Amelioration of graft versus host disease by galectin-1

Galectin-1 is associated with hematopoietic cell engraftment in murine MHC-mismatched allotransplantation

Haploidentical hematopoietic cell transplantation (haplo-HCT) is associated with an increased risk of allograft rejection. Here, we employed a major histocompatibility complex (MHC)-mismatched allogeneic HCT (allo-HCT) murine model to better understand the role of Gal-1 in immune tolerance. Transplanted mice were classified into either rejected or engrafted based on donor chimerism levels. We noted significantly higher frequencies of CD4+ T cells, CD8+ T cells, natural killer cells, IFN-γ and TNF-α producing CD4+ T cells, and IFN-γ producing dendritic cells and macrophages in rejected mice. Conversely, we found significantly increased frequencies of regulatory T cells (Tregs), predominantly Helios+, IL-10-producing CD4+ T cells, type 1 regulatory (Tr1) cells, and the proportion of Tr1+Gal-1+ cells in engrafted mice. Further, Gal-1 specific blockade in Tregs reduced suppression of effector T cells in engrafted mice. Lastly, effector T cells from engrafted mice were more prone to undergo apoptosis. Collectively, we have shown that Gal-1 may favor HSC engraftment in an MHC-mismatched murine model. Our results demonstrate that Gal-1-expressing Tregs, especially at earlier time points post-transplant, are associated with inducing immune tolerance and stable mixed chimerism after HCT.

Galectin-1: A Traditionally Immunosuppressive Protein Displays Context-Dependent Capacities

Galectin–Carbohydrate interactions are indispensable to pathogen recognition and immune response. Galectin-1, a ubiquitously expressed 14-kDa protein with an evolutionarily conserved β-galactoside binding site, translates glycoconjugate recognition into function. That galectin-1 is demonstrated to induce T cell apoptosis has led to substantial attention to the immunosuppressive properties of this protein, such as inducing naive immune cells to suppressive phenotypes, promoting recruitment of immunosuppressing cells as well as impairing functions of cytotoxic leukocytes. However, only in recent years have studies shown that galectin-1 appears to perform a pro-inflammatory role in certain diseases. In this review, we describe the anti-inflammatory function of galectin-1 and its possible mechanisms and summarize the existing therapies and preclinical efficacy relating to these agents. In the meantime, we also discuss the potential causal factors by which galectin-1 promotes the progression of inflammation.

Galectin-3 expression in donor T cells reduces GvHD severity and lethality after allogeneic hematopoietic cell transplantation

Abundant donor cytotoxic T cells that attack normal host organs remain a major problem for patients receiving allogeneic hematopoietic cell transplantation (allo-HCT). Despite an increase in our knowledge of the pathobiology of acute graft versus host disease (aGvHD), the mechanisms regulating the proliferation and function of donor T cells remain unclear. Here, we show that activated donor T cells express galectin-3 (Gal-3) after allo-HCT. In both major and minor histocompatibility-mismatched models of murine aGvHD, expression of Gal-3 is associated with decreased T cell activation and suppression of the secretion of effector cytokines, including IFN-γ and GM-CSF. Mechanistically, Gal-3 results in activation of NFAT signaling, which can induce T cell exhaustion. Gal-3 overexpression in human T cells prevents severe disease by suppressing cytotoxic T cells in xenogeneic aGvHD models. Together, these data identify the Gal-3-dependent regulatory pathway in donor T cells as a critical component of inflammation in aGvHD.

Galectin functions in cancer-associated inflammation and thrombosis

Galectins are carbohydrate-binding proteins that regulate many cellular functions including proliferation, adhesion, migration, and phagocytosis. Increasing experimental and clinical evidence indicates that galectins influence many steps of cancer development by inducing the recruitment of immune cells to the inflammatory sites and modulating the effector function of neutrophils, monocytes, and lymphocytes. Recent studies described that different isoforms of galectins can induce platelet adhesion, aggregation, and granule release through the interaction with platelet-specific glycoproteins and integrins. Patients with cancer and/or deep-venous thrombosis have increased levels of galectins in the vasculature, suggesting that these proteins could be important contributors to cancer-associated inflammation and thrombosis. In this review, we summarize the pathological role of galectins in inflammatory and thrombotic events, influencing tumor progression and metastasis. We also discuss the potential of anti-cancer therapies targeting galectins in the pathological context of cancer-associated inflammation and thrombosis.

Galectin-1 deletion in mice causes bone loss via impaired osteogenic differentiation potential of BMSCs

Bone formation is dependent on the osteoblasts which are differentiated from bone marrow stromal cells (BMSCs). In addition to potent proliferation, self-renewal, and pluripotent differentiation, BMSCs have been extensively studied due to their low immunogenicity and immunomodulatory effects. Recently, galectin-1 (Gal-1) has been proposed as a potent mediator of immunomodulatory properties of BMSCs. Previous study demonstrated that Gal-1 showed age-related decline in mice serum and serum Gal-1 was positively associated with bone mass in mice. The current study makes attempts to elucidate the functional role of Gal-1 in skeletal system by investigating the regulation of Gal-1 expression during BMSCs osteogenic differentiation and the molecular mechanisms underlying the effects of Gal-1 on BMSCs osteogenic differentiation. In Gal-1 null (-/-) mice, bone loss was observed due to bone formation attenuation. In in vitro experiments, Gal-1 supported the osteogenic differentiation of BMSCs by binding to CD146 to activate Lrp5 expression and Wnt/β-catenin signaling pathway. Meanwhile, there was positive feedback regulation via Wnt/β-catenin signaling to maintain Gal-1 high-level expression during osteogenic differentiation of BMSCs. More importantly, Gal-1 down-regulation in BMSCs and attenuation of osteogenic differentiation potential of BMSCs were observed in aged mice compared with young mice. Gal-1 over-expression could enhance osteogenic differentiation potential of aged BMSCs. Our study will benefit not only for deeper insights into the functional role of Gal-1 but also for finding new targets to modulate BMSCs osteogenic differentiation.

Galectins: An Ancient Family of Carbohydrate Binding Proteins with Modern Functions

Galectins are a large family of carbohydrate binding proteins with members in nearly every lineage of multicellular life. Through tandem and en-mass genome duplications, over 15 known vertebrate galectins likely evolved from a single common ancestor extant in pre-chordate lineages. While galectins have divergently evolved numerous functions, some of which do not involve carbohydrate recognition, the vast majority of the galectins have retained the conserved ability to bind variably modified polylactosamine (polyLacNAc) residues on glycans that modify proteins and lipids on the surface of host cells and pathogens. In addition to their direct role in microbial killing, many proposed galectin functions in the immune system and cancer involve crosslinking glycosylated receptors and modifying signaling pathways or sensitivity to antigen from the outside in. However, a large body of work has uncovered intracellular galectin functions mediated by carbohydrate- and non-carbohydrate-dependent interactions. In the cytoplasm, galectins can tune intracellular kinase and G-protein-coupled signaling cascades important for nutrient sensing, cell cycle progression, and transformation. Particularly, but interconnected pathways, cytoplasmic galectins serve the innate immune system as sensors of endolysosomal damage, recruiting and assembling the components of autophagosomes during intracellular infection through carbohydrate-dependent and -independent activities. In the nucleus, galectins participate in pre-mRNA splicing perhaps through interactions with non-coding RNAs required for assembly of spliceosomes. Together, studies of galectin function paint a picture of a functionally dynamic protein family recruited during eons of evolution to regulate numerous essential cellular processes in the context of multicellular life.

