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Abstract The crust and upper mantle structure of the Greater and Lesser Antilles Arc provides insights into key subduction zone processes in a unique region of slow convergence of old slow‐spreading oceanic lithosphere. We use ambient noise tomography gathered from island broadband seismic stations and the temporary ocean bottom seismometer network installed as part of the Volatile Recycling in the Lesser Antilles experiment to map crustal and upper mantle shear‐wave velocity of the eastern Greater Antilles and the Lesser Antilles Arc. Taking the depth to the 2.0 km/s contour as a proxy, we find sediment thickness up to 15 km in the south in the Grenada and Tobago basins and thinner sediments near the arc and to the north. We observe thicker crust, based on the depth to the 4.0 km/s velocity contour, beneath the arc platforms with the greatest crustal thickness of around 30 km, likely related to crustal addition from arc volcanism through time. There are distinct low velocity zones (4.2–4.4 km/s) in the mantle wedge (30–50 km depth), beneath the Mona Passage, Guadeloupe‐Martinique, and the Grenadines. The Mona passage mantle anomaly may be related to ongoing extension there, while the Guadeloupe‐Martinique and Grenadine anomalies are likely related to fluid flux, upwelling, and/or partial melt related to nearby slab features. The location of the Guadeloupe‐Martinique anomaly is slightly to the south of the obliquely subducted fracture zones. This feature could be explained by either three‐dimensional mantle flow, a gap in the slab, variable slab hydration, and/or melt dynamics including ponding and interactions with the upper plate.

Abstract The rs6265 single nucleotide polymorphism (SNP) in the gene for brain-derived neurotrophic factor is a common variant that alters therapeutic outcomes for individuals with Parkinson’s disease (PD). We previously investigated the effects of this SNP on the experimental therapeutic approach of neural grafting, demonstrating that young adult parkinsonian rats carrying the variant Met allele exhibited enhanced graft function compared to wild-type rats and also exclusively developed aberrant graft-induced dyskinesias (GID). Aging is the primary risk factor for PD and reduces graft efficacy. Here we investigated whether aging interacts with this SNP to further alter cell transplantation outcomes. We hypothesized that aging would reduce enhancement of graft function associated with this genetic variant and exacerbate GID in all grafted subjects. Unexpectedly, beneficial graft function was maintained in aged rs6265 subjects. However, aging was permissive to GID induction, regardless of genotype, with the greatest incidence and severity found in rs6265-expressing animals.

Abstract Background Plastic and reconstructive surgery (PRS) remains highly relevant to the unmet need for surgery in Malawi. Better understanding the current PRS landscape and its barriers may help address some of these challenges. This scoping review aimed to describe: (1) the scope and focus of the PRS literature being produced in Malawi and (2) the challenges, deficits, and barriers to providing accessible, high-quality PRS in Malawi. Methods This scoping review was conducted on four databases (SCOPUS, PubMed, Web of Science, EMBASE) from inception through September 1, 2020 following the PRISMA-ScR guidelines. Results The database search retrieved 3852 articles, of which 31 were included that examined the burden of PRS-related conditions in Malawi. Of these 31 articles, 25 primarily discussed burn-related care. Burns injuries have a high mortality rate; between 27 and 75% in the studies. The literature revealed that there are only two burn units nationally with one PRS specialist in each unit, compounded by a lack of interest in PRS specialization by Malawian medical students. Congenital anomalies were the only other PRS-related condition examined and reported in the literature, accounting for 23% of all pediatric surgeries in tertiary facilities. Conclusions There is a need to increase the country's capacity to handle burn reconstruction and other PRS-related conditions to reduce overall morbidity and mortality. Additional publicly funded research at the district and community level is warranted to determine the true burden of PRS disease in Malawi to derive health system strengthening and workforce capacity building strategies.

