The pesticide rotenone induces caspase-3-mediated apoptosis in ventral mesencephalic dopaminergic neurons

Neuroprotective effect of dexpanthenol on rotenone-induced Parkinson's disease model in rats

Parkinson's disease (PD) is the second most common and progressive neurodegenerative disease. This experimental study was designed to investigate the neuroprotective effects of dexpanthenol on antioxidant and anti-inflammatory processes in a rotenone-induced Parkinson's disease model in rats. Twenty-one male rats were randomly divided into 2 groups. The rotenone group (n = 14) was administered rotenone by intrastriatal injection, and the vehicle group (n = 7) was administered DMSO with the same application route. All animals underwent rotational movement testing with apomorphine injection 10 days later. Those with Parkinson's disease model were randomly divided into 2 groups. While 1 ml/kg of saline was applied to the saline group (n = 7), 500 mg/kg was administered to the dexpanthenol group intraperitoneally for 28 days. After 28 days, all rats were euthanized and brain tissue was removed. While striatal areas were evaluated immunohistochemically, brain MDA, TNF-α, and HVA levels were measured to evaluate their anti-oxidative and anti-inflammatory effects. In the dexpanthenol group, the total count (p < 0.001) and intensity (p < 0.001) of dopaminergic neurons in the striatal areas increased compared to the saline group. It was revealed that MDA (nmol/g) (p < 0.001) and TNF-α (pg/g) (p < 0.001) levels decreased in the dexpanthenol group, while HVA (ng/mg) levels increased (p < 0.01). This study suggests that dexpanthenol may have a neuroprotective effect by reducing neuronal loss, oxidative damage, and neuroinflammation in the striatum in rats.

Anti-inflammatory, anti-apoptotic, and neuroprotective potentials of anethole in Parkinson's disease-like motor and non-motor symptoms induced by rotenone in rats

Parkinson's disease (PD) is a complex neurological disorder characterized by a combination of motor and non-motor symptoms (NMS). Antioxidant and anti-inflammatory compounds are considered a potential therapeutic strategy against PD. The present study examined the neuroprotective effects of anethole as a potent antioxidant and anti-inflammatory agent against motor and non-motor deficits induced by rotenone toxicity. Rats were treated with anethole (62.5, 125, and 250 mg/kg, i.g) concomitantly with rotenone (2 mg/kg, s.c) for 5 weeks. After the treatment, behavioral tests were performed to evaluate motor function and depression-/anxiety-like behaviors. After the behavioral tests, rats were decapitated and brains were removed for histological analysis. Striatum samples were also isolated for neurochemical, and molecular analysis. Our data showed that rotenone-induced motor deficit, anxiety-and depression-like behaviors were significantly improved in rats treated with anethole. Furthermore, anethole treatment reduced inflammatory cytokines tumor necrosis factor α (TNFα) and Interleukin 6 (IL-6), and increased anti-inflammatory cytokine IL-4 in the striatum of rotenone-induced PD rats. Western blot analysis showed that treatment with anethole markedly suppressed caspase-3 activation induced by rotenone. Moreover, histological examination of striatum showed an increase in the number of surviving neurons after treatment with anethole. Anethole also significantly enhanced the striatal levels of dopamine in rotenone-induced PD rats. In addition, treatment with L-Dopa as a positive control group had effects similar to those of anethole on histological, neurochemical, and molecular parameters in rotenone-induced parkinsonian rats. Our results suggested the neuroprotective effects of anethole through anti-inflammatory, anti-apoptotic, and antioxidant mechanisms against rotenone-induced toxicity in rats.

LRRK2 Knockout Confers Resistance in HEK-293 Cells to Rotenone-Induced Oxidative Stress, Mitochondrial Damage, and Apoptosis

Leucine-rich repeat kinase 2 (LRRK2) has been linked to dopaminergic neuronal vulnerability to oxidative stress (OS), mitochondrial impairment, and increased cell death in idiopathic and familial Parkinson's disease (PD). However, how exactly this kinase participates in the OS-mitochondria-apoptosis connection is still unknown. We used clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 LRRK2 knockout (KO) in the human embryonic kidney cell line 293 (HEK-293) to evaluate the cellular response to the mitochondrial inhibitor complex I rotenone (ROT), a well-known OS and cell death inducer. We report successful knockout of the LRRK2 gene in HEK-293 cells using CRISPR editing (ICE, approximately 60%) and flow cytometry (81%) analyses. We found that HEK-293 LRRK2 WT cells exposed to rotenone (ROT, 50 μM) resulted in a significant increase in intracellular reactive oxygen species (ROS, +7400%); oxidized DJ-1-Cys¹⁰⁶-SO₃ (+52%); phosphorylation of LRRK2 (+70%) and c-JUN (+171%); enhanced expression of tumor protein (TP53, +2000%), p53 upregulated modulator of apoptosis (PUMA, +1950%), and Parkin (PRKN, +22%); activation of caspase 3 (CASP3, +8000%), DNA fragmentation (+35%) and decreased mitochondrial membrane potential (ΔΨm, -58%) and PTEN induced putative kinase 1 (PINK1, -49%) when compared to untreated cells. The translocation of the cytoplasmic fission protein dynamin-related Protein 1 (DRP1) to mitochondria was also observed by colocalization with translocase of the outer membrane 20 (TOM20). Outstandingly, HEK-293 LRRK2 KO cells treated with ROT showed unaltered OS and apoptosis markers. We conclude that loss of LRRK2 causes HEK-293 to be resistant to ROT-induced OS, mitochondrial damage, and apoptosis in vitro. Our data support the hypothesis that LRRK2 acts as a proapoptotic kinase by regulating mitochondrial proteins (e.g., PRKN, PINK1, DRP1, and PUMA), transcription factors (e.g., c-JUN and TP53), and CASP3 in cells under stress conditions. Taken together, these observations suggest that LRRK2 is an important kinase in the pathogenesis of PD.

Structure-based developmental toxicity and ASD-phenotypes of bisphenol A analogues in embryonic zebrafish

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that has become more prevalent in recent years. Environmental endocrine disruptor bisphenol A (BPA) has been linked to ASD. BPA analogues (BPs) are structure-modified substitutes widely used as safer alternatives in consumer products, yet few studies have explored the developmental neurotoxicity (DNT) of BPA analogues. In the present study, we used the larval zebrafish model to assess the DNT effects of BPA and its analogues. Our results showed that many BPA analogues are more toxic than BPA in the embryonic zebrafish assay regarding teratogenic effect and mortality, which may partially due to differences in lipophilicity and/or different substitutes of structural function groups such as CF3, benzene, or cyclohexane. At sublethal concentrations, zebrafish embryos exposed to BPA or BPs also displayed reduced prosocial behavior in later larval development, evidenced by increased nearest neighbor distance (NND) and the interindividual distance (IID) in shoaling, which appears to be structurally independent. An in-depth analysis of BPA, bisphenol F (BPF), and bisphenol S (BPS) revealed macrocephaly and ASD-like behavioral deficits resulting from exposures to sublethal concentrations of these chemicals. The ASD-like behavioral deficits were characterized by hyperactivity, increased anxiety-like behavior, and decreased social contact. Mechanistically, accelerated neurogenesis that manifested by increased cell proliferation, the proportion of newborn mature neurons, and the number of neural stem cells in proliferation, as well as upregulated genes related to the K⁺ channels, may have contributed to the observed ASD-like morphological and behavioral alterations. Our findings indicate that BPF and BPS may also pose significant risks to ASD development in humans and highlight the importance of a comprehensive assessment of DNT effects for all BPA analogues in the future.

