Modification of histone by glyoxal: recognition of glycated histone containing advanced glycation adducts by serum antibodies of type 1 diabetes patients

Dicarbonyl compounds react more rapidly, than glucose, with arginine and lysine in proteins to form advanced glycation end products (AGEs) and further produce free radicals which cause DNA damage. AGEs are reliable diagnostic biomarkers for most of the age-related diseases. In the present study histone was modified with glyoxal and it was characterized by various spectral techniques. Binding characteristics of the modified histone towards serum antibodies from type 1 diabetes patients was evaluated by solid phase enzyme immunoassay and the results were compared with normal human subjects. Fluorescence and Fourier transformed infrared analysis of the nuclear protein clearly indicated changes in their respective intensities upon modification with glyoxal. Liquid chromatography together with mass spectrometry showed new peaks and m/z values related to AGE adducts of dihydroimidazolidines/hydroimidazolones. This glyoxal modified protein was recognized by serum antibodies of the diabetes patients while it showed negligible binding with that of normal human subjects. Glyoxal modification of histone causes structural turbulence and formation of advanced glycation adducts in histone. These adducts might be the main antigenic epitope of the modified histone, leading to its recognition by circulating type 1 diabetes antibodies.