Permanent cell line expressing human factor VIII-related antigen established by hybridization

Staphylococcal enterotoxin B-specific adhesion of murine splenic T cells to a human endothelial cell line

The presence of a putative autoantigen of autoimmune disorder in a target organ may cause accumulation of specific T cells in the inflammatory region. One of the mechanisms of such accumulation involves the migration of specific-circulating T cells through the endothelial cells into the target lesion. The presence of only a few specific T cells responsive to a putative autoantigen has hampered the investigation of specific migration of circulating T cells to the target organ. We used a superantigen to investigate specific T-cell adhesion to endothelial cells, because it stimulates a large proportion of T cells with particular V beta elements and adhesion of T cells to the endothelium is a vital step in the migration process. Adhesion of murine T cells to the human endothelial cell line, EA.hy926, was specifically increased in the presence of staphylococcal enterotoxin B (SEB). The increase was interferon-gamma (IFN-gamma)-dependent, and consisted mainly of CD4+ T cells. V beta 8.1,2+ T cells preferentially adhered to endothelial cells in the presence of SEB compared with V beta 6+ T cells. Pretreatment of endothelial cells with SEB increased the adherence of V beta 8.1,2+ T cells, while anti-human leucocyte antigen (HLA)-DR and -DQ antibodies inhibited the increased adherence of V beta 8.1,2+ T cells. Our results demonstrate that increased T-cell adhesion to endothelial cells is SEB specific, and that the specificity is dependent on major histocompatibility complex (MHC) class II molecules expressed on endothelial cells and on the recognition of the SEB-MHC class II complex by V beta 8.1,2+ T cells.

Isolation and characterization of the kininogen-binding protein p33 from endothelial cells. Identity with the gC1q receptor

Kininogens, the precursor proteins of the vasoactive kinins, bind specifically, reversibly, and saturably to platelets, neutrophils, and endothelial cells. Two domains of the kininogens expose major cell binding sites: domain D3 that is shared by H- and L-kininogen and domain D5H that is exclusively present in H-kininogen. Previously we have mapped the kininogen cell binding sites to 27 residues of D3 ("LDC27") and 20 residues of D5H ("HKH20"", respectively (Herwald, H., Hasan, A. A. K., Godovac-Zimmermann, J., Schmaier, A. H., and Müller-Esterl, W. (1995) J. Biol. Chem. 270, 14634-14642; Hasan, A. A. K., Cines, D. B., Herwald, H., Schmaier, A. H., and Müller-Esterl, W. (1995) J. Biol. Chem. 270, 19256-19261). The corresponding kininogen acceptor site(s) exposed by the cell surfaces are still poorly defined. Using a non-ionic detergent, Nonidet P-40, we have been able to solubilize kininogen binding sites from an endothelial cell line, EA.hy926, in their functionally active form. Affinity chromatography of the solubilized kininogen binding sites on HKH20, a synthetic peptide representing the D5H cell binding site, allowed us to isolate a 33-kDa protein ("p33") that binds specifically and reversibly to H-kininogen with a KD (apparent dissociation constant) of 9 +/- 2 nM. Preparative SDS electrophoresis followed by NH2-terminal amino acid sequence analysis identified the kininogen-binding protein p33 as the gC1q receptor ("gC1qR"), an extrinsic membrane protein that interacts with the globular domains of the complement component C1q. The purified p33 binds C1q with moderate affinity, KD = 240 +/- 10 nM. Recombinant expression of the corresponding cDNA in Escherichia coli demonstrated that p33 binds H-kininogen, but not L-kininogen. Peptide HKH20 but not peptide LDC27 inhibited binding of H-kininogen to the recombinant p33 in a concentration-dependent manner, indicating that H-kininogen binds to p33 via domain D5H. Recombinant p33 efficiently inhibited the binding of H-kininogen to EA.hy926 cells. Factor XII, but not prekallikrein, competed with H-kininogen binding to p33. These findings suggest that an endothelial binding protein mediates the assembly of critical components of the kinin-generating pathway on the surface of endothelial cells, thereby linking the early events of kinin formation and complement activation.

Metallopeptidase inhibitors induce an up-regulation of endothelin-converting enzyme levels and its redistribution from the plasma membrane to an intracellular compartment

Endothelin-converting enzyme is a phosphoramidon-sensitive membrane metallopeptidase that catalyses the final step in biosynthesis of the potent vasoactive endothelin peptides. Immunomagnetic separation technology and immunohistochemistry have been used to demonstrate the co-localisation of endothelin-converting enzyme with the established ectoenzyme, aminopeptidase N, on the surface of endothelial cells. Unlike aminopeptidase N, however, endothelin-converting enzyme is seen to associate in clusters on the plasma membrane which can be distinguished from caveolae both biochemically and immunologically. Pre-treatment of endothelial cells with the metallopeptidase inhibitors phosphoramidon or thiorphan in the range 0.01-100 microM produced a dose-dependent increase in the levels of endothelin-converting enzyme protein and its accumulation in an intracellular compartment. No corresponding change in the levels of endothelin-converting enzyme-1 mRNA was detected under these conditions, nor in the levels of the closely related metalloenzyme, endopeptidase-24.11. The phosphoramidon and thiorphan-dependent increase is not due to direct inhibition of endothelin-converting enzyme not endopeptidase-24.11 but, rather, to an inhibition of the selective turnover of endothelin-converting enzyme protein.

Role of receptor desensitization, phosphatase induction and intracellular cyclic AMP in the termination of mitogen-activated protein kinase activity in UTP-stimulated EAhy 926 endothelial cells

We have investigated the mechanisms that bring about the termination of mitogen-activated protein kinase (MAP kinase) activation in response to UTP in EAhy 926 endothelial cells. UTP-stimulated MAP kinase activity was transient, returning to basal values by 60 min. At this time MAP kinase activation was desensitized; re-application of UTP did not further activate MAP kinase, full re-activation of MAP kinase being only apparent after a 1-2 h wash period. However, activation of MAP kinase by UTP could be sustained beyond 60 min by preincubation of the cells with the protein synthesis inhibitor cycloheximide. UTP also stimulated expression of MAP kinase phosphatase-1 and this was abolished after pretreatment with cycloheximide. Pretreatment of cells with forskolin abolished the initial activation of MAP kinase kinase or c-Raf-1 by UTP, but only affected MAP kinase activity during prolonged stimulation. The effect of forskolin on prolonged MAP kinase activation was also prevented by cycloheximide. These results suggest that the termination of MAP kinase activity in response to UTP involves a number of interacting mechanisms including receptor desensitization and the induction of a phosphatase. However, several pieces of evidence do not support a major role for MAP kinase phosphatase-1 in termination of the MAP kinase signal. Raising intracellular cyclic AMP may also be involved but only after an initial protein-synthesis step and by a mechanism that does not involve the inactivation of c-Raf-1 or MAP kinase kinase.

Establishment and characterization of permanent human endothelial cell clones

Though vasculitic diseases have been claimed to be associated with anti-endothelial cells antibodies (AECA), there is a widespread awareness of the limitations of the tests currently in use. Our objective was therefore to establish clones, in the hope that some of them would express disease-specific membrane autoantigens. Two EC lines and 7 clones were established by fusing human umbilical vein EC with epithelial A549/8 cells, and cloning by limiting dilution. An additional clone was derived from the EA.hy 926 cell line. All clones carried EC markers, such as thrombomoduline (TM) and platelet-EC adhesion molecule 1 but differed from each other, depending on whether they expressed HLA class II antigen, LFA-1, thrombospondin receptor or von Willebrand factor (vWf) antigen. Clones were also characterized by their ability to release tissue plasminogen activator, interleukin 6, TM and vWf. This panel is meant to distinguish reactivities of AECA.

