Evaluation of traditional medicines for neurodegenerative diseases using Drosophila models

Ribose-cysteine and levodopa abrogate Parkinsonism via the regulation of neurochemical and redox activities in alpha-synuclein transgenic Drosophila melanogaster models

Parkinson's disease (PD), the most prevalent type of parkinsonism, is a progressive neurodegenerative condition marked by several non-motor and motor symptoms. PD is thought to have a complex aetiology that includes a combination of age, genetic predisposition, and environmental factors. Increased expression of α-synuclein (α-Syn) protein is central to the evolvement of neuropathology in this devastating disorder, but the potential of ribose-cysteine and levodopa in abating pathophysiologic changes in PD model is unknown. Crosses were set up between flies conditionally expressing a pathological variant of human α-Syn (UAS-α-Syn) and those expressing GAL4 in neurons (elav-GAL4) to generate offspring referred to as PD flies. Flies were randomly assigned to five groups (n = 40) from the total population of flies, with each group having five replicates. Groups of PD flies were treated with either 500 mg/kg ribose-cysteine diet, 250 mg/kg levodopa diet, or a combination of the two compounds for 21 days, whereas the control group (w1118) and the PD group were exposed to a diet without ribose-cysteine or levodopa. In addition to various biochemical and neurochemical assays, longevity, larval motility, and gravitaxis assays were carried out. Locomotive capability, lifespan, fecundity, antioxidant state, and neurotransmitter systems were all significantly (p < 0.05) compromised by overexpression of α-Syn. However, flies treated both ribose cysteine and levodopa showed an overall marked improvement in motor functions, lifespan, fecundity, antioxidant status, and neurotransmitter system functions. In conclusion, ribose-cysteine and levodopa, both singly and in combination, potentiated a therapeutic effect on alpha-synuclein transgenic Drosophila melanogaster models of Parkinsonism.

Targeting Nrf2 signaling pathway and oxidative stress by resveratrol for Parkinson's disease: an overview and update on new developments

Parkinson's disease (PD) as a prevalent neurodegenerative condition impairs motor function and is caused by the progressive deterioration of nigrostriatal dopaminergic (DAergic) neurons. The current therapy solutions for PD are ineffective because they could not inhibit the disease's progression and they even have adverse effects. Natural polyphenols, a group of phytochemicals, have been found to offer various health benefits, including neuroprotection against PD. Among these, resveratrol (RES) has neuroprotective properties owing to its capacity to protect mitochondria and act as an antioxidant. An increase in the formation of reactive oxygen species (ROS) leads to oxidative stress (OS), which is responsible for cellular damage resulting in lipid peroxidation, oxidative protein alteration, and DNA damage. In PD models, it's been discovered that RES pretreatment can diminish oxidative stress by boosting endogenous antioxidant status and directly scavenging ROS. Several studies have examined the involvement of RES in the modulation of the transcriptional factor Nrf2 in PD models because this protein recognizes oxidants and controls the antioxidant defense. In this review, we have examined the molecular mechanisms underlying the RES activity and reviewed its effects in both in vitro and in vivo models of PD. The gathered evidence herein showed that RES treatment provides neuroprotection against PD by reducing OS and upregulation of Nrf2. Moreover, in the present study, scientific proof of the neuroprotective properties of RES against PD and the mechanism supporting clinical development consideration has been described.

Drosophila as an Animal Model for Testing Plant-Based Immunomodulators

Allopathic medicines play a key role in the prevention and treatment of diseases. However, long-term consumption of these medicines may cause serious undesirable effects that harm human health. Plant-based medicines have emerged as alternatives to allopathic medicines because of their rare side effects. They contain several compounds that have the potential to improve health and treat diseases in humans, including their function as immunomodulators to treat immune-related diseases. Thus, the discovery of potent and safe immunomodulators from plants is gaining considerable research interest. Recently, Drosophila has gained prominence as a model organism in evaluating the efficacy of plant and plant-derived substances. Drosophila melanogaster "fruit fly" is a well-known, high-throughput model organism that has been used to study different biological aspects of development and diseases for more than 110 years. Most developmental and cell signaling pathways and 75% of human disease-related genes are conserved between humans and Drosophila. Using Drosophila, one can easily examine the pharmacological effects of plants/plant-derived components by employing a variety of tests in flies, such as survival, anti-inflammatory, antioxidant, and cell death tests. This review focused on D. melanogaster's potential for identifying immunomodulatory features associated with plants/plant-derived components.

