Chagas Disease (CD) is one of the leading causes of heart failure and sudden death in Latin America. Treatments with antioxidants have provided promising alternatives to ameliorate CD. However, the specific roles of major reactive oxygen species (ROS) sources, including NADPH-oxidase 2 (NOX2), mitochondrial-derived ROS and nitric oxide (NO) in the progression or resolution of CD are yet to be elucidated. We used C57BL/6 (WT) and a gp91 PHOX knockout mice (PHOX-/-), lacking functional NOX2, to investigate the effects of ablation of NOX2-derived ROS production on the outcome of acute chagasic cardiomyopathy. Infected PHOX-/cardiomyocytes displayed an overall pro-arrhythmic phenotype, notably with higher arrhythmia incidence on ECG that was followed by higher number of early afterdepolarizations (EAD) and 2.5-fold increase in action potential (AP) duration alternans, compared to AP from infected WT mice. Furthermore, infected PHOX-/cardiomyocytes display increased diastolic [Ca 2+ ], aberrant Ca 2+ transient and reduced Ca 2+ transient amplitude. Cardiomyocyte contraction is reduced in infected WT and PHOX-/mice, to a similar extent. Nevertheless, only infected PHOX-/isolated cardiomyocytes displayed significant increase in non-triggered extra contractions (appearing in~75% of cells). Electro-mechanical remodeling of infected PHOX-/cardiomyocytes is associated with increase in NO and mitochondria-derived ROS production. Notably, EADs, AP duration alternans and in vivo arrhythmias were reverted by pre-incubation with nitric oxide synthase inhibitor L-NAME. Overall our data show for the first time that lack of NOX2-derived ROS promoted a pro-arrhythmic phenotype in the heart, in which the crosstalk between ROS and NO could play an important role in regulating cardiomyocyte electro-mechanical function during acute CD. Future studies designed to evaluate the potential role of NOX2-derived ROS in the chronic phase of CD could open new and more specific therapeutic strategies to treat CD and prevent deaths due to heart complications.

Involuntary choreiform movements are clinical hallmark of Huntington's disease, an autosomal dominant neurodegenerative disorder caused by an increased number of CAG trinucleotide repeats in the huntingtin gene. Involuntary movements start with an impairment of facial muscles and then affect trunk and limbs muscles. Huntington's disease symptoms are caused by changes in cortex and striatum neurons induced by mutated huntingtin protein. However, little is known about the impact of this abnormal protein in spinal cord motoneurons that control movement. Therefore, in this study we evaluated abnormalities in the motor unit (spinal cervical motoneurons, motor axons, neuromuscular junctions and muscle) in a mouse model for Huntington's disease (BACHD). Using light, fluorescence, confocal, and electron microscopy, we showed significant changes such as muscle fibers atrophy, fragmentation of neuromuscular junctions, axonal alterations, and motoneurons death in BACHD mice. Noteworthy, the surviving motoneurons from BACHD spinal cords were smaller than WT. We suggest that this loss of larger putative motoneurons is accompanied by a decrease in the expression of fast glycolytic muscle fibers in this model for Huntington's disease. These observations show spinal cord motoneurons loss in BACHD that might help to understand neuromuscular changes in Huntington's disease.

