Showing papers by "Matija Tomšič published in 2009"

Investigation of the influence of CYP1A2 and CYP2C19 genetic polymorphism on 2-Cyano-3-hydroxy-N-[4-(trifluoromethyl)phenyl]-2-butenamide (A77 1726) pharmacokinetics in leflunomide-treated patients with rheumatoid arthritis.

Abstract: Leflunomide is a disease-modifying antirheumatic drug used for the treatment of rheumatoid arthritis (RA). Cytochromes P450, mainly CYP1A2 and CYP2C19, may be involved in the transformation of leflunomide to leflunomide metabolite (A77 1726, 2-cyano-3-hydroxy-N-[4-(trifluoromethyl)phenyl]-2-butenamide). The aim of this study was to investigate whether genetic polymorphisms in CYP1A2 and CYP2C19 influence leflunomide pharmacokinetics, treatment response, and the occurrence of adverse drug reactions (ADRs). The study included 67 patients with RA and 4 patients with polyarthritis resembling RA and psoriasis treated with leflunomide. A77 1726 steady-state plasma concentrations were determined by validated high-performance liquid chromatography with UV detection. A population pharmacokinetic model was developed to estimate the oral clearance (CL/F) and volume of distribution (V/F). A genotyping approach was used to determine C-163A, C-729T, and T-739G in the CYP1A2 gene as well as single nucleotide polymorphisms that characterize CYP2C19*2, *3, *4, and *17 alleles. A large interindividual variability in trough A77 1726 steady-state plasma concentrations was observed (from 1.9 to 156.9 mg/l). A77 1726 CL/F was 71% higher in carriers of the CYP2C19*2 allele compared with noncarriers. The A77 1726 average steady-state plasma concentration was associated with the treatment response. Patients with a greater decrease in C-reactive protein (CRP) had higher average steady-state plasma A77 1726 concentrations: 49.7 ± 39.0 mg/l in patients with ΔCRP of more than 8.5 mg/l compared with 24.8 ± 13.7 mg/l in patients with ΔCRP of ≤8.5 mg/l (p = 0.015). No association of A77 1726 steady-state plasma concentrations with the occurrence of ADRs was observed. Our results suggest that genetic variability in leflunomide-metabolizing enzymes influences leflunomide metabolite concentrations that are associated with the treatment response but not with leflunomide-induced toxicity.

Structural characterization of nonionic mixed micelles formed by C12EO6 surfactant and P123 triblock copolymer.

Abstract: A structural characterization of mixed micelles formed in aqueous solution by the PEO-PPO-PEO triblock copolymer P123 and the nonionic surfactant C(12)EO(6) was carried out using various techniques, including ultralow shear viscosimetry, depolarized dynamic light scattering (VH-DLS), depolarized static light scattering (VH-SLS), and small-angle X-ray scattering (SAXS). The sphere-to-rod transition of the mixed micelles was studied in a diluted regime (P123 concentrations ranging from 0.5 to 10 wt %) at C(12)EO(6)/P123 molar ratios of 2.2, 3.2, 6.0, and 11 as well as for the pure C(12)EO(6). The data from VH-SLS and viscosimetry displayed a sharp increase in the intensity and viscosity, respectively, at the sphere-to-rod transition, and the results from the two methods were in accordance. In both techniques, an increased transition temperature with increasing content of C(12)EO(6) (in the molar ratio regime from 2.2 to 11) was observed. SAXS was used as the main technique, and a thorough structural characterization was performed, where indirect Fourier transformation (IFT) and generalized indirect Fourier transformation (GIFT) were employed in the analysis procedure of the SAXS data. The p(r) functions obtained from the IFT (employed at low P123 concentrations, i.e., 1.0 and 2.0 wt %) and GIFT (employed above 2.0 wt %) analyses revealed increased inhomogeneities in the mixed micelles when the molar ratio was increased. This suggested that the C(12)EO(6) organized themselves at the interface between the PPO core and the PEO corona of the P123 micelles, with the C(12) alkyl chain stretching into the hydrophobic core and the EO(6) part residing in the hydrophilic corona. The structure factor parameters obtained with GIFT for a molar ratio of 2.2 at a P123 concentration of 5.0 wt % showed radius values smaller than what was estimated from the p(r) functions. This was explained by an interpenetration of the PEO chains from one mixed micelle into a neighboring one. VH-DLS was performed on the mixed micelles at a temperature 3 degrees C above the transition temperature and at a molar ratio of 2.2. From the analyzed data, the average length L of the rods was estimated to be 102 nm.

Genetic polymorphisms of glutathione S-transferases and disease activity of rheumatoid arthritis.

