Galectin-9 protects mice from the Shwartzman reaction by attracting prostaglandin E2-producing polymorphonuclear leukocytes

A galectin-9 involved in the microbial recognition and haemocyte autophagy in the Pacific oyster Crassostrea gigas

Galectin-9 is a tandem-repeat type member of galectin family participating in various immune responses, such as cell agglutination, phagocytosis, and autophagy. In the present study, a tandem repeat galectin-9 (defined as CgGal-9) was identified from Pacific oyster Crassostrea gigas, which consisted of two conserved carbohydrate recognition domains (CRDs) joined by a linker peptide. CgGal-9 was closely clustered with CaGal-9 from C. angulata, and they were assigned into the branch of invertebrate galectin-9s in the phylogenetic tree. The mRNA transcripts of CgGal-9 were detected in all the tested tissues, with the highest expression level in haemocytes. The mRNA expressions of CgGal-9 in haemocytes increased significantly after lipopolysaccharide (LPS) and Vibrio splendidus stimulation. The recombinant CgGal-9 was able to bind all the examined pathogen-associated molecular patterns (LPS, peptidoglycan, and mannose) and microbes (V. splendidus, Escherichia coli, Micrococcus luteus, Staphylococcus aureus, Bacillus subtilis, and Pichia pastoris), and agglutinated most of them in the presence of Ca2+. In CgGal-9-RNAi oysters, the mRNA expressions of autophagy related genes (CgBeclin1, CgATG5, CgP62 and CgLC3) in haemocytes decreased significantly while that of CgmTOR increased significantly at 3 h after V. splendidus stimulation. The autophagy level and mRNA expressions of autophagy related genes decreased in haemocytes after CgGal-9 was blocked by the corresponding antibody. These results revealed that CgGal-9 was able to bind different microbes and might be involved in haemocyte autophagy in the immune response of oyster.

Galectin-9 in Gastroenterological Cancer

Immunochemotherapy has become popular in recent years. The detailed mechanisms of cancer immunity are being elucidated, and new developments are expected in the future. Apoptosis allows tissues to maintain their form, quantity, and function by eliminating excess or abnormal cells. When apoptosis is inhibited, the balance between cell division and death is disrupted and tissue homeostasis is impaired. This leads to dysfunction and the accumulation of genetically abnormal cells, which can contribute to carcinogenesis. Lectins are neither enzymes nor antibodies but proteins that bind sugar chains. Among soluble endogenous lectins, galectins interact with cell surface sugar chains outside the cell to regulate signal transduction and cell growth. On the other hand, intracellular lectins are present at the plasma membrane and regulate signal transduction by regulating receptor–ligand interactions. Galectin-9 expressed on the surface of thymocytes induces apoptosis of T lymphocytes and plays an essential role in immune self-tolerance by negative selection in the thymus. Furthermore, the administration of extracellular galectin-9 induces apoptosis of human cancer and immunodeficient cells. However, the detailed pharmacokinetics of galectin-9 in vivo have not been elucidated. In addition, the cell surface receptors involved in galectin-9-induced apoptosis of cancer cells have not been identified, and the intracellular pathways involved in apoptosis have not been fully investigated. We have previously reported that galectin-9 induces apoptosis in various gastrointestinal cancers and suppresses tumor growth. However, the mechanism of galectin-9 and apoptosis induction in gastrointestinal cancers and the detailed mechanisms involved in tumor growth inhibition remain unknown. In this article, we review the effects of galectin-9 on gastrointestinal cancers and its mechanisms.

Involvement of galectin-9 from koi carp (Cyprinus carpio) in the immune response against Aeromonas veronii infection

Galectins are β-galactoside sugar binding proteins which function as important pattern recognition receptors (PRRs) in innate immunity. Here, we identified a galectin-9 gene from koi carp (Cyprinus carpio), named kGal-9. The ORF of kGal-9 is 963 bp in length, which encodes a polypeptide of 320 amino acids without either signal peptide. The predicted molecular weight is 36.25 kDa, and the isoelectric point is 8.3. Multiple sequence alignment showed that the putative kGal-9 contains two carbohydrate recognition domains (CRD), which are conserved in Galectin-9s. The phylogenetic tree showed that kGal-9 clustered to Galectin-9s from other teleosts, and shared the highest identity of 87.5% with Qihe crucian (Carassius auratus). kGal-9 mRNA was abundant in head kidney, gills, and gut, but low in liver and muscle. Further, the expression level of kGal-9 in the head kidney and liver increased significantly after Aeromonas veronii (abbreviated A.v) infection. Unexpectedly, kGal-9 showed a remarkable downregulation in the spleen at various time points post A.v infection. Intramuscular injection of pckGal-9 not merely reduced the bacterial load of spleen tissue, but also improved the survival rate of koi carp post A.v challenge. Besides, administration of pckGal-9 stimulated the expression of several immuno-related genes including proinflammatory cytokines (IL-1β, IL-6), anti-inflammatory cytokine (IL-10), complement components (C4, C9), with fluctuation in spleen and head kidney. Taken together, the obtained results suggest that kGal-9 occupies an important role in innate immunity and defense against bacterial infection in koi carp.

Transcriptional regulation of LGALS9 by HAND2 and FOXO1 in human endometrial stromal cells in women with regular cycles

Uterine natural killer cells are regulated via surface inhibitory receptors for IL15 and galectin-9 (LGALS9) secreted by endometrial stromal cells (ESCs). However, the mechanism that regulates LGALS9 mRNA levels in ESCs is unclear. The aim of this study is to clarify the transcriptional regulation of LGALS9 in ESCs. Here, LGALS9 mRNA expression levels significantly decreased in the endometrial tissue in the early- to mid-secretory phase, and recovered in the mid- to late-secretory phase, compared to that in the proliferative phase. In ESCs, LGALS9 mRNA expression significantly decreased following estradiol + medroxyprogesterone acetate treatment for 1 day and increased after 12 days compared to that in the control. The transcriptional activity of the LGALS9 upstream region was upregulated by heart and neural crest derivatives expressed 2 (HAND2) and downregulated by forkhead box O1 (FOXO1). In ESCs, HAND2 expression significantly increased throughout the 12 days treatment with steroid hormones, whereas FOXO1 expression significantly increased on Day 1, reached a plateau, and significantly increased again after 6 days of treatment. Levels of FOXO1 phosphorylation (pFOXO1) remained unchanged after a 3-day treatment of ESCs with steroid hormones, but significantly increased following a 12-day treatment. pFOXO1 could not bind to the DNA and was thus unable to directly suppress LGALS9 transcription. Therefore, expression level of HAND2 and phosphorylation status of FOXO1 may determine LGALS9 mRNA expression. This study provides a novel molecular mechanism underlying the transcriptional regulation of LGALS9 mRNA in ESCs, which could be valuable in the treatment of diseases associated with decidualization failure.

Galectin-9 deficiency exacerbates lipopolysaccharide-induced hypothermia and kidney injury

BACKGROUND

Galectin-9 (Gal-9) is a multifunctional lectin that moderates inflammation and organ damage. In this study, we tested whether Gal-9 has a protective role in the pathogenesis of endotoxemic acute kidney injury.

