Drosophila melanogaster in the study of human neurodegeneration

Understanding role of pesticides in development of Parkinson's disease: Insights from Drosophila and rodent models

Parkinson's disease is a neurodegenerative illness linked to ageing, marked by the gradual decline of dopaminergic neurons in the midbrain. The exact aetiology of Parkinson's disease (PD) remains uncertain, with genetic predisposition and environmental variables playing significant roles in the disease's frequency. Epidemiological data indicates a possible connection between pesticide exposure and brain degeneration. Specific pesticides have been associated with important characteristics of Parkinson's disease, such as mitochondrial dysfunction, oxidative stress, and α-synuclein aggregation, which are crucial for the advancement of the disease. Recently, many animal models have been developed for Parkinson's disease study. Although these models do not perfectly replicate the disease's pathology, they provide valuable insights that improve our understanding of the condition and the limitations of current treatment methods. Drosophila, in particular, has been useful in studying Parkinson's disease induced by toxins or genetic factors. The review thoroughly analyses many animal models utilised in Parkinson's research, with an emphasis on issues including pesticides, genetic and epigenetic changes, proteasome failure, oxidative damage, α-synuclein inoculation, and mitochondrial dysfunction. The text highlights the important impact of pesticides on the onset of Parkinson's disease (PD) and stresses the need for more research on genetic and mechanistic alterations linked to the condition.

Toxicological analysis of chronic exposure to polymeric nanocapsules with different coatings in Drosophila melanogaster

Nanotechnology involves the utilization of nanomaterials, including polymeric nanocapsules (NCs) that are drug carriers. For modify drug release and stability, nanoformulations can feature different types of polymers as surface coatings: Polysorbate 80 (P80), Polyethylene glycol (PEG), Chitosan (CS) and Eudragit (EUD). Although nanoencapsulation aims to reduce side effects, these polymers can interact with living organisms, inducing events in the antioxidant system. Thus far, little has been described about the impacts of chronic exposure, with Drosophila melanogaster being an in vivo model for characterizing the toxicology of these polymers. This study analyzes the effects of chronic exposure to polymeric NCs with different coatings. Flies were exposed to 10, 50, 100, and 500 μL of NCP80, NCPEG, NCCS, or EUD. The survival rate, locomotor changes, oxidative stress markers, cell viability, and Nrf2 expression were evaluated. Between the coatings, NCPEG had minimal effects, as only 500 μL affected the levels of reactive species (RS) and the enzymatic activities of catalase (CAT) and glutathione S-transferase (GST) without reducing Nrf2 expression. However, NCEUD significantly impacted the total flies killed, RS, CAT, and Superoxide dismutase from 100 μL. In part, the toxicity mechanisms of these coatings can be explained by the imbalance of the antioxidant system. This research provided initial evidence on the chronic toxicology of these nanomaterials in D. melanogaster to clarify the nanosafety profile of these polymers in future nanoformulations. Further investigations are essential to characterize possible biochemical pathways involved in the toxicity of these polymeric coatings.

Early exposure to trans fat causes cognitive impairment by modulating the expression of proteins associated with oxidative stress and synaptic plasticity in Drosophila melanogaster

Evidence has shown that consuming trans fatty acids (TFA) during development leads to their incorporation into the nervous tissue, resulting in neurological changes in flies. In this study, Drosophila melanogaster was exposed to different concentrations of hydrogenated vegetable fat (HVF) during development: substitute hydrogenated vegetable fat (SHVF), HVF 10 %, and HVF 20 %. The objective was to evaluate the effects of early trans fat exposure on cognition and associated pathways in flies. The results showed that early TFA exposure provoked a cerebral redox imbalance, as confirmed by increased reactive species (HVF 10 and 20 %) and lipid peroxidation (SHVF, HVF 10, and 20 %), reduced nuclear factor erythroid 2-related factor 2 immunoreactivity (HVF 10 and 20 %), and increased heat shock protein 70 (HVF 20 %), which was possibly responsible for decreasing superoxide dismutase (SHVF, HVF 10, and 20 %) and catalase (HVF 20 %) activities. Furthermore, the presence of TFA in nervous tissue impaired learning (HVF 10 and 20 %) and memory at 6 and 24 h (SHVF, HVF 10, and 20 %). These cognitive impairments may be linked to reduced Shank levels (HVF 20 %) and increased acetylcholinesterase activity (SHVF, HVF 10 and 20 %) observed. Our findings demonstrate that early exposure to trans fat leads to cerebral redox imbalance, altering proteins associated with stress, synaptic plasticity, and the cholinergic system, consequently leading to cognitive impairment in flies.

Ashwagandha- Withania somnifera (L.) Dunal as a multipotent neuroprotective remedy for genetically induced motor dysfunction and cellular toxicity in human neurodegenerative disease models of Drosophila

ETHNOPHARMACOLOGICAL RELEVANCE

Ashwagandha-Withania somnifera (L.) Dunal, well known for its multipotent therapeutic properties has been used in Ayurveda for 3000 years. The plant with more than 50 active phytoconstituents is recognised for its anti-cancerous, anti-diabetic, anti-inflammatory, anti-microbial, and neurotherapeutic properties demonstrated in in vitro studies and chemically induced rodent models. Genetically targeted Parkinson's, Alzheimer's and other neurodegenerative disease models have been created in Drosophila and have been used to get mechanistic insight into the in vivo cellular events, and genetic pathways that underlie respective neurodegenerative condition. But hitherto, there aren't enough attempts made to capitalize the genetic potential of these disease models to validate the therapeutic efficacy of different reagents used in traditional medicine, in the context of specific disease-causing genetic mutations.

AIM OF THE STUDY

Drugs discovered using in vitro platforms might fail in several instances of clinical trials because of the genetic heterogeneity and variability in the physiological context found among the patients. Drosophila by virtue of its genetically regulated experimental potential forms an ideal in vivo model to validate the candidate reagents discovered in in vitro screens for their efficacy under specific genetic situations. Here we have used genetically induced α-synucleinopathy and tauopathy transgenic fly models to study the efficacy of Ashwagandha treatment, assessing cellular and behavioural parameters.

METHODS

We have expressed the disease-causing human gene mutations in specific cell types of Drosophila using GAL4/UAS targeted expression system to create disease models. Human α-synuclein mutant (A30P) was expressed in dopaminergic neurons using Ddc-GAL4 driver strain to induce dopaminergic neurodegeneration and assayed for motor dysfunction. Human TauE14, mutant protein was expressed in photoreceptor neurons using GMR-GAL4 driver to induce photoreceptor degeneration. Microtubular destability and mitotic arrest in the dividing photoreceptor precursor cells were studied using αPH3 antibody. Lysosomal dysregulation caused necrotic black spots were induced by TauE14 with GMR-GAL4 driver, in a white mutant background. These flies mimicking neurodegenerative conditions were supplemented with different concentrations of Ashwagandha aqueous root extract mixed with regular fly food. The treated flies were analysed for cellular and behaviour parameters.

RESULTS

Lifespan assay shows that, Ashwagandha-root extract imparts an extended lifespan in male Drosophila flies which are intrinsically less stress resistant. Motor dysfunction caused due to human α-synuclein mutant protein expressed in dopaminergic neurons is greatly brought down. Further, Ashwagandha extract treatment significantly reduces TauE14 induced microtubular destability, mitotic arrest and neuronal death in photoreceptor neurons. Our experiment with tauopathy model in white mutant background exemplify that, Ashwagandha-root extract treatment can bring down lysosomal dysregulation induced necrosis of photoreceptor neurons.

CONCLUSION

We have carried out a multifaceted study which elucidates that Ashwagandha can serve as a comprehensive, phytotherapeutic formulation to combat neurodegeneration, targeting multiple causative genetically defective conditions.

