Glycobiology Advance Access originally published online on August 25, 2008
Glycobiology 2008 18(11):905-912; doi:10.1093/glycob/cwn081
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The β-galactoside binding immunomodulatory lectin galectin-3 reverses the desensitized state induced in neutrophils by the chemotactic peptide f-Met-Leu-Phe: role of reactive oxygen species generated by the NADPH-oxidase and inactivation of the agonist
2 Department of Rheumatology and Inflammation Research, Göteborg University, Göteborg, Sweden
3 Department of Laboratory Medicine, Section for Microbiology, Immunology, and Glycobiology, University of Lund, Lund, Sweden
1 To whom correspondence should be addressed: Tel: +46-31-342-46-83; e-mail: Claes.Dahlgren{at}microbio.gu.se
Received on May 27, 2008; revised on August 19, 2008; accepted on August 19, 2008
Neutrophils interacting with a chemoattractant gradually become nonresponsive to further stimulation by the same agonist, a process known as desensitization. Receptor desensitization is a highly regulated process that involves different mechanisms depending on which receptor–ligand pair that is studied. Galectin-3, a member of a large family of β-galactoside-binding lectins, has been suggested to be a regulator of the inflammatory process, augmenting or directly triggering the neutrophil functional repertoire. We show here that the desensitized state of neutrophils interacting with the chemotactic peptide fMLF is broken by galectin-3 and that this is achieved through an oxygen radical-mediated inactivation of the chemoattractant. The effect was inhibited by the competitor lactose and required the affinity of galectin-3 for N-acetyllactosamine, a saccharide typically found on cell surface glycoproteins. The latter was shown using a galectin-3 mutant that lacked N-acetyllactosamine binding activity, and this protein was not active. The mechanism behind the inactivation of the chemoattractant was found to depend on the ability of galectin-3 to induce a neutrophil generation/secretion of reactive oxygen species which in combined action with myeloperoxidase inactivated the peptides.
Key words: formylpeptide receptors / hydrogen peroxide / lectin / myeloperoxidase / oxidants