Unilateral Intrastriatal 6-Hydroxydopamine Lesion in Mice: A Closer Look into Non-Motor Phenotype and Glial Response

Escitalopram moderately outperforms citalopram towards anti-neuroinflammation and neuroprotection in 6-hydroxydopamine-induced mouse model of Parkinson's disease

Citalopram and escitalopram are structurally close-related antidepressants and both forms are widely used in the world. We aimed to comparatively evaluate the anti-neuroinflammatory and neuroprotective effects of escitalopram and citalopram in Parkinson's disease (PD) mouse model. Mice were randomly divided into six groups and received 6-hydroxydopamine (6-OHDA) or vehicle administration. The mice were then treated with escitalopram, citalopram or saline for consecutive 7 days. Behaviors, neuroinflammation, neurotransmitters, and neurotoxicity were assessed. Results showed that citalopram but not escitalopram worsened body weight loss and increased freezing time in the PD mice. Both drugs had no impact on the anxiety-like behaviors but ameliorated the depressive-like behaviors as in elevated plus maze and sucrose splash tests. Escitalopram but not citalopram ameliorated motor discoordination in the PD mice as in rotarod test. In accordance, escitalopram but not citalopram attenuated the 6-OHDA-induced nigrostriatal dopaminergic loss. Further mechanistic investigations showed that both drugs mitigated activations of microglia and astrocytes and/or levels of pro-inflammatory cytokines in the PD mice, but escitalopram showed appreciably better effects in the substantia nigra. Neurotransmitter examination in the prefrontal cortex suggested that the two drugs had comparable effects on the disturbed neurotransmitters in the PD mice, but citalopram was prone to disrupt certain normal homeostasis. In conclusion, escitalopram is moderately superior than citalopram to suppress neuroinflammation and to protect against dopaminergic neuronal death and motor discoordination in the 6-OHDA-induced PD mice. Our findings imply that escitalopram shall be prescribed with priority over citalopram to treat PD patients with depression as escitalopram may meanwhile provide greater additional benefits to the patients.

Arrestin-3-assisted activation of JNK3 mediates dopaminergic behavioral sensitization

In rodents with unilateral ablation of neurons supplying dopamine to the striatum, chronic treatment with the dopamine precursor L-DOPA induces a progressive increase of behavioral responses, a process known as behavioral sensitization. This sensitization is blunted in arrestin-3 knockout mice. Using virus-mediated gene delivery to the dopamine-depleted striatum of these mice, we find that the restoration of arrestin-3 fully rescues behavioral sensitization, whereas its mutant defective in c-Jun N-terminal kinase (JNK) activation does not. A 25-residue arrestin-3-derived peptide that facilitates JNK3 activation in cells, expressed ubiquitously or selectively in direct pathway striatal neurons, also fully rescues sensitization, whereas an inactive homologous arrestin-2-derived peptide does not. Behavioral rescue is accompanied by the restoration of JNK3 activity, as reflected by JNK-dependent phosphorylation of the transcription factor c-Jun in the dopamine-depleted striatum. Thus, arrestin-3-assisted JNK3 activation in direct pathway neurons is a critical element of the molecular mechanism underlying sensitization upon dopamine depletion and chronic L-DOPA treatment.

Secretome of bone marrow mesenchymal stromal cells cultured in a dynamic system induces neuroprotection and modulates microglial responsiveness in an α-synuclein overexpression rat model

BACKGROUND AIMS

Parkinson's disease (PD) is the second most common neurodegenerative disorder. The etiology of the disease remains largely unknown, but evidence have suggested that the overexpression and aggregation of alpha-synuclein (α-syn) play key roles in the pathogenesis and progression of PD. Mesenchymal stromal cells (MSCs) have been earning attention in this field, mainly due to their paracrine capacity. The bioactive molecules secreted by MSCs, i.e. their secretome, have been associated with enhanced neuronal survival as well as a strong modulatory capacity of the microenvironments where the disease develops. The selection of the appropriate animal model is crucial in studies of efficacy assessment. Given the involvement of α-syn in the pathogenesis of PD, the evidence generated from the use of animal models that develop a pathologic phenotype due to the action of this protein is extremely valuable. Therefore, in this work, we established an animal model based on the viral vector-mediated overexpression of A53T α-syn and studied the impact of the secretome of bone marrow mesenchymal stromal cells MSC(M) as a therapeutic strategy.

