Apigenin-induced suicidal erythrocyte death

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.

On the traditional medicinal plants and plant-derived natural drugs used by indigenous people of Nagaland, India

An ethnobotanical documentation on the medicinal plants used by local people of Nagaland (North-east India) has been presented here. The study explored 33 plant species (with their local names, indigenous applications, sources/origins, parts of plants used, bioactive compounds present, process of preparing medicines from the plants) belonging to 28 families have been reviewed thoroughly. Some examples are, Catharanthus roseus (Tsuinrinaro, Periwinkle), Acacia pennata (Chakrangaing, Ballikhadira), Adhatoda vasica (Kicharangnaro, Malabar-nut), Ageratum conzyoides (Imchenriza, Billy-goat-weed,/Tropical-white-weed), Alstonia scholaris (Lazarongpang, Blackboard), Rauvolfia serpentina (Per-mozutong, Indian-snakeroot), etc. Plant based drugs are very popular and effective in Nagaland from ancient times but thorough-documentation with scientific-background of effectiveness, active chemical-compounds present, their action-mechanism, etc., are still scanty. Such review can be of useful for pharmacologist, phyto-chemists to a broad group of researchers and may lead to discovery of new sources of novel medicines through traditional therapeutic knowledge.

Induction of Erythrocyte Membrane Blebbing by Methotrexate-Induced Oxidative Stress

Methotrexate (MTX) is a common chemotherapeutical agent and folate antagonist with reported apoptotic activity in nucleated cells. The presented research work was planned to investigate the eryptotic effects of methotrexate after the exposure of erythrocytes to therapeutical doses (10–15 μM) of methotrexate. Eryptosis and the role of calcium in the stimulation of membrane blebbing were evaluated through the determination of mean cell volume. Oxidative stress induced by methotrexate (10–15 μM) was determined by antioxidative enzyme activities. Cytotoxic activity against human erythrocytes was examined through hemolysis assay. Exposure of erythrocytes to methotrexate results in significant reduction of superoxide dismutase, catalase, and superoxide dismutase activities at 10 and 15 μM in comparison to the untreated cells. Erythrocytes mean cell volume (MCV) was increased after 48 hours exposure of erythrocytes to methotrexate (10 μM). Significantly increased hemolysis percentage was observed at 10 μM after 48 hours incubation of erythrocytes with methotrexate. The results of the study suggested that the therapeutical doses (10–15 μM) of methotrexate may lead to increase in eryptotic and hemolytic activity of erythrocytes through free radical generation and subsequent calcium entry.

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.

Effect of apigenin on surface-associated characteristics and adherence of Streptococcus mutans

Apigenin is a type of flavonols that exhibits anti-caries properties. Bacterial adherence is the initial step in the forming of a stable biofilm that leads to caries. Bacterial adherence is affected by surface characteristics, including hydrophobicity and bacterial aggregation. However, the effect of apigenin on surface characteristics of cariogenic bacteria has not been reported. We aimed to examine the effects of apigenin on adherence and biofilm formation of Streptococcus mutans UA159. Hydrophobicity and bacterial aggregation, pac and gbpC gene expressions, and cytotoxicity on human dental pulp cells were also determined. Apigenin significantly inhibited the adherence and biofilm formation of S. mutans. Hydrophobicity decreased, whereas the aggregation rate was significantly increased compared with the control. Apigenin significantly suppressed pac and gbpC gene expressions. Apigenin exhibited acceptable biocompatibility on hDPCs. Thus, apigeinin may affect adherence and biofilm formation by altering the surface properties of S. mutans without obvious adverse effect on hDPCs.

Erythrocytes as model cells for biocompatibility assessment, cytotoxicity screening of xenobiotics and drug delivery

Erythrocytes (RBCs) represent the main cell component in circulation and recently have become a topic of intensive scientific interest. The relevance of erythrocytes as a model for cytotoxicity screening of xenobiotics is under the spotlight of this review. Erythrocytes constitute a fundamental cellular model to study potential interactions with blood components of manifold novel polymer or biomaterials. Morphological changes, subsequent disruption of RBC membrane integrity, and hemolysis could be used to determine the cytotoxicity of various compounds. Erythrocytes undergo a programmed death (eryptosis) which could serve as a good model for evaluating certain mechanisms which correspond to apoptosis taking place in nucleated cells. Importantly, erythrocytes can be successfully used as a valuable cellular model in examination of oxidative stress generated by certain diseases or multiple xenobiotics since red cells are subjected to permanent oxidative stress. Additionally, the antioxidant capacity of erythrocytes, and the activity of anti-oxidative enzymes could reflect reactive oxygen species (ROS) generating properties of various substances and allow to determine their effects on tissues. The last part of this review presents the latest findings on the possible application of RBCs as drug delivery systems (DDS). In conclusion, all these findings make erythrocytes highly valuable cells for in vitro biocompatibility assessment, cytotoxicity screening of a wide variety of substances as well as drug delivery.

