Inhibition of cardiac guanylate cyclase by doxorubicin and some of its analogs: possible relationship to cardiotoxicity

The anthracycline antibiotic doxorubicin induces a variety of cardiotoxic effects. We have recently demonstrated that this drug also causes a selective inhibition of rat and human cardiac guanylate cyclase activity in vitro. In the present study, we examined the effect of 30 analogs of doxorubicin on cardiac guanylate cyclase activity. Structural modifications of these anthracycline antibiotics were found to alter their effect on rat cardiac guanylate cyclase activity, N-Substitutions on the sugar moiety eliminated the inhibitory action observed with the parent compound. Long-chain hydrocarbon substitutions in place of the methylketone side chain had a similar effect. Removal or substitution of the C-4 methoxy group had little or no effect on the ability of these compounds to modify guanylate cyclase activity. Substitutions of the C-9 side chain by a hydrazone derivative resulted in compounds that stimulated the enzyme. All of the anthracenedione derivatives were inhibitory. A comparison of the inhibitory effect of some of these anthracycline derivatives on in vitro cardiac guanylate cyclase activity with their cardiotoxic potency suggests a possible relationship between these two parameters.     

Anthracycline cardiotoxicity in breast cancer patients: synergism with trastuzumab and taxanes

Doxorubicin is known to cause cardiomyopathy and congestive heart failure (CHF) upon chronic administration. A major obstacle to doxorubicin-containing multiagent therapies pertains to the possible development of cardiomyopathy and CHF at lower than expected cumulative doses of doxorubicin. For example, the cardiac toxicity of doxorubicin is aggravated by the anti-HER2 antibody Trastuzumab or by the tubulin-active taxane paclitaxel; however, the mechanisms by which Trastuzumab and paclitaxel aggravate doxorubicin-induced cardiotoxicity are mechanistically distinct: Trastuzumab interferes with cardiac-specific survival factors that help the heart to withstand stressor agents like anthracyclines, while paclitaxel acts by stimulating the formation of anthracycline metabolites that play a key role in the mechanism of cardiac failure. Here, we briefly review the molecular mechanisms of the cardiotoxic synergism of Trastuzumab or paclitaxel with doxorubicin, and we attempt to briefly outline how the mechanistic know-how translates into the clinical strategies for improving the safety of anthracycline-based multiagent therapies.     

Cardiac toxicity after anthracycline chemotherapy in childhood

The clinical use of anthracyclines, a family of chemotherapeutic agents with efficacy against many solid tumors and leukemias is limited by unique cumulative dose-limiting cardiotoxicity. Overt heart failure occurs in 4.5% to 7% of patients treated with anthracyclines and the incidence of cardiac function abnormalities increases with the time. Anthracycline-induced congestive heart failure is usually due to permanent changes in the myocardium, changes most consistent with the contractile failure of cardiomyopathy. Although the causes of anthracycline-induced cardiotoxicity are probably many, a large body of evidence points to free-radical-mediated myocyte damage. The risk of developing cardiac heart failure is modified by the presence of certain risk factors that reduce cardiac tolerance to anthracyclines. Age and female gender seem to have an important role in the anthracycline cardiotoxicity. This cardiotoxicity can be divided, on the base of when it started, into acute, subacute and progressive late, chronic form. Various invasive and non-invasive methods have been used to measure the extent of cardiac damage done. Depending on the sensitivity of the method employed, the proportion of hearts found to be damaged has varied widely. Attempts to ameliorate anthracycline cardiotoxicity have been directed toward: 1. decreasing myocardial concentrations of anthracyclines and their metabolites, 2. developing less cardiotoxic analogous, and 3. concurrently administering cardioprotectants to attenuate the effects of anthracyclines on the heart. Much progress has been made in terms of monitoring of clinical and subclinical anthracycline cardiotoxicity, finding alternative schedules, introducing special carriers of anthracyclines and using cardioprotecting agents. It is hoped that with all these effects and with results of ongoing and future trials, we will be able to reduce further or even eliminate anthracycline cardiotoxicity.     

