Dehydroepiandrosterone Reduces Plasma Plasminogen Activator Inhibitor Type 1 and Tissue Plasminogen Activator Antigen in Men

Dehydroepiandrosterone Reduces Plasma Plasminogen Activator Inhibitor Type 1 and Tissue Plasminogen Activator Antigen in Men

Dehydroepiandrosterone Reduces Plasma Plasminogen Activator Inhibitor Type 1 and Tissue Plasminogen Activator Antigen in Men NUSEN A. BEER, MD,* DANIE...

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Dehydroepiandrosterone Reduces Plasma Plasminogen Activator Inhibitor Type 1 and Tissue Plasminogen Activator Antigen in Men NUSEN A. BEER, MD,* DANIELA J. JAKUBOWICZ, MD,* RIVKA M. BEER, PHD,* JOHN E. NESTLER, MDt·f·§

ABSTRACT: Dehydroepiandrosterone (DHEA) may help prevent heart disease in men. To test the hypothesis that DHEA might exert its effects by enhancing endogenous fibrinolytic potential, a double-blind, placebo-controlled study was conducted that assessed the effects of DHEA administration on plasma plasminogen activator inhibitor type 1 (PAI-l) and tissue plasminogen activator (tPA) antigen. Eighteen men received 50 mg DHEA orally and 16 men received a placebo capsule thrice daily for 12 days. Serum DHEA-sulfate and plasma PAI-l and tP A antigen were measured before and after treatment. In the DHEA group, serum DHEA-sulfate (from 7.5 ± 1.2 #Lmol/L to 20.2 ± 1.5 #Lmol/L (P < 0.0001), androstenedione (from 2.6 ± 0.2 nmol/ L to 4.0 ± 0.4 nmolfL; P < 0.005) and estrone (from 172 ± 21 pmol/L to 352 ± 28 pmol/L; P < 0.005) increased, whereas plasma PAI-l (from 55.4 ± 3.8 ng/mL to 38.6 ± 3.3 ng/mL; P < 0.0001) and tPA antigen (from 8.1 ± 1.9 ng/mL to 5.4 ± 1.3 ng/mL; P < 0.0005) decreased. In the placebo group, serum DHEA-sulfate declined slightly from 8.0 ± 3.3 #Lmol/L to 7.3 ± 3.4 ~Lmol/ L (P < 0.05), but no other measured steroid changed. Plasma PAI-l and tPA antigen did not change in the placebo group. These findings suggest that DHEA administration reduces plasma PAI-l and tPA antigen concentrations in men. KEY INDEXING TERMS: Dehydroepiandrosterone; Steroids; Atherosclerosis; Plasminogen From the *Department of Internal Medicine, Hospital de Clinicas Caracas, Fundaci6n Cardiovascular Congreso National, Caracas, Venezuela, and the Departments of :j:Internal M edicine, §Pharmacology and Toxicology, and tObstetrics and Gynecology, Medical College of Virginia/Virginia Commonwealth University, Richmond, Virginia. Presented in abstract form at the 77th Annual Meeting of The Endocrine Society, Washington, DC, June 14-17, 1995. Supported in part by National Institutes of Health grant R01AG11227 (to J.E.N.) and a grant from the Venezuelan National Congress (to N.A.B.). Correspondence: John E. N estler, MD, Medical College of Virginia, P .O. Box 980111, Richmond, VA 23298-0111. THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES

DENNIS W. MATT, MD,t

activator; Plasminogen activator inhibitor. [Am J Med Sci 1996;311(5):205-210.]

