Aldosterone antagonism or synthase inhibition reduces end-organ damage induced by treatment with angiotensin and high salt

Abstract

In the setting of high salt intake, aldosterone stimulates fibrosis in the heart, great vessels, and kidney of rats. We used uninephrectomized rats treated with angiotensin II and placed on a high salt diet to exaggerate renal fibrosis. We then tested whether mineralocorticoid receptor blockade by spironolactone or aldosterone synthase inhibition by FAD286 have similar effects on end-organ damage and gene expression. Individually, both drugs prevented the hypertensive response to uninephrectomy and high salt intake but not when angiotensin II was administered. Following 4 weeks of treatment with FAD286, plasma aldosterone was reduced, whereas spironolactone increased aldosterone at 8 weeks of treatment. Angiotensin II and high salt treatment caused albuminuria, azotemia, renovascular hypertrophy, glomerular injury, increased plasminogen activator inhibitor-1 (PAI-1), and osteopontin mRNA expression, as well as tubulointerstitial fibrosis in the kidney. Both drugs prevented these renal effects and attenuated cardiac and aortic medial hypertrophy while reducing osteopontin and transforming growth factor-beta mRNA expression in the aorta. The two drugs also reduced cardiac interstitial fibrosis but had no effect on that of the perivascular region. Although spironolactone enhanced angiotensin II and salt-stimulated PAI-1 mRNA expression in aorta and heart, spironolactone and FAD286 prevented renal PAI-1 mRNA protein expression. Our study shows that mineralocorticoid receptor antagonism and aldosterone synthase inhibition similarly decrease hypertrophy and interstitial fibrosis of the kidney and heart caused by angiotensin II and high salt.

Figure 1. Effect of treatment on kidney injury

Effect of treatment on (a) kidney weight, (b) glomerular sclerosis, (c) tubulointerstitial fibrosis, and (d) renal vascular modeling. For post hoc comparisons, *P < 0.01 versus sham, ^†P < 0.05 versus uninephrectomy (Neph), ^‡P < 0.05 versus uninephrectomy + spironolactone (SPL), ^§P < 0.05 versus uninephrectomy + FAD286, ^||P < 0.05 versus uninephrectomy + Ang II + spironolactone, ^¶P < 0.05 versus uninephrectomy + Ang II + FAD286. Masson’s trichrome (original magnification ×100) of the kidney in (e) control, (f) Ang II/salt-treated, (g) Ang II/salt + spironolactone-treated, and (h) Ang II/salt + FAD286-treated. The asterisks in (f) denote areas of tubulointerstitial fibrosis.

Figure 2. Effect of treatment on cardiac injury

Effect of treatment on (a) heart weight, (b) cardiac interstitial fibrosis, and (c) perivascular adventitial fibrosis. For post hoc comparisons, *P < 0.01 versus sham, ^†P < 0.05 versus uninephrectomy (Neph), ^‡P < 0.05 versus uninephrectomy + spironolactone (SPL), ^§P < 0.05 versus uninephrectomy + FAD286, ^||P < 0.05 versus uninephrectomy + Ang II + spironolactone, ^¶P < 0.05 versus uninephrectomy + Ang II + FAD286. (d) Focal area of subendocardial interstitial and perivascular fibrosis in heart from Ang II-treated rat (Masson’s trichrome, original magnification ×100). Persistent perivascular fibrosis in Ang II/salt-treated rats receiving (e) spironolactone (×400) and (f) FAD286. The asterisks in (d) denote cardiac interstitial fibrosis; arrowhead denotes perivascular/periadventitial fibrosis.

Figure 3. Effect of treatment on expression of PAI-1, osteopontin, and tumor growth factor β (TGF-β) mRNA in the kidney, heart, and aorta

For post hoc comparisons, *P < 0.05 versus sham, ^†P < 0.01 versus uninephrectomy (Neph), ^‡P < 0.01 versus uninephrectomy + spironolactone (SPL), ^§P < 0.01 versus uninephrectomy + FAD286, ^||P < 0.01 versus uninephrectomy + Ang II + spironolactone, ^¶P < 0.01 versus uninephrectomy + Ang II + FAD286, ^#P < 0.01 versus uninephrectomy + Ang II.

Figure 4. Effect of spironolactone (SPL, 1 μM) on PAI-1 expression in rat vascular smooth muscle cells treated with angiotensin II (Ang II, 1 μM), aldosterone (aldo, 1 μM) or the combination

*P < 0.05 versus vehicle, ^†P < 0.05 versus Ang II alone, ^‡P < 0.05 versus spironolactone, ^§P < 0.05 versus aldo + Ang II.