Man-machine interaction-based phenotyping preprocedurally identifies patients with severe aortic stenosis, who will not recover from cardiac damage following transcatheter aortic valve replacement

Background

Severe aortic stenosis (AS) can lead to left heart dysfunction, pulmonary hypertension (PH), and eventually right heart failure. Clinical phenotypes therefore appear heterogeneous, depending on disease progression and comorbidities.

Purpose

This study therefore sought to improve diagnostic and prognostic resolution in patients undergoing transcatheter aortic valve replacement (TAVR) for severe AS by developing a man-machine interaction-based phenotyping approach.

Methods

Unsupervised agglomerative clustering was applied to preprocedural data from echocardiography and right heart catheterization from 366 consecutively enrolled patients undergoing TAVR for severe AS. Echocardiographic follow-up data, obtained on day 147±75.1 after TAVR, were available from 247 patients (67.5%).

Results

Cluster analysis revealed four distinct phenotypes, reflecting various extents of disease severity, and hence differing in mortality.

Patients from cluster 1 presented with preserved left ventricular ejection fraction (LVEF; 57.2±6.4%) and with normal mean pulmonary artery pressure (mPAP) levels (21.2±6.5 mmHg).

In contrast, patients in cluster 2 suffered from postcapillary PH (mPAP: 34.2±7.8 mmHg).

Left heart failure (LVEF: 42.4±15.7%), severe PH (mPAP: 46.9±8.5 mmHg), and right heart dysfunction (tricuspid annular plane systolic excursion [TAPSE]: 16.1±4.57 mm) characterized patients in cluster 3.

Patients from cluster 4 showed mild postcapillary PH (mPAP: 27.5±9.2 mmHg), yet dilatation of all heart chambers, biventricular dysfunction (LVEF: 47.3±12.2%, TAPSE: 16.8±4.5 mm), and a high prevalence of both mitral and tricuspid regurgitation (12.5% and 14.8%, respectively).

Correction of severe AS by TAVR significantly reduced the proportion of patients suffering from concurrent severe mitral regurgitation (from 9.29% to 3.64%, p-value: 0.0015). Moreover, pulmonary artery pressures were ameliorated (estimated systolic pulmonary artery pressure: from 47.2±15.8 mmHg to 43.3±15.1 mmHg, p-value: 0.0079). However, right heart dysfunction as well as the proportion of patients with severe tricuspid regurgitation remained unchanged. Clusters 3 and 4 with persistent right heart dysfunction ultimately displayed 2-year survival rates of 69.2% (95% CI: 56.6–84.7%) and 74.6% (95% CI: 65.9–84.4%), which were significantly lower compared to clusters 1 and 2 with little or no persistent cardiopulmonary impairment (88.3% [95% CI: 83.3–93.5%] and 85.5% [95% CI: 77.1–94.8%]).

Conclusion

This phenotyping approach preprocedurally identifies patients with severe AS, who will not recover from extra-aortic valve cardiac damage following TAVR and whose survival is therefore significantly reduced. Importantly, not the degree of PH at initial presentation, but the irreversibility of right heart dysfunction determines prognosis.

Funding Acknowledgement

Type of funding sources: None.

Influence of radiotherapy on cardiac implantable device lead parameters

Purpose

Incidences of both cardiac implantable electronic devices (CIED) and malignant tumors are rising, likewise the number of patients undergoing radiotherapy (RT) while having CIED increases. There is evidence that there is a higher failure rate with increasing cumulative dose at device and higher – neutron-inducing – photon beam energy above 10 MV. There is a paucity of data regarding lead function, lead insertion site dose and analysis of change of lead parameter during RT treatment. Aim of this work is a detailed analysis of CIED malfunctions and technical alterations in patients treated at our clinic with a special focus on device lead parameters.

Methods

In a total of 54 patients treated at our department, we evaluated the dose statistics for the leads and devices as well as lead parameters aggregated through telemetric device interrogations. Irradiation mostly took place in the thoracic (32%), pelvic (24%) and the head region (22%). A total of 80% of all patients had implanted a pacemaker and 17% an implantable cardioverter defibrillator. Two Patients (4%) were under cardiac resynchronization therapy. Overall 33% of patients were device-dependent.

Dose statistics for myocardial lead insertion sites and CIED were calculated. We collected interrogation data (intrinsic pacing impedance, pacing threshold, signal amplitude) before and after RT treatment (median number of interrogations was 3, range 1–22) and information about any CIED malfunction.

We assessed whether lead parameters changes exceeded predefined thresholds of 30% in pacing impedance, 50% in pacing threshold, or 50% in signal amplitude.

Results

24 of the 54 patients received a measurable dose at the device (median dose of patients with thoracic RT: 1.82 Gy, range 0.18–14.88 Gy). Dose data was available for atrial leads of 12 patients (median dose 7.27 Gy, ranging from barely measurable to 46.02 Gy) and right-ventricular leads of 13 patients (median dose 0.83 Gy, range 0.004–42.66 Gy).

There was no lead parameter threshold violation for pacing impedance detected, however predefined thresholds of signal amplitude and pacing threshold were exceeded in 14% and 15% of cases, respectively. These threshold violations did not compromise device function. There was no significant difference of lead parameter changes when patient groups receiving more and less than 10 Gy at lead insertion site were compared.

Two CIEDs (4%) showed a malfunction (electric restart of device) during RT, however no clinically relevant complication was reported. Both patients underwent thoracic RT (esophageal cancer) with a beam energy of 10 and 15 MV.

Conclusion

In the observed patient group, lead parameter threshold violation was neither able to predict a device malfunction nor dependent of cumulative dose at myocardial insertion side. Device malfunction occurred rarely and only at higher beam energies, however with no life-threatening outcome.

Funding Acknowledgement

Type of funding sources: None.

Man-machine interaction-based phenotyping identifies pathophysiologically and prognostically informative clusters among patients with mitral regurgitation undergoing transcatheter edge-to-edge repair

Background

Depending on etiology, extent of disease progression, and comorbidities, patients with severe mitral regurgitation (MR) typically present with considerable heterogeneity.

Purpose

This study therefore sought to improve diagnostic and prognostic resolution in patients undergoing mitral valve transcatheter edge-to-edge repair (MV TEER) for severe MR by developing a man-machine interaction-based phenotyping approach.

Methods

All 609 patients from this single-center registry underwent MV TEER for severe MR between 2009 and 2020. Unsupervised agglomerative clustering was applied to preprocedural echocardiography data, and an artificial neural network (ANN) was subsequently trained for future patient-to-cluster assignment. Primary outcome measure was postprocedural 5-year survival

Results

Cluster analysis revealed four pathophysiologically and prognostically informative phenotypes:

Cluster 1 was constituted by patients (n=188) presenting with preserved left ventricular ejection fraction (LVEF; 56.5±7.79%) and regular left ventricular end-systolic diameter (LVESD; 35.2±7.52 mm). 5-year survival in patients from cluster 1, hereinafter serving as a reference, was 60.9% (95% CI: 53.3–69.7%).

Patients from cluster 2 (n=102) also presented with preserved LVEF (55.7±7.82%) and regular LVESD (34.9±7.68 mm), but showed the largest mitral valve effective regurgitant orifice area (0.623±0.360 cm2) and highest systolic pulmonary artery pressures (68.4±16.2 mmHg). Consequently, their 5-year survival ranged at 43.7% (95% CI: 33.2–57.6%; p-value: 0.032).

Patients from cluster 3 (n=270) were predominantly characterized by impaired left ventricular systolic function (LVEF: 31.0±10.4%) and dilated left ventricular diameters (LVESD: 53.2±10.9 mm), and their 5-year survival was reduced to 38.3% (95% CI: 31.9–46.1%; p-value: <0.001).

Poorest 5-year survival (23.8% [95% CI: 12.8–44.3%]; p-value: <0.001) was observed in patients from cluster 4 (n=49) with biatrial dilatation (left atrial volume: 312±113 mL; right atrial area: 46.0±8.83 cm2) although LVEF was only slightly reduced (51.5±11.0%). All patients from cluster 4 were diagnosed with atrial fibrillation.

An ANN could precisely predict cluster assignment (accuracy: 85.2%), detecting patients from high-risk clusters 3 and 4 with excellent specificity (95.0% and 99.4%, respectively).

