Piezo1 stretch-activated channel activity differs between murine bone marrow-derived and cardiac tissue-resident macrophages

Macrophages (MΦ) play pivotal roles in tissue homeostasis and repair. Their mechanical environment has been identified as a key modulator of various cell functions, and MΦ mechanosensitivity is likely to be critical - in particular in a rhythmically contracting organ such as the heart. Cultured MΦ, differentiated in vitro from bone marrow (MΦBM), form a popular research model. This study explores the activity of mechanosensitive ion channels (MSC) in murine MΦBM and compares it to MSC activity in MΦ enzymatically isolated from cardiac tissue (tissue-resident MΦ; MΦTR). We show that MΦBM and MΦTR have stretch-induced currents, indicating the presence of functional MSC in their plasma membrane. The current profiles in MΦBM and in MΦTR show characteristics of cation non-selective MSC such as Piezo1 or transient receptor potential channels. While Piezo1 ion channel activity is detectable in the plasma membrane of MΦBM using the patch-clamp technique, or by measuring cytosolic calcium concentration upon perfusion with the Piezo1 channel agonist Yoda1, no Piezo1 channel activity was observed in MΦTR. The selective transient receptor potential vanilloid 4 (TRPV4) channel agonist GSK1016790A induces calcium entry in MΦTR and in MΦBM. In MΦ isolated from left-ventricular scar tissue 28 days after cryoablation, stretch-induced current characteristics are not significantly different compared to non-injured control tissue, even though scarred ventricular tissue is expected to be mechanically remodelled and to contain an altered composition of pre-existing cardiac and circulation-recruited MΦ. Our data suggest that the in vitro differentiation protocols used to obtain MΦBM generate cells that differ from MΦ recruited from the circulation during tissue repair in vivo. Further investigations are needed to explore MSC identity in lineage-traced MΦ in scar tissue, and to compare mechanosensitivity of circulating monocytes with that of MΦBM. KEY POINTS: Bone marrow-derived (MΦBM) and tissue resident (MΦTR) macrophages have stretch-induced currents, indicating expression of functional mechanosensitive channels (MSC) in their plasma membrane. Stretch-activated current profiles show characteristics of cation non-selective MSC; and mRNA coding for MSC, including Piezo1 and TRPV4, is expressed in murine MΦBM and in MΦTR. Calcium entry upon pharmacological activation of TRPV4 confirms functionality of the channel in MΦTR and in MΦBM. Piezo1 ion channel activity is detected in the plasma membrane of MΦBM but not in MΦTR, suggesting that MΦBM may not be a good model to study the mechanotransduction of MΦTR. Stretch-induced currents, Piezo1 mRNA expression and response to pharmacological activation are not significantly changed in cardiac MΦ 28 days after cryoinjury compared to sham operated mice.

Atlas of cardiac endothelial cell enhancer elements linking the mineralocorticoid receptor to pathological gene expression

Endothelial cells play crucial roles in physiology and are increasingly recognized as therapeutic targets in cardiovascular disease. Here, we analyzed the regulatory landscape of cardiac endothelial cells by assessing chromatin accessibility, histone modifications, and 3D chromatin organization and confirmed the functional relevance of enhancer-promoter interactions by CRISPRi-mediated enhancer silencing. We used this dataset to explore mechanisms of transcriptional regulation in cardiovascular disease and compared six different experimental models of heart failure, hypertension, or diabetes. Enhancers that regulate gene expression in diseased endothelial cells were enriched with binding sites for a distinct set of transcription factors, including the mineralocorticoid receptor (MR), a known drug target in heart failure and hypertension. For proof of concept, we applied endothelial cell-specific MR deletion in mice to confirm MR-dependent gene expression and predicted direct MR target genes. Overall, we have compiled here a comprehensive atlas of cardiac endothelial cell enhancer elements that provides insight into the role of transcription factors in cardiovascular disease.

Molecular pharmacology of mineralocorticoid receptor antagonists: The role of co-regulators

Mineralocorticoid receptor (MR) antagonists have shown remarkable benefits in the treatment of cardiovascular disease. However, their underutilization in clinical practice may be attributed to concerns regarding the risk of hyperkalemia. An ideal selective MR modulator would inhibit the detrimental effects of MR in non-epithelial cells of the cardiovascular system while sparing its physiological function in kidney epithelial cells, thereby reducing the risk of adverse events. To address this issue, a new generation of non-steroidal MR antagonists, including esaxereneone, balcinrenone, ocedurenone, and finerenone, has been developed with distinct molecular structures and pharmacology. They share a mechanism of action that is different from the previously developed steroidal MR antagonists, leading to altered co-regulator interaction, potentially involving conformational changes of the receptor. Interfering with MR co-regulator interaction or the co-regulator itself may enable selective targeting of downstream signaling cascades and - in the long term - lead to more personalized medicine. In this review article, we summarize what is currently known about the mechanisms of action of the different MR antagonists with a focus on MR co-factor interaction and what may be inferred from this for future developments.

The heterocellular heart: identities, interactions, and implications for cardiology

The heterocellular nature of the heart has been receiving increasing attention in recent years. In addition to cardiomyocytes as the prototypical cell type of the heart, non-myocytes such as endothelial cells, fibroblasts, or immune cells are coming more into focus. The rise of single-cell sequencing technologies enables  identification of ever more subtle differences and has reignited the question of what defines a cell's identity. Here we provide an overview of the major cardiac cell types, describe their roles in homeostasis, and outline recent findings on non-canonical functions that may be of relevance for cardiology. We highlight modes of biochemical and biophysical interactions between different cardiac cell types and discuss the potential implications of the heterocellular nature of the heart for basic research and therapeutic interventions.

Decreased level of serum NT-proCNP associates with disease severity in COVID-19

BACKGROUND

C-type natriuretic peptide (CNP) is an endothelium-derived paracrine molecule with an important role in vascular homeostasis. In septic patients, the serum level of the amino-terminal propeptide of CNP (NT-proCNP) shows a strong positive correlation with inflammatory biomarkers and, if elevated, correlates with disease severity and indicates a poor outcome. It is not yet known whether NT-proCNP also correlates with the clinical outcome of patients suffering from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In the current study, we aimed to determine possible changes in the NT-proCNP levels of patients with coronavirus disease 2019 (COVID-19), with special regard to disease severity and outcome.

METHODS

In this retrospective analysis, we determined the serum level of NT-proCNP in hospitalized patients with symptoms of upper respiratory tract infection, using their blood samples taken on admission, stored in a biobank. The NT-proCNP levels of 32 SARS-CoV-2 positive and 35 SARS-CoV-2 negative patients were measured to investigate possible correlation with disease outcome. SARS-CoV-2 positive patients were then divided into two groups based on their need for intensive care unit treatment (severe and mild COVID-19).

RESULTS

The NT-proCNP was significantly different in the study groups (e.g. severe and mild COVID-19 and non-COVID-19 patients), but showed inverse changes compared to previous observations in septic patients: lowest levels were detected in critically ill COVID-19 patients, while highest levels in the non-COVID-19 group. A low level of NT-proCNP on admission was significantly associated with severe disease outcome.

CONCLUSIONS

Low-level NT-proCNP on hospital admission is associated with a severe COVID-19 disease course. The pathomechanism underlying this observation remains to be elucidated, while future studies in larger patient cohorts are necessary to confirm these observations and reveal therapeutic importance. Trial registration DRKS00026655 Registered 26. November 2021.

