The Amphetamine Induced Rotation Test: A Re-Assessment of Its Use as a Tool to Monitor Motor Impairment and Functional Recovery in Rodent Models of Parkinson's Disease

The history and status of dopamine cell therapies for Parkinson's disease

Parkinson's disease (PD) is characterized by the loss of the dopaminergic nigrostriatal pathway which has led to the successful development of drug therapies that replace or stimulate this network pharmacologically. Although these drugs work well in the early stages of the disease, over time they produce side effects along with less consistent clinical benefits to the person with Parkinson's (PwP). As such there has been much interest in repairing this pathway using transplants of dopamine neurons. This work which began 50 years ago this September is still ongoing and has now moved to first in human trials using human pluripotent stem cell-derived dopaminergic neurons. The results of these trials are eagerly awaited although proof of principle data has already come from trials using human fetal midbrain dopamine cell transplants. This data has shown that developing dopamine cells when transplanted in the brain of a PwP can survive long term with clinical benefits lasting decades and with restoration of normal dopaminergic innervation in the grafted striatum. In this article, we discuss the history of this field and how this has now led us to the recent stem cell trials for PwP.

Aqueous extract of Swietenia macrophylla leaf exerts an anti-inflammatory effect in a murine model of Parkinson's disease induced by 6-OHDA

Introduction

Parkinson's disease affects 2% of the population aged over 65 years and is the second most common neurodegenerative disorder in the general population. The appearance of motor symptoms is associated with the degeneration of dopaminergic neurons in the nigrostriatal pathway. Clinically significant nonmotor symptoms are also important for severe disability with disease progression. Pharmacological treatment with levodopa, which involves dopamine restitution, results in a temporary improvement in motor symptoms. Among the mechanisms underlying the pathogenesis of the disease are exacerbated oxidative stress, mitochondrial dysfunction, and neuroinflammation. A phytochemical prospecting study showed that the aqueous extract of the leaves from Swietenia macrophylla (Melineaceae), known as mahogany, has polyphenols with antioxidant and anti-inflammatory capacity in a significantly higher percentage than leaf extracts from other Amazonian plants. Furthermore, the antioxidant and anti-inflammatory capacity of aqueous extract of mahogany leaf has already been demonstrated in an in vitro model. In this study, we hypothesized that the aqueous extract of mahogany leaf (AEML) has a neuroprotective effect in a murine model of Parkinson's disease induced by 6-hydroxidopamine (6-OHDA), due to antioxidant and anti-inflammatory properties of its phenolic compounds.

Methods

Mice were treated daily with the mahogany extract at a dose of 50 mg/kg, starting 7 days before 6-OHDA infusion until post-surgery day 7.

Results and discussion

The animals from the 6-OHDA/mahogany group, which corresponds to animals injected with the toxin and treated with aqueous extract of the mahogany leaf, presented distinct behavioral phenotypes after apomorphine challenge and were therefore subdivided into 2 groups, 6-OHDA/mahogany F1 and 6-OHDA/mahogany F2. The F1 group showed a significant increase in contralateral rotations, whereas the F2 group did not show rotations after the apomorphine stimulus. In the F1 group, there was an increase, although not significant, in motor performance in the open field and elevated plus maze tests, whereas in the F2 group, there was significant improvement, which may be related to the lesser degree of injury to the nigrostriatal dopaminergic pathway. The TH+ histopathological analysis, a dopaminergic neuron marker, confirmed that the lesion to the nigrostriatal dopaminergic pathway was more pronounced in 6-OHDA/mahogany F1 than in 6-OHDA/mahogany F2. Our main result consisted of signs of improvement in the inflammatory profile in both the F1 and F2 6-OHDA/mahogany groups, such as a lower number of IBA-1+ microglial cells in the ventral striatum and substantia nigra pars compacta and a reduction in GFAP+ expression, an astrocyte marker, in the dorsal striatum. In this study, several bioactive compounds in the aqueous extract of mahogany leaf may have contributed to the observed beneficial effects. Further studies are necessary to better characterize their applicability for treating chronic degenerative diseases with inflammatory and oxidative bases, such as Parkinson's disease.

Preclinical and dose-ranging assessment of hESC-derived dopaminergic progenitors for a clinical trial on Parkinson's disease

Human embryonic stem cell (hESC)-derived midbrain dopaminergic (mDA) cell transplantation is a promising therapeutic strategy for Parkinson's disease (PD). Here, we present the derivation of high-purity mDA progenitors from clinical-grade hESCs on a large scale under rigorous good manufacturing practice (GMP) conditions. We also assessed the toxicity, biodistribution, and tumorigenicity of these cells in immunodeficient rats in good laboratory practice (GLP)-compliant facilities. Various doses of mDA progenitors were transplanted into hemi-parkinsonian rats, and a significant dose-dependent behavioral improvement was observed with a minimal effective dose range of 5,000-10,000 mDA progenitor cells. These results provided insights into determining a low cell dosage (3.15 million cells) for human clinical trials. Based on these results, approval for a phase 1/2a clinical trial for PD cell therapy was obtained from the Ministry of Food and Drug Safety in Korea, and a clinical trial for treating patients with PD has commenced.

Neuroplasticity: Pathophysiology and Role in Major Depressive Disorder

Neuroplasticity is characterized by the brain's ability to change its activity in response to extrinsic and intrinsic factors and is thought to be the mechanism behind all brain functions. Neuroplasticity causes structural and functional changes on a molecular level, specifically the growth of different regions in the brain and changes in synaptic and post-synaptic activities. The four types of neuroplasticity are homologous area adaption, compensatory masquerade, cross-modal reassignment, and map expansion. All of these help the brain work around injuries or new information inputs. In addition to baseline physical functions, neuroplasticity is thought to be the basis of emotional and mental regulations and the impairment of it can cause various mental illnesses. Concurrently, these mental illnesses further the damage of synaptic plasticity in the brain. Major depressive disorder (MDD) is one of the most common mental illnesses. It is affected by and accelerates the impairment of neuroplasticity. It is characterized by a chronically depressed state of mind that can impact the patient's daily life, including work life and interests. This review will focus on highlighting the physiological aspects of the disease and the role of neuroplasticity in the pathogenesis and pathology of the disorder. Moreover, the role of monoamine regulation and ketamine uptake will be discussed in terms of their antidepressant effects on the outcomes of MDD.

CRISPR/sgRNA-directed synergistic activation mediator (SAM) as a therapeutic tool for Parkinson´s disease

Parkinson`s disease (PD) is the second most prevalent neurodegenerative disease, and different gene therapy strategies have been used as experimental treatments. As a proof-of-concept for the treatment of PD, we used SAM, a CRISPR gene activation system, to activate the endogenous tyrosine hydroxylase gene (th) of astrocytes to produce dopamine (DA) in the striatum of 6-OHDA-lesioned rats. Potential sgRNAs within the rat th promoter region were tested, and the expression of the Th protein was determined in the C6 glial cell line. Employing pseudo-lentivirus, the SAM complex and the selected sgRNA were transferred into cultures of rat astrocytes, and gene expression and Th protein synthesis were ascertained; furthermore, DA release into the culture medium was determined by HPLC. The DA-producing astrocytes were implanted into the striatum of 6-OHDA hemiparkinsonian rats. We observed motor behavior improvement in the lesioned rats that received DA-astrocytes compared to lesioned rats receiving astrocytes that did not produce DA. Our data indicate that the SAM-induced expression of the astrocyte´s endogenous th gene can generate DA-producing astrocytes that effectively reduce the motor asymmetry induced by the lesion.

Antagonism of kappa opioid receptors accelerates the development of L-DOPA-induced dyskinesia in a preclinical model of moderate dopamine depletion

Levels of the opioid peptide dynorphin, an endogenous ligand selective for kappa-opioid receptors (KORs), its mRNA and pro-peptide precursors are differentially dysregulated in Parkinson's disease (PD) and following the development of l-DOPA-induced dyskinesia (LID). It remains unclear whether these alterations contribute to the pathophysiological mechanisms underlying PD motor impairment and the subsequent development of LID, or whether they are part of compensatory mechanisms. We sought to investigate nor-BNI, a KOR antagonist, 1) in the dopamine (DA)-depleted PD state, 2) during the development phase of LID, and 3) via measuring of tonic levels of striatal DA. While nor-BNI (3 mg/kg; s.c.) did not lead to functional restoration in the DA-depleted state, it affected the dose-dependent development of abnormal voluntary movements (AIMs) in response to escalating doses of l-DOPA in a rat PD model with a moderate striatal 6-hydroxdopamine (6-OHDA) lesion. We tested five escalating doses of l-DOPA (6, 12, 24, 48, 72 mg/kg; i.p.), and nor-BNI significantly increased the development of AIMs at the 12 and 24 mg/kg l-DOPA doses. However, after reaching the 72 mg/kg l-DOPA, AIMs were not significantly different between control and nor-BNI groups. In summary, while blocking KORs significantly increased the rate of development of LID induced by chronic, escalating doses of l-DOPA in a moderate-lesioned rat PD model, it did not contribute further once the overall severity of LID was established. While we observed an increase of tonic DA levels in the moderately lesioned dorsolateral striatum, there was no tonic DA change following administration of nor-BNI.

