Simvastatin, Its Antimicrobial Activity and Its Prevention of Alzheimer's Disease.

Simvastatin, a blockbuster drug for treating hypercholesterolemia, has multifactorial benefits as an antimicrobial agent and plays a preventative role in reducing the incidence of Alzheimer's Disease (AD). Although most of the beneficial effects of simvastatin have been attributed to its ability to reduce cholesterol levels, recent scientific studies have suggested that its benefits are largely due to its pleiotropic effects in targeting other pathways, e.g., by inhibiting protein lipidation. There are certain pleiotropic effects that can be predicted from the inhibition of the mevalonate pathway; however, some of the effects of simvastatin in proteostasis lead to reduced levels of amyloid beta, the key contributor to AD. This review discusses the use of simvastatin as an antimicrobial agent and anti-AD drug.

The Use of Yeast in Biosensing.

Yeast has been used as a model for several diseases as it is the simplest unicellular eukaryote, safe and easy to culture and harbors most of the fundamental processes that are present in almost all higher eukaryotes, including humans. From understanding the pathogenesis of disease to drug discovery studies, yeast has served as an important biosensor. It is not only due to the conservation of genetics, amenable modification of its genome and easily accessible analytical methods, but also some characteristic features such as its ability to survive with defective mitochondria, making it a highly flexible microbe for designing whole-cell biosensing systems. The aim of this review is to report on how yeasts have been utilized as biosensors, reporting on responses to various stimuli.

Trans-Chalcone Plus Baicalein Synergistically Reduce Intracellular Amyloid Beta (Aß42) and Protect from Aß42 Induced Oxidative Damage in Yeast Models of Alzheimer's Disease.

Finding an effective therapeutic to prevent or cure AD has been difficult due to the complexity of the brain and limited experimental models. This study utilized unmodified and genetically modified Saccharomyces cerevisiae as model organisms to find potential natural bioactive compounds capable of reducing intracellular amyloid beta 42 (Aß42) and associated oxidative damage. Eleven natural bioactive compounds including mangiferin, quercetin, rutin, resveratrol, epigallocatechin gallate (EGCG), urolithin A, oleuropein, rosmarinic acid, salvianolic acid B, baicalein and trans-chalcone were screened for their ability to reduce intracellular green fluorescent protein tagged Aß42 (GFP-Aß42) levels. The two most effective compounds from the screens were combined in varying concentrations of each to study the combined capacity to reduce GFP-Aß42. The most effective combinations were examined for their effect on growth rate, turnover of native Aß42 and reactive oxygen species (ROS). The bioactive compounds except mangiferin and urolithin A significantly reduced intracellular GFP-Aß42 levels. Baicalein and trans-chalcone were the most effective compounds among those that were screened. The combination of baicalein and trans-chalcone synergistically reduced GFP-Aß42 levels. A combination of 15 µM trans-chalcone and 8 µM baicalein was found to be the most synergistic combination. The combination of the two compounds significantly reduced ROS and Aß42 levels in yeast cells expressing native Aß42 without affecting growth of the cells. These findings suggest that the combination of baicalein and trans-chalcone could be a promising multifactorial therapeutic strategy to cure or prevent AD. However, further studies are recommended to look for similar cytoprotective activity in humans and to find an optimal dosage.

A Toxic Synergy between Aluminium and Amyloid Beta in Yeast.

Alzheimer's disease (AD), the most prevalent, age-related, neurodegenerative disease, is associated with the accumulation of amyloid beta (Aß) and oxidative stress. However, the sporadic nature of late-onset AD has suggested that other factors, such as aluminium may be involved. Aluminium (Al3+) is the most ubiquitous neurotoxic metal on earth, extensively bioavailable to humans. Despite this, the link between Al3+ and AD has been debated for decades and remains controversial. Using Saccharomyces cerevisiae as a model organism expressing Aß42, this study aimed to examine the mechanisms of Al3+ toxicity and its interactions with Aß42. S. cerevisiae cells producing Aß42 treated with varying concentrations of Al3+ were examined for cell viability, growth inhibition, and production of reactive oxygen species (ROS). Al3+ caused a significant reduction in cell viability: cell death in yeast producing green fluorescent protein tagged with Aß42 (GFP-Aß42) was significantly higher than in cells producing green fluorescent protein (GFP) alone. Additionally, Al3+ greatly inhibited the fermentative growth of yeast producing GFP-Aß42, which was enhanced by ferric iron (Fe3+), while there was negligible growth inhibition of GFP cells. Al3+- induced ROS levels in yeast expressing native Aß42 were significantly higher than in empty vector controls. These findings demonstrate Al3+ has a direct, detrimental toxic synergy with Aß42 that can be influenced by Fe3+, causing increased oxidative stress. Thus, Al3+ should be considered as an important factor, alongside the known characteristic hallmarks of AD, in the development and aetiology of the disease.

