Role of toll-like receptor 4 and sex in 6-hydroxydopamine-induced behavioral impairments and neurodegeneration in mice.

Parkinson's disease (PD) is a neurodegenerative disease characterized by progressive loss of the nigrostriatal dopaminergic neurons that are associated with motor alterations and non-motor manifestations (such as depression). Neuroinflammation is a process with a critical role in the pathogenesis of PD. In this regard, toll-like receptor 4 (TLR4) is a central mediator of immune response in PD. Moreover, there are gender-related differences in the incidence, prevalence, and clinical features of PD. Therefore, we aimed to elucidate the role of TLR4 in the sex-dependent response to dopaminergic denervation induced by 6-hydroxydopamine (6-OHDA) in mice. Female and male adult wildtype (WT) and TLR4 knockout (TLR4-/-) mice were administered with unilateral injection of 6-OHDA in the dorsal striatum, and non-motor and motor impairments were evaluated for 30 days, followed by biochemistry analysis in the substantia nigra pars compacta (SNc), dorsal striatum, and dorsoventral cortex. Early non-motor impairments (i.e., depressive-like behavior and spatial learning deficits) induced by 6-OHDA were observed in the male WT mice but not in male TLR4-/- or female mice. Motor alterations were observed after administration of 6-OHDA in both strains, and the lack of TLR4 was also related to motor commitment. Moreover, ablation of TLR4 prevented 6-OHDA-induced dopaminergic denervation and microgliosis in the SNc, selectively in female mice. These results reinforced the existence of sex-biased alterations in PD and indicated TLR4 as a promising therapeutic target for the motor and non-motor symptoms of PD, which will help counteract the neuroinflammatory and neurodegenerative processes.

Protective effect of plastrum testudinis extract on dopaminergic neurons in a Parkinson's disease model through DNMT1 nuclear translocation and SNCA's methylation.

The pathological characteristics of Parkinson's disease (PD) include dopaminergic neuron damage, specifically disorders caused by dopamine synthesis, in vivo. Plastrum testudinis extract (PTE) and its bioactive ingredient ethyl stearate (PubChem CID: 8122) were reported to be correlated with tyrosine hydroxylase (TH), which is a biomarker of dopaminergic neurons. This suggests that PTE and its small-molecule active ingredient ethyl stearate have potential for development as a therapeutic drug for PD. In this study, we treated 6-hydroxydopamine (6-OHDA)-induced model rats and PC12 cells with PTE. The mechanism of action of PTE and ethyl stearate was investigated by western blotting, bisulfite sequencing PCR (BSP), real-time PCR, immunofluorescence and siRNA transfection. PTE effectively upregulated the TH expression and downregulated the alpha-synuclein expression in both the substantia nigra and the striatum of the midbrain in a PD model rat. The PC12 cell model showed that both PTE and its active monomer ethyl stearate significantly promoted TH expression and blocked alpha-synuclein, agreeing with the in vivo results. BSP showed that PTE and ethyl stearate increased the methylation level of the Snca intron 1 region. These findings suggest that some of the protective effects of PTE on dopaminergic neurons are mediated by ethyl stearate. The mechanism of ethyl stearate may involve disrupting the abnormal aggregation of DNA (cytosine-5)-methyltransferase 1 (DNMT1) with alpha-synuclein by releasing DNMT1, upregulating Snca intron 1 CpG island methylation, and ultimately, reducing the expression of alpha-synuclein.

Acrolein scavenger dimercaprol offers neuroprotection in an animal model of Parkinson's disease: implication of acrolein and TRPA1.

