PCSK9 regulates the chemokine receptor CCR2 on monocytes.

Monocyte migration is a key element in atherosclerosis. LDL-C facilitates monocyte migration via induction of CCR2. PCSK9 regulates cell surface expression of the LDL-R and is expressed in vascular smooth muscle cells (VSMCs). The present study was done to investigate the regulation of PCSK9 in VSMCs and its impact on monocyte function. METHODS AND RESULTS: PCSK9 mRNA and protein levels were upregulated in VSMCs by the TLR-4 ligand LPS, whereas TGF-ß or angiotensin II had no effect. Induction of PCSK9 was selectively inhibited by TLR-4 blockade and further downstream by the SAPK/JNK-inhibitor SP600125, whereas inhibitors of ERK1/2, p38 or PI3-kinase pathways had no effect. Incubation of monocytes in conditioned media from LPS-stimulated VSMCs resulted in a significant reduction of LDL-R levels on monocytes, comparable to the effects of recombinant PCSK9. LDL-C increased monocyte CCR2 expression, which augmented monocyte migration towards MCP-1. This LDL-C dependent monocyte chemotaxis was inhibited by supernatants from LPS-stimulated VSMCs, similar to recombinant PCSK9 and a specific LDL-R blocking antibody. CONCLUSION: PCSK9 is regulated in VSMCs by TLR-4 - SAPK/JNK signaling, a pathway important in inflammation and metabolism. VSMC-derived PCSK9 reduces monocyte LDL-R expression, affecting LDL-C/LDL-R-mediated CCR2-expression on monocytes, which is crucial to cell motility and atherogenesis.

Cardiovascular magnetic resonance feature tracking in small animals - a preliminary study on reproducibility and sample size calculation.

BACKGROUND: Cardiovascular magnetic resonance feature tracking (CMR-FT) is a novel tissue tracking technique developed for noninvasive assessment of myocardial motion and deformation. This preliminary study aimed to evaluate the observer's reproducibility of CMR-FT in a small animal (mouse) model and define sample size calculation for future trials. METHODS: Six C57BL/6 J mice were selected from the ongoing experimental mouse model onsite and underwent CMR with a 3 Tesla small animal MRI scanner. Myocardial deformation was analyzed using dedicated software (TomTec, Germany) by two observers. Left ventricular (LV) longitudinal, circumferential and radial strain (EllLAX, EccSAX and ErrSAX) were calculated. To assess intra-observer agreement data analysis was repeated after 4 weeks. The sample size required to detect a relative change in strain was calculated. RESULTS: In general, EccSAX and EllLAX demonstrated highest inter-observer reproducibility (ICC 0.79 (0.46-0.91) and 0.73 (0.56-0.83) EccSAX and EllLAX respectively). In contrast, at the intra-observer level EllLAX was more reproducible than EccSAX (ICC 0.83 (0.73-0.90) and 0.74 (0.49-0.87) EllLAX and EccSAX respectively). The reproducibility of ErrSAX was weak at both observer levels. Preliminary sample size calculation showed that a small study sample (e.g. ten animals to detect a relative 10% change in EccSAX) could be sufficient to detect changes if parameter variability is low. CONCLUSIONS: This pilot study demonstrates good to excellent inter- and intra-observer reproducibility of CMR-FT technique in small animal model. The most reproducible measures are global circumferential and global longitudinal strain, whereas reproducibility of radial strain is weak. Furthermore, sample size calculation demonstrates that a small number of animals could be sufficient for future trials.

Targeting density-enhanced phosphatase-1 (DEP-1) with antisense oligonucleotides improves the metabolic phenotype in high-fat diet-fed mice.

