Dietary selenium increases the antioxidant levels and ATPase activity in the arteries and veins of poultry

Selenium (Se) deficiency is associated with the pathogenesis of vascular diseases. It has been shown that oxidative levels and ATPase activity were involved in Se deficiency diseases in humans and mammals; however, the mechanism by how Se influences the oxidative levels and ATPase activity in the poultry vasculature is unclear. We assessed the effects of dietary Se deficiency on the oxidative stress parameters (superoxide dismutase, catalase, and hydroxyl radical) and ATPase (Na(+)K(+)-ATPase, Ca(++)-ATPase, Mg(++)-ATPase, and Ca(++)Mg(++)-ATPase) activity in broiler poultry. A total of 40 broilers (1-day old) were randomly divided into a Se-deficient group (L group, fed a Se-deficient diet containing 0.08 mg/kg Se) and a control group (C group, fed a diet containing sodium selenite at 0.20 mg/kg Se). Then, arteries and veins were collected following euthanasia when typical symptoms of Se deficiency appeared. Antioxidant indexes and ATPase activity were evaluated using standard assays in arteries and veins. The results indicated that superoxide dismutase activity in the artery according to dietary Se deficiency was significantly lower (p < 0.05) compared with the C group. The catalase activity in the veins and hydroxyl radical inhibition in the arteries and veins by dietary Se deficiency were significantly higher (p < 0.05) compared with the C group. The Se-deficient group showed a significantly lower (p < 0.05) tendency in Na(+)K(+)-ATPase activity, Ca(++)-ATPase activity, and Ca(++)Mg(++)-ATPase activity. There were strong correlations between antioxidant indexes and Ca(++)-ATPase activity. Thus, these results indicate that antioxidant indexes and ATPases may have special roles in broiler artery and vein injuries under Se deficiency.

Matrix metalloproteinase-9 deletion is associated with decreased mid-term vein wall fibrosis in experimental stasis DVT

INTRODUCTION

Post thrombotic syndrome therapy is primarily palliative, and the associated vein wall inflammatory mechanisms are unclear. Vein wall fibrotic injury following deep venous thrombosis (VT) is associated with elevated matrix metalloproteinases (MMPs). Whether and by what mechanism MMP9 directly contributes to vein wall remodeling after VT is unknown.

METHODS

WT and MMP9 -/- mice underwent stasis VT by ligation of the inferior vena cava (IVC) and tissue was harvested at 2, 8, and 21days. Assessment of thrombus size, and gene, protein and structural vein wall determinations were done.

RESULTS

VT resolution was increased in MMP9-/- mice as compared with controls at 21d only. The primary phenotypic fibrotic vein wall differences occurred at 8d post VT, with significantly less vein wall collagen content as assessed by Picosirius red staining in MMP9 -/- mice as compared with WT. Increased monocytic vein wall influx with less IL-1b and TGFb was found in MMP9 -/- vein walls as compared with WT. Corresponding levels of PAI-1 were increased in MMP9 -/- compared with WT, and no difference in FSP-1+cells as compared with controls.

CONCLUSIONS

In stasis VT, MMP9 modulates midterm vein wall collagen content, with an altered local inflammatory and profibrotic environment, likely directed by monocytes. Thus, MMP9 plays a role in both vein wall responses as well as late thrombus resolution.

Vein tissue expression of matrix metalloproteinase as biomarker for hemodialysis arteriovenous fistula maturation

Failure of arteriovenous fistula (AVF) maturation is attributed to impaired vein remodeling. The purpose of this study is to identify whether vein matrix metalloproteinase (MMP) expression and activity is associated with AVF maturation. Patients with renal insufficiency undergoing surgery had their vein segments harvested and snap-frozen at time of AVF construction. Expression of MMP-2, MMP-9, membrane type-1 MMP (MT1-MMP), tissue inhibitor of metallopreoteinases type 2 (TIMP-2), and TIMP-4 were measured using zymography and Western blotting techniques. Of 14 patients enrolled, 9 had successful maturation and 5 had failure of AVF maturation. Significantly higher levels of MT1-MMP (an MMP-2 activator; P = .01), TIMP-2 (an MMP-2 inhibitor; P = .03), MMP-2 latent (P = .02), and MMP-2 total (P = .03) were associated with AVF maturation. There was a trend toward higher levels of TIMP-4 in the successful group (P = .18). These data demonstrate a positive relationship between MMP-2 expression in veins and AVF maturation. MMP-2 could serve as a potential preoperative marker to predict maturation.

Protein kinase G regulates the basal tension and plays a major role in nitrovasodilator-induced relaxation of porcine coronary veins

BACKGROUND AND PURPOSE

Coronary venous activity is modulated by endogenous and exogenous nitrovasodilators. The present study was to determine the role of protein kinase G (PKG) in the regulation of the basal tension and nitrovasodilator-induced relaxation of coronary veins.

EXPERIMENTAL APPROACH

Effects of a PKG inhibitor on the basal tension and responses induced by nitroglycerin, DETA NONOate, and 8-Br-cGMP in isolated porcine coronary veins were determined. Cyclic cGMP was measured with radioimmunoassay. PKG activity was determined by measuring the incorporation of 32P from gamma-32P-ATP into the specific substrate BPDEtide.

KEY RESULTS

Rp-8-Br-PET-cGMPS, a specific PKG inhibitor, increased the basal tension of porcine coronary veins and decreased PKG activity. The increase in tension was 38% of that caused by nitro-L-arginine. Relaxation of the veins induced by nitroglycerin and DETA NONOate was accompanied with increases in cGMP content and PKG activity. These effects were largely eliminated by inhibiting soluble guanylyl cyclase with ODQ. The increase in PKG activity induced by the nitrovasodilators was abolished by Rp-8-Br-PET-cGMPS. The relaxation caused by these dilators and by 8-Br-cGMP at their EC50 was attenuated by the PKG inhibitor by 51-66%.

CONCLUSIONS AND IMPLICATIONS

These results suggest that PKG is critically involved in nitric oxide-mediated regulation of the basal tension in porcine coronary veins and that it plays a primary role in relaxation induced by nitrovasodilators. Since nitric oxide plays a key role in modulating coronary venous activity, augmentation of PKG may be a therapeutic target for improving coronary blood flow.

Desensitization of soluble guanylyl cyclase, the NO receptor, by S-nitrosylation

The molecular mechanism of desensitization of soluble guanylyl cyclase (sGC), the NO receptor, has long remained unresolved. Posttranslational modification and redox state have been postulated to affect sGC sensitivity to NO but evidence has been lacking. We now show that sGC can be S-nitrosylated in primary aortic smooth muscle cells by S-nitrosocysteine (CSNO), an S-nitrosylating agent, in human umbilical vein endothelial cells after vascular endothelial growth factor treatment and in isolated aorta after sustained exposure to acetylcholine. Importantly, we show that S-nitrosylation of sGC results in decreased responsiveness to NO characterized by loss of NO-stimulated sGC activity. Desensitization of sGC is concentration- and time-dependent on exposure to CSNO, and sensitivity of sGC to NO can be restored and its S-nitrosylation prevented with cellular increase of thiols. We confirm in vitro with semipurified sGC that S-nitrosylation directly causes desensitization, suggesting that other cellular factors are not required. Two potential S-nitrosylated cysteines in the alpha- and beta-subunits of sGC were identified by MS. Replacement of these cysteines, C243 in alpha and C122 in beta, created mutants that were mostly resistant to desensitization. Structural analysis of the region near beta-C122 in the homologous Nostoc H-NOX crystal structure indicates that this residue is in the vicinity of the heme and its S-nitrosylation could dampen NO activation by affecting the positions of key residues interacting with the heme. This study suggests that S-nitrosylation of sGC is a means by which memory of NO exposure is kept in smooth muscle cells and could be a mechanism of NO tolerance.

[Intensity of lipid peroxydation and antioxidant enzyme activity in walls of the arteries and veins in monoiodacetate intoxication]

The intensity of the lipid peroxydation (LPO) and the antioxidant enzyme activity (gluthathione peroxydase, superoxide dismutase and catalase) after monoiodacetate injection (10 mg/ kg) within 3, 7 and 14 days was examined in the arterial and venous walls of rabbits. The increase in the amount of the intermediate and final LPO products, and also the reduction in the antioxidant enzymes activity has been found in the vessels of all types. The changes in the studied parameters were more expressed in the venous vessels, than in the arteries. It is supposed that the activation of LPO is caused by the primary depression of antioxidant systems which arises as the consequence of the disorders of energy exchange in the vascular wall under the influence of monoiodacetate.