Ameliorative Role of Nutraceuticals on Neurodegenerative Diseases Using the Drosophila melanogaster as a Discovery Model to Define Bioefficacy

Neurodegeneration is the destruction of neurons, and once the neurons degenerate they can't revive. This is one of the most concerned health conditions among aged population, more than ∼70% of the elderly people are suffering from neurodegeneration. Among all of the neurodegenerative diseases, Alzheimer's disease (AD), Parkinson's disease (PD) and Poly-glutamine disease (Poly-Q) are the major one and affecting most of the people around the world and posing excessive burden on the society. In order to understand this disease in non-human animal models it is pertinent to examine in model organism and various animal model are being used for such diseases like rat, mice and non-vertebrate model like Drosophila. Drosophila melanogaster is one of the best animal proven by several eminent scientist and had received several Nobel prizes for uncovering mechanism of human related genes and highly efficient model for studying neurodegenerative diseases due to its great affinity with human disease-related genes. Another factor is also employed to act as therapeutic or preventive method that is nutraceuticals. Nutraceuticals are functional natural compounds with antioxidant properties and had extensively showed the neuroprotective effect in different organisms. These nutraceuticals having antioxidant properties act through scavenging free radicals or by increasing endogenous cellular antioxidant defense molecules. For the best benefit, we are trying to utilize these nutraceuticals, which will have no or negligible side effects. In this review, we are dealing with various types of such nutraceuticals which have potent value in the prevention and curing of the diseases related to neurodegeneration.HighlightsNeurodegeneration is the silently progressing disease which shows its symptoms when it is well rooted.Many chemical drugs (almost all) have only symptomatic relief with side effects.Potent mechanism of neurodegeneration and improvement effect by nutraceuticals is proposed.Based on the Indian Cuisine scientists are trying to find the medicine from the food or food components having antioxidant properties.The best model to study the neurodegenerative diseases is Drosophila melanogaster.Many nutraceuticals having antioxidant properties have been studied and attenuated various diseases are discussed.

Pharmacological Treatment of Alzheimer's Disease: Insights from Drosophila melanogaster

Aging is an ineluctable law of life. During the process of aging, the occurrence of neurodegenerative disorders is prevalent in the elderly population and the predominant type of dementia is Alzheimer’s disease (AD). The clinical symptoms of AD include progressive memory loss and impairment of cognitive functions that interfere with daily life activities. The predominant neuropathological features in AD are extracellular β-amyloid (Aβ) plaque deposition and intracellular neurofibrillary tangles (NFTs) of hyperphosphorylated Tau. Because of its complex pathobiology, some tangible treatment can only ameliorate the symptoms, but not prevent the disease altogether. Numerous drugs during pre-clinical or clinical studies have shown no positive effect on the disease outcome. Therefore, understanding the basic pathophysiological mechanism of AD is imperative for the rational design of drugs that can be used to prevent this disease. Drosophilamelanogaster has emerged as a highly efficient model system to explore the pathogenesis and treatment of AD. In this review we have summarized recent advancements in the pharmacological research on AD using Drosophila as a model species, discussed feasible treatment strategies and provided further reference for the mechanistic study and treatment of age-related AD.

Genetic Dissection of Alzheimer's Disease Using Drosophila Models

Alzheimer’s disease (AD), a main cause of dementia, is the most common neurodegenerative disease that is related to abnormal accumulation of the amyloid β (Aβ) protein. Despite decades of intensive research, the mechanisms underlying AD remain elusive, and the only available treatment remains symptomatic. Molecular understanding of the pathogenesis and progression of AD is necessary to develop disease-modifying treatment. Drosophila, as the most advanced genetic model, has been used to explore the molecular mechanisms of AD in the last few decades. Here, we introduce Drosophila AD models based on human Aβ and summarize the results of their genetic dissection. We also discuss the utility of functional genomics using the Drosophila system in the search for AD-associated molecular mechanisms in the post-genomic era.

