Characterization of galectin-1 from Chinese giant salamanders Andrias davidianus and its involvements during immune response

Galectins are considered as a multifunctional protein which play essential roles in cell adhesion and apoptosis, inflammation, tumor progression and immune response. In spite of extensive studies of galectin importance in immune system among different animals, few studies have been devoted to their functions in amphibian. In the present study, we characterized one proto type of galectin (named AdGal1) from Chinese giant salamander Andrias davidianus and studied its function in immune response. AdGal1 cDNA possesses an open reading frame of 598 bp, which encodes a putative galectin of 134 amino acids containing one carbohydrate recognition domains (CRDs). The constitutive expression of mRNA transcripts was detected in a wide range of tissues, with the highest expression in kidney. Immune challenges with Aeromonas hydrophila and Chinese giant salamander iridovirus (GSIV), the transcript level of AdGal1 in kidney was significantly upregulated. The mature protein of AdGal1 was successfully expressed and purified in Escherichia coli BL21 (DE3). The recombinant AdGal1 (rAdGal1) could show bind activity to different Gram negative and Gram positive bacteria. It could also strongly agglutinate different kinds of bacteria at different concentrations. Collectively, these data from the present study indicate that AdGal1 is a vital pattern recognition receptor to recognize different microbes in the innate immune system of Andrias davidianus.

Galectin-1-driven upregulation of SDF-1 in pancreatic stellate cells promotes pancreatic cancer metastasis

Galectin-1, mainly expressed in activated pancreatic stellate cells (PSCs), is involved in many important cancer-related processes. However, very little is known how Galectin-1 modulates PSCs and subsequently impacts pancreatic cancer cells (PCCs). Our chemokine antibody array and in vitro studies demonstrates that Galectin-1 induces secretion of stromal cell-derived factor-1(SDF-1) in PSCs by activating NF-κB signaling. The secreted SDF-1 increases migration and invasion of PCCs. Knockdown of Galectin-1 and inhibitor-mediated blockade of SDF-1 as well as its ligand CXCR4 and NF-κB verifies the findings. In vivo experiment by knockdown of Galectin-1 in PSCs further demonstrates the conclusion. Collectively, the present studies demonstrate that Galectin-1-driven production of SDF-1 in PSCs through activation of NF-κB promotes metastasis in PDAC, offering a potential target in the treatment of pancreatic cancer.

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.

TLR4-mediated galectin-1 production triggers epithelial-mesenchymal transition in colon cancer cells through ADAM10- and ADAM17-associated lactate production

Toll-like receptor 4 (TLR4) activation is a key contributor to the carcinogenesis of colon cancer. Overexpression of galectin-1 (Gal-1) also correlates with increased invasive activity of colorectal cancer. Lactate production is a critical predictive factor of risk of metastasis, but the functional relationship between intracellular lactate and Gal-1 expression in TLR4-activated colon cancer remains unknown. In this study, we investigated the underlying mechanism and role of Gal-1 in metastasis and invasion of colorectal cancer (CRC) cells after TLR4 stimulation. Exposure to the TLR4 ligand lipopolysaccharide (LPS) increased expression of Gal-1, induced EMT-related cytokines, triggered the activation of glycolysis-related enzymes, and promoted lactate production. Gene silencing of TLR4 and Gal-1 in CRC cells inhibited lactate-mediated epithelial-mesenchymal transition (EMT) after TLR4 stimulation. Gal-1-mediated activation of a disintegrin and metalloproteinase 10 (ADAM10) and ADAM 17 increased the invasion activity and expression of mesenchymal characteristics in LPS-activated CRC cells. Conversely, inhibition of ADAM10 or ADAM17 effectively blocked the generation of lactate and the migration capacity of LPS-treated CRC cells. Thus, the TLR4/Gal-1 signaling pathway regulates lactate-mediated EMT processes through the activation of ADAM10 and ADAM17 in CRC cells.

Galectin-1 from cancer-associated fibroblasts induces epithelial-mesenchymal transition through β1 integrin-mediated upregulation of Gli1 in gastric cancer

BACKGROUND

Gastric cancer (GC) is characterized by the excessive deposition of extracellular matrix, which is thought to contribute to this tumor's malignant behavior. Epithelial-mesenchymal transition (EMT) is regarded as a crucial contributing factor to cancer progression. Galectin-1 (Gal-1), a β-galactoside-binding protein abundantly expressed in activated cancer-associated fibroblasts (CAFs), has been reported to be involved in GC progression and metastasis by binding to β1 integrin, which, in turn, can bind to matrix proteins and activate intracellular cascades that mediate EMT. Increasing evidence suggests that abnormal activation of the hedgehog (Hh) signaling pathway enhances GC cell migration and invasion. The purpose of our study is to explore the role of Gal-1 in the GC progression and metastasis as well as the regulatory mechanism.