Guanylate cyclase activity in fetal, neonatal and adult rat heart.

Guanosine 3′, 5′-monophosphate is thought to be an important factor in promoting cell growth. We, therefore, measured the activity of guanylate cyclase, the enzyme which in the developing rat heart catalyzes the production of guanosine 3′, 5′-monophosphate. Cardiac guanylate cyclase activity was found to be increased to 405 ± 44 pmol accumulated/10/min/mg protein in utero and maintained this level of activity for the first 3 weeks after birth. By 28 days, cardiac guanylate cyclase activity had decreased to 165 ± 7 pmol accumulated/10 min/mg protein which paralleled the adult mother cardiac guanylate cyclase activity of 173 ± 9 pmol accumulated/10 min/mg protein. This period of maximal activity of cardiac guanylate cyclase corresponds to the period of rapid growth of the heart and the decreased activity approximates the period of time when cardiac DNA synthesis declines.     

Cyclic guanosine monophosphate signaling and phosphodiesterase-5 inhibitors in cardioprotection

Cyclic guanosine monophosphate (cGMP) is an important intracellular second messenger that mediates multiple tissue and cellular responses. The cGMP pathway is a key element in the pathophysiology of the heart and its modulation by drugs such as phosphodiesterase (PDE)-5 inhibitors and guanylate cyclase activators may represent a promising therapeutic approach for acute myocardial infarction, cardiac hypertrophy, heart failure, and doxorubicin cardiotoxicity in patients. In addition, PDE-5 inhibitors may prove to be innovative therapeutic agents for enhancing the chemosensitivity of doxorubicin while providing concurrent cardiac benefit.     

Doxorubicin-induced cardiomyopathy 17 years after chemotherapy

Doxorubicin, an anthracycline antibiotic commonly used as a chemotherapeutic agent for breast cancer, is well known to cause cardiotoxicity. We report the case of an active, otherwise healthy 57-year-old breast cancer survivor who, 17 years after chemotherapy, presented with symptoms of overt heart failure. She had no cardiac risk factors, and neither laboratory nor imaging findings suggested myocarditis or dilated cardiomyopathy. Echocardiographic findings and differential diagnosis led us to attribute her condition to late doxorubicin-induced cardiomyopathy. By virtue of tapered medical therapy, her left ventricular ejection fraction improved from 0.20 to 0.55 in 8 months, and she was asymptomatic after 1 year. The reversibility of left ventricular dysfunction in our patient and the very late appearance of cardiotoxicity secondary to doxorubicin therapy raise questions about the pathogenesis and prevalence of late doxorubicin-induced cardiomyopathy and how to improve outcomes in patients who present with related symptoms of heart failure.     

Chemotherapy-Induced Cardiotoxicity

Anthracycline-based chemotherapeutics have long been recognized as effective agents for treating a wide range of malignancies. However, their use is not without significant adverse cardiotoxic side effects. Strategies for prevention involve limiting free-radical production and subsequent cardiac myocyte damage. Dexrazoxane remains the most widely studied cardioprotective medication. Alternative agents may reduce cardiotoxicity but may still cause significant cardiovascular problems. The role of β-blockers and angiotensin-converting enzyme inhibitors in the treatment of heart failure is well proven. The role of these medications in the prevention and treatment of chemotherapy-induced cardiotoxicity is not well established.     