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ehydroepiandrosterone sulfate (DHEA-sulfate) is the most abundant circulating steroid hormone in humans, and can be readily converted to its parent steroid, DHEA, by tissue steroid sulfatases. Dehydroepiandrosterone exhibits a very high turnover, which is characteristic of a biologically active hormone, but a biologic role for DHEA and DHEA-sulfate has not yet been defined. In this regard, on the basis of recent and mounting epidemiologic evidence, DHEA and DHEA-sulfate may play an important physiologic role in the prevention of heart disease in men. 1- 6 These observations are supported by animal studies, in which DHEA administration protects against the development of experimentally-induced aortic 7•8 and coronary9 atherosclerosis. The mechanism(s) by which DHEA exerts these cardioprotective and antiatherogenic actions is not clear, although suggestions have included inhibition of cellular proliferation, reduction of serum lipids, and suppression of platelet reactivity. 4 Impaired endogenous fibrinolytic activity may accelerate atherosclerosis as a result of prolonged or recurrent exposure of luminal surfaces of arterial walls to microthrombi and clot-associated mitogens. These events can elicit chemotaxis, activation of macrophages, and migration and proliferation of vascular smooth muscle cells. Many studies of fibrinolyt£c capacity have measured circulating plasminogen activator inhibitor type 1 (PAI-l), a plasma protein that inhibits the activity of tissue plasminogen activator (tPA). Elevated plasma P AI -1 levels presumably reflect decreased fibrinolytic activity, and are associated with high risk for myocardial infarction in men.10- 13 Similarly, increased tPA antigen levels are a risk factor for coronary thrombosis and predict long-term mortality in patients with coronary artery disease, 12•14- 17 presumably because they also reflect depressed tPA activity. 16•18 Therefore, both

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DHEA, PAI-1, and tPA Antigen

PAI-l and tPA antigen are circulating markers of fibrinolytic potential, and elevated plasma PAI-l and tP A antigen levels are risk factors for heart disease in men.I0-17 It was shown in vitro 19- 23 and in vivo 24 ·25 that several steroids, such as dexamethasone, hydrocortisone, 17ahydroxyprogesterone, pregnenolone, medroxyprogesterone, and 17,8-estradiol, influence the biosynthesis of P AI -1 by endothelial cells via regulation of P AI -1 mRNA. Most recently, the Framingham Offspring Study reported that postmenopausal women receiving estrogen replacement therapy had lower levels of P AI1 and tP A antigen than women not receiving estrogens.26 In view of these observations, we hypothesized that a mechanism for DHEA's cardioprotective actions might include enhancement of fibrinolytic potential. To test this hypothesis, a prospective, randomized, double-blind and placebo-controlled study was conducted in which we assessed the effects of oral DHEA administration to men on plasma concentrations of P AI -1 and tP A antigen. Materials and Methods Study Design. A total of 34 men were enrolled in and

completed the study. The men ranged in age from 4 7 to 75 years old, and were not taking any medications before the study. The study was approved by the Institutional Review Board of the Hospital de Clinicas Caracas, where the study was conducted, and informed consent was obtained from each man. Eighteen men were assigned randomly in doubleblind fashion to receive DHEA, and 16 men were assigned to receive placebo. Baseline characteristics of the DHEA and placebo groups are listed in Table 1. At entry into the study, four men in the DHEA group and four men in the placebo group had elevated diastolic blood pressures (diastolic blood pressure >95 mm Hg), which were left untreated during the brief duration of the study. The men came to the Hospital de Clinicas Caracas as outpatients after a 12-hour overnight fast. Weight

