Increased CSF biomarkers of angiogenesis in Parkinson disease

Navigating the Landscape of Plasma Biomarkers in Alzheimer's Disease: Focus on Past, Present, and Future Clinical Applications

As the prevalence of Alzheimer's disease (AD) and its impact on healthcare systems increase, developing tools for accurate diagnosis and monitoring of disease progression is a priority. Recent technological advancements have allowed for the development of blood-based biomarkers (BBMs) to aid in the diagnosis of AD, but many questions remain regarding the clinical implementation of these BBMs. This review outlines the historical timeline of AD BBM development. It highlights key breakthroughs that have transformed the perspective of AD BBMs from theoretically ideal but unattainable markers, to clinically valid and reliable BBMs with potential for implementation in healthcare settings. Technological advancements like single-molecule detection and mass spectrometry methods have significantly improved assay sensitivity and accuracy. High-throughput, fully automated platforms have potential for clinical use. Despite these advancements, however, significant work is needed before AD BBMs can be implemented in widespread clinical practice. Cutpoints must be established, the influence of chronic conditions and medications on BBM levels must be better understood, and guidelines must be created for healthcare providers related to interpreting and communicating information obtained from AD BBMs. Additionally, the development of BBMs for synaptic dysfunction, inflammation, and cerebrovascular disease may provide better precision medicine approaches to treating AD and related dementia. Future research and collaboration between scientists and physicians are essential to addressing these challenges and further advancing AD BBMs, with the goal of integration in clinical practice.

Microphysiological Blood-Brain Barrier Systems for Disease Modeling and Drug Development

The blood-brain barrier (BBB) is a highly controlled microenvironment that regulates the interactions between cerebral blood and brain tissue. Due to its selectivity, many therapeutics targeting various neurological disorders are not able to penetrate into brain tissue. Pre-clinical studies using animals and other in vitro platforms have not shown the ability to fully replicate the human BBB leading to the failure of a majority of therapeutics in clinical trials. However, recent innovations in vitro and ex vivo modeling called organs-on-chips have shown the potential to create more accurate disease models for improved drug development. These microfluidic platforms induce physiological stressors on cultured cells and are able to generate more physiologically accurate BBBs compared to previous in vitro models. In this review, different approaches to create BBBs-on-chips are explored alongside their application in modeling various neurological disorders and potential therapeutic efficacy. Additionally, organs-on-chips use in BBB drug delivery studies is discussed, and advances in linking brain organs-on-chips onto multiorgan platforms to mimic organ crosstalk are reviewed.

Plasma VEGFA and PGF impact longitudinal tau and cognition in preclinical Alzheimer's disease

Vascular dysfunction is increasingly recognized as an important contributor to the pathogenesis of Alzheimer's disease. Alterations in vascular endothelial growth factor (VEGF) pathways have been implicated as potential mechanisms. However, the specific impact of VEGF proteins in preclinical Alzheimer's disease and their relationships with other Alzheimer's disease and vascular pathologies during this critical early period remain to be elucidated. We included 317 older adults from the Harvard Aging Brain Study, a cohort of individuals who were cognitively unimpaired at baseline and followed longitudinally for up to 12 years. Baseline VEGF family protein levels (VEGFA, VEGFC, VEGFD, PGF and FLT1) were measured in fasting plasma using high-sensitivity immunoassays. Using linear mixed effects models, we examined the interactive effects of baseline plasma VEGF proteins and amyloid PET burden (Pittsburgh Compound-B) on longitudinal cognition (Preclinical Alzheimer Cognitive Composite-5). We further investigated if effects on cognition were mediated by early neocortical tau accumulation (flortaucipir PET burden in the inferior temporal cortex) or hippocampal atrophy. Lastly, we examined the impact of adjusting for baseline cardiovascular risk score or white matter hyperintensity volume. Baseline plasma VEGFA and PGF each showed a significant interaction with amyloid burden on prospective cognitive decline. Specifically, low VEGFA and high PGF were associated with greater cognitive decline in individuals with elevated amyloid, i.e. those on the Alzheimer's disease continuum. Concordantly, low VEGFA and high PGF were associated with accelerated longitudinal tau accumulation in those with elevated amyloid. Moderated mediation analyses confirmed that accelerated tau accumulation fully mediated the effects of low VEGFA and partially mediated (31%) the effects of high PGF on faster amyloid-related cognitive decline. The effects of VEGFA and PGF on tau and cognition remained significant after adjusting for cardiovascular risk score or white matter hyperintensity volume. There were concordant but non-significant associations with longitudinal hippocampal atrophy. Together, our findings implicate low VEGFA and high PGF in accelerating early neocortical tau pathology and cognitive decline in preclinical Alzheimer's disease. Additionally, our results underscore the potential of these minimally-invasive plasma biomarkers to inform the risk of Alzheimer's disease progression in the preclinical population. Importantly, VEGFA and PGF appear to capture distinct effects from vascular risks and cerebrovascular injury. This highlights their potential as new therapeutic targets, in combination with anti-amyloid and traditional vascular risk reduction therapies, to slow the trajectory of preclinical Alzheimer's disease and delay or prevent the onset of cognitive decline.

Is white matter hyperintensity burden associated with cognitive and motor impairment in patients with parkinson's disease? A systematic review and meta-analysis

White matter damage quantified as white matter hyperintensities (WMH) may aggravate cognitive and motor impairments, but whether and how WMH burden impacts these problems in Parkinson's disease (PD) is not fully understood. This study aimed to examine the association between WMH and cognitive and motor performance in PD through a systematic review and meta-analysis. We compared the WMH burden across the cognitive spectrum (cognitively normal, mild cognitive impairment, dementia) in PD including controls. Motor signs were compared in PD with low/negative and high/positive WMH burden. We compared baseline WMH burden of PD who did and did not convert to MCI or dementia. MEDLINE and EMBASE databases were used to conduct the literature search resulting in 50 studies included for data extraction. Increased WMH burden was found in individuals with PD compared with individuals without PD (i.e. control) and across the cognitive spectrum in PD (i.e. PD, PD-MCI, PDD). Individuals with PD with high/positive WMH burden had worse global cognition, executive function, and attention. Similarly, PD with high/positive WMH presented worse motor signs compared with individuals presenting low/negative WMH burden. Only three longitudinal studies were retrieved from our search and they showed that PD who converted to MCI or dementia, did not have significantly higher WMH burden at baseline, although no data was provided on WMH burden changes during the follow up. We conclude, based on cross-sectional studies, that WMH burden appears to increase with PD worse cognitive and motor status in PD.

Brain microvascular endothelial cell metabolism and its ties to barrier function

Brain microvascular endothelial cells, which lie at the interface between blood and brain, are critical to brain energetics. These cells must precisely balance metabolizing nutrients for their own demands with transporting nutrients into the brain to sustain parenchymal cells. It is essential to understand this integrated metabolism and transport so that we can develop better diagnostics and therapeutics for neurodegenerative diseases such as Alzheimer's disease, multiple sclerosis, and traumatic brain injury. In this chapter, we first describe brain microvascular endothelial cell metabolism and how these cells regulate both blood flow and nutrient transport. We then explain the impact of brain microvascular endothelial cell metabolism on the integrity of the blood-brain barrier, as well as how metabolites produced by the endothelial cells impact other brain cells. We detail some ways that cell metabolism is typically measured experimentally and modeled computationally. Finally, we describe changes in brain microvascular endothelial cell metabolism in aging and neurodegenerative diseases. At the end of the chapter, we highlight areas for future research in brain microvascular endothelial cell metabolism. The goal of this chapter is to underscore the importance of nutrient metabolism and transport at the brain endothelium for cerebral health and neurovascular disease treatment.

IL-8 (CXCL8) Correlations with Psychoneuroimmunological Processes and Neuropsychiatric Conditions

Interleukin-8 (IL-8/CXCL8), an essential CXC chemokine, significantly influences psychoneuroimmunological processes and affects neurological and psychiatric health. It exerts a profound effect on immune cell activation and brain function, suggesting potential roles in both neuroprotection and neuroinflammation. IL-8 production is stimulated by several factors, including reactive oxygen species (ROS) known to promote inflammation and disease progression. Additionally, CXCL8 gene polymorphisms can alter IL-8 production, leading to potential differences in disease susceptibility, progression, and severity across populations. IL-8 levels vary among neuropsychiatric conditions, demonstrating sensitivity to psychosocial stressors and disease severity. IL-8 can be detected in blood circulation, cerebrospinal fluid (CSF), and urine, making it a promising candidate for a broad-spectrum biomarker. This review highlights the need for further research on the diverse effects of IL-8 and the associated implications for personalized medicine. A thorough understanding of its complex role could lead to the development of more effective and personalized treatment strategies for neuropsychiatric conditions.

