title: Evaluation of the anti-nitrative effect of plant antioxidants using a cowpea Fe-superoxide dismutase as a target.
abstract: Nitric oxide cytotoxicity arises from its rapid conversion to peroxynitrite (ONOO(-)) in the presence of superoxide, provoking functional changes in proteins by nitration of tyrosine residues. The physiological significance of this post-translational modification is associated to tissue injury in animals, but has not been yet clarified in plants. The objective of this study was to establish new approaches that could help to understand ONOO(-) reactivity in plants. A recombinant Fe-superoxide dismutase from cowpea (Vigna unguiculata (L.) Walp.), rVuFeSOD, was the target of the ONOO(-)-generator SIN-1, and the anti-nitrative effect of plant antioxidants and haemoglobins was tested in vitro. Nitration on rVuFeSOD was evaluated immunochemically or as the loss of its enzymatic activity. This assay proved to be useful to test a variety of plant compounds for anti-nitrative capacity. Experimental data confirmed that rice (Oryza sativa L.) haemoglobin-1 (rOsHbI) and cowpea leghaemoglobin-2 exerted a protective function against ONOO(-) by diminishing nitration on rVuFeSOD. Both plant haemoglobins were nitrated by SIN-1. The chelator desferrioxamine suppressed nitration in rOsHbI, indicating that Fe plays a key role in the reaction. The removal of the haem moiety in rOsHbI importantly suppressed nitration, evidencing that this reaction may be self-catalyzed. Among small antioxidants, ascorbate remarkably decreased nitration in all tests. The phenolic compounds caffeic acid, gallic acid, pyrogallol, 4-hydroxybenzoic acid and the flavonoid gossypin also diminished tyrosine nitration and protected rVuFeSOD to different extents. It is concluded that small plant antioxidants, especially ascorbate, and haemoglobins may well play key roles in ONOO(-) homeostasis in vivo.
authors.affiliation: Institute of Agrobiotechnology, IdAB-CSIC-Public University of Navarre-Government of Navarre, Avda. Pamplona 123, E-31192, Mutilva, Navarre, Spain.
authors.forename: Estibaliz
authors.initials: E
authors.lastname: Urarte
authors.affiliation: CEMITEC, Polígono Mocholí, Plaza Cein 4, E-31110, Noain, Navarre, Spain.
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Asensio
authors.affiliation: CEMITEC, Polígono Mocholí, Plaza Cein 4, E-31110, Noain, Navarre, Spain.
authors.forename: Edurne
authors.initials: E
authors.lastname: Tellechea
authors.affiliation: Institute of Agrobiotechnology, IdAB-CSIC-Public University of Navarre-Government of Navarre, Avda. Pamplona 123, E-31192, Mutilva, Navarre, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Pires
authors.affiliation: Institute of Agrobiotechnology, IdAB-CSIC-Public University of Navarre-Government of Navarre, Avda. Pamplona 123, E-31192, Mutilva, Navarre, Spain. Electronic address: jose.moran@unavarra.es.
authors.forename: Jose F
authors.initials: JF
authors.lastname: Moran
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D007887:Fabaceae / Q000201:enzymology*; D030421:Peroxynitrous Acid / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D013482:Superoxide Dismutase / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D010940:Plant Proteins; D011994:Recombinant Proteins; D030421:Peroxynitrous Acid; D013482:Superoxide Dismutase
keywords: Antioxidants; Haemoglobins; Peroxynitrite; RNS; SODs; Tyrosine nitration; Vigna unguiculata