The p38 pathway partially mediates caspase-3 activation induced by reactive oxygen species in Fanconi anemia C cells

Because Fanconi anemia (FA) cells display hypersensitivity to oxidative stress and reactive oxygen species (ROS) that act as second messengers in cellular signaling, we investigated c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) activation in two FA-C lymphocyte cell lines (HSC536/N and PD149L) and one FA-A cell line (HSC99) exposed to interferon (IFN)-γ or H₂O₂. IFN-γ induced accumulation of ROS and activation of JNK and p38 in HSC536/N and PD149L but not in HSC99 cells. Higher concentrations of H₂O₂ were needed to induce moderate intracellular levels of ROS and phosphorylation of MAPKs in FA-A than in FA-C cells. Pre-incubation with dehydroascorbic acid resulted in reduced intracellular ROS levels and inhibition of MAPK activation induced by the above treatments. To define the functional role of JNK and p38 in IFN-γ signaling, the effects of pharmacological inhibition of the MAPKs on induction of IFN-γ and anti-Fas antibody responses were determined. Treatment of HSC536/N cells with p38-specific inhibitors partially inhibited caspase-3 activation while pre-incubation with specific inhibitors of JNK had no effect. Altogether, these results suggest that FA-C cells are hypersensitive to IFN-γ and are more sensitive to oxidative stress than FA-A cells and that IFN-γ and anti-Fas antibody mediate signals for apoptosis in FA-C cells via p38 but not JNK pathways.