Vessel Fractional Flow Reserve and Graft Vasculopathy in Heart Transplant Recipients.

BACKGROUND: Cardiac allograft vasculopathy (CAV) remains the Achilles' heel of long-term survival after heart transplantation (HTx). The severity and extent of CAV is graded with conventional coronary angiography (COR) which has several limitations. Recently, vessel fractional flow reserve (vFFR) derived from COR has emerged as a diagnostic computational tool to quantify the functional severity of coronary artery disease. PURPOSE: The present study assessed the usefulness of vFFR to detect CAV in HTx recipients. METHODS: In HTx patients referred for annual check-up, undergoing surveillance COR, the extent of CAV was graded according to the criteria proposed by the international society of heart and lung transplantation (ISHLT). In addition, three-dimensional coronary geometries were constructed from COR to calculate pressure losses using vFFR. RESULTS: In 65 HTx patients with a mean age of 53.7 ± 10.1 years, 8.5 years (IQR 1.90, 15.2) years after HTx, a total number of 173 vessels (59 LAD, 61 LCX, and 53 RCA) were analyzed. The mean vFFR was 0.84 ± 0.15 and median was 0.88 (IQR 0.79, 0.94). A vFFR ≤ 0.80 was present in 24 patients (48 vessels). HTx patients with a history of ischemic cardiomyopathy (ICMP) had numerically lower vFFR as compared to those with non-ICMP (0.70 ± 0.22 vs. 0.79 ± 0.13, p = 0.06). The use of vFFR reclassified 31.9% of patients compared to the anatomical ISHLT criteria. Despite a CAV score of 0, a pathological vFFR ≤ 0.80 was detected in 8 patients (34.8%). CONCLUSION: The impairment in epicardial conductance assessed by vFFR in a subgroup of patients without CAV according to standard ISHLT criteria suggests the presence of a diffuse vasculopathy undetectable by conventional angiography. Therefore, we speculate that vFFR may be useful in risk stratification after HTx.

Treatment of Diuretic Resistance with a Novel Percutaneous Blood Flow Regulator: Concept and Initial Experience.

Diuretic resistance in acute heart failure is a common clinical problem, and it is associated with adverse outcomes. Effective therapies are still lacking. The Doraya catheter, a temporary intravenous flow regulator placed in the inferior vena cava below the level of the renal veins, is a novel device designed to target renal and cardiac congestion, thereby improving diuretic response. A first-in-man clinical study is currently ongoing.

Natriuretic Peptide Processing in Patients with and Without Left Ventricular Dysfunction.

This study aimed to examine the relationship between corin expression and circulating brain natriuretic peptide in patients with left ventricular (LV) dysfunction.Circulating levels of B-type natriuretic peptide (BNP) can be an indicator of LV dysfunction. The 32-amino-acid BNP is cleaved by corin, a cardiac serine protease, from its108-amino-acid pro-brain natriuretic peptide (proBNP) precursor.This study included 25 patients with idiopathic dilated cardiomyopathy (DCMP) and LV dysfunction and 44 heart transplant recipients with normal LV function who underwent diagnostic left and right heart catheterization. Blood samples were used to determine the ratio of plasma proBNP/BNP levels, and LV endomyocardial biopsies were used to determine the expression of NPPB, which encode BNP and corin, respectively, by quantitative reverse transcription-polymerase chain reaction.Patients with DCMP revealed worse hemodynamic profiles and higher plasma proBNP and BNP levels than those of the transplant recipients. Myocardial NPPB expression was higher and CORIN expression was lower in the DCMP patients than in the transplant recipients. CORIN expression significantly correlated with NPPB expression (r = -0.585; P < 0.001), ejection fraction (EF; r = 0.694; P < 0.01), LV end-diastolic pressure (r = -0.373; P < 0.05), and indexed end-diastolic LV volume (r = -0.452; P < 0.001). In addition, the plasma proBNP/BNP levels inversely correlated with the CORIN expression (r = -0.362; P < 0.005).Decreased myocardial CORIN expression and the corresponding higher levels of circulating unprocessed proBNP in DCMP may partly account for the relative BNP resistance observed in patients with LV dysfunction.

Protein aggregation as an antibiotic design strategy.

