1
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Wang X, Chen Y, Wang Y, Wang B, Zhang J, Jian X. Expression, Regulation, and Role of an Oligopeptide Transporter: PEPT1 in Tumors. Curr Med Chem 2022; 29:1596-1605. [PMID: 35546503 DOI: 10.2174/0929867328666210707170214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Revised: 04/04/2021] [Accepted: 04/21/2021] [Indexed: 11/22/2022]
Abstract
:
PEPT1 is a vital member of the proton-dependent oligopeptide transporters
family (POTs). Many studies have confirmed that PEPT1 plays a critical role in the absorption
of dipeptides, tripeptides, and pseudopeptides in the intestinal tract. In recent
years, several studies have found that PEPT1 is highly expressed in malignant tumor tissues
and cells. The abnormal expression of PEPT1 in tumors may be closely related to the
progress of tumors, and hence, could be considered as a potential molecular biomarker for
the diagnosis, treatment, and prognosis in malignant tumors. Furthermore, PEPT1 can be
used to mediate the targeted delivery of anti-tumor drugs. Herein, the expression, regulation,
and role of PEPT1 in tumors in recent years have been reviewed.
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Affiliation(s)
- Xi Wang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin Institute
of Digestive Disease, Tianjin 300052, China
- Tianjin Baodi Hospital/Baodi Clinical College of Tianjin
Medical University, Tianjin 300052, China
| | - Yiming Chen
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin Institute
of Digestive Disease, Tianjin 300052, China
| | - Yongjuan Wang
- Department of Gastroenterology and Hepatology, The Second
Affiliated Hospital of Hebei Medical University, Hebei, China
| | - Bangmao Wang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin Institute
of Digestive Disease, Tianjin 300052, China
| | - Jie Zhang
- Department of Gastroenterology and Hepatology, Tianjin Medical University General Hospital, Tianjin Institute
of Digestive Disease, Tianjin 300052, China
| | - Xu Jian
- Central Laboratory, Tianjin Medical University
General Hospital, Tianjin, 300052, China
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2
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Wen Y, Li R, Piao X, Lin G, He P. Different copper sources and levels affect growth performance, copper content, carcass characteristics, intestinal microorganism and metabolism of finishing pigs. ANIMAL NUTRITION (ZHONGGUO XU MU SHOU YI XUE HUI) 2022; 8:321-330. [PMID: 35024469 PMCID: PMC8718720 DOI: 10.1016/j.aninu.2021.10.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 08/24/2021] [Accepted: 10/19/2021] [Indexed: 02/08/2023]
Abstract
Copper (Cu) is an essential trace element in the production of swine. This study was conducted to investigate the effect of 3 different sources of Cu on growth performance, Cu metabolism, and intestinal microorganisms of finishing pigs, so as to estimate the bioavailability of the 3 sources for pigs. A total of 42 male finishing pigs (88.74 ± 5.74 kg) were randomly allocated to 7 treatments. The factors were 3 sources (CuSO4, Cu-glycine, Cu-proteinate) and 2 levels (5 and 20 mg/kg) of Cu, plus one negative control treatment (0 mg/kg added Cu level) for the entire 28-d experiment. The average daily gain (ADG) and feed to gain ratio (F:G) both increased when Cu was added. The Cu level in liver, bile, kidney, serum, lung, urine and feces rose (P < 0.001) with increasing dietary Cu level regardless of the source. Meanwhile, pigs receiving organic Cu (glycinate or proteinate) retained more Cu and excreted less Cu than those receiving inorganic Cu (CuSO4), which showed that organic forms were more bioavailable. At the transcriptional level, changes in the level and source of dietary Cu resulted in modulation of transporters. In the jejunal mucosa, import transporter high affinity copper uptake protein 1 (CTR1) and export transporter ATPase copper transporting alpha (ATP7A) in supplemental Cu treatments were down-regulated compared to the control. Also, peptide transporter 1 (PepT1) and lanine-serine-cysteine transporter, type-2 (ASCT2) were significantly (P < 0.01) up-regulated in 20 mg/kg Cu-proteinate and Cu-glycinate treatments, respectively. Microbial diversity was lowest in the 20 mg/kg CuSO4 treatment, and the ratio of Firmicutes to Bacteroidetes was higher in added Cu treatments, especially Cu-glycinate treatment. These results indicate that uptake of different Cu forms is facilitated by different transporters and transport mechanisms, and compared with inorganic Cu, organic Cu provides benefits to intestinal microflora and reduces Cu excretion.
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Affiliation(s)
- Yang Wen
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Runxian Li
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Xiangshu Piao
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
| | - Gang Lin
- Institute of Quality Standards and Testing Technology for Agricultural Products, Chinese Academy of Agricultural Science, Key Laboratory of Agrifood Safety and Quality, Ministry of Agriculture, Beijing 100081, China
| | - Pingli He
- State Key Laboratory of Animal Nutrition, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
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3
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Ota S, Sakuraba H, Hiraga H, Yoshida S, Satake M, Akemoto Y, Tanaka N, Watanabe R, Takato M, Murai Y, Ueno K, Niioka T, Hayakari M, Ishiguro Y, Fukuda S. Cyclosporine protects from intestinal epithelial injury by modulating butyrate uptake via upregulation of membrane monocarboxylate transporter 1 levels. Biochem Biophys Rep 2020; 24:100811. [PMID: 33102812 PMCID: PMC7578528 DOI: 10.1016/j.bbrep.2020.100811] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 08/25/2020] [Accepted: 08/27/2020] [Indexed: 01/22/2023] Open
Abstract
Background and aims A relationship between treatment outcomes and intestinal microbiota in patients with inflammatory bowel diseases has been demonstrated. Cyclosporine treatment leads to rapid improvement in severe ulcerative colitis. We hypothesized that the potent effects of cyclosporine would be exerted through relationships between intestinal epithelial cells (IECs) and the host microbiota. The present study was designed to elucidate the effects of cyclosporine on monocarboxylate transporter 1 (MCT1) regulation and butyrate uptake by IECs. Methods Colitis was induced in C57BL6 mice via the administration of 4% dextran sulfate sodium in drinking water, following which body weights, colon lengths, and histological scores were evaluated. To examine the role of butyrate in the protective effects of cyclosporine, MCT1 inhibitor and an antibiotic cocktail was administered and tributyrin (TB; a prodrug of butyrate) was supplemented; MCT1 protein expression and acetylated histone 3 (AcH3) signals in IECs, as well as the MCT1-membrane fraction of Caco-2 cells, were evaluated. To explore butyrate uptake, as s butyrate derivatives, 3-bromopyruvic acid (3-BrPA) and 1-pyrenebutyric acid were used. Results Treatment with cyclosporine inhibited body weight loss and colon length shortening. However, treatment with MCT1 inhibitor and the antibiotic cocktail negated the efficacy of cyclosporine, whereas TB supplementation restored its protective effect. Furthermore, cyclosporine upregulated MCT1 expression in the membrane and the AcH3 signal in IECs, while also inducing higher anti-inflammatory cytokine production compared to that in the vehicle-treated mice. The transcription level of MCT1 mRNA in IECs and Caco-2 cells did not increase with cyclosporine treatment; however, cyclosporine treatment increased membrane MCT1 expression in these cells and uptake of butyrate derivative. Conclusion Cyclosporine treatment modulates butyrate uptake via the post-transcriptional upregulation of membrane MCT1 levels in IECs. The protective effect of cyclosporine needs microbiota-derived butyrate. Cyclosporine increased the fraction of MCT1 at the cell membrane. Cyclosporine enhanced butyrate uptake and regulatory cytokine expression.
