A study to correlate rotenone induced biochemical changes and cerebral damage in brain areas with neuromuscular coordination in rats

Hesperetin protects against rotenone-induced motor disability and neurotoxicity via the regulation of SIRT1/NLRP3 signaling

Rotenone is a pesticide that causes complex I inhibition and is widely known to induce motor disability and experimental Parkinson's disease (PD) in rodents. Evidence suggests a crucial role for sirtuin/nuclear factor-kappaB/nod-like receptor family, pyrin domain-containing 3 (SIRT1/NFκB/NLRP3) signaling and inflammation in PD and rotenone neurotoxicity. Hesperetin (C16H14O6) is a citrus flavonoid with documented anti-inflammatory activity. We investigated the value of hesperetin in delaying rotenone-induced PD in mice and the possible modulation of inflammatory burden. PD was induced in mice via rotenone injections. Groups were assigned as a vehicle, PD, or PD + hesperetin (50 or 100 mg/kg) and compared for the motor function, protein level (by ELISA), and gene expression (by real-time PCR) of the target proteins, histopathology, and immunohistochemistry for tyrosine hydroxylase enzyme. Hesperetin (50 or 100 mg/kg) alleviated the motor disability and the striatal dopamine level and decreased the expression of NLRP3 and NF-κB but increased SIRT1 expression (p < 0.05). Further, it enhanced the neural viability and significantly decreased neural degeneration in the substantia nigra, hippocampus, and cerebral cortex (p < 0.05). Taken together, we propose that hesperetin mediates its neuroprotective function via alleviating modulation of the SIRT1/NFκB/NLRP3 pathway. Therefore, hesperetin might delay the PD progression.

Effects of fluoride on oxidative DNA damage, nitric oxide level, lipid peroxidation and cholinesterase enzyme activity in a rotenone-induced experimental Parkinson's model

OBJECTIVE

Environmental toxins are known to be one of the important factors in the development of Parkinson's disease (PD). This study was designed to investigate the possible contribution of fluoride (F) exposure to oxidative stress and neurodegeneration in rats with PD induced by rotenone (ROT).

MATERIALS AND METHODS

A total of 72 Wistar albino male rats were used in the experiment and 9 groups were formed with 8 animals in each group. ROT (2 mg/kg) was administered subcutaneously (sc) for 28 days. Different doses of sodium fluoride (NaF) (25, 50 and 100 ug/mL) were given orally (po) for 4 weeks. Malondialdehyde (MDA), glutathione (GSH), nitric oxide (NO), oxidative DNA damage (8-OHdG) and cholinesterase (AChE/BChE) enzyme activities were evaluated in serum and brain tissue homogenates.

RESULTS

Rats treated with ROT and NaF had significant increases in serum and brain MDA, NO content, and decreases in GSH. In addition, the combination of ROT and NaF triggered oxidative DNA damage and resulted in increased AChE/BChE activity.

CONCLUSIONS

Findings suggest that NaF and ROT may interact synergistically leading to oxidative damage and neuronal cell loss. As a result, we believe that exposure to pesticides in combination with NaF is one of the environmental factors that should not be ignored in the etiology of neurological diseases such as PD in populations in areas with endemic fluorosis.

Delayed in sensorimotor reflex ontogeny, slow physical growth, and impairments in behaviour as well as dopaminergic neuronal death in mice offspring following prenatally rotenone administration

The environment is varying day by day with the introduction of chemicals such as pesticides, most of which have not been effectively studied for their influence on a susceptible group of population involving infants and pregnant females. Rotenone is an organic pesticide used to prepare Parkinson's disease models. A lot of literature is available on the toxicity of rotenone on the adult brain, but to the best of our knowledge, effect of rotenone on prenatally exposed mice has never been investigated yet. Therefore, the recent work aims to evaluate the toxic effect of rotenone on mice, exposed prenatally. We exposed female mice to rotenone at the dose of 5 mg/Kg b.w. throughout the gestational period with oral gavage. We then investigated the effects of rotenone on neonate's central nervous systems as well as on postnatal day (PD) 35 offspring. In the rotenone group, we observed slow physical growth, delays in physical milestones and sensorimotor reflex in neonates and induction of anxiety and impairment in cognitive performances of offspring at PD-35. Additionally, immunohistochemical analysis revealed a marked reduction in TH-positive neurons in substantia nigra. Histological examination of the cerebellum revealed a decrease in Purkinje neurons in the rotenone exposed group as compared to the control. The data from the study showed that prenatally exposure to rotenone affects growth, physical milestones, neuronal population and behaviour of mice when indirectly exposed to the offspring through their mother. This study could provide a great contribution to researchers to find out the molecular mechanism and participating signalling pathway behind these outcomes.

β-carotene-loaded nanoparticles protect against neuromotor damage, oxidative stress, and dopamine deficits in a model of Parkinson's disease in Drosophila melanogaster

β-carotene-loaded nanoparticles improves absorption by increasing bioavailability. The Drosophila melanogaster model of Parkinson's disease must be helpful in investigating potential neuroprotective effects. Four groups of four-day-old flies were exposed to: (1) control; (2) diet containing rotenone (500 μM); (3) β-carotene-loaded nanoparticles (20 μM); (4) β-carotene-loaded nanoparticles and rotenone for 7 days. Then, the percentage of survival, geotaxis tests, open field, aversive phototaxis and food consumption were evaluated. At the end of the behaviors, the analyses of the levels of reactive species (ROS), thiobarbituric acid reactive substances (TBARS), catalase (CAT) and superoxide dismutase (SOD) activity was carried out, as well as an evaluation of the levels of dopamine and acetylcholinesterase (AChE) activity, in the head of flies. Nanoparticles loaded with β-carotene were able to improve motor function, memory, survival and also restored the oxidative stress indicators (CAT, SOD, ROS and TBARS), dopamine levels, AChE activity after exposure to rotenone. Overall, nanoparticles loaded with β-carotene showed significant neuroprotective effect against damage induced by the Parkinson-like disease model, emerging as a possible treatment. Overall, β-carotene-loaded nanoparticles presented significant neuroprotective effect against damage induced by model of Parkinson-like disease, emerging as a possible treatment.

