Patient-derived anti-ß2GP1 antibodies recognize a peptide motif pattern and not a specific sequence of residues.

Antiphospholipid antibody syndrome is an autoimmune disease characterized by the presence of so-called antiphospholipid antibodies and clinical manifestations such as recurrent thromboembolic or pregnancy complications. Although the main antigenic determinant for antiphospholipid antibodies has been identified as the ß-2-glycoprotein 1 (ß2GP1), the precise epitope recognized by antiphospholipid antibodies still remains largely unknown. In the study herein, we wanted to identify a sequence in domain I of ß2GP1 able to induce the proliferation of CD4+ T cells isolated from antiphospholipid antibody syndrome patients, but not from healthy donors, and to interact with antiphospholipid antibodies. We have characterized a sequence in domain I of ß2GP1 that triggers CD4+ T-cell proliferation. A comparison of this sequence with the previously reported binding of antiphospholipid antibodies to discontinuous epitope R39-R43 reveals the presence of an indeterminate motif in ß2GP1, in which the polarity determines the characteristics and specificity of antiphospholipid antibodies-interacting motifs. Using point mutations, we characterized the main antiphospholipid antibodies-interacting motif as ϕϕϕζζFxC, but also established ϕϕϕζζFxϕ-related motifs as potential antiphospholipid antibodies epitopes, in which ϕ represents nonpolar residues and ζ polar residues, with charges of the residues not being involved. Of specific importance, these different motifs are present at least once in all antiphospholipid antibodies-related receptors described so far. We have further demonstrated, in vitro, that peptides and domains of ß2GP1 containing these motifs were able to interact with antiphospholipid antibodies and inhibit their monocyte activating activity. These results established that the antiphospholipid antibodies-interacting motifs are determined by the polarity, but not by the sequence or charge, of amino acids. These data could also contribute to the future development of more sensitive and specific diagnostic tools for antiphospholipid antibody syndrome determination and potential peptide- or ß2GP1 domain-based clinical therapies.

Effect of ATRA and ATO on the expression of tissue factor in NB4 acute promyelocytic leukemia cells and regulatory function of the inflammatory cytokines TNF and IL-1ß.

The characteristic hemorrhages of acute promyelocytic leukemia (APL) are caused in part by the high expression of tissue factor (TF) on leukemic cells, which also produce TNF and IL-1ß, proinflammatory cytokines known to increase TF in various cell types. Exposure of NB4 cells, an APL cell line, to all-trans retinoic acid (ATRA) or arsenic trioxide (ATO) rapidly and strongly reduced TF mRNA. Both drugs also reduced TNF mRNA, but later, and moreover increased IL-1ß mRNA. The effect on procoagulant activity of cells and microparticles, as measured with calibrated automated thrombography, was delayed and only partial at 24 h. TNF and IL-1ß inhibition reduced TF mRNA and activity only partially. Inhibition of the inflammatory signaling intermediate p38 reduced TF mRNA by one third but increased TNF and IL-1ß mRNA. NF-κB inhibition reduced, within 1 h, TF and TNF mRNA but did not change IL-1ß mRNA, and rapidly and markedly reduced cell survival, with procoagulant properties still being present. In conclusion, although we provide evidence that TNF, IL-1ß, and their signaling intermediates have a regulatory function on TF expression by NB4 APL cells, the effect of ATRA and ATO on TF can only partially be accounted for by their impact on these cytokines.

Effect of Regulatory Element DNA Methylation on Tissue-Type Plasminogen Activator Gene Expression.

Expression of the tissue-type plasminogen activator gene (t-PA; gene name PLAT) is regulated, in part, by epigenetic mechanisms. We investigated the relationship between PLAT methylation and PLAT expression in five primary human cell types and six transformed cell lines. CpG methylation was analyzed in the proximal PLAT gene promoter and near the multihormone responsive enhancer (MHRE) -7.3 kilobase pairs upstream of the PLAT transcriptional start site (TSS, -7.3 kb). In Bowes melanoma cells, the PLAT promoter and the MHRE were fully unmethylated and t-PA secretion was extremely high. In other cell types the region from -647 to -366 was fully methylated, whereas an unmethylated stretch of DNA from -121 to +94 was required but not sufficient for detectable t-PA mRNA and t-PA secretion. DNA methylation near the MHRE was not correlated with t-PA secretion. Specific methylation of the PLAT promoter region -151 to +151, inserted into a firefly luciferase reporter gene, abolished reporter gene activity. The region -121 to + 94 contains two well-described regulatory elements, a PMA-responsive element (CRE) near -106 and a GC-rich region containing an Sp1 binding site near +59. Methylation of double-stranded DNA oligonucleotides containing the CRE or the GC-rich region had little or no effect on transcription factor binding. Methylated CpGs may attract co-repressor complexes that contain histone deacetylases (HDAC). However, reporter gene activity of methylated plasmids was not restored by the HDAC inhibitor trichostatin. In conclusion, efficient PLAT gene expression requires a short stretch of unmethylated CpG sites in the proximal promoter.

