Reciprocal induction of tumor necrosis factor-alpha and interleukin-1 beta activity mediates fibronectin synthesis in coronary artery smooth muscle cells

New Drugs and Therapies in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension is a chronic, progressive disorder of the pulmonary vasculature with associated pulmonary and cardiac remodeling. PAH was a uniformly fatal disease until the late 1970s, but with the advent of targeted therapies, the life expectancy of patients with PAH has now considerably improved. Despite these advances, PAH inevitably remains a progressive disease with significant morbidity and mortality. Thus, there is still an unmet need for the development of new drugs and other interventional therapies for the treatment of PAH. One shortcoming of currently approved vasodilator therapies is that they do not target or reverse the underlying pathogenesis of the disease process itself. A large body of evidence has evolved in the past two decades clarifying the role of genetics, dysregulation of growth factors, inflammatory pathways, mitochondrial dysfunction, DNA damage, sex hormones, neurohormonal pathways, and iron deficiency in the pathogenesis of PAH. This review focuses on newer targets and drugs that modify these pathways as well as novel interventional therapies in PAH.

Platelet-leukocyte aggregate formation and inflammation in patients with pulmonary arterial hypertension and CTEPH

Pulmonary hypertension (PH) is defined by increased mean pulmonary artery pressure, and the clinical classification includes five etiologies, of which we investigated subgroup 1, pulmonary arterial hypertension (PAH) and subgroup 4, chronic thrombotic and/or embolic disease (CTEPH). Platelets participate in both innate and adaptive immune responses and could possibly contribute to the suggested systemic inflammation associated with PAH. In this study, we utilized flow cytometry to analyze platelet activation and platelet-monocyte (PMA) and granulocyte (PGA) aggregates in PAH and CTEPH patients and healthy control subjects. The plasma concentration of proinflammatory cytokines was measured by multiplex electrochemiluminescence. Our main finding is that circulating platelets are activated in the circulation and form aggregates with both monocytes and granulocytes in patients with idiopathic PAH (IPAH), associated PAH (APAH) and pulmonary hypertension due to CTEPH. There was a strong correlation between the platelet activation, assessed as P-selectin, and the number of aggregates formed. IL-6, IL-8, IL-10 and TNF-α were increased in all PH subgroups as compared to healthy controls, and PMAs were associated with circulating IL-6, IL-8 and IL-10, whereas PGAs were associated with IL-6. The increased concentrations of platelet-leukocyte aggregates found in PAH/CTEPH patients might thus contribute to the inflammatory state in PH.

Novel Experimental Therapies for Treatment of Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease characterized by pulmonary artery vasoconstriction and vascular remodeling leading to vascular rarefaction with elevation of pulmonary arterial pressures and pulmonary vascular resistance. Often PAH will cause death from right heart failure. Current PAH-targeted therapies improve functional capacity, pulmonary hemodynamics and reduce hospitalization. Nevertheless, today PAH still remains incurable and is often refractory to medical therapy, underscoring the need for further research. Over the last three decades, PAH has evolved from a disease of unknown pathogenesis devoid of effective therapy to a condition whose cellular, genetic and molecular underpinnings are unfolding. This article provides an update on current knowledge and summarizes the progression in recent advances in pharmacological therapy in PAH.

Cytokines, Chemokines, and Inflammation in Pulmonary Arterial Hypertension

According to the World Symposium Pulmonary Hypertension (WSPH) classification, pulmonary hypertension (PH) is classified into five categories based on etiology. Among them, Group 1 pulmonary arterial hypertension (PAH) disorders are rare but progressive and often, fatal despite multiple approved treatments. Elevated pulmonary arterial pressure in patients with WSPH Group 1 PAH is mainly caused by increased pulmonary vascular resistance (PVR), due primarily to sustained pulmonary vasoconstriction and excessive obliterative pulmonary vascular remodeling. Growing evidence indicates that inflammation plays a critical role in the development of pulmonary vascular remodeling associated with PAH. While the role of auto-immunity is unclear, infiltration of inflammatory cells in and around vascular lesions, including T- and B-cells, dendritic cells, macrophages, and mast cells have been observed in PAH patients. Serum and plasma levels of chemokines, cytokines, and autoantibodies are also increased in PAH patients; some of these circulating molecules are correlated with disease severity and survival. Preclinical experiments have reported a key role of the inflammation in PAH pathophysiology in vivo. Importantly, anti-inflammatory and immunosuppressive agents have further exhibited therapeutic effects. The present chapter reviews published experimental and clinical evidence highlighting the canonical role of inflammation in the pathogenesis of PAH and as a major target for the development of anti-inflammatory therapies in patients with PAH.

Obesity, Systemic Hypertension, and Pulmonary Hypertension: A Tale of Three Diseases

Cardiovascular disease (CVD), especially ischemic heart disease and stroke, is the major cause of death worldwide, accounting for more than one-third of all deaths annually. Hypertension is the most prevalent and modifiable risk factor of CVD-related deaths. The same is true for obesity, which is currently being recognized as a major global epidemic. The prevalence of obesity in the United States has increased dramatically, from 13.4% in 1960 to 36.5% in 2014, with as much as 70.7% of the American adult population being overweight or obese (CDC). Epidemiological studies have shown that obesity predisposes to hypertension and CVD - with the relationship between markers of obesity and blood pressure being almost linear across different populations. In this review, we discuss systemic and pulmonary hypertension in the context of obesity.

