Inhibition of CD40 signaling limits evolution of established atherosclerosis in mice

Characterization of the proteins released from activated platelets leads to localization of novel platelet proteins in human atherosclerotic lesions

Proteins secreted by activated platelets can adhere to the vessel wall and promote the development of atherosclerosis and thrombosis. Despite this biologic significance, however, the complement of proteins comprising the platelet releasate is largely unknown. Using a proteomics approach, we have identified more than 300 proteins released by human platelets following thrombin activation. Many of the proteins identified were not previously attributed to platelets, including secretogranin III, a potential monocyte chemoattractant precursor; cyclophilin A, a vascular smooth muscle cell growth factor; calumenin, an inhibitor of the vitamin K epoxide reductase-warfarin interaction, as well as proteins of unknown function that map to expressed sequence tags. Secretogranin III, cyclophilin A, and calumenin were confirmed to localize in platelets and to be released upon activation. Furthermore, while absent in normal vasculature, they were identified in human atherosclerotic lesions. Therefore, these and other proteins released from platelets may contribute to atherosclerosis and to the thrombosis that complicates the disease. Moreover, as soluble extracellular proteins, they may prove suitable as novel therapeutic targets.

Near-infrared Raman spectroscopy of human coronary arteries: histopathological classification based on Mahalanobis distance

OBJECTIVE

In this study, near-infrared Raman spectroscopy (NIRS) was used for evaluation of human atherosclerotic lesions using a simple algorithm based on discriminant analysis. The Mahalanobis distance was used to classify the clustered spectral features extracted from NIRS of a total of 111 arterial fragments of human coronary arteries.

BACKGROUND DATA

Raman spectroscopy has been used for diagnosis of a variety of diseases. For real-time applications, it is important to have a simple algorithm that could perform fast data acquisition and analysis. The ultimate goal is to obtain a feasible diagnosis, which discriminates various atherosclerotic lesions with high sensitivities and specificities.

MATERIALS AND METHODS

Non-atherosclerotic (NA) arteries, atherosclerotic plaques without calcification (NC), and atherosclerotic plaques with classification (C) were obtained and scanned with an NIR Raman spectrometer with 830-nm laser excitation. An algorithm based on the discriminant analysis using the Mahalanobis distance of the clustered spectral features was used for tissue classification into three categories: Na, NC, and C.

RESULTS

Human coronary arteries exhibit different spectral signatures depending on different bio-chemicals present in each tissue type such as collagen, cholesterol, and calcium hydroxyapatite, respectively. It is shown that our algorithm has a maximum sensitivity and specificity of 85% and 89%, respectively, for the diagnosis of the NA tissue type, 85% and 89% for the NC tissue type, and 100% and 100% for the C tissue type.

CONCLUSION

An algorithm (with a minimum of mathematical and computational requirements) based on the discriminant analysis of spectral features has been developed to classify atherosclerotic lesions with high sensitivities and specificities.

Inflammatory biomarkers of the patient with myocardial insufficiency

PURPOSE OF REVIEW

Inflammation plays a central role in the genesis of atherosclerosis and its complications. In this regard, plasma levels of several markers of inflammation have been shown to predict risk of future cardiovascular events, including cardiovascular death, myocardial infarction, and ischemic stroke. Furthermore, the predictive value of inflammatory markers is independent of traditional risk markers such as lipid levels, or cardiac troponin levels among those with acute coronary syndromes.

RECENT FINDINGS

Indeed, recent data suggest that among more than 27,000 apparently healthy women, the predictive value of C-reactive protein, the most extensively studied marker of vascular inflammation, was at least as good as that of low-density lipoprotein cholesterol. In addition, hypothesis-generating data suggest that the benefits of proven interventions such as statin therapy and glycoprotein IIb/IIIa receptor blockade may be most effective among those with elevated markers of inflammation.

SUMMARY

Combining our evolving understanding of the vascular biology of atherosclerosis with clinical studies of inflammatory markers and mediators may help refine our diagnostic and therapeutic armamentarium for cardiovascular disease.

A20 protects from CD40-CD40 ligand-mediated endothelial cell activation and apoptosis

BACKGROUND

CD40/CD40 ligand (CD40L) signaling is a potent activator of endothelial cells (ECs) and promoter of atherosclerosis. In this study, we investigate whether A20 (a gene we have shown to be antiinflammatory and antiapoptotic in ECs) can protect from CD40/CD40L-mediated EC activation.

METHODS AND RESULTS

Overexpression of CD40, in a transient transfection system, activates the transcription factor NF-kappaB and upregulates IkappaBalpha, E-selectin, and tissue factor (TF) reporter activity. Coexpression of A20 inhibits NF-kappaB and upregulation of IkappaBalpha and E-Selectin but not TF, suggesting that CD40 induces TF in a non-NF-kappaB-dependent manner. In human coronary artery ECs (HCAECs), adenovirus-mediated overexpression of A20 blocks physiological, CD40-induced activation of NF-kappaB, upstream of IkappaBalpha degradation (Western blot) and subsequently upregulation of ICAM-1, VCAM-1, and E-selectin (flow cytometry). Although A20 does not block TF transcription its expression in HCAECs inhibits TF induction (colorimetric assay and RT-PCR) by blunting CD40 upregulation. We demonstrate that CD40 signaling induces apoptosis in a proinflammatory microenvironment. A20 overexpression protects from CD40-mediated EC apoptosis (DNA content analysis and trypan blue exclusion). We also demonstrate that signaling through CD40L activates NF-kappaB and induces apoptosis in ECs, both of which are inhibited by A20 overexpression.

CONCLUSIONS

A20 works at multiple levels to protect ECs from CD40/CD40L mediated activation and apoptosis. A20-based therapy could be beneficial for the treatment of vascular diseases such as atherosclerosis and transplant-associated vasculopathy.

The potential role of peroxisome proliferator-activated receptors on inflammation in type 2 diabetes mellitus and atherosclerosis

Increasing attention has focused on the role of inflammation in various chronic diseases, including atherosclerosis. Recent compelling data have begun to unite work from various arenas, such as epidemiology and vascular biology, and even clinical trials to provide evidence for inflammation as a mechanism underlying cardiovascular disease. Inflammation has been implicated in the pathogenesis, progression, and complications of both atherosclerosis and diabetes mellitus-2 complex disorders often found intertwined in patients. Although this story continues to evolve, peroxisome proliferator-activated receptors (PPARs) have been implicated as a molecular pathway involved in both these disease processes. In vitro data, animal work, and some human studies suggest that synthetic PPAR agonists in clinical use, such as thiazolidinediones, may not only regulate metabolic processes but may also limit inflammatory responses, including some involved in atherosclerosis.

