TGF-beta1 stimulates human AT1 receptor expression in lung fibroblasts by cross talk between the Smad, p38 MAPK, JNK, and PI3K signaling pathways.
Both angiotensin II (ANG II) and transforming growth factor-beta1 (TGF-beta1) are thought to be involved in mediating pulmonary fibrosis. Interactions between the renin-angiotensin system (RAS) and TGF-beta1 have been well documented, with most studies describing the effect of ANG II on TGF-beta1 expression. However, recent gene expression profiling experiments demonstrated that the angiotensin II type 1 receptor (AT(1)R) gene was a novel TGF-beta1 target in human adult lung fibroblasts. In this report, we show that TGF-beta1 augments human AT(1)R (hAT(1)R) steady-state mRNA and protein levels in a dose- and time-dependent manner in primary human fetal pulmonary fibroblasts (hPFBs). Nuclear run-on experiments demonstrate that TGF-beta1 transcriptionally activates the hAT(1)R gene and does not influence hAT(1)R mRNA stability. Pharmacological inhibitors and specific siRNA knockdown experiments demonstrate that the TGF-beta1 type 1 receptor (TbetaRI/ALK5), Smad2/3, and Smad4 are essential for TGF-beta1-stimulated hAT(1)R expression. Additional pharmacological inhibitor and small interference RNA experiments also demonstrated that p38 MAPK, JNK, and phosphatidylinositol 3-kinase (PI3K) signaling pathways are also involved in the TGF-beta1-stimulated increase in hAT(1)R density. Together, our results suggest an important role for cross talk among Smad, p38 MAPK, JNK, and PI3K pathways in mediating the augmented expression of hAT(1)R following TGF-beta1 treatment in hPFB. This study supports the hypothesis that a self-potentiating loop exists between the RAS and the TGF-beta1 signaling pathways and suggests that ANG II and TGF-beta1 may cooperate in the pathogenesis of pulmonary fibrosis. The synergy between these systems may require that both pathways be simultaneously inhibited to treat fibrotic lung disease.
Martin
Mickey M
MM
Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio 43210, USA.
Buckenberger
Jessica A
JA
Jiang
Jinmai
J
Malana
Geraldine E
GE
Knoell
Daren L
DL
Feldman
David S
DS
Elton
Terry S
TS
D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005333:Fetus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D051785:Smad Proteins / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D044140:Receptor, Angiotensin, Type 1; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta; D051785:Smad Proteins; D053773:Transforming Growth Factor beta1; D048051:p38 Mitogen-Activated Protein Kinases; C000625841:TGFBR1 protein, human