Inhibition of cholesterol absorption by the combination of dietary plant sterols and ezetimibe: effects on plasma lipid levels

Consumption of plant sterols and treatment with ezetimibe both reduce cholesterol absorption in the intestine. However, the mechanism of action differs between the two treatments, and the consequences of combination treatment are unknown. Therefore, we performed a double-blind, placebo-controlled, crossover study for the plant sterol component with open-label ezetimibe treatment. Forty mildly hypercholesterolemic subjects were randomized to the following treatments for 4 weeks each: 10 mg/day ezetimibe combined with 25 g/day control spread; 10 mg/day ezetimibe combined with 25 g/day spread containing 2.0 g of plant sterols; 25 g/day spread containing 2.0 g of plant sterols; and placebo treatment consisting of 25 g/day control spread. Combination treatment of plant sterols and ezetimibe reduced low density lipoprotein cholesterol (LDL-C) by 1.06 mmol/l (25.2%; P < 0.001) compared with 0.23 mmol/l (4.7%; P = 0.006) with plant sterols and 0.94 mmol/l (22.2%; P < 0.001) with ezetimibe monotherapy. LDL-C reduction conferred by the combination treatment did not differ significantly from ezetimibe monotherapy (-0.12 mmol/l or -3.5%; P = 0.13). Additionally, the plasma lathosterol-to-cholesterol ratio increased with all treatments. Sitosterol and campesterol ratios increased after plant sterol treatment and decreased upon ezetimibe and combination therapy. Our results indicate that the combination of plant sterols and ezetimibe has no therapeutic benefit over ezetimibe monotherapy in subjects with mild hypercholesterolemia.     

Intratumoral CC chemokine ligand 5 overexpression delays tumor growth and increases tumor cell infiltration

Chemokines participate in the antitumor immune response by regulating the movement and positioning of lymphocytes as well as effector functions and may thus be candidates for use in antitumor therapy. To test whether CCL5, a chemokine involved in the recruitment of a wide spectrum of immunocompetent cells, can control tumor growth, we forced its expression at mouse tumor sites. Tumor growth was reduced in mice with s.c. syngeneic CCL5-EL-4 compared with EL-4-injected mice, whereas both reduced tumor growth and incidence were observed in mice with OVA-expressing EG-7 transfected with CCL5 compared with EG-7-injected mice. Significant antitumor effects were observed soon after intratumoral injection of DNA plasmid coding for chimeric CCL5-Ig. Importantly, quantitative RT-PCR assays showed that the amount of CCL5 expression at the tumor site determined the effectiveness of the antitumor response, which was associated with infiltration of increased numbers of NK, CD4, and CD8 cells at the tumor site. This effect was lost in mice deficient for T/B lymphocytes (RAG-2 knockout) or for CCR5 (CCR5 knockout). Together, these data demonstrate the antitumor activity of intratumoral CCL5 overexpression, due to its recruitment of immunocompetent cells, and the potential usefulness of chimeric CCL5-Ig DNA as an agent in cancer therapy.     

Causal mechanisms underlying host specificity in bat ectoparasites

In parasites, host specificity may result either from restricted dispersal capacity or from fixed coevolutionary host-parasite adaptations. Knowledge of those proximal mechanisms leading to particular host specificity is fundamental to understand host-parasite interactions and potential coevolution of parasites and hosts. The relative importance of these two mechanisms was quantified through infection and cross-infection experiments using mites and bats as a model. Monospecific pools of parasitic mites (Spinturnix myoti and S. andegavinus) were subjected either to individual bats belonging to their traditional, native bat host species, or to another substitute host species within the same bat genus (Myotis). The two parasite species reacted differently to these treatments. S. myoti exhibited a clear preference for, and had a higher fitness on, its native host, Myotis myotis. In contrast, S. andegavinus showed no host choice, although its fitness was higher on its native host M. daubentoni. The causal mechanisms mediating host specificity can apparently differ within closely related host-parasite systems.     

N-terminal motifs in some plant disease resistance proteins function in membrane attachment and contribute to disease resistance

To investigate the role of N-terminal domains of plant disease resistance proteins in membrane targeting, the N termini of a number of Arabidopsis and flax disease resistance proteins were fused to green fluorescent protein (GFP) and the fusion proteins localized in planta using confocal microscopy. The N termini of the Arabidopsis RPP1-WsB and RPS5 resistance proteins and the PBS1 protein, which is required for RPS5 resistance, targeted GFP to the plasma membrane, and mutation of predicted myristoylation and potential palmitoylation sites resulted in a shift to nucleocytosolic localization. The N-terminal domain of the membrane-attached Arabidopsis RPS2 resistance protein was targeted incompletely to the plasma membrane. In contrast, the N-terminal domains of the Arabidopsis RPP1-WsA and flax L6 and M resistance proteins, which carry predicted signal anchors, were targeted to the endomembrane system, RPP1-WsA to the endoplasmic reticulum and the Golgi apparatus, L6 to the Golgi apparatus, and M to the tonoplast. Full-length L6 was also targeted to the Golgi apparatus. Site-directed mutagenesis of six nonconserved amino acid residues in the signal anchor domains of L6 and M was used to change the localization of the L6 N-terminal fusion protein to that of M and vice versa, showing that these residues control the targeting specificity of the signal anchor. Replacement of the signal anchor domain of L6 by that of M did not affect L6 protein accumulation or resistance against flax rust expressing AvrL567 but removal of the signal anchor domain reduced L6 protein accumulation and L6 resistance, suggesting that membrane attachment is required to stabilize the L6 protein.     

