engleski

Alteration of Cholinesterase Activity in Daphnia magna After the Exposure to Silver Nanoparticles

The environmental impact of nanomaterials is expected to increase in the near future as they are becoming a part of our daily life. Silver nanoparticles (AgNP) are widely used in the form of cosmetics, food packaging, drug delivery systems, therapeutics, antimicrobial agents, biosensors, or labelling agents. Effect of AgNPs on biomolecular level was studied by measuring activity of cholinesterases (ChE) in vitro. To asses possible mechanism of silver nanoparticle toxicity on the test organism Daphnia magna we measured ChE activity in vivo. Due to their sensitivity to toxicants following by rapid response in the aquatic system, Daphnia magna neonates are organism used as standardized test species for environmental risk of material with biocidal potency. AgNPs effect in vivo and in vitro was compared against the effect of ionic Ag+. Acetylcholinesterase (AChE) and related butyrylcholinesterase (BChE) are chosen because they are present in brain, blood and nervous system of mammals. Acetylcholinesterase (AChE) is a key enzyme in cholinergic neurotransmission and inhibition of AChE may lead to fatal outcome. BChE has important pharmacological and toxicological roles due to its hydrolysis of various xenobiotics, i.e. drugs. Presence of AgNPs and Ag+ reduced activity of both AChE and BChE in vitro. The major difference was in type of inhibition: AgNPs caused reversible inhibition of enzyme, whereas Ag+ caused irreversible inactivation of enzyme activity. For in vivo experiments, increase in AChE activity in D. magna neonates after acute exposure during 48 h to Ag+ or AgNPs was observed. Such result may be related to a de novo synthesis of the enzyme as a response to an initial inhibition as part of D. magna compensatory response to toxins. The data indicated also significantly different toxicity of nano and ionic form of Ag in the aquatic system, with Ag+ being more toxic to D. magna. Since many environmental contaminants exert toxic effects related to change in ChE activity, the more frequent use of various biochemical biomarkers, including ChE, as early indicators of toxic stress to aquatic biota is therefore recommended for evaluation of environmental risk.

Cholinesterase; Activity; Daphnia magna; Silver nanoparticles

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