Enhanced Susceptibility of Galectin-1 Deficient Mice to Experimental Colitis.

Galectin-1 is a ß-galactoside-binding lectin, ubiquitously expressed in stromal, epithelial, and different subsets of immune cells. Galectin-1 is the prototype member of the galectin family which shares specificity with ß-galactoside containing proteins and lipids. Immunomodulatory functions have been ascribed to endogenous galectin-1 due to its induction of T cell apoptosis, inhibitory effects of neutrophils and T cell trafficking. Several studies have demonstrated that administration of recombinant galectin-1 suppressed experimental colitis by modulating adaptive immune responses altering the fate and phenotype of T cells. However, the role of endogenous galectin-1 in intestinal inflammation is poorly defined. In the present study, the well-characterized acute dextran sulfate sodium (DSS)-induced model of ulcerative colitis was used to study the function of endogenous galectin-1 during the development of intestinal inflammation. We found that galectin-1 deficient mice (Lgals1-/- mice) displayed a more severe intestinal inflammation, characterized by significantly elevated clinical scores, than their wild type counterparts. The mechanisms underlying the enhanced inflammatory response in colitic Lgals1-/- mice involved an altered Th17/Th1 profile of effector CD4+ T cells. Furthermore, increased frequencies of Foxp3+CD4+ regulatory T cells in colon lamina propria in Lgals1-/- mice were found. Strikingly, the exacerbated intestinal inflammatory response observed in Lgals1-/- mice was alleviated by adoptive transfer of wild type Foxp3+CD4+ regulatory T cells at induction of colitis. Altogether, these data highlight the importance of endogenous galectin-1 as a novel determinant in regulating T cell reactivity during the development of intestinal inflammation.

Galectin-1 fosters an immunosuppressive microenvironment in colorectal cancer by reprogramming CD8+ regulatory T cells.

Colorectal cancer (CRC) represents the third most common malignancy and the second leading cause of cancer-related deaths worldwide. Although immunotherapy has taken center stage in mainstream oncology, it has shown limited clinical efficacy in CRC, generating an urgent need for discovery of new biomarkers and potential therapeutic targets. Galectin-1 (Gal-1), an endogenous glycan-binding protein, induces tolerogenic programs and contributes to tumor cell evasion of immune responses. Here, we investigated the relevance of Gal-1 in CRC and explored its modulatory activity within the CD8+ regulatory T cell (Treg) compartment. Mice lacking Gal-1 (Lgals1-/- ) developed a lower number of tumors and showed a decreased frequency of a particular population of CD8+CD122+PD-1+ Tregs in the azoxymethane-dextran sodium sulfate model of colitis-associated CRC. Moreover, silencing of tumor-derived Gal-1 in the syngeneic CT26 CRC model resulted in reduced number and attenuated immunosuppressive capacity of CD8+CD122+PD-1+ Tregs, leading to slower tumor growth. Moreover, stromal Gal-1 also influenced the fitness of CD8+ Tregs, highlighting the contribution of both tumor and stromal-derived Gal-1 to this immunoregulatory effect. Finally, bioinformatic analysis of a colorectal adenocarcinoma from The Cancer Genome Atlas dataset revealed a particular signature characterized by high CD8+ Treg score and elevated Gal-1 expression, which delineates poor prognosis in human CRC. Our findings identify CD8+CD122+PD-1+ Tregs as a target of the immunoregulatory activity of Gal-1, suggesting a potential immunotherapeutic strategy for the treatment of CRC.

Phenotyping placental oxygenation in Lgals1 deficient mice using 19F MRI.

