Widening the Prostacyclin Paradigm: Tissue Fibroblasts Are a Critical Site of Production and Antithrombotic Protection.

BACKGROUND: Prostacyclin is a fundamental signaling pathway traditionally associated with the cardiovascular system and protection against thrombosis but which also has regulatory functions in fibrosis, proliferation, and immunity. Prevailing dogma states that prostacyclin is principally derived from vascular endothelium, although it is known that other cells can also synthesize it. However, the role of nonendothelial sources in prostacyclin production has not been systematically evaluated resulting in an underappreciation of their importance relative to better characterized endothelial sources. METHODS: To address this, we have used novel endothelial cell-specific and fibroblast-specific COX (cyclo-oxygenase) and prostacyclin synthase knockout mice and cells freshly isolated from mouse and human lung tissue. We have assessed prostacyclin release by immunoassay and thrombosis in vivo using an FeCl3-induced carotid artery injury model. RESULTS: We found that in arteries, endothelial cells are the main source of prostacyclin but that in the lung, and other tissues, prostacyclin production occurs largely independently of endothelial and vascular smooth muscle cells. Instead, in mouse and human lung, prostacyclin production was strongly associated with fibroblasts. By comparison, microvascular endothelial cells from the lung showed weak prostacyclin synthetic capacity compared with those isolated from large arteries. Prostacyclin derived from fibroblasts and other nonendothelial sources was seen to contribute to antithrombotic protection. CONCLUSIONS: These observations define a new paradigm in prostacyclin biology in which fibroblast/nonendothelial-derived prostacyclin works in parallel with endothelium-derived prostanoids to control thrombotic risk and potentially a broad range of other biology. Although generation of prostacyclin by fibroblasts has been shown previously, the scale and systemic activity was unappreciated. As such, this represents a basic change in our understanding and may provide new insight into how diseases of the lung result in cardiovascular risk.

Association between serum prostacyclin and cerebrovascular reactivity in healthy young and older adults.

NEW FINDINGS: What is the central question of this study? What is the relationship between prostacyclin and cerebrovascular reactivity to hypercapnia before and after administration of a cyclooxygenase inhibitor, indomethacin, in healthy young and older adults? What is the main finding and importance? Serum prostacyclin was not related to cerebrovascular reactivity to hypercapnia before or after administration of indomethacin. However, in older adults, serum prostacyclin was related to the magnitude of change in cerebrovascular reactivity from before to after indomethacin administration. This suggests that older adults with higher serum prostacyclin may rely more on cyclooxygenase products to mediate cerebrovascular reactivity. ABSTRACT: Platelet activation may contribute to age-related cerebrovascular dysfunction by interacting with the endothelial cells that regulate the response to vasodilatory stimuli. This study evaluated the relationship between a platelet inhibitor, prostacyclin, and cerebrovascular reactivity (CVR) in healthy young (n = 35; 25 ± 4 years; 17 women, 18 men) and older (n = 12; 62 ± 2 years; 8 women, 4 men) adults, who were not daily aspirin users, before and after cyclooxygenase inhibition. Prostacyclin was determined by levels of 6-keto-prostaglandin F1α (6-keto PGF1α) in the blood. CVR was assessed by measuring the middle cerebral artery blood velocity response to hypercapnia using transcranial Doppler ultrasound before (CON) and 90 min after cyclooxygenase inhibition with indomethacin (INDO). In young adults, there were no associations between prostacyclin and middle cerebral artery CVR during CON (r = -0.14, P = 0.415) or INDO (r = 0.27, P = 0.118). In older adults, associations between prostacyclin and middle cerebral artery CVR during CON (r = 0.53, P = 0.075) or INDO (r = -0.45, P = 0.136) did not reach the threshold for significance. We also evaluated the relationship between prostacyclin and the change in CVR between conditions (ΔCVR). We found no association between ΔCVR and prostacyclin in young adults (r = 0.27, P = 0.110); however, in older adults, those with higher baseline prostacyclin levels demonstrated significantly greater ΔCVR (r = -0.74, P = 0.005). In conclusion, older adults with higher serum prostacyclin, a platelet inhibitor, may rely more on cyclooxygenase products for cerebrovascular reactivity to hypercapnia.

