Anthracycline cardiotoxicity

Effects of doxorubicin on myocardial expression of apolipoprotein-B

OBJECTIVE

Doxorubicin (DOX) is an effective antitumour agent against a variety of human malignancies but is associated with deleterious side effects, including myocardial damage and heart failure. Myocardial apoB-containing lipoprotein (apoB) is upregulated post myocardial infarction and has been shown to be cardioprotective in this setting by unloading excessive lipid. The aim of this study was to investigate whether apoB expression is increased also in DOX-induced heart failure and whether apoB overexpression protects the heart in DOX-induced myocardial injury.

DESIGN

Cardiac function and energy metabolism was studied in mice and rats 24 hours after intraperitoneally administered DOX.

RESULTS

We found that the content of apoB was decreased in rat myocardium 24 hours after DOX injection. In contrast, apoB content was increased in the infarcted myocardium of rats 24 hours post ischemia-reperfusion. Moreover, transgenic mice overexpressing apoB had better cardiac function and lower intracellular lipid accumulation compared to wild type mice 24 hours post DOX.

CONCLUSIONS

Our findings indicate that depression of the myocardial apoB system may contribute to DOX-induced cardiac injury and that overexpression of apoB is protective, not only in ischemically damaged myocardium, but also in DOX-induced heart failure.

Impact of the basic amine on the biological activity and intracellular distribution of an aza-anthrapyrazole: BBR 3422

The anthrapyrazoles have entered clinical trials and show significant activity against breast cancer. However, these drugs are cardiotoxic and ineffective in multidrug-resistant (MDR) tumor cells. We have reported previously on the synthesis and antitumor characteristics of the 9-aza-anthrapyrazoles and their lack of cardiotoxicity; unfortunately, the leading candidates are cross-resistant in MDR-expressing cells. The results also indicated that the side arm structures of 9-aza-anthrapyrazole play a critical role in determining the drug resistance in MDR-expressing cells-only compounds that have a tertiary amine on both side arms are not cross-resistant. To further elucidate the biochemical and pharmacological impact of the side arm structures, one of the 9-aza-anthrapyrazole compounds, BBR 3422 [2-(2-aminoethyl)-5-(2-methylaminoethyl)indazolo[4,3-g,h]isoquinoline-6(2H)-one], was selected to be photolabeled with N-hydroxysuccinimidyl-4-azidosalicylic acid (NHS-ASA). In comparison to the parental compound, the photolabeled BBR 3422 was not as cytotoxic or DNA active, but it competed better than the parental compound against azidopine on P-glycoprotein labeling. In addition, confocal microscopic studies showed that BBR 3422 was clustered mainly in the cell nucleus, but its photolabeled analogue was located in the cytoplasm of the human breast cancer cell line MCF-7. Only a trace amount of both compounds was detected in the doxorubicin-derived resistant cell line MCF-7/ADR. The treatment of MCF-7/ADR cells with verapamil increased the intracellular amounts of both compounds.

Apoptosis in adriamycin cardiomyopathy and its modulation by probucol

The dose-dependent cardiomyopathy and heart failure due to adriamycin have been shown to be due to increased oxidative stress and loss of myocytes. We examined the incidence of myocardial apoptosis as well as changes in the expression of apoptotic regulatory gene products in an established animal model of adriamycin cardiomyopathy. Rats were treated with adriamycin (cumulative dose, 15 mg/kg), and the hearts were examined for apoptosis as well as expression of Bax, caspase 3, and Bcl-2 at 0, 4, 10, 16, and 21 days after the treatment. A significant increase in the incidence of apoptosis was seen at 4 days, followed by a decline at 10 and 16 days of posttreatment. At 21 days, the number of apoptotic cells increased again and included cells of the conducting system. Expression of Bax corresponded to these biphasic changes, whereas the converse was true for the expression of Bcl-2. The latter peaked at 10 days followed by a decline at 16 and 21 days. The Bax/Bcl-2 ratio also correlated with the incidence of apoptosis. Expression of caspase 3 correlated with increased apoptosis, but only at early time points. Probucol (cumulative dose, 120 mg/kg), a known antioxidant as well as promoter of endogenous antioxidants, significantly reduced the incidence of apoptosis as well as expression of Bax. Adriamycin-induced hemodynamic changes were also prevented by probucol. These data suggest that adriamycin-induced apoptosis is mediated by oxidative stress and may play a role in the development of heart failure.

