Effect of nitazoxanide on erythrocytes

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.

Plant-Waste-Derived Sorbents for Nitazoxanide Adsorption

The increased application of drugs during the COVID-19 pandemic has resulted in their increased concentration in wastewater. Conventional wastewater treatment plants do not remove such pollutants effectively. Adsorption is a cheap, effective, and environmentally friendly method that can accomplish this. On the other hand, maintaining organic waste is required. Thus, in this study, plant waste-derived pelletized biochar obtained from different feedstock and pyrolyzed at 600 °C was applied for the adsorption of nitazoxanide, an antiparasitic drug used for the treatment of SARS-CoV-2. The adsorption was fast and enables one to remove the drug in one hour. The highest adsorption capacity was noted for biochar obtained from biogas production (14 mg/g). The process of NTZ adsorption was governed by chemisorption (k2 = 0.2371 g/mg min). The presence of inorganic ions had a detrimental effect on adsorption (Cl-, NO3- in 20-30%) and carbonates were the most effective in hindering the process (60%). The environmentally relevant concentration of DOM (10 mg/L) did not affect the process. The model studies were supported by the results with a real wastewater effluent (15% reduction). Depending on the applied feedstock, various models described nitazoxanide adsorption onto tested biochars. In summary, the application of carbonaceous adsorbents in the pelletized form is effective in nitazoxanide adsorption.

An In Vitro Study of the Effect of Cytotoxic Triorganotin Dimethylaminophenylazobenzoate Complexes on Red Blood Cells

Interactions of tributyltin (TBTA) and triphenyltin (TPhTA) 2-[4 (dimethylamino)phenylazo]benzoates, showing promising cytostatic activity against tumor cells, with erythrocytes and with erythrocyte membranes and model lipid membranes have been investigated. The effect of TBTA and TPhTA on the erythrocyte and its model membrane was investigated by the microscopic and spectroscopic methods. Interaction of tin complexes with the membrane was determined on the basis of hemolytic activity, changes induced in the shape of erythrocytes, as well as physicochemical parameters of the membrane, such as fluidity. The studies showed that the compounds in higher concentration induce hemolysis; however, TBTA is more toxic than TPhTA. Both TBTA and TPhTA induce morphological alterations in red blood cells-from discocytes to spherocytes and from discocytes to echinocytes. The results suggest that investigated complexes interact with the erythrocyte membrane, change its properties, and probably locate themselves in the hydrophilic part of the membrane, which agrees with conclusions drawn from investigation of erythrocyte membranes and model lipid membranes with the help of fluorescence and infrared spectroscopy.

Oxidative stress, eryptosis and anemia: a pivotal mechanistic nexus in systemic diseases

The average lifespan of circulating erythrocytes usually exceeds hundred days. Prior to that, however, erythrocytes may be exposed to oxidative stress in the circulation which could cause injury and trigger their suicidal death or eryptosis. Oxidative stress activates Ca²⁺ -permeable nonselective cation channels in the cell membrane, thus, stimulating Ca²⁺ entry and subsequent cell membrane scrambling resulting in phosphatidylserine exposure and activation of Ca²⁺ -sensitive K⁺ channels leading to K⁺ exit, hyperpolarization, Cl^- exit, and ultimately cell shrinkage due to loss of KCl and osmotically driven water. While the mechanistic link between oxidative stress and anemia remains ill-defined, several diseases such as diabetes, hepatic failure, malignancy, chronic kidney disease and inflammation have been identified to display both increased oxidative stress as well as eryptosis. Recent compelling evidence suggests that oxidative stress is an important perpetrator in accelerating erythrocyte loss in different systemic conditions and an underlying mechanism for anemia associated with these pathological states. In the present review, we discuss the role of oxidative stress in reducing erythrocyte survival and provide novel insights into the possible use of antioxidants as putative antieryptotic and antianemic agents in a variety of systemic diseases.

