Clinical Development of Sphingosine as Anti-Bacterial Drug: Inhalation of Sphingosine in Mini Pigs has no Adverse Side Effects

BACKGROUND/AIMS

Pulmonary infections with Pseudomonas aeruginosa (P. aeruginosa) or Staphylococcus aureus (S. aureus) are of utmost clinical relevance in patients with cystic fibrosis, chronic obstructive pulmonary disease, after trauma and burn, upon ventilation or in immuno-compromised patients. Many P. aeruginosa and S. aureus strains are resistant to many known antibiotics and it is very difficult or often impossible to eradicate the pathogens in patient´s lungs. We have recently shown that the sphingoid base sphingosine very efficiently kills many pathogens, including for instance P. aeruginosa, S. aureus or Acinetobacter baumannii, in vitro. In vivo experiments of our group on cystic fibrosis mice indicated that inhalation of sphingosine prevents or eliminates existing acute or chronic pneumonia with P. aeruginosa or S. aureus in these mice. We also demonstrated that sphingosine is safe to use for inhalation up to high doses, at least in mice. To facilitate development of sphingosine to an anti-bactericidal drug that can be used in humans for inhalation, safety data on non-rodents, larger animals are absolutely required.

METHODS

Here, we inhaled mini pigs with increasing doses of sphingosine for 10 days and analyzed the uptake of sphingosine into epithelial cells of bronchi as well as into the trachea and lung and the systemic circulation. Moreover, we measured the generation of ceramide and sphingosine 1-phosphate that potentially mediate inflammation, the influx of leukocytes, epithelial cell death and disruption of the epithelial cell barrier.

RESULTS

We demonstrate that inhalation of sphingosine results in increased levels of sphingosine in the luminal membrane of bronchi and the trachea, but not in systemic accumulation. Inhaled sphingosine had no side effects up to very high doses.

CONCLUSION

In summary, we demonstrate that inhalation of sphingosine results in an increase of sphingosine concentrations in the luminal plasma membrane of tracheal and bronchial epithelial cells. The inhalation has no systemic or local side effects.

Effects of immediate versus delayed ex-vivo lung perfusion in a porcine cardiac arrest donation model

OBJECTIVE

Ex-vivo lung perfusion is a promising tool to evaluate and recondition marginal donor lungs usually after a cold static preservation. The concept of continuous organ perfusion is supposed to reduce ischemic damage; however, the optimal perfusion protocol has not been established yet. The aim of this study was to compare immediate ex-vivo lung perfusion (I-EVLP) to delayed ex-vivo lung perfusion (D-EVLP) after a certain cold static preservation period on lung function in a large animal model.

METHODS

In a porcine model, lungs were procured after circulatory death and 60 min of no-touch warm ischemia. Lungs were preserved with single-flush cold low potassium dextran solution and prepared either for I-EVLP (n = 8) or stored cold for 9 h with subsequent D-EVLP (n = 8). Functional outcomes and morphology were compared during 4 h of ex-vivo lung perfusion, using STEEN Solution^TM as perfusion solution.

RESULTS

Pulmonary functional data, perfusate activities of lactate dehydrogenase, alkaline phosphatase, and products of lipid peroxidation did not differ significantly. There was a trend toward lower wet-dry ratio (I-EVLP: 13.4 ± 2.9; D-EVLP: 9.1 ± 2.5) and higher ΔpO₂ in D-EVLP group (I-EVLP: 209 ± 51.6 mmHg; D-EVLP: 236.3 ± 47.3 mmHg).

CONCLUSION

In this donation-after-circulatory-death model, 9 h of cold static preservation followed by ex-vivo lung perfusion results in comparable pulmonary function to I-EVLP as indicated by oxygenation capacities and wet-dry ratio. Our findings indicate that prolonged cold static preservation prior to ex-vivo lung perfusion is as safe and effective as I-EVLP in the procurement of donor lungs.

