Cyclo-oxygenase-1 inhibition increases acid secretion by modulating H+,K+-ATPase expression and activation in rabbit parietal cells.

1. In the present study, we evaluated the role of cyclo-oxygenase (COX)-1 and COX-2 on gastric acid secretion in rabbit isolated parietal cells and gastric glands by examining [(14)C]-aminopyrine uptake, prostaglandin (PG) E(2) synthesis and COX-1, COX-2 and proton pump expression at baseline and after treatment with various concentrations of specific COX-1 (SC-560), COX-2 (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methyl-sulphonyl)phenyl-2 (5H)-furanone; DFU) and non-specific COX (indomethacin) inhibitors. 2. In parietal cells, SC-560 and indomethacin, over the concentration range 10(-8) to 10(-4) mol/L, dose-dependently increased basal and 10(-4) mol/L histamine-stimulated aminopyrine uptake and inhibited PGE(2) synthesis, whereas DFU (10(-8) to 10(-5) mol/L) had no effect. However, at 10(-4) mol/L, DFU augmented histamine-stimulated aminopyrine uptake by 135% and inhibited PGE(2) synthesis by 39%, indicating an inhibition of COX-1 at this higher concentration. 3. The SC-560-, DFU- and indomethacin-induced augmentation of histamine-stimulated aminopyrine uptake was reduced to basal levels after 10(-5) mol/L lansoprazole treatment in parietal cells and gastric glands, whereas 10(-4) mol/L ranitidine only partially inhibited such augmentation. 4. Only COX-1 was detected in parietal cells. However, both COX-1 and COX-2 were expressed in gastric glands, with relative protein density of COX-1 being sixfold higher than that of COX-2. Protein levels of COX-1 in parietal cells and those of COX-1 and COX-2 in gastric glands remained unchanged, regardless of inhibitor treatment, either alone or with histamine. 5. Parietal cell proton pump expression was significantly enhanced by 10(-5) mol/L SC-560 and 10(-4) mol/L indomethacin (by 29 and 31%, respectively) and pump activity was enhanced by 61 and 65%, respectively. In contrast, 10(-5) mol/L DFU had no effect. 6. In conclusion, the data indicate that inhibition of COX-1- but not COX-2-derived PGE(2) synthesis is involved in augmentation of non-steroidal anti-inflammatory drug-induced gastric acid secretion in parietal cells by enhancing expression and activation of the proton pump.

Aberrant crypt foci as precursors in colorectal cancer progression.

Colorectal cancer progression originates when accumulated genetic and epigenetic alterations cause genomic instability and a malignant phenotype. Subsequent molecular pathway deregulation leads to histopathologic changes that are clinically evident as aberrant crypt foci (ACF) and visualized by high-magnification chromoscopic colonoscopy. ACF are biomarkers of increased colorectal cancer risk, particularly those with dysplastic features. Genetic profiling using genomic instability, loss of heterozygosity, and methylation analysis has revealed a minority population of ACF genotypically analogous to cancer.