanced stromal cell spreading and wound closure and modulated expression of profibrotic genes. Together, these results link the amine oxidase activity of VAP-1 with hepatic inflammation and fibrosis and suggest that targeting VAP-1 has therapeutic potential for NAFLD and other chronic fibrotic liver diseases.

Authors

Chris J. Weston, Emma L. Shepherd, Lee C. Claridge, Pia Rantakari, Stuart M. Curbishley, Jeremy W. Tomlinson, Stefan G. Hubscher, Gary M. Reynolds, Kristiina Aalto, Quentin M. Anstee, Sirpa Jalkanen, Marko Salmi, David J. Smith, Christopher P. Day, David H. Adams

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Figure 3

Isolated human hepatic stromal cells express functional VAP-1 capable of driving lymphocyte migration in vitro.

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Isolated human hepatic stromal cells express functional VAP-1 capable of...
(A) VAP-1 was detected in isolated human aHSCs (left) and aLMFs (right) (DAPI blue). Scale bars: 50 μm. (B) AOC3 mRNA was expressed by HSECs, aLMFs, aHSCs (4 independent patient isolates each) and by the HSC cell line LX2 (3 repeats) at similar levels (dotted line represents negative controls). (C) Expression of AOC3 could be induced following a 24-hour incubation with PDGF-BB or TGF-β1 (both at 10 ng/ml) but not with rVAP-1 (500 ng/ml). Data represent 2 independent experiments measured in triplicate. (D) Amine oxidase activity of aHSCs (n = 4 isolates) in the absence and presence of VAP-1/LOX inhibitor BEA or the LOX-specific inhibitor 2-APN. (E) CD3+ lymphocytes (left) and CD68+ macrophages (right) were closely associated with VAP-1+ vessels and stroma in cirrhotic livers. Scale bars: 50 μm. (F) Conditioned media from primary cell cultures of aHSCs (n = 3 isolates) promoted VAP-1–dependent migration of peripheral blood lymphocytes in modified Boyden chamber assays. (G) Highly purified sVAP-1 induced the migration of peripheral blood lymphocytes in modified Boyden chamber assays in vitro (n = 3 lymphocyte preparations, 12 random fields/sample). (H) Lymphocyte migration was induced by 100 ng/ml sVAP-1 and is shown compared with the baseline response to media alone (n = 3 lymphocyte preparations; 12 random fields per sample). Data were calculated by 1-way ANOVA with Tukey’s post-hoc test (C, G, and H), paired Student’s t test (D), and Mann-Whitney U test (F). *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001.