Abstract
Purpose :
The goal of this study is to investigate the effect of Apolipoprotein A-I binding protein (AIBP; gene name APOAIBP) on mitochondrial structure and function in Müller glia in response to elevated pressure.
Methods :
Retina tissues were prepared from wild-type (WT, C57BL/6J) and AIBP knockout (Apoa1bp-/-) mice. Mitochondrial morphology and ATP production were assessed by serial block-face scanning electron microscopy (SBEM) and electron microscope (EM) tomography. Rat Müller glia cell line (rMC-1) cultures were pretreated with BSA or recombinant human AIBP (0.2 μg/ml) at 2 hours before exposure to elevated hydrostatic pressure (HP, 30 mmHg) for 2 hours. Mitochondrial respiration in rMC-1 cells was assessed by measuring oxygen consumption rate using a Seahorse XF24 analyzer. Mitochondrial activity and cell viability were measured by MTT and CellTiter-GloTM luminescent assays.
Results :
Apoa1bp-/- mice showed mitochondrial fragmentation and reduction of ATP production in Müller glia mitochondria. Quantitative analyses showed that there were no significant changes in mitochondrial volume, volume density, or mitochondrial number in the Apoa1bp-/- Müller glia endfeet. The form factor for the Apoa1bp-/- mitochondria was significantly lower than for the WT, meaning more mitochondrial rounding in the Apoa1bp-/-. Mitochondrial length was significantly decreased in Apoa1b-/-. Similarly, the crista density and the modeled rate of ATP production per mitochondrial volume were lower in the Apoa1bp-/-. In contrast, the modeled rate of ATP production per mitochondrion was not lower in the Apoa1bp-/-, yet there was a significant decrease in cellular ATP production via mitochondria in the Apoa1bp-/-. AIBP treatment promoted basal and maximal respiration along with an increase of ATP production and spare respiratory capacity, as well as mitochondrial activity in rMC-1 cells exposed to normal pressure compared to BSA treatment. In BSA treatment, elevated HP significantly reduced maximal respiration and spare respiratory capacity in rMC-1 cells compared to cells exposed to normal pressure. In addition, AIBP treatment enhanced basal and maximal respiration, as well as mitochondrial activity and cell viability in rMC-1 cells exposed to elevated HP.
Conclusions :
These findings suggest that AIBP may protect retinal ganglion cells by promoting mitochondrial bioenergetics of Müller glia during glaucomatous neurodegeneration.
This is a 2021 ARVO Annual Meeting abstract.