METHODS

We hypothesized that Gal-1 binding to β1 integrin would lead to paracrine signaling between CAFs and GC cells, mediating EMT by upregulating Gli1. Invasion and metastasis effects of the Gal-1 and Gli1 were evaluated using wound healing and invasion assay following transfection with mimics. Additionally, to facilitate the delineation of the role of the Hh signaling in GC, we monitored the expression level of associated proteins. We also evaluated the effects of β1 integrin on these processes. Furthermore, Gal-1 and Gli1 expression in GC patient samples were examined by immunohistochemistry and western blot to determine the correlation between their expression and clinicopathologic characteristics. The Kaplan-Meier method and Cox proportional hazards model were used to analyze the relationship of expression with clinical outcomes.

RESULTS

Gal-1 was found to induce EMT, GC cell migration and invasion. Further data showed that Gal-1 up-regulated Gli1 expression. β1 integrin was responsible for Gal-1-induced Gli1 expression and EMT. In clinical GC tissue, it confirmed a positive relationship between Gal-1 and Gli1 expression. Importantly, their high expression is correlated to poor prognosis.

CONCLUSION

Gal-1 from CAFs binds to a carbohydrate structure in β1 integrin and plays an important role in the development of GC by inducing GC metastasis and EMT through targeting Gli1. This study highlights the potential therapeutic value of Gal-1 for suppression of GC metastasis.

The 88-kDa Eales' protein in serum is a complex of haptoglobin, complement C3, and galectin-1 as identified by liquid chromatography coupled mass spectrometry

PURPOSE

Eales' disease (ED), an enigmatic inflammatory disease, affects peripheral retinal veins and thereby vision in males. This study was aimed at identifying and deciphering the role of a novel 88-kDa protein reported in the serum and vitreous of patients with ED.

EXPERIMENTAL DESIGN

The purified 88-kDa protein was identified by UPLC coupled ESI-QTOF-MS. The identified proteins were quantified in the serum from 20 ED patients and controls (age and sex matched), respectively by ELISA. The interaction of these proteins was studied using co-immunoprecipitation, western blot, and MS analyses. N-glycosylation of protein was observed by MS and lectin blot.

RESULTS

The 88-kDa protein was identified to be a complex of haptoglobin, complement C3, and galectin-1. ELISA results showed a 1.5-fold increase in levels of haptoglobin (p = 0.008), with level of complement C3 unaltered and 1.2-fold decreased serum galectin-1 levels (p = 0.003) in ED patients compared to controls. Co-immunoprecipitation illustrated the interaction between haptoglobin and complement C3. Reduced sialylation and increased β-1, 6-N-acetyl-glucosamine branched N-glycans were observed in haptoglobin of ED patients.

CONCLUSION

The 88-kDa protein, a complex of haptoglobin, complement C3, and galectin-1, may play a potential role in ED pathogenesis while levels galectin-1 and haptoglobin may serve as potential biomarker of ED.

Galectin-1 circumvents lysolecithin-induced demyelination through the modulation of microglial polarization/phagocytosis and oligodendroglial differentiation

Galectin-1 (Gal-1), a member of a highly conserved family of animal lectins, binds to the common disaccharide [Galβ(1-4)-GlcNAc] on both N- and O-glycans decorating cell surface glycoconjugates. Current evidence supports a role for Gal-1 in the pathophysiology of multiple sclerosis (MS), one of the most prevalent chronic inflammatory diseases. Previous studies showed that Gal-1 exerts neuroprotective effects by promoting microglial deactivation in a model of autoimmune neuroinflammation and induces axonal regeneration in spinal cord injury. Seeking a model that could link demyelination, oligodendrocyte (OLG) responses and microglial activation, here we used a lysolecithin (LPC)-induced demyelination model to evaluate the ability of Gal-1 to preserve myelin without taking part in T-cell modulation. Gal-1 treatment after LPC-induced demyelination promoted a significant decrease in the demyelinated area and fostered more efficient remyelination, concomitantly with an attenuated oligodendroglial progenitor response reflecting less severe myelination damage. These results were accompanied by a decrease in the area of microglial activation with a shift toward an M2-polarized microglial phenotype and diminished astroglial activation. In vitro studies further showed that, mechanistically, Gal-1 targets activated microglia, promoting an increase in their myelin phagocytic capacity and their shift toward an M2 phenotype, and leads to oligodendroglial differentiation. Therefore, this study supports the use of Gal-1 as a potential treatment for demyelinating diseases such as MS.