Abstract The common brain-derived neurotrophic factor (BDNF) Val66Met polymorphism is associated with reduced activity-dependent BDNF release and increased risk for anxiety disorders and PTSD. Here we behaviorally phenotyped a novel Val66Met rat model with an equivalent valine to methionine substitution in the rat Bdnf gene (Val68Met). In a three-day fear conditioning protocol of fear learning and extinction, adult rats with the Met/Met genotype demonstrated impaired fear memory compared to Val/Met rats and Val/Val controls, with no genotype differences in fear learning or extinction. This deficit in fear memory occurred irrespective of the sex of the animals and was not seen in adolescence (4 weeks of age). There were no changes in open-field locomotor activity or anxiety measured in the elevated plus maze (EPM) nor in other types of memory measured using the novel-object recognition test or Y-maze. BDNF exon VI expression in the dorsal hippocampus was higher and BDNF protein level in the ventral hippocampus was lower in female Val/Met rats than female Val/Val rats, with no other genotype differences, including in total BDNF, BDNF long, or BDNF IV mRNA. These data suggest a specific role for the BDNF Met/Met genotype in fear memory in rats. Further studies are required to investigate gene–environment interactions in this novel animal model.

The role of transcriptional enhancers and 3D chromatin organisation in coordinating the transition from naive to primed pluripotency remains poorly understood. Here the authors generate a high-resolution atlas of gene regulatory interactions, chromatin profiles and transcription factor occupancy in naive and primed human pluripotent stem cells to provide insights into these developmental processes.

Biogeography has traditionally focused on the distribution of species, while community ecology has sought to explain the patterns of community composition. Species interactions networks have rarely been subjected to such analyses, as modeling tools have only recently been developed for interaction networks. Here, we examine beta diversity of ecological networks using pollination networks sampled along an urbanization and agricultural intensification gradient in east Leinster, Ireland. We show, for the first time, that anthropogenic gradients structure interaction networks, and exert greater structuring force than geographical proximity. We further showed that species turnover, especially of plants, is the major driver of interaction turnover, and that this contribution increased with anthropogenic induced environmental dissimilarity, but not spatial distance. Finally, to explore the extent to which it is possible to predict each of the components of interaction turnover, we compared the predictive performance of models that included site characteristics and interaction properties to models that contained species level effects. We show that if we are to accurately predict interaction turnover, data are required on the species-specific responses to environmental gradients. This study highlights the importance of anthropogenic disturbances when considering the biogeography of interaction networks, especially in human dominated landscapes where geographical effects can be secondary sources of variation. Yet, to build a predictive science of the biogeography of interaction networks, further species-specific responses need to be incorporated into interaction distribution modeling approaches.

Abstract Enlargements of distal airspaces can indicate pathological changes in the lung, but accessible and precise techniques able to measure these regions are lacking. Airspace Dimension Assessment with inhaled nanoparticles (AiDA) is a new method developed for in vivo measurement of distal airspace dimensions. The aim of this study was to benchmark the AiDA method against quantitative measurements of distal airspaces from hyperpolarised 129Xe diffusion-weighted (DW)-lung magnetic resonance imaging (MRI). AiDA and 129Xe DW-MRI measurements were performed in 23 healthy volunteers who spanned an age range of 23–70 years. The relationship between the 129Xe DW-MRI and AiDA metrics was tested using Spearman’s rank correlation coefficient. Significant correlations were observed between AiDA distal airspace radius (r AiDA) and mean 129Xe apparent diffusion coefficient (ADC) (p

POLRMT is key for transcription of the mitochondrial genome, yet has not been implicated in mitochondrial disease to date. Here, the authors identify mutations in POLRMT in individuals with mitochondrial disease-related phenotypes and characterise underlying defects in mitochondrial transcription.

