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The purpose of this study was to assess the biological and clinical effects of n-acetyl-cysteine (NAC) in Parkinson's disease (PD). The overarching goal of this pilot study was to generate additional data about potentially protective properties of NAC in PD, using an in vitro and in vivo approach. In preparation for the clinical study we performed a cell tissue culture study with human embryonic stem cell (hESC)-derived midbrain dopamine (mDA) neurons that were treated with rotenone as a model for PD. The primary outcome in the cell tissue cultures was the number of cells that survived the insult with the neurotoxin rotenone. In the clinical study, patients continued their standard of care and were randomized to receive either daily NAC or were a waitlist control. Patients were evaluated before and after 3 months of receiving the NAC with DaTscan to measure dopamine transporter (DAT) binding and the Unified Parkinson's Disease Rating Scale (UPDRS) to measure clinical symptoms. The cell line study showed that NAC exposure resulted in significantly more mDA neurons surviving after exposure to rotenone compared to no NAC, consistent with the protective effects of NAC previously observed. The clinical study showed significantly increased DAT binding in the caudate and putamen (mean increase ranging from 4.4% to 7.8%; p<0.05 for all values) in the PD group treated with NAC, and no measurable changes in the control group. UPDRS scores were also significantly improved in the NAC group (mean improvement of 12.9%, p = 0.01). The results of this preliminary study demonstrate for the first time a potential direct effect of NAC on the dopamine system in PD patients, and this observation may be associated with positive clinical effects. A large-scale clinical trial to test the therapeutic efficacy of NAC in this population and to better elucidate the mechanism of action is warranted. ClinicalTrials.gov NCT02445651.

In an open-label phase 1 trial, gene delivery of the trophic factor neurturin via an adeno-associated type-2 vector (AAV2) was well tolerated and seemed to improve motor function in patients with advanced Parkinson's disease. We aimed to assess the safety and efficacy of AAV2-neurturin in a double-blind, phase 2 randomised trial. We did a multicentre, double-blind, sham-surgery controlled trial in patients with advanced Parkinson's disease. Patients were randomly assigned (2:1) by a central, computer generated, randomisation code to receive either AAV2-neurturin (5·4×1011 vector genomes) injected bilaterally into the putamen or sham surgery. All patients and study personnel with the exception of the neurosurgical team were masked to treatment assignment. The primary endpoint was change from baseline to 12 months in the motor subscore of the unified Parkinson's disease rating scale in the practically-defined off state. All randomly assigned patients who had at least one assessment after baseline were included in the primary analyses. This trial is registered at ClinicalTrials.gov, NCT00400634. Between December, 2006, and November, 2008, 58 patients from nine sites in the USA participated in the trial. There was no significant difference in the primary endpoint in patients treated with AAV2-neurturin compared with control individuals (difference −0·31 [SE 2·63], 95% CI −5·58 to 4·97; p=0·91). Serious adverse events occurred in 13 of 38 patients treated with AAV2-neurturin and four of 20 control individuals. Three patients in the AAV2-neurturin group and two in the sham surgery group developed tumours. Intraputaminal AAV2-neurturin is not superior to sham surgery when assessed using the UPDRS motor score at 12 months. However, the possibility of a benefit with additional targeting of the substantia nigra and longer term follow-up should be investigated in further studies. Ceregene and Michael J Fox Foundation for Parkinson's Research.

