Adenosine A2A Receptor Blockade Provides More Effective Benefits at the Onset Rather than after Overt Neurodegeneration in a Rat Model of Parkinson's Disease.

Adenosine A2A receptor (A2AR) antagonists are the leading nondopaminergic therapy to manage Parkinson's disease (PD) since they afford both motor benefits and neuroprotection. PD begins with a synaptic dysfunction and damage in the striatum evolving to an overt neuronal damage of dopaminergic neurons in the substantia nigra. We tested if A2AR antagonists are equally effective in controlling these two degenerative processes. We used a slow intracerebroventricular infusion of the toxin MPP+ in male rats for 15 days, which caused an initial loss of synaptic markers in the striatum within 10 days, followed by a neuronal loss in the substantia nigra within 30 days. Interestingly, the initial loss of striatal nerve terminals involved a loss of both dopaminergic and glutamatergic synaptic markers, while GABAergic markers were preserved. The daily administration of the A2AR antagonist SCH58261 (0.1 mg/kg, i.p.) in the first 10 days after MPP+ infusion markedly attenuated both the initial loss of striatal synaptic markers and the subsequent loss of nigra dopaminergic neurons. Strikingly, the administration of SCH58261 (0.1 mg/kg, i.p. for 10 days) starting 20 days after MPP+ infusion was less efficacious to attenuate the loss of nigra dopaminergic neurons. This prominent A2AR-mediated control of synaptotoxicity was directly confirmed by showing that the MPTP-induced dysfunction (MTT assay) and damage (lactate dehydrogenase release assay) of striatal synaptosomes were prevented by 50 nM SCH58261. This suggests that A2AR antagonists may be more effective to counteract the onset rather than the evolution of PD pathology.

Whole brain pattern of iron accumulation in REM sleep behavior disorder.

Isolated REM sleep behavior disorder (iRBD) is an early stage of synucleinopathy with most patients progressing to Parkinson's disease (PD) or related conditions. Quantitative susceptibility mapping (QSM) in PD has identified pathological iron accumulation in the substantia nigra (SN) and variably also in basal ganglia and cortex. Analyzing whole-brain QSM across iRBD, PD, and healthy controls (HC) may help to ascertain the extent of neurodegeneration in prodromal synucleinopathy. 70 de novo PD patients, 70 iRBD patients, and 60 HCs underwent 3 T MRI. T1 and susceptibility-weighted images were acquired and processed to space standardized QSM. Voxel-based analyses of grey matter magnetic susceptibility differences comparing all groups were performed on the whole brain and upper brainstem levels with the statistical threshold set at family-wise error-corrected p-values <.05. Whole-brain analysis showed increased susceptibility in the bilateral fronto-parietal cortex of iRBD patients compared to both PD and HC. This was not associated with cortical thinning according to the cortical thickness analysis. Compared to iRBD, PD patients had increased susceptibility in the left amygdala and hippocampal region. Upper brainstem analysis revealed increased susceptibility within the bilateral SN for both PD and iRBD compared to HC; changes were located predominantly in nigrosome 1 in the former and nigrosome 2 in the latter group. In the iRBD group, abnormal dopamine transporter SPECT was associated with increased susceptibility in nigrosome 1. iRBD patients display greater fronto-parietal cortex involvement than incidental early-stage PD cohort indicating more widespread subclinical neuropathology. Dopaminergic degeneration in the substantia nigra is paralleled by susceptibility increase, mainly in nigrosome 1.

Mitochondrial complex I deficiency stratifies idiopathic Parkinson's disease.