Pulmonary hypertension: Pathophysiology beyond the lung

Pulmonary hypertension (PH) is classically considered a disease of pulmonary vasculature which has been the predominant target for drug development and PH therapy. Despite significant advancement in recent years in identification of new drug targets and innovative treatment strategies, the prognosis of PH remains poor, with median survival of 5 years. Recent studies have demonstrated involvement of neuroinflammation, altered autonomic and gastrointestinal functions and increased trafficking of bone marrow-derived cells in cardiopulmonary pathophysiology. This has led to the proposal that PH could be considered a systemic disease involving complex interactions among many organs. Our objectives in this review is to summarize evidence for the involvement of the brain, bone marrow and gut in PH pathophysiology. Then, to synthesize all evidence supporting a brain-gut-lung interaction hypothesis for consideration in PH pathophysiology and finally to summarize unanswered questions and future directions to move this novel concept forward. This forward-thinking view, if proven by further experiments, would provide new opportunities and novel targets for the control and treatment of PH.

An upregulation of CD8+CD25+Foxp3+ T cells with suppressive function through interleukin 2 pathway in pulmonary arterial hypertension

Accumulating evidence suggests that abnormal inflammation plays a critical role in the pathogenesis of pulmonary arterial hypertension (PAH). CD8⁺CD25⁺Foxp3⁺ T cell is a novel cell subtype, and its role in PAH is not yet investigated. Here, we observed that PAH patients presented a significant upregulation of CD8⁺CD25⁺Foxp3⁺ T cells and a downregulation of CD4⁺CD25⁺Foxp3⁺ T cells compared to healthy controls. Regardless, the total number of CD25⁺Foxp3⁺ T cells in PAH patients was still smaller than that in healthy controls. Compared to CD8⁺CD25^- T cells, CD8⁺CD25⁺ T cells presented higher Foxp3 expression, lower interferon (IFN)-γ expression and higher transforming growth factor (TGF)-β expression, in both healthy and PAH individuals. The CD8⁺CD25⁺ T cells in PAH patients also demonstrated regulatory function by suppressing the proliferation of CD4⁺CD25^- and CD8⁺CD25^- effector T cells, albeit at lower efficiency than CD4⁺CD25⁺ T cells from PAH patients and healthy volunteers. CD8⁺CD25⁺ T cells from PAH responded to interleukin (IL)-2 supplement by expansion and upregulating Foxp3 expression. In PAH patients, IL-2-treated CD8⁺CD25⁺ T cells were more potent at inhibiting CD4⁺CD25^- effector T cell proliferation than IL-2-untreated CD8⁺CD25⁺ T cells. Together, we found an upregulation of CD8⁺CD25⁺Foxp3⁺ T cells in PAH patients, and this T cell population presented suppressive activity that could be enhanced by IL-2 treatment.

Vascular smooth muscle cell in atherosclerosis

Vascular smooth muscle cells (VSMCs) exhibit phenotypic and functional plasticity in order to respond to vascular injury. In case of the vessel damage, VSMCs are able to switch from the quiescent 'contractile' phenotype to the 'proinflammatory' phenotype. This change is accompanied by decrease in expression of smooth muscle (SM)-specific markers responsible for SM contraction and production of proinflammatory mediators that modulate induction of proliferation and chemotaxis. Indeed, activated VSMCs could efficiently proliferate and migrate contributing to the vascular wall repair. However, in chronic inflammation that occurs in atherosclerosis, arterial VSMCs become aberrantly regulated and this leads to increased VSMC dedifferentiation and extracellular matrix formation in plaque areas. Proatherosclerotic switch in VSMC phenotype is a complex and multistep mechanism that may be induced by a variety of proinflammatory stimuli and hemodynamic alterations. Disturbances in hemodynamic forces could initiate the proinflammatory switch in VSMC phenotype even in pre-clinical stages of atherosclerosis. Proinflammatory signals play a crucial role in further dedifferentiation of VSMCs in affected vessels and propagation of pathological vascular remodelling.

Inflammation and immunity in the pathogenesis of pulmonary arterial hypertension

This review summarizes an expanding body of knowledge indicating that failure to resolve inflammation and altered immune processes underlie the development of pulmonary arterial hypertension. The chemokines and cytokines implicated in pulmonary arterial hypertension that could form a biomarker platform are discussed. Pre-clinical studies that provide the basis for dysregulated immunity in animal models of the disease are reviewed. In addition, we present therapies that target inflammatory/immune mechanisms that are currently enrolling patients, and discuss others in development. We show how genetic and metabolic abnormalities are inextricably linked to dysregulated immunity and adverse remodeling in the pulmonary arteries.