Placental hypoperfusion and hypoxia are key drivers in complications during fetal development such as fetal growth restriction and preeclampsia. In order to study the mechanisms of disease in mouse models, the development of quantitative biomarkers of placental hypoxia is a prerequisite. The goal of this exploratory study was to establish a technique to noninvasively characterize placental partial pressure of oxygen (PO2) in vivo in the Lgals1 (lectin, galactoside-binding, soluble, 1) deficient mouse model of preeclampsia using fluorine magnetic resonance imaging. We hypothesized a decrease in placental oxygenation in knockout mice. Wildtype and knockout animals received fluorescently labeled perfluoro-5-crown-15-ether nanoemulsion i.v. on day E14-15 during pregnancy. Placental PO2 was assessed via calibrated 19F MRI saturation recovery T1 mapping. A gas challenge with varying levels of oxygen in breathing air (30%, 60% and 100% O2) was used to validate that changes in oxygenation can be detected in freely breathing, anesthetized animals. At the end of the experiment, fluorophore-coupled lectin was injected i.v. to label the vasculature for histology. Differences in PO2 between breathing conditions and genotype were statistically analyzed with linear mixed-effects modeling. As expected, a significant increase in PO2 with increasing oxygen in breathing air was found. PO2 in Lgals1 knockout animals was decreased but this effect was only present at 30% oxygen in breathing air, not at 60% and 100%. Histological examinations showed crossing of the perfluorocarbon nanoemulsion to the fetal blood pool but the dominating contribution of 19F MR signal is estimated at > 70% from maternal plasma based on volume fraction measurements of previous studies. These results show for the first time that 19F MRI can characterize oxygenation in mouse models of placental malfunction.

Intracellular immune sensing promotes inflammation via gasdermin D-driven release of a lectin alarmin.

Inflammatory caspase sensing of cytosolic lipopolysaccharide (LPS) triggers pyroptosis and the concurrent release of damage-associated molecular patterns (DAMPs). Collectively, DAMPs are key determinants that shape the aftermath of inflammatory cell death. However, the identity and function of the individual DAMPs released are poorly defined. Our proteomics study revealed that cytosolic LPS sensing triggered the release of galectin-1, a ß-galactoside-binding lectin. Galectin-1 release is a common feature of inflammatory cell death, including necroptosis. In vivo studies using galectin-1-deficient mice, recombinant galectin-1 and galectin-1-neutralizing antibody showed that galectin-1 promotes inflammation and plays a detrimental role in LPS-induced lethality. Mechanistically, galectin-1 inhibition of CD45 (Ptprc) underlies its unfavorable role in endotoxin shock. Finally, we found increased galectin-1 in sera from human patients with sepsis. Overall, we uncovered galectin-1 as a bona fide DAMP released as a consequence of cytosolic LPS sensing, identifying a new outcome of inflammatory cell death.

Gal-1 (Galectin-1) Upregulation Contributes to Abdominal Aortic Aneurysm Progression by Enhancing Vascular Inflammation.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is a vascular degenerative disease causing sudden rupture of aorta and significant mortality in elders. Nevertheless, no prognostic and therapeutic target is available for disease management. Gal-1 (galectin-1) is a ß-galactoside-binding lectin constitutively expressed in vasculature with roles in maintaining vascular homeostasis. This study aims to investigate the potential involvement of Gal-1 in AAA progression. Approach and Results: Gal-1 was significantly elevated in circulation and aortic tissues of Ang II (angiotensin II)-infused apoE-deficient mice developing AAA. Gal-1 deficiency reduced incidence and severity of AAA with lower expression of aortic MMPs (matrix metalloproteases) and proinflammatory cytokines. TNFα (tumor necrosis factor alpha) induced Gal-1 expression in cultured vascular smooth muscle cells and adventitial fibroblasts. Gal-1 deletion enhanced TNFα-induced MMP9 expression in fibroblasts but not vascular smooth muscle cells. Cysteinyl-labeling assay demonstrated that aortic Gal-1 exhibited susceptibility to oxidation in vivo. Recombinant oxidized Gal-1 induced expression of MMP9 and inflammatory cytokines to various extents in macrophages, vascular smooth muscle cells, and fibroblasts through activation of MAP (mitogen-activated protein) kinase signaling. Clinically, serum MMP9 level was significantly higher in both patients with AAA and coronary artery disease than in control subjects, whereas serum Gal-1 level was elevated in patients with AAA but not coronary artery disease when compared with controls. CONCLUSIONS: Gal-1 is highly induced and contributes to AAA by enhancing matrix degradation activity and inflammatory responses in experimental model. The pathological link between Gal-1 and AAA is also observed in human patients. These findings support the potential of Gal-1 as a disease biomarker and therapeutic target of AAA.

Galectin-1 Expression in CD8+ T Lymphocytes Controls Inflammation in Contact Hypersensitivity.