and height were recorded, blood pressure was measured in the supine position by a single observer (N.A.B.), and at 8 AM, baseline blood samples were obtained for determination of serum steroids and plasma concentrations of P AI -1 and tP A antigen. The men then took orally either 50 mg DHEA (Diosynth; Amsterdam, The Netherlands) or placebo capsule three times daily for 12 days in double-blind fashion. The last dose ofDHEA or placebo was taken on the evening of the 12th day. The men returned to the hospital on the morning of the 13th day; weight and blood pressure were meas\,}red, and repeat blood samples were drawn 12 hours after the last dose of DHEA or placebo. Assays. Blood samples were centrifuged immediately, and plasma or sera separated and stored at -70° C until assayed. Steroid assays were performed in the laboratories of Drs. Matt and Nestler at the Medical College of Virginia. Plasma concentrations of P AI -1 and tP A antigen were determined in the laboratory of Dr. Beer using commercial enzyme-linked immunosorbent assay kits (Innotest; Antwerp, Belgium). These assays measure the free forms of P AI -1 or tP A, which are biologically active, and the inactive tPA-PAI-1 complex. Therefore, changes in total P AI -1 or tP A antigen as determined by these kits do not distinguish between changes in active or inactive protein. Serum testosterone, androstenedione, estrone, and 17,8-estradiol concentrations were measured by radioimmunoassay. Serum (0.5 mL) was extracted with diethyl ether, and steroids were isolated by celite column chromatography. Highly specific antisera were used to measure testosterone, androstenedione, estrone, and 17,8-estradiol. 3H -labeled steroids were added to serum before extraction to correct for procedural losses. Antiserum to estrone was purchased from Steranti Research Ltd. (London, England). The antiserum to testosterone was kindly provided by Dr. Gordon Niswender, Department of Physiology, Colorado State University (Fort Collins, CO), and the antisera to androstenedione and 17,8-estradiol by Dr. John Resko, Department of Physiology, University of Oregon School of Medicine (Portland, OR). Serum DHEA-

Table 1. Characteristics of Men Before (Baseline) and After Receiving Either 50 Mg DHEA or Placebo Capsule Thrice Daily for 12 Days DHEA Group (N Baseline Age (yrs) Weight (kg) Body mass index (kg/m2 ) Systolic blood pressure (mm Hg) Diastolic blood pressure (mm Hg)

59.7 76.4 24.9 139.9 89.1

± ± ± ± ±

2.1 1.8 0.4 2.6 1.3

=

18)

Placebo Group (N

After DHEA

76.6 25.0 137.7 85.7

± ± ± ±

1.8 0.4 2.8 1.5*

Baseline 59.3 76.7 25.8 138.8 89.6

± ± ± ± ±

2.5 1.4 0.5 3.7 2.4

=

16)

After Placebo

76.8 25.8 140.3 91.5

± ± ± ±

1.4 0.5 3.7 2.1 t

* P < 0.015 compared with baseline value in same group. t P < 0.05 compared with baseline value in same group. DHEA, dehydroepiandrosterone.

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sulfate levels were determined directly from serum by solid phase radioimmunoassay (Diagnostic Products, Los Angeles, CA). Serum DHEA was determined after organic extraction from serum by solid phase radioimmunoassay (Diagnostic Products), and 3 H-labeled steroid was added to serum before extraction to correct for procedural losses. The intraassay coefficients of variation for all steroid assays were less than 8.0%. To eliminate interassay variation, which ranges between 10% and 15%, all samples for each steroid were determined in a single assay. Statistical Analysis. Results are reported as mean ± standard error of the mean. Within a group, results before treatment (baseline) were compared with those after treatment by testing for normality with the WilkShapiro test and using Student's two-tailed paired ttest. Comparisons between groups were made by Student's two-tailed unpaired t-test. P < 0.05 was considered significant. Results Baseline Characteristics of Men. The DHEA and

placebo groups did not differ from one another at baseline with respect to age, body mass index, blood pressure, and plasma concentrations of P AI -1 and tP A antigen (Table 1 and Figure 1). Serum concentrations of DHEA, DHEA-sulfate, testosterone, estrone, andestradiol did not differ significantly between the two groups (Table 2 and Figure 1). Baseline serum androstenedione levels were slightly higher in the DHEA group than in the placebo group (Table 2).

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Serum DHEA levels did not change significantly in the DHEA group (Table 2). However, serum DHEA-sulfate concentration rose by greater than 2.5-fold from 7.5 ± 1.2 JLmoljL to 20.2 ± 1.5 JLmol/L (P < 0.0001; Figure 1). Dehydroepiandrosterone administration also was associated with a 55% rise in serum androstenedione concentration from 2.6 ± 0.2 nmol/L to 4.0 ± 0.4 nmolj L (P < 0.005) and a twofold rise in serum estrone concentration from 172 ± 21 pmol/L to 352 ± 28 pmol/L (P < 0.005). Serum testosterone and estradiol levels before and after DHEA administration did not differ significantly (Table 2). In the placebo group, there was a slight (9%) but statistically significant decline in serum DHEA-sulfate from 8.0 ± 3.3 JLmoljL to 7.3 ± 3.4 JLmol/L (P < 0.05; Figure 1). Serum DHEA, androstenedione, testosterone, estrone, and estradiol concentrations before and after placebo administration did not differ significantly (Table 2).

