Phosphoinositide 3-kinase gamma mediates chemotactic responses of human eosinophils to platelet-activating factor.
BACKGROUND
Eosinophils are characteristic participants in allergic inflammation. The intracellular signalling mechanisms involved in the migration of eosinophils to sites of allergic inflammation are poorly understood. Chemotactic responses of eosinophils to platelet-activating factor (PAF), but not eotaxin, have been demonstrated to be dependent upon the activation of phosphoinositide 3-kinase (PI3K) but the specific isoform of PI3K involved has not been identified.


OBJECTIVE
To determine the roles of the leukocyte-specific PI3K gamma and PI3K delta isoforms of PI3K in PAF-induced chemotaxis of human eosinophils.


METHODS
Chemotactic responses of the EoL-1 eosinophilic cell line and human peripheral blood eosinophils were measured. The effects of a PI3K gamma-selective inhibitor (5-[2,2-difluorobenzo(1,3)dioxol-5-ylmethylene]-thiazolidine-2,4-dione; AS604850) and gene knock-down of PI3K gamma and PI3K delta on chemotactic responses were determined.


RESULTS
AS604850 caused a concentration-dependent suppression of chemotactic responses of EoL-1 cells and blood eosinophils to PAF but not eotaxin. Specific siRNAs reduced the expression of PI3K gamma and PI3K delta in EoL-1 cells. Knock-down of PI3K gamma by siRNA resulted in a 75% inhibition of the chemotactic response to PAF but had no effect on the response to eotaxin. Knock-down of endogenous PI3K delta by siRNA resulted in a 38% inhibition of the chemotactic response to PAF but had no effect on the response to eotaxin.


CONCLUSIONS
PI3K gamma plays a major role in the induction of chemotaxis in PAF-stimulated eosinophils, while PI3K delta plays a lesser role. Interventions which reduce the activity of PI3K gamma may have therapeutic potential in allergic diseases.
Hasan
Anwar Matar
AM
Infection, Immunity and Inflammation Research Group, Institute of Science and Technology in Medicine, Keele University, Keele, Staffordshire, United Kingdom.
Mourtada-Maarabouni
Mirna
M
Hameed
Mohammed S
MS
Williams
Gwyn T
GT
Dent
Gordon
G
D002478:Cells, Cultured; D054413:Chemokine CCL11 / Q000502:physiology; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology*; D058534:Class I Phosphatidylinositol 3-Kinases; D058544:Class Ib Phosphatidylinositol 3-Kinase / Q000235:genetics / Q000502:physiology*; D004149:Dioxoles / Q000494:pharmacology; D004804:Eosinophils / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology*; D055785:Gene Knockdown Techniques; D006801:Humans; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000502:physiology; D010972:Platelet Activating Factor / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D045162:Thiazolidinediones / Q000494:pharmacology
C505145:5-(2,2-difluorobenzo(1,3)dioxol-5-ylmethylene)thiazolidine-2,4-dione; D054413:Chemokine CCL11; D004149:Dioxoles; D010972:Platelet Activating Factor; D047428:Protein Kinase Inhibitors; D045162:Thiazolidinediones; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; D058544:Class Ib Phosphatidylinositol 3-Kinase; C486018:PIK3CD protein, human; C546760:PIK3CG protein, human