Prostacyclin Synthase Research Articles

A Thromboxane A2 Receptor-Driven COX-2-Dependent Feedback Loop That Affects Endothelial Homeostasis and Angiogenesis.

Background:TP (thromboxane A2 receptor) plays an eminent role in the pathophysiology of endothelial dysfunction and cardiovascular disease. Moreover, its expression is reported to increase in the intimal layer of blood vessels of cardiovascular high-risk individuals. Yet it is unknown, whether TP upregulation per se has the potential to affect the homeostasis of the vascular endothelium.Methods:We combined global transcriptome analysis, lipid mediator profiling, functional cell analyses, and in vivo angiogenesis assays to study the effects of endothelial TP overexpression or knockdown/knockout on the angiogenic capacity of endothelial cells in vitro and in vivo.Results:Here we report that endothelial TP expression induces COX-2 (cyclooxygenase-2) in a Gi/o- and Gq/11-dependent manner, thereby promoting its own activation via the auto/paracrine release of TP agonists, such as PGH2 (prostaglandin H2) or prostaglandin F2 but not TxA2 (thromboxane A2). TP overexpression induces endothelial cell tension and aberrant cell morphology, affects focal adhesion dynamics, and inhibits the angiogenic capacity of human endothelial cells in vitro and in vivo, whereas TP knockdown or endothelial-specific TP knockout exerts opposing effects. Consequently, this TP-dependent feedback loop is disrupted by pharmacological TP or COX-2 inhibition and by genetic reconstitution of PGH2-metabolizing prostacyclin synthase even in the absence of functional prostacyclin receptor expression.Conclusions:Our work uncovers a TP-driven COX-2–dependent feedback loop and important effector mechanisms that directly link TP upregulation to angiostatic TP signaling in endothelial cells. By these previously unrecognized mechanisms, pathological endothelial upregulation of the TP could directly foster endothelial dysfunction, microvascular rarefaction, and systemic hypertension even in the absence of exogenous sources of TP agonists.

Cycloastragenol Inhibits Experimental Abdominal Aortic Aneurysm Progression.

The pathogenesis of abdominal aortic aneurysm involves vascular inflammation and elastin degradation. Astragalus radix contains cycloastragenol, which is known to be anti-inflammatory and to protect against elastin degradation. We hypothesized that cycloastragenol supplementation inhibits abdominal aortic aneurysm progression. Abdominal aortic aneurysm was induced in male rats by intraluminal elastase infusion in the infrarenal aorta and treated daily with cycloastragenol (125 mg/kg/day). Aortic expansion was followed weekly by ultrasound for 28 days. Changes in aneurysmal wall composition were analyzed by mRNA levels, histology, zymography and explorative proteomic analyses. At day 28, mean aneurysm diameter was 37% lower in the cycloastragenol group (p < 0.0001). In aneurysm cross sections, elastin content was insignificantly higher in the cycloastragenol group (10.5% ± 5.9% vs. 19.9% ± 16.8%, p = 0.20), with more preserved elastin lamellae structures (p = 0.0003) and without microcalcifications. Aneurysmal matrix metalloprotease-2 activity was reduced by the treatment (p = 0.022). Messenger RNA levels of inflammatory- and anti-oxidative markers did not differ between groups. Explorative proteomic analysis showed no difference in protein levels when adjusting for multiple testing. Among proteins displaying nominal regulation were fibulin-5 (p = 0.02), aquaporin-1 (p = 0.02) and prostacyclin synthase (p = 0.007). Cycloastragenol inhibits experimental abdominal aortic aneurysm progression. The suggested underlying mechanisms involve decreased matrix metalloprotease-2 activity and preservation of elastin and reduced calcification, thus, cycloastragenol could be considered for trial in abdominal aortic aneurysm patients.

Investigation of the characteristic binding mode of prostaglandin endoperoxide H2 formed by cyclooxygenase with a group of terminal prostanoid synthases

Free arachidonic acid mobilized from membrane glycerophospholipids by the cognate phospholipases is transformed into prostaglandin endoperoxide H2 (PGH2) by cyclooxygenase (COX), a common substrate for a group of terminal prostanoid synthases. COXs are thought to exhibit distinct functional coupling with these enzymes, which include prostaglandin E2, prostaglandin D2, prostaglandin F2α, prostacyclin, and thromboxane synthases. Three distinctive PGE2 synthases catalyzing nonoxidative rearrangement of PGH2 to PGE2 are identified, which are cytosolic PGES, two membrane-bound PGESs.

Expression of oxytocin receptors and oxytocin assisted electroejaculation in the domestic cat (Felis catus).

