Serum interleukin (IL-2, IL-10, IL-6, IL-4), TNFα, and INFγ concentrations are elevated in patients with atypical and idiopathic parkinsonism

Pesticides and the Gut Microbiota: Implications for Parkinson's Disease

Parkinson's disease (PD) affects more people worldwide than just aging alone can explain. This is likely due to environmental influences, genetic makeup, and changes in daily habits. The disease develops in a complex way, with movement problems caused by Lewy bodies and the loss of dopamine-producing neurons. Some research suggests Lewy bodies might start in the gut, hinting at a connection between these structures and gut health in PD patients. These patients often have different gut bacteria and metabolites. Pesticides are known to increase the risk of PD, with evidence showing they harm more than just dopamine neurons. Long-term exposure to pesticides in food might affect the gut barrier, gut bacteria, and the blood-brain barrier, but the exact link is still unknown. This review looks at how pesticides and gut bacteria separately influence PD development and progression, highlighting the harmful effects of pesticides and changes in gut bacteria. We have examined the interaction between pesticides and gut bacteria in PD patients, summarizing how pesticides cause imbalances in gut bacteria, the resulting changes, and their overall effects on the PD prognosis.

Immune responses to oligomeric α-synuclein in Parkinson's disease peripheral blood mononuclear cells

Parkinson's disease displays clinical heterogeneity, presenting with motor and non-motor symptoms. Heterogeneous phenotypes, named brain-first and body-first, may reflect distinct α-synuclein pathology starting either in the central nervous system or in the periphery. The immune system plays a prominent role in the central and peripheral pathology, with misfolded α-synuclein being placed at the intersection between neurodegeneration and inflammation. Here, we characterized the inflammatory profile and immune-phenotype of peripheral blood mononuclear cells (PBMCs) from Parkinson's disease patients upon stimulation with α-synuclein monomer or oligomer, and investigated relationships of immune parameters with clinical scores of motor and non-motor symptoms. Freshly isolated PBMCs from 21 Parkinson's disease patients and 18 healthy subjects were exposed in vitro to α-synuclein species. Cytokine/chemokine release was measured in the culture supernatant by Multiplex Elisa. The immune-phenotype was studied by FACS-flow cytometry. Correlation analysis was computed between immune parameters and parkinsonian motor and non-motor scales. We found that Parkinson's disease patients exhibited a dysregulated PBMC-cytokine profile, which remained unaltered after exposure to α-synuclein species and correlated with both motor and non-motor severity, with a strong correlation observed with olfactory impairment. Exposure of PBMCs from healthy controls to α-synuclein monomer/oligomer increased the cytokine/chemokine release up to patient's values. Moreover, the PBMCs immune phenotype differed between patients and controls and revealed a prominent association of the Mos profile with olfactory impairment, and of NK profile with constipation. Results suggest that a deranged PBMC-immune profile may reflect distinct clinical subtypes and would fit with the recent classification of Parkinson's disease into peripheral-first versus brain-first phenotype.

The impact of interleukin-6 (IL-6) and mesenchymal stem cell-derived IL-6 on neurological conditions

Interleukin-6 (IL-6) is a versatile cytokine crucial for immune response modulation, inflammation regulation, and various physiological processes in the body. Its wide-ranging functions underscore its importance in maintaining health. Dysregulated IL-6 is closely associated with many diseases, making it a key research and therapeutic target. Elevated IL-6 levels in the central nervous system worsen neuroinflammation in neurodegenerative diseases by activating microglia and astrocytes and releasing pro-inflammatory cytokines and neurotoxic molecules. Moreover, dysregulated IL-6 weakens the blood-brain barrier, exacerbating neuroinflammation and neuronal damage by allowing peripheral immune cells and inflammatory mediators to enter the brain. Mesenchymal stem cells (MSCs) show promise in modulating neuroinflammation by regulating IL-6 levels. They effectively suppress pro-inflammatory cytokines, including IL-6, while promoting anti-inflammatory factors. This therapeutic approach highlights the importance of targeting IL-6 and other inflammatory mediators to alleviate neuroinflammation and its adverse effects on neurological disorders. This review provides a comprehensive overview of IL-6's involvement in neurological disorders, examining endogenous IL-6 and IL-6 derived from MSCs. We explore IL-6's mechanisms affecting neuronal function, survival, and immune modulation in the central nervous system. Additionally, we discuss the potential of MSC-derived IL-6 in neuroregeneration and neuroprotection. By elucidating IL-6's interplay with neurological pathologies, this review offers insights into novel therapeutic strategies targeting IL-6 signaling pathways for neurological disorders.

Neurovascular and immune factors of vulnerability of substantia nigra dopaminergic neurons in non-human primates

Dopaminergic neurons in the ventral tier of the substantia nigra pars compacta (SNc) degenerate prominently in Parkinson's disease (PD), while those in the dorsal tier and ventral tegmental area are relatively spared. The factors determining why these neurons are more vulnerable than others are still unrevealed. Neuroinflammation and immune cell infiltration have been demonstrated to be a key feature of neurodegeneration in PD. However, the link between selective dopaminergic neuron vulnerability, glial and immune cell response, and vascularization and their interactions has not been deciphered. We aimed to investigate the contribution of glial cell activation and immune cell infiltration in the selective vulnerability of ventral dopaminergic neurons within the midbrain in a non-human primate model of PD. Structural characteristics of the vasculature within specific regions of the midbrain were also evaluated. Parkinsonian monkeys exhibited significant microglial and astroglial activation in the whole midbrain, but no major sub-regional differences were observed. Remarkably, the ventral substantia nigra was found to be typically more vascularized compared to other regions. This feature might play some role in making this region more susceptible to immune cell infiltration under pathological conditions, as greater infiltration of both T- and B- lymphocytes was observed in parkinsonian monkeys. Higher vascular density within the ventral region of the SNc may be a relevant factor for differential vulnerability of dopaminergic neurons in the midbrain. The increased infiltration of T- and B- cells in this region, alongside other molecules or toxins, may also contribute to the susceptibility of dopaminergic neurons in PD.

The potential significance of hepcidin evaluation in progressive supranuclear palsy

INTRODUCTION

Hepcidin is a peptide associated with controlling the distribution of iron in tissues. Growing interest is linked with its impact on neurodegenerative diseases, as disruption of the iron regulation may be considered an initiatory element of pathological protein accumulation. The possible impact of hepcidin was not previously sufficiently explored in progressive supranuclear palsy (PSP).

METHODS

Twelve patients with PSP-Richardson's syndrome (PSP-RS), 12 with PSP-Parkinsonism Predominant (PSP-P), and 12 controls were examined using Unified Parkinson's Disease Rating Scale-III part (UPDRS-III) in OFF stage and analyzed in the context of hepcidin levels in the serum.

RESULTS

The work revealed increased levels of hepcidin in PSP-RS when compared to PSP-P and controls. Moreover, hepcidin was found to be negatively correlated with UPDRS-III results in PSP-RS, whereas positively in PSP-P.

CONCLUSION

The work may suggest a possible impact of hepcidin in PSP, possibly differing depending on its subtype.

Investigation of the causal association between Parkinson's disease and autoimmune disorders: a bidirectional Mendelian randomization study

Background

To date, an increasing number of epidemiological evidence has pointed to potential relationships between Parkinson's disease (PD) and various autoimmune diseases (AIDs), however, no definitive conclusions has been drawn about whether PD is causally related to AIDs risk.

Methods

By employing summary statistics from the latest and most extensive genome-wide association studies (GWAS), we performed a bidirectional two-sample Mendelian randomization (MR) analysis to investigate the causal associations between PD and a variety of 17 AIDs, encompassing multiple sclerosis, neuromyelitis optica spectrum disorder, myasthenia gravis, asthma, inflammatory bowel disease, Crohn's disease, ulcerative colitis, irritable bowel syndrome, celiac disease, primary biliary cirrhosis, primary sclerosing cholangitis, type 1 diabetes, ankylosing spondylitis, rheumatoid arthritis, systemic lupus erythematosus, psoriasis and vitiligo. Inverse-variance weighted (IVW) was adopted as the main statistical approach to obtain the causal estimates of PD on different AIDs, supplemented by a series of complementary analyses (weighted median, MR Egger regression, and MR-PRESSO) for further strengthening the robustness of results.

Results

Our MR findings suggested that genetically predicted higher liability to PD was causally associated with a decreased risk of irritable bowel syndrome (OR = 0.98; 95% CI: 0.96-0.99; P = 0.032). On the contrary, IVW analysis showed a potential positive correlation between genetically determined PD and the incidence of type 1 diabetes (OR = 1.10; 95%CI: 1.02-1.19; P = 0.010). Subsequent MR tests ended up in similar results, confirming our findings were reliable. Additionally, in the reverse MR analyses, we did not identify any evidence to support the causal relationship of genetic predisposition to AIDs with PD susceptibility.