Idiopathic Parkinson's disease (iPD) is believed to have a heterogeneous pathophysiology, but molecular disease subtypes have not been identified. Here, we show that iPD can be stratified according to the severity of neuronal respiratory complex I (CI) deficiency, and identify two emerging disease subtypes with distinct molecular and clinical profiles. The CI deficient (CI-PD) subtype accounts for approximately a fourth of all cases, and is characterized by anatomically widespread neuronal CI deficiency, a distinct cell type-specific gene expression profile, increased load of neuronal mtDNA deletions, and a predilection for non-tremor dominant motor phenotypes. In contrast, the non-CI deficient (nCI-PD) subtype exhibits no evidence of mitochondrial impairment outside the dopaminergic substantia nigra and has a predilection for a tremor dominant phenotype. These findings constitute a step towards resolving the biological heterogeneity of iPD with implications for both mechanistic understanding and treatment strategies.

GGC expansions in NOTCH2NLC contribute to Parkinson disease and dopaminergic neuron degeneration.

BACKGROUND AND PURPOSE: The role of GGC repeat expansions within NOTCH2NLC in Parkinson's disease (PD) and the substantia nigra (SN) dopaminergic neuron remains unclear. Here, we profile the NOTCH2NLC GGC repeat expansions in a large cohort of patients with PD. We also investigate the role of GGC repeat expansions within NOTCH2NLC in the dopaminergic neurodegeneration of SN. METHODS: A total of 2,522 patients diagnosed with PD and 1,085 health controls were analyzed for the repeat expansions of NOTCH2NLC by repeat-primed PCR and GC-rich PCR assay. Furthermore, the effects of GGC repeat expansions in NOTCH2NLC on dopaminergic neurons were investigated by using recombinant adeno-associated virus (AAV)-mediated overexpression of NOTCH2NLC with 98 GGC repeats in the SN of mice by stereotactic injection. RESULTS: Four PD pedigrees (4/333, 1.2%) and three sporadic PD patients (3/2189, 0.14%) were identified with pathogenic GGC repeat expansions (larger than 60 GGC repeats) in the NOTCH2NLC gene, while eight PD patients and one healthy control were identified with intermediate GGC repeat expansions ranging from 41 to 60 repeats. No significant difference was observed in the distribution of intermediate NOTCH2NLC GGC repeat expansions between PD cases and controls (Fisher's exact test p-value = 0.29). Skin biopsy showed P62-positive intranuclear NOTCH2NLC-polyGlycine (polyG) inclusions in the skin nerve fibers of patient. Expanded GGC repeats in NOTCH2NLC produced widespread intranuclear and perinuclear polyG inclusions, which led to a severe loss of dopaminergic neurons in the SN. Consistently, polyG inclusions were presented in the SN of EIIa-NOTCH2NLC-(GGC)98 transgenic mice and also led to dopaminergic neuron loss in the SN. CONCLUSIONS: Overall, our findings provide strong evidence that GGC repeat expansions within NOTCH2NLC contribute to the pathogenesis of PD and cause degeneration of nigral dopaminergic neurons.

Cell senescence induced by toxic interaction between α-synuclein and iron precedes nigral dopaminergic neuron loss in a mouse model of Parkinson's disease.

Cell senescence has been implicated in the pathology of Parkinson's disease (PD). Both abnormal α-synuclein aggregation and iron deposition are suggested to be the triggers, facilitators, and aggravators during the development of PD. In this study, we investigated the involvement of α-synuclein and iron in the process of cell senescence in a mouse model of PD. In order to overexpress α-syn-A53T in the substantia nigra pars compacta (SNpc), human α-syn-A53T was microinjected into both sides of the SNpc in mice. We found that overexpression of α-syn-A53T for one week induced significant pro-inflammatory senescence-associated secretory phenotype (SASP), increased cell senescence-related proteins (ß-gal, p16, p21, H2A.X and γ-H2A.X), mitochondrial dysfunction accompanied by dysregulation of iron-related proteins (L-ferritin, H-ferritin, DMT1, IRP1 and IRP2) in the SNpc. In contrast, significant loss of nigral dopaminergic neurons and motor dysfunction were only observed after overexpression of α-syn-A53T for 4 weeks. In PC12 cells stably overexpressing α-syn-A53T, iron overload (ferric ammonium citrate, FAC, 100 µM) not only increased the level of reactive oxygen species (ROS), p16 and p21, but also exacerbated the processes of oxidative stress and cell senescence signalling induced by α-syn-A53T overexpression. Interestingly, reducing the iron level with deferoxamine (DFO) or knockdown of transferrin receptor 1 (TfR1) significantly improved both the phenotypes and dysregulated proteins of cell senescence induced by α-syn-A53T overexpression. All these evidence highlights the toxic interaction between iron and α-synuclein inducing cell senescence, which precedes nigral dopaminergic neuronal loss in PD. Further investigation on cell senescence may yield new therapeutic agents for the prevention or treatment of PD.