METHODS

Adult male rats were subjected to α-syn over expression in the nigrostriatal pathway to model dopaminergic neurodegeneration. The impact of locally administered secretome treatment from MSC(M) was studied. Motor impairments were assessed throughout the study coupled with whole-region (striatum and substantia nigra) confocal microscopy evaluation of histopathological changes associated with dopaminergic neurodegeneration and glial cell reactivity.

RESULTS

Ten weeks after lesion induction, the animals received secretome injections in the substantia nigra pars compacta (SNpc) and striatum (STR). The secretome used was produced from bone marrow mesenchymal stromal cells MSC(M) expanded in a spinner flask (SP) system. Nine weeks later, animals that received the viral vector containing the gene for A53T α-syn and treated with vehicle (Neurobasal-A medium) presented dopaminergic cell loss in the SNpc and denervation in the STR. The treatment with secretome significantly reduced the levels of α-syn in the SNpc and protected the dopaminergic neurons (DAn) within the SNpc and STR.

CONCLUSIONS

Our results are aligned with previous studies in both α-syn Caenorhabditis elegans models, as well as 6-OHDA rodent model, revealing that secretome exerted a neuroprotective effect. Moreover, these effects were associated with a modulation of microglial reactivity supporting an immunomodulatory role for the factors contained within the secretome. This further supports the development of new studies exploring the effects and the mechanism of action of secretome from MSC(M) against α-syn-induced neurotoxicity.

Ergothioneine-Mediated Neuroprotection of Human iPSC-Derived Dopaminergic Neurons

Cell death involving oxidative stress and mitochondrial dysfunction is a major cause of dopaminergic neuronal loss in the substantia nigra (SN) of Parkinson's disease patients. Ergothioneine (ET), a natural dietary compound, has been shown to have cytoprotective functions, but neuroprotective actions against PD have not been well established. 6-Hydroxydopamine (6-OHDA) is a widely used neurotoxin to simulate the degeneration of dopaminergic (DA) neurons in Parkinson's disease. In this study, we investigated the protective effect of ET on 6-OHDA treated iPSC-derived dopaminergic neurons (iDAs) and further confirmed the protective effects in 6-OHDA-treated human neuroblastoma SH-SY5Y cells. In 6-OHDA-treated cells, decreased mitochondrial membrane potential (ΔΨm), increased mitochondrial reactive oxygen species (mROS), reduced cellular ATP levels, and increased total protein carbonylation levels were observed. 6-OHDA treatment also significantly decreased tyrosine hydroxylase levels. These effects were significantly decreased when ET was present. Verapamil hydrochloride (VHCL), a non-specific inhibitor of the ET transporter OCTN1 abrogated ET's cytoprotective effects, indicative of an intracellular action. These results suggest that ET could be a potential therapeutic for Parkinson's disease.

Functional activation of dorsal striatum astrocytes improves movement deficits in hemi-parkinsonian mice

Parkinson's disease (PD) is characterized by the degeneration of dopaminergic nigrostriatal inputs, which causes striatal network dysfunction and leads to pronounced motor deficits. Recent evidence highlights astrocytes as a potential local source of striatal network modulation. However, it remains unknown how dopamine loss affects striatal astrocyte activity and whether astrocyte activity regulates behavioral deficits in PD. We addressed these questions by performing astrocyte-specific calcium recordings and manipulations using in vivo fiber photometry and chemogenetics. We find that locomotion elicits astrocyte calcium activity over a slower timescale than neurons. Unilateral dopamine depletion reduced locomotion-related astrocyte responses. Chemogenetic activation facilitated astrocyte activity, and improved asymmetrical motor deficits and open field exploratory behavior in dopamine lesioned mice. Together, our results establish a novel role for functional striatal astrocyte signaling in modulating motor function in PD and highlight non-neuronal targets for potential PD therapeutics.

