bluuebunny/crossref_metadata_2025 huggingface dataset:
Does Nitric Oxide Regulate Smooth Muscle Cell Proliferation?
Authors: Sarkar Rajabrata , Webb R. Clinton
Published: April 2003

Smooth muscle proliferation is involved in the pathogenesis of atherosclerosis, restenosis after angioplasty and vein graft failure due to neointimal hyperplasia. Nitric oxide (NO) inhibits smooth muscle cell growth in vitro and experimental neointimal hyperplasia in vivo, suggesting a role for NO as a regulator of smooth muscle cell proliferation. NO is also involved in the control of numerous other vascular functions including platelet and inflammatory cell adhesion, vascular reactivity and endothelial permeability. This review critically examines the experimental and clinical evidence that supports a role for NO as a modulator of smooth muscle cell proliferation, with an emphasis on the multiple mechanisms by which NO acts on vascular lesions.
Wall Remodeling after Wall Shear Rate Normalization in Rat Mesenteric Arterial Collaterals
Authors: Fath Steven W. , Burkhart Harold M. , Miller Scott C. , Dalsing Michael C. , Unthank Joseph L.
Published: April 2003

Previous studies have demonstrated endothelial and smooth muscle hyperplasia occur during arterial luminal expansion associated with elevation of arterial wall shear rates. The current study investigated whether remodeling induced by elevated wall shear would ultimately result in a vessel with intimal and medial cell densities and other wall characteristics similar to control arteries. A rat mesenteric model was used in which collateral wall shear is restored to normal 4 weeks after arterial occlusion. Twelve weeks after shear elevation, paired in vivo measurements indicated that the maximum collateral inner diameter was increased 27–75%. Morphometric evaluation of collateral cross sections indicated that, relative to control arteries, luminal and medial areas were increased 79 ± 22 and 56 ± 15%. Collateral medial cell density was decreased (1.12 ± 0.044 vs. 1.35 ± 0.005 nuclei/1,000 µm2) but intimal cell density was similar (2.86 ± 0.166 vs. 2.49 ± 0.102 nuclei/100 µm luminal perimeter). Medial thickness to radius ratio was also similar between control and collateral arteries. Thus, for the wall characteristics evaluated, there are many similarities between enlarged collaterals and control arteries. Comparison of nuclear numbers in arterial cross sections of the current and previous studies suggest that intimal and medial cellular regression is correlated with a decrease in wall shear force toward normal levels.
Characterization of Endothelium- Dependent Relaxation in Guinea Pig Basilar Artery – Effect of Hypoxia and Role of Cytochrome P450 Mono-Oxygenase
Authors: Petersson Jesper , Zygmunt Peter M. , Jönsson Peter , Högestätt Edward D.
Published: April 2003

In the guinea pig basilar artery, acetylcholine and the calcium ionophore A23187 induced endothelium-dependent relaxations, which were not significantly affected by the nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine (L-NOARG; 0.3 mM) or the guanylate cyclase inhibitor ODQ (1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one; 1-10 µM), or by these inhibitors combined. However, acetylcholine (10 µM) and A23187 (3 µM) each significantly increased the tissue level of cGMP in the absence but not in the presence of L-NOARG, suggesting that NO is released from the vascular endothelium in this blood vessel. Treatment with the potassium (K) channel inhibitors charybdotoxin (0.1 µM) plus apamin (0.1 µM), a toxin mixture previously shown to inhibit relaxations mediated by endothelium-derived hyperpolarizing factor (EDHF) in this artery, had no effect on the A23187-induced relaxation but slightly inhibited the response to acetylcholine (Emax was reduced by 24%). When the action of EDHF was prevented by these K channel inhibitors, the remaining relaxation was abolished by either ODQ (1 µM) or L-NOARG (0.3 mM), indicating that NO, apart from EDHF, contributes to the endothelium-dependent relaxations. Furthermore, ODQ (10 µM) abolished the relaxation induced by the NO donor S-nitroso-N-acetylpenicillamine. Thus, activation of soluble guanylate cyclase seems to be the only mechanism through which NO causes relaxation in this artery. When vessels were exposed to grave hypoxia (pO2 = 6 mm Hg), the NO-mediated relaxation (induced by acetylcholine in the presence of charybdotoxin plus apamin) disappeared. In contrast, EDHF-mediated responses (elicited by acetylcholine in the presence of L-NOARG) were only marginally affected by hypoxia (Emax was reduced by 16%). 17-Octadecynoic acid (50 µM) and 5,8,11,14-eicosatetraynoic acid (10 µM), inhibitors of cytochrome P450-dependent oxidation of arachidonic acid, failed to inhibit the acetylcholine-induced relaxation in the presence of L-NOARG. The cytochrome P450-dependent arachidonic acid metabolite 11,12-epoxyecosatrienoic acid (0.3–3.0 µM) had no relaxant effect per se. In conclusion, EDHF and NO are both mediators of endothelium-dependent relaxations in the guinea pig basilar artery. However, during grave hypoxia, EDHF alone mediates acetylcholine-induced relaxation. The results further suggest that EDHF is not a metabolite of arachidonic acid formed by cytochrome P450 mono-oxygenase or generated by another oxygen-dependent enzyme in this artery.
Parathyroid Hormone and Calcitriol in Hypertension Caused by Dietary Calcium Deficiency in Rats
Authors: López-Miranda Visitación , Civantos Beatriz , Blasco Rafael , Hernández Rosario , de Artiñano María Amaya Aleixandre
Published: April 2003

