High tissue factor-expressing human monocytes carry low surface CD36: application to intersubject variability.

BACKGROUND: The 'high and low responder' phenomenon describes an intersubject variability in mononuclear cell (MNC) prothrombotic reactivity to lipopolysaccharide (LPS) stimulation. Because alterations in surface CD36 expression in monocytes were associated with impaired monocyte function, we studied the relationship between the levels of surface CD36 presentation and the prothrombotic reactivity of monocytes from high-responder (HR) and low-responder (LR) individuals. METHODS AND RESULTS: The relationship between levels of tissue factor (TF) expression and surface CD36 presentation in MNCs from HR individuals (n = 7) and LR individuals (n = 8) was investigated. Resting MNCs from HR individuals contained significantly more TF mRNA but levels of TF antigen and procoagulant activity similar to MNCs from LR individuals. Resting CD14+ MNCs from HR individuals expressed significantly lower surface CD36, as mean fluorescence intensities (MFIs) were 70.4 +/- 6.3 vs. 132.0 +/- 14.5 arbitrary units (AU) in HR and LR individuals, respectively. MFI from surface TF negatively correlated with surface CD36 in the population of resting (r = -0.598, P = 0.031) and LPS-stimulated (r = -0.672, P = 0.009) CD14+ cells. LPS-stimulated MNCs from HR individuals contained significantly more TF in a surface pool (2079 +/- 199 vs. 786 +/- 57 AU) along with higher TF procoagulant activity (57.3 +/- 15.2 vs. 21.1 +/- 4.5 mU 10(6) cells(-1)) as compared with LR individuals. CD14+ MNCs from HR individuals expressed less surface CD36 during a 2-h LPS challenge. CONCLUSIONS: A novel phenotype of monocytes characterized by high TF and low CD36 presentation could be further developed for use as a marker for detection of HR individuals prone to developing prothrombotic conditions.

In-cell Western assay: a new approach to visualize tissue factor in human monocytes.

BACKGROUND: Tissue factor (TF) is an integral membrane protein essential for the initiation of the extrinsic pathway of hemostasis. A precise understanding of the TF regulation is still limited and dependent on the availability of methodological tools. Here, we describe a new approach for assessing TF amounts in human mononuclear cells (MNCs) by using the whole blood experimental conditions. AIM: In order to study TF antigen levels in human MNCs, we applied a quantitative immunostaining technique-- in-cell Western (ICW) assay using an Odyssey Infrared Imaging System. METHODS AND RESULTS: The ICW assay of TF in resting or lipopolysaccharide (LPS)-stimulated human MNCs was performed. Several sample preparation conditions were tested, namely the plating of MNCs prior to immunostaining, paraformaldehyde fixation, and an adequate cell number was used in the assay. By the use of recombinant human TF standards, it was possible, for the first time, to measure TF amounts in LPS-stimulated MNCs as 0.09 +/- 0.02 ng and 0.43 +/- 0.15 ng 10(-6) cells of surface and total TF, respectively. The concentrations of TF in resting MNCs, however, were below the detection limit. CONCLUSIONS: A novel TF ICW assay is a reproducible, time- and cost-saving method, which could become useful for studies in the fields of physiology and pathophysiology of human hemostasis.

Selecting and deselecting imatinib-resistant clones: observations made by longitudinal, quantitative monitoring of mutated BCR-ABL.

Resistance to imatinib during the treatment of chronic myeloid leukaemia (CML) is frequently associated with point mutations in the ABL gene encoding the ATP binding region likely to cause disease relapse. Early diagnosis and monitoring of these mutations may be important in order to prevent rapid expansion of resistant clones. We describe a quantitative mutation-specific PCR assay based on the readily available Taqman platform. Selectivity for the mutated target is conferred by mutation-specific primers destabilised by additional mismatches. The assay can be carried out in parallel to standard BCR-ABL quantification and is therefore more quickly compared to standard sequencing procedures. The sensitivity of the assay reaches 0.1%. It also allows for quantitative assessment of mutated clones. By analysing sequential samples of resistant subjects, we show how mutated clones were selected, maintained or deselected depending on the individual treatment setting. The high sensitivity and practical merits of this method makes it a good candidate for prospective molecular surveillance of patients at high risk for imatinib resistance.

