TGFβ1 induces IL-6 and inhibits IL-8 release in human bronchial epithelial cells: the role of Smad2/3.
Human bronchial epithelial (HBE) cells contribute to asthmatic airway inflammation by secreting cytokines, chemokines, and growth factors, including interleukin (IL)-6, IL-8 and transforming growth factor (TGF) β1, all of which are elevated in asthmatic airways. This study examines the signaling pathways leading to TGFβ1 induced IL-6 and IL-8 in primary HBE cells from asthmatic and non-asthmatic volunteers. HBE cells were stimulated with TGFβ1 in the presence or absence of signaling inhibitors. IL-6 and IL-8 protein and mRNA were measured by ELISA and real-time PCR respectively, and cell signaling kinases by Western blot. TGFβ1 increased IL-6, but inhibited IL-8 production in both asthmatic and non-asthmatic cells; however, TGF induced significantly more IL-6 in asthmatic cells. Inhibition of JNK MAP kinase partially reduced TGFβ1 induced IL-6 in both cell groups. TGFβ1 induced Smad2 phosphorylation, and blockade of Smad2/3 prevented both the TGFβ1 modulated IL-6 increase and the decrease in IL-8 production in asthmatic and non-asthmatic cells. Inhibition of Smad2/3 also increased basal IL-8 release in asthmatic cells but not in non-asthmatic cells. Using CHIP assays we demonstrated that activated Smad2 bound to the IL-6, but not the IL-8 promoter region. We conclude that the Smad2/3 pathway is the predominant TGFβ1 signaling pathway in HBE cells, and this is altered in asthmatic bronchial epithelial cells. Understanding the mechanism of aberrant pro-inflammatory cytokine production in asthmatic airways will allow the development of alternative ways to control airway inflammation.
Ge
Qi
Q
Respiratory Research Group, Discipline of Pharmacology, Faculty of Medicine, The University of Sydney, Sydney, NSW, Australia. qi.ge@sydney.edu.au
Moir
Lyn M
LM
Black
Judith L
JL
Oliver
Brian G
BG
Burgess
Janette K
JK
D000293:Adolescent; D000328:Adult; D000368:Aged; D001249:Asthma / Q000276:immunology* / Q000378:metabolism; D001665:Binding Sites; D015153:Blotting, Western; D001980:Bronchi / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D016022:Case-Control Studies; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D015536:Down-Regulation; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D005260:Female; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D015850:Interleukin-6 / Q000235:genetics / Q000378:metabolism*; D016209:Interleukin-8 / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D020545:Respiratory Mucosa / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D015398:Signal Transduction; D051899:Smad2 Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051900:Smad3 Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D015854:Up-Regulation; D055815:Young Adult
C508606:CXCL8 protein, human; C508600:IL6 protein, human; D018836:Inflammation Mediators; D015850:Interleukin-6; D016209:Interleukin-8; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; D051900:Smad3 Protein; D053773:Transforming Growth Factor beta1; D048031:JNK Mitogen-Activated Protein Kinases