Endovascular Injury Research Articles

The Aryl Hydrocarbon Receptor is a Critical Regulator of Tissue Factor Stability and an Antithrombotic Target in Uremia.

Patients with CKD suffer high rates of thrombosis, particularly after endovascular interventions, yet few options are available to improve management and reduce thrombotic risk. We recently demonstrated that indoxyl sulfate (IS) is a potent CKD-specific prothrombotic metabolite that induces tissue factor (TF) in vascular smooth muscle cells (vSMCs), although the precise mechanism and treatment implications remain unclear. Because IS is an agonist of the aryl hydrocarbon receptor (AHR), we first examined the relationship between IS levels and AHR-inducing activity in sera of patients with ESRD. IS levels correlated significantly with both vSMC AHR activity and TF activity. Mechanistically, we demonstrated that IS activates the AHR pathway in primary human aortic vSMCs, and further, that AHR interacts directly with and stabilizes functional TF. Antagonists directly targeting AHR enhanced TF ubiquitination and degradation and suppressed thrombosis in a postinterventional model of CKD and endovascular injury. Furthermore, AHR antagonists inhibited TF in a manner dependent on circulating IS levels. In conclusion, we demonstrated that IS regulates TF stability through AHR signaling and uncovered AHR as an antithrombotic target and AHR antagonists as a novel class of antithrombotics. Together, IS and AHR have potential as uremia-specific biomarkers and targets that may be leveraged as a promising theranostic platform to better manage the elevated thrombosis rates in patients with CKD.

Multi-selective catheter for MR-guided endovascular interventions

Selective catheters have predefined distal shapes and need to be exchanged to change tip geometry to facilitate selective catheterization of vascular side branches. These repeated insertions increase the risk of endovascular injury and radiation dose in conventional catheterization laboratories.The aim of this study is to develop a multi-selective catheter that can replace three conventional selective catheters that are commonly used sequentially in a single procedure. By integrating the different shapes in one instrument, it is possible to avoid the required time-consuming exchange. This new instrument is also made compatible with magnetic resonance imaging (MRI) guidance, which, unlike X-ray, presents variable soft tissue contrast without the use of ionizing radiation.A 1.2 m long and 2.15 mm diameter deflectable polymer-based catheter was assembled and three widely used selective catheters could be mimicked. The instrument was visible on the images without producing unwanted artifacts in an abdominal model and in an animal under real-time MRI guidance. Simple navigation tasks were performed together with a 0.035 in. MRI-safe guidewire. In these tasks, the iliac, renal, brachiocephalic, and left subclavian arteries were cannulated only by using the shape setting and without exchange of the instruments.

Valproic acid ameliorates ischemic brain injury in hyperglycemic rats with permanent middle cerebral occlusion

Valproic acid (VPA) is widely used for the clinical treatment of epilepsy. Previous studies have demonstrated that VPA ameliorates brain injury following experimental stroke. However, the effect of VPA in stroke models featuring comorbid conditions has not been fully explored. In this study, we investigate the effects of VPA on permanent ischemic stroke with hyperglycemia. Hyperglycemia was induced by streptozotocin (STZ) injection 3 days before. Test animals received a single injection of VPA immediately after induction of ischemia. Control animals received occlusion and physiological saline injection, or STZ, occlusion, and saline. Magnetic resonance imaging of cerebral blood flow (CBF) and apparent diffusion coefficient (ADC) was performed 60min after ischemia. Infarct volume, neurological deficits, rotarod test performance, and immunohistological markers were assessed 3 days after ischemia. Hyperglycemia significantly expanded the area of decreased of CBF and ADC, and increased the number of myeloperoxidase-positive cells, ionized calcium binding adapter molecule 1-positive cells, inducible nitric oxide synthase-positive cells, von Willebrand factor-positive cells, and Fluoro-Jade C-positive cells in the ischemic boundary zone, which was accompanied by increased infarct volume and deteriorated neurological deficit and rotarod test compared with normoglycemia (P<0.05). VPA significantly alleviated the aggravation of functional outcome accompanied by suppressing these inflammation, endothelial injury, and neuronal degeneration compared with saline-treated group (P<0.05). A single injection of VPA following permanent ischemia in STZ-induced hyperglycemic rats ameliorates neurological deficits and reduces neuronal degeneration by inhibiting inflammation and endovascular injury. VPA may be promising as a candidate therapy for human stroke.

