Spinal cord protection via alpha-2 agonist-mediated increase in glial cell-line-derived neurotrophic factor)

Objectives: Delayed paraplegia secondary to ischemia-reperfusion injury is a devastating complication of thoracoabdominal aortic surgery. Alpha-2 agonists have been shown to attenuate ischemia-reperfusion injury, but the mechanism for protection has yet to be elucidated. A growing body of evidence suggests that astrocytes play a critical role in neuroprotection by release of neurotrophins. We hypothesize that alpha-2 agonism with dexmedetomidine increases glial cell-line-derived neurotrophic factor in spinal cord astrocytes to provide spinal cord protection. Methods: Spinal cords were isolated en bloc from C57BL/6 mice, and primary spinal cord astrocytes and neurons were selected for and grown separately in culture. Astrocytes were treated with dexmedetomidine, and glial cell-line-derived neurotrophic factor was tested for by enzyme-linked immunosorbent assay. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to assess neuronal viability. Results: Spinal cord primary astrocytes treated with dexmedetomidine at 1 mu mol/L and 10 mmol/L had significantly increased glial cell-line-derived neurotrophic factor production compared with control (P <. 05). Neurons subjected to oxygen glucose deprivation had significant preservation (P <. 05) of viability with use of dexmedetomidine-treated astrocyte media. Glial cell-line-derived neurotrophic factor neutralizing antibody eliminated the protective effects of the dexmedetomidine-treated astrocyte media (P <. 05). Conclusions: Astrocytes have been shown to preserve neuronal viability via release of neurotrophic factors. Dexmedetomidine increases glial cell-derived neurotrophic factor from spinal cord astrocytes via the alpha-2 receptor. Treatment with alpha-2 agonist dexmedetomidine may be a clinical tool for use in spinal cord protection in aortic surgery.