Metabolic dysfunctions in the intranigral rotenone model of Parkinson's disease

Parkinson disease (PD) is a chronic neurodegenerative disorder characterized by a progressive loss of dopamine neurons in the substantia nigra pars compacta (SNpc). In the last years, a growing interest to study the relationship between metabolic dysfunction and neurodegenerative disease like PD has emerged. This study aimed to evaluate the occurrence of possible changes in metabolic homeostasis due to intranigral rotenone administration, a neurotoxin that damages dopaminergic neurons leading to motor impairments mimicking those that happen in PD. Male Wistar rats were distributed into two groups: sham (n = 10) or rotenone (n = 10). Sham group received, bilaterally, within the SNpc, 1 µL of vehicle dimethyl-sulfoxide (DMSO) and the experimental group was bilaterally injected with 1 µL of rotenone (12 µg/µL). Twenty-four hours after the stereotaxic surgeries, the animals underwent the open field test followed by subsequent peripheral blood and cerebrospinal fluid (CSF) samples collection for biochemical testing. The results showed that rotenone was able to replicate the typical motor behavior impairment seen in the disease, i.e., decrease in locomotion (P = 0.05) and increase in immobility (P = 0.01) with a strong correlation (r = - 0.85; P < 0.0001) between them. In addition, it was demonstrated that this model is able to decrease plasmatic total-cholesterol (P = 0.04) and HDL-cholesterol (P = 0.007) potentially impacting peripheral metabolism. Hence, it was revealed a potential ability to reproduce relevant metabolic dysfunctions like hyperglycemia which could be explained by acute and systemic mitochondrial rotenone toxicity and SNpc nigral toxicity. Such mechanisms may still be responsible for the potential occurrence of CSF-hyperglycemia (d = 0.7). Since intranigral rotenone is an early phase model of PD, the present results open a new road for studies aiming to investigate metabolic changes in PD.

Pharmacological evaluation of vanillic acid in rotenone-induced Parkinson's disease rat model

In the present study, we investigated the anti-Parkinson's effect of vanillic acid (VA) (12 mg/kg, 25 mg/kg, 50 mg/kg p.o.) against rotenone (2 mg/kg s.c.) induced Parkinson's disease (PD) in rats. The continuous administration of rotenone for 35 days resulted in rigidity in muscles, catalepsy, and decrease in locomotor activity, body weight, and rearing behaviour along with the generation of oxidative stress in the brain (rise in the TBARS, and SAG level and reduced CAT, and GSH levels). Co-treatment of VA and levodopa-carbidopa (100 mg/kg + 25 mg/kg p.o.) lead to a significant (P < 0.001) reduction in the muscle rigidity and catalepsy along with a significant (P < 0.001) increase in body weight, rearing behaviour, locomotion and muscle activity as compared to the rotenone-treated group in the dose dependent manner, showing maximum effect at the 50 mg/kg. It also showed reversal of levels of oxidative stress parameters thus, reducing the neuronal oxidative stress. The level of DA was also estimated which showed an increase in the level of DA in the VA plus standard drug treated animals as compared to rotenone treated group. Histopathological evaluation showed a high number of eosinophilic lesions in the rotenone group which were found to be very less in the VA co-treated group. The study thus proved that co-treatment of VA and levodopa-carbidopa, significantly protected the brain from neuronal damage due to oxidative stress and attenuated the motor defects indicating the possible therapeutic potential of VA as a neuroprotective in PD.

Rapid immunohistological measurement of tyrosine hydroxylase in rat midbrain by near-infrared instrument-based detection

We present a robust, fresh-frozen approach to immunohistochemistry (IHC), without committing the tissue to IHC via fixation and cryopreservation while maintaining long-term storage, using LiCor-based infrared (IR) quantification for sensitive assessment of TH in immunoreacted midbrain sections for quantitative comparison across studies. In fresh-frozen tissue stored up to 1 year prior to IHC reaction, we found our method to be highly sensitive to rotenone treatment in 3-month-old Sprague-Dawley rats, and correlated with a significant decline in rotarod latency-to-fall measurement by approximately 2.5 fold. The measured midbrain region revealed a 31 % lower TH signal when compared to control (p < 0.01 by t test, n = 5). Bivariate analysis of integrated TH counts versus rotarod latency-to-fall indicates a positive slope and modest but significant correlation of R² = 0.68 (p < 0.05, n = 10). These results indicate this rapid, instrument-based quantification method by IR detection successfully quantifies TH levels in rat brain tissue, while taking only 5 days from euthanasia to data output. This approach also allows for the identification of multiple targets by IHC with the simultaneous performance of downstream molecular analysis within the same animal tissue, allowing for the use of fewer animals per study.

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.

Cardinal role of eukaryotic initiation factor 2 (eIF2α) in progressive dopaminergic neuronal death & DNA fragmentation: Implication of PERK:IRE1α:ATF6 axis in Parkinson's pathology

The study was conducted to assess the role of eukaryotic initiation factor 2 (eIF2α) in progressive dopaminergic neuronal death employing various interventions (YM08, 4μ8C, AEBSF, salubrinal, ursolic acid) of endoplasmic reticulum (ER) stress signaling. The protein level of all the ER stress related signaling factors (GRP78, IRE1α, ATF6, eIF2α, ATF4, XBP-1, GADD153) were estimated after 3 and 7 day of experiment initiation. Findings with single administration of interventions showed that salubrinal exhibited significant protection against rotenone induced adverse alterations in comparison to other interventions. Therefore, further study was expanded with repeat dose of salubrinal. Rotenone administration in rat brain caused the significant biochemical alterations, dose dependent progressive neuronal apoptosis and altered neuronal morphology which was significantly attenuated with salubrinal treatment. In conclusion, findings showed that rotenone administration caused the dose dependent progressive neuronal death including cardinal role of eIF2α, suggesting the potential pharmacological utilization of salubrinal or salubrinal like molecules in therapeutics of Parkinson's diseases.

