Lipophilic prodrugs of a triazole-containing colchicine analogue in liposomes: Biological effects on human tumor cells

Colchicine site binders—blockers of tubulin polymerization—are potential antimitotic agents for anticancer therapy. To reduce their systemic toxicity and improve biodistribution, encapsulation in nanosized liposomes may be employed. Liposomes present a convenient means for preparation of injectable for-mulations of hydrophobic compounds, however colchicine as such is known to leak through the lipid bilayer. In this study, newly synthesized triazole-containing analogues of colchicine and allocolchicine, and their palmitic and oleic esters (lipophilic prodrugs) were tested for anti-proliferative activity and apoptosis-inducing potential. In contrast to colchicine conjugates, whose activities ranged with those of colchicine, allocolchicine derivatives exhibited drastically lower effects and were discarded. Liposomes of about 100 nm in diameter composed of egg phosphatidylcholine-yeast phosphatidylinositol-palmitic or oleic prodrug, 8: 1: 1, by mol, were prepared by standard extrusion technique and tested in a panel of four human tumor cell lines. Liposome formulations preserved the biological activities of the parent colchicinoid the most towards human epithelial tumor cells. Moreover, liposomal form of the oleoyl bearing colchicinoid inhibited cell proliferation more efficiently than free lipophilic prodrug. Due to substantial loading capacity of the liposomes, the dispersions contain sufficient concentration of the active agent to test wide dose range in experiments on systemic administration to animals.     

Water-based nanoparticulate polymeric system for protein delivery

This article features a new production technology for nanoparticles comprised of multicomponent polymeric complexes that are candidates for delivery vehicles of biological molecules such as proteins and drugs. Biocompatible and mostly natural polymers are fabricated into thermodynamically stable nanoparticles insoluble in water and buffered media, in the absence of organic solvents, using two types of processing: batch and continuous. Careful choice of construction materials and the superposition of several interacting principles during their production allow for the customization of the physicochemical properties of the structures. Detailed experiments in batch and continuous systems allowed time-dependent stoichiometric characterization of the production process and an understanding of fundamental assembly principles of such supramolecular structures. Continuous-flow production is shown to provide more consistent data in terms of product quality and consistency, with further possibility of process development and commercialization. The development of nanoparticles using the described methodology is expected to lead to a flexible nanoparticle drug delivery system for medical applications, which has particular bearing to the slow release of drugs, antigens (for vaccine design), and genes (for gene therapy). Several chemistries of particles are presented. Copyright John Wiley & Sons, Inc.     

even-skipped determines the dorsal growth of motor axons in Drosophila

Axon pathfinding and target choice are governed by cell type-specific responses to external cues. Here, we show that in the Drosophila embryo, motorneurons with targets in the dorsal muscle field express the homeobox gene even-skipped and that this expression is necessary and sufficient to direct motor axons into the dorsal muscle field. Previously, it was shown that motorneurons projecting to ventral targets express the LIM homeobox gene islet, which is sufficient to direct axons to the ventral muscle field. Thus, even-skipped complements the function of islet, and together these two genes constitute a bimodal switch regulating axonal growth and directing motor axons to ventral or to dorsal regions of the muscle field.     

Independent regulation of synaptic size and activity by the anaphase-promoting complex

Neuronal plasticity relies on tightly regulated control of protein levels at synapses. One mechanism to control protein abundance is the ubiquitin-proteasome degradation system. Recent studies have implicated ubiquitin-mediated protein degradation in synaptic development, function, and plasticity, but little is known about the regulatory mechanisms controlling ubiquitylation in neurons. In contrast, ubiquitylation has long been studied as a central regulator of the eukaryotic cell cycle. A critical mediator of cell-cycle transitions, the anaphase-promoting complex/cyclosome (APC/C), is an E3 ubiquitin ligase. Although the APC/C has been detected in several differentiated cell types, a functional role for the complex in postmitotic cells has been elusive. We describe a novel postmitotic role for the APC/C at Drosophila neuromuscular synapses: independent regulation of synaptic growth and synaptic transmission. In neurons, the APC/C controls synaptic size via a downstream effector Liprin-alpha; in muscles, the APC/C regulates synaptic transmission, controlling the concentration of a postsynaptic glutamate receptor.     

