CXCR 3 activation promotes lymphocyte transendothelial migration across human hepatic endothelium under fluid flow

T cells infiltrating the inflamed liver express high levels of CXCR 3 and show enhanced migration to CXCR 3 ligands in chemotactic assays. Moreover, CXCR 3 ligands are up-regulated on hepatic endothelium at sites of T-cell infiltration in chronic hepatitis, and their presence correlates with outcome of inflammatory liver disease. We used a flow-based adhesion assay with human hepatic endothelium to investigate the function of CXCR 3 on lymphocyte adhesion to and transmigration through hepatic endothelium under physiological conditions of blood flow. To more accurately model the function of in vivo activated CXCR 3(high) lymphocytes, we isolated T cells from human liver tissue and studied their behavior in flow-based adhesion assays. We demonstrate that CXCR 3 not only promoted the adhesion of effector T cells to endothelium from flow but also drove transendothelial migration. Moreover, these responses could be stimulated either by endogenous CXCR 3 ligands secreted by the endothelium or by exogenous CXCR 3 ligands derived from other cell types and presented by the endothelium. This study thus demonstrates that activation of CXCR 3 promotes lymphocyte adhesion and transendothelial migration under flow and that human hepatic endothelium can present functionally active chemokines secreted by other cell types within the liver.

Transmural gradient of leukocyte-endothelial interaction in the rat gastrointestinal tract

Gastrointestinal injury usually starts in the superficial mucosa. We investigated whether leukocyte-endothelial interactions were greater in the gastrointestinal mucosa than the submucosa and muscularis in control tissue and after upregulation of adhesion molecules with endotoxin and after chemical insult with nonsteroidal anti-inflammatory drugs. Inactin-anesthetized rats were given either endotoxin, flurbiprofen, or nitric oxide (NO)-flurbiprofen, after which ICAM-1 and P-selectin expression was measured with the dual-label antibody technique. Leukocyte-endothelial interactions in the different gastric layers were assessed after endotoxin using intravital microscopy. Endotoxin caused a two- to threefold increase in ICAM-1 expression in the stomach and duodenum. There was, however, a gradient in expression across the gut wall with the level of expression in the superficial mucosa (per g) being only 10-25% of that in the deeper layers in both control and endotoxin-treated animals. Constituitive expression of P-selectin in control animals was barely detectable. Endotoxin caused a modest increase in mucosal P-selectin but a very significant increase in the deeper layers. Flurbiprofen caused a slight upregulation of ICAM-1 in the gastric mucosa and duodenum, whereas NO-flurbiprofen had no affect on expression. Intravital microscopy revealed no adhesion and virtually no leukocyte rolling in the vessels of the gastric mucosa despite endotoxin treatment. There was, however, some adhesion and significant leukocyte rolling in the submucosa and muscularis. Thus the superficial gastric and duodenal mucosal microcirculations have a much lower density of ICAM-1 and P-selectin and less leukocyte-endothelial interactions than occurs in the deeper layers of the gut wall even during stimulated upregulation with endotoxin.

Enhanced oxidative stress and endothelial dysfunction in streptozotocin-diabetic rats exposed to fine particles

The association between ambient particulate matter (PM) and cardiovascular diseases has been demonstrated in epidemiological studies. Recent studies suggest that diabetic patients are at greater risk for PM-associated cardiovascular events. Although diabetes and PM exposure individually have been reported to be associated with increased oxidative stress, inflammation, and endothelial dysfunction, it is not clear whether PM may induce synergistic interaction effects on these parameters in diabetics. Strepotozotocin-induced diabetic (n=4) and healthy (n=4) rats were intratracheally administered with PM2.5 collected from a busy traffic area in a dose of 200 microg suspended in 0.5 mL phosphate-buffered saline (PBS). The same number of rats was exposed to PBS as controls. Cell and differential counts and protein and lactate dehydrogenase activity were determined in bronchoalveolar lavage. Markers of 8-hydroxydeoxy-guanosine (8-OHdG), endothelin-1 (ET-1), and [nitrate+nitrite], an indicator of nitric oxide (NO) production, in addition to C-reactive protein (CRP), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) in peripheral blood were also determined. Our results showed that diabetic rats were associated with increased 8-OHdG, IL-6, and ET-1 decreased [nitrate+nitrite]. In nondiabetic rats PM exposure was also associated with increased 8-OHdG, IL-6, TNF-alpha, and CRP but decreased [nitrate+nitrite]. Interestingly, increases of 8-OHdG and ET-1 after PM exposure were more prominent in diabetic rats than in nondiabetic rats. The general linear model further indicated that there were interactions between diabetes and PM on 8-OHdG (P<0.01) and ET-1 (P=0.08). We suggest that PM exposure may enhance the risk of cardiovascular diseases through interaction between PM and diabetes on excess reactive oxygen species generation and endothelial dysfunction. These findings provide further support for previous epidemiological studies.