Conclusion

Assigning patients to clusters using a multiparametric phenotypic approach can facilitate risk stratification in future clinical practice. Our unsupervised machine learning-based classification system differs from previous approaches for risk stratification, because we do neither hypothesize a linear sequence of accumulated pathologies caused by severe MR (potentially ignoring the aggravating impact of comorbidities), nor do we stratify patients into low- and high-risk cohorts in accordance with a single variable's dichotomy (prone to oversimplification).

Funding Acknowledgement

Type of funding sources: None.

Ticagrelor or prasugrel in patients with acute coronary syndrome and high bleeding risk

Background

The relative efficacy and safety of more potent P2Y12 inhibitors in patients with acute coronary syndrome (ACS) and high bleeding risk (HBR) undergoing percutaneous coronary intervention (PCI) remains unclear.

Purpose

To study the treatment effect of ticagrelor and prasugrel in PCI patients presenting with ACS and HBR.

Methods

This post-hoc analysis of the ISAR-REACT 5 trial included patients with ACS undergoing PCI, randomized to ticagrelor or prasugrel, in whom HBR was defined as per Academic Research Consortium criteria. The primary (efficacy) endpoint was the composite of all-cause death, myocardial infarction, or stroke. The secondary (safety) endpoint was Bleeding Academic Research Consortium (BARC) type 3 to 5 bleeding. Outcomes were assessed 12 months after randomisation.

Results

Out of the 3,239 patients included in this analysis, 486 fulfilled the criteria for ARC-HBR definition (HBR group; ticagrelor, n=230 and prasugrel, n=256), whilst 2,753 did not (non-HBR group; ticagrelor, n=1,375 and prasugrel, n=1,378). Compared to the non-HBR group, the HBR group had a higher risk for the primary (hazard ratio [HR]=3.57, 95% confidence interval [CI], 2.79–4.57, p<0.001), and secondary endpoint (HR=2.94 [2.17–3.99], p<0.001). In the HBR group, the primary (HR=1.09; [0.73–1.62]) and secondary (HR=1.18 [0.67–2.08]) endpoints were not statistically different between patients assigned to ticagrelor and prasugrel. In the non-HBR group, the primary endpoint (HR=1.62 [1.19–2.20]) occurred more frequently in patients assigned to ticagrelor as compared to patients assigned to prasugrel, without difference in safety (HR=1.08 [0.74–1.58]). There was no treatment allocation-by-HBR status interaction with respect to the primary (p for interaction = 0.123), or secondary (p for interaction = 0.803) endpoints.

Conclusions

In patients with ACS undergoing PCI, HBR status increased both ischemic and bleeding risks without significant impact on the relative efficacy or safety of ticagrelor versus prasugrel. These results warrant confirmation in larger cohorts.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Center for Cardiovascular Research (DZHK)Deutsches Herzzentrum München

Ticagrelor or prasugrel in patients with acute coronary syndrome and prior myocardial infarction

Objectives

To investigate the efficacy and safety of ticagrelor versus prasugrel in patients with acute coronary syndrome (ACS) and prior myocardial infarction (MI).

Background

The efficacy and safety of ticagrelor versus prasugrel in ACS patients with prior MI remains unstudied.

Methods

Patients with ACS scheduled for an invasive strategy and randomized to ticagrelor or prasugrel in the ISAR-REACT 5 trial with available information concerning prior MI were included in the present analysis. The primary endpoint was the composite of all-cause death, myocardial infarction, or stroke; the secondary endpoint was Bleeding Academic Research Consortium (BARC) type 3 to 5 bleeding. Endpoints were assessed 12 months after randomization.

Results

A total of 4,015 patients were included in this analysis (prior MI= 631 patients; no prior MI = 3,384 patients). As compared to patients without prior MI, the primary endpoint occurred more frequently in patients with prior MI (12.6% vs. 7.2%; hazard ratio [HR] = 1.78, 95% confidence interval [CI] 1.38–2.29; p= <0.001) without significant difference in terms of secondary endpoint between groups (5.8% vs. 5.7%; HR=1.02 [0.71–1.45]; p=0.921). Patients with prior MI randomized to ticagrelor versus prasugrel displayed higher risk for primary (HR=1.62 [1.03–2.55]) but not secondary endpoint (HR=1.28 [0.56–2.91]). Patients without prior MI randomized to ticagrelor or prasugrel displayed no significant difference in terms of primary (HR=1.28 [0.99–1.65]) or secondary endpoints (HR=1.13 [0.82–1.55]). There was no treatment assignment-by-prior MI status interaction with respect to the primary (p for interaction = 0.373) and the secondary (p for interaction= 0.786) endpoints.

Conclusions

Patients with ACS and prior MI are at higher risk for recurrent ischemic but not bleeding events. The history of MI does not affect the relative efficacy and safety of ticagrelor versus prasugrel in patients with ACS.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Center for Cardiovascular Research (DZHK)Deutsches Herzzentrum München

Beyond the prothrombotic transcript of RPs: alternative splicing and circular RNAs

Funding Acknowledgements

Type of funding sources: Foundation. Main funding source(s): German Center for Cardiovascular Research (DZHK)

Background/Introduction

RPs are young, hyper-reactive and RNA-rich platelets. They have a pro-thrombotic potential, are predictors of an insufficient response to antiplatelet therapy after myocardial infarction and are suggested to play a key role in patients with chronic coronary syndrome (CCS) and high on-treatment platelet reactivity. Moreover, RPs are promising novel biomarkers for the prediction of adverse cardiovascular events in different pathological settings.

Purpose

We aimed to compare for the first time the transcriptomic profiles of RPs and MPs in CCS patients.

Method

Using fluorescent activated cell sorting (FACS), we isolated RPs and MPs based on their RNA content from peripheral blood of 19 CCS patients. After sorting, RNA was extracted and quality, concentration and integrity were assessed with the Tapestation 4200 platform (Agilent). TotalRNA libraries were prepared, multiplexed and sequenced on a NextSeq 500 Illumina platform obtaining 80 to 100 million paired-end reads per sample. RNA-sequencing analysis was performed with R and DESeq2, a cut-off of p <0.005 and a log2fc >1 was applied. Alternative splicing event detection and analysis was performed with MAJIQ. We performed circular RNA (circRNA) analysis using CIRCexplorer.

Results

With total RNA-sequencing, we detected 1589 genes differentially expressed with 1100 transcripts upregulated in RPs, while 489 were enriched in MPs (Figure 1 A and B). In particular, transcripts for the collagen receptor GP6 (log2FC 1.12, p=6.89x10-41), thrombin receptor PAR4 (F2RL3, log2FC 1.1, p=3.54*10-21) and Von Willebrand Factor (log2FC 1.2, p value 1.26*10-38) were significantly enriched in RPs. We found an enrichment in MPs of transcript coding for genes involved in RNA processing such as the splicing regulator LUC7L3 (log2FC -1.01, p value 6.65*10-22). We detected several splicing events differentially regulated: an alternative splicing on the transcript GP6 is upregulated in RPs (Figure 1C); by the G-protein GNAQ transcript, one alternative splicing event was found upregulated in RPs, while two others were upregulated in MPs. Additionally, we detected an enrichment of the total level of circular RNAs in MPs compared to RPs (Figure 1E). Nevertheless, several circular RNAs that have not been described before were found enriched in RPs (Figure 1F).

Conclusion

This study represents the first transcriptomic profiling of RPs and MPs in patients with CCS and provides for the first time a biological explanation of RPs’ hyper-reactivity. The clear upregulation of prothrombotic signaling in RPs could provide and explanation to their hyperactivity and their correlation with cardiovascular events in different pathological settings. Altogether, these findings shed light on a new therapeutic niche in CCS patients. Nonetheless, the detrimental role of RPs in patients with coronary artery disease requires further investigations

Deep proteome profiling of mature and reticulated platelets in patients with chronic coronary syndrome using mass cytometry

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by the German Center for Cardiovascular

Research (DZHK grant number Deutsches Zentrum für Herz-

Kreislaufforschung 81 × 3600606 to D.B.).

Abstract:

Background/Introduction

Reticulated platelets (RPs) are prothrombotic RNA-rich platelets suggested to be detrimental in patients with chronic coronary syndrome (CCS) and high on treatment platelet reactivity. In addition, circulating RPs levels are independent predictor for adverse cardiovascular events in CCS patients and other pathological settings. However, RPs biology still need to be investigated.

Purpose

We thought to investigate the RPs proteome on single-cell level at rest and after activation using time-of-flight mass cytometry (CyTOF).

