Increased severity of glomerulonephritis in C-C chemokine receptor 2 knockout mice.

UNLABELLED: Increased severity of glomerulonephritis in C-C chemokine receptor 2 knockout mice. BACKGROUND: The C-C chemokine receptor 2 (CCR2) is expressed on monocytes and facilitates monocyte migration. CCR2 is a prominent receptor for monocyte chemoattractant protein-1 (MCP-1). This chemokine recruits monocytes to sites of inflammation. It has been suggested that CCR2 and its ligand, MCP-1, play a role in the pathogenesis of glomerulonephritis. The goal of this study was to determine the contribution of CCR2 in a murine model of accelerated nephrotoxic nephritis. We measured the extent of development of renal disease in CCR2 wild-type and knockout mice after the administration of antiglomerular basement membrane antibody. METHODS: Eight groups of animals were treated (N = 10 per group). Four days after IgG immunization, CCR2 wild-type and knockout mice received control serum or nephrotoxic serum. The urinary protein/creatinine ratio was measured on days 1 and 3; plasma and kidneys were collected on days 4 and 7. Kidneys were evaluated by light microscopy, immunohistochemistry, and immunofluorescence. The genotype of mice was confirmed by tissue analysis. RESULTS: Protective effects of CCR2 knockout on the urinary protein/creatinine ratio were observed on day 1, as values for this parameter were significantly lower (35 +/- 3.6) than in nephritic wild-type mice (50 +/- 6.8). There was a marked increase in proteinuria in nephritic wild-type mice on day 1 compared with vehicle-treated, wild-type animals (5 +/- 1.0). On day 3, the ameliorative effects of CCR2 knockout were not observed; the increase in the urinary protein/creatinine ratio was similar in nephritic CCR2 wild-type (92 +/- 11.2) and knockout mice (102 +/- 9. 2). Plasma markers of disease were evaluated on days 4 and 7. At these time points, there were no beneficial effects of CCR2 receptor knockout on plasma levels of urea nitrogen, creatinine, albumin, or cholesterol. On day 7, blood urea nitrogen (248 +/- 19.9 mg/dL) and plasma cholesterol were higher in nephritic CCR2 knockout mice than in wild-type mice (142 +/- 41.7 mg/dL) that received nephrotoxic serum. Histopathologic injury was more severe in nephritic CCR2 knockout mice than nephritic wild-type mice on day 4 (3.1 +/- 0.3 vs. 2.0 +/- 0.3) and day 7 (3.6 +/- 0.2 vs. 2.9 +/- 0.3). By immunohistochemical analysis at day 4, there were significantly fewer mac-2-positive cells, representative of macrophages in the glomeruli of nephritic CCR2 knockout (2.1 +/- 0.6) mice than nephritic wild-type (3.9 +/- 0.5) animals. By indirect immunofluorescence, there was a moderate, diffuse linear IgG deposition of equivalent severity present in glomeruli of both wild-type and CCR2 knockout nephritic mice. CONCLUSION: These results suggest that our strategy was successful in reducing macrophage infiltration, but this model of glomerulonephritis is not solely dependent on the presence of CCR2 for progression of disease. After a transient ameliorative effect on proteinuria, CCR2 knockout led to more severe injury in nephritic mice. This raises the intriguing possibility that a CCR2 gene product ameliorates glomerulonephritis in this murine model. Although effects that occur in chemokine knockout mice are not equivalent to those expected with prolonged use of a chemokine antagonist, this study may nevertheless have implications for consideration of long-term use of chemokine antagonists in renal disease.

Captopril prevents nephropathy in HIV-transgenic mice.

Transgenic mice (T26) bearing the envelope, regulatory, and accessory genes of HIV- I develop renal disease resembling human HIV-associated nephropathy (HIVAN). Effects of vehicle (VEH) and the angiotensin-converting enzyme inhibitor captopril (CAP) were examined in wild-type (WT) or T26 mice treated from 7 to 100 d of age. Mortality was lower in CAP T26 mice (30 mg/kg: 8%; 100 mg/kg: 12%) than VEH T26 mice (52%). The urinary protein/creatinine ratio was increased in VEH T26 mice (19.5+/-7.60) versus WT mice (6.1+/-0.83), but not in low-dose (7.3+/-0.94) or high-dose (8.2+/-1.02) CAP T26 mice. Blood urea nitrogen was higher in VEH T26 mice (52+/-16.2 mg/dl) than VEH WT mice (24+/-0.8). Blood urea nitrogen was also elevated in CAP WT (high dose: 43+/-2.1 mg/dl) and T26 mice (high dose: 42+/-2.4 mg/dl). Glomerular injury was higher in VEH T26 mice (6.8+/-0.58) than VEH WT mice (0.2+/-0.08) or CAP T26 mice (low dose: 1.1+/-0.17; high dose: 0.7+/-0.13). Tubulointerstitial injury was also greater in VEH T26 mice (1.1+/-0.10) than VEH WT mice (0.2+/-0.08) or CAP T26 mice (low dose: 0.4+/-0.10; high dose: 0.3+/-0.10). These data validate recent nonrandomized studies of captopril in HIV-infected patients, and suggest that an angiotensin-converting enzyme substrate is an important mediator in HIVAN. A randomized placebo-controlled trial of captopril in HIVAN may be warranted.