Antioxidant enzymes such as catalase, copper- and zinc-containing SOD (CuZnSOD or SOD1), and manganese superoxide dismutase (MnSOD or SOD2) were found to be upregulated in immunoblots of AMD donor eyes in the early and intermediate stages of AMD, which may reflect a compensatory mechanism of upregulating pro-survival signaling to counter increased ROS production in AMD eyes [125]. This evidence concerns the gene SOD1 and age-related macular degeneration.