Inhibition of TNFR/RIPK signaling pathway mitigate acute spinal cord injury in rats

English Keywords:Spinal cord injury  RIPK1  RIPK3  Bcl-2  Necroptosis  Functional recovery

English Abstract:

  【Abstract】 Objectives: To investigate the protective effect of inhibition of TNFR/RIPK signaling pathway by Necrostatin-1 after spinal cord injury(SCI), and to provide new reference for the treatment of SCI. Methods: 72 SPF level male S-D rats weighing 0.25-0.30kg were randomized equally into four groups: sham group(group A), sham+Nec-1 group(group B), DMSO group(group C), Nec-1 group(group D). Spinal cord clamp compression method was used to make rat acute spinal cord injury model in group C and D. After subdural catheterization, group A had no treatment, group B and D were injected with 1μl Nec-1(25μg/μl) by using a micro-syringe at 30 minutes after SCI, group C was injected with the same amount of DMSO solution, once a day until the time point of collection tissue. Each group was divided into three subgroups: 12h, 24h and 3d after SCI, and each subgroup included six rats. Rats conducted BBB score in each group to evaluate functional recovery. Six rats were intraperitoneally injected with propidine iodide(PI) 1h before sacrificed to detection PI positive cells at 12h in each group. Six rats were sacrificed in each group at 24h after modeling, then the removed spinal cords were taken HE staining to detect the nerve tissue pathological changes, Nissl staining to observe survivor number of nerve cells, western blot to detect Bcl-2, RIPK1 and RIPK3 protein expression level. And six rats were sacrificed at 3d in each group after modeling to take Tunel staining for the detection of apoptosis of nerve tissue. Results: After modeling, BBB scores were normal in group A and B, but in group C and D were significantly higher than those in group A and B. And the scores in group D were higher than those in group C in each time point(P<0.05). HE and Nissl staining showed nerve cells with normal morphology in group A and B at 24h after operation. The degree of SCI and the number of neuronal survival in group D were better than those in group C, the difference was statistically significant at 24h(P<0.05). The expression levels of Bcl-2, RIPK1 and RIPK3 protein were stable low in group A and B, and RIPK1 and RIPK3 expression upregulated in group C, in group D the expression level of Bcl-2 upregulated, but RIPK1 and RIPK3 expression downregulated, the difference was statistically significant(P<0.05). 3d after SCI, there were seldom apoptotic bodies in group A and B, but the numbers of apoptotic body in group C and D was significantly higher than those in group A and B. And the number in group D was lower than that in group C(P<0.05). Conclusions: Inhibition of TNFR/RIPK signal pathway after rats SCI could reduce the pathological changes of spinal cord, increase the number of surviving neurons, promote nerve functional recovery and improve BBB scores.