1
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Mathew M, Nguyen NT, Bhutia YD, Sivaprakasam S, Ganapathy V. Metabolic Signature of Warburg Effect in Cancer: An Effective and Obligatory Interplay between Nutrient Transporters and Catabolic/Anabolic Pathways to Promote Tumor Growth. Cancers (Basel) 2024; 16:504. [PMID: 38339256 PMCID: PMC10854907 DOI: 10.3390/cancers16030504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2023] [Revised: 01/19/2024] [Accepted: 01/22/2024] [Indexed: 02/12/2024] Open
Abstract
Aerobic glycolysis in cancer cells, originally observed by Warburg 100 years ago, which involves the production of lactate as the end product of glucose breakdown even in the presence of adequate oxygen, is the foundation for the current interest in the cancer-cell-specific reprograming of metabolic pathways. The renewed interest in cancer cell metabolism has now gone well beyond the original Warburg effect related to glycolysis to other metabolic pathways that include amino acid metabolism, one-carbon metabolism, the pentose phosphate pathway, nucleotide synthesis, antioxidant machinery, etc. Since glucose and amino acids constitute the primary nutrients that fuel the altered metabolic pathways in cancer cells, the transporters that mediate the transfer of these nutrients and their metabolites not only across the plasma membrane but also across the mitochondrial and lysosomal membranes have become an integral component of the expansion of the Warburg effect. In this review, we focus on the interplay between these transporters and metabolic pathways that facilitates metabolic reprogramming, which has become a hallmark of cancer cells. The beneficial outcome of this recent understanding of the unique metabolic signature surrounding the Warburg effect is the identification of novel drug targets for the development of a new generation of therapeutics to treat cancer.
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Affiliation(s)
| | | | | | | | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA; (M.M.); (N.T.N.); (Y.D.B.); (S.S.)
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2
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Selle PH, Macelline SP, Chrystal PV, Liu SY. The Contribution of Phytate-Degrading Enzymes to Chicken-Meat Production. Animals (Basel) 2023; 13:ani13040603. [PMID: 36830391 PMCID: PMC9951704 DOI: 10.3390/ani13040603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/31/2023] [Accepted: 02/02/2023] [Indexed: 02/11/2023] Open
Abstract
The contribution that exogenous phytases have made towards sustainable chicken-meat production over the past two decades has been unequivocally immense. Initially, their acceptance by the global industry was negligible, but today, exogenous phytases are routine additions to broiler diets, very often at elevated inclusion levels. The genesis of this remarkable development is based on the capacity of phytases to enhance phosphorus (P) utilization, thereby reducing P excretion. This was amplified by an expanding appreciation of the powerful anti-nutritive properties of the substrate, phytate (myo-inositol hexaphosphate; IP6), which is invariably present in all plant-sourced feedstuffs and practical broiler diets. The surprisingly broad spectra of anti-nutritive properties harbored by dietary phytate are counteracted by exogenous phytases via the hydrolysis of phytate and the positive consequences of phytate degradation. Phytases enhance the utilization of minerals, including phosphorus, sodium, and calcium, the protein digestion, and the intestinal uptakes of amino acids and glucose to varying extents. The liberation of phytate-bound phosphorus (P) by phytase is fundamental; however, the impacts of phytase on protein digestion, the intestinal uptakes of amino acids, and the apparent amino acid digestibility coefficients are intriguing and important. Numerous factors are involved, but it appears that phytases have positive impacts on the initiation of protein digestion by pepsin. This extends to promoting the intestinal uptakes of amino acids stemming from the enhanced uptakes of monomeric amino acids via Na+-dependent transporters and, arguably more importantly, from the enhanced uptakes of oligopeptides via PepT-1, which is functionally dependent on the Na+/H+ exchanger, NHE. Our comprehension of the phytate-phytase axis in poultry nutrition has expanded over the past 30 years; this has promoted the extraordinary surge in acceptance of exogenous phytases, coupled with the development of more efficacious preparations in combination with the deflating inclusion costs for exogenous phytases. The purpose of this paper is to review the progress that has been made with phytate-degrading enzymes since their introduction in 1991 and the underlying mechanisms driving their positive contribution to chicken-meat production now and into the future.
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Affiliation(s)
- Peter H. Selle
- Poultry Research Foundation within The University of Sydney, Camden, NSW 2570, Australia
- Sydney School of Veterinary Science, The University of Sydney, Camden, NSW 2570, Australia
- Correspondence:
| | - Shemil P. Macelline
- Poultry Research Foundation within The University of Sydney, Camden, NSW 2570, Australia
- School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camden, NSW 2570, Australia
| | - Peter V. Chrystal
- Poultry Research Foundation within The University of Sydney, Camden, NSW 2570, Australia
- Complete Feed Solutions, Pakuranga, Auckland 2140, New Zealand
| | - Sonia Yun Liu
- Poultry Research Foundation within The University of Sydney, Camden, NSW 2570, Australia
- School of Life and Environmental Sciences, Faculty of Science, The University of Sydney, Camden, NSW 2570, Australia
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Sennoune SR, Nandagopal GD, Ramachandran S, Mathew M, Sivaprakasam S, Jaramillo-Martinez V, Bhutia YD, Ganapathy V. Potent Inhibition of Macropinocytosis by Niclosamide in Cancer Cells: A Novel Mechanism for the Anticancer Efficacy for the Antihelminthic. Cancers (Basel) 2023; 15:759. [PMID: 36765717 PMCID: PMC9913174 DOI: 10.3390/cancers15030759] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 01/17/2023] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
Niclosamide, a drug used to treat tapeworm infection, possesses anticancer effects by interfering with multiple signaling pathways. Niclosamide also causes intracellular acidification. We have recently discovered that the amino acid transporter SLC38A5, an amino acid-dependent Na+/H+ exchanger, activates macropinocytosis in cancer cells via amino acid-induced intracellular alkalinization. Therefore, we asked whether niclosamide will block basal and SLC38A5-mediated macropinocytosis via intracellular acidification. We monitored macropinocytosis in pancreatic and breast cancer cells using TMR-dextran and the function of SLC38A5 by measuring Li+-stimulated serine uptake. The peptide transporter activity was measured by the uptake of glycylsarcosine. Treatment of the cancer cells with niclosamide caused intracellular acidification. The drug blocked basal and serine-induced macropinocytosis with differential potency, with an EC50 of ~5 μM for the former and ~0.4 μM for the latter. The increased potency for amino acid-mediated macropinocytosis is due to direct inhibition of SLC38A5 by niclosamide in addition to the ability of the drug to cause intracellular acidification. The drug also inhibited the activity of the H+-coupled peptide transporter. We conclude that niclosamide induces nutrient starvation in cancer cells by blocking macropinocytosis, SLC38A5 and the peptide transporter. These studies uncover novel, hitherto unknown, mechanisms for the anticancer efficacy of this antihelminthic.
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Affiliation(s)
- Souad R. Sennoune
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | | | - Sabarish Ramachandran
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Marilyn Mathew
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Sathish Sivaprakasam
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Valeria Jaramillo-Martinez
- Department of Pharmacology and Neuroscience, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Yangzom D. Bhutia
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA
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4
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Polycystic ovary syndrome and iron overload: biochemical link and underlying mechanisms with potential novel therapeutic avenues. Biosci Rep 2023; 43:232133. [PMID: 36408981 PMCID: PMC9867939 DOI: 10.1042/bsr20212234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 11/08/2022] [Accepted: 11/21/2022] [Indexed: 11/23/2022] Open
Abstract
Polycystic ovary syndrome (PCOS) is an endocrine and metabolic disorder in women with components of significant genetic predisposition and possibly multiple, but not yet clearly defined, triggers. This disorder shares several clinical features with hemochromatosis, a genetically defined inheritable disorder of iron overload, which includes insulin resistance, increased adiposity, diabetes, fatty liver, infertility, and hyperandrogenism. A notable difference between the two disorders, however, is that the clinical symptoms in PCOS appear at much younger age whereas they become evident in hemochromatosis at a much later age. Nonetheless, noticeable accumulation of excess iron in the body is a common finding in both disorders even at adolescence. Hepcidin, the iron-regulatory hormone secreted by the liver, is reduced in both disorders and consequently increases intestinal iron absorption. Recent studies have shown that gut bacteria play a critical role in the control of iron absorption in the intestine. As dysbiosis is a common finding between PCOS and hemochromatosis, changes in bacterial composition in the gut may represent another cause for iron overload in both diseases via increased iron absorption. This raises the possibility that strategies to prevent accumulation of excess iron with iron chelators and/or probiotics may have therapeutic potential in the management of polycystic ovary syndrome.
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Koehler S, Springer A, Issel N, Klinger S, Wendt M, Breves G, Strube C. Effects of adult Ascaris suum and their antigens (total and trans-cuticular excretory-secretory antigen, cuticular somatic antigen) on intestinal nutrient transport in vivo. Parasitology 2022; 150:1-34. [PMID: 36274629 PMCID: PMC10090646 DOI: 10.1017/s0031182022001512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 09/20/2022] [Accepted: 10/14/2022] [Indexed: 11/05/2022]
Abstract
Ascaris suum constitutes a major problem in commercial pig farming worldwide. Lower weight gains in infected pigs probably result from impaired nutrient absorption. This study investigated intestinal nutrient transport in 4 groups of 6 pigs each, which were inoculated with 30 living adult A. suum , or antigen fractions consisting of (1) total excretory–secretory (ES) antigens of adult worms, (2) ES antigens secreted exclusively from the parasites' body surface (trans-cuticular ES) and (3) cuticular somatic antigens of A. suum , compared to placebo-treated controls. Three days after inoculation into the gastrointestinal tract, glucose, alanine and glycyl-l -glutamine transport was measured in the duodenum, jejunum and ileum using Ussing chambers. Transcription of relevant genes [sodium glucose cotransporter 1 (SGLT1), glucose transporter 1 (GLUT1), GLUT2, hypoxia-inducible factor 1-alpha (Hif1α ), interleukin-4 (IL-4), IL-13, signal transducer and activator of transcription 6 (STAT6), peptide transporter 1 (PepT1)] and expression of transport proteins [SGLT1, phosphorylated SGLT1, GLUT2, Na+/K+-ATPase, amino acid transporter A (ASCT1), PepT1] were studied. Although no significant functional changes were noted after exposure to adult A. suum , a significant downregulation of jejunal GLUT1, STAT6, Hif1α and PepT1 transcription as well as ileal GLUT2 and PepT1 expression indicates a negative impact of infection on transport physiology. Therefore, the exposure period of 3 days may have been insufficient for functional alterations to become apparent. In contrast, A. suum antigens mainly induced an upregulation of transport processes and an increase in transcription of relevant genes in the duodenum and jejunum, possibly as a compensatory reaction after a transient downregulation. In the ileum, a consistent pattern of downregulation was observed in all inoculated groups, in line with the hypothesis of impaired nutrient transport.
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Affiliation(s)
- Sarina Koehler
- Institute for Parasitology, Centre for Infection Medicine, University of Veterinary Medicine Hannover, Hanover, Germany
| | - Andrea Springer
- Institute for Parasitology, Centre for Infection Medicine, University of Veterinary Medicine Hannover, Hanover, Germany
| | - Nicole Issel
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, Hanover, Germany
| | - Stefanie Klinger
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, Hanover, Germany
| | - Michael Wendt
- Clinic for Swine, Small Ruminants, Forensic Medicine and Ambulatory Service, University of Veterinary Medicine Hannover, Hanover, Germany
| | - Gerhard Breves
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, Hanover, Germany
| | - Christina Strube
- Institute for Parasitology, Centre for Infection Medicine, University of Veterinary Medicine Hannover, Hanover, Germany
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6
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Anderson CMH, Edwards N, Watson AK, Althaus M, Thwaites DT. Reshaping the Binding Pocket of the Neurotransmitter:Solute Symporter (NSS) Family Transporter SLC6A14 (ATB 0,+) Selectively Reduces Access for Cationic Amino Acids and Derivatives. Biomolecules 2022; 12:biom12101404. [PMID: 36291613 PMCID: PMC9599917 DOI: 10.3390/biom12101404] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2022] [Revised: 09/25/2022] [Accepted: 09/29/2022] [Indexed: 11/16/2022] Open
Abstract
SLC6A14 (ATB0,+) is unique among SLC proteins in its ability to transport 18 of the 20 proteinogenic (dipolar and cationic) amino acids and naturally occurring and synthetic analogues (including anti-viral prodrugs and nitric oxide synthase (NOS) inhibitors). SLC6A14 mediates amino acid uptake in multiple cell types where increased expression is associated with pathophysiological conditions including some cancers. Here, we investigated how a key position within the core LeuT-fold structure of SLC6A14 influences substrate specificity. Homology modelling and sequence analysis identified the transmembrane domain 3 residue V128 as equivalent to a position known to influence substrate specificity in distantly related SLC36 and SLC38 amino acid transporters. SLC6A14, with and without V128 mutations, was heterologously expressed and function determined by radiotracer solute uptake and electrophysiological measurement of transporter-associated current. Substituting the amino acid residue occupying the SLC6A14 128 position modified the binding pocket environment and selectively disrupted transport of cationic (but not dipolar) amino acids and related NOS inhibitors. By understanding the molecular basis of amino acid transporter substrate specificity we can improve knowledge of how this multi-functional transporter can be targeted and how the LeuT-fold facilitates such diversity in function among the SLC6 family and other SLC amino acid transporters.
