Changes of autophagy in rat lung tissue after acute spinal cord injury

Abstract

Objective To investigate the changes of autophagy in rat lung tissues after acute spinal cord injury (ASCI) and the possible mechanisms. Methods Sixty-three female SD rats were divided into sham operation group (n=21) and spinal cord injury group (n=42), according to the random number table. The modified Allen method with the impact energy of 10 × 25 g·mm at the T10 vertebra was used for preparation of ASCI models. The rats were sacrificed at 6, 12, 24, 48, 72 hours, 1 and 2 weeks after injury. Lung tissue damage and apoptosis were detected by HE staining and TUNEL method. The changes of autophagy and expressions of LC3-Ⅱ, P62, Beclin-1, interleukin (IL)-17A and Bcl-2 in lung were detected by Western blot and immunofluorescence. Results The pulmonary alveoli maintained normal structure in sham operation group, with no inflammation or pulmonary hemorrhage. Slight lung tissue damages were observed in spinal cord injury group at 12 h postinjury. Alveolar stroma widening, inflammatory infiltration, hemorrhage, and alveolar collapse became ingravescent at 24-72 hours postinjury. Numbers of apoptotic cells in spinal cord injury group were 551.22±135.94, 905.11±92.64, and 141.78±30.86 respectively at 24, 72 hours and 1 week postinjury, and were significantly increased at 24 and 72 hours postinjury, compared with sham operation group (P<0.05). Expression of LC3-II in spinal cord injury group was increased at 24-72 hours postinjury, compared with sham operation group (P<0.05). Expression of P62 in spinal cord injury group was up regulated at 24-72 hours postinjury, compared with sham operation group (P<0.05). Expression of Beclin-1 in spinal cord injury group was increased at 24 h postinjury and then dropped at 48-72 hours, compared with sham operation group (P<0.05). Expression of IL-17A in spinal cord injury group was increased at 24-48 hours, compared with sham operation group (P<0.05). Expression of Bcl-2 in spinal cord injury group was increased from 24 hours to 72 hours, compared with sham operation group (P<0.05). Conclusion Autophagosome formation is increased and accumulated in the lung tissues after ASCI, which might be related to the increased interaction between Beclin-1 and Bcl-2 because of the up regulation of Bcl-2 by IL 17A, ultimately leading to the inhibition of autophagy. Key words: Spinal cord injury; Lung; Autophagy; Interleukin -17A