Inhibitory Effect of Dextran Derivatives on Multidrug Resistance-Related Efflux Transporters in Vitro.

Dextran is a promising candidate as a nanocarrier of chemotherapeutic drugs due to its biocompatibility, biodegradability, and ability to accumulate in tumors. Furthermore, dextran derivatives interact with P-glycoprotein (P-gp), so we hypothesized that they may be available as tumor-specific drug delivery systems with the ability to reverse multidrug resistance. Here, to test this idea, we investigated whether dextran and its derivatives inhibit breast cancer resistance protein (BCRP), multidrug resistance associated protein 1 (MRP1), and P-gp in vitro. First, we examined their effect on the uptake of specific fluorescent substrates by inside-out Sf-9 membrane vesicles overexpressing BCRP, MRP1, and P-gp. BCRP and MRP1 were significantly inhibited by 2-hydroxypropyl-trimethylammonium-dextran of 4 and 70 kDa (Q-D4 and Q-D70) at a concentration near the clinically used concentration of dextran; however, P-gp was not inhibited. A structure-activity study showed that Q-D4, Q-D70, and 40 kDa diethylaminoethyl-dextran (DEAE-D40) significantly inhibited BCRP, while 4, 40, and 70 kDa dextrans (D4, D40, and D70), dextran sulfate (Sul-D40), and the individual saccharide components of dextran did not. These results suggest that the cationic side chains, but not the saccharides, are important for BCRP inhibition. Finally, cell-based efflux assay was conducted. Q-D4, Q-D70, and DEAE-D40 did not specifically increase the retention of Hoechst33342 in BCRP-overexpressing KB cells. Similarly, Q-D4 and Q-D70 did not affect the intracellular retention of specific fluorescent substrates in MRP1- and P-gp-overexpressing KB cells. The ineffectiveness in cellular systems is presumably due to inability of the dextran derivatives to access transporters located on the cytoplasmic side of the cell membrane.

Intestinal Absorption of Alogliptin Is Mediated by a Fruit-Juice-Sensitive Transporter.

Alogliptin (ALG), an inhibitor of dipeptidylpeptidase-4, is used in the management of type 2 diabetes mellitus, and has a high absorption rate (>60-71%), despite its low lipophilicity (logP=-1.4). Here, we aimed to clarify the mechanism of its intestinal absorption. ALG uptake into Caco-2 cells was time-, temperature-, and concentration-dependent, but was not saturated at concentrations up to 10 mmol/L. The uptake was significantly inhibited by the organic anion transporting polypeptide (OATP) substrate fexofenadine and by the OATP inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), but was not inhibited by organic cation transporter (OCT)/organic cation/carnitine transporter (OCTN) or peptide transporter 1 (PEPT1) substrates. Grapefruit, orange, and apple juices and their constituents, which are known to strongly inhibit intestinal OATPs, significantly inhibited ALG uptake into Caco-2 cells. The pH dependence was bell-shaped, indicating the involvement of a pH-sensitive transporter. However, ALG uptake by HEK293 cells overexpressing OATP2B1, a key intestinal OATP transporter of amphiphilic drugs, was not different from that of mock cells. In a rat in vivo study, apple juice reduced systemic exposure to orally administered ALG without changing the terminal half-life. These observations suggest that intestinal absorption of ALG is carrier-mediated, and involves a fruit-juice-sensitive transporter other than OATP2B1.

Increased membrane permeation and blood concentration of 6-carboxyfluorescein associated with dysfunction of paracellular route barrier in the small intestine of ulcerative colitis model rats.

