Human monocyte-endothelial cell interaction induces platelet-derived growth factor expression

Platelet-derived growth factor subunit-B mediating the effect of dickkopf-1 on acute myocardial infarction risk: a two-step Mendelian randomization study

Previous studies have indicated a potential connection between plasma levels of Dickkopf-1 (DKK1) and platelet-derived growth factor subunit-B (PDGF-B) with the development of atherosclerosis. However, the causal relationship between DKK1, PDGF-B, and the risk of acute myocardial infarction (AMI) is yet to be established. To address this research gap, we conducted Mendelian randomization (MR) and mediation analyses to investigate the potential mediating role of PDGF-B in the association between DKK1 and AMI risk. Summary statistics for DKK1 (n = 3,301) and PDGF-B (n = 21,758) were obtained from the GWAS meta-analyses conducted by Sun et al. and Folkersen et al., respectively. Data on AMI cases (n = 3,927) and controls (n = 333,272) were retrieved from the UK Biobank study. Our findings revealed that genetic predisposition to DKK1 (odds ratio [OR]: 1.00208; 95% confidence interval [CI]: 1.00056-1.00361; P = 0.0072) and PDGF-B (OR: 1.00358; 95% CI: 1.00136-1.00581; P = 0.0015) was associated with an increased risk of AMI. Additionally, genetic predisposition to DKK1 (OR: 1.38389; 95% CI: 1.07066-1.78875; P = 0.0131) was linked to higher PDGF-B levels. Furthermore, our MR mediation analysis revealed that PDGF-B partially mediated the association between DKK1 and AMI risk, with 55.8% of the effect of genetically predicted DKK1 being mediated through genetically predicted PDGF-B. These findings suggest that genetic predisposition to DKK1 is positively correlated with the risk of AMI, and that PDGF-B partially mediates this association. Therefore, DKK1 and PDGF-B may serve as promising targets for the prevention and treatment of AMI.

A multiphase model of growth factor-regulated atherosclerotic cap formation

Atherosclerosis is characterised by the growth of fatty plaques in the inner artery wall. In mature plaques, vascular smooth muscle cells (SMCs) are recruited from adjacent tissue to deposit a collagenous cap over the fatty plaque core. This cap isolates the thrombogenic plaque content from the bloodstream and prevents the clotting cascade that leads to myocardial infarction or stroke. Despite the protective role of the cap, the mechanisms that regulate cap formation and maintenance are not well understood. It remains unclear why some caps become stable, while others become vulnerable to rupture. We develop a multiphase PDE model with non-standard boundary conditions to investigate collagen cap formation by SMCs in response to diffusible growth factor signals from the endothelium. Platelet-derived growth factor stimulates SMC migration, proliferation and collagen degradation, while transforming growth factor (TGF)-[Formula: see text] stimulates SMC collagen synthesis and inhibits collagen degradation. The model SMCs respond haptotactically to gradients in the collagen phase and have reduced rates of migration and proliferation in dense collagenous tissue. The model, which is parameterised using in vivo and in vitro experimental data, reproduces several observations from plaque growth in mice. Numerical and analytical results demonstrate that a stable cap can be formed by a relatively small SMC population and emphasise the critical role of TGF-[Formula: see text] in effective cap formation. These findings provide unique insight into the mechanisms that may lead to plaque destabilisation and rupture. This work represents an important step towards the development of a comprehensive in silico plaque model.

Resident plasmacytoid dendritic cells patrol vessels in the naïve limbus and conjunctiva

Plasmacytoid dendritic cells (pDCs) constitute a unique population of bone marrow-derived cells that play a pivotal role in linking innate and adaptive immune responses. While peripheral tissues are typically devoid of pDCs during steady state, few tissues do host resident pDCs. In the current study, we aim to assess presence and distribution of pDCs in naïve murine limbus and bulbar conjunctiva. Immunofluorescence staining followed by confocal microscopy revealed that the naïve bulbar conjunctiva of wild-type mice hosts CD45⁺ CD11c^low PDCA-1⁺ pDCs. Flow cytometry confirmed the presence of resident pDCs in the bulbar conjunctiva through multiple additional markers, and showed that they express maturation markers, the T cell co-inhibitory molecules PD-L1 and B7-H3, and minor to negligible levels of T cell co-stimulatory molecules CD40, CD86, and ICAM-1. Epi-fluorescent microscopy of DPE-GFP×RAG1^-/- transgenic mice with GFP-tagged pDCs indicated lower density of pDCs in the bulbar conjunctiva compared to the limbus. Further, intravital multiphoton microscopy revealed that resident pDCs accompany the limbal vessels and patrol the intravascular space. In vitro multiphoton microscopy showed that pDCs are attracted to human umbilical vein endothelial cells and interact with them during tube formation. In conclusion, our study shows that the limbus and bulbar conjunctiva are endowed with resident pDCs during steady state, which express maturation and classic T cell co-inhibitory molecules, engulf limbal vessels, and patrol intravascular spaces.