MAPping Out Arteries and Veins

Growing evidence suggests that a genetic program specifies the identity of arteries and veins before the onset of circulation. A signaling cascade involving sonic hedgehog (Shh), vascular endothelial growth factor (VEGF), the VEGF receptor 2 (VEGFR2), homeobox proteins Foxc1 and Foxc2, the Notch receptor, and the downstream transcription factor gridlock is required for expression of arterial markers, whereas only a single transcription factor, COUP-TFII (chicken ovalbumin upstream promoter-transcription factor II), has previously been implicated in maintaining venous fate. Recent work has now implicated two competing pathways downstream of VEGFR2 in arterial versus venous specification: Activation of the phospholipase C-gamma (PLC-gamma)-mitogen-activated protein kinase (MAPK) pathway acts in arterial specification, whereas the phosphoinositide 3-kinase (PI3K)-Akt pathway acts to allow a venous fate by inhibition of the PLC-gamma-MAPK pathway. Here, we review this work and discuss how activation of the MAPK signaling cascade could stimulate an arterial fate.

Reactive oxygen species and antioxidants relationship in the internal spermatic vein blood of infertile men with varicocele

AIM

To assess the relation of reactive oxygen species (ROS) and antioxidants in the internal spermatic vein blood compared to the peripheral venous blood.

METHODS

Sixty-eight infertile oligoasthenozoospemic patients associated with varicocele were investigated. During inguinal varicocelectomy, blood samples of internal spermatic as well as median cubital veins were withdrawn. Three ROS factors (malondialdehyde [MDA], hydrogen peroxide H(2)O(2), nitric oxide [NO]) and four antioxidants (superoxide dismutase [SOD], catalase [Cat], glutathione peroxidase [GPx] and vitamin C) were estimated in these blood samples.

RESULTS

Mean levels of tested ROS factors were significantly higher in the internal spermatic venous blood compared to those in the peripheral one (mean+/-SD) (MDA 18.7+/-1.4 nmol/mL vs. 15.4+/-1.4 nmol/mL, H(2)O(2) 43.6+/-8.0 micromol/mL vs. 30.8+/-8.1 micromol/mL, NO 2.3+/-0.5 nmol/L vs. 1.6+/-0.4 nmol/L, P<0.01). Mean levels of tested antioxidants were significantly lower in the internal spermatic venous blood compared to those in the peripheral one (superoxide dismutase 1 690.7+/-130.0 U/mL vs. 1 818.5+/-143.0 U/mL, catalase 38.9+/-6.1 mol/L vs. 47.9+/-10.2 mol/L, GPx 20.4+/-8.1 U/mL vs. 23.0+/-8.4 U/mL, vitamin C 0.3+/-0.1 vs. 0.4+/-0.1 mg/dL, P<0.05).

CONCLUSION

Internal spermatic venous blood of infertile male cases associated with varicocele demonstrated elevated levels of ROS and decreased levels of antioxidants compared to peripheral venous circulation.

Endothelial cell activation in patients with decompensated heart failure

BACKGROUND

Vascular endothelial functions, other than nitric oxide (NO)-mediated control of vasomotor tone, are poorly characterized in patients with chronic heart failure (CHF). Veins and arteries are exposed to the same circulating proinflammatory mediators in patients with CHF. The present study tested whether endothelial cell activation occurs in veins of patients with decompensated CHF and whether activation, if present, subsides with return to a clinically compensated state.

METHODS AND RESULTS

Fifteen patients with decompensated CHF requiring transient inotropic support and 6 age-matched, healthy controls were studied. Endothelial cells and blood were collected from a forearm vein, and brachial artery flow-mediated dilation (FMD) was measured before and 24 hours after discontinuation of short-term inotropic therapy, when patients had returned to a steady compensated state. Nitrotyrosine immunoreactivity (an intracellular marker of oxidative stress), cyclooxygenase-2 (COX-2), and inducible NO synthase (iNOS) expression were significantly higher in venous endothelial cells of patients in clinical decompensation when compared with healthy subjects. Return to a compensated state resulted in a significant reduction in nitrotyrosine immunoreactivity, COX-2, and iNOS expression. Concomitantly, a significant increase in FMD and a decline in plasma total 8-isoprostane and bicycloprostaglandin E2 levels were observed. Venous endothelial NOS expression was unaffected by clinical decompensation.

CONCLUSIONS

Clinical decompensation in CHF is associated with activation of the venous endothelium. Return to a compensated state after short-term inotropic therapy results in a significant reduction in endothelial nitrotyrosine formation, COX-2, and iNOS expression.

Vein graft neointimal hyperplasia is exacerbated by tumor necrosis factor receptor-1 signaling in graft-intrinsic cells

OBJECTIVE

Vein graft remodeling and neointimal hyperplasia involve inflammation, graft-intrinsic cells, and recruitment of vascular progenitor cells. We sought to examine if the inflammatory cytokine tumor necrosis factor (TNF) affects vein graft remodeling via its p55 TNF receptor-1 (p55).

METHODS AND RESULTS

Inferior vena cava-to-carotid artery interposition grafting was performed between p55-/- and congenic (C57Bl/6) wild-type (WT) mice. Immunofluorescence revealed TNF in early (2-week) vein grafts. Six weeks postoperatively, luminal and medial areas were indistinguishable among all vein graft groups. However, neointimal area was reduced in p55-/- grafts: by 40% in p55-/- grafts placed in p55-/- recipients, and by 21% in p55-/- grafts placed in WT recipients, compared with WT grafts in WT recipients (P<0.05). In 2-week-old vein grafts, p55 deficiency reduced intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and monocyte chemoattractant protein-1 expression by 50% to 60%, and increased the extent of graft endothelialization. In vitro, TNF promoted chemokine expression and [3H]thymidine incorporation in vascular smooth muscle cells (SMCs) from WT, but not from p55-/- mice. However, responses of WT and p55-/- SMCs to other growth factors were equivalent.

CONCLUSIONS

Signaling via p55, in vein graft-intrinsic cells, contributes to the pathogenesis of vein graft neointimal hyperplasia.

Arterial endothelium-specific activin receptor-like kinase 1 expression suggests its role in arterialization and vascular remodeling

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by epistaxis, mucocutaneous telangiectases, and arteriovenous malformations (AVM). Two genes are linked to HHT: endoglin (ENG) in HHT1 and activin receptor-like kinase 1 (ACVRL1; ALK1) in HHT2. Although both genes are involved in the transforming growth factor beta signaling pathways, the pathogenetic mechanisms for HHT remain elusive. It was shown that mutations in the Alk1 gene in mice and zebrafish resulted in an embryonic lethal phenotype due to severe dilation of blood vessels. We created a novel null mutant mouse line for Alk1 (Alk1lacZ) by replacing its exons, including the one that encodes the transmembrane domain, with the beta-galactosidase gene. Using Alk1lacZ mice, we show that Alk1 is predominantly expressed in developing arterial endothelium. Alk1 expression is greatly diminished in adult arteries, but is induced in preexisting feeding arteries and newly forming arterial vessels during wound healing and tumor angiogenesis. We also show that hemodynamic changes, which require vascular remodeling, may regulate Alk1 expression. Our studies suggest the role of Alk1 signaling in arterialization and remodeling of arteries. Contrary to the current view of HHT as venous disease, our findings suggest that the arterioles rather than the venules are the primary vessels affected by the loss of an Alk1 allele, and that blood vessels with reduction in Alk1 expression may harbor defects in responding to demands for vascular remodeling.

Activation of mitogen-activated protein kinases during preparation of vein grafts and modulation by a synthetic inhibitor

OBJECTIVE

Long-term durability of saphenous vein grafts used for coronary artery bypass grafting is limited by neointimal formation. Arterial vascular injury is known to activate intracellular mitogen-activated protein kinases, including extracellular signal-regulated kinases and c-jun N-terminal kinases, that affect cell differentiation, proliferation, migration, and apoptosis. This study tests the hypothesis that these mitogen-activated protein kinases are activated in saphenous veins during preparation for coronary artery bypass grafting.

METHODS

Saphenous veins were harvested from 10 patients undergoing coronary artery bypass grafting. A specimen from each vein was placed in ice-cold lysis buffer immediately after harvesting (t = 0). The remaining tissue was incubated at room temperature in normal saline, 0.1% dimethylsulfoxide (vehicle), or 50 mmol/L PD98059 (mitogen-activated protein kinase kinase-1/2 inhibitor) until the vein was grafted (mean 50 minutes). To study kinetics of intracellular signaling pathways, canine saphenous veins were harvested, and mitogen-activated protein kinases and PI-3 kinase pathways were studied after different incubation time intervals. Extracted proteins were analyzed by Western blotting or in vitro kinase assay.

RESULTS

The human saphenous veins showed elevated levels of active extracellular signal-regulated kinase after harvesting (t = 0) and prior to implant (t = 1). Incubation with PD98059 resulted in decreased activation of extracellular signal-regulated kinase. Kinetics of canine saphenous veins showed extracellular signal-regulated kinase and c-jun N-terminal kinase activation, in a time-dependent manner, along with activation of the growth factor-regulated PI3 kinase pathway.

