High stretch induces endothelial dysfunction accompanied by oxidative stress and actin remodeling in human saphenous vein endothelial cells.

The rate of the remodeling of the arterialized saphenous vein conduit limits the outcomes of coronary artery bypass graft surgery (CABG), which may be influenced by endothelial dysfunction. We tested the hypothesis that high stretch (HS) induces human saphenous vein endothelial cell (hSVEC) dysfunction and examined candidate underlying mechanisms. Our results showed that in vitro HS reduces NO bioavailability, increases inflammatory adhesion molecule expression (E-selectin and VCAM1) and THP-1 cell adhesion. HS decreases F-actin in hSVECs, but not in human arterial endothelial cells, and is accompanied by G-actin and cofilin's nuclear shuttling and increased reactive oxidative species (ROS). Pre-treatment with the broad-acting antioxidant N-acetylcysteine (NAC) supported this observation and diminished stretch-induced actin remodeling and inflammatory adhesive molecule expression. Altogether, we provide evidence that increased oxidative stress and actin cytoskeleton remodeling play a role in HS-induced saphenous vein endothelial cell dysfunction, which may contribute to predisposing saphenous vein graft to failure.

Focal adhesion signaling: vascular smooth muscle cell contractility beyond calcium mechanisms.

Smooth muscle cell (SMC) contractility is essential to vessel tone maintenance and blood pressure regulation. In response to vasoconstrictors, calcium-dependent mechanisms promote the activation of the regulatory myosin light chain, leading to increased cytoskeleton tension that favors cell shortening. In contrast, SMC maintain an intrinsic level of a contractile force independent of vasoconstrictor stimulation and sustained SMC contraction beyond the timescale of calcium-dependent mechanisms suggesting the involvement of additional players in the contractile response. Focal adhesions (FAs) are conceivable candidates that may influence SMC contraction. They are required for actin-based traction employed by cells to sense and respond to environmental cues in a process termed mechanotransduction. Depletion of FA proteins impairs SMC contractility, producing arteries that are prone to dissection because of a lack of mechanical stability. Here, we discuss the role of calcium-independent FA signaling mechanisms in SMC contractility. We speculate that FA signaling contributes to the genesis of a variety of SMC phenotypes and discuss the potential implications for mechanical homeostasis in normal and diseased states.