Abstract 340: Novel Molecular Mechanisms Involved In VEGFR Inhibition In Human Endothelial Cells
VEGF/VEGFR inhibitors are increasingly being used as anti-angiogenic drugs to treat cancer. However these drugs are limited by the development of severe hypertension. Molecular mechanisms whereby VEGF inhibitors cause hypertension are unclear, but nitric oxide (NO) signalling may be involved. We questioned whether reactive oxygen species (ROS) and Ang II, important regulators of vascular function in hypertension, also play a role in VEGF inhibitor-induced vascular dysfunction. Human microvascular endothelial cells (HMECs) were stimulated with vatalanib (VAT-VEGFR inhibitor) and gefitinib (GEF-EGFR inhibitor) in the absence/presence of Ang II. Activation of eNOS and MAPKs were assessed by immunoblotting. Antioxidant enzyme mRNA was analyzed by qPCR. Phosphorylation of eNOS activation site (Ser1177) (28.3% ± 7.1) and p38 MAPK (55.4% ± 2.4) was decreased by VAT, while no changes were observed after exposure of HMECs to GEF (p<0.05). VAT also decreased mRNA expression of Nox4 (0.5 ± 0.2), and H2O2-related antioxidants enzymes such as catalase (0.4 ± 0.1) and glutathione peroxidase (0.4 ± 0.1). Ang II stimulation increased eNOS (171.2% ± 17.4), ERK1/2 (177.5% ± 38.5), p38 MAPK (186.9% ± 36.6) activation (p<0.05); an effect blocked by VAT and GEF. Inhibition of VEGFR also blocked Ang II effects on SOD1 (1.33 ± 0.1), HO-1 (1.6 ± 0.3) and NQO1 (1.6 ± 0.3) mRNA levels (p<0.05). In addition, Ang II increased Nox4 mRNA expression through VEGFR-dependent mechanisms. Interestingly, VEGFR1/2 and AT2R were expressed in HMEC, but not AT1R. Ang II effects on eNOS phosphorylation were inhibited by PDE123 (AT2R antagonist) but not by losartan (AT1R antagonist). In conclusion, our data elucidate novel mechanisms whereby AngII, possibly through AT2R-dependent VEGFR transactivation, regulates eNOS activation, MAPK signalling and H2O2-related antioxidant enzymes. In addition to changes in NO availability, VEGFR inhibition may interfere with the redox status of endothelial cells, leading to vascular dysfunction and hypertension.
Author Disclosures: H.Y. Small: None.
- © 2014 by American Heart Association, Inc.