Candidate inflammatory biomarkers display unique relationships with alpha-synuclein and correlate with measures of disease severity in subjects with Parkinson's disease

Interfering with aggregated α-synuclein in advanced melanoma leads to a major upregulation of MHC class II proteins

Melanoma is the most serious and deadly form of skin cancer and with progression to advanced melanoma, the intrinsically disordered protein α-synuclein is upregulated to high levels. While toxic to dopaminergic neurons in Parkinson's disease, α-synuclein is highly beneficial for primary and metastatic melanoma cells. To gain detailed insights into this exact opposite role of α-synuclein in advanced melanoma, we performed proteomic studies of high-level α-synuclein-expressing human melanoma cell lines that were treated with the diphenyl-pyrazole small-molecule compound anle138b, which binds to and interferes with the oligomeric structure of α-synuclein. We also performed proteomic and transcriptomic studies of human melanoma xenografts that were treated systemically with the anle138b compound. The results reveal that interfering with oligomerized α-synuclein in the melanoma cells in these tumor xenografts led to a substantial upregulation and expression of major histocompatibility complex proteins, which are pertinent to enhancing anti-melanoma immune responses.

Emerging insights into Lipocalin-2: Unraveling its role in Parkinson's Disease

Parkinson's disease (PD) ranks as the second most prevalent neurodegenerative disorder globally, marked by a complex pathogenesis. Lipocalin-2 (LCN2) emerges as a crucial factor during the progression of PD. Belonging to the lipocalin family, LCN2 is integral to several biological functions, including glial cell activation, iron homeostasis regulation, immune response, inflammatory reactions, and oxidative stress mitigation. Substantial research has highlighted marked increases in LCN2 expression within the substantia nigra (SN), cerebrospinal fluid (CSF), and blood of individuals with PD. This review focuses on the pathological roles of LCN2 in neuroinflammation, aging, neuronal damage, and iron dysregulation in PD. It aims to explore the underlying mechanisms of LCN2 in the disease and potential therapeutic targets that could inform future treatment strategies.

How Lifetime Evolution of Parkinson's Disease Could Shape Clinical Trial Design: A Shared Patient-Clinician Viewpoint

Parkinson's disease (PD) has a long, heterogeneous, pre-diagnostic phase, during which pathology insidiously accumulates. Increasing evidence suggests that environmental and lifestyle factors in early life contribute to disease risk and progression. Thanks to the extensive study of this pre-diagnostic phase, the first prevention trials of PD are being designed. However, the highly heterogenous evolution of the disease across the life course is not yet sufficiently taken into account. This could hamper clinical trial success in the advent of biological disease definitions. In an interdisciplinary patient-clinician study group, we discussed how an approach that incorporates the lifetime evolution of PD may benefit the design of disease-modifying trials by impacting population, target and outcome selection. We argue that the timepoint of exposure to risk and protective factors plays a critical role in PD subtypes, influencing population selection. In addition, recent developments in differential disease mechanisms, aided by biological disease definitions, could impact optimal treatment targets. Finally, multimodal biomarker panels using this lifetime approach will likely be most sensitive as progression markers for more personalized trials. We believe that the lifetime evolution of PD should be considered in the design of clinical trials, and that such initiatives could benefit from more patient-clinician partnerships.

Inflammation as common link to progressive neurological diseases

Life expectancy has increased immensely over the past decades, bringing new challenges to the health systems as advanced age increases the predisposition for many diseases. One of those is the burden of neurologic disorders. While many hypotheses have been placed to explain aging mechanisms, it has been widely accepted that the increasing pro-inflammatory status with advanced age or "inflammaging" is a main determinant of biological aging. Furthermore, inflammaging is at the cornerstone of many age-related diseases and its involvement in neurologic disorders is an exciting hypothesis. Indeed, aging and neurologic disorders development in the elderly seem to share some basic pathways that fundamentally converge on inflammation. Peripheral inflammation significantly influences brain function and contributes to the development of neurological disorders, including Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Understanding the role of inflammation in the pathogenesis of progressive neurological diseases is of crucial importance for developing effective treatments and interventions that can slow down or prevent disease progression, therefore, decreasing its social and economic burden.

Early-to-mid stage idiopathic Parkinson's disease shows enhanced cytotoxicity and differentiation in CD8 T-cells in females

Neuroinflammation in the brain contributes to the pathogenesis of Parkinson's disease (PD), but the potential dysregulation of peripheral immunity has not been systematically investigated for idiopathic PD (iPD). Here we showed an elevated peripheral cytotoxic immune milieu, with more terminally-differentiated effector memory (TEMRA) CD8 T, CD8+ NKT cells and circulating cytotoxic molecules in fresh blood of patients with early-to-mid iPD, especially females, after analyzing > 700 innate and adaptive immune features. This profile, also reflected by fewer CD8+FOXP3+ T cells, was confirmed in another subcohort. Co-expression between cytotoxic molecules was selectively enhanced in CD8 TEMRA and effector memory (TEM) cells. Single-cell RNA-sequencing analysis demonstrated the accelerated differentiation within CD8 compartments, enhanced cytotoxic pathways in CD8 TEMRA and TEM cells, while CD8 central memory (TCM) and naïve cells were already more-active and transcriptionally-reprogrammed. Our work provides a comprehensive map of dysregulated peripheral immunity in iPD, proposing candidates for early diagnosis and treatments.

Inflammatory hallmarks in 6-OHDA- and LPS-induced Parkinson's disease in rats

Parkinson's disease (PD) is the second most common neurodegenerative disease, affecting more than 1% of aged people. PD, which was previously identified as movement disorder, now is recognized as a multi-factorial systemic disease with important pathogenetic and pathophysiological role of inflammation. Reproducing local and systemic inflammation, which is inherent in PD, in animal models is essential for maximizing the translation of their potential to the clinic, as well as for developing putative anti-inflammatory neuroprotective agents. This study was aimed to compare activation patterns of microglia/macrophage population and systemic inflammation indices in rats with 6-Hydroxydopamine (6-OHDA)- and Lipopolysaccharide (LPS)-induced PD. Metabolic and phenotypic characteristics of microglia/macrophage population were examined by flow cytometry, systemic inflammatory markers were calculated using hematological parameters in 6-OHDA- and LPS-lesioned Wistar rats 29 days after the surgery. Microglia/macrophages from rats in both models exhibited pro-inflammatory metabolic shift. Nevertheless, in LPS-lesioned animals, highly increased proportion of CD80/86+ cells in microglia/macrophage population was registered alongside increased values of systemic inflammatory indices: neutrophil to lymphocyte ratio (NLR), derived neutrophil to lymphocyte ratio (dNLR), platelet to lymphocyte ratio and systemic immune inflammation index (SII). There was significant positive correlation between the count of CD80/86+ cells and systemic inflammatory indices in these animals. Microglia/macrophages from 6-OHDA-lesioned rats were characterized by the increased fraction of CD206+ cells alongside decreased proportion of CD80/86+ cells. No signs of systemic inflammation were observed. Negative correlation between quantitation characteristics of CD80/86+ cells and values of systemic inflammatory indices was registered. Collectively, our data show that LPS-PD model unlike 6-OHDA-PD replicates crosstalk between local and systemic inflammatory responses, which is inherent in PD pathogenesis and pathophysiology.

Defining the Riddle in Order to Solve It: There Is More Than One "Parkinson's Disease"

BACKGROUND

More than 200 years after James Parkinsondescribed a clinical syndrome based on his astute observations, Parkinson's disease (PD) has evolved into a complex entity, akin to the heterogeneity of other complex human syndromes of the central nervous system such as dementia, motor neuron disease, multiple sclerosis, and epilepsy. Clinicians, pathologists, and basic science researchers evolved arrange of concepts andcriteria for the clinical, genetic, mechanistic, and neuropathological characterization of what, in their best judgment, constitutes PD. However, these specialists have generated and used criteria that are not necessarily aligned between their different operational definitions, which may hinder progress in solving the riddle of the distinct forms of PD and ultimately how to treat them.