CONCLUSIONS

This study characterizes activation of extracellular signal-regulated kinases and c-jun N-terminal kinases during vein graft preparation and demonstrates the ability to inhibit extracellular signal-regulated kinase activation by simple incubation with a specific inhibitor. Further studies are needed to evaluate the significance of these findings with respect to graft durability.

Influence of coronary artery diameter on eNOS protein content

The purpose of this study was to test the hypothesis that the content of endothelial nitric oxide synthase (eNOS) protein (eNOS protein/g total artery protein) increases with decreasing artery diameter in the coronary arterial tree. Content of eNOS protein was determined in porcine coronary arteries with immunoblot analysis. Arteries were isolated in six size categories from each heart: large arteries [301- to 2,500-microm internal diameter (ID)], small arteries (201- to 300-microm ID), resistance arteries (151- to 200-microm ID), large arterioles (101- to 150-microm ID), intermediate arterioles (51- to 100-microm ID), and small arterioles(<50-microm ID). To obtain sufficient protein for analysis from small- and intermediate-sized arterioles, five to seven arterioles 1-2 mm in length were pooled into one sample for each animal. Results establish that the number of smooth muscle cells per endothelial cell decreases from a number of 10 to 15 in large coronary arteries to 1 in the smallest arterioles. Immunohistochemistry revealed that eNOS is located only in endothelial cells in all sizes of coronary artery and in coronary capillaries. Contrary to our hypothesis, eNOS protein content did not increase with decreasing size of coronary artery. Indeed, the smallest coronary arterioles had less eNOS protein per gram of total protein than the large coronary arteries. These results indicate that eNOS protein content is greater in the endothelial cells of conduit arteries, resistance arteries, and large arterioles than in small coronary arterioles.

Immunoreactivities of eNOS, ET-1 and ETB-R in blood vessels of the uterine mesometrium during the estrous cycle in the pig

Cryostat sections of arterial and venous vessels from various size branches of the uterine artery and utero-ovarian vein of the pig mesometrium in different phases of the estrous cycle were stained immunohistochemically for endothelial nitric oxide synthase (eNOS), endothelin-1 (ET-1) and endothelin B receptor (ETB-R) using ABC method. Immunoreactivity was evaluated according to 6-point scale under light microscope. The differences in immunostaining intensity in the endothelium of the vessels studied at various levels of mesometrium suggest a correlation of eNOS, ET-1 and ETB-R expression with the estrous cycle. In the follicular phase, the highest eNOS immunoreactivity was noticed in arcuate arteries and veins, while immunoreaction of ET-1 was much lower, just as ETB-R. On the other hand, the highest ET-1 immunoreactivity was observed during first 2 days afterovulation, while ETB-R showed low immunoreactivity level during the whole luteal phase. Vessels from the middle part of mesometrium (I degrees and II degrees branches) and large vascular trunks revealed similar staining for eNOS during the cycle as compared to arcuate arteries. Those vessels showed very high immunoreactivity levels for ET-I and ETB-R during first 2 days after ovulation. Our results suggest that during the estrus eNOS, ET-I and ETB-R play a significant role in the regulatory process of blood flow through the mesometrial vessels, that are connected to the uterine horn.

Alpha 2 adrenoceptor-mediated vasoconstriction in porcine palmar lateral vein: role of phosphatidylinositol 3-kinase and EGF receptor transactivation

1 Alpha(2) adrenoceptors cause vasoconstriction in the porcine palmar lateral vein through a mechanism involving the ERK signal transduction cascade, calcium influx, and a Src tyrosine kinase. The aim of the present study was to determine if phosphatidylinositol 3-kinase (PI 3-kinase) and/or epidermal growth factor (EGF) receptor transactivation are also involved. 2 alpha(2) Adrenoceptor-mediated vasoconstriction and ERK2 activation in the porcine palmar lateral vein was inhibited in the presence of either the PI 3-kinase inhibitor LY294002, or the EGF receptor tyrosine kinase inhibitor AG1478 suggesting the involvement of both PI 3-kinase and EGF receptor transactivation. 3 Akt phosphorylation was increased in segments of porcine palmar lateral vein contracted with UK14304 indicating an increase in Akt activation. This is a further indication that PI 3-kinase is involved in alpha(2) adrenoceptor-mediated vasoconstriction. Akt activation was inhibited by the Src tyrosine kinase inhibitor PP2, and removal of extracellular calcium. 4 UK14304 (10 microM) stimulated an increase in intracellular calcium in segments of palmar lateral vein. This was inhibited by removal of extracellular calcium, but not by nifedipine suggesting the rise in calcium is due to influx of calcium through non-L type calcium channels. The increase in calcium was also inhibited by LY294002 indicating that PI 3-kinase is upstream of calcium influx. 5 These data indicate that alpha(2) adrenoceptor-mediated vasoconstriction in the porcine palmar lateral vein is dependent upon stimulation of PI 3-kinase, leading to an influx of calcium. This results in activation of the EGF receptor tyrosine kinase, and finally activation of ERK-MAP kinase.

Effect of chymase inhibitor on vascular proliferation

In vascular tissues, angiotensin II is potentially cleaved from angiotensin I by chymase and angiotensin-converting enzyme (ACE). In the normal state, vascular ACE regulates local angiotensin II formation and plays a crucial role in the regulation of blood pressure, whereas chymase is stored in mast cells and has no enzymatic activity. Chymase is activated immediately upon its release into the extracellular matrix in vascular tissues after mast cells have been activated by stimuli such as vessel injury by grafting or a balloon catheter. In dog grafted veins, chymase activity is increased, and the vascular proliferation is suppressed by either a chymase inhibitor or an angiotensin II receptor blocker. After balloon injury in dog vessels, chymase activity is significantly increased in the injured artery, and a chymase inhibitor is effective in preventing the vascular proliferation, but an ACE inhibitor is ineffective. Chymase plays an important role in the development of vascular proliferation via the induction of local angiotensin II formation in injured vessels.

Superoxide radical concentration and superoxide dismutase (SOD) enzyme activity in varicose veins

The aim of this study is to measure the level of both the superoxide dismutase (SOD) enzyme and its substrate, superoxide radicals, in the wall of varicose veins. A total of 44 vein specimens were collected from 24 patients who underwent surgery for varicose veins at Asir Central Hospital (ACH), Abha, Saudi Arabia during the period from October 1999 to November 2000. The patients were 4 males and 20 females with a mean age of 35.3+/-SD 10.4 years (15-62 years). At operation, vein specimens were collected from both the stripped, mid-thigh long saphenous vein (LSV) and the avulsed distal calf varicosities, as appropriate. The samples were processed and both the SOD level and the superoxide radicals concentration were estimated using spectrophotometry. The mean SOD level in the distal calf varicosities (14.7+/-6.0 units/mg protein) was significantly higher than that in the mid-thigh LSV (8.2+/-2.9 units/mg protein, P<0.05). The mean superoxide radical concentration in the distal calf varicosities (69.5+/-11.9 nmol/ml) was also significantly higher than that in the mid-thigh LSV (33.8+/-10.5 nmol/ml, P<0.05). These results suggest that superoxide radicals play an important role in the pathogenesis of varicose veins.

Relationship of the 20S proteasome and the proteasome activator PA28 to atherosclerosis and intimal hyperplasia in the human vascular system

Down-regulation of the proteasome activator PA28 results in abnormal proteasome activation and has been implicated in the development of intimal hyperplasia (IH) in animal models. Demonstration of proteasome and PA28 expression has not yet been documented in the human vascular system. This study sought to define the distribution of the 20S proteasome and its activator PA28 in human vessels and determine the relationship between the expression of the proteasome and PA28 and the development of atherosclerosis and IH. Vascular biopsies were obtained from 70 patients at the time of surgery, were snap frozen and sectioned in 5-micron sections, and prepared using standard histological techniques. The immunoperoxidase technique was used to identify 20S proteasome and PA28 expression in diseased and normal human arteries and veins as well as in patent bypass grafts with and without IH. Expression was graded by a blinded pathologist (scale: 1-4). Repeat quantification of the immunopositive cells was also performed. Expression of 20S proteasome and PA28 was identified in all vascular tissues examined. The proteins were identified predominately within the cytoplasm of vascular smooth muscle cells and endothelial cells. PA28 was more intensely expressed in quiescent regions of the vessel wall as compared to areas undergoing active proliferation and remodeling. PA28-mediated activation of the proteasome may be necessary to maintain normal cellular homeostasis and prevent excessive cellular proliferation in the human vascular system. Abnormalities of proteasome activation may have a significant role in the development of atherosclerosis and IH.

