Loss of retinal pigment epithelial (RPE) cells via apoptosis plays a prominent role in several retinal degenerative diseases, such as age-related macular degeneration, and with light damage. Strategies for preservation of vision that would interrupt the apoptotic cascade require understanding the molecular events associated with apoptosis. This study investigated the susceptibility of RPE to caspase-dependent and -independent apoptotic pathways when challenged with different stimuli, including oxidants, anti-Fas antibody, and activated cytotoxic T lymphocytes (CTLs). These experiments used novel RPE cell lines developed from wildtype and heterozygous mice with reduced levels of either Mn superoxide dismutatse (SOD) or CuZnSOD. Peroxide and 4-hydroxynonenal induced apoptosis through both caspase-independent and -dependent pathways, respectively. With both oxidants, translocation of apoptosis inducing factor into the nucleus was observed. Cells containing reduced levels of CuZnSOD were the most susceptible to oxidant-induced cell death. Targeted killing by CTLs and activation of the Fas death receptor induced caspase-dependent apoptosis. These results show stimulus-specific activation of either the caspase-dependent or -independent pathway. Since cultured RPE express the protein components required for different apoptotic pathways, they provide a good model system for studying molecular events associated with multiple signals that lead to cell death.
Bibliographical noteFunding Information:
We acknowledge the following organizations for their financial support: National Institutes of Health Grants EY014176 (DAF), EY011542 (DSG), Core Grant for Vision Research (P30-EY11374), Training Grant for Vision Science (T32-EY07133), a Veterans Administration MERIT grant (HV), the Minnesota Lions and Lionesses, and an unrestricted grant to the Department of Ophthalmology from the Research to Prevent Blindness Foundation. We would like to thank Dr. Linda McLoon for the use of her microscope. Drs. Jian-Xing Ma and David Bernlohr provided antibodies to RPE65 and FABP5, respectively. The technical help of Neal Heuss is gratefully acknowledged.
- cytotoxic T lymphocytes
- retinal pigment epithelial cells