Behavioral and immunohistochemical effects of chronic intravenous and subcutaneous infusions of varying doses of rotenone

Effects and mechanisms of bisphenols exposure on neurodegenerative diseases risk: A systemic review

Environmental bisphenols (BPs) pose a global threat to human health because of their extensive use as additives in plastic products. BP residues are increasing in various environmental media (i.e., water, soil, and indoor dust) and biological and human samples (i.e., serum and brain). Both epidemiological and animal studies have determined an association between exposure to BPs and an increased risk of neurodegenerative diseases (e.g., Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis), including cognitive abnormalities and behavioral disturbances. Hence, understanding the biological responses to different BPs is essential for prevention, and treatment. This study provides an overview of the underlying pathogenic molecular mechanisms as a valuable basis for understanding neurodegenerative disease responses to BPs, including accumulation of misfolded proteins, reduction of tyrosine hydroxylase and dopamine, abnormal hormone signaling, neuronal death, oxidative stress, calcium homeostasis, and inflammation. These findings provide new insights into the neurotoxic potential of BPs and ultimately contribute to a comprehensive health risk evaluation.

Sericin alleviates motor dysfunction by modulating inflammation and TrkB/BDNF signaling pathway in the rotenone-induced Parkinson's disease model

BACKGROUND

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by the degeneration of nigrostriatal dopaminergic neurons and movement impairment. Based on theories, neuroinflammatory processes may be vital in the etiology of PD and other neurodegenerative diseases. Reports show that rotenone has neurotoxic, inflammatory, and motor impairment effects in PD. Sericin is a natural polymer with effective properties, such as neuroprotective and anti-inflammatory. Therefore, this study aimed to examine the effects of sericin administration on motor dysfunction by modulating inflammation and tyrosine kinase B/brain-derived neurotrophic factor (TrkB/BDNF) pathway in the rotenone-induced PD model.

METHODS

Wistar male rats (3-months-old) were treated with rotenone (2 mg/kg every 48 h for 30 days) to induce a rotenone-induced PD model. Also, sericin was administered orally at dose of 200 mg/kg every 48 h for 30 days. Rotarod and bar tests were performed for motor dysfunction. The protein levels of BDNF, c-fos, TrkB, tumor necrosis factor- α (TNF-α), interleukin-6 (IL-6) and catalase activity were evaluated in the striatum area.

RESULTS

Results showed that sericin increased latent time in the rotarod test and decreased the time staying on the pole in the bar test compared to the PD group (P < 0.001 for both tests). Moreover, sericin treatments decreased TNF-α (P < 0.001) and IL-6 (P < 0.001) concentration levels and enhanced the levels of BDNF (P < 0.001), c-fos (P < 0.001), TrkB (P < 0.001) proteins and catalase activity (P < 0.05) in the striatum area compared to the PD group.

CONCLUSION

These results support a protective benefit of sericin therapy in a rotenone-induced PD paradigm by reducing motor impairment, inflammatory response, and disruption of the TrkB/BDNF signaling pathway.

Neuroprotective effects of isatin and afobazole in rats with rotenone-induced Parkinsonism are accompanied by increased brain levels of Triton X-100 soluble alpha-synuclein

Effects of the endogenous neuroprotector isatin and the pharmacological drug afobazole (exhibiting neuroprotective properties) on behavioral reactions and quantitative changes in the brain proteomic profile have been investigated in rats with experimental rotenone Parkinsonism. A single dose of isatin (100 mg/kg subcutaneously on the last day of a 7-day course of rotenone administration) improved the motor activity of rats with rotenone-induced Parkinsonism in the open field test (horizontal movements) and the rotating rod test. Afobazole (10 mg/kg intraperitoneally, daily during the 7-day course of rotenone administration) reduced the manifestations of rigidity and postural instability. Proteomic analysis, performed using brain samples obtained the day after the last administration of rotenone and neuroprotectors, revealed similar quantitative changes in the brain of rats with rotenone Parkinsonism. An increase in the relative content of 65 proteins and a decrease in the relative content of 21 proteins were detected. The most pronounced changes - an almost ninety-fold increase in the alpha-synuclein content - were found in the brains of rats treated with isatin. In animals of the experimental groups treated with "Rotenone + Isatin", as well as "Rotenone + Afobazole", the increase in the relative content of this protein in the brain was almost 60 and 50 times higher than the control values. Taking into consideration the known data on the physiological role of alpha-synuclein, an increase in the content of this protein in the brain upon administration of neuroprotectors to animals with rotenone Parkinsonism may represent a compensatory reaction, at least in the early stages of this disease and the beginning of its treatment.

Animal models of Parkinson's disease: bridging the gap between disease hallmarks and research questions

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by motor and non-motor symptoms. More than 200 years after its first clinical description, PD remains a serious affliction that affects a growing proportion of the population. Prevailing treatments only alleviate symptoms; there is still neither a cure that targets the neurodegenerative processes nor therapies that modify the course of the disease. Over the past decades, several animal models have been developed to study PD. Although no model precisely recapitulates the pathology, they still provide valuable information that contributes to our understanding of the disease and the limitations of our treatment options. This review comprehensively summarizes the different animal models available for Parkinson's research, with a focus on those induced by drugs, neurotoxins, pesticides, genetic alterations, α-synuclein inoculation, and viral vector injections. We highlight their characteristics and ability to reproduce PD-like phenotypes. It is essential to realize that the strengths and weaknesses of each model and the induction technique at our disposal are determined by the research question being asked. Our review, therefore, seeks to better aid researchers by ensuring a concrete discernment of classical and novel animal models in PD research.

Rotenone-Induced Model of Parkinson's Disease: Beyond Mitochondrial Complex I Inhibition

Parkinson's disease (PD) is usually diagnosed through motor symptoms that make the patient incapable of carrying out daily activities; however, numerous non-motor symptoms include olfactory disturbances, constipation, depression, excessive daytime sleepiness, and rapid eye movement at sleep; they begin years before motor symptoms. Therefore, several experimental models have been studied to reproduce several PD functional and neurochemical characteristics; however, no model mimics all the PD motor and non-motor symptoms to date, which becomes a limitation for PD study. It has become increasingly relevant to find ways to study the disease from its slowly progressive nature. The experimental models most frequently used to reproduce PD are based on administering toxic chemical compounds, which aim to imitate dopamine deficiency. The most used toxic compounds to model PD have been 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which inhibit the complex I of the electron transport chain but have some limitations. Another toxic compound that has drawn attention recently is rotenone, the classical inhibitor of mitochondrial complex I. Rotenone triggers the progressive death of dopaminergic neurons and α-synuclein inclusions formation in rats; also, rotenone induces microtubule destabilization. This review presents information about the experimental model of PD induced by rotenone, emphasizing its molecular characteristics beyond the inhibition of mitochondrial complex I.

Cilostazol novel neuroprotective mechanism against rotenone-induced Parkinson's disease in rats: Correlation between Nrf2 and HMGB1/TLR4/PI3K/Akt/mTOR signaling

Neuroinflammation induced by activation of the high mobility group box 1/ toll-like receptor 4 (HMGB1/TLR4) axis is one of the principal mechanisms involved in dopaminergic neuronal loss in Parkinson's disease (PD), and its activation exacerbates oxidative stress augmenting neurodegeneration.

AIMS

This study investigated the novel neuroprotective effect of cilostazol on rotenone-intoxicated rats focusing on the HMGB1/TLR4 axis, erythroid-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1), and phosphoinositide 3-kinase (PI3K)/Protein kinase B (Akt)/the mammalian target of rapamycin (mTOR) pathway. The aim is extended to correlate the Nrf2 expression with all assessed parameters as promising therapeutic targets for neuroprotection.

MAIN METHODS

Our experiment was designed as follows: vehicle group, cilostazol group, rotenone group (1.5 mg/kg, s.c), and the rotenone pretreated with cilostazol (50 mg/kg, p.o.) group. Eleven rotenone injections were injected day after day, while cilostazol was administered daily for 21 days.

KEY FINDINGS

Cilostazol significantly improved the neurobehavioral analysis, the histopathological examination, and dopamine levels. Moreover, the immunoreactivity of tyrosine hydroxylase (TH) in substantia nigra pars compacta (SNpc) enhanced. These effects were associated with enhancement of the antioxidant expression of Nrf2 and HO-1 by 1.01 and 1.08-fold, respectively, and repression of HMGB1/TLR4 pathway by 50.2 % and 39.3 %, respectively. Upregulation of the neuro-survival PI3K and Akt expression by 2.26 and 2.69-fold, respectively, and readjusting mTOR overexpression.

