Engineering synucleinopathy‐resistant human dopaminergic neurons by CRISPR‐mediated deletion of the SNCA gene

An emerging treatment for Parkinson's disease (PD) is cell replacement therapy. Authentic midbrain dopaminergic (mDA) neuronal precursors can be differentiated from human embryonic stem cells (hESCs) and human induced pluripotent stem cells (iPSCs). These laboratory‐generated mDA cells have been demonstrated to mature into functional dopaminergic neurons upon transplantation into preclinical models of PD. However, clinical trials with human fetal mesenchephalic cells have shown that cell replacement grafts in PD are susceptible to Lewy body formation suggesting host‐to‐graft transfer of α‐synuclein pathology. Here, we have used CRISPR/Cas9n technology to delete the endogenous SNCA gene, encoding for α‐synuclein, in a clinical‐grade hESC line to generate SNCA^+/? and SNCA^?/? cell lines. These hESC lines were first differentiated into mDA neurons, and then challenged with recombinant α‐synuclein preformed fibrils (PFFs) to seed the formation for Lewy‐like pathology as measured by phosphorylation of serine‐129 of α‐synuclein (pS129‐αSyn). Wild‐type neurons were fully susceptible to the formation of protein aggregates positive for pS129‐αSyn, while SNCA^+/? and SNCA^?/? neurons exhibited significant resistance to the formation of this pathological mark. This work demonstrates that reducing or completely removing SNCA alleles by CRISPR/Cas9n‐mediated gene editing confers a measure of resistance to Lewy pathology.     

THIS ARTICLE HAS BEEN RETRACTED: Pathological biochemistry of α‐synucleinopathy

Lewy bodies (LBs) are hallmark lesions in the brains of patients with Parkinson's disease (PD) and dementia with Lewy bodies (DLB). We raised a monoclonal antibody LB509 against purified LBs from the brains of patients with DLB that strongly immuolabled LBs, and found that α‐synuclein is one of the major components of LBs. Thus, the deposition of α‐synuclein, an abundant presynaptic brain protein, as fibrillary aggregates in affected neurons or glial cells, was highlighted as a hallmark lesion of a subset of neurodegenerative disorders, including PD, DLB and multiple system atrophy collectively referred to as synucleinopathies. Importantly, the identification of missense mutations in and multiplication of α‐synuclein gene in some pedigrees of familial PD has strongly implicated α‐synuclein in the pathogenesis of PD and other synucleinopathies. We then examined the specific post‐translational modifications that characterize and underlie the aggregation of α‐synuclein in synucleinopathy brains by mass spectrometry and using a specific antibody, and found that serine 129 of α‐synuclein deposited in synucleinopathy lesions is selectively and extensively phosphorylated. Furthermore we generated transgenic C. elegans overexpressing α‐synuclein in neurons, and found that overexpression of familial PD‐linked mutant form of α‐synuclein impairs functions of dopamine neurons. These findings collectively underscore the importance of deposition of α‐synuclein as well as its phosphorylation in the pathogenesis of α‐synucleinopathies.     

Stimulation of synaptoneurosome glutamate release by monomeric and fibrillated α‐synuclein

The α‐synuclein protein exists in vivo in a variety of covalently modified and aggregated forms associated with Parkinson's disease (PD) pathology. However, the specific proteoform structures involved with neuropathological disease mechanisms are not clearly defined. Since α‐synuclein plays a role in presynaptic neurotransmitter release, an in vitro enzyme‐based assay was developed to measure glutamate release from mouse forebrain synaptoneurosomes (SNs) enriched in synaptic endings. Glutamate measurements utilizing SNs from various mouse genotypes (WT, over‐expressers, knock‐outs) suggested a concentration dependence of α‐synuclein on calcium/depolarization‐dependent presynaptic glutamate release from forebrain terminals. In vitro reconstitution experiments with recombinant human α‐synuclein proteoforms including monomers and aggregated forms (fibrils, oligomers) produced further evidence of this functional impact. Notably, brief exogenous applications of fibrillated forms of α‐synuclein enhanced SN glutamate release but monomeric forms did not, suggesting preferential membrane penetration and toxicity by the aggregated forms. However, when applied to brain tissue sections just prior to homogenization, both monomeric and fibrillated forms stimulated glutamate release. Immuno‐gold and transmission electron microscopy (TEM) detected exogenous fibrillated α‐synuclein associated with numerous SN membranous structures including synaptic terminals. Western blots and immuno‐gold TEM were consistent with SN internalization of α‐synuclein. Additional studies revealed no evidence of gross disruption of SN membrane integrity or glutamate transporter function by exogenous α‐synuclein. Overall excitotoxicity, due to enhanced glutamate release in the face of either overexpressed monomeric α‐synuclein or extrasynaptic exposure to fibrillated α‐synuclein, should be considered as a potential neuropathological pathway during the progression of PD and other synucleinopathies. © 2017 Wiley Periodicals, Inc.     

