Pulmonary disease in the immunocompromised child

Adhesion receptors that are known to initiate contact (tethering) between blood-borne leukocytes and their endothelial counterreceptors are frequently concentrated on the microvilli of leukocytes. Other adhesion molecules are displayed either randomly or preferentially on the planar cell body. To determine whether ultrastructural distribution plays a role during tethering in vivo, we used pre-B cell transfectants expressing L- or E-selectin ectodomains linked to transmembrane/intracellular domains that mediated different surface distribution patterns. We analyzed the frequency and velocity of transfectant rolling in high endothelial venules of peripheral lymph nodes using an intravital microscopy model. Ectodomains on microvilli conferred a higher efficiency at initiating rolling than random distribution which, in turn, was more efficient than preferential expression on the cell body. The role of microvillous presentation was less accentuated in venules below 20 micrometers in diameter than in larger venules. In the narrow venules, tethering of cells with cell body expression may have been aided by forced margination through collision with erythrocytes. L-selectin transfected cells rolled 10-fold faster than E-selectin transfectants. Interestingly, rolling velocity histograms of cell lines expressing equivalent copy numbers of the same ectodomain were always similar, irrespective of the topographic distribution. Our data indicate that the distribution of adhesion receptors has a dramatic impact on contact initiation between leukocytes and endothelial cells, but does not play a role once rolling has been established.     

Characterization of the pulmonary lesions induced in rats by human recombinant interleukin-2

Histologic, electron microscopic, and immunohistochemical studies were made to analyze the structural features and the cellular composition of the pulmonary lesions produced in rats by the administration of interleukin-2 (IL-2). This agent induced pulmonary edema; thickening of alveolar septa; damage to endothelial cells in capillaries and venules, marked interstitial infiltration by cytotoxic T lymphocytes, lymphokine-activated killer (LAK) cells, macrophages, and dendritic cells (as demonstrated by cell counting in preparations stained immunohistochemically with peroxidase- and fluorochrome-labeled antibodies); and injury to bronchiolar and alveolar epithelial cells. Granular and agranular lymphocytes often were closely apposed to endothelial cells in capillaries and venules. Contacts between lymphocytes and type II alveolar epithelial cells also were observed. Damaged type II alveolar epithelial cells showed nuclear and cytoplasmic features that are considered indicative of apoptosis (confirmed by nick end labeling). Phagocytosis of apoptotic bodies by macrophages was occasionally found. These results support the concept that IL-2 induces cytotoxic vascular and parenchymal cell damage that is mediated by LAK cells and cytotoxic T lymphocytes, which make contacts with endothelial cells and type II alveolar epithelial cells. This damage appears to be exacerbated by the secondary release of a variety of vasoactive agents and inflammatory mediators.     

Intracranial aneurysms treated with the Guglielmi detachable coil: midterm clinical results in a consecutive series of 100 patients

The purpose of this study was to investigate in vitro the potential effect of type 1 collagen gel containing alpha-elastin on the proliferation of vascular smooth muscle cells and vascular endothelial cells, and on smooth muscle cell migration. Vascular smooth muscle cell and endothelial cell were cultured in 12-well plates precoated with collagen gels and alpha-elastin. Cell proliferation rates were measured by monitoring [3H]-thymidine incorporation. After 2, 3 or 4 days of culture, the proliferation rate of both smooth muscle cells and endothelial cells was significantly decreased on collagen gel containing 10 mg/ml alpha-elastin compared with collagen gel only as control. Smooth muscle cell proliferation on collagen gel containing alpha-elastin on the 4th day of culture was decreased dose-dependently, e.g. 1 mg/ml of alpha-elastin (74.8(2.3)% of control, P=n.s.); 5 mg/ml (56.7(2.1)%; P<0.05); 10 mg/ml (30.3(3.1)%; P<0.005). In the case of cultured endothelial cells, however, [3H]-thymidine incorporation was not decreased significantly in the presence of 5 mg/ml alpha-elastin (83.1(7.9)%, P=n.s.). After stimulation by platelet-derived growth factor, the smooth muscle cell migration rate on collagen gel containing alpha-elastin (5 mg/ml) was decreased over time. The area of migration on the 6th day of culture was also significantly decreased dose-dependently in the presence of alpha-elastin, e.g. 1 mg/ml (72.6(3.4)% of control, P<0.05), 5 mg/ml (56.9%(1.5)%; P<0.05); 10 mg/ml (37.3(2.7)%; P<0.0005). In conclusion, alpha-elastin inhibited the proliferation and migration of smooth muscle cell in a dose-dependent manner on collagen gel culture, however, at high concentrations of alpha-elastin (10 mg/ml), the endothelial cell proliferation rate was also inhibited. At 5 mg/ml, alpha-elastin significantly inhibited smooth muscle cell proliferation and migration but did not significantly inhibit endothelial cell proliferation. Incorporation of collagen gel containing alpha-elastin into the structure of arterial prosthesis offers the possibility of inhibiting smooth muscle cell hyperplasia without significant effect on endothelial cell formation.     