Coronary artero-venous gradient of endogenous urokinase

Experimental data indicate that urokinase-type plasminogen activator (u-PA) contributes significantly to endogenous fibrinolysis and vascular remodeling in proportion to its local concentrations. In humans, however, it is not known whether u-PA levels vary at different sites and across specific vascular beds. We investigated possible regional and artero-venous differences in plasma u-PA concentrations in 15 patients undergoing cardiac catheterization. Three pairs of simultaneous samples were taken from: (1) the ascending aorta and coronary sinus; (2) left ventricle and right atrium; (3) femoral artery and femoral vein. Single-chain urokinase-type plasminogen activator (scu-PA) was measured by bioimmunoassay, and total u-PA antigen (including scu-Pa and two-chain urokinase-type plasminogen activator complexed with inhibitors (tcu-PA)) by enzyme-linked immunosorbent assay. Scu-PA represented, on average, 51+/-15% of total u-PA concentrations. Scu-PA and total u-PA levels were correlated (r=.72, P<.0001) and did not differ significantly among the arterial or venous locations. There was a small but consistent increase in mean (+/-standard deviation (S.D.)) scu-PA concentrations from all arterial to all venous samples (1.5+/-0.6 vs. 1.6+/-0.5 ng/ml, P=.038) and from ascending aorta to coronary sinus (1.6+/-0.5 vs. 1.7+/-0.6 ng/ml, P=.046). Similarly, total u-PA levels increased from femoral artery to femoral vein (2.9+/-0.7 vs. 3.0+/-0.8 ng/ml, P<.001). In contrast, across the lungs, no significant concentration-gradient was seen in either scu-PA or total u-PA. The changes in total u-PA roughly followed those of scu-PA. These data identify an artero-venous gradient in human plasma u-PA across the coronary and peripheral beds, but not across the lungs, suggesting differences in u-PA kinetics according to vascular location.

Cross-talk between the signals hypoxia and glucose at the glucose response element of the L-type pyruvate kinase gene

The signals oxygen and glucose play an important role in metabolism, angiogenesis, tumorigenesis, and embryonic development. Little is known about an interaction of these two signals. We demonstrate here the cross-talk between oxygen and glucose in the regulation of L-type pyruvate kinase (L-PK) gene expression in the liver. In the liver the periportal to perivenous drop in O(2) tension was proposed to be an endocrine key regulator for the zonated gene expression. In primary rat hepatocyte cultures the expression of the L-PK gene on mRNA and on protein level was induced by venous pO(2), whereas its glucose-dependent induction occurred predominantly under arterial pO(2). It was shown by transient transfection of L-PK promoter luciferase and glucose response element (Glc(PK)RE) SV40 promoter luciferase gene constructs that the modulation by O(2) of the glucose-dependent induction occurred at the Glc(PK)RE in the L-PK gene promoter. The reduction of the glucose-dependent induction of the L-PK gene expression under venous pO(2) appeared to be mediated via an interference between hypoxia inducible factor-1 (HIF-1) and upstream stimulating factor at the Glc(PK)RE. The glucose response element also functioned as an hypoxia response element which was confirmed in cotransfection assays with Glc(PK)RE luciferase gene constructs and HIF-1alpha expression vectors. Furthermore, it was found by gel shift and supershift assay that HIF-1alpha and USF-1 or USF-2 could bind to the Glc(PK)RE. Our findings implicate that the cross-talk between oxygen and glucose might have a fundamental role in the regulation of several physiological and pathophysiological processes.

Tu-M2-PK in the blood of testicular and cubital veins in men with testicular cancer

We wanted to verity whether M2-PK is a useful marker in testicular cancer. In a prospective study of 20 consecutive patients, blood was drawn from the testicular and the cubital vein before semicastration and later. For the detection of M2-PK we used the Assay of ScheboTech. In the testicular vein M2-PK was 11.2 U/ml. In the cubital vein it was 6.2 U/ml before semicastration, increasing in the following days. There were no significant differences between testicular and cubital vein blood, between the non-metastasized patients and the metastasized stages and between the patients with seminoma and non-seminomatous tumors. There is no profit in the diagnosis of testicular cancer using Tu-M2-PK.

Interleukin 1beta and GABA-transaminase activity in rat thymus

The occurrence and distribution of 4-aminobutyrate:2 oxoglutarate transaminase (GABA-t) activity were examined in the rat thymus of normal and immunostimulated rats using biochemical and histoenzymatical methods. Specific GABA-t reactivity was confined primarily to the arteries and, to a lesser extent, to the veins. Only a few activities could be observed in association with the subcapsular and medullar part of the parenchyma and nerve fibers. GABA-t was considered a linking enzyme between the immune and the nervous system and it was studied with the aim of analyzing the relationships between these two systems. Our findings indicate that the GABA-t activity in the thymus is specifically located in the wall of the blood vessels. Moreover, our results demonstrate the presence of a GABA-t activity in the peripheral blood vessels. Treatment with interleukin 1beta induces an increase of protein content of the amounts of GABA-t biochemically assayed and of the levels of histoenzymatically stained GABA-t. Furthermore, staining of the different structures of the thymus in treated or untreated rats shows that the significant modifications concern the parenchyma, the structures resembling nerve fibers and finally, the whole thymus. On the contrary, the highest activity of the GABA-t is located in the walls of arteries, veins and lymphatic vessels.

Acetylcholinesterase activity in rat thymus after immunostimulation with interleukin beta

The occurrence and distribution of Acetylcholinesterase (AChE) activity were examined in the thymus of normal and immuno-stimulated adult and aged rats using biochemical and enzymehistochemical methods. Specific AChE reactivity was found primarily in the arteries and, to a lesser extent, in the veins. Only a small amount of activity could be observed in association with the subcapsular and medullary part of the parenchyma and nerve fibers. Our findings indicate that AChE activity in the rat thymus increases after treatment with interleukin beta. In fact treatment with interleukin beta induces an increase of protein content, of the amounts of AChE biochemically assayed and at the levels of AChE histoenzymatically stained. Furthermore, staining of the different structures of the thymus in treated or untreated rats shows that the significant modifications concern the parenchyma, the structures resembling nerve fibers and the whole thymus, while only small changes are observed in AChE activity located in the walls of arteries, veins and lymphatic vessels.

Release of GM-CSF and G-CSF by human arterial and venous smooth muscle cells: differential regulation by COX-2

In addition to their traditional contractile function, vascular smooth muscle cells can be stimulated under inflammatory conditions to release a range of potent biological mediators. Indeed, we and others have shown that human vascular smooth muscle release the colony stimulating factors (CSF) granulocyte macrophage-CSF (GM-CSF) and granulocyte-CSF (G-CSF) as well as large amounts of prostaglandins following the induction of cyclo-oxygenase-2 (COX-2), when stimulated with cytokines. Here we demonstrate, for the first time, that co-induced COX-2 activity simultaneously suppresses GM-CSF release and potentiates G-CSF release by human vascular cells. Moreover, the differential regulation of GM-CSF and G-CSF release by COX-2 was mimicked by the prostacyclin (PGI(2)) mimetic, cicaprost. These observations suggest that PGI(2), released following the induction of COX-2, differentially regulates the release of GM-CSF (suppresses) and G-CSF (potentiates) from human vascular cells.

SERCA pump isoform expression in endothelium of veins and arteries: every endothelium is not the same

Endothelium from rat aorta expresses sarco/endoplasmic reticulum Ca2+(SERCA) pump gene SERCA3 where as the smooth muscle expresses SERCA2. This has led to the postulate that vascular endothelium expresses SERCA3. To test this postulate, we examined the SERCA2 and SERCA3 mRNA expression in endothelium and smooth muscle dissected from coronary artery, coronary vein, aorta and vena cava of pig. Smooth muscle from all arteries and veins expressed only the SERCA2 mRNA. Endothelium from coronary artery, coronary vein and aorta expressed both SERCA2 and SERCA3 mRNA but the endothelium from vena cava did not express SERCA3 mRNA although it expressed SERCA2. These observations support the postulate that vascular endothelium expresses SERCA3 but the affirmation is equivocal because vena cava endothelium does not express SERCA3.

