Impaired interleukin-8- and GROα-induced phosphorylation of extracellular signal-regulated kinase result in decreased migration of neutrophils from patients with myelodysplasia

Patients with myelodysplasia suffer from recurrent bacterial infections as a result of differentiation defects of the myeloid lineage and a disturbed functioning of neutrophilic granulocytes. Important physiological activators of neutrophils are the cytokines interleukin-8/CXC chemokine ligand 8 (IL-8/CXCL8), which activates CXC chemokine receptor 1 and 2 (CXCR1 and CXCR2), and growth-related oncogene (GRÓ)/CXCL1, which stimulates only CXCR2. In this study, we show that migration toward IL-8/GRÓ gradients is decreased in myelodysplastic syndrome (MDS) neutrophils compared with healthy donors. We investigated the signal transduction pathways involved in IL-8/GRÓ- induced migration and showed that specific inhibitors for extracellular signal-regulated kinase (ERK) 1/2 and phosphatidylinositol-3 kinase (PI-3K) abrogated neutrophil migration toward IL-8/GRÓ. In accordance with these results, we subsequently showed that IL-8/GRÓ-stimulated activation of ERK1/2 was substantially diminished in MDS neutrophils. Activation of the PI-3K downstream target protein kinase B/Akt was disturbed in MDS neutrophils when cells were activated with IL-8 but normal upon GRÓ stimulation. IL-8 stimulation resulted in higher migratory behavior and ERK1/2 activation than GRÓ stimulation, suggesting a greater importance of CXCR1. We then investigated IL-8-induced activation of the small GTPase Rac implicated in ERK1/2-dependent migration and found that it was less efficient in neutrophils from MDS patients compared with healthy donors. In contrast, IL-8 triggered a normal activation of the GTPases Ras and Ral, indicating that the observed defects were not a result of a general disturbance in CXCR1/2 signaling. In conclusion, our results demonstrate a disturbed CXCR1- and CXCR2-induced neutrophil chemotaxis in MDS patients, which might be the consequence of decreased Rac-ERK1/2 and PI-3K activation within these cells.