Infection by Trypanosoma cruzi enhances anion conductance in rat neonatal ventricular cardiomyocytes

Trade-off between photosymbiosis and innate immunity influences cnidarian's response to pathogenic bacteria

Mutualistic relationships with photosynthetic organisms are common in cnidarians, which form an intracellular symbiosis with dinoflagellates in the family Symbiodiniaceae. The establishment and maintenance of these symbionts are associated with the suppression of key host immune factors. Because of this, there are potential trade-offs between the nutrition that cnidarian hosts gain from their symbionts and their ability to successfully defend themselves from pathogens. To investigate these potential trade-offs, we utilized the facultatively symbiotic polyps of the upside-down jellyfish Cassiopea xamachana and exposed aposymbiotic and symbiotic polyps to the pathogen Serratia marcescens. Symbiotic polyps had a lower probability of survival following S. marcescens exposure. Gene expression analyses 24 hours following pathogen exposure indicate that symbiotic animals mounted a more damaging immune response, with higher levels of inflammation and oxidative stress likely resulting in more severe disruptions to cellular homeostasis. Underlying this more damaging immune response may be differences in constitutive and pathogen-induced expression of immune transcription factors between aposymbiotic and symbiotic polyps rather than broadscale immune suppression during symbiosis. Our findings indicate that in facultatively symbiotic polyps, hosting symbionts limits C. xamachana's ability to survive pathogen exposure, indicating a trade-off between symbiosis and immunity that has potential implications for coral disease research.

Molecular Remodeling of Cardiac Sinus Node Associated with Acute Chagas Disease Myocarditis

Chagas disease principally affects Latin-American people, but it currently has worldwide distribution due to migration. Death among those with Chagas disease can occur suddenly and without warning, even in those who may not have evidence of clinical or structural cardiac disease and who are younger than 60 years old. HCN4 channels, one of the principal elements responsible for pacemaker currents, are associated with cardiac fetal reprogramming and supraventricular and ventricular arrhythmias, but their role in chagasic arrhythmias is not clear. We found that a single-dose administration of ivabradine, which blocks HCN4, caused QTc and QRS enlargement and an increase in P-wave amplitude and was associated with ventricular and supraventricular arrhythmias in mice challenged with isoproterenol, a chronotropic/ionotropic positive agent. Continuous treatment with ivabradine did not alter the QTc interval, but P-wave morphology was deeply modified, generating supraventricular arrhythmias. In addition, we found that repolarization parameters improved with ivabradine treatment. These effects could have been caused by the high HCN4 expression observed in auricular and ventricular tissue in infected mice. Thus, we suggest, for the first time, that molecular remodeling by overexpression of HCN4 channels may be related to supraventricular arrhythmias in acute Chagas disease, causing ivabradine over-response. Thus, ivabradine treatment should be administered with caution, while HCN4 overexpression may be an indicator of heart failure and/or sudden death risk.