Time-dependent therapeutic roles of nitazoxanide on high-fat diet/streptozotocin-induced diabetes in rats: effects on hepatic peroxisome proliferator-activated receptor-gamma receptors

Targeting peroxisome proliferator-activated receptor-gamma (PPAR-γ) is an approved strategy in facing insulin resistance (IR) for diabetes mellitus (DM) type 2. The PPAR-γ modulators display improvements in the insulin-sensitizing and adverse effects of the traditional thiazolidinediones. Nitazoxanide (NTZ) is proposed as a PPAR-γ receptor ligand with agonistic post-transcriptional effects. Currently, NTZ antidiabetic activities versus pioglitazone (PIO) in a high-fat diet/streptozotocin rat model of type 2 diabetes was explored. Diabetic adult male Wistar rats were treated orally with either PIO (2.7 mg·kg^-1·day^-1) or NTZ (200 mg·kg^-1·day^-1) for 14, 21, and 28 days. Body masses, fasting blood glucose, IR, lipid profiles, and liver and kidney functions of rats were assayed. Hepatic glucose metabolism and PPAR-γ protein expression levels as well as hepatic, pancreatic, muscular, and renal histopathology were evaluated. Significant time-dependent euglycemic and insulin-sensitizing effects with preservation of liver and kidney functions were offered by NTZ. Higher hepatic levels of glucose-6-phosphatase and glucose-6-phosphate dehydrogenase enzymes and PPAR-γ protein expressions were acquired by NTZ and PIO, respectively. NTZ could be considered an oral therapeutic strategy for DM type 2. Further systematic NTZ/PPAR-γ receptor subtype molecular activations are recommended. Simultaneous use of NTZ with other approved antidiabetics should be explored.

Ceranib-2-induced suicidal erythrocyte death

Ceramide is known to trigger apoptosis of nucleated cells and eryptosis of erythrocytes. Eryptosis is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Besides ceramide, stimulators of eryptosis include increase of cytosolic Ca(2+) -activity ([Ca(2+) ]i ) and oxidative stress. Ceramide is degraded by acid ceramidase and inhibition of the enzyme similarly triggers apoptosis. The present study explored, whether ceramidase inhibitor Ceranib-2 induces eryptosis. Flow cytometry was employed to quantify phosphatidylserine-exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, [Ca(2+) ]i from Fluo3-fluorescence, reactive oxygen species (ROS) from DCF dependent fluorescence, and ceramide abundance utilizing specific antibodies. Hemolysis was estimated from hemoglobin concentration in the supernatant. A 48 h exposure of human erythrocytes to Ceranib-2 significantly increased the percentage of annexin-V-binding cells (≥50 μM) and the percentage of hemolytic cells (≥10 μM) without significantly modifying forward scatter. Ceranib-2 significantly increased Fluo3-fluorescence, DCF fluorescence and ceramide abundance. The effect of Ceranib-2 on annexin-V-binding was not significantly blunted by removal of extracellular Ca(2+) . Ceranib-2 triggers phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to increase of ceramide abundance and induction of oxidative stress, but not dependent on Ca(2+) entry. Copyright © 2016 John Wiley & Sons, Ltd.

Hydroxytyrosol inhibits phosphatidylserine exposure and suicidal death induced by mercury in human erythrocytes: Possible involvement of the glutathione pathway

Hydroxytyrosol (HT) is a phenolic antioxidant naturally occurring in virgin olive oil. In this study, we investigated the possible protective effects of HT on programmed suicidal death (eryptosis) induced by mercury (Hg) treatment in intact human erythrocytes (RBC). Our study confirms that the Hg-eryptosis is characterized by phosphatidylserine (PS) exposure at the cell surface, with cell shrinkage and ATP and glutathione depletion; calcium influx is also a key event that triggers eryptosis. Here we report that cell preconditioning with an optimal dose (1-5 μM) of HT prior to exposure to 2.5 μM HgCl2 causes a noteworthy decrease in PS-exposing RBC, almost restoring ATP and GSH content. Conversely, HT shows no effect against decrease in cell volume nor against influx of extracellular calcium. Taken together our data provide the first experimental evidence of the efficacy of HT in modulating the programmed suicidal death in non nucleated cells; the reported findings also confirm that the prevention of Hg toxicity should be regarded as an additional mechanism responsible for the health-promoting potential of this dietary phenol. Finally, virgin olive oil would appear to be a promising healthy food to reduce the adverse effects of chronic mercury exposure in humans.

