Erythrocyte membrane fluidity in mild cognitive impairment and Alzheimer's disease patients

Deformability of Heterogeneous Red Blood Cells in Aging and Related Pathologies

Aging is interrelated with changes in red blood cell parameters and functionality. In this article, we focus on red blood cells (RBCs) and provide a review of the known changes associated with the characterization of RBC deformability in aging and related pathologies. The biophysical parameters complement the commonly used biochemical parameters and may contribute to a better understanding of the aging process. The power of the deformability measurement approach is well established in clinical settings. Measuring RBCs' deformability has the advantage of relative simplicity, and it reflects the complex effects developing in erythrocytes during aging. However, aging and related pathological conditions also promote heterogeneity of RBC features and have a certain impact on the variance in erythrocyte cell properties. The possible applications of deformability as an early biophysical biomarker of pathological states are discussed, and modulating PIEZO1 as a therapeutic target is suggested. The changes in RBCs' shape can serve as a proxy for deformability evaluation, leveraging single-cell analysis with imaging flow cytometry and artificial intelligence algorithms. The characterization of biophysical parameters of RBCs is in progress in humans and will provide a better understanding of the complex dynamics of aging.

Hemoglobin levels and cognitive trajectory: unveiling prognostic insights in post-stroke geriatric cohort

PURPOSE

Evidence is scarce regarding the association between anemia and alterations in cognitive level among hospitalized older patients. We aimed to evaluate the associations between baseline hemoglobin (Hb) levels and changes in cognitive level in patients undergoing rehabilitation after stroke.

METHODS

A retrospective cohort study was conducted, encompassing consecutively hospitalized post-stroke patients. Data on serum Hb levels were extracted from medical records, specifically tests conducted within 24 hours of admission. Primary outcomes included discharge scores for cognitive function assessed by the cognitive domain of the Functional Independence Measure (FIM-cognition) and the corresponding change in FIM-cognition during hospitalization. Another outcome measure was the length of hospital stay. Multivariate linear regression analyses were employed to assess the association between Hb levels at admission and the designated outcomes, adjusting for potential confounding factors.

RESULTS

Data from 955 patients (mean age 73.2 years; 53.6% men) were included in the analysis. The median Hb level at admission was 13.3 [11.9, 14.5] g/dL. After fully adjusting for confounding factors, the baseline Hb level was significantly and positively associated with FIM-cognition at discharge (β = 0.045, p = 0.025) and its gain (β = 0.073, p = 0.025). Further, the baseline Hb level was independently and negatively associated with length of hospital stay (β = -0.013, p = 0.026).

CONCLUSION

Elevated baseline Hb levels are correlated with preserved cognitive level and shorter hospital stays in post-stroke patients. Evaluating anemia at the outset serves as a crucial prognostic indicator.

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.

Correlations among peripheral blood markers, white matter hyperintensity, and cognitive function in patients with non-disabling ischemic cerebrovascular events

BACKGROUND

Both inflammation and cerebral white matter injury are closely associated with vascular cognitive impairment (VCI). The aim of this study was to analyze the correlation between peripheral serological markers, white matter injury, and cognitive function in patients with non-disabling ischemic cerebrovascular events (NICE); to identify potential biological markers for the diagnosis and prediction of VCI; and to provide a basis for the early diagnosis and intervention of VCI.

METHODS

We collected clinical data, along with demographic and medical history data, from 151 NICE patients. Fasting venous blood samples were collected. Based on the Montreal Cognitive Assessment (MoCA) after admission, we divided the patients into normal cognitive function (NCF) and VCI groups, and then classified them into mild white matter hyperintensity (mWMH) and severe white matter hyperintensity (sWMH) based on Fazekas scores. The differences in serological marker levels were compared between the cognitive function groups and the white matter hyperintensity groups. Binary logistic regression models and receiver operating characteristic curves were used to analyze the diagnostic predictive value of serological markers for VCI in patients with NICE and in the white matter hyperintensity subgroups.

