Targeting of the renin-Angiotensin system as an adjunct to estrogen replacement therapy

In women with symptoms of cardiac ischemia, nonobstructive coronary arteries, and microvascular dysfunction, angiotensin-converting enzyme inhibition is associated with improved microvascular function: A double-blind randomized study from the National Heart, Lung and Blood Institute Women's Ischemia Syndrome Evaluation (WISE)

BACKGROUND

We investigated the role of the renin-angiotensin system in women with signs and symptoms of ischemia without obstructive coronary artery disease (CAD). Although microvascular dysfunction has been suggested to explain this syndrome and recently was found to predict adverse outcomes, the mechanisms and treatments remain unclear.

METHODS

In a substudy within the WISE, 78 women with microvascular dysfunction (coronary flow reserve [CFR] <3.0 following adenosine) and no obstructive CAD were randomly assigned to either an angiotensin-converting enzyme inhibition (ACE-I) with quinapril or a placebo treatment group. The primary efficacy parameter was CFR at 16 weeks adjusted for baseline characteristics and clinical site. The secondary response variable was freedom from angina symptoms assessed using the Seattle Angina Questionnaire.

RESULTS

A total of 61 women completed the 16-week treatment period with repeat CFR measurements, and treatment was well tolerated. For the primary outcome, at 16 weeks, CFR improved more with ACE-I than placebo (P < .02). For the secondary outcome of symptom improvement, ACE-I treatment (P = .037) and CFR increase (P = .008) both contributed.

CONCLUSIONS

Microvascular function improves with ACE-I therapy in women with signs and symptoms of ischemia without obstructive CAD. This improvement is associated with reduction in angina. The beneficial response of the coronary microvasculature was limited to women with lower baseline CFR values, suggesting that the renin-angiotensin system may be more involved among women with more severe microvascular defects.

Tumor Necrosis Factor-α and Vascular Angiotensin II in Estrogen-Deficient Rats

Alterations in the vascular angiotensin II system may play a role in the pathophysiology of vascular disease after menopause. In previous studies we have shown that an increase in tumor necrosis factor (TNF)-α levels in aging rats because of estrogen deficiency may result in vascular dysfunction. In this study we investigated the effect of TNF-α inhibition in angiotensin II modulation of vascular function in aging female animals. Female rats approaching reproductive senescence (12 to 15 months old) were ovariectomized and treated with placebo, estrogen, or a selective TNF-α inhibitor (etanercept) for 4 weeks. Expression of angiotensin II in mesenteric arteries was evaluated by immunofluorescence, and the expression of angiotensin-converting enzyme and angiotensin type I receptor (AT 1 R) was investigated by Western immunoblot. Vascular function was assessed in mesenteric arteries using the myograph system, and the role of endogenous angiotensin II on adrenergic vasoconstriction was evaluated in vitro by selective AT 1 R blockade (Candesartan; 10 μmol/L). Our data demonstrate that estrogen-depleted rats have higher serum levels of TNF-α and greater sensitivity to phenylephrine vasoconstriction compared with estrogen-replaced animals, which was attenuated by AT 1 R blockade. In vivo TNF-α inhibition or estrogen replacement reduced phenylephrine constriction of mesenteric arteries and decreased the modulation of this vasoconstriction by candesartan. These functional changes were accompanied by a reduction in the vascular expression of angiotensin II, angiotensin-converting enzyme, and AT 1 R. These observations indicate that upregulation of TNF-α during estrogen deficiency may contribute to enhance vascular constriction by altering the vascular angiotensin II system.