Epigenetic Regulation of Tissue-Type Plasminogen Activator in Human Brain Tissue and Brain-Derived Cells.

The serine protease tissue-type plasminogen activator (t-PA) is involved in both vital physiological brain processes, such as synaptic plasticity, and pathophysiological conditions, such as neurodegeneration and ischemic stroke. Recent data suggest that epigenetic mechanisms play an important role in the regulation of t-PA in human endothelial cells. However, there are limited data on epigenetic regulation of t-PA in human brain-derived cells. We demonstrate that treatment of cultured human neurons and human astrocytes with the histone deacetylase inhibitors trichostatin A (TSA) and MS-275 resulted in a two- to threefold increase in t-PA mRNA and protein expression levels. Next, we performed a chromatin immunoprecipitation assay on treated astrocytes with antibodies directed against acetylated histones H3 and H4 (both markers of gene activation). Treatment with MS-275 and TSA for 24 hours resulted in a significant increase in H3 acetylation, which could explain the observed increase in t-PA gene activity after the inhibition of histone deacety-lation. Furthermore, DNA methylation analysis of cultured human neurons and astrocytes, as well as human postmortem brain tissue, revealed a stretch of unmethylated CpG dinucleotides in the proximal t-PA promoter, whereas more upstream CpGs were highly methylated. Taken together, these results implicate involvement of epigenetic mechanisms in the regulation of t-PA expression in the human brain.

TLR2 ligands induce NF-κB activation from endosomal compartments of human monocytes.

Localization of Toll-like receptors (TLR) in subcellular organelles is a major strategy to regulate innate immune responses. While TLR4, a cell-surface receptor, signals from both the plasma membrane and endosomal compartments, less is known about the functional role of endosomal trafficking upon TLR2 signaling. Here we show that the bacterial TLR2 ligands Pam3CSK4 and LTA activate NF-κB-dependent signaling from endosomal compartments in human monocytes and in a NF-κB sensitive reporter cell line, despite the expression of TLR2 at the cell surface. Further analyses indicate that TLR2-induced NF-κB activation is controlled by a clathrin/dynamin-dependent endocytosis mechanism, in which CD14 serves as an important upstream regulator. These findings establish that internalization of cell-surface TLR2 into endosomal compartments is required for NF-κB activation. These observations further demonstrate the need of endocytosis in the activation and regulation of TLR2-dependent signaling pathways.

Receptors involved in cell activation by antiphospholipid antibodies.

The antiphospholipid syndrome (APS) is an autoimmune disease associated with arterial or venous thrombosis and/or recurrent fetal loss and is caused by pathogenic antiphospholipid antibodies (aPLA). The plasma protein ß2-glycoprotein 1 (ß2GP1) has been identified as a major target of aPLA associated with APS. Cell activation by aPLA appears to be a major pathogenic cause in the pathogenesis of APS. Receptors, co-receptors and accessory molecules are known to assist the pathogenic effects of aPLA. Members of the TLR family and the platelet receptor apolipoprotein E receptor 2' (apoER2'), a receptor belonging to the low-density lipoprotein receptor (LDL-R) family, as well as GPIbα, were identified as putative candidates for aPLA recognition. CD14, a co-receptor for TLR2 and TLR4, and annexin A2, a ubiquitous Ca2+ -binding protein that is essential for actin-dependent vesicle transport, could serve as important accessory molecules in mediating the pathogenic effects of aPLA. Finally, complement activation has been reported in association with the pathogenicity of APS. The relative contribution of these different mechanisms in the pathogenesis of APS is controversial. Here, we review the various in vivo and in vitro models that have been used to investigate the pathogenic mechanisms of aPLA in APS.

Characterization of human late outgrowth endothelial progenitor-derived cells under various flow conditions.

