Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.2 (guanylate cyclase)
 8,497 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied how the nitric oxide (NO*) donor 3-morpholinosydnonimine (SIN-1) alters the response to beta-adrenergic stimulation in cardiac rat myocytes. We found that SIN-1 decreases the positive inotropic effect of isoproterenol (Iso) and decreases the extent of both cell shortening and Ca2+ transient. These effects of SIN-1 were associated with an increased intracellular concentration of cGMP, a decreased intracellular concentration of cAMP, and a reduction in the levels of phosphorylation of phospholamban (PLB) and troponin I (TnI). The guanylyl cyclase inhibitor 1H-8-bromo-1,2,4-oxadiazolo (3,4-d)benz(b)(1,4)oxazin-1-one (ODQ) was not able to prevent the SIN-1-induced reduction of phosphorylation levels of PLB and TnI. However, the effects of SIN-1 were abolished in the presence of superoxide dismutase (SOD) or SOD and catalase. These data suggest that, in the presence of Iso, NO-related congeners, rather than NO*, are responsible for SIN-1 effects. Our results provide new insights into the mechanism by which SIN-1 alters the positive inotropic effects of beta-adrenergic stimulation.
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PMID:Anti-adrenergic effects of nitric oxide donor SIN-1 in rat cardiac myocytes. 1140 58

Nitric oxide (NO) can directly modulate cardiac contractility by accelerating relaxation and reducing diastolic tone. The intracellular mechanisms underlying these contractile effects are poorly understood. Here we investigate the role of cyclic GMP-dependent protein kinase (PKG) in the contractile response to exogenous NO in rat ventricular myocytes. Isolated ventricular myocytes were stimulated electrically and contractility was assessed by measuring cell shortening. Some cells were loaded with the fluorescent Ca(2+) probe indo-1 AM for simultaneous assessment of the intracellular Ca(2+) transient. The NO donor diethylamine NONOate (DEA/NO, 10 microM) significantly increased resting cell length, reduced twitch amplitude and accelerated time to 50 % relaxation (to 100.8 +/- 0.2, 83.7 +/- 3.0 and 88.9 +/- 3.7 % of control values, respectively). The contractile effects of DEA/NO occurred without significant changes in the amplitude or kinetics of the intracellular Ca(2+) transient, suggesting that the myofilament response to Ca(2+) was reduced. These effects were abolished by inhibition of either guanylyl cyclase (with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one; ODQ, 10 microM) or PKG (with Rp-8-Br-cGMPs, 10 microM) suggesting that, at the concentration investigated, the effects of DEA/NO were mediated exclusively by PKG, following activation of guanylyl cyclase and elevation of cGMP. Direct activation of PKG with 8-pCPT-cGMP (10 microM) mimicked the effects of DEA/NO (resting cell length and time to 50 % relaxation were 100.6 +/- 0.1 and 90.5 +/- 1.5 % of control values, respectively).The reduced myofilament Ca(2+) responsiveness was not attributable to an intracellular acidosis since the small reduction in pH(i) induced by DEA/NO was found to be uncoupled from its contractile effects. However, hearts treated with DEA/NO (10 microM) showed a significant increase (1.4-fold; P < 0.01) in troponin I phosphorylation compared to control, untreated hearts. These results suggest that the reduction in myofilament Ca(2+) responsiveness produced by DEA/NO results from phosphorylation of troponin I by PKG.
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PMID:Role of cyclic GMP-dependent protein kinase in the contractile response to exogenous nitric oxide in rat cardiac myocytes. 1195 36

Adenosine A1 receptor activation causes protein phosphatase 2a (PP2a) activation in ventricular myocytes. This attenuates beta-adrenergic functional effects in the heart (Liu Q and Hofmann PA. Am J Physiol Heart Circ Physiol 283: H1314-H1321, 2002). The purpose of the present study was to identify the signaling pathway involved in the translocation/activation of PP2a by adenosine A1 receptors in ventricular myocytes. We found that N6-cyclopentyladenosine (CPA; an adenosine A1 receptor agonist)-induced PP2a translocation was blocked by p38 MAPK inhibition but not by JNK inhibition. CPA increased phosphorylation of p38 MAPK, and this effect was abolished by pertussis toxin and inhibitors of the cGMP pathway. Moreover, CPA-induced PP2a translocation was blocked by inhibition of the cGMP pathway. Guanylyl cyclase activation mimicked the effects of CPA and caused p38 MAPK phosphorylation and PP2a translocation. Finally, CPA-induced dephosphorylations of troponin I and phospholamban were blocked by pertussis toxin and attenuated by p38 MAPK inhibition. These results suggest that adenosine A1 receptor-mediated PP2a activation uses a pertussis toxin-sensitive Gi protein-guanylyl cyclase-p38 MAPK pathway. This proposed, novel pathway may play a role in acute modulation of cardiac function.
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PMID:Modulation of protein phosphatase 2a by adenosine A1 receptors in cardiomyocytes: role for p38 MAPK. 1264 78

