Alzheimer's disease is characterized by more low-density erythrocytes with increased volume and enhanced β-amyloid x-40 content

Neutrophil-Mediated Progression of Mild Cognitive Impairment to Dementia

Cognitive impairment is a serious condition that begins with amnesia and progresses to cognitive decline, behavioral dysfunction, and neuropsychiatric impairment. In the final stage, dysphagia and incontinence occur. There are numerous studies and developed drugs for cognitive dysfunction in neurodegenerative diseases, such as Alzheimer's disease (AD); however, their clinical effectiveness remains equivocal. To date, attempts have been made to overcome cognitive dysfunction and understand and delay the aging processes that lead to degenerative and chronic diseases. Cognitive dysfunction is involved in aging and the disruption of inflammation and innate immunity. Recent reports have indicated that the innate immune system is prevalent in patients with AD, and that peripheral neutrophil markers can predict a decline in executive function in patients with mild cognitive impairment (MCI). Furthermore, altered levels of pro-inflammatory interleukins have been reported in MCI, which have been suggested to play a role in the peripheral immune system during the process from early MCI to dementia. Neutrophils are the first responders of the innate immune system. Neutrophils eliminate harmful cellular debris via phagocytosis, secrete inflammatory factors to activate host defense systems, stimulate cytokine production, kill pathogens, and regulate extracellular proteases and inhibitors. This review investigated and summarized the regulation of neutrophil function during cognitive impairment caused by various degenerative diseases. In addition, this work elucidates the cellular mechanism of neutrophils in cognitive impairment and what is currently known about the effects of activated neutrophils on cognitive decline.

APPswe /PS1ΔE9 mice exhibit low oxygen saturation and alterations of erythrocytes preceding the neuropathology and cognitive deficiency during Alzheimer's disease

AIM

The molecular mechanism underlying Alzheimer's disease (AD) pathologies remains unclear. The brain is extremely sensitive to oxygen deprivation, and brief interruptions in oxygen supply may lead to permanent brain damage. The objective here was to access the red blood cell (RBC) physiological alterations and the changes in blood oxygen saturation of an AD model as well as to explore the possible mechanism underlying these pathologies.

METHODS

We used female APPswe /PS1ΔE9 mice as AD models. Data were collected at the age of 3, 6, and 9 months. In addition to examining classic features of AD, namely cognitive deficiency and Aβ depositions, 24 h blood oxygen saturation was monitored by Plus oximeters in real time. In addition, RBC physiological parameters were measured by blood cell counter using peripheral blood from the epicanthal veins. Furthermore, in the mechanism investigations, the expression of phosphorylated band 3 protein was examined by a series of Western blot analyses, and the levels of soluble Aβ40 and Aβ42 on the membrane of RBCs were determined by ELISA.

RESULTS

Our results showed that the blood oxygen saturation in the AD mice was significantly reduced as early as at 3 months of age, preceding the neuropathological changes and cognitive impairments. Meanwhile, the expression of phosphorylated band 3 protein and levels of soluble Aβ40 and Aβ42 were all elevated in the erythrocytes of the AD mice.

CONCLUSION

APPswe /PS1ΔE9 mice exhibited decreased oxygen saturation together with reduced RBC counts and hemoglobin concentrations at the early stage, which may aid in the development of predictive markers for AD diagnosis. The increased expression of band 3 protein and elevated Aβ40 and Aβ42 levels may contribute to the deformation of RBCs and, in turn, cause the subsequent AD development.

Erythrocyte Amyloid Beta Peptide Isoform Distributions in Alzheimer and Mild Cognitive Impairment

INTRODUCTION

We recently showed that Amyloid Beta (Aβ)40 accumulates in erythrocytes and possibly causes cell damage as evidenced by an increased number of assumed injured low-density (kg/L) erythrocytes. Furthermore, we have suggested a separation technique to isolate and concentrate such damaged red blood cells for subsequent analysis.

OBJECTIVES

We isolated high- and low-density erythrocytes and investigated the accumulation patterns of the Aβ peptides (Aβ40, Aβ42, and Aβ43) in Alzheimer (AD), mild cognitive impairment (MCI), and Subjective Cognitive Impairment (SCI).

METHODS

Whole blood was fractionated through a density gradient, resulting in two concentrated highand presumed injured low-density erythrocyte fractions. After cell lysis, intracellular Aβ40, Aβ42, and Aβ43 were quantified by ELISA.

RESULTS

In both high- and low-density erythrocytes, Aβ40 displayed the lowest concentration in MCI, while it was equal and higher in AD and SCI. Aβ40 was detected at a 10-fold higher level than Aβ42, and in injured low-density erythrocytes, the lowest quantity of Aβ42 was found in AD and MCI. Aβ40 exhibited a 100-fold greater amount than Aβ43, and lighter erythrocytes of MCI subjects displayed less intracellular Aβ43 than SCI.

CONCLUSION

Red blood cell accumulation patterns of Aβ40, Aβ42, and Aβ43 differ significantly between AD, MCI, and SCI. The data must be verified through larger clinical trials. It is, however, tenable that Aβ peptide distributions in erythrocyte subpopulations have the potential to be used for diagnostic purposes.