Allergic contact dermatitis, also known as contact hypersensitivity, is a frequent T-cell‒mediated inflammatory skin disease characterized by red, itchy, swollen, and cracked skin. It is caused by the direct contact with an allergen and/or irritant hapten. Galectin-1 (Gal-1) is a ß-galactoside‒binding lectin, which is highly expressed in several types of immune cells. The role of endogenous Gal-1 in contact hypersensitivity is not known. We found that Gal-1‒deficient mice display more sustained and prolonged skin inflammation than wild-type mice after oxazolone treatment. Gal-1‒deficient mice have increased CD8+ T cells and neutrophilic infiltration in the skin. After the sensitization phase, Gal-1‒depleted mice showed an increased frequency of central memory CD8+ T cells and IFN-γ secretion by CD8+ T cells. The absence of Gal-1 does not affect the migration of transferred CD4+ and CD8+ T cells from the blood to the lymph nodes or to the skin. The depletion of CD4+ T lymphocytes as well as adoptive transfer experiments demonstrated that endogenous expression of Gal-1 on CD8+ T lymphocytes exerts a major role in the control of contact hypersensitivity model. These data underscore the protective role of endogenous Gal-1 in CD8+ but not CD4+ T cells in the development of allergic contact dermatitis.

Lack of galectin-1 exacerbates chronic hepatitis, liver fibrosis, and carcinogenesis in murine hepatocellular carcinoma model.

Chronic liver inflammation (CLI) is a risk factor for development of hepatocellular carcinoma (HCC). Galectin-1 (Gal1) is involved in the regulation of inflammation, angiogenesis, and tumorigenesis, exhibiting multiple anti-inflammatory and protumorigenic activities. We aimed to explore its regulatory role in CLI and HCC progression using an established model of CLI-mediated HCC development, Abcb4 [multidrug-resistance 2 (Mdr2)]-knockout (KO) mice, which express high levels of Gal1 in the liver. We generated double-KO (dKO) Gal1-KO/Mdr2-KO mice on C57BL/6 and FVB/N genetic backgrounds and compared HCC development in the generated strains with their parental Mdr2-KO strains. Loss of Gal1 increased liver injury, inflammation, fibrosis, and ductular reaction in dKO mice of both strains starting from an early age. Aged dKO mutants displayed earlier hepatocarcinogenesis and increased tumor size compared with control Mdr2-KO mice. We found that osteopontin, a well-known modulator of HCC development, and oncogenic proteins Ntrk2 (TrkB) and S100A4 were overexpressed in dKO compared with Mdr2-KO livers. Our results demonstrate that in Mdr2-KO mice, a model of CLI-mediated HCC, Gal1-mediated protection from hepatitis, liver fibrosis, and HCC initiation dominates over its known procarcinogenic activities at later stages of HCC development. These findings suggest that anti-Gal1 treatments may not be applicable at all stages of CLI-mediated HCC.-Potikha, T., Pappo, O., Mizrahi, L., Olam, D., Maller, S. M., Rabinovich, G. A., Galun, E., Goldenberg, D. S. Lack of galectin-1 exacerbates chronic hepatitis, liver fibrosis, and carcinogenesis in murine hepatocellular carcinoma model.

Galectin-1 is essential for efficient liver regeneration following hepatectomy.

Galectin-1 (Gal1) is a known immune/inflammatory regulator which acts both extracellularly and intracellularly, modulating innate and adaptive immune responses. Here, we explored the role of Gal1 in liver regeneration using 70% partial hepatectomy (PHx) of C57BL/6 wild type and Gal1-knockout (Gal1-KO, Lgals1-/-) mice. Gene or protein expression, in liver samples collected at time intervals from 2 to 168 hours post-operation, was tested by either RT-PCR or by immunoblotting and immunohistochemistry, respectively. We demonstrated that Gal1 transcript and protein expression was induced in the liver tissue of wild type mice upon PHx. Liver regeneration following PHx was significantly delayed in the Gal1-KO compared to the control liver. This delay was accompanied by a decreased Akt phosphorylation, and accumulation of the hepatocyte nuclear p21 protein in the Gal1-KO versus control livers at 24 and 48 hours following PHx. Transcripts of several known regulators of inflammation, cell cycle and cell signaling, including some known PHx-induced genes, were aberrantly expressed (mainly down-regulated) in Gal1-KO compared to control livers at 2, 6 and 24 hours post-PHx. Transient steatosis, which is imperative for liver regeneration following PHx, was significantly delayed and decreased in the Gal1-KO compared to the control liver and was accompanied by a significantly decreased expression in the mutant liver of several genes encoding lipid metabolism regulators. Our results demonstrate that Gal1 protein is essential for efficient liver regeneration following PHx through the regulation of liver inflammation, hepatic cell proliferation, and the control of lipid storage in the regenerating liver.

