NLRP3 inflammasome is a key driver of obesity-induced atrial arrhythmias

AIMS

Obesity, an established risk factor of atrial fibrillation (AF), is frequently associated with enhanced inflammatory response. However, whether inflammatory signaling is causally linked to AF pathogenesis in obesity remains elusive. We recently demonstrated that the constitutive activation of the 'NACHT, LRR, and PYD Domains-containing Protein 3' (NLRP3) inflammasome promotes AF susceptibility. In this study, we hypothesized that the NLRP3 inflammasome is a key driver of obesity-induced AF.

METHODS AND RESULTS

Western blotting was performed to determine the level of NLRP3 inflammasome activation in atrial tissues of obese patients, sheep, and diet-induced obese (DIO) mice. The increased body weight in patients, sheep, and mice was associated with enhanced NLRP3-inflammasome activation. To determine whether NLRP3 contributes to the obesity-induced atrial arrhythmogenesis, wild-type (WT) and NLRP3 homozygous knockout (NLRP3-/-) mice were subjected to high-fat-diet (HFD) or normal chow (NC) for 10 weeks. Relative to NC-fed WT mice, HFD-fed WT mice were more susceptible to pacing-induced AF with longer AF duration. In contrast, HFD-fed NLRP3-/- mice were resistant to pacing-induced AF. Optical mapping in DIO mice revealed an arrhythmogenic substrate characterized by abbreviated refractoriness and action potential duration (APD), two key determinants of reentry-promoting electrical remodeling. Upregulation of ultra-rapid delayed-rectifier K+-channel (Kv1.5) contributed to the shortening of atrial refractoriness. Increased profibrotic signaling and fibrosis along with abnormal Ca2+ release from sarcoplasmic reticulum (SR) accompanied atrial arrhythmogenesis in DIO mice. Conversely, genetic ablation of Nlrp3 (NLRP3-/-) in HFD-fed mice prevented the increases in Kv1.5 and the evolution of electrical remodeling, the upregulation of profibrotic genes, and abnormal SR Ca2+ release in DIO mice.

CONCLUSION

These results demonstrate that the atrial NLRP3 inflammasome is a key driver of obesity-induced atrial arrhythmogenesis and establishes a mechanistic link between obesity-induced AF and NLRP3-inflammasome activation.

Inhibition of acid sphingomyelinase by ambroxol prevents SARS-CoV-2 entry into epithelial cells

The acid sphingomyelinase/ceramide system has been shown to be important for cellular infection with at least some viruses, for instance, rhinovirus or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Functional inhibition of the acid sphingomyelinase using tricyclic antidepressants prevented infection of epithelial cells, for instance with SARS-CoV-2. The structure of ambroxol, that is, trans-4-[(2,4-dibromanilin-6-yl)-methyamino]-cyclohexanol, a mucolytic drug applied by inhalation, suggests that the drug might inhibit the acid sphingomyelinase and thereby infection with SARS-CoV-2. To test this, we used vesicular stomatitis virus pseudoviral particles presenting SARS-CoV-2 spike protein on their surface (pp-VSV-SARS-CoV-2 spike), a bona fide system for mimicking SARS-CoV-2 entry into cells. Viral uptake and formation of ceramide localization were determined by fluorescence microscopy, activity of the acid sphingomyelinase by consumption of [¹⁴C]sphingomyelin and ceramide was quantified by a kinase method. We found that entry of pp-VSV-SARS-CoV-2 spike required activation of acid sphingomyelinase and release of ceramide, events that were all prevented by pretreatment with ambroxol. We also obtained nasal epithelial cells from human volunteers prior to and after inhalation of ambroxol. Inhalation of ambroxol reduced acid sphingomyelinase activity in nasal epithelial cells and prevented pp-VSV-SARS-CoV-2 spike-induced acid sphingomyelinase activation, ceramide release, and entry of pp-VSV-SARS-CoV-2 spike ex vivo. The addition of purified acid sphingomyelinase or C16 ceramide restored entry of pp-VSV-SARS-CoV-2 spike into ambroxol-treated epithelial cells. We propose that ambroxol might be suitable for clinical studies to prevent coronavirus disease 2019.

