Moxifloxacin Disrupts and Attenuates Aβ42 Fibril and Oligomer Formation: Plausibly Repositioning an Antibiotic as Therapeutic against Alzheimer's Disease

Tetrahydrofolic acid accelerates amyloid fibrillization, decreases cytotoxic oligomers and suppresses their toxicity

Soluble cytotoxic oligomers produced during the fibrillation of both α-synuclein (αS) and amyloid-β protein (Aβ) are key pathogenic factors in Parkinson's disease (PD) and Alzheimer's disease (AD). Reducing toxic oligomers by regulating the aggregation process of αS and Aβ is an important strategy for the treatment of PD and AD. Herein, tetrahydrofolic acid (THF) is found to accelerate amyloid fibrillization, decreases cytotoxic oligomers and suppresses their toxicity. Thioflavin T and atomic force microscopy assays results showed that THF was able to accelerate the formation of dense fibrils from αS and Aβ in a dose-dependent manner. Strikingly, this was accompanied by a reduction in the abundance of toxic oligomers, and these results were confirmed by DB. Meanwhile, MTT and FDA/PI assays demonstrated that THF-induced accelerated fibril formation was accompanied by a reduction in αS- and Aβ-induced cytotoxicity. In addition, the lifespan of genetically modified αS and Aβ expressing C. elegans was extended by feeding THF, although plaque deposits of αS and Aβ increased. These findings suggest that THF enhances the conversion of αS and Aβ oligomers into less toxic fibrils and is a potential therapeutic agent for PD and AD.

Exploring Cimetidine as a Potential Therapeutic Attenuator against Amyloid Formation in Parkinson's Disease: Spectroscopic and Microscopic Insights into Alpha-Synuclein and Human Insulin

Neurodegenerative diseases, notably Alzheimer's and Parkinson's, hallmark their progression through the formation of amyloid aggregates resulting from misfolding. While current therapeutics alleviate symptoms, they do not impede disease onset. In this context, repurposing existing drugs stands as a viable therapeutic strategy. Our study determines the antihistamine drug Cimetidine's potential as an inhibitor using diverse spectroscopic and microscopic methods on alpha-synuclein and human insulin amyloid formation, unveiling its efficacy. The thioflavin T (ThT) assay illustrated a dose-dependent reduction in amyloid formation with escalating concentrations of Cimetidine. Notably, the antihistamine drug maintained a helical structure and showed no significant conformational changes in the secondary structure. Confocal microscopy validated fewer fibrils in the Cimetidine-treated samples. Remarkably, Cimetidine interacted with pre-existing fibrils, leading to their disintegration. Further analyses (ThT, circular dichroism, and dynamic light scattering) showcased the conversion of fibrils into smaller aggregates upon Cimetidine addition. These findings signify the potential of this antihistamine drug as a plausible therapeutic option for Parkinson's disease. This study may open avenues for deeper investigations and possible therapeutic developments, emphasizing Cimetidine's promising role in mitigating neurodegenerative diseases like Parkinson's.

Small molecule inhibits BACE1 activity by a dual mechanism confirmed by simulations-based study

Alzheimer's disease (AD) is a progressive and largely incurable neurodegenerative disorder that affects millions of people worldwide. It is characterised by the accumulation of amyloid-beta plaques and neurofibrillary tangles in the brain. It is commenced by cleavage of amyloid precursor protein (APP) by β-secretase, β-site amyloid precursor protein cleaving enzyme (BACE1; also called Asp2, memapsin 2). Therefore, BACE1 is a prime target for developing therapeutics against AD. In this study, we have identified a small molecule that potentially inhibits the activity of BACE1 by interacting with the active site residues. Also, the flap region seems to be involved in enhancing the stability of the small molecule at the active site. We have used Umibecestat (CNP-520) as a positive control. Our in silico results show that the identified molecule has a much better orientation at the active site of BACE1 than Umibecestat and inhibits by blocking the active site and modulating flap dynamics. We have utilised virtual high-throughput screening assay, ADME profiling, and blood-brain-barrier crossing ability to narrow down potential leads. The two shortlisted molecules were then subjected to atomistic molecular dynamics simulations study. Overall, our study proposes a much better inhibitor and a rational molecule for lead development against AD.