Thrombospondin-1, Platelet Factor 4, and Galectin-1 are Associated with Engraftment in Patients with Sickle Cell Disease Who Underwent Haploidentical HSCT

Sickle cell disease (SCD) is an inherited red blood cell disorder that leads to significant morbidity and early mortality. The most widely available curative approach remains allogeneic hematopoietic stem cell transplantation (HSCT). HLA-haploidentical (haplo) HSCT expands the donor pool considerably and is a practical alternative for these patients, but traditionally with an increased risk of allograft rejection. Biomarkers in patient plasma could potentially help predict HSCT outcome and allow treatment at an early stage to reverse or prevent graft rejection. Reliable, noninvasive methods to predict engraftment or rejection early after HSCT are needed. We sought to detect variations in the plasma proteomes of patients who engrafted compared with those who rejected their grafts. We used a mass spectrometry-based proteomics approach to identify candidate biomarkers associated with engraftment and rejection by comparing plasma samples obtained from 9 engrafted patients and 10 patients who experienced graft rejection. A total of 1378 proteins were identified, 45 of which were differentially expressed in the engrafted group compared with the rejected group. Based on bioinformatics analysis results, information from the literature, and immunoassay availability, 7 proteins-thrombospondin-1 (Tsp-1), platelet factor 4 (Pf-4), talin-1, moesin, cell division control protein 42 homolog (CDC42), galectin-1 (Gal-1), and CD9-were selected for further analysis. We compared these protein concentrations among 35 plasma samples (engrafted, n = 9; rejected, n = 10; healthy volunteers, n = 8; nontransplanted SCD, n = 8). ELISA analysis confirmed the significant up-regulation of Tsp-1, Pf-4, and Gal-1 in plasma samples from engrafted patients compared with rejected patients, healthy African American volunteers, and the nontransplanted SCD group (P < .01). By receiver operating characteristic analysis, these 3 proteins distinguished engrafted patients from the other groups (area under the curve, >0.8; P < .05). We then evaluated the concentration of these 3 proteins in samples collected pre-HSCT and at days +30, +60, +100, and +180 post-HSCT. The results demonstrate that Tsp-1 and Pf-4 stratified engrafted patients as early as day 60 post-HSCT (P < .01), and that Gal-1 was significantly higher in engrafted patients as early as day 30 post-HSCT (P < .01). We also divided the rejected group into those who experienced primary (n = 5) and secondary graft rejection (n = 5) and found that engrafted patients had significantly higher Tsp-1 levels compared with patients who developed primary graft rejection at days +60 and +100 (P < .05), as well as higher Pf-4 levels compared with patients who developed primary graft rejection at post-transplantation (PT) day 100. Furthermore, Tsp-1 levels were significantly higher at PT days 60 and 100 and Pf-4 levels were higher at PT day 100 in engrafted patients compared with those who experienced secondary graft rejection. Increased concentrations of plasma Gal-1, Tsp-1, and Pf-4 could reflect increased T regulatory cells, IL-10, and TGF-β, which are essential players in the initiation of immunologic tolerance. These biomarkers may provide opportunities for preemptive intervention to minimize the incidence of graft rejection.

Resolution of Inflammation in Acute Graft-Versus-Host-Disease: Advances and Perspectives

Inflammation is an essential reaction of the immune system to infections and sterile tissue injury. However, uncontrolled or unresolved inflammation can cause tissue damage and contribute to the pathogenesis of various inflammatory diseases. Resolution of inflammation is driven by endogenous molecules, known as pro-resolving mediators, that contribute to dampening inflammatory responses, promoting the resolution of inflammation and the recovery of tissue homeostasis. These mediators have been shown to be useful to decrease inflammatory responses and tissue damage in various models of inflammatory diseases. Graft-versus-host disease (GVHD) is a major unwanted reaction following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and is characterized by an exacerbated inflammatory response provoked by antigen disparities between transplant recipient and donor. There is no fully effective treatment or prophylaxis for GVHD. This review explores the effects of several pro-resolving mediators and discusses their potential use as novel therapies in the context of GVHD.

Elevated serum galectin-1 concentrations are associated with increased risks of mortality and acute kidney injury in critically ill patients

BACKGROUND

Galectin-1 (Gal-1), a member of the β-galactoside binding protein family, is associated with inflammation and chronic kidney disease. However, the effect of Gal-1 on mortality and acute kidney injury (AKI) in critically-ill patients remain unclear.

METHODS

From May 2018 to March 2020, 350 patients admitted to the medical intensive care unit (ICU) of Taipei Veterans General Hospital, a tertiary medical center, were enrolled in this study. Forty-one patients receiving long-term renal replacement therapy were excluded. Serum Gal-1 levels were determined within 24 h of ICU admission. The patients were divided into tertiles according to their serum Gal-1 levels (low, serum Gal-1 < 39 ng/ml; median, 39-70 ng/ml; high, ≥71 ng/ml). All patients were followed for 90 days or until death.

RESULTS

Mortality in the ICU and at 90 days was greater among patients with elevated serum Gal-1 levels. In analyses adjusted for the body mass index, malignancy, sepsis, Sequential Organ Failure Assessment (SOFA) score, and serum lactate level, the serum Gal-1 level remained an independent predictor of 90-day mortality [median vs. low: adjusted hazard ratio (aHR) 2.11, 95% confidence interval (CI) 1.24-3.60, p = 0.006; high vs. low: aHR 3.21, 95% CI 1.90-5.42, p < 0.001]. Higher serum Gal-1 levels were also associated with a higher incidence of AKI within 48 h after ICU admission, independent of the SOFA score and renal function (median vs. low: aHR 2.77, 95% CI 1.21-6.34, p = 0.016; high vs. low: aHR 2.88, 95% CI 1.20-6.88, p = 0.017). The results were consistent among different subgroups with high and low Gal-1 levels.

CONCLUSION

Serum Gal-1 elevation at the time of ICU admission were associated with an increased risk of mortality at 90 days, and an increased incidence of AKI within 48 h after ICU admission.

Structure-based identification of galectin-1 selective modulators in dietary food polyphenols: a pharmacoinformatics approach

Abstract

In this study, a set of dietary polyphenols was comprehensively studied for the selective identification of the potential inhibitors/modulators for galectin-1. Galectin-1 is a potent prognostic indicator of tumor progression and a highly regarded therapeutic target for various pathological conditions. This indicator is composed of a highly conserved carbohydrate recognition domain (CRD) that accounts for the binding affinity of β-galactosides. Although some small molecules have been identified as galectin-1 inhibitors/modulators, there are limited studies on the identification of novel compounds against this attractive therapeutic target. The extensive computational techniques include potential drug binding site recognition on galectin-1, binding affinity predictions of ~ 500 polyphenols, molecular docking, and dynamic simulations of galectin-1 with selective dietary polyphenol modulators, followed by the estimation of binding free energy for the identification of dietary polyphenol-based galectin-1 modulators. Initially, a deep neural network-based algorithm was utilized for the prediction of the druggable binding site and binding affinity. Thereafter, the intermolecular interactions of the polyphenol compounds with galectin-1 were critically explored through the extra-precision docking technique. Further, the stability of the interaction was evaluated through the conventional atomistic 100 ns dynamic simulation study. The docking analyses indicated the high interaction affinity of different amino acids at the CRD region of galectin-1 with the proposed five polyphenols. Strong and consistent interaction stability was suggested from the simulation trajectories of the selected dietary polyphenol under the dynamic conditions. Also, the conserved residue (His44, Asn46, Arg48, Val59, Asn61, Trp68, Glu71, and Arg73) associations suggest high affinity and selectivity of polyphenols toward galectin-1 protein.

