Expression In Microvascular Endothelial Cells Research Articles

Dynamic Changes in Endothelial Cell Adhesion Molecule Nepmucin/CD300LG Expression under Physiological and Pathological Conditions

Vascular endothelial cells often change their phenotype to adapt to their local microenvironment. Here we report that the vascular endothelial adhesion molecule nepmucin/CD300LG, which is implicated in lymphocyte binding and transmigration, shows unique expression patterns in the microvascular endothelial cells of different tissues. Under physiological conditions, nepmucin/CD300LG was constitutively and selectively expressed at the luminal surface of the small arterioles, venules, and capillaries of most tissues, but it was only weakly expressed in the microvessels of the splenic red pulp and thymic medulla. Furthermore, it was barely detectable in immunologically privileged sites such as the brain, testis, and uterus. The nepmucin/CD300LG expression rapidly decreased in lymph nodes receiving acute inflammatory signals, and this loss was mediated at least in part by TNF-α. It was also down-regulated in tumors and tumor-draining lymph nodes, indicating that nepmucin/CD300LG expression is negatively regulated by locally produced signals under these circumstances. In contrast, nepmucin/CD300LG was induced in the high endothelial venule-like blood vessels of chronically inflamed pancreatic islets in an animal model of non-obese diabetes. Interestingly, the activated CD4+ T cells infiltrating the inflamed pancreas expressed high levels of the nepmucin/CD300LG ligand(s), supporting the idea that nepmucin/CD300LG and its ligand interactions are locally involved in pathological T cell trafficking. Taken together, these observations indicate that the nepmucin/CD300LG expression in microvascular endothelial cells is influenced by factor(s) that are locally produced in tissues, and that its expression is closely correlated with the level of leukocyte infiltration in certain tissues.

Effect of chloroform extract of Zingiber miosa Roscoe on human dermal microvascular endothelial cell expression of cell adhesion molecules and adhesivity to lymphocytes.

Objective To investigate the effect of chloroform extract of Zingiber mioga Roscoe on human dermal microvascular endothelial cell (HDMEC) expression of cell adhesion molecules and adhesivity to lymphocytes.Methods HDMECs were isolated from human foreskin tissue and subjected to subculture.After several passages,some HDMECs were treated with chloroform extract from Zingiber mioga Roscoe (CFMG) of 200 mg/L for 30 minutes before or after 24-hour stimulation with tumor necrosis factor (TNF)-α or interleukin (IL)-1α.Subsequently,enzyme-linked immunosorbent assay was performed to determine the expression levels of intercellular adhesion molecule-1 (ICAM-1),vascular cell adhesion molecule-1 (VCAM-1) and E-selectin on HDMECs.Both T lymphocytes isolated from venous blood of healthy adults and Ramos Burkitt's lymphoma B cells were labelled with chromium-51 and incubated with the HDMECs for four hours followed by the determination of radiation intensity of lymphocytes adhering to HDMECs using a gamma-counter.Results Compared with 0.2％ dimethyl sulfoxide (DMSO),CFMG slightly down-regulated the expression of ICAM-1,VCAM-1 and E-selectin on resting HDMECs (all P ＞ 0.05).In comparison with culture medium,TNF-α enhanced the expressions of ICAM-1,VCAM-1 and E-selectin significantly (all P ＜ 0.01),and IL-1α elevated the expressions of ICAM-1 and E-selectin markedly(both P ＜ 0.01) as well as the expression of VCAM-1 slightly (P ＞ 0.05).The upregulating effects of TNF-α and IL-1α on the expressions of adhesion molecules were notably suppressed by the CFMG treatment prior to the stimulation with TNF-α and IL-1α(all P ＜ 0.01),but not affected by that after the stimulation (all P ＞ 0.05).The adhesivity of HDMECs to T lymphocytes and Ramos cells was slightly decreased by CFMG treatment compared with 0.2％ DMSO (both P ＞ 0.05),but was markedly increased by TNF-α and IL-1α compared with the culture medium (both P ＜ 0.01).Conclusions CFMG may play an antiinflammatory role via blocking the up-regulating effect of pre-inflammatory cytokines such as TNF-α and IL-1α on the expression of adherence molecules on HDMECs and,hence,inhibiting inflammatory cell infiltration in tissue. Key words: Zingiber mioga Roscoe; Endothelial cells; Cell adhesion molecules; Cytokines