A novel role of bone morphogenetic protein-7 in the regulation of adhesion and migration of human monocytic cells.

BACKGROUND: Bone morphogenetic protein (BMP) 7 is abundant in atherosclerotic plaques and increases monocyte pro-coagulant activity by enhancing tissue factor (TF) expression. While several members of the BMP superfamily are able to serve as chemotactic agents for monocytes, the role of BMP-7 in regulation of monocyte motility is not known. AIMS: To assess the effect of BMP-7 on adhesive and migratory properties of human monocytes. METHODS: Chemokinesis, adhesion, and transendothelial migration of BMP-7-treated THP-1 cells and human monocytes were analysed using live-cell imaging, orbital shear, and Boyden chamber assays. Surface presentation of ß2 integrins and phosphorylation status of Akt & focal adhesion kinase (FAK) were studied by flow cytometry and Western blot. RESULTS: High levels of BMP-7 protein were detectable in intimal regions of atherosclerotic plaques; BMP-7 significantly enhanced THP-1 and monocyte chemokinetic properties in vitro (1.21+0.01 and 1.76+0.21 fold increase in crawling distance, respectively). Under orbital shear, adhesion of monocytic cells to microvascular endothelial cell (MVEC) monolayers was also significantly increased by BMP-7 (3.89+1.56 and 2.57+0.97 fold over vehicle). Moreover, BMP-7 accelerated transendothelial migration of THP-1 cells and monocytes towards MCP-1 (5.91+0.88 and 2.96±0.65 fold increase, respectively). BMP-7 enhanced cell surface presentation of ß2 integrins in the active conformation. Observed effects were determined to be Akt and FAK dependent, as shown by pharmacological inhibition. CONCLUSION: BMP-7 directly upregulates adhesion and migration of human monocytic cells via activation of ß2 integrins, Akt, and FAK. Our findings suggest that BMP-7 may serve as a novel contributor to atherogenesis.

BMP-7 induces TF expression in human monocytes by increasing F3 transcriptional activity.

BACKGROUND: Bone morphogenetic protein (BMP)-7, a major regulator of bone metabolism, inhibits ectopic calcification in atherosclerotic plaques. We have recently reported that BMP-7 is also a potent inducer of tissue factor (TF) in human mononuclear cells (MNCs). While nuclear factor kappa beta (NF-kB) and activation protein-1 (AP-1) are the transcription factors essential for inducible expression of human TF gene (F3), the mechanisms responsible for TF induction by BMP-7 are not known. OBJECTIVE: To elucidate the molecular mechanisms governing BMP-7-triggered TF expression in human MNCs. METHODS: Human blood monocytes were stimulated with BMP-7 and western blotting, qRT-PCR, and flow cytometry studies were carried out to assess F3 expression; promoter studies were also performed using a panel of reporter constructs. Procoagulant TF activity was measured using a validated FXa generation assay. The significance of NF-kB transcriptional activity was verified via pharmacological inhibition. RESULTS: BMP-7 increased TF protein levels, procoagulant activity, surface presentation, and TF mRNA expression. This increase was accompanied by activation of NF-kB as evidenced by reduced IkB-α levels and elevated transcriptional activity of an NF-kB-sensitive reporter in transfected MNCs. Although treatment with BMP-7 also led to a strong phosphorylation of c-Jun, activation of AP-1 alone was not sufficient to induce TF expression: JSH-23, a potent and specific NF-kB inhibitor, completely blocked BMP-7-induced TF expression. CONCLUSIONS: We report that BMP-7-dependent activation of TF in human MNCs is mediated via increased activity of NF-kB, leading to enhanced F3 transcription in human MNCs.

BMP-2 inhibits TF expression in human monocytes by shutting down MAPK signaling and AP-1 transcriptional activity.