ZIF-C for targeted RNA interference and CRISPR/Cas9 based gene editing in prostate cancer.

Gene therapy is highly suited for prostate cancer (PC). Metal-organic-frameworks (MOFs) are potential gene delivery systems. Target-specific cytoplasmic and nuclear knockdown in host gene expression using ZIF-C is shown for the first time through RNAi and CRISPR/Cas9 based gene editing in PC cells. A green tea phytochemical coating enhances intracellular delivery.

Protein Homeostasis Networks and the Use of Yeast to Guide Interventions in Alzheimer's Disease.

Alzheimer's Disease (AD) is a progressive multifactorial age-related neurodegenerative disorder that causes the majority of deaths due to dementia in the elderly. Although various risk factors have been found to be associated with AD progression, the cause of the disease is still unresolved. The loss of proteostasis is one of the major causes of AD: it is evident by aggregation of misfolded proteins, lipid homeostasis disruption, accumulation of autophagic vesicles, and oxidative damage during the disease progression. Different models have been developed to study AD, one of which is a yeast model. Yeasts are simple unicellular eukaryotic cells that have provided great insights into human cell biology. Various yeast models, including unmodified and genetically modified yeasts, have been established for studying AD and have provided significant amount of information on AD pathology and potential interventions. The conservation of various human biological processes, including signal transduction, energy metabolism, protein homeostasis, stress responses, oxidative phosphorylation, vesicle trafficking, apoptosis, endocytosis, and ageing, renders yeast a fascinating, powerful model for AD. In addition, the easy manipulation of the yeast genome and availability of methods to evaluate yeast cells rapidly in high throughput technological platforms strengthen the rationale of using yeast as a model. This review focuses on the description of the proteostasis network in yeast and its comparison with the human proteostasis network. It further elaborates on the AD-associated proteostasis failure and applications of the yeast proteostasis network to understand AD pathology and its potential to guide interventions against AD.

Tyramine and Amyloid Beta 42: A Toxic Synergy.

Implicated in various diseases including Parkinson's disease, Huntington's disease, migraines, schizophrenia and increased blood pressure, tyramine plays a crucial role as a neurotransmitter in the synaptic cleft by reducing serotonergic and dopaminergic signaling through a trace amine-associated receptor (TAAR1). There appear to be no studies investigating a connection of tyramine to Alzheimer's disease. This study aimed to examine whether tyramine could be involved in AD pathology by using Saccharomyces cerevisiae expressing Aß42. S. cerevisiae cells producing native Aß42 were treated with different concentrations of tyramine, and the production of reactive oxygen species (ROS) was evaluated using flow cytometric cell analysis. There was dose-dependent ROS generation in wild-type yeast cells with tyramine. In yeast producing Aß42, ROS levels generated were significantly higher than in controls, suggesting a synergistic toxicity of Aß42 and tyramine. The addition of exogenous reduced glutathione (GSH) was found to rescue the cells with increased ROS, indicating depletion of intracellular GSH due to tyramine and Aß42. Additionally, tyramine inhibited the respiratory growth of yeast cells producing GFP-Aß42, while there was no growth inhibition when cells were producing GFP. Tyramine was also demonstrated to cause increased mitochondrial DNA damage, resulting in the formation of petite mutants that lack respiratory function. These findings indicate that there can be a detrimental synergy between Aß42 and tyramine, which could be considered in Alzheimer's disease. This work also demonstrates the utility of yeast as a model for studying toxic agents such as Aß42, tyramine, and agents that might exacerbate AD pathology.

Siccibacter turicensis from Kangaroo Scats: Possible Implication in Cellulose Digestion.

