C-reactive protein induces M-CSF release and macrophage proliferation

Area of Science:

• Cardiovascular Science
• Immunology
• Cell Biology

Background:

• Inflammation is central to atherosclerosis development.
• Macrophage colony-stimulating factor (M-CSF) regulates macrophage function and is implicated in atherogenesis.
• C-reactive protein (CRP) is a cardiovascular risk marker, but its direct effects on M-CSF and macrophage proliferation are unknown.

Purpose of the Study:

• To investigate the effects of CRP on M-CSF release from human aortic endothelial cells (HAEC) and human monocyte-derived macrophages (HMDM).
• To determine if CRP-induced M-CSF release influences macrophage proliferation.
• To elucidate the signaling pathways involved in CRP's effects on M-CSF and macrophages.

Main Methods:

• HAEC and HMDM were treated with native CRP, and M-CSF release was measured via ELISA and flow cytometry.
• Macrophage proliferation was assessed using conditioned medium from CRP-treated HAEC.
• NF-kappaB inhibition and antibodies against specific Fc receptors (CD32, CD64, CD16) were used to investigate signaling pathways.

Main Results:

• CRP significantly and dose-dependently increased M-CSF mRNA and secretion from HAEC and HMDM.
• Conditioned medium from CRP-treated HAEC enhanced HMDM proliferation, an effect blocked by M-CSF antibodies.
• Inhibition of NF-kappaB abrogated CRP-induced M-CSF release and macrophage proliferation.
• Antibodies to CD32 and CD64, but not CD16, blocked CRP-induced M-CSF release.

Conclusions:

• CRP up-regulates M-CSF release from endothelial cells and macrophages.
• CRP enhances macrophage proliferation, mediated by M-CSF.
• These proatherogenic effects of CRP are linked to NF-kappaB activation via CD32 and CD64 receptors.