Cerebrospinal fluid/serum albumin ratio in patients with Lewy body disease: a systematic review and meta-analysis

Background

Abnormal cerebrospinal fluid (CSF)/serum albumin ratio (Qalb) levels have been observed in patients with cognitive impairment. Few studies have specifically focused on Lewy Body Disease (LBD), and the results were controversial. Thus, we conducted this systematic review and meta-analysis to investigate Qalb levels in patients with LBD by including data from different studies.

Method

We systematically searched PubMed, Embase, Cochrane Library, and Web of Science databases for a collection of studies containing studies comparing Qalb levels in patients with LBD and healthy controls (including healthy controls and other dementia subtypes). In the initial search, 86 relevant papers were retrieved. Standardized mean differences (SMD) in Qalb levels were calculated using a random effects model.

Results

A total of 13 eligible studies were included. Mean Qalb levels were significantly higher in patients with LBD compared to healthy older adults [standardized mean difference (SMD): 2.95, 95% confidence interval (CI): 0.89-5.00, Z = 2.81, p = 0.005]; and were significantly higher in patients with LBD than in patients with Alzheimer's disease (AD) (SMD: 1.13, 95% CI: 0.42-1.83, Z = 3.15, p = 0.002);whereas mean Qalb levels were significantly higher in patients with frontotemporal lobar degeneration (FTLD) compared to those with AD (SMD: 1.13, 95% CI,0.14-2.13, Z = 2.24, p = 0.03).

Conclusion

Qalb levels were significantly elevated in LBD patients compared with normal older adults and were higher than those in AD patients and FTLD patients, which helped in the differential diagnosis of LBD from other neurodegenerative diseases.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024496616.

Amyloid-β and Phosphorylated Tau are the Key Biomarkers and Predictors of Alzheimer's Disease

Alzheimer's disease (AD) is a age-related neurodegenerative disease and is a major public health concern both in Texas, US and Worldwide. This neurodegenerative disease is mainly characterized by amyloid-beta (Aβ) and phosphorylated Tau (p-Tau) accumulation in the brains of patients with AD and increasing evidence suggests that these are key biomarkers in AD. Both Aβ and p-tau can be detected through various imaging techniques (such as positron emission tomography, PET) and cerebrospinal fluid (CSF) analysis. The presence of these biomarkers in individuals, who are asymptomatic or have mild cognitive impairment can indicate an increased risk of developing AD in the future. Furthermore, the combination of Aβ and p-tau biomarkers is often used for more accurate diagnosis and prediction of AD progression. Along with AD being a neurodegenerative disease, it is associated with other chronic conditions such as cardiovascular disease, obesity, depression, and diabetes because studies have shown that these comorbid conditions make people more vulnerable to AD. In the first part of this review, we discuss that biofluid-based biomarkers such as Aβ, p-Tau in cerebrospinal fluid (CSF) and Aβ & p-Tau in plasma could be used as an alternative sensitive technique to diagnose AD. In the second part, we discuss the underlying molecular mechanisms of chronic conditions linked with AD and how they affect the patients in clinical care.

Blood-brain barrier biomarkers

The blood-brain barrier (BBB) is a dynamic interface that regulates the exchange of molecules and cells between the brain parenchyma and the peripheral blood. The BBB is mainly composed of endothelial cells, astrocytes and pericytes. The integrity of this structure is essential for maintaining brain and spinal cord homeostasis and protection from injury or disease. However, in various neurological disorders, such as traumatic brain injury, Alzheimer's disease, and multiple sclerosis, the BBB can become compromised thus allowing passage of molecules and cells in and out of the central nervous system parenchyma. These agents, however, can serve as biomarkers of BBB permeability and neuronal damage, and provide valuable information for diagnosis, prognosis and treatment. Herein, we provide an overview of the BBB and changes due to aging, and summarize current knowledge on biomarkers of BBB disruption and neurodegeneration, including permeability, cellular, molecular and imaging biomarkers. We also discuss the challenges and opportunities for developing a biomarker toolkit that can reliably assess the BBB in physiologic and pathophysiologic states.

Transient Receptor Potential Channels in the Healthy and Diseased Blood-Brain Barrier

The large family of transient receptor potential (TRP) channels are integral membrane proteins that function as environmental sensors and act as ion channels after activation by mechanical (touch), physical (heat, pain), and chemical stimuli (pungent compounds such as capsaicin). Most TRP channels are localized in the plasma membrane of cells but some of them are localized in membranes of organelles and function as intracellular Ca2+-ion channels. TRP channels are involved in neurological disorders but their precise role(s) and relevance in these disorders are not clear. Endothelial cells of the blood-brain barrier (BBB) express TRP channels such as TRP vanilloid 1-4 and are involved in thermal detection by regulating BBB permeability. In neurological disorders, TRP channels in the BBB are responsible for edema formation in the brain. Therefore, drug design to modulate locally activity of TRP channels in the BBB is a hot topic. Today, the application of TRP channel antagonists against neurological disorders is still limited.

6PPD-quinone exposure induces neuronal mitochondrial dysfunction to exacerbate Lewy neurites formation induced by α-synuclein preformed fibrils seeding

The emerging toxicant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q) is of wide concern due to its ubiquitous occurrence and high toxicity. Despite regular human exposure, limited evidence exists about its presence in the body and potential health risks. Herein, we analyzed cerebrospinal fluid (CSF) samples from Parkinson's disease (PD) patients and controls. The CSF levels of 6PPD-Q were twice as high in PD patients compared to controls. Immunostaining assays performed with primary dopaminergic neurons confirm that 6PPD-Q at environmentally relevant concentrations can exacerbate the formation of Lewy neurites induced by α-synuclein preformed fibrils (α-syn PFF). Assessment of cellular respiration reveals a considerable decrease in neuronal spare respiratory and ATP-linked respiration, potentially due to changes in mitochondrial membrane potential. Moreover, 6PPD-Q-induced mitochondrial impairment correlates with an upsurge in mitochondrial reactive oxygen species (mROS), and Mito-TEMPO-driven scavenging of mROS can lessen the amount of pathologic phospho-serine 129 α-synuclein. Untargeted metabolomics provides supporting evidence for the connection between 6PPD-Q exposure and changes in neuronal metabolite profiles. In-depth targeted metabolomics further unveils an overall reduction in glycolysis metabolite pool and fluctuations in the quantity of TCA cycle intermediates. Given its potentially harmful attributes, the presence of 6PPD-Q in human brain could potentially be a risk factor for PD.

Potential Impact of Hypoxic Astrocytes on the Aggravation of Depressive Symptoms in Parkinson's Disease

Mounting evidence suggests a significant correlation between depressive disorders and neurodegenerative conditions, encompassing Alzheimer's disease and Parkinson's disease (PD). Depression represents a substantial non-motor manifestation frequently identified in individuals with PD, posing a significant threat to patients' overall well-being and necessitating the implementation of effective management strategies. Despite its high prevalence, impacting over 40% of PD patients, the precise cellular and molecular mechanisms underlying depression and its relationship to dopaminergic system degeneration remain largely ambiguous. In this study, we presented our findings demonstrating distinct characteristics of cortical astrocytes in PD patients compared to reactivated glial cells in the substantia nigra. We identified a subset of differentially expressed genes associated with depressive disorders from PD-associated cortical astrocytes. Furthermore, we uncovered the potential involvement of the hypoxia signaling in driving cortical astrocytic dysfunctions. Through a comprehensive investigation utilizing transcriptome and chromatin accessibility analyses on cultured human astrocytes, we revealed that hypoxic treatment could induce similar expression changes observed in cortex from PD patients. Additionally, we provided evidence that activation of the HIF-1 signaling pathway suppressed the expression of key components of mitochondrial ribosomes and electron transport chain proteins COX2 and CYTB, resulting in abnormal mitochondrial membrane potential. Our results underscore the potential impact of glial metabolic abnormalities on the development of depressive disorders associated with Parkinson's disease.

The VEGFs/VEGFRs system in Alzheimer's and Parkinson's diseases: Pathophysiological roles and therapeutic implications

The vascular endothelial growth factors (VEGFs) and their cognate receptors (VEGFRs), besides their well-known involvement in physiological angiogenesis/lymphangiogenesis and in diseases associated to pathological vessel formation, play multifaceted functions in the central nervous system (CNS). In addition to shaping brain development, by controlling cerebral vasculogenesis and regulating neurogenesis as well as astrocyte differentiation, the VEGFs/VEGFRs axis exerts essential functions in the adult brain both in physiological and pathological contexts. In this article, after describing the physiological VEGFs/VEGFRs functions in the CNS, we focus on the VEGFs/VEGFRs involvement in neurodegenerative diseases by reviewing the current literature on the rather complex VEGFs/VEGFRs contribution to the pathogenic mechanisms of Alzheimer's (AD) and Parkinson's (PD) diseases. Thereafter, based on the outcome of VEGFs/VEGFRs targeting in animal models of AD and PD, we discuss the factual relevance of pharmacological VEGFs/VEGFRs modulation as a novel and potential disease-modifying approach for these neurodegenerative pathologies. Specific VEGFRs targeting, aimed at selective VEGFR-1 inhibition, while preserving VEGFR-2 signal transduction, appears as a promising strategy to hit the molecular mechanisms underlying AD pathology. Moreover, therapeutic VEGFs-based approaches can be proposed for PD treatment, with the aim of fine-tuning their brain levels to amplify neurotrophic/neuroprotective effects while limiting an excessive impact on vascular permeability.

