Vasopressin Induces Vascular Superoxide Via Endothelin-1 in Mineralocorticoid Hypertension

Abstract

Abstract-We have recently reported that endothelin-1 (ET-1), which is increased in the arteries of deoxycorticosterone acetate (DOCA)-salt hypertensive rats, stimulates superoxide production. However, the humoral mechanisms responsible for ET-1-induced superoxide formation in low-renin models of hypertension, such as DOCA-salt hypertension, remain undefined. Vasopressin is known to upregulate vascular preproET-1 gene expression in DOCA-salt rats, an effect that is absent in vasopressin-deficient Brattleboro rats treated with DOCA-salt. The present study tested the hypothesis that vasopressin contributes to ET-1-induced vascular superoxide production in DOCA-salt hypertensive rats. Carotid arterial segments of DOCA, sham (uninephrectomized), or normal (untreated) rats were used for the study. In vitro vasopressin treatment of carotid arteries from normal rats for 24 hours, but not 4 hours, increased both ET-1 and superoxide levels. The increase of vasopressin-induced superoxide was reduced by pretreatment of the vessels with ABT627, a selective ET A receptor antagonist ABT627. Vasopressin, ET-1, and superoxide levels were significant elevated in carotid arteries of DOCA-salt rats compared with sham controls. The selective V1-vasopressin receptor antagonist (␤-Mercapto-␤, ␤-cyclopentamethylenepropiony 1 , O-Me-Tyr 2 , Arg 8 vasopressin, ME-AVP), decreased superoxide both in vasopressin-treated vessels of normal rats and in vessels of DOCA-salt rats, with a concomitant reduction of ET-1 content. These results suggest that vasopressin increases vascular superoxide levels by stimulating ET-1 formation in mineralocorticoid hypertension, and that V1-vasopressin receptors play an important role in this process. Ϫ is produced in activated endothelial cells, 4 smooth muscle cells, 5 and adventitial fibroblasts. 6 Vascular dysfunction is manifested as impaired endothelium-dependent NO-mediated relaxation, 1-3 adhesion molecule expression, 7 low-density lipoprotein oxidation, 8 and cell proliferation. 9 However, the detailed mechanisms responsible for O 2 Ϫ production under different pathophysiological circumstances remain to be defined.We have recently shown that arterial endothelin-1 (ET-1) levels are elevated in deoxycorticosterone acetate (DOCA)-salt hypertension, 10 and that this resulted in increased O 2 Ϫ production 7,10 via ET A receptor activation 10 in this low-renin hypertension model. 11 However, the mechanisms contributing to increased ET-1 are unknown. The peptide hormone 8-argininevasopressin (AVP) is able to stimulate preproendothenlin-1 mRNA expression in arteries and cultured endothelial cells. [12][13][14] Furthermore, the enhanced endothelin gene expression observed in DOCA-salt rats was absent in vasopressin-deficient Brattleboro rats treated with DOCA-salt, 13 suggesting a functional link between vasopressin and ET-1 gene expression.The biological effects of vasopressin are mediated through 2 AVP receptor subtypes, the V 1 and V 2 receptors. 15-17 V 1 receptors mediate vasoconstriction, proliferation, ...

Gene Transfer of Human Guanosine 5′-Triphosphate Cyclohydrolase I Restores Vascular Tetrahydrobiopterin Level and Endothelial Function in Low Renin Hypertension

“…16,17 Our recent studies indicate that endothelin-1 (ET-1) plays an important role in NADPH oxidase-derived O 2 Ϫ production in this model. [13][14][15] However, the interaction between ET-1-induced O 2 Ϫ and BH 4 on endothelial dysfunction and the underlying mechanisms are unknown. In the present study, we tested the hypothesis that ET-1-induced O 2 Ϫ reduces BH 4 and endothelium-dependent relaxation in carotid arteries of DOCA-salt rats, and gene transfer of human GTPCH I reverses the BH 4 deficiency and endothelial dysfunction by reducing O 2 Ϫ levels.…”

“…[13][14][15] Briefly, rats (250 to 275 g, Charles River, Portage, Mich) underwent uninephrectomy (flank incision, left side) and a silicon rubber DOCA implant (Sigma) (200 mg/kg) was placed subcutaneously between the shoulder blades. Sham rats were also uninephrectomized but received no implant.…”

“…[13][14][15] Some arterial segments from sham and DOCA-salt rats were incubated at 37°C for 4 hours with or without the respective agents before O 2 Ϫ , BH 4 , and GTPCH I measurements.…”

“…[13][14][15]18 The rings were then transferred to fresh Eagle minimal essential medium (EMEM) with 0.1% bovine serum albumin and incubated for 24 hours at 37°C. Some vessels from sham and DOCA-salt rats were incubated for 24 hours without transduction and served as normal negative controls.…”

“…[13][14][15] The oxidative fluorescent dye dihydroethidine was used to evaluate in situ O 2 Ϫ production. Unfixed frozen rings of carotid arteries were cut into 30 m sections and placed on a glass slide.…”