Integrin-Mediated Mechanotransduction in Vascular Smooth Muscle Cells: Frequency and Force Response Characteristics

• Published in: Circulation research 2001-04, Vol.88 (7), p.674-680
• Main Authors: Goldschmidt, Marc E, McLeod, Kenneth J, Taylor, W Robert
• Format: Article
• Language: English
• Subjects: Animals; Antibodies - metabolism; Aorta - physiology; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Blotting, Western; Cardiology. Vascular system; Cell Survival - radiation effects; Cells, Cultured; Electromagnetic Fields; Enzyme Activation - physiology; Experimental diseases; Extracellular Matrix Proteins - metabolism; Fibronectins - metabolism; Integrins - immunology; Integrins - metabolism; Magnetics - instrumentation; MAP Kinase Signaling System - physiology; Medical sciences; Microspheres; Mitogen-Activated Protein Kinase 1 - metabolism; Mitogen-Activated Protein Kinase 3; Mitogen-Activated Protein Kinases - metabolism; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - metabolism; Periodicity; Phosphorylation; Rats; Stress, Mechanical; Vitronectin - metabolism
• ISSN: 0009-7330; 1524-4571
• DOI: 10.1161/hh0701.089749

Blood vessels are continuously exposed to mechanical forces that lead to adaptive remodeling and atherosclerosis. Although there have been many studies characterizing the responses of vascular cells to mechanical stimuli, the precise mechanical characteristics of the forces applied to cells to elicit these responses are not clear. We designed a magnetic exposure system capable of producing a defined normal force on ferromagnetic beads that are specifically bound to cultured cells coated with extracellular matrix proteins or integrin-specific antibodies. Rat aortic smooth muscle cells were incubated with engineered fibronectin–coated ferromagnetic beads and then exposed to a magnetic field. With activation of extracellular signal–regulated mitogen-activated protein kinase 1/2 (ERK 1/2) used as a prototypical marker for cell responsiveness to mechanical forces, Western blot analysis demonstrated an increase in phosphorylated ERK 1/2 expression reaching a maximal response of a 3.5-fold increase at a total force of ≈2.5 pN per cell. The peak response occurred after 5 minutes of exposure and slowly decreased to baseline after 30 minutes. A cyclic, rather than static, force was required for this activation, and the frequency-response curve increased ≈2-fold between 0.5 and 2.0 Hz. Vitronectin- and β3 antibody–coated beads showed a response nearly identical to those coated with engineered fibronectin, whereas forces applied to beads coated with α2 and β1 antibodies did not significantly activate ERK 1/2. Mechanical activation of the ERK 1/2 system in rat aortic smooth muscle cells occurs through specific integrin receptors and requires a cyclic force with a magnitude estimated to be in the piconewton range.