Stable PGI2 Research Articles

Prostacyclin Synthesis and Prostacyclin Receptor Expression in the Porcine Myometrium: Prostacyclin Potential to Regulate Fatty Acid Transporters, Cytokines and Contractility-Related Factors.

Simple SummaryProstacyclin (prostaglandin I2; PGI2) is an important modulator of vascular functions and is involved in various reproductive processes. PGI2 was also described as a modulator of uterine contractility in several species, including the pig. However, its synthesis and role in the myometrium of the porcine uterus are still not fully described. The objective of this study was to evaluate profiles of PGI2 synthesis and PGI2 receptor expression in the myometrium of gilts throughout the estrous cycle and during early pregnancy and to investigate the in vitro effect of PGI2 on the mRNA expression of factors engaged in smooth muscle contraction, nutrient transport, prostaglandin synthesis and action, and inflammatory response. The obtained results showed that the synthesis of PGI2 changes in the myometrium of pigs during both the estrous cycle and early pregnancy, resulting in much greater concentrations of PGI2 in cyclic than in pregnant gilts. Moreover, PGI2 stimulated the expression of fatty acid transporters and contractility-related calponin 1 and caldesmon 1, whereas it decreased cytokine expression. This study indicates that PGI2 may participate in the regulation of myometrial functions modulating the availability of factors involved in smooth muscle activity and inflammatory reaction in the uterus of pigs.Although prostacyclin (PGI2) has been well described as a regulator of smooth muscle activity, limited data are available concerning its role in the myometrium of pigs. The present research aimed to examine profiles of PGI2 synthase (PTGIS) and PGI2 receptor (PTGIR) expression and 6-keto PGF1α (a PGI2 metabolite) concentrations in the myometrium of gilts throughout the estrous cycle and during early pregnancy using qPCR, Western blot, and/or ELISA methods. Furthermore, myometrial explants were exposed to iloprost (a stable PGI2 analog) to investigate the effect of PGI2 on the mRNA expression of factors engaged in smooth muscle contraction, nutrient transport, prostaglandin synthesis and action, and inflammatory response. PTGIS mRNA expression was greater in cyclic than in pregnant gilts on days 11–12 after estrus and was accompanied by greater concentrations of 6-keto PGF1α detected in cyclic than in pregnant animals on days 11–20. Iloprost stimulated fatty acid transporters and contractility-related calponin 1 and caldesmon 1 mRNA expression and decreased interleukin 1β and tumor necrosis factor transcript abundance. The obtained results indicate a physiologically relevant role of PGI2 during the estrous cycle in the porcine myometrium with its importance for regulating the expression of contractility-, nutrient transport- and inflammatory response-related factors.

Nanomaterial Inhalation During Pregnancy Alters Systemic Vascular Function in a Cyclooxygenase-Dependent Manner.

Pregnancy requires rapid adaptations in the uterine microcirculation to support fetal development. Nanomaterial inhalation is associated with cardiovascular dysfunction, which may impair gestation. We have shown that maternal nano-titanium dioxide (nano-TiO2) inhalation impairs microvascular endothelial function in response to arachidonic acid and thromboxane (TXA2) mimetics. However, the mechanisms underpinning this process are unknown. Therefore, we hypothesize that maternal nano-TiO2 inhalation during gestation results in uterine microvascular prostacyclin (PGI2) and TXA2 dysfunction. Pregnant Sprague-Dawley rats were exposed from gestational day 10-19 to nano-TiO2 aerosols (12.17 ± 1.67 mg/m3) or filtered air (sham-control). Dams were euthanized on gestational day 20, and serum, uterine radial arterioles, implantation sites, and lungs were collected. Serum was assessed for PGI2 and TXA2 metabolites. TXB2, the stable TXA2 metabolite, was significantly decreased in nano-TiO2 exposed dams (597.3 ± 84.4 vs 667.6 ± 45.6 pg/ml), whereas no difference was observed for 6-keto-PGF1α, the stable PGI2 metabolite. Radial arteriole pressure myography revealed that nano-TiO2 exposure caused increased vasoconstriction to the TXA2 mimetic, U46619, compared with sham-controls (-41.3% ± 4.3% vs -16.8% ± 3.4%). Nano-TiO2 exposure diminished endothelium-dependent vasodilation to carbaprostacyclin, a PGI2 receptor agonist, compared with sham-controls (30.0% ± 9.0% vs 53.7% ± 6.0%). Maternal nano-TiO2 inhalation during gestation decreased nano-TiO2 female pup weight when compared with sham-control males (3.633 ± 0.064 vs 3.995 ± 0.124 g). Augmented TXA2 vasoconstriction and decreased PGI2 vasodilation may lead to decreased placental blood flow and compromise maternofetal exchange of waste and nutrients, which could ultimately impact fetal health outcomes.

