Kohshi Nishiguchi

CYP2C19 Genotype and Pharmacokinetics of Three Proton Pump Inhibitors in Healthy Subjects

AbstractPurpose. To predict the CYP2C19 genotype-dependence in anti-Helicobacter pylori(H. pylori) therapy when lansoprazole or rabeprazole was used instead of omeprazole as a proton pump inhibitor (PPI). Methods. A comparative pharmacokinetic study with each PPI was designed as an open, randomized, and crossover study of 18 Japanese healthy volunteers who were classified into the homozygous, heterozygous extensive metabolizer and the poor metabolizer based on the CYP2C19 genotype determined by PCR-RFLP method. Each subject received a single oral dose of 20 mg omeprazole, 30 mg lansoprazole, or 20 mg sodium rabeprazole, with at least 1 week washout period between treatments. Plasma concentrations of PPIs and their metabolites were monitored until 12 h after medication. Results. Pharmacokinetic profiles of omeprazole and lansoprazole were well correlated with the CYP2C19 genotype. The heterozygous extensive metabolizer was slightly different from the homozygote, but there was no statistically significant difference. The CYP2C19 genotype dependence found for lansoprazole was not obvious compared with omeprazole. As for rabeprazole, the pharmacokinetic profile was independent of the CYP2C19 genotype. Conclusions. CYP2C19 genotype dependence will be found in the anti-H. pylori therapy even when lansoprazole is used as the PPI.

Effect of micafungin on cytochrome P450 3A4 and multidrug resistance protein 1 activities, and its comparison with azole antifungal drugs.

The effects of micafungin on cytochrome P450 3A4 (CYP3A4) metabolic and multidrug resistance protein 1 (MDR1) transport activities were investigated and compared with those of amphotericin B and four azole antifungal drugs (ketoconazole, itraconazole, fluconazole and miconazole). The effects on the metabolic activity of CYP3A4 were examined by measuring nifedipine oxidase activity in human liver microsomes and the effects on MDR1 transport activity were evaluated using [3H]digoxin in MDR1‐overexpressing LLC‐GA5‐COL150 cells. An inhibitory effect on CYP3A4 activity was found for ketoconazole, itraconazole and miconazole, with 50% inhibitory concentrations of 11.7, 32.6 and 74.2 nM, respectively. Fluconazole and micafungin had only slight inhibitory effects and amphotericin B had no effect. The MDR1‐mediated transport of [3H]digoxin was inhibited by ketoconazole and itraconazole, and slightly by miconazole. It is suggested that micafungin and amphotericin B would be unlikely to cause drug‐drug interactions by inhibition of CYP3A4 and MDR1. A positive correlation between the inhibitory effects on CYP3A4 and MDR1 activities was observed, and the physicochemical mechanisms involved and impact on clinical treatment should be studied further.

Effects of 12 Ca2+ antagonists on multidrug resistance, MDR1-mediated transport and MDR1 mRNA expression

The effects of 12 Ca(2+) antagonists on MDR1 were examined by two independent models: the inhibitory effect on MDR1-mediated transport of [(3)H]digoxin using MDR1-overexpressing LLC-GA5-COL150 cell monolayers and the reversal effect on cytotoxicity of vinblastine or paclitaxel using MDR1-overexpressing Hvr100-6 cells. The inhibitory effects on [(3)H]digoxin transport were assessed as the 50% inhibitory concentration during 4 h exposure, and the values were the lowest for nicardipine (4.54 microM), manidipine (4.65 microM) and benidipine (4.96 microM), followed by bepridil (10.6 microM), barnidipine (12.6 microM), efonidipine (13.0 microM), verapamil (13.2 microM) and nilvadipine (18.0 microM). The reversal effect on cytotoxicity was assessed by the 50% growth inhibitory concentration after 3 days exposure, and the resistance to vinblastine or paclitaxel in Hvr100-6 cells was reversed by manidipine, verapamil, benidipine, barnidipine, and nicardipine, in that order. Bepridil, barnidipine, efonidipine, verapamil and nilvadipine showed similar inhibitory effects on [(3)H]digoxin transport, but barnidipine and verapamil showed a stronger effect in reversal of cytotoxicity. Real-time quantitative RT-PCR assay indicated a decrease in MDR1 mRNA expression by barnidipine and verapamil. It is concluded that Ca(2+) antagonists cannot only be direct inhibitors of MDR1 but that some may at the same time act as inhibitors of expression of MDR1 via down-regulation of MDR1 mRNA.