Enhanced production of mesencephalic dopaminergic neurons from lineage-restricted human undifferentiated stem cells

Current differentiation protocols for generating mesencephalic dopaminergic (mesDA) neurons from human pluripotent stem cells result in grafts containing only a small proportion of mesDA neurons when transplanted in vivo. In this study, we develop lineage-restricted undifferentiated stem cells (LR-USCs) from pluripotent stem cells, which enhances their potential for differentiating into caudal midbrain floor plate progenitors and mesDA neurons. Using a ventral midbrain protocol, 69% of LR-USCs become bona fide caudal midbrain floor plate progenitors, compared to only 25% of human embryonic stem cells (hESCs). Importantly, LR-USCs generate significantly more mesDA neurons under midbrain and hindbrain conditions in vitro and in vivo. We demonstrate that midbrain-patterned LR-USC progenitors transplanted into 6-hydroxydopamine-lesioned rats restore function in a clinically relevant non-pharmacological behavioral test, whereas midbrain-patterned hESC-derived progenitors do not. This strategy demonstrates how lineage restriction can prevent the development of undesirable lineages and enhance the conditions necessary for mesDA neuron generation.

The Role of a Dopamine-Dependent Limbic-Motor Network in Sensory Motor Processing in Parkinson Disease

Limbic and motor integration is enabled by a mesial temporal to motor cortex network. Parkinson disease (PD) is characterized by a loss of dorsal striatal dopamine but relative preservation of mesolimbic dopamine early in disease, along with changes to motor action control. Here, we studied 47 patients with PD using the Simon conflict task and [18F]fallypride PET imaging. Additionally, a cohort of 16 patients participated in a single-blinded dextroamphetamine (dAMPH) study. Task performance was evaluated using the diffusion model for conflict tasks, which allows for an assessment of interpretable action control processes. First, a voxel-wise examination disclosed a negative relationship, such that longer non-decision time is associated with reduced D2-like binding potential (BPND) in the bilateral putamen, left globus pallidus, and right insula. Second, an ROI analysis revealed a positive relationship, such that shorter non-decision time is associated with reduced D2-like BPND in the amygdala and ventromedial OFC. The difference in non-decision time between off-dAMPH and on-dAMPH trials was positively associated with D2-like BPND in the globus pallidus. These findings support the idea that dysfunction of the traditional striatal-motor loop underlies action control deficits but also suggest that a compensatory parallel limbic-motor loop regulates motor output.

Effects of voluntary, and forced exercises on neurotrophic factors and cognitive function in animal models of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in the elderly. Cognitive dysfunction represents a common and challenging non-motor symptom for people with Parkinson's disease. The number of neurotrophic proteins in the brain is critical in neurodegenerative diseases such as Parkinson's. This research aims to compare the effects of two types of exercise, forced and voluntary, on spatial memory and learning and neurochemical factors (CDNF and BDNF).

METHODS

In this research, 60 male rats were randomly divided into six groups (n = 10): the control (CTL) group without exercise, the Parkinson's groups without and with forced (FE) and voluntary (VE) exercises, and the sham groups (with voluntary and forced exercise). The animals in the forced exercise group were placed on the treadmill for four weeks (five days a week). At the same time, voluntary exercise training groups were placed in a special cage equipped with a rotating wheel. At the end of 4 weeks, learning and spatial memory were evaluated with the Morris water maze test. BDNF and CDNF protein levels in the hippocampus were measured by the ELISA method.

RESULTS

The results showed that although the PD group without exercise was at a significantly lower level than other groups in terms of cognitive function and neurochemical factors, both types of exercise, could improve these problems.

CONCLUSION

According to our results, 4 weeks of voluntary and forced exercises were all found to reverse the cognitive impairments of PD rats.

Acyl-Ghrelin Attenuates Neurochemical and Motor Deficits in the 6-OHDA Model of Parkinson's Disease

The feeding-related hormone, acyl-ghrelin, protects dopamine neurones in murine 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-based models of experimental Parkinson's disease (PD). However, the potential protective effect of acyl-ghrelin on substantia nigra pars compacta (SNpc) dopaminergic neurones and consequent behavioural correlates in the more widely used 6-hydroxydopamine (6-OHDA) rat medial forebrain bundle (MFB) lesion model of PD are unknown. To address this question, acyl-ghrelin levels were raised directly by mini-pump infusion for 7 days prior to unilateral injection of 6-OHDA into the MFB with assessment of amphetamine-induced rotations on days 27 and 35, and immunohistochemical analysis of dopaminergic neurone survival. Whilst acyl-ghrelin treatment was insufficient to elevate food intake or body weight, it attenuated amphetamine-induced circling behaviour and SNpc dopamine neurone loss induced by 6-OHDA. These data support the notion that elevating circulating acyl-ghrelin may be a valuable approach to slow or impair progression of neurone loss in PD.

Neurite Outgrowth and Gene Expression Profile Correlate with Efficacy of Human Induced Pluripotent Stem Cell-Derived Dopamine Neuron Grafts

Transplantation of human induced pluripotent stem cell-derived dopaminergic (iPSC-DA) neurons is a promising therapeutic strategy for Parkinson's disease (PD). To assess optimal cell characteristics and reproducibility, we evaluated the efficacy of iPSC-DA neuron precursors from two individuals with sporadic PD by transplantation into a hemiparkinsonian rat model after differentiation for either 18 (d18) or 25 days (d25). We found similar graft size and dopamine (DA) neuron content in both groups, but only the d18 cells resulted in recovery of motor impairments. In contrast, we report that d25 grafts survived equally as well and produced grafts rich in tyrosine hydroxylase-positive neurons, but were incapable of alleviating any motor deficits. We identified the mechanism of action as the extent of neurite outgrowth into the host brain, with d18 grafts supporting significantly more neurite outgrowth than nonfunctional d25 grafts. RNAseq analysis of the cell preparation suggests that graft efficacy may be enhanced by repression of differentiation-associated genes by REST, defining the optimal predifferentiation state for transplantation. This study demonstrates for the first time that DA neuron grafts can survive well in vivo while completely lacking the capacity to induce recovery from motor dysfunction. In contrast to other recent studies, we demonstrate that neurite outgrowth is the key factor determining graft efficacy and our gene expression profiling revealed characteristics of the cells that may predict their efficacy. These data have implication for the generation of DA neuron grafts for clinical application.

Increased Physiological GDNF Levels Have No Effect on Dopamine Neuron Protection and Restoration in a Proteasome Inhibition Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disease that comprises a range of motor and nonmotor symptoms. Glial cell line-derived neurotrophic factor (GDNF) promotes the survival of dopamine neurons in vitro and in vivo, and intracranial delivery of GDNF has been tested in six clinical trials for treating PD. However, clinical trials with ectopic GDNF have yielded variable results, which could in part result from abnormal expression site and levels caused by ectopic overexpression. Therefore, an important open question is whether an increase in endogenous GDNF expression could be potent in reversing PD progression. Here, we tested the therapeutic potential of endogenous GDNF using mice in which endogenous GDNF can be conditionally upregulated specifically in cells that express GDNF naturally (conditional GDNF hypermorphic mice; Gdnf^cHyper ). We analyzed the impact of endogenous GDNF upregulation in both neuroprotection and neurorestoration procedures, and for both motor and nonmotor symptoms in the proteasome inhibitor lactacystin (LC) model of PD. Our results showed that upregulation of endogenous GDNF in the adult striatum is not protective in LC-induced PD model in mice. Since age is the largest risk factor for PD, we also analyzed the effect of deletion of endogenous GDNF in aged Gdnf conditional knock-out mice. We found that GDNF deletion does not increase susceptibility to LC-induced damage. We conclude that endogenous GDNF does not impact the outcome in the LC-induced proteasome inhibition mouse model of Parkinson's disease.

