Neuroprotective potential of cinnamoyl derivatives against Parkinson's disease indicators in Drosophila melanogaster and in silico models.

Parkinson's disease (PD) is a movement disorder resulting from the loss of dopaminergic neurons over time. While there is no cure for PD, available conventional therapies aid to manage the motor symptoms. Natural products (NPs) derived from plants are among the most potent alternative therapies for PD. This study explored the neuroprotective potential of selected cinnamoyl derivatives namely toussaintine A (1), E-toussaintine E (2), asperphenamate (3) and julocrotine (4) against PD indicators using rotenone-challenged Drosophila melanogaster and in silico models. The compounds were first assessed for their toxicity preceding treatment experiments. Adult flies (aged 1-4 days) were exposed to varying concentrations of the compounds for 7 days. During the experiment, the mortality of flies was observed, and the lethal concentration (LC50) of each tested compound was determined. The LC50 values were found to be 50.1, 55.6, 513.5, and 101.0 µM for compounds 1, 2, 3, and 4, respectively. For seven days, we exposed flies to 500 µM of rotenone and co-fed with a chosen dose of 40 µM of each test compound in the diet. Using a negative geotaxis test, rotenone-challenged flies exhibited compromised climbing ability in comparison to control flies, the condition that was reversed by the action of studied compounds. Rotenone exposure also elevated malondialdehyde levels in the brain tissues, as measured by lipid peroxidation, when compared to control flies. In flies exposed to rotenone and co-fed with the compounds, this effect was lessened. In flies exposed to rotenone, mRNA levels of antioxidant enzymes such as superoxide dismutase and catalase were raised but were normalized in flies treated with the investigated compounds. Moreover, in-silico studies examined the inhibitory ability of compounds 1-4 against selected PD molecular targets, revealing the strong power of toussaintine A (1) against Adenosine receptor 2 (A2AR) and monoamine oxidase B. Thus, our findings suggest that cinnamoyl derivatives have neuroprotective potential via reducing the oxidative burden and improving locomotor ability after toxin invectives. In particular, compound 1 at lower doses can simultaneously be a potential inhibitor of A2AR and an anti-oxidative mediator in the development of anti-PD agents.

Evaluation of the Efficacy of Flupyradifurone against Bemisia tabaci on Cassava in Tanzania.

A novel butenolide insecticide-flupyradifurone (Sivanto SL 200)-was evaluated for efficacy against cassava-colonizing Bemisia tabaci whitefly under laboratory, screenhouse and field conditions. LC50 values from leaf disc spray assays were comparable for both flupyradifurone (12.7 g a.i/100 L) and imidacloprid (12.6 g a.i/100 L). Both insecticides caused high levels of adult whitefly mortality in leaf disc and leaf dip assays when compared to untreated controls. In screenhouse-based trials, longer soaking (60 min) with flupyradifurone or imidacloprid was more effective than shorter soaking durations (15 or 30 min). In field spraying experiments, flupyradifurone significantly reduced whiteflies, and both insecticides demonstrated powerful knockdown effects on whitefly adult abundances over a period up to 24 h. Single cutting dip application of flupyradifurone reduced whitefly adult abundance by 2 to 6 times, and nymphs by 2 to 13 times. Lower whitefly abundances resulting from insecticide application reduced the incidence of CMD or CBSD. In addition, in field experiments, whiteflies were fewer during the long rainy season (Masika) and on cassava variety Mkuranga1. The findings from this study demonstrate that cutting dips with flupyradifurone could be incorporated as a management tactic against cassava whiteflies. This would ideally be combined in an IPM strategy with other cassava virus and virus vector management tactics including host-plant resistance, phytosanitation and the use of clean seed.

An assessment of the rescue action of resveratrol in parkin loss of function-induced oxidative stress in Drosophila melanogaster.

