Erythrocytes: Central Actors in Multiple Scenes of Atherosclerosis

Nonlinear relationship of red blood cell indices (MCH, MCHC, and MCV) with all-cause and cardiovascular mortality: A cohort study in U.S. adults

BACKGROUND

In recent years, increasing attention has been focused on the impact of red blood cell indices (RCIs) on disease prognosis. We aimed to investigate the association of mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and mean corpuscular volume (MCV) with mortality.

METHODS

The study used cohort data from U.S. adults who participated in the 1999-2008 National Health and Nutrition Examination Survey. All-cause mortality was the primary outcome during follow-up, with secondary cardiovascular mortality outcomes. COX regression was applied to analyze the connection between RCIs and mortality. We adopted three models to minimize potential bias. Smooth-fit curves and threshold effect analyses were utilized to observe the dose-response relationship between RCIs and all-cause and cardiovascular mortality. In addition, we performed sensitivity analyses.

RESULTS

21,203 individuals were enrolled in our research. During an average 166.2 ± 54.4 months follow-up, 24.4% of the population died. Curve fitting indicated a U-shaped relationship between MCV and MCH with all-cause mortality, and the relationship of MCHC to all-cause mortality is L-shaped. We identified inflection points in the relationship between MCV, MCH, and MCHC and all-cause mortality as 88.56732 fl, 30.22054 pg, 34.34624 g/dl (MCV <88.56732 fl, adjusted HR 0.99, 95 CI% 0.97-1.00; MCV >88.56732 fl, adjusted HR 1.05, 95 CI% 1.04-1.06. MCH <30.22054 pg, adjusted HR 0.95, 95 CI% 0.92-0.98; MCH >30.22054 pg, adjusted HR 1.08, 95 CI% 1.04-1.12. MCHC <34.34624 g/dl, adjusted HR 0.88, 95 CI% 0.83-0.93). Besides, the MCV curve was U-shaped in cardiovascular mortality (MCV <88.56732 fl, adjusted HR 0.97, 95 CI% 0.94-1.00; MCV >88.56732 fl, adjusted HR 1.04, 95 CI% 1.01-1.06).

CONCLUSION

This cohort study demonstrated that RCIs (MCH, MCHC, and MCV) were correlated with mortality in the general population. Three RCIs were nonlinearly correlated with all-cause mortality. In addition, there were nonlinear relationships between MCH and MCV and cardiovascular mortality.

Physiotypic variations lead to variations within the normal range for red blood cells and haemoglobin levels in a healthy human population: An evaluation using generalised additive modelling and hierarchical structure analysis

OBJECTIVES

Haematological parameters have been used for a long time for clinical evaluations, however the dynamics of these parameters has not been studied at length, in healthy populations. We aim to understand the dependence of haematological parameters on human physiotypes.

DESIGN AND METHODS

Using an age and gender restricted healthy human (male) population (n = 100), we attempt to analyse the dynamics of haemoglobin and red blood cells, with reference to age, height and weight of individuals. Using advanced generalised additive modelling and classical hierarchical structural analysis we aim to establish relationships between these parameters and human physiotypes.

RESULTS

We demonstrate that definitive relationships can be established for number of red blood cells, haemoglobin levels, RDW-CV, RDW-SD and weight, height and age of individuals.

CONCLUSION

This study provides a proof of principle, that haematological parameters are dependent on physiotypic variation, within the normal ranges in a healthy population. It may also be noted that there is a definitive influence of height, weight and age on normal ranges and stratification by these factors might therefore make reference intervals narrower, in turn, possibly allowing more precise clinical decisions based on the complete blood count (CBC).

Hemocompatibility studies in nanotoxicology: Hemolysis or eryptosis? (A review)

Hemocompatibility evaluation is an important step in nanotoxicological studies. It is generally accepted that nanomaterials promote lysis of erythrocytes, blood clotting, alter phagocytosis, and upregulate pro-inflammatory cytokines. However, there are no standardized guidelines for testing nanomaterials hemocompatibility despite the fact that nanomaterials enter the bloodstream and interact with blood cells. In this review, the current knowledge on the ability of nanomaterials to induce distinct cell death modalities of erythrocytes is highlighted primarily focusing on hemolysis and eryptosis. This review aims to summarize the molecular mechanisms underlying erythrotoxicity of nanomaterials and critically compare the sensitivity and efficiency of hemolysis or eryptosis assays for nanomaterials blood compatibility testing. The list of eryptosis-inducing nanomaterials is growing, but it is still difficult to generalize how physico-chemical properties of nanoparticles affect eryptosis degree and molecular mechanisms involved. Thus, another aim of this review is to raise the awareness of eryptosis as a nanotoxicological tool to encourage the corresponding studies. It is worthwhile to consider adding eryptosis to in vitro nanomaterials hemocompatibility testing protocols and guidelines.