Neurovascular coupling alteration in drug-naïve Parkinson's disease: The underlying molecular mechanisms and levodopa's restoration effects

BACKGROUND

Parkinson's disease (PD) patients exhibit an imbalance between neuronal activity and perfusion, referred to as abnormal neurovascular coupling (NVC). Nevertheless, the underlying molecular mechanism and how levodopa, the standard treatment in PD, regulates NVC is largely unknown.

MATERIAL AND METHODS

A total of 52 drug-naïve PD patients and 49 normal controls (NCs) were enrolled. NVC was characterized in vivo by relating cerebral blood flow (CBF) and amplitude of low-frequency fluctuations (ALFF). Motor assessments and MRI scanning were conducted on drug-naïve patients before and after levodopa therapy (OFF/ON state). Regional NVC differences between patients and NCs were identified, followed by an assessment of the associated receptors/transporters. The influence of levodopa on NVC, CBF, and ALFF within these abnormal regions was analyzed.

RESULTS

Compared to NCs, OFF-state patients showed NVC dysfunction in significantly lower NVC in left precentral, postcentral, superior parietal cortex, and precuneus, along with higher NVC in left anterior cingulate cortex, right olfactory cortex, thalamus, caudate, and putamen (P-value <0.0006). The distribution of NVC differences correlated with the density of dopaminergic, serotonin, MU-opioid, and cholinergic receptors/transporters. Additionally, levodopa ameliorated abnormal NVC in most of these regions, where there were primarily ALFF changes with limited CBF modifications.

CONCLUSION

Patients exhibited NVC dysfunction primarily in the striato-thalamo-cortical circuit and motor control regions, which could be driven by dopaminergic and nondopaminergic systems, and levodopa therapy mainly restored abnormal NVC by modulating neuronal activity.

Serum Placental Growth Factor as a Marker of Cerebrovascular Disease Burden in Alzheimer's Disease

BACKGROUND

Concomitant cerebrovascular diseases (CeVD) have been identified as an important determinant of Alzheimer's disease (AD) progression. Development of robust blood-based biomarkers will provide critical tools to evaluate prognosis and potential interventional strategies for AD with CeVD.

OBJECTIVE

This study investigated circulating placental growth factor (PlGF), a potent pro-angiogenic factor related to endothelial dysfunction and vascular inflammation, in an Asian memory clinic cohort of non-demented individuals as well as AD, including its associations with neuroimaging markers of CeVD.

METHODS

109 patients with AD, 76 cognitively impaired with no dementia (CIND), and 56 non-cognitively impaired (NCI) were included in this cross-sectional study. All subjects underwent 3T brain magnetic resonance imaging to assess white matter hyperintensities (WMH), lacunes, cortical infarcts, and cerebral microbleeds (CMBs). Serum PlGF concentrations were measured by electrochemiluminescence immunoassays.

RESULTS

Serum PlGF was elevated in AD, but not CIND, compared to the NCI controls. Adjusted concentrations of PlGF were associated with AD only in the presence of significant CeVD. Elevated PlGF was significantly associated with higher burden of WMH and with CMBs in AD patients.

CONCLUSIONS

Serum PlGF has potential utility as a biomarker for the presence of CeVD, specifically WMH and CMBs, in AD. Further studies are needed to elucidate the underlying pathophysiological mechanisms linking PlGF to CeVD, as well as to further assess PlGF's clinical utility.

Impaired neuronal activity as a potential factor contributing to the underdeveloped cerebrovasculature in a young Parkinson's disease mouse model

Misfolding of α-synuclein (α-Syn) in the brain causes cellular dysfunction, leading to cell death in a group of neurons, and consequently causes the progression of Parkinson's disease (PD). Although many studies have demonstrated the pathological connections between vascular dysfunction and neurodegenerative diseases, it remains unclear how neuronal accumulation of α-Syn affects the structural and functional aspects of the cerebrovasculature to accelerate early disease progression. Here, we demonstrated the effect of aberrant α-Syn expression on the brain vasculature using a PD mouse model expressing a familial mutant form of human α-Syn selectively in neuronal cells. We showed that young PD mice have an underdeveloped cerebrovasculature without significant α-Syn accumulation in the vasculature. During the early phase of PD, toxic α-Syn was selectively increased in neuronal cells, while endothelial cell proliferation was decreased in the absence of vascular cell death or neuroinflammation. Instead, we observed altered neuronal activation and minor changes in the activity-dependent gene expression in brain endothelial cells (ECs) in young PD mice. These findings demonstrated that neuronal expression of mutant α-Syn in the early stage of PD induces abnormal neuronal activity and contributes to vascular patterning defects, which could be associated with a reduced angiogenic potential of ECs.

Imaging of Angiogenesis in White Matter Hyperintensities

Background White matter hyperintensities (WMHs) are areas of increased signal intensity on T2-weighted magnetic resonance imaging (MRI). WMH penumbra may be a potential target for early intervention in WMHs. We explored the relationship between angiogenesis and WMH penumbra in patients with WMHs. Methods and Results Twenty-one patients with confluent WMHs of Fazekas grade ≥2 were included. All the participants underwent 68Ga-NOTA-PRGD2 positron emission tomography/magnetic resonance imaging. WMH penumbra was analyzed with masks created for the WMH and 7 normal-appearing white matter layers; each layer was dilated away from the WMH by 2 mm. Angiogenesis array and ELISA were used to detect the serum levels of angiogenic factors, inflammatory factors, HIF-1 alpha, and S100B. Fourteen patients with increased 68Ga-NOTA-PRGD2 maximum standardized uptake (>0.17) were classified into group 2. Seven patients with maximum standardized uptake ≤0.17 were classified as group 1. WMH volume and serum levels of integrin αvβ3, vascular endothelial growth factor receptor 22, and interleukin-1β tended to be higher in group 2 than in group 1. In group 2, 68Ga-NOTA-PRGD2 uptake was significantly increased at the border between the WMH and normal-appearing white matter than in WMHs (P=0.004). The structure penumbra, defined by fractional anisotropy, was wider in group 2 (8 mm) than in group 1 (2 mm). The cerebral blood flow penumbra was 12 mm in both groups. Angiogenesis showed a correlation with reduced cerebral blood flow and microstructure integrity. Conclusions Our study provides evidence that angiogenesis occurs in the WMH penumbra. Further studies are warranted to verify the effect of angiogenesis on WMH growth.

Subthalamic deep brain stimulation improves vascular endothelial function in Parkinson's disease

OBJECTIVES

Vascular health (white matter change, vascular risk factor, angiogenesis, microvascular alteration) is associated with clinical progression or levodopa-induced dyskinesia in PD. Vascular endothelial function is known to reflect the earliest vascular change. While DBS can improve motor and non-motor symptoms, the effect of DBS on vascular endothelial function is unknown. Thus, we aimed to investigate whether DBS surgery could impact vascular endothelial function in PD.

METHOD

A total of 20 PD patients were recruited. Vascular endothelial function was evaluated with flow-mediated dilation (FMD). FMD was investigated before and after one year of DBS surgery.

RESULTS

FMD improved (6.01 ± 1.58 to 6.84 ± 1.57, p = 0.027). While the level of homocysteine slightly decreased (13.8 ± 4.1 to 13.0 ± 3.2, p = 0.05), there was no significant correlation between FMD changes and homocysteine levels (r = 0.42, p = 0.065). FMD change was associated with baseline age (r = -0.59, p = 0.006) but not with disease duration (p = 0.73), baseline UPDRS III (p = 0.81), change of UPDRS III and dyskinesia, and LEDD change (p = 0.94). Multivariate linear regression analysis revealed that only age (B = -0.139; p = 0.024) was significantly and inversely correlated with the change of FMD.

CONCLUSIONS

We found that STN-DBS improves vascular endothelial function in PD. Further studies are needed to clarify the exact pathogenesis and clinical implication of beneficial effects on vascular endothelial dysfunction in PD.