Oxidative modifications of low-density lipoproteins (LDL) by the human endothelial cell line EA.hy 926

Modifications of LDL by the EA.hy 926 cell line were compared to those generated by human umbilical vein endothelial cells (HUVEC). Thiobarbituric acid reactive substances (TBARS) index values (TBARS sample/TBARS cell-free control ratio) were 2.64 +/- 0.18 (m +/- SE, n = 11) and 3.12 +/- 0.24 (n = 11), for HUVEC and EA.hy 926, respectively. The percentage of the most electronegative modified LDL fraction (fraction C), assessed by using an ion-exchange chromatographic method based on fast protein liquid chromatography (FPLC), represented 14 +/- 3% (n = 34) and 22 +/- 13% (n =10) of total modified LDL in HUVEC and EA.hy 926, respectively. LDL modified by both cell lines showed increased agarose electrophoretic mobility and apo B100 fragmentation on SDS-PAGE. None of the results were significantly different between the two cell lines. Superoxide anion production was 0.12 +/- 0.04 (n = 11) and 0.07 +/- 0.01 nmol/min/mg cell protein (n = 11) in HUVEC and EA.hy 926, respectively. Cell-specific effects on LDL were abrogated in cysteine-free medium. Moreover, cell-modified LDL were similarly degraded by J774 macrophage-like cells. We conclude that EA.hy 926 cells are a good model for investigating endothelial cell-induced modifications of LDL. Advantages include ready availability and less individual variability than with HUVEC.

Human ryudocan from endothelium-like cells binds basic fibroblast growth factor, midkine, and tissue factor pathway inhibitor

Ryudocan, a heparan sulfate proteoglycan, was isolated from human endothelium-like EAhy926 cells by a combination of ion-exchange and immunoaffinity chromatography. Purified human ryudocan has biochemical properties similar to those of rat ryudocan isolated from microvascular endothelial cells. Human ryudocan contains only heparan sulfate (HS) glycosaminoglycan chains along with a core protein with an apparent molecular mass of 30 kDa. We evaluated the interactions between purified human ryudocan and several extracellular ligands by using a solid-phase binding assay. We found that basic fibroblast growth factor (bFGF), midkine (MK), and tissue factor pathway inhibitor (TFPI) exhibit significant ryudocan binding. Heparitinase (but not chondroitin ABC lyase) treatment destroyed the ability of ryudocan binding to bFGF, MK, and TFPI. Heparin and HS, but not chondroitin sulfate, inhibited such ryudocan binding. Thus, the HS chains of ryudocan appear to be responsible for its binding to bFGF, MK, and TFPI. The apparent dissociation constants for purified ryudocan were as follows: bFGF, 0.50 nM; MK, 0.30 nM; and TFPI, 0.74 nM. Immunohistochemical analysis revealed that ryudocan was expressed in fibrous connective tissues, peripheral nerve tissues, and placental trophoblasts. These findings suggest that ryudocan may possess multiple biological functions, such as bFGF modulation, neurite growth promotion, and anticoagulation, via HS-binding effectors in the cellular microenvironment.

Stimulation by the nucleotides, ATP and UTP of mitogen-activated protein kinase in EAhy 926 endothelial cells

1. We have investigated the characteristics of activation of the 42kDa isoform of mitogen-activated protein (MAP) kinase in response to various nucleotides in the endothelial cell line EAhy 926. 2. Adenosine 5'-triphosphate (ATP) in the concentration range 0.1-100 microM stimulated the rapid and transient tyrosine phosphorylation and activation of the 42 kDa isoform of MAP kinase in EAhy 926 endothelial cells which peaked at 2 min and returned to basal values by 60 min. ATP also stimulated a similar response in primary cultured bovine aortic endothelial cells. 3. Uridine 5' triphosphate (UTP) also stimulated the 42 kDa isoform of MAP kinase with similar potency to ATP (EC50 values 5.1 +/- 0.2 microM for UTP; 2.9 +/- 0.8 microM for ATP), whilst the selective P2Y-purinoceptor agonist, 2-methylthioATP (2-meSATP) was without effect up to concentrations of 100 microM. In bovine aortic endothelial cells however, UTP and 2-meSATP both stimulated MAP kinase. 4. Pretreatment of cells for 24 h with 12-O tetradecanoyl phorbol 13-acetate resulted in the loss of the alpha and epsilon isoforms of protein kinase C (PKC) and virtual abolition of nucleotide-stimulated MAP kinase activity (> 90% inhibition). 5. Preincubation for 30 min with the PKC inhibitor, Ro-31 8220 (10 microM) reduced MAP-kinase activation at 2 min but potentiated the response at 60 min. 6. Removal of extracellular calcium in the presence of EGTA reduced the MAP kinase activation in response to UTP by approximately 30-50%. 7. Pretreatment with pertussis toxin (18 h, 50 ng ml-1) did not significantly affect the UTP-mediated activation of pp42 MAP kinase. 8. These results show that in the EAhy 926 endothelial cell line, nucleotides stimulate activation of MAP kinase in a protein kinase C-dependent manner through interaction with a P2U-purinoceptor.

Characterisation of proteins from two-dimensional electrophoresis gels by matrix-assisted laser desorption mass spectrometry and amino acid compositional analysis

Amino acid compositional analysis and peptide mass fingerprinting by matrix assisted laser desorption mass spectrometry have been used to characterise proteins obtained from two-dimensional electrophoresis (2-DE) separations of human cardiac proteins. A group of twelve protein spots was selected for analysis. The identities of eight of the proteins had been determined by conventional protein characterisation methods, two were unknown proteins and two had putative identities from protein database spot comparison. Amino acid analysis and peptide mass fingerprinting gave corresponding identities for seven of the twelve proteins, which also agreed with our initial identifications. Three proteins which had been identified previously were not confirmed in this study and putative identities were obtained for the two unknown proteins. The advantages, problems and use of amino acid analysis and peptide mass fingerprinting for the analysis of proteins from 2-DE are discussed. The data highlight the need to use orthogonal techniques for the unequivocal identification of proteins from 2-DE gels.

Thrombin-induced increase in endothelial permeability is associated with changes in cell-to-cell junction organization

Thrombin increases endothelial permeability in a rapid and reversible way. This effect requires the catalytic activity of the enzyme and thrombin receptor engagement. Endothelial cell permeability is mostly regulated by intercellular junction organization. In the present study, we investigated whether opening of intercellular gaps after thrombin treatment could be related to changes in adherence-junction molecular organization. By immunofluorescence analysis, we found that thrombin stimulation of endothelial cells caused a marked alteration of the distribution of vascular endothelial (VE)-cadherin and of the associated catenins. These molecules, which are strictly localized at intercellular boundaries in confluent resting cells, were absent in the areas of intercellular retraction. Immunoprecipitation analysis indicated that thrombin disrupted the VE-cadherin/catenin complex. This effect was reversible and correlated with the increase in endothelial permeability. The use of a protein kinase C inhibitor (calphostin C) blocked both thrombin-induced permeability and disassembly of adherence-junction components. We propose that thrombin's effect on endothelial cell junction organization is an important determinant in the increase in endothelial permeability induced by this agent.