Bromfenvinphos induced suicidal death of human erythrocytes

The organophosphorus pesticide bromfenvinphos ((E,Z)-O,O-diethyl-O-[1-(2,4-dichlorophenyl)-2-bromovinyl] phosphate) has been shown to decrease hematocrit and hemoglobin levels in blood presumably by triggering oxidative stress of erythrocytes. Oxidative stress is known to activate erythrocytic Ca(2+) permeable unselective cation channels leading to Ca(2+) entry and increase of cytosolic Ca(2+) activity ([Ca(2+)]i), which in turn triggers eryptosis, the suicidal death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. The present study explored, whether and how bromfenvinphos induces eryptosis. To this end, phosphatidylserine exposure at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, hemolysis from hemoglobin release, [Ca(2+)]i from Fluo3-fluorescence, and ROS formation from DCFDA dependent fluorescence. As a result, a 48hour exposure of human erythrocytes to bromfenvinphos (≥100μM) significantly increased the percentage of annexin-V-binding cells, significantly decreased forward scatter, significantly increased Fluo3-fluorescence, and significantly increased DCFDA fluorescence. The effect of bromfenvinphos on annexin-V-binding and forward scatter was significantly blunted, but not abolished by removal of extracellular Ca(2+). In conclusion, bromfenvinphos triggers cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane, an effect in part due to stimulation of ROS formation and Ca(2+) entry.

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.

The use of erythrocyte fragility to assess xenobiotic cytotoxicity

The erythrocytes of mammals represent a good model to evaluate the cytotoxicity of molecules, organic and inorganic, natural or synthetic, by cellular damage measure. Indeed, before any investigation on the mechanism of action of different molecules, it is important to perform a cytotoxicity assay. Among the different cytotoxicity assays that assess a possible toxicity in the red blood cells is the rate of haemolysis. This essay is based on the evaluation of the alterations of red cell membranes in the presence of an eventual xenobiotic. Red blood cells are the main cells in circulation, and they are responsible for transporting oxygen; in fact, any alterations of this process could be lethal. The plasma membrane of red blood cells is a multi-component structure such as to confer to these cells their characteristic biconcave shape, high flexibility, elasticity and deformability. However, there are clear signs of cellular suffering if there are any alterations to this structure. One method of toxicity assessment is based on measurement of the efflux of haemoglobin from suspended red blood cells. Haemolysis, and therefore the loss of haemoglobin, is the signal stability of the cell membrane of the erythrocytes. In recent years, the discovery of programmed cell death in mammalian red blood cells presented a diversification of the response to injury by these a-nucleated cells. This review shows that mammals' erythrocytes might serve well as a model cell to study on the cellular and molecular mechanisms of many treatments.

Triggering of Erythrocyte Death by Triparanol

The cholesterol synthesis inhibitor Triparanol has been shown to trigger apoptosis in several malignancies. Similar to the apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include oxidative stress which may activate erythrocytic Ca²⁺ permeable unselective cation channels with subsequent Ca²⁺ entry and increase of cytosolic Ca²⁺ activity ([Ca²⁺]_i). The present study explored whether and how Triparanol induces eryptosis. To this end, phosphatidylserine exposure at the cell surface was estimated from annexin-V-binding, cell volume from forward scatter, hemolysis from hemoglobin release, [Ca²⁺]_i from Fluo3-fluorescence, and ROS formation from 2’,7’-dichlorodihydrofluorescein diacetate (DCFDA) dependent fluorescence. As a result, a 48 h exposure of human erythrocytes to Triparanol (20 µM) significantly increased DCFDA fluorescence and significantly increased Fluo3-fluorescence. Triparanol (15 µM) significantly increased the percentage of annexin-V-binding cells, and significantly decreased the forward scatter. The effect of Triparanol on annexin-V-binding was significantly blunted, but not abolished by removal of extracellular Ca²⁺. In conclusion, Triparanol leads to eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and phospholipid scrambling of the erythrocyte cell membrane. Triparanol is at least in part effective by stimulating ROS formation and Ca²⁺ entry.

Induction of Suicidal Erythrocyte Death by Cantharidin

The natural phosphoprotein phosphatase inhibitor cantharidin, primarily used for topical treatment of warts, has later been shown to trigger tumor cell apoptosis and is thus considered for the treatment of malignancy. Similar to apoptosis of tumor cells, erythrocytes may undergo eryptosis, a suicidal cell death characterized by cell shrinkage and translocation of cell membrane phosphatidylserine to the erythrocyte surface. Signaling of eryptosis includes increase of cytosolic Ca²⁺-activity ([Ca²⁺]_i), ceramide, oxidative stress and dysregulation of several kinases. Phosphatidylserine abundance at the erythrocyte surface was quantified utilizing annexin-V-binding, cell volume from forward scatter, [Ca²⁺]_i from Fluo3-fluorescence, ceramide from antibody binding, and reactive oxidant species (ROS) from 2′,7′-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence. A 48 h treatment of human erythrocytes with cantharidin significantly increased the percentage of annexin-V-binding cells (≥10 μg/mL), significantly decreased forward scatter (≥25 μg/mL), significantly increased [Ca²⁺]_i (≥25 μg/mL), but did not significantly modify ceramide abundance or ROS. The up-regulation of annexin-V-binding following cantharidin treatment was not significantly blunted by removal of extracellular Ca²⁺ but was abolished by kinase inhibitor staurosporine (1 μM) and slightly decreased by p38 inhibitor skepinone (2 μM). Exposure of erythrocytes to cantharidin triggers suicidal erythrocyte death with erythrocyte shrinkage and erythrocyte membrane scrambling, an effect sensitive to kinase inhibitors staurosporine and skepinone.

