Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.6.1.2 (guanylate cyclase)
8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In a model of acute pulmonary hypertension in intact rabbits, we investigated the vasodilatory potency of intravascularly administered urodilatin, a renal natriuretic peptide type A known to stimulate particulate guanylate cyclase. Urodilatin infusion was performed in the absence and presence of the phosphodiesterase (PDE) type 5 inhibitor dipyridamole. Stable pulmonary hypertension was evoked by continuous infusion of the thromboxane mimetic U46619, resulting in approximate doubling of the pulmonary artery pressure (PAP). When infused as sole agents, both urodilatin and dipyridamole dose-dependently attenuated the pulmonary hypertension, with doses for a 20% decrease in PAP being 30 ng/kg min for urodilatin and 10 microg/kg min for dipyridamole. A corresponding decrease in systemic arterial pressure (SAP) was noted to occur in response to both agents. Sequential intravenous administration of a subthreshold dose of dipyridamole (1 microg/kg min), which per se did not affect pulmonary and systemic hemodynamics, and a standard dose of urodilatin (30 ng/kg min) resulted in a significant amplification of both the PAP and the SAP decrease in response to the natriuretic peptide. At the same time, manifold enhanced plasmatic cyclic guanosine monophosphate (cGMP) levels were detected. Aerosolized dipyridamole also dose-dependently attenuated pulmonary hypertension, with only 1 microg/kg min being sufficient for a 20% decrease in PAP, with no SAP decline. Preceding administration of subthreshold aerosolized dipyridamole (50 ng/kg min) did, however, cause only a minor amplification of the pulmonary vasodilatory response to a subsequently infused standard dose of urodilatin. In conclusion, this is the first study to show that urodilatin does possess vasodilatory potency in the pulmonary circulation, and enhanced plasma levels of cGMP and synergy with the PDE5 inhibitor dipyridamole both strongly suggest that this effect proceeds via guanylate cyclase activation. The effect of infused urodilatin is, however, not selective for the pulmonary vasculature, as the systemic vascular resistance declines in a corresponding fashion.
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PMID:Urodilatin, a natriuretic peptide stimulating particulate guanylate cyclase, and the phosphodiesterase 5 inhibitor dipyridamole attenuate experimental pulmonary hypertension: synergism upon coapplication. 1150 32

The regulation of cGMP-specific phosphodiesterase (PDE) 5 and soluble guanylate cyclase (GC) by cGMP- and cAMP-dependent protein kinases (PKG and PKA respectively) was examined in gastric smooth muscle. The NO donor, sodium nitroprusside (SNP), stimulated PDE5 phosphorylation and activity, which was blocked by the selective PKG inhibitor, KT5823, resulting in an elevation of cGMP levels. Activation of PKA either directly by Sp-5,6-dichloro-1-beta-d-ribofuranosyl benzimidazole 3',5'-cyclic monophosphothioate, or via isoproterenol- and forskolin-dependent increase in cAMP, also caused an increase in PDE5 phosphorylation and activity, but only in the presence of cGMP; consistent with the dependence of PDE5 phosphorylation and activity on cGMP binding to allosteric sites in the regulatory domain of PDE5. The selective PKA inhibitors, myristoylated protein kinase inhibitor and H-89, blocked the increase in PDE5 phosphorylation and activity induced by PKA. SNP also stimulated soluble GC phosphorylation and activity. KT5823 abolished phosphorylation and augmented soluble GC activity, implying feedback inhibition of soluble GC by PKG-dependent phosphorylation. Phosphorylation by PKG was direct and could be induced in vitro. Activation of PKA had no effect on soluble GC. Thus cGMP levels are regulated by PKG- and PKA-dependent activation of PDE5 and PKG-specific inhibition of soluble GC.
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PMID:Activation of phosphodiesterase 5 and inhibition of guanylate cyclase by cGMP-dependent protein kinase in smooth muscle. 1169 8