A Combined α-Synuclein/Fibril (SynFib) Model of Parkinson-Like Synucleinopathy Targeting the Nigrostriatal Dopamine System

Injections of pre-formed α-synuclein fibrils (PFFs) or overexpression of α-synuclein using AAV vectors are commonly used as models of Parkinson-like synucleinopathy in rats and mice. In the modified method reviewed here, the "SynFib" model, the PFFs and the AAV vector are administered together unilaterally into the substantia nigra. This approach combines the key features of these two models, i.e., the generation of toxic α-synuclein aggregates and Lewy body-like inclusions, in combination with the increased vulnerability caused by increased cellular levels of α-synuclein. The combined AAV/PFF delivery offers several advantages over the standard PFF model due to the enhanced and accelerated α-synuclein pathology and microglial response induced by the PFF seeds in the presence of an elevated α-synuclein level. Injection of the AAV/PFF mixture into the substantia nigra makes it possible to target a larger proportion of the nigral dopamine neurons and obtain a level of dopamine cell loss (>60%) needed to induce significant impairments in drug-induced and spontaneous motor tests. The SynFib model shares attractive features of the standard 6-OHDA lesion model: a single unilateral stereotaxic intervention; pathology and cell loss developing over a short time span; and the possibility to monitor the degenerative changes using tests of motor behavior.

Assessment of the anti-nociceptive effects of fetal ventral mesencephalic tissue allografts in a rat model of hemi-Parkinson's disease using fMRI

Extensive studies showed increased subjective pain sensitivity in Parkinson's disease (PD), which appeared to be partially reversed by dopaminergic (DA) treatment. Although cell replacement represents an attractive therapeutic strategy, its potential for PD-related hyperalgesia remains unclear. We investigated re-establishment of DA function via allografting exogenic DA cells on pain hypersensitivity in a rat model of PD. We evaluated the anti-nociceptive effects of fetal ventral mesencephalic (rVM) tissue allografts in PD rats after unilateral 6-OHDA-induced toxicity in the medial forebrain bundle. The drug -induced rotation test was used to validate the severity of the nigrostriatal lesion; von Frey and thermal pain tests were employed to evaluate nociceptive function. Nociception-induced cerebral blood volume (CBV) response was measured using a 4.7-T MR system. Finally, the immunohistochemical (IHC) studies were performed and the results were compared with the imaging findings from functional magnetic resonance imaging (fMRI). The grafts significantly improved drug-induced rotation behavior and increased mechanical and thermal nociceptive thresholds in PD rats. The elevation of CBV signals significantly recovered on the grafted striatum, whereas this effect was inhibited by the D2R antagonist eticlopride in each striatum. Quantitative IHC analysis revealed the transplantation markedly increased the numbers of tyrosine hydroxylase immunoreactive cells. Therefore, we concluded transplantation of rVM tissue results in anti-nociceptive effects and improves motor function. Moreover, in vivo CBV response confirmed the key role of D2R-mediated pain modulation. Therefore, we demonstrate fMRI as a reliable imaging index in evaluating the anti-nociceptive therapeutic effects of fetal rVM transplantation in the rat model of PD.

Determination of the Unilaterally Damaged Region May Depend on the Asymmetry of Carotid Blood Flow Velocity in Hemiparkinsonian Monkey: A Pilot Study

The hemiparkinsonian nonhuman primate model induced by unilateral injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) into the carotid artery is used to study Parkinson's disease. However, there have been no studies that the contralateral distribution of MPTP via the cerebral collateral circulation is provided by both the circle of Willis (CoW) and connections of the carotid artery. To investigate whether MPTP-induced unilaterally damaged regions were determined by asymmetrical cerebral blood flow, the differential asymmetric damage of striatal subregions, and examined structural asymmetries in a circle of Willis, and blood flow velocity of the common carotid artery were observed in three monkeys that were infused with MPTP through the left internal carotid artery. Lower flow velocity in the ipsilateral common carotid artery and a higher ratio of ipsilateral middle cerebral artery diameter to anterior cerebral artery diameter resulted in unilateral damage. Additionally, the unilateral damaged monkey observed the apomorphine-induced contralateral rotation behavior and the temporary increase of plasma RANTES. Contrastively, higher flow velocity in the ipsilateral common carotid artery was observed in the bilateral damaged monkey. It is suggested that asymmetry of blood flow velocity and structural asymmetry of the circle of Willis should be taken into consideration when establishing more efficient hemiparkinsonian nonhuman primate models.

Investigating cell therapies in animal models of Parkinson's and Huntington's disease: Current challenges and considerations

Cell therapeutics have entered into an exciting era, with first-in-person clinical trials underway for Parkinson's disease and novel cell therapies in development for other neurodegenerative diseases. In the hope of ensuring successful translation of these novel cell products to the clinic, a significant amount of preclinical work continues to be undertaken. Rodent models of neural transplantation are required to thoroughly assess the survival, safety and efficacy of novel therapeutics. It is critical to produce robust and reliable preclinical data, in order to increase the likelihood of clinical success. As a result, significant effort has been driven into generating ever more relevant model systems, from genetically modified disease models to mice with humanized immune systems. Despite this, several challenges remain in the quest to assess human cells in the rodent brain long-term. Here, with a focus on models of Parkinson's and Huntington's disease, we discuss key considerations for choosing an appropriate rodent model for neural transplantation. We also consider the challenges associated with long-term survival and assessment of functional efficacy in these models, as well as the need to consider the clinical relevance of the model. While the choice of model will be dependent on the scientific question, by considering the caveats associated with each model, we identify opportunities to optimize the preclinical assessment and generate reliable data on our novel cell therapeutics.

The potential use of mesenchymal stem cells and their exosomes in Parkinson's disease treatment

Parkinson's disease (PD) is the second most predominant neurodegenerative disease worldwide. It is recognized clinically by severe complications in motor function caused by progressive degeneration of dopaminergic neurons (DAn) and dopamine depletion. As the current standard of treatment is focused on alleviating symptoms through Levodopa, developing neuroprotective techniques is critical for adopting a more pathology-oriented therapeutic approach. Regenerative cell therapy has provided us with an unrivalled platform for evaluating potentially effective novel methods for treating neurodegenerative illnesses over the last two decades. Mesenchymal stem cells (MSCs) are most promising, as they can differentiate into dopaminergic neurons and produce neurotrophic substances. The precise process by which stem cells repair neuronal injury is unknown, and MSC-derived exosomes are suggested to be responsible for a significant portion of such effects. The present review discusses the application of mesenchymal stem cells and MSC-derived exosomes in PD treatment.

Olfactory Bulb D2/D3 Receptor Availability after Intrastriatal Botulinum Neurotoxin-A Injection in a Unilateral 6-OHDA Rat Model of Parkinson's Disease

Olfactory deficits occur as early non-motor symptoms of idiopathic Parkinson's disease (PD) in humans. The first central relay of the olfactory pathway, the olfactory bulb (OB), depends, among other things, on an intact, functional crosstalk between dopaminergic interneurons and dopamine receptors (D2/D3R). In rats, hemiparkinsonism (hemi-PD) can be induced by unilateral injection of 6-hydroxydopamine (6-OHDA) into the medial forebrain bundle (MFB), disrupting dopaminergic neurons of the substantia nigra pars compacta (SNpc). In a previous study, we showed that subsequent injection of botulinum neurotoxin-A (BoNT-A) into the striatum can reverse most of the pathological motor symptoms and normalize the D2/D3R availability. To determine whether this rat model is suitable to explain olfactory deficits that occur in humans with PD, we examined the availability of D2/D3R by longitudinal [18F]fallypride-PET/CT, the density of tyrosine hydroxylase immunoreactivity in the OB, olfactory performance by an orienting odor identification test adapted for rats, and a connectome analysis. PET/CT and immunohistochemical data remained largely unchanged after 6-OHDA lesion in experimental animals, suggesting that outcomes of the 6-OHDA hemi-PD rat model do not completely explain olfactory deficits in humans. However, after subsequent ipsilateral BoNT-A injection into the striatum, a significant 8.5% increase of the D2/D3R availability in the ipsilateral OB and concomitant improvement of olfactory performance were detectable. Based on tract-tracing meta-analysis, we speculate that this may be due to indirect connections between the striatum and the OB.

Coenzyme Q10 reduces expression of apoptotic markers in adult rat nucleus accumbens dopaminergic neurons treated with methamphetamine

BACKGROUND

Abuse of addictive drugs such as methamphetamine (METH) has become a global problem, leading to many social, economic, and health disturbances, including neurological and cognitive disorders. Neuronal damage is reported in chronic METH abusers. The neuroprotective role of CoQ10 has been shown in many studies. In the present study, we aimed to assess the pre and post-efficacy of CoQ10 on the dopaminergic neurons of the Nucleus Accumbens (de Miranda et al. in Food Res Int 121:641-647, 2019) in the male adult rats treated with METH.

METHODS

80 rats were randomly divided into eight groups (n = 10), including: negative control (intact), positive control (received 5 mg/kg/day METH/IP), three post-treatment groups (METH + 5, 10, 20 mg/kg CoQ10) and three pre-treatment groups (received 5, 10, 20 mg/kg CoQ10 as pre-treatment for 14 days before METH injection). The expression of Bax, Bcl-2, Bax/Bcl-2 ratio, P53, Caspase-3 and tyrosine hydroxylase in NAc studied using western blotting. Nissl staining was used to study the neuronal density of NAc.

