Endothelin-a receptor antagonism after renal angioplasty enhances renal recovery in renovascular disease

Abstract

Percutaneous transluminal renal angioplasty/stenting (PTRAS) is frequently used to treat renal artery stenosis and renovascular disease (RVD); however, renal function is restored in less than one half of the cases. This study was designed to test a novel intervention that could refine PTRAS and enhance renal recovery in RVD. Renal function was quantified in pigs after 6 weeks of chronic RVD (induced by unilateral renal artery stenosis), established renal damage, and hypertension. Pigs with RVD then underwent PTRAS and were randomized into three groups: placebo (RVD+PTRAS), chronic endothelin-A receptor (ET-A) blockade (RVD+PTRAS+ET-A), and chronic dual ET-A/B blockade (RVD+PTRAS+ET-A/B) for 4 weeks. Renal function was again evaluated after treatments, and then, ex vivo studies were performed on the stented kidney. PTRAS resolved renal stenosis, attenuated hypertension, and improved renal function but did not resolve renal microvascular rarefaction, remodeling, or renal fibrosis. ET-A blocker therapy after PTRAS significantly improved hypertension, microvascular rarefaction, and renal injury and led to greater recovery of renal function. Conversely, combined ET-A/B blockade therapy blunted the therapeutic effects of PTRAS alone or PTRAS followed by ET-A blockade. These data suggest that ET-A receptor blockade therapy could serve as a coadjuvant intervention to enhance the outcomes of PTRAS in RVD. These results also suggest that ET-B receptors are important for renal function in RVD and may contribute to recovery after PTRAS. Using clinically available compounds and techniques, our results could contribute to both refinement and design of new therapeutic strategies in chronic RVD.

Keywords: angioplasty; endothelin-1; imaging; microcirculation; renal artery stenosis.

Figure 1.

Renal angiography before and after PTRAS. Representative renal angiography showing the main renal artery (left panels) at baseline, (center panels) 6 weeks after induction of renal artery stenosis (RAS), and (right panels) 4 weeks after PTRAS. PTRAS was similarly effective in resolving RAS in all pigs, with a similar vascular patency 4 weeks after angioplasty. Residual vascular stenosis, when present, was between 6% and 11% at 10 weeks (not significant). Treatment with ET receptor blockers after PTRAS did not modify the success of the intervention.

Figure 2.

Blood pressure before and after treatments. (Upper panel) Graph showing the development of hypertension and changes (telemetry) after PTRAS followed by ET receptor blocker therapy. (Lower panel) Bar graph showing measurements of BP in anesthetized animals (direct intra-arterial measurement) during in vivo CT studies at 6 weeks (before PTRAS) and at 10 weeks (4 weeks after PTRAS and treatment with ET blockers or placebo) in normal (n=7), RVD (RVD+PTRAS; n=7), and RVD+PTRAS treated with ET-A (n=7) or ET-A/B (n=5) blockers for 4 weeks. Reduction of BP was significant in pigs treated with ET-A blockers after PTRAS. Pigs treated with PTRAS alone or combined PTRAS+ET-A/B blockers did not show significant reductions in BP compared with pre-PTRAS values. *P<0.05 versus normal. ^†P<0.05 versus RVD+PTRAS. ^‡P<0.05 versus 6 weeks.

Figure 3.

Renal hemodynamics and function before and after treatments. (Upper left and upper center panels) Average quantification (in bar graphs; mean±SEM) of RBF and GFR after 6 and 10 weeks of observation (post-PTRAS and ET blockers/placebo). (Upper right panel) Activity of NADP(H) oxidase in the stenotic kidney measured by lucigenin luminescence and expressed in relative light units (RLUs) per nanogram of tissue. (Lower left panel) Table showing absolute values of RBF and GFR at 6 and 10 weeks and the changes (expressed in percentage) after PTRAS followed by 4 weeks of ET receptor blockers treatment or placebo. (Lower right panel) Average quantification (in bar graphs; mean±SEM) showing the changes in plasma creatinine after PTRAS followed by ET receptor blockers or placebo in normal (n=7), RVD (RVD+PTRAS; n=7), and RVD+PTRAS treated with ET-A (n=7) or ET-A/B (n=5) blockers for 4 weeks. Administration of ET-A receptor blockers for 4 weeks resulted in a greater recovery of renal function, decreased oxidative stress, and reduction in plasma creatinine compared with PTRAS alone. However, combined blockade of the ET-A and ET-B receptors significantly blunted the beneficial effects of PTRAS and/or ET-A blockade. *P<0.05 versus normal. ^†P<0.05 versus RVD+PTRAS. ^‡P<0.05 versus 6 weeks. ^{^}P<0.05 versus RVD+PTRAS+ET-A.

Figure 4.

Renal microvascular density after treatments. Representative three-dimensional micro-CT (upper panel) reconstruction and (lower panel) quantification of the cortical and medullary MV densities (diameters under 500 μM) of the stenotic kidney 4 weeks after PTRAS and placebo, ET-A, or ET-A/B blocker therapy. PTRAS alone did not resolve MV rarefaction in the previously stenotic kidney, unlike those kidneys that underwent PTRAS followed by ET-A blockers, which showed a significant increase in cortical and medullary MV densities. However, PTRAS followed by ET-A/B blockers showed an additional decrease in renal MV density compared with PTRAS alone. *P<0.05 versus normal. ^†P<0.05 versus RVD+PTRAS. ^{^}P<0.05 versus RVD+PTRAS+ET-A.

Figure 5.

Renal morphology after treatments. Representative trichrome pictures (from stenotic kidneys) of the glomeruli, tubules, and tubulointerstitial regions (×20; shown as examples to illustrate renal damage) and quantification of (upper right panel) glomerulosclerosis and (lower right panel) tubulointerstitial fibrosis in normal, RVD (RVD+PTRAS), and RVD+PTRAS treated with ET-A or ET-A/B blockers for 4 weeks. Chronic ET-A blocker after PTRAS reduced renal fibrosis (although it was more evident in the tubulointerstitial space; arrows) to a greater extent compared with PTRAS+placebo or ET-A/B blockers. *P<0.05 versus normal. ^†P<0.05 versus RVD+PTRAS. ^{^}P<0.05 versus RVD+PTRAS+ET-A. ^#P>0.05 but P<0.10 versus RVD+PTRAS.