Estudio y modulación del metabolismo del glutatión en la tolerancia al estrés oxidativo generado por plaguicidas en organismos acuáticos de interés comercial

Resum

Pesticides used in rice crops near wetlands of high ecological value such as the Natural Parks of the Albufera of Valencia and the Ebro Delta (Tarragona, Spain) represent a risk not only for their ecosystems, but also for the fishing and aquaculture of the area. Thiocarbamate herbicides decreased and oxidised the levels of the most important intracellular antioxidant, glutathione, in the European eel (Anguilla anguilla). Their mechanism of toxicity was mainly through the generation of free radicals, producing an oxidative stress state that would be the responsible of the hemorrhagic anaemia observed in eels. In addition, pesticide tolerance depended principally on the individual capacity of maintaining and enhancing the glutathione redox status. An excessive oxidation produces oxidative stress, which could lead to a programmed cell death (apoptosis) or not (necrosis), depending on the intensity, resulting in tissular impairment and, eventually, the death of the organism. A similar pattern was also found in a natural population of the pectinid spat Flexopecten flexuosus and the mussel Mytilus galloprovincialis exposed to the organophosphorus insecticide fenitrothion, which is the most abundant pesticide detected in the Ebro Delta. The antioxidant and glutathione pro-drug N-acetylcysteine (NAC) improved the survival of eels exposed to the organophosphate pesticide dichlorvos (which has been extensively used against fish parasites) through enhancing the glutathione metabolism and diminishing the loss and oxidation of it, in addition to reducing the enzymatic inhibition caused by the pesticide. Although glutathione depletion is considered as a biochemical marker of exposure to pollution, the glutathione redox status can be used as a biomarker of effect and individual susceptibility to certain pesticides or other pollutants that induce oxidative stress in aquatic vertebrates and invertebrates. Moreover, treatment of dichlorvos-intoxicated eels with baths of NAC ameliorated the depletion and oxidation of muscular glutathione and the brain acetylcholinesterase and glutathione reductase activities, which are biomarkers of neurotoxicity and oxidative stress, respectively. Consequently, NAC enhances the recovery of pesticide-poisoned fish, representing an inexpensive antidote of easy administration.