J. Koudy Williams

Medroxyprogesterone Acetate Antagonizes Inhibitory Effects of Conjugated Equine Estrogens on Coronary Artery Atherosclerosis

Although estrogen replacement therapy is associated with reduced risk of coronary heart disease and reduced extent of coronary artery atherosclerosis, the effects of combined (estrogen plus progestin) hormone-replacement therapy are uncertain. Some observational data indicate that users of combined hormone replacement consisting of continuously administered oral conjugated equine estrogens (CEE) and oral sequentially administered (7 to 14 days per month) medroxyprogesterone acetate (MPA) experience a reduction in risk similar to that of users of CEE alone. However, the effects of combined, continuously administered CEE plus MPA (a prescribing pattern that has gained favor) on the risk of coronary heart disease or atherosclerosis are not known. We studied the effects of CEE (monkey equivalent of 0.625 mg/d) and MPA (monkey equivalent of 2.5 mg/d), administered separately or in combination, on the extent of coronary artery atherosclerosis (average plaque size) in surgically postmenopausal cynomolgus monkeys fed atherogenic diets and treated with these hormones for 30 months. Treatment with CEE alone resulted in atherosclerosis extent that was reduced 72% relative to untreated (estrogen-deficient) controls (P < .004). Atherosclerosis extent in animals treated with CEE plus MPA or MPA alone did not differ from that of untreated controls. Although treatment had marked effects on plasma lipoprotein patterns, statistical adjustment for variation in plasma lipoproteins did not alter the between-group relationships in atherosclerotic plaque size, suggesting that these factors do not explain substantially the atheroprotective effect of estrogen or the MPA-associated antagonism. Although the mechanism(s) remains unclear, we conclude that oral CEE inhibits the initiation and progression of coronary artery atherosclerosis and that continuously administered oral MPA antagonizes this atheroprotective effect.

Short-term administration of estrogen and vascular responce of atherosclerotic coronary arteries

OBJECTIVES This experiment sought to determine the effect of short-term administration of estrogen on endothelium-dependent dilation in the coronary arteries of 13 surgically postmenopausal female cynomolgus monkeys. BACKGROUND Long-term estrogen replacement therapy prevents impaired endothelium-dependent dilation of atherosclerotic coronary arteries in postmenopausal female monkeys. However, it remains unclear whether this action of estrogen is due to long-term effects on plasma lipids and atherogenesis or to direct short-term effects on the endothelium. METHODS The monkeys consumed an atherogenic diet for 18 months after bilateral ovariectomy. Vascular responses were measured just before euthanasia and necropsy. Dextrose in water (control), acetylcholine, 10(-6)M, and nitroglycerin were infused for 2.5 min each both before and 20 min after intravenous injection of 54 ng ethinyl estradiol. RESULTS Quantitative coronary angiography revealed that the arteries constricted (-17 +/- 3%) in response to intracoronary infusion of acetylcholine before estrogen treatment but dilated (+5 +/- 3%) 20 min after intravenous injection of ethinyl estradiol (p less than 0.05). Coronary arteries dilated in response to nitroglycerin both before and after administration of estrogen (p greater than 0.05). Vascular responses of coronary arteries, both before and after administration of estrogen, were not associated with variation in plasma lipid concentrations, blood pressure, heart rate or plaque size. CONCLUSIONS Estrogen affects endothelium-dependent coronary dilation within 20 min of administration and may have rapid direct effects on the vascular endothelium.

Pravastatin Has Cholesterol-Lowering Independent Effects on the Artery Wall of Atherosclerotic Monkeys☆

