Andreas Papapetropoulos

Bio: Andreas Papapetropoulos is an academic researcher from National and Kapodistrian University of Athens. The author has contributed to research in topics: Soluble guanylyl cyclase & Nitric oxide. The author has an hindex of 58, co-authored 214 publications receiving 17957 citations. Previous affiliations of Andreas Papapetropoulos include University of Texas Medical Branch & University of Ioannina.

Regulation of endothelium-derived nitric oxide production by the protein kinase Akt.

Abstract: Endothelial nitric oxide synthase (eNOS) is the nitric oxide synthase isoform responsible for maintaining systemic blood pressure, vascular remodelling and angiogenesis. eNOS is phosphorylated in response to various forms of cellular stimulation, but the role of phosphorylation in the regulation of nitric oxide (NO) production and the kinase(s) responsible are not known. Here we show that the serine/threonine protein kinase Akt (protein kinase B) can directly phosphorylate eNOS on serine 1179 and activate the enzyme, leading to NO production, whereas mutant eNOS (S1179A) is resistant to phosphorylation and activation by Akt. Moreover, using adenovirus-mediated gene transfer, activated Akt increases basal NO release from endothelial cells, and activation-deficient Akt attenuates NO production stimulated by vascular endothelial growth factor. Thus, eNOS is a newly described Akt substrate linking signal transduction by Akt to the release of the gaseous second messenger NO.

Biological Action of Leptin as an Angiogenic Factor

Abstract: Leptin is a hormone that regulates food intake, and its receptor (OB-Rb) is expressed primarily in the hypothalamus. Here, it is shown that OB-Rb is also expressed in human vasculature and in primary cultures of human endothelial cells. In vitro and in vivo assays revealed that leptin has angiogenic activity. In vivo, leptin induced neovascularization in corneas from normal rats but not in corneas from fa/fa Zucker rats, which lack functional leptin receptors. These observations indicate that the vascular endothelium is a target for leptin and suggest a physiological mechanism whereby leptin-induced angiogenesis may facilitate increased energy expenditure.

Nitric oxide production contributes to the angiogenic properties of vascular endothelial growth factor in human endothelial cells.

Abstract: Vascular endothelial growth factor (VEGF) is a regulator of vasculogenesis and angiogenesis. To investigate the role of nitric oxide (NO) in VEGF-induced proliferation and in vitro angiogenesis, human umbilical vein endothelial cells (HUVEC) were used. VEGF stimulated the growth of HUVEC in an NO-dependent manner. In addition, VEGF promoted the NO-dependent formation of network-like structures in HUVEC cultured in three dimensional (3D) collagen gels. Exposure of cells to VEGF led to a concentration-dependent increase in cGMP levels, an indicator of NO production, that was inhibited by nitro-L-arginine methyl ester. VEGF-stimulated NO production required activation of tyrosine kinases and increases in intracellular calcium, since tyrosine kinase inhibitors and calcium chelators attenuated VEGF-induced NO release. Moreover, two chemically distinct phosphoinositide 3 kinase (PI-3K) inhibitors attenuated NO release after VEGF stimulation. In addition, HUVEC incubated with VEGF for 24 h showed an increase in the amount of endothelial NO synthase (eNOS) protein and the release of NO. In summary, both short- and long-term exposure of human EC to VEGF stimulates the release of biologically active NO. While long-term exposure increases eNOS protein levels, short-term stimulation with VEGF promotes NO release through mechanisms involving tyrosine and PI-3K kinases, suggesting that NO mediates aspects of VEGF signaling required for EC proliferation and organization in vitro.

Dynamic activation of endothelial nitric oxide synthase by Hsp90

Abstract: Heat-shock protein 90 (Hsp90) coordinates the trafficking and regulation of diverse signalling proteins, but its precise role in regulating specific cellular targets is not known1,2. Here we show that Hsp90 associates with endothelial nitric oxide synthase (eNOS) and is rapidly recruited to the eNOS complex by agonists that stimulate production of nitric oxide, namely vascular endothelial growth factor, histamine and fluid shear stress. Moreover, the binding of Hsp90 to eNOS enhances the activation of eNOS. Inhibition of signalling through Hsp90 attenuates both agonist-stimulated production of nitric oxide and endothelium-dependent relaxation of isolated blood vessels. Our results indicate that Hsp90 facilitates signalling mediated by growth-factor, G-protein and mechanotransduction pathways that lead to the activation of eNOS. These observations indicate that in addition to its role as a molecular chaperone involved in protein folding and maturation, Hsp90 may also be recruited to cellular targets depending on the activation state of the cell.

Hydrogen sulfide is an endogenous stimulator of angiogenesis

Abstract: The goal of the current study was to investigate the role of exogenous and endogenous hydrogen sulfide (H2S) on neovascularization and wound healing in vitro and in vivo Incubation of endothelial cells (ECs) with H2S enhanced their angiogenic potential, evidenced by accelerated cell growth, migration, and capillary morphogenesis on Matrigel Treatment of chicken chorioallantoic membranes (CAMS) with H2S increased vascular length Exposure of ECs to H2S resulted in increased phosphorylation of Akt, ERK, and p38 The KATP channel blocker glibenclamide or the p38 inhibitor SB203580 abolished H2S-induced EC motility Since glibenclamide inhibited H2S-triggered p38 phosphorylation, we propose that KATP channels lay upstream of p38 in this process When CAMs were treated with H2S biosynthesis inhibitors dl-propylargylglycine or beta-cyano-L-alanine, a reduction in vessel length and branching was observed, indicating that H2S serves as an endogenous stimulator of the angiogenic response Stimulation of ECs with vascular endothelial growth factor (VEGF) increased H2S release, while pharmacological inhibition of H2S production or KATP channels or silencing of cystathionine gamma-lyase (CSE) attenuated VEGF signaling and migration of ECs These results implicate endothelial H2S synthesis in the pro-angiogenic action of VEGF Aortic rings isolated from CSE knockout mice exhibited markedly reduced microvessel formation in response to VEGF when compared to wild-type littermates Finally, in vivo, topical administration of H2S enhanced wound healing in a rat model, while wound healing was delayed in CSE−/− mice We conclude that endogenous and exogenous H2S stimulates EC-related angiogenic properties through a KATP channel/MAPK pathway

Angiogenesis in cancer and other diseases

Abstract: Pathological angiogenesis is a hallmark of cancer and various ischaemic and inflammatory diseases Concentrated efforts in this area of research are leading to the discovery of a growing number of pro- and anti-angiogenic molecules, some of which are already in clinical trials The complex interactions among these molecules and how they affect vascular structure and function in different environments are now beginning to be elucidated This integrated understanding is leading to the development of a number of exciting and bold approaches to treat cancer and other diseases But owing to several unanswered questions, caution is needed

Biochemistry and molecular cell biology of diabetic complications

Abstract: Diabetes-specific microvascular disease is a leading cause of blindness, renal failure and nerve damage, and diabetes-accelerated atherosclerosis leads to increased risk of myocardial infarction, stroke and limb amputation. Four main molecular mechanisms have been implicated in glucose-mediated vascular damage. All seem to reflect a single hyperglycaemia-induced process of overproduction of superoxide by the mitochondrial electron-transport chain. This integrating paradigm provides a new conceptual framework for future research and drug discovery.

Aggregation-Induced Emission: Together We Shine, United We Soar!

Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China