Expression of the EP4 prostaglandin E2 receptor subtype with rat dextran sodium sulphate colitis: colitis suppression by a selective agonist, ONO-AE1-329.

Expression of the EP4 receptor, a prostaglandin (PG)E2 receptor subtype, as well as disease suppression by the administration of a selective EP4 agonist (ONO-AE1-329) was investigated in the colorectal mucosa of rats with dextran sodium sulphate (DSS)-induced colitis. Rats were given drinking water containing 3% DSS for 2 weeks. Expression of EP4 receptor mRNA was barely detectable under normal conditions according to reverse transcription-polymerase chain reaction (RT-PCR). By 1 week after the initial administration of DSS, the receptor mRNA was strongly expressed. After ONO-AE1-329 was administered intracolonically to rats with DSS colitis for 7 consecutive days, erosion and ulceration decreased. Peripheral white blood cell (WBC) counts became less elevated. Interleukin (IL)-1beta and growth-regulated gene product/cytokine-induced neutrophil chemoattractant (GRO/CINC-1) concentrations in colorectal mucosa were lower than in colitis control group (IL-1beta: 12.8 +/- 4.6 and 30.8 +/- 6.2 microg/mg protein, P < 0.05; GRO/CINC-1: 15.5 +/- 3.0 and 39.2 +/- 5.4 microg/mg protein, P < 0.05), and the expression of the corresponding cytokine mRNA was strongly suppressed. IL-10 concentration was higher than in control group (14.5 +/- 1.7 and 7.9 +/- 1.2 microg/mg, P < 0.05), and the mRNA was more strongly expressed. These results suggest that the EP4 receptor is important in colonic inflammation, and that PGE2 suppresses DSS colitis at least partly via the EP4 receptor and the above cytokine changes. Intracolonic administration of selective EP4 agonist might have therapeutic applicability in inflammatory bowel disease such as ulcerative colitis.

Estimation of mucosal inflammatory mediators in rat DSS-induced colitis. Possible role of PGE(2) in protection against mucosal damage.

In order to investigate the mucosal injury mechanism in UC, we made dextran sulfate sodium (DSS)-induced colitis in rat and examined pathological findings, MPO activity, PGE(2) level, and local mRNA expression and secretion of IL-1 beta, TNF-alpha, GRO/CINC-1 and IL-10 in DSS colitis mucosa. Moreover, we estimated the correlation between the severity of mucosal damage and changes of these local inflammatory mediators' values. Neutrophil infiltration was marked and MPO activity was locally increased in proportion to the severity of mucosal damage. The mRNA expression and secretion of IL-1 beta, GRO/CINC-1 and IL-10 were increased. Especially, the secretions of IL-1 beta and GRO/CINC-1 were increased in proportion to the severity of mucosal damage. However, those of TNF-alpha were not increased in the colitis mucosa. An abnormal macrophage function and the presence of macrophage subtypes producing different cytokines would be predicted from our TNF-alpha data. The lesion was less severe in the colonic mucosa with higher levels of endogenous PGE(2), while it was more severe in the colonic mucosa with lower levels of endogenous PGE(2), implicating this compound as an inhibitory factor against the development of inflammation in the affected mucosa. Our results suggest that PGE(2) might have therapeutic applicability to UC.

Enprostil, a prostaglandin-E(2) analogue, inhibits interleukin-8 production of human colonic epithelial cell lines.