Prostacyclin receptor agonists induce DUSP1 to inhibit pulmonary artery smooth muscle cell proliferation.

AIMS: Upregulated p38MAPK signaling is implicated in the accelerated proliferation of pulmonary artery smooth muscle cells (PA-SMCs) and the pathogenesis of pulmonary artery remodeling observed in pulmonary arterial hypertension (PAH). Previously, we reported that after endothelin-1 (ET-1) pretreatment, bone morphogenetic protein 2 (BMP2) activates p38MAPK signaling and accelerates PA-SMC proliferation. The activity of p38MAPK signaling is tightly regulated by the inactivation of dual-specificity phosphatase 1 (DUSP1). Activated p38MAPK induces DUSP1 expression, forming a negative feedback loop. Prostacyclin IP receptor agonists (prostacyclin and selexipag) are used to treat PAH. In this study, we aimed to verify whether IP receptor agonists affect DUSP1 expression and accelerate the proliferation of PA-SMCs. MAIN METHODS: PA-SMCs were treated with BMP2, ET-1, prostacyclin, and MRE-269, an active metabolite of selexipag, either alone or in combination. We quantified mRNA expressions using real-time quantitative polymerase chain reaction. Pulmonary artery specimens and PA-SMCs were obtained during lung transplantation in patients with PAH. KEY FINDINGS: Both prostacyclin and MRE-269 increased DUSP1 expression. Combined treatment with BMP2 and ET-1 induced cyclin D1 and DUSP1 expression and increased PA-SMC proliferation. MRE-269 attenuated BMP2/ET-1-induced cell proliferation. ET-1 increased DUSP1 expression in PA-SMCs from control patients but not in PA-SMCs from patients with PAH. SIGNIFICANCE: This study showed that the p38MAPK/DUSP1 negative feedback loop is impaired in PAH, contributing to unregulated p38MAPK activation and PA-SMC hyperplasia. IP receptor agonist MRE-269 increases DUSP1 expression and inhibit p38MAPK-mediated PA-SMC proliferation. Future elucidation of the detailed mechanism underlying reduced DUSP1 expression would be informative for PAH treatment.

The Effect of the Extra Virgin Olive Oil Minor Phenolic Compound 3',4'-Dihydroxyphenylglycol in Experimental Diabetic Kidney Disease.

The aim of this study was to analyze the possible nephroprotective effect of 3',4'-dihydroxyphenylglycol (DHPG), a polyphenolic compound of extra virgin olive oil (EVOO), on renal lesions in an experimental model of type 1 diabetes. Rats were distributed as follows: healthy normoglycemic rats (NDR), diabetic rats treated with saline (DR), and DR treated with 0.5 mg/kg/day or 1 mg/kg/day of DHPG. DR showed a significantly higher serum and renal oxidative and nitrosative stress profile than NDR, as well as reduced prostacyclin production and renal damage (defined as urinary protein excretion, reduced creatinine clearance, increased glomerular volume, and increased glomerulosclerosis index). DHPG reduced the oxidative and nitrosative stress and increased prostacyclin production (a 59.2% reduction in DR and 34.7-7.8% reduction in DHPG-treated rats), as well as 38-56% reduction in urinary protein excretion and 22-46% reduction in glomerular morphological parameters (after the treatment with 0.5 or 1 mg/kg/day, respectively). Conclusions: DHPG administration to type 1-like diabetic rats exerts a nephroprotective effect probably due to the sum of its antioxidant (Pearson's coefficient 0.68-0.74), antinitrosative (Pearson's coefficient 0.83), and prostacyclin production regulator (Pearson's coefficient 0.75) effects.

Prostacyclin analogues decrease platelet aggregation but have no effect on thrombin generation, fibrin clot structure, and fibrinolysis in pulmonary arterial hypertension: PAPAYA coagulation.

