Signal transduction pathways involved in oxidative stress-induced intestinal epithelial cell apoptosis

Necrotizing enterocolitis (NEC) is a devastating inflammatory condition of the gut that occurs in premature infants. Ischemia-reperfusion gut injury with production of reactive oxygen species (ROS) is thought to contribute to NEC; the exact cellular mechanisms involved are largely unknown. The purpose of this study was to determine the intracellular signaling transduction pathways involved in oxidative stress-induced intestinal epithelial cell apoptosis. H₂O₂ treatment resulted in rat intestinal epithelial cell apoptosis in a dose- and time-dependent manner; the caspase inhibitor, zVAD-fmk, blocked this response. Western blotting was performed to determine phosphorylation of kinases and ELISA was used to assess DNA fragmentation, as a measure of apoptosis. A rapid increase in phosphorylation of extracellular signal-related kinase (ERK)1/2, c-Jun N-terminal kinase (JNK)1/2, and Akt was noted. Inhibition of ERK and JNK decreased H₂O₂-induced apoptosis. Additionally, inhibition of protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3-K) attenuated and enhanced H ₂O₂-mediated apoptosis and mitochondrial membrane potential decrease, respectively. Furthermore, activation of PKC reduced the Akt phosphorylation, whereas inhibition of PKC attenuated H₂O ₂-mediated activation of caspase-3 and enhanced the H ₂O₂-induced Akt phosphorylation. This study shows that activation of multiple signaling transduction pathways occurs during oxidative stress-induced intestinal epithelial cell injury. In contrast to ERK, JNK, and PKC, PI3-K/Akt may play an important role as a protective cellular signaling pathway during this process.