Complement dependent TNFα production in neutrophil-like HL60 cells

Area of Science:

• Immunology
• Hematology
• Molecular Biology

Background:

• Neutrophils are crucial immune cells originating from hematopoietic stem cells (HSCs) in the bone marrow (BM).
• Tumor necrosis factor alpha (TNFα) from immature neutrophils supports HSC development and vascular regeneration within the BM niche.
• The exact mechanisms regulating TNFα production in immature neutrophils are not fully understood.

Purpose of the Study:

• To investigate the link between complement C3 activation and TNFα production in immature neutrophils.
• To elucidate the regulatory pathways governing TNFα release mediated by complement components.

Main Methods:

• Utilized neutrophil-like HL60 cells and human polymorphonuclear cells (PMNs).
• Employed flow cytometry to detect complement receptors C3aR and CR3 (Mac-1) expression.
• Assessed TNFα production in response to zymosan-treated serum, complement inhibitors (compstatin), calcium modulators (thapsigargin, EGTA, BAPTA-AM), and extracellular matrix proteins (fibrinogen, fibronectin).

Main Results:

• HL60 cells express C3aR and CR3; zymosan-treated serum induced TNFα production in HL60 cells but not in PMNs.
• Compstatin significantly suppressed TNFα production, indicating mediation by complement C3 activation.
• TNFα production was enhanced by intracellular calcium elevation and suppressed by interactions with immobilized fibrinogen and fibronectin.

Conclusions:

• Complement C3 activation is a key mediator of TNFα production in immature neutrophils.
• Intracellular calcium signaling plays a critical role in regulating TNFα release.
• Neutrophil interactions with fibrinogen and fibronectin negatively modulate TNFα production.