Prostacyclin (PGI2) analogues (epoprostenol, treprostonil, iloprost) are the cornerstone of pulmonary arterial hypertension (PAH) treatment. PGI2 analogues inhibit platelet reactivity, but their impact on coagulation and fibrinolysis parameters has not been elucidated. We compared platelet reactivity, thrombin generation, clot permeation, and lysis properties in patients with PAH treated with PGI2 analogues (n = 20) and those not receiving PGI2 analogues (n = 20). Platelet reactivity was lower in patients treated with PGI2 analogues, compared to the control group, as evaluated with arachidonic acid (ASPI), adenosine diphosphate (ADP), and thrombin receptor-activating peptide-6 (TRAP) tests (p = .009, p = .02, p = .007, respectively). In the subgroup analysis, both treprostinil and epoprostenol decreased platelet reactivity to the similar extent. There were no differences regarding thrombin generation, clot permeation, and lysis parameters in patients receiving and not receiving PGI2 analogues (p ≥ .60 for all). In the subgroup analysis, there were no differences regarding coagulation and fibrinolysis parameters between treprostinil, epoprostenol, and no PGI2 analogues. To conclude, patients with PAH treated with PGI2 analogues have reduced platelet reactivity, but similar clot formation and lysis parameters, compared to patients not receiving PGI2 analogues. Further randomized clinical trials are required to confirm these findings.

Differential properties of E prostanoid receptor-3 and thromboxane prostanoid receptor in activation by prostacyclin to evoke vasoconstrictor response in the mouse renal vasculature.

Vasomotor reactions of prostacyclin (prostaglandin I2 ; PGI2 ) can be collectively modulated by thromboxane prostanoid receptor (TP), E-prostanoid receptor-3 (EP3), and the vasodilator I prostanoid receptor (IP). This study aimed to determine the direct effect of PGI2 on renal arteries and/or the whole renal vasculature and how each of these receptors is involved. Experiments were performed on vessels or perfused kidneys of wild-type mice and/or mice with deficiency in TP (TP-/- ) and/or EP3. Here we show that PGI2 did not evoke relaxation, but instead resulted in contraction of main renal arteries (from ~0.001-0.01 µM) or reduction of flow in perfused kidneys (from ~1 µM); either of them was reversed into a dilator response in TP-/- /EP3-/- counterparts. Also, we found that in renal arteries although it has a lesser effect than TP-/- on the maximal contraction to PGI2 (10 µM), EP3-/- but not TP-/- resulted in relaxation to the prostanoid at 0.01-1 µM. Meanwhile, TP-/- only significantly reduced the contractile activity evoked by PGI2 at ≥0.1 µM. These results demonstrate that PGI2 may evoke an overall vasoconstrictor response in the mouse renal vasculature, reflecting activities of TP and EP3 outweighing that of the vasodilator IP. Also, our results suggest that EP3, on which PGI2 can have a potency similar to that on IP, plays a major role in the vasoconstrictor effect of the prostanoid of low concentrations (≤1 µM), while TP, on which PGI2 has a lower potency but higher efficacy, accounts for a larger part of its maximal contractile activity.

Prostacyclin mimetics afford protection against lipopolysaccharide/d-galactosamine-induced acute liver injury in mice.

Prostacyclin (PGI2) serves as a protective, anti-inflammatory mediator and PGI2 mimetics may be useful as a hepatoprotective agent. We examined whether two PGI2 mimetics, ONO-1301 and beraprost, are beneficial in acute liver injury and attempted to delineate the possible mechanism underlying the hepatoprotective effect. Acute liver injury was induced by lipopolysaccharide/d-galactosamine (LPS/GalN) in mice. Mice were given an intraperitoneal injection of PGI2 mimetics 1h before LPS/GalN challenge. Both ONO-1301 and beraprost significantly declined the LPS/GalN-induced increase in serum aminotransferase activity. ONO-1301 and, to a lesser extent, beraprost inhibited hepatic gene expression levels of pro-inflammatory cytokines, which were sharply elevated by LPS/GalN. The hepatoprotective effects of ONO-1301, to a lesser extent, of beraprost were also supported by liver histopathological examinations. The PGI2 receptor antagonist CAY10441 abrogated their hepatoprotective effects. The mechanisms behind the benefit of PGI2 mimetics in reducing LPS/GalN-induced liver injury involved, in part, their suppressive effects on increased generation of reactive oxygen species (ROS), since their ability to prevent LPS/GalN-induced hepatic apoptosis was mimicked by the antioxidant N-acetyl-l-cysteine. They significantly diminished LPS/GalN-induced activation of signal transducers and activators of transcription 3 (STAT3) in liver tissues, an effect which was highly associated with their hepatoprotective effects. We indicate that IP receptor activation with PGI2 mimetics can rescue the damage in the liver induced by LPS/GalN by undermining activation of STAT3 and leading to a lower production of ROS. Our findings point to PGI2 mimetics, especially ONO-1301, as a potential novel therapeutic modality for the treatment of acute liver injury.