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Affiliation(s)
- Catriona M. H. Anderson
- School of Natural & Environmental Sciences, Faculty of Science, Engineering & Agriculture, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
- Correspondence: (C.M.H.A.); (D.T.T.)
| | - Noel Edwards
- Biosciences Institute, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Andrew K. Watson
- Biosciences Institute, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Mike Althaus
- School of Natural & Environmental Sciences, Faculty of Science, Engineering & Agriculture, Newcastle University, Newcastle upon Tyne NE1 7RU, UK
- Department of Natural Sciences & Institute for Functional Gene Analytics, Bonn-Rhein-Sieg University of Applied Sciences, 53359 Rheinbach, Germany
| | - David T. Thwaites
- Biosciences Institute, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
- Correspondence: (C.M.H.A.); (D.T.T.)
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7
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Khavinson V, Linkova N, Kozhevnikova E, Dyatlova A, Petukhov M. Transport of Biologically Active Ultrashort Peptides Using POT and LAT Carriers. Int J Mol Sci 2022; 23:ijms23147733. [PMID: 35887081 PMCID: PMC9323678 DOI: 10.3390/ijms23147733] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Revised: 07/11/2022] [Accepted: 07/12/2022] [Indexed: 01/27/2023] Open
Abstract
Ultrashort peptides (USPs), consisting of 2–7 amino-acid residues, are a group of signaling molecules that regulate gene expression and protein synthesis under normal conditions in various diseases and ageing. USPs serve as a basis for the development of drugs with a targeted mechanism of action. The purpose of this review is to systematize the available data on USP transport involving POT and LAT transporters in various organs and tissues under normal, pathological and ageing conditions. The carriers of the POT family (PEPT1, PEPT2, PHT1, PHT2) transport predominantly di- and tripeptides into the cell. Methods of molecular modeling and physicochemistry have demonstrated the ability of LAT1 to transfer not only amino acids but also some di- and tripeptides into the cell and out of it. LAT1 and 2 are involved in the regulation of the antioxidant, endocrine, immune and nervous systems’ functions. Analysis of the above data allows us to conclude that, depending on their structure, di- and tripeptides can be transported into the cells of various tissues by POT and LAT transporters. This mechanism is likely to underlie the tissue specificity of peptides, their geroprotective action and effectiveness in the case of neuroimmunoendocrine system disorders.
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Affiliation(s)
- Vladimir Khavinson
- Department of Biogerontology, Saint Petersburg Institute of Bioregulation and Gerontology, 197110 Saint Petersburg, Russia; (N.L.); (E.K.); (A.D.)
- Group of Peptide Regulation of Aging, Pavlov Institute of Physiology of Russian Academy of Sciences, 199034 Saint Petersburg, Russia
- Correspondence: or ; Tel.: +7-(921)-9110800
| | - Natalia Linkova
- Department of Biogerontology, Saint Petersburg Institute of Bioregulation and Gerontology, 197110 Saint Petersburg, Russia; (N.L.); (E.K.); (A.D.)
- The Laboratory “Problems of Aging”, Belgorod National Research University, 308015 Belgorod, Russia
| | - Ekaterina Kozhevnikova
- Department of Biogerontology, Saint Petersburg Institute of Bioregulation and Gerontology, 197110 Saint Petersburg, Russia; (N.L.); (E.K.); (A.D.)
| | - Anastasiia Dyatlova
- Department of Biogerontology, Saint Petersburg Institute of Bioregulation and Gerontology, 197110 Saint Petersburg, Russia; (N.L.); (E.K.); (A.D.)
| | - Mikhael Petukhov
- Petersburg Nuclear Physics Institute Named after B.P. Konstantinov, NRC “Kurchatov Institute”, 188300 Gatchina, Russia;
- Peter the Great St. Petersburg Group of Biophysics, Higher Engineering and Technical School, Peter the Great St. Petersburg Polytechnic University, 195251 Saint Petersburg, Russia
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8
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Expression and function of SLC38A5, an amino acid-coupled Na+/H+ exchanger, in triple-negative breast cancer and its relevance to macropinocytosis. Biochem J 2021; 478:3957-3976. [PMID: 34704597 PMCID: PMC8652584 DOI: 10.1042/bcj20210585] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Revised: 10/26/2021] [Accepted: 10/27/2021] [Indexed: 12/19/2022]
Abstract
Metabolic reprogramming in cancer necessitates increased amino acid uptake, which is accomplished by up-regulation of specific amino acid transporters. However, not all tumors rely on any single amino acid transporter for this purpose. Here, we report on the differential up-regulation of the amino acid transporter SLC38A5 in triple-negative breast cancer (TNBC). The up-regulation is evident in TNBC tumors, conventional and patient-derived xenograft TNBC cell lines, and a mouse model of spontaneous TNBC mammary tumor. The up-regulation is confirmed by functional assays. SLC38A5 is an amino acid-dependent Na+/H+ exchanger which transports Na+ and amino acids into cells coupled with H+ efflux. Since cell-surface Na+/H+ exchanger is an established inducer of macropinocytosis, an endocytic process for cellular uptake of bulk fluid and its components, we examined the impact of SLC38A5 on macropinocytosis in TNBC cells. We found that the transport function of SLC38A5 is coupled to the induction of macropinocytosis. Surprisingly, the transport function of SLC38A5 is inhibited by amilorides, the well-known inhibitors of Na+/H+ exchanger. Down-regulation of SLC38A5 in TNBC cells attenuates serine-induced macropinocytosis and reduces cell proliferation significantly as assessed by multiple methods, but does not induce cell death. The Cancer Genome Atlas database corroborates SLC38A5 up-regulation in TNBC. This represents the first report on the selective expression of SLC38A5 in TNBC and its role as an inducer of macropinocytosis, thus revealing a novel, hitherto unsuspected, function for an amino acid transporter that goes beyond amino acid delivery but is still relevant to cancer cell nutrition and proliferation.
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Koehler S, Springer A, Issel N, Klinger S, Wendt M, Breves G, Strube C. Ascaris suum Nutrient Uptake and Metabolic Release, and Modulation of Host Intestinal Nutrient Transport by Excretory-Secretory and Cuticle Antigens In Vitro. Pathogens 2021; 10:pathogens10111419. [PMID: 34832575 PMCID: PMC8618387 DOI: 10.3390/pathogens10111419] [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: 09/27/2021] [Revised: 10/27/2021] [Accepted: 10/29/2021] [Indexed: 11/16/2022] Open
Abstract
Ascaris suum, the most important pig parasite, also infects humans as a zoonotic pathogen. Malabsorption upon infection probably results from impaired nutrient transport, presumably mediated by the parasite’s excretory-secretory (ES) or cuticle somatic (CSO) antigens. The present study investigated the electrogenic transport (ΔIsc) of glucose, alanine and the dipeptide glycyl-l-glutamine (glygln), as well as glucose net flux rates in pig jejunal tissue after in vitro exposure to adult A. suum total ES or CSO antigens in Ussing chambers. ΔIsc of glucose, alanine and glucose net flux rate were significantly decreased after one hour of exposure to total ES antigen. In contrast, CSO antigens increased the transport of glygln. Additionally, nutrient uptake and ES antigen pattern were compared in culture medium from untreated adult worms and those with sealed mouth and anal openings. Untreated worms completely absorbed glucose, while cuticular absorption in sealed worms led to 90% reduction. Amino acid absorption was 30% less effective in sealed worms, and ammonia excretion decreased by 20%. Overall, the results show that A. suum total ES antigen rapidly impairs nutrient transport in vitro. Future studies confirming the results in vivo, narrowing down the ES components responsible and investigating underlying molecular mechanisms are needed.
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Affiliation(s)
- Sarina Koehler
- Institute for Parasitology, Centre for Infection Medicine, University of Veterinary Medicine Hannover, 30559 Hannover, Germany; (S.K.); (A.S.)
| | - Andrea Springer
- Institute for Parasitology, Centre for Infection Medicine, University of Veterinary Medicine Hannover, 30559 Hannover, Germany; (S.K.); (A.S.)
| | - Nicole Issel
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, 30173 Hannover, Germany; (N.I.); (S.K.); (G.B.)
| | - Stefanie Klinger
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, 30173 Hannover, Germany; (N.I.); (S.K.); (G.B.)
| | - Michael Wendt
- Clinic for Swine, Small Ruminants and Forensic Medicine, University of Veterinary Medicine Hannover, 30173 Hannover, Germany;
| | - Gerhard Breves
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, 30173 Hannover, Germany; (N.I.); (S.K.); (G.B.)
| | - Christina Strube
- Institute for Parasitology, Centre for Infection Medicine, University of Veterinary Medicine Hannover, 30559 Hannover, Germany; (S.K.); (A.S.)
- Correspondence: ; Tel.: +49-511-953-8711
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10
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Schniers BK, Rajasekaran D, Korac K, Sniegowski T, Ganapathy V, Bhutia YD. PEPT1 is essential for the growth of pancreatic cancer cells: a viable drug target. Biochem J 2021; 478:3757-3774. [PMID: 34569600 PMCID: PMC8589330 DOI: 10.1042/bcj20210377] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Revised: 09/17/2021] [Accepted: 09/27/2021] [Indexed: 12/14/2022]
Abstract
PEPT1 is a proton-coupled peptide transporter that is up-regulated in PDAC cell lines and PDXs, with little expression in the normal pancreas. However, the relevance of this up-regulation to cancer progression and the mechanism of up-regulation have not been investigated. Herein, we show that PEPT1 is not just up-regulated in a large panel of PDAC cell lines and PDXs but is also functional and transport-competent. PEPT2, another proton-coupled peptide transporter, is also overexpressed in PDAC cell lines and PDXs, but is not functional due to its intracellular localization. Using glibenclamide as a pharmacological inhibitor of PEPT1, we demonstrate in cell lines in vitro and mouse xenografts in vivo that inhibition of PEPT1 reduces the proliferation of the cancer cells. These findings are supported by genetic knockdown of PEPT1 with shRNA, wherein the absence of the transporter significantly attenuates the growth of cancer cells, both in vitro and in vivo, suggesting that PEPT1 is critical for the survival of cancer cells. We also establish that the tumor-derived lactic acid (Warburg effect) in the tumor microenvironment supports the transport function of PEPT1 in the maintenance of amino acid nutrition in cancer cells by inducing MMPs and DPPIV to generate peptide substrates for PEPT1 and by generating a H+ gradient across the plasma membrane to energize PEPT1. Taken collectively, these studies demonstrate a functional link between PEPT1 and extracellular protein breakdown in the tumor microenvironment as a key determinant of pancreatic cancer growth, thus identifying PEPT1 as a potential therapeutic target for PDAC.