Hypertension caused by calcium deficiency in the diet has been linked with an increase in parathyroid hormone (PTH) and calcitriol levels. We evaluated arterial blood pressure (ABP), PTH, and calcitriol in normotensive Sprague-Dawley rats (SDR) and in spontaneously hypertensive rats (SHR) fed from weaning on a control diet with a normal calcium content (1%) or a low-calcium diet (0.1%). The calcemia was also measured in the rats by colorimetric methods. The low-calcium diet decreased the calcemia in both strains and brought about an increase in the ABP which was significant in adult SDR and particularly noticeable during the early hypertensive phase in SHR. The rats fed on this diet had higher hormonal plasma levels when compared with the corresponding values in rats fed on the control diet. In particular, the SDR fed on the low-calcium diet showed much higher PTH (122.6 ± 31.0 pg/ml, p ≤ 0.05) and calcitriol (458.0 ± 13.1 pg/ml, p ≤ 0.01) values than the SDR fed on the control diet (PTH 31.7 ± 2.80 pg/ml; calcitriol 292.1 ± 17.5 pg/ml). These endocrine alterations could justify the increase in ABP caused by dietary calcium deficiency in normotensive rats. Nevertheless, the results of this study indicate that the modifications of the ABP caused by the low-calcium diet in SHR could not be correlated with significant increases in these hormones.
Medial and Endothelial Platelet-Derived Growth Factor A Chain Expression Is Regulated by in vivo Exposure to Elevated Flow
Authors: Tulis David A. , Prewitt Russell L.
Published: April 2003

Previous work from this laboratory demonstrated that in vivo exposure to elevated arterial flow stimulates endothelial and smooth muscle cell hyperplasia concomitant with lumen enlargement, medial wall hypertrophy, and increases in medial extracellular connective tissue in rat mesenteric small arteries. In an effort to elucidate the role of growth factors in mediating this arterial remodeling response, in situ hybridization was performed on control and high flow arterial sections using 35S-labeled riboprobes for PDGF-A, PDGF-B, basic FGF, and TGFβ1 mRNA. Results demonstrate that after exposure to elevated arterial flow for 24 h, expression of PDGF-A mRNA in the media was significantly elevated over basal levels (+215%, p < 0.001). This expression decreased towards control levels by 3 and 7 days. Increased endothelial expression of PDGF-A mRNA over basal levels was evident after 3 and 7 days of elevated flow (+129%, p < 0.01; +182%; p < 0.01, respectively). Acute medial PDGF-A mRNA expression may result from elevated circumferential hoop stress secondary to flow-induced dilation while delayed expression in the endothelium may result from normalization of wall shear stress. Endothelial expression of PDGF-B mRNA was significantly elevated over control levels (+62%, p < 0.01) after exposure to high flow for 7 days. Expression of bFGF and TGFβ1 mRNA was not significantly different between control and high flow vessels at all times measured. These results suggest a role for PDGF-A in regulating acute arterial remodeling following in vivo exposure to elevated flow.
Heparin Increases Protein S Levels in Cultured Endothelial Cells by Causing a Block in Degradation
Authors: Dougherty Cristy S. , Lowe-Krentz Linda J.
Published: April 2003

Heparin is a natural anticoagulant molecule that can alter the activity and/or levels of other molecules involved in blood coagulation. Protein S, an anticoagulant protein, is synthesized and released into the plasma by endothelial cells. Immunological assays revealed a significant increase in protein S found in the media and in the endothelial cells after heparin treatment. Time assays revealed a rapid heparin effect on protein S levels in the media. Upon treatment with chondroitin sulfate, a small increase in the amount of protein S in the conditioned medium was also detected but the change in the cell-associated protein S levels after chondroitin sulfate treatment was a decrease rather than the increase implying that heparin and chondroitin sulfate are operating through different mechanisms. Radioimmunoprecipitations and cycloheximide treatments indicated no significant difference in protein S synthesis in heparin treated cells. In experiments comparing heparin and ammonium chloride effects, heparin seems to mimic the ammonium chloride effect on the levels of protein S in the media. Together, the data indicate that heparin increases the levels of protein S found in the media of cultured endothelial cells by producing a specific block in protein S degradation.
Endothelin-1 Stimulates Hydrolysis of Phosphatidylcholine by Phospholipases C and D in Intact Rat Mesenteric Arteries
Authors: Liu GeLe , Shaw Linda , Heagerty AnthonyM. , Ohanian Vasken , Ohanian Jacqueline
Published: April 2003