Curcumin attenuates copper-induced oxidative stress and neurotoxicity in Drosophila melanogaster

Curcumin is a hydrophobic polyphenol derived from the rhizome of the Herb Curcuma longa belonging to the family Zingiberaceae. Curcumin possesses antioxidative, anti-inflammatory and anti-depressant-like properties. In this study, we evaluated the rescue role of Curcumin in Copper²⁺-induced toxicity in D. melanogaster. Adult, wild type flies were exposed to Cu²⁺ (1 mM) and/or Curcumin (0.2 and 0.5 mg/kg diet) in the diet for 7 days. The results indicated that Cu²⁺- fed flies had reduced survival compared to the control group. Copper toxicity was also associated with a marked decrease in total thiol (T-SH), as well as catalase and glutathione S-transferase activities, contemporaneous with increased acetylcholinesterase (AChE) activity, nitric oxide (nitrate and nitrite) and dopamine levels. Co-exposure of flies to Cu²⁺ and Curcumin prevented mortality, inhibited AChE activity and restored dopamine to normal levels (p < 0.05). Moreover, Curcumin restored eclosion rates, and the cellular antioxidant status, as well as alleviated the accumulation of nitric oxide level in the flies. Curcumin ameliorated oxidative damage in the flies as evidenced by the survival rates, longevity assay as well as the restoration of antioxidant status. Our findings thus suggest that Curcumin ameliorated Cu²⁺-induced neurotoxicity in D. melanogaster and as such could be considered an effective therapeutic agent in the prevention and treatment of disorders, where oxidative stress is implicated.

Insights into the Functions of LncRNAs in Drosophila

Long non-coding RNAs (lncRNAs) are a class of non-coding RNAs longer than 200 nucleotides (nt). LncRNAs have high spatiotemporal specificity, and secondary structures have been preserved throughout evolution. They have been implicated in a range of biological processes and diseases and are emerging as key regulators of gene expression at the epigenetic, transcriptional, and post-transcriptional levels. Comparative analyses of lncRNA functions among multiple organisms have suggested that some of their mechanisms seem to be conserved. Transcriptome studies have found that some Drosophila lncRNAs have highly specific expression patterns in embryos, nerves, and gonads. In vivo studies of lncRNAs have revealed that dysregulated expression of lncRNAs in Drosophila may result in impaired embryo development, impaired neurological and gonadal functions, and poor stress resistance. In this review, we summarize the epigenetic, transcriptional, and post-transcriptional mechanisms of lncRNAs and mainly focus on recent insights into the transcriptome studies and biological functions of lncRNAs in Drosophila.

Using Drosophila as a platform for drug discovery from natural products in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder with no cure. Despite intensive research, most of the currently available therapies are only effective in alleviating symptoms with no effect on disease progression. There is an urgent need for new therapeutics to impede disease progression. Natural products are valuable sources of bioactive compounds that can be exploited for novel therapeutic potential in PD pathogenesis. However, rapid screening of plant-derived natural products and characterization of bioactive compounds is costly and challenging. Drosophila melanogaster, commonly known as the fruit fly, has recently emerged as an excellent model for human neurodegenerative diseases, including PD. The high degree of conserved molecular pathways with mammalian models make Drosophila PD models an inexpensive solution to preliminary phases of target validation in the drug discovery pipeline. The present review provides an overview of drug discovery from natural extracts using Drosophila as a screening platform to evaluate the therapeutic potential of phytochemicals against PD.

Trypsin Inhibitors from Cajanus cajan and Phaseolus limensis Possess Antioxidant, Anti-Inflammatory, and Antibacterial Activity

Protease inhibitors are one of the most promising and investigated subjects for their role in pharmacognostic and pharmacological studies. This study aimed to investigate antioxidant, anti-inflammatory, and antimicrobial activities of trypsin inhibitors (TIs) from two plant sources (Cajanus cajan and Phaseolus limensis). TI was purified from C. cajan (PUSA-992) by ammonium sulfate precipitation followed by ion exchange chromatography. TI from Phaseolus limensis (lima bean trypsin inhibitor; LBTI) was procured from Sigma-Aldrich, St. Louis, Missouri, United States. The antioxidant activity was analyzed by ferric ion reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH). The anti-inflammatory property of TIs was determined by inhibition of albumin denaturation assay. Ascorbic acid and aspirin were used as standards for antioxidant and anti-inflammatory assays, respectively. These TIs were tested against various bacterial and fungal strains. The TIs showed DPPH radical-scavenging activity in a concentration-dependent manner with IC₅₀ values comparable to ascorbic acid. The FRAP values were also observed comparable to ascorbic acid and followed the trend of dose-dependent manner. The half maximal inhibitory concentration (IC₅₀) values of CCTI and LBTI in anti-inflammatory test showed that LBTI is more potent than CCTI. The TIs showed potent antibacterial activity, but apparently no action against fungi. This study has reported the biological properties of CCTI and LBTI for the first time. The results show that TIs possess the ability to inhibit diseases caused by oxidative stress, inflammation, and bacterial infestation.

