Optimizing microvessel counts according to tumor zone in invasive ductal carcinoma of the breast

We calculated microvessel counts (MVCs) by analyzing CD31-stained sections in three tumor zones (central, intermediate, and peripheral) in 147 cases of invasive ductal carcinoma (IDC). The purpose of the study was to discover whether there is a difference in MVC in the different zones of tumor, which zone contains the highest MVC within the tumor, from which zone the MVCs best correlate with tumor recurrence or tumor death, and which histologic factors correlate with the MVC of the tumor. Sections were scanned to assess the highest number of microvessels in any single 200 x field (0.384 mm2). In all of our cases, the average MVCs of the central, intermediate, and peripheral zones of the IDCs were 34.4, 39.4, and 51.5 per 200x field, respectively. The MVC significantly increased from the central to the peripheral zones (P < .001). In the univariate analysis, in at least one tumor zone, the MVC was correlated with T classification, tumor necrosis, fibrotic focus (a scar-like area within IDCs), and c-erbB-2 protein expression. The only factor significantly correlated with a higher MVC in all of the three zones was fibrotic focus. Moreover, in the multivariate analysis, tumors having high MVCs in the peripheral zone were significantly associated with higher hazard ratios for tumor recurrence (P < .05). This study showed that the MVC of an IDC significantly increases from the central to the peripheral zones, and it showed that angiogenesis in the peripheral zone is associated with prognosis. Therefore, estimation of angiogenesis should be performed in the peripheral zone for reliable prediction of outcome in breast cancer patients. As a surrogate for angiogenesis, fibrotic focus seems to be a useful marker for malignant potential in breast cancer.

Differential association of cytoplasmic signalling molecules SHP-1, SHP-2, SHIP and phospholipase C-gamma1 with PECAM-1/CD31

Recent studies have shown that, in addition to its role as an adhesion receptor, platelet endothelial cell adhesion molecule 1/CD31 becomes phosphorylated on tyrosine residues Y663 and Y686 and associates with protein tyrosine phosphatases SHP-1 and SHP-2. In this study, we screened for additional proteins which associate with phosphorylated platelet endothelial cell adhesion molecule 1, using surface plasmon resonance. We found that, besides SHP-1 and SHP-2, platelet endothelial cell adhesion molecule 1 binds the cytoplasmic signalling proteins SHIP and PLC-gamma1 via their Src homology 2 domains. Using two phosphopeptides, NSDVQpY663TEVQV and DTETVpY686SEVRK, we demonstrate differential binding of SHP-1, SHP-2, SHIP and PLC-gamma1. All four cytoplasmic signalling proteins directly associate with cellular platelet endothelial cell adhesion molecule 1, immunoprecipitated from pervanadate-stimulated THP-1 cells. These results suggest that overlapping immunoreceptor tyrosine-based inhibition motif/immunoreceptor tyrosine-based activation motif-like motifs within platelet endothelial cell adhesion molecule 1 mediate differential interactions between the Src homology 2 containing signalling proteins SHP-1, SHP-2, SHIP and PLC-gamma1.

Cobalt chloride-induced signaling in endothelium leading to the augmented adherence of sickle red blood cells and transendothelial migration of monocyte-like HL-60 cells is blocked by PAF-receptor antagonist

In response to hypoxia, sickle red blood cells (SS RBC) and leukocytes exhibit increased adherence to the vascular endothelium, while diapedesis of leukocytes through the blood vessel increases. However, the cellular signaling pathway(s) caused by hypoxia is poorly understood. We utilized CoCl2 as a mimetic molecule for hypoxia to study cellular signaling pathways. We found that in human umbilical vein endothelial cells (HUVEC), CoCl2 at 2 mM concentration induced the surface expression of a subset of CAMs (VCAM-1) and activation of transcription factor NF-kappaB in the nuclear extracts of HUVEC. Furthermore, CoCl2 also caused time-dependent tyrosine phosphorylation of mitogen-activated protein (MAP) kinase isoform ERK2 without significantly affecting ERK1, indicating ERK2 is the preferred substrate for upstream kinase of the MAPK pathway. Inhibitors of MAP kinase (PD98059) or platelet-activating factor (PAF)- receptor antagonist (CV3988) inhibited the CoCl2-induced NF-kappaB activation and VCAM-1 expression. Augmented expression of VCAM-1 led to increased SS RBC adhesion, inhibitable by a VCAM-1 antibody. Additionally, CoCl2 caused a two- to threefold increase in the rate of transendothelial migration of monocyte-like HL-60 cells and a twentyfold increase in phosphorylation of platelet endothelial cell adhesion molecules (PECAM-1). The transendothelial migration of monocytes was inhibited by an antibody to PECAM-1. Both phosphorylation of PECAM-1 and transendothelial migration of monocytes in response to CoCl2 were inhibited by protein kinase inhibitor (GF109203X) and augmented by protein phosphatase inhibitor (Calyculin A). Our data suggests that CoCl2-induced cellular signals directing increased expression of VCAM-1 in HUVEC involve downstream activation of MAP kinase and NF-kappaB, while the phosphorylation of PECAM-1 occurs as a result of activation of PKC. We conclude that PAF-receptor antagonist inhibits the CoCl2- or hypoxia-induced increase in the adhesion of SS RBC, PECAM-1 phosphorylation, and the concomitant transendothelial migration of monocytes.

Streptavidin facilitates internalization and pulmonary targeting of an anti-endothelial cell antibody (platelet-endothelial cell adhesion molecule 1): a strategy for vascular immunotargeting of drugs

Conjugation of drugs with antibodies to surface endothelial antigens is a potential strategy for drug delivery to endothelium. We studied antibodies to platelet-endothelial adhesion molecule 1 (PECAM-1, a stably expressed endothelial antigen) as carriers for vascular immunotargeting. Although 125I-labeled anti-PECAM bound to endothelial cells in culture, the antibody was poorly internalized by the cells and accumulated poorly after intravenous administration in mice and rats. However, conjugation of biotinylated anti-PECAM (b-anti-PECAM) with streptavidin (SA) markedly stimulated uptake and internalization of anti-PECAM by endothelial cells and by cells expressing PECAM. In addition, conjugation with streptavidin markedly stimulated uptake of 125I-labeled b-anti-PECAM in perfused rat lungs and in the lungs of intact animals after either intravenous or intraarterial injection. The antioxidant enzyme catalase conjugated with b-anti-PECAM/SA bound to endothelial cells in culture, entered the cells, escaped intracellular degradation, and protected the cells against H2O2-induced injury. Anti-PECAM/SA/125I-catalase accumulated in the lungs after intravenous injection or in the perfused rat lungs and protected these lungs against H2O2-induced injury. Thus, modification of a poor carrier antibody with biotin and SA provides an approach for facilitation of antibody-mediated drug targeting. Anti-PECAM/SA is a promising candidate for vascular immunotargeting of bioactive drugs.

Modulation of PECAM-1 (CD31) expression in human endothelial cells: effect of IFNgamma and IL-10

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

Irradiation induces upregulation of CD31 in human endothelial cells

Radiation-induced vascular injury is believed to be a major factor contributing to parenchymal atrophy, fibrosis and necrosis in normal tissue after radiotherapy. In this study irradiation of human umbilical vein endothelial cells (HUVECs) significantly increased adherence of U-937 cells in a time-dependent manner. Given the potential multifunctional role of CD31 in the vasculature we have examined the possible effects of irradiation on levels of CD31 expression in HUVECs. Irradiation upregulated CD31 expression on HUVECs, independently of initial plating density and radiation-induced changes such as cell number, cell cycle stage, or cell size. CD31 mRNA levels were raised in irradiated HUVECs relative to controls. Both CD31 mRNA and surface protein showed similar changes, suggesting that the increase in mRNA in irradiated HUVECs is responsible for the elevation in cell surface protein. A semi-quantitative study of tissue specimens from patients who had received radiotherapy indicated that CD31 staining in the blood vessels from irradiated tissues was increased compared with controls. Endothelial CD31 is important in the transmigration of leukocytes. We have demonstrated that the incorporation of monoclonal antibody to CD31 significantly inhibited the transmigration of human peripheral blood leukocytes through a monolayer of irradiated HUVECs. Taken together these data strongly suggest that irradiation induces a marked increase in CD31 expression on endothelial cells as part of a general response to irradiation. Its upregulation may play an important role in the development of radiation-induced normal tissue damage and thus is a possible target for therapeutic intervention.

Expression of immunoglobulin superfamily members on the lymphatic endothelium of inflamed human small intestine

Previously, lymphatic endothelium of human tissue has been shown to express only platelet-endothelial cell adhesion molecule-1 (PECAM-1). In this study we examined the expression of immunoglobulin superfamily members on the lymphatic endothelium of human small intestine while in the presence of inflammatory cytokines. Lymphatic vessels were identified by using a cocktail of IgGs for desmoplakin I and II while the presence of inflammatory cytokines was determined by the expression of major histocompatibility complex (MHC) class II in the venules. As a result, lymphatic vessels in the tissue with venules expressing MHC class II expressed PECAM-1, intercellular adhesion molecule (ICAM)-1, ICAM-3, and vascular cell adhesion molecule-1 (VCAM-1). The expression of ICAM-3 and VCAM-1 was significantly stronger in lymphatic vessels than in blood vessels. The results suggest that inflamed lymphatic endothelium may allow more lymphocyte subpopulations to adhere to the endothelium than non-inflamed lymphatic endothelium, due to the expression of multiple adhesion molecules playing a role.

