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Published on: March 20, 2018
Benzo(a)pyrene induces p73 mRNA expression and necrosis in human lung adenocarcinoma H1299 cells
Ying Jiang1, Kaimin Rao, Guangtao Yang
1Department of Occupational and Environmental Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China.
Abstract:
p53 can mediate DNA damage-induced apoptosis in various cell lines treated with Benzo(a)pyrene (BaP). However, the potential role of p73, one of the p53 family members, in BaP-induced apoptotic cell death remains to be determined. In this study, normal fetal lung fibroblasts (MRC-5) and human lung adenocarcinoma cells (H1299, p53-null) were treated with BaP at concentrations of 8, 16, 32, 64, and 128 μM for 4 and 12 h. The oxidative stress status, extent of DNA damage, expression of p53, p73, mdm2, bcl-2, and bax at the mRNA and protein levels, and the percentages of apoptosis and/or necrosis were assessed. In the two BaP-treated cell lines, we observed increased malondialdehyde (MDA) formation and decreased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity at 4 h after the treatment; furthermore, at the time points of 4 and 12 h, we observed extremely high levels of DNA damage. In addition, at 4 h after the treatment, BaP had induced necrosis in MRC-5 and H1299 cells, but it had inhibited apoptosis in MRC-5 cells (P < 0.01 for all). Furthermore, in BaP-treated H1299 cells, only the p73 mRNA level was up-regulated. The results suggested that BaP-induced DNA damage could trigger a shift from apoptotic cell death toward necrotic cell death and that necrotic cell death is independent of p53 and p73 in these cell lines. Future studies are needed to investigate the time course of changes in the type of BaP-induced cell death in more cell lines.
Insights
Benzo(a)pyrene (BaP) exposure causes DNA damage and oxidative stress, shifting cell death from apoptosis to necrosis. This necrotic cell death appears independent of p53 and p73 tumor suppressor proteins.
Area of Science:
- Toxicology
- Molecular Biology
- Cell Biology
Background:
- p53 protein mediates apoptosis following DNA damage.
- The role of p73, a p53 family member, in Benzo(a)pyrene (BaP)-induced apoptosis is unclear.
- Investigating p73's role in BaP-induced cell death is crucial for understanding lung cell responses to environmental toxins.
Purpose of the Study:
- To determine the role of p73 in Benzo(a)pyrene (BaP)-induced apoptosis.
- To assess the impact of BaP on oxidative stress, DNA damage, and cell death pathways (apoptosis vs. necrosis).
- To compare the effects of BaP in normal lung fibroblasts (MRC-5) and p53-null lung adenocarcinoma cells (H1299).
Main Methods:
- Cell treatment with varying concentrations of Benzo(a)pyrene (BaP).
- Assessment of oxidative stress markers: malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px).
- Evaluation of DNA damage, gene/protein expression (p53, p73, mdm2, bcl-2, bax), and apoptosis/necrosis percentages.
Main Results:
- BaP induced significant DNA damage and oxidative stress in both cell lines.
- BaP treatment resulted in a shift from apoptosis towards necrosis at 4 hours.
- p73 mRNA levels increased in H1299 cells, but necrosis was independent of both p53 and p73.
Conclusions:
- Benzo(a)pyrene-induced DNA damage promotes a switch to necrotic cell death.
- Necrotic cell death induced by BaP is independent of p53 and p73.
- Further research is needed to explore the temporal dynamics of BaP-induced cell death in diverse cell types.
