Name: induction of eryptosis in red blood cells using a calcium ionophore
Uploaded: 2020-01-21T15:00:00
Description: Watch this Scientific Journal Video about Induction of Eryptosis in Red Blood Cells Using a Calcium Ionophore at JoVE.com

This work was supported by NIH grant R15ES030140 and NSF grant CBET1903568. Financial support from the Russ College of Engineering and Technology and the Department of Chemical and Biomolecular Engineering at Ohio University is also acknowledged.

All human blood samples used in the protocol described below were purchased as de-identified samples. No human subjects were directly involved or recruited for this study. The guidelines of the Declaration of Helsinki should be used when research involves human subjects.
1. Erythrocyte isolation from whole blood
<ol>
	<li>Add 500 &#181;L of whole blood in acid citrate dextrose (ACD) (stored at 4 &#176;C) to a microcentrifuge tube. 
	NOTE: Whole blood was purchased in ACD. According to t...

<ol>
	<li>Bratosin, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programmed+Cell+Death+in+Mature+Erythrocytes:+A+Model+for+Investigating+Death+Effector+Pathways+Operating+in+the+Absence+of+Mitochondria.">Programmed Cell Death in Mature Erythrocytes: A Model for Investigating Death Effector Pathways Operating in the Absence of Mitochondria.</a> Cell Death and Differentiation. 8 (12), 1143-1156 (2001).</li><li>Lang, E., Lang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+and+Pathophysiological+Significance+of+Eryptosis,+the+Suicidal+Erythrocyte+Death.">Mechanisms and Pathophysiological Significance of Eryptosis, the Suicidal Erythrocyte Death.</a> Seminars in Cell and Developmental Biology. 39, 35-42 (2015).</li><li>Garnier, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Erythrocyte+Deformability+in+Diabetes+and+Erythrocyte+Membrane+Lipid+Composition.">Erythrocyte Deformability in Diabetes and Erythrocyte Membrane Lipid Composition.</a> Metabolism. 39 (8), 794-798 (1990).</li><li>Verkleij, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Asymmetric+Distribution+of+Phospholipids+in+the+Human+Red+Cell+Membrane.+A+Combined+Study+Using+Phospholipases+and+Freeze-Etch+Electron+Microscopy.">The Asymmetric Distribution of Phospholipids in the Human Red Cell Membrane. A Combined Study Using Phospholipases and Freeze-Etch Electron Microscopy.</a> Biochimica et Biophysica Acta (BBA) Biomembranes. 323 (2), 178-193 (1973).</li><li>de Back, D. Z., Kostova, E. B., van Kraaij, M., van den Berg, T. K., van Bruggen, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Of+Macrophages+and+Red+Blood+Cells;+A+Complex+Love+Story.">Of Macrophages and Red Blood Cells; A Complex Love Story.</a> Frontiers in Physiology. 5, 9 (2014).</li><li>Fadok, V. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Receptor+for+Phosphatidylserine-Specific+Clearance+of+Apoptotic+Cells.">A Receptor for Phosphatidylserine-Specific Clearance of Apoptotic Cells.</a> Nature. 405 (6782), 85-90 (2000).</li><li>Henson, P. M., Bratton, D. L., Fadok, V. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Phosphatidylserine+Receptor:+A+Crucial+Molecular+Switch.">The Phosphatidylserine Receptor: A Crucial Molecular Switch.</a> Nature Reviews Molecular Cell Biology. 2 (8), 627-633 (2001).</li><li>Messmer, U. K., Pfeilschifter, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=New+Insights+into+the+Mechanism+for+Clearance+of+Apoptotic+Cells.">New Insights into the Mechanism for Clearance of Apoptotic Cells.</a> BioEssays. 22 (10), 878-881 (2000).