Esch, J.H.M. van

Complex genetics of radial ray deficiencies: Screening of a cohort of 54 patients (Article)

2013-03-01T00:00:00Z

Purpose: Radial ray deficiencies are characterized by unilateral or bilateral absence of varying portions of the radius and thumb. Both isolated and syndromic forms have been described, and although for some of the syndromes the causal gene has been identified, many patients remain without a genetic diagnosis. Methods: In this study, a cohort of 54 patients with radial ray deficiencies was screened for genomic aberrations by molecular karyotyping. Results: In 8 of 54 cases, an aberration was detected. Two unrelated patients inherited a 1q21.1 microduplication from a healthy parent, whereas in a third patient, a 16p13.11 microduplication was identified. Two other interesting microdeletions were detected: a 10q24.3 deletion at the split hand-foot malformation (SHFM3) locus and a 7p22.1 deletion including the RAC1 gene. Conclusion: The finding of these microduplications may just be coincidental or, alternatively, they may illustrate the broad phenotypic spectrum of these microduplications. Duplications in the 10q24.3 region result in split hand-foot malformations, and our observation indicates that deletions may cause radial ray defects. Finally, a candidate gene for radial ray deficiencies was detected in the 7p22.1 deletion. RAC1 plays an important role in the canonical Wnt pathway and conditional RAC1 knockout mice exhibit truncated-limb defects. Copyright

Sunitinib-induced hypothyroidism is due to induction of type 3 deiodinase activity and thyroidal capillary regression (Article)

2011-10-01T00:00:00Z

Context: Anticancer treatment with the tyrosine kinase inhibitor sunitinib causes thyroid dysfunction. Objective: Our objective was to investigate the time course and underlying mechanisms of sunitinib-induced thyroid dysfunction. Design: Thyroid function tests of 83 patients on sunitinib were collected retrospectively for their total treatment duration between January 2006 and November 2009 and prospectively in 15 patients on sunitinib for 10 wk. Additionally, thyroid function and histology were assessed in rats on sunitinib (8 d; n = 10) and after sunitinib withdrawal (11 d; n = 7) and compared with controls (n = 7). Setting: Patients were seen at a university outpatient oncology clinic. Patients and Animals: Patients with metastatic renal cell carcinoma or gastrointestinal stromal tumors participated in the clinical study and Wistar Kyoto rats were used in the rat study. Intervention: Sunitinib was taken according to a 4 wk "on," 2 wk "off" treatment regimen. Blood samples for measurement of thyroid function were collected at baseline and at wk 4 and 10. In rats, blood, liver, and thyroid were collected to assess thyroid hormones, deiodinase activity, and thyroid histology. Main Outcome Measures: TSH and free T4levels, deiodinase activity, and thyroid histology were assessed. Results: Forty-two percent of patients in the retrospective study developed elevated TSH levels. Prospective analysis showed increased TSH levels within 10 wk of treatment, accompanied by a decreased T3/rT3ratio. In rats, serum T4and T3decreased, hepatic type 3 deiodinase activity increased, andthyroid histology showed marked capillary regression, which all but thyroid hormones reversed after sunitinib withdrawal. Conclusion: Sunitinib induces hypothyroidism due to alterations in T4/T3metabolism as well as thyroid capillary regression. Copyright

Impaired vascular contractility and aortic wall degeneration in fibulin-4 deficient mice: Effect of angiotensin II type 1 (AT1) receptor blockade (Article)

2011-08-12T00:00:00Z

Medial degeneration is a key feature of aneurysm disease and aortic dissection. In a murine aneurysm model we investigated the structural and functional characteristics of aortic wall degeneration in adult fibulin-4 deficient mice and the potential therapeutic role of the angiotensin (Ang) II type 1 (AT1) receptor antagonist losartan in preventing aortic media degeneration. Adult mice with 2-fold (heterozygous Fibulin-4+/R) and 4-fold (homozygous Fibulin-4R/R) reduced expression of fibulin-4 displayed the histological features of cystic media degeneration as found in patients with aneurysm or dissection, including elastin fiber fragmentation, loss of smooth muscle cells, and deposition of ground substance in the extracellular matrix of the aortic media. The aortic contractile capacity, determined by isometric force measurements, was diminished, and was associated with dysregulation of contractile genes as shown by aortic transcriptome analysis. These structural and functional alterations were accompanied by upregulation of TGF-β signaling in aortas from fibulin-4 deficient mice, as identified by genome-scaled network analysis as well as by immunohistochemical staining for phosphorylated Smad2, an intracellular mediator of TGF-β. Tissue levels of Ang II, a regulator of TGF-β signaling, were increased. Prenatal treatment with the AT1receptor antagonist losartan, which blunts TGF-β signaling, prevented elastic fiber fragmentation in the aortic media of newborn Fibulin-4R/Rmice. Postnatal losartan treatment reduced haemodynamic stress and improved lifespan of homozygous knockdown fibulin-4 animals, but did not affect aortic vessel wall structure. In conclusion, the AT1receptor blocker losartan can prevent aortic media degeneration in a non-Marfan syndrome aneurysm mouse model. In established aortic aneurysms, losartan does not affect aortic architecture, but does improve survival. These findings may extend the potential therapeutic application of inhibitors of the renin-angiotensin system to the preventive treatment of aneurysm disease.

