Quantifying regional α -synuclein, amyloid ß, and tau accumulation in lewy body dementia.

OBJECTIVE: Parkinson disease (PD) is defined by the accumulation of misfolded α-synuclein (α-syn) in Lewy bodies and Lewy neurites. It affects multiple cortical and subcortical neuronal populations. The majority of people with PD develop dementia, which is associated with Lewy bodies in neocortex and referred to as Lewy body dementia (LBD). Other neuropathologic changes, including amyloid ß (Aß) and tau accumulation, occur in some LBD cases. We sought to quantify α-syn, Aß, and tau accumulation in neocortical, limbic, and basal ganglia regions. METHODS: We isolated insoluble protein from fresh frozen postmortem brain tissue samples for eight brains regions from 15 LBD, seven Alzheimer disease (AD), and six control cases. We measured insoluble α-syn, Aß, and tau with recently developed sandwich ELISAs. RESULTS: We detected a wide range of insoluble α-syn accumulation in LBD cases. The majority had substantial α-syn accumulation in most regions, and dementia severity correlated with neocortical α-syn. However, three cases had low neocortical levels that were indistinguishable from controls. Eight LBD cases had substantial Aß accumulation, although the mean Aß level in LBD was lower than in AD. The presence of Aß was associated with greater α-syn accumulation. Tau accumulation accompanied Aß in only one LBD case. INTERPRETATION: LBD is associated with insoluble α-syn accumulation in neocortical regions, but the relatively low neocortical levels in some cases suggest that other changes contribute to impaired function, such as loss of neocortical innervation from subcortical regions. The correlation between Aß and α-syn accumulation suggests a pathophysiologic relationship between these two processes.

RT001 in Progressive Supranuclear Palsy-Clinical and In-Vitro Observations.

BACKGROUND: Progressive supranuclear palsy (PSP) is a progressive movement disorder associated with lipid peroxidation and intracerebral accumulation of tau. RT001 is a deuterium reinforced isotopologue of linoleic acid that prevents lipid peroxidation (LPO) through the kinetic isotope effect. METHODS: The effects of RT001 pre-treatment on various oxidative and bioenergetic parameters were evaluated in mesenchymal stem cells (MSC) derived from patients with PSP compared to controls. In parallel, 3 patients with PSP were treated with RT001 and followed clinically. RESULTS: MSCs derived from PSP patients had a significantly higher rate of LPO (161.8 ± 8.2% of control; p < 0.001). A 72-h incubation with RT001 restored the PSP MSCs to normal levels. Mitochondrial reactive oxygen species (ROS) overproduction in PSP-MSCs significantly decreased the level of GSH compared to control MSCs (to 56% and 47% of control; p < 0.05). Incubation with RT001 significantly increased level of GSH in PSP MSCs. The level of mitochondrial DNA in the cells was significantly lower in PSP-MSCs (67.5%), compared to control MSCs. Changes in mitochondrial membrane potential, size, and shape were also observed. Three subjects with possible or probable PSP were treated with RT001 for a mean duration of 26 months. The slope of the PSPRS changed from the historical decline of 0.91 points/month to a mean decline of 0.16 points/month (+/-0.23 SEM). The UPDRS slope changed from an expected increase of 0.95 points/month to an average increase in score of 0.28 points/month (+/-0.41 SEM). CONCLUSIONS: MSCs derived from patients with PSP have elevated basal levels of LPO, ROS, and mitochondrial dysfunction. These findings are reversed after incubation with RT001. In PSP patients, the progression of disease may be reduced by treatment with RT001.

Differential Inhibition of LRRK2 in Parkinson's Disease Patient Blood by a G2019S Selective LRRK2 Inhibitor.

BACKGROUND: A common genetic mutation that causes Parkinson's disease (PD) is the G2019S LRRK2 mutation. A precision medicine approach that selectively blocks only excess kinase activity of the mutant allele could yield a safe and effective treatment for G2019S LRRK2 PD. OBJECTIVE: To determine the activity of a G2019S mutant selective leucine-rich repeat kinase 2 (LRRK2) kinase inhibitor as compared to a nonselective inhibitor in blood of subjects with genetic and idiopathic PD on two LRRK2 biomarkers, pSer935 LRRK2 and pThr73 Rab10. METHODS: Blood was collected from 13 subjects with or without a G2019S LRRK2 mutation with PD and one healthy control. Peripheral blood mononuclear cells were treated ex vivo with a novel G2019S LRRK2 inhibitor (EB-42168) or the nonselective inhibitor MLi-2. Quantitative western immunoblot analyses were performed. RESULTS: EB-42168 was 100 times more selective for G2019S LRRK2 when compared to wild-type (WT) LRRK2. Concentrations that inhibited phosphorylation of pSer935 LRRK2 by 90% in homozygous G2019S LRRK2 patients, inhibited pSer935 LRRK2 by 36% in heterozygous patients, and by only 5% in patients carrying only the WT allele. Similar selectivity was seen for pThr73 Rab10. MLi-2 showed an equivalent level of inhibition across all genotypes. CONCLUSIONS: These findings demonstrate that EB-42168, a G2019S LRRK2 selective inhibitor, lowers mutant G2019S LRRK2 phosphorylated biomarkers while simultaneously sparing WT LRRK2. Selective targeting of G2019S LRRK2 with a small molecule lays the foundation for a precision medicine treatment of G2019S LRRK2 PD. © 2021 ESCAPE Bio, Inc. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Variants in GBA, SNCA, and MAPT influence Parkinson disease risk, age at onset, and progression.

Multiple genetic variants have been linked to risk of Parkinson disease (PD), but known mutations do not explain a large proportion of the total PD cases. Similarly, multiple loci have been associated with PD risk by genome-wide association studies (GWAS). The influence that genetic factors confer on phenotypic diversity remains unclear. Few studies have been performed to determine whether the GWAS loci are also associated with age at onset (AAO) or motor progression. We used 2 PD case-control data sets (Washington University and the Parkinson's Progression Markers Initiative) to determine whether polymorphisms located at the GWAS top hits (GBA, ACMSD/TMEM163, STK39, MCCC1/LAMP3, GAK/TMEM175, SNCA, and MAPT) show association with AAO or motor progression. We found associations between single nucleotide polymorphisms at the GBA and MAPT loci and PD AAO and progression. These findings reinforce the complex genetic basis of PD and suggest that distinct genes and variants explain the genetic architecture of PD risk, onset, and progression.

Neuromythology of Manganism.

Manganese is an essential trace element with neurotoxicant properties at high levels that were first described in the mid-nineteenth century. The largest sources of occupational and environmental exposures are mining, fossil fuel combustion, and iron and steel industries. Manganese neurotoxicity has been described in many workers with high levels of occupational manganese exposure and can cause a distinct neurologic phenotype known as manganism. Recently, our understanding of the clinical syndrome and pathophysiology of manganese toxicity has shifted. Modern day manganese exposures, which are an order of magnitude lower than previously described in cases of manganism, result in different clinical, imaging, and pathologic phenotypes. Here we will review three neurologic "myths" of manganism in the twenty-first century and will provide evidence that Mn is associated with a clinical syndrome of parkinsonism that resembles Parkinson disease, dopaminergic dysfunction on molecular imaging, and an inflammatory neuropathology in the striatum.