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Formulation technologies and advances for oral delivery of novel nitroimidazoles and antimicrobial peptides. J Control Release 2020; 324:728-749. [PMID: 32380201 DOI: 10.1016/j.jconrel.2020.05.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 05/01/2020] [Accepted: 05/02/2020] [Indexed: 02/06/2023]
Abstract
Antibiotic resistance has become a global crisis, driving the exploration for novel antibiotics and novel treatment approaches. Among these research efforts two classes of antibiotics, bicyclic nitroimidazoles and antimicrobial peptides, have recently shown promise as novel antimicrobial agents with the possibility to treat multi-drug resistant infections. However, they suffer from the issue of poor oral bioavailability due to disparate factors: low solubility in the case of nitroimidazoles (BCS class II drugs), and low permeability in the case of peptides (BCS class III drugs). Moreover, antimicrobial peptides present another challenge as they are susceptible to chemical and enzymatic degradation, which can present an additional pharmacokinetic hurdle for their oral bioavailability. Formulation technologies offer a potential means for improving the oral bioavailability of poorly permeable and poorly soluble drugs, but there are still drawbacks and limitations associated with this approach. This review discusses in depth the challenges associated with oral delivery of nitroimidazoles and antimicrobial peptides and the formulation technologies that have been used to overcome these problems, including an assessment of the drawbacks and limitations associated with the technologies that have been applied. Furthermore, the potential for supercritical fluid technology to overcome the shortcomings associated with conventional drug formulation methods is reviewed.
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Jiang Q, Zhang J, Tong P, Gao Y, Lv Y, Wang C, Luo M, Sun M, Wang J, Feng Y, Cao L, Wang G, Wang Y, Kan Q, Zhang T, Wang Y, Liu K, Sun J, He Z. Bioactivatable Pseudotripeptidization of Cyclic Dipeptides To Increase the Affinity toward Oligopeptide Transporter 1 for Enhanced Oral Absorption: An Application to Cyclo(l-Hyp-l-Ser) (JBP485). J Med Chem 2019; 62:7708-7721. [DOI: 10.1021/acs.jmedchem.9b00358] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
| | - Jiangnan Zhang
- Department of Clinical Pharmacology, Dalian Medical University, Dalian 116044, China
| | | | | | | | - Changyuan Wang
- Department of Clinical Pharmacology, Dalian Medical University, Dalian 116044, China
| | | | | | - Jian Wang
- Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, China
| | - Yao Feng
- Key Laboratory of Structure-Based Drug Design and Discovery, Shenyang Pharmaceutical University, Ministry of Education, Shenyang 110016, China
| | - Linlin Cao
- Department of Pharmaceutics, The Second Hospital of Dalian Medical University, Dalian 116023, China
| | - Gang Wang
- Department of Pharmaceutics, Guang Xi University of Chinese Medicine, Guangxi 530001, China
| | - Yang Wang
- Department of Pharmaceutics, Guang Xi University of Chinese Medicine, Guangxi 530001, China
| | | | | | | | - Kexin Liu
- Department of Clinical Pharmacology, Dalian Medical University, Dalian 116044, China
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3
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CZARNECKA ANNAM, NIEDZWIEDZKA MAGDALENA, PORTA CAMILLO, SZCZYLIK CEZARY. Hormone signaling pathways as treatment targets in renal cell cancer (Review). Int J Oncol 2016; 48:2221-35. [DOI: 10.3892/ijo.2016.3460] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2016] [Accepted: 02/14/2016] [Indexed: 11/06/2022] Open
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4
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Chen S, Einspanier R, Schoen J. Transepithelial electrical resistance (TEER): a functional parameter to monitor the quality of oviduct epithelial cells cultured on filter supports. Histochem Cell Biol 2015. [PMID: 26223877 PMCID: PMC4628619 DOI: 10.1007/s00418-015-1351-1] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cultivation of oviduct epithelial cells on porous filters fosters in vivo-like morphology and functionality. However, due to the optical properties of the filter materials and the cells’ columnar shape, cell quality is hard to assess via light microscopy. In this study, we aim to evaluate transepithelial electrical resistance (TEER) measurement as a prognostic quality indicator for the cultivation of porcine oviduct epithelial cells (POEC). POEC were maintained in four different types of media for 3 and 6 w to achieve diverse culture qualities, and TEER was measured before processing samples for histology. Culture quality was scored using morphological criteria (presence of cilia, confluence and cell polarity). We furthermore analyzed the correlation between cellular height (as a measure of apical–basal polarization) and TEER in fully differentiated routine cultures (biological variation) and in cultures with altered cellular height due to hormonal stimulation. Fully differentiated cultures possessed a moderate TEER between 500 and 1100 Ω*cm2. Only 5 % of cultures which exhibited TEER values in this defined range had poor quality. Sub-differentiated cultures showed either very low or excessively high TEER. We unveiled a highly significant (P < 0.0001) negative linear correlation between TEER and epithelial height in well-differentiated cultures (both routine and hormone stimulated group). This may point toward the interaction between tight junction assembly and epithelial apical–basal polarization. In conclusion, TEER is a straightforward quality indicator which could be routinely used to monitor the differentiation status of oviduct epithelial cells in vitro.
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Affiliation(s)
- Shuai Chen
- College of Life Science, Hebei University, Baoding, 071002, Hebei, People's Republic of China
- Institute of Reproductive Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany
| | - Ralf Einspanier
- Institute of Veterinary Biochemistry, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany
| | - Jennifer Schoen
- Institute of Reproductive Biology, Leibniz Institute for Farm Animal Biology, Wilhelm-Stahl-Allee 2, 18196, Dummerstorf, Germany.
