Bioreduction of Idarubicin and Formation of ROS Responsible for DNA Cleavage by NADPH-Cytochrome P450 Reductase and its Potential Role in the Antitumor Effect
Bibliographic record
Abstract
PURPOSE: Idarubicin is a clinically effective synthetic anthracycline analog used in the treatment of several human neoplasms. Anthracyclines have the potential to undergo bioactivation by flavoenzymes to free radicals and thus exert their cytotoxic actions. In this study, our main objective was to investigate the possible involvement of NADPH-cytochrome P450 reductase in the bioreductive activation of idarubicin to DNA-damaging species. METHODS: A pBR322 plasmid DNA damage assay was used as a sensitive method for detecting strand breaks in DNA exposed to idarubicin in the presence of P450 reductase and cofactor NADPH under various incubation conditions. In addition, the rates of idarubicin reduction by P450 reductases purified from phenobarbital-treated rabbit liver, beef liver and sheep lung microsomes were determined by measuring NADPH oxidation at 340 nm. RESULTS: The plasmid DNA experiments demonstrated that idarubicin could undergo bioreduction by P450 reductase with the resulting formation of DNA strand breaks. The antioxidant enzymes SOD and catalase, and hydroxyl radical scavengers, DMSO and thiourea, afforded significant levels of protection against idarubicin-induced DNA strand breaks. These findings suggested that DNA damage by idarubicin occurs through a mechanism which involves its redox cycling with P450 reductase to generate reactive oxygen species (ROS). The extent of DNA damage by idarubicin was found to increase with increasing concentrations of drug or enzyme as well as with increasing incubation time. The capacity of idarubicin to induce DNA damage under above incubation conditions was compared with that of a model compound, mitomycin C. Finally, enzyme assays carried out with purified P450 reductases revealed that idarubicin exhibited about two-fold higher rate of reduction than mitomycin C. CONCLUSION: Our findings implicated bioreduction of idarubicin by P450 reductase and subsequent redox cycling under aerobic conditions as being one mode of idarubicin action potentially contributing to its antitumor effect.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".