Regulation of sialyl-Lewis x epitope expression by TNF-α and EGF in an airway carcinoma cell line

N-Glycosylation and Inflammation; the Not-So-Sweet Relation

Chronic inflammation is the main feature of many long-term inflammatory diseases such as autoimmune diseases, metabolic disorders, and cancer. There is a growing number of studies in which alterations of N-glycosylation have been observed in many pathophysiological conditions, yet studies of the underlying mechanisms that precede N-glycome changes are still sparse. Proinflammatory cytokines have been shown to alter the substrate synthesis pathways as well as the expression of glycosyltransferases required for the biosynthesis of N-glycans. The resulting N-glycosylation changes can further contribute to disease pathogenesis through modulation of various aspects of immune cell processes, including those relevant to pathogen recognition and fine-tuning the inflammatory response. This review summarizes our current knowledge of inflammation-induced N-glycosylation changes, with a particular focus on specific subsets of immune cells of innate and adaptive immunity and how these changes affect their effector functions, cell interactions, and signal transduction.

Global analysis of human glycosyltransferases reveals novel targets for pancreatic cancer pathogenesis

BACKGROUND

Several reports have shown the role of glycosylation in pancreatic cancer (PC), but a global systematic screening of specific glycosyltransferases (glycoTs) in its progression remains unknown.

METHODS

We demonstrate a rigorous top-down approach using TCGA-based RNA-Seq analysis, multi-step validation using RT-qPCR, immunoblots and immunohistochemistry. We identified six unique glycoTs (B3GNT3, B4GALNT3, FUT3, FUT6, GCNT3 and MGAT3) in PC pathogenesis and studied their function using CRISPR/Cas9-based KD systems.

RESULTS

Serial metastatic in vitro models using T3M4 and HPAF/CD18, generated in house, exhibited decreases in B3GNT3, FUT3 and GCNT3 expression on increasing metastatic potential. Immunohistochemistry identified clinical significance for GCNT3, B4GALNT3 and MGAT3 in PC. Furthermore, the effects of B3GNT3, FUT3, GCNT3 and MGAT3 were shown on proliferation, migration, EMT and stem cell markers in CD18 cell line. Talniflumate, GCNT3 inhibitor, reduced colony formation and migration in T3M4 and CD18 cells. Moreover, we found that loss of GCNT3 suppresses PC progression and metastasis by downregulating cell cycle genes and β-catenin/MUC4 axis. For GCNT3, proteomics revealed downregulation of MUC5AC, MUC1, MUC5B including many other proteins.

CONCLUSIONS

Collectively, we demonstrate a critical role of O- and N-linked glycoTs in PC progression and delineate the mechanism encompassing the role of GCNT3 in PC.

Glycomic Signatures of Plasma IgG Improve Preoperative Prediction of the Invasiveness of Small Lung Nodules

Preoperative assessment of tumor invasiveness is essential to avoid overtreatment for patients with small-sized ground-glass nodules (GGNs) of 10 mm or less in diameter. However, it is difficult to determine the pathological state by computed tomography (CT) examination alone. Aberrant glycans has emerged as a tool to identify novel potential disease biomarkers. In this study, we used a lectin microarray-based strategy to investigate whether glycosylation changes in plasma immunoglobulin G (IgG) provide additional information about the invasiveness of small GGNs before surgery. Two independent cohorts (discovery set, n = 92; test set, n = 210) of GGN patients were used. Five of 45 lectins (Sambucus nigra agglutinin, SNA; Datura stramonium agglutinin, DSA; Galanthus nivalis agglutinin, GNA; Euonymus europaeus lectin, EEL; and Vicia villosa agglutinin, VVA) were identified as independent factors associated with pathological invasiveness of small GGNs (p < 0.01). Receiver-operating characteristic (ROC) curve analysis indicated the combination of these five lectins could significantly improve the accuracy of CT in diagnosing invasive GGNs, with an area under the curve (AUC) of 0.792 (p < 0.001), a sensitivity of 74.6%, and specificity of 74.4%, which was superior to current clinical biomarkers. These results suggest that the multilectin assay based on plasma IgG glycosylation may be a useful in vitro complementary test to enhance preoperative determination of the invasiveness of GGNs and guide surgeons to select proper clinical management to avoid overtreatment.

