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Sepsis Induces a Long-Lasting State of Trained Immunity in Bone Marrow Monocytes.

ABSTRACT: Innate immune memory describes the functional reprogramming of innate immune cells after pathogen contact, leading to either a boosted (trained immunity) or a diminished (immune tolerance) response to a secondary stimulus. Immune tolerance or "sepsis-induced immunosuppression" is a typical hallmark of patients after sepsis survival, characterized by hypo-responsiveness of the host's immune system. This condition renders the host vulnerable for a persisting infection or the occurrence of secondary, often opportunistic infections, along with an increased mortality rate. The mechanisms involved in the maintenance of this long-lasting condition are not examined yet. Polymicrobial abdominal sepsis was induced in 12 week old male C57BL/6 mice by cecal ligation and puncture. Mice were euthanized 3 months after insult. Immune cell composition of the spleen and whole blood, as well as stem and progenitor cells of the bone marrow, were assessed by flow cytometry. Whole blood and bone marrow monocytes were stimulated with LPS and supernatant levels of TNF and IL-6 detected by ELISA. Furthermore, naïve bone marrow monocytes were analyzed for metabolic (Seahorse technology) and transcriptomic (RNA sequencing) changes. Flow cytometric analysis revealed an increase of inflammatory monocytes and regulatory T cells in the spleen, whereby immune composition of whole blood kept unchanged. Granulocyte-monocyte progenitor cells are increased in sepsis survivors. Systemic cytokine response was unchanged after LPS challenge. In contrast, cytokine response of post-septic naïve bone marrow monocytes was increased. Metabolic analysis revealed enhanced glycolytic activity, whereas mitochondrial indices were not affected. In addition, RNA sequencing analysis of global gene expression in monocytes revealed a sustained signature of 367 differentially expressed genes. We here demonstrate that sepsis via functional reprogramming of naïve bone marrow monocytes induces a cellular state of trained immunity, which might be counteracted depending on the compartmental localization of the cell. These findings shed new light on the complex aftermath of sepsis and open up a new pathophysiological framework in need for further research.

SUBMITTER: Bomans K

PROVIDER: S-EPMC6254543 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Sepsis Induces a Long-Lasting State of Trained Immunity in Bone Marrow Monocytes.

Bomans Katharina K Schenz Judith J Sztwiertnia Isabella I Schaack Dominik D Weigand Markus Alexander MA Uhle Florian F

Frontiers in immunology 20181119

Innate immune memory describes the functional reprogramming of innate immune cells after pathogen contact, leading to either a boosted (trained immunity) or a diminished (immune tolerance) response to a secondary stimulus. Immune tolerance or "sepsis-induced immunosuppression" is a typical hallmark of patients after sepsis survival, characterized by hypo-responsiveness of the host's immune system. This condition renders the host vulnerable for a persisting infection or the occurrence of secondar ...[more]

PMID: 30510555

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Project description:IntroductionTrained Immunity represents a novel revolutionary concept of the immunological response involving innate immune cells. Bisphenol A is a well-known endocrine disrupter, widely disseminated worldwide and accumulated in the human body. Due to the increased interest regarding the effects of plastic-derived compounds on the immune system, our purpose was to explore whether BPA was able to induce trained immunity in human primary monocytes in vitro using low environmental concentrations.Materials and methodsWe extracted BPA from the serum of 10 healthy individuals through a liquid-liquid extraction followed by a solid phase extraction and measured the concentration using an HPLC system coupled to a triple quadrupole mass spectrometer. In parallel, monocytes were isolated from whole blood and acutely stimulated or trained with BPA at three different concentrations (1 nM, 10 nM, 20 nM). Pro- and anti-inflammatory cytokines (IL-1β, TNF-α, IL-6, and IL-10) production were assessed after 24 hours of acute stimulation and after Lipopolysaccharide (LPS) rechallenge. A comprehensive overview of the metabolic changes after BPA acute stimulation and trained immunity induction was assessed through extracellular lactate measurements, Seahorse XFb metabolic flux analysis and ROS production.ResultsMonocytes primed with BPA showed increased pro- and anti-inflammatory cytokine responses upon restimulation, sustained by the modulation of the immunometabolic circuits. Moreover, we proved the non-toxic effect of BPA at each experimental concentration by performing an MTT assay. Additionally, correlation analysis were performed between pro- and anti-inflammatory cytokines production after LPS acute stimulation or BPA-mediated trained immunity and BPA serum concentrations showing a significant association between TNF-α and BPA circulating levels.DiscussionOverall, this study pointed out for the first time the immunological effects of an environmental chemical and plastic-derived compound in the induction of trained immunity in a healthy cohort.

Dataset Information

Sepsis Induces a Long-Lasting State of Trained Immunity in Bone Marrow Monocytes.

Publications

Sepsis Induces a Long-Lasting State of Trained Immunity in Bone Marrow Monocytes.

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