Abstract P186: Selective ET A Receptor Antagonism versus Dual ET A /ET B Receptor Blockade for Preventing Angiogenesis Inhibitor-induced Hypertension

Abstract

Angiogenesis inhibitors are a mainstay treatment for cancer. While effective in preventing tumor growth, angiogenesis inhibitors cause off-target effects including cardiovascular toxicity and renal injury, most likely via endothelin-1 (ET-1) upregulation. ET-1 via stimulation of the ET A receptor causes pro-hypertensive effects whereas stimulation of the ET B receptor can elicit both pro- or anti-hypertensive effects. In the present study, we hypothesized that selective ET A receptor blockade versus dual ET A /ET B blockade provides better cardiovascular protection from angiogenesis inhibitor-induced hypertension. Male WKY rats were treated with vehicle, sunitinib (VEGF inhibitor; 14 mg/kg/day) alone or in combination with macitentan (ET A/B receptor antagonist; 30 mg/kg/day) or sitaxentan (ET A receptor antagonist; 30 or 100 mg/kg/day) for 8 days. Mean arterial pressure (MAP) was measured via radiotelemetry at baseline and days 1-6 of treatment. Vasoreactivity to acetylcholine (ACh) and ET-1 was assessed in iliac vessels. Compared to vehicle treatment, sunitinib treatment caused a rapid and sustained increase in MAP (1±1 versus 23±2 mmHg on day 6 of treatment, respectively, P<0.001). Co-treatment with macitentan blunted the pressor response to sunitinib, such that on day 6 of treatment the increase in MAP was 7±4 mmHg (P<0.01 versus sunitinib-treated). Similar results were observed for co-treatment with 30 mg/kg/day of sitaxentan. Conversely, co-treatment with 100 mg/kg/day sitaxentan, which has been shown to induce a depressor response in normotensive Wistar rats, completely abolished sunitinib-induced hypertension, with MAP actually decreasing before returning to near baseline level (-1±1 mmHg on day 6 of treatment, P<0.001 versus sunitinib-treated). Compared to vehicle treatment, ET B receptor stimulation yielded a constrictor response after 8 days of sunitinib treatment, while the response to ACh was unaltered. Both macitentan and sitaxentan reversed the constrictor ET B receptor response. Our results support a key role for the ET-1 system in the development of sunitinib-induced hypertension and suggest that selective ET A receptor blockade is sufficient to block this effect.