Reversal of Age-related Learning Deficits and Brain Oxidative Stress in Mice with Superoxide Dismutase/catalase Mimetics Liu, Liu, Bi, Thompson

Background Loss of learning and memory function from 8-11 months in aging mice is associated with increases in markers of brain oxidative stress. Contextual fear learning and levels of protein oxidation in brain show strong negative correlation.

Hypothesis Clinical application of synthetic catalytic scavengers of ROS are beneficial in reversing age-related learning deficits.

Treat mice with SOD mimetics SOD mimetics from Eukarion: EUK-189 and EUK-207. Female mice at 8 months old randomly assigned to 6 groups (16-18 per group) –control –untreated control –low dose EUK-189 –high dose EUK-189 –low dose EUK-207 –high doseEUK-207

Minipumps implanted in anesthetized mice. drug delivered for 28 days low rate ~9nmol/day high rate ~ 0.09  mol/day Pumps replaced twice of over 3 months of treatment.

Behavioral testing after 3 months Plexiglass cages. Videocam to record freezing behaviour (index of fear conditioning). Computer to control events. Mice placed alone in clean chamber.

Day 1: 3 minutes elapse, 3 tones sound, footshock, 1 minute later mouse removed. Day 2: testing for conditioning to context, no sound, no footshock, 8 minutes later mouse removed Day 3: testing for conditioning to tone, mice placed in different chamber,1 minute elapses, 1 tone sounds, 7 minutes later mouse removed

Behavioral Analysis Fear conditioning measured as % of time mice exhibited a freezing response (absence of all movement except breathing) Measured for auditory (startle threshold) and visual functions. Measured for nociception ( onset latency to tail flick at 51C hotplate)

Effects of SOD/catalase mimetic on fear conditioning learning control mice show low levels of freezing for both tone and context (indicates impaired learning and memory at middle age) SOD mimetic mice show increased tone and context freezing at both doses Compared EUK-207 mice at 11 months old to control mice at 8 months old: drug appears to reverse impairment of older mice

Effects of SOD/catalase mimetic on brain oxidative stress Mimetics decreased age-related free- radical damage: –decreased lipid peroxidation –decreased protein oxidation