OBJECTIVE

This task force has identified current in consistencies between the definitions of PD and its diverse variants in different domains: clinical criteria, neuropathological classification, genetic subtyping, biomarker signatures, and mechanisms of disease. This initial effort for "defining the riddle" will lay the foundation for future attempts to better define the range of PD and its variants, as has been done and implemented for other heterogeneous neurological syndromes, such as stroke and peripheral neuropathy. We strongly advocate for a more systematic and evidence-based integration of our diverse disciplines by looking at well-defined variants of the syndrome of PD.

CONCLUSION

Accuracy in defining endophenotypes of "typical PD" across these different but interrelated disciplines will enable better definition of variants and their stratification in therapeutic trials, a prerequisite for breakthroughs in the era of precision medicine. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Impact of microRNAs on Mitochondrial Function and Immunity: Relevance to Parkinson's Disease

Parkinson's Disease (PD), the second most common neurodegenerative disorder, is characterised by the severe loss of dopaminergic neurons in the Substantia Nigra pars compacta (SNpc) and by the presence of Lewy bodies. PD is diagnosed upon the onset of motor symptoms, such as bradykinesia, resting tremor, rigidity, and postural instability. It is currently accepted that motor symptoms are preceded by non-motor features, such as gastrointestinal dysfunction. In fact, it has been proposed that PD might start in the gut and spread to the central nervous system. Growing evidence reports that the gut microbiota, which has been found to be altered in PD patients, influences the function of the central and enteric nervous systems. Altered expression of microRNAs (miRNAs) in PD patients has also been reported, many of which regulate key pathological mechanisms involved in PD pathogenesis, such as mitochondrial dysfunction and immunity. It remains unknown how gut microbiota regulates brain function; however, miRNAs have been highlighted as important players. Remarkably, numerous studies have depicted the ability of miRNAs to modulate and be regulated by the host's gut microbiota. In this review, we summarize the experimental and clinical studies implicating mitochondrial dysfunction and immunity in PD. Moreover, we gather recent data on miRNA involvement in these two processes. Ultimately, we discuss the reciprocal crosstalk between gut microbiota and miRNAs. Studying the bidirectional interaction of gut microbiome-miRNA might elucidate the aetiology and pathogenesis of gut-first PD, which could lead to the application of miRNAs as potential biomarkers or therapeutical targets for PD.

Fecal and Urinary Adipokines as Disease Biomarkers

The use of biomarkers is of great clinical value for the diagnosis and prognosis of disease and the assessment of treatment efficacy. In this context, adipokines secreted from adipose tissue are of interest, as their elevated circulating levels are associated with a range of metabolic dysfunctions, inflammation, renal and hepatic diseases and cancers. In addition to serum, adipokines can also be detected in the urine and feces, and current experimental evidence on the analysis of fecal and urinary adipokine levels points to their potential as disease biomarkers. This includes increased urinary adiponectin, lipocalin-2, leptin and interleukin-6 (IL-6) levels in renal diseases and an association of elevated urinary chemerin as well as urinary and fecal lipocalin-2 levels with active inflammatory bowel diseases. Urinary IL-6 levels are also upregulated in rheumatoid arthritis and may become an early marker for kidney transplant rejection, while fecal IL-6 levels are increased in decompensated liver cirrhosis and acute gastroenteritis. In addition, galectin-3 levels in urine and stool may emerge as a biomarker for several cancers. With the analysis of urine and feces from patients being cost-efficient and non-invasive, the identification and utilization of adipokine levels as urinary and fecal biomarkers could become a great advantage for disease diagnosis and predicting treatment outcomes. This review article highlights data on the abundance of selected adipokines in urine and feces, underscoring their potential to serve as diagnostic and prognostic biomarkers.

The association between inflammatory markers in blood and cerebrospinal fluid: a systematic review and meta-analysis

BACKGROUND

Neuroinflammatory processes have been hypothesized to play a role in the pathogenesis of psychiatric and neurological diseases. Studies on this topic often rely on analysis of inflammatory biomarkers in peripheral blood. Unfortunately, the extent to which these peripheral markers reflect inflammatory processes in the central nervous system (CNS) is unclear.

METHODS

We performed a systematic review and found 29 studies examining the association between inflammatory marker levels in blood and cerebrospinal (CSF) samples. We performed a random effects meta-analysis of 21 studies (pooled n = 1679 paired samples) that reported the correlation of inflammatory markers in paired blood-CSF samples.

RESULTS

A qualitative review revealed moderate to high quality of included studies with the majority of studies reporting no significant correlation of inflammatory markers between paired blood-CSF. Meta-analyses revealed a significant low pooled correlation between peripheral and CSF biomarkers (r = 0.21). Meta-analyses of individual cytokines revealed a significant pooled correlation for IL-6 (r = 0.26) and TNFα (r = 0.3) after excluding outlier studies, but not for other cytokines. Sensitivity analyses showed that correlations were highest among participants with a median age above 50 (r = 0.46) and among autoimmune disorder patients (r = 0.35).

CONCLUSION

This systematic review and meta-analysis revealed poor correlation between peripheral and central inflammatory markers in paired blood-CSF samples, with increased correlations in certain study populations. Based on the current findings, peripheral inflammatory markers are a poor reflection of the neuroinflammatory profile.

Inflammatory CSF profiles and longitudinal development of cognitive decline in sporadic and GBA-associated PD

Inflammation modifies the incidence and progression of Parkinson's disease (PD). By using 30 inflammatory markers in CSF in 498 people with PD and 67 people with dementia with Lewy bodies (DLB) we show that: (1) levels of ICAM-1, Interleukin-8, MCP-1, MIP-1 beta, SCF and VEGF were associated with clinical scores and neurodegenerative CSF biomarkers (Aβ1-42, t-Tau, p181-Tau, NFL and α-synuclein). (2) PD patients with GBA mutations show similar levels of inflammatory markers compared to PD patients without GBA mutations, even when stratified by mutation severity. (3) PD patients who longitudinally developed cognitive impairment during the study had higher levels of TNF-alpha at baseline compared to patients without the development of cognitive impairment. (4) Higher levels of VEGF and MIP-1 beta were associated with a longer duration until the development of cognitive impairment. We conclude that the majority of inflammatory markers is limited in robustly predicting longitudinal trajectories of developing cognitive impairment.

Secretion of VGF relies on the interplay between LRRK2 and post-Golgi v-SNAREs

The neuropeptide VGF was recently proposed as a neurodegeneration biomarker. The Parkinson's disease-related protein leucine-rich repeat kinase 2 (LRRK2) regulates endolysosomal dynamics, a process that involves SNARE-mediated membrane fusion and could regulate secretion. Here we investigate potential biochemical and functional links between LRRK2 and v-SNAREs. We find that LRRK2 directly interacts with the v-SNAREs VAMP4 and VAMP7. Secretomics reveals VGF secretory defects in VAMP4 and VAMP7 knockout (KO) neuronal cells. In contrast, VAMP2 KO "regulated secretion-null" and ATG5 KO "autophagy-null" cells release more VGF. VGF is partially associated with extracellular vesicles and LAMP1+ endolysosomes. LRRK2 expression increases VGF perinuclear localization and impairs its secretion. Retention using selective hooks (RUSH) assays show that a pool of VGF traffics through VAMP4+ and VAMP7+ compartments, and LRRK2 expression delays its transport to the cell periphery. Overexpression of LRRK2 or VAMP7-longin domain impairs VGF peripheral localization in primary cultured neurons. Altogether, our results suggest that LRRK2 might regulate VGF secretion via interaction with VAMP4 and VAMP7.

Brain and Systemic Inflammation in De Novo Parkinson's Disease

OBJECTIVE

To assess the presence of brain and systemic inflammation in subjects newly diagnosed with Parkinson's disease (PD).

