Revealing concealed cardioprotection by platelet Mfsd2b-released S1P in human and murine myocardial infarction.

Antiplatelet medication is standard of care in acute myocardial infarction (AMI). However, it may have obscured beneficial properties of the activated platelet secretome. We identify platelets as major source of a sphingosine-1-phosphate (S1P) burst during AMI, and find its magnitude to favorably associate with cardiovascular mortality and infarct size in STEMI patients over 12 months. Experimentally, administration of supernatant from activated platelets reduces infarct size in murine AMI, which is blunted in platelets deficient for S1P export (Mfsd2b) or production (Sphk1) and in mice deficient for cardiomyocyte S1P receptor 1 (S1P1). Our study reveals an exploitable therapeutic window in antiplatelet therapy in AMI as the GPIIb/IIIa antagonist tirofiban preserves S1P release and cardioprotection, whereas the P2Y12 antagonist cangrelor does not. Here, we report that platelet-mediated intrinsic cardioprotection is an exciting therapeutic paradigm reaching beyond AMI, the benefits of which may need to be considered in all antiplatelet therapies.

Sphingosine-1-phosphate improves outcome of no-reflow acute myocardial infarction via sphingosine-1-phosphate receptor 1.

AIMS: Therapeutic options targeting post-ischaemic cardiac remodelling are sparse. The bioactive sphingolipid sphingosine-1-phosphate (S1P) reduces ischaemia/reperfusion injury. However, its impact on post-ischaemic remodelling independently of its infarct size (IS)-reducing effect is yet unknown and was addressed in this study. METHODS AND RESULTS: Acute myocardial infarction (AMI) in mice was induced by permanent ligation of the left anterior descending artery (LAD). C57Bl6 were treated with the S1P lyase inhibitor 4-deoxypyridoxine (DOP) starting 7 days prior to AMI to increase endogenous S1P concentrations. Cardiac function and myocardial healing were assessed by cardiovascular magnetic resonance imaging (cMRI), murine echocardiography, histomorphology, and gene expression analysis. DOP effects were investigated in cardiomyocyte-specific S1P receptor 1 deficient (S1PR1 Cardio Cre+) and Cre- control mice and S1P concentrations measured by LC-MS/MS. IS and cardiac function did not differ between control and DOP-treated groups on day one after LAD-ligation despite fourfold increase in plasma S1P. In contrast, cardiac function was clearly improved and myocardial scar size reduced, respectively, on Day 21 in DOP-treated mice. The latter also exhibited smaller cardiomyocyte size and reduced embryonic gene expression. The benefit of DOP treatment was abolished in S1PR1 Cardio Cre+. CONCLUSIONS: S1P improves cardiac function and myocardial healing post AMI independently of initial infarct size and accomplishes this via the cardiomyocyte S1PR1. Hence, in addition to its beneficial effects on I/R injury, S1PR1 may be a promising target in post-infarction myocardial remodelling as adjunctive therapy to revascularization as well as in patients not eligible for standard interventional procedures.

Only Acute but Not Chronic Thrombocytopenia Protects Mice against Left Ventricular Dysfunction after Acute Myocardial Infarction.

BACKGROUND: Platelets are major players of thrombosis and inflammation after acute myocardial infarction (AMI). The impact of thrombocytopenia on platelet-induced cellular processes post AMI is not well defined. METHODS: The left anterior descending artery was ligated in C57/Bl6 mice and in two thrombocytopenic mouse models to induce AMI. RESULTS: Platelets from STEMI patients and from C57/Bl6 mice displayed enhanced platelet activation after AMI. This allows platelets to migrate into the infarct but not into the remote zone of the left ventricle. Acute thrombocytopenia by antibody-induced platelet depletion resulted in reduced infarct size and improved cardiac function 24 h and 21 days post AMI. This was due to reduced platelet-mediated inflammation after 24 h and reduced scar formation after 21 days post AMI. The collagen composition and interstitial collagen content in the left ventricle were altered due to platelet interaction with cardiac fibroblasts. Acute inflammation was also significantly reduced in Mpl-/- mice with chronic thrombocytopenia, but cardiac remodeling was unaltered. Consequently, left ventricular function, infarct size and scar formation in Mpl-/- mice were comparable to controls. CONCLUSION: This study discovers a novel role for platelets in cardiac remodeling and reveals that acute but not chronic thrombocytopenia protects left ventricular function post AMI.

