Piezo1 activation augments sickling propensity and the adhesive properties of sickle red blood cells in a calcium-dependent manner

Pharmacology of PIEZO1 channels

PIEZO1 is a eukaryotic membrane protein that assembles as trimers to form calcium-permeable, non-selective cation channels with exquisite capabilities for mechanical force sensing and transduction of force into effect in diverse cell types that include blood cells, endothelial cells, epithelial cells, fibroblasts and stem cells and diverse systems that include bone, lymphatics and muscle. The channel has wide-ranging roles and is considered as a target for novel therapeutics in ailments spanning cancers and cardiovascular, dental, gastrointestinal, hepatobiliary, infectious, musculoskeletal, nervous system, ocular, pregnancy, renal, respiratory and urological disorders. The identification of PIEZO1 modulators is in its infancy but useful experimental tools emerged for activating, and to a lesser extent inhibiting, the channels. Elementary structure-activity relationships are known for the Yoda series of small molecule agonists, which show the potential for diverse physicochemical and pharmacological properties. Intriguing effects of Yoda1 include the stimulated removal of excess cerebrospinal fluid. Despite PIEZO1's broad expression, opportunities are suggested for selective positive or negative modulation without intolerable adverse effects. Here we provide a focused, non-systematic, narrative review of progress with this pharmacology and discuss potential future directions for research in the area.

Could oxygen gradient ektacytometry help to detect sickle cell trait carriers at risk for kidney disorders or exercise-related complications?

The study of Ellsworth et al. (Br J Haematol, 2024) demonstrated the usefulness of oxygen gradient ektacytometry technique to better identify the physiological parameters that could increase the risk of sickling of red blood cells (RBCs) from sickle cell trait (SCT) carriers. Oxygen gradient ektacytometry combined with pH and osmolality modulations could help in identifying SCT carriers at risk for kidney disorders or exercise-related complications. Other factors than the percentages of haemoglobin S are probably involved in the propensity of RBCs from SCT carriers to sickle during deoxygenation. Commentary on: Ellsworth et al. Hypertonicity and/or acidosis induce marked rheological changes under hypoxic conditions in sickle trait red blood cells. Br J Haematol 2024; 205:1565-1569.

Hypertonicity and/or acidosis induce marked rheological changes under hypoxic conditions in sickle trait red blood cells

Deformability and sickling of red blood cells (RBCs) from individuals with sickle cell trait (SCT) was evaluated under harsh biophysical conditions that mimic certain vascular beds in vivo. RBC deformability in osmotic-gradient ektacytometry was decreased in HbAS (SCT) compared to HbAA (wild-type) RBCs at supraphysiological osmolalities. RBC deformability was also measured by oxygen-gradient ektacytometry. Whereas RBC sickling was not observed under isotonic and neutral pH conditions, hypertonicity and acidosis alone or in combination induced reversible sickling of SCT RBC. These data suggest that hyperosmolality and/or acidosis enhance hypoxia-induced sickling of SCT RBC.

The Role of Lutheran/Basal Cell Adhesion Molecule in Hematological Diseases and Tumors

Cell adhesion is a dynamic process that plays a fundamental role in cell proliferation, maintenance, differentiation, and migration. Basal cell adhesion molecule (BCAM), also known as Lutheran (Lu), belongs to the immunoglobulin superfamily of cell adhesion molecules. Lu/BCAM, which is widely expressed in red blood cells, endothelial cells, smooth muscle cells and epithelial cells across various tissues, playing a crucial role in many cellular processes, including cell adhesion, cell motility and cell migration. Moreover, Lu/BCAM, dysregulated in many diseases, such as blood diseases and various types of cancer, may act as a biomarker and target for the treatment of these diseases. This review explores the significance of Lu/BCAM in cell adhesion and its potential as a novel target for treating hematological diseases and tumors.

Venous Thromboembolism in Individuals with Sickle Cell Disease: A Narrative Review

Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by vaso-occlusion, hemolysis of red blood cells (RBC), and a predisposition for venous thromboembolism (VTE). The sickling and hemolysis of RBC culminate in coagulation system abnormalities, platelet activation, endothelial dysfunction, and impaired blood flow manifesting as a prothrombotic state. In addition, individuals with SCD are often exposed to extrinsic risk factors for VTE including recurrent hospitalizations, central venous catheters, and acute medical illnesses. The diagnosis is often challenging as symptoms may mimic other complications of SCD, and there is little data to guide diagnostic algorithms involving probability scoring in the SCD population. Non-anticoagulant strategies aimed at reducing disease severity may aid in lowering the risk of VTE, but data is limited. Furthermore, high quality evidence regarding anticoagulation in prevention and treatment of SCD is severely lacking, resulting in heterogeneity in clinical practice. In this narrative review we aim to review the prothrombotic pathophysiology of SCD, to describe the risk factors, high risk of mortality, and types of VTE in SCD, to develop an approach to the diagnosis of VTE in SCD, and to understand the limited available evidence for the prevention and treatment of VTE in SCD.

