Abstract T P248: Leukemia Inhibitory Factor Induced-Akt Activation Protects Neurons from Ischemic Damage by Increasing Superoxide Dismutase Activity and Expression

Abstract

Objective: To determine the molecular mechanisms by which leukemia inhibitory factor (LIF) protects neurons during permanent middle cerebral artery occlusion (MCAO). Hypothesis: LIF protects neurons from ischemic oxidative injury through Akt-mediated increases in superoxide dismutase 3 (SOD3) expression and total SOD activity. Methods: Male Sprague-Dawley rats injected with vehicle (PBS) or LIF (125 μg/kg) were euthanized 24, 48, and 72 h post-MCAO or sham surgery for assessment of SOD activity and SOD3 expression. Rat cortical neurons were subjected to 24 h oxygen glucose deprivation or normoxia following treatment with vehicle , 50, 200, or 1000 ng/mL LIF (n=3 per group). In a third experiment, neurons were treated with vehicle, 50 ng/mL LIF,10 μM Akt inhibitor, or 50 ng/mL LIF+10 μM Akt inhibitor (n=3 per group) prior to oxygen glucose deprivation. Lactate dehydrogenase levels in media were measured to assess neuronal death. We used immunocytochemistry to assess expression of SOD3, phospho-Akt (Ser473), and myeloid zinc finger-1 in neurons. Results: LIF significantly increased brain SOD activity (2.085 ± 0.476 U/mg lysate; n=5) compared to vehicle (0.919 ± 0.285 U/mg lysate; n=7) 72 h post-MCAO (p<0.05). LIF significantly increased SOD3 protein expression in the brain (3.707 ± 0.541 units; n=3) compared to vehicle (1.401 ± 0.825 units; n=3) at 72 h post-MCAO (p<0.05). Co-localization of phospho-Akt and SOD3 occurred 24 h post-MCAO. Additionally, 50 ng/mL LIF (0.789 ± 0.018 U/mL media; n=3) significantly decreased lactate dehydrogenase levels in vitro compared to vehicle (1.000 ± 0.023 U/mL media; n=3) (p<0.0001). Co-incubation of 50/mL ng LIF with 10 μM Akt inhibitor (1.070 ±0.106 U/mL media; n=3) reversed the protective effect of LIF (0.705 ± 0.050 U/mL media; n=3) (p<0.01). Increases in SOD3, phospho-Akt, and myeloid zinc finger-1 staining after oxygen glucose deprivation and LIF were abolished upon Akt inhibition. Conclusion: Our data demonstrates that LIF-mediated protection against ischemia in vivo and in vitro results from Akt-dependent increases in SOD3 expression and SOD activity.