Inhibition of ACh-stimulated exocytosis by NSAIDs in guinea pig antral mucous cells: autocrine regulation of mucin secretion by PGE2.
The effects of indomethacin (IDM) and aspirin (ASA) on ACh (10 microM) -stimulated exocytotic events were studied in guinea pig antral mucous cells by using video optical microscopy. IDM or ASA, which inhibits cyclooxygenase (COX), decreased the frequency of ACh-stimulated exocytotic events by 30% or 60%, respectively. The extent of inhibition induced by ASA (60%) decreased by 30% when IDM or arachidonic acid (AA, the substrate of COX) was added. IDM, unlike ASA, appears to induce the accumulation of AA, which enhances the frequency of ACh-stimulated exocytotic events in ASA-treated cells. ONO-8713 (100 microM; an inhibitor of the EP1-EP4 prostaglandin receptors) and N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide, HCl (H-89, 20 microM; an inhibitor of PKA) also decreased the frequency of ACh-stimulated exocytotic events by 60%. However, the supplementation of PGE(2) (1 microM) prevented the IDM-induced decrease in the frequency of ACh-stimulated exocytotic events. SC-560 (an inhibitor of COX-1) decreased the frequency of ACh-stimulated exocytotic events by 30%, but NS-398 (an inhibitor of COX-2) did not. Moreover, IDM decreased the frequency of exocytotic events stimulated by ionomycin, suggesting that COX-1 activity is stimulated by an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)). ACh and ionomycin increased PGE(2) release in antral mucosal cells. In conclusion, in ACh-stimulated antral mucous cells, an increase in [Ca(2+)](i) activates Ca(2+)-regulated exocytotic events and PGE(2) release mediated by COX-1. The released PGE(2) induces the accumulation of cAMP, which enhances the Ca(2+)-regulated exocytosis. The autocrine mechanism mediated by PGE(2) maintains the high-level mucin release from antral mucous cells during ACh stimulation.
Shimamoto
Chikao
C
Dept. of Internal Medicine, Osaka Medical College, 2-7 Daigaku-cho, Takatsuki 569-8686, Japan.
Fujiwara
Shoko
S
Kato
Masumi
M
Ito
Shigenori
S
Katsu
Ken-ichi
K
Mori
Hiroshi
H
Nakahari
Takashi
T
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology*; D015232:Dinoprostone / Q000494:pharmacology*; D005089:Exocytosis; D006168:Guinea Pigs; D007213:Indomethacin / Q000494:pharmacology*; D008297:Male; D009077:Mucins / Q000378:metabolism*; D014665:Vasodilator Agents / Q000494:pharmacology*
D000894:Anti-Inflammatory Agents, Non-Steroidal; D009077:Mucins; D014665:Vasodilator Agents; D015232:Dinoprostone; D000109:Acetylcholine; D001241:Aspirin; D007213:Indomethacin