Glycosylation changes in inflammatory diseases

Glycosylation is one of the most important modifications of proteins and lipids, and cell surface glycoconjugates are thought to play important roles in a variety of biological functions including cell-cell and cell-substrate interactions, bacterial adhesion, cell immunogenicity and cell signaling. Alterations of glycosylation are observed in a number of inflammatory diseases. Pro-inflammatory cytokines have been shown to modulate cell surface glycosylation by regulating the expression of glycosyltransferases and sulfotransferases involved in the biosynthesis of glycan chains, inducing the expression of specific carbohydrate antigens at the cell surface that can be recognized by different types of lectins or by bacterial adhesins, contributing to the development of diseases. Glycosylation can also regulate biological functions of immune cells by recruiting leukocytes to inflammation sites with pro- or anti-inflammatory effects. Cell surface proteoglycans provide a large panel of binding sites for many mediators of inflammation, and regulate their bio-availability and functions. In this review, we summarize the current knowledge of the glycosylation changes occurring in mucin type O-linked glycans, glycosaminoglycans, as well as in glycosphingolipids, with a particular focus on cystic fibrosis and neurodegenerative diseases, and their consequences on cell interactions and disease progression.

Role of Cytokine-Induced Glycosylation Changes in Regulating Cell Interactions and Cell Signaling in Inflammatory Diseases and Cancer

Glycosylation is one of the most important modifications of proteins and lipids, and cell surface glycoconjugates are thought to play important roles in a variety of biological functions including cell-cell and cell-substrate interactions, bacterial adhesion, cell immunogenicity and cell signaling. Alterations of glycosylation are observed in number of diseases such as cancer and chronic inflammation. In that context, pro-inflammatory cytokines have been shown to modulate cell surface glycosylation by regulating the expression of glycosyltransferases involved in the biosynthesis of carbohydrate chains. These changes in cell surface glycosylation are also known to regulate cell signaling and could contribute to disease pathogenesis. This review summarizes our current knowledge of the glycosylation changes induced by pro-inflammatory cytokines, with a particular focus on cancer and cystic fibrosis, and their consequences on cell interactions and signaling.

Pseudomonas aeruginosa pyocyanin modulates mucin glycosylation with sialyl-Lewis(x) to increase binding to airway epithelial cells

Cystic fibrosis (CF) patients battle life-long pulmonary infections with the respiratory pathogen Pseudomonas aeruginosa (PA). An overabundance of mucus in CF airways provides a favorable niche for PA growth. When compared with that of non-CF individuals, mucus of CF airways is enriched in sialyl-Lewis(x), a preferred binding receptor for PA. Notably, the levels of sialyl-Lewis(x) directly correlate with infection severity in CF patients. However, the mechanism by which PA causes increased sialylation remains uncharacterized. In this study, we examined the ability of PA virulence factors to modulate sialyl-Lewis(x) modification in airway mucins. We found pyocyanin (PCN) to be a potent inducer of sialyl-Lewis(x) in both mouse airways and in primary and immortalized CF and non-CF human airway epithelial cells. PCN increased the expression of C2/4GnT and ST3Gal-IV, two of the glycosyltransferases responsible for the stepwise biosynthesis of sialyl-Lewis(x), through a tumor necrosis factor (TNF)-α-mediated phosphoinositol-specific phospholipase C (PI-PLC)-dependent pathway. Furthermore, PA bound more efficiently to airway epithelial cells pre-exposed to PCN in a flagellar cap-dependent manner. Importantly, antibodies against sialyl-Lewis(x) and anti-TNF-α attenuated PA binding. These results indicate that PA secretes PCN to induce a favorable environment for chronic colonization of CF lungs by increasing the glycosylation of airway mucins with sialyl-Lewis(x).

Inflammatory cytokines regulate the expression of glycosyltransferases involved in the biosynthesis of tumor-associated sialylated glycans in pancreatic cancer cell lines

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an abundant stroma containing several pro-inflammatory cytokines, which are described to modulate the expression of important genes related to tumor promotion and progression. In the present work we have investigated the potential role of these cytokines in the biosynthesis of tumor-associated carbohydrate antigens such as sialyl-Lewis(x) (SLe(x)) through the regulation of specific glycosyltransferase genes.

METHODS

Two human PDAC cell lines MDAPanc-3 and MDAPanc-28 were treated with pro-inflammatory cytokines IL-1β, TNFα, IL-6 or IL-8, and the content of tumor-associated carbohydrate antigens at the cell membrane was analyzed by flow cytometry. In addition, variation in the mRNA expression of sialyltransferase (ST) and fucosyltransferase (FUT) genes, which codify for the ST and FucT enzymes involved in the carbohydrate antigens' biosynthesis, was determined. The inflammatory microenvironment of PDAC tissues and the expression of Lewis-type antigens were analyzed by immunohistochemistry to find a possible correlation between inflammation status and the presence of tumor-associated carbohydrate antigens.

