Michela Rebsamen

A Critical Role for p38 Mitogen-Activated Protein Kinase in the Maturation of Human Blood-Derived Dendritic Cells Induced by Lipopolysaccharide, TNF-α, and Contact Sensitizers

We investigated the involvement of mitogen-activated protein kinases (MAPKs) in the maturation of CD83− dendritic cells (DC) derived from human blood monocytes. Maturating agents such as LPS and TNF-α induced the phosphorylation of members of the three families of MAPK (extracellular signal-regulated kinase l/2, p46/54 c-Jun N-terminal kinase, and p38 MAPK). SB203580, an inhibitor of the p38 MAPK, but not the extracellular signal-regulated kinase l/2 pathway blocker PD98059, inhibited the up-regulation of CD1a, CD40, CD80, CD86, HLA-DR, and the DC maturation marker CD83 induced by LPS and TNF-α. In addition, SB203580 inhibited the enhancement of the allostimulatory capacity and partially prevented the down-regulation of FITC-dextran uptake induced by LPS and TNF-α. Likewise, SB203580 partially prevented the up-regulation of IL-1α, IL-1β, IL-lRa, and TNF-α mRNA upon stimulation with LPS and TNF-α, as well as the release of bioactive TNF-α induced by LPS. DC maturation induced by the contact sensitizers 2,4-dinitrofluorobenzene and NiSO4, as seen by the up-regulation of CD80, CD86, and CD83, was also coupled to the phosphorylation of p38 MAPK, and was inhibited by SB203580. The irritants SDS and benzalkonium chloride that do not induce DC maturation did not trigger p38 MAPK phosphorylation. Together, these data indicate that phosphorylation of p38 MAPK is critical for the maturation of immature DC. These results also suggest that p38 MAPK phosphorylation in DC may become useful for the identification of potential skin contact sensitizers.

Genetic polymorphisms and drug interactions modulating CYP2D6 and CYP3A activities have a major effect on oxycodone analgesic efficacy and safety

Background and purpose:  The major drug‐metabolizing enzymes for the oxidation of oxycodone are CYP2D6 and CYP3A. A high interindividual variability in the activity of these enzymes because of genetic polymorphisms and/or drug–drug interactions is well established. The possible role of an active metabolite in the pharmacodynamics of oxycodone has been questioned and the importance of CYP3A‐mediated effects on the pharmacokinetics and pharmacodynamics of oxycodone has been poorly explored.

The AmpliChip CYP450 test: cytochrome P450 2D6 genotype assessment and phenotype prediction

Polymorphisms of the cytochrome P450 2D6 (CYP2D6) gene affecting enzyme activity are involved in interindividual variability in drug efficiency/toxicity. Four phenotypic groups are found in the general population: ultra rapid (UM), extensive (EM), intermediate (IM) and poor (PM) metabolizers. The AmpliChip CYP450 test is the first genotyping array allowing simultaneous analysis of 33 CYP2D6 alleles. The main aim of this study was to evaluate the performance of this test in CYP2D6 phenotype prediction. We first verified the AmpliChip CYP450 test genotyping accuracy for five CYP2D6 alleles routinely analysed in our laboratory (alleles 3,4,5,6, × N; n=100). Results confirmed those obtained by real-time PCR. Major improvements using the array are the detection of CYP2D6 intermediate alleles and identification of the duplicated alleles. CYP2D6 phenotype was determined by assessing urinary elimination of dextromethorphan and its metabolite dextrorphan and compared to the array prediction (n=165). Although a low sensitivity of UM prediction by genotyping was observed, phenotype prediction was optimal for PM and satisfying for EM and IM.

The effects of CYP2D6 and CYP3A activities on the pharmacokinetics of immediate release oxycodone

Background and purpose:  There is high interindividual variability in the activity of drug‐metabolizing enzymes catalysing the oxidation of oxycodone [cytochrome P450 (CYP) 2D6 and 3A], due to genetic polymorphisms and/or drug–drug interactions. The effects of CYP2D6 and/or CYP3A activity modulation on the pharmacokinetics of oxycodone remains poorly explored.

Relationship between paraoxonase-1 activity, its Q192R genetic variant and clopidogrel responsiveness in the ADRIE study.

