Sialylation of beta 1 Integrins blocks cell adhesion to galectin-3 and protects cells against galectin-3-induced apoptosis

In previous studies, we determined that beta 1 integrins from human colon tumors have elevated levels of alpha 2-6 sialylation, a modification added by beta-galactosamide alpha-2,6-sialyltranferase I (ST6Gal-I). Intriguingly, the beta 1 integrin is thought to be a ligand for galectin-3 (gal-3), a tumor-associated lectin. The effects of gal-3 are complex; intracellular forms typically protect cells against apoptosis through carbohydrate-independent mechanisms, whereas secreted forms bind to cell surface oligosaccharides and induce apoptosis. In the current study, we tested whether alpha 2-6 sialylation of the beta 1 integrin modulates binding to extracellular gal-3. Herein we report that SW48 colonocytes lacking alpha 2-6 sialylation exhibit beta 1 integrin-dependent binding to gal-3-coated tissue culture plates; however, binding is attenuated upon forced expression of ST6Gal-I. Removal of alpha 2-6 sialic acids from ST6Gal-I expressors by neuraminidase treatment restores gal-3 binding. Additionally, using a blot overlay approach, we determined that gal-3 binds directly and preferentially to unsialylated, as compared with alpha 2-6-sialylated, beta 1 integrins. To understand the physiologic consequences of gal-3 binding, cells were treated with gal-3 and monitored for apoptosis. Galectin-3 was found to induce apoptosis in parental SW48 colonocytes ( unsialylated), whereas ST6Gal-I expressors were protected. Importantly, gal-3-induced apoptosis was inhibited by function blocking antibodies against the beta 1 subunit, suggesting that beta 1 integrins are critical transducers of gal-3-mediated effects on cell survival. Collectively, our results suggest that the coordinate up-regulation of gal-3 and ST6Gal-I, a feature that is characteristic of colon carcinoma, may confer tumor cells with a selective advantage by providing a mechanism for blockade of the pro-apoptotic effects of secreted gal-3.

Surface-epitope masking and expression cloning identifies the human prostate carcinoma tumor antigen gene PCTA-1 a member of the galectin gene family.

The selective production of monoclonal antibodies (mAbs) reacting with defined cell surface-expressed molecules is now readily accomplished with an immunological subtraction approach, surface-epitope masking (SEM). Using SEM, prostate carcinoma (Pro 1.5) mAbs have been developed that react with tumor-associated antigens expressed on human prostate cancer cell lines and patient-derived carcinomas. Screening a human LNCaP prostate cancer cDNA expression library with the Pro 1.5 mAb identifies a gene, prostate carcinoma tumor antigen-1 (PCTA-1). PCTA-1 encodes a secreted protein of approximately 35 kDa that shares approximately 40% sequence homology with the N-amino terminal region of members of the S-type galactose-binding lectin (galectin) gene family. Specific galectins are found on the surface of human and marine neoplastic cells and have been implicated in tumorigenesis and metastasis. Primer pairs within the 3' untranslated region of PCTA-1 and reverse transcription-PCR demonstrate selective expression of PCTA-1 by prostate carcinomas versus normal prostate and benign prostatic hypertrophy. These findings document the use of the SEM procedure for generating mAbs reacting with tumor-associated antigens expressed on human prostate cancers. The SEM-derived mAbs have been used for expression cloning the gene encoding this human tumor antigen. The approaches described in this paper, SEM combined with expression cloning, should prove of wide utility for developing immunological reagents specific for and identifying genes relevant to human cancer.

Galectin-3 Up-regulation In Hypoxic And Nutrient Deprived Microenvironments Promotes Cell Survival.

