Mitochondrial dysfunction has been implicated in a wide variety of degenerative diseases, including age-related macular degeneration. Damage to mitochondria and mitochondrial DNA accumulates with age in the postmitotic retinal pigment epithelium (RPE), which could lead to RPE cell death and trigger disease. One possible mechanism for cells to avoid cell death is mitophagy, the targeted clearance of damaged mitochondria by autophagy. Here, we induced mitochondrial damage in human RPE cells (ARPE-19 and hRPE), using antimycin A, an inhibitor of complex III of the electron transport chain, and investigated cellular viability, mitochondrial structure and function, and autophagy activity. We observed that antimycin A evoked dose-dependent cell death, a rapid loss in mitochondrial membrane potential, and a collapse of oxidative phosphorylation. Mitochondria appeared swollen and there was clear damage to their cristae structure. At the same time, cells were undergoing active autophagy and were sensitive to autophagy inhibition by bafilomycin A1 or chloroquine. These results indicate that mitochondrial dysfunction can cause significant RPE damage and that autophagy is an important survival mechanism for cells suffering from mitochondrial damage.
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The authors wish to thank the University of Minnesota Imaging Center, St. Paul, MN, and Virpi Miettinen, UEF, Finland, for their excellent practical assistance in the preparation of the TEM samples and Ewen MacDonald for revising the language of the article. The authors also want to acknowledge the contribution of personnel from the Lions Gift of Sight for their assistance in procuring human donor eyes and Dr. Nathan Schuld and Professor M. Cristina Kenney for their advice with the Seahorse assays. This work was supported by the Finnish Cultural Foundation—North Savo Regional Fund (to MH), the Academy of Finland (Health Research Council projects 297267 and 307341), and the Emil Aaltonen Foundation. Work at the University of Minnesota was supported by the Elaine and Robert Larson Endowed Vision Research Chair (to DAF), the Lindsay Family Foundation, an anonymous donor for AMD research, and an unrestricted grant from the Research to Prevent Blindness to the Department of Ophthalmology.
Copyright © 2019 Maria Hytti et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.