A two-phase model of early fibrous cap formation in atherosclerosis

Atherosclerotic plaque growth is characterised by chronic, non-resolving inflammation that promotes the accumulation of cellular debris and extracellular fat in the inner artery wall. This material is highly thrombogenic, and plaque rupture can lead to the formation of blood clots that occlude major arteries and cause myocardial infarction or stroke. In advanced plaques, vascular smooth muscle cells (SMCs) are recruited from deeper in the artery wall to synthesise a cap of fibrous tissue that stabilises the plaque and sequesters the thrombogenic plaque content from the bloodstream. The fibrous cap provides crucial protection against the clinical consequences of atherosclerosis, but the mechanisms of cap formation are poorly understood. In particular, it is unclear why certain plaques become stable and robust while others become fragile and dangerously vulnerable to rupture. We develop a multiphase model with non-standard boundary conditions to investigate early fibrous cap formation in the atherosclerotic plaque. The model is parameterised using data from a range of in vitro and in vivo studies, and includes highly nonlinear mechanisms of SMC proliferation and migration in response to an endothelium-derived chemical signal. We demonstrate that the model SMC population naturally evolves towards a steady-state, and predict a rate of cap formation and a final plaque SMC content consistent with experimental observations in mice. Parameter sensitivity simulations show that SMC proliferation makes a limited contribution to cap formation, and demonstrate that stable cap formation relies primarily on a critical balance between the rates of SMC recruitment to the plaque, chemotactic SMC migration within the plaque and SMC loss by apoptosis or phenotype change. This model represents the first detailed in silico study of fibrous cap formation in atherosclerosis, and establishes a multiphase modelling framework that can be readily extended to investigate many other aspects of plaque development.

Effects of astragalus polysaccharide on the adhesion-related immune response of endothelial cells stimulated with CSFV in vitro

Background

Astragalus polysaccharide (APS) has immunomodulatory activities on porcine peripheral blood mononuclear cells. The immunomodulatory effects of APS on porcine endothelial cells (ECs) expose to classical swine fever virus (CSFV) remain unknown.

Methods

The virus was titrated using an indirect immune biotin enzyme standard method to confirm that porcine ECs were susceptible to CSFV infection and to determine the TCID50 of CSFV (C-strain). Porcine ECs were cultured with CSFV in the presence of APS. Relative quantitative PCR was used to assess the mRNA expression of factors that influence EC adhesion and immunity.

Results

The expression of adhesion factors mRNA increased following stimulation with CSFV; this effect was inhibited by pre-exposing the cells to APS. In addition, the expression of growth factors and some immune factors increased after infection with CSFV; this increase in tissue factor (TF), transforming growth factor (TGF-β), and interleukin-8 (IL-8) could be inhibited by the addition of APS. The immune response mediated by Toll-like receptor 4 (TLR4) in ECs may be unregulated by CSFV as it was also inhibited by pre-treatment with APS.

Discussion

The addition of APS to the culture can obviously regulate the expression of molecules related to the adhesion, growth, and immune response of ECs, as well as the production of cytokines. Therefore, it may have the potential to be an effective component in vaccines against CSFV.

Poliovirus Receptor–Related 2

Objective—

Recently, poliovirus receptor–related 2 ( Pvrl2 ) emerged as a top gene in a global gene expression study aiming to detect plasma cholesterol–responsive genes causally related to atherosclerosis regression in hypercholesterolemic mice. PVRL2 is an adherens junction protein implied to play a role in transendothelial migration of leukocytes, a key feature in atherosclerosis development. In this study, we investigated the effect of Pvrl2 deficiency on atherosclerosis development and transendothelial migration of leukocytes activity.

