Development Of Vascular Remodeling Research Articles

Abstract 9: Involvement of Caveolin-1 in Vascular Remodeling and Inflammation Induced by Angiotensin II

We have recently reported that caveolin-1 (Cav1) enriched membrane microdomains in vascular smooth muscle cells (VSMC) mediate a metalloprotease ADAM17-dependent EGF receptor (EGFR) transactivation, which is linked to vascular remodeling induced by AngII. We have tested our hypothesis that Cav1, a major structural protein of caveolae, plays a critical role for development of vascular remodeling by AngII via regulation of ADAM17 and EGFR. Here, 8 week old male Cav1-/- and control Cav+/+ wild-type mice (WT) were infused with AngII (1 μg/kg/min) for 2 weeks to induce vascular remodeling and hypertension. Upon AngII infusion, histological assessments demonstrated medial hypertrophy and perivascular fibrosis of coronary and renal arteries in WT mice compared with saline-infused control mice. The AngII-infused WT mice also showed a phenotype of cardiac hypertrophy with increased HW/BW ratio (mg/g: 8.0±0.6 vs 5.7±0.7 p<0.01) compared with WT control. In contrast to AngII-infused WT mice, Cav1-/- mice with AngII showed attenuation of vascular remodeling but not cardiac hypertrophy ; HW/BW ratio (8.6±0.5 vs 6.4±0.2 p<0.05). Similar levels of AngII-induced hypertension were observed in both WT and Cav1-/- mice assessed by telemetry (MAP mmHg: 142±9 vs 154±20). In WT mice, Ang II enhanced ADAM17 expression and phospho-Tyr EGFR staining in heart and kidney vasculature. These events were attenuated in vessels from Cav1-/- mice infused with AngII. In addition, IHC analysis revealed less ER stress in heart and kidney vasculature of AngII-infused Cav1-/- mice compared with WT mice. Enhanced Cav1 and VCAM-1 expression were also observed in the aorta from AngII-infused WT mice but not in Cav1-/- aorta. These data suggest that Cav1 and presumably vascular caveolae play critical roles for vascular remodeling and inflammation via induction of ADAM17 and activation of EGFR independent of blood pressure or cardiac hypertrophy regulation.

Noncoding RNAs in smooth muscle cell homeostasis: implications in phenotypic switch and vascular disorders.

Vascular smooth muscle cells (SMC) are a highly specialized cell type that exhibit extraordinary plasticity in adult animals in response to a number of environmental cues. Upon vascular injury, SMC undergo phenotypic switch from a contractile-differentiated to a proliferative/migratory-dedifferentiated phenotype. This process plays a major role in vascular lesion formation and during the development of vascular remodeling. Vascular remodeling comprises the accumulation of dedifferentiated SMC in the intima of arteries and is central to a number of vascular diseases such as arteriosclerosis, chronic obstructive pulmonary disease or pulmonary hypertension. Therefore, it is critical to understand the molecular mechanisms that govern SMC phenotype. In the last decade, a number of new classes of noncoding RNAs have been described. These molecules have emerged as key factors controlling tissue homeostasis during physiological and pathological conditions. In this review, we will discuss the role of noncoding RNAs, including microRNAs and long noncoding RNAs, in the regulation of SMC plasticity.

Abstract 11711: Valproic Acid, a Class [[Unable to Display Character: І]] Histone Deacetylase Inhibitor, Suppresses the Development of Severe Pulmonary Hypertension in Rats

