Extracellular superoxide dismutase overexpression protects against aging-induced cognitive impairment in mice

• Published in: Behavior genetics 2002-03, Vol.32 (2), p.119-125
• Main Authors: Levin, Edward D, Christopher, N Channelle, Lateef, Sohail, Elamir, Belal M, Patel, Manisha, Liang, Li-Ping, Crapo, James D
• Format: Article
• Language: English
• Subjects: Aging; Aging - genetics; Alzheimer's disease; Animals; Cognitive ability; Extracellular Space - enzymology; Female; Gene Expression Regulation, Enzymologic - physiology; Genotype; Humans; Maze Learning - physiology; Memory; Mice; Mice, Transgenic; Nitric oxide; Oxidative stress; Oxidative Stress - genetics; Retention (Psychology) - physiology; Signal Transduction - genetics; Superoxide Dismutase - genetics; Young adults
• ISSN: 0001-8244; 1573-3297
• DOI: 10.1023/A:1015201823417

Extracellular superoxide dismutase (EC-SOD) controls the availability of extracellular superoxide and appears to play a role in controlling oxidative stress and intercellular signaling. Whether EC-SOD overexpression would help or hinder neurobehavioral function appears to depend on the age of the individual. In young adult mice, we have found that EC-SOD overexpression can interfere with learning on the radial-arm maze, possibly by reducing control over nitric oxide neurotransmission. In aged mice, we found, in the current study, that EC-SOD overexpression greatly improves learning on the radial-arm maze. Control (N = 17) and EC-SOD overexpressing mice (N = 13) acquired the 8-arm radial maze over 21 sessions of training. The EC-SOD overexpressing mice had significantly better choice accuracy than the control mice (p < 0.005). The EC-SOD overexpressing mice averaged 6.34+/-0.22 correct arm entries before an error (entries to repeat) during the acquisition phase, while the control mice averaged 5.18+/-0.22 entries to repeat. EC-SOD genotype did not cause a main effect on response latency. The advantage held by the EC-SOD overexpressing mice persisted during the eight-session post-acquisition phase of testing (p < 0.01). When there was a shift from high to low levels of motivation by reducing the period of food restriction before testing, the EC-SOD overexpression-induced improvement was reduced slightly, but it was still significant compared with the wild-type controls (p < 0.025). Then, after 4 months of no testing, the mice were tested for retention and reacquisition of performance on the radial-arm maze. The EC-SOD overexpressing mice maintained their significantly better choice accuracy (p < 0.05). Enhancement of EC-SOD activity appears to improve learning and memory performance, specifically in aging mice. EC-SOD mimetic treatment during the course of aging may hold promise for aging-induced cognitive impairment.