Non-invasive systemic viral delivery of human alpha-synuclein mimics selective and progressive neuropathology of Parkinson's disease in rodent brains.

BACKGROUND: Alpha-synuclein (α-syn) aggregation into proteinaceous intraneuronal inclusions, called Lewy bodies (LBs), is the neuropathological hallmark of Parkinson's disease (PD) and related synucleinopathies. However, the exact role of α-syn inclusions in PD pathogenesis remains elusive. This lack of knowledge is mainly due to the absence of optimal α-syn-based animal models that recapitulate the different stages of neurodegeneration. METHODS: Here we describe a novel approach for a systemic delivery of viral particles carrying human α-syn allowing for a large-scale overexpression of this protein in the mouse brain. This approach is based on the use of a new generation of adeno-associated virus (AAV), AAV-PHP.eB, with an increased capacity to cross the blood-brain barrier, thus offering a viable tool for a non-invasive and large-scale gene delivery in the central nervous system. RESULTS: Using this model, we report that widespread overexpression of human α-syn induced selective degeneration of dopaminergic (DA) neurons, an exacerbated neuroinflammatory response in the substantia nigra and a progressive manifestation of PD-like motor impairments. Interestingly, biochemical analysis revealed the presence of insoluble α-syn oligomers in the midbrain. Together, our data demonstrate that a single non-invasive systemic delivery of viral particles overexpressing α-syn prompted selective and progressive neuropathology resembling the early stages of PD. CONCLUSIONS: Our new in vivo model represents a valuable tool to study the role of α-syn in PD pathogenesis and in the selective vulnerability of nigral DA neurons; and offers the opportunity to test new strategies targeting α-syn toxicity for the development of disease-modifying therapies for PD and related disorders.

Pathological mechanisms of neuroimmune response and multitarget disease-modifying therapies of mesenchymal stem cells in Parkinson's disease.

Parkinson's disease (PD) is a neurodegenerative disease characterized by the degeneration of dopaminergic neurons in the substantia nigra (SN); the etiology and pathological mechanism of the disease are still unclear. Recent studies have shown that the activation of a neuroimmune response plays a key role in the development of PD. Alpha-synuclein (α-Syn), the primary pathological marker of PD, can gather in the SN and trigger a neuroinflammatory response by activating microglia which can further activate the dopaminergic neuron's neuroimmune response mediated by reactive T cells through antigen presentation. It has been shown that adaptive immunity and antigen presentation processes are involved in the process of PD and further research on the neuroimmune response mechanism may open new methods for its prevention and therapy. While current therapeutic regimens are still focused on controlling clinical symptoms, applications such as immunoregulatory strategies can delay the symptoms and the process of neurodegeneration. In this review, we summarized the progression of the neuroimmune response in PD based on recent studies and focused on the use of mesenchymal stem cell (MSC) therapy and challenges as a strategy of disease-modifying therapy with multiple targets.

The Relationship between Iron and LRRK2 in a 6-OHDA-Induced Parkinson's Disease Model.

