Store-operated calcium entry facilitates LPS-induced superoxide anion-dependent macrophage extracellular traps

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Macrophage extracellular traps (METs) are a key defense mechanism against pathogens, distinct from phagocytosis.
• Calcium ions (Ca2+) have been implicated in MET formation, but their precise role remains incompletely understood.
• Existing methods for identifying METotic cells have limitations.

Purpose of the Study:

• To elucidate the role of calcium ions (Ca2+) in NADPH oxidase (NOX)-dependent macrophage extracellular trap formation (METosis).
• To establish a novel and efficient method for identifying METotic cells.
• To investigate the involvement of store-operated calcium entry (SOCE) in METosis.

Main Methods:

• Development of a digitonin-based method for identifying METotic cells via immunofluorescence staining with lamin antibodies.
• Stimulation of macrophages with lipopolysaccharide (LPS).
• Measurement of intracellular calcium levels and superoxide anion generation.

Main Results:

• Digitonin allows for specific intranuclear labeling of METotic cells, offering a refined identification technique.
• LPS stimulation induces store-operated calcium entry (SOCE) in macrophages, leading to increased intracellular Ca2+.
• Elevated cytoplasmic Ca2+ levels promote superoxide anion generation by NADPH oxidase (NOX), culminating in METosis.

Conclusions:

• This study confirms the critical role of Ca2+ in NOX-dependent METosis, differentiating it from previously described NOX-independent pathways.
• Ca2+-mediated regulation of NOX, particularly via SOCE, is essential for METosis.
• The findings provide new insights into the mechanisms of innate immunity and suggest avenues for future research.