Oxytocin is a peptide hormone that mainly functions to control the contractility of smooth muscles and sex-related steroidogenesis in male reproductive tracts. However, specific information concerning this hormone in controlling the reproductive organs of cats is limited. This study aimed to investigate the expression of oxytocin receptors (OTRs) and their signal mediator via prostacyclin synthase (PTGIS) in reproductive structures following oxytocin assisted electroejaculation. In Experiment 1, the testis, cauda epididymis and vas deferens from five cats were examined by immunohistochemistry and quantitative polymerase chain reaction in order to study the responses of OTR and PTGIS mRNA to oxytocin injection. Experiment 2 examined the effect of oxytocin administration prior to electroejaculation on ejaculate characteristics and sperm quality in terms of motility, viability and fertilizing ability. Immunohistochemistry revealed the expression of OTRs in Leydig's, peritubular myoid cells and some spermatogenic cells. The expression was found in the epithelium and smooth muscle of the epididymis and vas deferens. After oxytocin administration, the OTR mRNA was upregulated in the epididymis (p>.05) and vas deferens (p=.01). The expression level of PTGIS mRNA increased in the response to oxytocin treatment only for the vas deferens (p>.05). Oxytocin treatment before electroejaculation resulted in an approximately twofold increase in sperm concentration and total sperm output/ejaculate, while this intervention did not significantly affect ejaculate volume, sperm quality or fertilizing ability. This study concluded that the oxytocin cascade is locally present in the reproductive structures and plays a role in promoting sperm delivery during electroejaculation in cats.

Redox balance in human skeletal muscle-derived endothelial cells - Effect of exercise training

Aerobic training can improve vascular endothelial function in-vivo. The aim of this study was to elucidate the mechanisms underlying this improvement in isolated human microvascular endothelial cells. Sedentary males, aged 57 ± 6 years completed 8 weeks of intense aerobic training. Resting muscle biopsies were obtained from the thigh muscle and used for isolation of endothelial cells (pre n = 23, post n = 16). The cells were analyzed for mitochondrial respiration, H2O2 emission, glycolysis, protein levels of antioxidants, NADPH oxidase, endothelial nitric oxide (NO) synthase and prostacyclin synthase (PGI2S). In-vivo microvascular function, assessed by acetylcholine infusion and arterial blood pressure were also determined. Endothelial mitochondrial respiration and H2O2 formation were similar before and after training whereas the expression of superoxide dismutase and the expression of glutathione peroxidase were 2.4-fold (p = 0.012) and 2.3–fold (p = 0.006) higher, respectively, after training. In-vivo microvascular function was increased by 1.4-fold (p = 0.036) in parallel with a 2.1-fold increase in endothelial PGI2S expression (p = 0.041). Endothelial cell glycolysis was reduced after training, as indicated by a 65% lower basal production of lactate (p = 0.003) and a 30% lower expression of phosphofructokinase (p = 0.011). Subdivision of the participants according to blood pressure at base-line (n = 23), revealed a 2-fold higher (p = 0.049) rate of H2O2 production in endothelial cells from hypertensive participants. Our data show that exercise training increases skeletal muscle microvascular endothelial cell metabolism, antioxidant capacity and the capacity to form prostacyclin. Moreover, elevated blood pressure is associated with increased endothelial mitochondrial ROS formation.

Alternative activation of macrophages by prostacyclin synthase ameliorates alcohol induced liver injury

Alcoholic liver disease (ALD) is a major cause of chronic liver disease worldwide. Macrophages exhibit different functional states and are classified as classically activated (M1) and alternatively activated (M2) macrophages. However, the mechanisms that govern M1/M2 polarization in chronic ALD remain to be elucidated. Prostacyclin (PGI2) synthase (PTGIS) is an enzyme of the prostaglandin pathway which catalyzes the conversion of Prostaglandin H2 (PGH2) to PGI2. PTGIS has anti-inflammatory properties. However, the function of PTGIS in ALD has not yet been determined. In this study, we demonstrated that PTGIS was downregulated in ALD and forced PTGIS expression in vivo using recombinant adeno-associated viral vector-packed PTGIS overexpression plasmid, which alleviated the inflammatory response and suppressed the macrophage M1 phenotype in mice. Loss- and gain-of function-experiments demonstrated that forced PTGIS expression inhibited the macrophage switch to the M1 phenotype and promoted M2 polarization. Furthermore, we identified the genes regulated by PTGIS through RNA-sequencing (RNA-seq) analysis. Gene ontology and KEGG pathway analyses showed that PTGIS regulates many genes involved in the immune response and is enriched in the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signal transduction pathway, which plays an important role in regulating macrophage polarization. The proteins interacting with JAKs were predicted using the STRING database. The overlap between the RNA-seq and the STRING database was interleukin-6; this indicated that it was involved in macrophage polarization regulated by JAK/STAT signaling. We further explored the microRNAs that could regulate the expression of PTGIS through TargetScan. The results of luciferase assay illustrated that the expression of PTGIS was regulated by miR-140-3p.1. These results imply that PTGIS plays a pivotal role in ALD, partly by influencing macrophage polarization.Prostacyclin synthase (PTGIS) levels are decreased by elevated miR-140-3p.1 expression in chronic alcoholic liver disease. Inducing PTGIS expression alleviates chronic alcohol-induced liver injury by promoting macrophage M2 polarization and inhibiting the M1 phenotype through the JAK/STAT pathway. Interestingly, inducing PTGIS expression also increases IL-6 expression, which has not yet been explained.

