[Adenosine-triphosphate promoting repair of spinal cord injury by activating mammalian target of rapamycin/signal transducers and activators of transcription 3 signal pathway in rats].

OBJECTIVE: To investigate the mechanism of adenosine-triphosphate (ATP) activated mammalian target of rapamycin (mTOR)/signal transducer and activator of transcription 3 (STAT3) signal pathway in the physiology and pathology of spinal cord injury (SCI).

METHODS: Ninety-six adult healthy female Sprague-Dawley rats were randomly divided into 4 groups (groups A, B, C and D, n=24). In groups A, B and C, the rats were made the SCI models at T8-10 levels by using a modified Allen's stall, and in group D, rats were given laminectomy without SCI. The rats were subjected to the administration of ATP (40 mg/kg) for 7 days in group A, to the administration of physiological saline (equal-volume) for 7 days in group B, to the administration of ATP (40 mg/kg) and rapamycin (3 mg/kg) for 7 days in group C, and to the administration of physiological saline (equal-volume) for 7 days in group D. Locomotor activity was evaluated using the Basso-Beattie-Bresnahan rating scale at the postoperative 1st, 2nd, 3rd, and 4th weeks. Then, the expressions of spinal cord cell marker [Nestin, neuron-specific enolase (NSE), glial fibrillary acidic protein (GFAP)] and the mTOR/STAT3 pathway factors (mTOR, STAT3) were detected at the postoperative 1st, 2nd, 3rd, and 4th weeks by immunohistochemistry analysis, Western blot assay, and real-time fluorescence PCR analysis.

RESULTS: The BBB scores in group A showed a steady increase in the postoperative 1st-4th weeks and were significantly higher than those in groups B and C (P < 0.01), but were lower than that in group D (P < 0.01). Real-time fluorescence PCR results showed that the mRNA expressions of mTOR, STAT3, NSE of group A steadily increased, however, the Nestin mRNA expression gradually decreased in the postoperative 1st-4th weeks, which were all significantly higher than those of groups B, C, and D (P < 0.01). The mRNA expression of GFAP showed a steady increase in group A and was significantly less than those of groups B and C, but was higher than that of group D (P < 0.01). There were significant differences (P < 0.01) in all markers between groups B, C, and group D; there were significant differences in mTOR, P-mTOR, STAT3, and P-STAT3 mRNA between groups B and C at 1st-4th weeks (P < 0.05). The similar changes were found by Western blot assay.

CONCLUSION: ATP can activate the mTOR/STAT3 pathway to induce endogenic NSCs to proliferate and differentiate into neurons in rats, it enhances the healing of SCI.