Reduction of endoplasmic reticulum stress inhibits neointima formation after vascular injury

Endoplasmic reticulum (ER) stress and inappropriate adaptation through the unfolded protein response (UPR) are predominant features of pathological processes. However, little is known about the link between ER stress and endovascular injury. We investigated the involvement of ER stress in neointima hyperplasia after vascular injury. The femoral arteries of 7-8-week-old male mice were subjected to wire-induced vascular injury. After 4 weeks, immunohistological analysis showed that ER stress markers were upregulated in the hyperplastic neointima. Neointima formation was increased by 54.8% in X-box binding protein-1 (XBP1) heterozygous mice, a model of compromised UPR. Knockdown of Xbp1 in human coronary artery smooth muscle cells (CASMC) in vitro promoted cell proliferation and migration. Furthermore, treatment with ER stress reducers, 4-phenylbutyrate (4-PBA) and tauroursodeoxycholic acid (TUDCA), decreased the intima-to-media ratio after wire injury by 50.0% and 72.8%, respectively. Chronic stimulation of CASMC with PDGF-BB activated the UPR, and treatment with 4-PBA and TUDCA significantly suppressed the PDGF-BB-induced ER stress markers in CASMC and the proliferation and migration of CASMC. In conclusion, increased ER stress contributes to neointima formation after vascular injury, while UPR signaling downstream of XBP1 plays a suppressive role. Suppression of ER stress would be a novel strategy against post-angioplasty vascular restenosis.

Deficiency of Long Pentraxin PTX3 Promoted Neointimal Hyperplasia after Vascular Injury.

Pentraxin 3 (PTX3) is a novel marker for the primary local activation of innate immunity and inflammatory responses. Although clinical and experimental evidence suggests that PTX3 is associated with atherosclerosis, the relationship between PTX3 and vascular remodeling after wall injury remains to be determined. We investigated the effects of PTX3 on neointimal hyperplasia following wire vascular injury. PTX3 systemic knockout (PTX3-KO) mice and wild-type littermate (WT) mice were subjected to wire-mediated endovascular injury. At four weeks after wire-mediated injury, the areas of neointimal and medial hyperplasia were evaluated. The PTX3-KO mice exhibited higher hyperplasia/media ratios than the WT mice after wire injury, and the degree of Mac-3-positive macrophage accumulation was significantly higher in the PTX3-KO mice than in the WT mice. Furthermore, the PTX3-KO mice showed a much greater increase in the number of PCNA-stained cells in the vascular wall than that observed in the WT mice. A deficiency of PTX3 results in deteriorated neointimal hyperplasia after vascular injury via the effects of macrophage accumulation and vascular smooth muscle cell proliferation and migration.

Phosphodiesterase type 4 blockade prevents platelet-mediated neutrophil recruitment at the site of vascular injury.

Platelet-neutrophil interactions play a key role in cardiovascular disease and inflammatory processes. Src family kinases mediate P-selectin glycoprotein ligand-1-Mac-1 cross talk necessary for firm platelet-neutrophil adhesion. Because Src family kinase activity can be regulated by cAMP-dependent pathways, in this work, we evaluated the role of phosphodiesterases in the signaling events that are required to sustain platelet-neutrophil interactions and neutrophil recruitment at the site of vascular injury. In neutrophils exposed to P-selectin, selective phosphodiesterase 4 (PDE4) inhibition prevented Src family kinase-mediated phosphorylation of the proline-rich tyrosine kinase 2 on Tyr579/Tyr580. The effects of PDE4 inhibition required protein kinase A, likely through protein kinase A-mediated activation of COOH-terminal Src kinase, a major negative regulator of Src family kinases. PDE4, but not other phosphodiesterase inhibitors, reduced platelet-neutrophil conjugates as well as neutrophil firm adhesion on spread platelets under flow conditions. The effect of PDE4 inhibition on neutrophil adhesion was primarily mediated by downregulation of P-selectin-induced activation of Mac-1. In a murine model of endovascular injury, selective inhibition of PDE4 significantly reduced neutrophil recruitment at the site of vascular damage. This study identifies PDE4 as a central node in the signaling network that mediates platelet-neutrophil adhesion and suggests that pharmacological inhibition of PDE4 may represent a novel therapeutic avenue for the treatment of cardiovascular disease.