METHODS

We examined the levels of Gal-9 in control mice after lipopolysaccharide (LPS) administration. We developed Gal-9 knockout (KO) mice that lack Gal-9 systemically and evaluated the role of Gal-9 in LPS-induced proinflammatory cytokines, vascular permeability, and renal injury.

RESULTS

Gal-9 levels were increased in the plasma, kidney, and spleen within 4 h after LPS administration to wild-type mice. Gal-9 deficiency did not affect the LPS-induced increase in plasma tumor necrosis factor-α levels at 1 h or vascular permeability at 6 h. Lower urine volume and reduced creatinine clearance were observed in Gal-9-KO mice compared with wild-type mice after LPS administration. Gal-9-KO mice had limited improvement in urine volume after fluid resuscitation compared with wild-type mice. LPS reduced the body temperature 12 h after its administration. Hypothermia had disappeared in wild-type mice by 24 h, whereas it was sustained until 24 h in Gal-9-KO mice. Importantly, maintaining body temperature in Gal-9-KO mice improved the response of urine flow to fluid resuscitation.

CONCLUSION

Deficiency in Gal-9 worsened LPS-induced hypothermia and kidney injury in mice. The accelerated hypothermia induced by Gal-9 deficiency contributed to the blunted response to fluid resuscitation.

Galectin-9-based immune risk score model helps to predict relapse in stage I-III small cell lung cancer

Background

For small cell lung cancer (SCLC) therapy, immunotherapy might have unique advantages to some extent. Galectin-9 (Gal-9) plays an important role in antitumor immunity, while little is known of its function in SCLC.

Materials and methods

By mean of immunohistochemistry (IHC), we tested the expression level of Gal-9 and other immune markers on both tumor cells and tumor-infiltrating lymphocytes (TILs) in 102 surgical-resected early stage SCLC clinical samples. On the basis of statistical analysis and machine learning results, the Gal-9-based immune risk score model was constructed and its predictive performance was evaluated. Then, we thoroughly explored the effects of Gal-9 and immune risk score on SCLC immune microenvironment and immune infiltration in different cohorts and platforms.

Results

In the SCLC cohort for IHC, the expression level of Gal-9 on TILs was statistically correlated with the levels of program death-1 (p=0.001), program death-ligand 1 (PD-L1) (p<0.001), CD3 (p<0.001), CD4 (p<0.001), CD8 (p<0.001), and FOXP3 (p=0.047). High Gal-9 protein expression on TILs indicated better recurrence-free survival (30.4 months, 95% CI: 23.7–37.1 vs 39.4 months, 95% CI: 31.6–47.3, p=0.009). The immune risk score model which consisted of Gal-9 on TILs, CD4, and PD-L1 on TILs was established and validated so as to differentiate high-risk or low-risk patients with SCLC. The prognostic predictive performance of immune risk score model was better than single immune biomarker (area under the curve 0.671 vs 0.621–0.644). High Gal-9-related enrichment pathways in SCLC were enriched in immune system diseases and rheumatic disease. Furthermore, we found that patients with SCLC with low immune risk score presented higher fractions of activated memory CD4 T cells than patients with high immune risk score (p=0.048).

Conclusions

Gal-9 is markedly related to tumor-immune microenvironment and immune infiltration in SCLC. This study emphasized the predictive value and promising clinical applications of Gal-9 in stage I–III SCLC.

The Sweet-Side of Leukocytes: Galectins as Master Regulators of Neutrophil Function

Among responders to microbial invasion, neutrophils represent one of the earliest and perhaps most important factors that contribute to initial host defense. Effective neutrophil immunity requires their rapid mobilization to the site of infection, which requires efficient extravasation, activation, chemotaxis, phagocytosis, and eventual killing of potential microbial pathogens. Following pathogen elimination, neutrophils must be eliminated to prevent additional host injury and subsequent exacerbation of the inflammatory response. Galectins, expressed in nearly every tissue and regulated by unique sensitivity to oxidative and proteolytic inactivation, appear to influence nearly every aspect of neutrophil function. In this review, we will examine the impact of galectins on neutrophils, with a particular focus on the unique biochemical traits that allow galectin family members to spatially and temporally regulate neutrophil function.

Galectin-9 suppresses B cell receptor signaling and is regulated by I-branching of N-glycans

Leukocytes are coated with a layer of heterogeneous carbohydrates (glycans) that modulate immune function, in part by governing specific interactions with glycan-binding proteins (lectins). Although nearly all membrane proteins bear glycans, the identity and function of most of these sugars on leukocytes remain unexplored. Here, we characterize the N-glycan repertoire (N-glycome) of human tonsillar B cells. We observe that naive and memory B cells express an N-glycan repertoire conferring strong binding to the immunoregulatory lectin galectin-9 (Gal-9). Germinal center B cells, by contrast, show sharply diminished binding to Gal-9 due to upregulation of I-branched N-glycans, catalyzed by the β1,6-N-acetylglucosaminyltransferase GCNT2. Functionally, we find that Gal-9 is autologously produced by naive B cells, binds CD45, suppresses calcium signaling via a Lyn-CD22-SHP-1 dependent mechanism, and blunts B cell activation. Thus, our findings suggest Gal-9 intrinsically regulates B cell activation and may differentially modulate BCR signaling at steady state and within germinal centers.

Role of Lgals9 Deficiency in Attenuating Nephritis and Arthritis in BALB/c Mice in a Pristane-Induced Lupus Model

OBJECTIVE

In systemic lupus erythematosus (SLE), an autoimmune disease associated with multiple organ involvement, the development of lupus nephritis determines prognosis, and arthritis impairs quality of life. Galectin 9 (Gal-9, Lgals9) is a β-galactoside-binding lectin that has been used for clinical application in autoimmune diseases, since recombinant Gal-9, as a ligand for T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), induces apoptosis of activated CD4+TIM-3+ Th1 cells. This study was undertaken to investigate whether deficiency of Lgals9 has beneficial or deleterious effects on lupus in a murine model.

METHODS

Gal-9^+/+ and Gal-9^-/- female BALB/c mice were injected with pristane, and the severity of arthritis, proteinuria, and levels of autoantibody production were assessed at several time points immediately following injection. At 7 months after pristane injection, renal pathologic features, the severity of joint inflammation, and formation of lipogranulomas were evaluated. Subsets of inflammatory cells in the spleen and peritoneal lavage were characterized, and expression levels of cytokines from peritoneal macrophages were analyzed.

RESULTS

Lgals9 deficiency protected against the development of immune complex glomerulonephritis, arthritis, and peritoneal lipogranuloma formation in BALB/c mice in this murine model of pristane-induced lupus. The populations of T cell subsets and B cells in the spleen and peritoneum were not altered by Lgals9 deficiency in pristane-injected BALB/c mice. Furthermore, Lgals9 deficiency protected against pristane-induced lupus without altering the Toll-like receptor 7-type I interferon pathway.