Microarray analysis of endothelial differentially expressed genes in liver of cirrhotic rats

BACKGROUND & AIMS

There is a long-standing interest in the identification of endothelial-specific pathways for therapeutic targeting in cirrhosis. Therefore, the aim of this study was to evaluate differences in gene expression patterns between liver endothelial cells (LECs) from control and cirrhotic rats by using microarrays.

METHODS

LECs were obtained by isopycnic centrifugation. LECs gene expression was then analyzed on high-density oligonucleotide microarrays.

RESULTS

Analysis of gene expression revealed that most of the differentially expressed mRNA in cirrhosis are associated with extracellular matrix remodeling, inflammation, antioxidant/stress response, and cell signaling.

CONCLUSIONS

The collective expression changes observed within some functional groups of genes indicate that LECs in cirrhotic livers may contribute to lymphangiogenesis, enhancement of fibrogenesis and inflammatory processes, changes in cell-cell interaction with up-regulation of adherens junction proteins, and alterations in the intrahepatic vascular tone because of the down-regulation of genes involved in vasodilatation.

Effect of P–selectin inhibition on leukocyteendothelium interaction and survival after global cerebral ischemia

Cerebral ischemia induces activation of leukocyte-endothelium interactions requiring upregulation of specific adhesion molecules including the selectins. The aim of the current study was to elucidate the therapeutic potency of P-selectin blockade on microcirculatory disturbances and secondary brain damage after global cerebral ischemia. Global cerebral ischemia for 15 minutes was induced in Mongolian gerbils. Functional blockade of P-selectin was achieved by pretreatment with the antibody RB 40.34 (2 mg/kg, n = 7). In vivo observation of brain microcirculation was performed by epifluorescence microscopy of a cranial window. Survival was assessed daily up to 4 days after ischemia. In the control group leukocyte rolling increased during reperfusion with a maximum at 3 h (28 +/- 14 x 100 microm(-1) x min(-1)) and was significantly reduced by the P-selectin antibody (13 +/- 9 x 100 microm(-1) x min(-1), p < 0.05). No effect on firm leukocyte adhesion was observed (4 +/- 3 vs. 2 +/- 1 x 100 microm(-1) x min(-1)). The survival of animals that received the Pselectin antibody (28 %) was significantly reduced compared with controls (71 %). Anti-P-selectin antibody reduces leukocyte rolling but has no positive effect on survival. Our data question the role of the inflammatory response in the development of secondary brain damage and do not support this kind of therapeutical approach in global cerebral ischemia.

Neuron-astrocyte interactions: partnership for normal function and disease in the central nervous system

Interactions between neurons and astrocytes are critical for signaling, energy metabolism, extracellular ion homeostasis, volume regulation, and neuroprotection in the central nervous system. Astrocytes face the synapses, send end-foot processes that enwrap the brain capillaries, and form an extensive network interconnected by gap junctions. Astrocytes express several membrane proteins and enzymes that are critical for uptake of glutamate at the synapses, ammonia detoxification, buffering of extracellular K+, and volume regulation. They also participate in detection, propagation, and modulation of excitatory synaptic signals, provide metabolic support to the active neurons, and contribute to functional hyperemia in the active brain tissue. Disturbances of these neuron-astrocyte interactions are likely to play an important role in neurologic disorders including cerebral ischemia, neurodegeneration, migraine, cerebral edema, and hepatic encephalopathy.

