Galectin-1 regulates neurogenesis in the subventricular zone and promotes functional recovery after stroke

Galectin-1 (Gal-1) has recently been identified as a key molecule that plays important roles in the regulation of neural progenitor cell proliferation in two neurogenic regions: the subventricular zone (SVZ) of the lateral ventricle and the subgranular zone of the hippocampal dentate gyrus. To test the hypothesis that Gal-1 contributes to adult neurogenesis after focal ischemia, we studied the temporal profile of endogenous Gal-1 expression and the effects of human recombinant Gal-1 on neurogenesis and neurological functions in an experimental focal ischemic model. In the normal brain, Gal-1 expression was observed only in the SVZ. In the ischemic brain, Gal-1 expression was markedly upregulated in the SVZ and the area of selective neuronal death around the infarct in the striatum. The temporal profile of Gal-1 expression was correlated with that of neural progenitor cell proliferation in the SVZ of the ischemic hemisphere. Double-labeling studies revealed that Gal-1 was localized predominantly in both reactive astrocytes and SVZ astrocytes. Administration of Gal-1, which is known to have carbohydrate-binding ability, into the lateral ventricle increased neurogenesis in the ipsilateral SVZ and improved sensorimotor dysfunction after focal ischemia. By contrast, blockade of Gal-1 in the SVZ by the administration of anti-Gal-1 neutralizing antibody strongly inhibited neurogenesis and diminished neurological function. These results suggest that Gal-1 is one of the principal regulators of adult SVZ neurogenesis through its carbohydrate-binding ability and provide evidence that Gal-1 protein has a role in the improvement of sensorimotor function after stroke.

Dendritic Cells Expressing Transgenic Galectin-1 Delay Onset of Autoimmune Diabetes in Mice

Type 1 diabetes (T1D) is a disease caused by the destruction of the beta cells of the pancreas by activated T cells. Dendritic cells (DC) are the APC that initiate the T cell response that triggers T1D. However, DC also participate in T cell tolerance, and genetic engineering of DC to modulate T cell immunity is an area of active research. Galectin-1 (gal-1) is an endogenous lectin with regulatory effects on activated T cells including induction of apoptosis and down-regulation of the Th1 response, characteristics that make gal-1 an ideal transgene to transduce DC to treat T1D. We engineered bone marrow-derived DC to synthesize transgenic gal-1 (gal-1-DC) and tested their potential to prevent T1D through their regulatory effects on activated T cells. NOD-derived gal-1-DC triggered rapid apoptosis of diabetogenic BDC2.5 TCR-transgenic CD4+ T cells by TCR-dependent and -independent mechanisms. Intravenously administered gal-1-DC trafficked to pancreatic lymph nodes and spleen and delayed onset of diabetes and insulitis in the NODrag1(-/-) lymphocyte adoptive transfer model. The therapeutic effect of gal-1-DC was accompanied by increased percentage of apoptotic T cells and reduced number of IFN-gamma-secreting CD4+ T cells in pancreatic lymph nodes. Treatment with gal-1-DC inhibited proliferation and secretion of IFN-gamma of T cells in response to beta cell Ag. Unlike other DC-based approaches to modulate T cell immunity, the use of the regulatory properties of gal-1-DC on activated T cells might help to delete beta cell-reactive T cells at early stages of the disease when the diabetogenic T cells are already activated.

Galectin-1 Suppresses Autoimmune Retinal Disease by Promoting Concomitant Th2- and T Regulatory-Mediated Anti-Inflammatory Responses

Intraocular inflammatory diseases are a common cause of severe visual impairment and blindness. In this study, we investigated the immunoregulatory role of galectin-1 (Gal-1), an endogenous lectin found at sites of T cell activation and immune privilege, in experimental autoimmune uveitis (EAU), a Th1-mediated model of retinal disease. Treatment with rGal-1 either early or late during the course of interphotoreceptor retinoid-binding protein-induced EAU was sufficient to suppress ocular pathology, inhibit leukocyte infiltration, and counteract pathogenic Th1 cells. Administration of rGal-1 at the early or late phases of EAU ameliorated disease by skewing the uveitogenic response toward nonpathogenic Th2 or T regulatory-mediated anti-inflammatory responses. Consistently, adoptive transfer of CD4(+) regulatory T cells obtained from rGal-1-treated mice prevented the development of active EAU in syngeneic recipients. In addition, increased levels of apoptosis were detected in lymph nodes from mice treated with rGal-1 during the efferent phase of the disease. Our results underscore the ability of Gal-1 to counteract Th1-mediated responses through different, but potentially overlapping anti-inflammatory mechanisms and suggest a possible therapeutic use of this protein for the treatment of human uveitic diseases of autoimmune etiology.

