Prevention of trinitrobenzene sulfonic acid-induced experimental colitis by oral administration of a poly(lactic-coglycolic acid) microsphere containing prostaglandin E₂ receptor subtype 4 agonist.

Prostaglandin E₂ receptor subtype 4 (EP4) agonists are known to reduce intestinal inflammation and enhance epithelium regeneration. We explored the possibility of colonic delivery of an EP4 agonist, 2-[(4-{[2-((1R,2R,3R)-3-hydroxy-2-{(1E,3S)-3-hydroxy-4-[3-(methoxymethyl)phenyl]but-1-enyl}-5-oxocyclopentyl)ethyl]sulfanyl}butanoyl)oxy]ethyl nonanoate (ONO-AE2-724), using poly(lactic-coglycolic acid) (PLGA) microspheres. Colitis was induced in mice by the intrarectal administration of trinitrobenzene sulfonic acid (TNBS). ONO-AE2-724-PLGA microspheres (EP4-MS) were prepared by the standard technique. Drug distributions after oral administration of EP4-MS were determined by liquid chromatography-tandem mass spectrometry analysis. To evaluate the protective effect of EP4-MS, animals were orally treated by gavage with single doses of EP4-MS 24 h before TNBS instillation. The changes in body weight, histopathology, immunohistochemistry, and expression of inflammatory cytokines were evaluated. Oral administration of EP4-MS enhanced colonic tissue drug concentration without any increase in the serum concentration during the 48 h after intake. EP4-MS pretreatment, but not unloaded ONO-AE2-724, significantly attenuated TNBS-induced colitis and diminished colonic mRNA expression levels of proinflammatory cytokines. In addition, a significant increase in the expression of CD25 and FoxP3 was found in isolated lamina propria CD4+ T cells of EP4-MS-treated mice. Immunohistochemical analysis of Ki-67 and single-stranded DNA revealed that EP4-MS pretreatment significantly suppressed apoptosis of colonic cells and promoted epithelial cell proliferation. These results suggest that EP4-MS protect mice from TNBS-induced colitis by intestinal local ONO-AE2-724 delivery. The EP4-MS may offer a promising new therapeutic strategy to treat inflammatory bowel diseases.