Approach and Results—

Pvrl2 -deficient mice bred onto an atherosclerosis-prone background ( Pvrl2 −/− Ldlr −/− Apob 100/100 ) had less atherosclerotic lesions and more stable plaques compared with littermate controls ( Pvrl2 +/+ Ldlr −/− Apob 100/100 ). Pvrl2 −/− Ldlr −/− Apob 100/100 mice also showed a 49% decrease in transendothelial migration of leukocytes activity observed using the in vivo air pouch model. In accordance, augmented arterial wall expression of Pvrl2 during atherosclerosis progression coincided with an increased gene expression of migrating leukocytes into the vessel wall. Both in human and mice, gene and protein expression of PVRL2 was predominantly observed in the vascular endothelium according to the immunohistochemical and gene expression data. In addition, the cholesterol responsiveness of PVRL2 was also observed in humans.

Conclusions—

PVRL2 is a plasma cholesterol–responsive gene acting at endothelial sites of vascular inflammation that could potentially be a new therapeutic target for atherosclerosis prevention through its suggested transendothelial migration of leukocytes modulating activity.

Endothelial cells and magnesium: implications in atherosclerosis

There is no doubt that the functional and structural integrity of the endothelium is critical in maintaining vascular homoeostasis and in preventing atherosclerosis. In the light of epidemiological and experimental studies, magnesium deficiency is emerging as an inducer of endothelial dysfunction. In particular, data on the effects of low extracellular magnesium on cultured endothelial cells reinforce the idea that correcting magnesium homoeostasis might be a helpful and inexpensive intervention to prevent and treat endothelial dysfunction and, consequently, atherosclerosis.

Anatomic closure of the premature patent ductus arteriosus: The role of CD14+/CD163+ mononuclear cells and VEGF in neointimal mound formation

Permanent closure of the newborn ductus arteriosus requires the development of neointimal mounds to completely occlude its lumen. VEGF is required for neointimal mound formation. The size of the neointimal mounds (composed of proliferating endothelial and migrating smooth muscle cells) is directly related to the number of VLA4 mononuclear cells that adhere to the ductus lumen after birth. We hypothesized that VEGF plays a crucial role in attracting CD14/CD163 mononuclear cells (expressing VLA4) to the ductus lumen and that CD14/CD163 cell adhesion to the ductus lumen is important for neointimal growth. We used neutralizing antibodies against VEGF and VLA-4 to determine their respective roles in remodeling the ductus of premature newborn baboons. Anti-VEGF treatment blocked CD14/CD163 cell adhesion to the ductus lumen and prevented neointimal growth. Anti-VLA-4 treatment blocked CD14/CD163 cell adhesion to the ductus lumen, decreased the expression of PDGF-B (which promotes smooth muscle migration), and blocked smooth muscle influx into the neointimal subendothelial space (despite the presence of increased VEGF in the ductus wall). We conclude that VEGF is necessary for CD14/CD163 cell adhesion to the ductus lumen and that CD14/CD163 cell adhesion is essential for VEGF-induced expansion of the neointimal subendothelial zone.

Contribution of vascular cell-derived cytokines to innate and inflammatory pathways in atherogenesis

Inflammation is a central element of atherogenesis. Innate pathways contribute to vascular inflammation. However, the initial molecular process(es) starting atherogenesis remain elusive. The various risk factors, represented by particular compounds (activators), may cause altered cellular functions in the endothelium (e.g. vascular endothelial cell activation or -dysfunction), in invading cells (e.g. inflammatory mediator production) or in local vessel wall cells (e.g. inflammatory mediators, migration), thereby triggering the innate inflammatory process. The cellular components of innate immunology include granulocytes, natural killer cells and monocytes. Among the molecular innate constituents are innate molecules, such as the toll-like receptors or innate cytokines. Interleukin-1 (IL-1) and IL-6 are among the innate cytokines. Cytokines are potent activators of a great number of cellular functions relevant to maintain or commove homeostasis of the vessel wall. Within the vessel wall, vascular smooth muscle cells (SMCs) can significantly contribute to the cytokine-dependent inflammatory network by: (i) production of cytokines, (ii) response to cytokines and (iii) cytokine-mediated interaction with invading leucocytes. The cytokines IL-1 and IL-6 are involved in SMC-leucocyte interaction. The IL-6 effects are proposed to be mediated by trans-signalling. Dysregulated cellular functions resulting from dysregulated cytokine production may be the cause of cell accumulation, subsequent low-density lipoprotein accumulation and deposition of extracellular matrix (ECM). The deposition of ECM, increased accumulation of leucocytes and altered levels of inflammatory mediators may constitute an 'innate-immunovascular-memory' resulting in an ever-growing response to anew invasion. Thus, SMC-fostered inflammation, promoted by invading innate cells, may be a potent component for development and acceleration of atherosclerosis.

