Stress and vascular disease at the cellular and molecular levels

The role of nitric oxide in mediating smooth muscle relaxation is well established. Less is known about the downstream signaling events inside the smooth muscle cell that produce relaxation of the contractile machinery. One possible effector molecule is the small heat shock protein HSP20. Increased phosphorylation of HSP20 is associated with vasorelaxation. HSP20 is associated with elements of the contractile machinery such as another small heat shock protein (HSP27), actin, and myosin. Thus HSP20 may mediate vasorelaxation by directly modulating cytoskeletal or contractile elements in muscle cells.