OBJECTIVES This study examined the direct effects of pravastatin on the artery wall of atherosclerotic monkeys after dietary lipid lowering. BACKGROUND Clinical trials suggest that hepatic hydroxymethylglutaryl coenzyme A reductase inhibitors may reduce the risk of coronary heart disease out of proportion to their effect on angiographically assessed lumen stenosis. METHODS Thirty-two cynomolgus monkeys were fed an atherogenic diet for 2 years (progression phase) and then fed a lipid-lowering diet either containing (n = 14) or not containing (n = 18) pravastatin in the diet for an additional 2 years (treatment phase). As designed, total plasma cholesterol and high density lipoprotein concentrations did not differ between groups at the beginning of or during the treatment phase of the experiment (p > 0.05). RESULTS Quantitative angiography revealed that coronary arteries of the pravastatin-treated monkeys dilated 10 +/- 3%, whereas those from untreated control monkeys constricted -2 +/- 2% in response to acetylcholine (p < 0.05). There were no treatment effects on plaque size of coronary arteries measured at the end of the treatment phase of the study (0.110 +/- 0.048 mm2 [untreated] vs. 0.125 +/- 0.051 mm2 [pravastatin]; p > 0.05) or on the amount of reduction in plaque size in common iliac arteries during the treatment phase of the study (48 +/- 5% [untreated] vs. 45 +/- 6% [pravastatin]; p > 0.05). However, histochemical analysis of the atherosclerotic lesions indicated that the arteries from pravastatin-treated monkeys had significantly fewer macrophages in the intima and media, less calcification and less neovascularization in the intima (p < 0.05). CONCLUSIONS We conclude that compared with control monkeys, the arteries of pravastatin-treated monkeys had better dilator function and plaque characteristics more consistent with plaque stability than those of monkeys not receiving pravastatin. These beneficial arterial effects of pravastatin occurred independently of plasma lipoprotein concentrations and despite similar changes in plaque size between the groups.

Soy isoflavones enhance coronary vascular reactivity in atherosclerotic female macaques.

OBJECTIVE To examine the effects of soy phytoestrogens on coronary vascular reactivity in atherosclerotic male and female rhesus monkeys. DESIGN A prospective, randomized, blinded, controlled study. SETTING Comparative Medicine Clinical Research Center of an academic medical center. PATIENT(S) Twenty-two young adult rhesus monkeys with pre-existing diet-induced atherosclerosis. INTERVENTION(S) Monkeys were fed soy-based diets for 6 months identical in composition, except that the isoflavones were extracted from one flow-isoflavone) and intact in the other (high-isoflavone). Quantitative coronary angiography was performed at the end of the study period. Females in the low-isoflavone group under went a second angiography after an acute IV dose of genistein. MAIN OUTCOME MEASURE(S) Percent change in diameter of the proximal left circumflex coronary artery in response to intracoronary acetylcholine and nitroglycerin, compared with control diameter. RESULT(S) Arteries from males constricted in response to acetylcholine. Arteries from females in the low-isoflavone group constricted (-6.2% +/- 2.8%, mean +/- SEM), whereas arteries from females in the high-isoflavone group dilated (6.4% +/- 1.2%, mean +/- SEM). Intravenous administration of genistein caused dilation in the previously constricting low-isoflavone females (3.3% +/- 2.8%). CONCLUSION(S) Like mammalian estrogens, dietary soy isoflavones enhance the dilator response to acetylcholine of atherosclerotic arteries in female monkeys.

Effects of hormone replacement therapy on reactivity of atherosclerotic coronary arteries in cynomolgus monkeys

OBJECTIVES We attempted to determine whether continuous and cyclic medroxyprogesterone acetate modulates the effects of estrogen on dilation of atherosclerotic coronary arteries in surgically postmenopausal female monkeys. BACKGROUND Estrogen replacement in postmenopausal women preserves normal dilator responses of atherosclerotic coronary arteries. The effects of progestins on coronary artery reactivity have not been determined. METHODS Repeated quantitative coronary angiography was used to study the effects after 1 month of 1) no hormone replacement (control) or oral administration of 2) continuous conjugated equine estrogens, 3) cyclic high dose medroxyprogesterone acetate (MPA) given on days 16 to 26 of the month, 4) conjugated equine estrogens plus continuous low dose MPA, or 5) conjugated equine estrogens plus cyclic high dose MPA on endothelium-mediated dilation of atherosclerotic coronary arteries in 12 cynomolgus monkeys. Change in diameter of the left circumflex coronary artery was measured in response to intracoronary infusions of acetylcholine (10(-6) mol/liter per min) and nitroglycerin (15 micrograms/min). RESULTS Coronary arteries constricted during no hormone treatment (-8 +/- 3% [mean +/- SEM]), dilated during conjugated equine estrogen treatment (+3 +/- 1%, p < 0.05 vs. control) and constricted during cyclic MPA treatment (-3 +/- 2%). Addition of cyclic or continuous MPA to the conjugated equine estrogen regimen inhibited acetylcholine responses by 50% (p < 0.05 vs. conjugated equine estrogens). There was no effect of treatment on vascular response to nitroglycerin (p > 0.05). CONCLUSIONS Treatment with conjugated equine estrogens, but not MPA, augmented endothelium-mediated dilation of atherosclerotic coronary arteries. Addition of cyclic or continuous MPA to the conjugated equine estrogen regimen diminished endothelium-mediated dilation.