SIGNIFICANCE

Cilostazol exerts a novel neuroprotective strategy against rotenone-induced neurodegeneration via activation of Nrf2/HO-1, suppression of HMGB1/TLR4 axis, upregulation of PI3K/Akt besides mTOR inhibition that compels more investigations with different PD models to clarify its precise role.

[Characteristics of behavioral reactions and the profile of brain isatin-binding proteins of rats with the rotenone-induced experimental parkinsonism]

The neurotoxins rotenone and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (МPTP) are used for modeling Parkinson's disease in animals (PD). They induce the mitochondrial respiratory chain dysfunction, which leads to the dopaminergic (DA) neuron degeneration. The advantage of the rotenone model consists in ability of rotenone to cause neurodegeneration showing symptoms and molecular biological characteristics similar to those of PD. Isatin (indoldione-2,3) is an endogenous regulator found in tissues and biological fluids of humans and animals. It exhibits a broad range of biological activity mediated by numerous isatin-binding proteins. In this work we have investigated behavioral reactions and profiles of brain isatin-binding proteins of rats with Parkinson's syndrome (PS) in comparison with the corresponding parameters of MPTP-induced Parkinsonism in mice. Systemic injection of rotenone caused severe PS comparable with the effect of MPTP injection. It was accompanied by significant body weight loss, death, oligokinesia, muscular rigidity, and postural instability of animals. In spite of the same pathogenic basis of PS caused by rotenone and MPTP, the molecular mechanisms of their action differ. In the case of rotenone-induced PS, the pool of isatin-binding proteins common of the control rats and the rats with PS (146) significantly exceeded the pool of the common proteins of control mice and mice with PS induced by MPTP, whether right after neurotoxin injection (27), or (all the more) in a week after the MPTP injection (14). The comparison of isatin-binding proteins specific of the animals with MPTP-induced PS and with the rotenone-induced PS (as compared with the control animals) revealed total absence of proteins common of these two models of PD. It is to be noted that both neurotoxins particularly affected the proteins participating in the signal transmission and enzyme activity regulation. The changes of the profile of isatin-binding proteins in response to the injection of rotenone suggest that the neuroprotector isatin could also influence positively in the case of the rotenone model of PD.

Nutrition and Gut–Brain Pathways Impacting the Onset of Parkinson’s Disease

An emerging body of literature suggests that long-term gut inflammation may be a silent driver of Parkinson’s disease (PD) pathogenesis. Importantly, specific nutritive patterns might improve gut health for PD risk reduction. Here, we review the current literature on the nutritive patterns and inflammatory markers as a predictor for early detection of PD. This knowledge might be used to foster the detection of early nutritive patterns and preclinical biomarkers to potentially alter PD development and progression.

Nanostructure lipid carriers enhance alpha-mangostin neuroprotective efficacy in mice with rotenone-induced neurodegeneration

Neurodegenerative disease, for instance, Parkinson's disease (PD), is associated with substantia nigra dopaminergic neuronal loss with subsequent striatal dopamine reduction, leading to motor deficits. Currently, there is no available effective therapy for PD; thus, novel therapeutic agents such as natural antioxidants with neuroprotective effects are emerging. Alpha-mangostin (αM) is a xanthone derivative compound from mangosteen peel with a cytoprotective effect depicted in neurodegenerative disease models. However, αM has low aqueous solubility and low biodistribution in the brain. Nanostructured lipid carriers (NLC) have been used to encapsulate bioactive compounds delivered to target organs to improve the oral bioavailability and effectiveness. This study aimed to investigate the effect of αM and αM encapsulated in NLC (αM-NLC) in mice with rotenone-induced PD-like neurodegeneration. Forty male ICR mice were divided into normal, PD, PD + αM, and PD + αM-NLC groups. Vehicle, αM (25 mg/kg/48 h), and αM-NLC (25 mg/kg/48 h) were orally administered, along with PD induction by intraperitoneal injection of rotenone (2.5 mg/kg/48 h) for 4 consecutive weeks. Motor abilities were assessed once a week using rotarod and hanging wire tests. Biochemical analysis of brain oxidative status was conducted, and neuronal populations in substantia nigra par compacta (SNc), striatum, and motor cortex were evaluated using Nissl staining. Tyrosine hydroxylase (TH) immunostaining of SNc and striatum was also evaluated. Results showed that rotenone significantly induced motor deficits concurrent with significant SNc, striatum, and motor cortex neuronal reduction and significantly decreased TH intensity in SNc (p < 0.05). The significant reduction of brain superoxide dismutase activity (p < 0.05) was also detected. Administrations of αM and αM-NLC significantly reduced motor deficits, prevented the reduction of TH intensity in SNc and striatum, and prevented the reduction of neurons in SNc (p < 0.05). Only αM-NLC significantly prevented the reduction of neurons in both striatum and motor cortex (p < 0.05). These were found concurrent with significantly reduced malondialdehyde level and increased catalase and superoxide dismutase activities (p < 0.05). Therefore, this study depicted the neuroprotective effect of αM and αM-NLC against rotenone-induced PD-like neurodegeneration in mice. We indicated an involvement of NLC, emphasizing the protective effect of αM against oxidative stress. Moreover, αM-NLC exhibited broad protection against rotenone-induced neurodegeneration that was not limited to nigrostriatal structures and emphasized the benefit of NLC in enhancing αM neuroprotective effects.

Environmental neurotoxic pesticide exposure induces gut inflammation and enteric neuronal degeneration by impairing enteric glial mitochondrial function in pesticide models of Parkinson's disease: Potential relevance to gut-brain axis inflammation in Parkinson's disease pathogenesis

Despite the growing recognition that gastrointestinal (GI) dysfunction is prevalent in Parkinson's disease (PD) and occurs as a major prodromal symptom of PD, its cellular and molecular mechanisms remain largely unknown. Among the various types of GI cells, enteric glial cells (EGCs), which resemble astrocytes in structure and function, play a critical role in the pathophysiology of many GI diseases including PD. Thus, we investigated how EGCs respond to the environmental pesticides rotenone (Rot) and tebufenpyrad (Tebu) in cell and animal models to better understand the mechanism underlying GI abnormalities. Both Rot and Tebu induce dopaminergic neuronal cell death through complex 1 inhibition of the mitochondrial respiratory chain. We report that exposing a rat enteric glial cell model (CRL-2690 cells) to these pesticides increased mitochondrial fission and reduced mitochondrial fusion by impairing MFN2 function. Furthermore, they also increased mitochondrial superoxide generation and impaired mitochondrial ATP levels and basal respiratory rate. Measurement of LC3, p62 and lysosomal assays revealed impaired autolysosomal function in ECGs during mitochondrial stress. Consistent with our recent findings that mitochondrial dysfunction augments inflammation in astrocytes and microglia, we found that neurotoxic pesticide exposure also enhanced the production of pro-inflammatory factors in EGCs in direct correlation with the loss in mitochondrial mass. Finally, we show that pesticide-induced mitochondrial defects functionally impaired smooth muscle velocity, acceleration, and total kinetic energy in a mixed primary culture of the enteric nervous system (ENS). Collectively, our studies demonstrate for the first time that exposure to environmental neurotoxic pesticides impairs mitochondrial bioenergetics and activates inflammatory pathways in EGCs, further augmenting mitochondrial dysfunction and pro-inflammatory events to induce gut dysfunction. Our findings have major implications in understanding the GI-related pathogenesis and progression of environmentally linked PD.

Application of Neurotoxin-Induced Animal Models in the Study of Parkinson's Disease-Related Depression: Profile and Proposal

Depression can be a non-motor symptom, a risk factor, and even a co-morbidity of Parkinson's disease (PD). In either case, depression seriously affects the quality of life of PD patients. Unfortunately, at present, a large number of clinical and basic studies focused on the pathophysiological mechanism of PD and the prevention and treatment of motor symptoms. Although there has been increasing attention to PD-related depression, it is difficult to achieve early detection and early intervention, because the clinical guidelines mostly refer to depression developed after or accompanied by motor impairments. Why is there such a dilemma? This is because there has been no suitable preclinical animal model for studying the relationship between depression and PD, and the assessment of depressive behavior in PD preclinical models is as well a very challenging task since it is not free from the confounding from the motor impairment. As a common method to simulate PD symptoms, neurotoxin-induced PD models have been widely used. Studies have found that neurotoxin-induced PD model animals could exhibit depression-like behaviors, which sometimes manifested earlier than motor impairments. Therefore, there have been attempts to establish the PD-related depression model by neurotoxin induction. However, due to a lack of unified protocol, the reported results were diverse. For the purpose of further promoting the improvement and optimization of the animal models and the study of PD-related depression, we reviewed the establishment and evaluation strategies of the current animal models of PD-related depression based on both the existing literature and our own research experience, and discussed the possible mechanism and interventions, in order to provide a reference for future research in this area.

