Extracellular Histone-Induced Protein Kinase C Alpha Activation and Troponin Phosphorylation Is a Potential Mechanism of Cardiac Contractility Depression in Sepsis

Reduction in cardiac contractility is common in severe sepsis. However, the pathological mechanism is still not fully understood. Recently it has been found that circulating histones released after extensive immune cell death play important roles in multiple organ injury and disfunction, particularly in cardiomyocyte injury and contractility reduction. How extracellular histones cause cardiac contractility depression is still not fully clear. In this work, using cultured cardiomyocytes and a histone infusion mouse model, we demonstrate that clinically relevant histone concentrations cause significant increases in intracellular calcium concentrations with subsequent activation and enriched localization of calcium-dependent protein kinase C (PKC) α and βII into the myofilament fraction of cardiomyocytes in vitro and in vivo. Furthermore, histones induced dose-dependent phosphorylation of cardiac troponin I (cTnI) at the PKC-regulated phosphorylation residues (S43 and T144) in cultured cardiomyocytes, which was also confirmed in murine cardiomyocytes following intravenous histone injection. Specific inhibitors against PKCα and PKCβII revealed that histone-induced cTnI phosphorylation was mainly mediated by PKCα activation, but not PKCβII. Blocking PKCα also significantly abrogated histone-induced deterioration in peak shortening, duration and the velocity of shortening, and re-lengthening of cardiomyocyte contractility. These in vitro and in vivo findings collectively indicate a potential mechanism of histone-induced cardiomyocyte dysfunction driven by PKCα activation with subsequent enhanced phosphorylation of cTnI. These findings also indicate a potential mechanism of clinical cardiac dysfunction in sepsis and other critical illnesses with high levels of circulating histones, which holds the potential translational benefit to these patients by targeting circulating histones and downstream pathways

Extracellular Histone-Induced Protein Kinase C Alpha Activation and Troponin Phosphorylation Is a Potential Mechanism of Cardiac Contractility Depression in Sepsis

Reduction in cardiac contractility is common in severe sepsis. However, the pathological mechanism is still not fully understood. Recently it has been found that circulating histones released after extensive immune cell death play important roles in multiple organ injury and disfunction, particularly in cardiomyocyte injury and contractility reduction. How extracellular histones cause cardiac contractility depression is still not fully clear. In this work, using cultured cardiomyocytes and a histone infusion mouse model, we demonstrate that clinically relevant histone concentrations cause significant increases in intracellular calcium concentrations with subsequent activation and enriched localization of calcium-dependent protein kinase C (PKC) α and βII into the myofilament fraction of cardiomyocytes in vitro and in vivo. Furthermore, histones induced dose-dependent phosphorylation of cardiac troponin I (cTnI) at the PKC-regulated phosphorylation residues (S43 and T144) in cultured cardiomyocytes, which was also confirmed in murine cardiomyocytes following intravenous histone injection. Specific inhibitors against PKCα and PKCβII revealed that histone-induced cTnI phosphorylation was mainly mediated by PKCα activation, but not PKCβII. Blocking PKCα also significantly abrogated histone-induced deterioration in peak shortening, duration and the velocity of shortening， and re-lengthening of cardiomyocyte contractility. These in vitro and in vivo findings collectively indicate a potential mechanism of histone-induced cardiomyocyte dysfunction driven by PKCα activation with subsequent enhanced phosphorylation of cTnI. These findings also indicate a potential mechanism of clinical cardiac dysfunction in sepsis and other critical illnesses with high levels of circulating histones, which holds the potential translational benefit to these patients by targeting circulating histones and downstream pathways

Circulating histone concentrations differentially affect the predominance of left or right ventricular dysfunction in critical illness.

OBJECTIVES:Cardiac complications are common in critical illness and associated with grave consequences. In this setting, elevated circulating histone levels have been linked to cardiac injury and dysfunction in experimental models and patients with sepsis. The mechanisms underlying histone-induced cardiotoxicity and the functional consequences on left ventricle and right ventricle remain unclear. This study aims to examine dose-dependent effects of circulating histones on left ventricle and right ventricle function at clinically relevant concentrations. DESIGN: Prospective laboratory study with in vitro and in vivo investigations. SETTING:University research laboratory. SUBJECTS:Twelve-week old male C57BL/6N mice. INTERVENTIONS:Cultured cardiomyocytes were incubated with clinically relevant histone concentrations, and a histone infusion mouse model was also used with hemodynamic changes characterized by echocardiography and left ventricle/right ventricle catheter-derived variables. Circulating histones and cardiac troponin levels were obtained from serial blood samples. MEASUREMENTS AND MAIN RESULTS:IV histone infusion caused time-dependent cardiac troponin elevation to indicate cardiac injury. At moderate sublethal histone doses (30 mg/kg), left ventricular contractile dysfunction was the prominent abnormality with reduced ejection fraction and prolonged relaxation time. At high doses (≥ 60 mg/kg), pulmonary vascular obstruction induced right ventricular pressure increase and dilatation, but left ventricular end-diastolic volume improved because of reduced blood return from the lungs. Mechanistically, histones induced profound calcium influx and overload in cultured cardiomyocytes with dose-dependent detrimental effects on intracellular calcium transient amplitude, contractility, and rhythm, suggesting that histones directly affect cardiomyocyte function adversely. However, increasing histone-induced neutrophil congestion, neutrophil extracellular trap formation, and thrombosis in the pulmonary microvasculature culminated in right ventricular dysfunction. Antihistone antibody treatment abrogated histone cardiotoxicity. CONCLUSIONS:Circulating histones significantly compromise left ventricular and right ventricular function through different mechanisms that are dependent on histone concentrations. This provides a translational basis to explain and target the spectral manifestations of cardiac dysfunction in critical illness

Online and Collaborative Tools During Academic and Erasmus Studies

The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021 R. Babo et al. (eds.), Workgroups eAssessment: Planning, Implementing and Analysing Frameworks, Intelligent Systems Reference Library 199,Part of the students’ academic path is the elaboration, construction and presentation of works where there is an interaction between various elements of a group. It is common, in many countries, for students to actively participate in groups, either between classmates or even from another country, with the aim of designing, creating and presenting tasks, where information should be viewed and changed by all group members, if possible, simultaneously. A few years ago, in order to be able to carry out this kind of academic group work, it was necessary to synchronize times, days and places with the group members so that the work meeting could take place. Now, this interaction is virtually possible, first with chats, videoconferences and a variety of virtual tools and their many possibilities. This chapter starts from a literature review on studies with online collaborative work platforms to analyze, through testimonials from higher education students, if online collaborative work tools have been an asset for students during their academic career, including participation in the Erasmus Program in different countries. It was found that university students find these tools useful, despite the fact that the uses do not have the support or guidance of their educational institutions and are not accompanied by an in-depth study of these tools, which have caused problematic situations that could have been avoided

A robust computational pipeline for model-based and data-driven phenotype clustering

Precision medicine is a promising field that proposes, in contrast to a one-size-fits-all approach, the tailoring of medical decisions, treatments or products. In this context, it is crucial to introduce innovative methods to stratify a population of patients on the basis of an accurate system-level knowledge of the disease. This is particularly important in very challenging conditions, where the use of standard statistical methods can be prevented by poor data availability or by the need of oversimplifying the processes regulating a complex disease