Brain iron dyshomeostasis disrupts various critical cellular functions, and age‐related iron accumulation may contribute to deficient neurotransmission and cell death. While recent studies have linked excessive brain iron to cognitive function in the context of neurodegenerative disease, little is known regarding the role of brain iron accumulation in cognitive aging in healthy adults. Further, previous studies have focused primarily on deep gray matter regions, where the level of iron deposition is highest. However, recent evidence suggests that cortical iron may also contribute to cognitive deficit and neurodegenerative disease. Here, we used quantitative susceptibility mapping (QSM) to measure brain iron in 67 healthy participants 18–78 years of age. Speed‐dependent (fluid) cognition was assessed from a battery of 12 psychometric and computer‐based tests. From voxelwise QSM analyses, we found that QSM susceptibility values were negatively associated with fluid cognition in the right inferior temporal gyrus, bilateral putamen, posterior cingulate gyrus, motor, and premotor cortices. Mediation analysis indicated that susceptibility in the right inferior temporal gyrus was a significant mediator of the relation between age and fluid cognition, and similar effects were evident for the left inferior temporal gyrus at a lower statistical threshold. Additionally, age and right inferior temporal gyrus susceptibility interacted to predict fluid cognition, such that brain iron was negatively associated with a cognitive decline for adults over 45 years of age. These findings suggest that iron may have a mediating role in cognitive decline and may be an early biomarker of neurodegenerative disease. This study utilized a voxelwise, quantitative susceptibility mapping (QSM) approach and demonstrates that QSM is a valid brain iron measure. When coupled with voxelwise methods, QSM can elucidate iron‐age and iron‐cognition relations. Brain iron in the inferior temporal cortex mediates the association between age and fluid cognition. Additionally, age and right inferior temporal cortex susceptibility interact to predict fluid cognition such that brain iron is negatively associated with cognitive decline for adults over 45 years. This novel finding suggests that iron has a causal role in cognitive decline, is a critical source of variance in cognitive aging studies, and may be a biomarker of neurodegenerative disease.

Levodopa-induced dyskinesias (LIDs) are the most common and disabling adverse motor effect of therapy in Parkinson's disease (PD) patients. In this study, we investigated serotonergic mechanisms in LIDs development in PD patients using 11C-DASB PET to evaluate serotonin terminal function and 11C-raclopride PET to evaluate dopamine release. PD patients with LIDs showed relative preservation of serotonergic terminals throughout their disease. Identical levodopa doses induced markedly higher striatal synaptic dopamine concentrations in PD patients with LIDs compared with PD patients with stable responses to levodopa. Oral administration of the serotonin receptor type 1A agonist buspirone prior to levodopa reduced levodopa-evoked striatal synaptic dopamine increases and attenuated LIDs. PD patients with LIDs that exhibited greater decreases in synaptic dopamine after buspirone pretreatment had higher levels of serotonergic terminal functional integrity. Buspirone-associated modulation of dopamine levels was greater in PD patients with mild LIDs compared with those with more severe LIDs. These findings indicate that striatal serotonergic terminals contribute to LIDs pathophysiology via aberrant processing of exogenous levodopa and release of dopamine as false neurotransmitter in the denervated striatum of PD patients with LIDs. Our results also support the development of selective serotonin receptor type 1A agonists for use as antidyskinetic agents in PD.

Deciphering the striatal interneuron diversity is key to understanding the basal ganglia circuit and to untangling the complex neurological and psychiatric diseases affecting this brain structure. We performed snRNA-seq and spatial transcriptomics of postmortem human caudate nucleus and putamen samples to elucidate the diversity and abundance of interneuron populations and their inherent transcriptional structure in the human dorsal striatum. We propose a comprehensive taxonomy of striatal interneurons with eight main classes and fourteen subclasses, providing their full transcriptomic identity and spatial expression profile as well as additional quantitative FISH validation for specific populations. We have also delineated the correspondence of our taxonomy with previous standardized classifications and shown the main transcriptomic and class abundance differences between caudate nucleus and putamen. Notably, based on key functional genes such as ion channels and synaptic receptors, we found matching known mouse interneuron populations for the most abundant populations, the recently described PTHLH and TAC3 interneurons. Finally, we were able to integrate other published datasets with ours, supporting the generalizability of this harmonized taxonomy. Striatal interneuron diversity within the basal ganglia of human and non-human primates is not well understood. Here, authors reveal the diversity of interneurons in the human dorsal striatum based on the single-cell transcriptome, delineating unknown types and regional differences, and tracing parallels with those in mice.