BACKGROUND: Endothelial progenitor-derived cells (EPC) are a cell therapy tool in peripheral arterial disease and for re-endothelialization of bypasses and stents. OBJECTIVE: To assess EPC behavior under flow conditions normally found in vivo. RESULTS: EPC were isolated from human cord blood, cultured on compliant tubes and exposed in an in vitro flow system mimicking hemodynamic environments normally found in medium and large arteries. EPC exposed for 24 h to unidirectional (0.3 ± 0.1 or 6 ± 3 dynes/cm(2)) shear stress oriented along flow direction, while those exposed to bidirectional shear stress (0.3 ± 3 dynes/cm(2)) or static conditions had random orientation. Under bidirectional flow, tissue factor (TF) activity and mRNA expression were significantly increased (2.5- and 7.0-fold) compared to static conditions. Under low shear unidirectional flow TF mRNA increased 4.9 ± 0.5-fold. Similar flow-induced increases were observed for TF in mature umbilical vein-derived endothelial cells. Expression of tissue-type plasminogen activator (t-PA), urokinase (u-PA) and monocyte chemotactic protein 1 (MCP1) were reduced by 40-60% in late outgrowth endothelial progenitor-derived cells (LO-EPC) exposed to any flow environment, while MCP1, but not t-PA or u-PA, was decreased in HUVEC. CONCLUSIONS: Flow, in particular bidirectional, modifies the hemostatic balance in LO-EPC with increased TF and decreased plasminogen activator expression.

Toll-like receptor 2 mediates the activation of human monocytes and endothelial cells by antiphospholipid antibodies.

The presence of antiphospholipid antibodies (aPLAs) is associated with arterial or venous thrombosis and/or recurrent fetal loss. The proposed pathogenic mechanisms for aPLA effects include the inflammatory activation of monocytes and endothelial cells. Toll-like receptors (TLRs) are candidate signaling intermediates. The aim of this study was to investigate the relative contribution of TLR2 and TLR4 in cell activation by aPLAs. Of 32 patient-derived aPLAs, 19 induced an inflammatory activation of human monocytes and umbilical vein endothelial cells (HUVECs). In HUVECs, inflammatory responses to these aPLAs were increased by TNF pretreatment, which increases the expression of TLR2 but not TLR4. Anti-TLR2 but not anti-TLR4 antibodies reduced the aPLA-induced activation of monocytes and HUVECs. aPLAs activated TLR2-expressing human embryonic kidney 293 (HEK293) cells but not TLR4-expressing cells. Binding studies demonstrated an interaction between aPLAs and TLR2 but not TLR4. A role for CD14, a coreceptor for TLR2 and TLR4, can be inferred by observations that anti-CD14 antibodies reduced responses to aPLAs in monocytes, and that responses in HEK293 cells expressing TLR2 and CD14 were greater than in HEK293 cells expressing TLR2 alone. Our results demonstrate a role for TLR2 and CD14 in human endothelial cell and monocyte activation by aPLAs.

Epigenetic control of tissue-type plasminogen activator synthesis in human endothelial cells.

AIMS: Tissue-type plasminogen activator (t-PA) is produced by endothelial cells (EC) and is responsible for the removal of intravascular fibrin deposits. We investigated whether expression of t-PA by EC is under epigenetic control. METHODS AND RESULTS: Methylation analysis of the proximal t-PA promoter revealed a stretch of unmethylated CpG dinucleotides from position -121 to +59, while upstream CpG dinucleotides were all methylated. In contrast, in human primary hepatocytes, which express t-PA at much lower levels than EC, the proximal promoter was partially methylated. Treatment of EC with the non-specific histone deacetylase (HDAC) inhibitors butyrate and trichostatin and with MS275, a specific inhibitor of class I HDAC, resulted in a time- and dose-dependent increase in t-PA expression. Garcinol and anacardic acid, inhibitors of the histone acetyl transferases CBP/p300 and PCAF, reduced basal and HDAC inhibitor-induced t-PA expression, whereas curcumin, an inhibitor of CBP/p300 only, had no effect. We performed chromosome immunoprecipitation analysis of the t-PA promoter using antibodies specific for acetylated histone H3 or H4 and observed an increase in H3 acetylation of 10 ± 3 and 44 ± 14-fold in EC treated with trichostatin or MS275, respectively, and in H4 acetylation of 7.7 ± 1.4 and 16 ± 3-fold, respectively. CONCLUSION: The proximal t-PA promoter is unmethylated in human EC and partially methylated in human primary hepatocytes. Expression of t-PA by EC is repressed by HDACs in a mechanism that involves de-acetylation of histone H3 and H4.

