Stimulation of soluble guanylyl cyclase by BAY 41-2272 relaxes anococcygeus muscle: interaction with nitric oxide

BAY 41-2272 activates host defence against local and disseminated Candida albicans infections

In our previous study, we have found that 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]-pyrimidin-4-ylamine (BAY 41-2272), a guanylate cyclase agonist, activates human monocytes and the THP-1 cell line to produce the superoxide anion, increasing in vitro microbicidal activity, suggesting that this drug can be used to modulate immune functioning in primary immunodeficiency patients. In the present work, we investigated the potential of the in vivo administration of BAY 41-2272 for the treatment of Candida albicans and Staphylococcus aureus infections introduced via intraperitoneal and subcutaneous inoculation. We found that intraperitoneal treatment with BAY 41-2272 markedly increased macrophage-dependent cell influx to the peritoneum in addition to macrophage functions, such as spreading, zymosan particle phagocytosis and nitric oxide and phorbol myristate acetate-stimulated hydrogen peroxide production. Treatment with BAY 41-2272 was highly effective in reducing the death rate due to intraperitoneal inoculation of C. albicans, but not S. aureus. However, we found that in vitro stimulation of peritoneal macrophages with BAY 41-2272 markedly increased microbicidal activities against both pathogens. Our results show that the prevention of death by the treatment of C. albicans-infected mice with BAY 41-2272 might occur primarily by the modulation of the host immune response through macrophage activation.

Beneficial effect of the soluble guanylyl cyclase stimulator BAY 41-2272 on impaired penile erection in db/db-/- type II diabetic and obese mice

Type 2 diabetes mellitus (DM2) and obesity are major risk factors for erectile dysfunction (ED). In diabetes, increased oxidative stress leads to decreased nitric oxide (NO) bioavailability, and diabetic patients appear to be less responsive to conventional therapy with phosphodiesterase type 5 inhibitors. We investigated whether the soluble guanylyl cyclase stimulator BAY 41-2272 (5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4ylamine) is effective in improving impaired corpus cavernosum (CC) relaxation in obese DM2 mice by reducing oxidative stress. Adult db/db(-/-) mice or their lean db(/+) littermates were used to assess vascular function, cGMP levels, antioxidant status, NADPH oxidase expression, and superoxide formation in the absence or presence of BAY 41-2272. Results showed that BAY 41-2272 (10(-8) to 10(-5) M) potently relaxed CC from db(/+) or db/db(-/-) mice in a similar manner. BAY 41-2272 significantly enhanced both endothelium-dependent and nitrergic relaxation induced by electrical field stimulation (EFS), and improved the impaired relaxation to acetylcholine and EFS in the diabetic animals in a concentration-dependent manner (10(-8) to 10(-7) M). BAY 41-2272 increased cGMP levels and potentiated relaxation responses to exogenous NO in CC. Total antioxidant status was reduced in plasma and urine whereas expression of vascular NADPH oxidase subunits (gp91phox, p22phox, and p47phox) was increased in the CC of db/db(-/-) mice, suggesting a state of oxidative stress. These effects were prevented by BAY 41-2272 in a concentration-dependent manner. These results suggest that BAY 41-2272 improves CC relaxation in db/db(-/-) mice by increasing cGMP and augmenting antioxidant status, making this drug is a potential novel candidate to treat ED.

Heme-dependent and independent soluble guanylate cyclase activators and vasodilation

Since the discovery of nitric oxide (NO), which is released from endothelial cells as the main mediator of vasodilation, its target, the soluble guanylyl cyclase (sGC), has become a focus of interest for the treatment of diseases associated with endothelial dysfunction. NO donors were developed to suppress NO deficiency; however, tolerance to organic nitrates was reported. Non-NO-based drugs targeting sGC were developed to overcome the problem of tolerance. In this review, we briefly describe the process of sGC activation by its main physiological activator NO and the advances in the development of drugs capable of activating sGC in a NO-independent manner. sGC stimulators, as some of these drugs are called, require the integrity of the reduced heme moiety of the prosthetic group within the sGC and therefore are called heme-dependent stimulators. Other drugs are able to activate sGC independent of heme moiety and are hence called heme-independent activators. Because pathologic conditions modulate sGC and oxidize the heme moiety, the heme-independent sGC activators could potentially become drugs of choice because of their higher affinity to the oxidized enzyme. However, these drugs are still undergoing clinical trials and are not available for clinical use.