CONCLUSION

Gal-9 is required for the induction and development of lupus nephritis and arthritis in this murine model of SLE. The results of the current investigation provide a potential new strategy in which antagonism of Gal-9 may be beneficial for the treatment of nephritis and arthritis in patients with SLE through targeting of activated macrophages.

A unique role for galectin-9 in angiogenesis and inflammatory arthritis

Background

Galectin-9 (Gal-9) is a mammalian lectin secreted by endothelial cells that is highly expressed in rheumatoid arthritis synovial tissues and synovial fluid. Roles have been proposed for galectins in the regulation of inflammation and angiogenesis. Therefore, we examined the contribution of Gal-9 to angiogenesis and inflammation in arthritis.

Methods

To determine the role of Gal-9 in angiogenesis, we performed human dermal microvascular endothelial cell (HMVEC) chemotaxis, Matrigel tube formation, and mouse Matrigel plug angiogenesis assays. We also examined the role of signaling molecules in Gal-9-induced angiogenesis by using signaling inhibitors and small interfering RNA (siRNA). We performed monocyte (MN) migration assays in a modified Boyden chamber and assessed the arthritogenicity of Gal-9 by injecting Gal-9 into mouse knees.

Results

Gal-9 significantly increased HMVEC migration, which was decreased by inhibitors of extracellular signal-regulating kinases 1/2 (Erk1/2), p38, Janus kinase (Jnk), and phosphatidylinositol 3-kinase. Gal-9 HMVEC-induced tube formation was reduced by Erk1/2, p38, and Jnk inhibitors, and this was confirmed by siRNA knockdown. In mouse Matrigel plug assays, plugs containing Gal-9 induced significantly higher angiogenesis, which was attenuated by a Jnk inhibitor. Gal-9 also induced MN migration, and there was a marked increase in MN ingress when C57BL/6 mouse knees were injected with Gal-9 compared with the control, pointing to a proinflammatory role for Gal-9.

Conclusions

Gal-9 mediates angiogenesis, increases MN migration in vitro, and induces acute inflammatory arthritis in mice, suggesting a novel role for Gal-9 in angiogenesis, joint inflammation, and possibly other inflammatory diseases.

Expansion of CD11b+Ly-6C+ myeloid-derived suppressor cells (MDSCs) driven by galectin-9 attenuates CVB3-induced myocarditis

Galectin-9 is known to play a role in the modulation of innate and adaptive immunity to ameliorate CVB3-induced myocarditis. In the present study, we found that galectin-9 induced the expansion of CD11b⁺Ly-6C⁺ myeloid-derived suppressor cells (MDSCs) in the heart from CVB3-infected mice. Adoptive transfer of CD11b⁺Ly-6C⁺ MDSCs significantly alleviated myocarditis accompanied by increased Th2 and Treg frequency and anti-inflammatory cytokines expression in the heart tissue. Moreover, Ly6C⁺ MDSCs, but not Ly6G⁺ cells, expressed Arg-1 and NOS2, and suppressed CD4⁺ T cell proliferation in vitro in an Arg-1-dependent mechanism; an event that was reversed with treatment of either an Arg-1 inhibitor or addition of excess l-arginine. Furthermore, Ly6C⁺ MDSCs co-expressed higher levels of F4/80, Tim-3, and IL-4Rα, and had the plasticity to up-regulate NOS2 or Arg-1 in response to IFN-γ or IL-4 treatment. The present results indicate that galectin-9 expands CD11b⁺Ly-6C⁺ MDSCs to ameliorate CVB3-induced myocarditis.

Cancer Therapy Due to Apoptosis: Galectin-9

Dysregulation of apoptosis is a major hallmark in cancer biology that might equip tumors with a higher malignant potential and chemoresistance. The anti-cancer activities of lectin, defined as a carbohydrate-binding protein that is not an enzyme or antibody, have been investigated for over a century. Recently, galectin-9, which has two distinct carbohydrate recognition domains connected by a linker peptide, was noted to induce apoptosis in thymocytes and immune cells. The apoptosis of these cells contributes to the development and regulation of acquired immunity. Furthermore, human recombinant galectin-9, hG9NC (null), which lacks an entire region of the linker peptide, was designed to resist proteolysis. The hG9NC (null) has demonstrated anti-cancer activities, including inducing apoptosis in hematological, dermatological and gastrointestinal malignancies. In this review, the molecular characteristics, history and apoptosis-inducing potential of galectin-9 are described.

Cooperative Interactions of Oligosaccharide and Peptide Moieties of a Glycopeptide Derived from IgE with Galectin-9

We previously showed that galectin-9 suppresses degranulation of mast cells through protein-glycan interaction with IgE. To elucidate the mechanism of the interaction in detail, we focused on identification and structural analysis of IgE glycans responsible for the galectin-9-induced suppression using mouse monoclonal IgE (TIB-141). TIB-141 in combination with the antigen induced degranulation of RBL-2H3 cells, which was almost completely inhibited by human and mouse galectin-9. Sequential digestion of TIB-141 with lysyl endopeptidase and trypsin resulted in the identification of a glycopeptide (H-Lys13-Try3; 48 amino acid residues) with a single N-linked oligosaccharide near the N terminus capable of neutralizing the effect of galectin-9 and another glycopeptide with two N-linked oligosaccharides (H-Lys13-Try1; 16 amino acid residues) having lower activity. Enzymatic elimination of the oligosaccharide chain from H-Lys13-Try3 and H-Lys13-Try1 completely abolished the activity. Removal of the C-terminal 38 amino acid residues of H-Lys13-Try3 with glutamyl endopeptidase, however, also resulted in loss of the activity. We determined the structures of N-linked oligosaccharides of H-Lys13-Try1. The galectin-9-binding fraction of pyridylaminated oligosaccharides contained asialo- and monosialylated bi/tri-antennary complex type oligosaccharides with a core fucose residue. The structures of the oligosaccharides were consistent with the sugar-binding specificity of galectin-9, whereas the nonbinding fraction contained monosialylated and disialylated biantennary complex type oligosaccharides with a core fucose residue. Although the oligosaccharides linked to H-Lys13-Try3 could not be fully characterized, these results indicate the possibility that cooperative binding of oligosaccharide and neighboring polypeptide structures of TIB-141 to galectin-9 affects the overall affinity and specificity of the IgE-lectin interaction.

Fingerprinting of galectins in normal, P. aeruginosa-infected, and chemically burned mouse corneas

PURPOSE

In this study, we aimed to assess whether the expression pattern of galectins is altered in Pseudomonas aeruginosa-infected and chemically burned mouse corneas.

METHODS

Galectin (Gal) fingerprinting of normal, P. aeruginosa-infected, and silver nitrate-cauterized corneas was performed by Western blotting, immunofluorescence staining, and qRT-PCR.

