Impact of Femoral Ossification on Local and Systemic Cardiovascular Patients' Condition.

BACKGROUND: Vascular calcifications are associated with a high cardiovascular morbi-mortality in the coronary territory. In parallel, femoral arteries are more calcified and develop osteoid metaplasia (OM). This study was conducted to assess the predictive value of OM and local inflammation on the occurrence of mid- and long-term adverse cardiovascular events. METHOD: Between 2008 and 2015, 86 atheromatous samples were harvested during femoral endarterectomy on 81 patients and processed for histomorphological analyses of calcifications and inflammation (monocytes and B cells). Histological findings were compared with the long-term follow-up of patients, including major adverse cardiac event (MACE), major adverse limb event (MALE), and mortality. Frequencies were presented as percentage, and continuous data, as mean and standard deviation. A P-value < 0.05 was considered statistically significant. RESULTS: Median follow-up was 42.4 months (26.9-58.8). Twenty-eight percent of patients underwent a MACE; a MALE occurred in 18 (21%) limbs. Survival rate was 87.2% at 36 months. OM was found in 41 samples (51%), without any significant impact on the occurrence of MACE, MALE, or mortality. Preoperative white blood cell formulae revealed a higher rate of neutrophils associated with MACE (P = 0.04) and MALE (P = 0.0008), correlated with higher B cells counts in plaque samples. CONCLUSIONS: OM is part of femoral calcifications in almost 50% of the cases but does not seem to be an independent predictive variable for MACE or MALE. However, a higher rate of B cell infiltration of the plaque and preoperative neutrophil blood count may be predictive of adverse events during follow-up.

The FREEDOM Study: A Pilot Study Examining the Feasibility and Safety of Early Walking following Femoral Manual Compression after Endovascular Interventions Using 5F Sheath-Compatible Devices.

BACKGROUND: Increasing prevalence of peripheral arterial disease (PAD) burning and pressure to reduce costs and promote patient empowerment make outpatient endovascular procedures an attractive alternative to conventional hospitalization. For outpatient peripheral endovascular procedures, femoral manual compression could replace the use of arterial closure devices for small-bore punctures. Presently, safety and feasibility evidence for femoral manual compression is still lacking. FREEDOM is a pilot study designed to demonstrate the feasibility and safety of early walking after femoral manual puncture point compression following a therapeutic endovascular procedure for PAD. METHODS: From May to August 2015, all patients requiring endovascular treatment for PAD were prospectively screened. Those patients that received therapeutic endovascular procedures involving retrograde femoral punctures with a 5F sheath were included. Manual compression and pressure dressing of the femoral puncture points was applied. The primary end point was defined as the walking ability 5 hr after index procedure (H5), which was assessed by a walk test. RESULTS: In total, 129 consecutive patients were screened, and 30 patients met the study criteria. The mean age was 66 ± 11 years. The mean duration of the procedure and of the manual compression was 63 ± 24 min and 12.8 ± 4 min, respectively. At 5 hr following the procedure, 97% of the patients were able to walk 100 m. Two patients failed to walk due to cardiac arrhythmia and to a false aneurysm at the femoral puncture site. No further complications were observed at 1 month, and quality of life assessed by EQ-5D test was significantly increased compare to baseline (72.3 vs. 60.4; P = 0.001). CONCLUSIONS: This pilot study demonstrated the benefits of manual compression to close arterial punctures over procedures using 5F shealth-compatible endovascular devices. A sufficiently powered randomized controlled trial is needed to further characterize the potential benefits of manual compression following use of low-profile devices.

Impact of Vascular Calcifications on Long Femoropopliteal Stenting Outcomes.