Alzheimer Disease: Clues from traditional and complementary medicine

Despite modern medicine's incredible innovation and resulting accumulation of valuable knowledge, many of the world's most problematic diseases such as Alzheimer Disease (AD) still lack effective cures and treatments. Western medicine has revealed many genetic, cellular, and molecular processes that characterize AD such as protein aggregation and inflammation. As the need for novel and effective treatments increases, researchers have turned towards traditional medicine as a resource. Modern, evidence based research examining traditional and complementary remedies for AD has generated promising results within the last decade. Animal based products inhibiting cellular toxicity, anti-inflammatory nutraceuticals such as omega-3 fatty acids, and plant based compounds derived from herbal medicine demonstrate viability as neuroprotective treatments and possible application in developing pharmaceuticals. Analysis of antioxidant, anti-inflammatory, and neuroprotective phytochemicals used in various traditional medicines around the world reveal potential to ameliorate and prevent the devastating neurodegeneration observed in AD.

Alteration in biochemical parameters in the brain of transgenic Drosophila melanogaster model of Parkinson's disease exposed to apigenin

BACKGROUND

Oxidative stress is one of the key components of the pathology of various neurodegenerative disorders. Parkinson's disease (PD) is characterized by the progressive loss of dopaminergic neurons owing to the aggregation of alpha-synuclein (αS) in the brain. A number of polyphenols have been reported to inhibit the αS aggregation resulting in the possible prevention of PD. The involvement of free radicals in mediating the neuronal death in PD has also been implicated.

METHODS

In the present study, the transgenic flies expressing human αS in the brain were exposed to 10 μM, 20 μM, 40 μM, and 80 μM of apigenin established in diet for 24 days.

RESULTS

The flies showed an increase in life span, glutathione, and dopamine content. The exposure of PD flies to various doses of apigenin also results in the reduction of glutathione-S-transferase activity, lipid peroxidation, monoamine oxidase, caspase-3, and caspase-9 activity in a dose-dependent manner.

CONCLUSION

The results of the present study reveal that apigenin is potent in increasing the life span, dopamine content, reduced the oxidative stress as well as apoptosis in transgenic Drosophila model of PD.

Phenotypic differences between Drosophila Alzheimer's disease models expressing human Aβ42 in the developing eye and brain

Drosophila melanogaster expressing amyloid-β42 (Aβ42) transgenes have been used as models to study Alzheimer's disease. Various Aβ42 transgenes with different structures induce different phenotypes, which make it difficult to compare data among studies which use different transgenic lines. In this study, we compared the phenotypes of four frequently used Aβ42 transgenic lines, UAS-Aβ42^2X , UAS-Aβ42^BL33770 , UAS-Aβ42^11C39 , and UAS-Aβ42^H29.3 . Among the four transgenic lines, only UAS-Aβ42^2X has two copies of the upstream activation sequence-amyloid-β42 (UAS-Aβ42) transgene, while remaining three have one copy. UAS-Aβ42^BL33770 has the 3' untranslated region of Drosophila α-tubulin, while the others have that of SV40. UAS-Aβ42^11C39 and UAS-Aβ42^H29.3 have the rat pre-proenkephalin signal peptide, while UAS-Aβ42^2X and UAS-Aβ42^BL33770 have that of the fly argos protein. When the transgenes were expressed ectopically in the developing eyes of the flies, UAS-Aβ42^2X transgene resulted in a strongly reduced and rough eye phenotype, while UAS-Aβ42^BL33770 only showed a strong rough eye phenotype; UAS-Aβ42^H29.3 and UAS-Aβ42^11C39 had mild rough eyes. The levels of cell death and reactive oxygen species (ROS) in the eye imaginal discs were consistently the highest in UAS-Aβ42^2X , followed by UAS-Aβ42^BL33770 , UAS-Aβ42^11C39 , and UAS-Aβ42^H29.3 . Surprisingly, the reduction in survival during the development of these lines did not correlate with cell death or ROS levels. The flies which expressed UAS-Aβ42^11C39 or UAS-Aβ42^H29.3 experienced greatly reduced survival rates, although low levels of ROS or cell death were detected. Collectively, our results demonstrated that different Drosophila AD models show different phenotypic severity, and suggested that different transgenes may have different modes of cytotoxicity. Abbreviations: Aβ42: amyloid-β42; AD: Alzheimer's disease; UAS: upstream activation sequence.