Thrombospondin-1 modulates VEGF signaling via CD36 by recruiting SHP-1 to VEGFR2 complex in microvascular endothelial cells

AbstractThrombospondin-1 (TSP-1) inhibits growth factor signaling at the receptor level in microvascular endothelial cells (MVEC), and CD36 has been suggested to be involved in this inhibition, but the mechanisms are not known. We hypothesized that CD36-TSP-1 interaction recruits Src homology 2 domain–containing protein tyrosine phosphatase (SHP)-1 to the vascular endothelial growth factor receptor 2 (VEGFR2) signaling complex and attenuates vascular endothelial growth factor (VEGF) signaling. Western blots of anti-CD36 and anti-VEGFR2 immunoprecipitates from VEGF-treated MVEC showed that exposure of the cells to a recombinant protein containing the CD36 binding domain of thrombospondin-1 (known as the TSR domain) induced association of SHP-1 with the VEGFR2/CD36 signaling complex and thereby suppressed VEGFR2 phosphorylation. SHP-1 phosphatase activity was increased in immunoprecipitated VEGFR2 complexes from TSR-treated cells. Silencing CD36 expression in MVEC by small interfering RNA (siRNA) or genetic deletion of cd36 in mice showed that TSR-induced SHP-1/VEGFR2 complex formation required CD36 in vitro and in vivo. Silencing SHP-1 expression in MVEC by siRNA abrogated TSR-mediated inhibition of VEGFR2 phosphorylation as well as TSR-mediated inhibition of VEGF-induced endothelial cell migration and tube formation. These studies reveal a SHP-1–mediated antiangiogenic pathway induced by CD36-TSP-1 interaction that inhibits VEGFR2 signaling and they provide a novel target to modulate angiogenesis therapeutically.

HLA-DR Expressing Endothelial Cell Expansion of Allogeneic CD4+ T Lymphocytes Towards Either Pro-Inflammatory Th17 or Regulatory Populations

Introduction: The major obstacle to organ transplantation remained chronic rejection due to the generation and the persistence of an alloimmune response principally mediated by Major Histocompatibility Complex molecules (MHC) present on donor cells. Graft microvascular endothelial cells (ECs) express MHC class I and II molecules and have therefore a dual role as both a stimulator of, and a target for allo-immune responses. Recently, we have shown that ECs generate either regulatory CD4+ T cells (Tregs) or pro-inflammatory CD4+IL-17+ cells (Th17) but the factors which orient this CD4+ T cell allo-immune response remain to be determinate. Methods: We have established a model of either inducible or constitutive HLA-DR expression in microvascular ECs using lentiviral vector infection. This model was used to study (1) the mechanisms of EC induced activation of allogeneic CD4+ T cells and (2) to determine the effect of EC pre-activation with an HLA-DR antibody on the orientation of the allogeneic CD4+ T cell response. Results: Under inflammatory conditions, HLA-DR expression by human microvascular ECs allows them to orient the CD4+ T cell response towards either a Th17 pro-inflammatory response or a regulatory T cell response. Expansion of Th17 depended upon IL-6 secretion by ECs which led to STAT-3 activation in allogeneic CD4+ T cells associated with their proliferation, while Treg expansion was dependent upon their interaction with ECs mediated by the adhesion molecule ICAM-1 (CD54). HLA-DR antibody induced signaling in ECs leading to an increase in their secretion of IL-6 and their ability to expand alloreactive Th17 cells while lessening the regulatory T cell response. Conclusion: These data reveal that firstly human microvascular EC regulates polarization of the memory CD4+ T cell response towards either cytokine-dependent inflammation or contact-dependent regulation and secondly that HLA-DR antibody pre-activation of EC increases their ability to induce a pro-inflammatory Th17 response. Together these results provide evidence for a link between the roles of EC as a target of HLA-DR antibody binding and as an allo-stimulator of the pro-inflammatory Th17 response implicated in chronic rejection. Moreover, these data may contribute to our understanding of HLA class II allo-antibodies mediated complement independent mechanisms of EC damage.