OMEF biochip for evaluating red blood cell deformability using dielectrophoresis as a diagnostic tool for type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a prevalent and debilitating disease with numerous health risks, including cardiovascular diseases, kidney dysfunction, and nerve damage. One important aspect of T2DM is its association with the abnormal morphology of red blood cells (RBCs), which leads to increased blood viscosity and impaired blood flow. Therefore, evaluating the mechanical properties of RBCs is crucial for understanding the role of T2DM in cellular deformability. This provides valuable insights into disease progression and potential diagnostic applications. In this study, we developed an open micro-electro-fluidic (OMEF) biochip technology based on dielectrophoresis (DEP) to assess the deformability of RBCs in T2DM. The biochip facilitates high-throughput single-cell RBC stretching experiments, enabling quantitative measurements of the cell size, strain, stretch factor, and post-stretching relaxation time. Our results confirm the significant impact of T2DM on the deformability of RBCs. Compared to their healthy counterparts, diabetic RBCs exhibit ∼27% increased size and ∼29% reduced stretch factor, suggesting potential biomarkers for monitoring T2DM. The observed dynamic behaviors emphasize the contrast between the mechanical characteristics, where healthy RBCs demonstrate notable elasticity and diabetic RBCs exhibit plastic behavior. These differences highlight the significance of mechanical characteristics in understanding the implications for RBCs in T2DM. With its ∼90% sensitivity and rapid readout (ultimately within a few minutes), the OMEF biochip holds potential as an effective point-of-care diagnostic tool for evaluating the deformability of RBCs in individuals with T2DM and tracking disease progression.

Back to the Basics of SARS-CoV-2 Biochemistry: Microvascular Occlusive Glycan Bindings Govern Its Morbidities and Inform Therapeutic Responses

Consistent with the biochemistry of coronaviruses as well established over decades, SARS-CoV-2 makes its initial attachment to host cells through the binding of its spike protein (SP) to sialylated glycans (containing the monosaccharide sialic acid) on the cell surface. The virus can then slide over and enter via ACE2. SARS-CoV-2 SP attaches particularly tightly to the trillions of red blood cells (RBCs), platelets and endothelial cells in the human body, each cell very densely coated with sialic acid surface molecules but having no ACE2 or minimal ACE2. These interlaced attachments trigger the blood cell aggregation, microvascular occlusion and vascular damage that underlie the hypoxia, blood clotting and related morbidities of severe COVID-19. Notably, the two human betacoronaviruses that express a sialic acid-cleaving enzyme are benign, while the other three-SARS, SARS-CoV-2 and MERS-are virulent. RBC aggregation experimentally induced in several animal species using an injected polysaccharide caused most of the same morbidities of severe COVID-19. This glycan biochemistry is key to disentangling controversies that have arisen over the efficacy of certain generic COVID-19 treatment agents and the safety of SP-based COVID-19 vaccines. More broadly, disregard for the active physiological role of RBCs yields unreliable or erroneous reporting of pharmacokinetic parameters as routinely obtained for most drugs and other bioactive agents using detection in plasma, with whole-blood levels being up to 30-fold higher. Appreciation of the active role of RBCs can elucidate the microvascular underpinnings of other health conditions, including cardiovascular disease, and therapeutic opportunities to address them.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

Apolipoprotein E-ε2 and Resistance to Atherosclerosis in Midlife: The PESA Observational Study

BACKGROUND

APOE is a known genetic contributor to cardiovascular disease, but the differential role APOE alleles play in subclinical atherosclerosis remains unclear.

METHODS

The PESA (Progression of Early Subclinical Atherosclerosis) is an observational cohort study that recruited 4184 middle-aged asymptomatic individuals to be screened for cardiovascular risk and multiterritorial subclinical atherosclerosis. Participants were APOE-genotyped, and omics data were additionally evaluated.