Calcitonin gene-related peptide activates different signaling pathways in mesenteric lymphatics of guinea pigs

The effects of calcitonin gene-related peptide (CGRP) on constriction frequency, smooth muscle membrane potential (V(m)), and endothelial V(m) of guinea pig mesenteric lymphatics were examined in vitro. CGRP (1-100 nM) caused an endothelium-dependent decrease in the constriction frequency of perfused lymphatic vessels. The endothelium-dependent CGRP response was abolished by the CGRP-1 receptor antagonist CGRP-(8-37) (1 microM) and pertussis toxin (100 ng/ml). This action of CGRP was also blocked by the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine (L-NNA; 10 microM), an action that was reversed by the addition of L-arginine (100 microM). cGMP, adenylate cyclase, cAMP-dependent protein kinase (PKA), and ATP-sensitive K+ (K+(ATP)) channels were all implicated in the endothelium-dependent CGRP response because it was abolished by methylene blue (20 microM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 microM), dideoxyadenosine (10 microM), N-[2-(p-bromociannamylamino)-ethyl]-5-isoquinolinesulfonamide-dichloride (H89; 1 microM) and glibenclamide (10 microM). CGRP (100 nM), unlike acetylcholine, did not alter endothelial intracellular Ca2+ concentration or V(m). CGRP (100 nM) hyperpolarized the smooth muscle V(m), an effect inhibited by L-NNA, H89, or glibenclamide. CGRP (500 nM) also caused a decrease in constriction frequency. However, this was no longer blocked by CGRP-(8-37). CGRP (500 nM) also caused smooth muscle hyperpolarization, an action that was now not blocked by L-NNA (100 microM). It was most likely mediated by the activation of the cAMP/PKA pathway and the opening of K+(ATP) channels because it was abolished by H89 or glibenclamide. We conclude that CGRP, at low to moderate concentrations (i.e., 1-100 nM), decreases lymphatic constriction frequency primarily by the stimulation of CGRP-1 receptors coupled to pertussis toxin-sensitive G proteins and the release of NO from the endothelium or enhancement of the actions of endogenous NO. At high concentrations (i.e., 500 nM), CGRP also directly activates the smooth muscle independent of NO. Both mechanisms of activation ultimately cause the PKA-mediated opening of K+(ATP) channels and resultant hyperpolarization.

Proangiogenic stimulation of bone marrow endothelium engages mTOR and is inhibited by simultaneous blockade of mTOR and NF-kappaB

Most bone marrow (BM) malignancies develop in association with an angiogenic phenotype and increased numbers of endothelial cells. The molecular mechanisms involved in the modulation and recruitment of BM endothelium are largely unknown and may provide novel therapeutic targets for neoplastic diseases. We observed that angiogenic stimulation of BM endothelial cells activates mTOR and engages its downstream pathways 4E-BP1 and S6K1, which are inhibited by the mTOR-specific blockers rapamycin and CCI-779. Both mTOR blockers significantly inhibit growth factor- and leukemia-induced proliferation of BM endothelium by inducing G0/G1 cell-cycle arrest. This effect is associated with down-regulation of cyclin D1 and cdk2 phosphorylation, and up-regulation of the cdk inhibitors p27(kip1) and p21(cip1). Under conditions that reproduce the biomechanical fluidic environment of the BM, CCI-779 is equally effective in inhibiting BM endothelial-cell proliferation. Finally, simultaneous blockade of mTOR and NF-kappaB pathways synergize to significantly inhibit or abrogate the proliferative responses of BM endothelial cells to mitogenic stimuli. This study identifies mTOR as an important pathway for the proangiogenic stimulation of BM endothelium. Modulation of this pathway may serve as a valid therapeutic intervention in BM malignancies evolving in association with an angiogenic phenotype.