BACKGROUND: The mechanisms underlying lesions of dopaminergic (DA) neurons, an essential pathology of Parkinson's disease (PD), are largely unknown, although oxidative stress is recognized as a key factor. We have previously shown that the pro-oxidative aldehyde acrolein is a critical factor in PD pathology, and that acrolein scavenger hydralazine can reduce the elevated acrolein, mitigate DA neuron death, and alleviate motor deficits in a 6-hydroxydopamine (6-OHDA) rat model. As such, we hypothesize that a structurally distinct acrolein scavenger, dimercaprol (DP), can also offer neuroprotection and behavioral benefits. METHODS: DP was used to lower the elevated levels of acrolein in the basal ganglia of 6-OHDA rats. The acrolein levels and related pathologies were measured by immunohistochemistry. Locomotor and behavioral effects of 6-OHDA injections and DP treatment were examined using the open field test and rotarod test. Pain was assessed using mechanical allodynia, cold hypersensitivity, and plantar tests. Finally, the effects of DP were assessed in vitro on SK-N-SH dopaminergic cells exposed to acrolein. RESULTS: DP reduced acrolein and reversed the upregulation of pain-sensing transient receptor potential ankyrin 1 (TRPA1) channels in the substantia nigra, striatum, and cortex. DP also mitigated both motor and sensory deficits typical of PD. In addition, DP lowered acrolein and protected DA-like cells in vitro. Acrolein's ability to upregulate TRPA1 was also verified in vitro using cell lines. CONCLUSIONS: These results further elucidated the acrolein-mediated pathogenesis and reinforced the critical role of acrolein in PD while providing strong arguments for anti-acrolein treatments as a novel and feasible strategy to combat neurodegeneration in PD. Considering the extensive involvement of acrolein in various nervous system illnesses and beyond, anti-acrolein strategies may have wide applications and broad impacts on human health.

In vivo imaging of synaptic SV2A protein density in healthy and striatal-lesioned rats with [11C]UCB-J PET.

The number of functionally active synapses provides a measure of neural integrity, with reductions observed in neurodegenerative disorders. [11C]UCB-J binds to synaptic vesicle 2A (SV2A) transmembrane protein located in secretory vesicles. We aimed to assess [11C]UCB-J PET as an in vivo biomarker of regional cerebral synaptic SV2A density in rat lesion models of neurodegeneration. Healthy anesthetized rats had [11C]UCB-J PET and arterial blood sampling. We compared different models describing [11C]UCB-J brain uptake kinetics to determine its regional distribution. Blocking studies were performed with levetiracetam (LEV), an antiepileptic SV2A antagonist. Tracer binding was measured in rodent unilateral acute lesion models of Parkinsonism and Huntington's disease, induced with 6-hydroxydopamine (6-OHDA) and quinolinic acid (QA), respectively. [3H]UCB-J autoradiography was performed in postmortem tissue. Rat brain showed high and fast [11C]UCB-J uptake and washout with up to 80% blockade by LEV. [11C]UCB-J PET showed a 6.2% decrease in ipsilateral striatal SV2A binding after 6-OHDA and 39.3% and 55.1% decreases after moderate and high dose QA confirmed by autoradiography. In conclusion, [11C]UCB-J PET provides a good in vivo marker of synaptic SV2A density which can potentially be followed longitudinally along with synaptic responses to putative neuroprotective agents in models of neurodegeneration.

Genetic suppression of the dopamine D3 receptor in striatal D1 cells reduces the development of L-DOPA-induced dyskinesia.

Parkinson's Disease (PD) is symptomatically managed with L-DOPA but chronic use results in L-DOPA-induced dyskinesia (LID) characterized by abnormal involuntary movements (AIMs). In LID, dopamine D3 receptors (D3R) are upregulated on D1 receptor (D1R)-bearing medium spiny neurons where the can synergistically drive downstream signaling and motor behaviors. Despite evidence implying D1R-D3R cooperativity in LID, the dyskinesiogenic role of D3R has never been directly tested. To this end, we developed a specific cre-dependent microRNA (miRNA) to irreversibly prevent D3R upregulation in D1R striatal cells. D1-Cre rats received unilateral 6-hydroxydopamine lesions. Three weeks later, rats received an adeno-associated virus expressing either D3R miRNA or a scrambled (SCR) miRNA delivered into the striatum. After 4 weeks, rats received chronic L-DOPA (6 mg/kg) or vehicle. AIMs development and motor behaviors were assayed throughout treatment. At the conclusion of the experiment, efficacy and fidelity of the miRNA strategy was analyzed using in situ hybridization (ISH). ISH analyses demonstrated that D1R+/D3R+ cells were upregulated in LID and that the selective D3R miRNA reduced D1R+/D3R+ co-expression. Importantly, silencing of D3R also significantly attenuated LID development without impacting L-DOPA efficacy or other locomotion. These data highlight a dyskinesiogenic role of D3R within D1R cells in LID and highlight aberrant D1R-D3R interactions as targets of LID management.

