Acute effect of gold nanoparticles on neuropathic pain in a model of regional complex pain syndrome

We evaluated the effects of gold nanoparticles (AuNPs) administered in the acute phase of an animal model of Complex Regional Pain Syndrome Type I (CRPS-I). Oxidative stress parameters [substances reactive to thiobarbituric acid (TBA-RS), total sulfhydryl content (SH), protein carbonyl content and the activities of catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px)] and pain, through mechanical and thermal allodynia, were evaluated in the blood and sciatic nerves of mice. Animals were anesthetized and an elastic tourniquet was used around the left hind paw for 120 minutes, followed by measurements of the mechanical threshold and thermal. Animals received intraperitoneal administrations of AuNPs at concentrations of 2.5 mg/L, 7.0 mg/L and 22.0 mg/L, Ankyrin Transient Potential Receptor 1 (TRPA1) antagonist (HC030031) or saline vehicle after induction of CRPS-I. AuNPs showed significant results in thermal and mechanical anti-allodynic effects on day 1 (2.5 mg/L), days 2 and 3 (7.0 and 22.0 mg/L). The TRPA1 reduced mechanical allodynia (days 1 and 2) and thermal allodynia (days 1, 2 and 3), in addition to reversing the changes caused by CRPS-I in oxidative stress. The CRPS-I model increased TBA-RS, reduced the total sulfhydryl content and increased CAT activity. The results showed that, at all concentrations, AuNPs reversed the increase in CAT. At 7.0 mg/L partially reversed and at 22.0 mg/L completely reversed the increase in TBA-RS levels and at 22.0 mg/L reversed the reduction in sulfhydryl content.