Monocyte-endothelial cell interaction in atherogenesis and thrombosis

Cellular interactions between leukocytes and the endothelium are critical events in vascular biology, such as atherosclerosis and acute coronary syndrome. When monocytes and endothelial cells are activated via direct cell-cell interaction, both types of cells express several biologically active molecules such as adhesion molecules, cytokines, coagulation and fibrinolytic factors, metalloproteinases, and vasoactive substances. All of these molecules could contribute to atherogenesis and thrombosis.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

Nox5 mediates PDGF-induced proliferation in human aortic smooth muscle cells

The proliferation of vascular smooth muscle cells is important in the pathogenesis of many vascular diseases. Reactive oxygen species (ROS) produced by NADPH oxidases in smooth muscle cells have been shown to participate in signaling cascades regulating proliferation induced by platelet-derived growth factor (PDGF), a powerful smooth muscle mitogen. We sought to determine the role of Nox5 in the regulation of PDGF-stimulated human aortic smooth muscle cell (HASMC) proliferation. Cultured HASMC were found to express four isoforms of Nox5. When HASMC stimulated with PDGF were pretreated with N-acetyl cysteine (NAC), proliferation was significantly reduced. Proliferation induced by PDGF was also heavily dependent on JAK/STAT activation, as the JAK inhibitor, AG490, was able to completely abolish PDGF-stimulated HASMC growth. Specific knockdown of Nox5 with a siRNA strategy reduced PDGF-induced HASMC ROS production and proliferation. Additionally, siRNA to Nox5 inhibited PDGF-stimulated JAK2 and STAT3 phosphorylation. ROS produced by Nox5 play an important role in PDGF-induced JAK/STAT activation and HASMC proliferation.

Regulation of endothelial cell proliferation by primary monocytes

OBJECTIVE

Endothelial cell-monocyte cross talk is essential for vascular repair. Monocytes colocalize with endothelial cells forming a complex set of interactions distinct from the growth promoting cytokines secreted by differentiated macrophages. In the present work we examined the growth regulation and in vitro wound repair early after binding of monocytes to endothelial cells.

METHODS AND RESULTS

After direct contact with primary unactivated monocytes, endothelial cells enter S-phase through a mechanism mediated in part by contact-dependent activation of endothelial Met as demonstrated by siRNA silencing of Met, neutralizing antibodies for hepatocyte growth factor and Met as well as by specific inhibition of Met by the Met kinase inhibitor SU11274. Monocytes robustly promote endothelial cell proliferation and migration into a wounded endothelial monolayer. Monocyte-induced endothelial cell proliferation is accompanied by prolonged extracellular signal-regulated kinase (ERK) activation and is inhibited by the specific ERK inhibitor PD98059. The contact-mediated effect of monocytes is specific to endothelial cells and does not occur with vascular smooth muscle cells. Interestingly, although Flk1 is activated by monocytes, the proliferative effect of monocytes reported here is minimally mediated by Flk1 signaling.

CONCLUSIONS

These results suggest that the early interaction between endothelial cells and monocytes is critical for the regulation of endothelial cell proliferation. This complex regulation is mediated in part by contact-dependent Met and ERK phosphorylation. These findings add to a broader set of leukocyte-endothelial contact mediated signals that together regulate endothelial function in health and disease.

Cytomegalovirus enhance expression of growth factors during the development of chronic allograft nephropathy in rats

Cytomegalovirus (CMV) accelerates chronic rejection (CRX) in a model of rat kidney allograft. In this model, the expressions of transforming growth factor beta 1 (TGF-beta), platelet-derived growth factor (PDGF)-AA, PDGF-BB and connective tissue growth factor (CTGF) were investigated with and without CMV. Transplantations were performed under immunosuppression. One group of animals was infected with CMV and the other was left uninfected. The grafts were harvested on days 3-60 after transplantation. Growth factor proteins were demonstrated by immunohistochemistry, and mRNAs by in situ hybridization. A significantly more intense and earlier endothelial TGF-beta (2.4 +/- 0.8 vs. 1.0 +/- 0.0; P < 0.05) and PDGF-AA (1.8 +/- 0.4 vs. 1.0 +/- 0.0; P < 0.05) expressions, confirmed by mRNA hybridization, occurred in the CMV group compared with the noninfected group. PDGF-BB appeared in a few inflammatory cells only. In addition CTGF appeared earlier and has more intense in the CMV group (2.5 +/- 0.6 vs. 1.2 +/- 0.5) and the number of CTGF mRNA-positive fibroblasts (57 +/- 9 vs. 3 +/- 4; P < 0.05) was significantly higher. Thus, CMV enhanced expression of TGF-beta1, PDGF-AA and CTGF during the development of CRX.

