Suppression of Growth Arrest and DNA Damage-Inducible 45α Expression Confers Resistance to Sulindac and Indomethacin-Induced Gastric Mucosal Injury

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as sulindac and indomethacin are a major cause of gastric erosions and ulcers. Induction of apoptosis by NSAIDs is an important mechanism involved. Understanding how NSAIDs affect genes that regulate apoptosis is useful for designing therapeutic or preventive strategies and for evaluating the efficacy of safer drugs being developed. We investigated whether growth arrest and DNA damage-inducible 45 alpha (GADD45 alpha), a stress signal response gene involved in regulation of DNA repair and induction of apoptosis, plays a part in NSAID-induced gastric mucosal injury and apoptosis in vivo in mice and in vitro in cultured human AGS and rat RGM-1 gastric epithelial cells. Intraperitoneal administration of sulindac and indomethacin both resulted in up-regulation of GADD45 alpha expression and induction of significant injury and apoptosis in gastric mucosa of wild-type mice. GADD45 alpha(-/-) mice were markedly more resistant to both sulindac-and indomethacin-induced gastric mucosal injury and apoptosis than wild-type mice. Sulindac sulfide and indomethacin treatments also concentration-dependently increased GADD45 alpha expression and apoptosis in AGS and RGM-1 cells. Antisense suppression of GADD45 alpha expression significantly reduced sulindac and indomethacin-induced activation of caspase-9 and apoptosis in AGS cells. Pretreatments with exogenous prostaglandins and small interfering RNA suppression of cyclooxygenase (COX)-1 and -2 did not affect up-regulation of GADD45 alpha by sulindac sulfide and indomethacin in AGS cells. These findings indicate that GADD45 alpha up-regulation is a COX-independent mechanism that is required for induction of severe gastric mucosal apoptosis and injury by NSAIDs, probably via a capase-9-dependent pathway of programmed cell death.