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Dahley C, Garessus EDG, Ebert A, Goss KU. Impact of cholesterol and sphingomyelin on intrinsic membrane permeability. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:183953. [PMID: 35526600 DOI: 10.1016/j.bbamem.2022.183953] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/14/2022] [Accepted: 04/26/2022] [Indexed: 11/30/2022]
Abstract
Transwell experiments with Caco-2 or MDCK cells are the gold standard for determining the intestinal permeability of chemicals. The intrinsic membrane permeability (P0), that can be extracted from these experiments, might be comparable to P0 measured in black lipid membrane (BLM) experiments and P0 predicted by the solubility-diffusion model. Unfortunately, the overlap between experimental P0,Caco-2/MDCK and P0,BLM data is very small. So far, differences between both approaches have been attributed to the cholesterol and sphingomyelin content of cell membranes, but the database is too sparse to thoroughly test this theory. To create a diverse dataset, we measured P0,BLM of ten chemicals in BLM experiments using DPhPC and DPhPC/cholesterol/sphingomyelin membranes. The results were compared to predicted BLM data and experimental Caco-2/MDCK data obtained from literature. While P0,BLM of all chemicals was well predicted by the solubility-diffusion model, P0,Caco-2/MDCK was only predictable for rather hydrophilic compounds with logarithmic hexadecane/water partition coefficients below -0.5. The effect of cholesterol and sphingomyelin on P0,BLM was negligibly small.
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Affiliation(s)
- Carolin Dahley
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, 04318 Leipzig, Germany.
| | - Estella Dora Germaine Garessus
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, 04318 Leipzig, Germany
| | - Andrea Ebert
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, 04318 Leipzig, Germany.
| | - Kai-Uwe Goss
- Department of Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research (UFZ), Permoserstraße 15, 04318 Leipzig, Germany; Institute of Chemistry, University of Halle-Wittenberg, Kurt-Mothes-Straße 2, 06120 Halle, Germany.
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2
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Kim SM, Zou G, Kim H, Kang M, Ahn S, Heo HY, Kim JS, Lim KM, Ausubel FM, Mylonakis E, Gao H, Kim W. Antimicrobial activity of the membrane-active compound nTZDpa is enhanced at low pH. Biomed Pharmacother 2022; 150:112977. [PMID: 35447554 DOI: 10.1016/j.biopha.2022.112977] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 04/03/2022] [Accepted: 04/12/2022] [Indexed: 11/30/2022] Open
Abstract
The opportunistic human pathogen Staphylococcus aureus can evade antibiotics by acquiring antibiotic resistance genes or by entering into a non-growing dormant state. Moreover, the particular circumstances of a specific infection site, such as acidity or anaerobicity, often weaken antibiotic potency. Decreased bacterial susceptibility combined with diminished antibiotic potency is responsible for high failure rates when treating S. aureus infections. Here, we report that the membrane-active antimicrobial agent nTZDpa does not only exhibit enhanced antibiotic activity against multidrug-resistant Gram-positive pathogens in acidic pH, but also retains antimicrobial potency under anaerobic conditions. This agent completely eradicated highly antibiotic-tolerant cells and biofilms formed by methicillin-resistant S. aureus at pH 5.5 at concentrations at which it was not potent at pH 7.4. Furthermore, nTZDpa was more potent at synergistically potentiating gentamicin killing against antibiotic-tolerant MRSA cells at low pH than at high pH. All-atom molecular dynamics simulations combined with membrane-permeabilization assays revealed that the neutral form of nTZDpa, which contains carboxylic acid, is more effective than the deprotonated form at penetrating the bacterial membrane and plays an essential role in membrane activity. An acidic pH increases the proportion of the neutrally charged nTZDpa, which results in antimicrobial enhancement. Our results provide key insights into rational design of pH-sensitive membrane-active antimicrobials and antibiotic adjuvants that are effective in an infection environment. These findings demonstrate that nTZDpa is a promising lead compound for developing new therapeutics against hard-to-cure infections caused by drug-resistant and -tolerant S. aureus.
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Affiliation(s)
- Soo Min Kim
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Guijin Zou
- Institute of High Performance Computing, A⁎STAR, Singapore 138632, Singapore
| | - Hyerim Kim
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Minjeong Kang
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Soyeon Ahn
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Hee Young Heo
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Jae-Seok Kim
- Department of Laboratory Medicine, Kangdong Sacred Heart Hospital, Hallym University College of Medicine, Seoul 05355, Republic of Korea
| | - Kyung-Min Lim
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea
| | - Frederick M Ausubel
- Department of Molecular Biology, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Eleftherios Mylonakis
- Division of Infectious Diseases, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, RI 02903, USA
| | - Huajian Gao
- Institute of High Performance Computing, A⁎STAR, Singapore 138632, Singapore; School of Mechanical and Aerospace Engineering, College of Engineering, Nanyang Technological University, Singapore 639789, Singapore
| | - Wooseong Kim
- College of Pharmacy, Graduate School of Pharmaceutical Sciences, Ewha Womans University, Seoul 03760, Republic of Korea.
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3
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Tivony R, Fletcher M, Keyser UF. Quantifying proton-induced membrane polarization in single biomimetic giant vesicles. Biophys J 2022; 121:2223-2232. [DOI: 10.1016/j.bpj.2022.05.041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 05/19/2022] [Accepted: 05/24/2022] [Indexed: 11/25/2022] Open
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Schweizer M, von der Ohe PC, Gräff T, Kühnen U, Hebel J, Heid C, Kundy L, Kuttler J, Moroff FM, Schlösinger AF, Schulze-Berge P, Triebskorn R, Panagopoulou E, Damalas DE, Thomaidis NS, Köhler HR. Heart rate as an early warning parameter and proxy for subsequent mortality in Danio rerio embryos exposed to ionisable substances. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 818:151744. [PMID: 34808159 DOI: 10.1016/j.scitotenv.2021.151744] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 11/13/2021] [Accepted: 11/13/2021] [Indexed: 06/13/2023]
Abstract
Environmental risk assessments of organic chemicals usually do not consider pH as a key factor. Hence, most substances are tested at a single pH only, which may underestimate the toxicity of ionisable substances with a pKa in the range of 4-10. Thus, the ability to consider the pH-dependent toxicity would be crucial for a more realistic assessment. Moreover, there is a tendency in acute toxicity tests to focus on mortality only, while little attention is paid to sublethal endpoints. We used Danio rerio embryos exposed to ten ionisable substances (the acids diclofenac, ibuprofen, naproxen and triclosan and the bases citalopram, fluoxetine, metoprolol, propranolol, tramadol and tetracaine) at four external pH levels, investigating the endpoints mortality (LC50) and heart rate (EC20). Dose-response curves were fitted with an ensemble-model to determine the true uncertainty and variation around the mean endpoints. The ensemble considers eight (heart rate) or twelve (mortality) individual models for binominal and Poisson distributed data, respectively, selected based on the Akaike Information Criterion (AIC). In case of equally good models, the mean endpoint of all models in the ensemble was calculated, resulting in more robust ECx estimates with lower 'standard errors' as compared to randomly selected individual models. We detected a high correlation between mortality (LC50) at 96 hpf and reduced heart rate (EC20) at 48 hpf for all compounds and all external pH levels (r = 0.98). Moreover, the observed pH-dependent effects were strongly associated with log D and thus, likely driven by differences in uptake (toxicokinetic) rather than internal (toxicodynamic) processes. Prospectively, the a priori consideration of pH-dependent effects of ionisable substances might make testing at different pH levels redundant, while the endpoint of mortality might even be replaced by a reliable sublethal proxy that would reduce the exposure, accelerating the evaluation process.
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Affiliation(s)
- Mona Schweizer
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | | | - Thomas Gräff
- German Environment Agency, Wörlitzer Platz 1, 06844 Dessau-Roßlau, Germany
| | - Ute Kühnen
- German Environment Agency, Wörlitzer Platz 1, 06844 Dessau-Roßlau, Germany
| | - Janine Hebel
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Christoph Heid
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Lone Kundy
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Julia Kuttler
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Friederike-Marie Moroff
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Anne-Frida Schlösinger
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Pia Schulze-Berge
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
| | - Rita Triebskorn
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany; Steinbeis-Transfer Center Ecotoxicology and Ecophysiology, Blumenstrasse 13, D-72108 Rottenburg, Germany
| | - Elena Panagopoulou
- Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, GR-15784 Athens, Greece
| | - Dimitrios E Damalas
- Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, GR-15784 Athens, Greece
| | - Nikolaos S Thomaidis
- Laboratory of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, GR-15784 Athens, Greece
| | - Heinz-R Köhler
- Animal Physiological Ecology, Institute of Evolution and Ecology, University of Tübingen, Auf der Morgenstelle 5, D-72076 Tübingen, Germany
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Pohl P. Biophysical Reviews' "Meet the Councilor Series"-a profile of Peter Pohl. Biophys Rev 2021; 13:839-844. [PMID: 35035592 PMCID: PMC8724173 DOI: 10.1007/s12551-021-00897-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 11/01/2021] [Indexed: 10/30/2022] Open
Abstract
It is my pleasure to write a few words to introduce myself to the readers of Biophysical Reviews as part of the "Meet the Councilor Series." Currently, I am serving the second period as IUPAB councilor after having been elected first in 2017. Initially, I studied Biophysics in Moscow (Russia) and later Medicine in Halle (Germany). My scientific carrier took me from the Medical School of the Martin Luther University of Halle-Wittenberg, via the Leibniz Institute for Molecular Pharmacology (Berlin) and the Institute for Biology at the Humboldt University (Berlin) to the Physics Department of the Johannes Kepler University in Linz (Austria). My key research interests lie in the molecular mechanisms of transport phenomena occurring at the lipid membrane, including (i) spontaneous and facilitated transport of water and other small molecules across membranes in reconstituted systems, (ii) proton migration along the membrane surface, (iii) protein translocation, and (iv) bilayer mechanics. Training of undergraduate, graduate, and postdoctoral researchers from diverse academic disciplines has been-and shall remain-a consistent part of my work.
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Affiliation(s)
- Peter Pohl
- Institute of Biophysics, Johannes Kepler University, Linz, Austria
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6
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Hossain SI, Saha SC, Deplazes E. Phenolic compounds alter the ion permeability of phospholipid bilayers via specific lipid interactions. Phys Chem Chem Phys 2021; 23:22352-22366. [PMID: 34604899 DOI: 10.1039/d1cp03250j] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
This study aims to understand the role of specific phenolic-lipid interactions in the membrane-altering properties of phenolic compounds. We combine tethered lipid bilayer (tBLM) electrical impedance spectroscopy (EIS) with all-atom molecular dynamics (MD) simulations to study the membrane interactions of six phenolic compounds: caffeic acid methyl ester, caffeic acid, 3,4 dihydroxybenzoic acid, chlorogenic acid, syringic acid and p-coumaric acid. tBLM/EIS experiments showed that caffeic acid methyl ester, caffeic acid and 3,4 dihydroxybenzoic acid significantly increase the permeability of phospholipid bilayers to Na+ ions. In contrast, chlorogenic acid, syringic acid and p-coumaric acid showed no effect. Experiments with lipids lacking the phosphate group show a significant decrease in the membrane-altering effects indicating that specific phenolic-lipid interactions are critical in altering ion permeability. MD simulations confirm that compounds that alter ion permeability form stable interactions with the phosphate oxygen. In contrast, inactive phenolic compounds are superficially bound to the membrane surface and primarily interact with interfacial water. Our combined results show that compounds with similar structures can have very different effects on ion permeability in membranes. These effects are governed by specific interactions at the water-lipid interface and show no correlation with lipophilicity. Furthermore, none of the compounds alter the overall structure of the phospholipid bilayer as determined by area per lipid and order parameters. Based on data from this study and previous findings, we propose that phenolic compounds can alter membrane ion permeability by causing local changes in lipid packing that subsequently reduce the energy barrier for ion-induced pores.