Complex regulation and function of the inflammatory smooth muscle cell phenotype in atherosclerosis

Vascular smooth muscle cell (SMC) phenotypic modulation plays a key role in atherosclerosis and is classically defined as a switch from a 'contractile' phenotype to a 'synthetic' phenotype, whereby genes that define the contractile SMC phenotype are suppressed and proliferation and/or migratory mechanisms are induced. There is also evidence that SMCs may take on a 'proinflammatory' phenotype, whereby SMCs secrete cytokines and express cell adhesion molecules, e.g. IL-8, IL-6, and VCAM-1, respectively, which may functionally regulate monocyte and macrophage adhesion and other processes during atherosclerosis. Factors that drive the inflammatory phenotype are not limited to cytokines but also include hemodynamic forces imposed on the blood vessel wall and intimate interaction of endothelial cells with SMCs, as well as changes in matrix composition in the vessel wall. However, it is critical to recognize that our understanding of the complex interaction of these multiple signal inputs has only recently begun to shed light on mechanisms that regulate the inflammatory SMC phenotype, primarily through models that attempt to recreate this environment ex vivo. The goal of this review is to summarize our current knowledge in this area and identify some of the key unresolved challenges and questions requiring further study.

Notoginsenoside R1 inhibits TNF-alpha-induced fibronectin production in smooth muscle cells via the ROS/ERK pathway

The matrix fibronectin protein plays an important role in vascular remodeling. Notoginsenoside R1 is the main ingredient with cardiovascular activity in Panax notoginseng; however, its molecular mechanisms are poorly understood. We report that notoginsenoside R1 significantly decreased TNF-alpha-induced activation of fibronectin mRNA, protein levels, and secretion in human arterial smooth muscle cells (HASMCs) in a dose-dependent manner. Notoginsenoside R1 scavenged hydrogen peroxide (H2O2) in a dose-dependent manner in the test tube. TNF-alpha significantly increased intracellular ROS generation and then ERK activation, which was blocked by notoginsenoside R1 or DPI and apocynin, inhibitors of NADPH oxidase, or the antioxidant NAC. Our data demonstrated that TNF-alpha-induced upregulation of fibronectin mRNA and protein levels occurs via activation of ROS/ERK, which was prevented by treatment with notoginsenoside R1, DPI, apocynin, NAC, or MAPK/ERK inhibitors PD098059 and U0126. Notoginsenoside R1 significantly inhibited H2O2-induced upregulation of fibronectin mRNA and protein levels and secretion; it also significantly inhibited TNF-alpha and H2O2-induced migration. These results suggest that notoginsenoside R1 inhibits TNF-alpha-induced ERK activation and subsequent fibronectin overexpression and migration in HASMCs by suppressing NADPH oxidase-mediated ROS generation and directly scavenging ROS.

Prevention of intimal hyperplasia with recombinant soluble P-selectin glycoprotein ligand-immunoglobulin in the porcine coronary artery balloon injury model

OBJECTIVES

The role of P-selectin in the process of restenosis was evaluated using a recombinant immunoglobulin (Ig) chimera form of its ligand, soluble P-selectin glycoprotein ligand-Ig (rPSGL-Ig), as a competitive inhibitor for the natural ligand on leukocytes.

BACKGROUND

Inflammation and coagulation activation after vascular injury may be an important factor in the development of restenosis. P-selectin has been shown to mediate leukocyte-endothelium and leukocyte-platelet interaction. These interactions are mediated through binding of P-selectin to P-selectin glycoprotein ligand-1 (PSGL-1) located on the surface of leukocytes.

METHODS

Balloon injury was induced in the left anterior descending and right coronary arteries of 16 pigs at a balloon/artery diameter ratio of 1.5:1. Either rPSGL-Ig (1 mg/kg) or saline was randomly administered 15 min before balloon injury as an intravenous bolus. Four weeks after injury, morphometric analysis, immunohistochemistry and histological evaluation were performed on injured arterial segments.

RESULTS

Increased luminal area was found in the rPSGL-Ig group compared with the placebo group (1.63 +/- 0.57 mm2 vs. 1.26 +/- 0.32 mm2, p = 0.044) owing to significantly reduced neointimal hyperplasia (cross-sectional area, 0.46 +/- 0.45 mm2 vs. 0.13 +/- 0.11 mm2, p = 0.013). Immunohistochemistry and histological evaluation showed a significant decrease in the presence of tumor necrosis factor-alpha, interleukin-1 beta, and infiltration of macrophages in the injured vessel segments in the rPSGL-Ig group.

CONCLUSIONS

P-selectin antagonism using rPSGL-Ig decreases neointimal hyperplasia following balloon injury, by inhibiting the inflammatory and thrombotic responses at the site of balloon injury, which appears to play a pivotal role in the pathogenesis of restenosis.

