Inhibition of endothelial cell activation by the homeobox gene Gax

BACKGROUND

cardiovascular system, strongly inhibits growth factor-stimulated phenotypic modulation of vascular smooth muscle cells in vitro and in vivo. The function of Gax in vascular endothelium is unknown, but we hypothesized that it may play a similar role there. We therefore studied Gax expression in vascular endothelial cells and its effects on proliferation and tube formation.

MATERIALS AND METHODS

Gax expression in normal endothelial cells was examined in vitro by Northern blot and reverse transcriptase polymerase chain reaction and in vivo by immunohistochemistry. A replication-deficient adenovirus was then used to express Gax in human umbilical vein endothelial cells (HUVECs). HUVEC proliferation, 3H-thymidine uptake, p21 expression, and tube formation on reconstituted basement membrane were measured at different viral multiplicities of infection.

RESULTS

Gax mRNA was detected in HUVECs by reverse transcriptase polymerase chain reaction and Northern blot analysis and in normal vascular endothelium by immunohistochemistry. Compared with controls transduced with a virus expressing beta-galactosidase, Gax strongly inhibited HUVEC proliferation and mitogen-stimulated 3H-thymidine uptake. p21 expression in HUVECs transduced with Gax was increased up to 5-fold as measured by Northern blot, and p21 promoter activity was activated by 4- to 5-fold. Tube formation on Matrigel was strongly inhibited by Gax expression.

CONCLUSIONS

Gax is expressed in vascular endothelium and strongly inhibits endothelial cell activation in response to growth factors and tube formation in vitro. These observations suggest that Gax inhibits endothelial cell transition to the angiogenic phenotype in response to proangiogenic growth factors and, as a negative regulator of angiogenesis, may represent a target for the antiangiogenic therapy of cancer.

The small heat shock protein (HSP) 20 is dynamically associated with the actin cross-linking protein actinin

BACKGROUND

The heat shock-related protein (HSP) 20 is associated with actin and modulates smooth-muscle relaxation. We hypothesized that HSP20 mediates vasorelaxation via dynamic interactions with cytoskeletal proteins, such as actin, or actin binding proteins, such as alpha-actinin.

METHODS

Physiological responses of strips of bovine carotid artery were analyzed with a muscle bath. In other experiments, the arteries were homogenized, and imunoprecipitations were performed. Immunohistochemistry with anti-HSP20 and anti-actinin antibodies was used to determine co-localization of the two proteins.

RESULTS

Bovine carotid arteries contracted in response to serotonin and rapidly relaxed in response to forskolin. HSP20 co-immunoprecipitated with both actin and alpha-actinin, but not with HSP27 or paxillin. Immunostaining with HSP20 and alpha-actinin antibodies demonstrated that HSP20 and alpha-actinin co-localized. The amount of HSP20 that immunoprecipitated with alpha -actinin was markedly diminished in muscles that were treated with the vasorelaxant forskolin.

CONCLUSIONS

HSP20 is associated with both actin and alpha-actinin. Activation of cyclic nucleotide-dependent signaling pathways leads to increases in the phosphorylation of HSP20 and a decrease in the association of HSP20 with alpha-actinin. These data suggest that phosphorylation of HSP20 may lead to relaxation of vascular smooth muscles through a dynamic association with cytoskeletal elements.

Reduced expression of actin-binding proteins, h-caldesmon and calponin h1, in the vascular smooth muscle inside melanoma lesions: an adverse prognostic factor for malignant melanoma

BACKGROUND

The structural integrity of the blood vessels such as small arteries and veins is studied less frequently in malignant tumours than is angiogenesis. Objectives To clarify the characteristics of small arteries and small veins of melanoma lesions.

METHODS

We immunohistochemically investigated various types of melanocytic tumours using antibodies specific for endothelial and vascular smooth muscle cells, and analysed the relationship between the expression of these molecules in the blood vessels and the biological characteristics of the tumours. Formalin-fixed, paraffin-embedded sections of 15 cases of benign melanocytic tumours and 64 cases of malignant melanomas were investigated.

RESULTS

Significant suppression of expression of h-caldesmon (h-CD) and calponin h1 (CNh1) was observed in the blood vessels of malignant melanomas compared with both benign melanocytic tumours and normal tissues. In particular, the level of h-CD expression was inversely correlated with the frequency of metastasis and positively correlated with the survival rate in patients with malignant melanoma.

CONCLUSIONS

These findings suggest that alterations of the tumour vessels are an important factor for the prognosis of malignant melanoma, and that suppression of h-CD and CNh1 in the blood vessels in malignant melanoma reflects a structural fragility of the vessels, leading to their easy penetration by tumour cells. Defective expression of these molecules is likely to be an important marker for metastatic potential and for poor prognosis of melanoma.

Isolation of bone marrow stromal cell-derived smooth muscle cells by a human SM22alpha promoter: in vitro differentiation of putative smooth muscle progenitor cells of bone marrow

BACKGROUND

Bone marrow stromal cells (BMSCs) have many characteristics of mesenchymal stem cells that can differentiate into smooth muscle cells (SMCs). However, there have been few studies closely following the cell development of smooth muscle lineage among BMSCs.

METHODS AND RESULTS

To investigate the possible existence of a cell population committed to the SMC lineage among bone marrow adhesion cells, we tried to detect and follow the in vitro differentiation of such a cell type by using a promoter-sorting method with a human SM22alpha promoter (-480 bp)/green fluorescent protein (GFP) construct. The construct was transfected to adhesion cells that appeared 5 days after the seeding of mononuclear cells from bone marrow. GFP was first detectable 5 days after the transfection in a cell population [Ad(G) cells], which expressed PDGF-beta but neither mature (calponin) nor immature (SMemb) SMC-specific proteins at that time. However, the cells were eventually grown into individual clones that expressed SMC-specific proteins (alpha-smooth muscle actin, calponin, and SM-1), suggesting that Ad(G) cells have partly at least progenitor properties. Because early studies have reported that PDGF-beta signaling plays pivotal roles in the differentiation of mesenchymal smooth muscle progenitor cells, Ad(G) cells might be putative mesenchymal smooth muscle progenitors expressing PDGF-beta.

CONCLUSIONS

We demonstrated the presence of a cell population fated to become SMCs and followed their differentiation into SMCs among BMSCs.

Expression of caveolin-3 in rat aortic vascular smooth muscle cells is determined by developmental state

The presence of caveolin-3 was reinvestigated in smooth muscle cells in situ and in culture. Immunocytochemistry of aortic strips showed that both caveolins-1 and -3 are present, but that caveolin-3 is considerably less abundant and detected in only a fraction of the cells. Cultured smooth muscle cells of passage 4 or greater still expressed caveolin-1 but lacked caveolin-3, likely due to dedifferentiation. Cultures exposed to redifferentiation-inducing medium were found to re-express caveolin-3. The return of caveolin-3 protein in these cells was accompanied by a fourfold increase in cav-3 mRNA, as detected by quantitative PCR, suggesting that the loss of protein in untreated cells was due to transcriptional rather than translational inhibition. These results suggest that caveolin-3 has a specialized role associated with the differentiated state in certain types of smooth muscle cells.

Expression and cellular localisation of renal endothelin-1 and endothelin receptor subtypes in autosomal-dominant polycystic kidney disease

The major factors influencing the rate of progression of chronic renal disease in autosomal-dominant polycystic kidney disease (ADPKD) are unknown and there are currently no effective treatments for slowing the progression of chronic renal failure in ADPKD patients. As a first step in investigating the potential role of endothelin-1 (ET1) and its receptors (ETA and ETB) in the pathophysiology of progression in ADPKD, we have studied their expression and cellular localisation in ADPKD kidney. Immunoreactive ET1 was detected in cyst epithelia, mesangial cells and vascular smooth muscle cells suggesting continuing ET1 synthesis in the cystic kidney. Compared to healthy controls, ETA mRNA was 5-10-fold higher in ADPKD cystic kidney. In cystic kidney, neo-expression of ETA receptors was found overlying glomeruli and cysts and markedly increased in medium-sized renal arteries by microautoradiography. This is the first study to demonstrate a specific upregulation of ETA receptors in human renal disease. Future studies should address whether ETA selective antagonists may be effective in slowing renal disease progression in ADPKD.

Protein kinase C-epsilon-null mice have decreased hypoxic pulmonary vasoconstriction

PKC contributes to regulation of pulmonary vascular reactivity in response to hypoxia. The role of individual PKC isozymes is less clear. We used a knockout (null, -/-) mouse to test the hypothesis that PKC-epsilon is important in acute hypoxic pulmonary vasoconstriction (HPV). We asked whether deletion of PKC-epsilon would decrease acute HPV in adult C57BL6xSV129 mice. In isolated, salt solution-perfused lung, reactivity to acute hypoxic challenges (0% and 3% O(2)) was compared with responses to angiotensin II (ANG II) and KCl. PKC-epsilon -/- mice had decreased HPV, whereas responses to ANG II and KCl were preserved. Inhibition of nitric oxide synthase (NOS) with nitro-l-arginine augmented HPV in PKC-epsilon +/+ but not -/- mice. Inhibition of Ca(2+)-gated K(+) channels (K(Ca)) with charybdotoxin and apamin did not enhance HPV in -/- mice relative to wild-type (+/+) controls. In contrast, the voltage-gated K(+) channel (K(V)) antagonist 4-aminopyridine increased the response of -/- mice beyond that of +/+ mice. This suggested that increased K(V) channel expression could contribute to blunted HPV in PKC-epsilon -/- mice. Therefore, expression of the O(2)-sensitive K(V) channel subunit Kv3.1b (100-kDa glycosylated form and 70-kDa core protein) was compared in whole lung and pulmonary artery smooth muscle cell (PASMC) lysates from +/+ and -/- mice. A subtle increase in Kv3.1b was detected in -/- vs. +/+ whole lung lysates. A much greater rise in Kv3.1b expression was found in -/- vs. +/+ PASMC. Thus deletion of PKC-epsilon blunts murine HPV. The decreased response could not be attributed to a general loss in vasoreactivity or derangements in NOS or K(Ca) channel activity. Instead, the absence of PKC-epsilon allows increased expression of K(V) channels (like Kv3.1b) to occur in PASMC, which likely contributes to decreased HPV.

