Dmp53, basket and drICE gene knockdown and polyphenol gallic acid increase life span and locomotor activity in a Drosophila Parkinson's disease model

LRRK2 Kinase Inhibitor PF-06447475 Protects Drosophila melanogaster against Paraquat-Induced Locomotor Impairment, Life Span Reduction, and Oxidative Stress

Parkinson's disease (PD) is a complex multifactorial progressive neurodegenerative disease characterized by locomotor alteration due to the specific deterioration of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNpc). Mounting evidence shows that human LRRK2 (hLRRK2) kinase activity is involved in oxidative stress (OS)-induced neurodegeneration, suggesting LRRK2 inhibition as a potential therapeutic target. We report that the hLRRK2 inhibitor PF-06447475 (PF-475) prolonged lifespan, increased locomotor activity, maintained DAergic neuronal integrity, and reduced lipid peroxidation (LPO) in female Drosophila melanogaster flies chronically exposed to paraquat (PQ), a redox cycling compound, compared to flies treated with vehicle only. Since LRRK2 is an evolutionary conserved kinase, the present findings reinforce the idea that either reduction or inhibition of the LRRK2 kinase might decrease OS and locomotor alterations associated with PD. Our observations highlight the importance of uncovering the function of the hLRRK2 orthologue dLrrk2 in D. melanogaster as an excellent model for pharmacological screenings.

The multifaceted effects of flavonoids on neuroplasticity

 There has been a significant increase in the incidence of multiple neurodegenerative and terminal diseases in the human population with life expectancy increasing in the current times. This highlights the urgent need for a more comprehensive understanding of how different aspects of lifestyle, in particular diet, may affect neural functioning and consequently cognitive performance as well as in enhancing overall health. Flavonoids, found in a variety of fruits, vegetables, and derived beverages, provide a new avenue of research that shows a promising influence on different aspects of brain function. However, despite the promising evidence, most bioactive compounds lack strong clinical research efficacy. In the current scoping review, we highlight the effects of Flavonoids on cognition and neural plasticity across vertebrates and invertebrates with special emphasis on the studies conducted in the pond snail, Lymnaea stagnalis, which has emerged to be a functionally dynamic model for studies on learning and memory. In conclusion, we suggest future research directions and discuss the social, cultural, and ethnic dependencies of bioactive compounds that influence how these compounds are used and accepted globally. Bridging the gap between preclinical and clinical studies about the effects of bioactive natural compounds on brain health will surely lead to lifestyle choices such as dietary Flavonoids being used complementarily rather than as replacements to classical drugs bringing about a healthier future.

Melatonin Increases Life Span, Restores the Locomotor Activity, and Reduces Lipid Peroxidation (LPO) in Transgenic Knockdown Parkin Drosophila melanogaster Exposed to Paraquat or Paraquat/Iron

Parkinson's disease (PD) is a complex progressive neurodegenerative disorder involving impairment of bodily movement caused by the specific destruction of dopaminergic (DAergic) neurons. Mounting evidence suggests that PD might be triggered by an interplay between environmental neurotoxicants (e.g., paraquat, PQ), heavy metals (e.g., iron), and gene alterations (e.g., PARKIN gene). Unfortunately, there are no therapies currently available that protect, slow, delay, or prevent the progression of PD. Melatonin (Mel, N-acetyl-5-methoxy tryptamine) is a natural hormone with pleiotropic functions including receptor-independent pathways which might be useful in the treatment of PD. Therefore, as a chemical molecule, it has been shown that Mel prolonged the lifespan and locomotor activity, and reduced lipid peroxidation (LPO) in wild-type Canton-S flies exposed to PQ, suggesting antioxidant and neuroprotective properties. However, it is not yet known whether Mel can protect or prevent the genetic model parkin deficient in flies against oxidative stress (OS) stimuli. Here, we show that Mel (0.5, 1, 3 mM) significantly extends the life span and locomotor activity of TH > parkin-RNAi/ + Drosophila melanogaster flies (> 15 days) compared to untreated flies. Knock-down (K-D) parkin flies treated with PQ (1 mM) or PQ (1 mM)/iron (1 mM) significantly diminished the survival index and climbing abilities (e.g., 50% of flies were dead and locomotor impairment by days 4 and 3, respectively). Remarkably, Mel reverted the noxious effect of PQ or PQ/iron combination in K-D parkin. Indeed, Mel protects TH > parkin-RNAi/ + Drosophila melanogaster flies against PQ- or PQ/iron-induced diminish survival, locomotor impairment, and LPO (e.g., 50% of flies were death and locomotor impairment by days 6 and 9, respectively). Similarly, Mel prevented K-D parkin flies against both PQ and PQ/iron. Taken together, these findings suggest that Mel can be safely used as an antioxidant and neuroprotectant agent against OS-stimuli in selective individuals at risk to suffer early-onset Parkinsonism and PD.