Risk prediction of bleeding and MACCE by PRECISE-DAPT score post-PCI.

BACKGROUND: Guidelines recommend the PRECISE-DAPT (PD) score to adapt duration of dual antiplatelet therapy due to bleeding risk. However, there is first evidence that PD predicts mortality and ischemic events as well. METHODS: We investigated PD Score in 994 patients after percutaneous coronary intervention (PCI). PD was correlated with clinically frequently used scores. Major adverse cardiac and cerebrovascular events (MACCE) and Thrombolysis in Myocardial Infarction (TIMI) bleeding were assessed during one-year follow-up. RESULTS: 524 patients had PD < 25 and 470 patients PD ≥ 25 (47%). Rate of major and minor bleeding was higher in the PD ≥ 25 group (major bleeding: Hazard ratio [HR] 2.9, 95% confidence interval [Cl] 1.01-8.16, p = 0.049; minor bleeding: HR 3.94, 95% Cl 1.36-9.19, p = 0.0096). Rate of MACCE, death and myocardial infarction were higher as well (MACCE: HR 2.0, 95% Cl 1.52-2.71, p < 0.0001; death: HR 3.9, 95% Cl 2.12-5.68, p < 0.0001; MI: HR 2.1, 95% Cl 1.26-3.43, p = 0.0041). Rate of stroke/transient ischemic attack did not differ between groups. Discriminative potency to predict major and minor bleeding, MACCE, death and MI were high with nearly equal cut-off values calculated by Youden's index (YI) (major bleeding: Area under the curve [AUC] 0.66; p = 0.026; YI 32; minor bleeding: AUC 0.72; p = 0.001; YI 28; MACCE: AUC 0.62; p < 0.0001; YI 24). CONCLUSION: In our cohort, PD score predicted bleeding moderately in post-PCI patients. In this study, ischemic events were predicted as well. Adaption of antiplatelet therapy duration by PD score is accurate. Nevertheless, it should be well-balanced with patient-related risk for ischemic events.

Endothelial ß1 Integrin-Mediated Adaptation to Myocardial Ischemia.

BACKGROUND: Short episodes of myocardial ischemia can protect from myocardial infarction. However, the role of endothelial ß1 integrin in these cardioprotective ischemic events is largely unknown. OBJECTIVE: In this study we investigated whether endothelial ß1 integrin is required for cardiac adaptation to ischemia and protection from myocardial infarction. METHODS: Here we introduced transient and permanent left anterior descending artery (LAD) occlusions in mice. We inhibited ß1 integrin by intravenous injection of function-blocking antibodies and tamoxifen-induced endothelial cell (EC)-specific deletion of Itgb1. Furthermore, human ITGB1 was silenced in primary human coronary artery ECs using small interfering RNA. We analyzed the numbers of proliferating ECs and arterioles by immunohistochemistry, determined infarct size by magnetic resonance imaging (MRI) and triphenyl tetrazolium chloride staining, and analyzed cardiac function by MRI and echocardiography. RESULTS: Transient LAD occlusions were found to increase EC proliferation and arteriole formation in the entire myocardium. These effects required ß1 integrin on ECs, except for arteriole formation in the ischemic part of the myocardium. Furthermore, this integrin subunit was also relevant for basal and mechanically induced proliferation of human coronary artery ECs. Notably, ß1 integrin was needed for cardioprotection induced by transient LAD occlusions, and the absence of endothelial ß1 integrin resulted in impaired growth of blood vessels into the infarcted myocardium and reduced cardiac function after permanent LAD occlusion. CONCLUSION: We showed that endothelial ß1 integrin is required for adaptation of the heart to cardiac ischemia and protection from myocardial infarction.