BACKGROUND

Evidence for a pathophysiologic role of inflammation in PD is growing. However, several key gaps remain as to the role of inflammation in PD, including the extent of immune activation at early stages, potential effects of PD treatments on inflammation and whether pro-inflammatory signals are associated with clinical features and/or predict more rapid progression.

METHODS

We enrolled subjects with de novo PD (n = 58) and age-matched controls (n = 62). Subjects underwent clinical assessments, including the Movement Disorder Society-United Parkinson's Disease rating scale (MDS-UPDRS). Comprehensive cognitive assessment meeting MDS Level II criteria for mild cognitive impairment testing was performed. Blood was obtained for flow cytometry and cytokine/chemokine analyses. Subjects underwent imaging with ¹⁸ F-DPA-714, a translocator protein 18kd ligand, and lumbar puncture if eligible and consented.

RESULTS

Baseline demographics and medical history were comparable between groups. PD subjects showed significant differences in University of Pennsylvania Smell Identification Test, Schwab and England Activities of Daily Living, Scales for Outcomes in PD autonomic dysfunction, and MDS-UPDRS scores. Cognitive testing demonstrated significant differences in cognitive composite, executive function, and visuospatial domain scores at baseline. Positron emission tomography imaging showed increased ¹⁸ F-DPA-714 signal in PD subjects. ¹⁸ F-DPA-714 signal correlated with several cognitive measures and some chemokines.

CONCLUSIONS

¹⁸ F-DPA-714 imaging demonstrated increased central inflammation in de novo PD subjects compared to controls. Longitudinal follow-up will be important to determine whether the presence of inflammation predicts cognitive decline. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Blood Biomarkers in Patients with Parkinson's Disease: A Review in Context of Anesthetic Care

Parkinson's disease (PD) is the second most common inflammatory neurodegenerative disorder after dementia. Preclinical and epidemiological data strongly suggest that chronic neuroinflammation slowly induces neuronal dysfunction. Activated microglia secrete several neurotoxic substances, such as chemokines and proinflammatory cytokines, which may promote blood-brain barrier (BBB) permeabilization. CD4⁺ T cells comprise proinflammatory cells such as T helper (Th) 1 and Th17 cells, as well as anti-inflammatory cells such as Th2 and T regulatory cells (Tregs). Th1 and Th17 cells can be detrimental to dopamine neurons, whereas Th2 and Tregs are neuroprotective. The results of studies on the serum levels of cytokines such as IFN-γ and TNF-α secreted by Th1 T cells, IL-8 and IL-10 secreted by Th2 T cells, and IL-17 secreted by Th17 cells in PD patients are not uniform. In addition, the relationships between serum cytokine levels and motor and non-motor symptoms of PD are controversial. Surgical stress and anesthesia induce inflammatory responses by disturbing the balance between pro- and anti-inflammatory cytokines, which may exacerbate the neuroinflammatory response in PD patients. Here we review studies on blood inflammatory biomarkers in PD patients and discuss the roles of surgery and anesthesia in PD progression.

Microglia ferroptosis is regulated by SEC24B and contributes to neurodegeneration

Iron dysregulation has been implicated in multiple neurodegenerative diseases, including Parkinson's disease (PD). Iron-loaded microglia are frequently found in affected brain regions, but how iron accumulation influences microglia physiology and contributes to neurodegeneration is poorly understood. Here we show that human induced pluripotent stem cell-derived microglia grown in a tri-culture system are highly responsive to iron and susceptible to ferroptosis, an iron-dependent form of cell death. Furthermore, iron overload causes a marked shift in the microglial transcriptional state that overlaps with a transcriptomic signature found in PD postmortem brain microglia. Our data also show that this microglial response contributes to neurodegeneration, as removal of microglia from the tri-culture system substantially delayed iron-induced neurotoxicity. To elucidate the mechanisms regulating iron response in microglia, we performed a genome-wide CRISPR screen and identified novel regulators of ferroptosis, including the vesicle trafficking gene SEC24B. These data suggest a critical role for microglia iron overload and ferroptosis in neurodegeneration.

Emerging roles of leptin in Parkinson's disease: Chronic inflammation, neuroprotection and more?

An increasing body of experimental evidence implicates a relationship between immunometabolic deterioration and the progression of Parkinson's disease (PD) with a dysregulation of central and peripheral neuroinflammatory networks mediated by circulating adipokines, in particular leptin. We screened the current literature on the role of adipokines in PD. Hence, we searched known databases (PubMed, MEDLINE/OVID) and reviewed original and review articles using the following terms: "leptin/ObR", "Parkinson's disease", "immune-metabolism", "biomarkers" and "neuroinflammation". Focusing on leptin, we summarize and discuss the existing in vivo and in vitro evidence on how adipokines may be protective against neurodegeneration, but at the same time contribute to the progression of PD. These components of the adipose brain axis represent a hitherto underestimated pathway to study systemic influences on dopaminergic degeneration. In addition, we give a comprehensive update on the potential of adjunctive therapeutics in PD targeting leptin, leptin-receptors, and associated pathways. Further experimental and clinical trials are needed to elucidate the mechanisms of action and the value of central and peripheral adipose-immune-metabolism molecular phenotyping in order to develop and validate the differential roles of different adipokines as potential therapeutic target for PD patients.

Peripheral Inflammatory Markers TNF-α and CCL2 Revisited: Association with Parkinson's Disease Severity

One of the major mediators of neuroinflammation in PD is tumour necrosis factor alpha (TNF-α), which, similar to other cytokines, is produced by activated microglia and astrocytes. Although TNF-α can be neuroprotective in the brain, long-term neuroinflammation and TNF release can be harmful, having a neurotoxic role that leads to death of oligodendrocytes, astrocytes, and neurons and, therefore, is associated with neurodegeneration. Apart from cytokines, a wide family of molecules with homologous structures, namely chemokines, play a key role in neuro-inflammation by drawing cytotoxic T-lymphocytes and activating microglia. The objective of the current study was to examine the levels of the serum TNF-α and CCL2 (Chemokine (C-C motif) ligand 2), also known as MCP-1 (Monocyte Chemoattractant Protein-1), in PD patients compared with healthy controls. We also investigated the associations between the serum levels of these two inflammatory mediators and a number of clinical symptoms, in particular, disease severity and cognition. Such an assessment may point to their prognostic value and provide some treatment hints. PD patients with advanced stage on the Hoehn-Yahr scale showed an increase in TNF-α levels compared with PD patients with stages 1 and 2 (p = 0.01). Additionally, the UPDRS score was significantly associated with TNF-α levels. CCL2 levels, however, showed no significant associations.

Hibiscetin attenuates oxidative, nitrative stress and neuroinflammation via suppression of TNF-α signaling in rotenone induced parkinsonism in rats

Parkinson's disease (PD) is the gradual and selective degradation of dopamine-releasing neurons in substantia nigra pars compacta (SNpc) and results in postural instability, stiffness, bradykinesia, and resting tremor. The goal of this research was to see how hibiscetin action on PD in rotenone-treated rats. Rats were administered orally with hibiscetin (10 mg/kg) after 1 h rotenone (0.5 mg/kg, s.c.). This therapy regimen was followed on a daily basis for 28 days. Rats were tested for catalepsy and akinesia on day 29 after the last dosage of rotenone. Biochemical parameters were performed to measure reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), nitrite, neuroinflammatory cytokines, and neurotransmitter and their metabolite levels such as dopamine (DA), norepinephrine (NE), serotonin (5-HT), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA). Rotenone-induced akinesia and catatonia in rats decreased endogenous antioxidant (GSH, CAT, and SOD) levels, increased MDA and nitrite levels, and changed neurotransmitter and metabolite levels. Hibiscetin effectively reduced rotenone-induced akinesia and catatonia, improved endogenous antioxidant (GSH, CAT and SOD) levels, and reduced oxidative and nitrative stress in the treated rats. Moreover, hibiscetin restored altered neurotransmitters and their metabolites to normal levels in rotenone-treated rats. The study results showed that hibiscetin has anti-Parkinson's activity against rotenone-induced PD in rats.

