Induction of cardiac fibroblast lysyl oxidase by TGF-β1 requires PI3K/Akt, Smad3, and MAPK signaling

Cytokine. 2011 Jul;55(1):90-7. doi: 10.1016/j.cyto.2011.03.024. Epub 2011 Apr 17.


Lysyl oxidase (LOX) is a key extracellular enzyme responsible for the post-translational modification of collagens I and III to form mature fibrillar collagen. Increased expression of LOX is associated with fibrosis and cardiac dysfunction, yet little is known about the regulation of LOX in the heart. In this study, the cell signaling pathways responsible for the regulation of LOX expression by transforming growth factor (TGF)-β1 were assessed. Adult cardiac fibroblasts were isolated from male Sprague-Dawley rat hearts by enzymatic digestion. Fibroblasts were grown in DMEM with 10% FBS until approximately 80% confluent, growth arrested for 24h, and then treated with TGF-β1 (0-10 ng/ml), in the absence or presence of inhibitors of (1) PI3K (wortmannin), (2) Smad3 (SIS3), (3) p38-MAPK (PD169316), (4) JNK (SP600125) and (5) ERK1/2 (PD98059). TGF-β1 treatment significantly upregulated LOX mRNA and protein expression in cardiac fibroblasts, as well as activity in the cell-conditioned media. Concomitant increases in collagen types I and III, and bone morphogenic protein (BMP-1) expression were found in response to TGF-β1. The increase of LOX protein in response to TGF-β1 was prevented by inhibitors of PI3K, Smad3, p38-MAPK, JNK and ERK1/2. Blockade of PI3K also decreased TGF-β1 induced phosphorylation of Smad3, suggesting that the PI3K/Akt and Smad pathways may be integrated in TGF-β1 signaling. Further studies are warranted to address the regulation of LOX in the normal and diseased heart, and how this critical extracellular enzyme may be targeted for clinical benefit.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bone Morphogenetic Protein 1 / genetics
  • Bone Morphogenetic Protein 1 / metabolism
  • Collagen Type I / genetics
  • Collagen Type I / metabolism
  • Collagen Type III / metabolism
  • Enzyme Activation / drug effects
  • Enzyme Induction / drug effects
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / enzymology*
  • Gene Expression Regulation / drug effects
  • MAP Kinase Signaling System / drug effects*
  • Male
  • Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinases / metabolism
  • Myocardium / cytology
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein-Lysine 6-Oxidase / biosynthesis*
  • Proto-Oncogene Proteins c-akt / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Smad3 Protein / antagonists & inhibitors
  • Smad3 Protein / metabolism*
  • Transforming Growth Factor beta1 / pharmacology*


  • Collagen Type I
  • Collagen Type III
  • Phosphoinositide-3 Kinase Inhibitors
  • RNA, Messenger
  • Smad3 Protein
  • Smad3 protein, rat
  • Transforming Growth Factor beta1
  • Protein-Lysine 6-Oxidase
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinases
  • Bone Morphogenetic Protein 1