Role of Erythrocytes in Nitric Oxide Metabolism and Paracrine Regulation of Endothelial Function

Cell death signaling in human erythron: erythrocytes lose the complexity of cell death machinery upon maturation

Over the recent years, our understanding of the cell death machinery of mature erythrocytes has been greatly expanded. It resulted in the discovery of several regulated cell death (RCD) pathways in red blood cells. Apoptosis (eryptosis) and necroptosis of erythrocytes share certain features with their counterparts in nucleated cells, but they are also critically different in particular details. In this review article, we summarize the cell death subroutines in the erythroid precursors (apoptosis, necroptosis, and ferroptosis) in comparison to mature erythrocytes (eryptosis and erythronecroptosis) to highlight the consequences of organelle clearance and associated loss of multiple components of the cell death machinery upon erythrocyte maturation. Recent advances in understanding the role of erythrocyte RCDs in health and disease have expanded potential clinical applications of these lethal subroutines, emphasizing their contribution to the development of anemia, microthrombosis, and endothelial dysfunction, as well as their role as diagnostic biomarkers and markers of erythrocyte storage-induced lesions. Fas signaling and the functional caspase-8/caspase-3 system are not indispensable for eryptosis, but might be retained in mature erythrocytes to mediate the crosstalk between both erythrocyte-associated RCDs. The ability of erythrocytes to switch between eryptosis and necroptosis suggests that their cell death is not a simple unregulated mechanical disintegration, but a tightly controlled process. This allows investigation of eventual pharmacological interventions aimed at individual cell death subroutines of erythrocytes.

Therapeutic delivery of oxygen using artificial oxygen carriers demonstrates the possibility of treating a wide range of diseases

Artificial oxygen carriers have emerged as potential substitutes for red blood cells in situations of major blood loss, including accidents, surgical procedures, trauma, childbirth, stomach ulcers, hemorrhagic shock, and blood vessel ruptures which can lead to sudden reduction in blood volume. The therapeutic delivery of oxygen utilizing artificial oxygen carriers as red blood cell substitutes presents a promising avenue for treating a spectrum of disease models. Apart from that, the recent advancement of artificial oxygen carriers intended to supplant conventional blood transfusions draws significant attention due to the exigencies of warfare and the ongoing challenges posed by the COVID-19 pandemic. However, there is a pressing need to formulate stable, non-toxic, and immunologically inert oxygen carriers. Even though numerous challenges are encountered in the development of artificial oxygen carriers, their applicability extends to various medical treatments, encompassing elective and cardiovascular surgeries, hemorrhagic shock, decompression illness, acute stroke, myocardial infarction, sickle cell crisis, and proficient addressing conditions such as cerebral hypoxia. Therefore, this paper provides an overview of therapeutic oxygen delivery using assorted types of artificial oxygen carriers, including hemoglobin-based, perfluorocarbon-based, stem cell-derived, and oxygen micro/nanobubbles, in the treatment of diverse disease models. Additionally, it discusses the potential side effects and limitations associated with these interventions, while incorporating completed and ongoing research and recent clinical developments. Finally, the prospective solutions and general demands of the perfect artificial oxygen carriers were anticipated to be a reference for subsequent research endeavors.

Nanostructured zinc carbonate hydroxide microflakes: assessing the toxicity against erythrocytes and L929 cellsin vitro

Nanostructured materials have been suggested to be used as a source of dietary zinc for livestock animals. In this study, we assessed the cytotoxicity of newly synthesized nanostructured zinc carbonate hydroxide (ZnCH) Zn5(CO3)(OH)6microflakes. Cytotoxicity of the microflakes was assessed against murine L929 cell line and rat mature erythrocytes. Viability, motility, cell death pathways, implication of Ca2+, reactive oxygen species and reactive nitrogen species (RNS) signaling, caspases, and alterations of cell membranes following exposure of L929 cells to the microflakes were assessed. To assess hemocompatibility of the Zn-containing microflakes, osmotic fragility and hemolysis assays were performed, as well as multiple eryptosis parameters were evaluated. Our findings indicate a dose-response cytotoxicity of ZnCH microflakes against L929 cells with no toxicity observed for low concentrations (10 mg l-1and below). At high concentrations (25 mg l-1and above), ZnCH microflakes promoted nitrosyl stress, Ca2+- and caspase-dependent apoptosis, and altered lipid order of cell membranes in a dose-dependent manner, evidenced by up to 7-fold elevation of RNS-dependent fluorescence, 2.9-fold enhancement of Fura 2-dependent fluorescence, over 20-fold elevation of caspases-dependent fluorescence (caspase-3, caspase-8, and caspase-9), and up to 4.4-fold increase in the ratiometric index of the NR12S probe. Surprisingly, toxicity to enucleated mature erythrocytes was found to be lower compared to L929 cells. ZnCH microflakes induced eryptosis associated with oxidative stress, nitrosyl stress, Ca2+signaling and recruitment of caspases at 25-50-100 mg l-1. Eryptosis assays were found to be more sensitive than evaluation of hemolysis. Zn5(CO3)(OH)6microflakes show no cytotoxicity at low concentrations indicating their potential as a source of zinc for livestock animals.