Neuroprotective effects of pomegranate (Punica granatum L.) juice and seed extract in paraquat-induced mouse model of Parkinson's disease

BACKGROUND

Paraquat, (PQ), an herbicide that can induce Parkinsonian-like symptoms in rodents and humans. The consumption of phytochemical-rich plants can reduce the risk of chronic illnesses such as inflammation and neurodegenerative diseases. The present study aimed to investigate the protective effects of pomegranate seed extract (PSE) and juice (PJ) against PQ-induced neurotoxicity in mice.

METHODS

Mice were assigned into 4 groups; three groups received PQ (10 mg/kg, i.p.) twice a week for 3 weeks. Two of the PQ-induced groups pretreated with either PSE or PJ. Detection of phytochemicals, total phenolics, and total flavonoids in PSE and PJ was performed. Tyrosine hydroxylase (TH) level was measured in the substantia nigra (SN) by Western blotting technique. Striatal dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were detected using high-performance liquid chromatography (HPLC). The levels of adenosine triphosphate (ATP), malondialdehyde (MDA), and the activity of the antioxidant enzymes were estimated in the striatum by colorimetric analysis. Striatal pro-inflammatory and anti-inflammatory markers using enzyme-linked immunosorbent assay (ELISA) as well as DNA fragmentation degree by qualitative DNA fragmentation assay, were evaluated. Real-time polymerase chain reaction (qPCR) assay was performed for the detection of nuclear factor kappa B (NF-кB) gene expression. Moreover, Western blotting analysis was used for the estimation of the cluster of differentiation 11b (CD11b), transforming growth factor β (TGF-β), and glial cell-derived neurotrophic factor (GDNF) levels in the striatum.

RESULTS

Pretreatment with PSE or PJ increased the levels of TH in the SN as well as DA and its metabolite in the striatum that were reduced by PQ injection. PSE and PJ preadministration improved the PQ-induced oxidative stress via a significant reduction of the MDA level and the augmentation of antioxidant enzyme activities. PSE and PJ also significantly downregulated the striatal NF-кB gene expression, reduced the PQ-enhanced apoptosis, decreased the levels of; pro-inflammatory cytokines, CD11b, and TGF-β coupled with a significant increase of; interleukin-10 (IL-10), GDNF, and ATP levels as compared with PQ-treated mice.

CONCLUSIONS

The current study indicated that PSE and PJ consumption may exhibit protective effects against PQ-induced neurotoxicity in mice.

The Drosophila Model: Exploring Novel Therapeutic Compounds against Neurodegenerative Diseases

Polyphenols are secondary metabolites of plants, fruits, and vegetables. They act as antioxidants against free radicals from UV light, pathogens, parasites, and oxidative stress. In Drosophila models, feeding with various polyphenols results in increased antioxidant capacity and prolonged lifespan. Therefore, dietary polyphenols have several health advantages for preventing many human diseases, including cardiovascular diseases, cancer, and neurodegenerative diseases. However, the exact role of polyphenols in neurodegenerative diseases is still yet to be completely defined. This review focuses on the most recent studies related to the therapeutic effect of polyphenols in neurodegenerative disease management and provides an overview of novel drug discovery from various polyphenols using the Drosophila model.

Innate immune responses to paraquat exposure in a Drosophila model of Parkinson's disease

Parkinson’s disease (PD) is a progressive, neurodegenerative movement disorder characterized by the loss of dopaminergic (DA) neurons. Limited understanding of the early molecular pathways associated with the demise of DA neurons, including those of inflammatory exacerbation of neurodegeneration, is a major impediment to therapeutic development. Recent studies have implicated gene-environment interactions in PD susceptibility. We used transcriptomic profiling in a Drosophila PD model in response to paraquat (PQ)-induced oxidative stress to identify pre-symptomatic signatures of impending neuron dysfunction. Our RNAseq data analysis revealed extensive regulation of innate immune response genes following PQ ingestion. We found that PQ exposure leads to the activation of the NF-κB transcription factor, Relish, and the stress signaling factor JNK, encoded by the gene basket in Drosophila. Relish knockdown in the dopaminergic neurons confers PQ resistance and rescues mobility defects and DA neuron loss. Furthermore, PQ-induced toxicity is mediated through the immune deficiency signaling pathway. Surprisingly, the expression of Relish-dependent anti-microbial peptide (AMPs) genes is suppressed upon PQ exposure causing increased sensitivity to Gram-negative bacterial infection. This work provides a novel link between PQ exposure and innate immune system modulation underlying environmental toxin-induced neurodegeneration, thereby underscoring the role of the innate immune system in PD pathogenesis.