Stretch induces mitogen-activated protein kinase activation and myogenic tone through 2 distinct pathways

The aim of this study was to evaluate the involvement of the mitogen-activated protein kinase (ERK1/2) pathway in response to stretch in a blood vessel developing myogenic tone on stretch. Indeed, in resistance arteries and veins, the main effect of pressure is to induce a maintained vasoconstrictor (myogenic) tone. Isolated segments of rabbit facial vein were mounted in organ baths and submitted to isometric stretch. In this experimental model, myogenic tone was absent when the bath temperature was 33 degrees C. ERK1/2 activity was determined in each isolated segment by an in-gel kinase assay. Wall tension and ERK1/2 activity were measured in the same samples in the presence (39 degrees C) or in the absence of myogenic tone (33 degrees C). At 39 degrees C, a 5-mN wall tension induced myogenic tone (5.7+/-1.8 mN) and an increase in ERK1/2 activity (282+/-52% versus unstretched vessels, P<0.05). At 33 degrees C, in the absence of myogenic tone, ERK1/2 activity was similarly increased by stretch (254+/-35% versus unstretched vessels). The calcium-dependent and -independent protein kinase C (PKC) blocker Ro-31-8220 (5 x 10(-7) mol/L), but not the calcium-dependent PKC blocker Go-6976 (10(-6) mol/L), inhibited myogenic tone. However, ERK1/2 activity was not affected by either PKC blocker. Genistein (10(-7) mol/L), a general tyrosine kinase inhibitor, but not herbimycin A (5 x 10(-7) mol/L), a cSrc-family tyrosine kinase inhibitor, suppressed stretch-induced ERK1/2 activation (P<0.05) without affecting myogenic tone. Nifedipine (10(-6) mol/L), a voltage-dependent calcium entry inhibitor, and ryanodine (10(-6) mol/L), which depletes calcium stores, both inhibited ERK1/2 activity (113+/-12% and 121+/-7%, respectively; P<0. 05) without affecting myogenic tone. The mitogen-activated protein kinase kinase inhibitor PD 98059 (5 x 10(-6) mol/L) also inhibited ERK1/2 activation without affecting myogenic tone. The present results suggest that stretching the rabbit facial vein induced 2 distinct pathways, one leading to myogenic tone (via a non-calcium-dependent PKC activation) and one leading to ERK1/2 activation through a calcium-dependent pathway involving tyrosine kinase.

[The species characteristics of the elastolytic system of the arteries and veins in the early stages of experimental tunica media calcinosis and atherosclerosis]

The role of the elastolytic system arterial and venous tissues in pathogenesis of vascular pathology was investigated on rabbits and rats in experimental arterio-atherosclerosis. The obtained results indicate that elastase activity in aortic homogenates was significant higher in normal and pathological condition in rats than in rabbits. Elastase inhibitors (alpha 2-macroglobulin and alpha 1-proteinase inhibitor) also respond on angiosclerotic agent and level of alpha 2-macroglobulin increased significant in resistant animals (rats) but not in rabbits. In venous vessels determined more higher level of antielastase potential that may be explain its phenomenal resistance to different damage factors. The presented result confirm the importance of balance elastase and it inhibitors in pathogenesis of arterio-atherosclerosis.

Reduction of lipid peroxidation with intraoperative superoxide dismutase treatment decreases intimal hyperplasia in experimental vein grafts

BACKGROUND

Vein graft failure is commonly attributed to the development of intimal hyperplastic lesions. Oxidative stress has been implicated in the initiation and progression of atherosclerosis. In this study we examined the effects of local intraoperative treatment with polyethylene glycolated superoxide dismutase (PEG-SOD) on lipid peroxidation and on the development of intimal hyperplasia in experimental vein grafts.

MATERIALS AND METHODS

Forty-one New Zealand White male rabbits had a right carotid interposition bypass graft using the ipsilateral reversed jugular vein. Sixteen animals received local PEG-SOD (4,100 units) treatment; 9 animals received the polyethylene glycol (PEG) vehicle without SOD; 16 animals were used as controls. Postoperatively, malondialdehyde (MDA, a product of lipid peroxidation) concentration and SOD activity were assessed in 3-day vein grafts by colorimetric spectrophotometry. To determine wall dimensions and vasomotor function, morphometric and isometric tension studies were performed on 28-day vein grafts.

RESULTS

MDA concentration was increased 5. 7-fold (P < 0.05) in 3-day control vein grafts compared to ungrafted jugular veins. Intraoperative PEG-SOD treatment raised SOD activity 5.0-fold (P < 0.05) and reduced MDA concentration 8-fold (P < 0.05) in 3-day vein grafts compared to controls. At 28 days, intimal thickness was reduced by 35% with PEG-SOD treatment (54 +/- 4 vs 83 +/- 5; P < 0.001) compared to control vein grafts, without a change in medial thickness (77 +/- 4 vs 88 +/- 5; P = ns). The vasomotor functions of 28-day PEG-SOD-treated vein grafts to norepinephrine, serotonin, bradykinin, nitroprusside, and acetylcholine were not significantly changed when compared to controls. Treatment with PEG alone did not significantly alter lipid peroxidation, wall dimensions, or vasomotor function of vein grafts.

CONCLUSION

This study demonstrates that intraoperative local treatment of vein grafts with PEG-SOD increases SOD activity and decreases lipid peroxidation for at least 3 days, resulting in reduced intimal hyperplasia at 28 days. These findings further implicate oxidative stress in the hyperplastic response of vein grafts and suggest a potential therapeutic role for PEG-SOD in the prevention of vein graft failure.

Alterations in wall tension and shear stress modulate tyrosine kinase signaling and wall remodeling in experimental vein grafts

PURPOSE

Hemodynamic alterations have been implicated as major stimuli for the development of intimal hyperplasia in vein grafts that are implanted in the arterial circulation. Tyrosine kinase is known to mediate cell signaling. However, its role with in vivo mechanotransduction is not yet well defined. We used a novel bioprosthetic collagen tube to provide an external support to vein grafts and examined the subsequent changes in hemodynamics, tyrosine kinase signaling, wall remodeling, and vasomotor function.

METHODS

Carotid interposition bypass grafting was performed with the reversed jugular vein in New Zealand white rabbits. In the experimental group (n = 15), after the completion of the proximal anastomosis, the vein was passed through a 4-mm collagen tube and the distal anastomosis was performed. The tube support was fashioned to completely cover the vein grafts. The control animals (n = 14) had no tube support. After surgery, the blood pressure and flow rate were measured and the wall tension and shear stress were calculated in the vein grafts on day 3 or day 28 (n = 5 per group). Tyrosine phosphorylation was assessed with the Western blot test in vein grafts at day 3 (n = 4 per group). The intimal and medial dimensions of the vein grafts were assessed with videomorphometry on day 28 (n = 5 per group). The cumulative dose response curves of the vein grafts to contractile and relaxant agonists were determined in isometric tension studies on day 28 (n = 5 per group).

RESULTS

The use of tube support reduced wall tension 1.7-fold (P <.01) and increased shear stress 4.8-fold (P <.001) without altering the flow rate or blood pressure. The tyrosine kinase activity was reduced 15-fold (P <.001) in the tube-supported vein grafts. The intimal thickness was reduced by 45% in the tube-supported vein grafts as compared with the control grafts (46 +/- 2 mm vs 84 +/- 5 mm, respectively; P <.0001), and the media thickness was reduced by 20% (63 +/- 8 mm vs 79 +/- 4 mm, respectively; P <.05). Isometric tension studies showed preservation of contractile function and modulation of endothelial-dependent dysfunctional relaxation in tube-supported vein grafts.

CONCLUSION

These results show that reduced wall tension and increased shear stress with an external tube support can effectively modulate the signaling, functional, and hyperplastic responses in vein grafts. We conclude that this simple strategy deserves further study and clinical consideration.

Identification of arterial and venous segments of blood vessels using alkaline phosphatase staining of ink/gelatin injected tissues

The present study describes a method for discriminating between the arterial and venous segments of blood vessels in mouse tissues and organs using alkaline phosphatase (ALPase) staining of ink/gelatin injected tissues. Anesthetized mice were injected through the left ventricle with blue ink/gelatin, and various organs and tissues were removed from the body and fixed by immersion in 10% formalin. Sections 50-100 microm thick were incubated for ALPase in a medium containing naphthol AS-BI phosphate and fast red TR by the azocoupling method. In such specimens as the brain and skeletal muscles, ALPase activity was found in arterioles and capillaries on the arterial side, whereas it was absent in capillaries on the venous side and in venules. In the liver, only branches of the hepatic artery were positive. ALPase activity was absent in the vessels of the lung except for a positive reaction in branches of the bronchial arteries. These findings indicate that the ALPase activity is confined to the arterioles and arterial segments of the capillaries in the systemic circuit. Thus, ALPase staining of ink/gelatin injected specimens is a useful method for differentiating the arterial and venous segments of the micro-vascular bed in various organs and tissues in mice.

Nonuniformity of endothelial constitutive nitric oxide synthase distribution in cardiac endothelium

Endocardial endothelium and endothelium of coronary vessels produce NO. Histochemical methods have suggested that coronary arterial endothelial cells contain more endothelial constitutive NO synthase (ecNOS) than does coronary venous endothelium. We have further investigated the distribution of ecNOS in cardiac endothelium using immunofluorescence and en face confocal microscopy of rat heart. In endocardial endothelium, confocal microscopy revealed distinct ecNOS labeling of peripheral cell borders, cytoplasmic labeling, and labeling of the Golgi complexes. Labeling of the cell borders and of the Golgi complexes was confirmed by double staining for ecNOS and for platelet and endothelial cell adhesion molecule or Golgi 58k protein, respectively. Cytoplasmic labeling was strongest in coronary arterial endothelium. The size of the ecNOS-labeled Golgi complexes decreased from coronary arterial endothelial cells (8.63 +/- 0.39 microm2, mean +/- SE of 5 rats) to endocardial endothelium (7.07 +/- 0.61 microm2) and to coronary venous endothelium (3.65 +/- 0.20 microm2). In addition, pixel intensity of ecNOS labeling was higher in arterial endothelial cells than in venous endothelial cells. Endothelium of myocardial capillaries also contained small ecNOS-labeled Golgi complexes. No correlation was observed between endothelial cell surface area and Golgi complex size. Caveolin-1 labeling was strongest in capillaries and did not coincide completely with ecNOS labeling in endocardial and venous endothelium. These results suggest that endocardial and coronary arterial endothelium in the rat have a higher synthetic activity and might express more ecNOS than is expressed by cardiac venous and capillary endothelium. The observed heterogeneity in ecNOS distribution might be related to the specific mechanochemical environment and function of each endothelial compartment.