Loss-of-function mutations in parkin is associated with onset of juvenile Parkinson's disease (PD). Resveratrol is a polyphenolic stilbene with neuroprotective activity. Here, we evaluated the rescue action of resveratrol in parkin mutant D. melanogaster. The control flies (w1118) received diet-containing 2% ethanol (vehicle), while the PD flies received diets-containing resveratrol (15, 30 and 60 mg/kg diet) for 21 days to assess survival rate. Consequently, similar treatments were carried out for 10 days to evaluate locomotor activity, oxidative stress and antioxidant markers. We also determined mRNA levels of Superoxide dismutase 1 (Sod1, an antioxidant gene) and ple, which encodes tyrosine hydroxylase, the rate-limiting step in dopamine synthesis. Our data showed that resveratrol improved survival rate and climbing activity of PD flies compared to untreated PD flies. Additionally, resveratrol protected against decreased activities of acetylcholinesterase and catalase and levels of non-protein thiols and total thiols displayed by PD flies. Moreover, resveratrol mitigated against parkin mutant-induced accumulations of hydrogen peroxide, nitric oxide and malondialdehyde. Resveratrol attenuated downregulation of ple and Sod1 and reduction in mitochondrial fluorescence intensity displayed by PD flies. Overall, resveratrol alleviated oxidative stress and locomotor deficit associated with parkin loss-of-function mutation and therefore might be useful for the management of PD.

Ameliorative effects of flavonoids and polyketides on the rotenone induced Drosophila model of Parkinson's disease.

Parkinson's disease (PD) is a movement disorder associated with the progressive loss of dopaminergic neurons (DA). PD treatment remains unsatisfactory as the current synthetic drugs in clinical use relies on managing only motor symptoms. This study investigated antioxidant potentials of selected compounds namely, 5,6,7,4'-tetramethoxyflavone (1), 6-hydroxy-2,3,4,4'-tetramethoxychalcone (2), 6-methoxyhamiltone A (3), diosquinone (4) and toussantine D (5) against rotenone (6) induced PD in Drosophila melanogaster. Toxicity of these compounds was conducted by monitoring flies' survival for seven days and determining the lethal concentrations (LC50). Whereas compound 1 had LC50 value of 91.3 µM within three days, compounds 2, 3, 4, and 5 had LC50 values of 87.2, 58.0, 64.0 and > 1000 µM, respectively on the seventh day of the experiment. We exposed flies (1-4 days old) to 500 µM rotenone and co-treated with different doses of the test compounds in the diet for seven days at final concentrations of 11.0, 43.6 and 87.2 µM for compounds 2 and 3. The concentrations used for compound 4 were 8.0, 32.0 and 64.0 µM, while 250, 500 and 1000 µM were used for compound 5. Rotenone fed flies showed impaired climbing ability compared to control flies, the phenotype that was rescued by the treatment of tested phytochemicals. Rotenone toxicity also increased malondialdehyde levels assayed by lipid peroxidation in the brain tissues relative to control flies. This effect was reduced in flies exposed to rotenone and co-treated with the phytochemicals. Moreover, expression levels of mRNA of antioxidant enzymes; superoxide dismutase and catalase were elevated in flies exposed to rotenone and normalized in flies that were co-treated with tested compounds. Besides compound 1, this study provides overall evidence that the tested flavonoids and polyketides ameliorated the rotenone provoked neurotoxicity in D. melanogaster by battling the induced oxidative stress in brain cells including DA neurons and hence rescue the locomotor behaviour deficits.

Impaired Wnt signaling in dopamine containing neurons is associated with pathogenesis in a rotenone triggered Drosophila Parkinson's disease model.

Parkinson's disease, which is the one of the most common neurodegenerative movement disorder, is characterized by a progressive loss of dopamine containing neurons. The mechanisms underlying disease initiation and development are not well understood and causative therapies are currently not available. To elucidate the molecular processes during early stages of Parkinson's disease, we utilized a Drosophila model. To induce Parkinson's disease-like phenotypes, we treated flies with the pesticide rotenone and isolated dopamine producing neurons of animals that were at an early disease stage. Transcriptomic analyses revealed that gene ontologies associated with regulation of cell death and neuronal functions were significantly enriched. Moreover, the activities of the MAPK/EGFR- and TGF-ß signaling pathways were enhanced, while the Wnt pathway was dampened. In order to evaluate the role of Wnt signaling for survival of dopaminergic neurons in the disease model, we rescued the reduced Wnt signaling activity by ectopic overexpression of armadillo/ß-catenin. This intervention rescued the rotenone induced movement impairments in the Drosophila model. Taken together, this initial study showed a highly relevant role of Wnt signaling for dopamine producing neurons during pathogenesis in Parkinson's disease and it implies that interfering with this pathway might by a suitable therapeutic option for the future.

