Fosl1 Targets AMPK to Inhibit Autophagy-Mediated Anti-Apoptotic and Anti-Inflammatory Effects in Spinal Cord Injury

Abstract

Background: The objective of this study was to delineate the role of Fosl1 in regulating inflammation and apoptosis following spinal cord injury.Methods: GSE45006 datasets from Gene Expression Omnibus (GEO) were explored to analyze Fosl1 gene expression. Next, we established an animal model to assess Fosl1 and AMPK by western blotting, real-time PCR, and immunohistochemical staining and used immunofluorescence staining to check Fosl1 expression in neurons. Fosl1 silencing was used to assess the effect on AMPK, cell viability, autophagy, inflammation and apoptosis. Subsequently, an AMPK activator and inhibitor were added to PC-12 cells with H2O2-induced injury subjected to si-Fosl1 treatment to examine the change in the above indexes and to determine whether the benefits from Fosl1 silencing occurred via AMPK. Moreover, we employed chloroquine (CQ) and rapamycin (RAP) to activate and inhibit autophagy, respectively, and revealed the effects of the upregulation and downregulation of autophagy following AMPK interference. Finally, an animal model was used to identify the effect of si-Fosl1 in vivo.Results: Based on the analysis of the GSE45006 datasets, Fosl1 was found to be highly expressed and was also found to be significantly enhanced in our animal model. Fosl1 knockdown upregulated AMPK at the protein and mRNA levels, promoted autophagic proteins (LC3 II/I, Beclin1) and inhibited inflammatory factors (IL-1β, IL-6, TNF-α) and apoptosis markers (caspase3, Bax). However, Fosl1 decreased the negatively related autophagic protein p62, the anti-inflammatory factor IL-10 and the anti-apoptotic marker Bcl-2. By utilizing compound C (com, an AMPK inhibitor), we learned that AMPK inhibition exhibited unfavorable effects on autophagy but promoted inflammation and apoptosis following Fosl1 silencing. AMPK activation showed contrasting effects. Moreover, we used CQ (an autophagic inhibitor), which indicated that CQ reversed the benefits of AMPK activation on inflammation and apoptosis. The autophagic activator RAP attenuated the negative effects after com treatment. In vivo, si-Fosl1 increased BBB scores at 7 d and 14 d and motor neurons, meanwhile, it decreased the number of apoptotic cells, and inflammatory cytokine expression at 14 d postoperation. Conclusion: Fosl1 can suppress AMPK to promote inflammation and apoptosis through autophagy in SCI.