Involvement of ENaC in the development of salt-sensitive hypertension

Abstract

Salt-sensitive hypertension is associated with renal and vascular dysfunctions, which lead to impaired fluid excretion, increased cardiac output, and total peripheral resistance. It is commonly accepted that increased renal sodium handling and plasma volume expansion are necessary factors for the development of salt-induced hypertension. The epithelial sodium channel (ENaC) is a trimeric ion channel expressed in the distal nephron that plays a critical role in the regulation of sodium reabsorption in both normal and pathological conditions. In this mini-review, we summarize recent studies investigating the role of ENaC in the development of salt-sensitive hypertension. On the basis of experimental data obtained from the Dahl salt-sensitive rats, we and others have demonstrated that abnormal ENaC activation in response to a dietary NaCl load contributes to the development of high blood pressure in this model. The role of different humoral factors, such as the components of the renin-angiotensin-aldosterone system, members of the epidermal growth factors family, arginine vasopressin, and oxidative stress mediating the effects of dietary salt on ENaC are discussed in this review to highlight future research directions and to determine potential molecular targets for drug development.

Fig. 1.

Schematic illustration of epithelial sodium channel (ENaC) involvement in the development of salt-sensitive (SS) hypertension. High salt intake leads to lack of epidermal growth factor (EGF) in cortical tissue, low abundance of Rho GDP-dissociation inhibitor α (RhoGDIα), and abnormal activation of mineralocorticoid receptors (MR) via high activity of Rac1, which also serves as a structural unit of NADPH oxidase. Production of reactive oxygen species (ROS; as well as some other mechanisms not shown here) increases ENaC activity, which, in turn, contributes to the body fluid volume expansion required for the development of SS hypertension.