Aldosterone and not plasminogen activator inhibitor-1 is a critical mediator of early angiotensin II/NG-nitro-L-arginine methyl ester-induced myocardial injury.
ABSTRACT Angiotensin II (Ang II) increases levels of aldosterone and plasminogen activator inhibitor-1 (PAI-1). Both aldosterone and PAI-1 seem to promote cardiovascular (CV) injury. Our objective was to determine the roles of PAI-1 and aldosterone in the development of myocardial and renal damage in a model with high Ang II and low nitric oxide (NO) availability, a pattern seen in patients with heart failure, diabetes mellitus, and arteriosclerosis.
Mice on a moderately high sodium diet were treated with the NO synthase inhibitor NG-nitro-l-arginine methyl ester (L-NAME) for 14 days plus Ang II during days 8 through 14. The roles of aldosterone and PAI-1 in the development of CV injury were assessed using the mineralocorticoid receptor antagonist spironolactone (0, 1.5, 15, and 50 mg x 100 g(-1) x day(-1)) and PAI-1-deficient mice (PAI-1-/-). Ang II/L-NAME-treated mice showed glomerular ischemia, proteinuria, and necrosis of myocytes and vascular smooth muscle cells with an associated mixed inflammatory response, deposition of loose collagen, and neovascularization. Compared with saline-drinking mice, Ang II/L-NAME-treated mice had significantly increased heart to body weight (HW/BW) ratios, cardiac and renal damage assessed by histological examination, PAI-1 immunoreactivity, and proteinuria. Spironolactone treatment decreased PAI-1 immunoreactivity and reduced in a dose-dependent fashion cardiac and renal damage. PAI-1-/- animals had a similar degree of CV injury as PAI-1+/+ animals.
Mineralocorticoid receptor antagonism, but not PAI-1 deficiency, protected mice from developing Ang II/L-NAME-mediated myocardial and vascular injury and proteinuria, suggesting that aldosterone, but not PAI-1, plays a key role in the development of early Ang II/L-NAME-induced cardiovascular injury.
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ABSTRACT: Long-term inhibition of nitric oxide synthase (NOS) is known to induce hypertension and perivascular fibrosis. Recent evidence also suggests that long-term NOS inhibition induces expression of plasminogen activator inhibitor-1 (PAI-1) in vascular tissues and that PAI-1 may contribute to the development of fibrosis after chemical or ionizing injury. On the basis of these observations, we hypothesized that PAI-1 may influence the vascular response to long-term NOS inhibition by N(omega)-nitro-L-arginine methyl ester (L-NAME). We compared the temporal changes in systolic blood pressure and coronary perivascular fibrosis in PAI-1-deficient (PAI-1(-/-)) and wild-type (WT) male mice (N=6 per group). At baseline, there were no significant differences in blood pressure between groups. After initiation of L-NAME, systolic blood pressure increased in both groups at 2 weeks. Over an 8-week study period, systolic blood pressure increased to 141+/-3 mm Hg in WT animals versus 112+/-4 mm Hg in PAI-1(-/-) mice (P<0.0001). The extent of coronary perivascular fibrosis increased significantly in L-NAME-treated WT mice (P<0.01 versus PAI-1(-/-) mice). Cardiac type I collagen mRNA expression was greater in control (P<0.01) and L-NAME-treated PAI-1(-/-) (P<0.05) groups than in control WT mice, indicating that PAI-1 deficiency prevents the increase of collagen deposition by promoting matrix degradation. These findings suggest that PAI-1 deficiency alone is sufficient to protect against the structural vascular changes that accompany hypertension in the setting of long-term NOS inhibition. Direct inhibition of vascular PAI-1 activity may provide a new therapeutic strategy for the prevention of arteriosclerotic cardiovascular disease.Circulation 09/2001; 104(7):839-44. · 15.20 Impact Factor