The cell biology of atherosclerosis--new developments

In the development of atherosclerotic lesions, three basic processes occur: 1) invasion of the artery wall by leucocytes, particularly monocytes and T-lymphocytes; 2) smooth muscle phenotypic modulation, proliferation, and synthesis of extracellular matrix; and 3) intracellular (macrophage and smooth muscle) lipoprotein uptake and lipid accumulation. Invasion of the vessel wall by leucocytes is mediated through the expression of adhesion molecules on both leucocytes and the endothelium making them 'sticky'. The adhesion molecules are induced by inflammatory mediators released from leucocytes and endothelium, and these in turn are induced by high serum cholesterol levels or complement fragments. Leucocytes which have adhered to the endothelium are chemo-attracted into the vessel wall by cytokines produced by early arriving leucocytes or by low density lipoprotein which has passively passed into the wall, in the process being trapped and oxidised. The oxidised low density lipoprotein is taken up by scavenger receptors (which are not subject to down-regulation) on both macrophages and smooth muscle cells. The overaccumulation of lipid is toxic to the cells and they die contributing to the central necrotic core. The macrophages and T-lymphocytes produce substances which induce smooth muscle cells of the artery wall to change from a 'contractile' (high volume fraction of myofilaments [Vvmyo]) to a 'synthetic' (low Vvmyo) phenotype. In this altered state they respond to growth factors released from macrophages, platelets, regenerating endothelial cells and smooth muscle cells; produce large amounts of matrix; express lipoprotein scavenger receptors; express adhesion molecules for leucocytes; and express HLA-DR following exposure to the T-lymphocyte product, IFN-delta, suggesting that they can become involved in a generalised immune reaction.     

Selectins and their counter receptors: a bitter sweet attraction

Selectins are adhesion receptors expressed by leucocytes, platelets, and endothelial cells. They mediate the initial binding of leucocytes to vascular endothelium in the post-capillary venules. This is an essential first step in leucocyte migration into tissue. The selectin family of adhesion receptors consists of three C-type lectins (E, P, and L selectin). Their ligands (counter structures) are sialylated and fucosylated carbohydrate molecules which, in most cases, decorate mucin-like glycoprotein membrane receptors. Studies using blocking monoclonal antibodies have shown that inhibition of selectin function can ameliorate a range of inflammatory processes, offering the possibility that antagonists of selectin function may be useful in the treatment of inflammatory lung diseases such as asthma.     