Comparison of reagents for shape analysis of fixed cells by automated fluorescence microscopy

BACKGROUND

Cell size and shape have been implicated as potentiators of intracellular signaling events and as indicators of abnormal cell behavior. Automated microscopy and image analysis can provide quantitative information about the size and shape of cultured cells, but it requires that the edge of a cell be clearly identified. Generating adequate contrast at the edge of thin well-spread cells can be challenging.

METHODS

We compared six (five chemically reactive and one lipophilic) fluorescent molecules--5-chloromethyl fluorescein diacetate (CMFDA, CellTracker green), fluorescein-5-maleimide, fluorescein-5-isothiocyanate (FITC), 5-iodoacetamidofluorescein, 5(6)-carboxy fluorescein-N-hydroxysuccinimidyl ester, and N-fluorescein-1,2-dihexadecanoyl-sn-glycerol-3-phosphoethanolamine--for their effectiveness as stains for automated morphology analysis of fixed cells.

RESULTS

Formaldehyde-fixed rat aortic smooth muscle cells stained with fluorescein-5-maleimide or FITC exhibited an average intensity that was at least twofold greater than cells stained with CMFDA even when subjected to a 25-fold shorter exposure time. Cell area determined with the higher intensity stains was less sensitive to threshold settings during automated cell morphology analysis.

CONCLUSION

A procedure that includes the use of fluorescein-5-maleimide or FITC for staining fixed cell provides sensitivity sufficient to permit rapid, automated, morphologic analysis of well-spread fixed cells.

Early and intermediate Amadori glycosylation adducts, oxidative stress, and endothelial dysfunction in the streptozotocin-induced diabetic rats vasculature

AIMS/HYPOTHESIS

In a model of streptozotocin-induced Type 1 diabetes mellitus in rats of 9 weeks duration, we analysed time associations between the development of hyperglycaemia, early and intermediate glycosylation Amadori adducts, or AGE compared with enhancement of oxidative stress and endothelial dysfunction.

METHODS

Endothelial function was tested at several stages of streptozotocin-induced diabetes and after treatment with insulin, resulting in different concentrations of blood glucose, glycosylated haemoglobin (an Amadori adduct), and AGE. Other animals were studied antagonising the formation of AGE with aminoguanidine.

RESULTS

Relaxation in response to acetylcholine (1 nmol/l to 10 micro mol/l) was tested in isolated segments from aorta or mesenteric microvessels. Impairment of endothelium-dependent relaxations occurred after 2 weeks of untreated diabetes. Preincubation of vessels affected with 100 U/ml superoxide dismutase improved the relaxations to acetylcholine, along the time-course of the endothelial impairment. This indicates the participation of reactive oxygen species on diabetic endothelial dysfunction. The impairment of endothelium-dependent relaxations was recovered after 3 more weeks of insulin treatment. Aminoguanidine treatment did not modify this pattern of development. The time course of the rise and disappearance of endothelial dysfunction showed a higher correlation with glycosylated haemoglobin concentrations than with blood glucose or serum AGE.

CONCLUSION/INTERPRETATION

Enhancement of early and intermediate Amadori adducts of protein glycosylation was the factor showing a better relation with the development of endothelium impairment. These results are consistent with a role for these products in the development of diabetic vasculopathy.

Enhanced tumor necrosis factor- alpha expression in small sized abdominal aortic aneurysms

Circulating levels of tumor necrosis factor alpha (TNF- alpha) are elevated in the patients with abdominal aortic aneurysm (AAA). We investigated TNF- alpha expression and cellular infiltration in the walls of AAAs of different sizes. Twenty-seven surgical specimens of AAAs were categorized according to the maximum aneurysm diameter into a small size group (less than 50 mm in diameter, n = 8; S group), a medium-sized group (50 to 59 mm in diameter, n = 11; M group), and a large size group (larger than 59 mm in diameter, n = 8; L group). The level of TNF- alpha and interleukin-1 beta(IL-1 beta) in the aneurysm wall was measured by ELISA. Immunohistochemical staining was performed to observe the TNF- alpha expression and the infiltration of macrophages and lymphocytes in aneurysm walls. Enzyme-linked immunosorbent assay showed that the level of TNF- alpha in the S group (5.47 +/- 3.48 pg/mg protein) was significantly higher ( p < 0.05) than that in the M group (2.70 +/- 1.33 pg/mg protein) or the L group (1.82 +/- 1.21 pg/mg protein). No significant difference in IL-1 beta was observed between the S, M, and L groups. Immunohistochemical analysis also showed that TNF- alpha was expressed strongly in the S group but was negative or weakly positive in the M and L groups. Furthermore, the expression of TNF- alpha was seen mainly where the aneurysm wall showed atheromatous change and macrophage infiltration. These results indicated that the expression of TNF- alpha in the aneurysm wall was enhanced in small AAAs, and this enhancement might be related to the infiltration of macrophages.

Phenotype modulation in vascular tissue engineering using biochemical and mechanical stimulation

Biochemical stimulation was applied in combination with cyclic mechanical strain to engineered vascular constructs made of isolated smooth muscle cells in a three-dimensional (3D) collagen type 1 matrix. Platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF-beta) were added exogenously to the medium used to culture the constructs. Mechanical stimulation was applied using a bioreactor system that imparted a 10% circumferential strain at a frequency of 1 Hz. The parameters studied were gel compaction, cell proliferation, and expression of the contractile protein smooth muscle alpha-actin (SMA). Mechanical stimulation caused a characteristic increase in gel compaction and cell proliferation, relative to statically cultured controls. Stimulation with PDGF increased cell proliferation and decreased SMA expression in 3D gels, but inhibited the effects of mechanical stimulation and produced a more open matrix structure. TGF-beta strongly inhibited cell proliferation and increased SMA expression, especially in the presence of mechanical strain, and resulted in a dense matrix. These results show that cell phenotype can be modulated in engineered blood vessels by applying selected combinations of biochemical and mechanical stimuli, and suggest that such control over cell function can be used to tailor the properties of engineered tissues.

Deficiency of cathepsin S reduces atherosclerosis in LDL receptor-deficient mice

Human atherosclerotic lesions overexpress the lysosomal cysteine protease cathepsin S (Cat S), one of the most potent mammalian elastases known. In contrast, atheromata have low levels of the endogenous Cat S inhibitor cystatin C compared with normal arteries, suggesting involvement of this protease in atherogenesis. The present study tested this hypothesis directly by crossing Cat S-deficient (CatS(-/-)) mice with LDL receptor-deficient (LDLR(-/-)) mice that develop atherosclerosis on a high-cholesterol diet. Compared with LDLR(-/-) mice, double-knockout mice (CatS(-/-)LDLR(-/-)) developed significantly less atherosclerosis, as indicated by plaque size (plaque area and intimal thickening) and stage of development. These mice also had markedly reduced content of intimal macrophages, lipids, smooth muscle cells, collagen, CD4(+) T lymphocytes, and levels of IFN-gamma. CatS(-/-)LDLR(-/-) monocytes showed impaired subendothelial basement membrane transmigration, and aortas from CatS(-/-)LDLR(-/-) mice had preserved elastic laminae. These findings establish a pivotal role for Cat S in atherogenesis.

20-HETE-induced contraction of small coronary arteries depends on the activation of Rho-kinase

20-HETE is a potent constrictor of small blood vessels and has been suggested to play a crucial role in the generation of myogenic tone and the development of hypertension. In the present study, we investigated the mechanisms by which exogenously applied 20-HETE modulates vascular tone in small porcine coronary arteries. In organ chamber experiments, 20-HETE elicited a concentration-dependent contraction of small porcine coronary artery rings that was partially inhibited by the cyclooxygenase inhibitor diclofenac, the thromboxane and endoperoxide receptor antagonist SQ29548, and the thromboxane A2 synthase inhibitor furegrelate. Removal of endothelium attenuated the response to 20-HETE, whereas preconstriction of endothelium-denuded vessels to 25% of the maximum response with KCl markedly enhanced the response to 20-HETE. This 20-HETE-induced contraction was not associated with a significant increase in the intracellular concentration of Ca2+. 20-HETE-induced contraction was also observed in beta-escin-permeabilized arteries precontracted with a submaximal concentration of Ca2+ and was abolished by the Rho-kinase inhibitor Y27632, but was insensitive to the PKC inhibitor RO 31-8220. 20-HETE elicited the phosphorylation of the myosin light chain (MLC20) in coronary artery rings, an effect that was sensitive to Y27632 and mimicked by the thromboxane analog U46619. These data suggest that in small porcine coronary arteries, 20-HETE can induce contraction by 2 mechanisms, one endothelium-dependent involving the cyclooxygenase-dependent generation of vasoconstrictor prostanoids, and the other endothelium-independent. The latter response is associated with the activation of Rho-kinase, phosphorylation of MLC20, and sensitization of the contractile apparatus to Ca2+.

