Biomedical subjects

Elke Schaeffeler

Publications and source records attributed to Elke Schaeffeler.

At least 19 recordsLinked to original sources

PubMed2026

Targeting ACKR3/CXCR7 enhances platelet anticoagulant acylcarnitines and modulates procoagulant function.

Targeting ACKR3/CXCR7 regulates enzymatic generation of prothrombotic lipids while favoring antithrombotic lipids that inhibit platelets through the AC-cAMP-PKA pathway in coordination with prostacyclin IP receptor. This investigation validated the effect of CXCR7 in modulating nonenzymatic lipid (per)oxidation, platelet response to lipoproteins, mitochondrial metabolism, and procoagulant functions. CXCR7 agonist VUF11207 preserved mitochondrial membrane integrity, counteracted activation-induced mitochondrial superoxide generation, and reduced nonenzymatic lipid (per)oxidation. Moreover, it regulated lipoprotein-induced platelet adhesion to thrombogenic matrices, degranulation, αIIbβIII-integrin activation, aggregation, and thrombotic responses by reducing lipoprotein uptake through CD36 and ApoER2. CXCR7 ligation triggered the activation of AMP-dependent kinaseSer-172 and prompted AMPK-mediated inhibitory phosphorylation of acetyl-coenzyme A carboxylaseSer-79 to foster lipolysis over lipogenesis. Consequently, the AMPKSer-172-ACCSer-79 pathway increased generation of anticoagulant FXa-inhibitory long-chain acylcarnitines (LC-CAR) in platelets of healthy subjects and patients with coronary artery disease. Enrichment of intraplatelet LC-CARs was not attributable to dysregulated mitochondrial respiration because VUF11207 improved maximal respiration, spare respiratory capacity, and ATP-linked respiration in thrombin-activated platelets, suggesting sustained mitochondrial metabolism. Exerting a 2-pronged effect on procoagulant function, VUF11207 downregulated phosphatidylserine exposure on activated platelets and reduced FX/FXa binding, while platelet-derived anticoagulant LC-CARs regulated thrombin generation. VUF11207 administration reduced thrombus formation, platelet degranulation, αIIbβIII-integrin activation, procoagulant activity, and circulating platelet-leukocyte aggregates in murine venous thrombosis model, also decreased plasma procoagulant lipids derived from platelet cyclooxygenase-1 and 12-lipooxygenase (LOX), and leukocyte 5/15-LOX, decreased thromboinflammatory mediators (IL-1β, IL-6, IFN-γ, TNF-α, and MCP-1), and increased plasma LC-CAR levels. Therefore, pharmacological targeting of CXCR7 could regulate (non)enzymatic lipid processing and promote anticoagulant LC-CAR generation to limit platelet-driven thrombotic propensity and hypercoagulability, also replenish reduced levels of circulatory LC-CARs in patients with STEMI and VTE.

Humans↗

PubMed2006

MALDI-TOF mass spectrometry for multiplex genotyping of CYP2B6 single-nucleotide polymorphisms.

BACKGROUND: CYP2B6 is a highly variable and polymorphic cytochrome P450 (CYP) enzyme involved in the biotransformation of an increasing number of drugs, including cyclophosphamide, bupropion, and the nonnucleosidic reverse transcriptase inhibitor efavirenz. Several nonsynonymous and promoter single-nucleotide polymorphisms (SNPs) in the CYP2B6 gene are associated with altered hepatic expression and function, which affect drug plasma concentrations. METHODS: We used multiplex PCR to amplify relevant gene fragments while avoiding amplification of the CYP2B7P1 pseudogene. Polymorphic sites were analyzed by allele-specific primer extension followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Method evaluation was performed on a panel of 287 genomic DNA samples previously genotyped by other methods. RESULTS: Five multiplex assays were developed, comprising the following 15 SNPs: -82T --> C (*22); 86G --> C (R29T, *17); 136A --> G (M46V, *11); 296G --> A (G99E, *12); 415A --> G (K139E, *8, *13); 419G --> A (R140Q, *14); 516G --> T (Q172H, *6, *7, *9, *13, *19, *20), 547G --> A (V183I); 769G --> A (D257N); 785A --> G (K262R, *4, *6, *7, *13, *16, *19, *20); 983T-->C (I328T, *16, *18); 1006C --> T (R336C, *19); 1172T --> A (I391N, *15); 1282C --> A (P428T, *21); 1459C --> T (R487C, *5, *7). In 9 DNA samples showing discrepant genotypes, correctness of the MALDI-TOF MS result was confirmed by direct sequencing. CONCLUSIONS: This genotyping method enabled sensitive, specific, accurate, and comprehensive determination of 15 relevant SNPs of CYP2B6. The assay design allows analysis of SNP subsets, incorporation of additional SNPs, and performance of high-throughput genotyping.