Taking advantage of the xenobiotic nature of bacterial infections, we tested whether the cytotoxicity of protein aggregation can be targeted to bacterial pathogens without affecting their mammalian hosts. In particular, we examined if peptides encoding aggregation-prone sequence segments of bacterial proteins can display antimicrobial activity by initiating toxic protein aggregation in bacteria, but not in mammalian cells. Unbiased in vitro screening of aggregating peptide sequences from bacterial genomes lead to the identification of several peptides that are strongly bactericidal against methicillin-resistant Staphylococcus aureus. Upon parenteral administration in vivo, the peptides cured mice from bacterial sepsis without apparent toxic side effects as judged from histological and hematological evaluation. We found that the peptides enter and accumulate in the bacterial cytosol where they cause aggregation of bacterial polypeptides. Although the precise chain of events that leads to cell death remains to be elucidated, the ability to tap into aggregation-prone sequences of bacterial proteomes to elicit antimicrobial activity represents a rich and unexplored chemical space to be mined in search of novel therapeutic strategies to fight infectious diseases.

Should MRAs be at the front row in heart failure? A plea for the early use of mineralocorticoid receptor antagonists in medical therapy for heart failure based on clinical experience.

The brand new 2016 ESC guidelines for the treatment of acute and chronic heart failure continue to give a prominent place to mineralocorticoid receptor antagonists in the treatment of chronic heart failure with reduced ejection fraction (HFrEF). In the prevention of HF hospitalization and death, a class I, level of recommendation A, is given to MRAs for patients with HFrEF, who remain symptomatic despite treatment with an ACE-inhibitor and a beta-blocker and have an LVEF below 35 %. This recommendation is primarily based on two landmark trials, the RALES trial (for spironolactone) and the EMPHASIS-HF trial (for eplerenone). A crucial question is, however, why MRAs are advised only in "third place," i.e., after optimal up-titration of ACE-inhibitors and beta-blockers. We wonder whether MRAs could not or should not be given earlier in the treatment of HFrEF, namely before or together with the up-titration of ACE-inhibitors and beta-blockers. Several arguments to support this plea are described in this short paper.

The Arabidopsis metacaspase9 degradome.

Metacaspases are distant relatives of the metazoan caspases, found in plants, fungi, and protists. However, in contrast with caspases, information about the physiological substrates of metacaspases is still scarce. By means of N-terminal combined fractional diagonal chromatography, the physiological substrates of metacaspase9 (MC9; AT5G04200) were identified in young seedlings of Arabidopsis thaliana on the proteome-wide level, providing additional insight into MC9 cleavage specificity and revealing a previously unknown preference for acidic residues at the substrate prime site position P1'. The functionalities of the identified MC9 substrates hinted at metacaspase functions other than those related to cell death. These results allowed us to resolve the substrate specificity of MC9 in more detail and indicated that the activity of phosphoenolpyruvate carboxykinase 1 (AT4G37870), a key enzyme in gluconeogenesis, is enhanced upon MC9-dependent proteolysis.

The small GTPase Arf6 is essential for the Tram/Trif pathway in TLR4 signaling.

Recognition of lipopolysaccharides (LPS) by Toll-like receptor 4 (TLR4) at the plasma membrane triggers NF-κB activation through recruitment of the adaptor proteins Mal and MyD88. Endocytosis of the activated TLR4 allows recruitment of the adaptors Tram and Trif, leading to activation of the transcription factor IRF3 and interferon production. The small GTPase ADP-ribosylation factor 6 (Arf6) was shown to regulate the plasma membrane association of Mal. Here we demonstrate that inhibition of Arf6 also markedly reduced LPS-induced cytokine production in Mal(-/-) mouse macrophages. In this article, we focus on a novel role for Arf6 in the MyD88-independent TLR4 pathway. MyD88-independent IRF3 activation and IRF3-dependent gene transcription were strictly dependent on Arf6. Arf6 was involved in transport of Tram to the endocytic recycling compartment and internalization of LPS, possibly explaining its requirement for LPS-induced IRF3 activation. Together, these results show a critical role for Arf6 in regulating Tram/Trif-dependent TLR4 signaling.

Mechanism of cleavage of alpha-synuclein by the 20S proteasome and modulation of its degradation by the RedOx state of the N-terminal methionines.

