Inhibitory effects on human eosinophil chemotaxis in vitro by BAY 41-2272, an activator of nitric oxide-independent site of soluble guanylate cyclase

Pharmacological evaluation of a new nanoformulation in the erectile tissue of rabbits and humans

The failure of achieving a penile erection for satisfactory sexual intercourse is known as erectile dysfunction (ED). The primary mediator for penile erection is nitric oxide (NO). ED is often associated with endothelial/nitrergic dysfunction characterized by a reduction of the bioavailability of NO. Phosphodiesterase-5 inhibitors (PDE-5Is) clinical efficacy in the treatment of ED depends on the integrity of the NO-sGC-PKG pathway. In the present study, we probed the effect of sodium nitroprusside incorporated into mesoporous silica nanoparticles (MPSi-NP), which traps cyanide and slowly releases NO. MPSi-NP induced a maximal relaxation of 92.8 ± 5.2% in rabbit corpora cavernosa (RbCC), blunted by a soluble guanylate cyclase (sGC) inhibitor and blockers of calcium-dependent potassium channels. MPSi-NP abolished spontaneous contractions of human corpora cavernosa (HCC) strips. In addition, MPSi-NP induced maximal relaxation of phenylephrine precontracted HCC by 118.6 ± 3.6%, and in comparison, tadalafil induced a maximal relaxation of HCC by 98.3 ± 1.2%. Similarly, the sGC inhibitor blocked the MPSi-NP relaxation. MPSi-NP potentiated the relaxation induced by tadalafil. MPSi-NP increased cGMP levels in HCC strips by 2.6-fold and increased by 3.5-fold the phosphorylation level of the VASP protein, which is a downstream target to PKG. MPSi-NP effectively relaxes RbCC and HCC by activating the sGC-PKG pathway and potentiates the tadalafil response. MPSi-NP could be helpful in conditions where nitric oxide availability is decreased. A topical gel formulation of MPSi-NP could be used as a rescue therapy to treat true non-responders of PDE5Is drugs.

Nitric Oxide System and Bronchial Epithelium: More Than a Barrier

Airway epithelium forms a physical barrier that protects the lung from the entrance of inhaled allergens, irritants, or microorganisms. This epithelial structure is maintained by tight junctions, adherens junctions and desmosomes that prevent the diffusion of soluble mediators or proteins between apical and basolateral cell surfaces. This apical junctional complex also participates in several signaling pathways involved in gene expression, cell proliferation and cell differentiation. In addition, the airway epithelium can produce chemokines and cytokines that trigger the activation of the immune response. Disruption of this complex by some inflammatory, profibrotic, and carcinogens agents can provoke epithelial barrier dysfunction that not only contributes to an increase of viral and bacterial infection, but also alters the normal function of epithelial cells provoking several lung diseases such as asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) or lung cancer, among others. While nitric oxide (NO) molecular pathway has been linked with endothelial function, less is known about the role of the NO system on the bronchial epithelium and airway epithelial cells function in physiological and different pathologic scenarios. Several data indicate that the fraction of exhaled nitric oxide (FENO) is altered in lung diseases such as asthma, COPD, lung fibrosis, and cancer among others, and that reactive oxygen species mediate uncoupling NO to promote the increase of peroxynitrite levels, thus inducing bronchial epithelial barrier dysfunction. Furthermore, iNOS and the intracellular pathway sGC-cGMP-PKG are dysregulated in bronchial epithelial cells from patients with lung inflammation, fibrosis, and malignancies which represents an attractive drug molecular target. In this review we describe in detail current knowledge of the effect of NOS-NO-GC-cGMP-PKG pathway activation and disruption in bronchial epithelial cells barrier integrity and its contribution in different lung diseases, focusing on bronchial epithelial cell permeability, inflammation, transformation, migration, apoptosis/necrosis, and proliferation, as well as the specific NO molecular pathways involved.