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

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

Mechanistic evaluation of Ursolic acid against rotenone induced Parkinson's disease- emphasizing the role of mitochondrial biogenesis

Parkinson's disease (PD) is an age associated, progressive and a second most common neurodegenerative disease. It is caused due to degeneration of dopaminergic neurons in substantia nigra (SN). Various studies implicate mitochondrial dysfunction, oxidative stress, altered degradation of misfolded proteins in PD pathogenesis. Ursolic acid (UA), a natural pentacyclic triterpenoid carboxylic acid, is reported to possess a number of biological activities viz. anti-oxidant, anti-inflammatory etc. The focus of our study was to assess the neuroprotective potential of UA against the rotenone induced pathophysiological alterations. In this study rats were subjected to stereotaxic bilateral injection of rotenone (12 μg/μl) in SN. Further, they were treated per-orally with UA (5 and 10 mg/kg) for 30 days. During the study, neurobehavioral tests comprising Rota-rod, Open field and Barnes maze (BMT) were conducted. At the end of 30 days, the antioxidant (Reduced glutathione, superoxide dismutase, catalase and lipid peroxidation), inflammatory (TNF-α) parameters, mitochondrial complex I, mitochondrial biogenesis (MB) and immunohistochemical analysis (TH positive neurons, Glial Fibrillary Acidic Protein (GFAP)) was performed. The results exhibited significant amelioration in the motor deficits by UA which can be attributed to the protection of TH positive neurons from degeneration. A significant improvement in the cognitive function due to UA was observed in BMT. Biochemically, the oxidative stress and inflammation triggered by rotenone was significantly diminished by UA. It also significantly obviated the complex I inhibition and promoted MB. The preliminary results thus firmly advocate the neuroprotective potential of UA to prevent rotenone induced neurotoxicity in rats.

Comprehensive Analysis of Neurotoxin-Induced Ablation of Dopaminergic Neurons in Zebrafish Larvae

Neurotoxin exposure of zebrafish larvae has been used to mimic a Parkinson’s disease (PD) phenotype and to facilitate high-throughput drug screening. However, the vulnerability of zebrafish to various neurotoxins was shown to be variable. Here, we provide a direct comparison of ablative effectiveness in order to identify the optimal neurotoxin-mediated dopaminergic (DAnergic) neuronal death in larval zebrafish. Transgenic zebrafish, Tg(dat:eGFP), were exposed to different concentrations of the neurotoxins MPTP, MPP⁺, paraquat, 6-OHDA, and rotenone for four days, starting at three days post-fertilization. The LC₅₀ of each respective neurotoxin concentration was determined. Confocal live imaging on Tg(dat:eGFP) showed that MPTP, MPP⁺, and rotenone caused comparable DAnergic cell loss in the ventral diencephalon (vDC) region while, paraquat and 6-OHDA caused fewer losses of DAnergic cells. These results were further supported by respective gene expression analyses of dat, th, and p53. Importantly, the loss of DAnergic cells from exposure to MPTP, MPP⁺, and rotenone impacted larval locomotor function. MPTP induced the largest motor deficit, but this was accompanied by the most severe morphological impairment. We conclude that, of the tested neurotoxins, MPP⁺ recapitulates a substantial degree of DAnergic ablation and slight locomotor perturbations without systemic defects indicative of a Parkinsonian phenotype.

Prophylactic neuroprotective propensity of Crocin, a carotenoid against rotenone induced neurotoxicity in mice: behavioural and biochemical evidence

Previously we have demonstrated the potential neuroprotective propensity of saffron and Crocin (CR) employing a Drosophila model of Parkinsonism. Rotenone (ROT) has been extensively used as a model neurotoxin to induce Parkinson's disease (PD) like symptoms in mice. In the present study, as a proof of concept we evaluated the efficacy of CR prophylaxis (25 mg/ kg bw/d, 7d) to attenuate ROT(0.5 mg/Kg bw/d,7d) -induced neurotoxic effects in male mice focussing on neurobehavioural assessments and biochemical determinants in the striatum. CR prophylaxis significantly alleviated ROT-induced behavioural alterations such as increased anxiety, diminished exploratory behaviour, decreased motor co-ordination, and grip strength. Concomitantly, we evidenced diminution of oxidative stress markers, enhanced levels of antioxidant enzyme and mitochondrial enzyme function in the striatal region. Further, varying degree of restoration of cholinergic function, dopamine and α-synuclein levels were discernible suggesting the possible mechanism/s of action of CR in this model. Based on our earlier data in flies and in worm model, we propose its use as an adjuvant therapeutic agent in oxidative stress-mediated neurodegenerative conditions such as PD.

Creatine Protects Against Cytosolic Calcium Dysregulation, Mitochondrial Depolarization and Increase of Reactive Oxygen Species Production in Rotenone-Induced Cell Death of Cerebellar Granule Neurons

Rotenone is a neurotoxin that is an active component of many pesticides which has been shown to induce Parkinsonism in animal models. We show that the cytotoxicity of exposure to nanomolar concentrations of rotenone in cultures of mature cerebellar granule neurons (CGN) in serum-free medium is not due to phagocytosis by glial contamination. A concentration as low as 5.65 ± 0.51 nM of rotenone was enough to trigger 50% cell death of mature CGN in culture after 12 h. The addition of serum proteins to the culture medium attenuated rotenone neurotoxicity, and this can account at least in part for the requirement of higher rotenone concentrations to elicit neuronal cytotoxicity reported in previous works. Creatine partial protection against CGN death promoted by 5 nM rotenone correlated with creatine protection against rotenone-induced mitochondrial depolarization and oxidative stress. Furthermore, creatine largely attenuated the early dysregulation of cytosolic Ca²⁺ concentration after acute rotenone treatment. Noteworthy, our results also revealed that the sustained alteration of Ca²⁺ homeostasis induced by rotenone takes place at the onset of the enhancement of intracellular oxidative stress and before mitochondrial depolarization, pointing out that cytosolic Ca²⁺ dysregulation is a very early event in the rotenone toxicity to CGN.

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

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

Minocycline diminishes the rotenone induced neurotoxicity and glial activation via suppression of apoptosis, nitrite levels and oxidative stress

The study was conducted to evaluate the effect of minocycline against pesticide rotenone induced adverse effects in different rat brain regions. Assessment of oxidative stress, nitrite levels, degenerating neurons and level of cleaved caspase-3 was done in frontal cortex, mid brain, hippocampus and striatum regions of rat brain. In addition the expression profile of neuronal (MAP2), astrocytes (GFAP) and microglia (cd11b) markers was done after treatments. Rotenone induced DNA fragmentation was also assessed in all studied rat brain regions by utilizing comet assay. Rotenone administration caused significantly decreased level of glutathione along with increased level of nitrite and lipid peroxidation. Significant oxidative and nitrosative stress was also observed after rotenone administration which was considerably inhibited in minocycline treated rats in time dependent manner. Fluorojade staining and levels of cleaved caspase 3 showed the degeneration of neurons and apoptosis respectively in studied rat brain regions which were further inhibited with minocycline treatment. Rotenone administration caused significantly increased reactivity of astrocytes, microglia and altered neuronal morphology in rat brain regions which was also partially restored with minocycline treatment. In conclusion, present study showed that minocycline treatment attenuated the rotenone induced oxidative stress, nitrite level, degeneration of neurons, augmented glial reactivity and apoptosis.

