Stimulation of suicidal erythrocyte death by oridonin

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.

Oridonin from Rabdosia rubescens: An emerging potential in cancer therapy - A comprehensive review

Cancer incidences are rising each year. In 2020, approximately 20 million new cancer cases and 10 million cancer-related deaths were recorded. The World Health Organization (WHO) predicts that by 2024 the incidence of cancer will increase to 30.2 million individuals annually. Considering the invasive characteristics of its diagnostic procedures and therapeutic methods side effects, scientists are searching for different solutions, including using plant-derived bioactive compounds, that could reduce the probability of cancer occurrence and make its treatment more comfortable. In this regard, oridonin (ORI), an ent-kaurane diterpenoid, naturally found in the leaves of Rabdosia rubescens species, has been found to have antitumor, antiangiogenesis, antiasthmatic, antiinflammatory, and apoptosis induction properties. Extensive research has been performed on ORI to find various mechanisms involved in its anticancer activities. This review article provides an overview of ORI's effectiveness on murine and human cancer populations from 1976 to 2022 and provides insight into the future application of ORI in different cancer therapies.

Protein-protein interactions and related inhibitors involved in the NLRP3 inflammasome pathway

NOD-like receptor thermal protein domain-associated protein 3 (NLRP3) receptor serves as the central node of immune sensing in the innate immune system, and plays an important role in the initiation and progression of chronic diseases. Cryo-electron microscopy (cryo-EM) has provided insights into the conformation of various oligomers within the NLRP3 activation pathway, significantly advancing our understanding of the mechanisms underlying NLRP3 inflammasome activation. Despite the extensive network of protein-protein interactions (PPIs) involved in the assembly and activation of NLRP3 inflammasome, the utilization of protein-protein interactions has been relatively overlooked in the development of NLRP3 inhibitors. This review focuses on summarizing PPIs within the NLRP3 inflammasome activation pathway and small molecule inhibitors capable of interfering with PPIs to counteract the NLRP3 overactivation. Small molecule NLRP3 inhibitors have been gained significant attention owing to their remarkable efficacy, excellent safety profiles, and unique mechanisms of action.

Chalcone: A potential scaffold for NLRP3 inflammasome inhibitors

Overactivated NLRP3 inflammasome has been shown to associate with an increasing number of disease conditions. Activation of the NLRP3 inflammasome results in caspase-1-catalyzed formation of active pro-inflammatory cytokines (IL-1β and IL-18) resulting in pyroptosis. The multi-protein composition of the NLRP3 inflammasome and its sensitivity to several damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs) make this extensively studied inflammasome an attractive target to treat chronic conditions. However, none of the known NLRP3 inhibitors has been approved for clinical use. Sulfonylurea and covalent inhibitors with electrophilic warhead (Michael acceptor) are among the prominent classes of compounds explored for their NLRP3 inhibitory effects. Chalcone, a small molecule with α, β unsaturated carbonyl group (Michael acceptor), has also been studied as a promising scaffold for the development of NLRP3 inhibitors. Low molecular weight, easy to manipulate lipophilicity and cost-effectiveness have attracted many to use chalcone scaffold for drug development. In this review, we highlight chalcone derivatives with NLRP3 inflammasome inhibitory activities. Recent developments and potential new directions summarized here will, hopefully, serve as valuable perspectives for investigators including medicinal chemists and drug discovery researchers to utilize chalcone as a scaffold for developing novel NLRP3 inflammasome inhibitors.

