In vivo and ex vivo imaging was used to investigate the function of galectin-3 (Gal-3) during the process of leukocyte recruitment to the inflamed microcirculation. The cremasteric microcirculation of wild-type (C57BL/6), Gal-3-/- and CX3CR1gfp/+ mice was assessed by intravital microscopy following PBS, IL-1β, TNF-α or recombinant Gal-3 treatment. These cellular responses were investigated further using flow-chamber assays, confocal microscopy, flow cytometry, PCR analysis and proteome array. We show that mechanisms mediating leukocyte slow rolling and emigration are impaired in Gal-3-/- mice, which could be due to impaired expression of cell adhesion molecules and an altered cell surface glycoproteome. Local (intrascrotal) administration of recombinant Gal-3 to wild-type mice resulted in a dose-dependent reduction in rolling velocity associated with increased numbers of adherent and emigrated leukocytes, approximately 50% of which were Ly6G-positive neutrophils. Intrascrotal administration of Gal-3 to CX3CR1gfp/+ mice confirmed that approximately equal numbers of monocytes are also recruited in response to this lectin. Exogenous Gal-3 treatment was accompanied by increased pro-inflammatory cytokines and chemokines within the local tissue. In conclusion, this study unveils novel biology for both exogenous and endogenous Gal-3 in promoting leukocyte recruitment during acute inflammation.
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