Stimulation of Erythrocyte Cell Membrane Scrambling by Adarotene.

Original Paper

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Department of Internal Medicine III, University of Tuebingen, Gmelinstr. 5, 72076 Tuebingen (Germany)

Tel. +49 7071 29-72194, Fax +49 7071 29-5618, E-Mail florian.lang@uni-tuebingen.de Florian Lang

Stimulation of Erythrocyte Cell Membrane

Scrambling by Adarotene

Morena Mischitelli

_{Mohamed Jemaà}

_{Myriam Fezai}

_{Mustafa Almasry}

Caterina Faggio

_{Florian Lang}

a_{Department of Internal Medicine III, Eberhard-Karls-University of Tuebingen, Tuebingen, Germany;} b_{Department of Chemical, Biological, Pharmaceutical and Environmental Sciences-University of Messina} Viale Ferdinando Stagno d'Alcontres, S. Agata-Messina, Italy; c_{Department of Molecular Medicine II,} Heinrich Heine University Duesseldorf, Duesseldorf, Germany

Key Words

Phosphatidylserine • Cell volume • Eryptosis • Calcium • Ceramide

Abstract

Background/Aims: The atypical retinoid E23-(40-hydroxyl-30-adamantylbiphenyl-4-yl)

acrylic acid (ST1926, adarotene) is used in the treatment of malignancy. The effect of ST1926

is at least in part due to stimulation of apoptosis. Similar to apoptosis of nucleated cells,

erythrocytes may enter eryptosis, the suicidal death of erythrocytes. Hallmarks of eryptosis

include cell shrinkage and cell membrane scrambling with phosphatidylserine translocation

to the erythrocyte surface. Signaling involved in the stimulation of eryptosis includes

increase of cytosolic Ca

_{activity ([Ca}

_]

i

), oxidative stress and ceramide. The present study

explored, whether adarotene induces eryptosis and, if so, to test for the involvement of Ca

entry, oxidative stress and ceramide. Methods: Flow cytometry was employed to estimate

phosphatidylserine exposure at the cell surface from annexin-V-binding, cell volume from

forward scatter, [Ca

_]

i

from Fluo3-fluorescence, reactive oxygen species (ROS) formation

from DCFDA dependent fluorescence, and ceramide abundance utilizing specific antibodies.

Results: A 48 hours exposure of human erythrocytes to adarotene (9 µM) significantly increased

the percentage of annexin-V-binding cells, an effect paralleled by significant decrease of

forward scatter, as well as significant increase of Fluo3-fluorescence, DCFDA fluorescence, and

ceramide abundance. The effect of adarotene (9 µM) on annexin-V-binding was significantly

blunted but not abolished by removal of extracellular Ca

_{. Conclusions: Adarotene stimulates}

phospholipid scrambling of the erythrocyte cell membrane, an effect paralleled by and at least

in part due to Ca

_{entry, oxidative stress and ceramide.}

Introduction

The atypical retinoid E23-(40-hydroxyl-30-adamantylbiphenyl-4-yl) acrylic acid

(ST1926, adarotene) counteracts growth of several tumor cells [1, 2], including

rhabdomyo-sarcoma [3], neuroblastoma [4, 5], ovarian cancer [6-9], teratocarcinoma [10], chronic

my-eloid leukemia [11], acute mymy-eloid leukaemia [12, 13], and adult T-cell leukemia/lymphoma

[14]. ST1926 is at least in part effective by inducing apoptosis [1, 9, 13, 15].

Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal

death of erythrocytes [16]. The hallmark of eryptosis is cell membrane scrambling with

phosphatidylserine translocation to the cell surface [17]. Stimulators of eryptosis include

increase of cytosolic Ca

_{activity ([Ca}

_]

i

) [17], ceramide [18], oxidative stress [17] and

energy depletion [17]. Signaling of eryptosis may further involve the G-protein Galphai2 [19],

caspases [17, 20, 21], as well as activation of casein kinase 1α [17], Janus-activated kinase

JAK3 [17], protein kinase C [17], and p38 kinase [17]. Kinases inhibiting eryptosis include

AMP activated kinase AMPK [17], cGMP-dependent protein kinase [17], PAK2 kinase [17],

mitogen and stress activated kinase MSK1/2 [22], and sorafenib/sunitinib sensitive kinases

[17]. Eryptosis could be triggered by diverse xenobiotics [17, 23-75], and enhanced eryptosis

is observed in several clinical conditions including iron deficiency [17], dehydration [76],

hyperphosphatemia [77], hepatic failure [78], malignancy [79, 80], chronic kidney disease

(CKD) [81-85], hemolytic-uremic syndrome [86], arteriitis [87], diabetes [88], hepatic failure

[43], sepsis [89], sickle-cell disease [17], beta-thalassemia [17], Hb-C and G6PD-deficiency

[17], Wilsons disease [90] as well as advanced age [91]. Eryptosis further increases following

storage for transfusion [92].

The present study tested, whether adarotene is capable to stimulate eryptosis. To this

end, human erythrocytes were treated with adarotene and phosphatidylserine abundance

at the erythrocyte surface, erythrocyte volume, [Ca

_]

i

, and ceramide determined by flow

cytometry.

Materials and Methods

Erythrocytes, solutions and chemicals

Fresh Li-Heparin-anticoagulated blood samples were kindly provided by the blood bank of the University of Tübingen. The study is approved by the ethics committee of the University of Tübingen (184/2003 V). The blood was centrifuged at 120 g for 20 min at 21 °C and the platelets and leukocytes-containing supernatant was disposed. Erythrocytes were incubated in vitro at a hematocrit of 0.4% in Ringer solution containing (in mM) 125 NaCl, 5 KCl, 1 MgSO₄, 32 N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (HEPES; pH 7.4), 5 glucose, 1 CaCl₂,at 37°C for 48 hours. Where indicated, erythrocytes were exposed for 48 hours to adarotene (MedChem Express, Princeton, USA), or CaCl₂ was removed and 1 mM EGTA added.

Annexin-V-binding and forward scatter

After incubation under the respective experimental condition, a 150 µl cell suspension was washed in Ringer solution containing 5 mM CaCl₂ and then stained with Annexin-V-FITC (1:200 dilution; ImmunoTools, Friesoythe, Germany) in this solution at 37°C for 15 min under protection from light. The annexin-V-abundance at the erythrocyte surface was subsequently determined on a FACS Calibur (BD, Heidelberg, Germany). Annexin-V-binding was measured with an excitation wavelength of 488 nm and an emission wavelength of 530 nm. A marker (M1) was placed to set an arbitrary threshold between annexin-V-binding cells and control cells. The same threshold was used for untreated and adarotene treated erythrocytes. A dot plot of forward scatter (FSC) vs. side scatter (SSC) was set to linear scale for both parameters. The threshold of forward scatter was set at the default value of “52”.

Intracellular Ca2+

After incubation, erythrocytes were washed in Ringer solution and loaded with Fluo-3/AM (Biotium, Hayward, USA) in Ringer solution containing 5 mM CaCl₂ and 5 µM Fluo-3/AM. The cells were incubated at 37°C for 30 min. Ca2+_{-dependent fluorescence intensity was measured with an excitation wavelength of 488} nm and an emission wavelength of 530 nm on a FACS Calibur.

Reactive oxygen species (ROS)

Oxidative stress was estimated utilizing 2’,7’-dichlorodihydrofluorescein diacetate (DCFDA). After incubation, a 150 µl suspension of erythrocytes was washed in Ringer solution and stained with DCFDA (Sigma, Schnelldorf, Germany) in Ringer solution containing DCFDA at a final concentration of 10 µM. Erythrocytes were incubated at 37°C for 30 min in the dark and washed two times in Ringer solution. The DCFDA-loaded erythrocytes were resuspended in 200 µl Ringer solution and ROS-dependent fluorescence intensity was measured at an excitation wavelength of 488 nm and an emission wavelength of 530 nm on a FACS Calibur (BD).

