A Review of Differences in Clinical Characteristics between Tardive Syndrome Induced or Improved by Aripiprazole Treatment

INTRODUCTION

Tardive syndrome is a troublesome complication secondary to the long-term usage of antipsychotic medication. At present, there is a lack of effective treatment for tardive syndrome. Aripiprazole has been used in the treatment of tardive syndrome, with some reports of a good response. However, other reports have suggested that tardive syndrome can actually be induced by aripiprazole. The aim of current study was to investigate whether aripiprazole is beneficial or harmful for the treatment of tardive syndrome in specific patients.

METHOD

We performed a thorough literature search via PubMed. We included all of the studies discussing the relationship between tardive syndrome and aripiprazole, either with regards to "inducing" or "improving" the disease.

RESULT

None of the included studies were well-designed clinical trials, and all were case reports or case series. A total of 26 articles were included in which aripiprazole induced tardive syndrome, and another 24 in which tardive syndrome was improved by aripiprazole treatment. In the "improved" group, there were significantly more cases of schizophrenia than in the "induced" group (p=0.002). However, there were significantly more cases with other miscellaneous diagnoses in the "induced" group than in the "improved" group (p=0.003). In addition, the cases in the "induced" group had a significantly longer duration of aripiprazole usage than those in the "improved" group (p=0.001).

CONCLUSION

Current study is important for clinicians to pay attention to the risk of tardive syndrome when prescribing aripiprazole in patients with a diagnosis other than a psychiatric illness or in the long-term administration of aripiprazole.

Neuroprotective Effects of a Standardized Flavonoid Extract from Safflower against a Rotenone-Induced Rat Model of Parkinson's Disease

Parkinson’s disease (PD) is a major age-related neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra par compacta (SNpc). Rotenone is a neurotoxin that is routinely used to model PD to aid in understanding the mechanisms of neuronal death. Safflower (Carthamus tinctorius. L.) has long been used to treat cerebrovascular diseases in China. This plant contains flavonoids, which have been reported to be effective in models of neurodegenerative disease. We previously reported that kaempferol derivatives from safflower could bind DJ-1, a protein associated with PD, and that a flavonoid extract from safflower exhibited neuroprotective effects in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced mouse model of PD. In this study, a standardized safflower flavonoid extract (SAFE) was isolated from safflower and found to primarily contain flavonoids. The aim of the current study was to confirm the neuroprotective effects of SAFE in rotenone-induced Parkinson rats. The results showed that SAFE treatment increased body weight and improved rearing behavior and grip strength. SAFE (35 or 70 mg/kg/day) treatment reversed the decreased protein expression of tyrosine hydroxylase, dopamine transporter and DJ-1 and increased the levels of dopamine and its metabolite. In contrast, acetylcholine levels were decreased. SAFE treatment also led to partial inhibition of PD-associated changes in extracellular space diffusion parameters. These changes were detected using a magnetic resonance imaging (MRI) tracer-based method, which provides novel information regarding neuronal loss and astrocyte activation. Thus, our results indicate that SAFE represents a potential therapeutic herbal treatment for PD.

Dynamic DNA Methylation Regulates Levodopa-Induced Dyskinesia

Levodopa-induced dyskinesia (LID) is a persistent behavioral sensitization that develops after repeated levodopa (l-DOPA) exposure in Parkinson disease patients. LID is a consequence of sustained changes in the transcriptional behavior of striatal neurons following dopaminergic stimulation. In neurons, transcriptional regulation through dynamic DNA methylation has been shown pivotal to many long-term behavioral modifications; however, its role in LID has not yet been explored. Using a rodent model, we show LID development leads to the aberrant expression of DNA demethylating enzymes and locus-specific changes to DNA methylation at the promoter regions of genes aberrantly transcribed following l-DOPA treatment. Looking for dynamic DNA methylation in LID genome-wide, we used reduced representation bisulfite sequencing and found an extensive reorganization of the dorsal striatal methylome. LID development led to significant demethylation at many important regulatory areas of aberrantly transcribed genes. We used pharmacologic treatments that alter DNA methylation bidirectionally and found them able to modulate dyskinetic behaviors. Together, these findings demonstrate that l-DOPA induces widespread changes to striatal DNA methylation and that these modifications are required for the development and maintenance of LID.

SIGNIFICANCE STATEMENT

Levodopa-induced dyskinesia (LID) develops after repeated levodopa (l-DOPA) exposure in Parkinson disease patients and remains one of the primary obstacles to effective treatment. LID behaviors are a consequence of striatal neuron sensitization due to sustained changes in transcriptional behavior; however, the mechanisms responsible for the long-term maintenance of this cellular priming remain uncertain. Regulation of dynamic DNA methylation has been shown pivotal to the maintenance of several long-term behavioral modifications, yet its role in LID has not yet been explored. In this work, we report a pivotal role for the reorganization of DNA methylation in the development of LID and show that modification of DNA methylation may be a novel therapeutic target for use in preventing or reversing dyskinetic behaviors.

