THE EFFECT OF GRANULOCYTE-COLONY-STIMULATING FACTOR (G-CSF) ON THE DEGRANULATION OF SECONDARY GRANULE PROTEINS FROM HUMAN NEUTROPHILS IN-VIVO MAY BE INDIRECT

Granulocyte colony-stimulating factor (G-CSF) was administered at a do se of 7.5 or 10 mu g/kg s.c. once daily for 6 d (days 1-6) to two grou ps consisting of eight and six healthy volunteers. The administration of G-CSF resulted in a rapid decrease in neutrophil counts and serum l evels of the secondary granule protein, human neutrophil lipocalin (HN L) after 30 min, followed by a recovery and gradual increase within 18 0 min. The number of circulating neutrophils and plasma and serum leve ls of neutrophil secondary granule proteins were dramatically elevated on day 2 (1 d after the administration of G-CSF) and stayed so until day 7. The plasma levels of HNL and lactoferrin (LF) showed a bisphasi c pattern with peaks at day 2 and days 5-7, and remained highly elevat ed at day 12. The serum levels of HNL and LF increased rapidly (about 8-fold and 6-fold, respectively) on day 2 and stayed elevated until da y 7, subsequently returning to baseline levels. At day 5, neutorphil r elease induced in vitro by f-MLP was significantly enhanced. The cellu lar contents of HNL and LF were reduced to about 50% of levels before G-CSF administration at day 5. The release of lactoferrin and HNL, hut not of myeloperoxidase (MPO), was slightly enhanced after preincubati on of isolated normal neutrophils with G-CSF in vitro, but no obvious release of these proteins was observed with G-CSF alone, The administr ation of G-CSF resulted in a dramatic increase In the alkaline phospha tase (AP) activity in the plasma membrane, with maximal activity occur ring at day 5, Furthermore, during administration of G-CSF, TNF-alpha in plasma increased about 25-fold, TNF-alpha started to rise at day 2 and peaked al. day 6. After discontinuation of G-CSF the levels of TNF -alpha gradually decreased, The elevated levels of TNF-alpha (tumour n ecrosis factor-alpha were temporally correlated to tile other signs of neutrophil activation, GM-CSF and IL-8, however, were not detected in plasma. Our data suggest that G-CSF affects the neutrophils not only directly but also indirectly by the induction of the production of oth er cytokines such as TNF-alpha.