Plasminogen activator inhibitor-1 in neointima of vein grafts: its role in reduced fibrinolytic potential and graft failure

BACKGROUND

Intimal smooth muscle cell proliferation is an underlying pathogenetic mechanism for neointimal hyperplasia and consequent vein graft failure. This study characterizes the expression of tissue-type plasminogen activator (TPA), urokinase-type plasminogen activator (UPA), and plasminogen activator inhibitor-1 (PAI-1) in hyperplastic vein grafts and normal venous tissue.

METHODS AND RESULTS

Failing graft and control vein specimens from 14 donors were homogenized, and TPA and PAI-1 were quantified with ELISA. The amount of PAI-1 was seven times higher (4.2+/-2.1 versus 0.6+/-0.6 ng/mg protein, P<.005), but the TPA antigen content was markedly lower (3.1+/-2.1 versus 8.1+/-3.7 ng/mg protein, P<.005) in the stenosed grafts compared with the control veins. Strong immunohistochemical PAI-1 reactivity and in situ hybridization signals for PAI-1 and UPA mRNA were associated with the smooth muscle cells of the thickened intima of the grafts. Functional assays of the graft specimens showed an increased UPA/TPA ratio and a decreased total fibrinolytic activity in comparison with normal veins.

CONCLUSIONS

Upregulation of PAI-1 mRNA expression and markedly increased amounts of PAI-1 antigen were detected in the vein grafts after the development of neointima. Furthermore, augmented UPA activity was found in the graft wall, but TPA was clearly depleted. Altogether, our findings imply decreased fibrinolytic potential in the stenosed graft, which may contribute to the graft occlusion.

Inducible nitric oxide synthase expression in human vein grafts

BACKGROUND

The patency of vascular reconstructive procedures is limited by the development of intimal hyperplasia (IH). Nitric oxide (NO) seems to be beneficial in abrogating this process. Currently, there is little information concerning inducible nitric oxide synthase (iNOS), the enzyme responsible for NO synthesis, and human vein grafts. The purpose of this study was to examine iNOS gene expression in human aortocoronary vein grafts (ACVG) and infrainguinal vein bypass grafts (IVG).

METHODS

Nonthrombosed sections from ACVG (n = 5), IVG (n = 5), and control saphenous vein (SV; n = 4) were harvested and processed for RNA isolation. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed on samples using 32P radioactively end labeled primers. Glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) was the internal control, and results were expressed as iNOS pmol/GAPDH pmol.

RESULTS

There was a significant increase in the iNOS gene expression in the ACVG (0.049 +/- 0.01) when compared with IVG (0.019 +/- 0.001) or normal SV (0.011 +/- 0.002; P < or = 0.05). There was no significant difference between normal vein and the infrainguinal grafts. Sequencing of a fragment of the amplified 428 bp gene product confirmed 84% homology with the available gene bank human sequence.

CONCLUSIONS

This study proves that iNOS is expressed in human vein bypass grafts. Additionally, there is a significant elevation of iNOS message in human ACVGs compared with IVG or normal SV. This difference may be the result of the unique vascular beds supplied by these grafts. Ultimately, manipulation of iNOS expression may lead to therapies to alleviate IH in these grafts.

Alcohol dehydrogenase of human and rat blood vessels. Role in ethanol metabolism

Alcohol dehydrogenase (ADH) activity has been detected in all arteries and veins examined from humans and rat. In distinct human autopsy vessels, activity values range from 0.9 +/- 0.2 to 9.9 +/- 7.7 mU/mg. Distribution of the activity in human aorta was: intima (23.5%), media (74%) and adventia (2.5%). In most of the samples the beta1 beta1 isozyme of class I ADH was the only form responsible for the ADH activity. Class IV ADH (sigma sigma-ADH) was present in three of the 28 individuals examined. The rat blood vessels showed class IV, but not class I, ADH localized in endothelium and media. The physiological role of vascular ADH is probably related to retinoid metabolism and elimination of lipid peroxidation aldehydes. A contribution to human ethanol metabolism is supported by the significant amount of low-Km activity and the extension of the vascular system.

Localization of sterol 27-hydroxylase immuno-reactivity in human atherosclerotic plaques

It has recently been shown that extrahepatic cells can eliminate intracellular cholesterol by enzymatic conversion into 27-hydroxy-cholesterol and 3 beta-hydroxy-5-cholestenoic acid. Using immunohistochemical methods, we studied the presence of the enzyme responsible for these conversions, sterol 27-hydroxylase, in human carotid atherosclerotic plaques. All plaques examined were found to contain sterol 27-hydroxylase immuno-reactive cells. While some endothelial cells stained for sterol 27-hydroxylase, the majority of the immunoreactive cells co-localized with macrophages. Accumulation of sterol 27-hydroxylase-positive cells were often observed in macrophage-rich core regions of complicated lesions. High concentrations of 27-hydroxycholesterol were found in plaques, while the concentration in non-atherosclerotic human vessels was lower by two orders of magnitude. The rabbit, which is particularly sensitive to dietary cholesterol and easily develops fatty streaks, had low plasma levels of 27-hydroxycholesterol, 3 ng/ml compared to 150 ng/ml in humans. The concentration of 27-hydroxycholesterol in the atherosclerotic rabbit vessels was also lower compared to human atherosclerotic plaques. The results are consistent with our hypothesis that sterol 27-hydroxylase may be utilized by human macrophages as a defence towards a high cholesterol load. This mechanism may be less important in some other species.

[Metalloproteinases in vascular wall remodelling]

Metalloproteinases (MTP) are enzymes that degrade the extracellular matrix, mainly collagen tissue. Normally these enzymes are expressed in vascular walls as proenzyme together with inhibitors of the active enzymes. By effect of different cytokines, produced by an inflammatory process in the vascular wall, these proenzymes are activated to an extent that surpasses the action of the inhibitors and degrade collagen. This action may partly explain the rupture of atherosclerotic plaques ("vulnerability") and also the remodelling of the vessel wall with "compensatory enlargement" of the vessel (increase in the outer size of the vessel) that allows the plaques to develop inside the arterial wall without protruding into the vessel lumen for many years. The occlusion of saphenous vein in aortocoronary bypass grafts is due to fibromuscular proliferation and atheroma development and therefore the participation of MTP in the occlusion of these vessels is a reasonable hypothesis. However, the structural features of saphenous vein bypass grafts are different from those of atheroma in native coronary arteries. Mainly the compensatory enlargement of the vessels does not occur because of intense fibrous tissue development including the adventitia and therefore the new tissue in the wall is forced to protrude into the vessel lumen. The reason for this difference in the vessel wall remodeling is not clear and the article by Grez et al in this issue of this Journal is an starting and promising study in this regard.

Affinity of angiotensin I-converting enzyme (ACE) inhibitors for N- and C-binding sites of human ACE is different in heart, lung, arteries, and veins

Angiotensin-converting enzyme (ACE) has two enzymatically active domains: a C-domain in the carboxy terminal region and an N-domain in the amino terminal region. We based the pharmacologic characterization of these sites on the rat testis-lung model. In testis, only a truncate form of ACE is present (C-site), whereas both N- and C-sites are present in lung. In this model, captopril was shown to be N-selective and delaprilat to be C-selective. Ro 31-8472, a cilazapril derivative, and enalaprilat proved to be not site selective. We used these drugs to evaluate the affinity of C and N sites in various human tissues involved in the cardiovascular actions of ACE and used [125I]Ro31-8472 as ligand. The number and affinity of ACE binding sites were 17,680 +/- 2,345 fmol/mg protein (Kd = 0.32 +/- 0.04 nM) in lung, 560 +/- 65 (Kd = 0.36 +/- 0.05 nM) in heart, 237 +/- 51 (Kd = 0.37 +/- 0.06 nM) in coronary artery, 236 +/- 63 (Kd = 0.14 +/- 0.05 nM) in saphenous vein, and 603 +/- 121 (Kd = 0.50 +/- 0.06 nM) in mammary artery. The affinity (pKi) of captopril for the N sites ranged from 9.40 +/- 0.14 (lung) to 8.41 +/- 0.10 (coronary artery). The affinity for the C-site by delaprilat ranged from 9.97 +/- 0.15 (coronary artery) to 9.10 +/- 0.14 (mammary artery). Therefore, the affinity of C- and N-sites of ACE for ACE inhibitor (ACEI) drugs is different according to the organ involved. Because ACE is a glycosylated enzyme and glycosylation is organ dependent, we suggest that organ-specific glycosylation affects the binding characteristics of ACE inhibitors to N- or C-site of human tissular ACE.

