Essential hypertension and oxidative stress: New insights

Abstract

Essential hypertension is a highly prevalent pathological condition that is considered as one of the most relevant cardiovascular risk factors and is an important cause of morbidity and mortality around the world. Despite the fact that mechanisms underlying hypertension are not yet fully elucidated, a large amount of evidence shows that oxidative stress plays a central role in its pathophysiology. Oxidative stress can be defined as an imbalance between oxidant agents, such as superoxide anion, and antioxidant molecules, and leads to a decrease in nitric oxide bioavailability, which is the main factor responsible for maintaining the vascular tone. Several vasoconstrictor peptides, such as angiotensin II, endothelin-1 and urotensin II, act through their receptors to stimulate the production of reactive oxygen species, by activating enzymes like NADPH oxidase and xanthine oxidase. The knowledge of the mechanism described above has allowed generating new therapeutic strategies against hypertension based on the use of antioxidants agents, including vitamin C and E, N-Acetylcysteine, polyphenols and selenium, among others. These substances have different therapeutic targets, but all represent antioxidant reinforcement. Several clinical trials using antioxidants have been made. The aim of the present review is to provide new insights about the key role of oxidative stress in the pathophysiology of essential hypertension and new clinical attempts to demonstrate the usefulness of antioxidant therapy in the treatment of hypertension.

Keywords: Antioxidants; Endothelial dysfunction; Hypertension; Oxidative stress.

Figure 1

Schematic summary of the role of vascular oxidative stress in the pathogenesis of hypertension and the mechanisms of exogenous antioxidant accounting for anti-hypertensive effects. AT-II: Angiotensin II; AT₁R: Type 1 angiotensin II receptor; ET-1: Endothelin 1; ET_AR: Type A endothelin receptor; UT-II: Urotensin II; UTR: Urotensin-II receptor; NO: Nitric oxide; eNOS: Endothelial nitric oxide synthase; PGI₂: Prostacyclin; NAC: N-Acetylcysteine; NOX: NADPH oxidase; NF-κB: Nuclear factor kappa B.