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Macrophages as inflammatory cells are involved in the pathogenesis of atherosclerosis that today is recognized as an inflammatory disease. Activation of coagulation leads to the late complication of atherosclerosis, namely atherothrombosis with its clinical manifestations stroke, unstable angina, myocardial infarction, and sudden cardiac death. Thus inflammation and coagulation play fundamental roles in the pathogenesis of atherosclerosis. We show that the coagulation enzyme thrombin up-regulates oncostatin M (OSM), a pleiotropic cytokine implicated in the pathophysiology of vascular disease, in human monocyte-derived macrophages (MDMs) up to 16.8-fold. A similar effect was seen in human peripheral blood monocytes and human plaque macrophages. In MDMs, the effect of thrombin on OSM was abolished by PPACK and mimicked by a PAR-1-specific peptide. Thrombin induced phosphorylation of ERK1/2 and p38 in MDMs. The ERK1/2 inhibitor PD98059 blocked the effect of thrombin on OSM production in MDMs, whereas the p38 inhibitor SB202190 had no effect. Thrombin induced translocation of c-fos and c-jun to the nucleus of MDMs. Using OSM promoter-luciferase reporter constructs transfected into MDMs, we show that a functional AP-1 site is required for promoter activation by thrombin. We present another link between coagulation and inflammation, which could impact on the pathogenesis of atherosclerosis.

Activation of inflammatory and procoagulant mechanisms is thought to contribute significantly to the initiation of restenosis, a common complication after balloon angioplasty of obstructed arteries. During this process, expression of tissue factor (TF) represents one of the major physiologic triggers of coagulation that results in thrombus formation and the generation of additional signals leading to vascular smooth muscle cell (VSMC) proliferation and migration. In this study, we have investigated the mechanisms by which inhibition of coagulation at an early stage through overexpression of tissue factor pathway inhibitor (TFPI), an endogenous inhibitor of TF, might reduce restenosis. In a rabbit femoral artery model, percutaneous delivery of TFPI using a recombinant adenoviral vector resulted in a significant reduction of the intimamedia ratio 21 days after injury. Investigating several markers of inflammation and coagulation, we found reduced neointimal expression of monocyte chemoattractant protein-1 (MCP-1), lesional monocyte infiltration, and expression of vascular TF, matrix metalloproteinase-2 (MMP-2), and MMP-9. Moreover, overexpression of TFPI suppressed the autocrine release of platelet-derived growth factor BB (PDGF-BB), MCP-1, and MMP-2 in response to factors VIIa and Xa from VSMCs in vitro and inhibited monocyte TF activity. These results suggest that TFPI exerts its action in vivo through not only thrombotic, but also nonthrombotic mechanisms.

Granulocyte-macrophage colony-stimulating factor (GMCSF) has a central role in proliferation and differentiation of hematopoetic cells. Furthermore, it influences the proliferation and migration of endothelial cells. GMCSF elicits these functions by activating a receptor consisting of a ligand-specific alpha-chain and a beta-chain, which is common for GMCSF, interleukin-3 (IL-3), and IL-5. It is known that various signaling molecules such as Janus kinase 2 or transcription factors of the signal transducer and activator of transcription (STAT) family bind to the common beta-chain and initiate signaling cascades. However, alpha-chain-specific signal transduction adapters have to be postulated given that IL-3, IL-5, and GMCSF induce partly distinct biologic responses. Using a yeast 2-hybrid system, we identified the alpha-chain of the GMCSF receptor (GMRalpha) as putative interaction partner of IkappaB kinase beta, one of the central signaling kinases activating the transcription factor nuclear factor-kappaB (NF-kappaB). Using endogenous protein levels of endothelial cell extracts, we could verify the interaction by coimmunoprecipitation experiments. Fluorescence resonance energy transfer (FRET) microscopy confirmed the direct interaction of CFP-IKKbeta and YFPGMRalpha in living cells. Functional studies demonstrated GMCSF-dependent activation of IkappaB kinase activity in endothelial cells, degradation of IkappaB, and activation of NF-kappaB. Further biologic studies using GMCSF-dependent TF-1 cells indicated that GMCSF-triggered activation of NF-kappaB is important for cell survival and proliferation.