Mechanism of matrix metalloproteinase axis-induced neointimal growth

Tumor necrosis factor-α, platelet-derived growth factor, matrix metalloproteinases 9 and 2 have very important roles in neointimal hyperplasia, which develops after endovascular injury. However, the relationships among the four factors in inducing neointimal hyperplasia are unclear. Here, we used a mouse model of femoral arterial transluminal wire injury, and examined neointimal hyperplasia within the 28days that followed the injury. We confirmed that the neointima kept growing during the 28days, and found that expression of TNF-α and PDGF mRNAs in femoral arteries peaked within 24h after injury. However, MMP9 mRNA expression peaked 7days, and MMP2 mRNA expression peaked 28days after injury. Then, we administered exogenous TNF-α or PDGF to the peri-femoral artery following an injury, and found that exogenous TNF-α led to significantly more neointimal hyperplasia during the first 2weeks, and PDGF led to increased neointimal hyperplasia during the second 2weeks after injury. We also used the model of femoral artery injury in MMP9- or MMP2-deficient (MMP9−/− or MMP2−/−) mice. We found that neointimal hyperplasia was reduced in MMP9−/− mice during the first 2weeks after injury, and neointimal hyperplasia was reduced in MMP2−/− mice during the second 2weeks after injury. When TNF-α or PDGF was administered to the peri-femoral artery immediately after injury, TNF-α did not promote neointimal hyperplasia in MMP9−/− mice during the first 2weeks after injury but did in MMP2−/− mice, and PDGF did not promote neointimal hyperplasia in MMP2−/− mice during the second 2weeks after injury but did in MMP9−/− mice. We used an in vitro system to treat vascular smooth muscle cells (VSMCs) with TNF-α or PDGF; TNF-α induced MMP9, but not MMP2, expression at a fast reaction speed, while PDGF induced MMP2, but not MMP9, expression at a slow reaction speed. Meanwhile, TNF-α induced VSMC migration in a MMP9-dependent manner, and PDGF induced VSMC proliferation in a MMP2-dependent manner. Taken together, our studies elucidated the axis of TNF-α-MMP9-VSMC migration and PDGF-MMP2-VSMC proliferation, both of which contributed to the mechanism of neointimal hyperplasia formation.

The Transcription Factor E26 Transformation–Specific Sequence-1 Mediates Neointima Formation in Arteriovenous Fistula

Hemodialysis vascular access dysfunction contributes to increased morbidity and mortality in hemodialysis patients. Arteriovenous fistula (AVF) is the preferred type of vascular access for hemodialysis but has high rates of dysfunction, in part because of excessive neointima formation. The transcription factor E26 transformation-specific sequence-1 (ETS-1) is a mediator of proinflammatory responses in hypertension and endovascular injury. We examined the role of ETS-1 in the formation of neointima in AVF. Right carotid artery to internal jugular vein fistulas were created in C57BL/6 mice and assigned to treatment with an ETS-1-dominant negative peptide (ETS-DN), an inactive mutant peptide (ETS-MU), or vehicle (n=6 per group). After 7 and 21 days, AVFs or contralateral internal jugular veins were processed for PCR, immunofluorescence, immunohistochemistry, and morphometry. In AVFs, ETS-1 mRNA increased 2.5-fold at 7 days and 4-fold at 21 days. By immunofluorescence, we confirmed increased expression of ETS-1 predominantly in the neointima and overlying endothelium. Similarly, ETS-1 expression increased in human AVFs compared with normal veins. In mice, ETS-DN, but not ETS-MU, reduced neointima formation at days 7 and 21 and reduced the expression of nitric oxide synthase 2, NADPH oxidase (NOX) 2, NOX4, E-selectin, and monocyte chemotactic protein-1. Shear stress increased ETS-1 phosphorylation in human umbilical vein cells in a NOX-dependent manner, demonstrating a role for reactive oxygen species in ETS-1 activation. These results unveil the role of ETS-1 as a mediator of neointima formation in AVF and may result in the development of novel strategies for the treatment of AVF dysfunction.