Modulation of the myocardial effects of selective ETB receptor stimulation and its implications for heart failure

INTRODUCTION

Endothelin-1 (ET-1) acts on two types of receptors, ET(A) and ET(B). Recent functional studies suggest the existence of two ET(B) receptor subtypes in the heart: ET(B1), located on endocardial endothelial cells and responsible for negative inotropism, and ET(B2), located on myocardial cells and responsible for positive inotropism. The aim of the present study was to investigate the mechanisms underlying the myocardial effects of selective ET(B) receptor stimulation.

METHODS

The study was performed on right papillary muscles from New Zealand white rabbits (n = 39; Krebs-Ringer; 1.8 mM CaCl2; 35 degrees C). The effects of sarafotoxin S6c (SRTXc, ET(B) agonist; 0.2 microM) were evaluated in muscles with: (i) intact endocardial endothelium (EE) (n = 6); (ii) damaged EE (Triton X100; 0.5%; n = 6); (iii) intact EE, in the presence of N(G)-nitro-L-arginine (L-NNA, nitric oxide synthase inhibitor; n = 6); (iv) intact EE, in the presence of indomethacin (INDO, cyclooxygenase inhibitor; n = 6); (v) intact EE, in the presence of BQ-123 (ET(A) antagonist; n = 7); and (vi) damaged EE, in the presence of BQ-123 (n = 8). Only significant results (mean +/- SEM, p < 0.05) are given, expressed as % change from baseline.

RESULTS

In muscles with intact EE, SRTXc alone induced negative inotropic and lusitropic effects, decreasing active tension (AT) by 11.0 +/- 5.6%, maximum velocity of tension rise (dT/dt(max)) by 11.2 +/- 5.9% and maximum velocity of tension decline (dT/dt(min)) by 11.5 +/- 6.2%. However, after removal of EE, or in the presence of L-NNA or INDO, SRTXc increased AT by 35.2 +/- 11.7%, 22.8 +/- 2.9% and 15.2 +/- 3.4%, dT/dt(max) by 29.5 +/- 7.9%, 20.1 +/- 2.1% and 13.3 +/- 5.0%, and dT/dt(min) by 28.2 +/- 8.1%, 21.2 +/- 3.8% and 12.3 +/- 2.2%, respectively. In muscles with intact EE and in the presence of BQ-123, the negative inotropic and lusitropic effects of SRTXc were enhanced: AT decreased by 27.0 +/- 7.4%, dT/dt(max) by 13.3 +/- 4.9% and dT/dt(min) by 31.1 +/- 7.9%. On the other hand, the positive inotropic and lusitropic effects of SRTXc in the absence of intact EE were reversed in the presence of ET(A) blockade: AT decreased by 9.0 +/- 1.8%, dT/dt(max) by 4.1 +/- 3.5% and dT/dt(min) by 8.1 +/- 3.6%.

CONCLUSIONS

The present study shows that the inotropic and lusitropic effects mediated by ET(B) receptors are modulated by endocardial endothelium and by ET(A) receptor activity. These results may have pathophysiological and therapeutic implications in heart failure, a condition in which ET-1 levels are increased and endothelial dysfunction may be present.

Critical Role of Tight Junctions in Drug Delivery across Epithelial and Endothelial Cell Layers

Epithelia in multicellular organisms constitute the frontier that separates the individual from the environment. Epithelia are sites of exchange as well as barriers, for the transit of ions and molecules from and into the organism. Therapeutic agents, in order to reach their target, frequently need to cross epithelial and endothelial sheets. Two routes are available for such purpose: the transcellular and the paracellular pathways. The former is employed by lipophilic drugs and by molecules selectively transported by channels, pumps and carriers present in the plasma membrane. Hydrophilic molecules cannot cross biological membranes, therefore their transepithelial transport could be significantly enhanced if they moved through the paracellular pathway. Transit through this route is regulated by tight junctions (TJs). The discovery in recent years of the molecular mechanisms of the TJ has allowed the design of different procedures to open the paracellular route in a reversible manner. These strategies could be used to enhance drug delivery across epithelial and endothelial barriers. The procedures employed include the use of peptides homologous to external loops of integral TJ proteins, silencing the expression of TJ proteins with antisense oligonucleotides and siRNAs as well as the use of toxins and proteins derived from microorganisms that target TJ proteins.