Crosstalk between Ca2+ signaling and mitochondrial H2O2 is required for rotenone inhibition of mTOR signaling pathway leading to neuronal apoptosis

Rotenone, a neurotoxic pesticide, induces loss of dopaminergic neurons related to Parkinson's disease. Previous studies have shown that rotenone induces neuronal apoptosis partly by triggering hydrogen peroxide (H₂O₂)-dependent suppression of mTOR pathway. However, the underlying mechanism is not fully understood. Here, we show that rotenone elevates intracellular free calcium ion ([Ca²⁺]_i) level, and activates CaMKII, resulting in inhibition of mTOR signaling and induction of neuronal apoptosis. Chelating [Ca²⁺]_i with BAPTA/AM, preventing extracellular Ca²⁺ influx using EGTA, inhibiting CaMKII with KN93, or silencing CaMKII significantly attenuated rotenone-induced H₂O₂ production, mTOR inhibition, and cell death. Interestingly, using TTFA, antimycin A, catalase or Mito-TEMPO, we found that rotenone-induced mitochondrial H₂O₂ also in turn elevated [Ca²⁺]_i level, thereby stimulating CaMKII, leading to inhibition of mTOR pathway and induction of neuronal apoptosis. Expression of wild type mTOR or constitutively active S6K1, or silencing 4E-BP1 strengthened the inhibitory effects of catalase, Mito-TEMPO, BAPTA/AM or EGTA on rotenone-induced [Ca²⁺]_i elevation, CaMKII phosphorylation and neuronal apoptosis. Together, the results indicate that the crosstalk between Ca²⁺ signaling and mitochondrial H₂O₂ is required for rotenone inhibition of mTOR-mediated S6K1 and 4E-BP1 pathways. Our findings suggest that how to control over-elevation of intracellular Ca²⁺ and overproduction of mitochondrial H₂O₂ may be a new approach to deal with the neurotoxicity of rotenone.

Neuroprotective effect of curcumin as evinced by abrogation of rotenone-induced motor deficits, oxidative and mitochondrial dysfunctions in mouse model of Parkinson's disease

Curcumin, a natural polyphenolic compound extracted from rhizomes of Curcuma longa (turmeric), a plant in the ginger family (Zingiberaceae) has been used worldwide and extensively in Southeast Asia. Curcumin exhibited numerous biological and pharmacological activities including potent antioxidant, cardiovascular disease, anticancer, anti-inflammatory effects and neurodegenerative disorders in cell cultures and animal models. Hence, the present study was designed in order to explore the possible neuroprotective role of curcumin against rotenone induced cognitive impairment, oxidative and mitochondrial dysfunction in mice. Chronic administration of rotenone (1mg/kg i.p.) for a period of three weeks significantly impaired cognitive function (actophotometer, rotarod and open field test), oxidative defense (increased lipid peroxidation, nitrite concentration and decreased activity of superoxide dismutase, catalase and reduced glutathione level) and mitochondrial complex (II and III) enzymes activities as compared to normal control group. Three weeks of curcumin (50, 100 and 200mg/kg, p.o.) treatment significantly improved behavioral alterations, oxidative damage and mitochondrial enzyme complex activities as compared to negative control (rotenone treated) group. Curcumin treated mice also mitigated enhanced acetylcholine esterase enzyme level as compared to negative control group. We found that curcumin restored motor deficits and enhanced the activities of antioxidant enzymes suggesting its antioxidant potential in vivo. The findings of the present study conclude neuroprotective role of curcumin against rotenone induced Parkinson's in mice and offer strong justification for the therapeutic prospective of this compound in the management of PD.

Thiol Oxidation by Diamide Leads to Dopaminergic Degeneration and Parkinsonism Phenotype in Mice: A Model for Parkinson's Disease

AIMS

This study investigates the role of thiol homeostasis disruption in Parkinson's disease (PD) pathogenesis using a novel animal model. A single unilateral administration of the thiol oxidant, diamide (1.45 μmol) into substantia nigra (SN) of mice leads to locomotor deficits and degeneration of dopaminergic (DA) neurons in SN pars compacta (SNpc).

RESULTS

Diamide-injected mice showed hemiparkinsonian behavior, measured as spontaneous contralateral body rotations, poor grip strength, and impaired locomotion on a rotarod. We observed a significant loss of DA neurons in ipsilateral but not contralateral SNpc and their striatal fibers. This was accompanied by increased Fluoro-Jade C-positive cells and a loss of NeuN-positive neurons, indicative of neurodegeneration. Importantly, diamide injection led to α-synuclein aggregation in ipsilateral SNpc, a hallmark of PD pathology not often seen in animal models of PD. On investigating putative mechanism(s) involved, we observed a loss of glutathione, which is essential for maintaining protein thiol homeostasis (PTH). Concomitantly, the redox-sensitive ASK1-p38 mitogen-activated protein kinase (MAPK) death signaling pathway was activated in the ipsilateral but not contralateral ventral midbrain through dissociation of ASK1-Trx1 complex. In Neuro-2a cells, diamide activated ASK1-p38 cascade through Trx1 oxidation, leading to cell death, which was abolished by ASK1 knockdown.

INNOVATION

Since diamide selectively disrupts PTH, DA neurons appear to be vulnerable to such perturbations and even a single insult with a thiol oxidant can result in long-lasting degeneration.

CONCLUSION

Identification of the role of PTH dysregulation in neurodegeneration, especially in early PD, not only facilitates an understanding of novel regulatory features of molecular signaling cascades but also may aid in developing disease-modifying strategies for PD. Antioxid. Redox Signal. 25, 252-267.