Prediction of acute kidney injury after left ventricular assist device implantation: Evaluation of clinical risk scores

Acute kidney injury (AKI) is frequent in patients scheduled for implantation of a left ventricular assist device (LVAD) and associated with increased mortality. Although several risk models for the prediction of postoperative renal replacement therapy (RRT) have been developed for cardiothoracic patients, none of these scoring systems have been validated in LVAD patients. A retrospective, single center analysis of all patients undergoing LVAD implantation between September 2013 and July 2016 was performed. Primary outcome was AKI requiring RRT within 14 days after surgery. The predictive capacity of the Cleveland Clinic Score (CCS), the Society of Thoracic Surgeons Score (STS), and the Simplified Renal Index Score (SRI) were evaluated. 76 patients underwent LVAD implantation, 19 patients were excluded due to preoperative RRT. RRT was associated with a prolonged ventilation time, length of stay on the ICU and 180 day mortality (14(60.9%) vs 6(17.6%), P < .01). Whereas the Thakar Score (7.43 ± 1.75 vs 6.44 ± 1.44, P = .02) and the Mehta Score (28.12 ± 15.08 vs 21.53 ± 5.43, P = .02) were significantly higher in patients with RRT than in those without RRT, the SRI did not differ between these groups (3.96 ± 1.15 vs 3.44 ± 1.05, P = .08). Using ROC analyses, CCS, STS, and SRI showed moderate predictive capacity for RRT with an AUC of 0.661 ± 0.073 (P = .040), 0.637 ± 0.079 (P = .792), and 0.618 ± 0.075 (P = .764), respectively, with comparable accuracy in the Delong test. Using univariate logistic regression analysis, only the De Ritis Ratio (OR 2.67, P = .034) and MELD (OR 1.11, P = .028) were identified as predictors of postoperative RRT. Risk scores which are predictive in general cardiac surgery cannot predict RRT in patients after LVAD implantation. Therefore, it seems to be necessary to develop a specific risk score for this patient population.

Sphingosine-coating of plastic surfaces prevents ventilator-associated pneumonia

Ventilator-associated pneumonia (VAP) is a major cause of morbidity and mortality in critically ill patients. Here, we employed the broad antibacterial effects of sphingosine to prevent VAP by developing a novel method of coating surfaces of endotracheal tubes with sphingosine and sphingosine analogs. Sphingosine and phytosphingosine coatings of endotracheal tubes prevent adherence and mediate killing of Pseudomonas aeruginosa, Acinetobacter baumannii, and Staphylococcus aureus, even in biofilms. Most importantly, sphingosine-coating of endotracheal tubes also prevented P. aeruginosa and S. aureus pneumonia in vivo. Coating of the tubes with sphingosine was stable, without obvious side effects on tracheal epithelial cells and did not induce inflammation. In summary, we describe a novel method to coat plastic surfaces and provide evidence for the application of sphingosine and phytosphingosine as novel antimicrobial coatings to prevent bacterial adherence and induce killing of pathogens on the surface of endotracheal tubes with potential to prevent biofilm formation and VAP. KEY MESSAGES: Novel dip-coating method to coat plastic surfaces with lipids. Sphingosine and phytosphingosine as novel antimicrobial coatings on plastic surface. Sphingosine coatings of endotracheal tubes prevent bacterial adherence and biofilms. Sphingosine coatings of endotracheal tubes induce killing of pathogens. Sphingosine coatings of endotracheal tubes ventilator-associated pneumonia.

Loss of Protein Phosphatase 1 Regulatory Subunit PPP1R3A Promotes Atrial Fibrillation

BACKGROUND

Abnormal calcium (Ca²⁺) release from the sarcoplasmic reticulum (SR) contributes to the pathogenesis of atrial fibrillation (AF). Increased phosphorylation of 2 proteins essential for normal SR-Ca²⁺ cycling, the type-2 ryanodine receptor (RyR2) and phospholamban (PLN), enhances the susceptibility to AF, but the underlying mechanisms remain unclear. Protein phosphatase 1 (PP1) limits steady-state phosphorylation of both RyR2 and PLN. Proteomic analysis uncovered a novel PP1-regulatory subunit (PPP1R3A [PP1 regulatory subunit type 3A]) in the RyR2 macromolecular channel complex that has been previously shown to mediate PP1 targeting to PLN. We tested the hypothesis that reduced PPP1R3A levels contribute to AF pathogenesis by reducing PP1 binding to both RyR2 and PLN.

