Amygdalin Attenuates Atherosclerosis and Plays an Anti-Inflammatory Role in ApoE Knock-Out Mice and Bone Marrow-Derived Macrophages

Abstract Introduction NGAL/lipocalin-2 is a siderophore-binding protein stored in high amounts in specific granules of neutrophils. In addition, expression and constitutive secretion of lipocalin-2 can be induced in macrophages and epithelial cells under inflammatory conditions. In mice, lipocalin-2 is furthermore an acute phase-protein. Siderophores are the strongest iron chelators known and are produced by certain microorganisms to retrieve soluble iron from the host. By preventing uptake of siderophore bound iron, lipocalin-2 is bacteriostatic to bacteria that are dependent on this mechanism for uptake of iron. In accordance, lipocalin-2 knock-out mice are susceptible to infection by such bacteria. It is, however, not known whether it is the induced production of lipocalin-2 in epithelial cells and liver or the delivery of lipocalin-2 from infiltrating myeloid cells (neutrophils and macrophages) that is most important for these mechanisms of host defense against invading pathogens. Methods To study the contributions of lipocalin-2 from epithelial cells and liver compared to infiltrating myeloid cells, we used a Klebsiella pneumoniae lung infection model in C57BL/6 mice with chimeric expression of lipocalin-2. Bone marrow transplantation of lethally irradiated mice generated wild type-mice with a lipocalin-2 knock-out bone marrow (WT/KO) expressing lipocalin-2 in epithelium and liver but not in myeloid cells, and conversely knock out-mice with wild-type bone marrow (KO/WT) expressing lipocalin-2 in myeloid cells and not in epithelium and liver. Wild-type mice transplanted with wild-type bone marrow (WT/WT) and knock-out mice transplanted with knock-out bone marrow (KO/KO) were also generated. After 7 weeks of reconstitution, mice were nasally challenged with K. pneumoniae for induction of pneumonia and potential dissemination of the infection. The mice were sacrificed twenty-four hours after inoculation and examined. Results Lipocalin-2 levels in broncho alveolar lavage (BAL) fluid were comparable between WT/KO and KO/WT mice. Consistent with this, no difference in bacterial counts (CFU) in BAL fluid was seen. No differences in spleen CFUs were evident between the two chimeric subgroups WT/KO and KO/WT despite a quantitatively larger mean lipocalin-2 plasma level in WT/KO mice (almost 50 times) derived from epithelium and liver compared to the contribution from myeloid cells in KO/WT mice. However, mean CFU in spleen homogenates from KO/KO mice were more than 870 times higher compared to WT/WT mice. Both the lipocalin-2 contribution from myeloid cells and from epithelium and liver appeared to be indispensable judged by the higher spleen CFUs in mice lacking lipocalin-2 from either of the two compartments. Lipocalin-2 mRNA in the liver was present in equal amounts in mice with wild-type background despite the presence or absence of lipocalin-2 in the myeloid cells. No differences in neutrophil influx to the lungs were seen between groups as determined by MPO ELISA on lung homogenates. We conclude that lipocalin-2 derived both from myeloid cells and from epithelium and liver is required for full resistance to a siderophore-producing pathogen. Despite the higher levels of plasma lipocalin-2 in WT/KO mice compared to KO/WT mice, their bacteriostatic capacity is equal. The induction of lipocalin-2 in the liver is not dependent on the presence of lipocalin-2 in the myeloid cells, just as the migration of neutrophils to the infected lung is not, thus refuting a recent report that lipocalin-2 affects neutrophil migration. Disclosures No relevant conflicts of interest to declare.

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The immune reaction against allogeneic necrotic cells is reduced in Annexin A5 knock out mice whose macrophages display an anti-inflammatory phenotype

Journal of Cellular and Molecular Medicine ◽

10.1111/j.1582-4934.2008.00395.x ◽

2009 ◽

Vol 13 (7) ◽

pp. 1391-1399 ◽

Cited By ~ 18

Author(s):

Benjamin Frey ◽

Luis E. Munoz ◽

Friederike Pausch ◽

Renate Sieber ◽

Sandra Franz ◽

...