Galectin-3 (gal-3) is a β-galactoside binding protein related to many tumoral aspects, e.g. angiogenesis, cell growth and motility and resistance to cell death. Evidence has shown its upregulation upon hypoxia, a common feature in solid tumors such as glioblastoma multiformes (GBM). This tumor presents a unique feature described as pseudopalisading cells, which accumulate large amounts of gal-3. Tumor cells far from hypoxic/nutrient deprived areas express little, if any gal-3. Here, we have shown that the hybrid glioma cell line, NG97ht, recapitulates GBM growth forming gal-3 positive pseudopalisades even when cells are grafted subcutaneously in nude mice. In vitro experiments were performed exposing these cells to conditions mimicking tumor areas that display oxygen and nutrient deprivation. Results indicated that gal-3 transcription under hypoxic conditions requires previous protein synthesis and is triggered in a HIF-1α and NF-κB dependent manner. In addition, a significant proportion of cells die only when exposed simultaneously to hypoxia and nutrient deprivation and demonstrate ROS induction. Inhibition of gal-3 expression using siRNA led to protein knockdown followed by a 1.7-2.2 fold increase in cell death. Similar results were also found in a human GBM cell line, T98G. In vivo, U87MG gal-3 knockdown cells inoculated subcutaneously in nude mice demonstrated decreased tumor growth and increased time for tumor engraftment. These results indicate that gal-3 protected cells from cell death under hypoxia and nutrient deprivation in vitro and that gal-3 is a key factor in tumor growth and engraftment in hypoxic and nutrient-deprived microenvironments. Overexpression of gal-3, thus, is part of an adaptive program leading to tumor cell survival under these stressing conditions.

Lack of Galectin-3 Disturbs Mesenteric Lymph Node Homeostasis and B Cell Niches in the Course of Schistosoma mansoni Infection

Galectin-3 is a beta-galactoside-binding protein that has been shown to regulate pathophysiological processes, including cellular activation, differentiation and apoptosis. Recently, we showed that galectin-3 acts as a potent inhibitor of B cell differentiation into plasma cells. Here, we have investigated whether galectin-3 interferes with the lymphoid organization of B cell compartments in mesenteric lymph nodes (MLNs) during chronic schistosomiasis, using WT and galectin-3(-/-) mice. Schistosoma mansoni synthesizes GalNAc beta 1-4(Fuc alpha 1-3) GlcNAc(Lac-DiNAc) structures (N-acetylgalactosamine beta 1-4 N-acetylglucosamine), which are known to interact with galectin-3 and elicit an intense humoral response. Antigens derived from the eggs and adult worms are continuously drained to MLNs and induce a polyclonal B cell activation. In the present work, we observed that chronically-infected galectin-3(-/-) mice exhibited a significant reduced amount of macrophages and B lymphocytes followed by drastic histological changes in B lymphocyte and plasma cell niches in the MLNs. The lack of galectin-3 favored an increase in the lymphoid follicle number, but made follicular cells more susceptible to apoptotic stimuli. There were an excessive quantity of apoptotic bodies, higher number of annexin V(+)/PI(-) cells, and reduced clearance of follicular apoptotic cells in the course of schistosomiasis. Here, we observed that galectin-3 was expressed in nonlymphoid follicular cells and its absence was associated with severe damage to tissue architecture. Thus, we convey new information on the role of galectin-3 in regulation of histological events associated with B lymphocyte and plasma cell niches, apoptosis, phagocytosis and cell cycle properties in the MLNs of mice challenged with S. mansoni.

Absence of galectin-3 does not affect the development of experimental tongue carcinomas in mice

Background: Galectin-3 is a lectin that presents pivotal roles in tumor biology and there are no studies evaluating their expression in dysplasias and carcinomas developed from tongue carcinogenesis models. Aims: To investigate the role of galectin-3 in the development of tongue carcinomas using a mouse model of oral carcinogenesis. Methods: Galectin-3-deficient (gal3(-/-)) and wild-type (gal3(+/+)) mice were challenged with 4-nitroquinoline-1-oxide in drinking water for 16 weeks and killed at different times. Tongues were removed and the number of dysplasias and carcinomas was counted. An immunohistochemical study for galectin-3 was performed only in the tongue from gal3(+/+) mice. Results: In both groups, a reduction of dysplasias and an increase of carcinomas from week 16 to week 32 (p > 0.05) were observed. A predominance of high cytoplasmic and nuclear galectin-3 expression was observed in carcinomas (64.7%) and dysplasias (55.5%), respectively (p > 0.05). The perilesional areas always presented a statistical cytoplasmic and nuclear galectin-3 overexpression. Conclusions: Absence of galectin-3 did not directly affect the process of carcinogenesis and a cytoplasm shift of galectin-3 seems to be associated with development of tongue carcinomas. (C) 2010 Elsevier Inc. All rights reserved.

