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Fu-Tong Liu

Publications and source records attributed to Fu-Tong Liu.

51 records · Page 3Linked to original sources
PubMed2002

IgE-dependent mast cell activation potentiates airway responses in murine asthma models.

We have studied murine models of asthma using FcepsilonRIalpha-chain-deficient (FcepsilonRIalpha(-/-)) mice to investigate the role of IgE-dependent mast cell activation in these models. When mice were either 1) immunized once with OVA in alum i.p. and then challenged with OVA intranasally, or 2) repeatedly immunized with OVA in the absence of adjuvant and subsequently challenged with nebulized OVA, FcepsilonRalpha(-/-) mice had significantly fewer eosinophils and lower IL-4 levels in their bronchoalveolar lavage fluid compared with wild-type mice. When mice were given anti-IL-5 antibody before OVA challenge in protocol 1, eosinophilic infiltration into the airways was significantly suppressed in both genotypes, but only FcepsilonRIalpha(-/-) mice showed significantly reduced airway hyperresponsiveness (AHR). In addition, when mice immunized and challenged with OVA also received a late OVA provocation at a higher concentration and were then exposed to methacholine, only wild-type mice developed a substantial increase in AHR. Since FcepsilonRI is expressed mainly on mast cells in mouse airways, we conclude that IgE-dependent activation of this cell type plays an important role in the development of allergic airway inflammation and AHR in mice. The models used may be of value for testing inhibitors of IgE or mast cells for development of therapeutic agents for human asthma.

Allergens↗
PubMed2002

New alternatively spliced form of galectin-3, a member of the beta-galactoside-binding animal lectin family, contains a predicted transmembrane-spanning domain and a leucine zipper motif.

Osteoclasts or their precursors interact with the glycoprotein-enriched matrix of bone during extravasation from the vasculature, and upon attachment prior to resorption. Reverse transcriptase-PCR studies showed that two new alternatively spliced forms of chicken galectin-3, termed Gal-3TM1 and Gal-3TR1, were enriched and preferentially expressed in highly purified chicken osteoclast-like cells. Gal-3TM1 and Gal-3TR1 mRNA were also detected in chicken intestinal tissue, but not in kidney, liver, or lung. Gal-3TM1 and Gal-3TR1 messages both contain an open reading frame encoding a predicted 70-amino acid TM1 sequence inserted between the N-terminal Gly/Pro repeat domain and the carbohydrate recognition domain (exons 3 and 4). Gal-3TR1 mRNA contains an additional 241-bp sequence, which encodes a truncated open reading frame between the 4th and 5th exons, and, whose translation is expected to terminate within the carbohydrate recognition domain encompassing exons 4, 5, and 6. Immunoblotting and affinity chromatography showed that purified osteoclast preparations and intestinal homogenates contained a 36-kDa lactose-binding galectin. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analyses on chymotryptic peptides from the 36-kDa lectin confirmed its identity as Gal-3TM1. The TM1 insert contains a single transmembrane-spanning region and a leucine zipper-like stalk domain that is predicted to position the intact carbohydrate recognition domain of Gal-3TM1 on the exterior surface of the plasma membrane. Immunofluorescent staining of chicken osteoclasts confirmed the expression of Gal-3TM1 at the plasma membrane. Gal-3TM1 is the first example of a galectin superfamily member capable of being expressed as a soluble protein and as a transmembrane protein.

Alternative Splicing↗
PubMed2002

Regulation of cellular homeostasis by galectins.

Members of the galectin family are presently known to participate in cellular homeostasis by modulating cell growth, controlling cell cycle progression, and inducing or inhibiting apoptosis. Both intracellular and extracellular activities of galectins have been described, with the former typically independent of lectin activity, and the latter mediated by lectin activity. Galectin-1 and -3 are recognized as activators and inducers of cell stasis in extracellular capacities. Galectin-1, -7, -8, -9 and -12 are characterized as promoters or inducers of apoptosis, while galectin-3 is demonstrated as an inhibitor of apoptosis intracellularly. Localization studies of galectins have established that these proteins can segregate into multiple intracellular compartments, and the preference for segregation is dependent on the status of the cell. Localization would, therefore, likely correspond to compartmental function. While galectin-1 and -3 have been the most abundantly expressed and extensively studied, and therefore, the members best understood, expanding interest in galectins has resulted in description of new members that display more restricted expression patterns, suggesting more specific activity. Nevertheless, as demonstrated for many members, it appears that a major feature of the galectin family is the homeostatic regulation of cells.