Antioxidant and anti-Alzheimer's potential of Tetragonisca angustula (Jataí) stingless bee pollen

Alzheimer's disease (AD) is considered the leading cause of dementia in the elderly worldwide. It results in progressive memory loss and impairment of cognitive and motor skills, leading to a high degree of disability and dependence. The development of AD is associated with the accumulation of senile plaques in the brain, caused by the amyloidogenic pathway of the disease. Several genetic and biochemical events are linked to AD development, with oxidative stress being one of them. Due to the scarcity of drugs aimed at treating AD, antioxidant compounds are increasingly studied as therapeutic targets for the disease. In this study, we investigate the antioxidant and anti-Alzheimer potential of the Tetragonisca angustula (Jataí) pollen extract in a Drosophila melanogaster Alzheimer's model. For this purpose, we utilized a D. melanogaster AD-like model, which expresses genes related to the amyloidogenic pathway of Alzheimer's disease. We explored the floral origin of the collected pollen, conducted phytochemical prospecting, and evaluated its antioxidant capacity in vitro. In vivo experiments involved assessing the survival and climbing ability of the D. melanogaster AD-like model with various concentrations of the pollen extract. Our findings revealed that the pollen extract of Tetragonisca angustula exhibits a significant antioxidant response and high concentrations of important phytochemicals, such as flavonoids and polyphenols. Furthermore, it enhanced the survival rate of D. melanogaster, and across all concentrations tested, it improved the climbing ability of the flies after 15 days of treatment with methanolic pollen extract. Additionally, the pollen extract reduced the neurodegeneration index in histopathological analysis. Thus, our study demonstrates the potential of Tetragonisca angustula pollen as an important subject for further investigation, aiming to isolate molecules that could potentially serve as therapeutic targets for Alzheimer's disease.

Sirtuins, a key regulator of ageing and age-related neurodegenerative diseases

Sirtuins are Nicotinamide Adenine Dinucleotide (NAD+) dependent class ІΙΙ histone deacetylases enzymes (HDACs) present from lower to higher organisms such as bacteria (Sulfolobus solfataricus L. major), yeasts (Saccharomyces cerevisiae), nematodes (Caenorhabditis elegans), fruit flies (Drosophila melanogaster), humans (Homo sapiens sapiens), even in plants such as rice (Oryza sativa), thale cress (Arabidopsis thaliana), vine (Vitis vinifera L.) tomato (Solanum lycopersicum). Sirtuins play an important role in the regulation of various vital cellular functions during metabolism and ageing. It also plays a neuroprotective role by modulating several biological pathways such as apoptosis, DNA repair, protein aggregation, and inflammatory processes associated with ageing and neurodegenerative diseases. In this review, we have presented an updated Sirtuins and its role in ageing and age-related neurodegenerative diseases (NDDs). Further, this review also describes the therapeutic potential of Sirtuins and the use of Sirtuins inhibitor/activator for altering the NDDs disease pathology.

Thiadiazolidinone (TDZD) Analogs Inhibit Aggregation-Mediated Pathology in Diverse Neurodegeneration Models, and Extend C. elegans Life- and Healthspan

Chronic, low-grade inflammation has been implicated in aging and age-dependent conditions, including Alzheimer's disease, cardiomyopathy, and cancer. One of the age-associated processes underlying chronic inflammation is protein aggregation, which is implicated in neuroinflammation and a broad spectrum of neurodegenerative diseases such as Alzheimer's, Huntington's, and Parkinson's diseases. We screened a panel of bioactive thiadiazolidinones (TDZDs) from our in-house library for rescue of protein aggregation in human-cell and C. elegans models of neurodegeneration. Among the tested TDZD analogs, PNR886 and PNR962 were most effective, significantly reducing both the number and intensity of Alzheimer-like tau and amyloid aggregates in human cell-culture models of pathogenic aggregation. A C. elegans strain expressing human Aβ1-42 in muscle, leading to AD-like amyloidopathy, developed fewer and smaller aggregates after PNR886 or PNR962 treatment. Moreover, age-progressive paralysis was reduced 90% by PNR886 and 75% by PNR962, and "healthspan" (the median duration of spontaneous motility) was extended 29% and 62%, respectively. These TDZD analogs also extended wild-type C. elegans lifespan by 15-30% (p < 0.001), placing them among the most effective life-extension drugs. Because the lead drug in this family, TDZD-8, inhibits GSK3β, we used molecular-dynamic tools to assess whether these analogs may also target GSK3β. In silico modeling predicted that PNR886 or PNR962 would bind to the same allosteric pocket of inactive GSK3β as TDZD-8, employing the same pharmacophore but attaching with greater avidity. PNR886 and PNR962 are thus compelling candidate drugs for treatment of tau- and amyloid-associated neurodegenerative diseases such as AD, potentially also reducing all-cause mortality.

The impact of Parkinson's disease-associated gut microbiota on the transcriptome in Drosophila

Parkinson's disease (PD) is a common neurodegenerative disease in middle-aged and elderly people, and many studies have confirmed that the disorder of gut microbiota is involved in the pathophysiological process of PD. However, the molecular mechanism of gut microbiota in regulating the pathogenesis of PD is still lacking. In this study, to investigate the impact of PD-associated gut microbiota on host transcriptome, we established various PD models with fecal microbiota transplantation (FMT) in the model organism Drosophila followed by integrative data analysis of microbiome and transcriptome. We first constructed rotenone-induced PD models in Drosophila followed by FMT in different groups. Microbial analysis by 16S rDNA sequencing showed that gut microbiota from PD Drosophila could affect bacterial structure of normal Drosophila, and gut microbiota from normal Drosophila could affect bacterial structure of PD Drosophila. Transcriptome analysis revealed that PD-associated gut microbiota influenced expression patterns of genes enriched in neuroactive ligand-receptor interaction, lysosome, and diverse metabolic pathways. Importantly, to verify our findings, we transplanted Drosophila with fecal samples from clinical PD patients. Compared to the control, Drosophila transplanted with fecal samples from PD patients had reduced microbiota Acetobacter and Lactobacillus, and differentially expressed genes enriched in diverse metabolic pathways. In summary, our results reveal the influence of PD-associated gut microbiota on host gene expression, and this study can help better understand the link between gut microbiota and PD pathogenesis through gut-brain axis. IMPORTANCE Gut microbiota plays important roles in regulating host gene expression and physiology through complex mechanisms. Recently, it has been suggested that disorder of gut microbiota is involved in the pathophysiological process of Parkinson's disease (PD). However, the molecular mechanism of gut microbiota in regulating the pathogenesis of PD is still lacking. In this study, to investigate the impact of PD-associated gut microbiota on host transcriptome, we established various PD models with fecal microbiota transplantation in the model organism Drosophila followed by integrative data analysis of microbiome and transcriptome. We also verified our findings by transplanting Drosophila with fecal samples from clinical PD patients. Our results demonstrated that PD-associated gut microbiota can induce differentially expressed genes enriched in diverse metabolic pathways. This study can help better understand the link between gut microbiota and PD pathogenesis through gut-brain axis.

Relationship between toxicity and oxidative stress of the nanoencapsulated colchicine in a model of Drosophila melanogaster

Drug repurposing allows searching for new biological targets, especially against emerging diseases such as Covid-19. Drug colchicine (COL) presents recognized anti-inflammatory action, while the nanotechnology purpose therapies with low doses, efficacy, and decrease the drug's side-effects. This study aims to evaluate the effects of COL and colchicine nanocapsules (NCCOL) on survival, LC50, activity locomotor, and oxidative stress parameters, elucidating the toxicity profile in acute and chronic exposure in Drosophila melanogaster. Three-day-old flies were investigated into groups: Control, 0.001, 0.0025, 0.005, and 0.010 mg/mL of COL or NCCOL. The survival rate, open field test, LC50, oxidative stress markers (reactive species (RS) production, thiobarbituric acid reactive substances), antioxidant enzyme activity (catalase (CAT), superoxide dismutase (SOD), glutathione S-transferase), protein thiols, nonprotein thiols, acetylcholinesterase activity, and cell viability were measured. As a result, acute exposure to the COL decreases the number of crosses in the open field and increases CAT activity. NCCOL reduced RS levels, increased lipoperoxidation and SOD activity. Chronic exposure to the COL and NCCOL in high concentrations implied high mortality and enzymatic inhibition of the CAT and AChE, and only the COL caused locomotor damage in the open field test. Thus, NCCOL again reduced the formation of RS while COL increased. In this comparative study, NCCOL was less toxic to the antioxidant system than COL and showed notable involvement of oxidative stress as one of their toxicity mechanisms. Future studies are needed to elucidate all aspects of nanosafety related to the NCCOL.

