Gastroenterology

Gastroenterology

Volume 122, Issue 5, May 2002, Pages 1442-1454
Gastroenterology

Basic Research
Constitutive expression and function of cyclooxygenase-2 in murine gastric muscles,☆☆

https://doi.org/10.1053/gast.2002.33065Get rights and content

Abstract

Background & Aims: Cyclooxygenase enzymes (COX) generate intermediates in the prostaglandin (PG) cascade. COX-1 is constitutively expressed in many cells, and COX-2 is typically thought to be an inducible isoform. Methods: We evaluated constitutive expression and function of COX-2 in murine gastric muscles. Results: Immunohistochemistry showed COX-2–like immunoreactivity (COX-2–LI) in myenteric neurons. Half the neurons with COX-2–LI expressed nitric oxide synthase (NOS). COX-2–LI was not observed in smooth muscle cells. Interstitial cells of Cajal within muscle layers (IC-IM) expressed COX-2–LI, suggesting a novel role for IC-IM. Molecular studies verified expression of COX-2 in gastric muscles. Quantitative polymerase chain reaction (PCR) showed equal expression of COX-1 and COX-2 in the antrum. COX-2 was more abundant in fundus. Indomethacin and GR253035X, a COX-2 inhibitor, increased antral phasic contractions and potentiated responses to ACh. Indomethacin, but not GR253035X, increased contractions and potentiated responses in tissues of COX-2 knockout mice. Indomethacin and GR253035X reduced tone in the fundus. Conclusions: COX-2 is constitutively expressed by IC-IM and neurons in the stomach and at levels similar to COX-1. Prostanoids produced by COX-2 regulate mechanical activities of fundus and antral muscles.

GASTROENTEROLOGY 2002;122:1442-1454

Section snippets

Animals and tissue preparation

Twenty-eight Balb-C, 6 C57/BL6 wild-type and COX-2 +/−, and 6 C57/BL6 COX-2 −/− mice of either sex between the ages of 25–35 days old (30–35 g) were used. Animals were suffocated by CO2 inhalation and killed by cervical dislocation followed by exsanguination. The abdomens were cut open and the stomach of each animal was removed for further dissection. The use and treatment of animals were approved by the Institutional Animal Use and Care Committee at the University of Nevada.

Immunohistochemical studies

Segments of fundus

Distribution of COX-2 immunoreactivity

We used immunohistochemical techniques to identify the cell types that express COX-2 in the tunica muscularis of the stomach. COX-2–like immunoreactivity (COX-2–LI) was found in a subpopulation of enteric nerve cell bodies and nerve terminals within myenteric ganglia of the fundus (Figure 1C) and antrum (Figure 1D and F).

. (AF) COX-2–LI is expressed in a subpopulation of enteric neurons and ICC. (A and D) COX-2–LI (green) and (B and E) nuclear staining (propidium iodide; red) in the same

Discussion

These experiments show constitutive expression of COX-2 in cells within the tunica muscularis of the mouse. The major expression of COX-2 was a subpopulation of enteric neurons and IC-IM. These findings suggest a new role of ICC as a source of paracrine substances that contribute to the regulation of gastrointestinal motility. Functional data suggest that prostanoids produced by COX-2 may contribute significantly to the spontaneously generated prostanoids that provide ongoing regulation of

Acknowledgements

The authors are grateful to Lisa Miller for excellent technical assistance in genotyping mice.

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    Address requests for reprints to: Kenton M. Sanders, Ph.D., Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557. e-mail: [email protected]; fax: (775) 784-6903.

    ☆☆

    Supported by DK 40569 and a grant from Glaxo Smith Kline. Morphologic and molecular studies were supported by core laboratory facilities provided by DK 41513. Supported by a grant from the Fondation pour la Recherche Medicale (France) (to C.P.).

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