Ceramide abundance

For the determination of ceramide, a monoclonal antibody-based assay was used. To this end, cells were stained for 1 hour at 37°C with 1 µg/ml anti ceramide antibody (clone MID 15B4, Alexis, Grünberg, Germany) in PBS containing 0.1% bovine serum albumin (BSA) at a dilution of 1:10. The samples were washed twice with PBS-BSA. The cells were stained for 30 minutes with polyclonal fluorescein isothiocyanate (FITC) conjugated goat anti-mouse IgG and IgM specific antibody (Pharmingen, Hamburg, Germany) diluted 1:50 in PBS-BSA. Unbound secondary antibody was removed by repeated washing with PBS-BSA. The samples were analyzed by flow cytometric analysis with an excitation wavelength of 488 nm and an emission wavelength of 530 nm. As a control, secondary antibody alone was used.

Statistics

Data are expressed as arithmetic means ± SEM. As indicated in the figure legends, statistical analysis was made using ANOVA with Tukey’s test as post-test and t test as appropriate. n denotes the number of different erythrocyte specimens studied. Since different erythrocyte specimens used in distinct experiments are differently susceptible to triggers of eryptosis, the same erythrocyte specimens have been used for control and experimental conditions.

Results

The present study explored the putative effect of adarotene on eryptosis, the suicidal

erythrocyte death.

In a first series of experiments, erythrocyte volume was estimated from forward scatter

which was determined utilizing flow cytometry. Prior to measurements, the erythrocytes

were incubated for 48 hours in Ringer solution without or with adarotene (3 – 9 µM). As

illustrated in Fig. 1, adarotene did not significantly modify the average erythrocyte forward

scatter.

In a second series of experiments, phosphatidylserine exposing erythrocytes

were identified utilizing annexin-V-binding, as determined by flow cytometry. Prior to

measurements, the erythrocytes were again incubated for 48 hours in Ringer solution

Fig. 1. Effect of Adarotene on

eryth-rocyte forward scatter. A. Original his-tograms of forward scatter of erythro-cytes following exposure for 48 hours to Ringer solution without (grey area) and with (black line) presence of 9 µM Adarotene. B. Arithmetic means ± SEM (n = 10) of the erythrocyte forward scatter (FSC) following incubation for 48 hours to Ringer solution without (white bar) or with (black bars) Adar-otene (3 - 9 µM) or solvant DMSO alone (grey bar).

without or with adarotene (3 – 9 µM). As illustrated in Fig. 2, a 48 hours exposure to adarotene

significantly increased the percentage of phosphatidylserine exposing erythrocytes, an

effect reaching statistical significance at 6 µM adarotene. Further experiments addressed

the signaling involved in the stimulation of cell membrane scrambling.

Fluo3 fluorescence was taken as a measure of cytosolic Ca

_{activity ([Ca}

_]

i

). Prior

to measurements, the erythrocytes were again incubated for 48 hours in Ringer solution

without or with adarotene (3 – 9 µM). As illustrated in Fig. 3A,B, a 48 hours incubation

with adarotene significantly increased Fluo3 fluorescence, an effect reaching statistical

significance at 6 µM adarotene Fig. 4C).

A next series of experiments explored whether the adarotene-induced translocation

of phosphatidylserine required entry of extracellular Ca

_{. To this end, erythrocytes were}

incubated for 48 hours in the absence or presence of 9 µM adarotene in the presence or

nominal absence of extracellular Ca

_{. As illustrated in Fig. 4, removal of extracellular Ca}

significantly blunted the effect of adarotene on annexin-V-binding. However, even in the

absence of extracellular Ca

_,

_{adarotene significantly decreased the percentage}

annexin-V-binding erythrocytes. Thus, adarotene-induced cell membrane scrambling was in part but

not completely due to entry of extracellular Ca

_.