Inhibition of platelet-activating factor, intercellular adhesion molecule 1 and platelet endothelial cell adhesion molecule 1 reduces experimental pancreatitis-associated gut endothelial barrier dysfunction

BACKGROUND

Endothelial barrier dysfunction is a critical link in the development of tissue injury and organ dysfunction, via upregulation and exposure of adhesion molecules, intercellular signals and leucocyte-endothelial cell interactions. Inhibitors of inflammatory mediators and receptors have been suggested as a means of downregulating the cascade of both local and systemic inflammation.

METHODS

The potential therapeutic inhibition of platelet-activating factor (PAF), intercellular adhesion molecule (ICAM) 1 and platelet endothelial cell adhesion molecule (PECAM) 1 was investigated in pancreatitis-associated gut endothelial dysfunction in rats, by treatment with a PAF antagonist (lexipafant, BB-882) and monoclonal antibodies against rat ICAM-1 (anti-ICAM1-Mb) and PECAM (anti-PECAMA1-Mb). Alterations in gut endothelial barrier dysfunction and leucocyte recruitment, and systemic levels of interleukins were evaluated.

RESULTS

Plasma exudation measured by the albumin leakage index and tissue leucocyte recruitment in the distal small intestine and colon increased significantly 12 h after induction of pancreatitis and treatment with saline. These alterations were to varying degrees counteracted by treatment with lexipafant, anti-ICAM1-Mb or anti-PECAM1-Mb. Alterations in levels of interleukin (IL) 1 paralleled the changes in gut endothelial barrier dysfunction and leucocyte trapping.

CONCLUSION

Treatment with lexipafant and monoclonal antibodies against ICAM-1 or PECAM-1 reduced the severity of pancreatitis-associated gut endothelial dysfunction, and decreased systemic concentrations of IL-1 and local leucocyte recruitment.

Angiosarcomas express mixed endothelial phenotypes of blood and lymphatic capillaries: podoplanin as a specific marker for lymphatic endothelium

Angiosarcomas apparently derive from blood vessel endothelial cells; however, occasionally their histological features suggest mixed origin from blood and lymphatic endothelia. In the absence of specific positive markers for lymphatic endothelia the precise distinction between these components has not been possible. Here we provide evidence by light and electron microscopic immunohistochemistry that podoplanin, a approximately 38-kd membrane glycoprotein of podocytes, is specifically expressed in the endothelium of lymphatic capillaries, but not in the blood vasculature. In normal skin and kidney, podoplanin colocalized with vascular endothelial growth factor receptor-3, the only other lymphatic marker presently available. Complementary immunostaining of blood vessels was obtained with established endothelial markers (CD31, CD34, factor VIII-related antigen, and Ulex europaeus I lectin) as well as podocalyxin, another podocytic protein that is also localized in endothelia of blood vessels. Podoplanin specifically immunolabeled endothelia of benign tumorous lesions of undisputed lymphatic origin (lymphangiomas, hygromas) and was detected there as a 38-kd protein by immunoblotting. As paradigms of malignant vascular tumors, poorly differentiated (G3) common angiosarcomas (n = 8), epitheloid angiosarcomas (n = 3), and intestinal Kaposi's sarcomas (n = 5) were examined for their podoplanin content in relation to conventional endothelial markers. The relative number of tumor cells expressing podoplanin was estimated and, although the number of cases in this preliminary study was limited to 16, an apparent spectrum of podoplanin expression emerged that can be divided into a low-expression group in which 0-10% of tumor cells contained podoplanin, a moderate-expression group with 30-60% and a high-expression group with 70-100%. Ten of eleven angiosarcomas and all Kaposi's sarcomas showed mixed expression of both lymphatic and blood vascular endothelial phenotypes. By double labeling, most podoplanin-positive tumor cells coexpressed endothelial markers of blood vessels, whereas few tumor cells were positive for individual markers only. From these results we conclude that (1) podoplanin is a selective marker of lymphatic endothelium; (2) G3 angiosarcomas display a quantitative spectrum of podoplanin-expressing tumor cells; (3) in most angiosarcomas, a varying subset of tumor cells coexpresses podoplanin and endothelial markers of blood vessels; and (4) all endothelial cells of Kaposi's sarcomas expressed the lymphatic marker podoplanin.

Cellular response in subretinal neovascularization induced by bFGF-impregnated microspheres

PURPOSE

To determine the sequence of cellular changes associated with a new rabbit model of subretinal neovascularization (SRN) induced by subretinal injection of basic fibroblast growth factor (bFGF)-impregnated microspheres.

METHODS

bFGF-impregnated gelatin microspheres, prepared by forming a polyion complex between gelatin and bFGF, were subretinally implanted into rabbit eyes. The eyes were studied by immunochemistry at 3 days to 8 weeks after implantation. Antibodies to CD4, CD8, cytokeratin, CD31, glial fibrillary acidic protein (GFAP), and RAM11 were used.

RESULTS

Cytokeratin-positive retinal pigment epithelial (RPE) cells appeared on day 3 and continued to increase in number in the subretinal space throughout the growth of the SRN membrane, becoming the predominant cell type. Macrophages (RAM11-positive) appeared early, but most disappeared within 7 days. GFAP-positive Müller cells were evident early in the retina but migrated into the subretinal space after 7 days; the gliotic adhesion they formed between the retina and the SRN membrane was prominent at 8 weeks. CD31-positive endothelial cells were first evident at 14 days and formed neovascular channels that were still present for up to 8 weeks. CD4- and CD8-positive lymphocytes appeared in the early stages but were few in number.

CONCLUSIONS

SRN membranes are primarily composed of RPE cells and vascular endothelial cells. The membrane adheres to the retina by a gliotic band. The cellular components involved in the membrane of this model resemble those found in SRN membranes removed from patients with age-related macular degeneration.

Anti-inflammatory drugs and endothelial cell adhesion molecule expression in murine vascular beds

BACKGROUND

Inflammatory bowel diseases (IBD) are characterised by an intense infiltration of leucocytes that is mediated by adhesion molecules expressed on the surface of activated endothelial cells.

AIMS

To determine whether drugs used in the treatment of IBD, specifically dexamethasone (DEX), 5-aminosalicylic acid (5-ASA), methotrexate (MTX), and 6-mercaptopurine (6-MP), alter the expression of endothelial cell adhesion molecules (ECAMs).

METHODS

The expression of P-selectin, E-selectin, intercellular adhesion molecule 1 (ICAM-1), and vascular CAM 1 (VCAM-1) in different vascular beds of C57Bl/6J mice was measured using the dual radiolabelled monoclonal antibody technique.

RESULTS

Lipopolysaccharide (LPS) elicited a profound increase in the expression of all ECAMs in the mesentery, small intestine, caecum, and distal colon. The LPS induced increase in CAM expression was not significantly affected by prior treatment with either MTX or 6-MP. However, pretreatment with either DEX or 5-ASA significantly attenuated LPS induced increases in expression of P- and E-selectin, and VCAM-1 in the majority of tissues evaluated. DEX also blunted the LPS induced increase in ICAM-1 expression in the caecum and distal colon. DEX, but not 5-ASA, largely abolished the rise in plasma tumour necrosis factor alpha elicited by LPS.

CONCLUSIONS

These findings suggest that DEX and 5-ASA may exert their beneficial therapeutic action in IBD, at least in part, by inhibiting the expression of ECAMs which mediate leucocyte adhesion and transmigration in the microvasculature.

Activated T cells acquire endothelial cell surface determinants during transendothelial migration

Activated T cells acquire endothelial cell (EC) plasma membrane constituents during transendothelial migration. This was assessed using an in vitro model system in which human peripheral blood CD4+ T cells migrated through confluent monolayers of HUVEC. Flow cytometry of migrated CD4+ T cells demonstrated that activated, but not resting, T cells acquired a variety of endothelial surface determinants, including CD31, CD49d, CD54, CD61, and CD62E. The extracellular domains of these molecules were detected on migrated T cells with mAbs, including those directed to the ligand-binding regions. A number of approaches were employed to document that the acquisition of these molecules was uniquely accomplished by activated T cells and clearly involved transfer from both resting and TNF-alpha-activated EC. Acquisition of endothelial markers by activated T cells occurred as part of the transfer of membrane components, as migrating T cells acquired EC membranes prelabeled with the lipophilic dye, 3,3'-dihexadecyloxacarbocyanine perchlorate (DiOC-16), along with EC surface proteins. Thus, during transendothelial migration, activated T cells acquire endothelial membrane components, and as a result may deliver them to perivascular sites.