BACKGROUND: Insulin signaling is tightly controlled by tyrosine dephosphorylation of the insulin receptor through protein-tyrosine-phosphatases (PTPs). DEP-1 is a PTP dephosphorylating tyrosine residues in a variety of receptor tyrosine kinases. Here, we analyzed whether DEP-1 activity is differentially regulated in liver, skeletal muscle and adipose tissue under high-fat diet (HFD), examined the role of DEP-1 in insulin resistance in vivo, and its function in insulin signaling. RESULTS: Mice were fed an HFD for 10 weeks to induce obesity-associated insulin resistance. Thereafter, HFD mice were subjected to systemic administration of specific antisense oligonucleotides (ASOs), highly accumulating in hepatic tissue, against DEP-1 or control ASOs. Targeting DEP-1 led to improvement of insulin sensitivity, reduced basal glucose level, and significant reduction of body weight. This was accompanied by lower insulin and leptin serum levels. Suppression of DEP-1 in vivo also induced hyperphosphorylation in the insulin signaling cascade of the liver. Moreover, DEP-1 physically associated with the insulin receptor in situ, and recombinant DEP-1 dephosphorylated the insulin receptor in vitro. CONCLUSIONS: These results indicate that DEP-1 acts as an endogenous antagonist of the insulin receptor, and downregulation of DEP-1 results in an improvement of insulin sensitivity. DEP-1 may therefore represent a novel target for attenuation of metabolic diseases.

A clinical study to evaluate the safe and effective use of a new, single use stethoscope cover to enable reduction in pathogen transmission during auscultation.

Objectives: Stethoscopes carry a significant risk for pathogen transmission. Here, the safe use and performance of a new, non-sterile, single-use stethoscope cover (SC), that is impermeable for pathogens, was investigated by different healthcare professionals (HCPs) in the postoperative care setting of an intensive care unit (ICU). Methods: Fifty-four patients underwent routine auscultations with the use of the SC (Stethoglove®, Stethoglove GmbH, Hamburg, Germany). The participating HCPs (n = 34) rated each auscultation with the SC on a 5-point Likert scale. The mean ratings of acoustic quality and the SC handling were defined as primary and secondary performance endpoint. Results: 534 auscultations with the SC were performed (average 15.7/user) on the lungs (36.1%), the abdomen (33.2%), the heart (28.8%), or other body-sites (1.9%). No adverse device-effects occurred. The acoustic quality was rated at 4.2 ± 0.7 (mean) with a total of 86.1% of all auscultations being rated at least as 4/5, and with no rating as below 2. The SC handling was rated at 3.7 ± 0.8 (mean) with a total of 96.4% of all auscultations being rated at least 3/5. Conclusion: Using a real-world setting, this study demonstrates that the SC can be safely and effectively used as cover for stethoscopes during auscultation. The SC may therefore represent a useful and easy-to-implement tool for preventing stethoscope-mediated infections.Study Registration: EUDAMED no. CIV-21-09-037762.

Endothelial damage inhibitor preserves the integrity of venous endothelial cells from patients undergoing coronary bypass surgery.

OBJECTIVES: Despite the success of coronary artery bypass graft (CABG) surgery using autologous saphenous vein grafts (SVGs), nearly 50% of patients experience vein graft disease within 10 years of surgery. One contributing factor to early vein graft disease is endothelial damage during short-term storage of SVGs in inappropriate solutions. Our aim was to evaluate the effects of a novel endothelial damage inhibitor (EDI) on SVGs from patients undergoing elective CABG surgery and on venous endothelial cells (VECs) derived from these SVGs. METHODS: SVGs from 11 patients participating in an ongoing clinical registry (NCT02922088) were included in this study, and incubated with both full electrolyte solution (FES) or EDI for 1 h and then examined histologically. In 8 of 11 patients, VECs were isolated from untreated grafts, incubated with both FES and EDI for 2 h under hypothermic stress conditions and then analysed for activation of an inflammatory phenotype, cell damage and cytotoxicity, as well as endothelial integrity and barrier function. RESULTS: The EDI was superior to FES in protecting the endothelium in SVGs (74 ± 8% versus 56 ± 8%, P < 0.001). Besides confirming that the EDI prevents apoptosis in SVG-derived VECs, we also showed that the EDI temporarily reduces adherens junctions in VECs while protecting focal adhesions compared to FES. CONCLUSIONS: The EDI protects the connectivity and function of the SVG endothelium. Our data suggest that the EDI can preserve focal adhesions in VECs during short-term storage after graft harvesting. This might explain the superiority of the EDI in maintaining most of the endothelium in venous CABG surgery conduits.

Granulocyte colony-stimulating factor improves cerebrovascular reserve capacity by enhancing collateral growth in the circle of Willis.