Manipulation of vocal communication and anxiety through pharmacologic modulation of norepinephrine in the Pink1-/- rat model of Parkinson disease

Vocal deficits and anxiety are common, co-occurring, and interacting signs of Parkinson Disease (PD) that have a devastating impact on quality of life. Both manifest early in the disease process. Unlike hallmark motor signs of PD, neither respond adequately to dopamine replacement therapies, suggesting that their disease-specific mechanisms are at least partially extra-dopaminergic. Because noradrenergic dysfunction is also a defining feature of PD, especially early in the disease progression, drug therapies targeting norepinephrine are being trialed for treatment of motor and non-motor impairments in PD. Research assessing the effects of noradrenergic manipulation on anxiety and vocal impairment in PD, however, is sparse. In this pre-clinical study, we quantified the influence of pharmacologic manipulation of norepinephrine on vocal impairment and anxiety in Pink1-/- rats, a translational model of PD that demonstrates both vocal deficits and anxiety. Ultrasonic vocalization acoustics, anxiety behavior, and limb motor activity were tested twice for each rat: after injection of saline and after one of three drugs. We hypothesized that norepinephrine reuptake inhibitors (atomoxetine and reboxetine) and a β receptor antagonist (propranolol) would decrease vocal impairment and anxiety compared to saline, without affecting spontaneous motor activity. Our results demonstrated that atomoxetine and reboxetine decreased anxiety behavior. Atomoxetine also modulated ultrasonic vocalization acoustics, including an increase in vocal intensity, which is almost always reduced in animal models and patients with PD. Propranolol did not affect anxiety or vocalization. Drug condition did not influence spontaneous motor activity. These studies demonstrate relationships among vocal impairment, anxiety, and noradrenergic systems in the Pink1-/- rat model of PD.

Chemically induced models of Parkinson's disease

Environmental toxins are harmful substances detrimental to humans. Constant exposure to these fatal neurotoxins can cause various neurodegenerative disorders. Although poisonous, specific neurotoxins at optimal concentrations mimic the clinical features of neurodegenerative diseases in several animal models. Such chemically-induced model systems are beneficial in deciphering the molecular mechanisms of neurodegeneration and drug screening for these disorders. One such neurotoxin is 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a widely used chemical that recapitulates Parkinsonian features in various animal models. Apart from MPTP, other neurotoxins like 6-hydroxydopamine (6-OHDA), paraquat, rotenone also induce specific clinical features of Parkinson's disease in animal models. These chemically-induced Parkinson's disease models are playing a crucial role in understanding Parkinson's disease onset, pathology, and novel therapeutics. In this review, we provide a concise overview of various neurotoxins that can recapitulate Parkinsonian features in different in vivo and in vitro model systems specifically focusing on the different treatment methodologies of neurotoxins.

Nano-ivabradine averts behavioral anomalies in Huntington's disease rat model via modulating Rhes/m-tor pathway

Huntington's disease (HD) is characterized by abnormal involuntary movements together with cognitive impairment and disrupted mood changes. 3-nitropropionic acid (3-NP) is one of the chemo-toxic models used to address the striatal neurotoxicity pattern encountered in HD. This study aims to explain the neuroprotective effect of nano-formulated ivabradine (nano IVA) in enhancing behavioral changes related to 3-NP model and to identify the involvement of ras homolog enriched striatum (Rhes)/mammalian target of rapamycin (m-Tor) mediated autophagy pathway. Rats were divided into 6 groups, the first 3 groups received saline (control), ivabradine (IVA), nano IVA respectively, the fourth received a daily dose of 3-NP (20 mg/kg, s.c) for 2 weeks, the fifth received 3-NP + IVA (1 mg/kg, into the tail vein, every other day for 1 week) and the last group received 3-NP + nano IVA (1 mg/kg, i.v, every other day for 1 week). Interestingly, nano IVA reversed motor disabilities, improved memory function and overcame the psychiatric changes. It boosted expression of autophagy markers combined with down regulation of Rhes, m-Tor and b-cell lymphoma 2 protein levels. Also, it restored the normal level of neurotransmitters and myocardial function related-proteins. Histopathological examination revealed a preserved striatal structure with decreased number of darkly-degenerated neurons. In conclusion, the outcomes of this study provide a well-recognized clue for the promising neuroprotective effect of IVA and the implication of autophagy and Rhes/m-Tor pathways in the 3-NP induced HD and highlight the fact that nano formulations of IVA would be an auspicious approach in HD therapy.

Parkinson Disease: Translating Insights from Molecular Mechanisms to Neuroprotection

Parkinson disease (PD) used to be considered a nongenetic condition. However, the identification of several autosomal dominant and recessive mutations linked to monogenic PD has changed this view. Clinically manifest PD is then thought to occur through a complex interplay between genetic mutations, many of which have incomplete penetrance, and environmental factors, both neuroprotective and increasing susceptibility, which variably interact to reach a threshold over which PD becomes clinically manifested. Functional studies of PD gene products have identified many cellular and molecular pathways, providing crucial insights into the nature and causes of PD. PD originates from multiple causes and a range of pathogenic processes at play, ultimately culminating in nigral dopaminergic loss and motor dysfunction. An in-depth understanding of these complex and possibly convergent pathways will pave the way for therapeutic approaches to alleviate the disease symptoms and neuroprotective strategies to prevent disease manifestations. This review is aimed at providing a comprehensive understanding of advances made in PD research based on leveraging genetic insights into the pathogenesis of PD. It further discusses novel perspectives to facilitate identification of critical molecular pathways that are central to neurodegeneration that hold the potential to develop neuroprotective and/or neurorestorative therapeutic strategies for PD. SIGNIFICANCE STATEMENT: A comprehensive review of PD pathophysiology is provided on the complex interplay of genetic and environmental factors and biologic processes that contribute to PD pathogenesis. This knowledge identifies new targets that could be leveraged into disease-modifying therapies to prevent or slow neurodegeneration in PD.

Metabotropic glutamate receptors and nitric oxide in dopaminergic neurotoxicity

Dopaminergic neurotoxicity is characterized by damage and death of dopaminergic neurons. Parkinson's disease (PD) is a neurodegenerative disorder that primarily involves the loss of dopaminergic neurons in the substantia nigra. Therefore, the study of the mechanisms, as well as the search for new targets for the prevention and treatment of neurodegenerative diseases, is an important focus of modern neuroscience. PD is primarily caused by dysfunction of dopaminergic neurons; however, other neurotransmitter systems are also involved. Research reports have indicated that the glutamatergic system is involved in different pathological conditions, including dopaminergic neurotoxicity. Over the last two decades, the important functional interplay between dopaminergic and glutamatergic systems has stimulated interest in the possible role of metabotropic glutamate receptors (mGluRs) in the development of extrapyramidal disorders. However, the specific mechanisms driving these processes are presently unclear. The participation of the universal neuronal messenger nitric oxide (NO) in the mechanisms of dopaminergic neurotoxicity has attracted increased attention. The current paper aims to review the involvement of mGluRs and the contribution of NO to dopaminergic neurotoxicity. More precisely, we focused on studies conducted on the rotenone-induced PD model. This review is also an outline of our own results obtained using the method of electron paramagnetic resonance, which allows quantitation of NO radicals in brain structures.

Glial cells modulate retinal cell survival in rotenone-induced neural degeneration

Administration of the mitochondrial complex I inhibitor rotenone provides an excellent model to study the pathomechanism of oxidative stress-related neural degeneration diseases. In this study, we examined the glial roles in retinal cell survival and degeneration under the rotenone-induced oxidative stress condition. Mouse-derived Müller, microglial (BV-2), and dissociated retinal cells were used for in vitro experiments. Gene expression levels and cell viability were determined using quantitative reverse transcription-polymerase chain reaction and the alamarBlue assay, respectively. Conditioned media were prepared by stimulating glial cells with rotenone. Retinal ganglion cells (RGCs) and inner nuclear layer (INL) were visualized on rat retinal sections by immunohistochemistry and eosin/hematoxylin, respectively. Rotenone dose-dependently induced glial cell death. Treatment with rotenone or rotenone-stimulated glial cell-conditioned media altered gene expression of growth factors and inflammatory cytokines in glial cells. The viability of dissociated retinal cells significantly increased upon culturing in media conditioned with rotenone-stimulated or Müller cell-conditioned media-stimulated BV-2 cells. Furthermore, intravitreal neurotrophin-5 administration prevented the rotenone-induced reduction of RGC number and INL thickness in rats. Thus, glial cells exerted both positive and negative effects on retinal cell survival in rotenone-induced neural degeneration via altered expression of growth factors, especially upregulation of microglia-derived Ntf5, and proinflammatory cytokines.

