| Summary: | 碩士 === 國立成功大學 === 生物化學研究所 === 82 === Recent study showed that ox-LDL could stimulate migration of
smooth muscle cells. It has been proposed that protease is
required to digest the extracellular matrix before cell
migration. Therefore, it can be reasonably expected that the
proteolytic activity of smooth muscle cells may be regulated by
ox-LDL. The ox-LDL is also known to stimulate the biosynthesis
of plasminogen activator inhibitor PAI in the endothelial
cells. Experiments were designed to study the regulation of
proteolytic balance by ox-LDL in smooth muscle cells. The
treatment of smooth muscle cells with ox-LDL resulted in a
decrease in its ability to digest the labeled extracellular
matrix, suggesting that the protease activity of smooth muscle
cells was inhibited by ox-LDL. In vitro assay of smooth muscle
migration by Boyden chamber also showed that ox-LDL inhibited
both PDGF-BB-stimulated and non-PDGF-BB-stimulated cell
migration in a dose-dependent manner. Ox-LDL induced PAI-1
activity and protein synthesis by 1.7-fold and 1.2- fold,
respectively. The increase in PAI-1 protein synthesis was
ascribed to elevated levels of PAI-1 mRNA, however, the
increase of PAI-1 activity was more than the increase of PAI-1
protein synthesis. The increase of PAI-1 activity was most
likely associated with conversion of latent PAI-1 to active
PAI-1. The biosynthesis of t-PA antigen and the activation of
collagenase inhibitor were not affected by the treatment with
ox-LDL. Our experiments indicated that ox-LDL inhibited smooth
muscle cells migration was mainly due to the increase of PAI-1
activity.
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