BACKGROUND AND PURPOSE: Restoration of cerebrovascular reserve capacity (CVRC) depends on the recruitment and positive outward remodeling of preexistent collaterals (arteriogenesis). With this study, we provide functional evidence that granulocyte colony-stimulating factor (G-CSF) augments therapeutic arteriogenesis in two animal models of cerebral hypoperfusion. We identified an effective dosing regimen that improved CVRC and stimulated collateral growth, thereby improving the outcome after experimentally induced stroke. METHODS: We used two established animal models of (a) cerebral hypoperfusion (mouse, common carotid artery ligation) and (b) cerebral arteriogenesis (rat, 3-vessel occlusion). Following therapeutic dose determination, both models received either G-CSF, 40 µg/kg every other day, or vehicle for 1 week. Collateral vessel diameters were measured following latex angiography. Cerebrovascular reserve capacities were assessed after acetazolamide stimulation. Mice with left common carotid artery occlusion (CCAO) were additionally subjected to middle cerebral artery occlusion, and stroke volumes were assessed after triphenyltetrazolium chloride staining. Given the vital role of monocytes in arteriogenesis, we assessed (a) the influence of G-CSF on monocyte migration in vitro and (b) monocyte counts in the adventitial tissues of the growing collaterals in vivo. RESULTS: CVRC was impaired in both animal models 1 week after induction of hypoperfusion. While G-CSF, 40 µg/kg every other day, significantly augmented cerebral arteriogenesis in the rat model, 50 or 150 µg/kg every day did not show any noticeable therapeutic impact. G-CSF restored CVRC in mice (5 ± 2 to 12 ± 6%) and rats (3 ± 4 to 19 ± 12%). Vessel diameters changed accordingly: in rats, the diameters of posterior cerebral arteries (ipsilateral: 209 ± 7-271 ± 57 µm; contralateral: 208 ± 11-252 ± 28 µm) and in mice the diameter of anterior cerebral arteries (185 ± 15-222 ± 12 µm) significantly increased in the G-CSF groups compared to controls. Stroke volume in mice (10 ± 2%) was diminished following CCAO (7 ± 4%) and G-CSF treatment (4 ± 2%). G-CSF significantly increased monocyte migration in vitro and perivascular monocyte numbers in vivo. CONCLUSION: G-CSF augments cerebral collateral artery growth, increases CVRC and protects from experimentally induced ischemic stroke. When comparing three different dosing regimens, a relatively low dosage of G-CSF was most effective, indicating that the common side effects of this cytokine might be significantly reduced or possibly even avoided in this indication.

Anisotropic topographies restore endothelial monolayer integrity and promote the proliferation of senescent endothelial cells.

Thrombogenicity remains a major issue in cardiovascular implants (CVIs). Complete surficial coverage of CVIs by a monolayer of endothelial cells (ECs) prior to implantation represents a promising strategy but is hampered by the overall logistical complexity and the high number of cells required. Consequently, extensive cell expansion is necessary, which may eventually lead to replicative senescence. Considering that micro-structured surfaces with anisotropic topography may promote endothelialization, we investigated the impact of gratings on the biomechanical properties and the replicative capacity of senescent ECs. After cultivation on gridded surfaces, the cells showed significant improvements in terms of adherens junction integrity, cell elongation, and orientation of the actin filaments, as well as enhanced yes-associated protein nuclear translocation and cell proliferation. Our data therefore suggest that micro-structured surfaces with anisotropic topographies may improve long-term endothelialization of CVIs.

CD40/CD40L interaction induces E-selectin dependent leukocyte adhesion to human endothelial cells and inhibits endothelial cell migration.