The pathogenesis of Parkinson's disease (PD) is very complex and still needs further exploration. Leucine-rich repeat kinase 2 (LRRK2) is associated with familial PD in mutant forms and sporadic PD in the wild-type form. Abnormal iron accumulation is found in the substantia nigra of PD patients, but its exact effects are not very clear. Here, we show that iron dextran exacerbates the neurological deficit and loss of dopaminergic neurons in 6-OHDA lesioned rats. 6-OHDA and ferric ammonium citrate (FAC) significantly increase the activity of LRRK2 as reflected by the phosphorylation of LRRK2, at S935 and S1292 sites. 6-OHDA-induced LRRK2 phosphorylation is attenuated by the iron chelator deferoxamine, especially at the S1292 site. 6-OHDA and FAC markedly induce the expression of pro-apoptotic molecules and the production of ROS by activating LRRK2. Furthermore, G2019S-LRRK2 with high kinase activity showed the strongest absorptive capacity for ferrous iron and the highest intracellular iron content among WT-LRRK2, G2019S-LRRK2, and kinase-inactive D2017A-LRRK2 groups. Taken together, our results demonstrate that iron promotes the activation of LRRK2, and active LRRK2 accelerates ferrous iron uptake, suggesting that there exists an interplay between iron and LRRK2 in dopaminergic neurons, providing a new perspective to uncover the underlying mechanisms of PD occurrence.

Association Between Decreased Srpk3 Expression and Increased Substantia Nigra Alpha-Synuclein Level in an MPTP-Induced Parkinson's Disease Mouse Model.

Parkinson's disease (PD) is the second most common neurodegenerative disorder and is caused by the loss of dopaminergic neurons in the substantia nigra (SN). However, the reason for the death of dopaminergic neurons remains unclear. An increase in α-synuclein (α-syn) expression is an important factor in the pathogenesis of PD. In the current study, we investigated the association between serine/arginine-rich protein-specific kinase 3 (Srpk3) and PD in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model and in SH-SY5Y cells treated with 1-methyl-4-phenylpyridinium (MPP+). Srpk3 expression was significantly downregulated, while tyrosine hydroxylase (TH) expression decreased and α-syn expression increased after 4 weeks of MPTP treatment. Dopaminergic cell reduction and α-syn expression increase were demonstrated by Srpk3 expression inhibition by siRNA in SH-SY5Y cells. Moreover, a decrease in Srpk3 expression upon siRNA treatment promoted dopaminergic cell reduction and α-syn expression increase in SH-SY5Y cells treated with MPP+ . These results suggested that Srpk3 expression decrease due to Srpk3 siRNA caused both TH level decrease and α-syn expression increase. This raises new possibilities for studying how Srpk3 controls dopaminergic cells and α-syn expression, which may be related to PD pathogenesis. Our results provide an avenue for understanding the role of Srpk3 in dopaminergic cell loss and α-syn upregulation in SN. Furthermore, this study supports a therapeutic possibility for PD in that the maintenance of Srpk3 expression inhibits dopaminergic cell reduction.

S-adenosyl methionine improves motor co-ordination with reduced oxidative stress, dopaminergic neuronal loss, and DNA methylation in the brain striatum of 6-hydroxydopamine-induced neurodegeneration in rats.