Introduction: Pulmonary hypertension (PH) is a progressive vascular remodeling disease characterized by exuberant cell proliferation, apoptosis resistance, and inflammation that contributes to increased pulmonary arterial resistance. Histone deacetylases (HDACs) and histone acetyltransferases shift acetyl groups from histone and non-histone proteins and enhance gene transcription by post-translational modifications. Valproic acid, a class I HDAC inhibitor, is a widely used antiepileptic drug with low toxicity and also shows supportive efficacy in cancer treatment by inhibiting cancer cell proliferation and inflammation. Hypothesis: We assessed the hypothesis that HDAC inhibition may attenuate excessive cell proliferation and inflammation and improve vascular remodeling in a severe PH rat model. Methods: To compare the development of vascular remodeling, we assessed 6 rats that underwent a single monocrotaline injection, chronic hypoxic exposure, or a combination of both treatments. Valproic acid or vehicle was administered in rats with severe PH induced by the combination method to assess whether valproic acid has the ability to prevent severe PH development in the first 3 weeks or to reverse disease progression at 3-5 weeks. Results: The combination method induced PH of greater severity than that induced by any single stimulation in rats after 3 weeks. Compared with the vehicle-treated rats, valproic acid treatment blocked the elevation of right ventricular systolic pressure and right ventricle hypertrophy index (from 57 ± 3 to 49 ± 3 mmHg and from 46 ± 4 to 37 ± 3 %) in both the first 3 weeks and in the late treatment group (from 75 ± 2 to 61 ± 5mmHg and from 61 ± 7 to 48 ± 3 %, respectively; P < 0.01). Valproic acid attenuated the muscularization ratio of peripheral pulmonary vascular, repressed proliferation and inflammation marker expression (PCNA and ED1), and enhanced apoptosis (cleaved caspase 3) in severe PH rats. Conclusions: These data indicate that a selective HDAC inhibitor may be effective in the treatment of PH.

Activation of angiotensin II type 1 receptor-associated protein exerts an inhibitory effect on vascular hypertrophy and oxidative stress in angiotensin II-mediated hypertension

Activation of tissue angiotensin II (Ang II) type 1 receptor (AT1R) plays an important role in the development of vascular remodelling. We have shown that the AT1R-associated protein (ATRAP/Agtrap), a specific binding protein of AT1R, functions as an endogenous inhibitor to prevent pathological activation of the tissue renin-angiotensin system. In this study, we investigated the effects of ATRAP on Ang II-induced vascular remodelling. Transgenic (Tg) mice with a pattern of aortic vascular-dominant overexpression of ATRAP were obtained, and Ang II or vehicle was continuously infused into Tg and wild-type (Wt) mice via an osmotic minipump for 14 days. Although blood pressure of Ang II-infused Tg mice was comparable with that of Ang II-infused Wt mice, the Ang II-mediated development of aortic vascular hypertrophy was partially inhibited in Tg mice compared with Wt mice. In addition, Ang II-mediated up-regulation of vascular Nox4 and p22(phox), NADPH oxidase components, and 4-HNE, a marker of reactive oxygen species (ROS) generation, was significantly suppressed in Tg mice, with a concomitant inhibition of activation of aortic vascular p38MAPK and JNK by Ang II. This protection afforded by vascular ATRAP against Ang II-induced activation of NADPH oxidase is supported by in vitro experimental data using adenoviral transfer of recombinant ATRAP. These results indicate that activation of aortic vascular ATRAP partially inhibits the Nox4/p22(phox)-ROS-p38MAPK/JNK pathway and pathological aortic hypertrophy provoked by Ang II-mediated hypertension, thereby suggesting ATRAP as a novel receptor-binding modulator of vascular pathophysiology.

The role of disturbed blood flow in the development of pulmonary arterial hypertension: lessons from preclinical animal models

Pulmonary arterial hypertension (PAH) is a progressive pulmonary vasoproliferative disorder characterized by the development of unique neointimal lesions, including concentric laminar intima fibrosis and plexiform lesions. Although the histomorphology of neointimal lesions is well described, the pathogenesis of PAH and neointimal development is largely unknown. After three decades of PAH pathobiology research the focus has shifted from vasoconstriction towards a mechanism of cancer-like angioproliferation. In this concept the role of disturbed blood flow is seen as an important trigger in the development of vascular remodeling. For instance, in PAH associated with congenital heart disease, increased pulmonary blood flow (i.e., systemic-to-pulmonary shunt) is an essential trigger for the occurrence of neointimal lesions and PAH development. Still, questions remain about the exact role of these blood flow characteristics in disease progression. PAH animal models are important for obtaining insight in new pathobiological processes and therapeutical targets. However, as for any preclinical model the pathophysiological mechanism and clinical course has to be comparable to the human disease that it mimics. This means that animal models mimicking human PAH ideally are characterized by: a hit recognized in human disease (e.g., altered pulmonary blood flow), specific vascular remodeling resembling human neointimal lesions, and disease progression that leads to right ventriclular dysfunction and death. A review that underlines the current knowledge of PAH due to disturbed flow is still lacking. In this review we will summarize the current knowledge obtained from PAH animal models associated with disturbed pulmonary blood flow and address questions for future treatment strategies for PAH.