A Role of Gallic Acid in Oxidative Damage Diseases: A Comprehensive Review

Gallic acid is a trihydroxybenzoic acid of plant metabolites widely spread throughout the plant kingdom. It has characteristics of the strong antioxidant and free radical scavenging activities, and can protect biological cells, tissues, and organs from damages caused by oxidative stress. This review aims to summarize the protective roles of gallic acid and the underlying pharmacological mechanisms in the pathophysiological process of the oxidative damage diseases, such as cancer, cardiovascular, degenerative, and metabolic diseases. The studies reviewed herein showed that the main therapeutic effects of gallic acid were attributed to its antioxidant properties. It modulated various signaling pathways through a wide range of inflammatory cytokines, and enzymic and nonenzymic antioxidants. However, the available data were limited to few studies assessing the treatment effects of gallic acid in human subjects to confirm its therapeutic outcomes. Therefore, the clinical trials were urgently needed to investigate the safety and efficacy of gallic acid treatment on human beings. The scientific data summarized in this review highlighted the therapeutic potentials of gallic acid for oxidative damage diseases. It could be developed as versatile adjuvant or therapeutically lead compound in future.

The Therapeutic Implications of Tea Polyphenols Against Dopamine (DA) Neuron Degeneration in Parkinson's Disease (PD)

: Accumulative evidence indicated that the pathologically accumulated metal ions (iron species and Mn³⁺) and abnormally up-regulated monoamine oxidase B (MAOB) activity induced oxidation of endogenous dopamine (DA) can lead to mitochondria impairment, lysosome dysfunction, proteasome inhibition, and selective DA neuron vulnerability, which is implicated in the pathogenesis of Parkinson's disease (PD). The DA oxidation can generate deleterious reactive oxygen species (ROS) and highly reactive DA quinones (DAQ) to induce DA-related toxicity, which can be alleviated by DA oxidation suppressors, ROS scavengers, DAQ quenchers, and MAOB inhibitors. On the other hand, the nuclear factor erythroid 2-related factor 2 (Nrf2)-Keap1 and Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) anti-oxidative and proliferative signaling pathways play roles in anti-oxidative cell defense and mitochondria biogenesis, which is implicated in DA neuron protections. Therefore, agents with capabilities to suppress DA-related toxicity including inhibition of DA oxidation, scavenge of ROS, detoxification of DAQ, inhibition of MAOB, and modulations of anti-oxidative signaling pathways can be protective to DA neurons. Accumulative evidence shows that tea or coffee consumptions and smoking are related to deceased PD prevalence with unknown mechanisms. In this study, we investigate the protective capabilities of tea polyphenols and other PD relevant agents to inhibit DA-related toxicity and protect against environmental or genetic factors induced DA neuron degeneration in vitro and in vivo. We find that tea polyphenols can significantly suppress DA-related toxicity to protect DA neurons. The tea polyphenols can protect DA neurons via inhibition of DA oxidation, conjugation with DAQ, scavenge of ROS, inhibition of MAOB, and modulations of Nrf2-Keap1 and PGC-1α anti-oxidative signaling pathways. The tea polyphenols with more phenolic hydroxyl groups and ring structures have stronger protective functions. The protective capabilities of tea polyphenols is further strengthened by evidence that phenolic hydroxyl groups can directly conjugate with DAQ. However, GSH and other sulfhydyl groups containing agents have weaker capabilities to abrogate DA oxidation, detoxify ROS and DAQ and inhibit MAOB; whereas nicotine (NICO) and caffeine (CAF) can only modulate Nrf2-Keap1 and PGC-1α pathways to protect DA neurons weakly. The tea polyphenols are identified to protect against overexpression of mutant A30P α-synuclein (α-syn) induced DA neuron degeneration and PD-like symptoms in transgenic Drosophila. Based on achievements from current studies, the excellent and versatile protective capabilities of tea polyphenols are highlighted, which will contribute and benefit to future anti-PD therapy.

Pharmacological effects of gallic acid in health and diseases: A mechanistic review

OBJECTIVES

Gallic acid is a natural phenolic compound found in several fruits and medicinal plants. It is reported to have several health-promoting effects. This review aims to summarize the pharmacological and biological activities of gallic acid in vitro and animal models to depict the pharmacological status of this compound for future studies.