Isocyanate induces cytotoxicity via activation of phosphorylated alpha synuclein protein, nitrosative stress, and apoptotic pathway in Parkinson's Disease model-SHSY-5Y cells

BACKGROUND

Neurotoxic disorders account for a significant portion of the diseases that influence the worldwide disease burden. Parkinson's disease is one such disease that is linked with environmental toxin exposure. Isocyanates are a highly reactive industrial intermediate used widely in manufacturing plastic products, paints, etc. This study aims to delineate the neurotoxic potential of isocyanate in Parkinson's cell model-SHSY-5Y cells.

METHODOLOGY

SHSY-5Y cells were treated with isocyanate analogue (N succinimidyl N methyl carbamate) in time and dose dependant manner. Different parameters were assessed like protein expression, nitrosative stress level, antioxidant enzymes level and apoptosis.

RESULTS

Our findings demonstrate that dose- and time-dependent isocyanate exposure increases reactive nitrogen species and decreases the glutathione, SOD, and catalase levels. Further, increased phosphorylated alpha-synuclein protein and activation of caspase 3 exert cytotoxicity in SHSY-5Y cells.

CONCLUSION

Our research reveals that widely used isocyanate induces cytotoxicity, apoptosis, nitrosative stress, and protein dysfunction, which might constitute a potential mechanism of neurodegeneration in Parkinsonism.

Non-SUMOylated alternative spliced isoforms of alpha-synuclein are more aggregation-prone and toxic

The exon skipping of α-Synuclein (α-Syn), the main constituent of the abnormal protein aggregation in Lewy bodies of Parkinson's disease (PD), forms four isoforms. In contrast to the full length α-Syn (α-Syn 140), little is known about the splice isoforms' properties and functions. SUMOylation, a post-translational modification, regulates α-Syn function, aggregation, and degradation, but information about α-Syn isoforms and the effect of SUMOylation on them is unknown. Therefore, this study aims to characterize the SUMOylation of α-Syn isoforms and its impact on cell death and α-Syn aggregation. In a cellular model of PD induced by rotenone, cell toxicity, SUMOylation, and α-Syn aggregation with or without isoforms overexpression were evaluated. First, rotenone induced cell toxicity and α-Syn aggregation, with a significant reduction of SUMOylation and autophagy. Boosting SUMOylation prevented α-Syn aggregation, phosphorylation and recovery of autophagy. Moreover, α-Syn 140 and α-Syn 126 were SUMOylated while the other two isoforms, α-Syn 112 and 98 were not and their overexpression showed that were more toxic and induced more α-Syn aggregation. Rotenone increased their toxicity that was not affected by boosting SUMOylation. These results may indicate a role of SUMOylation in modulating α-Syn aggregation, inducing to understanding more about the behavior of α-Syn isoforms.

Environmentally relevant concentrations of organic (benzophenone-3) and inorganic (titanium dioxide nanoparticles) UV filters co-exposure induced neurodevelopmental toxicity in zebrafish

UV filters, widely used in personal care products, are ubiquitous environmental pollutants detected and pose a significant public health concern. Benzophenone-3 (BP3) and titanium dioxide nanoparticles (nano-TiO₂) are the predominant organic and inorganic UV filters in environmental media. However, few studies have explored the combined developmental neurotoxic (DNT) effects and the underlying mechanisms when co-exposed to BP3 and nano-TiO₂. In the present study, zebrafish (Danio rerio) embryos were exposed to environmentally relevant concentrations of BP3 (10 μg/L), nano-TiO₂ (100 μg/L), and mixtures starting from 6 h post fertilization (hpf), respectively. Developmental indicators and motor behaviors were investigated at various developmental stages. Our results showed that BP3 alone or co-exposed with nano-TiO₂ increased spontaneous movement at 24 hpf, co-exposure decreased touch response at 30 hpf and hatching rate at 60 hpf. Consistent with these motor deficits, co-exposure to BP3 and nano-TiO₂ inhibited relative axon length of primary motor neuron during the early developmental stages, disturbed the expression of axonal growth-related genes at 30 and 48 hpf, increased cell apoptosis on the head region and mRNA levels of apoptosis-related genes, and also increased reactive oxygen species (ROS) levels in zebrafish, suggesting the functional relevance of structural changes. Taken together, our findings demonstrated that BP3 alone or in combination with nano-TiO₂ at environmentally relevant concentrations induced evident neurotoxic effects on the developing embryos in zebrafish.

Can Berberine Serve as a New Therapy for Parkinson's Disease?

Parkinson's disease (PD) is a neurodegenerative disorder characterized by dopaminergic neurodegeneration and deposition of alpha-synuclein. Mechanisms associated with PD etiology include oxidative stress, apoptosis, autophagy, and abnormalities in neurotransmission, to name a few. Drugs used to treat PD have shown significant limitations in their efficacy. Therefore, recent focus has been placed on the potential of active plant ingredients as alternative, complementary, and efficient treatments. Berberine is an isoquinoline alkaloid that has shown promise as a pharmacological treatment in PD, given its ability to modulate several molecular pathway associated with the disease. Here, we review contemporary knowledge supporting the need to further characterize berberine as a potential treatment for PD.

Neuroprotective effects of ATPase inhibitory factor 1 preventing mitochondrial dysfunction in Parkinson's disease

Mitochondrial dysfunction is a key element in the progression of Parkinson’s disease (PD). The inefficient operation of the electron transport chain (ETC) impairs energy production and enhances the generation of oxidative stress contributing to the loss of dopaminergic cells in the brain. ATPase inhibitory factor 1 (IF1) is a regulator of mitochondrial energy metabolism. IF1 binds directly to the F₁Fo ATP synthase and prevents ATP wasting during compromised energy metabolism. In this study, we found treatment with IF1 protects mitochondria against PD-like insult in vitro. SH-SY5Y cells treated with IF1 were resistant to loss of ATP and mitochondrial inner membrane potential during challenge with rotenone, an inhibitor of complex I in the ETC. We further demonstrated that treatment with IF1 reversed rotenone-induced superoxide production in mitochondria and peroxide accumulation in whole cells. Ultimately, IF1 decreased protein levels of pro-apoptotic Bax, cleaved caspase-3, and cleaved PARP, rescuing SH-SY5Y cells from rotenone-mediated apoptotic death. Administration of IF1 significantly improved the results of pole and hanging tests performed by PD mice expressing human α-synuclein. This indicates that IF1 mitigates PD-associated motor deficit. Together, these findings suggest that IF1 exhibits a neuroprotective effect preventing mitochondrial dysfunction in PD pathology.

Fucoidan Modulated Oxidative Stress and Caspase-3 mRNA Expression Induced by Sulfoxaflor in the Brain of Mice

The current study aimed to investigate the role of fucoidan in the oxidative and apoptotic effects of sulfoxaflor, a neonicotinoid sulfoximine insecticide, in the brain of Swiss albino mice (Mus musculus). Sulfoxaflor and fucoidan were administered to mice at doses of 15 mg/kg/day (1/50 oral LD50) and 50 mg/kg/day, respectively, by oral gavage for 24 h or 7 days. The tGSH, TBARS and protein levels, and GPx, GR, and GST enzyme activities were determined by spectrophotometric methods. Caspase-3 gene expression level was determined by RT-PCR. Data analysis showed that brains of sulfoxaflor-treated mice exhibited higher TBARS levels; GPx, GR, and GST enzyme activities; and caspase-3 expression levels, as well as lower levels of tGSH. Co-administration of fucoidan and sulfoxaflor reduced the TBARS levels, increased tGSH levels, and increased GPx, GR, and GST enzyme activities. Fucoidan also decreased the sulfoxaflor-induced up-regulation of caspase-3 mRNA expression. Results of the present study showed that sulfoxaflor caused oxidative stress by inducing lipid peroxidation and altering GSH-dependent antioxidants in the brain of mice. In addition, sulfoxaflor may trigger apoptotic cell death shown by the up-regulation of caspase-3. Fucoidan treatment modulated all the aforementioned alterations in the brain of mice. It was concluded that fucoidan might have antioxidant effects that support the GSH-dependent antioxidant system and can play a modulator role in oxidative stress and caspase-3 expression in the brain of sulfoxaflor treated-mice.