Role of galectin-1 in urinary bladder urothelial carcinoma cell invasion through the JNK pathway

Human galectin-1 is a member of the galectin family, proteins with conserved carbohydrate-recognition domains that bind galactoside. Galectin-1 is highly expressed in various tumors and participates in various oncogenic processes. However, detailed descriptions of the function of galectin-1 in urinary bladder urothelial carcinoma have not been reported. Our previous cohort investigation showed that galectin-1 is associated with tumor invasiveness and is a possible independent prognostic marker of urinary bladder urothelial carcinoma. The present study aimed to clarify the relevance of galectin-1 expression level to tumor progression and invasion. In order to decipher a mechanism for the contribution of galectin-1 to the malignant behavior of urinary bladder urothelial carcinoma, two bladder cancer cell lines (T24 and J82) were established with knockdown of galectin-1 expression by shRNA. Bladder cancer cells with LGALS1 gene silencing showed reduced cell proliferation, lower invasive capability, and lower clonogenicity. Extensive signaling pathway studies indicated that galectin-1 participated in bladder cancer cell invasion by mediating the activity of MMP9 through the Ras-Rac1-MEKK4-JNK-AP1 signaling pathway. Our functional analyses of galectin-1 in urinary bladder urothelial carcinoma provided novel insights into the critical role of galectin-1 in tumor progression and invasion. These results revealed that silencing the galectin-1-mediated MAPK signaling pathway presented a novel strategy for bladder cancer therapy.

Stress-induced galectin-1 influences immune tolerance in the spleen and thymus by modulating CD45 immunoreactive lymphocytes

Galectin-1 (Gal-1) is differentially expressed in normal and pathological tissues and regulates immune cell homeostasis. Restraint stress increases serum Gal-1 in rats. However, the function of stress-induced Gal-1 in serum is unknown. We determined if stress-induced Gal-1 in serum accumulates in immunocompetent organs as protection from physiological and/or psychological stress. Western blotting showed that the intensity of Gal-1 bands in stressed groups was significantly higher than that in controls. RT-PCR analysis indicated that the Gal-1 mRNA level did not increase after restraint stress. The numbers of Gal-1 immunoreactive cells in the splenic periarterial lymphatic sheath (PLS) and the thymus medulla of the stressed group were increased compared with those in controls. Furthermore, stress-induced Gal-1 immunoreactive cells corresponded to CD45 immunoreactive lymphocytes (CD45⁺) in the PLS of the spleen and the medulla of the thymus. Thus, stress-induced Gal-1 immediately accumulates in the spleen and thymus, and may modulate the immune response through apoptosis by binding to CD45⁺ lymphocytes in immune organs following physiological and/or psychological stress.

Galectin-3 interacts with components of the nuclear ribonucleoprotein complex

Background

The multifunctional β-galactoside-binding protein galectin-3 is found in many distinct subcellular compartments including the cell nucleus. Expression and distribution of galectin-3 between the cell nucleus and the cytosol changes during cell differentiation and cancer development. Nuclear functions of galectin-3 and how they contribute to tumorigenesis are not understood.

Methods

In order to identify nuclear galectin-3 interaction partners, we used affinity chromatography and co-immunoprecipitation. Spatial proximity in the nucleus was assessed by immunofluorescence and proximity ligation assay. We also investigated the function of galectin-3 on mRNA-export by fluorescence in situ hybridization and on mRNA-processing by RNA-sequencing.

Results

The heterogeneous ribonucleoprotein particle component hnRNPA2B1 was identified as a novel galectin-3 binding protein that associates with the lectin in a lactose-dependent manner in the cell nucleus. Specific individual depletion of galectin-3 does not affect the mRNA distribution between cytoplasm and nucleus. A significant alteration of this distribution was observed after combined depletion of galectin-1 and −3. However, silencing of galectin-3 was sufficient to alter the splicing patterns of several genes.

