Age-related macular degeneration (AMD) is one of the leading causes of vision loss in developed countries. Although several drug treatments are in use for the wet form, there is no proven medical treatment for dry AMD. AMD is associated with disruption of the mitochondrial morphology, function and mitochondrial (mt) DNA integrity. Specific mtDNA variants are associated with AMD severity. Studies of retrograde signaling between mitochondria and nuclei show that mtDNA can mediate transcription of nuclear genes related to complement, inflammation, apoptosis, cell signaling, and methylation/acetylation patterns. Mitochondrial Derived Peptides (MDPs) are recently identified biologically active, short peptides (20-27 AAs) that protect cells in vitro and in vivo. Humanin (HN), a 24 amino acid peptide, is the first MDP described and has been shown to have anti- apoptotic, neuro-protective properties supporting cell survival. HN levels decline with age and low levels have been associated with many age-related and metabolic diseases. HN represents a new class of biologically active molecules with tremendous potential to protect retinal cells from aging and oxidative stress associated with retinal pathology, such as AMD. A potent analog of HN, known as Humanin-G (HNG), will be used in this proposal since it is 1000-fold more potent than HN, giving HNG increased efficiency and cyto-protection for cells.
Our Specific Aims are to test the following hypotheses:
Aim 1 : Cybrids with AMD mitochondria have lower levels of HN production and/or defective HN binding receptors and intracellular signaling pathways that contribute to higher levels of cell death;
Aim 2 : HNG-microspheres are an efficient way to deliver HNG over a long time frame in vitro and in vivo;
Aim 3 : Cybrids with mitochondria from Royal College of Surgeons (RCS) rats with retinal degeneration have higher levels of apoptosis, oxidative stress and cell death. Treatment with HNG will be cyto-protective to the RCS-cybrids;
and Aim 4 : HNG can be cyto-protective against retinal degeneration in the well-characterized RCS rat model. To test these hypotheses, we have assembled a network of three multidisciplinary clinical and basic scientists who have expertise in mitochondrial molecular biology (Dr. Cristina Kenney, University of California Irvine), Humanin and other MDPs (Dr. Pinchas Cohen, University of Southern California), and retinal degeneration animal models (Dr. Magdalene Seiler, University of California Irvine). Results from this mechanistic and translational project, will provide critical information related to whether Humanin-G may be used as a therapeutic agent to protect degenerating human retinal cells.
Age-related macular degeneration (AMD) is associated with damaged mitochondria that accelerate higher levels of apoptosis and cell death. As a potential therapeutic, Humanin-G will be tested in AMD-cybrids and a rat retinal degeneration model for their anti-apoptotic and neuro-protective properties.