Increased bleeding risk with phosphodiesterase-5 inhibitors after left ventricular assist device implantation

Aims

Therapy with phosphodiesterase‐5 inhibitors (PDE5Is) after left ventricular assist device (LVAD) implantation has been associated with lower mortality and device thrombosis but increased risk for post‐operative and gastrointestinal bleeding. We aimed to evaluate the impact of long‐term PDE5Is on the overall bleeding risk after LVAD implantation.

Methods and results

We retrospectively included patients who received a continuous‐flow LVAD at our site and were prescribed with long‐term oral PDE5Is after discharge from the index hospitalization. The primary endpoint was the occurrence of bleeding at 12 month follow‐up. Secondary endpoints were all‐cause death and the combination of bleeding and all‐cause death. Our analysis included 109 patients of whom 75 (69%) received long‐term PDE5Is. Mean age was 56 years, and 85% were male. At 12 months, 19 (17%) patients experienced at least one bleeding event. Patients on PDE5Is had higher bleeding rates (23% vs. 6%, P = 0.03) and more bleeding events per patient‐year (0.32 vs. 0.06, P = 0.03) compared with patients not on PDE5Is. While overall bleeding incidence was excessively higher in the PDE5I group, there were no significant differences in the incidence of major bleeding (19% vs. 6%, P = 0.08) and gastrointestinal bleeding (11% vs. 3%, P = 0.18). Kaplan–Meier analysis revealed higher cumulative incidence of bleeding for the PDE5I group (log rank = 0.04) with no difference on all‐cause death (log rank = 0.67) and the combination of bleeding and all‐cause death (log rank = 0.13). Hospitalizations for bleeding and their duration were numerically higher in the PDE5I group (0.28 vs. 0.03, P = 0.07 and 2.4 vs. 0.2, P = 0.07, respectively).

Conclusions

Phosphodiesterase‐5 inhibitor treatment after LVAD implantation is associated with increased bleeding risk after LVAD implantation. The safety of long‐term PDE5Is in LVAD patients remains unclear and needs to be further clarified in prospective studies with randomized study design.

Outcomes of left ventricular assist device implantation for advanced heart failure in critically ill patients (INTERMACS 1 and 2): A retrospective study

The use of left ventricular assist devices (LVADs) for advanced heart failure is becoming increasingly common. However, optimal timing and patient selection remain controversial. The aim of this study was to investigate outcomes of LVAD implantation for advanced heart failure in critically ill patients (INTERMACS 1 and 2). Between August 2010 and January 2020, 207 consecutive patients underwent LVAD implantation. Overall survival, major adverse events, and laboratory parameters were compared between patients in INTERMACS 1-2 (n = 107) and INTERMACS 3-5 (n = 100). Preoperative white blood cells, C-reactive protein, procalcitonin, bilirubin, alanine transaminase, and lactate dehydrogenase were all significantly higher in INTERMACS 1-2 when compared to INTERMACS 3-5 (P < .05). During hospitalization following LVAD implantation, patients in INTERMACS 1-2 were more likely to develop major infections (41.1% vs. 23.0%, P = .005), respiratory failure (57.9% vs. 25.0%, P < .001), mild (20.6% vs. 8.0%, P = .010), and moderate (31.8% vs. 7.0%, P < .001) right heart failure, and acute renal dysfunction (56.1% vs. 6.0%, P < .001). During a median follow-up of 2.00 years (interquartile range (IQR) 0.24-3.39 years), they had a higher incidence of thoracic (15.9% vs. 4.0%, P = .005) and gastrointestinal bleeding (21.5% vs. 11.0%, P = .042), as well as right heart failure (18.7% vs. 1%, P < .001). Risk of death was significantly higher in the INTERMACS 1-2 group (hazards ratio (HR) 1.64, 95% CI 1.12-2.40, P = .011). LVAD implantation in critically ill patients is associated with increased morbidity and mortality. Our results suggest that decision for LVAD should be not be delayed until INTERMACS 1 and 2 levels whenever possible.

