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After lung transplantation, itraconazole (ITCZ) is used as a prophylaxis for aspergillosis. ITCZ is a weak base with high lipophilicity, and the dissolution and absorption of ITCZ tablets and capsules are pH dependent. Therefore, ITCZ may not achieve sufficient serum concentrations in patients with higher gastric pH because of its poor bioavailability. We report a case of a woman in fifties with post-COVID-19 respiratory failure who successfully underwent lung transplantation, followed by improved bioavailability of ITCZ tablets when given with acidic lemon beverages. The patient was initially administered ITCZ oral solution; this was discontinued because of its unpleasant taste, nausea, and vomiting. The ITCZ oral solution was replaced with ITCZ tablets 78 days after transplantation; however, serum concentrations of ITCZ and hydroxy-ITCZ were below the detection limit (100 ng/mL). We co-administered ITCZ tablets with commercially available lemon beverages. Subsequently, serum concentrations of ITCZ and hydroxy-ITCZ increased to 341 and 673 ng/mL, respectively, on the 125th day after transplantation. Infection with fungi, including Aspergillus spp., was not observed in this case. The patient had no adverse events such as gastric ulcer or hyperglycemia. These results suggest that the co-administration of lemon beverages and ITCZ tablets may help achieve better absorption of ITCZ in patients taking acid suppressants.

The changes in the structure and composition of silicon (Si) nanoparticles supported on a multiwall carbon nanotube (MWCNT) during Joule heating of the MWCNT were studied by in situ high-resolution transmission electron microscopy. The Si nanoparticles reacted with the outer layers of the MWCNT to form silicon carbide (SiC) nanoparticles with increasing temperature. At temperatures of up to approximately 1900 K, silicon atoms were entirely sublimated from the SiC nanoparticles, and the remaining carbon atoms formed hollow carbon nanocapsules consisting of multilayered graphene shells on the MWCNT.

ABCB4 is necessary for the secretion of phospholipids from hepatocytes into bile and for the protection of cell membranes against bile salts. Lipid rafts are plasma membrane microdomains containing high contents of cholesterol and sphingolipids, which are separated by Triton X-100 extraction or OptiPrep gradient centrifugation. In this study, we investigated the relationship between the function of ABCB4 and lipid rafts using mouse canalicular membranes and HEK293 cells stably expressing ABCB4. ABCB4 and ABCB1 were mainly distributed in nonraft membranes. The expression of ABCB4, but not ABCB1, led to significant increases in the phosphatidylcholine (PC), phosphatidylethanolamine (PE), and sphingomyelin (SM) contents in nonraft membranes and further enrichment of SM and cholesterol in raft membranes. The ABCB4-mediated efflux of PC, PE, and SM was significantly stimulated by taurocholate, while the efflux of PE and SM was much less than that of PC. This ABCB4-mediated efflux was completely abolished by BODIPY-verapamil, which hardly partitioned into raft membranes. In addition, ABCB1 and ABCB4 mediated the efflux of rhodamine 123 and rhodamine 6G from nonraft membranes, which was not affected by taurocholate. We conclude that ABCB4 located in nonrafts, but not in rafts, is predominantly involved in the efflux of phospholipids and other substrates.

Background: Erlotinib is orally active and selectively inhibits the tyrosine kinase activity of the epidermal growth factor receptor. The pleural space penetration and exposure of erlotinib is poorly understood. Thus, we investigated the pharmacokinetics (PK) of erlotinib and its active metabolite OSI-420 in non–small-cell lung cancer (NSCLC) of malignant pleural effusion (MPE). Patients and Methods: We analyzed the PK of erlotinib and OSI-420 on days 1 and 8 after beginning erlotinib therapy in 9 patients with MPE. Their concentrations were determined by high-performance liquid chromatography with ultraviolet detection. Blood samples were obtained five times per day: before administration, and 2, 4, 8, and 24 hours after administration. Pleural effusions were obtained once per day, 2 hours after administration on day 1, and before administration on day 8. The exceptions were cases 2 and 4, which had pleural effusions obtained just before drug administration, and 2, 4, 8, and 24 hours after administration. Results: The mean percentage of penetration from plasma to pleural effusion for erlotinib was 18% on day 1 and 112% on day 8, while these values for OSI-420 were 9.5% on day 1 and 131% on day 8. The area under the drug concentration-time curve of pleural fluid for erlotinib was 28,406 ng-hr/mL for case 2 and 45,906 ng-hr/mL for case 4. Conclusions: There seems to be a significant accumulation of both erlotinib and OSI-420 in MPE with repeated dosing. Although larger studies will be necessary to determine the true impact of erlotinib MPE accumulation on plasma PK and safety, erlotinib can be administered safely to patients with MPE with respect to efficacy and side effects.