RESULTS

In the PESA study, the frequencies for APOE -ε2, -ε3, and -ε4 alleles were 0.060, 0.844, and 0.096, respectively. This study included a subcohort of 3887 participants (45.8±4.3 years of age; 62% males). As expected, APOE-ε4 carriers were at the highest risk for cardiovascular disease and had significantly greater odds of having subclinical atherosclerosis compared with ε3/ε3 carriers, which was mainly explained by their higher levels of low-density lipoprotein (LDL)-cholesterol. In turn, APOE-ε2 carriers were at the lowest risk for cardiovascular disease and had significantly lower odds of having subclinical atherosclerosis in several vascular territories (carotids: 0.62 [95% CI, 0.47-0.81]; P=0.00043; femorals: 0.60 [0.47-0.78]; P=9.96×10-5; coronaries: 0.53 [0.39-0.74]; P=0.00013; and increased PESA score: 0.58 [0.48-0.71]; P=3.16×10-8). This APOE-ε2 atheroprotective effect was mostly independent of the associated lower LDL-cholesterol levels and other cardiovascular risk factors. The protection conferred by the ε2 allele was greater with age (50-54 years: 0.49 [95% CI, 0.32-0.73]; P=0.00045), and normal (<150 mg/dL) levels of triglycerides (0.54 [0.44-0.66]; P=4.70×10-9 versus 0.90 [0.57-1.43]; P=0.67 if ≥150 mg/dL). Omics analysis revealed an enrichment of several canonical pathways associated with anti-inflammatory mechanisms together with the modulation of erythrocyte homeostasis, coagulation, and complement activation in ε2 carriers that might play a relevant role in the ε2's atheroprotective effect.

CONCLUSIONS

This work sheds light on the role of APOE in cardiovascular disease development with important therapeutic and prevention implications on cardiovascular health, especially in early midlife.

REGISTRATION

URL: https://www.clinicaltrials.gov: NCT01410318.

Glycosylation of blood cells during the onset and progression of atherosclerosis and myocardial infarction

Protein glycosylation controls cell-cell and cell-extracellular matrix (ECM) communication in immune, vascular, and inflammatory processes, underlining the critical role of this process in the identification of disease biomarkers and the design of novel therapies. Emerging evidence highlights the critical role of blood cell glycosylation in the pathophysiology of atherosclerosis (ATH) and myocardial infarction (MI). Here, we review the role of glycosylation in the interplay between blood cells, particularly erythrocytes, and endothelial cells (ECs), highlighting the involvement of this critical post/cotranslational modification in settings of cardiovascular disease (CVD). Importantly, we focus on emerging preclinical studies and clinical trials based on glycan-targeted drugs to validate their therapeutic potential. These findings may help establish new trends in preventive medicine and delineate novel targeted therapies in CVD.

Bisphenol S remodels red blood cell membrane lipids by altering plasma lipid levels, causing the risk of venous thrombosis in SD rats and zebrafish embryos

Bisphenol S (BPS) is a raw material that is used extensively in various manufacturing processes but possesses a high detection rate in human red blood cells (RBCs). Accordingly, BPS is a potential toxicant in disturbing the function of RBCs and causing RBC-related diseases. To date, the effects and mechanisms of BPS-induced RBC-related diseases have not been elucidated. Here, using different models, including rats, zebrafish embryos and RBCs, the underlying mechanism of RBC-related diseases induced by BPS was explored. The accumulation of BPS in tissue was colon > kidney > liver > plasma > testicle > heart > brain in SD rats orally administered BPS (10 and 50 mg/kg bw/day) for 32 days, which was similar in both 10 mg/kg bw/day and 50 mg/kg bw/day group. Rats given BPS orally developed hyperlipidemia and increased RBC membrane cholesterol, as well as changes in RBC morphology and function. Moreover, BPS at the concentrations measured in rats plasma caused oxidative stress and phosphatidylserine exposure in vitro RBCs. These combined factors led to RBC aggregation in blood and an increasing in the number of RBCs in the blood vessels of the liver in rats. The dynamic visual observation of RBCs in vein vessels of zebrafish embryos exposed to BPS at 0, 1, 10 and 100 μg/L further found that the flow of RBCs in the tail vein is slow or even immobile, posing the risk of venous thrombosis. The present study provides new insight into the links between environmental pollutants and venous thrombosis.