Interferon regulatory factor 8 regulates expression of acid ceramidase and infection susceptibility in cystic fibrosis

Most patients with cystic fibrosis (CF) suffer from acute and chronic pulmonary infections with bacterial pathogens, which often determine their life quality and expectancy. Previous studies have demonstrated a downregulation of the acid ceramidase in CF epithelial cells resulting in an increase of ceramide and a decrease of sphingosine. Sphingosine kills many bacterial pathogens, and the downregulation of sphingosine seems to determine the infection susceptibility of cystic fibrosis mice and patients. It is presently unknown how deficiency of the cystic fibrosis transmembrane conductance regulator (CFTR) connects to a marked downregulation of the acid ceramidase in human and murine CF epithelial cells. Here, we employed quantitative PCR, western blot analysis, and enzyme activity measurements to study the role of IRF8 for acid ceramidase regulation. We report that genetic deficiency or functional inhibition of CFTR/Cftr results in an upregulation of interferon regulatory factor 8 (IRF8) and a concomitant downregulation of acid ceramidase expression with CF and an increase of ceramide and a reduction of sphingosine levels in tracheal and bronchial epithelial cells from both human individuals or mice. CRISPR/Cas9- or siRNA-mediated downregulation of IRF8 prevented changes of acid ceramidase, ceramide, and sphingosine in CF epithelial cells and restored resistance to Pseudomonas aeruginosa infections, which is one of the most important and common pathogens in lung infection of patients with CF. These studies indicate that CFTR deficiency causes a downregulation of acid ceramidase via upregulation of IRF8, which is a central pathway to control infection susceptibility of CF cells.

Inositol Trisphosphate Receptors and Nuclear Calcium in Atrial Fibrillation

RATIONALE

The mechanisms underlying atrial fibrillation (AF), the most common clinical arrhythmia, are poorly understood. Nucleoplasmic Ca²⁺ regulates gene expression, but the nature and significance of nuclear Ca²⁺-changes in AF are largely unknown.

OBJECTIVE

To elucidate mechanisms by which AF alters atrial-cardiomyocyte nuclear Ca²⁺ ([Ca²⁺]_Nuc) and CaMKII (Ca²⁺/calmodulin-dependent protein kinase-II)-related signaling.

METHODS AND RESULTS

Atrial cardiomyocytes were isolated from control and AF dogs (kept in AF by atrial tachypacing [600 bpm × 1 week]). [Ca²⁺]_Nuc and cytosolic [Ca²⁺] ([Ca²⁺]_Cyto) were recorded via confocal microscopy. Diastolic [Ca²⁺]_Nuc was greater than [Ca²⁺]_Cyto under control conditions, while resting [Ca²⁺]_Nuc was similar to [Ca²⁺]_Cyto; both diastolic and resting [Ca²⁺]_Nuc increased with AF. IP₃R (Inositol-trisphosphate receptor) stimulation produced larger [Ca²⁺]_Nuc increases in AF versus control cardiomyocytes, and IP₃R-blockade suppressed the AF-related [Ca²⁺]_Nuc differences. AF upregulated nuclear protein expression of IP₃R1 (IP₃R-type 1) and of phosphorylated CaMKII (immunohistochemistry and immunoblot) while decreasing the nuclear/cytosolic expression ratio for HDAC4 (histone deacetylase type-4). Isolated atrial cardiomyocytes tachypaced at 3 Hz for 24 hours mimicked AF-type [Ca²⁺]_Nuc changes and L-type calcium current decreases versus 1-Hz-paced cardiomyocytes; these changes were prevented by IP₃R knockdown with short-interfering RNA directed against IP₃R1. Nuclear/cytosolic HDAC4 expression ratio was decreased by 3-Hz pacing, while nuclear CaMKII phosphorylation was increased. Either CaMKII-inhibition (by autocamtide-2-related peptide) or IP₃R-knockdown prevented the CaMKII-hyperphosphorylation and nuclear-to-cytosolic HDAC4 shift caused by 3-Hz pacing. In human atrial cardiomyocytes from AF patients, nuclear IP₃R1-expression was significantly increased, with decreased nuclear/nonnuclear HDAC4 ratio. MicroRNA-26a was predicted to target ITPR1 (confirmed by luciferase assay) and was downregulated in AF atrial cardiomyocytes; microRNA-26a silencing reproduced AF-induced IP₃R1 upregulation and nuclear diastolic Ca²⁺-loading.