In the colon of patients with ulcerative colitis (UC), decreased function of the paracellular barrier, especially hypofunction of the tight junction, is associated with pathological conditions. However, there has been no report to date on the function of tight junctions in the small intestine. Here, we focused on the barrier function of the small intestine, especially in tight junctions, and compared it with that of the colon. Dextran sulfate sodium (DSS) was used to induce ulcerative colitis in rats in order to evaluate the function of the paracellular barrier in the jejunum, ileum, and colon. An in vitro diffusion chamber method was used to evaluate membrane resistance, which is an index of tight junction function and mucosal permeability, using 6-carboxyfluorescein (6-CF), a paracellular marker. In the jejunum and colon, with decrease of membrane resistance in the DSS group, mucosal permeability increased, whereas no marked difference was observed in the ileum. In the in situ closed-loop method, absorption of 6-CF from the jejunum was higher than that from the ileum. Immunohistochemical staining of claudin-4 showed heterogeneous attenuation of claudin-4 in the jejunum. Pharmacokinetic parameters were calculated from the blood concentration after intravenous injection and oral administration of 6-CF. In the DSS group, there was a delay in the elimination phase, suggesting a decrease in renal function, and an increase in maximum blood concentration, associated with an increased absorption rate constant. The increased absorption and decreased renal function due to decreased paracellular barrier function in the small intestine and colon may cause fluctuations in drug efficacy and side effects.

Intestinal secretion of indoxyl sulfate as a possible compensatory excretion pathway in chronic kidney disease.

Indoxyl sulfate (IS) is a protein-bound uremic toxin that progressively accumulates in plasma during chronic kidney disease (CKD), and its accumulation is associated with the progression of CKD. This study examined the intestinal secretion of IS using in situ single-pass intestinal perfusion in a rat model of renal insufficiency, MRP2- and BCRP-overexpressing Sf9 membrane vesicles, and Caco-2 cell monolayers. An in situ single-pass perfusion study in CKD model rats demonstrated that a small amount of IS is secreted into intestinal lumen after iv administration of IS, and the clearance increased AUC-dependently. An excess amount of IS (3 mm) partially inhibited the MRP2- and BCRP-mediated uptake of specific fluorescent substrates, CDCF and Lucifer yellow, respectively, into the membrane vesicles, although IS was not taken up at a physiological concentration, 10 µm. In the Caco-2 cell monolayers, the IS transport was higher in the absorptive direction than in the secretory direction (p < 0.05). p-Aminohippuric acid (PAH) strongly inhibited IS transport in both directions (absorptive, p = 0.142; secretory, p < 0.01). Given that the blood IS levels are much higher than those in the intestinal lumen, it is possible that this unknown PAH-sensitive system contributes to the intestinal IS secretion. Although in situ inhibition study is needed to confirm that this unknown transporter mediates the in vivo intestinal secretion of IS, we speculate that this unknown active efflux system works as a compensatory excretion pathway for excess organic anions such as IS especially in end-stage renal disease.

Possible interaction of quinolone antibiotics with peptide transporter 1 in oral absorption of peptide-mimetic drugs.

The study investigated whether quinolone antibiotics inhibit the PEPT1-mediated uptake of its substrates. Among the quinolones examined, lomefloxacin, moxifloxacin (MFLX) and purlifloxacin significantly inhibited the uptake of PEPT1 substrate phenylalanine-Ψ(CN-S)-alanine (Phe-Ψ-Ala) in HeLa/PEPT1 cells to 31.6 ± 1.3%, 27.6 ± 2.9%, 36.8 ± 2.2% and 32.6 ± 1.4%, respectively. Further examination showed that MFLX was an uncompetitive inhibitor, with an IC50 value of 4.29 ± 1.29 mm. In addition, MFLX significantly decreased the cephalexin and valacyclovir uptake in HeLa/PEPT1 cells. In an in vivo study in rats, the maximum plasma concentration (C(max)) of orally administered Phe-Ψ-Ala was significantly decreased in the presence of MFLX (171 ± 1 ng/ml) compared with that in its absence (244 ± 9 ng/ml). The area under the concentration-time curve (AUC) of orally administered Phe-Ψ-Ala in the presence of MFLX (338 ± 50 ng/ml · h) tended to decrease compared with that in its absence (399 ± 75 ng/ml · h). The oral bioavailability of Phe-Ψ-Ala in the presence and absence of MFLX was 41.7 ± 6.2% and 49.2 ± 9.2%, respectively. The results indicate that administration of quinolone antibiotics concomitantly with PEPT1 substrate drugs may potentially result in drug-drug interaction.