MTX Treatment Does Not Improve Outcome in Mice with AMI.

BACKGROUND: Targeting inflammation in patients with coronary artery disease and/or acute myocardial infarction (AMI) is a matter of debate. Methotrexate (MTX) is one of the most widely used immunosuppressants. Cardiovascular Inflammation Reduction Trial (CIRT) recently failed to demonstrate reduced cardiovascular events in MTX-treated patients. However, it is not known if long-term MTX treatment improves cardiac outcome in AMI. Therefore, in this study, we investigated the postischemic phase in MTX-treated mice undergoing AMI. METHODS: Wild-type mice received MTX medication intraperitoneally for 2 weeks. Afterward, AMI was induced by transient left anterior ascending artery ligation. Postischemic cardiac damage after 24 h was assessed. RESULTS: MTX treatment did not affect infarct size as compared to control (IS/AAR: Con 76.20% ± 12.37%/AAR vs. MTX 73.51 ± 11.72%/AAR, p = 0.64). Moreover, systolic function and structural parameters did not differ between groups (24hejection fraction: Con 36.49 ± 3.23% vs. MTX 32.77 ± 2.29%, p = 0.41; 24hLVID; d: Con 3.57 ± 0.17 mm vs. MTX 3.19 ± 0.13 mm, p = 0.14). Platelets were increased by MTX (Con 1,442 ± 69.20 × 103/mm3 vs. MTX 1,920 ± 68.68 × 103/mm3, p < 0.0001). White blood cell and RBC as well as rate of monocytes, granulocytes, lymphocytes, and serum amyloid P levels were equal. CONCLUSION: MTX medication did not improve postischemic cardiac damage in a murine model of AMI. Future trials are needed to identify and investigate other anti-inflammatory targets to improve cardiovascular outcome.

Targeting the human microbiome and its metabolite TMAO in cardiovascular prevention and therapy.

The human gut microbiota is the most important active part of the intestinal micro-ecosystem. Lifestyle modification, drug intake and nutrition have an impact on the composition of the gut microbiota and its metabolites. This review focuses on the effects of changes in the gut microbiota as well as the important metabolite Trimethylamine-N-oxide (TMAO). Furthermore, relevant therapeutic options to target the human microbiome in patients with cardiovascular disease are presented.

Design, characterization and cellular uptake studies of fluorescence-labeled prototypic cathepsin inhibitors.

Besides their extracellular activity crucial for several pathophysiological conditions, human cysteine cathepsins, in particular cathepsins K and S, represent important intracellular targets for drug development. In the present study, a prototypic dipeptide nitrile inhibitor structure was equipped with a coumarin moiety to function as a fluorescent reporter group. In a second inhibitor, a PEG linker was introduced between the dipeptide nitrile and the fluorophore. These tool compounds 6 and 7 were characterized by kinetic investigations as covalent reversible inhibitors of human cathepsins L, S, K and B. Probe 6 showed a pronounced inhibitory activity against cathepsins K and S, which was corroborated by modeling of inhibition modes. Probe 7 was highly potent (Ki = 93 nM) and selective for cathepsin S. To examine the ability of both probes to enter living cells, human embryonic kidney 293 cells were targeted. At a concentration of 10 µM, cellular uptake of probe 6 was demonstrated by fluorescence measurement after an incubation time of 30 min and 3 h, respectively. The probe's concentration in cell lysates was ascertained on the basis of the emission at 492 nm upon excitation at 450 nm, and the results were expressed as concentrations of probe 6 relative to the protein concentration originating from the lysate. After incubation of 10 µM of probe 6 for 3 h, the cellular uptake was confirmed by fluorescence microscopy. HPLC was used to assess the probes' lipophilicity, and the obtained