THE CELLULAR-RESPONSE TO OXIDATIVE STRESS - INFLUENCES OF MITOGEN-ACTIVATED PROTEIN-KINASE SIGNALING PATHWAYS ON CELL-SURVIVAL

The mammalian response to stress is complex, often involving multiple signalling pathways that act in concert to influence cell fate. To exa mine potential interactions between the signalling cascades, we have f ocused on the effects of a model oxidant stress in a single cell type through an examination of the relative influences of mitogen-activated protein kinases (MAPKs) as well as two proposed apoptosis regulators, nuclear factor kappa B (NF-kappa B) and Bcl-2, in determining cell su rvival. Treatment of HeLa cells with H2O2 resulted in a time- and dose -dependent induction of apoptosis accompanied by sustained activation of all three MAPK subfamilies: extracellular signal-regulated protein kinase (ERK), c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) and p38. This H2O2-induced apoptosis was markedly enhanced when ERK2 activation was selectively inhibited by PD098059, Apoptosis decreased when JNK/SAPK activation was inhibited by expression of a do minant negative mutant form of SAPK/ERK kinase 1. Inhibition of the p3 8 kinase activity with p38-specific inhibitors SB202190 and SB203580 h ad no effect on cell survival. Because NF-kappa B activation by H2O2 i s potentially related to both the ERK and JNK/SAPK signalling pathways , we examined the effects of inhibiting the activation of NF-kappa B; this interference had no effect on the cellular response to H2O2, Over expression of the anti-apoptotic protein Bcl-2 significantly decreased the apoptosis seen after treatment with H2O2 without altering ERK or JNK/SAPK activities. Our results suggest that ERK and JNK/SAPK act in opposition to influence cell survival in response to oxidative stress, whereas neither p38 nor NF-kappa B affects the outcome. Bcl-2 acts in dependently and downstream of ERK and JNK/SAPK to enhance the survival of H2O2-treated cells.