RESULTS

Our results showed that the different doses of CoQ10 in METH-treated animals significantly changed pro-apoptotic proteins' expression in the benefit of neuronal survival of NAc (P < 0.05). Neuronal density in NAc were significantly lower in the METH group compared to the control and CoQ10 treated groups. Pre- and post-treatment with different doses of CoQ10 restored the neuronal damage in NAc.

CONCLUSIONS

CoQ10 could decrease the activation of pro-apoptotic proteins and reduce the neurodegenerative effects induced by METH. From a clinical point of view, it seems that certain antioxidants such as CoQ10 should receive more attention in clinical trial research. We believe that antioxidants could be the promising for drug abuse treatment in the future.

Exosomes in Parkinson: Revisiting Their Pathologic Role and Potential Applications

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by bradykinesia, rigidity, and tremor. Considerable progress has been made to understand the exact mechanism leading to this disease. Most of what is known comes from the evidence of PD brains' autopsies showing a deposition of Lewy bodies-containing a protein called α-synuclein (α-syn)-as the pathological determinant of PD. α-syn predisposes neurons to neurotoxicity and cell death, while the other associated mechanisms are mitochondrial dysfunction and oxidative stress, which are underlying precursors to the death of dopaminergic neurons at the substantia nigra pars compacta leading to disease progression. Several mechanisms have been proposed to unravel the pathological cascade of these diseases; most of them share a particular similarity: cell-to-cell communication through exosomes (EXOs). EXOs are intracellular membrane-based vesicles with diverse compositions involved in biological and pathological processes, which their secretion is driven by the NLR family pyrin domain-containing three proteins (NLRP3) inflammasome. Toxic biological fibrils are transferred to recipient cells, and the disposal of damaged organelles through generating mitochondrial-derived vesicles are suggested mechanisms for developing PD. EXOs carry various biomarkers; thus, they are promising to diagnose different neurological disorders, including neurodegenerative diseases (NDDs). As nanovesicles, the applications of EXOs are not only restricted as diagnostics but also expanded to treat NDDs as therapeutic carriers and nano-scavengers. Herein, the aim is to highlight the potential incrimination of EXOs in the pathological cascade and progression of PD and their role as biomarkers and therapeutic carriers for diagnosing and treating this neuro-debilitating disorder.

Sequential or Simultaneous Injection of Preformed Fibrils and AAV Overexpression of Alpha-Synuclein Are Equipotent in Producing Relevant Pathology and Behavioral Deficits

BACKGROUND

Preclinical rodent models for Parkinson's disease (PD) based on viral human alpha-synuclein (h-αSyn) overexpression recapitulate some of the pathological hallmarks as it presents in humans, such as progressive cell loss and additional synucleinopathy in cortical and subcortical structures. Recent studies have combined viral vector-based overexpression of human wild-type αSyn with the sequential or simultaneous inoculation of preformed fibrils (PFFs) derived from human αSyn.

OBJECTIVE

The goal of the study was to investigate whether sequential or combined delivery of the AAV vector and the PFFs are equipotent in inducing stable neurodegeneration and behavioral deficits.

METHODS

Here we compare between four experimental paradigms (PFFs only, AAV-h-αSyn only, AAV-h-αSyn with simultaneous PFFs, and AAV-h-αSyn with sequential PFFs) and their respective GFP control groups.

RESULTS

We observed reduction of TH expression and loss of neurons in the midbrain in all AAV (h-αSyn or GFP) injected groups, with or without additional PFFs inoculation. The overexpression of either h-αSyn or GFP alone induced motor deficits and dysfunctional dopamine release/reuptake in electrochemical recordings in the ipsilateral striatum. However, we observed a substantial formation of insoluble h-αSyn aggregates and inflammatory response only when h-αSyn and PFFs were combined. Moreover, the presence of h-αSyn induced higher axonal pathology compared to control groups.

CONCLUSION

Simultaneous AAV and PFFs injections are equipotent in the presented experimental setup in inducing histopathological and behavioral changes. This model provides new and interesting possibilities for characterizing PD pathology in preclinical models and means to assess future therapeutic interventions.

Design and Synthesis of Brain Penetrant Glycopeptide Analogues of PACAP With Neuroprotective Potential for Traumatic Brain Injury and Parkinsonism

There is an unmet clinical need for curative therapies to treat neurodegenerative disorders. Most mainstay treatments currently on the market only alleviate specific symptoms and do not reverse disease progression. The Pituitary adenylate cyclase-activating polypeptide (PACAP), an endogenous neuropeptide hormone, has been extensively studied as a potential regenerative therapeutic. PACAP is widely distributed in the central nervous system (CNS) and exerts its neuroprotective and neurotrophic effects via the related Class B GPCRs PAC1, VPAC1, and VPAC2, at which the hormone shows roughly equal activity. Vasoactive intestinal peptide (VIP) also activates these receptors, and this close analogue of PACAP has also shown to promote neuronal survival in various animal models of acute and progressive neurodegenerative diseases. However, PACAP's poor pharmacokinetic profile (non-linear PK/PD), and more importantly its limited blood-brain barrier (BBB) permeability has hampered development of this peptide as a therapeutic. We have demonstrated that glycosylation of PACAP and related peptides promotes penetration of the BBB and improves PK properties while retaining efficacy and potency in the low nanomolar range at its target receptors. Furthermore, judicious structure-activity relationship (SAR) studies revealed key motifs that can be modulated to afford compounds with diverse selectivity profiles. Most importantly, we have demonstrated that select PACAP glycopeptide analogues (2LS80Mel and 2LS98Lac) exert potent neuroprotective effects and anti-inflammatory activity in animal models of traumatic brain injury and in a mild-toxin lesion model of Parkinson's disease, highlighting glycosylation as a viable strategy for converting endogenous peptides into robust and efficacious drug candidates.

The Neuroprotective Effects of the CB2 Agonist GW842166x in the 6-OHDA Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is a chronic neurodegenerative disorder associated with dopamine neuron loss and motor dysfunction. Neuroprotective agents that prevent dopamine neuron death hold great promise for slowing the disease's progression. The activation of cannabinoid (CB) receptors has shown neuroprotective effects in preclinical models of neurodegenerative disease, traumatic brain injury, and stroke, and may provide neuroprotection against PD. Here, we report that the selective CB2 agonist GW842166x exerted protective effects against the 6-hydroxydopamine (6-OHDA)-induced loss of dopamine neurons and its associated motor function deficits in mice, as shown by an improvement in balance beam walking, pole, grip strength, rotarod, and amphetamine-induced rotation tests. The neuroprotective effects of GW842166x were prevented by the CB2 receptor antagonist AM630, suggesting a CB2-dependent mechanism. To investigate potential mechanisms for the neuroprotective effects of GW842166x, we performed electrophysiological recordings from substantia nigra pars compacta (SNc) dopamine neurons in ex vivo midbrain slices prepared from drug-naïve mice. We found that the bath application of GW842166x led to a decrease in action potential firing, likely due to a decrease in hyperpolarization-activated currents (Ih) and a shift of the half-activation potential (V1/2) of Ih to a more hyperpolarized level. Taken together, the CB2 agonist GW842166x may reduce the vulnerability of dopamine neurons to 6-OHDA by decreasing the action potential firing of these neurons and the associated calcium load.

Green coffee extract attenuates Parkinson's-related behaviors in animal models

Epidemiological studies have shown an inverse association between coffee consumption and the development of Parkinson's disease (PD). The effects of the oral treatment with green (non-roasted) coffee extracts (CE, 100 or 400 mg/kg) and caffeine (31.2 mg/kg) were evaluated on catalepsy induced by haloperidol in mice, and unilateral 6-OHDA lesion of medial forebrain bundle (MFB) or striatum in rats. Also, the in vitro antioxidant activity and the monoamine levels in the striatum were investigated. CE presented a mild antioxidant activity in vitro and its administration decreased the catalepsy index. CE at the dose of 400 mg/kg induced ipsilateral rotations 14 days after lesion; however, chronic 30-day CE and caffeine treatments did not interfere with the animals' rotation after apomorphine or methamphetamine challenges in animals with MFB lesion, nor on monoamines levels. Furthermore, CE and caffeine were effective in inhibiting the asymmetry between ipsilateral and contralateral rotations induced by methamphetamine and apomorphine in animals with lesion in the striatum but did not avoid the monoamines depletion. These results indicate that CE components indirectly modulate dopaminergic transmission, suggesting a pro-dopaminergic action of CE, and further investigation must be conducted to elucidate the mechanisms of action and the possible neuroprotective role in PD.

N-γ-(L-glutamyl)-L-selenomethionine shows neuroprotective effects against Parkinson's disease associated with SKN-1/Nrf2 and TRXR-1 in Caenorhabditis elegans

BACKGROUND

Parkinson's disease (PD) is a common neurodegenerative disease, yet fundamental treatments for the disease remain sparse. Thus, the search for potentially efficacious compounds from medicinal plants that can be used in the treatment of PD has gained significant interest.