Adenovirus-mediated gene delivery to the corneal endothelium

Genetic manipulation of donor cornea prior to transplantation has the potential to modulate the allogeneic response, as well as the endothelial cell function. This study examined the feasibility of gene transfer to corneal endothelial cells using replication-defective recombinant adenoviral vectors. Adult rabbits corneas were infected with recombinant adenovirus RAd35, containing the Escherichia coli beta-galactosidase (lacZ) gene. Localization of gene transfer was assessed by histochemical staining for beta-galactosidase and recombinant protein production was quantified by a soluble assay. In initial experiments, the efficiency of gene transfer and kinetics of expression were studied ex vivo, using organ culture of transfected corneas. Following coculture of whole corneal fragments with RAd35, high levels of gene expression were evident on days 107, diminishing after that time. Gene transfer was found to be almost entirely restricted to corneal endothelial cells, with scattered expression in epithelial cells. Following these ex vivo studies, genetically modified corneas were transplanted as orthotopic allografts in rabbits. Similar kinetics of gene expression were seen after transplantation as in the ex vivo experiment, with maximal levels of gene expression in endothelial cells on days 1-4 after grafting. Corneal function following transplantation was not affected by the gene transfer, with the corneas attaining clarity within 1 day of grafting, and thereafter showing the expected thinning on ultrasonic pachymetry. In the absence of any immunosuppression, no inflammation was evident in graft recipient eyes, with the exception of allograft rejection in 1 animal 23 days after grafting. In this study we show that gene transfer to nonreplicating corneal endothelial cells is feasible using recombinant adenovirus vectors, and so may have potential application in the setting of corneal transplantation.

Prevention of arterial thrombosis by adenovirus-mediated transfer of cyclooxygenase gene

BACKGROUND

Prostacyclin is an important vasoprotective molecule. It inhibits platelet aggregation, monocyte interaction with endothelium, and smooth muscle cell lipid accumulation. Vascular cyclooxygenase-1 (COX-1) is the rate-limiting step in prostacyclin synthesis. The objective of this study was to determine whether adenovirus-mediated transfer of COX-1 could restore COX-1 activity, augment prostacyclin synthesis, and prevent thrombus formation in a porcine carotid angioplasty model.

METHODS AND RESULTS

Human COX-1 cDNA driven by a cytomegalovirus promoter was constructed into a replication-defective adenovirus 5 vector by homologous recombination. Recombinant adenovirus without a foreign gene (Ad-RR) and buffer were included as controls. Recombinant Ad-LacZ was used for marking the transfected cells in vivo. In the in vitro experiments, cultured human endothelial cells (ECs) and porcine arterial smooth muscle cells (SMCs) were incubated with Ad-COX-1 for 2 hours and 6-keto-PGF(1 alpha) level and the transgene expression were determined 72 hours after infection. In the in vivo experiments, recombinant adenoviruses were directly instilled into angioplasty-injured porcine carotid arteries for 30 minutes. Cyclic flow changes were monitored for 10 days and thrombus formation was examined histologically thereafter. Transgene expression and prostaglandin I2 (PGI2) synthesis by the injured arteries were determined. Cultured ECs infected with Ad-COX-1 produced a fivefold to eightfold increase in PGI2, and the transgene expression in cultured porcine SMCs was demonstrated by Northern analysis. Direct administration of Ad-COX-1 at a dose of 3 x 10(10) pfu completely inhibited carotid cyclic flow changes and thrombus formation accompanied by a fourfold increase in PGI2 synthesis by the injured arteries 10 days after infection, whereas Ad-COX-1 at a lower dose, 5 x 10(9) pfu, had no antithrombotic effects when compared with Ad-RR vector and buffer controls.

CONCLUSIONS

Adenovirus-mediated transfer of COX-1 to angioplasty-injured carotid arteries was efficacious in augmenting PGI2 synthesis and was associated with an inhibition of thrombosis when a relatively high titer of adenovirus was instilled.

Tissue-specific expression of two aldose reductase-like genes in mice: abundant expression of mouse vas deferens protein and fibroblast growth factor-regulated protein in the adrenal gland

Aldose reductase (AR), the first enzyme in the polyol pathway, has been implicated in the pathogenesis of diabetic complications, although its physiological role is unclear. In mice, besides AR, two AR-like proteins, mouse vas deferens protein (MVDP) and fibroblast growth factor-regulated protein (FR-1), have been reported recently. Tissue-specific expression of these two genes was examined using the RNase protection assay method. Contrary to previous reports, MVDP was detected in a variety of tissues besides the vas deferens. High levels of MVDP mRNA were found in the adrenal glands, and low levels of expression were detected in eye, intestine, seminal vesicle, kidney, liver, testis and lung. The major gene expression pattern for FR-1 was slightly different from that of MVDP, with the highest levels of mRNA detected in testis, heart, adrenal gland, and ovary; less was found in the lung and it was barely detectable in eye, intestine, liver and seminal vesicle tissue. Mouse embryos, as early as 10.5 days post coitum, expressed both genes, although the levels of expression were different. Human AR mRNA was found in human vas deferens, although not at the high level found in mice. The localization of both MVDP and FR-1 transcripts in the adrenal cortex by in situ hybridization led to the speculation that these two AR-like proteins could be related to hormone production.

Cytotoxic effects of four antibiotics on endothelial cells

Intravenous administration of antibiotics often causes local pain and thrombophlebitis at the site of injection. An in vitro model that could predict these effects would be of great value. In this study the effects of four antibiotics, benzylpenicillin, cefuroxime, dicloxacillin and erythromycin, have been evaluated on three types of endothelial cells in culture. The cell types employed were primary culture from human umbilical vein, primary culture from bovine aorta, and the cell line EA-hy 926, a hybride endothelial cell. These cells were exposed to antibiotics for 24 hr and subsequently toxic effects on cells were evaluated by three different assays. Benzylpenicillin was atoxic in all types of cells and in all assays, in contrast to the other antibiotics. The other three antibiotics exerted dose dependent toxic effects in all investigated cells when DNA-synthesis and total cell protein were used as toxicity assays but the results varied between the cell types. There were no significant differences between the effects of cefuroxime, dicloxacillin and erythromycin on bovine endothelial cells. In the other cell types, however, there were significant differences between some drugs but the outcome depended on the cell type. It is concluded that it is possible to show differences between the effect of antibiotics on endothelial cells, but the result depends on the cell type employed.

Thrombin induces the redistribution and acute release of tissue factor pathway inhibitor from specific granules within human endothelial cells in culture

Tissue factor pathway inhibitor (TFPI) is a vascular anticoagulant that regulates the tissue (TF)-dependent pathway of coagulation. The majority of intravascular TFPI is thought to be noncovalently bound to the vessel wall. Our immunolocalization studies in cultures of human umbilical vein endothelial cells (HUVEC) and immortalized EA.hy926 cells that TFPI is located in well-defined granules evenly spread over the cell surface and with apical polarization within the cytoplasm. These granules are smaller than and distinct from Weibel-Palade bodies. Upon treatment of cultured cells with low concentrations of thrombin (0.01 to 1 NIH U/mL), a marked redistribution of TFPI, occurred with patching in focal points and increased exposure of both TFPI antigen and anticoagulant activity on the surface of the stimulated endothelial cells. This redistribution was paralleled by an acute release of TFPI in the cell medium. EA.hy926 cells responded more readily to thrombin stimulation than HUVECs. The process was inhibited by both hirudin and anti-thrombin receptor antibody. Our findings demonstrate a novel mechanism by which thrombin may exert a negative feedback control on blood coagulation. Therefore, this pathway can be physiological importance in controlling TF-mediated thrombin generation.

