Reinforcement of the Intestinal Mucus Layer Protects Against Clostridium difficile Intestinal Injury In Vitro (original) (raw)

2014, Journal of the American College of Surgeons

BACKGROUND: Clostridium difficile infection is increasing in incidence and severity. Attributable factors include virulence factors, including C difficile toxins A and B, as well as host immunologic status. The mucus component of the intestinal barrier is impaired by malnutrition, shock insults, and alterations in the gut microbiome. Exogenous phosphatidylcholine (PC) administration results in reinforcement of the mucus layer and is of therapeutic benefit in chronic ulcerative colitis. We therefore studied the role of exogenous PC combined with secretory immunoglobulin A (IgA) in intestinal barrier function against C difficile infection in vitro. STUDY DESIGN: Dimeric IgA was placed in the basal chambers of mucus-producing (HT29-methotrexate) and nonemucus-producing (HT29) strains of intestinal epithelial monolayers and allowed to undergo transcytosis and, in additional experiments, exogenous colostral IgA (30 ng/mL) was added to the apical media. After subsequent coculture with PC and C difficile toxin A in the apical chamber, tumor necrosis factor-a, interleukin-6, toxin A uptake, intestinal epithelial cell monolayer permeability, and necrosis were determined. RESULTS: A significant decrease of 4-to 5-fold in tumor necrosis factor-a and interleukin-6 levels and equally significant decreases in toxin A uptake and permeability changes in the intestinal cell monolayers with mucus or PC and transcytosed or colostral IgA vs control are shown. All groups analyzed also displayed a 2-to 3-fold reduction in necrosis. CONCLUSIONS: Mucus or "exogenous" mucus in the form of PC has a synergistic role with secretory IgA in barrier defense against C difficile toxin A. Exogenous PC administration can be a therapeutic adjunct in patients with severe or recalcitrant C difficile infection. (J Am Coll Surg 2014;219: 460e469. Ó 2014 by the American College of Surgeons) Clostridium difficile infection (CDI) is the leading cause of health care-associated diarrhea. 1 The clinical symptoms can range from asymptomatic carrier to self-limited diarrhea, to severe life-threatening colitis (toxic megacolon), and even death. Disease severity has been causally linked to C difficile virulence factors and the host immune and inflammatory responses. 2-5 Two main virulence factors, toxin A and toxin B have been described for C difficile. 6 Debate remains about the relative importance of these 2 toxins; however, it is likely that both toxin A and toxin B are important in CDI. 7,8 Even with the emergence of certain hypervirulent C difficile strains (NAPI/027), it is now recognized that the host immune and inflammatory responses are the primary determinants of clinical outcomes in CDI. 9 Host defense against C difficile include both the innate and adaptive immune systems. 4 Innate immunity of the mucosal surface at the gastrointestinal tract is provided by the intestinal epithelium and mucin-producing goblet cells, as well as antimicrobial peptides, lysozymes, and the commensal flora. 10-12 Mucins act as the main structural component of the mucus layer, giving rise to its viscoelastic protective properties. 13,14 Phospholipids account for a minor part of the mucus lipids. 15 However the hydrophobic properties of phospholipids result in significant protective properties of intestinal mucus. 16 Secretory immunoglobulin A (SIgA) is the major antibody at mucosal surfaces. 17-19 The primary function of SIgA is immune exclusion whereby access to the mucosal Disclosure Information: Nothing to disclose.