Changes of β-amyloid in age-related cataract and its protection on lens epithelial cells

Abstract

Purpose : Some studies demonstrated that cataract shared common characteristics with the conformational diseases, which are defined as a disease due to abnormal aggregation of protein, such as Alzheimer disease (AD). β-amyloid (Aβ) might be the key pathogenetic factor of AD. Some studies demonstrated that Aβ might also be related with age-related cataract (ARC). Our study is to evaluate the changes of Aβ expression in ARC patients and its effect on cultured human lens epithelium cells (HLECs).

Methods : We obtained lens anterior capsule and aqueous humor from ARC patients during cataract surgery. The specimens with ARC were divided into four groups according to the lens opacities classification system III (LOCS III) : Group A: C2-3N1-2; Group B: C4-5N1-2; Group C: C2-3N3-4; Group D: C4-5N4-5. We used WB, immunofluorescence, ELISA and RT-PCR to detect the expression of Aβ and β-amyloid precursor protein (APP). We also employed β-secretase activity assay. Besides, we applied cell viability assay to evaluate the effect of Aβ on the viability of HLECs under oxidative conditions.

Results : The expression of Aβ in ARC lens anterior capsule decreased from Group A to C, compared with the normal specimens, and finally increased in Group D (Figure 1). The concentration of Aβ in aqueous humor showed the similar changes as in the anterior capsule in ARC patients (Figure 1). In contrast, the expression of APP increased from Group A to C and decreased in Group D (Figure 2). The enzymatic activity of β-secretase was decreased in ARC specimens. The enzymatic activity of β- secretase was also found decreased in the cultured HLECs treated with H₂O_2, along with decreased Aβ and increased APP expression. In addition, we identified that low concentration of Aβ could relieve H₂O₂ induced cell damage in HLECs.

Conclusions : The expression of Aβ was decreased in the early and medium term of the onset of ARC, induced by the decrease of β- secretase, and increased in the terminal stage of cataract, which might be due to the feedback of increased APP expression. Low concentration of Aβ might play a protective role in cataractogenesis.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.

 

FIGURE 1. WB analysis, IF and ELISA of Aβ in lens capsules and aqueous humor.Group A- D: samples from the early to the final stage of ARC.

 

FIGURE 2. WB analysis, RT-PCR and IF of APP in lens capsules.