Differential effects of advanced glycation end-products on renal tubular cell inflammation

Abstract

Aim: The authors recently showed that advanced glycation end-products (AGE) in the form of glycated albumin (GA) upregulated renal tubular expression of interleukin (IL)-8 and soluble intercellular adhesion molecule-1 (sICAM-1), but not other important cytokines known to mediate diabetic nephropathy. This implies that other molecules such as the carbonyl intermediates of AGE or other modified protein lysine-albumin may participate in diabetic tubular injury. Methods: Human proximal tubular epithelial cells (PTEC) were growth-arrested and exposed to methylglyoxal (MG), MG-bovine serum albumin (BSA)-AGE, carboxymethyllysine (CML)-BSA, AGE-BSA or BSA with or without prior addition of rosiglitazone that was previously shown to attenuate the pro-inflammatory effect of GA alone. Results: MG-BSA-AGE and AGE-BSA upregulated tubular expression of connective tissue growth factor (CTGF), transforming growth factor (TGF)-β, and vascular endothelial growth factor (VEGF), whereas CML-BSA stimulated expression of IL-6, CCL-2, CTGF, TGF-β and VEGF. These AGE compounds also activated nuclear factor (NF)-ÎB and their effects were attenuated by pre-incubation with anti-RAGE antibody. MG and BSA did not affect the expression of any of these molecules. Rosiglitazone did not affect the in vitro biological effects of MG, MG-BSA-AGE, AGE-BSA or CML-BSA on PTEC. Conclusion: AGE exhibit differential inflammatory and fibrotic effects on PTEC via RAGE activation and NF-ÎB signal transduction. Rosiglitazone had no effect on these responses. Further investigations on compounds that nullify the downstream effects of these AGE are warranted. Tang and colleagues showed that various AGE formation (MG-BSA-AGE, AGE-BSA and CML-BSA are important AGE) have differential pro-inflammatory and profibrotic effects on cultured PTEC via RAGE activation and NF-ÎB signal transduction. © 2011 Asian Pacific Society of Nephrology.