Role of epigenetic DNA alterations in the pathogenesis of systemic lupus erythematosus

Epigenetic alternations in genomic DNA encompass cytosine methylation in cytosine and guanine (CpG) dinucleotide islands, which are usually extended in the promoter and first exon of genes. The DNA methylation is carried out by DNA methyltransferases (DNMT) and it serves as an epigenetic method of gene expression modulation. The epigenetic alternations in genomic DNA have been implicated in the development of malignant and autoimmune diseases. The epigenetic aberration in regulatory DNA sequences may also be responsible for the emergence of changes in the immune system in patients with systemic lupus erythematosus (SLE). The agents 5-azacytidine (azacitidine) and 5-aza-2'-deoxycytidine (decitabine) belong to inhibitors of methyltransferase. These compounds affect the methylation level of promoter sequences and cause phenotypic changes in peripheral blood mononuclear cells (PBMC), which are similar to those observed in PBMC of SLE patients. The lack of methylcytosine in CpG dinucleotides may be responsible for the antigenic properties of microbial DNA. The presence of low-apoptotic methylated DNA fragments has been identified in plasma of SLE patients. These DNA fragments exhibit antigenic properties and may elicit the humoral response responsible for the flare of SLE. The low methylation of CpG residues in the regulatory sequences may also contribute to the elevated expression of human endogenous retroviruses (HERVs) in PBMC of SLE patients. The HERV components exhibit a profound similarity with nuclear antigens and may be responsible for the enhancement of the production of anti-antinuclear antibodies (ANA). Recent advances in the investigation of epigenetic DNA changes have formed the basis of improved understanding of etiopathogenesis of SLE, which may thereby facilitate improvement in therapeutic principles of this disease.     

Haloalkane dehalogenase LinB from Sphingomonas paucimobilis UT26: X-ray crystallographic studies of dehalogenation of brominated substrates

The haloalkane dehalogenases are detoxifying enzymes that convert a broad range of halogenated substrates to the corresponding alcohols. Complete crystal structures of haloalkane dehalogenase from Sphingomonas paucimobilis UT26 (LinB), and complexes of LinB with 1,2-propanediol/1-bromopropane-2-ol and 2-bromo-2-propene-1-ol, products of debromination of 1,2-dibromopropane and 2,3-dibromopropene, respectively, were determined from 1.8 A resolution X-ray diffraction data. Published structures of native LinB and its complex with 1,3-propanediol [Marek et al. (2000) Biochemistry 39, 14082-14086] were reexamined. The full and partial debromination of 1,2-dibromopropane and 2,3-dibromopropene, respectively, conformed to the observed general trend that the sp(3)-hybridized carbon is the predominant electrophilic site for the S(N)2 bimolecular nucleophilic substitution in dehalogenation reaction. The 2-bromo-2-propene-1-ol product of 2,3-dibromopropene dehalogenation in crystal was positively identified by the gas chromatography-mass spectroscopy (GC-MS) technique. The 1,2-propanediol and 1-bromopropane-2-ol products of 1,2-dibromopropane dehalogenation in crystal were also supported by the GC-MS identification. Comparison of native LinB with its complexes showed high flexibility of residues 136-157, in particular, Asp146 and Glu147, from the cap domain helices alpha(4) and alpha(5)('). Those residues were shifted mainly in direction toward the ligand molecules in the complex structures. It seems the cap domain moves nearer to the core squeezing substrate into the active center closer to the catalytic triad. This also leads to slight contraction of the whole complex structures. The flexibility detected by crystallographic analysis is in remarkable agreement with flexibility observed by molecular dynamic simulations.     

