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Oxygen free radical generation and regulation of proliferative activity of human mononuclear cells responding to
1Section of Immunology, Cleveland Clinic Foundation, Ohio 44195.
Abstract:
We have compared various mitogenic stimuli for their ability to induce hydrogen peroxide (H2O2) and superoxide anion (O2-) production by PBMC and the effect of these reactive oxygen species and hydroxyl radical (OH.) has been assessed on proliferation. Our results show that pokeweed mitogen (PWM) stimulated PBMC to release H2O2 which interfered with proliferation since inclusion of catalase enhanced PBMC thymidine uptake. In contrast, phytohemagglutinin (PHA) and monoclonal antibody to CD3 (alpha CD3) did not induce PBMC to generate H2O2. O2- release by PBMC, which is readily induced by phorbol myristate acetate (PMA), did not occur when the cells were stimulated with PWM, PHA, or alpha CD3. In correlation, the O2- scavenger enzyme superoxide dismutase (SOD) had no effect on the proliferative response of the cells to the same mitogens, whereas it impaired the thymidine uptake of PMA-stimulated PBMC. A regulatory role for OH. was implied by studies using a battery of OH scavengers known to inhibit PMA-stimulated PBMC proliferation. OH. scavengers markedly inhibited the lymphoblastic transformation of alpha CD3-stimulated cells but had little or no effect on PHA- and PWM-stimulated PBMC. Thus, one manner by which PBMC proliferation is regulated is through oxygen free radical production which varies depending on the type of mitogenic stimulus.
Insights
Different mitogens trigger varying oxygen free radical production in peripheral blood mononuclear cells (PBMC), impacting cell proliferation. This study reveals how hydrogen peroxide and hydroxyl radicals regulate PBMC responses to stimuli.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Peripheral blood mononuclear cells (PBMC) play a crucial role in immune responses.
- Mitogenic stimuli are used to activate PBMC and study their proliferation.
- Reactive oxygen species (ROS) are implicated in cellular signaling and function, but their specific roles in PBMC proliferation require further elucidation.
Purpose of the Study:
- To compare the effects of different mitogenic stimuli on reactive oxygen species (ROS) production by PBMC.
- To investigate the influence of ROS, including hydrogen peroxide (H2O2), superoxide anion (O2-), and hydroxyl radical (OH.), on PBMC proliferation.
- To understand the regulatory role of ROS in mitogen-induced PBMC activation.
Main Methods:
- PBMC were stimulated with various mitogens: pokeweed mitogen (PWM), phytohemagglutinin (PHA), anti-CD3 antibody (alpha CD3), and phorbol myristate acetate (PMA).
- Production of H2O2 and O2- by stimulated PBMC was measured.
- The effects of ROS scavengers (catalase, superoxide dismutase, and hydroxyl radical scavengers) on PBMC proliferation (thymidine uptake and lymphoblastic transformation) were assessed.
Main Results:
- Pokeweed mitogen (PWM) stimulated PBMC to produce H2O2, which inhibited proliferation; catalase enhanced thymidine uptake.
- Phytohemagglutinin (PHA) and anti-CD3 (alpha CD3) did not induce H2O2 production.
- Superoxide anion (O2-) production was induced by PMA but not by PWM, PHA, or alpha CD3; superoxide dismutase (SOD) affected only PMA-stimulated proliferation.
- Hydroxyl radical (OH.) scavengers inhibited alpha CD3-stimulated lymphoblastic transformation but had minimal effect on PHA- and PWM-stimulated cells.
Conclusions:
- Mitogenic stimuli differentially induce ROS production in PBMC.
- Hydrogen peroxide (H2O2) can inhibit PBMC proliferation, depending on the stimulus.
- Hydroxyl radicals (OH.) appear to play a regulatory role in the proliferation of alpha CD3-stimulated PBMC.
- Oxygen free radical production varies with the mitogenic stimulus, suggesting a complex regulatory mechanism in PBMC proliferation.