Regulation of the endothelial plasminogen activator system by fluvastatin. Role of Rho family proteins, actin polymerisation and p38 MAP kinase.

Statins are cholesterol-lowering drugs that exert pleiotropic effects which include changes in the plasminogen activation (PA) system of endothelial cells (EC). It was the objective of this study to investigate the signal transduction pathways by which statins increase the expression of tissue-type PA (t-PA) and decrease PA inhibitor type 1 (PAI-1) in human umbilical vein EC. Fluvastatin treatment increased t-PA expression more than 10-fold and reduced PAI-1 expression up to five-fold. This effect was mimicked by geranylgeranyl transferase inhibition. The role of geranylgeranylated small G-proteins of the Rho family was assessed by adenovirus-mediated expression of dominant negative (DN) RhoA, Cdc42 and Rac1 and by siRNA-mediated suppression of these proteins. DN-Cdc42 and DN-Rac1, as well as siRNA for Cdc42, increased t-PA expression, while DN-RhoA and DN-Rac1 decreased PAI-1 expression. Latrunculin B, an inhibitor of actin polymerisation, increased t-PA mRNA and reduced PAI-1 mRNA to the same extent as fluvastatin. Inhibition of p38, as well as p38α or p38ß siRNA, reversed the effects of fluvastatin on t-PA expression. Treatment with p38ß siRNA partially reversed the effect of fluvastatin on PAI-1, whereas p38α siRNA had no significant effect. Inhibition of jun kinase reduced basal and fluvastatin-induced t-PA expression to the same extent and increased PAI-1. MEK/ERK inhibition had no effect. In human EC, the fluvastatin-induced increase in t-PA is mediated by Cdc42 and, as with t-PA induced by inhibition of actin polymerisation, requires activation of p38MAP kinase. The mechanisms by which fluvastatin treatment reduces PAI-1 are different from those that increase t-PA.

CD146 short isoform increases the proangiogenic potential of endothelial progenitor cells in vitro and in vivo.

RATIONALE: CD146, a transmembrane immunoglobulin mainly expressed at the intercellular junction of endothelial cells, is involved in cell-cell cohesion, paracellular permeability, monocyte transmigration and angiogenesis. CD146 exists as 2 isoforms, short (sh) and long (lg), but which isoform is involved remains undefined. OBJECTIVE: The recently described role of CD146 in angiogenesis prompted us to investigate which isoform was involved in this process in human late endothelial progenitors (EPCs), with the objective of increasing their proangiogenic potential. METHODS AND RESULTS: Immunofluorescence experiments showed that, in subconfluent EPCs, shCD146 was localized in the nucleus and at the migrating edges of the membrane, whereas lgCD146 was intracellular. In confluent cells, shCD146 was redistributed at the apical membrane and lgCD146 was directed toward the junction. In contrast to lgCD146, shCD146 was overexpressed in EPCs as compared to mature endothelial cells and upregulated by vascular endothelial growth factor and SDF-1 (stromal cell-derived factor 1). Study of the properties of both isoforms in vitro provided evidence that shCD146 was involved in EPC adhesion to activated endothelium, migration, and proliferation, with a paracrine secretion of interleukin-8 or angiopoietin 2, whereas lgCD146 was implicated in stabilization of capillary-like structures in Matrigel and transendothelial permeability. In an animal model of hindlimb ischemia, transplantation of shCD146-modified EPCs selectively promoted both EPC engraftment and blood flow. CONCLUSIONS: Altogether, these findings establish that CD146 isoforms display distinct functions in vessels regeneration. Selective improvement of therapeutic angiogenesis by shCD146 overexpression suggests a potential interest of shCD146-transduced EPCs for the treatment of peripheral ischemic disease.

Generation of human inflammation-resistant endothelial progenitor cells by A20 gene transfer.