Conclusion

In general, a bifunctional role that PD exerted on the risk of developing AIDs was detected in our studies, both protecting against irritable bowel syndrome occurrence and raising the incidence of type 1 diabetes. Future studies, including population-based observational studies and molecular experiments in vitro and in vivo, are warranted to validate the results of our MR analyses and refine the underlying pathological mechanisms involved in PD-AIDs associations.

Free water imaging in Parkinson's disease and atypical parkinsonian disorders

BACKGROUND

Free water (FW)-corrected diffusion measures are more precise compared to standard diffusion measures. This study comprehensively evaluates FW and corrected diffusion metrics for whole brain white and deep gray matter (WM, GM) structures in patients with Parkinson's disease (PD), progressive supranuclear palsy (PSP) and multiple system atrophy (MSA) and attempts to ascertain the probable patterns of WM abnormalities.

METHOD

Diffusion MRI was acquired for subjects with PD (n = 133), MSA (n = 25), PSP (n = 30) and matched healthy controls (HC) (n = 99, n = 24, n = 12). Diffusion metrics of FA, MD, AD, RD were generated and FW, corrected FA maps were calculated using a bi-tensor model. TBSS was carried out at 5000 permutations with significance at p < 0.05. For GM, diffusivity maps were extracted from the basal ganglia, and analyzed at an FDR with p < 0.05.

RESULTS

Compared to HC, PD showed focal changes in FW. MSA showed changes in the cerebellum and brainstem, and PSP showed increase in FW involving supratentorial WM and midbrain. All three showed increased substantia nigra FW. MSA, PSP demonstrated increased FW in bilateral putamen. PD showed increased FW in left GP externa, and bilateral thalamus. Compared to HC, MSA had increased FW in bilateral GP interna, and left thalamic. PSP had an additional increase in FW of the right GP externa, right GP interna, and bilateral thalamus.

CONCLUSION

The present study demonstrated definitive differences in the patterns of FW alterations between PD and atypical parkinsonian disorders suggesting the possibility of whole brain FW maps being used as markers for diagnosis of these disorders.

The Contribution of Type 2 Diabetes to Parkinson's Disease Aetiology

Type 2 diabetes (T2D) and Parkinson's disease (PD) are chronic disorders that have a significant health impact on a global scale. Epidemiological, preclinical, and clinical research underpins the assumption that insulin resistance and chronic inflammation contribute to the overlapping aetiologies of T2D and PD. This narrative review summarises the recent evidence on the contribution of T2D to the initiation and progression of PD brain pathology. It also briefly discusses the rationale and potential of alternative pharmacological interventions for PD treatment.

Association analysis of dopaminergic degeneration and the neutrophil-to-lymphocyte ratio in Parkinson's disease

Introduction

Peripheral inflammatory responses are suggested to play a major role in the pathophysiology of Parkinson's disease (PD). The neutrophil-to-lymphocyte ratio (NLR), a new recognized biomarker, can reflect peripheral inflammation in PD. However, the association between the NLR and dopaminergic degeneration in PD remains unclear.

Methods

In this retrospective study, 101 enrolled PD patients were categorized into early-stage and advanced-stage PD based on the Hoehn and Yahr (HY) scale. We evaluated the clinical characteristics, peripheral immune profile, and 11C-CFT striatal dopamine transporter (DAT) binding levels. Linear regression analyses were employed to assess the associations between NLR and striatal DAT levels at different stages in PD patients.

Results

Covariate-controlled regression analysis revealed that higher NLR was significantly associated with lower DAT levels in the caudate (β = -0.27, p = 0.003) and the putamen (β = -0.27, p = 0.011). Moreover, in the early-stage PD subgroup, a similar association was observed (caudate: β = -0.37, p = 0.013; putamen: β = -0.45, p = 0.005). The lymphocytes count was correlated positively with the striatal DAT levels in the Spearman correlation analysis whether in total patients (caudate: ρ = 0.25, p = 0.013; putamen: ρ = 0.22, p = 0.026) or in the early-stage subgroup (caudate: ρ = 0.31, p = 0.023, putamen: ρ = 0.34, p = 0.011).

Conclusion

Dopaminergic degeneration is associated with peripheral inflammation in PD. The NLR, a widely used inflammatory marker, may have the potential to reflect the degree of dopaminergic degeneration in individuals with early-stage PD.

Prodromal Parkinson disease signs are predicted by a whole-blood inflammatory transcriptional signature in young Pink1-/- rats

BACKGROUND

Parkinson disease (PD) is the fastest growing neurodegenerative disease. The molecular pathology of PD in the prodromal phase is poorly understood; as such, there are no specific prognostic or diagnostic tests. A validated Pink1 genetic knockout rat was used to model early-onset and progressive PD. Male Pink1-/- rats exhibit progressive declines in ultrasonic vocalizations as well as hindlimb and forelimb motor deficits by mid-to-late adulthood. Previous RNA-sequencing work identified upregulation of genes involved in disease pathways and inflammation within the brainstem and vocal fold muscle. The purpose of this study was to identify gene pathways within the whole blood of young Pink1-/- rats (3 months of age) and to link gene expression to early acoustical changes. To accomplish this, limb motor testing (open field and cylinder tests) and ultrasonic vocalization data were collected, immediately followed by the collection of whole blood and RNA extraction. Illumina® Total RNA-Seq TruSeq platform was used to profile differential expression of genes. Statistically significant genes were identified and Weighted Gene Co-expression Network Analysis was used to construct co-expression networks and modules from the whole blood gene expression dataset as well as the open field, cylinder, and USV acoustical dataset. ENRICHR was used to identify the top up-regulated biological pathways.

RESULTS

The data suggest that inflammation and interferon signaling upregulation in the whole blood is present during early PD. We also identified genes involved in the dysregulation of ribosomal protein and RNA processing gene expression as well as prion protein gene expression.

CONCLUSIONS

These data identified several potential blood biomarkers and pathways that may be linked to anxiety and vocalization acoustic parameters and are key candidates for future drug-repurposing work and comparison to human datasets.

The Spreading and Effects of Human Recombinant α-Synuclein Preformed Fibrils in the Cerebrospinal Fluid of Mice

Parkinson's disease (PD) patients harbor seeding-competent α-synuclein (α-syn) in their cerebrospinal fluid (CSF), which is mainly produced by the choroid plexus (ChP). Nonetheless, little is known about the role of the CSF and the ChP in PD pathogenesis. To address this question, we used an intracerebroventricular (icv) injection mouse model to assess CSF α-syn spreading and its short- and long-term consequences on the brain. Hereby, we made use of seeding-competent, recombinant α-syn preformed fibrils (PFF) that are known to induce aggregation and subsequent spreading of endogenous α-syn in stereotactic tissue injection models. Here, we show that icv-injected PFF, but not monomers (Mono), are rapidly removed from the CSF by interaction with the ChP. Additionally, shortly after icv injection both Mono and PFF were detected in the olfactory bulb and striatum. This spreading was associated with increased inflammation and complement activation in these tissues as well as leakage of the blood-CSF barrier. Despite these effects, a single icv injection of PFF didn't induce a decline in motor function. In contrast, daily icv injections over the course of 5 days resulted in deteriorated grip strength and formation of phosphorylated α-syn inclusions in the brain 2 months later, whereas dopaminergic neuron levels were not affected. These results point toward an important clearance function of the CSF and the ChP, which could mediate removal of PFF from the brain, whereby chronic exposure to PFF in the CSF may negatively impact blood-CSF barrier functionality and PD pathology.

