Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The present study was aimed to elucidate the cellular pathway(s) controlling vascular relaxation triggered by stimulation of prostaglandin I2 (PGI2, IP) receptor with a stable PGI2 analog, beraprost. Beraprost caused a concentration-dependent relaxation in de-endothelialized guinea-pig aorta contracted with prostaglandin F2alpha (PGF2alpha). Beraprost-induced relaxation was almost abolished in high-KCl-contracted tissue, indicating a major role of K+ conductances. In contrast to other PGI2 analogs (e.g. cicaprost and iloprost), beraprost-induced relaxation was practically abolished by a selective voltage and Ca2+-activated K+ (MaxiK, BK) channel blocker Iberiotoxin (10(-7) M) or by tetraethylammonium (2 x 10(-3) M). The relaxation induced by beraprost was not significantly affected by other K+ channel blockers glibenclamide (10(-6) M) or Ba2+ (10(-5) M), but was slightly attenuated by 4-aminopyridine (10(-4) M). Beraprost increased intracellular cyclic AMP levels, suggesting a role for cyclic AMP-dependent pathways. A selective inhibitor of cyclic AMP-specific phosphodiesterase, RO-20-1724 (10(-4) M), significantly potentiated beraprost-induced relaxation. Iberiotoxin (10(-7) M) completely counteracted this potentiation. Moreover, tension decrement due to forskolin (3 x 10(-7) M) or 8-bromo-cyclic AMP (10(-2) M) was thoroughly restored by Iberiotoxin (10(-7) M), confirming a role for a cyclic AMP-dependent mechanism. However, SQ 22,536 (10(-4) M), an adenylyl cyclase inhibitor, did not affect beraprost-induced relaxation though it almost totally inhibited the elevation of cyclic AMP contents induced by beraprost, suggesting the existence of an additional mechanism that is cyclic AMP-independent. Moreover, cholera toxin (CTX, 1 microg/ml for 6 h), which activates the stimulatory G protein of adenylyl cyclase (Gs), significantly suppressed PGF2alpha-induced contraction both in the absence and presence of SQ 22,536 (10(-4) M). Iberiotoxin (10(-7) M) was also capable of restoring the relaxation induced by CTX. These findings suggest that MaxiK channel plays a primary role in mediating smooth muscle relaxation following stimulation of IP receptor with beraprost in guinea-pig aorta. Both cyclic AMP-dependent and -independent pathways contribute to the MaxiK channel-mediated relaxation following IP receptor stimulation in this vascular tissue. Direct regulation of MaxiK channels by Gs may partly account for the cyclic AMP-independent relaxant mechanism.
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PMID:MaxiK channel-mediated relaxation of guinea-pig aorta following stimulation of IP receptor with beraprost via cyclic AMP-dependent and -independent mechanisms. 1177 9

Sildenafil, an oral phosphodiesterase type-5 inhibitor, has vasodilatory effects through a cyclic guanosine 3', 5'-monophosphate-dependent mechanism, whereas beraprost, an oral prostacyclin analog, induces vasorelaxation through a cAMP-dependent mechanism. We investigated whether the combination of oral sildenafil and beraprost is superior to each drug alone in the treatment of pulmonary hypertension. Rats were randomized to receive repeated administration of saline, sildenafil, beraprost, or both of these drugs twice a day for 3 weeks. Three weeks after monocrotaline (MCT) injection, there was significant development of pulmonary hypertension. The increases in right ventricular systolic pressure and ratio of right ventricular weight to body weight were significantly attenuated in the Sildenafil and Beraprost groups. Combination therapy with sildenafil and beraprost had additive effects on increases in plasma cAMP and cyclic guanosine 3', 5'-monophosphate levels, resulting in further improvement in pulmonary hemodynamics compared with treatment with each drug alone. Unlike MCT rats given saline, sildenafil, or beraprost alone, all rats treated with both drugs remained alive during 6-week follow-up. These results suggest that combination therapy with oral sildenafil and beraprost attenuates the development of MCT-induced pulmonary hypertension compared with treatment with each drug alone.
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PMID:A combination of oral sildenafil and beraprost ameliorates pulmonary hypertension in rats. 1469 2