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Affiliation(s)
- Shinji Ota
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Hirotake Sakuraba
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Hiroto Hiraga
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Shukuko Yoshida
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan.,Shibata Irika Co.Ltd.Hirosaki, Japan
| | - Miwa Satake
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Yui Akemoto
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Nahoko Tanaka
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Rina Watanabe
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Maeda Takato
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Yasuhisa Murai
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Kayo Ueno
- Division of Pharmaceutical Science, Hirosaki University Hospital, Hirosaki, Japan
| | - Takenori Niioka
- Division of Pharmaceutical Science, Hirosaki University Hospital, Hirosaki, Japan
| | - Makoto Hayakari
- Division of Pharmaceutical Science, Hirosaki University Hospital, Hirosaki, Japan
| | - Yoh Ishiguro
- Division of Clinical Research, Hirosaki National Hospital, National Hospital Organization, Hirosaki, Japan
| | - Shinsaku Fukuda
- Department of Gastroenterology and Hematology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
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4
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Drozdzik M, Czekawy I, Oswald S, Drozdzik A. Intestinal drug transporters in pathological states: an overview. Pharmacol Rep 2020; 72:1173-1194. [PMID: 32715435 PMCID: PMC7550293 DOI: 10.1007/s43440-020-00139-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Revised: 07/14/2020] [Accepted: 07/14/2020] [Indexed: 02/07/2023]
Affiliation(s)
- Marek Drozdzik
- Department of Pharmacology, Pomeranian Medical University, Powstancow Wlkp 72, 70-111, Szczecin, Poland.
| | - Izabela Czekawy
- Department of Pharmacology, Pomeranian Medical University, Powstancow Wlkp 72, 70-111, Szczecin, Poland
| | - Stefan Oswald
- Department of Pharmacology, Medicine University Greifswald, Friedrich-Ludwig-Jahn-Straße 17, 17489, Greifswald, Germany.,Institute of Pharmacology and Toxicology, Rostock University Medical Center, 18051, Rostock, Germany
| | - Agnieszka Drozdzik
- Department of Integrated Dentistry, Pomeranian Medical University, Powstancow Wlkp 72, 70-111, Szczecin, Poland
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5
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Different Sources of Copper Effect on Intestinal Epithelial Cell: Toxicity, Oxidative Stress, and Metabolism. Metabolites 2019; 10:metabo10010011. [PMID: 31877957 PMCID: PMC7022486 DOI: 10.3390/metabo10010011] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Revised: 12/19/2019] [Accepted: 12/20/2019] [Indexed: 12/19/2022] Open
Abstract
Copper (Cu) is widely used in the swine industry to improve the growth performance of pigs. However, high doses of copper will induce cell damage and toxicity. The aim of this study was to evaluate toxicity, bioavailability, and effects on metabolic processes of varying copper sources using porcine intestinal epithelial cells (IPEC-J2) as a model. The IPEC-J2 were treated with two doses (30 and 120 μM) of CuSO4, Cu Glycine (Cu-Gly), and Cu proteinate (Cu-Pro) for 10 h, respectively. Cell damage and cellular copper metabolism were measured by the changes in cell viability, copper uptake, oxidative stress biomarkers, and gene/protein expression levels. The results showed that cell viability and ratio of reduced and oxidized glutathione (GSH/GSSG) decreased significantly in all treatment groups; intracellular copper content increased significantly in all treatment groups; total superoxide dismutase (SOD) activity increased significantly in the 120 μM exposed groups; SOD1 protein expression levels were significantly upregulated in 30 μM Cu-Pro, 120 μM Cu-Gly, and 120 μM Cu-Pro treatment groups; intracellular reactive oxygen species (ROS) generation and malondialdehyde (MDA) content increased significantly in 30 μM treatment groups and 120 μM CuSO4 treatment group. CTR1 and ATP7A gene expression were significantly downregulated in the 120 μM exposed groups. While upregulation of ATOX1 expression was observed in the presence of 120 μM Cu-Gly and Cu-Pro. ASCT2 gene expression was significantly upregulated after 120 μM Cu-Glycine and CuSO4 exposure, and PepT1 gene expression was significantly upregulated after Cu-Pro exposure. In addition, CTR1 protein expression level decreased after 120 μM CuSO4 and Cu-Gly exposure. PepT1 protein expression level was only upregulated after 120 μM Cu-Pro exposure. These findings indicated that extra copper supplementation can induce intestinal epithelial cell injury, and different forms of copper may have differing effects on cell metabolism.
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6
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Al Wakeel RA, Saad MF, Abdel Azeez A, Elkhiat F, Shukry M. Both experimental hypo- and hyper-thyroidism exacerbate the adverse effects of chronic heat stress in broilers. Br Poult Sci 2019; 60:330-339. [PMID: 30939896 DOI: 10.1080/00071668.2019.1602248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
1. The effects of hypo- and hyper-thyroidism in mitigating or exacerbating the negative changes of chronic heat stress (HS) in broilers were investigated.2. Three-week-old broilers were distributed into six groups (n = 13 per group). Three groups were housed at ambient room temperature: control group (CN), propylthiouracil-treated group (AN) and thyroxine-treated group (TN). The other three groups were exposed to HS at 33 ± 1°C for 2 weeks: control heat stress (CH), propylthiouracil + heat stress (AH) and thyroxine + HS (TH).3. Induced hypothyroidy significantly decreased cloacal temperature and body weight gain in the birds in both the normal and HS groups (AN, AH). Conversely, hyperthyroidy resulted in a significant elevation in cloacal temperature in the TN and TH groups and a significant decline in weight gain in the TH group. Hyperthyroidy exacerbated the HS-induced degenerative changes in jejunal mucosa and caused noticeable vascular changes. A significant increase in the expression levels of jejunal nutrient transporter genes was observed in the AH and TH groups. The hyperthyroidic state significantly upregulated the HSP70 expression level in the TH group and the reverse occurred with propylthiouracil (PTU) treatment in the AH group.4. PTU supplementation to chicks reared under HS significantly decreased the triiodothyronine level, antibody (Ab) titre, and increased the heterophil-lymphocyte ratio. Furthermore, it induced higher hepatic glutathione peroxidase (GSH-Px) activity in the AN and AH groups and decreased the malondialdehyde content (MDA) in the AN group. Hyperthyroidy significantly increased triiodothyronine concentration, H/L ratio and decreased Hb concentration and Ab titres in the TH group. Additionally, this status increased the MDA content and decreased the GSH-Px activities.5. In conclusion, manipulation of thyroid status is not a remedy to overcome the undesirable effects of HS in broilers.
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Affiliation(s)
- R A Al Wakeel
- Department of Physiology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt
| | - M F Saad
- Department of Physiology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt
| | - A Abdel Azeez
- Department of Physiology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt
| | - F Elkhiat
- Department of Poultry Diseases, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt
| | - M Shukry
- Department of Physiology, Faculty of Veterinary Medicine, Kafrelsheikh University, Kafrelsheikh, Egypt
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7
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Xue Y, Ma C, Hanna I, Pan G. Intestinal Transporter-Associated Drug Absorption and Toxicity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1141:361-405. [DOI: 10.1007/978-981-13-7647-4_8] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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8
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Alghamdi OA, King N, Andronicos NM, Jones GL, Chami B, Witting PK, Moens PDJ. Molecular changes to the rat renal cotransporters PEPT1 and PEPT2 due to ageing. Mol Cell Biochem 2018; 452:71-82. [DOI: 10.1007/s11010-018-3413-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/13/2018] [Indexed: 12/14/2022]
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9
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Beale JH, Parker JL, Samsudin F, Barrett AL, Senan A, Bird LE, Scott D, Owens RJ, Sansom MSP, Tucker SJ, Meredith D, Fowler PW, Newstead S. Crystal Structures of the Extracellular Domain from PepT1 and PepT2 Provide Novel Insights into Mammalian Peptide Transport. Structure 2015; 23:1889-1899. [PMID: 26320580 PMCID: PMC4597091 DOI: 10.1016/j.str.2015.07.016] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Revised: 07/22/2015] [Accepted: 07/28/2015] [Indexed: 12/11/2022]
Abstract
Mammals obtain nitrogen via the uptake of di- and tri-peptides in the gastrointestinal tract through the action of PepT1 and PepT2, which are members of the POT family of proton-coupled oligopeptide transporters. PepT1 and PepT2 also play an important role in drug transport in the human body. Recent crystal structures of bacterial homologs revealed a conserved peptide-binding site and mechanism of transport. However, a key structural difference exists between bacterial and mammalian homologs with only the latter containing a large extracellular domain, the function of which is currently unknown. Here, we present the crystal structure of the extracellular domain from both PepT1 and PepT2 that reveal two immunoglobulin-like folds connected in tandem, providing structural insight into mammalian peptide transport. Functional and biophysical studies demonstrate that these domains interact with the intestinal protease trypsin, suggesting a role in clustering proteolytic activity to the site of peptide transport in eukaryotic cells. Crystal structure of the extracellular domains of PepT1 and PepT2 Modular architecture for a mammalian MFS transporter Extracellular domains contain immunoglobulin-like fold and interact with trypsin
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Affiliation(s)
- John H Beale
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Joanne L Parker
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Firdaus Samsudin
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Anne L Barrett
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK
| | - Anish Senan
- Department of Biological Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Louise E Bird
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; OPPF-UK, Research Complex at Harwell, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, UK
| | - David Scott
- Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0FA, UK; ISIS Spallation Neutron and Muon Source, Rutherford Appleton Laboratory, Oxfordshire OX11 0FA, UK; School of Biosciences, School of Biosciences, Sutton Bonington Campus, Leicestershire LE12 5RD, UK
| | - Raymond J Owens
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; OPPF-UK, Research Complex at Harwell, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, UK
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Membrane Transport, University of Oxford OX1 3PU, UK
| | - Stephen J Tucker
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK; OXION Initiative in Ion Channels and Membrane Transport, University of Oxford OX1 3PU, UK
| | - David Meredith
- Department of Biological and Medical Sciences, Faculty of Health and Life Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Philip W Fowler
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK
| | - Simon Newstead
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK; OXION Initiative in Ion Channels and Membrane Transport, University of Oxford OX1 3PU, UK.