Stromal Endothelial Cells Establish a Bidirectional Crosstalk with Chronic Lymphocytic Leukemia Cells through the TNF-Related Factors BAFF, APRIL, and CD40L

Chronic lymphocytic leukemia (CLL) is a clonal B cell disorder of unknown origin. Accessory signals from the microenvironment are critical for the survival, expansion, and progression of malignant B cells. We found that the CLL stroma included microvascular endothelial cells (MVECs) expressing BAFF and APRIL, two TNF family members related to the T cell-associated B cell-stimulating molecule CD40L. Constitutive release of soluble BAFF and APRIL increased upon engagement of CD40 on MVECs by CD40L aberrantly expressed on CLL cells. In addition to enhancing MVEC expression of CD40, leukemic CD40L induced cleavases that elicited intracellular processing of pro-BAFF and pro-APRIL proteins in MVECs. The resulting soluble BAFF and APRIL proteins delivered survival, activation, Ig gene remodeling, and differentiation signals by stimulating CLL cells through TACI, BAFF-R, and BCMA receptors. BAFF and APRIL further amplified CLL cell survival by upregulating the expression of leukemic CD40L. Inhibition of TACI, BCMA, and BAFF-R expression on CLL cells; abrogation of CD40 expression in MVECs; or suppression of BAFF and APRIL cleavases in MVECs reduced the survival and diversification of malignant B cells. These data indicate that BAFF, APRIL, and CD40L form a CLL-enhancing bidirectional signaling network linking neoplastic B cells with the microvascular stroma.

Regulation of endothelial cell activation and angiogenesis by injectable peptide nanofibers

RAD16-II peptide nanofibers are promising for vascular tissue engineering and were shown to enhance angiogenesis in vitro and in vivo, although the mechanism remains unknown. We hypothesized that the pro-angiogenic effect of RAD16-II results from low-affinity integrin-dependent interactions of microvascular endothelial cells (MVECs) with RAD motifs. Mouse MVECs were cultured on RAD16-II with or without integrin and MAPK/ERK pathway inhibitors, and angiogenic responses were quantified. The results were validated in vivo using a mouse diabetic wound healing model with impaired neovascularization. RAD16-II stimulated spontaneous capillary morphogenesis, and increased β3 integrin phosphorylation and VEGF expression in MVECs. These responses were abrogated in the presence of β3 and MAPK/ERK pathway inhibitors or on the control peptide without RAD motifs. Wide-spectrum integrin inhibitor echistatin completely abolished RAD16-II-mediated capillary morphogenesis in vitro and neovascularization and VEGF expression in the wound in vivo. The addition of the RGD motif to RAD16-II did not change nanofiber architecture or mechanical properties, but resulted in significant decrease in capillary morphogenesis. Overall, these results suggest that low-affinity non-specific interactions between cells and RAD motifs can trigger angiogenic responses via phosphorylation of β3 integrin and MAPK/ERK pathway, indicating that low-affinity sequences can be used to functionalize biocompatible materials for the regulation of cell migration and angiogenesis, thus expanding the current pool of available motifs that can be used for such functionalization. Incorporation of RAD or similar motifs into protein engineered or hybrid peptide scaffolds may represent a novel strategy for vascular tissue engineering and will further enhance design opportunities for new scaffold materials.