Activation of soluble guanylyl cyclase with inhibition of multidrug resistance protein inhibitor-4 (MRP4) as a new antiplatelet therapy

The intracellular levels of cyclic GMP are controlled by its rate of formation through nitric oxide-mediated stimulation of soluble guanylate cyclase (sGC) and its degradation by phosphodiesterases. Multidrug resistance protein 4 (MRP4) expressed in human platelets pumps cyclic nucleotides out of cells. In search for new antiplatelet strategies, we tested the hypothesis that sGC activation concomitant with MRP4 inhibition confers higher antiplatelet efficacy compared with monotherapy alone. This study was undertaken to investigate the pharmacological association of the sGC activator BAY 60-2770 with the MRP4 inhibitor MK571 on human washed platelets. Collagen- and thrombin-induced platelet aggregation and ATP-release reaction assays were performed. BAY 60-2770 (0.001-10 µM) produced significant inhibitions of agonist-induced platelet aggregation accompanied by reduced ATP-release. Pre-incubation with 10 µM MK571 alone had no significant effect on platelet aggregation and ATP release, but it produced a left displacement by about of 10-100-fold in the concentration-response curves to BAY 60-2770. Pre-incubation with MK571increased and decreased, respectively, the intracellular and extracellular levels of cGMP to BAY 60-2770, whereas the cAMP levels remained unchanged. The increased VASP-serine 239 phosphorylation in BAY 60-2770-treated platelets was enhanced by MK571. In Fluo-4-loaded platelets, BAY 60-2770 reduced the intracellular Ca2+ levels, an effect significantly potentiated by MK571. Flow cytometry assays showed that BAY 60-2770 reduces the αIIbβ3 integrin activation, which was further reduced by MK571 association. Blocking the MRP4-mediated efflux of cGMP may be a potential mechanism to enhance the antiplatelet efficacy of sGC activators.

Activation of haem-oxidized soluble guanylyl cyclase with BAY 60-2770 in human platelets lead to overstimulation of the cyclic GMP signaling pathway

BACKGROUND AND AIMS

Nitric oxide-independent soluble guanylyl cyclase (sGC) activators reactivate the haem-oxidized enzyme in vascular diseases. This study was undertaken to investigate the anti-platelet mechanisms of the haem-independent sGC activator BAY 60-2770 in human washed platelets. The hypothesis that sGC oxidation potentiates the anti-platelet activities of BAY 60-2770 has been tested.

METHODS

Human washed platelet aggregation and adhesion assays, as well as flow cytometry for α(IIb)β(3) integrin activation and Western blot for α1 and β1 sGC subunits were performed. Intracellular calcium levels were monitored in platelets loaded with a fluorogenic calcium-binding dye (FluoForte).

RESULTS

BAY 60-2770 (0.001-10 µM) produced significant inhibition of collagen (2 µg/ml)- and thrombin (0.1 U/ml)-induced platelet aggregation that was markedly potentiated by the sGC inhibitor ODQ (10 µM). In fibrinogen-coated plates, BAY 60-2770 significantly inhibited platelet adhesion, an effect potentiated by ODQ. BAY 60-2770 increased the cGMP levels and reduced the intracellular Ca(2+) levels, both of which were potentiated by ODQ. The cell-permeable cGMP analogue 8-Br-cGMP (100 µM) inhibited platelet aggregation and Ca(2+) levels in an ODQ-insensitive manner. The cAMP levels remained unchanged by BAY 60-2770. Collagen- and thrombin-induced α(IIb)β(3) activation was markedly inhibited by BAY 60-2770 that was further inhibited by ODQ. The effects of sodium nitroprusside (3 µM) were all prevented by ODQ. Incubation with ODQ (10 µM) significantly reduced the protein levels of α1 and β1 sGC subunits, which were prevented by BAY 60-2770.

CONCLUSION

The inhibitory effects of BAY 60-2770 on aggregation, adhesion, intracellular Ca(2+) levels and α(IIb)β(3) activation are all potentiated in haem-oxidizing conditions. BAY 60-2770 prevents ODQ-induced decrease in sGC protein levels. BAY 60-2770 could be of therapeutic interest in cardiovascular diseases associated with thrombotic complications.