Asthma causes inflammation of human pulmonary arteries and decreases vasodilatation induced by prostaglandin I2 analogs.

OBJECTIVE: Asthma is a chronic inflammatory disease associated with increased cardiovascular events. This study assesses the presence of inflammation and the vascular reactivity of pulmonary arteries in patients with acute asthma. METHODS: Rings of human pulmonary arteries obtained from non-asthmatic and asthmatic patients were set up in organ bath for vascular tone monitoring. Reactivity was induced by vasoconstrictor and vasodilator agents. Protein expression of inflammatory markers was detected by western blot. Prostanoid releases and cyclic adenosine monophosphate (cAMP) levels were quantified using specific enzymatic kits. RESULTS: Protein expression of cluster of differentiation 68, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and cyclooxygenase-2 was significantly increased in arteries obtained from asthmatic patients. These effects were accompanied by an alteration of vasodilatation induced by iloprost and treprostinil, a decrease in cAMP levels and an increase in prostaglandin (PG) E2 and PGI2 synthesis. The use of forskolin (50 µmol/L) has restored the vasodilatation and cAMP release. No difference was observed between the two groups in reactivity induced by norepinephrine, angiotensin II, PGE2, KCl, sodium nitroprusside, and acetylcholine. CONCLUSION: Acute asthma causes inflammation of pulmonary arteries and decreases vasodilation induced by PGI2 analogs through the impairment of cAMP pathway.

Inotropic Effects of Prostacyclins on the Right Ventricle Are Abolished in Isolated Rat Hearts With Right-Ventricular Hypertrophy and Failure.

BACKGROUND: Prostacyclin mimetics are vasodilatory agents used in the treatment of pulmonary arterial hypertension. The direct effects of prostanoids on right-ventricular (RV) function are unknown. We aimed to investigate the direct effects of prostacyclin mimetics on RV function in hearts with and without RV hypertrophy and failure. METHODS: Wistar rats were subjected to pulmonary trunk banding to induce compensated RV hypertrophy (n = 32) or manifest RV failure (n = 32). Rats without banding served as healthy controls (n = 30). The hearts were excised and perfused in a Langendorff system and subjected to iloprost, treprostinil, epoprostenol, or MRE-269 in increasing concentrations. The effect on RV function was evaluated using a balloon-tipped catheter inserted into the right ventricle. RESULTS: In control hearts, iloprost, treprostinil, and MRE-269 improved RV function. The effect was, however, absent in hearts with RV hypertrophy and failure. Treprostinil and MRE-269 even impaired RV function in hearts with manifest RV failure. CONCLUSIONS: Iloprost, treprostinil, and MRE-269 improved RV function in the healthy rat heart. RV hypertrophy abolished the positive inotropic effect, and in the failing right ventricle, MRE-269 and treprostinil impaired RV function. This may be related to changes in prostanoid receptor expression and reduced coronary flow reserve in the hypertrophic and failing right ventricle.

The evolution of prostacyclins in pulmonary arterial hypertension: from classical treatment to modern management.

