Effect of SC-560, a selective cyclooxygenase (COX)-1 inhibitor, and its modification by COX-2 inhibition in the rat stomach (original) (raw)

Epidermal growth factor (EGF) induces gastric epithelial cell migration, re-epithelialization, and thus is essential for gastric erosion and ulcer healing. The key events regulating cell motility and proliferation include polymerization of actin, formation of stress fibers and focal adhesions. Tensin crosslinks and caps actin filaments, and forms complexes with FAK and PI-3K in focal adhesions. The molecular mechanisms regulating reepithelialization, especially the roles of tensin, and focal adhesion kinase (FAK) remain unexplored. In this study, we investigated in wounded gastric epithelial monolayers, the effect of EGF on cell cytoskeletal architecture, EGF-receptor (EGF-R) phosphorylation and the rate of re-epithelialization. Methods: In confluent monolayers of rat gastric epithelial (RGMI) cells, standard excisional wounds were made and cultures incubated with medium only or medium containing EGF (10 nglmI) for 24 and 48 hours. Studies: 1) wound re-epithelialization with video image system, 2) actin stress fiber formation by phalloidin labeling, 3) EGF-R phosphorylation, 4) tensin and FAK distribution by immunostaining, and 5) tensin and FAK phosphorylation. Results: EGF significantly accelerated wound re-epithelialization by 2-fold within 24 hrs (p<O.OO1), increased lamelipodia and stress fiber formation (28% ± 3% increase; p<O.OI), EGF-R phosphorylation (231%±19% increase p<0.02), FAK and tensin expression (96%±8% and 58%±6% increase respectively; both p<O.OI) and their phosphorylation (all p<0.05). Conclusion: EGF-accelerated wound re-epithelialization in gastric epithelial monolayers involves EGF-R phosphorylation, cytoskeletal reorganization including increased stress fibers and lamelipodia formation and increased phosphorylation of FAK and tensin proteins. ). We examined the interaction of salicylate with selective COX-2 inhibitors using 2 models of gastric damage. Methods: Male Wistar rats were used. 1) Gastric ischaemia-reperfusion: Rats were anaesthetized with pentobarbital. The pylorus was ligated and 1 mI of 0.1 N HCl instilled p.o. The celiac artery was occluded for 15 min followed by 30 min reperfusion. Then gastric damage was assessed using a lesion index (LI). Groups of rats were pretreated with the selective COX-2 inhibitors DFU (2 mglkg, s.c., 30 min) or NS-398 (4 mglkg, s.c., 30 min) or the nitric oxide (NO) synthase inhibitor L-NAME (10 mglkg, i.v., 10 min). Further rats received sodium salicylate (0.01-0.05 mglkg, s.c.) 30 min before DFU and NS-398 or 50 min before L-NAME. 2) Mild irritant-induced gastroprotection: Conscious rats received 1 mI of 20% ethanol p.o. followed by 1 mI of 70% ethanol 30 min later. After further 5 min, mucosal damage was assessed. Groups of rats received DFU (0.2 mglkg, p.o., 30 min), NS-398 (1 mglkg, p.o., 30 min) or L-NAME (10 mglkg, i.v., 10 min) before 20% ethanol. Further groups ofrats received salicylate (0.01-0.05 mglkg, p.o.) 30 min before DFU, NS-398 or L-NAME. Results: Mucosal damage was minor after ischaemia-reperfusion alone (LI 4 ± 1) but was significantly (p<O.OOI) aggravated by pretreatment with DFU (LI 34±2), NS-398 (LI 39±2) or L-NAME (LI 42±2). Salicylate (0.05 mglkg) reversed (p<O.OO1) the effects of DFU (LI 1O± 1) and NS-398 (LI 1O± 1) but not L-NAME (LI 38±3). The salicylate effect was dose-dependent (1050 against NS-398: 0.02 mglkg). Instillation of 20% ethanol prevented damage caused by 70% ethanol (LI 4± 1 vs. 32± 1, p<O.OOI). The protection was inhibited (p<O.OOI) by DFU (LI 33±I), NS (LI 29±2) or L-NAME (LI 43±2). Salicylate (0.05 mglkg) given alone did not protect against damage caused by 70% ethanol (LI 29±3) but abolished (p<O.OOI) the inhibition of mild irritant-induced protection evoked by DFU (LI 1O±3) and NS-398 (LI 4±I) but not L-NAME (LI 4I±3). The salicylate effect was dose-dependent (1050 against NS-398: 0.02 mglkg). Conclusions: Salicylate at very low doses inhibits the effects of selective COX-2 inhibitors on rat gastric mucosal integrity. It remains to be investigated whether this drug interaction occurs at the level of COX-2 or is a prostanoidindependent phenomenon.