Analysis of a child who developed abnormal neuropsychiatric symptoms after administration of oseltamivir: a case report.

BACKGROUND: Neuropsychiatric side effects of oseltamivir occur occasionally, especially in infants and young patients, but nothing is known about possible contributory factors. CASE PRESENTATION: We report a case of a 15-year-old Japanese female with influenza infection who developed abnormal psychiatric symptoms after administration of standard doses of oseltamivir. She had no history of neurological illness, had never previously taken oseltamivir, and had not developed psychiatric reactions during previous influenza infection. Her delirium-like symptoms, including insomnia, visual hallucinations, and a long-term memory deficit, disappeared after cessation of oseltamivir and administration of benzodiazepine. Detailed assessment was performed, including neurological examination (electroencephalogram, brain magnetic resonance imaging, single photon emission computed tomography with 99mTc-ethyl cysteinate dimer and with (123)I-iomazenil, cerebrospinal fluid analysis and glutamate receptor autoantibodies), drug level determination and simulation, and genetic assessment (OAT1, OAT3, CES1, Neu2). CONCLUSIONS: Abnormal slowing in the electroencephalogram, which is characteristic of influenza-associated encephalopathy, was not observed in repeated recordings. The serum level determination of active metabolite Ro 64-0802 determined at 154 h after final dosing of oseltamivir was higher than the expected value, suggesting delayed elimination of Ro 64-0802. Thus, abnormal exposure to Ro 64-0802 might have contributed, at least in part, to the development of neuropsychiatric symptoms in this patient. The score on Naranjo's adverse drug reaction probability scale was 6. Mutation of c.122G > A (R41Q) in the sialidase Neu2 gene, increased CSF glutamate receptor autoantibodies, and limbic GABAergic dysfunction indicated by SPECT with (123)I-iomazenil were found as possible contributory factors to the CNS side effects.

Characterization of cesium uptake mediated by a potassium transport system of bacteria in a soil conditioner.

We found that bacteria in a commercial soil conditioner sold in Ishinomaki, Miyagi, exhibited concentrative and saturable cesium ion (Cs(+)) uptake in the natural range of pH and temperature. The concentration of intracellular Cs(+) could be condensed at least a few times higher compared with the outside medium of the cells. This uptake appeared to be mediated by a K(+) transport system, since Cs(+) uptake was dose-dependently inhibited by potassium ion (K(+)). Eadie-Hofstee plot analysis indicated that the Cs(+) uptake involved a single saturable process. The maximum uptake amount (Jmax) was the same in the presence and absence of K(+), suggesting that Cs(+) and K(+) uptakes were competitive with respect to each other. These bacteria might be useful for bioremediation of cesium-contaminated soil.

Alginate enhances excretion and reduces absorption of strontium and cesium in rats.

Alginate (ALA), which is an intercellular polysaccharide associated with brown algae, is used as a food additive, a health food and a medicine. Here, we first examined the adsorption of strontium (Sr) and cesium (Cs) by ALA in vitro, and then evaluated the effects of ALA on absorption and excretion of Sr and Cs in rats, in order to evaluate its potential usefulness for minimizing radiation damage from materials released after a nuclear accident. Both Sr and Cs were concentration-dependently adsorbed by sodium alginate (ALA-Na) in vitro. In rats given diet containing either ALA-Na or calcium alginate (ALA-Ca) for two weeks, the plasma concentration of Sr gradually decreased compared with the controls (normal diet); however, in the case of Cs, the plasma concentration was decreased only in the ALA-Ca group, but not the ALA-Na group. Moreover, we examined the effect of preadministration of diet containing either ALA-Na or ALA-Ca on absorption of Sr and Cs administered orally as the chloride salts to rats. Absorption of both Sr and Cs was reduced in the ALA-Ca group, while absorption of only Sr was reduced in the ALA-Na group. Safety assessments indicated that ALA-Ca is safer than ALA-Na. These results indicate that ALA-Ca reduces absorption and promotes excretion of both Sr and Cs, while ALA-Na does so only for Sr.