The usual suspects,dopamine and alpha‐synuclein,conspire to cause neurodegeneration

Parkinson's disease (PD) is primarily a movement disorder driven by the loss of dopamine‐producing neurons in the substantia nigra (SN). Early identification of the oxidative properties of dopamine implicated it as a potential source of oxidative stress in PD, yet few studies have investigated dopamine neurotoxicity in vivo. The discovery of PD‐causing mutations in α‐synuclein and the presence of aggregated α‐synuclein in the hallmark Lewy body pathology of PD revealed another important player. Despite extensive efforts, the precise role of α‐synuclein aggregation in neurodegeneration remains unclear. We recently manipulated both dopamine levels and α‐synuclein expression in aged mice and found that only the combination of these 2 factors caused progressive neurodegeneration of the SN and an associated motor deficit. Dopamine modified α‐synuclein aggregation in the SN, resulting in greater abundance of α‐synuclein oligomers and unique dopamine‐induced oligomeric conformations. Furthermore, disruption of the dopamine‐α‐synuclein interaction rescued dopaminergic neurons from degeneration in transgenic Caenorhabditis elegans models. In this Perspective, we discuss these findings in the context of known α‐synuclein and dopamine biology, review the evidence for α‐synuclein oligomer toxicity and potential mechanisms, and discuss therapeutic implications. © 2019 International Parkinson and Movement Disorder Society     

Alpha‐synuclein polymorphisms are associated with Parkinson's disease in a Saskatchewan population

Alpha‐synuclein gene (SNCA) mutations cause familial Parkinsonism but the role of SNCA variability in idiopathic Parkinson's disease (PD) remains incompletely defined. We report a study of SNCA genetic variation in 452 idiopathic PD cases and 245 controls. SNCA copy number mutations were not associated with early‐onset disease in this population. The minor allele “G” at rs356165 was associated with increased odds of PD (P = 0.013) and genetic variation in D4S3481 (Rep1) was associated with age of disease onset (P = 0.007). There was a trend toward association between variation at rs2583988 and rapid PD progression. © 2009 Movement Disorder Society     

Immunohistochemical localization of spatacsin in α‐synucleinopathies

Spatacsin (SPG11) is a major mutated gene in autosomal recessive spastic paraplegia with thin corpus callosum (ARHSP‐TCC) and is responsible for juvenile Parkinsonism. To elucidate the role of spatacsin in the pathogenesis of α‐synucleinopathies, an immunohistochemical investigation was performed on the brain of patients with Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA) using anti‐spatacsin antibody. In PD, Lewy bodies (LBs) in the brain stem were positive for spatacsin. These LBs showed intense staining in their peripheral portions and occasionally in the central cores. Lewy neurites were also spatacsin‐positive. In DLB, cortical LBs were immunolabeled by spatacsin. In MSA, glial cytoplasmic inclusions (GCI) and a small fraction of neuronal cytoplasmic inclusions (NCI) were positive for spatacsin. The widespread accumulation of spatacsin observed in pathologic α‐synuclein‐containing inclusions suggests that spatacsin may be involved in the pathogenesis of α‐synucleinopathies.     

