Dexmedetomidine attenuates spinal cord ischemia-reperfusion injury through both anti-inflammation and anti-apoptosis mechanisms in rabbits

Abstract

Background: Dexmedetomidine (Dex) can improve neuronal viability and protect the spinal cord from ischemia-reperfusion (I/R) injury, but the underlying mechanisms are not fully understood. This study investigated the effects of dexmedetomidine on the toll-like receptor 4 (TLR4)-mediated nuclear factor ΚB (NF-ΚB) inflammatory system and caspase-3 dependent apoptosis induced by spinal cord ischemia-reperfusion injury. Methods: Twenty-four rabbits were divided into three groups: I/R, Dex (10μg/kg/h prior to ischemia until reperfusion), and Sham. Abdominal aortic occlusion was carried out for 30min in the I/R and Dex groups. Hindlimb motor function was assessed using the Tarlov scoring system for gait evaluation. Motor neuron survival and apoptosis in the ventral grey matter were assessed by haematoxylin-eosin staining and terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end labelling staining. The expression and localisation of ionised calcium-binding adaptor molecule 1, TLR4, NF-ΚB and caspase-3 were assessed by immunoreactivity analysis. The levels of interleukin 1β and tumour necrosis factor α were assessed using enzyme-linked immunosorbent assays. Results: Perioperative treatment with dexmedetomidine was associated with a significant preservation of locomotor function following spinal cord ischemia-reperfusion injury with increased neuronal survival in the spinal cord compared to control. In addition, dexmedetomidine suppressed microglial activation, inhibited the TLR4-mediated NF-ΚB signalling pathway, and inhibited the caspase-3 dependent apoptosis. Conclusions: Dexmedetomidine confers neuroprotection against spinal cord ischemia-reperfusion injury through suppression of spinal cord inflammation and neuronal apoptosis. A reduction in microglial activation and inhibition of both the TLR4-mediated NF-ΚB signalling pathway and caspase-3 dependent apoptosis are implicated.