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Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes

Fatty acid nitroalkenes (NO(2)-FA) are endogenously-generated products of the reaction of metabolic and inflammatory-derived nitrogen dioxide ((.)NO(2)) with unsaturated fatty acids. These species mediate signaling actions and induce adaptive responses in preclinical models of inflammatory and metab...

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Autores principales: Grippo, Valentina, Mojovic, Milos, Pavicevic, Aleksandra, Kabelac, Martin, Hubatka, Frantisek, Turanek, Jaroslav, Zatloukalova, Martina, Freeman, Bruce A., Vacek, Jan
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Elsevier 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7658499/
https://www.ncbi.nlm.nih.gov/pubmed/33181478
http://dx.doi.org/10.1016/j.redox.2020.101756
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author Grippo, Valentina
Mojovic, Milos
Pavicevic, Aleksandra
Kabelac, Martin
Hubatka, Frantisek
Turanek, Jaroslav
Zatloukalova, Martina
Freeman, Bruce A.
Vacek, Jan
author_facet Grippo, Valentina
Mojovic, Milos
Pavicevic, Aleksandra
Kabelac, Martin
Hubatka, Frantisek
Turanek, Jaroslav
Zatloukalova, Martina
Freeman, Bruce A.
Vacek, Jan
author_sort Grippo, Valentina
collection PubMed
description Fatty acid nitroalkenes (NO(2)-FA) are endogenously-generated products of the reaction of metabolic and inflammatory-derived nitrogen dioxide ((.)NO(2)) with unsaturated fatty acids. These species mediate signaling actions and induce adaptive responses in preclinical models of inflammatory and metabolic diseases. The nitroalkene substituent possesses an electrophilic nature, resulting in rapid and reversible reactions with biological nucleophiles such as cysteine, thus supporting post-translational modifications (PTM) of proteins having susceptible nucleophilic centers. These reactions contribute to enzyme regulation, modulation of inflammation and cell proliferation and the regulation of gene expression responses. Herein, focus is placed on the reduction-oxidation (redox) characteristics and stability of specific NO(2)-FA regioisomers having biological and clinical relevance; nitro-oleic acid (NO(2)-OA), bis-allylic nitro-linoleic acid (NO(2)-LA) and the conjugated diene-containing nitro-conjugated linoleic acid (NO(2)-cLA). Cyclic and alternating-current voltammetry and chronopotentiometry were used to the study of reduction potentials of these NO(2)-FA. R–NO(2) reduction was observed around −0.8 V (vs. Ag/AgCl/3 M KCl) and is related to relative NO(2)-FA electrophilicity. This reduction process could be utilized for the evaluation of NO(2)-FA stability in aqueous milieu, shown herein to be pH dependent. In addition, electron paramagnetic resonance (EPR) spectroscopy was used to define the stability of the nitroalkene moiety under aqueous conditions, specifically under conditions where nitric oxide ((.)NO) release could be detected. The experimental data were supported by density functional theory calculations using 6–311++G (d,p) basis set and B3LYP functional. Based on experimental and computational approaches, the relative electrophilicities of these NO(2)-FA are NO(2)-cLA >> NO(2)-LA > NO(2)-OA. Micellarization and vesiculation largely define these biophysical characteristics in aqueous, nucleophile-free conditions. At concentrations below the critical micellar concentration (CMC), monomeric NO(2)-FA predominate, while at greater concentrations a micellar phase consisting of self-assembled lipid structures predominates. The CMC, determined by dynamic light scattering in 0.1 M phosphate buffer (pH 7.4) at 25 °C, was 6.9 (NO(2)-LA) 10.6 (NO(2)-OA) and 42.3 μM (NO(2)-cLA), respectively. In aggregate, this study provides new insight into the biophysical properties of NO(2)-FA that are important for better understanding the cell signaling and pharmacological potential of this class of mediators.
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spelling pubmed-76584992020-11-17 Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes Grippo, Valentina Mojovic, Milos Pavicevic, Aleksandra Kabelac, Martin Hubatka, Frantisek Turanek, Jaroslav Zatloukalova, Martina Freeman, Bruce A. Vacek, Jan Redox Biol Research Paper Fatty acid nitroalkenes (NO(2)-FA) are endogenously-generated products of the reaction of metabolic and inflammatory-derived nitrogen dioxide ((.)NO(2)) with unsaturated fatty acids. These species mediate signaling actions and induce adaptive responses in preclinical models of inflammatory and metabolic diseases. The nitroalkene substituent possesses an electrophilic nature, resulting in rapid and reversible reactions with biological nucleophiles such as cysteine, thus supporting post-translational modifications (PTM) of proteins having susceptible nucleophilic centers. These reactions contribute to enzyme regulation, modulation of inflammation and cell proliferation and the regulation of gene expression responses. Herein, focus is placed on the reduction-oxidation (redox) characteristics and stability of specific NO(2)-FA regioisomers having biological and clinical relevance; nitro-oleic acid (NO(2)-OA), bis-allylic nitro-linoleic acid (NO(2)-LA) and the conjugated diene-containing nitro-conjugated linoleic acid (NO(2)-cLA). Cyclic and alternating-current voltammetry and chronopotentiometry were used to the study of reduction potentials of these NO(2)-FA. R–NO(2) reduction was observed around −0.8 V (vs. Ag/AgCl/3 M KCl) and is related to relative NO(2)-FA electrophilicity. This reduction process could be utilized for the evaluation of NO(2)-FA stability in aqueous milieu, shown herein to be pH dependent. In addition, electron paramagnetic resonance (EPR) spectroscopy was used to define the stability of the nitroalkene moiety under aqueous conditions, specifically under conditions where nitric oxide ((.)NO) release could be detected. The experimental data were supported by density functional theory calculations using 6–311++G (d,p) basis set and B3LYP functional. Based on experimental and computational approaches, the relative electrophilicities of these NO(2)-FA are NO(2)-cLA >> NO(2)-LA > NO(2)-OA. Micellarization and vesiculation largely define these biophysical characteristics in aqueous, nucleophile-free conditions. At concentrations below the critical micellar concentration (CMC), monomeric NO(2)-FA predominate, while at greater concentrations a micellar phase consisting of self-assembled lipid structures predominates. The CMC, determined by dynamic light scattering in 0.1 M phosphate buffer (pH 7.4) at 25 °C, was 6.9 (NO(2)-LA) 10.6 (NO(2)-OA) and 42.3 μM (NO(2)-cLA), respectively. In aggregate, this study provides new insight into the biophysical properties of NO(2)-FA that are important for better understanding the cell signaling and pharmacological potential of this class of mediators. Elsevier 2020-10-12 /pmc/articles/PMC7658499/ /pubmed/33181478 http://dx.doi.org/10.1016/j.redox.2020.101756 Text en © 2020 The Authors https://creativecommons.org/licenses/by-nc-nd/4.0/This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
spellingShingle Research Paper
Grippo, Valentina
Mojovic, Milos
Pavicevic, Aleksandra
Kabelac, Martin
Hubatka, Frantisek
Turanek, Jaroslav
Zatloukalova, Martina
Freeman, Bruce A.
Vacek, Jan
Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
title Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
title_full Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
title_fullStr Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
title_full_unstemmed Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
title_short Electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
title_sort electrophilic characteristics and aqueous behavior of fatty acid nitroalkenes
topic Research Paper
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7658499/
https://www.ncbi.nlm.nih.gov/pubmed/33181478
http://dx.doi.org/10.1016/j.redox.2020.101756
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