Project description:Despite the prevalence and recognition of its detrimental impact, clinical complications of sepsis remain a major challenge. Here, we investigated the effects of myeloid ferritin heavy chain (FtH) in regulating the pathogenic sequelae of sepsis. We demonstrate that deletion of myeloid FtH leads to tolerance towards sepsis as evidenced by reduced serum cytokine levels, multi-organ dysfunction and subsequent mortality. We identified that such tolerance is predominantly mediated by the compensatory increase in circulating ferritin (ferritin light chain; FtL) in the absence of myeloid FtH. Our in vitro and in vivo studies indicate that prior exposure to ferritin provides significant tolerance to the septic process by restraining an otherwise dysregulated response to infection. These findings are mediated by an inhibitory action of ferritin on NF-κB activation and its downstream effects. Taken together, our findings suggest an essential immunomodulatory function for circulating ferritin and enhances our understanding of this acute phase reactant.
Project description:To investigate impact of myeloid ferritin heavy chain (FtH) deletion in kidney iron metabolism under baseline conditions, we performed bulk RNA sequencing on kidney tissues from FtHfl/fl (wild-type) and FtHΔ/Δ (myeloid-specific FtH-deficient) mice.
Project description:Sepsis-associated acute kidney injury (SA-AKI) is a key contributor to the life threatening sequalae attributed to sepsis. Mechanistically, SA-AKI is a consequence of unabated myeloid cell activation and oxidative stress that induces tubular injury. Iron mediates inflammatory pathways directly and through regulating the expression of myeloid-derived ferritin, an iron storage protein comprised of ferritin light (FtL) and ferritin heavy chain (FtH) subunits. Previous work revealed myeloid FtH deletion leads to a compensatory increase in intracellular and circulating FtL and is associated with amelioration of SA-AKI. We designed this study to test the hypothesis that loss of myeloid FtL and subsequently, circulating FtL will exacerbate the sepsis-induced inflammatory response and worsen SA-AKI. We generated a novel myeloid-specific FtL knockout mouse (FtLLysM-/-) and induced sepsis via cecal ligation and puncture or lipopolysaccharide endotoxemia. As expected, serum ferritin levels were significantly lower in the knockout mice, suggesting that myeloid cells dominantly contribute to circulating ferritin. Interestingly, while sepsis induction led to a marked production of pro- and anti-inflammatory cytokines, there was no statistical difference between the genotypes. There was a similar loss of kidney function, as evident by a rise in serum creatinine and cystatin C, and renal injury identified by expression of kidney injury molecule-1 and neutrophil gelatinase associated lipocalin. Finally, RNA sequencing revealed upregulation of pathways for cell cycle arrest and autophagy post-sepsis, but no significant differences were observed between genotypes, including in key genes associated with ferroptosis, an iron-mediated form of cell death. The loss of FtL did not impact sepsis-mediated activation of NFkB or HIF-1a signaling, key inflammatory pathways associated with dysregulated host response. Taken together, while FtL overexpression was shown to be protective against sepsis, loss of FtL did not influence sepsis pathogenesis.
Project description:This study aimed to investigate impact of myeloid ferritin heavy chain (FtH) deletion on iron trafficking in kidney health and disease. Myeloid FtH deletion (FtHΔ/Δ) led to upregulation of synuclein-α (Snca) as the only iron-binding protein. When exposed to kidney injury, FtHΔ/Δ mice exhibited significantly worse kidney function. Transcriptome analysis identified ferroptosis as a key pathway triggered by FtH deletion. This was confirmed by elevated expression of ferroptosis-related genes, oxidative stress markers, and increased iron deposition in the kidneys. The latter was mediated via reprogramming of macrophages to an iron-recycling phenotype by inducing Spic. Mechanistically, we demonstrate ferrireductase activity of monomeric Snca acts as a catalyst triggering oxidative stress and ferroptosis. Moreover, kidney accumulation of Snca is promoted in kidney diseases marked by heavy leukocyte infiltration in both mice and humans. These findings emphasize role of FtH in regulating iron metabolism and promoting kidney repair by suppressing Snca and Spic.
Project description:To investigate the functional significance of myocardial ferritin heavy chain (FtH) in a model of acute myocardial infarction (MI). FtH was deleted using FtH floxed mice and Sm-22 Cre mice on a C57/bl6 background At 3 hours following 45 minutes of ischemia induced via ligation of left ant. decsending coronary artery, ischemic regions were identified, dissected, and total RNA was isolated fand gene expression profiling analysis using data obtained from RNA-seq of 3 different animals. RNA Total RNA isolated from left ventricle under homeostatic (bseline conditions) served as negative ctr. (n=3/group)
Project description:α-myosin heavy chain promoter controlled MerCreMer expression enables conditional, cardiomyocyte specific and tamoxifen dependent gene inactivation of floxed genes. Administration of tamoxifen has been linked to development of acute and transient cardiomyopathy. The mechanism for this is unknown. We used microarrays to sort out factors relevant for adverse effects following tamoxifen dependent gene inactivation, to develop a protocol with minimal adverse effects, and to identify the most proper control animals.