Roles of NF-kappaB and SP-1 in oxidative stress-mediated induction of platelet-derived growth factor-B by TNFalpha in human endothelial cells

Platelet-derived growth factor-B (PDGF-B) is upregulated by proinflamatory stimuli in the early stages of atherosclerosis. However, its mechanisms are not fully elucidated. In the present study, by using the antioxidant N-acetylcysteine (NAC), we investigated in human umbilical vein endothelial cells (HUVECs) the roles of oxidative stress in PDGF-B expression induced by tumor necrosis factor alpha (TNFalpha) and its underlying mechanisms. Exposure of HUVECs to TNFalpha (200 U/ml) for 24 hours caused significant increases of both the PDGF-B expression and its promoter/enhancer activity, which were abolished by NAC (20 mmol/L). Accordingly, a prolonged oxidative stress was induced by TNFalpha and that was prevented by pretreatment with NAC. Electrophoresis mobility shift assay (EMSA) and Western blot analysis showed that both the nuclear factor-kappaB (NF-kappaB) and the specificity protein-1 (SP-1) were activated by TNFalpha. However, NAC only partially inhibited the TNFalpha-induced activation of NF-kappaB, but abolished the activation of SP-1. Mutation of the NF-kappaB binding site resulted in a moderate reduction in the TNFalpha-induced activity of PDGF-B promoter/enhancer, whereas mutation of SP-1 binding site resulted in an absence of induction by TNFalpha. These results suggest that oxidative stress mediates the TNFalpha-induced expression of PDGF-B in HUVECs through redox-sensitive transcription factors, predominantly the SP-1 and possibly, to some extent of NF-kappaB.

GM-CSF activates RhoA, integrin and MMP expression in human monocytic cells

Monocyte migration is one of the key events occurring in the early stage of atherosclerosis. This process includes monocytic adhesion to and penetration through the arterial intima. In such an environment, many factors stimulate the monocytes to enhance integrin activation and extracellular matrix degradation. To investigate the coordinative operation of these two events in relation to monocyte migration, we paid particular attention to the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on monocytes in terms of RhoA activation and matrix metalloproteinase (MMP) expression. RhoA and integrin clustering were activated by GM-CSF, monocyte chemoattractant protein-1 (MCP-1) and platelet-derived growth factor-BB (PDGF-BB) in human monocytic cell lines. Furthermore, enhancement of migration was observed with stimulation by MCP-1 and PDGF-BB. Granulocyte-macrophage colony-stimulating factor did not enhance the migration, even though it activated RhoA and integrin. However, GM-CSF is known to stimulate monocytes to express MCP-1, suggesting the presence of an indirect mechanism for GM-CSF-mediated migratory activity. In contrast, only GM-CSF enhanced the expression of MMP-1 and MMP-9. These results provide evidence that GM-CSF has multiple functions enhancing monocytic migration via RhoA and integrin activation, and via MMP expression.

Angiotensin II-induced MMP-2 release from endothelial cells is mediated by TNF-alpha

Angiotensin II (ANG II) has been etiologically linked to vascular disease; however, its role in the alterations of endothelial function that occur in vascular disorders is not completely understood. Matrix metalloproteinases (MMPs) and proinflammatory cytokines are involved in the pathological remodeling of blood vessels that occurs in vascular disease. In this study we evaluated the effects of ANG II on tumor necrosis factor (TNF)-alpha and MMP-2 production in endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with ANG II (0.1-10 microM) for 24 h, in the presence or absence of antagonists of ANG II type 1 (AT(1)R) and type 2 (AT(2)R) receptors, and the production and release of TNF-alpha and MMP-2 were assessed. ANG II increased TNF-alpha mRNA and protein expression and the release of bioactive TNF-alpha. Moreover, ANG II induced MMP-2 release and reduced the secretion of tissue inhibitor of MMP (TIMP)-2 from endothelial cells. To elucidate whether endogenous TNF-alpha could mediate the effects of ANG II on MMP-2 release, cells were pretreated with anti-TNF-alpha neutralizing antibodies or pentoxifylline (an inhibitor of TNF-alpha synthesis). TNF-alpha inhibition prevented the secretion of MMP-2 induced by ANG II. Furthermore, AT(1)R antagonism with candesartan prevented the formation of MMP-2 and TNF-alpha and the reduction of TIMP-2 induced by ANG II. These results indicate that ANG II, via AT(1)R, modulates the secretion of TNF-alpha and MMP-2 from endothelial cells and that TNF-alpha mediates the effects of ANG II on MMP-2 release.

