β-Carotene: A Natural Compound Improves Cognitive Impairment and Oxidative Stress in a Mouse Model of Streptozotocin-Induced Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by a cascade of changes in cognitive, behavioral, and social activities. Several areas of the brain are involved in the regulation of memory. Of most importance are the amygdala and hippocampus. Antioxidant therapy is used for the palliative treatment of different degenerative diseases like diabetes, cirrhosis, and Parkinson's, etc. The objective of this study was to assess the effectiveness of exogenous antioxidants, in particular, beta carotene (1.02 and 2.05 mg/kg) against intracerebroventricular injected streptozotocin-induced memory impairment in mice. Streptozotocin (3 mg/kg, i.c.v) was administered in two separate doses (on 1st and 3rd days of treatment) for neurodegeneration. Fifty Albino mice (male) were selected in the protocol, and they were classified into five groups (Group I-control, Group II-disease, Group III-standard, Group IV-V-beta-carotene-treated) to investigate the cognitive enhancement effect of selected antioxidants. The cognitive performance was observed following the elevated plus-maze, passive avoidance, and open field paradigms. Acetylcholine esterase, beta-amyloid protein, and biochemical markers of oxidative stress such as glutathione peroxidase, superoxide dismutase, and catalase were analyzed in brain homogenates. In silico activity against acetylcholinesterase (AChE) was determined by the molecular modeling of beta-carotene. beta-carotene at a dose of 2.05 mg/kg was found to attenuate the deleterious effects of streptozotocin-induced behavioral and biochemical impairments, including the inhibition of acetylcholinesterase activity. The in silico studies confirmed the binding capacity of beta-carotene with the acetylcholinesterase enzyme. The administration of beta-carotene attenuated streptozotocin-induced cognitive deficit via its anti-oxidative effects, inhibition of acetylcholinesterase, and the reduction of amyloid beta-protein fragments. These results suggest that beta-carotene could be useful for the treatment of neurodegenerative diseases such as Alzheimer's disease.