Method

Thrombocytes from peripheral blood of 11 CCS patients were isolated, prepared for CyTOF and stained with a custom-made CyTOF-antibody panel of 20 antibodies targeting important transmembrane proteins (anti-CD9, anti-CD29, anti-CD31, anti-CD36-, anti-CD40, anti-CD41, anti-CD42a, anti-CD42b-, anti-CD47, anti-CD61, anti-CD62P-, anti-CD63, anti-CD69, anti-CD107a, anti-CD154, anti-GPVI, anti-GPIIbIIa complex, anti-Par1, anti-PEAR-1 and the negative control anti-CD3 coupled with different metal isotopes). Two samples were prepared from each patient: one baseline sample (non-stimulated platelets) and one sample stimulated with 10 μM thrombin receptor-activating peptide (TRAP). According to previous experiences and common practice, we detected RPs and mature platelets (MPs) based on their RNA content. We analyzed the results with a custom bioinformatic pipeline comparing RPs to MPs expression. Earth mover’s distance (EMD) was assed as a measure of differential expression.

Results

While our bioinformatic analysis revealed that all transmembrane markers are significantly higher expressed in the larger RPs compared to MPs, not all markers differ to the same extend. Interestingly, the four markers with the highest calculated EMD (values in brackets) are all key regulators of platelet activation and aggregation: the collagen receptor GPVI (34.18), the collagen integrin receptor unit CD29 (ITGB1: 33.17), the adhesion protein CD9 (32.94) and the von Willebrand receptor unit CD42b (GPIbalpha) (30.08) (Figure 1A).

Regarding the activation marker expression upon TRAP stimulation, RPs show higher median signal intensities of all four activation markers compared to MPs (Figure 1B and C). Especially, the markers CD107a (LAMP-1) and CD154 (CD40L) are expressed in MPs only to a very low extend, whereas there is a clear overexpression in RPs.

Conclusion

This dataset provides the first high resolution analysis of RPs proteome at rest and upon activation. The pro-thrombotic profile of RPs explains their hyperactivity and could offer the first biomolecular explanation of the detrimental role of RPs in CCS patients. In addition, this dataset provide high resolution biomolecular information which could be useful to personalize antiplatelet therapy in patients with high RPs levels.

Efficacy and safety of ticagrelor versus prasugrel in smokers and nonsmokers with acute coronary syndromes

Background

The efficacy and safety of ticagrelor versus prasugrel according to smoking status in patients with acute coronary syndromes (ACS) are not known.

Purpose

The aim of this study was to assess the efficacy and safety of ticagrelor versus prasugrel according to smoking status in patients with ACS undergoing invasive evaluation.

Methods

This pre-specified analysis of the ISAR-REACT 5 trial included 1349 smokers and 2652 nonsmokers randomised to receive ticagrelor or prasugrel. The primary endpoint was the incidence of death, myocardial infarction, or stroke; the secondary endpoint was the incidence of Bleeding Academic Research Consortium (BARC) type 3 to 5 bleeding. Both endpoints were assessed at 12 months after randomisation.

Results

There was no significant treatment arm-by-smoking status interaction regarding the efficacy outcome. The primary endpoint occurred in 47 patients (7.0%) in the ticagrelor group and 41 patients (6.2%) in the prasugrel group in smokers (hazard ratio [HR]=1.15; 95% confidence interval [CI] 0.76–1.75; P=0.510) and in 133 patients (10.2%) in the ticagrelor group and 94 patients (7.2%) in the prasugrel group in nonsmokers (HR=1.44 [1.10–1.87], P=0.007; Pint=0.378). The secondary endpoint occurred in 27 patients (4.6%) in the ticagrelor group and 33 patients (5.6%) in the prasugrel group in smokers (HR=0.81 [0.49–1.35]; P=0.412) and in 66 patients (6.0%) in the ticagrelor group and 46 patients (4.4%) in the prasugrel group in nonsmokers (HR=1.38 [0.94–2.01]; P=0.097).

Conlusions

Although there was no significant interaction between smoking and treatment effect, the present findings suggest a greater advantage of prasugrel over ticagrelor in nonsmoker vs. smoker patients with ACS.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Centre for Cardiovascular Research;Deutsches Herzzentrum München, Germany

Reticulated platelet mass cytometry reveals unexplored therapeutic targets in patients with chronic coronary syndrome

Background

Reticulated platelets (RPs) are young, hyper-reactive thrombocytes that contain more RNA compared with mature platelets (MPs). The measurement of RPs level in peripheral blood with point-of-care systems is fast, reproducible, and inexpensive. Elevated RPs in peripheral blood predict adverse events in patients with acute and chronic coronary syndrome through unknown mechanisms. Preliminary transcriptome analyses reported an enrichment of pro-thrombotic transcripts. However, proteomic analyses are not available, and the biological features of RPs are largely unknown.

Purpose

We aimed to perform the largest proteomic characterization of RPs using mass cytometry with single-cell resolution in patients with chronic coronary syndrome (CCS) undergoing dual antiplatelet therapy (DAPT).

Methods

Thrombocytes from peripheral blood of CCS patients were isolated, prepared for mass cytometry (CyTOF) and stained with a custom-made CyTOF-panel of 20 antibodies targeting important transmembrane proteins (anti-CD9, anti-CD29, anti-CD31, anti-CD36-, anti-CD40, anti-CD41, anti-CD42a, anti-CD42b-, anti-CD47, anti-CD61, anti-CD62P-, anti-CD63, anti-CD69, anti-CD107a, anti-CD154, anti-GPVI, antiGPIIb/GPIIIa complex, anti-Par1, anti-PEAR-1 and the negative control anti-CD3 coupled with different metal isotopes). Two samples were prepared from each donor: one baseline sample (non-stimulated platelets) and one sample stimulated with 10 μM thrombin receptor-activating peptide (TRAP). According to previous experiences and common practice, we detected RPs and MPs based on their RNA content. We analyzed the results with a custom bioinformatic pipeline.

Results

13 patients with CCS on DAPT were included in this study. Mass cytometry highlighted an expression heterogeneity of relevant transmembrane proteins in thrombocytes of CCS patients (Figure 1A-B colored according to expression level: from blue-low to red-high). CyTOF detected an upregulation of important transmembrane receptors in RPs compared to MPs in quiescent platelets: GPVI (p<0.0001), PAR-1 (p<0.0001), GPIX (p<0.0001), and GPIbα (p<0.0001, Figure 1C). After TRAP-stimulation, RPs expressed higher levels of the activation markers P-Selectin (p=0.0016) and LAMP-3 (CD63, p<0.0001) compared to MPs confirming RPs hyperactivity (Figure 1D).

Conclusion

We here describe the first biological proteomic characterization with single-cell resolution of RPs biology in CCS patients. The upregulation of the activation markers P-Selectin and LAMP-3 as well as of specific transmembrane proteins as the collagen receptor GPVI and the thrombin receptor PAR-1 in patients treated with DAPT (schematic overview in Figure 2) provides the first solid biomolecular explanation of RPs hyper-reactivity and involvement in cardiovascular disease. Moreover, these results offer unexplored therapeutic targets to tailor antiplatelet therapy based on platelet protein expression in patients with elevated RPs

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Center for Cardiovascular Research (DZHK) Figure 1. Platelet expressionFigure 2. Schematic overview

Sub-phenotyping of patients with severe aortic stenosis undergoing transcatheter aortic valve replacement by unsupervised agglomerative clustering of echocardiographic and hemodynamic data

Background

Severe aortic stenosis (AS) can trigger a deleterious cascade of impairments including left heart dysfunction, pulmonary hypertension (PH), and eventually right heart failure. Clinical phenotypes therefore appear heterogeneous, depending on disease progression and comorbidities.

Purpose

This retrospective analysis aims to categorize patients with severe AS according to clinical presentation by applying unsupervised machine learning in combination with an artificial neural network (ANN).

Methods

Unsupervised agglomerative clustering was applied to pre-procedural data from echocardiography and right heart catheterization from 366 consecutively enrolled patients undergoing transcatheter aortic valve replacement (TAVR) for severe AS at two tertiary centers in Germany between 2014 and 2020. Association between cluster and 2-year all-cause mortality after TAVR was assessed, and an ANN was trained to open the avenue to prospectively predict cluster assignment in future patients.

Results

Cluster analysis revealed four distinct phenotypes, reflecting various extents of disease severity, and hence differing in mortality.