A characteristic of endothelin-1 (ET-1)-induced contraction is the prolonged duration of the response. Phosphatidylcholine (PC) hydrolysis has been implicated in sustained agonist-induced effects through the formation of the second messengers phosphatidic acid (PA) and diacylglycerol (DAG). Therefore, we have investigated the activation of PC-phospholipase D (PLD) and PC-phospholipase C (PLC) in intact rat mesenteric small arteries stimulated with ET-1 and determined whether PC-derived DAG is necessary for ET-1-induced contraction. PLD activity, measured as phosphatidylethanol (PEt) production in vessels labelled with [3H] or [14C]myristate, was increased in a concentration- and time-dependent manner following ET-1 stimulation, as were [3H]PA levels, peaking at 10 min (ET-1 100 nM) and remaining above control levels for up to 20 min. Inclusion of 0.5% ethanol during ET-1 stimulation reduced [3H]PA levels, but did not alter the time course of formation. In addition, [14C]choline release was increased, confirming PLD-mediated PC hydrolysis. In contrast, DAG levels, measured by [3H]myristate labelling and mass assay, increased transiently at 5 min of ET-1 stimulation only. Analysis of the subclasses of DAG demonstrated an increase in all types of DAG without any enrichment with arachidonate-containing species, indicating PC, not inositol lipid hydrolysis was the source of DAG. The PC-PLC inhibitor D609, 2.5 µg/ml, completely abolished the ET-1-induced increase in [14C]DAG without affecting the increase in [14C]PA, PLD activity or the contractile response. In [14C]choline-labelled vessels, [14C]phosphocholine levels were increased by ET-1 with a similar time course to DAG production. Removal of extracellular Ca2+ and addition of 0.1 or 2 mM EGTA completely inhibited ET-1-stimulated PLD activity. The tyrosine kinase inhibitor tyrphostin A23 (100 µM) abolished ET-1-induced [3H]PA, [3H]PEt and [14C]DAG increases, whilst the negative analogue A1 was without effect. These data suggest that ET-1 couples via a calcium-dependent tyrosine kinase mechanism to PLD and PC-PLC in vascular smooth muscle. PC-derived DAG did not appear to be necessary for the contractile response, whereas sustained formation of PA, generated by PLD activity, implies that this lipid second messenger could be involved in the prolonged contractile response to this peptide.
Modulation of PECAM-1 (CD31) Expression in Human Endothelial Cells: Effect of IFNγ and IL-10
Authors: Buján Julia , Gimeno Maria José , Prieto Alfredo , Pascual Gemma , Bellón Juan Manuel , Alvarez-Mon Melchor
Published: April 2003

Intercellular contacts formed between endothelial cells (EC) permit the formation of a confluent monolayer and play a major role in the recruitment and the migration of leukocytes in the inflammatory response. It is currently accepted that cytokines are responsible for the signals involved in the induction of such endothelial alterations. The platelet EC adhesion molecule (PECAM-1), a specific component of EC junctions, is one of many molecules which participate in the regulation of EC interaction with blood components. Given that the regulatory mechanisms which affect the expression of this adhesion molecule are only partially understood, the aim of the present study was to compare the effects of two antagonistic inflammatory cytokines, interferon (IFN)-γ and interleukin (IL)-10, on the expression of PECAM-1. Human umbilical vein EC grown to subconfluence were stimulated with IL-10 (10 ng/ml) and/or IFNγ (100 U/ml) for 24 h. PECAM-1 expression was determined by FACScan and immunofluorescence. Morphological analysis of the cell cultures was performed by optical and scanning electron microscopy. In the presence of IL-10, no changes in cell growth and morphology or in the intensity of PECAM-1 expression were observed. However, when the cultures were treated with IFNγ, the EC acquired a fibroblast-like appearance, growth was disorganized and PECAM-1 disappeared from cell junctions. The mean intensity expression and the percentage of EC expression of this antigen were analyzed by flow cytometry and significantly decreased after culture in the presence of IFNγ. The simultaneous addition of IFNγ and IL-10 to the EC cultures induced modifications similar to those observed in the presence of IFNγ alone. Regulation of the expression of PECAM-1 with the subsequent functional implications seems to be dependent upon the IFNγ signal and it is unaffected by IL-10. The different effects shown by IL-10 and IFNγ on the expression of PECAM-1 in EC could reflect opposite regulatory actions of the inflammatory response induced by these cytokines.
BMP-2 Gene Expression and Effects on Human Vascular Smooth Muscle Cells
Authors: Willette Robert N. , Gu Juan L. , Lysko Paul G. , Anderson Karen M. , Minehart Heather , Yue Tian-Li
Published: April 2003

Bone morphogenetic proteins (BMPs) and their serine/threonine kinase receptors have been identified in atherosclerotic arteries and vascular smooth muscle cells, respectively. Thus, BMPs (the largest subfamily of the TGF-β superfamily) have been implicated in the pathogenesis of atherosclerosis. However, the origins of BMP biosynthesis and the functional roles of BMP in blood vessels are unclear. The present study explored BMP-2 gene expression in various human blood vessels and vascular cell types. Functional in vitro studies were also performed to determine the effects of recombinant human BMP-2 on migration (transwell assay) and proliferation ([3H]-thymidine incorporation) of human aortic vascular smooth muscle cells (HASMC). RT-PCR experiments revealed BMP-2 gene expression in normal and atherosclerotic human arteries as well as cultured human aortic and coronary vascular smooth muscle cells, human umbilical vein endothelial cells (HUVECs) and human macrophages. In cellular migration studies, incubation with BMP-2 produced efficacious (≤610-fold), concentration- and time-dependent chemotaxis of HASMCs (EC50 = 0.8 μM) with little or no effect on HUVEC chemotaxis. The increased HASMC motility induced by BMP-2 was inhibited by coincubation with an anti-BMP-2 mAb. In addition, subthreshold concentrations of BMP-2 produced a dramatic synergistic effect upon platelet-derived growth factor (PDGF)-induced chemotaxis. In contrast to PDGF, BMP-2 had no significant effet on [3H]-thymidine incorporation in HASMC at chemotaxic concentrations (≤6.0 μM) nor did it synergize with the mitogenic effects of PDGF. In conclusion, the expression of BMP-2 by numerous cell types in the blood vessel wall may play a chemotactic or cochemotactic role in the smooth muscle cell response to vascular injury.
Collagen I and III and Mechanical Properties of Conduit Arteries in Rats with Genetic Hypertension
Authors: Clerc Ph. Chamiot , Renaud J.F. , Blacher J. , Legrand M. , Samuel J.L. , Levy B.I. , Sassard J. , Safar M.E.
Published: April 2003

