Cytotoxicity of Maillard reaction products determined with a peptide spot library

The reaction of reactive carbonyl compounds (RCCs) with lysine and arginine (Maillard reaction) is a common modification of proteins in thermally processed foods. In this study, the toxicity of Maillard reaction products (MRPs) formed from defined amino acids or dipeptides (bound to a cellulose membrane) with ribose, glycerinaldehyde or methylglyoxal was investigated. Murine RAW 264.7 macrophages were cultivated on the cellulose membrane and the effect of MRPs on cell viability was determined. The toxicity of MRPs was dependent on the RCC used and increased in the order of ribose < glycerinaldehyde < methylglyoxal. The dipeptides were more cytotoxic than the amino acids, with Lys-Lys MRPs being the most toxic of all tested MRPs. Cell numbers did not fall below the starting point, indicating that the MRPs rather inhibited proliferation than actually caused cell death. To develop an assay, in which whole membranes with multiple peptide spots could be tested simultaneously, we measured cell numbers on larger cellulose membranes using image analysis of the intracellularly formed formazan crystals. Although this method was technically feasable, it appears that uneven cell attachment on the membrane would require a way to detemine starting cell number by a non-destructive assay to yield more robust data.