Latent transforming growth factor-beta binding protein-1, a component of latent transforming growth factor-beta complex, accelerates the migration of aortic smooth muscle cells in diabetic rats through integrin-beta3

Aortic smooth muscle cells (SMCs) of diabetic animals have unique properties, including the overexpression of transforming growth factor-beta (TGF-beta) type II receptor, fibronectin, and platelet-derived growth factor beta-receptor. TGF-beta1 is produced and secreted as latent high-molecular weight complex consisting of mature TGF-beta1, latency-associated peptide (LAP), and a latent TGF-beta1 binding protein (LTBP-1). LAP has an important function in the latency of TGF-beta complex, but the role of LTBP-1 is not known in diabetic angiopathy. SMC migration from the medial layer to the intimal layer of an artery is an initial major process of the formation of intimal thickening of an artery. Migration activities of SMCs from diabetic rat with 1-500 pg/ml of LTBP-1 increased significantly compared with that without LTBP-1. LTBP-1 at 10-500 pg/ml stimulated the migration of diabetic SMCs more than SMCs from control rat. An anti-integrin-beta(3) antibody reduced LTBP-1-stimulated migration of diabetic SMCs to 51% compared with no antibody, but it did not reduce that of control SMCs. Furthermore, cross-linking experiments show that LTBP-1 binds integrin-beta(3) in diabetic SMCs much more than in control SMCs in coincidence with the increase of integrin-beta(3) in diabetic aorta by immunohistochemistry. Taken together, these observations suggest that LTBP-1 plays a critical role in intimal thickening of diabetic artery through the acceleration of SMC migration via integrin-beta(3).

Early inflammatory responses in experimental cardiac hypertrophy and fibrosis: effects of 11 beta-hydroxysteroid dehydrogenase inactivation

In epithelial tissues such as kidney, mineralocorticoid receptors (MR) are protected against glucocorticoid occupancy by the enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta HSD) type 2. If the enzyme is congenitally inactive, or blocked by carbenoxolone, physiologic glucocorticoids act as MR agonists in such tissues. In most nonepithelial tissues, including cardiomyocytes, 11 beta HSD2 is expressed at minimal levels; in these tissues physiologic glucocorticoids act as MR antagonists, with the basis for this tissue selectivity currently unknown. Vascular smooth muscle cells (VSMC) express MR and 11 beta HSD1/2, with 11 beta HSD1 reported to show uncharacteristic oxidase activity, so that VSMC thus constitute a potential physiologic aldosterone target tissue. Because mineralocorticoid/salt administration triggers marked inflammatory responses in coronary vasculature, we reasoned that VSMC (like epithelial) MR may be activated by glucocorticoids if the protective enzyme is blocked. We thus gave uninephrectomized rats 0.9% NaCl solution to drink, and deoxycorticosterone (DOC, as a single 20 mg sc dose) or carbenoxolone (CBX, 2.5 mg/d in the drinking solution). Both DOC and CBX increased systolic blood pressure, heart, and kidney weight, and expression of cyclooxygenase 2, ED-1-positive macrophages, and osteopontin, with effects of both DOC and CBX blocked by the selective MR antagonist eplerenone. These findings suggest that local glucocorticoid excess, reflecting lower VSMC 11 beta HSD1/2 activity may mimic systemic mineralocorticoid excess, and play a direct etiologic role in coronary vascular inflammatory responses under circumstances of a high salt intake.

Pulmonary expression of vascular endothelial growth factor in sepsis

CONTEXT

Vascular endothelial growth factor (VEGF), an angiogenic and chemotactic peptide, is abundantly expressed in normal lung tissue, especially in alveolar and bronchial epithelium, glandular cells of the bronchi, and activated alveolar macrophages.

OBJECTIVE

To investigate the role of VEGF in progressively impaired lung function as the major complication and cause of death in septic patients.

MATERIALS AND METHODS

We evaluated pulmonary VEGF expression in lung autopsy material from septic patients who had been cared for by intensive care medicine using enzyme-linked immunosorbent assay (ELISA), reverse transcriptase-polymerase chain reaction (RT-PCR), and immunohistochemical methods.

RESULTS

Compared with expression in nonseptic control individuals (n = 10), pulmonary VEGF expression as determined by ELISA was significantly (P <.001) decreased in septic patients (n = 8). As monitored by RT-PCR, mRNA for the 2 splice variants, VEGF(121) and VEGF(165), and for VEGFR-2/KDR were expressed in both groups, the yields being lower in the sepsis group. Samples from septic patients lacked or showed only sparse immunoreaction on bronchial and alveolar epithelium, whereas this reaction was strong in all control samples. However, alveolar macrophages were similarly immunopositive in both groups.

CONCLUSIONS

The precise underlying mechanisms for the distinctly different expression of pulmonary VEGF in septic patients and nonseptic control individuals are not clear at present. Particularly the role of VEGF in the development of sepsis-induced lung injury and acute respiratory distress syndrome in mechanically ventilated patients suffering from severe sepsis remains to be clarified.

Macrophage migration inhibitory factor is associated with aneurysmal expansion

BACKGROUND

Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine released mainly from macrophages and activated lymphocytes. Both atherosclerosis and abdominal aortic aneurysm (AAA) are inflammatory diseases tightly linked to the function of these cells. The correlation and contribution of MIF to these human diseases remain unknown, although a recent rabbit study showed expression of this cytokine in atherosclerotic lesions.

MATERIAL AND METHODS

MIF immunohistochemistry was performed on tissue sections from five normal aortas, seven atherosclerotic carotids, and six AAAs. A group of 112 men with small AAAs (defined as 3 to 5 cm) was recruited at the time of diagnosis, had serum samples taken, and was followed annually for 1 to 5 years (mean, 2.9 years) and referred for surgery if the AAA exceeded 5 cm in diameter. Of this study group, 98 had serum MIF measured with an enzyme-linked immunosorbent assay and 61 had detectable levels.

RESULTS

In human atherosclerotic and aneurysmal lesions, MIF protein colocalized in macrophages, endothelial cells, and smooth muscle cells, but normal arteries had negligible MIF expression. Furthermore, serum-MIF levels correlated significantly with annual expansion rate (r = 0.28; P =.005), persisting after adjustment for initial AAA size, smoking habits, diastolic blood pressure, ankle blood pressure index, and age. After exclusion of 38 cases with MIF levels below the detection limit, initial AAA size was also significantly correlated with the MIF levels (r = 0.42; P =.001), persisting after adjustment for similar confounders, and the correlation coefficient with expansion rate increased to 0.42 (P =.001).

CONCLUSION

Highly expressed MIF in macrophages, endothelial cells, and smooth muscle cells in lesions from atherosclerosis and AAA and significant association between serum MIF level and AAA initial size and AAA expansion rate in a group of patients with AAA suggest a potential involvement of this proinflammatory cytokine in the pathogenesis of these cardiovascular diseases.

Downregulation of vascular angiotensin II type 1 receptor by thyroid hormone

Thyroid hormone has a broad effect on cardiovascular system. 3,3',5-triiodo-l-thyronine (T3), a biologically active form of thyroid hormone, increases cardiac contractility. T3 causes arterial relaxation and reduction of systemic vascular resistance, resulting in an increase in cardiac output. However, the molecular mechanisms of vascular relaxation by T3 are incompletely characterized. We studied the effect of T3 on the angiotensin (Ang) II type 1 receptor (AT1R) expression in vascular smooth muscle cells. T3 dose-dependently decreased expression levels of AT1R mRNA, with a peak at 6 hours of stimulation. Binding assay using [125I]Sar1-Ile8-Ang II revealed that AT1R number was decreased by stimulation with T3 without changing the affinity to Ang II. T3 reduced calcium response of vascular smooth muscle cells to Ang II by 26%. AT1R promoter activity measured by luciferase assay was reduced by 50% after 9 hours of T3 administration. mRNA stability was also decreased by T3. Real-time quantitative reverse transcription-polymerase chain reaction and Western blot analysis revealed that AT1R mRNA and protein were downregulated in the aorta of T3-treated rats. These results suggest that T3 downregulates AT1R expression both at transcriptional and posttranscriptional levels, and attenuates biological function of Ang II. Our results suggest that downregulation of AT1R gene expression may play an important role for T3-induced vascular relaxation.