Conduit arteries of hypertensive rats are thicker and stiffer than those of normotensive controls. The possible role played by collagen type I and II subtypes in the mechanism of arterial stiffness remains unknown. The carotid and aortic arterial wall of rats of Japanese (Wistar-Kyoto and spontaneously hypertensive rats) and Lyon (normotensive and hypertensive rats) origin were studied. The stiffness of the carotid wall material (ultrasound), the histomorphometry of the aortic wall with the content in collagen I and III subtypes and their corresponding mRNA were analyzed. Independently of hypertension, the Japanese group differed from the Lyon group by a stiffer carotid wall material at any given value of wall stress; a lesser degree of aortic hypertrophy with a higher percentage of elastin, and a higher density of collagen III but not of collagen I. All other hemodynamic and histomorphometric parameters were affected by both the origin of the rats (Japanese vs. Lyon) and the presence of hypertension. Large artery stiffness in genetically hypertensive rats was not only influenced by hypertension itself, but also by differences in the contents of collagen subtypes which are also found in their corresponding normotensive controls.
Network Vascular Communication Initiated by Increases in Tissue Adenosine
Authors: Rivers Richard J. , Frame Mary D.S.
Published: April 2003

Vascular communication of vasomotor signals appears to coordinate the distribution of tissue blood flow. This study was performed to determine whether elevated tissue concentrations of adenosine or nitric oxide could induce vascular communicating signals. To test this, remote arteriolar responses were tested when drugs were applied either directly to an arteriole (∼20 μm diameter), or into the tissue in a region (with no vessels over 10 μm in diameter) that was 500 μm away from the arteriole and that bore no defined relationship to the flow path of the remote arteriole. In anesthetized hamster cheek pouch (n = 25), or cremaster muscle (n = 10), remote arteriolar responses were measured in response to nitric oxide (NO) donors (10–5 to 10–3 M), adenosine (10–5 to 10–3 M), or papaverine (10–5 to 10–2 M) applied for 40–120 s. Papaverine caused no remote response when applied directly while adenosine and NO donors caused similar, late-onset (10–20 s), dose-dependent, remote responses in both preparations. Remarkably however, only adenosine initiated a consistent remote arteriolar dilation when applied to the tissue site. Thus, increases in tissue adenosine may be critical for vascular communication of metabolic demands without regard to the specific blood flow path.
High-Dose, Not Low-Dose Insulin Increases the Vasoconstrictor Effect of Norepinephrine in Spontaneously Hypertensive Rats: Effects of Antihypertensive Treatment
Authors: Rizzoni Damiano , Porteri Enzo , Piccoli Alfonso , Castellano Maurizio , Pasini Giancarlo , Guelfi Daniele , Muiesan Maria Lorenza , Agabiti Rosei Enrico
Published: April 2003

The effect of insulin on the vasoconstriction induced by norepinephrine is presently controversial. Therefore, the aims of our study were: (1) to evaluate the effect of low- and high-dose insulin on the concentration-response curve to norepinephrine in small resistance arteries of spontaneously hypertensive rats (SHR) and Wistar Kyoto rats (WKY) before and after the development of hypertension, and (2) to evaluate the effects of antihypertensive treatment on vascular response to insulin and norepinephrine. Fifty-six rats were included in the study. Six SHR were treated with enalapril and 6 with candesartan cilexetil from the 4th to the 12th week of age, while 10 WKY and 14 SHR were kept untreated. Two additional groups of 10 untreated SHR and 10 WKY were killed at 4 weeks of age, in a prehypertensive phase. Mesenteric small arteries were dissected and mounted on a micromyograph. A dose-response curve to norepinephrine was performed at cumulative concentrations in the presence or absence of low- and high-dose insulin. We found that only high-dose insulin increased the vascular response to norepinephrine in 12-week-old SHR, but not in 4-week-old SHR or in age-matched WKY. The increased responsiveness to norepinephrine disappeared after preincubation of the vessels with a selective inhibitor of endothelin-1 type A receptors. After antihypertensive treatment with enalapril or candesartan cilexetil, the potentiation of the vasoconstrictor response to norepinephrine was abolished. In conclusion, insulin at high, nonphysiological doses seems to induce an increase in the reactivity to norepinephrine in mesenteric small arteries of SHR, possibly mediated by a local production of endothelin-1. Antihypertensive treatment with an ACE inhibitor or an angiotensin II receptor blocker may normalize this altered response. This mechanism may be relevant in the development of hypertension in SHR.
Heterogeneity of Vascular Innervation in Hamster Cheek Pouch and Retractor Muscle
Authors: Grasby Dallas J. , Morris Judy L. , Segal Steven S.
Published: April 2003

The hamster cheek pouch and its retractor muscle have provided valuable insights into microvascular physiology of an epithelial tissue and striated muscle, respectively. Nevertheless, the innervation of these vascular beds has not been resolved. This study has investigated the nature of autonomic and sensory innervation of these vascular beds and has tested whether it varies within or between tissues. Multiple-labelling immunohistochemistry identified autonomic and peptide-containing sensory nerve fibres. Presumptive sympathetic vasoconstrictor axons with immunoreactivity (IR) for tyrosine hydroxylase (TH) and neuropeptide Y (NPY) innervated feed arteries and arterioles (but not veins or venules) of the retractor and anterior (muscular) cheek pouch; these axons were absent from the posterior (epithelial) region of the cheek pouch, as confirmed by catecholamine fluorescence. Presumptive autonomic vasodilator axons with IR for vasoactive intestinal peptide (VIP) consistently innervated feed arteries and proximal arterioles of the cheek pouch, but generally not those of the retractor muscle nor distal arterioles of either tissue. Sparse presumptive sensory axons with IR for calcitonin gene-related peptide (CGRP) and substance P were found near arterial and venous vessels in all regions of the cheek pouch and retractor muscle; CGRP-IR was also located in motor end plates associated with striated muscle fibres. Such regional differences in vascular innervation by autonomic and sensory neurons may selectively effect local and regional control of blood flow between and within vascular beds.
Chemokine Receptors and Their Role in Vascular Biology
Authors: Murdoch Craig , Finn Adam
Published: April 2003

