Recombinant human erythropoietin enhances superoxide production by FMLP-stimulated polymorphonuclear leukocytes in hemodialysis patients

Recombinant human erythropoietin (rHuEPO) is a hematopoietic growth factor that has a broad spectrum of action. We have observed the in vivo and in vitro effects of rHuEPO on the superoxide production of circulating polymorphonuclear leukocytes (PMNs) in hemodialysis patients. The PMNs were separated from heparinized blood after dextran sedimentation and Ficoll-Conray centrifugation and stimulated with formyl-methionyl-leucyl-phenylalanine (FMLP), serum-treated zymosan (STZ), or phorbol myristate acetate (PMA). The in vivo study showed that rHuEPO therapy for 12 weeks enhanced the superoxide production by FMLP-stimulated PMNs (P < 0.01). However, no significant changes on superoxide production was found in either STZ- or PMA-stimulated PMNs. Simultaneous measurement of PGE(2) production by PMNs in response to all three stimulants did not show any significant changes after rHuEPO therapy. The direct in vitro effect, of rHuEPO on PMNs showed that rHuEPO does not enhance the superoxide production by nonstimulated PMNs. However, preincubation of rHuEPO enhanced superoxide production from FMLP- and STZ-stimulated PMNs. Our results indicate that rHuEPO enhanced FMLP-stimulated superoxide production of PMNs both in vivo and in vitro in hemodialysis patients, which may be responsible for the increased oxidant stress in hemodialysis patients after rHuEPO therapy.