Choroid plexus mis-splicing and altered cerebrospinal fluid composition in myotonic dystrophy type 1

Myotonic dystrophy type 1 is a dominantly inherited multisystemic disease caused by CTG tandem repeat expansions in the DMPK 3' untranslated region. These expanded repeats are transcribed and produce toxic CUG RNAs that sequester and inhibit activities of the MBNL family of developmental RNA processing factors. Although myotonic dystrophy is classified as a muscular dystrophy, the brain is also severely affected by an unusual cohort of symptoms, including hypersomnia, executive dysfunction, as well as early onsets of tau/MAPT pathology and cerebral atrophy. To address the molecular and cellular events that lead to these pathological outcomes, we recently generated a mouse Dmpk CTG expansion knock-in model and identified choroid plexus epithelial cells as particularly affected by the expression of toxic CUG expansion RNAs. To determine if toxic CUG RNAs perturb choroid plexus functions, alternative splicing analysis was performed on lateral and hindbrain choroid plexi from Dmpk CTG knock-in mice. Choroid plexus transcriptome-wide changes were evaluated in Mbnl2 knockout mice, a developmental-onset model of myotonic dystrophy brain dysfunction. To determine if transcriptome changes also occurred in the human disease, we obtained post-mortem choroid plexus for RNA-seq from neurologically unaffected (two females, three males; ages 50-70 years) and myotonic dystrophy type 1 (one female, three males; ages 50-70 years) donors. To test that choroid plexus transcriptome alterations resulted in altered CSF composition, we obtained CSF via lumbar puncture from patients with myotonic dystrophy type 1 (five females, five males; ages 35-55 years) and non-myotonic dystrophy patients (three females, four males; ages 26-51 years), and western blot and osmolarity analyses were used to test CSF alterations predicted by choroid plexus transcriptome analysis. We determined that CUG RNA induced toxicity was more robust in the lateral choroid plexus of Dmpk CTG knock-in mice due to comparatively higher Dmpk and lower Mbnl RNA levels. Impaired transitions to adult splicing patterns during choroid plexus development were identified in Mbnl2 knockout mice, including mis-splicing previously found in Dmpk CTG knock-in mice. Whole transcriptome analysis of myotonic dystrophy type 1 choroid plexus revealed disease-associated RNA expression and mis-splicing events. Based on these RNA changes, predicted alterations in ion homeostasis, secretory output and CSF composition were confirmed by analysis of myotonic dystrophy type 1 CSF. Our results implicate choroid plexus spliceopathy and concomitant alterations in CSF homeostasis as an unappreciated contributor to myotonic dystrophy type 1 CNS pathogenesis.

Investigation of Inflammation in Lewy Body Dementia: A Systematic Scoping Review

Inflammatory mechanisms are increasingly recognized as important contributors to the pathogenesis of neurodegenerative diseases, including Lewy body dementia (LBD). Our objectives were to, firstly, review inflammation investigation methods in LBD (dementia with Lewy bodies and Parkinson's disease dementia) and, secondly, identify alterations in inflammatory signals in LBD compared to people without neurodegenerative disease and other neurodegenerative diseases. A systematic scoping review was performed by searching major electronic databases (MEDLINE, Embase, Web of Science, and PSYCHInfo) to identify relevant human studies. Of the 2509 results screened, 80 studies were included. Thirty-six studies analyzed postmortem brain tissue, and 44 investigated living subjects with cerebrospinal fluid, blood, and/or brain imaging assessments. Largely cross-sectional data were available, although two longitudinal clinical studies investigated prodromal Lewy body disease. Investigations were focused on inflammatory immune cell activity (microglia, astrocytes, and lymphocytes) and inflammatory molecules (cytokines, etc.). Results of the included studies identified innate and adaptive immune system contributions to inflammation associated with Lewy body pathology and clinical disease features. Different signals in early and late-stage disease, with possible late immune senescence and dystrophic glial cell populations, were identified. The strength of these associations is limited by the varying methodologies, small study sizes, and cross-sectional nature of the data. Longitudinal studies investigating associations with clinical and other biomarker outcomes are needed to improve understanding of inflammatory activity over the course of LBD. This could identify markers of disease activity and support therapeutic development.

Sexually dimorphic differences in angiogenesis markers predict brain aging trajectories

Aberrant angiogenesis could contribute to cognitive impairment, representing a therapeutic target for preventing dementia. However, most angiogenesis studies focus on model organisms. To test the relevance of angiogenesis to human cognitive aging, we evaluated associations of circulating blood markers of angiogenesis with brain aging trajectories in two deeply phenotyped human cohorts (n=435, age 74 + 9) with longitudinal cognitive assessments, biospecimens, structural brain imaging, and clinical data. Machine learning and traditional statistics revealed sex dimorphic associations of plasma angiogenic growth factors with brain aging outcomes. Specifically, angiogenesis is associated with higher executive function and less brain atrophy in younger women (not men), a directionality of association that reverses around age 75. Higher levels of basic fibroblast growth factor, known for pleiotropic effects on multiple cell types, predicted favorable cognitive trajectories. This work demonstrates the relevance of angiogenesis to brain aging with important therapeutic implications for vascular cognitive impairment and dementia.

The contribution of inflammatory astrocytes to BBB impairments in a brain-chip model of Parkinson's disease

Astrocyte dysfunction has previously been linked to multiple neurodegenerative disorders including Parkinson's disease (PD). Among their many roles, astrocytes are mediators of the brain immune response, and astrocyte reactivity is a pathological feature of PD. They are also involved in the formation and maintenance of the blood-brain barrier (BBB), but barrier integrity is compromised in people with PD. This study focuses on an unexplored area of PD pathogenesis by characterizing the interplay between astrocytes, inflammation and BBB integrity, and by combining patient-derived induced pluripotent stem cells with microfluidic technologies to generate a 3D human BBB chip. Here we report that astrocytes derived from female donors harboring the PD-related LRRK2 G2019S mutation are pro-inflammatory and fail to support the formation of a functional capillary in vitro. We show that inhibition of MEK1/2 signaling attenuates the inflammatory profile of mutant astrocytes and rescues BBB formation, providing insights into mechanisms regulating barrier integrity in PD. Lastly, we confirm that vascular changes are also observed in the human postmortem substantia nigra of both males and females with PD.

Pazopanib alleviates neuroinflammation and protects dopaminergic neurons in LPS-stimulated mouse model by inhibiting MEK4-JNK-AP-1 pathway

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by the loss of dopaminergic (DA) neurons and the accumulation of Lewy bodies (LB) in the substantia nigra (SN). Evidence shows that microglia-mediated neuroinflammation plays a key role in PD pathogenesis. Using TNF-α as an indicator for microglial activation, we established a cellular model to screen compounds that could inhibit neuroinflammation. From 2471 compounds in a small molecular compound library composed of FDA-approved drugs, we found 77 candidates with a significant anti-inflammatory effect. In this study, we further characterized pazopanib, a pan-VEGF receptor tyrosine kinase inhibitor (that was approved by the FDA for the treatment of advanced renal cell carcinoma and advanced soft tissue sarcoma). We showed that pretreatment with pazopanib (1, 5, 10 μM) dose-dependently suppressed LPS-induced BV2 cell activation evidenced by inhibiting the transcription of proinflammatory factors iNOS, COX2, Il-1β, and Il-6 through the MEK4-JNK-AP-1 pathway. The conditioned medium from LPS-treated microglia caused mouse DA neuronal MES23.5 cell damage, which was greatly attenuated by pretreatment of the microglia with pazopanib. We established an LPS-stimulated mouse model by stereotactic injection of LPS into mouse substantia nigra. Administration of pazopanib (10 mg·kg-1·d-1, i.p., for 10 days) exerted significant anti-inflammatory and neuronal protective effects, and improved motor abilities impaired by LPS in the mice. Together, we discover a promising candidate compound for anti-neuroinflammation and provide a potential repositioning of pazopanib in the treatment of PD.

Sex Differences in the Inflammatory Profile in the Brain of Young and Aged Mice

Neurodegenerative diseases are a leading cause of death worldwide with no cures identified. Thus, there is a critical need for preventative measures and treatments as the number of patients is expected to increase. Many neurodegenerative diseases have sex-biased prevalence, indicating a need to examine sex differences when investigating prevention and treatment strategies. Inflammation is a key contributor to many neurodegenerative diseases and is a promising target for prevention since inflammation increases with age, which is known as inflammaging. Here, we analyzed the protein expression levels of cytokines, chemokines, and inflammasome signaling proteins in the cortex of young and aged male and female mice. Our results show an increase in caspase-1, interleukin (IL)-1β, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and ASC specks in females compared to males. Additionally, there was an increase in IL-1α, VEGF-A, CCL3, CXCL1, CCL4, CCL17, and CCL22 in aging females and an increase in IL-8, IL-17a, IL-7, LT-α, and CCL22 in aging males. IL-12/IL-23p40, CCL13, and IL-10 were increased in females compared to males but not with age. These results indicate that there are sex differences in cortical inflammaging and provide potential targets to attenuate inflammation to prevent the development of neurodegenerative disease.