Alpha-synuclein is a small protein implicated in the pathophysiology of Parkinson's disease (PD). We have investigated the mechanism of cleavage of alpha-synuclein by the 20S proteasome. Alpha-synuclein interacts with the C8 (α7) subunit of the proteasome. The N-terminal part of alpha-synuclein (amino acids 1-60) is essential for its proteasomal degradation and analysis of peptides released from proteasomal digestion allows concluding that initial cleavages occur within the N-terminal region of the molecule. Aggregated alpha-synucleins are also degraded by the proteasome with a reduced rate, likely due to Met oxidation. In fact, mild oxidation of alpha-synuclein with H2O2 resulted in the inhibition of its degradation by the proteasome, mainly due to oxidation of Met 1 and 5 of alpha-synuclein. The inhibition was reversed by treatment of the oxidized protein with methionine sulfoxide reductases (MsrA plus MsrB). Similarly, treatment with H2O2 of N2A cells transfected with alpha-synuclein resulted in the inhibition of its degradation that was also reverted by co-transfection of MsrA plus MsrB. These results clearly indicate that oxidative stress, a common feature of PD and other synucleinopathies, promotes a RedOx change in the proteostasis of alpha-synuclein due to Met oxidation and reduced proteasomal degradation; compromised reversion of those oxidative changes would result in the accumulation of oxidative damaged alpha-synuclein likely contributing to the pathogenesis of PD.

Taximin, a conserved plant-specific peptide is involved in the modulation of plant-specialized metabolism.

Small peptides play important roles in the signalling cascades that steer plant growth, development and defence, and often crosstalk with hormonal signalling. Thereby, they also modulate metabolism, including the production of bioactive molecules that are of high interest for human applications. Yew species (Taxus spp.) produce diterpenes such as the powerful anticancer agent paclitaxel, the biosynthesis of which can be stimulated by the hormone jasmonate, both in whole plants and cell suspension cultures. Here, we identified Taximin, as a gene encoding a hitherto unreported, plant-specific, small, cysteine-rich signalling peptide, through a transcriptome survey of jasmonate-elicited T. baccata suspension cells grown in two-media cultures. Taximin expression increased in a coordinated manner with that of paclitaxel biosynthesis genes. Tagged Taximin peptides were shown to enter the secretory system and localize to the plasma membrane. In agreement with this, the exogenous application of synthetic Taximin peptide variants could transiently modulate the biosynthesis of taxanes in T. baccata cell suspension cultures. Importantly, the Taximin peptide is widely conserved in the higher plant kingdom with a high degree of sequence conservation. Accordingly, Taximin overexpression could stimulate the production of nicotinic alkaloids in Nicotiana tabacum hairy root cultures in a synergistic manner with jasmonates. In contrast, no pronounced effects of Taximin overexpression on the specialized metabolism in Medicago truncatula roots were observed. This study increases our understanding of the regulation of Taxus diterpene biosynthesis in particular and plant metabolism in general. Ultimately, Taximin might increase the practical potential of metabolic engineering of medicinal plants.

Reduced protein stability of human DJ-1/PARK7 L166P, linked to autosomal recessive Parkinson disease, is due to direct endoproteolytic cleavage by the proteasome.

Parkinson's disease (PD) is characterized by dopaminergic dysfunction and degeneration. DJ-1/PARK7 mutations have been linked with a familial form of early onset PD. In this study, we found that human DJ-1 wild type and the missense mutants M26I, R98Q, A104T and D149A were stable proteins in cells, only the L166P mutant was unstable. In parallel, the former were not degraded and the L166P mutant was directly degraded in vitro by proteasome-mediated endoproteolytic cleavage. Furthermore, genetic evidence in fission yeast showed the direct involvement of proteasome in the degradation of human DJ-1 L166P and the corresponding L169P mutant of SPAC22E12.03c, the human orthologue of DJ-1 in Schizosaccharomyces Pombe, as their protein levels were increased at restrictive temperature in fission yeast (mts4 and pts1-732) harboring temperature sensitive mutations in proteasomal subunits. In total, our results provide evidence that direct proteasomal endoproteolytic cleavage of DJ-1 L166P is the mechanism of degradation contributing to the loss-of-function of the mutant protein, a property not shared by other DJ-1 missense mutants associated with PD.

