Effects of acute and sub-chronic L-dopa therapy on striatal L-dopa methylation and dopamine oxidation in an MPTP mouse model of Parkinsons disease

Normalization effect of dopamine replacement therapy on brain functional connectome in Parkinson's disease

Dopamine replacement therapy (DRT) represents the standard treatment for Parkinson's disease (PD), however, instant and long-term medication influence on patients' brain function have not been delineated. Here, a total of 97 drug-naïve patients, 43 patients under long-term DRT, and 94 normal control (NC) were, retrospectively, enrolled. Resting-state functional magnetic resonance imaging data and motor symptom assessments were conducted before and after levodopa challenge test. Whole-brain functional connectivity (FC) matrices were constructed. Network-based statistics were performed to assess FC difference between drug-naïve patients and NC, and these significant FCs were defined as disease-related connectomes, which were used for further statistical analyses. Patients showed better motor performances after both long-term DRT and levodopa challenge test. Two disease-related connectomes were observed with distinct patterns. The FC of the increased connectome, which mainly consisted of the motor, visual, subcortical, and cerebellum networks, was higher in drug-naïve patients than that in NC and was normalized after long-term DRT (p-value <.050). The decreased connectome was mainly composed of the motor, medial frontal, and salience networks and showed significantly lower FC in all patients than NC (p-value <.050). The global FC of both increased and decreased connectome was significantly enhanced after levodopa challenge test (q-value <0.050, false discovery rate-corrected). The global FC of increased connectome in ON-state was negatively associated with levodopa equivalency dose (r = -.496, q-value = 0.007). Higher global FC of the decreased connectome was related to better motor performances (r = -.310, q-value = 0.022). Our findings provided insights into brain functional alterations under dopaminergic medication and its benefit on motor symptoms.

HOTAIR Accelerates Dyskinesia in a MPTP-Lesioned Mouse Model of PD via SSTR1 Methylation-Mediated ERK1/2 Axis

Homeobox transcript antisense RNA (HOTAIR), has been associated with neuroprotective effects in Parkinson's disease (PD). However, the underlying mechanisms still remain unclear. Hence, this present study attempted to clarify the functional relevance of HOTAIR in PD. We established an in vivo mouse model of PD using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and an in vitro cell model of PD by treating dopaminergic neuron MN9D cells with 1-methyl-4-phenylpyridinium species (MPP+). The expressions of somatostatin receptor 1 (SSTR1) and HOTAIR were altered to examine their effects on MN9D cell viability and apoptosis, as well as on movement impairments in MPTP-induced PD mouse model. The results indicated that HOTAIR expression was upregulated and SSTR1 was downregulated in in vivo and in vitro PD models. HOTAIR could bind to the promoter region of SSTR1, resulting in an increase of SSTR1 methylation through the recruitment of DNA methyltransferases in PD cell models. Notably, overexpression of HOTAIR and silencing of SSTR1 enhanced dopaminergic neuron apoptosis in MN9D cells and exacerbated dyskinesia in MPTP-induced PD mouse model. Collectively, overexpressed HOTAIR stimulates DNA methylation of SSTR1 to reduce SSTR1 expression, thereby accelerating dyskinesia and facilitating dopaminergic neuron apoptosis in a MPTP-lesioned PD mouse model via activation of the ERK1/2 axis.

Brain-Region Specific Metabolic Abnormalities in Parkinson's Disease and Levodopa-Induced Dyskinesia

Several lines of evidence point to alteration in brain metabolic homeostasis in Parkinson’s disease (PD) and levodopa-induced dyskinesia (LID), yet the metabolic mechanism in different brain regions underlying PD and LID remains largely unknown. The present study aimed to uncover the metabolic pathways across anatomical regions in the brain of PD and LID. Using an NMR-based metabolomic approach, we generated the metabolomics profiling data from six different brain regions of PD rats and following the onset of LIDs. The diversity of metabolite patterns across the brain and its relation to PD and LID were further investigated through principal component analysis (PCA) and multivariate general linear model. Compared with control rats, dopamine loss in PD rats produced a marked and persistent metabolic disturbance in neurotransmitter metabolism and energy pathway, resulting in a metabolic imbalance among different brain regions. In LID rats, levodopa replacement did not restore the midbrain-striatum metabolic crosstalk and metabolic disturbance throughout the brain was involved in levodopa related involuntary movements. Most notably, the midbrain and right cortex were identified as the primary regions of metabolic abnormalities in PD and LID rats. Neurochemical differences in metabolic phenotypes were mainly defined by various neurotransmitters including glutamate, glutamine and aspartate. Accordingly, we found that the PD and LID rats exhibited lower levels of synaptophysin (SYP), a marker for synaptic plasticity, compared with control rats. These findings provide key insights into the metabolic mechanism underlying PD and LID by defining brain-region specific metabolic phenotype, with implications for developing targeted therapies.