Interplay Between Metabolic Pathways and Increased Oxidative Stress in Human Red Blood Cells

Red blood cells (RBCs) are highly specialized cells with a limited metabolic repertoire. However, it has been demonstrated that metabolic processes are affected by the production of reactive oxygen species (ROS), and critical enzymes allied to metabolic pathways can be impaired by redox reactions. Thus, oxidative stress-induced alternations in the metabolic pathways can contribute to cell dysfunction of human RBCs. Herein, we aim to provide an overview on the metabolic pathways of human RBCs, focusing on their pathophysiological relevance and their regulation in oxidative stress-related conditions.

Impact of Nitric Oxide on Polymorphonuclear Neutrophils' Function

BACKGROUND

There is increasing evidence that nitric oxide (nitrogen monoxide, NO) significantly influences immune cellular responses, including those from polymorphonuclear leukocytes (PMNs).

OBJECTIVE

The aim of this study was to examine a possible effect of NO on PMNs' function (chemotaxis, production of reactive oxygen species (ROS), and NETosis) using live cell imaging. Moreover, we investigated PMN surface epitope and neutrophil oxidative burst under the influence of NO by flow cytometric analysis.

METHODS

Whole blood samples were obtained from healthy volunteers, and PMNs were isolated by density centrifugation. Live cell imaging using type I collagen matrix in µSlide IBIDI chemotaxis chambers was conducted in order to observe N-formyl-L-methionyl-L-leucyl-phenylalanine (fMLP)-stimulated PMN chemotaxis, ROS production, and NETosis. In the test group, NO was continuously redirected into the climate chamber of the microscope, so the chemotaxis chambers were surrounded by NO. The same experimental setup without NO served as a control. In addition, isolated PMNs were incubated with nitrogen monoxide (NO) or without (the control). Subsequently, flow cytometry was used to analyze neutrophil antigen expression and oxidative burst.

RESULTS

Our live cell imaging results demonstrated a migration-promoting effect of NO on PMNs. We observed that in the case of prior stimulation by fMLP, NO has no effect on the time course of neutrophil ROS production and NET release. However, flow cytometric analyses demonstrated an increase in ROS production after pretreatment with NO. No NO-dependent differences for the expression of CD11b, CD62L, or CD66b could be observed.

CONCLUSIONS

We were able to demonstrate a distinct effect of NO on PMNs' function. The complex interaction between NO and PMNs remains a major research focus, as the exact mechanisms and additional influencing factors remain elusive. Future studies should explore how varying NO concentrations and the timing of NO exposure relative to PMN activation affect its influence.

ALDH2 rs671 and MTHFR rs1801133 polymorphisms are risk factors for arteriosclerosis in multiple arteries

BACKGROUND

Arteriosclerosis in multiple arteries has long been associated with heightened cardiovascular risk. Acetaldehyde dehydrogenase 2 (ALDH2) and methylenetetrahydrofolate reductase (MTHFR) play an important role in the pathogenesis of arteriosclerosis by participating in the oxidation and reduction reactions in vascular endothelial cells. The purpose was to investigate the relationship of ALDH2 and MTHFR gene polymorphisms with arteriosclerosis in multiple arteries.

METHODS

410 patients with arteriosclerosis in single artery and 472 patients with arteriosclerosis in multiple arteries were included. The relationship between ALDH2 rs671 and MTHFR rs1801133 polymorphisms and arteriosclerosis in single artery and arteriosclerosis in multiple arteries was analyzed.

RESULTS

The proportion of ALDH2 rs671 A allele (35.6% vs. 30.9%, P = 0.038) and MTHFR rs1801133 T allele (32.6% vs. 27.1%, P = 0.012) in patients with arteriosclerosis in multiple arteries was significantly higher than that in arteriosclerosis in single artery, respectively. The proportion of history of alcohol consumption in patients with ALDH2 rs671 G/G genotype was higher than those in ALDH2 rs671 G/A genotype and A/A genotype (P < 0.001). The results of logistic regression analysis indicated that ALDH2 rs671 A/A genotype (A/A vs. G/G: OR 1.996, 95% CI: 1.258-3.166, P = 0.003) and MTHFR rs1801133 T/T genotype (T/T vs. C/C: OR 1.943, 95% CI: 1.179-3.203, P = 0.009) may be independent risk factors for arteriosclerosis in multiple arteries (adjusted for age, sex, smoking, drinking, hypertension, and diabetes).

CONCLUSIONS

ALDH2 rs671 A/A and MTHFR rs1801133 T/T genotypes may be independent risk factors for arteriosclerosis in multiple arteries.