Evidence of synergistic/additive effects of sildenafil and erythropoietin in enhancing survival and migration of hypoxic endothelial cells

Endothelial cell dysfunction is a common event to several pathologies including pulmonary hypertension, which is often associated with hypoxia. As the endothelium plays an essential role in regulating the dynamic interaction between pulmonary vasodilatation and vasoconstriction, this cell type is fundamental in the development of vascular remodeling and increased vascular resistance. We investigated the protective effects of sildenafil, a phosphodiesterase type 5 inhibitor, given in combination with erythropoietin (Epo), as it has been demonstrated that both drugs have antiapoptotic effects on several cell types. Specifically, we examined the viability and angiogenic properties of rat pulmonary artery endothelial cells upon exposure to either 21% or 1% oxygen, in presence of sildenafil (1 and 100 nM) and Epo (5 and 20 U/ml) alone or in combination (1 nM and 20 U/ml). Cell proliferation and viability were analyzed by Trypan blue staining, MTT assay, and Annexin V/propidium iodide stainings. In all assays, the ability of the combination treatment in improving cell viability was superior to that of either drug alone. The angiogenic properties were studied using a migration and a 3D collagen assay, and the results revealed increases in the migration potential of endothelial cells as well as the ability to form tube-like structures in response to sildenafil and the combination treatment. We therefore conclude that both drugs exert protective effects on endothelial cells on hypoxia and that sildenafil enhances the migratory and angiogenic properties, especially in hypoxic conditions. Furthermore, we present evidence of possible additive or synergistic effects of both drugs.

Cross Talk between Autophagy and Apoptosis in Pulmonary Hypertension

Endothelial cell (EC) apoptosis and apoptosis resistant proliferation have been proposed to play crucial roles in the development of featured plexiform lesions in the pathogenesis of pulmonary hypertension (PH). Subsequently, EC injury associated smooth muscle cell (SMC) proliferation facilitates vascular remodeling and eventually leads to narrowed vascular lumen, increased pulmonary vascular resistance, increased pulmonary arterial pressure, and right heart failure. The imbalance between cell death and proliferation occurs in every stage of pulmonary vascular remodeling and pathogenesis of PH, and involves every cell type in the vasculature including, but not limited to ECs, SMCs, and fibroblasts. Despite extensive studies, the detailed cellular and molecular mechanisms on how the transition from initial apoptosis of ECs to apoptosis resistant proliferation on ECs and SMCs remains unclear. Recent knowledge on autophagy, a conservative and powerful regulatory machinery existing in almost all mammalian cells, has shed light on the complex and delicate control on cell fate in the development of vascular remodeling in PH. In this review, we will discuss the recent understandings on how the cross-talk between apoptosis and autophagy regulates cell death or proliferation in PH pathogenesis, particularly in pulmonary vascular remodeling involving ECs and SMCs.

Simvastatin attenuated cerebrovascular cell proliferation in the development of hypertension through Rho/Rho-kinase pathway.