Medicinal plant Combretum leprosum mart ameliorates motor, biochemical and molecular alterations in a Parkinson's disease model induced by MPTP

ETHNOPHARMACOLOGICAL RELEVANCE

Combretum leprosum is a popular medicinal plant distributed in north and northeastern regions of Brazil. Many different parts of this plant are used in traditional medicine to treat several inflammatory diseases. Parkinson's disease (PD) is a disorder associated with inflammatory toxic factors and the treatments available provide merely a delay of the neurodegeneration.

AIM OF THE STUDY

We investigated the potential neuroprotective properties of the C. leprosum ethanolic extract (C.l.EE) in a murine model of PD using the toxin 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP).

MATERIALS AND METHODS

The mice were split into four groups: V/S (vehicle/saline), E/S (extract/saline), V/M (vehicle/MPTP) and E/M (extract/ MPTP). Mice received MPTP (30mg/kg, i.p.) or vehicle (10ml/kg, i.p.) once a day for 5 consecutive days and vehicle (10ml/kg) or C.l.EE (100mg/kg) orally by intra-gastric gavage (i.g.) during a 14-d period, starting 3 days before the first MPTP injection. All groups were assessed for behavioural impairments (amphetamine-induced locomotor activity and muscle strength), dopamine content in striatum using high performance liquid chromatography (HPLC), tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions using qPCR.

RESULTS

Animals were injected with d-amphetamine (2mg/kg) and the activity was recorded. Amphetamine-induced hyperlocomotion was observed in all groups; however animals treated with MPTP showed exacerbated hyperlocomotion (approximately 3 fold increase compared to control groups). By contrast, mice treated with MPTP that received C.l.EE exhibited attenuation of the hyperlocomotion and did not differ from control groups. Muscle strength test pointed that C.l.EE strongly avoided muscular deficits caused by MPTP (approximately 2 fold increase compared to V/M group). Dopamine and its metabolites were measured in the striatum. The V/M group presented a dopamine reduction of 80%. On the other hand, the E/M group exhibited an increase in dopamine and its metabolites levels (approximately 3 fold increase compared to V/M group). Tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions were significantly reduced in the V/M group (60%). Conversely, C.l.EE treatment was able to increase the mRNA levels of those genes in the E/M group (approximately 2 fold for TH and DAT).

CONCLUSIONS

These data show, for the first time, that C. leprosum ethanolic extract prevented motor and molecular changes induced by MPTP, and partially reverted dopamine deficit. Thus, our results demonstrate that C.l.EE has potential for the treatment and prevention of PD.

MicroRNA-124 loaded nanoparticles enhance brain repair in Parkinson's disease

Modulation of the subventricular zone (SVZ) neurogenic niche can enhance brain repair in several disorders including Parkinson's disease (PD). Herein, we used biocompatible and traceable polymeric nanoparticles (NPs) containing perfluoro-1,5-crown ether (PFCE) and coated with protamine sulfate to complex microRNA-124 (miR-124), a neuronal fate determinant. The ability of NPs to efficiently deliver miR-124 and prompt SVZ neurogenesis and brain repair in PD was evaluated. In vitro, miR-124 NPs were efficiently internalized by neural stem/progenitors cells and neuroblasts and promoted their neuronal commitment and maturation. The expression of Sox9 and Jagged1, two miR-124 targets and stemness-related genes, were also decreased upon miR-124 NP treatment. In vivo, the intracerebral administration of miR-124 NPs increased the number of migrating neuroblasts that reached the granule cell layer of the olfactory bulb, both in healthy and in a 6-hydroxydopamine (6-OHDA) mouse model for PD. MiR-124 NPs were also able to induce migration of neurons into the lesioned striatum of 6-OHDA-treated mice. Most importantly, miR-124 NPs proved to ameliorate motor symptoms of 6-OHDA mice, monitored by the apomorphine-induced rotation test. Altogether, we provide clear evidences to support the use of miR-124 NPs as a new therapeutic approach to boost endogenous brain repair mechanisms in a setting of neurodegeneration.

Neuroleptic-induced Parkinsonism: Clinicopathological study

BACKGROUND

Drug-induced parkinsonism is a well-known complication of several different drugs--the most common being neuroleptic-induced parkinsonism. However, very few autopsies have been reported in such cases.

METHODS

Patients assessed at Movement Disorders Clinic Saskatchewan are offered brain autopsy. Detailed clinical records are kept.

RESULTS

Brains were obtained from 7 drug-induced parkinsonism patients with parkinsonian symptom onset coinciding with use of drugs known to produce parkinsonism. Six were on antipsychotics and 1 was on metoclopramide. Three cases were treated with levodopa for parkinsonism. In two cases, parkinsonian features reversed after stopping the offending agent. Both had autopsy evidence of preclinical PD. In 4 of the remaining 5, dopamine-blocking drugs were continued until death. In 4 of those 5, brain histology revealed no cause for the parkinsonism, but 1 had mild SN neuronal loss without Lewy bodies.