BACKGROUND: CD40 is a receptor expressed on a wide range of cells such as leukocytes and endothelial cells (EC). As a member of the tumor necrosis factor (TNF) superfamily the activation of CD40 by CD40-ligand (CD40L) plays a crucial role for the development and progression of a variety of inflammatory processes including atherosclerosis. The aim of the present study was to investigate the effect of CD40/CD40L interaction on leukocyte adhesion to the endothelium and on endothelial cell migration. METHODS AND RESULTS: Human umbilical vein endothelial cells (HUVEC) were stimulated with either stable transfectants of mouse myeloma cells expressing the CD40L or wild type cells (4 h). Subsequently adhesion of leukocytes expressing Sialyl Lewis X, the counterpart for E-selectin (HL60 cells), was measured under shear stress (2-2.6 dyne/cm(2)) using a flow chamber adhesion assay. Stimulation of CD40 led to a significant increase of E-selectin dependent adhesion of leukocytes to the endothelium. Incubation of cells with either the CD40L blocking antibody TRAP-1 or the E-selectin blocking antibody BBA2 during CD40 stimulation completely abolished adhesion of leukocytes to HUVEC. Similar results were found in human cardiac microvasculature endothelial cells (HCMEC). In contrast stimulation of CD40 had no effect on adhesion of L-selectin expressing NALM6-L cells. Furthermore, CD40/CD40L interaction abrogated VEGF-induced migration of HUVEC compared to non-stimulated controls. In comparison experiments, stimulation of endothelial cells with VEGF led to a significant phosphorylation of ERK1/2, Akt, and eNOS. Stimulation of endothelial CD40 had no effect on VEGF-induced phosphorylation of ERK1/2. However, VEGF-induced activation of Akt and eNOS was reduced to baseline levels when endothelial CD40 was stimulated. CONCLUSION: CD40/CD40L interaction induces E-selectin dependent adhesion of leukocytes to human endothelial cells and reduces endothelial cell migration by inhibiting the Akt/eNOS signaling pathway.

IGF-1 increases macrophage motility via PKC/p38-dependent alphavbeta3-integrin inside-out signaling.

UNLABELLED: Macrophage migration is a key aspect in the initiation and progression of atherosclerosis. Insulin-like growth factor (IGF)-1 is highly expressed in macrophages in human atheroma. Its function in macrophage motility, however, remains to be elucidated. The aim of this study was to investigate the impact of IGF-1 on macrophage migration, its signaling pathways and the involvement of integrins and/or matrix metalloproteinases (MMPs). RESULTS: Migration checker-box experiments demonstrated that IGF-1 induced chemotaxis in human THP-1/macrophages. IGF-1 induced migration was inhibited by RGD-containing peptides and the alphavbeta3-blocking antibody LM609, but was unaffected by the MMP-inhibitor GM6001. Immunoblotting demonstrated that IGF-1 did not affect the activation of MMPs or TIMPs, nor did it increase alphav-integrin protein levels. However, IGF-1 induced recruitment of alphavbeta3, as well as trans-location of the integrin adaptor protein phospho-paxillin to focal adhesion sites. Pharmacological blocking experiments with specific inhibitors of Akt, PKC and p38 MAP-kinase revealed that IGF-1-dependent activation of focal adhesion kinase (FAK) and paxillin, and consecutively IGF-1 facilitated migration, required IGF-1/IGF-1R-mediated PI3-kinase/PKC/p38-dependent integrin inside-out signaling. CONCLUSION: IGF-1 plays a vital role in macrophage migration critically implicated in tissue inflammation. This involves activation of integrins and focal adhesion formation via inside-out PI3-kinase/PKC/p38-dependent signaling, but does not require MMP activation.

MicroRNA Mediated Cardioprotection - Is There a Path to Clinical Translation?

In the past 20 years, there have been several approaches to achieve cardioprotection or cardiac regeneration using a vast variety of cell therapies and remote ischemic pre-conditioning (RIPC). To date, substantial proof that either cell therapy or RIPC has the potential for clinically relevant cardiac repair or regeneration of cardiac tissue is still pending. Preclinical trials indicate that the secretome of cells in situ (during RIPC) as well as of transplanted cells may exhibit cardioprotective properties in the acute setting of cardiac injury. The secretome generally consists of cell-specific cytokines and extracellular vesicles (EVs) containing microRNAs (miRNAs). It is currently hypothesized that a subset of known miRNAs play a crucial part in the facilitation of cardioprotective effects. miRNAs are small non-coding RNA molecules that inhibit post-transcriptional translation of messenger RNAs (mRNAs) and play an important role in gene translation regulation. It is also known that one miRNAs usually targets multiple mRNAs. This makes predictability of pharmacokinetics and mechanism of action very difficult and could in part explain the inferior performance of various progenitor cells in clinical studies. Identification of miRNAs involved in cardioprotection and remodeling, the composition of miRNA profiles, and the exact mechanism of action are important to the design of future cell-based but also cell-free cardioprotective therapeutics. This review will give a description of miRNA with cardioprotective properties and a current overview on known mechanism of action and potential missing links. Additionally, we will give an outlook on the potential for clinical translation of miRNAs in the setting of myocardial infarction and heart failure.

