Soluble Guanylate Cyclase Stimulation Prevents Fibrotic Tissue Remodeling and Improves Survival in Salt-Sensitive Dahl Rats

A direct pharmacological stimulation of soluble guanylate cyclase (sGC) is an emerging therapeutic approach to the management of various cardiovascular disorders associated with endothelial dysfunction. Novel sGC stimulators, including riociguat (BAY 63-2521), have a dual mode of action: They sensitize sGC to endogenously produced nitric oxide (NO) and also directly stimulate sGC independently of NO. Little is known about their effects on tissue remodeling and degeneration and survival in experimental malignant hypertension.Mortality, hemodynamics and biomarkers of tissue remodeling and degeneration were assessed in Dahl salt-sensitive rats maintained on a high salt diet and treated with riociguat (3 or 10 mg/kg/d) for 14 weeks. Riociguat markedly attenuated systemic hypertension, improved systolic heart function and increased survival from 33% to 85%. Histological examination of the heart and kidneys revealed that riociguat significantly ameliorated fibrotic tissue remodeling and degeneration. Correspondingly, mRNA expression of the pro-fibrotic biomarkers osteopontin (OPN), tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and plasminogen activator inhibitor-1 (PAI-1) in the myocardium and the renal cortex was attenuated by riociguat. In addition, riociguat reduced plasma and urinary levels of OPN, TIMP-1, and PAI-1.Stimulation of sGC by riociguat markedly improves survival and attenuates systemic hypertension and systolic dysfunction, as well as fibrotic tissue remodeling in the myocardium and the renal cortex in a rodent model of pressure and volume overload. These findings suggest a therapeutic potential of sGC stimulators in diseases associated with impaired cardiovascular and renal functions

Angiotensin Type 2 Receptor Stimulation Ameliorates Left Ventricular Fibrosis and Dysfunction via Regulation of Tissue Inhibitor of Matrix Metalloproteinase 1/Matrix Metalloproteinase 9 Axis and Transforming Growth Factor β1 in the Rat Heart

Left ventricular (LV) remodeling is the main reason for the development of progressive cardiac dysfunction after myocardial infarction (MI). This study investigated whether stimulation of the angiotensin type 2 receptor is able to ameliorate post-MI cardiac remodeling and what the underlying mechanisms may be. MI was induced in Wistar rats by permanent ligation of the left coronary artery. Treatment with the angiotensin type 2 receptor agonist compound 21 ( 0.03 mg/kg) was started 6 hours post-MI and continued for 6 weeks. Hemodynamic parameters were measured by echocardiography and intracardiac catheter. Effects on proteolysis were studied in heart tissue and primary cardiac fibroblasts. Compound 21 significantly improved systolic and diastolic functions, resulting in improved ejection fraction (71.2±4.7% versus 53.4±7.0%; P &lt;0.001), fractional shortening ( P &lt;0.05), LV internal dimension in systole ( P &lt;0.05), LV end-diastolic pressure (16.9±1.2 versus 22.1±1.4 mm Hg; P &lt;0.05), ratio of early (E) to late (A) ventricular filling velocities, and maximum and minimum rate of LV pressure rise ( P &lt;0.05). Compound 21 improved arterial stiffness parameters and reduced collagen content in peri-infarct myocardium. Tissue inhibitor of matrix metalloproteinase 1 was strongly upregulated, whereas matrix metalloproteinases 2 and 9 and transforming growth factor β1 were diminished in LV of treated animals. In cardiac fibroblasts, compound 21 initially induced tissue inhibitor of matrix metalloproteinase 1 expression followed by attenuated matrix metalloproteinase 9 and transforming growth factor β1 secretion. In conclusion, angiotensin type 2 receptor stimulation improves cardiac function and prevents cardiac remodeling in the late stage after MI, suggesting that angiotensin type 2 receptor agonists may be considered a future pharmacological approach for the improvement of post-MI cardiac dysfunction. </jats:p

Neue Therapieansätze für die Behandlung hypertensiver Endorganschädigung in tierexperimentellen Modellen der Hypertonie