Subthalamic beta oscillations correlate with dopaminergic degeneration in experimental parkinsonism.

Excessive beta activity has been shown in local field potential recordings from the cortico-basal ganglia loop of Parkinson's disease patients and in its various animal models. Recent evidence suggests that enhanced beta oscillations may play a central role in the pathophysiology of the disorder and that beta activity may be directly linked to the motor impairment. However, the temporal evolution of exaggerated beta oscillations during the ongoing dopaminergic neurodegeneration and its relation to the motor impairment and histological changes are still unknown. We investigated motor behavioral, in-vivo electrophysiological (subthalamic nucleus, motor cortex) and histological changes (striatum, substantia nigra compacta) 2, 5, 10 and 20-30 days after a 6-hydroxydopamine injection into the medial forebrain bundle in Wistar rats. We found strong correlations between subthalamic beta power and motor impairment. No correlation was found for beta power in the primary motor cortex. Only subthalamic but not cortical beta power was strongly correlated with the histological markers of the dopaminergic neurodegeneration. Significantly increased subthalamic beta oscillations could be detected before this increase was found in primary motor cortex. At the latest observation time point, a significantly higher percentage of long beta bursts was found. Our study is the first to show a strong relation between subthalamic beta power and the dopaminergic neurodegeneration. Thus, we provide additional evidence for an important pathophysiological role of subthalamic beta oscillations and prolonged beta bursts in Parkinson's disease.

Hesperidin downregulates kinases lrrk2 and gsk3ß in a 6-OHDA induced Parkinson's disease model.

The depletion of dopamine in the striatum region and Lewy bodies are the hallmark characteristics of Parkinson's disease. The pathology also includes the upregulation of various Parkinson's disease (PARK) genes and kinases. Two such kinases, LRRK2 and GSK-3ß have been directly implicated in the formation of tau and alpha-synuclein proteins, causing PD. Hesperidin (HES) is a flavanone glycoside that has multiple therapeutic benefits including neuroprotective effects. In this study, we examined the neuroprotective effects of HES against 6-hydroxydopamine (6-OHDA) induced-neurotoxicity in the in-vitro and in-vivo model. Hesperidin significantly protected the SH-SY5Y cells' stress against 6-OHDA induced toxicity by downregulating biomarkers of oxidative stress. Furthermore, HES downregulated the kinases lrrk2 and gsk3ß along with casp3, casp9, and polg in the zebrafish model. The treatment with HES also improved the locomotor pattern of zebrafish that was affected by 6-OHDA. This study suggests that hesperidin could be a drug of choice in targeting kinases against a 6-OHDA model of PD.

A novel dopamine D3R agonist SK609 with norepinephrine transporter inhibition promotes improvement in cognitive task performance in rodent and non-human primate models of Parkinson's disease.

Mild cognitive impairment is present in a number of neurodegenerative disorders including Parkinson's disease (PD). Mild cognitive impairment in PD (PD-MCI) often manifests as deficits in executive functioning, attention, and spatial and working memory. Clinical studies have suggested that the development of mild cognitive impairment may be an early symptom of PD and may even precede the onset of motor impairment by several years. Dysfunction in several neurotransmitter systems, including dopamine (DA), norepinephrine (NE), may be involved in PD-MCI, making it difficult to treat pharmacologically. In addition, many agents used to treat motor impairment in PD may exacerbate cognitive impairment. Thus, there is a significant unmet need to develop therapeutics that can treat both motor and cognitive impairments in PD. We have recently developed SK609, a selective, G-protein biased signaling agonist of dopamine D3 receptors. SK609 was successfully used to treat motor impairment and reduce levodopa-induced dyskinesia in a rodent model of PD. Further characterization of SK609 suggested that it is a selective norepinephrine transporter (NET) inhibitor with the ability to increase both DA and NE levels in the prefrontal cortex. Pharmacokinetic analysis of SK609 under systemic administration demonstrated 98% oral bioavailability and high brain distribution in striatum, hippocampus and prefrontal cortex. To evaluate the effects of SK609 on cognitive deficits of potential relevance to PD-MCI, we used unilateral 6-hydroxydopamine (6-OHDA) lesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated cynomolgus macaques, with deficits in performance in a sustained attention and an object retrieval task, respectively. SK609 dose dependently improved the performance of 6-OHDA-lesioned rats, with peak performance achieved using a 4 mg/kg dose. This improvement was predominantly due to a significant reduction in the number of misses and false alarm errors, contributing to an increase in sustained attention. In MPTP-lesioned monkeys, this same dose also improved performance in an object retrieval task, significantly reducing cognitive errors (barrier reaches) and motor errors (fine motor dexterity problems). These data demonstrate that SK609 with its unique pharmacological effects on modulating both DA and NE can ameliorate cognitive impairment in PD models and may provide a therapeutic option to treat both motor and cognitive impairment in PD patients.

