Ischemic Preconditioning and Lazaroid (u-74389g) Administration Similarly Attenuate Ischemia-Reperfusion-Induced Spinal Cord Inflammatory and Apoptotic Responses by Targeting the S100-Receptor for Advanced Glycation End Product Pathway

Introduction: Spinal cord injury and subsequent paraplegia represents a devastating complication of thoracoabdominal aortic surgery. Pro-inflammatory cytokine expression and spinal cord neuronal apoptosis have been implicated in inflammation and neurodegeneration respectively after ischemia. Hypothesis: We investigated the neuroprotective effects of the steroid antioxidant Lazaroid U-74389G versus conventional ischemic preconditioning (IPC) in a pig model of spinal cord ischemia-reperfusion injury by examining the expression of pro-inflammatory and pro-apoptotic S100 members and the receptor for advanced glycation end products (RAGE). Methods: Spinal cord ischemia was induced by thoracoabdominal aortic occlusion (TAO). A total of 27 pigs were randomized in four groups. Group I (n=5) sham operation, group II (n=7) TAO for 45min and received placebo, group III (n=8) received 3 doses of Lazaroid (3 mg/kg) 60min and 30min before and at 30min during TAO (duration 45min), and group IV (n=6) TAO for 20min followed by additional TAO for 45min and 80 minutes later. Neurologic evaluation was performed according to Tarlov score (0-4, 4=normal). The lumbar spinal cords were harvested at 7th postoperative day for the expression of inflammatory and apoptotic markers by real-time RT-PCR. Results: Group III and IV had better neurologic outcome postoperatively compared to group II where all animals developed paraplegia (Tarlov scores: 3.5 versus 3.6 versus 0.33, respectively, P<0.001). Group II showed marked pro-inflammatory responses as quantified by 2-4-fold increases in the mRNA of pro-inflammatory S100A6, S100A8 and high-mobility group box 1, and RAGE, compared to group I. Additionally, group II, exhibited apoptosis as quantified by a 40-60% decrease in the mRNA of anti-apoptotic BCL2 and BIRC2, and 2-3-fold increases in pro-apoptotic BAX mRNA and caspase 3 activity. Compared to group II, inflammatory and apoptotic responses were highly attenuated albeit to a similar degree in groups III and IV. Conclusions: In a large animal model very close to the clinical setting, we demonstrated that in addition to IPC, Lazaroid represents an alternative yet effective pharmacologic intervention in reducing spinal cord ischemia-reperfusion injury following TAO.