Background Salmonellosis, caused by Salmonella enterica serovar Typhimurium, is a significant global threat. Host immunity limits bacterial replication by inducing hepcidin, which degrades ferroportin, reducing iron transfer. However, this boosts macrophage iron storage, aiding intracellular pathogens like Salmonella. Mice lacking ferritin heavy chain (FTH1) in myeloid cells suffer worsened Salmonella infection. Myeloid Nuclear receptor co-activator 4 (NCOA4) regulates iron release via FTH1 autophagic degradation during low iron, but its role in salmonellosis is unclear.

Methods We generated transgenic mice with myeloid cell-specific loss-of-function (LysM-Cre Ncoa4 ^F/F, KO) and gain-of-function (LysM-Cre NCOA4 ^{Loxp-Stop-Loxp (LSL)/LSL}, OE) of NCOA4. These mice were treated with Salmonella to induce colitis. The effects of altered NCOA4 expression on disease progression were assessed using real-time qPCR, immunoblot, and ImageStream assays. Co-immunoprecipitation was employed to examine protein interactions and molecular pathways.

Results Here, we reveal that myeloid NCOA4 deficiency augments spleen iron levels and increases cellular iron accumulation, oxidative stress, and ferroptosis in bone marrow-derived macrophages (BMDM) cells. This deficiency also increases susceptibility to Salmonella-induced colitis in mice due to exacerbated oxidative stress and ferroptosis. Mechanistically, NCOA4 suppresses oxidative stress by directly binding to the E3 ubiquitin ligase Kelch-like ECH-associated protein 1 (KEAP1) and stabilizing the antioxidant transcription factor nuclear factor-erythroid 2-related factor 2 (NRF2). Activation of NRF2 protects myeloid NCOA4 knockout mice from Salmonella-induced colitis. Antioxidants Tempol and myeloid cell-targeted curcumin offer protection against colitis in myeloid NCOA4-deficient mice. A low iron diet and ferroptosis inhibition also mitigate the heightened colitis in these mice. Overexpression of myeloid cell-specific NCOA4 confers protection against Salmonella-induced colitis via upregulating NRF2 signaling.

Conclusions Together, this study not only advances our understanding of the NCOA4/KEAP1/NRF2/ferroptosis axis but also paves the way for novel myeloid cell-targeted therapies to combat salmonellosis.