Keyword(s):

Immune Reaction ◽

Annexin A5 ◽

Knock Out ◽

Inflammatory Phenotype ◽

Anti Inflammatory ◽

Knock Out Mice

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ITCH Deficiency Promotes an MPN Phenotype with Eosinophilia, Inflammation, Mislocalization and Overexpression of the Transcription Factor NF-E2

Blood ◽

10.1182/blood.v124.21.821.821 ◽

2014 ◽

Vol 124 (21) ◽

pp. 821-821

Author(s):

Jonas S. Jutzi ◽

A Gruender ◽

Konrad Aumann ◽

Heike L. Pahl

Keyword(s):

Bone Marrow ◽

Transcription Factor ◽

Subcellular Localization ◽

Ubiquitin Ligase ◽

Peripheral Blood ◽

Absolute Number ◽

Wild Type ◽

Knock Out ◽

Knock Out Mice ◽

Deficient Mice

Abstract Background: We have described overexpression of the transcription factor NF-E2 in MPN patients and shown that elevated NF-E2 levels cause a MPN phenotype in transgenic mice. This includes thrombocytosis, leukocytosis, splenomegaly as well as an expansion of the stem- and progenitor cell compartments in the bone marrow. Recently, we have shown that, counterintuitively for a transcription factor, NF-E2 is located exclusively in the cytoplasm in the vast majority of erythroid cells in the bone marrow (85%). Patients with PMF show a statistically highly significant elevation in the proportion of cells displaying nuclear NF-E2 compared to either healthy controls or ET and PV patients. However, the molecular mechanisms regulating the subcellular localization of NF-E2 and its aberrant localization in PMF remain to be investigated. The E3 ubiquitin ligase ITCH has been postulated to stabilize and retain NF-E2 in the cytosol by protein-protein interaction and subsequent ubiquitinylation. The phenotype of ITCH deficient mice, however, has only been described briefly: animals display splenomegaly and an expansion of the stem cell compartment. The effect of ITCH deficiency on peripheral blood counts and on NF-E2 activity has not been determined. Aims: To characterize the phenotype of ITCH deficient mice and investigate the effect of ITCH deficiency on NF-E2 localization and activity. Methods: The peripheral blood and bone marrow of ITCH knock out mice as well as of heterozygous and wild-type control animals was analyzed: CBCs were determined every four weeks, stem- and progenitor populations in the bone marrow were assessed by 7-color FACS. Expression levels of NF-E2 and its targets genes were measured by quantitative PCR. Plasma cytokine concentrations were measured by Cytometric Bead Array. To determine the subcellular localization of NF-E2, immunohistochemical stainings of ITCH knock out BMs and wild-type controls were conducted. Results: At several consecutive time points ITCH knock out mice displayed a statistically significant elevation in WBC compared to heterozygous and wild-type littermates. Interestingly, both the percentage and the absolute number of eosinophils were significantly increased, some animals presenting with a drastic eosinophilia, the differential containing over 60% eosinophils. Furthermore, ITCH knock out mice display a significant decrease in platelet count, accompanied by an increase in platelet mass and volume, indicative of giant platelets. In the bone marrow ITCH deficient mice show a significant increase in the absolute number of Common Myeloid Progenitors (CMP). NF-E2 expression levels in the peripheral blood as well as in the bone marrow were highly statistically significantly increased compared to the levels measured in wild-type or heterozygous control mice. Consequently, the NF-E2 target gene Thromboxane Synthase A was statistically significantly overexpressed in peripheral blood of ITCH knock out mice. Plamsa concentrations of the inflammatory cytokines INF-γ and TNF were statistically significantly elevated, reaching two to threefold higher levels in ITCH knock out mice compared to wild-type littermates. Lastly, NF-E2 subcellular localization was altered in ITCH deficient mice, which display a significant increase in the proportion of megakaryocytes positive for nuclear NF-E2. Summary/Conclusions: Our data identify the E3 ubiquitin ligase ITCH as a regulator of NF-E2 activity. Impaired ITCH activity leads to both an NF-E2 overexpression and an increased nuclear NF-E2 localization that together drive overexpression of NF-E2 target genes. Furthermore, ITCH deficiency leads to higher inflammatory cytokine levels, comparable to those seen in PMF patients. All of these factors contribute to the resulting myeloproliferative phenotype with eosinophilia. Our data provide the first pathophysiological explanation of the pathognomonic symptom of ITCH deletion: pruritus in "itchy" mice. Moreover, given the aberrant NF-E2 localization in PMF patients, our data provide a possible mechanism and underscore the role of elevated NF-E2 activity in the pathophysiology of myeloproliferative neoplasms. Disclosures No relevant conflicts of interest to declare.

