The Changes of 8-OHdG, hOGG1, APE1 and Pol beta in Lenses of Patients with Age-Related Cataract

Purpose: To evaluate the changes of oxidative DNA damage (in the form of 8-OHdG) and three key DNA base-excision repair (BER) proteins, human 8-oxoguanine DNA glycosylase 1 (hOGG1), apurinic/apyrimidinic endonuclease 1 (APE1) and DNA polymerase beta (Pol beta), in lens epithelium cells (LECs), cortex and nucleus of lenses with age-related cataract (ARC) and age-matched controls. Methods: A total of 90 patients with ARC and 21 control subjects were enrolled. The samples included the anterior lens capsules (mainly composed of LECs) and various portions of lens. An ELISA assay was used to assess the 8-OHdG levels of genomic DNA extracted. Immunofluorescence and Western blot were used to analyze the localization and quantification of three BER proteins, respectively. Results: The 8-OHdG levels in lenses with ARC were higher than those of controls, and were not different among ARC subtypes. The 8-OHdG levels were the highest in the nucleus, followed by the LECs and cortex. The repair proteins were predominantly detected in the cellular nuclei of the LECs and superficial cortical cells. In the LECs, the protein levels of the three BER enzymes were higher in ARC than in controls. In the cortex, a downward trend of the levels of three BER enzymes was found with the increasing opaque degrees. In the nucleus, no enzymes were detected. Conclusions: Our findings indicate that the oxidative DNA damage increases in lenses with ARC, and the three BER enzymes compensatively increase in the LECs, while decreasing in the opaque cortex. The results suggest that the oxidative DNA damage may be related ARC and the alteration of DNA repair enzyme levels in ARC is associated with the location and opaque degrees of lens.