Background:. Cleft lip and palate (CLP) comprise over 90% of the world’s congenital anomalies and cause significant disability worldwide, while disproportionally burdening low- and middle-income countries (LMICs). Research can help inform strategies that reduce disparities in accessing CLP care. We performed a scientometric analysis of CLP research in LMICs to identify influential contributors and themes. Methods:. The authors searched seven citation databases accessed via Web of Science, from inception to March 2, 2021. Social network analysis was done using VOSviewer. The Kruskal-Wallis test and linear regression were used. Results:. In total, 1561 articles authored by 6414 researchers affiliated with 2113 organizations in 119 countries were included. Most authors (n = 6387, 99.6%) had published two or more articles. The USA (454 articles), Brazil (211 articles), China (175 articles), and India (127 articles) published the most. The most prolific institutions were the University of Sao Paulo (94 articles), the University of Pittsburgh (57 articles), and the University of Iowa (55 articles). Marazita ML (33 articles), Shi B (27 articles), and Murray JC (22 articles) had the highest number of publications. An estimated 510 articles (32.7%) were focused on epidemiology, 240 (15.4%) on management, and 54 (3.5%) on global plastic surgery for CLP. Conclusions:. LMICs are disproportionally burdened by CLP, but research is limited and often produced by high-income countries. This study elucidates partnership and health system strengthening opportunities to improve LMIC research capacity and ultimately informs the management and outcomes for patients with CLP.

Background There are limited studies investigating the use of fecal microbial transplant (FMT) in dogs with inflammatory bowel disease (IBD). The aim of this preliminary study was to assess the feasibility of adding FMT to standard therapy (corticosteroids and a hypoallergenic diet) for dogs with IBD and to and to describe the changes in measured outcomes after 30 days of treatment. Methods Thirteen client-owned dogs with IBD were enrolled in this double blinded, randomized clinical trial. All dogs received corticosteroid therapy and a hypoallergenic diet; dogs were randomized to receive either placebo or FMT. Measured outcomes included the canine chronic enteropathy clinical activity index (CCECAI) at 1 week and 1 month after enrolment. Fecal microbiota were analyzed after extracting DNA from fecal samples and profiling using 16S amplicon sequencing. Dogs in the placebo group not responding to treatment after 1 month were offered FMT. Results The CCECAI significantly decreased over time in both groups (p = 0.001). There were no significant differences between the CCECAI of the placebo and FMT group at each time point (F test from ANOVA, p = 0.40). No adverse effects were reported in the 30 days following FMT. Conclusions The addition of FMT to standard therapy for IBD was feasible. No significant differences were observed in the CCECAI between groups at each time point. Large scale clinical trials can be performed using these methods to evaluate the longer term effect of FMT on clinical signs, microbial diversity, and other outcomes.

Abstract When standing waves are present in a rectangular waveguide, the resistive losses in the walls are not uniformly distributed. This affects the measurement of the attenuation constant. Here the phenomenon for the TE10 mode in air‐filled waveguide, where the deviation from the normal travelling wave attenuation constant is only about ±1% over the conventional bandwidth, is discussed. However, the paper also shows that nearer the cut‐off frequency for the waveguide, the deviation could be as high as ±100%.

Abstract Background The Phase III PINNACLE studies assessed the efficacy and safety of glycopyrrolate/formoterol fumarate metered dose inhaler (GFF MDI), a dual long-acting bronchodilator for chronic obstructive pulmonary disease (COPD). Here we present a pre-specified pooled analysis of PINNACLE-1, PINNACLE-2, and PINNACLE-4. Methods PINNACLE-1, -2, and -4 were multicenter, double-blind, randomized controlled trials that enrolled patients with moderate-to-very severe COPD, with no requirement for exacerbation history or a high symptom burden. Patients received GFF MDI 18/9.6 μg, glycopyrrolate (GP) MDI 18 μg, formoterol fumarate (FF) MDI 9.6 μg, or placebo MDI, twice-daily for 24 weeks. The primary endpoint of the pooled analysis was the change from baseline in morning pre-dose trough forced expiratory volume in 1 s (FEV1) at week 24. Secondary endpoints included COPD exacerbations and clinically important deterioration (CID). Adverse events were also assessed. Results The pooled intent-to-treat population included 4983 patients; of these, 61.9% had a COPD assessment test (CAT) score ≥15, and 25.0% had experienced ≥1 moderate/severe exacerbation in the past year. At week 24, GFF MDI improved morning pre-dose trough FEV1 versus GP MDI (least squares mean [LSM] difference [95% confidence interval (CI)]: 59 mL [43, 75]), FF MDI (65 mL [48, 81]), and placebo MDI (146 mL [125, 166]); all p

