Project description:Infection is able to elicit innate immunological memory by enhancing a long-term myeloid output even after the inciting infectious agent has been cleared. However, mechanisms underlying such a regulation are not fully understood. Using a mouse polymicrobial peritonitis (sepsis) model, we show that severe infection leads to increased, sustained myelopoiesis after the infection is resolved. The infection experience is imprinted in the bone marrow (BM) stromal cells, in the form of a constitutive upregulation of the tissue inhibitor of metalloproteinases 1 (TIMP1). TIMP1 antagonizes the function of ADAM10, an essential cleavage enzyme for the activation of Notch which in turn suppresses myelopoiesis. While TIMP1 is dispensable for myelopoiesis under the steady state, increased TIMP1 enhances myelopoiesis post infection. Thus, our data reveal that infection could establish an inflammatory memory in the BM niche to support a long-term enhanced output of innate immune cells.
Project description:Emergency myelopoiesis (EM) is critical for immune defense against pathogens, which requires rapid replenishing of mature myeloid cells. The EM process involves a rapid cell cycle switch from the quiescent hematopoietic stem cells (HSCs) to highly proliferative myeloid progenitors (MPs). How this cell cycle switch is regulated remains poorly understood. Here, we reveal that ATG7, a critical autophagy factor is essential for the rapid proliferation of MPs during human myelopoiesis. Peripheral blood (PB) mobilized HSPCs with ATG7 knock-down or HSPCs derived from ATG7-/- human embryonic stem cells (hESCs) exhibit severe defect in proliferation at MP stage during myeloid/granulocytes differentiation. ATG7 deficient MPs show substantially elevated P53 protein and up-regulation of P53 signaling pathway genes. Mechanistically, ATG7 dependent autophagy mediates P53 degradation in lysosome that allows normal proliferation of MPs. Together, we reveal an essential role of autophagy for P53 degradation in cell cycle switch during human myelopoiesis
Project description:Systemic inflammation (SI) is a prevalent condition with a high mortality rate1. Survivors of hyperinflammatory state of SI frequently enter a long-lasting immunosuppressive state2 deteriorating their life quality3,4. Due to the extensive heterogeneity in SI etiology, the underlying mechanisms are not well understood. Here, we characterized the short and long-term effects of lipopolysaccharide (LPS)-induced SI (LPS-SI, also called endotoxemia5) on blood monocytes and bone marrow (BM) cells. Similar to clinical features of SI, we observed a profound but transient acute LPS response, followed by a long-term immunosuppressed state. Single-cell transcriptomic analysis of LPS-SI acute phase unveiled the loss of BM monocytes and the appearance of an inflammatory monocyte-like (i-Mono’s) population, expressing gene programs similar to a cell state identified in early-stage sepsis patients6. We observed impairment of myelopoiesis one week after LPS-SI manifested by a significant loss of intermediate and non-classical monocytes which is associated with reduced expression of interferon type I (IFN-I) genes. We confirm that this compromised myelopoiesis also happens in late-stage sepsis patients. Importantly, IFNb treatment reverted the LPS-induced immunosuppression in monocytes. Our results deepened the knowledge about SI and its long-lasting effects on myelopoiesis, substantiating the importance of IFN-I in the pathophysiology of SI-induced immunosuppression.
Project description:Systemic inflammation (SI) is a prevalent condition with a high mortality rate1. Survivors of hyperinflammatory state of SI frequently enter a long-lasting immunosuppressive state2 deteriorating their life quality3,4. Due to the extensive heterogeneity in SI etiology, the underlying mechanisms are not well understood. Here, we characterized the short and long-term effects of lipopolysaccharide (LPS)-induced SI (LPS-SI, also called endotoxemia5) on blood monocytes and bone marrow (BM) cells. Similar to clinical features of SI, we observed a profound but transient acute LPS response, followed by a long-term immunosuppressed state. Single-cell transcriptomic analysis of LPS-SI acute phase unveiled the loss of BM monocytes and the appearance of an inflammatory monocyte-like (i-Mono’s) population, expressing gene programs similar to a cell state identified in early-stage sepsis patients6. We observed impairment of myelopoiesis one week after LPS-SI manifested by a significant loss of intermediate and non-classical monocytes which is associated with reduced expression of interferon type I (IFN-I) genes. We confirm that this compromised myelopoiesis also happens in late-stage sepsis patients. Importantly, IFNb treatment reverted the LPS-induced immunosuppression in monocytes. Our results deepened the knowledge about SI and its long-lasting effects on myelopoiesis, substantiating the importance of IFN-I in the pathophysiology of SI-induced immunosuppression.