Altered response of vascular smooth muscle cells to exogenous biochemical stimulation in two- and three-dimensional culture

Removal of vascular smooth muscle cells (SMC) from their native environment alters the biochemical and mechanical signals responsible for maintaining normal cell function, causing a shift from a quiescent, contractile phenotype to a more proliferative, synthetic state. We examined the effect on SMC function of culture on two-dimensional (2D) substrates and in three-dimensional (3D) collagen Type I gels, including the effect of exogenous biochemical stimulation on gel compaction, cell proliferation, and expression of the contractile protein smooth muscle alpha-actin (SMA) in these systems. Embedding of SMC in 3D collagen matrices caused a marked decrease in both cell proliferation and expression of SMA. The presence of the extracellular matrix modulated cellular responses to platelet-derived growth factor BB, heparin, transforming growth factor-beta1, and endothelial cell-conditioned medium. Cell proliferation and SMA expression were shown to be inversely related, while gel compaction and SMA expression were not correlated. Taken together, these results show that SMC phenotype and function can be modulated using biochemical stimulation in vitro, but that the effects produced are dependent on the nature of the extracellular matrix. These findings have implications for the study of vascular biology in vitro, as well as for the development of engineered vascular tissues.

Paracrine role of soluble guanylate cyclase and type III nitric oxide synthase in ovine fetal pulmonary circulation: a double labeling immunohistochemical study

Endothelial nitric oxide synthase (eNOS) or NOS-III in the endothelium catalyzes production of nitric oxide (NO). Nitric oxide diffuses freely into vascular smooth muscle, where it activates soluble guanylate cyclase (sGC) to produce guanosine 3',5'-cyclic monophosphate (cGMP) and causes vasorelaxation. The NO/cGMP pathway is an important signaling pathway in the control of perinatal pulmonary circulation. An exact colocalization of NOS-III in the pulmonary endothelium and sGC in the vascular smooth muscle was demonstrated using a double immunolabeling technique. The sGC immunoreactivity was higher in resistant pulmonary vessels and veins than in conduit arteries, whereas NOS-III immunoreactivity was higher in conduit arteries than in veins. These results demonstrated anatomically in situ a paracrine role of NOS-III and sGC in the regulation of fetal pulmonary circulation and suggested a heterogeneous distribution of NOS-III and sGC within fetal ovine pulmonary vasculature. Our results provided an anatomic basis that supported previous functional studies on perinatal control of pulmonary circulation.

Force maintenance in smooth muscle: analysis using sinusoidal perturbations

The "latch state" or force maintenance may be due to the emergence of a distinct set of dephosphorylated, slowly cycling "latch" cross-bridges, slowing of the overall cross-bridge cycling rate, or a non-cross-bridge contribution. This was investigated by sinusoidally oscillating strips of intact rabbit portal vein or aorta. Tissue strips were activated with KCl depolarization, resulting in a sustained increase of MLC(20) phosphorylation or 10 microM phenylephrine, resulting in a transient increase in MLC(20) phosphorylation. Stiffness was calculated from the force response to a small, sine-wave oscillation in muscle length (1-100 Hz). The results produced a 3-dimensional plot of stiffness versus the frequency of oscillation (Hz) versus time (s), or stiffness distribution profile. During KCl depolarization, the stiffness distribution profile displayed a shift toward lower frequencies, suggesting a general slowing in the overall cross-bridge cycling rate during force maintenance. On the other hand, phenylephrine stimulation did not display a significant change in the stiffness distribution profile, suggesting that the overall cross-bridge cycling rate did not significantly change during force maintenance.

Expression of A20 in the vessel wall of rat-kidney allografts correlates with protection from transplant arteriosclerosis

BACKGROUND

Chronic rejection with development of transplant arteriosclerosis is the major culprit involved in loss of kidney allografts. The allografts' fate was thought to depend on the intensity of the host immune responses and the potency of immunosuppressive regimens. Recent data suggests that grafts contribute to their own survival by way of up-regulation of "cytoprotective" genes.

METHODS

We analyzed the expression of four cytoprotective genes, A20, Bcl-2, Bcl-x(L) and heme oxygenase (HO)-1, in three rat renal allograft models of chronic rejection: Fisher 344-Lewis (F344/Lew), Dark Agouti-Brown Norway (DA/BN), and DA-Wistar-Furth (WF). We chose these genes for their known anti-inflammatory and anti-apoptotic function in endothelial cells (EC) and the atheroprotective function of A20 in smooth muscle cells (SMC).

RESULTS

Twenty-eight and 9 weeks following transplantation, F344/Lew and DA/BN transplants had stable graft function. Histopathologic analysis showed moderate tissue damage, minimal cellular infiltrates, and preserved vascular integrity correlating with high expression of A20 in SMC. Conversely, impaired allograft function in the DA/WF combination with substantial transplant arteriosclerosis was noted in 60% of the grafts correlating with absent or decreased A20 expression in EC and SMC. In all combinations, expression of HO-1, Bcl-2, and Bcl-x(L) colocalized with infiltrating cells and was not informative on the graft status.

CONCLUSIONS

We demonstrate for the first time a strict correlation between A20 expression in the vessel and the absence of transplant arteriosclerosis in rat kidney-allograft models. This data is similar to data obtained in human kidney allografts and suggests that A20 may represent a novel therapeutic target for the prevention of chronic allograft rejection.

Quantification of macrophage content in atherosclerotic plaques by optical coherence tomography

BACKGROUND

Macrophage degradation of fibrous cap matrix is an important contributor to atherosclerotic plaque instability. An imaging technology capable of identifying macrophages in patients could provide valuable information for assessing plaque vulnerability. Optical coherence tomography (OCT) is a new intravascular imaging modality that allows cross-sectional imaging of tissue with a resolution of approximately 10 micro m. The aim of this study was to investigate the use of OCT for identifying macrophages in fibrous caps.

METHODS AND RESULTS

OCT images of 26 lipid-rich atherosclerotic arterial segments obtained at autopsy were correlated with histology. Cap macrophage density was quantified morphometrically by immunoperoxidase staining with CD68 and smooth muscle actin and compared with the standard deviation of the OCT signal intensity at corresponding locations. There was a high degree of positive correlation between OCT and histological measurements of fibrous cap macrophage density (r=0.84, P<0.0001) and a negative correlation between OCT and histological measurements of smooth muscle actin density (r=-0.56, P<0.005). A range of OCT signal standard deviation thresholds (6.15% to 6.35%) yielded 100% sensitivity and specificity for identifying caps containing >10% CD68 staining.

CONCLUSIONS

The high contrast and resolution of OCT enables the quantification of macrophages within fibrous caps. The unique capabilities of OCT for fibrous cap characterization suggest that this technology may be well suited for identifying vulnerable plaques in patients.

TGF-beta stimulates collagen (I) in vascular smooth muscle cells via a short element in the proximal collagen promoter

BACKGROUND

Accumulation of extracellular matrix contributes to the development of intimal hyperplasia. Transforming growth factor beta (TGF-beta) stimulates the production of several matrix proteins in vascular smooth muscle cells (SMC) including type I collagen, but the underlying mechanisms of TGF-beta's effects are not well understood.

MATERIALS AND METHODS

The effect of TGF-beta on type I collagen biosynthesis was determined by a [3H]proline incorporation assay and Northern blotting. The promoter of human alpha2(I) procollagen (COL1A2) gene was analyzed by transient transfection analysis and gel mobility shift assay.

RESULTS

Treatment of human vascular SMC with TGF-beta stimulated collagen synthesis and increased the level of alpha2(I) collagen mRNA. A collagen-luciferase reporter gene, constructed by linking the human COL1A2 promoter with the firefly luciferase gene, was transiently expressed in human SMC. Treatment with TGF-beta significantly stimulated the activity of this collagen-luciferase reporter. Using deletion analysis, we identified a 150 bp DNA fragment (-334 to -184) in the human COL1A2 promoter as the site through which TGF-beta mediates collagen gene expression in human SMC. Gel mobility shift assays demonstrated that this 150 bp DNA fragment formed conjugates with multiple nuclear factors derived from SMC, a process that was further enhanced by TGF-beta.

CONCLUSIONS

TGF-beta stimulates the human type I collagen gene via a DNA element located in the proximal region of its promoter. Interventions that disrupt interaction between this DNA element and nuclear factors may block the production of collagen in response to TGF-beta and consequently may have a significant effect on the development of intimal hyperplasia.

Inhibitors of actin filament polymerisation attenuate force but not global intracellular calcium in isolated pressurised resistance arteries

Receptor-coupled contractile activation of arterial smooth muscle involves increases in intracellular calcium ([Ca(2+)](i)) and subsequent alteration of myosin light chain phosphorylation. An additional mechanism whereby agonists could regulate vascular contractility may be alteration of actin filament dynamics. Therefore, in this study, we have investigated the influence of two inhibitors of actin filament polymerisation, cytochalasin D and latrunculin B, on the [Ca(2+)](i) and force responsiveness of pressurised rat mesenteric arteries to alpha-adrenergic stimulation. Following cytochalasin D or latrunculin B treatment, phenylephrine-induced constrictions were significantly reduced to 11 +/- 3.2% (n = 6) and 10 +/- 4.4% (n = 6) of control, respectively, whereas [Ca(2+)](i) remained at 98 +/- 21% and 104 +/- 7.0% of control, respectively. Such effects of cytochalasin D were not restricted to mesenteric small arteries. Cytochalasin D also significantly reduced the force, but not [Ca(2+)](i) responses to agonist stimulation in other vascular (portal vein) and non-vascular (uterine) tissues. These data indicate that inhibitors of net actin polymerisation attenuate maximum agonist-induced force responsiveness without similar reductions in [Ca(2+)](i) in pressurised resistance vessels and other smooth muscle tissues. This suggests that modulation of the dynamic equilibrium between filamentous F-actin and monomeric globular actin (G-actin) may be an important mechanism, acting independently of global [Ca(2+)](i) homeostasis, to regulate the smooth muscle contractile state.