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Affiliation(s)
- Bradley K. Schniers
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, U.S.A
| | - Devaraja Rajasekaran
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, U.S.A
| | - Ksenija Korac
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, U.S.A
| | - Tyler Sniegowski
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, U.S.A
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, U.S.A
| | - Yangzom D. Bhutia
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, U.S.A
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11
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Kou L, Sun R, Xiao S, Cui X, Sun J, Ganapathy V, Yao Q, Chen R. OCTN2-targeted nanoparticles for oral delivery of paclitaxel: differential impact of the polyethylene glycol linker size on drug delivery in vitro, in situ, and in vivo. Drug Deliv 2020; 27:170-179. [PMID: 31913724 PMCID: PMC6968687 DOI: 10.1080/10717544.2019.1710623] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Targeted nanocarriers have shown great promise in drug delivery because of optimized drug
behavior and improved therapeutic efficacy. How to improve the targeting efficiency of
nanocarriers for the maximum possible drug delivery is a critical issue. Here we developed
L-carnitine-conjugated nanoparticles targeting the carnitine transporter OCTN2 on
enterocytes for improved oral absorption. As a variable, we introduced various lengths of
the polyethylene glycol linker (0, 500, 1000, and 2000) between the nanoparticle surface
and the ligand (CNP, C5NP, C10NP and C20NP) to improve the ligand flexibility, and
consequently for more efficient interaction with the transporter, to enhance the oral
delivery of the cargo load into cells. An increased absorption was observed in cellular
uptake in vitro and in intestinal perfusion assay in
situ when the polyethylene glycol was introduced to link L-carnitine to the
nanoparticles; the highest absorption was achieved with C10NP. In contrast, the linker
decreased the absorption efficiency in vivo. As the presence or absence
of the mucus layer was the primary difference between in vitro/in
situ versus in vivo, the presence of this layer was the likely
reason for this differential effect. In summary, the size of the polyethylene glycol
linker improved the absorption in vitro and in situ, but
interfered with the absorption in vivo. Even though this strategy of
increasing the ligand flexibility with the variable size of the polyethylene glycol failed
to increase oral absorption in vivo, this approach is likely to be useful
for enhanced cellular uptake following intravenous administration of the nanocarriers.
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Affiliation(s)
- Longfa Kou
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Rui Sun
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China.,School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, China
| | - Shuyi Xiao
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Xiao Cui
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
| | - Jin Sun
- Department of Pharmaceutics, Wuya College of Innovation, Shenyang Pharmaceutical University, Shenyang, China
| | - Vadivel Ganapathy
- Department of Cell Biology and Biochemistry, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, USA
| | - Qing Yao
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou, China
| | - Ruijie Chen
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, China
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12
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Kou L, Yao Q, Zhang H, Chu M, Bhutia YD, Chen R, Ganapathy V. Transporter-Targeted Nano-Sized Vehicles for Enhanced and Site-Specific Drug Delivery. Cancers (Basel) 2020; 12:E2837. [PMID: 33019627 PMCID: PMC7599460 DOI: 10.3390/cancers12102837] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Revised: 09/26/2020] [Accepted: 09/29/2020] [Indexed: 12/17/2022] Open
Abstract
Nano-devices are recognized as increasingly attractive to deliver therapeutics to target cells. The specificity of this approach can be improved by modifying the surface of the delivery vehicles such that they are recognized by the target cells. In the past, cell-surface receptors were exploited for this purpose, but plasma membrane transporters also hold similar potential. Selective transporters are often highly expressed in biological barriers (e.g., intestinal barrier, blood-brain barrier, and blood-retinal barrier) in a site-specific manner, and play a key role in the vectorial transfer of nutrients. Similarly, selective transporters are also overexpressed in the plasma membrane of specific cell types under pathological states to meet the biological needs demanded by such conditions. Nano-drug delivery systems could be strategically modified to make them recognizable by these transporters to enhance the transfer of drugs across the biological barriers or to selectively expose specific cell types to therapeutic drugs. Here, we provide a comprehensive review and detailed evaluation of the recent advances in the field of transporter-targeted nano-drug delivery systems. We specifically focus on areas related to intestinal absorption, transfer across blood-brain barrier, tumor-cell selective targeting, ocular drug delivery, identification of the transporters appropriate for this purpose, and details of the rationale for the approach.
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Affiliation(s)
- Longfa Kou
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Zhejiang 325027, China;
- Wenzhou Municipal Key Laboratory of Pediatric Pharmacy, Zhejiang 325027, China; (Q.Y.); (H.Z.); (M.C.)
| | - Qing Yao
- Wenzhou Municipal Key Laboratory of Pediatric Pharmacy, Zhejiang 325027, China; (Q.Y.); (H.Z.); (M.C.)
- Department of Pharmaceutical Sciences, Wenzhou Medical University, Zhejiang 325035, China
| | - Hailin Zhang
- Wenzhou Municipal Key Laboratory of Pediatric Pharmacy, Zhejiang 325027, China; (Q.Y.); (H.Z.); (M.C.)
- Department of Children’s Respiration Disease, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Zhejiang 325027, China
| | - Maoping Chu
- Wenzhou Municipal Key Laboratory of Pediatric Pharmacy, Zhejiang 325027, China; (Q.Y.); (H.Z.); (M.C.)
- Pediatric Research Institute, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Zhejiang 325027, China
| | - Yangzom D. Bhutia
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
| | - Ruijie Chen
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Zhejiang 325027, China;
- Wenzhou Municipal Key Laboratory of Pediatric Pharmacy, Zhejiang 325027, China; (Q.Y.); (H.Z.); (M.C.)
| | - Vadivel Ganapathy
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children’s Hospital of Wenzhou Medical University, Zhejiang 325027, China;
- Wenzhou Municipal Key Laboratory of Pediatric Pharmacy, Zhejiang 325027, China; (Q.Y.); (H.Z.); (M.C.)
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX 79430, USA;
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13
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Nielsen CU, Pedersen M, Müller S, Kæstel T, Bjerg M, Ulaganathan N, Nielsen S, Carlsen KL, Nøhr MK, Holm R. Inhibitory Effects of 17-α-Ethinyl-Estradiol and 17-β-Estradiol on Transport Via the Intestinal Proton-Coupled Amino Acid Transporter (PAT1) Investigated In Vitro and In Vivo. J Pharm Sci 2020; 110:354-364. [PMID: 32835702 DOI: 10.1016/j.xphs.2020.08.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 08/12/2020] [Accepted: 08/18/2020] [Indexed: 11/24/2022]
Abstract
The proton-coupled amino acid transporter, PAT1, is known to be responsible for intestinal absorption drug substances such as gaboxadol and vigabatrin. The aim of the present study was to investigate, if 17-α-ethinyl-estradiol (E-E2) and 17-β-estradiol (E) inhibit PAT1-mediated intestinal absorption of proline and taurine in vitro in Caco-2 cells and in vivo using Sprague-Dawley rats to assess the potential for taurine-drug interactions. E and E-E2 inhibited the PAT1-mediated uptake of proline and taurine in Caco-2 cells with IC50 values of 10.0-50.0 μM without major effect on other solute carriers such as the taurine transporter (TauT), di/tri-peptide transporter (PEPT1), and serotonin transporter (SERT1). In PAT1-expressing oocytes E and E-E2 were non-translocated inhibitors. In Caco-2 cells, E and E-E2 lowered the maximal uptake capacity of PAT1 in a non-competitive manner. Likewise, the transepithelial permeability of proline and taurine was reduced in presence of E and E-E2. In male Sprague Dawley rats pre-dosed with E-E2 a decreased maximal plasma concentration (Cmax) of taurine and increased the time (tmax) to reach this was indicated, suggesting the possibility for an in vivo effect on the absorption of PAT1 substrates. In conclusion, 17-α-ethinyl-estradiol and 17-β-estradiol were identified as non-translocated and non-competitive inhibitors of PAT1.
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Affiliation(s)
- Carsten Uhd Nielsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark.
| | - Maria Pedersen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Stefanie Müller
- Department of Pharmacy, Faculty of Health and Medical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Thea Kæstel
- Department of Pharmacy, Faculty of Health and Medical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - Maria Bjerg
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Nithiya Ulaganathan
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Salli Nielsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Krestine Lundgaard Carlsen
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, DK-5230 Odense M, Denmark
| | - Martha Kampp Nøhr
- Department of Pharmacy, Faculty of Health and Medical Sciences, Universitetsparken 2, DK-2100 Copenhagen, Denmark
| | - René Holm
- Drug Product Development, Janssen R&D, Johnson & Johnson, Turnhoutseweg 30, 2340 Beerse, Belgium; Department of Science and Environment, Roskilde University, 4000 Roskilde, Denmark
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14
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Klinger S. Segment-specific effects of resveratrol on porcine small intestinal dipeptide absorption depend on the mucosal pH and are due to different mechanisms: potential roles of different transport proteins and protein kinases. J Nutr Biochem 2020; 85:108467. [PMID: 32738496 DOI: 10.1016/j.jnutbio.2020.108467] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2019] [Revised: 07/02/2020] [Accepted: 07/13/2020] [Indexed: 12/15/2022]
Abstract
Numerous beneficial features of the polyphenol resveratrol (RSV) have been demonstrated in several tissues and cell culture models. There is also evidence, that RSV impairs intestinal nutrient transport but the underlying mechanisms are not understood. The aim of the present study was to evaluate whether RSV has also an impact on the H+-coupled transport of peptides via the peptide transporter 1 (PepT1) and to characterize RSV mediated changes in the apical abundance of nutrients transport proteins and protein kinases that may be involved. RSV decreased the H+-coupled transport of peptides in the porcine small intestines in a pH and location specific manner (jejunum vs ileum) as measured in Ussing chamber experiments. The comparison of the effects of RSV with the effects of the cAMP/PKA-activating agent forskolin indicates that different mechanisms may be responsible in the intestinal segments. Additionally, it seems that the transport of peptides and glucose in the jejunum are inhibited via the same mechanism while there might be two mechanisms involved in the ileum. Functional data and protein expression data indicate, that, besides PepT1, the activity of the Na+/H+-exchanger 3 (NHE3) may be involved. Protein kinase A (PKA) and AMP-activated kinase (AMPK) are both activated by RSV while the extracellular regulated kinase (ERK) and the serum and glucocorticoid induced kinase (SGK) are widely unaffected. Although PKA and AMPK are activated, AMPK seems not to be related to the effects of RSV. Additionally, both the functional data and the protein expression data reveal some interesting pH- and segment-specific differences.
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Affiliation(s)
- Stefanie Klinger
- Institute for Physiology and Cell Biology, University of Veterinary Medicine Hannover, Foundation, Hannover, Germany.
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15
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Kou L, Sun R, Jiang X, Lin X, Huang H, Bao S, Zhang Y, Li C, Chen R, Yao Q. Tumor Microenvironment-Responsive, Multistaged Liposome Induces Apoptosis and Ferroptosis by Amplifying Oxidative Stress for Enhanced Cancer Therapy. ACS APPLIED MATERIALS & INTERFACES 2020; 12:30031-30043. [PMID: 32459093 DOI: 10.1021/acsami.0c03564] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Tumor cells usually display metabolic, genetic, and microenvironment-related alterations, which are beneficial to tumor proliferation, tumor development, and resistance occurrence. Many transporters and enzymes, including ATB0,+, xCT, and matrix metalloproteinases (MMPs), are involved in the altered cell metabolism and tumor microenvironment and often abnormally upregulated in malignant tumors. Meanwhile, these dysregulated transporters and enzymes provide targets not only for a pharmacological blockage to suppress tumor progress but also for tumor-specific delivery. Although transporters and MMPs have been widely reported for antitumor drug delivery, the feasibility of utilizing two strategies has never been elucidated yet. Herein, we developed an MMP2-activated and ATB0,+-targeted liposome with doxorubicin and sorafenib (DS@MA-LS) loaded for optimal tumor drug delivery for cancer therapy. DS@MA-LS was designed to prolong blood circulation and deshield the PEG shell from MMP2 cleavage to expose lysine and target overexpressed ATB0,+ for enhanced tumor distribution and cancer cellular uptake. Besides the anticancer effects of loaded drugs, the endocytosed liposomes could further increase ROS production and suppress the antioxidant system to amplify oxidative stress. As expected, DS@MA-LS displayed enhanced targeted drug delivery to tumor sites with the MMP2-controlled ligand exposure and ATB0,+-mediated uptake. More importantly, DS@MA-LS successfully inhibited the tumor growth and cancer cell proliferation both in vitro and in vivo by enhancing apoptosis and ferroptosis, which thanks to the increased ROS generation and impaired GSH synthesis synergistically amplified oxidative stress. Our results suggested that the tumor microenvironment-responsive, multistaged nanoplatform, DS@MA-LS, has excellent potential for optimal drug delivery and enhanced cancer treatment.
