Mariëtte H.W. Kappers

The Vascular Endothelial Growth Factor Receptor Inhibitor Sunitinib Causes a Preeclampsia-Like Syndrome With Activation of the Endothelin System

Angiogenesis inhibition is an established treatment for several tumor types. Unfortunately, this therapy is associated with adverse effects, including hypertension and renal toxicity, referred to as “preeclampsia.” Recently, we demonstrated in patients and in rats that the multitarget tyrosine kinase inhibitor sunitinib induces a rise in blood pressure (BP), renal dysfunction, and proteinuria associated with activation of the endothelin system. In the current study we investigated the effects of sunitinib on rat renal histology, including the resemblance with preeclampsia, as well as the roles of endothelin 1, decreased nitric oxide (NO) bioavailability, and increased oxidative stress in the development of sunitinib-induced hypertension and renal toxicity. In rats on sunitinib, light and electron microscopic examination revealed marked glomerular endotheliosis, a characteristic histological feature of preeclampsia, which was partly reversible after sunitinib discontinuation. The histological abnormalities were accompanied by an increase in urinary excretion of endothelin 1 and diminished NO metabolite excretion. In rats on sunitinib alone, BP increased (&Dgr;BP: 31.6±0.9 mm Hg). This rise could largely be prevented with the endothelin receptor antagonist macitentan (&Dgr;BP: 12.3±1.5 mm Hg) and only mildly with Tempol, a superoxide dismutase mimetic (&Dgr;BP: 25.9±2.3 mm Hg). Both compounds could not prevent the sunitinib-induced rise in serum creatinine or renal histological abnormalities and had no effect on urine nitrates but decreased proteinuria and urinary endothelin 1 excretion. Our findings indicate that both the endothelin system and oxidative stress play important roles in the development of sunitinib-induced proteinuria and that the endothelin system rather than oxidative stress is important for the development of sunitinib-induced hypertension.

Sunitinib-Induced Systemic Vasoconstriction in Swine Is Endothelin Mediated and Does Not Involve Nitric Oxide or Oxidative Stress

Angiogenesis inhibition with agents targeting tyrosine kinases of vascular endothelial growth factor receptors is an established anticancer treatment, but is, unfortunately, frequently accompanied by systemic hypertension and cardiac toxicity. Whether vascular endothelial growth factor receptor antagonism also has adverse effects on the pulmonary and coronary circulations is presently unknown. In chronically instrumented awake swine, the effects of the vascular endothelial growth factor receptor antagonist sunitinib on the systemic, pulmonary, and coronary circulation were studied. One week after sunitinib (50 mg PO daily), mean aortic blood pressure (MABP) had increased from 83±5 mm Hg at baseline to 97±6 mm Hg (P<0.05) because of a 57±20% increase in systemic vascular resistance as cardiac output decreased. In contrast, sunitinib had no discernible effects on pulmonary and coronary hemodynamics or cardiac function. We subsequently investigated the mechanisms underlying the sunitinib-induced systemic hypertension. Intravenous administration of NO synthase inhibitor NG-nitro-L-arginine increased MABP by 24±1 mm Hg under baseline conditions, whereas it increased MABP even further after sunitinib administration (32±3 mm Hg; P<0.05). Reactive oxygen species scavenging with a mixture of antioxidants lowered MABP by 13±2 mm Hg before but only by 5±2 mm Hg (P<0.05) after sunitinib administration. However, intravenous administration of the dual endothelin A/endothelin B receptor blocker tezosentan, which did not lower MABP at baseline, completely reversed MABP to presunitinib values. These findings indicate that sunitinib produces vasoconstriction selectively in the systemic vascular bed, without affecting pulmonary or coronary circulations. The sunitinib-mediated systemic hypertension is principally attributed to an increased vasoconstrictor influence of endothelin, with no apparent contributions of a loss of NO bioavailability or increased oxidative stress.

Cardiovascular and renal toxicity during angiogenesis inhibition: clinical and mechanistic aspects

Inhibition of angiogenesis with humanized monoclonal antibodies to vascular endothelial growth factor (VEGF) or with tyrosine kinase inhibitors targeting VEGF receptors has become an established treatment for various tumor types. Contrary to expectations, angiogenesis inhibition by blocking VEGF-mediated signaling is associated with serious side effects including hypertension and renal and cardiac toxicity in a substantial proportion of patients. Fortunately, most of these side effects as discussed in this paper seem to be manageable, but likely become more problematic when survival increases. Although several hypotheses regarding the etiology of angiogenesis inhibition-related cardiovascular and renal side effects have been postulated, many of the underlying pathophysiological mechanisms remain to be elucidated. This may lead to the development of more specific angiogenesis inhibitors, better management of their side effects and may potentially provide new insights into the pathogenesis of cardiovascular disease in general.

