Ebselen inhibits tumor necrosis factor-alpha-induced c-Jun N-terminal kinase activation and adhesion molecule expression in endothelial cells

Tumor necrosis factor-alpha (TNF-alpha) stimulates expression of endothelial cell (EC) genes that may promote atherosclerosis in part by an activation of mitogen-activated protein (MAP) kinases. Ebselen (2-phenyl-1,2-benzisoselenazol-3[2H]-one), a selenoorganic compound, is effective for acute ischemic stroke; however, its effect on EC has not yet been elucidated. We examined the effect of ebselen on TNF-alpha-induced MAP kinase activation and adhesion molecule expression in cultured human umbilical vein endothelial cells (HUVEC). Extracellular signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK) and p38 were rapidly and significantly activated by TNF-alpha in HUVEC. TNF-alpha-induced JNK activation was inhibited by ebselen, whereas ERK1/2 and p38 were not affected. Apoptosis signal-regulated kinase 1 (ASK1) was suggested to be involved in TNF-alpha-induced JNK activation because transfection of kinase-inactive ASK1 inhibited TNF-alpha-induced JNK activation. Ebselen inhibited TNF-alpha-induced TNF receptor-associated factor 2 (TRAF2)-ASK1 complex formation and phosphorylation of stress-activated protein kinase ERK kinase 1 (SEK1), which is an upstream signaling molecule of JNK. Finally, TNF-alpha-induced activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) activation and resultant intracellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expressions were inhibited by ebselen. Specific inhibitors for JNK and NF-kappaB also inhibited TNF-alpha-induced ICAM-1 and VCAM-1 expressions in HUVEC. These findings suggest that ebselen prevents TNF-alpha-induced EC activation through the inhibition of TRAF2-ASK1-SEK1 signaling pathway, which leads to JNK activation. Inhibition of JNK by ebselen may imply its usefulness for the prevention of atherosclerosis relevant to EC activation.     

Endothelial adhesion molecule ESAM binds directly to the multidomain adaptor MAGI-1 and recruits it to cell contacts

Endothelial cell-selective adhesion molecule (ESAM) is an immunoglobulin-like transmembrane protein associated with endothelial tight junctions (TJ). Based on a yeast two-hybrid screen, we have identified the membrane-associated guanylate kinase protein MAGI-1 as an intracellular binding partner of ESAM. MAGI-1 is a multidomain adaptor protein, which binds to transmembrane, cytoskeletal, and signaling molecules, and has been localized to tight junctions in epithelial cells. MAGI-1 associates with the very C-terminal sequence of ESAM most likely through a PDZ domain-mediated interaction. The direct interaction between ESAM and MAGI-1 was confirmed by pull-down experiments. The two proteins formed stable complexes in transfected Chinese hamster ovary (CHO) cells, which could be immunoisolated. We found MAGI-1 to be associated with cell-cell contacts in human umbilical vein endothelial cells (HUVECs) and in mouse endothelium, where it colocalizes with ESAM. In CHO cells, recruitment of MAGI-1 to cell contacts required the presence of ESAM. Hence, ESAM may be involved in anchoring MAGI-1 at endothelial tight junctions.     

Identification and characterization of a novel gene EOLA1 stimulating ECV304 cell proliferation

To study the changes in gene expression in endothelial cells stimulated by lipopolysaccharide (LPS) we performed subtraction hybridization on control human umbilical vein endothelial cells (HUVEC) versus HUVEC stimulated by LPS. A novel cDNA, named endothelial-overexpressed lipopolysaccharide-associated factor 1 (EOLA1), was cloned from our differentially expressed EST database of HUVEC cDNA library (GenBank Accession No. ). Computational analysis showed that EOLA1 is 1404bp long, encoding a 158aa, 17.8kDa protein, mapped to chromosome Xq27.4 with 5 exons, expressed in different human normal tissues and cancer cell lines. Using the EOLA1 cDNA as bait, we performed a yeast two-hybrid screening of a human liver cDNA library and identified metallothionein 2A (MT2A) as associated protein. Stable transfection of EOLA1 stimulates ECV304 cell proliferation. Our data suggest that the physical interaction of EOLA1 and MT2A may have an important role of cell protection in inflammation reaction.     