METHODS

Immunoprecipitation, mass spectrometry, and complexome profiling were performed from the atrial tissue of patients with AF and from cardiac lysates of wild-type and Pln-knockout mice. Ppp1r3a-knockout mice were generated by CRISPR-mediated deletion of exons 2 to 3. Ppp1r3a-knockout mice and wild-type littermates were subjected to in vivo programmed electrical stimulation to determine AF susceptibility. Isolated atrial cardiomyocytes were used for Stimulated Emission Depletion superresolution microscopy and confocal Ca²⁺ imaging.

RESULTS

Proteomics identified the PP1-regulatory subunit PPP1R3A as a novel RyR2-binding partner, and coimmunoprecipitation confirmed PPP1R3A binding to RyR2 and PLN. Complexome profiling and Stimulated Emission Depletion imaging revealed that PLN is present in the PPP1R3A-RyR2 interaction, suggesting the existence of a previously unknown SR nanodomain composed of both RyR2 and PLN/sarco/endoplasmic reticulum calcium ATPase-2a macromolecular complexes. This novel RyR2/PLN/sarco/endoplasmic reticulum calcium ATPase-2a complex was also identified in human atria. Genetic ablation of Ppp1r3a in mice impaired binding of PP1 to both RyR2 and PLN. Reduced PP1 targeting was associated with increased phosphorylation of RyR2 and PLN, aberrant SR-Ca²⁺ release in atrial cardiomyocytes, and enhanced susceptibility to pacing-induced AF. Finally, PPP1R3A was progressively downregulated in the atria of patients with paroxysmal and persistent (chronic) AF.

CONCLUSIONS

PPP1R3A is a novel PP1-regulatory subunit within the RyR2 channel complex. Reduced PPP1R3A levels impair PP1 targeting and increase phosphorylation of both RyR2 and PLN. PPP1R3A deficiency promotes abnormal SR-Ca²⁺ release and increases AF susceptibility in mice. Given that PPP1R3A is downregulated in patients with AF, this regulatory subunit may represent a new target for AF therapeutic strategies.

Contemporaneous 3D characterization of acute and chronic myocardial I/R injury and response

Cardioprotection by salvage of the infarct-affected myocardium is an unmet yet highly desired therapeutic goal. To develop new dedicated therapies, experimental myocardial ischemia/reperfusion (I/R) injury would require methods to simultaneously characterize extent and localization of the damage and the ensuing inflammatory responses in whole hearts over time. Here we present a three-dimensional (3D), simultaneous quantitative investigation of key I/R injury-components by combining bleaching-augmented solvent-based non-toxic clearing (BALANCE) using ethyl cinnamate (ECi) with light sheet fluorescence microscopy. This allows structural analyses of fluorescence-labeled I/R hearts with exceptional detail. We discover and 3D-quantify distinguishable acute and late vascular I/R damage zones. These contain highly localized and spatially structured neutrophil infiltrates that are modulated upon cardiac healing. Our model demonstrates that these characteristic I/R injury patterns can detect the extent of damage even days after the ischemic index event hence allowing the investigation of long-term recovery and remodeling processes.

Prolonged mechanical ventilation after left ventricular assist device implantation: risk factors and clinical implications

Aims

Unsuccessful weaning from ventilator after major cardiovascular procedures has been shown to be associated with increased post‐operative morbidity and mortality. Our study aimed to identify predictors and clinical implications of prolonged mechanical ventilation (PMV) after left ventricular assist device (LVAD) implantation.