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sure changed with DHEA or placebo administration (Table 1). Dehydroepiandrosterone administration was associated with a small but significant fall in diastolic blood pressure from 89.1 ± 1.3 mm Hg to 85.7 ± 1.5 mm Hg (P< 0.015) in the DHEA group. In contrast,

Placebo Group (N=16)

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Effect of DHEA or Placebo on Weight and Blood Pressure. Neither body mass index nor systolic blood pres-

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Figure 1. Fasting serum dehydroepiandrosterone-sulfate (DHEAsulfate) and plasma concentrations of plasminogen activator inhibitor type 1 (PAI-l) and tissue plasminogen activator (tPA) antigen of men before (baseline) and after receiving either 50 mg DHEA or placebo capsule thrice daily for 12 days. *P < 0.0001 compared with baseline value in DHEA group. **P < 0.05 compared with baseline values in placebo group. ***P < 0.0005 compared with baseline value in DHEA group.

diastolic blood pressure rose slightly in men who received placebo (from 89.6 ± 2.4 mm Hg to 91.5 ± 2.1 mm Hg; P < 0.05). Effect of DHEA or Placebo on PAI-1 and TPA. In the DHEA group, DHEA administration was associated with highly significant decreases in plasma concentrations of PAI-l (from 55.4 ± 3.8 ng/mL to 38.6 ± 3.3

207

DHEA, PAI-1, and tPA Antigen

Table 2. Fasting Serum Steroid Levels of Men Before (Baseline) and After Receiving Either 50 Mg DHEA or Placebo Capsule Thrice Daily for 12 Days DHEA Group (N Baseline DHEA (nmol/L) DHEA-sulfate (~mol/L) Testosterone (nmol/L) Androstenedione (nmol/L) Estrone (pmol/L) 17(j-Estradiol (pmol/L)

18.3 7.5 22.3 2.6 172 101

± ± ± ± ± ±

3.3 1.2 1.4 0.2 21 23

=

18)

Placebo Group (N

After DHEA 27.0 20.2 21.5 4.0 352 82

± ± ± ± ± ±

2.8 1.5* 1.8 0.4t 28t 14

Baseline 14.7 8.0 22.5 2.0 135 73

± ± ± ± ± ±

3.4 3.3 3.5 0.1§ 23 19

=

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After Placebo 10.4 ± 7.3 ·± 23.4 ± 2.3 ± 164 ± 84 ±

1.1

3.4t 3.1 0.2 37 22

* P < 0.0001 compared with baseline value in same group. t P < 0.05 compared with baseline value in same group. t P < 0.005 compared with baseline value in same group. § P < 0.05 compared with baseline value in DHEA group. DHEA, dehydroepiandrosterone.

ng/mL; P < 0.0001) and tPA antigen (from 8.1 ± 1.9 ng/mL to 5.4 ± 1.3 ng/ml; P < 0.0005) (Figure 1). In contrast, plasma concentrations of PAI-l {53.1 ± 4.0 ng/mL versus 53.6 ± 4.3 ng/mL; P = not significant) and tPA antigen (7.8 ± 2.0 ng/mL versus 8.0 ± 2.0 ng/ mL; P = not significant) did not change in the placebo group (Figure 1). Discussion