</li><li>Basu, S., Banerjee, D., Chandra, S., Chakrabarti, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eryptosis+in+Hereditary+Spherocytosis+and+Thalassemia:+Role+of+Glycoconjugates.">Eryptosis in Hereditary Spherocytosis and Thalassemia: Role of Glycoconjugates.</a> Glycoconjugate Journal. 27 (9), 717-722 (2010).</li><li>Kuypers, F. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+Altered+Membrane+Phospholipid+Asymmetry+in+Subpopulations+of+Human+Red+Blood+Cells+Using+Fluorescently+Labeled+Annexin+V.">Detection of Altered Membrane Phospholipid Asymmetry in Subpopulations of Human Red Blood Cells Using Fluorescently Labeled Annexin V.</a> Blood. 87 (3), 1179-1197 (1996).</li><li>Lang, F., Lang, E., Fller, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Physiology+and+Pathophysiology+of+Eryptosis.">Physiology and Pathophysiology of Eryptosis.</a> Transfusion Medicine and Hemotherapy. 39 (5), 308-314 (2012).</li><li>Wr&#243;bel, A., Bobrowska-H&#228;gerstrand, M., Lindqvist, C., H&#228;gerstrand, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monitoring+of+Membrane+Phospholipid+Scrambling+in+Human+Erythrocytes+and+K562+Cells+with+FM1-43+-+a+Comparison+with+Annexin+V-FITC.">Monitoring of Membrane Phospholipid Scrambling in Human Erythrocytes and K562 Cells with FM1-43 - a Comparison with Annexin V-FITC.</a> Cellular and Molecular Biology Letters. 19 (2), 262-276 (2014).</li><li>Mohandas, N., Gallagher, P. 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A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Comprehensive+Review+on+Eryptosis.">A Comprehensive Review on Eryptosis.</a> Cellular Physiology and Biochemistry. 39 (5), 1977-2000 (2016).</li><li>Suzuki, J., Umeda, M., Sims, P. J., Nagata, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium-Dependent+Phospholipid+Scrambling+by+TMEM16F.">Calcium-Dependent Phospholipid Scrambling by TMEM16F.</a> Nature. 468 (7325), 834-838 (2010).</li><li>Bhuyan, A. A. M., Haque, A. A., Sahu, I., Coa, H., Kormann, M. S. 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R. R., Daniel-Ribeiro, C. T., Ferreira-da-Cru, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Refractoriness+of+Eryptotic+Red+Blood+Cells+to+Plasmodium+Falciparum+Infection:+A+Putative+Host+Defense+Mechanism+Limiting+Parasitaemia.">Refractoriness of Eryptotic Red Blood Cells to Plasmodium Falciparum Infection: A Putative Host Defense Mechanism Limiting Parasitaemia.</a> PLoS One. 6 (10), e26575 (2011).</li><li>Borst, O., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dynamic+Adhesion+of+Eryptotic+Erythrocytes+to+Endothelial+Cells+via+CXCL16/SR-PSOX.">Dynamic Adhesion of Eryptotic Erythrocytes to Endothelial Cells via CXCL16/SR-PSOX.</a> American Journal of Physiology - Cell Physiology. 302 (4), C644-C651 (2011).</li><li>Tagami, T., Yanai, H., Terada, Y., Ozeki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+Phosphatidylserine-Specific+Peptide-Conjugated+Liposomes+Using+a+Model+System+of+Malaria-Infected+Erythrocytes.">Evaluation of Phosphatidylserine-Specific Peptide-Conjugated Liposomes Using a Model System of Malaria-Infected Erythrocytes.</a> Biological and Pharmaceutical Bulletin. 38 (10), 1649-1651 (2015).</li><li>Mahmud, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Suicidal+Erythrocyte+Death,+Eryptosis,+as+a+Novel+Mechanism+in+Heart+Failure-Associated+Anaemia.">Suicidal Erythrocyte Death, Eryptosis, as a Novel Mechanism in Heart Failure-Associated Anaemia.</a> Cardiovascular Research. 98 (1), 37-46 (2013).