The effect of Oleuropein via High Mobility Group Box-1 protein on apoptosis and oxidative stress in experimental spinal cord injury

Objective: Spinal cord injury is an important result of traumatic injuries which cause morbidity and mortality. It can classify as a primary injury which cause irreversible effects and secondary injury which is the main target of medication studies. Inflammation cause secondary injury and HMGB-1 is an important mediator of inflammation. Protective effect of redox activated transcription factor Nrf2 against toxic injury has shown in many organ and cell type. Oleuropein has known anti-inflammatory features. In our study we investigate the effects of Oleuropein on HMGB-1, Nrf2, apoptosis and oxidative stress in experimental spinal cord injury model. Materials and Methods: Weighing 250-300 g, 8-10 weeks, a total of 24 adult female Sprague-Dawley rats were used for the experiment. T9-T10 laminectomy were made in laminectomy group, after T9-T10 laminectomy 30 second extradural compression with Yasargil temporary aneurysm clip were made in trauma group, after extradural compression 20 mg/kg Oleuropein immediately and first hour of trauma were done intraperitoneally in Oleuropein group. 24 hour after procedure rats were sacrified. Serum and spinal cord samples HMGB-1, TLR-4, RAGE, Nrf2, NF-κß expression levels analysed by western blot and immunohistochemistry examinations. Apoptosis was evaluated with TUNEL method and Bax, Bcl-2, p53, Aktive Caspase-3 levels analysed by western blot. Oxidative stress and antioxidant mechanisms were evaluated with TAS, TOS, OSI tests. Results: We compared trauma group with laminectomy group and detected HMGB-1 (P<0.001), TLR4 (P<0.001), RAGE (P<0.001) and NF-κB (P<0.001) levels increased significantly after trauma. OLE group HMGB-1 (P<0.001), TLR4 (P<0.001), RAGE (P<0.001) and NF-κB (P<0.001) levels decreased significantly according to trauma group. Nrf2 is an important part of antioxidant mechanisms and Nrf2 levels increased in trauma group (P<0.01). OLE group Nrf2 levels also increased according to trauma group (P<0.001). Apoptotic cell number which evaluated with TUNEL method increased in trauma group according to laminectomy group and it decreased significantly in OLE group according to trauma group (P<0.001). Conclusion : In this study with the investigation of spinal cord and serum samples we have shown Oleuropein has anti-inflammatory effect via HMGB-1 and antioxidant effect via Nrf2 3 and these result decrease in apoptosis and secondary injury. These results throw light on to clinical studies. Key words: Spinal Cord Injury, Oleuropein, HMGB-1, Nrf2, Apoptosis