Activation of the transcription factor NF-κB is critical for the tumor necrosis factor-α (TNF-α)-induced inflammatory response. Here we report the complete gene expression profile from activated microvascular endothelial cells emphasizing the direct contribution of the NF-κB pathway. Human microvascular endothelial cell line-1 (HMEC-1) cells were modified to express dominant interfering mutants of the IKK/NF-κB signaling module and expression profiles were determined. Our results provide compelling evidence for the virtually absolute dependence of TNF-α-regulated genes on NF-κB. A constitutively active IKK2 was sufficient for maximal induction of most target genes, whereas a transdominant IκBα suppressed gene expression. Several genes with a critical role in atherogenesis were identified. The endothelial lipase (EL) gene, a key enzyme involved in lipoprotein metabolism, was investigated more in detail. Binding sites interacting with NF-κB in vitro and in vivo were identified and co-transfection experiments demonstrated the direct regulation of the EL promoter by NF-κB. We conclude that targeting the IKK/NF-κB pathway or specific genes downstream may be effective for the control or prevention of chronic inflammatory diseases such as atherosclerosis.

Human cells acquire vitamin C using two different transporter systems, the sodium-ascorbic acid co-transporters with specificity for ascorbic acid, and the facilitative glucose transporters with specificity for dehydroascorbic acid. There is no information on the mechanism of vitamin C transport across the intestinal barrier, a step that determines the bioavailability of vitamin C in humans. We used the colon carcinoma cell line CaCo-2 as an in vitro model for vitamin C transport in enterocyte-like cells. The results of transport kinetics, sodium dependence, inhibition studies, and reverse transcriptase-PCR analysis indicated that CaCo-2 cells express the sodium-ascorbate co-transporters SVCT1 and SVCT2, the dehydroascorbic acid transporters GLUT1 and GLUT3, and a third dehydroascorbic acid transporter with properties expected for GLUT2. Analysis by real time quantitative PCR revealed that the post-confluent differentiation of CaCo-2 cells was accompanied by a marked increase (4-fold) in the steadystate level of SVCT1 mRNA, without changes in SVCT2 mRNA levels. Functional studies revealed that the differentiated cells expressed only one functional ascorbic acid transporter having properties expected for SVCT1, and transported ascorbic acid with a V max that was increased at least 2-fold compared with pre-confluent cells. Moreover, post-confluent Caco-2 cells growing as monolayers in permeable filter inserts showed selective sorting of SVCT1 to the apical membrane compartment, without functional evidence for the expression of SVCT2. The identification of SVCT1 as the transporter that allows vectorial uptake of ascorbic acid in differentiated CaCo-2 cells has a direct impact on our understanding of the mechanism for vitamin C transport across the intestinal barrier.

Atherosclerosis is characterized by a complex immune response in the vessel wall, involving both inflammation and autoimmune processes. EpsteinBarr virus-induced gene 3 (Ebi3) is a member of the interleukin (IL)-12 heterodimeric cytokine family, which has important immunomodulatory functions. To date, little is known about the role of Ebi3 in vascular disease. We examined the expression of Ebi3 in human atheromatous lesions and analyzed its transcriptional regulation in vascular cells. The in situ expression of Ebi3 in human endarterectomy specimens was analyzed by immunohistochemistry. In these lesions, smooth muscle cells expressed Ebi3 as well as the IL-27␣/p28 and IL-12␣/p35 subunits. Primary aortic smooth muscle cells up-regulated Ebi3 in response to proinflammatory stimuli like tumor necrosis factor-␣ and interferon-␥. Interestingly , pretreatment of these cells with the peroxisome proliferator-activated receptor-␥ agonist rosiglitazone strongly reduced Ebi3 induction. Chromatin immunoprecipitation experiments revealed that this inhibition is due to interference with p65/RelA recruitment to the Ebi3 promoter. Our data support a possible role of Ebi3 in atherogenesis either as homodimer or as IL-27/IL-35 heterodimer, and suggest that Ebi3 could be an interesting target for therapeutic manipulation in atherosclerosis.

