Prostaglandin E prevents indomethacin-induced gastric and intestinal damage through different EP receptor subtypes
Introduction
Non-steroidal anti-inflammatory drugs (NSAIDs; e.g. indomethacin) cause hemorrhagic mucosal injury in the gastrointestinal tract of man and experimental animals [2], [3], [13], [26]. Although the exact mechanism for these ulcerogenic responses remains unknown, it is believed that a deficiency of endogenous prostaglandins (PG) due to cyclooxygenase (COX) inhibition plays a critical part in the pathogenesis of these lesions in both tissues [13], [14]. Indeed, many studies showed that the supplementation with exogenous PGE prevents the occurrence of damage induced by indomethacin in both the stomach and intestine [12], [21], [22], [26].
On the other hand, the receptors activated by PGE2 are pharmacologically subdivided in at least four subtypes (EP1, EP2, EP3, and EP4), and the distribution of these receptors is thought to explain the multiple effects of PGE2 in various tissues including the gastrointestinal tract. Few studies have been so far reported on the relationship of EP receptor subtypes with various actions of PGE2 in the gastrointestinal tract, i.e. the EP1 receptors in smooth muscle contraction, the EP2/EP3 receptors in acid secretion, and the EP4 receptor in mucus secretion [5], [7], [16], [19], [28]. In addition, we have recently reported that PGE2, administered exogenously, exhibits gastric cytoprotection through activation of EP1 receptors [1]. However, the EP receptor subtype involved in the protective action of PGE2 against indomethacin-induced gastrointestinal damage remains unexplored.
In the present study, we examined the effects of various prostanoids, subtype-specific EP receptor agonists, on indomethacin-induced gastric and small intestinal lesions in rats, in attempts to determine the EP receptor subtypes responsible for the protective action of PGE2 against these lesions. Furthermore, because an animal model lacking various receptors for prostanoids has been recently established [18], [23], we also evaluated the protective activity of PGE2 in knockout mice lacking EP1 or EP3 receptors.
Section snippets
Animals
Male Sprague–Dawley (SD) rats (200–220 g) or C57BL/6 mice (25–30 g) were used. Mice lacking the EP1 or EP3 receptors were generated as described previously [18], [23]. These knockout mice and rats were deprived of food but allowed free access to tap water for 18 h before the experiments, and the studies were performed using 4∼6 animals per group. All experimental procedures employed in the present study were approved by the Experimental Animal Research Committee of the Kyoto Pharmaceutical
Changes in gastrointestinal lesions and PGE2 contents following administration of indomethacin
Subcutaneous administration of indomethacin at 35 mg/kg in fasted rats produced multiple lesions in the gastric mucosa within 1 h, and the damage progressively increased with time, reaching 34.8±6.2 mm2 at 4 h after the administration (Fig. 1). Likewise, indomethacin given at 10 mg/kg in non-fasted rats induced damage in the small intestine within 6 h, progressively increased with time, and the lesion score 24 h later was 246.3±41.9 mm2 (Fig. 2). On the other hand, the mucosal PGE2 in the
Discussion
Pathogenesis of gastrointestinal lesions induced by NSAID such as indomethacin involves multiple elements including various functional disorders such as microvascular disturbances [6], [18], [19], [20], yet a deficiency of endogneous PGs is prerequisite for these lesions in both tissues. Indeed, many studies showed that PGE2 or its derivatives inhibited gastrointestinal ulcerogenic effect of indomethacin [12], [14], [21], [22], although the mechanism for this action remains unknown. In the
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2011, Biochemical and Biophysical Research CommunicationsCitation Excerpt :The following lectins and antibodies were used for flow cytometry (FCM) and confocal laser scanning microscopy (CLSM): PE-conjugated UEA-1 (UEA-1-PE; Biogenesis, England, UK), tetramethylrhodamine isothiocyanate (TRITC)-conjugated UEA-1 (Vector Laboratories, Burlingame, CA), Alexa Fluor 633-conjugated wheat germ agglutinin (WGA-AF633; Molecular Probes, Eugene, OR), FITC-conjugated NKM 16-2-4 mAb (NKM 16-2-4-FITC) [22], APC-conjugated anti-mouse CD45 mAb (anti-CD45-APC; BD Biosciences, San Jose, CA). A mucosal adjuvant, CT (List Biologic Laboratories, Campbell, CA), and two pro-inflammatory agents, dextran sodium sulfate (DSS, m.w. 36,000–50,000; ICN Biomedicals, Irvine, CA) and indomethacin (Sigma–Aldrich, St. Louis, MO), were used as stress-inducing agents to alter the intestinal environment of mice as described previously [17,23,24] (see Supplementary information). The small intestinal epithelium was dissociated by a mechanical procedure as described previously [17].
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2010, Advances in Clinical ChemistryCitation Excerpt :These results strongly suggest that the intestinal protection by dmPGE2 against indomethacin is brought about by activation of EP3 and EP4 receptors, similar to the protective action in the duodenum. We confirmed this using EP-receptor knockout mice and showed that dmPGE2 provided less protection against indomethacin-induced intestinal damage in the animals lacking EP3 receptors, although the agent exhibited marked inhibition in both wild-type and EP1-receptor knockout mice [55]. The fact that even in EP3-receoptor knockout mice dmPGE2 provided partial protection against these lesions, supports the involvement of another EP receptor subtype, EP4, in the protective action of dmPGE2.