CONCLUSIONS

AF increases atrial-cardiomyocyte nucleoplasmic [Ca²⁺] by IP₃R1-upregulation involving miR-26a, leading to enhanced IP₃R1-CaMKII-HDAC4 signaling and L-type calcium current downregulation. Graphic Abstract: A graphic abstract is available for this article.

Ventricular assist device for a coronavirus disease 2019-affected heart

Coronavirus disease 2019 (COVID-19) is challenging the care for cardiovascular patients, resulting in serious consequences with increasing mortality in pre-diseased heart failure patients. In the current state of the pandemic, the physiopathology of COVID-19 affecting pre-diseased hearts and the management of terminal heart failure in COVID-19 patients remain unclear. We outline the findings of a young COVID-19 patient suffering from idiopathic cardiomyopathy who was treated for acute multi-organ failure and required cardiac surgery with implantation of a temporary right ventricular and durable left ventricular assist device (LVAD). For deeper translational insights, we used in-depth tissue analysis by electron and light sheet fluorescence microscopy revealing evidence for spatial distribution of severe acute respiratory syndrome coronavirus 2 in the heart. This indicates that in-depth analysis may represent a valuable tool in understanding indistinct clinical cases. We conclude that COVID-19 directly affects pre-diseased hearts, but the consequences can be treated successfully with LVAD implantation.

Pharmacological Inhibition of Acid Sphingomyelinase Prevents Uptake of SARS-CoV-2 by Epithelial Cells

The acid sphingomyelinase/ceramide system plays an important role in bacterial and viral infections. Here, we report that either pharmacological inhibition of acid sphingomyelinase with amitriptyline, imipramine, fluoxetine, sertraline, escitalopram, or maprotiline or genetic downregulation of the enzyme prevents infection of cultured cells or freshy isolated human nasal epithelial cells with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or vesicular stomatitis virus (VSV) pseudoviral particles (pp-VSV) presenting SARS-CoV-2 spike protein (pp-VSV-SARS-CoV-2 spike), a bona fide system mimicking SARS-CoV-2 infection. Infection activates acid sphingomyelinase and triggers a release of ceramide on the cell surface. Neutralization or consumption of surface ceramide reduces infection with pp-VSV-SARS-CoV-2 spike. Treating volunteers with a low dose of amitriptyline prevents infection of freshly isolated nasal epithelial cells with pp-VSV-SARS-CoV-2 spike. The data justify clinical studies investigating whether amitriptyline, a safe drug used clinically for almost 60 years, or other antidepressants that functionally block acid sphingomyelinase prevent SARS-CoV-2 infection.

Porcine slaughterhouse lungs for ex vivo lung perfusion - a pilot project

Ex vivo lung perfusion (EVLP) is an emerging technique for evaluation and eventual reconditioning of donor lungs. Before clinical use experiments with laboratory animals are standard. It was the aim of this study to compare lungs evaluated with EVLP from laboratory animals with slaughterhouse lungs and to investigate the potential use of a slaughterhouse lung model for ex vivo lung perfusion as an alternative for the use of laboratory animals. In a porcine model of Donation after Circulatory Determination of Death (DCDD) 16 lungs were obtained either from regular slaughterhouse animals (SL n = 8) or from laboratory animals in organ procurements (SS n = 8). Lungs were flushed and stored cold for four hours in Perfadex Plus™ and subsequently perfused ex vivo with Steen Solution™ for up to four hours. During 4 hours of EVLP lung functional parameters and activities of lactate, lactate dehydrogenase (LDH) and alkaline phosphatase (AP) in the perfusate were recorded hourly. Histological samples were taken and evaluated fur Lung Injury. Lungs showed no significant difference in oxygen capacity in between groups (∆ PO₂ averaged over 4 hours: SL 293 ± 187 mmHg SS 247 ± 199 mmHg). LDH concentration was significantly higher in slaughterhouse lungs (SL 438,5 ± 139,8 U/l, SS 258,42 ± 108,4 U/l P ≤ 0,01). We conclude that the use of slaughterhouse lungs for EVLP was feasible with no significant disadvantages compared to standard organ procurement lungs regarding lung functional outcomes. With the use of slaughterhouse lungs animal experiments in EVLP research could be successfully reduced.