Neuroinflammatory gene expression profiles of reactive glia in the substantia nigra suggest a multidimensional immune response to alpha synuclein inclusions

Parkinson's disease (PD) pathology is characterized by alpha-synuclein (α-syn) aggregates, degeneration of dopamine neurons in the substantia nigra pars compacta (SNpc), and neuroinflammation. The presence of reactive glia correlates with deposition of pathological α-syn in early-stage PD. Thus, understanding the neuroinflammatory response of microglia and astrocytes to synucleinopathy may identify therapeutic targets. Here we characterized the neuroinflammatory gene expression profile of reactive microglia and astrocytes in the SNpc during early synucleinopathy in the rat α-syn pre-formed fibril (PFF) model. Rats received intrastriatal injection of α-syn PFFs and expression of immune genes was quantified with droplet digital PCR (ddPCR), after which fluorescent in situ hybridization (FISH) was used to localize gene expression to microglia or astrocytes in the SNpc. Genes previously associated with reactive microglia (Cd74, C1qa, Stat1, Axl, Casp1, Il18, Lyz2) and reactive astrocytes (C3, Gbp2, Serping1) were significantly upregulated in the SN of PFF injected rats. Localization of gene expression to SNpc microglia near α-syn aggregates identified a unique α-syn aggregate microglial gene expression profile characterized by upregulation of Cd74, Cxcl10, Rt-1a2, Grn, Csf1r, Tyrobp, C3, C1qa, Serping1 and Fcer1g. Importantly, significant microglial upregulation of Cd74 and C3 were only observed following injection of α-syn PFFs, not α-syn monomer, confirming specificity to α-syn aggregation. Serping1 expression also localized to astrocytes in the SNpc. Interestingly, C3 expression in the SNpc localized to microglia at 2- and 4-months post-PFF, but to astrocytes at 6-months post-PFF. We also observed expression of Rt1-a2 and Cxcl10 in SNpc dopamine neurons. Cumulatively our results identify a dynamic, yet reproducible gene expression profile of reactive microglia and astrocytes associated with early synucleinopathy in the rat SNpc.

Advancements in Genetic and Biochemical Insights: Unraveling the Etiopathogenesis of Neurodegeneration in Parkinson's Disease

Parkinson's disease (PD) is the second most prevalent neurodegenerative movement disorder worldwide, which is primarily characterized by motor impairments. Even though multiple hypotheses have been proposed over the decades that explain the pathogenesis of PD, presently, there are no cures or promising preventive therapies for PD. This could be attributed to the intricate pathophysiology of PD and the poorly understood molecular mechanism. To address these challenges comprehensively, a thorough disease model is imperative for a nuanced understanding of PD's underlying pathogenic mechanisms. This review offers a detailed analysis of the current state of knowledge regarding the molecular mechanisms underlying the pathogenesis of PD, with a particular emphasis on the roles played by gene-based factors in the disease's development and progression. This study includes an extensive discussion of the proteins and mutations of primary genes that are linked to PD, including α-synuclein, GBA1, LRRK2, VPS35, PINK1, DJ-1, and Parkin. Further, this review explores plausible mechanisms for DAergic neural loss, non-motor and non-dopaminergic pathologies, and the risk factors associated with PD. The present study will encourage the related research fields to understand better and analyze the current status of the biochemical mechanisms of PD, which might contribute to the design and development of efficacious and safe treatment strategies for PD in future endeavors.

Differential profiles of serum cytokines in Parkinson's disease according to disease duration

OBJECTIVE

Neurodegeneration and neuroinflammation are two intertwined mechanisms contributing to the pathophysiology of Parkinson's disease. Whether circulating biomarkers reflecting those two processes differ according to disease duration remains to be established. The present study was conducted to characterize the biomarkers individuals with PD with short (≤5 years) or long disease duration (>5 years).

METHODS

We consecutively enrolled 104 patients with Parkinson's disease and evaluated them using validated clinical scales (MDS-UPDRS, Hoehn and Yahr staging, MMSE). Serum samples were assayed for the following biomarkers: neurofilament light chain (NfL), brain-derived neurotrophic factor (BDNF), interleukin (IL-) 1β, 4, 5, 6, 10, 17, interferon-γ, and tumor necrosis factor α.

RESULTS

Mean age of participants was 66.0 ± 9.6 years and 45 (34%) were women. The average disease duration was 8 ± 5 years (range 1 to 19 years). Patients with short disease duration (≤ 5 years) showed a pro-inflammatory profile, with significantly higher levels of pro-inflammatory IL-1β and lower concentrations of IL-5, IL-10 and IL-17 (p < 0.05). NfL serum levels showed a positive correlation with disease duration and age (respectively rho = 0.248, p = 0.014 and rho = 0.559, p < 0.001) while an opposite pattern was detected for BDNF (respectively rho -0,187, p = 0.034 and rho = -0.245, p = 0.014).

CONCLUSIONS

Our findings suggest that a pro-inflammatory status may be observed in PD patients in the early phases of the disease, independently from age.

Cytokine activity in Parkinson's disease

The contribution of the immune system to the pathophysiology of neurodegenerative Parkinson's disease (PD) is increasingly being recognised, with alterations in the innate and adaptive arms of the immune system underlying central and peripheral inflammation in PD. As chief modulators of the immune response, cytokines have been intensely studied in the field of PD both in terms of trying to understand their contribution to disease pathogenesis, and if they may comprise much needed therapeutic targets for a disease with no current modifying therapy. This review summarises current knowledge on key cytokines implicated in PD (TNFα, IL-6, IL-1β, IL-10, IL-4 and IL-1RA) that can modulate both pro-inflammatory and anti-inflammatory effects. Cytokine activity in PD is clearly a complicated process mediated by substantial cross-talk of signalling pathways and the need to balance pro- and anti-inflammatory effects. However, understanding cytokine activity may hold promise for unlocking new insight into PD and how it may be halted.

Natural products for the treatment of neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are among the most common diseases in older adults worldwide. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common neurodegenerative diseases, and are accompanied by cerebral cortical atrophy, neuronal loss, protein accumulation, and excessive accumulation of metal ions. Natural products exhibit outstanding performance in improving cerebral circulatory disorders, promoting cerebral haematoma absorption, repairing damaged nerve tissue, and improving damaged nerve function. In recent years, studies have shown that neuroinflammatory mechanisms and signalling pathways closely related to the occurrence and development of neurological diseases include microglial activation, nuclear factor-κB (NF-κB) pathway, mitogen activated protein kinases (MAPK) pathway, reactive oxygen pathway, nucleotide binding oligomerisation domain-like receptor protein3 (NLRP3) inflammasomes, toll-like receptor4 (TLR4) pathway, nuclear factor erythroid 2-related factor 2 (Nrf2)/hemeoxygenase-1 (HO-1) pathway, phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway, and intestinal flora. Therefore, this study considered the mechanism of neurological diseases as the starting point to review the mechanism of action of natural products in the prevention and treatment of AD and PD in recent years to provide a theoretical basis for clinical prevention and treatment.

AIM

Natural products are a promising source of novel lead structures that have long been used to treat various nervous system diseases.

METHODOLOGY

This review collected literature on neurological diseases and natural products from 2012 to 2022, which were mainly searched through databases such as ScienceDirect, Springer, PubMed, SciFinder, China National Knowledge Infrastructure (CNKI), Wanfang, Google Scholar, and Baidu Academic. The following keywords were searched: neurological disorders, natural products, signalling pathway, mechanism of action.

RESULTS

This review summarises the pathogenesis of degenerative neurological diseases, recent findings on natural products used in neurodegenerative diseases, and the molecular mechanisms underlying these effects.

Research progress in the molecular mechanism of ferroptosis in Parkinson's disease and regulation by natural plant products

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder of the central nervous system after Alzheimer's disease. The current understanding of PD focuses mainly on the loss of dopamine neurons in the substantia nigra region of the midbrain, which is attributed to factors such as oxidative stress, alpha-synuclein aggregation, neuroinflammation, and mitochondrial dysfunction. These factors together contribute to the PD phenotype. Recent studies on PD pathology have introduced a new form of cell death known as ferroptosis. Pathological changes closely linked with ferroptosis have been seen in the brain tissues of PD patients, including alterations in iron metabolism, lipid peroxidation, and increased levels of reactive oxygen species. Preclinical research has demonstrated the neuroprotective qualities of certain iron chelators, antioxidants, Fer-1, and conditioners in Parkinson's disease. Natural plant products have shown significant potential in balancing ferroptosis-related factors and adjusting their expression levels. Therefore, it is vital to understand the mechanisms by which natural plant products inhibit ferroptosis and relieve PD symptoms. This review provides a comprehensive look at ferroptosis, its role in PD pathology, and the mechanisms underlying the therapeutic effects of natural plant products focused on ferroptosis. The insights from this review can serve as useful references for future research on novel ferroptosis inhibitors and lead compounds for PD treatment.