PURPOSE: Parkinson's disease (PD) is the most common age-related neurodegenerative disease worldwide. S-adenosyl methionine (SAMe), a methyl donor that plays an important role in DNA methylation, could replenish the cellular antioxidant glutathione (GSH). Herein, we investigated the neuroprotective effects of SAMe in 6-hydroxydopamine (6-OHDA) rat models of PD and elucidated the underlying mechanism. METHODS: PD model rats were developed by injecting 6-OHDA stereotaxically into the striatum. In Phase 1 of the study, we performed the neurobehavioral tests, GSH assay, and histopathology to evaluate the neuroprotective effects of SAMe. The animals were treated with SAMe (150 or 300 mg/kg body weight) orally for 28 days. The positive control group received selegiline (5 mg/kg), whereas the disease control group received normal saline. In Phase 2, we evaluated the striatal dopamine levels and performed DNA methylation assay to uncover the mechanism of action of SAMe. In this phase, a higher dose of SAMe (300 mg/kg) was used. RESULTS: SAMe (300 mg/kg) treatment for 4 weeks significantly attenuated the abnormal circling behavior in PD rats (p < 0.05). Moreover, SAMe at both doses (150 and 300 mg/kg) enhanced the performance of PD rats in the open field test and stepping test (p < 0.05). SAMe treatment significantly increased the GSH levels, and at high dose, SAMe restricted neuronal loss in the striatum of PD-model rats (p < 0.05). Moreover, SAMe treatment led to a significant recovery in the dopamine levels and improved the DNA methylation status in the dopaminergic neurons (p < 0.05) of PD model rats. CONCLUSION: SAMe exhibits antioxidant activity and DNA methylation modulating effects in 6-OHDA model PD rats. Moreover, SAMe prevents neuronal loss in PD rats suggesting that SAMe has therapeutic potential in preventing PD development. The neuroprotective potential of SAMe is greater at high doses.

Relationship between Substantia Nigra Neuromelanin Imaging and Dual Alpha-Synuclein Labeling of Labial Minor in Salivary Glands in Isolated Rapid Eye Movement Sleep Behavior Disorder and Parkinson's Disease.

We investigated the presence of misfolded alpha-Synuclein (α-Syn) in minor salivary gland biopsies in relation to substantia nigra pars compacta (SNc) damage measured using magnetic resonance imaging in patients with isolated rapid eye movement sleep behavior disorder (iRBD) and Parkinson's disease (PD) as compared to healthy controls. Sixty-one participants (27 PD, 16 iRBD, and 18 controls) underwent a minor salivary gland biopsy and were scanned using a 3 Tesla MRI. Deposits of α-Syn were found in 15 (55.6%) PD, 7 (43.8%) iRBD, and 7 (38.9%) controls using the anti-aggregated α-Syn clone 5G4 antibody and in 4 (14.8%) PD, 3 (18.8%) iRBD and no control using the purified mouse anti-α-Syn clone 42 antibody. The SNc damages obtained using neuromelanin-sensitive imaging did not differ between the participants with versus without α-Syn deposits (irrespective of the antibodies and the disease group). Our study indicated that the α-Syn detection in minor salivary gland biopsies lacks sensitivity and specificity and does not correlate with the SNc damage, suggesting that it cannot be used as a predictive or effective biomarker for PD.

Beneficial effect of transient desflurane inhalation on relieving inflammation and reducing signaling induced by MPTP in mice.

OBJECTIVE: To determine if the beneficial effects of transient desflurane application mitigates inflammation and decrease associated signaling induced by 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP) in mice. METHODS: Mice were induced to develop Parkinson's disease (PD) by intraperitoneal injection with MPTP for 20 consecutive days, and validated mice were randomly allocated to four groups. Collected samples from euthanized mice were designated for the following analyses: 1) immunohistochemical staining for positive dopaminergic neurons in the substantia nigra and striatum, 2) immunofluorescence staining for ionized calcium binding adaptor molecule-1 (Iba1) and glial fibrillary acid protein (GFAP), and 3) western blotting for p38, p-p38, toll-like receptor 4, and tumor necrosis factor (TNF)-α. RESULTS: The inhalation of desflurane for 1 hour ameliorated locomotory dysfunctions of PD mice by recovering the loss of Iba1- and GFAP-positive dopaminergic neurons, deactivating microglial cells and astrocytes, and decreasing the amounts of inflammatory cytokines (TNF-α). CONCLUSIONS: These findings suggest that transient desflurane inhalation may provide some benefits for PD through ameliorating inflammation and enhancing locomotor activity.

Effects of hCG on DA neuronal death of Parkinson's disease.