The Regulation of MiTF/TFE Transcription Factors Across Model Organisms: from Brain Physiology to Implication for Neurodegeneration

The microphthalmia/transcription factor E (MiTF/TFE) transcription factors are responsible for the regulation of various key processes for the maintenance of brain function, including autophagy-lysosomal pathway, lipid catabolism, and mitochondrial homeostasis. Among them, autophagy is one of the most relevant pathways in this frame; it is evolutionary conserved and crucial for cellular homeostasis. The dysregulation of MiTF/TFE proteins was shown to be involved in the development and progression of neurodegenerative diseases. Thus, the characterization of their function is key in the understanding of the etiology of these diseases, with the potential to develop novel therapeutics targeted to MiTF/TFE proteins and to the autophagic process. The fact that these proteins are evolutionary conserved suggests that their function and dysfunction can be investigated in model organisms with a simpler nervous system than the mammalian one. Building not only on studies in mammalian models but also in complementary model organisms, in this review we discuss (1) the mechanistic regulation of MiTF/TFE transcription factors; (2) their roles in different regions of the central nervous system, in different cell types, and their involvement in the development of neurodegenerative diseases, including lysosomal storage disorders; (3) the overlap and the compensation that occur among the different members of the family; (4) the importance of the evolutionary conservation of these protein and the process they regulate, which allows their study in different model organisms; and (5) their possible role as therapeutic targets in neurodegeneration.

Mitochondrial function and cellular energy maintenance during aging in a Drosophila melanogaster model of Parkinson Disease

Parkinson's disease (PD) is a common neurodegenerative disease characterized by movement disorders as well as loss of dopaminergic neurons. Moreover, genes affecting mitochondrial function, such as SNCA, Parkin, PINK1, DJ-1 and LRRK2, were demonstrated to be associated with PD and other neurodegenerative disease. Additionally, mitochondrial dysfunction and cellular energy imbalance are common markers found in PD. In this study, we used the pink1 null mutants of Drosophila melanogaster as a Parkinson's disease model to investigate how the energetic pathways and mitochondrial functions change during aging in a PD model. In our study, the loss of the pink1 gene decreased the survival percent and the decreased climbing index during aging in pink1^-/- flies. Furthermore, there was an impairment in mitochondrial function demonstrated by a decrease in OXPHOS CI&CII-Linked and ETS CI&CII-Linked in pink1^-/- flies at 3, 15 and 30 days of life. Interestingly, OXPHOS CII-Linked and ETS CII-Linked presented decreases only at 15 days of life in pink1^-/- flies. Moreover, there was an increase in peroxide (H₂O₂) levels in pink1^-/- flies at 15 and 30 days of life. Loss of the pink1 gene also decreased the activity of citrate synthase (CS) and increased the activity of lactate dehydrogenase (LDH) in pink1^-/- flies head. Our results demonstrate a metabolic shift in ATP production in pink1^-/- flies, which changed from oxidative to glycolytic pathways from 15 days of age, and is apparently more pronounced in the central nervous system.

Roles for Mitochondrial Complex I Subunits in Regulating Synaptic Transmission and Growth

To identify conserved components of synapse function that are also associated with human diseases, we conducted a genetic screen. We used the Drosophila melanogaster neuromuscular junction (NMJ) as a model. We employed RNA interference (RNAi) on selected targets and assayed synapse function and plasticity by electrophysiology. We focused our screen on genetic factors known to be conserved from human neurological or muscle functions (300 Drosophila lines screened). From our screen, knockdown of a Mitochondrial Complex I (MCI) subunit gene (ND-20L) lowered levels of NMJ neurotransmission. Due to the severity of the phenotype, we studied MCI function further. Knockdown of core MCI subunits concurrently in neurons and muscle led to impaired neurotransmission. We localized this neurotransmission function to the muscle. Pharmacology targeting MCI phenocopied the impaired neurotransmission phenotype. Finally, MCI subunit knockdowns or pharmacological inhibition led to profound cytological defects, including reduced NMJ growth and altered NMJ morphology. Mitochondria are essential for cellular bioenergetics and produce ATP through oxidative phosphorylation. Five multi-protein complexes achieve this task, and MCI is the largest. Impaired Mitochondrial Complex I subunits in humans are associated with disorders such as Parkinson’s disease, Leigh syndrome, and cardiomyopathy. Together, our data present an analysis of Complex I in the context of synapse function and plasticity. We speculate that in the context of human MCI dysfunction, similar neuronal and synaptic defects could contribute to pathogenesis.

Animal Models of Neurodegenerative Disease: Recent Advances in Fly Highlight Innovative Approaches to Drug Discovery

Neurodegenerative diseases represent a formidable challenge to global health. As advances in other areas of medicine grant healthy living into later decades of life, aging diseases such as Alzheimer's disease (AD) and other neurodegenerative disorders can diminish the quality of these additional years, owed largely to the lack of efficacious treatments and the absence of durable cures. Alzheimer's disease prevalence is predicted to more than double in the next 30 years, affecting nearly 15 million Americans, with AD-associated costs exceeding $1 billion by 2050. Delaying onset of AD and other neurodegenerative diseases is critical to improving the quality of life for patients and reducing the burden of disease on caregivers and healthcare systems. Significant progress has been made to model disease pathogenesis and identify points of therapeutic intervention. While some researchers have contributed to our understanding of the proteins and pathways that drive biological dysfunction in disease using in vitro and in vivo models, others have provided mathematical, biophysical, and computational technologies to identify potential therapeutic compounds using in silico modeling. The most exciting phase of the drug discovery process is now: by applying a target-directed approach that leverages the strengths of multiple techniques and validates lead hits using Drosophila as an animal model of disease, we are on the fast-track to identifying novel therapeutics to restore health to those impacted by neurodegenerative disease.

Drosophila: A Model to Study the Pathogenesis of Parkinson's Disease

Human Central Nervous System (CNS) is the complex part of the human body, which regulates multiple cellular and molecular events taking place simultaneously. Parkinsons Disease (PD) is the second most common neurodegenerative disease after Alzheimer's disease (AD). The pathological hallmarks of PD are loss of dopaminergic neurons in the substantianigra (SN) pars compacta (SNpc) and accumulation of misfolded α-synuclein, in intra-cytoplasmic inclusions called Lewy bodies (LBs). So far, there is no cure for PD, due to the complexities of molecular mechanisms and events taking place during the pathogenesis of PD. Drosophila melanogaster is an appropriate model organism to unravel the pathogenicity not only behind PD but also other NDs. In this context as numerous biological functions are preserved between Drosophila and humans. Apart from sharing 75% of human disease-causing genes homolog in Drosophila, behavioral responses like memory-based tests, negative geotaxis, courtship and mating are also well studied. The genetic, as well as environmental factors, can be studied in Drosophila to understand the geneenvironment interactions behind the disease condition. Through genetic manipulation, mutant flies can be generated harboring human orthologs, which can prove to be an excellent model to understand the effect of the mutant protein on the pathogenicity of NDs.

The protective role of exercise against age-related neurodegeneration

Endurance exercise is a widely accessible, low-cost intervention with a variety of benefits to multiple organ systems. Exercise improves multiple indices of physical performance and stimulates pronounced health benefits reducing a range of pathologies including metabolic, cardiovascular, and neurodegenerative disorders. Endurance exercise delays brain aging, preserves memory and cognition, and improves symptoms of neurodegenerative pathologies like Amyotrophic Lateral Sclerosis, Alzheimer's disease, Parkinson's disease, Huntington's disease, and various ataxias. Potential mechanisms underlying the beneficial effects of exercise include neuronal survival and plasticity, neurogenesis, epigenetic modifications, angiogenesis, autophagy, and the synthesis and release of neurotrophins and cytokines. In this review, we discuss shared benefits and molecular pathways driving the protective effects of endurance exercise on various neurodegenerative diseases in animal models and in humans.