Atrial Myocyte NLRP3/CaMKII Nexus Forms a Substrate for Postoperative Atrial Fibrillation

RATIONALE

Postoperative atrial fibrillation (POAF) is a common and troublesome complication of cardiac surgery. POAF is generally believed to occur when postoperative triggers act on a preexisting vulnerable substrate, but the underlying cellular and molecular mechanisms are largely unknown.

OBJECTIVE

To identify cellular POAF mechanisms in right atrial samples from patients without a history of atrial fibrillation undergoing open-heart surgery.

METHODS AND RESULTS

Multicellular action potentials, membrane ion-currents (perforated patch-clamp), or simultaneous membrane-current (ruptured patch-clamp) and [Ca²⁺]_i-recordings in atrial cardiomyocytes, along with protein-expression levels in tissue homogenates or cardiomyocytes, were assessed in 265 atrial samples from patients without or with POAF. No indices of electrical, profibrotic, or connexin remodeling were noted in POAF, but Ca²⁺-transient amplitude was smaller, although spontaneous sarcoplasmic reticulum (SR) Ca²⁺-release events and L-type Ca²⁺-current alternans occurred more frequently. CaMKII (Ca²⁺/calmodulin-dependent protein kinase-II) protein-expression, CaMKII-dependent phosphorylation of the cardiac RyR2 (ryanodine-receptor channel type-2), and RyR2 single-channel open-probability were significantly increased in POAF. SR Ca²⁺-content was unchanged in POAF despite greater SR Ca²⁺-leak, with a trend towards increased SR Ca²⁺-ATPase activity. Patients with POAF also showed stronger expression of activated components of the NLRP3 (NACHT, LRR, and PYD domains-containing protein-3)-inflammasome system in atrial whole-tissue homogenates and cardiomyocytes. Acute application of interleukin-1β caused NLRP3-signaling activation and CaMKII-dependent RyR2/phospholamban hyperphosphorylation in an immortalized mouse atrial cardiomyocyte cell-line (HL-1-cardiomyocytes) and enhanced spontaneous SR Ca²⁺-release events in both POAF cardiomyocytes and HL-1-cardiomyocytes. Computational modeling showed that RyR2 dysfunction and increased SR Ca²⁺-uptake are sufficient to reproduce the Ca²⁺-handling phenotype and indicated an increased risk of proarrhythmic delayed afterdepolarizations in POAF subjects in response to interleukin-1β.

CONCLUSIONS

Preexisting Ca²⁺-handling abnormalities and activation of NLRP3-inflammasome/CaMKII signaling are evident in atrial cardiomyocytes from patients who subsequently develop POAF. These molecular substrates sensitize cardiomyocytes to spontaneous Ca²⁺-releases and arrhythmogenic afterdepolarizations, particularly upon exposure to inflammatory mediators. Our data reveal a potential cellular and molecular substrate for this important clinical problem.

Loss of SPEG Inhibitory Phosphorylation of Ryanodine Receptor Type-2 Promotes Atrial Fibrillation

BACKGROUND

Enhanced diastolic calcium (Ca²⁺) release through ryanodine receptor type-2 (RyR2) has been implicated in atrial fibrillation (AF) promotion. Diastolic sarcoplasmic reticulum Ca²⁺ leak is caused by increased RyR2 phosphorylation by PKA (protein kinase A) or CaMKII (Ca²⁺/calmodulin-dependent kinase-II) phosphorylation, or less dephosphorylation by protein phosphatases. However, considerable controversy remains regarding the molecular mechanisms underlying altered RyR2 function in AF. We thus aimed to determine the role of SPEG (striated muscle preferentially expressed protein kinase), a novel regulator of RyR2 phosphorylation, in AF pathogenesis.