Aryl Hydrocarbon Hydroxylases↗

PubMed2006

A chromosome 8 gene-cluster polymorphism with low human beta-defensin 2 gene copy number predisposes to Crohn disease of the colon.

Defensins are endogenous antimicrobial peptides that protect the intestinal mucosa against bacterial invasion. It has been suggested that deficient defensin expression may underlie the chronic inflammation of Crohn disease (CD). The DNA copy number of the beta-defensin gene cluster on chromosome 8p23.1 is highly polymorphic within the healthy population, which suggests that the defective beta-defensin induction in colonic CD could be due to low beta-defensin-gene copy number. Here, we tested this hypothesis, using genomewide DNA copy number profiling by array-based comparative genomic hybridization and quantitative polymerase-chain-reaction analysis of the human beta-defensin 2 (HBD-2) gene. We showed that healthy individuals, as well as patients with ulcerative colitis, have a median of 4 (range 2-10) HBD-2 gene copies per genome. In a surgical cohort with ileal or colonic CD and in a second large cohort with inflammatory bowel diseases, those with ileal resections/disease exhibited a normal median HBD-2 copy number of 4, whereas those with colonic CD had a median of only 3 copies per genome (P=.008 for the surgical cohort; P=.032 for the second cohort). Overall, the copy number distribution in colonic CD was shifted to lower numbers compared with controls (P=.002 for both the surgical cohort and the cohort with inflammatory bowel diseases). Individuals with < or = 3 copies have a significantly higher risk of developing colonic CD than did individuals with > or = 4 copies (odds ratio 3.06; 95% confidence interval 1.46-6.45). An HBD-2 gene copy number of < 4 was associated with diminished mucosal HBD-2 mRNA expression (P=.033). In conclusion, a lower HBD-2 gene copy number in the beta-defensin locus predisposes to colonic CD, most likely through diminished beta-defensin expression.

Chromosomes, Human, Pair 8↗

PubMed2006

Influence of gain of function epithelial chloride channel ClC-Kb mutation on hearing thresholds.

Hearing depends on functional ClC-K-type chloride channels composed of barttin with ClC-Ka or ClC-Kb. Loss-of-function mutations of the barttin gene BSND or of both, the ClC-Ka gene CLNKA and the ClC-Kb gene CLNKB lead to congenital deafness and renal salt wasting. Recently, we identified the gain-of-function mutation ClC-Kb(T481S) which is associated with increased blood pressure. To explore the impact of ClC-Kb(T481S) on hearing, healthy volunteers (n=329) and individuals suffering from tinnitus (n=246) volunteered for hearing tests (n=348) and genetic analysis (n=575). 19.1% of the individuals were heterozygote (ClC-Kb(T481S)/ClC-Kb) and 1.7% homozygote carriers. Pure tone average hearing threshold (PTAt) for air conduction was significantly (p<0.033) lower in ClC-Kb(T481S) carriers (13.2+/-1.2dB) than in wild-type individuals (17.1+/-0.9dB). The prevalence of ClC-Kb(T481S) carriers was significantly increased (29.7%) in individuals with PTAt<15dB (p<0.05) and significantly decreased (13.2%) in individuals with PTAt>30 dB (p<0.017). The difference was largely due to the female population. Bone conduction was less affected pointing to an effect of the mutation on middle ear function. Tinnitus tended to be more frequent in ClC-Kb(T481S) carriers, a difference, however, not statistically significant. In conclusion, hearing thresholds are slightly lower in carriers of ClC-Kb(T481S), i.e., the gain-of-function polymorphism ClC-Kb(T481S) exerts a subtle but significant protective effect against hearing loss.

