Peripheral inflammatory cytokines and motor symptoms in persons with Parkinson's disease

Potential Biomarkers and Treatment of Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is a degenerative disease of the central nervous system primarily affecting middle-aged and elderly individuals, significantly compromising their quality of life. Neuroinflammation is now recognized as a key feature in the pathogenesis of PD. This study reviews recent advances in the identification of potential biomarkers associated with neuroinflammation in PD and their significance for therapeutic strategies. These findings suggest that inflammatory factors play a pivotal role in PD treatment, and interventions involving anti-inflammatory drugs, physical exercise, and dietary modifications have shown promising results in mitigating disease progression.

Association Between Neuroinflammation and Parkinson's Disease: A Comprehensive Mendelian Randomization Study

The objective of the study is to determine the causal relationship and potential mechanisms between Parkinson's disease (PD) and neuroinflammatory and neurotoxic mediators. We conducted two-sample Mendelian randomization (2SMR) study and multivariable Mendelian randomization (MVMR) analysis to investigate the causality between PD and neuroinflammatory and neurotoxic mediators. The mediation analysis with MR was also conducted to determine the potential mediating effect of neuroinflammatory and neurotoxic mediators between asthma and PD. Genetically predicted levels of nine neuroinflammation were associated with changes in PD risk. The associations of PD with CCL24, galectin-3 levels, haptoglobin, and Holo-Transcobalamin-2 remained significant in multivariable analyses. The mediation analysis with MR revealed that asthma affects PD through CCL24 and galectin-3. The results showed neuroinflammation could affect the pathogenesis of PD. In the combined analysis of these nine variables, CCL24, galectin-3 levels, HP, and Holo-Transcobalamin-2 alone were found to be significant. Asthma plays an intermediary role through CCL24 and galectin-3 levels.

LRRK2 G2019S Mutated iPSC-Derived Endothelial Cells Exhibit Increased α-Synuclein, Mitochondrial Impairment, and Altered Inflammatory Responses

The blood-brain barrier (BBB) serves as an interface between the bloodstream and the central nervous system. It limits the movement of molecules and immune cells, regulates the entry of nutrients, and removes waste products from the brain. The dysfunction of the BBB has been identified in Parkinson's disease (PD) but the role of the BBB and endothelial cells (ECs) has not been well studied. LRRK2 G2019S mutation is the most common PD causing mutation with similar pathophysiology than in sporadic cases. How the mutation affects EC function has not been investigated previously in patient cells. In the study, we used iPSC-derived ECs from PD patients with the LRRK2 mutation as well as cells from healthy individuals. We report that PD patients' ECs have higher levels of α-synuclein and an decreased maximal and ATP-linked respiration and altered response to inflammatory exposure, especially to TNFα. In addition, transcriptomic analysis showed upregulation of fatty-acid-synthesis-related pathways in PD patients' ECs and the downregulation of lncRNA MEG3, both of which have been associated with PD. Altogether, PD patients' ECs manifest some of the PD-related hallmarks and are likely to contribute to the pathogenesis of PD.

ASC specks as a single-molecule fluid biomarker of inflammation in neurodegenerative diseases

Immunotherapeutic strategies for Alzheimer's and Parkinson's disease would be facilitated by better measures of inflammation. Here we established an ultra-sensitive single-molecule pull-down immunoassay combined with direct stochastic optical reconstruction microscopy (dSTORM) to measure the number, size and shape of individual extracellular inflammasome ASC specks. We assayed human post-mortem brain, serum and cerebrospinal fluid of patients with Parkinson's and Alzheimer's as well as healthy elderly. The number of ASC specks increased and showed altered morphology in the blood of early-stage Parkinson's and Alzheimer's patients compared to controls, mimicking those found in the brain and cerebrospinal fluid. In serum samples we also measured the number of Aβ, p-tau and α-syn aggregates and formed a composite biomarker of (ASC + p-tau)/Aβ and (ASC + α-syn)/Aβ ratios that distinguished age-matched healthy controls from patients with early-stage Alzheimer's with AUC of 92% and early-stage Parkinson's with AUC of 97%. Our findings confirm ASC specks as a fluid candidate biomarker of inflammation for neurodegenerative diseases with blood being the main focus for further development as convenient sample for diagnostics and clinical trials.