Extrahepatic synthesis of factor VII in human atherosclerotic vessels

OBJECTIVE

Coagulation is initiated by the interaction of tissue factor (TF) with plasma coagulation factors VII (FVII) and X (FX). TF is highly expressed in atherosclerotic lesions, but little is known about the synthesis of FX or FVII outside of the liver. Previous studies suggested that macrophages synthesize FVII. We therefore hypothesized that macrophages within atherosclerotic lesions may produce FVII, leading to partial activation of the coagulation cascade.

METHODS AND RESULTS

Immunohistochemistry was performed using antibodies against FVII, FX, and TF on normal and atherosclerotic vessels. In atherosclerotic lesions, FVII immunostaining was colocalized with TF in macrophages and spindle-shaped smooth muscle cells. FVII mRNA was also detected in these cells using in situ hybridization, suggesting the local synthesis of FVII in atherosclerosis. Reverse transcriptase-polymerase chain reaction confirmed the presence of FVII mRNA in normal and atherosclerotic vessels as well as smooth muscle cells, fibroblasts, and keratinocytes in vitro.

CONCLUSIONS

The localization of FVII synthesis outside the liver may be indicative of other cellular functions for this coagulation protein. The observed coexpression of TF and FVII may contribute to autocrine signaling via thrombin-independent mechanisms and may represent a novel mechanism contributing to growth in the setting of vascular disease.

Multiple forms of estrogen receptor-alpha in cerebral blood vessels: regulation by estrogen

The cerebral vasculature is an important target tissue for estrogen, as evidenced by significant effects of estrogen on vascular reactivity and protein levels of endothelial nitric oxide synthase and prostacyclin synthase. However, the presence, localization, and regulation of estrogen receptors in the cerebral vasculature have not been investigated. In this study, we identified the presence of estrogen receptor-alpha (ER-alpha) in female rat cerebral blood vessels and localized this receptor to both smooth muscle and endothelial cells by use of immunohistochemistry and confocal microscopy. With immunoblot analysis, multiple forms of ER-alpha were detected at 110, 93, 82, 50, and 45 kDa in addition to a relatively weak band corresponding to the 66-kDa putative unmodified receptor. The 82-kDa band was identified as Ser(118)-phosphorylated ER-alpha, whereas the 50-kDa band lacks the normal NH(2) terminus, suggestive of an ER-alpha splice variant. Lower molecular mass bands persisted after in vivo inhibition of 26S proteasome activity with lactacystin, whereas the 110- and 93-kDa bands increased. All forms of ER-alpha in cerebral vessels were decreased after ovariectomy but significantly increased after chronic estrogen exposure in vivo.

HMG-CoA reductase inhibitors regulate inflammatory transcription factors in human endothelial and vascular smooth muscle cells

OBJECTIVE

Pleiotropic atheroprotective effects of HMG-CoA reductase inhibitors may be mediated on the level of vascular gene transcription. The aim of this study was to characterize the effects of statins on the activation of transcription factors known to regulate inflammation and cell proliferation/differentiation.

METHODS AND RESULTS

Simvastatin, atorvastatin, and lovastatin (0.1 to 10 micro mol/L) inhibited the binding of nuclear proteins to both the nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) DNA consensus oligonucleotides in human endothelial and vascular smooth muscle cells as assessed by electrophoretic mobility shift assay (EMSA). The inhibitory effects of statins on NF-kappaB or AP-1-dependent transcriptional activity were examined by transient transfection studies. HMG-CoA reductase inhibitors upregulated IkappaB-alpha protein levels in endothelial cells and decreased c-Jun mRNA expression in smooth muscle cells as analyzed by Western and Northern blotting, respectively. Furthermore, statins inhibited DNA binding of hypoxia-inducible factor-1alpha. Downstream effects of statins included inhibition of plasminogen activator inhibitor-1 and vascular endothelial growth factor-A mRNA levels in endothelial cells.

CONCLUSIONS

HMG-CoA reductase inhibitors downregulate the activation of transcription factors NF-kappaB, AP-1, and hypoxia-inducible factor-1alpha. These findings support the concept that statins have antiinflammatory and antiproliferative effects that are relevant in the treatment of atherosclerotic diseases.

The serpin protease-nexin 1 is present in rat aortic smooth muscle cells and is upregulated in L-NAME hypertensive rats

OBJECTIVE

Protease-nexin 1 (PN-1) belongs to the serpin superfamily and behaves as a specific thrombin inhibitor in the pericellular environment. Little is known about PN-1 expression and its regulation in the vascular system. In this study, we examined the expression of functionally active PN-1 in vitro in rat aortic smooth muscle cells and in vivo in rat arterial media and its regulation in hypertensive rats.

METHODS AND RESULTS

The vascular PN-1 formed specific covalent complexes with thrombin involving the catalytic site of the protease, and heparin increased the formation of these complexes. We also demonstrated PN-1 in rat arterial media by immunohistochemical staining. Moreover, we examined in vivo vascular expression of PN-1 in a model of chronic hypertension induced by long-term administration of N(G)-nitro-L-arginine methyl ester (L-NAME). Marked increases in PN-1 mRNA (3-fold) and protein (2-fold) were observed after 2 months of hypertension. Increased expression of PN-1 in the vascular wall was associated with an increase in the formation of complexes between radiolabeled-thrombin and PN-1, indicating that PN-1 was functional.

CONCLUSIONS

PN-1 may thus participate in the mechanisms that regulate thrombin activity in the vessel wall.

A diffusible substance(s) mediates endothelium-dependent contractions in the aorta of SHR

A modified bioassay system was designed to demonstrate the diffusible nature of endothelium-derived contracting factor(s) released by acetylcholine in the aorta of spontaneously hypertensive rat. In "sandwich"-like layered preparation, isometric tension was recorded from a bioassay strip (without endothelium) in the presence of N(G)-nitro-L-arginine and tetrahydrobiopterin to selectively potentiate endothelium-dependent contractions. A donor strip (with or without endothelium) was stitched on the bioassay tissue so that it did not directly contribute to the recorded contractions. Acetylcholine induced contractions that occurred only when the donor strip was with endothelium. Superoxide dismutase did not affect but catalase and the combination of superoxide dismutase plus catalase significantly decreased the endothelium-dependent contraction. The contractions in the layered preparations were abolished when the donor strip with endothelium was treated previously with valeryl salicylate, an irreversible cyclooxygenase-1 inhibitor, but remained unaffected when the bioassay strip was treated with the compound. Previous treatment of the bioassay strip alone with S 18886 abolished the contractile response, whereas treatment of the donor strip with endothelium by the selective TP receptor antagonist only produced a moderate inhibition. These results indicate that in the aorta of spontaneously hypertensive rats, endothelium-dependent contractions to acetylcholine involve a diffusible substance(s) released by the endothelium. The production of this contracting factor(s) requires the activation of endothelial cyclooxygenase-1, and its action the activation of TP receptors on the vascular smooth muscle cells.

Gene expression profiling of apoptosis-related genes in human atherosclerosis: upregulation of death-associated protein kinase

OBJECTIVE

Apoptosis substantially affects the cellularity and integrity of atherosclerotic plaques. It remains, however, unclear which key regulatory genes are involved. In this study, cDNA expression arrays were used to analyze transcript levels of 205 apoptosis-related genes in human carotid endarterectomy specimens versus nonatherosclerotic mammary arteries.

METHODS AND RESULTS

Seventeen genes with a 2- to 5-fold relative expression difference were identified. One of the most apparent changes in human plaques was the overexpression of death-associated protein (DAP) kinase ( approximately 5-fold), a positive mediator of apoptotic cell death. Differential expression of DAP kinase mRNA in human plaques relative to mammary arteries was confirmed by quantitative reverse-transcription polymerase chain reaction. Western blotting and immunohistochemistry demonstrated enhanced levels of DAP kinase protein in the plaque with negligible expression in non-atherosclerotic vessels. DAP kinase was located predominantly in foam cells of smooth muscle cell (SMC) origin. Uptake of aggregated LDL by cultured aortic SMCs as well as exposure of SMCs to the short-chain acyl ceramide derivative N-hexanoyl-D-sphingosine (C6-ceramide) upregulated DAP kinase both at the mRNA and protein level.

CONCLUSIONS

Our data demonstrate that cDNA array technology can identify novel genes that might participate in cell death pathways underlying atherogenesis.

Expression profiling identifies 147 genes contributing to a unique primate neointimal smooth muscle cell phenotype

OBJECTIVE

This study represents the first in an effort to systematically characterize different intimas by using expression array analysis.

METHODS AND RESULTS

We compared smooth muscle cells (SMCs) of the neointima formed 4 weeks after aortic grafting with those from normal aorta and vena cava from cynomolgus monkeys. Hybridization to cDNA arrays identified subsets of 147 and 45 genes differentially expressed in the neointima versus the aorta and vena cava, respectively. The expression pattern differentiating neointima from aortic SMCs was characterized largely by suppression. Only 13 genes were induced in the neointima: 7 encoded matrix proteins (6 collagens and 1 versican) and 2 encoded inducers of matrix synthesis (osteoblast-specific factor-2/Cbfa1 and connective tissue growth factor). The genes suppressed most in the neointima included the regulator of G-protein signaling-5, SPARClike-1/hevin, and nonmuscle myosin heavy chain-B. A smaller gene set differentiated the neointima from the vena cava. Most were induced (39 of 45 genes), and overlap with the neointima-aorta set was significant (10 of 13 genes). Array results were validated with Northern analysis, in situ hybridization, or immunohistochemistry.