Plasminogen activator inhibitor 1 (PAI-1) is the main fibrinolysis inhibitor, and high plasma levels are associated with an increased risk for vascular diseases. Inflammatory cytokines regulate PAI-1 through a hitherto unclear mechanism. Using reporter gene analysis, we could identify a region in the PAI-1 promoter that contributes to basal expression as well as to tumor necrosis factor alpha (TNFalpha) induction of PAI-1 in endothelial cells. Using this region as bait in a genetic screen, we could identify Nur77 (NAK-1, TR3, NR4A1) as an inducible DNA-binding protein that binds specifically to the PAI-1 promoter. Nur77 drives transcription of PAI-1 through direct binding to an NGFI-B responsive element (NBRE), indicating monomeric binding and a ligand-independent mechanism. Nur77, itself, is transcriptionally up-regulated by TNFalpha. High expression levels of Nur77 and its colocalization with PAI-1 in atherosclerotic tissues indicate that the described mechanism for PAI-1 regulation may also be operative in vivo.

In a variety of cell types, the transcription factor nuclear factor kappaB (NF-kappaB) functions as a mediator of stress and immune responses. In endothelial cells (ECs), it controls the expression of genes encoding, eg, cytokines, cell adhesion molecules, and procoagulatory proteins. This study investigates the effect of NF-kappaB suppression on several pathophysiologic functions of ECs, including inflammation, coagulation, and angiogenesis. A recombinant adenovirus was generated for expression of a dominant negative (dn) mutant of IkappaB kinase 2 (IKK2), a kinase that acts as an upstream activator of NF-kappaB. dnIKK2 inhibited NF-kappaB, resulting in strongly reduced nuclear translocation and DNA binding activity of the transcription factor and lack of expression of several proinflammatory markers, including E-selectin, intercellular adhesion molecule 1, vascular cell adhesion molecule 1, and interleukin-8. Concomitantly, inhibition of leukocyte binding to dnIKK2-expressing ECs could be demonstrated in a cell adhesion assay. Furthermore, expression of tissue factor as well as the ability to form capillary tubes in a matrigel assay was impaired in dnIKK2-expressing ECs. These data demonstrate that NF-kappaB is of central importance not only for the inflammatory response but also for a number of other EC functions. Therefore, this transcription factor as well as its upstream regulatory signaling molecules may represent favorable targets for therapeutic interference.

Mobilization of nuclear factor-kappaB (NF-kappaB) activates transcription of genes encoding endothelial adhesion molecules and chemokines that contribute to monocyte infiltration critical in atherogenesis. Inhibition of NF-kappaB has been achieved by pharmacological and genetic approaches; however, monocyte interactions with activated endothelium in shear flow following gene transfer of the NF-kappaB inhibitor IkappaB-alpha have not been studied. We found that overexpression of IkappaB-alpha in endothelial cells using a recombinant adenovirus prevented tumor necrosis factor-alpha (TNF-alpha)-induced degradation of IkappaB-alpha and suppressed the upregulation of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and E-selectin mRNA and surface protein expression and the upregulation of transcripts for the chemokines monocyte chemoattractant protein 1 (MCP-1) and growth-related activity-alpha (GRO-alpha) by TNF-alpha. This was associated with a reduction in endothelial MCP-1 secretion and GRO-alpha immobilization. Adhesion assays under physiological shear flow conditions showed that firm arrest, spreading, and transmigration of monocytes on TNF-alpha-activated endothelium was markedly inhibited by IkappaB-alpha overexpression. Inhibition with monoclonal antibodies and peptide antagonists inferred that this was due to reduced expression of Ig integrin ligand as well as of chemokines specifically involved in these events. In contrast, rolling of monocytes was increased by IkappaB-alpha transfer and was partly mediated by P-selectin; however, it appeared to be unaffected by the inhibition of E-selectin induction. Thus, our data provide novel evidence that selective modulation of NF-kappaB by adenoviral transfer of IkappaB-alpha impairs the expression of multiple endothelial gene products required for subsequent monocyte arrest and emigration in shear flow and thus for monocyte infiltration in atherosclerotic plaques.