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Studies on the mechanism of chemosensitization by misonidazole in vitro
Abstract:
Misonidazole (MISO) depletes intracellular glutathione and is more toxic in glutathione depleted cells. The depletion is time, temperature, drug concentration and cell line dependent. The role of glutathione depletion in the chemosensitization to alkylating agents obtained after hypoxic pretreatments with MISO was investigated using diethylmaleate (DEM), a thiol-removing agent with specificity for glutathione, to simulate the effects of MISO on intracellular glutathione levels. Melphalan cytotoxicity and binding to macromolecules were measured after pretreatments with MISO or DEM in vitro. From these studies we found that glutathione depletion could account for only a part of the chemosensitization to melphalan and that this component of sensitization was quantitatively related to an increased rate of melphalan binding. Assessments of DNA damage by the alkaline elution assay suggest that DNA strand breaks and DNA crosslinks are enhanced by sublethal pretreatments with MISO.
Insights
Misonidazole (MISO) depletes glutathione, enhancing melphalan
Area of Science:
- Oncology
- Pharmacology
- Biochemistry
Background:
- Misonidazole (MISO) depletes intracellular glutathione.
- Glutathione depletion increases cellular sensitivity to MISO.
- MISO pretreatment can sensitize cells to alkylating agents.
Purpose of the Study:
- To investigate the role of glutathione depletion in MISO-induced chemosensitization to melphalan.
- To simulate MISO's effects using diethylmaleate (DEM), a glutathione-depleting agent.
- To assess the impact of MISO on melphalan binding and DNA damage.
Main Methods:
- In vitro chemosensitization studies using MISO and DEM.
- Measurement of melphalan cytotoxicity and macromolecular binding.
- Alkaline elution assay to assess DNA damage (strand breaks and crosslinks).
Main Results:
- Glutathione depletion accounted for only a portion of melphalan chemosensitization.
- The sensitization component related to glutathione depletion correlated with increased melphalan binding.
- Sublethal MISO pretreatment enhanced DNA strand breaks and crosslinks.
Conclusions:
- Glutathione depletion is partially responsible for MISO's chemosensitization effect.
- MISO enhances melphalan's efficacy through mechanisms beyond glutathione depletion, including increased DNA damage.
- MISO shows potential as a chemosensitizer in cancer therapy by increasing DNA damage.