New Clues to Cardiovascular Disease: Erythrocyte Lifespan

Determination of erythrocyte lifespan is an important part of the diagnosis of hemolytic diseases. Recent studies have revealed alterations in erythrocyte lifespan among patients with various cardiovascular diseases, including atherosclerotic coronary heart disease, hypertension, and heart failure. This review summarizes the progress of research on erythrocyte lifespan in cardiovascular diseases.

Iron and atherosclerosis: Lessons learned from rabbits relevant to human disease

The role of iron in promoting atherosclerosis, and hence the cardiovascular, neurodegenerative and other diseases that result from atherosclerosis, has been fiercely controversial. Many studies have been carried out on various rodent models of atherosclerosis, especially on apoE-knockout (apoE-/-) mice, which develop atherosclerosis more readily than normal mice. These apoE-/- mouse studies generally support a role for iron in atherosclerosis development, although there are conflicting results. The purpose of the current article is to describe studies on another animal model that is not genetically manipulated; New Zealand White (NZW) rabbits fed a high-cholesterol diet. This may be a better model than the apoE-/- mice for human atherosclerosis, although it has been given much less attention. Studies on NZW rabbits support the view that iron promotes atherosclerosis, although some uncertainties remain, which need to be resolved by further experimentation.

The accumulation of erythrocytes quantified and visualized by Glycophorin C in carotid atherosclerotic plaque reflects intraplaque hemorrhage and pre-procedural neurological symptoms

The accumulation of erythrocyte membranes within an atherosclerotic plaque may contribute to the deposition of free cholesterol and thereby the enlargement of the necrotic core. Erythrocyte membranes can be visualized and quantified in the plaque by immunostaining for the erythrocyte marker glycophorin C. Hence, we theorized that the accumulation of erythrocytes quantified by glycophorin C could function as a marker for plaque vulnerability, possibly reflecting intraplaque hemorrhage (IPH), and offering predictive value for pre-procedural neurological symptoms. We employed the CellProfiler-integrated slideToolKit workflow to visualize and quantify glycophorin C, defined as the total plaque area that is positive for glycophorin C, in single slides of culprit lesions obtained from the Athero-Express Biobank of 1819 consecutive asymptomatic and symptomatic patients who underwent carotid endarterectomy. Our assessment included the evaluation of various parameters such as lipid core, calcifications, collagen content, SMC content, and macrophage burden. These parameters were evaluated using a semi-quantitative scoring method, and the resulting data was dichotomized as predefined criteria into categories of no/minor or moderate/heavy staining. In addition, the presence or absence of IPH was also scored. The prevalence of IPH and pre-procedural neurological symptoms were 62.4% and 87.1%, respectively. The amount of glycophorin staining was significantly higher in samples from men compared to samples of women (median 7.15 (IQR:3.37, 13.41) versus median 4.06 (IQR:1.98, 8.32), p < 0.001). Glycophorin C was associated with IPH adjusted for clinical confounders (OR 1.90; 95% CI 1.63, 2.21; p =  < 0.001). Glycophorin C was significantly associated with ipsilateral pre-procedural neurological symptoms (OR:1.27, 95%CI:1.06-1.41, p = 0.005). Sex-stratified analysis, showed that this was also the case for men (OR 1.37; 95%CI 1.12, 1.69; p = 0.003), but not for women (OR 1.15; 95%CI 0.77, 1.73; p = 0.27). Glycophorin C was associated with classical features of a vulnerable plaque, such as a larger lipid core, a higher macrophage burden, less calcifications, a lower collagen and SMC content. There were marked sex differences, in men, glycophorin C was associated with calcifications and collagen while these associations were not found in women. To conclude, the accumulation of erythrocytes in atherosclerotic plaque quantified and visualized by glycophorin C was independently associated with the presence of IPH, preprocedural symptoms in men, and with a more vulnerable plaque composition in both men and women. These results strengthen the notion that the accumulation of erythrocytes quantified by glycophorin C can be used as a marker for plaque vulnerability.

