Effects of polymorphisms of MDR1, MRP1, and MRP2 genes on their mRNA expression levels in duodenal enterocytes of healthy Japanese subjects

In the present study, we examined whether polymorphisms in the ATP-binding cassette (ABC) transporter genes, MDR1, MRP1 and MRP2, were associated with their respective mRNA expression levels in duodenal enterocytes of 13 healthy Japanese volunteers. MDR1 genotypes of T-129C, G2677(A,T) and C3435T, MRP1 genotypes of G128C, C218T, G2168A and G3173A, and MRP2 genotypes of C-24T, G1249A, C2302T, C2366T and G4348A were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or direct sequencing. Mutations T-129C, G2677(A,T) and C3435T of MDRI gene were found at allele frequencies of 2/26, 16/26 and 12/26, respectively. Mutations G2168A of the MRPI gene and C-24T of the MRP2 gene were also found at allele frequencies of 1/26 and 6/26, respectively, whereas other mutations were not detected in MRP1 and MRP2 genes. The relative concentrations (mean +/- S.E.) of MDR1 mRNA to villin mRNA were 0.38 +/- 0.15, 0.56 +/- 0.14 and 1.13 +/- 0.42 in the subjects with C/C3435, C/T(3435) and T/T(3435), respectively, which supported the lower serum concentrations of digoxin after single oral administration in the subjects with the mutant T-allele at position 3435. Genetic collaboration between positions 3435 and 2677 was suggested, and those in G/G2677, G/(A,T)(2677) and T/(A,T)(2677) were 0.16 +/- 0.05, 1.10 +/- 0.40, and 0.63 +/- 0.16, respectively (p = 0.107). However, there was no remarkable effect of the G2168A of the MRP1 gene or of C-24T of the MRP2 gene on the relative MRP1 or MRP2 mRNA concentrations, respectively.     

Digoxin pharmacokinetics and MDR1 genetic polymorphisms

BACKGROUND: The effect of MDR1 C3435T single nucleotide polymorphism (SNP) in exon 26 on digoxin pharmacokinetics has recently been challenged. OBJECTIVE. To clarify the relationships between MDR1 genetic polymorphisms in exon 26 (C3435T) and 21 (G2677T/A) and digoxin pharmacokinetics. MATERIALS AND METHODS: MDR1 genotypes for C3435T and G2677T/A SNPs were determined in 32 healthy subjects whose single oral dose digoxin pharmacokinetics had been measured over 48 h. RESULTS: A significant relationship was observed between C3435T SNP and digoxin AUCs ( p<0,05). Homozygous TT subjects had 20% higher digoxin plasma concentrations than CT and CC subjects and a trend for higher 48 h digoxin urinary recoveries (TT>CT>CC). Similar results, although not statistically significant, were observed from the MDR1 G2677T/A SNP. CONCLUSIONS: Our results confirm that the MDR1 C3435T single nucleotide polymorphism (SNP) significantly affects digoxin disposition kinetics, with homozygous TT subjects presenting the highest plasma concentrations.     

MDR1 haplotypes derived from exons 21 and 26 do not affect the steady-state pharmacokinetics of tacrolimus in renal transplant patients

AIM: This retrospective study investigated the influence of MDR1 haplotypes derived from the polymorphisms 2677G > T (exon 21) and 3435C > T (exon 26) on the pharmacokinetics of the immunosuppressant drug tacrolimus in 73 renal transplant patients. METHODS: Based on both variants of SNPs 2677 and 3435, four different haplotypes and eight different genotypes were identified in the study sample. Tacrolimus trough concentrations (C(0)) were compared between different SNP variants and genotypes, as well as between carriers and noncarriers of each haplotype. Additionally, CYP3A5 genotype (6956G > A) was determined. RESULTS: No significant differences were observed between groups. Differences in mean tacrolimus C(0) values between carriers and noncarriers of each haplotype ranged from -0.04 microg/litre (95% confidence interval: -0.53 to 0.60) to -23 microg/litre (-1.07 to 1.53). No association was found between CYP3A5*1/*3 genotype and tacrolimus Co concentractions. CONCLUSION: MDR1 haplotypes derived from the SNPs 2677G > T (exon 21) and 3435C > T (exon 26) do not influence the pharmacokinetics of tacrolimus in renal transplant patients.     