Abstract: Objectives Glutathione S-transferases (GST); GST-mul (GSTM1), GST-pil (GSTP1) and GST-thetal (GSTT1) have peroxidase activity towards cytotoxic metabolites produced in inflammatory reactions, the main feature of rheumatoid arthritis (RA) Genetic polymorphisms in GSTMI, GSTPI and GSTT1 modify the enzyme conjugation capacity and may be associated with the activity of RA Methods A genotyping approach was used to analyze GSTM1-0, GSTTI-0 and GSTPI Ile105Val and Ala114Val polymorphisms in 213 RA patients Disease activity was assessed by the disease activity score of 28 joint counts (DAS28) twice for each patient and mean DAS28 values were calculated Results The patients with GSTT1-0 genotype had a higher risk for developing high activity RA than the patients with GSTT1 genes present (p=0028, OR=2761, 95% CI=1114-6843) An interaction between the GSTTI polymorphism and smoking was observed In the group of smokers, the carriers of a homozygous deletion GSTT1 had an 85-fold higher risk for developing high disease activity than the patients with the GSTT1-1 genotype (p=0004, OR=8640, 95% CI=1995-37426) GSTMI and GSTP1 polymorphisms were not associated with the disease activity Conclusions Our results suggest that the presence of the GSTT1 -0 genotype contributed to higher disease activity in RA patients The risk for developing highly active RA was the highest in smokers with the GSTT1-0 genotype

Genetic polymorphisms modifying oxidative stress are associated with disease activity in rheumatoid arthritis patients.

Abstract: Reactive oxygen and nitrogen species are involved in the pathology of rheumatoid arthritis (RA). Polymorphisms in genes coding for superoxide dismutases (SOD2 and SOD3), catalase (CAT), tumor necrosis factor-alpha (TNFA) and inducible NO synthase (NOS2A) may influence RA activity. We determined SOD2 Ala-9Val, SOD3 Arg213Gly, CAT C-262T, TNFA G-308A, TNFA C-857T and NOS2A (CCTTT)n polymorphisms in 327 RA patients. Carriers of CAT -262T and TNFA -308A allele had lower mean disease activity score of 28 joint count (DAS28) values than patients with CAT -262CC and TNFA -308GG genotypes (p = 0.014 and p = 0.046, respectively). Patients with the combination of CAT -262T and TNFA -308A allele had lower mean DAS28 values and a higher probability for low disease activity than non-carriers (p = 0.003, OR = 3.585, 95% CI = 1.538–8.357). Our results suggest that CAT and TNFA polymorphisms alone and in combination influence the activity of RA.

Solubilization of Poly {1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)] fluorene-2,7-diyl} in Water by Nonionic Amphiphiles

Abstract: In the presence of the nonionic alkyloxyethylene surfactant n-dodecylpentaoxyethylene glycol ether (C12E5), the anionic conjugated polyelectrolyte (CPE) poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) dissolves in water, leading to a blue shift in fluorescence and dramatic increases in fluorescence quantum yields above the surfactant critical micelle concentration (cmc). No significant changes were seen with a poly(ethylene oxide) of similar size to the surfactant headgroup, confirming that specific surfactant−polyelectrolyte interactions are important. From UV−visible and fluorescence spectroscopy, dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), cryogenic transmission electron microscopy (cryo-TEM), and electrical conductivity, together with our published NMR and small-angle neutron scattering (SANS) results, we provide a coherent model for this behavior in terms of breakup of PBS-PFP clusters through polymer−surfactant association leading to cylind...

Internally self-assembled thermoreversible gelling emulsions: ISAsomes in methylcellulose, kappa-carrageenan, and mixed hydrogels.

Abstract: Self-assembled thermo-gelling emulsions were developed by blending internally self-assembled particles (ISAsomes) with thermoreversible polysaccharide hydrogels of methylcellulose (MC), kappa-carrageenan (KC), and their 1:1 mixture. In this way, the hierarchical structure of ISAsome samples was successfully promoted. The gelified polymer network corresponds to the highest level of the hierarchical structure and as such represents the capturing matrix for the medium structural level, i.e., dispersed emulsion particles, which are further internally structured as the lowest level of structure. Utilizing small-angle X-ray scattering, differential scanning calorimetry, dynamic light scattering, and oscillatory rheological experiments in the temperature regime from 20 to 70 degrees C, we were able to show that the ISAsomes stay practically intact during such embedment into a hydrogel matrix retaining its internal self-assembled structure and its functionality. The characteristic sol-gel and gel-sol transition temperatures of the ISAsome-loaded hydrogel samples showed a slight shift in comparison to the unloaded hydrogel samples. Furthermore, we found that MC is actually able to stabilize the ISAsomes at higher temperatures (tests were conducted up to 90 degrees C). Gels made from MC and KC show quite different features in terms of rheology and differential scanning calorimetry. However, the most interesting results were obtained for the ISAsome-loaded MC-KC (1:1) gelifying system, which behaves as a low- and high-temperature gel with a narrow intermediate temperature window where it is a sol. This specific thermal behavior allows for easy temperature tuning of the system's aggregate state as well as the internal self-assembled structure. As such, this system is suggested to be further tested as the potential media for a temperature-controlled burst/sustained release media of various hydrophilic, hydrophobic, or amphiphilic guest functional molecules.

Internally self-assembled particles entrapped in thermoreversible hydrogels.