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Affiliation(s)
- Sheikh I Hossain
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia.
| | - Suvash C Saha
- School of Mechanical and Mechatronic Engineering, University of Technology Sydney, Ultimo, NSW 2007, Australia
| | - Evelyne Deplazes
- School of Life Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia. .,School of Chemistry and Molecular Biosciences, University of Queensland, St Lucia, QLD 4072, Australia
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7
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Dutta A, Vreeken J, Ghiringhelli LM, Bereau T. Data-driven equation for drug-membrane permeability across drugs and membranes. J Chem Phys 2021; 154:244114. [PMID: 34241352 DOI: 10.1063/5.0053931] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Drug efficacy depends on its capacity to permeate across the cell membrane. We consider the prediction of passive drug-membrane permeability coefficients. Beyond the widely recognized correlation with hydrophobicity, we additionally consider the functional relationship between passive permeation and acidity. To discover easily interpretable equations that explain the data well, we use the recently proposed sure-independence screening and sparsifying operator (SISSO), an artificial-intelligence technique that combines symbolic regression with compressed sensing. Our study is based on a large in silico dataset of 0.4 × 106 small molecules extracted from coarse-grained simulations. We rationalize the equation suggested by SISSO via an analysis of the inhomogeneous solubility-diffusion model in several asymptotic acidity regimes. We further extend our analysis to the dependence on lipid-membrane composition. Lipid-tail unsaturation plays a key role but surprisingly contributes stepwise rather than proportionally. Our results are in line with previously observed changes in permeability, suggesting the distinction between liquid-disordered and liquid-ordered permeation. Together, compressed sensing with analytically derived asymptotes establish and validate an accurate, broadly applicable, and interpretable equation for passive permeability across both drug and lipid-tail chemistry.
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Affiliation(s)
- Arghya Dutta
- Max Planck Institute for Polymer Research, Mainz, Germany
| | - Jilles Vreeken
- CISPA Helmholtz Center for Information Security, Saarbrücken, Germany
| | - Luca M Ghiringhelli
- The NOMAD Laboratory at the Fritz Haber Institute of the Max Planck Society and Humboldt University, Berlin, Germany
| | - Tristan Bereau
- Max Planck Institute for Polymer Research, Mainz, Germany
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8
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Distribution of ion pairs into a bilayer lipid membrane and its effect on the ionic permeability. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183724. [PMID: 34364888 DOI: 10.1016/j.bbamem.2021.183724] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 08/02/2021] [Accepted: 08/02/2021] [Indexed: 11/24/2022]
Abstract
This work reports the distribution constant of a target ion and a counter-ion between an aqueous phase and an artificial bilayer lipid membrane (BLM) and its influence to the ionic permeability through a BLM. A theoretical formula for ionic permeability through a BLM based on the distribution of the target ion and the counter-ion is also proposed and validated by analyzing the flux of a fluorescent cation [rhodamine 6G (R6G+)] through the BLM in the presence of counter-ions (X- = Br-, BF4-, and ClO4-). The transmembrane flux was evaluated by simultaneous measurement of the transmembrane current density and the transmembrane fluorescence intensity as a function of the membrane potential. The distribution constant of R6G+ and X- between the aqueous and BLM phases was determined by a liposome-extraction method. The measured ionic permeability exhibited non-linear dependent on the aqueous concentration of R6G+ or X-, but proportional to the concentration of R6G+ and X- inside the BLM evaluated from the distribution constant of R6G+ and X-. The proportionality demonstrates that the distribution of cations and anions between the aqueous and BLM phases dominates the flux of ion transport through the BLM. The proposed formula can express the dependence of the transmembrane current on the membrane potential and the concentrations of R6G+ and X- in the aqueous phase.
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9
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Bouret Y, Guille-Collignon M, Lemaître F. Simulations of amperometric monitoring of exocytosis: moderate pH variations within the cell-electrode cleft with the buffer diffusion. Anal Bioanal Chem 2021; 413:6769-6776. [PMID: 34120197 DOI: 10.1007/s00216-021-03443-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 05/28/2021] [Indexed: 10/21/2022]
Abstract
Amperometry with ultramicroelectrodes is nowadays a routine technique to investigate neurotransmitter secretion by vesicular exocytosis at the single-cell level. This electroanalytical tool allows one to understand many aspects of the vesicular release in terms of mechanisms. However, the electrochemical detection relies on the oxidation of released neurotransmitters that produce 2H+ and thus the possible acidification of the cell-electrode cleft. In a previous work, we considered a model involving the H+ diffusion or/and its reaction with buffer species. In this article, we report a more general model which takes into account the ability of buffer species to move and to be regenerated within the cell-electrode cleft. As a consequence, the pH within the cleft is still equal to its physiological value regardless of the electrochemical detection of the vesicular release for usual exocytotic cell frequencies. This confirms that amperometry at the single-cell level is a very robust technique for investigating vesicular exocytosis.
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Affiliation(s)
- Yann Bouret
- CNRS-UMR 7010 Institut de Physique de Nice, Université Nice Côte d'Azur, Av. Joseph Vallot, 06100, Nice, France
| | - Manon Guille-Collignon
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France
| | - Frédéric Lemaître
- PASTEUR, Département de chimie, École normale supérieure, PSL University, Sorbonne Université, CNRS, 75005, Paris, France.
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10
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Dank A, van Mastrigt O, Boeren S, Lillevang SK, Abee T, Smid EJ. Propionibacterium freudenreichii thrives in microaerobic conditions by complete oxidation of lactate to CO 2. Environ Microbiol 2021; 23:3116-3129. [PMID: 33955639 PMCID: PMC8360058 DOI: 10.1111/1462-2920.15532] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 04/13/2021] [Indexed: 11/28/2022]
Abstract
In this study we show increased biomass formation for four species of food-grade propionic acid bacteria (Acidipropionibacterium acidipropionici, Acidipropionibacterium jensenii, Acidipropionibacterium thoenii and Propionibacterium freudenreichii) when exposed to oxygen, implicating functional respiratory systems. Using an optimal microaerobic condition, P. freudenreichii DSM 20271 consumed lactate to produce propionate and acetate initially. When lactate was depleted propionate was oxidized to acetate. We propose to name the switch from propionate production to consumption in microaerobic conditions the 'propionate switch'. When propionate was depleted the 'acetate switch' occurred, resulting in complete consumption of acetate. Both growth rate on lactate (0.100 versus 0.078 h-1 ) and biomass yield (20.5 versus 8.6 g* mol-1 lactate) increased compared to anaerobic conditions. Proteome analysis revealed that the abundance of proteins involved in the aerobic and anaerobic electron transport chains and major metabolic pathways did not significantly differ between anaerobic and microaerobic conditions. This implicates that P. freudenreichii is prepared for utilizing O2 when it comes available in anaerobic conditions. The ecological niche of propionic acid bacteria can conceivably be extended to environments with oxygen gradients from oxic to anoxic, so-called microoxic environments, as found in the rumen, gut and soils, where they can thrive by utilizing low concentrations of oxygen.
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Affiliation(s)
- Alexander Dank
- Laboratory of Food MicrobiologyWageningen University & Research, P.O. Box 17Wageningen6700AAThe Netherlands
| | - Oscar van Mastrigt
- Laboratory of Food MicrobiologyWageningen University & Research, P.O. Box 17Wageningen6700AAThe Netherlands
| | - Sjef Boeren
- Laboratory of BiochemistryWageningen University & ResearchWageningenThe Netherlands
| | - Søren K. Lillevang
- Arla Innovation Centre, Arla Foods, Agro Food Park 19Aarhus N8200Denmark
| | - Tjakko Abee
- Laboratory of Food MicrobiologyWageningen University & Research, P.O. Box 17Wageningen6700AAThe Netherlands
| | - Eddy J. Smid
- Laboratory of Food MicrobiologyWageningen University & Research, P.O. Box 17Wageningen6700AAThe Netherlands
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11
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Pinheiro JPS, Windsor FM, Wilson RW, Tyler CR. Global variation in freshwater physico-chemistry and its influence on chemical toxicity in aquatic wildlife. Biol Rev Camb Philos Soc 2021; 96:1528-1546. [PMID: 33942490 DOI: 10.1111/brv.12711] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 03/16/2021] [Accepted: 03/17/2021] [Indexed: 12/28/2022]
Abstract
Chemical pollution is one of the major threats to global freshwater biodiversity and will be exacerbated through changes in temperature and rainfall patterns, acid-base chemistry, and reduced freshwater availability due to climate change. In this review we show how physico-chemical features of natural fresh waters, including pH, temperature, oxygen, carbon dioxide, divalent cations, anions, carbonate alkalinity, salinity and dissolved organic matter, can affect the environmental risk to aquatic wildlife of pollutant chemicals. We evidence how these features of freshwater physico-chemistry directly and/or indirectly affect the solubility, speciation, bioavailability and uptake of chemicals [including via alterations in the trans-epithelial electric potential (TEP) across the gills or skin] as well as the internal physiology/biochemistry of the organisms, and hence ultimately toxicity. We also show how toxicity can vary with species and ontogeny. We use a new database of global freshwater chemistry (GLORICH) to demonstrate the huge variability (often >1000-fold) for these physico-chemical variables in natural fresh waters, and hence their importance to ecotoxicology. We emphasise that a better understanding of chemical toxicity and more accurate environmental risk assessment requires greater consideration of the natural water physico-chemistry in which the organisms we seek to protect live.
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Affiliation(s)
- João Paulo S Pinheiro
- Instituto de Biociências, Universidade de São Paulo, Matão Street, 14 Lane, Number 101, Room 220, Cidade Universitária, São Paulo, 05508-090, Brazil
| | - Fredric M Windsor
- School of Natural and Environmental Sciences, Newcastle University, Newcastle, Tyne and Wear, NE1 7RU, U.K
| | - Rod W Wilson
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, U.K
| | - Charles R Tyler
- Biosciences, University of Exeter, Exeter, Devon, EX4 4QD, U.K
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12
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Cortes-López H, Castro-Rosas J, García-Contreras R, Rodríguez-Zavala JS, González-Pedrajo B, Díaz-Guerrero M, Hernández-Morales J, Muñoz-Cazares N, Soto-Hernández M, Ruíz-Posadas LDM, Castillo-Juárez I. Antivirulence Activity of a Dietary Phytochemical: Hibiscus Acid Isolated from Hibiscus sabdariffa L. Reduces the Virulence of Pseudomonas aeruginosa in a Mouse Infection Model. J Med Food 2021; 24:934-943. [PMID: 33751918 DOI: 10.1089/jmf.2020.0135] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Hibiscus sabdariffa L. (Hs) calyxes, rich in organic acids, are included in diets in different countries. In recent years, some phytochemicals have been shown to reduce bacterial virulence at sublethal concentrations by interfering with quorum sensing (QS) systems. Therefore, in this study the antivirulence properties of Hs calyxes and two γ-lactones (hibiscus acid [HA] and its methyl ester) in Pseudomonas aeruginosa were analyzed. Acetone and methanol extracts of Hs showed anti-QS activity by inhibiting violacein production (60% to 80% with 250 μg/mL). In molecular docking analysis, the γ-lactones registered a good binding score, which suggests strong interaction with the active site of LasR protein. To verify their effect in vitro, they were isolated from Hs and evaluated in six QS-regulated phenotypes, as well as in ExoU toxin that is released by the type III secretion system (T3SS). At 500 μg/mL they reduced alkaline protease (29-52%) and elastase (15-37%) activity, biofilm formation (∼75%), and swarming (50%), but there was no effect on pyocyanin production, hemolytic activity, or type III secretion. In a mouse abscess/necrosis model, HA at sublethal concentrations (15 and 31.2 μg/mL) affected infection establishment and prevented damage and systemic spread. In conclusion, HA is the first molecule identified with antivirulence properties in Hs with the potential to prevent infections caused by P. aeruginosa.