Methods and results

We analysed the data of patients receiving a continuous‐flow LVAD in our centre from December 2010 to September 2017. PMV was defined by a duration of invasive ventilation of >7 days after LVAD implantation. Multivariable logistic regression analysis was performed for predictors of PMV. Survival was estimated by the Kaplan–Meier method. During the study period, 156 patients received a continuous‐flow LVAD in our centre. Seventeen patients were excluded due to early death (<7 days), and 139 patients were enrolled in the study (mean age: 58 years; male: 84%). The median duration of mechanical ventilation post‐operatively was 94 h (range: 5 to 4192 h). PMV was observed in 43% of patients. Patients on PMV were characterized by a more severe disease state at baseline, compared with the group of early extubation, as reflected by their Interagency Registry for Mechanically Assisted Circulatory Support level (Level 1–3: 72 vs. 49%, P = 0.008). Patients on PMV exhibited higher pulmonary wedge pressures (25 vs. 21 mmHg, P = 0.04), lower estimated glomerular filtration rate (53 vs. 60 mL/min/1.73 m², P = 0.02), lower haemoglobin (10.6 vs. 11.6 g/dL, P = 0.02), and lower platelet counts (189 vs. 240/nL, P = 0.02). Previous sternotomy was more frequent in the PMV group (32 vs. 13%, P = 0.006). Higher rates of preoperative circulatory support (30 vs. 11.4%, P = 0.006), dialysis (31.7 vs. 10.1%, P = 0.001), and invasive ventilation (35 vs. 7.6%, P < 0.001) were reported for the PMV group. Logistic regression analysis revealed that estimated glomerular filtration rate [odds ratio (OR) 0.977, confidence interval (CI) 0.955–0.999, P = 0.038], platelet count (OR 0.994, CI 0.989–0.998, P = 0.008), and previous sternotomy (OR 5.079, CI 1.672–15.427, P = 0.004) were independent predictors of PMV. PMV was accompanied by longer intensive care unit (24 vs. 4 days, P < 0.001) and hospital stay (47 vs. 32 days, P = 0.003). Survival analysis revealed a profound increase in mortality at 180‐day post‐implantation in the PMV group (62 vs. 10%, log‐rank: P < 0.001).

Conclusions

Prolonged mechanical ventilation affects nearly half of patients after LVAD implantation. Previous sternotomy, renal function, and platelet counts are associated with increased risk for PMV. PMV is accompanied by decreased survival at 180‐day post‐implantation and longer hospitalizations.

Dynamics and prognostic value of B-type natriuretic peptide in left ventricular assist device recipients

Background

The prognostic utility of B-type natriuretic peptide (BNP) in heart failure is well recognized. Previous studies demonstrated that BNP levels decrease after left ventricular assist device (LVAD) implantation. We sought to investigate the predictive value of baseline and changes in BNP levels in LVAD recipients.

Methods

BNP was measured in baseline and follow-up plasma samples from consecutive patients receiving a continuous-flow LVAD from 2010 through 2016. Absolute values and changes from baseline were related to clinical outcomes.

Results

Median BNP at baseline was 885 [interquartile range (IQR): 450-1,624] pg/mL, decreasing to 289 (IQR: 154-534) pg/mL at 90 days after LVAD implantation. Cox regression analysis revealed that higher baseline and follow-up BNP levels were not associated with increased risk of death at 180 days (P=0.12 and P=0.32, respectively). In the univariate analysis 90-day BNP, but not baseline BNP, was significantly associated with the combined death/hospitalization outcome 180 days after LVAD implantation [hazard ratio (HR) 1.03, 95% CI: 1.01-1.06; P=0.006]. This significance was not preserved after adjusting for multiple covariates (HR 1.01, 95% CI: 0.98-1.04; P=0.62). At 90 days, there was no BNP lowering in 20.6% of subjects. This was not associated with higher risk for death or the composite of death/hospitalization (P=0.11 and P=0.06 respectively).

Conclusions

BNP absolute levels and changes from baseline are not independently associated with clinical outcomes after LVAD-implantation. These findings suggest an impaired prognostic performance of BNP after LVAD implantation.