Grape Seed and Skin Extract Protects Against Acute Chemotherapy Toxicity induced by Doxorubicin in Rat Heart

Doxorubicin (Dox), an antitumor anthracycline antibiotic, plays a key role in the treatment of many neoplastic diseases. However, its chronic administration induces cardiomyopathy. Increased oxidative stress is a major factor implicated in Dox-induced cardiotoxicity. We hypothesized that a pre-treatment with grape seed and skin extract (GSE), commonly used as an antioxidant agent, may alleviate this cardiotoxicity. Rats were treated with GSE (500 mg/kg bw) by intraperitoneal injection during 8 days. On the 4th day, rats were administered a single dose of Dox (20 mg/kg). At the end of the treatment, their hearts were Langendorff-perfused, subjected to ischemia/reperfusion (I/R) injury, and left ventricular functions as heart rate and developed pressure measured. Hearts were also used to determine free iron, H2O2, Ca2+, lipoperoxidation, carbonylation and antioxidant enzymes such as superoxide dismutase (SOD), catalase and peroxidase. Doxorubicin drastically affected heart activity as evidenced after I/R experiments. This effect was associated with an increase in heart free iron and a decrease in Ca2+ concentrations. This effect may have contributed to oxidative stress as assessed by high lipoperoxidation and carbonylation level. GSE counteracted Dox-induced disturbances of hemodynamic parameters, alleviated oxidative stress as assessed by normalized iron and Ca2+ levels and increased SOD activity especially the Mn isoform.     

Bromocriptine enhances guanylate cyclase activity

Bromocriptine and its parent compound alpha-ergocryptine were investigated with respect to their ability to interact with the guanylate cyclase (E.C.4.6.1.2)-cyclic GMP system in vitro in the rat pituitary and ovary. Both bromocriptine and alpha-ergocryptine enhanced guanylate cyclase two- to threefold in both of these tissues over a concentration range of 1 nM to 1 microM. Since bromocriptine is thought to be a dopamine agonist in the pituitary, dopamine's effects on guanylate cyclase were also tested. Dopamine caused a twofold enhancement of guanylate cyclase activity in the pituitary and ovary. When bromocriptine and dopamine were used in combination, bromocriptine had to be in equal or a greater concentration with respect to dopamine in vitro to enhance guanylate cyclase activity. These findings suggest that bromocriptine's effect at the level of the pituitary and ovary may be mediated through enhancement of guanylate cyclase activity.     

Long-term and short-term models for studying anthracycline cardiotoxicity and protectors

The clinical importance of the cardiotoxicity of anthracyclines requires the availability of preclinical models able to predict the cardiotoxicity of novel anthracycline analogs in reference to doxorubicin or of cardioprotectors aimed at circumventing the deleterious effects of these drugs. The reference model has been defined long ago and has proven its validity. Weanling rabbits given weekly injections of doxorubicin for 4 months developed a cardiomyopathy, which can be assessed from a clinical and pathological point of view. Models in other animals such as rats or mice were similarly implemented, also with long-term exposures to the drug, resulting in cardiac failure and severe pathological alterations, which could be graded for comparison. Starting from the evidence that the damage caused by anthracyclines on cardiomyocytes was immediate after each injection and that the functional efficiency of the myocardium should be affected long before the morphological alterations become detectable, we developed a short-term model studying the cardiac performances of isolated perfused hearts of rats that had been treated within 12 days by repetitive administrations of the molecule(s) to be tested. This model provided the data expected from clinical experience: epirubicin appeared less cardiotoxic than doxorubicin; liposomal formulations appeared less cardiotoxic than free drug formulations; dexrazoxane strongly protected against doxorubicin cardiotoxicity. We were then able to show that paclitaxel could potentialize doxorubicin cardiotoxicity, but that docetaxel did not so; or that a high dose of dexrazoxane brought significantly higher protection than a conventional dose. Based upon these contributions, we can encourage the use of the short-term model of isolated perfused rat heart to screen the preclinical cardiotoxicity of anthracycline molecules, formulations and combinations.     