Animals↗
PubMed2002

Association of a macrophage galactoside-binding protein with Mycobacterium-containing phagosomes.

Mycobacteria reside intracellularly in a vacuole that allows it to circumvent the antimicrobial environment of the host macrophage. Although the mycobacterial phagosome exhibits selective fusion with vesicles of the endosomal system, identification of host and bacterial factors associated with phagosome bio-genesis is limited. To identify these potential factors, mAbs were generated to a membrane preparation of mycobacterial phagosomes isolated from M. tuberculosis-infected macrophages. A mAb recognizing a 32-35 kDa macrophage protein associated with the phagosomal membrane of Mycobacterium was identified. N-terminal sequence analysis identified this protein as Mac-2 or galectin-3, a galactoside-binding protein of macrophages. Galectin-3 (gal-3) was shown to accumulate in Mycobacterium-containing phagosomes during the course of infection. This accumulation was specific for phagosomes containing live mycobacteria and occurred primarily at the cytosolic face of the phagosome membrane. In addition, bind-ing of gal-3 to mycobacterial phosphatidylinositol mannosides (PIMs) demonstrated a novel interaction between host carbohydrate-binding proteins and released mycobacterial glycolipids. Infection of macrophages from gal-3-deficient mice indicated that the protein did not play a role in infection in vitro. In contrast, infection of gal-3-deficient mice revealed a reduced capacity to clear late but not early infection.

Animals↗
PubMed2002

Optimized conjugation ratios lead to allergen immunostimulatory oligodeoxynucleotide conjugates with retained immunogenicity and minimal anaphylactogenicity.

BACKGROUND: Immunotherapy has gradually fallen out of favor for the treatment of many allergic diseases because of the overall convenience, safety, and efficacy of medications. However, investigations suggest that allergen/immunostimulatory sequence oligodeoxynucleotide (ISS-ODN) conjugates (AICs) might have improved safety and efficacy compared with allergen extracts. OBJECTIVE: We determined whether changes in the ISS-ODN conjugation ratio would effect the immunogenicity and allergenicity of AIC. METHODS: Immunogenicity was determined by means of AIC vaccination of mice, followed by analysis of antigen-specific antibody and cytokine responses. The allergenicity of AIC was determined in mast cell release studies and in murine models of anaphylaxis and the Arthus reaction. RESULTS: AIC induced a stronger immune response than allergen alone or allergen mixed with ISS-ODN, but higher-level ISS-ODN conjugation reduced its immunogenicity modestly. In mast cell degranulation studies AIC was approximately 100-fold less allergenic than native allergen, with stepwise increases in the ODN conjugation ratio leading to stepwise decreases in allergenicity. In anaphylaxis studies death rates were reduced from 100% with native allergen challenge to as low as 0% with high-ratio ISS-ODN AIC challenge. Similar results were obtained in an Arthus reaction model. CONCLUSION: These investigations establish that AIC is both significantly more immunogenic and less allergenic than native allergens and the techniques used might have further utility for the standardization and optimization of AIC formulations for use in allergic patients.

Adjuvants, Immunologic↗
PubMed2002

Galectin-3 is strongly up-regulated in nonapoptosing mammary epithelial cells during rat mammary gland involution.

Galectin-3 is an endogenous mammalian lectin that binds to ABH carbohydrate antigens. Here we show that galectin-3 is strongly up-regulated during mammary gland involution and that it is expressed virtually exclusively on nonapoptotic cells. We demonstrate that dexamethasone, an inhibitor of the second phase of mammary gland involution, potently suppresses up-regulation of galectin-3 as judged immunohistochemically and on western blots, suggesting that systemic hormone levels regulate galectin-3 expression during involution. However, at the RNA level galectin-3 expression is rapidly up-regulated on the onset of involution but remains consistantly high during the first and second phase of involution regardless of dexamethasone treatment. These data suggest that the up-regulation of galectin-3 in the involuting mammary gland is not only controlled transcriptionally but also regulated posttranscriptionally under the control of systemic glucocorticoid hormones involved in coordinating the involution process.