Galectin-1 deficiency improves axonal swelling of motor neurones in SOD1(G93A) transgenic mice.

AIMS: Galectin-1, a member of the ß-galactoside-binding lectin family, accumulates in neurofilamentous lesions in the spinal cords of both sporadic and familial amyotrophic lateral sclerosis (ALS) patients with a superoxide dismutase 1 gene (SOD1) mutation (A4V). The aim of this study was to evaluate the roles of endogenous galectin-1 in the pathogenesis of ALS. METHODS: Expression of galectin-1 in the spinal cord of mutant SOD1 transgenic (SOD1(G93A) ) mice was examined by pathological analysis, real-time RT-PCR and Western blotting. The effects of galectin-1 deficiency were evaluated by cross-breeding SOD1(G93A) mice with galectin-1 null (Lgals1(-/-) ) mice. RESULTS: Before ALS-like symptoms developed in SOD1(G93A) /Lgals1(+/+) mice, strong galectin-1 immunoreactivity was observed in swollen motor axons and colocalized with aggregated neurofilaments. Electron microscopic observations revealed that the diameters of swollen motor axons in the spinal cord were significantly smaller in SOD1(G93A) /Lgals1(-/-) mice, and there was less accumulation of vacuoles compared with SOD1(G93A) /Lgals1(+/+) mice. In symptomatic SOD1(G93A) /Lgals1(+/+) mice, astrocytes surrounding motor axons expressed a high level of galectin-1. CONCLUSIONS: Galectin-1 accumulates in neurofilamentous lesions in SOD1(G93A) mice, as previously reported in humans with ALS. Galectin-1 accumulation in motor axons occurs before the development of ALS-like symptoms and is associated with early processes of axonal degeneration in SOD1(G93A) mice. In contrast, galectin-1 expressed in astrocytes may be involved in axonal degeneration during symptom presentation.

Natural killer cells eradicate galectin-1-deficient glioma in the absence of adaptive immunity.

Natural killer (NK) cells safeguard against early tumor formation by destroying transformed target cells in a process referred to as NK immune surveillance. However, the immune escape mechanisms used by malignant brain tumors to subvert this innate type of immune surveillance remain unclear. Here we show that malignant glioma cells suppress NK immune surveillance by overexpressing the ß-galactoside-binding lectin galectin-1. Conversely, galectin-1-deficient glioma cells could be eradicated by host NK cells before the initiation of an antitumor T-cell response. In vitro experiments demonstrated that galectin-1-deficient GL26-Cit glioma cells are ∼3-fold more sensitive to NK-mediated tumor lysis than galectin-1-expressing cells. Our findings suggest that galectin-1 suppression in human glioma could improve patient survival by restoring NK immune surveillance that can eradicate glioma cells. Cancer Res; 74(18); 5079-90. ©2014 AACR.

Phosphoproteomic analyses reveal that galectin-1 augments the dynamics of B-cell receptor signaling.

