Lisa Gross

Angiopoietin 2 mediates microvascular and hemodynamic alterations in sepsis.

Septic shock is characterized by increased vascular permeability and hypotension despite increased cardiac output. Numerous vasoactive cytokines are upregulated during sepsis, including angiopoietin 2 (ANG2), which increases vascular permeability. Here we report that mice engineered to inducibly overexpress ANG2 in the endothelium developed sepsis-like hemodynamic alterations, including systemic hypotension, increased cardiac output, and dilatory cardiomyopathy. Conversely, mice with cardiomyocyte-restricted ANG2 overexpression failed to develop hemodynamic alterations. Interestingly, the hemodynamic alterations associated with endothelial-specific overexpression of ANG2 and the loss of capillary-associated pericytes were reversed by intravenous injections of adeno-associated viruses (AAVs) transducing cDNA for angiopoietin 1, a TIE2 ligand that antagonizes ANG2, or AAVs encoding PDGFB, a chemoattractant for pericytes. To confirm the role of ANG2 in sepsis, we i.p. injected LPS into C57BL/6J mice, which rapidly developed hypotension, acute pericyte loss, and increased vascular permeability. Importantly, ANG2 antibody treatment attenuated LPS-induced hemodynamic alterations and reduced the mortality rate at 36 hours from 95% to 61%. These data indicate that ANG2-mediated microvascular disintegration contributes to septic shock and that inhibition of the ANG2/TIE2 interaction during sepsis is a potential therapeutic target.

Antidiabetic gliptins in combination with G-CSF enhances myocardial function and survival after acute myocardial infarction.

BACKGROUND Medical stimulation of endogenous progenitor cell circulation may serve as a new therapeutic tool for treatment of acute myocardial infarction. We analyzed the effects of antidiabetic gliptins plus GCSF (granulocyte colony stimulating factor) on myocardial regeneration after myocardial infarction in a mouse model. METHODS AND RESULTS After surgical LAD-ligation (left anterior descending artery), Sitagliptin/Vildagliptin was applied yielding sufficient blood levels verified by mass spectrometry and significantly reducing activity of dipeptidyl peptidase (DPP) IV. GCSF or saline was administered intraperitoneally for 6 days. We assessed stem cell mobilization and homing (flow cytometry), infarct size (histology), neovascularization and cellular proliferation (immunohistology), heart function (Millar tip catheterization) and survival (Kaplan-Meier-curves). Gliptins±GCSF administration increased mobilization and cardiac homing of bone-marrow derived stem cells by stabilization of cardiac SDF1 (stromal cell-derived factor). For Sitagliptin, it could be shown that resident cardiac stem cells were stimulated, neovascularization was enhanced and cardiac remodeling was reduced. These effects finally improved myocardial function and increased survival for both gliptins. Although gliptins as a mono therapy lead to remarkable effects in a dose dependent manner and were superior to G-CSF mono-therapy, dual application of GCSF and gliptins revealed the best results. Since both gliptins yielded comparable effects concerning stem cell homing, cardiac function and survival, we suggest a class-effect of DPP-IV-inhibitors. CONCLUSIONS Thus, gliptins+GCSF and in high concentrations even as mono therapy have beneficial effects on cardiac regeneration after myocardial infarction beyond its anti-diabetic potential.

Transcatheter treatment of severe tricuspid regurgitation using the edge-to-edge repair technique.

AIMS The aim of this study was to investigate the procedural feasibility and short-term durability of the transcatheter tricuspid valve edge-to-edge repair technique in highly symptomatic patients with severe tricuspid regurgitation (TR). METHODS AND RESULTS Eighteen consecutive patients suffering from severe right-sided heart failure (NYHA Class III-IV), primarily due to moderate to severe tricuspid regurgitation, were included in the study. Applying a modified steering technique for the clip delivery system, six patients were treated for isolated severe TR, while 12 patients were treated for moderate to severe TR and concomitant severe mitral regurgitation. The primary objectives were procedural success, defined as reduction of at least one TR grade, and 30-day echocardiographic and clinical outcomes. A total of 41 clips (2.3±0.7 per patient) were placed into the tricuspid valve of high surgical risk patients (EuroSCORE II: 10±8%). Procedural success was achieved in all patients; no MACCE occurred in hospital. The presence of a TR grade ≥3 was reduced from 94% (17 patients) before the procedure to 33% (six patients) at 30-day follow-up (p<0.001). Sixteen patients (89%) reported an improvement in NYHA functional class at 30 days. CONCLUSIONS Applying a modified steering technique, the edge-to-edge repair technique can be successfully used for the treatment of TR. At 30-day follow-up, the short-term durability of TR reduction appeared promising and the majority of patients improved clinically. Further studies with larger patient populations and longer follow-up have to define the role of this novel treatment option for patients with right-sided heart failure and severe TR.