Tumor necrosis factor-alpha induces fibronectin synthesis in coronary artery smooth muscle cells by a nitric oxide-dependent posttranscriptional mechanism

Postcardiac transplant coronary arteriopathy is associated with tumor necrosis factor-alpha (TNF-alpha) induction of fibronectin-dependent smooth muscle cell (SMC) migration into the subendothelium, resulting in occlusive neointimal formation. Because expression of inducible nitric oxide synthase (iNOS) is elevated in neointimal formation after transplantation and upregulated in vascular SMCs by TNF-alpha, we investigated whether TNF-alpha induction of fibronectin synthesis in coronary artery (CA) SMCs is mediated by nitric oxide (NO). TNF-alpha caused a dose-dependent increase in reactive oxygen and nitrogen intermediates in CA SMCs (P<0.05). This correlated with increased NO production (P<0.05) and fibronectin synthesis (P<0.05). TNF-alpha induction of fibronectin synthesis was abrogated by the NOS inhibitor N(G)-monomethyl-L-arginine (L-NMMA) (P<0.05) or the flavonoid-containing enzyme inhibitor diphenyleneiodonium (DPI) (P<0.05) and reproduced with the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) (P<0.05). Northern blotting showed no effect of TNF-alpha on steady-state fibronectin mRNA levels. TNF-alpha increased expression of light chain 3 (LC-3), a protein shown previously to facilitate fibronectin mRNA translation through its interaction with an adenosine-uracil rich element (ARE) in the 3'-untranslated region of fibronectin mRNA. RNA gel mobility shift and UV cross-linking assays using CA SMC lysates revealed protein binding complexes with radiolabeled oligonucleotide containing the ARE, similar to those generated with recombinant LC-3. One of these complexes increased after TNF-alpha treatment, an effect inhibited with L-NMMA or DPI. These data demonstrate a novel paradigm whereby cytokines regulate mRNA translation of extracellular matrix proteins through NO-dependent modulation of RNA binding protein interaction with mRNA.

Nitric oxide mediates LC-3-dependent regulation of fibronectin in ductus arteriosus intimal cushion formation

Ductus arteriosus intimal cushion formation is characterized by fibronectin-dependent smooth muscle cell (SMC) migration. Enhanced fibronectin synthesis in ductus SMC is regulated by the interaction of LC-3, a microtubule-associated protein, with an AU-rich element (ARE) in the 3'-untranslated region of fibronectin mRNA, facilitating its recruitment to polyribosomes for translation. Since nitric oxide (NO) is implicated in posttranscriptional gene regulation and is produced in the ductus, we investigated its mechanistic role in LC-3-mediated fibronectin synthesis. NO production was sevenfold higher in ductus vs. aortic SMC (P<0.005) associated with increased neuronal NO synthase (nNOS) expression. The NOS inhibitor L-NMMA decreased fibronectin synthesis by approximately 45-50% (P<0.05), whereas the NO donor, SNAP, increased ductus fibronectin synthesis approximately onefold (P<0.05); neither agent altered fibronectin mRNA levels. Immunoblotting revealed that SNAP increased and L-NMMA reduced a membrane-associated phosphorylated form of LC-3. RNA gel mobility shift assays confirmed that NO enhanced LC-3 binding to the fibronectin mRNA ARE. Our studies indicate a tissue-specific program in the ductus arteriosus whereby elevated nNOS expression and NO production regulate the posttranscriptional increase in fibronectin synthesis required for SMC motility.

EVE and beyond, retro and prospective insights

Our work has focused on the discovery that an endogenous vascular elastase (EVE) plays a pivotal role in the vascular changes associated with the development and progression of pulmonary hypertension. Recent studies have identified serum factors that stimulate transcription of this enzyme and have elucidated a signal transduction process involving activation of the mitogen-activated protein kinase pathway and nuclear expression of the transcription factor AML1. Proteases release and activate growth factors that are bound to the extracellular matrix and also induce, in a beta(3)-integrin-dependent manner, the transcription of the gene for the matrix glycoprotein tenascin. Tenascin alters smooth muscle cell shape and facilitates the proliferative response to growth factors by clustering and activating growth factor receptors. In addition, breakdown products of elastin, elastin peptides, can upregulate the production of fibronectin, a glycoprotein that is critical to smooth muscle cell migration. The mechanisms regulating enhanced fibronectin production have recently been successfully targeted to prevent the development of intimal lesions.

Inhibitory mechanisms by which suramin may attenuate neointimal formation after balloon angioplasty

Restenotic neointimal lesions, a major limitation to coronary angioplasty, develop in response to diverse signals and depend on three properties of activated arterial smooth muscle cells (SMCs): proliferation, migration, and abnormal production of extracellular matrix. Most of the pharmacologic approaches targeting specific pathogenic factors facilitating development of restenosis have failed in clinical trials. Our results indicate that the polysulfonated naphthylurea suramin, a "non-specific drug" that interferes with multiple cellular proteins, inhibits neointimal formation in rabbit iliac arteries after balloon-catheter injury administered throughout the critical period of several weeks after the procedure. In vitro studies aimed at dissecting the mechanism(s) underlying the suramin-dependent effect demonstrated that, in addition to an inhibitory effect on SMC proliferation, suramin inhibited fibronectin and elastin deposition and the migration of SMCs through elastin membranes and into scratch gaps of monolayer cultures. We also demonstrated that suramin causes cell-surface accumulation of the elastin binding protein, a receptor that not only anchors SMCs to the extracellular matrix, but also inhibits SMC response to interleukin-1beta (IL-1beta). We conclude that suramin acts as a multitarget inhibitor of SMC activation and has a therapeutic potential as an agent that may attenuate arterial restenosis after angioplasty.

