Interleukin-10 regulates transforming growth factor-β signaling in cultured human bronchial epithelial cells

Background: The basic pathological features of bronchial asthma can be explained on the basis of chronic airway inflammation, involving inflammatory cells such as T cells (particularly type 2 helper T, Th2, cells) and mast cells, and airway remodeling. Many aspects of airway remodeling remain unclear at the molecular level. Recent attention has focused on the role of transforming growth factor (TGF)-beta, a fibrogenic cytokine, in airway remodeling. Currently available evidence suggests that airway remodeling is caused by an imbalance in regulatory mechanisms mediated by Smads, a family of signal-transducing molecules. Objectives: We studied the effects of the Th2 cytokines interleukin (IL)-5 and granulocyte-macrophage colony-stimulating factor (GM-CSF), and the regulatory cytokine IL-10 on the expression of inhibitory Smad7 protein in bronchial epithelial cells. Methods: Real-time reverse-transcriptase polymerase chain reaction was employed. Results: Stimulation with IL-10 upregulated the expression of Smad7 compared with control. Neither GM-CSF induced Smad7 expression. Smad7 expression was upregulated by IL-10 plus either IL-5 or GM-CSF. IL-10 inhibited the expression of TGF-beta-inducible early gene, which is known to downregulate Smad7 expression. Conclusions: Our results suggest that IL-10 acts as a regulatory cytokine in the inhibition of airway inflammation. Copyright (C) 2007 S. Karger AG, Basel.