Blockade of GABA transporter-1 and GABA transporter-3 in the lateral habenula improves depressive-like behaviors in a rat model of Parkinson's disease.

The hyperactivity of the lateral habenula (LHb) is closely associated with depression. At present, it is unknown how GABA transporter (GAT) in the LHb affects depressive-like behaviors, particularly in Parkinson's disease (PD)-related depression. In this study, unilateral 6-hydroxydopamine lesions of the substantia nigra pars compacta (SNc) in rats induced depressive-like behaviors and led to hyperactivity of LHb neurons compared to sham-lesioned rats. Intra-LHb injection of GAT-1 inhibitor NO-711 produced antidepressant-like responses, decreased firing rate of LHb neurons, and increased levels of LHb extracellular GABA in sham-lesioned and the lesioned rats. Further, the dose producing behavioral effects in the lesioned rats was lower than that of sham-lesioned rats. In the lesioned rats, the duration of inhibitory effect on the firing rate and increased levels of the GABA induced by NO-711 was longer than those in sham-lesioned rats, respectively. Intra-LHb injection of GAT-3 inhibitor SNAP-5114 improved depressive-like behaviors and decreased firing rate of LHb neurons in the lesioned rats, but not in sham-lesioned rats. SNAP-5114 increased LHb GABA levels in the lesioned rats, whereas did not alter that in sham-lesioned rats. These changes were involved in the down-regulated expression of LHb GAT-1 and GAT-3 after lesioning the SNc. These findings suggest that GAT-1 plays a major role in transporting LHb GABA under physiological conditions, and depletion of dopamine increases the transport capacity of GAT-3 in the LHb. Further, the study provides evidence that GAT-1 and GAT-3 in the LHb are involved in the regulation of PD-related depression.

Downregulation of lncRNA BACE1-AS improves dopamine-dependent oxidative stress in rats with Parkinson's disease by upregulating microRNA-34b-5p and downregulating BACE1.

Objective: Long noncoding RNAs (lncRNAs) have already been proposed to function in Parkinson's disease (PD). However, the role of lncRNA BACE1-AS in PD has never been discussed. This study aims to examine the mechanism of BACE1-AS on oxidative stress injury of dopaminergic neurons in PD rats.Methods: Rat models of PD were established through the injection of 6-hydroxydopamine. The rotation of rats was induced by intraperitoneal injection of apomorphine, and number of rotations per minute was detected. The levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px), glutamic acid (Glu), dopamine (DA), tyrosine hydroxylase (TH), α-synuclein and inducible nitric oxide synthase (iNOS) in the substantia nigra of rats in each group were detected. Apoptosis and pathological changes in the substantia nigra were also observed. BACE1-AS, miR-34b-5p, BACE1, Bax and Bcl-2 expression in the substantia nigra were detected. The binding of BACE1-AS and miR-34b-5p and the targeting relationship of miR-34b-5p and BACE1 were further determined.Results: Downregulated BACE1-AS reduced iNOS, α-synuclein and Glu levels and elevated DA and TH levels in the substantia nigra of PD rats. Downregulated BACE1-AS repressed apoptosis and oxidative stress injury in the substantia nigra neurons of PD rats. BACE1-AS specifically bound to miR-34b-5p. BACE1 was a direct target gene of miR-34b-5p.Conclusion: Collectively, our study reveals that downregulation of lncRNA BACE1-AS inhibits iNOS activation in the substantial nigra and improve oxidative stress injury in PD rats by upregulating miR-34b-5p and downregulating BACE1.

