TGF-beta suppresses the upregulation of MMP-2 by vascular smooth muscle cells in response to PDGF-BB.
During platelet-derived growth factor (PDGF)-BB-mediated recruitment to neovascular sprouts, vascular smooth muscle cells (VSMCs) dedifferentiate from a contractile to a migratory phenotype. This involves the downregulation of contractile markers such as smooth muscle (SM) alpha-actin and the upregulation of promigration genes such as matrix metalloproteinase (MMP)-2. The regulation of MMP-2 in response to PDGF-BB is complex and involves both stimulatory and inhibitory signaling pathways, resulting in a significant delay in upregulation. Here, we provide evidence that the delay in MMP-2 upregulation may be due to the autocrine expression and activation of transforming growth factor (TGF)-beta, which is known to promote the contractile phenotype in VSMCs. Whereas PDGF-BB could induce the loss of stress fibers and focal adhesions, TGF-beta was able to block or reverse this transition to a noncontractile state. TGF-beta did not, however, suppress early signaling events stimulated by PDGF-BB. Over time, though PDGF-BB induced increased TGF-beta1 levels, it suppressed TGF-beta2 and TGF-beta3 expression, leading to a net decrease in the total TGF-beta pool, resulting in the upregulation of MMP-2. Together, these findings indicate that MMP-2 expression is suppressed by a threshold level of active TGF-beta, which in turn promotes a contractile VSMC phenotype that prevents the upregulation of MMP-2.
Young Blvd., Biomedical Sciences Bldg., Rm 513, Oklahoma City, OK 73104, USA.
George M
GM
Risinger
Dawn L
DL
Updike
Elizabeth C
EC
Bullen
James J
JJ
Tomasek
Eric W
EW
Howard
D000199:Actins / Q000235:genetics; D000818:Animals; D000077214:Becaplermin; D017931:DNA Primers; D015536:Down-Regulation; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D016762:Genes, fos; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D020778:Matrix Metalloproteinase 2 / Q000235:genetics*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D020574:Proto-Oncogene Proteins c-sis; D051381:Rats; D011921:Rats, Inbred WKY; D011994:Recombinant Proteins / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000235:genetics; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
D000199:Actins; D017931:DNA Primers; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; D019715:Tissue Inhibitor of Metalloproteinase-1; D053773:Transforming Growth Factor beta1; D019716:Tissue Inhibitor of Metalloproteinase-2; D000077214:Becaplermin; D016173:Macrophage Colony-Stimulating Factor; D020778:Matrix Metalloproteinase 2