Biomedical subjects

Fu-Tong Liu

Publications and source records attributed to Fu-Tong Liu.

At least 19 recordsLinked to original sources

PubMed2024

B4GALT1-dependent galectin-8 binding with TGF-β receptor suppresses colorectal cancer progression and metastasis.

Transforming growth factor (TGF)-β signaling is critical for epithelial-mesenchymal transition (EMT) and colorectal cancer (CRC) metastasis. Disruption of Smad-depednent TGF-β signaling has been shown in CRC cells. However, TGF-β receptor remains expressed on CRC cells. Here, we investigated whether the cooperation between tumor-associated N-glycosylation and a glycan-binding protein modulated the TGF-β-driven signaling and metastasis of CRC. We showed that galectin-8, a galactose-binding lectin, hampered TGF-β-induced EMT by interacting with the type II TGF-β receptor and competing with TGF-β binding. Depletion of galectin-8 promoted the migration of CRC cells by increasing TGF-β-receptor-mediated RAS and Src signaling, which was attenuated after recombinant galectin-8 treatment. Treatment with recombinant galectin-8 also induces JNK-dependent apoptosis in CRC cells. The anti-migratory effect of galectin-8 depended on β4-galactosyltransferase-I (B4GALT1), an enzyme involved in N-glycan synthesis. Increased B4GALT1 expression was observed in clinical CRC samples. Depletion of B4GALT1 reduced the metastatic potential of CRC cells. Furthermore, inducible expression of galectin-8 attenuated tumor development and metastasis of CRC cells in an intra-splenic injection model. Our results thus demonstrate that galectin-8 alters non-canonical TGF-β response in CRC cells and suppresses CRC progression.

Humans↗

PubMed2007

Galectin-3 stimulates preadipocyte proliferation and is up-regulated in growing adipose tissue.

OBJECTIVE: Some cytokines and mediators of inflammation can alter adiposity through their effects on adipocyte number. To probe the molecular basis of obesity, this study determined whether galectin-3 was present in adipose tissue and investigated its effects on fat cell number. RESEARCH METHODS AND PROCEDURES: In the first study, obesity-prone C57BL/6J mice were fed with high-fat (58%) diet. Epididymal fat pads were collected at Day 0, Day 60, and Day 120 after the start of high-fat feeding. RESULTS: Levels of adipocyte galectin-3 protein, determined using Western blot analysis, increased as the mice became obese. Galectin-3 mRNA and protein were then detected in human adipose tissue, primarily in the preadipocyte fraction. It was found that recombinant human galectin-3 stimulated proliferation of primary cultured preadipocytes as well as DNA synthesis through lectin-carbohydrate interaction. DISCUSSION: Galectin-3, which has been known to play a versatile role especially in immune cells, might play a role also in adipose tissue and be associated with the pathophysiology of obesity.

Adipocytes↗

PubMed2006

Role of galectin-3 in mast cell functions: galectin-3-deficient mast cells exhibit impaired mediator release and defective JNK expression.

Galectin-3 is a member of the beta-galactoside-binding animal lectin family expressed in various cell types, including mast cells. To determine the role of galectin-3 in the function of mast cells, we studied bone marrow-derived mast cells (BMMC) from wild-type (gal3(+/+)) and galectin-3-deficient (gal3(-/-)) mice. Cells from the two genotypes showed comparable expression of IgE receptor and c-Kit. However, upon activation by FcepsilonRI cross-linkage, gal3(-/-) BMMC secreted a significantly lower amount of histamine as well as the cytokine IL-4, compared with gal3(+/+) BMMC. In addition, we found significantly reduced passive cutaneous anaphylaxis reactions in gal3(-/-) mice compared with gal3(+/+) mice. These results indicate that there is a defect in the response of mast cells in gal3(-/-) mice. Unexpectedly, we found that gal3(-/-) BMMC contained a dramatically lower basal level of JNK1 protein compared with gal3(+/+) BMMC, which is probably responsible for the lower IL-4 production. The decreased JNK1 level in gal3(-/-) BMMC is accompanied by a lower JNK1 mRNA level, suggesting that galectin-3 regulates the transcription of the JNK gene or processing of its RNA. All together, these results point to an important role of galectin-3 in mast cell biology.