Cannabis-like activity of Zornia latifolia Sm. detected in vitro on rat cortical neurons: major role of the flavone syzalterin

Zornia latifolia is a plant suspected to possess psychoactive properties and marketed as a marijuana substitute under the name 'maconha brava'. In this study, the effects of fractions obtained from a 2-propanol extract of aerial portions of the plant were determined by multielectrode array (MEA) analyses on cultured networks of rat cortical neurons. Lipophilic (ZL_lipo, mainly containing flavonoid aglycones), and hydrophilic (ZL_hydro, mainly containing flavonoid glycosides) fractions were initially obtained from the raw extract. ZL_lipo significantly inhibited mean firing rate (MFR) and mean bursting rate (MBR) of MEA recordings, while ZL_hydro induced no inhibition. Column chromatography separation of ZL_lipo yielded five fractions (ZL1-ZL5), among which ZL1 induced the strongest MFR and MBR inhibition. NMR and HPLC-MS analyses of ZL1 revealed the prevalence of the common flavonoids genistein (1) and apigenin (2) (in about a 1:1 ratio), and the presence of the rare flavone syzalterin (6,8-dimethylapigenin) (3) as a minor compound. Exposures of MEA to apigenin and genistein standards did not induce the MFR and MBR inhibition observed with ZL1, whereas exposure to syzalterin standard or to a 1:9 mixture syzalterin-genistein induced effects similar to ZL1. These inhibitory effects were comparable to that observed with high-THC hashish, possibly accounting for the plant psychoactive properties. Data indicate that Z. latifolia, currently marketed as a free herbal product, should be subjected to measures of control. In addition, syzalterin showed distinctive pharmacological properties, opening the way to its possible exploitation as a neuroactive drug.

Cancer Prevention and Therapy with Polyphenols: Sphingolipid-Mediated Mechanisms

Polyphenols, chemically characterized by a polyhydroxylated phenolic structure, are well known for their widespread pharmacological properties: anti-inflammatory, antibiotic, antiseptic, antitumor, antiallergic, cardioprotective and others. Their distribution in food products is also extensive especially in plant foods such as vegetables, cereals, legumes, fruits, nuts and certain beverages. The latest scientific literature outlines a resilient interconnection between cancer modulation and dietary polyphenols by sphingolipid-mediated mechanisms, usually correlated with a modification of their metabolism. We aim to extensively survey this relationship to show how it could be advantageous in cancer treatment or prevention by nutrients. From this analysis it emerges that a combination of classical chemotherapy with nutrients and especially with polyphenols dietary sources may improve efficacy and decreases negative side effects of the antineoplastic drug. In this multifaceted scenario, sphingolipids play a pivotal role as bioactive molecules, emerging as the mediators of cell proliferation in cancer and modulator of chemotherapeutics.

Phenol and chlorinated phenols exhibit different apoptotic potential in human red blood cells (in vitro study)

Phenol and chlorinated phenols are widely spread in the environment and human surrounding, which leads to a common environmental and occupational exposure of humans to these substances. The aim of this study was to assess eryptotic changes in human red blood cells treated with phenol, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and pentachlorophenol (PCP). The erythrocytes were incubated with phenols studied in the concentrations ranging from 1 to 100 μg/mL for 24 h or 48 h. The results of the study revealed that all compounds studied caused phosphatidylserine translocation and increased cytosolic calcium ions level in human erythrocytes. It was also noticed that phenol and chlorophenols caused an increase in caspase-3 and calpain activation, which confirmed that they were capable of inducing suicidal death of erythrocytes. The results also revealed that PCP most strongly altered the parameters studied, while phenol exhibited the weakest eryptotic potential in the incubated cells.

Effects of Plant Sterols or β-Cryptoxanthin at Physiological Serum Concentrations on Suicidal Erythrocyte Death

The eryptotic and hemolytic effects of a phytosterol (PS) mixture (β-sitosterol, campesterol, stigmasterol) or β-cryptoxanthin (β-Cx) at physiological serum concentration and their effect against oxidative stress induced by tert-butylhydroperoxide (tBOOH) (75 and 300 μM) were evaluated. β-Cryptoxanthin produced an increase in eryptotic cells, cell volume, hemolysis, and glutathione depletion (GSH) without ROS overproduction and intracellular Ca²⁺ influx. Co-incubation of both bioactive compounds protected against β-Cx-induced eryptosis. Under tBOOH stress, PS prevented eryptosis, reducing Ca²⁺ influx, ROS overproduction and GSH depletion at 75 μM, and hemolysis at both tBOOH concentrations. β-Cryptoxanthin showed no cytoprotective effect. Co-incubation with both bioactive compounds completely prevented hemolysis and partially prevented eryptosis as well as GSH depletion induced by β-Cx plus tBOOH. Phytosterols at physiological serum concentrations help to prevent pro-eryptotic and hemolytic effects and are promising candidate compounds for ameliorating eryptosis-associated diseases.