The cerebrovascular remodeling is a prominent feature of hypertension and considered as a major risk of stroke. Statins may suppress the activation of the Rho/Rho-kinase pathway and have pleiotropic actions against the development of vascular remodeling. We hypothesized that the inhibition of the Rho/Rho-kinase pathway by simvastatin during hypertension could recuperate the pathological changes of basilar artery through the downregulation of cell proliferation. To resolve the problem, we used 2-kid, 2-clip rat as a hypertension model and evaluated the effect of simvastatin on the Rho/Rho-kinase pathway. In addition, we assessed the changes of the proliferation rate by CCK-8 assay in basilar artery smooth muscle cells. Our results from this study showed that a continuous increase in the plasma endothelin-1 (ET-1) concentration and the Rho/Rho-kinase activity was positively correlated with changes in blood pressure in the hypertensive rat. Simvastatin ameliorated the upregulated Rho/Rho-kinase activity and cell proliferation during hypertension. Moreover, simvastatin, the RhoA inhibitor C3, and the RhoA-kinase inhibitor Y27632 all attenuated the proliferation rate induced by ET-1 in basilar artery smooth muscle cells via the Rho/Rho-kinase signaling pathway. In conclusion, simvastatin attenuated ET-1-induced proliferation through the Rho/Rho-kinase signaling pathway in hypertensive rat basilar artery, and it may be an excellent reagent to protect vascular remodeling and stroke.

Inflammation and vascular remodeling.

Cardio- and cerebrovascular diseases are the major causes of death worldwide. Accumulating evidence has revealed that inflammation plays a pivotal role in the progression of vascular remodeling and atherosclerosis leading to cardiovascular events. In fact, several inflammatory markers such as a high-sensitivity C-reactive protein have been shown to predict cardiovascular events. In addition, metabolic disorders, including hyperglycemia, hyperinsulinemia, and dyslipidemia, injure the vascular wall and contribute to the development of vascular remodeling. Most of these metabolic stimuli initially impair homeostasis of the cardiovascular system through inflammation with recruitment of leukocytes and increased secretion of adhesion molecules, chemoattractant cytokines, and proinflammatory cytokines from endothelial cells, vascular smooth muscle cells, fibroblasts, and macrophages. In this special issue, we invited front-line researchers and authors to submit original research and review articles that explore the interactions between inflammation and vascular remodeling. Finally, we were able to publish 6 review articles and 6 original research articles that provide pivotal evidence for understanding the pathophysiological roles of inflammation in vascular remodeling on a clinical basis and a molecular basis. The following papers will be useful for establishing treatment strategies to promote worldwide public health.

Effects of Fluid Shear Stress on a Distinct Population of Vascular Smooth Muscle Cells

Vascular smooth muscle cells (SMCs) are a major cell type involved in vascular remodeling. The various developmental origins of SMCs such as neural crest and mesoderm result in heterogeneity of SMCs, which plays an important role in the development of vascular remodeling and diseases. Upon vascular injury, SMCs are exposed to blood flow and subjected to fluid shear stress. Previous studies have shown that fluid shear stress inhibits SMC proliferation. However, the effect of shear stress on the subpopulation of SMCs from specific developmental origin and vascular bed is not well understood. Here we investigated how shear stress regulates human aortic SMCs positive for neural crest markers. DNA microarray analysis showed that shear stress modulates the expression of genes involved in cell proliferation, matrix synthesis, cell signaling, transcription and cytoskeleton organization. Further studies demonstrated that shear stress induced SMC proliferation and cyclin D1, downregulated cell cycle inhibitor p21, and activated Akt pathway. Inhibition of PI-3 kinase blocked these shear stress-induced changes. These results suggest that SMCs with neural crest characteristics may respond to shear stress in a different manner. This finding has significant implications in the remodeling and diseases of blood vessels.

Pathophysiological Response to Hypoxia — From the Molecular Mechanisms of Malady to Drug Discovery: Inflammatory Responses of Hypoxia-Inducible Factor 1α (HIF-1α) in T Cells Observed in Development of Vascular Remodeling

Recent studies have shown that the cellular immune response to the hypoxic microenvironment constructed by vascular remodeling development modulates the resulting pathologic alterations. A major mechanism mediating adaptive responses to reduced oxygen availability is the regulation of transcription by hypoxia-inducible factor 1 (HIF-1). Impairment of HIF-1–dependent inflammatory responses in T cells causes an augmented vascular remodeling induced by arterial injury, which is shown as prominent neointimal hyperplasia and increase in infiltration of inflammatory cells at the adventitia in mice lacking Hif-1α specifically in T cells. Studies to clarify the mechanism of augmented vascular remodeling in the mutant mice have shown enhanced production of cytokines in activated T cells and augmented antibody production in response to a T-dependent antigen in the mutant mice. This minireview shows that HIF-1α in T cells plays a crucial role in vascular inflammation and remodeling in response to cuff injury as a negative regulator of the T cell–mediated immune response and suggests potential new therapeutic strategies that target HIF-1α.