Drosophila expressing human SOD1 successfully recapitulates mitochondrial phenotypic features of familial amyotrophic lateral sclerosis

Mitochondrial pathology is a seminal pathogenic hallmark of familial amyotrophic lateral sclerosis (FALS) which is extensively manifested by human patients and mutant SOD1(G93A) mammalian models. Rodents expressing human FALS-associated mutations successfully mimic several human disease features; although they are not as amenable to genetic and therapeutic compound screenings as non-mammalian models. In this study, we report a newly generated and characterized Drosophila model that expresses human SOD1(G93A) in muscle fibers. Presence of SOD1(G93A) in thoracic muscles causes mitochondrial pathology and impairs normal motor behavior in these flies. Use of this new FALS-24B-SOD1(G93A) fly model holds promise for better understanding of the mitochondrial affectation process in FALS and for the discovery of novel therapeutic compounds able to reverse mitochondrial dysfunction in this fatal disease.

In Vivo Screening of Traditional Medicinal Plants for Neuroprotective Activity against Aβ42 Cytotoxicity by Using Drosophila Models of Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized by progressive neuronal loss with amyloid β-peptide (Aβ) plaques. Despite several drugs currently used to treat AD, their beneficial effects on AD progress remains under debate. Here, we established a rapid in vivo screening system using Drosophila AD models to assess the neuroprotective activities of medicinal plants that have been used in traditional Chinese medicine. Among 23 medicinal plants tested, the extracts from five plants, Coriandrum sativum, Nardostachys jatamansi, Polygonum multiflorum (P. multiflorum), Rehmannia glutinosa, and Sorbus commixta (S. commixta), showed protective effects against the Aβ42 neurotoxicity. We further characterized the neuroprotective activity of ethanol extracts from P. multiflorum and S. commixta. Aβ42-expressing flies that we used showed AD neurological phenotypes, such as decreased survival and motility and increased cell death and reactive oxygen species level. However, feeding these flies extracts from P. multiflorum or S. commixta showed strong suppression of such phenotypes. Similar results were observed in human cells, so that the treatment of P. multiflorum and S. commixta extracts increased the viability of Aβ-treated SH-SY5Y cells. Moreover, 2,3,5,4'-tetrahydroxystilbene-2-O-β-D-glucoside, one of the main constituents of P. multiflorum, also showed similar protective activity against Aβ42 cytotoxicity in both Drosophila and human cells. Taken together, our results suggest that both P. multiflorum and S. commixta have therapeutic potential for the treatment of neurodegenerative diseases, such as AD.

Curcumin's neuroprotective efficacy in Drosophila model of idiopathic Parkinson's disease is phase specific: implication of its therapeutic effectiveness

Selective degeneration of dopaminergic neurons in the substantia nigra underlies the basic motor impairments of Parkinson's disease (PD). Curcumin has been used for centuries in traditional medicines in India. Our aim is to understand the efficacy of genotropic drug curcumin as a neuroprotective agent in PD. Analysis of different developmental stages in model organisms revealed that they are characterized by different patterns of gene expression which is similar to that of developmental stages of human. Genotropic drugs would be effective only during those life cycle stages for which their target molecules are available. Hence there exists a possibility that targets of genotropic compounds such as curcumin may not be present in all life stages. However, no reports are available in PD models illustrating the efficacy of curcumin in later phases of adult life. This is important because this is the period during which late-onset disorders such as idiopathic PD set in. To understand this paradigm, we tested the protective efficacy of curcumin in different growth stages (early, late health stage, and transition phase) in adult Drosophila flies. Results showed that it can rescue the motor defects during early stages of life but is ineffective at later phases. This observation was substantiated with the finding that curcumin treatment could replenish depleted brain dopamine levels in the PD model only during early stages of life cycle, clearly suggesting its limitation as a therapeutic agent in late-onset neurodegenerative disorders such as PD.