Different forms of human vascular adhesion protein-1 (VAP-1) in blood vessels in vivo and in cultured endothelial cells: implications for lymphocyte-endothelial cell adhesion models

Vascular endothelium plays a pivotal role in controlling leukocyte extravasation from the blood into the tissues. Vascular adhesion protein-1 (VAP-1) is a novel endothelial cell molecule which mediates lymphocyte binding to the vascular lining (Salmi, M., and Jalkanen, S., Science 1992. 257:1407). In this study, we analyzed endothelial cell type-specific differences of VAP-1. In vivo, VAP-1 is a 90/170-kDa molecule which is mainly expressed on the lumenal surface and in cytoplasmic granules of peripheral lymph node-type postcapillary venules (high endothelial venules, HEV). In tonsil HEV, VAP-1 is modified with abundant sialic acids. VAP-1 is also detectable in the cytoplasm of human umbilical vein endothelial cells (HUVEC) and in an endothelial cell hybrid EaHy-926, although both cell types lack detectable surface VAP-1. Cultured endothelial cells do not express MECA-79-defined peripheral lymph node addressins either. VAP-1 was not translocated onto the endothelial cell surface after stimulation with multiple cytokines, mitogens or secretagogues which induced expression of other known endothelial adhesion molecules. Biochemical analyses revealed that VAP-1 is a approximately 180-kDa protein in these endothelial cell types. Digestions with neuraminidase, O-glycanase and N-glycanase, as well as treatment of cells with tunicamycin and benzyl-N-acetylgalactosaminide, did not alter the molecular mass of VAP-1 in EaHy-926. Pulse-chase experiments showed that VAP-1 is directly synthesized as a 180-kDa molecule without any detectable precursors. Thus, in cultured endothelial cells, VAP-1 is a 180-kDa protein which is devoid of post-translational modifications, and in particular, lacks the sialic acids crucial for the function of VAP-1 in tonsil vessels. Notably, the endothelial cell types commonly used as a model in studying lymphocyte-endothelial cell interactions lack surface expression of VAP-1 and peripheral node addressins, and hence are inherently of limited use in analyses of the initial adhesion of lymphocytes.

Endothelial cells and renal epithelial cells do not express the Wegener's autoantigen, proteinase 3

Proteinase 3 (PR3) is the major antigen for autoantibodies (C-ANCA) against cytoplasmic components of neutrophils which are strongly associated with Wegener's granulomatosis (WG). Recent data that PR3 may be expressed by renal tubular epithelial cells and endothelial cells suggest potential for a direct pathogenic effect against these cells by C-ANCA or cytoxic T lymphocytes. Using a semi-quantitative polymerase chain reaction (PCR), ELISA and indirect immunofluorescence staining we studied endothelial and epithelial cell PR3 expression. By PCR, no PR3 expression was found in human umbilical vein endothelial cells (HUVEC) either untreated, or when treated with interferon-gamma (IFN-gamma) (200 U/ml, 6 h, 24 h), IL-1 (20 U/ml, 6 h), tumour necrosis factor-alpha, (TNF-alpha) (200 U/ml, 0, 1, 2, 4, 6 h) or IFN-gamma + TNF-alpha (6 h); iliac vein and artery endothelial cells did not express PR3 either. In contrast, PR3 was detected in HL60 cells and neutrophils by PCR, expression being confirmed by sequence analysis. Three PR3 MoAbs showed no binding to unstimulated or TNF-alpha-stimulated HUVEC either by ELISA or by indirect immunofluorescence staining. The epithelial cell line A549 expressed PR3 when assayed by PCR. However, three renal epithelial cell lines (two tubular and one glomerular) showed little or no PR3 expression by PCR or ELISA. These studies fail to demonstrate evidence for PR3 expression by endothelial cells, even when using the highly sensitive PCR assay. Whilst PR3 expression by A549 cells is intriguing, the relevance of this in the pathology of WG is doubtful considering the negligible expression by renal epithelial cell lines.

Nitric oxide synthase: expression and expressional control of the three isoforms

Three isozymes of nitric oxide synthase (NOS) have been identified. Their cDNA- and protein structures as well as their genomic DNA structures have been described. NOS I (ncNOS, originally discovered in neurons) and NOS III (ecNOS, originally discovered in endothelial cells) are low output, Ca(2+)-activated enzymes whose physiological function is signal transduction. NOS II (iNOS, originally discovered in cytokine-induced macrophages) is a high output enzyme which produces toxic amounts of NO that represent an important component of the antimicrobial, antiparasitic and antineoplastic activity of these cells. Depending on the species, NOS II activity is largely (human) or completely (mouse and rat) Ca(2+)-independent. In the human species, the NOS isoforms I, II and III are encoded by three different genes located on chromosomes 12, 17 and 7, respectively. The amino acid sequences of the three human isozymes (deduced from the cloned cDNAs) show less than 59% identity. Across species, amino acid sequences are more than 90% conserved for NOS I and III, and greater 80% identical for NOS II. All NOS produce NO by oxidizing a guanidino nitrogen of L-arginine utilizing molecular oxygen and NADPH as co-substrates. All isoforms contain FAD, FMN and heme iron as prosthetic groups and require the cofactor BH4. NOS I and III are constitutively expressed in various cells. Nevertheless, expression of these isoforms is subject to regulation. Expression is enhanced by e.g. estrogens (for NOS I and III), shear stress, TGF-beta 1, and (in certain endothelial cells) high glucose (for NOS III). TNF-alpha reduces the expression of NOS III by a post-transcriptional mechanism destabilizing the mRNA. The regulation of the NOS I expression seems to be very complex as reflected by at least 8 different promoters transcribing 8 different exon 1 sequences which are expressed differently in different cell types. Expression of NOS II is mainly regulated at the transcriptional level and can be induced in many cell types with suitable agents such as LPS, cytokines, and other compounds. Whether some cells can express NOS II constitutively is still under debate. Pathways resulting in the induction of the NOS II promoter may vary in different cells. Activation of transcription factor NF-kappa B seems to be an essential step for NOS II induction in most cells. The induction of NOS II can be inhibited by a wide variety of immunomodulatory compounds acting at the transcriptional levels and/or post-transcriptionally.

Bacterial plasminogen receptors: in vitro evidence for a role in degradation of the mammalian extracellular matrix

The potential of bacterium-bound plasmin to degrade mammalian extracellular matrix and to enhance bacterial penetration through basement membrane was assessed with the adherent strain SH401-1 of Salmonella enterica serovar Typhimurium. Typhimurium SH401-1 was able to bind plasminogen and to enhance the tissue-type plasminogen activator-mediated activation of the single-chain plasminogen to the two-chain plasmin. The end product, the enzymatically active, bacterium-bound plasmin activity, was also formed in a normal human plasma milieu in the presence of exogenous tissue-type plasminogen activator, indicating that plasmin was protected from the plasminogen activator inhibitors and plasmin inhibitors of plasma. Plasmin bound on Typhimurium cells degraded 125I-labeled laminin as well as 3H-labeled extracellular matrix prepared from the human endothelial cell line EA.hy926. The degradations were not seen with Typhimurium cells without plasminogen and were inhibited by the low-molecular-weight plasmin inhibitor aprotinin. Plasmin bound on Typhimurium cells also potentiated penetration of bacterial cells through the basement membrane preparation Matrigel reconstituted on membrane filters. The results give in vitro evidence for degradation of the mammalian extracellular matrix by bacterium-bound plasmin and for a pathogenetic role for bacterial plasminogen receptors.