Iloprost, a prostacyclin analog, inhibits the invasion of ovarian cancer cells by downregulating matrix metallopeptidase-2 (MMP-2) through the IP-dependent pathway

Recent studies have shown that a bioactive lipid prostacyclin (PGI2) plays a role in various cancers, including lung cancer. However, the specific function of PGI2 in ovarian cancer progression has not been determined. This study investigated the effects of PGI2 on cell growth, migration, and invasion in ovarian cancer cells using iloprost, a stable PGI2 analog. Iloprost significantly inhibited migration and invasion, but not cell growth, in a dose-dependent manner in human ovarian cancer cells (A2780 and SKOV3). Interestingly, the cell surface Gs protein-coupled PGI2 receptor IP was enhanced in human ovarian cancer cells. The inhibitory effect of iloprost on migration and invasion was entirely reversed by an IP antagonist (CAY10449) and IP siRNA, whereas the knockdown of peroxisome proliferator-activated receptor δ (PPARδ), a nuclear receptor of PGI2, did not rescue the effect of iloprost. Additionally, iloprost markedly decreased the expression of matrix metallopeptidase-2 and -9 (MMP-2 and MMP-9), which may be induced in the process of ovarian cancer metastasis. IP siRNA inhibited iloprost-reduced MMP-2 expression but not MMP-9 expression. Moreover, inhibition of protein kinase A (PKA) and overexpression of Akt and p38 rescued the inhibition of invasion and the reduction of MMP-2 expression by iloprost. Furthermore, iloprost-induced activation of PKA was associated with PKA-mediated Akt and p38 inactivation in ovarian cancer cells. Taken together, these results demonstrate that iloprost inhibits ovarian cancer cell invasion by downregulating MMP-2 expression via the IP-mediated PKA pathway. This study is the first to reveal a novel role for iloprost and to clarify its underlying mechanism in human ovarian cancer cells.

Prostacyclin-producing human mesenchymal cells target H19 lncRNA to augment endogenous progenitor function in hindlimb ischaemia.

Promoting the paracrine effects of human mesenchymal stem cell (hMSC) therapy may contribute to improvements in patient outcomes. Here we develop an innovative strategy to enhance the paracrine effects of hMSCs. In a mouse hindlimb ischaemia model, we examine the effects of hMSCs in which a novel triple-catalytic enzyme is introduced to stably produce prostacyclin (PGI2-hMSCs). We show that PGI2-hMSCs facilitate perfusion recovery and enhance running capability as compared with control hMSCs or iloprost (a stable PGI2 analogue). Transplanted PGI2-hMSCs do not incorporate long term into host tissue, but rather they mediate host regeneration and muscle mass gain in a paracrine manner. Mechanistically, this involves long noncoding RNA H19 in promoting PGI2-hMSC-associated survival and proliferation of host progenitor cells under hypoxic conditions. Together, our data reveal the novel ability of PGI2-hMSCs to stimulate host regenerative processes and improve physical function by regulating long noncoding RNA in resident progenitor cells.

Mechanisms Underlying Enhanced Noradrenaline-Induced Femoral Arterial Contractions of Spontaneously Hypertensive Rats: Involvement of Endothelium-Derived Factors and Cyclooxygenase-Derived Prostanoids.