Patients from cluster 1, constituting the majority of cases and hereinafter referred to as reference, presented with regular cardiac function and without PH. Accordingly, estimated 2-year survival was 90.6% (95% CI: 85.8–95.6%).

Contrarily, patients from smallest cluster 3 displayed most extensive disease characteristics, i.e. left and right heart dysfunction together with combined pre- and postcapillary PH, and their 2-year mortality was increased (2-year survival: 77.3% (95% CI: 65.2–91.6%), HR for 2-year mortality: 2.6 (95% CI: 1.1–6.2); p-value: 0.025).

Clusters 2 and 4 comprised patients suffering from postcapillary PH. Whilst patients from cluster 2 showed similar survival as cluster 1 (2-year survival: 85.8% (95% CI: 76.9–95.6%)), patients from cluster 4 with right atrial enlargement and high prevalence of severe tricuspid regurgitation (TR) deceased more often (2-year survival: 74.9% (95% CI: 65.9–85.2%), HR for 2-year mortality: 2.8 (95% CI: 1.4–5.5); p-value: 0.004).

After randomly dividing the study population into derivation and validation cohorts, an ANN could precisely predict cluster assignment (accuracy: 83.5%), significantly outperforming the no information rate (46.8%; p-value: 2.26e-15). Importantly, patients from high-risk clusters 3 and 4 were detected with high sensitivity (100.0% and 85.2%, respectively) and specificity (95.9% and 95.1%, respectively).

Conclusion

Expanding the analytical armamentarium by machine learning technology aids in capturing complex clinical presentations as observed in patients with severe AS. Assigning patients to clusters can thus facilitate a more sophisticated risk stratification in future clinical practice. Addressing irreversibility of PH and persistence of severe TR after TAVR should obtain paramount priority in order to improve long-term survival.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Mark Lachmann receives funding from Technical University of Munich (Clinician Scientist Grant).

Body mass index and efficacy and safety of ticagrelor versus prasugrel in patients with acute coronary syndromes

Background

The efficacy and safety of ticagrelor versus prasugrel in patients with acute coronary syndromes (ACS) according to body mass index (BMI) remain unknown.

Purpose

To assess the efficacy and safety of ticagrelor versus prasugrel in patients with ACS according to BMI.

Methods

This post-hoc analysis of the ISAR-REACT 5 trial included 3987 patients with BMI data available. BMI was grouped in 3 categories: low (BMI<25 kg/m2, n=1084), intermediate (BMI ≥25 to <30 kg/m2, n=1890) and high (BMI≥30 kg/m2, n=1013). The primary endpoint was the 12-month incidence of all-cause death, myocardial infarction, or stroke. The secondary endpoint was the 12-month incidence of Bleeding Academic Research Consortium (BARC) type 3 to 5 bleeding.

Results

There was no significant treatment arm-by-BMI interaction regarding the primary endpoint (Pint=0.578). However, the primary endpoint occurred in 63 patients assigned to ticagrelor and 39 patients assigned to prasugrel in the low BMI group (11.7% vs. 7.5%; hazard ratio [HR]=1.62; 95% confidence interval [CI], 1.09–2.42; P=0.018), 78 patients assigned to ticagrelor and 58 patients assigned to prasugrel in the intermediate BMI group (8.3% vs. 6.2%; HR=1.36 [0.97–1.91]; P=0.076), and 43 patients assigned to ticagrelor and 37 patients assigned to prasugrel in the high BMI group (8.6% vs. 7.3%; HR=1.18 [0.76–1.84]; P=0.451). BARC type 3 to 5 bleeding events did not differ between ticagrelor and prasugrel in patients with low (6.5% vs. 6.6%), intermediate (5.6% vs. 5.0%), or high (4.4% vs. 2.8%) BMI.

Conclusions

BMI of patients with ACS did not impact significantly on the treatment effect of ticagrelor vs. prasugrel in terms of both efficacy and safety.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): German Center for Cardiovascular Research;Deutsches Herzzentrum München, Germany

Assessment of stent optimization in clinical practice using optical coherence tomography: a multicentric observational study

Background

Stent under-expansion obtained at the time of percutaneous coronary intervention (PCI) has been shown to be associated with worse outcomes.

Purpose

We sought to define OCT assessed optimal stent expansion index which associates with lower incidence of major adverse cardiac events (MACE) during follow-up in a sample of patients stented at five high volume centers of central Europe.

Methods

We analyzed 370 lesions stented during the period between 2012 and 2018, with their final procedural results imaged using optical coherence tomography (OCT). QIvus Research Edition v3.1 (Medis, Leiden, NL) was used for OCT analysis. The stented segment was split in two equal halves. Stent expansion index (SEI) was calculated for both halves separately by dividing minimum stent area by the mean reference lumen area [(proximal reference area + distal reference area)/2]. Smallest of the two prevailed as the SEI of that case. MACE during post-PCI follow-up was defined as composite of all-cause death, myocardial infarction, stent thrombosis and target lesion revascularization. Data is expressed as mean±SD or median (Interquartile range). Incidence of subsequent MACE is expressed as crude rates (%).

Results

A total of 316 cases (370 lesions), aged 64.6±11.7 years were included for OCT analysis. Of them, 78.8% were males, 22.8% were diabetics, 75.9% were hypertensives while 35.1% had family history of coronary artery disease. 38.0% of the cases had acute coronary syndrome at presentation. 62.4% of treated lesions were complex (Type B2/C). A mean of 1.11±0.34 stents/scaffolds were implanted per treated lesion. Analyzed segment length was 20.4 (15.17, 27.0) mm.

Minimal stent area (MSA) in the overall stented segment was 6.02 mm2 (4.65, 7.93). Median stent expansion index (minimum) was 0.79 (0.71, 0.86). Median follow-up duration was 557 days (326, 1,096). 47 lesions (12.7%) suffered MACE during follow-up. Receiver operating characteristic (ROC) curve analysis using Youden's rule identified 0.84 as SEI cut-off powered to predict post-PCI MACE (AUC= 0.60, sensitivity= 0.85, specificity= 0.34). MACE was observed in 38/249 (15.3%) of lesions with SEI≤0.84 and in 9/121 (7.4%) of lesions with SEI>0.84 (p=0.03). Univariate regression analysis of MACE revealed significant association with SEI≤0.84 (OR=2.2, 95% CI=1.1–4.8, p=0.04) Adaptive Lasso regression identified SEI≤0.84 (OR=4.1, 95% CI=1.3–12.6, p=0.02) and coronary calcification at baseline (OR=2.7, 95% CI=1.1–6.6, p=0.03) as independent predictors of MACE during follow-up. Kaplan-meier curve for MACE free survival with optimal SEI (n=121) and sub-optimal SEI (n=249) subgroups using SEI cut-off of 0.84, however showed modest separation (p=0.11).

Conclusions

The present study identified SEI>0.84 associated with lower incidence of MACE as optimal cut-off in daily practice. Along with SEI of ≤0.84, coronary calcification was also significantly associated with MACE during post PCI follow-up.

Funding Acknowledgement

Type of funding sources: None.

Somatic gene editing ameliorates skeletal and cardiac muscle failure in pig and human models of Duchenne muscular dystrophy

Frameshift mutations in the DMD gene, encoding dystrophin, cause Duchenne muscular dystrophy (DMD), leading to terminal muscle and heart failure in patients. Somatic gene editing by sequence-specific nucleases offers new options for restoring the DMD reading frame, resulting in expression of a shortened but largely functional dystrophin protein. Here, we validated this approach in a pig model of DMD lacking exon 52 of DMD (DMDΔ52), as well as in a corresponding patient-derived induced pluripotent stem cell model. In DMDΔ52 pigs1, intramuscular injection of adeno-associated viral vectors of serotype 9 carrying an intein-split Cas9 (ref. 2) and a pair of guide RNAs targeting sequences flanking exon 51 (AAV9-Cas9-gE51) induced expression of a shortened dystrophin (DMDΔ51-52) and improved skeletal muscle function. Moreover, systemic application of AAV9-Cas9-gE51 led to widespread dystrophin expression in muscle, including diaphragm and heart, prolonging survival and reducing arrhythmogenic vulnerability. Similarly, in induced pluripotent stem cell-derived myoblasts and cardiomyocytes of a patient lacking DMDΔ52, AAV6-Cas9-g51-mediated excision of exon 51 restored dystrophin expression and amelioreate skeletal myotube formation as well as abnormal cardiomyocyte Ca2+ handling and arrhythmogenic susceptibility. The ability of Cas9-mediated exon excision to improve DMD pathology in these translational models paves the way for new treatment approaches in patients with this devastating disease.