Osteopathic approach to sacroiliac joint pain in pregnant patients.

This paper aims to provide a comprehensive review of the management of sacroiliac (SI) joint pain in pregnant patients. Although SI joint pain is highly prevalent among pregnant patients, the unique anatomy of the joint is rarely discussed in a clinical setting. This paper provides comprehensive review of the epidemiology, anatomy, alarm findings, standard treatment, osteopathic assessment, and osteopathic manipulative treatment (OMT) of the SI joint, and it provides a general and in-depth understanding of the SI joint pain in pregnant patients and its management.

[Genetic marker of statin-induced rhabdomyolysis].

This review summarizes genetic factors predisposed to statin-induced rhabdomyolysis. The first genetic risk factor of statin myopathy uncovered by genome-wide analysis of single nucleotide polymorphisms was the common variant of SLCO1B1 gene. Analysis of 30000 genetic markers in 85 patients with myopathy induced by high-dose simvastatin showed a strong association with 521T>C polymorphism of SLCO1B1. Another study also showed that this variant of SLCO1B1 has a significant association with myopathy in patients taking pravastatin or atorvastatin although the number of patients analyzed was limited. In addition to SLCO1B1, recent studies suggested that variants of genes encoding transporters (ABCG2 and ABCB1) and metabolic enzymes (CYP2C8 and UGT1A3) involved in the disposition of statins, and those involved in the metabolic muscle disease (glycogen storage disorders, carnitine palmitoyl-2 deficiency and myoadenylate deaminase deficiency) are also risk factors of statin-induced myopathy. These genetic factors may provide predisposition testing for statin-induced rhabdomyolysis.

Third Trimester Lower Extremity Lymphorrhea.

INTRODUCTION: Lower extremity edema is one of the most common complaints among pregnant patients. However, there is no literature mentioning weeping edema (i.e., lymphorrhea) in a pregnant woman who has no concordant underlying renal and/or cardiac pathology. There is also a lack of evidence and recommendations regarding the therapeutic benefit and safety profile of diuretic use to treat profound pregnancy-associated edema. Herein, we present the case of 32-year-old female who presented with a significant lymphorrhea during the third trimester without cardiac or renal comorbidity and was successfully treated with torsemide. Case Report. We report a case of a 32-year-old multigravida patient pregnant with her third child and has two living full-term children (G3P2003). Her pregnancy was complicated by obesity, smoking (vape), and previous history of fetal growth restriction. The patient presented for routine prenatal care at 9-week gestation. She was diagnosed with chronic hypertension at 19 weeks of pregnancy based upon systolic blood pressure > 140. Lifestyle modifications were recommended, but the patient did not comply. At her 31-week office visit, the patient presented with anasarca and clear, slightly viscous fluid seeping through the atraumatic skin of her lower extremities. Preeclampsia, renal, cardiac, vascular, and infectious complications were all ruled out. The patient responded positively to loop diuretic therapy. Torsemide was found to be far more beneficial than furosemide. The patient was induced at 37 weeks secondary to chronic hypertension requiring antihypertensive therapy. Delivery was uncomplicated. The patient gave birth to a healthy male with birth weight of 2,920 g via spontaneous vaginal delivery. Discussion. Pitting edema of lower limbs frequently occurs as a result of fluid overload and chronic venous insufficiency, and pregnancy is one of the known risk factors. Additionally, the blockage of lymphatic channel with the gravida uterus likely was the main contributing factor for her lymphorrhea. In this patient, the capillary hydrostatic pressure was likely accentuated due to hypertension, obesity, and vaping. Furosemide was minimally effective to alleviate her symptoms. Torsemide provided much more effective diuresis and symptom control. However, her symptoms persisted until delivery. CONCLUSION: Torsemide provided significant therapeutic benefit over furosemide in this patient without adverse maternal, fetal, or neonatal outcomes. Further study is needed to assess the safe use of loop diuretics in the pregnant population who suffers from significant lower extremity edema.