We investigated the relationship between noradrenaline (NAd)-induced contractions, endothelial function, and hypertension in femoral arteries isolated from spontaneously hypertensive rats (SHR). In the femoral arteries of SHR, vs. age-matched control Wistar Kyoto (WKY) rats, contractions induced by NAd were increased. These effects were enhanced by endothelial denudation, which abolished the differences between the two groups. NAd-induced contractions were enhanced by nitric oxide (NO) synthase inhibition, and further increased by the blockade of endothelium-derived hyperpolarizing factor (EDHF). Conversely, NAd-induced contractions were inhibited by cyclooxygenase (COX) inhibition. In addition, in SHR arteries, acetylcholine-induced relaxation was reduced, and components of endothelium-derived factors were altered, such as increased COX-derived vasoconstrictor prostanoids, reduced EDHF, and preserved NO-mediated relaxation. In the femoral arteries of SHR, the production of prostanoids [6-keto prostaglandin (PG)F1α (a metabolite of prostacyclin (PGI2), PGE2, and PGF2α] and COX-2 protein were increased compared with that in WKY rats. By contrast, contractions induced by beraprost (a stable PGI2 analogue), PGE2, and U46619 (thromboxane/prostanoid receptor agonist) were similar between the SHR and WKY groups. Thus, NAd-induced femoral arterial contractions are augmented in SHR resulting from endothelial dysfunction and increased COX-derived vasoconstrictor prostanoid levels.

Beraprost sodium, a stable prostacyclin analogue, elicits dilation of isolated porcine retinal arterioles: roles of eNOS and potassium channels.

Prostacyclin (PGI2) is usually described as an endoEDRFsthelium-derived relaxing factor, but the vasoreactivity to PGI2 in the retinal arterioles and the underlying mechanisms are not fully understood. We examined the effects of PGI2 on the retinal microcirculation using beraprost sodium (BPS), a stable PGI2 analogue, and the signaling mechanisms involved in this vasomotor activity. Porcine retinal arterioles were isolated, cannulated, and pressurized without flow in vitro. Video microscopic techniques recorded the diametric responses to BPS. Beraprost sodium elicited dose-dependent (0.1 pM-0.1 μM) vasodilation of the retinal arterioles that was abolished by the PGI2 receptor (IP) antagonist CAY10441. Beraprost sodium-induced vasodilation decreased by 50% after the endothelium was removed and was inhibited by the nitric oxide (NO) synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) comparable with denudation. Inhibition of soluble guanylyl cyclase by 1H-1,2,4-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and blockage of protein kinase A (PKA) by Rp-8-Br-cAMPS were comparable to L-NAME. Beraprost sodium-induced vasodilation was also inhibited by the nonselective potassium channel inhibitor, tetraethylammonium, and the adenosine triphosphate-sensitive potassium (KATP) channel blocker, glibenclamide. Residual vasodilation in the presence of glibenclamide decreased further with subsequent application of ODQ. Beraprost sodium, a stable PGI2 analogue, causes vasodilation of the retinal arterioles mediated via the IP receptor. The current findings suggest that BPS elicits endothelium-dependent and -independent dilation of the retinal arterioles mediated by NO induced by activation of PKA in the endothelium and the KATP channel activation in the vascular smooth muscle, respectively.

Prostacyclin Regulates Spinal Nociceptive Processing through Cyclic Adenosine Monophosphate–induced Translocation of Glutamate Receptors

Prostacyclin (PGI2) is known to be an important mediator of peripheral pain sensation (nociception) whereas little is known about its role in central sensitization. The levels of the stable PGI2-metabolite 6-keto-prostaglandin F1α (6-keto-PGF1α) and of prostaglandin E2 (PGE2) were measured in the dorsal horn with the use of mass spectrometry after peripheral inflammation. Expression of the prostanoid receptors was determined by immunohistology. Effects of prostacyclin receptor (IP) activation on spinal neurons were investigated with biochemical assays (cyclic adenosine monophosphate-, glutamate release-measurement, Western blot analysis) in embryonic cultures and adult spinal cord. The specific IP antagonist Cay10441 was applied intrathecally after zymosan-induced mechanical hyperalgesia in vivo. Peripheral inflammation caused a significant increase of the stable PGI2 metabolite 6-keto-PGF1α in the dorsal horn of wild-type mice (n = 5). IP was located on spinal neurons and did not colocalize with the prostaglandin E2 receptors EP2 or EP4. The selective IP-agonist cicaprost increased cyclic adenosine monophosphate synthesis in spinal cultures from wild-type but not from IP-deficient mice (n = 5-10). The combination of fluorescence-resonance-energy transfer-based cyclic adenosine monophosphate imaging and calcium imaging showed a cicaprost-induced cyclic adenosine monophosphate synthesis in spinal cord neurons (n = 5-6). Fittingly, IP activation increased glutamate release from acute spinal cord sections of adult mice (n = 13-58). Cicaprost, but not agonists for EP2 and EP4, induced protein kinase A-dependent phosphorylation of the GluR1 subunit and its translocation to the membrane. Accordingly, intrathecal administration of the IP receptor antagonist Cay10441 had an antinociceptive effect (n = 8-11). Spinal prostacyclin synthesis during early inflammation causes the recruitment of GluR1 receptors to membrane fractions, thereby augmenting the onset of central sensitization.