Pleiotropic physiological functions of Piezo1 in human body and its effect on malignant behavior of tumors

Mechanosensitive ion channel protein 1 (Piezo1) is a large homotrimeric membrane protein. Piezo1 has various effects and plays an important and irreplaceable role in the maintenance of human life activities and homeostasis of the internal environment. In addition, recent studies have shown that Piezo1 plays a vital role in tumorigenesis, progression, malignancy and clinical prognosis. Piezo1 is involved in regulating the malignant behaviors of a variety of tumors, including cellular metabolic reprogramming, unlimited proliferation, inhibition of apoptosis, maintenance of stemness, angiogenesis, invasion and metastasis. Moreover, Piezo1 regulates tumor progression by affecting the recruitment, activation, and differentiation of multiple immune cells. Therefore, Piezo1 has excellent potential as an anti-tumor target. The article reviews the diverse physiological functions of Piezo1 in the human body and its major cellular pathways during disease development, and describes in detail the specific mechanisms by which Piezo1 affects the malignant behavior of tumors and its recent progress as a new target for tumor therapy, providing new perspectives for exploring more potential effects on physiological functions and its application in tumor therapy.

Calcium flux alterations in erythrocytes from sickle cell mice: The relevance of mean corpuscular volume

Red blood cells (RBC) from patients with sickle cell disease (SCD) have elevated calcium levels at baseline, which are further elevated upon deoxygenation. Here we examined baseline calcium levels and calcium flux in RBCs from a mouse model of SCD mice. We found that akin to humans with SCD, sickle (HbSS) Townes mice, have higher baseline levels and increased calcium flux in RBCs compared to control (HbAA) animals. As HbSS mice, unlike humans with SCD, have high mean corpuscular volume compared with HbAA, we highlight the importance of adjusting biochemical results to number of RBCs rather than hematocrit during the analysis and interpretation of the results. Our findings add to the face validity of humanized sickle cell mice and support its use for studies of RBC calcium flux in SCD.

Blood rheology and vascular function in sickle cell trait and sickle cell disease: From pathophysiological mechanisms to clinical usefulness

Sickle cell disease (SCD) is an autosomal recessive disorder. Although the molecular mechanisms at the origin of SCD have been well characterized, its clinical expression is highly variable. SCD is characterized by blood rheological abnormalities, increased inflammation and oxidative stress, and vascular dysfunction. Individuals with only one copy of the mutated β-globin gene have sickle cell trait (SCT) and are usually asymptomatic. The first part of this review focuses on the biological responses of SCT carriers during exercise and on the effects of combined SCT and diabetes on vascular function, several biomarkers and clinical complications. The second part of the review focuses on SCD and shows that the magnitude of red blood cell (RBC) rheological alterations is highly variable from one patient to another, and this variability reflects the clinical and hematological variability: patients with the less deformable RBCs have high hemolytic rate and severe anemia, and are prone to develop leg ulcers, priapism, cerebral vasculopathy, glomerulopathy or pulmonary hypertension. In contrast, SCD patients characterized by the presence of more deformable RBCs (but still rigid) are less anemic and may exhibit increased blood viscosity, which increases the risk for vaso-occlusive events. Several genetic and cellular factors may modulate RBC deformability in SCD: co-existence of α-thalassemia, fetal hemoglobin level, oxidative stress, the presence of residual mitochondria into mature RBCs, the activity of various non-selective cationic ion channels, etc. The last part of this review presents the effects of hydroxyurea and exercise training on RBC rheology and other biomarkers in SCD.

Piezo1 Regulation Involves Lipid Domains and the Cytoskeleton and Is Favored by the Stomatocyte-Discocyte-Echinocyte Transformation

Piezo1 is a mechanosensitive ion channel required for various biological processes, but its regulation remains poorly understood. Here, we used erythrocytes to address this question since they display Piezo1 clusters, a strong and dynamic cytoskeleton and three types of submicrometric lipid domains, respectively enriched in cholesterol, GM1 ganglioside/cholesterol and sphingomyelin/cholesterol. We revealed that Piezo1 clusters were present in both the rim and the dimple erythrocyte regions. Upon Piezo1 chemical activation by Yoda1, the Piezo1 cluster proportion mainly increased in the dimple area. This increase was accompanied by Ca2+ influx and a rise in echinocytes, in GM1/cholesterol-enriched domains in the dimple and in cholesterol-enriched domains in the rim. Conversely, the effects of Piezo1 activation were abrogated upon membrane cholesterol depletion. Furthermore, upon Piezo1-independent Ca2+ influx, the above changes were not observed. In healthy donors with a high echinocyte proportion, Ca2+ influx, lipid domains and Piezo1 fluorescence were high even at resting state, whereas the cytoskeleton membrane occupancy was lower. Accordingly, upon decreases in cytoskeleton membrane occupancy and stiffness in erythrocytes from patients with hereditary spherocytosis, Piezo1 fluorescence was increased. Altogether, we showed that Piezo1 was differentially controlled by lipid domains and the cytoskeleton and was favored by the stomatocyte-discocyte-echinocyte transformation.