BACKGROUND: Vascular calcifications (VCs) may be a prognostic factor for outcome after endovascular treatment of peripheral arterial disease (PAD). Semiquantitative analysis with X-ray imaging is the main limiting factor for assessing VCs. The aim of the present study was to find a correlation between the amount of VC with computed tomography (CT) scan quantification and midterm results of endovascular treatment of Trans-Atlantic Inter-Society Consensus C/D femoropopliteal (FP) lesions. METHODS: Patients belonging to 2 previously published registries (STELLA and STELLA PTX) and who underwent a preoperative CT scan were retrospectively included in the study. VC quantification was performed with a dedicated workstation (EndoSize, Therenva) on the basis of Hounsfield units (HU). The VC percentage was calculated as the ratio between VC volume and the volume of the region of interest. For the analysis, patients were divided into 3 groups according to VC percentage, from lowest to highest: group 1 (G1) included the first quartile of VCs, group 2 (G2) included the second and third quartiles, and group 3 (G3) included the fourth quartile. Risk of in-stent thrombosis was analysed using a multivariate model. RESULTS: Thirty-nine patients were included (10 in G1, 19 in G2, and 10 in G3), and mean follow-up duration was 24 ± 14.6 months. Patients in G1 and G3 had, respectively, a VC rate of <1% (no VC) and >20% (severe VC). In G2, VC was considered to be intermediate. There was no statistical difference in the cardiovascular risk factors and preoperative medication. A significant difference was found for the healthy FP diameter between G1 (4.6 ± 0.8 mm) and G3 (6.8 ± 0.8 mm, P < 0.0001) and between G2 (5.2 ± 1 mm) and G3 (P < 0.0001). The rate of drug-eluting stents was similar in all groups. There was no difference between groups concerning the rate of in-stent restenosis, target lesion revascularization, and target extremity revascularization. There was a higher rate of in-stent thrombosis for G1 versus G2 (P = 0.037), and no difference was noted between G1 versus G3 (P = 0.86) or G2 versus G3 (P = 0.12). G3 was associated with early stent thrombosis (<1 month), while G1 was associated with late stent thrombosis (6-24 months). On multivariate analysis, only one predictive factor for stent thrombosis was found: patients with intermediate VC seemed to be protected against in-stent thrombosis (odds ratio = 0.27, 95% confidence interval: 0.1-0.77; P = 0.014). CONCLUSIONS: The study showed that VC quantification with CT imaging is feasible and useful for comparing outcomes following PAD endovascular revascularization. Below a certain threshold, the presence of VC might be necessary for plaque stability and may protect against in-stent thrombosis.

Mechanisms of erosion of atherosclerotic plaques.

PURPOSE OF REVIEW: The present review explores the mechanisms of superficial intimal erosion, a common cause of thrombotic complications of atherosclerosis. RECENT FINDINGS: Human coronary artery atheroma that give rise to thrombosis because of erosion differ diametrically from those associated with fibrous cap rupture. Eroded lesions characteristically contain few inflammatory cells, abundant extracellular matrix, and neutrophil extracellular traps (NETs). Innate immune mechanisms such as engagement of Toll-like receptor 2 (TLR2) on cultured endothelial cells can impair their viability, attachment, and ability to recover a wound. Hyaluronan fragments may serve as endogenous TLR2 ligands. Mouse experiments demonstrate that flow disturbance in arteries with neointimas tailored to resemble features of human eroded plaques disturbs endothelial cell barrier function, impairs endothelial cell viability, recruits neutrophils, and provokes endothelial cells desquamation, NET formation, and thrombosis in a TLR2-dependent manner. SUMMARY: Mechanisms of erosion have received much less attention than those that provoke plaque rupture. Intensive statin treatment changes the characteristic of plaques that render them less susceptible to rupture. Thus, erosion may contribute importantly to the current residual burden of risk. Understanding the mechanisms of erosion may inform the development and deployment of novel therapies to combat the remaining atherothrombotic risk in the statin era.

Genesis and growth of extracellular-vesicle-derived microcalcification in atherosclerotic plaques.

Clinical evidence links arterial calcification and cardiovascular risk. Finite-element modelling of the stress distribution within atherosclerotic plaques has suggested that subcellular microcalcifications in the fibrous cap may promote material failure of the plaque, but that large calcifications can stabilize it. Yet the physicochemical mechanisms underlying such mineral formation and growth in atheromata remain unknown. Here, by using three-dimensional collagen hydrogels that mimic structural features of the atherosclerotic fibrous cap, and high-resolution microscopic and spectroscopic analyses of both the hydrogels and of calcified human plaques, we demonstrate that calcific mineral formation and maturation results from a series of events involving the aggregation of calcifying extracellular vesicles, and the formation of microcalcifications and ultimately large calcification areas. We also show that calcification morphology and the plaque's collagen content-two determinants of atherosclerotic plaque stability-are interlinked.

