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.
ABSTRACT
ObjectiveTo investigate the effects of lipopolysaccharide (LPS) on mRNA expression of iron metabolism related genes. Methods Ten male mice (2 months) were injected intraperitoneally with lipopolysaccharide(0.5 μg/g). After 6 hours, mice were sacrificed and then sera, liver and spleen were collected. The mice blood routine was measured. The serum iron and total iron binding capacity (TIBC) were determined with reagent kit. The quasi-quantitative reverse transcription polymerase chain reaction (RT-PCR) was performed for mRNA of hepatic hepcidin(HP), ferroportin1(Fpn1), transferrin receptor 1(TfR1) and spleenic HP, Fpn1 and interleukin-6(IL-6). Results The serum iron and TIBC were reduced in mice injected LPS, which exhibited mild anemia(P＜0.05) . LPS can increase the expression of hepatic hepcidin and decrease Fpn1 and TfR1 in liver after LPS administration 6 hours(P＜0.05). In spleen, IL-6 was upregulated and Fpn1 downregulated(P＜0.05). Conclusion LPS can influence serum iron through regulating the mRNA expression of hepatic and spleenic iron metabolism related genes, such as HP, Fpn1 and TfR1.
ABSTRACT
Objective To evaluate the influential factors of iron acquisition during Francisella tularensis LVS infection of mouse macrophages.Methods F.tularensis LVS expressing green fluorescent protein was used to infect murine macrophage J774A.1 cells.Transferrin receptor 1(Tfr1)was detected with mono-antibody and visualized with a goat-anti mouse IgG conjugated to Alexa 594.The expression profile of 5 iron metabolism related genes of J774A.1 murine macrophages uninfected or infected with F.tularensis LVS was determined with real-time PCR.Immunoblot analysis was used to compare the Tfr1 expression of live Francisella infected macrophage with dead bacteria.Tfr1 knock-off in J774A.1 cells was performed with siRNA.The transfected cells were infected with Francisella for immunoblotting and microscopy and infection assay.Results It was revealed that the live vaccine strain of F.tularensis induced the expression of Tfr1 in host macrophages.Gene expression analysis indicated that F.tularensis LVS drove an active iron acquisition program with induction of Tfr1 and iron regulatory proteins(Irp1 and Irp2).It was shown by Western-blotting that the siRNA-Tfrc-1 could knock off about 75% of Tfr1 in J774A.1 cells.It was determined by infection assay that,Tfr1 was knocked off,the bacteria number at 1h infection with Francisella was not different from that of control(F=1.06,P=0.326 5),while it was decreased significantly after 24h of infection(F=24.12,P=0.000 6).Conclusions It is demonstrated that upregulation of the Tfr1 may be mediated by post-transcriptional regulation during early infection,but sustained later through increased expression of Irp 1 and Irp 2.Increased expression of Tfr1 expands the intracellular iron pool through transferrin-mediated delivery and may thus be readily available for uptaking by Francisella.Knocking off the expression of Tfr1 does not affect bacterial invasion.Francisella,however,may fail to proliferate in macrophages in which the expression of transferrin receptor has been suppressed.