Establishing the Rotenone-Induced Parkinson's Disease Animal Model in Wistar Albino Rats

Objective The aim of this study was to establish the safe and effective dose of rotenone-induced Parkinson’s disease (PD) in Wistar albino rat.

Materials and Methods Male Wistar albino rats (n = 6) aged between 9 and 11 weeks, weight 200 to 250 g, were selected for the study. Rats were divided into four groups namely, A, B, C, and D; Group A served as control received only isotonic saline, groups B, C, and D were administered with rotenone 2, 2.5, and 3 mg/kg body weight (BW), respectively, with a specialized vehicle through intraperitoneal (IP) route once daily. During the procedure, they were observed for the development of the PD signs such as stooped posture, postural instability, akinesia, bradykinesia, and muscular rigidity. BW and behavioral pattern were recorded before the rotenone introduction and also after the onset of PD signs in them. They were sacrificed when the PD phenotype became debilitating and followed by neurochemical assay for dopamine and antioxidants; histological assay for TH-neuronal density and Lewy bodies were performed in the substantia nigra pars compacta (SNpc) of midbrain.

Results Group C and D animals were developed with the PD signs by the 9th day and also there was a significant decrease in the BW noticed in them. Additionally, histological studies revealed the decrease in neuronal density and the presence of Lewy bodies in the dopamine neurons of the SNpc. However, it was also noticed that the group D had shown more mortality rate when compared with the Group C.

Conclusion Rotenone with 2.5 mg/kg BW IP was an ideal dose to develop PD signs in Wistar albino rats model that is a highly reproducible and may offer an excellent tool to establish the new neuroprotective treatment strategies.

The dynamics of nigrostriatal system damage and neurobehavioral changes in the rotenone rat model of Parkinson's disease

Subcutaneous administration of rotenone to rats is currently a widely used method of reproducing Parkinson's disease (PD) symptoms, due to its convenience and effectiveness. Despite this, its influence on the temporal dynamics of parkinsonism development has yet to be investigated. The present study characterizes behavioral and neurochemical disruptancies underlying the dynamics of parkinsonism development in rats, induced by chronic subcutaneous administration of 2 mg/kg rotenone over the course of 18 days. In this article, the presence of two stages of pathology development in the model in question - the premotor and motor disability stages - are illustrated through a complex assessment of animal behavior, the development of an original neurological symptoms scale, and the establishment of the dynamics of histological and neurochemical changes in the brain. The premotor stage was observed up to 3 days of rotenone administration, and was characterized by a decrease in the motivational component of behavior, shown both in the food-getting task and in the "sucrose preference" test. A 30 % decrease in the number of cells in the substantia nigra pars compacta by the 3rd day of rotenone administration was also shown during the premotor stage. No changes in the metabolism of dopamine and other monoamine mediators were observed at this time. At the same time, acute administration of rotenone caused an increase in the GSH / GSSG ratio by 69 %. The motor stage developed after a decrease in the number of cells in the SNpc by more than 30 %, and was characterized by changes in the dopaminergic system, leading up to a 71 % reduction in dopamine levels in the striatum. It was shown that starting from 4 to 6 days of rotenone injection, experimental group animals begin to develop motor symptoms of Parkinson's disease, including bradykinesia, rigidity and postural instability. The development of motor impairment in all rats of this group was accompanied by significantly reduced activity of the antioxidant system in brain frontal lobe tissue homogenates, as compared to intact rats. Thus, in the used model of rotenone-induced parkinsonism, the dynamics of neuropathology development are described and the premotor stage of the disease is highlighted, which allows future using of this model in developing new approaches for treatment of parkinsonism at an early stage.

Proteotoxicity: A Fatal Consequence of Environmental Pollutants-Induced Impairments in Protein Clearance Machinery

A tightly regulated protein quality control (PQC) system maintains a healthy balance between correctly folded and misfolded protein species. This PQC system work with the help of a complex network comprised of molecular chaperones and proteostasis. Any intruder, especially environmental pollutants, disrupt the PQC network and lead to PQCs disruption, thus generating damaged and infectious protein. These misfolded/unfolded proteins are linked to several diseases such as Parkinson's disease, Alzheimer's disease, Huntington's disease, and cataracts. Numerous studies on proteins misfolding and disruption of PQCs by environmental pollutants highlight the necessity of detailed knowledge. This review represents the PQCs network and environmental pollutants' impact on the PQC network, especially through the protein clearance system.

Chemically Induced Models of Parkinson's Disease: History and Perspectives for the Involvement of Ferroptosis

Ferroptosis is a newly discovered form of necrotic cell death characterized by its dependency on iron and lipid peroxidation. Ferroptosis has attracted much attention recently in the area of neurodegeneration since the involvement of ferroptosis in Parkinson’s disease (PD), a major neurodegenerative disease, has been indicated using animal models. Although PD is associated with both genetic and environmental factors, sporadic forms of PD account for more than 90% of total PD. Following the importance of environmental factors, various neurotoxins are used as chemical inducers of PD both in vivo and in vitro. In contrast to other neurodegenerative diseases such as Alzheimer’s and Huntington’s diseases (AD and HD), many of the characteristics of PD can be reproduced in vivo by the use of specific neurotoxins. Given the indication of ferroptosis in PD pathology, several studies have been conducted to examine whether ferroptosis plays role in the loss of dopaminergic neurons in PD. However, there are still few reports showing an authentic form of ferroptosis in neuronal cells during exposure to the neurotoxins used as PD inducers. In this review article, we summarize the history of the uses of chemicals to create PD models in vivo and in vitro. Besides, we also survey recent reports examining the possible involvement of ferroptosis in chemical models of PD.

Adult Endogenous Dopaminergic Neuroregeneration Against Parkinson's Disease: Ideal Animal Models?

Parkinson's disease (PD) is the second most common neurodegenerative disease. The etiology of PD remains an enigma with no available disease modifying treatment or cure. Pharmacological compensation is the only quality of life improving treatments available. Endogenous dopaminergic neuroregeneration has recently been considered a plausible therapeutic strategy for PD. However, researchers have to first decipher the complexity of adult endogenous neuroregeneration. This raises the need of animal models to understand the underlying molecular basis. Mammalian models with highly conserved genetic homology might aid researchers to identify specific molecular mechanisms. However, the scarcity of adult neuroregeneration potential in mammals obfuscates such investigations. Nowadays, non-mammalian models are gaining popularity due to their explicit ability to neuroregenerate naturally without the need of external enhancements, yet these non-mammals have a much diverse gene homology that critical molecular signals might not be conserved across species. The present review highlights the advantages and disadvantages of both mammalian and non-mammalian animal models that can be essentially used to study the potential of endogenous DpN regeneration against PD.

Methanolic extracts of a selected Egyptian Vicia faba cultivar mitigate the oxidative/inflammatory burden and afford neuroprotection in a mouse model of Parkinson's disease

Vicia faba L. is a legume from the family Fabaceae. Ancient Egyptians consumed fava beans thousands of years ago and they are still one of the most popular foods in Egypt. The current study examined the anti-Parkinson effect of 80% methanolic extracts of seeds or sprouts of the fava 'Sakha 3 'cultivar which has been selected based on the total phenol content among three cultivars tested. In addition, the extracts were characterized by reversed-phase high-performance liquid chromatography coupled with diode array detection and quadrupole-time-of-flight-mass spectrometry (RP-HPLC-DAD-QTOF-MS). Three doses (200, 400, and 600 mg/kg) of 80% methanol extracts of seeds or sprouts of the Sakha 3 cultivar were evaluated in rotenone-Parkinsonian mice from behavioral, biochemical, and histopathological aspects. The extract of fava sprouts (600 mg/kg dose) showed the most beneficial effect. It improved motor activity, enhanced striatal dopamine level, and decreased the striatal malondialdehyde, as well as the expression of the inflammatory markers, compared with the rotenone control group and groups receiving lower therapeutic doses of the extracts or L-Dopa. In addition, these findings were supported by a histopathological investigation which indicated that mice treated with the 600-mg/kg dose of the sprout extract showed a low number of degenerated neurons. The application of RP-HPLC-DAD-QTOF-MS and mass/mass spectroscopy enabled the metabolic profiling of the sprouts and seeds of the 'Sakha 3' cultivar. It is obvious that germination increased the amounts of phenolic acids, saponins, and aromatic amino acids, together with a dramatic increase in flavonoids. In conclusion, the 80% methanolic extract of sprouts of the fava "Sakha 3" cultivar may be a promising candidate for treating Parkinsonism if appropriate safety data are available.