Inflammatory Blood Biomarkers Are Associated with Long-Term Clinical Disease Severity in Parkinson's Disease

An altered immune response has been identified as a pathophysiological factor in Parkinson's disease (PD). We aimed to identify blood immunity-associated proteins that discriminate PD from controls and that are associated with long-term disease severity in PD patients. Immune response-derived proteins in blood plasma were measured using Proximity Extension Technology by OLINK in a cohort of PD patients (N = 66) and age-matched healthy controls (N = 52). In a selection of 30 PD patients, we evaluated changes in protein levels 7-10 years after the baseline and assessed correlations with motor and cognitive assessments. Data from the Parkinson's Disease Biomarkers Program (PDBP) cohort and the Parkinson's Progression Markers Initiative (PPMI) cohort were used for independent validation. PD patients showed an altered immune response compared to controls based on a panel of four proteins (IL-12B, OPG, CXCL11, and CSF-1). The expression levels of five inflammation-associated proteins (CCL23, CCL25, TNFRSF9, TGF-alpha, and VEGFA) increased over time in PD and were partially associated with more severe motor and cognitive symptoms at follow-up. Increased CCL23 levels were associated with cognitive decline and the APOE4 genotype. Our findings provide further evidence for an altered immune response in PD that is associated with disease severity in PD over a long period of time.

Viral-like TLR3 induction of cytokine networks and α-synuclein are reduced by complement C3 blockade in mouse brain

Inflammatory processes and mechanisms are of central importance in neurodegenerative diseases. In the brain, α-synucleinopathies such as Parkinson's disease (PD) and Lewy body dementia (LBD) show immune cytokine network activation and increased toll like receptor 3 (TLR3) levels for viral double-stranded RNA (dsRNA). Brain inflammatory reactions caused by TLR3 activation are also relevant to understand pathogenic cascades by viral SARS-CoV-2 infection causing post- COVID-19 brain-related syndromes. In the current study, following regional brain TLR3 activation induced by dsRNA in mice, an acute complement C3 response was seen at 2 days. A C3 splice-switching antisense oligonucleotide (ASO) that promotes the splicing of a non-productive C3 mRNA, prevented downstream cytokines, such as IL-6, and α-synuclein changes. This report is the first demonstration that α-synuclein increases occur downstream of complement C3 activation. Relevant to brain dysfunction, post-COVID-19 syndromes and pathological changes leading to PD and LBD, viral dsRNA TLR3 activation in the presence of C3 complement blockade further revealed significant interactions between complement systems, inflammatory cytokine networks and α-synuclein changes.

Neurofilaments - Small proteins of physiological significance and predictive power for future neurodegeneration and cognitive decline across the life span

Neurofilaments (NFs) are not only important for axonal integrity and nerve conduction in large myelinated axons but they are also thought to be crucial for receptor and synaptic functioning. Therefore, NFs may play a critical role in cognitive functions, as cognitive processes are known to depend on synaptic integrity and are modulated by dopaminergic signaling. Here, we present a theory-driven interdisciplinary approach that NFs may link inflammation, neurodegeneration, and cognitive functions. We base our hypothesis on a wealth of evidence suggesting a causal link between inflammation and neurodegeneration and between these two and cognitive decline (see Fig. 1), also taking dopaminergic signaling into account. We conclude that NFs may not only serve as biomarkers for inflammatory, neurodegenerative, and cognitive processes but also represent a potential mechanical hinge between them, moreover, they may even have predictive power regarding future cognitive decline. In addition, we advocate the use of both NFs and MRI parameters, as their synthesis offers the opportunity to individualize medical treatment by providing a comprehensive view of underlying disease activity in neurological diseases. Since our society will become significantly older in the upcoming years and decades, maintaining cognitive functions and healthy aging will play an important role. Thanks to technological advances in recent decades, NFs could serve as a rapid, noninvasive, and relatively inexpensive early warning system to identify individuals at increased risk for cognitive decline and could facilitate the management of cognitive dysfunctions across the lifespan.

Prodromal Parkinson disease signs are predicted by a whole-blood inflammatory transcriptional signature in young Pink1-/- rats

Background

Parkinson disease (PD) is the fastest growing neurodegenerative disease. The molecular pathology of PD in the prodromal phase is poorly understood; as such, there are no specific prognostic or diagnostic tests. A validated Pink1 genetic knockout rat was used to model early-onset and progressive PD. Male Pink1-/- rats exhibit progressive declines in ultrasonic vocalizations as well as hindlimb and forelimb motor deficits by mid-to-late adulthood. Previous RNA-sequencing work identified upregulation of genes involved in disease pathways and inflammation within the brainstem and vocal fold muscle. The purpose of this study was to identify gene pathways within the whole blood of young Pink1-/- rats (3 months of age) and to link gene expression to early acoustical changes. To accomplish this, limb motor testing (open field and cylinder tests) and ultrasonic vocalization data were collected, immediately followed by the collection of whole blood and RNA extraction. Illumina® Total RNA-Seq TruSeq platform was used to profile differential expression of genes. Statistically significant genes were identified and Weighted Gene Co-expression Network Analysis was used to construct co-expression networks and modules from the whole blood gene expression dataset as well as the open field, cylinder, and USV acoustical dataset. ENRICHR was used to identify the top up-regulated biological pathways.

Results

The data suggest that inflammation and interferon signaling upregulation in the whole blood is present during early PD. We also identified genes involved in the dysregulation of ribosomal protein and RNA processing gene expression as well as prion protein gene expression.

Conclusions

These data identified several potential blood biomarkers and pathways that may be linked to anxiety and vocalization acoustic parameters and are key candidates for future drug-repurposing work and comparison to human datasets.

Cellular senescence and neurodegeneration

Advancing age is a major risk factor of Alzheimer's disease (AD). The worldwide prevalence of AD is approximately 50 million people, and this number is projected to increase substantially. The molecular mechanisms underlying the aging-associated susceptibility to cognitive impairment in AD are largely unknown. As a hallmark of aging, cellular senescence is a significant contributor to aging and age-related diseases including AD. Senescent neurons and glial cells have been detected to accumulate in the brains of AD patients and mouse models. Importantly, selective elimination of senescent cells ameliorates amyloid beta and tau pathologies and improves cognition in AD mouse models, indicating a critical role of cellular senescence in AD pathogenesis. Nonetheless, the mechanisms underlying when and how cellular senescence contributes to AD pathogenesis remain unclear. This review provides an overview of cellular senescence and discusses recent advances in the understanding of the impact of cellular senescence on AD pathogenesis, with brief discussions of the possible role of cellular senescence in other neurodegenerative diseases including Down syndrome, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis.

Assessing causal relationship between circulating cytokines and age-related neurodegenerative diseases: a bidirectional two-sample Mendelian randomization analysis

Numerous studies have reported that circulating cytokines (CCs) are linked to age-related neurodegenerative diseases (ANDDs); however, there is a lack of systematic investigation for the causal association. A two-sample bidirectional Mendelian Randomisation (MR) method was utilized to evaluate the causal effect. We applied genetic variants correlated with concentrations of CCs from a genome-wide association study meta-analysis (n = 8293) as instrumental variables. Summary data of three major ANDDs [Alzheimer's disease (AD), Parkinson's disease (PD), and Amyotrophic lateral sclerosis (ALS)] were identified from the IEU OpenGWAS platform (n = 627, 266). Inverse-variance weighted method is the main approach to analyse causal effect, and MR results are verified by several sensitivity and pleiotropy analyses. In directional MR, it suggested that several CCs were nominally correlated with the risk of ANDDs, with a causal odds ratio (OR) of Interleukin (IL)-5 of 0.909 for AD; OR of IL-2 of 1.169 for PD; and OR of Beta nerve growth factor of 1.142 for ALS). In reverse MR, there were some suggestively causal effects of ANDDs on CCs (AD on increased Basic fibroblast growth factor and IL-12 and decreased Stem cell growth factor beta; PD on decreased Monokine induced by interferon-gamma; ALS on decreased Basic fibroblast growth factor and IL-17). The findings were stable across sensitivity and pleiotropy analyses. However, after Bonferroni correction, there is no statistically significant association between CCs and ANDDs. Through the genetic epidemiological approach, our study assessed the role and presented possible causal associations between CCs and ANDDs. Further studies are warranted to verify the causal associations.

Inflammation in multiple system atrophy

Misfolding protein aggregation inside or outside cells is the major pathological hallmark of several neurodegenerative diseases. Among proteinopathies are neurodegenerative diseases with atypical Parkinsonism and an accumulation of insoluble fibrillary alpha-synuclein (synucleinopathies) or hyperphosphorylated tau protein fragments (tauopathies). As there are no therapies available to slow or halt the progression of these disea ses, targeting the inflammatory process is a promising approach. The inflammatory biomarkers could also help in the differential diagnosis of Parkinsonian syndromes. Here, we review inflammation's role in multiple systems atrophy pathogenesis, diagnosis, and treatment.

