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Sarkar S, Saika-Voivod I, Berry MD. Modelling of p-tyramine transport across human intestinal epithelial cells predicts the presence of additional transporters. Front Physiol 2022; 13:1009320. [PMID: 36505075 PMCID: PMC9733674 DOI: 10.3389/fphys.2022.1009320] [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: 08/01/2022] [Accepted: 09/22/2022] [Indexed: 11/12/2022] Open
Abstract
p-Tyramine (TYR) is an endogenous trace amine, which can also be synthesized by intestinal microbiota, and is present in commonly consumed diets. TYR is an agonist for the intracellular trace amine-associated receptor 1, which has been implicated in psychiatric, metabolic, and immune-related disorders. We have previously demonstrated TYR readily diffuses across lipid bilayers, while transport across Caco-2 cell membranes involves Organic Cation Transporter 2 (OCT2) and a Na+-dependent active transporter. Here we developed mathematical models to determine whether known kinetics for these processes are sufficient to explain observed transcellular TYR passage. Ordinary differential equations were developed for known TYR transport processes to predict concentration-time relationships. Michaelis-Menten kinetics were assumed for all transporter-mediated processes and a one phase exponential function used for simple diffusion. Modelled concentration-time plots were compared to published experimental results. Additional transporter functions were sequentially added to models to improve consistency, and a least squares error minimization approach utilized to determine added transporter kinetics. Finally, possible TYR compartmentalization was also modelled. Following apical loading, transport across the apical, but not the basolateral, membrane was modelled without additional transporters, suggesting a basolateral transporter was missing. Consistent with this, models of basolateral compartment loading did not match experimental observations, indicating missing basolateral transporters were bidirectional. Addition of a transporter with the kinetic characteristics of OCT2 did not improve models. Varying the kinetic parameters of the added transporter improved models of basolateral, but worsened apical, loading models, suggesting the need for either a directional preference in transporters, or intracellular TYR compartmentalization. Experimental parameters were recapitulated by introducing asymmetry into the apical OCT2 (Kt_OCT2_apicaltocell = 110.4 nM, Kt_OCT2_celltoapical = 1,227.9 nM), and a symmetric basolateral facilitated diffusion transporter (Vmax = 6.0 nM/s, Kt = 628.3 nM). The apparent directionality of OCT2 may reflect altered TYR ionization due to known pH differences between compartments. Models for asymmetry and compartmentalization were compared by root mean square deviation from experimental data, and it was found that TYR compartmentalization could only partially replace the need for asymmetry of OCT2. In conclusion, modelling indicates that known TYR transport processes are insufficient to explain experimental concentration-time profiles and that asymmetry of the apical membrane OCT2 combined with additional, low affinity, basolateral membrane facilitated diffusion transporters are required.
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Affiliation(s)
- Shreyasi Sarkar
- Department of Biochemistry, Memorial University of Newfoundland, St. John’s, NL, Canada,*Correspondence: Shreyasi Sarkar,
| | - Ivan Saika-Voivod
- Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John’s, NL, Canada
| | - Mark D. Berry
- Department of Biochemistry, Memorial University of Newfoundland, St. John’s, NL, Canada
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Hahn M, Lindemann V, Behrens M, Mulac D, Langer K, Esselen M, Humpf HU. Permeability of dopamine D2 receptor agonist hordenine across the intestinal and blood-brain barrier in vitro. PLoS One 2022; 17:e0269486. [PMID: 35709159 PMCID: PMC9202863 DOI: 10.1371/journal.pone.0269486] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Accepted: 05/20/2022] [Indexed: 11/23/2022] Open
Abstract
Hordenine, a bioactive food compound, has several pharmacological properties and has recently been identified as a dopamine D2 receptor (D2R) agonist. Since the pharmacokinetic profile of hordenine has been described to a limited extent, the present study focused on the transfer and transport of hordenine across the intestinal epithelium and the blood-brain barrier (BBB) in vitro. Hordenine was quickly transferred through the Caco-2 monolayer in only a few hours, indicating a rapid oral uptake. However, the high bioavailability may be reduced by the observed efflux transport of hordenine from the bloodstream back into the intestinal lumen and by first pass metabolism in intestinal epithelial cells. To determine the biotransformation rate of hordenine, the metabolite hordenine sulfate was synthesized as reference standard for analytical purposes. In addition, transfer studies using primary porcine brain capillary endothelial cells (PBCEC) showed that hordenine is able to rapidly penetrate the BBB and potentially accumulate in the brain. Thus, a D2R interaction of hordenine and activation of dopaminergic signaling is conceivable, assuming that the intestinal barrier can be circumvented by a route of administration alternative to oral uptake.