MDR1 genotypes do not influence the absorption of a single oral dose of 600 mg valacyclovir in healthy Chinese Han ethnic males

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• The absorption of valacyclovir presents a highly negative correlation with the level of P-glycoprotein expression.
• It has been confirmed that a polymorphism of the MDR1 gene in exon 26 is related to the level of P-glycoprotein expression in intestine.
• This study was conducted to find the relationship between polymorphism of MDR1 gene and absorption of valacyclovir.

WHAT THIS STUDY ADDS

• Linkage disequilibrium exists between G2677T/A in exon 21 and C3435T in exon 26, between C1236T in exon 12 and C3435T, but not between C1236T and G2677T/A of MDR1 gene in the Chinese Han ethnic population.
• Three single nucleotide polymorphisms of MDR1 gene do not influence the absorption of valacyclovir in the healthy Chinese Han ethnic population.

AIMS

To investigate the influence of three single nucleotide polymorphisms (SNPs) in exon 12 (C1236T), exon 21 (G2677T/A) and exon 26 (C3435T) of MDR1 gene on the absorption of valacyclovir after a single oral administration in the Chinese Han ethnic population.

METHODS

Two hundred healthy Chinese subjects were genotyped for the SNPs of C1236T, G2677T/A and C3435T in the MDR1 gene using allele-specific polymerase chain reaction. Linkage disequilibrium (LD) was analysed. Twenty-four subjects derived from a large random sample (n = 200) received a single oral dose of 600 mg valacyclovir. Plasma concentrations of acyclovir were determined up to 14 h after administration to obtain a pharmacokinetic profile.

RESULTS

LD existed between G2677T/A in exon 21 and C3435T in exon 26 (P < 0.001), between C1236T in exon 12 and C3435T (P < 0.001), but not between C1236T and G2677T/A (P > 0.05). C_max, AUC_{0–1.5 h} and AUC_0–∞ were used as indices of valacyclovir absorption. AUC_0–∞ for the 2677TA genotype was 17.45 ± 2.40 µg × h/ml, which was much higher compared with the 2677GG, GA and TT genotypes of 10.44 ± 1.00, 11.84 ± 2.83, 11.34 ± 2.32 µg × h/ml, respectively (P < 0.05). Similarly, a statistically significant difference of AUC_0–∞ was also observed for different linked genotypes at position 2677 vs. 3435, and 1236 vs. 3435 (P < 0.05). However, there was no significant difference in valacyclovir absorptive pharmacokinetics between carriers and noncarriers of different haplotypes (P > 0.05).

CONCLUSIONS

Three SNPs of MDR1 gene did not influence the absorption of a single oral dose of 600 mg valacyclovir in healthy Chinese Han ethnic subjects.     

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.     

Influence of the CYP3A5 and MDR1 genetic polymorphisms on the pharmacokinetics of tacrolimus in healthy Korean subjects

AIMS: To determine the frequencies of the genotypes of CYP3A5 and MDR1 and to examine the influence of the polymorphisms of these genes on tacrolimus pharmacokinetics in the Korean population. METHODS: Twenty-nine healthy Koreans who participated in the previous tacrolimus pharmacokinetic study were genotyped for CYP3A4*1B, CYP3A5*3, MDR1 c.1236C-->T, MDR1 c.2677G-->A/T and MDR1 c.3435C-->T. The relationship between the genotypes so obtained and tacrolimus pharmacokinetics observed in the previous study was examined. RESULTS: No subject in this study had the CYP3A4*1B variant. The observed frequencies of CYP3A5*1/*1, *1/*3, and *3/*3 were 0.069 [confidence interval (CI) -0.023, 0.161], 0.483 (CI 0.301, 0.665) and 0.448 (CI 0.267, 0.629), respectively. AUC(0-infinity) for the CYP3A5*1/*1 or *1/*3 genotype was 131.5 +/- 44.8 ng h ml(-1) (CI 109.6, 153.5), which was much lower compared with the CYP3A5*3/*3 genotype of 323.8 +/- 129.3 ng h ml(-1) (CI 253.5, 394.1) (P = 2.063E-07). Similarly, C(max) for the CYP3A5*1/*1 or *1/*3 genotype was 11.8 +/- 3.4 ng ml(-1) (CI 10.1, 13.5), which was also much lower compared with the CYP3A5*3/*3 genotype of 24.4 +/- 12.3 ng ml(-1) (CI 17.8, 31.1) (P = 0.0001). However, there was no significant difference in tacrolimus pharmacokinetics among the MDR1 diplotypes of CGC-CGC, CGC-TTT, CGC-TGC, TTT-TGC or TTT-TTT (P = 0.2486). CONCLUSIONS: This study shows that the CYP3A5*3 genetic polymorphisms may be associated with the individual difference in tacrolimus pharmacokinetics. An individualized dosage regimen design incorporating such genetic information would help increase clinical efficacy of the drug while reducing adverse drug reactions.     