Abstract The cardinal stages of macroautophagy are driven by core autophagy‐related (ATG) proteins, whose ablation largely abolishes intracellular turnover. Disrupting ATG genes is paradigmatic of studying autophagy deficiency, yet emerging data suggest that ATG proteins have extensive biological importance beyond autophagic elimination. An important example is ATG7, an essential autophagy effector enzyme that in concert with other ATG proteins, also regulates immunity, cell death and protein secretion, and independently regulates the cell cycle and apoptosis. Recently, a direct association between ATG7 dysfunction and disease was established in patients with biallelic ATG7 variants and childhood‐onset neuropathology. Moreover, a prodigious body of evidence supports a role for ATG7 in protecting against complex disease states in model organisms, although how dysfunctional ATG7 contributes to manifestation of these diseases, including cancer, neurodegeneration and infection, in humans remains unclear. Here, we systematically review the biological functions of ATG7, discussing the impact of its impairment on signalling pathways and human pathology. Future studies illuminating the molecular relationship between ATG7 dysfunction and disease will expedite therapies for disorders involving ATG7 deficiency and/or impaired autophagy.

Background Hyperpolarised gas magnetic resonance imaging (MRI) can be used to assess ventilation patterns. Previous studies have shown the image-derived metric of ventilation defect per cent (VDP) to correlate with forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) and FEV1 in asthma. Objectives The aim of this study was to explore the utility of hyperpolarised xenon-129 (129Xe) ventilation MRI in clinical care and examine its relationship with spirometry and other clinical metrics in people seen in a severe asthma service. Methods 26 people referred from a severe asthma clinic for MRI scanning were assessed by contemporaneous 129Xe MRI and spirometry. A subgroup of 18 patients also underwent reversibility testing with spirometry and MRI. Quantitative MRI measures of ventilation were calculated, VDP and the ventilation heterogeneity index (VHI), and compared to spirometry, Asthma Control Questionnaire 7 (ACQ7) and blood eosinophil count. Images were reviewed by a multidisciplinary team. Results VDP and VHI correlated with FEV1, FEV1/FVC and forced expiratory flow between 25% and 75% of FVC but not with ACQ7 or blood eosinophil count. Discordance of MRI imaging and symptoms and/or pulmonary function tests also occurred, prompting diagnostic re-evaluation in some cases. Conclusion Hyperpolarised gas MRI provides a complementary method of assessment in people with difficult to manage asthma in a clinical setting. When used as a tool supporting clinical care in a severe asthma service, occurrences of discordance between symptoms, spirometry and MRI scanning indicate how MRI scanning may add to a management pathway.

The signalling pathways that maintain primed human pluripotent stem cells (hPSCs) have been well characterised, revealing a critical role for TGFβ/Activin/Nodal signalling. In contrast, the signalling requirements of naïve human pluripotency have not been fully established. Here, we demonstrate that TGFβ signalling is required to maintain naïve hPSCs. The downstream effector proteins – SMAD2/3 – bind common sites in naïve and primed hPSCs, including shared pluripotency genes. In naïve hPSCs, SMAD2/3 additionally bind to active regulatory regions near to naïve pluripotency genes. Inhibiting TGFβ signalling in naïve hPSCs causes the downregulation of SMAD2/3-target genes and pluripotency exit. Single-cell analyses reveal that naïve and primed hPSCs follow different transcriptional trajectories after inhibition of TGFβ signalling. Primed hPSCs differentiate into neuroectoderm cells, whereas naïve hPSCs transition into trophectoderm. These results establish that there is a continuum for TGFβ pathway function in human pluripotency spanning a developmental window from naïve to primed states.