Anaphylaxis↗

PubMed2006

The COOH-terminal globular domain of fibrinogen gamma chain suppresses angiogenesis and tumor growth.

Fibrinogen is a major plasma protein (350 kDa) that induces proliferative signals by serving as a scaffold to support the binding of growth factors and to promote the cellular responses of adhesion, proliferation, and migration during wound healing, angiogenesis, and tumor growth. Fibrin(ogen) degradation products generated during fibrinolysis are implicated in tissue injury. The fibrinogen gamma chain has a COOH-terminal globular domain (gamma C, residues 151-411 of the gamma chain, 30 kDa) to which several integrin cell adhesion receptors (e.g., platelet alpha(IIb)beta(3), endothelial alpha(v)beta(3), and leukocyte alpha(M)beta(2)) bind. Integrins play a critical role in signal transduction from fibrin(ogen). We found that gamma C and its truncation mutant (designated gamma C399tr), with a deletion of the COOH-terminal 12 residues, induced apoptosis of endothelial cells and blocked tube formation of endothelial cells. DLD-1 human colon cancer cells that secrete gamma C or gamma C399tr grew at similar levels in vitro but grew much slower in vivo than mock-transfected cells. The recombinant purified gamma C399tr fragment markedly suppressed tumor growth, development of intratumoral vasculature, and tumor metastasis in vivo in the highly metastatic Met-1 breast cancer model. The determinant responsible for binding to endothelial cells is cryptic in native fibrinogen but is exposed in gamma C and gamma C399tr. These results suggest that fibrinogen has a novel cryptic determinant, which can exert apoptosis-inducing activity on endothelial cells when exposed, and polypeptides containing this determinant have therapeutic potential.

Angiogenesis Inhibitors↗

PubMed2006

Galectin-3 induces death of Candida species expressing specific beta-1,2-linked mannans.

Lectins play a critical role in host protection against infection. The galectin family of lectins recognizes saccharide ligands on a variety of microbial pathogens, including viruses, bacteria, and parasites. Galectin-3, a galectin expressed by macrophages, dendritic cells, and epithelial cells, binds bacterial and parasitic pathogens including Leishmania major, Trypanosoma cruzi, and Neisseria gonorrhoeae. However, there have been no reports of galectins having direct effects on microbial viability. We found that galectin-3 bound only to Candida albicans species that bear beta-1,2-linked oligomannans on the cell surface, but did not bind Saccharomyces cerevisiae that lacks beta-1,2-linked oligomannans. Surprisingly, binding directly induced death of Candida species containing specific beta-1,2-linked oligomannosides. Thus, galectin-3 can act as a pattern recognition receptor that recognizes a unique pathogen-specific oligosaccharide sequence. This is the first description of antimicrobial activity for a member of the galectin family of mammalian lectins; unlike other lectins of the innate immune system that promote opsonization and phagocytosis, galectin-3 has direct fungicidal activity against opportunistic fungal pathogens.

Candida↗

PubMed2006

Cell mechanics using atomic force microscopy-based single-cell compression.

We report herein the establishment of a single-cell compression method based on force measurements in atomic force microscopy (AFM). The high-resolution bright-field or confocal laser scanning microscopy guides the location of the AFM probe and then monitors the deformation of cell shape, while microsphere-modified AFM probes compress the cell and measure the force. Force and deformation profiles of living cells reveal a cubic relationship at small deformation (<30%), multiple peaks at 30-70% compression, and a rapid increase at over 80% deformation. The initial compression may be described qualitatively and quantitatively using a simple model of a nonpermeable balloon filled with incompressible fluid. Stress peaks reflect cell membrane rupture, followed by the deformation and rupture of intracellular components, beyond which the cell responses become irreversible. The Young's modulus and bending constant of living cell membranes are extracted from the balloon models, with 10-30 MPa and 17-52 kT, respectively. The initial compression of dead and fixed cells is modeled using Hertzian contact theory, assuming that the cell is a homogeneous sphere. Dead cells exhibit a cytoskeleton elasticity of 4-7.5 kPa, while fixation treatment leads to a dramatic increase in the cytoskeletal Young's modulus (150-230 kPa) due to protein cross-linking by imine bonds. These results demonstrate the high sensitivity of the single-cell compression method to the molecular-level structural changes of cells, which suggests a new generic platform for investigating cell mechanics in tissue engineering and cancer research.