Mitochondria Dysfunction in Frontotemporal Dementia/Amyotrophic Lateral Sclerosis: Lessons From Drosophila Models

Frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) are neurodegenerative disorders characterized by declining motor and cognitive functions. Even though these diseases present with distinct sets of symptoms, FTD and ALS are two extremes of the same disease spectrum, as they show considerable overlap in genetic, clinical and neuropathological features. Among these overlapping features, mitochondrial dysfunction is associated with both FTD and ALS. Recent studies have shown that cells derived from patients' induced pluripotent stem cells (iPSC)s display mitochondrial abnormalities, and similar abnormalities have been observed in a number of animal disease models. Drosophila models have been widely used to study FTD and ALS because of their rapid generation time and extensive set of genetic tools. A wide array of fly models have been developed to elucidate the molecular mechanisms of toxicity for mutations associated with FTD/ALS. Fly models have been often instrumental in understanding the role of disease associated mutations in mitochondria biology. In this review, we discuss how mutations associated with FTD/ALS disrupt mitochondrial function, and we review how the use of Drosophila models has been pivotal to our current knowledge in this field.

Tumor models in various Drosophila tissues

The development of cancer is a complex multistage process. Over the past few decades, the model organism Drosophila melanogaster has been crucial in identifying cancer-related genes and pathways and elucidating mechanisms underlying growth regulation in development. Investigations using Drosophila has yielded new insights into the molecular mechanisms involved in tumor initiation and progression. In this review, we describe various tumor models that have been developed in recent years using different Drosophila tissues, such as the imaginal tissue, the neural tissue, the gut, the ovary, and hematopoietic cells. We discuss underlying genetic alterations, cancer-like characteristics, as well as similarities and key differences among these models. We also discuss how disruptions in stem cell division and differentiation result in tumor formation in diverse tissues, and highlight new concepts developed using the fly model to understand context-dependent tumorigenesis. We further discuss the progress made in Drosophila to explore tumor-host interactions that involve the innate immune response to tumor growth and the cachexia wasting phenotype. This article is categorized under: Cancer > Genetics/Genomics/Epigenetics Cancer > Stem Cells and Development Cancer > Molecular and Cellular Physiology.

Lead (Pb) induced Oxidative Stress as a Mechanism to Cause Neurotoxicity in Drosophila melanogaster

The widespread use of lead (Pb) has caused global contamination, inevitable human exposure, and public health problems. Pb neurotoxicity has been linked to various human diseases, but its associated mechanism causing neurotoxicity is unknown. Drosophila melanogaster as a model organism has been used to study the mechanism involved in Pb-caused neurotoxicity and the potential role of antioxidants in ameliorating its harmful effects. The larval feeding technique was adopted to administer different concentrations of Pb (0.2-0.8 mM) to Oregon-R (ORR), superoxide dismutase (Sod), or catalase (Cat) overexpressing, and Sod or Cat knockdown flies to analyse Pb load, oxidative stress components, DNA damage, apoptosis and vacuolation in the brain. The results revealed that Pb accumulation in the Drosophila brain induces oxidative stress by generating reactive oxygen species (ROS) and lipid peroxidation (LPO), depleting antioxidant enzymes. Molecular docking studies have evidenced it. Pb directly binds to antioxidants and major grooves of DNA, leading to DNA damage. Increased DNA damage, apoptosis, vacuolation in brains of Pb-treated ORR, Sod, or Cat knockdown flies; and on the contrary, reduced oxidative DNA damage, apoptosis, and vacuolation in brains of Pb treated Sod or Cat overexpressed flies put forward that oxidative stress is the mechanism in Pb caused neurotoxicity.

Cell competition from development to neurodegeneration

Cell competition is a process by which suboptimal cells are eliminated to the benefit of cells with higher fitness. It is a surveillance mechanism that senses differences in the fitness status by several modes, such as expression of fitness fingerprints, survival factor uptake rate and resistance to mechanical stress. Fitness fingerprints-mediated cell competition recognizes isoforms of the transmembrane protein Flower, and translates the relative fitness of cells into distinct fates through the Flower code. Impairments in cell competition potentiate the development of diseases like cancer and ageing-related pathologies. In cancer, malignant cells acquire a supercompetitor behaviour, killing the neighbouring cells and overtaking the tissue, thus avoiding elimination. Neurodegenerative disorders affect millions of people and are characterized by cognitive decline and locomotor deficits. Alzheimer's disease is the most common form of dementia, and one of the largely studied diseases. However, the cellular processes taking place remain unclear. Drosophila melanogaster is an emerging neurodegeneration model due to its versatility as a tool for genetic studies. Research in a Drosophila Alzheimer's disease model detected fitness markers in the suboptimal and hyperactive neurons, thus establishing a link between cell competition and Alzheimer's disease. In this Review, we overview cell competition and the new insights related to neurodegenerative disorders, and discuss how research in the field might contribute to the development of new therapeutic targets for these diseases.

Recent updates on animal models for understanding the etiopathogenesis of polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) is the primary cause of female infertility affecting several women worldwide. Changes in hormonal functions such as hyperandrogenism are considered a significant factor in developing PCOS in women. In addition, many molecular pathways are involved in the pathogenesis of PCOS in women. To have better insights about PCOS, it is data from clinical studies carried on women suffering from PCOS should be collected. However, this approach has several implications, including ethical considerations, cost involved and availability of subject. Moreover, during the early drug development process, it is always advisable to use non-human models mimicking human physiology as they are less expensive, readily available, have a shorter gestation period and less risk involved. Many animal models have been reported that resemble the PCOS pathways in human subjects. However, the models developed on rats and mice are more preferred over other rodent/non-rodent models due to their closer resemblance with human PCOS development mechanism. The most extensively reported PCOS models for rats and mice include those induced by using testosterone, letrozole and estradiol valerate. As the pathophysiology of PCOS is complex, none of the explored models completely surrogates the PCOS related conditions occurring in women. Hence, there is a need to develop an animal model that can resemble the pathophysiology of PCOS in women. The review focuses on various animal models explored to understand the pathophysiology of PCOS. The article also highlights some environmental and food-related models that have been used to induce PCOS.

Exploring the alternative: Fish, flies and worms as preclinical models for ALS

Amyotrophic lateral sclerosis (ALS) is an incurable neurodegenerative disorder characterized by the loss of upper and lower motor neurons. In general, patients succumb to respiratory insufficiency due to respiratory muscle weakness. Despite many promising therapeutic strategies primarily identified in rodent models, patient trials remain rather unsuccessful. There is a clear need for alternative approaches, which could provide directions towards the justified use of rodents and which increase the likelihood to identify new promising clinical candidates. In the last decades, the use of fast genetic approaches and the development of high-throughput screening platforms in the nematode Caenorhabditis elegans, in the fruit fly (Drosophila melanogaster) and in zebrafish (Danio rerio) have contributed to new insights into ALS pathomechanisms, disease modifiers and therapeutic targets. In this mini-review, we provide an overview of these alternative small animal studies, modeling the most common ALS genes and discuss the most recent preclinical discoveries. We conclude that small animal models will not replace rodent models, yet they clearly represent an important asset for preclinical studies.

