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Formation of DNA-protein cross-links in mammalian cells by levuglandin E2
K K Murthi1, L R Friedman, N L Oleinick
1Department of Chemistry, Case Western Reserve University, Cleveland, Ohio 44106.
Abstract:
Levuglandin E2 (LGE2), a rearrangement product derived from the prostaglandin endoperoxide, PGH2, causes repair-resistant DNA-protein cross-links and cell death (LD50 = 230 nM) in V79 Chinese hamster lung fibroblasts. The half-life for sequestration of LGE2 by covalent binding to cellular nucleophiles is at least an hour for 10 microM LG. This suggests that the in vivo production and distribution of free LGs should be measurable on this time scale. Following removal of the LGE2 and the return of the cultures to normal growth medium, additional DNA-protein cross-links continued to form over the ensuing 6-24 h. The results suggest that LG adducts to DNA or protein are not repaired, but react further at sites on protein or DNA in close proximity to the initial adducts, forming cross-links in a slow phase of the process.
Insights
Levuglandin E2 (LGE2) forms DNA-protein cross-links and causes cell death in V79 fibroblasts. These adducts are not repaired and lead to further cross-linking over time.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Levuglandin E2 (LGE2) is a rearrangement product of prostaglandin endoperoxide (PGH2).
- LGE2 is known to induce DNA-protein cross-links and cytotoxicity.
Purpose of the Study:
- To investigate the mechanism of DNA-protein cross-link formation by LGE2.
- To determine the repairability and kinetics of LGE2-induced adducts in cellular systems.
Main Methods:
- Exposure of V79 Chinese hamster lung fibroblasts to varying concentrations of LGE2.
- Measurement of cell viability and DNA-protein cross-link formation.
- Assessment of adduct formation and cross-linking kinetics post-LGE2 removal.
Main Results:
- LGE2 caused significant DNA-protein cross-links and cell death with an LD50 of 230 nM.
- The sequestration half-life of LGE2 by cellular nucleophiles was at least one hour.
- Post-exposure, DNA-protein cross-links continued to form for 6-24 hours, indicating a slow secondary cross-linking phase.
Conclusions:
- LGE2-induced DNA-protein adducts are persistent and not repaired by cellular mechanisms.
- A delayed, slow phase of cross-linking occurs, suggesting further reactions at or near initial adduct sites.
- These findings highlight the potential for long-term genotoxic effects of LGE2 in vivo.