Development of Novel Herbal Compound Formulations Targeting Neuroinflammation: Network Pharmacology, Molecular Docking, and Experimental Verification

Neuroinflammation plays an important role in the onset and progression of neurodegenerative diseases. The multicomponent and multitarget approach may provide a practical strategy to address the complex pathological mechanisms of neuroinflammation. This study aimed to develop synergistic herbal compound formulas to attenuate neuroinflammation using integrated network pharmacology, molecular docking, and experimental bioassays. Eight phytochemicals with anti-neuroinflammatory potential were selected in the present study. A compound-gene target-signaling pathway network was constructed to illustrate the mechanisms of action of each phytochemical and the interactions among them at the molecular level. Molecular docking was performed to verify the binding affinity of each phytochemical and its key gene targets. An experimental study was conducted to identify synergistic interactions among the eight phytochemicals, and the associated molecular mechanisms were examined by immunoblotting based on the findings from the network pharmacology analysis. Two paired combinations, andrographolide and 6-shogaol (AN-SG) (IC50 = 2.85 μg/mL), and baicalein-6-shogaol (BA-SG) (IC50 = 3.28 μg/mL), were found to synergistically (combination index <1) inhibit the lipopolysaccharides (LPS)-induced nitric oxide production in microglia N11 cells. Network pharmacology analysis suggested that MAPK14, MAPK8, and NOS3 were the top three relevant gene targets for the three phytochemicals, and molecular docking demonstrated strong binding affinities of the phytochemicals to their coded proteins. Immunoblotting suggested that the AN-SG and BA-SG both showed prominent effects in inhibiting inducible nitric oxide synthase (iNOS) (p < 0.01 and p < 0.05, respectively) and MAPKp-p38 (both p < 0.05) compared with those induced by the LPS stimulation only. The AN-SG combination exhibited greater inhibitions of the protein expressions of iNOS (p < 0.05 vs. individual components), which may partly explain the mechanisms of the synergy observed. This study established a practical approach to developing novel herbal-compound formulations using integrated network pharmacology analysis, molecular docking, and experimental bioassays. The study provides a scientific basis and new insight into the two synergistic combinations against neuroinflammation.

RIPK1-Induced A1 Reactive Astrocytes in Brain in MPTP-Treated Murine Model of Parkinson's Disease

Neuroinflammation is one of the hallmarks of Parkinson's disease, including the massive activation of microglia and astrocytes and the release of inflammatory factors. Receptor-interacting protein kinase 1 (RIPK1) is reported to mediate cell death and inflammatory signaling, and is markedly elevated in the brain in PD mouse models. Here, we aim to explore the role of RIPK1 in regulating the neuroinflammation of PD. C57BL/6J mice were intraperitoneally injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 20 mg/kg four times/day), followed by necrostatin-1 treatment (Nec-1, RIPK1 inhibitor; 1.65 mg/kg once daily for seven days. Notably, the first Nec-1 was given 12 h before MPTP modeling). Behavioral tests indicated that inhibition of RIPK1 greatly relieved motor dysfunction and anxiety-like behaviors of PD mice. It also increased striatal TH expression, rescue the loss of dopaminergic neurons, and reduce activation of astrocytes in the striatum of PD mice. Furthermore, inhibition of RIPK1 expression reduced A1 astrocytes' relative gene expression (CFB, H2-T23) and inflammatory cytokine or chemokine production (CCL2, TNF-α, IL-1β) in the striatum of PD mice. Collectively, inhibition of RIPK1 expression can provide neuroprotection to PD mice, probably through inhibition of the astrocyte A1 phenotype, and thus RIPK1 might be an important target in PD treatment.

Upregulation of APAF1 and CSF1R in Peripheral Blood Mononuclear Cells of Parkinson's Disease

Increased oxidative stress and neuroinflammation play a crucial role in the pathogenesis of Parkinson's disease (PD). In this study, the expression levels of 52 genes related to oxidative stress and inflammation were measured in peripheral blood mononuclear cells of the discovery cohort including 48 PD patients and 25 healthy controls. Four genes, including ALDH1A, APAF1, CR1, and CSF1R, were found to be upregulated in PD patients. The expression patterns of these genes were validated in a second cohort of 101 PD patients and 61 healthy controls. The results confirmed the upregulation of APAF1 (PD: 0.34 ± 0.18, control: 0.26 ± 0.11, p < 0.001) and CSF1R (PD: 0.38 ± 0.12, control: 0.33 ± 0.10, p = 0.005) in PD patients. The expression level of APAF1 was correlated with the scores of the Unified Parkinson's Disease Rating Scale (UPDRS, r = 0.235, p = 0.018) and 39-item PD questionnaire (PDQ-39, r = 0.250, p = 0.012). The expression level of CSF1R was negatively correlated with the scores of the mini-mental status examination (MMSE, r = -0.200, p = 0.047) and Montréal Cognitive Assessment (MoCA, r = -0.226, p = 0.023). These results highly suggest that oxidative stress biomarkers in peripheral blood may be useful in monitoring the progression of motor disabilities and cognitive decline in PD patients.

Fish Models for Exploring Mitochondrial Dysfunction Affecting Neurodegenerative Disorders

Neurodegenerative disorders are characterized by the progressive loss of neuronal structure or function, resulting in memory loss and movement disorders. Although the detailed pathogenic mechanism has not been elucidated, it is thought to be related to the loss of mitochondrial function in the process of aging. Animal models that mimic the pathology of a disease are essential for understanding human diseases. In recent years, small fish have become ideal vertebrate models for human disease due to their high genetic and histological homology to humans, ease of in vivo imaging, and ease of genetic manipulation. In this review, we first outline the impact of mitochondrial dysfunction on the progression of neurodegenerative diseases. Then, we highlight the advantages of small fish as model organisms, and present examples of previous studies regarding mitochondria-related neuronal disorders. Lastly, we discuss the applicability of the turquoise killifish, a unique model for aging research, as a model for neurodegenerative diseases. Small fish models are expected to advance our understanding of the mitochondrial function in vivo, the pathogenesis of neurodegenerative diseases, and be important tools for developing therapies to treat diseases.

Microglia and Astrocytes Dysfunction and Key Neuroinflammation-Based Biomarkers in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, with symptoms such as tremor, bradykinesia with rigidity, and depression appearing in the late stage of life. The key hallmark of PD is the loss or death of dopaminergic neurons in the region substantia nigra pars compacta. Neuroinflammation plays a key role in the etiology of PD, and the contribution of immunity-related events spurred the researchers to identify anti-inflammatory agents for the treatment of PD. Neuroinflammation-based biomarkers have been identified for diagnosing PD, and many cellular and animal models have been used to explain the underlying mechanism; however, the specific cause of neuroinflammation remains uncertain, and more research is underway. So far, microglia and astrocyte dysregulation has been reported in PD. Patients with PD develop neural toxicity, inflammation, and inclusion bodies due to activated microglia and a-synuclein-induced astrocyte conversion into A1 astrocytes. Major phenotypes of PD appear in the late stage of life, so there is a need to identify key early-stage biomarkers for proper management and diagnosis. Studies are under way to identify key neuroinflammation-based biomarkers for early detection of PD. This review uses a constructive analysis approach by studying and analyzing different research studies focused on the role of neuroinflammation in PD. The review summarizes microglia, astrocyte dysfunction, neuroinflammation, and key biomarkers in PD. An approach that incorporates multiple biomarkers could provide more reliable diagnosis of PD.

Rotenone-Induced Model of Parkinson's Disease: Beyond Mitochondrial Complex I Inhibition

Parkinson's disease (PD) is usually diagnosed through motor symptoms that make the patient incapable of carrying out daily activities; however, numerous non-motor symptoms include olfactory disturbances, constipation, depression, excessive daytime sleepiness, and rapid eye movement at sleep; they begin years before motor symptoms. Therefore, several experimental models have been studied to reproduce several PD functional and neurochemical characteristics; however, no model mimics all the PD motor and non-motor symptoms to date, which becomes a limitation for PD study. It has become increasingly relevant to find ways to study the disease from its slowly progressive nature. The experimental models most frequently used to reproduce PD are based on administering toxic chemical compounds, which aim to imitate dopamine deficiency. The most used toxic compounds to model PD have been 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine (6-OHDA), which inhibit the complex I of the electron transport chain but have some limitations. Another toxic compound that has drawn attention recently is rotenone, the classical inhibitor of mitochondrial complex I. Rotenone triggers the progressive death of dopaminergic neurons and α-synuclein inclusions formation in rats; also, rotenone induces microtubule destabilization. This review presents information about the experimental model of PD induced by rotenone, emphasizing its molecular characteristics beyond the inhibition of mitochondrial complex I.