Bare Metal Versus Paclitaxel-Eluting Stents for Long Femoropopliteal Lesions: Prospective Cohorts Comparison Using a Propensity Score-Matched Analysis.

BACKGROUND: The study aims to compare outcomes of primary stenting of long femoropopliteal (FP) lesions with bare metal stent (BMS) versus paclitaxel eluting stent (PES). METHODS: In a single centre study, we established 2 consecutive and prospective cohorts with TASC C/D FP de novo lesions. The inclusion and exclusion criteria were similar. Bare metal stent (LifeStent®, Bard Peripheral) and PES (Zilver® PTX®, Cook Peripheral Vascular) were implanted. Prospective clinical and morphological follow-ups were carried out at 1, 3, 6, 12, and 18 months. Propensity score (inverse probability of treatment weighted method) stratification was used to minimize bias. RESULTS: In total, 110 limbs were treated (STELLA: n = 62; STELLA PTX: n = 48). We noted some difference between both cohorts regarding type 2 diabetes (P = 0.05), vitamin K antagonist use (P = 0.05), and angiotensin II receptor blocker use (P = 0.002). More stents were implanted in the STELLA PTX cohort (P < 0.0013). At 12 months, in univariate analysis, freedom from target lesion revascularization (TLR) was higher in the STELLA cohort (P = 0.005). No differences were found between both cohorts in terms of primary sustained clinical improvement (P = 0.25), primary patency (P = 0.07), and survival (P = 0.79). With the propensity score, no difference was observed in terms of primary sustained clinical improvement (P = 0.79), freedom from TLR (P = 0.59), and primary patency (P = 0.69). With Cox logistic regression, the number of implanted stents influenced the primary sustained clinical improvement, the freedom from TLR, and the primary patency. CONCLUSIONS: Paclitaxel-eluting stents do not seem to provide benefits in terms of clinical and morphological outcomes for TASC C/D lesions compared to BMS.

Moderate hypoxia potentiates interleukin-1ß production in activated human macrophages.

RATIONALE: Inflammation drives atherogenesis. Animal and human studies have implicated interleukin-1ß (IL-1ß) in this disease. Moderate hypoxia, a condition that prevails in the atherosclerotic plaque, may conspire with inflammation and contribute to the evolution and complications of atherosclerosis through mechanisms that remain incompletely understood. OBJECTIVE: This study investigated the links between hypoxia and inflammation by testing the hypothesis that moderate hypoxia modulates IL-1ß production in activated human macrophages. METHODS AND RESULTS: Our results demonstrated that hypoxia enhances pro-IL-1ß protein, but not mRNA, expression in lipopolysaccharide-stimulated human macrophages. We show that hypoxia limits the selective targeting of pro-IL-1ß to autophagic degradation, thus prolonging its half-life and promoting its intracellular accumulation. Furthermore, hypoxia increased the expression of NLRP3, a limiting factor in NLRP3 inflammasome function, and augmented caspase-1 activation in lipopolysaccharide-primed macrophages. Consequently, hypoxic human macrophages secreted higher amounts of mature IL-1ß than did normoxic macrophages after treatment with crystalline cholesterol, an endogenous danger signal that contributes to atherogenesis. In human atherosclerotic plaques, IL-1ß localizes predominantly to macrophage-rich regions that express activated caspase-1 and the hypoxia markers hypoxia-inducible factor 1α and hexokinase-2, as assessed by immunohistochemical staining of carotid endarterectomy specimens. CONCLUSIONS: These results indicate that hypoxia potentiates IL-1ß expression in cultured human macrophages and in the context of atheromata, therefore unveiling a novel proinflammatory mechanism that may participate in atherogenesis.

TLR2 and neutrophils potentiate endothelial stress, apoptosis and detachment: implications for superficial erosion.