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Affiliation(s)
- Longfa Kou
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Rui Sun
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Xinyu Jiang
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325027, China
| | - Xinlu Lin
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Huirong Huang
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Shihui Bao
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Youting Zhang
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Chao Li
- Scientific Center, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325027, China
| | - Ruijie Chen
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
| | - Qing Yao
- Department of Pharmacy, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou 325035, China
- School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325027, China
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16
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Chen Y, Dinges MM, Green A, Cramer SE, Larive CK, Lytle C. Absorptive transport of amino acids by the rat colon. Am J Physiol Gastrointest Liver Physiol 2020; 318:G189-G202. [PMID: 31760764 PMCID: PMC6985843 DOI: 10.1152/ajpgi.00277.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The capacity of the colon to absorb microbially produced amino acids (AAs) and the underlying mechanisms of AA transport are incompletely defined. We measured the profile of 16 fecal AAs along the rat ceco-colonic axis and compared unidirectional absorptive AA fluxes across mucosal tissues isolated from the rat jejunum, cecum, and proximal colon using an Ussing chamber approach, in conjunction with 1H-NMR and ultra-performance liquid chromatography-mass spectrometry chemical analyses. Passage of stool from cecum to midcolon was associated with segment-specific changes in fecal AA composition and a decrease in total AA content. Simultaneous measurement of up to 16 AA fluxes under native luminal conditions, with correction for endogenous AA release, demonstrated absorptive transfer of AAs across the cecum and proximal colon at rates comparable (30-80%) to those across the jejunum, with significant Na+-dependent and H+-stimulated components. Expression profiling of 30 major AA transporter genes by quantitative PCR revealed comparatively high levels of transcripts for 20 AA transporters in the cecum and/or colon, with the levels of 12 exceeding those in the small intestine. Our results suggest a more detailed model of major apical and basolateral AA transporters in rat colonocytes and provide evidence for a previously unappreciated transfer of AAs across the colonic epithelium that could link the prodigious metabolic capacities of the luminal microbiota, the colonocytes, and the body tissues.NEW & NOTEWORTHY This study provides evidence for a previously unappreciated transfer of microbially generated amino acids across the colonic epithelium under physiological conditions that could link the prodigious metabolic capacities of the luminal microbiota, the colonocytes, and the body tissues. The segment-specific expression of at least 20 amino acid transporter genes along the colon provides a detailed mechanistic basis for uniport, heteroexchange, Na+-cotransport, and H+-cotransport components of colonic amino acid absorption.
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Affiliation(s)
- Yuxin Chen
- 1Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California
| | - Meredith M. Dinges
- 2Department of Chemistry, University of California, Riverside, California
| | - Andrew Green
- 2Department of Chemistry, University of California, Riverside, California
| | - Scott E. Cramer
- 1Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California
| | - Cynthia K. Larive
- 2Department of Chemistry, University of California, Riverside, California
| | - Christian Lytle
- 1Division of Biomedical Sciences, School of Medicine, University of California, Riverside, California
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17
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Xu J, Zeug A, Riederer B, Yeruva S, Griesbeck O, Daniel H, Tuo B, Ponimaskin E, Dong H, Seidler U. Calcium-sensing receptor regulates intestinal dipeptide absorption via Ca 2+ signaling and IK Ca activation. Physiol Rep 2020; 8:e14337. [PMID: 31960592 PMCID: PMC6971415 DOI: 10.14814/phy2.14337] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Although absorption of di- and tripeptides into intestinal epithelial cells occurs via the peptide transporter 1 (PEPT1, also called solute carrier family 15 member 1 (SLC15A1)), the detailed regulatory mechanisms are not fully understood. We examined: (a) whether dipeptide absorption in villous enterocytes is associated with a rise in cytosolic Ca2+ ([Ca2+ ]cyt ), (b) whether the calcium sensing receptor (CaSR) is involved in dipeptide-elicited [Ca2+ ]cyt signaling, and (c) what potential consequences of [Ca2+ ]cyt signaling may enhance enterocyte dipeptide absorption. Dipeptide Gly-Sar and CaSR agonist spermine markedly raised [Ca2+ ]cyt in villous enterocytes, which was abolished by NPS-2143, a selective CaSR antagonist and U73122, an phospholipase C (PLC) inhibitor. Apical application of Gly-Sar induced a jejunal short-circuit current (Isc), which was reduced by NPS-2143. CaSR expression was identified in the lamina propria and on the basal enterocyte membrane of mouse jejunal mucosa in both WT and Slc15a1-/- animals, but Gly-Sar-induced [Ca2+ ]cyt signaling was significantly decreased in Slc15a1-/- villi. Clotrimazole and TRM-34, two selective blockers of the intermediate conductance Ca2+ -activated K+ channel (IKCa ), but not iberiotoxin, a selective blocker of the large-conductance K+ channel (BKCa ) and apamin, a selective blocker of the small-conductance K+ channel (SKCa ), significantly inhibited Gly-Sar-induced Isc in native tissues. We reveal a novel CaSR-PLC-Ca2+ -IKCa pathway in the regulation of small intestinal dipeptide absorption, which may be exploited as a target for future drug development in human nutritional disorders.
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Affiliation(s)
- Jingyu Xu
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
- Research GastroenterologyAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | - Andre Zeug
- Cellular NeurophysiologyHannover Medical SchoolHannoverGermany
| | - Brigitte Riederer
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
| | - Sunil Yeruva
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
| | | | - Hannelore Daniel
- Nutritional PhysiologyTechnical University of MunichFreisingGermany
| | - Biguang Tuo
- Research GastroenterologyAffiliated Hospital of Zunyi Medical UniversityZunyiChina
| | | | - Hui Dong
- Department of MedicineUniversity of California, San DiegoLa JollaCAUSA
| | - Ursula Seidler
- Department of Gastroenterology, Hepatology and EndocrinologyHannover Medical SchoolHannoverGermany
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18
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McCauley HA. Enteroendocrine Regulation of Nutrient Absorption. J Nutr 2020; 150:10-21. [PMID: 31504661 DOI: 10.1093/jn/nxz191] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/19/2019] [Accepted: 07/23/2019] [Indexed: 12/14/2022] Open
Abstract
Enteroendocrine cells (EECs) in the intestine regulate many aspects of whole-body physiology and metabolism. EECs sense luminal and circulating nutrients and respond by secreting hormones that act on multiple organs and organ systems, such as the brain, gallbladder, and pancreas, to control satiety, digestion, and glucose homeostasis. In addition, EECs act locally, on enteric neurons, endothelial cells, and the gastrointestinal epithelium, to facilitate digestion and absorption of nutrients. Many recent reports raise the possibility that EECs and the enteric nervous system may coordinate to regulate gastrointestinal functions. Loss of all EECs results in chronic malabsorptive diarrhea, placing EECs in a central role regulating nutrient absorption in the gut. Because there is increasing evidence that EECs can directly modulate the efficiency of nutrient absorption, it is possible that EECs are master regulators of a feed-forward loop connecting appetite, digestion, metabolism, and abnormally augmented nutrient absorption that perpetuates metabolic disease. This review focuses on the roles that specific EEC hormones play on glucose, peptide, and lipid absorption within the intestine.
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Affiliation(s)
- Heather A McCauley
- Division of Developmental Biology and the Center for Stem Cell and Organoid Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
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19
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Molecular mechanisms associated with acidification and alkalization along the larval midgut of Musca domestica. Comp Biochem Physiol A Mol Integr Physiol 2019; 237:110535. [DOI: 10.1016/j.cbpa.2019.110535] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 08/01/2019] [Accepted: 08/01/2019] [Indexed: 01/07/2023]
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20
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Gong X, Huang C, Yang X, Mao Q, Zeng L, Zheng P, Pu J, Chen J, Wang H, Xu B, Zhou C, Xie P. Proteomic analysis of the intestine reveals SNARE-mediated immunoregulatory and amino acid absorption perturbations in a rat model of depression. Life Sci 2019; 234:116778. [PMID: 31430454 DOI: 10.1016/j.lfs.2019.116778] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 08/08/2019] [Accepted: 08/16/2019] [Indexed: 02/07/2023]
Abstract
AIMS To clarify the role of the gut-brain axis in depression. MAIN METHODS We used the iTRAQ technique to identify differential proteins in the intestine of the rat model of chronic unpredictable mild stress (CUMS)-induced depression. Significant differential proteins were subjected to Gene Ontology (GO) functional annotations and KEGG pathway enrichment analysis. Key proteins were validated at the mRNA and protein levels. The levels of cytokines in the intestine, serum and hypothalamus were examined by ELISA. HPLC-UV was used to detect the levels of amino acids. KEY FINDINGS In the rat intestine, 349 differential proteins (209 downregulated, 140 upregulated) were identified. GO analysis indicated that "protein complex assembly" was the first-ranked biological process. SNARE complex components, including SNAP23, VAMP3 and VAMP8, were increased at the mRNA levels, while only VAMP3 and VAMP8 were also upregulated at the protein level. TNFα, IL6 and IL1β were upregulated in the CUMS rat intestine, while TNFα was decreased in the serum and hypothalamus. IL1β was decreased in the serum. "Protein digestion and absorption" was the most significantly enriched KEGG pathway, involving 5 differential proteins: SLC9A3, ANPEP, LAT1, ASCT2 and B0AT1. Glutamine, glycine and aspartic acid were perturbed in the CUMS rat intestine. SIGNIFICANCE Our findings suggest that CUMS enhances the adaptive immune response in the intestine through ER-phagosome pathway mediated by SNARE complex and disturb absorption of amino acids. It advances our understanding of the role of gut-brain axis in depression and provides a potential therapeutic target for the disease.
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Affiliation(s)
- Xue Gong
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Cheng Huang
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Xun Yang
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Qiang Mao
- Department of Pharmacy, the Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, China
| | - Li Zeng
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Department of Nephrology, the Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, China
| | - Peng Zheng
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Juncai Pu
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Jianjun Chen
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Haiyang Wang
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Bing Xu
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China
| | - Chanjuan Zhou
- Institute of Neuroscience and the Collaborative Innovation Center for Brain Science, Chongqing Medical University, Chongqing, China; Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China
| | - Peng Xie
- Chongqing Key Laboratory of Neurobiology, Chongqing 400016, China; Department of Neurology, the First Affiliated Hospital of Chongqing Medical University, Chongqing, China; Department of Neurology, Yongchuan Hospital, Chongqing Medical University, Chongqing 402160, China; Key Laboratory of Clinical Laboratory Diagnostics, Ministry of Education, Chongqing, China; South Australian Health and Medical Research Institute, Mind and Brain Theme, Adelaide, SA, Australia; Flinders University, Adelaide, SA, Australia.
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21
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Sun X, Zhu MJ. AMP-activated protein kinase: a therapeutic target in intestinal diseases. Open Biol 2018; 7:rsob.170104. [PMID: 28835570 PMCID: PMC5577448 DOI: 10.1098/rsob.170104] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 07/25/2017] [Indexed: 02/07/2023] Open
Abstract
Adenosine monophosphate (AMP)-activated protein kinase (AMPK), a highly conserved energy sensor, has a crucial role in cardiovascular, neurodegenerative and inflammatory diseases, as well as in cancer and metabolic disorders. Accumulating studies have demonstrated that AMPK activation enhances paracellular junctions, nutrient transporters, autophagy and apoptosis, and suppresses inflammation and carcinogenesis in the intestine, indicating an essential role of AMPK in intestinal health. AMPK inactivation is an aetiological factor in intestinal dysfunctions. This review summarizes the favourable outcomes of AMPK activation on intestinal health, and discusses AMPK as a potential therapeutic target for intestinal diseases.
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Affiliation(s)
- Xiaofei Sun
- School of Food Science, Washington State University, Pullman, WA 99164, USA.,School of Food Science, University of Idaho, Moscow, ID 83844, USA
| | - Mei-Jun Zhu
- School of Food Science, Washington State University, Pullman, WA 99164, USA .,School of Food Science, University of Idaho, Moscow, ID 83844, USA
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22
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Spanier B, Rohm F. Proton Coupled Oligopeptide Transporter 1 (PepT1) Function, Regulation, and Influence on the Intestinal Homeostasis. Compr Physiol 2018; 8:843-869. [DOI: 10.1002/cphy.c170038] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Viennois E, Pujada A, Zen J, Merlin D. Function, Regulation, and Pathophysiological Relevance of the POT Superfamily, Specifically PepT1 in Inflammatory Bowel Disease. Compr Physiol 2018; 8:731-760. [PMID: 29687900 DOI: 10.1002/cphy.c170032] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Mammalian members of the proton-coupled oligopeptide transporter family are integral membrane proteins that mediate the cellular uptake of di/tripeptides and peptide-like drugs and couple substrate translocation to the movement of H+ , with the transmembrane electrochemical proton gradient providing the driving force. Peptide transporters are responsible for the (re)absorption of dietary and/or bacterial di- and tripeptides in the intestine and kidney and maintaining homeostasis of neuropeptides in the brain. These proteins additionally contribute to absorption of a number of pharmacologically important compounds. In this overview article, we have provided updated information on the structure, function, expression, localization, and activities of PepT1 (SLC15A1), PepT2 (SLC15A2), PhT1 (SLC15A4), and PhT2 (SLC15A3). Peptide transporters, in particular, PepT1 are discussed as drug-delivery systems in addition to their implications in health and disease. Particular emphasis has been placed on the involvement of PepT1 in the physiopathology of the gastrointestinal tract, specifically, its role in inflammatory bowel diseases. © 2018 American Physiological Society. Compr Physiol 8:731-760, 2018.