Exercise associated with γ-oryzanol supplementation suppresses oxidative stress and prevents changes in locomotion in Drosophila melanogaster

Association to early mortality and sedentarism was already demonstrated in the literature; nevertheless, some possible biochemical mechanisms around physical inactivity still need answers. The use of an invertebrate model, such as Drosophila melanogaster, can reproduce reliable responses in inducing an exercise protocol with exogenous antioxidant supplementation. This study main evaluates the effect of exercise (EXE) associated with γ-oryzanol (ORY) supplementation to improve locomotor behavior, antioxidant defenses, and survival in Drosophila melanogaster. Two-day old flies were submitted to a protocol for seven days, divided into five groups: Control, Movement-Limited Flies (MLF), EXE, ORY [25 µM], and EXE + ORY [25 µM]. The survival rate was evaluated, followed by open field and negative geotaxis. Flies were euthanized and subjected to analysis for acetylcholinesterase (AChE) and antioxidant enzymes activity, glycidic and lipid parameters, body weight, reactive species (RS), and lipid peroxidation. EXE and EXE + ORY flies showed increased survival and locomotor activity, improved glycidic and lipid parameters, with a lower RS production, and increased antioxidant defenses compared to Control, and EXE + ORY when compared to the EXE group, obtained an increase in the ratio of protein levels/body weight, decreased ratio of triglyceride levels/body weight and decreased lipid peroxidation. However, MLF showed less survival and decreased locomotor activity, possibly due to increased AChE activity and reduced antioxidant defenses. The EXE and EXE + ORY demonstrate effective results in maintaining endogenous defenses, with increased locomotor activity, supporting evidence on EXE benefits, and supplementation with antioxidant compounds face of health paradigms.HighlightsNew protocol system of exercise on Drosophila melanogaster model.ORY demonstrates synergistic effect with EXE.Exercise with ORY supplementation increases locomotor behavior.Exercise with ORY supplementation decrease oxidative damages on flies.

γ-Oryzanol produces an antidepressant-like effect in a chronic unpredictable mild stress model of depression in Drosophila melanogaster

Chronic unpredictable mild stress (CUMS) is a valid model for inducing depression-like symptoms in animal models, causing predictive behavioral, neurochemical, and physiological responses to this condition. This work aims to evaluate the possible antidepressant effect of γ-oryzanol (ORY) in the CUMS-induced depressive model in male Drosophila melanogaster. We will use the CUMS protocol to continue the study previously conducted by our research group, mimicking a depressive state in these insects. Male flies were subjected to various stressors according to a 10-day randomized schedule and concomitantly treated with ORY or fluoxetine (FLX). After the experimental period, in vivo behavioral tests were performed (open field, forced swimming, aggressiveness test, mating test, male virility, sucrose preference index and light/dark test) and ex vivo analyses measuring serotonin (5HT), dopamine (DA), octopamine (OCT) levels and body weight. We report here that ORY-treated flies and concomitant exposure to CUMS did not exhibit obvious behaviors such as prolonged immobility or increased aggressive behavior, reduced male mating and virility behavior, and anxiolytic behavior, in contrast to ORY, not altering sucrose preference and body weight flies exposed to CUMS. ORY effectively prevented 5HT and OCT reduction and partially protected against DA reduction. The data presented here are consistent and provide evidence for the use of ORY as a potential antidepressant compound.Lay SummaryFlies treated with ORY and concomitant exposure to CUMS did not exhibit obvious depressive-like behaviors, such as prolonged immobility in the FST or increased aggressive behavior, or reduced mating behavior, male virility, or anxiolytic behavior. ORY did not change the preference for sucrose and body weight of flies, about the levels of monoamines in the heads of flies, ORY was effective in preventing the reduction of 5HT and OCT, and we had partial protection of ORY for reducing the levels of DA.

Modulation of Huntington's disease in Drosophila

Huntington's disease (HD) is a progressive neurodegenerative disorder which deteriorates the physical and mental abilities of the patients. It is an autosomal dominant disorder and is mainly caused by the expansion of a repeating CAG triplet. A number of animal models ranging from worms, fruit flies, mice and rats to pigs, sheep and monkeys are available which have been helpful in understanding various pathways involved during the progression of the disease. Drosophila is one of the most commonly used model organisms for biomedical science, due to low cost maintenance, short life span and easily implications of genetic tools. The present review provides brief description of HD and the studies carried out for HD to date taking Drosophila as a model.

Targeting the ALS/FTD-associated A-DNA kink with anthracene-based metal complex causes DNA backbone straightening and groove contraction

The use of a small molecule compound to reduce toxic repeat RNA transcripts or their translated aberrant proteins to target repeat-expanded RNA/DNA with a G4C2 motif is a promising strategy to treat C9orf72-linked disorders. In this study, the crystal structures of DNA and RNA–DNA hybrid duplexes with the -GGGCCG- region as a G4C2 repeat motif were solved. Unusual groove widening and sharper bending of the G4C2 DNA duplex A-DNA conformation with B-form characteristics inside was observed. The G4C2 RNA–DNA hybrid duplex adopts a more typical rigid A form structure. Detailed structural analysis revealed that the G4C2 repeat motif of the DNA duplex exhibits a hydration shell and greater flexibility and serves as a ‘hot-spot’ for binding of the anthracene-based nickel complex, Ni^II(Chro)₂ (Chro = Chromomycin A3). In addition to the original GGCC recognition site, Ni^II(Chro)₂ has extended specificity and binds the flanked G:C base pairs of the GGCC core, resulting in minor groove contraction and straightening of the DNA backbone. We have also shown that Chro-metal complexes inhibit neuronal toxicity and suppresses locomotor deficits in a Drosophila model of C9orf72-associated ALS. The approach represents a new direction for drug discovery against ALS and FTD diseases by targeting G4C2 repeat motif DNA.

Exposure to lutein-loaded nanoparticles attenuates Parkinson's model-induced damage in Drosophila melanogaster: Restoration of dopaminergic and cholinergic system and oxidative stress indicators

Parkinson's is a neurodegenerative disease, characterized by the loss of dopaminergic neurons, cholinergic alterations and oxidative damages. Lutein is widely known by its antioxidants properties. In the present study, we investigated whether lutein-loaded nanoparticles protects against locomotor damage and neurotoxicity induced by Parkinson's disease model in Drosophila melanogaster, as well as possible mechanisms of action. First, the nanoparticles were characterized by physicochemical methods, demonstrating that water affinity was improved by the encapsulation of lutein into the polymeric encapsulant matrix. The fruit flies of 1-4 days old were divided into four groups and exposed to a standard diet (control), a diet containing either rotenone (500 μM), lutein-loaded nanoparticles (6 μM) or rotenone (500 μM) and lutein-loaded nanoparticles (6 μM) for 7 days. The survival percentage was assessed, the flies were submitted to negative geotaxis, open field tasks and the determination of dopamine levels, tyrosine hydroxylase (TH) and acetylcholinesterase activities and oxidative stress indicators (superoxide dismutase, catalase, thiobarbituric acid reactive substances and glutathione S-transferase) were carried out. The exposure to lutein-loaded nanoparticles protected against locomotor damage and the decrease survival rate induced by rotenone, besides, it restored the dopamine levels, TH and acetylcholinesterase activities and oxidative stress indicators. These results provide evidence that lutein-loaded nanoparticles are an alternative treatment for rotenone-induced damage, and suggest the involvement of dopaminergic and cholinergic system and oxidative stress.

A toxicological comparison between two uranium compounds in Artemia salina: Artificial seawater containing CaCO3

Uranium (U) mining is an aquatic environmental concern because most of these harmful compounds are discharged into freshwater, reaching the saline environment as the final destination of this contaminated water. Carbonates are present in ocean waters and are essential for benthic organisms, however they may influence the U-induced toxicity. Thus, the aim of this study was to compare the toxicity of uranium nitrate (UN) and uranium acetate (UA) in Artemia salina (AS), which is one of the leading representatives of the marine biota. The cultures of AS (instar II) maintained in artificial seawater containing CaCO₃ were exposed for 24 h to different concentrations of U compounds. The results showed that AS were more sensitive to UN (LC₅₀ ≈ 15 μM) when compared with UA (LC₅₀ ≈ 245 μM) indicating higher toxicity of this U compound. Calculated U speciation indicated that Ca₂UO₂(CO₃)₃ and (UO₂)2CO₃(OH)₃^- complexes predominated under our experimental conditions. The immobilization/lethality was observed after 9 h of exposure for both U compounds. However, only UN caused a significant decrease (≈40%) in the acetylcholinesterase (AChE) activity when compared with control. In order to observe preliminary toxicity effects, we evaluated oxidative stress parameters, such as catalase (CAT) activity, TBARS formation, radical species (RS) generation and cell membrane injury and/or apoptosis (CMI). In this study, we demonstrate that U compounds caused a significant decrease in CAT activity. Similarly, we also observed that UN increased TBARS levels in AS at concentrations 5 times lower than AU (10 μM and 50 μM, respectively). Furthermore, RS generation and CMI were enhanced only on AS treated with UN. Overall, the effects observed here were remarkably significant in AS exposed to UN when compared with AU. In this study, we showed different profiles of toxicity for both U compounds, contributing significantly to the current and scarce understanding of the aquatic ecotoxicity of this heavy metal.