RESULTS

IL-1β stimuli increased SLe(x) and α2,6-sialic acid levels in MDAPanc-28 cells and enhanced the mRNA levels of ST3GAL3-4 and FUT5-7, which codify for ST and FucT enzymes related to SLe(x) biosynthesis, and of ST6GAL1. IL-6 and TNFα treatments increased the levels of SLe(x) and Le(y) antigens in MDPanc-3 cells and, similarly, the mRNA expression of ST3GAL3-4, FUT1-2 and FUT6, related to these Lewis-type antigens' biosynthesis, were increased. Most PDAC tissues stained for SLe(x) and SLe(a) and tended to be expressed in the tumor samples with a higher presence of inflammatory immune cells.

CONCLUSIONS

The inflammatory microenvironment can modulate the glycosylation pattern of PDAC cells, increasing the expression of tumor-associated sialylated antigens such as SLe(x), which contributes to pancreatic tumor malignancy.

Essential domains of Anaplasma phagocytophilum invasins utilized to infect mammalian host cells

Anaplasma phagocytophilum causes granulocytic anaplasmosis, an emerging disease of humans and domestic animals. The obligate intracellular bacterium uses its invasins OmpA, Asp14, and AipA to infect myeloid and non-phagocytic cells. Identifying the domains of these proteins that mediate binding and entry, and determining the molecular basis of their interactions with host cell receptors would significantly advance understanding of A. phagocytophilum infection. Here, we identified the OmpA binding domain as residues 59 to 74. Polyclonal antibody generated against a peptide spanning OmpA residues 59 to 74 inhibited A. phagocytophilum infection of host cells and binding to its receptor, sialyl Lewis x (sLe^x-capped P-selectin glycoprotein ligand 1. Molecular docking analyses predicted that OmpA residues G61 and K64 interact with the two sLe^x sugars that are important for infection, α2,3-sialic acid and α1,3-fucose. Amino acid substitution analyses demonstrated that K64 was necessary, and G61 was contributory, for recombinant OmpA to bind to host cells and competitively inhibit A. phagocytophilum infection. Adherence of OmpA to RF/6A endothelial cells, which express little to no sLe^x but express the structurally similar glycan, 6-sulfo-sLe^x, required α2,3-sialic acid and α1,3-fucose and was antagonized by 6-sulfo-sLe^x antibody. Binding and uptake of OmpA-coated latex beads by myeloid cells was sensitive to sialidase, fucosidase, and sLe^x antibody. The Asp14 binding domain was also defined, as antibody specific for residues 113 to 124 inhibited infection. Because OmpA, Asp14, and AipA each contribute to the infection process, it was rationalized that the most effective blocking approach would target all three. An antibody cocktail targeting the OmpA, Asp14, and AipA binding domains neutralized A. phagocytophilum binding and infection of host cells. This study dissects OmpA-receptor interactions and demonstrates the effectiveness of binding domain-specific antibodies for blocking A. phagocytophilum infection.

Anaplasma phagocytophilum causes the potentially deadly bacterial disease granulocytic anaplasmosis. The pathogen replicates inside white blood cells and, like all other obligate intracellular organisms, must enter host cells to survive. Multiple A. phagocytophilum surface proteins called invasins cooperatively orchestrate the entry process. Identifying these proteins’ domains that are required for function, and determining the molecular basis of their interaction with host cell receptors would significantly advance understanding of A. phagocytophilum pathogenesis. In this study, the binding domains of two A. phagocytophilum surface proteins, OmpA and Asp14, were identified. The specific OmpA residues that interact with its host cell receptor were also defined. An antibody cocktail generated against the binding domains of OmpA, Asp14, and a third invasin, AipA, blocked the ability of A. phagocytophilum to infect host cells. The data presented within suggest that binding domains of OmpA, Asp14, and AipA could be exploited to develop a vaccine for granulocytic anaplasmosis.

Differences between the glycosylation patterns of haptoglobin isolated from skin scales and plasma of psoriatic patients

