Rivaroxaban attenuates neutrophil maturation in the bone marrow niche.

Pharmacological inhibition of factor Xa by rivaroxaban has been shown to mediate cardioprotection and is frequently used in patients with, e.g., atrial fibrillation. Rivaroxaban's anti-inflammatory actions are well known, but the underlying mechanisms are still incompletely understood. To date, no study has focused on the effects of rivaroxaban on the bone marrow (BM), despite growing evidence that the BM and its activation are of major importance in the development/progression of cardiovascular disease. Thus, we examined the impact of rivaroxaban on BM composition under homeostatic conditions and in response to a major cardiovascular event. Rivaroxaban treatment of mice for 7 days markedly diminished mature leukocytes in the BM. While apoptosis of BM-derived mature myeloid leukocytes was unaffected, lineage-negative BM cells exhibited a differentiation arrest at the level of granulocyte-monocyte progenitors, specifically affecting neutrophil maturation via downregulation of the transcription factors Spi1 and Csfr1. To assess whether this persists also in situations of increased leukocyte demand, mice were subjected to cardiac ischemia/reperfusion injury (I/R): 7 d pretreatment with rivaroxaban led to reduced cardiac inflammation 72 h after I/R and lowered circulating leukocyte numbers. However, BM myelopoiesis showed a rescue of the leukocyte differentiation arrest, indicating that rivaroxaban's inhibitory effects are restricted to homeostatic conditions and are mainly abolished during emergency hematopoiesis. In translation, ST-elevation MI patients treated with rivaroxaban also exhibited reduced circulating leukocyte numbers. In conclusion, we demonstrate that rivaroxaban attenuates neutrophil maturation in the BM, which may offer a therapeutic option to limit overshooting of the immune response after I/R.

Dabigatran enhances platelet reactivity and platelet thrombin receptor expression in patients with atrial fibrillation.

Essentials Whether or not dabigatran enhances the risk of myocardial infarction is under discussion. We measured platelet reactivity and thrombin receptor expression in dabigatran patients. Platelet reactivity and thrombin receptor expression is enhanced during dabigatran treatment. This should be considered when choosing the optimal direct oral anticoagulant for individuals. SUMMARY: Background The direct oral anticoagulant (DOAC) dabigatran is a direct thrombin inhibitor. Its landmark trial, the RE-LY study, observed a trend towards a higher incidence of myocardial infarctions (MIs) in dabigatran-treated patients. Since then, there have been discussions on whether dabigatran increases the risk of MI. Objective In this study, we aimed to assess platelet reactivity and platelet thrombin receptor expression in dabigatran-treated patients. Methods We conducted a cross-sectional study in 13 hospitalized patients with planned initiation of dabigatran medication. Platelet reactivity was measured by light-transmission aggregometry and platelet thrombin receptor expression was measured by flow cytometry analysis. Results Platelet reactivity was higher after initiation of dabigatran medication as compared with baseline (baseline 44 ± 24% vs. dabigatran 70 ± 25%). Accordingly, the density of both platelet thrombin receptors (protease activated receptor [PAR]-1 and PAR-4) on platelets increased during dabigatran treatment (PAR1, baseline 63 ± 11% vs. dabigatran 70 ± 10%; PAR4, baseline 1.1 ± 0.5% vs. dabigatran 1.6 ± 0.9%). Conclusions Dabigatran increases platelet reactivity by enhancing the thrombin receptor density on platelets. This finding should be considered while choosing the optimal DOAC in individualized medicine.

Novel effects of adenosine receptors on pericellular hyaluronan matrix: implications for human smooth muscle cell phenotype and interactions with monocytes during atherosclerosis.

Hyaluronan (HA) is responsive to pro-atherosclerotic growth factors and cytokines and is thought to contribute to neointimal hyperplasia and atherosclerosis. However, the specific function of the pericellular HA matrix is likely depend on the respective stimuli. Adenosine plays an important role in the phenotypic regulation of vascular smooth muscle cells (VSMC) and is thought to inhibit inflammatory responses during atherosclerosis. The aim of this study was to examine the regulation and function of HA matrix in response to adenosine in human coronary artery SMC (HCASMC). The adenosine receptor agonist NECA (10 µM) caused a strong induction of HA synthase (HAS)1 at 6 h and a weaker induction again after 24 h. Use of selective adenosine receptor antagonists revealed that adenosine A2(B) receptors (A2(B)R) mediate the early HAS1 induction, whereas late HAS1 induction was mediated via A2(A)R and A3R. The strong response after 6 h was mediated in part via phosphoinositide-3 kinase- and mitogen-activated protein kinase pathways and was inhibited by Epac. Functionally, NECA increased cell migration, which was abolished by shRNA-mediated knock down of HAS1. In addition to HA secretion, NECA also stimulated the formation of pronounced pericellular HA matrix in HCASMC and increased the adhesion of monocytes. The adenosine-induced monocyte adhesion was sensitive to hyaluronidase. In conclusion, the current data suggest that adenosine via adenosine A2(B)R and A2(A)R/A3R induces HAS1. In turn a HA-rich matrix is formed by HCASMC which likely supports the migratory HCASMC phenotype and traps monocytes/macrophages in the interstitial matrix.