Proangiogenic function of CD40 ligand-CD40 interactions

Angiogenesis is a characteristic component of cell-mediated immune inflammation. However, little is known of the immunologic mediators of angiogenesis factor production. Interactions between CD40 ligand (CD40L) and CD40 have been shown to have pluripotent functions in inflammation, including the production of cytokines, chemokines, as well as the angiogenesis factor, vascular endothelial growth factor (VEGF), by endothelial cells. In this study we found that treatment of cultured human endothelial cells with an anti-CD40 Ab (to ligate CD40) resulted in the expression of several other angiogenesis factors, including fibroblast growth factor-2 and the receptors Flt-1 and Flt-4. To determine the proangiogenic effect of CD40L in vivo, human skin was allowed to engraft on SCID mice for 6 wk. These healed human skins express CD40 on resident endothelial cells and monocyte/macrophages, but not on CD20-expressing B cells. Skins were injected with saline, untransfected murine fibroblasts, or murine fibroblasts stably transfected with human CD40L. We found that the injection of CD40L-expressing cells, but not control cells, resulted in the in vivo expression of several angiogenesis factors (including VEGF and fibroblast growth factor) and a marked angiogenesis reaction. Mice treated with anti-VEGF failed to elicit an angiogenesis reaction in response to injection of CD40L-expressing cells, suggesting that the proangiogenic effect of CD40L in vivo is VEGF dependent. These observations imply that ligation of CD40 at a peripheral inflammatory site is of pathophysiological importance as a mediator of both angiogenesis and inflammation.

Elevated plasma levels of the atherogenic mediator soluble CD40 ligand in diabetic patients: a novel target of thiazolidinediones

BACKGROUND

Considerable evidence implicates the proinflammatory cytokine CD40 ligand (CD40L) in atherosclerosis and accumulating data link type 1 and 2 diabetes, conditions associated with accelerated atherosclerosis, to inflammation. This study therefore evaluated the hypothesis that diabetic patients have elevated plasma levels of soluble CD40L (sCD40L) and that treatment with the insulin-sensitizing thiazolidinediones lowers this index of inflammation.

METHODS AND RESULTS

Subjects with type 1 (n=49) or type 2 diabetes (n=48) had higher (P<0.001) sCD40L plasma levels (6.56+/-3.27 and 6.67+/-2.90 ng/mL, respectively) compared with age-matched control groups (1.40+/-2.21 and 1.32+/-2.68 ng/mL, respectively). Multiple regression analysis demonstrated a significant (P<0.001) association between plasma sCD40L and type 1 as well as type 2 diabetes, independent of total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, blood pressure, body mass index, gender, C-reactive protein, and soluble intracellular adhesion molecule-1. Furthermore, in a pilot study, administration of troglitazone (12 weeks, 600 mg/day), but not placebo, to type 2 diabetics (n=68) significantly (P<0.001) diminished sCD40L plasma levels by 29%. The thiazolidinedione lowered plasma sCD40L in type 2 diabetic patients with long-standing disease (>3 years) with or without macrovascular complications (-34% and -29%, respectively) as well as in type 2 diabetic patients with more recent (<3 years) onset of the disease (-27%; all P<0.05).

CONCLUSIONS

This study provides new evidence that individuals with type 1 or 2 diabetes have a proinflammatory state as indicated by elevated levels of plasma sCD40L. Troglitazone treatment of type 2 diabetic patients diminishes sCD40L levels, suggesting a novel antiinflammatory mechanism for limiting diabetes-associated arterial disease.

Beta3 integrin deficiency promotes atherosclerosis and pulmonary inflammation in high-fat-fed, hyperlipidemic mice

Hyperlipidemia promotes the chronic inflammatory disease atherosclerosis through poorly understood mechanisms. Atherogenic lipoproteins activate platelets, but it is unknown whether platelets contribute to early inflammatory atherosclerotic lesions. To address the role of platelet aggregation in diet-induced vascular disease, we studied beta3 integrin-deficient mice (lacking platelet integrin alphaIIbbeta3 and the widely expressed nonplatelet integrin alphavbeta3) in two models of atherosclerosis, apolipoprotein E (apoE)-null and low-density lipoprotein receptor (LDLR)-null mice. Unexpectedly, a high-fat, Western-type (but not a low-fat) diet caused death in two-thirds of the beta3-/-apoE-/- and half of the beta3-/-LDLR-/- mice due to noninfectious pneumonitis. In animals from both models surviving high-fat feeding, pneumonitis was absent, but aortic atherosclerosis was 2- to 6-fold greater in beta3-/- compared with beta+/+ littermates. Expression of CD36, CD40L, and CD40 was increased in lungs of beta3-/-LDLR-/- mice. Each was also increased in smooth muscle cells cultured from beta3-deficient mice and suppressed by retroviral reconstitution of beta3. These data show that the platelet defect caused by alphaIIbbeta3 deficiency does not impair atherosclerotic lesion initiation. They also suggest that alphavbeta3 has a suppressive effect on inflammation, the loss of which induces atherogenic mediators that are amplified by diet-induced hyperlipidemia.

CD40-dependent activation of phosphatidylinositol 3-kinase/Akt pathway mediates endothelial cell survival and in vitro angiogenesis

CD40 has been involved in tumor and inflammatory neoangiogenesis. In this study we determined that stimulation of endothelial CD40 with sCD154 induced resistance to apoptosis and in vitro vessel-like formation by human microvascular endothelial cells (HMEC). These effects were determined to be mediated by CD40-dependent signaling because they were inhibited by a soluble CD40-muIg fusion protein. Moreover, apoptosis of HMEC was associated with an impairment of Akt phosphorylation, which was restored by stimulation with sCD154. The anti-apoptotic effect as well as in vitro vessel-like formation and Akt phosphorylation were inhibited by treatment of HMEC with two unrelated pharmacological inhibitors of phosphatidylinositol 3-kinase (PI3K), wortmannin and LY294002. CD40 stimulation induced a rapid increase in Akt enzymatic activity that was not prevented by cycloheximide, an inhibitor of protein synthesis. The enhanced Akt activity induced by stimulation of endothelial CD40 was temporarily correlated with the association of CD40 with TRAF6, c-Cbl, and the p85 subunit of PI3K. Expression of negative-dominant Akt inhibited the activation of endogenous Akt through CD40 stimulation, despite the observation that association of CD40 with TRAF6, c-Cbl, and PI3K was intact. The defective activation of Akt abrogated not only the anti-apoptotic effect of CD40 stimulation but also the proliferative response, the enhanced motility, and the in vitro formation of vessel-like tubular structures by CD40-stimulated HMEC. In conclusion, these results suggest that endothelial CD40, through activation of the PI3K/Akt signaling pathway, regulates cell survival, proliferation, migration, and vessel-like structure formation, all steps considered critical for angiogenesis.