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, with the incidence in men being about twice as compared to women. Gender differences may provide clues for finding key targets that mediate the death of dopaminergic (DA) neurons in PD. Luteinizing hormone (LH), analog of human chorionic gonadotropin (hCG), and their receptor, luteinizing hormone/choriogonadotropin receptor (LHCGR), are associated with the pathogenesis of PD. Movement-related symptoms are partially improved by hCG in PD patients. However, the relationship between hCG and PD, as well as its roles in mediating DA neuronal death, has not been elucidated. In this study, we investigated the potential of hCG as a treatment during PD progression. After establishment of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse models, we found that hCG restored the decrease of LHCGR activity caused by down-regulation of LH in the substantia nigra. Furthermore, the reduction of LHCGR activity led to DA neuronal death through knocking down the LHCGR in DA neurons by AAV-mTH-shRNA. Treatment with hCG alleviated the DA neuronal death induced by MPTP. Finally, hCG exerted neuroprotective effects by inhibiting the activation of glycogen synthase kinase 3 beta (GSK3ß) in our MPTP-induced PD mouse and MPP+-treated SH-SY5Y cell models. Together, these results demonstrate that hCG exerts neuroprotective effects for PD through LHCGR, and the inhibition of GSK3ß activation is involved in this protective effect, suggesting that hCG can be taken as a potential therapeutic for the treatment of PD.

Inflammatory Animal Models of Parkinson's Disease.

Accumulating evidence suggests that microglia and peripheral immune cells may play determinant roles in the pathogenesis of Parkinson's disease (PD). Consequently, there is a need to take advantage of immune-related models of PD to study the potential contribution of microglia and peripheral immune cells to the degeneration of the nigrostriatal system and help develop potential therapies for PD. In this review, we have summarised the main PD immune models. From a historical perspective, we highlight first the main features of intranigral injections of different pro-inflammogens, including lipopolysaccharide (LPS), thrombin, neuromelanin, etc. The use of adenoviral vectors to promote microglia-specific overexpression of different molecules in the ventral mesencephalon, including α-synuclein, IL-1ß, and TNF, are also presented and briefly discussed. Finally, we summarise different models associated with peripheral inflammation whose contribution to the pathogenesis of neurodegenerative diseases is now an outstanding question. Illustrative examples included systemic LPS administration and dextran sulfate sodium-induced colitis in rodents.

Dynamics of Nigral Iron Accumulation in Parkinson's Disease: From Diagnosis to Late Stage.

BACKGROUND: Higher nigral iron has been reported in Parkinson's disease (PD). OBJECTIVE: The aim is to understand the dynamics of nigral iron accumulation in PD and its association with drug treatment. METHODS: Susceptibility magnetic resonance imaging data were obtained from 79 controls and 18 drug-naive (PDDN ) and 87 drug-treated (PDDT ) PD patients. Regional brain iron in basal ganglia and cerebellar structures was estimated using quantitative susceptibility mapping. Nigral iron was compared between PDDN and PDDT subgroups defined by disease duration (early [PDE, <2 years], middle [PDM, 2-6 years], and later [PDL, >6 years]). Associations with both disease duration and types of antiparkinson drugs were explored using regression analysis. RESULTS: Compared to controls, PDDN had lower iron in the substantia nigra (P = 0.018), caudate nucleus (P = 0.038), and globus pallidus (P = 0.01) but not in the putamen or red nucleus. In contrast, PDDT had higher iron in the nigra (P < 0.001) but not in other regions, compared to either controls or PDDN . Iron in the nigra increased with disease duration (PDE > PDDN [P = 0.001], PDM > PDE [P = 0.045]) except for PDM versus PDL (P = 0.226). Levodopa usage was associated with higher (P = 0.013) nigral iron, whereas lower nigral iron was correlated with selegiline usage (P = 0.030). CONCLUSION: Nigral iron is lower before the start of dopaminergic medication and then increases throughout the disease until it plateaus at late stages, suggesting increased iron may not be an etiological factor. Interestingly, PD medications may have differential associations with iron accumulation that need further investigation. © 2022 International Parkinson and Movement Disorder Society.