. The effects of LASSBio 294, a new 3,4-methylenedioxybenzoyl-2-thienylhydrazone, on vascular tonus were investigated in isolated rat aortic rings. 2. LASSBio 294 induced a concentration-dependent relaxation of intact rat aortic rings with an inhibitory concentration (IC(50)) of 74 microM (95% confidence limits: 59 - 92). The mechanical removal of the endothelium abolished this effect. 3. In aortic rings with intact endothelium the effect of 100 microM LASSBio 294 was not altered by the pharmacological inhibition of NOS and cyclo-oxygenase pathways with 500 microM L-NAME and 10 microM indomethacin, respectively. 4. LASSBio 294 (100 microM) was able to relax aortic rings pre-contracted with high extracellular K(+) (KCl 100 mM). 5. The relaxant effect of LASSBio 294 was fully reversed (and prevented) by the addition of 1 microM ODQ (1H-(1,2,4)oxadiazolo[4,3-a]quinoxaline-1-one), a selective inhibitor of soluble guanylate cyclase. 6. LASSBio 294 (100 microM) had no direct effect on PDE3 and PDE4 activities, however, it increased by 150% cyclic GMP content in aortic rings pre-treated with 100 microM L-NAME and 10 microM indomethacin, as did 1 microM zaprinast, a selective PDE5 inhibitor. 7. In conclusion, LASSBio 294 induced relaxation of isolated rat aorta probably by directly increasing cyclic GMP content, possibly as a consequence of PDE5 inhibition.
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PMID:Cyclic GMP-dependent vasodilatory properties of LASSBio 294 in rat aorta. 1178 6

The nitric oxide (NO)-cGMP pathway has been implicated as playing a crucial role in the induction of cerebellar long-term depression (LTD). The amplitude and duration of the cGMP signal is controlled by cyclic nucleotide phosphodiesterases (PDEs). Here we identify PDE5 and PDE1B as the two major cGMP-hydrolyzing PDEs specifically and differentially expressed in the Purkinje neurons of mouse cerebellum. PDE5 was found in all Purkinje neurons, whereas PDE1B was detected only in a subset of these cells, suggesting that individual Purkinje cells may differentially regulate cGMP, depending on the PDE isozymes expressed. Although expression of guanylate cyclase and/or cGMP-dependent protein kinase (PKG) in Purkinje cells have been reported, neither cGMP accumulation nor PKG activation in these cells in vivo has been demonstrated. To determine if changes in PKG activation and PDE5 regulation occur in vivo we have examined the phosphorylation of PDE5 in mouse cerebellar Purkinje cells by immunocytochemistry and Western blot analyses using a phosphospecific PDE5 antibody. Injection of sodium nitroprusside or selective PKG activators into the lateral ventricle of mouse brain induced PDE5 phosphorylation in vivo, but was completely missing in Purkinje cell-specific PKG I knock-out mice. In cerebellar slices, treatment with sildenafil or IBMX led to different levels of phospho-PDE5 accumulation and activation of PDE5. These results suggest that phosphorylation of PDE5 in Purkinje neurons after cGMP-PKG activation performs a critical role in the termination of the cGMP signal during LTD progression; moreover, PDE5 phosphorylation may be used as an in vivo indicator for PKG activation.
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PMID:Individual cerebellar Purkinje cells express different cGMP phosphodiesterases (PDEs): in vivo phosphorylation of cGMP-specific PDE (PDE5) as an indicator of cGMP-dependent protein kinase (PKG) activation. 1287 85