CONCLUSION

This study shows that reversal of parkinsonism after discontinuing offending drugs does not indicate absence of underlying pathology. Neuroleptics can unmask preclinical PD in patients with insufficient SN damage for the disease to manifest clinically. Though the mechanism of sustained parkinsonian features after discontinuing neuroleptics remains to be established, it is unlikely that dopamine receptor block leads to retrograde SN neuronal degeneration. Furthermore, L-dopa does not appear to be toxic to SN.

[THYMIC HORMONES, ANTIOXIDANT ENZYMES AND NEUROGENESIS OF BULBUS OLFACTORIUS IN RATS WITH PARKINSONISM: THE EFFECT OF MELATONIN]

The adult rats received both neurotoxin 6-hidroxidophamine and neurotoxin and melatonin. It was investigated a link between the disturbances of the brain antioxidant enzymes activity and thymic endocrine function, as possible pathogenic factors of parkinsonism, with changes in the number of neural stem cells (NSC) in the bulbus olfactorius. Rats with motor asymmetry in the apomorphine test and significant damage of the dopaminergic neurons in the-substantia nigra have decreased levels of superoxide dismutase, catalase and glutathione peroxidase activities in striatum (1.3-1.4 times) and blood thymulin content (8 times) compared to control group. On the contrary, examined indices were not changed in rats without motor asymmetry and correspondingly partly damaged neurons. The number of nestin(+)-cells in the bulbus olfactorius of rats without motor asymmetry increased from 91.2% to 99.3% and remained unchanged after melatonin administration course (10 mg/kg during 18 days). Melatonin administration resulted in the decrease in the number of nestin(+)-cells along with significant elevation of the decreased antioxidant enzymes activity and blood thymulin content in rats with circulatory movements. Possibilities of the enhancement of NSC differentiation in bulbus olfactorius into neuronal direction in such animals has been discussed. The conclusion about the potential use of melatonin as a neuroprotector in parkinsonism therapy has been made.

Comparison of Human Primary with Human iPS Cell-Derived Dopaminergic Neuron Grafts in the Rat Model for Parkinson's Disease

Neuronal degeneration within the substantia nigra and the loss of the dopaminergic nigro-striatal pathway are the major hallmarks of Parkinson's disease (PD). Grafts of foetal ventral mesencephalic (VM) dopaminergic (DA) neurons into the striatum have been shown to be able to restore striatal dopamine levels and to improve overall PD symptoms. However, human foetus-derived cell grafts are not feasible for clinical application. Autologous induced pluripotent stem cell (iPS cell)-derived DA neurons are emerging as an unprecedented alternative. In this review, we summarize and compare the efficacy of human iPS cell-derived DA neuron grafts to restore normal behaviour in a rat model for PD with that of human foetal primary DA neurons. The differences we observed in the efficacy to restore normal function between the 2 types of DA neuron grafts could be ascribed to intrinsic properties of the iPS cell-derived DA neurons that critically affected survival and proper neurite extension in the striatum after implantation.

TLR4 signaling mediates AP-1 activation in an MPTP-induced mouse model of Parkinson's disease

OBJECTIVE

To evaluate the effects of Toll-like receptor 4 (TLR4) signaling on the activation of the transcription factor activator protein-1 (AP-1) in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson's disease (PD).

METHODS

The following groups were evaluated: normal saline (NS)-treated WT mice, NS-treated TLR4-knockout (KO) mice, MPTP-treated WT mice, and MPTP-treated TLR4-KO mice. After establishing the mouse model, behavioral changes were evaluated. AP-1 expression was detected by RT-PCR, Western blotting, immunohistochemistry and immunofluorescence staining.

RESULTS

Compared to MPTP-treated WT mice, significantly reduced dyskinesia was observed in MPTP-treated TLR4-KO mice. AP-1 mRNA and protein levels were significantly up-regulated in the substantia nigras (SNs) of MPTP-treated WT mice relative to NS-treated mice (P<0.01); these levels were significantly reduced in MPTP-treated TLR4-KO mice relative to MPTP-treated WT mice (P<0.01). Immunohistochemical staining demonstrated that AP-1 was distributed throughout the SN in MPTP-treated mice, and immunofluorescence further showed that AP-1 was expressed in TH-positive neuronal cells and GFAP-positive astrocytes. In addition, immunofluorescence revealed that AP-1 expression was lower in TH-positive neurons and GFAP-positive astrocytes in the SNs of MPTP-treated TLR4-KO mice relative to MPTP-treated WT mice.

CONCLUSIONS

The TLR4 pathway may play an important role in regulating AP-1 activation.