Simvastatin Ameliorates Rat Cerebrovascular Remodeling During Hypertension via Inhibition of Volume-Regulated Chloride Channel

Statins have pleiotropic actions against the development of vascular remodeling and the incidence of ischemic stroke. Although previous studies have suggested that posttranslational modification of several proteins, such as Rho by mevalonate-derived isoprene groups, geranylgeranyl pyrophosphate or farnesyl pyrophosphate, underlie the pleiotropic effects of statins, the detailed mechanisms remain elusive. Recent growing evidence demonstrated that ClC-3 volume-regulated chloride channel plays an important role in cell proliferation, and the activity of this channel is increased in basilar smooth muscle cells from a hypertensive rat. We hypothesized that inhibition of volume-regulated chloride channel may contribute to the beneficial effects of statins on cerebrovascular remodeling during hypertension. Our study here demonstrated that simvastatin ameliorated hypertension-caused cerebrovascular remodeling. In rat basilar smooth muscle cells, simvastatin inhibited cell proliferation and activation of volume-regulated chloride channel, and these effects of simvastatin were abolished by pretreatment with mevalonate or geranylgeranyl pyrophosphate. In addition, Rho A inhibitor C3 exoenzyme and Rho kinase inhibitor Y-27632 both reduced cell proliferation and activation of volume-regulated chloride channel. Moreover, ClC-3 overexpression decreased the suppressive effect of simvastatin on cell proliferation and increased estimated IC(50) of simvastatin on endothelin 1- and hypo-osmolarity-induced cell proliferation from 3.40+/-0.08 and 3.50+/-0.10 micromol/L to 5.30+/-0.70 and 5.60+/-0.70 micromol/L, respectively (P<0.01; n=6). Furthermore, the expression of ClC-3 was increased in basilar artery during hypertension, and simvastatin normalized the upregulation of ClC-3. Our data suggested that simvastatin ameliorates cerebrovascular remodeling in the hypertensive rat through inhibition of vascular smooth muscle cell proliferation by suppression of volume-regulated chloride channel.