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Awortwe C, Fasinu PS, Rosenkranz B. Application of Caco-2 cell line in herb-drug interaction studies: current approaches and challenges. JOURNAL OF PHARMACY AND PHARMACEUTICAL SCIENCES 2014; 17:1-19. [PMID: 24735758 DOI: 10.18433/j30k63] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The Caco-2 model is employed in pre-clinical investigations to predict the likely gastrointestinal permeability of drugs because it expresses cytochrome P450 enzymes, transporters, microvilli and enterocytes of identical characteristics to the human small intestine. The FDA recommends this model as integral component of the Biopharmaceutics Classification System (BCS). Most dedicated laboratories use the Caco-2 cell line to screen new chemical entities through prediction of its solubility, bioavailability and the possibility of drug-drug or herb-drug interactions in the gut lumen. However, challenges in the inherent characteristics of Caco-2 cell and inter-laboratory protocol variations have resulted to generation of irreproducible data. These limitations affect the extrapolation of data from pre-clinical research to clinical studies involving drug-drug and herb-drug interactions. This review addresses some of these caveats and enumerates the plausible current and future approaches to reduce the anomalies associated with Caco-2 cell line investigations focusing on its application in herb-drug interactions.
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Affiliation(s)
- Charles Awortwe
- Division of Clinical Pharmacology, Faculty of Medicine and Health Sciences, University of Stellenbosch, Tygerberg, Cape Town, South Africa
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6
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Practical permeability-based hepatic clearance classification system (HepCCS) in drug discovery. Future Med Chem 2014; 6:1995-2012. [DOI: 10.4155/fmc.14.141] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Background: The use of liver microsomes and hepatocytes to predict total in vivo clearance is standard practice in the pharmaceutical industry; however, metabolic stability data alone cannot always predict in vivo clearance accurately. Results: Apparent permeability generated from Mardin–Darby canine kidney cells and rat hepatocyte uptake for 33 discovery compounds were obtained. Conclusion: When there is underprediction of in vivo clearance, compounds with low apparent permeability (less than 3 × 10-6 cm/s) all exhibited hepatic uptake. A systematic approach in the form of a classification system (hepatic clearance classification system) and decision tree that will help drug discovery scientists understand in vitro–in vivo clearance prediction disconnect early is proposed.
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Renukuntla J, Vadlapudi AD, Patel A, Boddu SHS, Mitra AK. Approaches for enhancing oral bioavailability of peptides and proteins. Int J Pharm 2013; 447:75-93. [PMID: 23428883 DOI: 10.1016/j.ijpharm.2013.02.030] [Citation(s) in RCA: 399] [Impact Index Per Article: 36.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 12/28/2012] [Accepted: 02/12/2013] [Indexed: 12/20/2022]
Abstract
Oral delivery of peptide and protein drugs faces immense challenge partially due to the gastrointestinal (GI) environment. In spite of considerable efforts by industrial and academic laboratories, no major breakthrough in the effective oral delivery of polypeptides and proteins has been accomplished. Upon oral administration, gastrointestinal epithelium acts as a physical and biochemical barrier for absorption of proteins resulting in low bioavailability (typically less than 1-2%). An ideal oral drug delivery system should be capable of (a) maintaining the integrity of protein molecules until it reaches the site of absorption, (b) releasing the drug at the target absorption site, where the delivery system appends to that site by virtue of specific interaction, and (c) retaining inside the gastrointestinal tract irrespective of its transitory constraints. Various technologies have been explored to overcome the problems associated with the oral delivery of macromolecules such as insulin, gonadotropin-releasing hormones, calcitonin, human growth factor, vaccines, enkephalins, and interferons, all of which met with limited success. This review article intends to summarize the physiological barriers to oral delivery of peptides and proteins and novel pharmaceutical approaches to circumvent these barriers and enhance oral bioavailability of these macromolecules.
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Affiliation(s)
- Jwala Renukuntla
- Division of Pharmaceutical Sciences, South College School of Pharmacy, 400 Goody's Lane, Knoxville, TN 37931, USA
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Mahat B, Chae JW, Baek IH, Song GY, Song JS, Ma JY, Kwon KI. Biopharmaceutical characterization of decursin and their derivatives for drug discovery. Drug Dev Ind Pharm 2012; 39:1523-30. [PMID: 23003006 DOI: 10.3109/03639045.2012.717296] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Angelica gigas Nakai and its components are known to have neuroprotective, antiplatelet, and anticancer activities. The present study evaluated the in vitro and in vivo biopharmaceutical characterization of Angelica gigas component substances, including decursin (the main substance), decursinol angelate (decursin isomer), JH714 (ether form of decursin) and epoxide decursin (epoxide form of decursin). Decursin, decursinol angelate and JH714 exhibited acceptable metabolic stability (>50%) in liver microsomes from human and higher bound fraction (>90%) in human plasma operating ultrafiltration. Decursin and decursinol angelate in CYP1A2 and CYP2C19 indicated less than 50% CYP activity, suggesting inhibition of the CYP isoforms using Vivid® CYP screening kit. JH714 only showed an apparent permeability coefficient of <10 × 10⁻⁶ cm/s in MDCK cells, suggesting that it is poorly absorbed. Blood brain barrier permeability was examined after oral administration to male Sprague-Dawley (SD) rats, and pharmacokinetic studies were performed after oral and intravenous administration of 10 mg/kg compounds. Decursin, decursinol angelate and JH714 showed ratios of compound concentration in brain with respect to plasma (Cbrain/Cplasma) of >1.5, suggesting good brain/plasma ratio at 0.5, 1, 3, and 5 h. In contrast, Cbrain/Cplasma was <0.5 for epoxide decursin. For all test compounds, >1.5% of the dose remained in GI tract after 8 h, and the excretion rate in urine was <0.5% which suggests that gastro intestinal tract may be major site of disposition following oral administration. Finally, these results may be useful for the design of dosage regimens of decursin and its derivatives.