Decreased sensitivity of neonatal rabbit sarcoplasmic reticulum to anthracycline cardiotoxicity

Anthracyclines are useful chemotherapeutic agents whose utility is limited by the development of irreversible cardiotoxicity. When tested, the pediatric population demonstrates an increased sensitivity to the cardiotoxicity of this class of agents, although the reasons for this increased sensitivity are unclear. The sarcoplasmic reticulum (SR) is a target for anthracycline cardiotoxicity in adults, but the effects of anthracycline on the SR in developing myocardium have not been examined. It may be possible to gain insight into the mechanisms of cardiotoxicity through a comparative approach. We compared the acute effects of doxorubicin, daunorubicin, and caffeine on contractile function in adult and neonatal rabbit myocardium. Frequency-dependent contratility, 90% relaxation times, and postrest potentiated contractions (a uniquely SR-dependent phenomenon) in adult myocardium were inhibited in a concentration-dependent manner. Neonatal myocardium, however, was resistant to the effects of these agents. The degree of contractile dysfunction wa consistent with the difference in SR maturation between adult and developing myocardium Anthracyclines exhibited effects similar to those of caffeine, an agent known to render the Sr nonfunctional by the depletion of the releasable SR calcium pool. These results suggest that anthracyclines induce acute cardiac lesions through effects on the SR in adults, whereas cardiotoxic effects in the developing myocardium may proceed by a different mechanism.     

Echocardiographic Assessment of Cardiotoxic Effects of Cancer Therapy

Patients with cancer can present with difficult management issues, as the medicine can sometimes cause sequelae destructive to healthy tissue. As this population lives longer, cardiotoxic effects are beginning to emerge, but the early recognition of this signal can prove difficult, with too late a recognition leading to lifelong cardiac impairment and dysfunction. Cardio-oncology can bridge this difficulty, and echocardiography and its newer imaging abilities are proving efficacious in this population. This article will address common sequelae of cardiotoxic treatment regimens and offer recommendations for echocardiographic surveillance. We recommend echocardiography, preferably three-dimensional and strain imaging, to monitor for cardiotoxic myocardial effects before, during, and after chemotherapy with cardiotoxic drug regimens, particularly anthracycline derivatives. A reduction in left ventricular (LV) global longitudinal strain in all patients, or reduction in LV global circumferential strain or global radial strain in patients at intermediate to high risk for cardiotoxicity, despite normal LV ejection fraction warrants a clinical assessment on the benefits of continuing cardiotoxic chemotherapeutic agents. Lifelong surveillance using echocardiography for cardiotoxicity and radiation-related valvular, pericardial, and coronary artery disease is prudent.     

Doxorubicin-induced ventricular arrhythmia treated by implantation of an automatic cardioverter-defibrillator.

Anthracyclines are a group of potent antitumour agents and cardiotoxicity is an important factor limiting their therapeutic effectiveness. Although cardiomyopathy is the most widely recognized type of cardiotoxic reaction, early arrhythmia following anthracycline administration may be of clinical significance as well. We report a case of ventricular tachycardia causing cardiac arrest in a female treated with doxorubicin as adjuvant therapy of breast cancer. Due to recurrence of the arrhythmia and a desire to continue chemotherapy, an automatic cardioverter-defibrillator was implanted with excellent effect.     

Role of mtDNA lesions in anthracycline cardiotoxicity

Doxorubicin (adriamycin) is an effective drug in the treatment of many malignancies. Its prolonged use is, however, limited by an irreversible, dose-dependent and progressive cardiomyopathy, which may become evident even years after completion of therapy. Data from rats and humans show that oxidative phosphorylation is impaired rapidly after acute doxorubicin-exposure. Such respiratory chain dysfunction is known to enhance the production of reactive oxygen species and may lead to quantitative and qualitative injury of mitochondrial DNA (mtDNA) and its encoded respiratory chain subunits. MtDNA depletion, mtDNA mutations and respiratory defects then accumulate with time also in the absence of continued anthracycline exposure. Chronic cardiotoxicity then manifests, when the bioenergetic capacity of the organelles is severely impaired. The mitochondrial damage in late-onset doxorubicin cardiomyopathy is heart specific and not found in skeletal muscle. DOXO-EMCH, a 6-maleimidocaproyl hydrazone derivative of doxorubicin has evolved from the search for less cardiotoxic anthracyclines. At equieffective antitumor doses, DOXO-EMCH has a substantially lower heart toxicity than free doxorubicin.     