Animals↗
PubMed2002

The constitutive expression of galectin-3 is downregulated in the intestinal epithelia of Crohn's disease patients, and tumour necrosis factor alpha decreases the level of galectin-3-specific mRNA in HCT-8 cells.

OBJECTIVE: Galectin-3, a lectin with specificity for beta galactoside, is expressed by a variety of cells, including intestinal epithelial cells. Among other functions, galectin-3 mediates cell adhesion and is involved in inflammatory processes. In this study, we assessed the expression of galectin-3 in intestinal epithelial cells from Crohn's disease patients (n = 10), ileum adjacent to resected colon carcinoma (n = 9), unspecific bowel inflammation (n = 1), diverticulosis (n = 1), ulcerative colitis (n = 3) and healthy jejunum used for interposition in larynx carcinoma (n = 1). The role of cytokines on galectin-3 expression was a further aim of our study. METHODS: The galectin-3 distribution in intestinal epithelia was analysed by immunohistochemistry, immunoblotting, immunofluorescence and reverse transcriptase polymerase chain reaction (RT-PCR). Human intestinal epithelial cell line (HCT-8) and primary cultured intestinal epithelial cells were treated with cytokines, and the effects on galectin-3 expression were determined by RT-PCR. RESULTS: Galectin-3 showed a homogeneous distribution in epithelia from control patients. In contrast, in epithelial cells from Crohn's disease lesions, galectin-3 staining was strongly spotted and heterogeneous. In inflamed and reorganized tissue, galectin-3 expression was markedly reduced, and was associated with disintegration of epithelia. Primary cultured epithelial cells as well as HCT-8 cells expressed galectin-3 protein and mRNA. Incubation of HCT-8 cells with tumour necrosis factor alpha (TNF-alpha), but not with other cytokines, substantially reduced galectin-3 expression as shown by semiquantitative RT-PCR. CONCLUSIONS: Downregulation of galectin-3 in the intestinal epithelium of Crohn's disease patients may be a consequence of enhanced TNF-alpha production by inflammatory cells, thereby contributing to the pathophysiology of the disease.

Antigens, Differentiation↗
PubMed2002

Changes in galectin-7 and cytokeratin-19 expression during the progression of malignancy in thyroid tumors: diagnostic and biological implications.

Galectin-7 is associated with p53-dependent onset of apoptosis and proliferation control/differentiation in keratinocyte development. It is also up-regulated in chemically induced rat mammary carcinogenesis. Because the levels of expression of galectin-7 have never been investigated in thyroid tumors (in contrast to those of galectin-1 and -3 associated with malignancy), we initiated analysis of the expression of galectin-7 in benign and malignant thyroid lesions together with that of cytokeratin-19 (CK19), a marker already demonstrated to be useful in diagnosing this kind of lesion. The immunohistochemical expression levels were quantitatively determined by means of computer-assisted microscopy on a series of 84 thyroid lesions including 10 multinodular goiters, 32 adenomas, and 42 carcinomas. Our data clearly indicate a marked down-regulation of galectin-7 expression in a large proportion of adenomas (including the normomacrofollicular, microfollicular, and trabecular variants) if compared with carcinomas. In accordance with results of previous studies, a marked up-regulation of CK19 expression was observed in the thyroid carcinomas, and this contrasted in particular with the low CK19 expression observed in the microfollicular adenomas. Of importance for diagnostic implications, the combination of these two markers enabled our series of microfollicular adenomas (characterized by low galectin-7 and CK19 expression) to be efficiently distinguished from the encapsulated follicular variant of papillary thyroid carcinomas (high galectin-7 and CK19 expression).

Adenoma↗
PubMed2002

Monoclonal antibodies against the C(epsilon)mX domain of human membrane-bound IgE and their potential use for targeting IgE-expressing B cells.

