1. Human eosinophils have an intact Smad signaling pathway leading to a major transforming growth factor-beta target gene expression
- Author
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Hideoki Ogawa, Mirei Kanzaki, Hiroshi Mitsui, Shinji Shimada, Atsushi Okamoto, Naotaka Shibagaki, Yoh Dobashi, Takashi Inozume, Atsuhito Nakao, and Kyosuke Hatsushika
- Subjects
Cell Survival ,Immunology ,Receptor, Transforming Growth Factor-beta Type I ,SMAD ,Smad2 Protein ,Biology ,Protein Serine-Threonine Kinases ,Allergic inflammation ,Smad7 Protein ,Interferon-gamma ,Transforming Growth Factor beta ,Gene expression ,medicine ,Immunology and Allergy ,Humans ,RNA, Messenger ,Smad3 Protein ,Receptor ,Cells, Cultured ,Smad4 Protein ,Receptor, Transforming Growth Factor-beta Type II ,Granulocyte-Macrophage Colony-Stimulating Factor ,General Medicine ,respiratory system ,Eosinophil ,Asthma ,Eosinophils ,medicine.anatomical_structure ,Gene Expression Regulation ,Transforming growth factor, beta 3 ,Signal transduction ,Activin Receptors, Type I ,Receptors, Transforming Growth Factor beta ,Transforming growth factor - Abstract
Background: There is a paradoxical finding that eosinophils are frequently accumulated at the sites of allergic inflammation where transforming growth factor (TGF)-β, a negative regulator of eosinophil survival, is upregulated; however, eosinophil accumulation is persistent. We thus hypothesized that eosinophils might have aberrant TGF-β signaling and be unresponsive to TGF-β. To test the hypothesis, we examined the expression and function of Smad proteins, which are central mediators for TGF-β signaling, in human eosinophils. Methods: Eosinophils were isolated from the peripheral blood of normal donors, and the expression and activation of endogenous Smad proteins were examined by reverse transcription polymerase chain reaction and Western blotting. The Smad function in the transcription of the major TGF-β target gene Smad7 was investigated using a dominant negative form of Smad3. The effect of TGF-β on eosinophil survival was then evaluated by a cell viability assay using normal and asthmatic eosinophils. Results: Human eosinophils expressed mRNAs and proteins of TGF-β typeI and type II receptors, Smad2, Smad3 and Smad4. TGF-β induced the phosphorylation of Smad2 in eosinophils, which was blocked by SB431542, an inhibitor of TGF-β type I receptor kinase. A dominant negative Smad3 protein suppressed TGF-β-induced Smad7 mRNA expression in eosinophils. Finally, TGF-β prevented granulocyte macrophage colony-stimulating factor- or interferon-γ-mediated survival of eosinophils obtained from asthmatic patients as well as normal subjects. Conclusion: Human eosinophils have an intact Smad signaling pathway leading to a major TGF-β target gene expression. Thus, eosinophils might become resistant to TGF-β only in in vivo circumstances.
- Published
- 2006