The Role of Monoaminergic Neurotransmission for Metabolic Control in the Fruit Fly Drosophila Melanogaster.

Hormones control various metabolic traits comprising fat deposition or starvation resistance. Here we show that two invertebrate neurohormones, octopamine (OA) and tyramine (TA) as well as their associated receptors, had a major impact on these metabolic traits. Animals devoid of the monoamine OA develop a severe obesity phenotype. Using flies defective in the expression of receptors for OA and TA, we aimed to decipher the contributions of single receptors for these metabolic phenotypes. Whereas those animals impaired in octß1r, octß2r and tar1 share the obesity phenotype of OA-deficient (tßh-deficient) animals, the octß1r, octß2r deficient flies showed reduced insulin release, which is opposed to the situation found in tßh-deficient animals. On the other hand, OAMB deficient flies were leaner than controls, implying that the regulation of this phenotype is more complex than anticipated. Other phenotypes seen in tßh-deficient animals, such as the reduced ability to perform complex movements tasks can mainly be attributed to the octß2r. Tissue-specific RNAi experiments revealed a very complex interorgan communication leading to the different metabolic phenotypes observed in OA or OA and TA-deficient flies.

Octopamine controls starvation resistance, life span and metabolic traits in Drosophila.

The monoamines octopamine (OA) and tyramine (TA) modulate numerous behaviours and physiological processes in invertebrates. Nevertheless, it is not clear whether these invertebrate counterparts of norepinephrine are important regulators of metabolic and life history traits. We show that flies (Drosophila melanogaster) lacking OA are more resistant to starvation, while their overall life span is substantially reduced compared with control flies. In addition, these animals have increased body fat deposits, reduced physical activity and a reduced metabolic resting rate. Increasing the release of OA from internal stores induced the opposite effects. Flies devoid of both OA and TA had normal body fat and metabolic rates, suggesting that OA and TA act antagonistically. Moreover, OA-deficient flies show increased insulin release rates. We inferred that the OA-mediated control of insulin release accounts for a substantial proportion of the alterations observed in these flies. Apparently, OA levels control the balance between thrifty and expenditure metabolic modes. Thus, changes in OA levels in response to external and internal signals orchestrate behaviour and metabolic processes to meet physiological needs. Moreover, chronic deregulation of the corresponding signalling systems in humans may be associated with metabolic disorders, such as obesity or diabetes.

Expression analysis of octopamine and tyramine receptors in Drosophila.

The monoamines octopamine and tyramine, which are the invertebrate counterparts of epinephrine and norepinephrine, transmit their action through sets of G protein-coupled receptors. Four different octopamine receptors (Oamb, Octß1R, Octß2R, Octß3R) and 3 different tyramine receptors (TyrR, TyrRII, TyrRIII) are present in the fruit fly Drosophila melanogaster. Utilizing the presumptive promoter regions of all 7 octopamine and tyramine receptors, the Gal4/UAS system is utilized to elucidate their complete expression pattern in larvae as well as in adult flies. All these receptors show strong expression in the nervous system but their exact expression patterns vary substantially. Common to all octopamine and tyramine receptors is their expression in mushroom bodies, centers for learning and memory in insects. Outside the central nervous system, the differences in the expression patterns are more conspicuous. However, four of them are present in the tracheal system, where they show different regional preferences within this organ. On the other hand, TyrR appears to be the only receptor present in the heart muscles and TyrRII the only one expressed in oenocytes. Skeletal muscles express octß2R, Oamb and TyrRIII, with octß2R being present in almost all larval muscles. Taken together, this study provides comprehensive information about the sites of expression of all octopamine and tyramine receptors in the fruit fly, thus facilitating future research in the field.