Zinc supplement reverses short-term memory deficit in sodium benzoate-induced neurotoxicity in male Wistar rats by enhancing anti-oxidative capacity via Nrf 2 up-regulation

Sodium benzoate (SB) is a commonly-used food preservative, with a controversial report to its neurological benefit and toxicity. Zinc (Zn) is a trace element that plays a crucial role in memory, inflammation and oxidative stress. This study was to investigate the effect of SB on rat cognition and memory and the possible modulatory effect of Zn supplement. Twenty four male Wistar rats were divided into four groups of six animals each. Animals in groups 1-4 were treated with normal saline 1 ml/kg, SB 200 mg/kg, zinc sulphate 10 ml/kg and SB 200 mg/kg + zinc sulphate 10 ml/kg/day daily respectively for three weeks. After treatment, the animals were subjected to different behavioural tests, and then sacrificed. Their blood samples were collected for catalase(CAT), superoxide dismutase(SOD) and interleukin-1B(IL-1B) assay. Brain samples were also collected for nuclear factor-erythroid-related factor 2(Nrf2), and acetylcholinesterase (AchE) mRNA gene expression. The serum levels of CAT and SOD were (p < 0.0001; p < 0.0001) reduced in the SB only-treated group compared to the other groups. Nrf2 gene expression was totally shut down in the SB only-treated group but, up-regulated in the Zn-treated groups (p < 0.0001). The serum level of IL-1B was higher in the SB only-treated group compared to the other groups. SB-treated group spent longer time in the close arm (p = <0.0001), shorter time in the open arm (p = <0.0001) and had higher anxiety index (p = 0.0045) than the Zn-treated groups. Conclusively, Zinc improves memory deficit, has anxiolytic, anti-oxidant and anti-inflammatory properties.