Luciano G. Frigeri

Accelerated diabetic glomerulopathy in galectin-3/AGE receptor 3 knockout mice

Several molecules were shown to bind advanced glycation end products (AGEs) in vitro, but it is not known whether they all serve as AGE receptors and which functional role they play in vivo. We investigated the role of galectin‐3, a multifunctional lectin with (anti)adhesive and growth‐regulating properties, as an AGE receptor and its contribution to the development of diabetic glomerular disease, using a knockout mouse model. Galectin‐3 knockout mice obtained by gene ablation and the corresponding wild‐type mice were rendered diabetic with streptozotocin and killed 4 months later, together with age‐matched nondiabetic controls. Despite a comparable degree of metabolic derangement, galectin‐3‐deficient mice developed ac‐celerated glomerulopathy vs. the wild‐type animals, as evidenced by the more pronounced increase in protein‐uria, extracellular matrix gene expression, and mesan‐gial expansion. This was associated with a more marked renal/glomerular AGE accumulation, indicating it was attributable to the lack of galectin‐3 AGE receptor function. The galectin‐3‐deficient genotype was associated with reduced expression of receptors implicated in AGE removal (macrophage scavenger receptor A and AGE‐R1) and increased expression of those mediating cell activation (RAGE and AGE‐R2). These results show that the galectin‐3‐regulated AGE receptor pathway is operating in vivo and protects toward AGE‐induced tissue injury in contrast to that through RAGE.—Pugliese, G., Pricci, F., Iacobini, C., Leto, G., Amadio, L., Barsotti, P., Frigeri L., Hsu, D. K., Vlassara, H., Liu, F.‐T., Di Mario, U. Accelerated diabetic glomerulopathy in galectin‐3/AGE receptor 3 knockout mice. FASEB J. 15, 2471–2479 (2001)

Comparative Analysis of Galectins in Primary Tumors and Tumor Metastasis in Human Pancreatic Cancer

Galectins are galactoside-binding proteins that exhibit an important function in tumor progression by promoting cancer cell invasion and metastasis formation. Using Northern blotting and Western blotting analysis, in situ hybridization (ISH), and immunohistochemistry (IHC), we studied galectin-1 and galectin-3 in tissue samples of 33 primary pancreatic cancers and in tumor metastases in comparison to 28 normal pancreases. Furthermore, the molecular findings were correlated with the clinical and histopathological parameters of the patients. Northern blotting and Western blotting analysis showed significantly higher galectin-1 and galectin-3 mRNA and protein levels in pancreatic cancer samples than in normal controls. For galectin-1, no ISH signals and immunoreactivity were observed in acinar or ductal cells in the normal pancreas and in pancreatic cancer cells, whereas fibroblasts and extracellular matrix cells around the cancer mass exhibited strong mRNA signals and immunoreactivity. Galectin-3 mRNA signals and immunoreactivity were strongly present in most pancreatic cancer cells, whereas in the normal controls only faint ISH and IHC signals were seen in some ductal cells. Metastatic pancreatic cancer cells exhibited moderate to strong galectin-3 immunoreactivity but were negative for galectin-1. No relationship between the galectin-1 and galectin-3 mRNA levels and the tumor stage or between the IHC staining score and the tumor stage was found. However, galectin-1 mRNA levels and the IHC staining score were significantly higher in poorly differentiated tumors compared with well/moderately differentiated tumors, whereas for galectin 3 no differences were found. The expression pattern of galectin-1 and galectin-3 in pancreatic cancer tissues indicates that galectin-1 plays a role in the desmoplastic reaction that occurrs around pancreatic cancer cells, whereas galectin-3 appears to be involved in cancer cell proliferation. High levels of galectin-3 in metastatic cancer cells suggest an impact on metastasis formation.

An endogenous lectin, galectin-3 (ϵBP / Mac-2), potentiates IL-1 production by human monocytes

Galectin-3 is a member of a growing family of beta-galactoside-binding animal lectins and previously designated as epsilon BP (IgE-binding protein) by this laboratory and as Mac-2, CBP35, L-34 and L-29 by other researchers. While possible intracellular functions have been proposed for galectin-3, existing data also suggest an extracellular modulatory role of this lectin. For example, epsilon BP/Mac-2 was found to be secreted by various cells and capable of activating mast cells, possibly through cross-linking of cell surface glycoproteins involved in cell activation. In this study, we showed that epsilon BP bound to human monocytes via its lectin function. Furthermore, we found that epsilon BP potentiated IL-1 production by monocytes in a manner that was inhibitable by the saccharide ligand of epsilon BP. The results further support a role of this lectin in potentiating activities of inflammatory cells and thereby amplifying inflammatory responses.

