Submission
| Title: | Müller cell Kir4.1 channel dysfunction in APOE4-KI model of Alzheimer’s disease |
| Presenter: | Surabhi Abhyankar |
| Institution: | Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indianapolis, Indiana |
| Authors: | Surabhi D. Abhyankar1,2; Xiao Yucheng3; Neha Mahajan1; Qianyi Luo1; Theodore R. Cummins3; Adrian L. Oblak4; Bruce T. Lamb4; Ashay Bhatwadekar1,2,4
1Department of Ophthalmology, Eugene and Marilyn Glick Eye Institute, Indianapolis, Indiana. |
Abstract
| Background/Significance/Rationale: | Worldwide, at least 55 million individuals have Alzheimer’s disease (AD). The most prevalent form of AD is late-onset AD (LOAD), and apolipoprotein E4 (APOE4) is the major genetic component in the pathogenesis of LOAD. As a central nervous system component, the eye displays a variety of abnormalities in AD. Müller cell (MC), a principal glia of the eye, possesses specialized functions such as neurotransmitter uptake and glycogen storage, thus serving as a metabolic powerhouse; however, in LOAD, the MCs are dysfunctional. While MCs regulate water and K+ balance via inwardly rectifying Kir4.1 channels, it remains unknown how APOE4 affects Kir4.1 channels and overall MC health in AD. Therefore, in this study, we assess the effect of APOE4 on Müller cell Kir4.1 channel in both animal and in vitro studies. |
| Methods: | Immunofluorescence staining for Kir4.1 and glutamate synthase-1 (GS-1) was performed on the retinas of 52-57-week-old APOE3 knock-in (KI, neutral for AD) and APOE4-KI mice. A whole-cell voltage-gated patch clamp was performed on the MCs isolated from the retinas of these mice. The in vitro experiments were performed on Rat MC (RMC-1) transfected with APOE2/ APOE3/ APOE4 plasmids. qRT-PCR and western blotting were performed to check Kir4.1 expression. Flow cytometry was used to check mitochondrial membrane potential (MMP) using JC-1 and mitochondrial reactive oxygen species (ROS) levels using MitoSOX-Red. |
| Results/Findings: | 52-57-weeks-old APOE4-KI mice showed decreased Kir4.1 and GS-1 expression and reduced Kir4.1 current densities compared to APOE3-KI mice. RMC-1 expressing APOE4 showed a reduction in the Kir4.1 gene and protein expression. Flow cytometry analysis showed APOE4 decreased MMP and increased mitochondrial ROS. |
| Conclusions/Discussion: | APOE4 causes structural and functional deficits in the MCs, potentially via mitochondrial dysfunction. |
| Translational/Human Health Impact: | These discoveries shed light on the mechanisms behind MC dysfunction in LOAD and help better understand whether enhancing mitochondrial health improves retinal health. |