Functional role of TRPC proteins in vivo: lessons from TRPC-deficient mouse models

In order to elucidate the functional role of TRPC genes, in vivo, the targeted inactivation of these genes in mice is an invaluable technique. In this review, we summarize the currently available results on the phenotype of TRPC-deficient mouse lines. The analysis of mice with targeted deletion in three TRPC genes demonstrates that these proteins represent essential constituents of agonist-activated and phospholipase C-dependent Ca2+ entry channels in primary cells. Furthermore, from the deficits observed in these TRPC-deficient mouse lines a striking number of biological functions could already be ascribed to TRPC2, TRPC4, and TRPC6, not only on the cellular level but also for complex organ functions and integrative physiology. Accordingly, TRPC2 proteins are critically involved in pheromone sensing by neurones of the vomeronasal organ and, thereby, in the regulation of sexual and social behavior of mice, TRPC4 proteins are essential determinants of endothelial-dependent regulation of vascular tone, endothelial permeability, and neurotransmitter release from thalamic interneurones, and TRPC6 proteins are supposed to have a fundamental role in the regulation of smooth muscle tone in blood vessels and lung.     

Approach for defining endogenous reference genes in gene expression experiments

The quantification of gene expression by real-time polymerase chain reaction (PCR) has revolutionized the field of gene expression analysis. Due to its sensitivity and flexibility it is becoming the method of choice for many investigators. However, good normalization protocols still have to be implemented to facilitate data exchange and comparison. We have designed primers for 10 unrelated genes and developed a simple protocol to detect genes with stable expression that are suitable for use as endogenous reference genes for further use in the normalization of gene expression data obtained by real-time PCR. Using this protocol, we were able to identify human proteosome subunit Y as a reliable endogenous reference gene for human umbilical vein endothelial cells treated for up to 18 h with TNFalpha, IL-4, or IFNgamma and for B cells isolated from healthy controls and patients suffering from IgA nephropathy. Other optional endogenous reference genes that can be considered are phosphomannomutase (PPMM) and actin for endothelial cells and glyceraldehyde-3-phosphate dehydrogenase and PPMM for B cells.     

Role of lateral cell-cell border location and extracellular/transmembrane domains in PECAM/CD31 mechanosensation

Phosphorylation of tyrosine residues on platelet-endothelial cell adhesion molecule-1 (PECAM-1), followed by signal transduction events, has been described in endothelial cells following exposure to hyperosmotic and fluid shear stress. However, it is unclear whether PECAM-1 functions as a primary mechanosensor in this process. Utilizing a PECAM-1-null EC-like cell line, we examined the importance of cellular localization and the extracellular and transmembrane domains in PECAM-1 phosphorylation responses to mechanical stress. Tyrosine phosphorylation of PECAM-1 was stimulated in response to mechanical stress in null cells transfected either with full length PECAM-1 or with PECAM-1 mutants that do not localize to the lateral cell-cell adhesion site and that do not support homophilic binding between PECAM-1 molecules. Furthermore, null cells transfected with a construct that contains the intact cytoplasmic domain of PECAM-1 fused to the extracellular and transmembrane domains of the interleukin-2 receptor also underwent mechanical stress-induced PECAM-1 tyrosine phosphorylation. These findings suggest that mechanosensitive PECAM-1 may lie downstream of a primary mechanosensor that activates a tyrosine kinase.     

