The mTOR/P70S6K signalling pathway regulates the effect of HIF-1α on LPS-induced barrier injury

Our previous studies have shown that hypoxia-inducible factor-1α (HIF-1α) has a protective effect on intestinal mucosal injury in septic rats, but the specific mechanism still needs to be clarified. In this study, we explored the protective effect of HIF-1α on intestinal mucosa in vitro and its molecular mechanism. Caco-2 cells were selected and experiment was divided into 2 parts. Part I: HIF-1α activator (DMOG) and inhibitor (BAY 87-2243) were used to treat LPS-stimulated Caco-2 cells respectively, to explore the effect of HIF-1α on LPS induced Caco-2 cell barrier injury; Part II: mTOR inhibitor (rapamycin), activator (MHY1485) combined with or without HIF-1α activator, inhibitor to treat LPS-stimulated Caco-2 cells respectively, and then the molecular mechanism of HIF-1α reducing LPS induced Caco-2 cell barrier damage was detected. The transmembrane resistance was measured by ERS-2 resistance meter, the permeation of fluorescein-labeled dextran (FD4) was measured by fluorescence method, and the protein levels of HIF-1α, Zona occludens 1 (ZO-1), occludin, claudin-1, p-mTOR and p-P70S6K were determined by Western blot. LPS induced Caco-2 cell injury, with decreased transepithelial electrical resistance (TEER) and increased FD-4 concentration. DMOG increased the TEER value, decreased the FD-4 concentration, and upregulated HIF-1α and tight junction (TJ) expression (P < 0.05) in Caco-2 cells, while BAY 87-2243 had the opposite effects. Rapamycin reduced the TEER, increased the FD-4 concentration, and downregulated the expression of p-mTOR, p-P70S6K, HIF-1α and TJs in Caco-2 cells (P < 0.05). MHY1487 increased the TEER, decreased the FD-4 concentration, and upregulated the expression levels of p-mTOR and p-P70S6K in Caco-2 cells (P < 0.05), while the expression levels of HIF-1α and TJs remained unchanged. Adding DMOG attenuated the effect caused by rapamycin, while adding BAY 87-2243 attenuated the effect caused by MHY1487. The results suggest that HIF-1α attenuate LPS-induced barrier injury in Caco-2 cells via regulation of the mTOR/P70S6K signalling pathway.