• This seminar will discuss the rapid and dynamic changes in adhesion and cell elasticity following agonist stimulation that culminate in a remodelled cytoskeleton in vascular smooth muscle.
• Evidence will be presented to show that the changes in adhesion and elasticity are coordinated and that these variables demonstrate temporal oscillation consisting of three major oscillation components.
• Eigen-decomposition spectrum analysis revealed that these components of oscillation in cell elasticity and adhesion may be linked by shared signalling pathways.
• Evidence is provided that the agonist angiotensin II and adenosine produce remodelling of actin cytoskeleton that may alter the properties of the observed oscillations in elasticity and adhesion.
• It is concluded that that angiotensin II and adenosine may regulate extracellular matrix adhesion and elasticity in vascular smooth muscle cells as a form of adaption to more efficiently support contractile behaviour.
In this study, we examined the ability of vasoactive agonists to induce dynamic changes in vascular smooth muscle cell (VSMC) elasticity and adhesion, and tested the hypothesis that these events are coordinated with rapid remodelling of the cortical cytoskeleton. Real-time measurement of cell elasticity was performed with atomic force microscopy (AFM) and adhesion was assessed with AFM probes coated with fibronectin (FN). Temporal data were analysed using an Eigen-decomposition method. Elasticity in VSMCs displayed temporal oscillations with three components at approximately 0.001, 0.004, and 0.07 Hz, respectively. Similarly, adhesion displayed a similar oscillatory pattern. Angiotensin II (ANG II, 10-6M) increased (+100%) the amplitude of the oscillations, whereas the vasodilator adenosine (ADO, 10-4M) reduced oscillation amplitude (-30%). To test whether the oscillatory changes were related to the architectural alterations in cortical cytoskeleton, the topography of the sub-membranous actin cytoskeleton (100-300 nm depth) was acquired with AFM. These data were analysed to compare cortical actin fibre distribution and orientation before and after treatment with vasoactive agonists. The results showed that ANG II increased the density of stress fibres by 23%, while ADO decreased density of the stress fibres by 45%. AFM data were supported by Western Blot and confocal microscopy. Collectively, these observations indicate that VSMC cytoskeletal structure and adhesion to the ECM are dynamically altered in response to agonist stimulation. Thus, vasoactive agonists likely invoke unique mechanisms that dynamically alter the behaviour and structure of both the VSMC cytoskeleton and focal adhesions to efficiently support the normal contractile behaviour of VSMC.
Gerald A. Meininger, Ph.D.
Dalton Cardiovascular Research Center
Margaret Proctor Mulligan Professor in Medical Research
Department of Medical Pharmacology and Physiology
University of Missouri-Columbia