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Affiliation(s)
- Humberto Cortes-López
- Posgrado de Botánica y, Colegio de Postgraduados, Campus Montecillo, Texcoco, Estado de México, México
| | - Javier Castro-Rosas
- Instituto de Ciencias Básicas e Ingeniería, Universidad Autónoma del Estado de Hidalgo, Mineral de la Reforma, Hidalgo, México
| | - Rodolfo García-Contreras
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, CDMX, México
| | | | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, CDMX, México
| | - Miguel Díaz-Guerrero
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, CDMX, México
| | - Javier Hernández-Morales
- Posgrado en Fitosanidad-Fitopatología, Colegio de Postgraduados, Campus Montecillo, Texcoco, Estado de México, México
| | - Naybi Muñoz-Cazares
- Posgrado de Botánica y, Colegio de Postgraduados, Campus Montecillo, Texcoco, Estado de México, México
| | - Marcos Soto-Hernández
- Posgrado de Botánica y, Colegio de Postgraduados, Campus Montecillo, Texcoco, Estado de México, México
| | | | - Israel Castillo-Juárez
- Posgrado de Botánica y, Colegio de Postgraduados, Campus Montecillo, Texcoco, Estado de México, México
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13
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Guo LX, Tong Y, Wang J, Yin G, Huang HS, Zeng L, Wang P, Li JP, Bi KS, Wang TJ. Determination and Comparison of Short-Chain Fatty Acids in Serum and Colon Content Samples: Alzheimer's Disease Rat as a Case Study. Molecules 2020; 25:molecules25235739. [PMID: 33291848 PMCID: PMC7729479 DOI: 10.3390/molecules25235739] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 11/20/2020] [Accepted: 12/02/2020] [Indexed: 01/16/2023] Open
Abstract
Short-chain fatty acids (SCFAs) are the main microbial fermentation products from dietary fibers in the colon, and it has been speculated that they play a key role in keeping healthy in the whole-body. However, differences in SCFAs concentration in the serum and colon samples had attracted little attention. In this study, we have optimized the extract and analysis methods for the determination of ten SCFAs in both serum and colon content samples. Methanol and acetonitrile were chosen for extraction of SCFAs from serum and colon content samples, respectively. Biological samples were collected from Alzheimer's disease rats treated by extract of Schisandra chinensis (Turcz.) Baill (SC-extract) were taken as research objects. The results showed that, the relative peak intensities of SCFAs in the colon content from all groups were quite similar, and the trend was identical in the serum samples. Compared with the values in humans, the ratio of ten SCFAs in rat's colon was similar, while the percent of acetate in rat's serum was significantly higher. For therapy of Alzheimer's disease (AD), SC-extract decreased the concentration of butyrate, 3-Methyvalerate, and caproate in the serum samples towards the trend of normal rats. This study may help our understanding of how SCFAs are transported across colonic epithelium in healthy and diseased organisms.
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Affiliation(s)
- Lin-Xiu Guo
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Yue Tong
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
| | - Jue Wang
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
| | - Guo Yin
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
| | - Hou-Shuang Huang
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
| | - Long Zeng
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
| | - Ping Wang
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
| | - Jun-Peng Li
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
| | - Kai-Shun Bi
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
- Correspondence: (K.-S.B.); (T.-J.W.); Tel.: +86-024-4352-0012 (K.-S.B.); +86-755-2603-1728 (T.-J.W.)
| | - Tie-Jie Wang
- Shenzhen Key Laboratory of Drug Quality Standard Research, Shenzhen Institute for Drug Control, Shenzhen 518057, China; (L.-X.G.); (Y.T.); (J.W.); (G.Y.); (H.-S.H.); (L.Z.); (P.W.); (J.-P.L.)
- School of Pharmacy, Shenyang Pharmaceutical University, Shenyang 110016, China
- Correspondence: (K.-S.B.); (T.-J.W.); Tel.: +86-024-4352-0012 (K.-S.B.); +86-755-2603-1728 (T.-J.W.)
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14
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Darby JF, Vidler LR, Simpson PJ, Al-Lazikani B, Matthews SJ, Sharp SY, Pearl LH, Hoelder S, Workman P. Solution structure of the Hop TPR2A domain and investigation of target druggability by NMR, biochemical and in silico approaches. Sci Rep 2020; 10:16000. [PMID: 32994435 PMCID: PMC7524759 DOI: 10.1038/s41598-020-71969-w] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 08/24/2020] [Indexed: 02/08/2023] Open
Abstract
Heat shock protein 90 (Hsp90) is a molecular chaperone that plays an important role in tumour biology by promoting the stabilisation and activity of oncogenic 'client' proteins. Inhibition of Hsp90 by small-molecule drugs, acting via its ATP hydrolysis site, has shown promise as a molecularly targeted cancer therapy. Owing to the importance of Hop and other tetratricopeptide repeat (TPR)-containing cochaperones in regulating Hsp90 activity, the Hsp90-TPR domain interface is an alternative site for inhibitors, which could result in effects distinct from ATP site binders. The TPR binding site of Hsp90 cochaperones includes a shallow, positively charged groove that poses a significant challenge for druggability. Herein, we report the apo, solution-state structure of Hop TPR2A which enables this target for NMR-based screening approaches. We have designed prototype TPR ligands that mimic key native 'carboxylate clamp' interactions between Hsp90 and its TPR cochaperones and show that they block binding between Hop TPR2A and the Hsp90 C-terminal MEEVD peptide. We confirm direct TPR-binding of these ligands by mapping 1H-15N HSQC chemical shift perturbations to our new NMR structure. Our work provides a novel structure, a thorough assessment of druggability and robust screening approaches that may offer a potential route, albeit difficult, to address the chemically challenging nature of the Hop TPR2A target, with relevance to other TPR domain interactors.
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Affiliation(s)
- John F Darby
- Division of Cancer Therapeutics, Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK
| | - Lewis R Vidler
- Division of Cancer Therapeutics, Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK
| | - Peter J Simpson
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
- Bruker UK Ltd, Banner Lane, Coventry, CV4 9GH, UK
| | - Bissan Al-Lazikani
- Division of Cancer Therapeutics, Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK
| | - Stephen J Matthews
- Department of Life Sciences, Imperial College London, London, SW7 2AZ, UK
| | - Swee Y Sharp
- Division of Cancer Therapeutics, Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK
| | - Laurence H Pearl
- Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton, UK
- Division of Structural Biology, The Institute of Cancer Research, 237 Fulham Road, London, SW3 6JB, UK
| | - Swen Hoelder
- Division of Cancer Therapeutics, Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK
| | - Paul Workman
- Division of Cancer Therapeutics, Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, SM2 5NG, UK.
- Cancer Research UK Convergence Science Centre, The Institute of Cancer Research and Imperial College London, London, UK.
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15
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Nath S, Sinha A, Singha YS, Dey A, Bhattacharjee N, Deb B. Prevalence of antibiotic-resistant, toxic metal-tolerant and biofilm-forming bacteria in hospital surroundings. Environ Anal Health Toxicol 2020; 35:e2020018. [PMID: 32979903 PMCID: PMC7656160 DOI: 10.5620/eaht.2020018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 08/31/2020] [Indexed: 01/26/2023] Open
Abstract
The emergence and rapid spread of antibiotic-resistant bacteria due to unethical and non-scientific disposal of hospital wastes and clinical by-products caused an alarming environmental concern and associated public health risks. The present study aims to assess the co-selection of antibiotic resistance and heavy metal tolerance by bacteria isolated from hospital effluents. These isolates were also tested for hemolytic activity, pH-tolerance, thermal inactivation, auto-aggregation, cell-surface hydrophobicity and interaction with other bacteria. The study reports the prevalence of antibiotic-resistant and heavy metal tolerant bacteria in clinical effluents and water samples. Most of these isolates were resistant to vancomycin, clindamycin, ampicillin, rifampicin, penicillin-G, methicillin and cefdinir, and evidenced the production of extended-spectrum β-lactamase enzyme. Toxic metals such as cadmium, copper, iron, lead and zinc also exert a selection pressure towards antibiotic resistance. Pseudomonas aeruginosa strain GCC_19W3, Bacillus sp. strain GCC_19S2 and Achromobacter spanius strain GCC_SB1 showed β-hemolysis, evidenced by the complete breakdown of the red blood cells. Highest auto-aggregation was exhibited by Bacillus sp. strain GCC_19S2; whereas, maximum cell-surface hydrophobicity was displayed by P. aeruginosa strain GCC_19W1. Antagonistic activity by Stenotrophomonas maltophilia strain GCC_19W2, P. aeruginosa strain GCC_19W3 and strains of Achromobacter restricts the growth of other microorganisms by producing some bactericidal substances. The study emphasises undertaking safety measures for the disposal of clinical effluents directly into the environment. The study suggests adopting necessary measures and regulations to restrict the spread of emerging pathogens within the hospital biome and community, which if unnoticed, might pose a significant clinical challenge.
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Affiliation(s)
- Soumitra Nath
- Department of Biotechnology, Gurucharan College, Silchar, Assam, India
- Bioinformatics Centre, Gurucharan College, Silchar, Assam, India
- Institutional Biotech Hub, Gurucharan College, Silchar, Assam, India
| | - Ahana Sinha
- Department of Biotechnology, Gurucharan College, Silchar, Assam, India
| | | | - Ankita Dey
- Department of Biotechnology, Gurucharan College, Silchar, Assam, India
| | | | - Bibhas Deb
- Department of Biotechnology, Gurucharan College, Silchar, Assam, India
- Bioinformatics Centre, Gurucharan College, Silchar, Assam, India
- Institutional Biotech Hub, Gurucharan College, Silchar, Assam, India
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16
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Biedermann F, Ghale G, Hennig A, Nau WM. Fluorescent artificial receptor-based membrane assay (FARMA) for spatiotemporally resolved monitoring of biomembrane permeability. Commun Biol 2020; 3:383. [PMID: 32669621 PMCID: PMC7363885 DOI: 10.1038/s42003-020-1108-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2019] [Accepted: 06/19/2020] [Indexed: 02/07/2023] Open
Abstract
The spatiotemporally resolved monitoring of membrane translocation, e.g., of drugs or toxins, has been a long-standing goal. Herein, we introduce the fluorescent artificial receptor-based membrane assay (FARMA), a facile, label-free method. With FARMA, the permeation of more than hundred organic compounds (drugs, toxins, pesticides, neurotransmitters, peptides, etc.) through vesicular phospholipid bilayer membranes has been monitored in real time (µs-h time scale) and with high sensitivity (nM-µM concentration), affording permeability coefficients across an exceptionally large range from 10-9-10-3 cm s-1. From a fundamental point of view, FARMA constitutes a powerful tool to assess structure-permeability relationships and to test biophysical models for membrane passage. From an applied perspective, FARMA can be extended to high-throughput screening by adaption of the microplate reader format, to spatial monitoring of membrane permeation by microscopy imaging, and to the compartmentalized monitoring of enzymatic activity.
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Affiliation(s)
- Frank Biedermann
- Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany.
| | - Garima Ghale
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
| | - Andreas Hennig
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany
| | - Werner M Nau
- Department of Life Sciences and Chemistry, Jacobs University Bremen, Campus Ring 1, 28759, Bremen, Germany.
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17
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Laure M, Hamza H, Koch-Heier J, Quernheim M, Müller C, Schreiber A, Müller G, Pleschka S, Ludwig S, Planz O. Antiviral efficacy against influenza virus and pharmacokinetic analysis of a novel MEK-inhibitor, ATR-002, in cell culture and in the mouse model. Antiviral Res 2020; 178:104806. [PMID: 32304723 DOI: 10.1016/j.antiviral.2020.104806] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Revised: 04/10/2020] [Accepted: 04/13/2020] [Indexed: 10/24/2022]
Abstract
Antiviral therapies against influenza are required, especially for high-risk patients, severe influenza and in case of highly pathogenic influenza virus (IV) strains. However, currently, licensed drugs that target the virus directly are not very effective and often lead to the development of resistant IV variants. This may be overcome by targeting host cell factors that are required for IV propagation. IV induces a variety of host cell signaling cascades, such as the Raf/MEK/ERK kinase pathway. The activation of this pathway is necessary for IV propagation. MEK-inhibitors block the activation of the pathway on the bottleneck of the signaling cascade leading to impaired virus propagation. In the present study, we aimed to compare the antiviral potency and bioavailability of the MEK-inhibitor CI-1040 versus its major active metabolite ATR-002, in vitro as well as in the mouse model. In cell culture assays, an approximately 10-fold higher concentration of ATR-002 is required to generate the same antiviral activity as for CI-1040. Interestingly, we observed that considerably lower concentrations of ATR-002 were required to achieve a reduction of the viral load in vivo. Pharmacokinetic studies with ATR-002 and CI-1040 in mice have found the Cmax and AUC to be far higher for ATR-002 than for CI-1040. Our results thereby demonstrate the in vivo superiority of the active metabolite ATR-002 over CI-1040 as an antiviral agent despite its weaker cell membrane permeability. Therefore, ATR-002 is an attractive candidate for development as an efficient antiviral agent, especially given the fact that a treatment based on cellular pathway inhibition would be far less likely to lead to viral drug resistance.