What is the central question of this study? Recently, there have been many studies exploring the biological effects of angiotensin-(1-7), which has been proved to have cardioprotective actions. However, the effects of this peptide on cardiac arrhythmias in vivo and details regarding its mechanism of action are still undetermined. What is the main finding and its importance? We investigated protective effects of angiotensin-(1-7) on cardiac arrhythmias in vivo, which were not properly explored in terms of cellular mechanisms. To verify effects of angiotensin-(1-7), we used different but complementary experimental approaches. Our data provide new evidence on the cellular mechanism and an in vivo demonstration of the acute antiarrhythmic effect of angiotensin-(1-7). Angiotensin-(1-7) [Ang-(1-7)] has been proved to have cardioprotective effects. However, the effects of this peptide on cardiac arrhythmias in vivo and details regarding its mechanism of action are still undetermined. The aim of this study was to investigate the protective effects of Ang-(1-7) against cardiac arrhythmias, its in vivo effects and cellular mechanism of action. We analysed the ECG upon inducement of arrhythmias in vivo in rats using a combination of halothane and adrenaline. To analyse the effects of Ang-(1-7) on cells, fresh mouse ventricular cardiomyocytes were isolated. The cardiomyocytes were superfused with a solution containing halothane and isoprenaline as a model to induce arrhythmias and used in three different approaches, namely a contractility assay, patch-clamp technique and confocal microscopy. The in vivo ECG showed that the injection of Ang-(1-7) (4 nm i.v.) significantly reduced cardiac arrhythmias [before, 49 ± 43 arrhythmic events versus after Ang-(1-7), 16 ± 14 arrhythmic events]. This effect was blocked by injection of A-779 and l-NAME, without changes in haemodynamic parameters. In addition, contractility experiments showed that Ang-(1-7) significantly decreased the number of arrhythmic events without changing the fractional shortening. This protection was associated with a reduction of the action potential repolarization and membrane hyperpolarization. Moreover, Ang-(1-7) decreased the number of calcium waves without any changes in the amplitude of the calcium transient, despite a significant reduction in the decay rate. Our data provide new evidence on the cellular mechanism together with an in vivo demonstration of the antiarrhythmic effects of Ang-(1-7).

Huntington's disease (HD) is a neurodegenerative genetic disorder. Although described as a brain pathology, there is evidence suggesting that defects in other systems can contribute to disease progression. In line with this, cardiovascular defects are a major cause of death in HD. To date, relatively little is known about the peripheral abnormalities associated with the disease. Here, we applied a range of assays to evaluate cardiac electro‐mechanical properties in vivo, using a previously characterized mouse model of HD (BACHD), and in vitro, using cardiomyocytes isolated from the same mice. We observed conduction disturbances including QT interval prolongation in BACHD mice, indicative of cardiac dysfunction. Cardiomyocytes from these mice demonstrated cellular electro‐mechanical abnormalities, including a prolonged action potential, arrhythmic contractions, and relaxation disturbances. Cellular arrhythmia was accompanied by an increase in calcium waves and increased Ca2+/calmodulin‐dependent protein kinase II activity, suggesting that disruption of calcium homeostasis plays a key part. We also described structural abnormalities in the mitochondria of BACHD‐derived cardiomyocytes, indicative of oxidative stress. Consistent with this, imbalances in superoxide dismutase and glutathione peroxidase activities were detected. Our data provide an in vivo demonstration of cardiac abnormalities in HD together with new insights into the cellular mechanistic basis, providing a possible explanation for the higher cardiovascular risk in HD.

Chagasic cardiomyopathy (CCC) is one of the main causes of heart failure and sudden death in Latin America. To date, there is no available medication to prevent or reverse the onset of cardiac symptoms. CCC occurs in a scenario of disrupted calcium dynamics and enhanced oxidative stress, which combined, may favor the hyper activation of calcium/calmodulin (Ca 2+ /CaM)-calcium/calmodulin-dependent protein kinase II (CaMKII) (Ca 2+ /CaM-CaMKII) pathway, which is fundamental for heart physiology and it is implicated in other cardiac diseases. Here, we evaluated the association between Ca 2+ /CaM-CaMKII in the electro-mechanical (dys)function of the heart in the early stage of chronic experimental Trypanosoma cruzi infection. We observed that in vitro and ex vivo inhibition of Ca 2+ /CaM-CaMKII reversed the arrhythmic profile of isolated hearts and isolated left-ventricles cardiomyocytes. The benefits of the limited Ca 2+ /CaM-CaMKII activation to cardiomyocytes' electrical properties are partially related to the restoration of Ca 2+ dynamics in a damaged cellular environment created after T. cruzi infection. Moreover, Ca 2+ /CaM-CaMKII inhibition prevented the onset of arrhythmic contractions on isolated heart preparations of chagasic mice and restored the responsiveness to the increase in the left-ventricle pre-load. Taken together, our data provide the first experimental evidence for the potential of targeting Ca 2+ /CaM-CaMKII pathway as a novel therapeutic target to treat CCC.