Galectin-1 induces chemokine production and proliferation in pancreatic stellate cells

Galectin-1 is a beta-galactoside-binding lectin. Previous studies have shown that galectin-1 was expressed in fibroblasts of chronic pancreatitis and of desmoplastic reaction associated with pancreatic cancer. These fibroblasts are now recognized as activated pancreatic stellate cells (PSCs). Here, we examined the role of galectin-1 in cell functions of PSCs. PSCs were isolated from rat pancreatic tissue and used in their culture-activated phenotype unless otherwise stated. Expression of galectin-1 was assessed by Western blot analysis, RT-PCR, and immunofluorescent staining. The effects of recombinant galectin-1 on chemokine production and proliferation were evaluated. Activation of transcription factors was assessed by EMSA. Activation of MAPKs was examined by Western blot analysis using anti-phosphospecific antibodies. Galectin-1 was strongly expressed in culture-activated but not freshly isolated PSCs. Recombinant galectin-1 increased proliferation and production of monocyte chemoattractant protein-1 and cytokine-induced neutrophil chemoattractant-1. Galectin-1 activated ERK, JNK, activator protein-1, and NF-kappaB, but not p38 MAPK or Akt. Galectin-1 induced proliferation through ERK and chemokine production mainly through the activation of NF-kappaB and in part by JNK and ERK pathways. These effects of galectin-1 were abolished in the presence of thiodigalactosie, an inhibitor of beta-galactoside binding. In conclusion, our results suggest a role of galectin-1 in chemokine production and proliferation through its beta-galactoside binding activity in activated PSCs.

Intravitreal macrophage activation enables cat retinal ganglion cells to regenerate injured axons into the mature optic nerve

In mature mammals, retinal ganglion cells (RGCs) are generally unable to regenerate injured axons into the optic nerve. Here, we report that an intravitreal injection of either of two macrophage activators, oxidized galectin-1 or zymosan, strongly enhanced the regeneration of transected RGC axons beyond an optic nerve crush site in adult cats. Using WGA-HRP as an anterograde tracer, we found that injection of either macrophage activator caused many axons to grow into the distal optic nerve when evaluated 14 days later, with the strongest effects seen after injecting 100 ng of galectin-1. Elongation continued for at least another 2 weeks. Control eyes injected with saline contained very few labeled axons extending across the crush site. Elevation of intracellular cAMP levels using forskolin also enhanced regeneration beyond the crush site to some extent, but this treatment did not augment the effect of galectin-1 any further. These results indicate that RGCs of adult cats are capable of reverting to an active growth state and at least partially overcoming an inhibitory CNS environment as a result of intravitreal macrophage activation.

A novel biological activity for galectin-1: inhibition of leukocyte-endothelial cell interactions in experimental inflammation

Galectin-1 (Gal-1), the prototype of a family of beta-galactoside-binding proteins, has been shown to attenuate experimental acute and chronic inflammation. In view of the fact that endothelial cells (ECs), but not human polymorphonuclear leukocytes (PMNs), expressed Gal-1 we tested here the hypothesis that the protein could modulate leukocyte-EC interaction in inflammatory settings. In vitro, human recombinant (hr) Gal-1 inhibited PMN chemotaxis and trans-endothelial migration. These actions were specific as they were absent if Gal-1 was boiled or blocked by neutralizing antiserum. In vivo, hrGal-1 (optimum effect at 0.3 micro g equivalent to 20 pmol) inhibited interleukin-1beta-induced PMN recruitment into the mouse peritoneal cavity. Intravital microscopy analysis showed that leukocyte flux, but not their rolling velocity, was decreased by an anti-inflammatory dose of hrGal-1. Binding of biotinylated Gal-1 to resting and postadherent human PMNs occurred at concentrations inhibitory in the chemotaxis and transmigration assays. In addition, the pattern of Gal-1 binding was differentially modulated by PMN or EC activation. In conclusion, these data suggest the existence of a previously unrecognized function of Gal-1, that is inhibition of leukocyte rolling and extravasation in experimental inflammation. It is possible that endogenous Gal-1 may be part of a novel anti-inflammatory loop in which the endothelium is the source of the protein and the migrating PMNs the target for its anti-inflammatory action.