Objectives COVIDTrach is a UK multicentre prospective cohort study project that aims to evaluate the outcomes of tracheostomy in patients with COVID-19 receiving mechanical ventilation and record the incidence of SARS-CoV-2 infection among healthcare workers involved in the procedure.Design Data on patient demographic, clinical history and outcomes were entered prospectively and updated over time via an online database (REDCap). Clinical variables were compared with outcomes, with logistic regression used to develop a model for mortality. Participants recorded whether any operators tested positive for SARS-CoV-2 within 2 weeks of the procedure.Setting UK National Health Service departments involved in treating patients with COVID-19 receiving mechanical ventilation.Participants The cohort comprised 1605 tracheostomy cases from 126 UK hospitals collected between 6 April and 26 August 2020.Main outcome measures Mortality following tracheostomy, successful wean from mechanical ventilation and length of time from tracheostomy to wean, discharge from hospital, complications from tracheostomy, reported SARS-CoV-2 infection among operators.Results The median time from intubation to tracheostomy was 15 days (IQR 11, 21). 285 (18%) patients died following the procedure. 1229 (93%) of the survivors had been successfully weaned from mechanical ventilation at censoring and 1049 (81%) had been discharged from hospital. Age, inspired oxygen concentration, positive end-expiratory pressure setting, fever, number of days of ventilation before tracheostomy, C reactive protein and the use of anticoagulation and inotropic support independently predicted mortality. Six reports were received of operators testing positive for SARS-CoV-2 within 2 weeks of the procedure.Conclusions Tracheostomy appears to be safe in mechanically ventilated patients with COVID-19 and to operators performing the procedure and we identified clinical parameters that are predictive of mortality.Trial registration number The study is registered with ClinicalTrials.Gov (NCT04572438).

Mitochondria exist as dynamic networks whose morphology is driven by the complex interplay between fission and fusion events. Failure to modulate these processes can be detrimental to human health as evidenced by dominantly inherited, pathogenic variants in OPA1, an effector enzyme of mitochondrial fusion, that lead to network fragmentation, cristae dysmorphology and impaired oxidative respiration, manifesting typically as isolated optic atrophy. However, a significant number of patients develop more severe, systemic phenotypes, although no genetic modifiers of OPA1‐related disease have been identified to date. In this issue of EMBO Molecular Medicine, supervised machine learning algorithms underlie a novel tool that enables automated, high throughput and unbiased screening of changes in mitochondrial morphology measured using confocal microscopy. By coupling this approach with a bespoke siRNA library targeting the entire mitochondrial proteome, the work described by Cretin and colleagues yielded significant insight into mitochondrial biology, discovering 91 candidate genes whose endogenous depletion can remedy impaired mitochondrial dynamics caused by OPA1 deficiency.

Parkinson’s disease (PD) is a prevalent neurodegenerative disease with no approved disease-modifying therapies. Multiplications, mutations, and single nucleotide polymorphisms in the SNCA gene, encoding α-synuclein (aSyn) protein, either cause or increase risk for PD. Intracellular accumulations of aSyn are pathological hallmarks of PD. Taken together, reduction of aSyn production may provide a disease-modifying therapy for PD. We show that antisense oligonucleotides (ASOs) reduce production of aSyn in rodent preformed fibril (PFF) models of PD. Reduced aSyn production leads to prevention and removal of established aSyn pathology and prevents dopaminergic cell dysfunction. In addition, we address the translational potential of the approach through characterization of human SNCA-targeting ASOs that efficiently suppress the human SNCA transcript in vivo. We demonstrate broad activity and distribution of the human SNCA ASOs throughout the nonhuman primate brain and a corresponding decrease in aSyn cerebral spinal fluid (CSF) levels. Taken together, these data suggest that, by inhibiting production of aSyn, it may be possible to reverse established pathology; thus, these data support the development of SNCA ASOs as a potential disease-modifying therapy for PD and related synucleinopathies.