CONCLUSIONS

These data underscore the importance of matrix synthesis in neointimal maturation, and novel genes, newly associated with neointimal SMCs (regulator of G-protein signaling-5 and osteoblast-specific factor-2/Cbfa1), have raised new hypotheses regarding the pathogenesis of intimal hyperplasia.

A novel class of endothelin-A receptor antagonists, (R)-2-(benzo[1,3]dioxol-5-yl)-6-isopropyloxy-2H-chromene-3-carboxylic acids (S-1255). Conformational analysis of basic structure, crucial for ET(A) antagonism, in solution and solid states

Conformational studies of potent and selective endothelin-A (ET(A)) receptor antagonists, 4-substituted (R)-2-(benzo[1,3]-dioxol-5-yl)-6-isopropoxy-2H-chromene-3-carboxylic acids, are reported. X-ray crystallography and NMR studies of the 4-anisyl derivative 2 (S-1255), the stable atropisomers 3 and the 4-n-butyl derivative 4 reveal that the A-, B- and C-rings in these compounds adopt a L-like conformation in both solution and solid states. Molecular mechanics calculation shows that this L-like conformation is an inevitable conformation as determined by intramolecular steric repulsions. These 2H-chromene derivatives bound to an ET(A) receptor with IC(50) values of less than 1 nM, whereas the dihydro compounds 7 and 9 not having the L-like conformation showed weaker affinities. These results suggest that the L-like conformation is specifically recognized by the active site of the ET(A) receptor. The roles of the L-like conformation in the receptor binding are discussed.

Expression of G2A, a receptor for lysophosphatidylcholine, by macrophages in murine, rabbit, and human atherosclerotic plaques

OBJECTIVE

Lysophosphatidylcholine (LPC), a major phospholipid component of oxidized low density lipoprotein, has been demonstrated to induce multiple functional alterations of vasculature that are potentially involved in atherosclerosis. Recently, an orphan G-protein-coupled receptor, G2A, has been identified as a high-affinity receptor for LPC. Although it has been demonstrated that G2A is expressed predominantly in lymphoid tissues and lymphocytes, there are no reports to determine whether G2A is expressed in atherosclerotic lesions and cardiovascular cells.

METHODS AND RESULTS

Immunohistochemistry with an anti-G2A antibody revealed that G2A was expressed predominantly by macrophages within atherosclerotic lesions at the aortic root of apolipoprotein E-deficient mice and the thoracic aortas of Watanabe heritable hyperlipidemic rabbits. In atherosclerotic plaques of human coronary arterial specimens, G2A was expressed by macrophages within the lipid-rich plaques, whereas no immunoreactivity of G2A was observed in fibrous plaques where macrophages did not exist. Reverse transcription-polymerase chain reaction analysis demonstrated that G2A mRNA was highly expressed in human and murine monocytes/macrophages. The expression of G2A protein was detected in human and murine monocytes/macrophages by immunoblotting.

CONCLUSIONS

These findings demonstrate that monocytes/macrophages abundantly express G2A and suggest that G2A may play a role in the formation and progression of atherosclerotic lesions.

Differential gene expression in vascular smooth muscle cells in primary atherosclerosis and in stent stenosis in humans

OBJECTIVE

We sought to identify differentially expressed genes in human in stent stenosis (ISS) to provide insights into the mechanism of disease.

METHODS AND RESULTS

Using representation difference analysis, we examined differential gene expression between cultured normal human medial vascular smooth muscle cells (VSMCs) and cells from primary atherosclerotic plaques or ISS sites. Specific groups of genes were overexpressed in ISS and plaque VSMCs, including cell cycle regulatory proteins and cell matrix and contractile proteins. Differential expression was validated by virtual Northern analysis, reverse transcriptase-polymerase chain reaction, in situ hybridization, and immunohistochemistry. All ISS genes were expressed by normal intima and had even higher expression in primary plaque VSMCs.

CONCLUSIONS

ISS VSMCs have a stable gene expression profile reflecting an intimal pattern, intermediate between normal medial and primary plaque VSMCs. Differential expression profiling may identify markers of disease that are overexpressed in ISS and also help elucidate the origin of the ISS lesion.

Endothelial cells freshly isolated from small pulmonary arteries of the rat possess multiple distinct k+ current profiles

This study demonstrates for the first time that endothelial cells freshly isolated from small pulmonary arteries of the rat, based on their electrophysiological profile, possess two distinct populations of cells. Immunohistochemical staining revealed the presence of both anti-Kv1.5 and anti-Kir2.1 immunoreactivity in the endothelium of small pulmonary arteries. Patch-clamp studies demonstrated that 90% of cells studied exhibited an electrophysiological profile that was characterized by a delayed rectifier K+ conductance. However, the remaining 10% of cells studied showed the complete absence of a delayed rectifier K+ current and were characterized by an inward rectifier K+ conductance. Together these results indicate that endothelial cells isolated from rat small pulmonary arteries possess a heterogeneous population of cells that may be distinguished by their markedly different electrophysiological profiles. These different populations of cells may differ in their control of the resting membrane potential of endothelial cells, and thereby altering Ca2+ homeostasis and release of vasoactive compounds. These findings may therefore have important implications for understanding the regulation of pulmonary vascular tone.

Canine mesenteric artery and vein convey no difference in the content of major contractile proteins

BACKGROUND

Mesenteric arteries and veins are composed of tonic smooth muscles and serve distinct functions in the peripheral circulation. However, the basis for the functional disparity of the resistive and capacitative parts of the mesenteric circulation is poorly understood. We studied potential differences in the expression levels of six contractile proteins in secondary and tertiary branches of the inferior mesenteric artery and vein along with differences in the vessel wall morphology.

RESULTS

Bright field and electron microscopy showed that both vessel walls had the same major structural elements. The arterial walls, however, had greater number, and more tightly assembled, smooth muscle cell layers compared to vein walls. The content of actin, myosin heavy chain, myosin light chain, and calponin was similar in the two blood vessels. The artery expressed higher amount of the actin-binding protein caldesmon than the vein (41.86 +/- 2.33 and 30.13 +/- 3.37 microg/mg respectively, n = 12). Although the total tropomyosin content was almost identical in both blood vessels, the alpha isoform dominated in the artery, while the beta isoform prevailed in the vein.

CONCLUSIONS

Canine mesenteric artery and vein differ in vessel wall morphology but do not convey differences in the expression levels of actin, myosin light chain, myosin heavy chain and calponin. The two vascular networks express distinct amounts of caldesmon and tropomyosin, which might contribute to the fine tuning of the contractile machinery in a manner consistent with the physiological functions of the two vascular networks.

Interleukin-1 receptor immunoreactivity in sympathetic vascular and non-vascular neurons in guinea-pig coeliac ganglion

Immunoreactivity (IR) for the interleukin-1 receptor type I (IL1RI) was examined in sympathetic neurons in guinea-pig coeliac ganglion using multiple-labelling immunofluorescence. IL1RI-IR was present in 8% of sympathetic neurons in untreated preparations. The proportion of neurons with IL1RI-IR increased significantly after incubation in interleukin-6 (200 ng/ml) for 2-4 h (16-26% neurons), or after incubation for 4 h without cytokine (16%), with interleukin-1beta (IL1beta, 200 ng/ml; 18%) or tumour necrosis factor-alpha (200 ng/ml; 16%). This increase occurred predominantly in neuropeptide Y-IR, vasoconstrictor neurons. IL1RI-IR also was present in varicose axons, some of which projected from the gut, and in vascular smooth muscle cells and endothelium. These potential binding sites for the proinflammatory cytokine, IL1beta, on vasoconstrictor neurons and blood vessels may modulate sympathetic regulation of intestinal blood flow in inflammatory conditions.

Growth factors enhance interleukin-1 beta-induced persistent activation of nuclear factor-kappa B in rat vascular smooth muscle cells

OBJECTIVE

Activation of extracellular signal-regulated kinases (ERKs) is required for interleukin-1beta to persistently activate nuclear factor (NF)-kappaB and concomitantly express inducible NO synthase (iNOS) in rat vascular smooth muscle cells (VSMCs). The present study examined whether platelet-derived growth factor (PDGF) or epidermal growth factor (EGF) could influence the VSMC response to interleukin-1beta via an ERK-related signaling pathway.

METHODS AND RESULTS

Treatment of VSMCs with PDGF or EGF alone potently induced ERK phosphorylation and DNA synthesis but did not induce NF-kappaB activation or iNOS expression. However, either PDGF or EGF markedly enhanced interleukin-1beta-induced persistent NF-kappaB activation and iNOS expression but did not affect the early and transient NF-kappaB activation. Growth factor-induced DNA synthesis was attenuated in the presence of interleukin-1beta. Inhibition of ERK phosphorylation with selective inhibitors (PD98059 or U0126) attenuated interleukin-1beta-induced persistent NF-kappaB activation and iNOS expression in either the absence or presence of the growth factors.