Cell Shape↗

PubMed2006

Molecular basis of interaction between NG2 proteoglycan and galectin-3.

Previous work has demonstrated the ability of the NG2 proteoglycan, a component of microvascular pericytes, to stimulate endothelial cell motility and morphogenesis. This function of NG2 depends on formation of a complex with galectin-3 and alpha3beta1 integrin to stimulate integrin-mediated transmembrane signaling. In addition, the co-expression of galectin-3 and NG2 in A375 melanoma cells suggests that the malignant properties of these cells may be affected by interaction between the two molecules. Here, we extend the theme of co-expression and interaction of NG2 and galectin-3 to human glioma cells. We also establish a molecular basis for the NG2/galectin-3 interaction. The C-terminal carbohydrate recognition domain of galectin-3 is responsible for binding to the NG2 core protein. Within the NG2 extracellular domain, the membrane-proximal D3 segment of the proteoglycan contains the primary binding site for interaction with galectin-3. The interaction between galectin-3 and NG2 is a carbohydrate-dependent one mediated by N-linked rather than O-linked oligosaccharides within the D3 domain of the NG2 core protein. These studies establish a foundation for attempts to reduce the aggressive properties of tumor cells by disrupting the NG2/galectin-3 interaction.

Antigens↗

PubMed2006

Galectin-3 and galectin-1 bind distinct cell surface glycoprotein receptors to induce T cell death.

Galectins are a family of mammalian beta-galactoside-binding proteins that positively and negatively regulate T cell death. Extracellular galectin-1 directly induces death of T cells and thymocytes, while intracellular galectin-3 blocks T cell death. In contrast to the antiapoptotic function of intracellular galectin-3, we demonstrate that extracellular galectin-3 directly induces death of human thymocytes and T cells. However, events in galectin-3- and galectin-1-induced cell death differ in a number of ways. Thymocyte subsets demonstrate different susceptibility to the two galectins: whereas galectin-1 kills double-negative and double-positive human thymocytes with equal efficiency, galectin-3 preferentially kills double-negative thymocytes. Galectin-3 binds to a complement of T cell surface glycoprotein receptors distinct from that recognized by galectin-1. Of these glycoprotein receptors, CD45 and CD71, but not CD29 and CD43, appear to be involved in galectin-3-induced T cell death. In addition, CD7 that is required for galectin-1-induced death is not required for death triggered by galectin-3. Following galectin-3 binding, CD45 remains uniformly distributed on the cell surface, in contrast to the CD45 clustering induced by galectin-1. Thus, extracellular galectin-3 and galectin-1 induce death of T cells through distinct cell surface events. However, as galectin-3 and galectin-1 cell death are neither additive nor synergistic, the two death pathways may converge inside the cell.

Antigens, CD↗

PubMed2006

Galectins in apoptosis.

Galectins are a family of animal lectins with affinity for beta-galactosides. By using recombinant proteins, a number of galectins have been shown to interact with cell-surface and extracellular matrix glycoconjugates through lectin-carbohydrate interactions. Through this action, they can affect a variety of cellular processes, and the most extensively documented function is induction of apoptosis. By using gene transfection approaches, galectins have been shown to regulate various cellular processes, including apoptosis. Evidence has been provided that some of these functions involve binding to cytoplasmic and nuclear proteins, through protein-protein interactions, and modulation of intracellular signaling pathways. Thus, some galectins are pro-apoptotic, whereas others are anti-apoptotic; some galectins induce apoptosis by binding to cell surface glycoproteins, whereas others regulate apoptosis through interactions with intracellular proteins. This review describes involvement of galectin-1, -2, -3, -7, -8, -9, and -12 in apoptosis.

Animals↗

PubMed2006

Toxoplasma gondii infection reveals a novel regulatory role for galectin-3 in the interface of innate and adaptive immunity.

