Neopterin induces pro-atherothrombotic phenotype in human coronary endothelial cells.

Division of Cardiology, University of Naples 'Federico II', Naples, Italy.
Journal of Thrombosis and Haemostasis (Impact Factor: 5.55). 11/2006; 4(10):2248-55. DOI: 10.1111/j.1538-7836.2006.02125.x
Source: PubMed

ABSTRACT Inflammation plays a pivotal role in atherothrombosis. Recent data indicate that serum levels of neopterin, a marker of inflammation and immune modulator secreted by monocytes/macrophages, are elevated in patients with acute coronary syndromes and seem to be a prognostic marker for major cardiovascular events. The aim of the present study was to determine whether neopterin might affect the thrombotic and atherosclerotic characteristics of human coronary artery endothelial cells (HCAECs).
In HCAECs, neopterin induced TF-mRNA transcription as demonstrated by real time polymerase chain reaction and expression of functionally active tissue factor (TF) as demonstrated by procoagulant activity assay, and of cellular adhesion molecules (CAMs) as demonstrated by FACS analysis, in a dose-dependent fashion. These neopterin effects were prevented by lovastatin, a HMG-CoA reductase inhibitor. Neopterin-induced TF and CAMs expression was mediated by oxygen free radicals through the activation of the transcription factor, nuclear factor-kappa B (NF-kappaB), as demonstrated by electrophoretic mobility shift assay and by suppression of CAMs and TF expression by superoxide dismutase and by NF-kappaB inhibitor, pyrrolidine-dithio-carbamate ammonium.
These data indicate that neopterin exerts direct effects on HCAECs by promoting CAMs and TF expression and support the hypothesis that neopterin, besides representing a marker of inflammation, might be an effector molecule able to induce a pro-atherothrombotic phenotype in cells of the coronary circulation.

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    ABSTRACT: In vitro, large amounts of neopterin are released from human monocyte-derived macrophages and dendritic cells primarily upon stimulation with Th1-type cytokine interferon-γ (IFN-γ). IFN-γ also induces the enzyme indoleamine 2,3-dioxygenase (IDO), which degrades tryptophan (TRP) to form kynurenine (KYN). IDO-mediated TRP catabolism is very effective in suppressing the proliferation of T lymphocytes as well as of pathogens in vitro and in vivo. In this study, we investigated whether exogenously added neopterin may influence IDO activity in resting and in stimulated peripheral blood mononuclear cells (PBMC). PBMC were isolated from healthy donors, and neopterin was added in a concentration range from 0.01 to 50 μmol/L. After 30 min, PBMC were stimulated or not with 10 μg/mL of mitogen phytohemagglutinin (PHA). After 48 h, culture supernatants were collected, KYN and TRP concentrations were measured by high-performance liquid chromatography, and the ratio of KYN vs. TRP was calculated as an estimate of IDO activity. Spontaneous as well as PHA-induced TRP breakdown was suppressed by exogenously added neopterin in a dose-dependent way; the lowest active concentration of neopterin was <100 nmol/L. As neopterin concentrations in the nanomolar range are commonly observed in patients suffering from infections, sepsis, or uremia, our results suggest that neopterin formation might also serve as a feedback mechanism to slow down TRP degradation in vivo.
    01/2013; 24(3-4). DOI:10.1515/pterid-2013-0037
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    ABSTRACT: Multiple factors are involved in the etiology of cardiovascular disease (CVD). Pathological changes occur in a variety of cell types long before symptoms become apparent and diagnosis is made. Dysregulation of physiological functions are associated with the activation of immune cells, leading to local and finally systemic inflammation that is characterized by production of high levels of reactive oxygen species (ROS). Patients suffering from inflammatory diseases often present with diminished levels of antioxidants either due to insufficient dietary intake or, and even more likely, due to increased demand in situations of overwhelming ROS production by activated immune effector cells like macrophages. Antioxidants are suggested to beneficially interfere with diseases-related oxidative stress, however the interplay of endogenous and exogenous antioxidants with the overall redox system is complex. Moreover, molecular mechanisms underlying oxidative stress in CVD are not fully elucidated. Metabolic dybalances are suggested to play a major role in disease onset and progression. Several central signaling pathways involved in the regulation of immunological, metabolic and endothelial function are regulated in a redox-sensitive manner. During cellular immune response, interferon γ-dependent pathways are activated such as tryptophan breakdown by the enzyme indoleamine 2,3-dioxygenase (IDO) in monocyte-derived macrophages, fibroblasts, endothelial and epithelial cells. Neopterin, a marker of oxidative stress and immune activation is produced by GTP-cyclohydrolase I in macrophages and dendritic cells. Nitric oxide synthase (NOS) is induced in several cell types to generate nitric oxide (NO). NO, despite its low reactivity, is a potent antioxidant involved in the regulation of the vasomotor tone and of immunomodulatory signaling pathways. NO inhibits the expression and function of IDO. Function of NOS requires the cofactor tetrahydrobiopterin (BH4), which is produced in humans primarily by fibroblasts and endothelial cells. Highly toxic peroxynitrite (ONOO(-)) is formed solely in the presence of superoxide anion (O2 (-)). Neopterin and kynurenine to tryptophan ratio (Kyn/Trp), as an estimate of IDO enzyme activity, are robust markers of immune activation in vitro and in vivo. Both these diagnostic parameters are able to predict cardiovascular and overall mortality in patients at risk. Likewise, a significant association exists between increase of neopterin concentrations and Kyn/Trp ratio values and the lowering of plasma levels of vitamin-C, -E and -B. Vitamin-B deficiency is usually accompanied by increased plasma homoycsteine. Additional determination of NO metabolites, BH4 and plasma antioxidants in patients with CVD and related clinical settings can be helpful to improve the understanding of redox-regulation in health and disease and might provide a rationale for potential antioxidant therapies in CVD.


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Jun 2, 2014