METHODS

Western blotting was performed with right atrial biopsies from patients with paroxysmal AF. SPEG atrial knockout mice were generated using adeno-associated virus 9. In mice, AF inducibility was determined using intracardiac programmed electric stimulation, and diastolic Ca²⁺ leak in atrial cardiomyocytes was assessed using confocal Ca²⁺ imaging. Phosphoproteomics studies and Western blotting were used to measure RyR2 phosphorylation. To test the effects of RyR2-S2367 phosphorylation, knockin mice with an inactivated S2367 phosphorylation site (S2367A) and a constitutively activated S2367 residue (S2367D) were generated by using CRISPR-Cas9.

RESULTS

Western blotting revealed decreased SPEG protein levels in atrial biopsies from patients with paroxysmal AF in comparison with patients in sinus rhythm. SPEG atrial-specific knockout mice exhibited increased susceptibility to pacing-induced AF by programmed electric stimulation and enhanced Ca²⁺ spark frequency in atrial cardiomyocytes with Ca²⁺ imaging, establishing a causal role for decreased SPEG in AF pathogenesis. Phosphoproteomics in hearts from SPEG cardiomyocyte knockout mice identified RyR2-S2367 as a novel kinase substrate of SPEG. Western blotting demonstrated that RyR2-S2367 phosphorylation was also decreased in patients with paroxysmal AF. RyR2-S2367A mice exhibited an increased susceptibility to pacing-induced AF, and aberrant atrial sarcoplasmic reticulum Ca²⁺ leak, as well. In contrast, RyR2-S2367D mice were resistant to pacing-induced AF.

CONCLUSIONS

Unlike other kinases (PKA, CaMKII) that increase RyR2 activity, SPEG phosphorylation reduces RyR2-mediated sarcoplasmic reticulum Ca²⁺ release. Reduced SPEG levels and RyR2-S2367 phosphorylation typified patients with paroxysmal AF. Studies in S2367 knockin mouse models showed a causal relationship between reduced S2367 phosphorylation and AF susceptibility. Thus, modulating SPEG activity and phosphorylation levels of the novel S2367 site on RyR2 may represent a novel target for AF treatment.

Off-label use of pulmonary vasodilators after left ventricular assist device implantation: Calling in the evidence

Left ventricular assist devices (LVAD) are increasingly implanted in advanced heart failure patients to improve survival and quality of life either as a bridge to transplant, bridge to recovery or as destination therapy. LVAD therapy is often accompanied by a profound lowering of pulmonary artery pressure due to mechanical unloading of the left ventricle. Persistent pulmonary hypertension (PH) after LVAD implantation increases the risk of right ventricular failure (RVF). In this context pulmonary vasodilators have been implemented: a) as a strategy to reduce afterload and wean patients with RVF from inotropes in the early postoperative period, b) as long-term therapy aiming to optimize right heart hemodynamics and prevent late RVF and c) in order to lower persistently elevated pulmonary artery pressure (PAP) and pulmonary vascular resistance (PVR) after LVAD and enable candidacy for heart transplantation. However, considerable uncertainty exists regarding the risks and benefits of these strategies and practices vary widely among institutions. This article provides an overview of the available evidence and existing recommendations regarding the use of pulmonary vasodilators in LVAD recipients.

Impact of normothermic ex vivo lung perfusion on early post-transplantation cytomegalovirus infection

Background

The low acceptance rates in lung transplantation underline the importance to use every potential transplantable organ. With the use of normothermic ex vivo lung perfusion (EVLP) there is a potential to use more donor lungs for transplantation. Aim of this study was to evaluate if EVLP has an effect on cytomegalovirus (CMV) infection after lung transplantation.

Methods

Between May 2016 and October 2018, 57 lung transplants were performed. Out of these 21 extended criteria lungs were evaluated by EVLP and 16 transplanted. In a retrospective study, results of EVLP treated lungs were compared with lungs after cold storage preservation (CSP). Donor/recipient CMV IgG status and seroconversion rate was examined.