Diet with Low Molecular Weight Chitosan exerts neuromodulation in Rotenone induced Drosophila model of Parkinson's disease

Rotenone (ROT) is well known pesticide been used in agriculture due to its low cost and rapid action. This has also been widely used to establish Parkinson's disease (PD) models in rodents. Here we have evaluated the role of well established potent molecule 'Low Molecular Weight Chitosan (LMWC)' against ROT induced neurotoxicity in Drosophila melanogaster. Male adult flies (8-10 days) were induced for neurotoxicity using ROT (500 μM) and treated with LMWC (5 & 10 mg/mL basal media) during 7 days experiment. Subsequently, neurodegenerative and behavioural parameters were assessed. As a result, flies exposed to ROT alone showed decreased locomotor behaviour in negative geotaxis and open-field studies and had a higher incidence of mortality compared to control group. These effects were accompanied by decrease in dopamine level, ETC complexes and increase in reactive oxygen species (ROS) production and cholinergic activities in head and body of the flies, suggesting ROT was able to induce oxidative stress. Co-exposure of LMWC reversed the ROT induced locomotor impairment, exploratory deficits and changes the biochemical parameters to normal level and increased the survival rate to 16 days. Thus, we suggested LMWC may be considered as better supplement in the prevention and management of Parkinson's disease.

Ring Finger Protein 11 (RNF11) Modulates Dopamine Release in Drosophila

Recent work indicates a role for RING finger protein 11 (RNF11) in Parkinson disease (PD) pathology, which involves the loss of dopaminergic neurons. However, the role of RNF11 in regulating dopamine neurotransmission has not been studied. In this work, we tested the effect of RNF11 RNAi knockdown or overexpression on stimulated dopamine release in the larval Drosophila central nervous system. Dopamine release was stimulated using optogenetics and monitored in real-time using fast-scan cyclic voltammetry at an electrode implanted in an isolated ventral nerve cord. RNF11 knockdown doubled dopamine release, but there was no decrease in dopamine from RNF11 overexpression. RNF11 knockdown did not significantly increase stimulated serotonin or octopamine release, indicating the effect is dopamine specific. Dopamine clearance was also changed, as RNF11 RNAi flies had a higher V_max and RNF11 overexpressing flies had a lower V_max than control flies. RNF11 RNAi flies had increased mRNA levels of dopamine transporter (DAT) in RNF11, confirming changes in DAT. In RNF11 RNAi flies, release was maintained better for stimulations repeated at short intervals, indicating increases in the recycled releasable pool of dopamine. Nisoxetine, a DAT inhibitor, and flupenthixol, a D2 antagonist, did not affect RNF11 RNAi or overexpressing flies differently than control. Thus, RNF11 knockdown causes early changes in dopamine neurotransmission, and this is the first work to demonstrate that RNF11 affects both dopamine release and uptake. RNF11 expression decreases in human dopaminergic neurons during PD, and that decrease may be protective by increasing dopamine neurotransmission in the surviving dopaminergic neurons.

Effect of Cabergoline on Cognitive Impairments in Transgenic Drosophila Model of Parkinson’s Disease

Background:

Parkinson’s disease is a common neurodegenerative disorder characterized by selective loss of dopaminergic neurons in the substantia nigra pars compacta.

Introduction:

The effects of alpha synuclein, parkin mutation and pharmacological agents have been studied in the Drosophila model.

Methods:

The effect of cabergoline was studied on the cognitive impairments exhibited by the transgenic Drosophila expressing human alpha-synuclein in the neurons. The PD flies were allowed to feed on the diet having 0.5, 1 and 1.5 μM of cabergoline.

Results and Discussion:

The exposure of cabergoline not only showed a dose-dependent significant delay in the cognitive impairments but also prevented the loss of dopaminergic neurons. Molecular docking studies showed the positive interaction between cabergoline and alpha-synuclein.

Conclusion:

The results suggest a protective effect of cabergoline against the cognitive impairments.

Impact of nano-conjugate on Drosophila for early diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is an irreversible neurodegenerative disease. Recent identification of AD biomarkers has led to the diagnosis of AD before the onset of dementia. It has been shown that Drosophila melanogaster is a valuable model for studying human neurodegeneration, including AD. According to its properties, curcumin shows promising potential for the diagnosis of AD. In order to improve its use, new formulations, including nanotechnology-based delivery systems, have been applied. The current study aims to diagnose AD by detecting the accumulation of amyloid beta-peptide via carbon-dot-curcumin nanoparticle conjugation in Drosophila. The accumulation of amyloid beta-peptide has been detected via the conjugate using the fluorescence imaging technique. These results suggest that carbon-dot-curcumin nanoparticle conjugation could be used as a diagnostic tool for AD.

Addition of Saturated and Trans-fatty Acids to the Diet Induces Depressive and Anxiety-like Behaviors in Drosophila melanogaster

This study aimed to evaluate the effects of the addition of saturated fat and hydrogenated vegetable fat (HVF) to the diet on depressive and anxiety-like behaviors in Drosophila melanogaster. Flies were exposed to experimental diets: regular diet (RD), or HVF in the concentrations of the substitute (SHVF), HVF 10% and HVF 20%, or Lard (L) in the concentrations of the substitute (SL), L 10% and L 20%, during seven days. Our results showed that flies fed with the HVF diet presented similar behaviors to depression, anxiety, and a higher number of aggressive events. Flies exposed to L showed only depressive-like behavior. Regarding serotonin levels (5HT), there was a significant reduction in the flies exposed to SHVF, HVF 10%, HVF 20%, and L 20%. Regarding the levels of octopamine (OA), there was a significant reduction in the flies exposed to both HVF and L rich diets when compared with the RD group. Also, there was a significant negative correlation between 5HT or OA levels and behaviors of aggressiveness, negative geotaxis, immobility time, light/dark, and grooming in the flies. This study shows that D. melanogaster can serve as a valuable model for understanding psychiatric disorders and that the type of fatty acid (FA) offered in the diet can influence these disorders. This demonstrates the importance of the composition of the FAs in the neural pathways, being able to influence the signaling of neurotransmitters, such as 5HT and OA, and thus, cause behavioral changes.

Spatially-resolved metabolic profiling of living Drosophila in neurodegenerative conditions using 1H magic angle spinning NMR

Drosophila flies are versatile animal models for the study of gene mutations in neuronal pathologies. Their small size allows performing in vivo Magic Angle Spinning (MAS) experiments to obtain high-resolution 1H nuclear magnetic resonance (NMR) spectra. Here, we use spatially-resolved 1H high-resolution MAS NMR to investigate in vivo metabolite contents in different segments of the fly body. A comparative study of metabolic changes was performed for three neurodegenerative disorders: two cell-specific neuronal and glial models of Huntington disease (HD) and a model of glutamate excitotoxicity. It is shown that these pathologies are characterized by specific and sometimes anatomically localized variations in metabolite concentrations. In two cases, the modifications of 1H MAS NMR spectra localized in fly heads were significant enough to allow the creation of a predictive model.