Introduction Although erlotinib, an orally active and selective tyrosine kinase inhibitor of epidermal growth factor receptor, is mainly metabolized in the liver, its effectiveness and safety for patients with chronic renal failure (CRF) undergoing hemodialysis (HD) has not been reported. Thus, we investigated the pharmacokinetics (PK) of erlotinib and its active metabolite OSI-420 in such patients with nonsmall cell lung cancer (NSCLC). Method We administered 150 mg erlotinib daily to three patients with NSCLC and CRF undergoing HD (HD group) and five patients with NSCLC and normal organ function (control group) and analyzed the PK of erlotinib and OSI-420. In the HD group, PK analyses were performed on day 1 (off HD), day 8 (off HD), and day 9 (on HD) after starting administration of erlotinib, and in the control group, they were performed on day 1 and day 8. Results In the HD group, there were little differences in the PK data between day 8 and day 9. The PK data on day 1 and day 8 of the HD group were also similar to those of the control group. There were no serious adverse events in any cases, and one of the HD patients achieved partial response. Conclusion Erlotinib was hardly affected by renal function and HD, which confirms the effectiveness and safety of erlotinib treatment in patients with NSCLC and CRF undergoing HD. Erlotinib can become one treatment option for such patients.

Vectorial secretion of cationic compounds across tubular epithelial cells is an important function of the kidney. This uni-directed transport is mediated by two cooperative functions, which are membrane potential-dependent organic cation transporters at the basolateral membranes and H+/organic cation antiporters at the brush-border membranes. More than 10 years ago, the basolateral organic cation transporters (OCT1-3/SLC22A1-3) were isolated, and molecular understandings for the basolateral entry of cationic drugs have been greatly advanced. However, the molecular nature of H+/organic cation antiport systems remains unclear. Recently, mammalian orthologues of the multidrug and toxin extrusion (MATE) family of bacteria have been isolated and clarified to function as H+/organic cation antiporters. In this commentary, the molecular characteristics and pharmacokinetic roles of mammalian MATEs are critically overviewed focusing on the renal secretion of cationic drugs.

Intestinal absorption and renal secretion of ionic drugs are controlled by a number of drug transporters expressed at the brush-border and basolateral membranes of epithelial cells. Over the last several years, considerable progress has been made regarding the molecular identification and functional characterization of drug transporters. Under some physiological and pathophysiological conditions, the expression and transport activity of drug transporters are changed, affecting the pharmacokinetics of substrate drugs. The regulation of transport activity in response to endogenous and exogenous signals can occur at various levels such as transcription, mRNA stability, translation, and posttranslational modification. Transcriptional regulation is of particular interest, because changes in transport activity are dynamically regulated by increases or decreases in levels of mRNA expression. The tissue-specific expression of drug transporters is also under transcriptional control, and recent studies using clinical samples from human tissues have revealed the expression profiles of drug transporters in the human body. The purpose of this research updates is to review the recent progress in the study of the gene expression and regulation of intestinal and renal drug transporters.

