Mechanistic insights into the potential role of dietary polyphenols and their nanoformulation in the management of Alzheimer's disease

Alzheimer's disease (AD) is a very common neurodegenerative disorder associated with memory loss and a progressive decline in cognitive activity. The two major pathophysiological factors responsible for AD are amyloid plaques (comprising amyloid-beta aggregates) and neurofibrillary tangles (consisting of hyperphosphorylated tau protein). Polyphenols, a class of naturally occurring compounds, are immensely beneficial for the treatment or management of various disorders and illnesses. Naturally occurring sources of polyphenols include plants and plant-based foods, such as fruits, herbs, tea, vegetables, coffee, red wine, and dark chocolate. Polyphenols have unique properties, such as being the major source of anti-oxidants and possessing anti-aging and anti-cancerous properties. Currently, dietary polyphenols have become a potential therapeutic approach for the management of AD, depending on various research findings. Dietary polyphenols can be an effective strategy to tackle multifactorial events that occur with AD. For instance, naturally occurring polyphenols have been reported to exhibit neuroprotection by modulating the Aβ biogenesis pathway in AD. Many nanoformulations have been established to enhance the bioavailability of polyphenols, with nanonization being the most promising. This review comprehensively provides mechanistic insights into the neuroprotective potential of dietary polyphenols in treating AD. It also reviews the usability of dietary polyphenol as nanoformulation for AD treatment.

A protein-miRNA biomic analysis approach to explore neuroprotective potential of nobiletin in human neural progenitor cells (hNPCs)

Chemical-induced neurotoxicity is increasingly recognized to accelerate the development of neurodegenerative disorders (NDs), which pose an increasing health burden to society. Attempts are being made to develop drugs that can cross the blood-brain barrier and have minimal or no side effects. Nobiletin (NOB), a polymethoxylated flavonoid with anti-oxidative and anti-inflammatory effects, has been demonstrated to be a promising compound to treat a variety of NDs. Here, we investigated the potential role of NOB in sodium arsenate (NA)-induced deregulated miRNAs and target proteins in human neural progenitor cells (hNPCs). The proteomics and microRNA (miRNA) profiling was done for different groups, namely, unexposed control, NA-exposed, NA + NOB, and NOB groups. Following the correlation analysis between deregulated miRNAs and target proteins, RT-PCR analysis was used to validate the selected genes. The proteomic analysis showed that significantly deregulated proteins were associated with neurodegeneration pathways, response to oxidative stress, RNA processing, DNA repair, and apoptotic process following exposure to NA. The OpenArray analysis confirmed that NA exposure significantly altered miRNAs that regulate P53 signaling, Wnt signaling, cell death, and cell cycle pathways. The RT-PCR validation studies concur with proteomic data as marker genes associated with autophagy and apoptosis (HO-1, SQSTM1, LC-3, Cas3, Apaf1, HSP70, and SNCA1) were altered following NA exposure. It was observed that the treatment of NOB significantly restored the deregulated miRNAs and proteins to their basal levels. Hence, it may be considered one of its neuroprotective mechanisms. Together, the findings are promising to demonstrate the potential applicability of NOB as a neuroprotectant against chemical-induced neurotoxicity.

Pharmacophore-Based Screening, Molecular Docking, and Dynamic Simulation of Fungal Metabolites as Inhibitors of Multi-Targets in Neurodegenerative Disorders