Inflammatory activation of the vascular endothelium is a major contributory factor to ischemic cardiovascular disease. Endothelial progenitor cells (EPCs) are being investigated for the treatment of ischemic disease or to coat vein grafts for bypass surgery. As an inflammatory environment might reduce their therapeutic efficacy, we sought to generate EPCs that are less sensitive to inflammatory activation. EPCs were obtained from human umbilical cord blood and transduced with a lentiviral vector for stable expression of A20, an anti-inflammatory protein. Nontransduced and green-fluorescent-protein-transduced cells were used as controls. Expression of A20 by EPCs did not modify cell morphology or expression of a panel of 20 proteins known to contribute to angiogenesis. Also, A20 had no effect on the capacity of EPCs to form tube-like structures in Matrigel. A20 expression reduced EPC activation by tumor necrosis factor-alpha and interleukin-1beta as determined from changes in vascular cell adhesion molecule 1 and E-selectin expression and decreased monocyte transmigration through a monolayer of EPCs. In conclusion, EPCs can be genetically modified to overexpress A20 in a stable fashion. These cells become less sensitive to inflammatory stimuli. This may be of interest in cell-based therapeutic approaches for clinical settings where inflammation is an important pathogenic factor.

Induction of TLR2 expression by inflammatory stimuli is required for endothelial cell responses to lipopeptides.

Human endothelial cells (EC) express Toll-like receptor 4 (TLR4), a receptor for lipopolysaccharides (LPS), but little or no TLR2, a lipopeptide receptor. The aim of this study was to investigate to what extent inflammatory stimuli modify the expression by EC of TLR4 and TLR2, of the TLR2 co-receptors TLR1 and TLR6 and of the TLR2-accessory proteins CD14 and CD36. Stimulation of umbilical vein derived EC with TNF-alpha, LPS or IL-1beta for 24h induced a strong increase in TLR2 mRNA but not in TLR1, TLR4 and TLR6 mRNA. Inflammatory activation had little effect on CD14 mRNA, but decreased the expression of CD36 mRNA. TLR2 antigen was readily detected by flow cytometry on activated EC, but not on resting EC. A significant proportion of TLR2 was found to be located intracellularly. By using specific signalling pathway inhibitors we established that the induction of TLR2 by inflammatory stimuli was dependent on NF-kappaB, p38-MAP kinase and c-Jun kinase. IRAK-1 phosphorylation after treatment with 10mug/ml of lipoteichoic acid (LTA), a TLR2 agonist, was only observed in TNF-alpha-stimulated EC and not in resting EC. Furthermore, LTA potentiated the increase of the inflammatory markers E-Selectin or IL-8 in EC pre-treated with TNF-alpha, LPS or IL-1beta, but not in resting EC. These results imply that the up-regulated TLR2 is functionally active. Interestingly, LTA had no effect on TLR2 expression, nor maintained TLR2 expression, in activated EC. This suggests that lipopeptide responses of EC are dependent on the continued presence of inflammatory cytokines, provided by other cell types, or LPS. In conclusion, inflammatory stimuli induce a high TLR2 expression in EC, which in turn enables the cells to strongly respond to lipopeptides. The up-regulation of TLR2 may be of relevance for the vascular effects of Gram-positive bacteria.

Regulation of plasminogen activator inhibitor type 1 gene expression by inflammatory mediators and statins.

Elevated plasma concentrations of plasminogen activator inhibitor type 1 (PAI-1), also named serpin E1, are encountered in patients with thrombophilia, atherosclerosis, septicemia and the metabolic syndrome and may be associated with an increased risk of complications. Expression of PAI-1 is increased by inflammatory stimuli and decreased by statins, drugs widely used in patients with cardiovascular disease. Increased expression of PAI-1 by inflammatory stimuli is mediated by a large variety of signal transduction pathways, which include the NF-kappaB and MAP kinase pathways. The downregulating effect of statins on PAI-1 expression is dependent on the inhibition of Rho family proteins and may involve an activation of PI-3 kinase/Akt signaling pathways. In this review we summarize the findings on the effect of inflammation and statins on PAI-1 expression.

Gene conversion limits divergence of mammalian TLR1 and TLR6.