Contribution of iNOS/sGC/PKG pathway, COX-2, CYP4A1, and gp91phox to the protective effect of 5,14-HEDGE, a 20-HETE mimetic, against vasodilation, hypotension, tachycardia, and inflammation in a rat model of septic shock

We have previously demonstrated that a stable synthetic analog of 20-hydroxyeicosatetraenoic acid (20-HETE), N-[20-hydroxyeicosa-5(Z),14(Z)-dienoyl]glycine (5,14-HEDGE), prevents vascular hyporeactivity, hypotension, tachycardia, and inflammation in rats treated with lipopolysaccharide (LPS) and mortality in endotoxemic mice. These changes were attributed to decreased production of inducible nitric oxide (NO) synthase (iNOS)-derived NO, cyclooxygenase (COX)-2-derived vasodilator prostanoids, and proinflammatory mediators associated with increased cyctochrome P450 (CYP) 4A1-derived 20-HETE and CYP2C23-dependent antiinflammatory mediator formation. The aim of this study was to determine whether decreased expression and activity of iNOS, soluble guanylyl cyclase (sGC), protein kinase G (PKG), COX-2, gp91phox (NOX2; a superoxide generating NOX enzyme), and peroxynitrite production associated with increased expression of COX-1 and CYP4A1 and 20-HETE formation in renal and cardiovascular tissues of rats contributes to the effect of 5,14-HEDGE to prevent vasodilation, hypotension, tachycardia, and inflammation in response to systemic administration of LPS. Mean arterial pressure fell by 28mmHg and heart rate rose by 47beats/min in LPS (10mg/kg, i.p.)-treated rats. Administration of LPS also increased mRNA and protein expression of iNOS and COX-2 associated with a decrease in COX-1 and CYP4A1 mRNA and protein expression. Increased NOS activity, iNOS-heat shock protein 90 complex formation (an index for iNOS activity), protein expression of phosphorylated vasodilator stimulated phosphoprotein (an index for PKG activity), gp91phox, p47phox (NOXO2; organizer subunit of gp91phox), and nitrotyrosine (an index for peroxynitrite production) as well as cGMP (an index for sGC activity), 6-keto-PGF1α (a stable metabolite PGI2) and PGE2 levels (indexes for COX activity), and nitrotyrosine levels by LPS were also associated with decreased CYP hydroxylase activity as measured by 20-HETE formation from arachidonic acid in renal microsomes of LPS-treated rats. These effects of LPS, except iNOS mRNA and COX-1 protein expression, were prevented by 5,14-HEDGE (30mg/kg, s.c.; 1h after LPS). A competitive antagonist of vasoconstrictor effects of 20-HETE, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (30mg/kg, s.c.; 1h after LPS) reversed the effects of 5,14-HEDGE, except iNOS and COX-1 mRNA and protein expression as well as expression of CYP4A1 mRNA. These results suggest that increased CYP4A1 expression and 20-HETE formation associated with suppression of iNOS/sGC/PKG pathway, COX-2, and gp91phox participate in the protective effect of 5,14-HEDGE against vasodilation, hypotension, tachycardia, and inflammation in the rat model of septic shock.

Effects of iloprost on bleomycin-induced pulmonary fibrosis in rats compared with methyl-prednisolone

ObjectiveProstacyclin (PGI2) has been shown to inhibit the expression of pro-inflammatory and pro-fibrotic mediators in pulmonary fibrosis. In this study, we aimed to test the preventive effects of intraperitoneally administered iloprost, a stable PGI2 analog, on bleomycin-induced pulmonary fibrosis in rats and to compare the effects of iloprost with the effects of methyl-prednisolone, a traditional therapy. MethodsRats were randomly allocated into four groups: 1. Saline alone (n=6); 2. Bleomycin+placebo (n=7); 3. Bleomycin+methyl-prednisolone (n=7); 4. Bleomycin+iloprost (n=7). Fibrotic changes in the lungs were demonstrated by analyzing the cellular composition of bronchoalveolar lavage fluid, histological evaluation and lung hydroxyproline content. ResultsFibrosis was made in the lungs of rats by bleomycin experimentally. Fibrosis scores in the methyl-prednisolone and the iloprost groups were significantly lower than in the placebo group (p<0.05). Furthermore, the score of the iloprost group was significantly lower than the score of the methyl-prednisolone group. The hydroxyproline content was significantly less in the methyl-prednisolone and the iloprost groups (p<0.05). In the placebo group, the neutrophil percentage in bronchoalveolar lavage was significantly higher than in the other groups, whereas the macrophage percentage in placebo group was significantly lower (p<0.05). ConclusionIloprost has protective effect on the pulmonary fibrosis induced by bleomycin and it may be more effective in decreasing fibrotic changes than methyl-prednisolone.