RESULTS

Among 151 patients with NICE, 95 were male and 56 were female. Lymphocyte count (OR = 0.405, p = 0.010, 95% CI [0.201, 0.806]), red blood cell count (OR = 0.433, p = 0.010, 95% CI [0.228, 0.821]), and hemoglobin level (OR = 0.979, p = 0.046, 95% CI [0.958, 0.999]) were protective factors for cognitive function in patients with NICE. The sWMH group had a higher age, granulocyte/lymphoid ratio (NLR), and neutrophil percentage but a lower MoCA score, hemoglobin level, and lymphocyte count than the mWMH group. In the mWMH group, lymphocyte count (AUC = 0.713, p = 0.003, 95% CI [0.593, 0.833]) had an acceptable predictive value for the diagnosis of VCI, whereas white blood cell count (AUC = 0.672, p = 0.011, 95% CI [0.545, 0.799]), red blood cell count (AUC = 0.665, p = 0.014, 95% CI [0.545, 0.784]), and hemoglobin level (AUC = 0.634, p = 0.047, 95% CI [0.502, 0.765]) had marginal predictive value for the diagnosis of VCI. In the sWMH group, no significant differences were found in serological markers between the NCF and VCI groups.

CONCLUSION

Lymphocyte count, red blood cell count, and hemoglobin level were independent protective factors for cognitive function in patients with NICE; they can be used as potential biological markers to distinguish VCI in patients with NICE and are applicable to subgroups of patients with mWMH.

Copolymer-1 as a potential therapy for mild cognitive impairment

Mild cognitive impairment (MCI) is a prodromal stage of memory impairment that may precede dementia. MCI is classified by the presence or absence of memory impairment into amnestic or non-amnestic MCI, respectively. More than 90% of patients with amnestic MCI who progress towards dementia meet criteria for Alzheimer's disease (AD). A combination of mechanisms promotes MCI, including intracellular neurofibrillary tangle formation, extracellular amyloid deposition, oxidative stress, neuronal loss, synaptodegeneration, cholinergic dysfunction, cerebrovascular disease, and neuroinflammation. However, emerging evidence indicates that neuroinflammation plays an important role in the pathogenesis of cognitive impairment. Unfortunately, there are currently no Food and Drug Administration (FDA)-approved drugs for MCI. Copolymer-1 (Cop-1), also known as glatiramer acetate, is a synthetic polypeptide of four amino acids approved by the FDA for the treatment of relapsing-remitting multiple sclerosis. Cop-1 therapeutic effect is attributed to immunomodulation, promoting a switch from proinflammatory to anti-inflammatory phenotype. In addition to its anti-inflammatory properties, it stimulates brain-derived neurotrophic factor (BDNF) secretion, a neurotrophin involved in neurogenesis and the generation of hippocampal long-term potentials. Moreover, BDNF levels are significantly decreased in patients with cognitive impairment. Therefore, Cop-1 immunization might promote synaptic plasticity and memory consolidation by increasing BDNF production in patients with MCI.

Infrared Spectroscopic Study of Multi-Component Lipid Systems: A Closer Approximation to Biological Membrane Fluidity

Membranes are essential to cellular organisms, and play several roles in cellular protection as well as in the control and transport of nutrients. One of the most critical membrane properties is fluidity, which has been extensively studied, using mainly single component systems. In this study, we used Fourier transform infrared spectroscopy to evaluate the thermal behavior of multi-component supported lipid bilayers that mimic the membrane composition of tumoral and non-tumoral cell membranes, as well as microorganisms such as Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus. The results showed that, for tumoral and non-tumoral membrane models, the presence of cholesterol induced a loss of cooperativity of the transition. However, in the absence of cholesterol, the transitions of the multi-component lipid systems had sigmoidal curves where the gel and fluid phases are evident and where main transition temperatures were possible to determine. Additionally, the possibility of designing multi-component lipid systems showed the potential to obtain several microorganism models, including changes in the cardiolipin content associated with the resistance mechanism in Staphylococcus aureus. Finally, the potential use of multi-component lipid systems in the determination of the conformational change of the antimicrobial peptide LL-37 was studied. The results showed that LL-37 underwent a conformational change when interacting with Staphylococcus aureus models, instead of with the erythrocyte membrane model. The results showed the versatile applications of multi-component lipid systems studied by Fourier transform infrared spectroscopy.