We previously reported that intracolonic administration of enprostil, a prostaglandin-E(2) (PGE(2)) analogue, had therapeutic effects on acute colitis induced in rodents by dextran sulfate sodium (DSS). In addition, production of growth-regulated gene product/cytokine-induced neutrophil chemoattractant-1 [GRO/CINC-1; an interleukin(IL)-8 like cytokine] was suppressed in the inflamed tissues. In the present study we used a human colon cancer cell line (HT-29) to investigate enprostil effects on the IL-8 production of intestinal epithelial cells stimulated by various stimulants. In a MTT assay, concentrations of enprostil >10(-5)M had cytotoxitic effects on HT-29 cells. Furthermore, 10(-6) M enprostil suppressed IL-8 production in HT-29 cells, SW620 and CaCo2 stimulated with interleukin-1 beta (IL-1 beta) or lipopolysaccharide (LPS), but did not suppress this response when cells were stimulated with tumour necrosis factor (TNF)-alpha. These results suggest that enprostil affects a point in the pathway between the IL-1 receptor or LPS receptor and nuclear factor-kappa B(NF-kappa B), without affecting the pathway between the TNF receptor and NF-kappa B, with the latter factor being required for the IL-8 gene transcription. The therapeutic effect of exogenous enprostil on DSS colitis may involve the inhibition of IL-8 production in colonic epithelial cells stimulated by IL-1 beta or LPS.

Therapeutic effect of intracolonically administered nuclear factor kappa B (p65) antisense oligonucleotide on mouse dextran sulphate sodium (DSS)-induced colitis.

Cytokines such as IL-1, tumour necrosis factor-alpha (TNF-alpha), IL-6 and IL-8 are increased in inflamed colonic mucosa after administration of mouse DSS. Nuclear factor kappaB (NF-kappaB) is a transcription factor which regulates the expression of these cytokine genes. The effect of intracolonically administered NF-kappaB (p65) antisense phosphorothioate oligonucleotide was examined in mouse DSS-induced colitis using drinking water containing 5% DSS. When antisense oligonucleotide was given on day 0, the disease activity index (DAI) representing clinical symptoms improved and the histological score decreased; furthermore, IL-1, IL-6, and TNF-alpha concentrations in rectal mucosa were lower compared with the control group. Clinical and histological improvement was also observed when antisense oligonucleotide was begun on day 2 but not on day 7. In addition, the distribution of antisense oligonucleotides was investigated by confocal laser microscopy. In colonic mucosa, oligonucleotides were predominantly localized to cells in the lamina propria, but also in the epithelium. Western blot analysis using homogenized rectal mucosa showed the decreased expression of NF-kappaB p65 in the antisense oligonucleotide-treated group, although it was increased in the colitis group. These results suggest that intracolonic administration of NF-kappaB antisense oligonucleotide may be effective in ulcerative colitis.

Prostaglandin E2 inhibits lesion formation in dextran sodium sulphate-induced colitis in rats and reduces the levels of mucosal inflammatory cytokines.

Effects of rectally injected prostaglandin E2 (PGE2) in rats with dextran sodium sulphate (DSS)-induced colitis were investigated in terms of histopathology, local myeloperoxidase (MPO) activity, local mRNA expression of interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and growth-regulated gene produced/cytokine-induced neutrophil chemoattractant (GRO/CINC)-1, and secretion of TNF-alpha and GRO/CINC-1. In animals with no PGE2 treatment, DSS-induced erosion and ulceration were particularly severe in the rectum and extended to the proximal colon. Neutrophil infiltration was characteristically present in the lesions and surrounding mucosa. MPO activity at lesion sites was increased. IL-1beta and GRO/CINC-1 mRNA expression was increased, while TNF-alpha mRNA expression was significantly decreased. GRO/CINC-1 secretion was increased but a similar elevation of TNF-alpha was not detected. In the PGE2-treated group, lesion formation was inhibited grossly and microscopically. Neutrophil infiltration and MPO activity in and around lesions were lessened. The reduction in TNF-alpha mRNA expression and secretion was not affected by PGE2. The expression of mRNA for IL-1beta and GRO/CINC-1 was reduced, as was the secretion of GRO/CINC-1. As mRNA expression and secretion of cytokines in lesions of non-PGE2-treated animals was similar to that reported in human ulcerative colitis, rectal injection of PGE2 may prove to be an effective therapy.