Effects of iloprost on bleomycin-induced pulmonary fibrosis in rats compared with methyl-prednisolone

ObjectiveProstacyclin (PGI2) has been shown to inhibit the expression of pro-inflammatory and pro-fibrotic mediators in pulmonary fibrosis. In this study, we aimed to test the preventive effects of intraperitoneally administered iloprost, a stable PGI2 analog, on bleomycin-induced pulmonary fibrosis in rats and to compare the effects of iloprost with the effects of methyl-prednisolone, a traditional therapy. MethodsRats were randomly allocated into four groups: 1. Saline alone (n=6); 2. Bleomycin+placebo (n=7); 3. Bleomycin+methyl-prednisolone (n=7); 4. Bleomycin+iloprost (n=7). Fibrotic changes in the lungs were demonstrated by analyzing the cellular composition of bronchoalveolar lavage fluid, histological evaluation and lung hydroxyproline content. ResultsFibrosis was made in the lungs of rats by bleomycin experimentally. Fibrosis scores in the methyl-prednisolone and the iloprost groups were significantly lower than in the placebo group (p<0.05). Furthermore, the score of the iloprost group was significantly lower than the score of the methyl-prednisolone group. The hydroxyproline content was significantly less in the methyl-prednisolone and the iloprost groups (p<0.05). In the placebo group, the neutrophil percentage in bronchoalveolar lavage was significantly higher than in the other groups, whereas the macrophage percentage in placebo group was significantly lower (p<0.05). ConclusionIloprost has protective effect on the pulmonary fibrosis induced by bleomycin and it may be more effective in decreasing fibrotic changes than methyl-prednisolone.

Impact of stable PGI2analog iloprost on early graft viability after liver transplantation: a pilot study

Ischemia/reperfusion injury after liver transplantation (LT) may be associated with primary graft dysfunction (PDF) or non-function. Prostaglandins were demonstrated to be beneficial in reducing ischemic injury by improving microcirculation and protecting endothelial cells. The aim of this study was to analyze the effect of the continuously administered prostaglandin I(2) analog iloprost on allograft function after LT. Eighty patients were prospectively randomized and assigned to two groups. Patients in the treatment group received iloprost for seven d after transplantation, and those in the control group did not. The primary end point was graft dysfunction. The incidence of PDF was 20% (n = 8) in the control group and 5% (n = 2) in the treatment group, respectively (p = 0.087). Four patients in the control group underwent re-transplantation for initial non-function (INF). There was no evidence for INF in the treatment group. Iloprost was associated with improved allograft function. Clinical course and outcome were comparable. We suggest iloprost to be beneficial for early post-transplant liver function. If the rate of PDF can be significantly reduced with this treatment concept, it should be analyzed in a larger number of patients (ISRCTN95672167).

Cyclooxygenase-2 Deficiency Attenuates Adipose Tissue Differentiation and Inflammation in Mice