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Affiliation(s)
- Emilie Viennois
- Institute for Biomedical Sciences, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia, USA
| | - Adani Pujada
- Institute for Biomedical Sciences, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia, USA
| | - Jane Zen
- Institute for Biomedical Sciences, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia, USA
| | - Didier Merlin
- Institute for Biomedical Sciences, Center for Diagnostics and Therapeutics, Georgia State University, Atlanta, Georgia, USA.,Veterans Affairs Medical Center, Decatur, Georgia, USA
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24
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Morris ME, Rodriguez-Cruz V, Felmlee MA. SLC and ABC Transporters: Expression, Localization, and Species Differences at the Blood-Brain and the Blood-Cerebrospinal Fluid Barriers. AAPS JOURNAL 2017; 19:1317-1331. [PMID: 28664465 DOI: 10.1208/s12248-017-0110-8] [Citation(s) in RCA: 101] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/05/2017] [Indexed: 12/11/2022]
Abstract
The blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB) separate the brain and cerebrospinal fluid (CSF) from the systemic circulation and represent a barrier to the uptake of both endogenous compounds and xenobiotics into the brain. For compounds whose passive diffusion is limited due to their ionization or hydrophilicity, membrane transporters can facilitate their uptake across the BBB or BCSFB. Members of the solute carrier (SLC) and ATP-binding case (ABC) families are present on these barriers. Differences exist in the localization and expression of transport proteins between the BBB and BCSFB, resulting in functional differences in transport properties. This review focuses on the expression, membrane localization, and different isoforms present at each barrier. Diseases that affect the central nervous system including brain tumors, HIV, Alzheimer's disease, Parkinson's disease, and stroke affect the integrity and expression of transporters at the BBB and BCSFB and will be briefly reviewed.
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Affiliation(s)
- Marilyn E Morris
- Department of Pharmaceutical Sciences, University at Buffalo, State University of New York at Buffalo, Buffalo, New York, 14214-8033, USA.
| | - Vivian Rodriguez-Cruz
- Department of Pharmaceutical Sciences, University at Buffalo, State University of New York at Buffalo, Buffalo, New York, 14214-8033, USA
| | - Melanie A Felmlee
- Department of Pharmaceutics and Medicinal Chemistry, Thomas J Long School of Pharmacy and Health Sciences, University of the Pacific, 3601 Pacific Ave, Stockton, California, 95211, USA
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25
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Johansson S, Rosenbaum DP, Palm J, Stefansson B, Knutsson M, Lisbon EA, Hilgendorf C. Tenapanor administration and the activity of the H + -coupled transporter PepT1 in healthy volunteers. Br J Clin Pharmacol 2017; 83:2008-2014. [PMID: 28432691 PMCID: PMC5582369 DOI: 10.1111/bcp.13313] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Revised: 04/06/2017] [Accepted: 04/18/2017] [Indexed: 12/24/2022] Open
Abstract
AIM Tenapanor (RDX5791/AZD1722), an inhibitor of gastrointestinal Na+ /H+ exchanger NHE3, is being evaluated for the treatment of patients with constipation-predominant irritable bowel syndrome and the treatment of hyperphosphataemia in patients with chronic kidney disease on dialysis. By reducing intestinal H+ secretion, inhibition of NHE3 by tenapanor could indirectly affect H+ -coupled transporter activity, leading to drug-drug interactions. We investigated the effect of tenapanor on the activity of the H+ -coupled peptide transporter PepT1 via assessment of the pharmacokinetics of cefadroxil - a compound transported by PepT1 - in healthy volunteers. METHODS In this open-label, two-period crossover, phase 1 study (NCT02140281), 28 volunteers received in random order: a single dose of cefadroxil 500 mg for 1 day; and tenapanor 15 mg twice daily over 4 days followed by single doses of both cefadroxil 500 mg and tenapanor 15 mg on day 5. There was a 4-day washout between treatment periods. RESULTS Cefadroxil exposure was similar when administered alone or in combination with tenapanor {geometric least-squares mean ratios [(cefadroxil + tenapanor)/cefadroxil] (90% confidence interval): area under the concentration-time curve 93.3 (90.6-96.0)%; maximum concentration in plasma 95.9 (89.8-103)%}. Tenapanor treatment caused a softening of stool consistency and an increase in stool frequency, consistent with its expected pharmacodynamic effect. No safety concerns were identified and tenapanor was not detected in plasma. CONCLUSIONS These results suggest that tenapanor 15 mg twice daily does not have a clinically relevant impact on the activity of the H+ -coupled transporter PepT1 in humans. This may guide future research on drug-drug interactions involving NHE3 inhibitors.
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Affiliation(s)
- Susanne Johansson
- Quantitative Clinical Pharmacology, Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Mölndal, Sweden
| | | | - Johan Palm
- Product Development, Pharmaceutical Technology & Development, Operations, AstraZeneca, Mölndal, Sweden
| | - Bergur Stefansson
- Cardiovascular Metabolic Diseases, Global Medicines Development, AstraZeneca, Mölndal, Sweden
| | - Mikael Knutsson
- Biometrics & Information Sciences, Global Medicines Development, AstraZeneca, Mölndal, Sweden
| | | | - Constanze Hilgendorf
- Drug Metabolism and Pharmacokinetics, Cardiovascular and Metabolic Diseases, Innovative Medicines and Early Development Biotech Unit, AstraZeneca, Mölndal, Sweden
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26
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Con P, Nitzan T, Cnaani A. Salinity-Dependent Shift in the Localization of Three Peptide Transporters along the Intestine of the Mozambique Tilapia ( Oreochromis mossambicus). Front Physiol 2017; 8:8. [PMID: 28167916 PMCID: PMC5253378 DOI: 10.3389/fphys.2017.00008] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2016] [Accepted: 01/05/2017] [Indexed: 12/15/2022] Open
Abstract
The peptide transporter (PepT) systems are well-known for their importance to protein absorption in all vertebrate species. These symporters use H+ gradient at the apical membrane of the intestinal epithelial cells to mediate the absorption of small peptides. In fish, the intestine is a multifunctional organ, involved in osmoregulation, acid-base regulation, and nutrient absorption. Therefore, we expected environmental stimuli to affect peptide absorption. We examined the effect of three environmental factors; salinity, pH and feeding, on the expression, activity and localization of three PepT transporters (PepT1a, PepT1b, PepT2) along the intestine of the Mozambique tilapia (Oreochromis mossambicus). Quantitative real time PCR (qPCR) analysis demonstrated that the two PepT1 variants are typical to the proximal intestinal section while PepT2 is typical to the distal intestinal sections. Immunofluorescence analysis with custom-made antibodies supported the qPCR results, localized both transporters on the apical membrane of enterocytes and provided the first evidence for the participation of PepT2 in nutrient absorption. This first description of segment-specific expression and localization points to a complementary role of the different peptide transporters, corresponding to the changes in nutrient availability along the intestine. Both gene expression and absorption activity assays showed that an increase in water salinity shifted the localization of the PepT genes transcription and activity down along the intestinal tract. Additionally, an unexpected pH effect was found on the absorption of small peptides, with increased activity at higher pH levels. This work emphasizes the relationships between different functions of the fish intestine and how they are affected by environmental conditions.
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Affiliation(s)
- Pazit Con
- Agricultural Research Organization, Institute of Animal ScienceRishon Letziyon, Israel; Department of Animal Sciences, Faculty of Agriculture, Food and Environment, The Hebrew University of JerusalemRehovot, Israel
| | - Tali Nitzan
- Agricultural Research Organization, Institute of Animal Science Rishon Letziyon, Israel
| | - Avner Cnaani
- Agricultural Research Organization, Institute of Animal Science Rishon Letziyon, Israel
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27
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Di- and tripeptide transport in vertebrates: the contribution of teleost fish models. J Comp Physiol B 2016; 187:395-462. [PMID: 27803975 DOI: 10.1007/s00360-016-1044-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/12/2016] [Accepted: 10/20/2016] [Indexed: 02/06/2023]
Abstract
Solute Carrier 15 (SLC15) family, alias H+-coupled oligopeptide cotransporter family, is a group of membrane transporters known for their role in the cellular uptake of di- and tripeptides (di/tripeptides) and peptide-like molecules. Of its members, SLC15A1 (PEPT1) chiefly mediates intestinal absorption of luminal di/tripeptides from dietary protein digestion, while SLC15A2 (PEPT2) mainly allows renal tubular reabsorption of di/tripeptides from ultrafiltration, SLC15A3 (PHT2) and SLC15A4 (PHT1) possibly interact with di/tripeptides and histidine in certain immune cells, and SLC15A5 has unknown function. Our understanding of this family in vertebrates has steadily increased, also due to the surge of genomic-to-functional information from 'non-conventional' animal models, livestock, poultry, and aquaculture fish species. Here, we review the literature on the SLC15 transporters in teleost fish with emphasis on SLC15A1 (PEPT1), one of the solute carriers better studied amongst teleost fish because of its relevance in animal nutrition. We report on the operativity of the transporter, the molecular diversity, and multiplicity of structural-functional solutions of the teleost fish orthologs with respect to higher vertebrates, its relevance at the intersection of the alimentary and osmoregulative functions of the gut, its response under various physiological states and dietary solicitations, and its possible involvement in examples of total body plasticity, such as growth and compensatory growth. By a comparative approach, we also review the few studies in teleost fish on SLC15A2 (PEPT2), SLC15A4 (PHT1), and SLC15A3 (PHT2). By representing the contribution of teleost fish to the knowledge of the physiology of di/tripeptide transport and transporters, we aim to fill the gap between higher and lower vertebrates.
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28
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Yang ZZ, Li L, Wang L, Xu MC, An S, Jiang C, Gu JK, Wang ZJJ, Yu LS, Zeng S. siRNA capsulated brain-targeted nanoparticles specifically knock down OATP2B1 in mice: a mechanism for acute morphine tolerance suppression. Sci Rep 2016; 6:33338. [PMID: 27629937 PMCID: PMC5024137 DOI: 10.1038/srep33338] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Accepted: 08/24/2016] [Indexed: 12/18/2022] Open
Abstract
Regulating main brain-uptake transporter of morphine may restrict its tolerance generation, then modify its antinociception. In this study, more than 2 fold higher intracellular uptake concentrations for morphine and morphine-6-glucuronide (M6G) were observed in stable expression cells, HEK293-hOATP2B1 than HEK293-MOCK. Specifically, the Km value of morphine to OATP2B1 (57.58 ± 8.90 μM) is 1.4-time more than that of M6G (80.31 ± 21.75 μM); Cyclosporine A (CsA), an inhibitor of OATP2B1, can inhibit their intracellular accumulations with IC50 = 3.90 ± 0.50 μM for morphine and IC50 = 6.04 ± 0.86 μM for M6G, respectively. To further investigate the role of OATP2B1 in morphine brain transport and tolerance, the novel nanoparticles of DGL-PEG/dermorphin capsulated siRNA (OATP2B1) were applied to deliver siRNA into mouse brain. Along with OATP2B1 depressed, a main reduction was found for each of morphine or M6G in cerebrums or epencephalons of acute morphine tolerance mice. Furthermore, calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) in mouse prefrontal cortex (mPFC) underwent dephosphorylation at Thr286. In conclusion, OATP2B1 downregulation in mouse brain can suppress tolerance via blocking morphine and M6G brain transport. These findings might help to improve the pharmacological effects of morphine.