Improved diagnosis of psoriasis, by new biomarkers, is required for evaluating the progression rate of the disease and the response to treatment. Haptoglobin (Hpt), a glycoprotein secreted by hepatocytes and other types of cells including keratinocytes, was found with glycan changes in psoriasis and other diseases. We previously reported that Hpt isolated from plasma of psoriatic patients is more fucosylated than Hpt of healthy subjects. The aim of this study was to compare the glycosylation pattern of Hpt isolated from skin scales or plasma of patients with psoriasis with that of Hpt from cornified epidermal layer or plasma of healthy subjects. High performance liquid chromatography analysis of the glycans isolated from the protein backbone revealed that glycan patterns from skin and plasma of patients were similar, and mostly displayed quantitative rather than qualitative differences from normal pattern. Biotin-labeled lectins were used to evaluate quantitative differences in the glycoforms of Hpt from plasma and psoriatic skin scales. Hpt from skin and plasma of patients showed more fucosylated and branched glycans than Hpt from plasma of healthy subjects. Tryptic glycopeptides of Hpt were also analyzed by mass spectrometry, and a decreased amount of sialylated glycan chains was found in glycopeptides of skin Hpt, as compared with Hpt from plasma. High levels of glycans with fucosylated and tetra-antennary chains were detected on the peptide NLFLNHSENATAK from Hpt of psoriatic patients. Our data demonstrate that specific changes in glycan structures of Hpt, such as enhanced glycan branching and fucose content, are associated with psoriasis, and that differences between circulating and skin Hpt do exist. A lower extent of glycan fucosylation and branching was found in Hpt from plasma of patients in disease remission. Altered glycoforms might reflect changes of Hpt function in the skin, and could be used as markers of the disease.

A new isoflavone glycitein 7-O-beta-D-glucoside 4''-O-methylate, isolated from Cordyceps militaris grown on germinated soybeans extract, inhibits EGF-induced mucus hypersecretion in the human lung mucoepidermoid cells

A new isoflavone glycitein 7-O-beta-d-glucoside 4''-O-methylate (CGLM) has been isolated recently from Cordyceps militaris grown on germinated soybean extract and has antioxidant activity. In the present study, CGLM was investigated for its suppression of airway mucous hyper-secretion in epidermal growth factor (EGF)-treated human lung mucoepidermoid cells. NCI-H292 cells were treated with CGLM for 1 h, followed by EGF treatment for 24 h. The decrease in cyclooxygenase-2 (COX-2) production was correlated with reduced levels of protein and mRNA of inducible matrix metalloproteinase 9 (MMP-9) and also MUC5AC gene expression. CGLM directly inhibited down-regulated NF-κB activity, and significantly inhibited the phosphorylation of p38 and ERK1/2 (p42/p44) in NCI-H292 cells. These results suggest that CGLM protects NCI-H292 cells from EGF-induced damage by down-regulation of COX-2, MMP-9 and MUC5AC gene expression, mediated via blocking the NF-kappa-B and p38/ERK MAPK pathways.

Periodic fever as the manifestation of primary Sjogren's syndrome: a case report and literature review

A 56-year-old male had periodic fever for 5 years and suffered from auditory hallucination and hearing impairment for 3 years. Xerostomia, xerophthalmia, elevated anti-SSA/Ro tilter, positive Schirmer's test, and lymphocyte infiltrate of mucoserous gland in lip biopsy of this case confirmed the diagnosis of primary Sjogren's syndrome (pSS). We review literature for fever and neuropsychiatric involvement in pSS case series. Though fever is present in 6-41 % pSS cases, periodic fever has not been reported. Auditory hallucination was rare in cases with pSS. The literature review alerts clinicians that fever and neurological manifestations were not uncommon in pSS cases.

TNF regulates sialyl-Lewisx and 6-sulfo-sialyl-Lewisx expression in human lung through up-regulation of ST3GAL4 transcript isoform BX

Bronchial mucins from severely infected patients suffering from lung diseases such as chronic bronchitis or cystic fibrosis exhibit increased amounts of sialyl-Lewis(x) (NeuAcα2-3Galβ1-4[Fucα1-3]GlcNAc-R, sLe(x)) glycan structures. In cystic fibrosis, sLe(x) and its sulfated form 6-sulfo-sialyl-Lewis(x) (NeuAcα2-3Galβ1-4[Fucα1-3](HO(3)S-6)GlcNAc-R, 6-sulfo-sLe(x)) serve as receptors for Pseudomonas aeruginosa and are involved in the chronicity of airway infection. However, little is known about the molecular mechanisms regulating the changes in glycosylation and sulfation of mucins in airways. Herein, we show that the pro-inflammatory cytokine TNF increases the expression of α2,3-sialyltransferase gene ST3GAL4, both in human bronchial mucosa and in A549 lung carcinoma cells. The role of sialyltransferase ST3Gal IV in sLe(x) biosynthesis was confirmed by siRNA silencing of ST3GAL4 gene. BX is the major transcript isoform expressed in healthy bronchial mucosa and in A549 cells, and is up-regulated by TNF in both models. Bioinformatics analysis and luciferase assays have confirmed that the 2 kb genomic sequence surrounding BX exon contains a promoter region regulated by TNF-related transcription factors. These results support further work aiming at the development of anti-inflammatory strategy to reduce chronic airway infection in diseases such as cystic fibrosis.