Lung volume reduction followed by lung transplantation-considerations on selection criteria and outcome

Lung transplantation (LuTX) and lung volume reduction (LVR), either surgical (LVRS: lung volume reduction surgery) or endoscopic (ELVR: endoscopic lung volume reduction), are established therapies in the treatment of end-stage chronic obstructive pulmonary disease (COPD) patients. Careful patient selection is crucial for each intervention. If these techniques are sequentially applied there is a paucity of available data and individual center experiences vary depending on details in selection criteria and operative technique. This review aims to summarize the published data with a focus on LuTX after LVRS. This review covers patient selection for LuTX and LVR, technical considerations, limitations and outcomes. Published literature was identified by systematic search on Medline and appropriate papers were reviewed. Seven case reports/series, 7 comparative observational studies and one multicenter database analysis incorporating a total of 284 patients with LuTX and LVR were evaluated. Prior LVR can significantly affect intraoperative and postoperative risks after subsequent LuTX. Careful patient selection and timing and the choice of appropriate techniques such as minimal invasive LVRS and using ECMO as extracorporeal support during LuTX if required can minimize those risks, ultimately leading to very good postoperative outcomes in terms of lung function and survival. LVRS has the potential to delay listing and to bridge patients to LuTX by improving their physical condition while on the waiting list. After single lung transplantation (SLuTX) contralateral LVRS can counteract the deleterious effects of native lung hyperinflation (NLH). LVR and LuTX are adjunct therapies in the treatment of end-stage COPD. The combination of both can safely be considered in selected patients.

Mitochondrial and Contractile Function of Human Right Atrial Tissue in Response to Remote Ischemic Conditioning

Background Remote ischemic preconditioning ( RIPC ) by repeated brief cycles of limb ischemia/reperfusion attenuates myocardial ischemia/reperfusion injury. We aimed to identify a functional parameter reflecting the RIPC -induced protection in human. Therefore, we measured mitochondrial function in right atrial tissue and contractile function of isolated right atrial trabeculae before and during hypoxia/reoxygenation from patients undergoing coronary artery bypass grafting with RIPC or placebo, respectively. Methods and Results One hundred thirty-seven patients under isoflurane anesthesia underwent RIPC (3×5 minutes blood pressure cuff inflation on the left upper arm/5 minutes deflation, n=67) or placebo (cuff uninflated, n=70), and right atrial appendages were harvested before ischemic cardioplegic arrest. Myocardial protection by RIPC was assessed from serum troponin I/T concentrations over 72 hours after surgery. Atrial tissue was obtained for isolation of mitochondria ( RIPC /placebo: n=10/10). Trabeculae were dissected for contractile function measurements at baseline and after hypoxia/reoxygenation (60 min/30 min) and for western blot analysis after hypoxia/reoxygenation ( RIPC /placebo, n=57/60). Associated with cardioprotection by RIPC (26% decrease in the area under the curve of troponin I/T), mitochondrial adenosine diphosphate-stimulated complex I respiration (+10%), adenosine triphosphate production (+46%), and calcium retention capacity (+37%) were greater, whereas reactive oxygen species production (-24%) was less with RIPC than placebo. Contractile function was improved by RIPC (baseline, +7%; reoxygenation, +24%). Expression and phosphorylation of proteins, which have previously been associated with cardioprotection, were not different between RIPC and placebo. Conclusions Cardioprotection by RIPC goes along with improved mitochondrial and contractile function of human right atrial tissue. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT 01406678.

Sphingolipids as targets for inhalation treatment of cystic fibrosis

Studies over the past several years have demonstrated the important role of sphingolipids in cystic fibrosis (CF), chronic obstructive pulmonary disease and acute lung injury. Ceramide is increased in airway epithelial cells and alveolar macrophages of CF mice and humans, while sphingosine is dramatically decreased. This increase in ceramide results in chronic inflammation, increased death of epithelial cells, release of DNA into the bronchial lumen and thereby an impairment of mucociliary clearance; while the lack of sphingosine in airway epithelial cells causes high infection susceptibility in CF mice and possibly patients. The increase in ceramide mediates an ectopic expression of β1-integrins in the luminal membrane of CF epithelial cells, which results, via an unknown mechanism, in a down-regulation of acid ceramidase. It is predominantly this down-regulation of acid ceramidase that results in the imbalance of ceramide and sphingosine in CF cells. Correction of ceramide and sphingosine levels can be achieved by inhalation of functional acid sphingomyelinase inhibitors, recombinant acid ceramidase or by normalization of β1-integrin expression and subsequent re-expression of endogenous acid ceramidase. These treatments correct pulmonary inflammation and prevent or treat, respectively, acute and chronic pulmonary infections in CF mice with Staphylococcus aureus and mucoid or non-mucoid Pseudomonas aeruginosa. Inhalation of sphingosine corrects sphingosine levels only and seems to mainly act against the infection. Many antidepressants are functional inhibitors of the acid sphingomyelinase and were designed for systemic treatment of major depression. These drugs could be repurposed to treat CF by inhalation.

