Ingemar Carlstedt

MUC5AC, but not MUC2, is a prominent mucin in respiratory secretions

Airway mucus was collected from healthy and chronic bronchitic subjects. The chronic bronchitic sputum was separated into gel and sol phase by centrifugation and mucins were isolated using isopycnic density-gradient centrfugation in CsCl. The presence of the MUC5AC and MUC2 mucins was investigated with antisera raised against synthetic peptides with sequences from the respective apoproteins. The gel and sol phase of chronic bronchitic sputum as well as healthy respiratory secretions were shown to contain MUC5AC whereas the MUC2 mucin could not be detected. Rate-zonal centrifugation showed that the MUC5AC mucin was large, polydisperse in size and that reduction yielded subunits. Ion-exchange HPLC revealed the presence of two subunit populations in all secretions, the MUC5AC subunits always being the more acidic. MUC5AC is thus the first large, subunit-based, gel-forming respiratory mucin identified and this glycoprotein is biochemically distinct from at least one other population of large, gel-forming mucins also composed of subunits but lacking a genetic identity.

Expression of respiratory mucins in fatal status asthmaticus and mild asthma

Expression of respiratory mucins in fatal status asthmaticus and mild asthma

Role of ABO Secretor Status in Mucosal Innate Immunity and H. pylori Infection

The fucosylated ABH antigens, which constitute the molecular basis for the ABO blood group system, are also expressed in salivary secretions and gastrointestinal epithelia in individuals of positive secretor status; however, the biological function of the ABO blood group system is unknown. Gastric mucosa biopsies of 41 Rhesus monkeys originating from Southern Asia were analyzed by immunohistochemistry. A majority of these animals were found to be of blood group B and weak-secretor phenotype (i.e., expressing both Lewis a and Lewis b antigens), which are also common in South Asian human populations. A selected group of ten monkeys was inoculated with Helicobacter pylori and studied for changes in gastric mucosal glycosylation during a 10-month period. We observed a loss in mucosal fucosylation and concurrent induction and time-dependent dynamics in gastric mucosal sialylation (carbohydrate marker of inflammation), which affect H. pylori adhesion targets and thus modulate host–bacterial interactions. Of particular relevance, gastric mucosal density of H. pylori, gastritis, and sialylation were all higher in secretor individuals compared to weak-secretors, the latter being apparently “protected.” These results demonstrate that the secretor status plays an intrinsic role in resistance to H. pylori infection and suggest that the fucosylated secretor ABH antigens constitute interactive members of the human and primate mucosal innate immune system.

Mucin expression in peripheral airways of patients with chronic obstructive pulmonary disease.

Aims:  To study the expression of mucins in peripheral airways in patients with chronic obstructive pulmonary disease (COPD).

A Drug Absorption Model Based on the Mucus Layer Producing Human Intestinal Goblet Cell Line HT29-H

A new drug absorption model based on monolayers of the human intestinal goblet cell line HT29-H grown on permeable filters has been characterized. HT29-H cells have been shown (a) to form monolayers of mature goblet cells under standard cell culture conditions, (b) to secrete mucin molecules, (c) to produce a mucus layer that covers the apical cell surface, and (d) that this mucus layer is a significant barrier to the absorption of the lipophilic drug testosterone. This is the first demonstration of an intact human mucus layer with functional barrier properties produced in cell culture. The results indicate that monolayers of HT29-H cells provide a valuable complement to mucus-free drug absorption models based on absorptive cell lines such as Caco-2 cells.

Role of fucosyltransferases in the association between apomucin and Lewis antigen expression in normal and malignant gastric epithelium