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ABSTRACT: The classical effects of aldosterone are mediated via epithelial mineralocorticoid receptors (MR), protected against cortisol/corticosterone occupancy and activation by the enzyme 11 beta hydroxysteroid dehydrogenase. The pathophysiological effects of aldosterone on non-epithelial tissues, in contrast, are mediated via unprotected MR in which occupancy by cortisol/corticosterone antagonises the effect of aldosterone. Aldosterone raises blood pressure by occupying MR in the circumventricular region of the brain, an effect antagonised by concomitant intracerebroventricular (ICV) infusion of similar doses of corticosterone. Peripheral infusion of aldosterone to salt loaded rats causes hypertension, cardiac hypertrophy and cardiac fibrosis; concomitant ICV infusion of the MR antagonist RU28318 abolishes the aldosterone-induced hypertension, but does not affect cardiac hypertrophy or fibrosis. These peripheral effects of aldosterone are presumably via cardiac MR; high glucose/PKC modulated, aldosterone-specific effects on protein synthesis have recently been demonstrated as direct MR-mediated actions on cultured neonatal rat cardiomyocytes. The pathophysiologic effects of aldosterone via nonepithelial MR have a time course of days/weeks rather than hours, reflect occupancy of only a small percentage of such receptors, and require salt loading. How the effects of salt loading are transduced in such circumstances remains to be explored.Clinical and Experimental Hypertension 01/1997; 19(5-6):885-99. · 1.28 Impact Factor
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ABSTRACT: Aldosterone promotes nephrosclerosis in several rat models, whereas aldosterone receptor antagonism blunts the effect of activation of the renin-angiotensin-aldosterone system (RAAS) on nephrosclerosis, independent of effects on blood pressure. Based on recent findings linking activation of the RAAS with impaired fibrinolytic balance, we hypothesized that aldosterone induces sclerosis through effects on plasminogen activator inhibitor-1 (PAI-1), the major physiological inhibitor of plasminogen activation. We examined the effect of aldosterone antagonism on the development of sclerosis and on renal PAI-1 expression following radiation injury in the rat. Following a single dose of 12 Gy to the kidneys, male Sprague-Dawley rats were treated with placebo, the aldosterone antagonist spironolactone (4.5 mg/day by time-release subcutaneous pellet), the angiotensin type 1 receptor antagonist L158-809 (AT1RA; 80 mg/L drinking water), or combined spironolactone and AT1RA. Rats treated with placebo developed significant proteinuria and nephrosclerosis 12 weeks following radiation associated with hypertension. Kidney PAI-1 mRNA expression was increased eightfold (P < 0.001 vs. nonradiated controls). Spironolactone alone had no effect on blood pressure (systolic blood pressure 149.0 +/- 5.4 mm Hg) compared with placebo (151.6 +/- 11.2 mm Hg, P = NS), whereas AT1RA alone (107.7 +/- 8.9 mm Hg, P = 0.013 vs. placebo) or in combination therapy (102.1 +/- 6.2 mm Hg, P = 0.001 vs. placebo) lowered blood pressure. Both the AT1RA and spironolactone decreased proteinuria following radiation (P < 0.001 vs. placebo for either drug), and the combination of AT1RA + spironolactone had a greater effect on proteinuria than spironolactone alone (P = 0.003). Aldosterone antagonism significantly decreased (P = 0.016 vs. placebo) and AT1RA virtually abolished (P = 0.001 vs. placebo) the development of sclerosis. Spironolactone significantly decreased PAI-1 mRNA expression in the kidneys of radiated animals (PAI-1 mRNA/GAPDH ratio 0.39 +/- 0.13 vs. placebo 0.84 +/- 0.05, P = 0.006), and there was a significant correlation between the degree of sclerosis and the level of PAI-1 immunostaining within individual rats (R2 = 0.97, P < 0.0001). This study is, to our knowledge, the first to demonstrate that aldosterone regulates PAI-1 expression in vivo, and supports the hypothesis that aldosterone induces renal injury through its effects on PAI-1 expression.Kidney International 10/2000; 58(3):1219-27. · 7.92 Impact Factor