Extracellular matrix regulates apoptosis in human neutrophils

Area of Science:

• Immunology
• Cell Biology

Background:

• During inflammation, polymorphonuclear neutrophils (PMNs) migrate to tissues and interact with extracellular matrix (ECM) proteins.
• The impact of PMN-ECM interactions on PMN apoptosis remains an area of investigation.

Purpose of the Study:

• To investigate the hypothesis that PMN-ECM interaction affects PMN apoptosis.
• To elucidate the role of tyrosine phosphorylation in this process.

Main Methods:

• Human PMN apoptosis was assessed using DNA fragmentation assays, flow cytometry, and microscopy.
• Cell adhesion and spreading were measured using toluidine blue assays and phase contrast microscopy.
• Protein tyrosine phosphorylation was analyzed via Western blotting and confocal microscopy.

Main Results:

• Tumor necrosis factor-alpha (TNF alpha) significantly increased PMN apoptosis on fibronectin and other ECM proteins compared to a non-adherent surface (PolyHema).
• Genistein, a tyrosine kinase inhibitor, reduced TNF alpha-mediated apoptosis and PMN spreading on fibronectin.
• Fibronectin strongly enhanced tyrosine phosphorylation at sites of cell-matrix interaction, suggesting its involvement in regulating apoptosis.

Conclusions:

• ECM significantly influences apoptosis in TNF alpha-activated, adherent, and spreading PMNs.
• Tyrosine phosphorylation is a key regulatory mechanism in ECM-mediated PMN apoptosis.
• Modulating PMN apoptosis via ECM interactions could offer a strategy for regulating local inflammation.