Inhibitory effects of glycoprotein IIb/IIIa antagonists and aspirin on the release of soluble CD40 ligand during platelet stimulation

BACKGROUND

Glycoprotein (GP) IIb/IIIa antagonists inhibit platelet aggregation, an activity attributed to the clinical benefits of these drugs in settings that involve acute coronary thrombosis. However, platelet activation and subsequent aggregation are now known to cause the release of a soluble form of CD40 ligand (sCD40L), a prothrombotic and proinflammatory protein with GP IIb/IIIa binding activity and an established role in atherosclerotic lesion progression. The present study was designed to determine what effect GP IIb/IIIa antagonists have on the release of sCD40L.

METHODS AND RESULTS

Doses of eptifibatide, abciximab, and tirofiban that inhibited platelet aggregation by at least 80% also inhibited sCD40L release in vitro (by 85%, 57%, and 80%, respectively). When platelets were stimulated with a thrombin receptor agonist, inhibition by GP IIb/IIIa antagonists occurred without affecting the release of betaTG, an alpha-granule protein. Unexpectedly, concentrations of the 3 antagonists that blocked aggregation by only 20% to 50% potentiated the release of sCD40L (by 19% to 26%). Platelets from aspirin-treated individuals were partially protected from sCD40L release, but only when the agonist was collagen, an affect augmented by the addition of GP IIb/IIIa antagonists.

CONCLUSIONS

These studies suggest that the mechanisms responsible for the clinical benefits of GP IIb/IIIa antagonists (at doses that optimally inhibit aggregation) and of aspirin may not be limited to the inhibition of thrombosis through their blockade of platelet aggregation but may also involve the inhibition of inflammation and thrombosis through their blockade of sCD40L release. These studies also provide a mechanism by which suboptimal doses of GP IIb/IIIa antagonists may be proinflammatory.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Vascular biology of atherosclerosis: overview and state of the art

Our current understanding of the vascular biology of atherogenesis and its clinical manifestations suggests a pathophysiology that is much more complex than mere lipid storage. Recent advances support the current view of atherosclerosis as an inflammatory process that initiates and promotes lesion development to the point of acute thrombotic complications and clinical events. Inflammatory cells localize in early-stage atherosclerotic lesions, and recent basic research has established a causal relation between inflammatory mediators or cytokines, and the steps involved in progressing from local inflammation through plaque formation. Inhibition of the action of certain specific proinflammatory cytokines, such as CD40 ligand, interferes with atherogenesis in mice. Increased circulating levels of inflammatory markers indicate increased cardiovascular risk. Thus, the time has come to embrace inflammation as a common pathway for atherogenic risk factors and for providing new opportunities for therapeutic intervention.

The role of platelet receptors and adhesion molecules in coronary artery disease

Platelets play a significant role in coronary artery disease through interactions with each other and with other cell types. These interactions are mediated by certain receptors on the surface of platelets and other cells which can lead to intra-coronary thrombus formation and occlusion that may result in acute coronary syndromes. The important roles of the currently available anti-platelet therapies have been well established in many clinical outcome trials in cardiovascular patients. An understanding of these different interactions provides the clinician with a background that supports the clinical importance of currently available anti-platelet therapies. Moreover, knowledge of the mechanisms of cellular crosstalk will lead to important advances in the development of better antithrombotic therapies.

Scientific and therapeutic advances in antiplatelet therapy

Over the past decade, the platelet has emerged as a pivotal entity in cardiovascular diseases. Indeed, the 'preeminence of the platelet' has spawned a variety of drugs that have been shown in large-scale randomized trials to improve patient outcomes in acute coronary syndromes and percutaneous revascularization procedures. Although the platelet was initially viewed only as a bystander in haemostasis, it is now evident that the platelet is in fact a key mediator of thrombosis as well as of inflammation. New insights at the cellular and genomic levels will probably generate novel drugs to inhibit platelet function more effectively and safely than previously possible.

Oxidized low-density lipoprotein augments and 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors limit CD40 and CD40L expression in human vascular cells

BACKGROUND

Although CD40 signaling participates in atherosclerosis, links between lipid risk factors and this inflammatory pathway remain obscure. Cardiovascular risk reduction by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) may involve actions beyond lipid lowering, including reduced inflammation. Therefore, this study analyzed whether oxidized low-density lipoprotein (oxLDL) induces CD40/CD40L expression on cells implicated in atherogenesis and whether statins affect their expression in vitro as well as the expression of soluble CD40L (sCD40L) in vivo.

METHODS AND RESULTS

Treatment of human vascular endothelial and smooth muscle cells and mononuclear phagocytes with oxLDL augmented the basal expression of CD40 and CD40L mRNA and protein. In contrast, cerivastatin, atorvastatin, or simvastatin concentration-dependently diminished the constitutive as well as oxLDL- or cytokine-induced expression of the receptor/ligand dyad, an effect reversed by mevalonate. Patients treated with statins had diminished sCD40L plasma levels compared with untreated control patients (8.3+/-3.1 ng/mL [n=11] versus 13.1+/-2.5 ng/mL [n=16], P<0.05), supporting the clinical relevance of the in vitro observations. Platelet-enriched plasma of mice deficient in CD40L showed markedly delayed fibrin clot formation, suggesting a role for the ligand in blood coagulation and supporting the hypothesis that statin-mediated reduction in CD40/CD40L expression might limit thrombosis.

CONCLUSIONS

OxLDL may promote expression of CD40 and CD40L in human atheroma. Statins may limit the expression of the CD40 receptor/ligand dyad in two ways, directly as well as through diminished lipoprotein levels. Thus, reduced CD40 signaling may account for some of the statins' antiinflammatory action.

Upregulation of CD40 expression on endothelial cells infected with human cytomegalovirus

CD40 has been identified as an important molecule for a number of processes, such as immune responses, inflammation, and the activation of endothelia. We investigated CD40 in endothelial cells (EC) following infection with an endotheliotropic strain of human cytomegalovirus (HCMV). Between 8 and 72 h postinfection, we observed a significant increase in CD40 levels on the surface of infected EC, as measured by fluorescence-activated cell sorting analysis. As a consequence of CD40 upregulation, increased levels of E-selectin were found on infected EC after stimulation with CD154-expressing T cells. Enhanced expression of CD40 was specific for EC, since infection of fibroblasts did not result in the upregulation of CD40. The addition of neutralizing antibodies as well as UV inactivation of virus completely prevented the upregulation of CD40 on EC. Also, laboratory-adapted HCMV strain AD169 was not able to induce CD40 on EC. De novo protein synthesis was necessary for the increased surface expression. At early times (4 to 24 h) postinfection, this change was not accompanied by increased levels of CD40 protein or mRNA. At late times (48 to 96 h) postinfection, increased amounts of CD40 protein and mRNA were detected. Immunohistochemical analysis of infected tissues demonstrated elevated levels of CD40 on HCMV-infected EC in vivo. Thus, infection of EC by HCMV may result in the activation of endothelia and in the augmentation of inflammatory processes.