Curcumin-Activated Mesenchymal Stem Cells Derived from Human Umbilical Cord and Their Effects on MPTP-Mouse Model of Parkinson's Disease: A New Biological Therapy for Parkinson's Disease

Background

The aim of this study was to investigate the effects of human umbilical cord mesenchymal stem cell activated by curcumin (hUC-MSCs-CUR) on Parkinson's disease (PD). hUC-MSCs can differentiate into many types of adult tissue cells including dopaminergic (DA) neurons. CUR could protect DA neurons from apoptosis induced by 6-hydroxydopamine (6-OHDA). Therefore, we used the hUC-MSCs activated by CUR for the treatment of PD in an animal model.

Methods

The hUC-MSCs-CUR was transplanted into the MPTP-induced PD mouse models via the tail vein. We found that hUC-MSCs-CUR significantly improved the motor ability, increased the tyrosine hydroxylase (TH), dopamine (DA), and Bcl-2 levels, and reduced nitric oxide synthase, Bax, and cleaved caspase 3 expression in PD mice. The supernatant of hUC-MSCs-CUR (CM-CUR) was used to stimulate the SH-SY5Y cellular model of PD; cell proliferation, differentiation, TH, and neuronal-specific marker microtubular-associated protein 2 (MAP2) expressions were examined.

Results

Our data showed that CM-CUR significantly promoted cell proliferation and gradually increased TH and MAP2 expression in SH-SY5Y PD cells. The beneficial effects could be associated with significant increase of rough endoplasmic reticulum in the hUC-MSCs-CUR, which secretes many cytokines and growth factors beneficial for PD treatment.

Conclusions

Transplantation of hUC-MSCs-CUR could show promise for improving the motor recovery of PD.

Activation of Peroxisome Proliferator-Activated Receptor-α Increases the Expression of Nuclear Receptor Related 1 Protein (Nurr1) in Dopaminergic Neurons

Nuclear receptor related 1 protein (Nurr1) is an important transcription factor required for differentiation and maintenance of midbrain dopaminergic (DA) neurons. Since decrease in Nurr1 function either due to diminished expression or rare mutation is associated with Parkinson's disease (PD), upregulation of Nurr1 may be beneficial for PD. However, such mechanisms are poorly understood. This study underlines the importance of peroxisome proliferator-activated receptor (PPAR)α in controlling the transcription of Nurr1. Our mRNA analyses followed by different immunoassays clearly indicated that PPARα agonist gemfibrozil strongly upregulated the expression of Nurr1 in wild-type, but not PPARα^-/-, DA neurons. Moreover, identification of conserved PPRE in the promoter of Nurr1 gene followed by chromatin immunoprecipitation analysis, PPRE luciferase assay, and manipulation of Nurr1 gene by viral transduction of different PPARα plasmids confirmed that PPARα was indeed involved in the expression of Nurr1. Finally, oral administration of gemfibrozil increased Nurr1 expression in vivo in nigra of wild-type, but not PPARα^-/-, mice identifying PPARα as a novel regulator of Nurr1 expression and associated protection of DA neurons.

