Regulation of matrix metalloproteinase-9 release from IL-8-stimulated human neutrophils

Area of Science:

• Immunology
• Cell Biology
• Biochemistry

Background:

• Neutrophils release matrix metalloproteinase-9 (MMP-9) from tertiary granules upon stimulation.
• Interleukin-8 (IL-8) is a key chemokine that activates neutrophils through CXC chemokine receptors 1 (CXCR1) and CXCR2.
• Understanding the signaling pathways governing MMP-9 release is crucial for inflammatory processes.

Purpose of the Study:

• To elucidate the specific signaling mechanisms regulating IL-8-mediated MMP-9 release from neutrophils.
• To determine the roles of CXCR1 and CXCR2 in IL-8-induced MMP-9 release.
• To identify the intracellular kinases and pathways involved in this process.

Main Methods:

• Neutrophil stimulation with IL-8 and receptor blocking using specific inhibitors.
• Assessment of MMP-9 release.
• Analysis of intracellular signaling pathways, including Src-family kinases, protein kinase C (PKC), extracellular signal-regulated kinase (ERK)1/2, and p38 mitogen-activated protein kinase.
• Measurement of intracellular calcium concentrations.

Main Results:

• IL-8-mediated MMP-9 release was primarily dependent on CXCR2, not CXCR1.
• Stimulation of CXCR2 alone induced MMP-9 release, independent of intracellular calcium.
• Two distinct signaling pathways were identified: one involving PKC and ERK1/2, and another involving Src-family kinases.
• ERK1/2 activation was downstream of PKC, but not Src-family kinases.
• p38 MAPK inhibition had no effect on MMP-9 release.

Conclusions:

• IL-8-induced MMP-9 release from neutrophils is mediated via CXCR2 through two parallel signaling cascades: one involving PKC-ERK1/2 and the other involving Src-family kinases.
• These findings highlight distinct mechanisms for MMP-9 release from tertiary granules compared to primary granule release.
• The study provides novel insights into neutrophil degranulation and inflammatory mediator release.