BACKGROUND: We have recently identified bone morphogenetic protein (BMP)-2 as a novel inhibitor of tissue factor (TF) expression in lipopolysaccharide (LPS)-activated human monocytes, and now sought for intracellular mechanisms. METHODS: Here, we studied activation status of mitogen activated protein kinases (MAPKs) extracellular signal-regulated protein kinase (Erk) 1/2, p38, and c-Jun N-terminal kinase (JNK) as well as transcription factors activator protein (AP)-1 and nuclear factor kappa B (NF-kB), which regulate inducible expression of TF. RESULTS: Human mononuclear cells (MNCs) responded to BMP-2 stimulation with activation of canonic Smad1/5/8 signaling. Pretreatment with BMP-2 prevented LPS-induced increase in surface presentation, intracellular accumulation, and fraction of TF-positive MNCs. Similarly, LPS-induced increase in levels of phosphorylated Erk1/2, p38, and JNK was markedly diminished by BMP-2 pretreatment. BMP-2 pretreatment prior to LPS significantly diminished LPS-induced transcriptional activation of AP-1-dependent reporter. In contrast, BMP-2 given prior to LPS did not dampen the transcriptional activation of NF-kB-sensitive luciferase reporter. CONCLUSIONS: BMP-2 can inhibit LPS-induced TF protein expression and surface presentation in human MNCs by downregulation of Erk1/2, p38, and JNK signaling, as well as reduced transcriptional activity of AP-1, but not NF-kB.

Increased expression of TF in BMP-7-treated human mononuclear cells depends on activation of select MAPK signaling pathways.

Bone morphogenetic protein (BMP)-7 regulates atherosclerotic plaque calcification, and it contributes to increased thrombogenicity of lipid-rich lesions by enhancement of TF expression in monocytes/macrophages by unknown mechanism. Since Erk1/2, JNK and p38 mitogen activated protein kinases (MAPKs) regulate TF expression, we studied involvement of MAPK pathways in BMP-7-induced activation of TF in human mononuclear cells (MNCs). Whole blood from healthy volunteers was treated with BMP-7, MNCs were isolated, and TF expression was assessed by western blot (WB) and In-Cell Western assay. Phosphorylation and nuclear translocation of Smad1/5/8 in response to BMP-7 stimulation of MNCs was evaluated by WB and confocal microscopy. Activation of MAPKs was judged by measuring the levels of phoshorylated Erk1/2, JNK, and p38 in the lysates of MNCs. The impact of Erk1/2 and p38 activation was studied by use of PD98059 and SB203580 inhibitors, respectively. Stimulation of whole blood with BMP-7 increased the levels of TF in the lysates of MNCs by 7-fold as compared to 12-fold after LPS stimulation. It was followed by elevation in TF fuctional activity. It was accompanied by elevated levels of phosphorylated Smad 1/5/8 and nuclear translocation of Smad1/5/8 proteins. Treatment of whole blood with BMP-7 led to a phosphorylation of Erk1/2, JNK and p38 MAPKs. BMP-7-induced TF expression was partially inhibited by Erk1/2 inhibitor, whereas TF expression was completely abolished by p38 inhibitor. BMP-7-dependent activation of TF in human MNCs by BMP-7 is accompanied by activation of canonic Smad1/5/8 signaling pathway and depends on activation of Erk1/2 and p38.

Bone morphogenetic protein -7 increases thrombogenicity of lipid-rich atherosclerotic plaques via activation of tissue factor.

Thrombogenicity of atherosclerotic plaques largely depends on plaque morphology. Tissue factor (TF) expression is higher in lipid-rich than in calcified lesions. Although bone morphogenetic protein (BMP) -7 is a known inhibitor of vascular calcification, the role of BMP-7 in the development of plaque thrombogenicity is uncertain. We hypothesized that increased thrombogenic potential of lipid-rich plaques is attributed to activation of TF by BMP-7. We measured levels of BMP-7 and TF proteins in lipid-rich and calcified carotid plaques, and tested the effects of BMP-7 on TF expression in human monocytes in vitro. Quantitative immunohistochemical analysis of endarterectomy specimens for TF and BMP-7 revealed that lipid-rich plaques contained more TF antigen than calcified ones (158.6±25.3 vs 37.4±8.8 AU, p<0.008). Lipid-rich plaques also expressed higher levels of BMP-7 (60.7±5.2 AU) than calcified lesions (31.8±8.6 AU, p<0.021). In vitro treatment of whole blood with BMP-7 markedly increased the population of TF-positive monocytes from 1.5±0.6 % to 31.0±7.6 % (p<0.001). Stimulation of blood with BMP-7 was accompanied by elevated surface presentation of TF antigen in monocytes as TF-dependent fluorescence intensity increased from 5.0±2.6 AU in unstimulated conditions to 15.8±1.9 AU after incubation with BMP-7 (p<0.002). Our data suggest that BMP-7 contributes to increased thrombogenicity of lipid-rich plaques via enhancement of TF expression.