RESULTS

In normal corneas, Gal-1 was distributed mainly in the stroma, Gal-3 was localized mainly in epithelium, and Gal-7, -8, and -9 were detected in both corneal epithelium and stroma. Expression levels of the five galectins were drastically altered under pathological conditions. In both infected and cauterized corneas, overall Gal-3 expression was downregulated, whereas overall Gal-8 and -9 were upregulated. Changes in the expression level of Gal-7, -8, and -9 were distinct in the epithelium of infected and cauterized corneas. Expression of these three galectins was upregulated in corneal epithelium of infected corneas but not in cauterized corneas. Consistent with the changes in protein expression: (1) Gal-7, -8, and -9 mRNA expression was upregulated in cauterized corneas, and (2) Gal-3 mRNA was downregulated and Gal-9 mRNA expression was upregulated in infected corneas.

CONCLUSIONS

Our data demonstrate differential regulation of various members of the galectin family in the course of corneal infection and neovascularization. The emerging functionality of the sugar code of cell surface receptors via endogenous galectins reflect to the pertinent roles of the five tested galectins in the diseases of cornea.

Regulation of osteoclastogenesis through Tim-3: possible involvement of the Tim-3/galectin-9 system in the modulation of inflammatory bone destruction

Galectins are a unique family of lectins bearing one or two carbohydrate recognition domains (CRDs) that have the ability to bind molecules with β-galactoside-containing carbohydrates. It has been shown that galectins regulate not only cell growth and differentiation but also immune responses, as well as inflammation. Galectin-9, a tandem repeat type of galectin, was originally identified as a chemotactic factor for eosinophils, and is also involved in the regulatory process of inflammation. Here, we examined the involvement of galectin-9 and its receptor, T-cell immunoglobulin- and mucin-domain-containing molecule 3 (Tim-3), in the control of osteoclastogenesis and inflammatory bone destruction. Expression of Tim-3 was detected in osteoclasts and its mononuclear precursors in vivo and in vitro. Galectin-9 markedly inhibited osteoclastogenesis as evaluated in osteoclast precursor cell line RAW-D cells and primary bone marrow cells of mice and rats. The inhibitory effects of galectin-9 on osteoclastogenesis was negated by the addition of β-lactose, an antagonist for galectin binding, suggesting that the inhibitory effect of galectin-9 was mediated through CRD. When galectin-9 was injected into rats with adjuvant-induced arthritis, marked suppression of bone destruction was observed. Inflammatory bone destruction could be efficiently ameliorated by controlling the Tim-3/galectin-9 system in rheumatoid arthritis.

Galectin-9-CD44 interaction enhances stability and function of adaptive regulatory T cells

The β-galactoside-binding protein galectin-9 is critical in regulating the immune response, but the mechanism by which it functions remains unclear. We have demonstrated that galectin-9 is highly expressed by induced regulatory T cells (iTreg) and was crucial for the generation and function of iTreg cells, but not natural regulatory T (nTreg) cells. Galectin-9 expression within iTreg cells was driven by the transcription factor Smad3, forming a feed-forward loop, which further promoted Foxp3 expression. Galectin-9 increased iTreg cell stability and function by directly binding to its receptor CD44, which formed a complex with transforming growth factor-β (TGF-β) receptor I (TGF-βRI), and activated Smad3. Galectin-9 signaling was further found to regulate iTreg cell induction by dominantly acting through the CNS1 region of the Foxp3 locus. Our data suggest that exogenous galectin-9, in addition to being an effector molecule for Treg cells, acts synergistically with TGF-β to enforce iTreg cell differentiation and maintenance.

Galectin-9 induced myeloid suppressor cells expand regulatory T cells in an IL-10-dependent manner in CVB3-induced acute myocarditis

The objective of the study was to explore the effects of galectin-9 on myeloid suppressor cells in Coxsackievirus B3 (CVB3)-induced myocarditis and the possible mechanisms involved. For this purpose, BALB/c male mice were infected with CVB3 on day 0 and then received intraperitoneal (IP) administration of recombinant galectin-9 or phosphate-buffered saline (PBS) daily from day 3 to day 7. The phenotypes and functions of myeloid suppressor cells were evaluated. The role and mechanism of myeloid suppressor cells and subsets in CVB3-induced myocarditis in vitro were explored. We found that galectin-9 remarkably increased the frequencies of CD11b+Gr-1+ cells in the cardiac tissue and spleen with myocarditis. Ly-6G+ cells were decreased and Ly-6C+ cells were increased in galectin-9-treated mice. In addition, CD11b+Gr-1+ cells were highly effective in suppressing CD4+ T cells. Moreover, our data demonstrate that CD11b+Gr-1+ cells are capable of expanding regulatory T cells (Tregs) from a preexisting population of natural Tregs, which depends on IL-10 but not TGF-β. Our results indicate that galectin-9 therapy may represent a useful approach to ameliorate CVB3-induced myocarditis.

Galectin-9 prolongs the survival of septic mice by expanding Tim-3-expressing natural killer T cells and PDCA-1+ CD11c+ macrophages

INTRODUCTION

Galectin-9 ameliorates various inflammatory conditions including autoimmune diseases by regulating T cell and macrophage/dendritic cell (DC) functions. However, the effect of galectin-9 on polymicrobial sepsis has not been assessed.

METHODS

We induced polymicrobial sepsis by cecal ligation and puncture (CLP) in mice. The survival rate was compared between galectin-9- and PBS-treated CLP mice. An ELISA was used to compare the levels of various cytokines in the plasma and culture supernatants. Fluorescence-activated cell sorting analysis was further performed to compare the frequencies of subpopulations of spleen cells.

RESULTS

Galectin-9 exhibited a protective effect in polymicrobial sepsis as demonstrated in galetin-9 transgenic mice and therapeutic galectin-9 administration. In contrast, such effect was not observed in nude mice, indicating the involvement of T cells in galectin-9-mediated survival prolongation. Galectin-9 decreased TNFα, IL-6, IL-10 and, high mobility group box 1 (HMGB1) and increased IL-15 and IL-17 plasma and spleen levels. Galectin-9 increased the frequencies of natural killer T (NKT) cells and PDCA-1+ CD11c+ macrophages (pDC-like macrophages) but did not change the frequency of CD4 or CD8 T cells, γδT cells or conventional DC. As expected, galectin-9 decreased the frequency of Tim-3+ CD4 T cells, most likely Th1 and Th17 cells. Intriguingly, many spleen NK1.1+ NKT cells and pDC-like macrophages expressed Tim-3. Galectin-9 increased the frequency of Tim-3-expressing NK1.1+ NKT cells and pDC-like macrophages. Galectin-9 further increased IL-17+ NK1.1+ NKT cells.

CONCLUSION

These data suggest that galectin-9 exerts therapeutic effects on polymicrobial sepsis, possibly by expanding NKT cells and pDC-like macrophages and by modulating the production of early and late proinflammatory cytokines.

Optimization of the inter-domain structure of galectin-9 for recombinant production

We previously developed a stable form of galectin-9, an immunomodulatory animal lectin with a truncated linker peptide (G9Null), to overcome the protease sensitivity of wild-type galectin-9. G9Null is highly resistant to proteolysis, while the modification marginally improved the low solubility of the wild-type protein. To increase its solubility, we further modified the remaining linker region of G9Null. A 10-amino acid deletion with a single amino acid substitution resulted in an ∼400% increase in solubility and yield without an adverse effect on its biological activity. This mutant protein might be useful for large-scale recombinant production needed for evaluation of the therapeutic potential of galectin-9.

