The effect of an AGE-rich dietary extract on the activation of NF-κB depends on the cell model used

Advanced glycation end products (AGEs) are the results of a chemical reaction of reactive aldehydes, such as sugars, with amino acid side chains. AGEs can be formed by the heating process of the food and taken up with the diet. They are thought to be at least in part responsible for major complications in age-related diseases. The activation of the transcription factor NF-κB plays a prominent role in AGE-induced cell signaling. This study aimed to elucidate the effect of exogenous AGEs on NF-κB activation in different cell models. Therefore a bread crust extract commonly found in a Western diet was chosen as an AGE-rich sample. Using RP-HPLC, 23 fractions from the bread crust extract were obtained. The immunodetection with specific antibodies for N-carboxymethyllysine arg-pyrimidine, pentosidine and 3-deoxyglucosone-imidazolone showed that the majority of the AGEs were located in the late fractions. Three different NF-κB reporter cell lines including NF-κB/293/GFP-Luc™, NF-κB/Jurkat/GFP™ and RAW/NF-κB/SEAPorter™ were stimulated with the 23 fractions. There was no direct correlation between the AGE content in the fractions and the cell activation. Whereas in Jurkat-T-cells, the stimulation seems to correlate at least in part with the AGE content, in HEK-293 epithelial cell nearly all fractions can stimulate NF-κB. In macrophages few fractions stimulate NF-κB whereas some fractions even inhibit the p38 MAP kinase. The highest expression of the AGE receptors like RAGE, AGER-1, AGER-2 and AGER-3 was detected in the macrophage RAW cell line. In conclusion the present study showed a new approach to study bioactive compounds in bread crust extract. The identification of the bioactive compounds is still ongoing.