Mercury chloride causes cognitive impairment, oxidative stress and neuroinflammation in male Wistar rats: The potential protective effect of 6-gingerol-rich fraction of Zingiber officinale via regulation of antioxidant defence system and reversal of pro-inflammatory markers increase

This study investigated the effects of 6-gingerol-rich fraction of Zingiber officinale (6-GIRIFZO) on mercury chloride (HgCl2)-induced neurotoxicity in Wistar rats. Thirty -five male Wistar rats weighing between (150-200 g) were divided randomly into five groups (n = 7): group 1: control, received 0.5 mL of normal saline, group 2: received HgCl2 (5 mg/kg), group 3: received N-acetylcysteine (NAC) (50 mg/kg) as well as HgCl2 (5 mg/kg), group 4: received 6-GIRIFZO (100 mg/kg) and HgCl2 (5 mg/kg), group 5: had 6-GIRIFZO (200 mg/kg) and HgCl2 (5 mg/kg), consecutively for 14 days. On the day14, the rats were subjected to behavioural tests using a Morris water maze and novel object recognition tests. The rats were then euthanized to obtain brain samples for the determination of biochemical parameters (acetylcholinesterase (AchE), nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), glutathione (GSH), tumor necrosis factor- alpha (TNF-alpha), nuclear factor kappa-B (NF-kappa B), interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6)) using standard methods. The result revealed a significant increase in escape latency and a significant decrease in recognition ratio in the rats that were exposed to HgCl2 only. However, 6-GIRIFZO produced a significant reduction in the escape latency and (p < 0.05) increase in the recognition ratio. Similarly, HgCl2 exposure caused a significant (p < 0.05) decrease in the brain SOD, GPx, CAT, GSH with increased brain levels of MDA, NO, AchE, TNF-alpha, NF-kappa B, IL-1 beta and IL-6. Similarly to the standard drug, NAC, 6-GIRIFZO (100 and 200 mg/kg) significantly (p < 0.05) increased brain SOD, GPx, CAT, and GSH levels with decreased concentrations of MDA, NO, AchE, TNF-alpha, NF-kappa B, IL-1 beta and IL-6. Also, pre-treatment with 6-GIRIFZO prevented the HgCl2-induced morphological aberrations in the rats. This study concludes that 6-GIRIFZO prevents HgCl2-induced cognitive deficit via reduction of brain inflammation as well as oxidative stress in rats.