Detrimental effect of fractalkine on myocardial ischaemia and heart failure

Fractalkine (FKN) is a newly identified membrane-bound chemokine; its role in myocardial ischaemia and heart failure is largely unknown. We attempted to investigate the role of FKN in myocardial ischaemia and ischaemia or pressure overload-induced ventricular remodelling and heart failure. FKN-induced changes of heart failure-related genes in cultured rat cardiac cells and the effect of FKN on cultured cardiomyocyte injury during anoxia/reoxygenation (A/R) were examined. The direct influence of FKN neutralization on heart failure and the potential mechanism was also investigated. In mice with failing hearts, myocardial FKN expression was correlated with the lung weight/body weight ratio, left ventricular fractional shortening, and brain natriuretic peptide expression. In cultured rat cells, exposure to FKN increased natriuretic peptide A expression in cardiomyocytes, matrix metalloproteinase-9 expression in fibroblasts, and intercellular adhesion molecule-1 expression in microvascular endothelial cells. FKN also promoted cardiomyocyte damage during A/R and neutralizing FKN antibody treatment improved heart failure induced by myocardial infarction or pressure overload. Neutralizing FKN or its receptor inhibited the activation of mitogen-activated protein kinases (MAPKs) in hypoxic cardiomyocytes or ischaemic myocardium. FKN promotes myocardial injury and accelerates the progress of heart failure, which is associated with the activation of MAPKs.

Tumor cells induce COX-2 and mPGES-1 expression in microvascular endothelial cells mainly by means of IL-1 receptor activation

Prostaglandin (PG) E 2 plays a key role in immune response, tumor progression and metastasis. We previously showed that macrovessel-derived endothelial cells do not produce PGE 2 enzymatically because they do not express the inducible microsomal PGE-synthase-1 (mPGES-1). Nevertheless, differences between macro- and micro-vessel-derived endothelial cells regarding arachidonic acid (AAc) metabolism profile have been reported. The present work was conducted to evaluate the expression of PGE 2-pathway-related enzymes in human microvascular endothelial cells (HMVEC) in culture and to test the hypothesis that the tumor cell-HMVEC cross talk could increase mPGES-1 expression in HMVEC. We treated HMVEC in culture with human recombinant IL-1β. IL-1β induced PGE 2 release and COX-2 and mPGES-1 expression in terms of mRNA and protein, determined by real-time PCR and immunoblotting, respectively. HMVEC constitutively expressed mPGES-2 and cytosolic PGES (cPGES) and the IL-1β treatment did not modify their expression. PGE 2 synthesized by HMVEC from exogenous AAc was linked to mPGES-1 expression. Immunohistochemistry analysis confirmed mPGES-1 expression in microvessels in vivo. COX-2 and mPGES-1 were also induced in HMVEC by the conditioned medium from two squamous head and neck carcinoma cell lines. Conditioned medium from tumor cell cultures contained several cytokines including the IL-1β and IL-1α. Tumor cell-induced COX-2 and mPGES-1 in HMVEC was strongly inhibited by the IL-1-receptor antagonist, indicating the important implication of IL-1 in this effect. HMVEC could therefore contribute directly to PGE 2 formed in the tumor. Our findings support the concept that mPGES-1 could be a target for therapeutic intervention in patients with cancer.

Alteration of gene expression in microvascular endothelial cells after exposure to foot-and-mouth disease virus 146S antigen

To investigate the global response of microvascular endothelial cells (MVECs) to foot-and-mouth (FMDV)disease vaccine (FMDV) antigen and to explore the role of MVECs in FMD vaccine immunity, the gene expression alterations of rat myocardium microvascular endothelial cells (RMMVECs) after stimulation with FMD virus (FMDV) 146S antigen were assayed using cDNA microarrays. We observed that 18 genes and 67 genes in RMMVECs were respectively altered by FMDV 146S antigen at 6 h and 24 h, respectively. The former were all up-regulated genes, and the latter included 60 up-regulated genes and 7 down-regulated genes. Among the differentially expressed genes, many were associated to immune response, such as the genes encoding chemokines, interleukins, complement components, and adhesion molecules. In particular, the chemokine genes had the greatest numbers and significant expression ratios. A part of the altered genes with immune function was validated by real-time reverse transcription-PCR. The influence of FMDV 146S antigen on the secretion of monocyte chemoattractant protein-1, interleukin-6 (IL-6), and IL-1 by RMMVECs was confirmed by enzyme-linked immunosorbent assay, and the expression of vascular cell adhesion molecule-1 was identified by immunocytochemistry. The results indicated that the FMDV 146S antigen induces the changes of immune-associated genes in RMMVECs, which suggests that MVECs play an important role in modulating how the innate immune system responds to FMD vaccine.

