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Modulation of cell and DNA damage by poly(ADP)ribose polymerase in lung cells exposed to H(2)O(2) or asbestos fibres
T Ollikainen1, A Puhakka, K Kahlos
1Department of Industrial Hygiene and Toxicology, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, FIN-00250, Helsinki, Finland. tiina.ollikainen@occuphealth.fi
Abstract:
Poly(ADP)ribose polymerase (PARP) may participate in cell survival, apoptosis and development of DNA damage. We investigated the role of PARP in transformed human pleural mesothelial (MeT-5A) and alveolar epithelial (A549) cells exposed from 0.05 to 5mM hydrogen peroxide (H(2)O(2)) or crocidolite asbestos fibres (1-10 microg/cm(2)) in the presence and absence of 3-aminobenzamide (ABA), a PARP inhibitor. The cells were investigated for the development of cell injury, DNA single strand breaks and depletion of the cellular high-energy nucleotides. Compared to H(2)O(2), fibres caused a minor decrease in cell viability and effect on the cellular high-energy nucleotide depletion, and a marginal effect on the development of DNA strand breaks when assessed by the single cell gel electrophoresis (the Comet assay). Inhibition of PARP transiently protected the cells against acute H(2)O(2) related irreversible cell injury when assessed by microculture tetrazolium dye (XTT) assay and potentiated oxidant related DNA damage when assessed by the Comet assay. However, PARP inhibition had no significant effect on fibre-induced cell or DNA toxicity with the exception of one fibre concentration (2 microg/cm(2)) in MeT-5A cells. Apoptosis is often associated with PARP cleavage and caspase activation. Fibres did not cause PARP cleavage or activation of caspase 3 further confirming previous results about relatively low apoptotic potential of asbestos fibres. In conclusion, maintenance of cellular high-energy nucleotide pool and high viability of asbestos exposed cells may contribute to the survival and malignant conversion of lung cells exposed to the fibres.
Insights
Poly(ADP)ribose polymerase (PARP) inhibition protected cells from hydrogen peroxide injury but not asbestos toxicity. Asbestos exposure maintained cell energy and viability, potentially aiding lung cell survival and malignant conversion.
Area of Science:
- Cell Biology
- Toxicology
- Biochemistry
Background:
- Poly(ADP)ribose polymerase (PARP) is implicated in cellular responses to DNA damage, apoptosis, and cell survival.
- Understanding PARP's role is crucial for assessing the toxicity of environmental agents like asbestos and hydrogen peroxide.
Purpose of the Study:
- To investigate the role of PARP in human pleural mesothelial (MeT-5A) and alveolar epithelial (A549) cells exposed to hydrogen peroxide (H(2)O(2)) or crocidolite asbestos fibers.
- To determine the effects of PARP inhibition using 3-aminobenzamide (ABA) on cell injury, DNA damage, and cellular energy levels.
Main Methods:
- Cells were exposed to varying concentrations of H(2)O(2) or asbestos fibers in the presence and absence of ABA.
- Cell injury was assessed using the microculture tetrazolium dye (XTT) assay.
- DNA single-strand breaks were evaluated using the single cell gel electrophoresis (Comet assay).
- Cellular high-energy nucleotide depletion was measured.
Main Results:
- Asbestos fibers caused less cell viability decrease, nucleotide depletion, and DNA strand breaks compared to H(2)O(2).
- PARP inhibition transiently protected cells against H(2)O(2)-induced injury but potentiated oxidant-related DNA damage.
- PARP inhibition had minimal impact on asbestos-induced toxicity, except at a specific fiber concentration in MeT-5A cells.
- Asbestos did not induce PARP cleavage or caspase 3 activation, indicating low apoptotic potential.
Conclusions:
- PARP inhibition offers protection against acute H(2)O(2) toxicity but not asbestos-related damage.
- Asbestos exposure preserves cellular energy and viability, potentially contributing to lung cell survival and malignant transformation.
- The findings highlight differential cellular responses to oxidative stress and fiber exposure mediated by PARP.