Therapeutic targeting of mineralocorticoid receptors in pulmonary hypertension: Insights from basic research

Pulmonary hypertension (PH) is characterized by pulmonary vascular remodeling and associated with adverse outcomes. In patients with PH, plasma aldosterone levels are elevated, suggesting that aldosterone and its receptor, the mineralocorticoid receptor (MR), play an important role in the pathophysiology of PH. The MR plays a crucial role in adverse cardiac remodeling in left heart failure. A series of experimental studies from the past few years indicate that MR activation promotes adverse cellular processes that lead to pulmonary vascular remodeling, including endothelial cell apoptosis, smooth muscle cell (SMC) proliferation, pulmonary vascular fibrosis, and inflammation. Accordingly, in vivo studies have demonstrated that pharmacological inhibition or cell-specific deletion of the MR can prevent disease progression and partially reverse established PH phenotypes. In this review, we summarize recent advances in MR signaling in pulmonary vascular remodeling based on preclinical research and discuss the potential, but also the challenges, in bringing MR antagonists (MRAs) into clinical application.

Early SARS-CoV-2 infection: Platelet-neutrophil complexes and platelet function

Background

Conflicting results have been reported on platelet activity ex vivo and responsiveness in vitro among patients with COVID-19 with or without thromboembolic complications.

Objectives

To assess platelet reactivity in patients with moderate disease at early stages of COVID-19.

Methods

We performed a prospective, descriptive analysis of 100 consecutive patients presenting with suspected SARS-CoV-2 infection at University Medical Center Freiburg during the first or second wave of the pandemic. Following polymerase chain reaction testing and compliance with study inclusion criteria, 20 SARS-CoV-2-positive and 55 SARS-CoV-2-negative patients (serving as patient controls) were enrolled. In addition, 15 healthy subjects were included. Platelet reactivity was assessed using whole-blood impedance aggregometry and flow cytometry in response to various agonists.

Results

Platelet aggregation was significantly impaired in the patients with COVID-19 compared with that in the patient controls or healthy subjects. The reduced platelet responsiveness in the patients with COVID-19 was associated with impaired activation of GPIIb/IIIa (α_IIbβ₃). In contrast, low expression of P-selectin at baseline and intact secretion upon stimulation in vitro suggest that no preactivation in vivo, leading to "exhausted" platelets, had occurred. The proportion of circulating platelet-neutrophil complexes was significantly higher in the patients with COVID-19 (mean ± SD, 41% ± 13%) than in the patient controls (18% ± 7%; 95% CI, 11.1-34.1; P = .0002) or healthy subjects (17% ± 4%; 95% CI, 13.8-33.8; P < .0001). An analysis of neutrophil adhesion receptors revealed upregulation of CD11b (α-subunit of α_Mβ₂) and CD66b (CEACAM8) but not of CD162 (PSGL-1) in the patients with COVID-19.

Conclusion

Despite reduced platelet responsiveness, platelet-neutrophil complexes are increased at early stages of moderate disease. Thus, this cellular interaction may occur during COVID-19 without preceding platelet activation.

Circulating multimeric immune complexes contribute to immunopathology in COVID-19

A dysregulated immune response with high levels of SARS-CoV-2 specific IgG antibodies characterizes patients with severe or critical COVID-19. Although a robust IgG response is considered to be protective, excessive triggering of activating Fc-gamma-receptors (FcγRs) could be detrimental and cause immunopathology. Here, we document excessive FcγRIIIA/CD16A activation in patients developing severe or critical COVID-19 but not in those with mild disease. We identify two independent ligands mediating extreme FcγRIIIA/CD16A activation. Soluble circulating IgG immune complexes (sICs) are detected in about 80% of patients with severe and critical COVID-19 at levels comparable to active systemic lupus erythematosus (SLE) disease. FcγRIIIA/CD16A activation is further enhanced by afucosylation of SARS-CoV-2 specific IgG. Utilizing cell-based reporter systems we provide evidence that sICs can be formed prior to a specific humoral response against SARS-CoV-2. Our data suggest a cycle of immunopathology driven by an early formation of sICs in predisposed patients. These findings suggest a reason for the seemingly paradoxical findings of high antiviral IgG responses and systemic immune dysregulation in severe COVID-19. The involvement of circulating sICs in the promotion of immunopathology in predisposed patients opens new possibilities for intervention strategies to mitigate critical COVID-19 progression.

During viral infections high levels of antibodies can form soluble immune complexes (sICs) with antigen and trigger Fcγ receptors (FcγR) leading to increased immunopathology. Here the authors measure FcγRs activation by sICs and consider how these may lead to excessive immunopathology during severe SARS-CoV-2 infection.

Histone Deacetylase 6 Inhibitor JS28 Prevents Pathological Gene Expression in Cardiac Myocytes

Background Epigenetic modulators have been proposed as promising new drug targets to treat adverse remodeling in heart failure. Here, we evaluated the potential of 4 epigenetic drugs, including the recently developed histone deacetylase 6 (HDAC6) inhibitor JS28, to prevent endothelin-1 induced pathological gene expression in cardiac myocytes and analyzed the chromatin binding profile of the respective inhibitor targets. Methods and Results Cardiac myocytes were differentiated and puromycin-selected from mouse embryonic stem cells and treated with endothelin-1 to induce pathological gene expression (938 differentially expressed genes, q<0.05). Dysregulation of gene expression was at least in part prevented by epigenetic inhibitors, including the pan-BRD (bromodomain-containing protein) inhibitor bromosporine (290/938 genes), the BET (bromodomain and extraterminal) inhibitor JQ1 (288/938), the broad-spectrum HDAC inhibitor suberoylanilide hydroxamic acid (227/938), and the HDAC6 inhibitor JS28 (210/938). Although the 4 compounds were similarly effective toward pathological gene expression, JS28 demonstrated the least adverse effects on physiological gene expression. Genome-wide chromatin binding profiles revealed that HDAC6 binding sites were preferentially associated with promoters of genes involved in RNA processing. In contrast, BRD4 binding was associated with genes involved in core cardiac myocyte functions, for example, myocyte contractility, and showed enrichment at enhancers and intronic regions. These distinct chromatin binding profiles of HDAC6 and BRD4 might explain the different effects of their inhibitors on pathological versus physiological gene expression. Conclusions In summary, we demonstrated, that the HDAC6 inhibitor JS28 effectively prevented the adverse effects of endothelin-1 on gene expression with minor impact on physiological gene expression in cardiac myocytes. Selective HDAC6 inhibition by JS28 appears to be a promising strategy for future evaluation in vivo and potential translation into clinical application.

Early and Rapid Identification of COVID-19 Patients with Neutralizing Type I Interferon Auto-antibodies

Purpose

Six to 19% of critically ill COVID-19 patients display circulating auto-antibodies against type I interferons (IFN-AABs). Here, we establish a clinically applicable strategy for early identification of IFN-AAB-positive patients for potential subsequent clinical interventions.

Methods

We analyzed sera of 430 COVID-19 patients from four hospitals for presence of IFN-AABs by ELISA. Binding specificity and neutralizing activity were evaluated via competition assay and virus-infection-based neutralization assay. We defined clinical parameters associated with IFN-AAB positivity. In a subgroup of critically ill patients, we analyzed effects of therapeutic plasma exchange (TPE) on the levels of IFN-AABs, SARS-CoV-2 antibodies and clinical outcome.

