Doxorubicin-induced delayed-onset subclinical cardiotoxicity in mice

Subclinical cardiotoxicity at low total cumulative doxorubicin (DOX) doses can manifest into cardiomyopathy in long-term cancer survivors. However, the underlying mechanisms are poorly understood. In male B6C3F₁ mice, assessment of cardiac function by echocardiography was performed at 1, 4, 10, 17, and 24 weeks after exposure to 6, 9, 12, and 24 mg/kg total cumulative DOX doses or saline (SAL) to monitor development of delayed-onset cardiotoxicity. The 6- or 9-mg/kg total cumulative doses resulted in a significant time-dependent decline in systolic function (left ventricular ejection fraction (LVEF) and fractional shortening (FS)) during the 24-week recovery although there was not a significant alteration in % LVEF or % FS at any specific time point during the recovery. A significant decline in systolic function was elicited by the cardiotoxic cumulative DOX dose (24 mg/kg) during the 4- to 24-week period after treatment compared to SAL-treated counterparts. At 24 weeks after DOX treatment, a significant dose-related decrease in the expression of genes and proteins involved in sarcoplasmic reticulum (SR) calcium homeostasis (Ryr2 and Serca2) was associated with a dose-related increase in the transcript level of Casp12 (SR-specific apoptosis) in hearts. These mice also showed enhanced apoptotic activity in hearts indicated by a significant dose-related elevation in the number of apoptotic cardiomyocytes compared to SAL-treated counterparts. These findings collectively suggest that a steady decline in SR calcium handling and apoptosis might be involved in the development of subclinical cardiotoxicity that can evolve into irreversible cardiomyopathy later in life.

Arrhythmias and device therapies in patients with cancer therapy-induced cardiomyopathy

Our knowledge of associated cardiotoxicities from novel therapeutics in oncology continues to expand. These include arrhythmias from cancer-therapy induced cardiomyopathy resulting from both direct and indirect effects on cardiomyocytes and other mechanisms that can adversely impact cardiovascular outcomes and overall mortality. In this review, we focus on both the arrhythmias of various classes of oncologic agents as well as the use of cardiac implantable electronic devices (cardioverter-defibrillators, permanent pacemakers, and cardiac resynchronization therapy) in cardio-oncology patients.

Complications of chemotherapy, a basic science update

Anthracyclines, discovered 50 years ago, are antibiotics widely used as antineoplastic agents and are among the most successful anticancer therapies ever developed to treat a wide range of cancers, including hematological malignancies, soft tissue sarcomas and solid tumors. However, some anthracyclines, including doxorubicin, exhibit major signs of cardiotoxicity that may ultimately lead to heart failure (HF). Despite intensive research on doxorubicine-induced cardiotoxicity, the underlying mechanisms responsible for doxorubicin-induced cardiotoxicity have not been fully elucidated yet. Published literature so far has focused mostly on mitochondria dysfunction with consequent oxidative stress, Ca(2+) overload, and cardiomyocyte death as doxorubicin side effects, leading to heart dysfunction. This review focuses on the current understanding of the molecular mechanisms underlying doxorubicin-induced cardiomyocyte death (i.e.: cardiomyocyte death, mitochondria metabolism and bioenergetic alteration), but we will also point to new directions of possible mechanisms, suggesting potent prior or concomitant alterations of specific signaling pathways with molecular actors directly targeted by the anticancer drugs itself (i.e. calcium homeostasis or cAMP signaling cascade). The mechanisms of anticancer cardiac toxicity may be more complex than just mitochondria dysfunction. Partnership of both basic and clinical research is needed to promote new strategies in diagnosis, therapies with concomitant cardioprotection in order to achieve cancer treatment with acceptable cardiotoxicity along life span.

Synthesis, characterization and biological evaluation of some 16E-arylidene androstane derivatives as potential anticancer agents

A series of new 16E-arylidene androstane derivatives were synthesized and characterized. The new compounds were screened for their anticancer activities against the human cancer cell lines SW480, A549, HepG2 and HeLa in vitro using the MTT assay. The results of the in vitro study showed that a number of compounds have shown IC(50) values lower than 20 μM against the four cancer cell lines.