Associations Between CSF Markers of Inflammation, White Matter Lesions, and Cognitive Decline in Individuals Without Dementia

BACKGROUND AND OBJECTIVES

Small vessel disease (SVD) and neuroinflammation both occur in Alzheimer disease (AD) and other neurodegenerative diseases. It is unclear whether these processes are related or independent mechanisms in AD, especially in the early stages of disease. We therefore investigated the association between white matter lesions (WML; the most common manifestation of SVD) and CSF biomarkers of neuroinflammation and their effects on cognition in a population without dementia.

METHODS

Individuals without dementia from the Swedish BioFINDER study were included. The CSF was analyzed for proinflammatory markers (interleukin [IL]-6 and IL-8), cytokines (IL-7, IL-15, and IL-16), chemokines (interferon γ-induced protein 10, monocyte chemoattractant protein 1), markers of vascular injury (soluble intercellular adhesion molecule 1, soluble vascular adhesion molecule 1), and markers of angiogenesis (placental growth factor [PlGF], soluble fms-related tyrosine kinase 1 [sFlt-1], vascular endothelial growth factors [VEGF-A and VEFG-D]), and amyloid β (Aβ)42 Aβ40, and p-tau217. WML volumes were determined at baseline and longitudinally over 6 years. Cognition was measured at baseline and follow-up over 8 years. Linear regression models were used to test associations.

RESULTS

A total of 495 cognitively unimpaired (CU) elderly individuals and 247 patients with mild cognitive impairment (MCI) were included. There was significant worsening in cognition over time, measured by Mini-Mental State Examination, Clinical Dementia Rating, and modified preclinical Alzheimer composite score in CU individuals and patients with MCI, with more rapid worsening in MCI for all cognitive tests. At baseline, higher levels of PlGF (β = 0.156, p < 0.001), lower levels of sFlt-1 (β = -0.086, p = 0.003), and higher levels of IL-8 (β = 0.07, p = 0.030) were associated with more WML in CU individuals. In those with MCI, higher levels of PlGF (β = 0.172, p = 0.001), IL-16 (β = 0.125, p = 0.001), IL-8 (β = 0.096, p = 0.013), IL-6 (β = 0.088, p = 0.023), VEGF-A (β = 0.068, p = 0.028), and VEGF-D (β = 0.082, p = 0.028) were associated with more WML. PlGF was the only biomarker that was associated with WML independent of Aβ status and cognitive impairment. Longitudinal analyses of cognition showed independent effects of CSF inflammatory markers and WML on longitudinal cognition, especially in people without cognitive impairment at baseline.

DISCUSSION

Most neuroinflammatory CSF biomarkers were associated with WML in individuals without dementia. Our findings especially highlight a role for PlGF, which was associated with WML independent of Aβ status and cognitive impairment.

Molecules of senescent glial cells differentiate Alzheimer's disease from ageing

BACKGROUND

Ageing is a major risk factor for Alzheimer's disease (AD), which is accompanied by cellular senescence and thousands of transcriptional changes in the brain.

OBJECTIVES

To identify the biomarkers in the cerebrospinal fluid (CSF) that could help differentiate healthy ageing from neurodegenerative processes.

METHODS

Cellular senescence and ageing-related biomarkers were assessed in primary astrocytes and postmortem brains by immunoblotting and immunohistochemistry. The biomarkers were measured in CSF samples from the China Ageing and Neurodegenerative Disorder Initiative cohort using Elisa and the multiplex Luminex platform.

RESULTS

The cyclin-dependent kinase inhibitors p16/p21-positive senescent cells in human postmortem brains were predominantly astrocytes and oligodendrocyte lineage cells, which accumulated in AD brains. CCL2, YKL-40, HGF, MIF, S100B, TSP2, LCN2 and serpinA3 are biomarkers closely related to human glial senescence. Moreover, we discovered that most of these molecules, which were upregulated in senescent glial cells, were significantly elevated in the AD brain. Notably, CSF YKL-40 (β=0.5412, p<0.0001) levels were markedly elevated with age in healthy older individuals, whereas HGF (β=0.2732, p=0.0001), MIF (β=0.33714, p=0.0017) and TSP2 (β=0.1996, p=0.0297) levels were more susceptible to age in older individuals with AD pathology. We revealed that YKL-40, TSP2 and serpinA3 were useful biomarkers for discriminating patients with AD from CN individuals and non-AD patients.

DISCUSSION

Our findings demonstrated the different patterns of CSF biomarkers related to senescent glial cells between normal ageing and AD, implicating these biomarkers could identify the road node in healthy path off to neurodegeneration and improve the accuracy of clinical AD diagnosis, which would help promote healthy ageing.

The effect of levodopa treatment on vascular endothelial function in Parkinson's disease

OBJECTIVE

There has been increasing awareness that micro-vascular alteration or vascular inflammation has been associated with levodopa-induced dyskinesia in PD. Vascular endothelial function assessed by flow mediated dilation (FMD) is known to reflect early microvascular change. We compare the impact of levodopa or dopamine agonist treatment on the change of FMD in de novo PD patients.

METHODS

This retrospective study used a selected sample from registry. We identified de-novo PD patients who underwent FMD at baseline, and follow-up FMD after 1 year (± 2 month) of levodopa (n = 18) or dopamine agonist (n = 18) treatment.

RESULTS

FMD decreased after levodopa (8.60 ± 0.46 to 7.21 ± 0.4, p = 0.002) but there were no significant changes after DA treatment (8.33 ± 0.38 to 8.22 ± 0.33, p = 0.26). Homocysteine rose (11.52 ± 0.45 to 14.33 ± 0.68, p < 0.05) during levodopa treatment, but dopamine agonist had no effect (10.59 ± 0.38 to 11.38 ± 0.67, p = 0.184). Correlation analysis revealed that the changes in homocysteine level had non-significant correlation with FMD change (r =  - 0.30, p = 0.06). FMD change was not associated with age (p = 0.47), disease duration (p = 0.81), baseline motor UPDRS (p = 0.43), motor UPDRS change (p = 0.64), levodopa equivalent dose change (p = 0.65).

CONCLUSIONS

We found that 1-year levodopa treatment may adversely affect vascular endothelial function in de novo PD. Further studies are needed to clarify the exact pathogenesis and clinical implication of levodopa-induced endothelial dysfunction in PD.

HMGB1 is a Potential and Challenging Therapeutic Target for Parkinson's Disease

Parkinson's disease (PD) is one of the most common degenerative diseases of the human nervous system and has a wide range of serious impacts on human health and quality of life. Recently, research targeting high mobility group box 1 (HMGB1) in PD has emerged, and a variety of laboratory methods for inhibiting HMGB1 have achieved good results to a certain extent. However, given that HMGB1 undergoes a variety of intracellular modifications and three different forms of extracellular redox, the possible roles of these forms in PD are likely to be different. General inhibition of all forms of HMGB1 is obviously not ideal and has become one of the biggest obstacles in the clinical application of targeting HMGB1. In this review, pure mechanistic research of HMGB1 and in vivo research targeting HMGB1 were combined, the effects of HMGB1 on neurons and immune cell responses in PD are discussed in detail, and the problems that need to be focused on in the future are addressed.

Blood-brain barrier endothelial cells in neurodegenerative diseases: Signals from the "barrier"

As blood-brain barrier (BBB) disruption emerges as a common problem in the early stages of neurodegenerative diseases, the crucial roles of barrier-type brain endothelial cells (BECs), the primary part of the BBB, have been reported in the pathophysiology of neurodegenerative diseases. The mechanisms of how early vascular dysfunction contributes to the progress of neurodegeneration are still unclear, and understanding BEC functions is a promising start. Our understanding of the BBB has gone through different stages, from a passive diffusion barrier to a mediator of central-peripheral interactions. BECs serve two seemingly paradoxical roles: as a barrier to protect the delicate brain from toxins and as an interface to constantly receive and release signals, thus maintaining and regulating the homeostasis of the brain. Most previous studies about neurodegenerative diseases focus on the loss of barrier functions, and far too little attention has been paid to the active regulations of BECs. In this review, we present the current evidence of BEC dysfunction in neurodegenerative diseases and explore how BEC signals participate in the pathogenesis of neurodegenerative diseases.

The Blood-Brain Barrier in Neuroimmune Interactions and Pathological Processes

The blood-brain barrier (BBB) is a kind of filter, highly selective in relation to various types of substances. The BBB supports the immune status of the brain and is an important regulator of neuroimmune interactions. Some of the molecular and cellular features of the BBB, as well as the five main pathways of neuroimmune communication mediated by the BBB, are analyzed in this article. The functions of the BBB in neuroimmune interactions in various diseases are discussed: multiple sclerosis and Alzheimer's and Parkinson's diseases. The latest data on BBB dysfunction in COVID-19 coronavirus infection caused by the SARS-CoV-2 virus are considered.