Results

The prevalence of neutralizing AABs to IFN-α and IFN-ω in COVID-19 patients from all cohorts was 4.2% (18/430), while being undetectable in an uninfected control cohort. Neutralizing IFN-AABs were detectable exclusively in critically affected (max. WHO score 6–8), predominantly male (83%) patients (7.6%, 18/237 for IFN-α-AABs and 4.6%, 11/237 for IFN-ω-AABs in 237 patients with critical COVID-19). IFN-AABs were present early post-symptom onset and at the peak of disease. Fever and oxygen requirement at hospital admission co-presented with neutralizing IFN-AAB positivity. IFN-AABs were associated with lower probability of survival (7.7% versus 80.9% in patients without IFN-AABs). TPE reduced levels of IFN-AABs in three of five patients and may increase survival of IFN-AAB-positive patients compared to those not undergoing TPE.

Conclusion

IFN-AABs may serve as early biomarker for the development of severe COVID-19. We propose to implement routine screening of hospitalized COVID-19 patients for rapid identification of patients with IFN-AABs who most likely benefit from specific therapies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10875-022-01252-2.

Effect of Cytokine Adsorption on Survival and Circulatory Stabilization in Patients Receiving Extracorporeal Cardiopulmonary Resuscitation

Even after the introduction of extracorporeal cardiopulmonary resuscitation (ECPR), survival after cardiac arrest remains poor. Excess release of vasoactive cytokines may be a reason for cardiovascular instability and death after ECPR. Recently, an extracorporeal cytokine adsorption device (CytoSorb) to reduce elevated levels of circulating cytokines has been introduced. So far, it remains unclear if this device may improve survival and cardiovascular stabilization after ECPR. We report data from our investigator-initiated, single-center ECPR registry. We compared 23 ECPR patients treated with cytokine adsorption with a propensity-matched cohort of ECPR patients without cytokine adsorption. We analyzed survival, lactate clearance, vasopressor need, and fluid demand in both groups and performed between-group comparisons. Survival to discharge from intensive care unit (ICU) was 17.4% (4/23) in the cytokine adsorption group and 21.7% in the control group (5/23, P > 0.99). In both groups, we observed a decrease of serum-lactate, need for vasopressors, and fluid demand during the first 72 hours after ECPR. However, in direct comparison, we did not find significant between-group differences. In this retrospective registry study employing propensity score matching, cytokine adsorption in severely ill patients after ECPR was not associated with improved ICU survival nor a decrease of lactate, fluid, or vasopressor levels. Due to small case numbers and the retrospective design of the study, our results neither disprove nor confirm a clinically relevant treatment effect of cytokine adsorption. Results from larger trials, preferably randomized-controlled trials are required to better understand the clinical benefit of cytokine adsorption after ECPR.

Approaches towards tissue-selective pharmacology of the mineralocorticoid receptor

Mineralocorticoid receptor antagonists (MRAs) are highly effective therapies for cardiovascular and renal disease. However, the widespread clinical use of currently available MRAs in cardiorenal medicine is hampered by an increased risk of hyperkalemia. The mineralocorticoid receptor (MR) is a nuclear receptor responsible for fluid and electrolyte homeostasis in epithelial tissues, whereas pathophysiological MR activation in nonepithelial tissues leads to undesirable pro-inflammatory and pro-fibrotic effects. Therefore, new strategies that selectively target the deleterious effects of MR but spare its physiological function are needed. In this review, we discuss recent pharmacological developments starting from novel non-steroidal MRAs that are now entering clinical use, such as finerenone or esaxerenone, to concepts arising from the current knowledge of the MR signaling pathway, aiming at receptor-coregulator interaction, epigenetics, or downstream effectors of MR.

Anti-platelet factor 4 antibodies causing VITT do not cross-react with SARS-CoV-2 spike protein

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is a severe adverse effect of ChAdOx1 nCoV-19 COVID-19 vaccine (Vaxzevria) and Janssen Ad26.COV2.S COVID-19 vaccine, and it is associated with unusual thrombosis. VITT is caused by anti-platelet factor 4 (PF4) antibodies activating platelets through their FcγRIIa receptors. Antibodies that activate platelets through FcγRIIa receptors have also been identified in patients with COVID-19. These findings raise concern that vaccination-induced antibodies against anti-SARS-CoV-2 spike protein cause thrombosis by cross-reacting with PF4. Immunogenic epitopes of PF4 and SARS-CoV-2 spike protein were compared using in silico prediction tools and 3D modeling. The SARS-CoV-2 spike protein and PF4 share at least 1 similar epitope. Reactivity of purified anti-PF4 antibodies from patients with VITT was tested against recombinant SARS-CoV-2 spike protein. However, none of the affinity-purified anti-PF4 antibodies from 14 patients with VITT cross-reacted with SARS-CoV-2 spike protein. Sera from 222 polymerase chain reaction-confirmed patients with COVID-19 from 5 European centers were tested by PF4-heparin enzyme-linked immunosorbent assays and PF4-dependent platelet activation assays. We found anti-PF4 antibodies in sera from 19 (8.6%) of 222 patients with COVID-19. However, only 4 showed weak to moderate platelet activation in the presence of PF4, and none of those patients developed thrombotic complications. Among 10 (4.5%) of 222 patients who had COVID-19 with thrombosis, none showed PF4-dependent platelet-activating antibodies. In conclusion, antibodies against PF4 induced by vaccination do not cross-react with the SARS-CoV-2 spike protein, indicating that the intended vaccine-induced immune response against SARS-CoV-2 spike protein is not the trigger of VITT. PF4-reactive antibodies found in patients with COVID-19 in this study were not associated with thrombotic complications.

Mineralocorticoid receptors in pulmonary hypertension and right heart failure: From molecular biology to therapeutic targeting

Pulmonary hypertension (PH) is a devastating condition characterized by pulmonary vascular remodelling, leading to progressive increase in pulmonary artery pressure and subsequent right ventricular failure. Aldosterone and the mineralocorticoid receptor (MR), a nuclear transcription factor, are key drivers of cardiovascular disease and MR antagonists are well-established in heart failure. Now, a growing body of evidence points at a detrimental role of MR in PH. Pharmacological MR blockade attenuated PH and prevented RV failure in experimental models. Mouse models with cell selective MR deletion suggest that this effect is mediated by MR in endothelial cells. While the evidence from experimental studies appears convincing, the available clinical data on MR antagonist use in patients with PH is more controversial. Integrated analysis of clinical data together with MR-dependent molecular alterations may provide insights why some patients respond to MRA treatment while others do not. Potential ways to identify MRA 'responders' include the analysis of underlying PH causes, stage of disease, or sex, as well as new biomarkers.

Cytokine adsorption in patients with severe COVID-19 pneumonia requiring extracorporeal membrane oxygenation (CYCOV): a single centre, open-label, randomised, controlled trial

Background

We sought to clarify the benefit of cytokine adsorption in patients with COVID-19 supported with venovenous extracorporeal membrane oxygenation (ECMO).

Methods

We did a single-centre, open-label, randomised, controlled trial to investigate cytokine adsorption in adult patients with severe COVID-19 pneumonia requiring ECMO. Patients with COVID-19 selected for ECMO at the Freiburg University Medical Center (Freiburg, Germany) were randomly assigned (1:1) to receive cytokine adsorption using the CytoSorb device or not. Randomisation was computer-generated, allocation was concealed by opaque, sequentially numbered sealed envelopes. The CytoSorb device was incorporated into the ECMO circuit before connection to the patient circuit, replaced every 24 h, and removed after 72 h. The primary endpoint was serum interleukin-6 (IL-6) concentration 72 h after initiation of ECMO analysed by intention to treat. Secondary endpoints included 30-day survival. The trial is registered with ClinicalTrials.gov (NCT04324528) and the German Clinical Trials Register (DRKS00021300) and is closed.