Chemokines play an important role in the process of leukocyte recruitment and activation at sites of inflammation. Until recently, the actions of chemokines and the expression of their receptors have only been described on different leukocyte populations. However, increasing evidence has suggested that non-haematopoietic cell types are capable of binding and responding to a number of chemokines. The functional expression of certain chemokine receptors has recently been described on vascular endothelial and smooth muscle cells. These findings provide new insight into the activities of chemokines and indicate that these molecules have a more widespread cellular target than first envisaged. Studies carried out to date indicate that chemokines and their respective receptors play an important role in the regulation of angiogenesis and angiostasis. They may also be involved in developmental and pathological processes such as organ vascularization, embryogenesis and arteriosclerosis.
Role of Voltage-Dependent and Ca2+-Activated K+ Channels on the Regulation of Isometric Force in Porcine Coronary Artery
Authors: Shimizu Shunichi , Yokoshiki Hisashi , Sperelakis Nicholas , Paul Richard J.
Published: April 2003

We investigated the role of K+ channels in the regulation of vascular tone in de-endothelialized porcine coronary artery. Isometric force and intracellular Ca2+ ([Ca2+]i) under resting conditions were increased by treatment with 4-aminopyridine (4-AP, 1 mM), an inhibitor of voltage-dependent K+ (Kv) channels, but not by tetraethylammonium chloride (TEA, 1 mM) or charybdotoxin (100 nM), both inhibitors of Ca2+-activated K+ (KCa) channels, or glibenclamide (10 μM), an inhibitor of ATP-sensitive K+ channels. Under stimulated conditions with 9,11-dideoxy-11α,9α-epoxymethano-prostaglandin F2α (U46619), 4-AP as well as TEA or charybdotoxin increased isometric force and [Ca2+]i, but not glibenclamide. 4-AP was the most potent in terms of depolarization of membrane potential compared with TEA or glibenclamide in the presence or absence of EGTA. In the presence of U46619, a high concentration of 4-AP (10 mM) caused a further contraction with oscillations. The force oscillations induced by 4-AP were inhibited by diltiazem (10 μM), an inhibitor of voltage-dependent Ca2+ channels, or TEA (1 mM), but not by glibenclamide (10 μM). These force oscillations may be associated with the periodic activation of KCa channels. These findings suggested that 4-AP-sensitive Kv channels play an important role in the control of vascular tone in both resting and stimulated conditions. Moreover, under stimulated conditions, KCa channels also have an important role in the regulation of vascular tone. Dysfunction of these channels induces abnormal vasoconstriction and may be implicated in vascular diseases such as hypertension and vasospasm.
Off-Line Analysis of Red Blood Cell Velocity in Renal Arterioles
Authors: De Vriese An S. , Verbeuren Tony J. , Vallez Marie-Odile , Lameire Norbert H. , De Buyzere Marc , Vanhoutte Paul M.
Published: April 2003

Videomicroscopic methods with off-line analysis of microcirculatory parameters by multifunctional computer-assisted image analysis systems have significant advantages for in vivo microvascular research. A limitation of these methods is, however, that red blood cell velocities (VRBC) exceeding 2 mm/s cannot be measured using standard video framing rates. In the present study, a high-speed video camera, recording up to 600 frames per second, was incorporated in the set-up, and VRBC was measured off-line with the line-shift-diagram method. The aim of this study was to test the reproducibility and validity of the method using a high-speed video camera and to evaluate its applicability in vivo. VRBC were measured in arterioles of the split hydronephrotic kidney. The intra- and interindividual variability was small for VRBC below 40 mm/s. The validity of the method was tested using the mass conservation principle and found to be at least as good as that of the dual-slit photometric technique. The present approach extends the application of videomicroscopy coupled to image analysis systems to the analysis of high VRBC.
Reactive Oxygen Species and Acute Modulation of Albumin Microvascular Leakage in the Microcirculation of Diabetic Rats in vivo
Authors: Bonnardel-Phu E. , Vicaut E.
Published: April 2003

Endothelial cells have been reported to generate reactive oxygen species such as the superoxide anion, hydrogen peroxide, and the hydroxyl radical. The aim of this work was to evaluate the role of reactive oxygen species in diabetes-induced changes in vascular permeability. Intravital videomicroscopy was used to study albumin microvascular leakage in the cremaster muscle. The extravasation of a fluorescent macromolecular tracer (FITC-albumin) was measured for 1 h and, after computer-aided image analysis, was expressed as variations of normalized gray levels (arbitrary units). The extravasation of the macromolecular tracer was greater in diabetic rats (5.28 ± 1.29 vs. 1.96 ± 0.41 AU at 1 h in diabetic and control rats, respectively). Administration of superoxide dismutase (SOD), which dismutates ·O–2 to H2O2, and of catalase which reacts with H2O2 to form H2O and molecular oxygen failed to inhibit the increased extravasation of the macromolecular tracer when administered separately. However, a significant inhibition of diabetic increase in albumin extravasation was found when these 2 drugs were administered simultaneously, and in this case, the extravasation of the macromolecular tracer at 1 h was similar in diabetic rats (2.11 ± 0.61 AU) and normoglycemic rats (1.43 ± 0.48 AU). No difference was found in adherent leukocytes or in the leukocyte rolling flux between diabetic and normoglycemic rats. We conclude that reactive oxygen species are responsible for an increase in microvascular permeability likely via leukocyte-independent mechanisms.
Localisation of mRNA for JE/MCP-1 and Its Receptor CCR2 in Atherosclerotic Lesions of the ApoE Knockout Mouse
Authors: Rayner Kim , van Eersel Sander , Groot Pieter H.E. , Reape Theresa J.
Published: April 2003

