Pattern of Mitochondrial Respiration in Peripheral Blood Cells of Patients with Parkinson's Disease

Pink1/Parkin deficiency alters circulating lymphocyte populations and increases platelet-T cell aggregates in rats

Parkinson's disease (PD) is the most common progressive neurodegenerative movement disorder and results from the selective loss of dopaminergic neurons in the substantia nigra pars compacta. Pink1 and Parkin are proteins that function together in mitochondrial quality control, and when they carry loss-of-function mutations lead to familial forms of PD. While much research has focused on central nervous system alterations in PD, peripheral contributions to PD pathogenesis are increasingly appreciated. We report Pink1/Parkin regulate glycolytic and mitochondrial oxidative metabolism in peripheral blood mononuclear cells (PBMCs) from rats. Pink1/Parkin deficiency induces changes in the circulating lymphocyte populations, namely increased CD4 + T cells and decreased CD8 + T cells and B cells. Loss of Pink1/Parkin leads to elevated platelet counts in the blood and increased platelet-T cell aggregation. Platelet-lymphocyte aggregates are associated with increased thrombosis risk, and venous thrombosis is a cause of sudden death in PD, suggesting targeting the Pink1/Parkin pathway in the periphery has therapeutic potential.

ALS-associated VRK1 R321C mutation causes proteostatic imbalance and mitochondrial defects in iPSC-derived motor neurons

Vaccinia-related kinase 1 (VRK1) is a gene which has been implicated in the pathological process of a broad range of neurodevelopmental disorders as well as neuropathies, such as Amyotrophic Lateral Sclerosis (ALS). Here we report a family presenting ALS in an autosomal recessive mode of inheritance, segregating with a homozygous missense mutation located in VRK1 gene (p.R321C; Arg321Cys). Proteomic analyses from iPSC-derived motor neurons identified 720 proteins eligible for subsequent investigation, and our exploration of protein profiles revealed significant enrichments in pathways such as mTOR signaling, E2F, MYC targets, DNA repair response, cell proliferation and energetic metabolism. Functional studies further validated such alterations, showing that affected motor neurons presented decreased levels of global protein output, ER stress and downregulation of mTOR signaling. Mitochondrial alterations also pointed to decreased reserve capacity and increased non-mitochondrial oxygen consumption. Taken together, our results present the main pathological alterations associated with VRK1 mutation in ALS.

Fluid and tissue biomarkers in Parkinson's disease: Immunodetection or seed amplification? Central or peripheral?

Over the last two decades there have been meaningful developments on biomarkers of neurodegenerative diseases, extensively (but not solely) focusing on their proteinopathic nature. Accordingly, in Alzheimer's disease determination of levels of total and phosphorylated tau (τ and p-τ, usually p-τ181) along with amyloid-beta1-42 (Aβ1-42) by immunodetection in cerebrospinal fluid (CSF) and currently even in peripheral blood, have been widely accepted and introduced to routine diagnosis. In the case of Parkinson's disease, α-synuclein as a potential biomarker (both for diagnosis and progression tracking) has proved more elusive under the immunodetection approach. In recent years, the emergence of the so-called seed amplification assays is proving to be a game-changer, with mounting evidence under different technical approaches and using a variety of biofluids or tissues, yielding promising diagnostic accuracies. Currently the least invasive but at once more reliable source of biosamples and techniques are being sought. Here we overview these advances.

YKL-40 and the Cellular Metabolic Profile in Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. A growing body of evidence suggests that mitochondrial dysfunction and inflammation play a crucial role as a pathogenetic mechanism in PD. The glycoprotein YKL-40 (CHI3L1) is a potential biomarker involved in inflammation and tumor processes. The aim of the present study was to investigate the metabolic profile of PBMCs from PD patients and to search for a possible relationship between cellular bioenergetics and YKL-40. The study included 18 naïve PD patients and an age-matched control group (HC, n = 7). Patients were diagnosed according to the MDS-PD, the UPDRS, and the Hoen-Yahr scales. Mitochondrial activity was measured by a metabolic analyzer on isolated PBMCs from PD patients. Gene (qPCR) and protein (ELISA) expression levels of YKL40 were investigated. New data are reported revealing changes in the mitochondrial activity and YKL-40 levels in PD patients. Bioenergetic parameters showed increased respiratory reserve capacity in PD compared to HC. The protein levels of YKL-40 were threefold higher in PD. We found a correlation between the YKL-40 protein levels and basal respiration and between YKL-40 and ATP production. These observations suggest an interplay between YKL-40 and mitochondrial function in PD. We assume that the YKL-40 gene and protein levels in combination with changes in mitochondrial function might serve as an additional tool to monitor the clinical course of PD.

