2,6-Diphenylthiazolo[3,2-b][1,2,4]triazoles as telomeric G-quadruplex stabilizers

The design and synthesis of 2,6-diphenylthiazolo[3,2-b][1,2,4]triazoles characterized by a large aromatic building block bearing cationic side chains are reported. These molecules are evaluated as telomeric G-quadruplex stabilizers and for their selectivity towards duplex DNA by competition experiments. Two compounds (14a, 19) were found active with high selectivity for telomeric G-quadruplex over duplex DNA.     

Low incidence of N-glycolylneuraminic acid in birds and reptiles and its absence in the platypus

The sialic acids of the platypus, birds, and reptiles were investigated with regard to the occurrence of N-glycolylneuraminic (Neu5Gc) acid. They were released from tissues, eggs, or salivary mucin samples by acid hydrolysis, and purified and analyzed by thin-layer chromatography, high-performance liquid chromatography, and mass spectrometry. In muscle and liver of the platypus only N-acetylneuraminic (Neu5Ac) acid was found. The nine bird species studied also did not express N-glycolylneuraminic acid with the exception of an egg, but not tissues, from the budgerigar and traces in poultry. Among nine reptiles, including one turtle, N-glycolylneuraminic acid was only found in the egg and an adult basilisk, but not in a freshly hatched animal. BLAST analysis of the genomes of the platypus, the chicken, and zebra finch against the CMP-N-acetylneuraminic acid hydroxylase did not reveal the existence of a similar protein structure. Apparently monotremes (platypus) and sauropsids (birds and reptiles) cannot synthesize Neu5Gc. The few animals where Neu5Gc was found, especially in eggs, may have acquired this from the diet or by an alternative pathway. Since Neu5Gc is antigenic to man, the observation that this monosaccharide does not or at least only rarely occur in birds and reptiles, may be of nutritional and clinical significance.     

Intramolecular hydrogen bonding as a determinant of the inhibitory potency of N-unsubstituted imidazole derivatives towards mammalian hemoproteins

Enzymes involved in the mammalian microsomal metabolism of drugs are, in numerous cases, inhibited by compounds bearing an imidazolyl scaffold. However, the inhibition potency is highly dependent upon the accessibility of the imidazolyl nitrogen lone pair. In order to highlight some structural parameters of inhibitors that control this phenomenon, a series of compounds containing a nitrogen unsubstituted imidazolyl moiety with varying degrees of nitrogen lone pair accessibility was tested on human and rat hepatic cytochromes P450 and microperoxidase 8, an enzymatically active peptide derived from cytochrome c. In each case, we have shown that the accessibility of the imidazole lone pair determined the extent of inhibition. Nitrogen accessibility was tuned not only by varying the steric hindrance in the vicinity of the imidazolyl ring but also by modifying its surrounding hydrogen bonding network. Compounds in which there exists intramolecular hydrogen bonding between the imidazole moiety and an H-bond acceptor, such as an appropriately positioned amide carbonyl group, demonstrated enhanced inhibitory effects. Conversely, imidazole moieties which are in proximity to H-bond donors, such as an amide NH group, displayed reduced potency. This trend was observed in cyclo-peptide derivatives in which the intramolecular H-bond network was adjusted through the modification of the stereochemistry of a dehydrohistidine residue. It was observed that (Z)-isomers weakly bind heme, whereas (E)-isomers demonstrated higher degrees of metal binding. Therefore, enzymatic inhibition of heme-containing proteins by compounds bearing a dehydrohistidine motif seems to be closely related to its stereochemistry and hydrogen binding propensity. At neutral pH, these differences in binding affinities can be confidently attributed to the ambident H-bond properties of imidazole nitrogen atoms. This structure-activity relationship may be of use for the design of novel imidazolyl compounds as new P450 inhibitors or drug candidates.     

Adult Stromal Cells Derived from Human Adipose Tissue Provoke Pancreatic Cancer Cell Death both In Vitro and In Vivo

Background

Normal tissue homeostasis is maintained by dynamic interactions between epithelial cells and their microenvironment. Disrupting this homeostasis can induce aberrant cell proliferation, adhesion, function and migration that might promote malignant behavior. Indeed, aberrant stromal-epithelial interactions contribute to pancreatic ductal adenocarcinoma (PDAC) spread and metastasis, and this raises the possibility that novel stroma-targeted therapies represent additional approaches for combating this malignant disease. The aim of the present study was to determine the effect of human stromal cells derived from adipose tissue (ADSC) on pancreatic tumor cell proliferation.