Stimulatory effects of the multi-kinase inhibitor sorafenib on human bladder cancer cells.

BACKGROUND AND PURPOSE: Sorafenib is an inhibitor of several intracellular signalling kinases with anti-proliferative, anti-angiogenic and pro-apoptotic effects in tumour cells. Sorafenib is used in the therapy of advanced renal cell carcinoma, and several phase II clinical trials are being carried out in patients with urothelial carcinomas. EXPERIMENTAL APPROACH: Using a panel of human bladder cancer cell lines (RT4, T24, J82), we characterized systematically the effects of sorafenib on intracellular signalling, migration, proliferation and apoptosis. KEY RESULTS: We demonstrated that at low concentrations (<1 microM), sorafenib is capable of significantly stimulating migration and proliferation of the bladder cancer cells. We hypothesize that these stimulatory effects on tumour cell functions might be explained by an activation of the Ras/ERK-1/2 signal transduction pathway. In addition, the comparison of different bladder cancer cell lines not only revealed a different biology (e.g. cell migration), but also a differential susceptibility to the anti-apoptotic effects of sorafenib. Finally, we confirmed in different bladder cancer cell lines the known inhibitory actions of sorafenib in pharmacological concentrations (> or =3 microM) on ERK-1/2 phosphorylation, migration and proliferation, as well as the pro-apoptotic effects of the compound. CONCLUSIONS AND IMPLICATIONS: Taken together, these findings suggest that although sorafenib has the potential to be used in the treatment of urothelial carcinoma, this compound might also activate bladder cancer cells at low concentrations. This should be relevant for dosing regiments to optimize the treatment with this promising anti-tumour drug.

Epac inhibits migration and proliferation of human prostate carcinoma cells.

BACKGROUND: It was recently found that cAMP mediates protein kinase A-independent effects through Epac proteins. The aim of this study was to investigate the role of Epac in migration and proliferation of prostate carcinoma cells. METHODS: The effect of Epac activation was determined by [(3)H]thymidine incorporation and scratch assays in PC-3 and DU 145 cells. Furthermore, cytoskeletal integrity was analysed by phalloidin staining. The participation of intracellular Epac effectors such as mitogen-activated protein (MAP) kinases, Rap1- and Rho-GTPases was determined by immunoblotting and pull-down assay. RESULTS: The specific Epac activator 8-pCPT-2'-O-Me-cAMP (8-pCPT) interfered with cytoskeletal integrity, reduced DNA synthesis, and migration. Although 8-pCPT activated Rap1, it inhibited MAP kinase signalling and RhoA activation. These findings were translated into functional effects such as inhibition of mitogenesis, cytoskeletal integrity, and migration. CONCLUSION: In human prostate carcinoma cells, Epac inhibits proliferative and migratory responses likely because of inhibition of MAP kinase and RhoA signalling pathways. Therefore, Epac might represent an attractive therapeutic target in the treatment of prostate cancer.

Epac inhibits apoptosis of human leukocytes.

cAMP is known to participate in the regulation of apoptosis in leukocytes. Depending on the cell type, pro- and antiapoptotic effects of cAMP have been described. Thus far, most of the cAMP-dependent effects have been attributed to the activation of PKA. However, Epac proteins (direct cAMP targets and guanine nucleotide exchange factors for Ras-like GTPases) have been shown recently to contribute to cAMP-dependent regulation of apoptosis. Therefore, we investigated the effects of the selective Epac activators 8-pCPT and Sp on apoptosis in human leukocytic cells (U937, HL-60, primary human mononuclear cells). We report here that Epac activation inhibits leukocyte apoptosis significantly.

[Methods to evaluate aspirin and clopidogrel resistance]. / Methoden zur Messung der Azetylsalizylsäure- bzw. Clopidogrelresistenz.

Based on the concept that the so-called resistance to anti-platelet drugs is meant to describe a phenomenon where the drug does not hit its direct pharmacodynamic target, assays, used to evaluated the effects of anti-platelet drugs, should as closely as possible measure the direct pharmacodynamic effect of a particular drug. Thus, for the detection of aspirin effects, thromboxane concentrations or arachidonic acid-induced responses (light aggregometry, whole-blood aggregometry) should be measured. For the detection of clopidogrel actions, VASP phosphorylation (flow cytometry) or ADP-induced responses (light aggregometry, whole blood aggregometry) should be analysed.