Pathology analysis of CD31,CD34 and vWF expression in vascular endothelial cell of granulation tissue of eyelid chalazion

To investigate the variable expressions of CD31, CD34, vWF during the vascular development process of growing granulation tissue of eyelid chalazion. The samples of growing granulation tissue were obtained during chalazion removal surgery. Immunohistochemistry staining technique was used to detect the expression of CD31, CD34 and vWF in vascular endothelial cells. CD31 and CD34 were expressed in all vascular endothelial cells, whereas the CD34 was more effectively expressed and strengthened in the capillary sprouts. The vWF was not expressed in capillary sprouts, but the expression was stronger in the tissues from superficial to deeper layers. CD31, CD34 and vWF expression in microvascular endothelial cells of growing granulation tissue is diversified. CD34 may be an import marker for active angiogenesis and vWF is an effective marker for inactive angiogenesis.

Different modulation of dipeptidyl peptidase-4 activity between microvascular and macrovascular human endothelial cells

Dipeptidyl peptidase 4 (DPP-4) is an enzyme that is produced by endothelial cells in different districts and circulates in plasma. Patients with type 2 diabetes show a reduction in active Glucagon-Like Peptide-1 (GLP-1) that could be due to impairment of secretion or its degradation or both. GLP-1 is rapidly inactivated in vivo, mainly by the DPP-4. Some authors suggest that Metformin has no direct inhibitory effect on DPP-4 activity and that Metformin and the other biguanides enhance GLP-1 secretion; others suggest a possible role of Metformin in the inhibition of the DPP-4 activity. In order to better elucidate the role of insulin sensitizers on the modulation of GLP-1 circulating levels, DPP-4 activity and mRNA expression were measured in cultured human aortic endothelial cells (HAEC) and human microvascular dermal endothelial cells (HMVEC) exposed to high glucose, Metformin and Rosiglitazone. Present data show that hyperglycemia is capable of increasing in a significant manner the DPP-4 activity only in microvascular endothelial cells. Rosiglitazone is able to modulate in a negative manner the expression of DPP-4 but not its activity in macrovascular endothelial cells, while at 24 h of exposure it is able to increase significantly DPP-4 activity but not its expression in microvascular endothelial cells. Metformin at 48 h only in microvascular endothelial cells is able to reduce in a significant manner (p = 0.01) the activity of DPP-4 but not its expression. The modulation of DPP-4 is site specific.

Increased retinopathy occurrence in type 1 diabetes patients with increased serum levels of the advanced glycation endproduct hydroimidazolone

We aimed to investigate associations between serum levels of the advanced glycation endproduct methylglyoxal-derived hydroimidazolone (MG-H1) and retinopathy in a sample of patients with type 1 diabetes. We conducted a cross-sectional study in a Scandinavian ophthalmology outpatient clinic on 61 randomly selected patients with type 1 diabetes. Blood samples and retinal photographs were taken at the same visit. Serum levels of hydroimidazolone immunoreactivity were determined using an immunoassay, and levels of retinopathy were determined from seven standard field stereo photographs of each eye according to the ETDRS method. Results were compared between patients with and without retinopathy. Hydroimidazolone quartiles were significantly associated with retinopathy (p = 0.013). The most profound increase in occurrence of retinopathy was observed from the lowest to the second-lowest hydroimidazolone quartile. Adjusted for duration of diabetes using logistic regression, a significant difference in the presence of retinopathy was found when comparing the lowest quartile with the rest (p = 0.022). In our patients with type 1 diabetes, serum levels of hydroimidazolone were found to be associated with retinopathy. This is in keeping with findings in a larger sample of patients with type 2 diabetes.

