The treatment with sGC stimulator improves survival of hypertensive rats in response to volume-overload induced by aorto-caval fistula

Heart failure (HF) has been declared as global pandemic and current therapies are still ineffective, especially in patients that develop concurrent cardio-renal syndrome. Considerable attention has been focused on the nitric oxide (NO)/soluble guanylyl cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway. In the current study, we aimed to investigate the effectiveness of sGC stimulator (BAY41-8543) with the same mode of action as vericiguat, for the treatment of heart failure (HF) with cardio-renal syndrome. As a model, we chose heterozygous Ren-2 transgenic rats (TGR), with high-output heart failure, induced by aorto-caval fistula (ACF). The rats were subjected into three experimental protocols to evaluate short-term effects of the treatment, impact on blood pressure, and finally the long-term survival lasting 210 days. As control groups, we used hypertensive sham TGR and normotensive sham HanSD rats. We have shown that the sGC stimulator effectively increased the survival of rats with HF in comparison to untreated animals. After 60 days of sGC stimulator treatment, the survival was still 50% compared to 8% in the untreated rats. One-week treatment with sGC stimulator increased the excretion of cGMP in ACF TGR (109 ± 28 nnmol/12 h), but the ACE inhibitor decreased it (-63 ± 21 nnmol/12 h). Moreover, sGC stimulator caused a decrease in SBP, but this effect was only temporary (day 0: 117 ± 3; day 2: 108 ± 1; day 14: 124 ± 2 mmHg). These results support the concept that sGC stimulators might represent a valuable class of drugs to battle heart failure especially with cardio-renal syndrome, but further studies are necessary.

Endothelin type A receptor blockade attenuates aorto-caval fistula-induced heart failure in rats with angiotensin II-dependent hypertension

OBJECTIVE

Evaluation of the effect of endothelin type A (ET A ) receptor blockade on the course of volume-overload heart failure in rats with angiotensin II-dependent hypertension.

METHODS

Ren-2 renin transgenic rats (TGR) were used as a model of hypertension. Heart failure was induced by creating an aorto-caval fistula (ACF). Selective ET A receptor blockade was achieved by atrasentan. For comparison, other rat groups received trandolapril, an angiotensin-converting enzyme inhibitor (ACEi). Animals first underwent ACF creation and 2 weeks later the treatment with atrasentan or trandolapril, alone or combined, was applied; the follow-up period was 20 weeks.

RESULTS

Eighteen days after creating ACF, untreated TGR began to die, and none was alive by day 79. Both atrasentan and trandolapril treatment improved the survival rate, ultimately to 56% (18 of 31 animals) and 69% (22 of 32 animals), respectively. Combined ACEi and ET A receptor blockade improved the final survival rate to 52% (17 of 33 animals). The effects of the three treatment regimens on the survival rate did not significantly differ. All three treatment regimens suppressed the development of cardiac hypertrophy and lung congestion, decreased left ventricle (LV) end-diastolic volume and LV end-diastolic pressure, and improved LV systolic contractility in ACF TGR as compared with their untreated counterparts.

CONCLUSION

The treatment with ET A receptor antagonist delays the onset of decompensation of volume-overload heart failure and improves the survival rate in hypertensive TGR with ACF-induced heart failure. However, the addition of ET A receptor blockade did not enhance the beneficial effects beyond those obtained with standard treatment with ACEi alone.

Effects of renal nerves and plasma epoxyeicosatrienoic acids on blood pressure, renal hemodynamics and excretion in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) display deficiency of epoxyeicosatrienoic acids (EETs). Their possible interaction with renal sympathetic nerves remains unexplored; synthesis of EET-A [disodium (S)-2-(13-(3-pentyl)ureido)-tridec-8(Z)-enamido)succinate], a stable 14,15-EET analog, helps clarify the issue. In anesthetized SHR, untreated or pretreated with EET-A, we assessed early responses of blood pressure (MAP), renal hemodynamics and excretion, and indices of nitric oxide (NO) activity, to bilateral noninvasive renal denervation (DNX). DNX significantly decreased MAP, with or without EET-A pretreatment. Renal perfusion decreased in EET-A treated but not in control rats. After EET-A pretreatment DNX decreased renal excretion of sodium and total solutes, compared to increasing tendency in untreated rats. In EET-A treated but not in untreated SHR denervation reduced the excretion of NO metabolites. Antihypertensive action of EET-A in anesthetized SHR was not clearly dependent on renal nerve activity. On the other hand, DNX unmasked the unexpected effect of EET-A to lower renal perfusion. The mechanism of this novel finding is unclear, as is also the simultaneous post-denervation decrease in renal excretion, again, observed only under EET-A treatment. Possibly, the decrease was secondary to falling MAP and renal perfusion. Increased renal excretion of nitric oxide metabolites under EETs elevation strongly suggests facilitation of NO release; the effect that was observed only with intact renal nerve activity.