Galectin-1 and galectin-3 in chronic pancreatitis.

Galectin-1 and galectin-3 have important functions in cell-cell interactions, cell adhesion to extracellular matrix, the organization of extracellular matrix, and tissue remodeling. To assess their potential role in chronic pancreatitis (CP), we examined their expression by Northern blot analysis, in situ hybridization, immunohistochemistry, and Western blot analysis in normal and CP pancreatic tissues. Northern blot analysis revealed a 4.5-fold increase of galectin-1 mRNA (p < 0.01) and a 3.8-fold increase of galectin-3 mRNA (p < 0.01) in CP samples compared with normal controls. In situ hybridization analysis of normal pancreas indicated low abundance of galectin-1 mRNA in fibroblasts, whereas galectin-3 mRNA was moderately present in ductal cells. CP samples exhibited moderate to intense galectin-1 mRNA signals in fibroblasts, whereas galectin-3 mRNA signals were intense in the cells of ductular complexes and weak in the degenerating acinar cells. In addition, intense galectin-1 and galectin-3 mRNA signals were present in nerves of normal and CP samples. Immunohistochemistry showed a distribution pattern of galectin-1 and galectin-3 similar to that described for in situ hybridization. Relative quantification of galectin-1 and galectin-3 protein by immunoblotting revealed an increase of 3.2-fold and 3.0-fold, respectively, in CP compared with normal controls. There was a significant correlation between galectin-1 and fibrosis and between galectin-3 and fibrosis and the density of ductular complexes. Up-regulation of galectin-1 in fibroblasts and galectin-3 in ductular complexes suggests a role of these lectins in tissue remodeling in CP. Galectin-1 might participate in ECM changes, whereas galectin-3 seems to be involved in both ECM changes and ductular complex formation.

Expression and function of an IgE-binding animal lectin (ϵBP) in mast cells

Abstract ϵBP (IgE-binding protein) is a 31,000 Mr protein originally identified in rat basophilic leukemia (RBL) cells. The protein is composed of two domains with the amino-terminal domain containing a highly conserved repetitive sequence and the carboxyl-terminal domain containing consensus sequences shared by other β-galactoside-binding soluble lectins. The protein has wide tissue distribution, is found on cell surfaces and in extracellular milieu. By combined efforts from several research groups including ours a multifunctional nature of this lectin began to emerge. This review emphasizes the following characteristics of ϵBP: (i) ϵBP is secreted by cells such as macrophages; (ii) like many other lectins, ϵBP functions at least bivalently; (iii) ϵBP has specificity for distinct oligosaccharide structures that have a terminal galactose not masked by sialic acids; and (iv) in addition to binding IgE, ϵBP binds to surfaces of various cell types via lectin-carbohydrate interaction. Importantly, ϵBP binds to the IgE receptor on mast cells. We propose that ϵBP can function as a modulatory protein on various cells by cross-linking critical cell surface glycoproteins. The proposed action of ϵBP on mast cells is presented as a model.

Galectin-3 inhibits granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven rat bone marrow cell proliferation and GM-CSF-induced gene transcription.

The expression of galectin-3 (formerly known as IgE-binding protein or Mac-2) in rat bone marrow (BM) was investigated by FACS, immunocytochemical and immunoblot analysis. The functional significance of rat recombinant galectin-3 on mouse recombinant granulocyte-macrophage colony-stimulating factor (GM-CSF)-driven proliferation of macrophage progenitors and gene transcription was further examined. Immunocytochemical analysis of in situ BM sections demonstrated galectin-3 in myelopoietic cells and surrounding stroma, whereas erythropoietic and lymphopoietic environments essentially lacked galectin-3 expression. FACS analysis demonstrated that incubation of freshly isolated BMC with lactose, a competing ligand for galectin-3 binding to glycoconjugates, decreased binding of antigalectin antibodies to cells primarily expressing the myeloid antigen recognized by mAb His-54. Similarly, lectin-mediated binding of exogenous galectin-3 to myeloid lineage cells was also demonstrated. Immunoblot analysis of BM eluates demonstrated galectin-3 both in the extracellular matrix and in a lactose elutable form, bound to the surface of BMC. [3H]Thymidine incorporation studies on BMC cultured in the presence of galectin-3 demonstrated suppression of GM-CSF-induced proliferation by galectin-3. In addition, differential display analysis of immediate early gene expression in BMC cultured in the presence of galectin-3 revealed a 76.2% inhibition of GM-CSF-induced gene transcription by galectin-3 assessed by the number of PCR-fragments generated. Our data suggest a role for galectin-3 in the organization of myelopoietic compartments in rat BM and regulation of the action of growth factors on myelopoietic precursor cells.