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Affiliation(s)
- Bimit Mahat
- College of Pharmacy, Chungnam National University, Republic of Korea
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Abstract
The model systems that are currently used to determine the intestinal permeability characteristics of discovery compounds often represent a combination of high-throughout, but less predictive, in silico and in vitro models and low-throughput, but more predictive, in vivo models. Cell-based permeability models have been integrated into the discovery paradigm for some time and represent the "method of choice" across the industry. Here, in addition to an objective analysis of the utility of cell culture models for permeability screening, anticipated future trends in the field of cell culture models are discussed.
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Affiliation(s)
- Praveen V Balimane
- Department of Metabolism and Pharmacokinetics, Bristol-Myers Squibb, Princeton, NJ 08543, USA.
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Salamat-Miller N, Johnston TP. Current strategies used to enhance the paracellular transport of therapeutic polypeptides across the intestinal epithelium. Int J Pharm 2005; 294:201-16. [PMID: 15814245 DOI: 10.1016/j.ijpharm.2005.01.022] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2004] [Revised: 01/12/2005] [Accepted: 01/27/2005] [Indexed: 11/26/2022]
Abstract
The intent of this paper is to update the reader on various strategies which have been utilized to increase the paracellular permeability of protein and polypeptide drugs across the intestinal epithelium. Structural features of protein and polypeptide drugs, together with the natural anatomical and physiological features of the gastrointestinal (GI) tract, have made oral delivery of this class of compounds extremely challenging. Interest in the paracellular route for the transport of therapeutic proteins and polypeptides following oral administration has recently intensified and continues to be explored. The assumption that molecules with a large molecular weight are not able to diffuse through the tight junctions of the intestinal membrane has been challenged by current research, along with an increased understanding of tight junction physiology.
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Affiliation(s)
- Nazila Salamat-Miller
- Division of Pharmaceutical Sciences, Room 211A, School of Pharmacy, University of Missouri-Kansas City, Kansas City, MO 64110-2499, USA
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Urayama A, Yamada S, Ohmori Y, Deguchi Y, Uchida S, Kimura R. Blood-brain permeability of [3H]-(3-methyl-His2)thyrotropin-releasing hormone (MeTRH) in mice: effects of TRH and its analogues. Drug Metab Pharmacokinet 2005; 18:310-8. [PMID: 15618750 DOI: 10.2133/dmpk.18.310] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The present study was undertaken to characterize the transport of (3-methyl-His(2)) thyrotropin-releasing hormone ([(3)H]MeTRH) across the blood-brain barrier in mice and the effects of thyrotropin-releasing hormone (TRH) and its analogues (taltirelin and montirelin) on the transport and brain distribution. Integration plot analysis was used to calculate the influx clearance (CL(in)) of [(3)H]MeTRH after intravenous (i.v.) injection in mice. Furthermore, the capillary depletion method was performed to determine whether [(3)H]MeTRH crossed the blood-brain barrier. The effects of TRH and its analogues on the brain distribution of [(3)H]MeTRH were also examined by co-injection with the radioligand. The brain distribution of [(3)H]MeTRH and [(14)C]sucrose increased with the time after i.v. injection in mice, and the level of [(3)H]MeTRH was significantly higher than that of [(14)C]sucrose 5 min after the injection. The CL(in) value of [(3)H]MeTRH was significantly higher than that of [(14)C]sucrose, and the value of [(3)H]MeTRH was reduced by co-injection with unlabeled MeTRH. Also, capillary depletion showed that [(3)H]MeTRH was distributed largely in the brain parenchyma and this distribution was significantly inhibited by co-injection of TRH and montirelin but not taltirelin. The present study indicates that the transport of [(3)H]MeTRH into the brain may be via a saturable process.
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Affiliation(s)
- Akihiko Urayama
- School of Pharmaceutical Sciences and COE21, University of Shizuoka, Japan
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12
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Behrens I, Kamm W, Dantzig AH, Kissel T. Variation of Peptide Transporter (PepT1 and HPT1) Expression in Caco‐2 Cells as a Function of Cell Origin. J Pharm Sci 2004; 93:1743-54. [PMID: 15176063 DOI: 10.1002/jps.20062] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Caco-2 cell cultures are a widely used in vitro model for the small intestinal drug transport, although large differences have been reported for actively transported substrates from different laboratories. Therefore, we compared three different Caco-2 clones: (1) from the American Culture Tissue Collection (ATCC), (2) from the German Cancer Research Center (DKFZ) in Heidelberg, and (3) from the University Hospital in Marburg in different passage numbers regarding their morphology, multilayers, and tight junction formation, as well as expression of the peptide transporters, HPT1 and PepT1. We determined tight junction formation by measurement of the transepithelial electrical resistance, multilayer formation by confocal laser scanning microscopy, the expression of PepT1 and HPT1 by RT-PCR, indirect immunofluorescence and the permeability of the PepT1 substrate, cephradine. Morphology and TEER-values varied strongly between the different clones. The expression of PepT1 and HPT1 increased in the following order: HD > ATCC > MR. Indirect immunofluorescence revealed a heterogeneous distribution of the transporters in ATCC-cells, whereas it was homogeneous in HD-cells. Only a very weak expression was found in MR-cells. While in ATCC-cells expression of transporters decreased with increasing passage number, it increased in HD-cells. Expression levels were congruent with the transport of cephradine. Expression of PepT1 and HPT1 was strongly affected by the culture conditions. Under identical culture conditions, Heidelberg (HD) Caco-2 cells seemed to be an appropriate in vitro cell culture model for the transport of actively transported drugs, because interpassage changes are low and the transporter distribution was homogeneous throughout the monolayer.