PURPOSE

In many medicinal plants, selenium is primarily found in an organic form. We investigated the neuroprotective potential of an organic form of selenium, N-γ-(L-glutamyl)-L-selenomethionine (Glu-SeMet) in a Caenorhabditis elegans PD model and its possible molecular mechanisms.

METHODS

We used a C. elegans pharmacological PD strain (BZ555) that specifically expresses green fluorescent protein (GFP) in dopaminergic neurons and a transgenic PD strain (NL5901) that expresses human α-synuclein (α-syn) in muscle cells to investigate the neuroprotective potential of Glu-SeMet against PD.

RESULTS

We found that Glu-SeMet significantly ameliorated 6-hydroxydopamine (6-OHDA)-induced dopaminergic neuron damage in the transgenic BZ555 strain, with corresponding improvements in slowing behavior and intracellular ROS levels. In addition, compared with clinical PD drugs (L-DOPA and selegiline), Glu-SeMet demonstrated stronger ameliorated effects on 6-OHDA-induced toxicity. Glu-SeMet also triggered the nuclear translocation of SKN-1/Nrf2 and significantly increased SKN-1, GST-4, and GCS-1 mRNA levels in the BZ555 strain. However, Glu-SeMet did not increase mRNA levels or ameliorate the damage to dopaminergic neurons when the BZ555 strain was subjected to skn-1 RNA interference (RNAi). Glu-SeMet also upregulated the mRNA levels of the selenoprotein TRXR-1 in both the BZ555 and BZ555; skn-1 RNAi strains and significantly decreased α-syn accumulation in the NL5901 strain, although this was not observed in the NL5901; trxr-1 strain.

CONCLUSION

We found that Glu-SeMet has a neuroprotective effect against PD in a C. elegans PD model and that the anti-PD effects of Glu-SeMet were associated with SKN-1/Nrf2 and TRXR-1. Glu-SeMet may thus have the potential for use in therapeutic applications or supplements to slow the progression of PD.

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

Parkinson’s disease (PD) is a prevalent movement disorder characterized by the progressive loss of dopaminergic neurons in substantia nigra pars compacta (SNpc). The 6-hydroxydopamine (6-OHDA) lesion is still one of the most widely used techniques for modeling Parkinson’s disease (PD) in rodents. Despite commonly used in rats, it can be challenging to reproduce a similar lesion in mice. Moreover, there is a lack of characterization of the extent of behavioral deficits and of the neuronal loss/neurotransmitter system in unilateral lesion mouse models. In this study, we present an extensive behavioral and histological characterization of a unilateral intrastriatal 6-OHDA mouse model. Our results indicate significant alterations in balance and fine motor coordination, voluntary locomotion, and in the asymmetry’s degree of forelimb use in 6-OHDA lesioned animals, accompanied by a decrease in self-care and motivational behavior, common features of depressive-like symptomatology. These results were accompanied by a decrease in tyrosine hydroxylase (TH)-labelling and dopamine levels within the nigrostriatal pathway. Additionally, we also identify a marked astrocytic reaction, as well as proliferative and reactive microglia in lesioned areas. These results confirm the use of unilateral intrastriatal 6-OHDA mice for the generation of a mild model of nigrostriatal degeneration and further evidences the recapitulation of key aspects of PD, thereby being suitable for future studies beholding new therapeutical interventions for this disease.

Early Cognitive Impairment Behind Nigrostriatal Circuit Neurotoxicity: Are Astrocytes Involved?

Cognitive dysfunction is one of the most severe nonmotor symptoms of nigrostriatal impairment. This occurs as a result of profound functional and morphological changes of different neuronal circuits, including modifications in the plasticity and architecture of hippocampal synapses. Such alterations can be implicated in the genesis and progression of dementia associated with neurodegenerative diseases including Parkinson-like symptoms. There are few studies regarding cognitive changes in nigrostriatal animal models. The aim of this study was to characterize the onset of memory deficit after induction of neurotoxicity with 6-hydroxydopamine (6-OHDA) and its correlation with hippocampal dysfunction. For this, we bilaterally microinjected 6-OHDA in dorsolateral Caudate-Putamen unit (CPu) and then, animals were tested weekly for working memory, spatial short-term memory, and motor performance. We evaluated tyrosine hydroxylase (TH) as a dopamine marker, aldehyde dehydrogenase 2 (ALDH2), a mitochondria detoxification enzyme and astrocyte glial fibrillar acid protein (GFAP) an immunoreactivity marker involved in different areas: CPu, substantia nigra, prefrontal cortex, and hippocampus. We observed a specific prefrontal cortex and nigrostriatal pathway TH reduction while ALDH2 showed a decrease-positive area in all the studied regions. Moreover, GFAP showed a specific CPu decrease and hippocampus increase of positively stained area on the third week after toxicity. We also evaluated the threshold to induce long-term potentiation in hippocampal excitability. Our findings showed that reduced hippocampal synaptic transmission was accompanied by deficits in memory processes, without affecting motor performance on the third-week post 6-OHDA administration. Our results suggest that 3 weeks after neurotoxic administration, astrocytes and ALDH2 mitochondrial enzyme modifications participate in altering the properties that negatively affect hippocampal function and consequently cognitive behavior.

Cerebral dopamine neurotrophic factor transfection in dopamine neurons using neurotensin-polyplex nanoparticles reverses 6-hydroxydopamine-induced nigrostriatal neurodegeneration

Overexpression of neurotrophic factors in nigral dopamine neurons is a promising approach to reverse neurodegeneration of the nigrostriatal dopamine system, a hallmark in Parkinson's disease. The human cerebral dopamine neurotrophic factor (hCDNF) has recently emerged as a strong candidate for Parkinson's disease therapy. This study shows that hCDNF expression in dopamine neurons using the neurotensin-polyplex nanoparticle system reverses 6-hydroxydopamine-induced morphological, biochemical, and behavioral alterations. Three independent electron microscopy techniques showed that the neurotensin-polyplex nanoparticles containing the hCDNF gene, ranging in size from 20 to 150 nm, enabled the expression of a secretable hCDNF in vitro. Their injection in the substantia nigra compacta on day 21 after the 6-hydroxydopamine lesion resulted in detectable hCDNF in dopamine neurons, whose levels remained constant throughout the study in the substantia nigra compacta and striatum. Compared with the lesioned group, tyrosine hydroxylase-positive (TH⁺) nigral cell population and TH⁺ fiber density rose in the substantia nigra compacta and striatum after hCDNF transfection. An increase in βIII-tubulin and growth-associated protein 43 phospho-S41 (GAP43p) followed TH⁺ cell recovery, as well as dopamine and its catabolite levels. Partial reversal (80%) of drug-activated circling behavior and full recovery of spontaneous motor and non-motor behavior were achieved. Brain-derived neurotrophic factor recovery in dopamine neurons that also occurred suggests its participation in the neurotrophic effects. These findings support the potential of nanoparticle-mediated hCDNF gene delivery to develop a disease-modifying treatment against Parkinson's disease. The Institutional Animal Care and Use Committee of Centro de Investigación y de Estudios Avanzados approved our experimental procedures for animal use (authorization No. 162-15) on June 9, 2019.

Dominant-negative actions of a dopamine transporter variant identified in patients with parkinsonism and neuropsychiatric disease

Dysfunctional dopaminergic neurotransmission is central to movement disorders and mental diseases. The dopamine transporter (DAT) regulates extracellular dopamine levels, but the genetic and mechanistic link between DAT function and dopamine-related pathologies is not clear. Particularly, the pathophysiological significance of monoallelic missense mutations in DAT is unknown. Here, we use clinical information, neuroimaging, and large-scale exome-sequencing data to uncover the occurrence and phenotypic spectrum of a DAT coding variant, DAT-K619N, which localizes to the critical C-terminal PSD-95/Discs-large/ZO-1 homology–binding motif of human DAT (hDAT). We identified the rare but recurrent hDAT-K619N variant in exome-sequenced samples of patients with neuropsychiatric diseases and a patient with early-onset neurodegenerative parkinsonism and comorbid neuropsychiatric disease. In cell cultures, hDAT-K619N displayed reduced uptake capacity, decreased surface expression, and accelerated turnover. Unilateral expression in mouse nigrostriatal neurons revealed differential effects of hDAT-K619N and hDAT-WT on dopamine-directed behaviors, and hDAT-K619N expression in Drosophila led to impairments in dopamine transmission with accompanying hyperlocomotion and age-dependent disturbances of the negative geotactic response. Moreover, cellular studies and viral expression of hDAT-K619N in mice demonstrated a dominant-negative effect of the hDAT-K619N mutant. Summarized, our results suggest that hDAT-K619N can effectuate dopamine dysfunction of pathological relevance in a dominant-negative manner.