AIMS: Superficial erosion of atheromata causes many acute coronary syndromes, but arises from unknown mechanisms. This study tested the hypothesis that Toll-like receptor-2 (TLR2) activation contributes to endothelial apoptosis and denudation and thus contributes to the pathogenesis of superficial erosion. METHODS AND RESULTS: Toll-like receptor-2 and neutrophils localized at sites of superficially eroded human plaques. In vitro, TLR2 ligands (including hyaluronan, a matrix macromolecule abundant in eroded lesions) induced endothelial stress, characterized by reactive oxygen species production, endoplasmic reticulum (ER) stress, and apoptosis. Co-incubation of neutrophils with endothelial cells (ECs) potentiated these effects and induced EC apoptosis and detachment. We then categorized human atherosclerotic plaques (n = 56) based on morphologic features associated with superficial erosion, 'stable' fibrotic, or 'vulnerable' lesions. Morphometric analyses of the human atheromata localized neutrophils and neutrophil extracellular traps (NETs) near clusters of apoptotic ECs in smooth muscle cell (SMC)-rich plaques. The number of luminal apoptotic ECs correlated with neutrophil accumulation, amount of NETs, and TLR2 staining in SMC-rich plaques, but not in 'vulnerable' atheromata. CONCLUSION: These in vitro observations and analyses of human plaques indicate that TLR2 stimulation followed by neutrophil participation may render smooth muscle cell-rich plaques susceptible to superficial erosion and thrombotic complications by inducing ER stress, apoptosis, and favouring detachment of EC.

Matrix metalloproteinase-13 predominates over matrix metalloproteinase-8 as the functional interstitial collagenase in mouse atheromata.

OBJECTIVE: Substantial evidence implicates interstitial collagenases of the matrix metalloproteinase (MMP) family in plaque rupture and fatal thrombosis. Understanding the compensatory mechanisms that may influence the expression of these enzymes and their functions, therefore, has important clinical implications. This study assessed in mice the relative effect of the 2 principal mouse collagenases on collagen content and other plaque characteristics. APPROACH AND RESULTS: Apolipoprotein E-deficient (apoE(-/-)) mice, MMP-13(-/-) apoE(-/-), MMP-8(-/-) apoE(-/-) double knockout mice, and MMP-13(-/-) MMP-8(-/-) apoE(-/-) triple knockout mice consumed a high-cholesterol diet for 10 and 24 weeks. Both double knockout and triple knockout mice showed comparable atherosclerotic lesion formation compared with apoE(-/-) controls. Analysis of aortic root sections indicated that lesions of MMP-8/MMP-13-deficient and MMP-13-deficient mice accumulate more fibrillar collagen than apoE(-/-) controls and MMP-8(-/-) apoE(-/-) double knockout. We further tested the relative effect of MMPs on plaque collagenolysis using in situ zymography. MMP-13 deletion alone abrogated collagenolytic activity in lesions, indicating a predominant role for MMP-13 in this process. MMP-13 and MMP-13/MMP-8 deficiency did not alter macrophage content but associated with reduced accumulation of smooth muscle cells. CONCLUSIONS: These results show that among MMP interstitial collagenases in mice, MMP-13 prevails over MMP-8 in collagen degradation in atheromata. These findings provide a rationale for the identification and selective targeting a predominant collagenase for modulating key aspects of plaque structure considered critical in clinical complications, although they do not translate directly to human lesions, which also contain MMP-1.

Molecular imaging of atherosclerosis for improving diagnostic and therapeutic development.

Despite recent progress, cardiovascular and allied metabolic disorders remain a worldwide health challenge. We must identify new targets for therapy, develop new agents for clinical use, and deploy them in a clinically effective and cost-effective manner. Molecular imaging of atherosclerotic lesions has become a major experimental tool in the last decade, notably by providing a direct gateway to the processes involved in atherogenesis and its complications. This review summarizes the current status of molecular imaging approaches that target the key processes implicated in plaque formation, development, and disruption and highlights how the refinement and application of such tools might aid the development and evaluation of novel therapeutics.

