Interferon (IFN)-gamma is highly expressed in atherosclerotic lesions and may have an important role in
atherogenesis.
Myeloperoxidase (MPO), the most abundant
protein in neutrophils, is a marker of plaque vulnerability and a possible bridge between
inflammation and
cardiovascular disease.
Granulocyte-macrophage colony-stimulating factor (
GM-CSF) has also been implicated in the pathogenesis of
atherosclerosis. The present study investigated the role of neutrophil activation in
atherosclerosis. Adherent macrophages were obtained from primary cultures of human mononuclear cells. Expression of IFN-gamma
protein by
GM-CSF-dependent-macrophages was investigated by
enzyme-linked
immunosorbent assay after stimulation with MPO.
GM-CSF enhanced macrophage expression of the
mannose receptor (CD206), which is involved in MPO uptake. MPO increased IFN-gamma production by
GM-CSF-dependent macrophages in a concentration-dependent manner. Pretreatment of macrophages with
small interfering RNA (
siRNA) for CD206 or
extracellular signal-regulated kinase (ERK)-2 attenuated IFN-gamma production, while
siRNA for ERK-1 did not. GAPDH is known to bind to adenylate/uridylate (AU)-rich elements of
RNA and may influence IFN-gamma
protein expression by binding to the AU-rich element of IFN-gamma
mRNA. Interestingly, pretreatment with
siRNA for GAPDH significantly reduced IFN-gamma production by macrophages, while it did not affect TF
protein expression. In conclusion, MPO upregulates IFN-gamma production by
GM-CSF-dependent-macrophages via the CD206/ERK-2 signaling pathway, while silencing GAPDH reduces IFN-gamma production.