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Pre-exposure to oxidative stress decreases the nuclear factor-kappa B-dependent transcription in T lymphocytes
N Lahdenpohja1, K Savinainen, M Hurme
1Department of Microbiology and Immunology, University of Tampere Medical School, Finland. llnila@uta.fi.
Abstract:
Reactive oxygen species (ROS) are used as signaling molecules in T cell activation. One of the main targets of ROS is the transcription factor nuclear factor-kappa B (NF-kappa B). NF-kappa B-dependent transcription is inhibited by antioxidants, and the activation is induced or potentiated by ROS. However, chronic oxidative stress is known to reduce the activation of T cells and NF-kappa B. To analyze these phenomena in more detail, we have exposed Jurkat T cells in vitro to oxidative stress (H2O2) at various times before or simultaneously with signals known to activate NF-kappa B (phorbol dibutyrate (PDBu) and TNF). Simultaneously applied H2O2 strongly potentiated the PDBu- or TNF-induced transcriptional activity of NF-kappa B. In contrast to this, H2O2 given 3 to 20 h before the activating signal reduced NF-kappa B-dependent transcriptional activity. This was not due to the oxidation-induced modification of NF-kappa B; cytoplasmic NF-kappa B was able to bind to DNA after dissociation from I kappa B alpha by detergent treatment. H2O2 pre-exposure effectively inhibited the PDBu- or TNF-induced phosphorylation and degradation of I kappa B alpha, but H2O2 given simultaneously with PDBu or TNF enhanced the degradation. Oxidative stress was also followed by a strongly decreased ability to form intracellular ROS. Taken together, these data indicate that I kappa B alpha phosphorylation is the target of action of ROS, and as the ROS-forming capacity is weaker after chronic oxidative stress, I kappa B alpha is not effectively phosphorylated and degraded, thus leading to decreased NF-kappa B-dependent transcription.
Insights
Reactive oxygen species (ROS) signal T cell activation, but chronic oxidative stress impairs it. This study shows ROS potentiate NF-kappa B activation when simultaneous, yet inhibit it when pre-applied, by targeting I kappa B alpha phosphorylation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Reactive oxygen species (ROS) act as signaling molecules in T cell activation.
- Nuclear factor-kappa B (NF-kappa B) is a key transcription factor targeted by ROS.
- While ROS can enhance NF-kappa B activity, chronic oxidative stress paradoxically reduces T cell activation.
Purpose of the Study:
- To investigate the dual role of oxidative stress on NF-kappa B signaling in T cells.
- To elucidate the mechanisms underlying the differential effects of acute versus chronic oxidative stress on T cell activation.
Main Methods:
- Jurkat T cells were exposed to hydrogen peroxide (H2O2) to induce oxidative stress.
- Cells were treated with H2O2 at different time points relative to NF-kappa B activators (phorbol dibutyrate and TNF).
- NF-kappa B transcriptional activity, I kappa B alpha phosphorylation and degradation, and intracellular ROS production were measured.
Main Results:
- Simultaneous H2O2 exposure potentiated NF-kappa B activity induced by phorbol dibutyrate or TNF.
- Pre-exposure to H2O2 (3-20 hours prior) significantly reduced NF-kappa B activity.
- H2O2 pre-exposure inhibited I kappa B alpha phosphorylation and degradation, while simultaneous H2O2 enhanced it.
- Chronic oxidative stress led to a decreased intracellular ROS-forming capacity.
Conclusions:
- I kappa B alpha phosphorylation is identified as the primary target of ROS in regulating NF-kappa B.
- Acute oxidative stress enhances NF-kappa B signaling by promoting I kappa B alpha degradation.
- Chronic oxidative stress impairs NF-kappa B signaling due to reduced I kappa B alpha phosphorylation and degradation, leading to decreased T cell activation.