i Therapeutic Effects of Rosmarinic Acid and Bacillus clausii on Aβ1-42-Induced Mouse Model of Alzheimer’s Disease

Abstract

Alzheimer's disease (AD) is a multifactorial neurodegenerative disorder, characterized by substantial neuronal damage due to formation of neurofibrillary tangles (NFTs) and amyloid beta plaques (Aβ), which results in cognitive deficits, oxidative stress and neuroinflammation. The present study elucidated the individual and combined neuroprotective potential of Rosmarinic acid (RA) and B. clausii on Aβ1-42-induced mice model of AD. RA is a bioactive compound of Rosmarinus officinalis, known to possess antioxidant and antiinflammatory properties. While emerging evidence indicates that probiotics have some role in the modulation of gut microbiota and may have ameliorative effect by regulating oxidative stress, neuroinflammation and Aβ aggregation associated mechanisms. The study used male BALB/c mice for the development of Aβ1-42-induced mouse model. There were 10 different goups of animals (n=6 each). Stereotaxic surgery was performed to administer Aβ1-42 (1 ug/ul) in the hippocampus of 5 groups. The remaining 5 groups received the phosphate buffered saline (PBS) in the same manner. RA (20 mg/kg) and Donepezil (2 mg/kg) as a positive control, were given through intraperitoneal (i.p.) injections whereas B. clausii (2x10^9 CFUs) was administered orally. One of the test groups received the combination of both RA and B. clausii. Behavior analyses were performed including Morris Water Maze (MWM) test and Novel Object Recognition (NOR) test. Recognition memory and novelty preference were observed by performing NOR test. The results showed that recognition memory was declined in mice treated with Aβ1-42 relative to control. Significant (57.76±2.01, p<0.0001) restoration of memory was displayed by the group receiving both RA and B. clausii treatment in combination, post Aβ1-42 administration. Marked amelioration in spatial memory (p<0.01) was observed for RA (31.0±1.58) and B. clausii (31.20±1.59)-treated groups post Aβ1-42 administration, whereas the combination treatment group exhibited the highest significance (36.80±2.42, p<0.0001). Gene expression analysis revealed significant amelioration of antioxidants (SOD1, Prdx6) and proinflammatory cytokines (IL-6, TNF-α) in the combination treatment group (p<0.0001) relative to Aβ1-42-treated group. The combination of RA and B. clausii indicated significant neuroprotective effect as compared to monotherapies and can be considered as disease modifying strategy in mitigating the onset and progression of AD, however, further understanding of underlying mechanisms is warranted.