Mechanistic insights into the protective effect of paracetamol against rotenone-induced Parkinson's disease in rats: Possible role of endocannabinoid system modulation

Parkinson's disease (PD) is a disabling progressive neurodegenerative disease. So far, PD's treatment remains symptomatic with no curative effects. Aside from its blatant analgesic and antipyretic efficacy, recent studies highlighted the endowed neuroprotective potentials of paracetamol (PCM). To this end: the present study investigated: (1) Possible protective role of PCM against rotenone-induced PD-like neurotoxicity in rats, and (2) the mechanisms underlying its neuroprotective actions including cannabinoid receptors' modulation. A dose-response study was conducted using three doses of PCM (25, 50, and 100 mg/kg/day, i.p.) and their effects on body weight changes, spontaneous locomotor activity, rotarod test, tyrosine hydroxylase (TH) and α-synuclein expression, and striatal dopamine (DA) content were evaluated. Results revealed that PCM (100 mg/kg/day, i.p.) halted PD motor impairment, prevented rotenone-induced weight loss, restored normal histological tissue structure, reversed rotenone-induced reduction in TH expression and striatal DA content, and markedly decreased midbrain and striatal α-synuclein expression in rotenone-treated rats. Accordingly, PCM (100 mg/kg/day, i.p.) was selected for further mechanistic investigations, where it ameliorated rotenone-induced oxidative stress, neuro-inflammation, apoptosis, and disturbed cannabinoid receptors' expression. In conclusion, our findings imply a multi-target neuroprotective effect of PCM in PD which could be attributed to its antioxidant, anti-inflammatory and anti-apoptotic activities, in addition to cannabinoid receptors' modulation.

The protective effect of biochanin A against rotenone-induced neurotoxicity in mice involves enhancing of PI3K/Akt/mTOR signaling and beclin-1 production

Rotenone is an insecticide that generates oxidative stress in the CNS and induces locomotor dysfunction and neurodegeneration in rodents. Biochanin A [BioA] is an isoflavone with antioxidant and anti-inflammatory actions. The antioxidant and the modulatory action of BioA on PI3K/Akt/mTOR signaling and autophagy were tested in rotenone-Parkinsonian mice. Mice were allocated into; Group I: oil control group, Group II: rotenone group [1-mg/kg/48h, subcutaneously], group III: rotenone and BioA [10-mg/kg]. Rotenone injection resulted in locomotor disturbances in mice, degeneration in dopaminergic neurons [tyrosine hydroxylase-immunoreactive cells], low striatal dopamine, increased malondialdehyde and decreased level of glutathione. Neuroinflammation was evidenced by upregulation of astrocytes [glia fibrillary acidic protein, GFAP] and elevated levels of cytokines. The phosphorylation of PI3K/Akt/mTOR and the autophagy-related protein, beclin-1, were decreased significantly as indicated by Western blot analysis. BioA treatment enhanced locomotor activity and afforded nigral neuroprotection. The mechanism by which BioA produced this effect includes increased antioxidant defenses, lessened proinflammatory cytokines, increased phosphorylation of PI3K/Akt/mTOR proteins and upregulated beclin-1. Importantly, BioA suppressed the striatal astrocyte marker [GFAP]. Overall, the currents study highlighted that BioA activates PI3K/Akt/mTOR signaling and enhances beclin-1 leading to neuroprotection for nigral dopaminergic neurons.

Isolongifolene mitigates rotenone-induced dopamine depletion and motor deficits through anti-oxidative and anti-apoptotic effects in a rat model of Parkinson's disease

Isolongifolene (ILF), a novel tricyclic sesquiterpene compound isolated from the Indian herb Murraya koenigii (M. koenigii), has been previously demonstrated to have a neuroprotective effect against rotenone-induced oxidative stress, mitochondrial dysfunction, and apoptosis in in vitro model. However, these neuroprotective and anti-apoptotic effects of ILF are not well understood and must be further investigated to elucidate the underlying molecular mechanism of ILF in animal experiments. The objective of this study was to evaluate the neuroprotective effect of ILF on motor impediments, neurochemical variables, anti-oxidative indices, and apoptotic protein expression in a rotenone-induced rat model of Parkinson's disease (PD). PD was induced in male albino Wistar rats via injection of 2.5 mg/kg rotenone for 4 weeks. Rotenone produces PD-like effects by promoting mitochondrial complex I inhibition and microglial activation properties. The protective effect of three different doses of ILF 5, 10 and 20 mg/kg were evaluated for spontaneous locomotion, rotarod performance, and striatal dopamine (DA) content. The results showed that ILF dose-dependently ameliorated the rotenone-induced striatal DA loss and motor impairment from 10 mg/kg. Therefore, we selected 10 mg/kg as the ILF dose for further investigation. Chronic administration of rotenone caused PD-related pathological processes like oxidative stress, and produced a significant decrease in tyrosine hydroxylase (TH), DA transporter (DAT), Vesicular monoamine transporter 2 (VMAT2), and a significant upregulated in α-synuclein and apoptotic protein expression of Bax, Cyt-C and caspases -3, -8 and -9 as well as by decreasing Bcl2 expression. Treatment with ILF 10 mg/kg mitigated oxidative stress in rotenone-treated rats. Furthermore, ILF dramatically alleviated rotenone-induced toxicity and cell death by increasing TH, DAT and VMAT2 expression and reducing the upregulation of α-synuclein, Bax, Cyt-C, caspases -3, -8 and -9. Together, our results confirm that ILF's protective effect against rotenone-induced PD is mediated through anti-oxidant and anti-apoptotic properties. However, further in-depth investigations on ILF's anti-inflammatory and mitochondrial protective abilities are needed to establish ILF as a potential drug candidate for the treatment of Parkinson's disease.

Autophagy and Redox Homeostasis in Parkinson's: A Crucial Balancing Act

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated primarily from endogenous biochemical reactions in mitochondria, endoplasmic reticulum (ER), and peroxisomes. Typically, ROS/RNS correlate with oxidative damage and cell death; however, free radicals are also crucial for normal cellular functions, including supporting neuronal homeostasis. ROS/RNS levels influence and are influenced by antioxidant systems, including the catabolic autophagy pathways. Autophagy is an intracellular lysosomal degradation process by which invasive, damaged, or redundant cytoplasmic components, including microorganisms and defunct organelles, are removed to maintain cellular homeostasis. This process is particularly important in neurons that are required to cope with prolonged and sustained operational stress. Consequently, autophagy is a primary line of protection against neurodegenerative diseases. Parkinson's is caused by the loss of midbrain dopaminergic neurons (mDANs), resulting in progressive disruption of the nigrostriatal pathway, leading to motor, behavioural, and cognitive impairments. Mitochondrial dysfunction, with associated increases in oxidative stress, and declining proteostasis control, are key contributors during mDAN demise in Parkinson's. In this review, we analyse the crosstalk between autophagy and redoxtasis, including the molecular mechanisms involved and the detrimental effect of an imbalance in the pathogenesis of Parkinson's.