Findings

From March 29, 2020, to Dec 29, 2020, of 34 patients assessed for eligibility, 17 (50%) were treated with cytokine adsorption and 17 (50%) without. Median IL-6 decreased from 357·0 pg/mL to 98·6 pg/mL in patients randomly assigned to cytokine adsorption and from 289·0 pg/mL to 112·0 pg/mL in the control group after 72 h. One patient in each group died before 72 h. Adjusted mean log IL-6 concentrations after 72 h were 0·30 higher in the cytokine adsorption group (95% CI −0·70 to 1·30, p=0·54). Survival after 30 days was three (18%) of 17 with cytokine adsorption and 13 (76%) of 17 without cytokine adsorption (p=0·0016).

Interpretation

Early initiation of cytokine adsorption in patients with severe COVID-19 and venovenous ECMO did not reduce serum IL-6 and had a negative effect on survival. Cytokine adsorption should not be used during the first days of ECMO support in COVID-19.

Funding

None.

Eplerenone Improves Pulmonary Vascular Remodeling and Hypertension by Inhibition of the Mineralocorticoid Receptor in Endothelial Cells

[Figure: see text].

Admission blood glucose level and outcome in patients requiring venoarterial extracorporeal membrane oxygenation

Background

Patients with cardiogenic shock or cardiac arrest undergoing venoarterial extracorporeal membrane oxygenation (V-A ECMO) frequently present with blood glucose levels out of normal range. The clinical relevance of such findings in the context of V-A ECMO is unknown. We therefore investigated the prognostic relevance of blood glucose at time of cannulation for V-A ECMO.

Methods

We conducted a single-center retrospective registry study. All patients receiving V-A ECMO from October 2010 to January 2020 were included if blood glucose level at time of cannulation were documented. Patients were divided in five groups according to the initial blood glucose level ranging from hypoglycemic (< 80 mg/dl), normoglycemic (80–140 mg/dl), to mild (141-240 mg/dl), moderate (241–400 mg/dl), and severe (> 400 mg/dl) hyperglycemia, respectively. Clinical presentation, arterial blood gas analysis, and survival were compared between the groups.

Results

392 patients met inclusion criteria. Median age was 62 years (51.5–70.0), SAPS II at admission was 54 (43.5–63.0), and 108/392 (27.6%) were female. 131/392 were discharged alive (hospital survival 33.4%). At time of cannulation, survivors had higher pH, hemoglobin, calcium, bicarbonate but lower potassium and lactate levels compared to non-survivors (all p < 0.01). Outcome of patients diagnosed with particularly high (> 400 mg/dl) and low (< 80 mg/dl) blood glucose at time of V-A ECMO cannulation, respectively, was worse compared to patients with normoglycemic, mildly or moderately elevated values (p = 0.02). Glucose was independently associated with poor outcome after adjustment for other predictors of survival and persisted in all investigated subgroups.

Conclusion

Arterial blood glucose at time of V-A ECMO cannulation predicts in-hospital survival of patients with cardiac shock or after ECPR. Whether dysglycemia represents a potential therapeutic target requires further evaluation in prospective studies.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00392-021-01862-7.

Novel insights into the electrophysiology of murine cardiac macrophages: relevance of voltage-gated potassium channels

AIMS

Macrophages (MΦ), known for immunological roles such as phagocytosis and antigen presentation, have been found to electrotonically couple to cardiomyocytes (CM) of the atrio-ventricular node via Cx43, affecting cardiac conduction in isolated mouse hearts. Here, we characterise passive and active electrophysiological properties of murine cardiac resident MΦ, and model their potential electrophysiological relevance for CM.

METHODS AND RESULTS

We combined classic electrophysiological approaches with 3 D florescence imaging, RNA-sequencing, pharmacological interventions and computer simulations. We used Cx3cr1eYFP/+ mice wherein cardiac MΦ were fluorescently labelled. FACS-purified fluorescent MΦ from mouse hearts were studied by whole-cell patch-clamp. MΦ electrophysiological properties include: membrane resistance 2.2 ± 0.1 GΩ (all data mean±SEM), capacitance 18.3 ± 0.1 pF, resting membrane potential -39.6 ± 0.3 mV, and several voltage-activated, outward or inwardly-rectifying potassium currents. Using ion channel blockers (barium, TEA, 4-AP, margatoxin, XEN-D0103, DIDS), flow cytometry, immuno-staining and RNA-sequencing, we identified Kv1.3, Kv1.5 and Kir2.1 as channels contributing to observed ion currents. MΦ displayed four patterns for outward and two for inward-rectifier potassium currents. Additionally, MΦ showed surface expression of Cx43, a prerequisite for homo- and/or heterotypic electrotonic coupling. Experimental results fed into development of an original computational model to describe cardiac MΦ electrophysiology. Computer simulations to quantitatively assess plausible effects of MΦ on electrotonically coupled CM showed that MΦ can depolarise resting CM, shorten early and prolong late action potential duration, with effects depending on coupling strength and individual MΦ electrophysiological properties, in particular resting membrane potential and presence/absence of Kir2.1.

CONCLUSIONS

Our results provide a first electrophysiological characterisation of cardiac resident MΦ, and a computational model to quantitatively explore their relevance in the heterocellular heart. Future work will be focussed at distinguishing electrophysiological effects of MΦ-CM coupling on both cell types during steady-state and in patho-physiological remodelling, when immune cells change their phenotype, proliferate, and/or invade from external sources.

TRANSLATIONAL PERSPECTIVE

Cardiac tissue contains resident macrophages (MΦ) which, beyond immunological and housekeeping roles, have been found to electrotonically couple via connexins to cardiomyocytes (CM), stabilising atrio-ventricular conduction at high excitation rates. Here, we characterise structure and electrophysiological function of murine cardiac MΦ and provide a computational model to quantitatively probe the potential relevance of MΦ-CM coupling for cardiac electrophysiology. We find that MΦ are unlikely to have major electrophysiological effects in normal tissue, where they would hasten early and slow late CM-repolarisation. Further work will address potential arrhythmogenicity of MΦ in patho-physiologically remodelled tissue containing elevated MΦ-numbers, incl. non-resident recruited cells.

Serum ACE2, Angiotensin II, and Aldosterone Levels Are Unchanged in Patients With COVID-19

Background

The role of the renin-angiotensin-aldosterone system in COVID-19 is controversially discussed. SARS-CoV-2 enters host cells by binding to angiotensin-converting enzyme 2 and activity of the renin-angiotensin-aldosterone system may affect susceptibility to SARS-CoV-2 infection and outcome of patients with COVID-19.

Methods

In this prospective single-center study, we determined the serum levels of ACE-2, angiotensin II and aldosterone in patients with COVID-19 compared to control patients presenting with similar symptoms in the emergency unit.

Results

We analyzed serum samples from 24 SARS-CoV-2 positive and 61 SARS-CoV-2 negative patients. SARS-CoV-2 positive and control patients did not differ in baseline patients characteristics, symptoms and clinical presentation. Mean serum concentrations of ACE2, angiotensin II, and aldosterone did not differ between the SARS-CoV-2 positive and the control group. In line with this, serum potassium as surrogate parameter for RAAS activity and blood pressure were similar in both groups.