Microglia Mediated Neuroinflammation in Parkinson’s Disease

Parkinson’s Disease (PD) is the second most common neurodegenerative disorder seen, especially in the elderly. Tremor, shaking, movement problems, and difficulty with balance and coordination are among the hallmarks, and dopaminergic neuronal loss in substantia nigra pars compacta of the brain and aggregation of intracellular protein α-synuclein are the pathological characterizations. Neuroinflammation has emerged as an involving mechanism at the initiation and development of PD. It is a complex network of interactions comprising immune and non-immune cells in addition to mediators of the immune response. Microglia, the resident macrophages in the CNS, take on the leading role in regulating neuroinflammation and maintaining homeostasis. Under normal physiological conditions, they exist as “homeostatic” but upon pathological stimuli, they switch to the “reactive state”. Pro-inflammatory (M1) and anti-inflammatory (M2) phenotypes are used to classify microglial activity with each phenotype having its own markers and released mediators. When M1 microglia are persistent, they will contribute to various inflammatory diseases, including neurodegenerative diseases, such as PD. In this review, we focus on the role of microglia mediated neuroinflammation in PD and also signaling pathways, receptors, and mediators involved in the process, presenting the studies that associate microglia-mediated inflammation with PD. A better understanding of this complex network and interactions is important in seeking new therapies for PD and possibly other neurodegenerative diseases.

Deep brain stimulation improves central nervous system inflammation in Parkinson's disease: Evidence and perspectives

BACKGROUND

In Parkinson's disease (PD), inflammation may lead to the degeneration of dopaminergic (DAergic) neurons. Previous studies showed that inflammatory mediators mainly contributed to this phenomenon. On the other hand, invasive neuromodulation methods such as deep brain stimulation (DBS) have better therapeutic effects for PD. One possibility is that DBS improves PD by influencing inflammation. Therefore, we further explored the mechanisms underlying inflammatory mediators and DBS in the pathogenesis of PD.

METHODS

We measured serum levels of two inflammatory markers, namely RANTES (regulated on activation, normal T cell expressed and secreted) and tumor necrosis factor-alpha (TNF-α), using Luminex assays in 109 preoperative DBS PD patients, 49 postoperative DBS PD patients, and 113 age- and sex-matched controls. The plasma protein data of the different groups were then statistically analyzed.

RESULTS

RANTES (p < 0.001) and TNF-α (p = 0.005) levels differed significantly between the three groups. A strong and significant correlation between RANTES levels and Hoehn-Yahr (H-Y) stage was observed in preoperative PD patients (r_s  = 0.567, p < 0.001). Significant correlations between RANTES levels and Unified Parkinson's Disease Rating Scale III (UPDRS III) score (r_s1  = 0.644, p = 0.033 and r_s2  = 0.620, p = 0.042) were observed in matched patients. No correlation was observed for TNF-α levels.

CONCLUSION

The results of this study indicate that PD patients have a persistent inflammatory profile, possibly via recruitment of activated monocytes, macrophages, and T lymphocytes to the central nervous system (CNS). DBS was shown to have a significant therapeutic effect on PD, which may arise by improving the inflammatory environment of the central nervous system.

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.

Intranasal Lipid Nanoparticles Containing Bioactive Compounds Obtained from Marine Sources to Manage Neurodegenerative Diseases

Marine sources contain several bioactive compounds with high therapeutic potential, such as remarkable antioxidant activity that can reduce oxidative stress related to the pathogenesis of neurodegenerative diseases. Indeed, there has been a growing interest in these natural sources, especially those resulting from the processing of marine organisms (i.e., marine bio-waste), to obtain natural antioxidants as an alternative to synthetic antioxidants in a sustainable approach to promote circularity by recovering and creating value from these bio-wastes. However, despite their expected potential to prevent, delay, or treat neurodegenerative diseases, antioxidant compounds may have difficulty reaching the brain due to the need to cross the blood–brain barrier (BBB). In this regard, alternative delivery systems administered by different routes have been proposed, including intranasal administration of lipid nanoparticles, such as solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), which have shown promising results. Intranasal administration shows several advantages, including the fact that molecules do not need to cross the BBB to reach the central nervous system (CNS), as they can be transported directly from the nasal cavity to the brain (i.e., nose-to-brain transport). The benefits of using SLN and NLC for intranasal delivery of natural bioactive compounds for the treatment of neurodegenerative diseases have shown relevant outcomes through in vitro and in vivo studies. Noteworthy, for bioactive compounds obtained from marine bio-waste, few studies have been reported, showing the open potential of this research area. This review updates the state of the art of using SLN and NLC to transport bioactive compounds from different sources, in particular, those obtained from marine bio-waste, and their potential application in the treatment of neurodegenerative diseases.

Silibinin chronic treatment in a rat model of Parkinson disease: A comprehensive in-vivo evaluation and in silico molecular modeling

BACKGROUND

Apoptosis, oxidative stress, and neuroinflammation have been linked to the onset of Parkinson's disease (PD). Although the pre-treatment effects of Silibinin on a PD model have been evaluated, in the current study we investigated the chronic therapeutic effects of Silibinin microinjection on a rat model of established parkinsonism along with behavioral and laboratory markers assessments.

METHOD

Parkinsonism was induced by 6-hydroxydopamine (6-OHDA, 8 μg/2μl/rat). 21 days after that, animals were treated with Silibinin (100, 200, and 300 mg/kg for 15 consecutive days). Every two days, the bar test was used to evaluate Silibinin's anti-cataleptic properties. At the end, myeloperoxidase (MPO) activity and toll-like receptor 4 (TLR4) expression in the substantia nigra pars compacta (SNc), along with cerebrospinal fluid (CSF) levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-6, caspase-3, Bax and Bcl-2 levels were assessed. We used homology modeling to predict the 3D structure of TLR4.

RESULT

Silibinin's Chronic treatment, dose-dependently decreased catalepsy. MPO activity and levels of TNF-α, IL-6, and IL-1β were reduced in Silibinin-treated rats in all three doses. Silibinin decreased Bax/Bcl-2 ratio, caspase-3, and downregulated TLR4 expression. Molecular docking revealed that there were hydrophobic and hydrogen bond interactions between the studied ligand and TLR4. Silibinin formed a stable complex with both monomer and dimer forms of TLR4.

CONCLUSION

In accordance with molecular modeling and alleviation of TLR4 activity with a consequent reduction in oxidative stress, restoration of CSF inflammatory cytokine, and minimization of SNc neuronal apoptosis, long-term therapy with Silibinin offers a potential opportunity for symptomatic PD treatment.

Review of Technological Challenges in Personalised Medicine and Early Diagnosis of Neurodegenerative Disorders

Neurodegenerative disorders are characterised by progressive neuron loss in specific brain areas. The most common are Alzheimer's disease and Parkinson's disease; in both cases, diagnosis is based on clinical tests with limited capability to discriminate between similar neurodegenerative disorders and detect the early stages of the disease. It is common that by the time a patient is diagnosed with the disease, the level of neurodegeneration is already severe. Thus, it is critical to find new diagnostic methods that allow earlier and more accurate disease detection. This study reviews the methods available for the clinical diagnosis of neurodegenerative diseases and potentially interesting new technologies. Neuroimaging techniques are the most widely used in clinical practice, and new techniques such as magnetic resonance imaging (MRI) and positron emission tomography (PET) have significantly improved the diagnosis quality. Identifying biomarkers in peripheral samples such as blood or cerebrospinal fluid is a major focus of the current research on neurodegenerative diseases. The discovery of good markers could allow preventive screening to identify early or asymptomatic stages of the neurodegenerative process. These methods, in combination with artificial intelligence, could contribute to the generation of predictive models that will help clinicians in the early diagnosis, stratification, and prognostic assessment of patients, leading to improvements in patient treatment and quality of life.

Type 2 Diabetes and Parkinson's Disease: A Focused Review of Current Concepts

Highly reproducible epidemiological evidence shows that type 2 diabetes (T2D) increases the risk and rate of progression of Parkinson's disease (PD), and crucially, the repurposing of certain antidiabetic medications for the treatment of PD has shown early promise in clinical trials, suggesting that the effects of T2D on PD pathogenesis may be modifiable. The high prevalence of T2D means that a significant proportion of patients with PD may benefit from personalized antidiabetic treatment approaches that also confer neuroprotective benefits. Therefore, there is an immediate need to better understand the mechanistic relation between these conditions and the specific molecular pathways affected by T2D in the brain. Although there is considerable evidence that processes such as insulin signaling, mitochondrial function, autophagy, and inflammation are involved in the pathogenesis of both PD and T2D, the primary aim of this review is to highlight the evidence showing that T2D-associated dysregulation of these pathways occurs not only in the periphery but also in the brain and how this may facilitate neurodegeneration in PD. We also discuss the challenges involved in disentangling the complex relationship between T2D, insulin resistance, and PD, as well as important questions for further research. © 2022 International Parkinson and Movement Disorder Society.

