Transforming growth factor-β stimulates the expression of eotaxin/CC chemokine ligand 11 and its promoter activity through binding site for nuclear factor-κβ in airway smooth muscle cells

BACKGROUND

Chemokines ligands of CCR3 including eotaxin/CC chemokine ligand 11 (CCL11) may contribute to the pathogenesis of asthma. These chemokines and a growth factor (TGF-beta) may be involved in the process of airway remodelling.

OBJECTIVE

We analysed the effects of TGF-beta on the expression of CCR3 ligands in human airway smooth muscle (HASM) cells and investigated the mechanisms.

METHODS

HASM cells were cultured and treated with TGF-beta and Th2 cytokines IL-4 or IL-13. Expression of mRNA was analysed by real-time PCR. Secretion of CCL11 into the culture medium was analysed by ELISA. Transcriptional regulation of CCL11 was analysed by luciferase assay using CCL11 promoter-luciferase reporter plasmids.

RESULTS

IL-4 or IL-13 significantly up-regulated the expression of mRNAs for CCL11 and CCL26. TGF-beta alone did not increase the expression of chemokine mRNAs, but enhanced the induction of only CCL11 by IL-4 or IL-13 among CCR3 ligands. Activity of the CCL11 promoter was stimulated by IL-4, and this activity was enhanced by TGF-beta. Activation by IL-4 or IL-4 plus TGF-beta was lost by mutation of the binding site for signal transducers and activators of transcription-6 (STAT6) in the promoter. Cooperative activation by IL-4 and TGF-beta was inhibited by mutation of the binding site for nuclear factor-kappaB (NF-kappaB) in the promoter. Pretreatment with an inhibitor of NF-kappaB and glucocorticoid fluticasone propionate significantly inhibited the expression of CCL11 mRNA induced by IL-4 plus TGF-beta, indicating the importance of NF-kappaB in the cooperative activation of CCL11 transcription by TGF-beta and IL-4.

CONCLUSION

These results indicate that Th2 cytokines and TGF-beta may contribute to the pathogenesis of asthma by stimulating expression of CCL11. The transcription factors STAT6 and NF-kappaB may play pivotal roles in this process.

Interleukin 12 is a primary cytokine responding to influenza virus infection in the respiratory tract of mice

We have reported previously that an increase in interleukin 12 (IL-12) production in the lungs of mice infected with Influenza A virus or an intranasal (i.n.) administration of IL-12 to the infected mice alleviated pneumonia (Tsurita et al., J. Pharmacol. Exp. Therapeut. 298, 362-368, 2001). In this study, we found that in the bronchoalveolar lavage fluids (BALF) obtained from mice infected i.n. with Influenza A virus IL-12 was elevated on day 1 post infection (p.i.) and was followed by tumor necrosis factor alfa (TNF-alfa), IL-18, and interferons alfa, beta, and gama (IFN-alfa, -beta, and -gama) on day 2 p.i. Histochemical analyses of the infected lungs on day 1 p.i. showed the presence of IL-12 and IL-12 mRNA in mononuclear and macrophage-like cells and co-localization of macrophages with viral antigen, while other cytokines were absent. Thus, IL-12 was produced by macrophages infiltrating the infected epithelium as the first response cytokine and its production at the site of infection may direct an early immune defense to alleviate the severity of infection.