The vascular endothelial growth factor receptor inhibitor sunitinib causes a preeclampsia-like syndrome with activation of the endothelin system (Article)

2011-08-01T00:00:00Z

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 (ΔBP: 31.6±0.9 mm Hg). This rise could largely be prevented with the endothelin receptor antagonist macitentan (ΔBP: 12.3±1.5 mm Hg) and only mildly with Tempol, a superoxide dismutase mimetic (ΔBP: 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.

The role of the renin-angiotensin system in thoracic aortic aneurysms: Clinical implications (Article)

2011-07-01T00:00:00Z

Thoracic aortic aneurysms (TAAs) are a potential life-threatening disease with limited pharmacological treatment options. Current treatment options are aimed at lowering aortic hemodynamic stress, predominantly with β-adrenoceptor blockers. Increasing evidence supports a role for the renin-angiotensin system (RAS) in aneurysm development. RAS blockade would not only lower blood pressure, but might also target the molecular pathways involved in aneurysm formation, in particular the transforming growth factor-β and extracellular signal-regulated kinase 1/2 pathways. Indeed, the angiotensin II type 1 (AT1) receptor blocker losartan was effective in lowering aortic root growth in mice and patients with Marfan's syndrome. RAS inhibition (currently possible at 3 levels, i.e. renin, ACE and the AT1receptor) is always accompanied by a rise in renin due to interference with the negative feedback loop between renin and angiotensin II. Only during AT1receptor blockade will this result in stimulation of the non-blocked angiotensin II type 2 (AT2) receptor. This review summarizes the clinical aspects of TAAs, provides an overview of the current mouse models for TAAs, and focuses on the RAS as a new target for TAA treatment, discussing in particular the possibility that AT2receptor stimulation might be crucial in this regard. If true, this would imply that AT1receptor blockers (and not ACE inhibitors or renin inhibitors) should be the preferred treatment option for TAAs.

Handle region peptide counteracts the beneficial effects of the renin inhibitor aliskiren in spontaneously hypertensive rats (Article)

2011-04-01T00:00:00Z

To investigate whether the putative (pro)renin receptor blocker, the handle region peptide (HRP), exerts effects on top of the blood pressure-lowering and cardioprotective effects of the renin inhibitor aliskiren, spontaneously hypertensive rats were implanted with telemetry transmitters to monitor heart rate and mean arterial pressure (MAP). After a 2-week recovery period, vehicle, aliskiren, HRP (100 and 1 mg/kg per day, respectively), and HRP+aliskiren were infused for 3 weeks using osmotic minipumps. Subsequently, the heart was removed to study coronary function according to Langendorff. Baseline MAP and heart rate in vehicle-treated rats were 146±3 mm Hg and 326±4 bpm. HRP did not affect MAP, whereas aliskiren and HRP+aliskiren lowered MAP (by maximally 29±2 and 20±1 mm Hg, respectively) without affecting heart rate. Aliskiren significantly reduced MAP throughout the 3-week infusion period, whereas the blood pressure-lowering effect of HRP+aliskiren returned to baseline within 2 weeks of treatment. In comparison with vehicle, aliskiren increased the endothelium-dependent response to bradykinin and decreased the response to angiotensin II in the coronary circulation, whereas these responses were not altered after treatment with HRP or HRP+aliskiren. HRP did not alter plasma renin activity, plasma angiotensin levels, or the renal angiotensin content, either alone or on top of aliskiren, nor did it alter the aliskiren-induced decrease in renal Ang II type 1 receptor expression. Yet, it did reverse the aliskiren-induced reduction in cardiomyocyte area, without affecting this area when given alone. In conclusion, HRP counteracts the beneficial effects of aliskiren on blood pressure, coronary function, and cardiac hypertrophy in an angiotensin-independent manner. Copyright

