Bernhard Pilz

Aliskiren, a Human Renin Inhibitor, Ameliorates Cardiac and Renal Damage in Double-Transgenic Rats

We tested the hypothesis that the renin inhibitor aliskiren ameliorates organ damage in rats transgenic for human renin and angiotensinogen genes (double transgenic rat [dTGR]). Six-week-old dTGR were matched by albuminuria (2 mg per day) and divided into 5 groups. Untreated dTGR were compared with aliskiren (3 and 0.3 mg/kg per day)-treated and valsartan (Val; 10 and 1 mg/kg per day)-treated rats. Treatment was from week 6 through week 9. At week 6, all groups had elevated systolic blood pressure (BP). Untreated dTGR showed increased BP (202±4 mm Hg), serum creatinine, and albuminuria (34±5.7 mg per day) at week 7. At week 9, both doses of aliskiren lowered BP (115±6 and 139±5 mm Hg) and albuminuria (0.4±0.1 and 1.6±0.6 mg per day) and normalized serum creatinine. Although high-dose Val lowered BP (148±4 mm Hg) and albuminuria (2.1±0.7 mg per day), low-dose Val reduced BP (182±3 mm Hg) and albuminuria (24±3.8 mg per day) to a lesser extent. Mortality was 100% in untreated dTGR and 26% in Val (1 mg/kg per day) treated rats, whereas in all other groups, survival was 100%. dTGR treated with low-dose Val had cardiac hypertrophy (4.4±0.1 mg/g), increased left ventricular (LV) wall thickness, and diastolic dysfunction. LV atrial natriuretic peptide and β-myosin heavy chain mRNA, albuminuria, fibrosis, and cell infiltration were also increased. In contrast, both aliskiren doses and the high-dose Val lowered BP to a similar extent and more effectively than low-dose Val. We conclude that in dTGR, equieffective antihypertensive doses of Val or aliskiren attenuated end-organ damage. Thus, renin inhibition compares favorably to angiotensin receptor blockade in reversing organ damage in dTGR.

Aldosterone Potentiates Angiotensin II–Induced Signaling in Vascular Smooth Muscle Cells

Background—In a double-transgenic human renin and human angiotensinogen rat model, we found that mineralocorticoid receptor (MR) blockade ameliorated angiotensin II (Ang II)–induced renal and cardiac damage. How Ang II and aldosterone (Ald) might interact is ill defined. Methods and Results—We investigated the effects of Ang II (10−7 mol/L) and Ald (10−7 mol/L) on extracellular signal–regulated kinase (ERK) and c-Jun N-terminal kinase (JNK) signaling in vascular smooth muscle cells (VSMCs) with Western blotting and confocal microscopy. Ang II induced ERK 1/2 and JNK phosphorylation by 2 minutes. Ald achieved the same at 10 minutes. Ang II+Ald had a potentiating effect by 2 minutes. Two oxygen radical scavengers and the epidermal growth factor receptor (EGFR) antagonist AG1478 reduced Ang II–, Ald-, and combination-induced ERK1/2 phosphorylation. Preincubating the cells with the MR blocker spironolactone (10−6 mol/L) abolished Ang II–induced ROS generation, EGFR transactivation, and ERK1/2 phosphorylation. Conclusions—Ald potentiates Ang II–induced ERK-1/2 and JNK phosphorylation. Oxygen radicals, the MR, and the EGFR play a role in early signaling induced by Ang II and Ald in VSMCs. These in vitro data may help explain the effects of MR blockade on Ang II–induced end-organ damage in vivo.

Mutations in the Human Muscle LIM Protein Gene in Families With Hypertrophic Cardiomyopathy