Characterization of graded 6-Hydroxydopamine unilateral lesion in medial forebrain bundle of mice

Parkinson's disease (PD) is the second most common age-related neurodegenerative disease, with a progressive loss of dopaminergic cells and fibers. The purpose of this study was to use different doses of 6-hydroxydopamine (6-OHDA) injection into the medial forebrain bundle (MFB) of mice to mimic the different stages of the disease and to characterize in detail their motor and non-motor behavior, as well as neuropathological features in the nigrostriatal pathway. MFB were injected with 0.5 μg, 1 μg, 2 μg of 6-OHDA using a brain stereotaxic technique. 6-OHDA induced mitochondrial damage dose-dependently, as well as substantia nigra pars compacta (SNpc) tyrosine hydroxylase-positive (TH+) cell loss and striatal TH fiber loss. Activation of astrocytes and microglia in the SNpc and striatum were consistently observed at 7 weeks, suggesting a long-term glial response in the nigrostriatal system. Even with a partial or complete denervation of the nigrostriatal pathway, 6-OHDA did not cause anxiety, although depression-like behavior appeared. Certain gait disturbances were observed in 0.5 μg 6-OHDA lesioned mice, and more extensive in 1 μg group. Despite the loss of more neurons from 2 μg 6-OHDA, there was no further impairment in behaviors compared to 1 μg 6-OHDA. Our data have implications that 1 μg 6-OHDA was necessary and sufficient to induce motor and non-motor symptoms in mice, thus a valuable mouse tool to explore disease progression and new treatment in PD.

Therapeutic Viewpoint on Rat Models of Locomotion Abnormalities and Neurobiological Indicators in Parkinson's Disease

BACKGROUND

Locomotion problems in Parkinson's syndrome are still a research and treatment difficulty. With the recent introduction of brain stimulation or neuromodulation equipment that is sufficient to monitor activity in the brain using electrodes placed on the scalp, new locomotion investigations in patients having the capacity to move freely have sprung up.

OBJECTIVE

This study aimed to find rat models and locomotion-connected neuronal indicators and use them all over a closed-loop system to enhance the future and present treatment options available for Parkinson's disease.

METHODS

Various publications on locomotor abnormalities, Parkinson's disease, animal models, and other topics have been searched using several search engines, such as Google Scholar, Web of Science, Research Gate, and PubMed.

RESULTS

Based on the literature, we can conclude that animal models are used for further investigating the locomotion connectivity deficiencies of many biological measuring devices and attempting to address unanswered concerns from clinical and non-clinical research. However, translational validity is required for rat models to contribute to the improvement of upcoming neurostimulation-based medicines. This review discusses the most successful methods for modelling Parkinson's locomotion in rats.

CONCLUSION

This review article has examined how scientific clinical experiments lead to localised central nervous system injuries in rats, as well as how the associated motor deficits and connection oscillations reflect this. This evolutionary process of therapeutic interventions may help to improve locomotion- based treatment and management of Parkinson's syndrome in the upcoming years.

Combining fibril-induced alpha-synuclein aggregation and 6-hydroxydopamine in a mouse model of Parkinson's disease and the effect of cerebral dopamine neurotrophic factor on the induced neurodegeneration