CYP3A5和MDR1基因多态性对中国肝移植患者他克莫司药动学的影响

目的探讨细胞色素P450酶3A5（CYP3A5）基因和多药耐药基因（MDR1）C1236T、G2677T／A、C3435T多态性对肝移植患者口服他克莫司（TAC）后体内药动学参数的影响。方法采集28例肝移植患者手术后第1周和第3周血标本,采用LC—MS／MS法检测TAC血药浓度,计算主要药动学参数。采用聚合酶链反应结合基因测序分析28例肝移植患者CYP3A5＊3和MDR1主要基因型。结果携带MDR1 3435T基因型的肝移植患者口服TAC后,药动学参数AUC0→1和ρmax明显高于3435CC型患者,而CYP3A5＊3、MDR1 C1236T和G2677T／A基因多态性对TAC的药动学参数无明显影响。结论携带MDR1 3435T基因型肝移植患者比3435CC型患者需要较高剂量才能达到目标浓度。     

Effects of various factors on steady-state plasma concentrations of risperidone and 9-hydroxyrisperidone: lack of impact of MDR-1 genotypes

AIMS: An in vitro study has suggested that risperidone is a substrate of P-glycoprotein, which is coded by MDR-1 gene. Thus, we studied the effects of major polymorphisms of the MDR-1 gene on plasma drug concentrations. METHODS: Subjects were 85 schizophrenic patients receiving 3 mg twice daily of risperidone. Sample collections were conducted 12 h after the bedtime dosing. Plasma concentrations of risperidone and 9-hydroxyrisperidone were quantified using LC/MS/MS. MDR-1 genotypes (C3435T and G2677T/A) and CYP2D6 genotypes were identified using PCR-RFLP methods. RESULTS: There was no difference in geometric mean (95% CI) of steady-state plasma concentration of risperidone between C3435T genotypes [C/C, C/T, T/T; 2.06 (1.63, 6.47), 2.96 (3.10, 7.91), 2.28 (1.81, 8.04) ng ml(-1), P = 0.759] or G2677T/A genotypes [G/G, G/T or A, T or A/T or A; 1.62 (0.08, 6.07), 2.64 (3.25, 7.10), 2.71 (2.77, 8.72) ng ml(-1), P = 0.625] or 9-hydroxyrisperidone between C3435T genotypes [38.3 (33.7, 50.1), 34.9 (32.9, 42.0), 35.7 (31.7, 42.3) ng ml(-1), P = 0.715] or G2677T/A genotypes [40.6 (33.0, 51.8), 35.0 (33.3, 42.4), 36.1 (32.8, 47.2) ng ml(-1), P = 0.601]. Multiple regression analyses including CYP2D6 genotypes, sex, and age revealed that steady-state plasma concentration of risperidone correlated with the number of mutated alleles for CYP2D6 (standardized partial correlation coefficients (beta) = 0.540, P < 0.001) and those of 9-hydroxyrisperidone (standardized beta = 0.244, P = 0.038) and active moiety (standardized beta = 0.257, P = 0.027) correlated with age. CONCLUSIONS: These findings suggest that the MDR-1 variants are not associated with steady-state plasma concentration of risperidone or 9-hydroxyrisperidone, but CYP2D6 genotypes and age are determinants of these concentrations.     