Connexin Isoform Expression in Smooth Muscle Cells and Endothelial Cells of Hamster Cheek Pouch Arterioles and Retractor Feed Arteries

Gap junction channels formed by connexin (Cx) protein subunits enable cell-to-cell conduction of vasoactive signals. Given the lack of quantitative measurements of Cx expression in microvascular endothelial cells (EC) and smooth muscle cells (SMC), the objective was to determine whether Cx expression differed between EC and SMC of resistance microvessels for which conduction is well-characterized. Cheek pouch arterioles (CPA) and retractor feed arteries (RFA) were hand-dissected and dissociated to obtain SMC or endothelial tubes. In complementary experiments, small intestine was dissociated to obtain SMC. Following reverse transcription, quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) was performed by using specific primers and fluorescent probes for Cx37, Cx40, and Cx43. Smooth muscle alpha-actin (SMAA) and platelet endothelial cell adhesion molecule-1 (PECAM-1) served as respective reference genes. Transcript copy numbers were similar for each Cx isoform in EC from CPA and RFA (approximately 0.5 Cx/PECAM-1). For SMC, Cx43 transcript in CPA and RFA (< 0.1 Cx/SMAA) was less (p < 0.05) than that in small intestine (approximately 0.4 Cx/SMAA). Transcripts for Cx37 and Cx40 were also detected in SMC. Punctate immunolabeling for each Cx isoform was pronounced at EC borders and that for Cx43 was pronounced in SMC of small intestine. In contrast, Cx immunolabeling was not detected in SMC of CPA or RFA. Connexin expression occurs primarily within the endothelium of arterioles and feed arteries, supporting a highly effective pathway for conducting vasoactive signals along resistance networks. The apparent paucity of Cx expression within SMC underscores discrete homocellular coupling and focal localization of myoendothelial gap junctions.

Shear stress‐induced Ets‐1 modulates protease inhibitor expression in microvascular endothelial cells

Elevated shear stress within the skeletal muscle microvasculature is implicated in the induction of a longitudinal splitting form of angiogenesis, which is characterized by the lack of basement membrane breakage. We investigated whether the transcriptional regulator, Ets-1, is responsive to changes in hemodynamic forces and if so, whether Ets-1 controls microvascular endothelial cell integrity by inducing the expression of inhibitors of matrix degrading proteases. Rats were treated with prazosin for 2, 4, and 7 days to increase in microvascular shear stress in hindlimb skeletal muscles. In complimentary in vitro experiments, rat microvascular skeletal muscle endothelial cells were exposed to laminar shear stress (15 dyne/cm(2)) for 0.5, 2, and 24 h. TaqMan PCR analysis of laser microdissected capillaries isolated from EDL muscles demonstrated transient (after 2 days) induction of Ets-1 gene expression. In cultured cells, a transient up-regulation of Ets-1 mRNA was observed after 2 h shear stimulation, accompanied by increased phosphorylation of Ets-1 and enhanced Ets-1 DNA binding activity. This response was modulated by ERK1/2 and p38 MAP kinases, but was not dependent on NOS or COX-2 activity. PAI-1, TIMP-1 and TIMP-3 mRNA were elevated significantly in prazosin treated EDL, and in response to shear stimulation in vitro. In cultured endothelial cells, Ets-1 RNA interference abolished the shear-induced increases in Ets-1, PAI-1, TIMP-1, and TIMP-3 mRNA expression. These results suggest that enhanced laminar shear stress may act to preserve the integrity of microvascular walls in part through Ets-1-dependent induction of protease inhibitors.

