Experimental coronary artery stenosis accelerates kidney damage in renovascular hypertensive swine

Abstract

The impact of coronary artery stenosis (CAS) on renal injury is unknown. Here we tested whether the existence of CAS, regardless of concurrent atherosclerosis, would induce kidney injury and magnify its susceptibility to damage from coexisting hypertension (HT). Pigs (seven each) were assigned to sham, left-circumflex CAS, renovascular HT, and CAS plus HT groups. Cardiac and nonstenotic kidney functions, circulating and renal inflammatory and oxidative markers, and renal and microvascular remodeling were assessed 10 weeks later. Myocardial perfusion declined distal to CAS. Systemic levels of PGF2-α isoprostane, a marker of oxidative stress, increased in CAS and CAS plus HT, whereas single-kidney blood flow responses to acetylcholine were significantly blunted only in CAS plus HT compared with sham, HT, and CAS, indicating renovascular endothelial dysfunction. Tissue expression of inflammatory and oxidative markers were elevated in the CAS pig kidney, and further magnified in CAS plus HT, whereas angiogenic factor expression was decreased. Bendavia, a mitochondria-targeted peptide, decreased oxidative stress and improved renal function and structure in CAS. Furthermore, CAS and HT synergistically amplified glomerulosclerosis and renal fibrosis. Thus, mild myocardial ischemia, independent of systemic atherosclerosis, induced renal injury, possibly mediated by increased oxidative stress. Superimposed HT aggravates renal inflammation and endothelial dysfunction caused by CAS, and synergistically promotes kidney fibrosis, providing impetus to preserve cardiac integrity in order to protect the kidney.

Figures

Figure 1

Systemic, cardiac, and renal characteristics in Sham, hypertension (HT), coronary artery stenosis (CAS), and CAS+HT pigs. A. Circulating PGF2-α isoprostane. B. Systemic transforming growth-factor (TGF)-β1. C-D. Representative cardiac CT images obtained at the middle left-ventricle (LV). In hypertensive animals (HT and CAS+HT), the LV wall is thickened. The arrow in C shows myocardial lateral wall thinning distal to a high-grade CAS (illustrated in D). E, Cardiac output. F, Myocardial perfusion. G, LV muscle mass (LVMM). H, Glomerular filtration rate (GFR). I, Change in renal blood flow (ΔRBF) in response to acetylcholine (Ach). J, Intratubular concentration (ITC) in the different nephron segments. *P<0.05 vs. Sham; #P<0.05 vs. HT; &P<0.05 vs. CAS.

Figure 2

Renal tissue remodeling. A. Representative renal trichrome (×20), dihydroethidium (DHE) (×20), CD31 immunofluorescence (×40), α-SMA (×20) and PAS staining (×20). Kidney fibrosis increased in hypertension (HT) and coronary artery stenosis (CAS) compared with Sham; kidney fibrosis and glomerular score increased synergistically in CAS+HT compared with the other groups (B, C). DHE staining (normalized to DAPI-positive nuclei) increased in CAS compared with Sham, and in CAS+HT compared with Sham and HT (D). Capillary density (CD31 immunofluorescence) in HT decreased compared with Sham, but in CAS +HT fell lower than all other groups (E). Renal microvascular media-to-lumen ratio (α-SMA) increased in CAS compared with Sham, and further in HT and CAS+HT compared with Sham and CAS (F). Tubular injury score (PAS staining) increased in HT and CAS, and further aggravated in CAS+HT (G). *P<0.05 vs. Sham; #P<0.05 vs. HT; &P<0.05 vs. CAS; ΔP<0.05 for synergistic interaction CAS×HT. Scale bar = 50μm.

Figure 3

Renal expression of inflammatory, oxidative, and growth factors. Representative (2 bands shown per group) immunoblotting of (A): tumor necrosis-factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, GP91-phox, nitrotyrosine (NT); (B): hypoxia-inducible factor (HIF)-1α, vascular endothelial growth-factor (VEGF), transforming growth-factor (TGF)-β1, tissue inhibitor of metalloproteinase (TIMP)-1, endothelial nitric-oxide synthase (eNOS). Inflammatory and oxidative markers were elevated in coronary artery stenosis (CAS), and further augmented in CAS+Hypertension (HT) (C). Hypoxia and fibrotic markers increased in CAS+HT, whereas eNOS decreased; VEGF expression decreased in HT and further fell in CAS+HT (D). * P<0.05 vs. Sham; #P<0.05 vs. HT; &P<0.05 vs. CAS; ΔP<0.05 for synergistic interaction CAS*HT.