H2O2 and tumor necrosis factor-alpha activate intercellular adhesion molecule 1 (ICAM-1) gene transcription through distinct cis-regulatory elements within the ICAM-1 promoter

We investigated the mechanisms by which H2O2 increases intercellular adhesion molecule 1 (ICAM-1; CD54) expression in endothelial cells. The H2O2-induced increase in ICAM-1 mRNA was inhibited by actinomycin D, by the antioxidant N-acetylcysteine, and by 3-amino-benzamide (which blocks oxidant-induced AP-1 activity), but not by pyrrolidine dithiocarbamate (which blocks oxidant-induced NF-kappa B activity). Nuclear run-on and transient transfections of ICAM-1 promoter constructs indicated that H2O2 stimulated ICAM-1 gene transcription by activation of a distinct region of the ICAM-1 promoter. The H2O2-responsive element was localized to sequences between -981 and -769 (relative to start codon). Located within this region are two 16-base pair repeats, each containing binding sites for the transcription factors AP-1 and Ets. A similar composite AP-1/Ets element isolated from the macrophage scavenger receptor gene conferred H2O2 responsiveness to a minimal promoter. Mutation of the 16-base pair repeats within the ICAM-1 promoter prevented H2O2-induced DNA binding activity, and their deletion abrogated the H2O2-induced transcriptional activity. In contrast, TNF alpha induced ICAM-1 transcription via activation of promoter sequences between -393 and -176, a region with C/EBP and NF-kappa B binding sites. The results indicate that H2O2 activates ICAM-1 transcription through AP-1/Ets elements within the ICAM-1 promoter, which are distinct from NF-kappa B-mediated ICAM-1 expression induced by TNF alpha.

Regulation of the function of the first component of complement by human C1q receptor

A membrane-associated receptor for the C1q subcomponent of complement is widely distributed among different cell types. While a number of possible physiological functions of the C1q receptor (C1qR) on different cell types have been described, the way in which C1qR regulates complement activity remains unclear. This report describes the mechanism by which C1qR regulates activation of the first component of complement, C1. Using purified components of complement, we were able to show that membrane-associated C1qR as well as detergent-solubilized C1qR, purified from polymorphonuclear leukocytes, human umbilical vein endothelial cells or an endothelial cell line, EA.hy 926, are able to inhibit complement-mediated lysis of C1q-sensitized erythrocytes. Using hemolytic assays, we were able to demonstrate that C1qR prevents the association of C1q with C1r and C1s to form macromolecular C1. In addition, incubation of C1qR with the collagen-like stalks, but not with the globular heads of C1q, inhibits the effect of C1qR. This demonstrates that C1qR exerts its complement inhibitory effect by binding to the collagen-like stalk of C1q. No complement regulatory effect of C1qR was observed on preformed macromolecular C1. These data suggest that besides such-well-known complement regulatory molecules as CD55 (DAF), CD46 (MCP), CD35 (CR1) and CD59 (HRF), C1qR too is able to regulate complement activity.

Requirement for protein kinase C activation in basic fibroblast growth factor-induced human endothelial cell proliferation

The intracellular signaling mechanisms that mediate basic fibroblast growth factor (bFGF)-induced angiogenesis have not been fully identified. In particular, whether activation of the intracellular enzyme protein kinase C (PKC) is necessary or sufficient for bFGF-induced mitogenesis of human endothelial cells is not clear. Accordingly, the effect of bFGF stimulation on the Ca2+ increase and PKC activity of normal human endothelial cells (HEC) was studied, as was the effect of inhibition of PKC and the distribution of PKC isoenzymes in these cells. The addition of bFGF to cultured HEC increased overall PKC activity in the absence of an increase in intracellular Ca2+ and markedly stimulated their proliferation, as did the addition of PKC-activating phorbol esters. bFGF-induced proliferation was prevented by the PKC inhibitors chelerythrine and H-7 and by downregulation of PKC after prolonged incubation with phorbol esters. In contrast, these inhibitors did not prevent HEC proliferation induced by epidermal growth factor. Because of the failure of bFGF to increase Ca2+, we determined whether bFGF-induced proliferation could be mediated by novel or atypical PKC isoenzymes (which are not regulated by Ca2+). Investigation of the isoenzyme distribution of confluent and subconfluent HEC by immunoblotting, Northern transfer analysis, and polymerase chain reaction of reverse-transcribed RNA revealed the presence of several novel and atypical isoenzymes (PKC-delta, -eta, -theta, and -zeta) as well as small amounts of the conventional (Ca(2+)-regulated) isoenzymes PKC-alpha and -beta. Activation of PKC by bFGF, in the absence of an increase in intracellular Ca2+, suggests that one or more of these Ca(2+)-independent PKC isoenzymes are both necessary and sufficient for HEC proliferation after bFGF.

Role of beta 2-glycoprotein I in the antiphospholipid antibody binding to endothelial cells

A group of anticardiolipin antibodies (aCL) require beta 2-glycoprotein I (beta 2GPI) to recognize their target, which might be located on endothelial cells (EC) and/or platelets. Following incubation with epithelial cells, 13 of 30 lupus sera retained EC-reactive antibodies of the IgG, IgA and IgM isotypes. Associated aCL and anti-phosphatidylethanolamine antibodies were partly absorbed on eC as well as EC. The former antibodies were more efficiently removed in the presence than in the absence of the latter. The presence of beta 2GPI in the affinity-purified aCL preparations may explain their binding to EC, as this cross-reaction was abrogated by the removal of the cofactor and restored by its re-introduction. Seventy four per cent of EC were faintly stained with polyclonal or monoclonal antibody directed to the cofactor. The beta 2GPI mediated aCL binding to EC membranes could this be influential in the development of thrombosis and/or thrombocytopenia in aCL-positive patients.

Angiogenic properties of human immunodeficiency virus type 1 Tat protein

Extracellular human immunodeficiency virus type 1 (HIV-1) Tat protein promotes growth of spindle cells derived from AIDS-associated Kaposi sarcoma (AIDS-KS), an angioproliferative disease very frequent in HIV-1-infected individuals. Normal vascular cells, progenitors of AIDS-KS cells, proliferate in response to Tat after exposure to inflammatory cytokines, whose levels are augmented in HIV-1-infected individuals and in KS lesions. Here we show that Tat also promotes AIDS-KS and normal vascular cells to migrate and to degrade the basement membrane and stimulates endothelial cell morphogenesis on a matrix substrate. These effects are obtained at picomolar concentrations of exogenous Tat and are promoted by the treatment of the cells with the same inflammatory cytokines stimulating expression of the receptors for Tat, the integrins alpha 5 beta 1 and alpha v beta 3. Thus, under specific circumstances, Tat has angiogenic properties. As Tat and its receptors are present in AIDS-KS lesions, these data may explain some of the mechanisms by which Tat can induce angiogenesis and cooperate in the development of AIDS-KS.