Effect of ABCB1 (MDR1) haplotypes derived from G2677T/C3435T on the pharmacokinetics of amlodipine in healthy subjects

AIM: We aimed to investigate the effect of the ABCB1 gene on the pharmacokinetics of amlodipine. METHODS: Based on polymorphisms of the ABCB1 gene at positions 2677 and 3435, 26 healthy male participants were divided into three groups: subjects with 2677GG/3435CC (n = 9), 2677GT/3435CT (n = 9) and 2677TT/3435TT (n = 8). After a single-dose administration of 5 mg amlodipine, plasma concentrations of amlodipine were measured and its pharmacokinetic characteristics were compared according to ABCB1 genotype. RESULTS: The area under the plasma concentration-time curve was significantly lower in subjects with 2677TT/3435TT (140.8 +/- 35.6 ng h(-1) ml(-1)) and 2677GT/3435CT (149.8 +/- 40.1 ng h(-1) ml(-1)) than in those with 2677GG/3435CC (208.6 +/- 39.2 ng h(-1) ml(-1)) [95% confidence interval (CI) on the difference, 2677GG/3435CC vs. 2677GT/3435CT 12.0, 105.6, P < 0.01; 2677GG/3435CC vs. 2677TT/3435TT 19.6, 116.0, P < 0.01; 2677GT/3435CT vs. 2677TT/3435TT - 39.2, 57.2, P > 0.05]. The peak plasma concentrations were highest in subjects with 2677GG/3435CC (3.8 +/- 0.5 ng ml(-1)), lower in subjects with 2677GT/3435CT (3.2 +/- 0.5 ng ml(-1)) and 2677TT/3435TT (2.7 +/- 0.5 ng ml(-1)) in rank and showed a significant difference between those with 2677GG/3435CC and with 2677TT/3435TT (95% CI on the difference 0.4, 2.0, P < 0.01). However, the oral clearance was higher in subjects with 2677TT/3435TT (37.7 +/- 10.2 l h(-1)) than in those with 2677GT/3435CT (35.7 +/- 9.9 l h(-1)) and with 2677GG/3435CC (24.8 +/- 5.4 l h(-1)) and exhibited a significant difference between ABCB1 genotype groups (95% CI on the difference, 2677GG/3435CC vs. 2677GT/3435CT - 21.5, - 0.3, P < 0.05; 2677GG/3435CC vs. 2677TT/3435TT - 23.8, - 2.0, P < 0.05). CONCLUSION: Amlodipine pharmacokinetics was affected by the genetic polymorphisms of the ABCB1 gene in humans. These findings may provide a plausible explanation for interindividual variation in the disposition of amlodipine, although our study could not explain the exact mechanism(s) by which the polymorphic ABCB1 gene paradoxically reduces the plasma levels of amlodipine. Further evaluation is thus warranted.     

Human MDR1 polymorphism: G2677T/A and C3435T have no effect on MDR1 transport activities

The two most frequently observed single nucleotide polymorphisms (SNPs) of the human multidrug resistance 1 (MDR1) gene are 2677G/T/A (893Ala/Ser/Thr) and 3435C/T (no amino acid substitution). In this study, six forms of MDR1 cDNAs with the SNPs were expressed in LLC-PK1 cells and their transport activities were determined. Nearly identical amounts of the recombinant MDR1 proteins were expressed in the established cell lines using the Flp recombinase, which integrates a gene of interest at a specific genomic location. Four structurally diverse compounds: verapamil, digoxin, vinblastine and cyclosporin A, were examined for transcellular transport activities and intracellular accumulation. No significant differences were observed between cells expressing five polymorphic types of the MDR1 cDNAs (2677G/3435T, 2677A/3435C, 2677A/3435T, 2677T/3435C, 2677T/3435T) and cells expressing the wild-type (2677G/3435C). These results suggested that the two frequently observed MDR1 SNPs had no effect on the transport activities of MDR1 proteins expressed in LLC-PK1 cells in vitro, and other genetic or environmental factors might control the expression of MDR1 and the in vivo activity of MDR1.     

