Enzymatic biomarkers can portray nanoCuO-induced oxidative and neuronal stress in freshwater shredders.

Commercial applications of nanometal oxides have increased concern about their release into natural waters and consequent risks to aquatic biota and the processes they drive. In forest streams, the invertebrate shredder Allogamus ligonifer plays a key role in detritus food webs by transferring carbon and energy from plant litter to higher trophic levels. We assessed the response profiles of oxidative and neuronal stress enzymatic biomarkers in A. ligonifer after 96h exposure to nanoCuO at concentration ranges <LC ₃₀ . To better understand the contribution of ionic form in nanoCuO-induced stress, Cu ²⁺ released from nanoCuO was quantified and the enzymatic responses to Cu ²⁺ exposure at similar effective concentrations were compared. The highest activities of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione reductase (GR) were observed at concentrations <LC ₅ . The enzymatic activities decreased at effective concentrations between LC ₁₀ and LC ₃₀ . GR activity remained higher than in control at all concentrations. The activity of glutathione S-transferase (GST) increased whereas that of catalase (CAT) decreased at concentrations between LC ₁₀ and LC ₃₀ . The response patterns suggested that antioxidant enzymes could prevent oxidative stress at low concentrations (<LC ₁₀ ) of nanoCuO, thereby contributing to the survival of A. ligonifer. At concentrations between LC ₁₀ and LC ₃₀ , effects of nanoparticulate or released ionic copper on enzyme activities were concentration-dependent, and led to oxidative stress and even to animal death. The activity of acetylcholinesterase (AChE) was strongly inhibited even at concentrations <LC ₁₀ , suggesting neuronal stress in A. ligonifer.
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