Increased expression of tumor necrosis factor-alpha in diabetic macrovasculopathy

Large vessel disease, a common feature of diabetes mellitus, appears to run an aggressive course, but its cellular and molecular aspects remain partially elucidated. Although in common atherosclerosis and especially in other forms of accelerated vasculopathy, immunoinflammatory mechanisms participate in the disease process, it is unclear whether this is present in diabetic vasculopathy. We hypothesized that diabetic macrovasculopathy, compared with classical atherosclerosis, is associated with increased immunoinflammatory features and matrix accumulation. In this study, vessel segments obtained after lower-limb amputation for advanced atherosclerotic disease, from type 2 diabetic patients (n = 20; 68.9+/-10.9 years) and nondiabetic patients (n = 16; 67.1+/-14.6 years) were analyzed. Histological characteristics (extent of intimal proliferation, cellularity, and fibrosis) were semiquantitatively graded in the two lesion types. Using immunohistochemistry, the presence of T cells and macrophages, accumulation of fibronectin, and expression of tumor necrosis factor-alpha was also assessed. Histological features of these advanced atherosclerotic lesions were similar in the two lesions examined. By immunohistochemistry, a similar pattern of T-cell and macrophage infiltration and fibronectin accumulation was observed. Nevertheless, increased expression of tumor necrosis factor-alpha was observed in diabetic lesions (13/19 patients had positive staining), whereas only 2 of 16 lesions from nondiabetic patients had positive staining (p < 0.003), with an odds ratio of 15.17 (confidence interval 2.12-139.5). These data suggest that increased expression of tumor necrosis factor-alpha observed in the diabetic lesions may reflect an enhanced inflammatory activity associated with the development of vascular lesions in type 2 diabetic patients.

TGF-beta induces fibronectin synthesis through a c-Jun N-terminal kinase-dependent, Smad4-independent pathway

Transforming growth factor-beta (TGF-beta) exerts its effects on cell proliferation, differentiation and migration in part through its modulation of extracellular matrix components, such as fibronectin and plasminogen activator inhibitor-1 (PAI-1). Although the SMAD family of proteins recently has been shown to be a key participant in TGF-beta signaling, other signaling pathways have also been shown to be activated by TGF-beta. We report here that c-Jun N-terminal kinase (JNK), a member of the MAP kinase family, is activated in response to TGF-beta in the human fibrosarcoma HT1080-derived cell line BAHgpt. Stable expression of dominant-negative forms of JNK1 and MKK4, an upstream activator of JNK, results in loss of TGF-beta-stimulated fibronectin mRNA and protein induction, while having little effect on TGF-beta-induced levels of PAI-1. The human fibronectin promoter contains three CRE elements, one of which has been shown to bind a c-Jun-ATF-2 heterodimer. Utilizing a GAL4 fusion trans-reporting system, we demonstrate a decrease in transactivating potential of GAL4-c-Jun and GAL4-ATF-2 in dominant-negative JNK1- and MKK4-expressing cells. Finally, we show that TGF-beta-induced fibronectin synthesis is independent of Smad4. These results demonstrate that TGF-beta-mediated fibronectin induction requires activation of JNK which in turn modulates the activity of c-Jun and ATF-2 in a Smad4independent manner.

Microtubule involvement in translational regulation of fibronectin expression by light chain 3 of microtubule-associated protein 1 in vascular smooth muscle cells

Our previous studies suggested that enhanced fibronectin mRNA translation in ductus arteriosus compared with aortic smooth muscle cells is related to increased expression of light chain 3 (LC3) of microtubule-associated protein 1, which binds an AU-rich element in the 3' untranslated region of fibronectin mRNA. We therefore hypothesized that microtubules are involved in LC3-mediated fibronectin mRNA translational regulation. In this study we show that disruption of microtubules by colchicine inhibits fibronectin mRNA translation in cultured ductus arteriosus smooth muscle cells. We proposed that the mechanism might be related to decreased docking of fibronectin mRNA on the translational machinery, ie, membrane-bound polysomes on rough endoplasmic reticulum, and confirmed this by Northern blot analysis. To investigate the mechanism further, we carried out polysome analysis using sucrose gradient centrifugation and fractionation and studied the polysomal distribution of fibronectin mRNA and LC3 protein in the sucrose gradient by using RNase protection assay and Western immunoblotting, respectively. Colchicine treatment shifts fibronectin mRNA from the fractions containing membrane-bound polysomes to the fractions carrying free polysomes and concomitantly decreases the amount of LC3 protein in the fractions containing membrane-bound polysomes. Furthermore, an EDTA-release experiment demonstrates that LC3 protein associates with the 60S ribosomal subunit. Our data support the concept that microtubules may function with LC3 to facilitate sorting of fibronectin mRNA onto rough endoplasmic reticulum and translation.