Host glycans and antigen presentation

The cell-mediated adaptive immune response depends upon the activation of T cells via recognition of antigen in the context of a major histocompatibility complex (MHC) molecule. Although studies have shown that alterations in T cell receptor glycosylation reduces the activation threshold, the data on MHC is far less definitive. Here, we discuss the data on MHC glycosylation and the role the glycans might play during the adaptive host response.

Infection, inflammation and host carbohydrates: a Glyco-Evasion Hypothesis

Microbial immune evasion can be achieved through the expression, or mimicry, of host-like carbohydrates on the microbial cell surface to hide from detection. However, disparate reports collectively suggest that evasion could also be accomplished through the modulation of the host glycosylation pathways, a mechanism that we call the "Glyco-Evasion Hypothesis". Here, we will summarize the evidence in support of this paradigm by reviewing three separate bodies of work present in the literature. We review how infection and inflammation can lead to host glycosylation changes, how host glycosylation changes can increase susceptibility to infection and inflammation and how glycosylation impacts molecular and cellular function. Then, using these data as a foundation, we propose a unifying hypothesis in which microbial products can hijack host glycosylation to manipulate the immune response to the advantage of the pathogen. This model reveals areas of research that we believe could significantly improve our fight against infectious disease.

TNFα enhances the motility and invasiveness of prostatic cancer cells by stimulating the expression of selective glycosyl- and sulfotransferase genes involved in the synthesis of selectin ligands

Sialyl Lewis x (sLe(x)) plays an important role in cancer metastasis. But, the mechanism for its production in metastatic cancers remains unclear. The objective of current study was to examine the effects of a proinflammatory cytokine on the expression of glycosyltransferase and sulfotransferase genes involved in the synthesis of selectin ligands in a prostate cancer cell line. Androgen-independent human lymph node-derived metastatic prostate cancer cells (C-81 LNCaP), which express functional androgen receptor and mimic the castration-resistant advanced prostate cancer, were used. TNFα treatment of these cells increased their binding to P-, E- and L-selectins, anti-sLe(x) antibody, and anti-6-sulfo-sialyl Lewis x antibody by 12%, 240%, 43%, 248% and 21%, respectively. Also, the expression of C2GnT-1, B4GalT1, GlcNAc6ST3, and ST3Gal3 genes was significantly upregulated. Further treatment of TNFα-treated cells with either anti-sLe(x) antibody or E-selectin significantly suppressed their in vitro migration (81% and 52%, respectively) and invasion (45% and 56%, respectively). Our data indicate that TNFα treatment enhances the motility and invasion properties of LNCaP C-81 cells by increasing the formation of selectin ligands through stimulation of the expression of selective glycosyl- and sulfotransferase genes. These results support the hypothesis that inflammation contributes to cancer metastasis.

Neutrophil interactions with sialyl Lewis X on human nonsmall cell lung carcinoma cells regulate invasive behavior

BACKGROUND

The carbohydrate sialyl Lewis X (sLeX) is expressed on leukocytes and carcinoma cells and binds to selectins during inflammatory processes and early metastasis. Synthesis of sLeX depends on activity of enzymes, including α(1,3/1,4) fucosyltransferase (FucT-III). Tumor necrosis factor-α (TNF-α) up-regulates FucT-III, resulting in increased sLeX in the airways of patients with respiratory disease; however, the mechanisms that regulate sLeX in the inflammatory tumor microenvironment are not well understood.

METHODS

The authors stably transfected human lung carcinoma cell lines with the FucT-III gene and exposed them to TNF-α to investigate its role in regulation of sLeX expression and selectin-binding ability using semiquantitative real-time polymerase chain reaction and flow cytometry. Cytokine expression was examined in transfected cells using chemiluminescent arrays and enzyme-linked immunosorbent assays, and invasion was studied using Matrigel assays and alterations in morphology. Human lung tissue arrays were analyzed for immunohistochemical detection of sLeX and neutrophils.

RESULTS

Stimulation of FucT-III-transfected cells with recombinant human (rh) TNF-α up-regulated sLeX expression and increased E-selectin binding. Transfected cells secreted high levels of interleukin 8, growth-regulated oncogene-α, and mast cell proteinase-1. Cells exposed to rhTNF-α, neutrophil-conditioned media, and cultures with a 5:1 ratio of neutrophils to cancer cells had significantly increased sLeX expression and invasiveness and underwent nonadherent morphologic changes. In lung carcinomas, but not in normal lung tissues, 71% of tumors were highly positive for sLeX expression in areas of increased neutrophil infiltration.

