Erythropoietin-mediated decrease of the redox-sensitive transcription factor NF-κB is inversely correlated with the hemoglobin level

The aim of this study was to determine the effect of rh-EPO on the redox-sensitive transcription factor (NF-κB) in vivo and in vitro. Ten patients (7 female, 3 male), mean age 69.2 ± 11 years, with end-stage renal failure and anemia prior to initiation of regular hemodialysis were enrolled and divided into 2 groups (group A "good responder", 7 patients and group B "poor responder", 3 patients) in accordance to the response to rh-EPO therapy. Nuclear binding activity of NF-κB was determined in ex vivo isolated mononuclear cells before, 4 and 8 weeks after onset of regular hemodialysis and rh-EPO therapy by electrophoretic mobility shift assays (EMSA). In group A, a reduction of NF-κB binding activity from 100% to 56 ± 6% was observed within the first four weeks of rh-EPO treatment, while mean hemoglobin rose from 8.2 ± 0.4 g/d1 to 11.1 ± 0.2 g/d1. However, this effect was abrogated after another 4 weeks of treatment when NF-κB signal increased back to 85.2 ± 10.6% despite consistent mean hemoglobin level of 11.3 ± 0.4 g/d1. Group B demonstrated a slight increase of NF-κB signal from 100% to 129 ± 18.5%, while mean hemoglobin only moderately rose from 7.6 ± 0.3 g/d1 to 8.3 ± 0.1 g/d1 within the first 4 weeks, and it further rose to 180 ± 45% after 8 weeks of treatment, while mean hemoglobin (9.5 ± 0.1 g/d1) remained low. The NF-κB binding activity differed significantly when comparing both groups (p = 0. 007). Binding activity of Oct-1, serving as control, did not change notably in either group (p = 0.34). In vitro studies showed that rh-EPO did not directly affect NF-κB binding activity in THP-1 cells. However, coincubation of THP-1 cells with erythrocytes led to a reduction of NF-κB binding activity only in THP-1 cells with a hemoglobin level adjusted to 11 g/dI compared to 8 g/d1 in the presence of rh-EPO. In vivo and in vitro data implicate a complex interaction between rh-EPO, stimulated RBC and the redox-sensitive transcription factor NF-κB in mononuclear cells.