Background—Muscle LIM protein (MLP) is an essential nuclear regulator of myogenic differentiation. Additionally, it may act as an integrator of protein assembly of the actin-based cytoskeleton. MLP-knockout mice develop a marked cardiac hypertrophy reaction and dilated cardiomyopathy (DCM). MLP is therefore a candidate gene for heritable forms of hypertrophic cardiomyopathy (HCM) and DCM in humans. Methods and Results—We analyzed 1100 unrelated individuals (400 patients with DCM, 200 patients with HCM, and 500 controls) for mutations in the human CRP3 gene that encodes MLP. We found 3 different missense mutations in 3 unrelated patients with familial HCM but detected no mutation in the DCM group or the controls. All mutations predicted an amino acid exchange at highly conserved residues in the functionally important LIM1 domain, which is responsible for interaction with &agr;-actinin and with certain muscle-specific transcription factors. Protein-binding studies indicate that mutations in the CRP3 gene lead to a decreased binding activity of MLP to &agr;-actinin. All 3 index patients were characterized by typical asymmetrical septal hypertrophy. Family studies revealed cosegregation of clinically affected individuals with the respective mutations in MLP. Conclusion—Here, we present evidence that mutations in the CRP3/MLP gene can cause HCM.

Aspirin inhibits NF-κB and protects from angiotensin II- induced organ damage

Angiotensin (Ang)‐II induces vascular wall inflammation by activating NF‐κB. Aspirin inhibits IKKβ in vitro; however, the in vivo relevance of the phenomenon is unclear. We tested the hypothesis that aspirin protects from Ang II‐induced endorgan damage by inhibiting NF‐κB activation in vivo. Rats harboring human renin and angiotensinogen genes received high‐ (600 mg/kg/day) or low‐ (25 mg/kg/day) dose aspirin. High‐dose aspirin reduced mortality, cardiac hypertrophy, fibrosis, and albuminuria independent of blood pressure, whereas both doses reduced cyclooxygenase activity. High‐dose aspirin inhibited NF‐κB and AP‐1 activation and inflammation in heart and kidney. These in vivo results serve to explain the clinical utility of high‐dose aspirin in inflammatory disorders and suggest additional therapeutic avenues that may be relevant to cardiovascular disease.

Measurement of left ventricular dimensions and function in patients with dilated cardiomyopathy

Studies on medical therapy in heart failure are focused on changes of left ventricular (LV) dimensions and function. These changes may be small, requiring a large study group. We measured LV parameters (LV volumes, LV ejection fraction (LV‐EF), and left ventricular mass (LVM)) with two‐dimensional echocardiography (2D‐echo) and magnetic resonance imaging (MRI) in 50 patients. Based on the difference between the measurements, we determined the variance of the results and calculated the sample sizes needed to detect changes of baseline values. For the calculated and measured parameters we found significant differences between the two techniques: LV‐EF and LVM were higher in 2D‐echo, and LV dimensions were comparable. The sample size to detect relevant changes from baseline with MRI was significantly (P < 0.01) smaller than in 2D‐echo. We conclude that MRI is superior in clinical studies on left ventricular dimensional and functional changes, since measurements are more reproducible and the required sample size is substantially smaller, thereby reducing costs. J. Magn. Reson. Imaging 2001;13:367–371.

Stabilization of hypoxia inducible factor rather than modulation of collagen metabolism improves cardiac function after acute myocardial infarction in rats

Prolyl hydroxylase domain‐containing enzymes (PHD) hydroxylate a proline residue that controls the degradation of hypoxia inducible factor (HIF). Hypoxia inhibits this hydroxylation thus increasing HIF levels. HIF is upregulated in ischemic tissues, growing tumors and in nonischemic, mechanically stressed myocardium. Pharmacological inhibition of prolyl 4‐hydroxylase (P4‐H) stabilizes HIF‐protein in vitro and may modulate collagen turnover. The aims of this study were to investigate whether inhibition of P4‐H protects myocardium against ischemia, and whether the observed effects are related to modulation of collagen metabolism or due to the stabilization of HIF.

Left Ventricular Outflow Tract Planimetry by Cardiovascular Magnetic Resonance Differentiates Obstructive from Non-Obstructive Hypertrophic Cardiomyopathy

The relation to the pressure gradient as assessed by echocardiography and the CMR-derived planimetry of the LVOT is not known, no values for the differentiation of obstruction exist. We studied 37 patients with hypertrophic cardiomyopathy and 14 healthy controls using standard sequences with 3D coverage of the left ventricular outflow tract. A cutoff value of 2.7 cm2 identified obstruction as defined by echocardiography with 100% accuracy. CMR planimetry at rest is a promising tool to evaluate patients with hypertrophic cardiomyopathy.

