Calcitonin gene-related peptide affords gastric mucosal protection by activating potassium channel in Wistar rat

doi:10.1016/S0016-5085(98)70634-1

Gastroenterology

Volume 114, Issue 1, January 1998, Pages 71-76

Presented in part at Digestive Disease Week in San Francisco, California, on May 19-22, 1996.

https://doi.org/10.1016/S0016-5085(98)70634-1 Get rights and content

Abstract

Background & Aims: Calcitonin gene-related peptide (CGRP) protects the gastric mucosa against injurious stimuli in various experimental models. The underlying mechanism could be the increase in gastric mucosal blood flow (GMBF). A number of endogenous vasodilators exert their effects through the activation of adenosine triphosphate (ATP)-sensitive potassium (K_ATP) channels on vascular smooth muscle. The present experiments were performed to elucidate whether CGRP increases GMBF through the activation of K_ATP channels and whether the channels are involved in the protection by CGRP of gastric mucosa. Methods: GMBF was determined by the hydrogen-clearance technique in male Wistar rats. Mucosal lesions were produced by intragastric superfusion with 0.15N HCl and 15% ethanol for 40 minutes. Effects of an agonist (Y-26763, intra-arterially) and an inhibitor (glibenclamide, intravenously) of K_ATP channels were tested. Results: Y-26763 increased GMBF, which was abolished by glibenclamide, and a CGRP-induced increase in GMBF was attenuated by glibenclamide. Macroscopic and microscopic lesions were exacerbated by human CGRP-(8-37) (a CGRP-1 receptor antagonist; intra-arterially) and glibenclamide but were ameliorated by exogenous CGRP (intra-arterially). Conclusions: CGRP protects the gastric mucosa against ulcerogenic stimuli, at least in part, through the activation of K_ATP channels in rats.

GASTROENTEROLOGY 1998;114:71-76

Section snippets

Animal preparation

This experiment was reviewed by the Committee of the Ethics on Animal Experiment in the Faculty of Medicine, Kyushu University, and was performed under the control of the Guideline for Animal Experiment in the Faculty of Medicine, Kyushu University, and the law (no. 105) and notification (no. 6) of the Government.

Male Wistar rats, weighing 240-330 g, were fasted for 24 hours but were allowed free access to water before experiments. After induction of anesthesia with amobarbital (100 mg/kg,

Physiological variables

There were no differences in physiological variables at baseline and pretreatment periods of Y-26763 between the two groups of rats. Arterial blood gas parameters and hematocrit were at constant levels throughout the experiment. The blood glucose level was lower in the glibenclamide + Y-26763 group but was within a physiological limit (Table 1).

. Physiological variables in experiment 1

Empty Cell	Empty Cell	Y-26763
Empty Cell	Baseline	Pretreatment	After 5 min
PaCO₂ (mm Hg)
Y	36.6 ± 0.8	35.9 ± 1.1	35.1 ± 3.6^a
G + Y	38.4 ± 2.0	37.1 ± 2.7	33.3

Discussion

There are three major findings in the present study. First, the activation of K_ATP channels increases GMBF. Second, a part of the increase in GMBF by CGRP is mediated by the activation of K_ATP channels. Finally, endogenous CGRP may protect the gastric mucosa against acid challenge, at least in part, through the activation of K_ATP channels.

In some previous studies in which GMBF was measured by a hydrogen clearance method, GMBF was approximately 40 mL · min⁻¹ · 100 g tissue⁻¹ in rats.8, 22 The

Acknowledgements

The authors thank Yoshitomi Pharmaceuticals Ind., Ltd., Fukuoka, Japan, for providing Y-26763; and Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan, for providing omeprazole.