BACKGROUND: IgE mediates immediate-type hypersensitivity reactions responsible for various allergic symptoms. It is secreted by IgE-producing plasma cells, which differentiate from B cells expressing membrane-bound IgE (mIgE) on their surface. The epsilon-chain of human mIgE contains a membrane-anchoring peptide and an extra 52-amino-acid (a.a.)-long domain (referred to as C(epsilon)mX) between the membrane anchor and the CH4 domain. OBJECTIVE: The study was designed to evaluate the effects of C(epsilon)mX-specific monoclonal antibodies (mAbs) to target IgE-expressing B cells and decrease IgE production. METHODS: A C(epsilon)mX-containing IgG1.Fc fusion protein was produced in CHO cells and used to immunize mice; five hybridoma clones secreting C(epsilon)mX-specific mAbs were obtained. RESULTS: Characterization of the mAbs using ELISA, immunoprecipitation, and immunoblotting methods showed that they could bind to both native and denatured forms of C(epsilon)mX. The mAbs exhibited mutual inhibition of binding to mIgE. Epitope mapping using synthetic peptides revealed that all five mAbs recognize the same epitope, RADWPGPP, located near the C-terminus of C(epsilon)mX. Binding of one of the mAbs to mIgE on SKO-007 cells induced the cross-linking of mIgE molecules on the cell surface, resulting in their patching and capping. In vitro functional analysis revealed that mAbs are able to cause complement-mediated cytotoxicity on transfectants expressing the Fc portion of mIgE. CONCLUSION: We have prepared several human mIgE-specific mAbs. The potential of the mAbs on targeting mIgE+ B cells was demonstrated by CDC analysis.

Amino Acid Sequence↗
PubMed2002

Galectins: novel anti-inflammatory drug targets.

Galectins are a protein family defined by their affinity for beta-galactosides and consensus sequences. They are pleiotropic regulators involved in a multitude of functions, both in and out of the cell. Extracellularly, they have the potential to bind to various surface receptors on a variety of cell types as well as extracellular matrix (ECM) proteins, thus causing cell activation or apoptosis, modulating cell adhesion and inducing cell migration. Intracellularly, they can regulate cell growth, apoptosis and cell cycle progression. Galectins are either pro-inflammatory or anti-inflammatory. Some, such as galectin-1, may be employed as anti-inflammatory agents, while others, such as galectin-3, are evidently suitable targets for anti-inflammatory drugs. The extracellular functions of galectins involve their lectin-carbohydrate interactions and thus their carbohydrate ligands or mimetics would be suitable inhibitors. While the intracellular functions of galectins do not appear to engage lectin-carbohydrate interactions, the carbohydrate-binding sites of these proteins may still be involved. Therefore, the same inhibitors may be used regardless of whether intracellular or extracellular galectins are to be targeted.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Galectin-7 (PIG1) exhibits pro-apoptotic function through JNK activation and mitochondrial cytochrome c release.

Galectin-7 is normally expressed in all types of stratified epithelia, but is significantly down-regulated in squamous cell carcinomas. This protein was recently found to be highly inducible by p53 in a colon carcinoma cell line, DLD-1, and designated as PIG1 (for p53-induced gene 1). We studied transfectants of HeLa and DLD-1 cells ectopically expressing this protein and found that they were more susceptible to apoptosis than control transfectants. This was observed in apoptosis induced by mechanistically distinct stimuli, suggesting that galectin-7 acts on a common point in the apoptosis signaling pathways. Further analyses of actinomycin D-induced apoptosis demonstrated that galectin-7 expression causes enhanced caspase-3 activity and poly(ADP-ribose) polymerase cleavage, and the potentiation of apoptosis by galectin-7 was completely abrogated by a caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone. In addition, galectin-7 transfectants displayed accelerated mitochondrial cytochrome c release and up-regulated JNK activity upon apoptosis induction. Several lines of evidence indicate that the effect on apoptosis is not due to the lectin functioning extracellularly through interactions with cell surface glycoconjugates. In fact, this lectin is found to localize in nuclei and cytoplasm of the transfectants and the transformed keratinocyte line HaCaT. Therefore, galectin-7 is a pro-apoptotic protein that functions intracellularly upstream of JNK activation and cytochrome c release. DNA microarray analysis revealed genes that are differentially expressed between galectin-7 and control transfectants. Some of them are potentially contributory to this lectin's proapoptotic function and these include redox-related genes monoamine oxidase B, ryanodine receptor 2, and glutathione S-transferase Mu 3.

Apoptosis↗
PubMedDate not supplied

Craniopharyngioma: a case report and comparative galectin histochemical analysis.

