Project description:Human newborns exhibit increased vulnerability and risk of mortality from infection. Increased susceptibility to infection during the neonatal period reflects key differences in the innate and adaptive immune responses relative to those in adult cells. We have previously shown an increase in the pleiotropic immune suppressive cytokine, IL-27, in macrophages derived from human umbilical cord blood compared with those obtained from adult peripheral blood. Similar findings exist in the neonatal murine system, as well as elevated splenic transcripts and serum levels. Recently, we established a murine model of neonatal sepsis to explore the impact of early life IL-27 levels on the host response to infection. In this model, neonatal mice deficient in IL-27 signaling exhibit reduced mortality, increased weight gain, and better control of the bacterial burden with reduced systemic inflammation. These results suggest that there is a reprogramming of the host response in the presence of IL-27 signaling. To explore this hypothesis, we profiled the neonatal transcriptome of the spleen in the presence or absence of Escherichia coli-induced sepsis in wild-type (WT) and IL-27Rα-deficient mice. The spleen, a known site of infection, exhibits increased IL-27 expression and bacterial burdens in WT pups that were significantly lower in IL-27Rα KO pups during infection. We identified 549 genes that were differentially expressed in WT neonates in response to E. coli infection. The upregulated genes were associated with inflammation, cytokine signaling, and G protein coupled receptor ligand binding and signaling. The expression level of these genes generally failed to increase in IL-27Rα KO mice upon the E. coli infection. We observed similar changes in gene expression, aligned with changes in chromatin accessibility, for macrophages isolated from the spleens of control and infected neonates with or without IL-27Rα KO, supporting macrophages as an innate myeloid population contributing to the inflammatory profile in septic WT pups. Collectively, our findings highlight a less inflammatory environment in KO pups that is not expected given the anti-inflammatory/suppressive activity of IL-27. However, it is consistent with a lower bacterial burden. This suggests that improved bacterial clearance in the absence of IL-27 signaling does not require a heightened inflammatory state, and instead, there is a direct relationship between IL-27 signaling and bacterial killing. An improved response to infection that is not reliant upon heightened levels of inflammation offers new promise to the potential of antagonizing IL-27 as a host-directed therapy for neonates without concern for driving inflammatory responses that are pathological to host tissues.

Project description:Background: Nrf2 is an essential cytoprotective transcription factor. However, association of Nrf2 in organ development and neonatal disease is rarely examined. Hyperoxia exposure to newborn rodents generates pulmonary phenotypes which resemble bronchopulmonary dysplasia (BPD) of prematurity. Methods: To investigate the role of Nrf2 in lung maturation and BPD pathogenesis, Nrf2-deficient (Nrf2-/-) and wild-type (Nrf2+/+) neonates were exposed to air or hyperoxia (O2). Transcriptome analysis determined Nrf2-directed mechanisms in premature lung. Lung injury was assessed by bronchoalveolar lavage analysis and histopathology. Results: In Nrf2-/- neonates, basal expression of cell cycle machinery, redox balance, and lipid/carbohydrate metabolism genes were suppressed while immunity genes were overexpressed compared to Nrf2+/+ pups. O2-induced mortality and pulmonary inflammation/injury were significantly higher in Nrf2-/- than in Nrf2+/+. Lung DNA lesion and oxidation were greater in Nrf2-/- than in Nrf2+/+, constitutively and after O2. Nrf2-dependent genes modulated cellular growth/proliferation, defense, immunity, and lipid metabolism against hyperoxia. Bioinformatic elucidation of Nrf2 binding motifs and augmented O2-induced inflammation in genetically deficient neonates validated Gpx2 and Marco as Nrf2 effectors. Conclusion: Overall, Nrf2 in underdeveloped lungs orchestrated cell cycle, morphogenesis, and immunity as well as cellular defense constitutively and under oxidant stress. Results provide putative molecular mechanisms of Nrf2-directed lung alveolarization and BPD of prematurity. PARALLEL study design with 42 samples comparing 14 groups of age (P1 to P4 corresponding to day 0 to day 3 animals), gene, and exposure: (4 groups Nrf+/+ wild type P1-P4 air exposure) (4 groups Nrf -/- knockout P1-P4 air exposure), (3 groups Nrf+/+ wild type P2-P4 with 100 percent O2 (hyperoxia exposure) and 3 groupsNrf -/- knockout P2-P4 with 100 percent O2 (hyperoxia exposure)) Biological replicates: 3 per group

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.

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Neutrophil KLF2 regulates inflammasome-dependent neonatal mortality from endotoxemia

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