BACKGROUND: Toll-like receptors (TLR) recognize pathogen-associated molecular patterns and are important mediators of the innate immune system. TLR1 and TLR6 are paralogs and located in tandem on the same chromosome in mammals. They form heterodimers with TLR2 and bind lipopeptide components of gram-positive and gram-negative bacterial cell walls. To identify conserved stretches in TLR1 and TLR6, that may be important for their function, we compared their protein sequences in nine mammalian species(Homo sapiens, Pan troglodytes, Macaca mulatta, Mus musculus, Rattus norvegicus; Erinaceus europaeus, Bos Taurus, Sus scrofa and Canis familiaris). RESULTS: The N-terminal sequences of the orthologous proteins showed greater similarity than corresponding paralog sequences. However, we identified a region of 300 amino acids towards the C-terminus of TLR1 and TLR6, where paralogs had a greater degree of sequence identity than orthologs. Preservation of DNA sequence identity of paralogs in this region was observed in all nine mammalian species investigated, and is due to independent gene conversion events. The regions having undergone gene conversion in each species are almost identical and encode the leucine-rich repeat motifs 16 to 19, the C-terminal cap motif, the transmembrane domain and most of the intracellular Toll/interleukin-1 receptor (TIR) domain. CONCLUSION: Our results show that, for a specific conserved region, divergence of TLR1 and TLR6 is limited by gene conversion, most likely because of the need for co-evolution with multiple intracellular and extracellular binding partners. Thus, gene conversion provides a mechanism for limiting the divergence of functional regions of protein paralogs, while allowing other domains to evolve diversified functions.

Fluvastatin inhibits regulated secretion of endothelial cell von Willebrand factor in response to diverse secretagogues.

Regulated secretion of EC (endothelial cell) vWF (von Willebrand factor) is part of the haemostatic response. It occurs in response to secretagogues that raise intracellular calcium or cAMP. Statins are cholesterol-lowering drugs used for the treatment of cardiovascular disease. We studied the effect of fluvastatin on regulated secretion of vWF from HUVEC (human umbilical-vein ECs). Secretion in response to thrombin, a protease-activated receptor-1 agonist peptide, histamine, forskolin and adrenaline (epinephrine) was inhibited. This inhibition was reversed by mevalonate or geranylgeranyl pyrophosphate, and mimicked by a geranylgeranyl transferase inhibitor, demonstrating that the inhibitory mechanism includes inhibition of protein geranylgeranylation. To investigate this mechanism further, calcium handling and NO (nitric oxide) regulation were studied in fluvastatin-treated HUVEC. Intracellular calcium mobilization did not correlate with vWF secretion. Fluvastatin increased eNOS [endothelial NOS (NO synthase)] expression, but NOS inhibitors failed to reverse the effect of fluvastatin on vWF secretion. Exogenous NO did not inhibit thrombin-induced vWF secretion. Many small GTPases are geranylgeranylated and some are activated by secretagogues. We overexpressed DN (dominant negative) Rho GTPases, RhoA, Rac1 and Cdc42 (cell division cycle 42), in HUVEC. DNCdc42 conferred inhibition of thrombin- and forskolin-induced vWF secretion. We conclude that, via inhibition of protein geranylgeranylation, fluvastatin is a broadspectrum inhibitor of regulated vWF secretion. Geranylgeranylated small GTPases with functional roles in regulated secretion, such as Cdc42, are potential targets for the inhibitory activity of fluvastatin.

Immunization of LDL receptor-deficient mice with beta2-glycoprotein 1 or human serum albumin induces a more inflammatory phenotype in atherosclerotic plaques.

Antiphospholipid antibodies are a risk factor for venous and arterial thrombosis and may contribute to the development of atherosclerosis.The aim of this study was to investigate whether antibodies to human beta2-glycoprotein 1 (beta2GP1), as a model of antiphospholipid antibodies, modify the phenotype of atherosclerotic lesions. LDL receptor-deficient mice were immunized with human beta2GP1, human serum albumin (HSA), or not immunized, and fed a high-cholesterol diet for 14 weeks. Some mice also received pravastatin. Immunization with human beta2GP1 or HSA resulted in formation of autoantibodies recognizing murine beta2GP1 or murine albumin, respectively. We quantified atherosclerotic lesion development and mRNA levels of inflammation associated proteins in the thoraco-abdominal aorta as well as lesion development,cellular composition and collagen content in the aortic roots. Immunization with beta2GP1 or HSA had no effect on lesion size,but modified the expression in plaque areas of several inflammation-associated proteins. Expression of matrix metalloproteinase-9, tissue factor, interferon-gamma and CD25 was highest in the thoraco-abdominal aorta of beta2GP1-immunized mice, lowest in non-immunized mice and intermediate in HSA-immunized animals. Immunization with beta2GP1, but not HSA, resulted in a lower smooth muscle cell and collagen content of lesions in aortic roots. Statin treatment partially reversed the effects of beta2GP1 immunization. We conclude that immunization with beta2GP1, and to a lesser extent with HSA, leads to modifications in the cellular and protein composition of atherosclerotic plaques, which are associated with a more inflammatory phenotype. Statin treatment partially prevents these changes.