Cyclic GMP (cGMP) made in response to atrial natriuretic peptide (ANP) or nitric oxide (NO) is an important regulator of short-term changes in smooth muscle tone and longer-term responses to chronic drug treatment or proliferative signals. The ability of smooth muscle cells (SMCs) to utilize different combinations of phosphodiesterase (PDE) isozymes allows cGMP to mediate these multiple processes. For example, PDE5 as a major cGMP-hydrolyzing PDE effectively controls the development of smooth muscle relaxation. In order for contraction to occur, PDE5 is activated and cGMP falls. Conversely, blockade of PDE5 activity allows the relaxation cycle to be prolonged and enhanced. A recently shown direct activation of PDE5 by cGMP binding to the GAF A domain suggests that this regulatory site might be a target for new drug development. The calcium surge associated with vasoconstrictor initiated contraction also activates a calcium/calmodulin-dependent PDE (PDE1A). Together, PDE5 and PDE1A lower cGMP sufficiently to allow contraction. Longer term, both PDE5 and PDE1A mRNA are induced by chronic stimulation of guanylyl cyclase. This induction is a major cause of the tolerance that develops to NO-releasing drugs. Finally, high levels of cGMP or cAMP also act as a brake to attenuate the proliferative response of SMCs to many mitogens. After vessel damage, in order for SMC proliferation to occur, the levels of cGMP and cAMP must be decreased. In humans, this decrease is caused in large part by induction of another Ca2+/calmodulin-dependent PDE (PDE1C) that allows the brake to be released and proliferation to start.
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PMID:Cyclic GMP phosphodiesterases and regulation of smooth muscle function. 1293 99

Sildenafil citrate (Viagra) is a relatively selective 5-phosphodiesterase (PDE) inhibitor. It is the first oral medication approved for the treatment of erectile dysfunction (ED). The neuronal release of NO which binds to the heme-containing region of guanylate cyclase increases levels of cGMP. This leads to a cascade of reaction which results in corporal smooth muscle relaxation and penile erection. Sildenafil causes an erection by inhibiting PDE5, which in turn causes an increase in the intracellular levels of cGMP. Sildenafil is well absorbed after a single oral administration with a t(1/2) of approximately 4 h. The mode of onset varies from 0.5-4 h. The drug has been used in millions of men since first approved by the U.S. FDA 1 year ago and has revolutionized the approach to, and therapy of, erectile dysfunction.
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PMID:Sildenafil: a new oral therapy for erectile dysfunction. 1297 86

We compared the effects of a nitric oxide (NO)-releasing sildenafil (NCX-911), NO-independent soluble guanylate cyclase activator (BAY41-2272) and sildenafil on the anococcygeus muscle from streptozotocin-induced 16-weeks diabetic rats. NCX-911, BAY41-2272 and sildenafil reduced the phenylephrine-induced tone in the control group (EC50=1088.8+/-165.0, 151.6+/-9.3 and 827.1+/-167.3 nM, respectively). The potencies of NCX-911 and BAY41-2272 were not altered, but that of sildenafil was significantly reduced in the diabetic group. EC50 values for NCX-911, BAY41-2272 and sildenafil in the diabetic group were 1765.9+/-303.5, 209.7+/-27.3 and 2842.2+/-640.3 nM, respectively (P<0.05 for sildenafil). Nitrergic relaxation responses were significantly decreased in the diabetic group. The remaining nitrergic relaxation responses were potentiated by BAY41-2272 but not by sildenafil or NCX-911. These results confirm that endogenous NO derived from nitrergic nerves is significantly decreased in diabetes, and suggest that NO-releasing PDE5 inhibitors and NO-independent soluble guanylate cyclase activators could be more useful than PDE5 inhibitors in the treatment of ED in long-term diabetes.
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PMID:A comparative study of sildenafil, NCX-911 and BAY41-2272 on the anococcygeus muscle of diabetic rats. 1502 25