Neurodegenerative disorders, such as Alzheimer's disease (AD), negatively affect the economic and psychological system. For AD, there is still a lack of disease-altering treatments and promising cures due to its complex pathophysiology. In this study, we computationally screened the natural database of fungal metabolites against three known therapeutic target proteins of AD. Initially, a pharmacophore-based, drug-likeness category was employed for screening, and it filtered the 14 (A-N) best hits out of 17,544 fungal metabolites. The 14 best hits were docked individually against GSK-3β, the NMDA receptor, and BACE-1 to investigate the potential of finding a multitarget inhibitor. We found that compounds B, F, and L were immuno-toxic, whereas E, H, I, and J had a higher LD50 dose (5000 mg/kg). Among the examined metabolites, the Bisacremine-C (compound I) was found to be the most active molecule against GSK-3β (ΔG: -8.7 ± 0.2 Kcal/mol, Ki: 2.4 × 106 M-1), NMDA (ΔG: -9.5 ± 0.1 Kcal/mol, Ki: 9.2 × 106 M-1), and BACE-1 (ΔG: -9.1 ± 0.2 Kcal/mol, Ki: 4.7 × 106 M-1). It showed a 25-fold higher affinity with GSK-3β, 6.3-fold higher affinity with NMDA, and 9.04-fold higher affinity with BACE-1 than their native ligands, respectively. Molecular dynamic simulation parameters, such as RMSD, RMSF, Rg, and SASA, all confirmed that the overall structures of the targeted enzymes did not change significantly after binding with Bisacremine-C, and the ligand remained inside the binding cavity in a stable conformation for most of the simulation time. The most significant hydrophobic contacts for the GSK-3β-Bisacremine-C complex are with ILE62, VAL70, ALA83, and LEU188, whereas GLN185 is significant for H-bonds. In terms of hydrophobic contacts, TYR184 and PHE246 are the most important, while SER180 is vital for H-bonds in NMDA-Bisacremine-C. THR232 is the most crucial for H-bonds in BACE-1-Bisacremine-C and ILE110-produced hydrophobic contacts. This study laid a foundation for further experimental validation and clinical trials regarding the biopotency of Bisacremine-C.

Multitargeted Virtual Screening and Molecular Simulation of Natural Product-like Compounds against GSK3β, NMDA-Receptor, and BACE-1 for the Management of Alzheimer's Disease

The complexity of Alzheimer's disease (AD) and several side effects of currently available medication inclined us to search for a novel natural cure by targeting multiple key regulatory proteins. We initially virtually screened the natural product-like compounds against GSK3β, NMDA receptor, and BACE-1 and thereafter validated the best hit through molecular dynamics simulation (MDS). The results demonstrated that out of 2029 compounds, only 51 compounds exhibited better binding interactions than native ligands, with all three protein targets (NMDA, GSK3β, and BACE) considered multitarget inhibitors. Among them, F1094-0201 is the most potent inhibitor against multiple targets with binding energy -11.7, -10.6, and -12 kcal/mol, respectively. ADME-T analysis results showed that F1094-0201 was found to be suitable for CNS drug-likeness in addition to their other drug-likeness properties. The MDS results of RMSD, RMSF, Rg, SASA, SSE and residue interactions indicated the formation of a strong and stable association in the complex of ligands (F1094-0201) and proteins. These findings confirm the F1094-0201's ability to remain inside target proteins' binding pockets while forming a stable complex of protein-ligand. The free energies (MM/GBSA) of BACE-F1094-0201, GSK3β-F1094-0201, and NMDA-F1094-0201 complex formation were -73.78 ± 4.31 kcal mol^-1, -72.77 ± 3.43 kcal mol^-1, and -52.51 ± 2.85 kcal mol^-1, respectively. Amongst the target proteins, F1094-0201 have a more stable association with BACE, followed by NMDA and GSK3β. These attributes of F1094-0201 indicate it as a possible option for the management of pathophysiological pathways associated with AD.

Antibacterial efficacy of synthesized silver nanoparticles of Microbacterium proteolyticum LA2(R) and Streptomyces rochei LA2(O) against biofilm forming meningitis causing microbes

Actinobacteria obtained from the least explored Indian regions were studied for their ability to suppress meningitis-causing bacteria in nanoparticle form. Drug-resistant bacteria and long-term treatment with different medications make meningitis control complicated. Thus, new meningitis drugs are required to combat MDR bacteria. In this study, secondary metabolites isolated from actinomycetes strains, Microbacterium proteolyticum LA2(R) and Streptomyces rochei LA2(O), were employed to synthesize silver nanoparticles (AgNPs) at 37 °C for seven days incubation. UV-Vis spectroscopy, TEM, FTIR, and HPLC studies were used for the confirmation of the synthesis of AgNPs. Furthermore, these NPs demonstrated antibacterial and antibiofilm activities against meningitis-causing bacteria. The average size of LA2(R) and LA2(O) isolated secondary metabolites mediated AgNPs was observed to be 27 ± 1and 29 ± 2 nm by TEM analysis. FTIR study of RAgNPs and OAgNPs revealed that presence of peaks with positions of 1637.17 cm¹ and 1636.10 cm¹ for C=O amide group appearances in the amide I linkage. These NPs were effective against bacterial pathogens such as S. pneumoniae, H. influenzae, and N. meningitidis and confirmed by their MICs, i.e., 109.4, 120.60, and 138.80 μg/ml of RAgNPs and 105.80, 114.40 and 129.06 μg/ml of OAgNPs, respectively. Additionally, the production of biofilms is impeded by these nanoparticles on S. pneumoniae, H. influenzae, and N. meningitidis by 73.14%, 71.89% and 64.81%, respectively. These findings confirm the potential role of synthesized AgNPs against biofilm forming meningitis causing Multidrug resistance (MDR) microbes.