GM1 ganglioside modifies microglial and neuroinflammatory responses to α-synuclein in the rat AAV-A53T α-synuclein model of Parkinson's disease.

Among the pathological events associated with the dopaminergic neurodegeneration characteristic of Parkinson's disease (PD) are the accumulation of toxic forms of α-synuclein and microglial activation associated with neuroinflammation. Although numerous other processes may participate in the pathogenesis of PD, the two factors mentioned above may play critical roles in the initiation and progression of dopamine neuron degeneration in PD. In this study, we employed a slowly progressing model of PD using adeno-associated virus-mediated expression of human A53T α-synuclein into the substantia nigra on one side of the brain and examined the microglial response in the striatum on the injected side compared to the non-injected (control) side. We further examined the extent to which administration of the neuroprotective ganglioside GM1 influenced α-synuclein-induced glial responses. Changes in a number of microglial morphological measures (i.e., process length, number of endpoints, fractal dimension, lacunarity, density, and cell perimeter) were indicative of the presence of activated microglial and an inflammatory response on the injected side of the brain, compared to the control side. In GM1-treated animals, no significant differences in microglial morphology were observed between the injected and control striata. Follow-up studies showed that mRNA expression for several inflammation-related genes was increased on the A53T α-synuclein injected side vs. the non-injected side in saline-treated animals and that such changes were not observed in GM1-treated animals. These data show that inhibition of microglial activation and potentially damaging neuroinflammation by GM1 ganglioside administration may be among the many factors that contribute to the neuroprotective effects of GM1 in this model and possibly in human PD.

[Morphochemical study of alpha-synuclein, iron and iron-containing proteins in the substantia nigra of the brain in Parkinson's disease]. / Morfokhimicheskoe issledovanie al'fa-sinukleina, zheleza i zhelezosoderzhashchikh belkov v chernom veshchestve golovnogo mozga pri bolezni Parkinsona.

OBJECTIVE: To study, using a complex morphochemical approach, the localization of alpha-synuclein, iron compounds and iron-containing proteins in the structures of the substantia nigra of the brain in Parkinson's disease (PD). MATERIAL AND METHODS: Histochemistry and immunohistochemistry methods have been used to study the localization of pathological alpha-synuclein (α-Syn-p129), iron compounds and iron-containing proteins - transferrin receptor and ferritin in neurons and neuroglia in the substantia nigra of the brain of deceased PD patients and persons with no neurological symptoms detected during life (control). RESULTS: In the substantia nigra of PD patients, in comparison with the control, a stable accumulation of pathological alpha-synuclein (α-Syn-p129) in the bodies and processes of neurons was found, and in the neuroglia and neuropil - the accumulation of iron (II) and ferritin heavy chain, the reaction of microglia to protein CD68 was moderately elevated. The transmembrane protein CD71 was detected equally in the brains of PD patients and in controls. CONCLUSION: Synaptic protein alpha-synuclein in PD turns into a pathological metabolite that accumulates in the structures of substantia nigra, and probably disrupts the conduction of nervous excitation. Excessive accumulation of the ferritin heavy chain in neuroglia can increase the concentration of reactive forms of iron and increase neurotoxicity. The uniform distribution of the transmembrane glycoprotein CD71 in the of substantia nigra structures both in the control and in PD patients indicates the preservation of non-heme iron transport during the neurodegenerative process.

PTEN-Induced Putative Kinase 1 Dysfunction Accelerates Synucleinopathy.