The role of TLR2 in the inflammatory activation of mouse fibroblasts by human antiphospholipid antibodies.

Antiphospholipid antibodies (APLAs) promote inflammatory and procoagulant responses in endothelial cells and monocytes. Previous studies have shown that MyD88, TRAF6, and NF-kappaB mediate cell activation by APLAs. These intermediates are also used by toll-like receptors (TLRs). We investigated the role of TLRs in the cellular response to APLAs. IgGs were isolated from the plasma of 5 patients with antiphospholipid syndrome along with immunopurified anti-beta2-glycoprotein 1 IgG from a sixth patient. Control IgG was obtained from a pool of healthy donor plasmas negative for APLAs. Wild-type mouse embryonic fibroblasts (EFs) and EFs deficient in TLR1, TLR2, TLR4, or TLR6 were incubated with APLAs, anti-beta2-glycoprotein 1 IgG, or control IgG. On incubation with the patient IgG, but not control IgG, a significant increase in mRNA levels of the inflammatory marker proteins MCP-1, ICAM-1, and IL-6 as well as IL-6 secretion was observed in wild-type EFs, whereas TLR2-deficient EFs did not respond. Responses in TLR1- and TLR6-deficient EFs were decreased and those in TLR4-deficient EFs comparable to those in wild-type EFs. Overexpression of human TLR2 in the TLR2-deficient EFs restituted the response to patient IgG. Our results imply that TLR2 plays a role in mouse fibroblast activation by APLAs.

Promoter dependence of transgene expression by lentivirus-transduced human blood-derived endothelial progenitor cells.

Peripheral blood- derived endothelial progenitor cells (EPCs) have considerable potential for the autologous therapy of vascular lesions or ischemic tissues. By introducing stable genetic modifications into these cells, this potential might be further enhanced. We investigated to what extent transgene expression can be controlled by using different transgene promoters. This was investigated in early- or late-outgrowth human EPCs obtained by culturing blood mononuclear cells for 1 or 4 weeks on type 1 collagen in medium containing endothelial growth supplements. A large fraction of these cells were stably transduced using lentiviral vectors for expression of the enhanced green fluorescent protein (EGFP). Transgene expression in vitro or in vivo after injection into nude mice was highest when under the control of the cytomegalovirus (CMV) promoter, intermediate with the EF1alpha promoter, and lowest with the phosphoglycerate kinase promoter. When blood mononuclear cells were cultured for 1 week in the absence of endothelial growth supplements, CMV promoter- driven expression of EGFP was two orders of magnitude lower than in similarly transduced EPCs. Our results show that lentiviral vectors are useful tools for the stable introduction of exogenous genes into EPCs and for their expression at desired levels using the appropriate gene promoter.

Evidence for serpinB2-independent protection from TNF-alpha-induced apoptosis.

Clade B serine proteinase inhibitors (serpins) are intracellular proteins, whereas most of their identified targets are extracellular. A proposed intracellular role for these inhibitors is protection from apoptosis. We investigated the contribution of serpinB2 (plasminogen activator inhibitor-2, PAI-2) activity in TNF-alpha-induced apoptosis. PAI-2 is expressed in many normal and transformed cell types, particularly after stimulation with inflammatory cytokines. PAI-2 has been linked to protection from TNF-alpha-induced apoptosis, and a stabilizing interaction with the retinoblastoma protein (Rb1) has been proposed. We examined the activity of PAI-2 in TNF-alpha-induced apoptosis using HeLa, Isreco-1 and HT1080 cell lines. Stimulation with TNF-alpha protected each cell type from apoptosis induced by TNF-alpha and cycloheximide. Protection correlated with an increase in PAI-2 expression in IS-1 and HT1080 cells but not in HeLa cells where PAI-2 mRNA and protein were undetectable. PAI-2 was overexpressed in each cell type but gave no protection from TNF-alpha-induced apoptosis measured by cell viability, annexinV binding and caspase-3/7 activity. We detected wild-type Rb1, unchanged TNF receptor levels and induction of other apoptosis-protective factors in all cell types. In conclusion, elevated PAI-2 levels do not protect cells from TNF-alpha-induced apoptosis, and the protective effect of prior stimulation with TNF-alpha does not require PAI-2.