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

摘要

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 1L-17, TNF-alpha, IL-1p 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, PGF2(,) or their corresponding ethanolamides (PGE2-EA or PGF2a-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-cc, IL-10 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; 10r4 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 g/ml) increased permeability over 24-48 h.