Dopamine-loaded nanoparticle systems circumvent the blood-brain barrier restoring motor function in mouse model for Parkinson's Disease

Parkinson's disease (PD) is a progressive and chronic neurodegenerative disease of the central nervous system. Early treatment for PD is efficient; however, long-term systemic medication commonly leads to deleterious side-effects. Strategies that enable more selective drug delivery to the brain using smaller dosages, while crossing the complex brain-blood barrier (BBB), are highly desirable to ensure treatment efficacy and decrease/avoid unwanted outcomes. Our goal was to design and test the neurotherapeutic potential of a forefront nanoparticle-based technology composed of albumin/PLGA nanosystems loaded with dopamine (ALNP-DA) in 6-OHDA PD mice model. ALNP-DA effectively crossed the BBB, replenishing dopamine at the nigrostriatal pathway, resulting in significant motor symptom improvement when compared to Lesioned and L-DOPA groups. Notably, ALNP-DA (20 mg/animal dose) additionally up-regulated and restored motor coordination, balance, and sensorimotor performance to non-lesioned (Sham) animal level. Overall, ALNPs represent an innovative, non-invasive nano-therapeutical strategy for PD, considering its efficacy to circumvent the BBB and ultimately deliver the drug of interest to the brain.

Antidepressant-Like Properties of Intrastriatal Botulinum Neurotoxin-A Injection in a Unilateral 6-OHDA Rat Model of Parkinson's Disease

Parkinson’s patients often suffer from depression and anxiety, for which there are no optimal treatments. Hemiparkinsonian (hemi-PD) rats were used to test whether intrastriatal Botulinum neurotoxin-A (BoNT-A) application could also have antidepressant-like properties in addition to the known improvement of motor performance. To quantify depression- and anxiety-like behavior, the forced swim test, tail suspension test, open field test, and elevated plus maze test were applied to hemi-PD rats injected with BoNT-A or vehicle. Furthermore, we correlated the results in the forced swim test, open field test, and elevated plus maze test with the rotational behavior induced by apomorphine and amphetamine. Hemi-PD rats did not show significant anxiety-like behavior as compared with Sham 6-OHDA- + Sham BoNT-A-injected as well as with non-injected rats. However, hemi-PD rats demonstrated increased depression-like behaviors compared with Sham- or non-injected rats; this was seen by increased struggling frequency and increased immobility frequency. Hemi-PD rats intrastriatally injected with BoNT-A exhibited reduced depression-like behavior compared with the respective vehicle-receiving hemi-PD animals. The significant effects of intrastriatally applied BoNT-A seen in the forced swim test are reminiscent of those found after various antidepressant drug therapies. Our data correspond with the efficacy of BoNT-A treatment of glabellar frown lines in treating patients with major depression and suggest that also intrastriatal injected BoNT-A may have some antidepressant-like effect on hemi-PD.

Vagus Nerve Stimulation with Mild Stimulation Intensity Exerts Anti-Inflammatory and Neuroprotective Effects in Parkinson's Disease Model Rats

Background: The major surgical treatment for Parkinson’s disease (PD) is deep brain stimulation (DBS), but a less invasive treatment is desired. Vagus nerve stimulation (VNS) is a relatively safe treatment without cerebral invasiveness. In this study, we developed a wireless controllable electrical stimulator to examine the efficacy of VNS on PD model rats. Methods: Adult female Sprague-Dawley rats underwent placement of a cuff-type electrode and stimulator on the vagus nerve. Following which, 6-hydroxydopamine (6-OHDA) was administered into the left striatum to prepare a PD model. VNS was started immediately after 6-OHDA administration and continued for 14 days. We evaluated the therapeutic effects of VNS with behavioral and immunohistochemical outcome assays under different stimulation intensity (0.1, 0.25, 0.5 and 1 mA). Results: VNS with 0.25–0.5 mA intensity remarkably improved behavioral impairment, preserved dopamine neurons, reduced inflammatory glial cells, and increased noradrenergic neurons. On the other hand, VNS with 0.1 mA and 1 mA intensity did not display significant therapeutic efficacy. Conclusions: VNS with 0.25–0.5 mA intensity has anti-inflammatory and neuroprotective effects on PD model rats induced by 6-OHDA administration. In addition, we were able to confirm the practicality and effectiveness of the new experimental device.

In vivo conversion of dopamine neurons in mouse models of Parkinson's disease - a future approach for regenerative therapy?

Recent advances in cell reprogramming have made it possible to form new therapeutic cells within the body itself via a process called direct conversion or lineage reprogramming. A series of studies have shown that it is possible to reprogram resident glia into new neurons within the brain parenchyma. These studies opened up for the targeted attempts to achieve functional brain repair using in vivo conversion. Because of the relatively focal degeneration, Parkinson's Disease (PD) is an attractive target for both transplantation-based and in vivo conversion-based reparative approaches. Fetal cell transplants have provided proof-of-concept and stem cell-based therapies for PD are now on the verge of entering clinical trials. In the future, in vivo conversion may be an alternative to transplantation-based therapies.

The C-Terminal Domain of LRRK2 with the G2019S Substitution Increases Mutant A53T α-Synuclein Toxicity in Dopaminergic Neurons In Vivo

Alpha-synuclein (α-syn) and leucine-rich repeat kinase 2 (LRRK2) play crucial roles in Parkinson's disease (PD). They may functionally interact to induce the degeneration of dopaminergic (DA) neurons via mechanisms that are not yet fully understood. We previously showed that the C-terminal portion of LRRK2 (ΔLRRK2) with the G2019S mutation (ΔLRRK2^G2019S) was sufficient to induce neurodegeneration of DA neurons in vivo, suggesting that mutated LRRK2 induces neurotoxicity through mechanisms that are (i) independent of the N-terminal domains and (ii) "cell-autonomous". Here, we explored whether ΔLRRK2^G2019S could modify α-syn toxicity through these two mechanisms. We used a co-transduction approach in rats with AAV vectors encoding ΔLRRK2^G2019S or its "dead" kinase form, ΔLRRK2^DK, and human α-syn with the A53T mutation (AAV-α-syn^A53T). Behavioral and histological evaluations were performed at 6- and 15-weeks post-injection. Results showed that neither form of ΔLRRK2 alone induced the degeneration of neurons at these post-injection time points. By contrast, injection of AAV-α-syn^A53T alone resulted in motor signs and degeneration of DA neurons. Co-injection of AAV-α-syn^A53T with AAV-ΔLRRK2^G2019S induced DA neuron degeneration that was significantly higher than that induced by AAV-α-syn^A53T alone or with AAV-ΔLRRK2^DK. Thus, mutated α-syn neurotoxicity can be enhanced by the C-terminal domain of LRRK2^G2019 alone^, through cell-autonomous mechanisms.

Intranasal delivery of mitochondria for treatment of Parkinson's Disease model rats lesioned with 6-hydroxydopamine

The feasibility of delivering mitochondria intranasally so as to bypass the blood-brain barrier in treating Parkinson's disease (PD), was evaluated in unilaterally 6-OHDA-lesioned rats. Intranasal infusion of allogeneic mitochondria conjugated with Pep-1 (P-Mito) or unconjugated (Mito) was performed once a week on the ipsilateral sides of lesioned brains for three months. A significant improvement of rotational and locomotor behaviors in PD rats was observed in both mitochondrial groups, compared to sham or Pep-1-only groups. Dopaminergic (DA) neuron survival and recovery > 60% occurred in lesions of the substantia nigra (SN) and striatum in Mito and P-Mito rats. The treatment effect was stronger in the P-Mito group than the Mito group, but the difference was insignificant. This recovery was associated with restoration of mitochondrial function and attenuation of oxidative damage in lesioned SN. Notably, P-Mito suppressed plasma levels of inflammatory cytokines. Mitochondria penetrated the accessory olfactory bulb and doublecortin-positive neurons of the rostral migratory stream (RMS) on the ipsilateral sides of lesions and were expressed in striatal, but not SN DA neurons, of both cerebral hemispheres, evidently via commissural fibers. This study shows promise for intranasal delivery of mitochondria, confirming mitochondrial internalization and migration via RMS neurons in the olfactory bulb for PD therapy.

Geometric deep learning enables 3D kinematic profiling across species and environments

Comprehensive descriptions of animal behavior require precise three-dimensional (3D) measurements of whole-body movements. Although two-dimensional approaches can track visible landmarks in restrictive environments, performance drops in freely moving animals, due to occlusions and appearance changes. Therefore, we designed DANNCE to robustly track anatomical landmarks in 3D across species and behaviors. DANNCE uses projective geometry to construct inputs to a convolutional neural network that leverages learned 3D geometric reasoning. We trained and benchmarked DANNCE using a dataset of nearly seven million frames that relates color videos and rodent 3D poses. In rats and mice, DANNCE robustly tracked dozens of landmarks on the head, trunk, and limbs of freely moving animals in naturalistic settings. We extended DANNCE to datasets from rat pups, marmosets, and chickadees, and demonstrate quantitative profiling of behavioral lineage during development.