Endothelin-Converting Enzyme Inhibition Ameliorates Angiotensin II–Induced Cardiac Damage

Abstract—We tested the hypothesis that endothelin-converting enzyme (ECE) inhibition ameliorates end-organ damage in rats harboring both human renin and human angiotensinogen genes (dTGR). Hypertension develops in the animals, and they die by age 7 weeks of heart and kidney failure. Three groups were studied: dTGR (n=12) receiving vehicle, dTGR receiving ECE inhibitor (RO0687629; 30 mg/kg by gavage; n=10), and Sprague-Dawley control rats (SD; n=10) receiving vehicle, all after week 4, with euthanasia at week 7. Systolic blood pressure was not reduced by ECE inhibitor compared with dTGR (205±6 versus 206±6 mm Hg at week 7, respectively). In contrast, ECE inhibitor treatment significantly reduced mortality rate to 20% (2 of 10), whereas untreated dTGR had a 52% mortality rate (7 of 12). ECE inhibitor treatment ameliorated cardiac damage and reduced left ventricular ECE activity below SD levels. Echocardiography at week 7 showed reduced cardiac hypertrophy (4.8±0.2 versus 5.7±0.2 mg/g, P <0.01) and increased left ventricular cavity diameter (5.5±0.3 versus 3.1±0.1 mm, P <0.001) and filling volume (0.42±0.04 versus 0.16±0.06 mL, P <0.05) after ECE inhibitor compared with untreated dTGR. ECE inhibitor treatment also reduced cardiac fibrosis, tissue factor expression, left ventricular basic fibroblast growth factor mRNA levels, and immunostaining in the vessel wall, independent of high blood pressure. In contrast, the ECE inhibitor treatment showed no renoprotective effect. These data are the first to show that ECE inhibition reduces angiotensin II–induced cardiac damage.

Low-dose renin inhibitor and low-dose AT1-receptor blocker therapy ameliorate target-organ damage in rats harbouring human renin and angiotensinogen genes

We studied the effects of extremely low-dose human renin inhibition (aliskiren) with low angiotensin II receptor blockade (losartan) in a novel double-transgenic rat model harbouring both human renin and angiotensinogen genes. We found that low-dose aliskiren and low-dose losartan effectively reduced mortality and target-organ damage with minimal, non-significant, effects on blood pressure (BP). Our data suggest that renin-angiotensin system (RAS) inhibition ameliorates target-organ damage in an Ang II-driven model of hypertension. Direct renin inhibition is equally efficacious in this regard. Our study does not fully answer the question of BP-lowering versus RAS inhibition. This question is important and was at least partially addressed with our low-dose model.

Percutaneous transluminal septal artery ablation using polyvinyl alcohol foam particles for septal hypertrophy in patients with hypertrophic obstructive cardiomyopathy: acute and 3-year outcomes.

Purpose: To investigate the effect of septal artery occlusion with transluminally delivered polyvinyl alcohol (PVA) foam particles for the treatment of hypertrophic obstructive cardiomyopathy (HOCM). Methods: Percutaneous septal artery ablation was performed in 18 symptomatic patients (13 men; mean age 60±17 years, range 28–89) with drug-resistant HOCM. PVA foam particles were mixed with contrast medium and injected through an angiographic catheter under fluoroscopic control until complete stasis in the septal branch was achieved. Patients were monitored with echocardiography and cardiovascular magnetic resonance imaging. Results: The septal artery was successfully occluded in all patients; no embolization of other coronary branches occurred after infusion of 3 to 8 mL (5.2±0.8) of PVA foam particles. The resting pressure gradient was diminished from 83±32 to 31±35 mmHg (p<0.05). Over a mean follow-up of 44±4 months, all patients had symptomatic improvement of their dyspnea and workload without the need for intensified drug therapy. The average NYHA functional class decreased from 3.3±0.5 to 1.3±0.7 (p<0.0001), with a significant increase in the area of the left ventricular outflow tract (1.3±0.2 to 2.6±0.2 cm2, p<0.0001). Three instances of transient atrioventricular block occurred, but no complete heart block was produced by the embolization procedure. Conclusions: Embolization of the septal artery with PVA foam particles appears effective and safe in this series of patients with hypertrophic obstructive cardiomyopathy. The pure ischemic infarction produced by PVA ablation might be the responsible for the lack of complete heart block and the need for permanent pacing.