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Affiliation(s)
- Zi-Zhao Yang
- Institute of Drug Metabolism and Pharmaceutical Analysis, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Li Li
- Zhejiang Provincial Key Laboratory of Geriatrics &Geriatrics Institute of Zhejiang Province, Zhejiang Hospital, 12 Lingyin Road, Hangzhou, Zhejiang Province 310013, China
| | - Lu Wang
- Institute of Drug Metabolism and Pharmaceutical Analysis, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Ming-Cheng Xu
- Institute of Drug Metabolism and Pharmaceutical Analysis, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Sai An
- Key Laboratory of Smart Drug Delivery, Ministry of Education, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China; State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Chen Jiang
- Key Laboratory of Smart Drug Delivery, Ministry of Education, Department of Pharmaceutics, School of Pharmacy, Fudan University, 826 Zhangheng Road, Shanghai 201203, China; State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200032, China
| | - Jing-Kai Gu
- School of Life Sciences, Jilin Univeristy, Changchun, 130012, China
| | - Zai-Jie Jim Wang
- Department of Biopharmaceutical Sciences, University of Illinois, 833 S. Wood Street, Chicago, IL 60612, USA
| | - Lu-Shan Yu
- Institute of Drug Metabolism and Pharmaceutical Analysis, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
| | - Su Zeng
- Institute of Drug Metabolism and Pharmaceutical Analysis, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, China
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30
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Daniel H, Zietek T. Taste and move: glucose and peptide transporters in the gastrointestinal tract. Exp Physiol 2015; 100:1441-50. [DOI: 10.1113/ep085029] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 06/26/2015] [Indexed: 12/14/2022]
Affiliation(s)
- Hannelore Daniel
- Nutritional Physiology; Technische Universität München; 85350 Freising Germany
- ZIEL Institute for Food & Health; 85350 Freising Germany
| | - Tamara Zietek
- Nutritional Physiology; Technische Universität München; 85350 Freising Germany
- ZIEL Institute for Food & Health; 85350 Freising Germany
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31
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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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Sanchez-Covarrubias L, Slosky LM, Thompson BJ, Davis TP, Ronaldson PT. Transporters at CNS barrier sites: obstacles or opportunities for drug delivery? Curr Pharm Des 2014; 20:1422-49. [PMID: 23789948 DOI: 10.2174/13816128113199990463] [Citation(s) in RCA: 154] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/18/2013] [Indexed: 01/11/2023]
Abstract
The blood-brain barrier (BBB) and blood-cerebrospinal fluid (BCSF) barriers are critical determinants of CNS homeostasis. Additionally, the BBB and BCSF barriers are formidable obstacles to effective CNS drug delivery. These brain barrier sites express putative influx and efflux transporters that precisely control permeation of circulating solutes including drugs. The study of transporters has enabled a shift away from "brute force" approaches to delivering drugs by physically circumventing brain barriers towards chemical approaches that can target specific compounds of the BBB and/or BCSF barrier. However, our understanding of transporters at the BBB and BCSF barriers has primarily focused on understanding efflux transporters that efficiently prevent drugs from attaining therapeutic concentrations in the CNS. Recently, through the characterization of multiple endogenously expressed uptake transporters, this paradigm has shifted to the study of brain transporter targets that can facilitate drug delivery (i.e., influx transporters). Additionally, signaling pathways and trafficking mechanisms have been identified for several endogenous BBB/BCSF transporters, thereby offering even more opportunities to understand how transporters can be exploited for optimization of CNS drug delivery. This review presents an overview of the BBB and BCSF barrier as well as the many families of transporters functionally expressed at these barrier sites. Furthermore, we present an overview of various strategies that have been designed and utilized to deliver therapeutic agents to the brain with a particular emphasis on those approaches that directly target endogenous BBB/BCSF barrier transporters.
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Affiliation(s)
| | | | | | | | - Patrick T Ronaldson
- Department of Medical Pharmacology, College of Medicine, University of Arizona, 1501 North Campbell Avenue, P.O. Box 245050, Tucson, AZ, 85724-5050.
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33
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Analysis of glycylsarcosine transport by lobster intestine using gas chromatography. J Comp Physiol B 2014; 185:37-45. [DOI: 10.1007/s00360-014-0863-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Revised: 09/05/2014] [Accepted: 09/11/2014] [Indexed: 01/29/2023]
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Abstract
The epithelium of the gastrointestinal tract is one of the most versatile tissues in the organism, responsible for providing a tight barrier between dietary and bacterial antigens and the mucosal and systemic immune system while maintaining efficient digestive and absorptive processes to ensure adequate nutrient and energy supply. Inflammatory bowel diseases (Crohn's disease and ulcerative colitis) are associated with a breakdown of both functions, which in some cases are clearly interrelated. In this updated literature review, we focus on the effects of intestinal inflammation and the associated immune mediators on selected aspects of the transepithelial transport of macronutrients and micronutrients. The mechanisms responsible for nutritional deficiencies are not always clear and could be related to decreased intake, malabsorption, and excess losses. We summarize the known causes of nutrient deficiencies and the mechanism of inflammatory bowel disease-associated diarrhea. We also overview the consequences of impaired epithelial transport, which infrequently transcend its primary purpose to affect the gut microbial ecology and epithelial integrity. Although some of those regulatory mechanisms are relatively well established, more work needs to be done to determine how inflammatory cytokines can alter the transport process of nutrients across the gastrointestinal and renal epithelia.
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Yoshimatsu H, Yonezawa A, Yao Y, Sugano K, Nakagawa S, Omura T, Matsubara K. Functional involvement of RFVT3/SLC52A3 in intestinal riboflavin absorption. Am J Physiol Gastrointest Liver Physiol 2014; 306:G102-10. [PMID: 24264046 DOI: 10.1152/ajpgi.00349.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Riboflavin, also known as vitamin B2, is transported across the biological membrane into various organs by transport systems. Riboflavin transporter RFVT3 is expressed in the small intestine and has been suggested to localize in the apical membranes of the intestinal epithelial cells. In this study, we investigated the functional involvement of RFVT3 in riboflavin absorption using intestinal epithelial T84 cells and mouse small intestine. T84 cells expressed RFVT3 and conserved unidirectional riboflavin transport corresponding to intestinal absorption. Apical [(3)H]riboflavin uptake was pH-dependent in T84 cells. This uptake was not affected by Na(+) depletion at apical pH 6.0, although it was significantly decreased at apical pH 7.4. The [(3)H]riboflavin uptake from the apical side of T84 cells was prominently inhibited by the RFVT3 selective inhibitor methylene blue and significantly decreased by transfection of RFVT3-small-interfering RNA. In the gastrointestinal tract, RFVT3 was expressed in the jejunum and ileum. Mouse jejunal and ileal permeabilities of [(3)H]riboflavin were measured by the in situ closed-loop method and were significantly reduced by methylene blue. These results strongly suggest that RFVT3 would functionally be involved in riboflavin absorption in the apical membranes of intestinal epithelial cells.
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Affiliation(s)
- Hiroki Yoshimatsu
- Dept. of Clinical Pharmacology and Therapeutics, Kyoto Univ. Hospital, Sakyo-ku, Kyoto 606-8507, Japan.
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Coon SD, Schwartz JH, Rajendran VM, Jepeal L, Singh SK. Glucose-dependent insulinotropic polypeptide regulates dipeptide absorption in mouse jejunum. Am J Physiol Gastrointest Liver Physiol 2013; 305:G678-84. [PMID: 24072682 PMCID: PMC3840233 DOI: 10.1152/ajpgi.00098.2013] [Citation(s) in RCA: 14] [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
Glucose-dependent insulinotropic polypeptide (GIP) secreted from jejunal mucosal K cells augments insulin secretion and plays a critical role in the pathogenesis of obesity and Type 2 diabetes mellitus. In recent studies, we have shown GIP directly activates Na-glucose cotransporter-1 (SGLT1) and enhances glucose absorption in mouse jejunum. It is not known whether GIP would also regulate other intestinal nutrient absorptive processes. The present study investigated the effect of GIP on proton-peptide cotransporter-1 (PepT1) that mediates di- and tripeptide absorption as well as peptidomimetic drugs. Immunohistochemistry studies localized both GIP receptor (GIPR) and PepT1 proteins on the basolateral and apical membranes of normal mouse jejunum, respectively. Anti-GIPR antibody detected 50-, 55-, 65-, and 70-kDa proteins, whereas anti-PepT1 detected a 70-kDa proteins in mucosal homogenates of mouse jejunum. RT-PCR analyses established the expression of GIPR- and PepT1-specific mRNA in mucosal cells of mouse jejunum. Absorption of Gly-Sar (a nondigestible dipeptide) measured under voltage-clamp conditions revealed that the imposed mucosal H(+) gradient-enhanced Gly-Sar absorption as an evidence for the presence of PepT1-mediated H(+):Gly-Sar cotransport on the apical membranes of mouse jejunum. H(+):Gly-Sar absorption was completely inhibited by cephalexin (a competitive inhibitor of PepT1) and was activated by GIP. The GIP-activated Gly-Sar absorption was completely inhibited by RP-cAMP (a cAMP antagonist). In contrast to GIP, the ileal L cell secreting glucagon-like peptide-1 (GLP-1) did not affect the H(+):Gly-Sar absorption in mouse jejunum. We conclude from these observations that GIP, but not GLP-1, directly activates PepT1 activity by a cAMP-dependent signaling pathway in jejunum.
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Affiliation(s)
- Steven D. Coon
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Veterans Affairs Boston Healthcare System, Boston, Massachusetts; ,3Boston University Clinical and Translational Science Institute, Boston, Massachusetts; and
| | - John H. Schwartz
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts;
| | - Vazhaikkurichi M. Rajendran
- 4Department of Biochemistry and Molecular Biology, West Virginia University School of Medicine, Morgantown, West Virginia
| | - Lisa Jepeal
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Veterans Affairs Boston Healthcare System, Boston, Massachusetts;
| | - Satish K. Singh
- 1Department of Medicine, Boston University School of Medicine, Boston, Massachusetts; ,2Veterans Affairs Boston Healthcare System, Boston, Massachusetts;
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Spanier B. Transcriptional and functional regulation of the intestinal peptide transporter PEPT1. J Physiol 2013; 592:871-9. [PMID: 23959672 DOI: 10.1113/jphysiol.2013.258889] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Dietary proteins are cleaved within the intestinal lumen to oligopeptides which are further processed to small peptides (di- and tripeptides) and free amino acids. Although the transport of amino acids is mediated by several specific amino acid transporters, the proton-coupled uptake of the more than 8000 different di- and tripeptides is performed by the high-capacity/low-affinity peptide transporter isoform PEPT1 (SLC15A1). Its wide substrate tolerance also allows the transport of a repertoire of structurally closely related compounds and drugs, which explains their high oral bioavailability and brings PEPT1 into focus for medical and pharmaceutical approaches. Although the first evidence for the interplay of nutrient supply and PEPT1 expression and function was described over 20 years ago, many aspects of the molecular processes controlling its transcription and translation and modifying its transporter properties are still awaiting discovery. The present review summarizes the recent knowledge on the factors modulating PEPT1 expression and function in Caenorhabditis elegans, Danio rerio, Mus musculus and Homo sapiens, with focus on dietary ingredients, transcription factors and functional modulators, such as the sodium-proton exchanger NHE3 and selected scaffold proteins.
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Affiliation(s)
- Britta Spanier
- Biochemistry, Technische Universität München, ZIEL Research Center of Nutrition and Food Sciences, Gregor-Mendel-Straße 2, D-85350 Freising, Germany.
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38
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Wuensch T, Schulz S, Ullrich S, Lill N, Stelzl T, Rubio-Aliaga I, Loh G, Chamaillard M, Haller D, Daniel H. The peptide transporter PEPT1 is expressed in distal colon in rodents and humans and contributes to water absorption. Am J Physiol Gastrointest Liver Physiol 2013; 305:G66-73. [PMID: 23660505 DOI: 10.1152/ajpgi.00491.2012] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The peptide transporter PEPT1, expressed in the brush border membrane of enterocytes, mediates the uptake of di- and tripeptides from luminal protein digestion in the small intestine. PEPT1 was proposed not to be expressed in normal colonic mucosa but may become detectable in inflammatory states such as Crohn's disease or ulcerative colitis. We reassessed colonic expression of PEPT1 by performing a systematic analysis of PEPT1 mRNA and protein levels in healthy colonic tissues in mice, rats, and humans. Immunofluorescence analysis of different mouse strains (C57BL/6N, 129/Sv, BALB/c) demonstrated the presence of PEPT1 in the distal part of the colon but not in proximal colon. Rat and human intestines display a similar distribution of PEPT1 as found in mice. However, localization in human sigmoid colon revealed immunoreactivity present at low levels in apical membranes but substantial staining in distinct intracellular compartments. Functional activity of PEPT1 in colonic tissues from mice was assessed in everted sac preparations using [¹⁴C]Gly-Sar and found to be 5.7-fold higher in distal compared with proximal colon. In intestinal tissues from Pept1-/- mice, no [¹⁴C]Gly-Sar transport was detectable but feces samples revealed significantly higher water content than in wild-type mice, suggesting that PEPT1 contributes to colonic water absorption. In conclusion, our studies unequivocally demonstrate the presence of PEPT1 protein in healthy distal colonic epithelium in mice, rats, and humans and proved that the protein is functional and contributes to electrolyte and water handling in mice.