Obesity is associated with a variety of disorders and is a significant health problem in developed countries. One factor controlling the level of adiposity is the differentiation of cells into adipocytes. Adipocyte differentiation requires expression of peroxisome proliferator-activated receptor γ (PPARγ), which is activated by ligands to regulate expression of genes involved in adipocyte differentiation. Although 15-deoxy-Δ(12,14)-prostaglandin (PG) J(2) (15d-PGJ(2)) has long been known to be a potent activator of PPARγ, the importance of its synthesis in adipose tissue in vivo is not clear. The current study utilized mice deficient in cyclooxygenase-2 (COX-2) to examine the role of COX-2-derived PGs as in vivo modulators of adiposity. As compared with strain- and age-matched wild-type controls, the genetic deficiency of COX-2 resulted in a significant reduction in total body weight and percent body fat. Although there were no significant differences in food consumption between groups, COX-2-deficient mice showed increased metabolic activity. Epididymal adipose tissue from wild-type mice produced a significantly greater level of 15d-PGJ(2), as compared with adipose tissue isolated from mice deficient in COX-2. Furthermore, production of the precursor required for 15d-PGJ(2) formation, PGD(2), was also significantly reduced in COX-2-deficient adipose tissue. The expression of markers for differentiated adipocytes was significantly reduced in adipose tissue from COX-2-deficient mice, whereas preadipocyte marker expression was increased. Macrophage-dependent inflammation was also significantly reduced in adipose tissue of COX-2-deficient mice. These findings suggest that reduced adiposity in COX-2-deficient mice results from attenuated PPARγ ligand production and adipocyte differentiation.

Cell-type- and cell-cycle-specific anti-mitogenesis by cicaprost

Stents eluting anti-proliferative drugs limit restenosis, but drugs commonly used to date are relatively non-specific cytostatic agents which inhibit proliferation of intimal endothelial cells as well as medial smooth muscle cells and may thereby contribute to the clinical complications associated with angioplasty. In an effort to identify a more specific anti-proliferative agent, we compared the effects of rapamycin to those of cicaprost, a mimetic of the naturally occurring anti-mitogen, PGI 2. Rapamycin and cicaprost were both strongly anti-mitogenic in vascular smooth muscle cells (VSMCs). But unlike rapamycin, cicaprost did not inhibit mitogenesis in aortic endothelial cells even when used at concentrations >10-fold higher than its ED 50 for VSMCs. Similarly, both rapamycin and cicaprost have been reported to regulate levels of the cdk inhibitor, p27 kip1. But rapamycin remained anti-mitogenic in p27 kip1-null VSMCs whereas the anti-mitogenic effect of cicaprost was completely dependent on p27 kip1. We conclude that stable PGI 2 mimetics may be highly specific inhibitors of p27 kip1-dependent VSMC proliferation after vascular injury.

A prostacyclin analogue, iloprost, protects from bleomycin-induced pulmonary fibrosis in mice

BackgroundMetabolites of arachidonic acid such as prostacyclin (PGI2) have been shown to participate in the pathogenesis of pulmonary fibrosis by inhibiting the expression of pro-inflammatory and pro-fibrotic mediators. In this investigation, we examined whether iloprost, a stable PGI2 analogue, could prevent bleomycin-induced pulmonary inflammation and fibrosis in a mouse model.MethodsMice received a single intratracheal injection of bleomycin with or without intraperitoneal iloprost. Pulmonary inflammation and fibrosis were analysed by histological evaluation, cellular composition of bronchoalveolar lavage (BAL) fluid, and hydroxyproline content. Lung mechanics were measured. We also analysed the expression of inflammatory mediators in BAL fluid and lung tissue.ResultsAdministration of iloprost significantly improved survival rate and reduced weight loss in the mice induced by bleomycin. The severe inflammatory response and fibrotic changes were significantly attenuated in the mice treated with iloprost as shown by reduction in infiltration of inflammatory cells into the airways and pulmonary parenchyma, diminution in interstitial collagen deposition, and lung hydroxyproline content. Iloprost significantly improved lung static compliance and tissue elastance. It increased the expression of IFNγ and CXCL10 in lung tissue measured by RT-PCR and their levels in BAL fluid as measured by ELISA. Levels of TNFα, IL-6 and TGFβ1 were lowered by iloprost.ConclusionsIloprost prevents bleomycin-induced pulmonary fibrosis, possibly by upregulating antifibrotic mediators (IFNγ and CXCL10) and downregulating pro-inflammatory and pro-fibrotic cytokines (TNFα, IL-6, and TGFβ1). Prostacyclin may represent a novel pharmacological agent for treating pulmonary fibrotic diseases.

