Interaction of silver nanoparticles with antioxidant enzymes

Abstract

Oxidative stress is accepted as a key mechanism of silver nanoparticle (AgNP) toxicity in living organisms. Therefore, mechanistic studies related to the impact of AgNPs on the structure and function of antioxidant enzymes at the molecular level are essential for a comprehensive evaluation of their toxicity. By using a combination of spectroscopic, imaging and fractionation techniques, we explored the interactions between citrate-coated AgNPs (20 nm) and two key antioxidant enzymes: catalase (CAT) and superoxide dismutase (SOD). Both enzymes interacted with AgNPs by forming surface complexes. Only CAT was able to promote AgNP dissolution, without the impact of the released Ag ions on its heme cofactor. Instead, our results suggest that the formation of the AgNP-CAT complex induced conformation changes in the CAT, which resulted in an impairment of its enzymatic activity together with AgIJI) adsorption. By contrast, the formation of the AgNP-SOD complex has only a marginal influence on the protein conformation and has no impact on its metallic cofactors, and thus its enzymatic activity. Overall, the results showed that the changes in the protein conformation and the dissolution of AgNPs depended on the protein structure and could result in different degrees of enzymatic activity modulation.Excessive production of reactive oxygen species in cells by direct interaction with particles and/or dissolved species is currently accepted as one of the main mechanisms of cellular toxicity of engineered nanoparticles. Therefore, studies related to the impact of silver nanoparticles (AgNPs) on the structure and function of antioxidant enzymes at the molecular level are crucial for a comprehensive evaluation of their toxicity. This study suggests that the conformation changes of two key antioxidant enzymes, catalase and superoxide dismutase, and the dissolution of AgNPs depended on the protein structure and could result in different degrees of enzymatic activity modulation. This research provides a basis to understand how the functional properties of the key antioxidant enzymes may affect the stability of nanoparticles in a biological context and give insights into the role of these enzymes in the mechanism of NP-induced redox stress in vivo.

Anticancer and antibacterial potentials induced post short-term exposure to electromagnetic field and silver nanoparticles and related pathological and genetic alterations: in vitro study

“…That was suggested to be related to the formation of AgNPs-CAT complex which in turn resulted in conformational changes in CAT enzyme leading to an impairment of its enzymatic activity. In contrast, the formation of AgNPs-SOD complex has no influence on its enzymatic activity [ 44 ].…”

Antioxidant‐modulated cytotoxicity of silver nanoparticles

“…Previously, it has been established that the activity of antioxidant enzymes strongly depends on the surface properties of AgNPs used in the cytotoxic tests (Barbasz et al, 2017). Recent studies have shown that AgNPs can form complexes with antioxidant enzymes and modify conformational changes in their structures (Liu et al, 2020). Independently of the changes at the cellular level, the surface properties of AgNPs influence the interactions with cell membranes and uptake mechanisms (Ahmed et al, 2017).…”

Nanosilver toxicity thresholds estimative for aquatic and sediment environmental safety

“…The toxicity of AgNPs is enhanced by PVP-and sodium citrate-coatings (Chen et al 2018). However, risk evaluation can be di cult due to the several AgNPs dissolution mechanisms (Liu et al 2020).…”