Impact of ABCB1 (MDR1) gene polymorphism and P-glycoprotein inhibitors on digoxin serum concentration in congestive heart failure patients

Digoxin, a drug of narrow therapeutic index, is a substrate for common transmembrane transporter, P-glycoprotein, encoded by ABCB1 ( MDR1 ) gene. It has been suggested that ABCB1 polymorphism, as well as co-administration of P-glycoprotein inhibitors, may influence digoxin bioavailability. The aim of the present study was to evaluate the effects of ABCB1 gene polymorphism and P-gp inhibitor co-administration on steady-state digoxin serum concentration in congestive heart failure patients. Digoxin concentrations as well as 3435C > T and 2677G > A,T ABCB1 single nucleotide polymorphisms, were determined in 77 patients administered digoxin (0.25 mg daily) and methyldigoxin (0.50 mg daily), some of them co-medicated with known P-glycoprotein (Pgp) inhibitors. Significant differences were noted in digoxin serum concentrations (C(min,ss)) between patients co-administered and not co-administered P-gp inhibitors: 0.868 +/- 0.348 and 0.524 +/- 0.281 for digoxin (p < 0.002), as well as 1.280 +/- 0.524 and 0.908 +/- 0.358 for methyldigoxin (p < 0.02), respectively. No influence of ABCB1 2677G > A,T and C3435C > T polymorphisms on digoxin concentration was noted. Although some of the previous studies have shown that digoxin pharmacokinetics might be affected by ABCB1 genetic polymorphism, those modest changes are probably clinically irrelevant, and digoxin dose adjustment should include P-gp inhibitor co-administration rather than ABCB1 genotyping.     

Tacrolimus dosing in adult lung transplant patients is related to cytochrome P4503A5 gene polymorphism

Tacrolimus is a potent immunosuppressive agent used in lung transplantation and is a substrate for both P-glycoprotein (P-gp, encoded by the gene MDR1) and cytochrome (CYP) P4503A. A previous study by the authors identified a correlation between the tacrolimus blood level per dose with CYP3A5 and MDR1 gene polymorphisms in pediatric heart transplant patients. The objective of this study was to confirm the influence of these polymorphisms on tacrolimus dosing in adult lung transplant patients. Adult lung transplant patients who had been followed for at least 1 year after lung transplantation were studied. Tacrolimus blood level (ng/mL) per dose (mg/day) at 1, 3, 6, 9, and 12 months after transplantation was calculated as [L/D]. DNA was extracted from blood. MDR1 3435 CC, CT, and TT; MDR1 2677 GG, GT, and TT; and CYP3A5*1 (expressor) and *3 (nonexpressor) genotypes were determined by PCR amplification, direct sequencing, and sequence evaluation. Eighty-three patients were studied. At 1, 3, 6, 9, and 12 months after the transplant, a significant difference in [L/D] was found between the CYP3A5 expressor versus nonexpressor genotypes (mean +/- SD of 1.49 +/- 0.88 vs. 3.11 +/- 4.27, p = 0.01; 1.23 +/- 0.82 vs. 3.44 +/- 8.97, p = 0.05; 1.32 +/- 0.96 vs. 3.81 +/- 6.66, p = 0.005; 0.95 +/- 1.19 vs. 3.74 +/- 5.98, p = 0.0015; and 0.45 +/- 0.2 vs. 3.76 +/- 6.75, p = 0.0001, respectively). MDR1 G2677T and C3435T genotypes had only minimal effects on [L/D] at 1 and 3 months after transplantation. This study confirms the relationship of CYP3A5 polymorphisms to tacrolimus dosing in organ transplant patients. CYP3A5 expressor genotypes required a larger tacrolimus dose to achieve the same blood levels than the CYP3A5 nonexpressors at all time points during the first posttransplant year. This was not uniformly true for MDR1. The authors therefore conclude that tacrolimus dosing in adult lung transplant patients is associated with CYP3A5 gene polymorphisms.     

