Abstract 44: VEGF Inhibitor-induced Vascular Dysfunction Is Ameliorated By PARP/TRPM2 Inhibition

Abstract

Hypertension is a common unwanted effect of VEGF inhibitors (VEGFi), which are used as anti-angiogenic drugs in cancer treatment. Clinical observations suggest that the combination of VEGFi with another anti-cancer drug, olaparib (PARP inhibitor [PARPi]), may attenuate the development of hypertension. However putative vascular mechanisms are unknown. PARP plays a major role in the activation of TRPM2, a redox-sensitive Ca 2+ channel, which is associated with hypertension-induced vascular dysfunction. We hypothesized that PARPi attenuates VEGFi-induced vascular injury through TRPM2/Ca 2+ -dependent pathways. Human vascular smooth muscle cells (hVSMC), human aortic endothelial cells (HAEC), and mouse mesenteric arteries were studied. Cells/arteries were exposed to axitinib (VEGFi) alone (3μM) or in combination with olaparib (1μM). Wire myography was used to assess vascular function. Axitinib reduced ACh-induced vasodilation (% relaxation: 70.5 [Ct] vs. 34.8 [Axi]), an effect blocked by olaparib. U46619- and ET-1-induced vasoconstriction were increased by axitinib (% KCl- U4 : 101.2 [Ct] vs. 141.4 [Axi]; ET-1 : 122.6 [Ct] vs. 152.5 [Axi]), an effect not observed with axitinib plus olaparib. TRPM2 channel blocker (8-Br-cADPR; 1μM) attenuated the hypercontractile effects and endothelial dysfunction induced by axitinib. Axitinib increased ROS production in hVSMC (RUL: 0.8±0.2 [Ct] vs. 1.1±0.09 [Axi]) and HAEC (0.7±0.4 [Ct] vs. 1.2±0.1 [Axi]), stimulated phosphorylation of the inhibitory site of eNOS (a.u.: 0.99±0.35 [Ct] vs. 1.35±0.10 [Axi]) and induced exaggerated Ca 2+ influx (AUC: 17541±4708 [Ct] vs. 22249±1438 [Axi]) in hVSMC. These effects were blocked by olaparib and 8-Br-cADPR. Axitinib also induced phosphorylation of MLC20 in hVSMC (a.u.: 0.028±0.02 [Ct] vs. 0.04±0.01 [Axi]) and aorta (a.u.: 0.3±0.01 [Ct] vs. 0.5±0.001 [Axi]). Our data indicate that PARP/TRPM2 inhibition attenuates axitinib-mediated vascular dysfunction and normalizes impaired hVSMC and HAEC signalling induced by VEGFi. We define a putative vasoprotective effect of olaparib that may ameliorate vascular injury and hypertension induced by VEGFi in cancer treatment.