BAY 41-2272, a soluble guanylate cyclase agonist, activates human mononuclear phagocytes

BACKGROUND AND PURPOSE

Phagocyte function is critical for host defense against infections. Defects in phagocytic function lead to several primary immunodeficiencies characterized by early onset of recurrent and severe infections. In this work, we further investigated the effects of BAY 41-2272, a soluble guanylate cyclase (sGC) agonist, on the activation of human peripheral blood monocytes (PBM) and THP-1 cells.

EXPERIMENTAL APPROACH

THP-1 cells and PBM viability was evaluated by methylthiazoletetrazolium assay; reactive oxygen species production by lucigenin chemiluminescence; gene and protein expression of NAPDH oxidase components by qRT-PCR and Western blot analysis, respectively; phagocytosis and microbicidal activity by co-incubation, respectively, with zymosan and Escherichia coli; and cytokine release by elisa.

KEY RESULTS

BAY 41-2272, compared with the untreated group, increased spreading of monocytes by at least 35%, superoxide production by at least 50%, and gp91(PHOX) and p67(PHOX) gene expression 20 to 40 times, in both PBM and THP-1 cells. BAY 41-2272 also augmented phagocytosis of zymosan particles threefold compared with control, doubled microbicidal activity against E. coli and enhanced the release of TNF-α and IL-12p70 by both PBM and THP-1 cells. Finally, by inhibiting sGC with ODQ, we showed that BAY 41-2272-induced superoxide production and phagocytosis is not dependent exclusively on sGC activation.

CONCLUSIONS AND IMPLICATIONS

In addition to its ability to induce vasorelaxation and its potential application for therapy of vascular diseases, BAY 41-2272 was shown to activate human mononuclear phagocytes. Hence, it is a novel pro-inflammatory drug that may be useful for controlling infections in the immunocompromised host.

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.

Mechanisms of relaxant activity of the nitric oxide-independent soluble guanylyl cyclase stimulator BAY 41-2272 in rat tracheal smooth muscle

The soluble guanylyl cyclase is expressed in airway smooth muscle, and agents that stimulate this enzyme activity cause airway smooth muscle relaxation and bronchodilation. The compound 5-Cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine (BAY 41-2272) is a potent nitric oxide (NO)-independent soluble guanylyl cyclase stimulator, but little is known about its effects in airway smooth muscle. Therefore, this study aimed to investigate the mechanisms underlying the relaxations of rat tracheal smooth muscle induced by BAY 41-2272. Tracheal rings were mounted in 10-ml organ baths for isometric force recording. BAY 41-2272 concentration-dependently relaxed carbachol-precontracted tracheal rings (pEC(50)=6.68+/-0.14). Prior incubation with the NO synthesis inhibitor l-NAME (100 microM) or the soluble guanylyl cyclase inhibitor ODQ (10 microM) caused significant rightward shifts in the concentration-response curves to BAY 41-2272. Sodium nitroprusside caused concentration-dependent relaxations, which were greatly potentiated by BAY 41-2272 and completely inhibited by ODQ. In addition, BAY 41-2272 shifted to the right the tracheal contractile responses to either carbachol (0.01-1 microM) or electrical field stimulation (EFS, 1-32 Hz). BAY 41-2272 (1 microM) also caused a marked rightward shift and decreased the maximal contractile responses to extracellular CaCl2, and such effect was not modified by pretreatment with ODQ. In addition, BAY 41-2272 (up to 1 microM) significantly increased the cGMP levels, and that was abolished by ODQ. Our results indicate that BAY 41-2272 causes cGMP-dependent rat tracheal smooth muscle relaxations in a synergistic fashion with exogenous NO. BAY 41-2272 has also an additional mechanism independently of soluble guanylyl cyclase activation possibly involving Ca(2+) entry blockade.

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.