Adult↗

PubMed2006

Interindividual variability of canalicular ATP-binding-cassette (ABC)-transporter expression in human liver.

Interindividual variability in hepatic canalicular transporter expression might predispose to the development of hepatic disorders such as acquired forms of intrahepatic cholestasis. We therefore investigated expression patterns of bile salt export pump (BSEP, ABCB11), multidrug resistance protein 3 (MDR3, ABCB4), multidrug resistance associated protein 2 (MRP2, ABCC2) and multidrug resistance protein 1 (MDR1, ABCB1) in healthy liver tissue of a white population. Protein expression levels were correlated with specific single nucleotide polymorphisms (SNPs) in the corresponding transporter genes. Hepatic protein expression levels from 110 individuals undergoing liver resection were assessed by Western blot analysis of liver plasma membranes enriched in canalicular marker enzymes. Each individual was genotyped for the following synonymous (s) and nonsynonymous (ns) SNPs: ABCB11: (ns:1457T>C and 2155A>G), ABCB4: (ns:3826A>G) and ABCC2 (ns:1286G>A,3600T>A and 4581G>A) and ABCB1 (ns:2677G>T/A and s:3435C>T). Transporter expression followed unimodal distribution. However, of all tested individuals 30% exhibited a high expression and 32% a low or very low expression phenotype for at least one of the four investigated transport proteins. Transporter expression levels did not correlate with age, sex, underlying liver disease, or presurgery medication. However, low BSEP expression was associated with the 1457C-allele in ABCB11 (P = .167) and high MRP2 expression was significantly correlated with the 3600A and 4581A ABCC2 variants (P = .006). In conclusion, the results demonstrate a considerable interindividual variability of canalicular transporter expression in normal liver. Furthermore, data suggest a polymorphic transporter expression pattern, which might constitute a risk factor for the development of acquired forms of cholestatic liver diseases.

ATP-Binding Cassette Transporters↗

PubMed2006

Three novel thiopurine S-methyltransferase allelic variants (TPMT20, 21, *22) - association with decreased enzyme function.

The genetic polymorphism of the thiopurine S-methyltransferase, TPMT, comprises at least 21 alleles causing three distinct drug metabolism phenotypes termed normal/high, intermediate, and deficient methylators. In consequence, adverse drug reactions may occur if standard doses of thiopurines are applied routinely. Genetic prediction of the methylator phenotype as a basis for dose selection requires the extensive knowledge of single nucleotide polymorphisms occurring naturally in the population. Here we describe three novel missense variants in the TPMT gene which were associated with an intermediate red blood cell TPMT activity in three Caucasians. The following alleles were designated: TPMT*20 (c.712A>G), *21 (c.205C>G), and *22 (c.488G>C). No further genetic variations in remaining coding regions as well as the 5'flanking region of TPMT were identified. These sequence variants are present in highly conserved nucleotide positions of the TPMT gene throughout various mammalian species and in zebra fish, and are predicted to be intolerant when the functional consequences of variations were analyzed using SIFT (Sorting Intolerant From Tolerant) algorithm. In Caucasians the occurrence of these genetic variants appears to be extremely rare since none of these alleles were identified in a randomly selected control population of 1048 individuals.

Algorithms↗

PubMed2006

Impaired expression of CYP2D6 in intermediate metabolizers carrying the *41 allele caused by the intronic SNP 2988G>A: evidence for modulation of splicing events.

