Tumor necrosis factor-alpha induces transforming growth factor-beta1 expression in lung fibroblasts through the extracellular signal-regulated kinase pathway.
Increased expression of transforming growth factor (TGF)-beta(1) and tumor necrosis factor (TNF)-alpha are thought to play important roles in the development of pulmonary fibrosis. We recently reported that TNF-alpha upregulates TGF-beta(1) expression in primary mouse lung fibroblasts (MLFs), a key cell population in fibrogenesis. In the present study, we have investigated signal transduction pathways involved in TNF-alpha upregulation of TGF-beta(1) in both primary MLFs and the Swiss 3T3 fibroblast cell line. Treatment of fibroblasts with TNF-alpha resulted in a significant increase in TGF-beta(1) protein as measured by ELISA. The increase in protein was preceded by a 200-400% increase in TGF-beta(1) mRNA detected by quantitative, real-time, reverse transcriptase-polymerase chain reaction. Western blot analysis showed that TNF-alpha activated the extracellular signal-regulated kinase (ERK), and inhibitors of the ERK-specific mitogen-activated protein kinase pathway (PD98059 or U0126) blocked TNF-alpha induction of TGF-beta(1) mRNA and protein. mRNA stability experiments showed that TNF-alpha increased the half-life of TGF-beta(1) mRNA to more than 24 h compared with approximately 15 h in unstimulated cells. Expression of constitutively active MEK1 that selectively phosphorylates ERK was sufficient for TGF-beta(1) mRNA stabilization in Swiss 3T3 fibroblasts. These results indicate that TNF-alpha activates the ERK-specific mitogen-activated protein kinase pathway leading to increased TGF-beta(1) production in fibroblasts, primarily via a post-transcriptional mechanism that involves stabilization of the TGF-beta(1) transcript.
Sullivan
Deborah E
DE
Department of Pathology and Laboratory Medicine, Lung Biology Program, Tulane University Health Sciences Center, 1430 Tulane Avenue, New Orleans, LA 70112, USA. dsulliva@tulane.edu
Ferris
MaryBeth
M
Pociask
Derek
D
Brody
Arnold R
AR
D000818:Animals; D001483:Base Sequence; D002070:Butadienes / Q000494:pharmacology; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D008168:Lung / Q000187:drug effects* / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D009570:Nitriles / Q000494:pharmacology; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology; D041701:Swiss 3T3 Cells; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics*; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D002070:Butadienes; D018076:DNA, Complementary; D004791:Enzyme Inhibitors; D005419:Flavonoids; D009570:Nitriles; D012333:RNA, Messenger; D011994:Recombinant Proteins; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; C113580:U 0126; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one