In vitro adhesion and migration of T lymphocytes across monolayers of human brain microvessel endothelial cells: regulation by ICAM-1, VCAM-1, E-selectin and PECAM-1

Increased lymphocyte traffic across an altered blood-brain barrier (BBB) is a prominent and early event in inflammatory and immune-mediated CNS diseases. The factors that control the entry of lymphocytes into the brain have not been fully elucidated. In this study, primary cultures of human brain microvessel endothelial cells (HBMEC) were used to investigate the role of endothelial cell (EC) adhesion molecules in the adhesion and migration of peripheral blood T lymphocytes across TNF-alpha treated and untreated monolayers. Adhesion of T cells to unstimulated HBMEC was minimal and few of the adherent cells migrated across the monolayers. Treatment of HBMEC with TNF-alpha augmented adhesion by 5-fold. The binding to activated EC was significantly, but not completely, inhibited by monoclonal antibodies (mAbs) to ICAM-1 and VCAM-1, whereas adhesion to unstimulated EC was blocked by mAb to ICAM-1 but not VCAM-1. Transendothelial migration of lymphocytes increased by up to 30-fold following treatment of HBMEC with TNF-alpha. Migration across activated monolayers, but not across untreated EC, was almost completely blocked by Ab to ICAM-1 and significantly inhibited by Abs to PECAM-1 and E-selectin. VCAM-1 was not utilized during transendothelial migration. Ultrastructurally, pseudopodia from lymphocytes contacted finger-like cytoplasmic projections on EC and eventually penetrated the EC cytoplasm at focal points along the apical surface. Migrating lymphocytes moved either through the EC cytoplasm or between adjacent EC across intercellular contacts. The overlying monolayers showed no evidence of disruption and intercellular junctions appeared intact over the migrated T cells. These studies indicate that adhesion and migration of T lymphocytes across the cerebral endothelial barrier are distinct processes that depend upon the activation state of EC and are controlled by diverse receptor-ligand interactions.

Primary ovarian angiosarcoma: a case report and literature review

Primary ovarian angiosarcoma is extremely rare. Only 16 cases have histologically been reported to date in the literature. A case of angiosarcoma arising in the right ovary of a 46-year-old female is presented. Grossly, the resected right ovary was completely replaced by a solid tumor mass, which revealed multiple necrotic and/or hemorrhagic foci. This case revealed the typical histological features of angiosarcoma with sinusoidal and solid patterns of anaplastic tumor cells. Immunohistochemically, tumor cells were strongly and diffusely positive for CD31 and CD34, in particular, along the cytoplasmic membrane of the tumor cells. Ultrastructurally, tumor cells possessed the intermediate junctions between tumor cells, discontinuous basal laminae attached to the irregularly shaped blood vessels and occasional cytoplasmic pinocytotic vesicles. These findings confirmed the case as being one of angiosarcoma of the ovary. The patient died 9 months after surgery as a result of developed multifocal brain metastases. A total of 17 cases reported as primary ovarian angiosarcoma, including this presented case, are clinicopathologically reviewed.

Vascular endothelial growth factor tightly regulates in vivo development of murine hepatocellular carcinoma cells

Angiogenesis is essential for the development of a solid tumor, including hepatocellular carcinoma (HCC). HCC is a well-known hypervascular tumor. Vascular endothelial growth factor (VEGF) is one of the most potent angiogenic factors. Its role has not been clarified in vivo in HCC development. We used a self-contained, tetracycline-regulated retroviral vector system to elucidate the effect of VEGF on murine HCC development in a xenograft experimental model. By delivering the VEGF gene within the retroviral vector and under the control of a tetracycline-regulated promoter, we were able to manipulate VEGF expression in vivo tumor by providing tetracycline in the drinking water. Overexpression of VEGF showed a marked increase in tumor development accompanied by augmentation of neovascularization. The degree of tumor enlargement corresponded to the level of VEGF gene expression. Suppression of VEGF led to a decrease in tumor growth at the established tumor size, whether relatively small or large. The level of VEGF expression did not alter the proliferation of HCC cells in vitro. In a double-chamber chemoinvasion assay, the in vitro invasion activity of VEGF-transduced cells was not changed. In the presence of endothelial cells (EC), however, VEGF-transduced cells showed a marked increase in their in vitro invasion activity. These results suggested that VEGF plays a critical role in the development of HCC in cooperation with EC

Integration of endothelial cells in multicellular spheroids prevents apoptosis and induces differentiation

Single endothelial cells (EC) seeded in suspension culture rapidly undergo apoptosis. Addition of survival factors, such as VEGF and FGF-2, does not prevent apoptosis of suspended EC. However, when cells are allowed to establish cell-cell contacts, they become responsive to the activities of survival factors. These observations have led to the development of a three-dimensional spheroid model of EC differentiation. EC spheroids remodel over time to establish a differentiated surface layer of EC and a center of unorganized EC that subsequently undergo apoptosis. Surface EC become quiescent, establish firm cell-cell contacts, and can be induced to express differentiation antigens (e.g., induction of CD34 expression by VEGF). In contrast, the unorganized center spheroid cells undergo apoptosis if they are not rescued by survival factors. The responsiveness to the survival factor activities of VEGF and FGF-2 was not dependent on cell shape changes since it was retained after cytochalasin D treatment. Taken together, these findings characterize survival factor requirements of unorganized EC and indicate that polarized surface EC differentiate to become independent of exogenous survival factors. Furthermore, they demonstrate that spheroid cell culture systems are useful not just for the study of tumor cells and embryonic stem cells but also for the analysis of differentiated functions of nontransformed cells.

Interaction of sickle erythrocytes with endothelial cells in the presence of endothelial cell conditioned medium induces oxidant stress leading to transendothelial migration of monocytes

The abnormal adherence of sickle red blood cells (SS RBC) to endothelial cells has been thought to contribute to vascular occlusion, a major cause of morbidity in sickle cell disease (SCD). We determined whether the interaction of SS RBC with cultured endothelial cells induced cellular oxidant stress that would culminate in expression of cell adhesion molecules (CAMs) involved in the adhesion and diapedesis of monocytes and the adherence of SS reticulocytes. We showed that the interaction of SS RBC at 2% concentration in the presence of multimers of von Willebrand factor (vWf), derived from endothelial cell-derived conditioned medium (E-CM) with cultured human umbilical vein endothelial cells (HUVEC), resulted in a fivefold increased formation of thiobarbituric acid-reactive substances (TBARS) and activation of the transcription factor NF-kB, both indicators of cellular oxidant stress. Normal RBC show none of these phenomena. The oxidant stress-induced signaling resulted in an increased surface expression of a subset of CAMs, ICAM-1, E-selectin, and VCAM-1 in HUVEC. The addition of oxygen radical scavenger enzymes (catalase, superoxide dismutase) and antioxidant (probucol) inhibited these events. Additionally, preincubation of HUVEC with a synthetic peptide Arg-Gly-Asp (RGD) that prevents vWf-mediated adhesion of SS RBC reduced the surface expression of VCAM-1 and NF-kB activation. Furthermore, SS RBC-induced oxidant stress resulted in a twofold increase in the transendothelial migration of both monocyte-like HL-60 cells and human peripheral blood monocytes, and approximately a sixfold increase in platelet-endothelial cell adhesion molecule-1 (PECAM-1) phosphorylation, each of which was blocked by protein kinase C inhibitor and antioxidants. These results suggest that the adherence/contact of SS RBC to endothelial cells in large vessel can generate enhanced oxidant stress leading to increased adhesion and diapedesis of monocytes, as well as heightened adherence of SS reticulocytes, indicating that injury/activation of endothelium can contribute to vaso-occlusion in SCD.

Endothelial cell VE-cadherin functions as a receptor for the beta15-42 sequence of fibrin

The contact of fibrin with the apical surface of human umbilical vein endothelial cells (HUVEC) can induce capillary tube formation via the interaction of fibrin beta15-42 with a putative cell receptor (Chalupowicz, D. G., Chowdhury, Z. A., Bach, T. L., Barsigian, C., and Martinez, J. (1995) J. Cell Biol. 130, 207-215). To characterize this interaction, we studied the binding of the thrombin-cleaved N-terminal disulfide knot of fibrin (NDSK II), a dimeric fragment with exposed beta15-42, to HUVEC in three separate assay systems. Time-course binding of 125I-NDSK II to HUVEC monolayers or suspensions revealed that binding was specific at 50-60%, as determined by the addition of unlabeled NDSK II. Specific binding of 125I-NDSK II to HUVEC was 70% reversible by dilution or by competition, and was found to be divalent cation-independent. Binding plateaued after 10 min at a saturation of 15-20 nM. Scatchard analysis using the LIGAND computer program defined a single population of receptors with a KD of 7.7 +/- 1.6 nM and approximately 21,000 +/- 7000 binding sites/cell. N-terminal disulfide knot derivatives in which beta15-42 was absent (NDSK 325) or unexposed (NDSK, NDSK I) did not show specific binding. Specific binding of 125I-NDSK II could not be inhibited by RGDS or by antibodies to the alphavbeta3 or beta1 integrins, PECAM-1, ICAM-1, or N-cadherin. In contrast, a synthetic beta15-42/ovalbumin conjugate inhibited total 125I-NDSK II binding by 47 +/- 19% (corresponding to 95% of specific 125I-NDSK II bound) and a monoclonal antibody to vascular endothelial cadherin (VE-cadherin) inhibited binding by 35 +/- 8% (corresponding to 70% of specific 125I-NDSK II bound). Another assay was based on the capture of cadherins from HUVEC lysates by a polyclonal pan-cadherin antibody immobilized on plastic dishes. Binding of NDSK II to the captured cadherins was 89 +/- 5% specific, while specific binding of NDSK 325 and NDSK was negligible. An immortalized line of human adipose-derived microvascular endothelial cells, which express N-cadherin but not VE-cadherin, demonstrated no specific binding of NDSK II by the capture assay. These data define a novel interaction of fibrin with VE-cadherin, which is mediated by the fibrin N-terminal beta15-42 sequence, and may contribute to the mechanism through which fibrin induces angiogenesis.