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Affiliation(s)
- Isabel Behrens
- Department of Pharmaceutics and Biopharmacy, University of Marburg, Ketzerbach 63, 35032 Marburg Germany
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Wang Z, Zhang Q. Transport of proteins and peptides across human cultured alveolar A549 cell monolayer. Int J Pharm 2004; 269:451-6. [PMID: 14706256 DOI: 10.1016/j.ijpharm.2003.09.033] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
An in vitro cultured monolayer system of alveolar epithelial cells was used as a model to investigate the transport pathway of the peptides and proteins, salmon calcitonin (sCT), insulin (INS), recombinant hirudin (rHAV2), and recombinant human growth hormone (rhGH), in pulmonary epithelium. Human lung adenocarcinoma A549 cells formed continuous monolayers when grown on the polycarbonate filters of Transwell plates. The transport of the peptides and proteins having MW of 3400-22,000 Da was studied under different conditions. The results showed that the apparent permeability coefficients (P(app)) of these macromolecules across A549 cell monolayers ranged from 2x10(-6) to 5x10(-6) cm s(-1) and exhibited a good inverse correlation with molecular weight. No concentration, direction, or temperature dependence was observed in the permeation of sCT, INS, and rHAV2. While the P(app) of rhGH in the BA direction (2.25x10(-6) cm s(-1)) was less than that in the AB direction at both concentrations (3.20x10(-6) and 3.29x10(-6) cm s(-1)). The P(app) values of rhGH were concentration and temperature independent in the AB direction. These findings suggest that the hydrophilic peptides and proteins used in this study, sCT, INS, rHAV2, and rhGH, appear to cross the A549 cell monolayers via a paracellular pathway by a passive diffusion mechanism.
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Affiliation(s)
- Zhiying Wang
- Department of Pharmaceutics, School of Pharmaceutical Sciences, Peking University Health Science Center, 38 Xue Yuan Road, Beijing 100083, PR China
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Behrens I, Kissel T. Do cell culture conditions influence the carrier-mediated transport of peptides in Caco-2 cell monolayers? Eur J Pharm Sci 2003; 19:433-42. [PMID: 12907294 DOI: 10.1016/s0928-0987(03)00146-5] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Despite the fact that different laboratories have reported large differences in permeability for actively transported substrates, Caco-2 cell monolayers are widely used as in vitro model to study small intestinal drug transport. Therefore, we investigated the effect of cell culture conditions, such as time in culture, membrane support, seeding density and supplements to the medium, on the morphology, the formation of tight junctions, as well as the expression of two peptide transporters (PepT1, HPT1) and the efflux pump, P-glycoprotein (Pgp), in Caco-2 cell monolayers. Tight junction formation was assessed by transepithelial electrical resistance measurements; multi-cell layer formation by confocal laser scanning microscopy, the expression of transporters by RT-PCR and the permeability of the PepT1 substrate, cephradine. Both morphology and the expression of carrier-mediated transporters, varied strongly as a function of culture conditions. An increase of differentiation, as documented by tight, homogeneous cell monolayer formation displaying a strong expression of all carrier-mediated transporters, was found up to 3 weeks post seeding. One week later, multi-layer structures were observed and the expression of Pgp decreased. Polyester and polyethylene terephthalate membrane supports decreased the paracellular transport rates substantially, while collagen-coating of PC inserts showed no influence on the morphology and even increased carrier-mediated transporter expression. An average seeding density of 6x10(4) cells/cm(2) seemed to be most favorable, since lower seeding densities led to thin monolayers with altered tight junctions and higher seeding densities to the formation of multilayers. In summary, the expression of carrier-mediated transporters was strongly affected by the culture conditions. The full differentiation was reached after 21 days on collagen-coated polycarbonate inserts at an initial seeding density of 6x10(4) cells/cm(2).
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Affiliation(s)
- Isabel Behrens
- Department of Pharmaceutics and Biopharmacy, University of Marburg, Philipps-University, Ketzerbach 63, D-35032, Marburg/Lahn, Germany
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Urayama A, Yamada S, Deguchi Y, Ohmori Y, Kimura R. Studies on the transport of thyrotropin-releasing hormone (TRH) analogues in Caco-2 cell monolayers. J Pharm Pharmacol 2003; 55:603-8. [PMID: 12831502 DOI: 10.1211/002235703765344504] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
The transport mechanisms of thyrotropin-releasing hormone (TRH) and its pharmacologically active analogues ((3-methyl-His(2))TRH (MeTRH), taltirelin, montirelin, azetirelin) across Caco-2 cell monolayers were characterized. The results of kinetic analysis showed a linear relationship between the concentration (over the range 0.5-10 mM) and apical-to-basolateral transport rate of these agents. The permeability coefficients (P(app)) of these agents were not substantially different from each other, and their P(app) ratios of the basolateral-to-apical over the apical-to-basolateral transport were close to one (0.73-1.23). The cellular transport of [(3)H]MeTRH at low concentrations (3-15 nM) showed a linear relationship between the concentration and transport rate. The transport of [(3)H]MeTRH in Caco-2 cell monolayers was neither affected by TRH nor TRH analogues, and there was little difference in P(app) values between [(3)H]MeTRH and [(14)C]mannitol. The cell-per-medium ratio of [(3)H]MeTRH in the cellular uptake experiment was similar to the value of [14C]mannitol. A large excess of TRH and MeTRH did not significantly influence cell-per-medium ratios of [(3)H]MeTRH in Caco-2 cell monolayers. The k'(IAM) value, which represents lipophilicity, was decreased in the following order: montirelin > taltirelin > TRH > azetirelin, and the values varied from 0.234 to 1.028. These results indicate that a paracellular passive diffusion may be the major route for the transport of TRH and its analogues in Caco-2 cell monolayers.