P4707Incidence and outcome of endovascular therapy in subclavian occlusive disease involving the vertebral artery origin

Background

Endovascular revascularization represents the treatment option of choice in symptomatic steno-occlusive disease of the subclavian artery (SA). While the majority of lesions are localized in the proximal segment of the subclavian artery, studies in regards to the medial segment involving the vertebral artery (VA) origin are scarce.

Purpose

The aim of this study was to analyze the technical approaches and outcome of endovascular therapy of subclavian artery disease with a special focus on medial lesions involving the VA origin.

Methods

We retrospectively analyzed all patients who underwent percutaneous revascularization of the subclavian or innominate artery with a special focus on medial lesions involving the VA origin.

Results

In total 196 patients with subclavian or innominate artery intervention were analyzed. The majority of lesions (83%) were located in the proximal, whereas 28 patients (14%) presented with lesions in the medial segment of the SA, and only 3% involved the distal segment. Overall procedural success was high for both stenosis (96%) and occlusion (89%) and did not differ according to the lesion location. Revascularization techniques in the medial segment included stenting of the SA only (13 patients), additional VA balloon-dilatation (6 Patients), and bifurcational stenting of the SA and VA using T-stenting technique (9 patients). Overall periprocedural complication rate was low (6%) and comparable between different SA segments (6% in proximal segment vs. 7% in medial segment vs. 0% in distal segment; p=0.81). Outcome assessed after a median of 12 months (interquartile range 4–30) showed no significant differences in terms of Kaplan-Meier estimated freedom from restenosis between proximal and medial lesions despite the technically demanding approach in the medial segment (90% vs. 95%; p=0.67).

Long-term patency

Conclusion

Endovascular revascularization of medial subclavian artery lesions involving the vertebral artery origin shows comparable safety and efficacy in terms of long-term patency rates compared to lesions located within the proximal subclavian artery. However, more complex endovascular techniques with bifurcational ballooning or stenting is required in a considerable number of patients with medial subclavian artery disease.

P5630Morphometric and qualitative differences in neointimal tissue six months after implantation of bioresorbable scaffolds versus conventional everolimus eluting stents in ISAR-Absorb MI trial

Background

Bioresorbable scaffolds (BRS) are novel devices designed to overcome the long-term limitations of permanent metallic stent implantation. Optical coherence tomography (OCT) surveillance can provide important insights on the process of vessel wall healing at follow-up.

Purpose

We sought to compare OCT-assessed healing at 6 months after implantation of everolimus-eluting BRS and everolimus-eluting metallic stents (EES) in patients treated for acute myocardial infarction (AMI).

Methods

ISAR-Absorb MI is a multicentre, 2:1 randomized trial comparing outcomes of patients with AMI stented with BRS or conventional EES. Angiographic surveillance was planned for all patients at 6–8 months follow-up. Patients who had OCT surveillance at follow-up were included for the present analysis. Analysis of contiguous OCT cross-sections- 1 mm apart was performed at a centralized core laboratory. Tissue characterisation using a 256-level grey-scale signal intensity (GSI) analysis was also performed for all neointimal regions of interest (ROI) with thickness of 100 to 400 μm. ROI's were classified as mature using a standard cut-off GSI score of 109.7. Generalised linear mixed model (GLMM) was used as appropriate. Statistical analysis was performed using R software. Data is presented as numbers, percentages or median (Interquartile range, IQR).

Results

Median follow-up interval was 216 days. 70 patients in the BRS arm and 33 patients in the EES arm were available for analysis. Stented length was 19.8 mm (13.6, 24.5) and 22.3 mm (16.7, 26.4) in BRS and EES arms respectively (p=0.73). Minimum lumen area [5.13 (3.95, 6.71) vs. 4.83 (3.63, 6.92) mm2] and minimum stent area [5.78 (4.88, 7.34) vs. 6.36 (4.70, 7.45) mm2] were comparable between BRS and EES.

2,262 frames (1,529 in BRS, 733 in EES) with 20,033 struts (12,704 in BRS, 7,329 in EES) were assessed. Overall strut coverage was better with BRS compared to EES (97.5% vs. 91.1% respectively, p<0.001). Malapposed (1.1% vs. 0.5%, p=0.54) and uncovered struts (7.3% vs. 1.3%, p<0.001) were more common with EES. Neointimal coverage was comparable amongst both stent groups [85.5 (61.9, 124.1) vs. 71.5 (33.4, 133.0) μm in BRS and EES groups respectively, p=0.50].

GSI analysis in 95 cases (65 cases, 2,233 ROIs in BRS; 30 cases, 1,210 ROIs in EES) showed that immature ROIs were numerically more common in the EES group as compared to the BRS group (75.4 vs. 57.0% respectively; p=0.35).

Two-year clinical follow-up and analysis of correlation of clinical outcomes with OCT findings will also be available for presentation at ESC Congress 2019.

Conclusions

In selected patients undergoing OCT imaging at 6–8 months after implantation of BRS and conventional EES for AMI, we observed generally favourable healing characteristics with high rates of strut coverage, low rates of strut malapposition and fewer areas of immature neointimal areas with BRS in comparison to EES.

Acknowledgement/Funding

The study was predominantly funded by Deutsches Herzzentrum München and in part by a grant from Abbott Vascular

P5574Prognostic impact of left atrial function following transcatheter mitral valve repair

Background

Left atrial (LA) function predicts clinical outcome in a variety of cardiovascular diseases. However, limited data is available in the setting of mitral regurgitation (MR).

Purpose

The aim of the present study was to assess potential changes in LA ejection fraction (LA-EF) and its prognostic value in patients following transcatheter mitral valve repair using the mitraclip.

Methods

A total of 88 consecutive patients undergoing mitraclip implantation with complete echocardiography at baseline and follow-up between 3 and 6 months post-procedure were enrolled.

Results

LA-EF improved in 58% of the population. Change in LA-EF was associated with residual MR, residual transmitral gradient and left ventricular ejection fraction (LV-EF) changes. Compared to their counterparts, patients with residual MR ≥ grade 2 (−6% [−9 to 1%] vs. 4% [−5 to 15%]; p=0.05) and with residual transmitral gradient ≥5 mmHg (−2% [−9 to 9%] vs. 5% [−4 to 16%]; p=0.03) showed a decline in LA-EF, respectively. Furthermore, LA-EF significantly correlated with changes in LV-EF (r=0.40; p=0.001). With regards to clinical outcome, heart failure symptoms as assessed by NYHA class were more severe in patients with worsened LA-EF at follow-up. Finally, LA-EF change was identified as independent predictor of all-cause mortality (HR 0.94 [0.90–0.98]; p=0.008).

Kaplan-Meier estimates for survival

Conclusion

The present analysis showed changes in LA function in patients undergoing mitraclip implantation to be associated with important measures including residual MR, elevated transmitral gradient and LV function. Importantly, LA function alterations represent a strong predictor for all-cause mortality.

5964Hybrid PET/MR imaging for the prediction of left ventricular (LV) recovery after revascularisation of chronic total occluded coronaries

Background

Percutaneous coronary intervention (PCI) of chronic total occlusion (CTO) represents one of the major challenges in interventional cardiology. Physicians are still reluctant in referring for PCI, assuming non viability of the myocardium subtended by the CTO. Data are controversial in assessing the improvement of left ventricular (LV) wall motion after revascularisation and the prognostic value of viability testing to guide patient selection.

Purpose

The aim of this study was to determine, whether hybrid fluorodeoxyglucose positron emission tomography/magnetic resonance (FDG PET/MR) imaging allows a more accurate prediction of LV regional wall motion recovery after successful PCI of CTOs in comparison to PET or MR alone.

Methods

We enrolled 49 consecutive symptomatic patients with CTO and evidence of wall motion abnormality in the corresponding CTO-territory. All patients underwent hybrid FDG PET/MR imaging as semi-quantitative assessment of myocardial viability - glucose metabolism in PET and late gadolinium enhancement (LGE) transmurality in MR – prior of PCI of the CTO. Follow-up MRI was performed in 23 patients 3–6 months after successful revascularisation to evaluate wall motion changes.

