Myeloid NCOA4 sequesters KEAP1 to reduce ferroptosis for protection against salmonellosis in mice.

Salmonellosis is a severe infection caused by Salmonella enterica serovar Typhimurium, leading to significant global morbidity and mortality. Host nutrition immunity restricts extracellular bacterial replication by reducing iron availability through the induction of the antimicrobial hormone hepcidin. Hepcidin degrades the iron exporter ferroportin, limiting intestinal iron uptake and reducing iron transfer into the blood. Paradoxically, this defense mechanism increases iron storage in macrophages, fostering an environment conducive to intracellular pathogens like Salmonella to proliferate and disseminate. Mice lacking the iron storage protein ferritin heavy chain (FTH1) in myeloid cells exhibit worsened Salmonella infection. Nuclear receptor co-activator 4 (NCOA4) directs FTH1 autophagic degradation to release iron from storage during conditions of low iron. However, the role of myeloid NCOA4 in regulating salmonellosis and gut pathophysiology remains unclear. 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 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. Together, this study not only advances our understanding of myeloid iron metabolism but also paves the way for novel myeloid cell-targeted therapies to combat salmonellosis.