Evaluation of the PREDIGT score’s performance in identifying newly diagnosed Parkinson’s patients without motor examination

Several recent publications described algorithms to identify subjects with Parkinson’s disease (PD). In creating the “PREDIGT Score”, we previously developed a hypothesis-driven, simple-to-use formula to potentially calculate the incidence of PD. Here, we tested its performance in the ‘De Novo Parkinson Study’ (DeNoPa) and ‘Parkinson’s Progression Marker Initiative’ (PPMI); the latter included participants from the ‘FOllow Up persons with Neurologic Disease’ (FOUND) cohort. Baseline data from 563 newly diagnosed PD patients and 306 healthy control subjects were evaluated. Based on 13 variables, the original PREDIGT Score identified recently diagnosed PD patients in the DeNoPa, PPMI + FOUND and the pooled cohorts with area-under-the-curve (AUC) values of 0.88 (95% CI 0.83–0.92), 0.79 (95% CI 0.72–0.85), and 0.84 (95% CI 0.8–0.88), respectively. A simplified version (8 variables) generated AUC values of 0.92 (95% CI 0.89–0.95), 0.84 (95% CI 0.81–0.87), and 0.87 (0.84–0.89) in the DeNoPa, PPMI, and the pooled cohorts, respectively. In a two-step, screening-type approach, self-reported answers to a questionnaire (step 1) distinguished PD patients from controls with an AUC of 0.81 (95% CI 0.75–0.86). Adding a single, objective test (Step 2) further improved classification. Among seven biological markers explored, hyposmia was the most informative. The composite AUC value measured 0.9 (95% CI 0.88–0.91) in DeNoPa and 0.89 (95% CI 0.84–0.94) in PPMI. These results reveal a robust performance of the original PREDIGT Score to distinguish newly diagnosed PD patients from controls in two established cohorts. We also demonstrate the formula’s potential applicability to enriching for PD subjects in a population screening-type approach.

Inflammation and immune dysfunction in Parkinson disease

Parkinson disease (PD) is a progressive neurodegenerative disease that affects peripheral organs as well as the central nervous system and involves a fundamental role of neuroinflammation in its pathophysiology. Neurohistological and neuroimaging studies support the presence of ongoing and end-stage neuroinflammatory processes in PD. Moreover, numerous studies of peripheral blood and cerebrospinal fluid from patients with PD suggest alterations in markers of inflammation and immune cell populations that could initiate or exacerbate neuroinflammation and perpetuate the neurodegenerative process. A number of disease genes and risk factors have been identified as modulators of immune function in PD and evidence is mounting for a role of viral or bacterial exposure, pesticides and alterations in gut microbiota in disease pathogenesis. This has led to the hypothesis that complex gene-by-environment interactions combine with an ageing immune system to create the 'perfect storm' that enables the development and progression of PD. We discuss the evidence for this hypothesis and opportunities to harness the emerging immunological knowledge from patients with PD to create better preclinical models with the long-term goal of enabling earlier identification of at-risk individuals to prevent, delay and more effectively treat the disease.

Changes Observed in Potential Key Candidate Genes of Peripheral Immunity Induced by Tai Chi among Patients with Parkinson's Disease

Parkinson’s disease (PD) is a common progressive neurodegenerative disease characterized by motor dysfunction. Although the inhibition of inflammation by Tai Chi has been demonstrated to involve a peripheral cytokine response and may play an important role in improving the motor function of PD patients, the related specific molecular mechanisms of the peripheral immune response to Tai Chi are not fully understood. The microarray dataset ‘GSE124676’ for the peripheral immune response to Tai Chi of PD patients was downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were screened and analyzed using weighted gene co-expression network analysis (WGCNA). A total of 136 DEGs were found in the PD patients after Tai Chi, suggesting an effect of Tai Chi on the peripheral immunity of PD patients. The DEGs are mainly involved in neutrophil activation, T-cell activation, and NOD-like receptor and IL-17 signaling pathways. Furthermore, six key candidate genes (FOS, FOSB, JUNB, ZFP36, CAMP and LCN2) that are involved in peripheral inflammation and the inhibition of inflammation induced by Tai Chi were observed. The results in the present study could be conducive to comprehensively understanding the molecular mechanism involved in the effect of Tai Chi on peripheral inflammation in PD patients and providing novel targets for future advanced research.

Identification and validation of key molecules associated with humoral immune modulation in Parkinson’s disease based on bioinformatics

Objective

Parkinson’s disease (PD) is the most common neurodegenerative movement disorder and immune-mediated mechanism is considered to be crucial to pathogenesis. Here, we investigated the role of humoral immune regulatory molecules in the pathogenesis of PD.

Methods

Firstly, we performed a series of bioinformatic analyses utilizing the expression profile of the peripheral blood mononuclear cell (PBMC) obtained from the GEO database (GSE100054, GSE49126, and GSE22491) to identify differentially expressed genes related to humoral immune regulatory mechanisms between PD and healthy controls. Subsequently, we verified the results using quantitative polymerase chain reaction (Q-PCR) and enzyme-linked immunosorbent assay (ELISA) in clinical blood specimen. Lastly, receiver operating characteristic (ROC) curve analysis was performed to determine the diagnostic effects of verified molecules.

Results

We obtained 13 genes that were mainly associated with immune-related biological processes in PD using bioinformatic analysis. Then, we selected PPBP, PROS1, and LCN2 for further exploration. Fascinatingly, our experimental results don’t always coincide with the expression profile. PROS1 and LCN2 plasma levels were significantly higher in PD patients compared to controls (p < 0.01 and p < 0.0001). However, the PPBP plasma level and expression in the PBMC of PD patients was significantly decreased compared to controls (p < 0.01 and p < 0.01). We found that PPBP, PROS1, and LCN2 had an area under the curve (AUC) of 0.663 (95%CI: 0.551–0.776), 0.674 (95%CI: 0.569–0.780), and 0.885 (95%CI: 0.814–0.955). Furthermore, in the biological process analysis of gene ontology (GO), the three molecules were all involved in humoral immune response (GO:0006959).

Conclusions

In general, PPBP, PROS1, and LCN2 were identified and validated to be related to PD and PPBP, LCN2 may potentially be biomarkers or therapeutic targets for PD. Our findings also provide some new insights on the humoral immune modulation mechanisms in PD.

Dietary Inflammatory Index score and prodromal Parkinson's disease incidence: The HELIAD study

AIM

The aim of the present study was to investigate the association of the inflammatory potential of diet with prodromal Parkinson's disease (pPD) probability and incidence among community-dwelling older individuals without clinical features of parkinsonism at baseline.

METHODS

The sample consisted of 1,030 participants 65 years old or older, drawn from a population-based cohort study of older adults in Greece (Hellenic Longitudinal Investigation of Aging and Diet - HELIAD). We calculated pPD probability, according to International Parkinson and Movement Disorder Society research criteria. Dietary Inflammatory Index (DII) was used to measure the dietary inflammatory potential, with higher index score reflecting a more pro-inflammatory diet. Associations of baseline DII with pPD probability cross-sectionally, and with possible/probable pPD incidence (pPD probability ≥30%) during the follow-up period, were examined via general linear models and generalized estimating equations, respectively.

RESULTS

Cross-sectionally, one unit increase of DII score[DII (min, max) = -5.83, 6.01]was associated with 4.9% increased pPD probability [β=0.049, 95%CI (0.025-0.090), p<0.001]. Prospectively, 62 participants developed pPD during 3.1±0.9 (mean±SD) years of follow-up. One unit increase in DII was associated with 20.3% increased risk for developing pPD [RR=1.203, 95%CI (1.070-1.351), p=0.002]. Participants in the highest tertile of DII score were 2.6 times more likely to develop pPD [β=2.594, 95%CI (1.332-5.050), p=0.005], compared to those in the lowest tertile.