Oridonin: A Review of Its Pharmacology, Pharmacokinetics and Toxicity

Oridonin, as a natural terpenoids found in traditional Chinese herbal medicine Isodon rubescens (Hemsl.) H.Hara, is widely present in numerous Chinese medicine preparations. The purpose of this review focuses on providing the latest and comprehensive information on the pharmacology, pharmacokinetics and toxicity of oridonin, to excavate the therapeutic potential and explore promising ways to balance toxicity and efficacy of this natural compound. Information concerning oridonin was systematically collected from the authoritative internet database of PubMed, Elsevier, Web of Science, Wiley Online Library and Europe PMC applying a combination of keywords involving "pharmacology," "pharmacokinetics," and "toxicology". New evidence shows that oridonin possesses a wide range of pharmacological properties, including anticancer, anti-inflammatory, hepatorenal activities as well as cardioprotective protective activities and so on. Although significant advancement has been witnessed in this field, some basic and intricate issues still exist such as the specific mechanism of oridonin against related diseases not being clear. Moreover, several lines of evidence indicated that oridonin may exhibit adverse effects, even toxicity under specific circumstances, which sparked intense debate and concern about security of oridonin. Based on the current progress, future research directions should emphasize on 1) investigating the interrelationship between concentration and pharmacological effects as well as toxicity, 2) reducing pharmacological toxicity, and 3) modifying the structure of oridonin-one of the pivotal approaches to strengthen pharmacological activity and bioavailability. We hope that this review can provide some inspiration for the research of oridonin in the future.

Eryptosis and Malaria: New Experimental Guidelines and Re-Evaluation of the Antimalarial Potential of Eryptosis Inducers

Erythrocytes possess an unusual programmed cell death mechanism termed eryptosis, and several compounds have been previously claimed to induce eryptosis in vitro. Malaria parasites (genus Plasmodium) reside in erythrocytes during the pathogenic part of their life cycle, and the potential of several eryptosis inducers to act as antimalarials has been tested in recent years. However, the eryptosis-inducing capacity of these compounds varies significantly between eryptosis-focused studies and malaria investigations. Here, we investigated the reasons for these discrepancies, we developed a protocol to investigate eryptosis in malaria cultures and we re-evaluated the potential of eryptosis inducers as antimalarials. First, we showed that eryptosis read-out in vitro is dependent on culture conditions. Indeed, conditions that have consistently been used to study eryptosis do not support P. falciparum growth and prime erythrocytes for eryptosis. Next, we defined culture conditions that allow the detection of eryptosis while supporting P. falciparum survival. Finally, we selected six eryptosis-inducers based on their clinical use, molecular target and antimalarial activities, and re-evaluated their eryptosis inducing capacities and their potential as antimalarials. We demonstrate that none of these compounds affect the viability of naïve or P. falciparum-infected erythrocytes in vitro. Nevertheless, three of these compounds impair parasite development, although through a mechanism unrelated to eryptosis and yet to be elucidated. We conclude that careful consideration of experimental set up is key for the accurate assessment of the eryptosis-inducing potential of compounds and their evaluation as potential antimalarials.

Eryptosis in health and disease: A paradigm shift towards understanding the (patho)physiological implications of programmed cell death of erythrocytes

During the course of their natural ageing and upon injury, anucleate erythrocytes can undergo an unconventional apoptosis-like cell death, termed eryptosis. Eryptotic erythrocytes display a plethora of morphological alterations including volume reduction, membrane blebbing and breakdown of the membrane phospholipid asymmetry resulting in phosphatidylserine externalization which, in turn, mediates their phagocytic recognition and clearance from the circulation. Overall, the eryptosis machinery is tightly orchestrated by a wide array of endogenous mediators, ion channels, membrane receptors, and a host of intracellular signaling proteins. Enhanced eryptosis shortens the lifespan of circulating erythrocytes and confers a procoagulant phenotype; this phenomenon has been tangibly implicated in the pathogenesis of anemia, deranged microcirculation, and increased prothrombotic risk associated with a multitude of clinical conditions. Herein, we reviewed the molecular mechanisms dictating eryptosis and erythrophagocytosis and critically analyzed the current evidence leading to the pathophysiological ramifications of eryptotic cell death in the context of human disease.