In attempts to investigate the role of galectin-3 in innate immunity, we studied galectin-3-deficient (gal3-/-) mice with regard to their response to Toxoplasma gondii infection, which is characterized by inflammation in affected organs, Th-1-polarized immune response, and accumulation of cysts in the central nervous system. In wild-type (gal3+/+) mice, infected orally, galectin-3 was highly expressed in the leukocytes infiltrating the intestines, liver, lungs, and brain. Compared with gal3+/+, infected gal3-/- mice developed reduced inflammatory response in all of these organs but the lungs. Brain of gal3-/- mice displayed a significantly reduced number of infiltrating monocytes/macrophages and CD8+ cells and a higher parasite burden. Furthermore, gal3-/- mice mounted a higher Th1-polarized response and had comparable survival rates on peroral T. gondii infection, even though they were more susceptible to intraperitoneal infection. Interestingly, splenic cells and purified CD11c+ dendritic cells from gal3-/- mice produced higher amounts of interleukin-12 than cells from gal3+/+ mice, possibly explaining the higher Th1 response verified in the gal3-/- mice. We conclude that galectin-3 exerts an important role in innate immunity, including not only a pro-inflammatory effect but also a regulatory role on dendritic cells, capable of interfering in the adaptive immune response.

Animals↗

PubMed2005

Genetic background determines susceptibility to experimental immune-mediated blepharoconjunctivitis: comparison of Balb/c and C57BL/6 mice.

Balb/c and C57BL/6 mice have been reported to be biased towards Th2 and Th1 immune responses, respectively. We investigated which strain is more susceptible to the development of experimental immune-mediated blepharoconjunctivitis (EC), which is predominantly mediated by Th2 immune responses. EC was induced by three different methods in Balb/c and C57BL/6 mice using ragweed (RW) as the antigen. The mice were thus either actively immunized with RW, passively immunized by transfer of RW-primed T cells, or passively immunized by transfer of RW-specific IgE, followed by RW challenge in eye drops. Twenty-four hours after the challenge, conjunctivas, sera and spleens were harvested for histological analysis, measurement of serum IgE and assessment of cellular immune responses, respectively. The responses of the Balb/c and C57BL/6 mice were compared. In addition, to assess the involvement of IFN-gamma in the development of EC in the two strains, IFN-gamma knockout (GKO) mice of the two strains were actively immunized and evaluated as above. Regardless of the method of induction, EC, as determined by the degree of eosinophil infiltration into the conjunctiva, was more severe in Balb/c mice than in C57BL/6 mice. Moreover, more IgE was produced by actively immunized Balb/c mice than C57BL/6 mice and RW-primed splenocytes from Balb/c mice produced more IL-4 but less IFN-gamma than those from C57BL/6 mice. EC could be induced in the GKO mice of both strains. However, when their EC was compared to that in WT mice, significantly less infiltration of eosinophils was noted in the Balb/c GKO mice. Taken together, Balb/c mice are more susceptible to EC than C57BL/6 mice and this higher susceptibility might be related to the Th2 immune response bias of Balb/c mice. Furthermore, the involvement of endogenous IFN-gamma in the development of EC in these two strains differs.

Adoptive Transfer↗

PubMed2005

Comparative phenotypic characterization of keratinocytes originating from hair follicles.

The principal pool of epidermal stem cells is located in the bulge region of the hair follicle root sheath. In this research project, we have used a refined procedure to isolate porcine hair follicles including their root sheath and for comparison purposes also human cell material. These cells migrating from the hair follicles were then cytochemically characterized. A panel of antibodies and two labeled plant lectins were tested on cell material obtained under a range of assorted experimental conditions. Due to their role in growth regulation we also studied two endogenous lectins, specifically monitoring their expression and the presence of accessible ligands. These in vitro results were compared with findings on porcine and human hair follicles and human basal cell carcinomas in situ. The keratinocytes originating from hair follicles in the presence of feeder cells are rather undifferentiated and express galectin-1/galectin-1-binding sites but not galectin-3 in their nuclei associated with DeltaNp63alpha positivity. Nuclear reactivity for galectin-1 was rarely observed in the bulge of the outer root sheath of the human hair follicle and of basal cell carcinomas and absent in porcine tissue samples. Exclusion of feeder cells from our cultivation system of porcine hair follicles led to the formation of spheroid bodies from these keratinocytes. Ki67 as a marker of proliferation was not present in the nuclei of cells forming these spheroids. One part of these bodies is positive for markers of post-mitotic differentiated cells, while the other spheroids are composed of poorly differentiated cells, which are able to adhere to feeder cells and form growing colonies. In summary, the detection of galectin-1 and also nuclear binding sites for this endogenous effector points to intracellular functionality of this lectin. It can be considered a potential marker of a distinct cell population, probably at the beginning of a differentiation cascade of keratinocytes.