CONCLUSION

More pro-inflammatory diet was related with higher pPD probability and pPD incidence (pPD probability ≥30%) in a community-dwelling older adult population. Further studies are needed to confirm these findings.

Update on CSF Biomarkers in Parkinson's Disease

Progress in developing disease-modifying therapies in Parkinson’s disease (PD) can only be achieved through reliable objective markers that help to identify subjects at risk. This includes an early and accurate diagnosis as well as continuous monitoring of disease progression and therapy response. Although PD diagnosis still relies mainly on clinical features, encouragingly, advances in biomarker discovery have been made. The cerebrospinal fluid (CSF) is a biofluid of particular interest to study biomarkers since it is closest to the brain structures and therefore could serve as an ideal source to reflect ongoing pathologic processes. According to the key pathophysiological mechanisms, the CSF status of α-synuclein species, markers of amyloid and tau pathology, neurofilament light chain, lysosomal enzymes and markers of neuroinflammation provide promising preliminary results as candidate biomarkers. Untargeted approaches in the field of metabolomics provide insights into novel and interconnected biological pathways. Markers based on genetic forms of PD can contribute to identifying subgroups suitable for gene-targeted treatment strategies that might also be transferable to sporadic PD. Further validation analyses in large PD cohort studies will identify the CSF biomarker or biomarker combinations with the best value for clinical and research purposes.

Evidence of Inflammation in Parkinson’s Disease and Its Contribution to Synucleinopathy

Accumulation of alpha-synuclein (αSyn) protein in neurons is a renowned pathological hallmark of Parkinson’s disease (PD). In addition, accumulating evidence indicates that activated inflammatory responses are involved in the pathogenesis of PD. Thus, achieving a better understanding of the interaction between inflammation and synucleinopathy in relation to the PD process will facilitate the development of promising disease-modifying therapies. In this review, the evidence of inflammation in PD is discussed, and human, animal, and laboratory studies relevant to the relationship between inflammation and αSyn are explored as well as new therapeutic targets associated with this relationship.

The Gut-Brain Axis and Its Relation to Parkinson's Disease: A Review

Parkinson's disease is a chronic neurodegenerative disease characterized by the accumulation of misfolded alpha-synuclein protein (Lewy bodies) in dopaminergic neurons of the substantia nigra and other related circuitry, which contribute to the development of both motor (bradykinesia, tremors, stiffness, abnormal gait) and non-motor symptoms (gastrointestinal issues, urinogenital complications, olfaction dysfunction, cognitive impairment). Despite tremendous progress in the field, the exact pathways and mechanisms responsible for the initiation and progression of this disease remain unclear. However, recent research suggests a potential relationship between the commensal gut bacteria and the brain capable of influencing neurodevelopment, brain function and health. This bidirectional communication is often referred to as the microbiome-gut-brain axis. Accumulating evidence suggests that the onset of non-motor symptoms, such as gastrointestinal manifestations, often precede the onset of motor symptoms and disease diagnosis, lending support to the potential role that the microbiome-gut-brain axis might play in the underlying pathological mechanisms of Parkinson's disease. This review will provide an overview of and critically discuss the current knowledge of the relationship between the gut microbiota and Parkinson's disease. We will discuss the role of α-synuclein in non-motor disease pathology, proposed pathways constituting the connection between the gut microbiome and the brain, existing evidence related to pre- and probiotic interventions. Finally, we will highlight the potential opportunity for the development of novel preventative measures and therapeutic options that could target the microbiome-gut-brain axis in the context of Parkinson's disease.

Surface Plasmon Resonance Identifies High-Affinity Binding of l-DOPA to Siderocalin/Lipocalin-2 through Iron-Siderophore Action: Implications for Parkinson's Disease Treatment

l-3,4-Dihydroxyphenylalanine (l-DOPA), the dopamine precursor, remains the frontline treatment for Parkinson's disease (PD). With the treatment progress, l-DOPA efficacy decreases, necessitating higher and more frequent doses, with higher risks of dyskinesia. l-DOPA chelates iron through its catechol group, forming the l-DOPA:Fe complex; however, the fate of this complex is unknown. Catechol siderophore-like compounds are known to bind siderocalin (Scn)/lipocalin-2 to form stable siderophore:Fe:Scn complexes. Scn is upregulated in PD patients' substantia nigra and may play a role in PD pathophysiology. Therefore, in this study, we used the surface plasmon resonance (SPR) technique to examine the binding properties of l-DOPA to Scn. We found that l-DOPA formed a stable complex with Scn in the presence of Fe³⁺. Our analysis of the binding properties of l-DOPA precursors and metabolites indicates that the catechol group is necessary but not sufficient to form a stable complex with Scn. Finally, the affinity constant (K_d) of DOPA:Fe³⁺ binding with Scn (0.8 μM) was lower than l-DOPA plasma peak concentrations in l-DOPA preparations in the past six decades. Our results speculate a significant role for the l-DOPA-Scn complex in the decreased bioavailability of l-DOPA with the progress of PD.

Blood and Cerebrospinal Fluid Biomarkers of Inflammation in Parkinson's Disease

Given the clear role of inflammation in the pathogenesis of Parkinson's disease (PD) and its impact on incidence and phenotypical characteristics, this review provides an overview with focus on inflammatory biofluid markers in blood and cerebrospinal fluid (CSF) in PD patient cohorts. In preparation for clinical trials targeting the immune system, we specifically address the following questions: 1) What evidence do we have for pro-inflammatory profiles in blood and in CSF of sporadic and genetic PD patients? 2) Is there a role of anti-inflammatory mediators in blood/CSF? 3) Do inflammatory profiles in blood reflect those in CSF indicative of a cross-talk between periphery and brain? 4) Do blood/CSF inflammatory profiles change over the disease course as assessed in repeatedly taken biosamples? 5) Are blood/CSF inflammatory profiles associated with phenotypical trajectories in PD? 6) Are blood/CSF inflammatory profiles associated with CSF levels of neurodegenerative/PD-specific biomarkers? Knowledge on these questions will inform future strategies for patient stratification and cohort enrichment as well as suitable outcome measures for clinical trials.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

Serum levels of lipocalin-2 in patients with Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is the second most common neurodegenerative disease. Evidence has shown that lipocalin-2 (LCN2) is involved in the pathological process of PD. We aimed to explore whether serum levels of LCN2 could be a biomarker of PD.

METHODS

We recruited consecutive PD patients and healthy controls (HC) in our hospital from June 2020 to July 2020. Serum LCN2 levels were detected using the LCN2 enzyme-linked immunosorbent assay (ELISA) kit. The motor section of the Unified Parkinson's Disease Rating Scale (UPDRS III) and the Hoehn and Yahr Staging Scale (H&Y) were assessed on admission to evaluate disease severity in patients with PD. Cognitive status was measured by the Montreal Cognitive Assessment (MoCA).

RESULTS

We finally recruited 75 patients, including 40 PD patients and 35 HC. Serum LCN2 levels were not significantly increased in PD patients compared with HC (4.9 [- 0.7 to 18.6] vs 1.9 [- 1.5 to 16.9] ng/mL, P = 0.33). Besides, there was no significant difference in LCN2 levels between patients at early and advanced stage of PD (P = 0.75), as well as between cognitively impaired PD patients, PD patients with normal cognition, and HC (P = 0.30). Moreover, LCN2 had no correlation with disease duration (r =  - 0.1, P = 0.37), UPDRS III score (r = 0.07, P = 0.65), and MoCA score (r = 0.221, P = 0.17).

CONCLUSIONS

Overall, our study suggests that serum LCN2 levels may not be a biomarker for PD.