No evidence for the presence of tissue factor in high-purity preparations of immunologically isolated eosinophils.

BACKGROUND: To date, there is no unequivocal opinion on whether human eosinophils express tissue factor (TF). Therefore, we studied the expression of TF protein and activity in resting or stimulated immunologically purified human eosinophils. METHODS AND RESULTS: By use of immunologic isolation, we achieved over 96% purity of eosinophil preparations, and contamination by CD14-positive cells was below 0.3%. Flow cytometric [fluorescence-activated cell sorting (FACS)] analysis of eosinophils revealed no surface expression of TF antigen in resting or stimulated eosinophils. Immunoblotting of eosinophil lysates did not show any TF protein under resting or stimulated conditions. The lysates of resting or stimulated eosinophils contained no detectable levels of TF procoagulant activity. In contrast, monocytes, stimulated in plasma or medium, possessed readily detectable TF levels on the cell surface and in cell lysates as detected by FACS and immunoblotting. This was active TF antigen, as confirmed by TF activity assay (19.2 +/- 4.2 and 28.6 +/- 3.1 mU per 10(6) cells, stimulated in medium or plasma, respectively). We found no detectable TF mRNA levels in resting or stimulated eosinophils by real-time polymerase chain reaction (PCR), whereas in monocytes TF mRNA levels were significantly increased after stimulation. CONCLUSIONS: Our data indicate that there is no evidence for TF expression in high-purity preparations of immunologically isolated eosinophils.

Infusion of methylene blue in human septic shock: a pilot, randomized, controlled study.

OBJECTIVE: To evaluate the effects of continuous infusion of methylene blue (MB), an inhibitor of the nitric oxide pathway, on hemodynamics and organ functions in human septic shock. DESIGN: Prospective, randomized, controlled, open-label, pilot study. SETTING: Multidisciplinary intensive care unit of a university hospital. PATIENTS: Twenty patients with septic shock diagnosed <24 hrs before randomization. INTERVENTIONS: Patients were randomized 1:1 to receive either MB (MB group, n = 10) or isotonic saline (control group, n = 10), adjunctive to conventional treatment. MB was administered as an intravenous bolus injection (2 mg/kg), followed 2 hrs later by infusion at stepwise increasing rates of 0.25, 0.5, 1, and 2 mg/kg/hr that were maintained for 1 hr each. During infusion, mean arterial pressure was maintained between 70 and 90 mm Hg, while attempting to reduce concurrent adrenergic support. MEASUREMENTS AND MAIN RESULTS: Hemodynamics and organ function variables were assessed over a 24-hr period, and the survival rate at day 28 was noted. Infusion of MB prevented the stroke volume and the left-ventricular stroke work indexes from falling and increased mean arterial pressure. Compared with the control group, MB reduced the requirement for norepinephrine, epinephrine, and dopamine by as much as 87%, 81%, and 40%, respectively. Oxygen delivery remained unchanged in the MB group and decreased in the control group. MB also reduced the body temperature and the plasma concentration of nitrates/nitrites. Leukocytes and organ function variables such as bilirubin, alanine aminotransferase, urea, and creatinine were not significantly affected. Platelet count decreased in both groups. Five patients treated with MB survived vs. three patients receiving conventional treatment. CONCLUSIONS: In human septic shock, continuously infused MB counteracts myocardial depression, maintains oxygen transport, and reduces concurrent adrenergic support. Infusion of MB appears to have no significant adverse effects on the selected organ function variables.