Fig. 2. Effect of Adarotene on

phosphatidylserine exposure. A. Original histogram of annexin-V-binding of erythrocytes following exposure for 48 hours to Ringer solution without (grey area) and with (black line) presence of 9 µM Adarotene. B. Arithmetic means ± SEM (n = 10) of erythrocyte annexin-V-binding following incu-bation for 48 hours to Ringer so-lution without (white bar) or with

Fig. 3. Effect of Adarotene on cytosolic

Ca2+ _{activity. A. Original histograms of} Fluo-3 fluorescence in erythrocytes fol-lowing exposure for 48 hours to Ringer solution without (grey area) and with (black line) presence of 9 µM Adaro-tene. B. Arithmetic means ± SEM (n = 10) of Fluo-3 fluorescence in erythro-cytes following incubation for 48 hours to Ringer solution without (white bar) or with (black bars) Adarotene (3 - 9 µM) or solvant DMSO alone (grey bar). C. Arithmetic means ± SEM of the per-centage of erythrocytes with enhanced Fluo-3 fluorescence following incuba-tion for 48 hours to Ringer soluincuba-tion without (white bar) or with (black bars) Adarotene (3 - 9 µM) or solvant DMSO alone (grey bar). ***(p<0.001) indicates significant difference from the absence of Adarotene (ANOVA).

(black bars) Adarotene (3 - 9 µM) or solvant DMSO alone (grey bar). ***(p<0.001) indicates significant dif-ference from the absence of Adarotene (ANOVA).

Further triggers of eryptosis include oxidative stress. Thus, the abundance of reactive

oxygen species was quantified utilizing 2’,7’-dichlorodihydrofluorescein diacetate (DCFDA)

fluorescence. As shown in Fig. 5, a 48 hours exposure to 9 µM adarotene significantly

increased the DCFDA fluorescence.

Cell membrane scrambling could further be triggered by ceramide. Ceramide abundance

at the erythrocyte surface was thus quantified utilizing specific antibodies. As illustrated

in Fig. 6, a 48 hours exposure to 10 µM adarotene significantly increased the ceramide

abundance.

Discussion

The present study reveals that adarotene (ST1926) stimulates erythrocyte cell membrane

scrambling with phosphatidylserine translocation to the erythrocyte surface. The adarotene

concentration required for stimulation of cell membrane scrambling was in the range of

concentrations encountered in vivo [3].

The effect of adarotene on cell membrane scrambling was paralleled by a significant

increase of average Fluo3 fluorescence indicating that adarotene increased cytosolic Ca

activity ([Ca

_]

i

). Moreover, the effect of adarotene on cell membrane scrambling was in part

-in-duced phosphatidylserine exposure. A,B. Original histogram of annexin-V-binding of erythrocytes following exposure for 48 hours to Ringer solution without (grey area) and with (black line) Adarotene (9 µM) in the presence (A) and absence (B) of extra-cellular Ca2+_{. C. Arithmetic means ± SEM (n} = 10) of annexin-V-binding of erythrocytes after a 48 hours treatment with Ringer so-lution without (white bars) or with (black bars) Adarotene (9 µM) in the presence (left bars, +Ca2+_{) and absence (right bars, -Ca}2+₎ of Ca2+_{. ***(p<0.001) indicates significant} difference from the absence of Adarotene, ###(p<0.001) indicates significant differ-ence from the presdiffer-ence of Ca2+ _(ANOVA).

Fig. 5. Effect of Adarotene on reactive oxygen

species. A. Original histograms of DCFDA flu-orescence in erythrocytes following exposure for 48 hours to Ringer solution without (grey area) and with (black line) presence of 9 µM Adarotene. B. Arithmetic means ± SEM (n = 10) of DCFDA fluorescence in erythrocytes following incubation for 48 hours to Ringer solution without (white bar) or with (black bar) Adarotene (9 µM). ***(p<0.001) indi-cates significant difference from the absence of Adarotene (ANOVA).

dependent on Ca

_{entry from the extracellular space and was significantly decreased by removal}

of extracellular Ca

_{. However, adarotene treatment significantly triggered erythrocyte cell}

membrane scrambling even in the nominal absence of extracellular Ca

_{. Thus, some additional}

mechanism must have contributed to the stimulation of cell membrane scrambling following

treatment of erythrocytes with adarotene. As a matter of fact, adarotene treatment increased

the abundance of reactive oxygen species and of ceramide, which are both known to stimulate

cell membrane scrambling [17].