The existent pre-clinical models of Parkinson's disease do not simultaneously recapitulate severe degeneration of dopamine neurons and the occurrence of alpha-synuclein (aSyn) aggregation in one study system. In this study, we injected aSyn pre-formed fibrils (PFF) and 6-hydroxydopamine (6-OHDA) unilaterally into the striatum of C57BL/6 wild-type male mice at an interval of 2 weeks to induce aggregation of aSyn protein and trigger the loss of dopamine neurons simultaneously in one model and studied the behavioural effects of the combination in these mice. 6-OHDA was tested at three different doses, and 2 μg of 6-OHDA combined with PFF-induced aSyn aggregation was found to produce the most optimal disease phenotype. At 14 weeks timepoint, mice injected with a combination of PFF and 6-OHDA sustained significant damage to the nigrostriatal pathway and exhibited aSyn-positive aggregation. Our data suggest that the neurons that formed large aSyn aggregates were particularly vulnerable to 6-OHDA-induced degeneration. We also demonstrate the manifestation of a relatively aggressive pathology in 2- to 4-month-old mice, as compared to younger 7- to 9-week-old ones. Furthermore, cerebral dopamine neurotrophic factor (CDNF) administered intrastriatally rescued dopamine neurons and motor behaviour of the animals to some extent from 6-OHDA toxicity. However, no such effect could be seen in the novel 6-OHDA + PFFs combination model. For the first time, we demonstrate the combined effect of PFF and 6-OHDA simultaneously in one model. We further discuss the scope for further optimizing this combination model to develop it as a promising pre-clinical platform for drug screening and development.

Behavioral, neural and ultrastructural alterations in a graded-dose 6-OHDA mouse model of early-stage Parkinson's disease

Studying animal models furthers our understanding of Parkinson's disease (PD) pathophysiology by providing tools to investigate detailed molecular, cellular and circuit functions. Different versions of the neurotoxin-based 6-hydroxydopamine (6-OHDA) model of PD have been widely used in rats. However, these models typically assess the result of extensive and definitive dopaminergic lesions that reflect a late stage of PD, leading to a paucity of studies and a consequential gap of knowledge regarding initial stages, in which early interventions would be possible. Additionally, the better availability of genetic tools increasingly shifts the focus of research from rats to mice, but few mouse PD models are available yet. To address these, we characterize here the behavioral, neuronal and ultrastructural features of a graded-dose unilateral, single-injection, striatal 6-OHDA model in mice, focusing on early-stage changes within the first two weeks of lesion induction. We observed early onset, dose-dependent impairments of overall locomotion without substantial deterioration of motor coordination. In accordance, histological evaluation demonstrated a partial, dose-dependent loss of dopaminergic neurons of substantia nigra pars compacta (SNc). Furthermore, electron microscopic analysis revealed degenerative ultrastructural changes in SNc dopaminergic neurons. Our results show that mild ultrastructural and cellular degradation of dopaminergic neurons of the SNc can lead to certain motor deficits shortly after unilateral striatal lesions, suggesting that a unilateral dose-dependent intrastriatal 6-OHDA lesion protocol can serve as a successful model of the early stages of Parkinson's disease in mice.

Treating Parkinson's Disease with Human Bone Marrow Mesenchymal Stem Cell Secretome: A Translational Investigation Using Human Brain Organoids and Different Routes of In Vivo Administration

Parkinson's disease (PD) is the most common movement disorder, characterized by the progressive loss of dopaminergic neurons from the nigrostriatal system. Currently, there is no treatment that retards disease progression or reverses damage prior to the time of clinical diagnosis. Mesenchymal stem cells (MSCs) are one of the most extensively studied cell sources for regenerative medicine applications, particularly due to the release of soluble factors and vesicles, known as secretome. The main goal of this work was to address the therapeutic potential of the secretome collected from bone-marrow-derived MSCs (BM-MSCs) using different models of the disease. Firstly, we took advantage of an optimized human midbrain-specific organoid system to model PD in vitro using a neurotoxin-induced model through 6-hydroxydopamine (6-OHDA) exposure. In vivo, we evaluated the effects of BM-MSC secretome comparing two different routes of secretome administration: intracerebral injections (a two-site single administration) against multiple systemic administration. The secretome of BM-MSCs was able to protect from dopaminergic neuronal loss, these effects being more evident in vivo. The BM-MSC secretome led to motor function recovery and dopaminergic loss protection; however, multiple systemic administrations resulted in larger therapeutic effects, making this result extremely relevant for potential future clinical applications.

