Cell Injury, Repair, Aging, and Apoptosis N -Acetylcysteine Amide (NACA) Prevents Retinal Degeneration by Up-Regulating Reduced Glutathione Production and Reversing Lipid Peroxidation Andrew M. Schimel,* Linu Abraham, † Douglas Cox,* Abdoulaye Sene,* Courtney Kraus,* Dru S. Dace,* Nuran Ercal, † and Rajendra S. Apte* ‡ From the Departments of Ophthalmology and Visual Sciences * and Developmental Biology, ‡ Washington University School of Medicine, St. Louis; and the Department of Chemistry, † Missouri University of Science and Technology, Rolla, Missouri Oxidative stress plays a critical role in accelerating ret- inal pigment epithelial dysfunction and death in degen- erative retinal diseases, including age-related macular degeneration. Given the key role of oxidative stress– induced retinal pigment epithelial cell death and sec- ondary photoreceptor loss in the pathogenesis of age- related macular degeneration, we hypothesized that a novel thiol antioxidant, N-acetylcysteine amide (NACA), might ameliorate cellular damage and subsequent loss of vision. Treatment of human retinal pigment epithe- lial cells with NACA protected against oxidative stress–induced cellular injury and death. NACA acted mechanistically by scavenging existing reactive oxy- gen species while halting production of reactive oxy- gen species by reversing lipid peroxidation. Further- more, NACA functioned by increasing the levels of reduced glutathione and the phase II detoxification en- zyme glutathione peroxidase. Treatment of mice ex- posed to phototoxic doses of light with NACA main- tained retinal pigment epithelial cell integrity and prevented outer nuclear layer cell death as examined by histopathologic methods and rescued photoreceptor function as measured by electroretinography. These ob- servations indicate that NACA protects against oxidative stress–induced retinal pigment epithelial and photore- ceptor cell death in vitro and in vivo. The data suggest that NACA may be a novel treatment in rescuing retinal function and preventing vision loss second- ary to retinal degenerative diseases, including age- related macular degeneration. (Am J Pathol 2011, 178: 2032–2043; DOI: 10.1016/j.ajpath.2011.01.036) Retinal pigment epithelial (RPE) cells execute critical functions, including regulation of ion and metabolite transport, phagocytosis of shed photoreceptor outer seg- ments (POSs), metabolism of retinol, formation of the outer blood-retinal barrier, and maintenance of the extra- cellular matrix. 1 The RPE is subject to a particularly high level of oxidative stress from lipid peroxidation, 2 intense exposure to light, 3 extreme oxygen tension in the macular region, 4 and its role in the phagocytosis of POSs. 5 Light- induced peroxidation of shed POS polyunsaturated fatty acids leads to the formation of toxic reactive oxygen species (ROS) and lipofuscin. These by-products induce recurrent oxidative damage in and around the RPE, lead to RPE cell death, and seem to activate the complement system. 6–8 The photoreceptors, which rely on the underly- ing RPE for nutritional and metabolic support, 1 subse- quently undergo secondary degeneration. As oxygen-using photoreceptors die, oxygen levels in the retina significantly increase due to lack of choroidal autoregulation. 9,10 This results in additional oxidative damage to surrounding cells and further propagation of the vicious cycle. 11,12 Secondary photoreceptor degeneration as a consequence of oxidative stress–induced RPE degeneration results in vision loss and Supported by NIH grants K08EY016139 and R01EY019287 (R.S.A.), NIH Vision core grant P30 EY 02687, a Carl Marshall Reeves and Mildred Almen Reeves Foundation Inc. Award (R.S.A.), a Research to Prevent Blindness Inc. Career Development Award (R.S.A.), the International Ret- ina Research Foundation (R.S.A.), an American Federation for Aging Research grant (R.S.A.), the American Retina Foundation (R.S.A.), an International Retinal Research Foundation Callahan Award (D.S.D.), a Lacey Foundation Research Award (A.S.), NIH and National Institute on Drug Abuse award R15DA023409 (N.E.), and a Research to Prevent Blindness Inc. unrestricted grant to Washington University. A.M.S. and L.A. contributed equally to this work. Accepted for publication January 25, 2011. CME Disclosure: The authors did not disclose any relevant financial relationships. Address reprint requests to Rajendra S. Apte, M.D., Ph.D, Associate Professor of Ophthalmology and Visual Science, Associate Professor of Developmental Biology, Washington University School of Medicine, 660 S. Euclid Ave., Box 8096, St. Louis, MO 63110. E-mail: apte@vision. wustl.edu. ASIP 2011 AJP CME Program The American Journal of Pathology, Vol. 178, No. 5, May 2011 Copyright © 2011 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved. DOI: 10.1016/j.ajpath.2011.01.036 2032