The cellular response to oxidative stress: influences of mitogen-activated protein kinase signalling pathways on cell survival

TLDR

Let's extract content. Background: "The mammalian response to stress is complex, often involving multiple signalling pathways that act in concert to influence cell fate." Purpose/Mechanism: The sentence labeled [Purpose, Mechanism] contains: "To examine potential interactions between the signalling cascades, we have focused 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 kappaB (NF-kappaB) and Bcl-2, in determining cell survival." So Purpose: The study aims to examine interactions between signalling cascades under oxidative stress in a single cell type, focusing on MAPKs, NF-kappaB, Bcl-2, to determine cell survival. Mechanism: They used H2O2 to induce oxidative stress in HeLa cells, examined MAPK subfamilies, used inhibitors PD098059, SB202190, SB203580, dominant negative mutant, etc. But the Mechanism sentence should summarize how they did it: "They treated HeLa cells with H2O2 and used pharmacological inhibitors and genetic manipulation to probe MAPK, NF-kappaB, and Bcl-2 pathways." Findings: Summarize all findings: H2O2 induced apoptosis with activation of ERK, JNK/SAPK, p38; ERK inhibition increased apoptosis; JNK/SAPK inhibition decreased apoptosis; p38 inhibition had no effect; NF-kappaB inhibition had no effect; Bcl-2 overexpression decreased apoptosis; ERK and JNK/SAPK act in opposition; p38 and NF-kappaB do not affect outcome; Bcl-2 acts independently downstream.

Abstract

The mammalian response to stress is complex, often involving multiple signalling pathways that act in concert to influence cell fate. To examine potential interactions between the signalling cascades, we have focused 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 kappaB (NF-kappaB) and Bcl-2, in determining cell survival. 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 dominant negative mutant form of SAPK/ERK kinase 1. Inhibition of the p38 kinase activity with p38-specific inhibitors SB202190 and SB203580 had no effect on cell survival. Because NF-kappaB activation by H2O2 is potentially related to both the ERK and JNK/SAPK signalling pathways, we examined the effects of inhibiting the activation of NF-kappaB; this interference had no effect on the cellular response to H2O2. Overexpression 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-kappaB affects the outcome. Bcl-2 acts independently and downstream of ERK and JNK/SAPK to enhance the survival of H2O2-treated cells.