Diabetes mellitus (DM) encompasses a multitude of secondary disorders, including heart disease. One of the most frequent and potentially life threatening disorders of DM-induced heart disease is ventricular tachycardia (VT). Here we show that toll-like receptor 2 (TLR2) and NLRP3 inflammasome activation in cardiac macrophages mediate the production of IL-1β in DM mice. IL-1β causes prolongation of the action potential duration, induces a decrease in potassium current and an increase in calcium sparks in cardiomyocytes, which are changes that underlie arrhythmia propensity. IL-1β-induced spontaneous contractile events are associated with CaMKII oxidation and phosphorylation. We further show that DM-induced arrhythmias can be successfully treated by inhibiting the IL-1β axis with either IL-1 receptor antagonist or by inhibiting the NLRP3 inflammasome. Our results establish IL-1β as an inflammatory connection between metabolic dysfunction and arrhythmias in DM.

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We evaluated the effect of chemotherapy with a sequential combined treatment of a low dose of benznidazole and allopurinol, in different schedules of administration, in experimental models of acute and chronic Trypanosoma cruzi infection. Mice were infected with Nicaragua T. cruzi isolate, a virulent parasite from an endemic area of Nicaragua, genotyped as TcI (Grosso et al. 2010). We assessed survival rate, IgG levels, histopathological studies and quantified parasitaemia. A 15% survival rate was recorded in untreated mice during the acute phase of T. cruzi infection. Allopurinol administered immediately after benznidazole treatment was able to reduce parasitaemia and attenuate tissue damage by reducing inflammation. Trypanosoma cruzi-specific antibodies also decreased in 40-50% of the treated mice. The addition of allopurinol during the chronic phase showed the highest beneficial effect, not only by reducing parasitaemia but also by lowering the degree of inflammation and fibrosis.

This study evaluated the effectiveness of low doses of benznidazole (BNZ) on continuous administration (BNZc), combined with allopurinol (ALO), in C57BL/6J and C3H/HeN mice infected with Trypanosoma cruzi Nicaragua strain and T. cruzi Sylvio-X10/4 clone. TcN-C57BL/6J was also treated with intermittent doses of BNZ (BNZit). The drug therapy started 3 months post infection (pi) in the chronic phase of mice with heart disease progression, followed-up at 6 months pi. TcN-C57BL/6J treated with BNZc was also monitored up to 12 months pi by serology and electrocardiogram. These mice showed severe electrical abnormalities, which were not observed after BNZc or BNZit. ALO only showed positive interaction with the lowest dose of BNZ. A clear parasitic effect, with significant reductions in antibody titres and parasitic loads, was achieved in all models with low doses of BNZ, and a 25% reduction of the conventional dose showed more efficacy to inhibit the development of the pathology. However, BNZ 75 showed partial efficacy in the TcSylvio-X10/4-C3H/HeN model. In our experimental designs, C57BL/6J allowed to clearly define a chronic phase, and through reproducible efficacy indicators, it can be considered a good preclinical model.

In the original version of this article the "Method" section stated an incorrect provenance for the cardiomyocytes Cor.4U. These were not derived from human iPS cells, as stated in the original article, but were derived from the human embryonic stem (hES) cell line RUES2, as has recently been determined following short tandem repeat testing carried out by Ncardia AG (formerly Axiogenesis). This does not alter the findings and interpretation of the data, as the cells are bone fide human pluripotent cell derived cardiomyocytes.

Recent advances in large scale production have made induced pluripotent stem cells (iPSCs) differentiated into cardiomyocytes feasible for use in drug discovery and safety pharmacology screening efforts. Recently developed partial or fully optical assays have suffered from either low bandwidth, or low throughput. We have developed a new high-throughput cardiac excitability assay suitable for use in multiwell assay plates using photodynamic genetically encoded actuators to control cellular membrane potential and ''molecular wire''-based fluorescent voltage sensors for high-bandwidth membrane potential monitoring. Here we present data from iPSC cardiomyoctyes (CDI icells) showing nicely resolved spontaneous activity. When known modifiers of the cardiac action potential are introduced, such as the hERG-blocking compound E-4031, the expected dose-dependent lengthening of the AP is seen, as well at higher concentrations secondary depolarizations, reminiscent of early after depolarizations (EADs) are evident. When an optogenetic actuator is introduced, the cells respond accordingly to short pacing light pulses.

Cardiac arrhythmias are one of the main causes of death worldwide. Several studies have shown that inflammation plays a key role in different cardiac diseases and Toll like receptors (TLR’s) play an important role in cardiac complications. In the present study, we investigated whether the activation of TLR4 induces cardiac electrical remodeling and arrhythmias. Also the signaling pathway involved in these phenomena was studied. Action potentials, the presence of cardiac arrhythmias and transient outward K + current (I to ) were recorded in Wistar rat’s hearts after 24 h exposure to the TLR4 agonist ultrapure Lipopolysaccharide (LPS - 1μg/ml). TLR4 stimulation in vitro promotes a cardiac electrical remodeling that leads to cardiac action potential prolongation which evokes arrhythmic events such as delayed after depolarization (DAD's) and triggered activity. The perfusion of LPS (1μg/ml) during 30 minutes did not modify I to . Conversely, after 24 h of LPS incubation I to was reduced, with no changes in the biophysical properties of the current. Major changes in Ca 2+ cycling were not observed in ventricular myocytes after 24 h exposure to LPS; however, extrasystolic activity was present in a considerable number of cells (25%). Neither the blockade of Interleulink-1 receptor-associated kinase 4 nor nuclear factor kappa B (NF-kB) prevented the LPS effect on I to . However, interferon regulatory factor 3 (IRF3) inhibition prevented the effect of TLR4 activation on I to . Activation of TLR4 induced extrasystolic activity, longer AP duration and evoked DAD's and triggered activity because of a reduction in I to . The mechanism involved is MyD88-independent and IRF3-dependent.

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