Neutrophil elastase contributes to the development of ischemia/reperfusion-induced liver injury by decreasing the production of insulin-like growth factor-I in rats

Neutrophil elastase (NE) decreases the endothelial production of prostacyclin (PGI(2)) through the inhibition of endothelial nitric oxide synthase (NOS) activation and thereby contributes to the development of ischemia/reperfusion (I/R)-induced liver injury. We previously demonstrated that calcitonin gene-related peptide (CGRP) released from sensory neurons increases the insulin-like growth factor- I (IGF-I) production and thereby reduces I/R-induced liver injury. Because PGI(2) is capable of stimulating sensory neurons, we hypothesized that NE contributes to the development of I/R-induced liver injury by decreasing IGF-I production. In the present study, we examined this hypothesis in rats subjected to hepatic I/R. Ischemia/reperfusion-induced decreases of hepatic tissue levels of CGRP and IGF-I were prevented significantly by NE inhibitors, sivelestat, and L-658, 758, and these effects of NE inhibitors were reversed completely by the nonselective cyclooxygenase inhibitor indomethacin (IM) and the nonselective NOS inhibitor L-NAME but not by the selective inducible NOS inhibitor 1400W. I/R-induced increases of hepatic tissue levels of caspase-3, myeloperoxidase and the number of apoptotic cells were inhibited by NE inhibitors, and these effects of NE inhibitors were reversed by IM and L-NAME but not by 1400W. Administration of iloprost, a stable PGI(2) analog, produced effects similar to those induced by NE inhibitors. Taken together, these observations strongly suggest that NE may play a critical role in the development of I/R-induced liver injury by decreasing the IGF-I production through the inhibition of sensory neuron stimulation, which may lead to an increase of neutrophil accumulation and hepatic apoptosis through activation of caspase-3 in rats.

Prostacyclin in Vascular Diseases - Recent Insights and Future Perspectives -

Prostacyclin (PGI(2)) is one of the important vascular prostanoids, the effects of which counteract those of thromboxane (TXA(2)), and these 2 prostanoids provide an important balance in cardiovascular homeostasis. The clinical experience of COX-2 selective inhibitors having unexpected adverse effects in patients with cardiovascular risk has opened up a debate about the role of COX-2-derived prostanoids in vascular pathophysiology. PGI(2) is a major anti-atherogenic prostanoid produced by COX-2 in vascular cells, including endothelial and vascular smooth muscle cells. The balance between COX-2-derived PGI(2), COX-1-derived TXA(2), and other COX-2-mediated atherogenic prostanoids is a crucial factor in determining pathophysiological outcomes. Recent studies using stable PGI(2) analogs and genetically deficient mice have revealed novel effects of PGI(2) on its target cells, such as endothelial and endothelial progenitor cells. The role PGI(2) in the physiology and pathophysiology of vascular diseases is reviewed and the recent findings linking PGI(2), COX-2 and atherothrombosis are summarized.

Prothrombotic effects of diclofenac on arteriolar platelet activation and thrombosis in vivo.

Diclofenac, like selective cyclooxygenase-2 inhibitors, which alter vascular levels of platelet active prostaglandins, has been reported to increase rates of acute myocardial infarction. The study was performed to investigate, in an animal model of arterial thrombosis in vivo, whether diclofenac differentially influences platelet activation and thrombosis in vessels under non-stimulated conditions or during acute systemic inflammation, such as induced by tumor necrosis factor-alpha (TNF-alpha). Platelet-vessel wall interaction (PVWI), firm platelet adhesion and arterial thrombosis following vessel injury were analyzed by intravital microscopy in arterioles of hamsters in the dorsal skinfold chamber model. Prostacyclin [prostaglandin I(2) (PGI(2))] and thromboxane A(2) (TxA(2)) metabolites were measured. In vitro, endothelial adhesion molecule expression in cultured human microvascular endothelial cells was analyzed. Under non-stimulated conditions, diclofenac (1 mg kg(-1)) enhanced PVWI, which was not mediated by increased adhesion molecule expression, but by decreased systemic PGI(2) levels. Following ferric chloride-induced endothelial injury, diclofenac accelerated thrombotic vessel occlusion time, an effect that was reversed by the stable PGI(2) analog iloprost. TNF-alpha, through induction of endothelial adhesion molecule expression, also enhanced PVWI, firm adhesion, and arterial thrombosis, but simultaneous treatment with TNF-alpha and diclofenac did not have an additive effect. By decreasing levels of PGI(2) without, at the same time, altering prothrombotic TxA(2) levels, diclofenac can exert prothrombotic effects. However, this is not the case when an inflammatory situation is created by TNF-alpha treatment. These data may explain the enhanced risk of acute myocardial infarction observed in patients taking diclofenac.

