Adriamycin-mediated inhibition of creatine phosphokinase binding to heart mitochondrial membrane

Mitochondrial creatine kinase interaction with phospholipid vesicles

The characteristics of the interaction of mitochondrial creatine kinase (mt-CK) with phospholipid vesicles are determined. The presence of negatively charged phospholipids is required to obtain a significant binding of mt-CK. The interaction seems to be largely of an electrostatic nature: it increases with increasing amounts of anionic phospholipid in liposomes and decreases when the ionic strength increases or when the pH of the medium is higher than the pI of mt-CK. We have compared the effects of various effectors used to solubilize mt-CK from the mitochondrial membrane on the binding of mt-CK to liposomes: the nucleotide substrates ATP and ADP have no influence, parahydroxymercuribenzoate, a negatively charged organomercurial compound, partially decreases mt-CK binding; and the anticancer agent adriamycin efficiently prevents mt-CK binding. As monitored by the increase in absorbance, mt-CK causes vesicle aggregation. A differential scanning calorimetry study, using dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol vesicles, shows that mt-CK produces a decrease in the enthalpy variation without any change in the position of the calorimetric peak maximum. This suggests a partial disorganization of the phospholipid bilayer upon interaction with mt-CK.

Detection of adriamycin-induced cardiotoxicity in cultured heart cells with technetium 99m-SESTAMIBI

Adriamycin, a broad-spectrum cytotoxic agent useful in cancer chemotherapy, is limited by a dose-dependent cardiomyopathy mediated in part by disruption of mitochondrial energetics. Hexakis(2-methoxyisobutyl isonitrile)technetium(I) (99mTc-SESTAMIBI) is a gamma-emitting radiopharmaceutical with myocellular accumulation properties dependent on mitochondrial membrane potential. To test the hypothesis that 99mTc-SESTAMIBI could monitor Adriamycin-induced alterations in cardiac energetics, cultured chick heart cells were treated with Adriamycin and 99mTc-SESTAMIBI tracer kinetics were determined. Concentration- and time-dependent depression of 99mTc-SESTAMIBI accumulation was evident within 60 min of treatment. The apparent Ki for acute Adriamycin inhibition of tracer accumulation was 82 microM. After 24 h of treatment, Adriamycin concentrations as low as 0.1 microM demonstrated detectable inhibitory effects. The apparent Ki for this subchronic Adriamycin inhibition of 99mTc-SESTAMIBI accumulation was 18 microM. Subchronic concentration-dependent increases in adriamycin-induced myocellular injury as reflected by lactate dehydrogenase (LDH) release correlated inversely with decreases in 99mTc-SESTAMIBI accumulation. These data further support a contribution from altered mitochondrial energetics to Adriamycin-induced injury and establish a pharmacological foundation for pursuing the possibility of noninvasive imaging of chronic Adriamycin cardiotoxicity in cancer patients using 99mTc-SESTAMIBI.

Hypoxia as a risk factor for doxorubicin-induced cardiotoxicity: a NMR evaluation

Previous studies suggested that one possible mechanism of doxorubicin (DXR)-induced cardiomyopathy involves the depletion of high-energy phosphate stores. In this study, we used 31P nuclear magnetic resonance to assess the high-energy phosphate content in Langendorff perfused rat hearts. Hearts were perfused in normoxic conditions (spontaneous flow) or in partially hypoxic conditions obtained by perfusing at 50% of the spontaneous flow. DXR was used at the subtoxic conditions of 50 mg/l for 15 min and at the cardiotoxic concentration of 100 mg/l for 60 min. Left ventricular pressure (dP/dt), heart rate, myocardial ATP and PCr levels and PCr/ATP ratio were measured. We found that, in normoxic conditions, DXR (50 mg/l, 15 min) does not impair cellular high-energy phosphate metabolism. However, in mild hypoxic conditions, DXR induces a significant decrease in PCr/ATP ratio, due to a decrease in PCr and to a simultaneous increase in ATP. Similar results are obtained after 60 min perfusion with the cardiotoxic dose of DXR. This study suggests that hypoxia may represent a risk factor for the development of DXR-induced acute cardiotoxicity.