Unique Novel Role of Adropin in a Gastric Ulcer in a Rotenone-Induced Rat Model of Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, frequently associated with a gastric ulcer. We aimed to investigate the adropin neuroprotective/gastroprotective potential in the indomethacin (IND)-induced gastric ulcer in a rotenone-induced PD model. Rats were randomly divided into four groups: normal control group, rotenone/IND treated (PD /Ulcer) group, adropin treated PD/Ulcer group, and l-dopa/omeprazole (Om) treated PD/Ulcer group. There were ten rats selected for the normal control group. Striatal dopamine (DA), apoptosis/redox status, and motor/behavioral impairments were evaluated. Gastric oxidative stress, H⁺/K⁺-ATPase activity, prostaglandin E2, mucin content, and von Willebrand factor were measured. Gastric/striatal phosphatidylinositol 3-kinase (PI3K)/phosphorylated Akt and gastric vascular endothelial growth factor (VEGF)/striatal P53 immunoreactivities were checked. Striatal P53 upregulated modulator of apoptosis (Puma)/gastric vascular endothelial growth factor receptor-2 (Vegfr-2) expressions were evaluated. Adropin successfully restored striatal DA and attenuated rotenone-induced motor/behavior deficits along with strong gastroprotective potential, possibly through antioxidant activity via reduction in malondialdehyde level and upregulated superoxide dismutase, catalase activities, and serum ferric reducing antioxidant power. Adropin restored the delicate balance between the defective pro-survival PI3K/Akt/murine double minute 2 signals and apoptotic P53/Puma pathways. Adropin can be considered as a uniquely attractive therapeutic target in PD and its associated gastric ulcer.

Naringin attenuates Bisphenol-A mediated neurotoxicity in hypertensive rats by abrogation of cerebral nucleotide depletion, oxidative damage and neuroinflammation

We examined whether active fruit naringin can reduce the risk of BPA-mediated neurotoxicity in L-NAME induced hypertensive rats and whether the modulation could be linked to improvement of brain NO signaling. Male albino rats were randomly distributed into eight (n = 7) groups. Group I was control animals, Group II was orally-treated with L-NAME, Group III was orally treated with 100 mg/kg BPA, Group IV was orally-treated with L-NAME +100 mg/kg BPA. Group V was orally-administered with L-NAME +80 mg/kg NAR. Group VI was orally-administered with 100 mg/kg BPA +80 mg/kg NAR. Group VII was orally-administered with L-NAME+100 mg/kg BPA +80 mg/kg NAR. Lastly, group VIII was orally-treated with 80 mg/kg NAR. The treatment lasted for 14 days. Sub-acute exposure to L-NAME and BPA induced hypertension and mediated-neuroinflammation at CA-2 and CA-4 of hippocampus cells. It was evident by increase in PDE-5¹ and enzymes of ATP hydrolysis (ATPase, ADPase and AMPase) with corresponding upsurge in cholinergic (AChE and BuChE), dopaminergic (MAO-A) and adenosinergic (ADA) enzymes as well as movement disorder. The hypertensive-mediated neurotoxicity was related to alteration of NO signaling and higher release of pro-inflammatory cytokines (TNF-α and IL-1β), apoptotic proteins (P53 and caspace-9) and facilitated entry of T-lymphocytes (CD43⁺) into CNS through blood brain barrier potentiated by antigen presenting cells. Hence, these features of BPA-mediated neurotoxicity in L-NAME induced hypertensive rats were prohibited by co-administration of NAR through production of neuro-inflammatory mediators, stabilizing neurotransmitter enzymes, normalizing NO signaling and improving brain histology.

Effects of Exercise and Ferulic Acid on Alpha Synuclein and Neuroprotective Heat Shock Protein 70 in An Experimental Model of Parkinsonism Disease

BACKGROUND & OBJECTIVE

This study investigated the effects of ferulic acid (FR), muscle exercise (Ex) and combination of them on rotenone (Rot)-induced Parkinson disease (PD) in mice as well as their underlying mechanisms.

METHOD

56 male C57BL/6 mice were allocated into 8 equal groups, 1) Normal control (CTL), 2) FR (mice received FR at 20 mg/kg/day), 3) Ex (mice received swimming Ex) and 4) Ex + FR (mice received FR and Ex), 5) Rot (mice received Rot 3 mg/Kg i.p. for 70 days), 6) ROT+ FR (mice received Rot + FR at 20 mg/kg/day), 7) ROT+ Ex (mice received Rot + swimming Ex) and 8) ROT+ Ex + FR (mice received Rot + FR and Ex). ROT group showed significant impairment in motor performance and significant reduction in tyrosine hydroxylase (TH) density and Hsp70 expression (p< 0.05) with Lewy bodies (alpha synuclein) aggregates in corpus striatum. Also, ROT+FR, ROT+EX and ROT + Ex+ FR groups showed significant improvement in behavioral and biochemical changes, however the effect of FR alone was more potent than Ex alone (p< 0.05) and addition of Ex to FR caused no more significant improvement than FR alone.

CONCLUSION

We concluded that, FR and Ex improved the motor performance in rotenone-induced PD rodent model which might be due to increased Hsp70 expression and TH density in corpus striatum and combination of both did not offer more protection than FR alone.

Animal models for preclinical Parkinson's research: An update and critical appraisal

Animal models of Parkinson's disease (PD) are essential to investigate pathogenic pathways at the whole-organism level. Moreover, they are necessary for a preclinical investigation of potential new therapies. Different pathological features of PD can be induced in a variety of invertebrate and vertebrate species using toxins, drugs, or genetic perturbations. Each model has a particular utility and range of applicability. Invertebrate PD models are particularly useful for high throughput-screening applications, whereas mammalian models are needed to explore complex motor and non-motor features of the human disease. Here, we provide a comprehensive review and critical appraisal of the most commonly used mammalian models of PD, which are produced in rats and mice. A substantial loss of nigrostriatal dopamine neurons is necessary for the animal to exhibit a hypokinetic motor phenotype responsive to dopaminergic agents, thus resembling clinical PD. This level of dopaminergic neurodegeneration can be induced using specific neurotoxins, environmental toxicants, or proteasome inhibitors. Alternatively, nigrostriatal dopamine degeneration can be induced via overexpression of α-synuclein using viral vectors or transgenic techniques. In addition, protein aggregation pathology can be triggered by inoculating preformed fibrils of α-synuclein in the substantia nigra or the striatum. Thanks to the conceptual and technical progress made in the past few years a vast repertoire of well-characterized animal models are currently available to address different aspects of PD in the laboratory.

Brain insulin resistance: role in neurodegenerative disease and potential for targeting

Introduction: This review evaluates the novel strategy of treating Alzheimer's and Parkinson's disease (AD and PD) withdrugs that initially have been developed to treat type 2 diabetes. As insulin signalling has been found to be de-sensitized in the brains of patients, drugs that can re-sensitize insulin signalling have been tested to evaluate if this strategy can alter disease progression.Areas covered: The review will give an overview of preclinical and clinical tests in AD and PD of drugs activating insulin receptors, glucagon-like peptide -1 (GLP-1) receptors, and glucose-dependent insulinotropic polypeptide (GIP) receptors.Expert opinion: Insulin, GLP-1 and GIP receptor agonists have shown good effects in preclinical studies. First clinical trials in MCI/AD patients have shown that insulin can improve on key pathological symptoms of AD such as memory impairment, brain activity, neuronal energy utilization, and inflammation markers. A GLP-1 receptor agonist has shown disease-modifying effects in PD patients, and first pilot studies have shown encouraging effects of a GLP-1 receptor agonist in AD patients. Novel dual GLP-1/GIP receptor agonists that cross the blood brain barrier show superior neuroprotective effects compared to single GLP-1 or GIP receptor agonists, and show great promise as novel treatments of AD and PD.

