Free radicals in heart failure: therapeutic targets for old and new drugs

Mechanisms of sudden cardiac death: oxidants and metabolism

Ventricular arrhythmia is the leading cause of sudden cardiac death (SCD). Deranged cardiac metabolism and abnormal redox state during cardiac diseases foment arrhythmogenic substrates through direct or indirect modulation of cardiac ion channel/transporter function. This review presents current evidence on the mechanisms linking metabolic derangement and excessive oxidative stress to ion channel/transporter dysfunction that predisposes to ventricular arrhythmias and SCD. Because conventional antiarrhythmic agents aiming at ion channels have proven challenging to use, targeting arrhythmogenic metabolic changes and redox imbalance may provide novel therapeutics to treat or prevent life-threatening arrhythmias and SCD.

Mitochondria and arrhythmias

Mitochondria are essential to providing ATP, thereby satisfying the energy demand of the incessant electrical activity and contractile action of cardiac muscle. Emerging evidence indicates that mitochondrial dysfunction can adversely affect cardiac electrical functioning by impairing the intracellular ion homeostasis and membrane excitability through reduced ATP production and excessive reactive oxygen species (ROS) generation, resulting in increased propensity to cardiac arrhythmias. In this review, the molecular mechanisms linking mitochondrial dysfunction to cardiac arrhythmias are discussed with an emphasis on the impact of increased mitochondrial ROS on the cardiac ion channels and transporters that are critical to maintaining normal electromechanical functioning of the cardiomyocytes. The potential of using mitochondria-targeted antioxidants as a novel antiarrhythmia therapy is highlighted.

HMG-CoA reductase inhibitors in chronic heart failure: potential mechanisms of benefit and risk

HMG-CoA reductase inhibitors (statins) have been shown to reduce mortality and cardiovascular morbidity in patients with hyperlipidaemia and those with coronary artery disease. However, evidence for statin treatment in patients with chronic heart failure (CHF) remains a subject of debate. Patients with heart failure were generally excluded in the existing trials and a different patient population with a distinct pattern of morbidity and treatment was studied. In addition, no safety data are available for statins in patients with heart failure, where there are potential concerns about coenzyme Q10 depletion and excessive low-density lipoprotein reduction. This review summarises the clinical and preclinical evidence for potential beneficial effects of statins in CHF. In experimental systems, statins have been shown to improve cardiac function through antioxidative and anti-inflammatory action. Statins improve endothelial function, may reduce neurohormonal activation, and stimulate endothelial progenitor cells. Some of these effects occur independently of cholesterol lowering and can be explained by inhibition of isoprenylation of signal transducing proteins of the family of Rho guanosine triphosphatases. Two ongoing controlled randomised trials (CORONA [Controlled Rosuvastatin Multinational Study in Heart Failure] and GISSI-HF [Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico--Heart Failure]) will help us to assess whether the described beneficial effects of statins in heart failure outweigh the potential negative effects and translate into the reduction of clinical endpoints.

Cardioprotection by intermittent fasting in rats

BACKGROUND

Intermittent fasting (IF), a dietary regimen in which food is available only every other day, increases the life span and reduces the incidence of age-associated diseases in rodents. We have reported neuroprotective effects of IF against ischemic injury of the brain. In this study, we examined the effects of IF on ischemic injury of the heart in rats.

METHODS AND RESULTS

After 3 months of IF or regular every-day feeding (control) diets started in 2-month-old rats, myocardial infarction (MI) was induced by coronary artery ligation. Twenty-four hours after MI, its size in the IF group was 2-fold smaller, the number of apoptotic myocytes in the area at risk was 4-fold less, and the inflammatory response was significantly reduced compared with the control diet group. Serial echocardiography revealed that during 10 weeks after MI (with continuation of the IF regimen), the left ventricular (LV) remodeling and MI expansion that were observed in the control diet group were absent in the IF group. In a subgroup of animals with similar MI size at 1 week after MI, further observation revealed less remodeling, better LV function, and no MI expansion in the IF group compared with the control group.

CONCLUSIONS

IF protects the heart from ischemic injury and attenuates post-MI cardiac remodeling, likely via antiapoptotic and antiinflammatory mechanisms.