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.

Eryptosis-inducing activity of bisphenol A and its analogs in human red blood cells (in vitro study)

Bisphenols are important chemicals that are widely used in the manufacturing of polycarbonates, epoxy resin and thermal paper, and thus the exposure of humans to these substances has been noted. The purpose of this study was to assess eryptotic changes in human erythrocytes exposed (in vitro) to bisphenol A (BPA) and its selected analogs, i.e.,bisphenol F (BPF), bisphenol S (BPS) and bisphenol AF (BPAF). The erythrocytes were incubated with compounds studied at concentrations ranging from 1 to 250μg/mL for 4, 12 or 24h. The results showed that BPA and its analogs increased cytosolic calcium ions level with the strongest effect noted for BPAF. It has also been revealed that all bisphenols analyzed, and BPAF and BPF in particular increased phosphatidylserine translocation in red blood cells, which confirmed that they exhibited eryptotic potential in this cell type. Furthermore, it was shown that BPA and its analogs caused significant increase in calpain and caspase-3 activities, while the strongest effect was noted for BPAF. BPS, which is the main substituent of bisphenol A in polymers and thermal paper production exhibited similar eryptotic potential to BPA. Eryptotic changes in human erythrocytes were provoked by bisphenols at concentrations, which may influence the human body during occupational exposure or subacute poisoning with these compounds.

A photostable fluorescent probe for rapid monitoring and tracking of a trans-membrane process and mitochondrial fission and fusion dynamics

The MT-PVIM probe was capable of monitoring and tracking a trans membrane process and mitochondrial fission and fusion dynamics.

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.

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.

Inhibitors of the glyoxylate cycle enzyme ICL1 in Candida albicans for potential use as antifungal agents

Candida albicans is an opportunistic pathogen that causes candidiasis in humans. In recent years, metabolic pathways in C. albicans have been explored as potential antifungal targets to treat candidiasis. The glyoxylate cycle, which enables C. albicans to survive in nutrient-limited host niches and its. Key enzymes (e.g., isocitrate lyase (ICL1), are particularly attractive antifungal targets for C. albicans. In this study, we used a new screening approach that better reflects the physiological environment that C. albicans cells experience during infection to identify potential inhibitors of ICL. Three compounds (caffeic acid (CAFF), rosmarinic acid (ROS), and apigenin (API)) were found to have antifungal activity against C. albicans when tested under glucose-depleted conditions. We further confirmed the inhibitory potential of these compounds against ICL using the ICL enzyme assay. Lastly, we assessed the bioavailability and toxicity of these compounds using Lipinski's rule-of-five and ADMET analysis.

Phytoestrogenic molecule desmethylicaritin suppressed adipogenesis via Wnt/β-catenin signaling pathway

Epimedium flavonoids inhibit extravascular lipid deposition during prevention of steroid-associated osteonecrosis. Desmethylicaritin is a bioactive metabolite of Epimedium flavonoids in serum. As it is well known that estrogen inhibits aidpogenesis, so we hypothesized that desmethylicaritin as a phytoestrogen might have the potential to inhibit lipid deposition. This study was designed to investigate the effect of desmethylicaritin on adipogenesis and its underlying mechanism in vitro. Adipogenesis was assessed by Oil Red O staining in 3T3-L1 preadipocytes. Bromodeoxyuridine was used to test the clonal expansion. Further, the mRNA level and protein expression of adipgenic and related factors were detected by qRT-PCR and western blot, respectively. The nuclear location of β-catenin was identified using immunofluoresence assay. Our results showed that desmethylicaritin suppressed the adipogenesis in 3T3-L1 cells in a dose-dependent manner. In addition, desmethylicaritin inhibited clonal expansion during adipogenesis. Desmethylicaritin did not affect CCAAT/enhancer binding protein δ and β mRNA expression, but decreased the mRNA expression of CCAAT/enhancer binding protein α, peroxisome proliferator-activated receptor γ, adipocyte lipid-binding protein and lipoprotein lipase. Desmethylicaritin up-regulated the mRNA expression of Wnt10b that was however down-regulated after adipogenic induction. Desmethylicaritin increased the protein expression of β-catenin both in the cytoplasm and nuclei and immunofluorescence results confirmed that desmethylicaritin increased nuclear translocation of β-catenin. Above findings implied that desmethylicaritin was able to inhibit adipogenesis and Wnt/β-catenin signaling pathway was regulated by desmethylicaritin in the process of suppression of adipogenesis. Above findings supported desmethylicaritin as a novel phytochemical agent for potential prevention of disorders involving lipid metabolism.

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.