Undersulfation of heparan sulfate restricts differentiation potential of mouse embryonic stem cells

Heparan sulfate proteoglycans, present on cell surfaces and in the extracellular matrix, interact with growth factors and morphogens to influence growth and differentiation of cells. The sulfation pattern of the heparan sulfate chains formed during biosynthesis in the Golgi compartment will determine the interaction potential of the proteoglycan. The glucosaminyl N-deacetylase/N-sulfotransferase (NDST) enzymes have a key role during biosynthesis, greatly influencing total sulfation of the heparan sulfate chains. The differentiation potential of mouse embryonic stem cells lacking both NDST1 and NDST2 was studied using in vitro differentiation protocols, expression of differentiation markers, and assessment of the ability of the cells to respond to growth factors. The results show that NDST1 and NDST2 are dispensable for mesodermal differentiation into osteoblasts but necessary for induction of adipocytes and neural cells. Gene expression analysis suggested a differentiation block at the primitive ectoderm stage. Also, GATA4, a primitive endoderm marker, was expressed by these cells. The addition of FGF4 or FGF2 together with heparin rescued the differentiation potential to neural progenitors and further to mature neurons and glia. Our results suggest that the embryonic stem cells lacking both NDST1 and NDST2, expressing a very low sulfated heparan sulfate, can take the initial step toward differentiation into all three germ layers. Except for their potential for mesodermal differentiation into osteoblasts, the cells are then arrested in a primitive ectoderm and/or endoderm stage.     

New insights into the organisation and intracellular localisation of the two subunits of glucose-6-phosphatase

Glucose-6 phosphatase (G6Pase), a key enzyme of glucose homeostasis, catalyses the hydrolysis of glucose-6 phosphate (G6P) to glucose and inorganic phosphate. A deficiency in G6Pase activity causes type 1 glycogen storage disease (GSD-1), mainly characterised by hypoglycaemia. Genetic analyses of the two forms of this rare disease have shown that the G6Pase system consists of two proteins, a catalytic subunit (G6PC) responsible for GSD-1a, and a G6P translocase (G6PT), responsible for GSD-1b. However, since their identification, few investigations concerning their structural relationship have been made. In this study, we investigated the localisation and membrane organisation of the G6Pase complex. To this aim, we developed chimera proteins by adding a fluorescent protein to the C-terminal ends of both subunits. The G6PC and G6PT fluorescent chimeras were both addressed to perinuclear membranes as previously suggested, but also to vesicles throughout the cytoplasm. We demonstrated that both proteins strongly colocalised in perinuclear membranes. Then, we studied G6PT organisation in the membrane. We highlighted FRET between the labelled C and N termini of G6PT. The intramolecular FRET of this G6PT chimera was 27%. The coexpression of unlabelled G6PC did not modify this FRET intensity. Finally, the chimera constructs generated in this work enabled us for the first time to analyze the relationship between GSD-1 mutations and the intracellular localisation of both G6Pase subunits. We showed that GSD1 mutations did neither alter the G6PC or G6PT chimera localisation, nor the interaction between G6PT termini. In conclusion, our results provide novel information on the intracellular distribution and organisation of the G6Pase complex.     

Copper redistribution in murine macrophages in response to Salmonella infection

The movement of key transition metal ions is recognized to be of critical importance in the interaction between macrophages and intracellular pathogens. The present study investigated the role of copper in mouse macrophage responses to Salmonella enterica sv. Typhimurium. The copper chelator BCS (bathocuproinedisulfonic acid, disodium salt) increased intracellular survival of S. Typhimurium within primary mouse BMM (bone-marrow-derived macrophages) at 24 h post-infection, implying that copper contributed to effective host defence against this pathogen. Infection of BMM with S. Typhimurium or treatment with the TLR (Toll-like receptor) 4 ligand LPS (lipopolysaccharide) induced the expression of several genes encoding proteins involved in copper transport [Ctr (copper transporter) 1, Ctr2 and Atp7a (copper-transporting ATPase 1)], as well as the multi-copper oxidase Cp (caeruloplasmin). Both LPS and infection with S. Typhimurium triggered copper accumulation within punctate intracellular vesicles (copper 'hot spots') in BMM as indicated by the fluorescent reporter CS1 (copper sensor 1). These copper hot spots peaked in their accumulation at approximately 18 h post-stimulation and were dependent on copper uptake into cells. Localization studies indicated that the copper hot spots were in discrete vesicles distinct from Salmonella containing vacuoles and lysosomes. We propose that copper hot spot formation contributes to antimicrobial responses against professional intracellular bacterial pathogens.     

Genetics of canine olfaction and receptor diversity

Olfaction is a particularly important sense in the dog. Humans selected for this capacity during the domestication process, and selection has continued to be employed to enhance this ability. In this review we first describe the different olfactory systems that exist and the different odorant receptors that are expressed in those systems. We then focus on the dog olfactory receptors by describing the olfactory receptor gene repertoire and its polymorphisms. Finally, we discuss the different uses of dog olfaction and the questions that still need to be studied.