Regulation of CD44 gene expression by the proinflammatory cytokine interleukin-1beta in vascular smooth muscle cells

The CD44 gene codes for a family of alternatively spliced, multifunctional adhesion molecules that participate in extracellular matrix binding, lymphocyte activation, cell migration, and tumor metastasis. In a mouse model of transplant-associated arteriosclerosis, CD44 protein was induced in the neointima of allografted vessels and colocalized with a subset of proliferating vascular smooth muscle cells (SMC). To elucidate the molecular mechanisms regulating CD44 expression in this model, we investigated the regulation of CD44 gene expression by interleukin (IL)-1beta. Treatment of rat aortic SMC with IL-1beta resulted in a 5.3-fold increase in cell surface CD44 expression. Northern analysis showed that IL-1beta promoted a dose- and time-dependent induction of CD44 mRNA which reached 6.6-fold after 48 h, and nuclear run-on analysis showed that IL-1beta increased the rate of CD44 gene transcription within 8 h of stimulation. In transient reporter gene transfection experiments in rat aortic SMC, a 1.4-kilobase fragment of the mouse CD44 5'-flanking sequence mediated this response to IL-1beta. Regulation of CD44 gene expression by the proinflammatory cytokine IL-1beta may contribute to SMC phenotypic modulation in the pathogenesis of arteriosclerosis.

The 67-kDa enzymatically inactive alternatively spliced variant of beta-galactosidase is identical to the elastin/laminin-binding protein

Our previous studies showed immunological and functional similarities, as well as partial sequence homology, between the enzymatically inactive alternatively spliced variant of human beta-galactosidase (S-gal) and the 67-kDa elastin/laminin-binding protein (EBP) from sheep. To define the genetic origin of the EBP further, a full-length human S-gal cDNA clone was constructed and subjected to in vitro transcription/translation. The cDNA was also transfected into COS-1 cells and into the EBP-deficient smooth muscle cells (SMC) from sheep ductus arteriosus (DA). In vitro translation yielded an unglycosylated form of the S-gal protein, which immunoreacted with anti-beta-galactosidase antibodies and bound to elastin and laminin affinity columns. S-gal cDNA transfections into COS-1 and DA SMC increased expression of a 67-kDa protein that immunolocalized intracellularly and to the cell surface and, when extracted from the cells, bound to elastin. The S-gal-transfected cells displayed increased adherence to elastin-covered dishes, consistent with the cell surface distribution of the newly produced S-gal-encoded protein. Transfection of DA SMC additionally corrected their impaired elastic fiber assembly. These results conclusively identify the 67-kDa splice variant of beta-galactosidase as EBP.

Cell-extracellular matrix interactions in the ductus arteriosus and perinatal pulmonary circulation

Our studies and those of others have shown that changes in the extracellular matrix have profound effects on vascular remodeling. In the ductus, increased production of endothelial hyaluronan and smooth muscle cell chondroitin sulfate and fibronectin and impaired elastin fiber assembly are features critical to smooth muscle cell migration into the subendothelium and intimal cushion formation. There is a developmentally orchestrated process that involves post-transcriptional mechanisms of gene regulation. Closure of the ductus arteriosus is associated with further changes in matrix expression and programmed cell death. The changes in the extracellular matrix that induce neointimal formation are also observed in pathological conditions in pulmonary and coronary arteries. Plasticity of the pulmonary circulation in the perinatal period also involves matrix regulation, and processes that prevent the normal decrease in pulmonary vascular resistance will result in impaired matrix regulation, and in the development of structural changes in the pulmonary arteries, including abnormal smooth muscle cell differentiation, hypertrophy and proliferation, which sustain the elevation in pulmonary artery pressure.

Elafin, a serine elastase inhibitor, attenuates post-cardiac transplant coronary arteriopathy and reduces myocardial necrosis in rabbits afer heterotopic cardiac transplantation

We have related experimentally induced post-cardiac transplant coronary arteriopathy to increased elastolytic activity, IL-1beta, fibronectin-mediated inflammatory and smooth muscle cell (SMC) migration, and SMC proliferation. Since our in vitro studies show that a serine elastase releases SMC mitogens and facilitates IL-lbeta induction of fibronectin, we hypothesized that administration in vivo of the specific serine elastase inhibitor, elafin, would decrease the post-cardiac transplant coronary arteriopathy. Cholesterol-fed rabbits underwent a heterotopic cardiac transplant without immunosuppression and received elafin (1.79 mg/kg per d continuous infusion after a 9 mg bolus, n = 6) or vehicle (n = 6). 1 wk later, hearts were harvested for morphometric, immunohistochemical, and biochemical analyses. A > 70% decrease in the total number of coronary arteries with intimal thickening in elafin-treated compared to control donor hearts (P < 0.002) was associated with reduced vascular elastolytic activity judged by fewer breaks in the internal elastic lamina (P < 0.03), less accumulation of immunoreactive fibronectin (P < 0.02), and reduced cell proliferation quantified by proliferating cell nuclear antigen (P < 0.0001). Despite myocardial lymphocytic infiltration, wet weight of elafin-treated donor hearts was reduced by 50% compared to untreated controls (P < 0.002) and associated with relative preservation of myocyte integrity, instead of extensive myocardial necrosis (P < 0.004). This protective effect correlated with decreased myocardial elastolytic activity (P < 0.0001) and inflammatory cell proliferation (P < 0.0001) and with an elafin-inhibitable elastase in lymphocytes. Serine elastase activity thus appears an important therapeutic target for post-cardiac transplant coronary arteriopathy and myocardial necrosis induced by rejection.