Age-associated impairment in TNF-alpha cardioprotection from myocardial infarction

Age-associated dysfunction in cardiac microvascular endothelial cells with impaired induction of cardioprotective platelet-derived growth factor (PDGF)-dependent pathways suggests that alterations in critical vascular receptor(s) may contribute to the increased severity of cardiovascular pathology in older persons. In vivo murine phage-display peptide library biopanning revealed a senescent decrease in cardiac microvascular binding of phage epitopes homologous to tumor necrosis factor-alpha (TNF-alpha), suggesting that its receptor(s) may be downregulated in older cardiac endothelial cells. Immunostaining demonstrated that TNF-receptor 1 (TNF-R1) density was significantly lower in the subendocardial endothelium of the aging murine heart. Functional studies confirmed the senescent dysregulation of TNF-alpha receptor pathways, demonstrating that TNF-alpha induced PDGF-B expression in cardiac microvascular endothelial cells of 4-mo-old, but not 24-mo-old, rats. Moreover, TNF-alpha mediated cardioprotective pathways were impaired in the aging heart. In young rat hearts, injection of TNF-alpha significantly reduced the extent of myocardial injury after coronary ligation: TNF-alpha, 7.9 +/- 1.9% left ventricular injury (n = 4) versus PBS, 16.2 +/- 7.9% (n = 10; P < 0.05). The addition of PDGF-AB did not augment the cardioprotective action of TNF-alpha. In myocardial infarctions of older hearts, however, TNF-alpha induced significant postcoronary occlusion mortality (TNF-alpha 80% vs. PBS 0%; n = 10 each, P < 0.05) that was reversed by the coadministration of PDGF-AB. Overall, these studies demonstrate that aging-associated alterations in TNF-alpha receptor cardiac microvascular pathways may contribute to the increased cardiovasular pathology of the aging heart. Strategies targeted at restoring TNF-alpha receptor-mediated expression of PDGF-B may improve cardiac microvascular function and provide novel approaches for treatment and possible prevention of cardiovascular disease in older individuals.

Increased levels of monocyte-related cytokines in patients with unstable angina

Inflammatory cytokines play important roles in coronary artery disease. We investigated the clinical significance of monocyte-related cytokine expression in patients with angina pectoris. We studied 26 patients with stable effort angina and 20 patients with unstable angina in whom stenotic lesions of the coronary arteries were confirmed by selective coronary angiography. Plasma levels of interleukin-6 (IL-6), macrophage colony stimulating factor (MCSF), and monocyte chemoattractant protein-1 (MCP-1) were measured. Plasma levels of IL-6, MCSF, and MCP-1 in patients with unstable angina were significantly higher than those in patients with stable angina or control subjects. Patients with unstable angina were further divided into sub-groups according to their clinical classification; Levels of IL-6, MCSF, and MCP-1 in patients, who had anginal attacks at rest within the 48 h prior to admission (Braunwald class IIIB) were significantly higher than those in patients, who did not have attacks at rest (class IB). Five unstable patients, who were refractory to medical therapy and were referred for emergency coronary revascularization showed marked elevation of plasma MCSF and MCP-1 levels. In conclusion, plasma levels of monocyte-related cytokines were elevated in unstable angina. These increases were marked in patients with unstable angina with recent ischemic attack at rest, suggesting that activation of monocytes is involved in vulnerability of underlying atheromatous plaque.

Thrombin regulates chemokine induction during human retinal pigment epithelial cell/monocyte interaction

Thrombin, an important clotting factor, extravasates at sites of blood-retina barrier breakdown that is often associated with many retinal diseases. Here we investigated the effects of thrombin on human retinal pigment epithelial (HRPE) cells, monocytes, and HRPE cell/monocyte co-cultures. Thrombin induced secretion and mRNA expression of HRPE interleukin (IL)-8 and monocyte chemoattractant protein-1 (MCP-1). Thrombin also enhanced IL-8 and MCP-1 by HRPE cell/monocyte co-cultures, by apparently enhancing cell-cell contact mechanisms. The thrombin effects on IL-6 secretion were similar to those on chemokine secretion. Thrombin-induced chemokines by co-cultures were inhibited by anti-tumor necrosis factor-alpha (TNF-alpha) antibody, but not by anti-IL-1beta antibody. TNF-alpha was detected in cell lysates of monocytes detached from HRPE cells after co-culture stimulation with thrombin. HRPE cells mainly produced these chemokines. However, thrombin generally potentiated exogenous IL-1beta- and TNF-alpha-induced chemokine production by HRPE cells, monocytes, and co-cultures. Interferon-gamma potentiated chemokine secretion by co-cultures with or without thrombin. Our results indicate that thrombin may cause leukocyte recruitment by inducing HRPE cell and monocyte chemokine and by enhancing HRPE cell/monocyte interactions, in part because of monocyte TNF-alpha induction, suggesting important mechanisms for ocular inflammation during blood-retina barrier breakdown and intra-ocular hemorrhage.