We investigated the molecular basis for low expression and activity of CYP2D6 associated with the CYP2D6*41 allele in about 10-15% of Caucasians with intermediate metabolizer phenotype. With respect to two previously described polymorphisms in the promoter (-1584C>G) and in intron 6 (2988G>A; c.985+39G>A), the three most frequent functional alleles have the distinct haplotypes 2D6*1[CG], 2D6*2[GG] and 2D6*41[CA], respectively. Reporter gene analyses in transiently transfected HepG2 and Huh7 hepatoma cells did not indicate changes in transcription rate by these polymorphisms. By reverse-transcription polymerase chain reaction analysis of liver RNA of genotyped patients, however, we discovered that the 2988G>A change was associated with increased levels of a nonfunctional splice variant lacking exon 6. Quantification by denaturing high-performance liquid chromatography revealed up to 7.3-fold increased levels of the splice variant and up to 2.9-fold less functional transcript in carriers of 2D6*41, in good concordance with concomitant changes in immunoquantified CYP2D6 protein. Recombinant expression of the entire genomic sequence coding for 2D6*41, 2D6*2 and 2D6*1 alleles but lacking the upstream region in COS-1 and Huh7 cell lines resulted in two-fold to five-fold reduced levels of CYP2D6 mRNA containing exon 6, apoprotein and enzyme activity of 2D6*41. These experiments establish the causal relationship between the intron 6 single-nucleotide polymorphism 2988G>A and the low expression phenotype associated with allele 2D6*41. These data improve the CYP2D6 genotype-phenotype relationship and they demonstrate that major phenotype changes occurring in large population subgroups can be caused by intronic polymorphisms outside of splice site consensus sequences.

Alleles↗

PubMed2005

Reduced Paneth cell alpha-defensins in ileal Crohn's disease.

The pathogenesis of Crohn's disease (CD), an idiopathic inflammatory bowel disease, is attributed, in part, to intestinal bacteria that may initiate and perpetuate mucosal inflammation in genetically susceptible individuals. Paneth cells (PC) are the major source of antimicrobial peptides in the small intestine, including human alpha-defensins HD5 and HD6. We tested the hypothesis that reduced expression of PC alpha-defensins compromises mucosal host defenses and predisposes patients to CD of the ileum. We report that patients with CD of the ileum have reduced antibacterial activity in their intestinal mucosal extracts. These specimens also showed decreased expression of PC alpha-defensins, whereas the expression of eight other PC products either remained unchanged or increased when compared with controls. The specific decrease of alpha-defensins was independent of the degree of inflammation in the specimens and was not observed in either CD of the colon, ulcerative colitis, or pouchitis. The functional consequence of alpha-defensin expression levels was examined by using a transgenic mouse model, where we found changes in HD5 expression levels, comparable to those observed in CD, had a pronounced impact on the luminal microbiota. Thus, the specific deficiency of PC defensins that characterizes ileal CD may compromise innate immune defenses of the ileal mucosa and initiate and/or perpetuate this disease.

Analysis of Variance↗

PubMed2005

Thiopurine methyltransferase (TPMT) genotype and early treatment response to mercaptopurine in childhood acute lymphoblastic leukemia.

CONTEXT: Early response to multiagent chemotherapy, including mercaptopurine, as measured by minimal residual disease is an important prognostic factor for children with acute lymphoblastic leukemia (ALL). Thiopurine methyltransferase (TPMT) is involved in the metabolism of mercaptopurine and subject to genetic polymorphism, with heterozygous individuals having intermediate and homozygous mutant individuals having very low TPMT activity. OBJECTIVE: To assess the association of TPMT genotype with minimal residual disease load before and after treatment with mercaptopurine in the early treatment course of childhood ALL. DESIGN, SETTING, AND PATIENTS: TPMT genotyping of childhood ALL patients (n = 814) in Germany consecutively enrolled in the ALL-BFM (Berlin-Frankfurt-Münster) 2000 study from October 1999 to September 2002. Minimal residual disease was analyzed on treatment days 33 and 78 for risk-adapted treatment stratification. A 4-week cycle of mercaptopurine was administered between these 2 minimal residual disease measurements. Patients (n = 4) homozygous for a mutant TPMT allele, and consequently deficient in TPMT activity, were treated with reduced doses of mercaptopurine and, therefore, not included in the analyses. MAIN OUTCOME MEASURES: Minimal residual disease load before (day 33) and after (day 78) mercaptopurine treatment. Loads smaller than 10(-4) were defined as negative. RESULTS: Patients (n = 55) heterozygous for allelic variants of TPMT conferring lower enzyme activity had a significantly lower rate of minimal residual disease positivity (9.1%) compared with patients (n = 755) with homozygous wild-type alleles (22.8%) on day 78 (P = .02). This translated into a 2.9-fold reduction in risk for patients with wild-type heterozygous alleles (relative risk, 0.34; 95% confidence interval, 0.13-0.86). CONCLUSIONS: TPMT genotype has a substantial impact on minimal residual disease after administration of mercaptopurine in the early course of childhood ALL, most likely through modulation of mercaptopurine dose intensity. Our findings support a role for minimal residual disease analyses in the assessment of genotype-phenotype associations in multiagent chemotherapeutic trials.