Prostacyclins for the treatment of pulmonary arterial hypertension (PAH) have historically been covered under the insurance medical benefit because they require durable medical equipment and are administered by an intravenous, subcutaneous, or inhalation route. However, more treatment options that target the prostacyclin pathway have become available. As the number and type of options expand, an improved understanding of these drugs will aid managed care decision makers in evaluating new treatment options and making clinically sound and cost-effective treatment decisions. PAH is a progressive disease of pulmonary vascular remodeling that increases pulmonary vascular resistance and often results in right-side heart failure and death if left untreated. Adverse event profiles, the complexity of administration modalities, and potential complications must be considered when administering prostacyclin therapy. Traditional modes of administration, with their potential challenges and complications, may have contributed to the unmet need for an oral agent. Another consideration for managed care decision makers is that oral agents are generally covered under the insurance pharmacy benefit. Access to oral medications with long-term outcomes data, as well as the improved convenience of oral therapy, may help patients with PAH maximize function by maintaining a more convenient and consistent therapeutic regimen.

Role of Krev Interaction Trapped-1 in Prostacyclin-Induced Protection against Lung Vascular Permeability Induced by Excessive Mechanical Forces and Thrombin Receptor Activating Peptide 6.

Mechanisms of vascular endothelial cell (EC) barrier regulation during acute lung injury (ALI) or other pathologies associated with increased vascular leakiness are an active area of research. Adaptor protein krev interaction trapped-1 (KRIT1) participates in angiogenesis, lumen formation, and stabilization of EC adherens junctions (AJs) in mature vasculature. We tested a role of KRIT1 in the regulation of Rho-GTPase signaling induced by mechanical stimulation and barrier dysfunction relevant to ventilator-induced lung injury and investigated KRIT1 involvement in EC barrier protection by prostacyclin (PC). PC stimulated Ras-related protein 1 (Rap1)-dependent association of KRIT1 with vascular endothelial cadherin at AJs, with KRIT1-dependent cortical cytoskeletal remodeling leading to EC barrier enhancement. KRIT1 knockdown exacerbated Rho-GTPase activation and EC barrier disruption induced by pathologic 18% cyclic stretch and thrombin receptor activating peptide (TRAP) 6 and attenuated the protective effects of PC. In the two-hit model of ALI caused by high tidal volume (HTV) mechanical ventilation and TRAP6 injection, KRIT1 functional deficiency in KRIT1(+/-) mice increased basal lung vascular leak and augmented vascular leak and lung injury caused by exposure to HTV and TRAP6. Down-regulation of KRIT1 also diminished the protective effects of PC against TRAP6/HTV-induced lung injury. These results demonstrate a KRIT1-dependent mechanism of vascular EC barrier control in basal conditions and in the two-hit model of ALI caused by excessive mechanical forces and TRAP6 via negative regulation of Rho activity and enhancement of cell junctions. We also conclude that the stimulation of the Rap1-KRIT1 signaling module is a major mechanism of vascular endothelial barrier protection by PC in the injured lung.

Prostacyclins.

Prostacyclins have a favourable pharmacological profile for treatment of pulmonary hypertension as they possess vasodilative, antiproliferative, antiaggregatory, and anti-inflammatory properties that may compensate the main pathologic changes in the small pulmonary arteries. In severe pulmonary hypertension these vessels show a deficit in the endogenous prostacyclin secretion. The therapeutic potential of prostacyclin for pulmonary hypertension has been known since 30 years, and since nearly 20 years prostacyclin has been approved for idiopathic PAH. There are intravenous, subcutaneous, and inhaled approaches of different substances who share many but not all pharmacologic properties. However, none of these approaches are easy and free of adverse effects. Long-term experience and careful decision-making are instrumental to achieve favourable clinical long-term results.

11-deoxy prostaglandin F(2α), a thromboxane A2 receptor agonist, partially alleviates embryo crowding in Lpar3((-/-)) females.

