Angiopoietin-1 (Ang1) is a strong apoptosis survival factor for endothelial cells. In this study, the receptor/second messenger signal transduction pathway for the antiapoptotic effect of Ang1 on human umbilical vein endothelial cells was examined. Pretreatment with soluble Tie2 receptor, but not Tie1 receptor, blocked the Ang1-induced antiapoptotic effect. Ang1 induced phosphorylation of Tie2 and the p85 subunit of phosphatidylinositol 3'-kinase (PI 3'-kinase) and increased PI 3'-kinase activity in a dose-dependent manner. The PI 3'-kinase-specific inhibitors wortmannin and LY294002 blocked the Ang1-induced antiapoptotic effect. Ang1 induced phosphorylation of the serine-threonine kinase Akt at Ser473 in a PI 3'-kinase-dependent manner. Expression of a dominant-negative form of Akt reversed the Ang1-induced antiapoptotic effect. Ang1 mRNA and protein were present in vascular smooth muscle cells but not in endothelial cells. Cultured vascular smooth muscle cells, but not human umbilical vein endothelial cells, secreted Ang1. These findings indicate that the Tie2 receptor, PI 3'-kinase, and Akt are crucial elements in the signal transduction pathway leading to endothelial cell survival induced by the paracrine activity of Ang1.
Abstract-Angiopoietin-1 (Ang1) is a strong inducer of endothelial cell sprouting, which is a first step in both angiogenesis and neovascularization. We examined the mechanisms underlying Ang1-induced cell sprouting using porcine pulmonary artery endothelial cells. Ang1 induced the nondirectional and directional migration of endothelial cells mediated through the Tie2 but not the Tie1 receptor. Ang1 induced tyrosine phosphorylation of p125 FAK , and this phosphorylation was dependent on phosphatidylinositol (PI) 3Ј-kinase activity. Ang1 induced the secretion of plasmin and matrix metalloproteinase-2 (MMP-2), which is inhibited by PI 3Ј-kinase inhibitors. Ang1 also induced the secretion of small amounts of proMMP-3 and proMMP-9 but not proMMP-1. Ang1 suppressed the secretion of tissue inhibitor of metalloproteinase-2 (TIMP-2), but not of TIMP-1. Addition of ␣ 2 -antiplasmin, a combination of TIMP-1 and TIMP-2, or PI 3Ј-kinase inhibitors inhibited Ang1-induced sprouting activity. Therefore, Ang1-induced sprouting activity in endothelial cells may be accomplished by cytoskeletal changes and secretion of proteinases and may be largely mediated through intracellular PI 3Ј-kinase activation. (Circ Res. 2000;86:952-959.)
Using degenerate PCR we isolated a cDNA encoding a novel 406- and 410-amino acid protein from human and mouse embryonic cDNAs and have designated it 'hepatic fibrinogen/angiopoietin-related protein' (HFARP). The N-terminal and C-terminal portions of HFARP contain the characteristic coiled-coil domains and fibrinogen-like domains that are conserved in angiopoietins. In human and mouse tissues, HFARP mRNA is specifically expressed in the liver. HFARP mRNA and protein are mainly present in the hepatocytes. HFARP has a highly hydrophobic region at the N-terminus that is typical of a secretory signal sequence and one consensus glycosylation site. Recombinant HFARP expressed in COS-7 cells is secreted and glycosylated. HFARP protein is present not only in the hepatocytes, but also in the circulating blood. Recombinant HFARP acts as an apoptosis survival factor for vascular endothelial cells, but does not bind to Tie1 or Tie2 (endothelial-cell tyrosine kinase receptors). These results suggest that HFARP may exert a protective function on endothelial cells through an endocrine action.
A new naphthoquinone-based chemosensor 2-((3hydroxyphenyl)amino)-3-(phenylthio)naphthalene-1,4-dione (2HPN) was successfully synthesized for the selective detection of Fe 2+ . The sensing property of the chemosensor 2HPN was evaluated in aqueous acetonitrile (CH 3 CN) medium by a fluorescence emission method. The metal-binding studies of the ligand 2HPN showed selective "turn-on" fluorescence responses for Fe 2+ (K a = 1.0 × 10 6 M −1 ). The detection limit of the ligand 2HPN to Fe 2+ was calculated to be 0.272 μM, which is lower than the World Health Organization recommendation (0.3 mg/L) in drinking water. The most significant feature of the obtained chemosensor 2HPN is its ability to sense Fe 2+ via naked-eye detection over various metal ions. The chemosensor operated via the intramolecular charge transfer effect, which was supported by Fourier transform infrared analysis, NMR titrations, and quantum chemical calculations. The efficiency of the chemosensor 2HPN as a biomarker for Fe 2+ was successfully proven by imaging in human cancer cells and zebrafish. Thus, the chemosensor 2HPN could be a useful biomarker for the precise sensing of Fe 2+ in clinical diagnosis.
A simple naphthoquinone−dopamine hybrid (2CND) was designed and fabricated as a colorimetric and fluorescence chemosensor for the selective recognition of Sn 2+ in the aqueous medium. This simply accessible chemosensor was prepared by connecting of naphthoquinone acceptor and dopamine donor moieties via Michael-like addition reaction. The chemosensor 2CND showed a turn-on fluorescence response which operated through the inhibited photoinduced electron transfer effect. The sensor probe shows remarkable performance, such as high selectivity, sensitivity, excellent water solubility, and rapid response to Sn 2+ (less than 5 s). The detection mechanism of the 2CND−Sn 2+ complex was supported by FT-IR analysis, 1 H NMR titration, and DFT calculations. Besides, the 1:1 binding stoichiometry was confirmed by the ESI-MS spectral analysis. Furthermore, the chemosensor 2CND has been successfully employed as a fluorescence probe to monitor trace Sn 2+ in live cells and zebrafish. The sensor probe 2CND could serve as an effective fluorescence bioimaging probe for the discriminative detection of diseased and normal human cells.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.