α-Bisabolol, a Dietary Bioactive Phytochemical Attenuates Dopaminergic Neurodegeneration through Modulation of Oxidative Stress, Neuroinflammation and Apoptosis in Rotenone-Induced Rat Model of Parkinson's disease

Rotenone (ROT), a plant-derived pesticide is a well-known environmental neurotoxin associated with causation of Parkinson’s disease (PD). ROT impairs mitochondrial dysfunction being mitochondrial complex-I (MC-1) inhibitor and perturbs antioxidant-oxidant balance that contributes to the onset and development of neuroinflammation and neurodegeneration in PD. Due to the scarcity of agents to prevent the disease or to cure or halt the progression of symptoms of PD, the focus is on exploring agents from naturally occurring dietary phytochemicals. Among numerous phytochemicals, α-Bisabolol (BSB), natural monocyclic sesquiterpene alcohol found in many ornamental flowers and edible plants garnered attention due to its potent pharmacological properties and therapeutic potential. Therefore, the present study investigated the neuroprotective effects of BSB in a rat model of ROT-induced dopaminergic neurodegeneration, a pathogenic feature of PD and underlying mechanism targeting oxidative stress, inflammation and apoptosis. BSB treatment significantly prevented ROT-induced loss of dopaminergic neurons and fibers in the substantia nigra and striatum respectively. BSB treatment also attenuated ROT-induced oxidative stress evidenced by inhibition of MDA formation and GSH depletion as well as improvement in antioxidant enzymes, SOD and catalase. BSB treatment also attenuated ROT-induced activation of the glial cells as well as the induction and release of proinflammatory cytokines (IL-1β, IL-6 and TNF-α) and inflammatory mediators (iNOS and COX-2) in the striatum. In addition to countering oxidative stress and inflammation, BSB also attenuated apoptosis of dopaminergic neurons by attenuating downregulation of anti-apoptotic protein Bcl-2 and upregulation of pro-apoptotic proteins Bax, cleaved caspases-3 and 9. Further, BSB was observed to attenuate mitochondrial dysfunction by inhibiting mitochondrial lipid peroxidation, cytochrome-C release and reinstates the levels/activity of ATP and MC-I. The findings of the study demonstrate that BSB treatment salvaged dopaminergic neurons, attenuated microglia and astrocyte activation, induction of inflammatory mediators, proinflammatory cytokines and reduced the expression of pro-apoptotic markers. The in vitro study on ABTS radical revealed the antioxidant potential of BSB. The results of the present study are clearly suggestive of the neuroprotective effects of BSB through antioxidant, anti-inflammatory and anti-apoptotic properties in ROT-induced model of PD.

Environmental relevant concentrations of benzophenone-3 induced developmental neurotoxicity in zebrafish

Benzophenone-3 (BP3 or oxybenzone) is an organic UV filter that has been widely used in personal care products. Its frequent detection in the environment and humans as well as its structural similarity to estradiol have prompted most research focus on its endocrine effect. However, these effects are usually associated with concentrations 10-100 fold higher than its environmental relevant concentrations. Few studies explore its adverse effects at environmental relevant concentrations. In the present study, we evaluated the developmental neurotoxic (DNT) effects of low concentration BP3 exposure during a sensitive developmental window in zebrafish. Our findings revealed that BP3 exposure at 10 μg/L (0.04 μM) during 6-24 h post fertilization (hpf) led to various DNT effects such as increased spontaneous movement at 21 and 24 hpf, decreased touch response at 27 hpf, heightened hyperactivity in locomotor response at 5 day post fertilization (dpf), decreased shoaling behavior at 11 dpf and decreased mirror attacks at 12 dpf. These effects were accompanied with decreased axonal growth at 27 hpf, decreased cell proliferation and increased cell apoptosis in the head region of larval zebrafish immediately after BP3 exposure at 24 hpf, and increased expression of retinoid X receptor gene rxrgb at 5 dpf. Interestingly, rxrgb knockdown through morpholino injection largely restored most of BP3-induced DNT effects, axonal growth delay, cell proliferation and cell apoptosis, suggesting that BP3-induced DNT effects are likely mediated through the Rxrgb receptor. In considering with recent findings on the endocrine effects of BP3, we conclude that BP3 at environmental relevant concentrations has limited estrogenic effect, but is neurotoxic to developing embryos in zebrafish.

Melatonin/polydopamine nanostructures for collective neuroprotection-based Parkinson's disease therapy

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in the substantia nigra and localized deposition of cytoplasmic fibrillary inclusions as Lewy bodies in the brain. The aberrant phosphorylation of α-synuclein at serine 129 is the key process on its early onset, which alters the cellular conformation to oligomers and insoluble aggregates, underpinning cellular oxidative stress and mitochondrial dysfunction, leading to devastating PD synucleinopathy. The multiple neuroprotective roles of dopamine and melatonin are often demonstrated separately; however, this approach suffers from low and short bioavailability and is associated with side-effects upon overdosing. Herein, highly pleiotropic melatonin-enriched polydopamine nanostructures were fabricated, which showed efficient brain tissue retention, sustainable and prolonged melatonin release, and prevented neuroblastoma cell death elicited by Parkinson's disease-associated and mitochondrial damaging stimuli. The synergistic neuroprotection re-established the mitochondrial membrane potential, reduced the generation of cellular reactive oxygen species (ROS), inhibited the activation of both the caspase-dependent and independent apoptotic pathways, and exhibited an anti-inflammatory effect. At the molecular level, it suppressed α-synuclein phosphorylation at Ser 129 and reduced the cellular deposition of high molecular weight oligomers. The therapeutic assessment on ex vivo organotypic brain slice culture, and in vivo experimental PD model confirmed the superior brain targeting, collective neuroprotection on dopaminergic neurons with reduced alpha-synuclein phosphorylation and deposition in the hippocampal and substantia nigra region of the brain. Thus, nature-inspired melatonin-enriched polydopamine nanostructures conferring collective neuroprotective effects attributes activation of anti-oxidative, anti-inflammatory, and anti-apoptotic pathways may be superior for application in a nanomedicine-based PD therapy.

Rotenone and 3-bromopyruvate toxicity impacts electrical and structural cardiac remodeling in rats

3-Bromopyruvate (3-BrPA) is a promising agent that has been widely studied in the treatment of cancer and pulmonary hypertension. Rotenone is a pesticide commonly used on farms and was shown to have anti-cancer activity and delay fibrosis progression in chronic kidney disease in a recent study. However, there are few studies showing the toxicity of rotenone and 3-BrPA in the myocardium. To support further medical exploration, it is necessary to clarify the side effects of these compounds on the heart. This study was designed to examine the cardiotoxicity of 3-BrPA and rotenone by investigating electrical and structural cardiac remodeling in rats. Forty male rats were divided into 4 groups (n = 10 in each group) and injected intraperitoneally with 3-BrPA, rotenone or a combination of 3-BrPA and rotenone. The ventricular effective refractory period (VERP), corrected QT interval (QTc), and ventricular tachycardia/ventricular fibrillation (VT/VF) inducibility were measured. The expression of Cx43, Kir2.1, Kir6.2, DHPRα₁, KCNH2, caspase3, caspase9, Bax, Bcl2, and P53 was detected. Masson's trichrome, TUNEL, HE, and PAS staining and transmission electron microscopy were used to detect pathological and ultrastructural changes. Our results showed that rotenone alone and rotenone combined with 3-BrPA significantly increased the risk of ventricular arrhythmias. Rotenone combined with 3-BrPA caused myocardial apoptosis, and rotenone alone and rotenone combined with 3-BrPA caused electrical and structural cardiac remodeling in rats.