The proton-coupled peptide transporter PEPT2 ( SLC15A2 ) mediates the high-affinity low-capacity transport of small peptides as well as various oral peptide-like drugs in the kidney. In contrast to its well-characterized transport properties, there is less information available on its regulatory mechanism, although the interaction of PEPT2 to the PDZ (PSD-95, DglA, and ZO-1)-domain protein PDZK1 has been preliminarily reported. To examine whether PDZK1 is a physiological partner of PEPT2 in kidneys, we started from a yeast two-hybrid screen of a human kidney cDNA library with the C-terminus of PEPT2 (PEPT2 C-terminus (PEPT2-CT)) as bait. We could identify PDZK1 as one of the positive clones. This interaction requires the PDZ motif of PEPT2-CT detected by a yeast two-hybrid assay, in vitro binding assay and co-immunoprecipitation. The binding affinities of second and third PDZ domains of PDZK1 to PEPT2-CT were measured by surface plasmon resonance. Co-immunoprecipitation using human kidney membrane fraction and localization of PEPT2 in renal apical proximal tubules revealed the physiological meaning of this interaction in kidneys. Furthermore, we clarified the mechanism of enhanced glycylsarcosine (Gly-Sar) transport activity in PEPT2-expressing HEK293 cells after the PDZK1 coexpression. This augmentation was accompanied by a significant increase in the V max of Gly-Sar transport via PEPT2 and it was also associated with the increased surface expression level of PEPT2. These results indicate that the PEPT2–PDZK1 interaction thus plays a physiologically important role in both oligopeptide handling as well as peptide-like drug transport in the human kidney.

H(+)/peptide cotransporter 1 (PEPT1, SLC15A1) localized at the brush-border membranes of intestinal epithelial cells plays important roles in the intestinal absorption of small peptides and a variety of peptidemimetic drugs. We previously demonstrated that transcription factor Sp1 functions as a basal transcriptional regulator of human PEPT1. However, the factor responsible for the intestine-specific expression of PEPT1 remains unknown. In the present study, we investigated the effect of the intestinal transcription factors on the transcription of the PEPT1 gene and found that only Cdx2 markedly trans-activated the PEPT1 promoter. However, the promoter region responsible for this effect lacked a typical Cdx2-binding sequence, but instead, possessed some Sp1-binding sites. In vitro experiments using Caco-2 cells showed that (1) mutation of the Sp1-binding site diminished the effect of Cdx2, (2) co-expression of Cdx2 and Sp1 synergistically trans-activated the PEPT1 promoter and (3) Sp1 protein was immunoprecipitated with Cdx2 protein. These results raise the possibility that Cdx2 modulates the PEPT1 promoter by interaction with Sp1. The significance of Cdx2 in vivo for PEPT1 regulation was shown by the determination of mRNA levels of Cdx2 and PEPT1 in human tissue. In gastric samples, some with intestinal metaplasia, the levels of PEPT1 and Cdx2 mRNA were highly correlated. Taken together, the present study suggests that Cdx2 plays a key role in the transcriptional regulation of the intestine-specific expression of PEPT1, possibly through interaction with Sp1.

Various transporters such as H+/peptide cotransporter PEPT1 are expressed in the intestine, and play important physiological and pharmacological roles in the body. Present study was performed to examine the expression profile of 20 kinds of transporters (PEPT1 and 2, P-glycoprotein, amino acid transporters and organic ion transporters) along the human digestive tract, especially focusing on PEPT1. Using normal mucosal specimens, real-time polymerase chain reactions were carried out. Immunoblot analyses were also performed for PEPT1 expression. PEPT1 mRNA was highly expressed in the small intestine (duodenum>jejunum>ileum) compared to other tissues, and some patients showed a significant level of expression in the stomach. The expressional pattern of PEPT1 in the stomach and histological diagnosis indicated that gastric PEPT1 originated from the intestinal metaplasia. The amino acid transporters showed unique mRNA expression levels and distributions in the digestive tract. For example, the expression levels of B(0)AT1, a Na+-dependent and chloride-independent neutral amino acid transporter, were increased from the duodenum to ileum, which pattern is completely inverted to that for PEPT1. There is little expression of organic ion transporters except for organic cation/carnitine transporter OCTN2. In conclusion, PEPT1 was abundantly expressed in the small intestine, and the reciprocal expression of PEPT1 and B(0)AT1 may serve for the efficient absorption of protein digestive products.

We evaluated the functional consequences of genetic variations in human H + /peptide cotransporter 2 (hPEPT2, SLC15A2 ) resulting in the amino acid changes Arg57His (R57H) and Pro409Ser (P409S). The transport activity of variant R57H was completely abolished, whereas that of variant P409S was comparable with that of wild-type hPEPT2 at pH 5.0–8.0. R57H variant protein was detected in the crude membranes of transiently expressed HEK293 cells by Western blot analysis. The expression of the R57H variant at the plasma membrane was confirmed by indirect immunofluorescence in Xenopus oocytes, suggesting that the loss of transport function of hPEPT2 R57H was not due to a change in membrane protein expression. This is the first demonstration of a functional impairment of the SLC15A family induced by a single nucleotide polymorphism.

