Redox signalling in vascular responses to shear and stretch.

Blood vessels are permanently exposed to stretch and shear stress due to blood pressure and blood flow. Significant variations in the mechanical environment, of physiological or pathophysiological nature, occur in vivo. These trigger acute changes in vessel diameter that tend to restore basal levels of tensile and shear stress. However, when altered mechanical conditions persist, they lead to compensatory phenotypical modulation of the endothelial and vascular smooth muscle cells, producing structural and functional modifications of the arterial wall. Such vascular remodelling is a fundamental basis of normal vessel growth and adaptation. However, when the vascular environment changes, due to humoral, metabolic or surgical alterations, for example, mechanical factors may actually exacerbate the underlying conditions and contribute significantly to disease progression. Several studies have demonstrated that reactive oxygen species are induced in the vascular response to changes in shear stress or stretch. It appears that the balance between oxidant and antioxidant generation, which is directly determined by the nature of the mechanical stimulus, can greatly influence the process of vascular remodelling, contributing to both transient and more prolonged adaptations.