HYPOXIA-HINDERED METHYLATION OF PTGIS IN ENDOMETRIAL STROMA CELLS ACCELERATES ENDOMETRIOSIS PROGRESSION BY INDUCING CD16- NK CELLS DIFFERENTIATION

To investigate the role of prostacyclin (PGI2) in the pathogenesis of endometriosis (EMS). Expression of prostacyclin synthase (PTGIS)/PGI2 in normal (nEM) and ectopic endometrium (eEM), normal (NESCs) and ovarian endometrial stroma cells (OESCs) were analyzed in Gene Expression Omnibus (GEO) and further verified with quantitative Real-Time PCR (qRT-PCR), immunohistochemistry (IHC), western blotting (WB), enzyme-linked immuno sorbent assay (ELISA) and flow cytometer (FCM) assays. Methylation status of PTGIS promoter was detected in NESCs, OESCs and hypoxia-conditioned human endometrial stroma cells (HESCs). PTGIS over-expressed HESCs underwent RNA-sequencing process and co-cultured with the human peripheral natural killer (pNK) cells, and percentage of CD3-CD56+CD16- (CD16-) pNK cells were detected. Additionally, role of PTGIS/PGI2 in EMS was explored in vivo by instructing PTGIS knocked out (KO) (PTGIS-/-) mice, CD16 KO (CD16-/-) mice and mouse spleen NK cells adoptive transferring EMS model. Lastly, statistical analysis was analyzed by Student's t-test, one-way analysis of variance (ANOVA) and Mann-Whitney test. The expression of PTGIS/PGI2 was augmented in EMS specimens, which attributed to hypoxia milieu in endometriotic lesions and hypoxia-inducible factor 1 alpha (HIF-1α) accelerated PTGIS transcription through DNMT1-mediated DNA methylation deficiency in PTGIS promoter. Furthermore, over-expression of PTGIS enhanced adhesion ability of ESCs and ESCs derived PGI2 promoted CD16- NK cells differentiation through PGI2 receptor (PTGIR) in vitro. More importantly, PGI2 analogue iloprost and CD16- mouse spleen NK cells adoptive transfer aggravated EMS severity, with PTGIS-/- uterus fragments recipient and PTGIR antagonist RO1138452 treatment EMS model being endowed with attenuated ectopic lesions in vivo. Endometriotic hypoxia milieu activated PTGIS/PGI2 signaling pathway through DNMT1-mediated DNA methylation depression in PTGIS promoter, and this pathway accelerated EMS progression by enhancing adhesion ability of ESCs and inducing CD16- NK cells differentiation.

Calculation of CYP450 protein-ligand binding and dissociation free energy paths.

The function of an enzyme depends on its dynamic structure, and the catalytic mechanism has long been an active focus of research. The principle for interpreting protein selectivity and fidelity stems from optimization of the active site upon protein-substrate complexation, i.e., a lock-and-key configuration, on which most protein-substrate molecule binding recognition, and hence drug discovery, relies. Yet another thought has been to incorporate the protein folding interior tunnels for stereo- and regio-selectivity along the protein-substrate or protein-ligand/inhibitor binding process. Free energy calculations provide valuable information for molecular recognition and protein-ligand binding dynamics and kinetics. In this study, we focused on the kinetics of cytochrome P450 proteins (CYP450s) and the protein interior tunnel structure-dynamics relationship in terms of the substrate binding and leaving mechanism. A case in point is given by the prostaglandin H2 (PGH2) homologous isomerase of prostacyclin synthase. To calculate the reactant and product traversing the tunnels to and from the heme site, the free energy paths and tunnel potentials of mean force are constructed from steered molecular dynamics simulations and adaptive basing force umbrella sampling simulations. We explore the binding tunnels and critical residue lining characteristics for the ligand traverse and the underlying mechanism of CYP450 activity. Our theoretical analysis provides insights into the decisive role of the substrate tunnel binding process of the CYP450 mechanism and may be useful in drug design and protein engineering contexts.