Conclusions

Galectin-3 and hnRNPA2B1 interact as members of the early splicing machinery. Galectin-3 and −1 have redundant functions in mRNA transport and at least in part in mRNA splicing. RNA-sequencing data points to a specific function of the hnRNPA2B1/galectin-3 interaction in the processing of transcripts coding for the nuclear oncoprotein SET.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2546-0) contains supplementary material, which is available to authorized users.

Molecular cloning and characterization of a galectin-1 homolog in orange-spotted grouper, Epinephelus coioides

As a member of animal lectin family, galectin has the functions of pathogen recognition, anti-bacteria and anti-virus. In the present study, a galectin-1 homolog (EcGel-1) from grouper (Epinephelus coioides) was cloned and its possible role in fish immunity was analyzed. The full length cDNA of EcGel-1 is 504 bp, including a 408 bp open reading frame (ORF) which encodes 135 amino acids with a molecular mass of 15.19 kDa. Quantitative real-time PCR analysis indicated that EcGel-1 was constitutively expressed in all analyzed tissues of healthy grouper. The expression of EcGel-1 in the spleen of grouper was differentially up-regulated challenged with Singapore grouper iridovirus (SGIV), poly (I:C), and LPS. EcGel-1 was abundantly distributed in the cytoplasm in GS cells. Recombinant EcGel-1(rEcGel-1) protein can make chicken erythrocyte aggregation, and combine with gram negative bacteria and gram positive bacteria in the presence of 2-Mercaptoethanol (β-ME). Taken together, the results showed that EcGel-1 may be an important molecule involved in pathogen recognition and pathogen elimination in the innate immunity of grouper.

Microdialysis and proteomics of subcutaneous interstitial fluid reveals increased galectin-1 in type 2 diabetes patients

OBJECTIVE

To identify a potential therapeutic target for type 2 diabetes by comparing the subcutaneous interstitial fluid from type 2 diabetes patients and healthy men.

METHODS

Proteomics was performed on the interstitial fluid of subcutaneous adipose tissue obtained by microdialysis from 7 type 2 diabetes patients and 8 healthy participants. 851 proteins were detected, of which 36 (including galectin-1) showed significantly altered expression in type 2 diabetes. We also measured galectin-1 expression in: (1) adipocytes isolated from adipose tissue biopsies from these participants; (2) subcutaneous adipose tissue of 24 obese participants before, during and after 16weeks on a very low calorie diet (VLCD); and (3) adipocytes isolated from 6 healthy young participants after 4weeks on a diet and lifestyle intervention to promote weight gain. We also determined the effect of galectin-1 on glucose uptake in human adipose tissue.

RESULTS

Galectin-1 protein levels were elevated in subcutaneous dialysates from type 2 diabetes compared with healthy controls (p<0.05). In agreement, galectin-1 mRNA expression was increased in adipocytes from the type 2 diabetes patients (p<0.05). Furthermore, galectin-1 mRNA expression was decreased in adipose tissue after VLCD (p<0.05) and increased by overfeeding (p<0.05). Co-incubation of isolated human adipocytes with galectin-1 reduced glucose uptake (p<0.05) but this was independent of the insulin signal.

CONCLUSION

Proteomics of the interstitial fluid in subcutaneous adipose tissue in vivo identified a novel adipokine, galectin-1, with a potential role in the pathophysiology of type 2 diabetes.

Ligand-mediated Galectin-1 endocytosis prevents intraneural H2O2 production promoting F-actin dynamics reactivation and axonal re-growth

Axonal growth cone collapse following spinal cord injury (SCI) is promoted by semaphorin3A (Sema3A) signaling via PlexinA4 surface receptor. This interaction triggers intracellular signaling events leading to increased hydrogen peroxide levels which in turn promote filamentous actin (F-actin) destabilization and subsequent inhibition of axonal re-growth. In the current study, we demonstrated that treatment with galectin-1 (Gal-1), in its dimeric form, promotes a decrease in hydrogen peroxide (H2O2) levels and F-actin repolimerization in the growth cone and in the filopodium of neuron surfaces. This effect was dependent on the carbohydrate recognition activity of Gal-1, as it was prevented using a Gal-1 mutant lacking carbohydrate-binding activity. Furthermore, Gal-1 promoted its own active ligand-mediated endocytosis together with the PlexinA4 receptor, through mechanisms involving complex branched N-glycans. In summary, our results suggest that Gal-1, mainly in its dimeric form, promotes re-activation of actin cytoskeleton dynamics via internalization of the PlexinA4/Gal-1 complex. This mechanism could explain, at least in part, critical events in axonal regeneration including the full axonal re-growth process, de novo formation of synapse clustering, axonal re-myelination and functional recovery of coordinated locomotor activities in an in vivo acute and chronic SCI model.