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Gene Profile of Myeloid-Derived Suppressive Cells from the Bone Marrow of Lysosomal Acid Lipase Knock-Out Mice

PLoS ONE ◽

10.1371/journal.pone.0030701 ◽

2012 ◽

Vol 7 (2) ◽

pp. e30701 ◽

Cited By ~ 14

Author(s):

Cong Yan ◽

Xinchun Ding ◽

Nupur Dasgupta ◽

Lingyan Wu ◽

Hong Du

Keyword(s):

Bone Marrow ◽

Acid Lipase ◽

Gene Profile ◽

Knock Out ◽

Lysosomal Acid ◽

Lysosomal Acid Lipase ◽

Knock Out Mice

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Lyl1 and Scl Dosage Is Critical for Adult Hematopoietic Stem Cell Function and Survival

Blood ◽

10.1182/blood.v112.11.281.281 ◽

2008 ◽

Vol 112 (11) ◽

pp. 281-281 ◽

Cited By ~ 2

Author(s):

George Souroullas ◽

Jessica Salmon ◽

David J. Curtis ◽

Margaret Goodell

Keyword(s):

Bone Marrow ◽

Stem Cell ◽

Hematopoietic Stem Cell ◽

Cell Function ◽

Genetic Interaction ◽

Lymphoblastic Leukemia ◽

Aberrant Expression ◽

Hematopoietic Stem ◽

Knock Out ◽

Knock Out Mice

Abstract The Stem Cell Leukemia gene (Scl) and the Lymphoblastic Leukemia gene 1 (Lyl1) genes encode two related basic-helix-loop-helix transcription factors that are involved in T-cell acute lymphoblastic leukemia via chromosomal translocations or aberrant expression due to other genetic or epigenetic abnormalities. Previous studies have shown that Scl is necessary for embryonic hematopoiesis and erythropoiesis, but dispensable for adult hematopoietic stem cell (HSC) function. Lyl1 on the other hand is important for adult HSC function and B-cell development. In order to elucidate in more detail the functions of Lyl1 and Scl in adult HSCs, we generated double knock-out mice and studied the function of their HSCs. Double knock-out mice demonstrate a striking genetic interaction between the two genes, with a clear dose-dependence for the presence of Scl or Lyl1 alleles for HSC function. Specifically, we carried out competitive fetal liver transplantation assays using mice with different combinations of Lyl1 and Scl alleles and analyzed their potential to repopulate the bone marrow of recipient mice. Peripheral blood chimerism of recipient mice shows that HSC function is lost with progressive loss of Lyl1 or Scl dosage, suggesting an overlap of function of the two genes in the HSCs (Figure) We have further investigated the function of Lyl1 and Scl in adult hematopoiesis by generating Lyl1/Scl-conditional double knock-out mice and studied adult HSC function measured by bone marrow repopulation assays. Donor engraftment dramatically decreased after deletion of the floxed Scl allele, demonstrating rapid loss of adult HSC function. Furthermore, Scl deletion in a Lyl1−/− background causes hematopoietic progenitors to rapidly undergo apoptosis in a cell-intrinsic fashion. These results demonstrate that at least one allele of either Lyl1 or Scl must be present for adult HSC survival, and show that their functions partly overlap in HSCs, suggesting that Lyl1 and Scl are crucial regulators of adult, as well as embryonic, hematopoiesis. Figure Figure

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TLE1 Null Mice Have Altered Myeloid and B-Cell Differentiation As Well As Impaired Regulation of Inflammation

Blood ◽

10.1182/blood.v120.21.1197.1197 ◽

2012 ◽

Vol 120 (21) ◽

pp. 1197-1197 ◽

Cited By ~ 1

Author(s):

Selvi Ramasamy ◽

Saez Borja ◽

Subhankar Mukhopadhyay ◽

Jianfeng Wang ◽

Daching Ding ◽

...

Keyword(s):