Understanding human aging and the fundamental cell signaling link in age-related diseases: the middle-aging hypovascularity hypoxia hypothesis

Aging-related hypoxia, oxidative stress, and inflammation pathophysiology are closely associated with human age-related carcinogenesis and chronic diseases. However, the connection between hypoxia and hormonal cell signaling pathways is unclear, but such human age-related comorbid diseases do coincide with the middle-aging period of declining sex hormonal signaling. This scoping review evaluates the relevant interdisciplinary evidence to assess the systems biology of function, regulation, and homeostasis in order to discern and decipher the etiology of the connection between hypoxia and hormonal signaling in human age-related comorbid diseases. The hypothesis charts the accumulating evidence to support the development of a hypoxic milieu and oxidative stress-inflammation pathophysiology in middle-aged individuals, as well as the induction of amyloidosis, autophagy, and epithelial-to-mesenchymal transition in aging-related degeneration. Taken together, this new approach and strategy can provide the clarity of concepts and patterns to determine the causes of declining vascularity hemodynamics (blood flow) and physiological oxygenation perfusion (oxygen bioavailability) in relation to oxygen homeostasis and vascularity that cause hypoxia (hypovascularity hypoxia). The middle-aging hypovascularity hypoxia hypothesis could provide the mechanistic interface connecting the endocrine, nitric oxide, and oxygen homeostasis signaling that is closely linked to the progressive conditions of degenerative hypertrophy, atrophy, fibrosis, and neoplasm. An in-depth understanding of these intrinsic biological processes of the developing middle-aged hypoxia could provide potential new strategies for time-dependent therapies in maintaining healthspan for healthy lifestyle aging, medical cost savings, and health system sustainability.

Myricetin-induced suicidal erythrocyte death

BACKGROUND

Myricetin, a type of flavonol commonly found in fruits and herbs, has demonstrated anticancer properties by triggering the process of apoptosis or programmed cell death in tumor cells. Despite the absence of mitochondria and nuclei, erythrocytes can undergo programmed cell death, also known as eryptosis.This process is characterized by cell shrinkage, externalization of phosphatidylserine (PS) on the cell membrane, and the formation of membrane blebs. The signaling of eryptosis involves Ca²⁺ influx, the formation of reactive oxygen species (ROS), and the accumulation of cell surface ceramide. The present study explored the effects of myricetin on eryptosis.

METHODS AND RESULTS

Human erythrocytes were exposed to various concentrations of myricetin (2-8 µM) for 24 h. Flow cytometry was used to assess the markers of eryptosis, including PS exposure, cellular volume, cytosolic Ca²⁺ concentration, and ceramide accumulation. In addition, the levels of intracellular ROS were measured using the 2',7'-dichlorofluorescin diacetate (DCFDA) assay. The myricetin-treated (8 µM) erythrocytes significantly increased Annexin-positive cells, Fluo-3 fluorescence intensity, DCF fluorescence intensity, and the accumulation of ceramide. The impact of myricetin on the binding of annexin-V was significantly reduced, but not completely eliminated, by the nominal removal of extracellular Ca²⁺.

CONCLUSION

Myricetin triggers eryptosis, which is accompanied and, at least in part, caused by Ca²⁺ influx, oxidative stress and increase of ceramide abundance.

Redox Status of Erythrocytes as an Important Factor in Eryptosis and Erythronecroptosis

Overall, reactive oxygen species (ROS) signalling significantly contributes to initiation and mo-dulation of multiple regulated cell death (RCD) pathways. Lately, more information has become available about RCD modalities of erythrocytes, including the role of ROS. ROS accumulation has therefore been increasingly recognized as a critical factor involved in eryptosis (apoptosis of erythrocytes) and erythro-necroptosis (necroptosis of erythrocytes). Eryptosis is a Ca2+-dependent apoptosis-like RCD of erythrocytes that occurs in response to oxidative stress, hyperosmolarity, ATP depletion, and a wide range of xenobiotics. Moreover, eryptosis seems to be involved in the pathogenesis of multiple human diseases and pathological processes. Several studies have reported that erythrocytes can also undergo necroptosis, a lytic RIPK1/RIPK3/MLKL-mediated RCD. As an example, erythronecroptosis can occur in response to CD59-specific pore-forming toxins. We have systematically summarized available studies regarding the involvement of ROS and oxidative stress in these two distinct RCDs of erythrocytes. We have focused specifically on cellular signalling pathways involved in ROS-mediated cell death decisions in erythrocytes. Furthermore, we have summarized dysregulation of related erythrocytic antioxidant defence systems. The general concept of the ROS role in eryptotic and necroptotic cell death pathways in erythrocytes seems to be established. However, further studies are required to uncover the complex role of ROS in the crosstalk and interplay between the survival and RCDs of erythrocytes.

Hemorheological and Microcirculatory Relations of Acute Pancreatitis

Acute pancreatitis still means a serious challenge in clinical practice. Its pathomechanism is complex and has yet to be fully elucidated. Rheological properties of blood play an important role in tissue perfusion and show non-specific changes in acute pancreatitis. An increase in blood and plasma viscosity, impairment of red blood cell deformability, and enhanced red blood cell aggregation caused by metabolic, inflammatory, free radical-related changes and mechanical stress contribute to the deterioration of the blood flow in the large vessels and also in the microcirculation. Revealing the significance of these changes in acute pancreatitis may better explain the pathogenesis and optimize the therapy. In this review, we give an overview of the role of impaired microcirculation by changes in hemorheological properties in acute pancreatitis.