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

Abstract

Brachyspira hyodysenteriae colonizes the pig colon, resulting in mucoid hemorrhagic diarrhea and mucus layer changes. These changes are characterized by a disorganized mucus structure and massive mucus induction with de novo expression of MUC5AC and increased production of MUC2. To investigate the mechanisms behind this altered mucin environment, we quantified the mRNA levels of mucin pathway genes and factors from the immune system in the colons of infected and control pigs and observed upregulation of neutrophil elastase, SPDEF, FOXA3, MAPK3/ ERK1, In vitro, colonic mucus-producing mucosal surfaces were treated with these factors along with B. hyodysenteriae infection and analyzed for their effect on mucin production. Neutrophil elastase and infection synergistically induced mucus production and transport speed, and interleukin 17A (IL-17A) also had similar effects, in both the presence and absence of infection. A mitogen-activated protein kinase 3 (MAPK3)/extracellular signal-regulated kinase 1 (ERK1) inhibitor suppressed these effects. Therefore, we suggest that the SPDEF, FOXA3, and MAPK3/ERK1 signaling pathways are behind the transcriptional program regulating mucin biosynthesis in the colon during B. hyodysenteriae infection. In addition to furthering the knowledge on this economically important disease, this mechanism may be useful for the development of therapies aimed at conditions where enhancing mucus production may be beneficial, such as chronic inflammatory disorders of the colon.KEYWORDS cytokine, goblet cell, mucus, spirochete, swine T he mucus layer that lines the gastrointestinal tract serves as an important barrier against bacterial pathogens (1). The main components of the mucus layer are heavily glycosylated mucins, which are secreted by goblet cells (1). The mucin composition of the mucus layer varies along the gut, with a predominance of the secreted gel-forming mucins MUC5AC and MUC6 in the stomach and MUC2 in the small and large intestines (1). Penetration of the mucus layer and colonization of the epithelial surface by bacterial pathogens are decisive events for disease outcome. Mucins can have a protective role during infections by binding to bacteria and preventing further

Interleukin 4 induces rapid mucin transport, increases mucus thickness and quality and decreases colitis andCitrobacter rodentiumin contact with epithelial cells

“…The increased mucus thickness during C. rodentium clearance is accompanied by increased mucin production and speed of transport en route exocytosis in vivo During C. rodentium infection, the mucus layer initially becomes thin, as measured at 4 and 10 dpi, followed by an increase in thickness during clearance, as measured at 14 and 19 dpi [41]. The azide-modified galactosamine (GalNAz) incorporates into the core region of mucin O-glycans and can be used to analyze mucin production and transport [22,42,43]. Newly synthesized mucins can be visualized in the supranuclear compartment of the cell one hour after injection [22] and reach the colonic lumen in 6-8 h [44].…”

An avirulent Brachyspira hyodysenteriae strain elicits intestinal IgA and slows down spread of swine dysentery

“…The importance of CD4+ cells in the immune response following B. hyodysenteriae infection has been described by several authors [ 15 , 35 ]. We have demonstrated a ninefold increase in mRNA levels of IL-17A in SD infected pigs before [ 36 ]. Taken together, it would be of most interest to determine if CD4+ cells and upregulation of IL-17A are present in the colonic mucosae of pigs immunised with our strain D28 and to explore ways to further optimise the intestinal IgA response.…”

Role of Sialic Acid in Brachyspira hyodysenteriae Adhesion to Pig Colonic Mucins

“…The host's colonic mucosal immune response to B. hyodysenteriae infection is involved in the regulatory networks determining mucin expression. Neutrophil elastase and interleukin-17 , part of the colonic mucosal immune response to B. hyodysenteriae infection, induce mucin production synergistically with B. hyodysenteriae via mitogen-activated protein kinase 3 (34). B. hyodysenteriae infection regulates mucin glycosylation synthesis in the colon, resulting in the loss of interindividual variation, shorter glycan chains, and a higher abundance of neutral, core 2, and N-glycolylneuraminic acid (NeuGc)-and sulfatecontaining structures compared to healthy pigs (8).…”