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10
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Coon SD, Rajendran VM, Schwartz JH, Singh SK. Glucose-dependent insulinotropic polypeptide-mediated signaling pathways enhance apical PepT1 expression in intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 2015; 308:G56-62. [PMID: 25377315 PMCID: PMC4281688 DOI: 10.1152/ajpgi.00168.2014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have shown recently that glucose-dependent insulinotropic polypeptide (GIP), but not glucagon-like peptide 1 (GLP-1) augments H(+) peptide cotransporter (PepT1)-mediated peptide absorption in murine jejunum. While we observed that inhibiting cAMP production decreased this augmentation of PepT1 activity by GIP, it was unclear whether PKA and/or other regulators of cAMP signaling pathway(s) were involved. This study utilized tritiated glycyl-sarcosine [(3)H-glycyl-sarcosine (Gly-Sar), a relatively nonhydrolyzable dipeptide] uptake to measure PepT1 activity in CDX2-transfected IEC-6 (IEC-6/CDX2) cells, an absorptive intestinal epithelial cell model. Similar to our earlier observations with mouse jejunum, GIP but not GLP-1 augmented Gly-Sar uptake (control vs. +GIP: 154 ± 22 vs. 454 ± 39 pmol/mg protein; P < 0.001) in IEC-6/CDX2 cells. Rp-cAMP (a PKA inhibitor) and wortmannin [phosophoinositide-3-kinase (PI3K) inhibitor] pretreatment completely blocked, whereas neither calphostin C (a potent PKC inhibitor) nor BAPTA (an intracellular Ca(2+) chelator) pretreatment affected the GIP-augmented Gly-Sar uptake in IEC-6/CDX2 cells. The downstream metabolites Epac (control vs. Epac agonist: 287 ± 22 vs. 711 ± 80 pmol/mg protein) and AKT (control vs. AKT inhibitor: 720 ± 50 vs. 75 ± 19 pmol/mg protein) were shown to be involved in GIP-augmented PepT1 activity as well. Western blot analyses revealed that both GIP and Epac agonist pretreatment enhance the PepT1 expression on the apical membranes, which is completely blocked by wortmannin in IEC-6/CDX2 cells. These observations demonstrate that both cAMP and PI3K signaling pathways augment GIP-induced peptide uptake through Epac and AKT-mediated pathways in intestinal epithelial cells, respectively. In addition, these observations also indicate that both Epac and AKT-mediated signaling pathways increase apical membrane expression of PepT1 in intestinal absorptive epithelial cells.
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Affiliation(s)
- Steven D. Coon
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Department of Medicine, Boston Veterans Affairs Healthcare System, Boston, Massachusetts; ,3Department of Medicine, Boston University Clinical & Translational Science Institute, Boston, Massachusetts; and
| | - Vazhaikkurichi M. Rajendran
- 4Department of Biochemistry and Molecular Biology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - John H. Schwartz
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts;
| | - Satish K. Singh
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Department of Medicine, Boston Veterans Affairs Healthcare System, Boston, Massachusetts;
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11
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Okamura A, Koyanagi S, Dilxiat A, Kusunose N, Chen JJ, Matsunaga N, Shibata S, Ohdo S. Bile acid-regulated peroxisome proliferator-activated receptor-α (PPARα) activity underlies circadian expression of intestinal peptide absorption transporter PepT1/Slc15a1. J Biol Chem 2014; 289:25296-305. [PMID: 25016014 DOI: 10.1074/jbc.m114.577023] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Digested proteins are mainly absorbed as small peptides composed of two or three amino acids. The intestinal absorption of small peptides is mediated via only one transport system: the proton-coupled peptide transporter-1 (PepT1) encoded from the soluble carrier protein Slc15a1. In mammals, intestinal expression of PepT1/Slc15a1 oscillates during the daily feeding cycle. Although the oscillation in the intestinal expression of PepT1/Slc15a1 is suggested to be controlled by molecular components of circadian clock, we demonstrated here that bile acids regulated the oscillation of PepT1/Slc15a1 expression through modulating the activity of peroxisome proliferator-activated receptor α (PPARα). Nocturnally active mice mainly consumed their food during the dark phase. PPARα activated the intestinal expression of Slc15a1 mRNA during the light period, and protein levels of PepT1 peaked before the start of the dark phase. After food intake, bile acids accumulated in intestinal epithelial cells. Intestinal accumulated bile acids interfered with recruitment of co-transcriptional activator CREB-binding protein/p300 on the promoter region of Slc15a1 gene, thereby suppressing PPARα-mediated transactivation of Slc15a1. The time-dependent suppression of PPARα-mediated transactivation by bile acids caused an oscillation in the intestinal expression of PepT1/Slc15a1 during the daily feeding cycle that led to circadian changes in the intestinal absorption of small peptides. These findings suggest a molecular clock-independent mechanism by which bile acid-regulated PPARα activity governs the circadian expression of intestinal peptide transporter.
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Affiliation(s)
- Ayako Okamura
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
| | - Satoru Koyanagi
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
| | - Adila Dilxiat
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
| | - Naoki Kusunose
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
| | - Jia Jun Chen
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
| | - Naoya Matsunaga
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
| | - Shigenobu Shibata
- Laboratory of Physiology and Pharmacology, School of Advanced Science and Engineering, Waseda University, Tokyo 162-8480, Japan
| | - Shigehiro Ohdo
- From the Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kyushu University, Fukuoka 812-8582, Japan and
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12
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Wang Y, Sun D, Song F, Hu Y, Smith DE, Jiang H. Expression and regulation of the proton-coupled oligopeptide transporter PhT2 by LPS in macrophages and mouse spleen. Mol Pharm 2014; 11:1880-8. [PMID: 24754256 PMCID: PMC4051248 DOI: 10.1021/mp500014r] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Membrane transporter PhT2 (SLC15A3), which belongs to the proton-coupled oligopeptide transporter family, mediates the transport of di/tripeptides and histidine utilizing an inwardly directed proton gradient and negative membrane potential. The aim of this study was to elucidate the molecular expression of PhT2 in macrophages and mouse tissues and to explore the regulation of PhT2 by lipopolysaccharide (LPS). The results showed relatively high expression of PhT2 in J774A.1 and THP-1 macrophage cells, mouse spleen, and lung. Using an LPS-induced inflammatory cell model, we found that hPhT2 mRNA expression was up-regulated in THP-1 cells and that the up-regulation was suppressed by pyrrolidine dithiocarbamate, a specific inhibitor of NF-κB. Similar results were observed in mouse spleen during LPS-induced acute inflammation. Using dual-labeling immunofluorescence and confocal laser scanning microscopy, we confirmed that mPhT2 was colocalizing with lysosome-associated membrane protein 1 in transfected HEK293 cells. These results suggested that PhT2, a lysosomal membrane transporter, was up-regulated by LPS via the NF-κB signaling pathway.