Adverse effects of delta-9-tetrahydrocannabinol on sickle red blood cells

THC triggers a pronounced entry of Ca2+ , which may be deleterious, into sickle cell red blood cells via activation of the TRPV2 channel.

Le globule rouge drépanocytaire : données fonctionnelles

Sickle cell anemia is a genetic disorder that affects hemoglobin leading to the production of an abnormal hemoglobin, called HbS. HbS has the property to polymerize under deoxygenated conditions, causing a mechanical distortion of red blood cells; a phenomenon called sickling. These sickle red blood cells are more fragile and rigid, leading to chronic hemolytic anemia and painful vaso-occlusive crises, as well as chronic vascular complications that can affect many organs. The abnormal functional properties of these sickle red blood cells are responsible for a wide range of clinical expression of the disease. HbS polymerization can be influenced by many factors, such as the hydration state of the red blood cells or the affinity of hemoglobin for oxygen. Moreover, the rheological characteristics of red blood cells, including their deformability and aggregation properties, are associated with specific clinical phenotypes. The pro-inflammatory and pro-oxidant state, as well as the repeated polymerization of HbS, accelerate the senescence of sickle red blood cells, promoting the release of microparticles and contributing to vascular dysfunction. Patients' red blood cells also have molecular characteristics that promote their adhesion to the endothelium and other circulating cells, contributing to the onset of vascular complications. Massive intravascular hemolysis, due to increased erythrocyte fragility, is also responsible for chronic vascular complications. These different alterations are privileged therapeutic targets, leading to the emergence of new specific treatments. © 2023 Société nationale française de médecine interne (SNFMI). Published by Elsevier Masson SAS. All rights reserved.

The cation-leaky hereditary stomatocytosis syndromes: A tale of six proteins

This review concerns a series of dominantly inherited haemolytic anaemias in which the membrane of the erythrocyte 'leaks' the univalent cations, compromising the osmotic stability of the cell. The majority of the conditions are explained by mutations in one of six genes, coding for multispanning membrane proteins of different structure and function. These are: RhAG, coding for an ammonium carrier; SLC4A1, coding for the band 3 anion exchanger; PIEZO1, coding for a mechanosensitive cation channel; GLUT1, coding for a glucose transporter; KCNN4, coding for an internal-calcium-activated potassium channel; and ABCB6, coding for a porphyrin transporter. This review describes the five clinical syndromes associated with genetic defects in these genes and their variable genotype/phenotype relationships.

A preliminary study of phosphodiesterases and adenylyl cyclase signaling pathway on red blood cell deformability of sickle cell patients

Sickle cell disease (SCD) is an inherited hemoglobinopathy characterized by chronic anemia, intravascular hemolysis, and the occurrence of vaso-occlusive crises due to the mechanical obstruction of the microcirculation by poorly deformable red blood cells (RBCs). RBC deformability is a key factor in the pathogenesis of SCD, and is affected by various factors. In this study, we investigated the effects of adenylyl cyclase (AC) signaling pathway modulation and different phosphodiesterase (PDE) modulatory molecules on the deformability and mechanical stress responses of RBC from SCD patients (HbSS genotype) by applying 5 Pa shear stress with an ektacytometer (LORRCA). We evaluated RBC deformability before and after the application of shear stress. AC stimulation with Forskolin had distinct effects on RBC deformability depending on the application of 5 Pa shear stress. RBC deformability was increased by Forskolin before shear stress application but decreased after 5 Pa shear stress. AC inhibition with SQ22536 and protein kinase A (PKA) inhibition with H89 increased RBC deformability before and after the shear stress application. Non-selective PDE inhibition with Pentoxifylline increased RBC deformability. However, modulation of the different PDE types had distinct effects on RBC deformability, with PDE1 inhibition by Vinpocetine increasing deformability while PDE4 inhibition by Rolipram decreased RBC deformability after the shear stress application. The effects of the drugs varied greatly between patients suggesting some could benefit from one drug while others not. Developing drugs targeting the AC signaling pathway could have clinical applications for SCD, but more researches with larger patient cohorts are needed to identify the differences in the responses of sickle RBCs.

A critical role for altered red cell cation permeability in pathogenesis of sickle cell disease and other haemolytic anaemias

The aetiology of sickle cell disease is well known, but pathogenesis is complicated and details remain uncertain. A thorough understanding may suggest novel ways for designing more effective therapies. One area of importance, covered here in Nader et al., is the altered cation permeability of sickle cells and how the co-ordinated operation of a number of membrane transport proteins contributes to disease progression, all driven by the initial event of HbS polymerisation. There are echoes here of the cation leaks of hereditary stomatocytosis. Nader et al. propose a central role for PIEZO1, a novel mechanosensitive channel found in red cells, which may be aberrantly activated in sickle cells following HbS polymerisation and which may have potential as a novel target for future chemotherapies. Commentary on: Nader et al. Piezo1 activation augments sickling propensity and the adhesive properties of sickle red blood cells in a calcium-dependent manner. Br J Haematol 2023;202:657-668.