Interaction of interstitial trophoblast with placental bed capillaries and venules of normotensive and pre-eclamptic pregnancies

While endovascular trophoblast invasion of the human placental bed spiral arteries has been studied extensively, no information is available on the interaction between interstitially invading trophoblast and uterine capillaries and venules. Placental bed biopsies of eight normotensive and 15 pre-eclamptic patients were double-immunostained for cytokeratin and the endothelial marker CD31, providing satisfactory staining results in six and 10 biopsies, respectively. Interstitial trophoblast tissue density did not differ between the two series of biopsies, implying that this pathway of invasion is not impaired in pre-eclampsia. Both groups showed a similar incidence of approach of non-arterial vascular structures by perivascular trophoblast. Differences in CD31 staining intensity were noticed in different vascular cross-sections. Lower staining intensity was related to the presence of perivascular trophoblast. Because of the identity of CD31 with the platelet-endothelial cell adhesion molecule (PECAM)-1, the trophoblast-dependent downregulation of CD31 may play a role in the control of leukocytic traffic within the placental bed. The phenomena described in this paper did not show any difference between the normotensive and pre-eclamptic patients, implying that interaction of interstitial trophoblast with venous and capillary structures is not related to the pathogenesis of pre-eclampsia.

[The role of cell adhesion molecules in certain neurological diseases]

Current data on the role of cell adhesion molecules (CAMs) in the pathophysiology of laboratory animal and human neurological diseases are presented. Classification of CAMs is given in short-Immunoglobulin (Ig) superfamily, selectins and integrins. Ig superfamily includes among others ICAM-1, 2, 3; VCAM-1; PECAM-1. They are glycoproteins located in cellular membrane of different cell types, e.g.: endotheliocytes, leucocytes. They facilitate leucocyte passage across the blood barrier into inflammatory tissues. We distinguish native forms of CAMs (linked with mother cell membrane) and soluble forms found in different body fluids. Expression of CAMs is increased in many neurological diseases as well as the elevation in the concentration of their soluble forms in blood or cerebrospinal fluid. Selections also play a role in creating interactions leucocyte-endothelium while integrins serve as a receptor for Ig superfamily molecules. In this article we present current views on the role of native forms of CAMs as a necessary factor for leucocyte extravasation and the role of soluble forms as an agent in negative feedback for leucocyte passage through the blood-brain barrier to inflammatory brain or peripheral nerves. We consider its significance for future treatment of neurological diseases as well.

Differential expression of platelet-endothelial cell adhesion molecule-1 (PECAM-1) in murine tissues

OBJECTIVE

To characterize and compare the expression of PECAM-1 in unstimulated and tumor necrosis factor alpha-(TNF-alpha)-stimulated tissues of mice.

METHODS

Binding and non-binding monoclonal antibodies (mAb) were radiolabeled and injected into wild-type mice and mice deficient of P-selectin, CD18, or ICAM-1. The relative accumulation of binding mAb (PECAM-1 mAb) was determined in wild-type mice following a 25 micrograms/kg i.p. injection of TNF-alpha and in mutant mice under basal conditions.

RESULTS

Under unstimulated conditions, PECAM-1 was significantly expressed in all tissues examined, with no changes occurring after TNF-alpha stimulation. An equivalence of PECAM-1 expression was observed in unstimulated tissues among wild-type mice and mice that are genetically deficient in either CD18, ICAM-1, or P-selectin. The level of PECAM-1 expression in different vascular beds was highly correlated to published values of endothelial surface area. Normalization of previously published values of ICAM-1, VCAM-1, E- and P-selectin expression relative to PECAM-1 expression in the same tissues revealed a diminished organ-to-organ variability in expression of the different adhesion molecules. Estimates of adhesion molecule expression in lung and brain were most profoundly affected by normalization to PECAM-1 expression.

CONCLUSIONS

These findings support the use of PECAM-1 expression in regional vascular beds as an indicator of endothelial cell surface area.

Functional association of platelet endothelial cell adhesion molecule-1 and phosphoinositide 3-kinase in human neutrophils

In this paper we show that the engagement of the platelet-endothelial cell adhesion molecule-1 (PECAM-1/CD31) up-regulates the adhesion of human neutrophils to the EA.hy926 endothelial cell line through a phosphoinositide 3-kinase (PI3K)-dependent pathway. Indeed, LY294002 and wortmannin prevented the effect of PECAM-1/CD31 cross-linking on cell adhesion, at concentrations known to inhibit PI3K without affecting other kinases. Both compounds blocked neutrophil binding to murine fibroblasts transfected with human ICAM-1, to purified ICAM-1 protein, or to fibronectin, suggesting that PECAM-1/CD31-mediated up-regulation of beta2 and beta1 integrin-mediated adhesion is PI3K-sensitive. We also provide evidence for the association of PECAM-1/CD31 to PI3K, because PI3K was detectable in neutrophil lysates after PECAM-1/CD31 cross-linking and immunoprecipitation. PECAM-1/CD31-dependent recruitment of PI3K was suggested by the finding that the serine/threonine kinase p70 S6 kinase (S6K), a signaling protein downstream of PI3K, is activated in neutrophils upon PECAM-1/CD31 cross-linking, based on the appearance of serine phosphorylation in S6K immunoprecipitates. In turn, S6K is not directly involved in the up-regulation of integrin function because rapamycin, which can inhibit S6K independent of PI3K, did not block PECAM-1/CD31-induced adhesion of neutrophils to beta1 and beta2 integrin substrates. In conclusion, PECAM-1/CD31 appears to be one of the molecules functionally coupled to PI3K, suggesting that this enzyme may represent a common pathway of integrin and adhesiveness regulation in leukocytes.

Recruitment and activation of SHP-1 protein-tyrosine phosphatase by human platelet endothelial cell adhesion molecule-1 (PECAM-1). Identification of immunoreceptor tyrosine-based inhibitory motif-like binding motifs and substrates

Stimulation of platelet aggregation leads to tyrosine phosphorylation of a number of receptors and signaling molecules including platelet endothelial cell adhesion molecule-1 (PECAM-1). In this report, we demonstrate that both protein-tyrosine phosphatases SHP-1 and SHP-2 physically associate with different kinetics of assembly with tyrosine-phosphorylated human PECAM-1 during integrin alphaIIbbeta3-mediated platelet aggregation. Peptido-precipitation analysis revealed that tyrosine-phosphorylated peptides encompassing residues 658-668 and 681-691 of PECAM-1 bound specifically to both protein-tyrosine phosphatases SHP-1 and SHP-2. We further show that the association of SHP-1 with PECAM-1 occurs through the direct interaction of the src homology region 2 domains of SHP-1 with two highly conserved phosphotyrosine binding motifs within PECAM-1 having the sequences NSDVQpY663TEVQV and DTETVpY686SEVRK (where pY represents phosphotyrosine). In vitro dephosphorylation experiments using phosphotyrosyl PECAM-1 peptides encompassing either Tyr-663 or Tyr-686 revealed induction of SHP-1 catalytic activity, suggesting that PECAM-1 serves as a SHP-1 substrate. Surface plasmon resonance studies reveal that recombinant SHP-2 binds PECAM-1 phosphopeptides with 5-fold higher affinity than recombinant SHP-1. These data suggest that in hematopoietic cells such as platelets, PECAM-1 cellular signaling is regulated by the selective recruitment and activation of two distinct protein-tyrosine phosphatases, SHP-1 and SHP-2, via a common immunoreceptor tyrosine-based inhibitory-like motif.

CD31 expression in benign, borderline, and malignant epithelial ovarian tumors: an immunohistochemical and serological analysis

OBJECTIVE

To evaluate (a) the expression of CD31 in benign, borderline, and maligant ovarian tumors; (b) the correlation between CD31 expression and the clinicopathological parameters; and (c) the diagnostic interest of serological soluble CD31 (sCD31) in patients with ovarian tumors.

