Background: Human airway smooth muscle cells (HASMs) are involved in the pathogenesis of asthma. By producing chemokines, HASMs play a role in the inflammatory processes observed in this disease. Eotaxin, eotaxin-2, and eotaxin-3 are important chemoattractants for eosinophils, and these chemokines are expressed during different phases of the allergic reaction. TH2 cytokines and TGF-beta can be found in increased levels in patients with asthma, and these cytokines may be involved in the regulation of chemokine expression.
Objective: The aim of this study was to determine the effect of TH2 cytokines and TGF-beta on the regulation of expression of eotaxin, eotaxin-2, and eotaxin-3 by HASMs.
Methods: HASMs were incubated for 24 hours with IL-4, IL-13, TGF-beta1, or combinations of these cytokines. Protein and mRNA levels of eotaxin and eotaxin-3 were evaluated by sandwich ELISA and reverse transcriptase-PCR.
Results: IL-4 and IL-13 induced mRNA and protein for both eotaxin and eotaxin-3. Eotaxin-2 mRNA and protein were not detected in HASMs. TGF-beta alone did not induce expression of the eotaxins. However, in combination with IL-4 or IL-13, TGF-beta enhanced eotaxin production and inhibited TH2 cytokine-induced eotaxin-3 production.
Conclusion: TGF-beta differentially regulates TH2 cytokine-induced eotaxin and eotaxin-3 release.