Results

We assessed viability in 124 myocardial segments subtended by a CTO in 23 patients with successful PCI who underwent serial imaging. Segments with wall motion abnormality at baseline (n=80) were analysed. Most of these segments (n=54, 68%) were concordantly assessed viable by PET and MR, conversely only 2 (2%) segments were assessed non-viable by both imaging techniques. However, almost one third of the segments showed discordant patterns of viability either PET not viable/ MR viable (3 (4%) segments) or PET viable/ MR not viable (21 (26%) segments): particularly the latter revealed a significant wall motion improvement (p=0.033).

The combination of PET and MR showed a fair accuracy in predicting myocardial segments with wall motion improvement after CTO revascularisation (PET/MR area under ROC curve (AUC) 0.72, SE 0.07, p=0.002), which was superior to MR-LGE (AUC=0.66, SE 0.09) and FDG-PET (AUC=0.58, SE 0.10) alone (Figure).

Comparisons of ROC curves

Conclusion

Hybrid PET/MR imaging prior to successful CTO showed a better performance than PET or MR alone in predicting regional improvement of disturbed wall motion.

The complimentary information derived from both modalities may particularly help to identify small amounts of viable epicardial myocardium within large scars which can improve contractility after CTO-revascularisation.

2181The prothrombotic transcriptome of reticulated platelets

Introduction

Reticulated platelets (RPs) are young, hyper-reactive platelets that are larger and contain significantly more RNA compared to older mature platelets. High levels of RPs in peripheral blood are predictors of an insufficient response to dual antiplatelet therapy in cardiovascular patients and of adverse cardiovascular events also in non-cardiac patients. However, the mechanisms underlying these correlations remains widely unknown and the biology of RPs has not been investigated yet.

Purpose

We aimed to compare for the first time the transcriptomic profiles of RPs and mature platelets (MPs).

Methods

RPs and MPs from peripheral blood of healthy donors were identified and isolated using FACS/Sorting based on their RNA-content. Immediately after sorting, RNA was extracted and quality, concentration and integrity was assessed with the Tapestation 4200 platform (Agilent). Total- and small-RNA libraries were prepared, multiplexed and sequenced on a NextSeq 500 Illumina platform

Results

Total-RNA-sequencing revealed 1744 differentially expressed genes (670 downregulated 1074 upregulated) in RPs compared to MPs (Figure 1A, B). In particular, transcripts for the collagen receptor GP6, thromboxane receptor A2 (TBXA2R), thrombin receptor PAR4 (F2RL3) and ATP receptor P2RX1 were significantly enriched in RPs, whereas several RNA regulators as the ribonuclease PARN, the RISC-component TNRC6A and the splicing factor LUC7L3 were downregulated in RPs. Gene ontology analysis revealed an enrichment of relevant biological categories in RPs including platelet activation and blood coagulation (Figure 1C). Gene Set Enrichment Analysis showed an enrichment of several activation pathways like thrombin, thromboxane and GPIIb/IIIa signaling in RPs. Small-RNA-sequencing reported 9 miRNAs significantly downregulated in RPs with targets involved in platelet reactivity.

Figure 1

Conclusions

This study represents the first comparative transcriptome analysis of RPs and MPs and reports for the first time a differential enrichment of transcripts involved in platelet activation. The clear upregulation of prothrombotic signaling in RPs could explain, at least in part, their hyper-activity and their correlation with cardiovascular events in different pathological settings (trancripts enriched in RPs: Figure 1D).

Acknowledgement/Funding

German Society of Cardiology (DGK Nr.102018) ESC First conctact initiative grant 2018

Blocking caspase-activated apoptosis improves contractility in failing myocardium

Cardiac myocyte apoptosis has been demonstrated in end-stage failing human hearts. The therapeutic utility of blocking apoptosis in congestive heart failure (CHF) has not been elucidated. This study investigated the role of caspase activation in cardiac contractility and sarcomere organization in the development of CHF. In a rabbit model of heart failure obtained by rapid ventricular pacing, we demonstrate, using in vivo transcoronary adenovirus-mediated gene delivery of the potent caspase inhibitor p35, that caspase activation is associated with a reduction in contractile force of failing myocytes by destroying sarcomeric structure. In this animal model gene transfer of p35 prevented the rise in caspase 3 activity and DNA-histone formation. Genetically manipulated hearts expressing p35 had a significant improvement in left ventricular pressure rise (+dp/dt), decreased end-diastolic chamber pressure (LVEDP), and the development of heart failure was delayed. To better understand this benefit, we examined the effects of caspase 3 on cardiomyocyte dysfunction in vitro. Microinjection of activated caspase 3 into the cytoplasm of intact myocytes induced sarcomeric disorganization and reduced contractility of the cells. These results demonstrate a direct impact of caspases on cardiac function and may lead to novel therapeutic strategies via antiapoptotic regimens.

Gene transfer of heterologous G protein-coupled receptors to cardiomyocytes: differential effects on contractility

In heart failure, reduced cardiac contractility is accompanied by blunted cAMP responses to beta-adrenergic stimulation. Parathyroid hormone (PTH)-related peptide and arginine vasopressin are released from the myocardium in response to increased wall stress but do not stimulate contractility or adenylyl cyclase at physiological concentrations. To bypass the defective beta-adrenergic signaling cascade, recombinant P1 PTH/PTH-related peptide receptors (rPTH1-Rs) and V(2) vasopressin receptors (rV(2)-Rs), which are normally not expressed in the myocardium and which are both strongly coupled to adenylyl cyclase, and recombinant beta(2)-adrenergic receptors (rbeta(2)-ARs) were overexpressed in cardiomyocytes by viral gene transfer. The capacity of endogenous hormones to increase contractility via the heterologous, recombinant receptors was compared. Whereas V(2)-Rs are uniquely coupled to Gs, PTH1-Rs and beta(2)-ARs are also coupled to other G proteins. Gene transfer of rPTH1-Rs or rbeta(2)-ARs to adult cardiomyocytes resulted in maximally increased basal contractility, which could not be further stimulated by adding receptor agonists. Agonists at rPTH1-Rs induced increased cAMP formation and phospholipase C activity. In contrast, healthy or failing rV(2)-R-expressing cardiomyocytes showed unaltered basal contractility. Their contractility and cAMP formation increased only at agonist exposure, which did not activate phospholipase C. In summary, we found that gene transfer of PTH1-Rs to cardiomyocytes results in constitutive activity of the transgene, as does that of beta(2)-ARS: In the absence of receptor agonists, rPTH1-Rs and rbeta(2)-ARs increase basal contractility, coupling to 2 G proteins simultaneously. In contrast, rV(2)-Rs are uniquely coupled to Gs and are not constitutively active, retaining their property to be activated exclusively on agonist stimulation. Therefore, gene transfer of V(2)-Rs might be more suited to test the effects of cAMP-stimulating receptors in heart failure than that of PTH1-Rs or beta(2)-ARS:

Enhanced cardiac contractility after gene transfer of V2 vasopressin receptors In vivo by ultrasound-guided injection or transcoronary delivery

BACKGROUND

Systemic levels of arginine vasopressin (AVP) are increased in congestive heart failure, resulting in vasoconstriction and reduced cardiac contractility via V(1) vasopressin receptors. V(2) vasopressin receptors (V2Rs), which promote activation of adenylyl cyclase, are physiologically expressed only in the kidney and are absent in the myocardium. Heterologous expression of V2Rs in the myocardium could result in a positive inotropic effect by using the endogenous high concentrations of AVP in heart failure.

METHODS AND RESULTS

We tested gene transfer with a recombinant adenovirus for the human V2R (Ad-V2R) to stimulate contractility of rat or rabbit myocardium in vivo. Ultrasound-guided direct injection or transcoronary delivery of adenovirus in vivo resulted in recombinant receptor expression in the myocardial target area, leading to a substantial increase in [(3)H]AVP binding. In 50% of the cardiomyocytes isolated from the directly injected area, single-cell shortening measurements detected a significant increase in contraction amplitude after exposure to AVP or the V2R-specific desmopressin (DDAVP). Echocardiography of the target myocardial area documented a marked increase in local fractional shortening after systemic administration of DDAVP in V2R-expressing animals but not in control virus-treated hearts. Simultaneous measurement of global contractility (dP/dt(max)) confirmed a positive inotropic effect of DDAVP on left ventricular function in the Ad-V2R-injected animals.

CONCLUSIONS

Adenoviral gene transfer of the V2R into the myocardium increases cardiac contractility in vivo. Heterologous expression of cAMP-forming receptors in the myocardium could lead to novel strategies in the therapy of congestive heart failure by bypassing the desensitized beta-adrenergic receptor-signaling cascade.