Tissue-specific hemostasis in mice

Blood coagulation is essential to maintain hemostasis in organisms with a vascular network. Formation of a fibrin-rich clot at a site of vessel injury is a highly complex process that is orchestrated by the coagulation protease cascade. This cascade is regulated by 3 major anticoagulant pathways. Removal of a clot is mediated by the fibrinolytic system. Defects in the regulation of clot formation lead to either hemorrhage or thrombosis. Tissue factor, the primary cellular initiator of blood coagulation, is a transmembrane receptor that is expressed in a tissue-specific manner. The 3 major anticoagulants are tissue factor pathway inhibitor, antithrombin, and protein C, the latter requiring a transmembrane receptor called thrombomodulin for its activation. Tissue factor pathway inhibitor and thrombomodulin are expressed by endothelial cells in a tissue-specific manner, whereas antithrombin and protein C circulate in the plasma. Fibrinolysis requires the activation of plasminogen to plasmin, which is mediated by tissue-type plasminogen activator and urokinase-type plasminogen activator. Interestingly, tissue-type plasminogen activator is expressed by a subset of endothelial cells of discrete size and location. These observations, together with the phenotypes of mice that have defects in the procoagulant, anticoagulant, and fibrinolytic pathways, indicate that hemostasis is regulated in a tissue-specific manner.

Dual interaction of JAM-C with JAM-B and alpha(M)beta2 integrin: function in junctional complexes and leukocyte adhesion

The junctional adhesion molecules (JAMs) have been recently described as interendothelial junctional molecules and as integrin ligands. Here we show that JAM-B and JAM-C undergo heterophilic interaction in cell-cell contacts and that JAM-C is recruited and stabilized in junctional complexes by JAM-B. In addition, soluble JAM-B dissociates soluble JAM-C homodimers to form JAM-B/JAM-C heterodimers. This suggests that the affinity of JAM-C monomers to form dimers is higher for JAM-B than for JAM-C. Using antibodies against JAM-C, the formation of JAM-B/JAM-C heterodimers can be abolished. This liberates JAM-C from its vascular binding partner JAM-B and makes it available on the apical side of vessels for interaction with its leukocyte counter-receptor alpha(M)beta2 integrin. We demonstrate that the modulation of JAM-C localization in junctional complexes is a new regulatory mechanism for alpha(M)beta2-dependent adhesion of leukocytes.

Estrogen receptor-alpha thymidine and adenine repeat polymorphism and endothelial fibrinolytic regulation in postmenopausal women

OBJECTIVE

We hypothesized that the capacity of the endothelium to release tissue-type plasminogen activator is blunted in postmenopausal women with long (TA)(n) repeat alleles (> or = 18 repeats).

STUDY DESIGN

Forty-two healthy postmenopausal women were studied: 10 women with short allele genotypes (both alleles, <18 repeats; age, 59 +/- 2 years), 8 women with long allele genotypes (both alleles, > or = 18 repeats; age, 59 +/- 3 years), and 24 women with mixed allele genotypes (1 short and 1 long allele; age, 56 +/- 1 years). Net endothelial tissue-type plasminogen activator release was determined in response to intra-arterial bradykinin and sodium nitroprusside.

RESULTS

Tissue-type plasminogen activator release in response to bradykinin was highest in homozygotes for the short allele. The total amount of tissue-type plasminogen activator antigen that was released was significantly higher (>55%) in the short (452 +/- 68 ng/100 mL tissue) compared with the mixed (248 +/- 27 ng/100 mL tissue) and long allele (290 +/- 53 ng/100 mL tissue) groups.

CONCLUSION

Our results demonstrate that the long (TA)n dinucleotide repeat allele is associated with blunted endothelial tissue-type plasminogen activator release in healthy postmenopausal women.