Selective coexpression of synaptic proteins, α‐synuclein,cysteine string protein‐α, synaptophysin,synaptotagmin‐1, and synaptobrevin‐2 in vesicular acetylcholine transporter‐immunoreactive axons in the guinea pig ileum

Parkinson's disease is a neurodegenerative disorder characterized by Lewy bodies and neurites composed mainly of the presynaptic protein α‐synuclein. Frequently, Lewy bodies and neurites are identified in the gut of Parkinson's disease patients and may underlie associated gastrointestinal dysfunctions. We recently reported selective expression of α‐synuclein in the axons of cholinergic neurons in the guinea pig and human distal gut; however, it is not clear whether α‐synuclein expression varies along the gut, nor how closely expression is associated with other synaptic proteins. We used multiple‐labeling immunohistochemistry to quantify which neurons in the guinea pig ileum expressed α‐synuclein, cysteine string protein‐α (CSPα), synaptophysin, synaptotagmin‐1, or synaptobrevin‐2 in their axons. Among the 10 neurochemically defined axonal populations, a significantly greater proportion of vesicular acetylcholine transporter‐immunoreactive (VAChT‐IR) varicosities (80% ± 1.7%, n = 4, P < 0.001) contained α‐synuclein immunoreactivity, and a significantly greater proportion of α‐synuclein‐IR axons also contained VAChT immunoreactivity (78% ± 1.3%, n = 4) compared with any of the other nine populations (P < 0.001). Among synaptophysin‐, synaptotagmin‐1‐, synaptobrevin‐2‐, and CSPα‐IR varicosities, 98% ± 0.7%, 96% ± 0.7%, 88% ± 1.6%, and 85% ± 2.9% (n = 4) contained α‐synuclein immunoreactivity, respectively. Among α‐synuclein‐IR varicosities, 96% ± 0.9%, 99% ± 0.6%, 83% ± 1.9%, and 87% ± 2.3% (n = 4) contained synaptophysin‐, synaptotagmin‐1‐, synaptobrevin‐2‐, and CSPα immunoreactivity, respectively. We report a close association between the expression of α‐synuclein and the expression of other synaptic proteins in cholinergic axons in the guinea pig ileum. Selective expression of α‐synuclein may relate to the neurotransmitter system utilized and predispose cholinergic enteric neurons to degeneration in Parkinson's disease. J. Comp. Neurol. 521:2523–2537, 2013. © 2013 Wiley Periodicals, Inc.     

The Lewy body in Parkinson's disease: Molecules implicated in the formation and degradation of α‐synuclein aggregates

The histological hallmark of Parkinson's disease (PD) is the presence of fibrillar aggregates called Lewy bodies (LBs). LB formation has been considered to be a marker for neuronal degeneration, because neuronal loss is found in the predilection sites for LBs. To date, more than 70 molecules have been identified in LBs, in which α‐synuclein is a major constituent of LB fibrils. α‐synuclein immunohistochemistry reveals that diffuse cytoplasmic staining develops into pale bodies via compaction, and that LBs arise from the peripheral portion of pale bodies. This α‐synuclein abnormality is found in 10% of pigmented neurons in the substantia nigra and more than 50% of those in the locus ceruleus in PD. Recent studies have suggested that oligomers and protofibrils of α‐synuclein are cytotoxic, and that LBs may represent a cytoprotective mechanism in PD.     

Increase of the plasma α‐synuclein levels in patients with multiple system atrophy

Multiple system atrophy, a sporadic neurodegenerative disease, is characterized by the presence of high numbers of glial cytoplasmic inclusions mainly formed by α‐synuclein protein, which is encoded by the SNCA gene. To date, however, few studies have investigated the plasma α‐synuclein levels in patients with multiple system atrophy. We studied plasma α‐synuclein concentrations by using an enzyme‐linked immunosorbent assay in 74 patients with multiple system atrophy and 90 healthy controls. The plasma α‐synuclein levels were significantly elevated in patients who had multiple system atrophy compared with the control group (P = 0.000). In a subgroup of 48 patients who had probable multiple system atrophy, there was a weakly negative correlation between plasma α‐synuclein levels and subscores on Unified Multiple System Atrophy Rating Scale item VI (r_s = ?0.307; P = 0.034). Plasma α‐synuclein levels were elevated in patients with multiple system atrophy, and these levels may be decreased with the development of disease. © 2013 International Parkinson and Movement Disorder Society.     