CONCLUSIONS

The current results indicated that neutrophils may be recruited to areas of FucT-III activity and sLeX expression in lung carcinomas to enhance the invasive and metastatic potential of lung cancer cells.

SPDEF is required for mouse pulmonary goblet cell differentiation and regulates a network of genes associated with mucus production

Various acute and chronic inflammatory stimuli increase the number and activity of pulmonary mucus-producing goblet cells, and goblet cell hyperplasia and excess mucus production are central to the pathogenesis of chronic pulmonary diseases. However, little is known about the transcriptional programs that regulate goblet cell differentiation. Here, we show that SAM-pointed domain-containing Ets-like factor (SPDEF) controls a transcriptional program critical for pulmonary goblet cell differentiation in mice. Initial cell-lineage-tracing analysis identified nonciliated secretory epithelial cells, known as Clara cells, as the progenitors of goblet cells induced by pulmonary allergen exposure in vivo. Furthermore, in vivo expression of SPDEF in Clara cells caused rapid and reversible goblet cell differentiation in the absence of cell proliferation. This was associated with enhanced expression of genes regulating goblet cell differentiation and protein glycosylation, including forkhead box A3 (Foxa3), anterior gradient 2 (Agr2), and glucosaminyl (N-acetyl) transferase 3, mucin type (Gcnt3). Consistent with these findings, levels of SPDEF and FOXA3 were increased in mouse goblet cells after sensitization with pulmonary allergen, and the proteins were colocalized in goblet cells lining the airways of patients with chronic lung diseases. Deletion of the mouse Spdef gene resulted in the absence of goblet cells in tracheal/laryngeal submucosal glands and in the conducting airway epithelium after pulmonary allergen exposure in vivo. These data show that SPDEF plays a critical role in regulating a transcriptional network mediating the goblet cell differentiation and mucus hyperproduction associated with chronic pulmonary disorders.

Evaluation of the serum N-linked glycome for the diagnosis of cancer and chronic inflammation

The identification of serum biomarkers has lead to improvements in the detection and diagnosis of cancer, and combinations of these biomarkers have increased further their sensitivity and specificity. Glycosylation is the most common PTM of secreted proteins and the identification of novel serum glyco-biomarkers has become a topic of increasing interest because the glycan processing pathways are frequently disturbed in cancer cells. A future goal is to combine current biomarkers with glyco-biomarkers to yield further improvements. Well characterised N-glycosylation changes in the serum glycome of cancer patients include changes in the levels of tri- and tetra-antennary glycan structures, sialyl Lewis X epitopes and agalactosylated bi-antennary glycans. Several of these glycosylated markers have been linked to chronic inflammatory diseases, promoting questions about the links between inflammation and cancer. In this review, the glycoproteins which display these glycan epitopes, the glycosyl transferases which can generate them, their potential functions and their use as biomarkers are evaluated.

Epidermal growth factor inhibits Campylobacter jejuni-induced claudin-4 disruption, loss of epithelial barrier function, and Escherichia coli translocation

Campylobacter jejuni is a leading cause of acute bacterial enteritis in humans. Poultry serves as a major reservoir of C. jejuni and is thought to act as a principal vehicle of transmission to humans. Epidermal growth factor (EGF) is a small amino acid peptide that exerts a broad range of activities on the intestinal epithelium. The aims of this study were to determine the effect of EGF on C. jejuni intestinal colonization in newly hatched chicks and to characterize its effects on C. jejuni-induced intestinal epithelial barrier disruption. White Leghorn chicks were treated with EGF daily, starting 1 day prior to C. jejuni infection, and were compared to control and C. jejuni-infected, EGF-treated chicks. Infected chicks shed C. jejuni in their feces throughout the study period. C. jejuni colonized the small intestine and cecum, disseminated to extraintestinal organs, and caused jejunal villus atrophy. EGF reduced jejunal colonization and dissemination of C. jejuni to the liver and spleen. In EGF-treated C. jejuni-infected chicks, villus height was not significantly different from that in untreated C. jejuni-infected chicks or controls. In vitro, C. jejuni attached to and invaded intestinal epithelial cells, disrupted tight junctional claudin-4, and increased transepithelial permeability. C. jejuni also promoted the translocation of noninvasive Escherichia coli C25. These C. jejuni-induced epithelial abnormalities were abolished by pretreatment with EGF, and the effect was dependent upon activation of the EGF receptor. These findings highlight EGF's ability to alter colonization of C. jejuni in the intestinal tract and to protect against pathogen-induced barrier defects.