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Affiliation(s)
- Akihiko Urayama
- Department of Biopharmacy, School of Pharmaceutical Sciences and COE21, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan
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Guo A, Marinaro W, Hu P, Sinko PJ. Delineating the contribution of secretory transporters in the efflux of etoposide using Madin-Darby canine kidney (MDCK) cells overexpressing P-glycoprotein (Pgp), multidrug resistance-associated protein (MRP1), and canalicular multispecific organic anion transporter (cMOAT). Drug Metab Dispos 2002; 30:457-63. [PMID: 11901101 DOI: 10.1124/dmd.30.4.457] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Multidrug resistance conferred to cancer cells is often mediated by the expression of efflux transporter "pumps". It is also believed that many of the same transporters are involved in drug efflux from numerous normal endothelial and epithelial cell types in the intestine, brain, kidney, and liver. Etoposide transport kinetics were characterized in Caco-2 cells and in well established Madin-Darby canine kidney (MDCKII) cell lines that were stably-transfected with a human cDNA encoding P-glycoprotein (Pgp), human multidrug resistance protein (MRP1), or the canalicular multispecific organic anion (cMOAT) transporters to determine the roles of these transporters in etoposide efflux. Etoposide transport kinetics were concentration-dependent in the MDCKII-MDR1 and MDCKII-cMOAT cells. The apparent secretory Michaelis constant (Km) and carrier-mediated permeability (Pc) values for Pgp and cMOAT were 254.96 +/- 94.39 microM and 5.96 +/- 0.41 x 10(-6) cm/s and 616.54 +/- 163.15 microM and 1.87 +/- 0.10 x 10(-5) cm/s, respectively. The secretory permeability of etoposide decreased significantly in the basal to apical (B to A) (i.e., efflux) direction, whereas the permeability increased 2.3-fold in the apical to basal (A to B) direction in MDCKII-MDR1 cells in the presence of elacridar (GF120918). Moderate inhibition of etoposide efflux by leukotriene C4 (LTC4) was observed in MDCKII-cMOAT cells. Furthermore, etoposide inhibited LTC4 efflux, confirming the involvement of cMOAT. The flux of etoposide in MDCKII-MRP1 cells was similar to that in MDCKII/wt control cells. The current results demonstrate that the secretory transport mechanism of etoposide involves multiple transporters, including Pgp and cMOAT but not MRP1. These results demonstrate that Pgp and cMOAT are involved in the intestinal secretory transport of etoposide. Since the intestinal secretion of etoposide was previously reported in the literature, it also suggests that they may be involved in the in vivo intestinal secretion of etoposide; however, mechanistic in vivo studies are required to confirm this.
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Affiliation(s)
- Ailan Guo
- Department of Pharmaceutics, School of Pharmacy, Rutgers University, Piscataway, New Jersey 08854, USA
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Lo CM, Keese CR, Giaever I. Cell-substrate contact: another factor may influence transepithelial electrical resistance of cell layers cultured on permeable filters. Exp Cell Res 1999; 250:576-80. [PMID: 10413610 DOI: 10.1006/excr.1999.4538] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Transepithelial resistance (TER) measurement has often been used to study the paracellular transport properties of epithelia grown on permeable filters, especially the barrier function of tight junctions. However, the TER value includes another source, the resistance caused by cell-substrate contact, that may give rise to a high TER value if cell-substrate separation is small. In this study we use electric cell-substrate impedance sensing (ECIS) to measure both paracellular resistance and the average cell-substrate distance of MDCK (II), HEp-2, and WI-38 VA13 cells. Comparing ECIS data with those from TER measurements of cell layers cultured on polycarbonate filters, we can obtain the approximate extra resistance resulting from cell-substrate contact for each cell type. The value of cell-substrate resistance was also estimated by two theoretical calculations that bracket the true values. Our results demonstrate that cell-substrate contact substantially influences the TER data measured using polycarbonate filters and that the extra resistance due to cell-substrate spaces depends on both cell type and filter property.
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Affiliation(s)
- C M Lo
- Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts, 01605, USA
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18
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Pauletti GM. Peptidomimetics designed for oral absorption. ACTA ACUST UNITED AC 1999. [DOI: 10.1016/s1874-5113(99)80005-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
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Irvine JD, Takahashi L, Lockhart K, Cheong J, Tolan JW, Selick HE, Grove JR. MDCK (Madin-Darby canine kidney) cells: A tool for membrane permeability screening. J Pharm Sci 1999; 88:28-33. [PMID: 9874698 DOI: 10.1021/js9803205] [Citation(s) in RCA: 629] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The goal of this work was to investigate the use of MDCK (Madin-Darby canine kidney) cells as a possible tool for assessing the membrane permeability properties of early drug discovery compounds. Apparent permeability (Papp) values of 55 compounds with known human absorption values were determined using MDCK cell monolayers. For comparison, Papp values of the same compounds were also determined using Caco-2 cells, a well-characterized in vitro model of intestinal drug absorption. Monolayers were grown on 0. 4-microm Transwell-COL membrane culture inserts. MDCK cells were seeded at high density and cultured for 3 days, and Caco-2 cells were cultured under standard conditions for 21 to 25 days. Compounds were tested using 100 microM donor solutions in transport medium (pH 7.4) containing 1% DMSO. The Papp values in MDCK cells correlated well with those in Caco-2 cells (r2 = 0.79). Spearman's rank correlation coefficient for MDCK Papp and human absorption was 0.58 compared with 0.54 for Caco-2 Papp and human absorption. These results indicate that MDCK cells may be a useful tool for rapid membrane permeability screening.