Phenotype, and migration properties of three major subsets of tissue homing T cells in sheep

T cells show a bias in their migration pathways: some T cells preferentially migrate to peripheral lymph nodes (LN), some to mucosal tissues, and some to peripheral tissues such as skin. These recirculation pathways were examined in sheep by collecting lymph draining into and out of peripheral and intestinal LN, and using fluorescent dyes to trace the recirculation of the lymph cells. Monoclonal antibodies (mAb) to alpha 4, beta 1, and beta 7 integrins, and L-selectin, were used to define three major populations of recirculating T cells. Naive-type T cells (L-selectin+, alpha 4 beta 1lo beta 7lo) migrated preferentially through peripheral LN. Two memory populations could be defined: alpha 4 beta 1hi beta 7- and alpha 4 beta 7hi beta 1lo. alpha 4 beta 1hi beta 7- T cells were present in lymph draining from the skin. T cells migrating preferentially through intestinal LN were alpha 4 beta 7hi beta 1lo. Consistent with this migration pattern, the endothelial receptor for alpha 4 beta 7, mucosal addressin cell adhesion molecule-1 (MAdCAM-1) was detected on high endothelial venules within intestinal LN and Peyer's patches, but only weakly on high endothelial venules within peripheral LN. Thus, there are at least three easily definable subsets of T cells, based on integrin expression, which show distinct migration preferences.     

Brazilian consensus on Helicobacter pylori and associated diseases

Non-granulomatous nodular accumulations of inflammatory cells in inflammatory myopathies were studied to characterize adhesion mechanisms used for leukocyte recruitment. The nodules had a B-cell-rich center surrounded by a helper T-cell-rich peripheral zone, resembling lymph nodes. The T-cell-rich zones harbored high-walled venules resembling high endothelial venules (HEV), whose endothelia frequently expressed ICAM-1, VCAM-1, and less constantly E-selectin. This endothelial adhesion molecule profile differs from that found in polymyositis, inclusion body myositis, or dermatomyositis, but resembles that in lymphoid tissues. Also, the peripheral lymph node addressin, a vascular addressin specific for peripheral lymphoid tissue HEV, was present on many HEV. This adhesion system is probably responsible for the excessive lymphocyte recruitment. The similar cellular organization and lymphocyte recirculation mechanisms of the nodular infiltrates in muscle and of lymph nodes suggest that the former may also produce antibodies.     

Galalpha1-->4Gal-glycans are expressed on myofibrillar associated proteins

There is evidence that glycans carrying terminal galactose residues are differently expressed in the sarcoplasm of different muscle fiber types. In this study monoclonal antibodies directed against P blood group antigens Pk: Galalpha1-4Galbeta1-4Glcbeta- and P1: Galalpha1-4Galbeta1-4GlcNAcbeta- were used to detect terminal alpha-galactosylated glycoconjugates on muscle proteins. Electrotransfer of proteins, extracted from human masseter and biceps muscles, to nitrocellulose after polyacrylamide gel electrophoresis (PAGE) and incubation with anti-Pk (CD77) consistently showed two bands with apparent molecular weights of 66 kDa and 64 kDa. In fresh frozen muscle sections from some humans there was endothelial reaction with anti-CD77 in capillaries, venules and veins but not in arterioles and arteries. In muscle samples from other humans there was no staining of endothelial cells. Formalin-fixed human muscle displayed a CD77 reaction with highest accumulation of reaction product at the periphery of the fibers. This may be explained by the presence of Pk glycoconjugates on intermediate filaments in muscle fibers. In preparations of cat masseter muscle proteins the antibodies against P1Pk antigens reacted with a 170 kDa and a 55 kDa band while in preparations of cat biceps brachii only a 55 kDa band was reactive. The specificities of the antibodies were investigated by fluorescence-activated cell sorter (FACS), alpha- and beta-galactosidase digestion and inhibitory sugars. This study indicates that glycans carrying Galalpha1-4Galbeta1- epitopes are expressed on myofibrillar associated proteins.     

Effect of tissue-plasminogen activator on leukocyte-endothelial interactions at the microcirculatory level