Biological bases for a possible effect of cannabidiol in Parkinson's disease

Current pharmacotherapy of Parkinson’s disease (PD) is palliative and unable to modify the progression of neurodegeneration. Treatments that can improve patients’ quality of life with fewer side effects are needed, but not yet available. Cannabidiol (CBD), the major non-psychotomimetic constituent of cannabis, has received considerable research attention in the last decade. In this context, we aimed to critically review the literature on potential therapeutic effects of CBD in PD and discuss clinical and preclinical evidence supporting the putative neuroprotective mechanisms of CBD. We searched MEDLINE (via PubMed) for indexed articles published in English from inception to 2019. The following keywords were used: cannabis; cannabidiol and neuroprotection; endocannabinoids and basal ganglia; Parkinson’s animal models; Parkinson’s history; Parkinson’s and cannabidiol. Few studies addressed the biological bases for the purported effects of CBD on PD. Six preclinical studies showed neuroprotective effects, while three targeted the antidyskinetic effects of CBD. Three human studies have tested CBD in patients with PD: an open-label study, a case series, and a randomized controlled trial. These studies reported therapeutic effects of CBD on non-motor symptoms. Additional research is needed to elucidate the potential effectiveness of CBD in PD and the underlying mechanisms involved.

Role of NADPH oxidase-2 in the progression of the inflammatory response secondary to striatum excitotoxic damage

Background

During excitotoxic damage, neuronal death results from the increase in intracellular calcium, the induction of oxidative stress, and a subsequent inflammatory response. NADPH oxidases (NOX) are relevant sources of reactive oxygen species (ROS) during excitotoxic damage. NADPH oxidase-2 (NOX-2) has been particularly related to neuronal damage and death, as well as to the resolution of the subsequent inflammatory response. As ROS are crucial components of the regulation of inflammatory response, in this work, we evaluated the role of NOX-2 in the progression of inflammation resulting from glutamate-induced excitotoxic damage of the striatum in an in vivo model.

Methods

The striata of wild-type C57BL/6 J and NOX-2 KO mice (gp91^Cybbtm1Din/J) were stereotactically injected with monosodium glutamate either alone or in combination with IL-4 or IL-10. The damage was evaluated in histological sections stained with cresyl violet and Fluoro-Jade B. The enzymatic activity of caspase-3 and NOX were also measured. Additionally, the cytokine profile was identified by ELISA and motor activity was verified by the tests of the cylinder, the adhesive tape removal, and the inverted grid.

Results

Our results show a neuroprotective effect in mice with a genetic inhibition of NOX-2, which is partially due to a differential response to excitotoxic damage, characterized by the production of anti-inflammatory cytokines. In NOX-2 KO animals, the excitotoxic condition increased the production of interleukin-4, which could contribute to the production of interleukin-10 that decreased neuronal apoptotic death and the magnitude of striatal injury. Treatment with interleukin-4 and interleukin-10 protected from excitotoxic damage in wild-type animals.

Conclusions

The release of proinflammatory cytokines during the excitotoxic event promotes an additional apoptotic death of neurons that survived the initial damage. During the subsequent inflammatory response to excitotoxic damage, ROS generated by NOX-2 play a decisive role in the extension of the lesion and consequently in the severity of the functional compromise, probably by regulating the anti-inflammatory cytokines production.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1478-4) contains supplementary material, which is available to authorized users.

Metabolic treatment of syndrome linked with Parkinson's disease and hypothalamus pituitary gonadal hormones by turmeric curcumin in Bisphenol-A induced neuro-testicular dysfunction of wistar rat

The metabolic shift in cholinesterase activity and inhibitor of hypothalamus pituitary gonadal hormones were hypothesized as resultant effect of Parkinson's disease (PD) which is clinically characterized by a movement disorder. This study therefore examined the effect of turmeric curcumin (CUR) on index of PD, acetylcholine esterase activity and disorder of hypothalamus pituitary gonadal hormone (HPGH) in Bisphenol-A induced injury using animal model. Forty adult male albino rats were randomly distributed into five (n = 8) groups. Group I: vehicle control (olive oil 0.5 ml), Group II was given 50 mg/kg of BPA only, Group III was given 50 mg/kg BPA + 50 mg/kg curcumin, Group IV was given 50 mg/kg BPA + 100 mg/kg curcumin and Group V was administered 50 mg/kg of curcumin only for 14 days. The study examined the effect of curcumin on acetylcholineesterase (AChE) activity, nitric oxide radical (NO•) production, HPGH (LH, FSH and testosterone), MDA level, antioxidant enzymes (SOD and CAT), in BPA induced male rat. Sperm parameters were similarly examined. The animals induced with BPA exhibited impairment to striatum, leydig cells and sertoli cells by depleting LH, FSH, testosterone and spermatozoa with reduced AChE activity and significant (p < 0.05) alteration in cerebral enzymatic antioxidants. Locomotive activity was impeded followed by the increase of brain NO• level (marker of pro-inflammation). Therapeutically, CUR promoted hypothalamus-pituitary-testicular hormones via modulation of AChE and locomotive activities, reduction of intracellular NO• level, prevention of striatum-endocrine injury as well as oxidative damage. Hence, CUR abolished HPGH dysfunction linked with PD mediated by BPA in rat.

The effects of rotenone on TH, BDNF and BDNF-related proteins in the brain and periphery: Relevance to early Parkinson's disease

Loss of dopaminergic neurons in the substantia nigra (SN) is one of the pathological hallmarks in Parkinson's disease (PD). This neuron loss is accompanied by reduced protein and activity levels of tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine synthesis. Reduced nigral brain-derived neurotrophic factor (BDNF) has been postulated to contribute to the loss of nigral dopaminergic neurons in PD by causing a lack of trophic support. Prior to this nigral cell loss many patients develop non-motor symptoms such as hyposmia, constipation and orthostatic hypotension. We investigated how TH, BDNF and BDNF related receptors are altered in the SN, olfactory bulb, adrenal glands and colon (which are known to be affected in PD) using rotenone-treated rats. Rotenone was administered to Sprague-Dawley rats at a dose of 2.75 mg/kg, 5 days/week for 4 weeks, via intraperitoneal injections. Rats underwent behavioural testing, and tissues were collected for western blot and ELISA analysis. This rotenone treatment induced reduced rears and distance travelled in the rearing and open field test, respectively but caused no impairments in forced movement (rotarod test). The SN had changes consistent with a pro-apoptotic state, such as increased proBDNF but no change in TH; whereas, the colon had significantly reduced TH and increased sortilin. Thus, our results indicate further investigation is warranted for this rotenone-dosing paradigm's capacity for reproducing the early stage of PD, as we observed impairments in voluntary movement and pathology in the colon without overt motor symptoms or nigral dopaminergic loss.

Treadmill Exercise Improves Motor Function by Suppressing Purkinje Cell Loss in Parkinson Disease Rats

PURPOSE

Rotenone is the most widely used neurotoxin for the making Parkinson disease (PD) animal model. The neurodegenerative disorder PD shows symptoms, such as slowness of movements, tremor at resting, rigidity, disturbance of gait, and instability of posture. We investigated whether treadmill running improves motor ability using rotenone-caused PD rats. The effect of treadmill running on PD was also assessed in relation with apoptosis of cerebellar Purkinje cells.

METHODS

Treadmill running was applied to the rats in the exercise groups for 30 minutes once a day for 4 weeks, starting 4 weeks after birth. We used rota-rod test for the determination of motor coordination and balance. In this experiment, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining, immunohistochemistry for calbindin, glial fibrillary acidic protein (GFAP), Iba-1, and western blot analysis for Bax and Bcl-2 were performed.

RESULTS

Treadmill running enhanced motor balance and coordination by preventing the loss of Purkinje cells in the cerebellar vermis. Treadmill running suppressed PD-induced expression of GFAP-positive reactive astrocytes and Iba-1-positive microglia, showing that treadmill running suppressed reactive astrogliosis and microglia activation. Treadmill running suppressed TUNEL-positive cell number and Bax expression and enhanced Bcl-2 expression, demonstrating that treadmill running inhibited the progress of apoptosis in the cerebellum of rotenone-induced PD rats.

CONCLUSION

Treadmill running improved motor ability of the rotenone-induced PD rats by inhibiting apoptosis in the cerebellum. Apoptosis suppressing effect of treadmill running on rotenone-induced PD was achieved via suppression of reactive astrocyte and inhibition of microglial activation.