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Affiliation(s)
- J D Irvine
- Affymax Research Institute (a Glaxo Wellcome Company), Santa Clara, California 95051,
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20
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Gangwar S, Pauletti GM, Wang B, Siahaan TJ, Stella VJ, Borchardt RT. Prodrug strategies to enhance the intestinal absorption of peptides. Drug Discov Today 1997. [DOI: 10.1016/s1359-6446(97)01011-8] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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21
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Okumu FW, Pauletti GM, Vander Velde DG, Siahaan TJ, Borchardt RT. Effect of restricted conformational flexibility on the permeation of model hexapeptides across Caco-2 cell monolayers. Pharm Res 1997; 14:169-75. [PMID: 9090704 DOI: 10.1023/a:1012092409216] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
PURPOSE To determine how restricted conformational flexibility of hexapeptides influences their cellular permeation characteristics. METHODS Linear (Ac-Trp-Ala-Gly-Gly-X-Ala-NH2; X = Asp, Asn, Lys) and cyclic (cyclo[Trp-Ala-Gly-Gly-X-Ala]; X = Asp, Asn, Lys) hexapeptides were synthesized, and their transport characteristics were assessed using the Caco-2 cell culture model. The lipophilicities of the hexapeptides were determined using an immobilized artificial membrane. Diffusion coefficients used to calculate molecular radii were determined by NMR. Two-dimensional NMR spectroscopy, circular dichroism, and molecular dynamic simulations were used to elucidate the most favorable solution structure of the cyclic Asp-containing peptide. RESULTS The cyclic hexapeptides used in this study were 2-3 times more able to permeate (e.g., Papp = 9.3 +/- 0.3 x 10(-8) cm/sec, X = Asp) the Caco-2 cell monolayer than were their linear analogs (e.g., Papp = 3.2 +/- 0.3 x 10(-8) cm/sec, X = Asp). In contrast to the linear hexapeptides, the flux of the cyclic hexapeptides was independent of charge. The cyclic hexapeptides were shown to be more lipophilic than the linear hexapeptides as determined by their retention times on an immobilized phospholipid column. Determination of molecular radii by two different techniques suggests little or no difference in size between the linear and cyclic hexapeptides. Spectroscopic data indicate that the Asp-containing linear hexapeptide exists in a dynamic equilibrium between random coil and beta-turn structures while the cyclic Asp-containing hexapeptide exists in a well-defined compact amphophilic structure containing two beta-turns. CONCLUSIONS Cyclization of the linear hexapeptides increased their lipophilicities. The increased permeation characteristics of the cyclic hexapeptides as compared to their linear analogs appears to be due to an increase in their flux via the transcellular route because of these increased lipophilicities. Structural analyses of the cyclic Asp-containing hexapeptide suggest that its well-defined solution structure and, specifically the existence of two beta-turns, explain its greater lipophilicity.
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Affiliation(s)
- F W Okumu
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66047, USA
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22
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23
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Tanaka K, Fujita T, Yamamoto Y, Murakami M, Yamamoto A, Muranishi S. Enhancement of intestinal transport of thyrotropin-releasing hormone via a carrier-mediated transport system by chemical modification with lauric acid. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1283:119-26. [PMID: 8765103 DOI: 10.1016/0005-2736(96)00087-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The transport characteristics of thyrotropin-releasing hormone (TRH) and its chemically modified derivative with lauric acid (Lau-TRH) across the rat small or large intestine were estimated by means of an in vitro everted sac experiment. Both compounds were especially absorbed from the upper small intestine. The penetration of TRH across the upper small intestine was significantly increased by conjugation with lauric acid. Lau-TRH administered to the mucosal side appeared as a native TRH form in the serosal side. On the other hand, a temperature dependency and a directional difference in the transfer rates of these compounds were observed in the everted and non-everted sacs of the upper small intestine. Moreover, the penetration of TRH and Lau-TRH across the upper small intestine was inhibited by 0.25 mM 2,4-dinitrophenol and 10 mM glycylglycine. In addition, Lau-TRH was very stable in the cytosolic fraction of the small intestinal mucosa, while it was gradually converted to the native TRH in the brush-border membrane (BBM) fraction. The binding amounts of TRH to the BBM were remarkably enhanced by the lauric acid conjugation; however, its binding was nonspecific. Therefore, it was suggested that Lau-TRH rapidly bound to the BBM in the small intestine, where Lau-TRH is converted to TRH, and this released TRH is efficiently transported by an oligopeptide transporter which exists in the upper small intestine.
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Affiliation(s)
- K Tanaka
- Department of Biopharmaceutics, Kyoto Pharmaceutical University, Japan
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25
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Lu S, Gough AW, Bobrowski WF, Stewart BH. Transport properties are not altered across Caco-2 cells with heightened TEER despite underlying physiological and ultrastructural changes. J Pharm Sci 1996; 85:270-3. [PMID: 8699327 DOI: 10.1021/js950269u] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Selected properties of Caco-2 cells were examined after disparate transepithelial electrical resistance (TEER) measurements were observed in two populations of Caco-2 cells. Comparisons were made between the early passages of Caco-2 cells (Caco-2E, passages 35-47) and the later passages of cells (Caco-2L, passages 87-112). Transmission electron microscopy revealed that regions of Caco-2L cells were composed of multiple cell layers rather than the monolayers observed in Caco-2E cells. Epithelial cell height (or barrier thickness) was not significantly different between the two cell populations. Intercellular and intracellular lumina were observed in the Caco-2L cells, but not in the Caco-2E cells. Results of [3H]thymidine incorporation assays showed significantly higher cell proliferation rates in Caco-2L cells relative to Caco-2E cells. Despite morphological and physiological changes, there were no significant differences in the apparent permeabilities for D-mannitol (paracellular diffusion marker), hydrocortisone (transcellular diffusion marker), or dipeptide, Gly-Sar (carrier-mediated transcellular transport marker) between the two populations of cells. The higher TEER values in Caco-2L cells may be the results of a slight perturbation of tight junctions associated with both the multiple cell layers and the presence of intercellular lumina.