Perivascular adipose tissue-secreted angiopoietin-like protein 2 (Angptl2) accelerates neointimal hyperplasia after endovascular injury

Much attention is currently focused on the role of perivascular adipose tissue in development of cardiovascular disease (CVD). Some researchers view it as promoting CVD through secretion of cytokines and growth factors called adipokines, while recent reports reveal that perivascular adipose tissue can exert a protective effect on CVD development. Furthermore, adiponectin, an anti-inflammatory adipokine, reportedly suppresses neointimal hyperplasia after endovascular injury, whereas such vascular remodeling is enhanced by pro-inflammatory adipokines secreted by perivascular adipose, such as tumor necrosis factor-α (TNF-α). These findings suggest that extent of vascular remodeling, a pathological process associated with CVD development, depends on the balance between pro- and anti-inflammatory adipokines secreted from perivascular adipose tissue. We previously demonstrated that angiopoietin-like protein 2 (Angptl2), a pro-inflammatory factor secreted by adipose tissue, promotes adipose tissue inflammation and subsequent systemic insulin resistance in obesity. Here, we examined whether Angptl2 secreted by perivascular adipose tissue contributes to vascular remodeling after endovascular injury in studies of transgenic mice expressing Angptl2 in adipose tissue (aP2-Angptl2 transgenic mice) and Angptl2 knockout mice (Angptl2−/− mice). To assess the role of Angptl2 secreted by perivascular adipose tissue on vascular remodeling after endovascular injury, we performed adipose tissue transplantation experiments using these mice. Wild-type mice with perivascular adipose tissue derived from aP2-Angptl2 mice exhibited accelerated neointimal hyperplasia after endovascular injury compared to wild-type mice transplanted with wild-type tissue. Conversely, vascular inflammation and neointimal hyperplasia after endovascular injury were significantly attenuated in wild-type mice transplanted with Angptl2−/− mouse-derived perivascular adipose tissue compared to wild-type mice transplanted with wild-type tissue. RT-PCR analysis revealed that mouse Angptl2 expression in perivascular adipose tissue was significantly increased by aging, hypercholesterolemia, and endovascular injury, all risk factors for coronary heart disease (CHD). Immunohistochemical and RT-PCR analysis of tissues from patients with CHD and from non-CHD patients indicated that ANGPTL2 expression in epicardial adipose tissue was unchanged. Interestingly, that analysis also revealed a positive correlation in ANGPTL2 and ADIPONECTIN expression in epicardial adipose tissue of non-CHD patients, a correlation not seen in CHD patients. However, in epicardial adipose tissue from CHD patients, ANGPTL2 expression was positively correlated with that of TNF-α, a correlation was not seen in non-CHD patients. These findings suggest that pro-inflammatory adipokines cooperatively accelerate CHD development and that maintaining a balance between pro- and anti-inflammatory adipokines likely protects non-CHD patients from developing CHD. Overall, our studies demonstrate that perivascular adipose tissue-secreted Angptl2 accelerates vascular inflammation and the subsequent CVD development.

Exendin-4, a glucagon-like peptide-1 receptor agonist, attenuates neointimal hyperplasia after vascular injury

Exendin-4 is a glucagon-like peptide-1 receptor agonist that has been used as a drug for treatment of type 2 diabetes. To investigate the effect of exendin-4 on the cardiovascular system, we investigated the impact of exendin-4 on neointimal hyperplasia of the femoral artery after vascular injury. We performed wire-mediated endovascular injury in C57BL/6 mice, followed by administration of exendin-4 24nmol/kg/day via infusion pump. Four weeks after the injury, exendin-4 treatment significantly attenuated neointimal hyperplasia of the injured artery, although it did not affect glucose metabolism and lipid profile in wild-type mice. Immunofluorescence study revealed abundant expression of GLP-1 receptor on α-smooth muscle actin-positive cells in the injured vessel. Cell proliferation assay using rat aortic smooth muscle cells showed that exendin-4 reduced PDGF-BB induced smooth muscle cell proliferation through the cAMP/PKA pathway. Exendin-4 also inhibited TNFα production by peritoneal macrophages in response to inflammatory stimulus. Our findings indicate that a GLP-1 receptor agonist attenuated neointimal formation after vascular injury. GLP-1 receptor agonists or drugs that raise endogenous GLP-1 level might be effective in the treatment of vascular diseases.