Evolving complexities of influenza virus and its receptors

Sialic acids (Sias) are regarded as receptors for influenza viruses and are usually bound to galactose (Gal) in an alpha2-3 or alpha2-6 configuration. The detection of these Sia configurations in tissues has commonly been through the use of plant lectins that are able to identify which cells contain Siaalpha2-3- and Siaalpha2-6-linked glycans, although other techniques for receptor distribution have been used. Initial experiments indicated that avian versus human influenza virus binding was determined by either Siaalpha2-6 or Siaalpha2-3 expression. In this review, we suggest that the distribution and detection of these terminal Siaalpha2-3- and Siaalpha2-6-linked receptors within the respiratory tract might not be as clear cut as has been reported. We will also review how other viral and receptor components might act as determinants for successful viral replication and transmission. Understanding these additional components is important in comprehending the infection and the transmission of both existing human influenza viruses and newly emerging avian influenza viruses.

IL-6 and IL-8 increase the expression of glycosyltransferases and sulfotransferases involved in the biosynthesis of sialylated and/or sulfated Lewisx epitopes in the human bronchial mucosa

Bronchial mucins from patients suffering from CF (cystic fibrosis) exhibit glycosylation alterations, especially increased amounts of the sialyl-Lewisx (NeuAcα2-3Galβ1-4[Fucα1-3]GlcNAc-R) and 6-sulfo-sialyl-Lewisx (NeuAcα2-3Galβ1-4[Fucα1-3][SO3H-6]GlcNAc-R) terminal structures. These epitopes are preferential receptors for Pseudomonas aeruginosa, the bacteria responsible for the chronicity of airway infection and involved in the morbidity and early death of CF patients. However, these glycosylation changes cannot be directly linked to defects in CFTR (CF transmembrane conductance regulator) gene expression since cells that secrete airway mucins express no or very low amounts of the protein. Several studies have shown that inflammation may affect glycosylation and sulfation of various glycoproteins, including mucins. In the present study, we show that incubation of macroscopically healthy fragments of human bronchial mucosa with IL-6 (interleukin-6) or IL-8 results in a significant increase in the expression of α1,3/4-fucosyltransferases [FUT11 (fucosyltransferase 11 gene) and FUT3], α2-6- and α2,3-sialyltransferases [ST3GAL6 (α2,3-sialyltransferase 6 gene) and ST6GAL2 (α2,6-sialyltransferase 2 gene)] and GlcNAc-6-O-sulfotransferases [CHST4 (carbohydrate sulfotransferase 4 gene) and CHST6] mRNA. In parallel, the amounts of sialyl-Lewisx and 6-sulfo-sialyl-Lewisx epitopes at the periphery of high-molecular-mass proteins, including MUC4, were also increased. In conclusion, our results indicate that IL-6 and -8 may contribute to the increased levels of sialyl-Lewisx and 6-sulfo-sialyl-Lewisx epitopes on human airway mucins from patients with CF.

Identification of differentially expressed genes in hepatocyte/endothelial cell co-culture system

Cell-cell communication between multiple-cell populations is believed to be important for the activation of many cellular functions. Previously, we showed that, in the rat hepatoma cell line Fao, grown in a layered co-culture system with a human umbilical vein endothelial cell (HUVEC) sheet, the expression of albumin and apolipoprotein A-I increased time-dependently for 10 days and was maintained at a significantly higher level than Fao without the HUVEC sheet. Because the gene-expression profile of hepatocytes and HUVECs under double-layered co-culture has not previously been elucidated, in the present study, we examined the difference in messenger ribonucleic acid expression between Fao or HUVEC monolayer cells and double-layered co-cultured Fao cells/HUVECs using suppression subtractive hybridization. More than 200 transcripts were differentially screened to ensure unique expression. The expression levels of genes in the co-cultured and monolayer cells were determined using SYBR Green I real-time reverse transcription polymerase chain reaction with species-specific primers. We found 23 genes that showed at least a 2-fold difference in expression level. Five hepatocyte-specific genes--alpha1-acidglycoprotein, alpha2-microglobulin, hepcidin, transferrin, and transthyretin--were identified from the Fao cells. Two cell-surface protein genes--bone morphogenetic protein receptor type II and CD82--which may be related to cell-cell communication, showed greater expression in the HUVECs co-cultured with Fao cells. These results indicate that many hepatocyte and endothelial cell functions increase in intensity upon layered co-culture.