DPP-4 inhibition ameliorates atherosclerosis by priming monocytes into M2 macrophages

OBJECTIVE Glipitins are widely used for the treatment of type 2 diabetic patients. In addition to their improvement of glycemic control, animal studies have suggested an independent anti-atherosclerotic effect of gliptins. Nevertheless, recent clinical trials regarding long-term effects of gliptin therapy on vascular events have been disappointing. This discrepancy led us to better dissect the functional role of SDF-1/CXCR4 signaling as a potential mechanism underlying gliptin action. The study should give improved understanding of the potential of gliptin therapy in the prevention and treatment of atherosclerosis. METHODS AND RESULTS In an ApoE-/- mouse model on high cholesterol diet, long-term treatment with the DPP-4 inhibitor Sitagliptin significantly reduced atherosclerosic plaque load in the aorta. Flow cytometry analyses showed an enrichment of M2 macrophages in the aortic wall under gliptin therapy. Importantly, the number of recruited CD206+ macrophages was inversely correlated with total plaque area while no correlation was found for the overall macrophage population or M1 macrophages. Blockade of CXCR4/SDF-1 signaling by AMD3100 inhibited aortic M2 accumulation and the therapeutic effect of Sitagliptin. Correspondingly, Sitagliptin shifted the polarization profile of macrophages towards a M2-like phenotype. CONCLUSION Sitagliptin-mediated inhibition of early atherosclerosis is based on M2-polarization during monocyte differentiation via the SDF-1/CXCR4 signaling. In contrast to earlier assumptions gliptin treatment might be especially effective in prevention of atherosclerosis.

Short-term inhibition of DPP-4 enhances endothelial regeneration after acute arterial injury via enhanced recruitment of circulating progenitor cells

BACKGROUND Endothelial injuries regularly occur in atherosclerosis and during interventional therapies of the arterial occlusive disease. Disturbances in the endothelial integrity can lead to insufficient blood supply and bear the risk of thrombus formation and acute vascular occlusion. At present, effective therapeutics to restore endothelial integrity are barely available. We analyzed the effect of pharmacological DPP-4-inhibition by Sitagliptin on endogenous progenitor cell-based endothelial regeneration via the SDF-1α/CXCR4-axis after acute endothelial damage in a mouse model of carotid injury. METHODS AND RESULTS Induction of a defined endothelial injury was performed in the carotid artery of C57Bl/6 mice which led to a local upregulation of SDF-1α expression. Animals were treated with placebo, Sitagliptin or Sitagliptin+AMD3100. Using mass spectrometry we could prove that Sitagliptin prevented cleavage of the chemokine SDF-1α. Accordingly, increased SDF-1α concentrations enhanced recruitment of systemically applied and endogenous circulating CXCR4+ progenitor cells to the site of vascular injury followed by a significantly accelerated reendothelialization as compared to placebo-treated animals. Improved endothelial recovery, as well as recruitment of circulating CXCR4+ progenitor cells (CD133+, Flk1+), was reversed by CXCR4-antagonization through AMD3100. In addition, short-term Sitagliptin treatment did not significantly promote neointimal or medial hyperplasia. CONCLUSION Sitagliptin can accelerate endothelial regeneration after acute endothelial injury. DPP-4 inhibitors prevent degradation of the chemokine SDF-1α and thus improve the recruitment of regenerative circulating CXCR4+ progenitor cells which mediate local endothelial cell proliferation without adversely affecting vessel wall architecture.

A randomised trial on platelet function-guided de-escalation of antiplatelet treatment in ACS patients undergoing PCI. Rationale and design of the Testing Responsiveness to Platelet Inhibition on chronic Antiplatelet Treatment for Acute Coronary Syndromes (TROPICAL-ACS) Trial.

