Singlet oxygen is essential for neutrophil extracellular trap formation

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Neutrophil extracellular traps (NETs) are crucial for innate immunity against microbial invasion.
• The precise mechanisms governing NET formation, particularly the role of reactive oxygen species (ROS), remain incompletely understood.
• Previous studies suggested ROS involvement in NET formation, but the specific ROS species were unidentified.

Purpose of the Study:

• To identify the specific reactive oxygen species responsible for mediating NADPH oxidase (Nox)-dependent NET formation.
• To elucidate the role of singlet oxygen in both Nox-dependent and independent NET formation pathways.
• To provide novel insights into the pathogenesis of infectious and inflammatory diseases through understanding NET formation.

Main Methods:

• Stimulation of neutrophils with phorbol myristate acetate (PMA) to induce Nox-dependent NET formation.
• Utilized chronic granulomatous disease (CGD) neutrophils, which lack functional NADPH oxidase (Nox), to differentiate Nox-dependent pathways.
• Generated singlet oxygen using porfimer sodium (Photofrin) and light to induce NET formation independently of Nox activation.

Main Results:

• Singlet oxygen was identified as the key ROS mediating Nox-dependent NET formation upon PMA stimulation.
• Singlet oxygen alone, generated via a distinct porfimer sodium-based system, could induce NET formation in both CGD and healthy neutrophils.
• This singlet oxygen-induced NET formation was independent of Nox activation, revealing an alternative pathway.

Conclusions:

• Singlet oxygen is an essential mediator of neutrophil extracellular trap (NET) formation.
• NET formation can be induced by singlet oxygen through both Nox-dependent and Nox-independent mechanisms.
• These findings offer critical new perspectives on the pathogenesis of infectious and inflammatory conditions.