Melatonin and Parkinson Disease: Current Status and Future Perspectives for Molecular Mechanisms

Parkinson disease (PD) is a chronic and neurodegenerative disease with motor and nonmotor symptoms. Multiple pathways are involved in the pathophysiology of PD, including apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and changes in the neurotransmitters. Preclinical and clinical studies have shown that melatonin supplementation is an appropriate therapy for PD. Administration of melatonin leads to inhibition of some pathways related to apoptosis, autophagy, oxidative stress, inflammation, α-synuclein aggregation, and dopamine loss in PD. In addition, melatonin improves some nonmotor symptom in patients with PD. Limited studies, however, have evaluated the role of melatonin on molecular mechanisms and clinical symptoms in PD. This review summarizes what is known regarding the impact of melatonin on PD in preclinical and clinical studies.

Pesticides as the drivers of neuropsychotic diseases, cancers, and teratogenicity among agro-workers as well as general public

The need to maximize agricultural productivity has made pesticides an indispensable part of current times. Farmers are unaware of the lurking consequences of the pesticide exposure, which endanger their health. It also puts the unsuspecting consumers in peril. The pesticides (from organophosphates, organochlorine, and carbamate class) disrupt the immune and hormonal signaling, causing recurrent inflammation, which leads to a wide array pathologies, including teratogenicity. Numerous farmers have fallen victim to neural disorders-driven suicides and lungs, prostate/breast cancer-caused untimely deaths. Green revolution which significantly escalated agricultural productivity is backfiring now. It is high time that environmental and agricultural authorities act to restrain the excessive usage of the detrimental chemicals and educate farmers regarding the crisis. This review discusses the biological mechanisms of pesticide-driven pathogenesis (such as the activation or inhibition of caspase, serine protease, acetylcholinesterase) and presents the pesticide-exposure-caused health deterioration in USA, India, and Africa. This holistic and critical review should be an eye-opener for general public, and a guide for researchers.

High-content imaging assays on a miniaturized 3D cell culture platform

The majority of high-content imaging (HCI) assays have been performed on two-dimensional (2D) cell monolayers for its convenience and throughput. However, 2D-cultured cell models often do not represent the in vivo characteristics accurately and therefore reduce the predictability of drug toxicity/efficacy in vivo. Recently, three-dimensional (3D) cell-based HCI assays have been demonstrated to improve predictability, but its use is limited due to difficulty in maneuverability and low throughput in cell imaging. To alleviate these issues, we have developed miniaturized 3D cell culture on a micropillar/microwell chip and demonstrated high-throughput HCI assays for mechanistic toxicity. Briefly, Hep3B human hepatoma cell line was encapsulated in a mixture of alginate and fibrin gel on the micropillar chip, cultured in 3D, and exposed to six model compounds in the microwell chip for rapidly assessing mechanistic hepatotoxicity. Several toxicity parameters, including DNA damage, mitochondrial impairment, intracellular glutathione level, and cell membrane integrity were measured on the chip, and the IC₅₀ values of the compounds at different readouts were determined to investigate the mechanism of toxicity. Overall, the Z' factors were between 0.6 and 0.8 for the HCI assays, and the coefficient of variation (CV) were below 20%. These results indicate high robustness and reproducibility of the HCI assays established on the miniaturized 3D cell culture chip. In addition, it was possible to determine the predominant mechanism of toxicity using the 3D HCI assays. Therefore, our miniaturized 3D cell culture coupled with HCI assays has great potential for high-throughput screening (HTS) of compounds and mechanistic toxicity profiling.

ROS-dependent Bax/Bcl2 and caspase 3 pathway-mediated apoptosis induced by zineb in human keratinocyte cells

There are a large number of agricultural workers who are exposed to pesticides through skin and inhalation. The best approach to identify altered molecular pathways during dermal exposure to pesticides is relevant to risk-associated concern about skin safety. In this study, we investigated the cytotoxic effect of zineb, a fungicide, in human keratinocyte (HaCaT) cells. HaCaT cells were treated with zineb (1–40 µg/mL) for 24 hours. Cellular and molecular mechanisms of cell toxicity were investigated through MTT and neutral red-uptake assays. Zineb reduced viability of HaCaT cells and induced apoptosis in a concentration-dependent manner. Zineb increased levels of Bax and caspase 3 and inhibited the level of Bcl2, which subsequently induced apoptosis via the Bax/Bcl2 and caspase pathway. Therefore, zineb could have induced apoptosis through the mitochondrial pathway in HaCaT cells. Our study suggests that zineb is cytotoxic to HaCaT cells via the induction of apoptosis and oxidative stress in vitro.

Developmental and behavioral alterations in zebrafish embryonically exposed to valproic acid (VPA): An aquatic model for autism

Autism spectrum disorder (ASD) has complex neurodevelopmental impairments and origins that are linked to both genetic and environmental factors. Hence, there is an urgency to establish animal models with ASD-like characteristics to understand the underlying mechanisms of ASD. Prenatal exposure to valproic acid (VPA) produced ASD-like symptoms in humans, rats, and recently zebrafish. The present study investigated the use of VPA exposure to generate an ASD model in zebrafish. Early life stage exposures produced ASD-like phenotypes in the developing brain development and behavioral changes in embryonic and larval zebrafish. Our findings revealed that treating zebrafish embryos with VPA starting at 8h post fertilization (hpf) resulted in significant: increase in the ASD macrocephalic phenotype; hyperactivity of embryo/larvae movement behaviors; and increases of ASD-like larval social behaviors. Further analysis showed increases in cell proliferation, the proportion of mature newborn neurons, and neural stem cell proliferation in the brain region, which may contribute to the brain overgrowth and macrocephaly observed following VPA exposure. Our study demonstrated that VPA exposure generates ASD-like phenotypes and behaviors, indicating that zebrafish is an alternative model to investigate underlying ASD mechanisms.

PARK14 PLA2G6 mutants are defective in preventing rotenone-induced mitochondrial dysfunction, ROS generation and activation of mitochondrial apoptotic pathway

Mutations in the gene encoding Ca²⁺-independent phospholipase A₂ group 6 (PLA2G6) cause the recessive familial type 14 of Parkinson’s disease (PARK14). Mitochondrial dysfunction is involved in the pathogenesis of Parkinson’s disease (PD). PLA2G6 is believed to be required for maintaining mitochondrial function. In the present study, rotenone-induced cellular model of PD was used to investigate possible molecular pathogenic mechanism of PARK14 mutant PLA2G6-induced PD. Overexpression of wild-type (WT) PLA2G6 ameliorated rotenone-induced apoptotic death of SH-SY5Y dopaminergic cells. PARK14 mutant (D331Y), (G517C), (T572I), (R632W), (N659S) or (R741Q) PLA2G6 failed to prevent rotenone-induced activation of mitochondrial apoptotic pathway and exert a neuroprotective effect. WT PLA2G6, but not PARK14 mutant PLA2G6, prevented rotenone-induced mitophagy impairment. In contrast to WT PLA2G6, PARK14 mutant PLA2G6 was ineffective in attenuating rotenone-induced decrease in mitochondrial membrane potential and increase in the level of mitochondrial superoxide. WT PLA2G6, but not PARK14 PLA2G6 mutants, restored enzyme activity of mitochondrial complex I and cellular ATP content in rotenone-treated SH-SY5Y dopaminergic cells. In contrast to WT PLA2G6, PARK14 mutant PLA2G6 failed to prevent rotenone-induced mitochondrial lipid peroxidation and cytochrome c release. These results suggest that PARK14 PLA2G6 mutants lose their ability to maintain mitochondrial function and are defective inpreventing mitochondrial dysfunction, ROS production and activation of mitochondrial apoptotic pathway in rotenone-induced cellular model of PD.