Amidization of doxorubicin alleviates doxorubicin-induced contractile dysfunction and reduced survival in murine cardiomyocytes

Doxorubicin is an effective anthracycline used for cancer therapy. However, the clinical application of doxorubicin has been largely limited by its irreversible cardiotoxicity, which is mainly induced by the primary amine group. In this study, we structurally modified doxorubicin by converting the primary amine into an acid-labile amide before assessing the acute cardiac effect of doxorubicin (pristine or modified) on cardiomyocyte contractile function. Contractile properties of murine cardiomyocytes were analyzed including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR(90)) and maximal velocity of shortening/re-lengthening (+/-dL/dt). Cell toxicity and survival rate were evaluated using the MTT assay. The doxorubicin-free base was amidized by reacting with 3,4,5,6-tetrahydophthalic anhydride (THPA) or 3,3,4,4-tetramethylsuccinic anhydride (TMSA) to yield doxorubicin-THPA or -TMSA. Acute exposure of pristine doxorubicin (10(-9)-10(-5)M) for 30 min significantly prolonged TPS and TR(90) without affecting PS and +/-dL/dt. Interestingly, doxorubicin-induced prolongation of TPS and TR(90) was significantly attenuated or abrogated by amidization of doxorubicin. Neither doxorubicin-THPA nor -TMSA affected PS and +/-dL/dt. ROS and MTT assay revealed significantly reduced ROS production and cardiac cell toxicity from amidized doxorubicin compared with the pristine compound. Comparable cytotoxicity in human ovarian cancer SKOV-3 cells was observed between amidized and pristine doxorubicin compounds. These data provide evidence for the first time that structural modification of doxorubicin alleviates its cardiac toxicity.

The Tei index identifies a differential effect on left and right ventricular function with low-dose anthracycline chemotherapy

OBJECTIVE

We sought to study the relative effect on left ventricular (LV) and right ventricular (RV) function of low-dose anthracycline-containing chemotherapy regimes.

METHODS

A total of 23 patients (mean age 48 +/- 20 years) underwent echocardiographic examinations before any anthracycline had been administered and then after low-dose anthracycline (doxorubicin 50-125 mg/m2). The Tei index was used to compare the relative effects on RV and LV function.

RESULTS

Anthracycline administration was significantly associated with an increase in the LV Tei index (0.38 +/- 0.12 vs 0.46 +/- 0.16, P = .02). There was no significant change in the RV Tei index (0.19 +/- 0.10 vs 0.20 +/- 0.10, P = .72). Comparing the relative effect on global LV and RV function the change in LV Tei was significantly greater than the change in RV Tei (0.07 +/- 0.13 vs 0.01 +/- 0.09, P = .044).

CONCLUSIONS

Low-dose anthracycline administration has a significant negative impact on LV function but does not affect RV function.

Chronic progressive cardiac dysfunction years after doxorubicin therapy for childhood acute lymphoblastic leukemia

PURPOSE

Cross-sectional studies show that cardiac abnormalities are common in long-term survivors of doxorubicin-treated childhood malignancies. Longitudinal data, however, are rare.

METHODS

Serial echocardiograms (N = 499) were obtained from 115 doxorubicin-treated long-term survivors of childhood acute lymphoblastic leukemia (median age at diagnosis, 4.8 years; median follow-up after completion of doxorubicin, 11.8 years). Results were expressed as z scores to indicate the number of standard deviations (SDs) above (+) or below (-) the normal predicted value. Median individual and cumulative doxorubicin doses were 30 mg/m2 per dose and 352 mg/m2, respectively.

RESULTS

Left ventricular fractional shortening was significantly reduced after doxorubicin therapy, and the reduction was related to cumulative dose. z scores for fractional shortening transiently improved before falling to -2.76 more than 12 years after diagnosis. Reduced fractional shortening was related to impaired contractility and increasing afterload, consequences of a progressive reduction of ventricular mass, and wall thickness relative to body-surface area. Left ventricular contractility fell significantly over time and was depressed at last follow-up in patients receiving more than 300 mg/m2 of doxorubicin. Systolic and diastolic blood pressures were below normal more than 9 years after diagnosis. Even patients receiving lower cumulative doxorubicin doses experienced reduced mass and dimension. Fractional shortening and dimension at the end of therapy predicted these parameters 11.8 years later.

CONCLUSION

Cardiac abnormalities were persistent and progressive after doxorubicin therapy. Inadequate ventricular mass with chronic afterload excess was associated with progressive contractile deficit and possibly reduced cardiac output and restrictive cardiomyopathy. The deficits were worst after highest cumulative doses of doxorubicin, but appeared even after low doses.

Late anthracyclines cardiotoxicity associated with infection by Mycoplasma pneumoniae. A case report

We report the case of a 15-year-old male developing progressive myocardiopathy secondary to late anthracycline cardiotoxicity. At 2 years of age, the patient received chemotherapy with anthracyclines (adriamycin) at an accumulated dose of 510 mg/m2 due to the presence of non-Hodgkin lymphoma which subsided completely and he has been asymptomatic since then. A number of recurrent respiratory infections occurred as triggering factors of the condition, and the laboratory tests evidenced positive serology for Mycoplasma pneumoniae suggesting a recent contact.