MiRNA Profiles of Extracellular Vesicles Secreted by Mesenchymal Stromal Cells-Can They Predict Potential Off-Target Effects?

The cardioprotective properties of extracellular vesicles (EVs) derived from mesenchymal stromal cells (MSCs) are currently being investigated in preclinical studies. Although microRNAs (miRNAs) encapsulated in EVs have been identified as one component responsible for the cardioprotective effect of MSCs, their potential off-target effects have not been sufficiently characterized. In the present study, we aimed to investigate the miRNA profile of EVs isolated from MSCs that were derived from cord blood (CB) and adipose tissue (AT). The identified miRNAs were then compared to known targets from the literature to discover possible adverse effects prior to clinical use. Our data show that while many cardioprotective miRNAs such as miR-22-3p, miR-26a-5p, miR-29c-3p, and miR-125b-5p were present in CB- and AT-MSC-derived EVs, a large number of known oncogenic and tumor suppressor miRNAs such as miR-16-5p, miR-23a-3p, and miR-191-5p were also detected. These findings highlight the importance of quality assessment for therapeutically applied EV preparations.

Serelaxin Improves Regional Myocardial Function in Experimental Heart Failure: An In Vivo Cardiac Magnetic Resonance Study.

Background Animal studies demonstrated that serelaxin lessens fibrosis in heart failure. This study assessed its effect on myocardial deformation using cardiac magnetic resonance and elucidated its relationship to gene regulation and histology in a mouse heart failure model. Methods and Results C57BL/6J mice were subjected to SHAM (n=4) or transverse aortic constriction (TAC). At week 10, TAC mice were randomized to receive either serelaxin (0.5 mg/kg per day; n=11) or vehicle (n=13) for 4 weeks. Cardiac magnetic resonance imaging was performed at baseline and repeated at the end of the study (week 14). Cine images were used to calculate left ventricular (LV) global longitudinal, circumferential, and radial strain. Hearts were examined for histology and gene expression. Compared with SHAM, mice 10 weeks after TAC showed increased LV mass with significant decreases in LV deformation parameters, indicating subclinical deterioration of myocardial function. At week 14, TAC mice given serelaxin demonstrated significant improvements in all LV strain parameters and no decrease in LV stroke volume and ejection fraction compared with TAC mice given vehicle. A significant positive correlation between global circumferential strain and the extent of myocardial fibrosis was found, and global circumferential strain correlated significantly with the expression of heart failure genes in serelaxin-treated mice. Conclusions Serelaxin improved cardiac magnetic resonance-derived myocardial deformation parameters as well as histomorphometric and gene expression findings in mice with heart failure. Cardiac magnetic resonance-derived myocardial mechanics correlate with histology and gene expression, stressing its utilization in myocardial remodeling.

Insulin facilitates monocyte migration: a possible link to tissue inflammation in insulin-resistance.

Mononuclear cells (MNCs) are the primary cell type involved in the pro-inflammatory state of obesity-linked insulin-resistance, and atherosclerosis. Increased serum levels of MMP-9 are reported in insulin-resistant type 2 diabetic patients. Here we demonstrate insulin facilitating human monocytic THP-1 cell chemotaxis via prolonged Erk1/2-dependent induction of MMP-9. In vivo, significantly increased serum levels of MMP-9 were found in obesity-induced hyperinsulinemic C57BL/J6 mice, which were diminished by treatment with the anti-diabetic PPARgamma-ligand pioglitazone. In line with this, pioglitazone inhibited Erk1/2-phosphorylation and subsequent insulin-dependent MMP-9 synthesis in THP-1 cells. Thus, insulin increases MMP-9 gelatinolytic activity in monocytic cells, which results in accelerated chemotaxis. Hyperinsulinemia is associated with enhanced MMP-9 serum levels, potentially facilitating monocyte migration to and infiltration of adipose tissue and the arterial wall, thereby contributing to the increased cardiovascular risk in obese, hyperinsulinemic patients.

Insulin augments matrix metalloproteinase-9 expression in monocytes.