Microbiome-gut-brain dysfunction in prodromal and symptomatic Lewy body diseases

Lewy body diseases, such as Parkinson's disease and dementia with Lewy bodies, vary in their clinical phenotype but exhibit the same defining pathological feature, α-synuclein aggregation. Microbiome-gut-brain dysfunction may play a role in the initiation or progression of disease processes, though there are multiple potential mechanisms. We discuss the need to evaluate gastrointestinal mechanisms of pathogenesis across Lewy body diseases, as disease mechanisms likely span across diagnostic categories and a 'body first' clinical syndrome may better account for the heterogeneity of clinical presentations across the disorders. We discuss two primary hypotheses that suggest that either α-synuclein aggregation occurs in the gut and spreads in a prion-like fashion to the brain or systemic inflammatory processes driven by gastrointestinal dysfunction contribute to the pathophysiology of Lewy body diseases. Both of these hypotheses posit that dysbiosis and intestinal permeability are key mechanisms and potential treatment targets. Ultimately, this work can identify early interventions targeting initial disease pathogenic processes before the development of overt motor and cognitive symptoms.

Investigating Therapeutic Effects of Indole Derivatives Targeting Inflammation and Oxidative Stress in Neurotoxin-Induced Cell and Mouse Models of Parkinson's Disease

Neuroinflammation and oxidative stress have been emerging as important pathways contributing to Parkinson's disease (PD) pathogenesis. In PD brains, the activated microglia release inflammatory factors such as interleukin (IL)-β, IL-6, tumor necrosis factor (TNF)-α, and nitric oxide (NO), which increase oxidative stress and mediate neurodegeneration. Using 1-methyl-4-phenylpyridinium (MPP⁺)-activated human microglial HMC3 cells and the sub-chronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced mouse model of PD, we found the potential of indole derivative NC009-1 against neuroinflammation, oxidative stress, and neurodegeneration for PD. In vitro, NC009-1 alleviated MPP⁺-induced cytotoxicity, reduced NO, IL-1β, IL-6, and TNF-α production, and suppressed NLR family pyrin domain containing 3 (NLRP3) inflammasome activation in MPP⁺-activated HMC3 cells. In vivo, NC009-1 ameliorated motor deficits and non-motor depression, increased dopamine and dopamine transporter levels in the striatum, and reduced oxidative stress as well as microglia and astrocyte reactivity in the ventral midbrain of MPTP-treated mice. These protective effects were achieved by down-regulating NLRP3, CASP1, iNOS, IL-1β, IL-6, and TNF-α, and up-regulating SOD2, NRF2, and NQO1. These results strengthen the involvement of neuroinflammation and oxidative stress in PD pathogenic mechanism, and indicate NC009-1 as a potential drug candidate for PD treatment.

Serum inflammatory cytokines levels and the correlation analyses in Parkinson's disease

Objective: To investigate the serum levels of inflammatory cytokines and the correlations with Parkinson's disease (PD) clinical symptoms. Methods: Serum levels of the cytokines, including IL-6, IL-8, and TNF-α, were measured in 273 PD patients and 91 healthy controls (HCs). The clinical manifestations of PD were assessed with nine different scales to evaluate the cognitive function, non-motor symptoms, motor symptoms, and disease severity. The differences in these inflammatory indicators were examined between PD patients and HCs, and the correlations of these inflammatory indicators with clinical variables were analyzed in PD patients. Results: Serum levels of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in PD patients were higher than those in HCs, but serum interleukin-8 (IL-8) level was not significantly different from that in HCs. In PD patients, serum IL-6 level was positively correlated with age of onset, the Hamilton Depression Scale (HAMD), and the Non-Motor Symptom Scale (NMSS), UPDRS part I, part II, and part III, but it was inversely correlated with the Frontal Assessment Battery (FAB) and the Montreal Cognitive Assessment (MoCA) scores. Serum TNF-α level was positively correlated with age of onset and H&Y stage in PD patients (p = .037), but negatively correlated with FAB scores in PD patients (p = .010). However, no associations were found between all the clinical variables and the serum IL-8 level. The forward binary logistic regression model revealed that serum IL-6 level was associated with MoCA (p = .023) and UPDRS I scores (p = .023), but no associations was found with the remaining factors. The ROC curve of TNF-α for the diagnosis of PD showed the area under the curve (AUC) was .719 (p < .05, 95% CI: .655-.784), and the critical value of TNF-α was 5.380 pg/ml, with a diagnostic sensitivity of 76.0% and a specificity of 59.3%. Conclusion: Our results suggest increased serum levels of IL-6 and TNF-α in PD, we further found that IL-6 level was associated with non-motor symptoms and cognitive dysfunction, and IL-6 may play a role in the pathophysiology of non-motor symptoms in PD. At the same time, we also propose that TNF-α has a good diagnostic value for PD despite its irrelevance to clinical symptoms.

Advances in NURR1-Regulated Neuroinflammation Associated with Parkinson's Disease

Neuroinflammation plays a crucial role in the progression of neurodegenerative disorders, particularly Parkinson's disease (PD). Glial cell activation and subsequent adaptive immune involvement are neuroinflammatory features in familial and idiopathic PD, resulting in the death of dopaminergic neuron cells. An oxidative stress response, inflammatory mediator production, and immune cell recruitment and activation are all hallmarks of this activation, leading to chronic neuroinflammation and progressive neurodegeneration. Several studies in PD patients' cerebrospinal fluid and peripheral blood revealed alterations in inflammatory markers and immune cell populations that may lead to or exacerbate neuroinflammation and perpetuate the neurodegenerative process. Most of the genes causing PD are also expressed in astrocytes and microglia, converting their neuroprotective role into a pathogenic one and contributing to disease onset and progression. Nuclear receptor-related transcription factor 1 (NURR1) regulates gene expression linked to dopaminergic neuron genesis and functional maintenance. In addition to playing a key role in developing and maintaining neurotransmitter phenotypes in dopaminergic neurons, NURR1 agonists have been shown to reverse behavioral and histological abnormalities in animal PD models. NURR1 protects dopaminergic neurons from inflammation-induced degeneration, specifically attenuating neuronal death by suppressing the expression of inflammatory genes in microglia and astrocytes. This narrative review highlights the inflammatory changes in PD and the advances in NURR1-regulated neuroinflammation associated with PD. Further, we present new evidence that targeting this inflammation with a variety of potential NURR1 target therapy medications can effectively slow the progression of chronic neuroinflammation-induced PD.

HLDF-6 peptides exhibit neuroprotective effects in the experimental model of preclinical Parkinson's disease

The mechanisms of the neuroprotective action of the hexapeptides HLDF-6 encoded by the amino acid sequence 41-46 of Human Leukemia Differentiation Factor and its homoserine derivative HLDF-6H were studied in an experimental 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced model of Parkinson's disease (PD). C57Bl/6 mice received two intraperitoneal injections of 18 mg/kg MPTP-HCl, with an interval of 2 hours. MPTP-induced motor dysfunction was assessed using horizontal grid test. Our data show that chronic intranasal administration of peptides (3 weeks, 300 μg/kg/day) restored normal levels of dopamine and improved its turnover rates in the striatum. Furthermore, peptide administration increased serum estradiol levels and led to a significant improvement in motor functions in MPTP-treated mice. Additionally, peptide treatment increased the levels of mRNA encoding neurotrophin BDNF, but normalized the levels of mRNA encoding the inflammatory mediators TGFβ1, IL1β and IFNγ in the brain. Collectively, our behavioral and biochemical studies demonstrate that HLDF-6 peptides have a therapeutic potential for treating PD. We propose that HLDF-6 peptides may exert their neuroprotective mechanism, at least in part, by normalizing estradiol levels and modulating the expression of key factors involved in neurotrophic support and neuroinflammation.

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.

Gut microbiota, pathogenic proteins and neurodegenerative diseases

As the world's population ages, neurodegenerative diseases (NDs) have brought a great burden to the world. However, effective treatment measures have not been found to alleviate the occurrence and development of NDs. Abnormal accumulation of pathogenic proteins is an important cause of NDs. Therefore, effective inhibition of the accumulation of pathogenic proteins has become a priority. As the second brain of human, the gut plays an important role in regulate emotion and cognition functions. Recent studies have reported that the disturbance of gut microbiota (GM) is closely related to accumulation of pathogenic proteins in NDs. On the one hand, pathogenic proteins directly produced by GM are transmitted from the gut to the central center via vagus nerve. On the other hand, The harmful substances produced by GM enter the peripheral circulation through intestinal barrier and cause inflammation, or cross the blood-brain barrier into the central center to cause inflammation, and cytokines produced by the central center cause the production of pathogenic proteins. These pathogenic proteins can produced by the above two aspects can cause the activation of central microglia and further lead to NDs development. In addition, certain GM and metabolites have been shown to have neuroprotective effects. Therefore, modulating GM may be a potential clinical therapeutic approach for NDs. In this review, we summarized the possible mechanism of NDs caused by abnormal accumulation of pathogenic proteins mediated by GM to induce the activation of central microglia, cause central inflammation and explore the therapeutic potential of dietary therapy and fecal microbiota transplantation (FMT) in NDs.