Epoxyeicosatrienoic Acid Analog and 20-HETE Antagonist Combination Prevent Hypertension Development in Spontaneously Hypertensive Rats

Numerous studies indicate a significant role for cytochrome P-450-dependent arachidonic acid metabolites in blood pressure regulation, vascular tone, and control of renal function. Epoxyeicosatrienoic acids (EETs) exhibit a spectrum of beneficial effects, such as vasodilatory activity and anti-inflammatory, anti-fibrotic, and anti-apoptotic properties. 20-Hydroxyeicosatetraenoic acid (20-HETE) is a potent vasoconstrictor that inhibits sodium reabsorption in the kidney. In the present study, the efficiency of EET-A (a stable analog of 14,15-EET) alone and combined with AAA, a novel receptor antagonist of 20-HETE, was tested in spontaneously hypertensive rats (SHR). Adult SHR (16 weeks old) were treated with two doses of EET-A (10 or 40 mg/kg/day). In the following experiments, we also tested selected substances in the prevention of hypertension development in young SHR (6 weeks old). Young rats were treated with EET-A or the combination of EET-A and AAA (both at 10 mg/kg/day). The substances were administered in drinking water for 4 weeks. Blood pressure was measured by telemetry. Once-a-week observation in metabolic cages was performed; urine, blood, and tissue samples were collected for further analysis. The combined treatment with AAA + EET-A exhibited antihypertensive efficiency in young SHR, which remained normotensive until the end of the observation in comparison to a control group (systolic blood pressure, 134 ± 2 versus 156 ± 5 mmHg, respectively; p < 0.05). Moreover the combined treatment also increased the nitric oxide metabolite excretion. Considering the beneficial impact of the combined treatment with EET-A and AAA in young rats and our previous positive results in adult SHR, we suggest that it is a promising therapeutic strategy not only for the treatment but also for the prevention of hypertension.

Role of chymase in blood pressure control, plasma and tissue angiotensin II, renal Haemodynamics, and excretion in spontaneously hypertensive rats

Background: Chymase generates angiotensin II (ANG II) independently of angiotensin-converting enzyme in tissues and it contributes to vascular remodeling and development of hypertension, however the exact mechanism of its action is unclear. Methods: Hence, the effects of chymase inhibition were examined in anesthetized spontaneously hypertensive rats (SHR) in two stages of the disease development, ie. pre-hypertensive (SHR7) and with established hypertension (SHR16). Chymostatin, a commercial chymase inhibitor, was infused intravenously alone or in subsequent groups co-infused with captopril. Results: Mean blood pressure (MBP), total renal blood flow (RBF) and ANG II content (plasma and tissues) were measured. In SHR16 chymase blockade significantly decreased MBP (-6%) and plasma (-38%), kidney (-71%) and heart (-52%) ANG II levels. In SHR7 chymostatin did not influence MBP or RBF, but significantly decreased heart ANG II level. Conclusion: Jointly, functional studies and ANG II determinations support the evidence that in SHR chymase can raise plasma ANG II and contribute to blood pressure elevation. We propose that addition of chymase blockade to ACE inhibition could be a promising approach in the treatment of hypertensive patients resistant to therapy with ACE-inhibitors alone.

