Production of Vascular Endothelial Growth Factor by Murine Macrophages

Abstract

Murine thioglycolate-induced peritoneal macrophages (MPMs) and the murine RAW264.7 macrophage-like cell line (RAW cells) constitutively produce vascular endothelial growth factor (VEGF). VEGF production is increased under hypoxic conditions or after cell activation with interferon-gamma (IFNgamma) and endotoxin (lipopolysaccharide, LPS). In contrast, tumor necrosis factor-alpha is produced only by IFNgamma/LPS-activated cells. Lactate (25 mmol/L) does not increase VEGF production by these cells. However, hypoxia, lactate, and IFNgamma/LPS-activated MPMs express angiogenic activity, whereas normoxic, nonactivated MPMs do not. Lack of angiogenic activity is not due to an antiangiogenic factor(s) in the medium of these cells. Angiogenic activity produced by hypoxia and lactate-treated MPMs is neutralized by anti-VEGF antibody, which also neutralizes most of the angiogenic activity produced by IFNgamma/LPS-activated MPMs. The inducible nitric oxide synthase inhibitors Ng-nitro-L-arginine-methyl ester (1.5 mmol/L) and aminoguanidine (1 mmol/L) block production of angiogenic activity by MPMs and RAW cells. In RAW cells, Ng-nitro-L-arginine-methyl ester and AG block IFNgamma/LPS-activated, but not constitutive, VEGF production, whereas in MPMs, neither constitutive nor IFNgamma/LPS-activated VEGF synthesis is affected. Synthesis of tumor necrosis factor-alpha is also unaffected. In contrast to normoxic, nonactivated MPMs, inducible nitric oxide synthase-inhibited, IFNgamma/LPS-activated MPMs produce an antiangiogenic factor(s). We conclude that VEGF is a major contributor to macrophage-derived angiogenic activity, and that activation by hypoxia, lactate, or IFNgamma/LPS switches macrophage-derived VEGF from a nonangiogenic to an angiogenic state. This switch may involve a posttranslational modification of VEGF, possibly by the process of ADP-ribosylation. ADP-ribosylation by MPM cytosolic extracts or by cholera toxin switches rVEGF165 from an angiogenic to a nonangiogenic state. In IFNgamma/LPS-activated MPMs, the inducible nitric oxide synthase-dependent pathway also regulates the expression of an antiangiogenic factor(s) that antagonizes the bioactivity of VEGF and provides an additional regulatory pathway controlling the angiogenic phenotype of macrophages.

Inhibitors of Nitric Oxide Production from Hops (Humulus lupulus L.).

“…Among the other fractions, fractions 9-11 also showed strong inhibitory activities but had no cytotoxic effects. The inhibitory effects of other fractions were much weaker, especially the last four fractions (12)(13)(14)(15), which contained high-polarity constituents.…”

“…10,11) It has been reported that NO is also involved in the production of vascular epidermal growth factor (VEGF), 12) the overexpression of which induces angiogenesis and vascular hyperpermeability, and accelerates tumor development.…”

Transcription of the Vascular Endothelial Growth Factor Gene in Macrophages Is Regulated by Liver X Receptors

“…VEGF mRNA expression is up-regulated by LXR agonists both in the presence and absence of LPS. Although VEGF has been reported to be responsive to NFB activation (19,20), it is also regulated by many other pathways. Unlike iNOS, VEGF expression in murine macrophages is not highly dependent on NFB (Fig.…”

“…Although resting monocytes and macrophages exhibit a nonangiogenic phenotype under normoxic conditions, hypoxia, elevated lactate levels, and inflammation strongly stimulate VEGF production (18). Treatment with bacterial lipopolysaccharide (LPS) or with CD40L stimulates VEGF production in human primary macrophages (19). This effect has been reported to be NFBdependent, because it is sensitive to the overexpression of the inhibitory protein, IB␣ (20).…”

Streptococcus pneumoniaeInduces Secretion of Vascular Endothelial Growth Factor by Human Neutrophils

“…VEGF is produced by a broad range of cell types, including macrophages, platelets, and neutrophils (4). The expression of VEGF is regulated by various stimuli, such as inflammatory cytokines (interleukin-1, tumor necrosis factor alpha, gamma interferon), hypoxia, and lipopolysaccharide (11,18). The first line of defense against pneumococci consists predominantly of neutrophils.…”