Hyperoxia induces retinal vascular endothelial cell apoptosis through formation of peroxynitrite

Hyperoxia exposure induces capillary endothelial cell apoptosis in the developing retina, leading to vaso-obliteration followed by proliferative retinopathy. Previous in vivo studies have shown that endothelial nitric oxide synthase (NOS3) and peroxynitrite are important mediators of the vaso-obliteration. Now we have investigated the relationship between hyperoxia, NOS3, peroxynitrite, and endothelial cell apoptosis by in vitro experiments using bovine retinal endothelial cells (BREC). We found that BREC exposed to 40% oxygen (hyperoxia) for 48 h underwent apoptosis associated with activation of caspase-3 and cleavage of the caspase substrate poly(ADP-ribose) polymerase. Hyperoxia-induced apoptosis was associated with increased formation of nitric oxide, peroxynitrite, and superoxide anion and was blocked by treatment with uric acid, nitro-L-arginine methyl ester, or superoxide dismutase. Analyses of the phosphatidylinositol 3-kinase/Akt kinase survival pathway in cells directly treated with peroxynitrite revealed inhibition of VEGF- and basic FGF-induced activation of Akt kinase. These results suggest that hyperoxia-induced formation of peroxynitrite induces BREC apoptosis by crippling key survival pathways and that blocking peroxynitrite formation prevents apoptosis. These data may have important clinical implications for infants at risk of retinopathy of prematurity. oxygen-induced retinopathy; vaso-obliteration; superoxide; nitric oxide     

Strategies for structural proteomics of prokaryotes: Quantifying the advantages of studying orthologous proteins and of using both NMR and X-ray crystallography approaches

Only about half of non-membrane-bound proteins encoded by either bacterial or archaeal genomes are soluble when expressed in Escherichia coli (Yee et al., Proc Natl Acad Sci USA 2002;99:1825-1830; Christendat et al., Prog Biophys Mol Biol 200;73:339-345). This property limits genome-scale functional and structural proteomics studies, which depend on having a recombinant, soluble version of each protein. An emerging strategy to increase the probability of deriving a soluble derivative of a protein is to study different sequence homologues of the same protein, including representatives from thermophilic organisms, based on the assumption that the stability of these proteins will facilitate structural analysis. To estimate the relative merits of this strategy, we compared the recombinant expression, solubility, and suitability for structural analysis by NMR and/or X-ray crystallography for 68 pairs of homologous proteins from E. coli and Thermotoga maritima. A sample suitable for structural studies was obtained for 62 of the 68 pairs of homologs under standardized growth and purification procedures. Fourteen (eight E. coli and six T. maritima proteins) samples generated NMR spectra of a quality suitable for structure determination and 30 (14 E. coli and 16 T. maritima proteins) samples formed crystals. Only three (one E. coli and two T. maritima proteins) samples both crystallized and had excellent NMR properties. The conclusions from this work are: (1) The inclusion of even a single ortholog of a target protein increases the number of samples for structural studies almost twofold; (2) there was no clear advantage to the use of thermophilic proteins to generate samples for structural studies; and (3) for the small proteins analyzed here, the use of both NMR and crystallography approaches almost doubled the number of samples for structural studies.     

Heterocyclic ketones as inhibitors of histone deacetylase

Several heterocyclic ketones were investigated as potential inhibitors of histone deacetylase. Nanomolar inhibitors such as 22 and 25 were obtained, the anti-proliferative activity of which were shown to be mediated by HDAC inhibition.     

Crystal structure of mycothiol synthase (Rv0819) from Mycobacterium tuberculosis shows structural homology to the GNAT family of N-acetyltransferases

Mycothiol is the predominant low-molecular weight thiol produced by actinomycetes, including Mycobacterium tuberculosis. The last reaction in the biosynthetic pathway for mycothiol is catalyzed by mycothiol synthase (MshD), which acetylates the cysteinyl amine of cysteine-glucosamine-inositol (Cys-GlcN-Ins). The crystal structure of MshD was determined in the presence of coenzyme A and acetyl-CoA. MshD consists of two tandem-repeated domains, each exhibiting the Gcn5-related N-acetyltransferase (GNAT) fold. These two domains superimpose with a root-mean-square deviation of 1.7 A over 88 residues, and each was found to bind one molecule of coenzyme, although the binding sites are quite different. The C-terminal domain has a similar active site to many GNAT members in which the acetyl group of the coenzyme is presented to an open active site slot. However, acetyl-CoA bound to the N-terminal domain is buried, and is apparently not positioned to promote acetyl transfer. A modeled substrate complex indicates that Cys-GlcN-Ins would only fill a portion of a negatively charged channel located between the two domains. This is the first structure determined for an enzyme involved in the biosynthesis of mycothiol.     