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Affiliation(s)
- Yuqing Wang
- Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University , Hangzhou, Zhejiang 310058, P. R. China
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13
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Qandeel HG, Alonso F, Hernandez DJ, Madhavan S, Duenes JA, Zheng Y, Sarr MG. Peptide absorption after massive proximal small bowel resection: mechanisms of ileal adaptation. J Gastrointest Surg 2011; 15:1537-47. [PMID: 21647767 PMCID: PMC3160514 DOI: 10.1007/s11605-011-1581-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Accepted: 05/25/2011] [Indexed: 02/07/2023]
Abstract
BACKGROUND Protein absorption occurs as di- and tri-peptides via H(+)/peptide co-transporter-1 (PepT1). AIM The aim of this study is to identify mechanisms of ileal adaptation after massive proximal enterectomy. HYPOTHESIS Ileal adaptation in uptake of peptides is mediated through upregulation of PepT1 gene expression. STUDY DESIGN Rats underwent 70% jejunoileal resection. Total mucosal cellular levels of messenger RNA (mRNA) and protein and transporter-mediated uptake per centimeter of the di-peptide glycyl-sarcosine (Gly-Sar) were compared in remnant ileum 1 and 4 weeks postoperatively to control and to 1-week sham laparotomy rats. Histomorphology, food consumption, and weights of rats were monitored. RESULTS After 70% resection, although mRNA per cell for PepT1 decreased at 1 week (p = 0.002), expression of mRNA at 4 weeks and protein at 1 and 4 weeks in remnant ileum were unchanged (p > 0.1). Ileal Gly-Sar uptake (V (max)-nanomoles per centimeter per minute, i.e., number of transporters per centimeter) increased at 1 and 4 weeks compared to control and 1-week sham (p < 0.05 each); K (m) (i.e., transporter function) was unchanged. Villous heights (millimeters) in remnant ileum increased at 1- and 4-week time points over controls (0.45 and 0.57 vs 0.21, resp; p < 0.001). CONCLUSIONS Ileal adaptation to proximal resection for peptide absorption occurs through cellular proliferation (hyperplasia) and not through cellular upregulation of PepT1 mRNA or protein per enterocyte.
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14
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Scow JS, Madhavan S, Chaudhry RM, Zheng Y, Duenes JA, Sarr MG. Differentiating passive from transporter-mediated uptake by PepT1: a comparison and evaluation of four methods. J Surg Res 2011; 170:17-23. [PMID: 21529830 DOI: 10.1016/j.jss.2011.02.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2010] [Revised: 01/18/2011] [Accepted: 02/10/2011] [Indexed: 12/24/2022]
Abstract
BACKGROUND To quantify transmembrane transport of dipeptides by PepT1, passive uptake (non-PepT1 mediated) must be subtracted from total (measured) uptake. Three methods have been described to estimate passive uptake: perform experiments at cold temperatures, inhibit target dipeptide uptake with a greater concentration of a second dipeptide, or use modified Michaelis-Menten kinetics. We hypothesized that performing uptake experiments at pH 8.0 would estimate passive uptake accurately, because PepT1 requires a proton gradient. Our aim was to determine the most accurate method to estimate passive uptake. METHODS Caco-2 cells were incubated with various concentrations of glycyl-sarcosine (gly-sar) at pH 6.0 and at 37°C to measure total uptake. Passive uptake was estimated: (1) by incubating Caco-2 cells with varying concentrations of gly-sar at 4°C, (2) in the presence of 50 mM glycyl-leucine, (3) in solution at pH 8.0, or (4) using modified Michaelis-Menten kinetics. PepT1-mediated uptake was calculated by subtracting passive uptake from total uptake. K(m), V(max), and % gly-sar transported by PepT1 were calculated and compared. RESULTS K(m), V(max), and % gly-sar transported by PepT1 varied from 0.7 to 2.4 mM, 8.4 to 21.0 nmol/mg protein/10 min, and 69% to 87%, respectively. Uptakes calculated with cold, 50 mM gly-leu and using modified Michaelis-Menten kinetics were similar but differed significantly from uptake at pH 8.0 (P < 0.001). CONCLUSIONS Estimating passive uptake at pH 8.0 does not appear to be accurate. Measuring uptake at cold temperatures or in the presence of a greater concentration of a second dipeptide, and confirming results with modified Michaelis-Menten kinetics is recommended.
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Affiliation(s)
- Jeffrey S Scow
- Department of Surgery and GI Research Unit, Mayo Clinic, Rochester, Minnesota 55905, USA
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15
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Abdel-Rahman SM, Newland JG, Kearns GL. Pharmacologic considerations for oseltamivir disposition: focus on the neonate and young infant. Paediatr Drugs 2011; 13:19-31. [PMID: 21162598 DOI: 10.2165/11536950-000000000-00000] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Across much of the world, pandemic H1N1 infection has produced a significant healthcare crisis, reflected in significant morbidity and mortality. Statistics reveal that infection-associated deaths among individuals without pre-existing conditions (e.g. immunosuppression) are clustered in pregnant women and young infants. In developing countries where the availability of influenzae vaccine is limited, the only currently available pharmacologic counter-measure for H1N1 disease is oseltamivir, a neuraminidase inhibitor with excellent in vitro activity against the virus. This drug is available in oral solid and liquid formulations, has excellent peroral bioavailability in adults, and generally has a very favorable safety profile. Many observational studies indicate that oseltamivir treatment is associated with symptomatic improvement in pediatric patients with H1N1 infection and, therefore, is considered to represent a viable therapeutic option for use in children. However, the disposition of the ethyl ester prodrug and its active metabolite has not been well characterized in infants and children. Presently, data are available from only two published investigations and preliminary summary information from a recent presentation of an ongoing study. Given that recent in vitro data support the importance of a target exposure-response profile for the active metabolite of oseltamivir and that many processes known to modulate drug disposition have a developmental basis, understanding the potential impact of age on oseltamivir disposition becomes crucial in the development of age-appropriate dosing regimens for the drug. In this review, the impact of ontogeny on processes that are important in regulating the absorption, distribution, metabolism, and excretion of oseltamivir and its active metabolite are considered. Data from both animal and human investigations are presented in the context of defining how development might influence the dose-exposure relationship and, most importantly, the significant variability associated with it. In addition, the available pediatric pharmacokinetic data for oseltamivir and its active metabolite are summarized and current 'information gaps' deserving of future study are presented.
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Affiliation(s)
- Susan M Abdel-Rahman
- Division of Clinical Pharmacology and Medical Toxicology, The Childrens Mercy Hospitals and Clinics, Kansas City, Missouri 64108, USA.
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16
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The effect of peptide absorption on PepT1 gene expression and digestive system hormones in rainbow trout (Oncorhynchus mykiss). Comp Biochem Physiol A Mol Integr Physiol 2010; 155:107-14. [DOI: 10.1016/j.cbpa.2009.10.017] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2009] [Revised: 10/12/2009] [Accepted: 10/14/2009] [Indexed: 01/28/2023]
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17
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Rubio-Aliaga I, Daniel H. Peptide transporters and their roles in physiological processes and drug disposition. Xenobiotica 2008; 38:1022-42. [PMID: 18668438 DOI: 10.1080/00498250701875254] [Citation(s) in RCA: 158] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
1. The peptide transporters belong to the peptide transporter (PTR) family and serve as integral membrane proteins for the cellular uptake of di- and tripeptides in the organism. By their ability also to transport peptidomimetics and other substrates with therapeutic activities or precursors of pharmacologically active agents, they are of considerable importance in pharmacology. 2. PEPT1 is the low-affinity, high-capacity transporter and is mainly expressed in the small intestine, whereas PEPT2 is the high-affinity, low-capacity transporter and has a broader distribution in the organism. 3. Targeted mouse models have revealed PEPT2 to be the dominant transporter for the reabsorption of di- and tripeptides and its pharmacological substrates in the organism, and for the removal of these substrates from the cerebrospinal fluid. Moreover, the peptide transporters undergo physiological and pharmacological regulation and, of great interest, are present in disease states where PEPT1 exhibits ectopic expression in colonic inflammation. 4. The paper reviews the structural characteristics of the peptide transporters, the structural requirements for substrates, the distribution of the peptide transporters in the organism, and finally their regulation in the organism in healthy and pathological situations.