Conclusions

In summary, we did not find evidence for altered RAAS activity including angiotensin II, aldosterone, or potassium levels, and blood pressure in patients with COVID-19.

Hemoadsorption eliminates remdesivir from the circulation: Implications for the treatment of COVID-19

Both antiviral treatment with remdesivir and hemoadsorption using a CytoSorb^® adsorption device are applied in the treatment of severe COVID-19. The CytoSorb^® adsorber consists of porous polymer beads that adsorb a broad range of molecules, including cytokines but also several therapeutic drugs. In this study, we evaluated whether remdesivir and its main active metabolite GS-441524 would be adsorbed by CytoSorb^® . Serum containing remdesivir or GS-441524 was circulated in a custom-made system containing a CytoSorb^® device. Concentrations of remdesivir and GS-441524 before and after the adsorber were analyzed by liquid chromatography-tandem mass spectrometry. Measurements of remdesivir in the outgoing tube after the adsorber indicated almost complete removal of remdesivir by the device. In the reservoir, concentration of remdesivir showed an exponential decay and was not longer detectable after 60 mins. GS-441524 showed a similar exponential decay but, unlike remdesivir, it reached an adsorption-desorption equilibrium at ~48 µg/L. Remdesivir and its main active metabolite GS-441524 are rapidly eliminated from the perfusate by the CytoSorb^® adsorber device in vitro. This should be considered in patients for whom both therapies are indicated, and simultaneous application should be avoided. In general, plasma levels of therapeutic drugs should be closely monitored under concurrent CytoSorb^® therapy.

Serum Protein Profiling Reveals a Specific Upregulation of the Immunomodulatory Protein Progranulin in Coronavirus Disease 2019

Background

Severe courses of COVID-19 are associated with elevated levels of interleukin 6. However, there is a growing body of evidence pointing to a broad and more complex disorder of pro-inflammatory and anti-viral responses with disturbed interferon signaling in COVID-19.

Methods

In this prospective single-center registry, we included SARS-CoV-2 positive patients and patients with similar symptoms and severity of disease but negative for SARS-CoV-2 admitted to the emergency department and compared their serum protein expression profiles.

Results

Interleukin-6 abundance was similar in SARS-CoV-2 positive patients (n = 24) compared to SARS-CoV-2 negative control (n = 61). In contrast, we observed a specific upregulation of the immunomodulatory protein progranulin (GRN). High GRN abundance was associated with adverse outcomes and increased expression of interleukin-6 in COVID-19.

Conclusion

The data from this registry reveals that GRN is specifically upregulated in SARS-CoV-2 positive patients while interleukin-6 may serve as marker for disease severity. The potential of GRN as a biomarker and a possible impact of increased GRN expression on interferon signaling, virus elimination, and virus-induced lung tissue damage in COVID-19 should be further explored.

Diabetes changes gene expression but not DNA methylation in cardiac cells

BACKGROUND

Diabetes mellitus is a worldwide epidemic that causes high mortality due to cardiovascular complications, in particular heart failure. Diabetes is associated with profound pathophysiological changes in the heart. The aim of this study was to investigate the impact of diabetes on gene expression and DNA methylation in cardiac cells.

METHODS AND RESULTS

Transcriptome analysis of heart tissue from mice with streptozotocin-induced diabetes revealed only 39 genes regulated, whereas cell type-specific analysis of the diabetic heart was more sensitive and more specific than heart tissue analysis and revealed a total of 3205 differentially regulated genes in five cell types. Whole genome DNA methylation analysis with basepair resolution of distinct cardiac cell types identified highly specific DNA methylation signatures of genic and regulatory regions. Interestingly, despite marked changes in gene expression, DNA methylation remained stable in streptozotocin-induced diabetes. Integrated analysis of cell type-specific gene expression enabled us to assign the particular contribution of single cell types to the pathophysiology of the diabetic heart. Finally, analysis of gene regulation revealed ligand-receptor pairs as potential mediators of heterocellular interaction in the diabetic heart, with fibroblasts and monocytes showing the highest degree of interaction.

CONCLUSION

In summary, cell type-specific analysis reveals differentially regulated gene programs that are associated with distinct biological processes in diabetes. Interestingly, despite these changes in gene expression, cell type-specific DNA methylation signatures of genic and regulatory regions remain stable in diabetes. Analysis of heterocellular interactions in the diabetic heart suggest that the interplay between fibroblasts and monocytes is of pivotal importance.

Prolonged SARS-CoV-2 shedding and mild course of COVID-19 in a patient after recent heart transplantation

In the coronavirus disease 2019 (COVID-19) pandemic, organ transplant recipients are considered to be at high risk for an unfavorable outcome. However, in particular the role of immunosuppression in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains undetermined. Here, we present a 62-year-old male COVID-19 patient with recent heart transplantation who developed only mild symptoms, but had prolonged virus shedding, and summarize the available data on COVID-19 in cardiac allograft recipients. Initially the patient presented with a transient episode of fever and sore throat but no other symptoms, in particular no cough or dyspnea at rest. After diagnosis, immunosuppression was continued unchanged. On day 7, his temperature increased again with concurrent mild rise of C-reactive protein, IL-6, and pro-B-type natriuretic peptide levels. Hydroxychloroquine was started and continued for 7 days. While the patient no longer had clinical symptoms 20 days after initial presentation, virus culture of throat swabs on days 18 and 21 confirmed active virus replication and SARS-CoV-2 PCR remained positive on day 35 with copy numbers similar to the onset of infection. In conclusion, the immunosuppression regimen in transplant recipients with mild COVID-19-associated symptoms may be continued unchanged. However, it may contribute to delayed virus polymerase chain reaction conversion and thus possible prolonged infectivity.

Rate of venous thromboembolism in a prospective all-comers cohort with COVID-19

COVID-19 is associated with a variety of clinical complications including coagulopathy, which frequently results in venous thromboembolism (VTE). Retrospective analyses reported a markedly increased rate of VTEs in COVID-19. However, most recent studies on coagulopathy in COVID-19 were only focused on critically ill patients, and without suitable control groups. We aimed to evaluate the rate of VTEs in an all-comers cohort with suspected COVID-19 during a 30-days follow-up period. We also studied the level of D-dimers and their association with the course of disease. In our prospective single-center study (DRKS00021206, 03/30/2020), we analyzed 190 patients with suspected COVID-19 admitted to the emergency department between March and April 2020. Forty-nine patients were SARS-CoV-2 positive (25.8%). The 141 SARS-CoV-2-negative patients served as control group. After completion of a 30-days follow-up, VTE was diagnosed in 3 patients of the SARS-CoV-2-positive group (6.1%, amongst these 2 ICU cases) versus 5 patients in the SARS-CoV-2-negative group (3.5%), however the difference was not statistically significant (p = 0.427). 30-days mortality was similar in both groups (6.1% vs. 5%, p = 0.720). Disease severity correlated with the maximum level of D-dimers during follow-up in COVID-19. The rate of VTE was numerically higher in SARS-CoV-2 positive all-comers presenting with suspected COVID-19 as compared to well-matched controls suffering from similar symptoms. VTEs in the COVID-19 group predominantly occurred in ICU courses. The maximum level of D-dimers during follow-up was associated with disease severity in COVID-19, whereas the level of D-dimers at admission was not.