A light scatter based model relating erythrocyte vesiculation to lifetime in circulation

Methods for measuring erythrocyte age distribution are not available as a simple analytical tool. Most of them utilize the fluorescence or radioactive isotopes labeling to construct the age distribution and support physicians with aging indices of donor's erythrocytes. The age distribution of erythrocyte may be a useful snapshot of patient state over 120-days period of life. Previously, we introduced the enhanced assay of erythrocytes with measurement of 48 indices in four categories: concentration/content, morphology, aging and function (10.1002/cyto.a.24554). The aging category was formed by the indices based on the evaluation of the derived age of individual cells. The derived age does not exactly mean the real age of erythrocytes and its evaluation utilizes changes of cellular morphology during a lifespan. In this study, we are introducing the improved methodological approach that allows us to retrieve the derived age of individual erythrocytes, to construct the aging distribution, and to reform the aging category consisting of eight indices. The approach is based on the analysis of the erythrocyte vesiculation. The erythrocyte morphology is analyzed by scanning flow cytometry that measures the primary characteristics (diameter, thickness, and waist) of individual cells. The surface area (S) and sphericity index (SI) are calculated from the primary characteristics and the scattering diagram SI versus S is used in the evaluation of the derived age of each erythrocyte in a sample. We developed the algorithm to evaluate the derived age that provides eight indices in the aging category based on a model using light scatter features. The novel erythrocyte indices were measured for simulated cells and blood samples of 50 donors. We determined the first-ever reference intervals for these indices.

Association of Atherogenic Index of Plasma with Cardiometabolic Risk Factors and Markers in Lean 14-to-20-Year-Old Individuals: A Cross-Sectional Study

Cardiometabolic risk factors at a young age pose a significant risk for developing atherosclerotic cardiovascular disease in adulthood. Atherogenic dyslipidemia is highly associated with obesity and metabolic syndrome already in young age. It remains unclear whether cardiometabolic risk factors associate with the atherogenic index of plasma (AIP = log (TAG/HDL-C) in lean subjects with low atherogenic risk. As both the AIP and markers of cardiometabolic risk are continuous variables, we expected their association to be linear before the manifestation of obesity and atherogenic dyslipidemia. We analyzed the prevalence of increased atherogenic risk (AIP ≥ 0.11) in 2012 lean 14-to-20-year-old subjects (55% females) and the trends of cardiometabolic risk factors across the quartiles (Q) of AIP in a subgroup of 1947 (56% females) subjects with low atherogenic risk (AIP < 0.11). The prevalence of AIP ≥ 0.11 reached 3.6% in females and 8.5% in males. HDL-C, non-HDL-C, triglycerides, and the continuous metabolic syndrome score showed a stepwise worsening across the AIP quartiles in both sexes. Measures of obesity and insulin resistance were worse in Q4 vs. Q1 groups, and leukocyte counts were higher in Q4 and Q3 vs. Q1. Females in Q4 presented with a higher C-reactive protein and lower adiponectin, estradiol, and testosterone levels. The multivariate regression model selected non-HDL-C, QUICKI, and erythrocyte counts as significant predictors of AIP in males; and non-HDL-C and C-reactive protein in females. A question arises whether the lean individuals on the upper edge of low atherogenic risk are prone to earlier manifestation of metabolic syndrome and shift to the higher AIP risk group.

Hypolipidemic and Anti-Inflammatory Effects of Curcuma longa-Derived Bisacurone in High-Fat Diet-Fed Mice

Turmeric (Curcuma longa) contains various compounds that potentially improve health. Bisacurone is a turmeric-derived compound but has been less studied compared to other compounds, such as curcumin. In this study, we aimed to evaluate the anti-inflammatory and lipid-lowering effects of bisacurone in high-fat diet (HFD)-fed mice. Mice were fed HFD to induce lipidemia and orally administered bisacurone daily for two weeks. Bisacurone reduced liver weight, serum cholesterol and triglyceride levels, and blood viscosity in mice. Splenocytes from bisacurone-treated mice produced lower levels of the pro-inflammatory cytokines IL-6 and TNF-α upon stimulation with a toll-like receptor (TLR) 4 ligand, lipopolysaccharide (LPS), and TLR1/2 ligand, Pam3CSK4, than those from untreated mice. Bisacurone also inhibited LPS-induced IL-6 and TNF-α production in the murine macrophage cell line, RAW264.7. Western blot analysis revealed that bisacurone inhibited the phosphorylation of IKKα/β and NF-κB p65 subunit, but not of the mitogen-activated protein kinases, p38 kinase and p42/44 kinases, and c-Jun N-terminal kinase in the cells. Collectively, these results suggest that bisacurone has the potential to reduce serum lipid levels and blood viscosity in mice with high-fat diet-induced lipidemia and modulate inflammation via inhibition of NF-κB-mediated pathways.