Evaluation of the relaxant effect of the nitric oxide-independent soluble guanylyl cyclase stimulator BAY 41-2272 in isolated detrusor smooth muscle

The nitric oxide (NO)-independent soluble guanylyl cyclase stimulator stimulator BAY 41-2272 was reported to produce relaxant response in different types of smooth muscle. However no study was carried out to investigate the effects of BAY 412282 in detrusor smooth muscle. Thus, this study aimed to evaluate the relaxant effects of BAY 41-2272, in isolated mouse, rat and rabbit detrusor smooth muscle. Mouse, rat and rabbit were anesthetized, and urinary bladder removed. Detrusor smooth muscle was transferred to 10-mL organ baths containing oxygenated and warmed Krebs-Henseleit solution. Tissues were connected to force-displacement transducers and changes in isometric force were recorded. BAY 41-2272 (0.001-100 microM) produced concentration-dependent detrusor smooth muscle relaxations in mouse, rat and rabbit with maximal responses of 61.3+/-6.6%, 95.1+/-9.9% and 91.7+/-5.9%, respectively. Sodium nitroprusside and glyceryl trinitrate, as well as 8-bromo-cGMP also produced detrusor relaxations, but to a much lesser extent than BAY 41-2272. The NO synthesis inhibitor L-NAME and the phosphodiesterase-5 inhibitor sildenafil had no effect in BAY 41-2272-induced responses. However, the soluble guanylyl cyclase inhibitor ODQ significantly reduced BAY 41-2272-induced relaxations. BAY 41-2272 increased the bladder cGMP levels by about of 14- and 20-fold for 10 and 100 microM, respectively, which were markedly reduced by ODQ. The cAMP levels were unaffected by BAY 41-2272. Moreover, BAY 41-2272 significantly reduced the contractile responses to extracellular Ca(2+) in an ODQ-insensitive manner. In conclusion, rabbit detrusor smooth muscle relaxations by BAY 41-2272 involve mainly cGMP production, but an additional mechanism involving Ca(2+) influx blockade independently of cGMP production appears to be involved.

NO-independent, haem-dependent soluble guanylate cyclase stimulators

The nitric oxide (NO) signalling pathway is altered in cardiovascular diseases, including systemic and pulmonary hypertension, stroke, and atherosclerosis. The vasodilatory properties of NO have been exploited for over a century in cardiovascular disease, but NO donor drugs and inhaled NO are associated with significant shortcomings, including resistance to NO in some disease states, the development of tolerance during long-term treatment, and non-specific effects such as post-translational modification of proteins. The development of pharmacological agents capable of directly stimulating the NO receptor, soluble guanylate cyclase (sGC), is therefore highly desirable. The benzylindazole compound YC-1 was the first sGC stimulator to be identified; this compound formed a lead structure for the development of optimized sGC stimulators with improved potency and specificity for sGC, including CFM-1571, BAY 41-2272, BAY 41-8543, and BAY 63-2521. In contrast to the NO- and haem-independent sGC activators such as BAY 58-2667, these compounds stimulate sGC activity independent of NO and also act in synergy with NO to produce anti-aggregatory, anti-proliferative, and vasodilatory effects. Recently, aryl-acrylamide compounds were identified independent of YC-1 as sGC stimulators; although structurally dissimilar to YC-1, they have a similar mode of action and promote smooth muscle relaxation. Pharmacological stimulators of sGC may be beneficial in the treatment of a range of diseases, including systemic and pulmonary hypertension, heart failure, atherosclerosis, erectile dysfunction, and renal fibrosis. An sGC stimulator, BAY 63-2521, is currently in clinical development as an oral therapy for patients with pulmonary hypertension. It has demonstrated efficacy in a proof-of-concept study, reducing pulmonary vascular resistance and increasing cardiac output from baseline. A full, phase 2 trial of BAY 63-2521 in pulmonary hypertension is underway.

Effect of the phosphodiesterase 5 inhibitors sildenafil, tadalafil and vardenafil on rat anococcygeus muscle: functional and biochemical aspects

1. The anococcygeus muscle is part of the erectile machinery in male rodents. Phosphodiesterase (PDE) 5 inhibitors enhance and prolong the effects of cGMP, which has a key role in penile erection. The aim of the present study was to provide a functional and biochemical comparison of the three PDE5 inhibitors, namely sildenafil, tadalafil and vardenafil, in the rat anococcygeus muscle. 2. Muscle strips were mounted in 4 mL organ baths and isometric force recorded. Levels of cGMP were measured using an enzyme immunoassay kit. Western blots were used to determine PDE5 protein expression. 3. The PDE5 inhibitors concentration-dependently relaxed carbachol-precontracted anococcygeus muscle; however, vardenafil was more potent (pEC(50) = 8.11 +/- 0.05) than sildenafil (7.72 +/- 0.06) or tadalafil (7.69 +/- 0.05). Addition of N(G)-nitro-l-arginine methyl ester (100 micromol/L) or 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (10 micromol/L) to the organ baths caused significant rightward shifts in concentration-response curves for all PDE5 inhibitors. 4. Sildenafil, tadalafil and vardenafil (all at 0.1 micromol/L) caused leftward shifts in the glyceryl trinitrate (GTN) concentration-response curves (by 4.0-, 3.7- and 5.5-fold, respectively). In addition, all three PDE5 inhibitors significantly potentiated relaxation responses to both GTN (0.01-10 micromol/L) and electrical field stimulation (EFS; 1-32 Hz), with vardenafil having more pronounced effects. 5. All three PDE5 inhibitors reduced EFS-evoked contractions in a concentration-dependent manner over the concentration range 0.001-1 micromol/L. There were no significant differences between the effects of the three PDE5 inhibitors. 6. Vardenafil (0.01-0.1 micromol/L) was more potent in preventing cGMP degradation in vitro than sildenafil (0.01-0.1 micromol/L) and tadalafil (0.01-0.1 micromol/L). 7. Under control conditions, the expression of PDE5 was higher in the anococcygeus muscle than in the corpus cavernosum. 8. In conclusion, PDE5 inhibitors enhance exogenous and endogenous nitric oxide-mediated relaxation in the rat anococcygeus muscle. The potency of vardenafil was greater than that of either sildenafil or tadalafil.