Differentiation and regulation of CD4+ T cell subsets in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease, and its hallmark pathological features are the loss of dopaminergic (DA) neurons in the midbrain substantia nigra pars compacta (SNpc) and the accumulation of alpha-synuclein (α-syn). It has been shown that the integrity of the blood-brain barrier (BBB) is damaged in PD patients, and a large number of infiltrating T cells and inflammatory cytokines have been detected in the cerebrospinal fluid (CSF) and brain parenchyma of PD patients and PD animal models, including significant change in the number and proportion of different CD4+ T cell subsets. This suggests that the neuroinflammatory response caused by CD4+ T cells is an important risk factor for the development of PD. Here, we systematically review the differentiation of CD4+ T cell subsets, and focus on describing the functions and mechanisms of different CD4+ T cell subsets and their secreted cytokines in PD. We also summarize the current immunotherapy targeting CD4+ T cells with a view to providing assistance in the diagnosis and treatment of PD.

Determining the role of statins in Parkinson's disease risk reduction and disease modification: A comprehensive meta-analysis of 4 million participants' data

BACKGROUND

Many observational studies have examined the association between statins and the incidence of Parkinson's disease (PD) in high-risk populations. On the other hand, clinical trials as well as other observational studies investigated the safety and efficacy of statins in slowing disease progression in PD patients. However, the evidence has been inconclusive in both questions. To that end, we conducted this systematic review and meta-analysis to synthesize evidence on the role of statins in decreasing the risk of PD among high-risk populations and as a possible disease-modifying agent for patients with PD.

METHODS

A comprehensive literature search of electronic databases including PubMed, Scopus, Cochrane, and Web of Science has been performed. Relevant studies were chosen and data were extracted and analyzed using RevMan software version 5.4.1.

RESULTS

Twenty-five studies (14 cohort, 9 case-control, and 2 randomized controlled trials) have been included in the present systematic review. Of them, 21 studies reported the association between statins and PD risk. Statins were found to significantly reduce the risk of developing PD (pooled RR 0.86, 95% CI [0.77-0.95], p < 0.005). Four studies investigated statins as a disease-modifying agent. The pooled mean difference (MD) in the UPDRS-III from baseline to endpoint did not differ significantly between the statin and control groups (MD -1.34 points, 95% CI [-3.81 to 1.14], p = 0.29).

CONCLUSION

Although epidemiological observational studies showed that statin use was associated with a reduced risk of PD, current evidence is insufficient to support the role of statins in slowing the progression of PD. These findings are limited by the fact that most of the included studies are observational studies which carry a high risk of confounding bias which highlights the need for future well-designed RCTs.

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.

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.

The clinical characteristics of neuronal intranuclear inclusion disease and its relation with inflammation

BACKGROUND

Neuronal intranuclear inclusion disease (NIID) is a great imitator with a broad spectrum of clinical manifestations that include dementia, parkinsonism, paroxysmal symptoms, peripheral neuropathy, and autonomic dysfunction. Hence, it may also masquerade as other diseases such as Alzheimer's disease, Parkinson's disease, and Charcot-Marie-Tooth disease. Recent breakthroughs on neuroimaging, skin biopsy, and genetic testing have facilitated the diagnosis. However, early identification and effective treatment are still difficult in cases of NIID.

OBJECTIVE

To further study the clinical characteristics of NIID and investigate the relationship between NIID and inflammation.

METHODS

We systematically evaluated the clinical symptoms, signs, MRI and electromyographical findings, and pathological characteristics of 20 NIID patients with abnormal GGC repeats in the NOTCH2NLC gene. Some inflammatory factors in the patients were also studied.

RESULTS

Paroxysmal symptoms such as paroxysmal encephalopathy, stroke-like episodes, and mitochondrial encephalomyopathy lactic acidosis and stroke (MELAS)-like episode were the most common phenotypes. Other symptoms such as cognitive dysfunction, neurogenic bladder, tremor, and vision disorders were also suggestive of NIID. Interestingly, not all patients showed apparent diffusion-weighted imaging (DWI) abnormality or intranuclear inclusions, while abnormal GGC repeats of NOTCH2NLC were seen in all patients. And fevers were noticed in some patients during encephalitic episodes, usually with increasing leukocyte counts and neutrophil ratios. Both IL-6 (p = 0.019) and TNF-α (p = 0.027) levels were significantly higher in the NIID group than in normal controls.

CONCLUSION

Genetic testing of NOTCH2NLC may be the best choice in the diagnosis of NIID. Inflammation might be involved in the pathogenesis of NIID.