B-cell activation is important for mounting humoral immune responses and antibody production. Galectin-1 has multiple regulatory functions in immune cells. However, the effects of galectin-1 modulation and the mechanisms underlying the coordination of B-cell activation are unclear. To address this issue, we applied label-free quantitative phosphoproteomic analysis to investigate the dynamics of galectin-1-induced signaling in comparison with that following anti-IgM treatment. A total of 3247 phosphorylation sites on 1245 proteins were quantified, and 70-80% of the 856 responsive phosphoproteins were commonly activated during various biological functions. The similarity between galectin-1- and anti-IgM-elicited B-cell receptor (BCR) signaling pathways was also revealed. Additionally, the mapping of the 149 BCR-responsive phosphorylation sites provided complementary knowledge of BCR signaling. Compared to anti-IgM induction, the phosphoproteomic profiling of BCR signaling, along with validation by western blot analysis and pharmacological inhibitors, revealed that the activation of Syk, Btk, and PI3K may be dominant in galectin-1-mediated activation. We further demonstrated that the proliferation of antigen-primed B cells was diminished in the absence of galectin-1 in an animal model. Together, these findings provided evidence for a new role and insight into the mechanism of how galectin-1 augments the strength of the immunological synapse by modulating BCR signaling. BIOLOGICAL SIGNIFICANCE: The current study revealed the first systematic phosphorylation-mediated signaling network and its dynamics in B cell activation. The comparative phosphoproteomic analysis on the dynamics of galectin-1 induced activation profiles not only showed that exogenously added galectin-1 augmented B-cell activation but also revealed its relatively enhanced activation in PI3K pathway. Together with proliferation assay, we further delineated that galectin-1 is important for B-cell proliferation in response to antigen challenge. Our phosphoproteomic study reveals a new role for galectin-1 in augmenting the strength of immunological synapse by modulating BCR signaling.

Endogenous galectin-1 exerts tonic inhibition on experimental arthritis.

Little is known about the role(s) of endogenous galectin-1 (Gal-1) in arthritis. In this study we queried whether antiarthritic functions for this effector of endogenous anti-inflammation could be unveiled by studying collagen-induced arthritis in Gal-1(-/-) mice. Gal-1(-/-) and C57BL/6J [wild-type (WT)] mice received an immunization of chicken type II collagen (CII) in CFA followed by a booster on day 21, which consisted of CII in IFA. Animals were monitored for signs of arthritis from day 14 onward. Clinical and histological signs of arthritis were recorded, and humoral and cellular immune responses against CII were analyzed. A distinct disease penetrance was apparent, with ~ 70% of Gal-1(-/-) mice developing arthritis compared with ~ 50% in WT animals. Gal-1(-/-) mice also exhibited an accelerated disease onset and more severe arthritis characterized by significantly elevated clinical scores. Postmortem analyses (day 42) revealed higher levels of IgG1 and IgG2b anti-CII Ig isotypes in the serum of Gal-1 null animals compared with WT. Finally, T cell responses following ex vivo stimulation with CII revealed a greater degree of proliferation in T cells of Gal-1(-/-) mice compared with WT, which was associated with increased production of IL-17 and IL-22. These data suggest the novel idea 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.

Mast cells rescue implantation defects caused by c-kit deficiency.

Various physiologically relevant processes are regulated by the interaction of the receptor tyrosine kinase (c-Kit) and its ligand stem cell factor (SCF), with SCF known to be the most important growth factor for mast cells (MCs). In spite of their traditional role in allergic disorders and innate immunity, MCs have lately emerged as versatile modulators of a variety of physiologic and pathologic processes. Here we show that MCs are critical for pregnancy success. Uterine MCs presented a unique phenotype, accumulated during receptivity and expanded upon pregnancy establishment. Kit(W-sh/W-sh) mice, whose MC deficiency is based on restricted c-Kit gene expression, exhibited severely impaired implantation, which could be completely rescued by systemic or local transfer of wild-type bone marrow-derived MCs. Transferred wild-type MCs favored normal implantation, induced optimal spiral artery remodeling and promoted the expression of MC proteases, transforming growth factor-ß and connective tissue growth factor. MCs contributed to trophoblast survival, placentation and fetal growth through secretion of the glycan-binding protein galectin-1. Our data unveil unrecognized roles for MCs at the fetomaternal interface with critical implications in reproductive medicine.

Binding of galectin-1 to αIIbß3 integrin triggers "outside-in" signals, stimulates platelet activation, and controls primary hemostasis.

