Abstract
Purpose :
Oxidative stress and mitochondrial dysfunction have been implicated in the pathway to cell death in diabetic retinopathy. Mitochondrial DNA (mtDNA) can be classified into haplogroups that represent different geographic origins of populations. Differences in maternally inherited mtDNA haplogroups can influence susceptibility to various ocular diseases. The influence of mtDNA haplogroups on mitochondrial metabolism in diabetes is not well characterized. The purpose of this study is to describe the differences in bioenergetic profile between mtDNA from European origin (H haplogroup) and African origin (L haplogroup) when exposed to high glucose and bevacizumab (beva) in vitro.
Methods :
Two groups of cytoplasmic hybrids (cybrids) were created by fusing ARPE-19 cells devoid of mtDNA with platelets from donors of either H or L haplogroups. Both groups of cybrids were exposed to: 1) normal glucose only (NG), 2) high glucose only (HG), 3) normal glucose + beva (NG+B) or 4) high glucose + beva (HG+B). Cells were assayed for levels of reactive oxygen species (ROS) using the fluorescent dye 2', 7’-dichlorodihydrofluorescein diacetate, cell viability (CV) measured by MTT assay and mitochondrial membrane potential (ΔΨm) as measured with JC-1 dye kit. Student’s t-test was used to compare mean percent change between sample groups, with the NG only samples set at 100% production or function
Results :
The L haplogroup showed a reduction in ROS production with groups NG+B (81.7%, P<0.001) and HG+B (66.6%, P<0.001). The H haplogroup also had a reduction in ROS production, NG+B (76.6%, P<0.001) and HG+B (68.8%, P=<0.001). CV was improved in the NG+B (+46.6%, p<0.001) and HG+B (+29.1%, p=0.001) cultures for the L haplogroup. This positive effect on CV was not seen in the H haplogroup. ΔΨm was significantly reduced in the L haplogroup cultures NG+B (-25.0%, p=0.004) and HG+B (-30.0%, p<0.001), as well as the H haplogroup cultures NG+B (-49.4%, p<0.001) and HG+B (-47.9%, p<0.001).
Conclusions :
ROS production was reduced by the addition of beva in both H and L haplogroups. Beva rescued CV in the L haplogroup, but not in the H haplogroup. ΔΨm was significantly reduced by the addition of Beva in both H and L haplogroups. The varied responses between the H (European) and L (African) cybrids to beva may reflect the diversity in mitochondrial response to energy metabolism and cellular damage in different racial populations.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.