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Affiliation(s)
- I Rubio-Aliaga
- Molecular Nutrition Unit, Technical University of Munich, Freising-Weihenstephan, Germany
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Hironaka T, Itokawa S, Ogawara KI, Higaki K, Kimura T. Quantitative evaluation of PEPT1 contribution to oral absorption of cephalexin in rats. Pharm Res 2008; 26:40-50. [PMID: 18784906 DOI: 10.1007/s11095-008-9703-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Accepted: 08/05/2008] [Indexed: 10/21/2022]
Abstract
PURPOSE PEPT1 mediates the intestinal absorption of many drugs, but its contribution to oral absorption of drugs is still controversial. The objective of this study is to quantitatively evaluate the contribution of PEPT1 to oral absorption of cephalexin, a typical substrate for PEPT1, in rats. MATERIALS AND METHODS The absorbability of cephalexin via PEPT1 or passive diffusion was assessed in five intestinal segments by utilizing glycyl-proline as a competitive inhibitor by in-situ closed loop method. Absorption kinetics of cephalexin after oral administration was predicted by GI-Transit-Absorption model. RESULTS Absorbability of cephalexin was segment-dependent, and concentration-dependent in all the segments except for the lower ileum. Intrinsic absorption rate constant via PEPT1 ranged from 0.64 to 4.07 h(-1). The absorption rate constants via passive diffusion ranged from 0.78 to 1.24 h(-1). Plasma concentration-time profile of cephalexin was successfully predicted and the substantial contribution of PEPT1 to the oral absorption was calculated to be from 46% to 60% of total absorption. Simulation study indicated that 83% bioavailability would be expected for cephalexin even though PEPT1 does not function. CONCLUSIONS PEPT1 substantially contributes to oral absorption of cephalexin, around a half of total absorption. However, the function of PEPT1 can be compensated by passive diffusion for cephalexin.
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Affiliation(s)
- Takanori Hironaka
- Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Okayama University, 1-1-1 Tsushima-naka, Okayama, 700-8530, Japan
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Saito H, Terada T, Shimakura J, Katsura T, Inui KI. Regulatory mechanism governing the diurnal rhythm of intestinal H+/peptide cotransporter 1 (PEPT1). Am J Physiol Gastrointest Liver Physiol 2008; 295:G395-402. [PMID: 18583459 DOI: 10.1152/ajpgi.90317.2008] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The intestinal H(+)/peptide cotransporter 1 (PEPT1) plays important roles as a nutrient and drug transporter. Previously, we reported that rat intestinal PEPT1 showed a diurnal rhythm and that this rhythm is closely related to the feeding schedule. Furthermore, we also demonstrated that transcription factors, Sp1, Cdx2, and peroxisome proliferator-activated receptor-alpha (PPAR-alpha) contribute to the basal, intestine-specific, and fasting-induced expression of PEPT1, respectively. In this study, to clarify the molecular mechanism governing the diurnal rhythm of PEPT1 expression, we compared expression profiles of these transcription factors under two kinds of feeding schedules. The intestinal Sp1 and Cdx2 did not show a circadian accumulation of mRNA or response to the daytime feeding regimen. Plasma free fatty acids, endogenous PPAR-alpha ligands, exhibited a robust circadian fluctuation in phase with that of PEPT1. However, subsequent experiments using PPAR-alpha-null mice revealed the absence of any association between the circadian rhythm of PEPT1 and PPAR-alpha. We then focused on the clock genes (Clock, Bmal1, Per1-2, and Cry1) and clock-controlled gene, albumin D site-binding protein (DBP). A robust and coordinated circadian expression of the clock genes was observed, and daytime feeding entirely inverted the phase except for Clock. The expression of DBP was in phase with that of PEPT1 in both groups. Electrophoretic mobility shift assays and reporter assays revealed that DBP has the ability to bind the DBP binding site located in the distal promoter region of the rat PEPT1 gene and induce the transcriptional activity. These findings indicate that DBP plays pivotal roles in the circadian oscillation of PEPT1.
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Affiliation(s)
- Hirofumi Saito
- Dept. of Pharmacy, Kyoto Univ. Hospital, Sakyo-ku, Kyoto 606-8507, Japan
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20
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Gilbert ER, Wong EA, Webb KE. Board-invited review: Peptide absorption and utilization: Implications for animal nutrition and health. J Anim Sci 2008; 86:2135-55. [PMID: 18441086 DOI: 10.2527/jas.2007-0826] [Citation(s) in RCA: 213] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Over the last 50 yr, the study of intestinal peptide transport has rapidly evolved into a field with exciting nutritional and biomedical applications. In this review, we describe from a historical and current perspective intestinal peptide transport, the importance of peptides to whole-body nutrition, and the cloning and characterization of the intestinal peptide transporter, PepT1. We focus on the nutritional significance of peptide transport and relate these findings to livestock and poultry. Amino acids are transported into the enterocyte as free AA by a variety of AA transporters that vary in substrate specificity or as di- and tripeptides by the peptide transporter, PepT1. Expression of PepT1 is largely restricted to the small intestine in most species; however, in ruminants, peptide transport and activity is observed in the rumen and omasum. The extent to which peptides are absorbed and utilized is still unclear. In ruminants, peptides make a contribution to the portal-drained visceral flux of total AA and are detected in circulating plasma. Peptides can be utilized by the mammary gland for milk protein synthesis and by a variety of other tissues. We discuss the factors known to regulate expression of PepT1 including development, diet, hormones, diurnal rhythm, and disease. Expression of PepT1 is detected during embryological stages in both birds and mammals and increases with age, a strategic event that allows for the immediate uptake of nutrients after hatch or birth. Both increasing levels of protein in the diet and dietary protein deficiencies are found to upregulate the peptide transporter. We also include in this review a discussion of the use of dietary peptides and potential alternate routes of nutrient delivery to the cell. Our goal is to impart to the reader the nutritional implications of peptide transport and dietary peptides and share discoveries that shed light on various biological processes, including rapid establishment of intestinal function in early neonates and maintenance of intestinal function during fasting, starvation, and disease states.
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Affiliation(s)
- E R Gilbert
- Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA
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21
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Li K, Xu L, Kulkarni AA, Perkins DI, Haworth IS, Davies DL. Ethanol inhibits functional activity of the human intestinal dipeptide transporter hPepT1 expressed in Xenopus oocytes. Alcohol Clin Exp Res 2008; 32:777-84. [PMID: 18336632 DOI: 10.1111/j.1530-0277.2008.00636.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND The pathological effects of high alcohol (ethanol) consumption on gastrointestinal and hepatic systems are well recognized. However, the effects of ethanol intake on gastric and intestinal absorption and transport systems remain unclear. The present study investigates the effects of ethanol on the human peptide transporter 1 (hPepT1) which mediates the transport of di-and tripeptides as well as several orally administered peptidomimetic drugs such as beta-lactam antibiotics (e.g., penicillin), angiotensin-converting enzyme inhibitors, the anti-neoplastic agent bestatin, and prodrugs of acyclovir. METHODS Xenopus oocytes were injected with hPepT1 cRNA and incubated for 3 to 10 days. Currents induced by glycyl-sarcosine (Gly-Sar), Ala-Ala (dipeptides), penicillin and enalapril measured in the presence or absence of ethanol were determined using an 8-channel 2-electrode voltage clamp system, with a membrane potential of -70 mV and 11 voltage steps of 100 milliseconds (from +50 mV to -150 mV in -20 mV increments). RESULTS Ethanol (200 mM) inhibited Gly-Sar and Ala-Ala currents by 42 and 30%, respectively, with IC(50)s of 184 and 371 mM, respectively. Ethanol reduced maximal transport capacity (I(max)) of hPepT1 for Gly-Sar without affecting Gly-Sar binding affinity (K(0.5) and Hill coefficient). Penicillin- and enalapril-induced currents were significantly less than those induced by dipeptides and were not inhibited by ethanol. CONCLUSION Ethanol significantly reduced transport of dipeptides via a reduction in transport capacity, rather than competing for binding sites in hPepT1. Ethanol inhibition or alteration of transport function may be a primary causative factor contributing to both the nutritional deficits as well as the immunological deficiencies that many alcoholics experience including alcohol liver disease and brain damage.
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Affiliation(s)
- Kaixun Li
- Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California 90033, USA.
