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

Abstract

The aim of this study was to determine the effect of rh-EPO on the redox-sensitive transcription factor (NF-kappaB) 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-kappaB 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-KB 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/dl to 11.1 +/- 0.2 g/dl. However, this effect was abrogated after another 4 weeks of treatment when NF-kappaB signal increased back to 85.2 +/- 10.6% despite consistent mean hemoglobin level of 11.3 +/- 0.4 g/dl. Group B demonstrated a slight increase of NF-kappaB signal from 100% to 129 +/- 18.5%, while mean hemoglobin only moderately rose from 7.6 +/- 0.3 g/dl to 8.3 +/- 0.1 g/dl 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/dl) remained low. The NF-kappaB 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-KB binding activity in THP-1 cells. However, coincubation of THP-1 cells with erythrocytes led to a reduction of NF-kappaB binding activity only in THP-1 cells with a hemoglobin level adjusted to 11 g/dl compared to 8 g/dl 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-kappaB in mononuclear cells.