Inhibiting thrombin improves motor function and decreases oxidative stress in the LRRK2 transgenic Drosophila melanogaster model of Parkinson's disease

Parkinson's disease (PD) is a complex neurodegenerative disease characterized by the presence of tremors, loss of dopaminergic neurons and accumulation of α-synuclein. While there is no single direct cause of PD, genetic mutations, exposure to pesticides, diet and traumatic brain injury have been identified as risk factors. Increasing evidence suggests that oxidative stress and neuroinflammation contribute to the pathogenesis of neuronal injury in neurodegenerative diseases such as PD and Alzheimer's disease (AD). We have previously documented that the multifunctional inflammatory mediator thrombin contributes to oxidative stress and neuroinflammation in AD. Here, for the first time, we explore the role of thrombin in a transgenic PD model, the LRRK2 mutant Drosophila melanogaster. Transgenic flies were treated with the direct thrombin inhibitor dabigatran for 7 days and locomotor activity and indices of oxidative stress evaluated. Our data show that dabigatran treatment significantly (p < 0.05) improved climbing activity, a measurement of locomotor ability, in male but had no effect on locomotor performance in female flies. Dabigatran treatment had no effect on tyrosine hydroxylase levels. Analysis of oxidative stress in male flies showed that dabigatran was able to significantly (p < 0.01) lower reactive oxygen species levels. Furthermore, Western blot analysis showed that the pro-oxidant proteins iNOS and NOX4 are elevated in LRRK2 male flies compared to wildtype and that treatment with dabigatran reduced expression of these proteins. Our results indicate that dabigatran treatment could improve motor function in PD by reducing oxidative stress. These data suggest that targeting thrombin may improve oxidative stress related pathologies in PD.

Loss of highwire Protects Against the Deleterious Effects of Traumatic Brain Injury in Drosophila Melanogaster

Traumatic brain injury is a major global cause of death and disability. Axonal injury is a major underlying mechanism of TBI and could represent a major therapeutic target. We provide evidence that targeting the axonal death pathway known as Wallerian degeneration improves outcome in a Drosophila Melanogaster model of high impact trauma. This cell-autonomous neurodegenerative pathway is initiated following axon injury, and in Drosophila, involves activity of the E3 ubiquitin ligase highwire. We demonstrate that a loss-of-function mutation in the highwire gene rescues deleterious effects of a traumatic injury, including-improved functional outcomes, lifespan, survival of dopaminergic neurons, and retention of synaptic proteins. This data suggests that highwire represents a potential therapeutic target in traumatic injury.

A Positive Feedback Loop of Hippo- and c-Jun-Amino-Terminal Kinase Signaling Pathways Regulates Amyloid-Beta-Mediated Neurodegeneration

Alzheimer's disease (AD, OMIM: 104300) is an age-related disorder that affects millions of people. One of the underlying causes of AD is generation of hydrophobic amyloid-beta 42 (Aβ42) peptides that accumulate to form amyloid plaques. These plaques induce oxidative stress and aberrant signaling, which result in the death of neurons and other pathologies linked to neurodegeneration. We have developed a Drosophila eye model of AD by targeted misexpression of human Aβ42 in the differentiating retinal neurons, where an accumulation of Aβ42 triggers a characteristic neurodegenerative phenotype. In a forward deficiency screen to look for genetic modifiers, we identified a molecularly defined deficiency, which suppresses Aβ42-mediated neurodegeneration. This deficiency uncovers hippo (hpo) gene, a member of evolutionarily conserved Hippo signaling pathway that regulates growth. Activation of Hippo signaling causes cell death, whereas downregulation of Hippo signaling triggers cell proliferation. We found that Hippo signaling is activated in Aβ42-mediated neurodegeneration. Downregulation of Hippo signaling rescues the Aβ42-mediated neurodegeneration, whereas upregulation of Hippo signaling enhances the Aβ42-mediated neurodegeneration phenotypes. It is known that c-Jun-amino-terminal kinase (JNK) signaling pathway is upregulated in AD. We found that activation of JNK signaling enhances the Aβ42-mediated neurodegeneration, whereas downregulation of JNK signaling rescues the Aβ42-mediated neurodegeneration. We tested the nature of interactions between Hippo signaling and JNK signaling in Aβ42-mediated neurodegeneration using genetic epistasis approach. Our data suggest that Hippo signaling and JNK signaling, two independent signaling pathways, act synergistically upon accumulation of Aβ42 plaques to trigger cell death. Our studies demonstrate a novel role of Hippo signaling pathway in Aβ42-mediated neurodegeneration.

7-chloro-4-(phenylselanyl) quinoline prevents dopamine depletion in a Drosophila melanogaster model of Parkinson's-like disease

Neurodegeneration in Parkinson's disease appears to be caused by multiple factors, including oxidative damage and an increase in acetylcholinesterase expression that can culminate in loss of dopaminergic neurons. A selenium-containing quinoline derivative, 7-chloro-4-(phenylselanyl) quinoline (4-PSQ), shows important pharmacological actions mainly attributed to its antioxidant and anticholinesterase properties. Thus, this study investigated the neuroprotective effect of 4-PSQ in a model of Parkinson's-like disease induced by rotenone (ROT) in Drosophila melanogaster and verified whether these effects are related to selenium levels. Adult flies were divided into: [1] control, [2] 4-PSQ (25 μM), [3] ROT (500 μM), and [4] 4-PSQ (25 μM) + ROT (500 μM) groups and exposed to a diet containing ROT and/or 4-PSQ for 7 days, according to their respective groups. Survival, behavioral, and ex vivo analyses were performed. Dopamine levels, reactive species levels (RS), lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) activity, and proteic thiol (PSH) and non-proteic thiol (NPSH) content in the head region were analyzed, while acetylcholinesterase (AChE) activity and selenium levels in the head and body regions were analyzed. 4-PSQ was able to reverse the ROT-induced deficits in flies, reestablish dopamine and selenium levels, reverse cholinergic deficits, improve motor function, and ameliorate mortality. Furthermore, 4-PSQ also reduced RS levels and LPO, and restored the activities of the antioxidant enzymes, SOD and CAT. Interestingly, a positive relationship between dopamine and selenium levels could be seen. Our results demonstrate the neuroprotective effect of 4-PSQ, and we suggest that the compound may act via different mechanisms, such as improving antioxidant defenses and consequently reducing oxidative damages, as well as having an anticholinesterase action, which together can prevent dopamine depletion, as these actions were correlated with the presence of selenium in the 4-PSQ molecule.

Live applications of norbormide-based fluorescent probes in Drosophila melanogaster

In this study we investigated the performance of two norbormide (NRB)-derived fluorescent probes, NRBMC009 (green) and NRBZLW0047 (red), on dissected, living larvae of Drosophila, to verify their potential application in live cell imaging confocal microscopy. To this end, larval tissues were exposed to NRB probes alone or in combination with other commercial dyes or GFP-tagged protein markers. Both probes were rapidly internalized by most tissues (except the central nervous system) allowing each organ in the microscope field to be readily distinguished at low magnification. At the cellular level, the probes showed a very similar distribution (except for fat bodies), defined by loss of signal in the nucleus and plasma membrane, and a preferential localization to endoplasmic reticulum (ER) and mitochondria. They also recognized ER and mitochondrial phenotypes in the skeletal muscles of fruit fly models that had loss of function mutations in the atlastin and mitofusin genes, suggesting NRBMC009 and NRBZLW0047 as potentially useful screening tools for characterizing ER and mitochondria morphological alterations. Feeding of larvae and adult Drosophilae with the NRB-derived dyes led to staining of the gut and its epithelial cells, revealing a potential role in food intake assays. In addition, when flies were exposed to either dye over their entire life cycle no apparent functional or morphological abnormalities were detected. Rapid internalization, a bright signal, a compatibility with other available fluorescent probes and GFP-tagged protein markers, and a lack of toxicity make NRBZLW0047 and, particularly, NRBMC009 highly performing fluorescent probes for live cell microscopy studies and food intake assays in Drosophila.