Age-Related Adaptive Immune Changes in Parkinson’s Disease

Ageing is a major risk factor for most neurodegenerative diseases, including Parkinson’s disease (PD). Progressive age-related dysregulation of the immune system is termed immunosenescence and is responsible for the weakened response to novel antigens, increased susceptibility to infections and reduced effectiveness of vaccines seen in the elderly. Immune activation, both within the brain and periphery, is heavily implicated in PD but the role of immunosenescence has not been fully explored. Studies to date provide some evidence for an attenuation in immunosenescence in PD, particularly a reduction in senescent CD8 T lymphocytes in PD cases compared to similarly aged controls. Here, we discuss recent evidence of age-related immune abnormalities in PD with a focus on T cell senescence and explore their potential role in disease pathogenesis and development.

Biofluid markers of blood-brain barrier disruption and neurodegeneration in Lewy body spectrum diseases: A systematic review and meta-analysis

BACKGROUND

Mixed evidence supports blood-brain barrier (BBB) dysfunction in Lewy body spectrum diseases.

METHODS

We compare biofluid markers in people with idiopathic Parkinson's disease (PD) and people with PD dementia (PDD) and/or dementia with Lewy bodies (DLB), compared with healthy controls (HC). Seven databases were searched up to May 10, 2021. Outcomes included cerebrospinal fluid to blood albumin ratio (Q_alb), and concentrations of 7 blood protein markers that also reflect BBB disruption and/or neurodegenerative co-pathology. We further explore differences between PD patients with and without evidence of dementia. Random-effects models were used to obtain standardized mean differences (SMD) with 95% confidence interval.

RESULTS

Of 13,949 unique records, 51 studies were meta-analyzed. Compared to HC, Q_alb was higher in PD (N_PD/N_HC = 224/563; SMD = 0.960 [0.227-1.694], p = 0.010; I² = 92.2%) and in PDD/DLB (N_PDD/DLB/N_HC = 265/670; SMD = 1.126 [0.358-1.893], p < 0.001; I² = 78.2%). Blood neurofilament light chain (NfL) was higher in PD (N_PD/N_HC = 1848/1130; SMD = 0.747 [0.442-1.052], p < 0.001; I² = 91.9%) and PDD/DLB (N_PDD/DLB/N_HC = 183/469; SMD = 1.051 [0.678-1.423], p = 0.004; I² = 92.7%) than in HC. p-tau 181 (N_PD/N_HC = 276/164; SMD = 0.698 [0.149-1.247], p = 0.013; I² = 82.7%) was also higher in PD compared to HC. In exploratory analyses, blood NfL was higher in PD without dementia (N_PDND/N_HC = 1005/740; SMD = 0.252 [0.042-0.462], p = 0.018; I² = 71.8%) and higher in PDD (N_PDD/N_HC = 100/111; SMD = 0.780 [0.347-1.214], p < 0.001; I² = 46.7%) compared to HC. Q_alb (N_PDD/N_PDND = 63/191; SMD = 0.482 [0.189-0.774], p = 0.010; I²<0.001%) and NfL (N_PDD/N_PDND = 100/223; SMD = 0.595 [0.346-0.844], p < 0.001; I² = 3.4%) were higher in PDD than in PD without dementia.

CONCLUSIONS

Biofluid markers suggest BBB disruption and neurodegenerative co-pathology involvement in common Lewy body diseases. Greater evidence of BBB breakdown was seen in Lewy body disease with cognitive impairment.

Association of Neurofilament Light With the Development and Severity of Parkinson Disease

BACKGROUND AND OBJECTIVES

Blood biomarkers may allow earlier identification of Parkinson disease (PD), parkinsonism, and poor PD-related outcomes, such as physical functioning. Neurofilament light (NfL), a neuronal cytoplasmic protein, is a biomarker of neurodegeneration measurable in biofluids. Our objective was to examine the association of serum NfL at baseline with clinically diagnosed PD, parkinsonian signs, and physical functioning change over 16 years in a population-based sample of older adults.

METHODS

Data came from 1,327 older participants from the Chicago Health and Aging Project, a longitudinal population-based study. Clinical evaluations included assessing parkinsonian signs in 4 domains-bradykinesia, parkinsonian gait, rigidity, and tremors-using a structured version of the Unified Parkinson's Disease Rating Scale. Board-certified neurologists diagnosed PD. Physical functioning was assessed using chair stands, tandem walk, and timed walk. An ultrasensitive immunoassay was used to measure the concentration of NfL in blood.

RESULTS

Of the 1,254 participants examined for clinical PD, 77 (6.1%) developed clinical PD and parkinsonian signs were on average 9.5 (range 0-66.0). After adjusting for demographic characteristics, APOE ε4 allele, and global cognition, a 2-fold higher concentration of serum NfL was associated with incident clinical PD (odds ratio [OR] 2.54, 95% CI 1.70, 3.81) and global parkinsonian signs (OR 2.44, 95% CI 1.94, 2.94). This association was significant >5 years before diagnosis. Compared with participants with levels below 18.5 pg/mL of serum NfL at baseline, participants with levels between 18.5 and 25.4 pg/mL, between 25.4 and 37.3 pg/mL, and above 37.3 pg/mL had a higher OR of clinical PD at all time intervals from the time of diagnosis to >5 years before diagnosis. A higher concentration of serum NfL was associated with a faster rate of physical functioning decline. In participants with 2-fold higher concentrations of serum NfL, the annual rate of decline in physical functioning increased by 0.15 units (95% CI 0.21, 0.08).

DICUSSION

Serum NfL was associated with incident clinical PD, parkinsonian signs, and physical functioning decline in a population-based sample. Our findings suggest that NfL may serve as a potential biomarker for neurodegeneration, including PD outcomes.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that serum NfL levels are associated with incident PD, parkinsonian signs, and physical functioning decline.

Microvascular Changes in Parkinson’s Disease- Focus on the Neurovascular Unit

Vascular alterations emerge as a common denominator for several neurodegenerative diseases. In Parkinson’s disease (PD), a number of observations have been made suggesting that the occurrence of vascular pathology is an important pathophysiological aspect of the disease. Specifically, pathological activation of pericytes, blood-brain barrier (BBB) disruption, pathological angiogenesis and vascular regression have been reported. This review summarizes the current evidence for the different vascular alterations in patients with PD and in animal models of PD. We suggest a possible sequence of vascular pathology in PD ranging from early pericyte activation and BBB leakage to an attempt for compensatory angiogenesis and finally vascular rarefication. We highlight different pathogenetic mechanisms that play a role in these vascular alterations including perivascular inflammation and concomitant metabolic disease. Awareness of the contribution of vascular events to the pathogenesis of PD may allow the identification of targets to modulate those mechanisms. In particular the BBB has for decades only been viewed as an obstacle for drug delivery, however, preservation of its integrity and/or modulation of the signaling at this interface between the blood and the brain may prove to be a new avenue to take in order to develop disease-modifying strategies for neurodegenerative disorders.

T cells, α-synuclein and Parkinson disease

The notion that autoimmune responses to α-synuclein may be involved in the pathogenesis of this disorder stems from reports that mutations in α-synuclein or certain alleles of the major histocompatibility complex (MHC) are associated with the disease and that dopaminergic and norepinephrinergic neurons in the midbrain can present antigenic epitopes. Here, we discuss recent evidence that a defined set of peptides derived from α-synuclein act as antigenic epitopes displayed by specific MHC alleles and drive helper and cytotoxic T cell responses in patients with PD. Moreover, phosphorylated α-synuclein may activate T cell responses in a less restricted manner in PD. While the roles for the acquired immune system in disease pathogenesis remain unknown, preclinical animal models and in vitro studies indicate that T cells may interact with neurons and exert effects related to neuronal death and neuroprotection. These findings suggest that therapeutics that target T cells and ameliorate the incidence or disease severity of inflammatory bowel disorders or CNS autoimmune diseases such as multiple sclerosis may be useful in PD.

The influence of cerebrovascular disease in dementia with Lewy bodies and Parkinson's disease dementia

INTRODUCTION

Lewy body dementia (LBD), including dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD), is a common form of neurodegenerative dementia. The frequency and influence of comorbid cerebrovascular disease is not understood but has potentially important clinical management implications.

METHODS

A systematic literature search was conducted (Medline and Embase) for studies including participants with DLB and/or PDD assessing cerebrovascular lesions (imaging and pathological studies). They included white matter changes, cerebral amyloid angiopathy (CAA), cerebral microbleeds (CMB), macroscopic infarcts, micro-infarcts and intracerebral haemorrhage.