Craniopharyngioma is a rare benign tumour originating from Rathke's pouch. This paper reports a tumour case studied with a set of markers defining protein-carbohydrate recognition. Expression of endogenous lectins and their reactive glycoligands is under differentiation-dependent control in many cell types. These parameters can be related to the degree of cell differentiation in tumours. Therefore, the expression patterns of endogenous lectins, namely galectins-1, -3, and -7, in the craniopharyngioma case were determined. Galectins-1 and -3 were also used to reveal glycoconjugates in cells and extracellular matrices, an approach that has heretofore relied largely on plant lectins. The staining pattern of craniopharyngioma is compared with that of two other types of ectodermally derived tumours, namely basal and squamous cell carcinomas. Clusters of polygonal and flattened cells with morphological characteristics of differentiated cells in the craniopharyngioma and the majority of poorly differentiated cells in squamous cell carcinomas were reactive with galectin-3. No binding of this probe was observed in cells of basal cell carcinomas and the majority of craniopharyngioma cells. In view of the lack of accessible binding in the basal layer of normal squamous epithelia where proliferative cells (including stem cells) are located, galectin-3 binding could be used to distinguish basal from suprabasal cells of squamous epithelial cells.

Adult↗
PubMedDate not supplied

Cyclosporin A inhibits eosinophilic infiltration into the conjunctiva mediated by type IV allergic reactions.

BACKGROUND: Eosinophils are important effector cells in severe allergic conjunctivitis such as vernal keratoconjunctivitis. Infiltration of eosinophils into the conjunctiva is mediated by type I and type IV allergic reactions. Cyclosporin A (CsA) eye drops are administered therapeutically for severe allergic conjunctivitis, but the mechanism by which CsA acts, that is, by inhibiting type I, type IV or both types of allergic reactions, is not known. We investigated whether CsA eye drops inhibit type I, type IV or both types of allergic reactions in the conjunctiva. METHODS: Experimental immune-mediated blepharoconjunctivitis (EC) was induced in BALB/c mice by either active immunization or passive immunization by transfer of ragweed (RW)-primed splenocytes and RW-specific IgE, followed by RW challenge to the conjunctiva. These mice were treated in eye drops with vehicle, 0.1% CsA, 0.5% CsA or 0.1% betamethasone five times (1 and 2 h before RW challenge and 1, 2 and 3 h after RW challenge). Twenty-four hours after the challenge, the conjunctivas were harvested for histological analysis to evaluate eosinophilic infiltration. To evaluate effects of CsA eye drops on systemic immune responses, sera and spleens were collected from actively immunized mice at the time of sacrifice to examine serum IgE levels and cellular immune responses, respectively. RESULTS: CsA eye drops significantly inhibited eosinophilic infiltration into the conjunctiva in actively immunized EC-developing mice compared with vehicle-treated mice. The CsA-induced inhibition was similar to inhibition induced by 0.1% betamethasone. Serum IgE levels and splenocyte responses in CsA-treated mice were equivalent to those in vehicle-treated mice. Betamethasone treatment inhibited eosinophilic infiltration into the conjunctiva induced by both splenocyte transfer and IgE transfer, while CsA treatment inhibited infiltration induced by splenocyte transfer. CONCLUSIONS: CsA eye drops inhibited eosinophilic infiltration into the conjunctiva without affecting systemic immune responses. CsA predominantly inhibits eosinophilic infiltration by interfering with the type IV allergic reaction in the conjunctiva.

Animals↗
PubMedDate not supplied

Roles of galectin-3 in immune responses.

Galectins are a family of animal lectins with conserved carbohydrate-recognition domains for beta-galactoside. Galectin-3 is the only family member that is composed of a glycine/prolinerich N-terminal repeated sequence and a C-terminal carbohydrate-binding domain.Multiple functions of galectin-3 have been reported, depending on its location. Extracellular galectin-3 can bind to cell surface through glycosylated proteins and thereby trigger or modulate cellular responses such as mediator release or apoptosis. Intracellular galectin-3 has been reported to inhibit apoptosis, regulate the cell cycle, and participate in the nuclear splicing of pre-mRNA. Recent studies have revealed that galectin-3 is expressed in a variety of cell types in the immune system, constitutively or in response to microbial invasion. These studies implicate galectin-3 in both innate and adaptive immune responses, where it participates in the activation or differentiation of immune cells. This review summarizes the roles of galectin-3 in the immune system and discusses the possible underlying mechanisms.

Animals↗