15-hydroxy-11-alpha-9-alpha-(epoxymethano)prosta-5-13-dienoic-acid and 8-bromoguanosino-3--5--cyclic-monophosphorothioate

Puerarin, an isoflavonoid derived from the Chinese medicinal herb Radix puerariae, has been suggested to be useful in the management of various cardiovascular disorders. The present study examined the effect of acute exposure (30 min) to puerarin on vascular relaxation. Rings from porcine coronary artery of either sex were used. The highest concentration of puerarin (100 microM) produced a small but statistically significant relaxation of U46619-contracted rings. Vascular relaxations were also studied in the presence of lower concentrations of puerarin (0.1, 1 and 10 microM) which had no direct relaxation effect. Puerarin enhanced vasorelaxation to endothelium-independent relaxing agents, sodium nitroprusside and cromakalim. However, puerarin had no effect on vasorelaxation induced by endothelium-dependent relaxing agents, bradykinin and calcium ionophore A23187. The potentiating action of puerarin (10 microM) on sodium nitroprusside-mediated relaxation was not affected by the nitric oxide synthase inhibitor, N(omega)-nitro-L-arginine methyl ester (L-NAME; 300 microM), or by the disruption of the endothelium with Triton X-100. The effect of puerarin was reversible following a washout period. The potentiating effects were comparable with the 3'-5'-cyclic adenosine monophosphate (cyclic AMP) analogues, 8-bromoadenosine-3'-5'-cyclic monophosphate (8-Br-cyclic AMP; 10 muM) and Sp-isomer [S nomenclature refers to phosphorus] of adenosine-3', 5'-cyclic monophosphorothioate (Sp-cyclic AMPS; 3 microM), but not the 3'-5'-cyclic guanosine monophosphate (cyclic GMP) analogue, 8-bromoguanosine-3'-5'-cyclic monophosphate (8-Br-cyclic GMP; 3 microM). The cyclic AMP antagonist, Rp-isomer [R nomenclature refers to phosphorus] of 8-bromoadenosine-3', 5'-cyclic monophosphorothioate (Rp-8-Br-cyclic AMPS; 10 microM), but not cyclic GMP antagonist, Rp-isomer of 8-bromoguanosine-3', 5'-cyclic monophosphorothioate (Rp-8-Br-cyclic GMPS; 10 microM), reversed the effects of puerarin (10 microM) on the enhancement of vasorelaxation to sodium nitroprusside. Our results demonstrated that puerarin enhanced sodium nitroprusside-induced relaxation, possibly via the cyclic AMP-dependent pathway.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8-Bromo Cyclic Adenosine Monophosphate; Animals; Coronary Vessels; Cyclic AMP; Cyclic GMP; Dose-Response Relationship, Drug; Drug Synergism; Endothelium, Vascular; Enzyme Inhibitors; Female; In Vitro Techniques; Isoflavones; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitroprusside; Plant Roots; Pueraria; Signal Transduction; Swine; Thionucleotides; Vasoconstriction; Vasoconstrictor Agents; Vasodilation; Vasodilator Agents

The aim of the present study was to investigate the involvement of adenosine 3',5'-cyclic monophosphate (cAMP) cascade in the acute impairment of contraction by 17beta-estradiol in porcine coronary arteries, and to elucidate the signaling pathway leading to the activation of this cascade by the hormone. Isometric tension was recorded in isolated rings of porcine coronary arteries. The contraction to U46619 was reduced significantly following 30 min incubation with 1 nM 17beta-estradiol or 1 nM isoproterenol. There was no additive effect when 17beta-estradiol and isoproterenol were administered together. The effect of 17beta-estradiol was mimicked by both the cyclic AMP analogue 8-Br-cAMP and the guanosine 3',5'-cyclic monophosphate (cyclic GMP) analogue 8-Br-cGMP. In rings with and without endothelium, the modulatory effect of 17beta-estradiol was abolished by the adenylyl cyclase inhibitor, SQ 22536, but was unaffected by the guanylyl cyclase inhibitor, ODQ. Both the cAMP antagonist Rp-8-Br-cAMPS and the cGMP antagonist inhibitor Rp-8-Br-cGMPS inhibited the effect of 17beta-estradiol. The effect of 17beta-estradiol was unaffected by the protein kinase A inhibitor, KT5720, but was abolished by the protein kinase G (PKG) inhibitor, KT5823, which also abolished the effect of isoproterenol. These data support our earlier findings that 17beta-estradiol (1 nM) acutely impairs contractile responses of porcine coronary arteries in vitro. This acute effect of 17beta-estradiol involves cAMP in vascular smooth muscles and the activation of PKG.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; 8-Bromo Cyclic Adenosine Monophosphate; Adenine; Adenylyl Cyclase Inhibitors; Animals; Carbazoles; Coronary Vessels; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; Drug Interactions; Estradiol; Indoles; Isometric Contraction; Isoproterenol; Muscle, Smooth, Vascular; Swine; Thionucleotides; Time Factors