Unmyelinated axons are more vulnerable to degeneration than myelinated axons of the cardiac nerve in Parkinson's disease

S. Orimo, T. Uchihara, T. Kanazawa, Y. Itoh, K. Wakabayashi, A. Kakita and H. Takahashi (2011) Neuropathology and Applied Neurobiology 37, 791–802 Unmyelinated axons are more vulnerable to degeneration than myelinated axons of the cardiac nerve in Parkinson's disease Aims: We recently demonstrated accumulation of α‐synuclein aggregates of the cardiac sympathetic nerve in Parkinson's disease (PD) and a possible relationship between degeneration of the cardiac sympathetic nerve and α‐synuclein aggregates. The aim of this study is to determine whether there is a difference in the degenerative process between unmyelinated and myelinated axons of the cardiac nerve. Methods: We immunohistochemically examined cardiac tissues from four pathologically verified PD patients, nine patients with incidental Lewy body disease (ILBD) and five control subjects, using antibodies against neurofilament, myelin basic protein (MBP) and α‐synuclein. First, we counted the number of neurofilament‐immunoreactive axons not surrounded by MBP (unmyelinated axons) and those surrounded by MBP (myelinated axons). Next, we counted the number of unmyelinated and myelinated axons with α‐synuclein aggregates. Results: (i) The percentage of unmyelinated axons in PD (77.5 ± 9.14%) was significantly lower compared to that in control subjects (92.2 ± 2.40%). (ii) The ratio of unmyelinated axons with α‐synuclein aggregates to total axons with α‐synuclein aggregates in ILBD ranged from 94.4 to 100 (98.2 ± 2.18%). Among axons with α‐synuclein aggregates, unmyelinated axons were the overwhelming majority, comprising 98.2%. Conclusion: These findings suggest that in PD unmyelinated axons are more vulnerable to degeneration than myelinated axons of the cardiac nerve, because α‐synuclein aggregates accumulate much more abundantly in unmyelinated axons.     

Brain region‐dependent differential expression of alpha‐synuclein

α‐Synuclein, the major constituent of Lewy bodies (LBs), is normally expressed in presynapses and is involved in synaptic function. Abnormal intracellular aggregation of α‐synuclein is observed as LBs and Lewy neurites in neurodegenerative disorders, such as Parkinson's disease (PD) or dementia with Lewy bodies. Accumulated evidence suggests that abundant intracellular expression of α‐synuclein is one of the risk factors for pathological aggregation. Recently, we reported differential expression patterns of α‐synuclein between excitatory and inhibitory hippocampal neurons. Here we further investigated the precise expression profile in the adult mouse brain with special reference to vulnerable regions along the progression of idiopathic PD. The results show that α‐synuclein was highly expressed in the neuronal cell bodies of some early PD‐affected brain regions, such as the olfactory bulb, dorsal motor nucleus of the vagus, and substantia nigra pars compacta. Synaptic expression of α‐synuclein was mostly accompanied by expression of vesicular glutamate transporter‐1, an excitatory presynaptic marker. In contrast, expression of α‐synuclein in the GABAergic inhibitory synapses was different among brain regions. α‐Synuclein was clearly expressed in inhibitory synapses in the external plexiform layer of the olfactory bulb, globus pallidus, and substantia nigra pars reticulata, but not in the cerebral cortex, subthalamic nucleus, or thalamus. These results suggest that some neurons in early PD‐affected human brain regions express high levels of perikaryal α‐synuclein, as happens in the mouse brain. Additionally, synaptic profiles expressing α‐synuclein are different in various brain regions. J. Comp. Neurol. 524:1236–1258, 2016. © 2015 Wiley Periodicals, Inc.     