OBJECTIVE: Insulin resistance and hyperinsulinemia are major causes of cardiovascular morbidity and mortality. Matrix metalloproteinases (MMPs), highly expressed in activated mononuclear cells in vulnerable atherosclerotic lesions, are the main proteolytic enzymes controlling plaque stability. The aim of this study was to investigate the regulation of monocyte MMP-9 by insulin. METHODS AND RESULTS: Stimulation of MMP-9 expression by insulin was time- and concentration-dependent in human monocytic THP-1 cells. Inhibition of insulin receptor (IR) maturation via inhibition of its activating convertase furin with the pharmacological furin-inhibitor decanoyl-RVKR-chloromethylketone, as well as blocking of IGF-1R function with a IGF-1R blocking antibody, demonstrated that insulin mediates increases in MMP-9 via IR activation. Inhibition of insulin's "metabolic" phosphatidylinositol 3-kinase signaling with wortmannin (50 nmol/L) or LY294002 (2.5 micromol/L) did not prevent insulin-dependent MMP-9 induction. In contrast inhibition of insulin's "mitogenic" Ras-Raf-mitogen-activated protein kinase-kinase pathways with PD98059 (15 micromol/L) or U0126 (2 micromol/L) inhibited insulin-induced MMP-9 gelatinolytic activity in THP-1 cells. Likewise, PD98059 inhibited insulin augmented MMP-9 levels in primary human monocytes, whereas wortmannin had no effect. CONCLUSION: This study demonstrates that insulin can induce MMP-9 via mitogenic signaling pathways in monocytes, whereas phosphatidylinositol 3-kinase-dependent signaling, typically altered in insulin resistance, is not required. Induction of MMP-9 by insulin may potentially contribute to a pro-inflammatory state and the increased cardiovascular morbidity and mortality in type 2 diabetics.

Furin-like proprotein convertases are central regulators of the membrane type matrix metalloproteinase-pro-matrix metalloproteinase-2 proteolytic cascade in atherosclerosis.

BACKGROUND: Accumulation of macrophages and their in situ expression of matrix metalloproteinases (MMPs) are important determinants of plaque stability. Activation of membrane-bound MT1-MMP, the major activator of pro-MMP-2, requires intracellular endoproteolytic cleavage of its precursor protein. This type of activation typically requires suitable furin-like proprotein convertases (PCs), specifically furin and PC5. The present study was done to investigate the function of MT1-MMP as well as furin-like PCs in mononuclear inflammatory cells. METHODS AND RESULTS: Macrophage differentiation of human monocytic THP-1 cells was accompanied by increased expression of furin, PC5, and MT1-MMP. Some pro-MMP-2 activation was found in macrophages, but pro-MMP-2 level or activation was not enhanced after stimulation with the proinflammatory mediators tumor necrosis factor-alpha or lipopolysaccharide. However, culturing of macrophages in conditioned medium from serum-starved vascular smooth muscle cells, which constitutively secrete pro-MMP-2, resulted in a strong pro-MMP-2 activation. Inhibition of furin-like PCs with the specific pharmacological inhibitor decanoyl-RVKR-chloromethylketone (dec-CMK) inhibited MT1-MMP activation in macrophages. Dec-CMK or furin-specific small interfering RNA significantly inhibited macrophage MT1-MMP-dependent activation of vascular smooth muscle cell-derived pro-MMP-2. Flow cytometry demonstrated that human circulating monocytes express furin and PC5, and MT1-MMP and immunohistochemistry revealed their colocalization in macrophages in advanced human atherosclerotic lesions. CONCLUSIONS: Furin-like PCs (furin and PC5) play a central role in a MT-MMP-MMP-2 proteolytic cascade, involving provision of macrophage MT1-MMP for the activation of pro-MMP-2 synthesized by other cells. Furin and PC5 are expressed in human peripheral blood mononuclear cells and colocalize with MT1-MMP in macrophages in the atherosclerotic plaque, supporting the hypothesis that they are potential targets in atherosclerosis.

Inhibition of Src homology 2 domain-containing phosphatase 1 increases insulin sensitivity in high-fat diet-induced insulin-resistant mice.

