Involvement of cytosolic and mitochondrial iron in iron overload cardiomyopathy: an update

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Abstract

<p class="first" id="P1">Iron overload cardiomyopathy (IOC) is a major cause of death in patients with diseases associated with chronic anemia such as thalassemia or sickle cell disease after chronic blood transfusions. Associated with iron overload conditions, there is excess free iron that enters cardiomyocytes through both L- and T-type calcium channels thereby resulting in increased reactive oxygen species being generated via Haber-Weiss and Fenton reactions. It is thought that an increase in reactive oxygen species contributes to high morbidity and mortality rates. Recent studies have, however, suggested that that it is iron overload in mitochondria that contributes to cellular oxidative stress, mitochondrial damage, cardiac arrhythmias as well as the development of cardiomyopathy. Iron chelators, antioxidants and/or calcium channel blockers has been demonstrated to prevent and ameliorate cardiac dysfunction in animal models as well as in patients suffering from cardiac iron overload. Hence, either a mono-therapy or combination therapies with any of the aforementioned agents may serve as a novel treatment in iron-overload patients in the near future. In the present article, we review the mechanisms of cytosolic and/or mitochondrial iron load in the heart which may contribute synergistically or independently to the development of iron associated cardiomyopathy. We also review available as well as potential future novel treatments. </p>

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Anthracyclines: molecular advances and pharmacologic developments in antitumor activity and cardiotoxicity.

Giorgio Minotti, Pierantonio Menna, Emanuela Salvatorelli … (2004)

The clinical use of anthracyclines like doxorubicin and daunorubicin can be viewed as a sort of double-edged sword. On the one hand, anthracyclines play an undisputed key role in the treatment of many neoplastic diseases; on the other hand, chronic administration of anthracyclines induces cardiomyopathy and congestive heart failure usually refractory to common medications. Second-generation analogs like epirubicin or idarubicin exhibit improvements in their therapeutic index, but the risk of inducing cardiomyopathy is not abated. It is because of their janus behavior (activity in tumors vis-à-vis toxicity in cardiomyocytes) that anthracyclines continue to attract the interest of preclinical and clinical investigations despite their longer-than-40-year record of longevity. Here we review recent progresses that may serve as a framework for reappraising the activity and toxicity of anthracyclines on basic and clinical pharmacology grounds. We review 1) new aspects of anthracycline-induced DNA damage in cancer cells; 2) the role of iron and free radicals as causative factors of apoptosis or other forms of cardiac damage; 3) molecular mechanisms of cardiotoxic synergism between anthracyclines and other anticancer agents; 4) the pharmacologic rationale and clinical recommendations for using cardioprotectants while not interfering with tumor response; 5) the development of tumor-targeted anthracycline formulations; and 6) the designing of third-generation analogs and their assessment in preclinical or clinical settings. An overview of these issues confirms that anthracyclines remain "evergreen" drugs with broad clinical indications but have still an improvable therapeutic index.

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Vitamins E and C in the prevention of cardiovascular disease in men: the Physicians' Health Study II randomized controlled trial.

Howard Sesso, Julie Buring, William Christen … (2008)

Basic research and observational studies suggest vitamin E or vitamin C may reduce the risk of cardiovascular disease. However, few long-term trials have evaluated men at initially low risk of cardiovascular disease, and no previous trial in men has examined vitamin C alone in the prevention of cardiovascular disease. To evaluate whether long-term vitamin E or vitamin C supplementation decreases the risk of major cardiovascular events among men. The Physicians' Health Study II was a randomized, double-blind, placebo-controlled factorial trial of vitamin E and vitamin C that began in 1997 and continued until its scheduled completion on August 31, 2007. There were 14,641 US male physicians enrolled, who were initially aged 50 years or older, including 754 men (5.1%) with prevalent cardiovascular disease at randomization. Individual supplements of 400 IU of vitamin E every other day and 500 mg of vitamin C daily. A composite end point of major cardiovascular events (nonfatal myocardial infarction, nonfatal stroke, and cardiovascular disease death). During a mean follow-up of 8 years, there were 1245 confirmed major cardiovascular events. Compared with placebo, vitamin E had no effect on the incidence of major cardiovascular events (both active and placebo vitamin E groups, 10.9 events per 1000 person-years; hazard ratio [HR], 1.01 [95% confidence interval {CI}, 0.90-1.13]; P = .86), as well as total myocardial infarction (HR, 0.90 [95% CI, 0.75-1.07]; P = .22), total stroke (HR, 1.07 [95% CI, 0.89-1.29]; P = .45), and cardiovascular mortality (HR, 1.07 [95% CI, 0.90-1.28]; P = .43). There also was no significant effect of vitamin C on major cardiovascular events (active and placebo vitamin E groups, 10.8 and 10.9 events per 1000 person-years, respectively; HR, 0.99 [95% CI, 0.89-1.11]; P = .91), as well as total myocardial infarction (HR, 1.04 [95% CI, 0.87-1.24]; P = .65), total stroke (HR, 0.89 [95% CI, 0.74-1.07]; P = .21), and cardiovascular mortality (HR, 1.02 [95% CI, 0.85-1.21]; P = .86). Neither vitamin E (HR, 1.07 [95% CI, 0.97-1.18]; P = .15) nor vitamin C (HR, 1.07 [95% CI, 0.97-1.18]; P = .16) had a significant effect on total mortality but vitamin E was associated with an increased risk of hemorrhagic stroke (HR, 1.74 [95% CI, 1.04-2.91]; P = .04). In this large, long-term trial of male physicians, neither vitamin E nor vitamin C supplementation reduced the risk of major cardiovascular events. These data provide no support for the use of these supplements for the prevention of cardiovascular disease in middle-aged and older men. clinicaltrials.gov Identifier: NCT00270647.

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Cardiotoxicity of doxorubicin is mediated through mitochondrial iron accumulation.

Y Ichikawa, Arineh Khechaduri, Hossein Ardehali … (2014)

Doxorubicin is an effective anticancer drug with known cardiotoxic side effects. It has been hypothesized that doxorubicin-dependent cardiotoxicity occurs through ROS production and possibly cellular iron accumulation. Here, we found that cardiotoxicity develops through the preferential accumulation of iron inside the mitochondria following doxorubicin treatment. In isolated cardiomyocytes, doxorubicin became concentrated in the mitochondria and increased both mitochondrial iron and cellular ROS levels. Overexpression of ABCB8, a mitochondrial protein that facilitates iron export, in vitro and in the hearts of transgenic mice decreased mitochondrial iron and cellular ROS and protected against doxorubicin-induced cardiomyopathy. Dexrazoxane, a drug that attenuates doxorubicin-induced cardiotoxicity, decreased mitochondrial iron levels and reversed doxorubicin-induced cardiac damage. Finally, hearts from patients with doxorubicin-induced cardiomyopathy had markedly higher mitochondrial iron levels than hearts from patients with other types of cardiomyopathies or normal cardiac function. These results suggest that the cardiotoxic effects of doxorubicin develop from mitochondrial iron accumulation and that reducing mitochondrial iron levels protects against doxorubicin-induced cardiomyopathy.