Erythrocyte membrane in the evaluation of neurodegenerative disorders

Alpha-synuclein in peripheral body fluid as a biomarker for Parkinson's disease

OBJECTIVE

Whether alpha-synuclein in peripheral body fluids can be used for the diagnosis of Parkinson's disease (PD) remains in controversy. This study evaluates diagnostic potential of alpha-synuclein for PD in various peripheral body fluids using a meta-analysis approach.

METHODS

Studies published before October 2022 were searched in Web of Science and PubMed databases. The results were computed using the STATA 12.0 statistical software.

RESULTS

In plasma, PD patients exhibited elevated alpha-synuclein levels relative to healthy controls (HCs) [standard mean difference (SMD) = 0.78, 95% confidence interval (CI) = 0.42 to 1.15] with a sensitivity of 0.79 (95% CI: 0.64-0.89) and a specificity of 0.95 (95% CI: 0.90-0.98). Higher plasma alpha-synuclein levels were correlated with longer disease durations, higher Unified Parkinson's Disease Rating Scale motor scores, and higher Hoehn and Yahr stages in PD patients. Plasma neural-derived exosomal alpha-synuclein levels (SMD = 1.82, 95% CI = 0.30 to 3.35), ratio of plasma neural-derived exosomal alpha-synuclein to total alpha-synuclein (SMD = 1.26, 95% CI = 0.19 to 2.33), and erythrocytic alpha-synuclein levels were also increased in PD patients (SMD = 6.57, 95% CI = 3.55 to 9.58). In serum, there was no significant difference in alpha-synuclein levels between PD patients and HCs (SMD = 0.54, 95% CI = - 0.27 to 1.34). In saliva, reduced alpha-synuclein levels were observed in PD patients (SMD = - 0.85, 95% CI = - 1.67 to - 0.04).

CONCLUSIONS

Alpha-synuclein levels in plasma, plasma neural-derived exosome, erythrocyte, and saliva may serve as potential biomarkers for the diagnosis of PD.

Recent Advances in the Study of Na+/K+-ATPase in Neurodegenerative Diseases

Na⁺/K⁺-ATPase (NKA), a large transmembrane protein, is expressed in the plasma membrane of most eukaryotic cells. It maintains resting membrane potential, cell volume and secondary transcellular transport of other ions and neurotransmitters. NKA consumes about half of the ATP molecules in the brain, which makes NKA highly sensitive to energy deficiency. Neurodegenerative diseases (NDDs) are a group of diseases characterized by chronic, progressive and irreversible neuronal loss in specific brain areas. The pathogenesis of NDDs is sophisticated, involving protein misfolding and aggregation, mitochondrial dysfunction and oxidative stress. The protective effect of NKA against NDDs has been emerging gradually in the past few decades. Hence, understanding the role of NKA in NDDs is critical for elucidating the underlying pathophysiology of NDDs and identifying new therapeutic targets. The present review focuses on the recent progress involving different aspects of NKA in cellular homeostasis to present in-depth understanding of this unique protein. Moreover, the essential roles of NKA in NDDs are discussed to provide a platform and bright future for the improvement of clinical research in NDDs.

Morphometry and Stiffness of Red Blood Cells—Signatures of Neurodegenerative Diseases and Aging

Human red blood cells (RBCs) are unique cells with the remarkable ability to deform, which is crucial for their oxygen transport function, and which can be significantly altered under pathophysiological conditions. Here we performed ultrastructural analysis of RBCs as a peripheral cell model, looking for specific signatures of the neurodegenerative pathologies (NDDs)—Parkinson’s disease (PD), amyotrophic lateral sclerosis (ALS) and Alzheimer’s disease (AD), utilizing atomic force (AFM) and conventional optical (OM) microscopy. We found significant differences in the morphology and stiffness of RBCs isolated from patients with the selected NDDs and those from healthy individuals. Neurodegenerative pathologies’ RBCs are characterized by a reduced abundance of biconcave discoid shape, lower surface roughness and a higher Young’s modulus, compared to healthy cells. Although reduced, the biconcave is still the predominant shape in ALS and AD cells, while the morphology of PD is dominated by crenate cells. The features of RBCs underwent a marked aging-induced transformation, which followed different aging pathways for NDDs and normal healthy states. It was found that the diameter, height and volume of the different cell shape types have different values for NDDs and healthy cells. Common and specific morphological signatures of the NDDs were identified.

