Abstract
Purpose :
Corneal endothelial cells (CEnCs) are post mitotically arrested cells that exhibit high metabolic activity and are susceptible to ROS-induced DNA damage. Fuchs Endothelial Corneal Dystrophy (FECD) is an age-related disorder identified by oxidative stress mediated loss of CEnCs. In our previous studies we detected increased nuclear and mitochondrial DNA damage causing an increase in 8-hydroxy 2′-deoxyguanine (8-OHdG) lesions in FECD. However, there is limited information on DNA repair activity in FECD cells. In this study, therefore, we sought to investigate the role of DNA damage repair enzymes in the pathogenesis of FECD
Methods :
Two immortalized normal CEnC lines HCEnC-SV-67F-16 and HCEnC-21T and three different FECD patient tissue derived cell lines FECDi, FECD-SV-61F-18 and FECD-SV-73F-74 were grown in Chen’s medium up to 80% confluence. Cells were treated with or without 25 µM Menadione (MN) dissolved in low glucose Dulbecco’s Modified Eagle Medium (DMEM) followed by post-treatment recovery in culture medium. Cells were collected following treatment and recovery and protein expression was analyzed by western blotting
Results :
MN-mediated oxidative stress in vitro in human CEnCs leads to rosette formation and DNA damage which are both noted in FECD ex vivo specimens. In this study, we tested the expression of OGG1 (8-oxoguanine DNA glycosylase 1), a key base excision repair (BER) enzyme that recognizes and removes 8-OhdG lesions. MN induced an increase in the protein level of OGG1 in normal HCEnC-21T while in FECDi basal level of OGG1 was comparatively lower and showed no further upregulation upon MN treatment. Lack of MN-mediated OGG1 upregulation was also observed in FECD-SV-61F-18 and FECD-SV-73F-74 cell lines. Further in HCEnC-SV-67F-16 cell line, the MN-induced increase in OGG1 was restored to baseline level in recovery medium post treatment; implying active repair pathway in normal cell line as opposed to FECD cell lines. To further investigate the mechanism of reduced DNA repair activation, we are testing several repair pathways in MN-mediated in vitro model, UV-based in vivo mouse model and ex vivo FECD specimens in on-going studies
Conclusions :
FECD cells show a lack of OGG1 up-regulation in response to MN-mediated oxidative stress indicating impaired base excision repair via this enzyme. This suggests that defective DNA repair may contribute to the extensive DNA damage with ensuing CEnC cell loss seen in FECD
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.