Project description:Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Here, we performed single-cell RNA sequencing with RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation trajectories of cells towards antioxidant, iron-recycling macrophages at the expense of dendritic cells, as these cells were selectively deficient in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning how hemolytic stress may provoke hyposplenism-related secondary immunodeficiency, which is a critical determinant of mortality in patients with genetic hemolytic anemias.
Project description:Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Here, we performed single-cell RNA sequencing with RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation trajectories of cells towards antioxidant, iron-recycling macrophages at the expense of dendritic cells, as these cells were selectively deficient in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning how hemolytic stress may provoke hyposplenism-related secondary immunodeficiency, which is a critical determinant of mortality in patients with genetic hemolytic anemias.
Project description:Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Here, we performed single-cell RNA sequencing with RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation trajectories of cells towards antioxidant, iron-recycling macrophages at the expense of dendritic cells, as these cells were selectively deficient in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning how hemolytic stress may provoke hyposplenism-related secondary immunodeficiency, which is a critical determinant of mortality in patients with genetic hemolytic anemias.
Project description:Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Here, we performed single-cell RNA sequencing with RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation trajectories of cells towards antioxidant, iron-recycling macrophages at the expense of dendritic cells, as these cells were selectively deficient in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning how hemolytic stress may provoke hyposplenism-related secondary immunodeficiency, which is a critical determinant of mortality in patients with genetic hemolytic anemias.
Project description:Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Here, we performed single-cell RNA sequencing with RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation trajectories of cells towards antioxidant, iron-recycling macrophages at the expense of dendritic cells, as these cells were selectively deficient in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning how hemolytic stress may provoke hyposplenism-related secondary immunodeficiency, which is a critical determinant of mortality in patients with genetic hemolytic anemias.
Project description:In mice lacking the heme exporter, FLVCR, differentiation fails at the CFU-E/proerythroblast stage from excessive heme and reactive oxygen species. We show that Flvcr1-deleted CFU-E/proerythroblasts have low GATA1 mRNA and GATA1-target gene mRNAs along with increased ribosomal protein mRNAs as a direct result of increased heme. Thus heme increases ribosomal protein transcription when globin production needs to be increased, and when heme is excessive, GATA1 is reduced allowing for normal termination of erythroid differentiation. This demonstrates that heme and GATA1 are co-master regulators of erythroid differentiation.