MCMV induces neointima in IFN-gammaR-/- mice: intimal cell apoptosis and persistent proliferation of myofibroblasts

BACKGROUND

CMV infections have been linked to vasculopathies like atherosclerosis and Scleroderma. CMV infects vascular endothelium with intermittent shedding of the virus and the development of latency.

METHODS

We adopted a model of arteritis, developed by Presti et al. (1998), triggered by murine cytomegalovirus (MCMV) infection. Our studies focused on neointima formation. Groups of mice include: 1) immunocompetent 129S, 2) immunocompetent 129S receiving whole body irradiation and MCMV, 3) IFN-gammaR-/- receiving MCMV, and 4) IFN-gammaR-/- receiving MCMV and whole body irradiation.

RESULTS

Mice were inoculated with MCMV (5 x 10(4) or 1 x 10(5) PFU's) by i.p. injection; hearts and abdominal aortas were collected and histopathology evaluated. Infected immunocompetent animals exhibited widespread perivascular inflammation, which subsided by 8 weeks. Intimal pathology was not observed in any control group. Immunocompetent animals receiving MCMV and irradiation developed mild to moderate intimal lesions associated with medial and adventitial inflammation. IFN-gammaR-/- mice infected for 4 months and receiving whole body irradiation 2 months after infection developed pathology characterized by extensive adventitial and medial infiltrate and significant neointima, suggesting that infection and immunosuppression were co-requisites of neointima formation. Immunohistochemical analysis revealed myofibroblasts as a major component of neointima. The disease is characterized by up-regulation of growth factors (TGF-beta1, PDGF-A and B). Apoptosis was detected in the intimal layer of affected aortas. Active proliferation of myofibroblasts and infiltrating cells was also detected.

CONCLUSION

These results indicate that CMV infections may lead to intimal injury that results in the formation of neointima characteristic of autoimmune vasculopathies.

Adeno-associated virus-mediated vascular endothelial growth factor gene transfer into cardiac myocytes

Vascular endothelial growth factor (VEGF) is an angiogenic growth factor that stimulates endothelial cell proliferation, increases endothelial permeability, and promotes collateral vessel formation. We transferred human VEGF gene into rat cardiac myocytes using adeno-associated virus (AAV) vectors and investigated whether VEGF secreted from the transduced cardiac myocytes promoted proliferation of endothelial cells. We produced VEGF-expressing AAV vectors (AAV-VEGF) by the adenovirus-free method. Immunoblotting revealed VEGF protein expression in AAV-VEGF-transduced rat cardiac myocytes. More than 60% of cardiac myocytes were stained positively on immunohistochemical staining using anti-VEGF antibody. Concentration of VEGF in the culture medium of AAV-VEGF-transduced myocytes was increased in a vector dose-dependent manner, and VEGF secretion from the transduced myocytes persisted for > or = 14 days. Thymidine incorporation into human vascular endothelial cells was significantly increased by incubation with the conditioned medium from AAV-VEGF-transduced myocytes. This increased thymidine uptake was significantly inhibited by anti-VEGF antibody. We demonstrated here that AAV-mediated VEGF gene transfer into cardiac myocytes induces the secretion of functional VEGF.

The quality of dialysate: an integrated approach

The role of bacterial contamination of dialysis water with respect to chronic inflammatory diseases associated with long-term hemodialysis therapy has been greatly underestimated in the last two decades. In the present article, recent multicenter studies assessing the bacteriological quality of water and dialysate are discussed. In addition, we describe that pyrogenic substances of bacterial origin derived from contaminated dialysate penetrate intact dialyzer membranes with the consequence of the induction of an inflammatory response in the patients. The influence of dialyzer membrane characteristics on the passage of bacterial substances from dialysate into blood are discussed. Reaching the patients blood, bacteria-derived substances activate circulating mononuclear cells to produce proinflammatory cytokines. Cytokines such as interleukin-1 beta and tumor necrosis factor-alpha are mediators of the acute phase response resulting in elevated levels of acute phase proteins (for example, C-reactive protein). The consequence is a state of microinflammation that may contribute to progressive inflammatory diseases in chronic renal failure such as beta2-microglobulin amyloidosis, protein catabolism, and atherosclerosis. The use of sterile dialysate reduces cytokine production and plasma levels of acute phase proteins, and may positively influence progressive inflammatory diseases in patients with end-stage renal failure.