Thin-capped atheromata with reduced collagen content in pigs develop in coronary arterial regions exposed to persistently low endothelial shear stress.

OBJECTIVE: The mechanisms promoting the focal formation of rupture-prone coronary plaques in vivo remain incompletely understood. This study tested the hypothesis that coronary regions exposed to low endothelial shear stress (ESS) favor subsequent development of collagen-poor, thin-capped plaques. APPROACH AND RESULTS: Coronary angiography and 3-vessel intravascular ultrasound were serially performed at 5 consecutive time points in vivo in 5 diabetic, hypercholesterolemic pigs. ESS was calculated along the course of each artery with computational fluid dynamics at all 5 time points. At follow-up, 184 arterial segments with previously identified in vivo ESS underwent histopathologic analysis. Compared with other plaque types, eccentric thin-capped atheromata developed more in segments that experienced lower ESS during their evolution. Compared with lesions with higher preceding ESS, segments persistently exposed to low ESS (<1.2 Pa) exhibited reduced intimal smooth muscle cell content; marked intimal smooth muscle cell phenotypic modulation; attenuated procollagen-I gene expression; increased gene and protein expression of the interstitial collagenases matrix-metalloproteinase-1, -8, -13, and -14; increased collagenolytic activity; reduced collagen content; and marked thinning of the fibrous cap. CONCLUSIONS: Eccentric thin-capped atheromata, lesions particularly prone to rupture, form more frequently in coronary regions exposed to low ESS throughout their evolution. By promoting an imbalance of attenuated synthesis and augmented collagen breakdown, low ESS favors the focal evolution of early lesions toward plaques with reduced collagen content and thin fibrous caps-2 critical determinants of coronary plaque vulnerability.

Impact of notch signaling on inflammatory responses in cardiovascular disorders.

Notch signaling is a major pathway in cell fate decisions. Since the first reports showing the major role of Notch in embryonic development, a considerable and still growing literature further highlights its key contributions in various pathological processes during adult life. In particular, Notch is now considered as a major player in vascular homeostasis through the control of key cellular functions. In parallel, confounding evidence emerged that inflammatory responses regulate Notch signaling in vitro in endothelial cells, smooth muscle cells or vascular infiltrating cells and in vivo in vascular and inflammatory disorders and in cardiovascular diseases. This review presents how inflammation influences Notch in vascular cells and, reciprocally, emphasizes the functional role of Notch on inflammatory processes, notably by regulating key cell functions (differentiation, proliferation, apoptosis/survival, activation). Understanding how the disparity of Notch receptors and ligands impacts on vasculature biology remains critical for the design of relevant and adequate therapeutic strategies targeting Notch in this major pathological context.

Inhibition of alkaline phosphatase impairs dyslipidemia and protects mice from atherosclerosis.

Calcium accumulation in atherosclerotic plaques predicts cardiovascular mortality, but the mechanisms responsible for plaque calcification and how calcification impacts plaque stability remain debated. Tissue-nonspecific alkaline phosphatase (TNAP) recently emerged as a promising therapeutic target to block cardiovascular calcification. In this study, we sought to investigate the effect of the recently developed TNAP inhibitor SBI-425 on atherosclerosis plaque calcification and progression. TNAP levels were investigated in ApoE-deficient mice fed a high-fat diet from 10 weeks of age and in plaques from the human ECLAGEN biocollection (101 calcified and 14 non-calcified carotid plaques). TNAP was inhibited in mice using SBI-425 administered from 10 to 25 weeks of age, and in human vascular smooth muscle cells (VSMCs) with MLS-0038949. Plaque calcification was imaged in vivo with 18F-NaF-PET/CT, ex vivo with osteosense, and in vitro with alizarin red. Bone architecture was determined with µCT. TNAP activation preceded and predicted calcification in human and mouse plaques, and TNAP inhibition prevented calcification in human VSMCs and in ApoE-deficient mice. More unexpectedly, TNAP inhibition reduced the blood levels of cholesterol and triglycerides, and protected mice from atherosclerosis, without impacting the skeletal architecture. Metabolomics analysis of liver extracts identified phosphocholine as a substrate of liver TNAP, who's decreased dephosphorylation upon TNAP inhibition likely reduced the release of cholesterol and triglycerides into the blood. Systemic inhibition of TNAP protects from atherosclerosis, by ameliorating dyslipidemia, and preventing plaque calcification.

