Modification of type I collagenous gels by alveolar epithelial cells

Contraction of type I collagen gels is an in vitro model of tissue remodeling. In addition to fibroblasts, some epithelial cells can mediate this process. We therefore hypothesized that alveolar epithelial cells might contract extracellular matrices and have the potential to directly participate in the remodeling of the lung after alveolar injury. A549 cells were plated on top of collagen gels, and the gels were floated in culture medium. A549 cells contracted the gels in a time- and cell density–dependent manner. A549 cells, as well as human bronchial epithelial cells (HBEC) and rat alveolar epithelial cells (RalvEC) contracted collagen gels more when they were plated on top of the gel than when they were embedded inside, in contrast to human fetal lung fibroblast (HFL1), which contracted more when cast inside. The amount of hydroxyproline in the collagen gels remained unchanged throughout the contraction. Anti– β1 integrin antibody inhibited A549 cell–mediated contraction. Transforming growth factor β a..

Interferon-γ Inhibits Transforming Growth Factor-β Production in Human Airway Epithelial Cells by Targeting Smads

Because interferon (IFN)-gamma may attenuate pulmonary fibrosis, we hypothesized that IFN-gamma may regulate transforming growth factor (TGF)-beta production by airway epithelial cells. Human bronchial epithelial cells (HBECs) were incubated with IFN-gamma +/- TGF-beta1, -beta3, or interleukin (IL)-1beta, platelet-derived growth factor (PDGF), epidermal growth factor, and IL-4. TGF-beta2 protein was measured by enzyme-linked immunosorbent assay and mRNA expression for TGF-beta2, Smad 2, 3, 4, and 7 was evaluated by real-time reverse transcriptase-polymerase chain reaction. Localization of Smads 2, 3, 4, and 7 was evaluated by immunostaining. Exogenous TGF-beta1 and 3, IL-1beta, PDGF, and IL-4 enhanced TGF-beta2 release by HBECs (P < 0.01). IFN-gamma reduced basal and TGF-beta or IL-4-augmented TGF-beta2 release, but had little effect on IL-1beta- or PDGF-augmented TGF-beta2 release. IFN-gamma stimulated Smad 7 protein and mRNA expression. Smad 7-specific siRNA decreased Smad 7 protein expression both in control and IFN-gamma-treated cells. The inhibitory effect of IFN-gamma on TGF-beta2 production was abrogated when the HBECs were treated with Smad 7 siRNA. These results suggest that IFN-gamma down regulates TGF-beta2 production by HBECs by regulating Smad 7. Through this mechanism, IFN-gamma may play an important role in tissue remodeling

TH2 cytokine-enhanced and TGF-β-enhanced vascular endothelial growth factor production by cultured human airway smooth muscle cells is attenuated by IFN-γ and corticosteroids

Abstract Background: T H 2 and T H 1 cytokines have opposite effects on many aspects of the inflammatory response. Methods: This study was designed to determine if cytokines possibly present in asthma can modulate airway smooth muscle cell (ASMC) production of vascular endothelial growth factor (VEGF) and thus contribute to altered airway vascularity. ASMC were incubated for 24 hours with various concentrations of T H 2 cytokines (IL-4, IL-5, IL-10, and IL-13); transforming growth factor (TGF)-β1, TGF-β2, or TGF-β3; and IL-1β or TNF-α with or without IFN-γ. Budesonide and exogenous prostaglandin (PG)E 2 were also evaluated. Postculture media were assayed for VEGF and PGE 2 by ELISA. Results: IL-4, IL-5, and IL-13 alone but not IL-10 enhanced VEGF production by ASMC in a concentration-dependent manner. IFN-γ alone inhibited spontaneous VEGF release by ASMC and concentration-dependently attenuated IL-4-augmented, IL-5-augmented, or IL-13-augmented production of VEGF ( P P P > .05). TNF-α alone had little effect on VEGF release by ASMC. Production of VEGF stimulated by all cytokines was inhibited by budesonide. Exogenous PGE 2 increased VEGF release, but cytokine modulation of PGE 2 release did not always correlate with VEGF release. Conclusions: T H 2 cytokines and TGF-β stimulate ASMC release of VEGF. This can be inhibited by IFN-γ and glucocorticoids. (J Allergy Clin Immunol 2003;111:1307-18.