Graphic Abstract

Increased Severity of Ulcerative Colitis in the Terminal Phase of the Metabolic Syndrome

Ulcerative colitis is chronic immune-mediated disorder that affects primarily colonic mucosa. The metabolic syndrome has increasing global prevalence with a significant impact on biology of chronic diseases, such as ulcerative colitis. Today it is known that the metabolic syndrome attenuates severity of ulcerative colitis. Still, there is no evidence that different stages of metabolic syndrome alter the course of the ulcerative colitis. The aim of this study was to dissect out how progression of the metabolic syndrome impacted the biology of ulcerative colitis and severity of clinical presentation. Seventy-two patients (41 men and 31 women, 22-81 years old) were enrolled in this observational cross-sectional study. Concentrations of pro- and anti-inflammatory cytokines in serum and feces samples were measured and phenotype of colon infiltrating cells was analyzed. Patients in the terminal phase of the metabolic syndrome have clinically and pathohistologically more severe form of ulcerative colitis, which is followed by decreased concentrations of systemic galectin-1, increased values of systemic pro-inflammatory mediators and increased influx of lymphocytes in affected colon tissue. Our data suggest that reduced concentrations of galectin-1 and predomination of the pro-inflammatory mediators in patients with terminal stage of the metabolic syndrome enhance local chronic inflammatory response and subsequent tissue damage, and together point on important role of galectin-1 in immune response in ulcerative colitis patients with the metabolic syndrome.

A chimeric, multivalent assembly of galectin-1 and galectin-3 with enhanced extracellular activity

Galectins are attractive therapeutic candidates to control aberrant immune system activation because they can alter the phenotype and function of various innate and adaptive immune cells. However, use of exogenous galectin-1 ("G1") and galectin-3 ("G3") as immunomodulators is challenged by their high dosing requirements and dynamic quaternary structures. Here we report a chimeric assembly of G1 and G3 with enhanced extracellular activity ("G1/G3 Zipper"), which was created by recombinant fusion of G1 and G3 via a peptide linker that forms a two-stranded α-helical coiled-coil. G1/G3 Zipper had higher apparent binding affinity for immobilized lactose and a lower concentration threshold for inducing soluble glycoprotein crosslinking than G1, a recombinant fusion of G1 and G3 with a flexible peptide linker ("G1/G3"), or a recently reported stable G1 dimer crosslinked by poly(ethylene glycol) diacrylate ("G1-PEG-G1"). As a result, G1/G3 Zipper was more effective at inducing Jurkat T cell apoptosis in media containing serum, and was the only variant that could induce apoptosis at low concentrations under serum-free conditions. The monomeric G1/G3 fusion protein lacked extracellular activity under all conditions tested, suggesting that the enhanced activity of G1/G3 Zipper was due to its quaternary structure and increased carbohydrate-recognition domain valency. Thus, combining G1 and G3 into a non-native chimeric assembly provides a new candidate therapeutic with greater immunomodulatory potency than the wild-type proteins and previously reported engineered variants.

An ex vivo abomasal ovine model to study the immediate immune response in the context of Haemonchus contortus larval-stage

We have set up an ex vivo ovine abomasal model, which can mimic the multicellular process to explore the early steps in haemonchine nematode infection using RNA-seq technology. Ovine abomasal explants were collected for histological and transcriptional analysis and supernatants collected to quantitate lactate dehydrogenase (LDH) enzymes. Atotal of 233 were substantially induced genes between L₄-inoculated and uninoculated-control tissues, respectively. However, a total of 14 were considerably down-regulated genes between the 51 aforementioned tissues. Fifteen pathways were annotated by Kyoto Encyclopedia of Genes, and Genomes pathway analysis accounted for the significant percentage in immediate response to larval-stage of H. contortus. Key genes upregulated in response to the addition of L₄-inoculum of H. contortus were IL-6, IL-8, C1q, Atypical chemokine receptor-3, chemokine ligand-2, manganese superoxide dismutase, integrin alpha-7, -8, -9, integrin subunit beta-1, integrin subunit beta 6, intercellular adhesion molecule-1 and actin alpha-1. This study shows for the first time that galectin-1 is up-regulated in an ex vivo abomasal segment model exposed to L₄-inoculum of H. contortus following 6 h of incubation. The abomasal segment model has been shown to be a suitable tool to study the haemonchine larval-stage effects on the ovine abomasal tissues prior to in vivo assessment.

An ex vivo ruminal ovine model to study the immediate immune response in the context of bacterial lipopolysaccharide

We have set up an ex vivo ovine ruminal model, which can mimic the multicellular process to explore the early steps in Salmonella typhimurium lipopolysaccharide (LPS) stimulation using RNA-seq technology. Ovine ruminal explants were collected for histological and transcriptional analysis and supernatants collected to quantitate lactate dehydrogenase (LDH) enzymes. A total of 8 and 523 genes were significantly over-expressed between LPS-treated and control tissues at 6 and 12 h, respectively. However, six and seven hundred and thirteen genes were substantially repressed between the aforementioned tissues, correspondingly. Key genes up-regulated in response to the addition of LPS were tumor necrosis factor (TNF), interlukin (IL)-1 beta(b), IL-6, IL-8, IL-17B, IL-19, MMP-1, MMP-3, and integrin alpha 2 (ITGA8, 9). This study shows for the first time that galectin-1 is up-regulated in an ex vivo ruminal segment model exposed to bacterial lipopolysaccharide following 6 h of incubation. The ruminal segment model has been shown to be a suitable tool to study the bacterial lipopolysaccharide effects on the ovine ruminal tissues prior to in vivo assessment.

Immunomodulatory activity of glycodelin: implications in allograft rejection

Glycodelin is an immunomodulator, indispensable for the maintenance of pregnancy in humans. The glycoprotein induces apoptosis in activated CD4⁺ T cells, monocytes and natural killer (NK) cells, and suppresses the activity of cytotoxic T cells, macrophages and dendritic cells. This study explores the immunosuppressive property of glycodelin for its possible use in preventing graft rejection. Because glycodelin is found only in certain primates, the hypothesis was investigated in an allograft nude mouse model. It is demonstrated that treatment of alloactivated mononuclear cells with glycodelin thwarts graft rejection. Glycodelin decreases the number of activated CD4⁺ and CD8⁺ cells and down-regulates the expression of key proteins known to be involved in graft demise such as granzyme-B, eomesodermin (EOMES), interleukin (IL)-2 and proinflammatory cytokines [tumour necrosis factor (TNF)-α and IL-6], resulting in a weakened cell-mediated immune response. Immunosuppressive drugs for treating allograft rejection are associated with severe side effects. Glycodelin, a natural immunomodulator in humans, would be an ideal alternative candidate.