Hydroxytyrosol Interference with Inflammaging via Modulation of Inflammation and Autophagy

Inflammaging refers to a chronic, systemic, low-grade inflammation, driven by immune (mainly macrophages) and non-immune cells stimulated by endogenous/self, misplaced or altered molecules, belonging to physiological aging. This age-related inflammatory status is characterized by increased inflammation and decreased macroautophagy/autophagy (a degradation process that removes unnecessary or dysfunctional cell components). Inflammaging predisposes to age-related diseases, including obesity, type-2 diabetes, cancer, cardiovascular and neurodegenerative disorders, as well as vulnerability to infectious diseases and vaccine failure, representing thus a major target for anti-aging strategies. Phenolic compounds-found in extra-virgin olive oil (EVOO)-are well known for their beneficial effect on longevity. Among them, hydroxytyrosol (HTyr) appears to greatly contribute to healthy aging by its documented potent antioxidant activity. In addition, HTyr can modulate inflammation and autophagy, thus possibly counteracting and reducing inflammaging. In this review, we reference the literature on pure HTyr as a modulatory agent of inflammation and autophagy, in order to highlight its possible interference with inflammaging. This HTyr-mediated activity might contribute to healthy aging and delay the development or progression of diseases related to aging.

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.

Study in Parkinson's disease of exercise phase 3 (SPARX3): study protocol for a randomized controlled trial

BACKGROUND

To date, no medication has slowed the progression of Parkinson's disease (PD). Preclinical, epidemiological, and experimental data on humans all support many benefits of endurance exercise among persons with PD. The key question is whether there is a definitive additional benefit of exercising at high intensity, in terms of slowing disease progression, beyond the well-documented benefit of endurance training on a treadmill for fitness, gait, and functional mobility. This study will determine the efficacy of high-intensity endurance exercise as first-line therapy for persons diagnosed with PD within 3 years, and untreated with symptomatic therapy at baseline.

METHODS

This is a multicenter, randomized, evaluator-blinded study of endurance exercise training. The exercise intervention will be delivered by treadmill at 2 doses over 18 months: moderate intensity (4 days/week for 30 min per session at 60-65% maximum heart rate) and high intensity (4 days/week for 30 min per session at 80-85% maximum heart rate). We will randomize 370 participants and follow them at multiple time points for 24 months. The primary outcome is the Movement Disorders Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS) motor score (Part III) with the primary analysis assessing the change in MDS-UPDRS motor score (Part III) over 12 months, or until initiation of symptomatic antiparkinsonian treatment if before 12 months. Secondary outcomes are striatal dopamine transporter binding, 6-min walk distance, number of daily steps, cognitive function, physical fitness, quality of life, time to initiate dopaminergic medication, circulating levels of C-reactive protein (CRP), and brain-derived neurotrophic factor (BDNF). Tertiary outcomes are walking stride length and turning velocity.

DISCUSSION

SPARX3 is a Phase 3 clinical trial designed to determine the efficacy of high-intensity, endurance treadmill exercise to slow the progression of PD as measured by the MDS-UPDRS motor score. Establishing whether high-intensity endurance treadmill exercise can slow the progression of PD would mark a significant breakthrough in treating PD. It would have a meaningful impact on the quality of life of people with PD, their caregivers and public health.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04284436 . Registered on February 25, 2020.

Association of Dietary Inflammatory Potential with Blood Inflammation: The Prospective Markers on Mild Cognitive Impairment

Inflammation is known as an important mechanism of cognitive dysfunction. Systemic immune inflammation index (SII) and system inflammation response index (SIRI) are two blood inflammatory markers, which are related to many chronic diseases including cognitive impairment. It is recognized that dietary inflammatory index (DII), which is used to estimate the overall inflammatory potential of diet, may be related to mild cognitive impairment (MCI) as well. This study aimed to explore the relationship between SII, SIRI and DII, as well as the role of these inflammatory indexes on MCI in elderly people. A total of 1050 participants from Beijing were included. Neuropsychological tests were used for cognitive evaluation. Energy-adjusted DII scores were calculated based on semi-quantitative food frequency questionnaire. Blood samples were tested for calculating SII and SIRI. Log-binomial regression models were used to estimate the correlation of indexes. After adjusting demographic characteristics, SII and SIRI in MCI individuals were higher than controls (p ≤ 0.001). DII, SII and SIRI had positive relationship with MoCA scores (p < 0.005). DII also correlated with SIRI in MCI (β = 0.11, p = 0.031). Higher DII and SIRI could definitely increase the risk of MCI, as well as DII and SII (p < 0.005). In conclusion, DII was positively correlated with blood inflammation. The elderly with higher level of DII and SIRI, or DII and SII could be considered as people with higher risk of developing MCI.