Pulmonary arterial hypertension (PAH) is an important cause of death in systemic sclerosis (SSc), despite the improvement of therapies. An early diagnosis and the use of drugs interfering with the main pathogenic pathways of PAH is pivotal for the improvement of prognosis in primary PAH and PAH secondary to autoimmune rheumatic diseases, mainly SSc. Lately, new specific therapies have been developed targeting prostacyclin, endothelin, and nitric oxide pathways, the major pathogenic pathways leading to endothelial dysfunction in PAH. Epoprostenol improved life expectancy of patients with primary and secondary PAH, but its continuous intravenous administration requires experienced centers. More stable analogues of prostacyclin, administrated by intravenous (iloprost, treprostinil), subcutaneous, inhalatory (treprostinil, iloprost), and oral route (Beraprost) have shown efficacy in PAH. Bosentan, the first oral endothelin receptor antagonist (with affinity for endothelin A and B receptors) improves exercise function and survival in PAH, both primary and secondary to autoimmune rheumatic diseases. This is confirmed also for Sitaxsentan and Ambrisentan, selective A receptor antagonists. Because of its short half-life and systemic side effects, short-term NO inhalation is used only in short-term management of PAH in critically ill adults. Inhibitors of NO degradation, such as sildenafil, a phosphodiesterase (PDE) type 5 inhibitor, improved functional and hemodynamic parameters without significant side effects. Vardenafil and taladafil, longer-acting PDE inhibitors, also have vascular pulmonary selectivity. All these drugs may be used in combination, to maximize their clinical benefit not only in patients unresponsive to single drugs, but also potentially as initial therapy of PAH.
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PMID:Therapeutic challenges for systemic sclerosis: facts and future targets. 1791 60

Patients with Eisenmenger syndrome form a small percentage of congenital heart disease patients. The rarity of this syndrome, combined with its complex pathophysiology, account for the insufficient understanding of the principles underlying its proper treatment. The main clinical symptoms are: cyanosis due to secondary erythrocytosis, resulting in increased blood viscosity, iron deficiency anemia (enhanced by unnecessary phlebotomies), blood clotting disturbances, heart failure and serious supraventricular and ventricular arrhythmias. Recent decades have seen developments in pulmonary hypertension pathophysiology which have led to the introduction of new groups of drugs: prostacycline analogs (Epoprostenol, Treprostinil, Beraprost, Illoprost), phosphodiesterase inhibitors (Sildenafil, Tadalafil), endothelin receptor antagonists (Bosentan, Sitaxantan, Ambrisentan) and nitric oxide. These drugs should be administered to patients in III-IV NYHA class. Despite successful early results, the therapeutic effect on patients with Eisenmenger syndrome has not been conclusively established. Our therapeutic efforts should be directed mainly towards preventing complications. As a rule, we should avoid agents with no established therapeutic efficacy and try to alleviate symptoms without any additional risk, so as not to disrupt the existing clinical balance.
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PMID:Therapeutic methods used in patients with Eisenmenger syndrome. 1995 85

A number of studies have reported that acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are independent risk factors for organ dysfunction and mortality in patients with sepsis. Although ALI/ARDS might be an essential therapeutic target during the management of sepsis, severe sepsis should be treated effectively and as soon as identified. We have classified three phases, ranging from sepsis to organ dysfunction, characterizing the interaction between neutrophils and platelets. The first phase is neutrophil extracellular trap (NET) formation and intravasated platelet aggregation. The next phase is extravasated platelet aggregation (EPA), promoted by NET-facilitated detachment of endothelial cells. The final phase is organ dysfunction, caused by pulmonary veno-occlusive disease (VOD), fibrosis, and immunoparalysis induced by EPA. Severe sepsis is characterized by a continuum of coagulopathy, with coagulation abnormalities often developing before the onset of clinical symptoms. The initial medical treatment for ALI/ARDS is inhibition of NET formation and intravasated platelet aggregation to prevent endothelial cell damage (Phase 1). Beraprost and silvestat, phosphodiesterase 3 (PDE3) inhibitors, are often administered in clinical practice. To determine hypercoagulopathy, plasma levels of thrombin-antithrombin complex and plasmin-plasmin inhibitor complex are continuously monitored in patients with suspected sepsis. Furthermore, the implementation of quality indicators for the early management of severe sepsis and septic shock is strongly associated with a reduced mortality. We conclude that pathophysiology of organ dysfunction from severe sepsis is caused by pulmonary VOD, fibrosis, and EPA-facilitated immunoparalysis. In order to prevent ALI/ARDS in patients with sepsis, countermeasures for NET and platelet aggregation should be pre-emptively employed and confirmed by several trials.
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PMID:A Three-phase Approach for the Early Identification of Acute Lung Injury Induced by Severe Sepsis. 2738 95