Elastase and cell matrix interactions in the pathobiology of vascular disease

Ultrastructural observations in lung tissue implicated an endogenous vascular elastase (EVE), in the pathobiology of pulmonary vascular disease. In experimental rats, increased activity of a 20 kDa serine proteinase related to adipsin precedes the development of sustained pulmonary hypertension and vascular abnormalities. A further increase in activity is related to malignant progression of the disease. A cause and effect relationship was suggested by studies in which elastase inhibitors successfully prevented or retarded progression of pulmonary hypertension. In vitro studies have shown that both serum and endothelial factors induce EVE via tyrosine kinase intracellular signalling. Induction of EVE can release basic fibroblast growth factor from the extracellular matrix in an active form stimulating smooth muscle cell proliferation. Elastase activity was also observed in the process of smooth muscle cell migration and neointimal formation in coronary arteries following experimental cardiac transplantation. An immune/inflammatory response is observed with increased production of cytokines, tumor necrosis factor-alpha and interleukin (IL)-1 beta, reciprocally up-regulating production of fibronectin, a glycoprotein which mediated smooth muscle cell migration. The action of IL-1 beta in inducing fibronectin is facilitated by the production of elastin peptides generated by increased activity of an elastase in the coronary arteries. Our studies suggest that ligation of the elastin binding protein by elastin peptides unmasks IL-1 receptors. Fibronectin also stimulates transendothelial migration of lymphocytes which perpetuates the inflammatory response leading to neointimal formation in this model. Masking integrins on T cells with a decoy synthetic CS-1 (fibronectin) peptide largely prevented transendothelial migration and coronary neointimal formation following cardiac transplant.

Lymphocyte transendothelial migration toward smooth muscle cells in interleukin-1 beta-stimulated co-cultures is related to fibronectin interactions with alpha 4 beta 1 and alpha 5 beta 1 integrins

We previously reported infiltration of immune-inflammatory cells in coronary arteries from cardiac allografts, associated with increased endothelial and smooth muscle cell fibronectin synthesis regulated by interleukin (IL)-1 beta. We now investigate, using a porcine endothelial-smooth muscle cell co-culture system, whether IL-1 beta-stimulated fibronectin production is functionally important in lymphocyte transendothelial migration. Lymphocytes were harvested from porcine peripheral blood and, in the unactivated state or following activation with phorbol myristic acetate (PMA) and IL-2, were characterized by fluorescence-activated cell sorter (FACS) analysis and added to a confluent endothelial monolayer on the upper chamber of a transwell system. Endothelial cells, as well as smooth muscle cells (in the bottom of the chamber), were stimulated with IL-1 beta. Then transendothelial lymphocyte migration was determined in the presence of CS1 and RGD (fibronectin) peptides, blocking alpha 4 beta 1 and alpha 5 beta 1 integrin receptors on lymphocyte surfaces, respectively. A 55-70% inhibition of lymphocyte migration was observed when compared to control peptides. The combination of CS1 and RGD peptides did not significantly enhance the inhibitory effect of either peptide alone. A similar decrease in lymphocyte transendothelial migration toward smooth muscle cells was documented using a monoclonal antibody to cellular fibronectin. Furthermore, using smooth muscle cell conditioned medium, we reproduced the enhanced transendothelial lymphocyte migration as well as the inhibition with blocking peptides or fibronectin antibodies. Our data suggest that cytokine-mediated fibronectin synthesis in vascular cells recruits inflammatory cells through interactions of specific peptides with cell surface alpha 4 beta 1 and alpha 5 beta 1 integrins.

Abnormalities in intramyocardial arteries detected in cardiac transplant biopsy specimens and lack of correlation with abnormal intracoronary ultrasound or endothelial dysfunction in large epicardial coronary arteries

OBJECTIVES

We sought to determine whether abnormalities in small intramyocardial vessels could be detected on routine cardiac transplant biopsy specimens and whether these features correlate with intimal thickening by intracoronary ultrasound and endothelial dysfunction in large epicardial vessels.

BACKGROUND

Variability in clinical presentation of allograft vasculopathy suggests differential involvement of large and small vessels. Intracoronary ultrasound and endothelial function studies detect large-vessel abnormalities but may not reflect changes in small intramyocardial arteries. The latter could be detected in routine cardiac biopsy specimens by histologic and immunohistochemical studies.

METHODS

Thirty-nine cardiac transplant recipients underwent intracoronary ultrasound and acetylcholine studies 5 to 7 days after endomyocardial biopsy. Biopsy tissue was evaluated for coronary artery endothelial plumping and intimal thickening and increased immunostaining for fibronectin, tumor necrosis factor-alpha and receptor for hyaluronan-mediated motility. Large-vessel disease was assessed by calculating an average intimal index from intracoronary ultrasound of the left anterior descending coronary artery. Endothelial function was determined by quantitative coronary analysis after acetylcholine challenge.

RESULTS

Coronary arteries were found in the biopsy tissue of 30 (76%) of the 39 patients who formed the study group. Fourteen of 30 patients had abnormal histologic findings. Immunohistochemical analysis for fibronectin, possible in 20 of 30 patients, was positive in 14 (70%) of 20 and correlated with abnormal histologic findings (p = 0.01). Immunostaining was positive for tumor necrosis factor-alpha and receptor for hyaluronan-mediated motility in 12 (40%) and 13 (43%) of 30 patients, respectively. All patients had intimal thickening by intracoronary ultrasound, but intimal index did not correlate significantly with small-artery disease by histologic or immunohistochemical analysis. Large-vessel endothelial dysfunction in 13 patients (43%) did not correlate with either abnormal ultrasound findings or small-vessel disease.

