Elasticity changes anti-correlate with NO production for human endothelial cells stimulated with TNF-α\alpha

Tumor necrosis factor alpha (TNF-$\alpha$) is a critical cytokine that is involved in systemic inflammatory response and contributes to the activation of the pro-inflammatory phenotype of the endothelium. In the present study, effects of TNF-$\alpha$ on morphology and elasticity of endothelium in relation to the production of NO and actin fiber reorganization were analyzed in human dermal microvascular endothelial cells. The cells were incubated in MCDB medium solution and stimulated with 10ng/ml of TNF-$\alpha$. Atomic force microscopy measurements have enabled characterization of cell morphology and elastic properties in physiological conditions. The spectrophotometric Griess method was applied to estimate nitric oxide (NO) production of the cells. We demonstrated that TNF-$\alpha$-induced changes in elasticity of endothelium anti-correlate with NO production and are associated with the reorganization of actin cytoskeleton

Surfactant modulated interactions of hydrophobically modified ethoxylated urethane (HEUR) polymers with penetrable surfaces

Hypothesis Adsorption of hydrophobically modified ethoxylated urethane polymers (HEURs) at the soft colloid interfaces of emulsion droplets will stabilise oil-in-water emulsions (a) via steric stabilisation induced by adsorption of the polymer at the droplet surfaces through the hydrophobic groups, and (b) via continuous phase viscosity enhancement through polymer self-association. Both of these mechanisms will be modulated by the presence of the surfactant, sodium dodecylsulfate (SDS). Experiments Dodecane-in-water emulsions stabilised by three HEUR polymers with different structural composition were examined in the absence and presence of SDS by NMR spectroscopy and small-angle neutron scattering (SANS). The effect of adsorption of the polymer to the dodecane droplet surfaces, and the conformation of the self-associating polymer in the aqueous solution were quantified. Findings All emulsions were stable for days-weeks. Diffusion data showed the formation of oil droplets of hundreds of nm in size in the presence of all three HEURs, here denoted C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10, and C18-L-(EO200-L)7-C18, where EOx represents a block of ethylene oxide of x monomers, L denotes the linker group, and Cn the length of the hydrophobic end-group. No significant changes in droplet size across this series of polymers was observed. Collectively, the results point to adsorption of the polymer to the droplet surfaces, which results in a small decrease in the effective polymer solution concentration, thereby driving to significant changes in the structure and dynamics of the system. Evident in the SANS data in particular, is a subtle balance between the characteristic features reflecting polymer self-association, and those associated with polymer structures commensurate with a larger length-scale, dependent on the system composition. Surprisingly, the polymer and polymer/SDS complex in the presence of oil show slightly greater diffusive rates relative to the analogous systems in the absence of the oil. Finally, the partitioning of the three polymers in phase-separated samples was studied by 1H NMR, and it was shown that the C18-L-(EO200-L)7-C18 exhibited a greater partitioning in the oil phase compared with C6-L-(EO100-L)9-C6 and C10-L-(EO200-L)4-C10, an observation that may be understood in terms of the structural composition of the HEURs. The SDS showed a positive correlation between its partitioning in the two layers with the polymer partitioning, evidence of a strong interaction between the surfactant and the polymer, consistent with the behaviour observed in the oil-free system

Studying the interaction of hydrophobically modified ethoxylated urethane (HEUR) polymers with sodium dodecylsulphate (SDS) in concentrated polymer solutions

Hypothesis: Hydrophobically modified ethoxylated urethane polymers (HEURs) are widely used to control the rheological profile of formulated particulate dispersions through associative network formation, the properties of which are perturbed by the presence of surfactants. At high polymer concentrations and in the presence of surfactants, it is hypothesised that the dominant factors in determining the rheological profile are the number and composition of the mixed hydrophobic aggregates, these being defined by the number and distribution of the hydrophobic linkers along the polymer backbone, rather than the end-group hydrophobe characteristics per se that dominate the low polymer concentration behaviour. Experiments: Three different HEUR polymers with formulae (C6-L-(EO100-L)9-C6, C10-L-(EO200-L)4-C10 and C18-L-(EO200-L)7-C18 (where L = urethane linker, Cn = hydrophobic end-group chain length, and EO = ethylene oxide block) have been studied in the absence and presence of SDS employing techniques that quantify (a) the bulk characteristics of the polymersurfactant blend, (b) the structure and composition of the hydrophobic domains, (c) the dynamics of the polymer and surfactant, and (d) the polymer conformation. Collectively, these experiments demonstrate how molecular-level interactions between the HEURs and sodium dodecylsulphate (SDS) define the macroscopic behaviour of the polymer/surfactant mixture. Findings: Binding of the SDS to the polymer via two mechanisms - monomeric anti-cooperative and micellar cooperative - leads to surfactant-concentration-specific macroscopic changes in the viscosity. Binding of the surfactant to the polymer drives a conformational rearrangement, and an associated redistribution of the polymer end-groups and linker associations throughout the hydrophobic domains. The composition and size of these domains are sensitive to the polymer architecture. Therefore, there is a complex balance between polymer molecular weight, ethylene oxide block size, and number of urethane linkers, coupled with the size of the hydrophobic end-groups. In particular, the urethane linkers are shown to play a hitherto largely neglected but important role in driving the polymer association

Surfactant modulated interaction of hydrophobically modified ethoxylated urethane (HEUR) polymers with impenetrable surfaces

Hypothesis: The presence of surfactant modulates the surface-chemistry-specific interaction of hard colloidal particles (latex) with HEUR polymers, principally through introducing a preferential solution interaction rather than a competitive surface interaction; addition of surfactant leads to a preponderance of polymer/surfactant solution complexes rather than surface-bound complexes. Experiments: A range of model formulations comprising a hexyl end-capped urethane polymer (C6-L-(EO100-L)9-C6), sodium dodecylsulfate (SDS) and a series of polystyrene-butylacrylate latices (PS-BA-L) have been characterised in terms of rheology, particle surface area (solvent relaxation NMR), polymer conformation (small-angle neutron scattering) and solution composition to build up a detailed picture of the distribution of the HEUR in the presence of both surfactant and latex. Findings: There is very weak adsorption of C6-L-(EO100-L)9-C6 to only the most hydrophobic latex surface studied, an adsorption that is further weakened by the addition of low levels of surfactant. Macroscopic changes in the hydrophobic latex system may be interpreted in terms of bridging flocculation at low polymer concentrations. No adsorption of C6-L-(EO100-L)9-C6 is observed in the case of hydrophilic surfaces. In most cases, the observed behaviour of the ternary system (polymer/surfactant/particle) is highly reminiscent of the binary (polymer/surfactant) system at the appropriate composition, suggesting that the polymer/surfactant solution interaction is the dominant one

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation