Upregulation of caspase-3, oxidative stress, neurobehavioural and histological alterations in mercury chloride-exposed rats: role of aqueous Allium sativum bulb extract

Mercury is a highly toxic metal that causes a variety of neurological disorders through oxidative stress. Allium sativum, a cooking spice in diverse cultures around the world, has a long history of medicinal use due to its rich antioxidant constituents. This study was designed to evaluate the protective activity of aqueous Allium sativum bulb extract (ASBE) on mercuric chloride (HgCl₂)-induced neurotoxicity. Forty Wistar rats were randomly divided into five groups namely I (control), II (HgCl₂; 4 mg/kg), III (250 mg/kg of ASBE and 4 mg/kg of HgCl₂), IV (500 mg/kg of ASBE and 4 mg/kg of HgCl₂) and V (500 mg/kg of Vitamin E and 4 mg/kg of HgCl₂). At the end of the administration, neurobehavioural, antioxidant enzymes, lipid peroxidation and apoptotic activities as well as the histology of the cerebrum, cerebellum and hippocampus were assessed. Body and brain weights, locomotion, exploration, cognition, memory and antioxidant enzymes were significantly impaired (p < 0.05) in HgCl₂-exposed rats following comparison to control. Lipid peroxidation, mercury concentration and caspase-3 activity were significantly upregulated (p < 0.05) in HgCl₂-exposed rats following comparison to control. In addition, significant alterations to the histology of the cerebrum, cerebellum and hippocampus were observed in the HgCl₂-exposed rats. Conversely, the adverse effects induced by HgCl₂ were significantly attenuated (p < 0.05) following ASBE and Vitamin E pretreatment. Taken together, these results suggest that ABSE exerts its neuroprotective activity through its potent antioxidant and anti-apoptotic properties.