Controlling macrophage responses to pathogenic stimuli is critical for prevention of and recovery from the inflammatory state associated with the pathogenesis of many diseases. The
adhesion receptor αVβ3
integrin is thought to be an important receptor that regulates macrophage differentiation and macrophage responses to external signaling, but it has not been previously identified as a contributor to macrophage-related
inflammation. Using an in vitro model of human blood monocytes (Mo) and monocyte-derived macrophages (MDMs) we demonstrate that αVβ3
ligation results in sustained increases of the
transcription factor NF-κB
DNA-binding activity, as compared with control isotype-matched
IgG(1). Activation of NF-κB parallels the increase of NF-κB-dependent pro-inflammatory
cytokine mRNA expression in MDMs isolated from individual donors, for example, TNF-α (8- to 28-fold), IL-1β (15- to 30-fold),
IL-6 (2- to 4-fold), and
IL-8 (5- to 15-fold) whereas there is more than a 10-fold decrease in
IL-10 mRNA level occurs. Upon
ligation of the αVβ3 receptor, treatment with TNF-α (10 ng/ml) or LPS (200 ng/ml, 1,000 EU) results in the enhanced and synergistic activation of NF-κB and LPS-induced TNF-α secretion. As additional controls, an inhibitor of αVβ3
integrin,
cyclic RGD (10 µg/ml; IC(50) = 7.6 µM), attenuates the effects of αVβ3
ligation, and the natural
ligand of αVβ3
integrin,
vitronectin, reproduces the effects of αVβ3 activation by an immobilizing anti-αVβ3
integrin mAb. We hypothesize that αVβ3 activation can maintain chronic inflammatory processes in pathological conditions and that the loss of αVβ3
ligation will allow macrophages to escape from the inflammatory state.