Statins Reduce Inflammation in Atheroma of Nonhuman Primates Independent of Effects on Serum Cholesterol

Objective—Some of the statin-induced reduction in cardiac events in patients with atherosclerosis may be derived from mechanisms independent of lipid lowering. This study tested in nonhuman primates whether statins can influence inflammation (indicated by vascular cell adhesion molecule-1, interleukin-1&bgr;, tissue factor, and macrophages) and features of plaque stability (indicated by collagen and smooth muscle cells) independent of their effect on plasma cholesterol level. Methods and Results—Adult male cynomolgus monkeys (n=12 per group) consumed an atherogenic diet for 12 months while receiving (1) no treatment (control), (2) pravastatin (Prava, 40 mg/kg per day), or (3) simvastatin (Simva, 20 mg/kg per day). Dietary cholesterol was adjusted to equalize plasma cholesterol levels among groups. Although the intima/media ratio in the abdominal aorta did not differ among groups, drug treatment reduced inflammation and features of plaque vulnerability. Macrophage content in the lesions of statin-treated animals was lowered (2.4-fold with Prava and 1.3-fold with Simva; both P<0.001 versus control). Furthermore, lesions had ≈2-fold less vascular cell adhesion molecule-1, interleukin-1&bgr;, and tissue factor expression in statin-treated versus control animals (P <0.005). Lesional smooth muscle cell and collagen content was 2.1-fold greater in the Prava-treated group (P <0.001) and 1.5-fold greater in the Simva-treated group (P <0.005) than in the control group. Conclusions—In primates, these results provide further support for the beneficial effect of statins on plaque inflammation and stability in addition to cholesterol lowering.

Regression of Atherosclerosis in Female Monkeys

The objective of this study was to determine the structural and functional changes that occur in the artery wall in response to plasma lipid lowering and hormone replacement in surgically postmenopausal monkeys with established coronary artery atherosclerosis. Eighty-eight surgically postmenopausal cynomolgus monkeys were fed an atherogenic diet for 24 months and were then allocated into 4 groups: group 1 (n = 20), a baseline necropsy group; group 2 (n = 25), a lipid-lowering diet only; group 3 (n = 22), lipid lowering plus conjugated equine estrogen treatment equivalent to 0.625 mg/d for a woman; and group 4 (n = 21), lipid lowering plus conjugated equine estrogen and medroxyprogesterone acetate treatment (equivalent to 2.5 mg/d for a woman). Treatment was for 30 months. Histomorphometric analysis of perfusion-fixed coronary arteries revealed that plaque size did not change significantly in any of the groups compared with group 1 (P > .20). Plasma lipid lowering permitted coronary artery remodeling to occur (coronary artery and lumen size doubled compared with group 1) (P < .05); however, hormone therapy did not augment remodeling. Quantitative angiographic analysis of coronary artery reactivity revealed that lipid lowering improved dilator responses to acetylcholine by 22 +/- 4% (P = .01) but not to nitroglycerin (P = .23). Hormone replacement did not further affect vascular reactivity to the agonists tested (P > .4), but addition of medroxyprogesterone acetate diminished the beneficial effects of conjugated estrogens on coronary flow reserve (P = .03). In summary, the major arterial sequelae of lipid lowering in female monkeys were artery and lumen enlargement and improved reactivity of large epicardial coronary arteries. Addition of hormone replacement to the dietary modification did not further augment these improvements, except for the dilator capacity of the coronary microcirculation.