Serum and cerebrospinal fluid Neutrophil gelatinase-associated lipocalin (NGAL) levels as biomarkers for the conversion from mild cognitive impairment to Alzheimer's disease dementia

Neutrophil gelatinase-associated lipocalin (NGAL) is an acute phase protein that has been reported as a potential marker for pre-dementia stages of Alzheimer's disease (AD). Longitudinal studies for its association with the conversion of mild cognitive impairment to AD is still lacking. This study included n = 268 study participants with subjective cognitive decline (SCD) (n=82), mild cognitive impairment (MCI) (n=98) and AD dementia (n=88) at baseline and two-year follow-up clinical assessments. Serum and cerebrospinal fluid (CSF)NGAL, CSF amyloid beta_1-42, total-Tau, and phospho-Tau levels were measured with ELISA analysis. CSF NGAL levels were significantly lower in MCI participants compared to people with SCD at baseline. Lower baseline CSF NGAL levels predicted MCI converters to AD dementia vs. non-converters after 2-years follow-up. A positive correlation between CSF NGAL and amyloid beta_1-42 was found particularly in MCI participants at baseline. NGAL in CSF holds potential to be used as a predictive marker for the conversion of MCI to AD dementia and may reflect pathophysiological processes of prodromal AD neuropathology.

Understanding LRRK2 kinase activity in preclinical models and human subjects through quantitative analysis of LRRK2 and pT73 Rab10

Variants in the leucine-rich repeat kinase 2 (LRRK2) gene are associated with increased risk for familial and sporadic Parkinson's disease (PD). Pathogenic variants in LRRK2, including the common variant G2019S, result in increased LRRK2 kinase activity, supporting the therapeutic potential of LRRK2 kinase inhibitors for PD. To better understand the role of LRRK2 in disease and to support the clinical development of LRRK2 inhibitors, quantitative and high-throughput assays to measure LRRK2 levels and activity are needed. We developed and applied such assays to measure the levels of LRRK2 as well as the phosphorylation of LRRK2 itself or one of its substrates, Rab10 (pT73 Rab10). We observed increased LRRK2 activity in various cellular models of disease, including iPSC-derived microglia, as well as in human subjects carrying the disease-linked variant LRRK2 G2019S. Capitalizing on the high-throughput and sensitive nature of these assays, we detected a significant reduction in LRRK2 activity in subjects carrying missense variants in LRRK2 associated with reduced disease risk. Finally, we optimized these assays to enable analysis of LRRK2 activity following inhibition in human peripheral blood mononuclear cells (PBMCs) and whole blood, demonstrating their potential utility as biomarkers to assess changes in LRRK2 expression and activity in the clinic.

Senescence and Inflammatory Markers for Predicting Clinical Progression in Parkinson's Disease: The ICICLE-PD Study

Background:

Cognitive decline is a frequent complication of Parkinson’s disease (PD) and the identification of predictive biomarkers for it would help in its management.

Objective:

Our aim was to analyse whether senescence markers (telomere length, p16 and p21) or their change over time could help to better predict cognitive and motor progression of newly diagnosed PD patients. We also compared these senescence markers to previously analysed markers of inflammation for the same purpose.

Methods:

This study examined the association of blood-derived markers of cell senescence and inflammation with motor and cognitive function over time in an incident PD cohort (the ICICLE-PD study). Participants (154 newly diagnosed PD patients and 99 controls) underwent physical and cognitive assessments over 36 months of follow up. Mean leukocyte telomere length and the expression of senescence markers p21 and p16 were measured at two time points (baseline and 18 months). Additionally, we selected five inflammatory markers from existing baseline data.

Results:

We found that PD patients had shorter telomeres at baseline and 18 months compared to age-matched healthy controls which also correlated to dementia at 36 months. Baseline p16 levels were associated with faster rates of motor and cognitive decline over 36 months in PD cases, while a simple inflammatory summary score at baseline best predicted cognitive score over this same time period in PD patients.

Conclusion:

Our study suggests that both inflammatory and senescence markers (p16) are valuable predictors of clinical progression in PD patients.

Single-Cell Transcriptomics and In Situ Morphological Analyses Reveal Microglia Heterogeneity Across the Nigrostriatal Pathway

Microglia are the resident immune effector cells of the central nervous system (CNS) rapidly reacting to various pathological stimuli to maintain CNS homeostasis. However, microglial reactions in the CNS may also worsen neurological disorders. Hence, the phenotypic analysis of microglia in healthy tissue may identify specific poised subsets ultimately supporting or harming the neuronal network. This is all the more important for the understanding of CNS disorders exhibiting regional-specific and cellular pathological hallmarks, such as many neurodegenerative disorders, including Parkinson's disease (PD). In this context, we aimed to address the heterogeneity of microglial cells in susceptible brain regions for PD, such as the nigrostriatal pathway. Here, we combined single-cell RNA-sequencing with immunofluorescence analyses of the murine nigrostriatal pathway, the most affected brain region in PD. We uncovered a microglia subset, mainly present in the midbrain, displaying an intrinsic transcriptional immune alerted signature sharing features of inflammation-induced microglia. Further, an in situ morphological screening of inferred cellular diversity showed a decreased microglia complexity in the midbrain when compared to striatum. Our study provides a resource for the identification of specific microglia phenotypes within the nigrostriatal pathway, which may be relevant in PD.

Is LRRK2 the missing link between inflammatory bowel disease and Parkinson's disease?

Links that implicate the gastrointestinal system in Parkinson's disease (PD) pathogenesis and progression have become increasingly common. PD shares several similarities with Crohn's disease (CD). Intestinal inflammation is common in both PD and CD and is hypothesized to contribute to PD neuropathology. Mutations in leucine-rich repeat kinase 2 (LRRK2) are one of the greatest genetic contributors to PD. Variants in LRRK2 have also been associated with increased incidence of CD. Since its discovery, LRRK2 has been studied intensely in neurons, despite multiple lines of evidence showing that LRRK2 is highly expressed in immune cells. Based on the fact that higher levels of LRRK2 are detectable in inflamed colonic tissue from CD patients and in peripheral immune cells from sporadic PD patients relative to matched controls, we posit that LRRK2 regulates inflammatory processes. Therefore, LRRK2 may sit at a crossroads whereby gut inflammation and higher LRRK2 levels in CD may be a biomarker of increased risk for sporadic PD and/or may represent a tractable therapeutic target in inflammatory diseases that increase risk for PD. Here we will focus on reviewing how PD and CD share overlapping phenotypes, particularly in terms of LRRK2 in the context of the immune system, that could be targeted in future therapies.

Relationships of gut microbiota, short-chain fatty acids, inflammation, and the gut barrier in Parkinson's disease

BACKGROUND

Previous studies have reported that gut microbiota, permeability, short-chain fatty acids (SCFAs), and inflammation are altered in Parkinson's disease (PD), but how these factors are linked and how they contribute to disease processes and symptoms remains uncertain. This study sought to compare and identify associations among these factors in PD patients and controls to elucidate their interrelations and links to clinical manifestations of PD.

METHODS

Stool and plasma samples and clinical data were collected from 55 PD patients and 56 controls. Levels of stool SCFAs and stool and plasma inflammatory and permeability markers were compared between patients and controls and related to one another and to the gut microbiota.

RESULTS

Calprotectin was increased and SCFAs decreased in stool in PD in a sex-dependent manner. Inflammatory markers in plasma and stool were neither intercorrelated nor strongly associated with SCFA levels. Age at PD onset was positively correlated with SCFAs and negatively correlated with CXCL8 and IL-1β in stool. Fecal zonulin correlated positively with fecal NGAL and negatively with PD motor and non-motor symptoms. Microbiota diversity and composition were linked to levels of SCFAs, inflammatory factors, and zonulin in stool. Certain relationships differed between patients and controls and by sex.

CONCLUSIONS

Intestinal inflammatory responses and reductions in fecal SCFAs occur in PD, are related to the microbiota and to disease onset, and are not reflected in plasma inflammatory profiles. Some of these relationships are distinct in PD and are sex-dependent. This study revealed potential alterations in microbiota-host interactions and links between earlier PD onset and intestinal inflammatory responses and reduced SCFA levels, highlighting candidate molecules and pathways which may contribute to PD pathogenesis and clinical presentation and which warrant further investigation.