The aspartate transaminase/alanine transaminase (DeRitis) ratio predicts mid-term mortality and renal and respiratory dysfunction after left ventricular assist device implantation

OBJECTIVES

Preoperative liver dysfunction is a well-known risk factor for adverse events after major surgery. However, there is only little data regarding the precise role of the Model of End-Stage Liver Disease (MELD) score and the De Ritis ratio (DRR, alanine transaminase/aspartate aminotransferase) as a predictor for outcome after left ventricular assist device (LVAD) implantation.

METHODS

A retrospective analysis of all patients undergoing LVAD implantation at our institution between January 2012 and August 2014 was performed. The primary outcome was survival at 180 days after surgery.

RESULTS

During the observation period, 63 patients underwent LVAD implantation (mean age 59.9 ± 8.3 years, 50% male). Mean preoperative ejection fraction was 16.3 ± 7.7, 13 patients required preoperative renal replacement therapy and 9 patients were on extracorporeal life support. Mean Interagency Registry for Mechanically Assisted Circulatory Support level was 2.8 ± 1.3, mean preoperative MELD was 12.7 ± 7.2, mean preoperative DRR was 2.01 ± 4.4. Aspartate aminotransferase (102 ± 220.8 vs 57.8 ± 123.4 U/l, P = 0.041), MELD score (16.1 ± 8.8 vs 11.4 ± 6.1, P = 0.017) and DRR (4.2 ± 7.8 vs 1.1 ± 1.1, P = 0.001) were significantly higher in non-survivors than in survivors after 180 days. Using logistic regression analyses, a DRR >1.37 was an independent predictor for 30-day mortality [odds ratio (OR) 4.5] and 180-day mortality (OR 4.1). In addition, the DRR was associated with postoperative acute kidney injury with need for renal replacement therapy (OR 4.2) and prolonged postoperative ventilation time >72 h (OR 3.8). Using receiver operator characteristics analyses, DRR showed a sensitivity of 0.80 and a specificity of 0.81 (area under the curve 0.834, cut-off 1.37) for 180-day mortality.

CONCLUSIONS

The DRR is predictive of early and mid-term mortality as well as relevant morbidities in patients undergoing LVAD implantation. Therefore, the DRR should be considered within the preoperative risk stratification and patient selection for LVAD implantation.

One-year experience with ex vivo lung perfusion: Preliminary results from a single center

Objective:

To enlarge the donor pool for lung transplantation, an increasing number of extended criteria donor lungs are used. However, in more than 50% of multi-organ donors the lungs are not used. Ex vivo lung perfusion offers a unique possibility to evaluate and eventually recondition the injured donor lungs. The aim of our study was to assess the enlargement of the donor pool and the outcome with extended criteria donor lungs after ex vivo lung perfusion.

Patients and Methods:

Data were prospectively collected in our lung transplant database. We compared the results of lung transplants after ex vivo lung perfusion with those after conventional cold static preservation. In total, 11 extended criteria donor lungs processed with ex vivo lung perfusion and 41 cold static preservation lungs transplanted consecutively between May 2016 and May 2017 were evaluated. Normothermic ex vivo lung perfusion was performed according to the Toronto protocol for 4 h. Cold static preservation lungs were stored in low-potassium dextran solution.

