Role of cyclooxygenase-1 and -2, phospholipase C, and protein kinase C in prostaglandin-mediated gastroprotection.
Oral administration of the nonselective cyclooxygenase (COX) inhibitor indomethacin (20 mg/kg), the COX-1 inhibitor 5-(4-chlorophenyl)-1-(4-methoxyphenyl)-3-trifluoromethylpyrazole (SC-560) (20 mg/kg), or the COX-2 inhibitor rofecoxib (1-20 mg/kg) antagonized the gastroprotective effects of 16,16-dimethyl-prostaglandin (PG) E2 (75 ng/kg p.o.) and 20% ethanol in rats. The effects of the COX inhibitors were reversed by the activator of ATP-sensitive potassium (KATP) channels cromakalim (0.3-0.5 mg/kg p.o.). The protective effects of 16,16-dimethyl-PGE2 and 20% ethanol were counteracted by the phospholipase C inhibitor 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione (U-73122), but not its inactive analog 1-(6-((17 beta-3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-2,5-pyrrolidine-dione (U-73343) (1 mg/kg each i.v.). Likewise, the protein kinase C inhibitors chelerythrine (0.7 mg/kg i.v.) and staurosporine (3 microg/kg i.v.) inhibited gastroprotection. Effects of these enzyme inhibitors were not reversed by cromakalim. Submaximally effective doses of SC-560 (0.2 mg/kg p.o.) and rofecoxib (0.02 mg/kg p.o.) were additive and abolished the protection induced by 20% ethanol. The findings show that inhibition of COX-1 or COX-2 antagonizes not only adaptive gastroprotection by 20% ethanol but also the protective effect of exogenous PG in a cromakalimsensitive manner. Endogenous PG obviously add to the protective activity of exogenous PG. Gastroprotection by PG involves phospholipase C, protein kinase C, and KATP channels. Activation of KATP channels does not exert protection when the activity of phospholipase C or protein kinase C is suppressed.
Peskar
Brigitta M
BM
Department of Experimental Clinical Medicine, Ruhr-University of Bochum, Universitaetsstr. 150, D-44801 Bochum, Germany. brigitta.m.peskar@ruhr-uni-bochum.de
Sawka
Nadia
N
Ehrlich
Karlheinz
K
Peskar
Bernhard A
BA
D000818:Animals; D019806:Cromakalim / Q000494:pharmacology; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004068:Digestive System Physiological Phenomena; D015237:Dinoprost / Q000031:analogs & derivatives* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology; D007527:Isoenzymes / Q000187:drug effects / Q000502:physiology*; D008297:Male; D008565:Membrane Proteins; D011451:Prostaglandin-Endoperoxide Synthases / Q000187:drug effects / Q000502:physiology*; D011453:Prostaglandins / Q000502:physiology*; D011493:Protein Kinase C / Q000187:drug effects / Q000502:physiology*; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D010738:Type C Phospholipases / Q000187:drug effects / Q000502:physiology*
D052246:Cyclooxygenase 2 Inhibitors; D016861:Cyclooxygenase Inhibitors; D004791:Enzyme Inhibitors; D004963:Estrenes; D007527:Isoenzymes; D008565:Membrane Proteins; D011453:Prostaglandins; D011760:Pyrrolidinones; D019806:Cromakalim; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C074854:U 73343; C022934:16,16-dimethylprostaglandin F2alpha; D000431:Ethanol; D015237:Dinoprost; D051545:Cyclooxygenase 1; D051546:Cyclooxygenase 2; D011451:Prostaglandin-Endoperoxide Synthases; C496513:Ptgs1 protein, rat; D011493:Protein Kinase C; D010738:Type C Phospholipases