ADME transcriptome in Hispanic versus White donor livers: Evidence of a globally enhanced NR1I3 (CAR, constitutive androstane receptor) gene signature in Hispanics

Previous studies have found that, compared with Whites, Hispanic donor livers had elevated expression of CYP2 enzymes, gene products regulated by the constitutive androstane receptor (CAR). The objectives of the current study were to determine (1) the CAR activation signature in human liver (2) whether other drug detoxification (absorption, distribution, metabolism and excretion (ADME)) genes were differentially expressed in Hispanic versus White livers, and (3) the extent of overlap in the CAR and Hispanic liver transcriptomes. The CAR transcriptome (ADME genes differentially expressed following phenobarbital versus vehicle treatment of human hepatocytes) and the Hispanic liver transcriptome (ADME genes differentially expressed in Hispanic versus White livers) were identified using Affymetrix oligonucleotide arrays. Quantitative real-time polymerase chain reaction (PCR) was used to verify candidate genes in a larger sample size. Comparison of the CAR and Hispanic liver ADME transcriptomes revealed a significant association between the gene changes. Sixty-four per cent of the ADME genes induced more than twofold by phenobarbital were also induced in Hispanics, and 14% of the ADME genes repressed more than twofold by phenobarbital were repressed in Hispanics. In conclusion, compared with Whites, Hispanic donor livers have increased expression of many genes that are transcriptionally regulated by CAR. This result has practical implications to the drug treatment of Hispanic patients.

The impact of pharmacogenomic factors on acute persistent rejection in adult lung transplant patients

Persistent rejection in the face of treatment and multiple episodes of rejection are associated with the development of chronic rejection and graft loss in solid organ transplantation. The factors that create an environment for rejection that persists in the face of treatment are as yet not understood. The objective of this study was to evaluate the risk factors, including human multidrug resistance gene (MDR1), cytochrome P4503A5 (CYP3A5) and cytokine gene polymorphisms, associated with acute persistent rejection (APR) in lung transplant patients. One hundred and twenty-five adult lung transplant patients were studied. MDR1 G2677T, C3435T and CYP3A5 polymorphisms were assessed by direct sequencing of the polymorphic region in patient DNA. Cytokine genotyping for five cytokines was performed using the polymerase chain reaction-sequence specific primers (PCR-SSP) technique. Multivariate regression analysis was used to identify the predictors of acute persistent rejection. The dependent variable was the presence or absence of acute persistent rejection based on lung biopsies during the first postoperative year. The independent variables were MDR1 G2677T and C3435T, CYP4503A5 and cytokine polymorphisms, survival status, age, gender, survival days and HLA mismatches. The MDR1 C3435T polymorphism and age were independently associated with acute persistent rejection (p = 0.025, odds ratio = 0.29, 95% CI 0.1-0.86 and p = 0.016, odds ratio = 0.94, 95% CI 0.89-0.98, respectively). For the MDR1 C3435T polymorphism, 72% of patients with the C allele had acute persistent rejection in comparison to 52% for TT patients (p = 0.04). For age, a significant difference was found between the nonrejection group and the rejection group (mean+/-S.D. 52.1+/-11.2 vs. 44.4+/-12.3, p = 0.01). This is the first report of the association of a drug disposition genotype with drug-resistant acute rejection in organ transplant patients. The major predictor of acute persistent rejection in the first postoperative year for lung transplant patients was the MDR1 C3435T genotype. This association could be due to drug resistance, altered drug disposition or other immunologic effects associated with P-glycoprotein (P-gp) function. Future prospective treatment algorithms should be developed that will incorporate the knowledge of gene polymorphisms into treatment regimens to improve the outcome following lung transplantation.

The impact of pharmacogenomic factors on steroid dependency in pediatric heart transplant patients using logistic regression analysis