The novel mechanism of rotenone-induced α-synuclein phosphorylation via reduced protein phosphatase 2A activity

Rotenone has been shown to induce many parkinsonian features and has been widely used in chemical models of Parkinson's disease (PD). Its use is closely associated with α-synuclein (α-syn) phosphorylation both in vivo and in vitro. However, the mechanisms whereby rotenone regulates α-syn phosphorylation remain unknown. Protein phosphatase 2A (PP2A) has been shown to play an important role in α-syn dephosphorylation. We therefore investigated if rotenone caused α-syn phosphorylation by down-regulation of PP2A activity in mice. Rotenone increased the phosphorylation of α-syn at Ser129, consistent with the inhibition of PP2A activity by increased phosphorylation of tyrosine 307 at the catalytic subunit of PP2A (pTyr307 PP2Ac). We further explored the interactions among rotenone, PP2A, and α-syn in SK-N-SH cells and primary rat cortical neurons. Rotenone inhibited PP2A activity via phosphorylation of PP2Ac at Tyr307. The reduction in PP2A activity and rotenone cytotoxicity were reversed by treatment with the PP2A agonist, C2 ceramide, and the Src kinase inhibitor, SKI606. Immunoprecipitation experiments showed that rotenone induced an increase in calmodulin-Src complex in SK-N-SH cells, thus activating Src kinase, which in turn phosphorylated PP2A at Tyr307 and inhibited its activity. C2 ceramide and SKI606 significantly reversed the rotenone-induced phosphorylation and aggregation of α-syn by increasing PP2A activity. These results demonstrate that rotenone-reduced PP2A activity via Src kinase is involved in the phosphorylation of α-syn. These findings clarify the novel mechanisms whereby rotenone can induce PD.

Curcumin ameliorates dopaminergic neuronal oxidative damage via activation of the Akt/Nrf2 pathway

Parkinson's disease (PD) is an age-related complex neurodegenerative disease that affects ≤ 80% of dopaminergic neurons in the substantia nigra pars compacta (SNpc). It has previously been suggested that mitochondrial dysfunction, oxidative stress and oxidative damage underlie the pathogenesis of PD. Curcumin, which is a major active polyphenol component extracted from the rhizomes of Curcuma longa (Zingiberaceae), has been reported to exert neuroprotective effects on an experimental model of PD. The present study conducted a series of in vivo experiments, in order to investigate the effects of curcumin on behavioral deficits, oxidative damage and related mechanisms. The results demonstrated that curcumin was able to significantly alleviate motor dysfunction and increase suppressed tyrosine hydroxylase (TH) activity in the SNpc of rotenone (ROT)-injured rats. Biochemical measurements indicated that rats pretreated with curcumin exhibited increased glutathione (GSH) levels, and reduced reactive oxygen species activity and malondialdehyde content. Mechanistic studies demonstrated that curcumin significantly restored the expression levels of heme oxygenase-1 and

NAD(P)H

quinone oxidoreductase 1, thus ameliorating ROT-induced damage in vivo, via the phosphorylation of Akt and nuclear factor erythroid 2-related factor 2 (Nrf2). Further studies indicated that the Akt/Nrf2 signaling pathway was associated with the protective role of curcumin in ROT-treated rats. Inhibiting the Akt/Nrf2 pathway using a lentiviral vector containing Nrf2-specific short hairpin RNA, or the phosphoinositide 3-kinase inhibitor LY294002, markedly reduced the expression levels of TH and GSH, ultimately attenuating the neuroprotective effects of curcumin against oxidative damage. These results indicated that curcumin was able to significantly ameliorate ROT-induced dopaminergic neuronal oxidative damage in the SNpc of rats via activation of the Akt/Nrf2 signaling pathway.

Endoplasmic Reticulum Stress Instigates the Rotenone Induced Oxidative Apoptotic Neuronal Death: a Study in Rat Brain

The present study was conducted to evaluate the involvement of endoplasmic reticulum stress in rotenone-induced oxidative neuronal death in rat brain. Rotenone (6 μg/3 μl) was administered intranigrally, unilaterally (right side) in SD rat brain. Neuronal morphology, expression level of tyrosine hydroxylase (TH) and endoplasmic reticulum (ER) stress markers like glucose-regulated protein 78 (GRP78), growth arrest and DNA damage-inducible gene 153 (GADD153), eukaryotic translation initiation factor 2α (p-eIF2α/eIF2α) and cleaved caspase-12 were estimated in the rat brain. Levels of reactive oxygen species (ROS), reduced glutathione (GSH) and enzymatic activities of glutathione peroxidase (GPx) and glutathione reductase (GRd) were estimated to assess the rotenone induced oxidative stress. Apoptotic death of neurons was assessed by estimating the mRNA level of caspase-3. Rotenone administration caused altered neuronal morphology, decreased expression of TH, augmented ROS level, decreased level of GSH and decreased activities of GPx and GRd enzymes which were significantly attenuated with the pretreatment of ER stress inhibitor, salubrinal (1 mg/kg, intraperitoneal). Significantly increased levels of GRP78, GADD, dephosphorylated eIF2α and cleaved caspase-12 was also observed after rotenone administration, which was inhibited with the pretreatment of salubrinal. Rotenone-induced increased mRNA level of caspase-3 was also attenuated by pretreatment of salubrinal. Findings suggested that salubrinal treatment significantly inhibited the rotenone-induced neurotoxicity implicating that ER stress initiates the rotenone-induced oxidative stress and neuronal death.

Astrocyte activation and neurotoxicity: A study in different rat brain regions and in rat C6 astroglial cells

The present study was conducted to investigate the effect of rotenone on astrocytes activation, their viability and its effect on neuronal death in different brain regions. Rotenone was injected in rat brain by intracerebroventricularly (bilateral) route at dose of 6 μg and 12 μg. In vitro C6 cells were treated with rotenone at concentration of 0.1, 0.25, 0.5, 1 and 2 μM. Rotenone administration to rat brain caused significant astrocytes activation in frontal cortex, cerebellum, cerebellar nucleus, substantia nigra, hypothalamus and hippocampus regions of the rat brain. Rotenone administration also led to significant degeneration of cells in all the studied regions along with altered nuclear morphology assessed by hematoxylin-eosin and cresyl violet staining. Histological staining showed the significantly decreased number of cells in all the studied regions except cerebellar nucleus in dose and time dependant manner. Rotenone administration in the rat brain also caused significant decrease in glutathione levels and augmented nitrite levels. In vitro treatment of rotenone to astrocytic C6 cells caused significantly increased expression of glial fibrillar acidic protein (GFAP) and decreased viability in dose and time dependent manner. Rotenone treatment to C6 cells exhibited significant generation of reactive oxygen species, augmented nitrite level, impaired mitochondrial activity, apoptotic chromatin condensation and DNA damage in comparison to control cells. Findings showed that oxidative stress play a considerable role in rotenone induced astrocyte death that was attenuated with co-treatment of antioxidant melatonin. In conclusion, results showed that rotenone caused significant astrocytes activation, altered nuclear morphology, biochemical alteration and apoptotic cell death in different rat brain regions. In vitro observations in C6 cells showed that rotenone treatment exhibited oxidative stress mediated apoptotic cell death, which was attenuated with co treatment of melatonin.