Investigating affective neuropsychiatric symptoms in rodent models of Parkinson's disease

Affective neuropsychiatric disorders such as depression, anxiety and apathy are among the most frequent non-motor symptoms observed in people with Parkinson's disease (PD). These conditions often emerge during the prodromal phase of the disease and are generally considered to result from neurodegenerative processes in meso-corticolimbic structures, occurring in parallel to the loss of nigrostriatal dopaminergic neurons. Depression, anxiety, and apathy are often treated with conventional medications, including selective serotonin reuptake inhibitors, tricyclic antidepressants, and dopaminergic agonists. The ability of these pharmacological interventions to consistently counteract such neuropsychiatric symptoms in PD is still relatively limited and the development of reliable experimental models represents an important tool to identify more effective treatments. This chapter provides information on rodent models of PD utilized to study these affective neuropsychiatric symptoms. Neurotoxin-based and genetic models are discussed, together with the main behavioral tests utilized to identify depression- and anxiety-like behaviors, anhedonia, and apathy. The ability of various therapeutic approaches to counteract the symptoms observed in the various models is also reviewed.

Hemispheric asymmetries in mental disorders: evidence from rodent studies

The brain is built with hemispheric asymmetries in structure and function to enable fast neuronal processing. In neuroimaging studies, several mental disorders have been associated with altered or attenuated hemispheric asymmetries. However, the exact mechanism linking asymmetries and disorders is not known. Here, studies in animal models of mental disorders render important insights into the etiology and neuronal alterations associated with both disorders and atypical asymmetry. In this review, the current literature of animal studies in rats and mice focusing on anxiety and fear, anhedonia and despair, addiction or substance misuse, neurodegenerative disorders as well as stress exposure, and atypical hemispheric asymmetries is summarized. Results indicate overall increased right-hemispheric neuronal activity and a left-sided behavioral bias associated with symptoms of anxiety, fear, anhedonia, behavioral despair as well as stress exposure. Addiction behavior is associated with right-sided bias and transgenic models of Alzheimer's disease indicate an asymmetrical accumulation of fibrillar plaques. Most studies focused on changes in the bilateral amygdala and frontal cortex. Across studies, two crucial factors influencing atypical asymmetries arose independently of the disorder modeled: sex and developmental age. In conclusion, animal models of mental disorders demonstrate atypical hemispheric asymmetries similar to findings in patients. Particularly, increased left-sided behavior and greater right-hemispheric activity were found across models applying stress-based paradigms. However, sex- and age-dependent effects on atypical hemispheric asymmetries are present that require further investigation. Animal models enable the analysis of hemispheric changes on the molecular level which may be most effective to detect early alterations.

N-Acetylcysteine Treatment May Compensate Motor Impairments through Dopaminergic Transmission Modulation in a Striatal 6-Hydroxydopamine Parkinson's Disease Rat Model

Preventing degeneration and the loss of dopaminergic neurons (DAn) in the brain while mitigating motor symptoms remains a challenge in Parkinson's Disease (PD) treatment development. In light of this, developing or repositioning potential disease-modifying approaches is imperative to achieve meaningful translational gains in PD research. Under this concept, N-acetylcysteine (NAC) has revealed promising perspectives in preserving the dopaminergic system capability and modulating PD mechanisms. Although NAC has been shown to act as an antioxidant and (neuro)protector of the brain, it has yet to be acknowledged how this repurposed drug can improve motor symptomatology and provide disease-modifying properties in PD. Therefore, in the present work, we assessed the impact of NAC on motor and histological deficits in a striatal 6-hydroxydopamine (6-OHDA) rat model of PD. The results revealed that NAC enhanced DAn viability, as we found that it could restore dopamine transporter (DAT) levels compared to the untreated 6-OHDA group. Such findings were positively correlated with a significant amelioration in the motor outcomes of the 6-OHDA-treated animals, demonstrating that NAC may, somehow, be a modulator of PD degenerative mechanisms. Overall, we postulated a proof-of-concept milestone concerning the therapeutic application of NAC. Nevertheless, it is extremely important to understand the complexity of this drug and how its therapeutical properties interact with the cellular and molecular PD mechanisms.