Cell surface galectin-9 expressing Th cells regulate Th17 and Foxp3+ Treg development by galectin-9 secretion

Galectin-9 (Gal-9), a β-galactoside binding mammalian lectin, regulates immune responses by reducing pro-inflammatory IL-17-producing Th cells (Th17) and increasing anti-inflammatory Foxp3(+) regulatory T cells (Treg) in vitro and in vivo. These functions of Gal-9 are thought to be exerted by binding to receptor molecules on the cell surface. However, Gal-9 lacks a signal peptide for secretion and is predominantly located in the cytoplasm, which raises questions regarding how and which cells secrete Gal-9 in vivo. Since Gal-9 expression does not necessarily correlate with its secretion, Gal-9-secreting cells in vivo have been elusive. We report here that CD4 T cells expressing Gal-9 on the cell surface (Gal-9(+) Th cells) secrete Gal-9 upon T cell receptor (TCR) stimulation, but other CD4 T cells do not, although they express an equivalent amount of intracellular Gal-9. Gal-9(+) Th cells expressed interleukin (IL)-10 and transforming growth factor (TGF)-β but did not express Foxp3. In a co-culture experiment, Gal-9(+) Th cells regulated Th17/Treg development in a manner similar to that by exogenous Gal-9, during which the regulation by Gal-9(+) Th cells was shown to be sensitive to a Gal-9 antagonist but insensitive to IL-10 and TGF-β blockades. Further elucidation of Gal-9(+) Th cells in humans indicates a conserved role of these cells through evolution and implies the possible utility of these cells for diagnosis or treatment of immunological diseases.

Galectin-9 ameliorates Con A-induced hepatitis by inducing CD4(+)CD25(low/int) effector T-Cell apoptosis and increasing regulatory T cell number

Background

T cell-mediated liver damage is a key event in the pathogenesis of many chronic human liver diseases, such as liver transplant rejection, primary biliary cirrhosis, and sclerosing cholangitis. We and other groups have previously reported that galectin-9, one of the β-galactoside binding animal lectins, might be potentially useful in the treatment of T cell-mediated diseases. To evaluate the direct effect of galectin-9 on hepatitis induced by concanavalin A (Con A) administration in mice and to clarify the mechanisms involved, we administered galectin-9 into mice, and evaluated its therapeutic effect on Con A-induced hepatitis.

Methodology/Principal Findings

Galectin-9 was administrated i.v. to Balb/c mice 30 min before Con A injection. Compared with no treatment, galectin-9 pretreatment significantly reduced serum ALT and AST levels and improved liver histopathology, suggesting an ameliorated hepatitis. This therapeutic effect was not only attributable to a blunted Th1 immune response, but also to an increased number in regulatory T cells, as reflected in a significantly increased apoptosis of CD4⁺CD25^low/int effector T cells and in reduced proinflammatory cytokine levels.

Conclusion/Significance

Our findings constitute the first preclinical data indicating that interfering with TIM-3/galectin-9 signaling in vivo could ameliorate Con A-induced hepatitis. This strategy may represent a new therapeutic approach in treating human diseases involving T cell activation.

Contrasting acute graft-versus-host disease effects of Tim-3/galectin-9 pathway blockade dependent upon the presence of donor regulatory T cells

T-cell immunoglobulin mucin-3 (Tim-3) is expressed on pathogenic T cells, and its ligand galectin-9 (gal-9) is up-regulated in inflamed tissues. When Tim-3(+) T cells encounter high gal-9 levels, they are deleted. Tim-3 is up-regulated on activated T cells during GVHD. Inhibition of Tim-3/gal-9 binding by infusion of a Tim-3-Ig fusion protein or Tim-3(-/-) donor T cells increased T-cell proliferation and GVHD lethality. When the Tim-3/gal-9 pathway engagement was augmented using gal-9 transgenic recipients, GVHD lethality was slowed. Together, these data indicate a potential for modulating this pathway to reduce disease by increasing Tim-3 or gal-9 engagement. Paradoxically, when Tim-3/gal-9 was inhibited in the absence of donor T-regulatory cells (Tregs), GVHD was inhibited. GVHD reduction was associated with decreased colonic inflammatory cytokines as well as epithelial barrier destruction. CD25-depleted Tim-3(-/-) donor T cells underwent increased activation-induced cell death because of increased IFN-γ production. To our knowledge, these studies are the first to show that although the absence of Tim-3/gal-9 pathway interactions augments systemic GVHD, concurrent donor Treg depletion paradoxically and surprisingly inhibits GVHD. Thus, although donor Tregs typically inhibit GVHD, under some conditions, such Tregs actually may contribute to GVHD by reducing activation-induced T-cell death.

Molecular characterization of a tandem-repeat galectin-9 (RuGlec9) from Korean rose bitterling (Rhodeus uyekii)

Galectin-9 is a b-galactoside-binding lectin that regulates many cellular functions, ranging from cell adhesion to pathogen recognition. We isolated and characterized the cDNA of tandem-repeat galectin-9 (RuGlec9) from the Korean rose bitterling (Rhodeus uyekii), an endemic Korean fish belonging to the Acheilognathinae subfamily of the Cyprinidae family. RuGlec9 cDNA is 1486 bp long and encodes a polypeptide of 323 amino acids containing two carbohydrate-recognition domains connected by a linker peptide. The deduced amino acid sequence of RuGlec9 shows 45-84% amino acid sequence identity to other galectin-9 sequences, including those from mammals and fish. RuGlec9 appeared in a large cluster with other galectin-9 sequences from fish and is more closely related to galectin-9 from Danio rerio than to those of other fish and mammals. RuGlec9 mRNA was expressed highly in the testis, spleen, intestine, stomach, and liver, and moderately in the brain, kidney, ovary, and gills of normal Korean rose bitterling. RuGlec9 mRNA expression in the spleen was increased by lipopolysaccharide. These results suggest that RuGlec9 plays a role in innate immunity in Korean rose bitterling.

The effect of galectins on leukocyte trafficking in inflammation: sweet or sour?

The trafficking of leukocytes from the blood stream to the surrounding tissue is a fundamental feature of an inflammatory response. Although many of the adhesion molecules and chemokines that direct leukocyte trafficking have been identified, there is still much to be discovered, particularly with regard to the persistence of leukocyte infiltrates in chronic inflammation. Elucidating the molecular mechanisms involved in this process is critical to understanding and treating inflammatory pathologies. Recent studies have identified members of the galectin family as immunoregulatory proteins. Included among the actions of galectins are modulatory effects, both positive and negative, on leukocyte recruitment. The focus of this review is to summarize current knowledge on the role of galectins in leukocyte trafficking during inflammation. A better understanding of the function of this family of endogenous lectins will open new avenues for innovative drug discovery.

