Therapeutic effect and mechanism of piracetam for the treatment of spinal cord injury in rats through MAPK pathway

Abstract

To explore mechanism of piracetam for the treatment of spinal cord injury in rats through mitogen-activated protein kinase (MAPK) pathway. Fifty-four healthy 6-week-old SD female rats with body weight of 80 to 100 g were divided into sham operation group, spinal cord injury group and piracetam group by random number table method, with 18 rats in each group. Spinal cord injury model was established in spinal cord injury group and piracetam group using percussion apparatus, while sham operation group did not damage spinal cord. Piracetam group was injected with piracetam injection through tail vein according to 5 ml·kg-1 standard, once a day for 3 days;the other two groups were injected with normal saline at the same dose, the same frequency and the same duration. The rats were sacrificed at 1, 3, and 7 days after surgery, and changes of Basso, Beattie and Bresnahan (BBB) locomotor rating scale was observed and compared. Enzyme-linked immunosorbent assay (ELISA) was used to detect spinal cord inflammatory factors, such as interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-1β (interleukin-1β), necrosis factor-α (IL-1β) and tumor necrosis factor-α (TNF-α);HE staining was used to observe morphological changes of rats with spinal cord injury, and immunohistochemistry was used to observe expression level of aquaporin 4 (AQP4). The activation of MAPK signaling pathway in spinal cord of rats after spinal cord injury was observed by western blotting (WB). BBB scores of sham operation group on 1, 3 and 7 day were 21 points. In spinal cord injury group, the scores were (1±1), (4±1) and (7±2);piracetam group was (1±1), (5±1), (9±2), respectively;the difference between spinal cord injury group and sham operation group was statistically significant (P<0.05). HE staining showed that no abnormality was found in sham operation group. In spinal cord injury group, bleeding and degeneration of spinal cord tissue appeared at 1 day after operation; flaky necrotic areas were appeared in spinal cord at 3 days after surgery, and spinal cord tissue began to slowly repair at 7 days after surgery. In piracetam group, the bleeding area was less than that of spinal cord injury group at 1 day after surgery;at 3 days after operation, the necrotic area was reduced and the range of nuclear disappearance was reduced; and the spinal cord began to recover slowly at 7 days after surgery. AQP4 staining of spinal cord of rats in sham operation group was weak at 1, 3 and 7 days after modeling, AQP4 staining was deepened and area increased in spinal cord injury group, AQP4 staining of piracetam group was lighter than that of spinal cord injury group, and the positive cells were slightly increased and the staining was slightly darker than that of sham operation group. At 1, 3 and 7 days, the level of IL-6, IL-10, IL-1β and TNF-α in spinal cord injury group were higher than those in sham operation group and piracetam group(P<0.05). Compared with spinal cord injury group, the area of spinal cord bleeding and necrosis were decreased by HE staining in piracetam group, and AQP4 staining was decreased by immunohistochemistry. WB results showed that P-ERK, P-JNK and P-P38 levels in spinal cord injury group at 3 days were higher than those in sham operation group and piracetam group(P<0.05). Piracetam not only showed significant effect in promoting motor function recovery after spinal cord injury, but also showed positive therapeutic potential in reducing lesion area, regulating AQP4 expression to reduce edema, and reducing inflammatory response by regulating MAPK signaling pathway.