Metabolic Disturbances in the Striatum and Substantia Nigra in the Onset and Progression of MPTP-Induced Parkinsonism Model

Metabolic confusion has been linked to the pathogenesis of Parkinson's disease (PD), while the dynamic changes associated with the onset and progression of PD remain unclear. Herein, dynamic changes in metabolites were detected from the initiation to the development of 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) -induced Parkinsonism model to elucidate its potential metabolic mechanism. Ex vivo¹H nuclear magnetic resonance (NMR) spectroscopy was used to measure metabolite changes in the striatum and substantia nigra (SN) of mice at 1, 7, and 21 days after injection of MPTP. Metabolomic analysis revealed a clear separation of the overall metabolites between PD and control mice at different time points. Glutamate (Glu) in the striatum was significantly elevated at induction PD day 1 mice, which persisted to day 21. N-acetylaspartate (NAA) increased in the striatum of induction PD mice on days 1 and 7, but no significant difference was found in striatum on day 21. Myo-Inositol (mI) and taurine (Tau) were also disturbed in the striatum in induction PD day 1 mice. Additionally, key enzymes in the glutamate-glutamine cycle were significantly increased in PD mice. These findings suggest that neuron loss and motor function impairment in induction PD mice may be linked to overactive glutamate-glutamine cycle and altered membrane metabolism.

Expanding the repertoire of L-DOPA's actions: A comprehensive review of its functional neurochemistry

Though a multi-facetted disorder, Parkinson's disease is prototypically characterized by neurodegeneration of nigrostriatal dopaminergic neurons of the substantia nigra pars compacta, leading to a severe disruption of motor function. Accordingly, L-DOPA, the metabolic precursor of dopamine (DA), is well-established as a treatment for the motor deficits of Parkinson's disease despite long-term complications such as dyskinesia and psychiatric side-effects. Paradoxically, however, despite the traditional assumption that L-DOPA is transformed in residual striatal dopaminergic neurons into DA, the mechanism of action of L-DOPA is neither simple nor entirely clear. Herein, focussing on its influence upon extracellular DA and other neuromodulators in intact animals and experimental models of Parkinson's disease, we highlight effects other than striatal generation of DA in the functional profile of L-DOPA. While not excluding a minor role for glial cells, L-DOPA is principally transformed into DA in neurons yet, interestingly, with a more important role for serotonergic than dopaminergic projections. Moreover, in addition to the striatum, L-DOPA evokes marked increases in extracellular DA in frontal cortex, nucleus accumbens, the subthalamic nucleus and additional extra-striatal regions. In considering its functional profile, it is also important to bear in mind the marked (probably indirect) influence of L-DOPA upon cholinergic, GABAergic and glutamatergic neurons in the basal ganglia and/or cortex, while anomalous serotonergic transmission is incriminated in the emergence of L-DOPA elicited dyskinesia and psychosis. Finally, L-DOPA may exert intrinsic receptor-mediated actions independently of DA neurotransmission and can be processed into bioactive metabolites. In conclusion, L-DOPA exerts a surprisingly complex pattern of neurochemical effects of much greater scope that mere striatal transformation into DA in spared dopaminergic neurons. Their further experimental and clinical clarification should help improve both L-DOPA-based and novel strategies for controlling the motor and other symptoms of Parkinson's disease.

The Effect of MSCs Derived from the Human Umbilical Cord Transduced by Fibroblast Growth Factor-20 on Parkinson's Disease

Cell therapy is a potential therapeutic approach for Parkinson's disease (PD). Mesenchymal stem cells derived from the human umbilical cord (hUC-MSCs) give priority to PD patients because of multiple advantages. The appropriate gene transduction of hUC-MSC before transplantation is a promising procedure for cell therapy. Fibroblast growth factor-20 (FGF-20) has been shown to protect dopaminergic neurons against a range of toxic insults in vitro. In this study, the hUC-MSCs were gene transduced with FGF-20, and then we transplanted them into the PD mice model. The results showed that MSC-FGF-20 treatment obviously improved the behavior of PD, accompanied by the increase of tyrosine carboxylase- (TH-) positive cell and dopamine (DA). Furtherly, immunohistochemistry disclosed that MSC-FGF-20 obviously promoted the degradation of nuclear factor-κB (NF-κB), a transcription factor that controls genes encoding proinflammatory cytokines, highly expressed in the nigrostriatal dopaminergic regions in PD patients. Therefore, MSC-FGF-20 has a potential for improving PD, closely related to the degradation of NF-κB.