Selective inhibition of matrix metalloproteinase-13 increases collagen content of established mouse atherosclerosis.

OBJECTIVE: Evidence has linked collagen loss with the onset of acute coronary events. This study tested the hypothesis that selective matrix metalloproteinase-13 (MMP-13) collagenase inhibition increases collagen content in already established and nascent mouse atheromas. METHODS AND RESULTS: In vitro and in situ experiments documented the selectivity and efficacy of an orally available MMP-13 inhibitor (MMP13i-A). In vivo observations monitored macrophage accumulation and MMP-13 activity using molecular imaging. After 10 weeks of MMP13i-A treatment, apolipoprotein E-deficient mice with evolving or established lesions exhibited reduced MMP-13 activity without affecting macrophage content, measured either by intravital microscopy or fluorescence reflectance imaging. Histological analysis indicated that MMP13-iA did not affect plaque size or macrophage or smooth muscle cell accumulation. Administration of MMP13i-A to mice with evolving or established atheromas substantially increased plaque interstitial collagen content in the intima and locally in the fibrous cap, compared with vehicle-treated controls. Analysis of collagen revealed thicker collagen fibers within the plaques of treated groups. CONCLUSION: Pharmacological MMP-13 inhibition yields collagen accumulation in plaques (a feature associated in humans with resistance to rupture), even in established plaques. This study, of considerable clinical relevance, furnishes new mechanistic insight into regulation of the plaque's extracellular matrix and validates molecular imaging for studying plaque biology.

TNAP as a therapeutic target for cardiovascular calcification: a discussion of its pleiotropic functions in the body.

Cardiovascular calcification (CVC) is associated with increased morbidity and mortality. It develops in several diseases and locations, such as in the tunica intima in atherosclerosis plaques, in the tunica media in type 2 diabetes and chronic kidney disease, and in aortic valves. In spite of the wide occurrence of CVC and its detrimental effects on cardiovascular diseases (CVD), no treatment is yet available. Most of CVC involve mechanisms similar to those occurring during endochondral and/or intramembranous ossification. Logically, since tissue-nonspecific alkaline phosphatase (TNAP) is the key-enzyme responsible for skeletal/dental mineralization, it is a promising target to limit CVC. Tools have recently been developed to inhibit its activity and preclinical studies conducted in animal models of vascular calcification already provided promising results. Nevertheless, as its name indicates, TNAP is ubiquitous and recent data indicate that it dephosphorylates different substrates in vivo to participate in other important physiological functions besides mineralization. For instance, TNAP is involved in the metabolism of pyridoxal phosphate and the production of neurotransmitters. TNAP has also been described as an anti-inflammatory enzyme able to dephosphorylate adenosine nucleotides and lipopolysaccharide. A better understanding of the full spectrum of TNAP's functions is needed to better characterize the effects of TNAP inhibition in diseases associated with CVC. In this review, after a brief description of the different types of CVC, we describe the newly uncovered additional functions of TNAP and discuss the expected consequences of its systemic inhibition in vivo.

Distinct role of mitochondrial function and protein kinase C in intimal and medial calcification in vitro.