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Affiliation(s)
- Tilo Wuensch
- Technische Universität München, Biochemistry Unit, ZIEL-Research Center for Nutrition and Food Science, CDD-Center for Diet and Disease, Freising-Weihenstephan, Germany
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39
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Frølund S, Nøhr M, Holm R, Brodin B, Nielsen C. Potential involvement of the proton-coupled amino acid transporter PAT1 (SLC36A1) in the delivery of pharmaceutical agents. J Drug Deliv Sci Technol 2013. [DOI: 10.1016/s1773-2247(13)50046-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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40
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Koven W, Schulte P. The effect of fasting and refeeding on mRNA expression of PepT1 and gastrointestinal hormones regulating digestion and food intake in zebrafish (Danio rerio). FISH PHYSIOLOGY AND BIOCHEMISTRY 2012; 38:1565-1575. [PMID: 22565667 DOI: 10.1007/s10695-012-9649-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Accepted: 04/21/2012] [Indexed: 05/31/2023]
Abstract
In vertebrates, a significant part of ingested protein is absorbed as di- and tripeptides through a brush border membrane proton/oligopeptide transporter protein called PepT1. The aim of the present study was to determine the effect of short-term food deprivation and refeeding in adult zebrafish (Danio rerio) on gastrointestinal mRNA expression of PepT1 as well as on the satiety hormones cholecystokinin (CCK), gastrin-releasing peptide (GRP) and ghrelin (GHR) in order to elucidate a potential mechanism driving compensatory growth. Sixty adult zebrafish were stocked in a 40-L aquarium and fed daily a commercial flake diet to satiation for 10 days where the digestive tracts (DT) of sampled fish (n = 5) were dissected out. Samplings were repeated following 1, 2 and 5 days of food deprivation and after 1, 2 and 5 days of refeeding. The RNA was extracted from all sampled DTs and analyzed by quantitative real-time PCR for the mRNA expression of PepT1, rRNA 18S, CCK, GRP and GHR. PepT1 mRNA expression increased with successive refeedings reaching a level approximately 8 times higher than pre-fast levels. CCK, GRP and GHR mRNA levels also decreased during fasting, but increased only to pre-fasting levels with refeeding. Overall, the results suggest that PepT1 may be a contributing mechanism to compensatory growth that could influence CCK secretion and GRP and GHR activity.
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Affiliation(s)
- William Koven
- Israel Oceanographic and Limnological Research, The National Center for Mariculture, P.O.B. 1212, 88112, Eilat, Israel.
| | - Patricia Schulte
- Department of Zoology, The University of British Columbia, 6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
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41
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Benner J, Daniel H, Spanier B. A glutathione peroxidase, intracellular peptidases and the TOR complexes regulate peptide transporter PEPT-1 in C. elegans. PLoS One 2011; 6:e25624. [PMID: 21980510 PMCID: PMC3182239 DOI: 10.1371/journal.pone.0025624] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 09/08/2011] [Indexed: 11/18/2022] Open
Abstract
The intestinal peptide transporter PEPT-1 in Caenorhabditis elegans is a rheogenic H+-dependent carrier responsible for the absorption of di- and tripeptides. Transporter-deficient pept-1(lg601) worms are characterized by impairments in growth, development and reproduction and develop a severe obesity like phenotype. The transport function of PEPT-1 as well as the influx of free fatty acids was shown to be dependent on the membrane potential and on the intracellular pH homeostasis, both of which are regulated by the sodium-proton exchanger NHX-2. Since many membrane proteins commonly function as complexes, there could be proteins that possibly modulate PEPT-1 expression and function. A systematic RNAi screening of 162 genes that are exclusively expressed in the intestine combined with a functional transport assay revealed four genes with homologues existing in mammals as predicted PEPT-1 modulators. While silencing of a glutathione peroxidase surprisingly caused an increase in PEPT-1 transport function, silencing of the ER to Golgi cargo transport protein and of two cytosolic peptidases reduced PEPT-1 transport activity and this even corresponded with lower PEPT-1 protein levels. These modifications of PEPT-1 function by gene silencing of homologous genes were also found to be conserved in the human epithelial cell line Caco-2/TC7 cells. Peptidase inhibition, amino acid supplementation and RNAi silencing of targets of rapamycin (TOR) components in C. elegans supports evidence that intracellular peptide hydrolysis and amino acid concentration are a part of a sensing system that controls PEPT-1 expression and function and that involves the TOR complexes TORC1 and TORC2.
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Affiliation(s)
- Jacqueline Benner
- ZIEL Research Center of Nutrition and Food Sciences, Abteilung Biochemie, Technische Universität München, Freising, Germany
| | - Hannelore Daniel
- ZIEL Research Center of Nutrition and Food Sciences, Abteilung Biochemie, Technische Universität München, Freising, Germany
| | - Britta Spanier
- ZIEL Research Center of Nutrition and Food Sciences, Abteilung Biochemie, Technische Universität München, Freising, Germany
- * E-mail:
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42
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Varma MV, Rotter CJ, Chupka J, Whalen KM, Duignan DB, Feng B, Litchfield J, Goosen TC, El-Kattan AF. pH-sensitive interaction of HMG-CoA reductase inhibitors (statins) with organic anion transporting polypeptide 2B1. Mol Pharm 2011; 8:1303-13. [PMID: 21710988 DOI: 10.1021/mp200103h] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The human organic anion transporting polypeptide 2B1 (OATP2B1, SLCO2B1) is ubiquitously expressed and may play an important role in the disposition of xenobiotics. The present study aimed to examine the role of OATP2B1 in the intestinal absorption and tissue uptake of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase inhibitors (statins). We first investigated the functional affinity of statins to the transporter as a function of extracellular pH, using OATP2B1-transfeced HEK293 cells. The results indicate that OATP2B1-mediated transport is significant for rosuvastatin, fluvastatin and atorvastatin, at neutral pH. However, OATP2B1 showed broader substrate specificity as well as enhanced transporter activity at acidic pH. Furthermore, uptake at acidic pH was diminished in the presence of proton ionophore, suggesting proton gradient as the driving force for OATP2B1 activity. Notably, passive transport rates are predominant or comparable to active transport rates for statins, except for rosuvastatin and fluvastatin. Second, we studied the effect of OATP modulators on statin uptake. At pH 6.0, OATP2B1-mediated transport of atorvastatin and cerivastatin was not inhibitable, while rosuvastatin transport was inhibited by E-3-S, rifamycin SV and cyclosporine with IC(50) values of 19.7 ± 3.3 μM, 0.53 ± 0.2 μM and 2.2 ± 0.4 μM, respectively. Rifamycin SV inhibited OATP2B1-mediated transport of E-3-S and rosuvastatin with similar IC(50) values at pH 6.0 and 7.4, suggesting that the inhibitor affinity is not pH-dependent. Finally, we noted that OATP2B1-mediated transport of E-3-S, but not rosuvastatin, is pH sensitive in intestinal epithelial (Caco-2) cells. However, uptake of E-3-S and rosuvastatin by Caco-2 cells was diminished in the presence of proton ionophore. The present results indicate that OATP2B1 may be involved in the tissue uptake of rosuvastatin and fluvastatin, while OATP2B1 may play a significant role in the intestinal absorption of several statins due to their transporter affinity at acidic pH.
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Affiliation(s)
- Manthena V Varma
- Pharmacokinetics Dynamics and Metabolism, Pfizer Global Research and Development, Pfizer Inc., Groton, Connecticut 06340, USA.
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43
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Sugiura T, Shimizu T, Kijima A, Minakata S, Kato Y. PDZ adaptors: their regulation of epithelial transporters and involvement in human diseases. J Pharm Sci 2011; 100:3620-35. [PMID: 21538352 DOI: 10.1002/jps.22575] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2011] [Revised: 03/28/2011] [Accepted: 03/31/2011] [Indexed: 12/17/2022]
Abstract
Homeostasis in the body is at least partially maintained by mechanisms that control membrane permeability, and thereby serve to control the uptake of essential substances (e.g., nutrients) and the efflux of unwanted substances (e.g., xenobiotics and metabolites) in epithelial cells. Various transporters play fundamental roles in such bidirectional transport, but little is known about how they are organized on plasma membranes. Protein-protein interactions may play a key role: several transporters in epithelial cells interact with the so-called adaptor proteins, which are membrane anchored and interact with both transporters and other membranous proteins. Although most of the evidences for transporter-adaptor interaction has been obtained in vitro, recent studies suggest that adaptor-mediated transporter regulation does occur in vivo and could be relevant to human diseases. Thus, protein-protein interaction is not only associated with the formation of macromolecular complexes but is also involved in various cellular events, and may provide transporters with additional functionality by forming transporter networks on plasma membranes. Interactions between xenobiotic transporters and PSD95/Dlg/ZO1 (PDZ) adaptors were previously reviewed by Kato and Tsuji (2006. Eur J Pharm Sci 27:487-500); the present review focuses on the latest findings about PDZ adaptors as regulators of transporter networks and their potential role in human diseases.
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Affiliation(s)
- Tomoko Sugiura
- Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa 920-1192, Japan
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44
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Anderson CMH, Thwaites DT. Hijacking solute carriers for proton-coupled drug transport. Physiology (Bethesda) 2011; 25:364-77. [PMID: 21186281 DOI: 10.1152/physiol.00027.2010] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The physiological role of mammalian solute carrier (SLC) proteins is to mediate transmembrane movement of electrolytes, nutrients, micronutrients, vitamins, and endogenous metabolites from one cellular compartment to another. Many transporters in the small intestine, kidney, and solid tumors are H(+)-coupled, driven by local H(+)-electrochemical gradients, and transport numerous drugs. These transporters include PepT1 and PepT2 (SLC15A1/2), PCFT (SLC46A1), PAT1 (SLC36A1), OAT10 (SLC22A13), OATP2B1 (SLCO2B1), MCT1 (SLC16A1), and MATE1 and MATE2-K (SLC47A1/2).
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Affiliation(s)
- Catriona M H Anderson
- Epithelial Research Group, Institute for Cell & Molecular Biosciences, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom
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45
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Coon S, Kekuda R, Saha P, Sundaram U. Reciprocal regulation of the primary sodium absorptive pathways in rat intestinal epithelial cells. Am J Physiol Cell Physiol 2010; 300:C496-505. [PMID: 21148403 DOI: 10.1152/ajpcell.00292.2010] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Sodium absorption in the mammalian small intestine occurs predominantly by two primary pathways that include Na/H exchange (NHE3) and Na-glucose cotransport (SGLT1) on the brush border membrane (BBM) of villus cells. However, whether NHE3 and SGLT1 function together to regulate intestinal sodium absorption is unknown. Nontransformed small intestinal epithelial cells (IEC-18) were transfected with either NHE3 or SGLT1 small interfering RNAs (siRNAs) and were grown in confluent monolayers on transwell plates to measure the effects on Na absorption. Uptake studies were performed as well as molecular studies to determine the effects on NHE3 and SGLT1 activity. When IEC-18 monolayers were transfected with silencing NHE3 RNA, the cells demonstrated decreased NHE3 activity as well as decreased NHE3 mRNA and protein. However, in NHE3 siRNA-transected cells, SGLT1 activity, mRNA, and protein in the BBM were significantly increased. Thus, inhibition of NHE3 expression regulates the expression and function of SGLT1 in the BBM of intestinal epithelial cells. In addition, IEC-18 cells transected with silencing SGLT1 RNA demonstrated an inhibition of Na-dependent glucose uptake and a decrease in SGLT1 activity, mRNA, and protein levels. However, in these cells, Na/H exchange activity was significantly increased. Furthermore, NHE3 mRNA and protein levels were also increased. Therefore, the inhibition of SGLT1 expression stimulates the transcription and function of NHE3 and vice versa in the BBM of intestinal epithelial cells. Thus this study demonstrates that the major sodium absorptive pathways together function to regulate sodium absorption in epithelial cells.