Abstract-Previous work has shown that c-Myc is required for adequate vasculogenesis and angiogenesis. To further investigate the contribution of Myc to these processes, we conditionally expressed c-Myc in embryonic endothelial cells using a tetracycline-regulated system. Endothelial Myc overexpression resulted in severe defects in the embryonic vascular system. Myc-expressing embryos undergo widespread edema formation and multiple hemorrhagic lesions. They die between embryonic days 14.5 and 17.5. The changes in vascular permeability are not caused by deficiencies in vascular basement membrane composition or pericyte coverage. However, the overall turnover of endothelial cells is elevated as is revealed by increased levels of both proliferation and apoptosis. Whole-mount immunohistochemical analysis revealed alterations in the architecture of capillary networks. The dermal vasculature of Myc-expressing embryos is characterized by a reduction in vessel branching, which occurs despite upregulation of the proangiogenic factors vascular endothelial growth factor-A and angiopoietin-2. Thus, the net outcome of an excess of vascular endothelial growth factor-A and angiopoietin-2 in the face of an elevated cellular turnover appears to be a defect in vascular integrity. by complex molecular and cellular processes and involves 2 distinct mechanisms. Vasculogenesis is responsible for de novo generation of vessels from angioblasts and occurs during the formation of the primitive vascular plexus in extraembryonic tissues and within the embryo. Angiogenesis subsumes formation of new vascular structures from preexisting vessels by sprouting and intussusception. 1 The immature vascular tree adjusts to changes in blood flow and oxygen demand by remodeling. This involves both new vessel growths by sprouting or intussusception, as well as vessel regression, a process called pruning. These processes result in a hierarchically organized vascular pattern that facilitates directional blood flow. 2 Later phases of vascular development involve the differential recruitment of associated support cells, such as smooth muscle cells and pericytes and the formation of vascular basement membranes. 1 Key molecular regulators of early vascular development are vascular endothelial growth factor (VEGF)-A and its cognate receptors VEGFR-1 and VEGFR-2. Mice with mutations in either VEGF-A or the receptors show severe defects in blood vessel formation and die early in embryogenesis before the establishment of blood circulation. Heterozygous VEGF-A embryos also show a lethal phenotype suggesting that fine-tuned regulation of components of the VEGF/ VEGFR system is essential for correct vascular differentiation. 3 Vascular remodeling and vessel stabilization depend on the angiopoietin (Ang)/Tie pathway. 3 The 2 Tie receptors, Tie1 and Tie2/Tek, encode receptor tyrosine kinases predominantly expressed in endothelial cells. 4 Tie2 expression is detectable starting in angioblasts and throughout development with reduced expression in quiescent endotheli...

Objective Determine the effect of bradykinin on solute permeability and cellular junctional proteins in human dermis microvascular endothelial cells. Methods Cells were characterized by immunofluorescence and fluorescence‐activated cell sorting. Macromolecular transport of dextran and albumin was monitored. Junctional protein expression and phosphorylation were determined by immunoblot analyses. Intracellular calcium and cAMP levels were evaluated. Target gene expression at mRNA and protein levels was determined. Results Human dermis microvascular endothelial cells comprised 97% lymphatic endothelial cells. Bradykinin increased the permeability to dextran in a concentration‐dependent manner, while reduced the permeability to albumin. Bradykinin treatment down‐regulated VE‐cadherin expression and affected its phosphorylation status at Tyr731. It also down‐regulated claudin‐5 expression at the transcriptional level through bradykinin‐2‐receptor signaling. An increase in the intracellular calcium levels and a reduction in the cAMP concentration were associated effects. Finally, bradykinin induced the up‐regulation of vascular endothelial growth factor‐C protein which was found increased in BK‐induced human dermis microvascular endothelial cells culture supernates. Conclusions Human dermis microvascular endothelial cells represent a model of lymphatic endothelial cells, in which bradykinin‐2‐receptor is expressed. Bradykinin‐induced bradykinin‐2‐receptor signaling through intracellular calcium mobilization and reduction in cAMP levels, triggered changes in solute permeability and cellular junction expression. It further up‐regulated vascular endothelial growth factors‐C protein expression, which is a key modulator of lymphatic vessels function and lymphangiogenesis.

Conclusion BK-induced B2R signaling promotes microvascular homeostasis destabilization by transiently disrupting the endothelial barrier function through the opening of cellular junctions, and up-regulation of vegfc and ang-2 expression.

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