【Aim】
Histamine is well known as an inflammatory mediator whereas little is demonstrated about the mechanism of histamine-induced angiogenesis. The role of histamine in angiogenesis was first reported in 1983 in the chorioallantoic membrane (CAM) assay. Still, the histamine-induced tube formation mechanism has not been investigated with histamine single-acting in vitro study. In the present study, we demonstrated the effects of histamine on the tube formation processes of human endothelial cells.
【Method】
Histamine-induced tube formation was analyzed by the matrigel assay using the human-derived vascular endothelial cell line EA.hy926. To investigate the effects of histamine H1 receptor (H1R) antagonist and protein kinase C (PKC) inhibitors vascular endothelial cells were stained with Calcein-AM and observed under a microscope. In addition, the expression of angiogenesis-related factors such as vascular endothelial growth factor (VEGF) and matrix metalloproteinases (MMPs) was analyzed by the RT-PCR method.
【Result】
Histamine concentration-dependently remarkably enhanced tube formation of EA.hy926 cells in a matrigel assay at 16 hours. In addition, histamine-induced tube formation was entirely blocked by inhibitors of H1R and PKC. This result suggests that H1R-PKC signaling is involved in histamine-induced tube formation. We have also shown treatment of EA.hy926 cells with 10 µM histamine resulted in a marked upregulation of VEGF mRNA expression with a peak at 3 hours and an inhibitor of VEGF Receptor (VEGFR) -2 suppressed histamine-induced tube formation. Additionally, histamine stimulation induced the expression of MMP-9 and MMP-14, which play important roles in the regulation of angiogenesis, and MMP inhibitors blocked histamine-induced tube formation.
【Conclusion】
In this study, we have shown a remarkable tube formation in vitro model induced by histamine in endothelial cells through the H1 receptor. In addition, this action was linked to the activation of PKC, VEGF, VEGFR2, and MMPs.