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Affiliation(s)
- S Lu
- Department of Pharmacokinetics/Drug Metabolism, Parke-Davis Research Division, Warner-Lambert Company, Ann Arbor, MI 48105, USA
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26
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Kobayashi S, Kondo S, Juni K. Permeability of peptides and proteins in human cultured alveolar A549 cell monolayer. Pharm Res 1995; 12:1115-9. [PMID: 7494821 DOI: 10.1023/a:1016295406473] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
PURPOSE The transport of peptides or proteins across the alveolar cell monolayer was studied in vitro in order to elucidate their transport pathway. METHODS The permeability of 14 peptides or proteins and 6 dextrans with MW 1,000-150,000 was measured in cultured human lung adenocarcinoma A549 cell monolayers at 37 degrees C or 4 degrees C. The stability of the tested peptides and proteins was also evaluated. RESULTS The permeability coefficients of these macromolecules across the A549 cell monolayer at 37 degrees C ranged from 10(-5) to 10(-7) (cm/sec), and exhibited a good inverse correlation with molecular weight. All macromolecules were stable throughout the transport experiment, and degradation by proteases was minimal. Permeability at 4 degrees C did not differ from that at 37 degrees C. Clear selectivity for direction of transport was not observed. CONCLUSIONS These results suggested that the tested peptides and proteins appeared to penetrate the A549 cell monolayer via a paracellular route by passive diffusion.
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Affiliation(s)
- S Kobayashi
- Pharma Research and Development Division, Hoechst Japan Limited, Saitama, Japan
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27
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Boulenc X, Roques C, Joyeux H, Berger Y, Fabre G. Bisphosphonates increase tight junction permeability in the human intestinal epithelial (Caco-2) model. Int J Pharm 1995. [DOI: 10.1016/0378-5173(95)00022-b] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Walter E, Kissel T. Transepithelial transport and metabolism of thyrotropin-releasing hormone (TRH) in monolayers of a human intestinal cell line (Caco-2): evidence for an active transport component? Pharm Res 1994; 11:1575-80. [PMID: 7870674 DOI: 10.1023/a:1018953603301] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Cell culture models for gastrointestinal transport and metabolism are important mechanistic tools. Our studies of Caco-2 monolayers demonstrate heterogeneity in transport characteristics depending on passage number and origin of the cells. In accordance with data obtained in animals and humans, TRH shows a carrier-mediated, saturable transport component, which operates parallel to a passive pathway in Caco-2 cells at passage number 89-99. At low TRH concentrations (< 3 mM) active transport becomes prominent, as demonstrated by the temperature dependence of TRH transport and inhibition experiments. The Michaelis-Menten parameters of the active, saturable transport component are: Km = 1.59 mM and Vmax = 1.84 microM/min. The pH optimum was determined to be at pH 6.0. On the other hand an exclusively paracellular passive route was found with Caco-2 cells at passage number 30-34. These results are also in agreement with observations made by others in cell culture experiments. The aspect of rigorously characterizing the specific Caco-2 clone under investigation is emphasized, especially when active transport mechanisms are suspected.
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Affiliation(s)
- E Walter
- Department of Pharmaceutics and Biopharmacy, University of Marburg, Germany
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Thwaites DT, Hirst BH, Simmons NL. Substrate specificity of the di/tripeptide transporter in human intestinal epithelia (Caco-2): identification of substrates that undergo H(+)-coupled absorption. Br J Pharmacol 1994; 113:1050-6. [PMID: 7858848 PMCID: PMC1510430 DOI: 10.1111/j.1476-5381.1994.tb17099.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
1. pH-dependent transepithelial transport and intracellular accumulation of the hydrolysis-resistant dipeptide glycylsarcosine (Gly-Sar) have been demonstrated in the model human intestinal epithelial cell line, Caco-2. 2. Experiments with BCECF (2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein)-loaded Caco-2 cells demonstrated that dipeptide (Gly-Sar) transport across the apical membrane is coupled to proton flow into the cell. 3. A range of postulated substrates for the intestinal di/tripeptide carrier were tested for their abilities to: (a) inhibit pH-dependent [14C]Gly-Sar apical-to-basal transport and intracellular accumulation and (b) stimulate H+ flow across the apical surface of BCECF-loaded Caco-2 cell monolayers. 4. A range of compounds (including Gly-Gly, Leu-Leu, Gly-Gly-Gly, cefadroxil and cephalexin) caused marked acidification of intracellular pH when perfused at the apical surface of Caco-2 cell monolayers. In contrast leucine and D-Leu-D-Leu failed to induce proton flow. The ability to induce proton-flow across the apical surface by these compounds, in this intestinal epithelium, was directly correlated to the relative inhibitory effects on [14C]-Gly-Sar transport and accumulation. 5. The determination of substrate-induced intracellular pH change in the Caco-2 cell system may provide a useful rapid screen for candidate substrates for absorption via H(+)-coupled transport mechanisms such as the intestinal di/tripeptide carrier in an appropriate physiological context.