SIGNIFICANCE STATEMENT

Axonal regeneration is a response of injured nerve cells critical for nerve repair in human spinal cord injury. Understanding the molecular mechanisms controlling nerve repair by Galectin-1, may be critical for therapeutic intervention. Our results show that Galectin-1; in its dimeric form, interferes with hydrogen peroxide production triggered by Semaphorin3A. The high levels of this reactive oxygen species (ROS) seem to be the main factor preventing axonal regeneration due to promotion of actin depolymerization at the axonal growth cone. Thus, Galectin-1 administration emerges as a novel therapeutic modality for promoting nerve repair and preventing axonal loss.

Galectin-1 is essential for the induction of MOG35-55 -based intravenous tolerance in experimental autoimmune encephalomyelitis

In experimental autoimmune encephalomyelitis (EAE), intravenous (i.v.) injection of the antigen, myelin oligodendrocyte glycoprotein-derived peptide, MOG35-55 , suppresses disease development, a phenomenon called i.v. tolerance. Galectin-1, an endogenous glycan-binding protein, is upregulated during autoimmune neuroinflammation and plays immunoregulatory roles by inducing tolerogenic dendritic cells (DCs) and IL-10 producing regulatory type 1 T (Tr1) cells. To examine the role of galectin-1 in i.v. tolerance, we administered MOG35-55 -i.v. to wild-type (WT) and galectin-1 deficient (Lgals1(-/-) ) mice with ongoing EAE. MOG35-55 suppressed disease in the WT, but not in the Lgals1(-/-) mice. The numbers of Tr1 cells and Treg cells were increased in the CNS and periphery of tolerized WT mice. In contrast, Lgals1(-/-) MOG-i.v. mice had reduced numbers of Tr1 cells and Treg cells in the CNS and periphery, and reduced IL-27, IL-10, and TGF-β1 expression in DCs in the periphery. DCs derived from i.v.-tolerized WT mice suppressed disease when adoptively transferred into mice with ongoing EAE, whereas DCs from Lgals1(-/-) MOG-i.v. mice were not suppressive. These findings demonstrate that galectin-1 is required for i.v. tolerance induction, likely via induction of tolerogenic DCs leading to enhanced development of Tr1 cells, Treg cells, and downregulation of proinflammatory responses.

Deguelin Induces the Apoptosis of Lung Squamous Cell Carcinoma Cells through Regulating the Expression of Galectin-1

Lung cancer is the leading cause of cancer mortality around the world. Despite advances in the targeted therapy, patients with lung squamous cell carcinoma(SCC) still benefit few from it, and the search for potential effective therapies is imperative. Here, we demonstrated that deguelin induced significant apoptosis of lung SCC cells in vitro. Importantly, we found deguelin down-regulated the expression of galectin-1, which was involved in a wide range of tumorous physiologic process. Thus, we both over-expressed and down-regulated galectin-1 to perform its role in deguelin-induced apoptosis. We found that increased galectin-1 attenuated apoptosis of SCC cells exposed to deguelin, while galectin-1 knockdown sensitized lung cancer cells to deguelin treatment. Additionally, we observed that down-regulation of galectin-1 resulted in suppression of Ras/Raf/ERK pathway which was involved in deguelin-induced cell apoptosis. We also found that deguelin had a significant anti-tumor ability with decline of galectin-1 in vivo. In conclusion, these findings confirm that deguelin may act as a new chemo-preventive agent through inducing apoptosis of lung SCC cells in a galectin-1 dependent manner.

