The NFκB Pathway Inhibitors Bay 11-7082 and Parthenolide Induce Programmed Cell Death in Anucleated Erythrocytes

The preclinical compounds Bay 11-7082 and parthenolide trigger apoptosis, an effect contributing to their antiinflammatory action. The substances interfere with the activation and nuclear translocation of nuclear factor NF kappa B, by inhibiting NF kappa B directly (parthenolide) or by interfering with the inactivation of the NF kappa B inhibitory protein I kappa B-alpha (Bay 11-7082). Beyond that, the substances may be effective in part by nongenomic effects. Similar to apoptosis of nucleated cells, erythrocytes may undergo apoptosis-like cell death (eryptosis) characterized by cell membrane scrambling with phosphatidylserine exposure, and cell shrinkage. Thus, erythrocytes allow the study of nongenomic mechanisms contributing to suicidal cell death, e.g. Ca2+ leakage or glutathione depletion. The present study utilized Western blotting to search for NF kappa B and I kappa B-alpha expression in erythrocytes, FACS analysis to determine cytosolic Ca2+ (Fluo3 fluorescence), phosphatidylserine exposure (annexin V binding), and cell volume (forward scatter), as well as an enzymatic method to determine glutathione levels. As a result, both NF kappa B and I kappa B-alpha are expressed in erythrocytes. Targeting the NF kappa B pathway by Bay 11-7082 (IC50 approximate to, 10 mu M) and parthenolide (IC50 approximate to 30 mu M) triggered suicidal erythrocyte death as shown by annexin V binding and decrease of forward scatter. Bay 11-7082 treatment further increased intracellular Ca2+ and led to depletion of reduced glutathione. The effects of Bay 11-7082 and parthenolide on annexin V binding could be fully reversed by the antioxidant N-acetylcysteine. In conclusion, the pharmacological inhibitors of NF kappa B, Bay 11-7082 and parthenolide, interfere with the survival of erythrocytes involving mechanisms other than disruption of NF kappa B-dependent gene expression. Copyright (C) 2011 S. Karger AG, Basel