Alzheimer's Disease: Erythrocyte 2,3-diphosphoglycerate Content and Circulating Erythropoietin

BACKGROUND

Alzheimer's Disease (AD) features the accumulation of β-amyloid in erythrocytes. The subsequent red cell damage may well affect their oxygen-carrying capabilities. 2,3- diphosphoglycerate (2,3-DPG) binds to the hemoglobin thereby promoting oxygen release. It is theorized that 2,3-DPG is reduced in AD and that the resulting hypoxia triggers erythropoietin (EPO) release.

METHODS & OBJECTIVE

To explore this theory, we analyzed red cell 2,3-DPG content and EPO in AD, mild cognitive impairment, and the control group, subjective cognitive impairment.

RESULTS

We studied (i) 2,3-DPG in red cells, and (ii) circulating EPO in AD, and both markers were unaffected by dementia. Disturbances of these oxygen-regulatory pathways do not appear to participate in brain hypoxia in AD.

Free Heme and Amyloid-β: A Fatal Liaison in Alzheimer's Disease

While the etiology of Alzheimer's disease (AD) is still unknown, an increased formation of amyloid-β (Aβ) peptide and oxidative processes are major pathological mechanism of the disease. The interaction of Aβ with free heme leads to the formation of peroxidase-active Aβ-heme complexes. However, enzyme-kinetic data and systematic mutational studies are still missing. These aspects were addressed in this study to evaluate the role of Aβ-heme complexes in AD. The enzyme-kinetic measurements showed peroxidase-specific pH- and H2O2-dependencies. In addition, the enzymatic activity of Aβ-heme complexes constantly increased at higher peptide excess. Moreover, the role of the Aβ sequence for the named enzymatic activity was tested, depicting human-specific R5, Y10, and H13 as essential amino acids. Also by studying Y10 as an endogenous peroxidase substrate for Aβ-heme complexes, ratio-specific effects were observed, showing an optimal dityrosine formation at an about 40-fold peptide excess. As dityrosine formation promotes Aβ fibrillation while free heme disturbs protein aggregation, we also investigated the effect of Aβ-heme complex-derived peroxidase activity on the formation of Aβ fibrils. The fluorescence measurements showed a different fibrillation behavior at strong peroxidase activity, leading also to altered fibril morphologies. The latter was detected by electron microscopy. As illustrated by selected in vivo measurements on a mouse model of AD, the disease is also characterized by Aβ-derived microvessel destructions and hemolytic processes. Thus, thrombo-hemorrhagic events are discussed as a source for free heme in brain tissue. In summary, we suggest the formation and enzymatic activity of Aβ-heme complexes as pathological key features of AD.

The peripheral blood of Aβ binding RBC as a biomarker for diagnosis of Alzheimer's disease

BACKGROUND

in vitro, it has been reported that amyloid β (Aβ) is bound to red blood cells (RBCs) and this process damages the red cell. Also, a possible relationship between RBCs and Alzheimer's disease (AD) is supported by the findings of RBC impairment in AD. Therefore, Aβ fibrils bounding RBC are of great interest as potential biomarkers.

METHODS

in this study, we focused on Aβ amyloid fibrils and/or aggregation on the peripheral RBC from 50 subjects with AD and 50 healthy controls (HCs) through thioflavin T (ThT) staining followed by immunofluorescence assay to confirm the presence of Aβ amyloid fibrils and/or aggregation on the RBC. Then we optimised fluorescence staining and imaging conditions and analysed the images obtained by image processing software.

RESULTS

we have analysed RBC morphology in blood from 50 subjects with AD and 50 HCs found that 16.8% of the RBCs are elongated as compared with 6.7% in normal controls (P < 0.01), and there is a negative correlation between the two parameters (P < 0.05). Our study showed that 98% of AD peripheral RBCs were amyloid binding-positive (ranging from 2 to 30%), while only 38% that of RBCs (ranging from 2 to 3.4%) were in HCs. We also found four modified morphologies of RBCs triggered by Aβ binding, which may serve as an ancillary investigation and indicate the progression of AD.

CONCLUSION

we first directly prove the existence of Aβ binding RBCs in peripheral blood. In addition, we observed new modified morphologies of RBC triggered by Aβ binding, all of those can serve as a biomarker for the diagnosis and progression of AD.

Alzheimer's disease and granulocyte density diversity

BACKGROUND

The current study investigates circulating eosinophils and neutrophils in Alzheimer's (AD) type dementia with respect to density (kg/L). The existence of β-amyloid plaques in the brain is a feature of AD. Sporadic scientific reports indicate that the disease affects circulating neutrophils. In contrast, numerous publications investigate inflammatory reactions in AD brains. Locally, the plaques evoke a substantial inflammatory response involving activated microglia and astrocytes.

METHODS

Subjects with probable AD (n = 39) were included and compared with elderly individuals (n = 22) lacking apparent memory problems. We sampled 10 mL venous blood in citrate. Granulocytes were separated according to density in linear Percoll™ gradients. Subsequently, the gradients were divided into density subfractions (n = 16). In every fraction, determination of eosinophil and neutrophil counts was carried out.

RESULTS

AD sufferers displayed less granulocytes in fractions nos. 13-15 containing light cells. For these fractions, the P-values proved to be (P < 0.001; not significant; P = 0.03) and (P = 0.01; P = 0.01; not significant), for eosinophils and neutrophils, respectively.

CONCLUSIONS

The present work describes that less circulating light granulocytes are a feature of AD demented individuals. It is to hypothesize that it is a sign of impaired granulocyte turnover and cell damage. It is concluded that AD affects inflammatory cells in the periphery and that the behaviour of granulocytes in dementia is worthwhile further studies.