MCP-1 has potent chemotactic activity for monocytes and is strongly implicated in the pathogenesis of atherosclerosis. In the present study, we have used in situ hybridisation to examine the gene expression of JE, the murine homologue of MCP-1, and its receptor, CCR2, during the development of atherosclerotic lesions in the ApoE knockout mouse. Interestingly, the earliest expression of JE detected during lesion development was found to be localised in mesenchymal cells in the adventitia and not in the intima. Macrophages were subsequently found to accumulate in these affected regions of the adventitia and these cells were found to express high levels of JE. At this stage, early macrophage-rich lesions with high expression of JE were also seen in the intima, but expression of mRNA for the receptor for JE (CCR2) was only found on adventitial macrophages and not in the intima. This sequence of events suggests that adventitial inflammation may be an important early event in lesion development and responsible for the subsequent accumulation of macrophages in the intima possibly by recruitment from the adventitia as well as via the vessel lumen.
Mean Wall Shear Stress in the Femoral Arterial Bifurcation Is Low and Independent of Age at Rest
Authors: Kornet Lilian , Hoeks Arnold P.G. , Lambregts Jacques , Reneman Robert S.
Published: April 2003

In elastic arteries, mean wall shear stress appears to be close to 1.5 Pa, the value predicted by the theory of minimal energy loss. This finding in elastic arteries does not necessarily represent the situation in muscular arteries. Elastic arteries have to store potential energy, while muscular arteries have mainly a conductive function. Therefore, we determined wall shear stress and its age dependency in the common and superficial femoral arteries, 2–3 cm from the flow divider in 54 presumed healthy volunteers between 21 and 74 years of age, using a non-invasive ultrasound system. Prior to the study, the reliability of this system was determined in terms of intrasubject variation. Mean wall shear stress was significantly lower in the common femoral artery (0.35 ± 0.18 Pa) than in the superficial femoral artery (0.49 ± 0.15 Pa). In all age categories, peak systolic wall shear stress and the maximal cyclic change in wall shear stress were not significantly different in the common and the superficial femoral arteries. Peak systolic wall shear stress in the common and the superficial femoral arteries was not significantly different from the value previously determined in the common carotid artery, but mean wall shear stress was lower in the common and superficial femoral arteries than in the common carotid artery by a factor of 2–4. In both the common and the superficial femoral arteries, mean, peak systolic and maximal cyclic change in wall shear stress did not change significantly with age, nor did diameter. We conclude that, as compared to elastic arteries, mean wall shear stress is low in the conductive arteries of a resting leg, due to backflow during the first part of the diastolic phase of the cardiac cycle and the absence of flow during the rest of the diastolic phase. Mean wall shear stress is lower in the common than in the superficial femoral artery due to additional reflections from the deep femoral artery.
Differential Transmural Distribution of Gene Expression for Collagen Types I and III Proximal to Aortic Coarctation in the Rabbit
Authors: Xu Chengpei , Zarins Christopher K. , Bassiouny Hisham S. , Briggs William H. , Reardon Catherine , Glagov Seymour
Published: April 2003

To assess the effects on the biosynthesis of collagen types I and III associated with an acute increase in blood pressure, we established a mid-thoracic aortic coarctation in the rabbit and studied gene expression and protein accumulation of these collagen types proximal to the stenosis 1, 3 and 7 days and 2, 4 and 8 weeks after coarctation. The mRNA level of type I collagen pro-α2(I) was maximal at 3 days and returned to normal at 4 weeks. mRNA of pro-α2(I) was localized mainly in the outer media, adventitia and intima. Accumulation of type I collagen and its precursors was increased by 3 days, peaked at 4 weeks, and decreased toward normal by 8 weeks, corresponding to the distribution of pro-α2(I) mRNA. Gene expression for pro-α1(III) was similar to that of pro-α2(I) but was distributed throughout the media. We conclude that the mechanical stresses associated with an acutely induced alteration in pressure initiate rapid gene expression for collagen types I and III in the aortic wall. The response for collagen type I, predominantly in the outer media and adventitia, suggests that these regions play an immediate role in the resistance to excessive dilatation of the aorta. The diffuse response for collagen type III in the media suggests participation in a more extensive remodeling response associated with the reinforcement and reorganization of the musculo-elastic fascicles.
Functional Characteristics of Optimized Arterial Tree Models Perfusing Volumes of Different Thickness and Shape
Authors: Karch Rudolf , Neumann Friederike , Neumann Martin , Schreiner Wolfgang
Published: April 2003