Adenoviral gene transfer of the human V2 vasopressin receptor improves contractile force of rat cardiomyocytes

BACKGROUND

In congestive heart failure, high systemic levels of the hormone arginine vasopressin (AVP) result in vasoconstriction and reduced cardiac contractility. These effects are mediated by the V1 vasopressin receptor (V1R) coupled to phospholipase C beta-isoforms. The V2 vasopressin receptor (V2R), which promotes activation of the Gs/adenylyl cyclase system, is physiologically expressed in the kidney but not in the myocardium. Expression of a recombinant V2R (rV2R) in the myocardium could result in a positive inotropic effect via the endogenous high concentrations of AVP in heart failure.

METHODS AND RESULTS

A recombinant adenovirus encoding the human V2R (Ad-V2R) was tested for its ability to modulate the cardiac Gs/adenylyl cyclase system and to potentiate contractile force in rat ventricular cardiomyocytes and in H9c2 cardiomyoblasts. Ad-V2R infection resulted in a virus concentration-dependent expression of the transgene and led to a marked increase in cAMP formation in rV2R-expressing cardiomyocytes after exposure to AVP. Single-cell shortening measurements showed a significant agonist-induced contraction amplitude enhancement, which was blocked by the V2R antagonist, SR 121463A. Pretreatment of Ad-V2R-infected cardiomyocytes with AVP led to desensitization of the rV2R after short-term agonist exposure but did not lead to further loss of receptor function or density after long-term agonist incubation, thus demonstrating resistance of the rV2R to downregulation.

CONCLUSIONS

Adenoviral gene transfer of the V2R in cardiomyocytes can modulate the endogenous adenylyl cyclase-signal transduction cascade and can potentiate contraction amplitude in cardiomyocytes. Heterologous expression of cAMP-forming receptors in the myocardium could lead to novel strategies in congestive heart failure by bypassing the desensitized beta-adrenergic receptor signaling.

Activated platelets induce monocyte chemotactic protein-1 secretion and surface expression of intercellular adhesion molecule-1 on endothelial cells

BACKGROUND

Platelet/endothelium interaction plays an important role in the pathophysiology of inflammation and atherosclerosis. The role of platelets for monocyte chemotactic protein-1 (MCP-1) secretion and surface expression of intercellular adhesion molecule-1 (ICAM-1) on endothelial cells has been assessed.

METHODS AND RESULTS

Monolayers of human umbilical vein endothelial cells were incubated with nonstimulated or ADP-activated platelets for 6 hours, and secretion of MCP-1 and surface expression of ICAM-1 were determined by ELISA and flow cytometry, respectively. In the presence of ADP-activated platelets, both MCP-1 secretion and ICAM-1 surface expression were significantly increased compared with nonstimulated platelets (P<0.02). Activation of the transcription factor nuclear factor-kappaB (NF-kappaB) determined by electrophoretic mobility shift assay and kappaB-dependent transcriptional activity was enhanced in the presence of activated platelets. In addition, ADP-activated platelets induced MCP-1 and ICAM-1 promoter-dependent transcription. Liposomal transfection of a double-stranded kappaB phosphorothioate oligonucleotide, but not of the mutated form, inhibited MCP-1 secretion and surface expression of ICAM-1 on activated endothelium (P<0.05).

CONCLUSIONS

The present study indicates that activated platelets modulate chemotactic (MCP-1) and adhesive (ICAM-1) properties of endothelial cells via an NF-kappaB-dependent mechanism. Platelet-induced activation of the NF-kappaB system might contribute to early inflammatory events in atherogenesis.

Odorants selectively activate distinct G protein subtypes in olfactory cilia

Chemoelectrical signal transduction in olfactory neurons appears to involve intracellular reaction cascades mediated by heterotrimeric GTP-binding proteins. In this study attempts were made to identify the G protein subtype(s) in olfactory cilia that are activated by the primary (odorant) signal. Antibodies directed against the alpha subunits of distinct G protein subtypes interfered specifically with second messenger reponses elicited by defined subsets of odorants; odor-induced cAMP-formation was attenuated by Galphas antibodies, whereas Galphao antibodies blocked odor-induced inositol 1,4, 5-trisphosphate (IP3) formation. Activation-dependent photolabeling of Galpha subunits with [alpha-32P]GTP azidoanilide followed by immunoprecipitation using subtype-specific antibodies enabled identification of particular individual G protein subtypes that were activated upon stimulation of isolated olfactory cilia by chemically distinct odorants. For example odorants that elicited a cAMP response resulted in labeling of a Galphas-like protein, whereas odorants that elicited an IP3 response led to the labeling of a Galphao-like protein. Since odorant-induced IP3 formation was also blocked by Gbeta antibodies, activation of olfactory phospholipase C might be mediated by betagamma subunits of a Go-like G protein. These results indicate that different subsets of odorants selectively trigger distinct reaction cascades and provide evidence for dual transduction pathways in olfactory signaling.

Characterization and inhibition of beta-adrenergic receptor kinase in intact myocytes

OBJECTIVES

beta-Adrenergic receptor kinase (beta ARK) phosphorylates and thereby inactivates agonist-occupied beta-adrenergic receptors (beta AR). beta ARK is thought to play an important role in the regulation of cardiac function. Therefore, we studied beta ARK activation and its inhibition in intact smooth muscle cells and in cardiomyoblasts.

METHODS AND RESULTS

beta AR agonist-stimulated translocation of beta ARK was monitored by immunofluorescence labelling with specific antibodies and confocal laser scanning microscopy in DDT-MF 2 hamster smooth muscle cells and in H9c2 rat cardiomyoblasts. In unstimulated cells. beta ARK was mainly located in the cytosol. After beta AR agonist stimulation, the beta ARK signal was partially translocated to the membranes. Liposomal gene transfer of the COOH-terminus of beta ARK ('beta ARKmini') as a beta ARK inhibitor led to functional expression of this protein in both cell lines with high efficiency. Western blots with beta ARK antibodies showed a gene concentration-dependent immunoreactivity of the 'beta ARKmini' protein. 'beta ARKmini'-transfected myocytes demonstrated reduced membrane targeting of the beta ARK immuno-fluorescence signal. Additionally, the effect of 'beta ARKmini' on beta AR-induced desensitization of myocytic cAMP accumulation was investigated. In control cells, desensitization with isoproterenol led to a subsequent reduction of beta AR-induced cAMP accumulation. In 'beta ARKmini'-transfected myocytes, this beta AR-induced desensitization was significantly diminished, whereas normal beta AR-induced cAMP accumulation was unaffected. A gene concentration of 2 micrograms 'beta ARKmini' DNA/100,000 cardiomyoblasts, and of 0.7 microgram 'beta ARKmini' DNA/100,000 DDT-MF2 smooth muscle cells led to approximately 5.9- and approximately 5.6-fold overexpressions of 'beta ARKmini' vs. native beta ARK, respectively. These gene doses proved sufficient to attenuate beta-adrenergic desensitization significantly.

CONCLUSIONS

(1) beta ARK translocation was evidenced in DDT-MF2 smooth muscle cells and in cardiomyoblasts by confocal laser scanning microscopy. (2) Feasibility of 'beta ARKmini' gene transfer to myocytes was demonstrated, and necessary gene doses for beta ARK inhibition were titered. (3) Overexpression of 'beta ARKmini' functionally interacted with endogenous beta-adrenergic signal transduction, leading to sustained cAMP accumulation after prolonged beta-adrenergic stimulation.

Multiple G-protein coupling of the dog thyrotropin receptor

We investigated, in dog thyroid membranes, the ability of the dog thyrotropin (TSH) receptor to interact with the endogenous G proteins expressed in this tissue. Activation of the receptor led to increased incorporation of the photoreactive GTP analog [alpha-(32)P]GTP azidoanilide into immunoprecipitated alpha subunits of three G protein families: G(s), G(q/11), G(i/o). This effect was not due to a general loss of receptor G protein specificity since carbamylcholine, in the same membrane preparations, only stimulated the binding of the GTP analog to the alpha subunits of G(q/11) proteins. To investigate the multiple coupling of the dog TSH receptor in intact cells, cyclic AMP accumulation, IP(3) formation and (45)Ca2+ efflux experiments were performed. When thyrocytes were pretreated with pertussis toxin (PTX), the TSH receptor-mediated accumulation of cAMP increased by approximately 45% with TSH at 1 mU/ml, suggesting that the TSH receptor coupled to both G(s) and G(i) in vivo. On the other hand, no increase in IP(3) accumulation nor Ca2+ efflux was observed in the presence of thyrotropin. These data in intact cells are thus in contradiction with those obtained in membranes, suggesting that receptor-mediated transmembrane signalling may implicate a specificity which itself may reflect a localization and organization of the different components (receptors, G proteins, ...) in the plasma membrane of intact cells. As in some cells, G(i) activates mitogenesis by hormone activated G-protein-coupled receptors, we tested its role in the stimulation by TSH of the proliferation of thyrocytes. This was not affected by PTX, suggesting that the mitogenic effect of TSH does not involve G(i)-proteins.

