Mechanism by which rapamycin protects spinal cord neurons in experimental autoimmune encephalomyelitis mice

doi:10.3969/j.issn.2095-4344.3001

Abstract

Abstract: BACKGROUND: There are increasing reports about autophagy, but the relationship between the level of autophagy in neurons and the neuroprotection mechanism is not clear.
OBJECTIVE: To investigate whether rapamycin, an mammalian target of rapacmycin (mTOR) autophagy pathway inhibitor, could activate autophagy by mediating the P70s6k and mTOR protein levels to protect spinal cord neurons in experimental autoimmune encephalomyelitis mice.
METHODS: Fifty-four healthy female C57BL/6 mice were divided into three groups: control group, model group and treatment group, with 18 mice in each group. Mice in the model group and treatment group were injected with complete Freund’s adjuvant containing MOG35-55 and pertussis diluent for establishing models of experimental autoimmune encephalomyelitis. At the same time, the mice in the treatment group were given rapamycin (1 mg/kg per day), and those in the model and control groups were given the same amount of normal saline. The mice in the model and treatment were sacrificed at the peak of the onset, and the non-morbid mice, including those in the control group, were sacrificed after 4 weeks of feeding. The spinal cord tissue from each animal was taken to isolate the intumescentia lumbalis of the spinal cord. Nissl staining was used for pathological observation of the spinal cord tissue. Immunofluorescence double staining was used to observe the expression and co-localization of autophagy markers LC3 and NeuN in spinal cord tissue. Western blot was used to detect mTOR, P70S6K proteins and their phosphorylation levels in spinal cord tissue.
RESULTS AND CONCLUSION: No mice in the control group had an attack, but those in the other groups developed experimental autoimmune encephalomyelitis to different extents. Compared with the model group, the treatment group had prolonged incubation time (P < 0.01), shortened progressive stage (P < 0.01), and decreased neurologic dysfunction score (P < 0.05). Compared with the control group, the model group had the significantly less number of Nissl bodies (P < 0.05), while the number of Nissl bodies in the treatment group was significantly higher than that in the model group, but still lower than that in the control group (P < 0.05). In the model group, LC3 was scattered in the spinal cord neurons and had no obvious dot-like aggregation, whereas in the treatment group, LC3 showed obvious dot-like aggregation, and its distribution was basically consistent with that of NeuN. The phosphorylation levels of mTOR and P70S6K proteins were highest in the model group, followed by the treatment group and control group in turn. To conclude, rapamycin might through inhibiting the phosphorylation levels of mTOR and P70S6K proteins activate the activity of autophagy to protect the spinal cord neurons in experimental autoimmune encephalomyelitis mice.

Key words: rapamycin, experimental autoimmune encephalomyelitis, spinal cord, neuron, Nissl body, autophagy, protein, mouse, experiment

CLC Number:

Xie Yang, Zhang Shujiang, Liu Menglan, Luo Ying, Yang Yang, Li Zuoxiao. Mechanism by which rapamycin protects spinal cord neurons in experimental autoimmune encephalomyelitis mice[J]. Chinese Journal of Tissue Engineering Research, 2021, 25(5): 695-700.

Figures/Tables 7

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