Chymase Dependent Pathway of Angiotensin II Generation and Rapeseed Derived Peptides for Antihypertensive Treatment of Spontaneously Hypertensive Rats

The contribution of chymase, one of the enzymes responsible for angiotensin II generation in non-ACE pathway, remains unclear in the development of hypertension. The aim of the study was to investigate chymase inhibition as potential antihypertensive therapy in spontaneously hypertensive rats (SHR). To block chymase we employed chymostatin, a commercial inhibitor, and new analogues of rapeseed-derived peptides, VWIS and RIY. These simple and easy to obtain peptides not only block chymase, but also possess weak activity to inhibit ACE. This is a first attempt to evaluate the impact of chronic administration of selected inhibitors on blood pressure of SHR in two phases of hypertension. Male SHR (6 or 16 weeks old) were treated daily for two weeks with chymostatin (CH; 2 mg/kg/day), the peptides VWIS (12.5 mg/kg/day) or RIY (7.5 mg/kg/day); control groups received chymostatin solvent (0.15% DMSO in saline) or peptide solvent (saline). The substances were administered intravenously to conscious animals via a chronically cannulated femoral vein. Systolic blood pressure (SBP) was measured by telemetry. Metabolic parameters were measured weekly, and tissue samples were harvested after two weeks of treatment. None of the administered chymase inhibitors affected the development of hypertension in young rats. Only RIY exhibited beneficial properties when administered in the established phase of hypertension: SBP decreased from 165 ± 10 to 157 ± 7 mmHg while the excretion of nitric oxide metabolites increased significantly. The glomerulosclerosis index was lower after RIY treatment in both age groups (significant only in young rats 0.29 ± 0.05 vs 0.48 ± 0.04 in the control group; p < 0.05). Hence, it seems that peptide RIY exhibits some positive effect on renal morphology. The results obtained suggest that the peptide RIY may be a useful tool in the treatment of hypertension, especially in cases when ACE inhibitors are not effective.

Effects of renal sympathetic denervation on the course of congestive heart failure combined with chronic kidney disease: Insight from studies with fawn-hooded hypertensive rats with volume overload induced using aorto-caval fistula

Background: The coincidence of congestive heart failure (CHF) and chronic kidney disease (CKD) results in poor survival rate. The aim of the study was to examine if renal denervation (RDN) would improve the survival rate in CHF induced by creation of aorto-caval fistula (ACF).Methods: Fawn-hooded hypertensive rats (FHH), a genetic model of spontaneous hypertension associated with CKD development, were used. Fawn-hooded low-pressure rats (FHL), without CKD, served as controls. RDN was performed 4 weeks after creation of ACF and the follow-up period was 10 weeks.Results: We found that intact (non-denervated) ACF FHH exhibited survival rate of 58.8% (20 out of 34 rats), significantly lower than in intact ACF FHL (81.3%, 26/32 rats). In intact ACF FHL albuminuria remained stable throughout the study, whereas in ACF FHH it increased significantly, up to a level 40-fold higher than the basal values. ACF FHL did not show increases in renal glomerular and tubulointerstitial injury as compared with FHL, while ACF FHH exhibited marked increases in kidney injury as compared with FHH. RDN did not improve the survival rate in either ACF FHL or ACF FHH and did not alter the course of albuminuria in ACF FHL. RDN attenuated the albuminuria, but did not reduce the kidney injury in ACF FHH.Conclusions: Our present results support the notion that even modest CKD increases CHF-related mortality. RDN did not attenuate CHF-dependent mortality in ACF FHH, it delayed the progressive rise in albuminuria, but it did not reduce the degree of kidney injury.

Renal Sympathetic Denervation Attenuates Congestive Heart Failure in Angiotensin II-Dependent Hypertension: Studies with Ren-2 Transgenic Hypertensive Rats with Aortocaval Fistula

OBJECTIVE

We examined if renal denervation (RDN) attenuates the progression of aortocaval fistula (ACF)-induced heart failure or improves renal hemodynamics in Ren-2 transgenic rats (TGR), a model of angiotensin II (ANG II)-dependent hypertension.

METHODS

Bilateral RDN was performed 1 week after creation of ACF. The animals studied were ACF TGR and sham-operated controls, and both groups were subjected to RDN or sham denervation. In separate groups, renal artery blood flow (RBF) responses were determined to intrarenal ANG II (2 and 8 ng), norepinephrine (NE) (20 and 40 ng) and acetylcholine (Ach) (10 and 40 ng) 3 weeks after ACF creation.