Identification and primary structure of the cardiolipin-binding domain of mitochondrial creatine kinase

It was recently shown that the mitochondrial isozyme of heart creatine kinase binds to cardiolipin on the outer half of the inner membrane [Müller, M., et al. (1985) J. Biol. Chem. 260, 3839-3843]. The enzyme has now been extracted and purified to homogeneity from rat heart mitochondria, and cleaved with CNBr. The fragments have been separated on an FPLC system using a Mono Q HR 5/5 column. Only one of these binds to cardiolipin-containing liposomes and has thus been identified as the cardiolipin-binding domain of the enzyme. Its amino acid sequence has been determined. The fragment contains 25 amino acids and corresponds to the N-terminal region of the protein. The binding of the fragment of cardiolipin-containing liposomes was inhibited by adriamycin. Another and larger CNBr fragment could be specifically labelled with periodate-oxidized (di-aldehyde) ATP and has thus been identified as the ATP-binding domain. Chemical modification of the basic amino acids Lys and Arg of the enzyme abolished its binding to cardiolipin.

Effects of adriamycin on respiratory chain activities in mitochondria from rat liver, rat heart and bovine heart. Evidence for a preferential inhibition of complex III and IV

The inhibition of respiratory chain activities in rat liver, rat heart and bovine heart mitochondria by the anthracycline antibiotic adriamycin was measured in order to determine the adriamycin-sensitive sites. It appeared that complex III and IV are efficiently affected such that their activities were reduced to 50% of control values at 175 +/- 25 microM adriamycin. Complex I displayed a minor sensitivity to the drug. Of the complex-I-related activities tested, only duroquinone oxidation appeared sensitive (50% inhibition at approx. 450 microM adriamycin). Electron-transfer activities catalyzed by complex II remained essentially unaltered up to high drug concentrations. Of the activities measured for this complex, only duroquinone oxidation was significantly affected. However, the adriamycin concentration required to reduce this activity to 50% exceeded 1 mM. Mitochondria isolated from rat liver, rat heart and bovine heart behaved essentially identical in their response to adriamycin. These data support the conclusion that, in these three mitochondrial systems, the major drug-sensitive sites lie in complex III and IV. Cytochrome c oxidase and succinate oxidase activity in whole mitochondria exhibited a similar sensitivity towards adriamycin, as inner membrane ghosts, suggesting that the drug has direct access to its inner membrane target sites irrespective of the presence of the outer membrane. By measuring NADH and succinate oxidase activities in the presence of exogenously added cytochrome c, it appeared that adriamycin was less inhibitory under these conditions. This suggests that adriamycin competes with cytochrome c for binding to the same site on the inner membrane, presumably cardiolipin.

Effects of the anti-cancer drug adriamycin on the energy metabolism of rat heart as measured by in vivo 31P-NMR and implications for adriamycin-induced cardiotoxicity

In vivo 31P-NMR was used to measure the effects of the anti-tumor drug adriamycin on the energy metabolism of rat heart. The exclusive acquisition of NMR signal from cardiac muscle was assured by positioning a solenoidal radio-frequency NMR coil around the heart. Appropriate control experiments verified that 31P-NMR spectra solely originated from this organ. Acute effects occurring shortly after adriamycin administration are expressed in 31P spectra as a dose-dependent decline in the cardiac levels of phosphocreatine, after which stabilization at a new steady-state level occurs. These acute effects of a single dose are complete in 30-60 min and no significant further changes take place within 150 min after drug introduction. Longer-term effects of single high doses and of multiple lower doses were measured up to a week after the initiation of treatment. It seemed that at a total dose of 20 mg/kg, drug-induced interference with cardiac energy metabolism was more pronounced than at the same dose in the acute phase. These 31P-NMR data demonstrate that adriamycin treatment is accompanied by a decrease of the cardiac phosphocreatine/ATP ratio which might be an expression of the well-established cardiotoxicity of the drug.