Insulin resistance plays a crucial role in the development of type 2 diabetes. Insulin receptor signalling is antagonized and tightly controlled by protein tyrosine phosphatases (PTPs). However, the precise role of the PTP src homology 2 domain-containing phosphatase 1 (SHP-1) in insulin resistance has not been explored. Male C57BL/6J mice were fed a high-fat diet (HFD, 60% kcal from fat), to induce insulin resistance, or a low-fat diet (LFD, 10% kcal from fat) for 10 weeks. Afterwards, HFD-fed mice were pharmacologically treated with the SHP-1 (Ptpn6) inhibitor sodium stibogluconate and the broad spectrum pan-PTP inhibitor bis(maltolato)oxovanadium(IV) (BMOV). Both inhibitors ameliorated the metabolic phenotype, as evidenced by reduced body weight, improved insulin sensitivity and glucose tolerance, which was not due to altered PTP gene expression. In parallel, phosphorylation of the insulin receptor and of the insulin signalling key intermediate Akt was enhanced, and both PTP inhibitors and siRNA-mediated SHP-1 downregulation resulted in an increased glucose uptake in vitro. Finally, recombinant SHP-1 was capable of dephosphorylating the ligand-induced tyrosine-phosphorylated insulin receptor. These results indicate a central role of SHP-1 in insulin signalling during obesity, and SHP-1 inhibition as a potential therapeutic approach in metabolic diseases.

Enhanced insulin signaling in density-enhanced phosphatase-1 (DEP-1) knockout mice.

OBJECTIVE: Insulin resistance can be triggered by enhanced dephosphorylation of the insulin receptor or downstream components in the insulin signaling cascade through protein tyrosine phosphatases (PTPs). Downregulating density-enhanced phosphatase-1 (DEP-1) resulted in an improved metabolic status in previous analyses. This phenotype was primarily caused by hepatic DEP-1 reduction. METHODS: Here we further elucidated the role of DEP-1 in glucose homeostasis by employing a conventional knockout model to explore the specific contribution of DEP-1 in metabolic tissues. Ptprj (-/-) (DEP-1 deficient) and wild-type C57BL/6 mice were fed a low-fat or high-fat diet. Metabolic phenotyping was combined with analyses of phosphorylation patterns of insulin signaling components. Additionally, experiments with skeletal muscle cells and muscle tissue were performed to assess the role of DEP-1 for glucose uptake. RESULTS: High-fat diet fed-Ptprj (-/-) mice displayed enhanced insulin sensitivity and improved glucose tolerance. Furthermore, leptin levels and blood pressure were reduced in Ptprj (-/-) mice. DEP-1 deficiency resulted in increased phosphorylation of components of the insulin signaling cascade in liver, skeletal muscle and adipose tissue after insulin challenge. The beneficial effect on glucose homeostasis in vivo was corroborated by increased glucose uptake in skeletal muscle cells in which DEP-1 was downregulated, and in skeletal muscle of Ptprj (-/-) mice. CONCLUSION: Together, these data establish DEP-1 as novel negative regulator of insulin signaling.

Proprotein convertase subtilisin/kexin type 3 promotes adipose tissue-driven macrophage chemotaxis and is increased in obesity.

BACKGROUND: Matrix metalloproteinase (MMP)-dependent extracellular matrix (ECM) remodeling is a key feature in cardiometabolic syndrome-associated adipogenesis and atherosclerosis. Activation of membrane-tethered (MT) 1-MMP depends on furin (PCSK3). However, the regulation and function of the natural furin-inhibitor serpinB8 and thus furin/MT1-MMP-activity in obesity-related tissue inflammation/remodeling is unknown. Here we aimed to determine the role of serpinB8/furin in obesity-associated chronic inflammation. METHODS AND RESULTS: Monocyte → macrophage transformation was characterized by decreases in serpinB8 and increases in furin/MT1-MMP. Rescue of serpinB8 by protein overexpression inhibited furin-dependent pro-MT1-MMP activation in macrophages, supporting its role as a furin-inhibitor. Obese white adipose tissue-facilitated macrophage migration was inhibited by furin- and MMP-inhibition, stressing the importance of the furin-MMP axis in fat tissue inflammation/remodeling. Monocytes from obese patients (body mass index (BMI) >30kg/m(2)) had higher furin, MT1-MMP, and resistin gene expression compared to normal weight individuals (BMI<25kg/m(2)) with significant correlations of BMI/furin and furin/MT1-MMP. In vitro, the adipocytokine resistin induced furin and MT1-MMP in mononuclear cells (MNCs), while MCP-1 had no effect. CONCLUSIONS: Acquisition of the inflammatory macrophage phenotype is characterized by an imbalance in serpinB8/furin, leading to MT1-MMP activation, thereby enhancing migration. Increases in MT1-MMP and furin are present in MNCs from obese patients. Dissecting the regulation of furin and its inhibitor serpinB8 should facilitate targeting inflammation/remodeling in cardiometabolic diseases.

