Endothelium-dependent hyperpolarization: age, gender and high blood pressure, does it matter?

Abstract

Vascular complications, such as atherosclerosis, develop with aging and hypertension. Female appears to have a lower risk of developing vascular diseases compared to age-matched male, until after menopause. Impairment of vascular function is associated with an impaired capacity of the endothelium to generate vasodilator signals, the major ones being nitric oxide (NO) and endothelium-dependent hyperpolarization (EDH). A reduction in the bioavailability of NO has been well documented with endothelial dysfunction. By contrast, although the contribution of EDH-like responses to the regulation of vascular tone increases as the diameter of the arteries decreases, the modulation of such relaxation by age, gender and hypertension is less clear. Whereas the mechanism involved in EDH-like relaxations varies with species and blood vessel types, activation of endothelial intermediate-and small-conductance calcium-activated potassium channels (IKCa and SKCa, respectively) are characteristic of this pathway. In superior mesenteric arteries of aged, hypertensive or post-menopausal atherosclerotic-prone rodents, EDH-type relaxations are reduced compared to those of preparations of respective controls. Pharmacological experiments in mesenteric arteries of hypertensive rats suggest a reduced involvement of SKCa, such that EDH-mediated relaxation becomes dependent on IKCa. This IKCa-mediated response appears to involve the activation of adenosine monophosphate-activated protein kinase (AMPK) and silent information regulator T1 (SIRT1), proteins associated with the process of cellular senescence and vascular signaling in response to female hormone. An understanding of the role of AMPK and/or SIRT1 in EDH-like responses may help identifying effective pharmacological strategies to prevent the development of vascular complications of different etiology.