METHODS

The intratumoral microvessel density was evaluated by an immunohistochemical technique with the monoclonal antibody JC70 against CD31 at two dilutions in 20 benign, 20 borderline, and 20 malignant tumors of the ovary. Serological determinations of sCD31 with ELISA technique was performed in 35 patients with ovarian tumors (24 benign, 5 borderline, and 6 malignant tumors).

RESULTS

The expression of CD31 was higher in ovarian carcinomas than in borderline and benign tumors (P < 0.001) irrespective of the dilutions of the antibody used. In ovarian carcinomas, a correlation was observed between CD31 expression and the stage of the disease, the histologic type, the degree of histological differentiation, and the survival of the patients. In borderline tumors, no correlation was noted between CD31 expression and the clinicopathologic parameters. No difference in serological levels of sCD31 was noted according to histologic types.

CONCLUSION

CD31 immunostaining may have a prognostic relevance in ovarian carcinoma but seems to be of limited value in borderline tumors. Serological levels of sCD31 have no diagnostic interest in ovarian tumors.

Intravascular Kaposi's-like spindle cell proliferation of the capsular vessels of follicular-derived thyroid carcinomas

The literature describes a number of vascular alterations in the thyroid gland and its tumors, the majority of which are related to fine-needle aspiration (FNA). These alterations include pseudoangiosarcomatous changes (Masson's lesion), pseudoinvasion in capsular veins, and endothelial proliferations in the needle tract. We present three cases of a unique intravascular endothelial proliferation in the capsular vessels of follicular and/or Hürthle cell thyroid neoplasms (two angioinvasive Hürthle cell carcinomas and one angioinvasive follicular carcinoma), which we think is unrelated to FNA. The lesion consists of spindle cells with plump nuclei, with focal nesting imparting an epithelioid pattern to the lesion. Focally red blood cells percolate between and mix with the spindle cells, recapitulating superficially a Kaposi's like appearance, but we identified no mitotic figures. Only one patient had a preoperative FNA; in that case, the lesions were spatially separate from the needle tract and the usual post-FNA reactive changes. The lesional cells were positive for Factor VIII and CD 31 and negative for cytokeratins and thyroglobulin immunostains. This immunopanel was helpful in distinguishing these lesions from true angioinvasion by thyroid tumor. To date, the etiology of these vascular lesions is unknown, but we postulate that certain follicular-derived thyroid tumors might elaborate angiogenic mediators, which in a cell culture system of follicular thyroid carcinoma can trigger endothelial proliferations.

Enrichment of T cells carrying beta7 integrins in inflamed synovial tissue from patients with early spondyloarthropathy, compared to rheumatoid arthritis

OBJECTIVE

To compare the expression of adhesion molecules on synovial T cells from patients with early spondyloarthropathy (SpA) and rheumatoid arthritis (RA), with special reference to the beta7 integrins alpha4beta7 and alphaEbeta7 in view of their intimate association with intestinal tissue.

METHODS

Twenty-five synovial cell lines were generated by interleukin 2 (IL-2) expansion from synovial biopsies of patients with early SpA and RA, obtained from macroscopically inflamed synovial tissue by needle arthroscopy, and subsequently characterized by flow cytometry for CD3, CD4, CD8, L-selectin, CD11a, CD31, CD44, and alpha4beta7 and alphaEbeta7 integrin.

RESULTS

In SpA, the beta7 integrin expression was increased, compared to RA. Furthermore, an inverse relation between alpha4beta7 and alphaEbeta7 was present in SpA (r = -0.75, p < 0.02), as on many mucosal T cells. In contrast, an opposite correlation was noted in RA (r = +0.84, p < 0.01), as similarly described on a subset of circulating T cells.

CONCLUSION

Increased expression of beta7 integrins was noted on synovial T cell lines from SpA compared to RA, with discriminative correlations between alpha4beta7 and alphaEbeta7. This suggests a different origin of the synovial T cells in these diseases.

Endotoxin-induced migration of monocytes and PECAM-1 phosphorylation are abrogated by PAF receptor antagonists

The trafficking of monocytes across the endothelial lining of the blood vessel increases in response to bacterial infection at sites of inflammation. However, the molecular events involved in the diapedesis of monocytes in response to endotoxin are not completely understood. Our studies revealed that signaling by lipopolysaccharide (LPS) in human umbilical vein endothelial cells (HUVEC) resulted in a threefold increase in the transendothelial migration of monocyte-like HL-60 cells and a sevenfold increase in the phosphorylation of platelet endothelial cell adhesion molecule-1 (PECAM-1). The transmigration induced by LPS was inhibited by an antibody to PECAM-1. Both the phosphorylation of PECAM-1 and transendothelial migration of monocytes were inhibited by a platelet-activating factor (PAF) receptor antagonist, indicating the autocrine effect of PAF in these events. Treatment of HUVEC with LPS caused a fourfold increase in PAF receptor mRNA expression that was completely blocked by the PAF receptor antagonist. We conclude that PAF, generated by HUVEC in response to LPS or gram-negative bacterial infection, acts in an autocrine manner, causing PECAM-1 phosphorylation and thus the transendothelial migration of monocytes.

The effect of melanin bleaching on immunohistochemical staining in heavily pigmented melanocytic neoplasms

The accumulation of excessive amounts of melanin in melanocytic lesions can obscure cellular morphology and can further hinder immunocytochemical procedures. We have used a modification of the potassium permanganate/oxalic acid melanin-bleaching technique, involving much reduced bleaching times, in order to remove melanin granules prior to incubation with primary antibody. We have assessed a panel of antibodies applicable to the evaluation of melanocytic lesions and in addition have also assessed antibodies that may be more useful in research. The study attempts to determine which antigens may be affected by bleaching and which are not. Antigens S100, HMB 45, NKIC3, CD34, and L26 are relatively unaffected by this procedure. Factor-VIII-related antigen and vimentin and CD68 antigens produced enhanced staining. In contrast, antigens CD3, CD31, and CD45RO were abolished. In addition, smooth muscle actin and desmin antigens demonstrated considerable nonspecific background staining and were not reliable in this study. This technique demonstrates that a fairly wide range of antigens are preserved after bleaching and that distinction between melanocytes and melanophages can reliably be performed using the conventional immunocytochemical chromogen 3,3-diaminobenzidine and without the need for elaborate counterstaining.

Expression of the vascular endothelial growth factor C receptor VEGFR-3 in lymphatic endothelium of the skin and in vascular tumors

It is difficult to identify lymph vessels in tissue sections by histochemical staining, and thus a specific marker for lymphatic endothelial cells would be more practical in histopathological diagnostics. Here we have applied a specific antigenic marker for lymphatic endothelial cells in the human skin, the vascular endothelial growth factor receptor-3 (VEGFR-3), and show that it identifies a distinct vessel population both in fetal and adult skin, which has properties of lymphatic vessels. The expression of VEGFR-3 was studied in normal human skin by in situ hybridization, iodinated ligand binding, and immunohistochemistry. A subset of developing vessels expressed the VEGFR-3 mRNA in fetal skin as shown by in situ hybridization and radioiodinated vascular endothelial growth factor (VEGF)-C bound selectively to a subset of vessels in adult skin that had morphological characteristics of lymphatic vessels. Monoclonal antibodies against the extracellular domain of VEGFR-3 stained specifically endothelial cells of dermal lymph vessels, in contrast to PAL-E antibodies, which stained only blood vessel endothelia. In addition, staining for VEGFR-3 was strongly positive in the endothelium of cutaneous lymphangiomatosis, but staining of endothelial cells in cutaneous hemangiomas was weaker. These results establish the utility of anti-VEGFR-3 antibodies in the identification of lymphovascular channels in the skin and in the differential diagnosis of skin lesions involving lymphatic or blood vascular endothelium.

An improved method for isolation of microvascular endothelial cells from normal and inflamed human lung

Microvascular endothelial cells (MVEC), which differ from large vessel endothelial cells, have been isolated successfully from lungs of various species, including man. However, contamination by nonendothelial cells remains a major problem in spite of several technical improvements. In view of the organ specificity of MVEC, endothelial cells should be derived from the tissue involved in the diseases one wishes to study. Therefore, to investigate some of the immunopathological mechanisms leading to acute respiratory distress syndrome (ARDS), we have attempted to isolate lung MVEC from patients undergoing thoracic surgery for lung carcinoma and patients dying of ARDS. The method described here includes four main steps: (1) full digestion of pulmonary tissue with trypsin and collagenase, (2) aggregation of MVEC induced by human plasma, (3) Percoll density centrifugation, and (4) selection and transfer of MVEC after local digestion with trypsin/EDTA under light microscopy. Normal and ARDS-derived lung MVEC purified by this technique presented contact inhibition (i.e., grew in monolayer), and expressed classical endothelial markers, including von Willebrand factor (vWF), platelet endothelial cell adhesion molecule 1(PECAM-1, CD31), and transcripts for the angiotensin converting enzyme (ACE). The cells also formed capillarylike structures, took up high levels of acetylated low-density lipoprotein (Ac-LDL), and exhibited ELAM-1 inducibility in response to TNF. Contaminant cells, such as fibroblasts, smooth muscle cells, or pericytes, were easily recognized on the basis of morphology and were eliminated by selection of plasma-aggregated cells under light microscopy. The technique presented here allows one to study the specific involvement and contribution of pulmonary endothelium in various lung diseases.