OBJECTIVE: To determine cyclooxygenase-derived prostanoid signaling in alleviating embryo crowding in the Lpar3((-/-)) females. DESIGN: Experimental mouse model. SETTING: Research laboratories. ANIMAL(S): Wild-type, Lpar3((+/-)), and Lpar3((-/-)) mice. INTERVENTION(S): Intraperitoneal (IP) administration of prostaglandin E(2) (PGE(2)), cPGI (a stable analogue of PGI(2)), and 11-deoxy prostaglandin F(2α) (11-deoxy PGF(2α), a thromboxane A(2) receptor agonist) to preimplantation gestation day 3.5 Lpar3((-/-)) females. MAIN OUTCOME MEASURE(S): Implantation sites were detected by blue dye reaction and embryo spacing was determined by the distribution of the implantation sites along the uterine horns on gestation day 4.5; pregnancy outcome was measured by litter size at birth. RESULT(S): Administration of PGE(2) + cPGI on gestation day 3.5 Lpar3((-/-)) females restored on-time implantation but did not affect embryo spacing or the number of implantation sites detected on gestation day 4.5; PGE(2) + cPGI treatment increased litter size at birth. Administration of PGE(2) + cPGI + 11-deoxy PGF(2α) on gestation day 3.5 Lpar3((-/-)) females rescued on-time implantation, partially dispersed the clustered implantation sites normally observed in the Lpar3((-/-)) females, increased the number of implantation sites detected on gestation day 4.5, and increased litter size at birth. CONCLUSION(S): The thromboxane A(2) receptor agonist 11-deoxy PGF(2α) can partially alleviate embryo crowding in the Lpar3((-/-)) females and embryo crowding likely contributes to reduced litter size in the Lpar3((-/-)) females.

Prostacyclin analogs stimulate VEGF production from human lung fibroblasts in culture.

Prostacyclin is a short-lived metabolite of arachidonic acid that is produced by several cells in the lung and prominently by endothelial cells. It increases intracellular cAMP levels activating downstream signaling thus regulating vascular mesenchymal cell functions. The alveolar wall contains a rich capillary network as well as a population of mesenchymal cells, i.e., fibroblasts. The current study evaluated the hypothesis that prostacyclin may mediate signaling between endothelial and mesenchymal cells in the alveolar wall by assessing the ability of prostacyclin analogs to modulate fibroblast release of VEGF. To accomplish this study, human lung fibroblasts were cultured in routine culture on plastic support and in three-dimensional collagen gels with or without three prostacyclin analogs, carbaprostacyclin, iloprost, and beraprost, and the production of VEGF was evaluated by ELISA and quantitative real-time PCR. Iloprost and beraprost significantly stimulated VEGF mRNA levels and protein release in a concentration-dependent manner. These effects were blocked by the adenylate cyclase inhibitor SQ-22536 and by the protein kinase A (PKA) inhibitor KT-5720 and were reproduced by a direct PKA activator but not by an activator of exchange protein directly activated by cAMP (Epac), indicating that cAMP-activated PKA signaling mediated the effect. Since VEGF serves to maintain the pulmonary microvasculature, the current study suggests that prostacyclin is part of a bidirectional signaling network between the mesenchymal and vascular cells of the alveolar wall. Prostacyclin analogs, therefore, have the potential to modulate the maintenance of the pulmonary microcirculation by driving the production of VEGF from lung fibroblasts.

Prostacyclin among prostanoids.