Adarotene treatment did not significantly modify average forward scatter and did not

significantly modifiy the percentage of shrunken and swollen cells. An increase of [Ca

_]

i

were expected to activate Ca

_{sensitive K}

_{channels with subsequent K}

_{exit, cell membrane}

hyperpolarization, Cl

_{exit and thus cellular loss of KCl with water [17]. The reason, why}

adarotene failed to trigger cell shrinkage, remained elusive.

Phosphatidylserine exposing erythrocytes are rapidly cleared from circulating blood

and stimulation of cell membrane scrambling may thus result in anemia to the extent that

the loss of erythrocytes outcasts the formation of new erythrocytes by erythropoiesis [17].

Phosphatidylserine exposing erythrocytes may further impair microcirculation [18,

93-97] by adherence to the vascular wall [98], stimulation of blood clotting and triggering of

thrombosis [93, 99, 100].

In conclusion, adarotene triggers cell membrane scrambling, an effect involving Ca

_entry

and ceramide.

Acknowledgements

The authors acknowledge the meticulous preparation of the manuscript by Tanja Loch. The

study was supported by the Deutsche Forschungsgemeinschaft and Open Access Publishing

Fund of Tuebingen University.

Disclosure Statement

All authors declare that there are no conflicts of interest.

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45 Officioso A, Alzoubi K, Lang F, Manna C: Hydroxytyrosol inhibits phosphatidylserine exposure and suicidal death induced by mercury in human erythrocytes: Possible involvement of the glutathione pathway. Food Chem Toxicol 2016;89:47-53.

46 Officioso A, Manna C, Alzoubi K, Lang F: Bromfenvinphos induced suicidal death of human erythrocytes. Pestic Biochem Physiol 2016;126:58-63.

47 Qadri SM, Donkor DA, Bhakta V, Eltringham-Smith LJ, Dwivedi DJ, Moore JC, Pepler L, Ivetic N, Nazi I, Fox-Robichaud AE, Liaw PC, Sheffield WP: Phosphatidylserine externalization and procoagulant activation of erythrocytes induced by Pseudomonas aeruginosa virulence factor pyocyanin. J Cell Mol Med 2016;10.1111/jcmm.12778

48 Zierle J, Bissinger R, Bouguerra G, Abbes S, Lang F: Triggering of Suicidal Erythrocyte Death by Regorafenib. Cell Physiol Biochem 2016;38:160-172.

49 Pagano M, Faggio C: The use of erythrocyte fragility to assess xenobiotic cytotoxicity. Cell Biochem Funct 2015;33:351-355.

50 Al Mamun Bhuyan A, Bissinger R, Stockinger K, Lang F: Stimulation of Suicidal Erythrocyte Death by Tafenoquine. Cell Physiol Biochem 2016;39:2464-2476.

51 Al Mamun Bhuyan A, Signoretto E, Bissinger R, Lang F: Enhanced Eryptosis Following Exposure to Dolutegravir. Cell Physiol Biochem 2016;39:639-650.

52 Al Mamun Bhuyan A, Signoretto E, Lang F: Triggering of Suicidal Erythrocyte Death by Psammaplin A. Cell Physiol Biochem 2016;39:908-918.

53 Almasry M, Jemaa M, Mischitelli M, Faggio C, Lang F: Stimulation of Suicidal Erythrocyte Death by Phosphatase Inhibitor Calyculin A. Cell Physiol Biochem 2016;40:163-171.

54 Bissinger R, Bhuyan AA, Signoretto E, Lang F: Stimulating Effect of Elvitegravir on Suicidal Erythrocyte Death. Cell Physiol Biochem 2016;38:1111-1120.

