A Membrane-free Liver-Gut-on-Chip Platform for the Assessment on Dysregulated Mechanisms of Cholesterol and Bile Acid Metabolism Induced by PM2.5.

Fine particulate matter (PM2.5)-induced metabolic diseases have attracted a great deal of attention recently. However, the relevant metabolic mechanisms of PM2.5 in vivo have not yet been fully described due to the lack of reliable platforms. Herein, a membrane-free liver-gut-on-chip (L-GOC) platform was developed to investigate metabolism dysregulation induced by PM2.5. A multiple organ system with a liver-gut structure and two circulation paths (L-G and G-L circulation paths) was created, and then cells were exposed to PM2.5 on this platform. Secreted high-density lipoprotein (HDL) levels were detected, which demonstrates that this multiple organ system functioned with normal physiological metabolism at the organ level. Untargeted metabolomic analysis showed that there were 364 metabolites of LO2 cells dysregulated after exposure to PM2.5 at a concentration of 200 μg/mL. Moreover, cholesterol and bile acid metabolism were significantly dysregulated. Further immunofluorescence and ELISA assays confirmed that signal transduction pathways related to cholesterol metabolism (LCAT-CE, PON1-HDL, and SRB1-HDL metabolic pathways) and bile acid metabolism (CYP7A1-CA/CDCA/DCA metabolic pathways) were disturbed. These results indicate that PM2.5 primarily disturbed cholesterol metabolism of the liver and then disrupted bile acid metabolism of the liver (primary bile acid biosynthesis) and gut (secondary bile acid biosynthesis) via related metabolic pathways. These findings may partially explain the metabolic mechanisms of cells triggered by PM2.5 exposure.