High-Resolution Optical Mapping of Inflammatory Macrophages Following Endovascular Arterial Injury

Inflammation following arterial injury mediates vascular restenosis, a leading cause of cardiovascular morbidity. Here we utilize intravital microscopy (IVM) and a dextran-coated nanosensor to spatially map inflammatory macrophages in vivo following endovascular injury of murine carotid arteries. C57Bl/6 mice (n = 23) underwent endovascular guidewire carotid arterial injury. At day 14 or day 28 post-injury, mice underwent fluorescence IVM, 24h after injection with the near-infrared fluorescent macrophage nanosensor CLIO-VT680. Adventitial collagen was concomitantly imaged using second harmonic generation (SHG) IVM. Correlative fluorescence microscopy and immunohistochemistry were performed. Two-plane IVM reconstructions detected macrophage inflammation in the arterial wall that was elevated at day 14 compared to day 28 animals (P < 0.05). SHG-based collagen imaging of the outer arterial wall facilitated analysis of the macrophage-rich, inflamed neointima. Histological analyses and fluorescence microscopy data demonstrated increased macrophage infiltration in day 14 compared to day 28 neointima. We demonstrate that the macrophage response to arterial injury can be imaged in vivo using IVM-based molecular imaging, and shows a higher macrophage influx at day 14 compared to day 28 post-injury.

The role of perivascular adipose tissue in vascular smooth muscle cell growth

Adipose tissue is the largest endocrine organ, producing various adipokines and many other substances. Almost all blood vessels are surrounded by perivascular adipose tissue (PVAT), which has not received research attention until recently. This review will discuss the paracrine actions of PVAT on the growth of underlying vascular smooth muscle cells (VSMCs). PVAT can release growth factors and inhibitors. Visfatin is the first identified growth factor derived from PVAT. Decreased adiponectin and increased tumour necrosis factor-α in PVAT play a pathological role for neointimal hyperplasia after endovascular injury. PVAT-derived angiotensin II, angiotensin 1-7, reactive oxygen species, complement component 3, NO and H(2) S have a paracrine action on VSMC contraction, endothelial or fibroblast function; however, their paracrine actions on VSMC growth remain to be directly verified. Factors such as monocyte chemoattractant protein-1, interleukin-6, interleukin-8, leptin, resistin, plasminogen activator inhibitor type-1, adrenomedullin, free fatty acids, glucocorticoids and sex hormones can be released from adipose tissue and can regulate VSMC growth. Most of them have been verified for their secretion by PVAT; however, their paracrine functions are unknown. Obesity, vascular injury, aging and infection may affect PVAT, causing adipocyte abnormality and inflammatory cell infiltration, inducing imbalance of PVAT-derived growth factors and inhibitors, leading to VSMC growth and finally resulting in development of proliferative vascular disease, including atherosclerosis, restenosis and hypertension. In the future, using cell-specific gene interventions and local treatments may provide definitive evidence for identification of key factor(s) involved in PVAT dysfunction-induced vascular disease and thus may help to develop new therapies. This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Magnoliae Cortex inhibits intimal thickening of carotid artery through modulation of proliferation and migration of vascular smooth muscle cells

Endovascular injury leads to proliferation and migration of vascular smooth muscle cells from the media to the intima leading to the intimal thickening. The objective of this study was to examine the effect of Magnoliae Cortex extract (MOE) on intimal thickening of rat carotid artery injured by balloon endothelial denudation. MOE was administered orally using gastric sonde at three different doses MOE200 (200mg/kg), MOE400 (400mg/kg), and MOE800 (800mg/kg) for 14days from the day of balloon injury. Also, in vitro assays of proliferation, migration and expression of matrix metalloproteinase-2 (MMP-2) in human aortic smooth muscle cells (HASMCs) were carried out using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, transwell boyden chamber method and gelatin zymography, respectively. Oral administration of MOE400 and MOE800 for 14days significantly inhibited intimal area, intimal/medial ratio (I/M), stenosis rate, expression of proliferating cell nuclear antigen (PCNA), MMP-2, and -9 in denudated rat carotid artery. Our in vitro assays revealed that MOE dose dependently inhibited proliferation, migration and expression of MMP-2 in HASMCs. Thus, the results suggest that MOE can be considered as a therapeutic value in the prevention of atherosclerosis because restenosis after percutaneous transluminal coronary angioplasty (PTCA) is supposed to be ‘accelerated atherosclerosis’.