CONCLUSIONS

These results indicate that interleukin-1beta-induced expression of NF-kappaB-dependent genes, such as iNOS, is potentiated in the presence of growth factors through a mechanism requiring ERK-dependent enhanced NF-kappaB activation, and the results also suggest that NF-kappaB activation is not required for PDGF or EGF to trigger DNA synthesis in VSMCs.

Differential role of heparan sulfate proteoglycans on aggregated LDL uptake in human vascular smooth muscle cells and mouse embryonic fibroblasts

OBJECTIVE

Low density lipoprotein (LDL) receptor-related protein (LRP) binds and internalizes aggregated LDL (agLDL) in human vascular smooth muscle cells (VSMCs). To analyze the contribution of proteoglycans (PGs) to agLDL uptake in human VSMCs, in wild-type mouse embryonic fibroblasts (MEF line), and in LRP-deficient mouse embryonic fibroblasts (PEA13 line).

METHODS AND RESULTS

PGs in the medium and cellular and extracellular matrix have been isolated by metabolic radiolabeling with [35S]Na2SO4 and characterized by selective digestion with heparinase I and III (4 U/mL each) and chondroitinase ABC (2 U/mL). To examine the contribution of PGs and LRPs to agLDL internalization, nonexpressing and LRP-expressing cells, treated or not with polysaccharidase, were incubated with agLDL (25, 50, and 100 micro g/mL) for 18 hours. In human VSMCs, agLDL was unable to induce cholesteryl ester (CE) accumulation in antisense LRP-oligodeoxynucleotide-treated cells, and heparan sulfate (HS)-PG depletion leads to a reduction of the CE accumulation. In mouse fibroblasts, PEA13 compared with MEF showed lower, but still considerable, CE accumulation, and HS-PG depletion almost completely inhibited CE accumulation.

CONCLUSIONS

In MEF, HS-PGs can function alone as receptors that bind and internalize agLDL in the absence of LRP, but in human VSMCs, although HS-PGs facilitate agLDL binding to the cells, LRP is essential for agLDL internalization.

Angiotensin II increases expression of cyclooxygenase-2: implications for the function of vascular smooth muscle cells

In vascular smooth muscle, increased expression of cyclooxygenase-2 (COX-2) has emerged as an important mechanism for regulation of prostanoid synthesis influenced by vessel injury, cytokines, and growth factors. We have investigated how COX-2 participates in angiotensin II (ANG II)-mediated cell responses in cultured human vascular smooth muscle cells (VSMCs). ANG II type 1 (AT1) receptors induce increased accumulation of COX-2, both at the mRNA and protein levels. ANG II increased transcription of the COX-2 gene; also, nuclear extracts from stimulated cells had increased NF-kappa B binding to its DNA consensus sequence. ANG II-induced COX-2 expression was markedly blunted by inhibition of mitogen-activated protein kinase. Furthermore, the ANG II-induced increase in COX-2 protein abundance was attenuated by both the peroxisome proliferator-activated receptor alpha (PPARalpha) activator Wy-14,643 [pyrinixic acid; 4-chloro-6-(2,3-xylidino)-2-pyrimidinyl) thioacetic acid] and the PPARgamma activator 15d-PGJ2 (15-deoxy-Delta(12-14)-prostaglandin J2). Not only did ANG II increase COX-2 expression and prostaglandin synthesis, ANG II-stimulated DNA synthesis and cell migration were dependent on COX-2 activity. PPARalpha and PPARgamma activators inhibited ANG II-stimulated DNA synthesis and cell migration. These results suggest that ANG II enhances COX-2 expression at the transcription level; also, COX-2 activity plays an important role in mediating ANG II- induced proliferation and migration of VSMCs, suggesting the possibility of magnification of ANG II effects over time due to the induction of COX-2 expression. These results also demonstrate that both the alpha and gamma type of PPAR activators inhibit COX-2 expression induced by angiotensin II in VSMCs which may have therapeutic significance in vascular diseases.

ATP-binding cassette transporter 1 participates in LDL oxidation by artery wall cells

OBJECTIVE

We have previously reported that products of the lipoxygenase pathway, hydroperoxyoctadecadienoic acid and hydroperoxyeicosatetraenoic acid, as well as cholesterol linoleate hydroperoxides, collectively termed seeding molecules, are removed by apolipoprotein A-I (apoA-I) from the artery wall cells and render low density lipoprotein (LDL) resistant to oxidation by human artery wall cells. The mechanisms by which oxidized lipids are transported and/or transferred to lipoproteins and the pathways by which apoA-I facilitates their removal remain unclear. ATP-binding cassette transporter 1 (ABCA1) is known to facilitate the release of cellular phospholipids and cholesterol from the plasma membrane to apoA-I and high density lipoprotein. Therefore, we evaluated whether ABCA1 participates in LDL oxidation.

METHODS AND RESULTS

In this report, we show that (1) chemical inhibitors of ABCA1 function, glyburide and DIDS, block artery wall cell-mediated oxidative modification of LDL, (2) inhibition of ABCA1 with the use of antisense (but not sense) oligonucleotides prevents LDL-induced lipid hydroperoxide formation and LDL-induced monocyte chemotactic activity by the artery wall cells, and (3) oxysterols that induce ABCA1 expression, such as 22(R)hydroxycholesterol, enhance cell-mediated LDL oxidation. Furthermore, we also show that 22(R)hydroxycholesterol induces the production of reactive oxygen species in the artery wall cells, which can be removed by incubating the artery wall cells with apoA-I.

CONCLUSIONS

Our data suggest that ABCA1 plays an important role in artery wall cell-mediated modification/oxidation of LDL by modulating the release of reactive oxygen species from artery wall cells that are necessary for LDL oxidation.

Detection of superoxide in vascular tissue

During the past decade, it has become apparent that reactive oxygen species play a critical role in the genesis of many vascular diseases. The superoxide anion is among the most important of these, not only because of its rapid reaction with NO but also because it serves as a progenitor for many other reactive oxygen species. Although there are many approaches to detecting and quantifying superoxide in chemical systems, its detection in intact tissues is more difficult. The validity of the most popular and frequently used assay for this purpose, lucigenin-enhanced chemiluminescence, has been recently questioned. It has been suggested that lucigenin itself, especially at high concentrations (>50 micromol/L), may act as a source for superoxide via redox cycling. Lower lucigenin concentrations (5 micromol/L) do not participate in redox cycling to an important extent in intact tissues and, therefore, provide an accurate assessment of the rate of superoxide production in such samples. Other useful assays for superoxide include those using the fluorescent dye dihydroethidine, 2-methyl-6-phenyl-3,7-dihydroimidazo(1,2-alpha)pyrazin-3-one (CLA), and 2-(p-hydroxybenzyl)-6-(p-hydroxyphenyl) 8-benzylimidazo[1,2-alpha]pyrazin-3-one (coelenterazine). The chemiluminescent compound 5-amino-2,3-dihydroxy-1,4-phthalayineidone (luminol) may also be used to detect various reactive oxygen species and may be made specific for various oxidants, such as hydrogen peroxide, superoxide, and peroxynitrite, by altering the experimental conditions. Although each of these methods may be associated with potential artifacts, the use of > or =2 different techniques that yield similar results provides a reliable approach for the study of reactive oxygen species in intact vascular tissues.

Both donor and recipient origins of smooth muscle cells in vein graft atherosclerotic lesions

Smooth muscle cell (SMC) accumulation in the inner layer of the vessel wall is a key event in the pathogenesis of atherosclerosis in vein grafts, but the origin of the cells in these lesions has yet to be shown. Herein, we use animal models of vein grafts in transgenic mice to clearly identify the sources of SMCs in atherosclerosis. Vena cava segments were isografted to carotid arteries between four types of transgenic mice, including SM-LacZ expressing beta-galactosidase (beta-gal) in vascular SMCs, SM-LacZ/apoE(-/-), ROSA26 expressing beta-gal in all tissues, and wild-type mice. beta-gal-positive cells were observed in neointimal and atherosclerotic lesions of all vein segments grafted between LacZ transgenic and wild-type mice. Double staining for beta-gal and cell nuclei revealed that about 40% of SMCs originated from hosts and 60% from the donor vessel. This was confirmed by double labeling of the Y-chromosome and alpha-actin in the lesions of sex-mismatched vein grafts. The possibility that bone marrow cells were the source of SMCs in grafts was eliminated by the absence of beta-gal staining in atherosclerotic lesions of chimeric mice. Furthermore, vein SMCs of SM-LacZ mice did not express beta-gal in situ, but did so when these cells appeared in atherosclerotic lesions in vivo, suggesting that hemodynamic forces may be crucial for SMC differentiation. Thus, we provide the first evidence of SMC origins in the atherosclerotic lesions of vein grafts, which will be essential for providing insight into new types of therapy for the disease. The full text of this article is available at http://www.circresaha.org.

Lipid accumulation in smooth muscle cells under LDL loading is independent of LDL receptor pathway and enhanced by hypoxic conditions

OBJECTIVE

The effect of a variety of hypoxic conditions on lipid accumulation in smooth muscle cells (SMCs) was studied in an arterial wall coculture and monocultivation model.