Coexpression of periportal and perivenous enzymes in rat hepatocytes after experimental bile duct ligation: comparison with intrasplenically transplanted hepatocytes

The coexpression of normally periportal and perivenous markers has been described in heterotopically transplanted hepatocytes. To determine whether such a coexpression might also occur in hepatocytes retaining their original intrahepatic location, we compared in bile-duct-ligated livers and intrasplenically transplanted hepatocytes, the expression and distribution of the predominantly periportal glucose-phosphatase, succinate dehydrogenase, and lactate dehydrogenase, the predominantly perivenous glutamate dehydrogenase, NADPH-dehydrogenase, and beta-hydroxybutyrate dehydrogenase, and the strictly perivenous glutamine synthetase. The coexpression of high levels of the two periportal markers glucose-6-phosphatase and lactate dehydrogenase and of the perivenous marker NADPH dehydrogenase was observed in two situations: in clusters of hepatocytes isolated within the ductular proliferation in bile-duct-ligated livers and the majority of intrasplenically transplanted hepatocytes. The expression of glutamine synthetase was different according to the site. The protein was observed in certain intrasplenically transplanted hepatocytes bordering the splenic vessels but was never detected in hepatocyte clusters found in bile-duct-ligated livers. Our study therefore suggests that the coexpression of periportal and perivenous markers in the same hepatocytes is likely to be a non-specific consequence of the loss of the normal connections of hepatocytes with the normal liver microcirculation.

Histochemical evaluation of placental angiotensinase A in pre-eclampsia: enzyme activity in villous trophoblast indicates an enhanced likelihood of gestational proteinuric hypertension

The aim of this study was to examine whether differences in placental angiotensinase A (glutamyl aminopeptidase, EC 3.4.11.7) activities occurred in hypertensive complications of pregnancy compared with uncomplicated pregnancies. Biochemical and semiquantitative histochemical methods were used and compared for their applicability. Angiotensinase A activity was detected using L-alpha glutamyl-4-methoxy-2-naphthylamide (alpha-Glu-MNA) as substrate and Fast Blue B salt for simultaneous azo-coupling in cryostat sections of placental tissue samples from 32 patients with pre-eclampsia, 11 patients with pregnancy-induced hypertension and 44 participants with uncomplicated pregnancies. The graduated intensity of reaction product in the villous trophoblast and in fetal blood vessels was evaluated semiquantitatively in a double-blind study by light microscopy (semiquantitative score method). Score levels were related to relative frequencies of hypertensive disorders (proportional odds model) and correlated to the severity of gestational hypertension (Spearman's rank correlation). After detection of enzyme activity, the same tissue samples were homogenized and used for kinetic fluorometric measurements under the same substrate and buffer conditions as in enzyme histochemistry. Enhanced villous trophoblastic angiotensinase A activity was significantly associated with an increased frequency of pre-eclampsia in pregnant women (cumulative odds ratio x 0(1) 6.37; P < 0.001) and showed significant correlations with the severity of gestational hypertensive disorders, represented by systolic (r = 0.31; P < 0.05) and diastolic (r = 0.34; P < 0.05 blood pressure and by concomitant proteinuria (r = 044; P < 0.01). Histochemical evaluation of fetal blood vessels and biochemical measurements revealed no statistically significant results. In conclusion this study demonstrates for the first time that increased villous trophoblastic angiotensinase A activity indicates an increased likelihood of the presence of pre-eclampsia and the severity of hypertensive disorders in pregnancy.

An investigation into the direct and indirect venoconstrictor effects of endothelin-1 and big endothelin-1 in man

1. Endothelin-1 is a potent endothelium-derived vasoconstrictor peptide that is generated through cleavage of its precursor big endothelin-1 by 'endothelin converting enzyme' (ECE) in resistance vessels, including those of the forearm vascular bed. In some animal tissues, but not in resistance vessels of healthy human subjects, endothelin-1 appears to potentiate the actions of the sympathetic nervous system. We examined whether ECE activity is present in human hand veins and whether endothelin-1 or big endothelin-1 potentiate sympathetically mediated venoconstriction. 2. Six healthy subjects received dorsal hand vein infusion of local, non-systemic doses of endothelin-1 (5 pmol min-1), big endothelin-1 (50 pmol min-1) and, as a control, sodium chloride (0.9%; w/v) for 90 min. Vein diameter was measured using the Aellig displacement technique. Sympathetically mediated venoconstriction was elicited using the single deep breath reflex. 3. Endothelin-1 caused a progressive decrease in hand vein diameter, by 49% at 90 min (95% confidence intervals [CI]: -68 to -30%; P = 0.0001). Vein diameter did not change significantly after 90 min infusion of big endothelin-1 (+3%; CI: -11 to +17%; P = 0.0007 vs endothelin-1; P = 0.40 vs baseline) or sodium chloride (+2%; CI: -12 to +16%; P = 0.0002 vs endothelin-1; P = 0.60 vs baseline). Venoconstriction to deep breath was not potentiated by endothelin-1. 4. These results suggest that, in contrast to the situation in forearm resistance vessels, there is little or no local ECE activity in human hand veins and that endothelin does not potentiate sympathetic responses in these cutaneous capacitance vessels.

Selective pulmonary and venous smooth muscle relaxation by furosemide: a comparison with morphine

Furosemide and morphine reduce pulmonary edema associated with congestive heart failure. It is uncertain whether furosemide or morphine are direct-acting relaxants of arterial and venous smooth muscle. The authors compared the effect of furosemide and morphine on isolated rings of canine pulmonary artery (PA) and vein (PV) and mesenteric, splenic and anterior tibial arteries and their corresponding veins precontracted with norepinephrine or (15S)-hydroxy-11 alpha, 9 alpha-(epoxymethano)prosta-5Z,13E-dienoic acid. Furosemide (10-300 microM) selectively relaxed veins by an endothelium-independent mechanism, with its greatest efficacy on the PV. Morphine (10-1000 microM) relaxed both arteries and veins. The mechanism of relaxation by furosemide and morphine was examined in the PV and PA. Morphine-induced relaxation of the PV and PA was dependent on prostanoid release from endothelium and smooth muscle because it was attenuated in endothelium-rubbed and ibuprofen-treated PV and PA but not in blood vessels treated with inhibitors of nitric oxide system/cyclic GMP system (I-NG-nitroarginine and methylene blue). Furosemide-mediated relaxation of the PV was refractory to each of these interventions. Similarly, furosemide- and morphine-induced relaxation of the PV were unaffected by 4-aminopyridine, tetraethylammonium, glibenclamide, dendrodotoxin and apamin and, thereby, were independent of an action on K+ channels. Reduction of extracellular K+ or Cl- attenuated furosemide-mediated relaxation of, and inhibition of 86Rb+ uptake by, PV even in the presence of ouabain. It was concluded that furosemide relaxes veins by an effect on Na+/K+/Cl- cotransport or chloride-mediated refilling of intracellular calcium stores.

Increased concentrations of angiotensin-converting enzyme in the intimal hyperplasia of experimental vein grafts

Local renin and angiotensin-converting enzyme (ACE) activity were recently implicated in development of intimal hyperplasia after vascular injury, but little is known about the local responses of angiotensin I/II (AI/AII) and local ACE activity in vein graft physiology. The activity of the local ACE system of experimental vein grafts was examined in this study. The right carotid artery was divided and bypassed in 21 New Zealand White rabbits, using the right external jugular vein. The left external jugular vein was used as a control. Veins and vein grafts were harvested after 14 days. Rings from both vessels were studied in vitro under isometric tension, and dose-response curves to AI and AII were obtained. AI responses were also measured in the presence of captopril. The tissue concentrations of ACE in both vessels were estimated by spectrophotometry and were localized by immunohistochemistry. The responses of the veins to AI and AII were multiphasic, whereas the responses of vein grafts were sigmoid-shaped. Incubation of vein grafts with captopril significantly decreased the sensitivity to AI (p < 0.0001). Immunohistochemical localization identified ACE in the endothelial layer of the veins and vein grafts, but also at a greater density in the intimal hyperplasia of the vein graft. The concentration of ACE was 1.92 +/- 0.16 U/g (wet weight; mean +/- SEM, n = 9) in vein grafts and 1.39 +/- 0.05 U/g in the veins (38% increase, p < 0.05, n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of an inhibitor of nitric oxide synthase in human-hand veins

The enzyme nitric oxide synthase mediates synthesis of nitric oxide (NO) from 1-arginine in endothelial cells. NO, also known as endothelium-dependent relaxing factor (EDRF), diffuses to smooth muscle cells where it leads to cGMP production and dilation. We characterized the potency, efficacy and time course of NG-monomethyl-l-arginine (l-NMMA) as an inhibitor of bradykinin-mediated, endothelium-dependent dilation using the human hand-vein compliance technique. We also compared the efficacy of l-NMMA with methylene blue, an inhibitor of guanylate cyclase, in blocking bradykinin-mediated vasodilation. l-NMMA potently inhibited bradykinin-induced venodilation with a log ED50 of 3.74 +/- 0.52 (geometric mean of 5.5 micrograms/min). Responses to bradykinin (0.27-555 ng/min) were tested in veins pre-constricted with the alpha-adrenergic agonist phenylephrine. l-NMMA (25 micrograms/min) decreased bradykinin's maximal venodilatory response from 90 +/- 22% to 39 +/- 15% (p < 0.05). Complete recovery of bradykinin venodilation was obtained within 155 minutes after stopping l-NMMA infusion, indicating that its effects were reversible. In another set of experiments we compared the efficacy of methylene blue to l-NMMA; methylene blue decreased bradykinin-mediated venodilatory response to 53 +/- 17%; when l-NMMA was added, the response was further decreased to 32 +/- 9% (p < 0.002). We conclude that l-NMMA is a very efficacious NO synthase inhibitor in human veins and it is likely functionally reversible.