Asn3, a reliable, robust, and universal lock mass for improved accuracy in LC-MS and LC-MS/MS.

The use of internal calibrants (the so-called lock mass approach) provides much greater accuracy in mass spectrometry based proteomics. However, the polydimethylcyclosiloxane (PCM) peaks commonly used for this purpose are quite unreliable, leading to missing calibrant peaks in spectra and correspondingly lower mass measurement accuracy. Therefore, we here introduce a universally applicable and robust internal calibrant, the tripeptide Asn3. We show that Asn3 is a substantial improvement over PCM both in terms of consistent detection and resulting mass measurement accuracy. Asn3 is also very easy to adopt in the lab, as it requires only minor adjustments to the analytical setup.

Redox proteomics of protein-bound methionine oxidation.

We here present a new method to measure the degree of protein-bound methionine sulfoxide formation at a proteome-wide scale. In human Jurkat cells that were stressed with hydrogen peroxide, over 2000 oxidation-sensitive methionines in more than 1600 different proteins were mapped and their extent of oxidation was quantified. Meta-analysis of the sequences surrounding the oxidized methionine residues revealed a high preference for neighboring polar residues. Using synthetic methionine sulfoxide containing peptides designed according to the observed sequence preferences in the oxidized Jurkat proteome, we discovered that the substrate specificity of the cellular methionine sulfoxide reductases is a major determinant for the steady-state of methionine oxidation. This was supported by a structural modeling of the MsrA catalytic center. Finally, we applied our method onto a serum proteome from a mouse sepsis model and identified 35 in vivo methionine oxidation events in 27 different proteins.

Probing the efficiency of proteolytic events by positional proteomics.

Several mass spectrometry-driven techniques allow to map the substrate repertoires and specificities of proteases. These techniques typically yield long lists of protease substrates and processed sites with (potential) physiological relevance, but in order to understand the primary function of a protease, it is important to discern bystander substrates from critical substrates. Because the former are generally processed with lower efficiency, data on the actual substrate cleavage efficiency could assist in categorizing protease substrates. In this study, quantitative mass spectrometry following metabolic proteome labeling (SILAC), combined with the isolation of N-terminal peptides by Combined Fractional Diagonal Chromatography, was used to monitor fluxes in the concentration of protease-generated neo-N-termini. In our experimental setup, a Jurkat cell lysate was treated with the human serine protease granzyme B (hGrB) for three different incubation periods. The extensive list of human granzyme B substrates previously catalogued by N-terminal Combined Fractional Diagonal Chromatography (1) was then used to assign 101 unique hGrB-specific neo-N-termini in 86 proteins. In this way, we were able to define several sites as getting efficiently cleaved in vitro and consequently recognize potential physiologically more relevant substrates. Among them the well-known hGrB substrate Bid was confirmed as being an efficient hGrB substrate next to several other potential regulators of hGrB induced apoptosis such as Bnip2 and Akap-8. Several of our proteomics results were further confirmed by substrate immunoblotting and by using peptide substrates incubated with human granzyme B.

Serial Non-Invasive Myocardial Work Measurements for Patient Risk Stratification and Early Detection of Cancer Therapeutics-Related Cardiac Dysfunction in Breast Cancer Patients: A Single-Centre Observational Study.

Serial transthoracic echocardiographic (TTE) assessment of LVEF and GLS are the gold standard in screening Cancer Therapeutics-Related Cardiac Dysfunction (CTRCD). Non-invasive left-ventricle (LV) pressure-strain loop (PSL) emerged as a novel method to quantify Myocardial Work (MW). This study aims to describe the temporal changes and longitudinal trajectories of MW indices during cardiotoxic treatment. We included 50 breast cancer patients with normal LV function referred for anthracycline therapy w/wo Trastuzumab. Medical therapy, clinical and echocardiographic data were recorded before and 3, 6, and 12 months after initiation of the chemotherapy. MW indices were calculated through PSL analysis. According to ESC guidelines, mild and moderated CTRCD was detected in 10 and 9 patients, respectively (20% CTRCDmild, 18% CTRCDmod), while 31 patients remained free of CTRCD (62% CTRCDneg). Prior to chemotherapy MWI, MWE and CW were significantly lower in CTRCDmod than in CTRCDneg and CTRCDmild. Overt cardiac dysfunction in CTRCDmod at 6 months was accompanied by significant worse values in MWI, MWE and WW compared to CTRCDneg and CTRCDmild. MW features such as low baseline CW, especially when associated with a rise in WW at follow-up, may identify patients at risk for CTRCD. Additional studies are needed to explore the role of MW in CRTCD.