Animals↗

PubMed2005

Galectins as modulators of tumour progression.

Galectins are a family of animal lectins with diverse biological activities. They function both extracellularly, by interacting with cell-surface and extracellular matrix glycoproteins and glycolipids, and intracellularly, by interacting with cytoplasmic and nuclear proteins to modulate signalling pathways. Current research indicates that galectins have important roles in cancer; they contribute to neoplastic transformation, tumour cell survival, angiogenesis and tumour metastasis. They can modulate the immune and inflammatory responses and might have a key role helping tumours to escape immune surveillance. How do the different members of the Galectin family contribute to these diverse aspects of tumour biology?

Cell Survival↗

PubMed2005

Dissection of antigen-specific humoral and cellular immune responses for the development of experimental immune-mediated blepharoconjunctivitis in C57BL/6 mice.

PURPOSE: Allergic conjunctivitis is characterized by allergen-specific IgE in the serum and infiltration of eosinophils into the conjunctiva. However, it remains unclear whether early-phase reaction (EPR) mediated by Ag-specific IgE links to late-phase reaction (LPR) in the conjunctiva. We aimed to investigate whether LPR is mediated by either cellular or humoral immune responses. METHODS: Experimental immune-mediated blepharoconjunctivitis (EC) was induced in C57BL/6 mice by either active immunization or passive immunization by transfer of ragweed (RW)-primed lymphocytes and RW-specific IgE, followed by RW challenge onto the conjunctiva. Transferring RW-primed lymphocytes were prepared from RW-primed splenocytes which were stimulated in vitro with RW for 3 days. Fifteen minutes after RW challenge, clinical findings were evaluated and 24 hr after challenge, the conjunctivas and sera were harvested for histologic analysis and measurement of IgE, respectively. RESULTS: EPR was most prominent when EC was induced by transfer of RW-specific IgE. EPR was hardly detectable if EC was induced by transfer of RW-primed lymphocytes. Mild EPR was noted when EC was induced by active immunization. LPR, evaluated by infiltration of eosinophils into the conjunctiva, was most severe when EC was induced by transfer of RW-primed lymphocytes. Minimal, but definite LPR was induced when EC was induced by transfer of RW-specific IgE. Intermediate severity of LPR was induced when EC was induced by active immunization. CONCLUSIONS: LPR in the conjunctiva is dominantly mediated by cellular immune responses, whereas EPR in the conjunctiva is putatively mediated by humoral immune responses. Importantly, LPR in the conjunctiva is inducible by Ag-specific IgE alone, although minute.

Allergens↗

PubMed2005

Regulatory roles of galectins in the immune response.

Galectins are a family of animal lectins with affinity for beta-galactosides. They are differentially expressed by various immune cells and their expression levels appear to be dependent on cell differentiation and activation. They can interact with cell-surface and extracellular matrix glycoconjugates (glycoproteins and glycolipids), through lectin-carbohydrate interactions. Through this action, they can promote cell growth, affect cell survival, modulate cell adhesions, and induce cell migration. They appear to do so by binding to different glycoconjugates decorated by suitable saccharides, rather than through specific receptors. Galectins do not have a classical signal peptide and are often localized in intracellular compartments, including the nucleus. Intracellularly, they can regulate cell growth and survival by interacting with cytoplasmic and nuclear proteins, through protein-protein interactions, thereby affecting intracellular signaling pathways. Current research indicates that galectins play important roles in the immune response through regulating the homeostasis and functions of the immune cells.

Adjuvants, Immunologic↗

PubMed2005

Impaired retinal angiogenesis in diabetes: role of advanced glycation end products and galectin-3.

