ABSTRACT

Lead toxicity has been and is still a significant public health problem in many parts of the world and its widespread use has resulted in extensive environmental contamination and human exposure, which has led to a variety of neurological disorders. Once ingested in the body, it affects various systems of the body especially the nervous system. Oxidative stress is implicated in the pathogenesis of lead-induced toxicity and antioxidants found in the body (endogenous antioxidants) can help remedy the excessive production of reactive oxygen species (ROS) caused by lead exposure. The use of exogenous antioxidants to counteract the oxidative damages of lead accumulation in the brain has been reported. Rosmarinus officinalis, commonly known as rosemary, is known for its anti-inflammatory, antiulcerogenic, hepatoprotective and antioxidant effects. Thirty adult Wistar rats which weighed between 120g to 172g were used for this study. The rats were grouped into six groups (A, B, C, D, E and F) with a total of five rats each. Group A served as the control, Group B was administered 100mg/kg bodyweight of lead only, Group C was administered 100mg/kg body weight of aqueous Rosmarinus officinalis leaf extract and 100mg/kg bodyweight of lead, Group D was administered 200mg/kg body weight of aqueous Rosmarinus officinalis leaf extractand 100mg/kg bodyweight of lead, Group E was administered 100mg/kg body weight of aqueous Rosmarinus officinalis leaf extract only, while Group F was administered 200mg/kg body weight of aqueous Rosmarinus officinalis leaf extract only. All administrations were given orally, through an orogastric tube and the experiment lasted for twenty-eight days. At the end of the study period, the rats were weighed and neurobehavioral activities such as novel object recognition test (NOR) and y-maze test were evaluated. The rats were euthanized through cervical dislocation and their brains dissected out. Brain weight was recorded and antioxidant parameters such as catalase (CAT), malondialdehyde (MDA), glutathione peroxidase (GPx) and superoxide dismutase (SOD) were investigated. Histology of the hippocampus was also examined in all groups. From the results, body weight increased in all groups except for the lead treated group which had a significant decrease in final body weight. For the NOR test, Rosmarinus officinalis produced a significant increase in the ability to discriminate between novel and familiar objects. For the Y-maze test, Rosmarinus officinalis demonstrated significant inhibition of lead-induced cognitive dysfunction. Rosmarinus officinalis produced a significant decrease in MDA level and increased SOD, CAT, GPx enzymes when compared to the lead treated group. For the histology of the hippocampus, lead treated group shows altered morphology with vacuolated cellular architecture, pyknotic nuclei and fewer cells in the CA1 region. Rosmarinus officinalis extract pretreated groups shows that the severity of the hippocampal damage is decreased. These findings suggest that aqueous Rosmarinus officinalis leaf extract exert its neuroprotective activity possibly via its potent antioxidant properties, and could be regarded as a promising neuroprotective agent relevant in the management of lead-induced toxicity.