Evaluation of changed metabolite profiles in SIM-A9 microglial cells under the influence of hypoxia and lipopolysaccharide

Microglial cells play a leading role in development of neuroinflammation. Activation of microglia leads to the formation of reactive phenotypes that can both contribute to the development of neuroinflammation and ensure its relief. Microglia activation is accompanied by metabolic reprogramming or changes in the metabolic pathways activity and the content of specific metabolites supporting a particular phenotype. An opportunity of phenotype switching due to metabolomic reprogramming may have real therapeutic potential. However, currently there are limited data on changes in composition of metabolites and activity of metabolic pathways in microglial cells under the influence of neuroinflammatory factors. In this regard, the purpose of this work was to conduct a non-targeted metabolomic study to assess changes of metabolites profiles in microglial cell line SIM-A9 exposed to hypoxia, as well as during TLR4 activation. Metabolite profiling of cell extracts exposed to hypoxia or lipopolysaccharide was performed using high-performance liquid chromatography and high-resolution mass spectrometry, followed by bioinformatics analysis of the data. The performed studies have shown that hypoxia, as well as TLR4 stimulation, lead to noticeable changes in the metabolism of microglial cells. At the same time, the nature of these changes depends on the type of stress exposure and its duration. Changed activity of glutathione and arginine metabolic pathways may serve as a marker of the polarization of microglial cells after hypoxic exposure. The activation of TLR4 by lipopolysaccharide leads to modulation of pathways associated with energy metabolism, as well as changes in the metabolic pathways of aromatic amino acids. One may suggest that the analytic approach used in this work will allow us to further investigate the dynamics of metabolic changes under the influence of proinflammatory factors of various origin and to gain detailed data on their role in metabolic reprogramming of microglial cells at various stages of neuroinflammation.