Roles of the NFκB and glutathione pathways in mature human erythrocytes

Anucleated erythrocytes were long considered as oxygen-transporting cells with limited regulatory functions. Components of different nuclear signaling pathways have not been investigated in those cells, yet. Surprisingly, we repeatedly found significant amounts of transcription factors in purified erythrocyte preparations, i.e. nuclear factor kappa B (NF kappa B), and major components of the canonical NF kappa B signaling pathway. To investigate the functional role of NF kappa B signaling, the effects of the preclinical compounds Bay 11-7082 and parthenolide on the survival of highly purified erythrocytes were investigated. Interestingly, both inhibitors of the NF kappa B pathway triggered erythrocyte programmed cell death as demonstrated by enhanced phospholipid scrambling (phosphatidylserine exposure) and cell shrinkage. Anucleated erythrocytes are an ideal cellular model allowing the study of nongenomic mechanisms contributing to suicidal cell death. As NF kappa B inhibitors might also interfere with the anti-oxidative defense systems of the cell, we measured the levels of reduced glutathione (GSH) after challenge with the inhibitors. Indeed, incubation of erythrocytes with Bay 11-7082 clearly decreased erythrocyte GSH levels. In conclusion, the pharmacological inhibitors of the NF kappa B pathway Bay 11-7082 and parthenolide interfere with the survival of erythrocytes involving mechanisms other than disruption of NF kappa B-dependent gene expression. Besides affecting erythrocyte survival, NF kappa B inhibition and induction of erythrocyte phosphatidylserine exposure may influence blood clotting. Future studies will be aimed at discriminating between NF kappa B-dependent and NF kappa B-independent GSH-mediated effects of Bay 11-7082 and parthenolide on erythrocyte death.