Results:

Ex vivo lung perfusion lungs before procurement had significantly lower PaO2/FiO2 (P/F) ratios and more X-ray abnormalities. There were no statistically significant differences for pre-donation ventilation time, smoking history, or sex. After reconditioning with ex vivo lung perfusion, 9 out of 11 processed lungs were considered suitable and successfully transplanted. The mean postoperative ventilation time and in-hospital stay were not significantly different in ex vivo lung perfusion and cold static preservation recipients.

Conclusion:

Ex vivo lung perfusion can safely be used in the evaluation of lungs initially considered not suitable for transplantation. The primary outcome was not negatively affected and normothermic ex vivo lung perfusion is a useful tool to increase the usage of potentially transplantable lungs.

Acute Stent Migration into the Right Ventricle in a Patient with Iliac Vein Stenting

Endovascular stent placement for chronic postthrombotic iliofemoral venous obstructive lesions is an effective therapeutic option and might be complicated by stent migration. We report a case of a venous stent that was lost from the iliac vein into the right ventricle rescued by emergent open-heart surgery.

Resternotomy does not adversely affect outcome after left ventricular assist device implantation

Background

Resternotomy in cardiac surgery is considered a risk factor for postoperative complications. Previous studies have demonstrated an ambiguous relationship between resternotomy and clinical outcomes. Registry data from a mixed population of durable circulatory support devices suggest that history of cardiac surgery is a risk factor for mortality. Our study investigates the prognostic significance of resternotomy in a homogenous cohort of left ventricular assist device (LVAD) recipients.

Methods

The study included adult patients receiving a continuous-flow LVAD at our institution during the period 2010–2016. Postoperative adverse events and length of stay were analyzed. Survival was assessed at 6 months and by the end of the study. Multivariate risk factor analysis was conducted for independent predictors of death.

Results

One hundred twelve patients, who received an intrapericardial LVAD (HVAD, HeartWare), were included in our analysis. Twenty-four patients (21.4%) had a history of previous sternotomy. These patients were older and non-eligible for bridging, and had more frequently coronary heart disease. Univariate analysis demonstrated no differences in the observed complications postoperatively. Survival was similar among groups. Destination therapy was the only predictor of mortality in our analysis (p = 0.02).

Conclusions

Resternotomy was not associated with worse outcomes after LVAD implantation in our cohort.

Neutrophils Kill Reactive Oxygen Species-Resistant Pseudomonas aeruginosa by Sphingosine

BACKGROUND/AIMS

Cystic fibrosis (CF) is dominated by chronic inflammation and infection of the lung resulting in lung destruction and early death of patients. The lungs of CF patients are characterized by a massive accumulation of neutrophils. It requires definition why these massive numbers of neutrophils fail to eliminate typical CF pathogens like Staphylococcus aureus and Pseudomonas aeruginosa (P. aeruginosa) in CF lungs.

METHODS

We determined ceramide, sphingosine and reactive oxygen species (ROS) in neutrophils from wildtype and CF mice and determined the effect of sphingosine and ROS alone or in combination on killing of different P. aeruginosa strains.

RESULTS

We demonstrate that wildtype neutrophils are able to kill non-mucoid and mucoid clinical P. aeruginosa strains, while neutrophils from CF mice are insufficient to kill these P. aeruginosa strains, although both types of neutrophils infected with P. aeruginosa produce comparable levels of superoxide. All three analyzed P. aeruginosa strains are resistant to reactive oxygen species. The inability of CF neutrophils to kill P. aeruginosa is caused by a marked decrease of surface sphingosine levels in CF neutrophils. Wildtype neutrophils contain much higher concentrations of surface sphingosine than CF neutrophils. Further, wildtype neutrophils, but not CF neutrophils, release sphingosine, most likely as microparticles, upon infection. Sphingosine kills P. aeruginosa in vitro at low micromolar concentrations. Reconstitution of sphingosine in CF neutrophils restores their ability to kill these pathogens, demonstrating the significance of sphingosine for bacterial killing.

CONCLUSION

The data provide evidence for a new paradigm explaining how neutrophils kill ROS-resistant P. aeruginosa, i.e. by sphingosine that kills P. aeruginosa at low concentrations. This mechanism is defective in CF neutrophils.