Methylene blue (MB), generic name methylthioninium (C(16)H(18)ClN(3) S . 3H(2)O), is a blue dye synthesized in 1876 by Heinrich Caro for use as a textile dye and used in the laboratory and clinically since the 1890s, with well-known toxicity and pharmacokinetics. It has experimentally proven neuroprotective and cardioprotective effects in a porcine model of global ischemia-reperfusion in experimental cardiac arrest. This effect has been attributed to MB's blocking effect on nitric oxide synthase and guanylyl cyclase, the latter blocking the synthesis of the second messenger of nitric oxide. The physiological effects during reperfusion include stabilization of the systemic circulation without significantly increased total peripheral resistance, moderately increased cerebral cortical blood flow, a decrease of lipid peroxidation and inflammation, and less anoxic tissue injury in the brain and the heart. The last two effects are recorded as less increase in plasma concentrations of astroglial protein S-100beta, as well as troponin I and creatine kinase isoenzyme MB, respectively.
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PMID:Neuro- and cardioprotective effects of blockade of nitric oxide action by administration of methylene blue. 1807 76

Our objective was to investigate the role of phosphodiesterase (PDE)3 and PDE4 and cGMP in the control of cAMP metabolism and of phosphorylation of troponin I (TnI) and phospholamban (PLB) when 5-HT4 receptors are activated in pig left atrium. Electrically paced porcine left atrial muscles, mounted in organ baths, received stimulators of particulate guanylyl cyclase (pGC) or soluble guanylyl cyclase (sGC) and/or specific PDE inhibitors followed by 5-HT or the 5-HT4 receptor agonist prucalopride. Muscles were freeze-clamped at different moments of exposure to measure phosphorylation of the cAMP/protein kinase A targets TnI and PLB by immunoblotting and cAMP levels by enzyme immunoassay. Corresponding with the functional results, 5-HT only transiently increased cAMP content, but caused a less quickly declining phosphorylation of PLB and did not significantly change TnI phosphorylation. Under combined PDE3 and PDE4 inhibition, the 5-HT-induced increase in cAMP levels and PLB phosphorylation was enhanced and sustained, and TnI phosphorylation was now also increased. Responses to prucalopride per se and the influence thereupon of PDE3 and PDE4 inhibition were similar except that responses were generally smaller. Stimulation of pGC together with PDE4 inhibition increased 5-HT-induced PLB phosphorylation compared to 5-HT alone, consistent with functional responses. sGC stimulation hastened the fade of inotropic responses to 5-HT, while cAMP levels were not altered. PDE3 and PDE4 control the cAMP response to 5-HT4 receptor activation, causing a dampening of downstream signalling. Stimulation of pGC is able to enhance inotropic responses to 5-HT by increasing cAMP levels, while sGC stimulation decreases contraction to 5-HT cAMP independently.
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PMID:Influence of phosphodiesterases and cGMP on cAMP generation and on phosphorylation of phospholamban and troponin I by 5-HT4 receptor activation in porcine left atrium. 2354 71

In vitro assays could replace animal experiments in drug screening and disease modeling, but have shortcomings in terms of functional readout. Force-generating engineered heart tissues (EHT) provide simple automated measurements of contractile function. Here we evaluated the response of EHTs to hypoxia/reoxygenation (H/R) and the effect of known cardiocytoprotective molecules. EHTs from neonatal rat heart cells were incubated for 24 h in EHT medium. Then they were subjected to 180 min hypoxia (93% N2, 7% CO2) and 120 min reoxygenation (40% O2, 53% N2, 7% CO2), change of medium and additional follow-up of 48 h. Time-matched controls (40% O2, 53% N2, 7% CO2) were run for comparison. The following conditions were applied during H/R: fresh EHT medium (positive control), the NO-donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP, 10(-7), 10(-6), 10(-5) M) or the guanylate cyclase activator brain type natriuretic peptide (BNP, 10(-9), 10(-8), 10(-7) M). Frequency and force of contraction were repeatedly monitored over the entire experiment, pH, troponin I (cTnI), lactate dehydrogenase (LDH) and glucose concentrations measured in EHT medium. Beating activity of EHTs in 24 h-medium ceased during hypoxia, partially recovered during reoxygenation and reached time-control values during follow-up. H/R was accompanied by a small increase in LDH and non-significant increase in cTnI. In fresh medium, some EHTs continued beating during hypoxia and all EHTs recovered faster during reoxygenation. SNAP and BNP showed small but significant protective effects during reoxygenation. EHTs are applicable to test potential cardioprotective compounds in vitro, monitoring functional and biochemical endpoints, which otherwise could be only measured by using in vivo or ex vivo heart preparations. The sensitivity of the model needs improvement.
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PMID:Protection by the NO-Donor SNAP and BNP against Hypoxia/Reoxygenation in Rat Engineered Heart Tissue. 2614 89