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

Evaluation of the Adulticidal Efficacy of Imidacloprid 10 %/Moxidectin 2.5 % (w/v) Spot-on (Advocate®, Advantage® Multi) against Dirofilaria repens in Experimentally Infected Dogs

This study aimed to evaluate the efficacy of imidacloprid 10 %/moxidectin 2.5 % (w/v) spot-on (Advocate®/Advantage® Multi, Bayer) against adult Dirofilaria repens in a blinded, placebo-controlled randomised laboratory study. Twenty-four Beagle dogs were experimentally infected with approximately 75 infective D. repens larvae each on study day (SD) 0. Treatment was initiated on SD 228 after patency had been confirmed in 21 dogs, using a modified Knott Test. Eleven dogs received monthly treatments with imidacloprid/moxidectin at the minimum therapeutic dose (10 mg/kg imidacloprid and 2.5 mg/kg moxidectin) for six consecutive months and 12 control dogs were treated with a placebo formulation. Approximately one month after the last treatment, all dogs were euthanised and necropsied for the detection of D. repens worms. Eleven control dogs harboured live adult D. repens (range 2-11, geometric mean 5.44). Eight of 11 imidacloprid/moxidectin-treated dogs were free of live worms. The live worm count was reduced by 96.2 % (range 0-1, geometric mean 0.21). The majority of dead worms were encapsulated and degenerated. After the first treatment, Knott Tests were negative in all imidacloprid/moxidectin-treated dogs and this status was maintained in 10 dogs until study end. One dog showed a low microfilariae count (1 and 4/mL) on four occasions but was also negative before necropsy. The treatment was well tolerated by all study animals. It is concluded that six consecutive monthly treatments with imidacloprid/moxidectin spot-on are effective and safe against adult D. repens and provide an option for preventing the further spread of this zoonotic parasit

Evaluation of the adulticidal efficacy of imidacloprid 10%/ moxidectin 2.5% spot-on (Advocate®, Advantage® Multi, Bayer) against Dirofilaria repens in experimentally infected dogs

This study aimed to evaluate the efficacy of imidacloprid 10%/moxidectin 2.5% spot-on (Advocate®/Advantage® Multi, Bayer) against adult Dirofilaria (D.) repens in a blinded, placebo controlled randomised laboratory study. 24 Beagle dogs were experimentally infected with approximately 75 infective D. repens larvae on study day (SD) 0. A modified Knott test was used in monthly intervals to monitor the onset of patency and to follow the course of microfilariaemia after treatment. Treatment was initiated on SD 228 after patency had been confirmed in 21 dogs. 11 dogs received monthly treatments with imidacloprid/moxidectin at the minimum therapeutic dose for six consecutive months and 12 control dogs were treated with a placebo formulation. Approximately one month after the last treatment, all dogs were euthanized and necropsied for the detection of D. repens worms. 11 control dogs harbored live adult D. repens (range 2-11, geometric mean 5.44). 8 of 11 imidacloprid/moxidectin treated dogs were free of live worms. The live worm count was reduced by 96.2% (range 0-1, geometric mean 0.21). The majority of dead worms was encapsulated and degenerated. After the first treatment, Knott Tests were negative in all imidacloprid/moxidectin treated dogs and this status was maintained in 10 dogs until study end. One dog showed a low microfilariae count (1 and 4/ml) on four occasions but was also negative before necropsy. The treatment was well tolerated in all study animals. It is concluded that six consecutive monthly treatments with imidacloprid/moxidectin topical solution are effective and safe against adult D. repens and provide an option for the prevention of further spreading of this zoonotic parasite

Chronic Activation of Heme Free Guanylate Cyclase Leads to Renal Protection in Dahl Salt-Sensitive Rats

<div><p>The nitric oxide (NO)/soluble guanylate cyclase (sGC)/cyclic guanosine monophasphate (cGMP)-signalling pathway is impaired under oxidative stress conditions due to oxidation and subsequent loss of the prosthetic sGC heme group as observed in particular in chronic renal failure. Thus, the pool of heme free sGC is increased under pathological conditions. sGC activators such as cinaciguat selectively activate the heme free form of sGC and target the disease associated enzyme. In this study, a therapeutic effect of long-term activation of heme free sGC by the sGC activator cinaciguat was investigated in an experimental model of salt-sensitive hypertension, a condition that is associated with increased oxidative stress, heme loss from sGC and development of chronic renal failure. For that purpose Dahl/ss rats, which develop severe hypertension upon high salt intake, were fed a high salt diet (8% NaCl) containing either placebo or cinaciguat for 21 weeks. Cinaciguat markedly improved survival and ameliorated the salt-induced increase in blood pressure upon treatment with cinaciguat compared to placebo. Renal function was significantly improved in the cinaciguat group compared to the placebo group as indicated by a significantly improved glomerular filtration rate and reduced urinary protein excretion. This was due to anti-fibrotic and anti-inflammatory effects of the cinaciguat treatment. Taken together, this is the first study showing that long-term activation of heme free sGC leads to renal protection in an experimental model of hypertension and chronic kidney disease. These results underline the promising potential of cinaciguat to treat renal diseases by targeting the disease associated heme free form of sGC.</p></div

Histological analysis of tissues from rats on a high salt diet with or without (placebo) cinaciguat.

<p>Respective sections of myocardial (a) and pulmonary (b) artery, kidney (c) and lung (d) are shown. Sections were HE-stained, kidney sections are additionally PAS-stained. Magnitude is given beyond the respective picture.</p

Results of M-Mode echocardiographic analysis performed one week before study end.

<p>Fractional shortening (a), diastolic (b) and systolic (c) diameter of the left ventricle, diametric increase between diastole and systole of the septum (d) and left free wall (e), conditions between septum and left free wall (f) as well as diastolic diameter of left free wall (g) and septum (h) were analysed in 14 (placebo) and 16 (cinaciguat) animals. Data are means ± SEM. ***p < 0.005: Student’s t-test (cinaciguat vs. placebo). 14 animals of the placebo group and 16 animals of the cinaciguat group were analyzed.</p

<i>In vivo</i>-parameters.

<p>Relative effects of oral treatment with cinaciguat on systolic blood pressure (a), heart rate (b), survival (c) and body weight (d) of Dahl/ss rats on high salt diet (8% NaCl). Data are shown as means ± SEM. Initial values of systolic blood pressure were 176.7 ± 3.6 mmHg and 182.8 ± 3.5 and heart rate were 409.4 ± 3.6 bpm and 407.2 ± 4.9 bpm in the placebo and the cinaciguat group, respectively. At beginning of the study animals weighed 335.5 ± 5.1 g and 339.9 ± 3.9 g in the placebo and the cinaciguat group, respectively. *<i>p</i> < 0.05; ***<i>p</i> < 0.005: Student’s <i>t</i>-test (cinaciguat vs. placebo).</p