Georges Pollakis

Mitochondrial membrane modifications induced by adriamycin-mediated electron transport.

Adriamycin (ADM) was found to have a two-step mode of action on the cardiac mitochondrial membrane. (1) An interaction with cardiolipin (CL) resulted in the formation of an ADM-CL complex able to transfer electrons from NADH to cytochrome c (cyt.c) as well as coenzyme Q (CoQ). This complex formation stimulates an increased activity of NADH-CoQ oxidoreductase (complex I) and CoQ-cyt.c oxidoreductase (complex III). (2) Transfer of electrons through ADM resulted in the formation of a very strong complex between ADM and CL. This new complex is different and much stronger than the already known ADM-CL complex.

Role of the quinone structure in the mitochondrial damage induced by antitumor anthracyclines. Comparison of adriamycin and 5-iminodaunorubicin.

Adriamycin cardiotoxicity has been correlated with a disturbance of heart mitochondrial functions. Here, 5‐iminodaunorubicin was compared with adriamycin for its capability to interfere in the mitochondrial electron transport with subsequent membrane damaging. The results suggest that minor chemical modifications of the anthraquinone moiety of anthracycline glycoside drugs should be a promising way to decrease mitochondrial membrane damage induced by this class of antitumor drugs.

A new class of free radical scavengers reducing adriamycin mitochondrial toxicity.

Beef heart mitochondria were incubated with ADM and NADH. An adriamycin semiquinone radical was detected using ESR spectroscopy. The semiquinone radical production rate is decreased upon addition of a scavenger (AD 20) in the reaction medium. NMRI mice were treated with AD 20 (70 mg/kg, i.p.) 15 min prior ADM injection (20 mg/kg, i.p.) or with ADM alone. Heart mitochondria were isolated 48 hr later. The enzymatic activities of complex I-III and complex IV of the mitochondrial respiratory chain were strongly depressed in animals receiving ADM alone, whereas these activities were almost completely restored in animals receiving AD 20 and ADM. Fluorescence depolarization measurements indicated that only mice treated with ADM alone presented a decreased fluidity of their cardiac mitochondrial membrane.

Damages of the mitochondrial membrane in Adriamycin treated mice.

OF1 Swiss male and female mice received adriamycin (ADM) i.p. in increasing doses. Animals were killed after 2 or 4 days. Hearts were removed and mitochondria were isolated. ADM induced an inactivation of the respiratory enzymes closely related to an increase of the mitochondrial membrane viscosity and of the lipid peroxidation. Two ADM derivatives studied similarly did not produce these effects.

Electronic properties of anthraquinone drugs in the inner mitochondrial membrane

Adriamycin was shown to affect electron transport in the inner mitochondrial membrane in two ways. In a first step, adriamycin inhibits the cytochrome c oxidase activity. In a second step, adriamycin catalyzes the deviation of the electron flow between NADH and cytochrome c towards oxygen. Most likely, highly reactive oxygen species induce polymerization of the membrane components.

Adriamycin-Mitochondrial Membrane Interactions and Cardiotoxicity

Adriamycin (ADM) is one of the most effective agents against leukemia and solid tumors. Its mode of interaction with its nuclear target has been extensively reviewed (Berman and Young 1981) and is assumed to be responsible for the antimitotic activity. Both X-ray measurements and conformational analysis indicate that the planar moiety of adriamycin intercalates between the base pairs, whereas the sugar moiety fits into the large DNA groove. Adriamycin displays also toxic side effects against a large variety of cells. Its cardiotoxicity is, however, very specific and places a limit on the total dose that may be given; the effect is cumulative over several months. Such a dose-limiting cardiotoxicity is not observed with the administration of other anticancer drugs. Interestingly, in a series of related anthracycline glycoside drugs, this cardiac toxicity can be dissociated from the antitumor activity suggesting a distinct mode of action (Casazza 1979). Much evidence suggests that the mitochondrial membrane could be the target responsible for the cardiac toxicity; indeed, the development of cardiac failure induced by adriamycin is characterized by a good correlation with the impairment of mitochondrial functions such as O2 consumption and ATP synthesis. Rhythmic contractions characteristic of myocardiac cells in culture cease with adriamycin treatment concomitant with a significant decrease of ATP and phosphocreatine concentrations.

Free radicals formation and membrane damages induced by adriamycin in mitochondria: A study in vivo and in vitro

Adriamicin (ADM) is one of the most effective anthracycline glycoside antibiotic in the treatment of several types of cancer. Its clinical use is however limited by a specific cardiotoxicity. Deviation of electrons from NADPH supplemented cytochrome P-450 to the anthracycline results in the formation of a semiquinone radical which react with O2 to form toxic oxygen species (O2-, OH). These reactions were suggested to be involved in the cardiac toxicity process of ADM till the recent finding that cardiac microsomes do not participate to such reactions (Nohl & Jordan, 1983). Using the spin trapper DMPO combined with a flow technique, we were able to demonstrate that beef heart mitochondria, submitochondrial particles and complex I containing proteoliposomes catalyse the formation of O2- and OH species when incubated in presence of ADM and NADH. The semiquinone radical was also observed by ESR with a characteristic g value of 2.0024 and a line width of 0.4 mT. Interestingly, the 5-iminodaunorubicin analog did not induce the formation of oxygen radical species in good correlation with its weak cardiac toxicity. Membrane damages were further studied on heart mitochondria extracted from ADM-treated mice. A strong rigidifi-cation of the mitochondrial membrane was observed using fluorescence depolarization of a probe (DPH) embedded in the membrane. The rigidification can be considered as resulting from polymerization of peroxidized lipids in presence of O2- and OH species. No rigidification was observed on mitochondrial memmembrane extracted from 5-iminodaunorubicin-tretead mice in good agreement with our ESR results.