Hypertension and the associated target organ damage remain uncontrolled in many affected patients despite receiving an optimal therapy. This has spurred the search for new agents that can effectively control blood pressure and reduce target organ damage. The aims of this work were to examine protective effects of three new pharmacological agents representing different pathways for antihypertensive treatments. We analyzed the effects of riociguat, a novel stimulator of the soluble guanylate cyclase (sGC); SLV338, the combined inhibitor of neutral endopeptidase (NEP) and endothelin-converting enzyme (ECE); and the novel adenosine A1 receptor antagonist, SLV320, in experimental models of hypertension and chronic renal failure. The cardio- and renoprotective effects of riociguat were evaluated in hypertensive renin- transgenic rats with additional blockade of the nitric oxide (NO) system by the nitric oxide-synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME) (high-renin model), and in rats with 5/6 nephrectomy (NX) (low-renin model). The cardioprotective actions of SLV338 were evaluated in experimental renovascular hypertension (2-kidney, 1-clip [2K1C] model).The protective effects of SLV320 were examined in the heart and kidney of rats with 5/6 nephrectomy (NX). Riociguat treatment improved the survival rate, normalized blood pressure, improved renal function and significantly ameliorated fibrotic tissue remodeling in the heart and kidney in the low- and high-renin models. Treatment with the dual ECE/NEP inhibitor SLV338 completely normalized cardiac interstitial fibrosis, perivascular fibrosis, myocyte diameter and media-to- lumen ratio of cardiac arteries, and it attenuated cardiac transforming growth factor- ß1 expression. These effects were similar to those of losartan. The observed cardioprotective benefits of SLV338 were independent of blood pressure. The A1 receptor antagonist SLV320 significantly decreased cardiac fibrosis and albuminuria in rats with 5/6 NX. These protective effects occurred without changes in blood pressure. In summary, these results demonstrate that the sGC stimulator riociguat, the combined inhibitor of NEP/ECE SLV338, and the adenosin A1 receptor antagonist SLV 320 play important roles in cardio-renal protection in experimental models of hypertension and chronic renal failure. In the future, these approaches need to be balanced with the established beneficial effects of current antihypertensive therapies.Arterielle Hypertonie und die damit assoziierten Organschäden bleiben bei vielen betroffenen Patienten unkontrolliert, obwohl sie eine optimale Therapie erhalten. Die Entwicklung neuer, wirksamerer Arzneimittel zur Kontrolle des Blutdrucks ist daher nach wie vor erforderlich. Das Ziel dieser Arbeit war die Auswertung der protektiven Effekte dreier, sich momentan in der Entwicklungsphase befindender Pharmaka. Es wurden Substanzen ausgewählt, die in verschiedene Signalketten eingreifen: Riociguat, ein neuer Stimulator der löslichen Guanylatcyclase (sGC); SLV338, ein kombinierter Hemmer der neutralen Endopeptidase (NEP) und des Endothelin converting enzyme (ECE); SLV 320, ein Adenosin-A1-Rezeptorantagonist. Die protektive Wirkung dieser Substanzen auf hypertensive Organschäden und chronische Niereninsuffizienz wurde mit Hilfe von tierexperimentellen Modellen der Hypertonie evaluiert. Kardio- und nephroprotektive Wirkungen von Riociguat wurden an hypertensiven Ratten mit Überexpression von Renin und zusätzlicher Blockade des Stickstoffmonoxid (NO) Systems durch N-nitro-L-arginine methyl ester (L-NAME), einem hoch-Renin- Modell, und an Ratten mit 5/6 Nephrectomie (NX), einem niedrig-Renin-Modell untersucht. Organprotektive Effekte von SLV320 auf Herz und Nieren wurden an Ratten mit 5/6 NX evaluiert. Die kardioprotektive Effekte von SLV338 wurden am Modell der renovaskulären Hypertonie (2-kidney, 1-clip [2K1C]) untersucht. Die Therapie mit Riociguat führte zur Verbesserung der Überlebensrate, Normalisierung des Blutdrucks, Verbesserung der Nierenfunktion und zu einer signifikanten Verringerung der Fibrose in Herz und Nieren sowohl im niedrig- als auch im hoch-Renin-Modell. Die Therapie mit SLV338 führte zur vollständigen Normalisierung der interstitiellen Fibrose des Herzens, der perivaskulären Fibrose, des Myozytendurchmessers, des Media-Lumen- Verhältnisses von Herzkranzgefäßen, sowie zur Senkung der Expression von Transforming growth factor- ß1 bei hypertensiven 2K1C-Ratten. Ähnliche Effekte wies auch Losartan auf. Die kardioprotektiven Effekte von SLV338 waren blutdruckunabhängig. Die Therapie mit SLV320 führte zur signifikanten Reduktion der Herzfibrose und der Albuminurie bei Ratten mit 5/6 NX; diese Effekte waren nicht mit Veränderungen des Blutdrucks assoziiert. Zusammenfassend zeigen diese Resultate, dass der Stimulator der sGC, Riociguat, der kombinierte Hemmer der NEP und des ECE, SLV338, und der Antagonist des A1 Rezeptors, SLV320, wichtige Rollen in der Kardio- und Nephroprotektion bei experimenteller arterieller Hypertonie spielen können. Allerdings müssen die drei untersuchten Pharmaka zukünftig mit den positiven Effekten der aktuell etablierten antihypertensiven Therapien abgeglichen werden

Plasma biochemical measurements in the vehicle- and riociguat-treated Dahl/ss rats maintained on a high-salt diet.

<p>AST = aspartate amino transferase, ALT = alanine amino transferase, GLDH = glutamate dehydrogenase, LDH = lactate dehydrogenase, CK = creatinine kinase, PRA = plasma renin activity, ANP = atrial natriuretic peptide, BNP = B-type natriuretic peptide. Data are mean±SEM;</p><p>*p<0.05,</p><p>**p<0.01,</p><p>***p<0.001 vs. the vehicle-treated animals.</p

Histopathological evaluation of the hearts and kidneys from the vehicle- and riociguat-treated Dahl/ss rats maintained on a high-salt diet.

<p>Data are mean±SEM;</p><p>*p<0.05,</p><p>**p<0.01,</p><p>***p<0.001 vs. the vehicle-treated animals.</p

Effects of riociguat on plasma and urinary protein levels of osteopontin (OPN), plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in the vehicle (n = 7) - and riociguat-treated (3 or 10 mg/kg/d, n = 11 per group) Dahl/ss rats maintained on a high-salt diet.

<p>Healthy, age-matched animals were used as controls (n = 10). Data are mean±SEM; *p<0.05, **p<0.01, ***p<0.001 vs. the vehicle-treated animals; ##p<0.01, ###p<0.001 vs. healthy controls.</p