Nitric oxide activates guanylate cyclase and increases guanosine 3′:5′-cyclic monophosphate levels in various tissue preparations

Nitric oxide gas (NO) increased guanylate cyclase [GTP pyrophosphate-lyase (cyclizing), EC 4.6.1.2] activity in soluble and particulate preparations from various tissues. The effect was dose-dependent and was observed with all tissue preparations examined. The extent of activation was variable among different tissue preparations and was greatest (19- to 33-fold) with supernatant fractions of homogenates from liver, lung, tracheal smooth muscle, heart, kidney, cerebral cortex, and cerebellum. Smaller effects (5- to 14-fold) were observed with supernatant fractions from skeletal muscle, spleen, intestinal muscle, adrenal, and epididymal fat. Activation was also observed with partially purified preparations of guanylate cyclase. Activation of rat liver supernatant preparations was augmented slightly with reducing agents, decreased with some oxidizing agents, and greater in a nitrogen than in an oxygen atmosphere. After activation with NO, guanylate cyclase activity decreased with a half-life of 3-4 at 4 degrees but re-exposure to NO resulted in reactivation of preparations. Sodium azide, sodium nitrite, hydroxylamine, and sodium nitroprusside also increased guanylate cyclase activity as reported previously. NO alone and in combination with these agents produced approximately the same degree of maximal activation, suggesting that all of these agents act through a similar mechanism. NO also increased the accumulation of cyclic GMP but not cyclic AMP in incubations of minces from various rat tissues. We propose that various nitro compounds and those capable of forming NO in incubations activate guanylate cyclase through a similar but undefined mechanism. These effects may explain the high activities of guanylate cyclase in certain tissues (e.g., lung and intestinal mucosa) that are exposed to environmental nitro compounds.     

Anthracycline-induced cardiotoxicity: A case report and review of literature

BACKGROUNDDoxorubicin and other anthracycline derivatives inhibit topoisomerase II and is an important class of cytotoxic chemotherapy in cancer treatment. The use of anthracycline is limited by dose-dependent cardiotoxicity, which may manifest initially as asymptomatic cardiac dysfunction with subsequent progression to congestive heart failure. Despite baseline assessment and periodic monitoring of cardiac function for patients receiving anthracycline agents, there are unmet needs in prediction and prevention of anthracycline-induced cardiotoxicity (AIC).CASE SUMMARYA 35-year-old African American female was found to have a 9-cm high-grade osteosarcoma of right femur and normal baseline cardiac function with left ventricular ejection fraction of approximately 60%-70% determined by transthoracic and dobutamine stress echocardiogram. She underwent perioperative doxorubicin and cisplatin chemotherapy with 3 cycles before surgery and 3 cycles after surgery, and received a total of 450 mg/m² doxorubicin at the end of her treatment course. She was evaluated regularly during chemotherapy without any cardiac or respiratory symptoms. Approximately two months after her last chemotherapy, the patient presented to the emergency department with dyspnea for one week and was intubated for acute hypoxic respiratory failure. Echocardiogram showed an ejection fraction of 5%-10% with severe biventricular failure. Despite attempts to optimize cardiac function, the patient’s hemodynamic status continued to decline, and resuscitation was not successful on the seventh day of hospitalization. The autopsy showed no evidence of osteosarcoma, and the likely cause of death was cardiac failure with the evidence of pulmonary congestion, liver congestion, and multiple body cavity effusions.CONCLUSIONWe present a case of 35-year-old African American female developing cardiogenic shock shortly after receiving a cumulative dose of 450 mg/m² doxorubicin over 9 mo. Cardiac monitoring and management of patients receiving anthracycline chemotherapy have been an area of intense research since introduction of these agents in clinical practice. We have reviewed literature and recent advances in the prediction and prevention of AIC. Although risk factors currently identified can help stratify patients who need closer monitoring, there are limitations to our current understanding and further research is needed in this field.     