55 Egler J, Zierle J, Lang F: Stimulating Effect of Manumycin A on Suicidal Erythrocyte Death. Cell Physiol Biochem 2016;38:1147-1156.

56 Jemaa M, Mischitelli M, Fezai M, Almasry M, Faggio C, Lang F: Stimulation of Suicidal Erythrocyte Death by the CDC25 Inhibitor NSC-95397. Cell Physiol Biochem 2016;40:597-607.

57 Lang E, Pozdeev VI, Gatidis S, Qadri SM, Haussinger D, Kubitz R, Herebian D, Mayatepek E, Lang F, Lang KS, Lang PA: Bile Acid-Induced Suicidal Erythrocyte Death. Cell Physiol Biochem 2016;38:1500-1509.

58 Mischitelli M, Jemaa M, Almasry M, Faggio C, Lang F: Stimulation of Erythrocyte Cell Membrane Scrambling by Quinine. Cell Physiol Biochem 2016;40:657-667.

59 Mischitelli M, Jemaa M, Almasry M, Faggio C, Lang F: Stimulation of Suicidal Erythrocyte Death by Rottlerin. Cell Physiol Biochem 2016;40:558-566.

60 Mischitelli M, Jemaa M, Almasry M, Faggio C, Lang F: Triggering of Erythrocyte Cell Membrane Scrambling by Emodin. Cell Physiol Biochem 2016;40:91-103.

61 Mischitelli M, Jemaa M, Almasry M, Faggio C, Lang F: Triggering of Suicidal Erythrocyte Death by Fascaplysin. Cell Physiol Biochem 2016;39:1638-1647.

62 Mischitelli M, Jemaa M, Almasry M, Faggio C, Lang F: Ca2+ Entry, Oxidative Stress, Ceramide and Suicidal Erythrocyte Death Following Diosgenin Treatment. Cell Physiol Biochem 2016;39:1626-1637.

63 Peter T, Bissinger R, Lang F: Stimulation of Eryptosis by Caspofungin. Cell Physiol Biochem 2016;39:939-949.

64 Peter T, Bissinger R, Liu G, Lang F: Anidulafungin-Induced Suicidal Erythrocyte Death. Cell Physiol Biochem 2016;38:2272-2284.

65 Peter T, Bissinger R, Signoretto E, Mack AF, Lang F: Micafungin-Induced Suicidal Erythrocyte Death. Cell Physiol Biochem 2016;39:584-595.

66 Pretorius E, du Plooy JN, Bester J: A Comprehensive Review on Eryptosis. Cell Physiol Biochem 2016;39:1977-2000.

67 Shan F, Yang R, Ji T, Jiao F: Vitamin C Inhibits Aggravated Eryptosis by Hydrogen Peroxide in Glucose-6-Phosphated Dehydrogenase Deficiency. Cell Physiol Biochem 2016;39:1453-1462.

68 Signoretto E, Bissinger R, Castagna M, Lang F: Stimulation of Eryptosis by Combretastatin A4 Phosphate Disodium (CA4P). Cell Physiol Biochem 2016;38:969-981.

69 Signoretto E, Castagna M, Al Mamun Bhuyan A, Lang F: Stimulating Effect of Terfenadine on Erythrocyte Cell Membrane Scrambling. Cell Physiol Biochem 2016;38:1425-1434.

70 Signoretto E, Castagna M, Lang F: Stimulation of Eryptosis, the Suicidal Erythrocyte Death by Piceatannol. Cell Physiol Biochem 2016;38:2300-2310.

71 Signoretto E, Honisch S, Briglia M, Faggio C, Castagna M, Lang F: Nocodazole Induced Suicidal Death of Human Erythrocytes. Cell Physiol Biochem 2016;38:379-392.

72 Signoretto E, Laufer SA, Lang F: Stimulating Effect of Sclareol on Suicidal Death of Human Erythrocytes. Cell Physiol Biochem 2016;39:554-564.

