Poster Presentation The Australasian Society for Immunology 2017 Annual Scientific Meeting

Multiple luminal factors impair epithelial barrier function and activate colonic sensory nerves in Ulcerative Colitis (#238)

Hannah R Wardill 1 2 , Joanne M Bowen 2 , Nicole Dmochowska 1 2 , Melissa Campaniello 1 , Chris Mavrangelos 1 2 , Scott Smid 2 , Sam P Costello 3 , Jane M Andrews 4 , Patrick A Hughes 1 2
  1. South Australian Health and Medical Research Institute, Adelaide, SA, Australia
  2. Adelaide Medical School, University of Adelaide, Adelaide, South Australia, Australia
  3. Department of Gastroenterology, Queen Elizabeth Hospital, Adelaide, South Australia, Australia
  4. IBD Service Dept. Gastroenterology and Hepatology, Royal Adelaide Hospital, Adelaide, South Australia, Australia

Background: Ulcerative colitis (UC) is characterised by colonic mucosal inflammation and abdominal pain. The luminal environment is altered in UC, however it remains unclear if these mediators are actively involved in underlying pathology or are epiphenomena. We therefore aimed to determine the mechanisms by which luminal mediators affect epithelial barrier function and nociceptive colonic afferent nerve function.

Methods: Stool and colonic biopsies were collected from 10 active UC patients (Endoscopic Mayo≥2) and 8 sex/age-matched healthy controls (HC). Macrophage (HLADR+,CD33+) infiltration was compared between the left (rectosigmoid) and right (ascending) colon using flow cytometry. Faecal supernatants (FSNs) were prepared to model the luminal environment of each group. IL-1β concentration and protease activity were compared between UC-FSN and HC-FSN. FSN effects on epithelial barrier integrity and nociceptive colonic sensory afferent nerves from healthy mice were compared by Ussing chamber and electrophysiological approaches, respectively, in the presence and absence of broad protease inhibitor cocktail and IL-1β neutralisation. ZO-1 and IL1R1 expression was assessed following FSN exposure by qRT-PCR and immunofluorescence.

Results: In UC biopsies, macrophage infiltration was increased in the left (inflamed) colon relative to the right (uninflamed) colon. IL-1β and protease activity were increased in UC-FSN compared to HC-FSN. Relative to HC-FSN, UC-FSN caused a significant decrease in transepithelial resistance and ZO-1 expression, and sensitised colonic nerves. IL-1R1 was located apically, however remained unchanged following FSN exposure. Protease inhibition partially rescued UC-FSN-induced barrier dysfunction and high-threshold sensory afferent mechanosensitivity, although a more profound effect was seen with IL-1β neutralisation. 

Conclusions: Luminal contents of the inflamed colon contribute to the underlying pathophysiology of UC by disrupting the epithelial barrier and activating pain sensing colonic sensory afferent nerves. These effects are predominately driven by IL-1β and proteases, and targeting these mediators in the lumen may reverse disease pathology.

Supported by NHMRC Australia.