Therapeutic potential of manipulating suicidal erythrocyte death

INTRODUCTION

Eryptosis, the suicidal erythrocyte death, is characterized by erythrocyte shrinkage and phosphatidylserine translocation to the erythrocyte surface. Eryptosis is triggered by cell stress such as energy depletion and oxidative stress, by Ca(2+)-entry, ceramide, caspases, calpain and/or altered activity of several kinases. Phosphatidylserine-exposing erythrocytes adhere to the vascular wall and may thus impede microcirculation. Eryptotic cells are further engulfed by phagocytes and thus rapidly cleared from circulation.

AREAS COVERED

Stimulation of eryptosis contributes to anemia of several clinical conditions such as metabolic syndrome, diabetes, malignancy, hepatic failure, heart failure, uremia, hemolytic uremic syndrome, sepsis, fever, dehydration, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose-6-phosphate dehydrogenase deficiency and Wilson's disease. On the other hand, eryptosis with subsequent clearance of infected erythrocytes in malaria may counteract parasitemia.

EXPERT OPINION

In theory, anemia due to excessive eryptosis could be alleviated by treatment with small molecules inhibiting eryptosis. In malaria, stimulators of eryptosis may accelerate death of infected erythrocytes and thus favorably influence the clinical course of the disease. Many small molecules inhibit or stimulate eryptosis. Several stimulators favorably influence murine malaria. Further preclinical and subsequent clinical studies are required to elucidate the therapeutic potential of stimulators or inhibitors of eryptosis.

Induction of suicidal erythrocyte death by nelfinavir

The HIV protease inhibitor, nelfinavir, primarily used for the treatment of HIV infections, has later been shown to be effective in various infectious diseases including malaria. Nelfinavir may trigger mitochondria-independent cell death. Erythrocytes may undergo eryptosis, a mitochondria-independent suicidal cell death characterized by cell shrinkage and phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include oxidative stress and increase of cytosolic Ca²⁺-activity ([Ca²⁺]_i). During malaria, accelerated death of infected erythrocytes may decrease parasitemia and thus favorably influence the clinical course of the disease. In the present study, phosphatidylserine abundance at the cell surface was estimated from annexin V binding, cell volume from forward scatter, reactive oxidant species (ROS) from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence, and [Ca²⁺]_i from Fluo3-fluorescence. A 48 h treatment of human erythrocytes with nelfinavir significantly increased the percentage of annexin-V-binding cells (≥5µg/mL), significantly decreased forward scatter (≥2.5µg/mL), significantly increased ROS abundance (10 µg/mL), and significantly increased [Ca²⁺]_i (≥5 µg/mL). The up-regulation of annexin-V-binding following nelfinavir treatment was significantly blunted, but not abolished by either addition of the antioxidant N-acetylcysteine (1 mM) or removal of extracellular Ca²⁺. In conclusion, exposure of erythrocytes to nelfinavir induces oxidative stress and Ca²⁺ entry, thus leading to suicidal erythrocyte death characterized by erythrocyte shrinkage and erythrocyte membrane scrambling.

Enhanced eryptosis following gramicidin exposure

The peptide antibiotic and ionophore gramicidin has previously been shown to trigger apoptosis of nucleated cells. In analogy to apoptosis, the suicidal death of erythrocytes or eryptosis involves cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosis include oxidative stress, increase of cytosolic Ca²⁺ activity ([Ca²⁺]_i), and ceramide. The present study explored, whether gramicidin triggers eryptosis. To this end phosphatidylserine exposure at the cell surface was estimated from annexin V binding, cell volume from forward scatter, red blood cell distribution width (RDW) from electronic particle counting, reactive oxidant species (ROS) from 2',7'-dichlorodihydrofluorescein diacetate (DCFDA) fluorescence, [Ca²⁺]_i from Fluo3- and Fluo4 fluorescence, and ceramide abundance from binding of specific antibodies. As a result, a 24 h exposure of human erythrocytes to gramicidin significantly increased the percentage of annexin-V-binding cells (≥1 µg/mL), forward scatter (≥0.5 µg/mL) and hemolysis. Gramicidin enhanced ROS activity, [Ca²⁺]_i and ceramide abundance at the erythrocyte surface. The stimulation of annexin-V-binding by gramicidin was significantly blunted but not abolished by removal of extracellular Ca²⁺. In conclusion, gramicidin stimulates phospholipid scrambling of the erythrocyte cell membrane, an effect at least partially due to induction of oxidative stress, increase of [Ca²⁺]_i and up-regulation of ceramide abundance. Despite increase of [Ca²⁺]_i, gramicidin increases cell volume and slightly reduces RWD.