A balance exists between thrombosis and fibrinolysis in healthy men, and a disturbance in this balance may be central to the evolution of the acute coronary syndromes. Specifically, diminished endogenous fibrinolytic activity was implicated in the etiology of coronary artery disease and thrombosis, 10•11 and may underlie the observation that coronary artery thrombosis and myocardial infarction often occur in the absence of severe coronary stenosis. 27 Activity of the endogenous fibrinolytic system depends on the balance between plasminogen activators, primarily tP A, and plasminogen activator inhibitors, of which PAI-l is considered the most important. A large proportion {approximately 90%) of tPA in plasma is in the form of an inactive complex with P AI -1. 10•28 Plasma tPA antigen determination by radioimmunoassay includes both free tPA and the inactive complex oftPA bound to PAI-l (tPA-PAI-1). As a result, high plasma tPA antigen levels, when associated with high levels of plasma PAl -1, often reflect impairment of fibrinolytic capacity. 10•29 This explains why in numerous studies, men with elevated plasma levels of P AI -1 and tP A antigen were at greater risk for ischemic heart disease. 10- 17 For example, elevated levels of P AI -1 were identified in young survivors of myocardial infarction and were associated with an increased risk of reinfarction. 10·11 Increased levels of tP A antigen were a marker of risk for coronary thrombosis in healthy men in the Physicians' Health Study/ 4 in patients with angina, 12·15·17

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and in patients with myocardial infarction. 10·13 Increased plasma tPA antigen levels also predicted longterm mortality in patients with coronary artery disease.16 Therefore, it has been a consistent finding that plasma P AI -1 and tP A antigen levels are elevated in patients with ischemic heart disease. In the current study, short-term (2 weeks) oral DHEA administration to men is associated with substantial reductions in plasma concentrations of P AI -1 and tP A antigen. These findings are consistent with the possibility that DHEA may alter fibrinolytic potential. We caution, however, that it is unknown whether the changes observed in the current study were associated with any alteration in fibrinolysis, because fibrinolytic activity was not measured directly. Of note, serum DHEA levels were not elevated significantly in the DHEA group 12 hours after the last dose ofDHEA, whereas a 2.5-fold rise in serum DHEAsulfate was present. This is consistent with rapid in vivo conversion of DHEA to its sulfate ester. It is commonly presumed that the biologically active form of DHEA is the unconjugated steroid, whereas DHEAsulfate may function as a pool or storage form for DHEA. Dehydroepiandrosterone-sulfate can be hydrolyzed to DHEA by tissue steroid sulfatases that appear to be nearly ubiquitous. Notably, although serum DHEA-sulfate rose substantially in these middle-aged men, the serum value remained in the high physiologic range. In fact, serum DHEA-sulfate concentrations were representative of those that might be observed in individuals 20-30 years of age. 30 This suggests that DHEA and/or DHEA-sulfate modulate plasma PAI-l and tP A antigen concentrations under physiologic conditions. The mechanism by which DHEA reduces plasma P AI -1 levels is unknown. In previous studies, albeit at times conflicting, several steroids influenced the fibrinolytic system via transcriptional and posttranscriptional regulation of P AI -1 gene expression. 21 ·24·25·31 -35 May 1996 Volume 311 Number 5

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For example, administration of low doses of ethinyl estradiol decreased P AI -1 plasma levels. 24 In contrast, estrogen administration to men with prostatic cancer produced a marked elevation of plasma PAI-llevels. 25 Most recently, it was reported that postmenopausal women taking estrogen replacement therapy had lower levels of P AI -1 and tP A antigen compared with postmenopausal women not on replacement. 26 In the current study, both serum androstenedione and estrone increased with DHEA administration, whereas serum testosterone and estradiol remained · unchanged. In vivo effects of androstenedione or estrone on P AI -1 metabolism have not been reported, but the possibility that DHEA affected PAI-l metabolism via its conversion to these metabolites cannot be excluded. Alternatively, it is equally possible that the reduction in plasma PAI-l observed with DHEA administration was mediated directly by DHEA itself, acting perhaps through the putative DHEA binding site that was reported on human leukocytes. 36 It also was suggested that DHEA may function as a biologic antagonist to glucocorticoids.37 Of note, dexamethasone was reported to increase PAI-l biosynthesis and PAI-l mRNA levels in human fibrosarcoma cells. 32 However, dexamethasone did not influence the secretion of P AI -1 by the human HepG2 cell line, 33 and dexamethasone was found to inhibit PAI-l gene expression and activity in cultured porcine kidney cells. 35 Therefore, it is difficult to predict how DHEA would influence circulating PAIl levels if it were to exert a biologic antiglucocorticoid action. It is noteworthy that circulating DHEA and DHEAsulfate levels exhibit a unique and progressive age-related decline. Peak serum DHEA and DHEA-sulfate levels occur at approximately age 20-30 years, diminish progressively thereafter, and are reduced by >90% by age 80 years. 30 Whereas aging in humans is characterized by a progressive decrease in circulating DHEA and DHEA-sulfate, plasma levels of PAI-l and tPA antigen concurrently increase. 18 The findings of the current study raise the intriguing possibility that the age-related increase in plasma PAI-l and tPA antigen levels may be related causally to the decline in circulating DHEA and/or DHEA-sulfate. In summary, based on findings from the current study, oral administration of DHEA to men of advancing age causes a reduction in plasma concentrations of PAI-l and tPA antigen. Therefore, these findings support the initiation of future studies to examine directly the effects of DHEA on fibrinolysis in men. Acknowledgments