Cerebrospinal fluid lysosomal enzymes and alpha‐synuclein in Parkinson's disease

To assess the discriminating power of multiple cerebrospinal fluid (CSF) biomarkers for Parkinson's disease (PD), we measured several proteins playing an important role in the disease pathogenesis. The activities of β‐glucocerebrosidase and other lysosomal enzymes, together with total and oligomeric α‐synuclein, and total and phosphorylated tau, were thus assessed in CSF of 71 PD patients and compared to 45 neurological controls. Activities of β‐glucocerebrosidase, β‐mannosidase, β‐hexosaminidase, and β‐galactosidase were measured with established enzymatic assays, while α‐synuclein and tau biomarkers were evaluated with immunoassays. A subset of PD patients (n = 44) was also screened for mutations in the β‐glucocerebrosidase‐encoding gene (GBA1). In the PD group, β‐glucocerebrosidase activity was reduced (P < 0.05) and patients at earlier stages showed lower enzymatic activity (P < 0.05); conversely, β‐hexosaminidase activity was significantly increased (P < 0.05). Eight PD patients (18%) presented GBA1 sequence variations; 3 of them were heterozygous for the N370S mutation. Levels of total α‐synuclein were significantly reduced (P < 0.05) in PD, in contrast to increased levels of α‐synuclein oligomers, with a higher oligomeric/total α‐synuclein ratio in PD patients when compared with controls (P < 0.001). A combination of β‐glucocerebrosidase activity, oligomeric/total α‐synuclein ratio, and age gave the best performance in discriminating PD from neurological controls (sensitivity 82%; specificity 71%, area under the receiver operating characteristic curve = 0.87). These results demonstrate the possibility of detecting lysosomal dysfunction in CSF and further support the need to combine different biomarkers for improving the diagnostic accuracy of PD. © 2014 International Parkinson and Movement Disorder Society     

First appraisal of brain pathology owing to A30P mutant alpha‐synuclein

Familial Parkinson disease (PD) due to the A30P mutation in the SNCA gene encoding alpha‐synuclein is clinically associated with PD symptoms. In this first pathoanatomical study of the brain of an A30P mutation carrier, we observed neuronal loss in the substantia nigra, locus coeruleus, and dorsal motor vagal nucleus, as well as widespread occurrence of alpha‐synuclein immunopositive Lewy bodies, Lewy neurites, and glial aggregates. Alpha‐synuclein aggregates ultrastructurally resembled Lewy bodies, and biochemical analyses disclosed a significant load of insoluble alpha‐synuclein, indicating neuropathological similarities between A30P disease patients and idiopathic PD, with a more severe neuropathology in A30P carriers. ANN NEUROL 2010;67:684–689     

Cardiac sympathetic denervation correlates with clinical and pathologic stages of Parkinson's disease

Attention has been drawn to cardiac sympathetic denervation in Parkinson's disease (PD) based on clinical studies using [123I] metaiodobenzylguanidine scintigraphy; however, the histologic correlates and time course of cardiac sympathetic denervation are poorly understood. To address these issues, we used tyrosine hydroxylase (TH) immunohistochemistry to detect cardiac sympathetic nerve fibers in the epicardium of 4 normal controls, 11 cases with incidental Lewy bodies (iLBs), and 14 cases of PD. Cardiac sympathetic innervation was significantly less in PD than in normal controls and cases with iLBs (P < 0.05). There was also a decrease in TH‐immunoreactive fibers in iLB cases compared to normal controls (P < 0.01). TH‐immunoreactive fibers correlated with the PD stage (r = ?0.75, P < 0.001), as well as with Hoehn & Yahr clinical stage (r = ?0.61, P < 0.001), and disease duration (r = ?0.63, P < 0.001). Immunohistochemistry for α‐synuclein showed neurites in epicardium in PD and iLB cases, but not in normal controls. The density of α‐synuclein neurites correlated with Braak PD stage (r = 0.38, P < 0.05), Hoehn & Yahr clinical stage (r = 0.44, P < 0.05), and disease duration (r = 0.42, P < 0.05). This study demonstrates that cardiac sympathetic degeneration and α‐synuclein pathology is present in presymptomatic phase of PD, and that both increase with disease duration and severity. © 2008 Movement Disorder Society.     

Definite familial multiple system atrophy with unknown genetics

Multiple system atrophy (MSA) is an oligodendrogliopathy of presumably sporadic origin, characterized by prominent α‐synuclein inclusions with neuronal multisystem degeneration, although a few Mendelian pedigrees have been reported. Here we report two familial cases of MSA of unknown genetic background. One patient was diagnosed as a possible MSA‐C (cerebellar dysfuntion) case, and the other as clinically possible MSA‐P (parkinsonism), which turned out to be definite MSA, based on a detailed autopsy. The neuropathology showed extensive deposition of α‐synuclein in the glia as well as in the neurons located in the cerebral cortices and hippocampal systems, although neither multiplication of the SNCA gene or mutations in COQ2 gene were identified in the family concerned.     

