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Galectin-3 modulates phagocytosis-induced stellate cell activation and liver fibrosis in vivo.

Authors
  • Jx, Jiang
  • X, Chen
  • Dk, Hsu
  • K, Baghy
  • N, Serizawa
  • F, Scott
  • Yoshikazu Takada
  • Y, Takada
  • H, Fukada
  • J, Chen
  • S, Devaraj
  • R, Adamson
  • Ft, Liu
  • Nj, Török
Type
Published Article
Journal
AJP Gastrointestinal and Liver Physiology
Publisher
American Physiological Society
Volume
302
Issue
4
Identifiers
DOI: 10.1152/ajpgi.00257.2011
Source
Takada Lab - UC Davis dermatology-ucdavis
License
Unknown

Abstract

Hepatic stellate cells (HSC), the key fibrogenic cells of the liver, transdifferentiate into myofibroblasts upon phagocytosis of apoptotic hepatocytes. Galectin-3, a β-galactoside-binding lectin, is a regulator of the phagocytic process. In this study, our aim was to study the mechanism by which extracellular galectin-3 modulates HSC phagocytosis and activation. The role of galectin-3 in engulfment was evaluated by phagocytosis and integrin binding assays in primary HSC. Galectin-3 expression was studied by real-time PCR and enzyme-linked immunosorbent assay, and in vivo studies were done in wild-type and galectin-3(-/-) mice. We found that HSC from galectin-3(-/-) mice displayed decreased phagocytic activity, expression of transforming growth factor-β1, and procollagen α1(I). Recombinant galectin-3 reversed this defect, suggesting that extracellular galectin-3 is required for HSC activation. Galectin-3 facilitated the α(v)β(3) heterodimer-dependent binding, indicating that galectin-3 modulates HSC phagocytosis via cross-linking this integrin and enhancing the tethering of apoptotic cells. Blocking integrin α(v)β(3) resulted in decreased phagocytosis. Galectin-3 expression and release were induced in active HSC engulfing apoptotic cells, and this was mediated by the nuclear factor-κB signaling. The upregulation of galectin-3 in active HSC was further confirmed in vivo in bile duct-ligated (BDL) rats. Galectin-3(-/-) mice displayed significantly decreased fibrosis, with reduced expression of α-smooth muscle actin and procollagen α1(I) following BDL. In summary, extracellular galectin-3 plays a key role in liver fibrosis by mediating HSC phagocytosis, activation, and subsequent autocrine and paracrine signaling by a feedforward mechanism.

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