The role of beta 1 integrins in adhesion of two breast carcinoma cell lines to a model endothelium

Interactions between tumour cells and the endothelium are vital to the formation of haematogenous metastases. Binding to model endothelium of one oestrogen receptor positive breast carcinoma cell line (MCF-7) and one receptor negative line (HS578T) was examined in vitro together with endothelial retraction induced by these tumour cells. Adhesion was inhibited by monoclonal antibodies specific for the VLA integrins and by peptides containing the RGD motif which is commonly recognised as a ligand by the VLA adhesion molecules. However, binding of the two tumour cell lines was inhibited by monoclonal antibodies specific for different VLA molecules; anti-alpha 6 beta 1 inhibited MCF-7 adhesion but anti-alpha 5 beta 1 inhibited Hs578T. These results were consistent with flow cytometric quantification of the expression of these VLA integrins on the surfaces of the two tumour cell lines. Enzyme-linked immunosorbent assays (ELISA) demonstrated that laminin was present on the endothelial cell surface but collagen IV was absent. ELISA failed to detect increased exposure of the subendothelial matrix during the first hour after addition of either cancer cell type. This was supported by assays which demonstrated maintenance of the endothelial permeability barrier during this period. Slight endothelial retraction was detected within 2 hours of the addition of tumour cells. It is concluded that binding between tumour cells and confluent endothelium is inhibited by the blockade of adhesion molecules which are normally associated with interactions between the cell and the subendothelial matrix. Tumour cell to matrix interactions rather than direct tumour to endothelial cell adhesion may be the limiting step in tumour cell binding to the endothelium.

Regulation of lysophosphatidic acid-stimulated tyrosine phosphorylation of mitogen-activated protein kinase by protein kinase C- and pertussis toxin-dependent pathways in the endothelial cell line EAhy 926

In the endothelial cell line EAhy 926, 1-oleoyl-lysophosphatidic acid (LPA) stimulated the tyrosine phosphorylation of the pp42 isoform of mitogen-activated protein (MAP) kinase. Maximum phosphorylation was observed within 5 min of LPA addition, but the response was sustained for up to 120 min. Re-addition of LPA after 60 min stimulated a further sustained increase in the tyrosine phosphorylation of MAP kinase. In cells pretreated with phorbol 12-myristate 13-acetate (PMA; 24 h) or preincubated with the protein kinase C inhibitor Ro-318220, LPA-induced tyrosine phosphorylation of pp42 MAP kinase was substantially reduced at 2 min but potentiated at 60 min. Ro-318220 in combination with either PMA or pertussis toxin pretreatment abolished the LPA response at all time points, suggesting an involvement of protein kinase C in the pertussis toxin-sensitive part of the pathway. Agents which raised intracellular cyclic AMP levels did not affect the initial phase of LPA-stimulated MAP kinase activation, but abolished the late phase. However, this effect was prevented by Ro-318220, implicating a greater role for protein kinase C than protein kinase A in the regulation of sustained MAP kinase responses. LPA stimulated an increase in the tyrosine phosphorylation of focal adhesion kinase pp125 (pp125FAK) in EAhy 926 cells which was both protein kinase C- and pertussis toxin-independent. These results are discussed in terms of the pathways regulating both MAP kinase and pp125FAK in response to LPA in the EAhy 926 endothelial cells line.

Sphingolipid-gated Ca2+ release from intracellular stores of endothelial cells is mediated by a novel Ca(2+)-permeable channel

Sphingolipid-gated Ca2+ signaling is mediated through Ca(2+)-permeable channels. In this report, we characterize the properties of the channel in a human endothelial cell line (EA.hy926). Ca2+ release from intracellular stores is not antagonized by nifedipine, omega conotoxin G-VIa, or heparin. To further characterize the molecular properties of the channel, we developed a novel assay to directly measure efflux of Ca2+ from intracellular stores of permeabilized Xenopus oocytes. Following size fractionation by sucrose gradient, poly(A)+ RNA from EA.hy926 cells is microinjected into oocytes of Xenopus laevis. We find that the mRNA encoding Ca2+ release activity is approximately 1.5-2.0 kilobases in length. The sphingolipid-gated Ca(2+)-permeable channel is thus likely to be a novel Ca(2+)-permeable channel distinct from other characterized intracellular Ca2+ channels such as the ryanodyne receptor and the inositol 1,4,5-trisphosphate receptor. The method described here provides a new approach to further characterizing this channel and other intracellular Ca2+ channels.

Apoptosis and interleukin 7 gene expression in chronic B-lymphocytic leukemia cells

mRNA for interleukin 7 (IL-7) was readily detected in leukemic cells immediately upon their removal from patients with chronic B-lymphocytic leukemia (B-CLL). IL-7 mRNA expression and IL-7 gene transcription were down regulated, however, when B-CLL cells were placed in culture at 37 degrees C for 4 hr. Down regulation of the IL-7 gene was prevented in cells maintained at 4 degrees C. Continued culture of B-CLL cells at 37 degrees C resulted in programmed cell death, or apoptosis, as evidenced by DNA fragmentation. The coincident kinetics of IL-7 gene down regulation and apoptosis suggested that IL-7 gene expression may be required for maintenance of CLL viability in vivo. Signals for IL-7 gene regulation and apoptosis induction were thus examined. Activation of normal B cells through their immunoglobulin receptors did not result in upregulation of IL-7 gene expression. Reagents required for CLL cell purification and culture also did not contribute to IL-7 gene regulation and apoptosis induction. IL-7 gene expression was retained and apoptosis was prevented, however, in CLL cells cultured on a monolayer of EA.hy926 human umbilical cord endothelial hybrid cells. Signals specifically presented by EA.hy926 cells supported both CLL cell viability and IL-7 gene expression, whereas culture of CLL cells on A549/8 carcinoma cells, the fusion partner used to generate the EA.hy926 cells, did not. Cell-cell contact was required, as culture supernatants did not prevent apoptosis. Specifically, IL-7 mRNA expression was retained and apoptosis was prevented only by contact with the endothelial cell hybrids. Preliminary data indicated that integrins expressed on CLL cells affected modulation of apoptosis and IL-7 gene regulation, suggesting that integrins may play significant roles in regulating viability of CLL cells.

Anti-inflammatory lipocortin-derived peptides

Peptide Ac2-26, drawn from the sequence of human lipocortin 1, inhibited the release of elastase activity from cytoplasmic granules of human neutrophils, and neutrophil adhesion to monolayers of endothelial cells, in a concentration-dependent manner (approximate IC50 of 100 micrograms/ml, 33 microM). The effect of peptide Ac2-26 was not restricted to a specific neutrophil activator, being effective against formyl-Met-Leu-Phe (FMLP), leukotriene B4 (LTB4) and platelet-activating factor (PAF). Peptide Ac2-26 did not alter FMLP binding to its receptor. These in vitro observations complement in vivo data obtained with this peptide and may enable a better understanding of its pharmacology and, perhaps, that of of lipocortin 1 too.

The effects of beta-adrenoceptor stimulation on adhesion of human natural killer cells to cultured endothelium