Galectin-1 and galectin-3 expression in equine mesenchymal stromal cells (MSCs), synovial fibroblasts and chondrocytes, and the effect of inflammation on MSC motility

Background

Mesenchymal stromal cells (MSCs) can be used intra-articularly to quell inflammation and promote cartilage healing; however, mechanisms by which MSCs mitigate joint disease remain poorly understood. Galectins, a family of β-galactoside binding proteins, regulate inflammation, adhesion and cell migration in diverse cell types. Galectin-1 and galectin-3 are proposed to be important intra-articular modulators of inflammation in both osteoarthritis and rheumatoid arthritis. Here, we asked whether equine bone marrow-derived MSCs (BMSCs) express higher levels of galectin-1 and -3 relative to synovial fibroblasts and chondrocytes and if an inflammatory environment affects BMSC galectin expression and motility.

Methods

Equine galectin-1 and -3 gene expression was quantified using qRT-PCR in cultured BMSCs, synoviocytes and articular chondrocytes, in addition to synovial membrane and articular cartilage tissues. Galectin gene expression, protein expression, and protein secretion were measured in equine BMSCs following exposure to inflammatory cytokines (IL-1β 5 and 10 ng/mL, TNF-α 25 and 50 ng/mL, or LPS 0.1, 1, 10 and 50 μg/mL). BMSC focal adhesion formation was assessed using confocal microscopy, and BMSC motility was quantified in the presence of inflammatory cytokines (IL-1β or TNF-α) and the pan-galectin inhibitor β-lactose (100 and 200 mM).

Results

Equine BMSCs expressed 3-fold higher galectin-1 mRNA levels as compared to cultured synovial fibroblasts (p = 0.0005) and 30-fold higher galectin-1 (p < 0.0001) relative to cultured chondrocytes. BMSC galectin-1 mRNA expression was significantly increased as compared to carpal synovial membrane and articular cartilage tissues (p < 0.0001). IL-1β and TNF-α treatments decreased BMSC galectin gene expression and impaired BMSC motility in dose-dependent fashion but did not alter galectin protein expression. β-lactose abrogated BMSC focal adhesion formation and inhibited BMSC motility.

Conclusions

Equine BMSCs constitutively express high levels of galectin-1 mRNA relative to other articular cell types, suggesting a possible mechanism for their intra-articular immunomodulatory properties. BMSC galectin expression and motility are impaired in an inflammatory environment, which may limit tissue repair properties following intra-articular administration. β-lactose-mediated galectin inhibition also impaired BMSC adhesion and motility. Further investigation into the effects of joint inflammation on BMSC function and the potential therapeutic effects of BMSC galectin expression in OA is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0691-2) contains supplementary material, which is available to authorized users.

Galectin-1 Impairs the Generation of Anti-Parasitic Th1 Cell Responses in the Liver during Experimental Visceral Leishmaniasis

Many infectious diseases are characterized by the development of immunoregulatory pathways that contribute to pathogen persistence and associated disease symptoms. In diseases caused by intracellular parasites, such as visceral leishmaniasis (VL), various immune modulators have the capacity to negatively impact protective CD4⁺ T cell functions. Galectin-1 is widely expressed on immune cells and has previously been shown to suppress inflammatory responses and promote the development of CD4⁺ T cells with immunoregulatory characteristics. Here, we investigated the role of galectin-1 in experimental VL caused by infection of C57BL/6 mice with Leishmania donovani. Mice lacking galectin-1 expression exhibited enhanced tissue-specific control of parasite growth in the liver, associated with an augmented Th1 cell response. However, unlike reports in other experimental models, we found little role for galectin-1 in the generation of IL-10-producing Th1 (Tr1) cells, and instead report that galectin-1 suppressed hepatic Th1 cell development. Furthermore, we found relatively early effects of galectin-1 deficiency on parasite growth, suggesting involvement of innate immune cells. However, experiments investigating the impact of galectin-1 deficiency on dendritic cells indicated that they were not responsible for the phenotypes observed in galectin-1-deficient mice. Instead, studies examining galectin-1 expression by CD4⁺ T cells supported a T cell intrinsic role for galectin-1 in the suppression of hepatic Th1 cell development during experimental VL. Together, our findings provide new information on the roles of galectin-1 during parasitic infection and indicate an important role for this molecule in tissue-specific Th1 cell development, but not CD4⁺ T cell IL-10 production.

Serum galectin-1 levels are positively correlated with body fat and negatively with fasting glucose in obese children

Galectin-1, a recently identified peptide, is primarily released from the adipose tissue. Although galectin-1 was shown to have an anti-inflammatory effect, its specific function is not clearly understood. We aimed to evaluate the relationship of serum galectin-1 levels with clinical and laboratory parameters in childhood obesity. A total of 45 obese children (mean age: 12.1±3.1years) and 35 normal-weight children (mean age: 11.8±2.2years) were enrolled. Clinical [body mass index (BMI), waist circumference (WC), percentage of body fat and blood pressure] and biochemical [glucose, insulin, lipids, galectin-1, high-sensitive C-reactive protein (hsCRP) and leptin levels] parameters were assessed. Serum galectin-1, hsCRP and leptin levels were significantly higher in obese children than those in normal-weight children (12.4 vs 10.2ng/mL, p<0.001; 3.28 vs 0.63mg/L, p<0.001; 8.3 vs 1.2ng/mL, p<0.001, respectively). In obese children, galectin-1 levels correlated negatively with fasting glucose (r=-0.346, p=0.020) and positively with fat mass (r=0.326, p=0.026) and WC standard deviation score (SDS) (r=0.451, p=0.002). The multivariate regression analysis demonstrated that serum galectin-1 levels were significantly associated with fasting glucose and WC SDS. This study showed that obese children had significantly higher galectin-1 levels in proportion to fat mass in obese cases than those in healthy children, which may be interpreted as a compensatory increase in an attempt to improve glucose metabolism.

Mesenchymal stem cells and their immunosuppressive role in transplantation tolerance

Since they were first described, mesenchymal stem cells (MSCs) have been shown to have important effector mechanisms and the potential for use in cell therapy. A great deal of research has been focused on unveiling how MSCs contribute to anti-inflammatory responses, including describing several cell populations involved and identifying soluble and other effector molecules. In this review, we discuss some of the contemporary evidence for use of MSCs in the field of immune tolerance, with a special emphasis on transplantation. Although considerable effort has been devoted to understanding the biological function of MSCs, additional resources are required to clarify the mechanisms of their induction of immune tolerance, which will undoubtedly lead to improved clinical outcomes for MSC-based therapies.

Engineering galectin-glycan interactions for immunotherapy and immunomodulation

Galectins, a 15-member family of soluble carbohydrate-binding proteins, are receiving increasing interest as therapeutic targets for immunotherapy and immunomodulation due to their role as extracellular signals that regulate innate and adaptive immune cell phenotype and function. However, different galectins can have redundant, synergistic, or antagonistic signaling activity in normal immunological responses, such as resolution of inflammation and induction of antigen-specific tolerance. In addition, certain galectins can be hijacked to promote progression of immunopathologies, such as tumor immune privilege, metastasis, and viral infection, while others can inhibit these processes. Thus, eliciting a desired immunological outcome will likely necessitate therapeutics that can precisely enhance or inhibit particular galectin-glycan interactions. Multivalency is an important determinant of the affinity and specificity of natural galectin-glycan interactions, and is emerging as a key design element for therapeutics that can effectively manipulate galectin bioactivity. This minireview surveys current molecular and biomaterial engineering approaches to create therapeutics that can stabilize galectin multivalency or recapitulate natural glycan multivalency (i.e. "the glycocluster effect"). In particular, we highlight examples of using natural and engineered multivalent galectins for immunosuppression and immune tolerance, with a particular emphasis on treating autoimmune diseases or avoiding transplant rejection. In addition, we present examples of multivalent inhibitors of galectin-glycan interactions to maintain or restore T-cell function, with a particular emphasis on promoting antitumor immunity. Finally, we discuss emerging opportunities to further engineer galectin-glycan interactions for immunotherapy and immunomodulation.