Neuroprotective Potential of Superparamagnetic Iron Oxide Nanoparticles Along with Exposure to Electromagnetic Field in 6-OHDA Rat Model of Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder affecting mainly the dopaminergic neurons of the substantia nigra leading to various motor and non-motor deficits. We explored the neuroprotective potential of superparamagnetic iron oxide nanoparticles (IONPs) along with exposure to EMF in 6-OHDA rat model of PD. IONPs were implanted at the site of lesion and 24 h thereafter the rats were exposed to magnetic fields 2 h/day for one week. Bilateral lesions of the striatum were made with 6-OHDA. The rats in all the intervention groups improved progressively over the days and by post-surgery day 4 they were active and bright. We observed a significant beneficial effect of the IONPs implantation and MF exposure on feeding behavior, gait and postural stability. There was a significant enhancement of mitochondrial function and attenuation of lesion volume in all the intervention groups as compared to PD. The results demonstrate neuroprotective effect of iron oxide nanoparticle implantation and magnetic field exposure in an in vivo 6-OHDA rat model of PD.

GDNF Overexpression from the Native Locus Reveals its Role in the Nigrostriatal Dopaminergic System Function

Degeneration of nigrostriatal dopaminergic system is the principal lesion in Parkinson’s disease. Because glial cell line-derived neurotrophic factor (GDNF) promotes survival of dopamine neurons in vitro and in vivo, intracranial delivery of GDNF has been attempted for Parkinson’s disease treatment but with variable success. For improving GDNF-based therapies, knowledge on physiological role of endogenous GDNF at the sites of its expression is important. However, due to limitations of existing genetic model systems, such knowledge is scarce. Here, we report that prevention of transcription of Gdnf 3’UTR in Gdnf endogenous locus yields GDNF hypermorphic mice with increased, but spatially unchanged GDNF expression, enabling analysis of postnatal GDNF function. We found that increased level of GDNF in the central nervous system increases the number of adult dopamine neurons in the substantia nigra pars compacta and the number of dopaminergic terminals in the dorsal striatum. At the functional level, GDNF levels increased striatal tissue dopamine levels and augmented striatal dopamine release and re-uptake. In a proteasome inhibitor lactacystin-induced model of Parkinson’s disease GDNF hypermorphic mice were protected from the reduction in striatal dopamine and failure of dopaminergic system function. Importantly, adverse phenotypic effects associated with spatially unregulated GDNF applications were not observed. Enhanced GDNF levels up-regulated striatal dopamine transporter activity by at least five fold resulting in enhanced susceptibility to 6-OHDA, a toxin transported into dopamine neurons by DAT. Further, we report how GDNF levels regulate kidney development and identify microRNAs miR-9, miR-96, miR-133, and miR-146a as negative regulators of GDNF expression via interaction with Gdnf 3’UTR in vitro. Our results reveal the role of GDNF in nigrostriatal dopamine system postnatal development and adult function, and highlight the importance of correct spatial expression of GDNF. Furthermore, our results suggest that 3’UTR targeting may constitute a useful tool in analyzing gene function.

Intracranial delivery of GDNF has been attempted for Parkinson’s disease (PD) treatment but with variable success. For improving GDNF-based therapies, knowledge on physiological role of endogenous GDNF at the sites of its expression is important. However, due to limitations of existing genetic model systems, such knowledge is scarce. Here, we utilize an innovative genetic approach by targeting the 3’UTR regulation of Gdnf in mice. Such animals express elevated levels of Gdnf exclusively in natively Gdnf-expressing cells, enabling dissection of endogenous GDNF functions in vivo. We show that endogenous GDNF regulates dopamine system development and function and protects mice in a rodent PD model without side effects associated with ectopic GDNF applications. Further, we report how GDNF levels regulate kidney development and identify microRNAs which control GDNF expression. Our study highlights the importance of correct spatial expression of GDNF and opens a novel approach to study gene function in mice.

Efficacy, safety, and tolerability of augmentation pharmacotherapy with aripiprazole for treatment-resistant depression in late life: a randomised, double-blind, placebo-controlled trial

BACKGROUND

Treatment-resistant major depression is common and potentially life-threatening in elderly people, in whom little is known about the benefits and risks of augmentation pharmacotherapy. We aimed to assess whether aripiprazole is associated with a higher probability of remission than is placebo.

METHODS

We did a randomised, double-blind, placebo-controlled trial at three centres in the USA and Canada to test the efficacy and safety of aripiprazole augmentation for adults aged older than 60 years with treatment-resistant depression (Montgomery Asberg Depression Rating Scale [MADRS] score of ≥15). Patients who did not achieve remission during a pre-trial with venlafaxine extended-release (150-300 mg/day) were randomly assigned (1:1) to the addition of aripiprazole (target dose 10 mg [maximum 15 mg] daily) daily or placebo for 12 weeks. The computer-generated randomisation was done in blocks and stratified by site. Only the database administrator and research pharmacists had knowledge of treatment assignment. The primary endpoint was remission, defined as an MADRS score of 10 or less (and at least 2 points below the score at the start of the randomised phase) at both of the final two consecutive visits, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00892047.