Increases of Galectin-1 and its S-nitrosylated form in the Brain Tissues of Scrapie-Infected Rodent Models and Human Prion Diseases

Galectin-1 (Gal-1) shows neuroprotective activity in brain ischemia, spinal cord injury, and autoimmune neuroinflammation. To evaluate the Gal-1 situation in the brains of prion disease, the brain levels of Gal-1 in several scrapie-infected experimental rodent models were tested by Western blot, including agents 263K-infected hamsters, 139A-, ME7-, and S15-infected mice. Remarkable increases of brain Gal-1 were observed in all tested scrapie-infected rodents at the terminal stage. The brain levels of Gal-1 showed time-dependent increases along with the prolonging of incubation times. Immunohistochemical assays illustrated much stronger stainings in the brain sections of scrapie-infected rodents. Quantitative RT-PCR of Gal-1 gene demonstrated increased transcription in the brains of scrapie-infected mice. Gal-1 was colocalized with GFAP- and NeuN-positive cells, but not with Iba-1-positive cells in immunofluorescent test. Increases of Gal-1 were also detected in the several postmortem cortex regions of human prion diseases. Moreover, the S-nitrosylated forms of Gal-1 in the brains of scrapie-infected rodents were significantly higher than those of normal ones. Our finding here demonstrates markedly increased brain Gal-1 and S-nitrosylated Gal-1 both in scrapie-infected rodents and human prion diseases.

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.

Antimicrobial response of galectin-1 from rock bream Oplegnathus fasciatus: Molecular, transcriptional, and biological characterization

In this study, we describe the identification and characterization of a proto type galectin, galectin-1, from rock bream Oplegnathus fasciatus (OfGal-1). Galectins are evolutionarily conserved carbohydrate binding lectins that show a wide range of functions related to development and immune physiology. They have been identified as pattern recognition receptors of innate immune system that recognize a broad range of microbes. OfGal-1 cDNA comprised of 993 bp with an open reading frame of 408 bp that encodes 135 amino acids. A single carbohydrate recognition domain was present in the OfGal-1 amino acid sequence. The sequence comparison by multiple and pairwise alignments and the phylogenetic tree emphasized the strong evolutionary conservation of Gal-1. The typical β-sandwich structure was identified from the predicted tertiary structure. The constitutive expression of mRNA transcripts was detected in a wide range of tissues examined, with the highest expression in the heart. Immune challenges with live bacteria (Edwardsiella tarda and Streptococcus iniae), rock bream irido virus, and mitogens (lipopolysaccharide and poly I:C) modulated the expression of OfGal-1 mRNAs in the gills, head kidney, and liver. The recombinant OfGal-1 (rOfGal-1) strongly agglutinatinated the human erythrocytes, and this hemagglutination was inhibited by lactose and D-galactose. A wide range of bacteria (S. iniae, S. parauberis, Escherichia coli, Edwardsiella tarda, Vibrio anguillarum, Vibrio harveyi, and Vibrio tapetis) and a ciliate (Miamiensis avidus) were also effectively recognized by rOfGal-1. Significant antiviral activity against rock bream irido virus was also demonstrated by rOfGal-1. Collectively, results from the present study indicate that OfGal-1 can recognize a wide range of microbes and is a vital pattern recognition receptor in the innate immune system of rock bream.

Elevated systemic galectin-1 levels characterize HELLP syndrome

Galectin-1 (gal-1), a member of a family of conserved β-galactoside-binding proteins, has been shown to exert a key role during gestation. Though gal-1 is expressed at higher levels in the placenta from HELLP patients, it is still poorly understood whether systemic gal-1 levels also differ in HELLP patients. In the present study, we evaluated the systemic expression of gal-1, together with the angiogenic factors, placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1) in conjunction with HELLP syndrome severity. Systemic levels of gal-1 and sFlt-1 were elevated in patients with both early- and late-onset HELLP syndrome as compared to healthy controls. In contrast, peripheral PlGF levels were decreased in early- and late-onset HELLP. A positive correlation between systemic gal-1 levels and sFlt-1/PlGF ratios was found in early onset HELLP patients. Our results show that HELLP syndrome is associated with increased circulating levels of gal-1; integrating systemic gal-1 measurements into the diagnostic analyses of pregnant women may provide more effective prediction of HELLP syndrome development.