Cardiac phenotype and angiotensin II levels in AT1a, AT 1b, and AT2 receptor single, double, and triple knockouts (Article)

2010-06-01T00:00:00Z

AimsOur aim was to determine the contribution of the three angiotensin (Ang) II receptor subtypes (AT1a, AT1b, AT2) to coronary responsiveness, cardiac histopathology, and tissue Ang II levels using mice deficient for one, two, or all three Ang II receptors.Methods and resultsHearts of knockout mice and their wild-type controls were collected for histochemistry or perfused according to Langendorff, and kidneys were removed to measure tissue Ang II. Ang II dose-dependently decreased coronary flow (CF) and left ventricular systolic pressure (LVSP), and these effects were absent in all genotypes deficient for AT1a, independently of AT1band AT2. The deletion of Ang II receptors had an effect neither on the morphology of medium-sized vessels in the heart nor on the development of fibrosis. However, the lack of both AT1subtypes was associated with atrophic changes in the myocardium, a reduced CF and a reduced LVSP. AT1adeletion alone, independently of the presence or absence of AT1band/or AT2, reduced renal Ang II by 50 despite a five-fold rise of plasma Ang II. AT1bdeletion, on top of AT1adeletion (but not alone), further decreased tissue Ang II, while increasing plasma Ang II. In mice deficient for all three Ang II receptors, renal Ang II was located only extracellularly. Conclusion The lack of both AT1subtypes led to a baseline reduction of CF and LVSP, and the effects of Ang II on CF and LVSP were found to be exclusively mediated via AT1a. The lack of AT1aor AT1bdoes not influence the development or maintenance of normal cardiac morphology, whereas deficiency for both receptors led to atrophic changes in the heart. Renal Ang II levels largely depend on AT1binding of extracellularly generated Ang II, and in the absence of all three Ang II receptors, renal Ang II is only located extracellularly.

Effects of angiotensin metabolites in the coronary vascular bed of the spontaneously hypertensive rat loss of angiotensin II type 2 receptor-mediated vasodilation (Article)

2010-02-01T00:00:00Z

Because angiotensin (Ang) metabolites mediate functions independent of Ang II, we investigated their effects on coronary flow in spontaneously hypertensive rats (SHRs). Results were compared with those in the iliac artery and abdominal aorta and the coronary circulation of the Wistar rat. Ang II, III, and IV decreased coronary flow in SHRs and Wistar rats, with Ang III and IV being ≈10 and ≈1000 times less potent than Ang II. Ang-(1-7) decreased coronary flow at concentrations >1 μmol/L in SHRs. The Ang II type 1 receptor antagonist irbesartan blocked the effects of Ang II, III, and IV, whereas the Ang II type 2 receptor antagonist PD123319 blocked the effects of Ang-(1-7). The maximal Ang II-and III-induced decreases in coronary flow in SHRs were twice as large as those in Wistar rats. PD123319 enhanced the constrictor effects of Ang II and III in Wistar rats so that, in the presence of this drug, their effects were comparable to those in SHRs. In contrast, PD123319 did not alter the Ang II-and III-induced responses in SHRs and blocked the constrictor effect of Ang II in iliac arteries. Ang II type 2 receptor-mediated relaxation did not occur in iliac arteries and abdominal aortas, and the constrictor effects of Ang metabolites in these vessels were identical in Wistar rats and SHRs. In conclusion, coronary constriction induced by Ang II, Ang III, and Ang-(1-7) is enhanced in SHRs as compared with Wistar rats. This is attributable to the absence of counterregulatory Ang II type 2 receptor-mediated relaxation and/or a change of the Ang II type 2 receptor phenotype from relaxant to constrictor.

Cardiovascular and renal toxicity during angiogenesis inhibition: Clinical and mechanistic aspects (Article)

2009-12-01T00:00:00Z

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.