Soluble P-selectin level correlates with acetylsalicylic acid but not with clopidogrel response in patients with stable coronary artery disease after a percutaneous coronary intervention.

BACKGROUND: Impaired response to dual antiplatelet therapy is associated with worse cardiovascular outcome. Besides antiplatelet effects, there is evidence that both clopidogrel and acetylsalicylic acid (ASA) have anti-inflammatory properties. However, little is known about the relationship between platelet function and inflammation under dual antiplatelet therapy in patients with stable coronary artery disease. PURPOSE: The purpose of the study was to investigate the correlation of platelet function with soluble (s)P-selectin and soluble (s)CD40L in patients undergoing elective percutaneous coronary intervention. Poor response to ASA and clopidogrel could lead to increased levels of inflammatory markers. METHODS: A total of 148 patients were included. Eighty percent of the patients were on 100 mg ASA and all patients were clopidogrel naive. They underwent percutaneous coronary intervention and received a loading dose of 600 mg clopidogrel. Platelet function was assessed by light transmittance aggregometry (LTA) and vasodilator-stimulated phosphoprotein analysis at baseline, 24 h after loading, and after 1 month of maintenance therapy, respectively. Plasma levels of sP-selectin and sCD40L were measured. To classify low responders to clopidogrel, patients were screened for genetic variants determining clopidogrel absorption and metabolization. RESULTS: sP-selectin levels correlated with LTA findings after stimulation with arachidonic acid (P=0.012). Further, in addition to decreased platelet reactivity observed on LTA, lower sP-selectin levels were seen in patients under ASA therapy (P=0.004). CYP2C19*2 allele carriers had a higher platelet reactivity after clopidogrel loading measured by adenosine diphosphate-induced aggregation in LTA (P=0.008) and vasodilator-stimulated phosphoprotein phosphorylation (P=0.035); however, there was no difference in the inflammatory markers. Multiple regression analysis showed that variables significantly related to sP-selectin plasma levels were sCD40L (P<0.001), LTA after stimulation with arachidonic acid (P<0.001), adenosine diphosphate (20 µmol/l, P=0.009), collagen (P<0.001), and ejection fraction (P=0.001). CONCLUSION: sP-selectin was decreased in patients receiving ASA but did not reflect a CYP2C19*2-defined clopidogrel response. This underlines that sP-selectin is a useful marker for ASA, but not for clopidogrel response, in stable coronary artery disease.

Proprotein convertase furin enhances survival and migration of vascular smooth muscle cells via processing of pro-nerve growth factor.

Maturation of nerve growth factor (NGF) in neuronal cells requires endoproteolytic processing of the precursor protein proNGF to ß-NGF by the proprotein convertase furin. Pro- and ß-NGF elicit opposite biological functions by differential neurotrophin-receptor binding, leading to apoptosis via sortilin or survival via neurotrophic tyrosine kinase receptor type-1 (TrkA), respectively. The present study was done to investigate the impact of furin-dependent proNGF processing on vascular smooth muscle cell (VSMC) function. We found that ß-NGF mRNA and protein expression was upregulated in platelet-derived growth factor-BB/transforming growth factor-ß1-stimulated, proliferating rat aortic VSMCs. Although ß-NGF itself did not affect VSMC proliferation, it promoted VSMC motility in an autocrine fashion via TrkA/Akt-dependent integrin inside-out signalling. The ß-NGF-induced migration of VSMCs required proNGF processing by furin, which was co-regulated with NGF. Furin-inhibition increased proNGF and reduced ß-NGF secretion, leading to apoptosis rather than migration. In line with our in vitro demonstration, we found co- and upregulation of NGF, its convertase furin and its high-affinity receptor TrkA in the neointima of balloon-injured rodent arteries. These results indicate that furin determines the balance between proNGF and ß-NGF in proliferating VSMCs, thus impacting on VSMC survival and migration and is also important in neointima formation.