Utilizing longitudinal data in assessing all-cause mortality in patients hospitalized with heart failure.

AIMS: Risk stratification in patients with a new onset or worsened heart failure (HF) is essential for clinical decision making. We have utilized a novel approach to enrich patient level prognostication using longitudinally gathered data to develop ML-based algorithms predicting all-cause 30, 90, 180, 360, and 720 day mortality. METHODS AND RESULTS: In a cohort of 2449 HF patients hospitalized between 1 January 2011 and 31 December 2017, we utilized 422 parameters derived from 151 451 patient exams. They included clinical phenotyping, ECG, laboratory, echocardiography, catheterization data or percutaneous and surgical interventions reflecting the standard of care as captured in individual electronic records. The development of predictive models consisted of 101 iterations of repeated random subsampling splits into balanced training and validation sets. ML models yielded area under the receiver operating characteristic curve (AUC-ROC) performance ranging from 0.83 to 0.89 on the outcome-balanced validation set in predicting all-cause mortality at aforementioned time-limits. The 1 year mortality prediction model recorded an AUC of 0.85. We observed stable model performance across all HF phenotypes: HFpEF 0.83 AUC, HFmrEF 0.85 AUC, and HFrEF 0.86 AUC, respectively. Model performance improved when utilizing data from more hospital contacts compared with only data collected at baseline. CONCLUSIONS: Our findings present a novel, patient-level, comprehensive ML-based algorithm for predicting all-cause mortality in new or worsened heart failure. Its robust performance across phenotypes throughout the longitudinal patient follow-up suggests its potential in point-of-care clinical risk stratification.

Hemodynamic Response to Acute Volume Load and Endomyocardial NO-synthase Gene Expression in Heart Transplant Recipients.

A pulmonary capillary wedge pressure (PCWP) >18 mm Hg following volume load has been proposed as a partition value for the detection of heart failure with preserved ejection fraction. As hemodynamic changes in filling pressures (FP) have been attributed to a nitric oxide (NO)-mediated rightward shift of the pressure-volume relationship, we investigated the hemodynamic response to volume load in heart transplant recipients (HTx) and examined the role of inducible NO synthase (iNOS) gene expression on diastolic function changes. Methods: In 36 HTx, FPs were measured before and after volume load, following which Starling curves were constructed using PCWP and cardiac index (CI). Patients were categorized into those with normal (group A, n = 21) and abnormal hemodynamics (group B, n = 15, PCWP >15 mm Hg at rest or >18 mm Hg following volume load). For the establishment of the potential role of NO, endomyocardial iNOS gene expression level was measured. Results: Except for PCWP (P < 0.001) and mean pulmonary artery pressure (P < 0.001) no differences in age, baseline characteristics, and ejection fraction were observed between both groups, and volume load significantly increased PCWP in both groups (group A: P < 0.001 and group B: P < 0.001) without any change in heart rate. Interestingly, volume load significantly increased CI in group A (P < 0.001) but not in group B (P = 0.654), and the Starling curves revealed a higher CI at any given PCWP in group A together with significantly higher iNOS gene expression (P = 0.009). Conclusions: In HTx, volume load increases FP and unmasks the presence of left ventricular diastolic dysfunction. Interestingly, following saline load group B shows a blunted Starling response, with higher PCWP and lack of CI increase at any given PCWP. The higher iNOS gene expression level in group A suggests a potential role of NO as mediator of diastolic function.

Analysis of protein processing by N-terminal proteomics reveals novel species-specific substrate determinants of granzyme B orthologs.