Bleeding Complications Drive In-Hospital Mortality of Patients with Atrial Fibrillation after Transcatheter Aortic Valve Replacement

Background Atrial fibrillation (AF) is a risk factor for poor postoperative outcome after transfemoral transcatheter aortic valve replacement (TF-TAVR). The present study analyses the outcomes after TF-TAVR in patients with or without AF and identifies independent predictors for in-hospital mortality in clinical practice.

Methods and Results Among all 57,050 patients undergoing isolated TF-TAVR between 2008 and 2016 in Germany, 44.2% of patients (n = 25,309) had AF. Patients with AF were at higher risk for unfavorable in-hospital outcome after TAVR. Including all baseline characteristics for a risk-adjusted comparison, AF was an independent risk factor for in-hospital mortality after TAVR. Among patients with AF, EuroSCORE, New York Heart Association classification class, or renal disease had only moderate effects on mortality, while the occurrence of postprocedural stroke or moderate to major bleeding substantially increased in-hospital mortality (odds ratio [OR] 3.35, 95% confidence interval [CI] 2.61–4.30, p < 0.001 and OR 3.12, 95% CI 2.68–3.62, p < 0.001). However, the strongest independent predictor for in-hospital mortality among patients with AF was severe bleeding (OR 18.00, 95% CI 15.22–21.30, p < 0.001).

Conclusion The present study demonstrates that the incidence of bleeding defines the in-hospital outcome of patients with AF after TF-TAVR. Thus, the periprocedural phase demands particular care in bleeding prevention.

Use of the CytoSorb adsorption device in MDMA intoxication: a first-in-man application and in vitro study

Background

3,4-Methylenedioxymethamphetamine (MDMA, “ecstasy”) abuse is frequent, and overdosing might cause severe and eventually lethal multi-organ failure. To date, there is no causal therapy of MDMA intoxication and removal of MDMA from the circulation might be a reasonable measure to prevent adverse courses after overdosing. We present here first-in-man experience and in vitro data supporting a potential role of an adsorber device in severe MDMA overdosing.

Results

We applied a CytoSorb adsorber device in a 21-year-old male presenting with severe MDMA intoxication and multi-organ failure, including neurological impairment, hyperpyrexia, rhabdomyolysis, oliguric renal failure, liver failure, and coagulopathy with disseminated gastrointestinal and intramuscular bleeding. Use of the adsorber device was associated with a decline in MDMA concentrations in serum from 540 to 140 ng/ml within the first 24 h, a decrease of interleukin 6 and myoglobin levels, and subsequent clinical improvement. The patient was discharged from hospital after restoration of organ function and full neurological recovery. Effective elimination of MDMA by the adsorber device could be confirmed in vitro, when the device lowered MDMA concentrations to non-detectable levels.

Conclusions

We report here first-in-man experience and in vitro data showing the capacity of a CytoSorb adsorber device for MDMA removal. Early integration of CytoSorb use may enhance the management of severe MDMA intoxication, though we cannot prove whether clinical improvement was directly related to elimination of MDMA or beneficial effects on rhabdomyolysis, hyperinflammation, or liver failure. Our findings encourage further investigation of the CytoSorb adsorber device in a prospective study and to evaluate its use for other intoxications.

Abstract 466: Myopathy Causing Bag3 P209L Protein Leads to Restrictive Cardiomyopathy Caused by Aggregate Formation and Sarcomere Disruption in Cardiomyocytes

The co-chaperone BAG3 (Bcl-2 associated athanogene 3) is strongly expressed in cross-striated muscles and plays a key role in the turnover of muscle-proteins as a member of the CASA (chaperone-assisted selected autophagy) complex. An amino acid exchange (P209L) in the human BAG3 gene, caused by a single base mutation, gives rise to a severe dominant childhood muscular dystrophy, restrictive cardiomyopathy, and respiratory insufficiency. To get deeper insights into the pathophysiological mechanisms of the disease, we generated a transgenic mouse model of the human mutation BAG3 P209L , in which a fusion protein consisting of the human BAG3 P209L and the green fluorescent protein eGFP can be conditionally overexpressed. Ubiquitous overexpression of BAG3 P209L -eGFP leads to a severe phenotype between the second and fourth week of life, including decreased body weight, skeletal muscle weakness, and heart failure. Echocardiography revealed that the BAG3 P209L -mice suffer from restrictive cardiomyopathy and Sirius-red-staining of heart tissue showed extensive fibrosis. In cardiomyocytes, isolated from hearts of transgenic mice overexpressing BAG3 wt -eGFP or BAG3 P209L -eGFP, BAG3 wt -eGFP stringently localizes to sarcomeres and intercalated discs, whereas cardiomyocytes from BAG3 P209L -eGFP mice displayed formation of BAG3 containing aggregates and disruption of sarcomeres in vivo . While BAG3 P209L -eGFP binding to á-Hsp70, Filamin C and á-HspB8 was unchanged it was less soluble than BAG3 and had a tendency to aggregate, thereby sequestering BAG3 and its clients. Depletion of the BAG3 pool leads to an impairment of CASA and accumulation of damaged proteins, causing sarcomere disintegration leading to restrictive cardiomyopathy.

Cytokine Adsorption in Critically Ill Patients Requiring ECMO Support

Systemic inflammation is a key characteristic of sepsis but also also in non-infectious conditions such as post-cardiac arrest syndrome. Cytokine adsorption and extracorporeal membrane oxygenation are emerging therapies applied in these critically ill patients, but the experience with their concurrent use is limited. We evaluated cytokine adsorption in critically ill patients requiring support with either veno-venous (vv) or veno-arterial (va) extracorporeal membrane oxygenation (ECMO) support and hypothesized that adsorber incorporation into the ECMO circuit was technically feasible and not associated with imminent risk. We analyzed data from the first six cases of a prospective single-center registry of patients undergoing veno-venous (vv) or veno-arterial (va) ECMO therapy. While in most published cases cytokine adsorbers were inserted into a hemofiltration circuit, we directly incorporated the adsorber into the ECMO circuit without interruption of continuous ECMO support. We observed no relevant side effects attributable to cytokine adsorption. Thirty-day mortality was 83% (predicted mortality 87%), indicating that the decision for adding cytokine adsorption may have been considered as an ultima ratio decision in severe cases with poor prognosis. Vasopressor or inotrope use, lactate level, and fluid balance did not change significantly when comparing pre- vs. post-cytokine adsorption values. Interestingly, the real-time course of the mentioned three surrogate parameters remained unaltered in all but two cases, regardless of cytokine removal. Beneficial effects of cytokine adsorption are plausible in two va-ECMO-treated patient, where increasing lactate began to drop after initiation of cytokine adsorption. Taken together, these data suggest that incorporation of cytokine adsorption into the management of critically ill patients requiring continued ECMO support is feasible and easy to handle. Whether cytokine removal improves clinical outcome in ECMO-treated patients should now be investigated in randomized controlled trials.

Inhibition of the cardiac myocyte mineralocorticoid receptor ameliorates doxorubicin-induced cardiotoxicity

Aim

Anthracyclines such as doxorubicin are widely used in cancer therapy but their use is limited by cardiotoxicity. Up to date there is no established strategy for the prevention of anthracyclin-induced heart failure. In this study, we evaluated the role of the cardiac myocyte mineralocorticoid receptor (MR) during doxorubicin-induced cardiotoxicity.