Up-regulation of vascular endothelial growth factor in stromal cells of hemangioblastomas is correlated with up-regulation of the transcription factor HRF/HIF-2alpha

Hemangioblastomas, the most frequent manifestation of the hereditary von Hippel-Lindau disease (VHL), are highly vascularized tumors of the central nervous system. In previous studies, the endothelial-specific mitogen vascular endothelial growth factor (VEGF) was shown to be up-regulated in the stromal cells, the putative neoplastic cells in hemangioblastomas. Therefore, it was suggested that secretion of VEGF by stromal cells is the pathogenetic cause of the vascular lesions in hemangioblastomas. The novel basic helix loop helix transcription factor HRF/HIF-2alpha is a candidate regulator of VEGF expression during development. We therefore investigated expression of HRF/HIF-2alpha in hemangioblastomas and found the overexpression of VEGF mRNA in stromal cells to be highly correlated with elevated expression levels of HRF/HIF-2alpha mRNA. This finding is suggestive for a role of HRF in VEGF-dependent vascular growth in hemangioblastomas and could provide a link between transcriptional activation of the VEGF gene and loss of function of the VHL gene product.

Role of PECAM-1 in the adherence of PMN to hypoxic endothelial cells

Hypoxia induces an increase in PMN adherence to endothelial cells for which an interaction between ICAM-1 and CD18/CD11b has been demonstrated. Since PECAM-1 has been shown to be involved in PMN transmigration through the endothelium and to increase the binding capacity of leukocyte CD18/CD11b, the role of this molecule in the hypoxia-induced PMN adherence was investigated. Hypoxia did not change the total surface expression of PECAM-1 on HUVEC and did not change the cell-cell border localization of this molecule as TNF-alpha did. In addition, blocking anti-PECAM-1 antibodies could not inhibit the increased adherence of unstimulated human PMN to hypoxia-incubated HUVEC while anti-ICAM-1 partially inhibited this process. These results indicate that PECAM-1 is probably not involved in the hypoxia-induced PMN adherence to endothelial cells.

Analysis of the distribution of human CD38 and of its ligand CD31 in normal tissues

Human CD38 is a 45 kD ectoenzyme endowed with ADP-ribosyl cyclase and hydrolase activities. The molecule plays a central role in lymphocyte activation, proliferation and selectin-type adhesion with endothelial cells (HEC). A HEC surface molecule displaying all the features of a CD38L has been identified by means of a mAb (Moon-1), able to block CD38-mediated adhesion processes. The 130 kD molecule recognized by Moon-1 is CD31, a member of the Ig superfamily. This paper reports on the analysis of the surface expression of CD38 and CD38L in various human tissues of adult origin and compared in some instances to the fetal (9-14 weeks) counterparts. This was achieved by means of immunohistochemical techniques and analysis of purified cell populations. Among the specimens analyzed, CD38 is expressed by a vast array of cells of lymphatic origin as well as by the skeletal and cardiac muscle fibers, the bronchi (epithelial cells), the parotid gland (ductal epithelial cells) and hepatic sinusoids. On the contrary, CD31 proved constantly expressed by HEC at high levels, independent of the organ or tissue analyzed or of the kind of vessel. Other cells expressing CD38L were found in the lymphoid compartment (follicle mantle B cells and plasma cells), in the lungs (alveolar ducts, alveoli and lymphatic vessels) and in the kidney (glomerular cells). Interestingly, no fetal organ or tissue ever expressed CD38 and its ligand. The above results were enriched by the analysis of the expression of the two molecules on purified populations including mononuclear cells from the lamina propria of the gastro-intestinal tract and broncho-alveolar lavage lymphocytes.

Regulation of mouse PECAM-1 tyrosine phosphorylation by the Src and Csk families of protein-tyrosine kinases

PECAM-1 is an adhesion molecule expressed on hemopoietic and endothelial cells. Recently, it was observed that PECAM-1 becomes tyrosine-phosphorylated in response to a variety of physiological stimuli. Furthermore, tyrosine-phosphorylated PECAM-1 was shown to associate with SHP-2, a Src homology 2 (SH2) domain-containing protein-tyrosine phosphatase expressed ubiquitously. In light of the significance of tyrosine protein phosphorylation as a regulatory mechanism, we wished to understand better the nature and impact of the protein-tyrosine kinases (PTKs) mediating PECAM-1 tyrosine phosphorylation. Through reconstitution experiments in COS-1 cells, we determined that mouse PECAM-1 could be tyrosine-phosphorylated by Src-related PTKs and Csk-related PTKs, but not by other kinases such as Syk, Itk, and Pyk2. Using site-directed mutagenesis and peptide phosphorylation studies, we found that these PTKs were efficient at phosphorylating Tyr-686, but not Tyr-663, of PECAM-1. Src-related enzymes also phosphorylated mouse PECAM-1 at one or more yet to be identified sites. In other studies, we demonstrated that phosphorylation of PECAM-1 by Src or Csk family kinases was sufficient to trigger its association with SHP-2. Moreover, it was able to promote binding of PECAM-1 to SHP-1, a SHP-2-related protein-tyrosine phosphatase expressed in hemopoietic cells. Taken together, these findings indicated that the Src and Csk families of kinases are strong candidates for mediating tyrosine phosphorylation of PECAM-1 and triggering its association with SH2 domain-containing phosphatases under physiological circumstances.

Ligation of CD31/PECAM-1 modulates the function of lymphocytes, monocytes and neutrophils

CD31 or platelet/endothelial cell adhesion molecule (PECAM-1) is a 130-kDa glycoprotein expressed on endothelial cells, granulocytes, a subset of lymphocytes and platelets. In this study, we examined the ability of four monoclonal antibodies (mAb) against different domains of CD31 to modulate the function of T lymphocytes, monocytes and neutrophils. Engagement of CD31 on T lymphocytes results in co-stimulation of T lymphocyte proliferation to suboptimal doses of anti-CD31 mAb. This proliferation is accompanied by secretion of numerous cytokines and chemokines, up-regulation of CD25 and an increase in cell size. Purification of T lymphocytes into CD45RO and CD45RA subsets showed that only naive CD45RA T lymphocytes are co-stimulated by anti-CD31 mAb. Further studies on neutrophils show that engagement of CD31 results in down-regulation of CD62L and up-regulation of CD11b/CD18 as well as oxidative burst, as assessed by superoxide release. In addition, ligation of CD31 on monocytes results in TNF-alpha secretion, and studies with various cell signaling inhibitors indicate that tyrosine kinases and cAMP-dependent kinases are involved in monocyte activation via CD31. Of the four mAb used in this study, only two activated human leukocytes. These mAb were PECAM-1.3 and hec7, which bind to domains 1 and 2 of CD31. We conclude that engagement of domains 1 and 2 of CD31 results in outside-in signaling in leukocytes.

Cell surface glycosaminoglycans do not serve as ligands for PECAM-1. PECAM-1 is not a heparin-binding protein

Previous studies have suggested that PECAM-1 mediates cellular interactions via both homophilic and heterophilic adhesive mechanisms. Cell surface glycoaminoglycans have been implicated as one of the heterophilic ligands for PECAM-1. To determine whether PECAM-1 is capable of interacting directly with glycosaminoglycans, we examined the adhesive properties of multiple monovalent and multivalent forms of this adhesion molecule. We found that the binding of a bivalent PECAM-1/IgG chimeric protein or multivalent PECAM-1-containing proteoliposomes to multiple different cell lines was 1) strictly dependent upon cell surface expression of PECAM-1 and 2) unaffected by the presence of excess heparin or heparan sulfate. The extracellular domain of PECAM-1 failed to interact specifically with heparin-Sepharose, 3H-labeled heparin, or a heparin-bovine serum albumin conjugate. In addition, an amino acid sequence motif inadvertently created by the juxtaposition of PECAM-1 and IgG sequences within the hinge region of certain PECAM-1/IgG chimeric constructs was found to confer glycosaminoglycan binding properties not normally present within the extracellular domain of the native molecule. Together, these data suggest that the mechanism by which heparin is able to affect PECAM-1-dependent cell-cell adhesion is indirect and occurs via inhibition of events that occur downstream from PECAM-1 engagement.

Isolation, culture and characteristics of human foetal and adult retinal pigment epithelium

BACKGROUND

Current methods for the isolation and culture of adult retinal pigment epithelium (RPE) provide successful primary culture. However, most methods result in contamination with other cell types and low cell yields. The isolation and culture of human foetal RPE presents further problems associated with the limited size of the eye cup and adherence among cells. Reliable methods are necessary for the culture of human RPE and subsequent functional studies.