5-Fluorouracil-based therapy induces endovascular injury having potential significance to development of clinically overt cardiotoxicity

This study aimed to elucidate the influence of 5-fluorouracil (5-FU)-based therapy on the vascular endothelium and its association with 5-FU-induced heart ischemia. The study prospectively accrued patients (n=106) having completely resected colorectal cancer and receiving adjuvant treatment with 5-FU, folinic acid, and oxaliplatin. The levels of plasma von Willebrand factor (vWf), urine albumin-to-creatinine ratio (UACR), coagulation factor II+VII+X, and fibrin D-dimer were serially assessed before, during, and after chemotherapy. The vWf level increased from median (range) 1.43 kU/l (0.48 to >3) to 2.64kU/l (0.23 to >3) (P=0.001), the UACR increased from 1.1±0.2mg/mmol (mean±SE) to 2.1±0.3mg/mmol (P=0.001), the coagulation factor II+VII+X activity decreased from 1.00±0.02 to 0.94±0.02U/l (P=0.001), and the fibrin D-dimer level increased from 1.1±0.2 to 2.1±0.3kU/l (P=0.001) at baseline and during chemotherapy, respectively. The changes in the levels of vWf (P=0.3), UACR (P=0.8), coagulation factor II+VII+X (P=0.8), and fibrin D-dimer (P=0.6) in nine (8.5%) patients having clinical signs of cardiotoxicity were not significantly different from that of the patients not having cardiotoxicity. The 5-FU-induced rise in plasma biomarkers was not significantly related to the cardiovascular morbidity or its risk factors (P=0.9). 5-FU therapy induces global reversible endothelial injury leading to a procoagulant state. The ensuing endothelial dysfunction may be of significance to the pathogenesis of 5-FU-induced clinically overt cardiotoxicity. Cardiovascular disease is not significant for the vulnerability of the endothelium to 5-FU-based chemotherapy.

Expressão gênica de adiponectina no tecido adiposo epicárdico após intervenção coronária percutânea com implante de stent metálico

The classical view of adipose tissue as a passive reservoir for energy storage is no longer valid. In the past decade, adipose tissue has been shown to have endocrine functions and the most abundant peptide secreted by adipocytes is adiponectin. Pericardial adipose tissue (PAT) is distributed around coronary arteries and endovascular injury, caused by the presence of intracoronary bare-metal stent (BMS), could promote inflammatory changes in the periadvential fat, contributing to vascular restenosis. We sought to determine gene expression of inflammatory mediator in pericardial adipose tissue after bare-metal stent implantation and vascular restenosis that had been referred to operative treatment. Paired samples of PAT were harvested at the time of elective coronary artery bypass surgery (CABG) in 11 patients (n = 22), one sample was obtained of the tissue around BMS area and another sample around coronary artery without stent. Local expression of adiponectin was determined by real-time polymerase chain reaction (RT-PCR) using Taq DNA polymerase. In two samples, there was no gene expression of adiponectin. We are able to identify adiponectin in 20 samples, however, the pattern of gene expression were heterogeneous.We did not notice specificity when we compared PAT obtained near BMS area or far from BMS area. There were no correlation between adiponectin gene expression and presence of BMS.

Cardiac allograft vasculopathy: do adipocytes bridge alloimmune and metabolic risk factors?

