Matrix metalloproteinase-9 in peripheral blood eosinophils

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Matrix metalloproteinases (MMPs) are implicated in tumor invasion and inflammation.
• Eosinophils in asthmatic airways show overexpression of MMP-9 mRNA.
• The role of eosinophils as a source of MMPs in allergic inflammation requires clarification.

Purpose of the Study:

• To quantify matrix metalloproteinase-9 (MMP-9) content in peripheral blood eosinophils.
• To compare MMP-9 levels in eosinophils with other leukocyte populations (neutrophils, mononuclear cells).
• To investigate the potential for eosinophils to produce MMP-9 upon stimulation.

Main Methods:

• Purification of peripheral blood eosinophils, neutrophils, and mononuclear cells using Percoll gradient centrifugation and CD16 negative selection.
• Quantification of MMP-9 in cell lysates and culture supernatants using gelatin zymography and ELISA.
• Stimulation of purified eosinophils with IL-5, PAF, and PMA to assess MMP-9 production.

Main Results:

• Eosinophils contained significantly lower amounts of MMP-9 (2.5 ng/5x10^6 cells) compared to neutrophils (4,073 ng/5x10^6 cells).
• MMP-9 content in eosinophils did not differ between normal donors and asthma patients.
• IL-5 stimulation did not induce MMP-9 production in eosinophils; PMA and other secretogogues resulted in minimal MMP-9 secretion.

Conclusions:

• Circulating eosinophils possess only small intrinsic amounts of MMP-9.
• Eosinophils may require complex activation pathways to generate MMP-9 levels observed in allergic inflammation tissues.
• These findings suggest eosinophils are not a primary source of MMP-9 in circulation but may contribute under specific inflammatory conditions.