Adolescent↗

PubMed2005

ABCB1 genotype of the donor but not of the recipient is a major risk factor for cyclosporine-related nephrotoxicity after renal transplantation.

Cyclosporine (CsA) nephrotoxicity is a severe complication in organ transplantation because it leads to impaired renal function and chronic allograft nephropathy, which is a major predictor of graft loss. Animal models and in vivo studies indicate that the transmembrane efflux pump P-glycoprotein contributes substantially to CsA nephrotoxicity. It was hypothesized that the TT genotype at the ABCB1 3435C-->T polymorphism, which is associated with decreased expression of P-glycoprotein in renal tissue, is a risk factor for developing CsA nephrotoxicity. In a case-control study, 18 of 97 patients developed CsA nephrotoxicity and showed complete recovery of renal function in all cases when switched to a calcineurin inhibitor-free regimen. Both recipients and donors were genotyped for ABCB1 polymorphisms at the positions 3435C-->T and 2677G-->T/A. For controlling for population stratification, two additional polymorphisms, CYP2D6*4 and CYP3A5*3, with intermediate allelic frequencies were studied. The P-glycoprotein low expressor genotype 3435TT only of renal organ donors but not of the recipients was overrepresented in patients with CsA nephrotoxicity as compared with patients without toxicity (chi2 = 10.5; P = 0.005). CsA dosage, trough levels, and the concentration per dose ratio were not different between the patient groups. In a multivariate model that included several other nongenetic covariates, only the donor's ABCB1 3435TT genotype was strongly associated with CsA nephrotoxicity (odds ratio, 13.4; 95% confidence interval, 1.2 to 148; P = 0.034). A dominant role of the donor's ABCB1 genotype was identified for development of CsA nephrotoxicity. This suggests that P-glycoprotein is an important factor in CsA nephrotoxicity.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Antimalarial artemisinin drugs induce cytochrome P450 and MDR1 expression by activation of xenosensors pregnane X receptor and constitutive androstane receptor.

Artemisinin drugs are of utmost importance in the treatment of malaria, because they represent the sole class of therapeutically used antimalarial drugs to which malaria parasites have not yet developed resistance. The major disadvantage of these medicines is the comparatively high recrudescence rate, which has been attributed to the remarkable decrease of artemisinin plasma concentrations during multiple dosing. Autoinduction of CYP2B6-mediated metabolism has been implicated as the underlying mechanism. So far, the molecular mechanism of induction by artemisinin has not been resolved. Because the xenosensors pregnane X receptor (PXR) and constitutive androstane receptor (CAR) have been shown to mediate induction of drug-metabolizing enzymes and drug transporters, we investigated the hypothesis that artemisinin induces cytochrome P450 expression by activating PXR and/or CAR. By combining in vitro transfection methods and quantitative analyses of gene expression in cell lines and primary human hepatocytes, we here show that artemisinin drugs activate human PXR as well as human and mouse CAR and induce the expression of CYP2B6, CYP3A4, and MDR1 in primary human hepatocytes and in the human intestinal cell line LS174T. Furthermore, we demonstrate that artemisinin acts as a ligand of both nuclear receptors, because it modulates the interaction of the receptors with coregulators. In conclusion, activation of PXR and CAR and especially the resulting induction of CYP3A4 and MDR1 demonstrate that artemisinin has a higher risk of potential drug interactions than anticipated previously.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2005

Impact of CYP2D6 genotype on adverse effects during treatment with metoprolol: a prospective clinical study.