Using a targeted peptide-centric proteomics approach, we performed in vitro protease substrate profiling of the apoptotic serine protease granzyme B resulting in the delineation of more than 800 cleavage sites in 322 human and 282 mouse substrates, encompassing the known substrates Bid, caspase-7, lupus La protein, and fibrillarin. Triple SILAC (stable isotope labeling by amino acids in cell culture) further permitted intra-experimental evaluation of species-specific variations in substrate selection by the mouse or human granzyme B ortholog. For the first time granzyme B substrate specificities were directly mapped on a proteomic scale and revealed unknown cleavage specificities, uncharacterized extended specificity profiles, and macromolecular determinants in substrate selection that were confirmed by molecular modeling. We further tackled a substrate hunt in an in vivo setup of natural killer cell-mediated cell death confirming in vitro characterized granzyme B cleavages next to several other unique and hitherto unreported proteolytic events in target cells.

In vitro and in vivo protein-bound tyrosine nitration characterized by diagonal chromatography.

A new proteomics technique for analyzing 3-nitrotyrosine-containing peptides is presented here. This technique is based on the combined fractional diagonal chromatography peptide isolation procedures by which specific classes of peptides are isolated following a series of identical reverse-phase HPLC separation steps. Here dithionite is used to reduce 3-nitrotyrosine to 3-aminotyrosine peptides, which thereby become more hydrophilic. Our combined fractional diagonal chromatography technique was first applied to characterize tyrosine nitration in tetranitromethane-modified BSA and further led to a high quality list of 335 tyrosine nitration sites in 267 proteins in a peroxynitrite-treated lysate of human Jurkat cells. We then analyzed a serum sample of a C57BL6/J mouse in which septic shock was induced by intravenous Salmonella infection and identified six in vivo nitration events in four serum proteins, thereby illustrating that our technique is sufficiently sensitive to identify rare in vivo tyrosine nitration sites in a very complex background.

Acalculous cholecystitis and tamponade: an unusual combination?

Although pericardial effusion is a well-known feature of Churg-Strauss syndrome, cardiac tamponade has rarely been encountered. The present report describes a case of Churg-Strauss syndrome that presented as an acute cholecystitis and was complicated by tamponade. Histopathological exam of both pericardium and gall bladder was conclusive for Churg-Strauss syndrome.

Circulating SERPINA3 improves prognostic stratification in patients with a de novo or worsened heart failure.

AIMS: We investigated the prognostic relevance of serpin peptidase inhibitor, clade A member 3 (SERPINA3) in patients admitted with a de novo or worsened heart failure (HF). METHODS AND RESULTS: In the first stage, 83 HF-related left ventricular (LV) transcripts were examined in patients with congestive cardiomyopathy (CCMP, n = 44) who died within 5 years and compared with age-matched and haemodynamically matched CCMP survivors (n = 39) and controls with normal LV function (n = 17). Among 14 differentially expressed transcripts, myocardial gene and circulating SERPINA3 levels were up-regulated in non-survivors vs. survivors (2.40 ± 3.66 vs. 0.36 ± 0.22 units, P < 0.01 and 334.7 ± 138.7 vs. 228.2 ± 83.1 µg/mL, P < 0.01, respectively). While no significant transmyocardial gradient was detected, cytokine stimulation of human endothelial cells induced SERPINA3 secretion. In an independent validation cohort with a de novo or worsened HF (n = 387), circulating SERPINA3 levels > 316 µg/mL were associated with increased all-cause mortality {hazard ratio [HR] [95% confidence interval (CI)]: 2.4 [1.5-3.9], P = 0.0002} and its composite with unplanned cardiovascular readmission [HR (95% CI): 2.0 (1.2-3.3), P = 0.004]. Patients with elevated SERPINA3 levels and elevated either N-terminal pro brain natriuretic peptide or ST2 showed worse freedom from both endpoints. In a multivariate analysis, including established clinical risk factors, SERPINA3 remained independent predictor of all-cause mortality together with age, gender, ST2, glomerular filtration, and pulmonary capillary wedge pressure. CONCLUSION: In patients with a de novo or worsened HF, increased SERPINA3 levels > 316 µg/mL are associated with increased mortality or unplanned cardiac readmission. Elevated SERPINA3 levels on top of established clinical predictors appear to identify a subgroup of HF patients at higher mortality risk. Prospective studies should further validate its value in prognostic stratification of HF.