Comprehensive insight into the neurotoxic mechanisms of low dose Pb exposure in Wistar rats: Benchmark dose analysis

Abstract

Lead (Pb) is a toxic metal that affects almost all human's system and organs, with the nervous system as the most sensitive. Better understanding of the Pb neurobehavioral effects and neurotoxicity requires realistic study scenarios based on low level exposure. The aim of this study was to determine neurotoxic effects and mechanisms of Pb in six low doses and to establish dose-response relationship for these effects and related Benchmark dose (BMD). Forty-two, male albino Wistar rats were randomized into seven groups, control and Pb-exposed: 0.1, 0.5, 1, 3, 7 and 15 mg Pb/kg body weight/day (oral gavage) for 28 days. Behavioural tests (Elevated plus maze test, Spontaneous locomotor activity test and Novel object recognition test) were conducted in the last week of experiment, in the control, lower (0.5 mg Pb/kg), middle (3 mg Pb/kg) and higher (15 mg Pb/kg) dose groups. The acetylcholinesterase activity, oxidative status and essential elements levels (Cu, Zn, Mn and Fe) were measured in brain tissue along with histological analyses. External and internal dose-response analyses were performed using PROASTweb 70.1 software. The results have shown that subacute exposure to very low doses of Pb resulted in memory deficits in rats that was accompanied with acetylcholinesterase enzyme activity decrease. The observed hyperactive behaviour was accompanied by dose-dependent induction of brain oxidative stress and Zn elevation. The histological alterations in Purkinje cells were only detected in the group treated with the highest Pb dose. The lowest BMD considering entire oxidative status was calculated based on total oxidative status (4.5e-06 mg Pb/kg b.w./day). The findings reported in our study may be beneficial in further evaluating the health consequences and human health risk assessment of low-level Pb exposure.