Screening of Endothelial Expression Libraries for the Identification of Novel Autoantigens Involved in Distinct Autoimmune Diseases Characterized by Endothelial Dysfunction

Screening a cDNA expression library is a powerful technique that allows identification of previously uncharacterized antigens. Proteins recognized by antibodies from patients with autoimmune diseases have been intensively studied over the past two decades since cDNAs encoding autoantigens have become available. Identity of many of them has been defined, and specific structural motifs or post-translational modifications, which may be important to explain the generation of such antibodies during the autoimmune process, have been pointed out. The screening of human umbilical artery or microvascular endothelial cell expression libraries appears to be a useful tool for the characterization of endothelial autoantigens allowing us to identify several molecules recognized from serum anti-endothelial cell antibodies of patients with diseases characterized by immune-mediated endothelial dysfunctions.

Molecular Mechanisms of Oxidative Stress‐induced STAT3 Activation in Endothelial Cells

We and others have established that STAT3 is a critical mediator of VEGF function and expression in microvascular endothelial cells (EC). In inflammatory diseases, including diabetic microangiopathies, enhanced STAT3 activation has been correlated with increased oxidative stress and VEGF expression. Here we wanted to determine whether and how elevation of reactive oxygen species (ROS) formation affects the activation of STAT3 in endothelial cells. EC were cultured in the presence of 25mM D-glucose for 24 hours and then challenged with 20ng/ml VEGF for different times. This treatment resulted in enhanced reactive oxygen species (ROS) formation, as demonstrated by hydroethidine staining. Furthermore, western blotting and immunoprecipitation analyses revealed that EC cultured in the presence of HG showed sustained VEGF-dependent STAT3 tyrosine phosphorylation which correlated with decreased phosphorylation of the tyrosine phosphatase SHP-1 and blockade of STAT3/SHP-1 interaction. These HG/ oxidative stress effects were blocked by concomitant treatment of EC with the antioxidants superoxide dismutase and catalase. In addition, antisense-mediated inhibition of SHP-1 expression resulted in constitutive STAT3 tyrosine phosphorylation. In conclusion, these results demonstrate a key role for SHP-1 in the regulation of VEGF-dependent STAT3 activation in EC and suggest that oxidative stress-mediated STAT3 activation occurs through inhibition of SHP-1.

Lysophosphatidylcholine: an enigmatic lysolipid

increased endothelial permeability of pulmonary microvessels is the major contributor of acute lung injury, sepsis, and acute respiratory distress syndrome ([2][1], [7][2]). Studies have established that change in cell shape resulting in concurrent formation of gaps between endothelial cells is a

Bcl-2 Acts in a Proangiogenic Signaling Pathway through Nuclear Factor-κB and CXC Chemokines

Vascular endothelial growth factor (VEGF) induces expression of Bcl-2 in tumor-associated microvascular endothelial cells. We have previously reported that up-regulated Bcl-2 expression in microvascular endothelial cells is sufficient to enhance intratumoral angiogenesis and to accelerate tumor growth. We initially attributed these results to Bcl-2-mediated endothelial cell survival. However, in recent experiments, we observed that conditioned medium from Bcl-2-transduced human dermal microvascular endothelial cells (HDMEC-Bcl-2) is sufficient to induce potent neovascularization in the rat corneal assay, whereas conditioned medium from empty vector controls (HDMEC-LXSN) does not induce angiogenesis. These results cannot be attributed to the role of Bcl-2 in cell survival. To understand this unexpected observation, we did gene expression arrays that revealed that the expression of the proangiogenic chemokines interleukin-8 (CXCL8) and growth-related oncogene-alpha (CXCL1) is significantly higher in HDMEC exposed to VEGF and in HDMEC-Bcl-2 than in controls. Inhibition of Bcl-2 expression with small interfering RNA-Bcl-2, or the inhibition of Bcl-2 function with small molecule inhibitor BL-193, down-regulated CXCL8 and CXCL1 expression and caused marked decrease in the angiogenic potential of endothelial cells without affecting cell viability. Nuclear factor-kappaB (NF-kappaB) is highly activated in HDMEC exposed to VEGF and HDMEC-Bcl-2 cells, and genetic and chemical approaches to block the activity of NF-kappaB down-regulated CXCL8 and CXCL1 expression levels. These results reveal a novel function for Bcl-2 as a proangiogenic signaling molecule and suggest a role for this pathway in tumor angiogenesis.

