Hif-1 Alpha Mediates The Induction Of Il-8 And Vegf Expression On Infection With Afa/Dr Diffusely Adhering E-Coli And Promotes Emt-Like Behaviour

P>Microbes regulate a large panel of intracellular signalling events that can promote inflammation and/or enhance tumour progression. Indeed, it has been shown that infection of human intestinal cells with the Afa/Dr diffusely adhering E. coli C1845 strain induces expression of pro-angiogenic and pro-inflammatory genes. Here, we demonstrate that exposure of cryptic-like intestinal epithelial cells to C1845 bacteria induces HIF-1 alpha protein levels. This effect depends on the binding of F1845 adhesin to the membrane-associated DAF receptor that initiates signalling cascades promoting translational mechanisms. Indeed, inhibition of MAPK and PI-3K decreases HIF-1 alpha protein levels and blocks C1845-induced phosphorylation of the ribosomal S6 protein. Using RNA interference we show that bacteria-induced HIF-1 alpha regulates the expression of IL-8, VEGF and Twist1, thereby pointing to a role for HIF-1 in angiogenesis and inflammation. In addition, infection correlates with a loss of E-cadherin and cytokeratin 18 and a rise in fibronectin, suggesting that bacteria may induce an epithelial to mesenchymal transition-like phenotype. Since HIF-1 alpha silencing results in reversion of bacteria-induced EMT markers, we speculate that HIF-1 alpha plays a key role linking bacterial infection to angiogenesis, inflammation and some aspects of cancer initiation.