Effects of BAY 41-2272, an activator of nitric oxide-independent site of soluble guanylate cyclase, on human NADPH oxidase system from THP-1 cells

We investigated the effects of the 5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b] pyridin-3-yl]-pyrimidin-4-ylamine (BAY 41-2272) on the NADPH oxidase activity, gp91(phox) gene expression, cyclic guanosine-3',5'-monophosphate (cGMP) and cyclic adenosine-3',5'-monophosphate (cAMP) levels in the human myelomonocytic THP-1 cell line. THP-1 cells treated with BAY 41-2272 (0.3-10 microM) for 48 h significantly increased the superoxide anion (O(2)(*-)) release. This increase was not affected when cells were pre-treated with the specific cGMP-phosphodiesterase inhibitor zaprinast, the soluble guanylate cyclase inhibitor 1H-[1,2,4] oxidiazolo[4,3-alpha] quinoxalin-1-one (ODQ), the adenylate cyclase inhibitor 9-(tetrahydro-2-furanyl) adenine (SQ 22,536) or the nitric oxide synthase inhibitor N(omega)-nitro-l-arginine methyl ester (l-NAME). In addition, BAY 41-2272 (3 and 10 microM; 48 h) was able to increase gp91(phox) gene expression on THP-1 cells. The pre-treatment with zaprinast, 3-isobutyl-l-methyl-xanthine (IBMX; 0.5 mM), ODQ, SQ 22,536 or l-NAME caused no additional effect on the expression of gp91(phox) evoked by BAY 41-2272. Treatment of THP-1 cells with BAY 41-2272 caused a significant increase in cGMP and cAMP levels. Our findings show that BAY 41-2272 caused a significant increase on the O(2)(*-) release and gp91(phox) gene expression by THP-1 cells, and an elevation of intracellular cGMP and cAMP levels. However, we could not detect a clear correlation between both O(2)(*-) release and gp91(phox) gene expression with activation of cGMP and cAMP signaling pathways.

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

The compound BAY 41-2272 stimulates the soluble guanylyl cyclase in a nitric oxide (NO)-independent manner. We have investigated the potency and efficacy of BAY 41-2272 in the rat anococcygeus muscle, as well as the effects of BAY 41-2272 on NO-mediated anococcygeus relaxations. BAY 41-2272 (0.01-10 microM) potently relaxed precontracted anococcygeus muscle strips, with a pEC(50) value of 6.44 +/- 0.03 and maximum response of 100 +/- 2%. The soluble guanylyl cyclase inhibitor 1H-[1,2,4]-oxidiazolo[4,3-a] quinoxalin-1-one (ODQ, 1 microM) and the NO inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM) caused significant rightward shifts in the concentration-response curves to BAY 41-2272. The phosphodiesterase type-5 inhibitor tadalafil (0.1 microM) markedly enhanced the relaxations evoked by BAY 41-2272. In addition, BAY 41-2272 increased the duration of nitrergic relaxations by approximately 55%. The relaxations induced by glyceryl trinitrate were also significantly potentiated by BAY 41-2272. In conclusion, BAY 41-2272 interacts with endogenous and exogenous NO causing a potent relaxation of rat anococcygeus muscle.

Molecular Mechanisms Underlying Rat Mesenteric Artery Vasorelaxation Induced by the Nitric Oxide-Independent Soluble Guanylyl Cyclase Stimulators BAY 41-2272 [5-Cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]pyrimidin-4-ylamine] and YC-1 [3-(5′-Hydroxymethyl-2′-furyl)-1-benzyl Indazole]