Functional analysis of a mutation in the SLCO1B1 gene (c.1628T>G) identified in a Japanese patient with pravastatin-induced myopathy.

In the present study, we analyzed the function of a novel mutation (c.1628T>G, p.Leu543Trp) in the solute carrier organic anion transporter (SLCO) 1B1 gene, encoding organic anion transporting polypeptide (OATP) 1B1, which was identified in a patient with pravastatin-induced myopathy. OATP1B1 variants carrying the mutation (OATP1B1*1a+c.1628T>G or *1b+c.1628T>G) showed a reduced transporting activity toward typical substrates and pravastatin compared with the activity of the references (OATP1B1*1a or *1b). This was due to reduction in V(max) values of the variants, not due to change in their K(m) values. OATP1B1*1b+c.1628T>G was normally expressed on the plasma membrane of HEK293 cells at the same level as that of OATP1B1*1b. Taken together, our results suggest that the mutation c.1628T>G (p.Leu543Trp) reduced the function of OATP1B1 probably due to decrease in turnover rate of one OATP1B1 molecule rather than impairment of protein sorting to the plasma membrane.

Oseltamivir (tamiflu) is a substrate of peptide transporter 1.

Oseltamivir, an ester-type prodrug of the neuraminidase inhibitor [3R,4R,5S]-4-acetamido-5-amino-3-(1-ethylpropoxy)-1-cyclohexene-1-carboxylate phosphate (Ro 64-0802), has been developed for the treatment of A and B strains of the influenza virus but has neuropsychiatric and other side effects. In this study, we characterized the transport across intestinal epithelial cells and the absorption of oseltamivir in rats. Uptake by Caco-2 cells (human carcinoma cell line) and HeLa cells transfected with peptide transporter 1 (HeLa/PEPT1) was time- and temperature-dependent and was inhibited by typical PEPT1 inhibitors such as glycyl-sarcosine (Gly-Sar). The uptake by Caco-2 cells and HeLa/PEPT1 was saturable, with similar K(m) values. Oseltamivir absorption in adult rats was greatly reduced by simultaneous administration of milk, casein, or Gly-Sar. Furthermore, the plasma and brain concentrations of oseltamivir were higher in fasting than in nonfasting rats after oral administration. These results suggest that oseltamivir is a substrate of PEPT1 and that PEPT1 is involved in its intestinal absorption.

Oseltamivir (Tamiflu) efflux transport at the blood-brain barrier via P-glycoprotein.

Oseltamivir (Tamiflu, Roche, Nutley, NJ), an ester-type prodrug of the anti-influenza drug Ro 64-0802 (oseltamivir carboxylate), has been reported to be associated with neuropsychiatric side effects, which are likely to be caused by distribution of oseltamivir and/or its metabolite into the central nervous system. Enhanced toxicity and brain distribution of oseltamivir in unweaned rats led us to hypothesize that the low level of distribution of oseltamivir and/or Ro 64-0802 in adult brain was caused by the presence of a specific efflux transporter at the blood-brain barrier. We examined the possible role of P-glycoprotein (P-gp) as the determinant of brain distribution of oseltamivir and Ro 64-0802 both in vitro using LLC-GA5-COL150 cells, which overexpress human multidrug resistance protein 1 P-gp on the apical membrane, and in vivo using mdr1a/1b knockout mice. The permeability of oseltamivir in the basal-to-apical direction was significantly greater than that in the opposite direction. The directional transport disappeared on addition of cyclosporin A, a P-gp inhibitor. The brain distribution of oseltamivir was increased in mdr1a/1b knockout mice compared with wild-type mice. In contrast, negligible transport of Ro 64-0802 by P-gp was observed in both in vitro and in vivo studies. These results show that oseltamivir, but not Ro 64-0802, is a substrate of P-gp. Accordingly, low levels of P-gp activity or drug-drug interactions at P-gp may lead to enhanced brain accumulation of oseltamivir, and this may in turn account for the central nervous system effects of oseltamivir observed in some patients.

