Induction of apoptotic DNA fragmentation by nonsteroidal anti-inflammatory drugs in cultured rat gastric mucosal cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been shown to cause apoptosis in several cell lines including transformed chicken embryo fibroblasts and human colon cancer cells. We herein report the apoptotic effect of NSAIDs in a non-transformed cell line derived from the rat gastric mucosa, RGM1 (rat gastric mucosa cell first). 1-[ p-Chlorobenzoyl]-5-methoxy-2-methylindole-3-acetic acid (indomethacin) and sodium 2-(2,6-dichloroanilino)phenylacetate (sodium diclofenac), potent and non-selective inhibitors of cyclooxygenase, were found to induce DNA fragmentation in RGM1 cells in a time- and concentration-dependent manner. The expression of mRNA for cyclooxygenase-2 was hardly detected in the intact cells but was clearly enhanced when the cells were incubated with the two NSAIDs. In contrast, the expression of mRNA for cyclooxygenase-1 was constitutive and was never affected by NSAIDs. The effect of [3,4-di(4-methoxyphenyl)-5-isoxazolyl] acetic acid (mofezolac), a potent and highly preferential inhibitor of cyclooxygenase-1, and N-[2-(cyclohexyloxy)-4-nitrophenyl]methanesulphonamide (NS-398), a selective inhibitor of cyclooxygenase-2, on DNA fragmentation and cyclooxygenase-2 mRNA expression was weak compared to the effect of indomethacin or sodium diclofenac. The DNA fragmentation induced by sodium diclofenac was hardly affected by the exogenous addition of 16,16-dimethyl prostaglandin E 2 but was inhibited by caspase inhibitors such as Ac-YVAD-CHO and Ac-DEVD-CHO. The present data provide the first evidence that NSAIDs, such as indomethacin and sodium diclofenac, cause apoptotic DNA fragmentation in cultured gastric mucosal cells, and also indicate the involvement of caspases rather than the inhibition of cellular prostaglandin synthesis in the apoptotic process.