Immune response modulation by Galectin-1 in a transgenic model of neuroblastoma

Galectin-1 (Gal-1) has been described to promote tumor growth by inducing angiogenesis and to contribute to tumor immune escape by promoting apoptosis of activated T cells. We had previously identified upregulation of Gal-1 in preclinical models of aggressive neuroblastoma (NB), a solid tumor of childhood. However, the clinical and biological relevance of Gal-1 in this tumor entity is unclear. Here, the effect of Gal-1 on the immune system and tumorigenesis was assessed using modulation of Gal-1 expression in immune effector cells and in a transgenic NB model, designated TH-MYCN. The fraction of CD4(+) T cells was decreased in tumor-bearing TH-MYCN mice compared to tumor-free littermates, while both CD4(+) T cells as well as CD8(+) T cells were less activated, compatible with a reduced immune response in tumor-bearing mice. Tumor incidence was not significantly altered by decreasing Gal-1/LGALS1 gene dosage in TH-MYCN mice, but TH-MYCN/Gal-1(-/-) double transgenic mice displayed impaired tumor angiogenesis, splenomegaly, and impaired T cell tumor-infiltration with no differences in T cell activation and apoptosis rate. Additionally, a lower migratory capacity of Gal-1 deficient CD4(+) T cells toward tumor cells was observed in vitro. Transplantation of TH-MYCN-derived tumor cells into syngeneic mice resulted in significantly reduced tumor growth and elevated immune cell infiltration when Gal-1 was downregulated by shRNA. We therefore conclude that T cell-derived Gal-1 mediates T cell tumor-infiltration, whereas NB-derived Gal-1 promotes tumor growth. This opposing effect of Gal-1 in NB should be considered in therapeutic targeting strategies, as currently being developed for other tumor entities.

Pharmacological inhibition of galectin-1 by lactulose alleviates weight gain in diet-induced obese rats

AIMS

Galectin-1 (GAL1) is an important member of the lectin family with a carbohydrate recognition domain and has recently been demonstrated to be involved in adipose metabolism. In the present study, we investigated the effects of targeted inhibition of GAL1 by its binding inhibitor lactulose under high fat diet (HFD)-induced obesity.

MAIN METHODS

Effects of targeted inhibition of GAL1 by lactulose on lipid metabolism were investigated in vitro and in vivo. Changes in lipogenic capacity in lactulose-treated adipocytes were demonstrated by Oil Red O staining, triglyceride quantification and major adipogenic marker expression patterns. After lactulose treatment in Sprague-Dawley rats, various important body weight parameters, food efficiency, plasma metabolic parameters (glucose, ALT, free fatty acid, triglycerides, leptin, and insulin) and metabolic protein expression patterns were evaluated.

KEY FINDINGS

Lactulose treatment reduced adipogenesis and fat accumulation in vitro by down-regulation of major adipogenic transcription factors such as C/EBPα and PPARγ. In vivo treatment of lactulose to 5-week-old Sprague-Dawley male rats significantly alleviated HFD-induced body weight gain and food efficiency as well as improved plasma and other metabolic parameters. In addition, lactulose treatment down-regulated major adipogenic marker proteins (C/EBPα and PPARγ) in adipose tissue as well as stimulated expression of proteins involved in energy expenditure and lipolysis (ATP5B, COXIV, HSL, and CPT1).

SIGNIFICANCE

In conclusion, reduced adipogenesis and increased energy expenditure mediated by lactulose treatment synergistically contribute to alleviation of HFD-induced body weight gain. Therefore, pharmaceutical targeting of GAL1 using lactulose would be a novel therapeutic approach for the treatment of obesity.

Galectin-1 is associated with poor prognosis in patients with cutaneous head and neck cancer with perineural spread

Spread of head and neck cancer along the cranial nerves is often a lethal complication of this tumour. Current treatment options include surgical resection and/or radiotherapy, but recurrence is a frequent event suggesting that our understanding of this tumour and its microenvironment is incomplete. In this study, we have analysed the nature of the perineural tumour microenvironment by immunohistochemistry with particular focus on immune cells and molecules, which might impair anti-tumour immunity. Moderate to marked lymphocyte infiltrates were present in 58.8% of the patient cohort including T cells, B cells and FoxP3-expressing T cells. While human leukocyte antigen (HLA) class I and more variably HLA class II were expressed on the tumour cells, this did not associate with patient survival or recurrence. In contrast, galectin-1 staining within lymphocyte areas of the tumour was significantly associated with a poorer patient outcome. Given the known role of galectin-1 in immune suppression, the data suggest that galectin inhibitors might improve the prognosis of patients with perineural spread of cancer.

Cancer-associated fibroblasts promote angiogenesis in gastric cancer through galectin-1 expression

BACKGROUND

Galectin-1, an evolutionarily conserved glycan-binding protein with angiogenic potential, was recently identified as being overexpressed in cancer-associated fibroblasts (CAFs) of gastric cancer. The role of endogenous CAF-derived galectin-1 on angiogenesis in gastric cancer and the mechanism involved remain unknown.

