Contributions of endoplasmic reticulum stress and reactive oxygen species to renal injury in aldosterone/salt-induced rats.

Background: Recent studies have suggested that aldosterone (Aldo) plays a key role in the pathogenesis of renal injury; however, the molecular mechanisms of Aldo-induced renal injury have not been characterized. This study was performed to test the hypothesis that reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress contribute to the pathogenesis of Aldo- and salt-induced renal injury.

Methods: Rats were uninephrectomized and treated with one of the following for 4 weeks: (1) vehicle, (2) vehicle + NaCl, (3) Aldo + NaCl or (4) Aldo + NaCl + N-acetyl-L-cysteine (NAC). Following this treatment period, the extent of renal injury was assessed by periodic acid-Schiff staining and immunohistochemistry, and the expression levels of proteins related to ER stress, as well as p47phox and p67phox in the kidney, were measured by Western blot. Intracellular ROS generation was evaluated by 2'7'-dichlorofluorescin diacetate fluorescence and ELISA kits.

Results: Rats that received Aldo + 1% NaCl exhibited severe renal injury. ROS levels were higher in Aldo-infused rats and were inhibited by NAC. Renal cortical protein levels of GRP78, GRP94, CHOP, ATF-4, p47phox and p67phox were significantly upregulated in rats that received Aldo + 1% NaCl. Treatment with NAC significantly ameliorated the increase in the expression of these proteins.

Conclusion: These data suggest that ROS and ER stress play a role in the progression of Aldo- and salt-induced renal injury.