Transcriptome kinetics of circulating neutrophils during human experimental endotoxemia

Area of Science:

• Immunology
• Molecular Biology
• Systems Biology

Background:

• Polymorphonuclear cells (neutrophils) are crucial in inflammatory responses and sepsis.
• Neutrophil activity is tightly regulated to balance host defense and prevent tissue damage.
• Previous research on neutrophil gene transcription during endotoxemia focused on whole blood or mononuclear cells, leaving the circulating neutrophil response unclear.

Purpose of the Study:

• To investigate the gene transcription kinetics of circulating neutrophils following in vivo systemic inflammatory stimulation.
• To identify stimulus-specific gene transcription patterns in neutrophils stimulated ex vivo with various inflammatory agents.

Main Methods:

• Healthy human subjects (n=4) received a single intravenous dose of endotoxin (LPS).
• Circulating neutrophils were analyzed using whole transcriptome microarray at 2, 4, and 6 hours post-LPS infusion.
• Freshly isolated neutrophils were stimulated ex vivo with LPS, TNFα, G-CSF, and GM-CSF.

Main Results:

• Endotoxin infusion activated inflammatory gene networks in circulating neutrophils, including those involved in TNFα and IL-1 signaling.
• The neutrophil transcriptome profile indicated prolonged survival and regulated inflammatory responses.
• Ex vivo stimulation identified stimulus-specific gene transcription patterns.

Conclusions:

• In vivo endotoxin challenge activates inflammatory pathways in circulating neutrophils.
• Neutrophil transcriptome changes suggest a combination of early activation by TNFα and G-CSF, and mobilization of immature neutrophils from bone marrow.
• These findings enhance understanding of neutrophil behavior during systemic inflammation and sepsis.