Endothelium- and nitric oxide-dependent vasorelaxing activities of gamma-butyrobetaine esters: possible link to the antiischemic activities of mildronate

Mildronate [3-(2,2,2-trimethylhydrazine) propionate (THP)] is an antiischemic drug acting mainly via inhibition of fatty acid beta-oxidation. Some effects of the drug cannot be explained by the latter mechanism. We tested the eventual nitric oxide (NO) dependence of the mildronate action. Mildronate, gamma-butyrobetaine (GBB) and GBB methyl ester induced transient increases in nitric oxide (NO) concentrations in rat blood and myocardium. In vitro, these compounds neither modified the activities of purified neuronal and endothelial recombinant nitric oxide synthases (NOSs) nor were able to interact with their active site. GBB induced vasodilatation at high concentrations only (EC50 = 5 x 10(-5) M) while mildronate alone displayed no vasodilating effect although it enhanced the GBB vasodilating activity. GBB methyl and ethyl esters were found more potent vasodilators (EC50 = 2.5 x 10(-6) M). Pretreatment of aortic rings with NOS inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME) abolished vasodilating effects of the compounds. A hypothesis explaining NO and endothelium-dependent effects of mildronate and its analogues is proposed.

Pleiotropic effects of statins in atherosclerosis: role on endothelial function, inflammation and immunomodulation

Atherosclerosis and its complications still represent the major cause of death in developed countries. Statins have been described as the most potent class of drugs to reduce serum cholesterol levels. The effectiveness and rapidity of statin-induced decreases in coronary events led to the speculation that statins possess also cholesterol-independent effects. By the inhibition of 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase, an enzyme crucial to cholesterol synthesis, statins reduce not only cholesterol but also non steroidal isoprenoid intermediates production. Since these isoprenoids, such as farnesyl pyrophosphate and geranylgeranyl pyrophosphate, regulate the small signaling proteins, Ras and Rho, inhibition of these prenylated proteins by statins might account for their non-lipid-related effects. In this review, we describe the numerous beneficial pleiotropic effects of statins that could modulate atherogenesis.

Toll-like receptor 4 detected in exocrine pancreas and the change of expression in cerulein-induced pancreatitis

OBJECTIVES

To detect Toll-like receptor 4 (TLR4) expression and distribution in rat pancreas and the change of TLR4 expression in cerulein-induced pancreatitis (CIP).

METHODS

Acute pancreatitis was induced by subcutaneous injections of cerulein at a total dose of 20 microg/kg. Immunohistochemistry (IHC) was used to detect and localize TLR4 in rat pancreas, and real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to quantitatively determine the expression of TLR4 mRNA in CIP.

RESULTS

IHC showed the presence of TLR4 in rat pancreas, and its distribution was specifically localized to pancreatic ductal epithelium, vascular endothelium, and islet. No TLR4 staining was detected in exocrine acinar cells. Real-time RT-PCR results revealed low-level TLR4 mRNA expression in the rat pancreas, and the change of TLR4 in CIP only developed within the first 4 hours, which is a rapid up-regulation process that peaks at the first hour. TLR4 mRNA was sustained at baseline level from 4 to 24 hours.

CONCLUSIONS

TLR4 protein was expressed in pancreas and localized to epithelial (pancreatic duct) or endothelial (vessels) tissues; TLR4 responded favorably to the inflammatory process, and the change of expression was characterized as a rapid up-regulation in the early stage of CIP.

roundabout4 is essential for angiogenesis in vivo

Stereotypical patterns of vascular and neuronal networks suggest that specific genetic programs tightly control path determination and, consequently, angiogenesis and axon-guidance mechanisms. Our study focuses on one member of the roundabout family of receptors, which traditionally mediate repulsion from the midline. Here, we characterize a fourth member of this family, roundabout4 (robo4), which is the predominant roundabout (robo) that is expressed in embryonic zebrafish vasculature. Gene knockdown and overexpression approaches show that robo4 is essential for coordinated symmetric and directed sprouting of intersomitic vessels and provide mechanistic insights into this process. Also, human robo4 gene functionally compensates for loss of robo4 gene function, suggesting evolutionary conservation. This article reports an endothelial-specific function for a robo gene in vertebrates in vivo.