The authors thank Terre Williams for technical assistance. References 1. Barrett-Connor E, Khaw KT, Yen SSC. A prospective study of dehydroepiandrosterone sulfate, mortality, and cardiovascular disease. N Eng! J Med. 1986;315:1519-24. THE AMERICAN JOURNAL OF THE MEDICAL SCIENCES

2. Slowinska-Srzednicka J, Zgliczynski S, CiswickaSznajderman M, Srzednicki M, Soszynski P, Biernacka M, et al. Decreased plasma dehydroepiandrosterone sulfate and dihydrotestosterone concentrations in young men after myocardial infarction. Atherosclerosis. 1989;79:197-203. 3. Herrington DM, Gordon GB, Achuff SC, Trejo JF, Weisman HF, Kwiterovich PO, et al. Plasma dehydroepiandrosterone and dehydroepiandrosterone sulfate in patients undergoing diagnostic coronary angiography. J Am Coli Cardiol. 1990;16:862-70. 4. Nestler JE, Clore JN, Blackard WG. Dehydroepiandrosterone: The "missing link" between hyperinsulinemia and atherosclerosis? FASEB J. 1992;6:3073-5. 5. Nafziger AN, Herrington DM, Bush TL. Dehydroepiandrosterone and dehydroepiandrosterone sulfate: their relation to cardiovascular disease. Epidemiol Rev. 1991;13:267-93. 6. Mitchell LE, Sprecher DL, Borecki IB, Rice T, Laskarzewski PM, Rao DC. Evidence for an association between dehydroepiandrosterone sulfate and nonfatal, premature myocardial infarction in males. Circulation. 1994;89:89-93. 7. Gordon GB, Bush DE, Weisman HF. Reduction of atherosclerosis by administration of dehydroepiandrosterone. A study in the hypercholesterolemic New Zealand White rabbit with aortic intimal injury. J Clin Invest. 1988;82:712-20. 8. Arad Y, Badimon JO, Badimon L, Hembree W, Ginsberg HN. Dehydroepiandrosterone feeding prevents aortic fatty streak formation and cholesterol accumulation in cholesterol-fed rabbit. Arteriosclerosis. 1989;9:159-66. 9. Eich DM, Nestler JE, Johnson DE, Dworkin GH, Ko D, Wechsler AS, et al. Inhibition of accelerated coronary atherosclerosis with dehydroepiandrosterone in the heterotopic rabbit model of cardiac transplantation. Circulation. 1993;87:261-9. 10. Hamsten A, Wiman B, de Faire U, Blombiick M. Increased plasma levels of a rapid inhibitor of tissue plasminogen activator in young survivors of myocardial infarction. N Eng! J Med. 1985;313:1557-63. 11. Hamsten A, de Faire U, Walldius G, Dahlen G, Szamosi A, Landou C, et al. Plasminogen activator inhibitor in plasma: Risk factor for recurrent myocardial infarction. Lancet. 1987;2: 3-9. 12. Munkvad S, Gram J, Jespersen J. A depression of active tissue plasminogen activator in plasma characterizes patients with unstable angina pectoris who develop myocardial infarction. Eur Heart J . 1990;11:525-8. 13. Keber I, Keber D. Increased plasminogen activator inhibitor activity in survivors of myocardial infarction is associated with metabolic risk factors of atherosclerosis. Haemostasis. 1992;22: 187-94. 14. Ridker PM, Vaughan DE, Stampfer . MJ, Manson JE, Hennekens CH. Endogenous tissue-type plasminogen activator and risk of myocardial infarction. Lancet. 1993;341:1165-8. 15. Jansson JH, Nilsson TK, Olofsson BO. Tissue plasminogen activator and other risk factors as predictors of cardiovascular events in patients with severe angina pectoris. Eur Heart J. 1991;12:157-61. 16. Jansson JH, Olofsson BO, Nilsson TK. Predictive value of tissue plasminogen activator mass concentration on long-term mortality in patients with coronary artery disease. A 7-year follow-up. Circulation. 1993;88:2030-4. 17. Thompson SG, Kienast J, Pyke SD, Hayerkate F, van de Loo JC. Hemostatic factors and the risk of myocardial infarction or sudden death in patients with angina pectoris. N Eng! J Med. 1995;332:635-41. 18. Kluft C, Jie AF, Rijken DC, Verheijen JH. Daytime fluctuations in blood of tissue-type plasminogen activator (t-PA) and its fast-acting inhibitor (PAI-l). Thromb Haemost. 1988;59: 329-32. 19. Coleman PL, Barouski PA, Gelehrter TD. The dexamethasone-induced inhibitor of fibrinolytic activity in hepatoma cells.