Augmented heme oxygenase-1 induces prostaglandin uptake via the prostaglandin transporter in micro-vascular endothelial cells

Previous studies show that expression of heme oxygenase-1 (HO-1) in endothelial cells results in decreased cyclooxygenase expression and prostaglandin (PG) levels through limiting heme availability. Regulation of PGs, important inflammatory mediators, may contribute to the anti-inflammatory potential of HO-1. Here we examine the effects of HO-1 expression on PG clearance via the prostaglandin transporter (PGT). Endothelial cells expressing human HO-1 via retroviral transfer exhibit approximately 7-fold higher levels of PGT RNA and equivalently elevated uptake of [(3)H]PGE(2). The pattern and extent of uptake and the substrate inhibitory constants of PGE(2), PGF(2alpha), and thromboxane B(2) are similar to those of cloned PGT. Treatment of cells with stannous chloride, an inducer of HO-1, results in increased expression of PGT while incubation of cells expressing human HO-1 with stannic mesophorphyrin, a substrate inhibitor of HO-1, decreases PG uptake. Therefore, PG clearance via PGT may contribute to the cellular regulation of PG levels by HO-1.     

A novel RGDS-analog inhibits angiogenesis in vitro and in vivo

In this study the anti-angiogenic action of a novel non-peptide RGDS-analog named RAM was tested in vitro and in vivo. RAM inhibited FGF-2-induced chemotaxis by 80% in an adhesion-independent way. Further, it induced HUVEC-apoptosis in collagen-seeded HUVEC, indicating that such pro-apoptotic effect was adhesion-independent. In vivo studies revealed that RAM inhibited FGF-2 induced angiogenesis by 60% in the mouse Matrigel-assay and in the chicken-egg chorion-allantoic membrane assay. Finally, RAM was markedly more stable in serum as compared to the template RGDS and after 24 h incubation in 100% serum was significantly more active than RGDS. Taken together these results show that RAM exerts anti-chemotactic and pro-apoptotic effects, by an unexpected adhesion-independent mechanism, as we have recently shown for the template RGDS molecule [Blood 103 (2004) 4180], and has in vivo relevant anti-angiogenic properties, with marked stability in serum; therefore, RAM represents a novel promising anti-angiogenic molecule.     

Anti-inflammatory effects of tocopherol metabolites

Our objective was to assess the anti-inflammatory effects of alpha-tocopherol, gamma-tocopherol, and their metabolites 2,5,7,8-tetramethyl-2-(beta-carboxyethyl)-6-hydroxychroman (alpha-CEHC) and 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxychroman (gamma-CEHC) in defined cell culture systems. Rat aortic endothelial cells and mouse microglial cultures were treated with tumor necrosis factor TNFalpha or bacterial lipopolysaccharide (LPS) and nitrite and prostaglandin E(2) (PGE(2)) were measured. alpha-CEHC suppressed TNFalpha-stimulated nitrite production in both cell types, whereas both CEHC derivatives inhibited LPS-stimulated microglial nitrite efflux. Both alpha-CEHC and gamma-CEHC inhibited microglial PGE(2) production, but neither alpha- nor gamma-tocopherol was effective at inhibiting cytokine-stimulated inflammatory processes. These results show that the anti-inflammatory effects of tocopherols are highly cell type-, stimulus-, and endpoint-dependent.     

Critical conditions for pattern formation and in vitro tubulogenesis driven by cellular traction fields

In vitro angiogenesis assays have shown that tubulogenesis of endothelial cells within biogels, like collagen or fibrin gels, only appears for a critical range of experimental parameter values. These experiments have enabled us to develop and validate a theoretical model in which mechanical interactions of endothelial cells with extracellular matrix influence both active cell migration--haptotaxis--and cellular traction forces. Depending on the number of cells, cell motility and biogel rheological properties, various 2D endothelial patterns can be generated, from non-connected stripe patterns to fully connected networks, which mimic the spatial organization of capillary structures. The model quantitatively and qualitatively reproduces the range of critical values of cell densities and fibrin concentrations for which these cell networks are experimentally observed. We illustrate how cell motility is associated to the self-enhancement of the local traction fields exerted within the biogel in order to produce a pre-patterning of this matrix and subsequent formation of tubular structures, above critical thresholds corresponding to bifurcation points of the mathematical model. The dynamics of this morphogenetic process is discussed in the light of videomicroscopy time lapse sequences of endothelial cells (EAhy926 line) in fibrin gels. Our modeling approach also explains how the progressive appearance and morphology of the cellular networks are modified by gradients of extracellular matrix thickness.