Introduction: Vascular calcification (VC) is a major risk factor for cardiovascular morbidity and mortality. Depending on the location of mineral deposition within the arterial wall, VC is classified as intimal and medial calcification. Using in vitro mineralization assays, we developed protocols triggering both types of calcification in vascular smooth muscle cells (SMCs) following diverging molecular pathways. Materials and methods and results: Human coronary artery SMCs were cultured in osteogenic medium (OM) or high calcium phosphate medium (CaP) to induce a mineralized extracellular matrix. OM induces osteoblast-like differentiation of SMCs-a key process in intimal calcification during atherosclerotic plaque remodeling. CaP mimics hyperphosphatemia, associated with chronic kidney disease-a risk factor for medial calcification. Transcriptomic analysis revealed distinct gene expression profiles of OM and CaP-calcifying SMCs. OM and CaP-treated SMCs shared 107 differentially regulated genes related to SMC contraction and metabolism. Real-time extracellular efflux analysis demonstrated decreased mitochondrial respiration and glycolysis in CaP-treated SMCs compared to increased mitochondrial respiration without altered glycolysis in OM-treated SMCs. Subsequent kinome and in silico drug repurposing analysis (Connectivity Map) suggested a distinct role of protein kinase C (PKC). In vitro validation experiments demonstrated that the PKC activators prostratin and ingenol reduced calcification triggered by OM and promoted calcification triggered by CaP. Conclusion: Our direct comparison results of two in vitro calcification models strengthen previous observations of distinct intracellular mechanisms that trigger OM and CaP-induced SMC calcification in vitro. We found a differential role of PKC in OM and CaP-calcified SMCs providing new potential cellular and molecular targets for pharmacological intervention in VC. Our data suggest that the field should limit the generalization of results found in in vitro studies using different calcification protocols.

Protective cross talk between activated protein C and TNF signaling in vascular endothelial cells: implication of EPCR, noncanonical NF-κB, and ERK1/2 MAP kinases.

Activated protein C (APC) is a natural anticoagulant protease that displays cytoprotective and antiinflammatory activities and has been demonstrated to reduce mortality of patients with severe sepsis. However, APC signaling is not fully understood. This study further investigated the antiinflammatory effects of APC in vascular endothelial cells (EC) and examined the cross talk between APC and TNF signaling. Analysis of the regulatory mechanisms mediated by APC on vascular human EC shows that APC impairs TNF signaling by triggering a preemptive activation of intracellular pathways. We found that APC signaling causes a moderate but significant induction of cell adhesion molecules (CAMs) including VCAM-1 at mRNA and protein levels. Activation of the noncanonical NF-κB and ERK1/2 are both pivotal to APC signaling leading to VCAM-1 expression. APC upregulates TNF receptor-associated factor 2 (TRAF2) and phosphorylates NF-κB p65 at Ser276 and Ser536 independently of IκB degradation. The ultimate protective antiinflammatory effect of APC in response to TNF is associated with a sustained activation of ERK1/2 and Akt while phosphorylation of NF-κB p65 is precluded. Inhibitors of ERK (PD98059 and U0126) abolish the antiinflammatory signal mediated by APC. Blocking antibodies and silencing assays also suggest that, in EC, protease-activated receptor 1 and endothelial protein C receptor (EPCR) both conduct ERK activation and VCAM-1 induction in response to APC. To conclude, APC protects EC by attenuating CAM expression during inflammation. APC engages a regulatory cross talk involving EPCR, ERK, and NF-κB that impairs TNF signaling.

Circulating endothelial cell protein C receptor: endothelial regulation and cumulative impact of gender and A3 haplotype.

BACKGROUND: The endothelial cell (EC) protein C receptor (EPCR) negatively regulates coagulation and inflammation. Factors and mechanisms regulating the expression of cell-bound EPCR and the release of soluble (s) EPCR are still unclear. METHODS: We investigated the reciprocal regulation of membrane-bound and sEPCR upon inflammation using primary cultures of vascular EC. The impact of 2 parameters, gender and EPCR gene A3 haplotype, on sEPCR plasma basal level and endothelial expression was examined by Elisa and flow cytometry. RESULTS: Exposure of EC to tumor necrosis factor α causes a rapid downregulation of membrane-associated EPCR expression without affecting markedly the spontaneous release of sEPCR by EC. In a cohort of 100 healthy donors, we show that males express significantly higher basal sEPCR in plasma than females (194 ± 12 vs. 145 ± 9 ng/ml, respectively, p<0.01). Both gender and EPCR A3 haplotype affect sEPCR plasma levels but have no apparent effect on EPCR expression by EC. No quantitative correlation between cellular expression and circulating blood sEPCR was observed, suggesting that endothelial expression may not reflect the plasma level. CONCLUSION: Male gender is another parameter with A3 haplotype associated with elevated sEPCR levels in blood, and both parameters may contribute to selective regulatory mechanisms of EPCR release upon inflammation.

