Antihypertensive and renoprotective actions of soluble epoxide hydrolase inhibition in ANG II-dependent malignant hypertension are abolished by pretreatment with L-NAME

Abstract

Objective: The present study was performed to investigate in a model of malignant hypertension if the antihypertensive actions of soluble epoxide hydrolase (sEH) inhibition are nitric oxide (NO)-dependent.

Methods: ANG II-dependent malignant hypertension was induced through dietary administration for 3 days of the natural xenobiotic indole-3-carbinol (I3C) in Cyp1a1-Ren-2 transgenic rats. Blood pressure (BP) was monitored by radiotelemetry and treatment with the sEH inhibitor [cis-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyl-oxy]-benzoic acid (c-AUCB)] was started 48 h before administration of the diet containing I3C. In separate groups of rats, combined administration of the sEH inhibitor and the nonspecific NO synthase inhibitor [Nω-nitro-L-arginine methyl ester (L-NAME)] on the course of BP in I3C-induced and noninduced rats were evaluated. In addition, combined blockade of renin-angiotensin system (RAS) was superimposed on L-NAME administration in separate groups of rats. After 3 days of experimental protocols, the rats were prepared for renal functional studies and renal concentrations of epoxyeicosatrienoic acids (EETs) and their inactive metabolites dihydroxyeicosatrienoic acids (DHETEs) were measured.

Results: Treatment with c-AUCB increased the renal EETs/DHETEs ratio, attenuated the increases in BP, and prevented the decreases in renal function and the development of renal damage in I3C-induced Cyp1a1-Ren-2 rats. The BP lowering and renoprotective actions of the treatment with the sEH inhibitor c-AUCB were completely abolished by concomitant administration of L-NAME and not fully rescued by double RAS blockade without altering the increased EETs/DHETEs ratio.

Conclusion: Our current findings indicate that the antihypertensive actions of sEH inhibition in this ANG II-dependent malignant form of hypertension are dependent on the interactions of endogenous bioavailability of EETs and NO.

FIGURE 1

Course of mean arterial pressure (measured by radiotelemetry) (a and c) and body weight (b and d) in indole-3-carbinol (I3C)-induced and noninduced Cyp1a1-Ren-2 transgenic rats and the effects of isolated cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB) or Nω-nitro-l-arginine methyl ester (L-NAME) administration and either combined treatment with c-AUCB and L-NAME or combined RAS blockade and L-NAME treatment in these rats. *P < 0.05 vs. basal values. ^#P < 0.05 vs. c-AUCB unmarked values at the same time point. ^@P < 0.05 vs. all values at the same time point.

FIGURE 2

Urinary albumin excretion (a and c) and kidney tubulointerstitial injury (b and d) in indole-3-carbinol (I3C)-induced and noninduced Cyp1a1-Ren-2 transgenic rats and the effects of isolated cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB) or Nω-nitro-l-arginine methyl ester (L-NAME) administration and either combined treatment with c-AUCB and L-NAME or combined RAS blockade and Nω-nitro-l-arginine methyl ester (L-NAME) treatment in these rats. *P < 0.05 vs. unmarked values. ^#P < 0.05 vs. all values.

FIGURE 3

Epoxyeicosatrienoic acids (EETs) (a and c) and dihydroxyeicosatrienoic acids (DHETEs) (b and d) in kidney in indole-3-carbinol (I3C)-induced and noninduced Cyp1a1-Ren-2 transgenic rats and the effects of isolated cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB) or Nω-nitro-l-arginine methyl ester (L-NAME) administration and either combined treatment with c-AUCB and L-NAME or combined RAS blockade and L-NAME treatment in these rats. *P < 0.05 vs. unmarked values.

FIGURE 4

EETs/DHETEs ratio (a and b) in kidney in indole-3-carbinol (I3C)-induced and noninduced Cyp1a1-Ren-2 transgenic rats and the effects of isolated cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB) or Nω-nitro-l-arginine methyl ester (L-NAME) administration and either combined treatment with c-AUCB and L-NAME or combined RAS blockade and L-NAME treatment on this ratio in these rats. *P < 0.05 vs. unmarked values.

FIGURE 5

Plasma (a and c) and kidney (b and d) angiotensin II levels in indole-3-carbinol (I3C)-induced and noninduced Cyp1a1-Ren-2 transgenic rats and effects of isolated cis-4-[4-(3-adamantan-1-yl-ureido)cyclohexyloxy]benzoic acid (c-AUCB) or Nω-nitro-l-arginine methyl ester (L-NAME) administration and either combined treatment with c-AUCB and L-NAME or combined RAS blockade and L-NAME treatment in these rats. *P < 0.05 vs. unmarked values. ^#P < 0.05 vs. all values.