MATERIALS AND METHODS

All relevant papers in the English language were collected up to June 2018. The keywords of gallic acid, antioxidant, anticancer, antimicrobial, gastrointestinal-, cardiovascular-, metabolic-, neuropsychological-, and miscellaneous- diseases were searched in Google Scholar, PubMed, and Scopus.

RESULTS

Several beneficial effects are reported for gallic acid, including antioxidant, anti-inflammatory, and antineoplastic properties. This compound has been reported to have therapeutic activities in gastrointestinal, neuropsychological, metabolic, and cardiovascular disorders.

CONCLUSION

Current evidence confirms the pharmacological and therapeutic interventions of gallic acid in multiple health complications; however, available data are limited to just cellular and animal studies. Future investigations are essential to further define the safety and therapeutic efficacy of gallic acid in humans.

A standardized Hippophae extract (SBL-1) counters neuronal tissue injuries and changes in neurotransmitters: implications in radiation protection

CONTEXT

Effects of a radioprotective, standardized leaf extract (code SBL-1) from traditional medicinal plant, sea buckthorn [Hippophae rhamnoides L. (Elaeagnaceae)], on neurotransmitters and brain injuries in rats showing radiation-induced conditioned taste aversion (CTA), are not known. Understanding CTA in rats is important because its process is considered parallel to nausea and vomiting in humans.

OBJECTIVE

This study investigated the levels of neurotransmitters, antioxidant defences and histological changes in rats showing radiation CTA, and their modification by SBL-1.

MATERIALS AND METHODS

The inbred male Sprague-Dawley rats (age 65 days, weighing 190 ± 10 g) were used. Saccharin-preferring rats were selected using standard procedure and divided into groups. Group I (untreated control) was administered sterile water, group II was 60Co-γ-irradiated (2 Gy), and group III was administered SBL-1 before irradiation. Observations were recorded up to day 5.

RESULTS

Irradiation (2 Gy) caused (i) non-recoverable CTA (≥ 64.7 ± 5.0%); (ii) degenerative changes in cerebral cortex, amygdala and hippocampus; (iii) increases in brain dopamine (DA, 63.4%), norepinephrine (NE, 157%), epinephrine (E, 233%), plasma NE (103%) and E (160%); and (iv) decreases in brain superoxide dismutase (67%), catalase (60%) and glutathione (51%). SBL-1 treatment (12 mg/kg body weight) 30 min before irradiation (i) countered brain injuries, (ii) reduced CTA (38.7 ± 3.0%, day 1) and (iii) normalized brain DA, NE, E, superoxide dismutase, catalase and CTA from day 3 onwards.

DISCUSSION AND CONCLUSION

Radiation CTA was coupled with brain injuries, disturbances in neurotransmitters and antioxidant defences. SBL-1 pretreatment countered these disturbances, indicating neuroprotective action.

Minocycline protects, rescues and prevents knockdown transgenic parkin Drosophila against paraquat/iron toxicity: Implications for autosomic recessive juvenile parkinsonism

Autosomal recessive Juvenile Parkinsonism (AR-JP) is a chronic, progressive neurodegenerative disorder caused by mutation in the PARKIN gene, and invariably associated with dopaminergic (DAergic) neuronal loss and brain iron accumulation. Since current medical therapy is symptomatic and lacks significant disease-modifying effects, other treatment approaches are urgently needed it. In the present work, we investigate the role of minocycline (MC) in paraquat (PQ)/iron-induced neurotoxicity in the Drosophila TH>parkin-RNAi/+ (w[*]; UAS-parkin-RNAi; TH-GAL4) fly and have shown the following: (i) MC increased life span and restored the locomotor activity of knockdown (KD) transgenic parkin flies in comparison with the control (vehicle) group; (ii) MC at low (0.1 and 0.3mM) and middle (0.5mM) concentrations protected, rescued and prevented KD parkin Drosophila against PQ toxicity. However, MC at high (1mM) concentration aggravated the toxic effect of PQ; (iii) MC protected and rescued DAergic neurons against the PQ toxic effect according to tyrosine hydroxylase (TH)>green-fluorescent protein (GFP) reporter protein microscopy and anti-TH Western blotting analysis; (iv) MC protected DAergic neurons against PQ/iron toxicity; (v) MC significantly abridged lipid peroxidation (LPO) in the protection, rescue and prevention treatment in TH>parkin-RNAi/+ flies against PQ or iron alone or combined (PQ/iron)-induced neuronal oxidative stress (OS). Our results suggest that MC exerts neuroprotection against PQ/iron-induced OS in DAergic neurons most probably by the scavenging activity of reactive oxygen species (ROS), and by chelating iron. Therefore, MC might be a potential therapeutic drug to delay, revert, or prevent AR-JP.