Oxidative Stress and Natural Antioxidants: Back and Forth in the Neurological Mechanisms of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by the progressive degeneration of neuronal cells. With the increase in aged population, there is a prevalence of irreversible neurodegenerative changes, causing a significant mental, social, and economic burden globally. The factors contributing to AD are multidimensional, highly complex, and not completely understood. However, it is widely known that aging, neuroinflammation, and excessive production of reactive oxygen species (ROS), along with other free radicals, substantially contribute to oxidative stress and cell death, which are inextricably linked. While oxidative stress is undeniably important in AD, limiting free radicals and ROS levels is an intriguing and potential strategy for deferring the process of neurodegeneration and alleviating associated symptoms. Therapeutic compounds from natural sources have recently become increasingly accepted and have been effectively studied for AD treatment. These phytocompounds are widely available and a multitude of holistic therapeutic efficiencies for treating AD owing to their antioxidant, anti-inflammatory, and biological activities. Some of these compounds also function by stimulating cholinergic neurotransmission, facilitating the suppression of beta-site amyloid precursor protein-cleaving enzyme 1, α-synuclein, and monoamine oxidase proteins, and deterring the occurrence of AD. Additionally, various phenolic, flavonoid, and terpenoid phytocompounds have been extensively described as potential palliative agents for AD progression. Preclinical studies have shown their involvement in modulating the cellular redox balance and minimizing ROS formation, displaying them as antioxidant agents with neuroprotective abilities. This review emphasizes the mechanistic role of natural products in the treatment of AD and discusses the various pathological hypotheses proposed for AD.

Homology Modelling, Molecular Docking and Molecular Dynamics Simulation Studies of CALMH1 against Secondary Metabolites of Bauhinia variegata to Treat Alzheimer's Disease

Calcium homeostasis modulator 1 (CALHM1) is a protein responsible for causing Alzheimer’s disease. In the absence of an experimentally designed protein molecule, homology modelling was performed. Through homology modelling, different CALHM1 models were generated and validated through Rampage. To carry out further in silico studies, through molecular docking and molecular dynamics simulation experiments, various flavonoids and alkaloids from Bauhinia variegata were utilised as inhibitors to target the protein (CALHM1). The sequence of CALHM1 was retrieved from UniProt and the secondary structure prediction of CALHM1 was done through CFSSP, GOR4, and SOPMA methods. The structure was identified through LOMETS, MUSTER, and MODELLER and finally, the structures were validated through Rampage. Bauhinia variegata plant was used to check the interaction of alkaloids and flavonoids against CALHM1. The protein and protein–ligand complex were also validated through molecular dynamics simulations studies. The model generated through MODELLER software with 6VAM A was used because this model predicted the best results in the Ramachandran plot. Further molecular docking was performed, quercetin was found to be the most appropriate candidate for the protein molecule with the minimum binding energy of −12.45 kcal/mol and their ADME properties were analysed through Molsoft and Molinspiration. Molecular dynamics simulations showed that CALHM1 and CALHM1–quercetin complex became stable at 2500 ps. It may be seen through the study that quercetin may act as a good inhibitor for treatment. With the help of an in silico study, it was easier to analyse the 3D structure of the protein, which may be scrutinized for the best-predicted model. Quercetin may work as a good inhibitor for treating Alzheimer’s disease, according to in silico research using molecular docking and molecular dynamics simulations, and future in vitro and in vivo analysis may confirm its effectiveness.