Salmonella typhimurium induces intestinal inflammatory response through activation of Cav- 1/Akt/IKKα/NF-κB signaling pathway

Abstract Salmonella, a pathogenic gram-negative bacterium, has been reported to cause intestinal inflammatory response, which is found in both humans and animals. However, the underlying mechanism is not quite clear. To this end, we used Salmonella typhimurium (ST)-infected mice or intestinal epithelioid cell line 6 (IEC-6 cells) as a model to explore the roles of ST in reducing inflammatory response and elucidate the potential mechanisms. In in vivo experiments, mice were given ST with different concentrations (2.5×106 cfu/mL, 2.5×107 cfu/mL and 2.5×108 cfu/mL). The inflammatory markers in the serum were measured and the changes of small intestinal structures were observed. Differentially expressed proteins in the jejunum were screened using TMT-based quantitative proteomic analysis, and verified using real-time quantitative PCR (qPCR) and western blotting. In in vitro experiments, IEC-6 cells were pretreated with particular inhibitor for 24 h and then infected with ST (1×103 cfu/mL) for 12 h. The lactic dehydrogenase (LDH), C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) levels in the supernatants were measured by enzyme-linked immunosorbent assay (ELISA) while the protein expression of caveolin-1 (Cav-1), protein kinase B (Akt), inhibitor kappa B kinaseα (IKKα) and nuclear factor-kappaB (NF-κB) p65 were measured by western blotting. ST promoted the production of serum inflammatory markers and the disruption of duodenal and jejunal structures in a dose-dependent manner over a specific period of time. Proteomic analysis showed that ST-induced intestinal inflammatory response was associated with the expression of Cav, Akt, IKK and NF-κB. In addition, we further confirmed that the activation of Cav-1/Akt/IKKα/NF-κB signaling pathway played a critical role in ST infection prompting the production of inflammatory markers and causing inflammatory response in IEC-6 cells. Taken together, our finding revealed that ST could induce intestinal inflammatory response through activating the Cav-1/Akt/IKKα/NF-κB signaling pathway.