Involvement of Abnormal p-α-syn Accumulation and TLR2-Mediated Inflammation of Schwann Cells in Enteric Autonomic Nerve Dysfunction of Parkinson's Disease: an Animal Model Study

The study was designed to investigate the pathogenesis of gastrointestinal (GI) impairment in Parkinson's disease (PD). We utilized 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 20 mg/kg) and probenecid (250 mg/kg) to prepare a PD mice model. MPTP modeling was first confirmed. GI motility was measured using stool collection test and enteric plexus loss was also detected. Intestinal phosphorylated α-synuclein (p-α-syn), inflammation, and S100 were assessed using western blotting. Association between Toll-like receptor 2(TLR2) and GI function was validated by Pearson's correlations. Immunofluorescence was applied to show co-localizations of intestinal p-α-syn, inflammation, and Schwann cells (SCs). CU-CPT22 (3 mg/kg, a TLR1/TLR2 inhibitor) was adopted then. Success in modeling, damaged GI neuron and function, and activated intestinal p-α-syn, inflammation, and SCs responses were observed in MPTP group, with TLR2 related to GI damage. Increased p-α-syn and inflammatory factors were shown in SCs of myenteron for MPTP mice. Recovered fecal water content and depression of inflammation, p-α-syn deposition, and SCs activity were noticed after TLR2 suppression. The study investigates a novel mechanism of PD GI autonomic dysfunction, demonstrating that p-α-syn accumulation and TLR2 signaling of SCs were involved in disrupted gut homeostasis and treatments targeting TLR2-mediated pathway might be a possible therapy for PD.

Lipocalin-2 Is a Key Regulator of Neuroinflammation in Secondary Traumatic and Ischemic Brain Injury

Reactive glial cells are hallmarks of brain injury. However, whether these cells contribute to secondary inflammatory pathology and neurological deficits remains poorly understood. Lipocalin-2 (LCN2) has inflammatory and neurotoxic effects in various disease models; however, its pathogenic role in traumatic brain injury remains unknown. The aim of the present study was to investigate the expression of LCN2 and its role in neuroinflammation following brain injury. LCN2 expression was high in the mouse brain after controlled cortical impact (CCI) and photothrombotic stroke (PTS) injury. Brain levels of LCN2 mRNA and protein were also significantly higher in patients with chronic traumatic encephalopathy (CTE) than in normal subjects. RT-PCR and immunofluorescence analyses revealed that astrocytes were the major cellular source of LCN2 in the injured brain. Lcn2 deficiency or intracisternal injection of an LCN2 neutralizing antibody reduced CCI- and PTS-induced brain lesions, behavioral deficits, and neuroinflammation. Mechanistically, in cultured glial cells, recombinant LCN2 protein enhanced scratch injury-induced proinflammatory cytokine gene expression and inhibited Gdnf gene expression, whereas Lcn2 deficiency exerted opposite effects. Together, our results from CTE patients, rodent brain injury models, and cultured glial cells suggest that LCN2 mediates secondary damage response to traumatic and ischemic brain injury by promoting neuroinflammation and suppressing the expression of neurotropic factors.

Role of α-synuclein in microglia: autophagy and phagocytosis balance neuroinflammation in Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease, and is characterized by accumulation of α-synuclein (α-syn). Neuroinflammation driven by microglia is an important pathological manifestation of PD. α-Syn is a crucial marker of PD, and its accumulation leads to microglia M1-like phenotype polarization, activation of NLRP3 inflammasomes, and impaired autophagy and phagocytosis in microglia. Autophagy of microglia is related to degradation of α-syn and NLRP3 inflammasome blockage to relieve neuroinflammation. Microglial autophagy and phagocytosis of released α-syn or fragments from apoptotic neurons maintain homeostasis in the brain. A variety of PD-related genes such as LRRK2, GBA and DJ-1 also contribute to this stability process.

OBJECTIVES

Further studies are needed to determine how α-syn works in microglia.