73 Signoretto E, Zierle J, Bissinger R, Castagna M, Bossi E, Lang F: Triggering of Suicidal Erythrocyte Death by Pazopanib. Cell Physiol Biochem 2016;38:926-938.

74 Wesseling MC, Wagner-Britz L, Huppert H, Hanf B, Hertz L, Nguyen DB, Bernhardt I: Phosphatidylserine Exposure in Human Red Blood Cells Depending on Cell Age. Cell Physiol Biochem 2016;38:1376-1390. 75 Zierle J, Bissinger R, Lang F: Inhibition by Teriflunomide of Erythrocyte Cell Membrane Scrambling

Following Energy Depletion, Oxidative Stress and Ionomycin. Cell Physiol Biochem 2016;39:1877-1890. 76 Abed M, Feger M, Alzoubi K, Pakladok T, Frauenfeld L, Geiger C, Towhid ST, Lang F: Sensitization

of erythrocytes to suicidal erythrocyte death following water deprivation. Kidney Blood Press Res 2013;37:567-578.

77 Voelkl J, Alzoubi K, Mamar AK, Ahmed MS, Abed M, Lang F: Stimulation of suicidal erythrocyte death by increased extracellular phosphate concentrations. Kidney Blood Press Res 2013;38:42-51.

78 Lang E, Gatidis S, Freise NF, Bock H, Kubitz R, Lauermann C, Orth HM, Klindt C, Schuier M, Keitel V, Reich M, Liu G, Schmidt S, Xu HC, Qadri SM, Herebian D, Pandyra AA, Mayatepek E, Gulbins E, Lang F, Haussinger D, Lang KS, Foller M, Lang PA: Conjugated bilirubin triggers anemia by inducing erythrocyte death. Hepatology 2015;61:275-284.

79 Bissinger R, Schumacher C, Qadri SM, Honisch S, Malik A, Gotz F, Kopp HG, Lang F: Enhanced eryptosis contributes to anemia in lung cancer patients. Oncotarget 2016;7:14002-14014.

80 Qadri SM, Mahmud H, Lang E, Gu S, Bobbala D, Zelenak C, Jilani K, Siegfried A, Foller M, Lang F: Enhanced suicidal erythrocyte death in mice carrying a loss-of-function mutation of the adenomatous polyposis coli gene. J Cell Mol Med 2012;16:1085-1093.

81 Abed M, Artunc F, Alzoubi K, Honisch S, Baumann D, Foller M, Lang F: Suicidal erythrocyte death in end-stage renal disease. J Mol Med (Berl) 2014;92:871-879.

82 Ahmed MS, Langer H, Abed M, Voelkl J, Lang F: The uremic toxin acrolein promotes suicidal erythrocyte death. Kidney Blood Press Res 2013;37:158-167.

83 Polak-Jonkisz D, Purzyc L: Ca(2+) influx versus efflux during eryptosis in uremic erythrocytes. Blood Purif 2012;34:209-210; author reply 210.

84 Calderon-Salinas JV, Munoz-Reyes EG, Guerrero-Romero JF, Rodriguez-Moran M, Bracho-Riquelme RL, Carrera-Gracia MA, Quintanar-Escorza MA: Eryptosis and oxidative damage in type 2 diabetic mellitus patients with chronic kidney disease. Mol Cell Biochem 2011;357:171-179.

85 Bissinger R, Artunc F, Qadri SM, Lang F: Reduced Erythrocyte Survival in Uremic Patients Under Hemodialysis or Peritoneal Dialysis. Kidney Blood Press Res 2016;41:966-977.

86 Lang PA, Beringer O, Nicolay JP, Amon O, Kempe DS, Hermle T, Attanasio P, Akel A, Schafer R, Friedrich B, Risler T, Baur M, Olbricht CJ, Zimmerhackl LB, Zipfel PF, Wieder T, Lang F: Suicidal death of erythrocytes in recurrent hemolytic uremic syndrome. J Mol Med (Berl) 2006;84:378-388.