FINDINGS

From July 20, 2009, to Dec 30, 2013, we recruited 468 eligible participants, 181 (39%) of whom did not remit and were randomly assigned to aripiprazole (n=91) or placebo (n=90). A greater proportion of participants in the aripiprazole group achieved remission than did those in the placebo group (40 [44%] vs 26 [29%] participants; odds ratio [OR] 2·0 [95% CI 1·1-3·7], p=0·03; number needed to treat [NNT] 6·6 [95% CI 3·5-81·8]). Akathisia was the most common adverse effect of aripiprazole (reported in 24 [26%] of 91 participants on aripiprazole vs 11 [12%] of 90 on placebo). Compared with placebo, aripiprazole was also associated with more Parkinsonism (15 [17%] of 86 vs two [2%] of 81 participants), but not with treatment-emergent suicidal ideation (13 [21%] of 61 vs 19 [29%] of 65 participants) or other measured safety variables.

INTERPRETATION

In adults aged 60 years or older who do not achieve remission from depression with a first-line antidepressant, the addition of aripiprazole is effective in achieving and sustaining remission. Tolerability concerns include the potential for akathisia and Parkinsonism.

FUNDING

National Institute of Mental Health, UPMC Endowment in Geriatric Psychiatry, Taylor Family Institute for Innovative Psychiatric Research, National Center for Advancing Translational Sciences, and the Campbell Family Mental Health Research Institute.

Thiazolidinediones and Parkinson Disease: A Cohort Study

Thiazolidinediones, a class of medications indicated for the treatment of type 2 diabetes mellitus, reduce inflammation and have been shown to provide a therapeutic benefit in animal models of Parkinson disease. We examined the association between treatment with thiazolidinediones and the onset of Parkinson disease in older individuals. We performed a cohort study of 29,397 Medicare patients enrolled in state pharmaceutical benefits programs who initiated treatment with thiazolidinediones or sulfonylureas during the years 1997 through 2005 and had no prior diagnosis of Parkinson disease. New users of thiazolidinediones were propensity score matched to new users of sulfonylureas and followed to determine whether they were diagnosed with Parkinson disease. We used Cox proportional hazards models to compare time to diagnosis of Parkinson disease in the propensity score-matched populations. To assess the association with duration of use, we performed several analyses that required longer continuous use of medications. In the primary analysis, thiazolidinedione users had a hazard ratio for a diagnosis of Parkinson disease of 1.09 (95% confidence interval: 0.71, 1.66) when compared with sulfonylurea users. Increasing the duration-of-use requirements to 10 months did not substantially change the association; the hazard ratios ranged from 1.00 (95% confidence interval: 0.49, 2.05) to 1.17 (95% confidence interval: 0.60, 2.25). Thiazolidinedione use was not associated with a longer time to diagnosis of Parkinson disease than was sulfonylurea use, regardless of duration of exposure.

Proteasome subunit and opioid receptor gene expression down-regulation induced by paraquat and maneb in human neuroblastoma SH-SY5Y cells

Paraquat (PQ) and maneb (MB) are able to induce neurotoxic effects by promoting α-synuclein (α-syn) aggregates and altering tyrosine hydroxylase (TH), thus increasing the risk of Parkinson's disease (PD). These pesticides promote neurotoxic effects also by affecting proteasome function that normally regulate protein turnover. We investigated the effects of the two pesticides exposure on multiple targets involved in PD, using SH-SY5Y cells. First, we evaluated TH and α-syn protein levels following PQ and MB cell exposure and a significant increase of these protein levels was observed. Subsequently, since a relationship between ubiquitin/proteasome and opioid receptors has been proposed, the effects of pesticides on their gene expression have been investigated. A decrease of β1 and Rpt3 proteasome subunit mRNA levels, together with the μ and δ opioid receptor down-regulation, was detected. The reported alterations, here simultaneously observed, help to clarify the involvement of multiple biological markers implicated in PD, often separately evaluated.

[Early Stages of Parkinson's Disease: Comparative Characteristics of Sleep-Wakefulness Cycle in Patients and Model Animals]

The results of study of sleep-wakefulness cycle in experimental models of pre-clinical and early clinical stages of Parkinson's disease present and compared to some clinical examples. The conclusion is, the increase in activity level and decrease in total amount of slow wave and paradoxical sleep in model animals are taking place at the same circadian period of the secretion of pineal melatonin as sleep disorders in patients.