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Affiliation(s)
- Martin Laure
- Interfaculty Institute for Cell Biology, Department of Immunology, Eberhard Karls University, Tübingen, Germany; Atriva Therapeutics GmbH, Christophstr. 32, 72072, Tübingen, Germany
| | - Hazem Hamza
- Interfaculty Institute for Cell Biology, Department of Immunology, Eberhard Karls University, Tübingen, Germany; Atriva Therapeutics GmbH, Christophstr. 32, 72072, Tübingen, Germany; Virology Laboratory, Environmental Research Division, National Research Centre, Cairo, Egypt
| | - Julia Koch-Heier
- Interfaculty Institute for Cell Biology, Department of Immunology, Eberhard Karls University, Tübingen, Germany; Atriva Therapeutics GmbH, Christophstr. 32, 72072, Tübingen, Germany
| | - Martin Quernheim
- Chemcon GmbH, Engesserstr. 4B, 79108, Freiburg I. Brsg., Germany
| | - Christin Müller
- Institute of Medical Virology, Justus Liebig University, Giessen, Germany
| | - Andre Schreiber
- Institute of Virology, Westfaelische Wilhelms-University, Muenster, Germany
| | | | - Stephan Pleschka
- Institute of Medical Virology, Justus Liebig University, Giessen, Germany
| | - Stephan Ludwig
- Institute of Virology, Westfaelische Wilhelms-University, Muenster, Germany
| | - Oliver Planz
- Interfaculty Institute for Cell Biology, Department of Immunology, Eberhard Karls University, Tübingen, Germany; Atriva Therapeutics GmbH, Christophstr. 32, 72072, Tübingen, Germany.
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18
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Gabba M, Frallicciardi J, van 't Klooster J, Henderson R, Syga Ł, Mans R, van Maris AJA, Poolman B. Weak Acid Permeation in Synthetic Lipid Vesicles and Across the Yeast Plasma Membrane. Biophys J 2019; 118:422-434. [PMID: 31843263 PMCID: PMC6976801 DOI: 10.1016/j.bpj.2019.11.3384] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2018] [Revised: 11/10/2019] [Accepted: 11/14/2019] [Indexed: 12/29/2022] Open
Abstract
We present a fluorescence-based approach for determination of the permeability of small molecules across the membranes of lipid vesicles and living cells. With properly designed experiments, the method allows us to assess the membrane physical properties both in vitro and in vivo. We find that the permeability of weak acids increases in the order of benzoic > acetic > formic > lactic, both in synthetic lipid vesicles and the plasma membrane of Saccharomyces cerevisiae, but the permeability is much lower in yeast (one to two orders of magnitude). We observe a relation between the molecule permeability and the saturation of the lipid acyl chain (i.e., lipid packing) in the synthetic lipid vesicles. By analyzing wild-type yeast and a manifold knockout strain lacking all putative lactic acid transporters, we conclude that the yeast plasma membrane is impermeable to lactic acid on timescales up to ∼2.5 h.
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Affiliation(s)
- Matteo Gabba
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | - Jacopo Frallicciardi
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | - Joury van 't Klooster
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | - Ryan Henderson
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | - Łukasz Syga
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands
| | - Robert Mans
- Department of Industrial Biotechnology, Delft University of Technology, Delft, the Netherlands
| | - Antonius J A van Maris
- Department of Industrial Biotechnology, Delft University of Technology, Delft, the Netherlands; Industrial Biotechnology Division, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Bert Poolman
- Department of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Groningen, the Netherlands.
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19
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Schweizer M, Brilisauer K, Triebskorn R, Forchhammer K, Köhler HR. How glyphosate and its associated acidity affect early development in zebrafish ( Danio rerio). PeerJ 2019; 7:e7094. [PMID: 31249735 PMCID: PMC6589083 DOI: 10.7717/peerj.7094] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 05/07/2019] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Glyphosate is among the most extensively used pesticides worldwide. Following the ongoing highly controversial debate on this compound, its potential impact on non-target organisms is a fundamental scientific issue. In its pure compound form, glyphosate is known for its acidic properties. METHODS We exposed zebrafish (Danio rerio) embryos to concentrations between 10 μM and 10 mM glyphosate in an unbuffered aqueous medium, as well as at pH 7, for 96 hours post fertilization (hpf). Furthermore, we investigated the effects of aqueous media in the range of pH 3 to 8, in comparison with 1 mM glyphosate treatment at the respective pH levels. Additionally, we exposed zebrafish to 7-deoxy-sedoheptulose (7dSh), another substance that interferes with the shikimate pathway by a mechanism analogous to that of glyphosate, at a concentration of one mM. The observed endpoints included mortality, the hatching rate, developmental delays at 24 hpf, the heart rate at 48 hpf and the malformation rate at 96 hpf. LC10/50, EC10 and, if reasonable, EC50 values were determined for unbuffered glyphosate. RESULTS The results revealed high mortalities in all treatments associated with low pH, including high concentrations of unbuffered glyphosate (>500 μM), low pH controls and glyphosate treatments with pH < 3.4. Sublethal endpoints like developmental delays and malformations occurred mainly at higher concentrations of unbuffered glyphosate. In contrast, effects on the hatching rate became particularly prominent in treatments at pH 7, showing that glyphosate significantly accelerates hatching compared with the control and 7dSh, even at the lowest tested concentration. Glyphosate also affected the heart rate, resulting in alterations both at pH 7 and, even more pronounced, in the unbuffered system. In higher concentrations, glyphosate tended to accelerate the heart rate in zebrafish embryos, again, when not masked by the decelerating influence of its low pH. At pH > 4, no mortality occurred, neither in the control nor in glyphosate treatments. At 1 mM, 7dSh did not induce any mortality, developmental delays or malformations; only slightly accelerated hatching and a decelerated heart rate were observed. Our results demonstrate that lethal impacts in zebrafish embryos can be attributed mainly to low pH, but we could also show a pH-independent effect of glyphosate on the development of zebrafish embryos on a sublethal level.
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Affiliation(s)
- Mona Schweizer
- Institute of Evolution and Ecology, Animal Physiological Ecology, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Klaus Brilisauer
- Microbiology, Organismic Interactions, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Rita Triebskorn
- Institute of Evolution and Ecology, Animal Physiological Ecology, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
- Steinbeis Transfer-Center for Ecotoxicology and Ecophysiology, Rottenburg am Neckar, Germany
| | - Karl Forchhammer
- Microbiology, Organismic Interactions, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
| | - Heinz-R. Köhler
- Institute of Evolution and Ecology, Animal Physiological Ecology, Eberhard-Karls-Universität Tübingen, Tübingen, Germany
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20
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Abstract
Spontaneous solute and solvent permeation through membranes is of vital importance to human life, be it gas exchange in red blood cells, metabolite excretion, drug/toxin uptake, or water homeostasis. Knowledge of the underlying molecular mechanisms is the sine qua non of every functional assignment to membrane transporters. The basis of our current solubility diffusion model was laid by Meyer and Overton. It correlates the solubility of a substance in an organic phase with its membrane permeability. Since then, a wide range of studies challenging this rule have appeared. Commonly, the discrepancies have their origin in ill-used measurement approaches, as we demonstrate on the example of membrane CO2 transport. On the basis of the insight that scanning electrochemical microscopy offered into solute concentration distributions in immediate membrane vicinity of planar membranes, we analyzed the interplay between chemical reactions and diffusion for solvent transport, weak acid permeation, and enzymatic reactions adjacent to membranes. We conclude that buffer reactions must also be considered in spectroscopic investigations of weak acid transport in vesicular suspensions. The evaluation of energetic contributions to membrane translocation of charged species demonstrates the compatibility of the resulting membrane current with the solubility diffusion model. A local partition coefficient that depends on membrane penetration depth governs spontaneous membrane translocation of both charged and uncharged molecules. It is determined not only by the solubility in an organic phase but also by other factors like cholesterol concentration and intrinsic electric membrane potentials.
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Affiliation(s)
- Christof Hannesschlaeger
- From the Institute of Biophysics , Johannes Kepler University Linz , Gruberstrasse 40 , 4020 Linz , Austria
| | - Andreas Horner
- From the Institute of Biophysics , Johannes Kepler University Linz , Gruberstrasse 40 , 4020 Linz , Austria
| | - Peter Pohl
- From the Institute of Biophysics , Johannes Kepler University Linz , Gruberstrasse 40 , 4020 Linz , Austria
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21
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The Effect of Buffers on Weak Acid Uptake by Vesicles. Biomolecules 2019; 9:biom9020063. [PMID: 30781892 PMCID: PMC6406578 DOI: 10.3390/biom9020063] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 02/07/2019] [Accepted: 02/08/2019] [Indexed: 11/16/2022] Open
Abstract
The assessment of weak acid membrane permeability (Pm) frequently involves large unilamellar vesicles. It relies on measurements of the intravesicular pH drop, ΔpHin, in response to a sudden augmentation of external acid concentration. However, ΔpHin may be primarily governed by non-instantaneous protonation and deprotonation reactions of (i) the acid itself, (ii) the buffer molecules, and (iii) the fluorescent pH reporter dye. Moreover, buffer concentration and acid gradient also serve as determinants of ΔpHin, as we show here. The uniexponential time constant (τ) of ΔpHin(t) is an invalid measure of Pm as Arrhenius plots of Pm and τ reveal different activation energies for acid influx. We calculate Pm by fitting a mathematical model to experimental stopped-flow traces. The model takes into account not only the time course of total internal buffer capacity but also (i) water self-dissociation, (ii) volume changes due to acid induced osmotic water flow, and (iii) the spontaneous membrane proton leak. It allows extracting a Pm of 30.8 ± 3.5 μm/s for formic acid for 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) vesicles.
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22
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Bushell FML, Tonner PD, Jabbari S, Schmid AK, Lund PA. Synergistic Impacts of Organic Acids and pH on Growth of Pseudomonas aeruginosa: A Comparison of Parametric and Bayesian Non-parametric Methods to Model Growth. Front Microbiol 2019; 9:3196. [PMID: 30671033 PMCID: PMC6331447 DOI: 10.3389/fmicb.2018.03196] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 12/10/2018] [Indexed: 01/05/2023] Open
Abstract
Different weak organic acids have significant potential as topical treatments for wounds infected by opportunistic pathogens that are recalcitrant to standard treatments. These acids have long been used as bacteriostatic compounds in the food industry, and in some cases are already being used in the clinic. The effects of different organic acids vary with pH, concentration, and the specific organic acid used, but no studies to date on any opportunistic pathogens have examined the detailed interactions between these key variables in a controlled and systematic way. We have therefore comprehensively evaluated the effects of several different weak organic acids on growth of the opportunistic pathogen Pseudomonas aeruginosa. We used a semi-automated plate reader to generate growth profiles for two different strains (model laboratory strain PAO1 and clinical isolate PA1054 from a hospital burns unit) in a range of organic acids at different concentrations and pH, with a high level of replication for a total of 162,960 data points. We then compared two different modeling approaches for the interpretation of this time-resolved dataset: parametric logistic regression (with or without a component to include lag phase) vs. non-parametric Gaussian process (GP) regression. Because GP makes no prior assumptions about the nature of the growth, this method proved to be superior in cases where growth did not follow a standard sigmoid functional form, as is common when bacteria grow under stress. Acetic, propionic and butyric acids were all more detrimental to growth than the other acids tested, and although PA1054 grew better than PAO1 under non-stress conditions, this difference largely disappeared as the levels of stress increased. As expected from knowledge of how organic acids behave, their effect was significantly enhanced in combination with low pH, with this interaction being greatest in the case of propionic acid. Our approach lends itself to the characterization of combinatorial interactions between stressors, especially in cases where their impacts on growth render logistic growth models unsuitable.