Bringing Neural Cell Therapies to the Clinic: Past and Future Strategies

Cell replacement therapy in the nervous system has a rich history, with ∼40 years of research and ∼30 years of clinical experience. There is compelling evidence that appropriate cells can integrate and function in the dysfunctioning human nervous system, but the clinical results are mixed in practice. A number of factors conspire to vary patient outcome: the indication, cell source, patient selection, and team performing transplantation are all variables that can affect efficacy. Most early clinical trials have used fetal cells, a limited cell source that resists scale and standardization. Direct fetal cell transplantation creates significant challenges to commercialization that is the ultimate goal of an effective cell therapy. One approach to help scale and standardize fetal cell preparations is the expansion of neural cells in vitro. Expansion is achieved by transformation or through the application of mitogens before cryopreservation. Recently, neural cells derived from pluripotent stem cells have provided a scalable alternative. Pluripotent stem cells are desirable for manufacturing but present alternative concerns and manufacturing obstacles. All cell sources require robust and reproducible manufacturing to make nervous system cell replacement therapy an option for patients. Here, we discuss the challenges and opportunities for cell replacement in the nervous system. In this review, we give an overview of completed and ongoing neural cell transplantation clinical trials, and we discuss the challenges and opportunities for future cell replacement trials with a particular focus on pluripotent stem cell-derived therapies.

TBBPA exposure during a sensitive developmental window produces neurobehavioral changes in larval zebrafish

Tetrabromobisphenol A (TBBPA), one of the most widely used brominated flame retardants (BFRs), is a ubiquitous contaminant in the environment and in the human body. This study demonstrated that zebrafish embryos exposed to TBBPA during a sensitive window of 8-48 h post-fertilization (hpf) displayed morphological malformations and mortality. Zebrafish exposed exclusively between 48 and 96 hpf were phenotypically normal. TBBPA was efficiently absorbed and accumulated in zebrafish embryos, but was eliminated quickly when the exposure solution was removed. Larval behavior assays conducted at 120 hpf indicated that exposure to 5 μM TBBPA from 8 to 48 hpf produced larvae with significantly lower average activity and speed of movement in the normal condition than in those exposed from 48 to 96 hpf. Specifically, 8-48 hpf-exposed larvae spent significantly less time in both activity bursts and gross movements compared to control or 48-96 hpf exposed larvae. Consistent with the motor deficits, TBBPA induced apoptotic cell death, delayed cranial motor neuron development, inhibited primary motor neuron development and loosed muscle fiber during the early developmental stages. To further explore TBBPA-induced developmental and neurobehavioral toxicity, RNA-Seq analysis was used to identify early transcriptional changes following TBBPA exposure. In total, 1969 transcripts were significantly differentially expressed (P < 0.05, FDR < 0.05, 1.5-FC) upon TBBPA exposure. Functional and pathway analysis of the TBBPA transcriptional profile identified biological processes involved in nerve development, muscle filament sliding and contraction, and extracellular matrix disassembly and organization changed significantly. In addition, TBBPA also led to an elevation in the expression of genes encoding uridine diphosphate glucuronyl transferases (ugt), which could affect thyroxine (T4) metabolism and subsequently lead to neurobehavioral changes. In summary, TBBPA exposure during a narrow, sensitive developmental window perturbs various molecular pathways and results in neurobehavioral deficits in zebrafish.

Tetramethylpyrazine Ameliorates Rotenone-Induced Parkinson's Disease in Rats: Involvement of Its Anti-Inflammatory and Anti-Apoptotic Actions

Parkinson's disease (PD) is a slowly progressive neurodegenerative movement disorder. Apoptosis, neuroinflammation, and oxidative stress are the current hypothesized mechanisms for PD pathogenesis. Tetramethylpyrazine (TMP), the major bioactive component of Ligusticum wallichii Franchat (ChuanXiong), Family Apiaceae, reportedly has anti-apoptotic, anti-inflammatory and antioxidant effects. This study investigated the role of 'TMP' in preventing rotenone-induced neurobiological and behavioral sequelae. A preliminary dose-response study was conducted where rats received TMP (10, 20, and 40 mg/kg, i.p.) concomitantly with rotenone (2 mg/kg, s.c.) for 4 weeks. Catalepsy, locomotor activity, striatal dopamine content, and tyrosine hydroxylase "TH" and α-synuclein immunoreactivity were evaluated. The selected TMP dose (20 mg/kg) was used for western blot analysis of Bax, Bcl2, and DJ-1, immunohistochemical detection of nuclear factor kappa B (NF-кB), inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and glial fibrillary acidic protein (GFAP) expression, in addition to biochemical analysis of caspase-3 activity, nuclear factor erythroid 2-related factor 2 (Nrf2), and heme oxygenase-1 (HO-1) levels. Results showed that TMP (20 mg/kg) significantly improved midbrain and striatal TH expression and striatal dopamine content as well as the motor deficits, compared to rotenone-treated group. These results were correlated with reduction in caspase-3 activity and α-synuclein expression, along with improvement of midbrain and striatal Bax/Bcl2 ratio compared to rotenone-treated group. TMP also attenuated rotenone-induced upregulation of Nrf2/HO-1 pathway. Furthermore, TMP downregulated rotenone-induced neuroinflammation markers: NF-кB, iNOS, COX2, and GFAP expression in both the midbrain and striatum. Taken together, the current study suggests that TMP is entitled to, at least partially, preventing PD neurobiological and behavioral deficits by virtue of its anti-apoptotic, anti-inflammatory, and antioxidant actions.

Enhancing Beta-Catenin Activity via GSK3beta Inhibition Protects PC12 Cells against Rotenone Toxicity through Nurr1 Induction

Parkinson’s disease (PD) is characterized by progressive degeneration of dopaminergic (DA) neurons in the substantial nigra pars compacta. Increasing evidence showed that Wnt/β-catenin pathway and the orphan nuclear receptor Nurr1 play crucial roles in the survival and functional maintenance of DA neurons in the midbrain and GSK-3β antagonists LiCl and SB216763 were used to activate Wnt/β-catenin pathway experimentally. However, the detail mechanism underlying the neuroprotection against apoptosis on DA neuron is still unclear and the interaction between Wnt/β-catenin and Nurr1 remains undisclosed. In this study, using cell biological assay we investigated the function of Wnt/β-catenin and its crosstalk with Nurr1 on the course of PC12 cell degeneration in vitro. Our data showed that PC12 cell viability was inhibited by rotenone, but attenuated by GSK-3β antagonists LiCl or SB216763. The activity of Wnt/β-catenin pathway was deregulated on exposure of rotenone in a concentration-dependent manner. After the interference of β-catenin with siRNA, LiCl or SB216763 failed to protect PC12 cells from apoptosis by the rotenone toxicity. Our data confirmed that Wnt/β-catenin signaling activated by LiCl or SB216763 enhanced Nurr1 expression to 2.75 ± 0.55 and 4.06 ± 0.41 folds respectively compared with control detected by real-time PCR and the interaction of β-catenin with Nurr1 was identified by co-immunoprecipitate analysis. In conclusion, the data suggested that Wnt/β-catenin and Nurr1 are crucial factors in the survival of DA neurons, and the activation of Wnt/β-catenin pathway exerts protective effects on DA neurons partly by mean of a co-active pattern with Nurr1. This finding may shed a light on the potential treatment of Parkinson disease.

New insights on the mitochondrial proteome plasticity in Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases whose relentless progression results in severe disability. Although PD aetiology is unknown, growing evidences point to the mitochondrial involvement in the pathobiology of this disorder. So, it seems imperative to understand the means by which the molecular pathways harboured in this organelle are regulated. With the advances in MS-based proteomics, there is a substantial expectation in the increased knowledge of mitochondrial protein dynamics. Still, few studies have been performed on mitochondrial protein profiling in the context of PD. In order to integrate data from these studies, network analyses were performed taking into consideration variables such as model of PD, cell line, or tissue origin. Overall, data retrieved from these analyses highlighted the modulation of the biological processes related with "generation of energy," "cellular metabolism," and "mitochondrial transport" in PD. However, it was noted that the impact of sample type and/or PD model on the biological processes was modulated by the disease. Moreover, technical considerations related to protein characterization using gel-based or gel-free MS approaches should be considered in data comparison among different studies. Data from the present review will help to envisage future studies targeting these mechanisms.