Prevalent in approximately 20% of the worldwide human population, the rs6265 (also called ‘Val66Met’) single nucleotide polymorphism (SNP) in the gene for brain-derived neurotrophic factor (BDNF) is a common genetic variant that can alter therapeutic responses in individuals with Parkinson’s disease (PD). Possession of the variant Met allele results in decreased activity-dependent release of BDNF. Given the resurgent worldwide interest in neural transplantation for PD and the biological relevance of BDNF, the current studies examined the effects of the rs6265 SNP on therapeutic efficacy and side-effect development following primary dopamine (DA) neuron transplantation. Considering the significant reduction in BDNF release associated with rs6265, we hypothesized that rs6265-mediated dysfunctional BDNF signaling contributes to the limited clinical benefit observed in a subpopulation of PD patients despite robust survival of grafted DA neurons, and further, that this mutation contributes to the development of aberrant graft-induced dyskinesias (GID). To this end, we generated a CRISPR knock-in rat model of the rs6265 BDNF SNP to examine for the first time the influence of a common genetic polymorphism on graft survival, functional efficacy, and side-effect liability, comparing these parameters between wild-type (Val/Val) rats and those homozygous for the variant Met allele (Met/Met). Counter to our hypothesis, the current research indicates that Met/Met rats show enhanced graft-associated therapeutic efficacy and a paradoxical enhancement of graft-derived neurite outgrowth compared to wild-type rats. However, consistent with our hypothesis, we demonstrate that the rs6265 genotype in the host rat is strongly linked to development of GID, and that this behavioral phenotype is significantly correlated with neurochemical signatures of atypical glutamatergic neurotransmission by grafted DA neurons.

Abstract Background Written participant information materials are important for ensuring that potential trial participants receive necessary information so that they can provide informed consent. However, such materials are frequently long and complex, which may negatively impact patient understanding and willingness to participate. Improving readability, ease of comprehension and presentation may assist with improved participant recruitment. The Systematic Techniques for Assisting Recruitment to Trials (MRC START) study aimed to develop and evaluate interventions to improve trial recruitment. This study aimed to assess the effectiveness of an optimised participant information brochure and cover letter developed by MRC START regarding response and participant recruitment rates. Methods We conducted a study within a trial (SWAT) embedded in the EarlyCDT Lung Cancer Scotland (ECLS) trial that aimed to assess the effectiveness of a new test in reducing the incidence of patients with late-stage lung cancer at diagnosis compared with standard care. Potential participants approached for ECLS were randomised to receive the original participant information brochure and accompanying letter (control group) or optimised versions of these materials which had undergone user testing and a process of re-writing, re-organisation and professional graphic design (intervention group). The primary outcome was the number of patients recruited to ECLS. The secondary outcome was the proportion of patients expressing an interest in participating in ECLS. Results In total, 2262 patients were randomised, 1136 of whom were sent the intervention materials and 1126 of whom were sent the control materials. The proportion of patients enrolled and randomised into ECLS was 180 of 1136 (15.8%) in the intervention group and 176 of 1126 (15.6%) in the control group (OR = 1.016, 95% CI, 0.660 to 1.564). The proportion of patients who positively responded to the invitation was 224 of 1136 (19.7%) in the intervention group and 205 of 1126 (18.2%) in the control group (OR = 1.103, 95% CI, 0.778 to 1.565). Conclusions Optimised patient information materials made little difference to the proportion of patients positively responding to a trial invitation or to the proportion subsequently randomised to the host trial. Trial registration ClinicalTrials.gov, NCT01925625. Registered on 15 August 2015. Study Within A Trial, SWAT-23. Registered on 12 April 2016.

Animal models that accurately recapitulate the accumulation of alpha-synuclein (α-syn) inclusions, progressive neurodegeneration of the nigrostriatal system and motor deficits can be useful tools for Parkinson's disease (PD) research. The preformed fibril (PFF) synucleinopathy model in rodents generally displays these PD-relevant features, however, the magnitude and predictability of these events is far from established. We therefore sought to optimize the magnitude of α-syn accumulation and nigrostriatal degeneration, and to understand the time course of both. Rats were injected unilaterally with different quantities of α-syn PFFs (8 or 16 μg of total protein) into striatal sites selected to concentrate α-syn inclusion formation in the substantia nigra pars compacta (SNpc). Rats displayed an α-syn PFF quantity-dependent increase in the magnitude of ipsilateral SNpc inclusion formation at 2 months and bilateral loss of nigral dopamine neurons at 6 months. Unilateral 16 μg PFF injection also resulted in modest sensorimotor deficits in forelimb adjusting steps associated with degeneration at 6 months. Bilateral injection of 16 μg α-syn PFFs resulted in symmetric bilateral degeneration equivalent to the ipsilateral nigral degeneration observed following unilateral 16 μg PFF injection (~50% loss). Bilateral PFF injections additionally resulted in alterations in several gait analysis parameters. These α-syn PFF parameters can be applied to generate a reproducible synucleinopathy model in rats with which to study pathogenic mechanisms and vet potential disease-modifying therapies.