Transplantation of Nurr1-overexpressing neural stem cells and microglia for treating parkinsonian rats.

BACKGROUND: Neural stem cells (NSCs) transplantation is considered a promising treatment for Parkinson's disease. But most NSCs are differentiated into glial cells rather than neurons, and only a few of them survive after transplantation due to the inflammatory environment. METHODS: In this study, neural stem cells (NSCs) and microglial cells both forced with the Nurr1 gene were transplanted into the striatum of the rat model of PD. The results were evaluated through reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunofluorescence analysis. RESULTS: The behavioral abnormalities of PD rats were improved by combined transplantation of NSCs and microglia, both forced with Nurr1. The number of tyrosine hydroxylase+ cells in the striatum of PD rats increased, and the number of Iba1+ cells decreased compared with the other groups. Moreover, the dopamine neurons differentiated from grafted NSCs could still be detected in the striatum of PD rats after 5 months. CONCLUSIONS: The results suggested that transplantation of Nurr1-overexpressing NSCs and microglia could improve the inhospitable host brain environments, which will be  a new potential strategy for the cell replacement therapy in PD.

A functionalized hydroxydopamine quinone links thiol modification to neuronal cell death.

Recent findings suggest that dopamine oxidation contributes to the development of Parkinson's disease (PD); however, the mechanistic details remain elusive. Here, we compare 6-hydroxydopamine (6-OHDA), a product of dopamine oxidation that commonly induces dopaminergic neurodegeneration in laboratory animals, with a synthetic alkyne-functionalized 6-OHDA variant. This synthetic molecule provides insights into the reactivity of quinone and neuromelanin formation. Employing Huisgen cycloaddition chemistry (or "click chemistry") and fluorescence imaging, we found that reactive 6-OHDA p-quinones cause widespread protein modification in isolated proteins, lysates and cells. We identified cysteine thiols as the target site and investigated the impact of proteome modification by quinones on cell viability. Mass spectrometry following cycloaddition chemistry produced a large number of 6-OHDA modified targets including proteins involved in redox regulation. Functional in vitro assays demonstrated that 6-OHDA inactivates protein disulfide isomerase (PDI), which is a central player in protein folding and redox homeostasis. Our study links dopamine oxidation to protein modification and protein folding in dopaminergic neurons and the PD model.

Strengths and limitations of morphological and behavioral analyses in detecting dopaminergic deficiency in Caenorhabditis elegans.

In order to develop a better understanding of the role environmental toxicants may play in the onset and progression of neurodegenerative diseases, it has become increasingly important to optimize sensitive methods for quickly screening toxicants to determine their ability to disrupt neuronal function. The nematode Caenorhabditis elegans can help with this effort. This species has an integrated nervous system producing behavioral function, provides easy access for molecular studies, has a rapid lifespan, and is an inexpensive model. This study focuses on methods of measuring neurodegeneration involving the dopaminergic system and the identification of compounds with actions that disrupt dopamine function in the model organism C. elegans. Several dopamine-mediated locomotory behaviors, Area Exploration, Body Bends, and Reversals, as well as Swimming-Induced Paralysis and Learned 2-Nonanone Avoidance, were compared to determine the best behavioral method for screening purposes. These behavioral endpoints were also compared to morphological scoring of neurodegeneration in the dopamine neurons. We found that in adult worms, Area Exploration is more advantageous than the other behavioral methods for identifying DA-deficient locomotion and is comparable to neuromorphological scoring outputs. For larval stage worms, locomotion was an unreliable endpoint, and neuronal scoring appeared to be the best method. We compared the wild-type N2 strain to the commonly used dat-1p::GFP reporter strains BY200 and BZ555, and we further characterized the dopamine-deficient strains, cat-2 e1112 and cat-2 n4547. In contrast to published results, we found that the cat-2 strains slowed on food almost as much as N2s. Both showed decreased levels of cat-2 mRNA and DA content, rather than none, with cat-2 e1112 having the greatest reduction in DA content in comparison to N2. Finally, we compared and contrasted strengths, limitations, cost, and equipment needs for all primary methods for analysis of the dopamine system in C. elegans.