Cardiovascular phenotype of mice lacking all three subtypes of angiotensin II receptors (Article)

2008-08-01T00:00:00Z

Angiotensin II activates two distinct receptors, the angiotensin II receptors type 1 (AT1) and type 2 (AT2). In rodents, two AT1subtypes were identified (AT1aand AT1b). To determine receptor-specific functions and possible angiotensin II effects independent of its three known receptors we generated mice deficient in either one of the angiotensin II receptors, in two, or in all three (triple knockouts). Triple knockouts were vital and fertile, but survival was impaired. Hypotension and renal histological abnormalities in triple knockouts were comparable to those in mice lacking both AT1subtypes. All combinations lacking AT1awere distinguished by reduced heart rate. AT1adeletion impaired the in vivo pressor response to angiotensin II bolus injection, whereas deficiency for AT1band/or AT2had no effect. However, the additional lack of AT1bin AT1a-deficient mice further impaired the vasoconstrictive capacity of angiotensin II. Although general vasoconstrictor properties were not changed, angiotensin II failed to alter blood pressure in triple knockouts, indicating that there are no other receptors involved in direct angiotensin II pressor effects. Our data identify mice deficient in all three angiotensin II receptors as an ideal tool to better understand the structure and function of the reninangiotensin system and to search for angiotensin II effects independent of AT1and AT2.

Effects of angiotensin II and its metabolites in the rat coronary vascular bed: Is angiotensin III the preferred ligand of the angiotensin AT2 receptor? (Article)

2008-07-07T00:00:00Z

Aminopeptidases metabolize angiotensin II to angiotensin-(2-8) (= angiotensin III) and angiotensin-(3-8) (= angiotensin IV), and carboxypeptidases generate angiotensin-(1-7) from angiotensin I and II. Angiotensin-converting enzyme (ACE) inhibitors and/or angiotensin II type 1 (AT1) receptor blockers affect the concentrations of these metabolites, and they may thus contribute to the beneficial effects of these drugs, possibly through stimulation of non-classical angiotensin AT receptors. Here, we investigated the effects of angiotensin II, angiotensin III, angiotensin IV and angiotensin-(1-7) in the rat coronary vascular bed, with or without angiotensin AT1- or angiotensin II type 2 (AT2) receptor blockade. Results were compared to those in rat iliac arteries and abdominal aortas. Angiotensin II, angiotensin III and angiotensin IV constricted coronary arteries via angiotensin AT1receptor stimulation, angiotensin III and angiotensin IV being ≈ 20- and ≈ 8000-fold less potent than angiotensin II. The angiotensin AT2receptor antagonist PD123319 greatly enhanced the constrictor effects of angiotensin III, starting at angiotensin III concentrations in the low nanomolar range. PD123319 enhanced the angiotensin II-induced constriction at submicromolar angiotensin II concentrations only. Angiotensin-(1-7) exerted no effects in the coronary circulation, although, at micromolar concentrations, it blocked angiotensin AT1receptor-induced constriction. Angiotensin AT2receptor-mediated relaxation did not occur in iliac arteries and abdominal aortas, and the constrictor effects of the angiotensin metabolites in these vessels were identical to those in the coronary vascular bed. In conclusion, angiotensin AT2receptor activation in the rat coronary vascular bed results in vasodilation, and angiotensin III rather than angiotensin II is the preferred endogenous agonist of these receptors. Angiotensin II, angiotensin III, angiotensin IV and angiotensin-(1-7) do not exert effects through non-classical angiotensin AT receptors in the rat coronary vascular bed, iliac artery or aorta.

Unraveling the Complexities of the Renin-Angiotensin System: From ACE to renin inhibition (Doctoral Thesis)

2008-06-04T00:00:00Z

Ang II generated at tissue sites stimulates both AT1 and AT2 receptors. This local generation depends largely on angiotensinogen and renin and/or prorenin taken up from blood, the latter uptake possibly involving the recently discovered (pro)renin receptor. ACE is generated locally, and appears to be the main, if not the only, Ang II-generating enzyme. Ang II has a whole range of metabolites, the most important of which are Ang-(1-7), Ang III and Ang IV. The enzymes generating these metabolites, including ACE2, have recently been characterized, as well as their putative (non- AT1/AT2) receptors, like the Mas and AT4 receptor. Stimulation of AT2 receptors most likely contributes to the benefi cial effect of RAS blockers, in particular during AT1 receptor antagonism. These receptors are upregulated under pathophysiological conditions, and are generally believed to counteract the effects of AT1 receptor stimulation. However, not all studies agree on this aspect, and thus it remains to be seen how the effect of drugs that completely suppress the RAS, i.e., renin inhibitors, compare to those that allow/require AT2 receptor stimulation, like ACE inhibitors and AT1 receptor antagonists.