Hepatocyte nuclear factor 1 alpha and 4 alpha are factors involved in interindividual variability in the expression of UGT1A6 and UGT1A9 but not UGT1A1, UGT1A3 and UGT1A4 mRNA in human livers.

UDP-glucuronosyltransferases (UGTs) catalyze phase-II biotransformation reaction of a variety of substances. Among the UGT1A isoforms, UGT1A1, UGT1A3, UGT1A4, UGT1A6 and UGT1A9 are predominantly expressed in the liver. Interindividual variability in expression of these isoforms would cause interindividual differences in drug response, toxicity and cancer susceptibility. In the present study, we investigated the interindividual variability in UGT1A mRNA expression and whether hepatocyte nuclear factor 1alpha (HNF1alpha) and HNF4alpha were factors responsible for their variability in human livers. The amounts of UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, HNF1alpha and HNF4alpha mRNA in 18 human livers were measured by quantitative real-time polymerase chain reaction. The largest and smallest interindividual differences in expression levels were observed in UGT1A1 (8.6-fold) and UGT1A4 (2.5-fold) mRNA, respectively. The amounts of HNF1alpha and HNF4alpha mRNA were strongly correlated with the amount of UGT1A9 mRNA and moderately correlated with that of UGT1A6 mRNA, whereas no significant correlation was found with the amounts of UGT1A1, UGT1A3 and UGT1A4 mRNA. Our results suggest that HNF1alpha and HNF4alpha are the factors involved in the interindividual variability of UGT1A6 and UGT1A9 mRNA expression. Further studies of other transcription factors are needed to clarify the factor(s) determining the interindividual variations in UGT1A1, UGT1A3 and UGT1A4 mRNA expression.

Carbonic anhydrase inhibitors: DNA cloning and inhibition studies of the alpha-carbonic anhydrase from Helicobacter pylori, a new target for developing sulfonamide and sulfamate gastric drugs.

We have cloned and sequenced Helicobacter pylori alpha-class carbonic anhydrase (hpCA) from patients with different gastric mucosal lesions, including gastritis (n=15), ulcer (n=6), and cancer (n=16). Although several polymorphisms were newly identified such as 12Ala, 13Thr, 16Ile, and 168Phe, there was no significant relevance of any polymorphism with gastric mucosal lesion types. A library of sulfonamides/sulfamates has been investigated for the inhibition of hpCA, whereas new derivatives have been obtained by attaching 4-tert-butyl-phenylcarboxamido/sulfonamido tails to benzenesulfonamide/1,3,4-thiadiazole-2-sulfonamide scaffolds. All types of activity for inhibition of hpCA have been detected. Dorzolamide and simple 4-substituted benzenesulfonamides were weak inhibitors (KI 873-4360 nM). Sulfanilamide, orthanilamide, some of their derivatives, and indisulam showed better activity (KI 413-640 nM), whereas most of the clinically used inhibitors, such as methazolamide, ethoxzolamide, dichlorophenamide, brinzolamide, topiramate, zonisamide, etc., acted as medium-potency inhibitors (KI 105-378 nM). Some potent hpCA inhibitors were detected too (KI 12-84 nM) among acetazolamide, 4-amino-6-chloro-1,3-benzenedisulfonamide and some newly designed compounds incorporating lipophilic tails. Some of the newly prepared derivatives had selectivity ratios for inhibiting hpCA over hCA II in the range of 1.25-3.48, showing thus some selectivity for inhibiting the bacterial enzyme. Since hpCA is essential for the survival of the pathogen in acid, it might be used as a new pharmacologic tool in the management of drug-resistant H. pylori.

Interaction of Peptide Transporter 1 With D-Glucose and L-Glutamic Acid; Possible Involvement of Taste Receptors.