The putamen is a subcortical structure that forms part of the dorsal striatum of basal ganglia, and has traditionally been associated with reinforcement learning and motor control, including speech articulation. However, recent studies have shown involvement of the left putamen in other language functions such as bilingual language processing (Abutalebi et al. 2012 ) and production, with some authors arguing for functional segregation of anterior and posterior putamen (Oberhuber et al. 2013 ). A further step in exploring the role of putamen in language would involve identifying the network of coactivations of not only the left, but also the right putamen, given the involvement of right hemisphere in high order language functions (Vigneau et al. 2011 ). Here, a meta-analytic connectivity modeling technique was used to determine the patterns of coactivation of anterior and bilateral putamen in the language domain. Based on previous evidence, we hypothesized that left putamen coactivations would include brain regions directly associated with language processing, whereas right putamen coactivations would encompass regions involved in broader semantic processes, such as memory and visual imagery. The results showed that left anterior putamen coactivated with clusters predominantly in left hemisphere, encompassing regions directly associated with language processing, a left posterior putamen network spanning both hemispheres, and cerebellum. In right hemisphere, coactivations were in both hemispheres, in regions associated with visual and orthographic processing. These results confirm the differential involvement of right and left putamen in different language components, thus highlighting the need for further research into the role of putamen in language.

BACKGROUND. Recombinant human PDGF-BB (rhPDGF-BB) reduces Parkinsonian symptoms and increases dopamine transporter (DAT) binding in several animal models of Parkinson's disease (PD). Effects of rhPDGF-BB are the result of proliferation of ventricular wall progenitor cells and reversed by blocking mitosis. Based on these restorative effects, we assessed the safety and tolerability of intracerebroventricular (i.c.v.) rhPDGF-BB administration in individuals with PD. METHODS. We conducted a double-blind, randomized, placebo-controlled phase I/IIa study at two clinical centers in Sweden. Twelve patients with moderate PD received rhPDGF-BB via an implanted drug infusion pump and an investigational i.c.v. catheter. Patients were assigned to a dose cohort (0.2, 1.5, or 5 μg rhPDGF-BB per day) and then randomized to active treatment or placebo (3:1) for a 12-day treatment period. The primary objective was to assess safety and tolerability of i.c.v.-delivered rhPDGF-BB. Secondary outcome assessments included several clinical rating scales and changes in DAT binding. The follow-up period was 85 days. RESULTS. All patients completed the study. There were no unresolved adverse events. Serious adverse events occurred in three patients; however, these were unrelated to rhPDGF-BB administration. Secondary outcome parameters did not show dose-dependent changes in clinical rating scales, but there was a positive effect on DAT binding in the right putamen. CONCLUSION. At all doses tested, i.c.v. administration of rhPDGF-BB was well tolerated. Results support further clinical development of rhPDGF-BB for patients with PD. TRIAL REGISTRATION. Clinical Trials.gov NCT00866502. FUNDING. Newron Sweden AB (former NeuroNova AB) and Swedish Governmental Agency for Innovation Systems (VINNOVA).

Oligodendroglia are the responsible cells for myelination in the central nervous system and their involvement in Parkinson’s disease (PD) is poorly understood. We performed sn-RNA-seq and image-based spatial transcriptomics of human caudate nucleus and putamen (dorsal striatum) from PD and control brain donors to elucidate the diversity of oligodendroglia and how they are affected by the disease. We profiled a total of ~ 200.000 oligodendroglial nuclei, defining 15 subclasses, from precursor to mature cells, 4 of which are disease-associated. These PD-specific populations are characterized by the overexpression of heat shock proteins, as well as distinct expression signatures related to immune responses, myelination alterations, and disrupted cell signaling pathways. We have also identified impairments in cell communication and oligodendrocyte development, evidenced by changes in neurotransmitter receptors expression and cell adhesion molecules. In addition, we observed significant disruptions in oligodendrocyte development, with aberrant differentiation trajectories and shifts in cell proportions, particularly in the transition from mature oligodendrocytes to disease-associated states. Quantitative immunohistochemical analysis revealed decreased myelin levels in the PD striatum, which correlated with transcriptomic alterations. Furthermore, spatial transcriptomics mapping revealed the distinct localization of disease-associated populations within the striatum, with evidence of impaired myelin integrity. Thus, we uncover oligodendroglia as a critical cell type in PD and a potential new therapeutic target for myelin-based interventions.