Targeting inflammation and gut microbiota with antibacterial therapy: Implications for central nervous system health

The complex symbiotic relationship between inflammation, the gut microbiota, and the central nervous system (CNS) has become a pivotal focus of contemporary biomedical research. Inflammation, as a physiological defense mechanism, plays a dual role as both a protective and pathological factor, and is intricately associated with gut microbiota homeostasis, often termed the "second brain." The gutbrain axis (GBA) exemplifies this multifaceted interaction, where gut health exerts significantly regulatory effects on CNS functions. Antibacterial therapies represent both promising and challenging strategies for modulating inflammation and gut microbiota composition to confer CNS benefits. However, while such therapies may exert positive modulatory effects on the gut microbiota, they also carry the potential to disrupt microbial equilibrium, potentially exacerbating neurological dysfunction. Recent advances have provided critical insights into the therapeutic implications of antibacterial interventions; nevertheless, the application of these therapies in the context of CNS health warrants a judicious and evidence-based approach. As research progresses, deeper investigation into the microbial-neural interface is essential to fully realize the potential of therapies targeting inflammation and the gut microbiota for CNS health. Future efforts should focus on refining antibacterial interventions to modulate the gut microbiota while minimizing disruption to microbial balance, thereby reducing risks and enhancing efficacy in CNS-related conditions. In conclusion, despite challenges, a more comprehensive understanding of the GBA, along with precise modulation through targeted antibacterial therapies, offers significant promise for advancing CNS disorder treatment. Continued research in this area will lead to innovative interventions and improved patient outcomes.

Natural compound plumbagin based inhibition of hIAPP revealed by Markov state models based on MD data along with experimental validations

Human islet amyloid polypeptide (amylin or hIAPP) is a 37 residue hormone co-secreted with insulin from β cells of the pancreas. In patients suffering from type-2 diabetes, amylin self-assembles into amyloid fibrils, ultimately leading to the death of the pancreatic cells. However, a research gap exists in preventing and treating such amyloidosis. Plumbagin, a natural compound, has previously been demonstrated to have inhibitory potential against insulin amyloidosis. Our investigation unveils collapsible regions within hIAPP that, upon collapse, facilitates hydrophobic and pi-pi interactions, ultimately leading to aggregation. Intriguingly plumbagin exhibits the ability to bind these specific collapsible regions, thereby impeding the aforementioned interactions that would otherwise drive hIAPP aggregation. We have used atomistic molecular dynamics approach to determine secondary structural changes. MSM shows metastable states forming native like hIAPP structure in presence of PGN. Our in silico results concur with in vitro results. The ThT assay revealed a striking 50% decrease in fluorescence intensity at a 1:1 ratio of hIAPP to Plumbagin. This finding suggests a significant inhibition of amyloid fibril formation by plumbagin, as ThT fluorescence directly correlates with the presence of these fibrils. Further TEM images revealed disappearance of hIAPP fibrils in plumbagin pre-treated hIAPP samples. Also, we have shown that plumbagin disrupts the intermolecular hydrogen bonding in hIAPP fibrils leading to an increase in the average beta strand spacing, thereby causing disaggregation of pre-formed fibrils demonstrating overall disruption of the aggregation machinery of hIAPP. Our work is the first to report a detailed atomistic simulation of 22 μs for hIAPP. Overall, our studies put plumbagin as a potential candidate for both preventive and therapeutic candidate for hIAPP amyloidosis.

Doxorubicin as a Drug Repurposing for Disruption of α-Chymotrypsinogen-A Aggregates