ROSUVASTATIN IMPROVES VASCULAR CHANGES AND OXIDATIVE STRESS IN ANGIOTENSIN II-INFUSED RATS: 1D.04

Objective: Angiotensin (Ang) II is involved in the development of vascular remodelling and reduced nitric oxide (NO) availability due to oxidant excess. An increased COX-1 activity contributes to Ang II-induced endothelial dysfunction. Statins exert beneficial vascular effects independently of their lipid lowering action. We assessed the effects of rosuvastatin (rosu) on vascular remodeling and endothelial dysfunction of small mesenteric arteries from Ang II-treated rats. Methods: Male Sprague Dawley rats, which received vehicle or Ang II (120 ng/kg/min by subcutaneous osmotic minipumps), were treated with rosu for 2 weeks (10 mg/Kg/day, by intragastric route). Vascular function and structure were studied on pressurized myograph. Plasma total cholesterol and malondialdehyde (MDA) were also assayed. Results: Ang II-rats showed an increased media/lumen vs controls (M/L: 7.1 ± 0.4% vs 4.8 ± 0.2; p < 0.05), with normal media cross sectional area (MCSA: 12.8 ± 1.1 vs 10.3 ± 0.3 μm2 × 103), an alteration partly prevented by Rosu (M/L: 6.5 ± 0.6%; MCSA: 12.9 ± 0.9 μm2 x 103). In controls, relaxation to acetylcholine (Ach, 97.5 ± 0.7%) was blunted by L-NAME (52.4 ± 0.4%; p < 0.05), whereas SC-560 or DFU, selective COX-1 and COX-2 inhibitors respectively, were ineffective. Ascorbic acid (Asc. Ac.) failed to affect the response to Ach. In Ang II group, the blunted response to Ach (57.5 ± 0.4%; p < 0.05 vs controls) was slightly affected by L-NAME (45.5 ± 3.9%) and improved by SC-560 (81.4 ± 0.6%; p < 0.05), while DFU was ineffective. Asc. Ac. ameliorated ACh-induced relaxation (93.4 ± 1.2%) and restored the inhibition by L-NAME (57.1 ± 2.3%). Rosu normalized the relaxation to Ach (96.3 ± 1.3%) and restored the inhibition by L-NAME (55.6 ± 2.1%). COX-1, COX-2 inhibitors and Asc. Ac. became ineffective on relaxation to ACh. Plasma MDA was increased by Ang II (22.8 ± 2.1 vs 12.6 ± 2.4 ìM) and normalized by rosu (13.4 ± 1.8 μM). Rosu also reduced (p < 0.05) plasma cholesterol (61.4 ± 6.1 vs 79.2 ± 5.5 mg/dL). Conclusions: Rosuvastatin ameliorates Ang II-induced vascular eutrophic remodeling and endothelial dysfunction in small resistance arteries. This beneficial effect is exerted through an abrogation of oxidative stress, a restoration of NO availability, and a reduction of COX-1-dependent contracting activity.

Expression Analysis of Angiogenic Growth Factors and Biological Axis CXCL12/CXCR4 Axis in Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is associated with aberrant repair, persistence of collagen deposition, and the development of vascular remodeling. However, the role of angiogenesis in the pathogenesis of IPF is still undetermined. The aim of this study was to evaluate the combined mRNA expression of vascular endothelial growth factor A (VEGFA), fibroblast growth factor 2 (FGF2), insulin-like growth factor 1 (IGF1) epidermal growth factor (EGF), and its receptor (EGFR) in lung tissue obtained from IPF patients. We have also investigated the expression of chemokine CXCL12/stromal cell-derived factor-1 (SDF-1) and its receptor, CXCR4, to identify alterations that maybe implicated in the pathogenesis of IPF. The subjects studied consisted of two distinct groups: patients with IPF (n = 25) and subjects (control) undergoing thoracic surgery for reasons other than interstitial lung disease (n = 10). Expression analysis of the aforementioned growth factors and biological axis CXCL12/CXR4 analysis were performed using real-time RT-PCR. IGF-1, EGF, and FGF2 mRNA levels are significantly decreased in the patients compared to the controls (p = 0.028, p = 0.023 and p = 0.009, respectively). SDF1-TR1 and SDF1-TR2 transcript levels were significantly lower in patients compared to controls (p = 0.017 and p = 0.001). Significant coexpression of VEGF mRNA with IGF mRNA was observed in the group of the patients (p = 0.017). An additional coexpression of VEGF mRNA with SDF1-TR1 mRNA was demonstrated(p = 0.030). Our results show a downregulation in angiogenetic mechanisms in IPF. However, our results should be further verified by measuring other angiogenetic pathways in more samples.

Heparin Cofactor II Attenuates Vascular Remodeling in Humans and Mice

Heparin cofactor II (HCII), a serine protease inhibitor (serpin), inactivates thrombin action in the subendothelial layer of the vascular wall. Because a congenitally HCII-deficient patient has been shown to have multiple atherosclerotic lesions, it is hypothesized that HCII plays a pivotal role in the development of vascular remodeling, including atherosclerosis. To clarify this issue, 3 clinical studies concerning plasma HCII activity and atherosclerosis were carried out, and results demonstrated that a higher incidence of in-stent restenosis after percutaneous coronary intervention, maximum carotid arterial plaque thickness, and prevalence of peripheral arterial disease occurred in subjects with low plasma HCII activity. Furthermore, HCII-deficient mice were generated by a gene targeting method to determine the mechanism of the vascular protective action of HCII. Because HCII(-/-) mice were embryonically lethal, we used HCII(+/-) mice and found that they manifested augmentation of intimal hyperplasia and increased thrombosis after cuff or wire injury to the femoral arteries. HCII(+/-) mice with vascular injury showed augmentation of inflammatory cytokines and chemokines and oxidative stress. These abnormal phenotypes of vascular remodeling observed in HCII(+/-) mice were almost restored by human HCII protein supplementation. HCII protects against vascular remodeling, including atherosclerosis, in both humans and mice, and plasma HCII activity might be a predictive biomarker and novel therapeutic target for the prevention of cardiovascular diseases.