Many pharmacogenomic predictors of drug response are now available, and include both drug metabolism-disposition factors and drug targets. Information on statistical approaches to analyzing large clinical data sets in relation to genetic polymorphisms is limited. The objective of this study was to evaluate whether logistic regression could identify pharmacogenomic predictors of outcome in a large data set in a complex transplant patient population. Seventy pediatric heart transplant patients were studied. Patients were followed for at least 1 yr post-transplantation as outpatients, and weaned from corticosteroids if clinically appropriate. Logistic regression analysis was used to identify the predictors of steroid dependency. The dependent variable was the presence or absence of steroid therapy at 1 yr post-transplantation. The independent variables were the patients' transplant age, gender, MDR1 C3435T and G2677T, CYP3A53B and cytokine polymorphisms. By chi-square test for the MDR1 C3435T polymorphism, 12 of 18 (67%) patients in the CC group were still on prednisone, whereas only 18 of 47 (38%) of the CT/TT group were still receiving prednisone (p = 0.04). For the IL-10 groups, two of 15 patients with the high producer genotype (13.3%) remained on prednisone, in comparison with 16 of 28 patients with the intermediate producer genotype (57.1%) and 15 of 26 patients with the low producer genotype (57.7%, p = 0.01). Logistic regression analysis confirmed MDR1 C3435T (p = 0.021), and IL-10 polymorphisms (intermediate producer genotype p = 0.015; low producer genotype p = 0.013) as independent risk factors for steroid dependency at 1 yr after transplantation. This approach identifies pharmacogenomic factors, which can be studied more extensively in larger data sets, and used in prospective studies to individualize immunosuppressive therapy following solid organ transplantation.

Transcriptional control of intestinal cytochrome P-4503A by 1alpha,25-dihydroxy vitamin D3

It was previously shown that CYP3A4 is induced in the human intestinal Caco-2 cell model by treatment with 1alpha,25-dihydroxy vitamin D3 (1,25-D3). We demonstrate the vitamin D analog, 19-nor-1alpha,25-dihydroxy vitamin D2, is also an effective inducer of CYP3A4 in Caco-2 cells, but with half the potency of 1,25-D3. We report that treatment of LS180 cells, a human intestinal cell line, with 1 to 10 nM 1,25-D3 dose dependently increased CYP3A4 protein and CYP3A4 mRNA expression. CYP3A4- and CYP3A23-promoter-Luciferase reporter constructs transiently transfected into LS180 cells were transcriptionally activated in a dose-dependent manner by 1,25-D3, whereas mutation of the nuclear hormone receptor binding motif (ER6) in the CYP3A4 promoter abrogated 1,25-D3 activation of CYP3A4. Although the CYP3A4 ER6 promoter element has been shown to bind the pregnane X receptor (PXR), this receptor does not mediate 1,25-D3 induction of CYP3A4 because a) PXR is not expressed in Caco-2 cells; b) PXR mRNA expression is not induced by 1,25-D3 treatment of LS180 cells; and c) the ligand binding domain of human PXR was not activated by 1,25-D3. 1,25-D3 uses the vitamin D receptor to induce CYP3A4 because a) the vitamin D receptor (VDR)-retinoid X receptor (RXR) heterodimer binds specifically to the CYP3A4 ER6; b) selective mutation of the CYP3A4 ER6 disrupted the binding of VDR-RXR; and c) reporter constructs containing only three copies of the CYP3A4 ER6 linked to a TK-CAT reporter were activated by 1,25-D3 only in cells cotransfected with a human VDR expression plasmid. These data support the hypothesis that 1,25-D3 and VDR induce expression of intestinal CYP3A by binding of the activated VDR-RXR heterodimer to the CYP3A PXR response element and promoting gene transcription.

Sequence diversity in CYP3A promoters and characterization of the genetic basis of polymorphic CYP3A5 expression

Variation in the CYP3A enzymes, which act in drug metabolism, influences circulating steroid levels and responses to half of all oxidatively metabolized drugs. CYP3A activity is the sum activity of the family of CYP3A genes, including CYP3A5, which is polymorphically expressed at high levels in a minority of Americans of European descent and Europeans (hereafter collectively referred to as 'Caucasians'). Only people with at least one CYP3A5*1 allele express large amounts of CYP3A5. Our findings show that single-nucleotide polymorphisms (SNPs) in CYP3A5*3 and CYP3A5*6 that cause alternative splicing and protein truncation result in the absence of CYP3A5 from tissues of some people. CYP3A5 was more frequently expressed in livers of African Americans (60%) than in those of Caucasians (33%). Because CYP3A5 represents at least 50% of the total hepatic CYP3A content in people polymorphically expressing CYP3A5, CYP3A5 may be the most important genetic contributor to interindividual and interracial differences in CYP3A-dependent drug clearance and in responses to many medicines.