Abstract: The present study describes the development of thermogelling emulsions by the entrapment of internally self-assembled emulsion droplets (ISAsomes) within a thermoreversible hydrogel made of κ -carrageenan. The droplets are emulsified mesophases of cubic or hexagonal order, or emulsified micro-emulsions. Above 60 °C, the system was fluid and composed of a mixture of internally nanostructured small droplets and polymer chains dispersed in water. Below 60 °C, a physical gel with entrapped droplets was formed. A tuning of the temperature in order to switch between the gel and solution state did not affect the particles in terms of size. The thermoreversible behavior of the loaded polymer network and the effects on the internal structure of cubosomes, hexosomes and emulsified micro-emulsions was investigated by SAXS. We showed that the phase borders may be shifted due to the presence of the κ -carrageenan network, which alter the internal nanostructure of the droplets. This can induce a transformation from emulsified micro-emulsions to micellar cubosomes. In the hexagonal case, the lattice parameters of the hexosomes are slightly modified.

Exploring the structural properties of simple aldehydes: a Monte Carlo and small-angle X-ray scattering study.

Abstract: The structure of simple linear alkanals from propanal to nonanal was studied utilizing configurational bias Monte Carlo (MC) simulations of the aldehydes modeled according to the transferable potential for phase equilibria-united atom force field (TraPPE-UA) and was compared to experimental small-angle X-ray scattering (SAXS) results. This was done by exploiting a recently developed approach for calculating the scattering intensities from theoretically obtained MC data by utilizing the Debye equation (Tomsic et al. J. Phys. Chem. B 2007, 111, 1738). Similar calculations were also performed utilizing a well-established approach based on the reciprocal lattice. Comparison of the calculated scattering data with the experimental SAXS results in the first instance revealed information on the molecular organization in simple aldehydes and in addition also served as a good structural test of the TraPPE-UA force field used to model the aldehydes studied. However, it turned out that such a structural test is a rather strict test for the model which otherwise showed good agreement with the experimental data from the thermodynamic point of view.

Depletion effects in a mixture of hard and attractive colloids

Abstract: Monte Carlo simulation and theory were used to study the potential of mean force (PMF) between a pair of big colloidal (solute) particles suspended in a sea of smaller particles (solvent) interacting via Baxter’s sticky hard sphere (SHS) potential. Simulation results were obtained by applying a special simulation technique developed for sampling the hard sphere collision force, while the theoretical predictions were calculated from the analytic solution of the Percus–Yevick/Ornstein–Zernike integral equation for spatial correlations in a two-component mixture at vanishing solute concentration. Both theory and simulation revealed oscillations of the solute-solute PMF with a period equal to the diameter of the solvent molecules. Further, the attractive PMF between solute particles in the SHS fluid decays slower than in a hard sphere solvent. Upon increasing the strength of attraction (stickiness) between the molecules of solvent, these oscillations gradually disappear, the PMF becoming long ranged and attra...

Ordering of Attractive Colloids near a Planar Wall: Theory and Simulation

Abstract: Structural properties of asymmetric binary sticky hard-sphere (SHS) mixture (the particular components being denoted by SHS 1 and SHS2), mimicking a system of interacting spherical colloidal particles in suspensions, near a planar wall, maintaining the equilibrium with the homogeneous (bulk) phase, are investigated. The wall-SHSl and wall-SHS2 correlations of the SHS mixture are studied using the grand canonical Monte Carlo simulation and Percus-Yevick/Omstein-Zemike integral equation. The density profiles of particular components show interesting shapes stemming from the interplay between the steric effects and the competitive adhesion among all possible species pairs, a characteristic feature being the discontinuities in the shapes of the profiles at the distances from the wall-SHS1 and wall-SHS2 contact planes, which correspond to different sums of the multiples of particular hard core diameters. The agreement between the theoretical predictions and simulation data is fair to very good and is better for the component comprised of weakly attractive (adhesive) particles.

Salt-Specific Effects in Solutions of Human Serum Albumin : Small-Angle X-Ray Scattering and Osmometry

Abstract: Small-angle X-ray scattering (SAXS) method and membrane osmometry were used to study salt-specific effects of various 1:1 salts at pH 4.0 and 8.0 on interparticle interactions and thermodynamic quantities in aqueous solutions of human serum albumin (HSA) at 25 °C. Our results show that Donnan pressures of HSA solutions exhibit stronger dependence on the type of anion than on the type of cation in the solution. However, the presence of different salts in the HSA solutions only weakly affects the SAXS curves in the accessible q regime (0.1 nm -1 < q < 7 nm -1 ). SAXS data were analyzed utilizing generalized indirect Fourier transformation, which indicated weak repulsive interactions between HSA molecules in all cases. Further, this analysis of the experimental SAXS curves strongly suggests that HSA molecules in the studied solutions have the shape of oblate ellipsoid with dimensions of approximately 8.5 x 8.5 x 4 nm. Both SAXS and membrane osmometry results can be satisfactorily explained in terms of the strength of the inter-particle interactions and conform to the trends of the Hofmeister series.