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28. Wiman B, Chmielewska J, Ran by M. Inactivation of tissue plasminogen activator in plasma. Demonstration of a complex with a new rapid inhibitor. J Bioi Chern. 1984;259:3644-7. 29. Juhan-Vague I, Alessi MC. Plasminogen activator inhibitor 1 and atherothrombosis. Thromb Haemost. 1993;70:138-43. 30. Orentreich N, Brind JL, Rizer RL, Vogelman JH. Age changes and sex differences in serum dehydroepiandrosterone sulfate concentrations throughout adulthood. J Clin Endocrinol Metab. 1984;59:551-5. 31. Heaton JH, Kathju S, Gelehrter TD. Transcriptional and posttranscriptional regulation of type 1 plasminogen activator inhibitor and tissue-type plasminogen activator gene expression in HTC rat hepatoma cells by glucocorticoids and cyclic nucleotides. Mol Endocrinol. 1992;6:53-60. 32. Andreasen P A, Pyke C, Riccio A, Kristensen P, Nielsen LS, Lund LR, et al. Plasminogen activator inhibitor type 1 biosynthesis and mRNA level are increased by dexamethasone in human fibrosarcoma cells. Mol Cell Bioi. 1987;7:3021-5. 33. Sprengers ED, Princen HM, Kooistra T, van Hinsbergh VW. Inhibition of plasminogen activators by conditioned medium of human hepatocytes and hepatoma cell line Hep G2. J Lab Clin Med. 1985;105:751-8. 34. Mayer M, Finci Z, Chaouat M. Suppression of plasminogen activator activity by dexamethasone in cultured cardiac myocytes. J Mol Cell Cardiol. 1986;18:1117-24. 35. Pearson D, Altus MS, Horiuchi A, Nagamine Y. Dexamethasone coordinately inhibits plasminogen activator gene expression and enzyme activity in porcine kidney cells. Biochem Biophys Res Commun. 1987;143:329-36. 36. Okabe T, Haji M, Takayanagi R, Adachi M, Imasaki K, Kurimoto F, et al. Up-regulation of high-affinity dehydroepiandrosterone binding activity by dehydroepiandrosterone in activated human T lymphocytes. J Clin Endocrinol Metab. 1995;80:2993-6. 37. Browne ES, Wright BE, Porter JR, Svec F. Dehydroepiandrosterone: Antiglucocorticoid action in mice. Am J Med Sci. 1992;303:366-71.

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