Growth factors stimulate neointimal cells in vitro and increase the thickness of the neointima formed at the neck of porcine aneurysms treated by embolization

BACKGROUND AND PURPOSE

Growth factors (GFs) may favor the healing of aneurysms treated with endovascular techniques by stimulating neointima formation.

METHODS

Bilateral carotid aneurysms were constructed with venous pouches in 50 pigs and embolized intraoperatively with collagen sponges with and without GFs (platelet-derived growth factor-BB [PDGF-BB] 0.15 or 1.5 microg or transforming growth factor-beta(1) [TGF-beta(1)] 60 or 600 ng) in each animal. DNA synthesis, cell proliferation, and collagen secretion assays were performed to assess the in vitro effects of GFs on neointimal cells harvested from the treated aneurysms. (125)I-PDGF-BB was used to study in vivo GF release from sponges. The thickness of the neointima at the surface of the sponges was measured 2 weeks after surgery. Since porcine aneurysms tend to heal after collagen sponge embolization, this experiment was repeated in dogs, which have shown a propensity for recurrence with the same technique, with 600 ng TGF-beta(1) or platelet extracts.

RESULTS

PDGF-BB stimulated DNA synthesis and cell proliferation, while TGF-beta(1) strongly increased collagen synthesis of neointimal cells in vitro. Clearance of (125)I-PDGF-BB from the sponges followed a biphasic curve, with 1.5% of exogenous PDGF-BB remaining at 1 week. The local delivery of PDGF-BB (0.15 or 1.5 microg) and TGF-beta(1) (600 ng) significantly increased neointimal thickness at the neck of porcine aneurysms, while 60 ng of TGF-beta(1) had no demonstrable effect. TGF-beta(1) (600 ng) or platelet extracts had no influence on canine aneurysms.

CONCLUSIONS

PDGF-BB and TGF-beta(1) can stimulate neointimal cells in vitro and neointima formation in vivo, but TGF-beta(1) and platelet extracts do not compensate for deficient thrombosis in canine aneurysms. Effects on the long-term results of embolization remain speculative.

Adhesion of monocyte very late antigen-4 to endothelial vascular cell adhesion molecule-1 induces interleukin-1beta-dependent expression of interleukin-6 in endothelial cells

In atheroma, T cell-derived interferon-gamma (INF-gamma) stimulates endothelial cells and facilitates recruitment of monocytes. We investigated potential mechanisms by which these interactions could contribute to local and systemic inflammatory responses. Specifically, we analyzed the expression of interleukin (IL)-1beta and IL-6 in both cell types after coculture, the relevant adhesion molecules in this interaction, and transcriptional control by NF-kappaB. We studied coculture of purified peripheral blood monocytes with human umbilical vein endothelial cells (HUVECs), which were stimulated with INF-gamma (10(6) U/L) to model the activated endothelium of atherosclerotic lesions. Coculture of monocytes with activated HUVECs resulted in release of IL-1beta (40. 6+/-3 pg/24 h, P=0.002) and IL-6 (46.6+/-7 ng/24 h, P=0.0015). Electrophoretic mobility gel shift assay and Northern blotting in each cell type separately revealed NF-kappaB activation in both cell types, IL-1beta mRNA expression predominantly in monocytes, and IL-6 mRNA expression predominantly in HUVECs. The endothelial IL-6 release was IL-1-dependent, because it was suppressed by IL-1 receptor antagonist. Experiments with blocking antibodies demonstrated that binding of monocyte very late antigen-4 (VLA-4) to endothelial vascular cell adhesion molecule-1 (VCAM-1) was necessary for the induction of IL-1beta in monocytes. Binding of monocyte VLA-4 to endothelial VCAM-1 induces NF-kappaB activation in both cell types with expression and release of IL-1beta by monocytes, which in turn stimulates endothelial release of IL-6. The beta(1)-integrin-mediated expression of IL-1beta and IL-6 could contribute to local and systemic inflammatory reactions in atherosclerosis.