Transforming growth factor-beta 1 increases lysyl oxidase enzyme activity and mRNA in rat aortic smooth muscle cells.
OBJECTIVE
This investigation was designed to test the hypothesis that transforming growth factor-beta 1 (TGF-beta 1) regulates lysyl oxidase secretion from vascular smooth muscle cells. Lysyl oxidase is an enzyme that catalyzes an essential step in collagen and elastin cross-linking in the extracellular matrix, and TGF-beta 1 has been implicated in the pathogenesis of restenosis after vascular injury. The effect of TGF-beta 1 on lysyl oxidase in vascular smooth muscle cells has not been previously defined.


METHODS
Rat aortic smooth muscle cells were grown in culture to confluence. Cells in passage 2 to 6 were incubated for 24 hours in media containing 0.1, 0.5, 1.0, or 10.0 ng/ml of TGF-beta 1. Lysyl oxidase activity in the media was quantitated with a tritium-release bioassay against an insoluble 3H-labeled aortic clastin substrate. Northern blot analyses were performed to determine steady-state levels of lysyl oxidase mRNA in the smooth muscle cells.


RESULTS
Lysyl oxidase activity in the media increased 1.5-fold above control levels after exposure to 10 ng/ml of TGF-beta 1 (p < 0.01). This increase in lysyl oxidase activity was associated with a concentration-dependent increase in steady-state levels of lysyl oxidase mRNA, being 4.3- and 6.2-fold above control levels after exposure to 1 and 10 ng/ml TGF-beta 1, respectively (p < 0.01). The observed increase in steady-state lysyl oxidase mRNA after exposure to TGF-beta 1 was also time-dependent over the 24-hour experimental period.


CONCLUSIONS
TGF-beta 1 appears to regulate lysyl oxidase in cultured rat aortic smooth muscle cells. Increases in lysyl oxidase activity may be one of the mechanisms by which TGF-beta 1 contributes to arterial restenosis after vascular injury.
Shanley
C J
CJ
Department of Surgery, Jobst Laboratories, University of Michigan Medical School, USA.
Gharaee-Kermani
M
M
Sarkar
R
R
Welling
T H
TH
Kriegel
A
A
Ford
J W
JW
Stanley
J C
JC
Phan
S H
SH
D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000201:enzymology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D008249:Protein-Lysine 6-Oxidase / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D016212:Transforming Growth Factor beta / Q000494:pharmacology* / Q000502:physiology
D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D008249:Protein-Lysine 6-Oxidase