Role of CD40 ligand in amyloidosis in transgenic Alzheimer's mice

We have shown that interaction of CD40 with CD40L enables microglial activation in response to amyloid-beta peptide (Abeta), which is associated with Alzheimer's disease (AD)-like neuronal tau hyperphosphorylation in vivo. Here we report that transgenic mice overproducing Abeta, but deficient in CD40L, showed decreased astrocytosis and microgliosis associated with diminished Abeta levels and beta-amyloid plaque load. Furthermore, in the PSAPP transgenic mouse model of AD, a depleting antibody against CD40L caused marked attenuation of Abeta/beta-amyloid pathology, which was associated with decreased amyloidogenic processing of amyloid precursor protein (APP) and increased circulating levels of Abeta. Conversely, in neuroblastoma cells overexpressing wild-type human APP, the CD40-CD40L interaction resulted in amyloidogenic APP processing. These findings suggest several possible mechanisms underlying mitigation of AD pathology in response to CD40L depletion, and validate the CD40-CD40L interaction as a target for therapeutic intervention in AD.

Anti-monocyte chemoattractant protein-1 gene therapy limits progression and destabilization of established atherosclerosis in apolipoprotein E-knockout mice

BACKGROUND

Monocyte infiltration into the arterial wall and its activation is the central event in atherogenesis. Thus, monocyte chemoattractant protein-1 (MCP-1) might be a novel therapeutic target against atherogenesis. We and others recently reported that blockade or abrogation of the MCP-1 pathway attenuates the initiation of atheroma formation in hypercholesterolemic mice. It remains unclear, however, whether blockade of MCP-1 can limit progression or destabilization of established lesions.

METHODS AND RESULTS

We report here that blockade of MCP-1 by transfecting an N-terminal deletion mutant of the MCP-1 gene limited progression of preexisting atherosclerotic lesions in the aortic root in hypercholesterolemic mice. In addition, blockade of MCP-1 changed the lesion composition into a more stable phenotype, ie, containing fewer macrophages and lymphocytes, less lipid, and more smooth muscle cells and collagen. This strategy decreased expression of CD40 and the CD40 ligand in the atherosclerotic plaque and normalized the increased chemokine (RANTES and MCP-1) and cytokine (tumor necrosis factor alpha, interleukin-6, interleukin-1beta, and transforming growth factor beta(1)) gene expression. These data suggest that MCP-1 is a central mediator in the progression and destabilization of established atheroma.

CONCLUSIONS

The results of the present study suggest that the inflammatory responses mediated by MCP-1 are important in atherosclerosis and its complications.

Cooperation between secretory phospholipase A2 and TNF-receptor superfamily signaling: implications for the inflammatory response in atherogenesis

Atherogenesis is the consequence of a variety of effector mechanisms rather than the result of a single functional molecule. In this connection, type IIA secretory phospholipase A2 (sPLA2) is an acute-phase reactant, which accumulates in atherosclerotic arterial walls, elicits several effects on monocytes, and has been related to the development of atherosclerosis. CD40/CD40 ligand pair is also a strong proatherogenic system. sPLA2 produced an increase of the surface expression of CD40 in THP-1 monocytes and enhanced the effect of CD40 ligation on the expression of both Fas and FasL, thus indicating the existence of a positive cooperation between sPLA2 and different elements of the TNF-receptor superfamily. Activation of the CD40/CD40L dyad with anti-CD40 antibody produced a small release of arachidonic acid and lacked any significant effect on the induction of cyclooxygenase-2, whereas the secretion of the chemokine MCP-1 and the surface display of CD11b, the alpha chain of the integrin Mac-1, were upregulated. Engagement of CD40 did not influence the survival of THP-1 monocytes, but coincubation of THP-1 monocytes pretreated with anti-CD40 antibody and Jurkat cells induced a significant increase of the number of Jurkat cells showing binding of annexin-V, and nuclear condensation and fragmentation, thus indicating that this treatment might trigger a juxtacrine/paracrine mechanism of apoptotic death in sensitive cell types. This data indicates the existence of overlapping routes for the response to CD40, TNF-alpha, and sPLA2, thus allowing the development of distinct patterns of response in monocytic cells.

Inflammatory bio-markers and cardiovascular risk prediction

Inflammatory processes are now recognized to play a central role in the pathogenesis of atherosclerosis and its complications. Plasma levels of several markers of inflammation have been found to be associated with future cardiovascular risk in a variety of clinical settings. These markers include cell adhesion molecules, cytokines, pro-atherogenic enzymes and C-reactive protein (CRP). Initially thought of as an inactive downstream marker of the inflammatory cascade, emerging evidence suggests that CRP may be directly involved in atherogenesis, and that arterial plaque can produce CRP, independent of traditional hepatic pathways. In addition to being a strong predictor of future cardiovascular risk amongst patients presenting with acute coronary syndromes, numerous studies have found that baseline levels of CRP are associated with risk of future myocardial infarction, stroke, peripheral vascular disease and cardiovascular death amongst apparently healthy populations. The combination of measurement of a marker of inflammation with lipid testing may improve upon risk stratification based on lipid testing alone, and intensification of programmes for exercise, weight loss, and smoking cessation is recommended for those with elevated CRP levels. Further trials are needed to confirm the potential benefits of statins amongst individuals with elevated CRP levels.

Innate and adaptive immunity in the pathogenesis of atherosclerosis

This review considers critically the evidence for the involvement of mediators of innate and acquired immunity in various stages of atherosclerosis. Rapidly mobilized arms of innate immunity, including phagocytic leukocytes, complement, and proinflammatory cytokines, contribute to atherogenesis. In addition, adaptive immunity, with its T cells, antibodies, and immunoregulatory cytokines, powerfully modulates disease activity and progression. Atherogenesis involves cross talk between and shared pathways involved in adaptive and innate immunity. Immune processes can influence the balance between cell proliferation and death, between synthetic and degradative processes, and between pro- and antithrombotic processes. Various established and emerging risk factors for atherosclerosis modulate aspects of immune responses, including lipoproteins and their modified products, vasoactive peptides, and infectious agents. As we fill in the molecular details, new potential targets for therapies will doubtless emerge.