METHODS AND RESULTS

Low density lipoprotein (LDL) was loaded under various levels of oxygen tension. Oil red O staining of rabbit and human SMCs revealed that lipid accumulation was greater under lower oxygen tension. Cholesterol esters were shown to accumulate in an oxygen tension-dependent manner by high-performance liquid chromatographic analysis. Autoradiograms using radiolabeled LDL indicated that LDL uptake was more pronounced under hypoxia. This result holds in the case of LDL receptor-deficient rabbit SMCs. However, cholesterol biosynthesis and cellular cholesterol release were unaffected by oxygen tension.

CONCLUSIONS

Hypoxia significantly increases LDL uptake and enhances lipid accumulation in arterial SMCs, exclusive of LDL receptor activity. Although the molecular mechanism is not clear, the model is useful for studying lipid accumulation in arterial wall cells and the difficult-to-elucidate events in the initial stage of atherogenesis.

Human in-stent restenosis tissue obtained by means of coronary atherectomy consists of an abundant proteoglycan matrix with a paucity of cell proliferation

BACKGROUND

In-stent restenosis (ISR) is a shortcoming of percutaneous coronary revascularization. Although neointimal cell proliferation is suspected to be the cause of this problem, little histological characterization of this tissue or data on cell replication exist. The purpose of this study was to examine the histologic features and proliferation profile of coronary ISR tissue derived from atherectomy procedures performed on patients with clinical evidence of ISR.

METHODS

ISR tissue retrieved by means of atherectomy from 20 coronary lesions was subjected to histomorphological analyses and immunocytochemistry as a means of examining proteoglycan expression. Cell proliferation was assessed with 2 sensitive markers of replication, in situ hybridization for histone 3 messenger RNA expression and immunocytochemistry for Ki-67 expression.

RESULTS

The ISR atherectomy specimens consisted primarily of smooth muscle cells, with occasional focal collections of inflammatory cells and organizing thrombus. All specimens had low levels of interstitial collagen and an abundant proteoglycan matrix, with biglycan being overexpressed more commonly than decorin. Cell proliferation was found in only 1 of 20 specimens (2 cells).

CONCLUSION

Established ISR lesions contained an abundant proteoglycan matrix and a paucity of proliferating cells. Future therapeutic strategies for ISR should include targeting extracellular matrix production.

Expression and Regulation of Calcitonin Gene-Related Peptide Receptor in Rat Placentas1

Calcitonin gene-related peptide (CGRP), one of the most potent vasodilators known, exerts its biological action by interacting with its receptors. Recent reports suggest the existence of two types of CGRP receptors, CGRP-A and CGRP-B. The current study was designed to examine whether CGRP-B receptors are present in the rat placenta, and if they are, whether they are modulated by gestational age and by sex-steroid hormones. Placentas were obtained from timed pregnant Sprague-Dawley rats that were killed on Days 17-21 and 22 before and during labor (n = 6 for each gestational age). In addition, placentas were also obtained from pregnant rats injected with progesterone (P(4); 4 mg per rat per day s.c. on Days 20-22), antiprogesterone RU-486 (10 mg/rat s.c. on Day 17), 17beta-estradiol (5 micro g/rat s.c. on Day 17), and antiestrogen ICI 182780 (0.3 micro g/rat s.c. on Day 17). Results showed that first, immunoflourescent staining of rat placentas using monoclonal anti-CGRP-B receptor antibody revealed the presence of CGRP-B receptors in the labyrinthine layer of the placenta, specifically to the trophoblast and blood vessel endothelium and underlying smooth muscle cells. The intensity of staining was lower in placentas obtained during labor. Second, a single band of 66 kDa, reactive to CGRP-B receptor antibody, was obtained in Western blotting of the rat placenta; third, densitometric analysis of protein bands showed that CGRP-B receptors were increased from Day 17 to Day 22, with maximal levels obtained on Day 22 before labor, which was 10 times higher than that of Day 17 (P < 0.01); fourth, expression of CGRP-B receptors in rat placenta decreased during labor (8% vs. 100% on Day 22 before labor, P < 0.01); fifth, P(4) given during Days 20-22 attenuated the fall in placental CGRP-B receptors at term labor; sixth, RU-486 given on Day 17 of gestation significantly decreased expression of placental CGRP-B receptors (18% vs. 100% in controls at 6 h, P < 0.01); seventh, a significant decrease in CGRP-B receptor expression was noted 48 h after estrogen administration; and eighth, ICI 182780 treatment on Day 17 increased placental CGRP-B receptors (152% vs. 100% in control at 48 h, P < 0.01). These results indicate that CGRP-B receptors are present in rat placenta and that receptor levels are higher with gestational age and lower at term labor. Progesterone stimulated and estrogen inhibited placental CGRP-B receptor expression. Thus, elevations in placental CGRP-B receptors in late pregnancy could play a role in increasing blood flow through the fetoplacental unit associated with rapid fetal growth during late gestation.

Fibrillar collagen regulation of plasminogen activator inhibitor-1 is involved in altered smooth muscle cell migration

OBJECTIVE

Vascular smooth muscle cells (SMCs) cultured on polymerized type I collagen fibrils are arrested in the G1 phase of the cell cycle, and their phenotypic markers and pattern of expressed genes are markedly altered. In this study, we examined polymerized collagen regulation of plasminogen activator inhibitor (PAI)-1 and its involvement in SMC migration.

METHODS AND RESULTS

We demonstrate that secretion and cell surface accumulation of PAI-1 are suppressed in SMCs cultured on polymerized collagen compared with SMCs cultured on monomer collagen. SMCs replated on vitronectin after culture on monomer collagen result in PAI-1 accumulation at focal adhesions and colocalization with alpha(v)beta3 integrins. In contrast, polymerized collagen inhibits PAI-1 accumulation at focal adhesions when the SMCs are replated on vitronectin. Furthermore, for SMCs cultured on polymerized collagen, platelet-derived growth factor-stimulated migration on vitronectin is enhanced by PAI-1, with its function counteracted by urinary plasminogen activator. Finally, exogenous addition of PAI-1 appears to partly restore platelet-derived growth factor-stimulated alpha(v)beta3-dependent SMC migration that is specifically suppressed by polymerized collagen.

CONCLUSIONS

Polymerized type I collagen fibrils dynamically regulate PAI-1, which may be involved in altered alpha(v)beta3 integrin-dependent SMC migration.

Differential accumulation of proteoglycans and hyaluronan in culprit lesions: insights into plaque erosion

OBJECTIVE

The importance of the extracellular matrix molecules versican, biglycan, decorin, and hyaluronan in plaque instability has not been recognized.

METHODS AND RESULTS

Coronary lesions with acute thrombi and stable plaques were examined for the accumulation and distribution of specific proteoglycans and hyaluronan at culprit sites. The cell surface receptor for hyaluronan, CD44, and smooth muscle (SM) cell maturation markers were also assessed. Proteoglycans and hyaluronan accumulated in distinct patterns depending on plaque type. The fibrous cap of stable lesions was enriched in versican and biglycan, with considerably less staining for decorin and hyaluronan, whereas picrosirius red revealed a heavy accumulation of collagen type I. In contrast, intense staining for hyaluronan and versican was found in erosions at the plaque/thrombus interface, with weak staining for biglycan and decorin; collagen content was predominantly type III. Rupture sites showed little immunoreactivity for proteoglycans or hyaluronan. CD44 was localized along the plaque/thrombus interface in erosions, whereas in ruptures and stable plaques, it was mostly confined to inflammatory cells. Positive immunostaining for immature SM cells (SM myosin heavy chain SM1 and SMemb) was present in stable and eroded plaques, whereas the presence of SM2 and smoothelin was weak or nonexistent.

CONCLUSIONS

Specific accumulation of versican, hyaluronan, and CD44 at the sites of plaque erosion implicates an involvement of these molecules in events associated with acute coronary thrombosis.

Lysophosphatidylcholine stimulates monocyte chemoattractant protein-1 gene expression in rat aortic smooth muscle cells

OBJECTIVE

Monocyte chemoattractant protein (MCP)-1 is a proatherogenic factor that is responsible for approximately 60% of plaque macrophages in mouse models of atherosclerosis. We investigated whether lysophosphatidylcholine (LPC), enriched in oxidized low density lipoprotein, can modulate the expression of MCP-1 in arterial wall cells.

METHODS AND RESULTS

LPC induced a 3-fold increase in MCP-1 mRNA in rat vascular smooth muscle cells (VSMCs) in a time- and dose-dependent manner. Nuclear runon analysis showed that this increase was attributable to increased MCP-1 gene transcription. There was a 2-fold increase in MCP-1 protein in the conditioned media of cells treated with LPC. LPC-associated increases of MCP-1 mRNA and protein were similar to those produced by platelet-derived growth factor-BB, a known inducer of MCP-1. Analyses of the MCP-1 promoter in transiently transfected VSMCs indicated an LPC-responsive element(s) between base pairs -146 and -261 (relative to transcription initiation). Further studies suggested that LPC-induced MCP-1 expression partially involves mitogen-activated protein kinase/extracellular signal-regulated kinase, a tyrosine kinase(s), and (to a lesser extent) protein kinase C but not the activation of the platelet-derived growth factor receptor.

CONCLUSIONS

LPC stimulates MCP-1 expression at the transcriptional level in VSMCs, suggesting a molecular mechanism by which LPC contributes to the atherogenicity of oxidized low density lipoprotein.