*Division of Angiology and Hemostasis, Division of Endocrinology, Diabetology and Nutrition, Department of Medical Specialties, GenevaUniversity Hospitals and Faculty of Medicine, Geneva, Switzerland; Hematology Laboratory, §Division of Cardiology, Be´ziers Hospital, Be´ziers;–Hematology Laboratory, Montpellier University Hospital, Montpellier, France; **Division of Laboratory Medicine, Department of Genetics andLaboratory Medicine, Geneva University Hospitals, Geneva; and Division of General Internal Medicine, Geneva University Hospital and Facultyof Medicine, Geneva, SwitzerlandTo cite this article: Fontana P, James R, Barazer I, Berdague´ P, Schved JF, Rebsamen M, Vuilleumier N, Reng JL. Relationship betweenparaoxonase-1 activity, its Q192R genetic variant and clopidogrel responsiveness in the ADRIE study. J Thromb Haemost 2011; 9: 1664–6.

Geneva Cocktail for Cytochrome P450 and P‐Glycoprotein Activity Assessment Using Dried Blood Spots

The suitability of the capillary dried blood spot (DBS) sampling method was assessed for simultaneous phenotyping of cytochrome P450 (CYP) enzymes and P‐glycoprotein (P‐gp) using a cocktail approach. Ten volunteers received an oral cocktail capsule containing low doses of the probes bupropion (CYP2B6), flurbiprofen (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), midazolam (CYP3A), and fexofenadine (P‐gp) with coffee/Coke (CYP1A2) on four occasions. They received the cocktail alone (session 1), and with the CYP inhibitors fluvoxamine and voriconazole (session 2) and quinidine (session 3). In session 4, subjects received the cocktail after a 7‐day pretreatment with the inducer rifampicin. The concentrations of probes/metabolites were determined in DBS and plasma using a single liquid chromatography–tandem mass spectrometry method. The pharmacokinetic profiles of the drugs were comparable in DBS and plasma. Important modulation of CYP and P‐gp activities was observed in the presence of inhibitors and the inducer. Minimally invasive one‐ and three‐point (at 2, 3, and 6 h) DBS‐sampling methods were found to reliably reflect CYP and P‐gp activities at each session.

Influence of ABCB1 Gene Polymorphisms and P-Glycoprotein Activity on Cyclosporine Pharmacokinetics in Peripheral Blood Mononuclear Cells in Healthy Volunteers

The calcineurin inhibitor cyclosporine is removed from lymphocytes by the drug efflux transporter P-glycoprotein (P-gp) encoded by the ABCB1 gene for which several single nucleotide polymorphisms (SNPs) have been identified. Of a total of 87 healthy volunteers genotyped for ABCB1 G2677T/A and C3435T SNPs, 10 GG-CC and 9 TT-TT individuals were selected and received a single oral dose of cyclosporine. Peripheral blood mononuclear cell (PBMC) ABCB1 mRNA expression, P-gp activity in CD4(+) and CD8(+) cells and the 24h cyclosporine pharmacokinetics in PBMCs and whole blood were determined. No correlation was observed between cyclosporine PBMC and whole blood levels (AUC(0-24), Spearman, r(S)=0.09, p=0.71). Intraindividual PBMC and whole blood levels followed parallel profiles that did not significantly differ with respect to t(max) (Wilcoxon, p=0.53) and t((1/2)) (p=0.49). Significant negative correlations between cyclosporine t((1/2)) in PBMCs and P-gp activity in CD4(+) (r(S)=-0.82, p=0.007) and CD8(+) (r(S)=-0.72, p=0.03) were observed among TT-TT subjects. Similarly, a negative correlation was detected in the GG-CC group between P-gp activity in CD4(+) and cyclosporine PBMC AUC(0-24) (r(S)=-0.69, p=0.03), as well as PBMC to whole blood AUC(0-24) ratio (r(S)=-0.60, p=0.07). Tested ABCB1 genotypes had no influence on cyclosporine pharmacokinetic parameters in PBMCs and whole blood. The haplotypes investigated were neither significantly correlated with PBMC ABCB1 mRNA expression nor with P-gp activity in CD4(+) and CD8(+). In conclusion, cyclosporine PBMC pharmacokinetics was influenced by P-gp activity and cyclosporine whole blood concentrations did not predict PBMC drug levels, suggesting that despite values in the therapeutic range, some subjects could have inadequate intracellular drug levels.

Role of cyclooxygenase 2, p38 and p42/44 MAPK in the secretion of prostacyclin induced by epidermal growth factor, endothelin-1 and angiotensin II in rat ventricular cardiomyocytes.