CD40 ligand inhibits endothelial cell migration by increasing production of endothelial reactive oxygen species

BACKGROUND

The CD40/CD40 ligand system is involved in atherogenesis. Activated T lymphocytes and platelets, which express high amounts of CD40 ligand (CD40L) on their surface, contribute significantly to plaque instability with ensuing thrombus formation, leading to acute coronary syndromes. Because reendothelialization may play a pivotal role for plaque stabilization, we investigated a potential role of CD40L on endothelial cell (EC) migration.

METHODS AND RESULTS

Stimulation of ECs with recombinant CD40L prevented vascular endothelial growth factor (VEGF)-induced EC migration, as determined by a "scratched wound assay." In addition, activated T lymphocytes and platelets significantly inhibited VEGF-induced EC migration and tube formation in vitro. Because the activation of endothelial nitric oxide (NO) synthase and the release of NO are required for EC migration and angiogenesis, we analyzed the effect of NO. Coincubation with the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) did not reverse the inhibitory effect of CD40L on VEGF-induced EC migration and tube formation. In addition, EC migration induced by SNAP was completely inhibited by CD40L. CD40L, however, induced the production of reactive oxygen species and reduced endothelial NO bioavailability. This reactive oxygen species-dependent effect of CD40L stimulation was reversed with vitamin C or N-acetylcysteine.

CONCLUSIONS

The activation of the CD40 receptor inhibits EC migration by increasing reactive oxygen species. The blockade of EC migration by CD40L may critically affect endothelial regeneration after plaque erosion and thereby may contribute to the increased risk for development of acute coronary events in patients with high circulating levels of CD40L.

Roles of IL-1 in the development of rheumatoid arthritis: consideration from mouse models

Expression of inflammatory cytokines is augmented in the joints of patients with rheumatoid arthritis (RA). We found that cytokine levels are also elevated in the joints of a mouse arthritis model, human T-cell leukemia virus type I (HTLV-I) transgenic (Tg) mouse. Depletion of IL-1 by gene targeting greatly reduced the incidence of the disease, indicating the importance of this cytokine in the development of arthritis. Furthermore, IL-1 receptor antagonist (IL-1Ra)-deficient mice develop autoimmunity and arthritis spontaneously. These observations suggest that excess IL-1 signaling the causes autoimmunity. We show that IL-1 activates the immune system non-specifically by inducing CD40L and OX40 co-signaling molecules on T cells. In this review, the roles of IL-1 in the development of autoimmunity and arthritis in mouse models will be discussed.

Modulation of the CD40-CD40 ligand interaction using human anti-CD40 single-chain antibody fragments obtained from the n-CoDeR phage display library

CD40 plays a central regulatory role in the immune system and antibodies able to modulate CD40 signalling may consequently have a potential in immunotherapy, in particular for treatment of lymphomas and autoimmune disease like multiple sclerosis. As a first step to achieve this goal, we describe the selection and characterization of a novel set of fully human anti-CD40 antibody fragments (scFv) from a phage display library (n-CoDeR). In order to determine their biological potential, these antibody fragments have been analysed for their ability to promote B-cell activation, rescue from apoptosis and to block the CD40-CD40 ligand (CD40L) interaction. The selected cohort of human scFv could be subcategorized, each expressing a distinct functional signature. Thus scFv were generated that induced B-cell proliferation, rescued B cells from apoptosis and blocked the CD40-CD40L interaction to different extents. In particular, one of the scFv clones (F33) had the ability to abrogate completely this interaction. The epitope recognition patterns as well as individual rate constants were also determined and the affinity was shown to vary from low to high nanomolar range. In conclusion, this panel of human anti-CD40 scFv fragments displays a number of distinct properties, which may constitute a valuable source when evaluating candidates for in vivo trials.

Association between enhanced soluble CD40L and prothrombotic state in hypercholesterolemia: effects of statin therapy

BACKGROUND

Hypercholesterolemia is associated with inflammation and the prothrombotic state. CD40-CD40 ligand (CD40L) interactions promote a prothrombotic response in nucleated cells. The aim of this study was to characterize the in vivo expression of soluble CD40L (sCD40L) in hypercholesterolemia, to correlate it with the extent of the prothrombotic state, and to investigate whether it may be modified by statins.

METHODS AND RESULTS

We studied 80 hypercholesterolemic patients and 80 matched healthy subjects. Hypercholesterolemic subjects had enhanced levels of sCD40L, factor VIIa (FVIIa), and prothrombin fragment 1+2 (F1+2) compared with healthy subjects. sCD40L correlated with total cholesterol and LDL cholesterol. Moreover, sCD40L was positively associated with in vivo platelet activation, as reflected by plasma P-selectin and urinary 11-dehydro-thromboxane B2, and with procoagulant state, as reflected by FVIIa and F1+2. Inhibition of cholesterol biosynthesis by pravastatin or cerivastatin was associated with comparable, significant reductions in sCD40L, FVIIa, and F1+2.

CONCLUSIONS

This study suggests that sCD40L may represent the molecular link between hypercholesterolemia and the prothrombotic state and demonstrates that statin therapy may significantly reduce sCD40L and the prothrombotic state.

Induction of cyclooxygenase-2 and enhanced release of prostaglandin E(2) and I(2) in human endothelial cells by engagement of CD40

OBJECTIVES

The hypothesis was tested that CD40-CD154 interaction is involved in the induction of cyclooxygenase-2 and the release of prostanoids in human endothelial cells.

METHODS AND RESULTS

In a coculture model of human endothelial cells and a transfected CD154 positive cell line, engagement of CD40 on endothelial cells dramatically increased the synthesis of prostacyclin, prostaglandin E(2) and thromboxane A(2). This upregulation was mediated through an induction of cyclooxygenase-2 (Cox-2), as it was blocked by Cox-2-selective inhibitors. Western blot analysis demonstrated that Cox-2 protein was markedly increased in endothelial cells following CD40 engagement, an effect that was inhibited by pretreatment of cells with an anti-CD154 antibody.

CONCLUSION

The data indicate that signaling via CD40 constitutes a major pathway in human endothelial cells for the induction of Cox-2 and release of prostanoids. The CD40-Cox-2 axis thus may represent an important pathway for initiating or maintaining an inflammatory process at the vessel wall.

Correlation between near-infrared Raman spectroscopy and the histopathological analysis of atherosclerosis in human coronary arteries

BACKGROUND AND OBJECTIVES

Modern diagnostic methods such as near-infrared Raman spectroscopy (NIRS) allow quantification and evaluation of human atherosclerotic lesions, which can be useful in diagnosing coronary artery disease. The objective of the present study is to obtain feasible diagnostic information to detect atheromatous plaque using NIRS combined with discriminant analysis.