Bone Marrow ◽

Tumor Suppressor ◽

Inflammatory Cytokines ◽

Knockout Mice ◽

Suppressor Gene ◽

Wild Type ◽

Hematopoietic System ◽

Knock Out ◽

Knock Out Mice

Abstract Abstract 1197 TLE1 belongs to the Groucho/TLE family of co-repressors that act as master regulators during development affecting segmentation, neurogenesis, myogenesis, and multiple cell fate decisions. TLE1 modulate several major signaling pathways including Wnt and Notch, and specifically interacts with multiple transcription factors involved in hematopoiesis such TCF/LEF, HES1, RUNX1/AML. TLE1 has also been implicated in Crohn's disease via its interaction with NOD2, a regulator of NFkB. Our laboratory identified TLE1 as a likely AML tumor suppressor gene, commonly deleted in subgroups of AML, and others have shown its role as a tumor suppressor gene in myeloid and other hematopoietic malignancies. To better understand the role of TLE1 in hematopoiesis and leukemogenesis we created a line of Tle1 null mice. Tle1 null mice are born normally, but become progressively growth retarded by 3 days of life, with only 50% survival by 4 weeks as compared to heterozygous and wild type littermates. Abnormalities are observed in several organs systems including the hematopoietic system. We characterized the hematopoietic system in Tle1 knock out mice between two and 12 weeks of age. The bone marrow cellularity in the Tle1 knock out mice is comparable to the wild type mice at all time points examined. However, frequency of granulocyte macrophage progenitors in bone marrow mononuclear cells is significantly higher in the Tle1 knockout bone marrow compared to heterozygous and wild type mice. The proportion and number of myeloid cells as evidenced by Gr1, Mac1 expression are significantly higher in the bone marrow, spleen and blood of these knockout mice. There were significantly lower B-cells (B220+cells) in the Tle1 knockout mice compared to heterozygous and wild type. In colony forming assays there was a trend towards higher number of CFU-GM (7.66 vs 5), p=0.07) and CFU-M (27.16 vs 12.5, p=0.05) colonies from Tle1 null bone marrow as compared to wild type bone marrow. The spleens from four week and 17 months old Tle1 knockout mice had higher frequency of Gr1-negative, Mac1-positive and F4/80 positive macrophages. We also observed a significantly higher production of the inflammatory cytokines IL6 and TNFafrom peritoneal macrophages harvested from Tle1 null mice as compared to those from wild type mice in response to TLR ligand stimulation. To investigate the potential mechanism of this inhibitory effect of TLE1 on inflammation we demonstrated that TLE1 expression is able to block the nuclear translocation of NFkB in THP1 cells in response to LPS-K12 (p<0.05). In summary this work demonstrates that the lack of Tle1 expression biases hematopoiesis towards myeloid differentiation, a finding of potential relevance given the inactivation of TLE1 seen in subsets of myeloid malignancies. We further show that inactivation of Tle1 leads to an increase in macrophages primed to release increased inflammatory cytokines. This is notable given the recent observation that TLE1 may modulate the effects of NOD2 in the pathogenesis of Crohn's disease. These Tle1 null mice will allow the investigation of the potential role of TLE1 as a modulator of a variety of other inflammatory diseases. Disclosures: No relevant conflicts of interest to declare.

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Essential Role of the Transcription Factor ZBP-89 in Lymphopoiesis

Blood ◽

10.1182/blood.v120.21.277.277 ◽

2012 ◽

Vol 120 (21) ◽

pp. 277-277

Author(s):

Andrew J. Woo ◽

Hui Huang ◽

Taylor Piers ◽

Alan B Cantor

Keyword(s):

Bone Marrow ◽

T Cells ◽

Transcription Factor ◽

Conflicts Of Interest ◽

Embryonic Stem ◽

Dependent Manner ◽

Chimeric Mouse ◽

Knock Out ◽

Erythroid Maturation ◽

Knock Out Mice

Abstract Abstract 277 We previously identified the Krüppel-type zinc finger transcription factor ZBP-89 (also called zfp148) as a novel GATA1 associated protein in erythroid and megakaryocytic cells. ZBP-89 also associates with other GATA family members such as GATA2 and GATA3, Friend of GATA (FOG) cofactors, and RUNX1. It is ubiquitously expressed, but has high-level expression in a subset of tissues including thymus, spleen, bone marrow, lung and brain. Our prior studies using morpholino knockdown in zebrafish, in vitro differentiation and chimeric mouse analysis of ZBP-89 genetrap embryonic stem cells, and lentiviral shRNA knock down in primary human CD34+ cells demonstrated a functional role for ZBP-89 in erythroid and megakaryocyte maturation. In this study, we generated conditional knock out mice to further examine the requirements for ZBP-89 in vivo. On a mixed strain background, full ZBP-89 knock out mice were born at close to Mendelian ratios. However, the ZBP-89−/− mice were severely runted and had increased mortality over the first 30 days of life. Surviving pups had significant growth failure, but eventually matched their wild type and heterozygous littermates by about 6 weeks of age. Analysis of erythroid maturation in bone marrow and spleen using flow cytometry for CD71 and Ter119 demonstrated impaired erythroid maturation in a ZBP-89 allele-dose dependent manner. On a pure C57BL/6 genetic background, nearly 100% of the ZBP-89−/− mice died within the first 10 days of life from unclear causes. ZBP-89fl/fl, Mx1-Cre mice developed lymphopenia and platelet abnormalities following activation of Cre by polyI-polyC injection. The lymphopenia was due to reduction in both B and T cells. Further delineation of the T-cell defect using ZBP-89fl/fl, Lck-Cre mice demonstrated impaired maturation of double negative (CD4−CD8−) T cells at the DN3 (CD25+ CD44−) to DN4 (CD25−CD44−) stages in thymi from 5–6 week old mice. These findings indicate that ZBP-89 plays functional roles in multiple hematopoietic lineages. Moreover, they identify ZBP-89 as a novel transcriptional regulator of lymphocyte development. We speculate that this latter role involves its known interactions with GATA3, FOG-1, and/or RUNX1, which are all similarly involved in lymphopoiesis. We also show that the ZBP-89 family member ZBP-99 is highly expressed in thymus and other hematopoietic tissues, and may therefore play partially overlapping roles with ZBP-89. Disclosures: No relevant conflicts of interest to declare.