1. The circulation of natural killer (NK) cells in vivo is influenced by physical exercise, mental stress, and infusion of beta-adrenoceptor agonists. We have previously presented in vitro data, showing that beta 2-adrenoceptor agonists induce detachment of NK cells from endothelial cells (EC), supporting the hypothesis that NK cells can be recruited from the marginating pool in blood vessels. 2. Because NK cells as well as EC express beta 2-adrenoceptors, the present study was conducted to investigate whether stimulation of the beta-adrenoceptors on NK cells, EC or both cell types is required to induce detachment from EC. 3. Cells were pretreated (15 min) with a selective beta 2-adrenoceptor antagonist, GR81706, at various concentrations. The duration of beta-adrenoceptor blockade was tested by determining the adenosine 3',5'-cyclic monophosphate (cyclic AMP) production induced by terbutaline (a beta 2-adrenoceptor specific agonist). This receptor-mediated response was effectively inhibited for at least 4 h, whereas the cyclic AMP production in response to forskolin (a direct activator of adenylate-cyclase) was not affected. 4. Functional adhesion assays were then performed to determine the role of beta-adrenoceptors on the different cell types involved (NK and EC) in catecholamine-induced detachment. Peripheral blood mononuclear cells were allowed to adhere for 1 h to monolayers of unstimulated EC in the presence or absence of cyclic AMP inducing agents, and the percentage of NK cells in the adhering lymphocyte fraction was determined by flow cytometry. 5. Both adrenaline (10(-5) M) and forskolin (10(-5) M) caused detachment of NK cells from EC. After blockade of the P2-adrenoceptors on NK cells by pretreatment with GR81706 (10-6 M), the effect of adrenaline on NK cells adhesion was pretented; after blockade of the beta2-adrenoceptors on EC, NK cell adhesion was still significantly reduced by adrenaline. In all cases, forskolin caused detachment of NKcells.6. To establish further that stimulation of beta-adrenoceptors on NK cells is sufficient to cause detachment,we showed that adrenaline also reduced adhesion of NK cells to monolayers of Chinese hamster ovary cells, which do not express beta-adrenoceptors.7. Together, these results show that stimulation of beta2-adrenoceptors on NK cells negatively influences their capacity to adhere to EC, and that beta2-adrenoceptors on EC play a negligible role in this phenomenon.

The widespread expression of angiogenin in different human cells suggests a biological function not only related to angiogenesis

Angiogenin is a secreted polypeptide that induces neovascularization in vivo. The expression of angiogenin by human cells in culture was investigated by using a specific radioimmunoassay and by cDNA hybridization. Angiogenin immunoreactivity was widely but differentially produced by anchorage-dependent growing cells including vascular endothelial cells from saphenous and umbilical veins, aortic smooth muscle cells, fibroblasts (from embryos, new-borns and adults), and tumour cells. Endothelial cells from saphenous veins and the endothelium-derived EA.hy926 cell line released immunoreactivity whatever the stage of the culture, including release at the lag phase, during exponential growth and at the confluent phase. However, the rate of accumulation of angiogenin varied as a function of EA.hy926 cell density. As compared to anchored cells, normal peripheral blood cells and tumour cells of myelomonocytic and megakaryocytic origin did not noticeably secrete angiogenin except at low levels. A myeloma cell line supernatant contained as much angiogenin cross-reactivity as did anchored cells, while four tumour T-cell lines expressed the cross-reactivity at different levels, i.e. from undetectable levels to a high level. A 0.9-kb angiogenin messenger RNA was detected by Northern-blot analyses in a variety of representative cells correlating with the presence of immunoreactivity in the cell-culture media. The widespread expression pattern of angiogenin suggests a physiological function that is not restricted to the neovascularization process.

Differential role of protein kinase C in cytokine induced lymphocyte-endothelium interaction in vitro

In the present study we investigated the influence of the PKC-inhibitor GF109203X on cytokine- and endotoxin-induced expression of intercellular adhesion molecule 1 (ICAM-1) and on the adhesion of lymphocytes to cytokine-activated endothelial cells. We found that tumour necrosis factor alpha (TNF-alpha)- and lipopolysaccharide (LPS)-induced ICAM-1 expression on a human endothelium-derived cell line (EA.hy926) were unaffected by the PKC-inhibitor and thus appeared to be independent of PKC activation. In contrast, GF109203X significantly reduced ICAM-1 expression induced by interferon-gamma (IFN-gamma) and interleukin-1 (IL-1). The functional relevance of these findings was evaluated in an adhesion assay using human umbilical vein endothelial cells (HUVEC) and peripheral blood mononuclear cells (PBMC). In fact, the IFN-gamma- and IL-1-induced adhesion of PBMC to cytokine treated HUVEC could be down-regulated by the PKC-inhibitor, whereas TNF alpha- and LPS-mediated adhesion was not affected. Additionally, the IL-1-driven ICAM-1 expression on HUVEC as well as the IL-1 induced adhesion of PBMC to HUVEC was found to be TNF-dependent, as both effects could be inhibited by an anti-TNF-alpha monoclonal antibody (MoAb) (MAK195). Based on these data on differential regulation of cytokine-induced lymphocyte-endothelium interactions our study supports the use of PKC-inhibitors as additive modulators in cytokine related pathophysiological conditions.

Serum immunoglobulin G reactive with endothelial cells in inflammatory bowel disease

Evidence of a humoral immune response to endothelium was sought in the sera of patients with inflammatory bowel disease. In an ELISA, IgG binding to human umbilical vein endothelial cells was found in 21% of Crohn's disease sera, 10% of ulcerative colitis sera, 6% of sera from patients with acute infective diarrhea, and 8% of normal control sera. The increased prevalence in Crohn's disease sera was significant (P < 0.05). IgG-endothelial cell binding was cell specific, was not Fc-mediated, and did not mediate complement-dependent cell lysis. It was not increased by pretreatment of cells with interleukin-1 or tumor necrosis factor. Endothelial cell binding was retained by IgG F(ab')2 fragments from one of three reactive Crohn's sera, but none of three nonreactive sera. The low prevalence of this interaction, even in patients with immunohistochemically confirmed vasculitis, makes it unlikely that Crohn's disease is determined by a humoral autoimmune response to endothelium.

High-density lipoproteins can act as carriers of glycophosphoinositol lipid-anchored CD59 in human plasma

CD59 (protectin) is a glycophosphoinositol (GPI) lipid-anchored inhibitor of complement lysis that is expressed on the membranes of blood cells, endothelial cells, epithelial cells and cardiomyocytes. CD59 may be shed from cell surfaces, e.g. during cell injury, but when entering human plasma its fate is unknown. In this study we observed that radiolabelled lipid-anchored CD59, but not soluble urinary CD59 without anchor lipid, incorporated into high-density lipoprotein (HDL) particles when mixed with human serum and analysed by high resolution gel filtration and anti-apoA-I affinity chromatography. Only a small proportion of CD59 entered the low-density lipoprotein (LDL) fraction. HDL particles were capable of incorporating 25-42% of [125I]CD that was preinserted into the membranes of rabbit erythrocytes (RaE) and transferred 7-14% of [125I]CD59 back to RaE or to cultured human endothelial cells (EA.hy 926). Immunoaffinity purification and immunoblotting analysis demonstrated that HDL isolated from normolipidemic human serum contained small amounts of CD59. These results suggest that HDL particles could be involved in the recycling of GPI lipid-anchored molecules released from cell surfaces.

Anti-endothelial cell antibodies: a need for standardization

Twenty years have passed since the original description of the anti-endothelial cell antibodies (AECA). It is widely acknowledged that the presence of circulating autoantibodies against endothelial cells surface antigens, found in a number of patients with connective tissue disease and vasculitis, is one of the driving mechanisms for the observed vascular injury and might be an important factor in initiating the pathogenesis of vascular abnormalities. AECA data regarding the prevalence, technical problems, presence with other autoantibodies, antigen distribution and immune endothelial cell injury associated with these autoantibodies, requires standardization for determining the precise pathophysiologic and immunologic role of anti-endothelial cell antibodies.