Activation of the Wnt/Beta-catenin Signaling Pathway during Oral Carcinogenesis Process Is Not Influenced by the Absence of Galectin-3 in Mice

Background/Aim: Galectin-3 has been associated with activated Wnt pathway, translocating beta-catenin into the nucleus. However, it is still unknown whether this lectin drives the Wnt signaling activation in lesions from galectin-3-deficient (Gal3(-/-)) mice. The purpose was to study beta-catenin expression in tongue lesions from Gal3(-/-) and wildtype (Gal3(+/+)) mice and the status of Wnt signaling. Materials and Methods: Twenty Gal3(-/-) and Gal3(+/+) male mice were challenged with 4-nitroquinolin-1-oxide and killed at week 16 and 32. Tongues were processed and stained with H&E to detect dysplasias and carcinomas. An imunohistochemical assay was performed to evaluate beta-catenin expression. Results: Carcinomas were more evident in Gal3(+/+) than Gal3(-/-) mice (55.5% vs. 28.5%, respectively; p>0.05). Elevated expression of non-membranous beta-catenin was observed in dysplasias and carcinomas from both groups (p>0.05). Conclusion: Absence of galectin-3 does not interfere in the pattern of beta-catenin expression and therefore in the mediation of the Wnt signaling pathway.

Lack of galectin-3 alters the balance of innate immune cytokines and confers resistance to Rhodococcus equi infection

Galectin-3 is a p-galactoside-binding lectin implicated in the fine-tuning of innate immunity. Rhodococcus equi, a facultative intracellular bacterium of macrophages, causes severe granulomatous bronchopneumonia in young horses and immunocompromised humans. The aim of this study is to investigate the role of galectin-3 in the innate resistance mechanism against R. equi infection. The bacterial challenge of galectin-3-deficient mice (gal3(-/-)) and their wild-type counterpart (gal3(+/+)) revealed that the LD50 for the gal3(-/-) mice was about seven times higher than that for the gal3(+/+) mice. When challenged with a sublethal dose, gal3(-/-) mice showed lower bacteria counts and higher production of IL-12 and IFN-gamma production, besides exhibiting a delayed although increased inflammatory reaction. Gal3(-/-) macrophages exhibited a decreased frequency of bacterial replication and survival, and higher transcript levels of IL-1 beta, IL-6, IL-10, TLR2 and MyD88. R. equi-infected gal3(+/+) macrophages showed decreased expression of TLR2, whereas R. equi-infected gal3(-/-) macrophages showed enhanced expression of this receptor. Furthermore, galectin-3 deficiency in macrophages may be responsible for the higher IL-1 beta serum levels detected in infected gal3(-/-) mice. Therefore galectin-3 may exert a regulatory role in innate immunity by diminishing IL-1 beta production and thus affecting resistance to R. equi infection.

Galectin-3 regulates peritoneal B1-cell differentiation into plasma cells

Extracellular galectin-3 participates in the control of B2 lymphocyte migration and adhesion and of their differentiation into plasma cells. Here, we analyzed the role of galectin-3 in B1-cell physiology and the balance between B1a and B1b lymphocytes in the peritoneal cavity. In galectin-3(-/-) mice, the total number of B1a lymphocytes was lower, while B1b lymphocyte number was higher as compared to wild-type mice. The differentiation of B1a cells into plasma cells was associated with their abnormal adhesion and location on the mesentery. The B220 and CD43, constitutively expressed by B1 lymphocytes, were respectively up- and downregulated in galectin-3(-/-) mice. Mononuclear cells were strongly adhered to the mesenteric membranes of both CD43(-/-) and galectin-3(-/-) mice, but in contrast to CD43(-/-) mice, the accumulation of B1 cells in peritoneal membranes in galectin-3(-/-) mice was accompanied by their functional differentiation into plasma cells. We have shown that in the absence of galectin-3, B1-cell differentiation into plasma cells is favored and the dynamic equilibrium of B1-cell populations in the peritoneum is maintained through a compensatory increase in B1b lymphocytes.