Microbiota in the kangaroo gut degrade cellulose, contributing to the kangaroo's energy and survival. In this preliminary study, to discover more about the gut microbes that contribute to the survival of kangaroos, cellulose-degrading bacteria were isolated from kangaroo scats by selection on solidified media containing carboxymethyl cellulose as the main carbon source. One frequently occurring aerobic bacterium was Siccibacter turicensis, a microbe previously isolated in fruit powder and from a patient with angular cheilitis. The whole genome sequence of the kangaroo isolate was obtained using the Illumina MiSeq platform. Its sequence shared 97.98% identity of the S. turicensis Type strain, and the ability of the Type strain to degrade cellulose was confirmed. Analysis of the genomic data focused on the cellulose operon. In addition to genes from the operon, we suggest that a gene following the operon may have an important role in regulating cellulose metabolism by signal transduction. This is the first report of S. turicensis found within microbiota of the animal gut. Because of its frequent presence in the kangaroo gut, we suggest that S. turicensis plays a role in cellulose digestion for kangaroos.

Dietary Polyphenols: A Multifactorial Strategy to Target Alzheimer's Disease.

Ageing is an inevitable fundamental process for people and is their greatest risk factor for neurodegenerative disease. The ageing processes bring changes in cells that can drive the organisms to experience loss of nutrient sensing, disrupted cellular functions, increased oxidative stress, loss of cellular homeostasis, genomic instability, accumulation of misfolded protein, impaired cellular defenses and telomere shortening. Perturbation of these vital cellular processes in neuronal cells can lead to life threatening neurological disorders like Alzheimer's Disease, Parkinson's Disease, Huntington's Disease, Lewy body dementia, etc. Alzheimer's Disease is the most frequent cause of deaths in the elderly population. Various therapeutic molecules have been designed to overcome the social, economic and health care burden caused by Alzheimer's Disease. Almost all the chemical compounds in clinical practice have been found to treat symptoms only limiting them to palliative care. The reason behind such imperfect drugs may result from the inefficiencies of the current drugs to target the cause of the disease. Here, we review the potential role of antioxidant polyphenolic compounds that could possibly be the most effective preventative strategy against Alzheimer's Disease.

Simvastatin Efficiently Reduces Levels of Alzheimer's Amyloid Beta in Yeast.

A large-scale epidemiology study on statins previously showed that simvastatin was unique among statins in reducing the incidence of dementia. Since amyloid beta (Aß42) is the protein that is most associated with Alzheimer's disease, this study has focused on how simvastatin influences the turnover of native Aß42 and Aß42 fused with green fluorescent protein (GFP), in the simplest eukaryotic model organism, Saccharomyces cerevisiae. Previous studies have established that yeast constitutively producing Aß42 fused to GFP offer a convenient means of analyzing yeast cellular responses to Aß42. Young cells clear the GFP fusion protein and do not have green fluorescence while the older population of cells retains the fusion protein and exhibits green fluorescence, offering a fast and convenient means of studying factors that affect Aß42 turnover. In this study the proportion of cells having GFP fused to Aß after exposure to simvastatin, atorvastatin and lovastatin was analyzed by flow cytometry. Simvastatin effectively reduced levels of the cellular Aß42 protein in a dose-dependent manner. Simvastatin promoted the greatest reduction as compared to the other two statins. A comparison with fluconazole, which targets that same pathway of ergosterol synthesis, suggests that effects on ergosterol synthesis do not account for the reduced amounts of Aß42 fused to GFP. The levels of native Aß42 following treated with simvastatin were also examined using a more laborious approach, quantitative MALDI TOF mass spectrometry. Simvastatin efficiently reduced levels of native Aß42 from the population. This work indicates a novel action of simvastatin in reducing levels of Aß42 providing new insights into how simvastatin exerts its neuroprotective role. We hypothesize that this reduction may be due to protein clearance.

Encapsulation, Visualization and Expression of Genes with Biomimetically Mineralized Zeolitic Imidazolate Framework-8 (ZIF-8).

Recent work in biomolecule-metal-organic framework (MOF) composites has proven to be an effective strategy for the protection of proteins. However, for other biomacromolecules such as nucleic acids, the encapsulation into nano MOFs and the related characterizations are in their infancy. Herein, encapsulation of a complete gene-set in zeolitic imidazolate framework-8 (ZIF-8) MOFs and cellular expression of the gene delivered by the nano MOF composites are reported. Using a green fluorescent protein (GFP) plasmid (plGFP) as a proof-of-concept genetic macromolecule, successful transfection of mammalian cancer cells with plGFP for up to 4 days is shown. Cell transfection assays and soft X-ray cryo-tomography (cryo-SXT) demonstrate the feasibility of DNA@MOF biocomposites as intracellular gene delivery vehicles. Expression occurs over relatively prolonged time points where the cargo nucleic acid is released gradually in order to maintain sustained expression.