Eryptosis as an Underlying Mechanism in Systemic Lupus Erythematosus-Related Anemia

Background/Aims: The neurodegenerative disease Chorea-Acanthocytosis (ChAc) is caused by loss-of-function-mutations of the chorein-encoding gene VPS13A. In ChAc neurons transcript levels and protein abundance of Ca²⁺ release activated channel moiety (CRAC) Orai1 as well as its regulator STIM1/2 are decreased, resulting in blunted store operated Ca²⁺-entry (SOCE) and enhanced suicidal cell death. SOCE is up-regulated and cell death decreased by lithium. The effects of lithium are paralleled by upregulation of serum & glucocorticoid inducible kinase SGK1 and abrogated by pharmacological SGK1 inhibition. In other cell types SGK1 has been shown to be partially effective by upregulation of NFκB, a transcription factor stimulating the expression of Orai1 and STIM. The present study explored whether pharmacological inhibition of NFκB interferes with Orai1/STIM1/2 expression and SOCE and their upregulation by lithium in ChAc neurons. Methods: Cortical neurons were differentiated from induced pluripotent stem cells generated from fibroblasts of ChAc patients and healthy volunteers. Orai1 and STIM1 transcript levels and protein abundance were estimated from qRT-PCR and Western blotting, respectively, cytosolic Ca²⁺-activity ([Ca²⁺]_i) from Fura-2-fluorescence, SOCE from increase of [Ca²⁺]_i following Ca²⁺ re-addition after Ca²⁺-store depletion with sarco-endoplasmatic Ca²⁺-ATPase inhibitor thapsigargin (1µM), as well as CRAC current utilizing whole cell patch clamp recording. Results: Orai1 and STIM1 transcript levels and protein abundance as well as SOCE and CRAC current were significantly enhanced by lithium treatment (2 mM, 24 hours). These effects were reversed by NFκB inhibitor wogonin (50 µM). Conclusion: The stimulation of expression and function of Orai1/STIM1/2 by lithium in ChAc neurons are disrupted by pharmacological NFκB inhibition.

Section: Neuronal Differentiation and Treatment Of Ipscsmentioning

confidence: 99%

Inhibition of Lithium Sensitive Orai1/ STIM1 Expression and Store Operated Ca2+ Entry in Chorea-Acanthocytosis Neurons by NF-κB Inhibitor Wogonin

Sukkar¹,

Hauser²,

Pelzl³

et al. 2018

“…The adherence of eryptotic cells to vascular wall endothelial CXCL16/SR-PSO [61] and the binding of phosphatidylserine-exposing erythrocytes to blood platelets could further stimulate blood clotting and trigger thrombosis [62]. Eryptosis could also be induced by a wide range of xenobiotics [63-74], and enhanced eryptosis is observed in several clinical conditions, such as systemic lupus erythematosus [75], uremia under hemodialysis or peritoneal dialysis [76], pulmonary tumor [77], Parkinson’s disease [78], arteritis [79], hepatic failure [80, 81], tumor-induced anemia [82], vitamin D excess [83], advanced age [84], G6PD deficiency [85], sepsis [86], APC gene mutation and colon carcinoma [87]. Eryptosis can also be triggered by erythrocyte storage [88-90].…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Suicidal Erythrocyte Death by Indirubin-3’-Monoxime

Liu

Jiang

et al. 2018

Self Cite

Background/Aims: Qing Dai is a prized traditional Chinese medicine whose major component, indirubin, and its derivative, indirubin-3’-monoxime (IDM), have inhibitory effects on the growth of many human tumor cells and pronounced anti-leukemic activities. However, the effects of IDM on mature human erythrocytes are unclear. This study aimed to evaluate the potential impact of IDM on erythrocytes and the mechanisms underlying that impact. Methods: Utilizing flow cytometry and confocal laser scanning microscopy, phosphatidylserine exposure at the cell surface was estimated by annexin V-fluorescein isothiocyanate (FITC). The relative cell size, expressed in arbitrary units, was evaluated by forward scatter in a flow cytometer. Fluo-3 fluorescence was used to bewrite changes in cytosolic Ca²⁺ activity, reactive oxygen species (ROS) formation was assessed by 2,7-dichlorodihydrofluorescein diacetate (DCFH-DA) fluorescence, and ceramide abundance was evaluated by FITC-conjugated specific antibodies. Results: The 24-h exposure of human erythrocytes to IDM (12 µM) significantly decreased the percentage of annexin V-binding erythrocytes and the intracellular calcium concentration ([Ca²⁺]_i). IDM (3-12 µM) did not significantly modify the ceramide level or DCFH-DA fluorescence. Energy depletion (removal of glucose for 24 hours) significantly increased annexin V binding and Fluo-3 fluorescence and diminished forward scatter, and these effects were significantly mitigated by IDM (12 µM). Moreover, the Ca²⁺ ionophore ionomycin (1 µM, 60 min) and oxidative stress (30 min exposure to 0.05 mM tert-butyl hydroperoxide, t-BHP) similarly triggered eryptosis, which was also significantly suppressed by IDM. Conclusions: IDM is a novel inhibitor of suicidal erythrocyte death following ionomycin treatment, t-BHP treatment and energy depletion. Thus, IDM may counteract anemia and impairment of microcirculation, at least in part, by inhibition of Ca²⁺ entry into erythrocytes.

“…Several substances inhibit eryptosis [113][114][115][116]. Enhanced eryptosis is observed in diverse clinical conditions including iron deficiency [58], vitamin D excess [117], chronic kidney disease (CKD) [118][119][120][121][122][123], hemolytic-uremic syndrome [124], autoimmune hemolytic anemia [125], diabetes [126], hypertension and dyslipidemia [127], hepatic failure [128], malignancy [129][130][131], arteritis [132], systemic lupus erythematosus [133], sepsis [134,135], malaria [58,136,137], sicklecell disease [58], beta-thalassemia [58], Hb-C and G6PD-deficiency [58], Wilsons disease [134], as well as advanced age [138]. Eryptosis further increases following storage for transfusion [67,68,83,139] and is enhanced in erythrocytes from newborns exposed to oxidative stress [58,140].…”

Section: Introductionmentioning

confidence: 99%

Stimulation of Eryptosis by Afatinib

Bhuyan

Läng

2018

Background/Aims: The epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor afatinib is primarily utilized for the treatment of non-small cell lung carcinoma. The drug is at least partially effective by triggering suicidal tumor cell death. Side effects of afatinib treatment include anemia. At least in theory, afatinib induced anemia could be secondary to stimulation of suicidal erythrocyte death or eryptosis, characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Signaling potentially stimulating eryptosis include increase of cytosolic Ca 2+ activity ([Ca 2+ ] i ), induction of oxidative stress, and increase of ceramide abundance. The present study explored, whether afatinib induces eryptosis and, if so, whether its effect involves Ca 2+ entry, oxidative stress, and/or ceramide. Methods: 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) abundance from DCFDA dependent fluorescence, and ceramide abundance utilizing specific antibodies. Results: A 48 hours exposure of human erythrocytes to afatinib (≥ 4 µg/ml) significantly increased the percentage of annexin-V-binding cells and significantly decreased forward scatter. Afatinib significantly increased Fluo3-fluorescence, DCFDA fluorescence and ceramide abundance. The effect of afatinib on annexin-V-binding and forward scatter was significantly blunted by removal of extracellular Ca 2+ . Conclusions: Afatinib triggers phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to Ca 2+ entry, oxidative stress, and ceramide.