Tomomi Iwakiri

Effect of P-Glycoprotein Modulator, Cyclosporin A, on the Gastrointestinal Excretion of Irinotecan and Its Metabolite SN-38 in Rats

AbstractPurpose. The purpose of this work was to investigate the role of the hepatic and intestinal P-glycoprotein (P-gp) and canalicular multispecific organic anion transporter /multidrug resistance-associated protein 2 (cMOAT/MRP2) on both biliary excretion and intestinal exsorption of irinotecan hydrochloride (CPT-11) and its metabolite, SN-38, in the lactone and carboxylate forms. Cyclosporin A (CsA) was used to modulate P-gp and cMOAT/MRP2. Methods. The transcellular transport of CPT-11 and SN-38 was examined by using LLC-PK1 derivative cell lines transfected with murine mdr1a both in the absence or in the presence of CsA. The excretions of the compounds through the biliary and intestinal membrane routes were investigated by in situ perfusion technique. Results. Basolateral-to-apical transport of CPT-11 lactone in L-mdr1a cells was significantly decreased by CsA (10 μM). The trans- cellular transport of SN-38 lactone showed similar behaviors as those of CPT-11 lactone. The biliary excretion and the intestinal exsorption of both forms of CPT-11 and SN-38 were significantly inhibited when the drug was co-administered with CsA. Conclusions. The transports of CPT-11 and SN-38 via the biliary route seem to be essentially related with cMOAT/MRP2, whereas those of both compounds via the intestinal membrane seem to be related with P-gp.

Transient inhibition of CYP3A in rats by star fruit juice

Star fruit juice is a potent in vitro inhibitor of CYP3A; however, few reports are available on the inhibition of CYP3A activities by star fruit juice in vivo. Therefore, in this study, we investigated the CYP3A-mediated star fruit-drug interaction in vivo. The effect of star fruit juice on carbamazepine pharmacokinetics was examined in rats. In comparison with water, the area under the concentration-time curve (AUC) of carbamazepine was approximately 1.3-fold greater when star fruit juice (2 ml) was orally administered 1 h before the oral administration of carbamazepine (50 mg/kg). In contrast, the elimination half-life of carbamazepine and the AUC ratio of carbamazepine 10,11-epoxide to carbamazepine were not altered by the administration of star fruit juice. These results suggest that star fruit juice impairs the function of enteric CYP3A, but not of hepatic CYP3A. In addition, we evaluated the time course of recovery of CYP3A activity that was reduced after the treatment with star fruit juice. The inhibition by star fruit juice was recovered within approximately 24 h. These data suggest that the effect of star fruit juice is mainly reversible and transient. Thus, we discovered that star fruit juice alters the carbamazepine pharmacokinetics in rats.

Adrenomedullin increases phosphatidylcholine secretion in rat type II pneumocytes

Adrenomedullin, a novel hypotensive peptide, has been reported to be produced in the lung as well as in the adrenal medulla. However, the effect of adrenomedullin on lung function is still poorly understood. In this study, we detected the expression of both adrenomedullin mRNA and putative adrenomedullin receptor mRNA in primary cultures of rat type II pneumocytes. Adrenomedullin increased the secretion of phosphatidylcholine, the predominant component of pulmonary surfactant, by type II pneumocytes. The increase was partly inhibited by pretreatment with the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP-(8-37). Furthermore, the increased phosphatidylcholine secretion was significantly inhibited by several protein kinase C inhibitors, such as sphingosine, 2-[1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl]3-(1H-indol-3-yl) maleimide (Gö6983), 3-[1-(3-amidinothio)-propyl-1H-indoyl-3-yl]3-(1-methyl-1H-++ +indoyl-3-yl ) maleimide methane sulfonate (Ro-31-8220), and staurosporine. Our results suggest that adrenomedullin can be considered a candidate autocrine modulator of surfactant secretion in type II pneumocytes.