Erythrocyte Deformability and Na,K-ATPase Activity in Various Pathophysiological Situations and Their Protection by Selected Nutritional Antioxidants in Humans

The physicochemical and functional properties of erythrocytes are worsened in a variety of diseases. Erythrocyte deformability refers to their ability to adjust their shape according to external forces exerted against them in the circulation. It is influenced by the functionality of the Na,K-ATPase enzyme, which is localized in their membranes. The proposed review is focused on knowledge regarding changes in erythrocyte Na,K-ATPase activity, and their impact on erythrocyte deformability in various pathophysiological situations observed exclusively in human studies, as well as on the potential erytroprotective effects of selected natural nutritional antioxidants. A clear link between the erythrocyte properties and the parameters of oxidative stress was observed. The undesirable consequences of oxidative stress on erythrocyte quality and hemorheology could be at least partially prevented by intake of diverse antioxidants occurring naturally in foodstuffs. Despite intensive research concerning the effect of antioxidants, only a small number of investigations on erythrocyte properties in humans is available in databases. It is worth shifting attention from animal and in vitro experiments and focusing more on antioxidant administration in human studies in order to establish what type of antioxidant, in what concentration, and in which individuals it may provide a beneficial effect on the human organism, by protecting erythrocyte properties.

A Comparative Study of the Diagnostic Potential of Plasma and Erythrocytic α-Synuclein in Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disease characterized by intracellular α-synuclein (α-Syn) deposition. Alternation of the α-Syn expression level in plasma or erythrocytes may be used as a potential PD biomarker. However, no studies have compared their prognostic value directly with the same cohort.

METHODS

The levels of α-Syn in plasma and erythrocytes, obtained from 45 PD patients and 45 control subjects, were measured with enzyme-linked immunosorbent assay. Then, correlation and receiver operating characteristic curve (ROC) analysis were performed to characterize the predictive power of erythrocytic and plasma α-Syn.

RESULTS

Our results showed that α-Syn expression levels in both plasma and erythrocytes were significantly higher in PD patients than in control subjects (823.14 ± 257.79 vs. 297.10 ± 192.82 pg/mL, p < 0.0001 in plasma; 3,104.14 ± 143.03 vs. 2,944.82 ± 200.41 pg/mL, p < 0.001 in erythrocytes, respectively). The results of the ROC analysis suggested that plasma α-Syn exhibited better predictive power than erythrocytic α-Syn with a sensitivity of 80.0%, specificity of 97.7%, and a positive predictive value of 77.8%. The expression level of plasma α-Syn correlated well with the age of patients, H-Y stage, MoCA scale, and UPDRS motor scale. On the contrary, there was no correlation between erythrocytic α-Syn level and clinical parameters in this study.

CONCLUSION

Our results suggest that plasma α-Syn could be a specific and sensitive potential diagnostic biomarker for PD.

Fluoride Exposure Induces Inhibition of Sodium-and Potassium-Activated Adenosine Triphosphatase (Na+, K+-ATPase) Enzyme Activity: Molecular Mechanisms and Implications for Public Health

In this study, several lines of evidence are provided to show that Na + , K + -ATPase activity exerts vital roles in normal brain development and function and that loss of enzyme activity is implicated in neurodevelopmental, neuropsychiatric and neurodegenerative disorders, as well as increased risk of cancer, metabolic, pulmonary and cardiovascular disease. Evidence is presented to show that fluoride (F) inhibits Na + , K + -ATPase activity by altering biological pathways through modifying the expression of genes and the activity of glycolytic enzymes, metalloenzymes, hormones, proteins, neuropeptides and cytokines, as well as biological interface interactions that rely on the bioavailability of chemical elements magnesium and manganese to modulate ATP and Na + , K + -ATPase enzyme activity. Taken together, the findings of this study provide unprecedented insights into the molecular mechanisms and biological pathways by which F inhibits Na + , K + -ATPase activity and contributes to the etiology and pathophysiology of diseases associated with impairment of this essential enzyme. Moreover, the findings of this study further suggest that there are windows of susceptibility over the life course where chronic F exposure in pregnancy and early infancy may impair Na + , K + -ATPase activity with both short- and long-term implications for disease and inequalities in health. These findings would warrant considerable attention and potential intervention, not to mention additional research on the potential effects of F intake in contributing to chronic disease.