The relationship between the ‘shape of an organ’ and the ‘cost of blood transport’ to perfuse its tissue was evaluated on the basis of optimized arterial model trees simulated to perfuse square-based 100-cm3 volumes of different shape (‘flat’ versus ‘thick’ as defined by the ratio of thickness to side-length h/s ≤1). Specifically, the effects of ‘shape’ on tree structure, blood transport, and on hemodynamic characteristics were investigated. Branching models of arterial trees were generated by constrained constructive optimization (CCO), based on an identical set of model parameters. All model trees were geometrically and topologically optimized for intravascular volume. Tree structures achieved tremendous savings of blood (transport medium) in comparison to a system of separate tubes. Thickening the perfusion volume (increasing h/s) resulted in a significant decrease of mean transport length, deposition time, and intravascular total volume in the tree. ‘Thick’ perfusion volumes induced CCO trees to branch more symmetrically into a number of equivalent subtrees repetitiously splitting into smaller ones; ‘flat’ structures were dominated throughout by a few asymmetrically branching major vessels. In summary, we conclude from systematic variation of shape that thicker perfusion volumes (h/s >0.1) facilitate efficient delivery of blood in comparison to large amounts of ‘dead volume’ to be carried over long distances in very thin pieces of tissue.
Myofibroblast Involvement in Glycosaminoglycan Synthesis and Lipid Retention during Coronary Repair
Authors: Shi Yi , Niculescu Rodica , Wang Dian , Ormont Michael , Magno Michael , San Antonio James D. , Williams Kevin J. , Zalewski Andrew
Published: April 2003

Myofibroblasts of adventitial origin have been linked to neointimal formation and remodeling after coronary injury. Accordingly, the goal of this study was to examine whether myofibroblasts contribute to focal accumulation of glycosaminoglycans (GAGs) and lipids during coronary repair. GAG synthesis was assessed by ex vivo labeling of balloon-injured porcine coronary arteries with 14C-glucosamine. The synthesis of total GAGs transiently increased at 8 days in the normolipemic model (a 2.2-fold increase over baseline, p < 0.05). The majority of newly synthesized GAGs were sensitive to chondroitin ABC lyase (chondroitin/dermatan sulfate GAGs). Versican was localized to myofibroblast-rich regions in the adventitia and neointima [positive for α-smooth muscle (SM) actin, negative for h-caldesmon and SM myosin heavy chain]. In contrast, the adjacent SM-rich media showed no increase in versican expression. The association between injury-induced GAG accumulation and lipid retention was examined at 2 weeks after coronary injury in the hyperlipemic model. Lipid (Oil Red O) accumulated in the neointima and adventitia, but not in the adjacent media. Coronary repair under hyperlipemic conditions was associated with macrophage infiltration (19 ± 5 vs. 3 ± 2% of neointimal cells in normolipemic animals, p < 0.001) and increased neointimal formation (1.8 ± 0.5 vs. 1.0 ± 0.3 mm2 in normolipemic animals, p < 0.01). In conclusion, this study demonstrated a transient increase in GAG synthesis following coronary injury. Chondroitin sulfate proteoglycans (e.g., versican) were rapidly synthesized by activated adventitial and neointimal cells which could contribute to early lipid retention in injured vessels.
Transforming Growth Factor-β in Renal Disease
Authors: Bitzer Markus , Sterzel R. Bernd , Böttinger Erwin P.
Published: April 2003

An extensive number of animal and clinical studies indicate that transforming growth factors-β (TGF-βs) play an important role in inflammatory and fibrotic diseases, including renal fibrosis. Recent mouse models harboring genetically engineered alterations in TGF-β pathways reveal complicated mechanisms of regulation of TGF-β activity in vivo. The purpose of this review is to present recent advances relevant to our understanding of the TGF-β-signaling system in renal physiology and pathophysiology.
Na+ -Dependent and -Independent Amino Acid Transport Systems in Immortalized Human Kidney Epithelial Cells Derived from the Proximal Tubule
Authors: Hirsch Jochen R. , Gonska Tanja , Waldegger Siegfried , Lang Florian , Schlatter Eberhard
Published: April 2003

In the proximal tubule Na+-dependent (SDAT) and Na+-independent (SIAT) amino acid (AA) transporters are present. The effects of neutral, basic, and acidic AA on membrane voltage (Vm) of immortalized human kidney epithelial (IHKE-1) cells derived from the proximal tubule were examined using the slow whole-cell patch-clamp technique. In the presence of Na+ AA depolarized Vm in a concentration-dependent manner (0.05–5 mM) with Asp = Arg = Glu =2Cys < Pro = Leu < Phe = AIB = Ala = Pro = Asn < Gly. In the absence of extracellular Na+ a decreased depolarization was seen with most neutral AA (Ala, Pro, Asn, Gly, Phe, and Leu), and the depolarization was increased with Asp, Glu, Arg, and 2Cys (1 mM each). In the absence of Na+ and a reduction in Cl– (5 mM) the depolarization by Arg was reduced. Unlike that predicted for transport by system b0,+ which exchanges neutral against dibasic amino acids, Leu does not hyperpolarize but depolarize Vm of IHKE-1 cells in the absence of extracellular Na+. After removal of Na+ (0 mM) and a reduction in Cl– (5 mM) in the extracellular solution, Leu or Glu hyperpolarized Vm, indicating that IHKE-1 cells possess two different SIAT systems, one Cl–-independent and similar to system b0,+ and one novel Cl–-dependent system, which might be a Cl–/AA exchanger and can be blocked by the Cl–-channel blockers 5-nitro-2-(3-phenylpropylamino)-benzoate (10 μM) and 4,4′-diisothiocyanostibene-2,2′-disulfonic acid (50 μM). B system-related AA transporters might be responsible for the C–-independent SIAT, since we were able to detect its signal by Northern blot analysis.
Epidermal Growth Factor Upregulates Aminopeptidase N and 5′–Nucleotidase in Human Glomerular Mesangial Cells
Authors: Stefanovi´c Vladisav , Vlahovi´c Predrag , Miti´c-Zlatkovi´c Marina
Published: April 2003