•Putamen vessel distance mapping via high-resolution 7T ToF angiography.•Higher CSVD severity predicts increased mean vessel distance in putamen.•Greater vessel distance associates with prolonged arterial transit time.•Right-putamen vessel distance associates with lower global cognitive performance. In cerebral small vessel disease (CSVD), compromised arterial supply to the deep gray matter contributes to cognitive decline. While CSVD frequently involves lenticulostriate arteries supplying the putamen, the functional consequences of altered putaminal vascular architecture remain unclear. We hypothesized that a less homogeneous arterial network in the putamen is associated with impaired perfusion and worse cognitive performance in CSVD. We enrolled 16 CSVD patients with cerebral microbleeds and 21 age‑matched controls (mean age 71 years; 38 % female). High-resolution 7 T time‑of‑flight angiography was used to segment all visible intraputaminal vessels. For each voxel in the putamen, the distance to its nearest segmented vessel was computed to generate a vessel distance map; the mean vessel distance reflects the homogeneity of the arterial network. Putaminal perfusion was quantified via multi‑inversion time pulsed arterial spin labeling (ASL) at 3 T, and CSVD severity was scored on clinical 3 T MRI. All participants completed a comprehensive neuropsychological battery to derive a global cognition composite score. Linear regression revealed that higher CSVD MRI scores predicted larger mean vessel distance, reflecting a sparser arterial network, in both the right (B = 0.12, β = 0.42, p = 0.010) and left putamen (B = 0.13, β = 0.43, p = 0.014). Across all participants, increased vessel distance was also associated with prolonged arterial transit time in the right (B = 0.044, β = 0.50, p = 0.009) and left putamen (B = 0.042, β = 0.49, p = 0.009). Finally, in a multivariable linear regression adjusting for demographics, vascular risk factors, and CSVD severity, greater vessel distance in the right putamen was associated with lower global cognitive performance (B = –1.26, β = –0.34, p = 0.012). This study demonstrates the impact of an impaired arterial network in the putamen on blood supply and cognitive function across the continuum of CSVD.

The dorsal striatum (DS) is implicated in behavioral and neural processes including action control and reinforcement. Alcohol alters these processes in rodents, and it is believed that the development of alcohol use disorder involves changes in DS dopamine signaling. In nonhuman primates, the DS can be divided into caudate and putamen subregions. As part of a collaborative effort examining the effects of long-term alcohol self-administration in rhesus macaques, we examined DS dopamine signaling using fast-scan cyclic voltammetry. We found that chronic alcohol self-administration resulted in several dopamine system adaptations. Most notably, dopamine release was altered in a sex- and region-dependent manner. Following long-term alcohol consumption, male macaques, regardless of abstinence status, had reduced dopamine release in putamen, while only male macaques in abstinence had reduced dopamine release in caudate. In contrast, female macaques had enhanced dopamine release in the caudate, but not putamen. Dopamine uptake was also enhanced in females, but not males (regardless of abstinence state). We also found that dopamine D2/3 autoreceptor function was reduced in male, but not female, alcohol drinkers relative to control groups. Finally, we found that blockade of nicotinic acetylcholine receptors inhibited evoked dopamine release in nonhuman primates. Altogether, our findings demonstrate that long-term alcohol consumption can sex-dependently alter dopamine release, as well as its feedback control mechanisms in both DS subregions.