Iqbal, Asif JKrautter, FranziskaBlacksell, Isobel AWright, Rachael DAustin-Williams, Shani NVoisin, Mathieu-BenoitHussain, Mohammed TLaw, Hannah LNiki, ToshiroHirashima, MitsuomiBombardieri, MichelePitzalis, CostantinoTiwari, AlokNash, Gerard BNorling, Lucy VCooper, Dianne2024-06-272024-06-272022-01Iqbal AJ, Krautter F, Blacksell IA, Wright RD, Austin-Williams SN, Voisin MB, Hussain MT, Law HL, Niki T, Hirashima M, Bombardieri M, Pitzalis C, Tiwari A, Nash GB, Norling LV, Cooper D. Galectin-9 mediates neutrophil capture and adhesion in a CD44 and β2 integrin-dependent manner. FASEB J. 2022 Jan;36(1):e22065. doi: 10.1096/fj.202100832R0892-66381530-686010.1096/fj.202100832R34847625http://hdl.handle.net/20.500.14200/4987Neutrophil trafficking is a key component of the inflammatory response. Here, we have investigated the role of the immunomodulatory lectin Galectin-9 (Gal-9) on neutrophil recruitment. Our data indicate that Gal-9 is upregulated in the inflamed vasculature of RA synovial biopsies and report the release of Gal-9 into the extracellular environment following endothelial cell activation. siRNA knockdown of endothelial Gal-9 resulted in reduced neutrophil adhesion and neutrophil recruitment was significantly reduced in Gal-9 knockout mice in a model of zymosan-induced peritonitis. We also provide evidence for Gal-9 binding sites on human neutrophils; Gal-9 binding induced neutrophil activation (increased expression of β2 integrins and reduced expression of CD62L). Intra-vital microscopy confirmed a pro-recruitment role for Gal-9, with increased numbers of transmigrated neutrophils following Gal-9 administration. We studied the role of both soluble and immobilized Gal-9 on human neutrophil recruitment. Soluble Gal-9 significantly strengthened the interaction between neutrophils and the endothelium and inhibited neutrophil crawling on ICAM-1. When immobilized, Gal-9 functioned as an adhesion molecule and captured neutrophils from the flow. Neutrophils adherent to Gal-9 exhibited a spread/activated phenotype that was inhibited by CD18 and CD44 neutralizing antibodies, suggesting a role for these molecules in the pro-adhesive effects of Gal-9. Our data indicate that Gal-9 is expressed and released by the activated endothelium and functions both in soluble form and when immobilized as a neutrophil adhesion molecule. This study paves the way for further investigation of the role of Gal-9 in leukocyte recruitment in different inflammatory settings.en© 2021 The Authors. The FASEB Journal published by Wiley Periodicals LLC on behalf of Federation of American Societies for Experimental Biology.CardiologyMicrobiology. ImmunologyArticle