Influence of Serum in Hemodialysis Patients on the Expression of Intestinal and Hepatic Transporters for the Excretion of Pravastatin

It is known that the lipid‐lowering agent pravastatin, which is not metabolized by cytochrome P450, is eliminated as an unchanged drug in bile and urine. It is interesting to note that the non‐renal clearance of pravastatin in end‐stage renal failure patients is decreased compared with that of healthy volunteers. This study investigated the influence of uremic serum and toxins on the transport mechanisms of pravastatin to elucidate the cause of decreased non‐renal clearance in end‐stage renal failure patients. Caco‐2 and Hep3B cells were used as models of intestinal epithelial cells and hepatocytes respectively. Normal and uremic serum were deproteinized by treatment with methanol. 3‐Carboxy‐4‐methyl‐5propyl‐2‐furanpropanoic acid (CMPF), hippuric acid, indole‐3‐acetic acid, 3‐indoxyl sulfate, and p‐cresol were chosen as uremic toxins. Uremic serum‐treated Caco‐2 cells exhibited significantly increased accumulation of pravastatin and significantly decreased expression of MRP2 mRNA compared with normal serum‐treated Caco‐2 cells. In addition, the expression of MRP2 mRNA tended to decrease in cells treated with CMPF, indole‐3‐acetic acid, or 3‐indoxyl sulfate. Uremic serum‐treated Hep3B cells showed a significantly decreased initial uptake rate of pravastatin; furthermore, the expressions of OATP1B1 and OATP2B1 mRNA were decreased compared to normal serum‐treated Hep3B cells. These results suggest that the decrease in the non‐renal clearance of pravastatin in end‐stage renal failure patients is partly induced by the downregulation of intestinal MRP2 and hepatic OATP1B1 and/or OATP2B1 by various uremic toxins in end‐stage renal failure patients.

Pharmacokinetics and pharmacogenomics in esophageal cancer chemoradiotherapy

Esophageal cancer is one of the most lethal malignancies. Surgical resection of the tumor from the primary site has been the standard treatment, especially for localized squamous cell carcinoma, but considerable clinical efforts during the last decade have resulted in novel courses of treatment. These options include chemoradiotherapy, consisting of a continuous infusion of 5-fluorouracil (5-FU), cisplatin (CDDP), and concurrent radiation. Given the substantial inter- and/or intra-individual variation in clinical outcome, future improvements will likely require the incorporation of a novel anticancer drug, pharmacokinetically guided administration of CDDP or 5-FU, and identification of potential responders by patient genetic profiling prior to treatment. In this review, the latest information on incidence, risk factors, biomarkers, therapeutic strategies, and the pharmacokinetically guided or genotype-guided administration of CDDP and 5-FU is summarized for future individualization of esophageal cancer treatment.

Inhibitory effects of uraemic toxins 3-indoxyl sulfate and p-cresol on losartan metabolism in vitro

Objectives The purpose of this study was to clarify the cause of decreased metabolic clearance of losartan in patients with end‐stage renal failure. The influence of serum from haemodialysis patients (uraemic serum) and uraemic toxins on the metabolism of losartan to EXP‐3174 was investigated in vitro.

Molecular changes to HeLa cells on continuous exposure to SN-38, an active metabolite of irinotecan hydrochloride

It is important to clarify the molecular characteristics of tumor cells showing multidrug resistance (MDR) and to identify the novel targets or biomarkers for chemotherapy. The aim of this study is to establish resistant HeLa sublines through exposure to SN-38, an active metabolite of irinotecan hydrochloride, and to investigate their molecular changes. HeLa cells were exposed to SN-38 at 1, 10, or 100 nM, and resistant clones were isolated and named HeLa/SN1, HeLa/SN10, and HeLa/SN100, respectively. Their cellular changes were examined based on growth inhibition assays, the function of ABCG2/BCRP, and a RT-PCR analysis of MDR-related protein. The sublines showed a decrease in sensitivity to not only SN-38 but also other chemotherapeutic agents as compared with HeLa cells. mRNA and protein levels of ABCG2/BCRP were increased, and the transport activity of ABCG2/BCRP was enhanced, in the resistant cells. In addition, the expression levels of ABCC1/MRP1, ABCC3/MRP3, and ABCC5/MRP5 were higher than in HeLa cells. The mRNA levels of GGT1 encoding a gamma-glutamyl transferase, but not GCS encoding a gamma-glutamyl cysteine synthetase, were also higher. Other factors examined, i.e., topoisomerase, SLCO1B1, and apoptosis-regulating factors, were comparable among the cells. The overexpression of ABCG2/BCRP was involved in the mechanism of resistance in SN-38-tolerant cells, and ABCC1/MRP1, ABCC3/MRP3, ABCC5/MRP5, and GGT1 may also have participated.