Endoplasmic Reticulum Stress Plays a Key Role in Rotenone-Induced Apoptotic Death of Neurons

Rotenone, a pesticide, causes neurotoxicity via the mitochondrial complex-I inhibition. The present study was conducted to evaluate the role of endoplasmic reticulum (ER) stress in rotenone-induced neuronal death. Cell viability, cytotoxicity, reactive oxygen species (ROS) generation, nitrite level, mitochondrial membrane potential (MMP), and DNA damage were assessed in rotenone-treated neuro-2A cells. Protein levels of ER stress markers glucose regulated protein 78 (GRP78), growth arrest- and DNA damage-inducible gene 153 (GADD153), and phosphorylation of eukaryotic translation initiation factor 2 subunit α (eIF2-α) were estimated to assess the ER stress. To confirm the apoptotic death of neurons, mRNA levels of caspase-9, caspase-12 and caspase-3 were estimated. Further, to confirm the involvement of ER stress, neuro-2A cells were pretreated with ER stress inhibitor salubrinal. Co-treatment of antioxidant melatonin was also given to assess the role of oxidative stress in rotenone-induced apoptosis. Rotenone (0.1, 0.5, and 1 μM) treatment to neurons caused significantly decreased cell viability, increased cytotoxicity, increased ROS generation, increased expression of GRP78 and GADD, DNA damage and activation of caspase-12 and caspase-3 which were significantly attenuated by pretreatment of salubrinal (25 μM). Rotenone-induced dephosphorylation of eIF2α was also inhibited with salubrinal treatment. However, pretreatment of salubrinal did not affect the rotenone-induced increased nitrite levels, decreased MMP and caspase-9 activation. Co-treatment of antioxidant melatonin (1 mM) did not offer attenuation against rotenone-induced increased expression of caspase-9, caspase-12 and caspase-3. In conclusion, results indicated that ER stress plays a key role in rotenone-induced neuronal death, rather than oxidative stress. Graphical Abstract Pictorial presentation showed the involvement of endoplasmic reticulum (ER) stress, increased reactive oxygen species (ROS), nitrite level, decreased mitochondrial membrane potential (MMP), caspase activation and DNA damage in neuronal cells after rotenone treatment. ER stress inhibitor-salubrinal showed significant attenuation against most of the rotenone-induced adverse effects reflecting its key involvement in rotenone-induced neuronal death.

The rotenone-induced rat model of Parkinson's disease: behavioral and electrophysiological findings

Exposure to rotenone leads to parkinsonian features, such as loss of dopaminergic neurons in the substantia nigra and motor impairment, however, the validity of this model has recently been questioned. In rodent and monkey models of Parkinson's disease (PD) abnormal neuronal activity in the basal ganglia motor loop has been described, with hyperactivity of the subthalamic nucleus (STN) similar to that found in PD. The present study aims at providing new and more specific evidence for the validity of the rotenone rat model of PD by examining whether neuronal activity in the STN is altered. Male Sprague Dawley rats were treated with rotenone injections (2.5mg/kg bodyweight intraperitoneally) for 60 days. Behavioral analysis showed an impairment in the rotarod and hanging wire test in the rotenone group (p<0.05), accompanied by a decline in tyrosine hydroxylase immunoreactive neurons in the nigro-striatal region (p<0.001). Thereafter, single unit (SU) activities and local field potentials were recorded in the STN in urethane anesthetized rats. The SU analysis revealed a higher neuronal discharge rate (p<0.001), more bursts per minute (p=0.006) and a higher oscillatory activity (p=0.008) in the STN of rotenone treated rats. Spectral analysis showed an increase of relative beta power in the STN as well as in the motor cortex. We found electrophysiological key features of PD pathology and pathophysiology in the STN of rotenone treated rats. Therefore, the rotenone-induced rat model of PD deserves further attention since it covers more aspects than dopamine depletion and implies the reproducibility of PD specific features.

Standardized extract of Withania somnifera (Ashwagandha) markedly offsets rotenone-induced locomotor deficits, oxidative impairments and neurotoxicity in Drosophila melanogaster

Withania somnifera (Ashwagandha, WS) or Indian ginseng possesses multiple pharmacological properties which are mainly attributed to the active constituents, withanolides. Despite its extensive usage as a memory enhancer and a nerve tonic, few attempts have been made to ascertain its usage in the management of Parkinson's disease. In the present study, we investigated the neuroameliorative effects of WS in a rotenone (ROT) model of Drosophila melanogaster (Oregon-K). Initially, we ascertained the ability of WS-enriched diet (0-0.05 %) to protect against ROT induced lethality and locomotor phenotype in adult male flies. Further, employing a co-exposure paradigm, we investigated the propensity of WS to offset ROT-induced oxidative stress, mitochondrial dysfunctions and neurotoxicity. WS conferred significant protection against ROT-induced lethality, while the survivor flies exhibited improved locomotor phenotype. Biochemical investigations revealed that ROT-induced oxidative stress was significantly diminished by WS enrichment. WS caused significant elevation in the levels of reduced GSH/non-protein thiols. Furthermore, the altered activity levels of succinate dehydrogenase, MTT, membrane bound enzymes viz., NADH-cytochrome-c reductase and succinate-cytochrome-c reductase were markedly restored to normalcy. Interestingly, ROT-induced perturbations in cholinergic function and depletion in dopamine levels were normalized by WS. Taken together these data suggests that the neuromodulatory effect of WS against ROT- induced neurotoxicity is probably mediated via suppression of oxidative stress and its potential to attenuate mitochondrial dysfunctions. Our further studies aim to understand the underlying neuroprotective mechanisms of WS and withanolides employing neuronal cell models.

