Staurosporine restores signaling and inhibits interleukin‐8‐induced chemotactic desensitization

Abstract

Interleukin 8 (IL-8) is a chemotactic cytokine (chemokine) that plays a key role in the accumulation and activation of neutrophils at inflammatory sites. In this report we demonstrate that homologous chemotactic desensitization occurs upon pretreatment of neutrophils with IL-8 or N-formyl-methionyl-leucyl-phenylalanine (FMLP) and results in the inhibition of neutrophil chemotaxis upon subsequent challenge with the same ligand. This homologous chemotactic desensitization could be prevented by pretreating the neutrophils with the protein kinase inhibitor staurosporine, indicating that protein kinases may play an essential role. The attenuation of homologous desensitization by staurosporine restored chemotaxis but was not associated with a change in IL-8 receptor expression, affinity or the rate of ligand internalization, indicating that homologous desensitization does not alter ligand-receptor interaction. Using two-dimensional analysis we have shown that IL-8 induced a rapid serine/threonine phosphorylation of a number of neutrophil substrates the most prominent being phosphoprotein 39 (pp39), extracellular signal-related kinase-1, pp55 and pp66. Prior desensitization of neutrophils with IL-8 blocked all subsequent phosphorylation upon rechallenge with IL-8. However, the desensitization was specific for IL-8 since normal phosphorylation of identical substrates was observed in response to FMLP. When neutrophils were pretreated with staurosporine, prior to desensitization, phosphorylation of pp39 was observed upon restimulation with IL-8. Further study revealed that pp55 and pp66 were not phosphorylated in the presence of staurosporine. Thus, homologous desensitization of neutrophils in response to IL-8 does not result from changes in receptor expression, but rather from a staurosporine-sensitive inactivation of subsequent signal transduction. This desensitization is selective since the cells are able to respond to other ligands.

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

“…Upon stimulation of the neutrophils with IL-8, its receptors become desensitized and are less susceptible to subsequent restimulation with IL-8. Desensitization results in a decreased migration and phosphorylation of IL-8 receptor targets [50]. A recent study has suggested that in MDS patients, serum levels of IL-8 are elevated [51].…”

The Phosphatidyl Inositol 3 Kinase-Glycogen Synthase Kinase 3β Pathway Mediates Bilobalide-Induced Reduction in Amyloid β-Peptide

“…Cells were treated with 10 lM BB for 12 h. In some cases, to test if the effects of BB on APP processing were associated with modulation of the PI3K pathway, LY294002 (10 lM) was also added to the medium 30 min prior to the addition of BB [8,12,15]. To test whether GSK3b, a downstream target of the PI3K pathway, was involved in BB regulation of APP processing, cells were treated with 30 lM SB 415286, a known GSK3 inhibitor, for 12 h. In all experiments, an equivalent volume of vehicle was added to control cultures.…”

Relationship between interleukin-8 and neutrophil adhesion molecules in rheumatoid arthritis

“…This could be explained by prior desensitisation of the peripheral blood neutrophils with IL-8 [5,6]. Since serum IL-8 was not increased, it can be speculated that the concentration of IL-8 produced by activated endothelium [16] in the synovial tissue was high enough to desensitise the passing neutrophils.…”

“…IL-8 stimulation of neutrophils was performed to examine whether homologous desensitisation for IL-8 was present, as has been reported to occur in vitro [5,6]. …”