Wnt-3a improves functional recovery through autophagy activation via inhibiting the mTOR signaling pathway after spinal cord injury

Abstract

Little is known about the effect of wnt-3a on motor nerve function and its specific molecular mechanisms after spinal cord injury (SCI). This study demonstrates that the downregulated expression levels of caspases-3, caspases-9 and chondroitin sulfate proteoglycan (CSPG) proteins and number of proportion of transferase UTP nick end labeling (TUNEL)-positive neurons by wnt-3a treatment. Then, Nissl and hematoxylin-eosin (HE) staining showed that wnt-3a significantly reduced the loss of spinal anterior horn motor neurons and promoted repair of injured spinal cord tissues after SCI. The above factors constructed a favorable microenvironment for the recovery of motor nerve function after SCI. To elucidate the molecular mechanism of neuroprotection of wnt-3a on SCI, the study showed that the expression levels of Beclin-1 and light chain (LC)3-II/I in spinal cord neurons were significantly improved by wnt-3a after SCI in vitro and vivo experiments, while the effect of wnt-3a was inhibited after mechanistic target of rapamycin (mTOR) signaling pathway being activated by MHY-1485. Besides, the level of p70S6K phosphorylation was inhibited by wnt-3a treatment, on the contrary, the level of p70S6K protein was elevated by wnt-3a, indicating that wnt-3a significantly activated neuronal autophagy by inhibiting mTOR signaling pathway after SCI. To further verify the correlation between neuroprotection of wnt-3a and autophagy, we found that after the rats and spinal cord neurons were combined treatment with wnt-3a and MHY-1485, the neuroprotection of wnt-3a on SCI was significantly inhibited. This study is the first to report that wnt-3a improves functional recovery through autophagy activation via inhibiting the mTOR signaling pathway after SCI.