Adaptive cytoprotection mediated by prostaglandin I(2) is attributable to sensitization of CRGP-containing sensory nerves.
OBJECTIVE
The phenomenon by which the gastric mucosa is protected in response to mild irritants has been called adaptive cytoprotection, a mechanism believed to be related to production of endogenous prostaglandins (PGs). We tested whether PGs generated by mild irritant prevent injury through the release of calcitonin gene-related peptide (CGRP) from the sensory nerves using prostanoid receptor-knockout mice.


METHODS
The stomach was doubly cannulated and perfused with 1 mol/L NaCl or 50% ethanol. CGRP levels in the perfusate were determined by enzyme immunoassay, and the injured area was estimated at the end of perfusion.


RESULTS
Preperfusion with mildly hypertonic saline (1 mol/L NaCl) increased generation of gastric PGE(2) and PGI(2) and reduced ethanol-induced mucosal damage. Exposure of ethanol after 1 mol/L NaCl increased intragastric CGRP levels from 166 +/- 27 to 713 +/- 55 pg/2 min (n = 4, P < 0.05), and the protective action of 1 mol/L NaCl was inhibited by indomethacin treatment. CGRP antagonist blocked 1 mol/L NaCl-induced protective effect. Intragastric perfusion of 50% ethanol after administration of PGI(2), but not of PGE(2), increased CGRP levels. Application of 1 mol/L NaCl to IP receptor-knockout mice (IP(-/-)) did not elicit the protective effects seen in the wild-type on ethanol-induced gastric mucosal lesions. Protective effect of 1 mol/L NaCl was observed in EP3 receptor-knockout mice (EP3(-/-)). CGRP level during ethanol perfusion was not increased in IP(-/-) but was increased in EP3(-/-) and wild-type counterparts after preperfusion of 1 mol/L NaCl.


CONCLUSIONS
These results indicate that the endogenous PGI(2) generated by 1 mol/L NaCl may have a protective role in gastric mucosal injury through enhancement of CGRP release from gastric mucosa. This mechanism may explain the adaptive cytoprotection observed after treatment with mild irritants.
Boku
K
K
Department of Internal Medicine, Kitasato University School of Medicine, Sagamihara, Kanagawa, Japan.
Ohno
T
T
Saeki
T
T
Hayashi
H
H
Hayashi
I
I
Katori
M
M
Murata
T
T
Narumiya
S
S
Saigenji
K
K
Majima
M
M
D015121:6-Ketoprostaglandin F1 alpha / Q000378:metabolism; D000222:Adaptation, Physiological / Q000187:drug effects; D000758:Anesthesia; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D015740:Calcitonin Gene-Related Peptide / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D002492:Central Nervous System Depressants / Q000494:pharmacology; D015232:Dinoprostone / Q000378:metabolism / Q000494:pharmacology; D011464:Epoprostenol / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D005753:Gastric Mucosa / Q000187:drug effects / Q000294:innervation* / Q000378:metabolism*; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009475:Neurons, Afferent / Q000378:metabolism*; D010446:Peptide Fragments / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D013276:Stomach Ulcer / Q000139:chemically induced / Q000378:metabolism
D000894:Anti-Inflammatory Agents, Non-Steroidal; D002492:Central Nervous System Depressants; D010446:Peptide Fragments; C491910:Ptgir protein, mouse; C491909:Ptgir protein, rat; D044006:Receptors, Epoprostenol; D011982:Receptors, Prostaglandin; C058636:calcitonin gene-related peptide (8-37); D000431:Ethanol; D012965:Sodium Chloride; D015121:6-Ketoprostaglandin F1 alpha; D011464:Epoprostenol; D015740:Calcitonin Gene-Related Peptide; D015232:Dinoprostone; D007213:Indomethacin