Animal models of Parkinson's disease: An updated overview

Parkinson's disease (PD) is a progressive neurodegenerative disorder whose etiology, besides a minority of genetic cases, is still largely unknown. Animal models have contributed to elucidate PD etiology and pathogenesis, as well as its cellular and molecular mechanisms, leading to the general hypothesis that this neurological disorder is due to complex interactions between environmental and genetic factors. However, the full understanding of PD is still very far from being achieved, and new potential treatments need to be tested to further improve patients' quality of life and, possibly, slow down the neurodegenerative process. In this context, animal models of PD are required to address all these issues. "Classic" models are based on neurotoxins that selectively target catecholaminergic neurons (such as 6-hydroxydopamine, 1-methyl-1,2,3,6-tetrahydropiridine, agricultural pesticides, etc.), while more recent models employ genetic manipulations that either introduce mutations similar to those find in familial cases of PD (α-synuclein, DJ-1, PINK1, Parkin, etc.) or selectively disrupt nigrostriatal neurons (MitoPark, Pitx3, Nurr1, etc.). Each one of these models has its own advantages and limitations, thus some are better suited for studying PD pathogenesis, while others are more pertinent to test therapeutic treatments. Here, we provide a critical and updated review of the most used PD models.

Cognitive Dysfunction in Drug-induced Parkinsonism Caused by Prokinetics and Antiemetics

The use of prokinetics/antiemetics is one of the leading causes of drug-induced parkinsonism (DIP) observed in neurology clinics. Cognitive dysfunction in DIP has recently been recognized, but pathologies related with cognitive dysfunction is unknown. Among our retrospective cohort of 385 consecutive parkinsonian patients enrolled in our parkinsonism registry, 14 patients were identified who satisfied our inclusion criteria: parkinsonism caused by prokinetics/antiemetics, existing T1-weighted 3D volumetric MR images, and normal [(18)F]-N-3-fluoropropyl-2-β-carboxymethoxy-3-β-(4-iodophenyl) nortropane PET scan images. For the comparison of volumetric MR data, 30 age- and sex-matched healthy individuals were included in this study. Among 14 patients with DIP, 4 patients were diagnosed with dementia, and all other patients had mild cognitive impairment (MCI). Comparisons of MR volumetric data between DIP patients with MCI and controls show that cortical gray matter volumes are reduced bilaterally in DIP (P=0.041) without changes in either total white matter volume or total intracranial volume. Among subcortical structures, the volume of the right hippocampus is reduced in DIP patients compared with controls (P=0.011, uncorrected). In DIP, cortical thickness is reduced in the bilateral lingual (P=0.002), right fusiform (P=0.032) and part of the left lateral occipital gyri (P=0.007). Our results suggests that cognitive dysfunction in DIP caused by prokinetics/antiemetics is common. Structural changes in the brain by 3D MRI may be associated with cognitive decline in DIP.

Sigma-1 receptor deficiency reduces MPTP-induced parkinsonism and death of dopaminergic neurons

Sigma-1 receptor (σ1R) has been reported to be decreased in nigrostriatal motor system of Parkinson's disease patients. Using heterozygous and homozygous σ1R knockout (σ1R+/- and σ1R-/-) mice, we investigated the influence of σ1R deficiency on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-impaired nigrostriatal motor system. The injection of MPTP for 5 weeks in wild-type mice (MPTP-WT mice), but not in σ1R+/- or σ1R-/- mice (MPTP-σ1R+/- or MPTP-σ1R-/- mice), caused motor deficits and ~40% death of dopaminergic neurons in substantia nigra pars compacta with an elevation of N-methyl-d-aspartate receptor (NMDAr) NR2B phosphorylation. The σ1R antagonist NE100 or the NR2B inhibitor Ro25-6981 could alleviate the motor deficits and the death of dopaminergic neurons in MPTP-WT mice. By contrast, MPTP-σ1R+/- mice treated with the σ1R agonist PRE084 or MPTP-σ1R-/- mice treated with the NMDAr agonist NMDA appeared to have similar motor deficits and loss of dopaminergic neurons as MPTP-WT mice. The pharmacological or genetic inactivation of σ1R suppressed the expression of dopamine transporter (DAT) in substantia nigra, which was corrected by NMDA. The activation of σ1R by PRE084 enhanced the DAT expression in WT mice or σ1R+/- mice. By contrast, the level of vesicular monoamine transporter 2 (VMAT2) in σ1R+/- mice or σ1R-/- mice had no difference from WT mice. Interestingly, MPTP-WT mice showed the reduction in the levels of DAT and VMAT2, but MPTP-σ1R-/- mice did not. The inactivation of σ1R by NE100 could prevent the reduction of VMAT2 in MPTP-WT mice. In addition, the activation of microglia cells in substantia nigra was equally enhanced in MPTP-WT mice and MPTP-σ1R-/- mice. The number of activated astrocytes in MPTP-σ1R-/- mice was less than that in MPTP-WT mice. The findings indicate that the σ1R deficiency through suppressing NMDAr function and DAT expression can reduce MPTP-induced death of dopaminergic neurons and parkinsonism.