Increased cyclic guanosine monophosphate synthesis and calcium entry blockade account for the relaxant activity of the nitric oxide-independent soluble guanylyl cyclase stimulator BAY 41-2272 in the rabbit penile urethra

OBJECTIVES

To study the direct relaxant activity of 5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]pyrimidin-4-ylamine (BAY 41-2272) in the rabbit penile urethra and to investigate its modulatory effect on nitric oxide (NO)-mediated responses.

METHODS

Urothelium-intact (U+) and denuded (U-) rings were mounted in 10-mL organ baths for isometric force recording. Intracellular cyclic guanosine monophosphate (cGMP) levels were quantified with specific kits.

RESULTS

BAY 41-2272 (0.0001 to 10 micromol/L) caused relaxation of urethral rings contracted with phenylephrine (10 micromol/L), with higher potency (P <0.01) in U+ (pEC(50) 7.77 +/- 0.09) compared with U- (pEC(50) 6.84 +/- 0.19) preparations. The NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (100 micromol/L) or the soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3,-a]quinoxalin-1-one (ODQ) (10 micromol/L) had no effect on BAY 41-2272 responses in U+ or U- rings. The phosphodiesterase-5 inhibitor vardenafil (0.1 micromol/L) potentiated the relaxant effects of BAY 41-2272 in both U+ (10-fold) and U- (sevenfold) tissues. Ca(2+)-induced contractions in K(+) depolarized rings were significantly attenuated by BAY 41-2272 (1 micromol/L) in an ODQ-insensitive manner. BAY 41-2272 (0.03-0.3 micromol/L) increased the amplitude and duration of electrical field stimulation-induced relaxations (1 to 32 Hz), as well as those evoked by the NO donor glyceryl trinitrate (0.0001 to 10 micromol/L). BAY 41-2272 induced ODQ-resistant increases in cGMP levels above baseline (approximately twofold) in both U+ and U- rings.

CONCLUSIONS

BAY 41-2272 relaxes penile urethra in a synergic fashion with NO. Targeting soluble guanylate cyclase with BAY 41-2272 may represent a new therapy in the management of voiding disturbances associated with impaired NO-cGMP signaling.

Effects of 5-Cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4-ylamine (BAY 41-2272) on Smooth Muscle Tone, Soluble Guanylyl Cyclase Activity, and NADPH Oxidase Activity/Expression in Corpus Cavernosum from Wild-Type, Neuronal, and Endothelial Nitric-Oxide Synthase Null Mice

We aimed to characterize the relaxation induced by the soluble guanylyl cyclase (sGC) stimulator 5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridine-3-yl]pyrimidin-4-ylamine (BAY 41-2272) and its pharmacological interactions with nitric oxide (NO) in the corpus cavernosum (CC) from wild-type (WT), endothelial nitric-oxide synthase (eNOS)(-/-), and neuronal (n)NOS(-/-) mice. The effect of BAY 41-2272 on superoxide formation and NADPH oxidase expression was also investigated. Tissues were mounted in myographs for isometric force recording. Enzyme immunoassay kits were used for cGMP determination. sGC activity was determined in the supernatant fractions of the cavernosal samples by the conversion of GTP to cGMP. Superoxide formation and expression of NADPH oxidase subunits were studied using the reduction of ferricytochrome c and Western blot analysis, respectively. BAY 41-2272 (0.01-10 microM) relaxed CC with pEC(50) values of 6.36 +/- 0.07 (WT), 6.27 +/- 0.06 (nNOS(-/-)), and 5.88 +/- 0.07 (eNOS(-/-)). The relaxations were accompanied by increases in cGMP levels. N(omega)-Nitro-L-arginine methyl ester inhibited BAY 41-2272-evoked responses in CC from WT and nNOS(-/-), but not eNOS(-/-).1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one reduced and sildenafil potentiated the relaxations induced by BAY 41-2272 in all groups. BAY 41-2272 enhanced NO (endogenous and exogenous)-induced relaxations in a concentration-dependent manner. Expression and activity of sGC was similar among the different groups. Superoxide formation was reduced by BAY 41-2272 (0.1-1 microM). The compound also inhibited p22(phox) and gp91(phox) expression induced by 9,11-dideoxy-11 alpha,9 alpha-epoxymethanoprostaglandin F(2 alpha (U46619). Our results demonstrated that sGC activation in the penis by BAY 41-2272 directly or via enhancement of NO effects may provide a novel treatment for erectile dysfunction, particularly in the event of an increased intrapenile oxidative stress.