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Affiliation(s)
- Francesca M. L. Bushell
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - Peter D. Tonner
- Department of Biology, Duke University, Durham, NC, United States
- Statistical Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD, United States
| | - Sara Jabbari
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
- School of Mathematics, University of Birmingham, Birmingham, United Kingdom
| | - Amy K. Schmid
- Department of Biology, Duke University, Durham, NC, United States
- Center for Genomics and Computational Biology, Duke University, Durham, NC, United States
| | - Peter A. Lund
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
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23
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Ebert A, Hannesschlaeger C, Goss KU, Pohl P. Passive Permeability of Planar Lipid Bilayers to Organic Anions. Biophys J 2018; 115:1931-1941. [PMID: 30360927 PMCID: PMC6303230 DOI: 10.1016/j.bpj.2018.09.025] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 09/20/2018] [Accepted: 09/26/2018] [Indexed: 11/23/2022] Open
Abstract
The membrane permeability P of organic ions was reported to be governed by the structure of the permeating molecule. Thus far, it is unclear whether the ion structure alters membrane partition or translocation proper across the membrane. Here, we obtained P values for 24 anionic compounds (18 concrete values, 6 upper limits) measuring the current that they carry through folded planar lipid bilayers. The P values range over more than 10 log units. Our measured permeability values correlate well (r = 0.95; logRMSE 0.74) with the hexadecane/water partition coefficients of the respective chemicals predicted by the COSMO-RS theory. Other attempts to predict P from the partition coefficient of the neutral molecule and from the solvation energy (Born energy) that opposes transfer into the membrane once the molecule is charged were unsuccessful. The uncertainties in assigning an effective radius to nonspherical molecules were much too large. The observation underlines that the actual structure of the molecules needs to be considered to predict partition and thus P by the solubility-diffusion model.
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Affiliation(s)
- Andrea Ebert
- Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany; Institute of Biophysics, Johannes Kepler University, Linz, Austria
| | | | - Kai-Uwe Goss
- Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research-UFZ, Leipzig, Germany; Institute of Chemistry, Martin Luther University, Halle, Germany
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University, Linz, Austria.
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24
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Ozu M, Galizia L, Acuña C, Amodeo G. Aquaporins: More Than Functional Monomers in a Tetrameric Arrangement. Cells 2018; 7:E209. [PMID: 30423856 PMCID: PMC6262540 DOI: 10.3390/cells7110209] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 10/27/2018] [Accepted: 11/07/2018] [Indexed: 12/11/2022] Open
Abstract
Aquaporins (AQPs) function as tetrameric structures in which each monomer has its own permeable pathway. The combination of structural biology, molecular dynamics simulations, and experimental approaches has contributed to improve our knowledge of how protein conformational changes can challenge its transport capacity, rapidly altering the membrane permeability. This review is focused on evidence that highlights the functional relationship between the monomers and the tetramer. In this sense, we address AQP permeation capacity as well as regulatory mechanisms that affect the monomer, the tetramer, or tetramers combined in complex structures. We therefore explore: (i) water permeation and recent evidence on ion permeation, including the permeation pathway controversy-each monomer versus the central pore of the tetramer-and (ii) regulatory mechanisms that cannot be attributed to independent monomers. In particular, we discuss channel gating and AQPs that sense membrane tension. For the latter we propose a possible mechanism that includes the monomer (slight changes of pore shape, the number of possible H-bonds between water molecules and pore-lining residues) and the tetramer (interactions among monomers and a positive cooperative effect).
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Affiliation(s)
- Marcelo Ozu
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
| | - Luciano Galizia
- Instituto de investigaciones Médicas A. Lanari, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires C1427ARO, Argentina.
- Consejo Nacional de Investigaciones Científicas y Técnicas, Laboratorio de Canales Iónicos, Instituto de Investigaciones Médicas (IDIM), Universidad de Buenos Aires, Buenos Aires C1427ARO, Argentina.
| | - Cynthia Acuña
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
| | - Gabriela Amodeo
- Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EGA, Argentina.
- Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA), Universidad de Buenos Aires y Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Buenos Aires C1428EGA CABA, Argentina.
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25
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Hannesschlaeger C, Pohl P. Membrane Permeabilities of Ascorbic Acid and Ascorbate. Biomolecules 2018; 8:E73. [PMID: 30126165 PMCID: PMC6164163 DOI: 10.3390/biom8030073] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 08/10/2018] [Accepted: 08/13/2018] [Indexed: 01/05/2023] Open
Abstract
Vitamin C (VC)-a collective term for the different oxidation and protonation forms of ascorbic acid (AscH)-is an essential micronutrient that serves as (i) a potent antioxidant and (ii) a cofactor of a manifold of enzymatic processes. Its role in health is related to redox balance maintenance, which is altered in diseases such as obesity, cancer, neurodegenerative diseases, hypertension, and autoimmune diseases. Despite its importance, VC uptake has been poorly investigated. Available literature values for the passive membrane permeability P of lipid bilayers for AscH scatter by about 10 orders of magnitude. Here, we show by voltage clamp that P - of AscH's anionic form (ascorbate Asc - ) is negligible. To cross the membrane, Asc - picks up a proton in the membrane vicinity and releases it on the other side of the membrane. This leads to a near-membrane pH drop that was visualized by scanning pH microelectrodes. The AscH concentration dependent pH profiles indicated P = 1.1 ± 0.1 × 10 - 8 cm / s . Thus, AscH's P is comparable to that of sorbitol and much lower than that of other weak acids like acetic acid or salicylic acid. The observation suggests that the capacity of the passive transcellular transport pathway across the lipid matrix does not suffice to ensure the required VC intake from the gastrointestinal tract.
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Affiliation(s)
| | - Peter Pohl
- Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria.
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26
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Bittner L, Teixido E, Seiwert B, Escher BI, Klüver N. Influence of pH on the uptake and toxicity of β-blockers in embryos of zebrafish, Danio rerio. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2018; 201:129-137. [PMID: 29906695 DOI: 10.1016/j.aquatox.2018.05.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2018] [Revised: 05/24/2018] [Accepted: 05/26/2018] [Indexed: 05/22/2023]
Abstract
ß-Blockers are weak bases with acidity constants related to their secondary amine group. At environmental pH they are protonated with the tendency to shift to their neutral species at more alkaline pH. Here we studied the influence of pH from 5.5 to 8.6 on the toxicity of the four ß-blockers atenolol, metoprolol, labetalol and propranolol in zebrafish embryos, relating toxicity not only in a conventional way to external aqueous concentrations but also to measured internal concentrations. Besides lethality, we evaluated changes in swimming activity and heartbeat, using the Locomotor Response (LMR) method and the Vertebrate Automated Screening Technology (VAST) for high throughput imaging. Effects of metoprolol, labetalol and propranolol were detected on phenotype, heart rate and swimming activity. External effect concentrations decreased with increasing neutral fraction for all three pharmaceuticals, attributed by an enhanced uptake of the neutral species in comparison to the corresponding charged form. The LC50 of metoprolol decreased by a factor of 35 from 1.91 mM with almost complete cationic state at pH 7.0 to 0.054 mM with 8% neutral fraction at pH 8.6. For propranolol the LC50 of 2.42 mM at pH 5.5 was even 100 fold higher than the LC50 at pH 8 with 0.023 mM where 3% were neutral fraction. No effects were detected in the zebrafish embryo exposed to atenolol. The internal concentrations for metoprolol and propranolol were quantified at non-toxic concentrations and at the LC10. Apparent bioconcentration factors (BCF) ranged from 1.96 at pH 7.0 to 32.0 at pH 8.6 for metoprolol and from 1.86 at pH 5.5 to 169 at pH 8.0 for propranolol. The BCFs served to predict the internal effect concentrations from the measured external effect concentrations. Internal effect concentrations of metoprolol and propranolol were in a similar range for all pH-values and for all endpoints. Interestingly, the internal effect concentrations were in the internal concentration range of baseline toxicity, which suggests that the effects of the ß-blockers are rather unspecific, even for sublethal effects on heart rate. In summary, our data confirm that the pH-dependent toxicity related to external concentrations can be explained by toxicokinetic effects and that the internal effect concentrations are pH-independent.
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Affiliation(s)
- Lisa Bittner
- Department Cell Toxicology, Helmholtz-Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany
| | - Elisabet Teixido
- Department Bioanalytical Toxicology, Helmholtz-Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany
| | - Bettina Seiwert
- Department Analytical Chemistry, Helmholtz-Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany
| | - Beate I Escher
- Department Cell Toxicology, Helmholtz-Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany; Environmental Toxicology, Centre for Applied Geoscience, Eberhard-Karls University, Hölderlinstr. 12, 72074 Tübingen, Germany
| | - Nils Klüver
- Department Cell Toxicology, Helmholtz-Centre for Environmental Research - UFZ, Permoserstr. 15, 04318 Leipzig, Germany.
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27
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Rokitskaya TI, Korshunova GA, Antonenko YN. Effect of Alkyl Chain Length on Translocation of Rhodamine B n-Alkyl Esters across Lipid Membranes. Biophys J 2018; 115:514-521. [PMID: 30031539 DOI: 10.1016/j.bpj.2018.07.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 06/27/2018] [Accepted: 07/02/2018] [Indexed: 01/03/2023] Open
Abstract
Voltage-dependent translocation of a series of cationic rhodamine B derivatives differing in n-alkyl chain length (ethyl, butyl, octyl, dodecyl, octadecyl) from one lipid monolayer to another was studied by measuring electrical current relaxation after a voltage jump on a planar bilayer phosphatidylcholine (PC) membrane. The rate of the translocation decreased in the following series of lipids: diphytanyl-PC > dioleyl-PC > diphytanoyl-PC > dierucoyl-PC. For all the lipids studied, the rate increased with lengthening of the hydrocarbon chain of the rhodamine derivatives, with the increase being most pronounced for the compounds having a short alkyl chain. The results could be well explained by involvement of molecule reorientations in the process of transmembrane flip-flop of the hydrophobic membrane-bound compounds. However, an impact of membrane dipole potential on the translocation rate could not be excluded, because the dipole potential could contribute to the energy barrier for translocation of the compounds located at different depths in the water-membrane interface. Based on the data obtained, a difference in the dipole potential of ester diphytanoyl-PC membranes with respect to ether diphytanyl-PC was estimated to be 108 mV, highlighting the contribution of a layer of oriented carbonyl groups of the lipids to the membrane dipole potential.
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Affiliation(s)
- Tatyana I Rokitskaya
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.
| | - Galina A Korshunova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Yuri N Antonenko
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
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28
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Goss KU, Bittermann K, Henneberger L, Linden L. Equilibrium biopartitioning of organic anions - A case study for humans and fish. CHEMOSPHERE 2018; 199:174-181. [PMID: 29438944 DOI: 10.1016/j.chemosphere.2018.02.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Revised: 01/31/2018] [Accepted: 02/04/2018] [Indexed: 05/21/2023]
Abstract
In this work we combine partition coefficients between water and membrane lipid, storage lipid, the plasma protein albumin as well as structural protein with the tissue dependent fraction of the respective phases in order to obtain a clearer picture on the relevance of various biological tissues for the bioaccumulation of 31 organic anions. Most of the partition coefficients are based on experimental data, supplemented by some predicted ones. The data suggest that the plasma protein, albumin, will be the major sorption matrix in mammals. Only small fractions of the studied chemicals will occur freely dissolved in an organism. For the investigated acids with pKa <5, partitioning is dominated by the ionic species rather than the corresponding neutral species. Bioconcentration in fish is not expected to occur for many of these acids unless pH in the aqueous environment is low or specific sorption mechanisms are relevant. In contrast, biomagnification in terrestrial mammals would be expected for most organic anions if they are not sufficiently metabolized. We conclude that sorption is important for the toxicokinetics of ionizable organic chemicals and the dominating sorbing matrices are quite different from those for neutral species.
