Docosahexaenoic acid and 17 beta-estradiol co-treatment is more effective than 17 beta-estradiol alone in maintaining bone post-ovariectomy

Bone-protective effects of combined treatment with long chain polyunsaturated fatty acids (LCPUFAs) and estrogenic compounds following ovariectomy have previously been reported. Recent evidence suggests the n-3 LCPUFA docosahexaenoic acid (DHA, 22:6n-3) is particularly bone-protective. The aim of this study was to determine whether combined treatment with DHA and estrogenic compounds has a beneficial effect on bone mass in ovariectomized (OVX) rats. Rats were randomized into 9 groups and either ovariectomized (8 groups) or sham-operated (1 group). Using a 2 x 4 factorial design approach, OVX animals received either no estrogenic compound, genistein (20 mg/kg body weight/day), daidzein, (20 mg/kg body weight/day) or 17 beta-estradiol (1 microg/day) with or without DHA (0.5 g/kg body weight/day) for 18 weeks. Bone mineral content (BMC), area (BA), and density (BMD), plasma osteocalcin and IL-6 concentrations, and red blood cell (RBC) fatty acid composition were measured. Femur BMC was significantly greater in animals treated with DHA or 17 beta-estradiol than in ovariectomized controls. Plasma carboxylated osteocalcin was significantly higher in DHA-treated animals and total osteocalcin significantly lower in 17 beta-estradiol-treated animals compared with ovariectomized controls. There were significant interactions between treatment with estrogenic compounds and DHA for femur BMC, plasma IL-6 concentration, and RBC fatty acid composition. Combined treatment with 17beta-estradiol+DHA was more effective than either treatment alone at preserving femur BMC and lowering circulating concentrations of pro-inflammatory IL-6. The percentage of n-3 LCPUFAs in RBCs was significantly greater in animals receiving 17 beta-estradiol+DHA compared with either treatment alone. There was no beneficial effect of combined DHA and phytoestrogen treatment on bone. Results from this study raise the possibility that co-treatment with 17 beta-estradiol and DHA may allow a lower dose of 17 beta-estradiol to be used to provide the same bone-protective effects as when 17 beta-estradiol is administered alone.     

A robust screen for novel antibiotics: specific knockout of the initiator of bacterial DNA replication

We have developed a novel type of a positive screen for the discovery of antibacterial compounds that target the Escherichia coli replication initiator protein DnaA. DnaA is an essential replication protein, conserved in (almost) all bacteria--including all human pathogens--and no existing antibiotics target the main components of the DNA replication machinery. This makes DnaA an attractive target and compounds discovered by this screen will constitute a new group of antibiotics. The conditional mutant, dnaA219, has a cold sensitive phenotype due to overreplication. In the screen, a DnaA inhibitor will reduce DnaA overactivity and thus restore growth at the nonpermissive temperature. This positive type of selection utilizes the rare phenomenon of lethal overactivity. In addition, the mutant strain has been made independent of DnaA activity by introduction of an alternative initiation pathway that allows growth under conditions of complete knockdown of DnaA. The resulting dnaA219rnhA strain is the basis of a robust, cell-based assay amenable to high-throughput screening. The screening assay has been validated against (1) a library of microbial fermentation extracts and (2) a known intracellular DnaA inhibitor.     

Synthesis and antiviral activity of HCV NS3/4A peptidomimetic boronic acid inhibitors

A new series of NS3/4A protease boronic acid inhibitors is described. The compounds show good biochemical potency and cellular activity. The peptidomimetic inhibitors were evaluated against proteases from different HCV genotypes and clinically relevant NS3/4A mutants. Compound 28 displayed subnanomolar to single digit nanomolar potencies in the enzymatic assays and an EC₅₀ of 25 nM in the replicon cell-based assay.     

PBX1 is dispensable for neural commitment of RA-treated murine ES cells

Experimentation with PBX1 knockout mice has shown that PBX1 is necessary for early embryogenesis. Despite broad insight into PBX1 function, little is known about the underlying target gene regulation. Utilizing the Cre–loxP system, we targeted a functionally important part of the homeodomain of PBX1 through homozygous deletion of exon-6 and flanking intronic regions leading to exon 7 skipping in embryonic stem (ES) cells. We induced in vitro differentiation of wild-type and PBX1 mutant ES cells by aggregation and retinoic acid (RA) treatment and compared their profiles of gene expression at the ninth day post-reattachment to adhesive media. Our results indicate that PBX1 interactions with HOX proteins and DNA are dispensable for RA-induced ability of ES to express neural genes and point to a possible involvement of PBX1 in the regulation of imprinted genes.     

Conformational Targeting of Fibrillar Polyglutamine Proteins in Live Cells Escalates Aggregation and Cytotoxicity

Background

Misfolding- and aggregation-prone proteins underlying Parkinson''s, Huntington''s and Machado-Joseph diseases, namely α-synuclein, huntingtin, and ataxin-3 respectively, adopt numerous intracellular conformations during pathogenesis, including globular intermediates and insoluble amyloid-like fibrils. Such conformational diversity has complicated research into amyloid-associated intracellular dysfunction and neurodegeneration. To this end, recombinant single-chain Fv antibodies (scFvs) are compelling molecular tools that can be selected against specific protein conformations, and expressed inside cells as intrabodies, for investigative and therapeutic purposes.

Methodology/Principal Findings

Using atomic force microscopy (AFM) and live-cell fluorescence microscopy, we report that a human scFv selected against the fibrillar form of α-synuclein targets isomorphic conformations of misfolded polyglutamine proteins. When expressed in the cytoplasm of striatal cells, this conformation-specific intrabody co-localizes with intracellular aggregates of misfolded ataxin-3 and a pathological fragment of huntingtin, and enhances the aggregation propensity of both disease-linked polyglutamine proteins. Using this intrabody as a tool for modulating the kinetics of amyloidogenesis, we show that escalating aggregate formation of a pathologic huntingtin fragment is not cytoprotective in striatal cells, but rather heightens oxidative stress and cell death as detected by flow cytometry. Instead, cellular protection is achieved by suppressing aggregation using a previously described intrabody that binds to the amyloidogenic N-terminus of huntingtin. Analogous cytotoxic results are observed following conformational targeting of normal or polyglutamine-expanded human ataxin-3, which partially aggregate through non-polyglutamine domains.

Conclusions/Significance

These findings validate that the rate of aggregation modulates polyglutamine-mediated intracellular dysfunction, and caution that molecules designed to specifically hasten aggregation may be detrimental as therapies for polyglutamine disorders. Moreover, our findings introduce a novel antibody-based tool that, as a consequence of its general specificity for fibrillar conformations and its ability to function intracellularly, offers broad research potential for a variety of human amyloid diseases.     

Synthesis and activity of novel bile-acid conjugated glucocorticoid receptor antagonists

A series of potent steroidal glucocorticoid receptor antagonists has been discovered. After conjugation to cholic acid, the compounds retained an affinity for GR in vitro and had modest in vivo efficacy.     

Thyroid receptor ligands. Part 5: novel bicyclic agonist ligands selective for the thyroid hormone receptor beta

Based on the examination of the crystal structure of rat TRbeta complexed with 3,5,3'-triiodo-l-thyronine (2) a novel TRbeta-selective indole derivative 6b was prepared and tested in vitro. This compound was found to be 14 times selective for TRbeta over TRalpha in binding and its beta-selectivity could be rationalized through the comparison of the X-ray crystallographic structures of 6b complexed with TRalpha and TRbeta.