Regulation of collagen synthesis by inhibitory Smad7 in cardiac myofibroblasts.
Transforming growth factor-beta(1) (TGF-beta(1)) signal and downstream Smads play an important role in tissue fibrosis and matrix remodeling in various etiologies of heart failure. Inhibitory Smad7 (I-Smad7) is an inducible regulatory Smad protein that antagonizes TGF-beta(1) signal mediated via direct abrogation of R-Smad phosphorylation. The effect of ectopic I-Smad7 on net collagen production was investigated using hydroxyproline assay. Adenovirus-mediated I-Smad7 gene (at 100 multiplicity of infection) transfer was associated with significant decrease of collagen synthesis in the presence and absence of TGF-beta(1) in primary rat cardiac myofibroblasts. In I-Smad7-infected cells, we also observed the ablation of TGF-beta(1)-induced R-Smad2 phosphorylation vs. LacZ controls. Overdriven I-Smad7 was associated with significantly increased expression of immunoreactive 65-kDa matrix metalloproteinase-2 (MMP-2) protein in culture medium of myofibroblast compared with LacZ-infected cells. Expression of the 72-kDa MMP-2 variant, e.g., the inactive form, was not altered by exogenous I-Smad7 transfection/overexpression. Furthermore, I-Smad7 overexpression was associated with a significant increase and decrease in expression of p27 and phospho-Rb protein, respectively, as well as reduced [(3)H]thymidine incorporation vs. Ad-LacZ-infected controls. We suggest that negative modulation of R-Smad phosphorylation by ectopic I-Smad7 may contribute to the downregulation of collagen in cardiac myofibroblasts and may suppress the proliferation of these cells. Thus treatments targeting the collagen deposition by overexpression of I-Smad7 may provide a new therapeutic strategy for cardiac fibrosis.
Wang
Baiqiu
B
Institute of Cardiovascular Science, St. Boniface General Hospital Research Centre and Department of Physiology, University of Manitoba, Winnipeg, Canada.
Omar
Amer
A
Angelovska
Tatjana
T
Drobic
Vanja
V
Rattan
Sunil G
SG
Jones
Stephen C
SC
Dixon
Ian M C
IM
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004789:Enzyme Activation; D004790:Enzyme Induction; D005347:Fibroblasts / Q000378:metabolism*; D005822:Genetic Vectors; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008297:Male; D020778:Matrix Metalloproteinase 2 / Q000096:biosynthesis; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010766:Phosphorylation; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction; D051897:Smad Proteins, Inhibitory / Q000235:genetics / Q000378:metabolism*; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases / Q000096:biosynthesis; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D015854:Up-Regulation
C493962:Cdkn1b protein, rat; D016160:Retinoblastoma Protein; D051897:Smad Proteins, Inhibitory; D051896:Smad Proteins, Receptor-Regulated; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D019714:Tissue Inhibitor of Metalloproteinases; D053773:Transforming Growth Factor beta1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003094:Collagen; D020928:Mitogen-Activated Protein Kinases; D020778:Matrix Metalloproteinase 2