The relationship between serum interleukin-1β, interleukin-6, interleukin-8, interleukin-10, tumor necrosis factor-α levels and clinical features in essential tremor

BACKGROUND

In recent years, there has been discussion that essential tremor (ET) might be a neurodegenerative disease. Indicators of inflammation are considered as possible biomarkers of neurodegeneration. In this connection, the aim of our study was to identify the relationship between serum inflammation markers and clinical features in ET, including the severity of tremor, cognitive decline, depression.

METHODS

The serum interleukin-1β (IL-1β), IL-6, IL-8, IL-10, and tumor necrosis factor-α (TNF-α) levels were measured in 90 ET patients and 90 healthy control people of the corresponding age and gender. Fahn-Tolosa-Marin scale was used for the severity of the tremor. Cognitive function was assessed using the MoCA. Affective symptoms were measured by the Beck Depression Inventory.

RESULTS

ET patients had significantly lower serum TNF-α (p < 0.01) but higher serum IL-8 (p < 0.02) and IL-10 (p < 0.01) levels compared to the control patients. The severity of tremor positively correlated with the serum IL-8 level, R = 0.3 (p < 0.01). The serum IL-6 level was higher in ET patients with cognitive impairment compared with normal cognitive ability (p < 0.01). ROC analysis showed that an IL-8 level of 4 pg/ml and higher related with a high risk of severe tremor in ET (AUC-ROC = 0.761).

CONCLUSIONS

Our findings demonstrate that neuroinflammation makes a certain contribution to the development of ET.

Iron Dysregulation and Inflammagens Related to Oral and Gut Health Are Central to the Development of Parkinson's Disease

Neuronal lesions in Parkinson's disease (PD) are commonly associated with α-synuclein (α-Syn)-induced cell damage that are present both in the central and peripheral nervous systems of patients, with the enteric nervous system also being especially vulnerable. Here, we bring together evidence that the development and presence of PD depends on specific sets of interlinking factors that include neuroinflammation, systemic inflammation, α-Syn-induced cell damage, vascular dysfunction, iron dysregulation, and gut and periodontal dysbiosis. We argue that there is significant evidence that bacterial inflammagens fuel this systemic inflammation, and might be central to the development of PD. We also discuss the processes whereby bacterial inflammagens may be involved in causing nucleation of proteins, including of α-Syn. Lastly, we review evidence that iron chelation, pre-and probiotics, as well as antibiotics and faecal transplant treatment might be valuable treatments in PD. A most important consideration, however, is that these therapeutic options need to be validated and tested in randomized controlled clinical trials. However, targeting underlying mechanisms of PD, including gut dysbiosis and iron toxicity, have potentially opened up possibilities of a wide variety of novel treatments, which may relieve the characteristic motor and nonmotor deficits of PD, and may even slow the progression and/or accompanying gut-related conditions of the disease.

Microglia, inflammation and gut microbiota responses in a progressive monkey model of Parkinson's disease: A case series

Inflammation has been linked to the development of nonmotor symptoms in Parkinson's disease (PD), which greatly impact patients' quality of life and can often precede motor symptoms. Suitable animal models are critical for our understanding of the mechanisms underlying disease and the associated prodromal disturbances. The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkey model is commonly seen as a "gold standard" model that closely mimics the clinical motor symptoms and the nigrostriatal dopaminergic loss of PD, however MPTP toxicity extends to other nondopaminergic regions. Yet, there are limited reports monitoring the MPTP-induced progressive central and peripheral inflammation as well as other nonmotor symptoms such as gastrointestinal function and microbiota. We report 5 cases of progressive parkinsonism in non-human primates to gain a broader understanding of MPTP-induced central and peripheral inflammatory dysfunction to understand the potential role of inflammation in prodromal/pre-motor features of PD-like degeneration. We measured inflammatory proteins in plasma and CSF and performed [¹⁸F]FEPPA PET scans to evaluate translocator proteins (TSPO) or microglial activation. Monkeys were also evaluated for working memory and executive function using various behavior tasks and for gastrointestinal hyperpermeability and microbiota composition. Additionally, monkeys were treated with a novel TNF inhibitor XPro1595 (10 mg/kg, n = 3) or vehicle (n = 2) every three days starting 11 weeks after the initiation of MPTP to determine whether XPro1595 would alter inflammation and microglial behavior in a progressive model of PD. The case studies revealed that earlier and robust [¹⁸F]FEPPA PET signals resulted in earlier and more severe parkinsonism, which was seen in male cases compared to female cases. Potential other sex differences were observed in circulating inflammation, microbiota diversity and their metabolites. Additional studies with larger group sizes of both sexes would enable confirmation and extension of these findings. If these findings reflect potential differences in humans, these sex differences have significant implications for therapeutic development of inflammatory targets in the clinic.

Association of inflammatory factors and aging in Parkinson's disease

BACKGROUND

Parkinson's disease as a common neurodegenerative disease, has been found to be related to inflammation. So we observed the characteristics of inflammatory indexes in patients with Parkinson's disease and investigated the relationship between inflammatory cytokines and clinical characteristics. Emerging data may reveal novel neuroinflammatory pathways and identify new targets for treatment of Parkinson's disease.

METHODS

We examined the inflammatory indexes in 183 patients and 89 healthy controls in association with clinical characteristics.

RESULTS

Patients had significantly higher levels of monocytes, neutrophils, high-sensitivity C-reactive protein, and monocyte-to-high-density lipoprotein ratios (p < 0.01) and lower levels of lymphocytes (p = 0.02) than the controls. There were no significant differences in age, leukocytes, high-density lipoprotein, or neutrophil-lymphocyte ratios between the two groups (p > 0.05). Multivariate logistic regression analysis of these indicators revealed that lymphocyte level was a protective factor (p = 0.025, OR=-0.679), while high-sensitivity C-reactive protein level was a risk factor (p = 0.000, OR=1.168) for Parkinson's disease. High-sensitivity C-reactive protein levels were higher in older Parkinson's disease patients.

CONCLUSION

High-sensitivity C-reactive protein is positively related to the risk of Parkinson's disease, especially in aging patients. High-sensitivity C-reactive protein is a potential biomarker for disease progression and treatment response for Parkinson's disease.

Cerebrospinal Fluid Cytokines and Neurodegeneration-Associated Proteins in Parkinson's Disease

INTRODUCTION

Immune markers are altered in Parkinson's disease (PD), but relationships between cerebrospinal fluid (CSF) and plasma cytokines and associations with neurodegeneration-associated proteins remain unclear.

METHODS

CSF and plasma samples and demographic/clinical measures were obtained from 35 PD patients. CSF samples were analyzed for cytokines (together with plasma) and for α-synuclein, amyloid β(1-42) peptide, total tau, and phospho(Thr231)-tau.

RESULTS

There were no CSF-plasma cytokine correlations. Interleukin (IL)-8 was higher and interferon-γ, IL-10, and tumor necrosis factor-α were lower in CSF versus plasma. In CSF, total tau correlated positively with IL-8 and IL-1β, whereas α-synuclein correlated positively with amyloid β(1-42) and negatively with semantic fluency (a known marker of PD dementia risk).

DISCUSSION

CSF and peripheral cytokine profiles in PD are not closely related. Associations between CSF IL-8 and IL-1β and tau suggest that CSF inflammatory changes may relate to tau pathology within PD. CSF α-synuclein/amyloid β may reflect the risk of developing PD dementia. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Systemic activation of NLRP3 inflammasome and plasma α-synuclein levels are correlated with motor severity and progression in Parkinson's disease

Background

Emerging evidence indicates that inflammasome-induced inflammation plays a crucial role in the pathogenesis of Parkinson’s disease (PD). Several proteins including α-synuclein trigger the activation of NLRP3 inflammasome. However, few studies examined whether inflammasomes are activated in the periphery of PD patients and their possible value in the diagnosis or tracking of the progress of PD. The aim of this study was to determine the association between inflammasome-induced inflammation and clinical features in PD.