Outcomes of acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) have been significantly improved with the use of potent P2Y12 receptor inhibitors like prasugrel. While most of the ischaemic risk reduction for prasugrel versus clopidogrel was demonstrated in the early treatment period, the risk of bleeding became particularly prominent during the chronic course of therapy. It may therefore be a valid approach to substitute prasugrel for clopidogrel in the early phase of chronic antiplatelet treatment after PCI. In the Testing Responsiveness To Platelet Inhibition On Chronic Antiplatelet Treatment For Acute Coronary Syndromes (TROPICAL-ACS) trial, we aim to compare standard prasugrel therapy with a de-escalating antiplatelet treatment approach guided by platelet function testing (PFT). The study is an investigator-initiated European multicentre, randomised clinical trial in biomarker-positive ACS patients after successful PCI. Two thousand six hundred patients will be randomised prior to hospital discharge in a 1:1 fashion to either receive standard prasugrel therapy (control group) or de-escalating therapy (one-week prasugrel followed by one-week clopidogrel and PFT-guided maintenance therapy from day 14 after hospital discharge, monitoring group). Patients of the monitoring group with high on-clopidogrel platelet reactivity (HPR) based on Multiplate analyzer testing (HPR: ≥ 46U per consensus definition) will be switched back to prasugrel, whereas those without HPR (<46 U) will continue clopidogrel treatment. The overall study treatment duration will be one year in both groups. The primary endpoint of the study is net clinical benefit (combined incidence of cardiovascular death, myocardial infarction, stroke and bleeding ≥ grade 2 according to BARC criteria) one-year after randomisation. TROPICAL-ACS is the first large-scale, randomised controlled trial assessing the clinical value of a PFT-guided de-escalation of antiplatelet treatment in biomarker positive ACS patients undergoing PCI.

Predictors of antiplatelet response to prasugrel during maintenance treatment

Abstract Insufficient P2Y12 receptor inhibition is associated with a higher risk of thrombotic events after percutaneous coronary intervention (PCI). The third generation thienopyridine prasugrel achieves stronger platelet inhibition as compared to its predecessor clopidogrel. Little is known about predictors of prasugrel drug responsiveness. The aim of this study was to explore predictors of prasugrel responsiveness in patients with a recent PCI on prasugrel maintenance dose (MD) treatment. In a registry of PCI-treated patients (n = 163, recruited between August 2009 and March 2012) on prasugrel MD treatment, the ADP-induced platelet aggregation (PA) was assessed on a Multiplate analyzer. The mean (interquartile range (IQR)) ADP-induced PA on prasugrel MD treatment was 206 (138–331) AU × min. Obese (defined by a body mass index (BMI) ≥ 30) patients (n = 42) (303 [192–467] vs. 187 [117–305] AU × min, p = 0.0001), patients (n = 70) with a history of clopidogrel low responsiveness (278 [161–409] vs. 192 [126–282] AU × min, p = 0.002) and patients (n = 18) on a low (5 mg) prasugrel MD (483 [252–798] vs. 198 [133–313] AU × min; p = 0.0001) showed higher PA values on prasugrel MD as compared to the remaining patients. In a multivariable linear regression model, the latter three variables were independently associated with higher PA values on prasugrel MD treatment. In summary response variability is observed in patients on prasugrel MD treatment. Obesity, a history of clopidogrel low responsiveness and a reduced prasugrel MD of 5 mg are independent predictors of an attenuated response to prasugrel treatment. Further studies are needed to explore clinical implications of this observation.

Platelet Function Testing in Patients on Antiplatelet Medications

Guidelines provide a Class IA recommendation for the use of dual antiplatelet therapy in patients undergoing percutaneous coronary intervention (PCI). However, there is interindividual variability in the pharmacodynamic response to antiplatelet medications. Some patients present with a status of high on-treatment platelet reactivity (HPR) during platelet function testing after standard doses of antiplatelet drugs, reflecting a failure to achieve adequate platelet inhibition. As an example, patients with HPR on clopidogrel are at increased risk for thrombotic events, particularly for stent thrombosis and myocardial infarction, but cardiovascular mortality is also elevated. On the contrary, low on-treatment platelet reactivity or an enhanced response to antiplatelet medications has been linked to a higher risk for bleeding. Although both thrombotic and bleeding events are multifactorial in origin, there is supportive evidence for the prognostic value of platelet function testing for risk prediction of both sides of the coin. However, although small studies have provided evidence that treatment adjustments based on platelet function testing results may improve clinical outcomes, the available randomized controlled trials showed no benefit of modifying antiplatelet treatment based on platelet function testing. This review presents the current evidence regarding platelet function testing in patients undergoing PCI. The prognostic value of platelet function testing regarding ischemic and bleeding events is highlighted. Furthermore, the value of platelet function testing for guiding treatment and possible explanations for the so-far negative trial results are presented. The possible future role of platelet function testing for individualized antiplatelet treatment regimens in high-risk patients will be also discussed.