Treatment of Hypertension and Renal Injury Induced by the Angiogenesis Inhibitor Sunitinib: Preclinical Study

Common adverse effects of angiogenesis inhibition are hypertension and renal injury. To determine the most optimal way to prevent these adverse effects and to explore their interdependency, the following drugs were investigated in unrestrained Wistar Kyoto rats exposed to the angiogenesis inhibitor sunitinib: the dual endothelin receptor antagonist macitentan; the calcium channel blocker amlodipine; the angiotensin-converting enzyme inhibitor captopril; and the phosphodiesterase type 5 inhibitor sildenafil. Mean arterial pressure was monitored telemetrically. After 8 days, rats were euthanized and blood samples and kidneys were collected. In addition, 24-hour urine samples were collected. After sunitinib start, mean arterial pressure increased rapidly by ≈30 mm Hg. Coadministration of macitentan or amlodipine largely prevented this rise, whereas captopril or sildenafil did not. Macitentan, captopril, and sildenafil diminished the sunitinib-induced proteinuria and endothelinuria and glomerular intraepithelial protein deposition, whereas amlodipine did not. Changes in proteinuria and endothelinuria were unrelated. We conclude that in our experimental model, dual endothelin receptor antagonism and calcium channel blockade are suitable to prevent angiogenesis inhibition–induced hypertension, whereas dual endothelin receptor antagonism, angiotensin-converting enzyme inhibitor, and phosphodiesterase type 5 inhibition can prevent angiogenesis inhibition–induced proteinuria. Moreover, the variable response of hypertension and renal injury to different antihypertensive agents suggests that these side effects are, at least in part, unrelated.

Mechanism of hypertension and proteinuria during angiogenesis inhibition: Evolving role of endothelin-1

Angiogenesis inhibition by blocking vascular endothelial growth factor (VEGF)-mediated signalling with monoclonal antibodies or tyrosine kinase inhibitors has become an established treatment of various forms of cancer. This treatment is frequently associated with the development of hypertension and proteinuria. As VEGF increases the expression and the activity of nitric oxide synthase in endothelial cells, a decrease in the bioavailability of nitric oxide has been proposed as a key mechanism leading to hypertension during angiogenesis inhibition. However, results of clinical and experimental studies exploring this possibility are conflicting. Rarefaction, that is a structural decrease of microcirculatory vessels, has been reported during antiangiogenic treatment, but evidence that it plays a role in development of hypertension is lacking. Elevated circulating and urinary levels of endothelin-1 have been observed in clinical and experimental studies with angiogenesis inhibitors. Furthermore, the observation that endothelin receptor blockers can prevent or revert the rise in blood pressure during angiogenesis inhibition and attenuate proteinuria provides strong evidence that an activated endothelin-signalling pathway is a final common mediator of angiogenesis inhibition-induced rise in blood pressure and renal toxicity.

Light-induced vs. bradykinin-induced relaxation of coronary arteries: do S-nitrosothiols act as endothelium-derived hyperpolarizing factors?

Background Light-induced relaxation depends on S-nitrosothiols. S-Nitrosothiols may also serve as endothelium-derived hyperpolarizing factors, mediating the relaxant response of porcine coronary arteries (PCAs) to bradykinin. Here we compared the mechanism of light-induced and bradykinin-induced PCA relaxation. Methods PCAs were mounted in organ baths in the dark, preconstricted and exposed to polychromatic light (5 min) or 100 nmol/l bradykinin. Results Light relaxed PCAs by maximally 71 ± 1%. S-Nitrosothiol depletion abolished this relaxation. Relaxations diminished following repetitive light exposures, particularly if the dark periods between the light exposures were less than 10 min, and increased following endothelium removal or nitric oxide synthase blockade with Nω-nitro-L-arginine methyl ester (L-NAME), despite the prevention of guanosine-3′,5′-cyclic monophosphate generation by the latter two procedures. Thus, reloading of the storage pools occurs in the dark, endothelial nitric oxide inhibits this process and photorelaxation does not depend on guanosine-3′,5′-cyclic monophosphate. Bradykinin relaxed PCAs by 69 ± 3%. The nitric oxide scavenger hydroxocobalamin and the Na+-K+ ATPase inhibitor ouabain abolished the responses to bradykinin and light. The guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one abolished the response to light, and, like L-NAME, blocked the response to bradykinin by more than 50%. On top of L-NAME, intermediate and small conductance Ca2+-dependent K+ channel (IKCa/SKCa) blockade further reduced the response to bradykinin and enhanced photorelaxation. Conclusion Photorelaxation depends on stored S-nitrosothiols and their release/synthesis is negatively affected by endothelial nitric oxide and IKCa/SKCa. S-Nitrosothiols activate endothelial IKCa/SKCa and, via guanylyl cyclase, smooth muscle Na+-K+ ATPase. Thus, they possess all properties of a bradykinin-induced endothelium-derived hyperpolarizing factor.