Methods and results

A single high-dose or repetitive low-dose doxorubicin administration lead to markedly reduced left ventricular function in mice. Treatment with the MR antagonist eplerenone prevented doxorubicin-induced left ventricular dysfunction. In order to identify the cell types and molecular mechanisms involved in this beneficial effect we used a mouse model with cell type-specific MR deletion in cardiac myocytes. Cardiac myocyte MR deletion largely reproduced the effect of pharmacological MR inhibition on doxorubicin-induced cardiotoxicity. RNAseq from isolated cardiac myocytes revealed a repressive effect of doxorubicin on gene expression which was prevented by MR deletion.

Conclusions

We show here that (i) eplerenone prevents doxorubicin-induced left ventricular dysfunction in mice, and (ii) this beneficial effect is related to inhibition of MR in cardiac myocytes. Together with present clinical trial data our findings suggest that MR antagonism may be appropriate for the prevention of doxorubicin-induced cardiotoxicity.

Endothelial cell mineralocorticoid receptors oppose VEGF-induced gene expression and angiogenesis

Aldosterone is a key factor in adverse cardiovascular remodeling by acting on the mineralocorticoid receptor (MR) in different cell types. Endothelial MR activation mediates hypertrophy, inflammation and fibrosis. Cardiovascular remodeling is often accompanied by impaired angiogenesis, which is a risk factor for the development of heart failure. In this study, we evaluated the impact of MR in endothelial cells on angiogenesis. Deoxycorticosterone acetate (DOCA)-induced hypertension was associated with capillary rarefaction in the heart of WT mice but not of mice with cell type-specific MR deletion in endothelial cells. Consistently, endothelial MR deletion prevented the inhibitory effect of aldosterone on the capillarization of subcutaneously implanted silicon tubes and on capillary sprouting from aortic ring segments. We examined MR-dependent gene expression in cultured endothelial cells by RNA-seq and identified a cluster of differentially regulated genes related to angiogenesis. We found opposing effects on gene expression when comparing activation of the mineralocorticoid receptor in ECs to treatment with vascular endothelial growth factor (VEGF), a potent activator of angiogenesis. In conclusion, we demonstrate here that activation of endothelial cell MR impaired angiogenic capacity and lead to capillary rarefaction in a mouse model of MR-driven hypertension. MR activation opposed VEGF-induced gene expression leading to the dysregulation of angiogenesis-related gene networks in endothelial cells. Our findings underscore the pivotal role of endothelial cell MR in the pathophysiology of hypertension and related heart disease.

Abstract P293: Chronic Pressure Overload Impacts Cardiac Endothelial Cell and Macrophage Gene Expression

Introduction: The heart is composed of various different cell types that show distinct differences in gene expression. Inflammation is a key driver of adverse cardiac remodeling and endothelial cells and macrophages are crucially involved in that process. Thus, the aim of this study was to investigate cell type-specific changes in gene expression in cardiac endothelial cells and macrophages after left ventricular pressure overload.

Methods and Results: Wildtype mice underwent transverse aortic constriction (TAC) to induce cardiac remodeling. After pressure overload, the number of macrophages in the heart increased about 3-fold (TAC 1755 ± 214 vs. CTRL 533 ± 76 macrophages / mg tissue, P < 0.001) as determined by flow cytometry. Lectin + endothelial cells and CD45 + CD11b + F4/80 high Ly6C low macrophages from CTRL and pressure overloaded hearts were isolated by fluorescence-assisted cell sorting. Cell type-specific gene expression was determined by RNAseq. We found 207 genes differentially expressed in cardiac endothelial cells isolated from pressure overloaded vs. CTRL hearts (n = 3-4 per group, q < 0.05). Approximately 25 % (52 genes) of these genes were highly enriched in endothelial cells vs. heart tissue (> 8-fold, q < 0.05). In cardiac macrophages, 1.359 genes were differentially expressed after pressure overload (n = 4-5 per group, q < 0.05). Bioinformatics analysis were performed to identify affected gene networks and putative key transcription factors involved in the regulation of these genes during cardiac remodeling. Integration of these datasets allowed to determine common, distinct and potentially interacting features of gene expression in both cell types.

Conclusion: Chronic pressure overload induces distinct changes in gene expression in isolated cardiac endothelial cells and macrophages. Ongoing epigenetic analysis will provide insight into mechanisms of cell type-specific transcriptional regulation in these cells during cardiac remodeling.

Cardiac Endothelial Cell Transcriptome

OBJECTIVE

Endothelial cells (ECs) are a highly specialized cell type with marked diversity between different organs or vascular beds. Cardiac ECs are an important player in cardiac physiology and pathophysiology but are not sufficiently characterized yet. Thus, the aim of the present study was to analyze the cardiac EC transcriptome.

APPROACH AND RESULTS

We applied fluorescence-assisted cell sorting to isolate pure ECs from adult mouse hearts. RNAseq revealed 1288 genes predominantly expressed in cardiac ECs versus heart tissue including several transcription factors. We found an overrepresentation of corresponding transcription factor binding motifs within the promotor region of EC-enriched genes, suggesting that they control the EC transcriptome. Cardiac ECs exhibit a distinct gene expression profile when compared with renal, cerebral, or pulmonary ECs. For example, we found the Meox2/Tcf15, Fabp4, and Cd36 signaling cascade higher expressed in cardiac ECs which is a key regulator of fatty acid uptake and involved in the development of atherosclerosis.

CONCLUSIONS

The results from this study provide a comprehensive resource of gene expression and transcriptional control in cardiac ECs. The cardiac EC transcriptome exhibits distinct differences in gene expression compared with other cardiac cell types and ECs from other organs. We identified new candidate genes that have not been investigated in ECs yet as promising targets for future evaluation.

The neuronal transcription factor NPAS4 is a strong inducer of sprouting angiogenesis and tip cell formation

RATIONALE

Regarding branching morphogenesis, neurogenesis and angiogenesis share common principle mechanisms and make use of the same molecules. Therefore, the investigation of neuronal molecules involved in vascular morphogenesis provides new possibilities for pro-angiogenic approaches in cardiovascular diseases.

OBJECTIVE

In this study, we investigated the role of the neuronal transcription factor NPAS4 in angiogenesis.

METHODS AND RESULTS

Here, we demonstrate that the neuronal transcription factor NPAS4 is expressed in endothelial cells of different origin using reverse transcription PCR and western blot analysis. To investigate how NPAS4 affects endothelial cell function, NPAS4 was overexpressed by plasmid transfection or depleted from human umbilical vein endothelial cells (HUVECs) by specific siRNAs. In vitro HUVEC sprouting assays showed that sprouting and branching of endothelial cells was enhanced by NPAS4 overexpression. Consistently, silencing of NPAS4 resulted in reduced HUVEC sprouting and branching. Mechanistically, we identified as target gene vascular endothelial adhesion molecule VE-cadherin to be involved in the pro-angiogenic function of NPAS4. In endothelial cell mosaic spheroid sprouting assays, NPAS4 was involved in tip cell formation. In vivo experiments in mouse and zebrafish confirmed our in vitro findings. NPAS4-deficient mice displayed reduced ingrowth of endothelial cells in the Matrigel plug assay. Consistent with a regulatory role of NPAS4 in endothelial cell function silencing of NPAS4 in zebrafish by specific morpholinos resulted in perturbed intersegmental vessels growth.

CONCLUSIONS

NPAS4 is expressed in endothelial cells, regulates VE-cadherin expression and regulates sprouting angiogenesis.