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Affiliation(s)
- D T Thwaites
- Department of Physiological Sciences, University of Newcastle upon Tyne, Medical School
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Collares-Buzato CB, McEwan GT, Jepson MA, Simmons NL, Hirst BH. Paracellular barrier and junctional protein distribution depend on basolateral extracellular Ca2+ in cultured epithelia. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1222:147-58. [PMID: 8031850 DOI: 10.1016/0167-4889(94)90163-5] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The polarised nature of the increase in paracellular permeability induced by Ca(2+)-chelation with EGTA was investigated in several cultured epithelial cell lines. In strain I MDCK cells (canine kidney cells), a marked decrease (> 90%) in transepithelial electrical resistance (RT) and increase in mannitol and inulin permeabilities were only observed after addition of EGTA (for 4 h) to either basolateral (basal) or both (apical+basal) bathing solutions; apical Ca(2+)-chelation resulted in significant smaller changes (approximately 30%) in these variables. The increase in paracellular permeability upon basal EGTA addition was significantly lower than that produced by simultaneous apical and basal addition of 2 mM EGTA. A higher concentration of EGTA (20 mM) did not significantly eliminate this difference in potency between basal and apical+basal Ca(2+)-chelation. The polarised Ca(2+)-dependence of the paracellular barrier was associated with polarised effects on the junctional/cytoskeletal protein distribution. Basal or apical+basal EGTA addition induced substantial internalisation of uvomorulin with some cellular redistribution of the perijunctional actin ring and desmosomes and gaps in ZO-1 location between adjacent cells. In addition, polarised Ca(2+)-dependence of the paracellular barrier (assessed by measuring RT) was observed also in strain II MDCK and two human adenocarcinoma intestinal cell lines, Caco-2 and HCT-8, demonstrating generality of the phenomenon. Therefore, the data show a polarity in the ability of EGTA to enhance epithelial permeability and induce cellular redistribution of cytoskeletal/junctional proteins in several epithelia. The basolateral membrane sensitivity to Ca(2+)-chelation might be explained by the polarised distribution of uvomorulin.
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Affiliation(s)
- C B Collares-Buzato
- Gastrointestinal Drug Delivery Research Centre, University of Newcastle upon Tyne, Medical School, UK
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Thwaites DT, Brown CD, Hirst BH, Simmons NL. H(+)-coupled dipeptide (glycylsarcosine) transport across apical and basal borders of human intestinal Caco-2 cell monolayers display distinctive characteristics. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1151:237-45. [PMID: 8373798 DOI: 10.1016/0005-2736(93)90108-c] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Transepithelial transport and intracellular accumulation of the dipeptide glycylsarcosine (Gly-Sar) were studied using intact monolayers of the human intestinal epithelial cell line, Caco-2. Gly-Sar transport was demonstrated in both absorptive (apical-to-basal) and secretory (basal-to-apical) directions. In both directions, transport and accumulation were enhanced in the presence of a pH gradient (pHo < pHi). Under conditions similar to those found at the intestinal membrane in vivo (apical pH 6.0, basolateral pH 7.4), net absorption (145.2 pmol/cm2 per h) was observed, although experimental conditions could also be manipulated (apical pH 7.4, basolateral pH 6.0) so that net secretion was observed. Transport and accumulation (in both directions) were inhibited in the presence of either 20 mM (unlabelled) Gly-Sar or 20 mM cephalexin (an aminocephalosporin antibiotic). When added to either the apical or basolateral surface of BCECF (2',7',-bis(2-carboxyethyl)-5(6)-carboxyfluorescein)-loaded Caco-2 cell monolayers Gly-Sar (20 mM), at pH 6.0, caused a marked intracellular acidification, demonstrating that dipeptide absorption is accompanied by H(+)-flow into the cells. Cephalexin (20 mM) had similar effects (as Gly-Sar) when presented at the apical surface but also caused a marked intracellular acidification when perfused into the basolateral chamber at pH 7.4. In contrast, addition of Gly-Sar (20 mM) to the basolateral chamber (at pH 7.4) had no effect. Transepithelial absorption of dipeptides (Gly-Sar) and beta-lactam antibiotics (cephalexin) at low concentrations is predominately via a transcellular route mediated by carrier mechanisms located at both apical and basolateral membranes. Interestingly, Gly-Sar and cephalexin transport across the basolateral membrane (and, therefore, exit from the cell) display both common and distinct characteristics suggesting that more than one mechanism may be responsible for exit into the basolateral space.
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Affiliation(s)
- D T Thwaites
- Department of Physiological Sciences, University of Newcastle upon Tyne, Medical School, UK
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Thwaites DT, Simmons NL, Hirst BH. Thyrotropin-releasing hormone (TRH) uptake in intestinal brush-border membrane vesicles: comparison with proton-coupled dipeptide and Na(+)-coupled glucose transport. Pharm Res 1993; 10:667-73. [PMID: 8391693 DOI: 10.1023/a:1018995313180] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The mechanism of thyrotropin-releasing hormone (pGlu-His-Pro-NH2; TRH) uptake across the luminal membrane of intestinal enterocytes was investigated using brush-border membrane vesicles (BBMV) from rabbit duodenum and jejunum and rat upper small intestine. [14C]Glucose accumulated within the intestinal vesicles (at 10 sec), in the presence of an inwardly directed Na+ gradient, 7- to 14-fold higher than equilibrium values (65 min). The vesicles also accumulated the dipeptide [14C]Gly-Sar. Dipeptide uptake was greatest in the presence of both an inwardly directed proton gradient and an inside negative membrane potential. The H(+)-dependent Gly-Sar transport was not affected by the presence of an excess (46-fold) of cold TRH. In contrast to the observations with glucose and Gly-Sar, the uptake of [3H]TRH after 10 or 60 sec (in each of the vesicle preparations) was not enhanced by either Na+ or H+ gradient conditions. The absence of vesicular accumulation of TRH was not due to peptide hydrolysis. For example, after a 60-sec incubation with rabbit jejunal BBMV no degradation of the tripeptide was evident. After 65 min, 6% of [3H]TRH had undergone degradation, by deamidation, to form TRH-OH. These studies provide no evidence for the oral absorption of TRH by a Na(+)- or H(+)-dependent carrier system in the brush-border membrane. Previous observations of TRH absorption in vivo may be accounted for by passive absorption of the peptide combined with its relative resistance to luminal hydrolysis.
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Affiliation(s)
- D T Thwaites
- Gastrointestinal Drug Delivery Research Centre, University of Newcastle upon Tyne, U.K
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