Results

Donors were CMV IgG+ in EVLP 69% and CSP 61% (n.s.). Best pO₂ on procurement at FiO₂ 1.0 was in EVLP 278±76 versus CSP 413±96 mmHg (P≤0.05). Recipients were CMV IgG+ in EVLP 38% and CSP 63% (P<0.07). CMV seroconversion: EVLP 12%, CSP 20% (P<0.05), in the CSP group in 5% recipients with more than 1,000 copies/mL were diagnosed by PCR and treated for CMV infection. Procalcitonin (PCT) levels from day 1 to day 5 were significantly lower for CSP group (P<0.05). 30-day mortality was 12% for EVLP recipients.

Conclusions

Normothermic EVLP did not influence CMV infection rate, however early PCT levels were higher in EVLP group. Short-term results were comparable to standard lung transplantation.

Sex is no determinant of cardioprotection by ischemic preconditioning in rats, but ischemic/reperfused tissue mass is for remote ischemic preconditioning

We determined the impact of sex on the magnitude of cardioprotection by local and remote ischemic preconditioning (IPC and RIPC) and of ischemic/reperfused peripheral tissue mass on protection by RIPC. Hearts of female and male Lewis rats were excised, perfused with buffer, and underwent either IPC by 3 × 5/5 min global zero‐flow ischemia/reperfusion (GI/R) or time‐matched perfusion (TP) before 30/120 min GI/R. In a second approach, anesthetized female and male Lewis rats underwent RIPC, 3 × 5/5 min ischemia/reperfusion of one or both hindlimbs (1‐RIPC or 2‐RIPC), or placebo. Thirty minutes after the RIPC/placebo protocol, hearts were excised and subjected to GI/R. In female and male hearts, infarct size was less with IPC than with TP before GI/R (IPC+GI/R_female: 12 ± 5%; IPC+GI/R_male: 12 ± 7% vs. TP+GI/R_female: 33 ± 5%; TP+GI/R_male: 37 ± 7%, P < 0.001). With 2‐RIPC, infarct size was less than with 1‐RIPC in female and male rat hearts, respectively (2‐RIPC+GI/R_female: 15 ± 5% vs. 1‐RIPC+GI/R_female: 22 ± 7%, P = 0.026 and 2‐RIPC+GI/R_male: 16 ± 5% vs. 1‐RIPC+GI/R_male: 22 ± 8%, P = 0.016). Infarct size after the placebo protocol and GI/R was not different between female and male hearts (36 ± 8% vs. 34 ± 5%). Sex is no determinant of IPC‐ and RIPC‐induced cardioprotection in isolated Lewis rat hearts. RIPC‐induced cardioprotection is greater with greater mass of ischemic/reperfused peripheral tissue.

Acid sphingomyelinase regulates TH 2 cytokine release and bronchial asthma

BACKGROUND

Allergic diseases and especially allergic asthma are widespread diseases with high prevalence in childhood, but also in adults. Acid sphingomyelinase (ASM) is a key regulator of the sphingolipid pathway. Previous studies defined the association of ASM with the pathogenesis of T_H 1-directed lung diseases like cystic fibrosis and acute lung injury. Here, we define the role of ASM in T_H 2-regulated allergic bronchial asthma.

METHODS

To determine the role of Asm under baseline conditions, wild-type (WT) and Asm^-/- mice were ventilated with a flexiVent setup and bronchial hyperresponsiveness was determined using acetylcholine. Flow cytometry and cytokine measurements in bronchoalveolar lavage fluid and lung tissue were followed by in vitro T_H 2 differentiations with cells from WT and Asm^-/- mice and blockade of Asm with amitriptyline. As proof of principle, we conducted an ovalbumin-induced model of asthma in WT- and Asm^-/-  mice.