Ceramide in the regulation of eryptosis, the suicidal erythrocyte death

Similar to apoptosis of nucleated cells, erythrocytes may undergo eryptosis, a suicidal death characterized by cell shrinkage and phospholipid scrambling of the cell membrane leading to phosphatidylserine exposure at the cell surface. As eryptotic erythrocytes are rapidly cleared from circulating blood, excessive eryptosis may lead to anemia. Moreover, eryptotic erythrocytes may adhere to the vascular wall and thus impede microcirculation. Stimulators of eryptosis include osmotic shock, oxidative stress and energy depletion. Mechanisms involved in the stimulation eryptosis include ceramide formation which may result from phospholipase A2 dependent formation of platelet activating factor (PAF) with PAF dependent stimulation of sphingomyelinases. Enhanced erythrocytic ceramide formation is observed in fever, sepsis, HUS, uremia, hepatic failure, and Wilson's disease. Enhanced eryptosis is further observed in iron deficiency, phosphate depletion, dehydration, malignancy, malaria, sickle-cell anemia, beta-thalassemia and glucose-6-phosphate dehydrogenase-deficiency. Moreover, eryptosis is triggered by osmotic shock and a wide variety of xenobiotics, which are again partially effective by enhancing ceramide abundance. Ceramide formation is inhibited by high concentrations of urea. As shown in Wilson's disease, pharmacological interference with ceramide formation may be a therapeutic option in the treatment of eryptosis inducing clinical disorders.

Triggers, inhibitors, mechanisms, and significance of eryptosis: the suicidal erythrocyte death

Suicidal erythrocyte death or eryptosis is characterized by erythrocyte shrinkage, cell membrane blebbing, and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include Ca(2+) entry, ceramide formation, stimulation of caspases, calpain activation, energy depletion, oxidative stress, and dysregulation of several kinases. Eryptosis is triggered by a wide variety of xenobiotics. It is inhibited by several xenobiotics and endogenous molecules including NO and erythropoietin. The susceptibility of erythrocytes to eryptosis increases with erythrocyte age. Phosphatidylserine exposing erythrocytes adhere to the vascular wall by binding to endothelial CXC-Motiv-Chemokin-16/Scavenger-receptor for phosphatidylserine and oxidized low density lipoprotein (CXCL16). Phosphatidylserine exposing erythrocytes are further engulfed by phagocytosing cells and are thus rapidly cleared from circulating blood. Eryptosis eliminates infected or defective erythrocytes thus counteracting parasitemia in malaria and preventing detrimental hemolysis of defective cells. Excessive eryptosis, however, may lead to anemia and may interfere with microcirculation. Enhanced eryptosis contributes to the pathophysiology of several clinical disorders including metabolic syndrome and diabetes, malignancy, cardiac and renal insufficiency, hemolytic uremic syndrome, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose 6-phosphate dehydrogenase deficiency, and Wilson's disease. Facilitating or inhibiting eryptosis may be a therapeutic option in those disorders.

Physiology and pathophysiology of eryptosis

SUMMARY

Suicidal erythrocyte death (eryptosis) is characterized by cell shrinkage, cell membrane blebbing, and cell membrane phospholipid scrambling with phosphatidylserine exposure at the cell surface. Eryptotic cells adhere to the vascular wall and are rapidly cleared from circulating blood. Eryptosis is stimulated by an increase in cytosolic Ca(2)+ activity, ceramide, hyperosmotic shock, oxidative stress, energy depletion, hyperthermia, and a wide variety of xenobiotics and endogenous substances. Inhibitors of eryptosis include erythropoietin and nitric oxide. Enhanced eryptosis is observed in diabetes, renal insufficiency, hemolytic uremic syndrome, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, beta-thalassemia, glucose-6-phosphate dehydrogenase-(G6PD) deficiency, hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria, Wilson's disease, myelodysplastic syndrome, and phosphate depletion. Eryptosis is further enhanced in gene-targeted mice with deficient annexin 7, cGMP-dependent protein kinase type I (cGKI), AMP-activated protein kinase (AMPK), anion exchanger 1 (AE1), adenomatous polyposis coli (APC), and Klotho, as well as in mouse models of sickle cell anemia and thalassemia. Decreased eryptosis is observed in mice with deficient phosphoinositide-dependent kinase 1 (PDK1), platelet activating factor (PAF) receptor, transient receptor potential channel 6 (TRPC6), janus kinase 3 (JAK3), and taurine transporter (TAUT). Eryptosis may be a useful mechanism to remove defective erythrocytes prior to hemolysis. Excessive eryptosis may, however, compromise microcirculation and lead to anemia.