Desferrioxamine and dextromethorphan combination exhibited synergistic effect and reversed the catalepsy behaviour in 6-hydroxydopamine hydroydopamine administered rats through regulating brain glutamate levels.

OBJECTIVE: To investigate the effect of desferrioxamine (DFO) and dextromethorphan (DXM) combination in animal model of Parkinson's disease (PD). METHODS: The PD was induced in rats through intracerebroventricular administration of 6-hydroxydopamine (6-OHDA) using stereotaxic apparatus. The animals were subjected to behavioural assessments and neurobiochemicals estimation followed by immunohistochemistry staining of neuron specific enolase (NSE) in striatum. KEY FINDINGS: Desferrioxamine and DXM combination has significantly reversed the catalepsy behaviour and elevated the antioxidant enzymes (SOD, CAT, GSH) and dopamine levels. Interestingly, the level of glutamate, nitric oxide, cytokines (IL-1ß, TNF-α) and NSE expressions were found to be decreased in striatum region of 6-OHDA-administered rats. The combination of DFO and DXM has shown synergism in most of the parameters studied, when compared to per se treatment. CONCLUSIONS: The reversal of catalepsy behaviour represents the protective effect of above combination on dopamine neurons in striatum from 6-OHDA toxicity. The mechanism of DFO and DXM combination might be attributed through attenuation of glutamate-induced excitotoxicity in neurons through ameliorating the reactive oxygen species and pro-inflammatory cytokines release. Treatment with DFO and DXM combination could control the multiple events in the pathogenesis of PD.

Deep brain stimulation of the ventroanterior and ventrolateral thalamus improves motor function in a rat model of Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disease with affected individuals exhibiting motor symptoms of bradykinesia, muscle rigidity, tremor, postural instability and gait dysfunction. The current gold standard treatment is pharmacotherapy with levodopa, but long-term use is associated with motor response fluctuations and can cause abnormal movements called dyskinesias. An alternative treatment option is deep brain stimulation (DBS) with the two FDA-approved brain targets for PD situated in the basal ganglia; specifically, in the subthalamic nucleus (STN) and globus pallidus pars interna (GPi). Both improve quality of life and motor scores by ~50-70% in well-selected patients but can also elicit adverse effects on cognition and other non-motor symptoms. Therefore, identifying a novel DBS target that is efficacious for patients not optimally responsive to current DBS targets with fewer side-effects has clear clinical merit. Here, we investigate whether the ventroanterior (VA) and ventrolateral (VL) motor nuclei of the thalamus can serve as novel and effective DBS targets for PD. In the limb-use asymmetry test (LAT), hemiparkinsonian rats showcased left forelimb akinesia and touched only 6.5 ±â€¯1.3% with that paw. However, these animals touched equally with both forepaws with DBS at 10 Hz, 100 µsec pulse width and 100 uA cathodic stimulation in the VA (n = 7), VL (n = 8) or at the interface between the two thalamic nuclei which we refer to as the VA|VL (n = 12). With whole-cell patch-clamp recordings, we noted that VA|VL stimulation in vitro increased the number of induced action potentials in proximal neurons in both areas albeit VL neurons transitioned from bursting to non-bursting action potentials (APs) with large excitatory postsynaptic potentials time-locked to stimulation. In contrast, VA neurons were excited with VA|VL electrical stimulation but with little change in spiking phenotype. Overall, our findings show that DBS in the VA, VL or VA|VL improved motor function in a rat model of PD; plausibly via increased excitation of residing neurons.

Central neuropeptide-S treatment improves neurofunctions of 6-OHDA-induced Parkinsonian rats.