METHODS

A keyword-based search was performed using the PubMed database for published articles.

CONCLUSION

In this review, we discuss the interaction between microglia and α-syn in PD pathogenesis and the possible mechanism of microglial autophagy and phagocytosis in α-syn clearance and inhibition of neuroinflammation. This may provide a novel insight into treatment of PD.

Non-motor manifestation of Parkinson's disease: a cross-sectional study in a teaching hospital in Jordan

Background

Parkinson's disease (PD) is the most common degenerative movement disorder. It is featured by motor manifestations and up till now the clinical diagnosis is based on them. Since the progress in the symptomatic treatment of PD and the longer survival of patients, non-motor manifestations (NMM) were more recognized and considered to be significant. The importance of NMM is that they reflect the more diffuse pathology of PD and may represent an opportunity of earlier diagnosis and treatment. Here in this cross-sectional study, we try to estimate the frequency of such manifestations in PD patients in the country. Using slightly modified PD non-motor (28 of 30 responses) questionnaire (NMS Quest), we studied the incidence of NMM in 100 PD patients attending one major teaching hospital and compared their occurrence in 130 age- and gender-matched non-PD controls.

Results

Out of 100 PD patients (40% females) mean age 67.4 ± 12 with disease duration of 7.3 ± 5.8, range < 1–33.2 years), and 130 control subjects (48.5% females), mean age 65.0 ± 7.0. PD patients had 8.6 ± 5.3 NMM while controls had 3.4 ± 3.3 NMM, respectively (p < 0.00001 t test). Constipation, urgency, insomnia, sad feeling, panic, light headedness and recent memory impairment were the most prevalent NMM in PD compared to controls, while nocturia, restless legs, encopresis and falling were not different in the two groups. The number of NMM ranged from 0 to 21 in PD patients with 50% having ≥ 8 manifestations. The number of NMM did not correlate with age, gender, or disease duration as defined by the classical motor symptoms. Frequency of 23 of these 28 manifestations differed significantly in PD patients compared to controls.

Conclusions

This study confirms that NMM in Jordanian PD patients are very common as reported in other populations. This signifies the universal prevalence of such NMM reflecting their important impact on their daily life and their relevant contribution to better understanding of this disease.

Lima B, Araújo AAS, de Albuquerque-Junior RLC, Gramacho KP, Padilha FF, da Costa LP, Severino P, Cardoso JC, Souto EB, Gomes MZ. Africanized Bee Venom (Apis mellifera Linnaeus): Neuroprotective Effects in a Parkinson's Disease Mouse Model Induced by 6-hydroxydopamine

This study evaluated the neuroprotective effects of the Africanized bee venom (BV) and its mechanisms of action after 6-hydroxydopamine-(6-OHDA)-induced lesion in a mice model. Prior to BV treatment, mice received intrastriatal microinjections of 6-OHDA (no induced dopaminergic neuronal death) or ascorbate saline (as a control). BV was administered subcutaneously at different dosages (0.01, 0.05 or 0.1 mg·Kg^-1) once every two days over a period of 3 weeks. The open field test was carried out, together with the immunohistochemical and histopathological analysis. The chemical composition of BV was also assessed, identifying the highest concentrations of apamin, phospholipase A₂ and melittin. In the behavioral evaluation, the BV (0.1 mg·Kg^-1) counteracted the 6-OHDA-induced decrease in crossings and rearing. 6-OHDA caused loss of dopaminergic cell bodies in the substantia nigra pars compacta and fibers in striatum (STR). Mice that received 0.01 mg·Kg^-1 showed significant increase in the mean survival of dopaminergic cell bodies. Increased astrocytic infiltration occurred in the STR of 6-OHDA injected mice, differently from those of the groups treated with BV. The results suggested that Africanized BV has neuroprotective activity in an animal model of Parkinson's disease.

