Lectins offer new perspectives in the development of macrophage-targeted therapies for COPD/emphysema

PLoS One. 2013;8(2):e56147. doi: 10.1371/journal.pone.0056147. Epub 2013 Feb 18.

Abstract

We have previously shown that the defective ability of alveolar macrophages (AM) to phagocytose apoptotic cells ('efferocytosis') in chronic obstructive pulmonary disease/emphysema (COPD) could be therapeutically improved using the C-type lectin, mannose binding lectin (MBL), although the exact mechanisms underlying this effect are unknown. An S-type lectin, galectin-3, is also known to regulate macrophage phenotype and function, via interaction with its receptor CD98. We hypothesized that defective expression of galectin/CD98 would be associated with defective efferocytosis in COPD and that mechanisms would include effects on cytoskeletal remodeling and macrophage phenotype and glutathione (GSH) availability. Galectin-3 was measured by ELISA in BAL from controls, smokers and current/ex-smokers with COPD. CD98 was measured on AM using flow cytometry. We assessed the effects of galectin-3 on efferocytosis, CD98, GSH, actin polymerisation, rac activation, and the involvement of PI3K (using β-actin probing and wortmannin inhibition) in vitro using human AM and/or MH-S macrophage cell line. Significant decreases in BAL galectin-3 and AM CD98 were observed in BAL from both current- and ex-smoker COPD subjects vs controls. Galectin 3 increased efferocytosis via an increase in active GTP bound Rac1. This was confirmed with β-actin probing and the role of PI3K was confirmed using wortmannin inhibition. The increased efferocytosis was associated with increases in available glutathione and expression of CD98. We provide evidence for a role of airway lectins in the failed efferocytosis in COPD, supporting their further investigation as potential macrophage-targeted therapies.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Adult
  • Aged
  • Androstadienes / pharmacology
  • Animals
  • Arginase / metabolism
  • Bronchoalveolar Lavage Fluid / immunology
  • Female
  • Fusion Regulatory Protein-1 / metabolism
  • Galectin 3 / metabolism
  • Galectin 3 / pharmacology
  • Glutathione / metabolism
  • Humans
  • Lectins / metabolism*
  • Lectins / pharmacology
  • Macrophages, Alveolar / drug effects
  • Macrophages, Alveolar / immunology*
  • Macrophages, Alveolar / metabolism
  • Male
  • Mice
  • Middle Aged
  • Phagocytosis / drug effects
  • Phagocytosis / immunology
  • Phosphatidylinositol 3-Kinases / metabolism
  • Pulmonary Disease, Chronic Obstructive / immunology*
  • Pulmonary Disease, Chronic Obstructive / metabolism*
  • Pulmonary Emphysema / immunology*
  • Pulmonary Emphysema / metabolism*
  • Smoking
  • Wortmannin
  • rac1 GTP-Binding Protein / metabolism

Substances

  • Actins
  • Androstadienes
  • Fusion Regulatory Protein-1
  • Galectin 3
  • Lectins
  • Phosphatidylinositol 3-Kinases
  • Arginase
  • rac1 GTP-Binding Protein
  • Glutathione
  • Wortmannin

Grants and funding

Supported by a National Health and Medical Research Council Project Grant and Career Development Award and Practitioner Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.