Recently, increased serum levels of vascular endothelial growth factor (VEGF) have been shown in patients with inflammatory bowel disease, The origins of the circulating VEGF are still not described. Monocytes play an important role in the inflammatory process. VEGF binding to monocytes mediates monocyte recruitment and activation. The present study investigates the VEGF production of peripheral blood mononuclear cells and the ability of peripheral monocytes to bind VEGF(165) in patients with Crohn's disease. Nineteen patients with Crohn's disease and 10 healthy volunteers were studied. VEGF(165) labeling of CD14(+) monocytes was measured using two-color flow cytometry, Density of VEGF labeling was expressed as the mean fluorescence intensity (MFI). Furthermore, VEGF levels were determined in culture supernatants of unstimulated peripheral blood mononuclear cells. VEGF in culture supernatants was measured using a solid-phase enzyme-linked immunosorbent assay. There was a significantly decreased VEGF(165) labeling: of monocytes of patients with active Crohn's disease (MFI: 369.9 +/- 131.6, N = 7, P < 0.002) compared to patients with inactive disease (MFI: 457.7 +/- 74.5, N = 6) and healthy controls (MFI: 542.9 +/- 96.2, N = 10). Unstimulated peripheral blood mononuclear cells of patients with active Crohn's disease produced significantly higher amounts of VEGF (1142.6 +/- 483.9 pg/ml, N = 12, P < 0.001) compared with peripheral blood mononuclear cells of healthy volunteers (113.4 +/- 101.8 pg/ml, N = 10). VEGF production by peripheral blood mononuclear cells of patients with active disease was significantly increased compared to patients with quiescent disease (261.6 +/- 254.8 pg/ml, N = 7, P < 0.001), In conclusion, our data describe peripheral blood mononuclear cells as one of the origins of the elevated VEGF serum levels in patients with active Crohn's disease. Furthermore, a decrease in VEGF(165) binding sites on peripheral monocytes of patients with active Crohn's disease has been shown. The study underlines the important role of VEGF in Crohn's disease.