Disease Modification in Parkinson's Disease: Current Approaches,Challenges, and Future Considerations

The greatest unmet therapeutic need in Parkinson's disease is the development of treatment that slows the relentless progression of the neurodegenerative process. The concept of “disease modification” encompasses intervention types ranging from those designed to slow the underlying degeneration to treatments directed at regenerating or replacing lost neurons. To date all attempts to develop effective disease‐modifying therapy have failed. Many reasons have been proposed for these failures including our rudimentary understanding of disease pathogenesis and the assumption that each targeted mechanisms of disease apply to most patients with the same clinical diagnosis. Here we review all aspects of this broad field including general concepts and past challenges followed by a discussion of treatment approaches under the following 4 categories: (1) α‐synuclein, (2) pathogenic mechanisms distinct from α‐synuclein (most also potentially triggered by α‐synuclein toxicity), (3) non‐SNCA genetic subtypes of “PD,” and (4) possible disease‐modifying interventions not directly influencing the underlying PD pathobiology. We emphasize treatments that are currently under active clinical development and highlight a wide range of important outstanding questions and concerns that will need to be considered to advance the field of disease modification in PD. Critically, it is unknown whether the dysfunctional molecular pathways/organelles amenable to modification occur in a sequential fashion across most clinically affected individuals or manifest differentially in independent molecular subtypes of PD. It is possible that there is no “order of disruption” applicable to most patients but, rather, “type of disruption” applicable to subtypes dependent on unknown factors, including genetic variability and other causes for heterogeneity in PD. Knowing when (early vs late), which (eg, synaptic transmission, endosomal sorting and maturation, lysosomal degradation, mitochondrial biogenesis), and in whom (PD subtype) specific disrupted cell pathways are truly pathogenic versus compensatory or even protective, will be important in considering the use of single or combined (“cocktails”) putative disease‐modifying therapies to selectively target these processes. Beyond the current phase 2 or 3 studies underway evaluating treatments directed at oxidative stress (inosine), cytosolic Ca²⁺ (isradipine), iron (deferiprone), and extracellular α‐synuclein (passive immunization), and upcoming trials of interventions affecting c‐Abl, glucagon‐like peptide‐1, and glucocerebrosidase, it might be argued that further trials in populations not enriched for the targeted pathogenic process are doomed to repeat the failures of the past. © 2018 International Parkinson and Movement Disorder Society     

Diurnal secretion profiles of growth hormone, thyrotrophin and prolactin in Parkinson's disease

Recently, a massive loss of both hypocretin and melanin‐concentrating hormone (MCH) neurones was found in the hypothalamus of Parkinson’s disease (PD) patients. Because both hypocretin and MCH play a key role in the regulation of sleep, energy homeostasis and autonomic function, partly by modulation of the somatotrophic, thyrotrophic and lactotrophic axes, neuroendocrine dysregulation may contribute to some of the non‐motor features of PD. In eight de novo, medication‐free PD patients and eight age‐, sex‐ and body mass index‐matched controls, we measured serum levels of growth hormone (GH), thyroid‐stimulating hormone (TSH) and prolactin every 10 min for 24 h. Auto‐deconvolution, cosinor and approximate entropy analysis were applied to quantify GH, TSH and prolactin secretion rates, diurnal rhythmicity, as well as regularity of hormone release. Sleep was polygraphically‐recorded throughout the night. Total 24‐h secretion of GH (191 ± 31 versus 130 ± 39 mU/l/24 h), TSH (38 ± 9 versus 36 ± 2 mU/l/24 h) and prolactin (102 ± 14 versus 116 ± 17 μg/l/24 h), as well as their diurnal rhythmicity and regularity of release, were not significantly different between PD patients and controls (all P ≥ 0.12). Fasting levels of insulin‐like growth factor‐1 were also unaltered in PD patients. However, free thyroxine (T₄) levels were significantly higher in PD patients compared to controls (16.19 ± 0.80 versus 13.88 ± 0.40 pmol/l; P = 0.031). In PD patients, prolactin levels were related to disease duration (r = 0.76, P = 0.028), whereas both GH (r = ?0.91, P = 0.002) and free T₄ (r = ?0.71, P = 0.050) levels correlated inversely with body fat content. Apart from a mild increase in free T₄ levels, we found no indications for altered somatotrophic, thyrotrophic and lactotrophic axes activity in early‐stage PD patients.     