Systemic lupus erythematosus in the light of the regulatory effects of galectin-1 on T-cell function

Galectin-1 is an endogenous immunoregulatory lectin-type protein. Its most important effects are the inhibition of the differentiation and cytokine production of Th1 and Th17 cells, and the induction of apoptosis of activated T-cells. Galectin-1 has been identified as a key molecule in antitumor immune surveillance, and data are accumulating about the pathogenic role of its deficiency, and the beneficial effects of its administration in various autoimmune disease models. Initial animal and human studies strongly suggest deficiencies in both galectin-1 production and responsiveness in systemic lupus erythematosus (SLE) T-cells. Since lupus features widespread abnormalities in T-cell activation, differentiation and viability, in this review the authors wished to highlight potential points in T-cell signalling processes that may be influenced by galectin-1. These points include GM-1 ganglioside-mediated lipid raft aggregation, early activation signalling steps involving p56Lck, the exchange of the CD3 ζ-ZAP-70 to the FcRγ-Syk pathway, defective mitogen-activated protein kinase pathway activation, impaired regulatory T-cell function, the failure to suppress the activity of interleukin 17 (IL-17) producing T-cells, and decreased suppression of the PI3K-mTOR pathway by phosphatase and tensin homolog (PTEN). These findings place galectin-1 into the group of potential pathogenic molecules in SLE.

Galectin-1 inhibitors and their potential therapeutic applications: a patent review

INTRODUCTION

Galectins have affinity for β-galactosides. Human galectin-1 is ubiquitously expressed in the body and its expression level can be a marker in disease. Targeted inhibition of galectin-1 gives potential for treatment of inflammatory disorders and anti-cancer therapeutics.

AREAS COVERED

This review discusses progress in galectin-1 inhibitor discovery and development. Patent applications pertaining to galectin-1 inhibitors are categorised as monovalent- and multivalent-carbohydrate-based inhibitors, peptides- and peptidomimetics. Furthermore, the potential of galectin-1 protein as a therapeutic is discussed along with consideration of the unique challenges that galectin-1 presents, including its monomer-dimer equilibrium and oxidized and reduced forms, with regard to delivering an intact protein to a pathologically relevant site.

EXPERT OPINION

Significant evidence implicates galectin-1's involvement in cancer progression, inflammation, and host-pathogen interactions. Conserved sequence similarity of the carbohydrate-binding sites of different galectins makes design of specific antagonists (blocking agents/inhibitors of function) difficult. Key challenges pertaining to the therapeutic use of galectin-1 are its monomer-dimer equilibrium, its redox state, and delivery of intact galectin-1 to the desired site. Developing modified forms of galectin-1 has resulted in increased stability and functional potency. Gene and protein therapy approaches that deliver the protein toward the target are under exploration as is exploitation of different inhibitor scaffolds.

Galectin-1 in stable liver transplant recipients

INTRODUCTION

The achievement of a state of tolerance and minimization of the immunosuppressive load form part of the "Holy Grail" in solid organ transplantation. Galectin-1 recently has been described to be involved in the maintenance of a tolerant environment, but there is no evidence of its role in human liver transplantation. The aim of our study was to measure the serum levels of galectin-1 in stable liver transplant recipients.

METHODS

Serum levels of galectin-1 were determined in 30 stable liver transplant recipients who had been free of rejection episodes for at least 8 years. Fifteen patients with an acute rejection episode and 34 healthy subjects were used as the control group.

RESULTS

The concentrations of galectin-1 were significantly higher in stable liver transplant recipients compared with healthy subjects and with the acute rejection group.

CONCLUSIONS

These preliminary results indicate that galectin-1 is upregulated in stable liver transplant recipients. Thus, our results extend the recent findings that galectin-1 may play an immune-suppressive role in liver transplantation. It remains to be established whether it might help to induce tolerance in liver transplantation.

Re-wiring regulatory cell networks in immunity by galectin-glycan interactions

Programs that control immune cell homeostasis are orchestrated through the coordinated action of a number of regulatory cell populations, including regulatory T cells, regulatory B cells, myeloid-derived suppressor cells, alternatively-activated macrophages and tolerogenic dendritic cells. These regulatory cell populations can prevent harmful inflammation following completion of protective responses and thwart the development of autoimmune pathology. However, they also have a detrimental role in cancer by favoring escape from immune surveillance. One of the hallmarks of regulatory cells is their remarkable plasticity as they can be positively or negatively modulated by a plethora of cytokines, growth factors and co-stimulatory signals that tailor their differentiation, stability and survival. Here we focus on the emerging roles of galectins, a family of highly conserved glycan-binding proteins in regulating the fate and function of regulatory immune cell populations, both of lymphoid and myeloid origins. Given the broad distribution of circulating and tissue-specific galectins, understanding the relevance of lectin-glycan interactions in shaping regulatory cell compartments will contribute to the design of novel therapeutic strategies aimed at modulating their function in a broad range of immunological disorders.

Galectin-1 regulates tissue exit of specific dendritic cell populations

During inflammation, dendritic cells emigrate from inflamed tissue across the lymphatic endothelium into the lymphatic vasculature and travel to regional lymph nodes to initiate immune responses. However, the processes that regulate dendritic cell tissue egress and migration across the lymphatic endothelium are not well defined. The mammalian lectin galectin-1 is highly expressed by vascular endothelial cells in inflamed tissue and has been shown to regulate immune cell tissue entry into inflamed tissue. Here, we show that galectin-1 is also highly expressed by human lymphatic endothelial cells, and deposition of galectin-1 in extracellular matrix selectively regulates migration of specific human dendritic cell subsets. The presence of galectin-1 inhibits migration of immunogenic dendritic cells through the extracellular matrix and across lymphatic endothelial cells, but it has no effect on migration of tolerogenic dendritic cells. The major galectin-1 counter-receptor on both dendritic cell populations is the cell surface mucin CD43; differential core 2 O-glycosylation of CD43 between immunogenic dendritic cells and tolerogenic dendritic cells appears to contribute to the differential effect of galectin-1 on migration. Binding of galectin-1 to immunogenic dendritic cells reduces phosphorylation and activity of the protein-tyrosine kinase Pyk2, an effect that may also contribute to reduced migration of this subset. In a murine lymphedema model, galectin-1(-/-) animals had increased numbers of migratory dendritic cells in draining lymph nodes, specifically dendritic cells with an immunogenic phenotype. These findings define a novel role for galectin-1 in inhibiting tissue emigration of immunogenic, but not tolerogenic, dendritic cells, providing an additional mechanism by which galectin-1 can dampen immune responses.

