Probing the Molecular Mechanism of Human Soluble Guanylate Cyclase Activation by NO in vitro and in vivo

Although inhaled NO (iNO) therapy is often effective in treating infants with persistent pulmonary hypertension of the newborn (PPHN), up to 40% of patients fail to respond, which may be partly due to abnormal expression and function of soluble guanylate cyclase (sGC). To determine whether altered sGC expression or activity due to oxidized sGC contributes to high pulmonary vascular resistance (PVR) and poor NO responsiveness, we studied the effects of cinaciguat (BAY 58-2667), an sGC activator, on pulmonary artery smooth muscle cells (PASMC) from normal fetal sheep and sheep exposed to chronic intrauterine pulmonary hypertension (i.e., PPHN). We found increased sGC α1- and β1-subunit protein expression but lower basal cGMP levels in PPHN PASMC compared with normal PASMC. To determine the effects of cinaciguat and NO after sGC oxidation in vitro, we measured cGMP production by normal and PPHN PASMC treated with cinaciguat and the NO donor, sodium nitroprusside (SNP), before and after exposure to 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, an sGC oxidizer), hyperoxia (fraction of inspired oxygen 0.50), or hydrogen peroxide (H2O2). After treatment with ODQ, SNP-induced cGMP generation was markedly reduced but the effects of cinaciguat were increased by 14- and 64-fold in PPHN fetal PASMC, respectively ( P < 0.01 vs. controls). Hyperoxia or H2O2enhanced cGMP production by cinaciguat but not SNP in PASMC. To determine the hemodynamic effects of cinaciguat in vivo, we compared serial responses to cinaciguat and ACh in fetal lambs after ductus arteriosus ligation. In contrast with the impaired vasodilator response to ACh, cinaciguat-induced pulmonary vasodilation was significantly increased. After birth, cinaciguat caused a significantly greater fall in PVR than either 100% oxygen, iNO, or ACh. We conclude that cinaciguat causes more potent pulmonary vasodilation than iNO in experimental PPHN. We speculate that increased NO-insensitive sGC may contribute to the pathogenesis of PPHN, and cinaciguat may provide a novel treatment of severe pulmonary hypertension.

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Reduction of ICAM-1 expression by carbon monoxide via soluble guanylate cyclase activation accounts for modulation of neutrophil migration

Naunyn-Schmiedeberg s Archives of Pharmacology ◽

10.1007/s00210-010-0500-2 ◽

2010 ◽

Vol 381 (6) ◽

pp. 483-493 ◽

Cited By ~ 12

Author(s):

Daniela Dal-Secco ◽

Andressa Freitas ◽

Monica A. Abreu ◽

Thiago P. Garlet ◽

Marcos A. Rossi ◽

...

Keyword(s):

Carbon Monoxide ◽

Guanylate Cyclase ◽

Soluble Guanylate Cyclase ◽

Neutrophil Migration ◽

Cyclase Activation ◽

Guanylate Cyclase Activation

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Hydrogen peroxide elicits pulmonary arterial relaxation and guanylate cyclase activation

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1987.252.4.h721 ◽

1987 ◽

Vol 252 (4) ◽

pp. H721-H732 ◽

Cited By ~ 51

Author(s):

T. M. Burke ◽

M. S. Wolin

Keyword(s):

Hydrogen Peroxide ◽

Guanylate Cyclase ◽

Superoxide Anion ◽

Vascular Tone ◽

Soluble Guanylate Cyclase ◽

Compound I ◽

Cyclase Activation ◽

Arterial Relaxation ◽

Pulmonary Arterial ◽

Guanylate Cyclase Activation

Hydrogen peroxide produces concentration-dependent relaxation of precontracted isolated bovine intrapulmonary arterial rings by a mechanism which is independent of the endothelium or prostaglandin mediators. Relaxant responses to hydrogen peroxide concentrations of up to 100 microM were markedly attenuated by the inhibitor of soluble guanylate cyclase activation, methylene blue (10 microM). Micromolar concentrations of hydrogen peroxide elicit time- and concentration-dependent increase in arterial levels of guanosine 3',5'-cyclic monophosphate that are associated with decreases in force. Soluble guanylate cyclase activity is markedly activated by enzymatically generated hydrogen peroxide in a manner that is most closely associated with the concentration of catalase present in the assay, by a mechanism that is inhibited by superoxide anion and the inactivation of catalase. Our data are most consistent with the involvement of compound I, a species of catalase formed during the metabolism of peroxide, in the mechanism of guanylate cyclase activation. The nature of this mechanism of arterial relaxation suggests that it could contribute to the regulation of pulmonary vascular tone by oxygen tension.

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Effects of soluble guanylate cyclase activation on heart transplantation in a rat model

The Journal of Heart and Lung Transplantation ◽

10.1016/j.healun.2015.05.006 ◽

2015 ◽

Vol 34 (10) ◽

pp. 1346-1353 ◽

Cited By ~ 14

Author(s):

Sivakkanan Loganathan ◽

Sevil Korkmaz-Icöz ◽

Tamás Radovits ◽

Shiliang Li ◽

Beatrice Mikles ◽

...

Keyword(s):

Heart Transplantation ◽

Guanylate Cyclase ◽

Rat Model ◽

Soluble Guanylate Cyclase ◽

Cyclase Activation ◽

Guanylate Cyclase Activation

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Nitrite-dependent vasodilation is facilitated by hypoxia and is independent of known NO-generating nitrite reductase activities

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.01298.2006 ◽

2007 ◽

Vol 292 (6) ◽

pp. H3072-H3078 ◽

Cited By ~ 78

Author(s):

Thomas Dalsgaard ◽

Ulf Simonsen ◽

Angela Fago

Keyword(s):

Xanthine Oxidase ◽

Guanylate Cyclase ◽

Nitrite Reductase ◽

Soluble Guanylate Cyclase ◽

Nitrite Concentration ◽

Inositol Hexaphosphate ◽

Relative Contribution ◽

Norepinephrine Concentration

The reduction of circulating nitrite to nitric oxide (NO) has emerged as an important physiological reaction aimed to increase vasodilation during tissue hypoxia. Although hemoglobin, xanthine oxidase, endothelial NO synthase, and the bc1 complex of the mitochondria are known to reduce nitrite anaerobically in vitro, their relative contribution to the hypoxic vasodilatory response has remained unsolved. Using a wire myograph, we have investigated how the nitrite-dependent vasodilation in rat aortic rings is controlled by oxygen tension, norepinephrine concentration, soluble guanylate cyclase (the target for vasoactive NO), and known nitrite reductase activities under hypoxia. Vasodilation followed overall first-order dependency on nitrite concentration and, at low oxygenation and norepinephrine levels, was induced by low-nitrite concentrations, comparable to those found in vivo. The vasoactive effect of nitrite during hypoxia was abolished on inhibition of soluble guanylate cyclase and was unaffected by removal of the endothelium or by inhibition of xanthine oxidase and of the mitochondrial bc1 complex. In the presence of hemoglobin and inositol hexaphosphate (which increases the fraction of deoxygenated heme), the effect of nitrite was not different from that observed with inositol hexaphosphate alone, indicating that under the conditions investigated here deoxygenated hemoglobin did not enhance nitrite vasoactivity. Together, our results indicate that the mechanism for nitrite vasorelaxation is largely intrinsic to the vessel and that under hypoxia physiological nitrite concentrations are sufficient to induce NO-mediated vasodilation independently of the nitrite reductase activities investigated here. Possible reaction mechanisms for nitrite vasoactivity, including formation of S-nitrosothiols within the arterial smooth muscle, are discussed.

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