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Affiliation(s)
- Maria Hahn
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Viktoria Lindemann
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Matthias Behrens
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Dennis Mulac
- Institute of Pharmaceutical Technology and Biopharmacy, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Klaus Langer
- Institute of Pharmaceutical Technology and Biopharmacy, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Melanie Esselen
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany
| | - Hans-Ulrich Humpf
- Institute of Food Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany
- * E-mail:
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Horvath TD, Ihekweazu FD, Haidacher SJ, Ruan W, Engevik KA, Fultz R, Hoch KM, Luna RA, Oezguen N, Spinler JK, Haag AM, Versalovic J, Engevik MA. Bacteroides ovatus colonization influences the abundance of intestinal short chain fatty acids and neurotransmitters. iScience 2022; 25:104158. [PMID: 35494230 PMCID: PMC9038548 DOI: 10.1016/j.isci.2022.104158] [Citation(s) in RCA: 46] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 11/01/2021] [Accepted: 03/23/2022] [Indexed: 12/18/2022] Open
Abstract
Gut microbes can synthesize multiple neuro-active metabolites. We profiled neuro-active compounds produced by the gut commensal Bacteroides ovatus in vitro and in vivo by LC-MS/MS. We found that B. ovatus generates acetic acid, propionic acid, isobutyric acid, and isovaleric acid. In vitro, B. ovatus consumed tryptophan and glutamate and synthesized the neuro-active compounds glutamine and GABA. Consistent with our LC-MS/MS-based in vitro data, we observed elevated levels of acetic acid, propionic acid, isobutyric acid, and isovaleric acid in the intestines of B. ovatus mono-associated mice compared with germ-free controls. B. ovatus mono-association also increased the concentrations of intestinal GABA and decreased the concentrations of tryptophan and glutamine compared with germ-free controls. Computational network analysis revealed unique links between SCFAs, neuro-active compounds, and colonization status. These results highlight connections between microbial colonization and intestinal neurotransmitter concentrations, suggesting that B. ovatus selectively influences the presence of intestinal neurotransmitters.
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Affiliation(s)
- Thomas D. Horvath
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Faith D. Ihekweazu
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
- Section of Gastroenterology, Hepatology, and Nutrition, Texas Children’s Hospital, Houston, TX, USA
| | - Sigmund J. Haidacher
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Wenly Ruan
- Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
- Section of Gastroenterology, Hepatology, and Nutrition, Texas Children’s Hospital, Houston, TX, USA
| | - Kristen A. Engevik
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, TX, USA
| | - Robert Fultz
- Department of Neuroscience, Cell Biology, and Anatomy, University of Texas Medical Branch, Galveston, TX, USA
| | - Kathleen M. Hoch
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Ruth Ann Luna
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Numan Oezguen
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Jennifer K. Spinler
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Anthony M. Haag
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - James Versalovic
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Pathology, Texas Children’s Hospital, Houston, TX, USA
| | - Melinda A. Engevik
- Department of Pathology and Immunology, Baylor College of Medicine, Houston, TX, USA
- Department of Regenerative Medicine & Cell Biology, Medical University of South Carolina, 173 Ashley Ave, BSB 621, Charleston, SC 29425, USA
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Carrillo E, Gonzalez CU, Berka V, Jayaraman V. Delta glutamate receptors are functional glycine- and ᴅ-serine-gated cation channels in situ. SCIENCE ADVANCES 2021; 7:eabk2200. [PMID: 34936451 PMCID: PMC8694607 DOI: 10.1126/sciadv.abk2200] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Delta receptors are members of the ionotropic glutamate receptor superfamily and form trans-synaptic connections by interacting with the extracellular scaffolding protein cerebellin-1 and presynaptic transmembrane protein neurexin-1β. Unlike other family members, however, direct agonist-gated ion channel activity has not been recorded in delta receptors. Here, we show that the GluD2 subtype of delta receptor forms cation-selective channels when bound to cerebellin-1 and neurexin-1β. Using fluorescence lifetime measurements and chemical cross-linking, we reveal that tight packing of the amino-terminal domains of GluD2 permits glycine- and d-serine–induced channel openings. Thus, cerebellin-1 and neurexin-1β act as biological cross-linkers to stabilize the extracellular domains of GluD2 receptors, allowing them to function as ionotropic excitatory neurotransmitter receptors in synapses.
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Affiliation(s)
- Elisa Carrillo
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, TX 77030, USA
| | - Cuauhtemoc U. Gonzalez
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, TX 77030, USA
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, TX 77030, USA
| | - Vladimir Berka
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, TX 77030, USA
| | - Vasanthi Jayaraman
- Center for Membrane Biology, Department of Biochemistry and Molecular Biology, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, TX 77030, USA
- MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, University of Texas Health Science Center at Houston, 6431 Fannin St., Houston, TX 77030, USA
- Corresponding author.
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