Self-assembled glycopeptide nanofibers as modulators of galectin-1 bioactivity

Galectins are carbohydrate-binding proteins that act as extracellular signaling molecules in various normal and pathological processes. Galectin bioactivity is mediated by specific non-covalent interactions with cell-surface and extracellular matrix (ECM) glycoproteins, which can enhance or inhibit signaling events that influence various cellular behaviors, including adhesion, proliferation, differentiation, and apoptosis. Here, we developed a materials approach to modulate galectin bioactivity by mimicking natural galectin-glycoprotein interactions. Specifically, we created a variant of a peptide that self-assembles into β-sheet nanofibers under aqueous conditions, QQKFQFQFEQQ (Q11), which has an asparagine residue modified with the monosaccharide N-acetylglucosamine (GlcNAc) at its N-terminus (GlcNAc-Q11). GlcNAc-Q11 self-assembled into β-sheet nanofibers under similar conditions as Q11. Nanofibrillar GlcNAc moieties were efficiently converted to the galectin-binding disaccharide N-acetyllactosamine (LacNAc) via the enzyme β-1,4-galactosyltransferase and the sugar donor UDP-galactose, while retaining β-sheet structure and nanofiber morphology. LacNAc-Q11 nanofibers bound galectin-1 and -3 in a LacNAc concentration-dependent manner, although nanofibers bound galectin-1 with higher affinity than galectin-3. In contrast, galectin-1 bound weakly to GlcNAc-Q11 nanofibers, while no galectin-3 binding to these nanofibers was observed. Galectin-1 binding to LacNAc-Q11 nanofibers was specific because it could be inhibited by excess soluble β-lactose, a galectin-binding carbohydrate. LacNAc-Q11 nanofibers inhibited galectin-1-mediated apoptosis of Jurkat T cells in a LacNAc concentration-dependent manner, but were unable to inhibit galectin-3 activity, consistent with galectin-binding affinity of the nanofibers. We envision that glycopeptide nanofibers capable of modulating galectin-1 bioactivity will be broadly useful as biomaterials for various medical applications, including cancer therapeutics, immunotherapy, tissue regeneration, and viral prophylaxis.

Evolving mechanistic insights into galectin functions

Galectins are an evolutionarily ancient family of glycan-binding proteins (GBPs) and are found in all animals. Although they were discovered over 30 years ago, ideas about their biological functions continue to evolve. Current evidence indicates that galectins, which are the only known GBPs that occur free in the cytoplasm and extracellularly, are involved in a variety of intracellular and extracellular pathways contributing to homeostasis, cellular turnover, cell adhesion, and immunity. Here we review evolving insights into galectin biology from a historical perspective and explore current evidence regarding biological roles of galectins.

The leukocyte activation receptor CD69 controls T cell differentiation through its interaction with galectin-1

CD69 is involved in immune cell homeostasis, regulating the T cell-mediated immune response through the control of Th17 cell differentiation. However, natural ligands for CD69 have not yet been described. Using recombinant fusion proteins containing the extracellular domain of CD69, we have detected the presence of a ligand(s) for CD69 on human dendritic cells (DCs). Pulldown followed by mass spectrometry analyses of CD69-binding moieties on DCs identified galectin-1 as a CD69 counterreceptor. Surface plasmon resonance and anti-CD69 blocking analyses demonstrated a direct and specific interaction between CD69 and galectin-1 that was carbohydrate dependent. Functional assays with both human and mouse T cells demonstrated the role of CD69 in the negative effect of galectin-1 on Th17 differentiation. Our findings identify CD69 and galectin-1 to be a novel regulatory receptor-ligand pair that modulates Th17 effector cell differentiation and function.

Transcriptional and metabolic pre-B cell receptor-mediated checkpoints: implications for autoimmune diseases

At the pre-B cell stage of lymphocyte development, immunoglobulin light-chains are not yet produced, and heavy-chains are covalently linked to surrogate light-chains composed of VpreB and λ5 to form the pre-B cell receptor (pre-BCR) in a non-covalent association with signal-transducing modules. Even tough the pre-BCR does not have the potential to bind conventional antigens, accumulating evidence indicates that pre-BCR-mediated checkpoints are important both for negative and positive selection of self-reactivity, and that defects in these regulatory nodes may be associated with autoimmune disease. Thus, the transcription factor BACH2, which represents a susceptibility locus for rheumatoid arthritis, has recently emerged as a crucial mediator of negative selection at a pre-BCR checkpoint. The lysosome-associated protein LAPTM5, which is highly expressed in an animal model of Sjögren's syndrome, plays a role in down-modulation of the pre-BCR. Studies of copy number variation in rheumatoid arthritis suggest that a reduced dosage of the VPREB1 gene is involved in disease pathogenesis. Notably, animal models of autoimmune disease exhibit defects in pre-B to naïve B cell checkpoints. Administration of a pre-BCR ligand, which also plays a role in anergy both in human and murine B lymphocytes, ameliorates disease in experimental models of autoimmunity. Further investigation is required to gain a better insight into the molecular mechanisms of pre-BCR-mediated checkpoints and to determine their relevance to autoimmune diseases.

Proliferation rate of stem cells derived from human dental pulp and identification of differentially expressed genes

Stem cells from human exfoliated deciduous teeth (SHED) and dental pulp stem cells (DPSCs) obtained from the dental pulp of human extracted tooth were cultured and characterized to confirm that these were mesenchymal stem cells. The proliferation rate was assessed using AlamarBlue® cell assay. The differentially expressed genes in SHED and DPSCs were identified using the GeneFishing™ technique. The proliferation rate of SHED (P < 0.05) was significantly higher than DPSCs while SHED had a lower multiplication rate and shorter population doubling time (0.01429, 60.57 h) than DPSCs (0.00286, 472.43 h). Two bands were highly expressed in SHED and three bands in DPSCs. Sequencing analysis showed these to be TIMP metallopeptidase inhibitor 1 (TIMP1), and ribosomal protein s8, (RPS8) in SHED and collagen, type I, alpha 1, (COL1A1), follistatin-like 1 (FSTL1), lectin, galactoside-binding, soluble, 1, (LGALS1) in DPSCs. TIMP1 is involved in degradation of the extracellular matrix, cell proliferation and anti-apoptotic function and RPS8 is involved as a rate-limiting factor in translational regulation; COL1A1 is involved in the resistance and elasticity of the tissues; FSTL1 is an autoantigen associated with rheumatoid arthritis; LGALS1 is involved in cell growth, differentiation, adhesion, RNA processing, apoptosis and malignant transformation. This, along with further protein expression analysis, holds promise in tissue engineering and regenerative medicine.

Lack of galectin-1 or galectin-3 alters B cell deletion and anergy in an autoantibody transgene model

Members of the galectin family of proteins have been shown to regulate the development and the function of immune cells. We previously identified the increased expression of galectin-1 and galectin-3 mRNA and protein in anergic B cells relative to their naïve counterparts. To investigate the role of these galectins in maintaining B cell tolerance, we crossed mice deficient in galectin-1 or galectin-3 with mice bearing a lupus autoantigen-binding transgenic (Tg) B cell receptor, using a model with a well-characterized B cell tolerance phenotype of deletion, receptor editing and anergy. Here, we present data showing that the global knockout of galectin-1 or galectin-3 yields subtle alterations in B cell fate in autoantibody Tg mice. The absence of galectin-3 leads to a significant increase in the number of Tg spleen B cells, with the recovery of anti-laminin antibodies from a subset of mice. The B cell number increases further in antibody Tg mice with the dual deficiency of both galectin-1 and galectin-3. Isolated galectin-1 deficiency significantly enhances the proliferation of Tg B cells in response to lipopolysaccharide stimulation. These findings add to the growing body of evidence indicating a role for the various galectin family members, and for galectins 1 and 3 in particular, in the regulation of autoimmunity.