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.

Mechanisms and pathophysiological significance of eryptosis, the suicidal erythrocyte death

Eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling, is stimulated by Ca(2+) entry through Ca(2+)-permeable, PGE2-activated cation channels, by ceramide, caspases, calpain, complement, hyperosmotic shock, energy depletion, oxidative stress, and deranged activity of several kinases (e.g. AMPK, GK, PAK2, CK1α, JAK3, PKC, p38-MAPK). Eryptosis is triggered by intoxication, malignancy, hepatic failure, diabetes, chronic renal insufficiency, hemolytic uremic syndrome, dehydration, phosphate depletion, fever, sepsis, mycoplasma infection, malaria, iron deficiency, sickle cell anemia, thalassemia, glucose 6-phosphate dehydrogenase deficiency, and Wilson's disease. Eryptosis may precede and protect against hemolysis but by the same token result in anemia and deranged microcirculation.

Enhanced eryptosis following juglone exposure

Juglone, a quinone isolated from Juglans mandshurica Maxim, has previously been shown to be effective against malignancy. The effect is at least partially due to stimulation of suicidal death or apoptosis of tumour cells. On the other hand, juglone has been shown to counteract apoptosis, for example, of neurons. In analogy to apoptosis of nucleated cells, erythrocytes may enter eryptosis, a suicidal death characterized by cell shrinkage and breakdown of phosphatidylserine asymmetry of the cell membrane with phosphatidylserine exposure at the erythrocyte surface. Stimulators of eryptosis include increase in cytosolic Ca(2+) activity [(Ca(2+) )i]. This study explored whether juglone stimulates eryptosis. To this end, erythrocyte volume was estimated from forward scatter, phosphatidylserine exposure at the erythrocyte surface from FITC annexin V binding, ceramide abundance from binding of fluorescent antibodies in flow cytometry and cytosolic ATP with a luciferin-luciferase-based assay. As a result, a 24-hr exposure of human erythrocytes to juglone (5 μM) significantly decreased erythrocyte forward scatter. Juglone (1-5 μM) significantly increased the percentage of annexin V binding cells. Juglone (5 μM) significantly increased ceramide abundance at the erythrocyte surface and decreased erythrocyte ATP concentration. The effect of juglone (10 μM) on annexin V binding was slightly but significantly blunted by removal of extracellular Ca(2+) and by addition of protein kinase C (PKC) inhibitor staurosporine (1 μM). In conclusion, juglone stimulates suicidal erythrocyte death or eryptosis at least in part by upregulation of ceramide abundance, energy depletion and activation of PKC.

Nitazoxanide, an antiviral thiazolide, depletes ATP-sensitive intracellular Ca(2+) stores

Nitazoxanide (NTZ) inhibits influenza, Japanese encephalitis, hepatitis B and hepatitis C virus replication but effects on the replication of other members of the Flaviviridae family has yet to be defined. The pestivirus bovine viral diarrhoea virus (BVDV) is a surrogate model for HCV infection and NTZ induced PKR and eIF2α phosphorylation in both uninfected and BVDV-infected cells. This led to the observation that NTZ depletes ATP-sensitive intracellular Ca(2+) stores. In addition to PKR and eIF2α phosphorylation, consequences of NTZ-mediated Ca(2+) mobilisation included induction of chronic sub-lethal ER stress as well as perturbation of viral protein N-linked glycosylation and trafficking. To adapt to NTZ-mediated ER stress, NTZ treated cells upregulated translation of Ca(2+)-binding proteins, including the ER chaperone Bip and the cytosolic pro-survival and anti-viral protein TCTP. Depletion of intracellular Ca(2+) stores is the primary consequence of NTZ treatment and is likely to underpin all antiviral mechanisms attributed to the thiazolide.