title: The contribution of interleukin (IL)-4 and IL-13 to the epithelial-mesenchymal trophic unit in asthma.
abstract: Interleukin (IL)-4 and IL-13 are key proinflammatory cytokines in asthma. Studies in transgenic mice show that both cytokines cause inflammation, but only IL-13 causes subepithelial fibrosis, a characteristic feature of asthma. We compared the in vitro profibrogenic effects of IL-4 and IL-13 using bronchial fibroblasts from asthmatic subjects. In the presence of transforming growth factor (TGF)-beta the cells transformed into contractile myofibroblasts and expressed alpha-smooth muscle actin and procollagen I. IL-4 and IL-13 also stimulated proliferation, but were relatively ineffective in promoting myofibroblast transformation. TGF-beta was more potent than the cytokines in stimulating release of endothelin-1 and vascular endothelial growth factor, whereas IL-4 and IL-13 were more potent stimuli for eotaxin release. Although neither IL-4 nor IL-13 induced profibrotic responses, both cytokines caused a corticosteroid-insensitive stimulation of TGF-beta2 release from primary bronchial epithelial cells. These data indicate that epithelial activation by IL-13 or IL-4 plays a critical role in initiating remodeling through release of TGF-beta2. TGF-beta2 then activates the underlying myofibroblasts to secrete matrix proteins and smooth muscle and vascular mitogens to propagate remodeling changes into the submucosa. In contrast, direct activation of submucosal fibroblasts by IL-4 and IL-13 has a proinflammatory effect via eotaxin release and recruitment of eosinophils into the airways.
authors.affiliation: Respiratory, Cell and Molecular Biology Division, School of Medicine, Southampton General Hospital, Southampton, United Kingdom. aud@soton.ac.uk
authors.forename: A
authors.initials: A
authors.lastname: Richter
authors.forename: S M
authors.initials: SM
authors.lastname: Puddicombe
authors.forename: J L
authors.initials: JL
authors.lastname: Lordan
authors.forename: F
authors.initials: F
authors.lastname: Bucchieri
authors.forename: S J
authors.initials: SJ
authors.lastname: Wilson
authors.forename: R
authors.initials: R
authors.lastname: Djukanovic
authors.forename: G
authors.initials: G
authors.lastname: Dent
authors.forename: S T
authors.initials: ST
authors.lastname: Holgate
authors.forename: D E
authors.initials: DE
authors.lastname: Davies
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000328:Adult; D001249:Asthma / Q000276:immunology / Q000503:physiopathology*; D001980:Bronchi / Q000503:physiopathology*; D002455:Cell Division / Q000502:physiology; D002478:Cells, Cultured; D054413:Chemokine CCL11; D019742:Chemokines, CC; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D017077:Culture Media, Conditioned; D016207:Cytokines / Q000378:metabolism; D016228:Endothelial Growth Factors / Q000378:metabolism; D019332:Endothelin-1 / Q000378:metabolism; D004847:Epithelial Cells / Q000502:physiology; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology / Q000503:physiopathology; D018793:Interleukin-13 / Q000494:pharmacology*; D015847:Interleukin-4 / Q000494:pharmacology*; D008222:Lymphokines / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
chemical_list: D000199:Actins; C515456:CCL11 protein, human; D054413:Chemokine CCL11; D019742:Chemokines, CC; D024042:Collagen Type I; D017077:Culture Media, Conditioned; D016207:Cytokines; D016228:Endothelial Growth Factors; D019332:Endothelin-1; D018793:Interleukin-13; D008222:Lymphokines; D020033:Protein Isoforms; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D015847:Interleukin-4