Drosophila strain specific response to cisplatin neurotoxicity

Drosophila melanogaster has recently been developed as a simple, in vivo, genetic model of chemotherapy-induced peripheral neuropathy. Flies treated with the chemotherapy agent cisplatin display both a neurodegenerative phenotype and cell death in rapidly dividing follicles, mimicking the cell specific responses seen in humans. Cisplatin induces climbing deficiencies and loss of fertility in a dose dependent manner. Drosophila sensitivity to cisplatin in both cell types is affected by genetic background. We show that mutation or RNAi-based knockdown of genes known to be associated with CIPN incidence in humans affect sensitivity of flies to CIPN. Drosophila is a promising model with which to study the effect of genetics on sensitivity to CIPN.

A soy protein Lunasin can ameliorate amyloid-beta 42 mediated neurodegeneration in Drosophila eye

Alzheimer's disease (AD), a fatal progressive neurodegenerative disorder, also results from accumulation of amyloid-beta 42 (Aβ42) plaques. These Aβ42 plaques trigger oxidative stress, abnormal signaling, which results in neuronal death by unknown mechanism(s). We misexpress high levels of human Aβ42 in the differentiating retinal neurons of the Drosophila eye, which results in the Alzheimer's like neuropathology. Using our transgenic model, we tested a soy-derived protein Lunasin (Lun) for a possible role in rescuing neurodegeneration in retinal neurons. Lunasin is known to have anti-cancer effect and reduces stress and inflammation. We show that misexpression of Lunasin by transgenic approach can rescue Aβ42 mediated neurodegeneration by blocking cell death in retinal neurons, and results in restoration of axonal targeting from retina to brain. Misexpression of Lunasin downregulates the highly conserved cJun-N-terminal Kinase (JNK) signaling pathway. Activation of JNK signaling can prevent neuroprotective role of Lunasin in Aβ42 mediated neurodegeneration. This neuroprotective function of Lunasin is not dependent on retinal determination gene cascade in the Drosophila eye, and is independent of Wingless (Wg) and Decapentaplegic (Dpp) signaling pathways. Furthermore, Lunasin can significantly reduce mortality rate caused by misexpression of human Aβ42 in flies. Our studies identified the novel neuroprotective role of Lunasin peptide, a potential therapeutic agent that can ameliorate Aβ42 mediated neurodegeneration by downregulating JNK signaling.

Dme-Hsa Disease Database (DHDD): Conserved Human Disease-Related miRNA and Their Targeting Genes in Drosophila melanogaster

Abnormal expressions of microRNA (miRNA) can result in human diseases such as cancer and neurodegenerative diseases. MiRNA mainly exert their biological functions via repressing the expression of their target genes. Drosophila melanogaster (D. melanogaster) is an ideal model for studying the molecular mechanisms behind biological phenotypes, including human diseases. In this study, we collected human and D. melanogaster miRNA as well as known human disease-related genes. In total, we identified 136 human disease-related miRNA that are orthologous to 83 D. melanogaster miRNA by mapping "seed sequence", and 677 human disease-related genes that are orthologous to 734 D. melanogaster genes using the DRSC Integrative Ortholog Prediction Tool Furthermore, we revealed the target relationship between genes and miRNA using miRTarBase database and target prediction software, including miRanda and TargetScan. In addition, we visualized interaction networks and signalling pathways for these filtered miRNA and target genes. Finally, we compiled all the above data and information to generate a database designated DHDD This is the first comprehensive collection of human disease-related miRNA and their targeting genes conserved in a D. melanogaster database. The DHDD provides a resource for easily searching human disease-related miRNA and their disease-related target genes as well as their orthologs in D. melanogaster, and conveniently identifying the regulatory relationships among them in the form of a visual network.

CNS repurposing - Potential new uses for old drugs: Examples of screens for Alzheimer's disease, Parkinson's disease and spasticity

Drug repurposing is recently gaining increasing attention, not just from pharmaceutical companies but also from government agencies in an attempt to generate new medications to address increasing unmet medical needs in a cost effective and expedite manner. There are several approaches to identify novel indications for known drugs. Many are based on rational selection e.g. the known or a new mechanism of action of a drug. This review will focus rather on phenotypic or high content screening of compounds in models that are believed to be predictive of effectiveness of compounds irrespective of their mechanism of action. Three short cases studies of screens for Alzheimer's disease, Parkinson's disease and spasticity will be given as examples. This article is part of the Special Issue entitled 'Drug Repurposing: old molecules, new ways to fast track drug discovery and development for CNS disorders'.

Combined Donepezil and Ethanolic Extract of Propolis Improved Memory Better Than Donepezil and Propolis Monotherapy in Wild Type Drosophila melanogaster

BACKGROUND

Donepezil is the most common drug used in the treatment of disorders associated with memory loss, especially that in Alzheimer's disease. Healthy individuals however have continued to use it as a memory enhancer. This study was aimed at evaluating the combined therapy of donepezil and propolis on cognition in Drosophila melanogaster. Method. Drosophila melanogaster flies were divided into five groups and fed with the different treatment doses of ethanolic extract of propolis and donepezil as follows: normal food, propolis 250 mg/mL, propolis 50 mg/mL, donepezil 0.001M, and donepezil 0.001M/propolis 50 mg/mL added to their food. The flies were fed from larval stage for 30 days. The memory and learning tests were conducted after every 10 days to assess improvement with time.

RESULTS

The results obtained showed that the combination of propolis with donepezil caused a remarkable improvement in both the short- and long-term memory. In addition, there was a dose dependent improvement with the administration of propolis.

CONCLUSION

Propolis extract obtained from different parts of Uganda expressed cognitive improvement when coadministered with donepezil in wild type Drosophila melanogaster.

Pathways to neurodegeneration: lessons learnt from unbiased genetic screens in Drosophila

Neurodegenerative diseases are a complex set of disorders that are known to be caused by environmental as well as genetic factors. In the recent past, mutations in a large number of genes have been identified that are linked to several neurodegenerative diseases. The pathogenic mechanisms in most of these disorders are unknown. Recently, studies of genes that are linked to neurodegeneration in Drosophila, the fruit flies, have contributed significantly to our understanding of mechanisms of neuroprotection and degeneration. In this review, we focus on forward genetic screens in Drosophila that helped in identification of novel genes and pathogenic mechanisms linked to neurodegeneration. We also discuss identification of four novel pathways that contribute to neurodegeneration upon mitochondrial dysfunction.

Garcinia kola seed biflavonoid fraction (Kolaviron), increases longevity and attenuates rotenone-induced toxicity in Drosophila melanogaster

Rotenone, a naturally occurring and commonly used pesticide, has been established as a model for inducing Parkinson's Disease (PD) in rodents. Kolaviron is a biflavonoid complex from Garcinia kola seeds with anti-oxidative and anti-inflammatory properties. Here, we evaluated the ameliorative role of Kolaviron on rotenone-induced toxicity in Drosophila melanogaster. Flies for longevity study were exposed to Kolaviron (100-500mg/kg diet) throughout the lifespan. For biochemical study, Groups A, B and C flies were treated with ethanol (2.0%, control, vehicle), Kolaviron (200mg/kg diet) and rotenone (250μM) respectively. Flies in Group D were co-treated with both rotenone (250μM) and Kolaviron (200mg/kg diet) for 7days. Subsequently, selected markers of antioxidant status, inflammatory and neurotoxicity were evaluated in the flies. The results from longevity experiment showed that Kolaviron (200, 100, 300 and 400mg/kg) extended lifespan of flies by 38.2%, 20.6%, 11.8% and 2.9% respectively. Also, Kolaviron attenuated rotenone-induced inhibition of catalase, glutathione-S-transferase and acetylcholinesterase activities and depletion of total thiols content in flies. Moreover, Kolaviron prevented rotenone-induced increases in hydrogen peroxide and nitric oxide (nitrite and nitrate) levels and improved rotenone-induced decrease in locomotor performance of flies (p<0.05). Overall, this study evidenced for the first time, the lifespan extension property of Kolaviron and its chemoprotective role on rotenone-induced toxicity in D. melanogaster via anti-oxidative and anti-inflammatory mechanisms.