CONCLUSIONS

Intramyocardial arteries are readily observed in biopsy specimens from cardiac transplant recipients and provide useful information about allograft vasculopathy. Lack of correlation between intramyocardial and epicardial vessel disease suggests discordant progression of allograft vasculopathy.

Blockade of very late antigen-4 integrin binding to fibronectin with connecting segment-1 peptide reduces accelerated coronary arteriopathy in rabbit cardiac allografts

Graft arteriopathy, a leading cause of cardiac allograft failure, is associated with increased intimal smooth muscle cells, inflammatory cells, and accumulation of extracellular matrix. We hypothesized that cellular fibronectin plays a pivotal role in the progression of the allograft arteriopathy by directing the transendothelial trafficking of inflammatory cells through interaction of the connecting segment-1 (CS1) motif with the very late antigen-4 (VLA-4) integrin, and tested this in vivo using a blocking peptide. Cholesterol-fed rabbits underwent heterotopic cardiac transplantation without immunosuppression. The treatment group (n = 7) received a synthetic CS1 peptide (1 mg/kg per d, subcutaneously), and the controls (n = 7) received an inactive peptide (1 mg/kg per d, subcutaneously). At 7-8 d after transplantation, hearts were harvested and sectioned for morphometric analysis and immunohistochemical studies. We observed a > 50% decrease in the incidence (P < 0.001) and severity (P < 0.001) of donor coronary artery intimal thickening in the CS1-treated compared with the control group. These findings correlated with reduced infiltration of T cells (P < 0.05), a trend toward decreased expression of adhesion molecules (P < 0.06), and less accumulation of fibronectin (P < 0.03). Our data suggest that the VLA-4-fibronectin interaction is critical to the progression of the allograft arteriopathy by perpetuating the immune-inflammatory response in the vessel wall.

ICAM-1 and VCAM-1 expression in accelerated cardiac allograft arteriopathy and myocardial rejection are influenced differently by cyclosporine A and tumour necrosis factor-alpha blockade

Expression of the vascular cell adhesion molecules intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) occurs in allograft myocardium and in coronary arteries, promoting adhesion and transendothelial migration of inflammatory cells. We therefore investigated, in cholesterol-fed rabbits 9-10 days following heterotopic cardiac transplantation, whether the reduction of both myocardial rejection and graft arteriopathy with cyclosporine A (CsA) or graft arteriopathy alone with tumour necrosis factor-alpha soluble receptor (TNFsr) was associated with suppression of ICAM-1 and VCAM-1 expression. Host hearts showed negative immunostaining for these adhesion molecules, whereas donor specimens from untreated (control) rabbits showed moderate immunostaining for ICAM-1 and weaker immunostaining for VCAM-1 in the coronary arteries, myocardium (cardiac myocytes), and perivenular regions. The selective reduction of the coronary arteriopathy with TNFsr was associated with somewhat reduced expression of these adhesion molecules in the arteries, whereas CsA also suppressed myocardial rejection and markedly decreased both vascular and myocyte expression of ICAM-1 and VCAM-1.

Expression of tumour necrosis factor alpha and accumulation of fibronectin in coronary artery restenotic lesions retrieved by atherectomy

BACKGROUND

The formation of coronary artery neointima experimentally induced in piglets after cardiac transplantation is related to an immune-inflammatory reaction associated with increased expression of T cells and inflammatory mediators (tumour necrosis factor alpha and interleukin 1 beta) and upregulation of fibronectin. In vivo blockade of tumour necrosis factor alpha in rabbits after cardiac transplantation results in reduced neointimal formation. The objective of this study was to investigate the hypothesis that coronary restenosis after atherectomy or percutaneous balloon angioplasty is associated with a similar inflammatory cascade initiated by mechanical injury.

METHODS

Specimens taken at coronary atherectomy were analysed from 16 patients. Nine had had the procedure performed twice, firstly, to remove a primary lesion, and secondly, to remove a restenotic lesion. Seven had percutaneous balloon angioplasty after removal of restenotic tissue. Coronary atherectomy specimens were analysed by immunohistochemistry for the presence of T cells, macrophages, major histocompatibility complex II, interleukin 1 beta, tumour necrosis factor alpha, fibronectin, and the receptor for hyaluronan mediated motility.

RESULTS

The groups were clinically and angiographically similar with equivalent lumens before and after atherectomy. Restenotic lesions had increased expression of tumour necrosis factor alpha and fibronectin compared with the primary lesions (P < 0.05 for both). There was also a trend towards a greater number of T cells and increased expression of interleukin 1 beta.

CONCLUSIONS

Restenosis is associated with increased expression of tumour necrosis factor alpha and fibronectin, suggesting that an immune-inflammatory reaction probably contributes to neointimal formation and may represent a form of wound healing and repair secondary to mechanical injury.