Cardiac allograft vasculopathy (CAV) is still a major cause of chronic graft failure. CAV develops in the coronary arteries as a diffuse, concentric expansion of the intima in conjunction with inflammation and fibrosis of the adventitia. We review recent publications that could link metabolic and immunologic risk factors for CAV.A concept is offered that periarterial adipocytes may provide proinflammatory cytokines that augment immune injury of the coronary arteries. Clinical and experimental evidence indicate that some alloantibodies and autoantibodies are associated with CAV. Limited data are available on the expression of target antigens on coronary arteries at different times after transplantation. Perivascular adipose tissue is an abundant source of IL-6, IL-8 and MCP-1. Adding to the inflammatory bias, perivascular adipocytes secrete less of the anti-inflammatory adiponectin in comparison to other types of fat. Adiponectin modulates expression of adhesion molecules on the vascular endothelium. It also decreases neointimal formation in arteries following mechanical endovascular injury. Alterations in the balance between proinflammatory and anti-inflammatory cytokines secreted by perivascular fat have been implicated in atherosclerosis and restenosis. This imbalance may also augment the immune responses in the coronary arteries of transplanted hearts.

Endovascular Injury Induces Rapid Phenotypic Changes in Perivascular Adipose Tissue

Accumulating evidence suggests that adipose tissue not only stores energy but also secretes various bioactive substances called adipocytokines. Periadventitial fat is distributed ubiquitously around arteries throughout the body. It was reported that inflammatory changes in the periadventitial fat may have a direct role in the pathogenesis of vascular diseases accelerated by obesity. We investigated the effect of endovascular injury on the phenotype of perivascular fat. Endovascular injury significantly upregulated proinflammatory adipocytokines and downregulated adiponectin within periadventitial fat tissue in models of mouse femoral artery wire injury and rat iliac artery balloon injury. Genetic disruption of tumor necrosis factor (TNF)-alpha attenuated upregulation of proinflammatory adipocytokine expression, with reduced neointimal hyperplasia after vascular injury. Local delivery of TNF-alpha to the periadventitial area enhanced inflammatory adipocytokine expression, which was associated with augmented neointimal hyperplasia in TNF-alpha-deficient mice. Conditioned medium from a coculture of 3T3-L1 and RAW264 cells stimulated vascular smooth muscle cell proliferation. An anti-TNF-alpha neutralizing antibody in the coculture abrogated the stimulating effect of the conditioned medium. Our findings indicate that endovascular injury induces rapid and marked changes in perivascular adipose tissue, mainly mediated by TNF-alpha. It is suggested that the phenotypic changes in perivascular adipose tissue may have a role in the pathogenesis of neointimal hyperplasia after angioplasty.

Abstract 5169: Endovascular Injury Induces Rapid Phenotypic Changes in Perivascular Adipose Tissue

Background: It was reported that the serum levels of circulating proinflammatory cytokines are increased in overweight people with enhanced accumulation of visceral fat. In contrast to visceral fat, little attention has been paid to the role of perivascular fat in the pathogenesis of obesity-associated diseases. Here, we investigated the effect of endovascular injury on the phenotype of perivascular fat. Methods and Results: First, endovascular injury significantly down-regulated adiponectin and up-regulated proinflammatory adipocytokines, TNF-alpha, IL-6, PAI-1 and MCP-1 within perivascular fat tissue in models of murine femoral artery wire injury and rat iliac artery balloon injury (p&lt;0.05). Second, diet-induced obesity augmented endovascular injury-induced up-regulation of proinflammatory adipocytokines within perivascular fat tissue (p&lt;0.05) and neointimal hyperplasia (p&lt;0.05) compared with standard chow diet in wild-type mice. Third, up-regulation of proinflammatory adipocytokines within perivascular fat by endovascular injury was significantly blunted in TNF-alpha deficient mice (p&lt;0.05). Neointima formation was attenuated in TNF-alpha deficient mice compared with wild-type mice (p&lt;0.05). Furthermore, perivascular delivery of TNF-alpha to the femoral artery using osmotic minipump enhanced endovascular injury-induced up-regulation of proinflammatory adipocy-tokines within perivascular fat (p&lt;0.05) and neointimal hyperplasia (p&lt;0.05) compared with contralateral PBS delivered artery in TNF-alpha deficient mice. Fourth, conditioned medium from the coculture of 3T3L1-derived adipocyte and RAW264 macrophage stimulated rat vascular smooth muscle cells proliferation relative to the control medium from 3T3L1-derived adipocyte (p&lt;0.05). Blockade of TNF-alpha in the co-culture using an anti-TNF-alpha neutralizing antibody reduced the stimulatory activity of the condition medium (p&lt;0.05). Conclusions: Our findings indicate that endovascular injury induces rapid and marked changes in perivascular adipose tissue, mainly mediated by TNF-alpha. It is suggested that the phenotypic changes in perivascular adipose tissue may have a role in the pathogenesis of neointimal hyperplasia after angioplasty.