RESULTS

Of 4411 articles, 63 studies were included. Cerebrovascular lesions commonly studied included white matter changes (41 studies) and CMB (18 studies). There was an increased severity of white matter changes on magnetic resonance imaging (visualized as white matter hyperintensities, WMH), but not neuropathology, in LBD compared to PD without dementia and age-matched controls. CMB prevalence in DLB was highly variable but broadly similar to Alzheimer's disease (AD) (0-48%), with a lobar predominance. No relationship was found between large cortical or small subcortical infarcts or intracerebral haemorrhage and presence of LBD.

CONCLUSION

The underlying mechanisms of WMH in LBD require further exploration, as their increased severity in LBD was not supported by neuropathological examination of white matter. CMB in LBD had a similar prevalence as AD. There is a need for larger studies assessing the influence of cerebrovascular lesions on clinical symptoms, disease progression and outcomes.

CSF MicroRNAs Reveal Impairment of Angiogenesis and Autophagy in Parkinson Disease

Background and Objectives

We assessed longitudinal changes in CSF microRNAs (miRNAs) in patients with moderately severe Parkinson disease.

Methods

We used next-generation whole-genome miRNA sequencing to determine CSF miRNA expression in 75 patients with Parkinson disease after single random ascending doses of nilotinib and longitudinal miRNA expression after daily nilotinib, 150 and 300 mg, vs placebo for 1 year.

Results

Significant changes in the expression of miRNAs that control genes and pathways that regulate angiogenesis, autophagy, and the blood-brain-barrier components, primarily collagen, were observed over 1 year, suggesting impairment of these pathways in Parkinson progression in these patients. Different miRNAs that indicate activation of genes associated with autophagy flux and clearance and angiogenesis were significantly altered in the nilotinib, 300 mg vs 150 mg, or placebo group, and these changes correlated with clinical outcomes. No changes were observed in miRNAs after a single dose of nilotinib vs placebo.

Discussion

This study suggests vascular and autophagy defects in Parkinson progression. Nilotinib, 300 mg, reverses these effects via alteration of miRNA expression, suggesting epigenomic changes that may underlie long-term disease-modifying effects.

Trial Registration Information

Clinical trial registration number: NCT02954978.

Angiogenesis as a potential treatment strategy for rheumatoid arthritis

Angiogenesis is an early and key event in the pathogenesis of rheumatoid arthritis (RA) and is crucial for the proliferation of synovial tissue and the formation of pannus. This process is regulated by both angiogenesis-stimulating factors and angiogenesis inhibitors, the basis for the "on-off hypothesis of angiogenesis." In RA, inflammation, immune imbalance, and hypoxia can further turn on the switch for blood vessel formation and induce angiogenesis. The new vasculature can recruit white blood cells, induce immune imbalance, and aggravate inflammation. At the same time, it also can provide oxygen and nutrients for the proliferating synovial tissue, which can accelerate the process of RA. The current therapies for RA mainly target the inflammatory response of autoimmune activation. Although these therapies have been greatly improved, there are still many patients whose RA is difficult to treat or who do not fully respond to treatment. Therefore, new innovative therapies are still urgently needed. This review covers the mechanism of synovial angiogenesis in RA, including the detailed process of angiogenesis and the relationship between inflammation, immune imbalance, hypoxia, and synovial angiogenesis, respectively. At the same time, in the context of the development of angiogenesis inhibition therapy for cancer, we also discuss similar treatment strategies for RA, especially the combination of targeted angiogenesis inhibition therapy and immunotherapy.

The Metabolomic Approach Reveals the Alteration in Human Serum and Cerebrospinal Fluid Composition in Parkinson's Disease Patients

Parkinson’s disease (PD) is a major public health problem. Since currently there are no reliable diagnostic tools to reveal the early steps of PD, new methods should be developed, including those searching the variations in human metabolome. Alterations in human metabolites could help to establish an earlier and more accurate diagnosis. The presented research shows a targeted metabolomics study of both of the serum and CSF from PD patients, atypical parkinsonian disorders (APDs) patients, and the control. The use of the LC-MS/MS system enabled to quantitate 144 analytes in the serum and 51 in the CSF. This information about the concentration enabled for selection of the metabolites useful for differentiation between the studied group of patients, which should be further evaluated as candidates for markers of screening and differential diagnosis of PD and APDs. Among them, the four compounds observed to be altered in both the serum and CSF seem to be the most important: tyrosine, putrescine, trans-4-hydroxyproline, and total dimethylarginine. Furthermore, we indicated the metabolic pathways potentially related to neurodegeneration processes. Our studies present evidence that the proline metabolism might be related to neurodegeneration processes underlying PD and APDs. Further studies on the proposed metabolites and founded metabolic pathways may significantly contribute to understanding the molecular background of PD and improving the diagnostics and treatment in the future.

High-fat diet-induced diabetes leads to vascular alterations, pericyte reduction, and perivascular depletion of microglia in a 6-OHDA toxin model of Parkinson disease

Background

Diabetes has been recognized as a risk factor contributing to the incidence and progression of Parkinson’s disease (PD). Although several hypotheses suggest a number of different mechanisms underlying the aggravation of PD caused by diabetes, less attention has been paid to the fact that diabetes and PD share pathological microvascular alterations in the brain. The characteristics of the interaction of diabetes in combination with PD at the vascular interface are currently not known.

Methods

We combined a high-fat diet (HFD) model of diabetes mellitus type 2 (DMT2) with the 6-OHDA lesion model of PD in male mice. We analyzed the association between insulin resistance and the achieved degree of dopaminergic nigrostriatal pathology. We further assessed the impact of the interaction of the two pathologies on motor deficits using a battery of behavioral tests and on microglial activation using immunohistochemistry. Vascular pathology was investigated histologically by analyzing vessel density and branching points, pericyte density, blood–brain barrier leakage, and the interaction between microvessels and microglia in the striatum.

Results

Different degrees of PD lesion were obtained resulting in moderate and severe dopaminergic cell loss. Even though the HFD paradigm did not affect the degree of nigrostriatal lesion in the acute toxin-induced PD model used, we observed a partial aggravation of the motor performance of parkinsonian mice by the diet. Importantly, the combination of a moderate PD pathology and HFD resulted in a significant pericyte depletion, an absence of an angiogenic response, and a significant reduction in microglia/vascular interaction pointing to an aggravation of vascular pathology.

Conclusion

This study provides the first evidence for an interaction of DMT2 and PD at the brain microvasculature involving changes in the interaction of microglia with microvessels. These pathological changes may contribute to the pathological mechanisms underlying the accelerated progression of PD when associated with diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02218-8.

Blood-Brain Barrier and Neurodegenerative Diseases-Modeling with iPSC-Derived Brain Cells

The blood-brain barrier (BBB) regulates the delivery of oxygen and important nutrients to the brain through active and passive transport and prevents neurotoxins from entering the brain. It also has a clearance function and removes carbon dioxide and toxic metabolites from the central nervous system (CNS). Several drugs are unable to cross the BBB and enter the CNS, adding complexity to drug screens targeting brain disorders. A well-functioning BBB is essential for maintaining healthy brain tissue, and a malfunction of the BBB, linked to its permeability, results in toxins and immune cells entering the CNS. This impairment is associated with a variety of neurological diseases, including Alzheimer's disease and Parkinson's disease. Here, we summarize current knowledge about the BBB in neurodegenerative diseases. Furthermore, we focus on recent progress of using human-induced pluripotent stem cell (iPSC)-derived models to study the BBB. We review the potential of novel stem cell-based platforms in modeling the BBB and address advances and key challenges of using stem cell technology in modeling the human BBB. Finally, we highlight future directions in this area.

Role of Liver Growth Factor (LGF) in Parkinson's Disease: Molecular Insights and Therapeutic Opportunities

Parkinson's disease is the most common neurodegenerative movement disorder with unclear etiology and only symptomatic treatment to date. Toward the development of novel disease-modifying agents, neurotrophic factors represent a reasonable and promising therapeutic approach. However, despite the robust preclinical evidence, clinical trials using glial-derived neurotrophic factor (GDNF) and neurturin have been unsuccessful. In this direction, the therapeutic potential of other trophic factors in PD and the elucidation of the underlying molecular mechanisms are of paramount importance. The liver growth factor (LGF) is an albumin-bilirubin complex acting as a hepatic mitogen, which also exerts regenerative effects on several extrahepatic tissues including the brain. Accumulating evidence suggests that intracerebral and peripheral administration of LGF can enhance the outgrowth of nigrostriatal dopaminergic axonal terminals; promote the survival, migration, and differentiation of neuronal stem cells; and partially protect against dopaminergic neuronal loss in the substantia nigra of PD animal models. In most studies, these effects are accompanied by improved motor behavior of the animals. Potential underlying mechanisms involve transient microglial activation, TNF-α upregulation, and activation of the extracellular signal-regulated kinases 1/2 (ERK1/2) and of the transcription factor cyclic AMP response-element binding protein (CREB), along with anti-inflammatory and antioxidant pathways. Herein, we summarize recent preclinical evidence on the potential role of LGF in PD pathogenesis, aiming to shed more light on the underlying molecular mechanisms and reveal novel therapeutic opportunities for this debilitating disease.