Prostanoids are cyclic lipid mediators which arise from enzymic cyclooxygenation of linear polyunsaturated fatty acids, e.g. arachidonic acid (20:4 n 6, AA). Biologically active prostanoids deriving from AA include stable prostaglandins (PGs), e.g. PGE(2), PGF(2alpha), PGD(2), PGJ(2) as well as labile prostanoids, i.e. PG endoperoxides (PGG(2), PGH(2)), thromboxane A(2) (TXA(2)) and prostacyclin (PGI(2)). A "Rabbit aorta Contracting Substance" (RCS) played important role in discovering of labile PGs. RCS was discovered in the Vane's Cascade as a labile product released along with PGs from the activated lung or spleen. RCS was identified as a mixture of PG endoperoxides and thromboxane A(2). Stable PGs regulate the cell cycle, smooth muscle tone and various secretory functions; they also modulate inflammatory and immune reactions. PG endoperoxides are intermediates in biosynthesis of all prostanoids. Thromboxane A(2) (TXA(2)) is the most labile prostanoid (with a half life of 30 s at 37 degrees C). It is generated mainly by blood platelets. TXA(2) is endowed with powerful vasoconstrictor, cytotoxic and thrombogenic properties. Again the Vane's Cascade was behind the discovery of prostacyclin (PGI(2)) with a half life of 4 min at 37 degrees C. It is produced by the vascular wall (predominantly by the endothelium) and it acts as a physiological antagonist of TXA(2). Moreover, prostacyclin per se is a powerful cytoprotective agent that exerts its action through activation of adenylate cyclase, followed by an intracellular accumulation of cyclic-AMP in various types of cells. In that respect PGI(2) collaborates with the system consisting of NO synthase (eNOS)/nitric oxide free radical (NO)/guanylate cyclase/cyclic-GMP. Both cyclic nucleotides (c-AMP and c-GMP) act in synergy as two energetic fists which defend the cellular machinery from being destroyed by endogenous or exogenous aggressors. Recently, a new partner has been recognized in this endogenous defensive squadron, i.e. a system consisting of heme oxygenase (HO-1)/carbon monoxide (CO)/biliverdin/biliverdin reductase/bilirubin. The expanding knowledge on the pharmacological steering of this enzymic triad (PGI(2)-S/eNOS/HO-1) is likely to contribute to the rational therapy of many systemic diseases such as atherosclerosis, diabetes mellitus, arterial hypertension or Alzheimer diseases. The discovery of prostacyclin broadened our pathophysiological horizon, and by itself opened new therapeutic possibilities. Prostacyclin sodium salt and its synthetic stable analogues (iloprost, beraprost, treprostinil, epoprostenol, cicaprost) are useful drugs for the treatment of the advanced critical limb ischemia, e.g. in the course of Buerger's disease, and also for the treatment of pulmonary artery hypertension (PAH). In this last case a synergism between prostacyclin analogues and sildenafil (a selective phosphodiesterase 5 inhibitor) or bosentan (an endothelin ET-1 receptor antagonist) points our to complex mechanisms controlling pulmonary circulation. At the Jagiellonian University we have demonstrated that several well recognised cardiovascular drugs, e.g. ACE inhibitors (ACE-I), statins, some of beta-adrenergic receptor antagonists, e.g. carvedilol or nebivolol, anti-platelet thienopyridines (ticlopidine, clopidogrel) and a metabolite of vitamin PP--N(1)-methyl-nicotinamide--all of them are endowed with the in vivo PGI(2)-releasing properties. In this way, the foundations for the Endothelial Pharmacology were laid.

[Treatment of pulmonary arterial hypertension: prostacyclin analogs]. / Therapie der pulmonalarteriellen Hypertonie: Prostazyklin-Analoga.

Prostanoids continue to be of great importance in the treatment of pulmonary hypertension (PHT). Their vasodilatory, antiproliferative, anti-inflammatory and anticoagulant profile of effects makes them suitable substances in the treatment of PHT whose pathogenesis, vasoconstriction, proliferation, vascular modelling and in-situ thromboses play a role. Current tendency is to use other oral drugs as primary and initial treatment. But it is important not to miss the point when prostanoids are required as additional or alternative treatment. Prostanoids are indicated in current treatment algorithms for patients in NYHA class III or IV, especially those in right ventricular failure. Prostanoids can be given by continual intravenous or subcutaneous infusion, by mouth or as inhalants. Inhalant isoprost is practicable and well tolerated and improves the clinical condition and survival prognosis when given to patients with severe PHT. New developments with prostanoids apply largely to combination treatment.

Prostacyclin analogues: prevention of cardiovascular diseases.

