Background: Biologically uncommon D-β-aspartic acid residues have been reported to accumulate in various proteins of the living body during aging. In the present study, the localization of D-β-aspartic acid containing proteins was found in pinguecula, in which one of the most prominent age-related ocular changes generate.
Methods: Surgical specimens of conjunctiva with or without pinguecula were prepared from nine patients. Immunohistochemical localization of D-β-aspartic acid containing proteins was investigated using polyclonal antibody against D-β-aspartic acid-containing peptides.
Results: Strong immunoreactivity to D-β-aspartic acid-containing peptides was detected in the subepithelial amorphous materials of all the surgical specimens with pinguecula. In contrast, no immunoreactivities to D-β-aspartic acid-containing peptides were detected in the specimens without pinguecula.
Conclusions: Pinguecula was thought to aggregates consist of proteins contain D-β-aspartic acid residues. It is known that conversion of L- to D- aspartyl residues is accelerated by ultraviolet irradiation. In addition, D-β-aspartic acid-containing proteins in general tend to aggregate in each other and accumulate in tissues. These facts indicate that ultraviolet-induced racemization of aspartic acids is closely related to the development of pinguecula.