Intracellular signaling pathway mediated by
small GTPase Rho and its effector
Rho-kinase plays an important role in regulation of vascular smooth muscle contraction and other cellular functions. We have recently demonstrated that
Rho-kinase is substantially involved in
angiotensin II-induced gene expressions and various cellular responses in vitro. However, it remains to be examined whether
Rho-kinase is involved in the
angiotensin II-induced cardiovascular
hypertrophy in vivo and, if so, what mechanisms are involved. Long-term infusion of
angiotensin II for 4 weeks caused hypertrophic changes of vascular smooth muscle and cardiomyocytes in rats. Both changes were significantly suppressed by concomitant oral treatment with
fasudil, which is metabolized to a specific
Rho-kinase inhibitor,
hydroxyfasudil, after
oral administration.
Angiotensin II caused a perivascular accumulation of macrophages and
Rho-kinase activation, both of which were also significantly suppressed by
fasudil. Vascular
NAD(P)H oxidase expression (nox1, nox4, gp91phox, and p22phox) and endothelial production of
superoxide anions were markedly increased by
angiotensin II, both of which were also significantly suppressed by
fasudil. Thus,
fasudil ameliorated the impaired endothelium-dependent relaxations caused by
angiotensin II without affecting
vasodilator function of vascular smooth muscle. These results provide evidence that
Rho-kinase is substantially involved in the
angiotensin II-induced cardiovascular
hypertrophy in rats in vivo. The suppression of endothelial
NAD(P)H oxidase upregulation and resultant
superoxide production and the amelioration of endothelial
vasodilator function may be involved in this process.