Prostacyclin (PGI(2)) inhibits platelet aggregation and vasoconstriction. PGI(2) synthase (PGIS), a catalyst of PGI(2) formation from prostaglandin H2, is widely distributed and predominantly found in vascular endothelial and smooth muscle cells. Vane et al. first discovered PGI(2) in 1976, for which they received the Nobel Prize in medicine and physiology in 1982. However, the later discovery of nitric oxide (NO), which also resulted in a Nobel Prize for the scientists involved, led to less attention being focused on PGI(2). The reason for this is somewhat perplexing and may have been due to the lack of information on how to correctly use PGI(2). Current findings suggest that researchers concentrated too much effort on the therapeutic effects of PGI(2), while largely ignoring the potential for preventative effects. In addition, PGI(2) was shown to be effective against diseases in some studies but was without effect in others. The present paper contains a review of PGI(2) and PGIS, in addition to an examination of the relationship between PGIS gene mutations and cardiovascular diseases. PGI(2) analogues that can be used in the prevention of cardiovascular diseases are also discussed.

Cyclooxygenases regulation by estradiol on endothelium.

Estrogen and hormone replacement therapies are being tested to prevent the incidence of cardiovascular disease in postmenopausal women. In spite of the evidence from several epidemiological studies suggesting that estrogens protect against atherosclerosis and associated diseases, controversy exists. Moreover, it is important to develop synthetic compounds that achieve the beneficial effects of estrogens on the cardiovascular system while minimizing such undesirable effects on other tissues as the increased risk of endometrial and breast cancer. Some drugs that modulate estrogen function in a tissue-specific manner (Selective Estrogen Receptor Modulators; SERMs) have been discovered and are currently being used in clinical practice. An example of these is raloxifene. Clinical and experimental data support the consideration of endothelium as a target for estradiol and other sexual hormones. Among other actions, estradiol has been implicated in the control of prostacyclin production through cyclooxygenases (COX) regulation in endothelial cells. Prostacyclins are powerful vasodilators and potent inhibitors of platelet aggregation which are produced from free arachidonic acid through the catalytic activity of two COX: COX-1 and COX-2. Together, these COX represent the main control mechanism for prostacyclin production. Although several non-specific COX inhibitors have been available for decades (aspirin, indomethacin, ibuprofen), COX-2 selective inhibitors have been commercialized only within the last few years, thus making it possible to increase the study and treatment of different disorders. This review will discuss clinical and experimental data that document the endothelial effects of estradiol and SERMs on prostacyclin production and COX regulation, their vascular consequences, and their possible interactions with COX inhibitors.

Acetylcholine-induced endothelium-dependent contractions in the SHR aorta: the Janus face of prostacyclin.

In the spontaneously hypertensive rat (SHR) and aging Wistar-Kyoto rats (WKY), acetylcholine releases an endothelium-derived contracting factor (EDCF) produced by endothelial cyclooxygenase-1, which stimulates thromboxane A2 receptors (TP receptors) on vascular smooth muscle. The purpose of the present study was to identify this EDCF by measuring changes in isometric tension and the release of various prostaglandins by acetylcholine. In isolated aortic rings of SHR, U 46619, prostaglandin (PG) H2, PGF2alpha, PGE2, PGD2, prostacyclin (PGI2) and 8-isoprostane, all activate TP receptors of the vascular smooth muscle to produce a contraction (U 46619>>8-isoprostane=PGF2alpha=PGH2>PGE2=PGD2>PGI2). The contractions produced by PGH2 and PGI2 were fast and transient, mimicking endothelium-dependent contractions. PGI2 did not relax isolated aortic rings of WKY and SHR. Acetylcholine evoked the endothelium-dependent release of thromboxane A2, PGF2alpha, PGE2, PGI2 and most likely PGH2 (PGI2>>PGF2alpha>or=PGE2>TXA2>8-isoprostane, PGD2). Dazoxiben abolished the production of thromboxane A2, but did not influence the endothelium-dependent contractions to acetylcholine. The release of PGI2 was significantly larger in the aorta of SHR than in WKY, and the former was more sensitive to the contractile effect of PGI2 than the latter. The inhibition of PGI-synthase was associated with an increase in PGH2 spillover and the enhancement of acetylcholine-induced endothelium-dependent contractions. Thus, in the aorta of SHR and aging WKY, the endothelium-dependent contractions elicited by acetylcholine most likely involve the release of PGI2 with a concomitant contribution of PGH2.