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Affiliation(s)
- Steven Coon
- West Virginia Univ. School of Medicine, Morgantown, WV 26506, USA
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46
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Pieri M, Christian HC, Wilkins RJ, Boyd CAR, Meredith D. The apical (hPepT1) and basolateral peptide transport systems of Caco-2 cells are regulated by AMP-activated protein kinase. Am J Physiol Gastrointest Liver Physiol 2010; 299:G136-43. [PMID: 20430871 PMCID: PMC2904111 DOI: 10.1152/ajpgi.00014.2010] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The effect of 5-aminoimidazole-4-carboxamide-ribonucleoside (AICAR) activation of the AMP-activated protein kinase (AMPK) on the transport of the model radiolabeled dipeptide [(3)H]-D-Phe-L-Gln was investigated in the human epithelial colon cancer cell line Caco-2. Uptake and transepithelial fluxes of [(3)H]-D-Phe-L-Gln were carried out in differentiated Caco-2 cell monolayers, and hPepT1 and glucose transporter 2 (GLUT2) protein levels were quantified by immunogold electron microscopy. AICAR treatment of Caco-2 cells significantly inhibited apical [(3)H]-D-Phe-L-Gln uptake, matched by a decrease in brush-border membrane hPepT1 protein but with a concomitant increase in the facilitated glucose transporter GLUT2. A restructuring of the apical brush-border membrane was seen by electron microscopy. The hPepT1-mediated transepithelial (A-to-B) peptide flux across the Caco-2 monolayers showed no significant alteration in AICAR-treated cells. The electrical resistance in the AICAR-treated monolayers was significantly higher compared with control cells. Inhibition of the sodium/hydrogen exchanger 3 (NHE3) had an additive effect to AICAR, suggesting that the AMPK effect is not via NHE3. Fluorescence measurement of intracellular pH showed no reduction in the proton gradient driving PepT1-mediated apical uptake. The reduction in apical hPepT1 protein and dipeptide uptake after AICAR treatment in Caco-2 cells demonstrates a regulatory effect of AMPK on hPepT1, along with an influence on both the microvilli and tight junction structures. The absence of an associated reduction in transepithelial peptide movement implies an additional stimulatory effect of AICAR on the basolateral peptide transport system in these cells. These results provide a link between the hPepT1 transporter and the metabolic state of this model enterocyte.
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Affiliation(s)
- Myrtani Pieri
- 1School of Life Sciences, Oxford Brookes University, Headington, Oxford; ,2Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Helen C. Christian
- 2Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - Robert J. Wilkins
- 2Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - C. A. R. Boyd
- 2Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
| | - David Meredith
- 1School of Life Sciences, Oxford Brookes University, Headington, Oxford; ,2Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom
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47
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Chen M, Singh A, Xiao F, Dringenberg U, Wang J, Engelhardt R, Yeruva S, Rubio-Aliaga I, Nässl AM, Kottra G, Daniel H, Seidler U. Gene ablation for PEPT1 in mice abolishes the effects of dipeptides on small intestinal fluid absorption, short-circuit current, and intracellular pH. Am J Physiol Gastrointest Liver Physiol 2010; 299:G265-74. [PMID: 20430876 DOI: 10.1152/ajpgi.00055.2010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
PEPT1 function in mouse intestine has not been assessed by means of electrophysiology and methods to assess its role in intracellular pH and fluid homeostasis. Therefore, the effects of the dipeptide glycilsarcosin (Gly-Sar) on jejunal fluid absorption and villous enterocyte intracellular pH (pH(i)) in vivo, as well as on enterocyte[(14)C]Gly-Sar uptake, short-circuit current (I(sc)) response, and enterocyte pH(i) in vitro were determined in wild-type and PEPT1-deficient mice and in mice lacking PEPT1. Immunohistochemistry for PEPT1 failed to detect any protein in enterocyte apical membranes in Slc15a1(-/-) animals. Saturable Gly-Sar uptake in Slc15a1(-/-) everted sac preparations was no longer detectable. Similarly, Gly-Sar-induced jejunal I(sc) response in vitro was abolished. The dipeptide-induced increase in fluid absorption in vivo was also abolished in animals lacking PEPT1. Since PEPT1 acts as an acid loader in enterocytes, enterocyte pH(i) was measured in vivo by two-photon microscopy in SNARF-4-loaded villous enterocytes of exteriorized jejuni in anesthetized mice, as well as in BCECF-loaded enterocytes of microdissected jejunal villi. Gly-Sar-induced pH(i) decrease was no longer observed in the absence of PEPT1. A reversal of the proton gradient across the luminal membrane did not significantly diminish Gly-Sar-induced I(sc) response, whereas a depolarization of the apical membrane potential by high K(+) or via Na(+)-K(+)-ATPase inhibition strongly diminished Gly-Sar-induced I(sc) responses. This study demonstrates for the first time that proton-coupled electrogenic dipeptide uptake in the native small intestine, mediated by PEPT1, relies on the negative apical membrane potential as the major driving force and contributes significantly to intestinal fluid transport.
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Affiliation(s)
- Mingmin Chen
- Department of Gastroenterology, Hepatology and Endocrinology, Hannover Medical School, Carl-Neuberg-Strasse 1, D-30625 Hannover, Germany
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48
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Simpson JE, Walker NM, Supuran CT, Soleimani M, Clarke LL. Putative anion transporter-1 (Pat-1, Slc26a6) contributes to intracellular pH regulation during H+-dipeptide transport in duodenal villous epithelium. Am J Physiol Gastrointest Liver Physiol 2010; 298:G683-91. [PMID: 20150244 PMCID: PMC2867431 DOI: 10.1152/ajpgi.00293.2009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The majority of dietary amino acids are absorbed via the H(+)-di-/tripeptide transporter Pept1 of the small intestine. Proton influx via Pept1 requires maintenance of intracellular pH (pH(i)) to sustain the driving force for peptide absorption. The apical membrane Na(+)/H(+) exchanger Nhe3 plays a major role in minimizing epithelial acidification during H(+)-di-/tripeptide absorption. However, the contributions of HCO(3)(-)-dependent transporters to this process have not been elucidated. In this study, we investigate the role of putative anion transporter-1 (Pat-1), an apical membrane anion exchanger, in epithelial pH(i) regulation during H(+)-peptide absorption. Using wild-type (WT) and Pat-1(-) mice, Ussing chambers were employed to measure the short-circuit current (I(sc)) associated with Pept1-mediated glycyl-sarcosine (Gly-Sar) absorption. Microfluorometry was used to measure pH(i) and Cl(-)/HCO(3)(-) exchange in the upper villous epithelium. In CO(2)/HCO(3)(-)-buffered Ringers, WT small intestine showed significant Gly-Sar-induced I(sc) and efficient pH(i) regulation during pharmacological inhibition of Nhe3 activity. In contrast, epithelial acidification and reduced I(sc) response to Gly-Sar exposure occurred during pharmacological inhibition of Cl(-)/HCO(3)(-) exchange and in the Pat-1(-) intestine. Pat-1 interacts with carbonic anhydrase II (CAII), and studies using CAII(-) intestine or the pharmacological inhibitor methazolamide on WT intestine resulted in increased epithelial acidification during Gly-Sar exposure. Increased epithelial acidification during Gly-Sar exposure also occurred in WT intestine during inhibition of luminal extracellular CA activity. Measurement of Cl(-)/HCO(3)(-) exchange in the presence of Gly-Sar revealed an increased rate of Cl(-)(OUT)/HCO(3)(-)(IN) exchange that was both Pat-1 dependent and CA dependent. In conclusion, Pat-1 Cl(-)/HCO(3)(-) exchange contributes to pH(i) regulation in the villous epithelium during H(+)-dipeptide absorption, possibly by providing a HCO(3)(-) import pathway.
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Affiliation(s)
- Janet E. Simpson
- 1Dalton Cardiovascular Research Center and the ,Departments of 2Biomedical Sciences and ,3Veterinary Pathobiology, University of Missouri, Columbia, Missouri;
| | | | - Claudiu T. Supuran
- 4Laboratorio di Chimica Bioinorganica, Dipartimento di Chimica, Universit'a di Firenze, Firenze, Italy;
| | | | - Lane L. Clarke
- 1Dalton Cardiovascular Research Center and the ,Departments of 2Biomedical Sciences and
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Anderson CMH, Jevons M, Thangaraju M, Edwards N, Conlon NJ, Woods S, Ganapathy V, Thwaites DT. Transport of the photodynamic therapy agent 5-aminolevulinic acid by distinct H+-coupled nutrient carriers coexpressed in the small intestine. J Pharmacol Exp Ther 2009; 332:220-8. [PMID: 19789362 DOI: 10.1124/jpet.109.159822] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
5-Aminolevulinic acid (ALA) is a prodrug used in photodynamic therapy, fluorescent diagnosis, and fluorescent-guided resection because it leads to accumulation of the photosensitizer protoporphyrin IX (PpIX) in tumor tissues. ALA has good oral bioavailability, but high oral doses are required to obtain selective PpIX accumulation in colonic tumors because accumulation is also observed in normal gut mucosa. Structural similarities between ALA and GABA led us to test the hypothesis that the H(+)-coupled amino acid transporter PAT1 (SLC36A1) will contribute to luminal ALA uptake. Radiolabel uptake and electrophysiological measurements identified PAT1-mediated H(+)-coupled ALA symport after heterologous expression in Xenopus oocytes. The selectivity of the nontransported inhibitors 5-hydroxytryptophan and 4-aminomethylbenzoic acid for, respectively, PAT1 and the H(+)-coupled di/tripeptide transporter PepT1 (SLC15A1) were examined. 5-Hydroxytryptophan selectively inhibited PAT1-mediated amino acid uptake across the brush-border membrane of the human intestinal (Caco-2) epithelium whereas 4-aminomethylbenzoic acid selectively inhibited PepT1-mediated dipeptide uptake. The inhibitory effects of 5-hydroxytryptophan and 4-aminomethylbenzoic acid were additive, demonstrating that both PAT1 and PepT1 contribute to intestinal transport of ALA. This is the first demonstration of overlap in substrate specificity between these distinct transporters for amino acids and dipeptides. PAT1 and PepT1 expression was monitored by reverse transcriptase-polymerase chain reaction using paired samples of normal and cancer tissue from human colon. mRNA for both transporters was detected. PepT1 mRNA was increased 2.3-fold in cancer tissues. Thus, increased PepT1 expression in colonic cancer could contribute to the increased PpIX accumulation observed. Selective inhibition of PAT1 could enhance PpIX loading in tumor tissue relative to that in normal tissue.
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Affiliation(s)
- Catriona M H Anderson
- Epithelial Research Group, Institute for Cell and Molecular Biosciences, Faculty of Medical Sciences, Framlington Place, Newcastle University, Newcastle upon Tyne, UK
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50
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Allman E, Johnson D, Nehrke K. Loss of the apical V-ATPase a-subunit VHA-6 prevents acidification of the intestinal lumen during a rhythmic behavior in C. elegans. Am J Physiol Cell Physiol 2009; 297:C1071-81. [PMID: 19741196 DOI: 10.1152/ajpcell.00284.2009] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In Caenorhabditis elegans, oscillations of intestinal pH contribute to the rhythmic defecation behavior, but the acid-base transport mechanisms that facilitate proton movement are not well understood. Here, we demonstrate that VHA-6, an intestine-specific a-subunit of the H(+)-K(+)-ATPase complex (V-ATPase), resides in the apical membrane of the intestinal epithelial cells and is required for luminal acidification. Disruption of the vha-6 gene led to early developmental arrest; the arrest phenotype could be complemented by expression of a fluorescently labeled vha-6 transgene. To study the contribution of vha-6 to pH homeostasis in larval worms, we used a partial reduction of function through postembryonic single-generation RNA interference. We demonstrate that the inability to fully acidify the intestinal lumen coincides with a defect in pH recovery of the intestinal epithelial cells, suggesting that VHA-6 is essential for proton pumping following defecation. Moreover, intestinal dipeptide accumulation and fat storage are compromised by the loss of VHA-6, suggesting that luminal acidification promotes nutrient uptake in worms, as well as in mammals. Since acidified intracellular vesicles and autofluorescent storage granules are indistinguishable between the vha-6 mutant and controls, it is likely that the nutrient-restricted phenotype is due to a loss of plasma membrane V-ATPase activity specifically. These data establish a simple genetic model for proton pump-driven acidification. Since defecation occurs at 45-s intervals in worms, this model represents an opportunity to study acute regulation of V-ATPase activity on a short time scale and may be useful in the study of alternative treatments for acid-peptic disorders.
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Affiliation(s)
- Erik Allman
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, New York 14642, USA
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