Effects of combined treatment of minocycline and methylprednisolone on the expression of tumor necrosis factor alpha and interleukine-6 in experimental spinal cord injury

Spinal cord injury (SCI) includes primary injury that is resulted in neural tissue damage due to the direct mechanical trauma, and secondary injury mechanisms which are induced by primary injury. In the first 24 hours following SCI, pro-enflammatory mediators such as TNF-? and IL-6 increase at the lesion site and play important role in secondary tissue damage. SCI is an important health problem and there is no universal treatment protocol for it today. MP is an important glucocorticoid and it has been using for the treatment of SCI because of its anti-inflammatory effects. However, MP is not effective alone for the treatment of SCI and it?s mechanisms and beneficial effects are not clear. In recent years it has been reported that minocycline which is a tetracycline-derived antibiotic has neuroprotective effects on central nervous system trauma. But there are limited studies on minocycline?s effects on SCI. Furthermore, there is no research on the cellular distrubition and localization of TNF-? and IL-6 after SCI. Seventy eight wistar rats were divided into 3 main groups as intact control group; they did not receive any operation, sham operation group; we created laminectomy on T2-T7 levels of spinal cord, and experimental control group received spinal cord compression injury. Following injury the experimental control group subdivided into 4 groups as: control group, which did not receive any drug administration, methylprednisolone treatment group; they received MP following injury, minocycline treatment group; they received minocycline following injury and, MP+Minocycline combined treatment group; a combination of MP and minocycline were administered to these rats. Tissue samples were obtained from all groups at 24 hours and 72 hours after injury for light and electron microscopic, immunohistochemical and biochemical examinations. We found an increase in TNF-? levels in experimental control group at 24th hour. We also found that there were a significant decrease in TNF-? expressions in MP treatment group and MP+minocycline combined treatment group at 24 hours after injury. We observed an increase on IL-6 levels at 24th hour in experimental control group, on the other hand, in combined treatment group there were a significant decrease in IL-6 levels at the same time. It was remarkable that both cytokine?s levels were decreased in all groups at 72 hours after injury. We found structural degenerations in neurons, glia cells and axons in the SCI groups of the light and electron microscopic examinations. We also found that MP was more effective than minocycline when we compared the treatment groups. However, the ultrastructure of the cells were well preserved in MP+Minocycline combined treatment group when compared with other injury groups. Furthermore when we compared all the groups, in combined treatment group there were a significant decrease in MDA levels which is an important indicator for lipid peroxidation, on the other hand, there were a significant increase in SOD levels in the same group. When all results are evaluated together, we found the combined treatment of MP and minocycline gives rise to a significant decrease in proinflammatory cytokines levels, which upregulate after injury. We also observed decreased lipid peroxidation and neuronal and glial cell death in this group. These results suggest that this combined treatment promotes functional recovery and, it should be considered as an effective treatment protocol following spinal cord injury.