Publications (82) View all
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Article: Comparison of two immortalized human cell lines to study nuclear receptor-mediated CYP3A4 induction.
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ABSTRACT: Since CYP3A4 is responsible for the biotransformation of over 50% of all clinically used drugs, induction results in an increased clearance of many concomitantly administered drugs, thereby decreasing treatment efficacy or, in the case of prodrugs, lead to severe intoxications. CYP3A4 induction is regulated by the pregnane X receptor, constitutive androstane receptor, and vitamin D receptor. Since these nuclear receptors show large interspecies differences, accurate prediction of nuclear receptor-mediated CYP3A4 induction in humans requires the use of human systems. Because primary cultures of human hepatocytes or enterocytes have major drawbacks like poor availability and poor reproducibility, human cell lines are a good alternative. In this study, the widely used HepG2 cell line was compared with the LS180 cell line to serve as a model to study CYP3A4 induction. There was a clear difference between the cell lines with respect to CYP3A enzyme expression and induction. In LS180, CYP3A4 was expressed and was found to be induced by prototypical nuclear receptor agonists, whereas in HepG2, CYP3A4 was nonresponsive to treatment with rifampicin, CITCO [6-(4-chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-3,4-dichlorobenzyl) oxime], or calcitriol. We subsequently evaluated whether these host-cell differences also have an effect on CYP3A4 reporter gene activity. We clearly show that there are differences in CYP3A4 reporter activity between the cell lines, and based on these results and those found on mRNA and protein level, we conclude that LS180 is a more suitable cell line to study CYP3A4 induction than the widely used HepG2.Drug metabolism and disposition: the biological fate of chemicals 07/2008; 36(6):1166-71. · 3.74 Impact Factor -
Article: Apocynin and 1400 W prevents airway hyperresponsiveness during allergic reactions in mice.
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ABSTRACT: 1. The contribution of reactive nitrogen species to the development of airway hyperresponsiveness in a mouse model of allergic inflammation was investigated by the use of selective inhibitors of nitric oxide and superoxide formation. 2. Sensitized mice, repeatedly challenged with ovalbumin showed a significant (P<0.001, n=9) increase in airway responsiveness measured using whole body plethysmography. This hyperresponsiveness was accompanied by an influx of eosinophils into the airway lumen and increased levels of ovalbumin-specific serum IgE. 3. Treatment of mice with the iNOS inhibitor 1400 W or the NADPH-oxidase inhibitor apocynin did not significantly alter cellular influx into the airway lumen nor serum ovalbumin specific IgE. In contrast, apocynin as well as 1400 W inhibited ovalbumin-induced airway hyperresponsiveness (P<0.001 and P<0.05 respectively, n=9). Furthermore, the airways of allergen challenged animals showed clear 3-nitrotyrosine staining, which was mainly located in eosinophils. Remarkably, treatment with apocynin or 1400 W did not alter 3-nitrotyrosine staining. 4. These data suggest that the development of airway hyperresponsiveness during the airway inflammation upon ovalbumin challenge is dependent on the release of both superoxide and nitric oxide and is therefore likely to be dependent on reactive nitrogen species. This mechanism, however, is not reflected by 3-nitrotyrosine formation in the airways.British Journal of Pharmacology 09/2001; 134(2):434-40. · 4.41 Impact Factor -
Article: Integrin VLA-5: modulator and activator of mast cells.
Clinical & Experimental Allergy 07/2001; 31(6):817-22. · 5.03 Impact Factor -
Article: Attenuation of very late antigen-5-mediated adhesion of bone marrow-derived mast cells to fibronectin by peptides with inverted hydropathy to EF-hands.
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ABSTRACT: Release of allergic mediators from mast cells is enhanced by very late Ag (VLA)-5-mediated interaction of these cells with fibronectin. In this report, we show that VLA-5-mediated adhesion of bone marrow-derived mast cells to fibronectin can be induced by two different pathways: first, FcepsilonRI clustering, which depends on calmodulin activation and extracellular Ca(2+), and, second, by Mn(2+) stimulation, which is independent of calmodulin activation and antagonized by Ca(2+). Previous studies have shown the presence of several cation-binding domains in VLA-5 that are homologous to the calcium-binding EF-hands of calmodulin. To show a role for EF-hands of different proteins in VLA-5-mediated adhesion, we used calcium-like peptides (CALP), CALP1 and CALP2, designed to bind to EF-hands based on inverted hydropathy. CALP1 and, more potently, CALP2 inhibited FcepsilonRI-induced adhesion to fibronectin via different mechanisms. The target for the effects of CALP1 and 2 on FcepsilonRI-induced adhesion and degranulation was intracellular and likely involved calmodulin. Interestingly only CALP2 was able to inhibit Mn(2+)-induced calmodulin-independent adhesion by interfering with an extracellular target, which is probably VLA-5. We conclude that CALP1 and 2 can inhibit VLA-5-mediated adhesion of mast cells to fibronectin through binding to EF-hands of multiple proteins, and that these peptides can be used as lead compounds for the development of future therapy against allergy.The Journal of Immunology 02/2001; 166(2):861-7. · 5.79 Impact Factor -
Article: Integrin VLA-5: modulator and activator of mast cells
Clin Exp Allergy. 01/2001; 31(6):817-22.