Principal Findings

Co-culturing pancreatic tumor cells with ADSC and ADSC-conditioned medium sampled from different donors inhibited cancer cell viability and proliferation. ADSC-mediated inhibitory effect was further extended to other epithelial cancer-derived cell lines (liver, colon, prostate). ADSC conditioned medium induced cancer cell necrosis following G1-phase arrest, without evidence of apoptosis. In vivo, a single intra-tumoral injection of ADSC in a model of pancreatic adenocarcinoma induced a strong and long-lasting inhibition of tumor growth.

Conclusion

These data indicate that ADSC strongly inhibit PDAC proliferation, both in vitro and in vivo and induce tumor cell death by altering cell cycle progression. Therefore, ADSC may constitute a potential cell-based therapeutic alternative for the treatment of PDAC for which no effective cure is available.     

Transfusion-transmitted infectious diseases

A spectrum of blood-borne infectious agents is transmitted through transfusion of infected blood donated by apparently healthy and asymptomatic blood donors. The diversity of infectious agents includes hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency viruses (HIV-1/2), human T-cell lymphotropic viruses (HTLV-I/II), Cytomegalovirus (CMV), Parvovirus B19, West Nile Virus (WNV), Dengue virus, trypanosomiasis, malaria, and variant CJD. Several strategies are implemented to reduce the risk of transmitting these infectious agents by donor exclusion for clinical history of risk factors, screening for the serological markers of infections, and nucleic acid testing (NAT) by viral gene amplification for direct and sensitive detection of the known infectious agents. Consequently, transfusions are safer now than ever before and we have learnt how to mitigate risks of emerging infectious diseases such as West Nile, Chikungunya, and Dengue viruses.     

The paradox of viable <Emphasis Type="Italic">sup45</Emphasis> STOP mutations: a necessary equilibrium between translational readthrough,activity and stability of the protein

The mechanisms leading to non-lethality of nonsense mutations in essential genes are poorly understood. Here, we focus on the factors influencing viability of yeast cells bearing premature termination codons (PTCs) in the essential gene SUP45 encoding translation termination factor eRF1. Using a dual reporter system we compared readthrough efficiency of the natural termination codon of SUP45 gene, spontaneous sup45-n (nonsense) mutations, nonsense mutations obtained by site-directed mutagenesis (76Q → TAA, 242R → TGA, 317L → TAG). The nonsense mutations in SUP45 gene were shown to be situated in moderate contexts for readthrough efficiency. We showed that readthrough efficiency of some of the mutations present in the sup45 mutants is not correlated with full-length Sup45 protein amount. This resulted from modification of both sup45 mRNA stability which varies 3-fold among sup45-n mutants and degradation rate of mutant Sup45 proteins. Our results demonstrate that some substitutions in the place of PTCs decrease Sup45 stability. The viability of sup45 nonsense mutants is therefore supported by diverse mechanisms that control the final amount of functional Sup45 in cells.     

Towards the human intestinal microbiota phylogenetic core

The paradox of a host specificity of the human faecal microbiota otherwise acknowledged as characterized by global functionalities conserved between humans led us to explore the existence of a phylogenetic core. We investigated the presence of a set of bacterial molecular species that would be altogether dominant and prevalent within the faecal microbiota of healthy humans. A total of 10 456 non-chimeric bacterial 16S rRNA sequences were obtained after cloning of PCR-amplified rDNA from 17 human faecal DNA samples. Using alignment or tetranucleotide frequency-based methods, 3180 operational taxonomic units (OTUs) were detected. The 16S rRNA sequences mainly belonged to the phyla Firmicutes (79.4%), Bacteroidetes (16.9%), Actinobacteria (2.5%), Proteobacteria (1%) and Verrumicrobia (0.1%). Interestingly, while most of OTUs appeared individual-specific, 2.1% were present in more than 50% of the samples and accounted for 35.8% of the total sequences. These 66 dominant and prevalent OTUs included members of the genera Faecalibacterium , Ruminococcus , Eubacterium , Dorea , Bacteroides , Alistipes and Bifidobacterium . Furthermore, 24 OTUs had cultured type strains representatives which should be subjected to genome sequence with a high degree of priority. Strikingly, 52 of these 66 OTUs were detected in at least three out of four recently published human faecal microbiota data sets, obtained with very different experimental procedures. A statistical model confirmed these OTUs prevalence. Despite the species richness and a high individual specificity, a limited number of OTUs is shared among individuals and might represent the phylogenetic core of the human intestinal microbiota. Its role in human health deserves further study.     