STUDY DESIGN/MATERIAL AND METHODS

An 830 nm Ti: sapphire laser pumped by an argon laser provides near-infrared excitation. A spectrograph disperses light scattered from arterial tissue and a liquid-nitrogen cooled CCD detects the Raman spectra. A total of 111 arterial fragments were scanned and Raman results were compared with histopathology. Principal components analysis (PCA) and Mahalanobis distance (m-distance) were used to model an algorithm for tissue classification into three categories: non-atherosclerotic (NA), non-calcified (NC), and calcified (C) using Raman spectra. Spectra were randomly separated into training and prospective groups.

RESULTS

It has been found that, for the NA tissue, the algorithm has sensitivity of 84 and 78% and specificity of 91 and 93% for training and prospective groups, respectively. For the NC tissue the algorithm has sensitivity of 88 and 90% and specificity of 88 and 83%. For the C tissue both sensitivity and specificity were maximum, 100%.

CONCLUSIONS

An algorithm using PCA and discriminant analysis based on m-distance has been developed and successfully applied to diagnose coronary artery disease by NIRS obtaining good sensitivity and specificity for each tissue category.

Transforming growth factor-beta mediates balance between inflammation and fibrosis during plaque progression

The transition from stable to rupture-prone and ruptured atherosclerotic plaques involves many processes, including an altered balance between inflammation and fibrosis. An important mediator of both is transforming growth factor (TGF)-beta, and a pivotal role for TGF-beta in atherogenesis has been postulated. Here, we determine the in vivo effects of TGF-beta inhibition on plaque progression and phenotype in atherosclerosis. Recombinant soluble TGF-beta receptor II (TGFbetaRII:Fc), which inhibits TGF-beta signaling, was injected in apolipoprotein E-deficient mice for 12 weeks (50 microg, twice a week intraperitoneally) as early treatment (treatment age 5 to 17 weeks) and delayed treatment (age 17 to 29 weeks). In the early treatment group, inhibition of TGF-beta signaling treatment resulted in a prominent increase in CD3- and CD45-positive cells in atherosclerotic lesions. Most profound effects were found in the delayed treatment group. Plaque area decreased 37.5% after TGFbetaRII:Fc treatment. Moreover, plaque morphology changed into an inflammatory phenotype that was low in fibrosis: lipid cores were 64.6% larger, and inflammatory cell content had increased 2.7-fold. The amount of fibrosis decreased 49.6%, and intraplaque hemorrhages and iron and fibrin deposition were observed frequently. TGFbetaRII:Fc treatment did not result in systemic effects. These results reveal a pivotal role for TGF-beta in the maintenance of the balance between inflammation and fibrosis in atherosclerotic plaques.

Overexpression of interleukin-10 by activated T lymphocytes inhibits atherosclerosis in LDL receptor-deficient Mice by altering lymphocyte and macrophage phenotypes

Previous studies demonstrated that interleukin-10 (IL-10) overexpression decreases formation of early fatty-streak lesions in mice independent of lipoprotein levels. The present studies, using bone marrow transplantation, demonstrate that overexpression of IL-10 by T cells inhibits advanced atherosclerotic lesions in LDL receptor-null mice fed an atherogenic diet. In mice receiving bone marrow from the IL-10 transgenic mice compared with those receiving wild-type marrow, there was a 47% decrease in lesion size and a marked decrease in lesion complexity with an 80% reduction in the necrotic core. Accumulation of cholesterol and phospholipid oxidation products in the aorta was decreased by 50% to 80%, unrelated to plasma lipid or IL-10 levels. Our studies also provide insight into the mechanism of the IL-10-mediated decrease in lesion size. Although a strong influence toward a Th1 phenotype has previously been demonstrated in atherosclerotic models, T lymphocytes in the IL-10 transgenic (Tg) group revealed a marked shift to a Th2 phenotype, with decreased IFN-gamma production and an increase in IL-10. Evaluation of specific immunoglobulin subclasses demonstrated a preponderance of IgG(1) isotype, characteristic of a Th2 influence on B cell immunoglobulin class-switching in the IL-10 Tg group. A major finding of these studies was altered monocyte/macrophage function in the IL-10 Tg group. Monocytes showed a decrease in activation resulting in decreased expression of IFN-gamma. Furthermore, macrophage foam cells within lesions of the IL-10 Tg group exhibited markedly decreased apoptosis. These studies demonstrate that T lymphocyte IL-10 can influence the function of other immune cells to reduce the development of advanced atherosclerotic lesions in mice.

Elevated soluble CD40 ligand is related to the endothelial adhesion molecules in patients with acute coronary syndrome

BACKGROUND

Increasing evidence indicates that the CD40-CD40L interaction plays a pivotal role in the inflammatory regulation of atherosclerosis. Adhesion molecules especially the vascular adhesion molecules also play an important role in the pathogenesis of atherosclerosis which act as markers of inflammation. These inflammatory factors render vulnerability to the atherosclerotic plaque by triggering the fissure, rupture, and subsequent thrombosis, leading to the clinical scenario of unstable angina and acute myocardial infarction.

METHODS

The difference of sCD40L concentration in different subtype of coronary heart disease and its relationship with vascular adhesion molecules was investigated. Enzyme-linked Immunosorbent Assay (EIA) was used to measure the serum sCD40L, soluble intercellular adhesion molecule-1 (sICAM-1), and soluble vascular cell adhesion molecule-1 (sVCAM-1).

RESULTS

The sCD40L concentration was significantly higher in patients with acute coronary syndrome (ACS) (3.17+/-2.84 ng/ml) than in controls (1.19+/-1.05 ng/ml, p<0.01) and in patients with stable coronary heart disease (1.61+/-1.46 ng/ml, p<0.05). The sCD40L concentration was positively correlated with sICAM-1 (r=0.413, p<0.01), triglycerides (TG) (r=0.23, p<0.05), apoB (r=0.248, p<0.05), and HDL-cholesterol (r=-0.253, p<0.05).

CONCLUSIONS

The sCD40L concentration was increased in acute coronary syndrome, suggesting the possible relation of CD40L to the pathogenesis. The serum CD40L concentration was positively correlated with adhesion molecule and was negatively associated with serum high-density lipoprotein cholesterol (HDL-C).