Role of Hypoxia-Inducible Factor 1α in T Cells as a Negative Regulator in Development of Vascular Remodeling

Recent studies have shown that the cellular immune response in the development of vascular remodeling modulates the resulting pathological alterations. We show that hypoxia-inducible factor 1 (Hif-1) (specifically expressed in T cells) is involved in the immune response to vascular remodeling that accompanies arteriosclerosis. To study the role of T cells in the development of vascular remodeling, femoral arterial injury induced by an external vascular polyethylene cuff was examined in mice lacking Hif-1 (specifically in T cells). We found that cuff placement caused prominent neointimal hyperplasia of the femoral artery in Hif-1- (T-cell)-deficient mice compared with that in control mice and that infiltration of inflammatory cells at the adventitia was markedly increased in the mutant mice. Studies to clarify the mechanism of augmented vascular remodeling in the mutant mice showed enhanced production of cytokines by activated T cells and augmented antibody production in response to a T-dependent antigen in the mutant mice. The results of this study revealed that Hif-1alpha in T cells plays a crucial role in vascular inflammation and remodeling in response to cuff injury as a negative regulator of T cell-mediated immune response. Potential new therapeutic strategies that target Hif-1alpha are described.

Flow-induced vascular remodeling in the mesenteric artery of spontaneously hypertensive rats

The effect of an increased blood flow on vascular remodeling was studied in the mesenteric arteries of 11-12-week-old spontaneously hypertensive rats (SHR) and age-matched normotensive Wistar-Kyoto rats (WKY). Increased blood flow was induced by selective ligation of mesenteric arteries. Nearby arteries with normal blood flow were used as controls. 7-10 days after the ligation procedure, mesenteric arteries were fixed in situ at maximal relaxation by perfusion fixation. Morphometric measurement of vascular dimension was carried out with confocal microscopy. Apoptotic cells were detected by the TdT-mediated dUTP nick-end labelling method. Cell growth was quantified by using proliferating cell nuclear antigen (PCNA) in sections of paraffin-embedded vessels. In SHR, elevated blood flow increased the vessel wall dimension and the number of smooth muscle cell (SMC) layers and also increased the wall-to-lumen ratio and the number of PCNA-positive SMC, but did not change lumen size or number of apoptotic SMC. In WKY, on the other hand, increased blood flow resulted in an increase in lumen diameter, a reduction of apoptotic SMC, but no change in wall-to-lumen ratio, number of SMC layers, or number of PCNA-positive SMC. These results showed that mesenteric arteries from hypertensive and normotensive rats respond to an increase in blood flow differently: a lumen enlargement with reduced SMC apoptosis in WKY, but an increased wall-to-lumen ratio with enhanced SMC growth in SHR. Although it remains to be determined whether flow alteration is one of the initiating factors in the development of vascular remodeling in hypertension, we speculate that an increase in cardiac output, and therefore an increase in shear stress that occurs in young SHR, contributes to vascular remodelling in this model of hypertension.