Dietary and supplemental long-chain omega-3 fatty acids as moderators of cognitive impairment and Alzheimer's disease

Purpose

There is an ever-growing body of literature examining the relationship between dietary omega-3 polyunsaturated fatty acids (ω3 PUFAs) and cerebral structure and function throughout life. In light of this, the use of ω3 PUFAs, namely, long-chain (LC) ω3 PUFAs (i.e., eicosapentaenoic acid and docosahexaenoic acid), as a therapeutic strategy to mitigate cognitive impairment, and progression to Alzheimer’s disease is an attractive prospect. This review aims to summarise evidence reported by observational studies and clinical trials that investigated the role of LC ω3 PUFAs against cognition impairment and future risk of Alzheimer’s disease.

Methods

Studies were identified in PubMed and Scopus using the search terms “omega-3 fatty acids”, “Alzheimer’s disease” and “cognition”, along with common variants. Inclusion criteria included observational or randomised controlled trials (RCTs) with all participants aged ≥ 50 years that reported on the association between LC ω3 PUFAs and cognitive function or biological markers indicative of cognitive function linked to Alzheimer’s disease.

Results

Evidence from 33 studies suggests that dietary and supplemental LC ω3 PUFAs have a protective effect against cognitive impairment. Synaptic plasticity, neuronal membrane fluidity, neuroinflammation, and changes in expression of genes linked to cognitive decline have been identified as potential targets of LC ω3 PUFAs. The protective effects LC ω3 PUFAs on cognitive function and reduced risk of Alzheimer’s disease were supported by both observational studies and RCTs, with RCTs suggesting a more pronounced effect in individuals with early and mild cognitive impairment.

Conclusion

The findings of this review suggest that individuals consuming higher amounts of LC ω3 PUFAs are less likely to develop cognitive impairment and that, as a preventative strategy against Alzheimer’s disease, it is most effective when dietary LC ω3 PUFAs are consumed prior to or in the early stages of cognitive decline.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00394-021-02655-4.

Erythrocytes as markers of oxidative stress related pathologies

Erythrocytes are deeply sensitive cells and important health indicators. During inflammatory response RBC, as a part of haematological system, are exposed to circulating inflammatory mediators and related oxidative stress. They present a highly specialized and organized cell membrane that interacts with inflammatory mediators and oxidative agents, leading to a variety of structural changes that promptly signal an abnormal situation. This review is aimed to provide an overview on erythrocyte involvement in physiological and pathological processes related to oxidative stress, such as aging, Down syndrome, neurodegenerative diseases, for instance Alzheimer Disease, erectile dysfunction and cardiovascular diseases. In particular this review will focus on the effects of oxidative stress on structural changes in the cell membrane and also on in the activity of erythrocyte enzymes such as membrane-bound, cytosolic glycohydrolases and RBC-eNOS. This review also underlines the potential clinical application of erythrocyte specific related parameters, which can be important tools not only for the study but also for the monitoring of several oxidative stress related diseases.

Mesenchymal stem cell-derived exosomal miR-223 regulates neuronal cell apoptosis

Hypoxia limits the survival and function of neurons in the development of Alzheimer’s diseases. Exosome-dependent intercellular communication is an emerging signaling mechanism involved in tissue repair and regeneration; however, the effect and underlying mechanism of mesenchymal stem cell-derived exosomes in regulating neuronal cell apoptosis have not been determined. Here, we showed that the establishment of an AD cell model was accompanied by increased HIF-1α expression and cell apoptosis, impaired cell migration, and decreased miR-223. MSC-derived exosomes were internalized by the AD cell coculture model in a time-dependent manner, resulting in reduced cell apoptosis, enhanced cell migration and increased miR-223, and these effects were reversed by KC7F2, a hypoxic inhibitor. Furthermore, MSC-derived exosomal miR-223 inhibited the apoptosis of neurons in vitro by targeting PTEN, thus activating the PI3K/Akt pathway. In addition, exosomes isolated from the serum of AD patients promoted cell apoptosis. In short, our study showed that MSC-derived exosomal miR-223 protected neuronal cells from apoptosis through the PTEN-PI3K/Akt pathway and provided a potential therapeutic approach for AD.