OBJECTIVE: Our objective was to study the impact of the cytochrome P450 (CYP) 2D6 polymorphism on the tolerability of metoprolol in a real-life primary care setting. The adverse effects studied comprised effects related to the central nervous system, cardiovascular effects, and sexual dysfunction. METHODS: Patients in whom treatment with metoprolol was considered were enrolled into this prospective, 6-week multicenter study. The dosage of metoprolol was determined on an individual basis and could be freely adjusted on clinical grounds. The indication for treatment was hypertension in about 90% of cases. Systolic and diastolic blood pressure, resting heart rate, and plasma metoprolol and alpha-hydroxymetoprolol concentrations were measured. CYP2D6 genotyping covered alleles *3 to *10 and *41 and the duplications. Possible adverse effects of metoprolol were systematically assessed over a 6-week period by means of standardized rating scales and questionnaires. RESULTS: The final study population comprised 121 evaluable patients (all white patients); among them, there were 5 ultrarapid metabolizers (UMs) (4.1%), 91 extensive metabolizers (EMs) (75%), 21 intermediate metabolizers (IMs) (17%), and 4 poor metabolizers (PMs) (3.3%). Plasma metoprolol concentrations normalized for the daily dose and metoprolol/alpha-hydroxymetoprolol ratios at steady state were markedly influenced by CYP2D6 genotype and displayed a gene-dose effect. The median of the dose-normalized metoprolol concentration was 0.0088 ng/mL, 0.047 ng/mL, 0.34 ng/mL, and 1.34 ng/mL among UMs, EMs, IMs, and PMs, respectively (P<.0001). There was no significant association between CYP2D6 genotype-derived phenotype (EMs and UMs combined versus PMs and IMs combined) and adverse effects during treatment with metoprolol. There was a tendency toward a more frequent occurrence of cold extremities in the PM plus IM group as compared with the EM plus UM group (16.0% versus 4.2%, P=.056; relative risk, 3.8 [95% confidence interval, 1.03--14.3]). CONCLUSIONS: CYP2D6 genotype-derived phenotype was not significantly associated with a propensity for adverse effects to develop during treatment with metoprolol. However, the results concerning tolerability of metoprolol in PMs were inconclusive because of the small number of PMs enrolled.

Adrenergic beta-1 Receptor Antagonists↗

PubMed2005

Esomeprazole-induced healing of gastroesophageal reflux disease is unrelated to the genotype of CYP2C19: evidence from clinical and pharmacokinetic data.

BACKGROUND: The clinical outcome of acid-related disorders treated by proton pump inhibitors (PPIs) might be dependent on the polymorphically expressed cytochrome P450 (CYP) 2C19, which is involved in PPI metabolism. We tested whether esomeprazole-induced healing of gastroesophageal reflux disease (GERD) is related to CYP2C19 genotype. METHODS: Two hundred five patients with GERD (Los Angeles classification grade A or B) were included in a case-control study according to endoscopic outcome (healed versus unhealed group, matched for confounders) after treatment with 40 mg esomeprazole daily for 4 weeks. The frequency of CYP2C19 genotypes was determined as the primary outcome measure for both groups. In a second trial plasma levels of esomeprazole and corresponding CYP2C19 and CYP3A4 metabolites (5-hydroxyomeprazole and omeprazole sulfone) were monitored in 10 CYP2C19 wild-type patients with GERD after the first and last doses (day 7) of 40 mg esomeprazole daily to calculate metabolic ratios. RESULTS: CYP2C19 wild-type (n = 148) and heterozygous (n = 51) or homozygous variant (n = 6) patients did not differ with respect to baseline characteristics. The frequency distribution of CYP2C19 genotypes was not different between patients with complete (75/100) and incomplete (73/105) healing (P = .65). When a single esomeprazole dose and multiple dosing were compared, the low contribution of CYP2C19 to the elimination of esomeprazole decreased further by 50%. In contrast, the CYP3A4-dependent formation of omeprazole sulfone increased by 40%, and consequently, the metabolic ratio of omeprazole sulfone to 5-hydroxyomeprazole was elevated from 7.9 to 19.3 (P = .0004). CONCLUSION: In contrast to other PPIs, esomeprazole-induced healing of GERD is unrelated to the CYP2C19 genotype, which can be explained by the metabolic shift toward the CYP3A4-mediated pathway.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2005

A prospective, open-label trial of 6-thioguanine in patients with ulcerative or indeterminate colitis.

