Abstract: BACKGROUND: It is of great significance to find new diagnostic markers of the disease and molecular targets for the treatment of the disease and the alleviation of organ injury. Ferroptosis is a newly discovered form of cell death. Overactivation of ferroptosis in animal models of sepsis is associated with the activation of inflammatory response and the injury of the liver, heart, kidney and other important organs, but the relationship between ferroptosis and bloodstream infection is not very clear.
OBJECTIVE: To study the changes and biological significance of ferroptosis in a mouse model of blood stream infection induced by different bacteria. 
METHODS: Blood stream infection models induced by gram negative bacteria Escherichia coli, Klebsiella pneumoniae and gram positive bacteria Staphylococcus aureus and Enterococcus faecalis were established in SPF-grade ICR male mice, with 42 mice in each group. The mRNA expression levels of ferroptosis marker genes transferrin receptor 1 and glutathione peroxidase 4 in the liver, myocardium and kidney were detected at 0.5, 1, 3, 6, 12, 24 and 48 hours after modeling. Another 18 SPF-grade ICR male mice were selected and randomly divided into dimethyl sulfoxide (DMSO) control group, DMSO+Klebsiella pneumoniae group, and Ferrostatin-1+Klebsiella pneumoniae group, with 6 mice in each group. In the latter two groups, animal models of Klebsiella pneumoniae bloodstream infection were established by tail vein injection of Klebsiella pneumoniae suspension, and 5 mg/kg Ferrostatin-1 and an equal dose of DMSO were given intraperitoneally 1 hour prior to the modeling of bloodstream infection, respectively. Serum levels of alanine aminotransferase, aspartate aminotransferase, blood creatinine, blood urea nitrogen, phosphocreatine kinase isoenzyme, lactate dehydrogenase, and mRNA expression levels of ferroptosis marker genes in various tissues were assayed at 6 hours after modeling.
RESULTS AND CONCLUSION: After bloodstream infection modeling, the mRNA expression levels of transferrin receptor 1 in the liver, myocardium and kidney of bloodstream infection mice with different bacteria increased first and then decreased; and the mRNA expression level of glutathione peroxidase 4 decreased first, then increased, and reached the peak at 6 hours after modeling. The changes in transferrin receptor 1 and glutathione peroxidase 4 mRNA levels in bloodstream infection mice induced by gram-negative bacteria were more significant than those in blood stream infection mice induced by gram-positive bacteria, especially in bloodstream infection mice induced by Klebsiella pneumoniae. At 6 hours after bloodstream infection induced by Klebsiella pneumoniae, the levels of alanine aminotransferase, aspartate aminotransferase, serum creatinine, blood urea nitrogen, creatine phosphate kinase isoenzyme, lactate dehydrogenase in mice were significantly increased. Before modeling, Ferrostatin-1 intervention significantly reduced the levels of alanine aminotransferase, aspartate aminotransferase, serum creatinine, blood urea nitrogen, creatine phosphate kinase isoenzyme, and lactate dehydrogenase. All these findings indicate that the activation of ferroptosis in bloodstream infection mice induced by different bacteria is obvious, and the activation of ferroptosis in bloodstream infection mice induced by gram-negative bacteria is more obvious. Inhibition of iron death significantly attenuates liver, myocardial, and kidney injury in the mouse model of bloodstream infection induced by Klebsiella pneumoniae.

Key words: bloodstream infection, mouse model, ferroptosis, transferrin receptor 1, glutathione peroxidase 4