Glomerular-derived proteins may activate tubular cells to express the macrophage-directed chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2). Macrophages at interstitial sites have a central role in directing renal scarring. We have prospectively assessed the relationship between albuminuria, urinary MCP-1/CCL2, interstitial macrophage infiltration, in situ damage, and clinical outcomes in a large group of patients with chronic kidney disease. We studied 215 patients and quantified albumin-creatinine ratio (ACR), urinary MCP-1/CCL2, interstitial macrophage numbers, and in situ damage. ACR correlated with urinary MCP-1/CCL2 (correlation 0.499; P<0.001), interstitial macrophage numbers (correlation 0.481; P<0.001), and index of chronic damage (correlation 0.363; P<0.001). Macrophage numbers closely correlated with in situ damage (correlation 0.755; P<0.001). By multivariate analysis ACR, urinary MCP-1/CCL2, and interstitial macrophage numbers were interdependent. By Kaplan-Meier survival analysis albuminuria, urinary MCP-1/CCL2, interstitial macrophages, and chronic damage predict the outcome. ACR, macrophage numbers, chronic damage, and creatinine independently predicted renal survival. The association of ACR with other variables was strongest in patients with less advanced disease states. There is a close association between albuminuria, urinary MCP-1/CCL2, and interstitial macrophage infiltration with in situ damage and clinical outcomes. These findings support the hypothesis that albuminuria triggers tubular MCP-1/CCL2 expression with subsequent macrophage infiltration. These processes may represent the dominant pathway for the progression of renal injury before the establishment of advanced renal scarring.

To assess the relationship between interstitial capillary density and interstitial macrophages we prospectively measured these factors in situ in 110 patients with chronic kidney disease. Macrophage numbers and urinary MCP-1/CCL2 levels significantly correlated inversely with capillary density which itself significantly correlated inversely with chronic damage and predicted disease progression. In 54 patients with less than 20% chronic damage, there was a significant correlation between the urinary albumin to creatinine ratio and MCP-1/CCL2, and MCP-1/CCL2 and macrophages but not between MCP-1/CCL2 and capillary density. Conversely, in 56 patients with over 20% chronic damage there was no correlation between MCP-1/CCL2 and macrophages but there were significant inverse correlations between capillary density and both macrophages and chronic damage. The expression of VEGF mRNA significantly correlated with macrophage infiltration, capillary density and chronic scarring. In an ischemic-hypertensive subgroup there was upregulation of the hypoxia marker carbonic anhydrase IX and with over 20% chronic damage an increased macrophage to CCR2 ratio. Our study shows that proteinuria and MCP-1/CCL2 are important for macrophage recruitment in early disease. As renal scarring evolves, alternative pathways relating to progressive tissue ischemia secondary to obliteration of the interstitial capillary bed predominate.

Background-Aldosterone has emerged as a deleterious hormone in the heart, with mineralocorticoid receptor (MR) blockade reducing mortality in patients with severe heart failure. There is also experimental evidence that aldosterone contributes to the development of nephrosclerosis and renal fibrosis in rodent models, but little is known of its role in clinical renal disease. Methods and Results-We quantified MR, serum-and glucocorticoid-regulated kinase 1 (sgk1), and mRNA expression of inflammatory mediators such as macrophage chemoattractant protein-1 (MCP-1), transforming growth factor-␤1, and interleukin-6 in 95 human kidney biopsies in patients with renal failure and mild to marked proteinuria of diverse etiologic origins. We measured renal function, serum aldosterone, urinary MCP-1 protein excretion, and the amount of chronic renal damage. Macrophage invasion was quantified by CD68 and vascularization by CD34 immunostaining. Serum aldosterone correlated negatively with creatinine clearance (PϽ0.01) and positively with renal scarring (PϽ0.05) but did not correlate with MR mRNA expression or proteinuria. Patients with heavy albuminuria (Ͼ2 g/24 h; nϭ15) had the most renal scarring and the lowest endothelial CD34 staining. This group showed a significant 5-fold increase in MR, a 2.5-fold increase in sgk1 expression and a significant increase in inflammatory mediators (7-fold increase in MCP-1, 3-fold increase in transforming growth factor-␤1, and 2-fold increase in interleukin-6 mRNA). Urinary MCP-1 protein excretion and renal macrophage invasion were significantly increased in patients with heavy albuminuria. Conclusions-These studies support animal data linking aldosterone/MR activation to renal inflammation and proteinuria.Further studies are urgently required to assess the potential beneficial effects of MR antagonism in patients with renal disease.