In free tissue transfer and replantation surgery, there is a debate over whether any pharmacologic agents should be used to improve vessel patency and tissue survival. Because tissue-plasminogen activator (t-PA) is a highly effective and safe fibrinolytic, it may be useful in obtaining and maintaining vessel patency. The direct effects of t-PA on skeletal muscle hemodynamics and leukocyte activation at the microcirculatory level were investigated. Male Sprague-Dawley rats (n = 20) were divided into three experimental groups: control (n = 8), vehicle (n = 6), and t-PA (n = 6). Using the cremaster muscle flap model and intravital microscopy, red blood cell velocity, vessel diameter, capillary perfusion, endothelial edema index, and leukocyte-endothelial interactions (rolling, adhering, and transmigrating leukocytes) in postcapillary venules were measured. In the vehicle and t-PA groups, vehicle or t-PA was infused by means of a catheter inserted into the lower abdominal aorta for local infusion. Except for a significant reduction in the diameter of the first order arterioles from 117 microm to 82 microm (medians; p = 0.026), t-PA did not significantly affect red blood cell velocity, vessel diameter, or capillary perfusion compared with vehicle. However, leukocyte-endothelial interactions did differ significantly in postcapillary venules. Adhering leukocytes counted per visual field decreased from 4.67 in the vehicle group and 3.50 in the control group to 1.67 in the t-PA group (medians; p = 0.015 and p = 0.005, respectively); transmigrating leukocytes in the t-PA group decreased from 4.75 in the vehicle group and 3.50 in the control group to 1.67 in the t-PA group (medians; p = 0.002 and p = 0.043, respectively). t-PA treatment significantly decreased the number of both adhering and transmigrating leukocytes. These novel findings on leukocyte-endothelial interactions suggest that t-PA has anti-inflammatory effect.     

Changes in vessel ultrastructure during ischemia and reperfusion of rabbit hindlimb: implications for therapeutic intervention

Peripheral ischemia was induced in the rabbit by occlusion of the left iliac artery for 6 hr, followed by 24 hr of reperfusion. Biochemical and morphological investigations were performed to evaluate the extent of vascular and tissue injury. Blood samples for plasma enzyme determinations (creatine kinase (CK) and lactate dehydrogenase (LDH) activities) were obtained at times t = 0, t = 6, t = 30 hr. Plasma CK and LDH activities in ischemic animals were approximately twice as high as those in sham-operated animals at the end of reperfusion, although no difference was observed at the end of the period of ischemia. Morphological and morphometric analysis of extensor digitorum longus muscle from ischemic animals showed a reduction in the number of patent capillary vessels per muscle fiber (1.54 +/- 0.1 and 1.04 +/- 0.09, P < 0.05, in sham and ischemic groups, respectively; mean +/- SEM). In addition, the number of microvilli on endothelial surfaces were considerably increased in the ischemic group (0.14 +/- 0.02 and 0.41 +/- 0.01 microns -2, P < 0.001, in sham and ischemic groups, respectively). A great number of adhered leucocytes were found on the vessel surface with some leucocytes having migrated through the vessel wall. Microcirculatory damage was accompanied by the formation of microthrombi which sometimes occluded the entire vessel lumen. The infusion of 1 mg/kg/hr of cloricromene for 6 hr prevented ischemic injury in microvessels and also prevented swelling of muscle mitochondria. In the treated group the number of patent capillaries per muscle fiber was very similar to that found in sham-operated animals (1.49 +/- 0.08; P < 0.01 vs. ischemic control). In conclusion, several different cell types are involved in the pathophysiological changes which occur in microvessels during ischemia/reperfusion injury. Pharmacological interventions, which inhibit the interactions of blood cells with endothelium, may be of value in the treatment of peripheral ischemia/reperfusion injury.     

Role of the endothelial cytoskeleton in blood-brain-barrier permeability to protein

