Neutrophil extracellular traps have active DNAzymes that promote bactericidal activity

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Neutrophil extracellular traps (NETs) are crucial in innate immunity, primarily composed of DNA.
• The antimicrobial mechanisms of NETs are not fully understood, with DNA previously considered a passive scaffold.

Purpose of the Study:

• To elucidate the precise mechanisms of bacterial killing by NETs.
• To investigate the antimicrobial role of DNA within NETs beyond its structural function.

Main Methods:

• Immunofluorescence staining to detect G-quadruplex and hemin colocalization in NETs DNA.
• Amplex UltraRed assay to assess peroxidase activity of NETs DNA.
• Proximity labeling and ex vivo bactericidal assays to evaluate radical production and killing efficacy.

Main Results:

• NETs DNA contains spatially concentrated G-quadruplex/hemin DNAzyme complexes.
• These DNAzyme complexes produce hydroxyl free radicals, demonstrating peroxidase activity.
• Radical production is localized to bacteria trapped by NETs, driving significant bactericidal effects.

Conclusions:

• NETs DNA functions as a DNAzyme, actively killing bacteria through radical production.
• The G-quadruplex/hemin DNAzyme complex is the primary driver of NETs' bactericidal activity.
• This discovery reveals a novel biological function for NETs with potential implications in host defense.