RESULTS

At baseline, Asm^-/- mice showed better lung mechanics, but unaltered bronchial hyperresponsiveness. Higher numbers of Asm^-/- T cells in bronchoalveolar lavage fluid released lower levels of IL-4 and IL-5, and these results were paralleled by decreased production of typical T_H 2 cytokines in Asm^-/- T lymphocytes in vitro. This phenotype could be imitated by incubation of T cells with amitriptyline. In the ovalbumin asthma model, Asm^-/- animals were protected from high disease activity and showed better lung functions and lower levels of eosinophils and T_H 2 cytokines.

CONCLUSION

Asm deficiency could induce higher numbers of T_H 2 cells in the lung, but those cells release decreased T_H 2 cytokine levels. Hereby, Asm^-/- animals are protected from bronchial asthma, which possibly offers novel therapeutic strategies, for example, with ASM blockade.

Use of modified Custodiol-N as perfusion solution in ex vivo lung perfusion

OBJECTIVES

Ex vivo Lung Perfusion (EVLP) is a promising tool to increase the donor pool for lung transplantation. Custodiol-N solution was originally designed for organ preservation during cold static preservation (CSP) and was successfully used for machine perfusion in kidneys. It was the aim of this study to compare the lung functional outcomes after 4 hours of EVLP using modified Custodiol-N or STEEN Solution^TM as perfusion solution.

METHODS

In a porcine DCD model, lungs were perfused either with STEEN Solution^TM (Standard SS, n=8) or modified Custodiol-N with added 1.1 g/l glucose monohydrate and 50 g/l dextran 40 (CD, n=8). For a third group 7 g/l albumin was supplemented to modified Custodiol-N (CDA, n=8). During four hours of EVLP pulmonary gas exchange and activities of lactate dehydrogenase (LDH) and alkaline phosphatase (AP) in perfusate were recorded.

RESULTS

Lungs that underwent EVLP with modified Custodiol-N showed significantly higher oxygen capacity (ΔpO₂ averaged over four hours of EVLP: SS: 236.28 ± 47.26 mmHg, CD: 402.79 ± 30.33 mmHg, CDA: 414.86 ± 9.77 mmHg) than lungs perfused with STEEN Solution^TM. The addition of albumin did not have a significant effect on lung function but these lungs showed lower wet/dry ratio.

CONCLUSION

In a porcine DCD model of 9 hours CSP followed by four hours of EVLP the use of modified Custodiol-N as perfusion solution was feasible and associated with higher oxygen capacity than STEEN Solution^TM. The addition of albumin seems to further stabilize lung function.

Safety and efficacy of a novel algorithm to guide decision-making in high-risk interventional coronary procedures

BACKGROUND

Patients with severe coronary artery disease (CAD), comorbidities, or impaired hemodynamics are at risk during percutaneous coronary interventions. The aim of the study was to investigate the safety and efficacy of a novel risk-stratification algorithm for high-risk coronary procedures.

METHODS AND RESULTS

We prospectively screened 1189 patients with CAD requiring revascularization (period 07/2017-06/2018). The algorithm was designed to select high-risk procedures. Patients with elevated risk (n = 150) were classified into 3 risk groups (high-risk intervention [HRI] I-III) and procedural management was adjusted according to HRI group. Overall, 55 patients were categorized as HRI I, 52 as HRI II, and 43 as HRI III. With increasing HRI-level, SYNTAX score increased (HRI I:15 ± 5% vs. HRI II:24 ± 8% vs. HRI III:34 ± 7%; p < 0.001), and ejection-fraction decreased (HRI I:48 ± 10% vs. HRI II:49 ± 10% vs. HRI III:40 ± 11%; p < 0.001). The primary endpoint (hemodynamic compromise requiring mechanical circulatory support [MCS] [HRI I/II], unsuccessful weaning from MCS in the catheterization laboratory[HRI III], or periprocedural death[HRI I-III]) occurred in no case. The secondary endpoint of hemodynamic deterioration occurred in 26% (n = 39) but did not result in hemodynamic instability due to the risk-adjusted procedural management. The composite endpoint of in-hospital major adverse cardiac and cerebrovascular events (death, new myocardial infarction, cerebrovascular accident) occurred in 4 patients (3%).

CONCLUSIONS

The novel algorithm is a safe team-based stratification method for the identification and management of patients undergoing high-risk coronary interventions.