METHODS

The present procedure is based on mechanical peeling of the whole RPE layer under the dissecting microscope. Dissected pieces are subsequently explanted to a 35 mm culture dish and are cultured with Dulbecco's modified Eagle's medium containing 10% foetal bovine serum. Peroxidase immunohistochemical methods were used to investigate cell phenotypes.

RESULTS

Primary cultures were obtained within 10-14 days with high yields, good viability and purity in subsequent culture. Cultured cells were vimentin and cytokeratin positive and CD31 negative.

CONCLUSIONS

This mechanical dissection technique is recommended for the isolation of foetal and young adult RPE cells, while the enzyme digestion method is preferred for aged adult tissue.

Platelet endothelial cell adhesion molecule-1 expression modulates endothelial cell migration in vitro

Endothelial cell migration is an important process that occurs during embryonic vasculogenesis and angiogenesis, wound healing, and tumor growth and metastasis, and after denudation injury following angioplasty and bypass grafting. Mechanisms regulating this process involve a complex interplay of cytoskeletal reorganization, cell-cell adhesion, and cell-extracellular matrix interactions. Platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) is constitutively expressed in endothelial cells, leukocytes, monocytes, lymphocytes, and platelets. PECAM-1 undergoes dynamic dephosphorylation during endothelial cell migration in vitro and during vasculogenesis in the murine conceptus. In transfected 3T3 cells, in cultured endothelial cells, and in the murine conceptus undergoing vasculogenesis, the tyrosine phosphorylation state of PECAM-1 Y686 correlates with the migratory state of the cells. In the present study, we investigate the role of PECAM-1 in modulating endothelial cell migration in vitro using retroviral transduction of c-myc epitope-tagged, wild-type, Y686 to F-mutated PECAM-1 and extracellular domain-deleted PECAM-1 constructs in endothelial cells devoid of endogenous PECAM-1 (ECV304 cells) and in endothelial cells expressing high levels of endogenous PECAM-1 (bovine aortic endothelial cells, BAEC). In ECV304 cells, the expression of wild-type PECAM-1 inhibited migration rates, whereas in BAEC, overexpression of wild-type PECAM-1 had no effect. Expression of Y686 to F-mutated PECAM-1 or extracellular domain-deleted PECAM-1 in BAEC increased migration rates. These data support the concept that endothelial cell migration is modulated, in part, by a balance between PECAM-1 cytoplasmic domain-mediated "inside-out" and "outside-out" signaling resulting from PECAM-1-mediated cell-cell interactions and integrin-extracellular matrix interactions.

Upregulation of VCAM-1 and ICAM-1 at atherosclerosis-prone sites on the endothelium in the ApoE-deficient mouse

Focal recruitment of monocytes and lymphocytes is one of the earliest detectable cellular responses in the formation of lesions of atherosclerosis. This localized accumulation of leukocytes is a multistep process in which the endothelium remains intact and may regulate leukocyte recruitment by expressing specific adhesion molecules. To examine the relationship of adhesion molecule expression to initiation factors and the sites of lesion formation, we analyzed the expression of vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and platelet-endothelial cell adhesion molecule-1 (PECAM-1) en face on the aortic endothelium of control mice and homozygous apolipoprotein E-deficient (ApoE -/-) mice that develop complex lesions of atherosclerosis similar to those in humans. In control mice, VCAM-1 staining was weak and limited to sites of altered blood flow. In contrast, in the ApoE -/- mice, VCAM-1 appeared to be localized over the surface of groups of endothelial cells in lesion-prone sites. Expression of VCAM-1 preceded lesion formation, and increased expression above control levels appeared to be correlated with the extent of exposure to plasma cholesterol. Although ICAM-1 was the most prominent adhesion molecule in lesion-prone sites, its expression appeared to be independent of plasma cholesterol levels and was upregulated in both ApoE -/- and control mice. At lesion-prone sites associated with altered blood flow, ICAM-1 was located over the surface of each endothelial cell and on microvilli, whereas VCAM-1 was confined to the cell periphery in non-lesion-prone sites. PECAM-1 was localized at the cell periphery throughout the aorta, and its expression did not appear to be regulated. Thus, the levels, localization, and characteristics of expression of VCAM-1, ICAM-1, and PECAM-1 appear to be differentially regulated. Upregulation of VCAM-1 and ICAM-1 is associated with sites of lesion formation.

Down-regulation of platelet endothelial cell adhesion molecule-1 results in thrombospondin-1 expression and concerted regulation of endothelial cell phenotype

bEND.3 cells are polyoma middle T-transformed mouse brain endothelial cells that express very little or no thrombospondin-1, a natural inhibitor of angiogenesis, but express high levels of platelet endothelial cell adhesion molecule-1 (PECAM-1) that localizes to sites of cell-cell contact. Here, we have examined the role of PECAM-1 in regulation of bEND.3 cell proliferation, migration, morphogenesis, and hemangioma formation. We show that down-regulating PECAM-1 expression by antisense transfection of bEND. 3 cells has a dramatic effect on their morphology, proliferation, and morphogenesis on Matrigel. There is an optimal level for PECAM-1 expression such that high levels of PECAM-1 inhibit, whereas moderate levels of PECAM-1 stimulate, endothelial cell morphogenesis. The down-regulation of PECAM-1 in bEND.3 cells resulted in reexpression of endogenous thrombospondin-1 and its antiangiogenic receptor CD36. The expression of the vascular endothelial growth factor receptors flk-1 and flt-1, as well as integrins and metalloproteinases (which are involved in angiogenesis), were also affected. These observations are consistent with the changes observed in proliferation, migration, and adhesion characteristics of the antisense-transfected bEND.3 cells as well as with their lack of ability to form hemangiomas in mice. Thus, a reciprocal relationship exists between thrombospondin-1 and PECAM-1 expression, such that these two molecules appear to be constituents of a "switch" that regulates in concert many components of the angiogenic and differentiated phenotypes of endothelial cells.

Heterogeneity in Lewis-X and sialyl-Lewis-X antigen expression on monocytes in whole blood: relation to stimulus-induced oxidative burst

By using flow cytometric analysis of cells in whole blood expressing high levels of CD14, we found a subpopulation of monocytes (8% of total) with higher scatter parameters, high capacity to produce reactive oxygen species (ROS), stronger expression of Lewis-X (CD15), sialyl-Lewis-X, CD11b and CD18 antigens, as well as an increased polymerized actin content. The size of this subpopulation increased after stimulation with lipopolysaccharide at the expense of the remaining monocytes, suggesting that its features were inducible. The membrane increase in Lewis-X and sialyl-Lewis-X expression observed during this conversion was largely due to the translocation of these carbohydrate structures from intracellular pools. Moreover, this subpopulation behaved as a primed monocyte subpopulation producing large amounts of H2O2 in response to N-formyl-methionyl-leucyl-phenylalanine. Increased H2O2 production was inhibited not only by anti-CD14 but also by anti-CD15 and anti-sialyl-Lewis-X monoclonal antibodies when added before lipopolysaccharide. These results show that lipopolysaccharide priming is regulated, at least in part, by Lewis-X and sialyl-Lewis-X structures expressed on the monocyte membrane. All together, this highly reactive and inducible subpopulation of monocytes, which share phenotypic and functional characteristics with neutrophils, might play an important role in host defenses and inflammatory responses.

CD38 binding to human myeloid cells is mediated by mouse and human CD31

Soluble forms of membrane receptors are emerging candidates as physiological regulators of leukocyte trafficking. In the present study, we found that the soluble form of the CD38 antigen (sCD38) bears a binding domain of low affinity for a cellular receptor on U937 cells. Cross-linking and peptide-mapping studies confirmed the physical association and the identification of the U937 receptor as a 130 kDa protein. The binding of sCD38 to the receptor was differentially inhibited by several monoclonal antibodies against the CD31 cell-adhesion molecule. Thus the interaction was analysed through direct association of soluble and membrane CD38 with soluble recombinant murine CD31 with three N-terminal and with all six extracellular Ig domains. Cross-linking experiments on U937 intact cells, and ligand blot assays of the immunoprecipitated CD38 molecule, indicated that (i) the recognized epitope is determined by the tertiary structure of the molecule, and that (ii) the binding domain involved resides in the ectocellular portion of the CD31 molecule, more precisely in the first three N-terminal domains. A comparative functional activity between murine and human CD31 was also explored. The data presented suggest that (i) human CD31 bears a highly functional similarity with its murine counterpart, as it is a receptor in myeloid cells with more than one ligand (the alphavbeta3 integrin and the CD38 molecule), and that (ii) the activity of sCD38 as decoy molecule for CD31 may play an important role in cell-cell interactions in physiological and pathological conditions.

