Mechanotransduction of Rat Aortic Vascular Smooth Muscle Cells Requires RhoA and Intact Actin Filaments

Abstract

The growth-promoting effect of mechanical stress on vascular smooth muscle cells (VSMCs) has been implicated in the progress of vascular disease in hypertension. Extracellular signal-regulated kinases (ERKs) have been implicated in cellular responses, such as vascular remodeling, induced by mechanical stretch. However, it remains to be determined how mechanical stretch activates ERKs. The cytoskeleton seems the most likely candidate for force transmission into the interior of the cell. Therefore, we examined (1) whether the cytoskeleton involves mechanical stretch-induced signaling, (2) whether Rho is activated by stretch, and (3) whether Rho mediates the stretch-induced signaling in rat cultured VSMCs. Mechanical stretch activated ERKs, with a peak response observed at 20 minutes, followed by a significant increase in DNA synthesis. Treatment with the ERK kinase-1 inhibitor, PD98059, inhibited the stretch-induced increase in DNA synthesis. Cytochalasin D, which selectively disrupts the network of actin filaments, markedly inhibited stretch-induced ERK activation. In the control state, RhoA was observed predominantly in the cytosolic fraction, but it was translocated in part to the particulate fraction in response to mechanical stretch. Botulinum C3 exoenzyme, which inactivates Rho p21 (known to participate in the reorganization of the actin cytoskeleton), attenuated stretch-induced ERK activation. Inhibition of Rho kinase (p160ROCK) also suppressed stretch-induced ERK activation dose dependently. Our results suggest that mechanotransduction in VSMCs is dependent on intact actin filaments, that Rho is activated by stretch, and that Rho/p160ROCK mediates stretch-induced ERK activation and vascular hyperplasia.

Stretch-induced contractile differentiation of vascular smooth muscle: sensitivity to actin polymerization inhibitors

“…These effects are similar to those produced by latrunculin B and likely reflect the role of RhoA in regulating actin cytoskeletal assembly (13). Activation of RhoA by stretch has been demonstrated in cultured cells (26) but, to our knowledge, not in intact vascular tissue. In the present experiments C2-C3 toxin had no effect on weight or protein synthesis in unloaded tissue, whereas the growth responses to load during culture were inhibited.…”

“…Lack of effect of Y-27632 on ERK1/2 activation was also found in pressurized mesenteric arteries by Matrougui et al (24), whereas activation was inhibited in aortic cells exposed to cyclic strain as described by Numaguchi et al (26). Mack et al (18) found decreased ␣-actin promoter activity and SM22 synthesis in cultured vascular cells exposed to Y-27632.…”

“…Investigations of signal mechanisms involved in stretch-sensitive protein synthesis in the heart and vascular wall have concentrated on the roles of endogenous release of growth promoters such as angiotensin (ANG) II and on the roles of integrins and the cytoskeleton (1,3,26). In vascular tissue, both pressure (6,39) and exogenous ANG II (23) activate extracellular signal-regulated kinase (ERK)1/2 (44 and 42 kDa, respectively).…”

Molecular Mechanisms of Low Intensity Pulsed Ultrasound in Human Skin Fibroblasts

“…Focal adhesions act as a bridge to link integrin cytoplasmic domain to the cytoskeleton and activate integrin-associated signaling pathways, such as the mitogen-activated protein kinase (MAPK) pathway (17) and the Rho pathway (18,19). Rho and its downstream target Rho kinase/Rho-associated coiled-coil-containing protein kinase (ROCK) (20) are involved in the reorganization of cytoskeletal components (21,22) as well as cell cycle progression (1,23, 24). Integrin-dependent adhesion can also trigger ligand-independent epidermal growth factor receptor (EGFR) activation to transduce downstream signaling (25).…”

Mechanical Strain on Osteoblasts Activates Autophosphorylation of Focal Adhesion Kinase and Proline-rich Tyrosine Kinase 2 Tyrosine Sites Involved in ERK Activation

“…There is a large body of evidence showing that extracellular signal-regulated kinase 1/2 (ERK1/2) 1 controls cell proliferation in various cell types, including osteoblasts (5). Recent reports demonstrated that mechanical strain is able to activate ERK1/2 in several adherent cells such as mesangial cells (6), smooth muscle cells (7), and chondrocytes (8). In osteoblasts, ERK activation was mostly reported in fluid flow (9 -12), centrifugation (13), or magnetic drag force (14) experiments and in only one study using cyclic stretch (albeit combined with fluid flow) (15).…”