Galectin-3: A Link between Myocardial and Arterial Stiffening in Patients with Acute Decompensated Heart Failure?

Abstract Background: Heart failure is accompanied by abnormalities in ventricular-vascular interaction due to increased myocardial and arterial stiffness. Galectin-3 is a recently discovered biomarker that plays an important role in myocardial and vascular fibrosis and heart failure progression. Objectives: The aim of this study was to determine whether galectin-3 is correlated with arterial stiffening markers and impaired ventricular-arterial coupling in decompensated heart failure patients. Methods: A total of 79 inpatients with acute decompensated heart failure were evaluated. Serum galectin-3 was determined at baseline, and during admission, transthoracic echocardiography and measurements of vascular indices by Doppler ultrasonography were performed. Results: Elevated pulse wave velocity and low arterial carotid distensibility are associated with heart failure in patients with preserved ejection fraction (p = 0.04, p = 0.009). Pulse wave velocity, carotid distensibility and Young’s modulus did not correlate with serum galectin-3 levels. Conversely, raised galectin-3 levels correlated with an increased ventricular-arterial coupling ratio (Ea/Elv) p = 0.047, OR = 1.9, 95% CI (1.0‑3.6). Increased galectin-3 levels were associated with lower rates of left ventricular pressure rise in early systole (dp/dt) (p=0.018) and raised pulmonary artery pressure (p = 0.046). High galectin-3 levels (p = 0.038, HR = 3.07) and arterial pulmonary pressure (p = 0.007, HR = 1.06) were found to be independent risk factors for all-cause mortality and readmissions. Conclusions: This study showed no significant correlation between serum galectin-3 levels and arterial stiffening markers. Instead, high galectin-3 levels predicted impaired ventricular-arterial coupling. Galectin-3 may be predictive of raised pulmonary artery pressures. Elevated galectin-3 levels correlate with severe systolic dysfunction and together with pulmonary hypertension are independent markers of outcome.

Detection of the Tim-3 ligand, galectin-9, inside the allograft during a rejection episode

Introduction: Tim-3 is a Th1 lymphocytes membrane protein with inhibitory function. Its ligand, galectin-9, was recently identified and it is expressed in some lymphocyte subpopulation. In addition, endothelial cells and fibroblasts can also express galectin-9 according to the local cytokine milieu. Both molecules can act as important regulatory tools in the immune system. Aim: Evaluate the expression of these immunoregulatory molecules inside kidney allografts during acute rejection episodes. Methods: By using a quantitative polymerase chain reaction assay, we measured the levels of messenger RNA (mRNA) for galectin-9 and Tim-3 in 21 samples obtained at allograft nephrectomy. Five samples received the histological diagnosis of acute non-vascular rejection (ANVR), twelve of acute vascular rejection (AVR), and five of loss of non-immune cause (LNIC; as control). As cytolytic response markers we measured mRNA levels of granzyme B, interferon-gamma and perforin. The statistic analysis was performed using one way analysis of variance (ANOVA) and Pearson correlation. Results: The mean levels of Tim-3 mRNA expression were 13.99 +/- 6.99 for LNIC, 48.13 +/- 54.47 for RACNV and 238.63 +/- 333.14 for RAV (p = 0.004). For galectin-9, the mean values were 0.57 +/- 0.49 for LNIC, 0.66 +/- 0.36 for RACNV and 2.34 +/- 1.62 for RAV (p = 0.006). Furthermore, there was a positive correlation between both molecules (r = 0.526, p = 0.016). Also. granzyme B, perforin and interferon-gamma mRNA expression were different among the three groups. Conclusion: Messenger RNA level expressions of all the studied molecules were higher inside allografts with more severe rejection. Moreover, there was a positive correlation between galectin-9 and Tim-3 mRNA levels. The simultaneous expression of galectin-9 and Tim-3 may indicate an immunoregulatory function, during the ongoing cytotoxic response. (C) 2008 Elsevier B.V. All rights reserved.