Strontium carbonate grown in silica gel showed a variety of complex morphologies including sheets and spirals associated with biogenetic products. The non-crystallographic architecture had a hierarchical structure consisting of nanoscale needle-like building blocks enveloped with a silicate sheath. By monitoring the time-dependent growth, a spherical cluster of the fibrous crystals was transformed into the highly ordered morphologies with strange outgrowths in the progressive stages. The unusual morphologies were achieved with a reduction of the subunit size and restriction of the growth direction by selective adsorption of silicate anions on the specific crystal surfaces of the carbonate crystals.

Coral-like porous morphologies with nanoscale cellular framework of CaCO 3 crystals were produced through self-organized precipitation with silicate ions. Platy aragonite subunits in the porous structures were individually covered with silicate envelopes. Addition of seed crystals initiated preferential formation of the cellular aragonite. Spherical clusters of the cellular structures developed into coral-like morphologies with outgrowth of strange projections.

The novel oral hypoglycemic agent nateglinide (AY4166) is a nonsulfonylurea insulin secretagogue, and its pharmacokinetic features include rapid absorption and elimination. As nateglinide is a dipeptide-like drug, we investigated the interaction of nateglinide with peptide transporters PEPT1 and PEPT2, which mediate the absorption of various peptide-like drugs. Nateglinide exhibited a potent inhibitory effect on [ 14 C]glycylsarcosine uptake by the human colon adenocarcinoma cell line Caco-2 and rat PEPT-transfectants. Kinetic analysis revealed that these inhibitory effects were noncompetitive. Na + -coupled alanine or threonine uptake by Caco-2 cells was not inhibited by nateglinide, suggesting that the inhibitory effect of nateglinide on peptide transporters was not due to nonspecific interaction. There was little uptake of [ 14 C]nateglinide by peptide transporters. Various sulfonylureas, such as glibenclamide, also inhibited [ 14 C]glycylsarcosine uptake by rat PEPT-transfectants. In conclusion, nateglinide as well as sulfonylureas inhibit the transport activity of PEPT1 and PEPT2, although nateglinide itself is not transported by these transporters.

Peptide transporters mediate the H+-coupled uphill transport of oligopeptides and peptide-like drugs such as beta-lactam antibiotics in the intestinal and renal brush-border membranes. Two H+/peptide cotransporters, PEPT1 and PEPT2, have been cloned and functionally characterized. In this study, we examined the interaction of the dipeptides and beta-lactam antibiotics with the histidine residue of rat PEPT1 and PEPT2 transfected into the renal epithelial cell line LLC-PK1. Diethylpyrocarbonate (DEPC), which is a histidine residue modifier, abolished the glycylsarcosine uptake by both transfectants. The DEPC-induced inhibition of glycylsarcosine uptake via PEPT1 or PEPT2 was attenuated by an excess of dipeptide or aminocephalosporin. In contrast, anionic cephalosporins without an alpha-amino group and bestatin, which is an antineoplastic drug with a beta-amino group, did not attenuate the DEPC-induced inactivation of PEPT1 and PEPT2. The DEPC inactivation of PEPT1 was almost prevented by various charged dipeptides, which suggests that the inability of the drugs without an alpha-amino group to prevent the DEPC inactivation was not due to their ionic charge. These findings suggest that the alpha-amino group of beta-lactam antibiotics interacts with the histidine residue of PEPT1 and PEPT2 and may be involved in the mechanism of substrate recognition by the peptide transporters.

A cDNA encoding rat H+-coupled peptide transporter PEPT2 was isolated. The cDNA encoded a protein of 729 amino acids with 48% amino acid identity to the rat PEPT1. The mRNA expression of rat PEPT2 was predominant in the kidney. When expressed in Xenopus oocytes, rat PEPT2 stimulated the uptake of bestatin, a dipeptide-like drug.