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Albumin stimulation of eosinophil migration involves PI3-kinases and is associated with diminished eosinophil CD49d
Maria Lampinen1, Lena Douhan Håkansson, Per Venge
1Asthma Research Centre, University Hospital, Uppsala, Sweden. maria.lampinen@medsci.uu.se
Background:
Albumin is known to induce chemokinesis and facilitate chemotaxis of human granulocytes in the Boyden chamber assay, but its mechanisms of action remain obscure. We have previously found that IL-2 inhibits albumin-stimulated eosinophil migration. The aim of this study was to identify the mechanisms behind the effects of albumin and IL-2 on the migration of human eosinophils.
Methods:
Purified eosinophils were preincubated with inhibitors of signal transduction molecules before incubation with or without albumin and IL-2. The migration assay was performed in a 48-well microchemotaxis chamber. The effect of albumin and IL-2 on cell size and on the surface expression of adhesion molecules was studied with flow cytometry.
Results:
Albumin-stimulated migration was inhibited by the PI3-kinase inhibitors wortmannin and LY-294002, but not by the PKC inhibitor RO-31-8220. IL-2 had no effect after preincubation with wortmannin or LY-294002. In contrast, the inhibitory effect of IL-2 remained after preincubation with RO-31-8220. Albumin increased the cell size as measured by forward scatter, and the expression of CD49d and CD49f decreased after incubation with albumin. IL-2 affected neither the expression of adhesion molecules nor the forward scatter.
Conclusions:
The stimulation of eosinophil migration by albumin is mediated by PI3-kinase, and the increase in cell size caused by albumin indicates activation of the cells. Decreased expression of CD49d and CD49f by albumin may diminish the adhesiveness of the cells, which in turn may facilitate migration. These are novel findings that indicate an active role for albumin in eosinophil migration.
Insights
Albumin enhances eosinophil migration via PI3-kinase signaling, increasing cell size and reducing adhesion molecule expression. Interleukin-2
Area of Science:
- Immunology
- Cell Biology
Background:
- Albumin is known to influence granulocyte migration, but its precise mechanisms are unclear.
- Interleukin-2 (IL-2) has been observed to inhibit albumin-induced eosinophil migration.
Purpose of the Study:
- To elucidate the underlying mechanisms of albumin and IL-2 effects on human eosinophil migration.
Main Methods:
- Eosinophils were preincubated with signal transduction inhibitors before exposure to albumin and IL-2.
- Migration assays were conducted in a 48-well microchemotaxis chamber.
- Flow cytometry assessed changes in cell size and surface adhesion molecule expression.
Main Results:
- Albumin-stimulated migration was blocked by PI3-kinase inhibitors (wortmannin, LY-294002) but not a PKC inhibitor.
- IL-2's inhibitory effect was unaffected by PI3-kinase inhibitors but persisted with the PKC inhibitor.
- Albumin increased eosinophil size and decreased CD49d/CD49f expression; IL-2 had no effect on these parameters.
Conclusions:
- Albumin-induced eosinophil migration is mediated by phosphoinositide 3-kinase (PI3-kinase) signaling.
- Albumin's effects on cell size and adhesion molecules suggest active cell activation and modulated adhesiveness, facilitating migration.
- These findings highlight a novel, active role for albumin in regulating eosinophil migration.
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