Suppression of angiogenesis during diabetes is a recognized phenomenon but is less appreciated within the context of diabetic retinopathy. The current study has investigated regulation of retinal angiogenesis by diabetic serum and determined if advanced glycation end products (AGEs) could modulate this response, possibly via AGE-receptor interactions. A novel in vitro model of retinal angiogenesis was developed and the ability of diabetic sera to regulate this process was quantified. AGE-modified serum albumin was prepared according to a range of protocols, and these were also analyzed along with neutralization of the AGE receptors galectin-3 and RAGE. Retinal ischemia and neovascularization were also studied in a murine model of oxygen-induced proliferative retinopathy (OIR) in wild-type and galectin-3 knockout mice (gal3(-/-)) after perfusion of preformed AGEs. Serum from nondiabetic patients showed significantly more angiogenic potential than diabetic serum (P < 0.0001) and within the diabetic group, poor glycemic control resulted in more AGEs but less angiogenic potential than tight control (P < 0.01). AGE-modified albumin caused a dose-dependent inhibition of angiogenesis (P < 0.001), and AGE receptor neutralization significantly reversed the AGE-mediated suppression of angiogenesis (P < 0.01). AGE-treated wild-type mice showed a significant increase in inner retinal ischemia and a reduction in neovascularization compared with non-AGE controls (P < 0.001). However, ablation of galectin-3 abolished the AGE-mediated increase in retinal ischemia and restored the neovascular response to that seen in controls. The data suggest a significant suppression of angiogenesis by the retinal microvasculature during diabetes and implicate AGEs and AGE-receptor interactions in its causation.

Adult↗

PubMed2004

Suppression of tumor growth by galectin-7 gene transfer.

Galectin-7 is a beta-galactoside-binding animal lectin specifically expressed in stratified epithelia. Its expression is inducible by p53 and is down-regulated in squamous cell carcinomas. Other investigators previously showed that galectin-7 is a proapoptotic protein, and we showed that ectopic expression of galectin-7 in HeLa cells renders the cells more sensitive to a variety of apoptotic stimuli. In the present study, we showed that ectopic expression of galectin-7 in the human colon carcinoma cell line DLD-1 also made the cells more sensitive to apoptosis under various conditions. We also found that galectin-7-transfected DLD-1 (DLD-1-Gal7) cells grew significantly more slowly than control transfectants (DLD-1-V) under normal culture conditions in the absence of apoptosis. Moreover, a significantly lower number of colonies were formed from DLD-1-Gal7 cells than from DLD-1-V cells under anchorage-independent cell growth conditions. Most importantly, tumor formation from DLD-1-Gal7 cells was dramatically reduced compared with DLD-1-V cells when these cells were inoculated s.c. into severe combined immunodeficient mice. DLD-1-Gal7 tumors showed a significantly lower proliferation rate than DLD-1-V tumors as determined by in vivo 5-bromo-2'-deoxyuridine incorporation. DLD-1-Gal7 tumors also contained a lower density of blood vessels than DLD-1-V tumors, suggesting that ectopic expression of galectin-7 suppresses angiogenesis. This may partially account for the greater suppressive effect of galectin-7 on tumor growth in vivo than in vitro. Our results show that galectin-7 has a suppressive effect on tumor growth, suggesting that galectin-7 gene transfer or other means of specifically inducing galectin-7 expression may be a new approach for management of cancers.

Animals↗

PubMed2004

LacdiNAc-glycans constitute a parasite pattern for galectin-3-mediated immune recognition.

Although Gal beta 1-4GlcNAc (LacNAc) moieties are the most common constituents of N-linked glycans on vertebrate proteins, GalNAc beta 1-4GlcNAc (LacdiNAc, LDN)-containing glycans are widespread in invertebrates, such as helminths. We postulated that LDN might be a molecular pattern for recognition of helminth parasites by the immune system. Using LDN-based affinity chromatography and mass spectrometry, we have identified galectin-3 as the major LDN-binding protein in macrophages. By contrast, LDN binding was not observed with galectin-1. Surface plasmon resonance (SPR) analysis and a solid phase binding assay demonstrated that galectin-3 binds directly to neoglycoconjugates carrying LDN glycans. In addition, galectin-3 bound to Schistosoma mansoni soluble egg Ags and a mAb against the LDN glycan inhibited this binding, suggesting that LDN glycans within S. mansoni soluble egg Ags contribute to galectin-3 binding. Immunocytochemistry demonstrated high levels of galectin-3 in liver granulomas of S. mansoni-infected hamsters, and a colocalization of galectin-3 and LDN glycans was observed on the parasite eggshells. Finally, we demonstrate that galectin-3 can mediate recognition and phagocytosis of LDN-coated particles by macrophages. These findings provide evidence that LDN-glycans constitute a parasite pattern for galectin-3-mediated immune recognition.

Animals↗