Impact of Bacopa and Elytrigia Bioactives on Effects Associated with Β-Amyloid Plaque Formation: A Three-Tiered Approach Employing in Silico, in Vitro and C. Elegans Based Studies
Posted: 11 Feb 2020 Last revised: 20 Feb 2020
Date Written: February 3, 2020
One of the hallmarks of Alzheimer's disease is the accumulation of amyloid plaques between neurons in the brain. In a healthy brain, these protein fragments are broken down and eliminated but these fragments accumulate to form hard insoluble plaques in disease condition leading to neural toxicity. This provokes a drastic effect on choline acetyltransferase and acetylcholine-hydrolyzing enzyme which play a vital role in the cholinergic nervous system; eventuating in a profound loss of forebrain cholinergic neurons and also sequentially accompanied by its progressive deterioration. Thus therapies are to be designed to reverse the cholinergic deficit due to amyloid agglomeration for restoring cognition and also preventing further damage. For the very same reason, the ethnobotanical approach brings a positive outlook to revert the damages while maintaining its feasible and herbal structured system. Thus initiation in this direction can lead to a promising therapeutic cure. The work done is the preliminary study to understand the amyloid aggregation and also to see how these fibrillar networks interact with the phytochemicals administered. The first phase involves in silico studies where Docking receptor Amyloid-β peptide (PDB: 2BEG) was studied using Protein preparation wizard in Schrodinger suite from which minimized 5-stranded Amyloid structure (11-42) was obtained, then it was processed for peptide docking (self-dimerization using Cluspro platform) from this,20 dimers were obtained which were used for virtual screening. With the help of Dr. Duke's phytochemical dictionary, the Knapsack database; ligand repository was constructed 60,000 molecules were procured(collected and constructed for 3D).This ligand preparation (LigPrep) aimed at optimizing the structures and preparing them for virtual screening with the target receptor. A virtual screening workflow was performed using the Schrodinger suite. Congo red dye was used as a positive control, About 1500 phytochemicals were obtained as the best hits having Glide score better than -4 (Note: HTVS->SP->XP~ 5 ligands/ protein dimer). When these compounds were traced, Bacopa monneri (Brahmi) and Elytrigia (Wheatgrass) were taken as the lead for in vitro studies. The second phase was to generate a model system mimicking Alzheimer's disease, different cell lines were screened for plaque formation from which THP-1 cell line was chosen as a suitable model system. The goal was to visualize Amyloid-β fibril interactions with the cells and also if the phytochemicals could halt the plaque formation and help in clearance. It was observed that when human β-amyloid peptide (1-42) was introduced, a positive plaque formation was seen and was tested by Congo red then these plant extracts of wheatgrass and Bacopa was given. Cytotoxicity and LDH assay showed that 1mg/ml was safe to administer for Brahmi and 0.5 mg/ml for wheatgrass. Also upon Bacopa treatment, there was a decrease in amyloid accumulation and cells survived the AD Scenario. Intriguing was the scavenging activity of wheatgrass that came up as a good hint for further studies. Studies employing transgenic C. elegans strain expressing ‘human’ amyloid beta are presently ongoing and the findings are expected to provide an understanding of Bacopa and Elytrigia effects vis-à-vis aggregation of amyloid-beta in a whole-organismal environment.
Keywords: Alzheimer's, Brahmi, Elytrigia, Amyloid plaque, Structural-functional studies
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