The C-type lectin-like receptor CLEC-1, expressed by myeloid cells and endothelial cells, is up-regulated by immunoregulatory mediators and moderates T cell activation.

C-type lectin receptors have recently been described as playing crucial roles in immunity and homeostasis since these proteins are able to recognize pathogens as well as self-Ags. We identified the C-type lectin-like receptor-1, CLEC-1, as being overexpressed in a model of rat allograft tolerance. We previously described in this model the expression of numerous cytoprotective molecules by graft endothelial cells and their interplay with regulatory CD4(+)CD25(+) T cells. In this study, we demonstrate that CLEC-1 is expressed by myeloid cells and specifically by endothelial cells in tolerated allografts and that CLEC-1 expression can be induced in endothelial cells by alloantigen-specific regulatory CD4(+)CD25(+) T cells. Analysis of CLEC-1 expression in naive rats demonstrates that CLEC-1 is highly expressed by myeloid cells and at a lower level by endothelial cells, and that its expression is down-regulated by inflammatory stimuli but increased by the immunoregulators IL-10 or TGFbeta. Interestingly, we demonstrate in vitro that inhibition of CLEC-1 expression in rat dendritic cells increases the subsequent differentiation of allogeneic Th17 T cells and decreases the regulatory Foxp3(+) T cell pool. Additionally, in chronically rejected allograft, the decreased expression of CLEC-1 is associated with a higher production of IL-17. Taken together, our data suggest that CLEC-1, expressed by myeloid cells and endothelial cells, is enhanced by regulatory mediators and moderates Th17 differentiation. Therefore, CLEC-1 may represent a new therapeutic agent to modulate the immune response in transplantation, autoimmunity, or cancer settings.

MicroRNA-17-5p Reduces Inflammation and Bone Erosions in Mice With Collagen-Induced Arthritis and Directly Targets the JAK/STAT Pathway in Rheumatoid Arthritis Fibroblast-like Synoviocytes.

OBJECTIVE: We undertook this study to examine microRNA (miRNA) expression across rheumatoid arthritis (RA) phenotypes, along with the effects and mechanisms of action of miRNA-17-5p (miR-17). METHODS: A miRNA array was performed in synovial tissue biopsied from patients with naive erosive RA (n = 3) and patients with nonerosive RA (n = 3). MicroRNA-17 lipoplex was delivered intraarticularly in the murine collagen-induced arthritis model. Clinical, histologic, and structural effects were studied over the course of arthritis. In-depth studies of the mechanisms of action of miR-17 were performed in primary RA fibroblast-like synoviocytes (FLS) isolated from synovial tissue. RESULTS: Fifty-five miRNAs including miR-17 were reduced in erosive RA. The miR-17 transfection into arthritic paws reduced the clinical inflammation score between day 2 and day 7 (2.8 versus 1.9; P = 0.03). Synovial B cell, T cell, macrophage, and polynuclear neutrophil infiltration was significantly reduced. Structural damage was also decreased, as shown by a reduction in the number of osteoclasts detected using tartrate-resistant acid phosphatase staining (osteoclast surface/bone surface 32% versus 18%; P = 0.005) and erosion score by computed tomography analysis (2.9 versus 1.7; P = 0.023). Proinflammatory cytokines from the interleukin-6 (IL-6) family and IL-1ß expression were also significantly reduced, but tumor necrosis factor was not. MicroRNA-17 directly targeted the 3'-untranslated regions of STAT3 and JAK1. STAT3 and JAK1 messenger RNA (mRNA) and protein expression were reduced in RA FLS following miR-17 transfection. STAT3 and JAK1 mRNA and activation of STAT3, as assessed by immunohistochemistry, were also reduced in injected paws (% stained area 93% versus 62%; P = 0.035). CONCLUSION: We demonstrate an antiinflammatory and antierosive role of miR-17 in vivo. This effect involves the suppression of the IL-6 family autocrine-amplifying loop through the direct targeting of JAK1 and STAT3.