Effects of pro-inflammatory cytokines, lipopolysaccharide and COX-2 mediators on human colonic neuromuscular function and epithelial permeability

B. K. Safdari, T. C. Sia, D. A. Wattchow, S. D. Smid

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)

Abstract

Chronic colitis is associated with decreased colonic muscle contraction and loss of mucosal barrier function. Pro-inflammatory cytokines and bacterial lipopolysaccharide (LPS) are important in the generation and maintenance of inflammation. While colitis is associated with upregulated COX-2 -derived prostanoids and nitric oxide (NO), the direct activity of pro-inflammatory cytokines on human colonic neuromuscular function is less clear. This study investigated the effects of IBD-associated pro-inflammatory cytokines IL-17, TNF-α, IL-1β and LPS on human colonic muscle strip contractility, alone and following inhibition of COX-2 or nitric oxide production. In addition, human colonic epithelial Caco-2 cell monolayers were treated with LPS or COX-2 mediators including prostaglandins (PGE2, PGF) or their corresponding ethanolamides (PGE2-EA or PGF-EA) over 48 h and trans-epithelial electrical resistance used to record permeability changes. Longitudinal muscle strips were obtained from healthy colonic resection margins and mounted in organ baths following IL-17, TNF-α, IL-1β and bacterial LPS incubations in an explant setting over 20 h. Contraction in response to acetylcholine (ACh) was then measured, before and after either COX-2 inhibition (nimesulide; 10-5 M) or nitric oxide synthase (NOS) inhibition (l-NNA; 10-4 M). None of the cytokine or LPS explant incubations affected the potency or maximum cholinergic contraction in vitro, and subsequent COX-2 blockade with nimesulide revealed a significant but similar decrease in potency of ACh-evoked contraction in control, LPS and cytokine-incubated muscle strips. Pre-treatment with l-NNA provided no functional differences in the potency or maximum contractile responses to ACh in cytokine or LPS-incubated colonic longitudinal smooth muscle. Only PGE2 transiently increased Caco-2 monolayer permeability at 24 h, while LPS (10 μg/ml) increased permeability over 24-48 h.These findings indicate that cholinergic contractility in the human colon can be decreased by the blockade of COX-2 generated excitatory prostanoids, but major pro-inflammatory cytokines or LPS do not alter the sensitivity or amplitude of this contraction ex vivo. While PGE2 transiently increase epithelial permeability, LPS generates a significant and sustained increase in permeability indicative of an important role on barrier function at the mucosal interface.

Original languageEnglish
Pages (from-to)231-238
Number of pages8
JournalCytokine
Volume83
DOIs
Publication statusPublished - 1 Jul 2016
Externally publishedYes

Keywords

  • Colitis
  • COX-2
  • Epithelial permeability
  • Interleukin 17
  • Prostaglandin ethanolamides
  • Prostaglandins

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