Galectin-9 protein expression in endothelial cells is positively regulated by histone deacetylase 3

Galectin-9 expression in endothelial cells can be induced in response to inflammation. However, the mechanism of its expression remains unclear. In this study, we found that interferon-γ (IFN-γ) induced galectin-9 expression in human endothelial cells in a time-dependent manner, which coincided with the activation of histone deacetylase (HDAC). When endothelial cells were treated with the HDAC3 inhibitor, apicidin, or shRNA-HDAC3 knockdown, IFN-γ-induced galectin-9 expression was abolished. Overexpression of HDAC3 induced the interaction between phosphoinositol 3-kinase (PI3K) and IFN response factor 3 (IRF3), leading to IRF3 phosphorylation, nuclear translocation, and galectin-9 expression. HDAC3 functioned as a scaffold protein for PI3K/IRF3 interaction. In addition to galectin-9 expression, IFN-γ also induced galectin-9 location onto plasma membrane, which was HDAC3-independent. Importantly, HDAC3 was essential for the constitutive transcription of PI3K and IRF3, which might be responsible for the basal level of galectin-9 expression. The phosphorylation of IRF3 was essential for galectin-9 expression. This study provides new evidence that HDAC3 regulates galectin-9 expression in endothelial cells via interaction with PI3K-IRF3 signal pathway.

Therapeutic potential of Galectin-9 in human disease

In recent years, an important role has emerged for the glycan-binding protein Galectin-9 (Gal-9) in health and disease. In normal physiology, Gal-9 seems to be a pivotal modulator of T-cell immunity by inducing apoptosis in specific T-cell subpopulations. Because these T-cell populations are associated with autoimmunity, inflammatory disease, and graft rejection, it was postulated that application of exogenous Gal-9 may limit pathogenic T-cell activity. Indeed, treatment with recombinant Gal-9 ameliorates disease activity in various preclinical models of autoimmunity and allograft graft rejection. In many solid cancers, the loss of Gal-9 expression is closely associated with metastatic progression. In line with this observation, treatment with recombinant Gal-9 prevents metastatic spread in various preclinical cancer models. In addition, various hematological malignancies are sensitive to apoptotic elimination by recombinant Gal-9. Here, we review the biology and physiological role of this versatile lectin and discuss the therapeutic potential of Gal-9 in various diseases, including autoimmunity, asthma, infection, and cancer.

Increased interleukin-10 production by ASC-deficient CD4+ T cells impairs bystander T-cell proliferation

Apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) is an important component of the inflammasome, functioning as an adaptor protein that facilitates the recruitment and activation of procaspases that in turn promote the maturation of interleukin-1β (IL-1β) and IL-18. Despite initial focus on the inflammatory properties of ASC there is emerging evidence that highlights the importance of ASC in facilitating adaptive immune responses. However, the cellular and molecular basis for the involvement of ASC in adaptive immunity remains largely unexplored. We have previously demonstrated that activated ASC-deficient T cells have dampened proliferative responses. We have therefore explored the underlying cellular mechanism(s) by which ASC regulates T-cell proliferation. We show that under activating conditions (anti-CD3/CD28 stimulation) in bulk T-cell cultures the presence of ASC(-/-) CD4(+) T cells is sufficient to suppress the proliferative responses of neighbouring T cells. Furthermore, ASC(-/-) CD4(+) T cells upon activation exhibit a suppressive cytokine profile, with elevated production of IL-10 and reduced secretion of T helper type 1 cytokines, interferon-γ and IL-2. This increase in IL-10 secretion within the activated ASC(-/-) CD4(+) T-cell compartment was not associated with a proportional increase in conventional Foxp3(+) regulatory T (Treg) cells. Interestingly, when equal numbers of fluorescence-activated cell sorted ASC(+/+) and ASC(-/-) Treg cells (CD4(+) CD44(intermediate/high) CD25(+)) were activated in vitro, the ASC(-/-) fraction produced significantly more IL-10 than their wild-type counterparts, suggesting that ASC(-/-) Treg cells have greater suppressive capacity. Collectively, these results imply that the ASC may influence the development and functioning of Treg cells.

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.

Galectin-9 attenuates acute lung injury by expanding CD14- plasmacytoid dendritic cell-like macrophages

RATIONALE

Galectin (Gal)-9 plays a crucial role in the modulation of innate and adaptive immunity.

OBJECTIVES

To investigate whether Gal-9 plays a role in a murine acute lung injury (ALI) model.

METHODS

C57BL/6 mice were pretreated with Gal-9 by subcutaneous injection 24 and 48 hours before intranasal LPS inoculation.

MEASUREMENTS AND MAIN RESULTS

Gal-9 suppressed pathological changes of ALI induced by LPS. Gal-9 reduced levels of proinflammatory cytokines and chemokines, such as tumor necrosis factor (TNF)-α, IL-1β, IL-6, and keratinocyte-derived cytokine; decreased neutrophils; and increased IL-10 and CD11b(+)Gr-1(+) macrophages in the bronchoalveolar lavage fluid of ALI mice. In Gal-9-deficient mice, pathological changes of ALI were exaggerated, and the number of neutrophils and the TNF-α level were increased. CD11b(+)Gr-1(+) cells were increased in the spleen of both Gal-9-treated and phosphate-buffered saline (PBS)-treated ALI mice, but only Gal-9 increased the ability of CCR2-expressing macrophages to migrate toward monocyte chemoattractant protein-1. Transfer of CD11b(+)Gr-1(+) macrophages obtained from Gal-9-treated mice ameliorated ALI. CD11b(+)Gr-1(+) macrophages obtained from Gal-9-treated but not PBS-treated mice suppressed TNF-α and keratinocyte-derived cytokine production from LPS-stimulated macrophages, and down-regulated Toll-like receptor-4 (TLR4) and TLR2 expression on thioglycollate-elicited macrophages. Fluorescence-activated cell-sorting analysis revealed that CD14 is negligible on CD11b(+)Gr-1(+) macrophages obtained from Gal-9-treated mice, although those from both groups resembled plasmacytoid dendritic cells (pDCs). Gal-9 down-regulated CD14 on pDC-like macrophages from PBS-treated mice independently of Gal-9/Tim-3 (T-cell immunoglobulin- and mucin domain-containing molecule-3) interaction, resulting in the acquisition of suppressive function, suggesting that the loss of CD14 by Gal-9 is critical for the suppression of pDC-like macrophages.

CONCLUSIONS

Gal-9 attenuates ALI by expanding CD14(-)CD11b(+)Gr-1(+) pDC-like macrophages by preferentially suppressing macrophage functions to release proinflammatory cytokines through TLR4 and TLR2 down-regulation.

Galectin-9 administration ameliorates CVB3 induced myocarditis by promoting the proliferation of regulatory T cells and alternatively activated Th2 cells

In this study we explored the effects of galectin-9 on CVB3 induced myocarditis and its possible mechanisms involved. We demonstrated that galectin-9 expression was significantly up-regulated in the myocardium following CVB3 infection and was correlated with the severity of viral myocarditis. To explore whether galectin-9 may have therapeutic effect on the CVB3 induced myocarditis, galectin-9 was administered daily to mice following CVB3 infection. Significantly reduced CD4(+) T cells and remarkably increased regulatory T cells frequency in the heart tissue were found as compared to the non-treated mice. It was accompanied by a significant decreased level of Th1 cytokines as TNF-α and IFN-γ both in the myocardium and serum, and an increased level of Th2 cytokines such as IL-4 and IL-10. Galectin-9 was further found to promote the proliferation of regulatory T cells and elevated IL-4-secreting Th2 cells. It may represent as a novel therapeutic strategy in treating Th1-mediated inflammatory cardiac disease.