MDR1基因多态性和单倍体对肾移植术后稳定期患者他克莫司浓度/剂量比值的影响

目的 探讨MDR1 C1236T、G2677T/A和C3435T 基因多态性和单倍体对中国汉族肾移植术后稳定期患者他克莫司浓度/剂量比值的影响,为他克莫司个体化用药提供依据。方法 采用PCR-基因测序法检测104例肾移植术后稳定期患者MDR1 C1236T、G2677T/A和C3435T 的基因多态性,采用均相酶免疫测定方法(EMIT法)测定他克莫司的谷浓度,比较不同基因型患者之间他克莫司血药浓度/(剂量×体质量)(C/D)比值。结果 104例患者中,MDR1 C1236T、G2677T/A和C3435T突变频率分别为56.73%、55.77%和33.17%。MDR1 C3435T、MDR1 TTT单倍体与他克莫司C/D比值具有相关性(P<0.05)。CYP3A5*3*3患者中,MDR1 TTT单倍体与他克莫司C/D比值仍存在显著相关(P<0.05)。MDR1 C1236T、G2677T/A、CGC单倍体与他克莫司C/D比值无显著性差异(P>0.05)。结论 MDR1 C3435T、MDR1 TTT单倍体与中国汉族肾移植术后稳定期患者他克莫司C/D比值具有显著相关性,是影响肾移植患者他克莫司浓度个体化差异的重要因素。     

Disposition of a CYP2C9 phenotyping agent, losartan, is not influenced by the common 3435C > T variation of the drug transporter gene ABCB1 (MDR1)

Losartan is oxidized to E3174 by cytochrome P450 2C9 (CYP2C9); it has been suggested as a useful probe drug for CYP2C9 activity. It has also been shown to be a substrate for the drug-efflux transporter ATP-binding cassette sub-family B member 1 (ABCB1, MDR1). Both CYP2C9 and ABCB1 genes are polymorphic. The aim of the study was to determine if losartan disposition was influenced by the 3435C > T polymorphism of ABCB1 in healthy persons. These participants (n = 58) whose CYP2C9 genotypes and phenotypes were determined previously were genotyped for 3435C > T polymorphism in ABCB1. The concentrations of losartan and E3174 were compared across genotypes for ABCB1 3435C > T variation. For persons with the ABCB1 3435 CC, CT, TT genotypes, the concentrations (microM, means +/- S.D.) of neither losartan (1.76 +/- 0.87, 1.68 +/- 0.84 and 1.80 +/- 0.85, respectively, P = 0.70) nor E3174 (2.97 +/- 2.49, 2.53 +/- 2.09 and 3.18 +/- 2.75, respectively, P = 0.65) were significantly different. These results suggest that ABCB1 3435C > T polymorphism does not have any influence on losartan disposition. Therefore, ABCB1 3435C > T polymorphism is probably not a confounding factor in the prediction of CYP2C9 activity by using losartan as a probe agent.     

MDR1(ABCB1) gene polymorphisms associated with steroid-induced osteonecrosis of femoral head in systemic lupus erythematosus

This study investigated the relationship between genetic polymorphism in the MDR1 (C3435T, G2677T) and the development of steroid-induced osteonecrosis of femoral head (ONF) in Chinese systemic lupus erythematosus (SLE) patients. 127 patients with active SLE, receiving 40 mg/day or more prednisolone were included. Patients were observed for the development of ONF by magnetic resonance imaging (MRI) and plain radiography first at three months after the beginning of steroid treatment and subsequently every year for five years. Genomic DNA was obtained from peripheral blood lymphocytes. The MDR1 2677G > T and 3435C > T genotypes were determined by the PCR-RFLP assay. 21 patients developed steroid-induced ONF. The incidence of ONF was significantly higher in steroid pulse therapy. The MDR1 3435 TT genotypes were significantly lower in the incidence of ONF (adjusted odds ratio = 0.14, 95% CI 0.017-1.153, p = 0.038). The MDR1 2677 TT was also lower in the incidence of ONF (adjusted odds ratio = 0.21, 95% CI 0.018-1.301, p = 0.05). Our findings suggest that MDR1 (ABCB1) gene polymorphisms can be used for predicting the development of ONF.     