Comparative Microarray Analysis Identifies Commonalities in Neuronal Injury: Evidence for Oxidative Stress, Dysfunction of Calcium Signalling, and Inhibition of Autophagy-Lysosomal Pathway

Mitochondrial dysfunction, ubiquitin-proteasomal system impairment and excitotoxicity occur during the injury and death of neurons in neurodegenerative conditions. The aim of this work was to elucidate the cellular mechanisms that are universally altered by these conditions. Through overlapping expression profiles of rotenone-, lactacystin- and N-methyl-D-aspartate-treated cortical neurons, we have identified three affected biological processes that are commonly affected; oxidative stress, dysfunction of calcium signalling and inhibition of the autophagic-lysosomal pathway. These data provides many opportunities for therapeutic intervention in neurodegenerative conditions, where mitochondrial dysfunction, proteasomal inhibition and excitotoxicity are evident.

Sex-specific disruption of murine midbrain astrocytic and dopaminergic developmental trajectories following antenatal GC treatment

The mammalian midbrain dopaminergic systems arising in the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) are critical for coping behaviours and are implicated in neuropsychiatric disorders where early life challenges comprise significant risk factors. Here, we aimed to advance our hypothesis that glucocorticoids (GCs), recognised key players in neurobiological programming, target development within these systems, with a novel focus on the astrocytic population. Mice received antenatal GC treatment (AGT) by including the synthetic GC, dexamethasone, in the mothers' drinking water on gestational days 16-19; controls received normal drinking water. Analyses of regional shapes and volumes of the adult SNc and VTA demonstrated that AGT induced long-term, dose-dependent, structural changes that were accompanied by profound effects on astrocytes (doubling/tripling of numbers and/or density). Additionally, AGT induced long-term changes in the population size and distribution of SNc/VTA dopaminergic neurons, confirming and extending our previous observations made in rats. Furthermore, glial/neuronal structural remodelling was sexually dimorphic and depended on the AGT dose and sub-region of the SNc/VTA. Investigations within the neonatal brain revealed that these long-term organisational effects of AGT depend, at least in part, on targeting perinatal processes that determine astrocyte density and programmed cell death in dopaminergic neurons. Collectively, our characterisation of enduring, AGT-induced, sex-specific cytoarchitectural disturbances suggests novel mechanistic links for the strong association between early environmental challenge (inappropriate exposure to excess GCs) and vulnerability to developing aberrant behaviours in later life, with translational implications for dopamine-associated disorders (such as schizophrenia, ADHD, autism, depression), which typically show a sex bias.

Mitochondrial mechanisms of redox cycling agents implicated in Parkinson's disease

Environmental agents have been implicated in Parkinson's disease (PD) based on epidemiological studies and the ability of toxicants to replicate features of PD. However, the precise mechanisms by which toxicants induce dopaminergic toxicity observed in the idiopathic form of PD remain to be fully understood. The roles of ROS and mitochondria are strongly suggested in the mechanisms by which these toxicants exert dopaminergic toxicity. There are marked differences and similarities shared by the toxicants in increasing steady-state levels of mitochondrial ROS. Furthermore, toxicants increase steady-state mitochondrial ROS levels by stimulating the production, inhibiting the antioxidant pathways of both. This review will focus on the role of mitochondria and ROS in PD associated with environmental exposures to redox-based toxicants.

Carbosilane dendrimers inhibit α-synuclein fibrillation and prevent cells from rotenone-induced damage

This study investigates the role of carbosilane dendrimers in fibrillation of α-synuclein and prevention of the mouse hippocampal cell (mHippoE-18) from rotenone-induced damage. Examining the interaction between carbosilane dendrimers and α-synuclein, we found that the dendrimers inhibit fibril formation. We also investigated cell viability, the production of reactive oxygen species (ROS), and mitochondrial membrane potential. mHippoE-18 cells were preincubated with carbosilane dendrimers before rotenone was added. All the dendrimers possess potential protection activity. Preincubation with dendrimers contributed to: increased viability, higher mitochondrial membrane potential, and reduced ROS level in cells. The probable mechanism of cell protection lies in the ability of dendrimers to capture rotenone by encapsulating or binding to its surface groups. The fact that dendrimers have prevention potential is important in the search for new pharmacological strategies against neurodegenerative disorders.

4-Hydroxy TEMPO attenuates dichlorvos induced microglial activation and apoptosis

Microglial cells have been implicated in various neurodegenerative diseases. Previous studies from our lab have shown that dichlorvos (an organophosphate) could induce Parkinson's like features in rats. Recently, we have shown that dichlorvos can induce microglial activation, and if not checked in time could ultimately induce neuronal apoptosis. However, this activation does not always pose a threat to the neurons. Activated microglia also secrete various neuronal growth factors, suggesting that they have beneficial roles in CNS repair. Therefore, it is essential to control their detrimental functions selectively. Here, we tried to find out how microglial cells behave when exposed to dichlorvos in either the presence or absence of potent nitric oxide scavenger and superoxide dismutase mimetic, 4-hydroxy TEMPO (4-HT). Wistar rat pups (1 day) were used to isolate and culture primary microglial cells. We found 4-HT pretreatment successfully attenuated the dichlorvos mediated microglial activation. Moreover, 4-HT pretreatment decreased the up-regulated levels of p53 and its downstream effector, p21. The expression of various cell cycle regulators such as Chk2, CDC25a, and cyclin A remained close to their basal levels when 4-HT pretreatment was given. DNA fragmentation analysis showed significant reduction in the DNA damage of 4-HT pretreated microglia as compared to dichlorvos treated cells. In addition to this, we found 4-HT pretreatment prevented the microglial cells from undergoing apoptotic cell death even after 48 h of dichlorvos exposure. Taken together, our results showed 4-HT pretreatment could successfully ameliorate the dichlorvos induced microglial cell damage.

Impairment of Atg5-dependent autophagic flux promotes paraquat- and MPP⁺-induced apoptosis but not rotenone or 6-hydroxydopamine toxicity

Controversial reports on the role of autophagy as a survival or cell death mechanism in dopaminergic cell death induced by parkinsonian toxins exist. We investigated the alterations in autophagic flux and the role of autophagy protein 5 (Atg5)-dependent autophagy in dopaminergic cell death induced by parkinsonian toxins. Dopaminergic cell death induced by the mitochondrial complex I inhibitors 1-methyl-4-phenylpyridinium (MPP⁺) and rotenone, the pesticide paraquat, and the dopamine analog 6-hydroxydopamine (6-OHDA) was paralleled by increased autophagosome accumulation. However, when compared with basal autophagy levels using chloroquine, autophagosome accumulation was a result of impaired autophagic flux. Only 6-OHDA induced an increase in autophagosome formation. Overexpression of a dominant negative form of Atg5 increased paraquat- and MPP⁺-induced cell death. Stimulation of mammalian target of rapamycin (mTOR)-dependent signaling protected against cell death induced by paraquat, whereas MPP⁺-induced toxicity was enhanced by wortmannin, a phosphoinositide 3-kinase class III inhibitor, rapamycin, and trehalose, an mTOR-independent autophagy activator. Modulation of autophagy by either pharmacological or genetic approaches had no effect on rotenone or 6-OHDA toxicity. Cell death induced by parkinsonian neurotoxins was inhibited by the pan caspase inhibitor (Z-VAD), but only caspase-3 inhibition was able to decrease MPP⁺-induced cell death. Finally, inhibition of the lysosomal hydrolases, cathepsins, increased the toxicity by paraquat and MPP⁺, supporting a protective role of Atg5-dependent autophagy and lysosomes degradation pathways on dopaminegic cell death. These results demonstrate that in dopaminergic cells, Atg5-dependent autophagy acts as a protective mechanism during apoptotic cell death induced by paraquat and MPP⁺ but not during rotenone or 6-OHDA toxicity.