Defining the unknowns for cell therapies in Parkinson's disease

First-in-human clinical trials have commenced to test the safety and efficacy of cell therapies for people with Parkinson's disease (PD). Proof of concept that this neural repair strategy is efficacious is based on decades of preclinical studies and clinical trials using primary foetal cells, as well as a significant literature exploring more novel stem cell-derived products. Although several measures of efficacy have been explored, including the successful in vitro differentiation of stem cells to dopamine neurons and consistent alleviation of motor dysfunction in rodent models, many unknowns still remain regarding the long-term clinical implications of this treatment strategy. Here, we consider some of these outstanding questions, including our understanding of the interaction between anti-Parkinsonian medication and the neural transplant, the impact of the cell therapy on cognitive or neuropsychiatric symptoms of PD, the role of neuroinflammation in the therapeutic process and the development of graft-induced dyskinesias. We identify questions that are currently pertinent to the field that require further exploration, and pave the way for a more holistic understanding of this neural repair strategy for treatment of PD.

Striatal synaptic adaptations in Parkinson's disease

The striatum is densely innervated by mesencephalic dopaminergic neurons that modulate acquisition and vigor of goal-directed actions and habits. This innervation is progressively lost in Parkinson's disease (PD), contributing to the defining movement deficits of the disease. Although boosting dopaminergic signaling with levodopa early in the course of the disease alleviates these deficits, later this strategy leads to the emergence of debilitating dyskinesia. Here, recent advances in our understanding of how striatal cells and circuits adapt to this progressive de-innervation and to levodopa therapy are discussed. First, we discuss how dopamine (DA) depletion triggers cell type-specific, homeostatic changes in spiny projection neurons (SPNs) that tend to normalize striatal activity but also lead to disruption of the synaptic architecture sculpted by experience. Second, we discuss the roles played by cholinergic and nitric oxide-releasing interneurons in these adaptations. Third, we examine recent work in freely moving mice suggesting that alterations in the spatiotemporal dynamics of striatal ensembles contributes to PD movement deficits. Lastly, we discuss recently published evidence from a progressive model of PD suggesting that contrary to the classical model, striatal pathway imbalance is necessary but not sufficient to produce frank parkinsonism.

Pharmacological Rescue with SR8278, a Circadian Nuclear Receptor REV-ERBα Antagonist as a Therapy for Mood Disorders in Parkinson's Disease

Parkinson's disease is a neurodegenerative disease characterized by progressive dopaminergic neuronal loss. Motor deficits experienced by patients with Parkinson's disease are well documented, but non-motor symptoms, including mood disorders associated with circadian disturbances, are also frequent features. One common phenomenon is "sundowning syndrome," which is characterized by the occurrence of neuropsychiatric symptoms at a specific time (dusk), causing severe quality of life challenges. This study aimed to elucidate the underlying mechanisms of sundowning syndrome in Parkinson's disease and their molecular links with the circadian clock. We demonstrated that 6-hydroxydopamine (6-OHDA)-lesioned mice, as Parkinson's disease mouse model, exhibit increased depression- and anxiety-like behaviors only at dawn (the equivalent of dusk in human). Administration of REV-ERBα antagonist, SR8278, exerted antidepressant and anxiolytic effects in a circadian time-dependent manner in 6-OHDA-lesioned mice and restored the circadian rhythm of mood-related behaviors. 6-OHDA-lesion altered DAergic-specific Rev-erbα and Nurr1 transcription, and atypical binding activities of REV-ERBα and NURR1, which are upstream nuclear receptors for the discrete tyrosine hydroxylase promoter region. SR8278 treatment restored the binding activities of REV-ERBα and NURR1 to the tyrosine hydroxylase promoter and the induction of enrichment of the R/N motif, recognized by REV-ERBα and NURR1, as revealed by ATAC-sequencing; therefore, tyrosine hydroxylase expression was elevated in the ventral tegmental area of 6-OHDA-injected mice, especially at dawn. These results indicate that REV-ERBα is a potential therapeutic target, and its antagonist, SR8278, is a potential drug for mood disorders related to circadian disturbances, namely sundowning syndrome, in Parkinson's disease.