Intracarotid Infusion of Mesenchymal Stem Cells in an Animal Model of Parkinson's Disease, Focusing on Cell Distribution and Neuroprotective and Behavioral Effects

Mesenchymal stem cells (MSCs) have been proposed as a potential therapeutic tool for Parkinson's disease (PD) and systemic administration of these cells has been tested in preclinical and clinical studies. However, no information on survival and actual capacity of MSCs to reach the brain has been provided. In this study, we evaluated homing of intraarterially infused rat MSCs (rMSCs) in the brain of rats bearing a 6-hydroxydopamine (6-OHDA)-induced lesion of the nigrostriatal tract, to establish whether the toxin-induced damage is sufficient to grant MSC passage across the blood-brain barrier (BBB) or if a transient BBB disruption is necessary. The rMSC distribution in peripheral organs and the effects of cell infusion on neurodegenerative process and motor deficits were also investigated. rMSCs were infused 14 days after 6-OHDA injection. A hyperosmolar solution of mannitol was used to transiently permeabilize the BBB. Behavioral impairment was assessed by adjusting step test and response to apomorphine. Animals were sacrificed 7 and 28 days after cell infusion. Our work shows that appreciable delivery of rMSCs to the brain of 6-OHDA-lesioned animals can be obtained only after mannitol pretreatment. A notable percentage of infused cells accumulated in peripheral organs. Infusion of rMSCs did not modify the progression of 6-OHDA-induced damage or the motor impairment at the stepping test, but induced progressive normalization of the pathological response (contralateral turning) to apomorphine administration. These findings suggest that many aspects should be further investigated before considering any translation of MSC systemic administration into the clinical setting for PD treatment.

SIGNIFICANCE

This study demonstrates that mesenchymal stem cells infused through the carotid artery do not efficiently cross the blood-brain barrier in rats with a Parkinson's disease-like degeneration of nigrostriatal neurons, unless a permeabilizing agent (e.g., mannitol) is used. The infusion did not reduce the neuronal damage and associated motor impairment, but abolished the motor abnormalities these animals typically show when challenged with a dopaminergic agonist. Therefore, although arterially infused mesenchymal stem cells did not show neurorestorative effects in this study's Parkinson's disease model, they appeared to normalize the pathological responsiveness of striatal neurons to dopaminergic stimulation. This capability should be further explored in future studies.

Somatostatin prevents lipopolysaccharide-induced neurodegeneration in the rat substantia nigra by inhibiting the activation of microglia

Somatostatin (SST) is a neuromodulator which is abundant throughout the central nervous system (CNS) and has a crucial role in neurodegenerative disorders. However, little is known about the effects and mechanisms of SST in dopaminergic (DA) neurons in the context of Parkinson's disease (PD). In the present study, a model of PD was generated by injecting lipopolysaccharide (LPS) into the substantia nigra (SN) of rats in order to investigate the effects of SST on LPS-induced degeneration of DA in vivo. Intramural injection of LPS resulted in a significant loss of DA neurons, while reduction of neuronal death by SST pretreatment was confirmed using immunohistochemical staining for tyrosine hydroxylase and Nissl. In parallel, immunohistochemical detection of OX-42 and hydroethidine staining were employed to determine the activation of microglia and production of reactive oxygen species (ROS), respectively. It was found that SST inhibited the LPS-induced microglial activity and ROS production. ELISA revealed a decreased production of pro-inflammatory mediators, including tumor necrosis factor-α, interleukin-1β and prostaglandin E2 when SST was administered prior to LPS treatment. Western blot analysis showed that LPS-induced expression of inducible nitric oxide synthase, cyclooxygenase-2 and nuclear factor κB (NF-κB) p-p65 was attenuated by administration of SST prior to LPS application. The results indicated that LPS-induced loss of nigral DA neurons was inhibited by SST and the observed effects of SST on neuroprotection were associated with suppression of microglial activation and the NF-κB pathway, ensuing decreases of neuroinflammation and oxidative stress. The present study therefore suggested that SST is beneficial for treating neurodegenerative diseases, such as PD, through inhibiting the activation of microglia.

Targeted Overexpression of α-Synuclein by rAAV2/1 Vectors Induces Progressive Nigrostriatal Degeneration and Increases Vulnerability to MPTP in Mouse

Mutations, duplication and triplication of α-synuclein genes are linked to familial Parkinson's disease (PD), and aggregation of α-synuclein (α-syn) in Lewy bodies (LB) is involved in the pathogenesis of the disease. The targeted overexpression of α-syn in the substantia nigra (SN) mediated by viral vectors may provide a better alternative to recapitulate the neurodegenerative features of PD. Therefore, we overexpressed human wild-type α-syn using rAAV2/1 vectors in the bilateral SN of mouse and examined the effects for up to 12 weeks. Delivery of rAAV-2/1-α-syn caused significant nigrostriatal degeneration including appearance of dystrophic striatal neurites, loss of nigral dopaminergic (DA) neurons and dissolving nigral neuron bodies in a time-dependent manner. In addition, the α-syn overexpressed mice also developed significant deficits in motor function at 12 weeks when the loss of DA neurons exceeded a threshold of 50%. To investigate the sensitivity to neurotoxins in mice overexpressing α-syn, we performed an MPTP treatment with the subacute regimen 8 weeks after rAAV injection. The impact of the combined genetic and environmental insults on DA neuronal loss, striatal dopamine depletion, dopamine turnover and motor dysfunction was markedly greater than that of either alone. Moreover, we observed increased phosphorylation (S129), accumulation and nuclear distribution of α-syn after the combined insults. In summary, these results reveal that the overexpressed α-syn induces progressive nigrostriatal degeneration and increases the susceptibility of DA neurons to MPTP. Therefore, the targeted overexpression of α-syn and the combination with environmental toxins may provide valuable models for understanding PD pathogenesis and developing related therapies.