Charting the Drosophila neuropile: a strategy for the standardised characterisation of genetically amenable neurites

Insect neurons are individually identifiable and have been used successfully to study principles of the formation and function of neuronal circuits. In the fruitfly Drosophila, studies on identifiable neurons can be combined with efficient genetic approaches. However, to capitalise on this potential for studies of circuit formation in the CNS of Drosophila embryos or larvae, we need to identify pre- and postsynaptic elements of such circuits and describe the neuropilar territories they occupy. Here, we present a strategy for neurite mapping, using a set of evenly distributed landmarks labelled by commercially available anti-Fasciclin2 antibodies which remain comparatively constant between specimens and over developmental time. By applying this procedure to neurites labelled by three Gal4 lines, we show that neuritic territories are established in the embryo and maintained throughout larval life, although the complexity of neuritic arborisations increases during this period. Using additional immunostainings or dye fills, we can assign Gal4-targeted neurites to individual neurons and characterise them further as a reference for future experiments on circuit formation. Using the Fasciclin2-based mapping procedure as a standard (e.g., in a common database) would facilitate studies on the functional architecture of the neuropile and the identification of candiate circuit elements.     

TRITON: in silico construction of protein mutants and prediction of their activities

MOTIVATION: One of the objectives of protein engineering is to propose and construct modified proteins with improved activity for the substrate of interest. Systematic computational investigation of many protein variants requires the preparation and handling of a large number of data files. The type of the data generated during the modelling of protein variants and the estimation of their activities offers the possibility of process automatization. RESULTS: The graphical program TRITON has been developed for modelling protein mutants and assessment of their activities. Protein mutants are modelled from the wild type structure by homology modelling using the external program MODELLER. Chemical reactions taking place in the mutants active site are modelled using the semi-empirical quantum mechanic program MOPAC. Semi-quantitative predictions of mutants activities can be achieved by evaluating the changes in energies of the system and partial atomic charges of active site residues during the reaction. The program TRITON offers graphical tools for the preparation of the input data files, for calculation and for the analysis of the generated output data. AVAILABILITY: The program TRITON can run under operating systems IRIX, Linux and NetBSD. The software is available at http://www.chemi.muni.cz/lbsd/triton.ht ml.     

Netilmicin in the treatment of bacterial respiratory tract infections

Netilmicin - a semisynthetic aminoglycoside - was administered to 33 patients with the acute or chronic lower respiratory tract or pulmonary infections in a daily dose of 5 mg/kg body weight for 10 days. A principle criterium of patients classification to netilmicin therapy were sensitive bacterial strains either in sputum or in BAL liquid. A significant clinical improvement was noted in 88% of the treated patients. However, elimination of pathogens from the sputum was achieved only in 52% of these patients. No improvement was observed in 4% of the treated patients. No adverse reactions were noted. Netilmicin proved safe and effective antibacterial agent in patients with respiratory infections.     

FireProt: Energy- and Evolution-Based Computational Design of Thermostable Multiple-Point Mutants

There is great interest in increasing proteins’ stability to enhance their utility as biocatalysts, therapeutics, diagnostics and nanomaterials. Directed evolution is a powerful, but experimentally strenuous approach. Computational methods offer attractive alternatives. However, due to the limited reliability of predictions and potentially antagonistic effects of substitutions, only single-point mutations are usually predicted in silico, experimentally verified and then recombined in multiple-point mutants. Thus, substantial screening is still required. Here we present FireProt, a robust computational strategy for predicting highly stable multiple-point mutants that combines energy- and evolution-based approaches with smart filtering to identify additive stabilizing mutations. FireProt’s reliability and applicability was demonstrated by validating its predictions against 656 mutations from the ProTherm database. We demonstrate that thermostability of the model enzymes haloalkane dehalogenase DhaA and γ-hexachlorocyclohexane dehydrochlorinase LinA can be substantially increased (ΔT _m = 24°C and 21°C) by constructing and characterizing only a handful of multiple-point mutants. FireProt can be applied to any protein for which a tertiary structure and homologous sequences are available, and will facilitate the rapid development of robust proteins for biomedical and biotechnological applications.