Apoptosis in isolated adult cardiomyocytes exposed to adriamycin

Adriamycin (doxorubicin) is a highly potent antineoplastic agent, but its use is limited by the risk of developing cardiomyopathy and congestive heart failure. Available evidence suggests that adriamycin-induced congestive heart failure is mediated by oxidative stress. We examined the possibility of adriamycin-induced apoptosis in isolated adult rat cardiomyocytes and its inhibition by trolox, a water-soluble antioxidant. Cardiomyocytes isolated from rat hearts were exposed to 20 microM adriamycin for 1 h and examined at different post-treatment durations (0-23 h). Adriamycin caused a significant decrease in rod-shaped cells and an increase in round cells. Both Hoechst 33258 staining and TUNEL assay revealed a significantly increased number of apoptotic myocytes and nucleosomal fragmentation upon exposure to adriamycin. In agarose gel electrophoresis, DNA laddering was found to be more intense in adriamycin-exposed myocytes. A bright smear at the leading edge of the gels suggested indiscriminate fragmentation of DNA and myocyte necrosis by adriamycin. Both types of DNA degradations due to adriamycin were significantly reduced by trolox. We suggest that adriamycin-induced cell death involves both apoptosis and necrosis and these may be mediated by oxidative stress.

Etiology of sarcoplasmic reticulum calcium release channel lesions in doxorubicin-induced cardiomyopathy

Alterations in the native function of the ryanodine-sensitive Ca2+ release channel complex of sarcoplasmic reticulum (SR) isolated from rat cardiac ventricles during acute and chronic exposure to doxorubicin are examined. Compared to control SR, actively loaded SR from animals exposed to a single intravenous dose of doxorubicin exhibit faster rates of doxorubicin-induced Ca2+ release and the occupancy of [3H]ryanodine is significantly enhanced with subsequent exposure of SR membranes to doxorubicin in vitro. One week after acute exposure to doxorubicin in vitro, the EC50 for activation of the binding of [3H]ryanodine by Ca2+ is not significantly different from control SR. However, the persistence of doxorubicin-sensitized SR channels appears to be latent since repeated exposure to doxorubicin in vitro significantly enhances receptor occupancy in SR obtained from the treated rats compared to control SR. Ryanodine receptors from rats chronically exposed to doxorubicin consistently exhibit a higher sensitivity to activation Ca2+ which persists at least 4 weeks following the last injection of drug. Chronic exposure produces a concomitant reduction in the capacity of [3H]ryanodine binding sites. The marked decrease in receptor density observed with SR from doxorubicin-treated rats coincides with significant reduction in body weight, suggesting a possible influence of nutrition. However, sodium dodecyl sulfate polyacrylamide electrophoresis indicates no significant loss of the high molecular weight subunit of the ryanodine receptor, suggesting that loss of [3H]ryanodine-binding capacity may be the result of progressive and permanent channel desensitization. Consistent with desensitized receptors, membrane vesicles prepared from rats chronically exposed to doxorubicin take up significantly more Ca2+ and exhibit significantly reduced rates of doxorubicin or Ca2+/ryanodine induced Ca2+ release. The data demonstrates (i) doxorubicin inflicts cumulative SR channel lesions in vivo, (ii) a persistent sensitization of the SR channel to activation by Ca2+ and (iii) a significant and apparently irreversible reduction in the number of functional channel complexes.

Symptomatic pericardial effusion in breast cancer patients: the role of fluid cytology

Clinical and cytologic findings in 21 breast cancer patients with symptomatic pericardial effusion are presented. The etiology of the pericardial effusion was definitely malignant, by cytology/histology in 13 patients (62%), and suspected malignant by cytology in 2 patients (9%). One patient (5%) with definitely nonmalignant pericardial effusion by cytology was found to be histologically positive at autopsy. In 5 patients (24%) there was no histological/cytological evidence of malignancy; radiation pericarditis could be the etiology in 4 of these 5 patients. The median time from the diagnosis of breast cancer to the development of symptomatic pericardial effusion was 60 months (range: 1-219 months). Ten patients developed cardiac tamponade; they were treated by either pericardiocentesis or pericardiectomy. The mean survival of patients with negative cytology/histology was 12 months; patients with suspicious cytology had a mean survival of 9 months; patients with malignant effusion, treated by pericardiectomy, had a mean survival of 22.3 months, while patients with malignant pericardial effusion, who were not subjected to surgery, had a mean survival of 4.7 months, only. It is concluded that the etiology of symptomatic pericardial effusion in breast cancer patients is not always malignant, which emphasizes the role of fluid cytology in establishing definite diagnosis. The survival probability is a function of the extent of extracardiac disease; among patients with malignant pericardial effusion those selected for pericardiectomy have a longer than average survival.