Killing me softly - suicidal erythrocyte death

Similar to nucleated cells, erythrocytes may undergo suicidal death or eryptosis, which is characterized by cell shrinkage, cell membrane blebbing and cell membrane phospholipid scrambling. Eryptotic cells are removed and thus prevented from undergoing hemolysis. Eryptosis is stimulated by Ca(2+) following Ca(2+) entry through unspecific cation channels. Ca(2+) sensitivity is enhanced by ceramide, a product of acid sphingomyelinase. Eryptosis is triggered by hyperosmolarity, oxidative stress, energy depletion, hyperthermia and a wide variety of xenobiotics and endogenous substances. Eryptosis is inhibited by nitric oxide, catecholamines and a variety of further small molecules. Erythropoietin counteracts eryptosis in part by inhibiting the Ca(2+)-permeable cation channels but by the same token may foster formation of erythrocytes, which are particularly sensitive to eryptotic stimuli. Eryptosis is triggered in several clinical conditions such as iron deficiency, diabetes, renal insufficiency, myelodysplastic syndrome, phosphate depletion, sepsis, haemolytic uremic syndrome, mycoplasma infection, malaria, sickle-cell anemia, beta-thalassemia, glucose-6-phosphate dehydrogenase-(G6PD)-deficiency, hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria, and Wilson's disease. Enhanced eryptosis is observed in mice with deficient annexin 7, cGMP-dependent protein kinase type I (cGKI), AMP-activated protein kinase AMPK, anion exchanger AE1, adenomatous polyposis coli APC and Klotho as well as in mouse models of sickle cell anemia and thalassemia. Eryptosis is decreased in mice with deficient phosphoinositide dependent kinase PDK1, platelet activating factor receptor, transient receptor potential channel TRPC6, janus kinase JAK3 or taurine transporter TAUT. If accelerated eryptosis is not compensated by enhanced erythropoiesis, clinically relevant anemia develops. Eryptotic erythrocytes may further bind to endothelial cells and thus impede microcirculation.

Mechanisms and significance of eryptosis, the suicidal death of erythrocytes

Eryptosis, the suicidal death of erythrocytes, is characterized by erythrocyte shrinkage, blebbing, and phospholipid scrambling of the cell membrane. Eryptosis is triggered by increased cytosolic Ca(2+) activity, which may result from Ca(2+) entry through PGE(2)-activated Ca(2+)-permeable cation channels. The Ca(2+) sensitivity of the scrambling machinery is enhanced by ceramide, which is formed by an acid sphingomyelinase, an enzyme stimulated by platelet-activating factor. Eryptosis is enhanced in a variety of clinical conditions such as sickle-cell anemia, β-thalassemia, glucose-6-phosphate dehydrogenase deficiency, hereditary spherocytosis, paroxysmal nocturnal hemoglobinuria, myelodysplastic syndrome, phosphate depletion, iron deficiency, sepsis, hemolytic uremic syndrome, renal insufficiency, diabetes, malaria, mycoplasma infection, and Wilson's disease. Eryptosis is enhanced in mouse models of sickle cell anemia and thalassemia, as well as in mice lacking functional annexin 7, cGMP-dependent protein kinase type I, AMP-activated protein kinase, Janus kinase 3, anion exchanger 1, adenomatous polyposis coli, or Klotho. Eryptosis is triggered by osmotic shock, oxidative stress, energy depletion, hyperthermia, and a myriad of small molecules. Eryptosis is inhibited by a variety of substances including nitric oxide and catecholamines. Erythropoietin counteracts eryptosis in part by inhibiting the Ca(2+)-permeable cation channels. Excessive erythropoietin concentrations lead, however, to formation of erythrocytes, which are particularly sensitive to eryptotic stimuli. Accelerated eryptosis may be compensated by enhanced erythropoiesis, which is apparent from reticulocytosis. If the compensation is not sufficient, clinically relevant anemia develops. Beyond that, adhesion of eryptotic erythrocytes to the vascular wall may lead to impairment of microcirculation.