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Hematopoiesis in 5-Fluorouracil-Treated Adenosine A3 Receptor Knock-Out Mice

Physiological Research ◽

10.33549/physiolres.932847 ◽

2015 ◽

pp. 255-262

Author(s):

M. HOFER ◽

M. POSPÍŠIL ◽

L. DUŠEK ◽

D. KOMŮRKOVÁ

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Peripheral Blood ◽

Cytotoxic Action ◽

Adenosine A3 Receptor ◽

Knock Out ◽

Bone Marrow Progenitor Cells ◽

Bone Marrow Progenitor ◽

Hematological Analysis ◽

Knock Out Mice

The purpose of the study was to describe and compare normal and 5-fluorouracil (5-FU)-suppressed hematopoiesis in adenosine A3 receptor knock-out (A3AR KO) mice and their wild-type (WT) counterparts. To meet the purpose, a complex hematological analysis comprising nineteen peripheral blood and bone marrow parameters was performed in the mice. Defects previously observed in the peripheral blood erythrocyte and thrombocyte parameters of the A3AR KO mice were confirmed. Compartments of the bone marrow progenitor cells for granulocytes/macrophages and erythrocytes were enhanced in the control, as well as in the 5-FU-administered A3AR KO mice. 5-FU-induced hematopoietic suppression, evaluated on day 2 after the administration of the cytotoxic drug, was found to be significantly deeper in the A3AR KO mice compared with their WT counterparts, as measured at the level of the bone marrow progenitor cells. The rate of regeneration, as assessed between days 2 and 7 after 5-FU administration, was observed in the population of the granulocyte/macrophage progenitor cells to be higher in the A3AR KO mice in comparison with the WT ones. The increased depth of 5-FU-induced suppression in the compartments of the hematopoietic progenitor cells in the A3AR KO mice represents probably a hitherto undescribed further consequence of the lack of adenosine A3 receptors and indicates its synergism with the pharmacologically induced cytotoxic action of 5-FU.

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Erythropoiesis- and Thrombopoiesis-Characterizing Parameters in Adenosine A3 Receptor Knock-Out Mice

Physiological Research ◽

10.33549/physiolres.932489 ◽

2013 ◽

pp. 305-311 ◽

Cited By ~ 3

Author(s):

M. HOFER ◽

M. POSPÍŠIL ◽

L. DUŠEK ◽

Z. HOFEROVÁ ◽

L. WEITEROVÁ ◽

...

Keyword(s):

Bone Marrow ◽

Platelet Count ◽

Regulatory System ◽

Blood Platelet ◽

Wild Type ◽

Adenosine A3 Receptor ◽

Knock Out ◽

Males And Females ◽

Knock Out Mice ◽

Blood Platelet Count

Influence of the regulatory system mediated by adenosine A3 receptors on the functioning of erythropoiesis and thrombopoiesis was studied by means of evaluation of the numbers and attributes of peripheral blood erythrocytes and platelets, as well as of erythroid bone marrow progenitor cells in adenosine A3 receptor knock-out (Adora3tm1Jbsn/Adora3tm1Jbsn, A3AR(-/-)) mice and their wild-type C57BL/6 counterparts, both males and females. Minor but statistically significant disturbances in the properties of erythrocytes, namely in the parameters of mean erythrocyte volume and mean erythrocyte hemoglobin were observed in A3AR(-/-) mice. In addition, adenosine A3 receptor knock-out mice were found to exhibit an expressive, statistically significant decrease of their blood platelet count, amounting to 17 % and 21 % in males and females, respectively. This decrease in platelet levels was accompanied by a significant 17 % decline in the plateletcrit in both sexes. The obtained data can help to define therapeutic applications based on the principle of adenosine receptor signaling.