A multicentre validation study of the diagnostic value of plasma neurofilament light

Increased cerebrospinal fluid neurofilament light (NfL) is a recognized biomarker for neurodegeneration that can also be assessed in blood. Here, we investigate plasma NfL as a marker of neurodegeneration in 13 neurodegenerative disorders, Down syndrome, depression and cognitively unimpaired controls from two multicenter cohorts: King’s College London (n = 805) and the Swedish BioFINDER study (n = 1,464). Plasma NfL was significantly increased in all cortical neurodegenerative disorders, amyotrophic lateral sclerosis and atypical parkinsonian disorders. We demonstrate that plasma NfL is clinically useful in identifying atypical parkinsonian disorders in patients with parkinsonism, dementia in individuals with Down syndrome, dementia among psychiatric disorders, and frontotemporal dementia in patients with cognitive impairment. Data-driven cut-offs highlighted the fundamental importance of age-related clinical cut-offs for disorders with a younger age of onset. Finally, plasma NfL performs best when applied to indicate no underlying neurodegeneration, with low false positives, in all age-related cut-offs.

Cerebrospinal fluid neurofilament light (NfL) is a biomarker for neurodegeneration that can also be assessed in blood. Here the authors show in a validation study the potential for plasma NfL as a biomarker for several neurodegenerative diseases.

Blood-brain barrier permeability in Parkinson's disease patients with and without dyskinesia

OBJECTIVE

Recent studies on a rodent model of Parkinson's disease (PD) have raised the possibility of increased blood-brain barrier (BBB) permeability, demonstrated by histology, autoradiography, and positron emission tomography (PET). However, in human PD patients, in vivo evidence of increased BBB permeability is lacking. We examined the hypothesis that levodopa treatment increases BBB permeability in human subjects with PD, particularly in those with levodopa-induced dyskinesia (LID).

METHODS

We used rubidium-82 (82Rb) and PET to quantify BBB influx in vivo in 19 PD patients, including eight with LID, and 12 age- and sex-matched healthy subjects. All subjects underwent baseline 82Rb scans. Seventeen chronically levodopa-treated patients were additionally rescanned during intravenous levodopa infusion. Influx rate constant, K1, by compartmental modeling or net influx transport, Ki, by graphical approach could not be estimated reliably. However, Vd, the "apparent volume of distribution" based on the 82Rb concentration in brain tissue and blood, was estimated with good stability as a local measure of the volume of distribution.

RESULTS

Rubidium influx into brain tissue was undetectable in PD patients with or without LID, scanned on and off drug. No significant differences in regional Vd were observed for PD patients with or without LID relative to healthy subjects, except in left thalamus. Moreover, changes in Vd measured off- and on-levodopa infusion were also not significant for dyskinetic and non-dyskinetic subjects.

CONCLUSION

82Rb PET did not reveal significant changes in BBB permeability in PD patients.

Impaired cerebral microcirculation in isolated REM sleep behaviour disorder

During the prodromal period of Parkinson's disease and other α-synucleinopathy-related parkinsonisms, neurodegeneration is thought to progressively affect deep brain nuclei, such as the locus coeruleus, caudal raphe nucleus, substantia nigra, and the forebrain nucleus basalis of Meynert. Besides their involvement in the regulation of mood, sleep, behaviour, and memory functions, these nuclei also innervate parenchymal arterioles and capillaries throughout the cortex, possibly to ensure that oxygen supplies are adjusted according to the needs of neural activity. The aim of this study was to examine whether patients with isolated REM sleep behaviour disorder, a parasomnia considered to be a prodromal phenotype of α-synucleinopathies, reveal microvascular flow disturbances consistent with disrupted central blood flow control. We applied dynamic susceptibility contrast MRI to characterize the microscopic distribution of cerebral blood flow in the cortex of 20 polysomnographic-confirmed patients with isolated REM sleep behaviour disorder (17 males, age range: 54-77 years) and 25 healthy matched controls (25 males, age range: 58-76 years). Patients and controls were cognitively tested by Montreal Cognitive Assessment and Mini Mental State Examination. Results revealed profound hypoperfusion and microvascular flow disturbances throughout the cortex in patients compared to controls. In patients, the microvascular flow disturbances were seen in cortical areas associated with language comprehension, visual processing and recognition and were associated with impaired cognitive performance. We conclude that cortical blood flow abnormalities, possibly related to impaired neurogenic control, are present in patients with isolated REM sleep behaviour disorder and associated with cognitive dysfunction. We hypothesize that pharmacological restoration of perivascular neurotransmitter levels could help maintain cognitive function in patients with this prodromal phenotype of parkinsonism.

Arterial Blood Pressure Variability and Other Vascular Factors Contribution to the Cognitive Decline in Parkinson's Disease

Dementia is one of the most disabling non-motor symptoms in Parkinson’s disease (PD). Unlike in Alzheimer’s disease, the vascular pathology in PD is less documented. Due to the uncertain role of commonly investigated metabolic or vascular factors, e.g., hypertension or diabetes, other factors corresponding to PD dementia have been proposed. Associated dysautonomia and dopaminergic treatment seem to have an impact on diurnal blood pressure (BP) variability, which may presumably contribute to white matter hyperintensities (WMH) development and cognitive decline. We aim to review possible vascular and metabolic factors: Renin-angiotensin-aldosterone system, vascular endothelial growth factor (VEGF), hyperhomocysteinemia (HHcy), as well as the dopaminergic treatment, in the etiopathogenesis of PD dementia. Additionally, we focus on the role of polymorphisms within the genes for catechol-O-methyltransferase (COMT), apolipoprotein E (APOE), vascular endothelial growth factor (VEGF), and for renin-angiotensin-aldosterone system components, and their contribution to cognitive decline in PD. Determining vascular risk factors and their contribution to the cognitive impairment in PD may result in screening, as well as preventive measures.

Sex differences in the blood-brain barrier and neurodegenerative diseases

The number of people diagnosed with neurodegenerative diseases is on the rise. Many of these diseases, including Alzheimer's disease, Parkinson's disease, multiple sclerosis, and motor neuron disease, demonstrate clear sexual dimorphisms. While sex as a biological variable must now be included in animal studies, sex is rarely included in in vitro models of human neurodegenerative disease. In this Review, we describe these sex-related differences in neurodegenerative diseases and the blood-brain barrier (BBB), whose dysfunction is linked to neurodegenerative disease development and progression. We explain potential mechanisms by which sex and sex hormones affect BBB integrity. Finally, we summarize current in vitro BBB bioengineered models and highlight their potential to study sex differences in BBB integrity and neurodegenerative disease.

Neuroinflammation in Parkinson's Disease: Triggers, Mechanisms, and Immunotherapies

Parkinson's disease (PD) is a heterogeneous neurodegenerative disease involving multiple etiologies and pathogenesis, in which neuroinflammation is a common factor. Both preclinical experiments and clinical studies provide evidence for the involvement of neuroinflammation in the pathophysiology of PD, although there are a number of key issues related to neuroinflammatory processes in PD that remain to be addressed. In this review, we highlight the relationship between the common pathological mechanisms of PD and neuroinflammation, including aggregation of α-synuclein, genetic factors, mitochondrial dysfunction, and gut microbiome dysbiosis. We also describe the two positive feedback loops initiated in PD after the immune system is activated, and their role in the pathogenesis of PD. In addition, the interconnections and differences between the central and peripheral immune systems are discussed. Finally, we review the latest progress in immunotherapy research for PD patients, and propose future directions for clinical research.

Human α-synuclein overexpression in a mouse model of Parkinson's disease leads to vascular pathology, blood brain barrier leakage and pericyte activation

The pathological hallmark of Parkinson's disease (PD) is the formation of Lewy bodies containing aggregated alpha-synuclein (α-syn). Although PD is associated with these distinct histological changes, other pathological features such as microvascular alterations have been linked to neurodegeneration. These changes need to be investigated as they create a hostile brain microenvironment and may contribute to the development and progression of the disease. We use a human α-syn overexpression mouse model that recapitulates some of the pathological features of PD in terms of progressive aggregation of human α-syn, impaired striatal dopamine fiber density, and an age-dependent motor deficit consistent with an impaired dopamine release. We demonstrate for the first time in this model a compromised blood-brain barrier integrity and dynamic changes in vessel morphology from angiogenesis at earlier stages to vascular regression at later stages. The vascular alterations are accompanied by a pathological activation of pericytes already at an early stage without changing overall pericyte density. Our data support and further extend the occurrence of vascular pathology as an important pathophysiological aspect in PD. The model used provides a powerful tool to investigate disease-modifying factors in PD in a temporal sequence that might guide the development of new treatments.