Effect of heparin affin regulatory peptide on the expression of vascular endothelial growth factor receptors in endothelial cells.

BACKGROUND Heparin affin regulatory peptide (HARP) is an 18-kDa secreted protein that has been implicated in tumor growth and angiogenesis, although the mechanisms involved remain largely unknown. In the present work, the effect of human recombinant HARP on the expression of the vascular endothelial growth factor (VEGF) receptors KDR, Flt-1 and neuropilin-1 was studied in cultured human umbilical vein endothelial cells (HUVEC). MATERIALS AND METHODS The mRNA and protein levels of VEGF receptors were estimated by semi-quantitative RT-PCR and Western blot, respectively. Cell proliferation and migration were measured by MTT, direct counting of the cells and modified Boyden chamber assays. RESULTS HARP decreased the expression of KDR but increased the expression of Flt-1 and neuropilin-1 at both the mRNA and protein level. The effect reached a maximum 4 h after the addition of HARP into the cell culture medium and was reversed at later time-points. When HARP was added to the culture medium 4 h before the addition of VEGF165, it inhibited VEGF165-induced proliferation and migration of HUVEC. CONCLUSION These data suggest that HARP affects the expression of VEGF receptors and inhibits VEGF165-induced activation of HUVEC.