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Inhibition of doxorubicin-induced apoptosis in vivo by 2-deoxy-D-glucose
1CRC Department of Epithelial Biology, Paterson Institute of Cancer Research, Christie Hospital National Health Service Trust, Manchester, United Kingdom.
Abstract:
Previous studies have shown that DNA cleavage by mammalian topoisomerase II is ATP dependent and can be inhibited by metabolic inhibitors. Furthermore, it has been shown that metabolic inhibitors also have a cytoprotective effect in vitro against topoisomerase II-targeting antitumor drugs. However, the nature of the ATP-dependent process is not known. We have previously shown that doxorubicin induces apoptosis (programmed cell death) in the murine small intestine which can be inhibited by the protein synthesis inhibitor cycloheximide. In the present study, we have demonstrated that 2-deoxy-D-glucose reduces the incidence of doxorubicin-induced apoptosis in vivo if administered within 45 min of the doxorubicin. Maximum reduction was observed at 2 h after treatment (approximately 66%); however, significant reduction was still observable at 9 h after treatment (approximately 33%). Significant positive correlation was observed between protein synthesis inhibition and apoptosis inhibition. Other possible mechanisms of action of the inhibitor do not appear to be important in cytoprotection. The inhibitor did not reduce the uptake of doxorubicin into the intestinal epithelium; however, it caused a significant increase in retention of the drug. The kinetics of inhibition suggest that alteration of cell cycle kinetics, inhibition of formation of doxorubicin-topoisomerase II complex or induction of glucose-regulated proteins are not significant factors in cytoprotection. These studies indicate that at least in the mouse small intestinal epithelium, the ATP-dependent process in cell killing by doxorubicin may involve protein synthesis.
Insights
Metabolic inhibitors like 2-deoxy-D-glucose can reduce doxorubicin-induced apoptosis in mouse intestines by inhibiting protein synthesis. This suggests ATP-dependent cell death by doxorubicin involves protein synthesis in the intestinal epithelium.
Area of Science:
- Molecular Biology
- Pharmacology
- Cell Biology
Background:
- Mammalian topoisomerase II (TOP2) DNA cleavage is ATP-dependent and inhibitable by metabolic agents.
- Metabolic inhibitors demonstrate in vitro cytoprotective effects against TOP2-targeting anticancer drugs.
- The precise nature of the ATP-dependent process in TOP2-mediated DNA damage remains unclear.
Purpose of the Study:
- To investigate the role of protein synthesis in doxorubicin-induced apoptosis in the murine small intestine.
- To determine if 2-deoxy-D-glucose, a metabolic inhibitor, can prevent doxorubicin-induced apoptosis in vivo.
- To elucidate the mechanism by which metabolic inhibitors confer cytoprotection against doxorubicin.
Main Methods:
- Administration of 2-deoxy-D-glucose to mice at varying times relative to doxorubicin treatment.
- Quantification of doxorubicin-induced apoptosis in the intestinal epithelium.
- Measurement of doxorubicin uptake and retention in intestinal cells.
- Correlation analysis between protein synthesis inhibition and apoptosis inhibition.
Main Results:
- 2-deoxy-D-glucose significantly reduced doxorubicin-induced apoptosis in vivo, with maximum effect observed 2 hours post-treatment.
- A strong positive correlation was found between the degree of protein synthesis inhibition and apoptosis inhibition.
- The cytoprotective effect was not attributed to reduced doxorubicin uptake but rather increased drug retention.
- Mechanisms like cell cycle alteration or direct inhibition of doxorubicin-TOP2 complex formation were ruled out.
Conclusions:
- Protein synthesis is a key ATP-dependent component in doxorubicin-induced cell killing within the mouse small intestinal epithelium.
- 2-deoxy-D-glucose exerts cytoprotection by inhibiting protein synthesis, thereby mitigating doxorubicin's apoptotic effects.
- These findings highlight a potential therapeutic strategy involving metabolic modulation to reduce chemotherapy-induced intestinal toxicity.