No abstract

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 CX 3 CR1 gfp/+ 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 CX 3 CR1 gfp/+ mice confirmed that approximately equal numbers of monocytes are also recruited in response to this lectin. Exogenous Gal-3 treatment was accompanied by increased proinflammatory 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.

Little is known about the role(s) of endogenous Gal-1 during arthritis. In this study we queried whether anti-arthritic functions for this effector of endogenous anti-inflammation could be unveiled, by studying collagen-induced arthritis (CIA) in Gal-1−/− mice. Gal-1−/− and C57BL/6J (WT) mice received an immunisation of chicken type II collagen (CII) in complete Freund’s adjuvant (FA) followed by a booster on day 21, which consisted of CII in incomplete FA. Animals were monitored for signs of arthritis from day 14 onwards. Clinical and histological signs of arthritis were recorded and humoral and cellular immune responses against CII were analysed. A distinct disease penetrance was apparent, with ~70% of Gal-1−/− mice developing arthritis compared to ~50% in WT animals. Gal-1−/− mice also exhibited an accelerated disease onset and more severe arthritis characterised by significantly elevated clinical scores. Post-mortem analyses (day 42) revealed higher levels of IgG1 and IgG2b anti-CII immunoglobulin isotypes in the serum of Gal-1 null animals compared to WT. Lastly, T cell responses following ex-vivo stimulation with CII revealed a greater degree of proliferation in T cells of Gal-1−/− mice compared to WT, which was associated with increased production of IL-17 and IL-22. These data provide the novel notion that endogenous Gal-1 is an inhibitory factor in the development of arthritis affecting disease severity. We have also highlighted the importance of endogenous Gal-1 in regulating T cell reactivity during experimental arthritis.