87 Bissinger R, Kempe-Teufel DS, Honisch S, Qadri SM, Randrianarisoa E, Haring HU, Henes J, Lang F: Stimulated Suicidal Erythrocyte Death in Arteritis. Cell Physiol Biochem 2016;39:1068-1077. 88 Nicolay JP, Schneider J, Niemoeller OM, Artunc F, Portero-Otin M, Haik G, Jr., Thornalley PJ, Schleicher

E, Wieder T, Lang F: Stimulation of suicidal erythrocyte death by methylglyoxal. Cell Physiol Biochem 2006;18:223-232.

89 Kempe DS, Akel A, Lang PA, Hermle T, Biswas R, Muresanu J, Friedrich B, Dreischer P, Wolz C, Schumacher U, Peschel A, Gotz F, Doring G, Wieder T, Gulbins E, Lang F: Suicidal erythrocyte death in sepsis. J Mol Med (Berl) 2007;85:273-281.

90 Lang PA, Schenck M, Nicolay JP, Becker JU, Kempe DS, Lupescu A, Koka S, Eisele K, Klarl BA, Rubben H, Schmid KW, Mann K, Hildenbrand S, Hefter H, Huber SM, Wieder T, Erhardt A, Haussinger D, Gulbins E, Lang F: Liver cell death and anemia in Wilson disease involve acid sphingomyelinase and ceramide. Nat Med 2007;13:164-170.

91 Lupescu A, Bissinger R, Goebel T, Salker MS, Alzoubi K, Liu G, Chirigiu L, Mack AF, Qadri SM, Lang F: Enhanced suicidal erythrocyte death contributing to anemia in the elderly. Cell Physiol Biochem 2015;36:773-783.

92 Lang E, Pozdeev VI, Xu HC, Shinde PV, Behnke K, Hamdam JM, Lehnert E, Scharf RE, Lang F, Haussinger D, Lang KS, Lang PA: Storage of Erythrocytes Induces Suicidal Erythrocyte Death. Cell Physiol Biochem 2016;39:668-676.

93 Andrews DA, Low PS: Role of red blood cells in thrombosis. Curr Opin Hematol 1999;6:76-82.

94 Closse C, Dachary-Prigent J, Boisseau MR: Phosphatidylserine-related adhesion of human erythrocytes to vascular endothelium. Br J Haematol 1999;107:300-302.

95 Gallagher PG, Chang SH, Rettig MP, Neely JE, Hillery CA, Smith BD, Low PS: Altered erythrocyte endothelial adherence and membrane phospholipid asymmetry in hereditary hydrocytosis. Blood 2003;101:4625-4627.

96 Pandolfi A, Di Pietro N, Sirolli V, Giardinelli A, Di Silvestre S, Amoroso L, Di Tomo P, Capani F, Consoli A, Bonomini M: Mechanisms of uremic erythrocyte-induced adhesion of human monocytes to cultured endothelial cells. J Cell Physiol 2007;213:699-709.

97 Wood BL, Gibson DF, Tait JF: Increased erythrocyte phosphatidylserine exposure in sickle cell disease: flow-cytometric measurement and clinical associations. Blood 1996;88:1873-1880.

98 Borst O, Abed M, Alesutan I, Towhid ST, Qadri SM, Foller M, Gawaz M, Lang F: Dynamic adhesion of eryptotic erythrocytes to endothelial cells via CXCL16/SR-PSOX. Am J Physiol Cell Physiol 2012;302:C644-C651.

99 Chung SM, Bae ON, Lim KM, Noh JY, Lee MY, Jung YS, Chung JH: Lysophosphatidic acid induces

thrombogenic activity through phosphatidylserine exposure and procoagulant microvesicle generation in human erythrocytes. Arterioscler Thromb Vasc Biol 2007;27:414-421.

100 Zwaal RF, Comfurius P, Bevers EM: Surface exposure of phosphatidylserine in pathological cells. Cell Mol Life Sci 2005;62:971-988.