We investigated the influence of sweet and umami (savory) tastants on the intestinal absorption of cephalexin (CEX), a substrate of peptide transporter 1 (PEPT1, SLC15A1) in rats. After oral administration of glucose or mannitol to rats, CEX was administered together with a second dose of glucose or mannitol. Western blot analysis indicated that expression of PEPT1 in rat jejunum membrane was decreased by glucose, compared to mannitol. Furthermore, the maximum plasma concentration (Cmax) of orally administered CEX was reduced by glucose compared to mannitol. The effect of glucose was diminished by nifedipine, a L-type Ca(2+) channel blocker. We also found that Cmax of orally administered CEX was reduced by treatment with L-glutamic acid, compared to D-glutamic acid. Thus, excessive intake of glucose and L-glutamic acid may impair oral absorption of PEPT1 substrates.

Overexpression of carbonic anhydrase-related protein XI promotes proliferation and invasion of gastrointestinal stromal tumors.

Three isoforms of carbonic anhydrase-related protein (CA-RP) are evolutionally well conserved among the CA gene family but lack classical CA activity. Although the biological function of CA-RPs is unknown, overexpression of CA-RP VIII has been reported in certain tumor types. Based on the finding that CA-RPs are commonly expressed in the neuronal cells, we investigated expression of all three CA-RPs in gastrointestinal stromal tumor (GIST). In contrast to no detectable signal of any of the three CA-RPs in intestinal cells of Cajal, immunohistochemical analysis showed distinct cytoplasmic expressions of CA-RPs VIII and XI in 13 (59%) and 20 (91%) of 22 GIST tissue specimens, respectively. The positive signals for both CA-RPs VIII and XI were more intense in the periphery than in the central part of GISTs, whereas no significant signal for CA-RP X expression was observed in any of the GISTs. These expression patterns of CA-RPs were consistently observed by reverse transcription-polymerase chain reaction-Southern blot and immunocytochemistry in the cultured GIST cell line GIST-T1. Ectopic expression of CA-RP XI in GIST-T1 cells induced cell proliferation and invasion in vitro. These findings indicate that CA-RP XI plays a role in the development of GIST.

Multiple Linear Regression Analysis Indicates Association of P-Glycoprotein Substrate or Inhibitor Character with Bitterness Intensity, Measured with a Sensor.

P-glycoprotein (P-gp) regulates absorption of many drugs in the gastrointestinal tract and their accumulation in tumor tissues, but the basis of substrate recognition by P-gp remains unclear. Bitter-tasting phenylthiocarbamide, which stimulates taste receptor 2 member 38 (T2R38), increases P-gp activity and is a substrate of P-gp. This led us to hypothesize that bitterness intensity might be a predictor of P-gp-inhibitor/substrate status. Here, we measured the bitterness intensity of a panel of P-gp substrates and nonsubstrates with various taste sensors, and used multiple linear regression analysis to examine the relationship between P-gp-inhibitor/substrate status and various physical properties, including intensity of bitter taste measured with the taste sensor. We calculated the first principal component analysis score (PC1) as the representative value of bitterness, as all taste sensor's outputs shared significant correlation. The P-gp substrates showed remarkably greater mean bitterness intensity than non-P-gp substrates. We found that Km value of P-gp substrates were correlated with molecular weight, log P, and PC1 value, and the coefficient of determination (R(2) ) of the linear regression equation was 0.63. This relationship might be useful as an aid to predict P-gp substrate status at an early stage of drug discovery.

A novel variant allele of OATP-C (SLCO1B1) found in a Japanese patient with pravastatin-induced myopathy.

We have recently found that the frequency of OATP-C*15 is significantly higher in patients who experienced myopathy after receiving pravastatin or atorvastatin than in patients without myopathy. However, there were two patients who experienced pravastatin-induced myopathy despite the fact that they did not possess OATP-C*15 or other known mutations of OATP-C that have been reported to decrease the function of OATP-C. In this study, we sequenced all of the exons and exon-intron junctions of OATP-C of the two patients and found a novel mutation in exon 12 of OATP-C in one of the patients. In this mutation (1628T>G), there is a substitution of Leu to Trp at position 543 in transmembrane-spanning domain 10 of OATP-C. However, the frequency of this mutation in the Japanese population appears to be very low (<1%).