Abstract 5569: Neointimal Hyperplasia After Mechanical Endovascular Injury is Augmented Through Angiotensin II-mediated Regional Vascular Inflammation via Activation of the JNK Pathway in Angiotensin-converting Enzyme 2-deficient Mice

Background: Angiotensin-converting enzyme 2 (ACE2) is a negative regulator of the renin-angiotensin system, although its role on vascular inflammation and atherosclerosis remains unclear. Methods and Results: Male ACE2-deficient (ACE2 − /y ) and wild-type (ACE2 + /y ) mice underwent wire-mediated endovascular injury in femoral artery. After 4 weeks, the injured artery in ACE2 − /y mice exhibited marked neointimal hyperplasia compared with that in ACE2 + /y mice. The intima/media ratio in the vascular lesion was 1.97±0.31 in ACE2 + /y mice and 2.78±0.49 in ACE2 − /y mice ( P &lt;0.05). There were no significant differences in blood pressure between both mice. In histology, the accumulation of macrophages in lesions was significantly augmented in ACE2 − /y mice. ACE2 protein expression in vascular cells in wild-type mice was detected by immunohistochemistry and western blotting, and the concentration of angiotensin II (Ang-II) in the injured artery was higher in ACE2 − /y mice than in ACE2 + /y mice. In addition, in the injured artery, quantitative mRNA expressions of vascular inflammatory molecules such as VCAM-1, MCP-1, TNF α , and MMP9 were increased more markedly in ACE2 − /y mice. In contrast, an ARB, olmesartan, attenuated the lesion formation and mRNA expressions of these molecules in the injured artery in ACE2 − /y mice. Next, we analyzed phosphorylation status of ERK and JNK in aortic vascular smooth muscle cells (VSMCs), which were derived from ACE2 + /y or ACE2 − /y mice and were stimulated with Ang-II. Although Ang-II increased ERK and JNK phosphorylation in VSMCs of both mice, the increase was greater in VSMCs of ACE2 − /y mice. Moreover, we evaluated which signaling pathway mediated Ang-II-induced upregulation of VCAM-1 and MMP9 in VSMCs. Although an ERK inhibitor PD98059 had no impact on Ang-II-induced upregulation of VCAM-1 and MMP9 mRNA expressions, a JNK inhibitor SP600125 significantly attenuated them, suggesting the central role of the JNK pathway in transducing the impact of Ang-II on vascular inflammation. Conclusions: ACE2 deletion induces marked neointimal formation in femoral artery after vascular injury through Ang-II-mediated regional vascular inflammation via activation of the JNK pathway. ACE2 may confer protection against vascular diseases.

Periadventitial Adipose Tissue Plays a Critical Role in Vascular Remodeling

Obesity is associated with a high incidence of cardiovascular complications. However, the molecular link between obesity and vascular disease is not fully understood. Most previous studies have focused on the association between cardiovascular disease and accumulation of visceral fat. Periadventitial fat is distributed ubiquitously around arteries throughout the body. Here, we investigated the impact of obesity on inflammation in the periadventitial adipose tissue and on lesion formation after vascular injury. High-fat, high-sucrose feeding induced inflammatory changes and decreased adiponectin expression in the periadventitial adipose tissue, which was associated with enhanced neointima formation after endovascular injury. Removal of periadventitial fat markedly enhanced neointima formation after injury, which was attenuated by transplantation of subcutaneous adipose tissue from mice fed on regular chow. Adiponectin-deficient mice showed markedly enhanced lesion formation, which was reversed by local delivery, but not systemic administration, of recombinant adiponectin to the periadventitial area. The conditioned medium from subcutaneous fat attenuated increased cell number of smooth muscle cells in response to platelet derived growth factor-BB. Our findings suggest that periadventitial fat may protect against neointimal formation after angioplasty under physiological conditions and that inflammatory changes in the periadventitial fat may have a direct role in the pathogenesis of vascular disease accelerated by obesity.