4-PBA enhances autophagy by inhibiting endoplasmic reticulum stress in recombinant human beta nerve growth factor induced PC12 cells after mechanical injury via PI3K/AKT/mTOR signaling pathway.

OBJECTIVE: To investigate mechanism of endoplasmic reticulum (ER) stress-mediated autophagy in spinal cord injury (SCI).

METHODS: An in vitro model of spinal cord injury(SCI)was established by recombinant human beta nerve growth factor (NGF)-induced PC12 cells. Immunofluorescence was used to detect properties of PC12 cells induced by NGF. Western blot assay was used to detect expressions of the autophagy-related protein microtubule-associated protein 1 light chain 3 (LC3)I/II, the ER stress-related protein (HSPA5/GRP78) as well as the PI3K/AKT/mTOR signaling pathway-related proteins after mechanical injury at different time points. Then the sample assigned into sham, SCI, LY294002, SCI+LY294002, 4-PBA (4-phenylbutyric acid) and SCI+4-PBA groups. The expressions of the LC3I/II and PI3K/AKT/mTOR signaling pathway-related proteins were detected by Western blot assay.

RESULT: NGF-induced PC12 cells have neurophysiological characteristics. Following administration of the PI3K-specific inhibitor LY294002, phosphorylation levels of AKT and mTOR decreased, and the ratio of LC3II/I was higher in the inhibitor-treated injury group than the simple-injury group. Following administration of the ER stress inhibitor 4-PBA, the results were similar to LY294002 group's results compared with SCI group.

CONCLUSION: Our study showed that NGF-induced PC12 cells can induce autophagy and ER stress after mechanical injury. ER stress inhibitor 4-PBA obtained similar effects to PI3K inhibitor LY294002, enhanced autophagy via PI3K/AKT/mTOR signaling pathway.