Histamine-4 receptor antagonist ameliorates Parkinson-like pathology in the striatum

Growing evidence indicates that microglia activation and a neuroinflammatory trigger contribute to dopaminergic cell loss in Parkinson's disease (PD). Furthermore, increased density of histaminergic fibers and enhanced histamine levels have been observed in the substantia nigra of PD-postmortem brains. Histamine-induced microglial activation is mediated by the histamine-4 receptor (H₄R). In the current study, gene set enrichment and pathway analyses of a PD basal ganglia RNA-sequencing dataset revealed that upregulation of H₄R was in the top functional category for PD treatment targets. Interestingly, the H₄R antagonist JNJ7777120 normalized the number of nigrostriatal dopaminergic fibers and striatal dopamine levels in a rotenone-induced PD rat model. These improvements were accompanied by a reduction of α-synuclein-positive inclusions in the striatum. In addition, intracerebroventricular infusion of JNJ7777120 alleviated the morphological changes in Iba-1-positive microglia and resulted in a lower tumor necrosis factor-α release from this brain region, as well as in ameliorated apomorphine-induced rotation behaviour. Finally, JNJ7777120 also restored basal ganglia function by decreasing the levels of γ-aminobutyric acid (GABA) and the 5-hydroxyindoleactic acid to serotonin (5-HIAA/5-HT) concentration ratios in the striatum of the PD model. Our results highlight H₄R inhibition in microglia as a promising and specific therapeutic target to reduce or prevent neuroinflammation, and as such the development of PD pathology.

Early Repetitive Transcranial Magnetic Stimulation Exerts Neuroprotective Effects and Improves Motor Functions in Hemiparkinsonian Rats

Repetitive transcranial magnetic stimulation (rTMS) is a popular noninvasive technique for modulating motor cortical plasticity and has therapeutic potential for the treatment of Parkinson's disease (PD). However, the therapeutic benefits and related mechanisms of rTMS in PD are still uncertain. Accordingly, preclinical animal research is helpful for enabling translational research to explore an effective therapeutic strategy and for better understanding the underlying mechanisms. Therefore, the current study was designed to identify the therapeutic effects of rTMS on hemiparkinsonian rats. A hemiparkinsonian rat model, induced by unilateral injection of 6-hydroxydopamine (6-OHDA), was applied to evaluate the therapeutic potential of rTMS in motor functions and neuroprotective effect of dopaminergic neurons. Following early and long-term rTMS intervention with an intermittent theta burst stimulation (iTBS) paradigm (starting 24 h post-6-OHDA lesion, 1 session/day, 7 days/week, for a total of 4 weeks) in awake hemiparkinsonian rats, the effects of rTMS on the performance in detailed functional behavioral tests, including video-based gait analysis, the bar test for akinesia, apomorphine-induced rotational analysis, and tests of the degeneration level of dopaminergic neurons, were identified. We found that four weeks of rTMS intervention significantly reduced the aggravation of PD-related symptoms post-6-OHDA lesion. Immunohistochemically, the results showed that tyrosine hydroxylase- (TH-) positive neurons in the substantia nigra pars compacta (SNpc) and fibers in the striatum were significantly preserved in the rTMS treatment group. These findings suggest that early and long-term rTMS with the iTBS paradigm exerts neuroprotective effects and mitigates motor impairments in a hemiparkinsonian rat model. These results further highlight the potential therapeutic effects of rTMS and confirm that long-term rTMS treatment might have clinical relevance and usefulness as an additional treatment approach in individuals with PD.

A comparison of AAV-vector production methods for gene therapy and preclinical assessment

Adeno Associated Virus (AAV)-mediated gene expression in the brain is widely applied in the preclinical setting to investigate the therapeutic potential of specific molecular targets, characterize various cellular functions, and model central nervous system (CNS) diseases. In therapeutic applications in the clinical setting, gene therapy offers several advantages over traditional pharmacological based therapies, including the ability to directly manipulate disease mechanisms, selectively target disease-afflicted regions, and achieve long-term therapeutic protein expression in the absence of repeated administration of pharmacological agents. Next to the gold-standard iodixanol-based AAV vector production, we recently published a protocol for AAV production based on chloroform-precipitation, which allows for fast in-house production of small quantities of AAV vector without the need for specialized equipment. To validate our recent protocol, we present here a direct side-by-side comparison between vectors produced with either method in a series of in vitro and in vivo assays with a focus on transgene expression, cell loss, and neuroinflammatory responses in the brain. We do not find differences in transduction efficiency nor in any other parameter in our in vivo and in vitro panel of assessment. These results suggest that our novel protocol enables most standardly equipped laboratories to produce small batches of high quality and high titer AAV vectors for their experimental needs.

Behavioral Tests in Neurotoxin-Induced Animal Models of Parkinson's Disease

Currently, neurodegenerative diseases are a major cause of disability around the world. Parkinson's disease (PD) is the second-leading cause of neurodegenerative disorder after Alzheimer's disease. In PD, continuous loss of dopaminergic neurons in the substantia nigra causes dopamine depletion in the striatum, promotes the primary motor symptoms of resting tremor, bradykinesia, muscle rigidity, and postural instability. The risk factors of PD comprise environmental toxins, drugs, pesticides, brain microtrauma, focal cerebrovascular injury, aging, and hereditary defects. The pathologic features of PD include impaired protein homeostasis, mitochondrial dysfunction, nitric oxide, and neuroinflammation, but the interaction of these factors contributing to PD is not fully understood. In neurotoxin-induced PD models, neurotoxins, for instance, 6-hydroxydopamine (6-OHDA), 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-Methyl-4-phenylpyridinium (MPP+), paraquat, rotenone, and permethrin mainly impair the mitochondrial respiratory chain, activate microglia, and generate reactive oxygen species to induce autooxidation and dopaminergic neuronal apoptosis. Since no current treatment can cure PD, using a suitable PD animal model to evaluate PD motor symptoms' treatment efficacy and identify therapeutic targets and drugs are still needed. Hence, the present review focuses on the latest scientific developments in different neurotoxin-induced PD animal models with their mechanisms of pathogenesis and evaluation methods of PD motor symptoms.

Changes in Day/Night Activity in the 6-OHDA-Induced Experimental Model of Parkinson's Disease: Exploring Prodromal Biomarkers

The search for experimental models mimicking an early stage of Parkinson's disease (PD) before motor manifestations is fundamental in order to explore early signs and get a better prognosis. Interestingly, our previous studies have indicated that 6-hydroxydopamine (6-OHDA) is a suitable model to induce an early degeneration of the nigrostriatal system without any gross motor impairment. Considering our previous findings, we aim to implement a novel system to monitor rats after intrastriatal injection of 6-OHDA to detect and analyze physiological changes underlying prodromal PD. Twenty male Sprague-Dawley rats were unilaterally injected with 6-OHDA (n = 10) or saline solution (n = 10) into the right striatum and placed in enriched environment cages where the activity was monitored. After 2 weeks, the amphetamine test was performed before the sacrifice. Immunohistochemistry was developed for the morphological evaluation and western blot analysis to assess molecular changes. Home-cage monitoring revealed behavioral changes in response to 6-OHDA administration including significant hyperactivity and hypoactivity during the light and dark phase, respectively, turning out in a change of the circadian timing. A preclinical stage of PD was functionally confirmed with the amphetamine test. Moreover, the loss of tyrosine hydroxylase expression was significantly correlated with the motor results, and 6-OHDA induced early proapoptotic events. Our findings provide evidence for a novel prodromal 6-OHDA model following a customized monitoring system that could give insights to detect non-motor deficits and molecular targets to test neuroprotective/neurorestorative agents.

The Inhibition of miR-873 Provides Therapeutic Benefit in a Lipopolysaccharide-Induced Neuroinflammatory Model of Parkinson's Disease

Background and Purpose. Alterations in cholesterol homeostasis have been reported in cell and animal models of Parkinson's disease (PD), although there are inconsistent data about the association between serum cholesterol levels and risk of PD. Here, we investigated the effects of miR-873 on lysosomal cholesterol homeostasis and progressive dopaminergic neuron damage in a lipopolysaccharide-(LPS) induced model of PD. Experimental Approach. To evaluate the therapeutic benefit of the miR-873 sponge, rats were injected with a LV-miR-873 sponge or the control vector 3 days before the right-unilateral injection of LPS into the substantia nigra (SN) pars compacta, or 8 and 16 days after LPS injection. Normal SH-SY5Y cells or SH-SY5Y cells overexpressing α-synuclein were used to evaluate the distribution of α-synuclein and cholesterol in lysosomes and to assess the autophagic flux after miR-873 transfection or ABCA1 silencing. The inhibition of miR-873 significantly ameliorated the LPS-induced accumulation of α-synuclein and loss of dopaminergic neurons in the SN at the early stage. miR-873 mediated the inhibition of ABCA1 by LPS. miR-873 transfection or ABCA1 silencing increased the lysosomal cholesterol and α-synuclein levels, and decreased the autophagic flux. The knockdown of ABCA1 or A20, which are the downstream target genes of miR-873, exacerbated the damage to LPS-induced dopaminergic neurons. Conclusion and Implications. The results suggest that the inhibition of miR-873 may play a dual protective role by improving intracellular cholesterol homeostasis and neuroinflammation in PD. The therapeutic effects of the miR-873 sponge in PD may be due to the upregulation of ABCA1 and A20.