Coexpression of Tim-3 and PD-1 identifies a CD8+ T-cell exhaustion phenotype in mice with disseminated acute myelogenous leukemia

Tumor-associated immune suppression can lead to defective T cell-mediated antitumor immunity. Here, we identified a unique phenotype of exhausted T cells in mice with advanced acute myelogenous leukemia (AML). This phenotype is characterized by the coexpression of Tim-3 and PD-1 on CD8(+) T cells in the liver, the major first site of AML metastases. PD-1 and Tim-3 coexpression increased during AML progression. PD-1(+)Tim-3(+) CD8(+) T cells were deficient in their ability to produce IFN-γ, TNF-α, and IL-2 in response to PD-1 ligand (PDL1) and Tim-3 ligand (galectin-9) expressing AML cells. PD-1 knockout (KO), which were partially resistant to AML challenge, up-regulated Tim-3 during AML progression and such Tim-3(+)PD-1- KO CD8(+) T cells had reduced cytokine production. Galectin-9 KO mice were more resistant to AML, which was associated with reduced T-regulatory cell accumulation and a modest induction of PD-1 and Tim-3 expression on CD8(+) T cells. Whereas blocking the PD-1/PDL1 or Tim-3/galectin-9 pathway alone was insufficient to rescue mice from AML lethality, an additive effect was seen in reducing-albeit not eliminating-both tumor burden and lethality when both pathways were blocked. Therefore, combined PD-1/PDL1 and Tim-3/galectin-9 blockade may be beneficial in preventing CD8(+) T-cell exhaustion in patients with hematologic malignancies such as advanced AML.

Dysregulation of TIM-3-galectin-9 pathway in the cystic fibrosis airways

The T-cell Ig and mucin domain-containing molecules (TIMs) have emerged as promising therapeutic targets to correct abnormal immune function in several autoimmune and chronic inflammatory conditions. It has been reported that proinflammatory cytokine dysregulation and neutrophil-dominated inflammation are the main causes of morbidity in cystic fibrosis (CF). However, the role of TIM receptors in CF has not been investigated. In this study, we demonstrated that TIM-3 is constitutively overexpressed in the human CF airway, suggesting a link between CF transmembrane conductance regulator (CFTR) function and TIM-3 expression. Blockade of CFTR function with the CFTR inhibitor-172 induced an upregulation of TIM-3 and its ligand galectin-9 in normal bronchial epithelial cells. We also established that TIM-3 serves as a functional receptor in bronchial epithelial cells, and physiologically relevant concentrations of galectin-9 induced TIM-3 phosphorylation, resulting in increased IL-8 production. In addition, we have demonstrated that both TIM-3 and galectin-9 undergo rapid proteolytic degradation in the CF lung, primarily because of neutrophil elastase and proteinase-3 activity. Our results suggest a novel intrinsic defect that may contribute to the neutrophil-dominated immune response in the CF airways.

The road less traveled: regulation of leukocyte migration across vascular and lymphatic endothelium by galectins

Leukocyte entry from the blood into inflamed tissues, exit into the lymphatics, and migration to regional lymph nodes are all crucial processes for mounting an effective adaptive immune response. Leukocytes must cross two endothelial cell layers, the vascular and the lymphatic endothelial cell layers, during the journey from the blood to the lymph node. The proteins and cellular interactions which regulate leukocyte migration across the vascular endothelium are well studied; however, little is known about the factors that regulate leukocyte migration across the lymphatic endothelium. Here, we will summarize evidence for a role for galectins, a family of carbohydrate-binding proteins, in regulating leukocyte migration across the vascular endothelium and propose that galectins are also involved in leukocyte migration across the lymphatic endothelium.

Tim-3/galectin-9 pathway: regulation of Th1 immunity through promotion of CD11b+Ly-6G+ myeloid cells

IFN-gamma plays a central role in antitumor immunity. T cell Ig and mucin domain (Tim-3) is expressed on IFN-gamma-producing Th1 cells; on interaction with its ligand, galectin-9, Th1 immunity is terminated. In this study, we show that transgenic overexpression of Tim-3 on T cells results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Molecular characterization of CD11b(+)Ly-6G(+) cells reveals a phenotype consistent with granulocytic myeloid-derived suppressor cells. Accordingly, we find that modulation of the Tim-3/galectin-9 (Gal-9) pathway impacts on tumor growth. Similarly, overexpression of Tim-3 ligand, Gal-9, results in an increase in CD11b(+)Ly-6G(+) cells and inhibition of immune responses. Loss of Tim-3 restores normal levels of CD11b(+)Ly-6G(+) cells and normal immune responses in Gal-9 transgenic mice. Our data uncover a novel mechanism by which the Tim-3/Gal-9 pathway regulates immune responses and identifies this pathway as a therapeutic target in diseases where myeloid-derived suppressor cells are disadvantageous.

Deletion of lec-10, a galectin-encoding gene, increases susceptibility to oxidative stress in Caenorhabditis elegans

Galectins are a family of beta-galactoside-binding lectins. They are involved in the regulation of a variety of biological phenomena in mammals. However, little is known about their roles in invertebrates. Caenorhabditis elegans is a well-characterized model organism whose complete genome has been sequenced. C. elegans is now being studied extensively in various fields of medical sciences. In this study, we examined the phenotypes of a mutant strain of C. elegans (tm1262) lacking lec-10, a galectin-encoding gene. We observed no difference in the rates of embryonic lethality and larval arrest/slow growth between this mutant strain and the wild-type strain. No apparent morphological defect was observed in the lec-10-deletion mutant (tm1262). Moreover, the life-spans of this mutant and the wild-type strain were equivalent. However, this mutant showed significantly greater susceptibility to paraquat and hydrogen peroxide than the wild type did. The lec-10-deletion mutants (tm1262) were as susceptible as the daf-16-deletion mutants (mu86) to paraquat and hydrogen peroxide. These results suggest that the deletion of lec-10 does not have a notable effect on the worm's survival under laboratory conditions. However, this study indicates that lec-10 does confer some protection against oxidative stress.