RESULTS

In nondenervated ACF TGR, the final survival rate was 10 versus 50% in RDN rats. RBF was significantly lower in ACF TGR than in sham-operated TGR (6.2 ± 0.3 vs. 9.7 ± 0.5 mL min-1 g-1, p < 0.05), the levels unaffected by RDN. Both doses of ANG II decreased RBF more in ACF TGR than in sham-operated TGR (-19 ± 3 vs. -9 ± 2% and -47 ± 3 vs. -22 ± 2%, p < 0.05 in both cases). RDN did not alter RBF responses to the lower dose, but increased it to the higher dose of ANG II in sham-operated as well as in ACF TGR. NE comparably decreased RBF in ACF TGR and sham-operated TGR, and RDN increased RBF responsiveness. Intrarenal Ach increased RBF significantly more in ACF TGR than in sham-operated TGR (29 ± 3 vs. 17 ± 3%, p < 0.05), the changes unaffected by RDN. ACF creation induced marked bilateral cardiac hypertrophy and lung congestion, both attenuated by RDN. In sham-operated but not in ACF TGR, RDN significantly decreased mean arterial pressure.

CONCLUSION

The results show that RDN significantly improved survival rate in ACF TGR; however, this beneficial effect was not associated with improvement of reduced RBF or with attenuation of exaggerated renal vascular responsiveness to ANG II.

Deleterious Effects of Hyperactivity of the Renin-Angiotensin System and Hypertension on the Course of Chemotherapy-Induced Heart Failure after Doxorubicin Administration: A Study in Ren-2 Transgenic Rat

Doxorubicin's (DOX) cardiotoxicity contributes to the development of chemotherapy-induced heart failure (HF) and new treatment strategies are in high demand. The aim of the present study was to characterize a DOX-induced model of HF in Ren-2 transgenic rats (TGR), those characterized by hypertension and hyperactivity of the renin-angiotensin-aldosterone system, and to compare the results with normotensive transgene-negative, Hannover Sprague-Dawley (HanSD) rats. DOX was administered for two weeks in a cumulative dose of 15 mg/kg. In HanSD rats DOX administration resulted in the development of an early phase of HF with the dominant symptom of bilateral cardiac atrophy demonstrable two weeks after the last DOX injection. In TGR, DOX caused substantial impairment of systolic function already at the end of the treatment, with further progression observed throughout the experiment. Additionally, two weeks after the termination of DOX treatment, TGR exhibited signs of HF characteristic for the transition stage between the compensated and decompensated phases of HF. In conclusion, we suggest that DOX-induced HF in TGR is a suitable model to study the pathophysiological aspects of chemotherapy-induced HF and to evaluate novel therapeutic strategies to combat this form of HF, which are urgently needed.

Polyprenol-Based Lipofecting Agents for In Vivo Delivery of Therapeutic DNA to Treat Hypertensive Rats

Development of efficient vectors for transfection is one of the major challenges in genetic engineering. Previous research demonstrated that cationic derivatives of polyisoprenoids (PTAI) may serve as carriers of nucleic acids. In the present study, the effectiveness of two PTAI-based formulations (PTAI-6–8 and 10–14) was investigated and compared to the commercial reagents. The purpose of applied gene therapy was to enhance the expression of vascular endothelial growth factor (VEGF-A) in the renal medulla of spontaneously hypertensive rats (SHR) and to test its potential as a novel antihypertensive intervention. In the first part of the study (in vitro), we confirmed that PTAI-based lipoplexes efficiently transfect XC rat sarcoma cells and are stable in 37 °C for 7 days. In the in vivo experiments, we administered selected lipoplexes directly to the kidneys of conscious SHR (via osmotic pumps). There were no blood pressure changes and VEGF-A level in renal medulla was significantly higher only for PTAI-10–14-based formulation. In conclusion, despite the promising results, we were not able to achieve VEGF-A expression level high enough to verify VEGF-A gene therapy usefulness in SHR. However, results of our study give important indications for the future development of PTAI-based DNA carriers and kidney-targeted gene delivery.