A prebiotic diet modulates microglial states and motor deficits in α-synuclein overexpressing mice

Parkinson's disease (PD) is a movement disorder characterized by neuroinflammation, α-synuclein pathology, and neurodegeneration. Most cases of PD are non-hereditary, suggesting a strong role for environmental factors, and it has been speculated that disease may originate in peripheral tissues such as the gastrointestinal (GI) tract before affecting the brain. The gut microbiome is altered in PD and may impact motor and GI symptoms as indicated by animal studies, although mechanisms of gut-brain interactions remain incompletely defined. Intestinal bacteria ferment dietary fibers into short-chain fatty acids, with fecal levels of these molecules differing between PD and healthy controls and in mouse models. Among other effects, dietary microbial metabolites can modulate activation of microglia, brain-resident immune cells implicated in PD. We therefore investigated whether a fiber-rich diet influences microglial function in α-synuclein overexpressing (ASO) mice, a preclinical model with PD-like symptoms and pathology. Feeding a prebiotic high-fiber diet attenuates motor deficits and reduces α-synuclein aggregation in the substantia nigra of mice. Concomitantly, the gut microbiome of ASO mice adopts a profile correlated with health upon prebiotic treatment, which also reduces microglial activation. Single-cell RNA-seq analysis of microglia from the substantia nigra and striatum uncovers increased pro-inflammatory signaling and reduced homeostatic responses in ASO mice compared to wild-type counterparts on standard diets. However, prebiotic feeding reverses pathogenic microglial states in ASO mice and promotes expansion of protective disease-associated macrophage (DAM) subsets of microglia. Notably, depletion of microglia using a CSF1R inhibitor eliminates the beneficial effects of prebiotics by restoring motor deficits to ASO mice despite feeding a prebiotic diet. These studies uncover a novel microglia-dependent interaction between diet and motor symptoms in mice, findings that may have implications for neuroinflammation and PD.

WDR43 is a potential diagnostic biomarker and therapeutic target for osteoarthritis complicated with Parkinson’s disease

Osteoarthritis (OA) and Parkinson’s disease (PD) are on the rise and greatly impact the quality of individuals’ lives. Although accumulating evidence indicates a relationship between OA and PD, the particular interactions connecting the two diseases have not been thoroughly examined. Therefore, this study explored the association through genetic characterization and functional enrichment. Four datasets (GSE55235, GSE12021, GSE7621, and GSE42966) were chosen for assessment and validation from the Gene Expression Omnibus (GEO) database. Weighted Gene Co-Expression Network Analysis (WGCNA) was implemented to determine the most relevant genes for clinical features. Then, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were carried out to explore the biological processes of common genes, and to display the interrelationships between common genes, the STRING database and the application Molecular Complex Detection Algorithm (MCODE) of Cytoscape software were leveraged to get hub genes. By intersecting the common genes with the differentially expressed genes (DEGs) acquired from GSE12021 and GSE42966, the hub genes were identified. Finally, we validated the diagnostic efficacy of hub genes and explored their correlation with 22 immune infiltrating cells. As a consequence, we discovered 71 common genes, most of which were functionally enriched in antigen processing and presentation, mitochondrial translation, the mRNA surveillance pathway, and nucleocytoplasmic transport. Furthermore, WDR43 was found by intersecting eight hub genes with 28 DEGs from the two validation datasets. Receiver Operating Characteristic (ROC) implied the diagnostic role of WDR43 in OA and PD. Immune infiltration research revealed that T-cell regulatory (Tregs), monocytes, and mast cells resting were associated with the pathogenesis of OA and PD. WDR43 may provide key insights into the relationship between OA and PD.

Paraquat exposure induces Parkinsonism by altering lipid profile and evoking neuroinflammation in the midbrain

Paraquat (PQ) is the most widely used herbicide in the world and a well-known potent neurotoxin for humans. PQ exposure has been linked to increase the risk of Parkinson's disease (PD). However, the mechanism underlying its neurotoxic effects in PD pathogenesis is unclear. In our present study, C57BL/6J mice treated with PQ manifested severe motor deficits indicated by the significant reductions in suspension score, latency to fall from rotarod, and grip strength at 8 weeks after PQ exposure. Pathological hallmarks of Parkinsonism in the midbrain such as dopaminergic neuron loss, increased α-synuclein protein, and dysregulated PD-related genes were observed. Non-targeted lipidome analysis demonstrated that PQ exposure alters lipid profile and abundance, increases pro-inflammatory lipids.27 significantly altered subclasses of lipids belonged to 6 different lipid categories. Glycerophospholipids, sphingolipids, and glycerides were the most abundant lipids. Abundance of pro-inflammatory lipids such as Cer, LPC, LPS, and LPI was significantly increased in the midbrain. mRNA expressions of genes regulating ceramide biosynthesis in the midbrain were markedly up-regulated. Moreover, PQ exposure increased serum pro-inflammatory cytokines and provoked neuroinflammation in the midbrain. Pro-inflammatory lipids and cytokines in the midbrain were positively correlated with motor deficits. PQ poisoning in humans significantly also elevated serum pro-inflammatory cytokines and induced an intense systemic inflammation. In summary, we presented initial investigations of PQ induced molecular events related to the PD pathogenesis, capturing aspects of disturbed lipid metabolism, neuroinflammation, impairment of dopaminergic neurons in the midbrain, and an intense systemic inflammation. These neurotoxic effects of PQ exposure may mechanistically contribute to the pathogenesis of PQ induced Parkinsonism. Results of this study also strongly support the hypothesis that ever-increasing prevalence of Parkinson's disease is etiologically linked to the health risk of exposure to neurotoxic environmental pollutants.

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.

Targeting the inflammasome in Parkinson's disease

Parkinson's disease (PD) is one of the most common neurodegenerative diseases in which neuroinflammation plays pivotal roles. An important mechanism of neuroinflammation is the NLRP3 inflammasome activation that has been implicated in PD pathogenesis. In this perspective, we will discuss the relationship of some key PD-associated proteins including α-synuclein and Parkin and their contribution to inflammasome activation. We will also review promising inhibitors of NLRP3 inflammasome pathway that have potential as novel PD therapeutics. Finally, we will provide a summary of current and potential in vitro and in vivo models that are available for therapeutic discovery and development.

Identification of Immune-Related Hub Genes in Parkinson’s Disease

Background: Parkinson’s disease (PD) is a common, age-related, and progressive neurodegenerative disease. Growing evidence indicates that immune dysfunction plays an essential role in the pathogenic process of PD. The objective of this study was to explore potential immune-related hub genes and immune infiltration patterns of PD.

Method: The microarray expression data of human postmortem substantia nigra samples were downloaded from GSE7621, GSE20141, and GSE49036. Key module genes were screened via weighted gene coexpression network analysis, and immune-related genes were intersected to obtain immune-key genes. Functional enrichment analysis was performed on immune-key genes of PD. In addition to, immune infiltration analysis was applied by a single-sample gene set enrichment analysis algorithm to detect differential immune cell types in the substantia nigra between PD samples and control samples. Least absolute shrinkage and selection operator analysis was performed to further identify immune-related hub genes for PD. Receiver operating characteristic curve analysis of the immune-related hub genes was used to differentiate PD patients from healthy controls. Correlations between immune-related hub genes and differential immune cell types were assessed.

Result: Our findings identified four hub genes (SLC18A2, L1CAM, S100A12, and CXCR4) and seven immune cell types (neutrophils, T follicular helper cells, myeloid-derived suppressor cells, type 1 helper cells, immature B cells, immature dendritic cells, and CD56 bright natural killer cells). The area under the curve (AUC) value of the four-gene-combined model was 0.92. The AUC values of each immune-related hub gene (SLC18A2, L1CAM, S100A12, and CXCR4) were 0.81, 0.78, 0.78, and 0.76, respectively.

Conclusion: In conclusion, SLC18A2, L1CAM, S100A12, and CXCR4 were identified as being associated with the pathogenesis of PD and should be further researched.