Because epidermal growth factor (EGF) is likely to be released in the glomeruli during glomerular injury and mesangial cells possess specific receptors for EGF, we thought it to be of interest to examine whether this growth factor could influence the expression of ectoenzymes in cultured human mesangial cells. EGF stimulated 5′–nucleotidase and aminopeptidase N activities in intact human mesangial cells in a time– (24–72 h) and dose–dependent (0.1–50 ng·ml–1) manner. Maximum stimulation represented 2.7– and 2–fold basal activities for 5′–nucleotidase and aminopeptidase N, respectively. EGF did not influence cyclic AMP production, and its effect on 5′–nucleotidase was additive to that of forskolin or 8–bromo–cAMP. In contrast, genistein (10 mg·ml–1), an inhibitor of tyrosine kinase, prevented EGF–dependent stimulation of aminopeptidase N and 5′–nucleotidase, suggesting that protein phosphorylation was involved in the signaling mechanism. EGF stimulated specifically the latter two enzymes since it had no effect on other ectoenzymes including alkaline phosphodiesterase I and Mg2+–ATPase activities. These results demonstrate that EGF, via the control of 5′–nucleotidase and aminopeptidase N, which are implied in adenosine formation and peptide processing, respectively, could play a role in human cultured mesangial cell contractility and proliferation.
Role of Mesangial Cell Damage in Progressive Renal Disease
Authors: Shimizu F. , Kawachi H. , Orikasa M.
Published: April 2003

Mesangial cell proliferation and matrix accumulation are considered to contribute to the development of glomerulosclerosis. To investigate the pathological role played by mesangial cell damage in progressive renal disease appropriate progressive models initiated by a mesangial cell injury should be developed. Monoclonal antibody (mAb) 1–22–3 (IgG3) recognizes a critical epitope of the Thy–1.1 molecule on the mesangial cell surface, binding of which induces more severe mesangial cell injury than in the case of OX–7, a commercially obtainable anti–Thy–1.1 mAb. The mAb 1–22–3 has enabled us to develop irreversible models of renal damage induced by two consecutive injections, by a single injection into unilaterally nephrectomized rats, or by a single simultaneous injection with another mAb, in addition to the corresponding reversible model. Detailed examinations using the combination of both types of models, all of which are initiated by an immune mechanism directed against the identical epitope on the Thy–1.1 molecule, are expected to provide new insights into mechanisms of irreversible renal injury initiated by mesangial cell damage and also to develop novel and rational therapeutic approaches to progressive, primarily mesangial diseases.
Proteinuria as a Mediator of Tubulointerstitial Injury
Authors: Abbate Mauro , Remuzzi Giuseppe
Published: April 2003

Proteinuria is one of the most potent risk factors for renal disease progression in patients with glomerular diseases. Studies in disease models have helped to delineate mechanisms leading to renal structural damage due to persistent dysfunction of the glomerular barrier to proteins, even when the primary immune or nonimmune insult to the kidney has ceased. The main focus of this review is the role of the tubular epithelial cell in the induction of interstitial inflammatory and fibrogenic reactions to ultrafiltered proteins. Antiproteinuric drugs (angiotensin–converting enzyme inhibitors, ACEi) while preserving the integrity of the glomerular permselective barrier limit both proteinuria and protein–dependent processes which contribute to tubulointerstitial injury, and in so doing ACEi halt the progression of proteinuric nephropathies toward terminal renal failure.
Wrist Measurement of Blood Pressure: Some Critical Remarks to Oscillometry
Authors: Weber F. , Erbel R. , Schäfers R. , Philipp T.
Published: April 2003

Oscillometric blood pressure measuring devices worn at the wrist are preferred by a growing part of hypertensive patients for self–measurement because of their compactness and ease of use. However, little is known about the accuracy of such instruments. The accuracy of such devices was evaluated by measuring the blood pressure at the end of a coronary angiography procedure in 27 subjects nearly simultaneously in the aortic arch, using a Statham P23 transducer, and at the wrist, using the blood pressure watch (BPW) by NAIS–Matsushita. Four replicate comparative measurements were performed in each subject. On average, the blood pressure measured by the BPW was found to be higher: systolic +1.2±(SD)10.2 mm Hg, diastolic +4.1±7.2 mm Hg. The correlation coefficient between the two methods was 0.85 for the systolic and 0.84 for the diastolic pressure, but 39% of the systolic and 22% of the diastolic differences were outside the range of ±1 SD. There was no correlation between systolic differences and blood pressure or patients’ variables, but multiple regression analysis revealed that the diastolic blood pressure differences were negatively correlated with the aortic diastolic pressure (r = 0.89, p<0.001), indicating that the BPW is less accurate to detect lower values. Conclusions: (1) Though the average systolic and diastolic deviations between both methods and the relative correlation coefficients suggest that the BPW is to be used carefully for monitoring blood pressure, the great variability of differences and the inability of the BPW to detect lower diastolic blood pressure calls for a mandatory validation test by an approved protocol before this new device can be recommended for general use. (2) On the basis of our results for wrist oscillometry with the BPW and data reported in the literature for upper–arm oscillometric devices, we recommend to use oscillometric devices only when they were validated properly. In particular, the oscillometric measurement should be employed with caution for epidemiological studies or for investigation of population groups (e.g., children or pregnant women) that are expected to display lower diastolic pressures.