METHODS

Immunohistochemical staining was used to investigate the correlation between galectin-1 and vascular endothelial growth factor (VEGF) and CD31 expression in gastric cancer tissues and normal gastric tissues. Galectin-1 was knocked down in CAFs isolated from gastric cancer using small interfering ribonucleic acid (RNA), or overexpressed using recombinant lentiviruses, and the CAFs were co-cultured with human umbilical vein endothelial cells (HUVECs) or cancer cells. Subsequently, proliferation, migration, tube formation, and VEGF/VEGF receptor (VEGFR) 2 expression were detected. The role of CAF-derived galectin-1 in tumor angiogenesis in vivo was studied using the chick chorioallantoic membrane (CAM) assay.

RESULTS

Galectin-1 was highly expressed in the CAFs and was positively associated with VEGF and CD31 expression. In the co-culture, high expression of galectin-1 in the CAFs increased HUVEC proliferation, migration, tube formation, and VEGFR2 phosphorylation and enhanced VEGF expression in gastric cancer cells. The CAM assay indicated that high expression of galectin-1 in the CAFs accelerated tumor growth and promoted angiogenesis. In contrast, galectin-1 knockdown in the CAFs significantly inhibited this effect.

CONCLUSION

CAF-derived galectin-1 significantly promotes angiogenesis in gastric cancer and may be a target for angiostatic therapy.

3D tumor tissue analogs and their orthotopic implants for understanding tumor-targeting of microenvironment-responsive nanosized chemotherapy and radiation

An appropriate representation of the tumor microenvironment in tumor models can have a pronounced impact on directing combinatorial treatment strategies and cancer nanotherapeutics. The present study develops a novel 3D co-culture spheroid model (3D TNBC) incorporating tumor cells, endothelial cells and fibroblasts as color-coded murine tumor tissue analogs (TTA) to better represent the tumor milieu of triple negative breast cancer in vitro. Implantation of TTA orthotopically in nude mice, resulted in enhanced growth and aggressive metastasis to ectopic sites. Subsequently, the utility of the model is demonstrated for preferential targeting of irradiated tumor endothelial cells via radiation-induced stromal enrichment of galectin-1 using anginex conjugated nanoparticles (nanobins) carrying arsenic trioxide and cisplatin. Demonstration of a multimodal nanotherapeutic system and inclusion of the biological response to radiation using an in vitro/in vivo tumor model incorporating characteristics of tumor microenvironment presents an advance in preclinical evaluation of existing and novel cancer nanotherapies.

FROM THE CLINICAL EDITOR

Existing in-vivo tumor models are established by implanting tumor cells into nude mice. Here, the authors described their approach 3D spheres containing tumor cells, enodothelial cells and fibroblasts. This would mimic tumor micro-environment more realistically. This interesting 3D model should reflect more accurately tumor response to various drugs and would enable the design of new treatment modalities.

Galectin-1 suppresses methamphetamine induced neuroinflammation in human brain microvascular endothelial cells: Neuroprotective role in maintaining blood brain barrier integrity

Methamphetamine (Meth) abuse can lead to the breakdown of the blood-brain barrier (BBB) integrity leading to compromised CNS function. The role of Galectins in the angiogenesis process in tumor-associated endothelial cells (EC) is well established; however no data are available on the expression of Galectins in normal human brain microvascular endothelial cells and their potential role in maintaining BBB integrity. We evaluated the basal gene/protein expression levels of Galectin-1, -3 and -9 in normal primary human brain microvascular endothelial cells (BMVEC) that constitute the BBB and examined whether Meth altered Galectin expression in these cells, and if Galectin-1 treatment impacted the integrity of an in-vitro BBB. Our results showed that BMVEC expressed significantly higher levels of Galectin-1 as compared to Galectin-3 and -9. Meth treatment increased Galectin-1 expression in BMVEC. Meth induced decrease in TJ proteins ZO-1, Claudin-3 and adhesion molecule ICAM-1 was reversed by Galectin-1. Our data suggests that Galectin-1 is involved in BBB remodeling and can increase levels of TJ proteins ZO-1 and Claudin-3 and adhesion molecule ICAM-1 which helps maintain BBB tightness thus playing a neuroprotective role. Galectin-1 is thus an important regulator of immune balance from neurodegeneration to neuroprotection, which makes it an important therapeutic agent/target in the treatment of drug addiction and other neurological conditions.