Objective: To analyse the neuroprotective effect of Netrin-1 on spinal cord injury in rats by activating the adenosine monophosphate-activated protein kinase/mammalian target protein of rapamycin (AMPK/mTOR) signalling pathway to promote neuronal autophagy and inhibit neuronal apoptosis. Methods: A total of 72 healthy male Sprague Dawley (SD) rats of clean grade were randomly divided into a sham operation group (treated with excision of the conical plate without spinal cord attack and intraperitoneal injection of 1 mL phosphate solution), model group (treated with intraperitoneal injection of 1 mL phosphate solution), and Netrin-1 group (treated with intraperitoneal injection of Netrin-1 recombinant protein), with 24 rats in each group. The BBB method was used to determine the motor function score of each group of rats. Survival of anterior horn neurons in the spinal cord of rats in each group was detected by Nissls staining. The residual tissue area of the spinal cord cross section was determined by HE staining. The expression levels of p-mTOR, p-AMPT, autophagy-associated protein Beclin-1, microtubule-associated protein light chain 3 (LC3) and C-caspase-3 in spinal cord tissues after spinal cord injury in each group of rats were measured by western blot assay. The number of TUNEL-positive neurons in each group was determined by immunofluorescence. Results: The BBB scores in the sham operation group were significantly higher than those in the model and Netrin-1 groups from day 1 to day 21 (P<0.05). The BBB scores of the model group were the same as those of the Netrin-1 group at Day 1, and those of the Netrin-1 group were higher than the model group at Day 3 and day 7, but there was no significant difference between the two groups (P>0.05). At day 14 and day 21, the BBB score of the Netrin-1 group was significantly higher than that of the model group (P<0.05). The survival number of anterior horn neurons in the spinal cord, residual tissue area of the spinal cord cross section and the expression of p-mTOR were lower in the model group and the Netrin-1 group than in the sham operation group. Moreover, the expression of P-AMPK, C-caspase-3, Beclin-1 and LC3 in the model group and the Netrin-1 group were significantly higher than those in the sham operation group. Compared with the model group, the survival number of anterior horn neurons in the spinal cord, residual tissue area of the spinal cord cross section, p-AMPK, LC3 and Beclin-1 of the Netrin-1 group were markedly increased, and the expression levels of p-mTOR and C-caspase-3 were significantly decreased (P<0.05). Compared with the sham operation group, the number of TUNEL-positive neurons in the model group increased markedly. Compared with the model group, the number of TUNEL-positive neurons in the Netrin-1 group decreased significantly (P<0.05). Conclusion: Netrin-1 can significantly promote neuronal autophagy, inhibit neuronal apoptosis, improve motor function and increase the survival number of anterior horn neurons in the spinal cord and the residual tissue area of the spinal cord cross section. Netrin-1 has an obvious neuroprotective effect, which may be achieved through the AMPK/mTOR signalling pathway.
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