Cilostazol disrupts TLR-4, Akt/GSK-3β/CREB, and IL-6/JAK-2/STAT-3/SOCS-3 crosstalk in a rat model of Huntington's disease

Countless neurodegenerative diseases are associated with perverse multiple targets of cyclic nucleotide signalling, hastening neuronal death. Cilostazol, a phosphodiesterase-III inhibitor, exerts neuroprotective effects against sundry models of neurotoxicity, however, its role against Huntington's disease (HD) has not yet been tackled. Hence, its modulatory effect on several signalling pathways using the 3-nitropropionic acid (3-NP) model was conducted. Animals were injected with 3-NP (10 mg/kg/day, i.p) for two successive weeks with or without the administration of cilostazol (100 mg/kg/day, p.o.). Contrary to the 3-NP effects, cilostazol largely preserved striatal dopaminergic neurons, improved motor coordination, and enhanced the immunohistochemical reaction of tyrosine hydroxylase enzyme. The anti-inflammatory effect of cilostazol was documented by the pronounced reduction of the toll like receptor-4 (TLR-4) protein expression and the inflammatory cytokine IL-6, but with a marked elevation in IL-10 striatal contents. As a consequence, cilostazol reduced IL-6 downstream signal, where it promoted the level of suppressor of cytokine signalling 3 (SOCS3), while abated the phosphorylation of Janus Kinase 2 (JAK-2) and Signal transducers and activators of transcription 3 (STAT-3). Phosphorylation of the protein kinase B/glycogen synthase kinase-3β/cAMP response element binding protein (Akt/GSK-3β/CREB) cue is another signalling pathway that was modulated by cilostazol to further signify its anti-inflammatory and antiapoptotic capacities. The latter was associated with a reduction in the caspase-3 expression assessed by immunohistochemical assay. In conclusion the present study provided a new insight into the possible mechanisms by which cilostazol possesses neuroprotective properties. These intersecting mechanisms involve the interference between TLR-4, IL-6-IL-10/JAK-2/STAT-3/SOCS-3, and Akt/GSK-3β/CREB signalling pathways.

Parkinson's disease research: adopting a more human perspective to accelerate advances

Parkinson's disease (PD) affects 1% of the population over 60 years old and, with global increases in the aging population, presents huge economic and societal burdens. The etiology of PD remains unknown; most cases are idiopathic, presumed to result from genetic and environmental risk factors. Despite 200 years since the first description of PD, the mechanisms behind initiation and progression of the characteristic neurodegenerative processes are not known. Here, we review progress and limitations of the multiple PD animal models available and identify advances that could be implemented to better understand pathological processes, improve disease outcome, and reduce dependence on animal models. Lessons learned from reducing animal use in PD research could serve as guideposts for wider biomedical research.

Caffeic acid improves locomotor activity and lessens inflammatory burden in a mouse model of rotenone-induced nigral neurodegeneration: Relevance to Parkinson's disease therapy

BACKGROUND

Caffeic acid phenethyl ester is found in honey bee propolis. It has immunomodulatory, anti-inflammatory and anti-cancer properties. Rotenone is a pesticide commonly used for inducing experimental Parkinson's disease (PD) due to complex I inhibition and microglia activating properties. The current study examined neuroprotective effect of caffeic acid against rotenone-induced neurodegeneration in groups of seven mice.

METHODS

Mice received protective doses of caffeic acid (2.5, 5 or 10 mg/kg) daily and nine injections of rotenone (1 mg kg, subcutaneously) - every 48 h. Behavioral evaluation of motor function was done by a battery of tests including open-field test, cylinder test, pole test and rotarod test; all these tests showed motor impairment.

RESULTS

Assay of striatal dopamine highlighted a significant decrease and increases in inflammatory markers. In addition, histopathological assessment of substantia nigra neurons demonstrated low immunostaining for tyrosine hydroxylase (TH) in rotenone treated mice. PCR analysis highlighted upregulation for genes encoding CD₁₁b (a microglia surface antigen), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS) and nuclear factor-κB (NFκB). Treatment with caffeic acid (5 or 10 mg/kg) amended most of rotenone-induced motor deficits, lessened microglia expression and inflammatory mediators and improved the nigral TH immunostaining.

CONCLUSION

These results confirmed the anti-inflammatory activity of caffeic acid and highlighted its neuroprotective activity against rotenone-induced neurodegeneration in mice.

NCX1 and NCX3 as potential factors contributing to neurodegeneration and neuroinflammation in the A53T transgenic mouse model of Parkinson's Disease

Na⁺-Ca²⁺ exchanger (NCX) isoforms constitute the major cellular Ca²⁺ extruding system in neurons and microglia. We herein investigated the role of NCX isoforms in the pathophysiology of Parkinson's disease (PD). Their expression and activity were evaluated in neurons and glia of mice expressing the human A53T variant of α-synuclein (A53T mice), an animal model mimicking a familial form of PD. Western blotting revealed that NCX3 expression in the midbrain of 12-month old A53T mice was lower than that of wild type (WT). Conversely, NCX1 expression increased in the striatum. Immunohistochemical studies showed that glial fibrillary acidic protein (GFAP)-positive astroglial cells significantly increased in the substantia nigra pars compacta (SNc) and in the striatum. However, the number and the density of tyrosine hydroxylase (TH)-positive neurons decreased in both brain regions. Interestingly, ionized calcium binding adaptor molecule 1 (IBA-1)-positive microglial cells increased only in the striatum of A53T mice compared to WT. Double immunostaining studies showed that in A53T mice, NCX1 was exclusively co-expressed in IBA-1-positive microglial cells in the striatum, whereas NCX3 was solely co-expressed in TH-positive neurons in SNc. Beam walking and pole tests revealed a reduction in motor performance for A53T mice compared to WT. In vitro experiments in midbrain neurons from A53T and WT mice demonstrated a reduction in NCX3 expression, which was accompanied by mitochondrial overload of Ca²⁺ ions, monitored with confocal microscopy by X-Rhod-1 fluorescent dye. Collectively, in vivo and in vitro findings suggest that the reduction in NCX3 expression and activity in A53T neurons from midbrain may cause mitochondrial dysfunction and neuronal death in this brain area, whereas NCX1 overexpression in microglial cells may promote their proliferation in the striatum.

Zebrafish as an Animal Model for Drug Discovery in Parkinson's Disease and Other Movement Disorders: A Systematic Review

Movement disorders can be primarily divided into hypokinetic and hyperkinetic. Most of the hypokinetic syndromes are associated with the neurodegenerative disorder Parkinson’s disease (PD). By contrast, hyperkinetic syndromes encompass a broader array of diseases, including dystonia, essential tremor, or Huntington’s disease. The discovery of effective therapies for these disorders has been challenging and has also involved the development and characterization of accurate animal models for the screening of new drugs. Zebrafish constitutes an alternative vertebrate model for the study of movement disorders. The neuronal circuitries involved in movement in zebrafish are well characterized, and most of the associated molecular mechanisms are highly conserved. Particularly, zebrafish models of PD have contributed to a better understanding of the role of several genes implicated in the disease. Furthermore, zebrafish is a vertebrate model particularly suited for large-scale drug screenings. The relatively small size of zebrafish, optical transparency, and lifecycle, are key characteristics that facilitate the study of multiple compounds at the same time. Several transgenic, knockdown, and mutant zebrafish lines have been generated and characterized. Therefore, it is central to critically analyze these zebrafish lines and understand their suitability as models of movement disorders. Here, we revise the pathogenic mechanisms, phenotypes, and responsiveness to pharmacotherapies of zebrafish lines of the most common movement disorders. A systematic review of the literature was conducted by including all studies reporting the characterization of zebrafish models of the movement disorders selected from five bibliographic databases. A total of 63 studies were analyzed, and the most relevant data within the scope of this review were gathered. The majority (62%) of the studies were focused in the characterization of zebrafish models of PD. Overall, the zebrafish models included display conserved biochemical and neurobehavioral features of the phenomenology in humans. Nevertheless, in light of what is known for all animal models available, the use of zebrafish as a model for drug discovery requires further optimization. Future technological developments alongside with a deeper understanding of the molecular bases of these disorders should enable the development of novel zebrafish lines that can prove useful for drug discovery for movement disorders.

Quantitative Analysis of Catecholamines in the Pink1 -/- Rat Model of Early-onset Parkinson's Disease

Parkinson's disease (PD) related to homozygous mutations in the Pink1 gene is associated with nigrostriatal dopamine depletion and a wide range of sensorimotor deficits. In humans and animal models of PD, not all sensorimotor deficits are levodopa-responsive. We hypothesized that the underlying mechanisms of locomotion, limb control, and vocal communication behavior include other pathologies. Here, Pink1 -/- rats were treated with an oral dose of levodopa and limb motor and vocal communication behaviors were measured. Levodopa significantly improved some aspects of locomotion but did not improve ultrasonic vocalization intensity or frequency. Catecholamine concentrations in the striatum (SR), substantia nigra (SN), and locus coeruleus (LC) were analyzed to test the hypothesis that behavioral deficits would correlate to altered protein levels. There were no differences in dopamine concentrations in the SR and SN of Pink1 -/- animals compared to wild-type controls. There was a significant increase in norepinephrine concentration in the SN of Pink1 -/- animals. Moreover, an observed decrease in norepinephrine concentrations in the LC is consistent with the hypothesis that early-stage PD includes noradrenergic loss in the brainstem, and is congruent with a significant increase in catechol-O-methyltransferase expression in the LC of Pink1 -/- animals. Pearson's correlations showed that increases in time to traverse a tapered balance beam are significantly associated with reductions in striatal dopamine. Ultrasonic vocalization complexity was positively correlated with LC norepinephrine concentrations. These data support the evolving hypothesis that differences in neural substrates and early-onset noradrenergic mechanisms in the brainstem may contribute to pathogenesis in the Pink1 -/- rat.