Huntington's disease (HD) is a neurodegenerative disease caused by a CAG repeat expansion in the gene encoding the huntingtin protein (HTT). This expansion leads to the formation of mutant huntingtin protein (mHTT) that is expressed in many body tissue cells. The mHTT interacts with several molecular pathways within different cell types, affecting the regulation of the immune system cells. It is still very limited the understanding of the immune changes in peripheral tissues in HD. Herein, we investigated the levels of inflammatory and regulatory cytokines in peripheral organs (i.e. kidney, heart, liver and spleen) of the 12-month-old BACHD model of HD. This robust murine model closely resembles the human disease. We found significant changes in cytokine levels in all organs analyzed. Increased levels of IL-6 were found in the kidney, while levels of IL-6 and IL-12p70 were increased in the heart of BACHD mice in comparison with wild-type (WT) animals. In the liver, we observed enhanced IL-12p70 and TNF-α levels. In the spleen, there was an increase in the levels of IL-4 and a decrease in the levels of IL-5 and IL-6 in BACHD compared to WT. Our findings provide the first evidence that the BACHD model also exhibits immune changes in peripheral organs, opening an avenue for the investigation of the potential role played by peripheral inflammatory response in HD. Further studies are needed to systematically address the mechanisms and pathways underlying immune signaling in peripheral organs in HD.

Background Chagas disease (CD) is a neglected disease that induces heart failure and arrhythmias in approximately 30% of patients during the chronic phase of the disease. Despite major efforts to understand the cellular pathophysiology of CD there are still relevant open questions to be addressed. In the present investigation we aimed to evaluate the contribution of the Na+/Ca2+ exchanger (NCX) in the electrical remodeling of isolated cardiomyocytes from an experimental murine model of chronic CD. Methodology/Principal findings Male C57BL/6 mice were infected with Colombian strain of Trypanosoma cruzi. Experiments were conducted in isolated left ventricular cardiomyocytes from mice 180–200 days post-infection and with age-matched controls. Whole-cell patch-clamp technique was used to measure cellular excitability and Real-time PCR for parasite detection. In current-clamp experiments, we found that action potential (AP) repolarization was prolonged in cardiomyocytes from chagasic mice paced at 0.2 and 1 Hz. After-depolarizations, both subthreshold and with spontaneous APs events, were more evident in the chronic phase of experimental CD. In voltage-clamp experiments, pause-induced spontaneous activity with the presence of diastolic transient inward current was enhanced in chagasic cardiomyocytes. AP waveform disturbances and diastolic transient inward current were largely attenuated in chagasic cardiomyocytes exposed to Ni2+ or SEA0400. Conclusions/Significance The present study is the first to describe NCX as a cellular arrhythmogenic substrate in chagasic cardiomyocytes. Our data suggest that NCX could be relevant to further understanding of arrhythmogenesis in the chronic phase of experimental CD and blocking NCX may be a new therapeutic strategy to treat arrhythmias in this condition.

Diminazene aceturate (DIZE) is an anti‐protozoan compound that has been previously reported to increase the activity of the angiotensin‐converting enzyme 2 (ACE2) and thus increase Angiotensin‐(1‐7) production, leading to cardioprotection against post‐myocardial infarction dysfunction and structural remodelling. Moreover, DIZE is able to ameliorate morpho‐functional changes after myocardial infarction by enhancing ACE2 activity, thus increasing Angiotensin‐(1‐7) production (a benefic peptide of the renin‐angiotensin system). However, despite the improvement in cardiac function/structure, little is known about DIZE effects on arrhythmia suppression, contraction/excitable aspects of the heart and importantly its mechanisms of action. Thus, our aim was to test the acute effect of DIZE cardioprotection at the specific level of potential antiarrhythmic effects and modulation in excitation‐contraction coupling. For this, we performed in vitro and in vivo techniques for arrhythmia induction followed by an acute administration of DIZE. For the first time, we described that DIZE can reduce arrhythmias which is explained by modulation of cardiomyocyte contraction and excitability. Such effects were independent of Mas receptor and nitric oxide release. Development of a new DIZE‐based approach to ameliorate myocardial contractile and electrophysiological dysfunction requires further investigation; however, DIZE may provide the basis for a future beneficial therapy to post‐myocardial infarction patients.