Doxorubicin induces cardiomyocyte dysfunction via a p38 MAP kinase-dependent oxidative stress mechanism

Doxorubicin, an anthracycline used for cancer therapy, is known to elicit an irreversible cardiotoxicity. Several mechanisms were postulated for its cardiac toxicity including generation of reactive oxygen species (ROS). This study was designed to determine the acute effect of doxorubicin on cardiac mechanical and intracellular Ca(2+) properties in isolated ventricular myocytes. Contractile properties of male adult rat ventricular myocytes were analyzed including peak shortening (PS), time-to-PS (TPS), time-to-90% relengthening (TR(90)) and maximal velocity of shortening/relengthening (+/-dL/dt). Intracellular Ca(2+) transients and generation of ROS were measured with fura-2 and fluoroprobe 5-(6)-chloromethyl-2',7'-dichlorodihydrofluorescein diacetate, respectively. Acute (5 min) incubation of myocytes with doxorubicin (10(-9)-10(-4)M) significantly prolonged TPS, TR(90) and intracellular Ca(2+) transient decay rate without affecting PS, +/-dL/dt, resting intracellular Ca(2+) levels and electrically triggered intracellular Ca(2+) rise. Interestingly, the doxorubicin-induced prolongation of TPS and TR(90) was ablated by treatment of the antioxidant Vitamin C (100 microM) or the p38 MAP kinase inhibitor SB203580 (10 microM). Both Vitamin C and SB203580 unmasked a doxorubicin-induced positive response in PS. Vitamin C itself enhanced basal +/-dL/dt, whereas, SB203580 unmasked a doxorubicin-induced positive response of +/-dL/dt. The doxorubicin-induced response of intracellular Ca(2+) transients was essentially unaffected by Vitamin C. The role of ROS in doxorubicin-induced cardiac contractile response was confirmed with the ability of doxorubicin to enhance ROS generation, which was prevented by Vitamin C and SB203580. These data provide evidence that doxorubicin impairs cardiac contractile property in single myocytes through an oxidative stress-mediated pathway.

Nitric oxide and oxidative stress in brain and heart of normal rats treated with doxorubicin: Role of aminoguanidine

Doxorubicin (DOX) is a potent antitumor antibiotic drug known to cause severe cardiac toxicity. Moreover, its adverse effects were found to be extended to the cerebral tissue. Several mechanisms for this toxicity have been ascribed. Currently, one of the most accepted mechanisms is through free radicals; however, the exact role of nitric oxide (NO) is still unclear. Accordingly, a NO-synthase inhibitor with some antioxidant property, aminoguanidine (AG), was selected to examine its potential protective effect against DOX-induced toxicity. Male Wistar albino rats (150-200 g) were allocated into a normal control group, DOX-induced toxicity group, and DOX + AG-treated group. DOX was injected i.p. at a dose of 10 mg/kg divided into four equal injections over a period of 2 weeks. AG was injected i.p. at a dose of 100 mg/kg 1 h before each DOX injection. The animals were sacrificed 24 h after the last DOX injection and the following parameters were measured: serum lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) activities, cardiac and cerebral contents of malondialdehyde (MDA), conjugated diene (CD), glutathione (GSH), NO, and cytosolic calcium, as well as superoxide dismutase (SOD) and glutathione peroxidase (GSHP(X)) activities. Cardiotoxicity was manifested by a marked increase in serum LDH and CPK in addition to the sharp increase in MDA reaching eightfolds the basal level. This was accompanied by significant increase in CD, NO, cytosolic calcium, SOD, and GSHP(X) content/activity by 69, 85, 76, 125, and 41% respectively as compared to normal control. On the other hand, GSH was significantly depressed. In brain, only significant increase in MDA and GSHP(X) and decrease in GSH were obtained but to a lesser extent than the cardiac tissue. AG treatment failed to prevent the excessive release of cardiac enzymes; however, it alleviated the adverse effects of DOX in heart. AG administration resulted in marked decrease in the elevated levels of MDA, NO, SOD, and GSHP(X), however, MDA level was still pathological. The altered parameters in brain were restored by AG. It is concluded that, AG could not provide complete protection against DOX-induced toxicity. Therefore, it is recommended that, maintenance of the endogenous antioxidant, GSH, and regulation of calcium homeostasis must be considered, rather than NO formation, to guard against DOX-induced toxicity.