A Role for galectin-3 in renal tissue damage triggered by ischemia and reperfusion injury

Ischemic-reperfusion injury (IRI) triggers an inflammatory response involving neutrophils/macrophages, lymphocytes and endothelial cells. Galectin-3 is a multi-functional lectin with a broad range of action such as promotion of neutrophil adhesion, induction of oxidative stress, mastocyte migration and degranulation, and production of pro-inflammatory cytokines. The aim of this study was evaluate the role of galectin-3 in the inflammation triggered by IRI. Galectin-3 knockout (KO) and wild type (wt) mice were subjected to 45 min of renal pedicle occlusion. Blood and kidney samples were collected at 6, 24, 48 and 120 h. Blood urea was analyzed enzymatically, while MCP-1, IL-6 and IL-1 beta were studied by real-time PCR. Reactive oxygen species (ROS) was investigated by flow cytometry. Morphometric analyses were performed at 6, 24, 48 and 120 h after reperfusion. Urea peaked at 24 h, being significantly lower in knockout animals (wt = 264.4 +/- 85.21 mg/dl vs. gal-3 KO = 123.74 +/- 29.64 mg/dl, P = 0.001). Galectin-3 knockout animals presented less acute tubular necrosis and a more prominent tubular regeneration when compared with controls concurrently with lower expression of MCP-1, IL-6, IL-1 beta, less macrophage infiltration and lower ROS production at early time points. Galectin-3 seems to play a role in renal IRI involving the secretion of macrophage-related chemokine, pro-inflammatory cytokines and ROS production.

Monocyte migration driven by galectin-3 occurs through distinct mechanisms involving selective interactions with the extracellular matrix

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The involvement of the spleen during chronic phase of Schistosoma mansoni infection in galectin-3(-/-) mice

Schistosoma mansoni synthesizes glycoconjugates which interact with galectin-3, eliciting an intense humoral immune response. Moreover, it was demonstrated that galectin-3 regulates B cell differentiation into plasma cells. Splenomegaly is a hallmark event characterized by polyclonal B cell activation and enhancement of antibody production. Here, we investigated whether galectin-3 interferes with spleen organization and B cell compartment during chronic schistosomiasis, using wild type (WT) and galectin-3(-/-) mice. In chronically-infected galectin-3(-/-) mice the histological architecture of the spleen, including white and red pulps, was disturbed with heterogeneous lymphoid follicles, an increased number of plasma cells (CD19(-)B220(-/low)CD138(+)) and a reduced number of macrophages (CD19(-)B220(-)Mac-1(+)CD138(-)) and B lymphocytes (CD19(+)B220(+/high)CD138(-)), compared with the WT infected mice. In the absence of galectin-3 there was an increase of annexin-V+PI- cells and a major presence of apoptotic cells in spleen compared with WT infected mice. In spleen of WT infected mice galectin-3 was largely expressed in lymphoid follicles and extrafollicular sites. Thus, we propose that galectin-3 plays a role in splenic architecture, controlling distinct events such as apoptosis, macrophage activity, B cell differentiation and plasmacytogenesis in the course of S. mansoni infection.

Up-regulation Of Dnam-1 And Nkp30, Associated With Improvement Of Nk Cells Activation After Long-term Culture Of Mononuclear Cells From Patients With Ovarian Neoplasia.

This study aimed at evaluating the functional activation and activating receptors expression on resting, short- and long-term NK and NK-like T cells from blood of ovarian neoplasia patients. Blood from patients with adnexal benign alterations (n = 10) and ovarian cancer (grade I-IV n = 14) were collected after signed consent. Effector cells activation was evaluated by the expression of the CD107a molecule. Short-term culture was conducted overnight with IL-2 and long-term culture for 21 days, by a method designed to expand CD56(+) lymphocytes. Short-term culture significantly increased NK cells activation compared to resting NK cells (p<0.05), however, the long-term procedure supported an even higher increase (p<0.001). Resting NK-like T cells showed poor activation, which was not altered by the culture procedures. The long-term culture effectively increased the expression of the activating receptors on NK and NK-like T cells, either by increasing the number of cells expressing a given receptor and/or by up-regulating their expression intensity. As a conclusion, the long-term culture system employed, resulted in a high number of functional NK cells. The culture system was particularly efficient on the up-regulation of NKp30 and DNAM-1 receptors on NK cells.