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Contribution of KATP channels to the gastric protective effect of prostaglandins and NO during indomethacin- and ethanol-induced gastric injury has been previously reported (Chavez-Pina et al., 2011; Medeiros et al., 2008; Peskar and Ehrlich, 2002). Furthermore, the gastric protective action of several compounds such as Zanthoxylum rhoifolium (Freitas et al., 2011), carbenoxolone (Chavez-Pina et al., 2011), sildenafil (Medeiros et al., 2008), nicorandil (Ismail et al., 2007), calcitonin gene-related peptide (CGRP) (Doi et al., 1998), l-cysteine and H2S (Medeiros et al., 2009), has been associated with the opening of KATP channels. It is suggested that KATP channels participate in the mucosal defense by modulation of primary afferent nerve fibers which in turn regulate the gastric blood flow and gastric mucus secretion (Iwata et al., 1997).
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The activation of afferent nerves of the gastric mucosa releases calcitonin gene-related peptide (CGRP). Doi et al. (1998) reported that CGRP increases gastric blood flow concomitantly with reduction of gastric lesion area and this effect is abolished by glibenclamide, a KATP channel blocker. Besides, NO plays a partial role in CGRP-induced KATP channels opening.
Cenostigma macrophyllum Tul. var. acuminata Teles Freire (Leguminosae-Caesalpinioideae), popularly known in Brazil as “caneleiro”, is widely used in folk medicine against gastrointestinal diseases. In previous studies, the ethanol extract of leaves from Cenostigma macrophyllum Tul. var. acuminata Teles Freire had shown antinociceptive, anti-inflammatory, antibacterial, antioxidant and antiulcerogenic activities.
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Background & Aims: Hydrogen sulfide (H₂S), an endogenous gaseous mediator that causes vasodilation, is generated in mammalian tissues by cystathionine β-synthase (CBS) and cystathionine-γ-lyase (CSE). Here, we have investigated the role of H₂S in a rodent model of nonsteroidal anti-inflammatory drug (NSAID) gastropathy. Methods: Rats were given acetyl salycilic acid (ASA) or an NSAID alone or in combination with NaHS, an H₂S donor, and killed 3 hours later. Gastric blood flow was measured by laser-Doppler flowmetry, whereas intravital microscopy was used to quantify adhesion of leukocytes to mesenteric postcapillary endothelium. Results: At a dose of 100 μmol/kg, NaHS attenuated by 60%–70% the gastric mucosal injury, and tumor necrosis factor (TNF)-α, intercellular adhesion molecule (ICAM)-1, and lymphocyte function-associated antigen (LFA)-1 mRNA up-regulation induced by NSAIDs (P < .05) NaHS administration prevented the associated reduction of gastric mucosal blood flow (P < .05) and reduced ASA-induced leukocyte adherence in mesenteric venules. NaHS did not affect suppression of prostaglandin E₂ (PGE₂) synthesis by NSAIDs. Glibenclamide, a K_ATP channel inhibitor, and DL-propargylglycine, a CSE inhibitor, exacerbated, whereas pinacidil, a K_ATP opener, attenuated gastric injury caused by ASA. Exposure to NSAIDs reduced H₂S formation and CSE expression (mRNA and protein) and activity by 60%–70%. By promoter deletion and mutation analysis, an Sp1 consensus site was identified in the CSE promoter. Exposure to NSAIDs inhibits Sp1 binding to its promoter and abrogates CSE expression in HEK-293 cells transfected with a vector containing the core CSE promoter. Exposure to NSAIDs inhibits Sp1 and ERK phosphorylation. Conclusions: These data establish a physiologic role for H₂S in regulating the gastric microcirculation and identify CSE as a novel target for ASA/NSAIDs.
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^☆: Address requests for reprints to: Kosei Doi, M.D., Second Department of Internal Medicine, Faculty of Medicine, Kyushu University, Maidashi 3-1-1, Higashi-ku, Fukuoka 812-82, Japan. Fax: (81) 92-642-5273.

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Alimentary TractCalcitonin gene-related peptide affords gastric mucosal protection by activating potassium channel in Wistar rat☆

Abstract

Section snippets

Animal preparation

Physiological variables

Discussion

Acknowledgements

Gastroenterology

Gastroenterology

Gastroenterology

Gastroenterology

Gastroenterology

Eur J Pharmacol

Eur J Pharmacol

Role of ATP-sensitive K+ channels in CGRP-induced dilation of basilar artery in vivo

Am J Physiol

Calcitonin gene-related peptide activated ATP-sensitive K+ currents in rabbit arterial smooth muscle via protein kinase A

J Physiol Lond

Cromakalim dilates rat cerebral arteries in vivo

Stroke

Glibenclamide decreases basal coronary blood flow in anesthetized dogs

Am J Physiol

Arterial dilations in response to calcitonin gene-related peptide involve activation of K+ channels

Nature

Nitric oxide hyperpolarized rabbit mesenteric arteries via ATP-sensitive potassium channels

J Physiol Lond

Adenosine-activated potassium current in smooth muscle cells isolated from the pig coronary ar tery

J Physiol Lond

Role of calcitonin gene-related peptide in gastric hyperemic response to intragastric capsaicin

Am J Physiol

Alimentary Tract
Calcitonin gene-related peptide affords gastric mucosal protection by activating potassium channel in Wistar rat☆

Role of ATP-sensitive K⁺ channels in CGRP-induced dilation of basilar artery in vivo

Calcitonin gene-related peptide activated ATP-sensitive K⁺ currents in rabbit arterial smooth muscle via protein kinase A

Arterial dilations in response to calcitonin gene-related peptide involve activation of K⁺ channels