Abstract Background Converging evidence suggests a role for microglia-mediated neuroinflammation in Parkinson’s disease (PD). Animal models of PD can serve as a platform to investigate the role of neuroinflammation in degeneration in PD. However, due to features of the previously available PD models, interpretations of the role of neuroinflammation as a contributor to or a consequence of neurodegeneration have remained elusive. In the present study, we investigated the temporal relationship of neuroinflammation in a model of synucleinopathy following intrastriatal injection of pre-formed alpha-synuclein fibrils (α-syn PFFS). Methods Male Fischer 344 rats (N = 114) received unilateral intrastriatal injections of α-syn PFFs, PBS, or rat serum albumin with cohorts euthanized at monthly intervals up to 6 months. Quantification of dopamine neurons, total neurons, phosphorylated α-syn (pS129) aggregates, major histocompatibility complex-II (MHC-II) antigen-presenting microglia, and ionized calcium-binding adaptor molecule-1 (Iba-1) immunoreactive microglial soma size was performed in the substantia nigra. In addition, the cortex and striatum were also examined for the presence of pS129 aggregates and MHC-II antigen-presenting microglia to compare the temporal patterns of pSyn accumulation and reactive microgliosis. Results Intrastriatal injection of α-syn PFFs to rats resulted in widespread accumulation of phosphorylated α-syn inclusions in several areas that innervate the striatum followed by significant loss (~ 35%) of substantia nigra pars compacta dopamine neurons within 5–6 months. The peak magnitudes of α-syn inclusion formation, MHC-II expression, and reactive microglial morphology were all observed in the SN 2 months following injection and 3 months prior to nigral dopamine neuron loss. Surprisingly, MHC-II immunoreactivity in α-syn PFF injected rats was relatively limited during the later interval of degeneration. Moreover, we observed a significant correlation between substantia nigra pSyn inclusion load and number of microglia expressing MHC-II. In addition, we observed a similar relationship between α-syn inclusion load and number of microglia expressing MHC-II in cortical regions, but not in the striatum. Conclusions Our results demonstrate that increases in microglia displaying a reactive morphology and MHC-II expression occur in the substantia nigra in close association with peak numbers of pSyn inclusions, months prior to nigral dopamine neuron degeneration, and suggest that reactive microglia may contribute to vulnerability of SNc neurons to degeneration. The rat α-syn PFF model provides an opportunity to examine the innate immune response to accumulation of pathological α-syn in the context of normal levels of endogenous α-syn and provides insight into the earliest neuroinflammatory events in PD.

The pathology of Parkinson's disease and other synucleinopathies is characterized by the formation of intracellular inclusions comprised primarily of misfolded, fibrillar α-synuclein (α-syn). One strategy to slow disease progression is to prevent the misfolding and aggregation of its native monomeric form. Here we present findings that support the contention that the tricyclic antidepressant compound nortriptyline (NOR) has disease-modifying potential for synucleinopathies. Findings from in vitro aggregation and kinetics assays support the view that NOR inhibits aggregation of α-syn by directly binding to the soluble, monomeric form, and by enhancing reconfiguration of the monomer, inhibits formation of toxic conformations of the protein. We go on to demonstrate that NOR inhibits the accumulation, aggregation and neurotoxicity of α-syn in multiple cell and animal models. These findings suggest that NOR, a compound with established safety and efficacy for treatment of depression, may slow progression of α-syn pathology by directly binding to soluble, native, α-syn, thereby inhibiting pathological aggregation and preserving its normal functions.