Analysis and biological relevance of advanced glycation end-products of DNA in eukaryotic cells

Advanced glycation end-products (AGEs) of DNA are formed spontaneously by the reaction of carbonyl compounds such as sugars, methylglyoxal or dihydroxyacetone in vitro and in vivo. Little is known, however, about the biological consequences of DNA AGEs. In this study, a method was developed to determine the parameters that promote DNA glycation in cultured cells. For this purpose, the formation rate of N-2-carboxyethyl-2'-deoxyguanosine (CEdG), a major DNA AGE, was measured in cultured hepatic stellate cells by liquid chromatography (LC)-MS/MS. In resting cells, a 1.7-fold increase of CEdG formation rate was observed during 14 days of incubation. To obtain insights into the functional consequences of DNA glycation, CEdG was introduced into a luciferase reporter gene vector and transfected into human embryonic kidney (HEK 293 T) cells. Gene activity was determined by chemiluminescence of the luciferase. Thus, CEdG adducts led to a dose-dependent and highly significant decrease in protein activity, which is caused by loss of functionality of the luciferase in addition to reduced transcription of the gene. When the CEdG-modified vector was transformed into Escherichia coli, a loss of ampicillin resistance was observed in comparison to transformation with the unmodified plasmid. These results indicate that CEdG accumulates in the genomic DNA of resting cells, which could lead to diminished protein activity.