Activation of receptor for advanced glycation end products: a mechanism for monocyte-mediated inflammation in chronic renal failure

Abstract

To investigate the expression of receptor for advanced glycation end products (RAGE) in chronic renal failure (CRF) and its role in monocyte-mediated inflammation associated with chronic renal failure (CRF). Peripheral monocytes (PMC) were isolated from 96 non-diabetic patients with varying severity of CRF. RAGE expression on monocytes was quantitated by flow cytometry. The binding capacity of monocytes with advanced glycation end products (AGE) was determined by 125I-AGEs-HSA binding assay. The plasma level of pentosidine, a marker of AGE, was determined by competitive ELISA. Commercially available kits were used for measuring the plasma levels of neopterin, TNF-alpha and C-reactive protein (CRP), a systemic acute phase reactant. Flow cytometry showed that the RAGE expression at the PMC surface of CRF patients was 8.02 +/- 0.43, significantly higher than that of the normal controls (P < 0.001). The number of functional sites to bind 125I-AGEs-HSA at the surface of PMC of CRF patients was increased in comparison with the normal control group. The biding capacity (Ka) at the surface of PMC of CRF patients was 2 times that of normal control group. Stimulated by AGEs-HAS, the TNF-alpha level in the supernatant of PMC increased dose-dependently in both the normal control and CRF patients, especially in the latter (P < 0.01). After pretreatment of anti-RAGE or non-immune rabbit IgG and then by AGEs-HAS the levels of TNF-alpha in the PMC supernatants of CRF patients and normal controls decreased form 90.52 pg/(10(5) cell) +/- 2.82 pg/(10(5) cell) to 17.86 pg/(10(5) cell) +/- 1.05 pg/(10(5) cell) and from 26.38 pg/(10(5) cell) +/- 1.54 pg/(10(5) cell) to 6.76 pg/(10(5) cell) +/- 0.20 pg/(10(5) cell). HAS not modified by AGEs and non-immune rabbit IgG showed no influence on the secretion of TNF-alpha. The plasma levels of TNF-alpha, neopterin, and CRP increased along with the worsening of renal function. The RAGE expression and pentosidine level at the surface of PMC in CPR patients without hemodialysis were positively correlated with plasma neopterin, TNF-alpha, and CRP levels, even after correction of creatine clearance rate (r = 0.53, P < 0.001; r = 0.58, P < 0.001; r = 0.40, P = 0.001). The expression of RAGE in CRF patients with hemodialysis was positively correlated with the plasma TNF-alpha level (r = 0.33, P = 0.029, n = 36), however, not correlated with neopterin or CRP. Enhanced RAGE may trigger a positive feed back loop of AGEs-induced monocyte perturbation, and may contribute to the monocyte-mediated systemic inflammation in CRF.