Acute respiratory distress syndrome (ARDS) is associated with increased superoxide (O(2)(*-)) formation in the pulmonary vasculature and negation of the bioavailability of nitric oxide (NO). Since NO inhibits NADPH oxidase expression through a cyclic GMP-mediated mechanism, sildenafil, a type V phosphodiesterase inhibitor, may be therapeutically effective in ARDS through an augmentation of NO-mediated inhibition of NADPH oxidase. Therefore, the effect of sildenafil citrate and NO-donating sildenafil (NCX 911) on O(2)(*-) formation and gp91(phox) (active catalytic subunit of NADPH oxidase) expression was investigated in cultured porcine pulmonary artery endothelial cells (PAECs). PAECs were incubated with 10 nM TXA(2) analogue, 9,11-dideoxy-9alpha,11alpha-methanoepoxy-prostaglandin F(2alpha) (U46619) (+/-sildenafil or NCX 911), for 16 h and O(2)(*-) formation measured spectrophometrically and gp91(phox) using Western blotting. The role of the NO-cGMP axis was studied using morpholinosydnonimine hydrochloride (SIN-1), the diethylamine/NO complex (DETA-NONOate), the guanylyl cyclase inhibitor, 1H-{1,2,4}oxadiazolo{4,3-a}quinoxalin-1-one (ODQ), and the protein kinase G inhibitor, 8-bromoguanosine-3',5'-cyclic monophosphorothioate, Rp-isomer (Rp-8-Br-cGMPS). NO release was studied using a fluorescence assay and O(2)(*-)-NO interactions by measuring nitrites. After a 16-h incubation with 10 nM U46619, both NCX 911 and sildenafil elicited a concentration-dependent inhibition of O(2)(*-) formation and gp91(phox) expression, NCX 911 being more potent (IC(50); 0.26 nM) than sildenafil citrate (IC(50); 1.85 nM). These inhibitory effects were reversed by 1 microM ODQ and 10 microM Rp-8-Br-cGMPS. NCX 911 stimulated the formation of cGMP in PAECs and generated NO in a cell-free system to a greater degree than sildenafil citrate. The inhibitory effect of sildenafil was augmented by 1 muM SIN-1 and blocked partially by the eNOS inhibitor 10 microM N(5)-(1-iminoethyl)-ornithine (L-NIO). Acutely, sildenafil and NCX 911 also inhibited O(2)(*-) formation, again blocked by 1 microM ODQ. NCX 911 reacted with O(2)(*-) generated by xanthine oxidase, an effect that was inhibited by superoxide dismutase (500 U ml(-1)). Since O(2)(*-) formation plays contributory role in ARDS, both sildenafil citrate and NCX 911 may be indicated for treating ARDS through suppression of NADPH oxidase expression and therefore of O(2)(*-) formation and preservation of NO bioavailability.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Cells, Cultured; Cyclic GMP; Endothelial Cells; Guanylate Cyclase; Male; Membrane Glycoproteins; NADPH Oxidases; Nitric Oxide; Nitric Oxide Synthase; Ornithine; Oxadiazoles; Piperazines; Protein Kinase Inhibitors; Pulmonary Artery; Purines; Quinoxalines; Sildenafil Citrate; Sulfones; Superoxides; Swine; Thionucleotides