Rotenone-induced oxidative stress and apoptosis in human liver HepG2 cells

Rotenone, a commonly used pesticide, is well documented to induce selective degeneration in dopaminergic neurons and motor dysfunction. Such rotenone-induced neurodegenration has been primarily suggested through mitochondria-mediated apoptosis and reactive oxygen species (ROS) generation. But the status of rotenone induced changes in liver, the major metabolic site is poorly investigated. Thus, the present investigation was aimed to study the oxidative stress-induced cytotoxicity and apoptotic cell death in human liver cells-HepG2 receiving experimental exposure of rotenone (12.5-250 μM) for 24 h. Rotenone depicted a dose-dependent cytotoxic response in HepG2 cells. These cytotoxic responses were in concurrence with the markers associated with oxidative stress such as an increase in ROS generation and lipid peroxidation as well as a decrease in the glutathione, catalase, and superoxide dismutase levels. The decrease in mitochondrial membrane potential also confirms the impaired mitochondrial activity. The events of cytotoxicity and oxidative stress were found to be associated with up-regulation in the expressions (mRNA and protein) of pro-apoptotic markers viz., p53, Bax, and caspase-3, and down-regulation of anti-apoptotic marker Bcl-2. The data obtain in this study indicate that rotenone-induced cytotoxicity in HepG2 cells via ROS-induced oxidative stress and mitochondria-mediated apoptosis involving p53, Bax/Bcl-2, and caspase-3.

Rotenone-induced neurotoxicity in rat brain areas: a study on neuronal and neuronal supportive cells

The present study was conducted to correlate rotenone-induced neurotoxicity with cellular and molecular modifications in neuronal and neuronal supportive cells in rat brain regions. Rotenone was administered (3, 6 and 12 μg/μl) intranigrally in adult male Sprague-Dawley rats. After the 7th day of rotenone treatment, specific protein markers for neuronal cells - tyrosine hydroxylase (TH), astroglial cells - glial fibrillary acidic protein (GFAP), microglial cells - CD11b/c, and Iba-1 were evaluated by immunoblotting and immunofluorescence in the striatum (STR) and mid brain (MB). Apoptotic cell death was assessed by caspase-3 gene expression. Higher doses of rotenone significantly lowered TH protein levels and elevated Iba-1 levels in MB. All the doses of rotenone significantly increased GFAP and CD11b/c protein in the MB. In STR, rotenone elevated GFAP levels but did not affect TH, CD11b/c and Iba-1 protein levels. Caspase-3 expression was increased significantly by all the doses of rotenone in MB but in STR only by higher doses (6 and 12 μg). It may be suggested that astroglial activation and apoptosis play an important role in rotenone-induced neurotoxicity. MB appeared as more sensitive than STR toward rotenone-induced cell toxicity. The astroglial cells emerged as more susceptible than neuronal and microglial cells to rotenone in STR.

Astrocyte activation: a key step in rotenone induced cytotoxicity and DNA damage

Astrocytes are the most abundant glial cells, which provide metabolic support for neurons. Rotenone is a botanical pesticide of natural origin, known to exhibit neurotoxic potential via inhibition of mitochondrial complex-I. This study was carried out to explore the effect of rotenone on C6 cells. The cell line C6 derived from rat glioma cells represents astrocyte-like cell. C6 cells were treated with rotenone (0.1, 1 and 10 μM) for 4 h. The effect of rotenone was studied on cell survival (MTT reduction and PI uptake); free radicals (ROS and RNS) and DNA damage (comet assay and Hoechst staining). The glial cell activation and apoptotic cell death was evaluated by expression of Glial fibrillary acidic protein (GFAP) and caspase-3 respectively. The treatment with rotenone resulted in decreased cell survival and increased free radical generation. Altered nuclear morphology and DNA damage were evident following rotenone treatment in Hoechst staining and Comet assay. Rotenone elevated expression of GFAP and caspase-3 that indicates glial cell activation and apoptosis, respectively. We further studied the effect of melatonin, an antioxidant, on the observed toxic effects. Co-incubation of antioxidant, melatonin (300 μM), significantly suppressed rotenone induced above-mentioned effects in C6 cells. Inhibitory effects of melatonin suggest that free radicals play a major role in rotenone induced astrocyte activation and cellular toxicity leading to apoptosis of astroglial cells.

Induction of apoptotic erythrocyte death by rotenone

The pesticide rotenone stimulates apoptosis and rotenone intoxication has been considered a cause of Parkinson's disease. Rotenone further sensitizes tumor cells to cytotoxic drugs. The apoptotic effect of rotenone is at least partially due to mitochondrial injury. Even though lacking mitochondria and nuclei, erythrocytes may undergo eryptosis, an apoptosis-like suicidal death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine-exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+)-activity ([Ca(2+)](i)) and enhanced ceramide formation. The present study explored, whether rotenone elicits eryptosis. To this end, [Ca(2+)](i) was estimated utilizing Fluo3-fluorescence, cell volume from forward scatter, phosphatidylserine-exposure from annexin-V-binding, ceramide utilizing fluorescence antibodies and hemolysis from hemoglobin release. A 48 h exposure to rotenone significantly increased Fluo3-fluorescence(i) (≥1 μM), increased ceramide abundance (10 μM), decreased forward scatter (≥2.5 μM) and increased annexin-V-binding (≥ 1 μM). Rotenone exposure was further followed by slight but significant hemolysis. Rotenone-induced cell membrane scrambling was significantly blunted, but not completely abrogated by removal of extracellular Ca(2+). The present observations disclose a novel effect of rotenone, i.e. triggering of erythrocyte shrinkage and cell membrane scrambling, an effect paralleled by and partially dependent on Ca(2+)-entry.