Protein conformation is affected by interaction of several small molecules resulting either stabilization or disruption depending on the nature of the molecules. In our earlier communication, Hg2+ was known to disrupt the native structure of α-Cgn A leading to aggregation (Ansari, N.K., Rais, A. & Naeem, A. Methotrexate for Drug Repurposing as an Anti-Aggregatory Agent to Mercuric Treated α-Chymotrypsinogen-A. Protein J (2024). https://doi.org/10.1007/s10930-024-10187-z ). Accumulation of β-rich aggregates in the living system is found to be linked with copious number of disorders. Here, we have investigated the effect of varying concentration of doxorubicin (DOX) i.e. 0-100 µM on the preformed aggregates of α-Cgn A upon incubation with 120 µM Hg2+. The decrease in the intrinsic fluorescence and enzyme activity with respect to increase in the Hg2+ concentration substantiate the formation of aggregates. The DOX showed the dose dependent decrease in the ThT fluorescence, turbidity and RLS measurements endorsing the dissolution of aggregates which were consistent with red shift in ANS, confirming the breakdown of aggregates. The α-Cgn A has 30% α-helical content which decreases to 3% in presence of Hg2+. DOX increased the α-helicity to 28% confirming its anti-aggregatory potential. The SEM validates the formation of aggregates with Hg2+ and their dissolution upon incubation with the DOX. Hemolysis assay checked the cytotoxicity of α-Cgn A aggregates. Docking revealed that the DOX interacted Lys203, Cys201, Cys136, Ser159, Leu10, Trp207, Val137 and Thr134 of α-Cgn A through hydrophobic interactions and Gly133, Thr135 and Lys202 forms hydrogen bonds.

Protein misfolding and related human diseases: A comprehensive review of toxicity, proteins involved, and current therapeutic strategies

Most of the cell's chemical reactions and structural components are facilitated by proteins. But proteins are highly dynamic molecules, where numerous modifications or changes in the cellular environment can affect their native conformational fold leading to protein aggregation. Various stress conditions, such as oxidative stress, mutations and metal toxicity may cause protein misfolding and aggregation by shifting the conformational equilibrium towards more aggregation-prone states. Most of the protein misfolding diseases (PMDs) involve aggregation of protein. We have discussed such proteins like Aβ peptide, α-synuclein, amylin and lysozyme involved in Alzheimer's, Parkinson's, type II diabetes and non-neuropathic systemic amyloidosis respectively. Till date, all advances in PMDs therapeutics help symptomatically but do not prevent the root cause of the disease, i.e., the aggregation of protein involved in the diseases. Current efforts focused on developing therapies for PMDs have employed diverse strategies; repositioning pre-existing drugs as it saves time and money; natural compounds that are touted as potential drug candidates have an advantage of being taken in diet normally and will induce lesser side effects. This review also covers recently developed therapeutic strategies like antisense drugs and disaggregases which has yielded therapeutic agents that have transitioned from preclinical studies into human clinical trials.

Benefit and safety of antibiotics for Alzheimer's disease: Protocol for a systematic review and meta-analysis

BACKGROUND

Alzheimer's disease (AD) is an age-related degenerative change of the central nervous system, the cause of which remains unclear. Recent studies have found that brain inflammation caused by microbial infections may be one of the etiologies of AD, and antibiotics as novel treatments may be beneficial for delaying the development of AD. Several prospective studies have investigated the effects of different antibiotics on Alzheimer's disease. However, no systematic review or meta-analysis has evaluated the benefits and safety of antibiotics in AD patients.

METHODS

This study will analyze randomized controlled trials and observational studies published from database inception to December 31, 2022, and included direct or indirect evidence. Studies will be retrieved by searching PubMed, Scopus, Web of Science, Cochrane Central Register of Controlled Clinical Trials, CNKI, and Wan Fang databases. The outcomes of this study included the Alzheimer's Disease Assessment Scale cognitive subscale (ADAS-cog), Montreal Cognitive Assessment (MoCA), Standardized Mini-Mental State Examination (SMMSE), Clinical Dementia Rating (CDR), Frontal Functioning Scale (FAB), Dysfunctional Behavior Rating Instrument (DBRI), Activities of Daily Living (ADLs) Index, and Geriatric Depression Scale (GDS). The risk of bias will be assessed using the Cochrane risk-of-bias assessment instrument for randomized controlled trials. A random-effect/fixed-effects model will be used to summarize the estimates of the mean difference/risk ratio using a 95% confidence interval.

RESULTS

This study will analyze the benefits and safety of antibiotics in patients with AD.

CONCLUSION

The results of this analysis will provide evidence to evaluate the benefits and safety of antibiotics in the treatment of AD.