cyclic-gmp and 4-methyl-3-(phenylsulfonyl)furoxan

The study shows that endothelial cells from human umbilical veins have a soluble guanylate cyclase which can be activated by sodium nitroprusside (SNP), SIN-1 (3-morpholinosydnonimine) and S35b (4-methyl-3-phenylsulfonylfuroxan). Cells which were pretreated with these compounds showed an inhibition of thrombin-induced arachidonic acid release, PGI2 formation, PAF synthesis and PMNL adhesion. Endothelial guanylate cyclase can also be activated by nitric oxide (NO) which is generated in endothelial cells upon stimulation with thrombin or ionomycin. It is suggested that endogenously produced NO might control cell activation and endothelial function through a cGMP-dependent mechanism.

Topics: Arachidonic Acid; Cell Adhesion; Cyclic GMP; Endothelium, Vascular; Enzyme Activation; Epoprostenol; Guanylate Cyclase; Humans; Molsidomine; Nitric Oxide; Nitroprusside; Oxadiazoles; Platelet Activating Factor; Thrombin; Umbilical Veins

Endothelial cells (EC) produce platelet activating factor (PAF) and prostacyclin (PGI2) in response to inflammatory agents such as thrombin. Upon cell stimulation a calcium-dependent phospholipase A2 (PLA2) is activated which hydrolyzes a membrane phospholipid to yield 1-0-alkyl-2-lyso-sn-glycero-3-phospho-choline (lyso-PAF) and free arachidonic acid. Lyso-PAF is in turn converted into PAF by a specific acetyltransferase and arachidonic acid is metabolized via cyclic endoperoxides to PGI2. In the present study we report that S35b (4-methyl-3-phenylsulfonylfuroxan), a new phenyl-sulfonylfuroxan compound with potent antiaggregatory effect, inhibits thrombin-induced PAF synthesis and acetyltransferase activation as well as PGI2 production in human umbilical vein endothelial cells (HUVEC) in a concentration-dependent way. Additionally, we show that S35b stimulates the production of cyclic GMP (cGMP) in HUVEC in a concentration- and time-dependent manner. At high concentration, S35b potentiates the cAMP increase induced by iloprost or forskolin without having a significant influence on cAMP level itself. Potentiation of cAMP increase during agonist-induced EC stimulation seems not to be important for the effect of S35b on cellular function as the compound is active in inhibiting PAF production when endothelial cells are pretreated with indomethacin to block PGI2 synthesis. The increase of cGMP evoked by S35b may account for the effect on endothelial cell function.

Topics: 1-Methyl-3-isobutylxanthine; Acetyltransferases; Cells, Cultured; Colforsin; Cyclic AMP; Cyclic GMP; Endothelium, Vascular; Enzyme Activation; Epoprostenol; Humans; Iloprost; Oxadiazoles; Platelet Activating Factor; Platelet Aggregation Inhibitors; Thrombin; Umbilical Veins

A series of 4-methyl-3-(arylthio)furoxans were synthesized by oxidation of 1-(arylthio)-2-methylglyoxymes with dinitrogen tetroxide. Reduction with trimethyl phosphite of the furoxan derivatives afforded the corresponding furazans, while oxidation with an equimolar amount of 30% hydrogen peroxide in acetic acid or with an excess of 81% hydrogen peroxide in trifluoroacetic acid afforded the corresponding arylsulfinyl and arylsulfonyl analogues, respectively. All the furoxan and furazan derivatives showed activity as inhibitors of platelet aggregation. 4-Methyl-3-(arylsulfonyl)furoxans were the most potent derivatives of the series. 4-Methyl-3-(phenylsulfonyl)furoxan (10a), one of the most active derivatives, inhibits the AA-induced increase of cytosolic free Ca2+ and production of malondialdehyde. A primary action of the compound on cyclooxygenase is excluded, as a stable epoxymethano analogue of prostaglandin H2 does not reverse the inhibitory effect of 10a. This compound produces a significant increase in cGMP which is likely to cause inhibition at an early stage of the platelet activation pathway.

Topics: Arachidonic Acid; Blood Platelets; Calcium; Cyclic GMP; Humans; Malondialdehyde; Molecular Structure; Oxadiazoles; Platelet Aggregation Inhibitors; Structure-Activity Relationship

The effects of S35b (4-methyl-3-phenyl sulfonylfuroxan), a new phenyl sulfonylfuroxan compound, were investigated on human platelets activated by different agonists. Platelet aggregation evoked by arachidonic acid (AA), collagen, ADP and thrombin was inhibited by the drug in a dose-dependent manner. S35b inhibited the AA-induced increase of cytosolic free Ca2+ ([Ca2+]i) and production of malondialdehyde. A primary action of the compound on cyclooxygenase is unlikely since: (1) U-46619 (15s-hydroxy-11,9-[epoxymethano]-prosta-5Z,13E-dienoic acid, a stable epoxymethano analog of prostaglandin H2) could not reverse the inhibitory effect of S35b on AA-induced aggregation and [Ca2+]i increase; (2) U-46619-induced aggregation and [Ca2+]i rise were inhibited by S35b; and (3) at high collagen concentrations platelet aggregation (which is unresponsive to aspirin under such conditions) was blocked by S35b as well. Thus the drug action is likely to be exerted at an early step of the platelet activation pathway. The elevation in the platelet cGMP level evoked by S35b in a time- and concentration-dependent manner can account for the inhibitory effect: increased cGMP levels could interfere, for instance, with G protein-phospholipase C coupling and subsequent phosphoinositide hydrolysis.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Arachidonic Acid; Blood Platelets; Calcium; Cyclic GMP; Enzyme Activation; Furans; Glutathione; Guanylate Cyclase; Humans; Oxadiazoles; Platelet Aggregation; Platelet Aggregation Inhibitors; Prostaglandin Endoperoxides, Synthetic