DNA-glycation leads to depurination by the loss of N2-carboxyethylguanine in vitro.

D-Glucose reacts with nucleosides, mainly guanosine, and DNA in a similar way as with proteins, and DNA-bound advanced glycation endproducts (AGE) are formed. Guanosine (Gua) was incubated with D-glucose or dihydroxyacetone (DHA) under variation of temperature and reaction time, and the formation of the glycation products N2-carboxyethylguanosine (CEG) and N2-carboxymethylguanosine (CMG) was monitored by HPLC/DAD. DHA proved to be a very potent glycating agent which specifically produces CEG. When deoxyguanosine (dGua) was glycated under the same conditions, formation of the glycation product N2-carboxyethyldeoxyguanosine (CEdG) resulted in a significant decrease in stability of the N-glycosidic bond. As a consequence more than 25% of CEdG was hydrolysed to give the corresponding guanine derivative CEguanine, whereas unmodified dGua was stable under these conditions. Glycated DNA was then incubated and depurination by the loss of CEguanine was monitored by HPLC. Significant release of CEguanine was observed, whereas free guanine was neither formed from glycated nor from control DNA in detectable amounts. These data suggest that CEdG which is formed during the glycation of DNA in vitro causes increased depurination of DNA and produces abasic sites.