Invasive characteristics of human prostatic epithelial cells: understanding the metastatic process

Prostate cancer has a predilection to metastasise to the bone marrow stroma (BMS) by an as yet uncharacterised mechanism. We have defined a series of coculture models of invasion, which simulate the blood/BMS boundary and allow the elucidation of the signalling and mechanics of trans-endothelial migration within the complex bone marrow environment. Confocal microscopy shows that prostate epithelial cells bind specifically to bone marrow endothelial-to-endothelial cell junctions and initiate endothelial cell retraction. Trans-endothelial migration proceeds via an epithelial cell pseudopodial process, with complete epithelial migration occurring after 232±43 min. Stromal-derived factor-1 (SDF-1)/CXCR4 signalling induced PC-3 to invade across a basement membrane although the level of invasion was 3.5-fold less than invasion towards BMS (P=0.0007) or bone marrow endothelial cells (P=0.004). Maximal SDF-1 signalling of invasion was completely inhibited by 10 μM of the SDF-1 inhibitor T140. However, 10 μM T140 only reduced invasion towards BMS and bone marrow endothelial cells by 59% (P=0.001) and 29% (P=0.011), respectively. This study highlights the need to examine the potential roles of signalling molecules and/or inhibitors, not just in single-cell models but in coculture models that mimic the complex environment of the bone marrow.

Endothelial dysfunction and activation as an expression of disease: role of prostacyclin analogs

The endothelium is now considered a real endocrine-paracrine organ, important not only as a structural barrier between the circulation and surrounding tissue, but also because it plays an essential role for local hemodynamics, releasing substances that modulate the vascular calibre and blood cell activation. Here, after a brief but detailed analysis of the importance of the endothelium in vascular homeostasis, in the control of coagulation and in the relations with the different blood cells, we will explain the concept of endothelial dysfunction (altered NO release) and activation (amplified adhesion molecule expression) in inflammatory, connective tissue and post-trasplantation diseases. Furthermore, this review will focus on the activity of prostacyclin and synthetic analogs, especially their ability to interact with the vasodilatation system and their role in modulating cell interaction by surface adhesion molecule expression, cytokines and growth factors release as well as gene transcription factors. Finally, we will consider the therapeutic role of prostacyclin analogs in the prevention and treatment of connective tissue diseases.

Effects of Arg-Gly-Asp sequence peptide and hyperosmolarity on the permeability of interstitial matrix and fenestrated endothelium in joints

OBJECTIVES

The aims were to assess the contribution of arg-gly-asp (RGD) mediated cell integrin-matrix bonds to interstitial hydraulic resistance and to fenestrated endothelial permeability in joints. Joint fluid is generated by filtration from fenestrated capillaries and drains through a fibronectin-rich synovial intercellular matrix. The role of parenchymal cell-matrix bonding in determining tissue hydraulic resistance is unknown.

METHODS

The knee cavity of anesthetized rabbits was infused with saline or the competitive hexapeptide blocker GRGDTP, with or without added osmotic stress (600 mosm saline). Intra-articular pressure Pj, net trans-synovial drainage rate s, and the permeation of Evans blue-labeled albumin (EVA) from plasma into the joint cavity were measured.

RESULTS

GRGDTP increased the hydraulic conductance of the synovial drainage pathway, ds/dPj, by 71% (p =.02, paired t test, n = 6 animals). Synovial plasma EVA clearance (control 7.1 +/- 0.8 microL h-1, mean +/- SEM, n = 15) was unaffected by GRGDTP (7.0 +/- 2.3 microL h(-1), n = 6) or hyperosmolarity (4.9 +/- 1.5 microL h(-1), n = 8) but was increased by GRGDTP and hyperosmolarity together (15.9 +/- 4.8 microL h(-1), n = 5) (p =.01, ANOVA). Changes in dPj/dt evoked by GRGDTP plus hyperosmolarity, but neither alone, demonstrated increased microvascular filtration into the joint cavity (p <.001, ANOVA), as did changes in fluid absorption from the infusion system at fixed Pj.