Integrating Mechanisms in Thrombotic Peripheral Arterial Disease

Peripheral arterial disease (PAD), a manifestation of systemic atherosclerosis, is underdiagnosed in the general population. Despite the extensive research performed to unravel its pathophysiology, inadequate knowledge exists, thus preventing the development of new treatments. This review aims to highlight the essential elements of atherosclerosis contributing to the pathophysiology of PAD. Furthermore, emphasis will be placed on the role of thrombo-inflammation, with particular focus on platelet and coagulation activation as well as cell-cell interactions. Additional insight will be then discussed to reveal the contribution of hypercoagulability to the development of vascular diseases such as PAD. Lastly, the current antithrombotic treatments will be discussed, and light will be shed on promising new targets aiming to aid the development of new treatments.

Relationship between Red Blood Cell Indices (MCV, MCH, and MCHC) and Major Adverse Cardiovascular Events in Anemic and Nonanemic Patients with Acute Coronary Syndrome

BACKGROUND

Previous studies have shown that increased mean corpuscular volume (MCV) is an independent predictor for worse outcomes in coronary artery disease. However, as parameters to classify different types of anemia together with MCV, the relationship between mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), and long-term outcomes in acute coronary syndrome (ACS) remains obscure. Moreover, few studies have compared the prognostic value of these red blood cell indices in anemic and nonanemic patients with ACS.

METHODS AND RESULTS

In this single-center observational cohort study, we enrolled 393 patients diagnosed with ACS, including 75 anemic and 318 nonanemic patients. The composite end points were defined as major adverse cardiovascular events (MACEs). After a median follow-up of 31.24 months, Kaplan-Meier survival analysis showed that higher MCV and MCH but not MCHC were significantly associated with increased MACEs in nonanemic ACS patients. Among the enrolled ACS patients without anemia, Cox regression analysis revealed that high MCV and MCH were correlated with increased MACEs after adjustment for cardiovascular risk factors, and receiver operating characteristic (ROC) curve analysis further confirmed the predictive value of high MCV and MCH. In bivariate correlation and linear regression analysis, plasma homocysteine was positively correlated with MCV and MCH but not MCHC in the nonanemic group even after adjusting for age, male sex, BMI, SBP, DBP, smoking, and diabetes. However, MCV, MCH, and MCHC showed no predictive value for MACEs, and no correlation was found between these red blood cell indices and homocysteine in ACS patients with anemia.

CONCLUSION

After adjusting for cardiovascular risk factors, this study showed that higher admission MCV and MCH but not MCHC were independent predictors for long-term MACEs and positively correlated with homocysteine levels in the blood among the nonanemic but not anemic patients with ACS in China.

Low grade intravascular hemolysis associates with peripheral nerve injury in type 2 diabetes

Type 2 diabetes (T2D) induces hyperglycemia, alters hemoglobin (Hb), red blood cell (RBC) deformability and impairs hemorheology. The question remains whether RBC breakdown and intravascular hemolysis (IVH) occur in T2D patients. We characterized RBC-degradation products and vesiculation in a case-control study of 109 T2D patients and 65 control subjects. We quantified heme-related absorbance by spectrophotometry and circulating extracellular vesicles (EV) by flow cytometry and electron microscopy. Heme-related absorbance was increased in T2D vs. control plasma (+57%) and further elevated in obese T2D plasma (+27%). However, large CD235a+ EV were not increased in T2D plasma. EV from T2D plasma, or shed by isolated T2D RBC, were notably smaller in diameter (-27%) and carried heme-related absorbance. In T2D plasma, higher heme-related absorbance (+30%) was associated to peripheral sensory neuropathy, and no other vascular complication. In vitro, T2D RBC-derived EV triggered endothelial stress and thrombin activation in a phosphatidylserine- and heme-dependent fashion. We concluded that T2D was associated with low-grade IVH. Plasma absorbance may constitute a novel biomarker of peripheral neuropathy in T2D, while flow cytometry focusing on large EV may be maladapted to characterize RBC EV in T2D. Moreover, therapeutics limiting IVH or neutralizing RBC breakdown products might bolster vasculoprotection in T2D.