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The Bacterial Microbiota Promotes Normal Hematopoiesis Via Interferon Alpha and NOD1 Signaling Pathways

Blood ◽

10.1182/blood-2021-151494 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 1080-1080

Author(s):

Hannah Yan ◽

Forrest C Walker ◽

Hyojeong Han ◽

Megan T Baldridge ◽

Katherine Y. King

Keyword(s):

Bone Marrow ◽

Bone Marrow Suppression ◽

Host Cells ◽

Type I ◽

Type I Ifn ◽

Knock Out ◽

Commensal Microbiota ◽

Stat1 Signaling ◽

Knock Out Mice

Abstract Long-term antibiotic therapy is associated with hematological side effects such as neutropenia and anemia. Our lab and others have shown that long-term antibiotic treatment in mice leads to bone marrow suppression and agranulocytosis in mice through depletion of the commensal bacteria. Our work further showed that Stat1-deficient mice phenocopy the bone marrow suppression phenotype of antibiotic-treated mice, suggesting that commensal microbiota mediate hematopoiesis via Stat1 signaling. However, the upstream actors of this pathway and the bacterial mediators required for commensal microbiota regulation of normal hematopoiesis still remain poorly understood. Such knowledge will be essential for understanding how to treat antibiotic-associated cytopenias. We hypothesize that microbial products detected by host cells trigger STAT1 signaling to potentiate normal hematopoiesis. To identify the host cells that require Stat1 for microbiota-promoted hematopoiesis, we treated conditional Stat1 knock-out mice with two weeks of antibiotic therapy. Of the four conditional knock-out mice we evaluated (LepR-Cre, Villin-Cre, Vav-iCre, LysM-Cre), only the mice deficient in STAT1 in hematopoietic cells (Vav-iCre Stat1 fl/fl) phenocopied the bone marrow suppression of antibiotic-treated mice. Our data suggest that STAT1 signaling is necessary in non-myeloid hematopoietic cells, but not intestinal epithelial cells or mesenchymal stromal cells for microbiota-promoted hematopoiesis. Non-competitive transplantation of Stat1 -/- bone marrow into wild type mice validated these findings; mice lacking STAT1 only in hematopoietic tissues phenocopied the Vav-iCre mice, consistent with a specific role for microbiota-mediated STAT1 signaling in the hematopoietic compartment. To assess the upstream mediator of STAT1 signaling in this biological context, we treated interferon (IFN) receptor knock out mice with two weeks of antibiotics. Of the three types of IFN receptor knock-outs evaluated, only mice deficient in type I IFN signaling phenocopied the bone marrow suppression of antibiotic-treated mice. These findings suggest that type I IFN signaling, and not type II or III, was required for microbiota-dependent hematopoiesis. These results were validated by showing that the administration of pegylated-IFNα was sufficient to rescue the depletion of type I IFN-STAT1 signaling in antibiotic-treated mice. To determine the microbial signals that may potentiate hematopoiesis, we evaluated two microbial products that were previously shown to alter hematopoiesis and to activate type I IFN signaling (Iwamura et al. Blood 2017 & Steed et al. Science 2017). We discovered that oral administration of these commensal-derived products, the metabolite desaminotyrosine (DAT) or NOD1 ligand (NOD1L), a motif of peptidoglycan, were each sufficient to rescue the hematopoietic defects induced by antibiotics in mice. To test whether these products rescue hematopoiesis by activating STAT1 signaling, we attempted to rescue the hematopoietic defects in Stat1 -/- mice. These studies showed that NOD1L rescues granulocyte but not progenitor counts in Stat1 -/- mice, suggesting that NOD1 and type I IFN signaling work together at the progenitor level, but independently at the downstream myeloid progenitor level to promote granulopoiesis. Overall, our studies expand our understanding of the signaling pathways by which the microbiota promotes normal hematopoiesis and identify novel therapeutic agents that can be used to ameliorate antibiotic-induced BM suppression. Disclosures No relevant conflicts of interest to declare.

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