MDR1 genetic polymorphisms and comparison of MDR1 haplotype profiles in Korean and Vietnamese populations

Two representative genetic variants of the MDR1 gene, 3435C>T and 2677G>T/A, show wide interethnic differences in its genetic polymorphism. In this study, the authors evaluated the genetic polymorphisms of MDR1 and directly compared MDR1 haplotype profiles of the Korean and Vietnamese populations. The 3435C>T and 2677G>T/A variations were analyzed in 632 Koreans and 142 Vietnamese using pyrosequencing. The allelic frequencies of 3435C>T did not significantly differ between the Korean (39.3%) and Vietnamese (36.6%) groups. However, the frequencies of mutant alleles at 2677 locus (T or A allele) showed a significant difference between Koreans (56.2%) and Vietnamese (41.9%), as the frequency of 2677A allele in the Korean subjects (17.1%) was much higher than that of the Vietnamese subjects (6.3%). Linkage analysis revealed that 2677A allele is closely linked to 3435C allele. The frequency of 2677A-3435C haplotype in Koreans was 15.4%, which was significantly higher than that found in Vietnamese subjects (6.3%). In conclusion, the frequencies of MDR1 variants and haplotype profiles showed significant differences between the Korean and Vietnamese populations, especially with respect to the 2677G>T/A variants. Because the 2677A allele was recently found to be functional in vivo and was detected at a high frequency in Koreans, the genotyping of this variant is necessary for pharmacogenetic studies of MDR1 in this population. In addition, by virtue of strong linkage disequilibrium, 2677A-3435C haplotype may help improve the predictability of MDR1 genetic polymorphism for MDR1 functional changes.     

The effect of CYP2J2, CYP3A4, CYP3A5 and the MDR1 polymorphisms and gender on the urinary excretion of the metabolites of the H-receptor antihistamine ebastine: a pilot study

AIMS: To determine the effect of gender and the genetic polymorphisms of CYP2J2, CYP3A4, CYP3A5 and MDR1 on the urinary excretion of the H(1) antihistamine ebastine in healthy subjects. METHODS: Eighty-nine Caucasians were studied. The presence of polymorphisms in genes known to be involved in ebastine metabolism and transport (CYP2J2*2,*3,*4,*6,*7, CYP3A4*1B, CYP3A5*3, *6 and MDR1(ABCB1)(C3435T)) was assessed by means of PCR-restriction fragment length polymorphism and sequencing methods. Genotype was correlated with the urinary excretion of the main ebastine metabolites (desalkylebastine and carebastine) under basal conditions and after administration of grapefruit juice. RESULTS: Women excreted statistically greater amounts of desalkylebastine in urine (mean +/- SD (95% confidence intervals, 95% CI), 23.0 +/- 19.5 (18.1, 27.9) micromol) than men (12.4 +/- 11.0 (7.9, 16.9)), (mean difference: 10.6 (2.4, 18.7), P < 0.005). The CYP2J2, CYP3A4 and CYP3A5 analysed polymorphisms did not greatly affect ebastine metabolite excretion. The MDR1(C3435T) polymorphism was found to affect both the urinary excretion of the active metabolite carebastine (32.3 +/- 18.3 (23.1, 41.4), 22.8 +/- 14.7 (18.6, 27.0) and 21.5 +/- 15.3 (14.7, 28.3) for CC, CT and TT carriers, respectively; P < 0.05) and the grapefruit juice-induced inhibition of its transport/formation (mean fold-decrease +/- SD (95% CI), 1.5 +/- 0.8 (1.0, 2.0), 1.1 +/- 0.9 (0.7, 1.4) and 0.9 +/- 0.4 (0.6, 1.2) for CC, CT and TT carriers, respectively; P = 0.01). CONCLUSIONS: Gender and the presence of the MDR1(C3435T) polymorphism both influence the excretion of ebastine metabolites in urine.     