Pericardial effusion complicating breast cancer

Thirty-five patients with metastatic breast cancer and pericardial effusions are described. They were treated with specific endocrine or chemotherapy. Twenty-two (63%) had presented in cardiac tamponade and were rapidly relieved by pericardiocentesis. Eighteen (82%) of these required no further local treatment, 2 obtained relief from a second aspiration and 2 needed additional treatment (intrapericardial bleomycin instillation and surgical pleuropericardial window). The median survival was 13.2 months. No patient relapsed again in the pericardium, suggesting that their prognosis was that of the underlying disease. Cardiac tamponade should be considered in any breathless patient with malignancy. In breast cancer, periocardiocentesis is lifesaving and systemic treatment can usefully prolong life.

Mitigation of an anthracycline-induced cardiomyopathy by pretreatment with razoxane: a quantitative morphological assessment

A quantitative evaluation of structural modifications was undertaken in the myocardium of daunorubicin (DNR)-treated and razoxane (RZ)-protected mice. BDF1 mice were injected with DNR, 15 mg/kg; a second group of mice was subjected to the same conditions but, in addition, received a pretreatment of RZ, 200 mg/kg. Representative cubes of myocardial tissue were processed for viewing with the electron microscope. Five hundred myocardial cells in each group were examined for the presence of lesions which had been categorized as early, moderate, or advanced. Contrasting the total number of demonstrable lesions in each group revealed a statistically significant reduction of 38% in abnormalities present in RZ-protected mice. By category, RZ-pretreated mice showed a mitigation in the appearance of early and moderate alterations and a striking reduction in the incidence of advanced, irreversible lesions. These results indicate that the cardiomyopathy associated with DNR administration can be ameliorated by pretreatment with RZ; this protective effect is markedly exerted by preventing the development of severe, irreversible lesions in the murine myocardium; the initial, non-transient structural alteration subsequent to DNR-exposure appears to affect the myocardial sarcoplasmic reticulum.

Cardiotoxicity mechanisms from the point of view of preclinical or premarketing safety evaluation

The most commonly occurring cardiotoxic reactions in humans are due to over-exposure to chemicals that affect physiological function of the heart. These effects, which are usually receptor-mediated, are dose related and can generally be predicted from safety studies in animals. Direct chemical toxicity is initiated by an interaction of a reactive metabolite of the xenobiotic with cellular macromolecules. The incidence of such cardiotoxicity is low because few of these chemicals are metabolized in the heart. The concentration of cellular protective substances influences the development of such toxicity, and therefore species variation should be considered in safety studies. Chemically induced immune system-mediated reactions can develop in the heart, and may occur in anaphylaxis. Antibody mediated cytotoxic or immune complex reactions are rare events, and the predictability is poor. In some instances sensitivity is immunogenetically controlled. Cardiotoxic effects can also develop after prenatal exposure to chemicals, and thus consideration should be given to examining the offspring for those effects in teratology studies.

Effect of liposomal-encapsulated superoxide dismutase on active oxygen-related human disorders. A preliminary study

Liposomal-encapsulated superoxide dismutase was clinically applied to patient showing an increase in neutrophil active oxygen generation, and those with diseases such as severe rheumatoid arthritis (RA), Crohn's disease and progressive systemic sclerosis (PSS) in which presence of a plasmatic clastogenic factor has been demonstrated. Liposomal SOD injection (2.5 mg twice a week) resulted in marked remission in 12 out of 16 patients with active Behcet's disease. The drug was impressively effective on patients with intestinal Behcet. Remission rates in the other diseases was 7 out of 8 mucocutaneous lymphnode syndrome (MCLS, Kawasaki disease) 3 out of 5 dermatitis herpetiformis, IgA linear bullous dermatosis or severe cement dermatitis, 4 out of 9 active and severe RA, 3 out of 3 PSS, 4 out of 4 Crohn's disease, 3 out of 4 colitis ulcerosa, and 2 out of 2 unresponsive (hemolytic) anemia. To be emphasized was that three severe active RA patients and two terminal-stage PSS patients with dyspnea due to lung fibrosis showed dramatic improvement after administration of liposomal SOD. In addition, in 13 out of 15 malignant neo plastic patients including cancer, malignant lymphoma and leucemia who were receiving radiotherapy (total dose, more than 4000 rads) and chemotherapy including anthracycline analogs (total over 450 mg/m2) and bleomycin, the drug also prevented the appearance of myocardiac injury and fibrosis, sometimes seen as a consequence of chemotherapy. Liposomal SOD, which shows no toxicity, has various advantages compared to free SOD preparations, and is highly and broadly applicable to various clinical disorders.