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Affiliation(s)
- Kai-Uwe Goss
- Helmholtz Centre for Environmental Research UFZ, Department of Analytical Environmental Chemistry, Permoserstr. 15, D-04318 Leipzig, Germany; University of Halle-Wittenberg, Institute of Chemistry, Kurt-Mothes-Str. 2, D-06120 Halle, Germany.
| | - Kai Bittermann
- Helmholtz Centre for Environmental Research UFZ, Department of Analytical Environmental Chemistry, Permoserstr. 15, D-04318 Leipzig, Germany
| | - Luise Henneberger
- Helmholtz Centre for Environmental Research UFZ, Department of Cell Toxicology, Permoserstr. 15, D-04318 Leipzig, Germany
| | - Lukas Linden
- Helmholtz Centre for Environmental Research UFZ, Department of Analytical Environmental Chemistry, Permoserstr. 15, D-04318 Leipzig, Germany
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29
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Stumpff F. A look at the smelly side of physiology: transport of short chain fatty acids. Pflugers Arch 2018; 470:571-598. [PMID: 29305650 DOI: 10.1007/s00424-017-2105-9] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 12/19/2017] [Accepted: 12/20/2017] [Indexed: 12/14/2022]
Abstract
Fermentative organs such as the caecum, the colon, and the rumen have evolved to produce and absorb energy rich short chain fatty acids (SCFA) from otherwise indigestible substrates. Classical models postulate diffusional uptake of the undissociated acid (HSCFA). However, in net terms, a major part of SCFA absorption occurs with uptake of Na+ and resembles classical, coupled electroneutral NaCl transport. Considerable evidence suggests that the anion transporting proteins expressed by epithelia of fermentative organs are poorly selective and that their main function may be to transport acetate-, propionate-, butyrate- and HCO3- as the physiologically relevant anions. Apical uptake of SCFA thus involves non-saturable diffusion of the undissociated acid (HSCFA), SCFA-/HCO3- exchange via DRA (SLC26A3) and/or SCFA--H+ symport (MCT1, SLC16A1). All mechanisms lead to cytosolic acidification with stimulation of Na+/H+ exchange via NHE (SLC9A2/3). Basolaterally, Na+ leaves via the Na+/K+-ATPase with recirculation of K+. Na+ efflux drives the transport of SCFA- anions through volume-regulated anion channels, such as maxi-anion channels (possibly SLCO2A1), LRRC8, anoctamins, or uncoupled exchangers. When luminal buffering is inadequate, basolateral efflux will increasingly involve SCFA-/ HCO3- exchange (AE1/2, SCL4A1/2), or efflux of SCFA- with H+ (MCT1/4, SLC16A1/3). Furthermore, protons can be basolaterally removed by NHE1 (SCL9A1) or NBCe1 (SLC4A4). The purpose of these transport proteins is to maximize the amount of SCFA transported from the tightly buffered ingesta while minimizing acid transport through the epithelium. As known from the rumen for many decades, a disturbance of these processes is likely to cause severe colonic disease.
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Affiliation(s)
- Friederike Stumpff
- Institute of Veterinary Physiology, Department of Veterinary Medicine, Freie Universität Berlin, Oertzenweg 19b, 14163, Berlin, Germany.
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30
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Bittermann K, Goss KU. Predicting apparent passive permeability of Caco-2 and MDCK cell-monolayers: A mechanistic model. PLoS One 2017; 12:e0190319. [PMID: 29281711 PMCID: PMC5744993 DOI: 10.1371/journal.pone.0190319] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 12/12/2017] [Indexed: 01/16/2023] Open
Abstract
Experimentally derived apparent permeabilities, Papp, through cell monolayers such as Caco-2 and MDCK are considered to be an in-vitro gold standard for assessing the uptake efficiency of drugs. Here, we present a mechanistic model that describes 'passive' Papp values (i.e., neglecting active transport) by accounting for the different resistances solutes encounter when permeating a cell monolayer. We described three parallel permeation pathways, namely a cytosolic-, paracellular-, and lateral route, each of which consists of a number of serial resistances. These resistances were accounted for via a mechanistic depiction of the underlying processes that are largely based on literature work. For the present Papp dataset, about as much chemicals are dominated by the cytosolic route as were dominated by the paracellular route, while the lateral route was negligible. For the cytosolic route by far the most chemicals found their main resistance in the various water layers and not in the membrane. Although correlations within the subclasses of chemicals dominated by a specific permeation route were rather poor, we could overall satisfyingly predict Papp for 151 chemicals at a pH of 7.4 (R2 = 0.77, RMSE = 0.48). For a specific evaluation of the intrinsic membrane permeability, Pm, a second experimental dataset based on experiments with black lipid membranes, BLM, was evaluated. Pm could be predicted for 37 chemicals with R2 = 0.91 and RMSE = 0.64 log units.
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Affiliation(s)
- Kai Bittermann
- Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Kai-Uwe Goss
- Analytical Environmental Chemistry, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
- Department of Chemistry, University of Halle-Wittenberg, Halle, Germany
- * E-mail:
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31
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Bittermann K, Goss KU. Assessing the toxicity of ionic liquids - Application of the critical membrane concentration approach. CHEMOSPHERE 2017; 183:410-418. [PMID: 28554025 DOI: 10.1016/j.chemosphere.2017.05.097] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Revised: 05/13/2017] [Accepted: 05/15/2017] [Indexed: 06/07/2023]
Abstract
Charged organic chemicals are a prevailing challenge for toxicity modelling. In this contribution we strive to recapitulate the lessons learned from the well-known modelling of narcosis (or baseline toxicity) of neutral chemicals and apply the concept to charged chemicals. First we reevaluate the organism- and chemical independent critical membrane concentration causing 50% mortality,.cmemtox, based on a critical revision of a previously published toxicity dataset for neutral chemicals. In accordance to values reported in the literature we find a mean value for cmemtox of roughly 100 mmol/kg (membrane lipid) for a broad variety of 42 aquatic organisms (333 different chemicals), albeit with a considerable scatter. Then we apply this concept to permanently charged ionic liquids (ILs). Using COSMOmic, a quantum mechanically based mechanistic model that makes use of the COSMO-RS theory, we predict membrane-water partition coefficients (Kmem/w) of the anionic and cationic IL components. Doing so, cmemtox(total) for permanently charged ILs can be estimated assuming independent, concentration additive contributions of the cationic and its respective anionic species. The resulting values for some of the toxicity data for ionic liquids are consistent with the expected range for baseline toxicity for neutral chemicals while other values are consistently greater or smaller. Based on the calculation of toxic ratios we identify ILs that exert a specific mode of toxic action. Limitations of the modelling approach especially but not exclusively due to the use of nominal concentrations instead of freely-dissolved concentrations in the published literature are critically discussed.
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Affiliation(s)
- Kai Bittermann
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, D-04318 Leipzig, Germany.
| | - Kai-Uwe Goss
- UFZ - Helmholtz Centre for Environmental Research, Permoserstr. 15, D-04318 Leipzig, Germany; University of Halle-Wittenberg, Institute of Chemistry, Kurt Mothes Str. 2, D-06120 Halle, Germany.
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32
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Papagiannakis A, de Jonge JJ, Zhang Z, Heinemann M. Quantitative characterization of the auxin-inducible degron: a guide for dynamic protein depletion in single yeast cells. Sci Rep 2017; 7:4704. [PMID: 28680098 PMCID: PMC5498663 DOI: 10.1038/s41598-017-04791-6] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 05/22/2017] [Indexed: 11/24/2022] Open
Abstract
Perturbations are essential for the interrogation of biological systems. The auxin-inducible degron harbors great potential for dynamic protein depletion in yeast. Here, we thoroughly and quantitatively characterize the auxin-inducible degron in single yeast cells. We show that an auxin concentration of 0.25 mM is necessary for fast and uniform protein depletion between single cells, and that in mother cells proteins are depleted faster than their daughters. Although, protein recovery starts immediately after removal of auxin, it takes multiple generations before equilibrium is reached between protein synthesis and dilution, which is when the original protein levels are restored. Further, we found that blue light, used for GFP excitation, together with auxin results in growth defects, caused by the photo-destruction of auxin to its toxic derivatives, which can be avoided if indole-free auxin substitutes are used. Our work provides guidelines for the successful combination of microscopy, microfluidics and the auxin-inducible degron, offering the yeast community an unprecedented tool for dynamic perturbations on the single cell level.
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Affiliation(s)
- Alexandros Papagiannakis
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Janeska J de Jonge
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Zheng Zhang
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
| | - Matthias Heinemann
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
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33
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Sezer D, Oruç T. Protonation Kinetics Compromise Liposomal Fluorescence Assay of Membrane Permeation. J Phys Chem B 2017; 121:5218-5227. [DOI: 10.1021/acs.jpcb.7b01881] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Deniz Sezer
- Faculty of Engineering and
Natural Sciences, Sabancı University, Orhanlı-Tuzla, 34956 Istanbul, Turkey
| | - Tuğçe Oruç
- Faculty of Engineering and
Natural Sciences, Sabancı University, Orhanlı-Tuzla, 34956 Istanbul, Turkey
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34
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Alkyl-substituted phenylamino derivatives of 7-nitrobenz-2-oxa-1,3-diazole as uncouplers of oxidative phosphorylation and antibacterial agents: involvement of membrane proteins in the uncoupling action. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:377-387. [DOI: 10.1016/j.bbamem.2016.12.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2016] [Revised: 12/15/2016] [Accepted: 12/19/2016] [Indexed: 11/19/2022]
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Belda E, van Heck RGA, José Lopez-Sanchez M, Cruveiller S, Barbe V, Fraser C, Klenk HP, Petersen J, Morgat A, Nikel PI, Vallenet D, Rouy Z, Sekowska A, Martins dos Santos VAP, de Lorenzo V, Danchin A, Médigue C. The revisited genome ofPseudomonas putidaKT2440 enlightens its value as a robust metabolicchassis. Environ Microbiol 2016; 18:3403-3424. [DOI: 10.1111/1462-2920.13230] [Citation(s) in RCA: 217] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 01/16/2016] [Indexed: 01/08/2023]
Affiliation(s)
- Eugeni Belda
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute & CNRS-UMR8030 & Evry University, Laboratory of Bioinformatics Analysis in Genomics and Metabolism; 2 rue Gaston Crémieux 91057 Evry France
- Institut Pasteur, Unit of Insect Vector Genetics and Genomics, Department of Parasitology and Mycology; 28, rue du Dr. Roux, Paris, Cedex 15 75724 France
| | - Ruben G. A. van Heck
- Laboratory of Systems and Synthetic Biology, Wageningen University; Dreijenplein 10, Building number 316 6703 HB Wageningen The Netherlands
| | - Maria José Lopez-Sanchez
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute & CNRS-UMR8030 & Evry University, Laboratory of Bioinformatics Analysis in Genomics and Metabolism; 2 rue Gaston Crémieux 91057 Evry France
- AMAbiotics SAS, Institut du Cerveau et de la Moëlle Épinière, Hôpital de la Pitié-Salpêtrière; Paris France
| | - Stéphane Cruveiller
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute & CNRS-UMR8030 & Evry University, Laboratory of Bioinformatics Analysis in Genomics and Metabolism; 2 rue Gaston Crémieux 91057 Evry France
| | - Valérie Barbe
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute, National Sequencing Center; 2 rue Gaston Crémieux 91057 Evry France
| | - Claire Fraser
- Institute for Genome Sciences, Department of Microbiology and Immunology, University of Maryland School of Medicine; Baltimore MD USA
| | - Hans-Peter Klenk
- Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures; Braunschweig Germany
- School of Biology, Newcastle University; Newcastle upon Tyne NE1 7RU UK
| | - Jörn Petersen
- Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures; Braunschweig Germany
| | - Anne Morgat
- Swiss-Prot Group, SIB Swiss Institute of Bioinformatics; Geneva CH-1206 Switzerland
| | - Pablo I. Nikel
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC); C/Darwin 3 28049 Madrid Spain
| | - David Vallenet
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute & CNRS-UMR8030 & Evry University, Laboratory of Bioinformatics Analysis in Genomics and Metabolism; 2 rue Gaston Crémieux 91057 Evry France
| | - Zoé Rouy
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute & CNRS-UMR8030 & Evry University, Laboratory of Bioinformatics Analysis in Genomics and Metabolism; 2 rue Gaston Crémieux 91057 Evry France
| | - Agnieszka Sekowska
- AMAbiotics SAS, Institut du Cerveau et de la Moëlle Épinière, Hôpital de la Pitié-Salpêtrière; Paris France
| | - Vitor A. P. Martins dos Santos
- Laboratory of Systems and Synthetic Biology, Wageningen University; Dreijenplein 10, Building number 316 6703 HB Wageningen The Netherlands
| | - Víctor de Lorenzo
- Systems and Synthetic Biology Program, Centro Nacional de Biotecnología (CNB-CSIC); C/Darwin 3 28049 Madrid Spain
| | - Antoine Danchin
- AMAbiotics SAS, Institut du Cerveau et de la Moëlle Épinière, Hôpital de la Pitié-Salpêtrière; Paris France
| | - Claudine Médigue
- Alternative Energies and Atomic Energy Commission (CEA), Genomic Institute & CNRS-UMR8030 & Evry University, Laboratory of Bioinformatics Analysis in Genomics and Metabolism; 2 rue Gaston Crémieux 91057 Evry France
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Awoonor-Williams E, Rowley CN. Molecular simulation of nonfacilitated membrane permeation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1858:1672-87. [PMID: 26706099 DOI: 10.1016/j.bbamem.2015.12.014] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Revised: 12/05/2015] [Accepted: 12/09/2015] [Indexed: 12/29/2022]
Abstract
This is a review. Non-electrolytic compounds typically cross cell membranes by passive diffusion. The rate of permeation is dependent on the chemical properties of the solute and the composition of the lipid bilayer membrane. Predicting the permeability coefficient of a solute is important in pharmaceutical chemistry and toxicology. Molecular simulation has proven to be a valuable tool for modeling permeation of solutes through a lipid bilayer. In particular, the solubility-diffusion model has allowed for the quantitative calculation of permeability coefficients. The underlying theory and computational methods used to calculate membrane permeability are reviewed. We also discuss applications of these methods to examine the permeability of solutes and the effect of membrane composition on permeability. The application of coarse grain and polarizable models is discussed. This article is part of a Special Issue entitled: Membrane Proteins edited by J.C. Gumbart and Sergei Noskov.
