Abstract 17512: Toll-Like Receptor 4 Dependent Macrophage Activation is Critical in Spinal Cord Ischemia-Reperfusion Injury
Background Paraplegia continues to complicate complex thoracoabdominal aortic interventions. The elusive mechanism of this spinal cord ischemia-reperfusion injury has delayed the development of pharmacological adjuncts. Microglia, the resident macrophages of the CNS, can have pathologic responses following a variety of insults. This can occur through Toll-Like Receptor 4 (TLR-4) in stroke models. We hypothesize that spinal cord ischemia-reperfusion (IR) injury following aortic occlusion results from TLR-4 mediated microglial activation in mice.
Methods Isolated microglia from C57BL/6 mice were subjected oxygen and glucose deprivations (OGD) for 24 hours, after which the expression of TLR-4 analyzed via immunoblotting. TLR-4 mutant and wild type mice underwent aortic occlusion for 5 min followed by 60 hours of reperfusion. Spinal cords were removed for histological analysis. Microglial activation was assessed at 12 hours following aortic occlusion using IBA-1 stain for activated microglia. TNF-α production was quantified 6 hours following IR or sham surgery by ELISA.
Results Following OGD, there was a 28% increase in TLR-4 on microglial cells. Mice with functional TLR-4 receptors demonstrated significantly worse functional outcomes and neuronal viability following aortic occlusion (p<0.05). Additionally, wild-type mice showed significant increase in microglial activation and TNF-α production (p<0.05).
Conclusion These data demonstrate TLR-4 up-regulation occurs with microglial OGD. Furthermore, this finding correlates with significant neurotoxic effects in the spinal cord following IR. In conclusion, TLR-4 mediated activation of microglia in the spinal cord following IR injury is critical in the mechanism of paraplegia following aortic cross clamping, which may provide a target for pharmacological intervention.
- © 2012 by American Heart Association, Inc.