The Role of Oxidative and Nitrosative Stress of Silver Nanoparticles in Human Parasitic Helminth Brugia malayi: A Mechanistic Insight.

Purpose: Silver nanoparticles (AgNPs) mediated apoptosis is well-known but its rationale is yet to be elucidated. This study explored the mechanistic underpinning of the apoptosis in the Brugia malayi parasitic model.

Method: Silver nanoparticles were synthesized and tested against B. malayi microfilariae (Mf) to explore the role of oxidative and nitrosative stress in its apoptotic effect.

Results: AgNPs caused significant decrease in reduced glutathione (GSH) level and increase in both protein carbonylation and nitric oxide (NO) level indicating oxidative as well as nitrosative stress. Both GSH and nitric oxide synthase (NOS) inhibitors exhibited marked reversal. Nanoparticles and NO-donor in combination but not the NO-donor alone showed significant antiparasitic effect implying the requisite of combined oxidative and nitrosative stress to induce apoptosis. Synthetically prepared peroxynitrite from NaNO to HO showed marked antiparasitic effect in very low dose which could be achieved neither by NaNO or HO alone. GSH reversed the effect of peroxynitrite similar to its specific inhibitor, acetaminophen. GSH also reversed the plummet in mitochondrial oxygen consumption by AgNPs.

Conclusion: We conclude that apoptosis by AgNPs is possibly mediated through peroxynitrite dependent depletion of GSH; this provides a significant insight into the pharmacological as well as toxicological impact of AgNPs.