Neuronal Replacement as a Tool for Basal Ganglia Circuitry Repair: 40 Years in Perspective

The ability of new neurons to promote repair of brain circuitry depends on their capacity to re-establish afferent and efferent connections with the host. In this review article, we give an overview of past and current efforts to restore damaged connectivity in the adult mammalian brain using implants of fetal neuroblasts or stem cell-derived neuronal precursors, with a focus on strategies aimed to repair damaged basal ganglia circuitry induced by lesions that mimic the pathology seen in humans affected by Parkinson’s or Huntington’s disease. Early work performed in rodents showed that neuroblasts obtained from striatal primordia or fetal ventral mesencephalon can become anatomically and functionally integrated into lesioned striatal and nigral circuitry, establish afferent and efferent connections with the lesioned host, and reverse the lesion-induced behavioral impairments. Recent progress in the generation of striatal and nigral progenitors from pluripotent stem cells have provided compelling evidence that they can survive and mature in the lesioned brain and re-establish afferent and efferent axonal connectivity with a remarkable degree of specificity. The studies of cell-based circuitry repair are now entering a new phase. The introduction of genetic and virus-based techniques for brain connectomics has opened entirely new possibilities for studies of graft-host integration and connectivity, and the access to more refined experimental techniques, such as chemo- and optogenetics, has provided new powerful tools to study the capacity of grafted neurons to impact the function of the host brain. Progress in this field will help to guide the efforts to develop therapeutic strategies for cell-based repair in Huntington’s and Parkinson’s disease and other neurodegenerative conditions involving damage to basal ganglia circuitry.

Intracellular delivery of Parkin rescues neurons from accumulation of damaged mitochondria and pathological α-synuclein

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by mitochondrial dysfunction, Lewy body formation, and loss of dopaminergic neurons. Parkin, an E3 ubiquitin ligase, is thought to inhibit PD progression by removing damaged mitochondria and suppressing the accumulation of α-synuclein and other protein aggregates. The present study describes a protein-based therapy for PD enabled by the development of a cell-permeable Parkin protein (iCP-Parkin) with enhanced solubility and optimized intracellular delivery. iCP-Parkin recovered damaged mitochondria by promoting mitophagy and mitochondrial biogenesis and suppressed toxic accumulations of α-synuclein in cells and animals. Last, iCP-Parkin prevented and reversed declines in tyrosine hydroxylase and dopamine expression concomitant with improved motor function induced by mitochondrial poisons or enforced α-synuclein expression. These results point to common, therapeutically tractable features in PD pathophysiology, and suggest that motor deficits in PD may be reversed, thus providing opportunities for therapeutic intervention after the onset of motor symptoms.

Comparison between Tail Suspension Swing Test and Standard Rotation Test in Revealing Early Motor Behavioral Changes and Neurodegeneration in 6-OHDA Hemiparkinsonian Rats

The unilateral 6-hydroxydopamine (6-OHDA) model of Parkinson’s disease (PD) is one of the most commonly used in rodents. The anatomical, metabolic, and behavioral changes that occur after severe and stable 6-OHDA lesions have been extensively studied. Here, we investigated whether early motor behavioral deficits can be observed in the first week after the injection of 6-OHDA into the right substantia nigra pars compacta (SNc), and if they were indicative of the severity of the dopaminergic (DAergic) lesion in the SNc and the striatum at different time-points (day 1, 3, 5, 7, 14, 21). With this aim, we used our newly modified tail suspension swing test (TSST), the standard rotation test (RT), and immunohistochemical staining for tyrosine hydroxylase (TH). The TSST, but not the standard RT, revealed a spontaneous motor bias for the 6-OHDA-lesioned rats from the day 1 post-surgery. Both tests detected the motor asymmetry induced by (single and repeated) apomorphine (APO) challenges that correlated, in the first week, with the DAergic neuronal degeneration. The described TSST is fast and easy to perform, and in the drug-free condition is useful for the functional assessment of early motor asymmetry appearing after the 6-OHDA-lesion in the SNc, without the confounding effect of APO challenges.

Dopaminergic Progenitors Derived From Epiblast Stem Cells Function Similarly to Primary VM-Derived Progenitors When Transplanted Into a Parkinson's Disease Model

Neural transplantation in neurodegenerative diseases such as Parkinson’s disease (PD) offers to replace cells lost during the progression of the disease process. Primary fetal ventral mesencephalon (VM), the origin of bona fide midbrain dopaminergic (DAergic) precursors, is currently the gold standard source of cells for transplantation in PD. However, the use of tissue from this source raises ethical and logistical constraints necessitating the need for alternative supplies of donor cells. The requirement of any alternative donor cell source is to have the capability to generate authentic mature DAergic neurons, which could be utilized in cell-replacement strategies. Mouse pluripotent stem cells can efficiently generate electrochemically mature midbrain DAergic precursors in vitro using a stepwise control of FGF signaling. Here, we have compared DAergic transplants derived from two progenitor cell sources in an allograft system: mouse epiblast stem cells (EpiSC) and primary fetal mouse VM tissue. Cells were transplanted into the striatum of 6-OHDA lesioned mice pre-treated with L-DOPA. Drug-induced rotations, a number of motor tests and drug-induced abnormal involuntary movements (AIMs) were assessed. Functional improvements were demonstrated post-transplantation in some behavioral tests, with no difference in graft volume or the number of TH immuno-positive cells in the grafts of the two transplant groups. L-DOPA-induced AIMs and amphetamine-induced AIMs were observed in both transplant groups, with no differences in rate or severity between the two groups. Collectively, in this mouse-to-mouse allograft system, we report no significant differences in the functional ability between the gold standard primary VM derived and pluripotent stem cell-derived DAergic transplants.

6-OH-BDE-47 exposure-induced Parkinson's disease pathology in Sprague Dawley rat

6-Hydroxy-BDE-47 (6-OH-BDE-47) is an important in vivo metabolite derived from 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), a ubiquitous environmental pollutant. The chemical has been widely detected in environmental and biological samples. However, as a potential neurotoxin, whether 6-OH-BDE-47 could promote the development of typical neurodegenerative diseases such as Parkinson's disease (PD) is still unknown. Here, we tested the potential PD-related neurotoxic effect of 6-OH-BDE-47 in rat. The chemical with levels of 0.1, 1 and 10 µg was stereotaxically injected into the right midbrain regions of rat where contain abundant dopaminergic neurons. The resulting deteriorated motor function and decreased levels of striatal dopamine and nigrostriatal tyrosine hydroxylase indicate the dopaminergic neuron loss after the injection. Proteomics study revealed that protein degradation pathways were affected. Western blot analysis confirmed that 6-OH-BDE-47 could inhibit ubiquitination and autophagy, resulting in the increased formation of α-synuclein (α-syn) aggregate, an important pathological hallmark of PD. Overall, our study demonstrated that the 6-OH-BDE-47 administration could induce motor defect by impairing dopaminergic system and promote α-syn aggregation by inhibiting ubiquitination and autophagy, suggesting that the occurrence of 6-OH-BDE-47 in brain could be a risk for developing PD.

Effects of the probiotic formulation SLAB51 in in vitro and in vivo Parkinson's disease models

Parkinson is a common neurodegenerative disorder, characterized by motor and non-motor symptoms, including abnormalities in the gut function, which may appear before the motor sign. To date, there are treatments that can help relieve Parkinson’ disease (PD)-associated symptoms, but there is no cure to control the onset and progression of this disorder. Altered components of the gut could represent a key role in gut-brain axis, which is a bidirectional system between the central nervous system and the enteric nervous system. Diet can alter the microbiota composition, affecting gut-brain axis function. Gut microbiome restoration through selected probiotics’ administration has been reported. In this study, we investigated the effects of the novel formulation SLAB51 in PD. Our findings indicate that this probiotic formulation can counteract the detrimental effect of 6-OHDA in vitro and in vivo models of PD. The results suggest that SLAB51 can be a promising candidate for the prevention or as coadjuvant treatment of PD.