Galectin-1 prolongs survival of mouse liver allografts from Flt3L-pretreated donors

Liver allografts are spontaneously accepted across MHC barriers in mice. The mechanisms underlying this phenomenon remain poorly understood. Galectin-1, an endogenous lectin expressed in lymphoid organs, plays a vital role in maintaining central and peripheral tolerance. This study was to investigate the role of galectin-1 in spontaneous tolerance of liver allografts in mice, and to evaluate the therapeutic effects of galectin-1 on liver allograft rejection induced by donor Flt3L pretreatment. Blockade of the galectin-1 pathway via neutralizing antigalectin-1 mAb did not affect survival of the liver allografts from B6 donors into C3H recipients. Administration of rGal-1 significantly prolonged survival of liver allografts from Flt3L-pretreated donors and ameliorated Flt3L-triggered liver allograft rejection. This effect was associated with increased apoptosis of T cells in both allografts and spleens, decreased frequencies of Th1 and Th17 cells, decreased expression of Th1-associated cytokines (IL-12, IL-2 and IFN-γ), Th17-associated cytokines (IL-23 and IL-17) and granzyme B, in parallel with selectively increased IL-10 expression in liver allografts. In vitro, galectin-1 inhibited Flt3L-differentiated DC-mediated proliferation of allo-CD4(+) T cells and production of IFN-γ and IL-17. These data provide new evidence of the potential regulatory effects of galectin-1 in alloimmune responses in a murine model of liver transplantation.

Galectins in the Pathogenesis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a complex and common systemic autoimmune disease characterized by synovial inflammation and hyperplasia. Multiple proteins, cells, and pathways have been identified to contribute to the pathogenesis of RA. Galectins are a group of lectins that bind to β-galactoside carbohydrates on the cell surface and in the extracellular matrix. They are expressed in a wide variety of tissues and organs with the highest expression in the immune system. Galectins are potent immune regulators and modulate a range of pathological processes, such as inflammation, autoimmunity, and cancer. Accumulated evidence shows that several family members of galectins play positive or negative roles in the disease development of RA, through their effects on T and B lymphocytes, myeloid lineage cells, and fibroblast-like synoviocytes. In this review, we will summarize the function of different galectins in immune modulation and their distinct roles in RA pathogenesis.

Absence of Galectin-1 accelerates CD8⁺ T cell-mediated graft rejection

Galectin-1 (Gal-1) is a member of a family of endogenous β-galactose-binding proteins with a role in preventing autoimmune diseases and chronic inflammation. In this study, the involvement of Gal-1 in graft rejection was investigated by using Gal-1-deficient mice (Gal-1⁻/⁻). We demonstrate that in the absence of Gal-1, skin grafts are rejected earlier compared with those of WT mice, and that this is due to the role played by CD8⁺ T cells in graft rejection. The difference in graft survival observed between Gal-1⁻/⁻ and WT mice was explained by both an increase in the percentage of antigen-specific CD8+ T cells and by preferential secretion of IFN-γ and IL-17 by CD8⁺ T cells in Gal-1⁻/⁻ mice compared with WT mice. This study suggests that endogenous expression of Gal-1 contributes to graft survival. The results obtained from the use of mice deficient in Gal-1 also confirm a key role for CD8⁺ T cells in graft rejection.

Prevalence of intracellular galectin-1-expressing lymphocytes in umbilical cord blood in comparison with adult peripheral blood

Umbilical cord blood (UCB) is a promising alternative for the treatment of hematological malignancies. The lower immune reactivity of UCB lymphocytes is a well-known phenomenon; however, immune tolerance mechanisms are not fully elucidated. Galectin-1 has strong immunosuppressive properties and plays a key role in the regulation of immune reactivity. We aimed to determine the properties of intracellular galectin-1 (Gal-1)-producing cells within CD3, CD4, CD8, regulatory T (Treg), and natural killer (NK) cells in UCB compared to adult peripheral blood (APB). We took peripheral blood samples from 22 healthy adults and cord blood samples from 19 healthy, term neonates. Intracellular Gal-1 expression was determined by flow cytometry in the above subsets. Furthermore, we assessed the prevalence of naive and memory T cells that play a role in the regulation of immune reactivity. We also performed functional analyses to assess the effect of exogenous Gal-1 on the rate of proliferation of T lymphocytes isolated from APB and UCB. The prevalence of intracellular Gal-1-expressing CD3, CD4, CD8, Treg and NK lymphocytes was lower in UCB than in APB. However, their capability to produce Gal-1 reaches the level seen in adults. The prevalence of naive cells was higher, whereas that of central and effector memory T cells was lower in UCB compared with APB. Lower Gal-1-producing cell proportion might be due to the naivety of neonatal lymphocytes, as indicated by the positive correlation detected between the number of CD3 lymphocytes expressing intracellular Gal-1 and the prevalence of memory T cells. The intracellular expression of Gal-1 may be down-regulated in neonatal lymphocytes due to the already reduced immune reactivity of UCB. In contrast with previous findings, our results indicate that the administration of exogenous Gal-1 failed to decrease the rate of proliferation in T lymphocytes isolated from either APB or UCB. This suggests that Gal-1-expressing lymphocytes are unlikely to play a major role in mitigating the immune reactivity of UCB.

High expression of Galectin-1 in pancreatic stellate cells plays a role in the development and maintenance of an immunosuppressive microenvironment in pancreatic cancer

Galectin-1 is implicated in making tumor cells immune privileged, in part by regulating the survival of infiltrating T cells. Galectin-1 is strongly expressed in activated pancreatic stellate cells (PSCs); however, whether this is linked to tumor cell immune escape in pancreatic cancer is unknown. Galectin-1 was knocked down in PSCs isolated from pancreatic tissues using small interfering RNA (siRNA), or overexpressed using recombinant lentiviruses, and the PSCs were cocultured with T cells. CD3(+) , CD4(+) and CD8(+) T cell apoptosis was detected by flow cytometry; T cell IL-2, IL-4, IL-5 and INF-γ production levels were quantified using ELISA. Immunohistochemical analysis showed increased numbers of PSCs expressed Galectin-1 (p < 0.01) and pancreatic cancers had increased CD3(+) T cell densities (p < 0.01) compared to normal pancreas or chronic pancreatitis samples. In coculture experiments, PSCs that overexpressed Galectin-1 induced apoptosis of CD4(+) T cells (p < 0.01) and CD8(+) T cells (p < 0.05) significantly, compared to normal PSCs. Knockdown of Galectin-1 in PSCs increased CD4(+) T cell (p < 0.01) and CD8(+) T cell viability (p < 0.05). Supernatants from T cells cocultured with PSCs that overexpressed Galectin-1 contained significantly increased levels of Th2 cytokines (IL-4 and IL-5, p < 0.01) and decreased Th1 cytokines (IL-2 and INF-γ, p < 0.01). However, the knockdown of PSC Galectin-1 had the opposite effect on Th1 and Th2 cytokine secretion. Our study suggests that the overexpression of Galectin-1 in PSCs induced T cell apoptosis and Th2 cytokine secretion, which may regulate PSC-dependent immunoprivilege in the pancreatic cancer microenvironment. Galectin-1 may provide a novel candidate target for pancreatic cancer immunotherapy.