Transcriptional up-regulation of cell surface NaV1.7 sodium channels by insulin-like growth factor-1 via inhibition of glycogen synthase kinase-3β in adrenal chromaffin cells: enhancement of 22Na+ influx, 45Ca2+ influx and catecholamine secretion

Insulin-like growth factor-1 (IGF-1) plays important roles in the regulation of neuronal development. The electrical activity of Na(+) channels is crucial for the regulation of synaptic formation and maintenance/repair of neuronal circuits. Here, we examined the effects of chronic IGF-1 treatment on cell surface expression and function of Na(+) channels. In cultured bovine adrenal chromaffin cells expressing Na(V)1.7 isoform of voltage-dependent Na(+) channels, chronic IGF-1 treatment increased cell surface [(3)H]saxitoxin binding by 31%, without altering the Kd value. In cells treated with IGF-1, veratridine-induced (22)Na(+) influx, and subsequent (45)Ca(2+) influx and catecholamine secretion were augmented by 35%, 33%, 31%, respectively. Pharmacological properties of Na(+) channels characterized by neurotoxins were similar between nontreated and IGF-1-treated cells. IGF-1-induced up-regulation of [(3)H]saxitoxin binding was prevented by phosphatydil inositol-3 kinase inhibitors (LY204002 or wortmannin), or Akt inhibitor (Akt inhibitor IV). Glycogen synthase kinase-3 (GSK-3) inhibitors (LiCl, valproic acid, SB216763 or SB415286) also increased cell surface [(3)H]saxitoxin binding by ∼ 33%, whereas simultaneous treatment of IGF-1 with GSK-3 inhibitors did not produce additive increasing effect on [(3)H]saxitoxin binding. IGF-1 (100 nM) increased Ser(437)-phosphorylated Akt and Ser(9)-phosphorylated GSK-3β, and inhibited GSK-3β activity. Treatment with IGF-1, LiCl or SB216763 increased protein level of Na(+) channel α-subunit; it was prevented by cycloheximide. Either treatment increased α-subunit mRNA level by ∼ 48% and accelerated α-subunit gene transcription by ∼ 30% without altering α-subunit mRNA stability. Thus, inhibition of GSK-3β caused by IGF-1 up-regulates cell surface expression of functional Na(+) channels via acceleration of α-subunit gene transcription.

Effect of acute hepatic failure on the hepatic first-pass effect of 5-fluorouracil in rats.

Objectives In cancer chemotherapy for hepatocellular carcinoma, 5‐fluorouracil is widely used and has typically been given by intrahepatic arterial (i.a.) infusion to increase treatment efficacy and reduce systemic toxicity. 5‐Fluorouracil is eliminated primarily by the liver and so the hepatic first‐pass effect after intrahepatic arterial administration of 5‐fluorouracil may be lower in patients with hepatic failure, and systemic toxicity may not be reduced. In this study, we have investigated the effect of acute hepatic failure on the first‐pass effect of 5‐fluorouracil in rats.

Relationship between UGT1A1*27 and UGT1A1*7 polymorphisms and irinotecan-related toxicities in patients with lung cancer

The objective of this study was to evaluate the effects of gene polymorphisms, including UGT1A1*7, *27, and *29, on the safety of irinotecan therapy.

Hepatic fibrosis does not affect the pharmacokinetics of 5-fluorouracil in rats.

In the case of cancer chemotherapy for hepatocellular carcinoma, 5-fluorouracil (5-FU) is used widely, and has typically been given by intrahepatic arterial (i.a.) infusion to increase treatment efficacy and to reduce systemic toxicity. 5-Fluorouracil is eliminated primarily by the liver, and so its use in patients with hepatic disease can be difficult. This study investigated the effect of hepatic fibrosis on the pharmacokinetics of 5-FU in rats. Experimental hepatic fibrosis was induced by carbon tetrachloride treatment. 5-fluorouracil was infused for 15 min into the hepatic artery or the saphenous vein of the rats at a dose of 1.25 mg/kg. There were no significant differences in the plasma concentration and AUC of 5-FU between hepatic disease rats and their controls after both intravenous and intraarterial injection. This result is probably attributed to the fact that there were no significant differences in hepatic blood flow and dihydropyrimidine dehydrogenase (DPD; an initial and rate-limiting enzyme in 5-FU catabolism) activity between hepatic disease rats and their controls, because the total clearance of 5-FU after intravenous and intraarterial administration is mainly limited by hepatic blood flow and DPD activity, respectively. In conclusion, the pharmacokinetics of 5-FU is not affected by hepatic fibrosis, unlike that of many hepatically metabolized drugs.

