Danny T. Dinh

The Prevention of Colitis by E Prostanoid Receptor 4 Agonist through Enhancement of Epithelium Survival and Regeneration

Inflammatory bowel disease (IBD) is often triggered and/or exacerbated by nonsteroidal anti-inflammatory drugs (NSAIDs). Among various prostanoids affected by NSAIDs, prostaglandin E2 (PGE2), in particular, seems to play critical roles in IBD via the EP4 receptor, one of the four PGE2 receptor subtypes (EP1–4). An EP4 agonist, [[3-[[(1R,2S,3R)-3-hydroxy-2-[(1E,3S)-3-hydroxy-4-[3-(methoxymethyl)phenyl]-1-butenyl]-5-oxocyclopentyl]thio]propyl]thio]-acetic acid, C22H30O6S2 (ONO-AE1–329), for example, when topically applied, has been reported to ameliorate typical colitis symptoms by suppressing the production of cytotoxic cytokines in the dextran sodium sulfate (DSS)-induced colitis model. EP4 agonists are also known, however, for their ability to protect epithelial cells from apoptosis in vitro, which may contribute to the protection of mucosal barrier functions. To investigate this potential application, we have tested another EP4-selective agonist in the DSS-indomethacin mouse colitis model. 7-[2-(3-Hydroxy-4-phenyl-but-1-enyl)-6-oxo-piperidin-1-yl]-heptanoic acid methyl ester, C23H33NO4 (AGN205203), an analog from the 8-azapiperidinone series of EP4 agonists, is metabolically and chemically more stable than the ONO agonist, because of its lack of oxidizable sulfur atoms in the α-chain and of 11-OH group, a potential source of β-elimination reaction. Treatment of mice subcutaneously with AGN205203 at 3 mg/kg/day minimized colitis symptoms, such as weight loss, diarrhea, and colonic bleeding. Further histological examination of colons revealed healthy surface columnar epithelial cells free of erosion and ulceration compared with those without the drug treatment. At cellular level, the drug treatment decreased colon epithelial apoptosis, prevented goblet cell depletion, and promoted epithelial regeneration. AGN205203 may be unique among known EP4 agonists for its metabolic and chemical stability, and it is amenable to systemic applications for the prevention and recovery of IBD.

Prostaglandin E2 receptor subtype EP2- and EP4-regulated gene expression profiling in human ciliary smooth muscle cells

Prostanoids are an important class of intraocular pressure (IOP)-lowering antiglaucoma agents that act primarily via increased uveo-scleral aqueous humor outflow through the ciliary body. We have developed two novel PGE(2) analogs that are specific agonists for the PGE(2) receptor subtypes EP2 and EP4, respectively. To identify gene regulatory networks and key players that mediate the physiological effects observed in vivo, we performed genomewide expression studies using human ciliary smooth muscle cells. Quantitative real-time RT-PCR confirmed a largely overlapping gene expression profile subsequent to EP2 and EP4 agonist treatment, with 65 significantly regulated genes identified overall, 5 being specific for the EP2 agonist and 6 specific for the EP4 agonist. We found predicted functional cAMP-response elements in promoter regions of a large fraction of the predominantly upregulated genes, which suggests that the cAMP signaling pathway is the most important intracellular signaling pathway for these agonists in these cells. Several target genes were identified that, as part of complex regulatory networks, are implicated in tissue remodeling processes and osmoregulation (e.g., AREG, LOXL3, BMP2, AQP3) and thus may help elucidate the mechanism of action of these IOP-lowering drugs involving the uveo-scleral outflow path.