The role of platelet-derived growth factor receptor in eotaxin signaling of eosinophils.
BACKGROUND
Receptor tyrosine kinases (RTKs) such as epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor (PDGFR) are capable of eliciting kinase activity after ligand binding. In several cells, RTKs are activated via the G-protein-coupled receptor independent of the ligand-RTK interaction. We have previously found that EGFR is transactivated via CC chemokine receptor 3 in bronchial epithelial cells and that this pathway is important for mitogen-activated protein (MAP) kinase activation and cytokine production. It has recently been suggested that hypereosinophilic syndrome results from the fusion tyrosine kinase FIP1L1-PDGFRA. Although it is possible that the PDGFR signal is involved in eosinophil function, the details are still unclear.


METHODS
Blood eosinophils were purified using Percoll and anti-CD16 antibody-coated magnetic beads. Expression of PDGFR mRNA was examined by RT-PCR. After stimulating eosinophils with eotaxin, the phosphorylation of MAP kinases was examined by Western blotting with the antiphosphospecific MAP kinase antibody. The eotaxin-induced eosinophil chemotaxis was studied using Boyden chambers.


RESULTS
Eosinophils expressed PDGFRbeta mRNA in 4 out of 8 donors, while PDGFRalpha mRNA was expressed in only 1 donor. Protein expression of PDGFR was also detectable in eosinophils from some donors. AG1295, a specific inhibitor of PDGFR, showed dose-dependent inhibition of eotaxin-induced MAP kinase phosphorylation in the eosinophils expressing PDGFRbeta mRNA. The chemotaxis of these eosinophils was significantly inhibited by AG1295 (n = 3).


CONCLUSIONS
Our results suggest that PDGFR modifies the CCR3-MAP kinase signaling pathway and chemotactic response in some donors. The pharmacological targeting of PDGFR may be a new strategy to treat eosinophilic disorders.
Adachi
Tetsuya
T
Department of Internal Medicine, Teikyo University School of Medicine, Tokyo, Japan. tadachi@med.teikyo-u.ac.jp
Hanaka
Satoko
S
Yano
Tomoko
T
Yamamura
Koichi
K
Yoshihara
Hisanao
H
Nagase
Hiroyuki
H
Chihara
Junichi
J
Ohta
Ken
K
D015153:Blotting, Western; D054413:Chemokine CCL11; D019742:Chemokines, CC / Q000276:immunology / Q000378:metabolism*; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000276:immunology*; D004804:Eosinophils / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases; D005434:Flow Cytometry; D006801:Humans; D010766:Phosphorylation; D012333:RNA, Messenger / Q000032:analysis; D054397:Receptors, CCR3; D019707:Receptors, Chemokine / Q000276:immunology / Q000378:metabolism; D017479:Receptors, Platelet-Derived Growth Factor / Q000276:immunology / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020032:Tyrphostins / Q000494:pharmacology
C407689:6,7-dimethoxy-2-phenylquinoxaline; C515456:CCL11 protein, human; C515350:CCR3 protein, human; D054413:Chemokine CCL11; D019742:Chemokines, CC; D012333:RNA, Messenger; D054397:Receptors, CCR3; D019707:Receptors, Chemokine; D020032:Tyrphostins; D017479:Receptors, Platelet-Derived Growth Factor; D048049:Extracellular Signal-Regulated MAP Kinases