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22
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Nishio N, Katsura T, Inui KI. Thyroid Hormone Regulates the Expression and Function of P-glycoprotein in Caco-2 Cells. Pharm Res 2007; 25:1037-42. [DOI: 10.1007/s11095-007-9495-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 01/26/2007] [Indexed: 10/22/2022]
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Terada T, Inui KI. Gene expression and regulation of drug transporters in the intestine and kidney. Biochem Pharmacol 2007; 73:440-9. [PMID: 17137557 DOI: 10.1016/j.bcp.2006.10.010] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2006] [Revised: 10/06/2006] [Accepted: 10/09/2006] [Indexed: 01/09/2023]
Abstract
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.
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Affiliation(s)
- Tomohiro Terada
- Department of Pharmacy, Kyoto University Hospital, Kyoto 606-8507, Japan
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Shimakura J, Terada T, Saito H, Katsura T, Inui KI. Induction of intestinal peptide transporter 1 expression during fasting is mediated via peroxisome proliferator-activated receptor alpha. Am J Physiol Gastrointest Liver Physiol 2006; 291:G851-6. [PMID: 16751172 DOI: 10.1152/ajpgi.00171.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We previously demonstrated that starvation markedly increased the amount of mRNA and protein levels of the intestinal H+/peptide cotransporter (PEPT1) in rats, leading to altered pharmacokinetics of the PEPT1 substrates. In the present study, the mechanism underlying this augmentation was investigated. We focused on peroxisome proliferator-activated receptor alpha (PPARalpha), which plays a pivotal role in the adaptive response to fasting in the liver and other tissues. In 48-h fasted rats, the expression level of PPARalpha mRNA in the small intestine markedly increased, accompanied by the elevation of serum free fatty acids, which are endogenous PPARalpha ligands. Oral administration of the synthetic PPARalpha ligand WY-14643 to fed rats increased the mRNA level of intestinal PEPT1. Furthermore, treatment of the human intestinal model, Caco-2 cells, with WY-14643 resulted in enhanced PEPT1 mRNA expression and uptake activity of glycylsarcosine. In the small intestine of PPARalpha-null mice, augmentation of PEPT1 mRNA during fasting was completely abolished. In the kidney, fasting did not induce PEPT1 expression in either PPARalpha-null or wild-type mice. Together, these results indicate that PPARalpha plays critical roles in fasting-induced intestinal PEPT1 expression. In addition to the well-established roles of PPARalpha, we propose a novel function of PPARalpha in the small intestine, that is, the regulation of nitrogen absorption through PEPT1 during fasting.
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Affiliation(s)
- Jin Shimakura
- Department of Pharmacy, Kyoto University Hospital, Kyoto 606-8507, Japan
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25
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Shimakura J, Terada T, Shimada Y, Katsura T, Inui KI. The transcription factor Cdx2 regulates the intestine-specific expression of human peptide transporter 1 through functional interaction with Sp1. Biochem Pharmacol 2006; 71:1581-8. [PMID: 16616718 DOI: 10.1016/j.bcp.2006.03.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Revised: 03/02/2006] [Accepted: 03/02/2006] [Indexed: 01/12/2023]
Abstract
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.
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Affiliation(s)
- Jin Shimakura
- Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
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26
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Lu H, Klaassen C. Tissue distribution and thyroid hormone regulation of Pept1 and Pept2 mRNA in rodents. Peptides 2006; 27:850-7. [PMID: 16202478 DOI: 10.1016/j.peptides.2005.08.012] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Revised: 08/22/2005] [Accepted: 08/23/2005] [Indexed: 01/13/2023]
Abstract
Peptide transporters (Pept) have essential physiological functions and also transport various drugs. Information regarding tissue distribution and gene regulation of Pept in rodents is limited. The present study investigated the distribution of Pept1 and Pept2 mRNA in 19 tissues of male and female Sprague-Dawley rats and C57BL/6 mice, as well as thyroid hormone regulation of renal Pept expression in male rats, using the branched DNA signal amplification assay. Pept1 mRNA was not only highly expressed in small intestine, but also detectable in gonads of both species, kidney of rats, and large intestine of mice. Pept2 mRNA was the highest in kidney, followed by brain and lung. The present study offers the first evidence of considerable Pept2 mRNA expression in pituitary and reproductive organs (testis, prostate, ovary, and uterus). Interestingly, Pept2 mRNA expression in mouse prostate appeared to be much higher than that in rat prostate. Thyroidectomy increased Pept1 and Pept2 mRNA in male rat kidney; such increases were abolished by thyroid hormone replacement.
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Affiliation(s)
- Hong Lu
- Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City, KS 66160-7417, USA
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27
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Inoue M, Terada T, Okuda M, Inui KI. Regulation of human peptide transporter 1 (PEPT1) in gastric cancer cells by anticancer drugs. Cancer Lett 2005; 230:72-80. [PMID: 16253763 DOI: 10.1016/j.canlet.2004.12.023] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2004] [Revised: 12/15/2004] [Accepted: 12/18/2004] [Indexed: 10/25/2022]
Abstract
Human peptide transporter 1 (PEPT1) mediates the cellular uptake of di- and tripeptides and peptide-like drugs in the small intestine. In the present study, we examined the regulation of PEPT1 by anticancer drugs in the gastric cancer cell line MKN45. PEPT1 was expressed and functioned in MKN45 cells. The transport activity and mRNA expression of the facilitative glucose transporter 1 (GLUT1) were significantly decreased by 5-fluorouracil treatment, but those of PEPT1 were slightly increased. Cisplatin treatment affected neither PEPT1 nor GLUT1 activity. In conclusion, PEPT1 expressed in MKN45 cells are resistant against the cellular injury induced by 5-fluorouracil and cisplatin.
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Affiliation(s)
- Mayumi Inoue
- Department of Pharmacy, Faculty of Medicine, Kyoto University Hospital, Kyoto University, Sakyo-ku, Kyoto 606-8507, Japan
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28
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Terada T, Shimada Y, Pan X, Kishimoto K, Sakurai T, Doi R, Onodera H, Katsura T, Imamura M, Inui KI. Expression profiles of various transporters for oligopeptides, amino acids and organic ions along the human digestive tract. Biochem Pharmacol 2005; 70:1756-63. [PMID: 16259962 DOI: 10.1016/j.bcp.2005.09.027] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2005] [Revised: 09/27/2005] [Accepted: 09/28/2005] [Indexed: 01/11/2023]
Abstract
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.
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Affiliation(s)
- Tomohiro Terada
- Department of Pharmacy, Kyoto University Hospital, Sakyo-ku, Kyoto 606-8507, Japan
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Shimakura J, Terada T, Katsura T, Inui KI. Characterization of the human peptide transporter PEPT1 promoter: Sp1 functions as a basal transcriptional regulator of human PEPT1. Am J Physiol Gastrointest Liver Physiol 2005; 289:G471-7. [PMID: 15905415 DOI: 10.1152/ajpgi.00025.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
H+-coupled peptide transporter 1 (PEPT1, SLC15A1) localized at the brush-border membranes of intestinal epithelial cells plays an important role in the intestinal absorption of small peptides and a variety of peptidemimetic drugs. PEPT1 is regulated by various factors, including hormones, dietary conditions, some pharmaceutics, and diurnal rhythm. But there is little information about the transcriptional regulation of PEPT1. In the present study, therefore, we cloned the human (h)PEPT1 promoter region and examined its promoter activity using a human intestinal cell line, Caco-2. Deletion analysis of the hPEPT1 promoter suggested that the region spanning -172 to -35 bp was essential for basal transcriptional activity. This region lacked a TATA-box but contained some GC-rich sites that supposedly bind with the transcription factor Sp1. Mutational analysis revealed that three of these putative Sp1 sites contributed to the transcriptional activity. EMSA showed that Sp1 bound to two GC-rich sites. Furthermore, inhibition of Sp1 binding by mithramycin A treatment significantly reduced the transcriptional activity. Finally, overexpression of Sp1 increased the transcriptional activity in a dose-dependent manner. This study reports the first characterization of the hPEPT1 promoter and shows the significant role of Sp1 in the basal transcriptional regulation of hPEPT1.