Establishment of a survival and toxic cellular model for Parkinson's disease from chicken mesencephalon

Cellular models for Parkinson’s disease (PD) represent a fast and efficient tool in the screening for drug candidates and factors involved in the disease pathogenesis. The objective of this study was to establish and characterize a survival and toxic cellular model for PD by culturing dopaminergic neurons from embryonic chicken ventral midbrain. We show that as in rodents, the common neurotrophic factors—brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), and fibroblast growth factor 2 (FGF2)—are able to support the survival of chicken midbrain dopaminergic neurons. Furthermore, after treatment with MPP⁺ or rotenone as in vitro models for PD, the number of tyrosine hydroxylase-positive cells decreased drastically. This effect could be significantly rescued by treatment with BDNF or GDNF. Together, our results indicate that mechanisms of neuroprotection of dopaminergic neurons are conserved between chicken and mammals. This supports the use of primary culture from chicken embryonic midbrain as a suitable tool for the study of neuroprotection in vitro.

Mitochondrial complex I inhibitor rotenone-induced toxicity and its potential mechanisms in Parkinson's disease models

The etiology of Parkinson's disease (PD) is attributed to both environmental and genetic factors. The development of PD reportedly involves mitochondrial impairment, oxidative stress, α-synuclein aggregation, dysfunctional protein degradation, glutamate toxicity, calcium overloading, inflammation and loss of neurotrophic factors. Based on a link between mitochondrial dysfunction and pesticide exposure, many laboratories, including ours, have recently developed parkinsonian models by utilization of rotenone, a well-known mitochondrial complex I inhibitor. Rotenone models for PD appear to mimic most clinical features of idiopathic PD and recapitulate the slow and progressive loss of dopaminergic (DA) neurons and the Lewy body formation in the nigral-striatal system. Notably, potential human parkinsonian pathogenetic and pathophysiological mechanisms have been revealed through these models. In this review, we summarized various rotenone-based models for PD and discussed the implied etiology of and treatment for PD.

Toxin models of mitochondrial dysfunction in Parkinson's disease

SIGNIFICANCE

Parkinson's disease (PD) is a neurodegenerative disorder characterized, in part, by the progressive and selective loss of dopaminergic neuron cell bodies within the substantia nigra pars compacta (SNpc) and the associated deficiency of the neurotransmitter dopamine (DA) in the striatum, which gives rise to the typical motor symptoms of PD. The mechanisms that contribute to the induction and progressive cell death of dopaminergic neurons in PD are multi-faceted and remain incompletely understood. Data from epidemiological studies in humans and molecular studies in genetic, as well as toxin-induced animal models of parkinsonism, indicate that mitochondrial dysfunction occurs early in the pathogenesis of both familial and idiopathic PD. In this review, we provide an overview of toxin models of mitochondrial dysfunction in experimental Parkinson's disease and discuss mitochondrial mechanisms of neurotoxicity.

RECENT ADVANCES

A new toxin model using the mitochondrial toxin trichloroethylene was recently described and novel methods, such as intranasal exposure to toxins, have been explored. Additionally, recent research conducted in toxin models of parkinsonism provides an emerging emphasis on extranigral aspects of PD pathology.

CRITICAL ISSUES

Unfortunately, none of the existing animal models of experimental PD completely mimics the etiology, progression, and pathology of human PD.

FUTURE DIRECTIONS

Continued efforts to optimize established animal models of parkinsonism, as well as the development and characterization of new animal models are essential, as there still remains a disconnect in terms of translating mechanistic observations in animal models of experimental PD into bona fide disease-modifying therapeutics for human PD patients.

Mitochondria and programmed cell death in Parkinson's disease: apoptosis and beyond

Abstract Significance: Activation of mitochondrion-dependent programmed cell death (PCD) pathways is instrumental to the demise of substantia nigra pars compacta dopaminergic neurons in experimental mouse models of Parkinson's disease (PD). Supporting the relevance of these findings for PD, key molecular elements of this pathogenic cascade have also been demonstrated in postmortem brain samples of PD patients. Recent Advances and Critical Issues: Mounting evidence indicates that different morphological types of cell death co-exist in the brain of PD patients, all of which may result from the activation of common upstream PCD pathways. Indeed, contrary to initial views, it is now established that the deleterious effects of PCD pathways are not limited to mitochondrion-mediated caspase-dependent apoptosis but also involve caspase-independent nonapoptotic cell death, including necrosis. This notion may help reconcile the observation of both apoptotic and nonapoptotic dopaminergic cell death in postmortem PD samples.

FUTURE DIRECTIONS

Potential neuroprotective strategies for PD should be aimed at targeting both apoptotic and nonapoptotic pathways, all of which may simultaneously occur in PD patients through activation of common upstream PCD pathways involving the mitochondria. Antioxid. Redox Signal. 16, 883-895.

Mechanisms to prevent caspase activation in rotenone-induced dopaminergic neurodegeneration: role of ATP depletion and procaspase-9 degradation

The evidence implicating a mode of cell death that either favors or argues against caspase-dependent apoptosis is available in studies that used experimental models of Parkinson's disease. We sought to investigate the mechanisms by which release of cytochrome c is not linked to caspase activation during rotenone-induced dopaminergic (DA) neurodegeneration. Unlike caspase activation in 6-hydroxydopamine-treated cells, both MN9D DA neuronal cells and primary cultures of mesencephalic neurons showed no obvious signs of caspase activation upon exposure to rotenone. We found that intracellular levels of ATP significantly decreased at the early phase of neurodegeneration (<~24 h) and therefore external addition of ATP to the lysates obtained at this stage reconstituted caspase-3 activity. At a later phase of cell death (>~24 h), both decreased levels of ATP and procaspase-9 contributed to the lack of caspase-3 activation. Under this condition, calpain and the proteasome system were responsible for the degradation of procaspase-9. Consequently, external addition of ATP and procaspase-9 to the lysates harvested at the later phase was required for activation of caspase-3. Similarly, caspase-3 activity was also reconstituted in the lysates harvested from cells co-treated with inhibitors of these proteases and incubated in the presence of external ATP. Taken together, our findings provided a sequential mechanism underlying how DA neurons may undergo caspase-independent cell death, even in the presence of cytoplasmic cytochrome c following inhibition of mitochondrial complex I.

Trimethyltin chloride (TMT) neurobehavioral toxicity in embryonic zebrafish

Trimethyltin chloride (TMT) is a neurotoxicant that is widely present in the aquatic environment, primarily from the manufacture of PVC plastic, but few studies have evaluated aquatic neurotoxicity. We have examined TMT dose-dependent malformation and neurobehavioral toxicity in the embryonic zebrafish model. Exposure of embryos to TMT (0-10 μM) from 48 to 72 hours post fertilization (hpf) elicited a concentration-related increase (0-100%) in malformation incidence with an EC(25) of 5.55 μM. TMT also significantly modulated the frequency of tail flexion, the earliest motor behavior observed in developing zebrafish, and the ability to respond to a mechanical tail touch. Exposure to 5 μM TMT from 48 to 72 hpf modulated the photomotor response at 4 and 5 days post fertilization and significantly promoted apoptosis in the tail. Our study demonstrates the morphological and behavioral sensitivity of the developing zebrafish to TMT and establishes a platform for future identification of the affected pathways and chemical modulators of TMT toxicity.