Association of chicken mitochondrial creatine kinase with the inner mitochondrial membrane

The stoichiometry and dissociation constant for the binding of homogeneous chicken heart mitochondrial creatine kinase (MiMi-CK) to mitoplasts was examined under a variety of conditions. Salts and substrates release MiMi-CK from mitoplasts in a manner that suggests an ionic interaction. The binding of MiMi-CK to mitoplasts is competitively inhibited by Adriamycin, suggesting that they compete for the same binding site. Fluorescence measurements also show that Adriamycin binds to MiMi-CK so that the effect of Adriamycin on the binding of MiMi-CK to mitoplasts is not simple. Titrating mitoplasts with homogeneous MiMi-CK at different pH values shows a pH-dependent equilibrium involving a group(s) on either the membrane or the enzyme with a pKa = 6. Extrapolating these titrations to infinite MiMi-CK concentration gives 14.6 IU bound/nmol cytochrome aa3 corresponding to 1.12 mol MiMi-CK/mol cytochrome aa3. Chicken heart mitochondria contain, after isolation, 2.86 +/- 0.42 IU/nmol cytochrome aa3. Titrating respiring mitoplasts with carboxyatractyloside gives at saturation 3.3 mol ADP/ATP translocase/mol cytochrome aa3. Therefore, chicken heart mitoplasts can maximally bind about 1 mol of MiMi-CK per 3 mol translocase; in normal chicken heart mitochondria about 1 mol of MiMi-CK is present per 13 mol translocase.

Doxorubicin binds in a cooperative manner to myocardial cells. Two binding sites

Experimental evidence indicates that the anthracycline antibiotic doxorubicin (adriamycin) localizes mainly in cell nuclei of cardiac cells and has a high affinity to several cellular constituents in addition to DNA. In the present study the cellular kinetics of doxorubicin in cultured rat myocardial cells were determined by measuring its uptake, its binding pattern over a concentration range of 0.1 mM to 80 microM, and the cellular release by means of [14-14C]doxorubicin. The binding kinetics of doxorubicin were compared with the doxorubicin-induced inhibition of [methyl-3H]thymidine incorporation into DNA. It is demonstrated that at micromolar concentrations doxorubicin is readily taken up by myocardial cells and that myocardial cells have the ability to bind doxorubicin at two specific binding sites and that a noncooperative high-affinity/low-capacity type and a positive cooperative type of binding are involved, as indicated by the positive slope in the initial region of the binding isotherm (Scatchard plot). A dose-dependent inhibition of [methyl-3H]thymidine incorporation into DNA is demonstrated. It is suggested that this is associated with the positive cooperative binding of doxorubicin. The cellular release of doxorubicin appeared to be biphasic, with estimated half-lives of about 5-6 h for the initial phase and 50-60 h for the terminal phase. The results of this study indicate that doxorubicin preferably binds to sites within myocardial cells and that the positive cooperative binding pattern is due to DNA as one of the binding sites. A relationship between the noncooperative high-affinity/low capacity binding and the pharmacological activity has yet to be determined.