We studied the respective roles of cyclooxygenases (COX) isoforms as well as the p38 and p42/44 MAP kinase cascades in angiotensin II (AngII)-, endothelin-1 (ET-1)- and epidermal growth factor (EGF)-induced prostacyclin (PGI(2)) secretion in neonatal rat ventricular cardiomyocytes. Exposure of these cells for 1 h to 100 nM AngII, ET-1 or EGF resulted in an increase in prostacyclin formation which was abolished by the COX-2 specific inhibitor NS-398 (1 microM), while the COX-1 inhibitor valeryl salicylate (5 microM) had no effect. Agonist-induced prostacyclin secretion was also abolished in the presence of cycloheximide (10 microg/ml), indicating that newly synthesized proteins are necessary for this response. In this context, the COX-2 protein amount was significantly increased following 1 h incubation of cardiomyocytes, with AngII, ET-1 and EGF. These results indicate that in cardiomyocytes AngII, ET-1 and EGF induce both the synthesis and the activity of COX-2. Investigating the role of MAPK in the stimulation of prostacyclin induced by these three agonists, we found that both the p42/44 MAPK inhibitor PD 98059 (50 microM) and the p38 MAPK blocker SB 203580 (5 microM) prevented agonist-induced PGI(2) secretion without affecting COX-2 activity or synthesis. Our results show that p42/44 and p38 MAPK activation is at the basis of AngII-, ET-1- and EGF-induced prostacyclin secretion in cardiomyocytes. They further suggest that these MAPK act on a target(s) located upstream of COX-2.

First evidence of a polygenic susceptibility to pain in a pediatric cohort.

BACKGROUND:There is currently no evidence about the genetic bases of postoperative pain variability in children. METHODS:We prospectively followed a cohort of 168 children after orthopedic or abdominal surgery, who were under morphine patient-controlled analgesia. The children and their parents were genotyped for 6 candidate-gene polymorphisms (single-nucleotide polymorphisms [SNPs]) implicated in nociception and opiate metabolism: ABCB1C3435T, COMTVal158Met, NTRK1His40Tyr, OPRMA118G, POMCArg236Gln, and a haplotype of CYP2D6. Postoperative pain was assessed using the Faces Pain Scale (FPS), at rest and during mobilization, 11 times during the first 24 postoperative hours. RESULTS:At rest, and to a lesser extent, at mobilization, having at least 4 pain peaks of FPS score >6 in 24 hours was more frequent in children with ABCB1_CC than in children with ABCB1_CT and ABCB1_TT (adjusted risk ratio = 4.5; 95% confidence interval [CI],1.5–13.4; corrected CI for multiple comparisons, 0.98–20.55) and was more frequent in children with OPRM_GA than those with OPRM_AA (adjusted risk ratio = 3.5; 95% CI, 1.1–11.2; corrected CI, 0.70–17.30). After adjusting for parental mating type and correcting for multiple comparisons, mean FPS scores across the 24 postoperative hours were higher for OPRM_GA than for OPRM_AA at rest (P < 0.0002), higher for NTRK1_ CT or NTRK1_ TT than NTRK1_ CC during mobilization (P = 0.002), and lower for COMT_GG than COMT_AA and COMT_GA, during mobilization (P = 0.005). CONCLUSIONS:ABCB1 and OPRM genotypes are associated with clinically meaningful pain variability, whereas NTRK1 and COMT are linked to subclinical effects. This first but small cohort study provides clues to further explore the genetic foundations of pediatric pain.

Intraplatform Reproducibility and Technical Precision of Gene Expression Profiling in 4 Laboratories Investigating 160 Leukemia Samples: The DACH Study

BACKGROUND Gene expression profiling has the potential to offer consistent, objective diagnostic test results once a standardized protocol has been established. We investigated the robustness, precision, and reproducibility of microarray technology. METHODS One hundred sixty individual patient samples representing 11 subtypes of acute and chronic leukemias, myelodysplastic syndromes, and nonleukemia as a control group were centrally collected and diagnosed as part of the daily routine in the Munich Leukemia Laboratory. The custom AmpliChip Leukemia research microarray was used for technical analyses of quadruplicate mononuclear cell lysates in 4 different laboratories in Germany (D), Austria (A), and Switzerland (CH) (the DACH study). RESULTS Total-RNA preparations were successfully performed in 637 (99.5%) of 640 cases. Mean differences between pairs of laboratories in the total-RNA yield from the same sample ranged from 0.02 mug to 1.03 mug. Further processing produced 622 successful in vitro transcription reactions (97.6%); the mean differences between laboratories in the cRNA yield from the same sample ranged from 0.40 mug to 6.18 mug. After hybridization to microarrays, a mean of 47.6%, 46.5%, 46.2%, and 46.4% of probe sets were detected as present for the 4 laboratories, with mean signal-intensity scaling factors of 3.1, 3.7, 4.0, and 4.2, respectively. In unsupervised hierarchical cluster and principal component analyses, replicates from the same patient always clustered closely together, with no indications of any association between gene expression profiles due to different operators or laboratories. CONCLUSIONS Microarray analysis can be performed with high interlaboratory reproducibility and with comparable quality and high technical precision across laboratories.