The exon 6ABC region of amelogenin mRNA contribute to increased levels of amelogenin mRNA through amelogenin protein-enhanced mRNA stabilization

We recently demonstrated that the reuptake of full-length amelogenin protein results in increased levels of amelogenin mRNA through enhanced mRNA stabilization (Xu, L., Harada, H., Tamaki, T. Y., Matsumoto, S., Tanaka, J., and Taniguchi, A. (2006) J. Biol. Chem. 281, 2257-2262). Here, we examined the molecular mechanism of enhanced amelogenin mRNA stabilization. To identify the cis-regulatory region within amelogenin mRNA, we tested various reporter systems using a deletion series of reporter plasmids. A deletion at exon 6ABC of amelogenin mRNA resulted in a 2.5-fold increase in the amelogenin mRNA expression level when compared with that of full-length mRNA, indicating that a cis-element exists in exon 6ABC of amelogenin mRNA. Furthermore, Northwestern analysis demonstrated that amelogenin protein binds directly to its mRNA in vitro, suggesting that amelogenin protein acts as a trans-acting protein that specifically binds to this cis-element. Moreover, recombinant mouse amelogenin protein extended the half-life of full-length amelogenin mRNA but did not significantly alter the half-life of exon 6ABC-deletion mutant mRNA. The splice products produced by deletion of exon 6ABC are known as leucine-rich amelogenin peptides and have signaling effects on cells. Our findings also suggest that the regulation of full-length amelogenin protein expression differs from the regulation of leucine-rich amelogenin peptide expression.

Relationship between calcium-activated chloride channel 1 and MUC5AC in goblet cell hyperplasia induced by interleukin-13 in human bronchial epithelial cells

BACKGROUND

Interleukin (IL)-13 has recently been reported as the major T-helper 2 cytokine involved in mucus overproduction and oversecretion in allergic airways. However, the relationship between human calcium-activated chloride channel-1 (hCLCA1) and MUC5AC induced by IL-13 in vitro has not been fully investigated.

OBJECTIVES

The present study examines whether IL-13 induces the expression of hCLCA1 in normal human bronchial epithelial (NHBE) cells. We also investigated the relationship between hCLCA1 and MUC5AC expression and the development of goblet cell hyperplasia (GCH).

METHODS

NHBE cells were isolated from human bronchi, and cultured with an air-liquid interface. hCLCA1 and MUC5AC gene and protein expression, as well as GCH were examined in the cells after exposure to IL-13.

RESULTS

Incubation with IL-13 for 14 and 21 days increased the total number of epithelial cells, the number of periodic acid-Schiff (PAS)-stained epithelial cells, the number of goblet cells, as well as expression of mRNA and protein of hCLCA1 and MUC5AC. The number of goblet cells with secretory granules also increased after 21 days of incubation with IL-13. Niflumic acid, a chloride channel inhibitor, reduced mRNA expression of hCLCA1 and MUC5AC, and reduced the number of PAS-positive cells after incubation with IL-13. NHBE cells exposed or not to IL-13 expressed IL-13 receptor alpha(1) (IL-13Ralpha(1)), and an antibody to IL-13 Ralpha(1) also reduced the number of PAS-positive cells after exposure to IL-13.

CONCLUSIONS

IL-13 might induce the expression of MUC5AC and hCLCA1 gene and protein in well-differentiated NHBE cells. These cells might also differentiate into goblet cells and become hyperplastic.

Effects of carbocisteine on sialyl-Lewis x expression in an airway carcinoma cell line stimulated with tumor necrosis factor-alpha

Carbocisteine is a mucoregulatory drug normalizing sialic acid and fucose contents in mucins through the regulation of glycosyltransferase activities. Tumor necrosis factor (TNF)-alpha-induced overexpression of sialyl-Lewis x epitopes, containing sialic acid and fucose, in mucins were previously reported to be regulated by glycosyltransferase mRNAs expression through phosphatidyl inositol-specific phospholipase C (PI-PLC) signaling pathways [Ishibashi, Y., Inouye, Y., Okano, T., Taniguchi, A., 2005. Regulation of sialyl-Lewis x epitope expression by TNF-alpha and EGF in an airway carcinoma cell line. Glycoconj. J. 22, 53-62]. To investigate the mechanism behind the mucoregulatory action of carbocisteine, the present study evaluated the effects of carbocisteine on TNF-alpha-induced overexpression of sialyl-Lewis x epitopes in NCI-H292 cells. 100 mug/ml of carbocisteine was able to inhibit the TNF-alpha-induced expression of hST3GallV mRNA, FUT3 mRNA, C2/4GnT mRNA and sialyl-Lewis x epitopes as well as the TNF-alpha-induced activity of PI-PLC in NCI-H292 cells. These findings suggest that carbocisteine may normalize the sialyl-Lewis x epitopes expression in mucins through the inhibition of cellular PI-PLC activity in vivo.