Synthesis and structure-activity relationship of 2-amino-3-heteroaryl-quinoxalines as non-peptide,small-molecule antagonists for interleukin-8 receptor

Interleukin-8 modulation is implicated in many inflammatory and cancer diseases. Starting from a mass-screening hit, the synthesis and structure-activity relationship of 2-amino-3-heteroarylquinoxalines as non-peptide, small molecule interleukine-8 receptor antagonists have been developed. The optimized derivatives, PD 0210293 (13y) and PD 0220245 (13r), show inhibition of both IL-8 receptor binding and IL-8-mediated neutrophil chemotaxis.     

Solid-phase synthesis and biochemical evaluation of conformationally constrained analogues of deglycobleomycin A5

Deglycobleomycin binds to and degrades the self-complementary oligonucleotide d(CGCTAGCG)(2) in a sequence selective fashion. A previous modeling study [J. Am. Chem. Soc. 120, (1998), 7450] had shown that, during binding to double stranded DNA, the conformation of the methylvalerate domain of deglycoBLM approximated that of S-proline. In the belief that an analogue of deglycoBLM structurally constrained to mimic the DNA-bound conformation might exhibit facilitated DNA binding and cleavage, an analogue of deglycoBLM was prepared in which the methylvalerate moiety was replaced by S-proline. This deglycoBLM analogue, as well as the related analogue containing R-proline, was synthesized on a TentaGel resin. Both of the analogues were found to be capable of binding Fe(2+) and activating O(2) for transfer to styrene. However, both deglycoBLM analogues exhibited diminished abilities to effect the relaxation of supercoiled plasmid DNA, and neither mediated sequence selective DNA cleavage.     

Intrauterine hypertension decreases lung VEGF expression and VEGF inhibition causes pulmonary hypertension in the ovine fetus

Although vascular endothelial growth factor (VEGF) plays a vital role in lung vascular growth in the embryo, its role in maintaining endothelial function and modulating vascular structure during late fetal life has not been studied. We hypothesized that impaired lung VEGF signaling causes pulmonary hypertension, endothelial dysfunction, and structural remodeling before birth. To determine whether lung VEGF expression is decreased in an experimental model of persistent pulmonary hypertension of the newborn (PPHN), we measured lung VEGF and VEGF receptor protein content from fetal lambs 7-10 days after ductus arteriosus ligation (132-140 days gestation; term = 147 days). In contrast with the surge in lung VEGF expression during late gestation in controls, chronic intrauterine pulmonary hypertension reduced lung VEGF expression by 78%. To determine whether VEGF inhibition during late gestation causes pulmonary hypertension, we treated fetal lambs with EYE001, an aptamer that specifically inhibits VEGF(165). Compared with vehicle controls, EYE001 treatment elevated pulmonary artery pressure and pulmonary vascular resistance by 22 and 50%, respectively, caused right ventricular hypertrophy, and increased wall thickness of small pulmonary arteries. EYE001 treatment reduced lung endothelial nitric oxide synthase protein content by 50% and preferentially impaired the pulmonary vasodilator response to ACh, an endothelium-dependent agent. We conclude that chronic intrauterine pulmonary hypertension markedly decreases lung VEGF expression and that selective inhibition of VEGF(165) mimics the structural and physiological changes of experimental PPHN. We speculate that hypertension downregulates VEGF expression in the developing lung and that impaired VEGF signaling may contribute to the pathogenesis of PPHN.     

Hybrids of dendritic cells and tumor cells generated by electrofusion simultaneously present immunodominant epitopes from multiple human tumor-associated antigens in the context of MHC class I and class II molecules

Hybrid cells generated by fusing dendritic cells with tumor cells (DC-TC) are currently being evaluated as cancer vaccines in preclinical models and human immunization trials. In this study, we evaluated the production of human DC-TC hybrids using an electrofusion protocol previously defined for murine cells. Human DCs were electrically fused with allogeneic melanoma cells (888mel) and were subsequently analyzed for coexpression of unique DC and TC markers using FACS and fluorescence microscopy. Dually fluorescent cells were clearly observed using both techniques after staining with Abs against distinct surface molecules suggesting that true cell fusion had occurred. We also evaluated the ability of human DC-TC hybrids to present tumor-associated epitopes in the context of both MHC class I and class II molecules. Allogeneic DCs expressing HLA-A*0201, HLA-DR beta 1*0401, and HLA-DR beta 1*0701 were fused with 888mel cells that do not express any of these MHC molecules, but do express multiple melanoma-associated Ags. DC-888mel hybrids efficiently presented HLA-A*0201-restricted epitopes from the melanoma Ags MART-1, gp100, tyrosinase, and tyrosinase-related protein 2 as evaluated by specific cytokine secretion from six distinct CTL lines. In contrast, DCs could not cross-present MHC class I-restricted epitopes after exogenously loading with gp100 protein. DC-888mel hybrids also presented HLA-DR beta 1*0401- and HLA-DR beta 1*0701-restricted peptides from gp100 to CD4(+) T cell populations. Therefore, fusions of DCs and tumor cells express both MHC class I- and class II-restricted tumor-associated epitopes and may be useful for the induction of tumor-reactive CD8(+) and CD4(+) T cells in vitro and in human vaccination trials.