FDG-PET reveals improved cardiac regeneration and attenuated adverse remodelling following Sitagliptin + G-CSF therapy after acute myocardial infarction

AIMS Dual therapy comprising G-CSF for mobilization of bone marrow-derived progenitor cells (BMPCs), with simultaneous pharmacological inhibition of dipeptidylpeptidase-IV for enhanced myocardial recruitment of circulating BMPC via the SDF-1α/CXCR4-axis, has been shown to improve survival after acute myocardial infarction (AMI). Using an innovative method to provide non-invasive serial in vivo measurements and information on metabolic processes, we aimed to substantiate the possible effects of this therapeutic concept on cardiac remodelling after AMI using 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography (FDG-PET). METHODS AND RESULTS AMI was induced in C57BL/6 mice by performing surgical ligation of the left anterior descending artery in these mice. Animals were then treated with granulocyte-colony stimulating factor + Sitagliptin (GS) or placebo for a duration of 5 days following AMI. From serial PET scans, we verified that the infarct size in GS-treated mice (n = 13) was significantly reduced at Day 30 after AMI when compared with the mice receiving placebo (n = 10). Analyses showed a normalized FDG uptake on Day 6 in GS-treated mice, indicating an attenuation of the cardiac inflammatory response to AMI in treated animals. Furthermore, flow cytometry showed a significant increase in the anti-inflammatory M2-macrophages subpopulation in GS-treated animals. In comparing GS treated with placebo animals, those receiving GS-therapy showed a reduction in myocardial hypertrophy and left ventricular dilatation, which indicates the beneficial effect of GS treatment on cardiac remodelling. Remarkably, flow cytometry and immunohistochemistry showed an increase of myocardial c-kit positive cells in treated mice (n = 12 in both groups). CONCLUSION Using the innovative method of micro-PET for non-invasive serial in vivo measurements of metabolic myocardial processes in mice, we were able to provide mechanistic evidence that GS therapy improves cardiac regeneration and reduces adverse remodelling after AMI.

Global metabolite profiling of mice with high-fat diet-induced obesity chronically treated with AMPK activators R118 or metformin reveals tissue-selective alterations in metabolic pathways.

BackgroundThe novel small molecule R118 and the biguanide metformin, a first-line therapy for type 2 diabetes (T2D), both activate the critical cellular energy sensor 5′-AMP-activated protein kinase (AMPK) via modulation of mitochondrial complex I activity. Activation of AMPK results in both acute responses and chronic adaptations, which serve to restore energy homeostasis. Metformin is thought to elicit its beneficial effects on maintenance of glucose homeostasis primarily though impacting glucose and fat metabolism in the liver. Given the commonalities in their mechanisms of action and that R118 also improves glucose homeostasis in a murine model of T2D, the effects of both R118 and metformin on metabolic pathways in vivo were compared in order to determine whether R118 elicits its beneficial effects through similar mechanisms.ResultsGlobal metabolite profiling of tissues and plasma from mice with diet-induced obesity chronically treated with either R118 or metformin revealed tissue-selective effects of each compound. Whereas metformin treatment resulted in stronger reductions in glucose and lipid metabolites in the liver compared to R118, upregulation of skeletal muscle glycolysis and lipolysis was apparent only in skeletal muscle from R118-treated animals. Both compounds increased β-hydroxybutyrate levels, but this effect was lost after compound washout. Metformin, but not R118, increased plasma levels of metabolites involved in purine metabolism.ConclusionsR118 treatment but not metformin resulted in increased glycolysis and lipolysis in skeletal muscle. In contrast, metformin had a greater impact than R118 on glucose and fat metabolism in liver tissue.