OBJECTIVE: 6-thioguanine (6-TG) has emerged as a promising therapeutic alternative in patients with Crohn's disease intolerant or resistant to azathioprine (AZA) and/or 6-mercaptopurine (6-MP). The aim of the present study was to evaluate the safety and efficacy of 6-TG in patients with ulcerative colitis (UC) or indeterminate colitis (IC) intolerant or resistant to AZA/6-MP. MATERIAL AND METHODS: Twenty patients with an acute flare, steroid-dependent or steroid-refractory disease attending our outpatient department were included in the study. Measurement of 6-TG nucleotide levels was done to check compliance. Complete, partial and non-response were defined by means of the clinical activity index and the daily steroid demand. Secondary outcome parameters included changes in cumulative steroid doses, C-reactive protein (CRP) levels, and an endoscopic score. RESULTS: Out of 20 patients 4 were excluded owing to noncompliance; 2/16 compliant patients (13%) had to be prematurely withdrawn because of adverse events, which ceased upon drug discontinuation. By per-protocol analysis, 5/14 patients (36%) were complete, 6/14 (43%) partial and 3/14 (21%) non-responders. In addition to the reduction of the cumulative steroid dose over 3 months, CRP decreased in the study population and the endoscopic score decreased in treatment responders. CONCLUSIONS: Treatment with 6-TG was effective in patients with UC or IC previously intolerant or resistant to AZA/6-MP. Future work is needed to define a subpopulation of patients at low risk for its potential hepatotoxicity, which we assume will benefit from 6-TG.

Adult↗

PubMed2005

CYP3A5 genotype is associated with diagnosis of hypertension in elderly patients: data from the DEBATE Study.

OBJECTIVE: The aim of this study was to address the presently controversial question of whether cytochrome P450 (CYP) 3A5 polymorphism is associated with hypertension. METHOD: We studied 373 elderly (age > or =75 years) Finnish (Caucasian) patients from the ongoing DEBATE (Drugs and Evidence Based Medicine in the Elderly) trial. The patients were classified into those with a history of hypertension (n = 229) and those without a history of hypertension (n = 144) on the basis of a detailed questionnaire on each patient's medical history and an interview. The patients were genotyped for the CYP3A5 6986A/G single nucleotide polymorphism (SNP) [CYP3A5*1/*3 alleles]. RESULTS: The proportion of individuals with the CYP3A5*1/*3 genotype, i.e. CYP3A5 expressors, was significantly higher among patients with a diagnosis of hypertension than among patients without (18.3% vs 9.0%, p = 0.016). The corresponding odds ratio was 2.26 (95% CI 1.17, 4.38). The allele and genotype frequencies for the two control SNPs, ABCB1 (MDR1) 3435C/T and SLCO1B1 521T/C, did not differ between the two groups. CONCLUSION: This work lends support to the theory that the polymorphic CYP3A5 enzyme may be involved in regulation of blood pressure. The possible role of CYP3A5 as a genetic contributor to hypertension susceptibility warrants further study.

Aged↗

PubMed2004

Activating mutation of the renal epithelial chloride channel ClC-Kb predisposing to hypertension.

The chloride channel ClC-Kb is expressed in the basolateral cell membrane of the distal nephron and participates in renal NaCl reabsorption. Loss-of-function mutations of ClC-Kb lead to classic Bartter syndrome, a rare salt-wasting disorder. Recently, we identified the ClC-Kb(T481S) polymorphism, which confers a strong gain-of-function effect on the ClC-Kb chloride channel. The present study has been performed to explore the prevalence of the mutation and its functional significance in renal salt handling and blood pressure regulation. As evident from electrophysiological analysis with the 2-electrode voltage-clamp technique, heterologous expression of ClC-Kb(T481S) in Xenopus oocytes gave rise to a current that was 7-fold larger than the current produced by wild-type ClC-Kb. The prevalence of the mutant allele was significantly higher in an African population from Ghana (22%) than in whites (12%). As tested in 1 white population, carriers of ClC-Kb(T481S) were associated with significantly higher systolic (by approximately 6.0 mm Hg) and diastolic (by approximately 4.2 mm Hg) blood pressures and significantly higher prevalence (45% versus 25%) of hypertensive (> or =140/90 mm Hg) blood pressure levels. Individuals carrying ClC-Kb(T481S) had significantly higher plasma Na+ concentrations and significantly decreased glomerular filtration rate. In conclusion, the mutation ClC-Kb(T481S) of the renal epithelial Cl- channel ClC-Kb strongly activates ClC-Kb chloride channel function in vitro and may predispose to the development of essential hypertension in vivo.