Greater Sensitivity of Blood Pressure Than Renal Toxicity to Tyrosine Kinase Receptor Inhibition with Sunitinib

Hypertension and renal injury are off-target effects of sunitinib, a tyrosine kinase receptor inhibitor used for the treatment of various tumor types. Importantly, these untoward effects are accompanied by activation of the endothelin system. Here, we set up a study to explore the dose dependency of these side effects. Normotensive Wistar Kyoto rats were exposed to 3 different doses of sunitinib or vehicle. After 8 days, rats were euthanized. Telemetrically measured blood pressure rose dose dependently, from 13 to 30 mm Hg. Proteinuria was present at all doses, but a rise in cystatin C occurred only at the intermediate and high doses. Compared with vehicle circulating endothelin-1 increased dose dependently, whereas 24-hour urinary endothelin excretion decreased. Light and electron microscopy revealed glomerular endotheliosis and ischemia with the intermediate and high doses of sunitinib but completely absent histological abnormalities with the low dose. Podocyte number per glomerular circumference did not change. Glomerular nephrin, Neph1, podocin, and endothelin-converting enzyme gene expression were downregulated in a dose-dependent manner. We conclude that the sunitinib-induced rise in blood pressure requires lower doses than its induction of renal function impairment and that functional changes in glomerular filtration barrier contribute to the occurrence of proteinuria, given the lack of histopathologic changes with the low dose of sunitinib.

Re: Hypertension as a Biomarker of Efficacy in Patients With Metastatic Renal Cell Carcinoma Treated With Sunitinib

Rini et al. (1) reported a large retrospective analysis that showed that patients with metastatic renal cell carcinoma who developed hypertension when treated with the tyrosine kinase inhibitor sunitinib have improved overall survival and progressionfree survival compared with patients who remained free of hypertension. The authors concluded that the development of hypertension is a potential valuable biomarker for the prediction of treatment response. However, we wonder whether a categorical division of patients is the most appro

Hypertension induced by antiangiogenic therapy: clinical and pathophysiological aspects

Angiogenesis inhibition with humanised monoclonal antibodies to vascular endothelial growth factor (VEGF) or with VEGF receptor tyrosine kinase inhibitors targeting VEGF receptors has become an established treatment for various forms of cancer. Unfortunately, inhibition of the VEGF pathway is associated with serious side effects including hypertension. The development of this hypertension is likely to be multifactorial with a major role of the endothelin system. Although initially considered as a toxic effect, the development of hypertension may predict a favourable antitumour response. As a consequence, hypertension should not be a reason for dose reduction or discontinuation of antiangiogenic therapy but should be treated with antihypertensive therapy according to existing guidelines.

Treatment of Hypertension and Renal Injury Induced by the Angiogenesis Inhibitor Sunitinib

Common adverse effects of angiogenesis inhibition are hypertension and renal injury. To determine the most optimal way to prevent these adverse effects and to explore their interdependency, the following drugs were investigated in unrestrained Wistar Kyoto rats exposed to the angiogenesis inhibitor sunitinib: the dual endothelin receptor antagonist macitentan; the calcium channel blocker amlodipine; the angiotensin-converting enzyme inhibitor captopril; and the phosphodiesterase type 5 inhibitor sildenafil. Mean arterial pressure was monitored telemetrically. After 8 days, rats were euthanized and blood samples and kidneys were collected. In addition, 24-hour urine samples were collected. After sunitinib start, mean arterial pressure increased rapidly by ≈30 mm Hg. Coadministration of macitentan or amlodipine largely prevented this rise, whereas captopril or sildenafil did not. Macitentan, captopril, and sildenafil diminished the sunitinib-induced proteinuria and endothelinuria and glomerular intraepithelial protein deposition, whereas amlodipine did not. Changes in proteinuria and endothelinuria were unrelated. We conclude that in our experimental model, dual endothelin receptor antagonism and calcium channel blockade are suitable to prevent angiogenesis inhibition–induced hypertension, whereas dual endothelin receptor antagonism, angiotensin-converting enzyme inhibitor, and phosphodiesterase type 5 inhibition can prevent angiogenesis inhibition–induced proteinuria. Moreover, the variable response of hypertension and renal injury to different antihypertensive agents suggests that these side effects are, at least in part, unrelated.