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Growth arrest in G1 protects against oxygen-induced DNA damage and cell death
Raymond C Rancourt1, Daniel D Hayes, Patricia R Chess
1Department of Environmental Medicine, The University of Rochester, Rochester, New York 14642, USA.
Abstract:
Although oxygen is required for normal aerobic respiration, hyperoxia (95% O(2)/5% CO(2)) damages DNA, inhibits proliferation in G1, S and G2 phases of the cell cycle, and induces necrosis. The current study examines whether growth arrest in G1 protects pulmonary epithelial cells from oxidative DNA damage and cell death. Mv1Lu pulmonary adenocarcinoma cells were chosen for studies because hyperoxia inhibits their proliferation in S and G2 phase, while they can be induced to arrest in G1 by altering culture conditions. Hyperoxia inhibited proliferation, increased intracellular redox, and rapidly reduced clonogenic survival. In contrast, Mv1Lu cells treated with transforming growth factor (TGF)-beta1, deprived of serum or grown to confluency, arrested and remained predominantly in G1 even during exposure. Growth arrest in G1 significantly enhanced clonogenic survival by 10-50-fold. Enhanced survival was not due to reduction in the intracellular redox-state of the cells, but instead was associated with reduced DNA strand breaks and p53 expression. Our findings suggest that the protective effects of G1 is mediated not simply by a reduction in intracellular ROS, but rather through an enhanced ability to limit or rapidly recognize and repair damaged DNA.
Insights
Protecting pulmonary cells from hyperoxia involves cell cycle arrest. Growth arrest in the G1 phase significantly enhances cell survival by reducing DNA damage and p53 expression, not just redox state.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Hyperoxia (high oxygen levels) causes DNA damage, cell cycle inhibition, and necrosis.
- Pulmonary epithelial cells are susceptible to oxidative stress and DNA damage under hyperoxic conditions.
Purpose of the Study:
- To investigate if G1 phase cell cycle arrest protects pulmonary epithelial cells against hyperoxia-induced DNA damage and cell death.
- To understand the mechanisms underlying this protective effect.
Main Methods:
- Utilized Mv1Lu pulmonary adenocarcinoma cells, inducing G1 arrest via TGF-beta1, serum deprivation, or confluency.
- Exposed arrested and non-arrested cells to hyperoxia (95% O(2)/5% CO(2)).
- Assessed cell proliferation, intracellular redox state, clonogenic survival, DNA strand breaks, and p53 expression.
Main Results:
- Hyperoxia inhibited proliferation, increased intracellular redox, and reduced survival in non-arrested cells.
- G1-arrested cells showed significantly enhanced clonogenic survival (10-50 fold) under hyperoxia.
- Enhanced survival in G1-arrested cells correlated with reduced DNA strand breaks and p53 expression, independent of redox state changes.
Conclusions:
- G1 cell cycle arrest confers significant protection to pulmonary epithelial cells against hyperoxia.
- Protection is mediated by an enhanced capacity to limit or repair DNA damage, rather than solely by reducing reactive oxygen species (ROS).
- This suggests G1 arrest strengthens DNA repair mechanisms or recognition pathways.