Adult↗

PubMed2004

CYP2C19 polymorphism is a major predictor of treatment failure in white patients by use of lansoprazole-based quadruple therapy for eradication of Helicobacter pylori.

OBJECTIVE: Proton pump inhibitors, metabolized by the polymorphic enzyme cytochrome P450 (CYP) 2C19, are essential drugs for Helicobacter pylori eradication. It was reported that patients with CYP2C19 wild type in Asia had lower eradication rates. This study tests the hypothesis that CYP2C19 wild type ( wt/wt ) in white patients is also associated with a higher probability of treatment failure. METHODS: This was a cohort study involving 131 H pylori -positive white (German) patients treated by quadruple therapy including lansoprazole (30 mg twice daily for 5 days). Eradication success, as well as lansoprazole trough steady-state serum concentrations, was determined according to different CYP2C19 genotypes. RESULTS: We found 3 homozygous variant patients (2.3%) ( mt/mt, CYP2C19*2/*2 ), 42 heterozygous patients (32.1%) ( wt/mt, CYP2C19*1/*2 ), and 86 wild-type individuals (65.6%). Significant differences in eradication success could be found between wt/wt patients (80.2%) versus combined mt/mt (100%) and wt/mt patients (97.8%) ( P <.01; odds ratio, 10.8 [confidence interval, 1.4-84]), which were associated with corresponding changes in the serum levels of lansoprazole (median, 753 ng/mL for mt/mt, 59 ng/mL for wt/mt, and 21 ng/mL for wt/wt; P <.001). Apart from antibiotic resistance, CYP2C19 polymorphism was the most important influencing factor for eradication success on multivariate analysis ( P <.0001). CONCLUSION: Eradication rates of H pylori highly depend on CYP2C19 in white patients if standard doses of lansoprazole (30 mg twice daily) are administered within a quadruple regimen. Because wt/wt individuals have lower eradication rates and lower serum concentrations of lansoprazole, these patients might benefit from a higher proton pump inhibitor dosage.

2-Pyridinylmethylsulfinylbenzimidazoles↗

PubMed2004

Variable expression of P-glycoprotein in the human placenta and its association with mutations of the multidrug resistance 1 gene (MDR1, ABCB1).

The MDR1 gene product P-glycoprotein in the human placenta is important for protecting the fetus from unintended, harmful drug exposure, but also for limiting the access of therapeutic drugs to the fetus after maternal drug intake. A polymorphism in exon 26 of the MDR1 gene (C3435T) has previously been shown to be associated with reduced P-glycoprotein expression in the small intestine, kidney and lymphocytes. In the present study, we examined systematically whether MDR1 polymorphisms also have an impact on P-glycoprotein expression in the human placenta. MDR1 mRNA and P-glycoprotein were analysed in 73 full-term human placentas of Caucasians, as well as respective MDR1 genotypes/haplotypes, for the C3435T and G2677T/A polymorphisms of mothers and infants. MDR1 mRNA levels were not different between these genotype groups. However, P-glycoprotein expression was significantly lower when both mother and infant were homozygous for the 3435T allele (TT/tt) compared to maternal and fetal homozygotes for the C-allele (0.40 +/- 0.18 a.u. for TT/tt versus 0.66 +/- 0.30 a.u. for CC/cc, P = 0.01). Moreover, placentas from mothers carrying both polymorphisms (3435T and 2677T; TT/TT) also had a significantly lower P-glycoprotein expression (0.31 +/- 0.12 a.u.) compared to placentas of wild-type individuals (CC/GG, 0.71 +/- 0.31 a.u., P = 0.02). Taken together, the MDR1 polymorphisms C3435T and G2677T are associated with altered P-glycoprotein expression in the human placenta, and may have clinical consequences due to genetically determined, variable drug exposure of the fetus.

ATP Binding Cassette Transporter, Subfamily B, Mem↗