Methods

There were a total of 67 participants, including 43 patients with PD and 24 controls, in the study. Participants received a complete evaluation of motor and non-motor symptoms, including Hoehn and Yahr (H-Y) staging scale. Blood samples were collected from all participants. The protein and mRNA expression levels of inflammasomes subtypes and components in peripheral blood mononuclear cells (PBMCs) were determined using western blotting and RT-qPCR. We applied Meso Scale Discovery (MSD) immunoassay to measure the plasma levels of IL-1β and α-synuclein.

Results

We observed increased gene expression of NLRP3, ASC, and caspase-1 in PBMCs, and increased protein levels of NLRP3, caspase-1, and IL-1β in PD patients. Plasma levels of IL-1β were significantly higher in patients with PD compared with controls and have a positive correlation with H-Y stage and UPDRS part III scores. Furthermore, plasma α-synuclein levels were also increased in PD patients and have a positive correlation with both UPDRS part III scores and plasma IL-1β levels.

Conclusions

Our data demonstrated that the NLRP3 inflammasome is activated in the PBMCs from PD patients. The related inflammatory cytokine IL-1β and total α-synuclein in plasma were increased in PD patients than controls, and both of them presented a positive correlation with motor severity in patients with PD. Furthermore, plasma α-synuclein levels have a positive correlation with IL-1β levels in PD patients. All these findings suggested that the NLRP3 inflammasome activation-related cytokine IL-1β and α-synuclein could serve as non-invasive biomarkers to monitor the severity and progression of PD in regard to motor function.

Salsolinol-neurotoxic or Neuroprotective?

Salsolinol (6,7-dihydroxy-1-methyl-1,2,3,4-tetrahydroisoquinoline), widely available in many edibles, is considered to alter the function of dopaminergic neurons in the central nervous system and thus, multiple hypotheses on its either physiological and/or pathophysiological role have emerged. The aim of our work was to revisit its potentially neurotoxic and/or neuroprotective role through a series of both in vitro and in vivo experiments. Salsolinol in the concentration range 10-250 μM did not show any significant release of lactate dehydrogenase from necrotic SH-SY5Y cells and was able in the concentration of 50 and 100 μM to rescue SH-SY5Y cells from death induced by H₂O₂. Its neuroprotective effect against neurotoxin 6-hydroxydopamine was also determined. Salsolinol was found to decrease significantly the reactive oxygen species level in SH-SY5Y cells treated by 500 μM H₂O₂ and the caspase activity induced by 300 μM of H₂O₂ or 100 μM of 6-hydroxydopamine. Serum levels of TNFα and CRP of salsolinol-treated rats were not significantly different from control animals. Both TNFα and CRP served as indirect markers of neurotoxicity and/or neuroprotection. Although the neurotoxic properties of salsolinol have numerously been emphasized, its neuroprotective properties should not be neglected and need greater consideration.

Biomarkers for Parkinson's Disease: How Good Are They?

Parkinson's disease (PD) is a complex neurodegenerative disorder with no cure in sight. Clinical challenges of the disease include the inability to make a definitive diagnosis at the early stages and difficulties in predicting the disease progression. The unmet demand to identify reliable biomarkers for early diagnosis and management of the disease course of PD has attracted a lot of attention. However, only a few reported candidate biomarkers have been tried in clinical practice at the present time. Studies on PD biomarkers have often overemphasized the discovery of novel identity, whereas efforts to further evaluate such candidates are rare. Therefore, we update the new development of biomarker discovery in PD and discuss the standard process in the evaluation and assessment of the diagnostic or prognostic value of the identified potential PD biomarkers in this review article. Recent developments in combined biomarkers and the current status of clinical trials of biomarkers as outcome measures are also discussed. We believe that the combination of different biomarkers might enhance the specificity and sensitivity over a single measure that might not be sufficient for such a multiplex disease.

Exploring the "Multiple-Hit Hypothesis" of Neurodegenerative Disease: Bacterial Infection Comes Up to Bat

Despite major strides in personalized genomics, it remains poorly understood why neurodegenerative diseases occur in only a fraction of individuals with a genetic predisposition and conversely, why individuals with no genetic risk of a disorder develop one. Chronic diseases like Alzheimer's, Parkinson's, and Multiple sclerosis are speculated to result from a combination of genetic and environmental factors, a concept commonly referred to as the “multiple hit hypothesis.” A number of bacterial infections have been linked to increased risk of neurodegeneration, and in some cases, clearance of bacterial pathogens has been correlated with amelioration of central nervous system (CNS) deficits. Additionally, mutations in several genes known to contribute to CNS disorders like Parkinson's Disease have repeatedly been implicated in susceptibility to intracellular bacterial infection. Recent data has begun to demonstrate roles for these genes (PARK2, PINK1, and LRRK2) in modulating innate immune outcomes, suggesting that immune dysregulation may play an even more important role in neurodegeneration than previously appreciated. This review will broadly explore the connections between bacterial infection, immune dysregulation, and CNS disorders. Understanding this interplay and how bacterial pathogenesis contributes to the “multiple-hit hypothesis” of neurodegeneration will be crucial to develop therapeutics to effectively treat both neurodegeneration and infection.

Peripheral-Central Neuroimmune Crosstalk in Parkinson's Disease: What Do Patients and Animal Models Tell Us?

The brain is no longer considered an immune privileged organ and neuroinflammation has long been associated with Parkinson's disease. Accumulating evidence demonstrates that innate and adaptive responses take place in the CNS. The extent to which peripheral immune alterations impacts on the CNS, or vice and versa, is, however, still a matter of debate. Gaining a better knowledge of the molecular and cellular immune dysfunctions present in these two compartments and clarifying their mutual interactions is a fundamental step in understanding and preventing Parkinson's disease (PD) pathogenesis. This review provides an overview of the current knowledge on inflammatory processes evidenced both in PD patients and in toxin-induced animal models of the disease. It discusses differences and similarities between human and animal studies in the context of neuroinflammation and immune responses and how they have guided therapeutic strategies to slow down disease progression. Future longitudinal studies are necessary and can help gain a better understanding on peripheral-central nervous system crosstalk to improve therapeutic strategies for PD.

Translocator Protein Ligand Protects against Neurodegeneration in the MPTP Mouse Model of Parkinsonism

Parkinson's disease is the second most common neurodegenerative disease, after Alzheimer's disease. Parkinson's disease is a movement disorder with characteristic motor features that arise due to the loss of dopaminergic neurons from the substantia nigra. Although symptomatic treatment by the dopamine precursor levodopa and dopamine agonists can improve motor symptoms, no disease-modifying therapy exists yet. Here, we show that Emapunil (AC-5216, XBD-173), a synthetic ligand of the translocator protein 18, ameliorates degeneration of dopaminergic neurons, preserves striatal dopamine metabolism, and prevents motor dysfunction in female mice treated with the MPTP, as a model of parkinsonism. We found that Emapunil modulates the inositol requiring kinase 1α (IRE α)/X-box binding protein 1 (XBP1) unfolded protein response pathway and induces a shift from pro-inflammatory toward anti-inflammatory microglia activation. Previously, Emapunil was shown to cross the blood-brain barrier and to be safe and well tolerated in a Phase II clinical trial. Therefore, our data suggest that Emapunil may be a promising approach in the treatment of Parkinson's disease.SIGNIFICANCE STATEMENT Our study reveals a beneficial effect of Emapunil on dopaminergic neuron survival, dopamine metabolism, and motor phenotype in the MPTP mouse model of parkinsonism. In addition, our work uncovers molecular networks which mediate neuroprotective effects of Emapunil, including microglial activation state and unfolded protein response pathways. These findings not only contribute to our understanding of biological mechanisms of translocator protein 18 (TSPO) function but also indicate that translocator protein 18 may be a promising therapeutic target. We thus propose to further validate Emapunil in other Parkinson's disease mouse models and subsequently in clinical trials to treat Parkinson's disease.