Age Sensitivity of NFκB Abundance and Programmed Cell Death in Erythrocytes Induced by NFκB Inhibitors

Abstract

Background/Aims: Erythrocytes may enter eryptosis, a suicidal death characterized by cell shrinkage and phosphatidylserine exposure at the erythrocyte outer membrane. Susceptibility to eryptosis is enhanced in aged erythrocytes and stimulated by NFκB-inhibitors Bay 11-7082 and parthenolide. Here we explored whether expression of NFκB and susceptibility to inhibitor-induced eryptosis is sensitive to erythrocyte age. Methods: Human erythrocytes were separated into five fractions, based on age-associated characteristics cell density and volume. NFκB compared to ß-actin protein abundance was estimated by Western blotting and cell volume from forward scatter. Phosphatidylserine exposure was identified using annexin-V binding. Results: NFκB was most abundant in young erythrocytes but virtually absent in aged erythrocytes. A 24h or 48h exposure to Ringer resulted in spontaneous decrease of forward scatter and increase of annexin V binding, effects more pronounced in aged than in young erythrocytes. Both, Bay 11-7082 (20 µM) and parthenolide (100 µM) triggered eryptosis, effects again most pronounced in aged erythrocytes. Conclusion: NFκB protein abundance is lowest and spontaneous eryptosis as well as susceptibility to Bay 11-7082 and parthenolide highest in aged erythrocytes. Thus, inhibition of NFκB signalling alone is not responsible for the stimulation of eryptosis by parthenolide or Bay 11-7082.