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Affiliation(s)
- Jin Shimakura
- Dept. of Pharmacy, Kyoto Univ. Hospital, Sakyo-ku, Kyoto 606-8507, Japan
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Döring F, Schmitt R, Bernhardt WM, Klapper M, Bachmann S, Daniel H, Groneberg DA. Hypothyroidism induces expression of the peptide transporter PEPT2. Biol Chem 2005; 386:785-90. [PMID: 16201874 DOI: 10.1515/bc.2005.092] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
The kidney is a target organ for thyroid hormone action and a variety of renal transport processes are altered in response to impaired thyroid functions. To investigate the effect of thyroid hormone on the expression of the renal proximal tubular high-affinity-type H+-peptide cotransporter (PEPT2) in rats, hypothyroidism was induced in animals by administration of methimazole (0.05%) via drinking water. After 7 weeks of treatment, hypothyroidism was confirmed by determining serum free T3 and free T4 concentrations. Northern blotting was used to examine the expression of PEPT2 mRNA in kidney tissues from hypothyroid rats compared to control rats. Hypothyroidism resulted in an increased level of total renal PEPT2 mRNA (121.1±3.3% vs. control 100±2.8%; p=0.008). The mRNA results were confirmed by immuno-blotting, which demonstrated significantly increased protein levels (162% vs. control 100%; p<0.01). Immunohistochemistry also revealed increased PEPT2 protein levels in the proximal tubules of treated compared to non-treated rats. In summary, PEPT2 is the first proximal tubule transporter protein that shows increased expression in states of hypothyreosis. As PEPT2 reabsorbs filtered di- and tripeptides and peptide-like drugs, the present findings may have important implications in nutritional amino acid homeostasis and for drug dynamics in states of altered thyroid function.
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Affiliation(s)
- Frank Döring
- Otto-Heubner-Center, Biomedical Research Center, Charité - Medical School of the Free University and Humboldt-University, D-13353 Berlin, Germany
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Shimizu Y, Masuda S, Nishihara K, Ji L, Okuda M, Inui KI. Increased protein level of PEPT1 intestinal H+-peptide cotransporter upregulates absorption of glycylsarcosine and ceftibuten in 5/6 nephrectomized rats. Am J Physiol Gastrointest Liver Physiol 2005; 288:G664-70. [PMID: 15528259 DOI: 10.1152/ajpgi.00270.2004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
In chronic renal failure (CRF), dietary protein is one of the factors that deteriorates residual renal functions. Numerous studies have indicated that the products of protein digestion are mainly absorbed as small peptides. However, how small peptides are absorbed in CRF remains poorly understood. H(+)-coupled peptide transporter (PEPT1/SLC15A1) plays an important role in the absorption of small peptides and peptide-like drugs in the small intestine. Because dietary protein intake is one of the risk factors for renal failure, the alteration of intestinal PEPT1 might have implications in the progression of renal disease as well as the pharmacokinetics of peptide-like drugs. In this study, we examined the alteration of intestinal PEPT1 in 5/6 nephrectomized (5/6 NR) rats, extensively used as a model of chronic renal failure. Absorption of [(14)C]glycylsarcosine and ceftibuten was significantly increased in 5/6 NR rats compared with sham-operated rats, without a change in intestinal protease activity. Western blot analysis indicated that the amount of intestinal PEPT1 protein in 5/6 NR rats was increased mainly at the upper region. On the other hand, the amount of intestinal PEPT1 mRNA was not significantly different from that of sham-operated rats. These findings indicate that the increase in absorption of small peptides and peptide-like drugs, caused by the upregulation of intestinal PEPT1 protein, might contribute to the progression of renal failure as well as the alteration of drug pharmacokinetics.
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Affiliation(s)
- Yuriko Shimizu
- Dept. of Pharmacy, Kyoto Univ. Hospital, Sakyo-ku, Kyoto 606-8507, Japan
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Katsura T, Inui KI. Intestinal absorption of drugs mediated by drug transporters: mechanisms and regulation. Drug Metab Pharmacokinet 2005; 18:1-15. [PMID: 15618714 DOI: 10.2133/dmpk.18.1] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The absorption of drugs from the gastrointestinal tract is one of the important determinants for oral bioavailability. Development of in vitro experimental techniques such as isolated membrane vesicles and cell culture systems has allowed us to elucidate the transport mechanisms of various drugs across the plasma membrane. Recent introduction of molecular biological techniques resulted in the successful identification of drug transporters responsible for the intestinal absorption of a wide variety of drugs. Each transporter exhibits its own substrate specificity, though it usually shows broad substrate specificity. In this review, we first summarize the recent advances in the characterization of drug transporters in the small intestine, classified into peptide transporters, organic cation transporters and organic anion transporters. In particular, peptide transporter (PEPT1) is the best-characterized drug transporter in the small intestine, and therefore its utilization to improve the oral absorption of poorly absorbed drugs is briefly described. In addition, regulation of the activity and expression levels of drug transporters seems to be an important aspect, because alterations in the functional characteristics and/or expression levels of drug transporters in the small intestine could be responsible for the intra- and interindividual variability of oral bioavailability of drugs. As an example, regulation of the activity and expression of PEPT1 is summarized.
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Affiliation(s)
- Toshiya Katsura
- Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Kyoto University, Japan
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Watanabe K, Terada K, Jinriki T, Sato J. Effect of insulin on cephalexin uptake and transepithelial transport in the human intestinal cell line Caco-2. Eur J Pharm Sci 2004; 21:87-95. [PMID: 14706815 DOI: 10.1016/j.ejps.2003.10.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
We investigated whether cephalexin transport in Caco-2 cells is regulated by insulin. After the insulin pretreatment, cephalexin uptake, and transport as well as PEPT1 mRNA and protein expression in the cells were measured. Cephalexin uptake was significantly increased by the insulin pretreatment. Insulin significantly increased cephalexin saturable uptake, but had no significant effect on the non-saturable one. PEPT1 protein expression on the apical membrane, but not PEPT1 mRNA expression, was increased by the insulin pretreatment. The enhancement of cephalexin uptake by the insulin pretreatment was inhibited by genistein, a tyrosine kinase inhibitor, and colchicine, an agent that disrupts protein translocation. Apical-to-basolateral transport of cephalexin has increased by the insulin pretreatment at the apical side and long-term insulin pretreatment at the basolateral side. It is considered that insulin mainly binds to its receptor on the apical and basolateral membranes, thereby promoting PEPT1 translocation from the intracellular pool to the apical membrane surface; consequently, PEPT1 protein expression on the apical membrane is increased.
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Affiliation(s)
- Kazuhiro Watanabe
- Hokkaido College of Pharmacy, 7-1 Katsuraoka-cho, Otaru, Hokkaido 047-0264, Japan.
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Abstract
Intestinal protein digestion generates a huge variety and quantity of short chain peptides that are absorbed into intestinal epithelial cells by the PEPT1 transporter in the apical membrane of enterocytes. PEPT1 operates as an electrogenic proton/peptide symporter with the ability to transport essentially every possible di- and tripeptide. Transport is enantio-selective and involves a variable proton-to-substrate stoichiometry for uptake of neutral and mono- or polyvalently charged peptides. Neither free amino acids nor peptides containing four or more amino acids are accepted as substrates. The structural similarity of a variety of drugs with the basic structure of di- or tripeptides explains the transport of aminocephalosporins and aminopenicillins, selected angiotensin-converting inhibitors, and amino acid-conjugated nucleoside-based antiviral agents by PEPT1. The high transport capacity of PEPT1 allows fast and efficient intestinal uptake of the drugs but also of amino acid nitrogen even in states of impaired mucosal functions. Transcriptional and post-transcriptional regulation of PEPT1 occurs in response to alterations in the nutritional status and in disease states, suggesting a prime role of this transporter in amino acid absorption.
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Affiliation(s)
- Hannelore Daniel
- Molecular Nutrition Unit, Technical University of Munich, D-85350 Freising-Weihenstephan, Germany.