Lysophosphatidylcholine regulates human microvascular endothelial cell expression of chemokines

The role of lysophosphatidylcholine (LPC) in the induction of MCP-1, IL-8 and RANTES, which are chemotactic factors to monocytes, neutrophils and lymphocytes, respectively, by human vascular endothelial cells (EC), was examined. LPC induced the expression of MCP-1 and IL-8 in a concentration- and time-dependent manner in microvascular EC (MVEC) and in large vessel EC from aorta, pulmonary artery and umbilical vein. LPC also induced RANTES in MVEC but not in large vessel EC. Signaling pathways responsible for LPC induction of chemokines were examined in MVEC. LPC and TNFα, a cytokine secreted in sites of inflammation, additively stimulated RANTES expression. LPC did not augment TNFα induction of MCP-1 or IL-8. A platelet-activating factor receptor antagonist (BN52021) failed to block LPC induction of MVEC chemokines, but the G i-protein inhibitor pertussis toxin partially blocked LPC induction of RANTES and IL-8. LPC activated multiple kinases in MVEC; it increased the phosphorylation of ERK1/2, AKT and p38 MAP kinase in a time-dependent manner. An inhibitor of the MAPK/ERK pathway, PD98059, blocked the phosphorylation of ERK1/2 and RANTES induction by LPC, but augmented IL-8 induction. LY294002, a specific inhibitor of phosphoinositide 3 kinase (PI3 kinase), blunted the phosphorylation of AKT and inhibited LPC induction of RANTES more strongly than IL-8. Inhibition of p38 MAP kinase pathway by SB202190 also blocked LPC-induced expression of IL-8 and RANTES. Our results suggest that LPC induction of chemokines in MVEC is distinct from that in large vessel EC, and required the activities of MAP kinases and PI3 kinase for the induction of RANTES and IL-8. We speculate that the presence of LPC, a bioactive lipid product of phospholipase A 2 (PLA 2) and a constituent of oxidized low-density lipoprotein, can differentially influence the chemotaxis of particular leukocyte subpopulations during inflammation.

Estrogen receptor-alpha and -beta expression in microvascular endothelial cells and smooth muscle cells of myometrium and leiomyoma.

The two estrogen receptors, ERalpha and ERbeta, are likely to have roles in the pathophysiology of fibroid development. They have been detected in myometrial and leiomyoma (fibroid) tissue, but the cell types expressing ERalpha and ERbeta have not been determined. ERs have also been detected in human endothelial cells. The aims of the present study were to determine whether pure populations of myometrial microvascular endothelial cells (MEC) express ERalpha and ERbeta, to compare MEC ERalpha/ERbeta expression with that of pure populations of myometrial smooth muscle cells (SMC) and to determine if ERalpha/ERbeta are differentially expressed in MEC and SMC of myometrium and fibroids from nine paired samples. Using RT-PCR (for ERalpha and ERbeta) and Western blotting (for ERalpha only), we demonstrated that all cultures of early passage myometrial and fibroid SMC (>99% pure) expressed ERalpha but not ERbeta, while myometrial and fibroid MEC (>99% CD31+) constitutively expressed ERbeta. However, both myometrial and fibroid MEC showed variable expression of ERalpha, with approximately 60% of MEC samples expressing ERalpha. While the majority (6/9) of MEC from myometrial and fibroid pairs demonstrated the same pattern of ERalpha expression, 3/9 pairs showed discordant ERalpha expression. These results show that ERalpha and ERbeta are differentially expressed in SMC and MEC of human myometrium and fibroids. Since ERalpha and ERbeta mediate opposing transcriptional activities, any effect of estrogen on the growth and development of fibroids is likely to be complex and may involve both SMC and MEC.