Soluble epoxide hydrolase inhibition exhibits antihypertensive actions independently of nitric oxide in mice with renovascular hypertension

Abstract

Objective: The present study was performed to examine whether the blood pressure (BP)-lowering effects of soluble epoxide hydrolase (sEH) inhibition in two-kidney, one-clip (2K1C) Goldblatt hypertension are nitric oxide (NO) dependent.

Methods: Mice lacking the endothelial NO synthase (eNOS) gene (eNOS-/-) and their wild-type controls (eNOS+/+) underwent clipping of one renal artery. BP was monitored by radiotelemetry and the treatment with the sEH inhibitor cis-4-[4-(3-adamantan-1-yl-ureido)cyclohex-yloxy]-benzoic acid (c-AUCB) was initiated on day 25 after clipping and lasted for 14 days. Renal concentrations of epoxyeicosatrienoic acids (EETs) and their inactive metabolite dihydroxyeicosatrienoic acids (DHETs) were measured in the nonclipped kidney. Renal NO synthase (NOS) activity was determined by measuring the rate of formation of L-[(14)C]citruline from L-[(14)C]arginine.

Results: Treatment with the sEH inhibitor elicited similar BP decreases that were associated with increases in daily sodium excretion in 2K1C eNOS+/+ as well as 2K1C eNOS-/- mice. In addition, treatment with the sEH inhibitor increased the ratio of EETs/DHETs in the nonclipped kidney of 2K1C eNOS+/+ as well as 2K1C eNOS-/- mice. Treatment with the sEH inhibitor did not alter renal NOS activity in any of the experimental groups.

Conclusions: Collectively, our present data suggest that the BP-lowering effects of chronic sEH inhibition in 2K1C mice are mainly associated with normalization of the reduced availability of biologically active EETs in the nonclipped kidney and their direct natriuretic actions.

Figure 1

Mean arterial pressure (A and B) and heart rate (C and D) after clip placement or sham operation in wild-type (eNOS+/+) or knockout mice (eNOS−/−) and effects of c-AUCB treatment in these mice. ^*P<0.05 versus basal values. ^# P<0.05 versus untreated mice.

Figure 2

Effects of c-AUCB treatment on daily sodium excretion in sham-operated (A) and 2K1C (B) eNOS+/+ and eNOS−/− mice. ^*P<0.05 versus basal values.

Figure 3

Plasma (A) and nonclipped kidney tissue (B) ANG II levels and intrarenal ratio of EETs/DHETs (C) and 20-HETE concentrations (D) in sham-operated and 2K1C eNOS+/+ and eNOS−/− mice at the end of experimental period. ^*P<0.05 versus unmarked values. ^# P<0.05 versus all other values.

Figure 4

Renal cortical protein expression of CYP2C44 (A), sEH (B), CYP4A (C) and renal NOS activity (D) in sham-operated and 2K1C eNOS+/+ and eNOS−/− mice. ^*P<0.05 versus unmarked values.

Figure 5

Glomerulosclerosis index in sham-operated (A), nonclipped (B) and clipped (C) kidneys2K1C eNOS+/+ and eNOS−/− mice. ^*P<0.05 versus unmarked values. ^# P<0.05 versus all other values.

Figure 6

Representative renal parenchyme in sham-operated eNOS+/+ (A) and eNOS−/− (D), nonclipped kidneys of untreated 2K1C eNOS+/+ (B) and 2K1C eNOS−/− (E), and nonclipped kidneys of c-AUCB-treated 2K1C eNOS+/+ (C) and 2K1C eNOS−/− (F).

Figure 7

Representative renal parenchyme in clipped kidneys of untreated 2K1C eNOS+/+ (A) and 2K1C eNOS−/− (C), and clipped kidneys of c-AUCB-treated 2K1C eNOS+/+ (B) and 2K1C eNOS−/− (D).