</li><li>Signoretto, E., Castagna, M., Lang, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stimulation+of+Eryptosis,+the+Suicidal+Erythrocyte+Death+by+Piceatannol.">Stimulation of Eryptosis, the Suicidal Erythrocyte Death by Piceatannol.</a> Cellular Physiology and Biochemistry. 38 (6), 2300-2310 (2016).</li><li>Lange, Y., Ye, J., Steck, T. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Scrambling+of+Phospholipids+Activates+Red+Cell+Membrane+Cholesterol.">Scrambling of Phospholipids Activates Red Cell Membrane Cholesterol.</a> Biochemistry. 46 (8), 2233-2238 (2007).</li><li>Lang, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eryptosis,+a+Window+to+Systemic+Disease.">Eryptosis, a Window to Systemic Disease.</a> Cellular Physiology and Biochemistry. 22 (6), 373-380 (2008).</li><li>Gil-Parrado, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ionomycin-Activated+Calpain+Triggers+Apoptosis.+A+Probable+Role+for+Bcl-2+Family+Members.">Ionomycin-Activated Calpain Triggers Apoptosis. A Probable Role for Bcl-2 Family Members.</a> Journal of Biological Chemistry. 277 (30), 27217-27226 (2002).</li><li>Liu, C. M., Hermann, T. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+Ionomycin+as+a+Calcium+Ionophore.">Characterization of Ionomycin as a Calcium Ionophore.</a> Journal of Biological Chemistry. 253 (17), 5892-5894 (1978).</li><li>Klarl, B. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protein+Kinase+C+Mediates+Erythrocyte+"Programmed+Cell+Death"+Following+Glucose+Depletion.">Protein Kinase C Mediates Erythrocyte "Programmed Cell Death" Following Glucose Depletion.</a> American Journal of Physiology - Cell Physiology. 290 (1), C244-C253 (2006).</li><li>Danilov, Y. N., Cohen, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wheat+Germ+Agglutinin+but+Not+Concanavalin+A+Modulates+Protein+Kinase+C-Mediated+Phosphorylation+of+Red+Cell+Skeletal+Proteins.">Wheat Germ Agglutinin but Not Concanavalin A Modulates Protein Kinase C-Mediated Phosphorylation of Red Cell Skeletal Proteins.</a> FEBS Letters. 257 (2), 431-434 (1989).</li><li>Nazemidashtarjandi, S., Farnoud, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+Outer+Leaflet+Is+the+Primary+Regulator+of+Membrane+Damage+Induced+by+Silica+Nanoparticles+in+Vesicles+and+Erythrocytes.">Membrane Outer Leaflet Is the Primary Regulator of Membrane Damage Induced by Silica Nanoparticles in Vesicles and Erythrocytes.</a> Environmental Science Nano. 6 (4), 1219-1232 (2019).</li><li>Jaroszeski, M. J., Heller, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Flow Cytometry Protocols. , (2003).</li><li>Ghashghaeinia, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Impact+of+Erythrocyte+Age+on+Eryptosis.">The Impact of Erythrocyte Age on Eryptosis.</a> British Journal of Haematology. 157 (5), 1365 (2012).</li><li>Repsold, L., Joubert, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Eryptosis:+An+Erythrocyte's+Suicidal+Type+of+Cell+Death.">Eryptosis: An Erythrocyte's Suicidal Type of Cell Death.</a> Biomed Research International. 2018 (5), 9405617 (2018).</li><li>Tait, J. 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The goal of this procedure is to provide optimal values for ionophore concentration, treatment time, and extracellular glucose concentration, which are important factors in ensuring successful induction of eryptosis. A critical step in the protocol is the depletion of extracellular glucose, which, despite its importance, has not been sufficiently emphasized in the literature. The sugar content in normal Ringer solution (5 mM) has an inhibitory effect on eryptosis. Glucose depletion in the extracellular environment induce...