Haloperidol is an inhibitor but not substrate for MDR1/P-glycoprotein

The involvement of the multidrug resistant transporter MDR1/P‐glycoprotein in the penetration of haloperidol into the brain and absorption in the intestine was investigated to examine its role in inter/intra‐individual variability, using the porcine kidney epithelial cell line LLC‐PK1 and its MDR1‐overexpressing transfectant, LLC‐GA5‐COL150. The inhibitory effect of haloperidol on other MDR1 substrates was also investigated in terms of the optimization of haloperidol‐based pharmacotherapy. The transepithelial transport of [3H]haloperidol did not differ between the two cell lines, and vinblastine, a typical MDR1 substrate, had no effect on the transport, suggesting that haloperidol is not a substrate for MDR1, and it is unlikely that MDR function affects haloperidol absorption and brain distribution, and thereby the response to haloperidol. However, haloperidol was found to have an inhibitory effect on the MDR1‐mediated transport of [3H]digoxin and [3H]vinblastine with an IC50 value of 7.84 ± 0.76 and 3.60 ± 0.64 μM, respectively, suggesting that the intestinal absorption, not distribution into the brain, of MDR1 substrate drugs could be altered by the co‐administration of haloperidol in the clinical setting, although further clinical studies are needed.

VEGF -634C/G genotype is predictive of long-term survival after treatment with a definitive 5-fluorouracil/cisplatin-based chemoradiotherapy in Japanese patients with esophageal squamous cell carcinoma.

Background: Reports have been accumulating that genetic properties are predictive of clinical response after and/or toxicity during cancer chemotherapy, but little information is available concerning effects on long-term survival. In this study, 49 Japanese patients with esophageal squamous cell carcinoma (ESCC) were followed up for 5 years after treatment with a definitive 5-fluorouracil (5-FU)/cisplatin (CDDP)-based chemoradiotherapy (CRT), and the effects of genotypes of vascular endothelial growth factor (VEGF) were retrospectively revaluated in terms of prediction of long-term survival. Methods: A course consisted of the continuous infusion of 5-FU at 400 mg/m2/day for days 1-5 and 8-12, the infusion of CDDP at 40 mg/m2/day on days 1 and 8, and radiation at 2 Gy/day on days 1 to 5, 8 to 12, and 15 to 19, with a second course repeated after a 2-week interval. The VEGF genotypes -1498T/C, -1154G/A, -634C/G, -7C/T, 936C/T, and 1612G/A were evaluated. Results: The complete response (CR) rate was 46.9% (23/49). The 5-year survival rate was 42.9 % (21/49). There were 7 patients with a CR, but survival of less than 5 years. They died from myocardial infarction (N=1), sudden cardiac death after suffering from heart failure (N=1), acute myeloid leukemia that developed from myelodysplastic syndromes (N=1), factors not specified (N=2), oropharynx cancer (N=1), and tongue cancer (N=1). VEGF -634C/G had no effect on clinical response, but long-term survival depended on the genotype (p=0.033, Fishers; p=0.038, Cochran-Armitage; p=0.079, Log-rank). The genotype frequency of 7 patients with a CR, but survival of less than 5 years was different from that for the other 42 patients (p=0.032, Fishers). None of the other 5 genotypes evaluated affected either clinical response or survival. Conclusions: VEGF -634C/G is possibly predictive of long-term survival after treatment with a definitive 5-FU/CDDP-based CRT. Further clinical studies with a larger number of cases are needed to clarify the effects of this genotype.

Effects of Decreased Vitamin D and Accumulated Uremic Toxin on Human CYP3A4 Activity in Patients with End-Stage Renal Disease

In patients with end-stage renal disease, not only renal clearance but also hepatic clearance is known to be impaired. For instance, the concentration of erythromycin, a substrate of cytochrome P450 3A4 (CYP3A4), has been reported to be elevated in patients with end-stage renal disease. The purpose of this study is to elucidate the reason for the decrease in hepatic clearance in patients with end-stage renal disease. Deproteinized pooled sera were used to assess the effects of low-molecular-weight uremic toxins on CYP3A4 activity in human liver microsomes and human LS180 cells. Four uremic toxins (3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, hippuric acid, indole-3-acetic acid, and 3-indoxyl sulfate) present at high concentrations in uremic serum were also studied. Simultaneous treatment of uremic serum (less than 10%) or uremic toxins did not affect testosterone 6β-hydroxylation in human liver microsomes. On the other hand, pretreatment of each serum activates CYP3A4 in LS180 cells, and the increased CYP3A4 activity in uremic serum-treated cells was smaller than normal serum-treated cells. In addition, CYP3A4 and CYP24A1 mRNA levels also increased in LS180 cells exposed to normal serum, and this effect was reduced in uremic serum-treated cells and in cells exposed to uremic serum added to normal serum. Furthermore, addition of 1,25-dihydroxyvitamin D to uremic serum partially restored the serum effect on CYP3A4 expression. The present study suggests that the decrease of 1,25-dihydroxyvitamin D and the accumulation of uremic toxins contributed to the decreased hepatic clearance of CYP3A4 substrates in patients with end-stage renal disease.