Atrial remodeling in permanent atrial fibrillation : Mechanisms and pharmacological implications

Atrial fibrillation (AF), the most prevalent rhythm disorder in clinical practice, is currently significantly contributing to morbidity and mortality of the ageing population. In the past decades, a tremendous amount of research resulted in valuable insights into AF pathophysiology, with a primary focus on atrial remodeling. Defined as a persistent change in atrial function and structure, remodeling has the intrinsic properties to enhance the probability of focal (ectopic) and/or re-entrant pursuits, thus supporting AF persistence. The hallmark of structural remodeling is represented by atrial fibrosis, a multifactorial process involving an interaction between neurohormonal and cellular mediators. This paper provides a brief summary of the recent knowledge with respect to electrical and structural remodeling and novel insights into the pathogenesis of atrial fibrosis. Since current drug options for AF treatment are far from being optimal we also discuss the therapeutic principles and current alternatives for counteracting atrial fibrosis, and thus preventing arrhythmia recurrence

Metabolic therapy: cardioprotective effects of orotic acid and its derivatives

Metabolic therapy involves the administration of a substance normally found in the human body to enhance cellular reactions involved in the pathogenesis of disease. Myocardial ischaemia/reperfusion injury represents a leading cause of morbidity and mortality, also in cardiovascular disease. Therapeutic strategies aimed at limiting cardiomyocyte death during the postischaemic reperfusion and in the perioperative settings are nowadays extensively studied. Conceived originally as a dietary constituent (known as vitamin B13) only, it is now apparent that most orotic acid is synthesized in the human body where it arises as an intermediate in the biosynthetic pathway of pyrimidine nucleotides. Previous investigations in the heart suggest that orotate and its derivatives could be of significant clinical benefit in the treatment of heart disease. The present brief review is concerned with the current knowledge of the major effects of these compounds in both experimental and clinical cardiology. The potential mechanisms and biochemical pathways responsible for cardioprotection are highlighted.Biomedical Reviews 2010; 21: 47-55

Examination of the role of mitochondrial morphology and function in the cardioprotective effect of sodium nitrite administered 24 h before Ischemia/reperfusion injury

Background: We have previous evidence that in anesthetized dogs the inorganic sodium nitrite protects against the severe ventricular arrhythmias, resulting from coronary artery occlusion and reperfusion, when administered 24 h before. The present study aimed to examine, whether in this effect changes in mitochondrial morphology and function would play a role. Methods: Thirty dogs were infused intravenously either with saline (n = 15) or sodium nitrite (0.2 μmol/kg/min; n = 15) for 20 min, and 24 h later, 10 dogs from each group were subjected to a 25 min period of occlusion and then reperfusion of the left anterior descending coronary artery. The severity of ischaemia and ventricular arrhythmias were examined in situ. Left ventricular tissue samples were collected either before the occlusion (5 saline and 5 nitrite treated dogs) or, in dogs subjected to occlusion, 2 min after reperfusion. Changes in mitochondrial morphology, in complex I and complex II-dependent oxidative phosphorylation (OXPHOS), in ATP, superoxide, and peroxynitrite productions were determined. Results: The administration of sodium nitrite 24 h before ischemia/reperfusion significantly attenuated the severity of ischaemia, and markedly reduced the number and incidence of ventricular arrhythmias. Nitrite also attenuated the ischaemia and reperfusion (I/R)-induced structural alterations, such as reductions in mitochondrial area, perimeter, and Feret diameter, as well as the increase in mitochondrial roundness. The administration of nitrite, however, enhanced the I/R-induced reduction in the mitochondrial respiratory parameters; compared to the controls, 24 h after the infusion of nitrite, there were further significant decreases, e.g., in the complex I-dependent OXPHOS (by -20 vs. -53%), respiratory control ratio (by -14 vs. -61%) and in the P/E control coupling ratio (by 2 vs. -36%). Nitrite also significantly reduced the I/R-induced generation of superoxide, without substantially influencing the ATP production. Conclusions: The results suggest that sodium nitrite may have an effect on the mitochondria; it preserves the mitochondrial structure and modifies the mitochondrial function, when administered 24 h prior to I/R. We propose that nitrite affects primary the phosphorylation system (indicated by the decreased P/E ratio), and the reduction in superoxide production would result from the subsequent suppression of the ROS producing complexes; an effect which may certainly contribute to the antiarrhythmic effect of nitrite. © 2018 Demeter-Haludka, Kovács, Petrus, Patai, Muntean, Siklós and Végh