Programmed cell death in erythrocytes, also known as eryptosis, is common in many clinical conditions and hematological disorders. Eryptosis is associated with cell shrinkage and the loss of phospholipid asymmetry in the cell plasma membrane1,2. Loss of asymmetry results in the translocation of phosphatidylserine (PS), a lipid normally localized in the inner leaflet3,4, to the cell outer leaflet, which signals to macrophages to phagocytose and remove defective erythrocytes5,6,7,8. At the end of the normal life span of erythrocytes, removal of eryptotic cells by macrophages ensures the balance of erythrocytes in circulation. However, in diseased conditions, such as sickle cell disease and thalassemia9,10,11, enhanced eryptosis may result in severe anemia2. Due to its importance in hematological diseases, there is significant interest in examining the factors inducing or inhibiting eryptosis and the molecular mechanisms underlying this process.
The plasma membrane of healthy erythrocytes is asymmetric, with different phospholipids localizing at the outer and inner leaflets. Membrane asymmetry is primarily regulated by the action of membrane enzymes. Aminophospholipid translocase facilitates the transport of aminophospholipids, PS and phosphatidylethanolamine (PE), by directing these lipids to the cell inner leaflet. On the other hand, floppase transports the choline containing phospholipids, phosphatidylcholine (PC) and sphingomyelin (SM), from the inner to the outer leaflet of the cell membrane12. However, unlike healthy cells, the membrane of eryptotic erythrocytes is scrambled. This is due to the action of a third enzyme, scramblase, which disrupts phospholipid asymmetry by facilitating the bidirectional transport of aminophospholipids13,14,15,16. Scramblase is activated by elevated intracellular levels of Ca2+. Therefore, calcium ionophores, which facilitate the transport of Ca2+ across the cell membrane12, are efficient inducers of eryptosis.
Ionomycin, a calcium ionophore, has been widely used to induce eryptosis in erythrocytes12,17,18,19,20,21,22,23,24,25,26. Ionomycin has both hydrophilic and hydrophobic groups, which are necessary to bind and capture Ca2+ ion, and transport it to the cytosolic space27,28,29. This leads to the activation of scramblase and translocation of PS to the outer leaflet, which can be easily detected using annexin-V, a cellular protein with a high affinity to PS12. Although triggering eryptosis by ionomycin is commonly reported, there is considerable method discrepancy in the literature (Table 1). The population of erythrocytes undergoing eryptosis depends on different factors such as ionophore concentration, treatment time with ionophore, and the sugar content of extracellular environment (glucose depletion activates cation channels and facilitates the entry of Ca2+ into the cytosolic space)30,31. However, there is little consistency in these factors in the literature, making it difficult to perform eryptosis reproducibly in vitro.
In this protocol, we present a step-by-step procedure to induce eryptosis in human erythrocytes. Factors affecting successful eryptosis including Ca2+ concentration, ionophore concentration, treatment time, and pre-incubation in glucose-depleted buffer are examined and optimal values are reported. This procedure demonstrates that pre-incubation of erythrocytes in a glucose-free buffer significantly increases the percentage of eryptosis compared to glucose-containing buffer. This protocol can be used in the laboratory to produce eryptotic erythrocytes for various applications.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>96-well plate</td>
			<td>Fisher Scientific</td>
			<td>12-565-331</td>
			<td></td>
		</tr>
		<tr>
			<td>Annexin V Alexa Fluor 488 - apoptosis kit</td>
			<td>Fisher Scientific</td>
			<td>A10788</td>
			<td>Store at 4 &#176;C</td>
		</tr>
		<tr>
			<td>BD FACSAria II flow cytometer</td>
			<td>BD Biosciences</td>
			<td>643177</td>
			<td></td>
		</tr>
		<tr>
			<td>CaCl2</td>
			<td>Fisher Scientific</td>
			<td>C79-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Millipore Sigma</td>
			<td>M7157</td>
			<td>Model Eppendorf 5415C</td>
		</tr>
		<tr>
			<td>Confocal fluorescence microscopy</td>
			<td>Zeiss, LSM Tek Thornwood</td>
			<td></td>
			<td>Model LSM 510, Argon laser excited at 488 nm for taking images</td>
		</tr>
		<tr>
			<td>Cover glasses circles</td>
			<td>Fisher Scientific</td>
			<td>12-545-100</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable round bottom flow cytometry tube</td>
			<td>VWR</td>
			<td>VWRU47729-566</td>
			<td></td>
		</tr>
		<tr>
			<td>DMSO</td>
			<td>Sigma-Aldrich</td>
			<td>472301-100ML</td>
			<td></td>
		</tr>
		<tr>
			<td>DPBS</td>
			<td>VWR Life Science</td>
			<td>SH30028.02</td>
			<td></td>
		</tr>
		<tr>
			<td>Glucose monohydrate</td>
			<td>Sigma-Aldrich</td>
			<td>Y0001745</td>
			<td></td>
		</tr>
		<tr>
			<td>HEPES Buffer (1 M)</td>
			<td>Fisher Scientific</td>
			<td>50-751-7290</td>
			<td>Store at 4 &#176;C</td>
		</tr>
		<tr>
			<td>Ionomycin calcium salt</td>
			<td>EMD Milipore Corp.</td>
			<td>407952-1MG</td>
			<td>Dissolve in DMSO to reach 2 mM. Store at -20 &#176;C</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Fisher Scientific</td>
			<td>P330-500</td>
			<td></td>
		</tr>
		<tr>
			<td>MgSO4</td>
			<td>Fisher Scientific</td>
			<td>M65-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Microcentrifuge tube</td>
			<td>Fisher Scientific</td>
			<td>02-681-5</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Fisher Scientific</td>
			<td>S271-500</td>
			<td></td>
		</tr>
		<tr>
			<td>Plain glass microscope slides</td>
			<td>Fisher Scientific</td>
			<td>12-544-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Synergy HFM microplate reader</td>
			<td>BioTek</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Whole blood in ACD</td>
			<td>Zen-Bio</td>
			<td></td>
			<td>Store at 4 &#176;C and warm to 37 &#176;C prior to use</td>
		</tr>
	</tbody>
</table>

