We will investigate whether human endotoxemia induces changes in human bone marrow cells and their downstream effector cells. To comprehensively investigate underlying mechanisms behind functional and transcriptional changes in these cell types, we will use state-of-the-art systems biology techniques, including single cell transcriptomics (epi)genetics, and metabolomics.

In the present study, we want to further elucidate the mechanisms behind systemic inflammation and endotoxin tolerance in vivo in humans by focusing on functional changes in hematopoietic stem and progenitor cells. Healthy male volunteers will be challenged with endotoxin to evoke a transient systemic inflammatory response. To evaluate the responses over time, blood and bone marrow aspirates will be collected at multiple timepoints. To comprehensively investigate underlying mechanisms behind functional changes, we will use state-of-the-art systems biology techniques, including single cell transcriptomics, epigenetics (e..g. scATACseq), and metabolomic. As such, this study will yield a comprehensive insight into inflammatory signaling in the different compartments of the body and will thereby improve our understanding of systemic inflammation, endotoxin tolerance,and sepsis, possibly revealing new therapeutic targets to improve sepsis outcome.

Inclusion Criteria:

• Written informed consent
• Age ≥18 and ≤35 yrs
• Male
• Healthy (as confirmed by medical history, examination, ECG, blood sampling)

Exclusion Criteria:

• Use of any medication
• Smoking
• History or signs of atopic syndrome (asthma, rhinitis with medication and/or eczema)
• Known anaphylaxis or hypersensitivity to the non-investigational products or their excipients.
• History or signs of hematological disease (bone marrow dysfunction):
• Thrombocytopenia (<150*10^9/ml) or anemia (hemoglobin < 8.0 mmol/L)
• Abnormalities in leukocyte differential counts
• History, signs or symptoms of cardiovascular disease, in particular:
• Previous spontaneous vagal collapse
• History of atrial or ventricular arrhythmia
• Cardiac conduction abnormalities on the ECG consisting of a 2nd degree atrioventricular block or a complete left bundle branch block
• Hypertension (defined as RR systolic > 160 or RR diastolic > 90)
• Hypotension (defined as RR systolic < 100 or RR diastolic < 50)
• Renal impairment (defined as plasma creatinine >120 μmol/l)
• Liver enzyme abnormalities (above 2x the upper limit of normal)
• Medical history of any disease associated with immune deficiency
• CRP > 20 mg/L, WBC > 12x109/L or < 4 x109/L, or clinically significant acute illness, including infections, within 3 weeks before labeling day
• Previous (participation in a study with) LPS administration
• Any vaccination within 3 months prior to labeling day
• Participation in a drug trial or donation of blood 3 months prior to labeling day
• Recent hospital admission or surgery with general anesthesia (<3 months to labeling day)
• Use of recreational drugs within 21 days prior to labeling day
• Inability to personally provide written informed consent (e.g. for linguistic or mental reasons) and/or take part in the study.

Single cell transcriptional/gene expression data will be shared.

Bulk RNA-seq and scRNA-seq data for this study can be downloaded from GEO database (https://www.ncbi.nlm.nih.gov/geo/) with the accession number: GSE212093.

Codes used to perform the data analysis related to this study are available at https://github.com/fkeramati/LPS-SI

LPS is a non-investigational product and will only be used as a challenge agent to induce systemic inflammation. Since the effects op LPS-induced systemic inflammation are profound, no masking will be required.