Lycorine improves peripheral nerve function by promoting Schwann cell autophagy via AMPK pathway activation and MMP9 downregulation in diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes mellitus and no effective therapy is approved. Here, lycorine, a natural alkaloid, was identified as a potential drug for DPN by the bioinformatics analysis of GEO datasets and Connectivity Map database. Lycorine administration improved peripheral nerve function and autophagy-associated proteins of diabetic mice. Again, in vitro high glucose-cultured rat Schwann cells (RSC96) showed enhanced autophagosome marker LC3-II with the treatment of lycorine. Additionally, beclin-1 and Atg3 were decreased in high glucose-stimulated RSC96 cells, which were reversed by lycorine treatment. Furthermore, DPN-associated differentially expressed genes (DEGs) from GEO datasets and lycorine-drug targets from PubChem and PharmMapper were visually analyzed and revealed that MMP9 was both DPN-associated DEGs and lycorine-drug target. Functional enrichment analysis of MMP9-relevant genes showed that cell energy metabolism was involved. Moreover, lycorine reduced high glucose-enhanced MMP9 expression in RSC96 cells. Overexpression of MMP9 attenuated lycorine-induced the expression of beclin-1, Atg3 and LC3-II in high glucose-cultured RSC96 cells. In addition, AMPK pathway activation was confirmed in lycorine-treated high glucose-cultured RSC96 cells. Then AMPK pathway inhibition attenuated lycorine-reduced MMP9 expression in high glucose-treated RSC96 cells. Molecular docking analysis revealed that lycorine bound the domain of AMPK containing Thr 172 site, which affected AMPK (Thr 172) phosphorylation. Finally, AMPK pathway activation and MMP9 downregulation were also revealed in the sciatic nerves of diabetic mice administrated with lycorine. Taken together, lycorine was advised to promote Schwann cell autophagy via AMPK pathway activation and MMP9 downregulation-induced LC3-II transformation in diabetic peripheral neuropathy.