Aims/hypothesis
Activation of the receptor for advanced glycation end products (RAGE) reportedly triggers cellular responses implicated in the pathogenesis of diabetes, such as increasing vascular cell adhesion molecule-1 (VCAM-1) expression on vascular endothelial cells and inducing TNF-
secretion by mononuclear cells. The objective of this study was to evaluate whether RAGE binding affinity of AGE-BSAs and cellular activation correlate.
Methods
To produce AGEs with varying glycation, bovine albumin AGEs were prepared with 500 mmol/l of glucose, fructose or ribose at times of incubation from 1 to 12 weeks. In addition, AGE-BSA was generated using either glyoxylic acid or glycolaldehyde. Cellular binding of the AGE-BSAs and the effect on endothelial cell VCAM-1 expression were studied in RAGE-expressing human microvascular endothelial cell line-4 cells. Induction of TNF-
secretion was assessed using RAGE-expressing human peripheral blood mononuclear cells (PBMCs).
Results
Cellular binding of the different AGE preparations correlated well with RAGE affinity. Interestingly, we found that the AGE preparations, which were essentially endotoxin free (
0.2 ng/mg protein), were incapable of inducing VCAM-1 or TNF-
secretion regardless of RAGE binding affinity, AGE concentration or incubation time. In contrast, the reported RAGE ligand S100b was confirmed to induce VCAM-1 expression on endothelial cells and TNF-
secretion by PBMCs after 24 h of treatment.
Conclusions/interpretation
The results of this study suggest that AGE modification and high RAGE binding affinity are not sufficient to generate pro-inflammatory signalling molecules. Thus, RAGE binding affinity of AGE-BSAs does not seem to correlate with cellular activation. Our findings using AGEs with strong RAGE-binding properties indicate that AGEs may not uniformly play a role in cellular activation.Keywords AGE - Glycation - Inflammation - Maillard reaction - RAGE - Serum albumin