Related Experiment Videos
Rhein enhances the effect of adriamycin on mitochondrial respiration by increasing antibiotic-membrane interaction
A Floridi1, R Pulselli, F P Gentile
1Laboratory of Cell Metabolism and Pharmacokinetics, Regina Elena Institute for Cancer Research, Rome, Italy.
Abstract:
The effect of the combination of Adriamycin (ADM) with rhein (RH), an anti-inflammatory drug, on the electron flow through site III and IV of the respiratory chain of rat liver mitochondria was investigated. RH, even at high concentrations, does not inhibit either duroquinol (DHQ) oxidation or cytochrome oxidase activity both of which are decreased by ADM in a dose-dependent manner. The analysis of interaction, performed with the isobolar method, shows a strong synergistic effect that cannot be ascribed to increased permeability of the mitochondrial membranes brought about by RH. The mechanism by which RH potentiates the effect of ADM on DHQ oxidation and cytochrome oxidase activity is most likely to be changes induced in the physical status of the inner mitochondrial membrane such as to permit low ADM concentrations to bind and segregate enough cardiolipin to inhibit electron transport through complex III and IV.
Insights
The anti-inflammatory drug rhein (RH) enhances Adriamycin's (ADM) mitochondrial toxicity. This synergy, observed in rat liver mitochondria, suggests RH alters membrane properties, increasing ADM's inhibitory effect on electron transport.
Area of Science:
- Biochemistry
- Mitochondrial Physiology
- Pharmacology
Background:
- Adriamycin (ADM) is a chemotherapy drug known to inhibit mitochondrial electron transport.
- Rhein (RH) is an anti-inflammatory compound with potential effects on cellular processes.
- Mitochondrial dysfunction is implicated in various disease states and drug toxicities.
Purpose of the Study:
- To investigate the combined effect of Adriamycin (ADM) and rhein (RH) on mitochondrial electron transport.
- To determine if RH influences ADM's inhibitory action on specific respiratory chain complexes.
- To elucidate the mechanism underlying any observed synergistic or antagonistic interactions.
Main Methods:
- Isolated rat liver mitochondria were used to assess electron flow.
- Enzyme activities of duroquinol oxidation (site III) and cytochrome oxidase (site IV) were measured.
- The isobolar method was employed to analyze drug interactions.
Main Results:
- ADM inhibited duroquinol oxidation and cytochrome oxidase activity in a dose-dependent manner.
- RH alone did not inhibit these activities, even at high concentrations.
- A strong synergistic effect was observed between ADM and RH, not attributable to increased membrane permeability.
Conclusions:
- Rhein (RH) potentiates Adriamycin's (ADM) inhibitory effects on mitochondrial electron transport at sites III and IV.
- The synergy likely results from RH-induced alterations in the inner mitochondrial membrane's physical state.
- These changes may facilitate ADM binding to cardiolipin, leading to enhanced inhibition of electron transport.