Liver membrane proteome glycosylation changes in mice bearing an extra-hepatic tumor

Cancer is well known to be associated with alterations in membrane protein glycosylation (Bird, N. C., Mangnall, D., and Majeed, A. W. (2006) Biology of colorectal liver metastases: A review. J. Surg. Oncol. 94, 68-80; Dimitroff, C. J., Pera, P., Dall'Olio, F., Matta, K. L., Chandrasekaran, E. V., Lau, J. T., and Bernacki, R. J. (1999) Cell surface n-acetylneuraminic acid alpha2,3-galactoside-dependent intercellular adhesion of human colon cancer cells. Biochem. Biophys. Res. Commun. 256, 631-636; and Arcinas, A., Yen, T. Y., Kebebew, E., and Macher, B. A. (2009) Cell surface and secreted protein profiles of human thyroid cancer cell lines reveal distinct glycoprotein patterns. J. Proteome Res. 8, 3958-3968). Equally, it has been well established that tumor-associated inflammation through the release of pro-inflammatory cytokines is a common cause of reduced hepatic drug metabolism and increased toxicity in advanced cancer patients being treated with cytotoxic chemotherapies. However, little is known about the impact of bearing a tumor (and downstream effects like inflammation) on liver membrane protein glycosylation. In this study, proteomic and glycomic analyses were used in combination to determine whether liver membrane protein glycosylation was affected in mice bearing the Engelbreth-Holm Swarm sarcoma. Peptide IPG-IEF and label-free quantitation determined that many enzymes involved in the protein glycosylation pathway specifically; mannosidases (Man1a-I, Man1b-I and Man2a-I), mannoside N-acetylglucosaminyltransferases (Mgat-I and Mgat-II), galactosyltransferases (B3GalT-VII, B4GalT-I, B4GalT-III, C1GalT-I, C1GalT-II, and GalNT-I), and sialyltransferases (ST3Gal-I, ST6Gal-I, and ST6GalNAc-VI) were up-regulated in all livers of tumor-bearing mice (n = 3) compared with nontumor bearing controls (n = 3). In addition, many cell surface lectins: Sialoadhesin-1 (Siglec-1), C-type lectin family 4f (Kupffer cell receptor), and Galactose-binding lectin 9 (Galectin-9) were determined to be up-regulated in the liver of tumor-bearing compared with control mice. Global glycan analysis identified seven N-glycans and two O-glycans that had changed on the liver membrane proteins derived from tumor-bearing mice. Interestingly, α (2,3) sialic acid was found to be up-regulated on the liver membrane of tumor-bearing mice, which reflected the increased expression of its associated sialyltransferase and lectin receptor (siglec-1). The overall increased sialylation on the liver membrane of Engelbreth-Holm Swarm bearing mice correlates with the increased expression of their associated glycosyltransferases and suggests that glycosylation of proteins in the liver plays a role in tumor-induced liver inflammation.

Galectin-9 significantly prolongs the survival of fully mismatched cardiac allografts in mice

BACKGROUND

The involvement of T-cell immunoglobulin mucin-3 (Tim-3) in the regulation of solid organ transplantation rejection is largely unknown. We used galectin-9 (Tim-3 ligand) to evaluate the effect and mechanisms of Tim-3/galectin-9 pathway in an allogeneic heart transplant model.

METHODS

The murine cardiac transplant model from BALB/c (H-2d) to C57BL/6 (H-2b) was built. The recipients were administered with galectin-9 for 7 days from day 1 or day 3 posttransplant. The complete cessation of cardiac contractility was defined as the observation endpoint. The effect of galectin-9 on cell proliferation was assessed by mixed lymphocyte reaction. Histology and immunohistochemistry were performed to estimate the severity of rejection. The phenotype and cytokine profile of lymphocytes were analyzed by flow cytometry.

RESULTS

In vitro, galectin-9 suppressed the proliferation of lymphocytes mixed lymphocyte reactions in a dose- and beta-galactoside-dependent manner. In vivo, galectin-9 treatment from day 1 to day 3 posttransplant achieved similar survival time of grafts (median survival time, 22.7+/-1.2 vs. 23.0+/-1.0 days). The prolonged survival time was associated with reduced infiltration of CD4 and CD8 lymphocytes in allografts. Furthermore, the intragraft transcriptional profiling in galectin-9-treated group showed reduction of IFN-gamma and IL-17 mRNA but elevation of Ebi-3 and galectin-9 mRNA. Flow cytometry analysis indicated that galectin-9 treatment reduced the ratio of T helper (Th) 1 and Th17 cells in the draining lymph nodes and peripheral blood.

CONCLUSIONS

A short-course administration of galectin-9 significantly prolonged the survival of fully allogeneic cardiac allografts, which was associated with the suppression of Th1 and Th17 immune responses.

Galectin-9 ameliorates immune complex-induced arthritis by regulating Fc gamma R expression on macrophages

Galectin-9 up-regulated Fc gamma RIIb expression of mouse peritoneal macrophages in vitro but down-regulated Fc gamma RIII expression. Galectin-9-treated macrophages stimulated with immune complexes (IC) produced less TNFalpha and IL-1 beta but more IL-10 than PBS-treated macrophages. Macrophage enhancing effects on IC-induced C5a and neutrophil chemotactic activity were also diminished for galectin-9-treated macrophages. In galectin-9-treated mice, the severity of IC-induced arthritis was reduced, as were pro-inflammatory cytokine levels in inflamed joints and serum C5a. Fc gamma RIIb expression of macrophages from galectin-9-treated mice was up-regulated, whereas Fc gamma RIII expression was down-regulated. Macrophages from galectin-9-treated mice produced less TNFalpha and IL-1 beta but more IL-10 than PBS-treated mice. Disease severity of galectin-9-transgenic mice was milder than wild-type mice, whereas that of galectin-9-deficient mice was exaggerated. Furthermore, macrophage Fc gamma RIIb expression in galectin-9-deficient mice was down-regulated, while Fc gamma RIII expression was up-regulated. These results suggest that galectin-9 suppresses IC-induced inflammation partly by regulating Fc gamma R expression on macrophages.

Structural features of galectin-9 and galectin-1 that determine distinct T cell death pathways

The galectin family of lectins regulates multiple biologic functions, such as development, inflammation, immunity, and cancer. One common function of several galectins is the ability to trigger T cell death. However, differences among the death pathways triggered by various galectins with regard to glycoprotein receptors, intracellular death pathways, and target cell specificity are not well understood. Specifically, galectin-9 and galectin-1 both kill thymocytes, peripheral T cells, and T cell lines; however, we have found that galectin-9 and galectin-1 require different glycan ligands and glycoprotein receptors to trigger T cell death. The two galectins also utilize different intracellular death pathways, as galectin-9, but not galectin-1, T cell death was blocked by intracellular Bcl-2, whereas galectin-1, but not galectin-9, T cell death was blocked by intracellular galectin-3. Target cell susceptibility also differed between the two galectins, as galectin-9 and galectin-1 killed different subsets of murine thymocytes. To define structural features responsible for distinct activities of the tandem repeat galectin-9 and dimeric galectin-1, we created a series of bivalent constructs with galectin-9 and galectin-1 carbohydrate recognition domains connected by different peptide linkers. We found that the N-terminal carbohydrate recognition domain and linker peptide contributed to the potency of these constructs. However, we found that the C-terminal carbohydrate recognition domain was the primary determinant of receptor recognition, death pathway signaling, and target cell susceptibility. Thus, carbohydrate recognition domain specificity, presentation, and valency make distinct contributions to the specific effects of different galectins in initiating T cell death.