[Modification of experimental rotenone model of Parkinson's disease]

A modification of experimental model of Parkinson's disease is proposed presuming the stereotaxic infusion of rotenone solution using a special device into the cental part of substantia nigra (SN) pars compacta of adult Wistar rats. It was shown that 10 days after infusion of the neurotoxin the density of dopaminergic (DA) neurons in the infusion area drops nearly six-fold, to 20.2±3.2 neurons/mm2, with respect to the corresponding value in non-affected controlateral SN, 119.0±3.3 neurons/mm2. Electron microscopy has shown ultrastructural impairments in mitochondria of SN neurons in the infusion area displayed mainly as a cristae disarray. The absence of overall toxicity and selectivity of the brain tissue impairments provide an evidence that the proposed rotenone model modification is adequate and can be used to study the effects of DA neuronal degeneration typical of Parkinson's disease.

Combined exposure to agriculture pesticides, paraquat and maneb, induces alterations in the N/OFQ-NOPr and PDYN/KOPr systems in rats: Relevance to sporadic Parkinson's disease

Despite several years of research, the aetiology of Parkinson's disease (PD) is quite far from being solved. In PD, as well as in other neurodegenerative disorders, it has been proposed that the combination of multiple factors might contribute to the onset of the disease. Indeed, several authors have suggested that environmental factors, such as pollutants and chemicals, might be associated with the onset of several neurodegenerative disorders. On the other hand, several studies have described that the nociceptin/orphanin-NOP and prodynorphin-KOP opioid systems are implicated in the pathology of Parkinson's disease. Considering the nonrestricted commercial availability and common use of several pesticides, such as paraquat and maneb, in agriculture of less developed countries, the aim of our study was to investigate the involvement of nociceptin/orphanin-NOP and prodynorphin-KOP systems in a chronic paraquat and maneb animal model of Parkinson's disease. Our results showed that after paraquat/maneb (5/15 mg kg(-1) ) treatment, a significant reduction in tyrosine hydroxylase (TH) levels, the rate-limiting enzyme for dopamine synthesis, was observed. Also, the association of paraquat and maneb (5/15 mg kg(-1) ) induced an increase in nociceptin/orphanin and a decrease of prodynorphin gene expression levels in the substantia nigra with a down-regulation of NOP and KOP receptors after both treatments in the substantia nigra and caudate putamen. These data further confirm that paraquat and maneb toxicity can modulate gene expression of the nociceptin/orphanin-NOP receptor and prodynorphin-KOP receptor systems in the substantia nigra and caudate putamen, offering further support to the hypothesis that chronic exposure to these agrochemicals might be implicated in the mechanisms underlying sporadic Parkinson's disease. © 2013 Wiley Periodicals, Inc. Environ Toxicol 30: 656-663, 2015.

Activin A protects midbrain neurons in the 6-hydroxydopamine mouse model of Parkinson's disease

Parkinson’s disease (PD) is a chronic neurodegenerative disease characterized by a significant loss of dopaminergic neurons within the substantia nigra pars compacta (SNpc) and a subsequent loss of dopamine (DA) within the striatum. Despite advances in the development of pharmacological therapies that are effective at alleviating the symptoms of PD, the search for therapeutic treatments that halt or slow the underlying nigral degeneration remains a particular challenge. Activin A, a member of the transforming growth factor β superfamily, has been shown to play a role in the neuroprotection of midbrain neurons against 6-hydroxydopamine (6-OHDA) in vitro, suggesting that activin A may offer similar neuroprotective effects in in vivo models of PD. Using robust stereological methods, we found that intrastriatal injections of 6-OHDA results in a significant loss of both TH positive and NeuN positive populations in the SNpc at 1, 2, and 3 weeks post-lesioning in drug naïve mice. Exogenous application of activin A for 7 days, beginning the day prior to 6-OHDA administration, resulted in a significant survival of both dopaminergic and total neuron numbers in the SNpc against 6-OHDA-induced toxicity. However, we found no corresponding protection of striatal DA or dopamine transporter (DAT) expression levels in animals receiving activin A compared to vehicle controls. These results provide the first evidence that activin A exerts potent neuroprotection in a mouse model of PD, however this neuroprotection may be localized to the midbrain.