Effects of Androgens on Coronary Artery Atherosclerosis and Atherosclerosis-Related Impairment of Vascular Responsiveness

The factors responsible for the marked gender differences in risk of coronary heart disease and atherosclerosis severity remain largely undetermined. While some clinical and experimental evidence supports a protective effect of endogenous estrogen on the initiation and progression of atherosclerosis and incidence of coronary heart disease, much of the epidemiological data do not support this conclusion. The possibility that endogenous androgens may have adverse effects on atherosclerosis progression and coronary risk has received little attention. We investigated the effects of experimentally induced hyperandrogenism in female cynomolgus monkeys with diet-induced atherosclerosis. Animals were assigned randomly to one of four treatment groups: (1) untreated controls, (2) ovariectomized (sex hormone-deficient) controls, (3) treated with androstenedione and estrone (mild hyperandrogenism), or (4) treated with testosterone (male plasma androgen pattern). At necropsy, coronary atherosclerosis was approximately twice as extensive (P < .05) in testosterone-treated animals relative to untreated controls, while treatment with androstenedione and estrone had no effect on atherosclerosis extent. Coronary plaque size was positively correlated with lumen size in intact and ovariectomized controls; however, there was no evidence of a similar relation between animals in either androgen treatment group. The atherogenic effects of testosterone were independent of variations in plasma lipoprotein and nonlipoprotein risk variables. Although chronic hyperandrogenism had adverse effects on atherosclerosis progression, it reversed (P < .03) atherosclerosis-related impairment of endothelium-dependent vasodilator responses. We conclude that an experimentally induced male plasma androgen pattern results in exacerbation of diet-induced atherosclerosis-related arterial remodeling in female monkeys.(ABSTRACT TRUNCATED AT 250 WORDS)

Endothelial-dependent coronary vasomotor responsiveness in postmenopausal women with and without estrogen replacement therapy.

Recently, Williams et al’ reported that acute administration of estrogen attenuates the coronary vasoconstrictor response to acetylcholine in atherosclerotic cynomolgus monkeys. These observations suggest that estrogen plays a fundamentally important role in the relationship between coronary vascular endothelium and vascular smooth muscle. This study examines the influence of current estrogen replacement therapy in postmenopausal women on endothelial-dependent and independent vasomotor responsiveness to acetylcholine. Ten postmenopausal women with exertional angina undergoing routine diagnostic coronary angiography or percutaneous transluminal coronary angioplasty were studied. The protocol was approved by the Clinical Research Practices Committee and each subject gave informed consent before the study, Four women were taking estrogen replacement therapy (PremarinB 0.625 to 1.25 mglday or topical estradiol 0.1 mg). None of the women were taking progesterone. All of the women had minimal coronary artery narrowings in the proximal portion of the left anterior descending or a nondominant circumflex coronary artery. Vasoactive medications were withheld for 12-24 hours before the procedure. A 3Fr infusion catheter was positioned in the proximal left anterior descending or proximal circumflex artery through the guiding catheter. After the baseline angiogram was recorded, 3 consecutive 2-minute infusions of acetylcholine were administered into the proximal coronary artery. The

The Pathogenicity of Behavior and Its Neuroendocrine Mediation: An Example From Coronary Artery Disease

ow rate (0.8 mllmin) was calculated to deliver a final estimated blood concentration of 10s, 10m7 and 10m6 M. After each acetylcholine infusion, repeat angiography was performed in an identical fashion to baseline. After the third acetylcholine in& sion and angiogram, a 50 pg bolus of nitroglycerin was administered and a final coronary angiogram was recorded. Heart rate, blood pressure and appropriate electrocardiographic leads were monitored during the infusions to verify the absence of any changes in hemodynamic status or evidence of &hernia. Proximal and midvessel segments of the coronary artery distal to the tip of the infusion catheter were analyzed without knowledge of the estrogen status using a quantitative coronary angiography method (Gammasonits, Chicago, Illinois). When possible, coronary segments from the noninfused half of the left coronary distribution