Prorenin anno 2008 (Article)

2008-06-01T00:00:00Z

For many years, prorenin has been considered to be nothing more than the inactive precursor of renin. Yet, its elevated levels in diabetic subjects with microvascular complications and its extrarenal production at various sites in the body suggest otherwise. This review discusses the origin, regulation, and enzymatic activity of prorenin, its role during renin inhibition, and the angiotensin-dependent and angiotensin-independent consequences of its binding to the recently discovered (pro)renin receptor. The review ends with the concept that prorenin rather than renin determines tissue angiotensin generation.

Different contributions of the angiotensin-converting enzyme C-domain and N-domain in subjects with the angiotensin-converting enzyme II and DD genotype (Article)

2008-04-01T00:00:00Z

BACKGROUND: Angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism-related differences in ACE concentration do not result in differences in angiotensin levels. METHODS AND RESULTS: To investigate whether this relates to differences in the contribution of the ACE C-domain and N-domain, we quantified, using the C-domain-selective inhibitors quinaprilat and RXPA380, and the N-domain-selective inhibitor RXP407, the contribution of both domains to the metabolism of angiotensin I, bradykinin, the C-domain-selective substrate Mca-BK(1-8), and the N-domain-selective substrate Mca-Ala in serum of IIs, DDs, and 'hyperACE' subjects (i.e., subjects with increased ACE due to enhanced shedding). During incubation with angiotensin I, the highest angiotensin II levels were observed in sera with the highest ACE activity. This confirms that ACE is rate-limiting with regard to angiotensin II generation. C-domain-selective concentrations of quinaprilat fully blocked angiotensin I-II conversion in DDs, whereas additional N-domain blockade was required to fully block conversion in IIs. Both domains contributed to bradykinin hydrolysis in all subjects, and the inhibition profile of RXP407 when using Mca-Ala was identical in IIs and DDs. In contrast, the RXPA380 concentrations required to block C-domain activity when using Mca-BK (1-8) were three-fold higher in IIs than DDs. CONCLUSION: The contributions of the C-domain and N-domain differ between DDs and IIs, and RXPA380 is the first inhibitor capable of distinguishing D-allele ACE from I-allele ACE. The lack of angiotensin II accumulation in DDs in vivo is not because of the often quoted concept that ACE is a nonrate-limiting enzyme. It may relate to the fact that in IIs both the N-domain and C- domain generate angiotensin II, whereas in DDs only the C-domain converts angiotensin I.

Prorenin and the (pro)renin receptor - An update (Article)

2007-05-01T00:00:00Z

Selective angiotensin-converting enzyme C-domain inhibition is sufficient to prevent angiotensin I-induced vasoconstriction. (Article)

2005-01-01T00:00:00Z

Somatic angiotensin-converting enzyme (ACE) contains 2 domains (C-domain and N-domain) capable of hydrolyzing angiotensin I (Ang I) and bradykinin. Here we investigated the effect of the selective C-domain and N-domain inhibitors RXPA380 and RXP407 on Ang I-induced vasoconstriction of porcine femoral arteries (PFAs) and bradykinin-induced vasodilation of preconstricted porcine coronary microarteries (PCMAs). Ang I concentration-dependently constricted PFAs. RXPA380, at concentrations >1 mumol/L, shifted the Ang I concentration-response curve (CRC) 10-fold to the right. This was comparable to the maximal shift observed with the ACE inhibitors (ACEi) quinaprilat and captopril. RXP407 did not affect Ang I at concentrations < or =0.1 mmol/L. Bradykinin concentration-dependently relaxed PCMAs. RXPA380 (10 micromol/L) and RXP407 (0.1 mmol/L) potentiated bradykinin, both inducing a leftward shift of the bradykinin CRC that equaled approximately 50% of the maximal shift observed with quinaprilat. Ang I added to blood plasma disappeared with a half life (t(1/2)) of 42+/-3 minutes. Quinaprilat increased the t(1/2) approximately 4-fold, indicating that 71+/-6% of Ang I metabolism was attributable to ACE. RXPA380 (10 micromol/L) and RXP407 (0.1 mmol/L) increased the t(1/2) approximately 2-fold, thereby suggesting that both domains contribute to conversion in plasma. In conclusion, tissue Ang I-II conversion depends exclusively on the ACE C-domain, whereas both domains contribute to conversion by soluble ACE and to bradykinin degradation at tissue sites. Because tissue ACE (and not plasma ACE) determines the hypertensive effects of Ang I, these data not only explain why N-domain inhibition does not affect Ang I-induced vasoconstriction in vivo but also why ACEi exert blood pressure-independent effects at low (C-domain-blocking) doses.