Amelioration of nephropathy with apoA-1 mimetic peptide in apoE-deficient mice

Abstract

Background: There is mounting evidence that dyslipidaemia may contribute to development and progression of renal disease. For instance, hyperlipidaemia in apolipoprotein E-deficient (apoE(-/-)) mice is associated with glomerular inflammation, mesangial expansion and foam cell formation. ApoA-1 mimetic peptides are potent antioxidant and anti-inflammatory compounds which are highly effective in ameliorating atherosclerosis and inflammation in experimental animals. Given the central role of oxidative stress and inflammation in progression of renal disease, we hypothesized that apoA-1 mimetic peptide, D-4F, may attenuate renal lesions in apoE(-/-) mice.

Methods: Twenty-five-month-old female apoE(-/-) mice were treated with D-4F (300 µg/mL in drinking water) or placebo for 6 weeks. Kidneys were harvested and examined for histological and biochemical characteristics.

Results: Compared with the control mice, apoE(-/-) mice showed significant proteinuria, tubulo-interstitial inflammation, mesangial expansion, foam cell formation and up-regulation of oxidative [NAD(P)H oxidase subunits] and inflammatory [NF-κB, MCP-1, PAI-1 and COX-2] pathways. D-4F administration lowered proteinuria, improved renal histology and reversed up-regulation of inflammatory and oxidative pathways with only minimal changes in plasma lipid levels.

Conclusions: The apoE(-/-) mice develop proteinuria and glomerular and tubulo-interstitial injury which are associated with up-regulation of oxidative and inflammatory mediators in the kidney and are ameliorated by the administration of apoA-1 mimetic peptide. These observations point to the role of oxidative stress and inflammation in the pathogenesis of renal disease in hyperlipidaemic animals and perhaps humans.

Fig. 1

Representative photomicrographs of glomeruli from an untreated apoE-deficient mouse showing capillary occlusion by microthrombi (arrowhead) and mesangiolysis with capillary dilatation (asterisk) (A) and mild mesangial expansion, collapsed glomerulus with foam cells (asterisks) and focal infiltration of inflammatory cells in the adjacent tubulo-interstitial region (arrowhead) (B). (PAS staining, original magnification ×400).

Fig. 2

Representative photomicrographs illustrating the contrasting features of renal biopsies of an untreated apoE-deficient mouse (A, B) and D-4F-treated apoE-deficient mouse (C, D). Infiltrating macrophages are present in A (arrows) and absent in C (immuno-peroxidase staining). Mesangial expansion and foam cells (asterisks) in B are absent in the glomerulus in D that shows normal appearance (PAS staining) (original magnification ×400).

Fig. 3

Bar graphs depicting macrophage and lymphocyte infiltration in the glomeruli and tubulo-interstitial regions of the kidney in the wild-type (control) and untreated and D-4F-treated apoE^−/− mice. The untreated apoE-deficient mice showed macrophage and lymphocyte accumulation in glomeruli and tubulointerstitium that was suppressed by treatment. *P < 0.05, **P < 0.01, *** P < 0.005.

Fig. 4

Representative Western blots and group data depicting protein abundance of the NAD(P)H oxidase subunits (NOX-4, gp91^phox and p47^phox) in the renal tissues of the wild-type (control) and untreated and D-4F-treated apoE^−/− mice. n = 6 in each group. a: P < 0.05 vs control group, b: P < 0.05, D-4F-treated vs untreated apoE-deficient group.

Fig. 5

Representative Western blots and group data depicting protein abundance of the CuZn-SOD, extracellular SOD, catalase and glutathione peroxidase (GPX) in the renal tissues of the wild-type (control) and untreated and D-4F-treated apoE^−/− mice. n = 6 in each group. a: P < 0.05 vs control group, b: P < 0.05, D-4F-treated vs untreated apoE-deficient group.

Fig. 6

Representative Western blots and group data depicting protein abundance of phospho-IκB and nuclear p65 active subunit of NF-κB in the renal tissues of the wild-type (control) and untreated and D-4F-treated apoE^−/− mice. n = 6 in each group. a: P < 0.05 vs control group, b: P < 0.05, D-4F-treated vs untreated apoE-deficient group.

Fig. 7

Representative Western blots and group data depicting protein abundance of MCP-1, PAI-1, COX-1, COX-2 and 12-lipoxygenase (12-LPO) in the renal tissues of the wild-type (control) and untreated and D-4F-treated apoE^−/− mice. n = 6 in each group. a: P < 0.05 vs control group, b: P < 0.05, D-4F-treated vs untreated apoE-deficient group.

Fig. 8

Bar graphs depicting LDL and HDL chemotactic activities in the wild-type and untreated- and D-4F-treated apoE^−/− groups. Standard LDL and standard HDL were from healthy donors were used as controls. Mouse LDL and HDL were isolated from plasma by FPLC and inflammatory index determined in the as described in the Methods section. The values are presented as mean ± SD of migrated monocytes per high power field. The value for the standard LDL was taken as 1.0 and used as basis against which the inflammatory indices of the test samples were calculated. n = 6 in each group.