BACKGROUND: Mutations in PTEN-induced putative kinase 1 (PINK1) cause autosomal recessive Parkinson's disease (PD) and contribute to the risk of sporadic PD. However, the relationship between PD-related PINK1 mutations and alpha-synuclein (α-syn) aggregation-a main pathological component of PD-remains unexplored. OBJECTIVE: To investigate whether α-syn pathology is exacerbated in the absence of PINK1 after α-syn preformed fibril (PFF) injection in a PD mouse model and its effects on neurodegeneration. METHODS: In this study, 10-week-old Pink1 knockout (KO) and wildtype (WT) mice received stereotaxic unilateral striatal injection of recombinant mouse α-syn PFF. Then, α-syn pathology progression, inflammatory responses, and neurodegeneration were analyzed via immunohistochemistry, western blot analysis, and behavioral testing. RESULTS: After PFF injection, the total α-syn levels significantly increased, and pathological α-syn was markedly aggregated in Pink1 KO mice compared with Pink1 WT mice. Then, earlier and more severe neuronal loss and motor deficits occurred. Moreover, compared with WT mice, Pink1 KO mice had evident microglial/astrocytic immunoreactivity and prolonged astrocytic activation, and a higher rate of protein phosphatase 2A phosphorylation, which might explain the greater α-syn aggravation and neuronal death. CONCLUSION: The loss of Pink1 function accelerated α-syn aggregation, accumulation and glial activation, thereby leading to early and significant neurodegeneration and behavioral impairment in the PD mouse model. Therefore, our findings support the notion that PINK1 dysfunction increases the risk of synucleinopathy.

Interleukin-6 triggers toxic neuronal iron sequestration in response to pathological α-synuclein.

α-synuclein (α-syn) aggregation and accumulation drive neurodegeneration in Parkinson's disease (PD). The substantia nigra of patients with PD contains excess iron, yet the underlying mechanism accounting for this iron accumulation is unclear. Here, we show that misfolded α-syn activates microglia, which release interleukin 6 (IL-6). IL-6, via its trans-signaling pathway, induces changes in the neuronal iron transcriptome that promote ferrous iron uptake and decrease cellular iron export via a pathway we term the cellular iron sequestration response, or CISR. The brains of patients with PD exhibit molecular signatures of the IL-6-mediated CISR. Genetic deletion of IL-6, or treatment with the iron chelator deferiprone, reduces pathological α-syn toxicity in a mouse model of sporadic PD. These data suggest that IL-6-induced CISR leads to toxic neuronal iron accumulation, contributing to synuclein-induced neurodegeneration.

Time-Course of Alterations in the Endocannabinoid System after Viral-Mediated Overexpression of α-Synuclein in the Rat Brain.

Since the discovery of α-synuclein as the major component in Lewy bodies, research into this protein in the context of Parkinson's disease pathology has been exponential. Cannabinoids are being investigated as potential therapies for Parkinson's disease from numerous aspects, but still little is known about the links between the cannabinoid system and the pathogenic α-synuclein protein; understanding these links will be necessary if cannabinoid therapies are to reach the clinic in the future. Therefore, the aim of this study was to investigate the time-course of alterations in components of the endocannabinoid system after viral-mediated α-synuclein overexpression in the rat brain. Rats were given unilateral intranigral injections of AAV-GFP or AAV-α-synuclein and sacrificed 4, 8 and 12 weeks later for qRT-PCR and liquid chromatography-mass spectrometry analyses of the endocannabinoid system, in addition to histological visualization of α-synuclein expression along the nigrostriatal pathway. As anticipated, intranigral delivery of AAV-α-synuclein induced widespread overexpression of human α-synuclein in the nigrostriatal pathway, both at the mRNA level and the protein level. However, despite this profound α-synuclein overexpression, we detected no differences in CB1 or CB2 receptor expression in the nigrostriatal pathway; however, interestingly, there was a reduction in the expression of neuroinflammatory markers. Furthermore, there was a reduction in the levels of the endocannabinoid 2-AG and the related lipid immune mediator OEA at week 12 post-surgery, indicating that α-synuclein overexpression triggers dysregulation of the endocannabinoid system. Although this research does show that the endocannabinoid system is impacted by α-synuclein, further research is necessary to more comprehensively understand the link between the cannabinoid system and the α-synuclein aspect of Parkinson's disease pathology in order for cannabinoid-based therapies to be feasible for the treatment of this disease in the coming years.