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Affiliation(s)
- Ernest Awoonor-Williams
- Department of Chemistry, Memorial University of Newfoundland, St. John's, NL, A1B 3X7 Canada
| | - Christopher N Rowley
- Department of Chemistry, Memorial University of Newfoundland, St. John's, NL, A1B 3X7 Canada.
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Meadows KE, Nadappuram BP, Unwin PR. A new approach for the fabrication of microscale lipid bilayers at glass pipets: application to quantitative passive permeation visualization. SOFT MATTER 2014; 10:8433-8441. [PMID: 25221789 DOI: 10.1039/c3sm51406d] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
A new method of planar bilayer lipid membrane (BLM) formation is presented that allows stable, solvent-free lipid bilayers exhibiting high seal resistances to be formed rapidly, easily and reproducibly. Using these bilayers the passive permeation of a series of carboxylic acids is investigated, to determine quantitatively the trend in permeability with lipophilicity of the acid. BLMs are formed at the tip openings of pulled theta pipets, and the rate of permeation of each carboxylic acid across the bilayer, from within the pipet into the bulk solution is determined. This is achieved through spatially-resolved measurements of the pH change that occurs upon the permeation of the weak acid, visualized using a pH-sensitive fluorophore with a confocal laser scanning microscope. The extracted fluorescence profiles are matched to finite element method (FEM) simulations, to allow the associated permeation coefficient for each weak acid to be determined with high accuracy, since this is the only adjustable parameter used to fit the experimental data. For bilayers formed in this way, the weak acids show increasing permeability with lipophilicity. Furthermore, the arrangement allows the effect of a trans-membrane electric field on permeation to be explored. For both propanoic and hexanoic acid it is found that an applied electric field enhances molecular transport, which is attributed to the formation of pores within the membrane.
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Zocher F, van der Spoel D, Pohl P, Hub JS. Local partition coefficients govern solute permeability of cholesterol-containing membranes. Biophys J 2014; 105:2760-70. [PMID: 24359748 DOI: 10.1016/j.bpj.2013.11.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 10/31/2013] [Accepted: 11/04/2013] [Indexed: 11/25/2022] Open
Abstract
The permeability of lipid membranes for metabolic molecules or drugs is routinely estimated from the solute's oil/water partition coefficient. However, the molecular determinants that modulate the permeability in different lipid compositions have remained unclear. Here, we combine scanning electrochemical microscopy and molecular-dynamics simulations to study the effect of cholesterol on membrane permeability, because cholesterol is abundant in all animal membranes. The permeability of membranes from natural lipid mixtures to both hydrophilic and hydrophobic solutes monotonously decreases with cholesterol concentration [Chol]. The same is true for hydrophilic solutes and planar bilayers composed of dioleoyl-phosphatidylcholine or dioleoyl-phosphatidyl-ethanolamine. However, these synthetic lipids give rise to a bell-shaped dependence of membrane permeability on [Chol] for very hydrophobic solutes. The simulations indicate that cholesterol does not affect the diffusion constant inside the membrane. Instead, local partition coefficients at the lipid headgroups and at the lipid tails are modulated oppositely by cholesterol, explaining the experimental findings. Structurally, these modulations are induced by looser packing at the lipid headgroups and tighter packing at the tails upon the addition of cholesterol.
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Affiliation(s)
- Florian Zocher
- Institut für Biophysik, Johannes Kepler Universität, Linz, Austria
| | - David van der Spoel
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden; Science for Life Laboratory, Uppsala, Sweden
| | - Peter Pohl
- Institut für Biophysik, Johannes Kepler Universität, Linz, Austria.
| | - Jochen S Hub
- Institute for Microbiology and Genetics, Georg-August-University Göttingen, Göttingen, Germany.
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Jennings ML. Transport of H2S and HS(-) across the human red blood cell membrane: rapid H2S diffusion and AE1-mediated Cl(-)/HS(-) exchange. Am J Physiol Cell Physiol 2013; 305:C941-50. [PMID: 23864610 PMCID: PMC4042536 DOI: 10.1152/ajpcell.00178.2013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The rates of H2S and HS(-) transport across the human erythrocyte membrane were estimated by measuring rates of dissipation of pH gradients in media containing 250 μM H2S/HS(-). Net acid efflux is caused by H2S/HS(-) acting analogously to CO2/HCO3(-) in the Jacobs-Stewart cycle. The steps are as follows: 1) H2S efflux through the lipid bilayer and/or a gas channel, 2) extracellular H2S deprotonation, 3) HS(-) influx in exchange for Cl(-), catalyzed by the anion exchange protein AE1, and 4) intracellular HS(-) protonation. Net acid transport by the Cl(-)/HS(-)/H2S cycle is more efficient than by the Cl(-)/HCO3(-)/CO2 cycle because of the rapid H2S-HS(-) interconversion in cells and medium. The rates of acid transport were analyzed by solving the mass flow equations for the cycle to produce estimates of the HS(-) and H2S transport rates. The data indicate that HS(-) is a very good substrate for AE1; the Cl(-)/HS(-) exchange rate is about one-third as rapid as Cl(-)/HCO3(-) exchange. The H2S permeability coefficient must also be high (>10(-2) cm/s, half time <0.003 s) to account for the pH equilibration data. The results imply that H2S and HS(-) enter erythrocytes very rapidly in the microcirculation of H2S-producing tissues, thereby acting as a sink for H2S and lowering the local extracellular concentration, and the fact that HS(-) is a substrate for a Cl(-)/HCO3(-) exchanger indicates that some effects of exogenous H2S/HS(-) may not result from a regulatory role of H2S but, rather, from net acid flux by H2S and HS(-) transport in a Jacobs-Stewart cycle.
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Affiliation(s)
- Michael L Jennings
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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40
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Yamagishi T, Sahni S, Sharp DM, Arvind A, Jansson PJ, Richardson DR. P-glycoprotein mediates drug resistance via a novel mechanism involving lysosomal sequestration. J Biol Chem 2013; 288:31761-71. [PMID: 24062304 PMCID: PMC3814770 DOI: 10.1074/jbc.m113.514091] [Citation(s) in RCA: 150] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Revised: 09/16/2013] [Indexed: 11/06/2022] Open
Abstract
Localization of the drug transporter P-glycoprotein (Pgp) to the plasma membrane is thought to be the only contributor of Pgp-mediated multidrug resistance (MDR). However, very little work has focused on the contribution of Pgp expressed in intracellular organelles to drug resistance. This investigation describes an additional mechanism for understanding how lysosomal Pgp contributes to MDR. These studies were performed using Pgp-expressing MDR cells and their non-resistant counterparts. Using confocal microscopy and lysosomal fractionation, we demonstrated that intracellular Pgp was localized to LAMP2-stained lysosomes. In Pgp-expressing cells, the Pgp substrate doxorubicin (DOX) became sequestered in LAMP2-stained lysosomes, but this was not observed in non-Pgp-expressing cells. Moreover, lysosomal Pgp was demonstrated to be functional because DOX accumulation in this organelle was prevented upon incubation with the established Pgp inhibitors valspodar or elacridar or by silencing Pgp expression with siRNA. Importantly, to elicit drug resistance via lysosomes, the cytotoxic chemotherapeutics (e.g. DOX, daunorubicin, or vinblastine) were required to be Pgp substrates and also ionized at lysosomal pH (pH 5), resulting in them being sequestered and trapped in lysosomes. This property was demonstrated using lysosomotropic weak bases (NH4Cl, chloroquine, or methylamine) that increased lysosomal pH and sensitized only Pgp-expressing cells to such cytotoxic drugs. Consequently, a lysosomal Pgp-mediated mechanism of MDR was not found for non-ionizable Pgp substrates (e.g. colchicine or paclitaxel) or ionizable non-Pgp substrates (e.g. cisplatin or carboplatin). Together, these studies reveal a new mechanism where Pgp-mediated lysosomal sequestration of chemotherapeutics leads to MDR that is amenable to therapeutic exploitation.
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Affiliation(s)
- Tetsuo Yamagishi
- From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia
| | - Sumit Sahni
- From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia
| | - Danae M. Sharp
- From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia
| | - Akanksha Arvind
- From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia
| | - Patric J. Jansson
- From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia
| | - Des R. Richardson
- From the Molecular Pharmacology and Pathology Program, Department of Pathology and Bosch Institute, Blackburn Building (D06), University of Sydney, Sydney, New South Wales 2006, Australia
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Akopyan K, Trchounian A. Proton cycles through membranes in bacteria: Relationship between proton passive and active fluxes and their dependence on some external physico-chemical factors under fermentation. Biophysics (Nagoya-shi) 2013. [DOI: 10.1134/s0006350913050023] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Li L, Lieleg O, Jang S, Ribbeck K, Han J. A microfluidic in vitro system for the quantitative study of the stomach mucus barrier function. LAB ON A CHIP 2012; 12:4071-4079. [PMID: 22878692 DOI: 10.1039/c2lc40161d] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
In the stomach, a layer of gastric mucus protects the epithelial cells of the stomach wall against damage by the acidic digestive juices in the gastric lumen. Despite considerable research, the biophysical mechanisms for this acid barrier are not understood. We present an in vitro microfluidic tool to characterize the stomach acid barrier, in which purified mucin polymers are "secreted" against an acidic zone on chip, mimicking the in vivo secretion of gastric mucus into an acidic stomach lumen. This device reconstitutes both the H(+) concentration gradient and outward flow environment of the mucus layer in vivo. Our experiments demonstrate that a continuously secreted mucin layer hinders acid diffusion, suggesting novel insights into the barrier role of mucins. More broadly, our system may serve as a platform tool for studying the barrier functions provided by mucus layers in the body and for studying mucus drug interactions.
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Affiliation(s)
- Leon Li
- Harvard-MIT Division of Health Sciences and Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
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Cuevasanta E, Denicola A, Alvarez B, Möller MN. Solubility and permeation of hydrogen sulfide in lipid membranes. PLoS One 2012; 7:e34562. [PMID: 22509322 PMCID: PMC3324494 DOI: 10.1371/journal.pone.0034562] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 03/05/2012] [Indexed: 11/27/2022] Open
Abstract
Hydrogen sulfide (H2S) is mainly known for its toxicity but has recently been shown to be produced endogenously in mammalian tissues and to be associated with physiological regulatory functions. To better understand the role of biomembranes in modulating its biological distribution and effects; we measured the partition coefficient of H2S in models of biological membranes. The partition coefficients were found to be 2.1±0.2, 1.9±0.5 and 2.0±0.6 in n-octanol, hexane and dilauroylphosphatidylcholine liposome membranes relative to water, respectively (25°C). This two-fold higher concentration of H2S in the membrane translates into a rapid membrane permeability, Pm = 3 cm s−1. We used a mathematical model in three dimensions to gain insight into the diffusion of total sulfide in tissues. This model shows that the sphere of action of sulfide produced by a single cell expands to involve more than 200 neighboring cells, and that the resistance imposed by lipid membranes has a significant effect on the diffusional spread of sulfide at pH 7.4, increasing local concentrations. These results support the role of hydrogen sulfide as a paracrine signaling molecule and reveal advantageous pharmacokinetic properties for its therapeutic applications.