Low Levels of High-Density Lipoprotein Cholesterol Are Associated With Vascular Remodeling in Cardiac Transplant Recipients

Background Early atherosclerosis may be associated with compensatory vessel enlargement, termed positive remodeling. Enlarged brachial artery diameter has been reported in patients with risk factors for atherosclerosis and in individuals with coronary atherosclerosis, indicating that brachial artery enlargement is a marker for the presence of atherosclerotic changes. Cardiac transplant recipients often have abnormal lipid levels, but the effect of specific lipid abnormalities on vascular remodeling in this population has not been evaluated. This study examined the relationship between lipid levels and brachial artery diameter in cardiac transplant recipients. Methods Thirty-five stable cardiac transplant recipients underwent high-resolution brachial artery ultrasound to evaluate resting brachial artery diameter. Levels of high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides were determined and the presence of other cardiac risk factors was assessed. Results Brachial artery diameter was larger (4.3 ± 0.1 mm) in subjects with low levels of HDL-C (<40 mg/dL, n = 11) compared to subjects with high HDL-C (≥40 mg/dL, n = 24), who had a mean brachial artery diameter of 3.7 ± 0.1 mm ( P = .006). Neither high LDL-C (≥100 mg/dL) nor high triglycerides (≥200 mg/dL) were associated with differences in brachial artery diameter. Multivariate analysis demonstrated that the relationship between low HDL-C and increased brachial artery diameter was independent of body surface area or statin use. Conclusions Low levels of HDL-C are an independent predictor of brachial artery enlargement in stable cardiac transplant recipients. These findings suggest that suboptimal HDL-C levels may be associated with the development of vascular remodeling and atherosclerosis in this population.

Effect of a synthetic matrix metalloproteinase inhibitor (ONO-4817) on neointima formation in hypercholesterolemic hamsters.

Degradation of extracellular matrix (ECM) proteins plays an important role in the development of vascular remodeling. We investigated the alteration of matrix metalloproteinases (MMPs) on the development of neointima formation and the effect of a newly synthesized MMP inhibitor using hypercholesterolemic hamsters. Endothelial injury was achieved by a catheter in the hamster carotid artery. Two weeks after the injury, neointima was detected in all hamsters. Oral administration (twice a day) of ONO-4817 was started 2 hours before injury and continued for the next 2 weeks. The neointimal area, with appearance of maze-like structures, was markedly reduced by 52.4 +/- 8.4% by treatment with ONO-4817 at a dose of 20 mg/kg per day. The treatment by ONO-4817 (20 mg/kg per day) significantly reduced the indexes of histone H1 on day 1, 5, and 10 and the BrdU index of intimal smooth muscle cells on day 5 and 10, but not on day 1. Whereas DNA synthesis was not reduced by ONO-4817, in vitro SMC migration on the other hand was reduced dose dependently. According to the results of western-blotting analysis, the expressions of MMPs were increased 1 week after injury. Especially, MMP-12 was not detected in hamsters without cholesterol diet, but it was much increased after injury in hypercholesterolemic hamsters. Additionally, active form of MMP-12 increased in the injured artery of hypercholesterolemic hamsters. In conclusion, inhibition of MMPs results in the suppression of neointima following vascular injury via both prevention of SMC migration and SMC proliferation of late phase in hypercholesterolemic hamsters. MMP-12 plays an important role on vascular stenosis in hypercholesterolemia and ONO-4817 could be a useful compound for the therapy for this field.

Role of bone marrow-derived progenitor cells in cuff-induced vascular injury in mice.

Arterial injury results in vascular remodeling associated with proliferation and migration of smooth muscle cells (SMCs) and the development of intimal hyperplasia, which is a critical component of restenosis after angioplasty of human coronary arteries and an important feature of atherosclerotic lesions. However, the origin of SMCs and other cells in the development of vascular remodeling is not yet fully understood. We utilized a cuff-induced vascular injury model after transplantation of the bone marrow (BM) from green fluorescent protein (GFP)-transgenic mice. We found that macrophages were major cells recruited to the adventitia of the vascular injury lesion along with SMCs and endothelial cells (ECs). While investigating whether those cells are derived from the donor, we found that most of the macrophages were GFP-positive, and some of the SMCs and ECs were also GFP-positive. Administration of the anti-c-fms antibody resulted in a marked decrease in macrophages and a relative increase of SMCs, while administration of antibodies against the platelet-derived growth factor receptor-beta caused a prominent decrease in SMCs and a relative increase in macrophages. The current study indicates that BM-derived cells play an important role in vascular injury, and that differentiation of macrophages and SMCs might be dependent on each other.