Pervasive effects of dispersal limitation on within- and among-community species richness in agricultural landscapes

Aim To determine whether the effect of habitat fragmentation and habitat heterogeneity on species richness at different spatial scales depends on the dispersal ability of the species assemblages and if this results in nested species assemblages. Location Agricultural landscapes distributed over seven temperate Europe countries covering a range from France to Estonia. Methods We sampled 16 local communities in each of 24 agricultural landscapes (16 km²) that differ in the amount and heterogeneity of semi‐natural habitat patches. Carabid beetles were used as model organisms as dispersal ability can easily be assessed on morphological traits. The proximity and heterogeneity of semi‐natural patches within the landscape were related to average local (alpha), between local (beta) and landscape (gamma) species richness and compared among four guilds that differ in dispersal ability. Results For species assemblages with low dispersal ability, local diversity increased as the proximity of semi‐natural habitat increased, while mobile species showed an opposite trend. Beta diversity decreased equally for all dispersal classes in relation to proximity, suggesting a homogenizing effect of increased patch isolation. In contrast, habitat diversity of the semi‐natural patches affected beta diversity positively only for less mobile species, probably due to the low dispersal ability of specialist species. Species with low mobility that persisted in highly fragmented landscapes were consistently present in less fragmented ones, resulting in nested assemblages for this mobility class only. Main conclusions The incorporation of dispersal ability reveals that only local species assemblages with low dispersal ability show a decrease of richness as a result of fragmentation. This local species loss is compensated at least in part by an increase in species with high dispersal ability, which obscures the effect of fragmentation when investigated across dispersal groups. Conversely, fragmentation homogenizes the landscape fauna for all dispersal groups, which indicates the invasion of non‐crop habitats by similar good dispersers across the whole landscape. Given that recolonization of low dispersers is unlikely, depletion of these species in modern agricultural landscapes appears temporally pervasive.     

Transient Neuronal Populations Are Required to Guide Callosal Axons: A Role for Semaphorin 3C

The corpus callosum (CC) is the main pathway responsible for interhemispheric communication. CC agenesis is associated with numerous human pathologies, suggesting that a range of developmental defects can result in abnormalities in this structure. Midline glial cells are known to play a role in CC development, but we here show that two transient populations of midline neurons also make major contributions to the formation of this commissure. We report that these two neuronal populations enter the CC midline prior to the arrival of callosal pioneer axons. Using a combination of mutant analysis and in vitro assays, we demonstrate that CC neurons are necessary for normal callosal axon navigation. They exert an attractive influence on callosal axons, in part via Semaphorin 3C and its receptor Neuropilin-1. By revealing a novel and essential role for these neuronal populations in the pathfinding of a major cerebral commissure, our study brings new perspectives to pathophysiological mechanisms altering CC formation.     

Intracellular ca2+ stores could participate to abscisic acid-induced depolarization and stomatal closure in Arabidopsis thaliana

In Arabidopsis thaliana cell suspension,abscisic acid (aBa) induces changes in cytosolic calcium concentration ([Ca²⁺]_cyt) which are the trigger for aBa-induced plasma membrane anion current activation, H⁺-aTPase inhibition, and subsequent plasma membrane depolarization. In the present study, we took advantage of this model to analyze the implication of intracellular Ca²⁺ stores in aBa signal transduction through electrophysiological current measurements, cytosolic Ca²⁺ activity measurements with the apoaequorin Ca²⁺ reporter protein and external pH measurement. Intracellular Ca²⁺ stores involvement was determined by using specific inhibitors of CICR channels: the cADP-ribose/ryanodine receptor (Br-cADPR and dantrolene) and of the inositol trisphosphate receptor ({"type":"entrez-nucleotide","attrs":{"text":"U73122","term_id":"4098075","term_text":"U73122"}}U73122). In addition experiments were performed on epidermal strips of A. thaliana leaves to monitor stomatal closure in response to ABA in presence of the same pharmacology. Our data provide evidence that ryanodine receptor and inositol trisphosphate receptor could be involved in ABA-induced (1) Ca²⁺ release in the cytosol, (2) anion channel activation and H⁺-ATPase inhibition leading to plasma membrane depolarization and (3) stomatal closure. Intracellular Ca²⁺ release could thus contribute to the control of early events in the ABA signal transduction pathway in A. thaliana.