The role of the cytoskeletal elements, microfilaments and microtubules in cerebral endothelial permeability to protein during steady states was investigated by studies of cerebrovascular permeability to horseradish peroxidase (HRP) in rats pretreated with cytochalasin B or colchicine, agents known to disrupt microfilaments and microtubules, respectively. In addition, the effect of colchicine pretreatment on the alterations in cerebrovascular permeability that occur in acute hypertension were studied. Rats infused with cytochalasin B showed increased cerebrovascular permeability to HRP in multifocal areas of the ipsilateral hemisphere. Most of the permeable vessels were arterioles; however, capillaries and venules also showed increased permeability. Ultrastructural studies of permeable vessels showed HRP in all layers of vessel walls and in endothelial and smooth muscle cell pinocytotic vesicles, which were increased in number. Although segments of interendothelial spaces were labeled by tracer, continuous labeling of interendothelial spaces from the luminal to the abluminal end was not seen and tight junctions were not disrupted. Normotensive rats pretreated with colchicine showed no alteration in cerebrovascular permeability to HRP. Colchicine pretreatment attenuated the permeability alterations that were observed in acutely hypertensive rats. This study demonstrates that integrity of endothelial actin filaments is important for maintenance of the blood-brain barrier to protein during steady states since increased permeability occurred in the presence of an actin disrupting agent. The microtubular network had no demonstrable role during steady states; however, disruption of the microtubular network had a protective effect and prevented the development of alterations in permeability to protein in acute hypertension.     

Mechanisms of endothelin-induced macromolecular leakage in microvascular beds of rat mesentery

Microvascular responses to endothelin-3 were investigated in the rat mesentery under fluorescence microscopy. Endothelin-3 in a range of 0.1-100 pM induced arteriolar constriction in a dose-dependent manner, and stimulated Ca2+ mobilization, demonstrated by fura-2-associated fluorography, in both arterioles and venules. Cyclo(-D-Trp-D-Asp-Pro-D-Val-Leu-) (BQ123), and endothelin ETA receptor antagonist, at a concentration of 10 microM inhibited the endothelin-3 (100 pM)-induced arteriolar constriction and Ca2+ mobilization in arterioles but not in venules. In venules, an early onset leakage of FITC (fluorescein isothiocyanate)-labeled albumin and subsequent reduction of red blood cell velocity without arteriolar constriction were observed after the superfusion of endothelin-3 with BQ123, suggesting that a non-endothelin ETA receptor mediates macromolecular leakage followed by a decrease in blood flow. Endothelin-3 with BQ123 neither stimulated leukocyte adhesion nor activated luminol-dependent chemiluminescence in venules, showing that endothelin-3-increased permeability may be induced by leukocyte-independent and oxyradical-independent mechanisms. These microvascular alterations of permeability and red blood cell velocity were significantly attenuated by the addition of phalloidin, an F-actin stabilizer, suggesting the involvement of endothelial cell contraction. Nicardipine (1,4-dihydro-2,6-dimethyl-4-[3-nitrophenyl]methyl-2- [methyl(phenylmethyl)amino]-3,5-pyridinedicarboxylic acid ethyl ester), a dihydropyridine-type Ca2+ channel antagonist, eliminated endothelin-3-induced arteriolar constriction; however, it did not affect albumin leakage promoted by endothelin-3 with BQ123, suggesting that a non-voltage-dependent Ca2+ channel(s) is involved in non-endothelin ETA receptor-mediated Ca2+ mobilization and contraction of venular endothelial cells. Overall, it is conceivable that endothelin ETA receptor and voltage-dependent Ca2+ channel are involved in endothelin-3-induced arteriolar constriction. In addition, the present results suggest that Ca2+ mobilization in venular endothelium, which is mediated by a non-endothelin ETA receptor, possibly endothelin ETB receptor and regulated by non-voltage-dependent Ca2+ channel(s), may cause endothelial cell contraction and subsequently increase macromolecular permeability in microvascular beds treated with endothelin-3.     

Adhesion molecules in inflammatory diseases

Cell adhesion molecules (CAM) have a key role in the inflammatory response. Selectins, integrins and immunoglobulin (Ig) gene superfamily adhesion receptors mediate the different steps of the migration of leucocytes from the blood-stream towards inflammatory foci. The activation of endothelial cells (EC) upregulates the expression of several CAM and triggers the interaction of these cells with leucocytes. Selectins are involved in the initial interactions (tethering/rolling) of leucocytes with activated endothelium, whereas integrins and Ig superfamily CAM mediate the firm adhesion of these cells and their subsequent extravasation. During rolling, leucocytes are activated through the intracellular signals generated by CAM and chemokine receptors. Blockade of the function or expression of CAM has emerged as a new therapeutic target in inflammatory diseases. Different drugs are able to interfere with cell adhesion phenomena. In addition, new antiadhesion therapeutic approaches (blocking monoclonal antibodies, soluble receptors, synthetic peptides, peptidomimetics, etc.) are currently in development.     