C3435T polymorphism in the MDR1 gene affects the enterocyte expression level of CYP3A4 rather than Pgp in recipients of living-donor liver transplantation

The bioavailability of structurally unrelated drugs is limited by active secretion via the multidrug resistance gene (MDR1) product P-glycoprotein (Pgp) from enterocyte into lumen as well as intestinal metabolism by cytochrome P450 IIIA4 (CYP3A4). In the present study, we analyzed whether genetic polymorphism of the MDR1 had some influence on the intestinal expression levels of Pgp and CYP3A4 and the tacrolimus concentration/dose ratio over the first postoperative days in recipients of living-donor liver transplantation (LDLT). Genotyping assays were performed for the major 10 polymorphisms in the MDR1 gene by the polymerase chain reaction-restriction enzyme length polymorphism method. The allele frequencies of variations at five positions were almost comparable with those in the former studies in Caucasians and Japanese, but there was no variation at the other five positions. Although no polymorphism correlated with the intestinal expression of MDR1 mRNA or the tacrolimus concentration/dose ratio in the LDLT recipients, the C3435T polymorphism significantly affected the intestinal expression level of CYP3A4 mRNA as follows; 3435C/C>3435C/T (P < 0.05 vs. 3435C/C)>3435T/T (P < 0.01 vs. 3435C/C). Therefore, the identified polymorphisms including C3435T in the MDR1 gene were indicated to have no influence on the intestinal expression level of Pgp or the tacrolimus concentration/dose ratio in the recipients of LDLT. On the other hand, the C3435T polymorphism of MDR1 was suggested to correlate with the enterocyte expression of CYP3A4 rather than Pgp linking unknown genetic variation in CYP3A4 gene.     

<Emphasis Type="BoldItalic">MDR1</Emphasis> Haplotypes Conferring an Increased Expression of Intestinal CYP3A4 Rather than MDR1 in Female Living-Donor Liver Transplant Patients

Purpose  This study investigated whether haplotypes in the multidrug resistance 1 (MDR1) gene had effects on mRNA expression levels of MDR1 and cytochrome P450 (CYP) 3A4, and on the pharmacokinetics of tacrolimus in living-donor liver transplant (LDLT) patients, considering the gender difference. Methods  Haplotype analysis of MDR1 with G2677T/A and C3435T was performed in 63 de novo Japanese LDLT patients (17 to 55 years; 44.4% women). The expression levels of MDR1 and CYP3A4 mRNAs in jejunal biopsy specimens were quantified by real-time PCR. Results  Intestinal CYP3A4 mRNA expression levels (amol/μg total RNA) showed significantly higher values in women carrying the 2677TT-3435TT haplotype (median, 10.7; range, 5.92–15.2) than those with 2677GG-3435CC (3.03; range 1.38–4.68) and 2677GT-3435CT (median, 4.31; range, 0.07–9.42) (P = 0.022), but not in men (P = 0.81). However, MDR1 haplotype did not influence mRNA expression levels of MDR1 nor the concentration/dose ratio [(ng/mL)/(mg/day)] of oral tacrolimus for the postoperative 7 days, irrespective of gender. Conclusion   MDR1 haplotype may have a minor association with the tacrolimus pharmacokinetics after LDLT, but could be a good predictor of the inter-individual variation of intestinal expression of CYP3A4 in women.     

Frequency of common MDR1 gene variants in a Polish population

P-glycoprotein (P-gp) is a transmembrane transporter playing an important role in drug efflux. There is growing evidence that P-gp activity may be related to haplotypes of MDR1 gene. In the current study, the frequencies of common functional polymorphisms in MDR1 gene (2677G > A,T and 3435C > T) were evaluated using PCR-RFLP and allele-specific amplification, in a group of 204 healthy individuals of Caucasian origin from Poland. It was found that the frequencies of the studied single nucleotide polymorphisms were similar to those reported for other Caucasian populations, and were as follows: 2677G-3435C--0.453, 2677G-3435T--0.143, 2677T-3435C--0.015, 2677T-3435T--0.370, 2677A-3435C--0.008, 2677A-3435T--0.011. The results of our study may give the basis for predicting pharmacokinetic and pharmacodynamic effects of many commonly used drugs in the Polish population.