RESUMEN

Reactive oxygen species (ROS) are important mediators in a number of neurodegenerative diseases and molecules capable of scavenging ROS may be a feasible strategy for protecting neuronal cells. We previously demonstrated a powerful iron-chelating action of Guttiferone-A (GA), a naturally occurring polyphenol, on oxidative stress injuries initiated by iron overload. Here we addressed the neuroprotective potential of GA in hydrogen peroxide and glutamate-induced injury on rat's primary culture of cortical neurons and PC12 cells, respectively, and antioxidant properties concerning scavenging and anti-lipoperoxidative activities in cell-free models. The decrease in cell viability induced by each of the toxins, assessed by [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) assay, was significantly attenuated by GA. In addition, GA was found to be a potent antioxidant, as shown by (i) inhibition of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical reduction (EC50=20.0 µM), (ii) prevention against chemically or electrochemically generated superoxide radicals, (iii) inhibition of spontaneous brain lipid peroxidation and (iv) interference with the Fenton reaction. These results indicate that GA exerts neuroprotective effects against H2O2 or glutamate toxicity and its antioxidant activity, demonstrated in vitro, could be at least partly involved. They also suggest a promising potential for GA as a therapeutic agent against neurodegenerative diseases involving ROS and oxidative damage.

Asunto(s)

RESUMEN

Mangiferin acts as a strong antioxidant on mitochondria. However, when in the presence of Ca2+, mangiferin elicits mitochondrial permeability transition (MPT), as evidenced by cyclosporin A-sensitive mitochondrial swelling. We now provide evidence, by means of electrochemical and UV-visible spectroscopical analysis, that Fe(III) coordinates with mangiferin. The resulting mangiferin-Fe(III) complex does not elicit MPT and prevents MPT by scavenging reactive oxygen species. Indeed, the complex protects mitochondrial membrane protein thiols and glutathione from oxidation. Fe(III) also significantly increases the ability of mangiferin to scavenge the 2,2-diphenyl-1-picrylhydrazyl radical, as well as to display antioxidant activity toward antimycin A-induced H2O2 production and t-butyl hydroperoxide-promoted membrane lipid peroxidation in mitochondria. We postulate that coordination with Fe(III) constitutes a potential protective mechanism toward the prooxidant action of mangiferin and other catechol-containing antioxidants regarding MPT induction. Potential therapeutic relevance of this finding for conditions of pathological iron overload is discussed(AU)

Mangiferin actúa como un antioxidante fuerte en la mitocondria. Sin embargo, cuando en presencia de Ca2 +, mangiferin provoca transición de permeabilidad mitocondrial (MPT), como lo demuestra la ciclosporina A mitocondrial sensible a la hinchazón. Ahora aportar pruebas, a través de electroquímica y UV-visible spectroscopical análisis, que el Fe (III) se coordina con mangiferin. El resultado mangiferin-Fe (III) del complejo no impide obtener y MPT MPT barrido por especies reactivas de oxígeno. De hecho, el complejo de proteínas de membrana mitocondrial protege tioles y glutatión de la oxidación. Fe (III), también aumenta significativamente la capacidad de mangiferin a buscar la 2,2-difenil-1-picrylhydrazyl radicales, así como para mostrar la actividad antioxidante antimycin hacia una producción inducida por H2O2 y t-butil-hidroperóxido promovido la peroxidación lipídica en la membrana mitocondria. Postulamos que la coordinación con Fe (III), constituye un posible mecanismo de protección hacia prooxidant la acción de la catecol mangiferin y otras que contienen antioxidantes en relación con la inducción MPT. Relevancia potencial terapéutico de este hallazgo para las condiciones patológicas de sobrecarga de hierro se discute

Asunto(s)

RESUMEN

The preparation and characterization of an amperometric 2,4,6-trinitrotoluene (TNT) biosensor based on the surface immobilization of a maltose binding protein (MBP) nitroreductase (NR) fusion (MBP-NR) onto an electrode modified with an electropolymerized film of N-(3-pyrrol-1-ylpropyl)-4,4'-bipyridine (PPB) are described. The MBP domain of MBP-NR exhibits a high and specific affinity toward electropolymerized films of PPB with the immobilized enzyme retaining virtually all of its enzymatic activity. Under similar conditions, the wild-type NR enzyme (i.e., without the MBP domain) loses most of its enzymatic activity. The kinetics of the catalytic reaction between the biosensor and TNT and 2,4-dinitrotoluene (DNT) were characterized using rotated disk electrode and cyclic voltammetry techniques, and values of 1.4 x 10(4) and 7.1 x 10(4) M(-1) s(-1) were obtained for TNT and DNT, respectively. The apparent Michaelis-Menten constants (KM) for MBP-NR in solution and on the surface, using TNT as substrate, were determined to be 27 and 95 microM, respectively. The corresponding value for "wild-type" NR in solution containing TNT was 78 microM, which is very close to the value obtained for MBP-NR on the surface. The limits of detection for both TNT and DNT were estimated to be 2 microM, and the sensitivities were determined to be 205 and 222 nA/microM, respectively.

Asunto(s)