Activation of GTP formation and high-affinity GTP hydrolysis by mastoparan in various cell membranes. G-protein activation via nucleoside diphosphate kinase, a possible general mechanism of mastoparan action

The wasp venom, mastoparan (MP), is a direct activator of reconstituted pertussis toxin-sensitive G-proteins and of purified nucleoside diphosphate kinase (NDPK) [E.C. 2.6.4.6.]. In HL-60 membranes, MP activates high-affinity GTPase [E.C. 3.6.1.-] and NDPK-catalyzed GTP formation, but not photolabeling of G-protein alpha-subunits with GTP azidoanilide; this suggests that the venom activates G-proteins in this system indirectly via stimulation of NDPK. Moreover, the MP analogue, mastoparan 7 (MP 7), is a much more effective activator of reconstituted G-proteins than MP, whereas with regard to NDPK and GTPase in HL-60 membranes, the two peptides are similarly effective. In our present study, we investigated NDPK- and G-protein activation by MP in membranes of the human neuroblastoma cell line, SH-SY5Y, the human erythroleukemia cell line, HEL, the rat basophilic leukemia cell line, RBL 2H3, and the hamster ductus deferens smooth muscle cell line, DDT1MF-2. All these membranes exhibited high NDPK activities that were increased by MP. Compared to basal GTP formation rates, basal rates of high-affinity GTP hydrolysis in cell membranes were low. MP activated high-affinity GTP hydrolysis in cell membranes but did not enhance incorporation of GTP azidoanilide into G-protein alpha-subunits. As with HL-60 membranes, MP and MP 7 were similarly effective activators of NDPK and GTPase in SH-SY5Y membranes. Pertussis toxin inhibited MP-stimulated GTP hydrolyses in SH-SY5Y- and HEL membranes, whereas NDPK activations by MP were pertussis toxin-insensitive. Our data suggest that indirect G-protein activation via NDPK is not restricted to HL-60 membranes but is a more general mechanism of MP action in cell membranes. Pertussis toxin-catalyzed ADP-ribosylation of alpha-subunits may inhibit the transfer of GTP from NDPK to G-proteins. NDPK may play a much more important role in transmembrane signal transduction than was previously appreciated and, moreover, the GTPase of G-protein alpha-subunits may serve as GDP-synthase for NDPK.

The human thyrotropin receptor: a heptahelical receptor capable of stimulating members of all four G protein families

Thyrotropin is the primary hormone that, via one heptahelical receptor, regulates thyroid cell functions such as secretion, specific gene expression, and growth. In human thyroid, thyrotropin receptor activation leads to stimulation of the adenylyl cyclase and phospholipase C cascades. However, the G proteins involved in thyrotropin receptor action have been only partially defined. In membranes of human thyroid gland, we immunologically identified alpha subunits of the G proteins Gs short, Gs long, Gi1, Gi2, Gi3, G(o) (Go2 and another form of Go, presumably Go1), Gq, G11, G12, and G13. Activation of the thyrotropin (TSH) receptor by bovine TSH led to increased incorporation of the photoreactive GTP analogue [alpha-32P]GTP azidoanilide into immunoprecipitated alpha subunits of all G proteins detected in thyroid membranes. This effect was receptor-dependent and not due to direct G protein stimulation because it was mimicked by TSH receptor-stimulating antibodies of patients suffering from Grave disease and was abolished by a receptor-blocking antiserum from a patient with autoimmune hypothyroidism. The TSH-induced activation of individual G proteins occurred with EC50 values of 5-50 milliunits/ml, indicating that the activated TSH receptor coupled with similar potency to different G proteins. When human thyroid slices were pretreated with pertussis toxin, the TSH receptor-mediated accumulation of cAMP increased by approximately 35% with TSH at 1 milliunits/ml, indicating that the TSH receptor coupled to Gs and G(i). Taken together, these findings show that, at least in human thyroid membranes, in which the protein is expressed at its physiological levels, the TSH receptor resembles a naturally occurring example of a general G protein-activating receptor.

The human platelet ADP receptor activates Gi2 proteins

We have previously shown that platelet ADP receptors are coupled to G-proteins by measuring the binding of [35S]guanosine-5'-[gamma-thio]triphosphate ([35S]GTP gamma S) to human platelet membranes stimulated with ADP. In order to identify the activated G-proteins, we used an approach which combines photolabelling of receptor-activated G-proteins with 4-azidoanilido-[alpha-32P]GTP and immunoprecipitation of the G-protein alpha-subunits with subtype-specific antibodies. Stimulation of human platelet membranes with ADP resulted in an increase in 4-azidoanilido-[alpha-32P]GTP incorporation into the immunoprecipitates of G alpha i but not of G alpha q proteins, whereas stimulation with the thromboxane analogue U46619 resulted in an increase in 4-azidoanilido-[alpha-32P]GTP incorporation into the immunoprecipitates of G alpha q but not of G alpha i proteins, and thrombin activated both G-proteins. This effect of ADP was concentration dependent and inhibited by the class P2 purinoceptor (P2T) antagonist ATP. Using specific antisera against subtypes of Gi proteins, we found that ADP stimulated labelling of the G alpha 12 immunoprecipitate, but not of the G alpha 13 precipitate. G alpha i1 was not detectable by immunoblotting of platelet membrane proteins. These data suggest that ADP inhibits cAMP formation by activation of G alpha 12 proteins and add evidence in support of the hypothesis that human platelet ADP receptors do not activate PLC through Gq activation.

G proteins of the G12 family are activated via thromboxane A2 and thrombin receptors in human platelets

Using subtype-specific antisera, we were able to identify the recently described alpha subunits of G12 and G13 in platelet membranes as 43-kDa proteins. Activation of the thromboxane A2 and the thrombin receptors in platelet membranes led to increased incorporation of the photoreactive GTP analogue [alpha-32P]GTP azidoanilide into immunoprecipitated alpha 12 and alpha 13, indicating that both receptors couple to G12 and G13. In addition, both activated receptors were demonstrated to couple to one or more members of the Gq family. In the absence of receptor agonists, incorporation of [alpha-32P]GTP azidoanilide into alpha 12 and alpha 13 was low over a long time period (up to 45 min) due to an obviously low basal nucleotide exchange rate, whereas an agonist-stimulated photolabeling of alpha 12 and alpha 13 could be observed after 4-8 min and reached a maximum after 30-45 min. Effective activation of G12 and G13 via the thromboxane A2 and the thrombin receptors was not dependent on the presence of GDP. Our results provide evidence that G12 and G13 play a functional role in transmembrane signal transduction and suggest that both proteins are involved in pathways leading to platelet activation.

mu and delta opioid receptors differentially couple to G protein subtypes in membranes of human neuroblastoma SH-SY5Y cells

Opioids are regarded to act via receptors interacting with heterotrimeric pertussis toxin (PTX)-sensitive G proteins. In membranes of SH-SY5Y cells, the mu-selective agonist [D-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAGO) and the delta-selective agonist [D-Pen2,Pen5]-enkephalin (DPDPE) stimulated incorporation of the photoreactive GTP analog [alpha-32P]GTP azidoanilide into proteins comigrating with the alpha subunits of G(i1), G(i2), G(i3), G(o1), and another form of G(o), presumably G(o2). In membranes of PTX-treated cells, both agonists were ineffective. Subtype-specific immunoprecipitation of G protein alpha subunits photolabeled in the absence or presence of agonists revealed profound differences between mu and delta opioid receptors in coupling to PTX-sensitive G proteins. Whereas activated delta opioid receptors preferentially coupled to G(i1), activated mu opioid receptors more effectively coupled to G(i3). Additionally, we provide evidence that G(o) subtypes are also differentially activated by the two receptors. Thus, mu and delta opioid receptors appear to discriminate between PTX-sensitive G proteins and lead to activation of distinct G protein subtypes.