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Affiliation(s)
- Ernesto Cuevasanta
- Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
| | - Ana Denicola
- Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
- Laboratorio de Fisicoquímica Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
| | - Beatriz Alvarez
- Laboratorio de Enzimología, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
- * E-mail: (BA); (MNM)
| | - Matías N. Möller
- Center for Free Radical and Biomedical Research, Universidad de la República, Montevideo, Uruguay
- Laboratorio de Fisicoquímica Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay
- * E-mail: (BA); (MNM)
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Jones RL, Woodward DF, Wang JW, Clark RL. Roles of affinity and lipophilicity in the slow kinetics of prostanoid receptor antagonists on isolated smooth muscle preparations. Br J Pharmacol 2011; 162:863-79. [PMID: 20973775 PMCID: PMC3042197 DOI: 10.1111/j.1476-5381.2010.01087.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 08/24/2010] [Accepted: 10/04/2010] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE The highly lipophilic acyl-sulphonamides L-798106 and L-826266 showed surprisingly slow antagonism of the prostanoid EP₃ receptor system in guinea-pig aorta. Roles of affinity and lipophilicity in the onset kinetics of these and other prostanoid ligands were investigated. EXPERIMENTAL APPROACH Antagonist selectivity was assessed using a panel of human recombinant prostanoid receptor-fluorimetric imaging plate reader assays. Potencies/affinities and onset half-times of agonists and antagonists were obtained on guinea-pig-isolated aorta and vas deferens. n-Octanol-water partition coefficients were predicted. KEY RESULTS L-798106, L-826266 and the less lipophilic congener (DG)-3ap appear to behave as selective, competitive-reversible EP₃ antagonists. For ligands of low to moderate lipophilicity, potency increments for EP₃ and TP (thromboxane-like) agonism on guinea-pig aorta (above pEC₅₀ of 8.0) were associated with progressively longer onset half-times; similar trends were found for TP and histamine H₁ antagonism above a pA₂ limit of 8.0. In contrast, L-798106 (EP₃), L-826266 (EP₃, TP) and the lipophilic H₁ antagonists astemizole and terfenadine exhibited very slow onset rates despite their moderate affinities; (DG)-3ap (EP₃) had a faster onset. Agonism and antagonism on the vas deferens EP₃ system were overall much faster, although trends were similar. CONCLUSIONS AND IMPLICATIONS High affinity and high liphophilicity may contribute to the slow onsets of prostanoid ligands in some isolated smooth muscle preparations. Both relationships are explicable by tissue disposition under the limited diffusion model. EP₃ antagonists used as research tools should have moderate lipophilicity. The influence of lipophilicity on the potential clinical use of EP₃ antagonists is discussed.
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MESH Headings
- Acrylamides/chemistry
- Acrylamides/metabolism
- Acrylamides/pharmacology
- Animals
- Aorta, Thoracic/metabolism
- Guinea Pigs
- HEK293 Cells
- Humans
- Hydrophobic and Hydrophilic Interactions
- In Vitro Techniques
- Isoenzymes/antagonists & inhibitors
- Isoenzymes/genetics
- Isoenzymes/metabolism
- Kinetics
- Ligands
- Male
- Models, Biological
- Muscle Contraction/drug effects
- Muscle Relaxation/drug effects
- Muscle, Smooth/drug effects
- Muscle, Smooth/metabolism
- Naphthalenes/chemistry
- Naphthalenes/metabolism
- Naphthalenes/pharmacology
- Neuromuscular Agents/chemistry
- Neuromuscular Agents/metabolism
- Neuromuscular Agents/pharmacology
- Receptors, Eicosanoid/agonists
- Receptors, Eicosanoid/antagonists & inhibitors
- Receptors, Eicosanoid/genetics
- Receptors, Eicosanoid/metabolism
- Receptors, Prostaglandin E, EP3 Subtype/agonists
- Receptors, Prostaglandin E, EP3 Subtype/antagonists & inhibitors
- Receptors, Prostaglandin E, EP3 Subtype/genetics
- Receptors, Prostaglandin E, EP3 Subtype/metabolism
- Recombinant Proteins/agonists
- Recombinant Proteins/antagonists & inhibitors
- Recombinant Proteins/metabolism
- Sulfonamides/metabolism
- Sulfonamides/pharmacology
- Vas Deferens/metabolism
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Affiliation(s)
- R L Jones
- Cardiovascular Research Group, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK.
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Neuwoehner J, Escher BI. The pH-dependent toxicity of basic pharmaceuticals in the green algae Scenedesmus vacuolatus can be explained with a toxicokinetic ion-trapping model. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2011; 101:266-275. [PMID: 21084122 DOI: 10.1016/j.aquatox.2010.10.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2010] [Revised: 10/13/2010] [Accepted: 10/19/2010] [Indexed: 05/30/2023]
Abstract
Several previous studies revealed that pharmaceuticals with aliphatic amine function exhibit a higher toxicity toward algae than toward other aquatic organisms. Here we investigated the pH-dependent toxicity of the five basic pharmaceuticals fluoxetine, its metabolite norfluoxetine, propranolol, lidocaine, and trimipramine. For all of them, the toxicity increased with increasing pH when aqueous effect concentrations were considered. Since these pharmaceuticals contain a basic amine group that is protonated and thus positively charged at physiological pH and because algae are capable of biological homeostasis, i.e., pH inside the algal cell remains virtually independent of variable external pH, the speciation of aliphatic amines can be different inside the algal cell compared to the external medium. Therefore, we hypothesized that the high toxicity of aliphatic amines in algae is a toxicokinetic effect caused by speciation and not a toxicodynamic effect caused by a specific mode of toxic action. This hypothesis also implies that internal effect concentrations are independent on external pH. On this basis we developed a simple toxicokinetic model, which assumes that only the neutral molecule is bioavailable and can pass the plasma membrane. This assumption is likely to be valid at pH values down to two units below the acidity constant (pK(a)). For lower pH values a more complex model would have to be evoked that includes, an, albeit smaller, permeability of the charged species. For pH>pK(a)-2, we can safely assume that the outer membrane serves as insulator and that the charged species is formed inside the cell according to the pH in the cytoplasm. Thus this toxicokinetic model is an ion-trapping model. The input parameters of this model are the measured aqueous effect concentrations determined as a function of pH and the membrane-water partitioning, which was modelled by the liposome-water partition coefficients of the neutral and cationic species. They were deduced from experimentally determined liposome-water distribution ratios at various pH values measured with an equilibrium dialysis method. The modelled internal effect concentrations were independent of the external pH and effective membrane burdens were in the same range as for other baseline toxicants found in the literature for algae, daphnids and fish. These results confirm that the higher algal toxicity of pharmaceuticals with an aliphatic amine group can be explained by a toxicokinetic effect and that these pharmaceuticals do not exhibit a specific mode of action in algae but act as baseline toxicants.
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Affiliation(s)
- Judith Neuwoehner
- Eawag, Swiss Federal Institute of Aquatic Science and Technology, Dübendorf, Switzerland
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Sugano K, Kansy M, Artursson P, Avdeef A, Bendels S, Di L, Ecker GF, Faller B, Fischer H, Gerebtzoff G, Lennernaes H, Senner F. Coexistence of passive and carrier-mediated processes in drug transport. Nat Rev Drug Discov 2010; 9:597-614. [PMID: 20671764 DOI: 10.1038/nrd3187] [Citation(s) in RCA: 435] [Impact Index Per Article: 31.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The permeability of biological membranes is one of the most important determinants of the pharmacokinetic processes of a drug. Although it is often accepted that many drug substances are transported across biological membranes by passive transcellular diffusion, a recent hypothesis speculated that carrier-mediated mechanisms might account for the majority of membrane drug transport processes in biological systems. Based on evidence of the physicochemical characteristics and of in vitro and in vivo findings for marketed drugs, as well as results from real-life discovery and development projects, we present the view that both passive transcellular processes and carrier-mediated processes coexist and contribute to drug transport activities across biological membranes.
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Affiliation(s)
- Kiyohiko Sugano
- Pfizer, Research Formulation, Sandwich Laboratories, Ramsgate Road, Sandwich, Kent CT13 9NJ, UK.
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47
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Heikkinen AT, Mönkkönen J, Korjamo T. Determination of permeation resistance distribution in in vitro cell monolayer permeation experiments. Eur J Pharm Sci 2010; 40:132-42. [DOI: 10.1016/j.ejps.2010.03.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 03/09/2010] [Accepted: 03/13/2010] [Indexed: 10/19/2022]
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48
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Membrane transport of singlet oxygen monitored by dipole potential measurements. Biophys J 2010; 96:77-85. [PMID: 18931253 DOI: 10.1529/biophysj.108.135145] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 09/03/2008] [Indexed: 11/18/2022] Open
Abstract
The efficiency of photodynamic reactions depends on 1), the penetration depth of the photosensitizer into the membrane and 2), the sidedness of the target. Molecules which are susceptible to singlet oxygen ((1)O(2)) experience less damage when separated from the photosensitizer by the membrane. Since (1)O(2) lifetime in the membrane environment is orders of magnitude longer than the time required for nonexcited oxygen (O(2)) to cross the membrane, this observation suggests that differences between the permeabilities or membrane partition of (1)O(2) and O(2) exist. We investigated this hypothesis by releasing (1)O(2) at one side of a planar membrane while monitoring the kinetics of target damage at the opposite side of the same membrane. Damage to the target, represented by dipole-modifying molecules (phloretin or phlorizin), was indicated by changes in the interleaflet dipole potential difference Deltaphi(b). A simple analytical model allowed estimation of the (1)O(2) interleaflet concentration difference from the rate at which Deltaphi(b) changed. It confirmed that the lower limit of (1)O(2) permeability is approximately 2 cm/s; i.e., it roughly matches O(2) permeability as predicted by Overton's rule. Consequently, the membrane cannot act as a barrier to (1)O(2) diffusion. Differences in the reaction rates at the cytoplasmic and extracellular membrane leaflets may be attributed only to (1)O(2) quenchers inside the membrane.
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Krämer S, Lombardi D, Primorac A, Thomae A, Wunderli-Allenspach H. Lipid-Bilayer Permeation of Drug-Like Compounds. Chem Biodivers 2009; 6:1900-16. [DOI: 10.1002/cbdv.200900122] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Crans DC, Trujillo AM, Bonetti S, Rithner CD, Baruah B, Levinger NE. Penetration of negatively charged lipid interfaces by the doubly deprotonated dipicolinate. J Org Chem 2009; 73:9633-40. [PMID: 19053583 DOI: 10.1021/jo801707y] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The possibility that a negatively charged organic molecule penetrates the lipid interface in a reverse micellar system is examined using UV-vis absorption and NMR spectroscopy. The hypothesis that deprotonated forms of dipicolinic acid, H(2)dipic, such as Hdipic(-) and dipic(2-), can penetrate the lipid interface in a microemulsion is based on our previous finding that the insulin-enhancing anionic [VO(2)dipic](-) complex was found to reside in the hydrophobic layer of the reverse micelle (Crans et al. J. Am. Chem. Soc. 2006, 128, 4437-4445). Penetration of a polar and charged compound, namely Hdipic(-) or dipic(2-), into a hydrophobic environment is perhaps unexpected given the established rules regarding the fundamental properties of compound solubility. As such, this work has broad implications in organic chemistry and other disciplines of science. These studies required a comprehensive investigation of the different dipic species and their association in aqueous solutions at varying pH values. Combining the aqueous studies using absorption and NMR spectroscopy with those in microemulsions defines the differences observed in the heterogeneous environment. Despite the expected repulsion between the surfactant head groups and the dianionic probe molecule, these studies demonstrate that dipic resides deep in the hydrophobic portion of the reverse micellar interface. In summary, these results provide evidence that ionic molecules can reside in nonpolar locations in microheterogeneous environments. This suggests that additional factors such as solvation are important to molecule location. Documented ability to penetrate lipid surfaces of similar charge provides a rationale for why specific drugs with less than optimal hydrophobicity are successful even though they violate Lipinski's rules.
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Affiliation(s)
- Debbie C Crans
- Department of Chemistry, Colorado State University, Fort Collins, Colorado 80513, USA.
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