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Updated: Sep 11, 2025
Visualizing Macrophage Extracellular Traps Using Confocal Microscopy
Published on: October 19, 2017
Molecular and subcellular mechanisms of vital macrophage extracellular trap formation
Yongchan Lee1, Max Brenner1,2, Monowar Aziz1,2
1Center for Immunology and Inflammation, The Feinstein Institutes for Medical Research, Manhasset, NY, United States.
Abstract:
Macrophage extracellular traps (METs) are a poorly understood process beneficial for infection control but detrimental in inflammation, autoimmunity and cancer. Our research shows that viable macrophages release METs even when plasma membrane lysis is blocked. We demonstrate, for the first time, that nuclear DNA is extruded directly into the cytoplasm through Gasdermin D pores on the nuclear envelope. Gasdermin D pore formation was triggered by extracellular cold-inducible RNA-binding protein, which activates the TLR4 signal transduction pathway. This DNA is processed in the cytoplasm, enters the vesicular transport system aided by autophagic flux and the Endosomal Sorting Complex. The DNA then enters the lysosomal compartment, where it undergoes histone 3 citrullination, forms nascent traps containing myeloperoxidase, and is released to the extracellular space. Our study provides valuable insights into vital MET formation and its mechanism that will enable future studies on the role of METs in health and disease.
Insights
Viable macrophages form extracellular traps (METs) by extruding nuclear DNA through Gasdermin D pores, even without cell death. This process, triggered by extracellular cold-inducible RNA-binding protein, offers new insights into MET formation in health and disease.
Area of Science:
- Immunology
- Cell Biology
Background:
- Macrophage extracellular traps (METs) play dual roles in infection control and detrimental inflammatory conditions.
- The precise mechanisms of MET formation, especially in viable cells, remain incompletely understood.
Purpose of the Study:
- To elucidate the novel mechanism of viable macrophage-mediated extracellular trap (MET) formation.
- To identify key molecular players and pathways involved in nuclear DNA extrusion and trap assembly.
Main Methods:
- Investigated MET formation in viable macrophages using advanced microscopy and molecular biology techniques.
- Utilized Gasdermin D knockout models and specific pathway inhibitors to dissect the mechanism.
- Analyzed DNA processing, vesicular transport, and lysosomal involvement in trap biogenesis.
Main Results:
- Demonstrated that viable macrophages extrude nuclear DNA directly into the cytoplasm via Gasdermin D pores on the nuclear envelope.
- Identified extracellular cold-inducible RNA-binding protein as a trigger for Gasdermin D pore formation, activating the TLR4 pathway.
- Showcased cytoplasmic DNA processing, vesicular transport, and lysosomal modification including histone 3 citrullination for nascent trap formation.
Conclusions:
- Provided the first detailed mechanistic insight into how viable macrophages form extracellular traps (METs).
- Highlighted the critical roles of Gasdermin D, TLR4 signaling, and intracellular trafficking in MET biogenesis.
- Established a foundation for future research into METs' involvement in various physiological and pathological processes.
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