CONCLUSIONS

RGD-mediated bonds between the parenchymal cells and interstitial polymers reduce the interstitial hydraulic conductance by 42%. This helps to retain the lubricating fluid inside a joint cavity. RGD-mediated bonds also support the macromolecular barrier function of fenestrated endothelium, but in vivo this is evident only in stressed endothelium (cf. in vitro).

Genome-wide identification of cis -regulatory sequences controlling blood and endothelial development

The development of blood has long served as a model for mammalian cell type specification and differentiation, and yet the underlying transcriptional networks remain ill defined. Characterization of such networks will require genome-wide identification of cis-regulatory sequences and an understanding of how regulatory information is encoded in the primary DNA sequence. Despite progress in lower organisms, genome-wide computational identification of mammalian cis-regulatory sequences has been hindered by increased genomic complexity and cumbersome transgenic assays. Starting with a well-characterized blood stem cell enhancer from the SCL gene, we have developed computational tools for the identification of functionally related gene regulatory sequences. Two candidate enhancers discovered in this way were located in intron 1 of the Fli-1 and PRH/Hex genes, both transcription factors previously implicated in controlling blood and endothelial development. Subsequent transgenic and biochemical analysis demonstrated that the two computationally identified enhancers are functionally related to the SCL stem cell enhancer. The approach developed here may therefore be useful for identifying additional enhancers involved in the control of early blood and endothelial development, and may be adapted to decipher transcriptional regulatory codes controlling a broad range of mammalian developmental programmes.

K(+)-induced vasodilation in the rat kidney is dependent on the endothelium and activation of K+ channels

Increased extracellular K+ is reported to cause endothelium-independent vasodilation and K+ has been proposed as an endothelium-derived hyperpolarizing factor. However, the endothelium is endowed with K+ channels that may also be responsive to increased K+. We examined the vasodilator effect of bolus administration of 20, 40 and 60 micromol KCl in the rat isolated kidney in which perfusion pressure was elevated with phenylephrine. KCl produced dose-dependent vasodilator responses that were virtually abolished by removal of the endothelium which also abolished the vasodilator effect of bradykinin without affecting that to nitroprusside. The vasodilator effect of KCl was unaffected by inhibition of cyclooxygenase, nitric oxide synthase or cytochrome P450 but reduced by inhibition of K+ channels with tetraethylammonium (TEA). Barium chloride reduced the vasodilator effects of KCl but charybdotoxin/apamin was without effect. These results indicate that KCl results in endothelium-dependent vasodilation that is independent of nitric oxide (NO), prostaglandins and cytochrome P450 but dependent on activation of endothelial K+ channels.

Effects of changes in body weight and insulin resistance on inflammation and endothelial function in morbid obesity after bariatric surgery

Metabolic alterations such as insulin resistance are thought to underlie the endothelial dysfunction and low grade inflammation found in morbid obesity. Twenty-six morbidly obese patients, aged 39.0 +/- 10.0 (mean +/- sd), were evaluated before and 4.2 +/- 0.8 months after bariatric surgery. A marked increment in the insulin sensitivity index (S(I)) and the endothelium-dependent vasodilatory response in a dorsal hand vein was observed after weight loss following bariatric surgery. Circulating levels of E-selectin, P-selectin, plasminogen activator inhibitor-1, and von Willebrand factor, which were higher than those in the control group, decreased significantly after surgery. Plasma vascular cell adhesion molecule-1, angiotensin-converting enzyme, intercellular adhesion molecule-1, thrombomodulin, and plasma and intraplatelet cGMP levels did not change after weight loss. All inflammatory markers were higher in morbidly obese patients. After surgery, C- reactive protein and sialic acid diminished, whereas circulating levels of IL-6, TNF-alpha, and its soluble receptors did not. Positive correlations were found between changes in adiposity and S(I) and changes in C-reactive protein and between changes in sialic acid and changes in endothelial function. In conclusion, a marked improvement in S(I), endothelial function, and low grade inflammation was observed in the weight-losing, morbidly obese patients after bariatric surgery. S(I) and adiposity appear to play roles in obesity-related, low grade inflammation that contribute to the endothelial dysfunction observed in morbid obesity.