Modified pentamer formation assay for measurement of tacrolimus and its active metabolites: comparison with liquid chromatography-tandem mass spectrometry and microparticle enzyme-linked immunoassay (MEIA-II)

A modified pentamer formation assay (PFA) for quantification of tacrolimus and active metabolites after extraction from whole blood is described. The lower limit of detection was 2 microg/L. Intraassay precision (CV) was 5.7-13.7%, and the interassay CV was 6. 1-14.9%. Tacrolimus trough concentrations in 104 whole blood specimens from liver and kidney transplant recipients were compared with results from HPLC-tandem mass spectrometry (LC/MS/MS) and microparticle enzyme immunoassay (MEIA-II). Data were analyzed by difference plots and are presented as median (95% confidence intervals) of the method differences. MEIA-II results were on average 2.00 microg/L (range, -0.08 to 5.17 microg/L) higher than LC/MS/MS, whereas PFA results were only 1.07 microg/L (range, -2.62 to 5.33 microg/L) higher. Of 104 specimens tested, 25 displayed differences >/=3 microg/L between MEIA-II and PFA: median difference, 4.65 microg/L (range, 3.01-8.79 microg/L). The corresponding median difference between PFA and LC/MS/MS was -0.91 microg/L (range, -4.11 to 0.85 microg/L), and the difference between MEIA-II and LC/MS/MS was 3.67 microg/L (range, 1.88-6.34 microg/L), suggesting the presence of inactive metabolites that caused a positive bias in the immunoassay. In contrast, similar median differences were observed for the remaining 79 specimens: MEIA-II minus LC/MS/MS, 1.78 microg/L (range, -0.45 to 4.11 microg/L); PFA minus LC/MS/MS, 1.90 microg/L (range, -1.70 to 5.50 microg/L). Active tacrolimus metabolites may have contributed to the higher apparent tacrolimus concentrations in these specimens.

High Helicobacter pylori eradication rate with a 1-week regimen containing ranitidine bismuth citrate

BACKGROUND

High Helicobacter pylori eradication rates have consistently been reported with 2-week dual therapy regimens of ranitidine bismuth citrate plus clarithromycin. Ranitidine bismuth citrate with two antibiotics may provide an alternative 1-week eradication regimen.

METHODS

This double-blind, randomized, parallel group, international, multicentre study compared ranitidine bismuth citrate 400 mg b.d. and clarithromycin 500 mg b.d. for 2 weeks (RC) with ranitidine bismuth citrate 400 mg b.d., clarithromycin 500 mg b.d. and metronidazole 400 mg b.d. for 1 week (RCM) for eradication of H. pylori in 350 patients with dyspepsia.

RESULTS

Treatment with RC and RCM eradicated H. pylori (established by the combination of two negative results from two discrete 13C-UBTs at nominal weeks 4 and 12) from 89% (95% CI: 84-94) and 92% (95% CI: 88-97) of the observed population, and from 78% (95% CI: 72-84) and 80% (95% CI: 75-86) of the intention-to-treat population. When established only by one negative 13C-UBT result at least 28 days after the end of treatment, the respective intention-to-treat rates were 85% (95% CI: 79-90) and 88% (95% CI: 83-93). Both regimens were well-tolerated, only 6% of patients given RC and 4% given RCM discontinued treatment. Median plasma bismuth concentrations at the end of the second week of study were low, at 3.5 and 0.4 ng/ mL, respectively.

CONCLUSIONS

Ranitidine bismuth citrate triple therapy for 1 week (RCM) and dual therapy for 2 weeks (RC) were equally effective for the eradication of H. pylori infection.

Stat5a and Stat5b proteins have essential and nonessential, or redundant, roles in cytokine responses

A variety of cytokines mediate the activation of Janus protein tyrosine kinases (Jaks). The Jaks then phosphorylate cellular substrates, including members of the signal transducers and activators of transcription (Stat) family of transcription factors. Among the Stats, the two highly related proteins, Stat5a and Stat5b, are activated by a variety of cytokines. To assess the role of the Stat5 proteins, mutant mice were derived that have the genes deleted individually or together. The phenotypes of the mice demonstrate an essential, and often redundant, role for the two Stat5 proteins in a spectrum of physiological responses associated with growth hormone and prolactin. Conversely, the responses to a variety of cytokines that activate the Stat5 proteins, including erythropoietin, are largely unaffected.

Critical role of extracellular matrix on induction by phenobarbital of cytochrome P450 2B1/2 in primary cultures of adult rat hepatocytes

BACKGROUND

Although it has been known for more than three decades that administration of lipophilic chemicals, including phenobarbital, produces liver hypertrophy, proliferation of smooth endoplasmic reticulum, and induction of liver microsomal enzymes such as cytochromes P450 (CYP) 2B1 and 2B2, the mechanism of this adaptive response remains largely unknown. An important advance was the recognition that, unlike cultures of continuously proliferating liver cell lines or cultures of primary non-proliferating adult rat hepatocytes maintained on either plastic or collagen-coated dishes, hepatocytes cultured on a basement membrane gel, Matrigel, formed rounded clusters and permitted phenobarbital-mediated induction in vitro of CYP 2B1/2 mRNAs and immunoreactive proteins (1).

