Activation of Rho/Rho-Associated Kinase Pathway Is Involved in the Induction of Vascular Fibrogenesis.

Abstract

56 Abnormal extracellular accumulation of collagens and reorganization of the contractile cytoskeleton network in the vascular smooth muscle cells are characteristic features of angiosclerosis and end-organ damage during cardiovascular diseases. Rho-associated kinase (ROCK) activation is a key factor controling myosin phosphoryation and thus, its availability to form stress fibers. We have found previously that vasoconstrictor agents, such as angiotensin II (Ang II) or endothelin-1 (ET-1) play a major role in the activation of collagen I gene expression and synthesis within blood vessels . In the present study we investigated whether ROCK activation is involved in the profibrotic action of these peptides. Experiments were performed in transgenic mice harboring the luciferase reporter gene under the control of the collagen I- chain α2 promoter. Bolus iv. administration of pressive doses of Ang II or ET-1 induced an early (1 h) two-fold increase of collagen I gene activity in aortas. Co-administration of Y-27632, a selective inhibitor of ROCK, blocked the vasoconstrictor peptide-induced collagen I gene activation. Similar effects were obtained in freshly isolated aortas in vitro: Y-27632 blunted the Ang II- and ET-1-induced collagen I gene activation and the clustering of contractile cytoskeleton as evidenced by immunicytochemistry and confocal microscopy. Cytochalasin D, a potent inhibitor of actin polymerization also prevented the effect of Ang II and ET-1 on collagen I gene. In addition, aortic smooth muscle cells transfected with a constitutively active ROCK exhibited a two-fold increase in collagen I gene activity vs. control. These data suggest that ROCK is a major intracellular signaling pathway required for the early in vivo activation of collagen I gene induced by vasoactive peptides such as Ang II and ET-1 within the vasculature. It would be interesting to pursue in chronic studies whether ROCK inhibitors can be effeciently used as drugs against the development of vascular fibrogenesis.