induction of eryptosis in red blood cells using a calcium ionophore

Eryptosis, erythrocyte programmed cell death, occurs in a number of hematological diseases and during injury to erythrocytes. A hallmark of eryptotic cells is the loss of compositional asymmetry of the cell membrane, leading to the translocation of phosphatidylserine to the membrane outer leaflet. This process is triggered by increased intracellular concentration of Ca2+, which activates scramblase, an enzyme that facilitates bidirectional movement of phospholipids between membrane leaflets. Given the importance of eryptosis in various diseased conditions, there have been efforts to induce eryptosis in vitro. Such efforts have generally relied on the calcium ionophore, ionomycin, to enhance intracellular Ca2+ concentration and induce eryptosis. However, many discrepancies have been reported in the literature regarding the procedure for inducing eryptosis using ionomycin. Herein, we report a step-by-step protocol for ionomycin-induced eryptosis in human erythrocytes. We focus on important steps in the procedure including the ionophore concentration, incubation time, and glucose depletion, and provide representative result. This protocol can be used to reproducibly induce eryptosis in the laboratory.

Optimization of ionomycin concentration
While ionomycin is required to induce eryptosis, increased ionomycin concentrations can lead to hemolysis (i.e. lysis of erythrocytes and release of hemoglobin), which needs to be avoided. Treatment of erythrocytes with 1 &#181;M ionomycin in Ringer solution for 2 h is enough to induce eryptosis, as evidenced by successful labeling with annexin-V Alexa Flour 488 conjugate ...

Watch this Scientific Journal Video about Induction of Eryptosis in Red Blood Cells Using a Calcium Ionophore at JoVE.com

Induction of Eryptosis in Red Blood Cells Using a Calcium Ionophore

A protocol for the induction of eryptosis, programmed cell death in erythrocytes, using the calcium ionophore, ionomycin, is provided. Successful eryptosis is evaluated by monitoring the localization phosphatidylserine in the membrane outer leaflet. Factors affecting the success of the protocol have been examined and optimal conditions provided.

Eryptosis, erythrocyte programmed cell death, occurs in a number of hematological diseases and during injury to erythrocytes. A hallmark of eryptotic ...

