title: Role of galectin-3 as an adhesion molecule for neutrophil extravasation during streptococcal pneumonia.
abstract: Recruitment of neutrophils from blood vessels to sites of infection represents one of the most important elements of innate immunity. Movement of neutrophils across blood vessel walls to the site of infection first requires that the migrating cells firmly attach to the endothelial wall. Generally, neutrophil extravasation is mediated at least in part by two classes of adhesion molecules, beta(2) integrins and selectins. However, in the case of streptococcal pneumonia, recent studies have revealed that a significant proportion of neutrophil diapedesis is not mediated by the beta(2) integrin/selectin paradigm. Galectin-3 is a beta-galactoside-binding lectin implicated in inflammatory responses as well as in cell adhesion. Using an in vivo streptococcal pneumonia mouse model, we found that accumulation of galectin-3 in the alveolar space of streptococcus-infected lungs correlates closely with the onset of neutrophil extravasation. Furthermore, immunohistological analysis of infected lung tissue revealed the presence of galectin-3 in the lung tissue areas composed of epithelial and endothelial cell layers as well as of interstitial spaces. In vitro, galectin-3 was able to promote neutrophil adhesion to endothelial cells. Promotion of neutrophil adhesion by galectin-3 appeared to result from direct cross-linking of neutrophils to the endothelium and was dependent on galectin-3 oligomerization. Together, these results suggest that galectin-3 acts as an adhesion molecule that can mediate neutrophil adhesion to endothelial cells. However, accumulation of galectin-3 in lung was not observed during neutrophil emigration into alveoli induced by Escherichia coli infection, where the majority of neutrophil emigration is known to be beta(2) integrin dependent. Thus, based on our results, we propose that galectin-3 plays a role in beta(2) integrin-independent neutrophil extravasation, which occurs during alveolar infection with Streptococcus pneumoniae.
authors.affiliation: Glycobiology Laboratory, Research Center for Infectious Disease, Laval University Medical Center, Centre Hospitalier Universitaire de Québec, Québec, Canada. Sachiko.Sato@crchul.ulaval.ca
authors.forename: Sachiko
authors.initials: S
authors.lastname: Sato
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ouellet
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pelletier
authors.forename: Marie
authors.initials: M
authors.lastname: Simard
authors.forename: Ann
authors.initials: A
authors.lastname: Rancourt
authors.forename: Michel G
authors.initials: MG
authors.lastname: Bergeron
mesh_terms: D000818:Animals; D000943:Antigens, Differentiation / Q000502:physiology*; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000502:physiology; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000502:physiology; D004927:Escherichia coli Infections / Q000276:immunology; D005260:Female; D037502:Galectin 3; D006801:Humans; D007700:Kinetics; D008168:Lung / Q000276:immunology; D016676:Macrophages, Alveolar / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D020556:Neutrophil Infiltration; D009504:Neutrophils / Q000276:immunology*; D011018:Pneumonia, Pneumococcal / Q000276:immunology*; D011650:Pulmonary Alveoli / Q000276:immunology
chemical_list: D000943:Antigens, Differentiation; D015815:Cell Adhesion Molecules; D037502:Galectin 3