Vascular kallikrein in deoxycorticosterone acetate-salt hypertensive rats

We determined the status of vascular kallikrein in rats with severe hypertension caused by treatment with deoxycorticosterone acetate (DOCA) and drinking of 1% NaCl for 6 weeks. We assayed active and total kininogenase (kallikrein) activity in the perfusate and in arterial and venous tissue. DOCA-salt rats had higher systolic blood pressure at 6 weeks (214 +/- 5 mm Hg) than rats drinking tap water (135 +/- 4 mm Hg) or saline (145 +/- 8 mm Hg). Kininogenase in the perfusate (nanograms bradykinin per minute per kilogram body weight) increased significantly at 2 weeks, from 5.8 +/- 2.1 to 8.9 +/- 1.4 for active kallikrein and from 28.7 +/- 0.4 to 48.7 +/- 2.9 for total kallikrein. Total kallikrein returned to control values at 4 weeks, whereas it was significantly reduced at 6 weeks (20.9 +/- 0.7). Active kallikrein was significantly depressed at 4 and 6 weeks (1.08 +/- 0.1 and 0.85 +/- 0.1, respectively [P < .05]). Active kallikrein in arterial tissue (picograms bradykinin per milligram per minute) showed a small but significant increase at 2 weeks, from 156 +/- 7 to 201 +/- 10 (P < .05), finally decreasing significantly by 6 weeks to 64 +/- 3; however, total kallikrein showed a significant decrease only at 6 weeks, from 844 +/- 17 to 427 +/- 27. Both active and total kallikrein in the veins were higher than control values at 2 weeks, changing from 437 +/- 7 to 541 +/- 19 and from 1619 +/- 17 to 2062 +/- 86, respectively. Venous kallikrein remained elevated until the end of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of matrix metalloproteinase expression in human vein and microvascular endothelial cells. Effects of tumour necrosis factor alpha, interleukin 1 and phorbol ester

Matrix metalloproteinases (MMPs) play a role in tissue remodelling and angiogenesis. We have investigated the expression and regulation of MMP-1 (interstitial collagenase), MMP-2 (gelatinase A), MMP-3 (stromelysin 1), MMP-7 (matrilysin), MMP-9 (gelatinase B) and their inhibitors TIMP-1 and TIMP-2 in human umbilical vein, femoral vein and microvascular endothelial cells, and compared these data with those obtained with human synovial fibroblasts. Non-stimulated vein endothelial cells expressed the mRNAs for MMP-1, MMP-2, TIMP-1 and TIMP-2. MMP-3 mRNA and protein were undetectable or only weakly expressed, but could be stimulated by the inflammatory mediator tumour necrosis factor alpha (TNF alpha). The expression of MMP-3 and MMP-1 was further enhanced by phorbol 12-myristate 13-acetate (PMA). Phorbol ester also induced TIMP-1 and MMP-9, the expression of the latter being further enhanced by TNF alpha or interleukin 1 alpha (IL-1 alpha). Similar stimulatory effects were observed in microvascular endothelial cells. Hence the inflammatory mediator TNF alpha induces/enhances the production of several matrix metalloproteinases in human endothelial cells. On the other hand, MMP-2 and TIMP-2 were not affected or were affected in a variable way by TNF alpha and/or phorbol ester, suggesting a dissimilar regulation of these proteins. The cyclic AMP-enhancing agent forskolin affected the production of MMPs in a cell-type-specific way. In human vein endothelial cells it enhanced the PMA-mediated induction of MMP-9, whereas it suppressed this induction in human microvascular endothelial cells and in synovial fibroblasts. On the other hand, forskolin suppressed the PMA-mediated induction of MMP-1 and MMP-3 in synovial fibroblasts, while it enhanced or did not affect this induction in various types of human endothelial cells. These observations may have implications for future pharmacological intervention in angiogenesis.

[Ectonucleotidase activity of isolated strips of arteries and veins of experimental animals. Influence of various damaging agents on ecto-ATPase activity of blood vessels]

It is shown that ectonucleotidase activity of the venous vessels of rabbits is significantly higher than that of the arteries. The aorta of rats exhibits a higher ecto-ATPase activity as compared with the aortas of pigeons, guinea-pigs and rabbits. Administration of cholesterol to rabbits is accompanied by the increase of ecto-ATPase activity of blood vessels, and use of epinephrine, vitamin D2, mono-iodoacetate causes a significant decrease of that index.

Alkaline phosphatase and dipeptidylpeptidase IV staining of tissue components of skeletal muscle: a comparative study

A combined alkaline phosphatase (AP) and dipeptidlypeptidase IV (DPP IV) staining reaction has demonstrated enzymatic heterogeneity of the arterial and venous segments of capillaries in rat skeletal muscle. This study compared the staining reactions of skeletal muscles in many commonly used laboratory animals, including the axolotl, chick, quail, Monodelphys, rat, mouse, hamster, guinea pig, rabbit, dog, monkey, and human. DPP IV activity was found in the venous ends of the capillaries and in the endothelium of some larger veins in many of the species but was never demonstrated in the arterial side of the circulation. AP was found in the arterial ends of capillaries in all species except the axolotl, and it was also found in the endothelium of larger arteries of most species. AP activity was absent in venous endothelium of all species except for birds and Monodelphys. DPP IV activity was found in the perineurium of intramuscular nerves of most species, and AP activity was commonly seen in tendons and intramuscular connective tissue. The interspecies variability found in this study shows that care must be taken in comparing experimental data involving this technique from one species to another, but within a species the technique allows a fine level of discrimination between functionally distinct compounds of skeletal muscle tissue.

Kallikrein messenger RNA in rat arteries and veins

Glandular kallikrein (EC 3.4.21.8) belongs to a subgroup of serine proteases coded by a multigene family. A kininogenase resembling glandular kallikrein has been identified in vascular tissue; however, it is not clear whether it is synthesized by vascular tissue or taken up from plasma. To determine the potential for kallikrein synthesis in vascular tissues, we tested whether messenger RNA (mRNA) for glandular kallikrein is present in rat arteries and veins. Poly(A+) RNA was isolated from pools of arteries or veins (n = 3, 30 rats each). Poly(A+) RNA from the kidney and liver was used as a positive and negative control, respectively. As a probe, we used rat pancreatic kallikrein 32P-labeled complementary DNA, which recognizes mRNA of the entire rat kallikrein family. Slot-blot analysis indicated that kallikrein mRNA was present in mRNA from the arteries, veins, and kidney but not from the liver. Poly(A+) RNA from arteries and veins contained approximately 1% as much kallikrein mRNA as that from the kidney. To confirm the slot-blot results and determine whether the mRNA for true glandular kallikrein was present in vascular tissue, we employed a polymerase chain reaction assay, first using primers specific for the entire kallikrein family (which amplify a 430-bp fragment) and then using primers specific for true glandular kallikrein mRNA (which amplify a 370-bp fragment). After the polymerase chain reaction assay, both arteries and veins showed fragments of these sizes when tested with rat kallikrein complementary DNA probe, thus confirming the presence of glandular kallikrein mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)

The activity of diagnostic enzymes and the concentration of lipids in the blood vessels of cattle

Blood vessel walls are shown to contain creatine phosphokinase, lactate dehydrogenase, gamma glutamyl transpeptidase and aspartate transaminase activity. The activity of these enzymes in the serum may be enhanced by leakage from damaged blood vessels. The activity of the enzymes alanine transaminase and alkaline phosphatase as well as the content of triglycerides, cholesterol and lipoproteins are very low in the vascular tissue and are unlikely to be of diagnostic value in vascular tissue injury.