The aim of this study was to investigate the mechanisms of relaxation to the nitric oxide (NO)-independent soluble guanylyl cyclase (sGC) stimulators 5-cyclopropyl-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]pyrimidin-4-ylamine (BAY 41-2272) and 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1) in the rat mesenteric artery. In endothelium-intact rings, BAY 41-2272 (0.0001-1 microM) and YC-1 (0.001-30 microM) caused concentration-dependent relaxations (pEC(50) values of 8.21 +/- 0.05 and 6.75 +/- 0.06, respectively), which were shifted to the right by 6-fold in denuded rings. The sGC inhibitor H-[1,2,4]oxadiazolo [4,3,-a]quinoxalin-1-one (ODQ) (10 microM) partially attenuated the maximal responses to BAY 41-2272 and YC-1 and displaced their curves to the right by 9- to 10-fold in intact and 3-fold in denuded vessels. The NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (100 microM) and the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (100 microM) reduced BAY 41-2272 and YC-1 relaxations, whereas the phosphodiesterase type 5 inhibitor sildenafil (0.1 microM) potentiated these responses. The phosphatase inhibitor calyculin A (50 nM) reduced the relaxant responses, and high concentrations of BAY 41-2272 (1 micorM) and YC-1 (10 microM) inhibited Ca(2+)-induced contractions in K(+)-depolarized rings. BAY 41-2272 (0.1 microM) and YC-1 (1 microM) markedly elevated cGMP levels in an ODQ-sensitive manner. Coincubation of BAY 41-2272 or YC-1 with a NO donor resulted in a synergistic inhibition of phenylephrine-induced contractions paralleled by marked increases in cGMP levels. In conclusion, BAY 41-2272 and YC-1 relax the mesenteric artery through cGMP-dependent and -independent mechanisms, including blockade of Ca(2+) influx. The synergistic responses probably reflect the direct effects of NO and NO-independent sGC stimulators on the enzyme, thus representing a potential therapeutic effect by permitting reductions of nitrovasodilator dose.

MECHANISMS UNDERLYING RELAXATION OF RABBIT AORTA BY BAY 41-2272, A NITRIC OXIDE-INDEPENDENT SOLUBLE GUANYLATE CYCLASE ACTIVATOR

1. The compound BAY 41-2272 (5-cyclopropyl-2-[1-(2-fluoro-benzyl)-1H-pyrazolo[3,4-b]pyridin-3-yl]-pyrimidin-4-ylamine) has been described as a potent, nitric oxide (NO)-independent, stimulator of soluble guanylate cyclase. In the present study, the mechanisms underlying the relaxant effect of BAY 41-2272 in endothelium-intact and -denuded precontracted rabbit aortic rings were investigated. 2. Male New Zealand white rabbits were anaesthetized with pentobarbital sodium. Aortic rings were transferred to 10 mL organ baths containing oxygenated and warmed Krebs' solution. Tissues were connected to force-displacement transducers and changes in isometric force were recorded. Aortic rings were precontracted submaximally with phenylephrine (1 micromol/L). 3. The addition of BAY 41-2272 (0.01-10 micromol/L) to the organ bath produced concentration-dependent relaxations of the aortic rings with a higher potency in endothelium-intact (pEC50 6.59 +/- 0.05) compared with endothelium-denuded (pEC50 6.19 +/- 0.04; P < 0.05) preparations. No differences in maximal responses were observed in either preparation. The NO synthesis inhibitor NG-nitro-L-arginine methyl ester (100 micromol/L) produced a 2.1-fold rightward shift in endothelium-intact (P < 0.01) rings, but had no effect in endothelium-denuded rings. The soluble guanylate cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 micromol/L) caused significant rightward shifts of the concentration-response curves to BAY 41-2272 of 4.9- and 2.6-fold in endothelium-intact and -denuded rings, respectively. The phosphodiesterase-5 inhibitor sildenafil (0.1 micromol/L) significantly potentiated the relaxant effects of BAY 41-2272 in both endothelium-intact and -denuded rings. 4. At 1 micromol/L, BAY 41-2272 significantly elevated the aortic cGMP content above basal levels in both endothelium-intact and -denuded rings. Furthermore, ODQ reduced BAY 41-2272-elicited increases in cGMP content by 17 and 90% in endothelium-intact and -denuded rings, respectively (P < 0.01). 5. In conclusion, BAY 41-2272 potently relaxes endothelium-intact and -denuded rabbit aortic rings. The basal release of endothelium-derived NO enhances BAY 41-2272-induced relaxations, suggesting a synergistic effect of BAY 41-2272 and NO on soluble guanylate cyclase. In addition, the endothelium-independent relaxation involves both GMP-dependent and -independent mechanisms.