Understanding noncanonical mechanisms of platelet activation represents an important challenge for the identification of novel therapeutic targets in bleeding disorders, thrombosis, and cancer. We previously reported that galectin-1 (Gal-1), a ß-galactoside-binding protein, triggers platelet activation in vitro. Here we investigated the molecular mechanisms underlying this function and the physiological relevance of endogenous Gal-1 in hemostasis. Mass spectrometry analysis, as well as studies using blocking antibodies against the anti-α(IIb) subunit ofα(IIb)ß(3) integrin or platelets from patients with Glanzmann's thrombasthenia syndrome (α(IIb)ß(3) deficiency), identified this integrin as a functional Gal-1 receptor in platelets. Binding of Gal-1 to platelets triggered the phosphorylation of ß(3)-integrin, Syk, MAPKs, PI3K, PLCγ2, thromboxane (TXA(2)) release, and Ca(2+) mobilization. Not only soluble but also immobilized Gal-1 promoted platelet activation. Gal-1-deficient (Lgals1(-/-)) mice showed increased bleeding time (P<0.0002, knockout vs. wild type), which was not associated with an abnormal platelet count. Lgals1(-/-) platelets exhibited normal aggregation to PAR4, ADP, arachidonic acid, or collagen but abnormal ATP release at low collagen concentrations. Impaired spreading on fibrinogen and clot retraction with normal levels of α(IIb)ß(3) was also observed in Lgals1(-/-) platelets, indicating a failure in the "outside-in" signaling through this integrin. This study identifies a noncanonical mechanism, based on galectin-integrin interactions, for regulating platelet activation.

Identification of galectin-1 and galectin-3 as novel partners for von Willebrand factor.

OBJECTIVE: Although von Willebrand factor (VWF) is a heavily glycosylated protein, its potential to associate with glycan-binding proteins is poorly investigated. Here, we explored its interaction with the glycan-binding proteins galectin-1 and galectin-3. METHODS AND RESULTS: Immunofluorescence analysis using Duolink proximity ligation assays revealed that VWF colocalizes with galectin-1 and galectin-3 in endothelial cells, both before and after stimulation of endothelial cells. Moreover, galectin-1 was found along the typical VWF bundles that are released by endothelial cells. Galectin-1 and galectin-3 could be coprecipitated with VWF from plasma in immunoprecipitation assays, whereas plasma levels of galectin-1 and galectin-3 were significantly reduced in VWF-deficient mice. Binding studies using purified proteins confirmed that VWF could directly interact with both galectins, predominantly via its N-linked glycans. In search of the physiological relevance of the VWF-galectin interaction, we found that inhibition of galectins in in vitro perfusion assays was associated with increased VWF-platelet string formation, a phenomenon that was reproduced in galectin-1/galectin-3 double-deficient mice. These mice were also characterized by a more rapid formation of initial thrombi following ferric chloride-induced injury. CONCLUSIONS: We have identified galectin-1 and galectin-3 as novel partners for VWF, and these proteins may modulate VWF-mediated thrombus formation.

Tissue plasminogen activator induces microglial inflammation via a noncatalytic molecular mechanism involving activation of mitogen-activated protein kinases and Akt signaling pathways and AnnexinA2 and Galectin-1 receptors.

Inflammatory responses mediated by glial cells play a critical role in many pathological situations related to neurodegeneration such as Alzheimer's disease. Tissue plasminogen activator (tPA) is a serine protease which best-known function is fibrinolysis, but it is also involved in many other physiological and pathological events as microglial activation. Here, we found that tPA is required for Aß-mediated microglial inflammatory response and tumor necrosis factor-α release. We further investigated the molecular mechanism responsible for tPA-mediated microglial activation. We found that tPA induces a catalytic-independent rapid and sustained activation of extracellular signal-regulated kinase (ERK)1/2, Jun N-terminal kinase (JNK), Akt, and p38 signaling pathways. Inhibition of ERK1/2 and JNK resulted in a strong inhibition of microglial activation, whereas Akt inhibition led to increased inflammatory response, suggesting specific functions for each signaling pathway in the regulation of microglial activation. Furthermore, we demonstrated that AnnexinA2 and Galectin-1 receptors are involved in tPA signaling and inflammatory response in glial cells. This study provides new evidences supporting that tPA plays a cytokine-like role in glial activation by triggering receptor-mediated intracellular signaling circuits and opens new therapeutic strategies for the treatment of neurological disorders in which neuroinflammation plays a pathogenic role.

Impaired spatial and contextual memory formation in galectin-1 deficient mice.

