The Neuroprotective Mechanism of Spinal Cord Stimulation in Spinal Cord Ischemia/Reperfusion Injury

BACKGROUND: Spinal cord ischemia/reperfusion (I/R) injury following thoracoabdominal aneurysm surgery can lead to severe lower limb neurologic defect. The preliminary result of our study suggested that spinal cord stimulation (SCS) postconditioning effectively protected spinal cord from I/R injury on rabbits. But the mechanism is unknown. In this study, we further investigated the mechanism of SCS postconditioning. METHOD: New Zealand white rabbits were randomly divided into sham, I/R, I/R + 2 Hz SCS, and I/R + 50 Hz SCS group (n = 24/group). Transient spinal cord ischemia was induced by infrarenal aortic balloon occlusion and performed on all rabbits except rabbits of sham group. Rabbits of I/R group received no further intervention. Rabbits of I/R + 2 Hz SCS and I/R + 50 Hz SCS group received 2 Hz or 50 Hz SCS for 30 min at the onset of reperfusion and then daily. The expression of Akt (serine-threonine kinase)/p-Akt, STAT3 (signal transducer and activator of transcription 3)/p-STAT3 and GSK-3beta (glycogen synthase kinase)/p-GSK-3beta of spinal cord were measured by Western blot analysis at 8 h, 1 day, 3 day, and 7 day of reperfusion. RESULT: The Akt expressions of sham, I/R, I/R + 2 Hz SCS, and I/R + 50 Hz SCS group were not significantly different at all prescribed time points, while the p-Akt expression of I/R + 2 Hz SCS group was significantly higher than that of I/R group and sham group at all prescribed time points; The STAT3 and p-STAT3 expression of I/R, I/R + 2 Hz SCS, and I/R + 50 Hz SCS group were not significantly different at all prescribed time points except that at 1day of reperfusion the p-STAT3 expression of I/R + 50 Hz SCS group was significantly lower than I/R group. The GSK-3beta and p-GSK-3beta expressions of I/R, I/R + 2 Hz SCS and I/R + 50 Hz SCS group were not significantly different at all prescribed time points. CONCLUSION: The neuroprotective effect of 2 Hz SCS postconditioning in spinal cord I/R injury is related to Akt activation but not regulation of STAT3 and GSK-3beta phosphorylation.