Enhanced ICAM-1-dependent adhesion of myelomonocytic cells expressing increased levels of beta 2-integrins and CD43

Interaction of ICAM-1 and its ligands plays an important role in the leukocyte binding to endothelium. The best characterized ICAM-ligands belong to the family of beta 2-integrins (CD11/CD18), but recently it has been suggested that CD43, a molecule with no structural resemblance to integrins binds ICAM-1 also. On the leukocytes the main regulatory pathway for ICAM-mediated binding is believed to be a short-term regulation of the avidity of CD11/CD18. In this study the authors investigated whether a quantitative increase in the surface expression of ICAM-ligands also can lead to enhanced binding to purified ICAM-1. PMA-treatment differentiates myelomonocytic cell lines into macrophages with a concomitant increase in the surface expression and mRNA-levels of the beta 2-integrin alpha- and beta-chains as well as that of CD43, another ICAM-ligand. The binding of the PMA-treated THP-1 cells to ICAM-1 was increased simultaneously compared to non-treated cells. The binding was blocked completely with antibodies to CD18 and ICAM-1. It is concluded that in addition to the transient qualitative regulation, a long-term quantitative regulation of ICAM-1 ligands also plays a role in increasing the adhesiveness of myelomonocytic cells. This may be relevant in chronic inflammation episodes.

Targeted neutralization of the complement membrane attack complex inhibitor CD59 on the surface of human melanoma cells

Major problems in the immunotherapy of human tumors with complement-activating monoclonal antibodies (mAb) are (i) inherent resistance of tumor cells to complement cytolysis and (ii) a possible undiscriminatory attack against normal cells. In the present study we have developed a procedure to simultaneously direct the complement membrane attack complex and neutralize its inhibitor CD59 (protectin) on human melanoma cells in vitro. G361 melanoma cells were selectively recognized in heterogenous cell mixtures by a complement-fixing mAb (R24) against the tumor cell GD3-ganglioside. Biotinylated anti-CD59 mAb (YTH53.1) was directed to the tumor cells with a high-affinity biotin-avidin bridge using a proportion of R24 as a biotinylated targeting mAb and avidin as a linker. Biotinylated anti-CD59 mAb lost its ability to activate complement, but retained its CD59-neutralizing activity. Thus, it was possible to avoid nonspecific lysis of surrounding erythrocytes and endothelial cells and direct the CD59-neutralizing effect to the tumor cells. As a result the tumor cells were efficiently killed by R24 plus complement while the bystander cells remained viable. These results suggest that it is possible to target an unrestricted complement membrane attack against GD3- and CD59-positive melanoma cells.

Complement-mediated cytotoxic activity of anti-heart antibodies present in the sera of patients with dilated cardiomyopathy

A microcytotoxicity assay has been used to determine the cytotoxic activity of anti-heart antibodies which we have previously shown to be present with greater frequencies and reactivities in patients with dilated cardiomyopathy (DCM) than in patients with ischaemic heart disease (IHD). Serum samples from 45 patients with DCM and 43 patients with IHD were screened against W1, a transformed human fetal cardiac cell line and also against EA.hy 926, an endothelial and IBR3, a fibroblast cell line. In the presence of complement, sera from 28 (62%) DCM patients showed killing of the W1 cell line as compared to sera from 13 (30%) of IHD patients (p < 0.005) and 3 (15%) of normal individuals. In contrast, only 1 patient with DCM showed killing of the endothelial cell line and 1 patient with IHD showed killing of the fibroblast cell line. These results provide evidence for a complement-dependent, antibody-mediated mechanism of damage to cardiac myocytes which may contribute to the pathogenesis of DCM.

Ets transcription factor binding site is required for positive and TNF alpha-induced negative promoter regulation

Thrombomodulin (TM) is expressed on vascular endothelial cells and plays an important role in the anticoagulant pathway by maintaining the thrombo-resistance of the blood vessel wall. We show that in primary human endothelial cells TM gene expression is repressed at the transcriptional level by Tumour necrosis factor (TNF alpha) through a protein kinase C independent pathway. The TM promoter is highly active in endothelial cells and is inhibited by TNF alpha. The -76/-56 region mediates both specific high basal activity and TNF alpha-repression. It binds a nuclear factor specific to endothelial cells, that appears to belong to the Ets-family by various criteria. The -76/-56 region contains three direct repeats of the ets-core sequence GGAA that are important for specific high basal activity, TNF alpha repression and trans-activation by expression of Ets-1 and 2. Although human Ets-1 (h-Ets-1) and chicken c-Ets-1 and 2 stimulate the TM promoter through the -76/-56 element, their activity is not suppressed by TNF alpha. c-Ets-1 competes and overrides TNF alpha repression in a concentration dependent manner. We propose that either a different member of the Ets domain protein family, or an Ets-associated co-factor, is the target of the TNF alpha signalling cascade in endothelial cells.

Regulation of CD59 expression on the human endothelial cell line EA.hy 926

CD59 (protectin) is an 18-20-kDa inhibitor of the membrane attack complex of complement. It protects homologous cells from complement-mediated damage and has been shown to be present on the endothelial cell membranes both in vitro and in vivo. In this study we observed that the surface expression of CD59 on the cultured EA.hy 926 endothelial cell line can be up-regulated to an approximately threefold higher level after a 72-h stimulation by the protein kinase C inducers phorbol-12-myristate-13 acetate (PMA; 10 nM) and calcium ionophore, A23187 (100 nM). Similarly, an increase in the level of CD59 expression was seen by the protein kinase A inducer dibutyryl-cyclic adenosine monophosphate. In Northern blot analysis increases were observed in CD59 mRNA expression, particularly in the level of the longest 1.9-kb, 2.1-kb and 5.8-kb transcripts. A functional significance for the increased CD59 expression was implied by an observed increased resistance of the PMA-stimulated EA.hy 926 cells to complement-mediated cell lysis.

Sialyloligosaccharide chains of laminin as an extracellular matrix target for S fimbriae of Escherichia coli

S fimbriae purified from recombinant Escherichia coli HB101(pANN801-13) bound strongly to extracellular matrices of cultured endothelial and epithelial cells; only poor binding was seen with the fimbriae purified from the sfaS mutant strain HB101(pANN801-1321). E. coli HB101(pANN801-13) adhered strongly to laminin immobilized on glass; no adhesion was seen to type I, III, IV, or V collagen. Strain HB101(pANN801-1321) failed to adhere to any of the target proteins. Adhesion to laminin of strain HB101(pANN801-13) was inhibited by sialyl-alpha-2,3-lactose as well as by periodate oxidation and neuraminidase treatment of laminin. In Western blotting, the purified S fimbriae recognized more strongly the A chain than the B chains of laminin.

Cell adhesion markers are expressed by a stable human endothelial cell line transformed by the SV40 large T antigen under vimentin promoter control

Markers of endothelium have been studied in a new endothelial cell line derived from human umbilical cord vein cells by microinjection of a recombinant gene that includes a deletion mutant of the human vimentin gene regulatory region controlling the large T and small t antigen coding region of the SV40 virus. In culture, this immortalized venous endothelial cell line (IVEC) demonstrated morphological characteristics of endothelium; uptake of acetylated low density lipoprotein and presence of the Factor VIII-related antigen. Treatment of IVEC cells with Interleukin-1 beta (IL-1 beta) at 10 U.ml-1 activates the expression of cell adhesion molecules such as endothelial leucocyte adhesion molecule (ELAM-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1), as observed in primary culture. Prostacyclin secretion was induced in the IVEC cells by 100 nM PMA treatment and thrombin at 0.5 U/ml. Angiotensin converting enzyme (ACE) activity detected in IVEC cells was present but lower than ACE activity in primary endothelial cells and was completely blocked by enalaprilat (1 microM), a specific ACE inhibitor. The presence of ACE mRNA was also demonstrated in IVEC cells by RT-PCR amplification. Our data demonstrate that endothelial cells immortalized by use of this recombinant gene retain the morphological organization and numerous differentiated properties of endothelium.