Tyrosine phosphorylation of platelet endothelial cell adhesion molecule-1 induced by lysophosphatidylcholine in cultured endothelial cells

Lysophosphatidylcholine (lyso-PC), a biologically active phospholipid, appears to modulate various endothelial cell functions through tyrosine kinase-dependent signaling pathways. In cultured bovine aortic endothelial cells (BAEC), we have found that a 130 kDa protein (p130) was rapidly tyrosine phosphorylated within 2 min and sustained for, at least, 1 hr in response to 10 mumol/L of lyso-PC but not to phorbol myristate acetate (PMA). Prolonged preexposure to PMA did not affect lyso-PC-induced p130 tyrosine phosphorylation, suggesting that mechanisms independent of protein kinase C may be involved. Fractionation of the cell lysates revealed that p130 was detectable in the membrane fraction but not in the cytosolic fraction. Immunoprecipitation followed by immunoblotting of lyso-PC-treated BAEC identified p130 as bovine PECAM-1. Tyrosine phosphorylation of PECAM-1 appears to be one of the earliest events elicited by lyso-PC, and may play a role in lyso-PC-induced modulation of endothelial functions.

Leishmania lipophosphoglycan reduces monocyte transendothelial migration: modulation of cell adhesion molecules, intercellular junctional proteins, and chemoattractants

We previously identified the structural requirement for the inhibitory activity of Leishmania lipophosphoglycan (LPG) to block endothelial adhesion to monocytes. Here we showed that LPG reduces transendothelial migration of monocytes. LPG pretreatment of endothelial cells (2 microM, 1 h) reduced monocyte migration across endothelial cells activated by bacterial endotoxin (LPS) or IL-1beta (60 and 46%, respectively). A fragment of LPG (i.e., repeating phosphodisaccharide (consisting of galactosyl-mannose)) and LPG coincubated with LPG-neutralizing mAb lacks inhibitory activity on monocyte migration. Pretreatment of monocytes with LPG (2 microM, 1 h) also did not affect monocyte migration through control or LPS-activated endothelial cells. FACS analysis reveals that LPG treatment blocked the LPS-mediated expression of E-selectin, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1 on endothelial cells and monocyte adhesion without altering the integrity of the endothelial monolayer. LPG (2 microM, 1 h) alone was capable of altering the expression and distribution of two junctional adhesion molecules, CD31 and vascular endothelium cadherin, as well as reversing the effects of LPS on these proteins. The induction of endothelial cells by LPS to transcribe and release monocyte chemoattractant protein-1 (MCP-1) was significantly reduced by LPG (40-65%). LPG treatment of nonactivated endothelial cells also suppressed by 55 to 75% the monocyte migration triggered by a MCP-1 chemoattractant gradient, and coincubation of LPG with neutralizing mAb abrogated the inhibitory activity. Together, these data point to a novel anti-inflammatory function of LPG in reducing monocyte migration across endothelial cells via a mechanism of inhibition of endothelial expression of cell adhesion molecules, modulation of intercellular junctional proteins, and synthesis of MCP-1.

Endovascular papillary angioendothelioma (Dabska tumor) in an elderly woman

A patient with endovascular papillary angioendothelioma with a low grade of malignancy showing papillary proliferation of endothelioid cells is presented. The patient, an 83-year-old woman, underwent resection of a tumor of the neck. At operation a 9 x 7 cm cystic tumor containing yellow transparent liquid with clots was found in the subcutaneous tissue. Histological studies showed endothelioid cells with spindle-shaped nuclei proliferated in layers around the fibrovascular cores, which showed the characteristic appearance of papillary proliferation. These cells were immunohistochemically positive for CD31, CD34 and factor VIII-related antigen. Based on these observations, the tumor was considered to be an endovascular papillary angioendothelioma (Dabska tumor). Dabska tumor is a vascular tumor with a low grade of malignancy and usually occurs in infants and young children. About 13 cases of Dabska tumor have been reported. The occurrence of a Dabska tumor in an aged patient is considered to be rare.

Focal expression of thymidine phosphorylase associates with CD31 positive lymphocytic aggregation and local neo-angiogenesis in non-small cell lung cancer

Platelet-derived endothelial cell growth factor (PDECGF) also called thymidine phosphorylaze (TP) has been shown to have considerable angiogenic activity. 141 cases of early stage non-small cell lung cancer were stained for TP and vascular grade using the P-GF.44C and JC70 MoAbs, respectively. The early steps of TP activation could be identified in 27 cases, where one or two foci of cancer cell TP overexpression occurred within a general pattern of negative/weak staining. Thirty-three foci of overexpression were analyzed for the local microvessel density in the adjacent stroma, assessed by microvessel counting (MC) and Chalkley Score (CS) comparatively with the remaining TP negative tumor areas. The degree of local inflammatory (lymphocyte and macrophage) infiltration was also assessed. A statistically significant increase of mean MC and mean CS was observed in areas of TP overexpression in both low and high angiogenesis cases. Overall, the mean MC in overexpressing areas, assessed in 250x fields, was 20.4 +/- 12.8 vs. 13.6 +/- 9.5 in areas with no TP expression (p = 0.0001). The mean CS was 5.7 +/- 3.3 and 4.0 +/- 2.1, respectively (p = 0.0003). Ten out of 19 (54%) cases with low lymphocytic infiltration showed marked stromal lymphocytic infiltration in the area of focal TP overexpression (p = 0.01). The present study provides further evidence of a direct association of TP and the process of angiogenesis in non-small cell lung cancer.

Adhesion molecule expression in the lung: a comparison between normal and diffuse interstitial lung disease

Cellular adhesion molecules are crucial determinants of the migration of immune effector cells to the tissues. In chronic inflammatory diseases, upregulation of the expression of these molecules may contribute to the persistent inflammatory process. The aim of this study was to determine whether there is evidence of adhesion molecule expression in chronically inflamed lung. Soluble adhesion molecules in bronchoalveolar lavage fluid (BALF) were measured by enzyme-linked immunoassay in 54 patients with chronic interstitial lung diseases and 16 normal controls. Adhesion molecule expression in fibrosing alveolitis (FA) lung and in control lung was assessed using immunohistology and reverse transcription-polymerase chain reaction (RT-PCR) amplification. Soluble intercellular adhesion molecule-1 (ICAM-1) was detected in all but two subjects. There was no difference in ICAM-1 concentration between disease groups and normal subjects. In contrast, soluble E-selectin was detected in 17 of the 70 subjects and was significantly associated with the presence of lung disease (p=0.0173). Furthermore, the presence of soluble E-selectin was associated with a raised lymphocyte percentage in BALF (p=0.0069). Soluble VCAM was only detected in five of the 70 subjects (two normals, three patients). There was no difference in adhesion molecule expression in lung parenchyma between FA and controls assessed by immunohistology and RT-PCR. The most striking finding of our study was the universal expression of intercellular adhesion molecule-1 in both normal and diseased lung, emphasizing the important role of the lung in immune function. Upregulation of E-selectin may contribute to inflammatory cell accumulation in chronic interstitial lung diseases.

The effect of synthetic malaria pigment (beta-haematin) on adhesion molecule expression and interleukin-6 production by human endothelial cells

The effects of synthetic malaria pigment (beta-haematin, BH) on the expression of the intercellular adhesion molecule 1 (ICAM-1) and platelet endothelial cell adhesion molecule 1 (PECAM-1) and the production of interleukin-6 (IL-6) by human microvascular endothelial cells were measured using flow cytometry analysis and immunoenzymatic assay. BH alone did not affect basal levels of ICAM-1, PECAM-1 or IL-6. When added to cell cultures before or with, but not after, lipopolysaccharide or tumour necrosis factor alpha, BH at 1-100 micrograms/mL induced a dose-dependent inhibition of ICAM-1 and PECAM-1 expression and IL-6 production. Cell viability and human leucocyte antigen A,B,C expression remained unaffected. Similar, though more variable, results were obtained using human umbilical vein endothelial cells. These results suggested that accumulation of pigment within endothelial cells following repeated malaria infection reduces local inflammation and parasite sequestration through inhibition of either cytokine production or parasitized erythrocyte receptors on endothelial cells.

Engagement of human PECAM-1 (CD31) on human endothelial cells increases intracellular calcium ion concentration and stimulates prostacyclin release

Platelet-endothelial cell adhesion molecule-1 (PECAM-1) is a member of the immunoglobulin superfamily that plays a role in a number of endothelial cell (EC) functions including migration, angiogenesis, and transmigration of leukocytes across endothelium. We postulated that one way PECAM-1 might exert its effects was by regulating intracellular EC levels of calcium. Using single-cell fluorometry, we found that engagement of PECAM-1 by mAbs induced a slow but sustained increase in intracellular calcium, both in EC and in an adherent PECAM-1-transfected cell line that models endothelium. Generation of this signal was specific for certain anti-PECAM-1 antibodies, required the presence of the cytoplasmic domain, depended on extracellular calcium and on tyrosine phosphorylation, but did not require cross-linking; in fact, calcium increases were stimulated by certain Fab fragments. Activation of EC by PECAM-1 also caused a time-dependent increase in prostacyclin release. Given the importance of intracellular calcium and prostacyclin release as signaling molecules, engagement of PECAM-1 during cell-cell interactions may alter a number of EC functions including secretion of vasoactive mediators.