Clinical and neurochemical correlates of the APOE genotype in early-stage Parkinson's disease

Emerging evidence indicates that apolipoprotein E (APOE) genotype may influence Parkinson's disease (PD) course, although clinical and neurochemical correlates have not been completely established. This study aimed to determine the associations of APOE genotypes (ε4 vs. non-ε4) with cerebrospinal fluid (CSF) neurodegeneration biomarkers and clinical parameters in early-stage PD patients. One hundred and seventy-five PD patients and 89 non-neurodegenerative controls grouped in APOE-ε4 carriers (28 PD; 12 controls) and non-APOE-ε4 carriers (147 PD; 78 controls) were enrolled. CSF levels of amyloid-β-42, amyloid-β-40, total and 181-phosphorylated tau, and clinical scores were compared among groups adjusting for main covariates. APOE genotypes prevalence was similar in PD and controls. PD APOE-ε4 carriers had lower amyloid-β-42 CSF levels than PD non-APOE-ε4 carriers and controls, independently from age. PD APOE-ε4 carriers also had higher total and "item 5" (attention and memory) non-motor symptoms scale scores than PD non-APOE-ε4 carriers, independently from confounding factors. APOE-ε4 genotype might thus account for a more vulnerable PD subtype characterized by prominent amyloidopathy and a greater burden of non-motor symptoms in the early disease stages. DATA AVAILABILITY: Data are available upon reasonable request.

Neutrophil-to-lymphocyte ratio and lymphocyte count reflect alterations in central neurodegeneration-associated proteins and clinical severity in Parkinson Disease patients

INTRODUCTION

Peripheral inflammation has been recently associated to Parkinson disease (PD). However, how the peripheral inflammatory immune response could affect the clinical-pathological features of the disease is not fully understood. In this study, we assessed the peripheral immune profile of a well-characterized PD cohort, examining several correlations with CSF biomarkers of neurodegeneration and the main clinical parameters, aimed at better elucidating the complex dynamics of the brain-periphery interactions in PD.

METHODS

The leukocyte populations counts (neutrophils, lymphocytes, monocytes, eosinophils, and basophils) and the neutrophil-to-lymphocyte ratio (NLR) were collected and compared in 61 PD patients and 60 sex/age matched controls (CTRLs). Immune parameters were correlated with CSF levels of total α-synuclein, amyloid-β-42, total and phosphorylated-tau and main motor and non-motor scores.

RESULTS

PD patients had lower lymphocyte and higher NLR counts compared to CTRLs. In PD patients, the lymphocyte count directly correlated with CSF α-synuclein levels, whereas NLR displayed an inverse correlation with the CSF amyloid-β42 levels. The lymphocyte count also negatively correlated with HY stage, while NLR positively with the disease duration.

CONCLUSIONS

This study provided in vivo evidence that, in PD, changes in leukocytes in the periphery, assessed as relative lymphopenia and NLR increase, reflect in central neurodegeneration-associated proteins modifications, especially in α-synuclein and amyloid-β pathways, and greater clinical burden.

Mitochondrial Bioenergy in Neurodegenerative Disease: Huntington and Parkinson

Strong evidence suggests a correlation between degeneration and mitochondrial deficiency. Typical cases of degeneration can be observed in physiological phenomena (i.e., ageing) as well as in neurological neurodegenerative diseases and cancer. All these pathologies have the dyshomeostasis of mitochondrial bioenergy as a common denominator. Neurodegenerative diseases show bioenergetic imbalances in their pathogenesis or progression. Huntington's chorea and Parkinson's disease are both neurodegenerative diseases, but while Huntington's disease is genetic and progressive with early manifestation and severe penetrance, Parkinson's disease is a pathology with multifactorial aspects. Indeed, there are different types of Parkinson/Parkinsonism. Many forms are early-onset diseases linked to gene mutations, while others could be idiopathic, appear in young adults, or be post-injury senescence conditions. Although Huntington's is defined as a hyperkinetic disorder, Parkinson's is a hypokinetic disorder. However, they both share a lot of similarities, such as neuronal excitability, the loss of striatal function, psychiatric comorbidity, etc. In this review, we will describe the start and development of both diseases in relation to mitochondrial dysfunction. These dysfunctions act on energy metabolism and reduce the vitality of neurons in many different brain areas.