Androgen-dependent hypertension is mediated by 20-hydroxy-5,8,11,14-eicosatetraenoic acid-induced vascular dysfunction: role of inhibitor of kappaB Kinase

Abstract

Increased vascular synthesis of 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE) is associated with increased vascular contraction, endothelial dysfunction, and endothelial activation; all are believed to account for 20-HETE prohypertensive properties. We demonstrated previously that the 20-HETE-dependent inhibition of NO production is mediated through inhibitor of κB kinase (IKK), suggesting a cross-talk between 20-HETE-mediated endothelial dysfunction and activation. In this study, we examined the temporal relationship among blood pressure, endothelial dysfunction, and endothelial activation and the role of IKK in the rat model of androgen-driven 20-HETE-mediated hypertension. In Sprague-Dawley rats treated with 5α-dihydrotestosterone, renal vascular 20-HETE levels increased by day 2 of treatment from 17.7±2.4 to 57.7±9.7 ng/mg, whereas blood pressure elevation reached significance by day 3 (132.7±1.7 versus 117.2±0.8 mm Hg). In renal interlobar arteries, when compared with vehicle, 5α-dihydrotestosterone treatment increased the sensitivity to phenylephrine-induced vasoconstriction by 3.5-fold, decreased acetylcholine-induced vasorelaxation, and increased nuclear factor κB activity, all of which were attenuated by treatment with the 20-HETE antagonist, 20 hydroxyeicosa-6(Z),15(Z)-dienoic acid, (20-6,15-HEDE). Cotreatment with parthenolide, an IKK inhibitor, attenuated the androgen-dependent 20-HETE-mediated elevation in blood pressure (from 133.7±3.1 to 109.8±3.0 mm Hg). In addition, parthenolide treatment negated 20-HETE-mediated inhibition of the relaxing response to acetylcholine and 20-HETE-mediated increase in vascular nuclear factor κB activity. These findings suggest that inhibition of IKK attenuates the androgen-dependent 20-HETE-mediated increase in blood pressure by inhibiting both 20-HETE-dependent endothelial activation and dysfunction.

Figure 1. Inhibition of 20-HETE synthesis or activity attenuates androgen-dependent 20-HETE-mediated hypertension

DHT-treated rats were co-administered either HET0016 or 20-6,15-HEDE at the start of the experiment (A) or after systolic blood pressure plateaued at 7 days of treatment (B). Results are mean±SE (N=4) *p<0.05 vs vehicle treated rats; ^#p<0.05 vs DHT treated rats.

Figure 2. DHT-induced changes in vascular function are 20-HETE-dependent

DHT-treated rats were co-administered 20-6,15-HEDE for three days. The constrictor responses to phenylephrine (A) and the relaxing responses to acetylcholine (B) of renal interlobar arteries were measured. Results are mean±SE (N=3–7); *p<0.05 vs vehicle treated rats; ^#p<0.05 vs DHT treated rats.

Figure 3. DHT treatment leads to NF-κB activation that is 20-HETE-dependent

(A) Representative Western blots and densitometry analysis of p-IκBα (n=3–6; *p<0.05 vs vehicle) and (B) nuclear NF-κB activity (n=6–18; *p<0.05 vs vehicle treated rats; ^#p<0.05 vs DHT treated rats) in renal interlobar arteries from from rats treated for 3 days with vehicle, DHT and DHT+20-6,15-HEDE (n=6–18; *p<0.05 vs vehicle treated rats; ^#p<0.05 vs DHT treated rats).

Figure 4. Inhibition of NF-kB activation attenuates androgen-dependent 20-HETE-mediated hypertension

(A) Systolic blood pressure (N=8), (B) NF-κB activity in nuclear extract of renal interlobar arteries (N=8–10) and (C) 20-HETE levels in interlobar arteries from rats treated with vehicle, DHT, parthenolide and DHT+parthenolide. Results are mean ± SE. *P<0.05 vs vehicle-treated rats; ^#P<0.05 vs DHT-treated rats.

Figure 5. Effect of parthenolide on DHT-induced changes in vascular function

DHT-treated rats were co-administered Parthenolide for three days. The constrictor responses to phenylephrine (A) and the relaxing responses to acetylcholine (B) and SNP (C) of renal interlobar arteries were measured. Results are mean±SE (N=6–8) *p<0.05 vs vehicle treated rats; ^#p<0.05 vs DHT treated rats.