Helicobacter pylori Infection Impairs the Mucin Production Rate and Turnover in the Murine Gastric Mucosa

Abstract

To protect the surface of the stomach, the epithelial cells secrete a mucus layer, which is mainly comprised of the MUC5AC mucin. Further protection is provided by a thick glycocalyx on the apical surface of the epithelial cell, with the cell surface mucin MUC1 as a major component. Here, we investigate the production rate and turnover of newly synthesized mucin in mice and analyze the effects of early colonization and chronic infection with H. pylori. Metabolic incorporation of an azido GalNAc analog (GalNAz) was used as a nonradioactive method to perform pulse experiments in the whole animal. First, the subcellular movement of newly synthesized mucin and mucin turnover was determined in uninfected mice. Based on the time line for mucin transport and dissemination, 2, 6, and 12 h after GalNAz injection was selected to collect the stomachs from mice infected with H. pylori strain SS1 during early colonization (7 days) and chronic infection (90 days). The results demonstrated that the speed from the start of glycosylation to the final destination is faster for the membrane-bound mucin to reach the glycocalyx (2 h) than for the secretory mucins to become secreted into the mucus layer (5 h). Furthermore, infection with H. pylori reduces the rate of mucin turnover and decreases the levels of Muc1. Since H. pylori colonizes this mucus niche, the decreased turnover rate indicates that H. pylori creates a more stable and favorable environment for itself by impairing the defense mechanism for clearing the mucosal surface of pathogens by mucus flow.

Neutrophil Elastase and Interleukin 17 Expressed in the Pig Colon during Brachyspira hyodysenteriae Infection Synergistically with the Pathogen Induce Increased Mucus Transport Speed and Production via Mitogen-Activated Protein Kinase 3

“…An overall assessment of these aspects was obtained by measuring production and transport of newly synthesized mucin after basolateral administration of the in vitro mucosal surfaces with an azide-modified galactosamine (GalNAz), which was metabolically incorporated into the mucin O-glycans for later detection by fluorescence staining. Previous experiments demonstrated efficient incorporation of GalNAz into mucin O-glycans both in vitro and in vivo (10,(20)(21)(22). Incorporation of GalNAz into newly synthesized mucins in the supranuclear compartment of the cell can be visualized 1 h after injection in the mouse stomach (10), and the time from incorporation of GalNAz to release of the labeled mucin to the lumen of the distal colon is 6 to 8 h (22).…”

“…Previous experiments demonstrated efficient incorporation of GalNAz into mucin O-glycans both in vitro and in vivo (10,(20)(21)(22). Incorporation of GalNAz into newly synthesized mucins in the supranuclear compartment of the cell can be visualized 1 h after injection in the mouse stomach (10), and the time from incorporation of GalNAz to release of the labeled mucin to the lumen of the distal colon is 6 to 8 h (22). To determine the best time point to study changes in mucin production rate in the in vitro mucosal surfaces with different treatments and infections, we harvested the mucosal surfaces 1, 2, 3, 6, 8, and 12 h after addition of GalNAz.…”

“…In addition to being of veterinary and medical importance, B. hyodysenteriae infection also represents an interesting and unusual model in that it is a bacterial colonic infection that leads to increased mucus layer thickness. In the stomach and intestine, several chronic infections and chronic inflammatory conditions have been linked to a decreased mucus layer/mucus depletion (10,11). Therefore, knowledge from this model may aid in identifying strategies to replenish the mucus layer under such conditions to allow the epithelium to heal and remove commensal bacteria from direct contact with the epithelium.…”

Avances en la búsqueda de la vacuna contra Helicobacter pylori

“…La acción de estas células en la infección por H. pylori parece ser promovida y potenciada, por lo menos en parte, por la acción inmunosupresora de la citoquina TGF-β1, secretada por múltiples células inmunes locales y por los mismos LTreg [46][47][48][49] . Además la infección por H. pylori altera las defensas innatas básicas del estómago por diferentes mecanismos, como el daño directo al epitelio por la inflamación, que es mediada principalmente por IL-1; la alteración en la velocidad de síntesis y composición del moco y la disminución en la secreción de ácido clorhídrico 50,51 . En la Figura 1 se resumen algunos de los aspectos de la respuesta inmunológica a H. pylori.…”

Statistics in Infection and Immunity Revisited

“…1. Figure 2 is taken from the work of Navabi et al (4) and shows an example where Dunnett's post hoc test was used to compare each group to the control group. Comparisons between all pairs of means (using the Tukey-Kramer or other tests) or between each mean and the mean from a control group (using Dunnett's test) are the most common applications of multiplecomparison procedures, but other approaches, such as the Dunn (for nonparametric analyses), Bonferroni, Holm-Šidák (less conservative than the Bonferroni test), or Scheffé test may be appropriate for different scenarios.…”