EXPERIMENTAL DESIGN AND RESULTS

We cultured adult rat hepatocytes on Type 1 collagen (Vitrogen) and allowed the cells to spread, flatten, and firmly attach to the substratum. Subsequent incubation in medium containing Matrigel as a soluble component, fully restored, in a dose-dependent manner, the ability to respond to phenobarbital with induction of CYP 2B1/2 mRNAs. Repeating this experiment with medium containing equivalent amounts of purified laminin, a major component of Matrigel, or with YIGSR or SIKVAV, two peptides known to mimic various activities of laminin, similarly restored phenobarbital responsiveness to hepatocytes cultured on Vitrogen. In contrast, use of equal amounts of SHA-23, a scrambled peptide relevant to SIKVAV, produced no such effect. None of these treatments caused a rounding or any other observable change in the flattened, cellular morphology, making it unlikely that cell-spreading or alterations in cell shape account for loss of such differentiated liver functions as phenobarbital induction of CYP 2B1/2 mRNAs in cultured hepatocytes on Vitrogen. Hepatocytes cultured on Matrigel in the presence of either colchicine, cytochalasins B and D, nocodazole, or taxol did not show induction of 2B1/2 mRNAs by phenobarbital specifically, while the amounts of both albumin and glucose-6-phosphate dehydrogenase (G6PD) mRNAs were unaffected.

CONCLUSIONS

We conclude that the process by which phenobarbital induced 2B1/2 mRNAs in hepatocytes appears to require highly concerted effects of specific extracellular components prominently involving laminin. This likely occurs through a signal transduction process requiring probably both microfilament and microtubular integrity.

Effect of diuresis on urinary erythrocyte morphology in glomerulonephritis

The differentiation between glomerular and non-glomerular haematuria by phase-contrast microscopy has proved to be a useful tool in the diagnosis of glomerulonephritis. In an attempt to evaluate the effect of marked diuresis on the altered red cell morphology in patients with biopsy proven glomerulonephritis, urinary sediments were examined following water or furosemide-induced diuresis. In both diuretic states urine flow increased, urine osmolality decreased and the percentage of glomerular erythrocytes was significantly reduced in the urinary sediment. These data demonstrate that the alteration in urinary red cells in glomerulonephritis is mainly caused by tubular forces. The diagnostic significance is reduced during increased diuresis and the evaluation of urinary red cell morphology should not be performed.

A comparative retrospective analysis of data from short- and long-term animal toxicity studies on 40 pharmaceutical compounds

A comparative retrospective survey of data from chronic toxicity studies has been carried out on 40 pharmaceutical compounds based on comprehensive information from 19 pharmaceutical companies. The results showed that no new salient toxicological effects were observed in tests of more than 6 months duration excluding carcinogenicity studies. Since no additional information was identified by dosing animals continuously for 12-18 months, the value of prolonging chronic toxicity studies in animals beyond 6 months should be carefully reassessed.

Reliability of antiarrhythmic drug plasma concentration monitoring

Measurement of drug levels is becoming increasingly popular to optimise the dosage of various drugs. In the case of antiarrhythmic drugs, the narrow therapeutic margin of most of these agents and a direct relationship between their pharmacological effects and plasma concentrations would justify more widespread use of monitoring. Optimum plasma concentration ranges have been described for lignocaine (lidocaine), procainamide, quinidine and, more recently, also for disopyramide, mexiletine, tocainide and other new antiarrhythmics. A critical analysis of the original data shows, however, that therapeutic and toxic levels are not so well defined as often assumed: small numbers of patients, marked interindividual variability, sometimes inadequate documentation of arrhythmias and lack of standardised blood sampling characterise many of these studies. Uncertainty about the reliability of concentration-effect relationships also arises when active drug metabolites are identified or there are marked concentration-dependent changes of drug protein-binding. In addition, abolition of various types of arrhythmias might require different drug concentrations. Nevertheless, therapeutic monitoring can be of practical value in patients with life-threatening ventricular arrhythmias and can also greatly facilitate dosage adjustment in cases with renal hepatic or severe cardiac failure. For a correct interpretation of drug levels, the time of blood sampling, dosage regimen, duration of treatment, pharmacokinetic principles, and the clinical condition of the patient must be taken into account. Further studies are needed to define the optimum therapeutic range for several drugs and to evaluate the usefulness of plasma concentration measurements in routine antiarrhythmic treatment.