Abstract 5032: The relationship between theUGT1A1*27andUGT1A1*7genetic polymorphisms and irinotecan-related toxicities in patients with lung cancer

Background: Genetic polymorphisms in the UDP-glucuronosyltransferase 1A1 (UGT1A1), UGT1A7, and UGT1A9 genes are associated with interindividual differences in irinotecan toxicities. The UGT1A1*7, *27, and *29 gene polymorphisms occur within the common exons of UGT1A1 isoforms and cause substantial reductions in their functional activity; however, few clinical studies have examined the effects of these polymorphisms. Purpose: To evaluate the effects of gene polymorphisms, including UGT1A1*7, *27, and *29, on the safety of irinotecan therapy. Patients and methods: The eligibility criteria were as follows: lung cancer patients who were scheduled to undergo irinotecan therapy, aged ≥20 years, and had a performance status of 0-2. After informed consent had been obtained, patients were enrolled, and their blood was collected and used to examine the frequency of the UGT1A1*6, *7, *27, *28, and *29 polymorphisms and the drug concentrations of irinotecan, SN-38, and SN-38G after irinotecan therapy. Results: Thirty-one patients were enrolled. The patients’ characteristics were as follows: male/female = 25/6, median age (range) = 71 (55-84), stage IIB/IIIA/IIIB/IV = 2/6/11/12, and Ad/Sq/Sm/Oth = 14/10/3/4. The -/-, *6/-, *7/-, *27/-, *28/-, and *29/- UGT1A1 gene polymorphisms were observed in 10 (32%), 10 (32%), 2 (6%), 2 (6%), 7 (23%), and 0 (0%) cases, respectively. There were no homozygous or complex heterozygous polymorphisms. The UGT1A1*27 polymorphism occurred separately from the UGT1A1*28 polymorphism. The lowest leukocyte counts of the patients with the UGT1A1*27 and UGT1A1*6 gene polymorphisms were lower than those seen in the wild-type patients. SN-38 tended to remain in the blood for a prolonged period after the infusion of irinotecan in patients with the UGT1A1*27 or UGT1A1*28 polymorphism. No severe myelotoxicity was seen in the patients with UGT1A1*7. Conclusions: UGT1A1*27 and UGT1A1*7 are both rare gene polymorphisms. UGT1A1*27 can occur separately from UGT1A1*28 in some circumstances and is related to leukopenia during irinotecan treatment. UGT1A1*7 is less relevant to irinotecan-induced toxicities, and UGT1A1*29 seems to have little clinical impact. Citation Format: Minoru Fukuda, Manabu Okumura, Tomomi Iwakiri, Arimori Kazuhiko, Shinnosuke Takemoto, Takaya Ikeda, Takuya Honda, Hiroyuki Yamaguchi, Katsumi Nakatomi, Kazuma Kobayashi, Mitsuko Masutani, Mikio Oka, Kazuto Ashizawa, Hiroshi Mukae. The relationship between the UGT1A1*27 and UGT1A1*7 genetic polymorphisms and irinotecan-related toxicities in patients with lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5032. doi:10.1158/1538-7445.AM2017-5032

Change in Drug Concentration in Serum Stored in Sterilized Vacuum Tubes for Serum Separation

We investigated the change in drug concentrations in serum stored in sterilized vacuum tubes for serum separation. The serum concentrations of seven drugs-phenytoin, phenobarbital, carbamazepine, vancomycin, valproate, theophylline and digoxin-were determined after storage in three different vacuum tubes-Vacutainer® SST and SST II (SST, SST II, Becton Dickinson Co. Ltd.) and Neo-Tube® GP-SP 1029 (GP-SP, Nipro Co.). Though there was no change in the serum drug concentrations for any of the tested drugs in GP-SP, the concentrations of phenytoin, phenobarbital and carbamazepine in the serum stored in SST and SST II were significantly decreased due to adsorption onto the serum separator. The degree of adsorption was greater for the SST tube than the SST II tube and for the drugs, the order of adsorption was phenytoin>carbamazepine>phenobarbital. The adsorption of phenytoin onto the separator of SST depended on several storage conditions, such as initial drug concentration, storage temperature and storage volume, while its adsorption onto the SST II separator depended on storage temperature and storage volume. In addition, the change in phenytoin concentration during storage in the SST tube was well correlated with the free fraction of the drug. This indicates that protein binding is an important factor affecting the stability of drug concentrations in serum stored in separation tubes. Overall, the results of our study indicate that for accurate therapeutic drug monitoring, it is necessary to select vacuum serum separation tubes on the basis of drug concentration stability data for them.