Survey of rheumatic heart disease in school children of Kinshasa town

Leukocyte adhesion under flow is preferentially mediated by the selectins. In this study we used intravital microscopy to investigate whether E-selectin may promote firm leukocyte adhesion in vivo. E-Selectin is expressed by endothelial cells activated with tumor necrosis factor-alpha (TNF-alpha) and causes slow leukocyte rolling. Microinjection of formyl-methionyl-leucyl-phenylalanine (fMLP) or macrophage inflammatory protein-2 (MIP-2) next to a venule of the TNF-alpha-treated mouse cremaster muscle significantly increased the number of adherent leukocytes. In gene-targeted mice homozygous for a null mutation in the E-selectin gene or in wild-type mice treated with an E-selectin monoclonal antibody (mAb), this response was significantly attenuated (by >80%). No such defect was seen in intercellular adhesion molecule-1 (ICAM-1)-deficient mice. E-Selectin-null mice showed more rapid leukocyte rolling than wild-type or ICAM-1-deficient mice, resulting in significantly shortened leukocyte transit times through venules. Topical application of fMLP onto the whole cremaster muscle generated the same number of adherent leukocytes in wild-type and E-selectin-deficient mice. We conclude that slow leukocyte rolling through E-selectin results in long transit times, which are essential for efficient leukocyte adhesion in response to a local chemotactic stimulus.     

Endothelin-1-induced vasoconstriction causes a significant increase in portal pressure of rat liver: localized constrictive effect on the distal segment of preterminal portal venules as revealed by light and electron microscopy and serial reconstruction

Intraportal infusion of endothelin-1 (ET-1), a potent vasoconstrictor, significantly elevates portal venous pressure. To determine the major site of vascular constriction in the intrahepatic porto-sinusoidal system, we performed an in situ perfusion of rat livers with 1 nmol/L ET-1 at a flow rate of 20 mL/min. Portal pressure rose from 22 cm H2O to 54 cm H2O within 25 minutes. Specimens were prepared for light-microscopic serial reconstruction and electron microscopy. The distal segment of preterminal portal venules (DS/PPV) with an inner diameter of 40 to 80 microm showed complete obliteration of the lumen over a 300-microm distance caused by the intense contraction of perivascular smooth muscle cells and protruding of endothelial cells into the lumen. The proximal segment of preterminal portal venules (PS/PPV) with a larger diameter up to 150 microm also underwent strong constriction, but still had luminal space for the flow, while the PS/PPV with a diameter of 150 to 400 microm showed moderate or mild constriction and retained a wide lumen. Neither terminal portal venules, inlet venules, sinusoids, nor central veins, however, exhibited demonstrable constriction. Liver parenchyma fed by the inlet venules that emerged from the PS/PPV exhibited a wide sinusoidal lumen and vacuolated hepatocytes caused by the influx of excess portal perfusate that escaped from the occlusive areas. The present study has revealed that the DS/PPV functions as a presinusoidal quasi-sphincter mechanism and is involved in the redistribution of intrahepatic portal flow under increased portal pressure.     

Angiotensin-converting enzyme inhibitor cilazapril suppresses expression of basic fibroblast growth factor messenger ribonucleic acid and protein in endothelial and intimal smooth muscle cells in a vascular injury model of spontaneous hypertensive rats

