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Methyl methanesulfonate and hydrogen peroxide differentially regulate p53 accumulation in hepatoblastoma cells
M C Jiang1, H J Liang, C F Liao
1Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei, Republic of China.
Abstract:
Genotoxic chemicals not only damage cellular DNA, but may also induce cell apoptosis if they are lethal to the cell. p53, Bcl-2 and Bax play important roles in the regulation of genotoxic chemical induced cell apoptosis. Since the mechanisms by which cellular DNA damaged by different DNA-damaging chemicals may not be the same, we studied the involvement of p53, Bcl-2 and Bax in apoptosis induced by methyl methanesulfonate (MMS) and hydrogen peroxide (H2O2). H2O2 damages DNA by free radical generation and MMS damages DNA by DNA methylation. At non-lethal doses, both H2O2 and MMS induced high level of p53 protein accumulation. Nevertheless, while the amount of p53 protein increased with the dose of MMS and the occurrence of apoptotic cell death events, H2O2 doses that induce cell apoptosis attenuated the p53 protein accumulation level. Lethal MMS treatment also increased Bax, but not Bcl-2 expression, whereas in H2O2 induced apoptosis, the level of both Bcl-2 and Bax declined. These results indicate that toxic chemicals differentially regulate the accumulation of p53 protein. Thus, the pathways of toxic chemicals induced cell apoptosis are different and independent.
Insights
Genotoxic chemicals like MMS and H2O2 trigger cell apoptosis through distinct pathways. These chemicals differentially regulate p53 protein accumulation and apoptosis markers, indicating independent mechanisms of cell death induction.
Area of Science:
- Molecular Biology
- Toxicology
- Cell Biology
Background:
- Genotoxic chemicals damage DNA and can induce apoptosis.
- Key proteins like p53, Bcl-2, and Bax regulate apoptosis.
- Different chemicals may have unique DNA-damaging mechanisms.
Purpose of the Study:
- Investigate the roles of p53, Bcl-2, and Bax in apoptosis induced by methyl methanesulfonate (MMS) and hydrogen peroxide (H2O2).
- Compare the distinct cellular responses to DNA methylation (MMS) versus free radical generation (H2O2).
Main Methods:
- Treatment of cells with varying doses of MMS and H2O2.
- Quantification of p53 protein levels.
- Analysis of Bcl-2 and Bax expression.
- Assessment of apoptotic cell death events.
Main Results:
- Both MMS and H2O2 induced p53 accumulation at non-lethal doses.
- MMS treatment increased p53 and Bax, while decreasing Bcl-2.
- H2O2 treatment attenuated p53 accumulation at apoptotic doses and decreased both Bcl-2 and Bax.
- Apoptosis levels correlated with p53 accumulation for MMS but not H2O2.
Conclusions:
- Toxic chemicals differentially regulate p53 protein accumulation.
- Cell apoptosis pathways induced by MMS and H2O2 are distinct and independent.
- The study highlights differential protein regulation in response to various genotoxic insults.