Parkinson's disease (PD) is characterized by degeneration of the dopaminergic neurons in substantia nigra (SN). The motor symptoms of PD include tremor, rigidity, bradykinesia and postural impairment. In rodents, central administration of neuropeptide-S (NPS) has been shown to induce locomotor activity, dopamine release and neuronal survival by decreasing lipid peroxidation, additionally, the NPS receptor (NPSR) was detected in SN. Accumulating findings suggest that central NPS may ameliorate the parkinsonian symptoms, however, this has been explored incompletely due to the scarcity of experimental studies. Therefore, the present study was designed to test whether central NPS treatment exerts protective and/or alleviative effects on 6-OHDA-induced rat experimental PD model. Adult male Wistar rats received acute (alleviate; 10 nmol, icv) or chronic (protective; 1 nmol, icv for 7 days) NPS treatment following the central injection of 6-OHDA in medial forebrain bundle. Motor performance tests and in vivo nigral microdialysis were performed before and 7 days after the central 6-OHDA injection. The immunoreactivities for tyrosine hydroxylase (TH), NPSR, 4-hydroxynonenal (4-HNE) and c-Fos were detected by immunohistochemistry in frozen SN sections. Our double immunofluorescence labeling studies demonstrated that NPSR is present in the nigral TH-positive neurons. Central NPS injection caused a remarkable c-Fos expression in SN; whereas, no change was observed following vehicle injection. In both chronic and acute treatment groups, the 6-OHDA-induced motor dysfunction and impaired nigral dopamine release were improved significantly. However, only chronic, but not acute treatment restored the loss of nigral TH-positive cells, while decreasing the 4-HNE immunoreactivity in SN. Our findings demonstrate that central NPS treatment not only exerts a neuroprotective action on nigral dopaminergic neurons, it also improves the striatal dopaminergic signaling. Therefore, the present study candidates the NPSR agonism as a novel therapeutic approach for PD treatment.

Parkinson's disease and pain: Modulation of nociceptive circuitry in a rat model of nigrostriatal lesion.

Parkinson's disease (PD) is a neurodegenerative disorder that causes progressive dysfunction of dopaminergic and non-dopaminergic neurons, generating motor and nonmotor signs and symptoms. Pain is reported as the most bothersome nonmotor symptom in PD; however, pain remains overlooked and poorly understood. In this study, we evaluated the nociceptive behavior and the descending analgesia circuitry in a rat model of PD. Three independent experiments were performed to investigate: i) thermal nociceptive behavior; ii) mechanical nociceptive behavior and dopaminergic repositioning; and iii) modulation of the pain control circuitry. The rat model of PD, induced by unilateral striatal 6-hydroxydopamine (6-OHDA), did not interfere with thermal nociceptive responses; however, the mechanical nociceptive threshold was decreased bilaterally compared to that of naive or striatal saline-injected rats. This response was reversed by apomorphine or levodopa treatment. Striatal 6-OHDA induced motor impairments and reduced dopaminergic neuron immunolabeling as well as the pattern of neuronal activation (c-Fos) in the substantia nigra ipsilateral (IPL) to the lesion. In the midbrain periaqueductal gray (PAG), 6-OHDA-induced lesion increased IPL and decreased contralateral PAG GABAergic labeling compared to control. In the dorsal horn of the spinal cord, lesioned rats showed bilateral inhibition of enkephalin and µ-opioid receptor labeling. Taken together, we demonstrated that the unilateral 6-OHDA-induced PD model induces bilateral mechanical hypernociception, which is reversed by dopamine restoration, changes in the PAG circuitry, and inhibition of spinal opioidergic regulation, probably due to impaired descending analgesic control. A better understanding of pain mechanisms in PD patients is critical for developing better therapeutic strategies to improve their quality of life.

Secretome of Undifferentiated Neural Progenitor Cells Induces Histological and Motor Improvements in a Rat Model of Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative movement disorder that results from the death of dopamine (DA) neurons. Over recent years, differentiated or undifferentiated neural stem cells (NSCs) transplantation has been widely used as a means of cell replacement therapy. However, compelling evidence has brought attention to the array of bioactive molecules produced by stem cells, defined as secretome. As described in the literature, other cell populations have a high-neurotrophic activity, but little is known about NSCs. Moreover, the exploration of the stem cell secretome is only in its initial stages, particularly as applied to neurodegenerative diseases. Thus, we have characterized the secretome of human neural progenitor cells (hNPCs) through proteomic analysis and investigated its effects in a 6-hydroxidopamine (6-OHDA) rat model of PD in comparison with undifferentiated hNPCs transplantation. Results revealed that the injection of hNPCs secretome potentiated the histological recovery of DA neurons when compared to the untreated group 6-OHDA and those transplanted with cells (hNPCs), thereby supporting the functional motor amelioration of 6-OHDA PD animals. Additionally, hNPCs secretome proteomic characterization has revealed that these cells have the capacity to secrete a wide range of important molecules with neuroregulatory actions, which are most likely support the effects observed. Overall, we have concluded that the use of hNPCs secretome partially modulate DA neurons cell survival and ameliorate PD animals' motor deficits, disclosing improved results when compared to cell transplantation approaches, indicating that the secretome itself could represent a route for new therapeutic options for PD regenerative medicine. Stem Cells Translational Medicine 2018;7:829-838.

