Angiotensin II (Ang II) is a potent stimulator of
plasminogen activator inhibitor-1 (PAI-1) expression, which is an important regulator of pathogenesis of
atherosclerosis.
Rho-kinase, a downstream target
protein of small
GTP-binding protein Rho, plays a key role for various cellular functions. We evaluated the cardioprotective effects of a specific
Rho-kinase inhibitor, (R)-(+)-trans-N-(4-pyridyl)-4-(1-aminoethyl)-cyclohexanecarboxamide (Y-27632), and an Ang II type 1 receptor antagonist,
candesartan, on
PAI-1 gene expression and cardiovascular remodeling in Ang II-induced hypertensive rats. Rats given Ang II alone (200 ng.kg(-1).min(-1)) were compared with rats also receiving Ang II plus
Y-27632 or Ang II plus
candesartan. Ang II-induced
PAI-1 mRNA up-regulation in the left ventricle was inhibited by
Y-27632 and
candesartan. In addition, increased
RhoA protein,
Rho-kinase, and c-fos gene expression, and
myosin light chain phosphorylation were suppressed by
Y-27632 and
candesartan. In contrast,
Y-27632 had no effect on Ang II-stimulated phospho-p42/p44
extracellular signal-regulated kinases (ERK) and phospho-p70S6
kinase activities, which are reported to be involved in Ang II-induced
protein synthesis. Moreover, activated Ang II-induced phosphorylation of ERK and p70S6
kinase were blocked by
candesartan.
Y-27632 or
candesartan administration resulted in significant improvements in the wall-to-lumen ratio, perivascular
fibrosis, and myocardial
fibrosis. These results suggested that differential activation of
Rho-kinase and ERK pathways may play a critical role in Ang II-induce
PAI-1 gene expression, and up-regulation of
Rho-kinase plays a key role in the pathogenesis of Ang II-induced hypertensive rats. Thus, inhibition of the
Rho-kinase pathway may be at least a useful therapeutic strategy for treating cardiovascular remodeling.