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: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: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.
Project description:NF-kB is a transcriptional factor that consists in homo and heterodimers of the large family of Rel subunits. Among the most important functions for NF-kB, initiation of immunological/inflammatory responses and regulation of cell proliferation/apoptosis which are the major features of severe infections. Although the role of NF-kB is crucial in host defense against pathogens, mice deficient for individual subunits of NF-kB have not been explored in murine models of polymicrobial infection. In this report, we have investigated in vivo the consequences of cRel subunit deficiency in the survival to polymicrobial infection. We have also approached the underlying mechanisms of the host defense by analyzing cytokine production, bacterial clearance and the distribution of innate and adaptive immune cells. Absence of cRel enhances mice mortality to polymicrobial sepsis. The decreased survival of cRel-/- animals upon infection is not related to altered local mechanisms of innate defense such as the peritoneal recruitment of the Gr.1+CD11b+ phagocytic cells and the bacterial clearance. However, cRel deficiency allows to altered systemic cytokine response associated to sustained loss of the lymphoïd subset CD8a+ of spleen dendritic cells, key antigen-presenting cells for the initiation of the adaptive immunity. Genome-wide analysis of the systemic host response to polymicrobial sepsis reveals inflammatory/immune and apoptotic gene signatures associated to cRel subunit. In this study we identified the NF-kB member cRel, as a key factor which plays a critical role in survival to polymicrobial sepsis and also as a regulatory transcription subunit controlling the inflammatory and the adaptive immune responses in severe infection.
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. Mus musculus Tg(αMHC-MerCreMer) and wild type were sacrificed 4 days after 1 or 4 consecutive days of 40 mg/kg tamoxifen injected intraperitoneally, or after corresponding control injection treatment.