Rotenone exerts developmental neurotoxicity in a human brain spheroid model

Growing concern suggests that some chemicals exert (developmental) neurotoxicity (DNT and NT) and are linked to the increase in incidence of autism, attention deficit and hyperactivity disorders. The high cost of routine tests for DNT and NT assessment make it difficult to test the high numbers of existing chemicals. Thus, more cost effective neurodevelopmental models are needed. The use of induced pluripotent stem cells (iPSC) in combination with the emerging human 3D tissue culture platforms, present a novel tool to predict and study human toxicity. By combining these technologies, we generated multicellular brain spheroids (BrainSpheres) from human iPSC. The model has previously shown to be reproducible and recapitulates several neurodevelopmental features. Our results indicate, rotenone's toxic potency varies depending on the differentiation status of the cells, showing higher reactive oxygen species (ROS) and higher mitochondrial dysfunction during early than later differentiation stages. Immuno-fluorescence morphology analysis after rotenone exposure indicated dopaminergic-neuron selective toxicity at non-cytotoxic concentrations (1 μM), while astrocytes and other neuronal cell types were affected at (general) cytotoxic concentrations (25 μM). Omics analysis showed changes in key pathways necessary for brain development, indicating rotenone as a developmental neurotoxicant and show a possible link between previously shown effects on neurite outgrowth and presently observed effects on Ca2+ reabsorption, synaptogenesis and PPAR pathway disruption. In conclusion, our BrainSpheres model has shown to be a reproducible and novel tool to study neurotoxicity and developmental neurotoxicity. Results presented here support the idea that rotenone can potentially be a developmental neurotoxicant.

[A study of combination treatment with nacom (levodopa + carbodope) and citicoline in the model of Parkinson disease in rats]

AIM

To evaluate the efficacy of the combined use of citicoline (neipilept) and levodopa/carbidopa (nakom) in the rotenone model of Parkinson's disease in rats.

MATERIAL AND METHODS

Rotenone was administrated during 14 days in dose 2 mg/kg/day subcutaneously. The duration of treatment was 7 days, intragastrically. Alteration of locomotor behavior components, muscular rigidity in resistance to passive flexion in the ankle joint and signs of extrapyramidal disorders were assessed.

RESULTS AND CONCLUSION

Combined therapy led to the decrease in muscle rigidity (the decrease of gibbosity in resistance to passive flexion in the ankle joint). There was a decrease in oligokinesia that emerged in higher vertical and horizontal locomotor activity of experimental animals, decrease in the time of head turning during climbing down the pole and total time of climbing down the pole. The combination of drugs had a more pronounced therapeutic effect on extrapyramidal disorders compared to monotherapy.

An adverse outcome pathway for parkinsonian motor deficits associated with mitochondrial complex I inhibition

Epidemiological studies have observed an association between pesticide exposure and the development of Parkinson's disease, but have not established causality. The concept of an adverse outcome pathway (AOP) has been developed as a framework for the organization of available information linking the modulation of a molecular target [molecular initiating event (MIE)], via a sequence of essential biological key events (KEs), with an adverse outcome (AO). Here, we present an AOP covering the toxicological pathways that link the binding of an inhibitor to mitochondrial complex I (i.e., the MIE) with the onset of parkinsonian motor deficits (i.e., the AO). This AOP was developed according to the Organisation for Economic Co-operation and Development guidelines and uploaded to the AOP database. The KEs linking complex I inhibition to parkinsonian motor deficits are mitochondrial dysfunction, impaired proteostasis, neuroinflammation, and the degeneration of dopaminergic neurons of the substantia nigra. These KEs, by convention, were linearly organized. However, there was also evidence of additional feed-forward connections and shortcuts between the KEs, possibly depending on the intensity of the insult and the model system applied. The present AOP demonstrates mechanistic plausibility for epidemiological observations on a relationship between pesticide exposure and an elevated risk for Parkinson's disease development.

Metformin lowers α-synuclein phosphorylation and upregulates neurotrophic factor in the MPTP mouse model of Parkinson's disease

In spite of the massive research for the identification of neurorestorative or neuroprotective intervention for curing Parkinson's disease (PD), there is still lack of clinically proven neuroprotective agents. Metformin, a common anti-hyperglycemic drug has been known to possess neuroprotective properties. However, specific mechanisms by which metformin protects neurons from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity remain to be elucidated. In this study, we assessed the neuroprotective effects of metformin in the subchronic MPTP model of PD, and explored its feasible mechanisms for neuroprotection. Animals received saline or MPTP injection (30 mg/kg/day) for the first 7 days, and then saline or metformin (200 mg/kg/day) for the next 7 days. Immunohistochemical stainings showed that metformin rescued the tyrosine hydroxylase-positive neurons and attenuated astroglial activation in the nigrostriatal pathway. In parallel, metformin restored dopamine depletion and behavioral impairments exerted by MPTP. Western blot analysis revealed that metformin ameliorated MPTP-induced α-synuclein phosphorylation which was accompanied by increased methylation of protein phosphatase 2A (PP2A), a phosphatase related to α-synuclein dephosphorylation. Moreover, the metformin regimen significantly increased the level of brain derived neurotrophic factor in the substantia nigra, and activated signaling pathways related to cell survival. Proof of concept study revealed that inhibition of PP2A or tropomyosin receptor kinase B reversed neuroprotective property of metformin in SH-SY5Y cells. Our results indicate that metformin provides neuroprotection against MPTP neurotoxicity, which might be mediated by inhibition of α-synuclein phosphorylation and induction of neurotrophic factors.

Neural Repair Strategies for Parkinson's Disease: Insights from Primate Models

Nonhuman primate models of Parkinson's disease (PD) have been invaluable to our understanding of the human disease and in the advancement of novel therapies for its treatment. In this review, we attempt to give a brief overview of the animal models of PD currently used, with a more comprehensive focus on the advantages and disadvantages presented by their use in the nonhuman primate. In particular, discussion addresses the 6-hydroxydopamine (6-OHDA), 1-methyl-1,2,3,6-tetrahydopyridine (MPTP), rotenone, paraquat, and maneb parkinsonian models. Additionally, the role of primate PD models in the development of novel therapies, such as trophic factor delivery, grafting, and deep brain stimulation, are described. Finally, the contribution of primate PD models to our understanding of the etiology and pathology of human PD is discussed.

Adulthood Exposure to Lipopolysaccharide Exacerbates the Neurotoxic and Inflammatory Effects of Rotenone in the Substantia Nigra

Parkinson's disease (PD) is the second most neurodegenerative disorder with a regional decrease of dopamine (DA) neurons in the substantia nigra (SN). Despite intense exploration, the etiology of PD progressive process remains unclear. This study was to investigate the synergistic effects of systemic inflammation of lipopolysaccharide (LPS) and neurotoxicity of rotenone (ROT) on exacerbating DA neuron lesion. Male SD adulthood rats received a single intraperitoneal injection of LPS. Seven months later, rats were subcutaneously given ROT five times a week for consecutive 4 weeks. Rat behavior changes were assessed via rotarod and open-field tests. Brain SN was immunostained to evaluate DA neuronal loss and microglia activation. Striatum DA and its metabolites levels were determined by high performance liquid chromatography (HPLC) coupled with electrochemistry. The protein levels of α-synuclein (α-Syn), inflammatory factors and mitogen-activated protein kinase (MAPK) pathway activation were detected by western blotting analysis. Results indicated that no significant difference between the control and LPS alone groups was shown. Compared with ROT alone group, LPS combined with ROT significantly reduced motor activity and induced SN DA neurons loss accompanied by the decreased contents of striatum DA and its metabolites. Furthermore, LPS together with ROT enhanced microglia activation and the increased expressions of α-Syn and inflammatory factors and also MAPK signaling pathway activation. However, LPS alone had no significant effects on the above parameters. These findings suggest that adulthood exposure to LPS exacerbates the neurotoxic and inflammatory effects of ROT in the SN.