The relationship between the expression of basic fibroblast growth factor (bFGF) messenger ribonucleic acid (mRNA) and protein, a potent mitogen for vascular smooth muscle cells in vivo, and administration of the angiotensin-converting enzyme inhibitor cilazapril, which suppresses smooth muscle cells proliferation in denuded arteries, was studied in spontaneously hypertensive rats using the in situ hybridization technique and immunohistochemical study. The effect of cilazapril on neointimal formation through modification of bFGF expression was evaluated using the increased tissue expression of the renin-angiotensin system in spontaneously hypertensive rats. Arterial injury was produced by using balloon catheter denudation in the left carotid artery of rats. The effects were evaluated 2 weeks later. bFGF mRNA and protein were observed only in the endothelial cells of sham-operated rats. bFGF mRNA and protein were observed in both endothelial cells and intimal smooth muscle cells in operated rats receiving only vehicle. Expression of bFGF mRNA and protein was suppressed in both endothelial cells and intimal smooth muscle cells of operated rats receiving cilazapril. These data suggest that cilazapril suppresses smooth muscle cell proliferation through modification of the expression of bFGF mRNA and bFGF protein in addition to other genes.     

Osteochondrodysplasia occurring in transgenic mice expressing interferon-gamma

Arterial thrombi are primarily composed of platelets. Platelets are bound to injured endothelial cells, sub-endothelial matrices, and other platelets by a range of adhesive proteins. Some of these reactions are governed by shear forces. The role of adhesive proteins in the pathogenesis of arterial thrombosis is not fully understood. The aim of this study was to examine the involvement of von Willebrand factor (vWF), fibrinogen (Fg), and fibronectin (FN) in the formation of microvascular thrombi in vivo using a helium-neon laser-induced thrombosis method. Transmission electron microscopy demonstrated that laser irradiation resulted in platelet-rich thrombosis in arterioles and venules, and revealed that this occurred in the absence of endothelial denudation. The mean wall shear rates in mesenteric arterioles and venules were 641 +/- 40 and 280 +/- 20 s-1, respectively. Shear rates increased approximately fivefold in arterioles and tenfold in venules during the formation of occlusive thrombi. Antibody to vWF inhibited thrombosis in arterioles and venules. Antibodies to Fg and FN inhibited thrombosis in venules but not in arterioles. These results confirm that vWF, Fg and FN were involved in thrombogenesis in vivo and demonstrated that significantly higher shear rates were required for the reactions involving vWF than those involving either Fg or FN.     

B1 receptor involvement in the effect of bradykinin on venular endothelial cell proliferation and potentiation of FGF-2 effects

1. Bradykinin (BK) contributes to the inflammatory response inducing vasodilation of postcapillary venules and has been demonstrated to induce neovascular growth in subcutaneous rat sponges. 2. In this study the ability of BK to stimulate cell growth and migration in cultured endothelium from coronary postcapillary venules (CVEC) has been investigated. 3. [3H]-thymidine incorporation in subconfluent and synchronised CVEC was used to monitor DNA synthesis over 24 h. BK promoted a concentration-dependent increase of DNA synthesis with maximal activity at 100 nM. At this concentration BK also induced 18 fold accumulation of c-Fos protein immunoreactivity in the nucleus within 1 h from peptide exposure. 4. The total number of cells recovered after 48 h exposure to BK was increased in a concentration-dependent manner. Maximal effect was produced by 100 nM concentration of the peptide which produced 50% increase in cell number. The selective B1 receptor agonist Des-Arg9-BK mimicked the proliferative effect of BK, while the B2 receptor agonist kallidin was devoid of any activity. The proliferation induced by BK was abolished in a concentration-dependent manner by the addition of the B1 selective antagonist Des-Arg9-Leu8-BK, while the selective B2 receptor antagonist HOE140 did not modify BK-induced growth. 5. DNA synthesis and growth promoted by a threshold concentration of fibroblast growth factor-2 (FGF-2) (0.25 nM) were potentiated by increasing concentrations of BK and Des-Arg9-BK. 6. Endothelial cell migration assessed by the Boyden Chamber procedure was not promoted by BK or the selective B1 and B2 receptor agonists. 7. These data are the first demonstration that BK promotes growth of endothelial cells from postcapillary venules. The mitogenic activity of BK involves c-Fos expression and potentiates the growth promoting effect of FGF-2. Only the B1 receptor appears to be responsible for the proliferation induced by BK and suggests that this type of receptor might be implicated in favouring angiogenesis of coronary venules.