Galectin-1 research in T cell immunity: past, present and future

Galectin-1 (Gal-1) is one of 15 evolutionarily conserved ß-galactoside-binding proteins that display biologically-diverse activities in pathogenesis of inflammation and cancer. Gal-1 is variably expressed on immune cells and endothelial cells, though is commonly found and secreted at high levels in cancer cells. It induces apoptosis in effector T cells through homodimeric binding of N-acetyllactosamines on membrane glycoproteins (Gal-1 ligands). There is also compelling evidence in models of cancer and autoimmunity that recombinant Gal-1 (rGal-1) can potentiate immunoregulatory function of T cells. Here, we review Gal-1's structural and functional features, while analyzing potential drawbacks and technical difficulties inherent to rGal-1's nature. We also describe new Gal-1 preparations that exhibit dimeric stability and functional activity on T cells, providing renewed excitement for studying Gal-1 efficacy and/or use as anti-inflammatory therapeutics. We lastly summarize strategies targeting the Gal-1-Gal-1 ligand axis to circumvent Gal-1-driven immune escape in cancer and boost anti-tumor immunity.

Human regulatory T cells in allogeneic stem cell transplantation

GVHD is still one of the major complications after allogeneic stem cell transplantation. Whereas murine data have clearly shown the beneficial effects of regulatory T cells (Tregs) on the prevention of GVHD, data from the human system are rare. Here, we present a comparative dynamic analysis of CD4+CD25hiCD127lo/− Tregs from patients with and without GVHD analyzing the whole genome profile over the first 6 months after stem cell transplantation, representing the most sensitive time window for tolerance induction. The Treg transcriptome showed a high stability. However, the comparison of Treg transcriptomes from patients with and without GVHD uncovered regulated gene transcripts highly relevant for Treg cell function. The confirmative protein analyses demonstrated a significantly higher expression of granzyme A, CXCR3, and CCR5 in Tregs of immune tolerant patients. These results point to a reduced suppressive function of Tregs from GVHD patients with diminished migration capacity to the target organs.

Therapeutic plasticity of stem cells and allograft tolerance

Transplantation is the treatment of choice for many diseases that result in organ failure, but its success is limited by organ rejection. Stem cell therapy has emerged in the last years as a promising strategy for the induction of tolerance after organ transplantation. Here we discuss the ability of different stem cell types, in particular mesenchymal stromal cells, neuronal stem/progenitor cells, hematopoietic stem cells and embryonic stem cells, to modulate the immune response and induce peripheral or central tolerance. These stem cells have been studied to explore tolerance induction to several transplanted organs, such as heart, liver and kidney. Different strategies, including approaches to generating tolerance in islet transplantation, are discussed here.

Galectin-1-induced down-regulation of T lymphocyte activation protects (NZB x NZW) F1 mice from lupus-like disease

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by a hyperactive immune system, including activation of autoreactive T and B cells. These studies demonstrate that administration of recombinant galectin-1, a β-galactose binding protein, to SLE-prone (NZB × NZW) F1 mice reduced lymphocyte activation, inhibited serum anti-double-stranded DNA(dsDNA) IgG antibody production, decreased the incidence of proteinuria, and increased survival rate. In addition, recombinant galectin-1'-treated mice had a higher frequency of Foxp3 expression, which suggested an increase in the percentage of peripheral regulatory T cells. Consistent with the finding that there were fewer activated T lymphocytes, ex vivo T cells from mice treated with recombinant galectin-1 exhibited less proliferation in response to TCR stimulation. Furthermore, these cells were less efficient at lipid raft clustering in response to TCR/CD28 engagement, consistent with published reports that galectin-1 can reorganize the synaptic contact to interfere with TCR signaling and activation to prevent T cell activation. Aged galectin-1-deficient mice had higher serum levels of antibodies against dsDNA, elucidating a role for endogenous galectin-1 in decreasing susceptibility to autoimmunity. Together, the findings highlight galectin-1 as a novel potential therapeutic immune modulator for treatment of lupus-like disease.

Development of a nascent galectin-1 chimeric molecule for studying the role of leukocyte galectin-1 ligands and immune disease modulation

Galectin-1 (Gal-1), a β-galactoside-binding lectin, plays a profound role in modulating adaptive immune responses by altering the phenotype and fate of T cells. Experimental data showing recombinant Gal-1 (rGal-1) efficacy on T cell viability and cytokine production, nevertheless, is controversial due to the necessity of using stabilizing chemicals to help retain Gal-1 structure and function. To address this drawback, we developed a mouse Gal-1 human Ig chimera (Gal-1hFc) that did not need chemical stabilization for Gal-1 ligand recognition, apoptosis induction, and cytokine modulation in a variety of leukocyte models. At high concentrations, Gal-1hFc induced apoptosis in Gal-1 ligand(+) Th1 and Th17 cells, leukemic cells, and granulocytes from synovial fluids of patients with rheumatoid arthritis. Importantly, at low, more physiologic concentrations, Gal-1hFc retained its homodimeric form without losing functionality. Not only did Gal-1hFc-binding trigger IL-10 and Th2 cytokine expression in activated T cells, but members of the CD28 family and several other immunomodulatory molecules were upregulated. In a mouse model of contact hypersensitivity, we found that a non-Fc receptor-binding isoform of Gal-1hFc, Gal-1hFc2, alleviated T cell-dependent inflammation by increasing IL-4(+), IL-10(+), TGF-β(+), and CD25(high)/FoxP3(+) T cells, and by decreasing IFN-γ(+) and IL-17(+) T cells. Moreover, in human skin-resident T cell cultures, Gal-1hFc diminished IL-17(+) T cells and increased IL-4(+) and IL-10(+) T cells. Gal-1hFc will not only be a useful new tool for investigating the role of Gal-1 ligands in leukocyte death and cytokine stimulation, but for studying how Gal-1-Gal-1 ligand binding shapes the intensity of immune responses.

Suppression of renal fibrosis by galectin-1 in high glucose-treated renal epithelial cells

Diabetic nephropathy is the most common cause of chronic kidney disease. We investigated the ability of intracellular galectin-1 (Gal-1), a prototype of endogenous lectin, to prevent renal fibrosis by regulating cell signaling under a high glucose (HG) condition. We demonstrated that overexpression of Gal-1 reduces type I collagen (COL1) expression and transcription in human renal epithelial cells under HG conditions and transforming growth factor-β1 (TGF-β1) stimulation. Matrix metalloproteinase 1 (MMP1) is stimulated by Gal-1. HG conditions and TGF-β1 treatment augment expression and nuclear translocation of Gal-1. In contrast, targeted inhibition of Gal-1 expression reduces COL1 expression and increases MMP1 expression. The Smad3 signaling pathway is inhibited, whereas two mitogen-activated protein kinase (MAPK) pathways, p38 and extracellular signal-regulated kinase (ERK), are activated by Gal-1, indicating that Gal-1 regulates these signaling pathways in COL1 production. Using specific inhibitors of Smad3, ERK, and p38 MAPK, we showed that ERK MAPK activated by Gal-1 plays an inhibitory role in COL1 transcription and that activation of the p38 MAPK pathway by Gal-1 plays a negative role in MMP1 production. Taken together, two MAPK pathways are stimulated by increasing levels of Gal-1 in the HG condition, leading to suppression of COL1 expression and increase of MMP1 expression.