Anthracycline cardiotoxicity in long-term survivors of childhood cancer

Anthracycline chemotherapy is a widely-used and effective treatment for a wide spectrum of childhood cancers. Its use is limited by associated progressive and clinically significant cardiotoxic effects. Onset can be acute, early, or late. While acute onset is rare, long-term survivors have significantly elevated rates of cardiac morbidity and mortality. Major complications include cardiomyopathy, coronary artery disease, and atherosclerosis. Means of prevention and treatment continue to be explored including limiting cumulative anthracycline dose, controlling the rate of administration, and using liposomal preparations and novel anthracycline analogues. Dexrazoxane prior to anthracycline chemotherapy has been shown to significantly lower rates of elevated serum cardiac troponin levels, a marker of myocyte injury, indicating a cardioprotective effect. Pilot studies indicate that exercise interventions may also be beneficial in long-term survivors with cardiac damage. Support and study of this population to decrease the morbidity and morality associated with anthracycline-induced cardiotoxicity is indicated in a time sensitive fashion.     

Antioxidant defense against anthracycline cardiotoxicity by metallothionein

Anthracycline cardiotoxicity is related to oxidative stress generated from the metabolism of anthracyclines in the heart. Studies using transgenic mice with high levels of antioxidants such as catalase or metallothionein (MT) specifically in the heart have demonstrated that elevation of cardiac antioxidant defense leads to intervention of anthracycline cardiotoxicity. MT protection against anthracycline-induced cardiac toxicity is related to its anti-apoptotic effect by inhibiting both p38-MAPK-mediated and mitochondrial cytochrome c-release-mediated apoptotic signaling. The anti-apoptotic effect of MT is closely related to its antioxidant action, which involves regulation of zinc homeostasis by the MT redox cycle. MT interferes with oxidant-mediated detrimental process through at least in part zinc release and zinc transfers directly from MT to acceptor proteins. In addition, MT posttranslationally modulates critical proteins involved in mitochondrial respiration and energy metabolism. All of these processes constitute the mechanisms by which MT protects from anthracycline cardiotoxicity.     

Role of anthracyclines in the era of targeted therapy

Anthracyclines such as doxorubicin, epirubicin, and daunorubicin are among the most active cytoxic agents for treatment of a wide variety of solid tumors and hematological malignancies. The downside associated with chronic administration of anthracyclines is the induction of cardiomyopathy and congestive heart failure, usually refractory to common treatments. Anthracycline liposomal formulations are currently the best-known alternatives to improve the index and spectrum of anticancer activity of these drugs and decrease their cardiotoxicity. In the current target therapy era in oncology, anthracyclines increase the antitumor effects in more than additive fashion, being excellent partners for other active agents like taxanes and trastuzumab. It is important to note, however, that the enhanced antitumor activity of these combination therapies is often accompanied with increased cardiotoxicity. The issue of anthracycline cardiotoxicity has not been solved so far and it is also important to stress the current lack of proper prevention and treatment strategies.     

Cardiotoxicity of interferon. A review of 44 cases.

Cardiovascular complications have occurred in clinical trials of interferon. We review herein experience to date of cardiotoxicity with all types of interferons in cancer patients. The most common presentations of cardiotoxicity were cardiac arrhythmia, dilated cardiomyopathy, and symptoms of ischemic heart disease, including myocardial infarction and sudden death. The cardiac effects were not related to the daily dose, cumulative total dose, or period of therapy. Some of the patients in whom interferon has caused cardiovascular sequelae have had a history of coronary heart disease or have previously been given chemotherapy with drugs known to be cardiotoxic. In most of the patients, cardiac toxicity was reversible following the cessation of the drug therapy.