Rotenone-induced apoptosis and role of calcium: a study on Neuro-2a cells

Rotenone causes cytotoxicity in astrocytic cell culture by glial activation, which is linked to free radical generation. The present study is an investigation to explore whether rotenone could also cause cellular toxicity in mouse neuroblastoma cells (Neuro-2a) under treatment similar to astroglial cells. The effect of rotenone (0.1, 1, and 10 μM) on mitochondrial dehydrogenase enzyme activity by MTT reduction assay, PI uptake, total reactive oxygen species (ROS)/superoxide levels, nitrite levels, extent of DNA damage (by comet assay), and nuclear morphological alteration by Hoechst staining was studied. Caspase-3 and Ca⁺²/calmodulin-dependent protein kinase II (CaMKIIα) gene expression was determined to evaluate the apoptotic cell death and calcium kinase, respectively. Calcium level was estimated fluorometrically using fura-2A stain. Rotenone decreased mitochondrial dehydrogenase enzyme activity and generated ROS, superoxide, and nitrite. Rotenone treatment impaired cell intactness and nuclear morphology as depicted by PI uptake and chromosomal condensation of Neuro-2a cells, respectively. In addition, rotenone resulted in increased intracellular Ca⁺² level, caspase-3, and CaMKIIα expression. Furthermore, co-exposure of melatonin (300 μM), an antioxidant to cell culture, significantly suppressed the rotenone-induced decreased mitochondrial dehydrogenase enzyme activity, elevated ROS and RNS. However, melatonin was found ineffective to counteract rotenone-induced increased PI uptake, altered morphological changes, DNA damage, elevated Ca⁺², and increased expression of caspase-3 and CaMKIIα. The study indicates that intracellular calcium rather than oxidative stress is a major factor for rotenone-induced apoptosis in neuronal cells.

Protection by an antioxidant of rotenone-induced neuromotor decline, reactive oxygen species generation and cellular stress in mouse brain

Exposure to environmental toxins, including rotenone, results in central nervous system and systemic toxicity. Rotenone is a widely used pesticide and a mitochondrial complex I (CI) inhibitor. This study reports effectiveness of a synthetic lipoylcarnitine antioxidant compound, lipoylcarnitine methyl ester iodide (PMX-500F), for treatment of chronic rotenone induced neurological deficits in mice. Mice (C57BL/6NTac; two months of age) received oral administration of rotenone (30 mg/kg/day) or vehicle, preceded by intraperitoneal injection of PMX-500F (19 mg/kg) or vehicle for four weeks. In the Rota-rod test, rotenone treatment had no effect (P>0.05); however, PMX-500F treatment improved locomotor coordination and endurance (latency to fall time; P<0.05). For neuromuscular strength (wire hang test), rotenone treated mice showed reduced latency to fall compared to control mice (P<0.05). PMX-500F treatment improved the outcome in both control and rotenone exposed mice (P<0.05). Rotenone administration increased ROS generation in the forebrain and midbrain regions, but not in the cerebellum (P<0.05). Co-treatment with PMX-500F normalized the ROS in forebrain and midbrain regions to that of the control concentrations. In rotenone administered mice, activated stress-activated protein kinase/c-Jun NH2-terminal kinase (pSAPK/JNK) was higher in forebrain and midbrain lysates than in control mice (P<0.05) and treatment with PMX-500F reduced pSAPK/JNK to control levels. The pSAPK/JNK levels in the cerebellum were similar in all four groups (P>0.05). Total SAPK/JNK was not altered by either rotenone or PMX-500F treatment (P>0.05). These results illustrate that an antioxidant, here PMX-500F, provides protection against rotenone induced decline in neuromotor function, reactive oxygen species (ROS) generation and cellular stress.

Development and characterisation of a novel rat model of Parkinson's disease induced by sequential intranigral administration of AAV-α-synuclein and the pesticide, rotenone

Modeling Parkinson's disease remains a major challenge for preclinical researchers, as existing models fail to reliably recapitulate all of the classic features of the disease, namely, the progressive emergence of a bradykinetic motor syndrome with underlying nigrostriatal α-synuclein protein accumulation and nigrostriatal neurodegeneration. One limitation of the existing models is that they are normally induced by a single neuropathological insult, whereas the human disease is thought to be multifactorial with genetic and environmental factors contributing to the disease pathogenesis. Thus, in order to develop a more relevant model, we sought to determine if administration of the Parkinson's disease-associated pesticide, rotenone, into the substantia nigra of rats overexpressing the Parkinson's disease-associated protein, α-synuclein, could reliably model the triad of classic features of the human disease. To do so, rats underwent stereotaxic surgery for unilateral delivery of the adeno-associated virus (AAV)-α-synuclein into the substantia nigra. This was followed 13 weeks later by delivery of rotenone into the same site. The effect of the genetic and environmental insults alone or in combination on lateralised motor performance (Corridor, Stepping, and Whisker Tests), nigrostriatal integrity (tyrosine hydroxylase immunohistochemistry), and α-synucleinopathy (α-synuclein immunohistochemistry) was assessed. We found that rats treated with either AAV-α-synuclein or rotenone developed significant motor dysfunction with underlying nigrostriatal neurodegeneration. However, when the genetic and environmental insults were sequentially administered, the detrimental impact of the combined insults on motor performance and nigrostriatal integrity was significantly greater than the impact of either insult alone. This indicates that sequential exposure to relevant genetic and environmental insults is a valid approach to modeling human Parkinson's disease in the rat.

Bacopa monnieri extract offsets rotenone-induced cytotoxicity in dopaminergic cells and oxidative impairments in mice brain

Bacopa monnieri (BM), an ayurvedic medicinal herb is widely known for its memory enhancing ability and improvement of brain function. In this study, we tested the hypothesis that BM extract (BME) could offset neurotoxicant-induced oxidative dysfunctions in developing brain in a rotenone (ROT) mouse model. Pretreatment of dopaminergic (N27 cell lines) cells with BME exhibited significant cytoprotective effect as evidenced by the attenuation of ROT-induced oxidative stress and cell death. Further, the neuroprotective efficacy of BME was assessed in prepubertal mice administered ROT (i.p. 1.0 mg/kg b.w./day) for 7 days. BME treatment significantly offset ROT-induced oxidative damage in striatum (St) and other brain regions as evident by the normalized levels of oxidative markers (malondialdehyde, ROS levels, and hydroperoxides) and restoration of depleted GSH levels. Further, BME effectively normalized the protein carbonyl content in all brain regions suggesting its ability to prevent protein oxidation. Furthermore, BME treatment restored the activity levels of cytosolic antioxidant enzymes, neurotransmitter function, and dopamine levels in St. Based on our findings, we hypothesize that the neuroprotective effects of BM extract may be at least in part related to its ability to enhance reduced glutathione and antioxidant defenses in brain regions. It is suggested that BM may be effectively exploited as a prophylactic/therapeutic adjuvant for neurodegenerative disorders involving oxidative stress.