Endothelial Progenitor Cells and Angiogenesis Join the PPARty

See related article, pages 80–88 Peroxisome proliferator-activated receptors (PPARs) are ligand-inducible transcription factors that belong to the nuclear hormone receptor superfamily.1 In mammals, the PPAR family consists of 3 subtypes of proteins encoded by separate genes: PPARα (NR1C1), PPARγ (NR1C3), and PPARδ (also known as β or NR1C2).2 They act as heterodimers with the retinoid X receptor and regulate gene transcription by binding to specific response elements in the promoter of the target genes.3 The classical biological activity of PPARα is the regulation of the rate of fatty acid uptake and their esterification into triglyceride or oxidation,4–7 whereas PPARγ is classically involved in adipocyte differentiation, regulation of fat storage, and maintenance of glucose homeostasis.5 The physiological functions of PPARδ are instead still unclear, although it is known that this receptor contributes to an inflammatory switch through its association and disassociation with transcriptional repressors.8 The clinical importance of PPARs originates with fibrates and thiazolidinediones (TZDs), which respectively act on PPARα and PPARγ and are used to ameliorate hyperlipidemia and hyperglycemia in subjects with type 2 diabetes mellitus (T2DM). Fibrates, such as gemfibrozil, clofibrate, fenofibrate, and bezofibrate, are drugs that effectively reduce triglycerides (TG) and free …

Postconditioning and intermittent bradykinin induced cardioprotection require cyclooxygenase activation and prostacyclin release during reperfusion

Postconditioning (PostC), obtained with brief intermittent cycles of ischemia alternating with reperfusion applied after the ischemic event, has been shown to reduce infarct size. Recently, we have shown that PostC triggering includes B2 receptor activation and its downstream pathway. Moreover, we showed that BK intermittent infusion induces a cardioprotection similar to PostC. The aim of this study was to investigate the involvement of cyclooxygenase-(COX)-derivated prostaglandins, such as prostacyclin (PGI2) pathway in the cardioprotective action mediated by intermittent BK infusion. Isolated rat hearts underwent 30 min ischemia and 120 min reperfusion. Myocardial damage was evaluated using nitro-blue-tetrazolium staining. The production of metabolite of PGI2, 6-keto-PGF1alpha, was evaluated with EIA assay on the samples collected during reperfusion. The perfusion pressure and the left ventricular pressure were monitored. In Control hearts, the infarct size was 64% +/- 4% of risk area. PostC reduced significantly the infarct size (28% +/- 4% P < 0.001 Vs. Control). BK intermittent protocol to mimic PostC, attenuated infarct size (40% +/- 2% P < 0.01 Vs. Control). The BK-intermittent and PostC protections were abolished with COX-inhibition. Intermittent BK and PostC enhanced the release of prostacyclin metabolite, 6-keto-PGF1alpha, in the late phase of reperfusion (i.e., 6-keto-PGF1alpha peaked 30 min after protective maneuvers). Also the stable PGI2 analogue, Iloprost, given in the early reperfusion reduced infarct size and improved post-ischemic heart function. In conclusion, protection by PostC and intermittent BK requires COX activation and PGI2 release during late reperfusion. These data suggest that COX must not be inhibited to have PostC protection. This finding should be kept present by future clinical studies on PostC.

Prostacyclin receptor signaling and early embryo development in the mouse

Prostacyclin (PGI(2)) plays an important role in mouse embryo development and implantation. However, it is unclear whether its action is mediated via the I prostaglandin receptor (IP). We compared the preimplantation development of IP deleted (IP-/-) embryos and wild-type (WT) embryos. We also evaluated the effect of iloprost, a stable PGI(2) analog, and L-165041, a peroxisome proliferator activated receptor delta (PPARdelta) ligand, on IP-/- versus WT embryos. Finally, we compared the development of heterozygous IP deficient embryos carrying a normal maternal IP allele versus paternal IP allele. Development of IP-/- embryos lagged behind WT embryos and was not enhanced by either the PGI(2) analog or the PPARdelta ligand. WT embryos had slightly higher, although statistically not significant, implantation rates than IP-/- embryos. Heterozygous IP deficient embryos carrying a normal maternal IP allele showed better development and responded to the PGI(2) analog, unlike those carrying the normal paternal IP allele. IP receptors play an important role in preimplantation embryo development and mediate the embryo's response to exogenous PGI(2). Early embryo development depends on the oocyte IP receptor.