Maillard reaction-like lysine modification by a lipid peroxidation product: immunochemical detection of protein-bound 2-hydroxyheptanal in vivo.

2-Hydroxyheptanal (2-HH) is one of the reactive aldehyde species generated during the peroxidation of n-6 polyunsaturated fatty acids, such as linoleic and arachidonic acids. Analogous to the Maillard reaction of reducing sugars, 2-HH readily reacts with lysine epsilon-amino groups. In the present study, to define the occurrence of the Maillard reaction-like lysine modification by 2-HH in vivo, we raised a monoclonal antibody directed to a trihydropyridinone (THPO) structure, 1-alkyl-4-butyl-5-pentyl-1,2,6-trihydropyridin-3-one, formed from 2-HH and lysine, and examined the presence of the antigenic structure in the human atherosclerotic aorta. Mice were immunized with the 2-HH-modified keyhole limpet hemocyanin (KLH) as the immunogen. Using a THPO-carrier protein conjugate, we screened the hybridomas and finally obtained a clone that produced the monoclonal antibody 3C8 (mAb3C8). The antibody strongly recognized bovine serum albumin (BSA) treated with 2-HH, but showed no cross-reactivity with BSAs modified with other related aldehydes. By using this antibody, it was revealed that the antigenic structure was indeed present in atherosclerotic lesions of the human aorta.