title: Angiotensin II- and salt-induced kidney injury through Rac1-mediated mineralocorticoid receptor activation.
abstract: Experiments with hyperaldosteronemic animals suggest that, despite lowering plasma aldosterone, salt worsens renal injury by paradoxical activation of the mineralocorticoid receptor (MR). Salt and aldosterone synergistically contribute to renal impairment through Rac1-mediated activation of the MR, but whether angiotensin II also promotes renal injury through this mechanism is unknown. Here, we placed angiotensin II-overproducing double transgenic Tsukuba hypertensive mice on a low- or high-salt intake for 6 weeks and treated some animals with adrenalectomy, the MR antagonist eplerenone, the Rac inhibitor EHT1864, or hydralazine. High-salt intake, but not low-salt intake, led to hypertension and prominent kidney injury. Adrenalectomy prevented angiotensin II/salt-induced nephropathy in mice receiving high-salt intake, which was recapitulated by aldosterone supplementation, suggesting the involvement of aldosterone/MR signaling. Plasma aldosterone levels, however, were lower in high- than low-salt conditions. Instead, angiotensin II/salt-evoked MR activation associated with Rac1 activation and was not dependent on plasma aldosterone level. Both EHT1864 and eplerenone repressed the augmented MR signaling and mitigated kidney injury with partial but significant reduction in BP with high-salt intake. Hydralazine similarly reduced BP, but it neither suppressed the Rac1-MR pathway nor ameliorated the nephropathy. Taken together, these results show that angiotensin II and salt accelerate kidney injury through Rac1-mediated MR activation. Rac inhibition may be a promising strategy for the treatment of CKD.
authors.affiliation: Department of Nephrology and Endocrinology, University of Tokyo Graduate School of Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Wakako
authors.initials: W
authors.lastname: Kawarazaki
authors.forename: Miki
authors.initials: M
authors.lastname: Nagase
authors.forename: Shigetaka
authors.initials: S
authors.lastname: Yoshida
authors.forename: Maki
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Kenichi
authors.initials: K
authors.lastname: Ishizawa
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Ayuzawa
authors.forename: Kohei
authors.initials: K
authors.lastname: Ueda
authors.forename: Toshiro
authors.initials: T
authors.lastname: Fujita
mesh_terms: D058186:Acute Kidney Injury / Q000378:metabolism* / Q000473:pathology* / Q000503:physiopathology; D000315:Adrenalectomy / Q000379:methods; D000450:Aldosterone / Q000097:blood / Q000378:metabolism*; D000704:Analysis of Variance; D000804:Angiotensin II / Q000009:adverse effects* / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D000077545:Eplerenone; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D018161:Receptors, Mineralocorticoid / Q000378:metabolism*; D015398:Signal Transduction; D017673:Sodium Chloride, Dietary / Q000009:adverse effects* / Q000494:pharmacology; D013148:Spironolactone / Q000031:analogs & derivatives / Q000494:pharmacology; D018709:Statistics, Nonparametric; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism
chemical_list: D018161:Receptors, Mineralocorticoid; D017673:Sodium Chloride, Dietary; D000804:Angiotensin II; D013148:Spironolactone; D000450:Aldosterone; D000077545:Eplerenone; D020830:rac1 GTP-Binding Protein