CD40 ligand (CD40L) does not stimulate proliferation of vascular smooth muscle cells

The present study investigates the effects of CD40 ligand (CD40L) on mitogenic signalling, proliferation, and migration of cultured bovine coronary artery smooth muscle cells (SMC). A time- and concentration-dependent phosphorylation of the extracellular signal-regulated kinases-1/2 (ERK-1/2) and the mitogen-activated protein kinase p38 (p38-MAPK) was observed upon stimulation with soluble CD40L (sCD40L). This phosphorylation was inhibited by neutralizing antibodies against the CD40 and CD40L, respectively. Activation of the phosphatidylinositol-3-phosphate (PI-3) kinase pathway by sCD40L, as determined by the measurement of Akt phosphorylation, was not detected. However, there was evidence for direct activation of the NFkappaB system (degradation of IkappaBalpha and nuclear translocation of the p65 NFkappaB subunit) by sCD40L. Accordingly, sCD40L caused a small but significant increase in DNA synthesis. However, sCD40L-induced DNA synthesis was not followed by proliferation (increase in cell number). Furthermore, sCD40L did not potentiate SMC mitogenesis induced by known mitogens such as platelet-derived growth factor-BB, thrombin or serum. The lack of cell proliferation was not caused by a concomitant induction of SMC apoptosis by sCD40L. The possible role of membrane-bound CD40L in SMC mitogenesis was also studied using different membrane preparations (platelets, lymphocytes). However, no mitogenic effects of membrane-bound CD40L were detected. Finally, sCD40L did not induce SMC migration. From these data it is concluded that CD40L activates mitogenic signalling and DNA synthesis but does not contribute to proliferation or migration of vascular SMC.

CD40L stabilizes arterial thrombi by a beta3 integrin--dependent mechanism

CD40L, a member of the tumor necrosis factor family of ligands, plays a major role in immune responses via its receptor, CD40. Recently, CD40L has been detected on the surfaces of activated platelets and shown to activate endothelium. Here we further addressed the function of platelet CD40L. We show that absence of CD40L affects the stability of arterial thrombi and delays arterial occlusion in vivo. Infusion of recombinant soluble (rs)CD40L restored normal thrombosis, whereas rsCD40L lacking the KGD integrin-recognition sequence did not. CD40-deficient mice exhibited normal thrombogenesis. rsCD40L specifically bound to purified integrin alphaIIbbeta3 and to activated platelets in a beta3-dependent manner and induced platelet spreading. In addition, rsCD40L promoted the aggregation of either human or mouse platelets under high shear rates. Thus, CD40L appears to be an alphaIIbbeta3 ligand, a platelet agonist, and necessary for stability of arterial thrombi.

CD40 signaling and plaque instability

Today, multiple lines of evidence support the view of atherosclerosis as a chronic inflammatory disease and implicate components of the immune system in atherogenesis. Recent work has documented overexpression of the potent immune mediator CD40 and its counterpart CD40 ligand (CD40L) in experimental and human atherosclerotic lesions. Notably, interruption of CD40/CD40L interactions not only diminished the formation and progression of mouse atheroma, but also fostered changes in lesion biology and structure, which are associated in humans with "plaque stabilization." In accordance with the hypothesis that CD40 signaling promotes plaque instability, in vitro studies demonstrated that ligation of CD40 on atheroma-associated cell types, namely endothelial cells, smooth muscle cells, and macrophages, mediates functions considered crucial to the process of atherogenesis, such as the expression of cytokines, chemokines, growth factors, matrix metalloproteinases, and procoagulants. The combination of the broad gamut of proatherogenic biological responses triggered by ligation of CD40 on endothelial cells, smooth muscle cells, and macrophages in vitro and the results of in vivo studies of interruption of CD40 signaling suggests a central role for this receptor/ligand dyad during atherogenesis, proposing CD40/CD40L interactions as a novel potential therapeutic target for this prevalent human disease.

Ligation of CD40 onvascular smooth muscle cells mediates loss of interstitial collagen via matrix metalloproteinase activity

Interstitial collagen constitutes the predominant structural component of the fibrous cap of atherosclerotic plaque. The balance between synthesis and degradation of this extracellular matrix protein probably determines plaque stability and hence the tendency for plaque rupture. The CD40/CD40L signaling dyad has been implicated as an important regulatory pathway of collagen-degrading activity in atherosclerosis via the induction of matrix metalloproteinases (MMPs). However, the role of CD40 signaling in the synthesis of interstitial collagen and thus in the overall rate of collagen turnover has remained unknown. We demonstrate here that CD40 ligation on cultured human vascular smooth muscle cells (SMCs) diminishes the detectable content of de novo synthesized interstitial procollagens. Notably, the loss of collagen is not accompanied by a reduction in collagen transcript expression but can be prevented by MMP inhibition. These data demonstrate that CD40 signaling in human vascular SMC shifts interstitial collagen turnover towards the loss of this extracellular matrix protein by accelerating its degradation without concomitantly diminishing its synthesis. Thus, CD40/CD40L interactions might play a key role in rendering atheromatous lesions prone to rupture.

Patients with acute coronary syndromes express enhanced CD40 ligand/CD154 on platelets

OBJECTIVE

To investigate whether CD40L/CD154 on platelets and soluble CD40L/CD154 may play a role in the inflammatory process of acute coronary syndromes.

DESIGN AND SETTING

Observational study in a university hospital.

PATIENTS

15 patients with acute myocardial infarction, 25 patients with unstable angina, 15 patients with stable angina, and 12 controls.

MAIN OUTCOME MEASURES

CD40L/CD154 on platelets, P-selectin/CD62P on platelets, soluble CD40L/CD154 serum concentrations.

RESULTS

Mean (SD) CD40L/CD154 expression on platelets was 6.2 (2.8) MFI (mean fluorescence intensity) in the infarct group, 11 (3.3) MFI in the unstable angina group (p < 0.001 v infarction), 3.6 (0.9) MFI in the stable angina group (p < 0.01 v infarction; p < 0.001 v unstable angina), and 3.2 (1.0) MFI in the controls (p < 0.01 v infarction; p < 0.001 v unstable angina; NS v stable angina). Soluble CD40L/CD154 concentration was 5.2 (1.1) ng/ml in the infarct group, 4.2 (0.7) ng/ml in the unstable angina group (p < 0.001 v infarction), 2.9 (1.0) ng/ml in stable angina group (p < 0.001 v infarction and unstable angina), and 3.0 (0.5) ng/ml in the controls (p < 0.001 v infarction and unstable angina; NS v stable angina). At a six months follow up, there was lower expression of CD40L/CD154 on platelets in patients with unstable angina (12.3 (3.6) v 3.8 (1.2) MFI, p < 0.0001) and acute myocardial infarction (6.2 (2.8) v 3.5 (0.8) MFI, p < 0.01) compared with their admission values six months earlier. Patients with unstable angina who needed redo coronary angioplasty (PTCA) or who had recurrence of angina were characterised by increased CD40L/CD154 expression on platelets compared with the remainder of the study group (recurrence of angina: 12.7 (3.2) v 9.7 (1.6) MFI, p < 0.05; re-do PTCA: 14.3 (4.2) v 10.3 (2.1) MFI, p < 0.05).