Cerebrospinal fluid,plasma, and saliva in the BioFIND study: Relationships among biomarkers and Parkinson's disease Features

Objective: Examine relationships among neurodegenerative biomarkers and PD motor and nonmotor symptoms. Background: CSF alpha‐synuclein is decreased in PD versus healthy controls, but whether plasma and saliva alpha‐synuclein differentiate these groups is controversial. Correlations of alpha‐synuclein among biofluids (CSF, plasma, saliva) or biomarkers (eg, beta‐amyloid, tau [total, phosphorylated]) are not fully understood. The relationships of these biomarkers with PD clinical features remain unclear. Methods: BioFIND, a cross‐sectional, observational study, examines clinical and biomarker characteristics in moderate‐advanced PD and matched healthy controls. We compared alpha‐synuclein concentrations across diagnosis, biofluids, and CSF biomarkers. Correlations of CSF biomarkers and MDS‐UPDRS, motor phenotype, MoCA, and rapid eye movement sleep behavior disorder questionnaire scores in PD were examined. Results: CSF alpha‐synuclein was lower in PD versus controls (P = .01), controlling for age, gender, and education. Plasma and saliva alpha‐synuclein did not differ between PD and controls, and alpha‐synuclein did not significantly correlate among biofluids. CSF beta‐amyloid_1‐42 was lower in PD versus controls (P < .01), and correlated weakly with MoCA recall scores (r = 0.23, P = .02). CSF alpha‐synuclein was lower in the postural instability/gait difficulty phenotype than other motor phenotypes (P < .01). No CSF biomarkers predicted or correlated with total motor or rapid eye movement sleep behavior disorder scores. CSF alpha‐synuclein correlated with beta‐amyloid_1‐42, total‐tau, and phosphorylated‐tau (r = 0.41, 0.81, 0.43, respectively; Ps < .001). Conclusion: Lower CSF alpha‐synuclein is associated with diagnosis and motor phenotype in moderate‐advanced PD. Plasma and saliva alpha‐synuclein neither correlate with CSF alpha‐synuclein, nor distinguish PD from controls. CSF beta‐amyloid_1‐42 remains a potential biomarker for cognitive impairment in PD. © 2017 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.     

Lysosomal impairment in Parkinson's disease

Impairment of autophagy‐lysosomal pathways (ALPs) is increasingly regarded as a major pathogenic event in neurodegenerative diseases, including Parkinson's disease (PD). ALP alterations are observed in sporadic PD brains and in toxic and genetic rodent models of PD‐related neurodegeneration. In addition, PD‐linked mutations and post‐translational modifications of α‐synuclein impair its own lysosomal‐mediated degradation, thereby contributing to its accumulation and aggregation. Furthermore, other PD‐related genes, such as leucine‐rich repeat kinase‐2 (LRRK2), parkin, and phosphatase and tensin homolog (PTEN)‐induced putative kinase 1 (PINK1), have been mechanistically linked to alterations in ALPs. Conversely, mutations in lysosomal‐related genes, such as glucocerebrosidase (GBA) and lysosomal type 5 P‐type ATPase (ATP13A2), have been linked to PD. New data offer mechanistic molecular evidence for such a connection, unraveling a causal link between lysosomal impairment, α‐synuclein accumulation, and neurotoxicity. First, PD‐related GBA deficiency/mutations initiate a positive feedback loop in which reduced lysosomal function leads to α‐synuclein accumulation, which, in turn, further decreases lysosomal GBA activity by impairing the trafficking of GBA from the endoplasmic reticulum‐Golgi to lysosomes, leading to neurodegeneration. Second, PD‐related mutations/deficiency in the ATP13A2 gene lead to a general lysosomal impairment characterized by lysosomal membrane instability, impaired lysosomal acidification, decreased processing of lysosomal enzymes, reduced degradation of lysosomal substrates, and diminished clearance of autophagosomes, collectively contributing to α‐synuclein accumulation and cell death. According to these new findings, primary lysosomal defects could potentially account for Lewy body formation and neurodegeneration in PD, laying the groundwork for the prospective development of new neuroprotective/disease‐modifying therapeutic strategies aimed at restoring lysosomal levels and function. © 2013 Movement Disorder Society