Spatial Reorganization of Liquid Crystalline Domains of Red Blood Cells in Type 2 Diabetic Patients with Peripheral Artery Disease

In this work, we will investigate if red blood cell (RBC) membrane fluidity, influenced by several hyperglycemia-induced pathways, could provide a complementary index of HbA1c to monitor the development of type 2 diabetes mellitus (T2DM)-related macroangiopathic complications such as Peripheral Artery Disease (PAD). The contextual liquid crystalline (LC) domain spatial organization in the membrane was analysed to investigate the phase dynamics of the transition. Twenty-seven patients with long-duration T2DM were recruited and classified in DM, including 12 non-PAD patients, and DM + PAD, including 15 patients in any stage of PAD. Mean values of RBC generalized polarization (GP), representative of membrane fluidity, together with spatial organization of LC domains were compared between the two groups; p-values < 0.05 were considered statistically significant. Although comparable for anthropometric characteristics, duration of diabetes, and HbA1c, RBC membranes of PAD patients were found to be significantly more fluid (GP: 0.501 ± 0.026) than non-PAD patients (GP: 0.519 ± 0.007). These alterations were shown to be triggered by changes in both LC microdomain composition and distribution. We found a decrease in Feret diameter from 0.245 ± 0.281 μm in DM to 0.183 ± 0.124 μm in DM + PAD, and an increase in circularity. Altered RBC membrane fluidity is correlated to a spatial reconfiguration of LC domains, which, by possibly altering metabolic function, are associated with the development of T2DM-related macroangiopathic complications.

Methodologies and tools to shed light on erythrophagocytosis

Red blood cells (RBC) are the most abundant circulating cell of the human body. RBC are constantly exposed to multiple stresses in the circulation, leading to molecular and structural impairments and death. The physiological process of RBC senescence or ageing is referred to as eryptosis. At the end of their lifespan, aged RBC are recognized and removed from the blood by professional phagocytes via a phenomenon called erythrophagocytosis (EP); the phagocytosis of RBC. Some genetic and acquired diseases can influence eryptosis, thereby affecting RBC lifespan and leading to hemolytic anemia. In some diseases, such as diabetes and atherosclerosis, eryptosis and EP can participate in disease progression with both professional and non-professional phagocytes. Therefore, investigating the process of EP in vivo and in vitro, as well as in different cell types, will not only contribute to the understanding of the physiological steps of EP, but also to the deciphering of the specific mechanisms involving RBC and EP that underlie certain pathologies. In this review, the process of EP is introduced and the different methods for studying EP are discussed together with examples of the experimental procedures and materials required.

Impact of Enhanced Phagocytosis of Glycated Erythrocytes on Human Endothelial Cell Functions

Diabetes is associated with a high mortality rate due to vascular complications. Chronic hyperglycemia in diabetes leads to enhanced oxidative stress and glycation. Here, we explored the impact of glycation on human erythrocyte characteristics and capacity to affect endothelial cell function following erythrophagocytosis. Native and glucose-mediated glycated erythrocytes were prepared and characterized in terms of structural and deformability modifications. Erythrocyte preparations were tested for their binding and phagocytosis capacity as well as the potential functional consequences on human endothelial cell lines and primary cultures. Oxidative modifications were found to be enhanced in glycated erythrocytes after determination of their deformability, advanced glycation end-product content and eryptosis. Erythrophagocytosis by endothelial cells was significantly increased when incubated in the presence of glycated erythrocytes. In addition, higher iron accumulation, oxidative stress and impaired endothelial cell permeability were evidenced in cells previously incubated with glycated erythrocytes. When cultured under flow conditions, cellular integrity was disrupted by glycated erythrocytes at microvessel bifurcations, areas particularly prone to vascular complications. This study provides important new data on the impact of glycation on the structure of erythrocytes and their ability to alter endothelial cell function. Increased erythrophagocytosis may have a deleterious impact on endothelial cell function with adverse consequences on diabetic vascular complications.

In Sickness and in Health: Erythrocyte Responses to Stress and Aging

Mature red blood cells (RBC) are the most abundant host cell in our body [...]