Galectins are a 15 member family of carbohydrate-binding proteins that have been implicated in cancer, immunity, inflammation and development. While galectins are expressed in the central nervous system, little is known about their function in the adult brain. Previously we have shown that galectin-1 (gal-1) is expressed in the adult hippocampus, and, in particular, in putative neural stem cells in the subgranular zone. To evaluate how gal-1 might contribute to hippocampal memory function here we studied galectin-1 null mutant (gal-1-/-) mice. Compared to their wildtype littermate controls, gal-1-/- mice exhibited impaired spatial learning in the water maze and contextual fear learning. Interestingly, tone fear conditioning was normal in gal-1-/- mice suggesting that loss of gal-1 might especially impact hippocampal learning and memory. Furthermore, gal-1-/- mice exhibited normal motor function, emotion and sensory processing in a battery of other behavioral tests, suggesting that non-mnemonic performance deficits are unlikely to account for the spatial and contextual learning deficits. Together, these data reveal a role for galectin-carbohydrate signalling in hippocampal memory function.

The glycan-binding protein galectin-1 controls survival of epithelial cells along the crypt-villus axis of small intestine.

Intestinal epithelial cells serve as mechanical barriers and active components of the mucosal immune system. These cells migrate from the crypt to the tip of the villus, where different stimuli can differentially affect their survival. Here we investigated, using in vitro and in vivo strategies, the role of galectin-1 (Gal-1), an evolutionarily conserved glycan-binding protein, in modulating the survival of human and mouse enterocytes. Both Gal-1 and its specific glyco-receptors were broadly expressed in small bowel enterocytes. Exogenous Gal-1 reduced the viability of enterocytes through apoptotic mechanisms involving activation of both caspase and mitochondrial pathways. Consistent with these findings, apoptotic cells were mainly detected at the tip of the villi, following administration of Gal-1. Moreover, Gal-1-deficient (Lgals1(-/-)) mice showed longer villi compared with their wild-type counterparts in vivo. In an experimental model of starvation, fasted wild-type mice displayed reduced villi and lower intestinal weight compared with Lgals1(-/-) mutant mice, an effect reflected by changes in the frequency of enterocyte apoptosis. Of note, human small bowel enterocytes were also prone to this pro-apoptotic effect. Thus, Gal-1 is broadly expressed in mucosal tissue and influences the viability of human and mouse enterocytes, an effect which might influence the migration of these cells from the crypt, the integrity of the villus and the epithelial barrier function.

Endogenous galectin-1 and acute inflammation: emerging notion of a galectin-9 pro-resolving effect.

The role of endogenous galectin-1 (Gal-1) in acute inflammation has been poorly investigated. We therefore performed the carrageenan-induced paw edema model in wild-type and Gal-1(-/-) mice. On subplantar injection of carrageenan, Gal-1(-/-) mice displayed a similar first phase of edema (≤24 hours) to wild-type mice; however, a much less pronounced second phase (48 to 96 hours) was evident in this genotype. This reduced inflammation was associated with lower paw expression of inflammatory genes and cell infiltrates. Analysis of galectin protein and mRNA expression revealed high expression of Gal-1 in wild-type paws during resolution (≥48 hours), with some expression of galectin-9 (Gal-9). Administration of stable Gal-1 to wild-type mice completely ablated the first phase of edema but was ineffective when administered therapeutically at the 24-hour time point. Conversely, Gal-9 administration did not alter the first phase of edema but significantly reduced the second phase when administered therapeutically. This suggests anti-inflammatory actions for both proteins in this model albeit at different phases of the inflammatory response. Collectively, these data indicate that the absence of endogenous Gal-1 results in an abrogated response during the second phase of the edema reaction.

The immunoregulatory mechanisms of carcinoma for its survival and development.

The immune system in patients detects and eliminates tumor cells, but tumors still progress persistently. The mechanisms by which tumor cells survive under the pressure of immune surveillance are not fully understood. This review is to present the evidence from clinical studies, showing a significant correlation of clinicopathological features of carcinoma with: (1) the loss of classical human leukocyte antigen class I, (2) the up-regulation of non-classical human leukocyte antigen class I, pro-apoptotic Fas ligand and receptor-binding cancer antigen expressed on SiSo cells I, and (3) the formation of immunosuppressive microenvironment by up-regulation of transforming growth factor-beta, Galectin-1, inhibitory ligand B7s, indoleamine 2,3-dioxygenase and arginase, as well as by recruitment of tumor-induced myeloid-derived suppressor cells and regulatory T cells. All of these factors may together protect carcinoma cells from the immune-cytotoxicity.