Hypericum polyanthemum cyclohexane extract potentiates behavioral effects and neurodegeneration induced by nigral infusions of 6-hydroxydopamine in rats.

INTRODUCTION: Parkinson's Disease (PD) is a progressive neurodegenerative disorder, hallmark of which is loss of nigral dopaminergic neurons. Since a Hypericum polyanthemum extract inhibits monoamine reuptake and some of its constituents present cytotoxic properties, the aim of this study was to evaluate the effect of this extract in an animal PD model. METHODS: Adult Wistar rats (110 days old) received 6-hydroxydopamine (6-OHDA) infusions into the right medial forebrain bundle. A cyclohexane extract from aerial parts of H. polyanthemum (POL; 90 mg/kg/administration; gavage) was administered in three different regimens. In Regimens 1 and 2, rats received 3 administrations of POL starting 4 or 24 h after 6-OHDA infusion, respectively. In Regimen 3, these administrations were carried out 1 day before any evaluation of ipsilateral rotational activity induced by methylphenidate (MP, 20 mg/kg, i.p.). MP was administered 10, 45, and 85 days after 6-OHDA infusion in all groups. Nigral tyrosine hydroxylase (TH) immunocontent was evaluated 120 days after 6-OHDA infusion in animals submitted to Regimen 2 only. The effect of POL on apomorphine-induced climbing behavior in non-lesioned adult CF1 mice (60 days old) treated with POL was also evaluated. RESULTS: Regimen 2 increased MP-induced rotational activity and decreased nigral TH levels in 6-OHDA-lesioned rats. Rotational activity was not altered in regimens 1 and 3. In addition, no change in climbing behavior was observed in non-lesioned mice. CONCLUSION: Together, these results indicate that, in 6-OHDA-lesioned rats, a cyclohexane H. polyanthemum extract potentiates neurotoxicity and MP-induced motor asymmetry depending on the time of administration. In the short term, it seems to not act directly on mice dopaminergic receptors.

Target-specific forebrain projections and appropriate synaptic inputs of hESC-derived dopamine neurons grafted to the midbrain of parkinsonian rats.

Dopamine (DA) neurons derived from human embryonic stem cells (hESCs) are a promising unlimited source of cells for cell replacement therapy in Parkinson's disease (PD). A number of studies have demonstrated functionality of DA neurons originating from hESCs when grafted to the striatum of rodent and non-human primate models of PD. However, several questions remain in regard to their axonal outgrowth potential and capacity to integrate into host circuitry. Here, ventral midbrain (VM) patterned hESC-derived progenitors were grafted into the midbrain of 6-hydroxydopamine-lesioned rats, and analyzed at 6, 18, and 24 weeks for a time-course evaluation of specificity and extent of graft-derived fiber outgrowth as well as potential for functional recovery. To investigate synaptic integration of the transplanted cells, we used rabies-based monosynaptic tracing to reveal the origin and extent of host presynaptic inputs to grafts at 6 weeks. The results reveal the capacity of grafted neurons to extend axonal projections toward appropriate forebrain target structures progressively over 24 weeks. The timing and extent of graft-derived dopaminergic fibers innervating the dorsolateral striatum matched reduction in amphetamine-induced rotational asymmetry in the animals where recovery could be observed. Monosynaptic tracing demonstrated that grafted cells integrate with host circuitry 6 weeks after transplantation, in a manner that is comparable with endogenous midbrain connectivity. Thus, we demonstrate that VM patterned hESC-derived progenitors grafted to midbrain have the capacity to extensively innervate appropriate forebrain targets, integrate into the host circuitry and that functional recovery can be achieved when grafting fetal or hESC-derived DA neurons to the midbrain.