CONCLUSIONS

Both CD40L/CD154 on platelets and soluble CD40L/CD154 are raised in patients with unstable angina and myocardial infarction. These findings suggest that CD40-CD40L/CD154 interactions may play a pathogenic role in triggering and propagation of acute coronary syndromes.

Tubular lesions and tubular cell adhesion molecules for the prognosis of lupus nephritis

BACKGROUND

To assess the prognostic value of tubular lesions and cell adhesion molecules' expression, a retrospective study with immunohistochemistry was performed on 152 patients presenting lupus nephritis from January 1985 to December 1999.

METHODS

The following clinical parameters were recorded: age, sex, race, time of systemic lupus erythematosus (SLE) diagnosis, time of the biopsy, proteinuria, creatininemia, and renal function at the end of follow-up. All biopsies were re-evaluated according to a tubular grading, an inflammatory grading, the percentage of sclerosed glomeruli, the percentage of crescents, and the current WHO classification. Immunohistochemistry was performed with anti-CD40, anti-CD44, and anti-intercellular adhesion molecule-1 (anti-ICAM-1) antibodies.

RESULTS

Patients were 136 women (89.5%) and 16 men with a mean age of 31.2 years +/- 12.8 at the time of biopsy. The mean follow-up period was 94.3 months +/- 64.1. Eighty-eight biopsies (58%) showed various degrees of tubular atrophy. Males (P = 0.001) and tubular grading (P = 0.0001) were linked with renal survival in univariate and multivariate analysis. CD40 (P = 0.01) and ICAM-1 (P = 0.001) tubular expressions were linked with renal survival. ICAM-1 tubular expression provided additional information for the prognosis of the patients with biopsies showing tubular atrophy (P = 0.005) or not (P = 0.05).

CONCLUSIONS

Our study shows that tubular lesions are good indicator of lupus nephritis outcome. Furthermore, tubular expression of cell adhesion molecules like ICAM-1 and CD40 also serves to predict the outcome.

Upregulation of TRAF-3 by shear stress blocks CD40-mediated endothelial activation

Atherosclerosis is an inflammatory disease of large arteries that is initiated through the activation of endothelium by proinflammatory mediators. CD40 receptor stimulation has been implicated in the pathogenesis of atherosclerosis. One of the most important atheroprotective stimuli is the viscous drag (shear stress) generated by the streaming blood acting on the endothelial monolayer. Here, we demonstrate that shear stress prevents CD40 ligand-induced endothelial cell activation, and we identify upregulation of TNF receptor-associated factor-3 (TRAF-3) as a potent CD40-inhibitory mechanism. Shear stress specifically upregulates TRAF-3 in cultured endothelial cells. Moreover, in the endothelial cells overlying human atherosclerotic plaques, TRAF-3 expression is upregulated in areas with high shear stress. Overexpression of TRAF-3 inhibits endothelial expression of proinflammatory cytokines and tissue factor and blocks DNA-binding activity of the transcription factor AP-1; it thereby prevents CD40-induced endothelial activation. Thus, upregulation of TRAF-3 represents a novel mechanism for preserving the functional integrity of the endothelial monolayer.

Soluble CD40L and cardiovascular risk in women

BACKGROUND

The immune-signaling dyad CD40/CD40L promotes atherogenesis, and patients with unstable angina have elevated plasma levels of soluble CD40L (sCD40L) and membrane-bound CD40L. It is unknown, however, whether elevations of circulating sCD40L precede the onset of acute cardiovascular symptoms.

METHODS AND RESULTS

In a prospective, nested case-control evaluation of healthy middle-aged women, mean concentrations of sCD40L at baseline were significantly higher among 130 participants who subsequently developed myocardial infarction, stroke, or cardiovascular death (cases), compared with 130 age- and smoking-matched women who remained free of cardiovascular disease (controls) during a 4-year follow-up (2.86 ng/mL for cases versus 2.09 ng/mL for controls; P=0.02). Women with concentrations above the 95th percentile of the control distribution (>3.71 ng/mL) had a significantly increased relative risk (RR) of developing future cardiovascular events (RR, 3.3; 95% CI, 1.2 to 8.6; P=0.01) that remained after adjustment for usual cardiovascular risk factors (multivariate RR, 2.8; 95% CI, 0.9 to 8.0; P=0.05).

CONCLUSIONS

High plasma concentrations of sCD40L may be associated with increased vascular risk in apparently healthy women.

Fibrosis of the lung and other tissues: new concepts in pathogenesis and treatment

Tissue fibrosis can lead to significant organ dysfunction and resulting patient morbidity and mortality. Unfortunately, the therapeutic repertoire is currently limited, nonspecific, and largely ineffective. While the pathogenesis is incompletely understood, evidence is accumulating that immune and cytokine mediated mechanisms are critical. In this review, data will be provided to support the role of Type 2 cytokines in the pathogenesis of fibrosis. The importance of the role of the pro-fibrogenic cytokine TGF-beta and CD40-CD40 ligand mediated fibroblast activation will also be evaluated. Finally, novel therapeutic options based on inhibiting these pathways will be described.

The role of chemokines in atherosclerosis

Recruitment of mononuclear leukocytes and the migration, growth, and activation of the multiple cell types within atherosclerotic lesions are critical features of the chronic inflammatory and fibroproliferative response central to atherosclerosis. Attraction of leukocyte to tissues is controlled by chemokines, whose presence is well documented in atherosclerotic lesions. Studies using knockout and transgenic murine models have demonstrated that chemokine receptor/ligand interactions are of crucial importance in the development of atherosclerosis. Beyond their chemotactic effect on mononuclear leukocytes, chemokines may also interfere with smooth muscle cell migration and growth, as well as platelet activation and other well-defined features of the atherosclerotic process. There is no doubt that the identification of chemokines as important vascular signals has provided insights into our understanding of basic cellular and molecular mechanism of atherosclerosis. Thus, there is evidence that chemokine receptor/ligands could be identified as potential new targets for therapeutic intervention to prevent or control atherosclerosis in the near future.

Mouse models of atherosclerosis

Atherosclerosis bears many features of a chronic inflammation that affects the intima of large and medium-sized arteries. In recent years apolipoprotein E-deficient and LDL receptor-deficient mice have been used to examine the effects of various gene products on the development of atherosclerosis. In the present review the effects of genetics, apolipoprotein E, inflammatory gene modifiers, lipoprotein modifications, lipoprotein receptors, vessel wall expression of lipoprotein-metabolizing enzymes, and the atheroprotective role of HDL on atherosclerosis in these mice are discussed. The importance of examining lesions that are more advanced than fatty streaks and careful histologic and immunologic examination of lesion composition is emphasized.