BACKGROUND In normal gastric epithelium, MUC5AC is detected in superficial epithelium associated with Lewis type 1 antigens and MUC6 is detected in antral glands with Lewis type 2. Therefore, the stomach constitutes an excellent model to examine the role of glycosyltransferases in determining the specificity of apomucin glycosylation. AIMS To determine the molecular basis of this association and to examine changes in expression of gastric and intestinal apomucins and their association with Lewis antigens during the gastric carcinogenesis process. METHODS Fucosyltransferase (FUT1, FUT2, FUT3) and mucin (MUC5AC, MUC6) transcripts were detected using reverse transcription-polymerase chain reaction. Apomucin (MUC2, MUC4, MUC5AC, MUC6) and Lewis antigen (types 1 and 2) expression were analysed using single and double immunohistochemistry and in situ hybridisation. RESULTS In the normal stomach, FUT1 is exclusively detected associated with MUC6; FUT2 is only detected when MUC5AC is present. This co-regulation is lost in gastric tumours, as is differential expression of MUC5AC and MUC6 in normal gastric epithelial cells. In gastric tumours, especially those with the intestinal phenotype, MUC2 and MUC4 genes are upregulated, and gastric-type and intestinal-type mucins are coexpressed. These changes are early events in the gastric carcinogenesis process, as they are detected in intestinal metaplasia. CONCLUSIONS The glycosylation pattern found in normal gastric epithelium is dictated by the specific set of fucosyltranferases expressed by the cells rather than by the apomucin sequence. The development of intestinal metaplasia and gastric cancer is associated with the appearance of cellular phenotypes that are absent from normal epithelium.

Effects of pH on Helicobacter pylori binding to human gastric mucins: identification of binding to non-MUC5AC mucins

Helicobacter pylori causes gastritis, peptic ulcer disease and gastric cancer. The microbe is found in the gastric mucus layer where a pH gradient ranging from acidic in the lumen to neutral at the cell surface is maintained. The aim of the present study was to investigate the effects of pH on H. pylori binding to gastric mucins from healthy individuals. At pH 3, all strains bound to the most charged MUC5AC glycoform and to a putative mucin of higher charge and larger size than subunits of MUC5AC and MUC6, irrespective of host blood-group. In contrast, at pH 7.4 only Le(b)-binding BabA-positive strains bound to Le(b)-positive MUC5AC and to smaller mucin-like molecules, including MUC1. H. pylori binding to the latter component(s) seems to occur via the H-type-1 structure. All strains bound to a proteoglycan containing chondroitin sulphate/dermatan sulphate side chains at acidic pH, whereas binding to secreted MUC5AC and putative membrane-bound strains occurred both at neutral and acidic pH. The binding properties at acidic pH are thus common to all H. pylori strains, whereas mucin binding at neutral pH occurs via the bacterial BabA adhesin and the Le(b) antigen/related structures on the glycoprotein. Our work shows that microbe binding to membrane-bound mucins must be considered in H. pylori colonization, and the potential of these glycoproteins to participate in signalling events implies that microbe binding to such structures may initiate signal transduction over the epithelial layer. Competition between microbe binding to membrane-bound and secreted mucins is therefore an important aspect of host-microbe interaction.

Four modes of adhesion are used during Helicobacter pylori binding to human mucins in the oral and gastric niches.

Background:  Helicobacter pylori causes peptic ulcer disease and gastric cancer, and the oral cavity is likely to serve as a reservoir for this pathogen. We investigated the binding of H. pylori to the mucins covering the mucosal surfaces in the niches along the oral to gastric infection route and during gastric disease and modeled the outcome of these interactions.

Distribution of respiratory mucin proteins in human nasal mucosa.

Objectives/Hypothesis The upper respiratory tract is involved in many acute and chronic respiratory tract diseases that present with the symptom of mucus hypersecretion. Mucin genes that encode for the backbone of glycoproteins contribute to the viscoelastic property of airway mucus. We examined the cellular expression and distribution of two major respiratory mucus‐forming glycoproteins, MUC5AC and MUC5B, in normal human nasal tissues.

Mucin layers on hydrophobic surfaces studied with ellipsometry and surface force measurements

Abstract The forces acting between layers of gastric mucins from rat (RGM) and pig (PGM) adsorbed onto hydrophobized mica surfaces were investigated by using the surface force technique, whereas information on the kinetics and the reversibility of the adsorption process was obtained with ellipsometry. From the surface force measurements, we found that the amount adsorbed from a 0.1 mg/ml RGM solution was 3.5 ± 1.5 mg/m2 at adsorption equilibrium, within experimental error equal to that (about 3 mg/m2) found with ellipsometry. The forces obtained with RGM were purely repulsive, whereas those displayed by PGM were partially attractive. Dilution of the bulk solution caused only minor desorption and the interaction force between the RGM layers was only weakly dependent on the excess electrolyte concentration. Hence, steric forces predominate the interaction in the RGM system. Both RGM and PGM adsorb in a flat conformation with compressed adsorbed layer thicknesses of 10–20 nm and 3–4 nm, respectively. The interaction force was essentially reversible on approach and separation for RGM, whereas “relaxation effects” were prominent for PGM layers.