Introduction: Salt-induced hypertension in the Dahl rat is associated with increases in angiotensin II, aldosterone, free radical generation and endothelial dysfunction. However, little is known about the specific mechanism(s) associated with the end-organ damage effects of aldosterone. We hypothesised that eplerenone reduces kidney damage by blocking nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity.
Methods: Dahl salt-sensitive rats fed either a low-salt (LS) or high-salt (HS) diet were treated with aldosterone in the presence of eplerenone or apocynin. Indirect blood pressure was measured prior to start of diet and weekly thereafter. Levels of plasma nitric oxide (NO) and urinary 8-isoprostane were measured following treatment. Protein levels of selected subunits of NADPH were assessed by western blot.
Results: Eplerenone and apocynin inhibited the rise in blood pressure induced by HS and/or aldosterone. This observation was accompanied with a parallel change in kidney protein levels of NADPH oxidase 4 (NOX-4) and p22phox. Aldosterone and high salt were associated with lower NO levels and greater renal oxidative stress.
Conclusions: NADPH oxidase is associated with the vascular and renal remodelling observed in high dietary salt intake. Aldosterone-induced expression of NOX-4 plays a pivotal role in the end-organ damage effect of aldosterone, as eplerenone tended to reduce kidney damage and inhibit NOX expression.