There have been many efforts to induce eryptosis using ionomycin. However, the exact procedure for this process is not clearly outlined in the literature. We provide a step-by-step procedure to induce eryptosis using ionomycin.The main advantage of this procedure is to induce eryptosis in human erythrocytes in a reliable and reproducible manner. To begin, add 500 microliters of cold whole blood in acid citrate dextrose to a microcentrifuge tube. Centrifuge the whole blood at 700 times g for five minutes at room temperature and remove the clear plasma and the thin buffy coat using a pipette to leave the red erythrocyte layer.Prepare one liter of Ringer solution containing 125 millimolar sodium chloride, five millimolar potassium chloride, one millimolar magnesium sulfate, 32 millimolar HEPES, five millimolar glucose, and one millimolar calcium chloride. Adjust the pH to 7.4 by adding two microliter drops of one molar sodium hydroxide. To prepare glucose-free Ringer solution, follow the same protocol but do not include glucose in the solution.Wash the erythrocytes twice in Ringer solution by suspending the cell pellet in 1.5 milliliters of Ringer solution, centrifuging at 700 times g for five minutes at room temperature and removing the supernatant. Then make a 0.4%hematocrit by resuspending 40 microliters of the erythrocyte pellet in 9, 960 microliters of glucose-free Ringer solution to reach a final volume of 10 milliliters. Incubate the cell suspension at 37 degrees Celsius for seven days.Pre-incubation of erythrocytes in a glucose-free buffer significantly triggers eryptosis. High eryptosis was obtained after seven days of pre-incubation in the sugar-free buffer. Dissolve one milligram of ionomycin calcium salt in 630 microliters of DMSO to reach a final concentration of two millimolar.Aliquot in 20 milliliters and store at minus 20 degrees Celsius. Take one milliliter of the prepared 0.4%hematocrit and add 0.5 microliters of two millimolar ionomycin to reach a final concentration of one micromolar. Incubate for two hours at 37 degrees Celsius.Use one milliliter of the hematocrit with no ionomycin treatment as a negative control. Centrifuge the ionomycin treated and untreated hematocrits at 700 times g for five minutes at room temperature and remove their supernatants to leave the cell pellets at the bottom of the tubes. Wash the cells three times with Ringer solution by suspending the cell pellets in 1.5 milliliters of Ringer solution, centrifuging at 700 times g for five minutes at room temperature and discarding the supernatants.To measure hemolysis, add one milliliter of the untreated 0.4%hematocrit to a microcentrifuge tube and incubate for two hours at 37 degrees Celsius as the negative control of 0%hemolysis. To prepare the positive control of 100%hemolysis, add one milliliter of the untreated 0.4%hematocrit to a microcentrifuge tube and centrifuge at 700 times g for five minutes at room temperature. Remove the supernatant and add one milliliter of distilled water to the cell pellet to resuspend and incubate for two hours at 37 degrees Celsius.Next, add one milliliter of the ionomycin treated 0.4%hematocrit to a microcentrifuge tube. Centrifuge the untreated cells, treated cells, and the cells in distilled water at 700 times g for five minutes at room temperature. Transfer 200 microliters of the supernatants into each well of a 96-well plate.Measure the absorbance at 541 nanometers using a micro plate reader. Calculate the hemolysis using the equation where A0, A100, and AT are the absorbance of erythrocytes in Ringer solution in water and the absorbance of treated erthyrocytes by ionomycin. Dilute two milliliters of the 5X Annexin-V binding buffer in eight milliliters of PBS to obtain 1X binding buffer.Resuspend the ionomycin-treated and untreated cell pellets in one milliliter of the 1X binding buffer. Take 235 microliters of the cell suspensions in the binding buffer and add 15 microliters of Annexin-V Alexa Fluor 488 conjugate in a microcentrifuge tube. Incubate the cells at room temperature for 20 minutes in a dark place.Centrifuge at 700 times g for five minutes at room temperature. Remove the supernatant. Wash the cells twice with 1X binding buffer by suspending the cell pellet in 1.5 milliliters of the binding buffer and centrifuging at 700 times g for five minutes at room temperature.Remove the supernatant and resuspend the cell pellets in 250 microliters of 1X binding buffer for flow cytometry measurement. Now transfer 200 microliters of the Annexin-V stained erythrocytes to one milliliter round bottom polystyrene tubes compatible with flow cytometry. Log in to the flow cytometry software and click on the new experiment button.Click on the new tube button. Select the global sheet and choose the apply analysis to measure the fluorescence intensity with an excitation wavelength of 488 nanometers and an emission wavelength of 530 nanometers. Set number of cells to 20, 000 to be collected for fluorescence activated cell sorting analysis.Select the desired tube and click on the load button. Click on record button for forward scatter and side scatter measurement. Repeat for all samples.Right click on the specimen button and click on apply batch analysis to generate the result file. Right click on specimen button and click on generate FSC files. In this protocol, treatment of erythrocytes with one micromolar ionomycin and Ringer solution for two hours was enough to induce eryptosis as evidenced by successful labeling with Annexin-V Fluor 488 conjugate and quantification by FACS analysis.Higher concentrations of ionomycin at five and 10 micromolar resulted in a slight increase in eryptosis. However, such concentrations also enhanced hemolysis. Incubation of erythrocytes in ionomycin and Ringer solution for as little as 30 minutes was enough to induce eryptosis.Increased incubation time increased the level of eryptosis for up to two hours. However, further incubation time resulted in a slight decrease in the level of eryptosis. The higher value of hemolysis after 180 minutes explains the reduction in eryptosis after the same amount of incubation as less viable cells existed upon 180 minutes of treatment with ionomycin.Erythrocytes with ionomycin treatment showed a bright fluorescence signal to the binding of Annexin-V to phosphatidyl serine in the outer leaflet. In contrast, cells with no treatment showed a very weak fluorescence signal indicating very low eryptosis. Pre-incubation in a glucose-free buffer is an important trigger for induction of eryptosis.Since eryptosis is observed in a wide range of diseases, the experiments following this protocol are field specific. In our lab, we are interested in examining the effects of eryptosis on membrane biophysical properties and membrane interactions with nanomaterials. Eryptosis is associated with a large number of diseases including diabetes, sickle cell anemia, and thalassemia.Having a reproducible protocol for inducing eryptosis can help researchers in any of these fields to investigate further scientific questions specific to each field.

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