Cytofluorescence detection of adriamycin-mitochondria interactions in isolated, perfused rat heart

The major side-effect of the anthracycline anti-tumor drug adriamycin is a specific, dose-dependent cardiotoxicity. Impairment of mitochondrial function has been suggested to play an important role in this toxicity. The present study addresses the question as to whether direct drug-mitochondria interactions occur in the isolated, perfused rat heart. To this aim, cytofluorescence microscopy experiments were performed on thin cryosections. To demonstrate the applicability of this technique it is shown that adriamycin bound to isolated rat liver and heart mitochondria can be visualized through its characteristic fluorescence. Longitudinal sections from heart tissue perfused with 50 microM adriamycin display two distinct cellular sites of drug accumulation, i.e., nuclei which exhibit very bright fluorescence and, in addition, mitochondria which become significantly labeled with the drug. The mitochondrial localization of adriamycin is confirmed independently by quantification of the drug content of the mitochondrial fraction after cell fractionation. These results are discussed in the light of the potential role of adriamycin-nuclei versus adriamycin-mitochondria interactions in the deterioration of heart performance.

Effects of intravenous infusion of doxorubicin on blood chemistry, blood pressure and heart rate in rabbits

The effects of a 1 h continuous infusion of doxorubicin (12.5 mg kg-1, 200 mg M-2) on blood chemistry was examined in rabbits over a 6-h period. Plasma glucose levels remained unchanged while insulin levels were significantly decreased to 39, 45 and 61% of the zero time value (12.8 +/- 2.9 ng ml-1) at 30, 60 and 120 min, respectively, after starting the drug infusion. Plasma cortisol levels were increased to 141, 140 and 131% of the initial zero time value (12.3 +/- 2.2 ng ml-1) at 120, 240 and 360 min, respectively. Doxorubicin had no effect on plasma electrolytes, osmolality and urea nitrogen but significantly increased plasma creatinine over the corresponding control value (2.2 +/- 0.8 micrograms ml-1 to 4.9 +/- 0.7 micrograms ml-1) at 120 min and the level remained elevated for the remaining period of the study. Systolic and diastolic pressure, and heart rate were also depressed at 240 and 360 min. The data collected in the present study indicate that the doxorubicin infusion might have a direct effect on beta cells in the pancreas as well as muscle tissue. Changes in cortisol, blood pressure and heart rate appear to be secondary to other effects produced by doxorubicin.

Enhancement of reactive oxygen-dependent mitochondrial membrane lipid peroxidation by the anticancer drug adriamycin

Mitochondrial degeneration is a consistently prominent morphological alteration associated with adriamycin toxicity which may be the consequence of adriamycin-enhanced peroxidative damage to unsaturated mitochondrial membrane lipids. Using isolated rat liver mitochondria as an in vitro model system to study the effects of the anticancer drug adriamycin on lipid peroxidation, we found that NADH-dependent mitochondrial peroxidation--measured by the 2-thiobarbituric acid method--was stimulated by adriamycin as much as 4-fold. Marker enzyme analysis indicated that the mitochondria were substantially free of contaminating microsomes (less than 5%). Lipid peroxidation in mitochondria incubated in KCl-Tris-HCl buffer (pH 7.4) under an oxygen atmosphere was optimal at 1-2 mg of mitochondrial protein/ml and with NADH at 2.5 mM. Malonaldehyde production was linear with time to beyond 60 min, and the maximum enhancement of peroxidation was observed with adriamycin at 50-100 microM. Interestingly, in contrast to its stimulatory effect on NADH-supported mitochondrial peroxidation, adriamycin markedly diminished ascorbate-promoted lipid peroxidation in mitochondria. Superoxide dismutase, catalase, 1,3-dimethylurea, reduced glutathione, alpha-tocopherol and EDTA added to incubation mixtures inhibited endogenous and adriamycin-augmented NADH-dependent peroxidation of mitochondrial lipids, indicating that multiple species of reactive oxygen (superoxide anion radical, hydrogen peroxide and hydroxyl radical) and possibly trace amounts of endogenous ferric iron participated in the peroxidation reactions. In submitochondrial particles freed of endogenous defenses against oxyradicals, lipid peroxidation was increased 7-fold by adriamycin. These observations suggest that some of the effects of adriamycin on mitochondrial morphology and biochemical function may be mediated by adriamycin-enhanced reactive oxygen-dependent mitochondrial lipid peroxidation.