Acetylcholine and cholinomimetic agents with predominant muscarinic action are known to increase the concentration of cGMP by activation of nitric oxide signaling pathway in the nociceptive conditions. The present study was aimed to investigate the NO-cGMP-PDE5 pathway in nociceptive conditions in the experimental animals. Nociceptive threshold was assessed by acetic acid-induced writhing assay (chemonociception) or carrageenan-induced hyperalgesia. Sildenafil [1-5 mg/kg, ip, 50-200 microg/paw, intraplantar (ipl)] produced dose dependent antinociception in both the tested models. Coadministration of acetylcholine (50 mcg/paw, ipl) or cholinomimetic agent, neostigmine (0.1 mcg/kg, ip and 25 ng/paw, ipl) augmented the peripheral antinociceptive effect of sildenafil. This effect was sensitive to blockade by L-NAME (20 mg/kg, ip, 100 microg/paw, ipl), a non-selective NOS inhibitor and methylene blue (1 mg/kg, ip), a guanylate cyclase inhibitor, which per se had little or no effect in both the models of nociception. Further, the per se analgesic effect of acetylcholine and neostigmine was blocked by both L-NAME and methylene blue in the models of nociception, suggesting the activation of NO-cGMP pathway. Also, both L-NAME and methylene blue blocked the per se analgesic effect of sildenafil. These results indicate the peripheral accumulation of cGMP may be responsible for antinociceptive effect, and a possible interaction between cholinergic agents and PDE5 system in models of nociception.
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PMID:Cholinergic-NO-cGMP mediation of sildenafil-induced antinociception. 1508 85

The aim of the study was to compare the localization of the nitric oxide (NO)-cGMP pathway in hippocampus of mice and rats using cGMP- and soluble guanylyl cyclase (GC) immunocytochemistry and in situ hybridization of the cGMP-hydrolysing phosphodiesterase types 2, 5 and 9. In vitro incubation of hippocampus slices in the absence of a guanylyl cyclase stimulator or a phosphodiesterase inhibitor resulted in cGMP-positive astrocytes mainly in the CA1 area in mouse slices. In contrast, no cGMP immunoreactivity was observed under these conditions in the rat hippocampus. Treatment with an NO synthase inhibitor or inhibitors of soluble or particulate GC did not abolish cGMP immunoreactivity in astrocytes. Incubation with the NO donors sodium nitroprusside or diethylamino NONOate, or with the NO-independent activators of soluble GC, YC-1 and BAY 41-2272, in combination with phosphodiesterase inhibitors, resulted in an increase in cGMP immunoreactivity in numerous astrocytes throughout the mouse hippocampus. In contrast, under these conditions cGMP immunoreactivity was primarily observed in varicose fibers in rat hippocampus. Comparison of the cellular localization of the beta1 subunit of soluble GC and the mRNAs of PDE2, PDE5 and PDE9 revealed that in both species the beta1 subunit was observed in pyramidal and granule cells, which also expressed the mRNAs of the three phosphodiesterase families. Although the beta1 subunit was observed in astrocytes, none of the phosphodiesterases were detected in these cells. We conclude that, although the expression profiles of the soluble GC beta1 subunit and cGMP-hydrolysing phosphodiesterase mRNAs were identical, the cellular patterns of cGMP immunoreactivity differ between rat and mouse hippocampus.
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PMID:Species differences in the localization of cGMP-producing and NO-responsive elements in the mouse and rat hippocampus using cGMP immunocytochemistry. 1509 42

Cardiovascular smooth muscle cells (SMCs) exist as resting or activated cells. Resting SMCs produce contractile proteins and are nearly transcriptionally inactive; activated SMCs are transcriptionally active and are involved in pathological processes such as atherosclerosis. Soluble guanylate cyclase, protein kinase G, and protein kinase A are present in SMCs, but their levels can be decreased in activated cells. Phosphodiesterase 3 (PDE3) activity is abundant in cardiovascular tissues; both PDE3A and PDE3B are involved in cyclic adenosine monophosphate (cAMP) hydrolysis in these tissues. Cyclic-AMP-hydrolyzing PDE activities are altered during the phenotypic transition of SMCs from the resting to the activated phenotype. Similar changes have been observed in cyclic guanosine monophosphate cGMP-hydrolyzing PDEs, although the impact of these alterations on PDE5 inhibitor-mediated effects requires further study. This report presents the changes in PDE expression that accompany phenotypic modulation of SMCs and discusses the potential impact of these events on PDE5-mediated cell functions.
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PMID:Cardiovascular implications in the use of PDE5 inhibitor therapy. 1522 31


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