Olive Oil Phenols Prevent Mercury-Induced Phosphatidylserine Exposure and Morphological Changes in Human Erythrocytes Regardless of Their Different Scavenging Activity

Phosphatidylserine (PS) translocation to the external membrane leaflet represents a key mechanism in the pathophysiology of human erythrocytes (RBC) acting as an "eat me" signal for the removal of aged/stressed cells. Loss of physiological membrane asymmetry, however, can lead to adverse effects on the cardiovascular system, activating a prothrombotic activity. The data presented indicate that structurally related olive oil phenols prevent cell alterations induced in intact human RBC exposed to HgCl₂ (5-40 µM) or Ca²⁺ ionophore (5 µM), as measured by hallmarks including PS exposure, reactive oxygen species generation, glutathione depletion and microvesicles formation. The protective effect is observed in a concentration range of 1-30 µM, hydroxytyrosol being the most effective; its in vivo metabolite homovanillic alcohol still retains the biological activity of its dietary precursor. Significant protection is also exerted by tyrosol, in spite of its weak scavenging activity, indicating that additional mechanisms are involved in the protective effect. When RBC alterations are mediated by an increase in intracellular calcium, the protective effect is observed at higher concentrations, indicating that the selected phenols mainly act on Ca²⁺-independent mechanisms, identified as protection of glutathione depletion. Our findings strengthen the nutritional relevance of olive oil bioactive compounds in the claimed health-promoting effects of the Mediterranean Diet.

Eryptosis: Programmed Death of Nucleus-Free, Iron-Filled Blood Cells

Human erythrocytes are organelle-free cells packaged with iron-containing hemoglobin, specializing in the transport of oxygen. With a total number of approximately 25 trillion cells per individual, the erythrocyte is the most abundant cell type not only in blood but in the whole organism. Despite their low complexity and their inability to transcriptionally upregulate antioxidant defense mechanisms, they display a relatively long life time, of 120 days. This ensures the maintenance of tissue homeostasis where the clearance of old or damaged erythrocytes is kept in balance with erythropoiesis. Whereas the regulatory mechanisms of erythropoiesis have been elucidated over decades of intensive research, the understanding of the mechanisms of erythrocyte clearance still requires some refinement. Here, we present the main pathways leading to eryptosis, the programmed death of erythrocytes, with special emphasis on Ca²⁺ influx, the generation of ceramide, oxidative stress, kinase activation, and iron metabolism. We also compare stress-induced erythrocyte death with erythrocyte ageing and clearance, and discuss the similarities between eryptosis and ferroptosis, the iron-dependent regulated death of nucleated blood cells. Finally, we focus on the pathologic consequences of deranged eryptosis, and discuss eryptosis in the context of different infectious diseases, e.g., viral or parasitic infections, and hematologic disorders.

Hemoglobin concentration, hematocrit and red blood cell count predict major adverse cardiovascular events in patients with familial hypercholesterolemia

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is a genetic disease associated with an important risk of premature and recurrent atherosclerotic cardiovascular disease (ASCVD). Red blood cell (RBC) parameters such as cell count and hematocrit (HCT) have previously been associated with ASCVD risk in the general population. However, little is known concerning their effect in FH. The aim of the present study is to investigate the effect of the different RBC parameters on the incidence of major adverse cardiovascular events (MACE) in FH patients.

METHODS

In this prospective cohort study, genetically-confirmed FH patients aged between 18 and 65 years and without history of a prior ASCVD event were included. MACE included myocardial infarction, stroke, coronary revascularization, unstable angina or cardiovascular death.

RESULTS

A total of 482 subjects (6217 person-years of follow-up) were included in the analysis. Hemoglobin (HB), RBC count, and HCT were significant predictors of MACE risk (HR 1.04 (95% CI 1.01-1.06) p = 0.001, HR 2.69 (95% CI 1.49-4.86) p = 0.001, and HR 1.16 (95% CI 1.08-1.26) p < 0.0001, respectively) and these associations remained significant when adjusted for traditional cardiovascular risk factors. In addition, the frequency of recurrent MACE was 4-fold and 7-fold higher in the group above vs below the median for HB (p = 0.002) and RBC count (p = 0.001), respectively.

CONCLUSIONS

HB, RBC count and HCT were significant predictors of incident and recurring MACE in FH patients. These parameters could therefore be used to further refine the ASCVD risk prediction in this vulnerable population.