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Daniel H, Kottra G. The proton oligopeptide cotransporter family SLC15 in physiology and pharmacology. Pflugers Arch 2004; 447:610-8. [PMID: 12905028 DOI: 10.1007/s00424-003-1101-4] [Citation(s) in RCA: 320] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2003] [Revised: 04/25/2003] [Accepted: 04/29/2003] [Indexed: 02/07/2023]
Abstract
Mammalian members of the SLC15 family are electrogenic transporters that utilize the proton-motive force for uphill transport of short chain peptides and peptido-mimetics into a variety of cells. The prototype transporters of this family are PEPT1 (SLC15A1) and PEPT2 (SLC15A2), which mediate the uptake of peptide substrates into intestinal and renal epithelial cells. More recently, other sites of functional expression of the two proteins have been identified such as bile duct epithelium (PEPT1), glia cells and epithelia of the choroid plexus, lung and mammary gland (PEPT2). Both proteins can transport essentially every possible di- and tripeptide regardless of the substrate's net charge, but operate stereoselectively. Based on peptide-like structures, various drugs and prodrugs are transported as well, allowing efficient intestinal absorption of the compounds via PEPT1. In kidney tubules both peptide transporters can mediate the renal reabsorption of the filtered compounds thus affecting their pharmacokinetics. Recently, two new peptide transporters, PHT1 (SLC15A4) and PHT2 (SLC15A3), were identified in mammals. They possess an overall amino acid identity with the PEPT-series of 20% to 25%. PHT1 and PHT2 were shown to transport free histidine and certain di- and tripeptides, but it is not yet clear whether they are located on the plasma membrane or represent lysosomal transporters for the proton-dependent export of histidine and dipeptides from lysosomal protein degradation into the cytosol.
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Affiliation(s)
- Hannelore Daniel
- Molecular Nutrition Unit, Institute of Nutritional Sciences, Technical University of Munich, Hochfeldweg 2, 85354, Freising-Weihenstephan, Germany
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Adibi SA. Regulation of expression of the intestinal oligopeptide transporter (Pept-1) in health and disease. Am J Physiol Gastrointest Liver Physiol 2003; 285:G779-88. [PMID: 14561585 DOI: 10.1152/ajpgi.00056.2003] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The abundance of the oligopeptide transporter (Pept-1) in the brush-border membrane of the intestinal epithelium is the central mechanism for regulation of transport of products of protein digestion (dipeptides and tripeptides) and peptidomimetic drugs (for example, beta-lactam antibiotics). Within the past few years, there has been substantial progress in identifying the factors controlling this regulation and the mechanisms of their actions. The purpose of this report is to review this progress. The studies of individual substrates and hormones in a human intestinal cell line (Caco-2) have shown that dipeptides, certain amino acids, insulin, and leptin increase and epidermal growth factor and triiodothyronine decrease the membrane population of Pept-1. In the case of dipeptides, epidermal growth factor, and thyroid hormone, there are parallel changes in the gene expression brought about by alteration of transcription and/or stability of Pept-1 mRNA. In contrast, the treatment with insulin and leptin does not induce any alteration in the Pept-1 gene expression, and the mechanism of increased protein expression appears to be increased trafficking from a preformed cytoplasmic pool to the apical membrane. In vivo studies in rats have shown modulation of protein and gene expressions of the intestinal oligopeptide transporter during the day and during development and in nutritional and metabolic alterations, such as high-protein diet, fasting, and diabetes. Patients with intestinal diseases, such as ulcerative colitis, Crohn's disease, and short-bowel syndrome, may have induction of the Pept-1 expression in their colon. Finally, pharmacological studies have shown that the expression of Pept-1 can be upregulated by agents such as 5 fluorouracil and downregulated by agents such as cyclosporine. In conclusion, the above studies have produced a wealth of new information on regulation of a key transporter in the intestine. This information may have useful applications in nutritional and pharmacological treatments, for example, in diabetic patients needing enteral nutrition or in ulcerative colitis patients needing the suppression of the intestinal inflammation.
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Affiliation(s)
- Siamak A Adibi
- Emeritus Professor of Medicine, Univ. of Pittsburgh, 601 Kaufmann Bldg., 3471 Fifth Ave., Pittsburgh, PA 15213, USA.
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37
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Abstract
The brush-border membrane of renal epithelial cells contains PEPT1 and PEPT2 proteins that are rheogenic carriers for short-chain peptides. The carrier proteins display a distinct surface expression pattern along the proximal tubule, suggesting that initially di- and tripeptides, either filtered or released by surface-bound hydrolases from larger oligopeptides, are taken up by the low-affinity but high-capacity PEPT1 transporter and then by PEPT2, which possesses a higher affinity but lower transport capacity. Both carriers transport essentially all possible di- and tripeptides and numerous structurally related drugs. A unique feature of the mammalian peptide transporters is the capability of proton-dependent electrogenic cotransport of all substrates, regardless of their charge, that is achieved by variable coupling in proton movement along with the substrate down the transmembrane potential difference. This review focuses on the postcloning research efforts to understand the molecular physiology of peptide transport processes in renal tubules and summarizes available data on the underlying genes, protein structures, and transporter function as derived from studies in heterologous expression systems.
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Affiliation(s)
- Hannelore Daniel
- Molecular Nutrition Unit, Technical University of Munich, D-85350 Freising-Weihenstephan, Germany.
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Herrera-Ruiz D, Knipp GT. Current perspectives on established and putative mammalian oligopeptide transporters. J Pharm Sci 2003; 92:691-714. [PMID: 12661057 DOI: 10.1002/jps.10303] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Peptides and peptide-based drugs are increasingly being utilized as therapeutic agents for the treatment of numerous disorders. The increasing development of peptide-based therapeutic agents is largely due to technological advances including the advent of combinatorial peptide libraries, peptide synthesis strategies, and peptidomimetic design. Peptides and peptide-based agents have a broad range of potential clinical applications in the treatment of many disorders including AIDS, hypertension, and cancer. Peptides are generally hydrophilic and often exhibit poor passive transcellular diffusion across biological barriers. Insights into strategies for increasing their intestinal absorption have been derived from the numerous studies demonstrating that the absorption of protein digestion products occurs primarily in the form of small di- and tripeptides. The characterization of the pathways of intestinal, transepithelial transport of peptides and peptide-based drugs have demonstrated that a significant degree of absorption occurs through the role of proteins within the proton-coupled, oligopeptide transporter (POT) family. Considerable focus has been traditionally placed on Peptide Transporter 1 (PepT1) as the main mammalian POT member regulating intestinal peptide absorption. Recently, several new POT members, including Peptide/Histidine Transporter 1 (PHT1) and Peptide/Histidine Transporter 2 (PHT2) and their splice variants have been identified. This has led to an increased need for new experimental methods enabling better characterization of the biophysical and biochemical barriers and the role of these POT isoforms in mediating peptide-based drug transport.
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Affiliation(s)
- Dea Herrera-Ruiz
- Department of Pharmaceutics, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, New Jersey 08854-8022, USA
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D'Souza VM, Buckley DJ, Buckley AR, Pauletti GM. Extracellular glucose concentration alters functional activity of the intestinal oligopeptide transporter (PepT-1) in Caco-2 cells. J Pharm Sci 2003; 92:594-603. [PMID: 12587121 DOI: 10.1002/jps.10325] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The objective of this study was to determine the effect of different cell culture media glucose concentrations on the functional activity of PepT-1 in Caco-2 cells. Uptake kinetics of Gly-Sar into Caco-2 cells that were maintained in iso-osmotic media containing 25 or 5.5 mM glucose were determined in the presence and absence of amino acid-selective chemical modifiers and dithiothreitol. Inhibition of Gly-Sar uptake into Caco-2 cells was measured in the presence of dipeptides and xenobiotics exhibiting various binding affinities for the PepT-1. The effect of extracellular glucose on PepT-1 gene expression was assessed using comparative RT-PCR. Long-term exposure of Caco-2 cells to 25 mM glucose reduced maximum transport capacity for Gly-Sar uptake without altering PepT-1 gene expression. In contrast, binding affinity of Gly-Sar and other dipeptides or xenobiotics was not significantly changed. Chemical modification of Lys and Tyr residues decreased V(max), while Cys modification increased the maximum transport capacity of the carrier. Preincubation of Caco-2 cells with dithiothreitol restored PepT-1 activity in cells maintained at 25 mM glucose. In conclusion, cell culture media containing 25 mM glucose decreases maximum transport capacity of PepT-1 in Caco-2 cells without affecting substrate recognition, at least in part, mediated via an oxidative pathway.
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Affiliation(s)
- Vanessa M D'Souza
- College of Pharmacy, University of Cincinnati Medical Center, 3223 Eden Avenue, Cincinnati, OH 45267, USA
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