Ablation of biglycan attenuates cardiac hypertrophy and fibrosis after left ventricular pressure overload

AIMS

Biglycan, a small leucine-rich proteoglycan, has been shown to play an important role in stabilizing fibrotic scars after experimental myocardial infarction. However, the role of biglycan in the development and regression of cardiomyocyte hypertrophy and fibrosis during cardiac pressure overload and unloading remains elusive. Thus, the aim of the present study was to assess the effect of biglycan on cardiac remodeling in a mouse model of left ventricular pressure overload and unloading.

METHODS AND RESULTS

Left ventricular pressure overload induced by transverse aortic constriction (TAC) in mice resulted in left ventricular dysfunction, fibrosis and increased biglycan expression. Fluorescence- and magnetic-assisted sorting of cardiac cell types revealed upregulation of biglycan in the fibroblast population, but not in cardiomyocytes, endothelial cells or leukocytes after TAC. Removal of the aortic constriction (rTAC) after short-term pressure overload (3weeks) improved cardiac contractility and reversed ventricular hypertrophy but not fibrosis in wild-type (WT) mice. Biglycan ablation (KO) enhanced functional recovery but did not resolve cardiac fibrosis. After long-term TAC for 9weeks, ablation of biglycan attenuated the development of cardiac hypertrophy and fibrosis. In vitro, biglycan induced hypertrophy of neonatal rat cardiomyocytes and led to activation of a hypertrophic gene program. Putative downstream mediators of biglycan signaling include Rcan1, Abra and Tnfrsf12a. These genes were concordantly induced by TAC in WT but not in biglycan KO mice.

CONCLUSIONS

Left ventricular pressure overload induces biglycan expression in cardiac fibroblasts. Ablation of biglycan improves cardiac function and attenuates left ventricular hypertrophy and fibrosis after long-term pressure overload. In vitro biglycan induces hypertrophy of cardiomyocytes, suggesting that biglycan may act as a signaling molecule between cell types to modulate cardiac remodeling.

Abstract P300: Cardiac Ly6C high Monocyte Accumulation and Remodeling Depend on the Mineralocorticoid Receptor in Endothelial Cells

Introduction: Inflammation is a key driver for the development of cardiac fibrosis and diastolic dysfunction. Aldosterone promotes the expression of adhesion molecules and vascular inflammation. Thus, the goal of the present study was to examine the significance of endothelial MR for pressure overload induced cardiac inflammation and remodeling.

Methods and results: Mice with endothelial cell-specific deletion of the mineralocorticoid receptor (MR Cdh5Cre ) were generated using the Cre/loxP system. MR Cdh5Cre and Cre-negative littermates (MR wildtype ) underwent transverse aortic constriction (TAC, n=5-7 per group).

After two weeks of pressure overload echocardiography revealed diastolic dysfunction in MR wildtype (mitral valve E acceleration time TAC 15.7 ± 0.5 vs. sham 12.8 ± 0.4 ms, P<0.05) but not in MR Cdh5Cre mice (TAC 11.2 ± 0.6 vs. sham 12.2 ± 0.9 ms, n.s.).

Cardiac hypertrophy (ventricle weight 143.2 ± 5.2 vs. MR wildtype 167.3 ± 6.7 mg, P<0.001) and interstitial fibrosis (sirius red stained area 8.2 ± 4.7 vs. MR wildtype 13.5 ± 4.5 %, P<0.05) following TAC were attenuated in MR Cdh5Cre mice. mRNA expression of atrial natriuretic peptide ( Nppa , 2429 ± 1230 vs. MR wildtype 7051 ± 3182 copies/10 4 copies Rps29 , P<0.01) or the fibrosis marker gene collagen 1a1 ( Col1a1 , 256 ± 89 vs. MR wildtype 432 ± 165 copies/10 4 copies Rps29 , P<0.05) as determined by qRT-PCR confirmed these findings.

Cardiac leukocytes were quantitatively analyzed by fluorescence assisted cell sorting using specific antibodies. Numbers of CD45 + leukocytes were similarly increased after TAC in the hearts of both genotypes (MR Cdh5Cre 3840 ± 443 vs. MR wildtype 4051 ± 385 /mg tissue, n.s.). Subtype analysis revealed a shift towards CD45 + CD11b + F4/80 low Ly6C high monocytes vs. CD45 + CD11b + F4/80 high Ly6C low macrophages in the heart of MR wildtype (TAC 20 ± 6 vs. sham 4 ± 1 % of CD45 + CD11b + , P<0.05) but not of MR Cdh5Cre mice (TAC 6 ± 2 vs. sham 3 ± 1 % of CD45 + CD11b + , n.s.).

Conclusion: MR deletion from endothelial cells ameliorates left ventricular remodeling and diastolic dysfunction after pressure overload. The protective effect of endothelial MR deletion is associated with a shift towards less pro-inflammatory Ly6C high monocytes and more reparative Ly6C low macrophages.

Pharmacology of heart failure: From basic science to novel therapies

Chronic heart failure is one of the leading causes for hospitalization in the United States and Europe, and is accompanied by high mortality. Current pharmacological therapy of chronic heart failure with reduced ejection fraction is largely based on compounds that inhibit the detrimental action of the adrenergic and the renin-angiotensin-aldosterone systems on the heart. More than one decade after spironolactone, two novel therapeutic principles have been added to the very recently released guidelines on heart failure therapy: the HCN-channel inhibitor ivabradine and the combined angiotensin and neprilysin inhibitor valsartan/sacubitril. New compounds that are in phase II or III clinical evaluation include novel non-steroidal mineralocorticoid receptor antagonists, guanylate cyclase activators or myosine activators. A variety of novel candidate targets have been identified and the availability of gene transfer has just begun to accelerate translation from basic science to clinical application. This review provides an overview of current pharmacology and pharmacotherapy in chronic heart failure at three stages: the updated clinical guidelines of the American Heart Association and the European Society of Cardiology, new drugs which are in clinical development, and finally innovative drug targets and their mechanisms in heart failure which are emerging from preclinical studies will be discussed.

Fatal air embolism as complication of percutaneous dilatational tracheostomy on venovenous extracorporeal membrane oxygenation, two case reports

BACKGROUND

Tracheostomy is recommended in case of prolonged mechanical ventilation. Therefore, most patients with an indication for venovenous extracorporeal membrane oxygenation (ECMO) will also have an indication for tracheostomy.

CASE PRESENTATION

We report 2 cases of fatal air embolism into the ECMO system as complication of percutaneous dilatational tracheostomy. Both patients had an AVALON ELITE® bi-caval cannula implanted draining blood from the vena cava superior and inferior.

CONCLUSION

Since there is limited safety data on this specific group of patients, a routine early dilatational tracheostomy might be associated with a significant risk.

Recurrent pulseless electrical activity in a patient with coronary vasospasm and supravalvular aortic stenosis: a case report

BACKGROUND

Pulseless electrical activity cardiac arrest is associated with poor outcomes and the identification of potentially reversible reasons for cardiac arrest is fundamental.

CASE PRESENTATION

We describe the case of a 46-year-old male with the rare coincidental finding of supravalvular aortic stenosis and coronary vasospasm leading to recurrent pulseless electrical activity cardiac arrest. Extracorporeal life support was successfully applied for hemodynamic stabilization. Supravalvular aorticstenosis underwent surgical repair. The patient survived five time resuscitation and was discharged after full neurological recovery.

CONCLUSIONS

Coronary vasospasm and supravalvular aortic stenosis are rare but potentially reversible causes of pulseless electrical activity cardiac arrest. Extracorporeal life support allows accurate diagnostic and possibly therapy even of uncommon reasons for cardiac arrest.