Acute effects of inhaled iloprost on intracardiac conduction in patients with pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is asevere, life-threatening disorder despite the availability of specific drug therapy. Alack of endogenous prostacyclin secondary to downregulation of prostacyclin synthase in PAH may contribute to vascular pathologies. Therefore, prostacyclin and its analogs including inhaled iloprost may decrease pulmonary arterial pressure and ventricular pressure. Here, we studied that acute effects of iloprost used in pulmonary vasoreactivity testing on the intracardiac conduction system in patients with PAH. Atotal of35 (15idiopathic PAH, 20congenital heart disease) patients with PAH were included in this prospective study. Patients were divided into two groups: 22patients with negative pulmonary vasoreactivity in group1 and 13with positive pulmonary vasoreactivity in group2. Electrophysiological parameters including basic cycle length, atrium-His (AH) interval, His-ventricle (HV) interval, PR interval, QT interval, QRS duration, Wenckebach period, and sinus node recovery time (SNRT) were evaluated before and after pulmonary vasoreactivity testing in both groups. The AH interval (81 [74-93]; 80 [65.5-88], p = 0.019) and SNRT (907.7 ± 263.4; 854.0 ± 288.04, p = 0.027) was significantly decreased after pulmonary vasoreactivity testing. Mean right atrium pressure was found to be correlated with baseline AH (r = 0.371, p = 0.031) and SNRT (r = 0.353, p = 0.037). Inhaled iloprost can improve cardiovascular performance in the presence of PAH, primarily through areduction in right ventricular afterload and interventricular pressure. Decreased pressure on the interventricular septum and ventricles leads to conduction system normalization including of the AH interval and SNRT due to resolution of inflammation and edema.

Engineering 'Enzymelink' for screening lead compounds to inhibit mPGES-1 while maintaining prostacyclin synthase activity.

Aim: This study investigatedour Enzymelinks, COX-2-10aa-mPGES-1 and COX-2-10aa-PGIS, as cellular cross-screening targets for quick identification of lead compounds to inhibit inflammatory PGE2 biosynthesis while maintaining prostacyclin synthesis. Methods: We integrated virtual and wet cross-screening using Enzymelinks to rapidly identify lead compounds from a large compound library. Results: From 380,000 compounds virtually cross-screened with the Enzymelinks, 1576 compounds were identified and used for wet cross-screening using HEK293 cells that overexpressed individual Enzymelinks as targets. The top 15 lead compounds that inhibitedmPGES-1 activity were identified. The top compound that specifically inhibited inflammatory PGE2 biosynthesis alone without affecting COX-2 coupled to PGI2 synthase (PGIS) for PGI2 biosynthesis was obtained. Conclusion: Enzymelink technology could advance cyclooxygenase pathway-targeted drug discoveryto a significant degree.

A new insight intosubinteractomes of functional antagonists: Thromboxane (CYP5A1) and prostacyclin (CYP8A1) synthases.

The current article aims to summarize all possible spectrum of protein-protein interactions for thromboxane A synthase (CYP5A1) and prostacyclin synthase (CYP8A1). These enzymes metabolize the same substrate (prostaglandin H2 ) and can participate in cardiovascular, inflammatory, immune processes, and apoptosis modulation, as well as significantly influence the risk of cancers. Binary protein-protein and multiprotein complexes are of great importance in enzyme-regulating and signal-transduction pathways. However, protein partners of CYP5A1 and CYP8A1 are not yet fully identified, although both synthases are considered as prospective drug targets. At least 36 novel protein partners of CYP5A1 and CYP8A1 were revealed from different tissue types using an approach based on affinity isolation and mass spectrometry. Enrichment analysis showed that these proteins have different molecular functions: folding (refolding), unfolded protein and chaperon binding, protein transport (export/import), posttranslational modification, protein domain-specific binding, antioxidant activity, and glutathione homeostasis. A significant part of them, belonging to molecular chaperones, were common partners for CYP5A1 and CYP8A1, while other proteins were unique with the tissue-dependent distribution. New aspects of CYP5A1 and CYP8A1 interactomics and hetero-complex formation with different protein partners, including cytochrome P450s are discussed.

Coordinated action of microsomal prostaglandin E synthase-1 and prostacyclin synthase on contact hypersensitivity

Microsomal prostaglandin (PG) E synthase-1 (mPGES-1) and prostacyclin (PGI2) synthase (PGIS) are PG terminal synthases that work downstream of cyclooxygenase and synthesize PGE2 and PGI2, respectively. Although the involvement of PG receptors in acquired cutaneous immune responses was recently shown, the roles of these PG terminal synthases remain unclear. To identify the pathophysiological roles of mPGES-1 and PGIS in cutaneous immune systems, we applied contact hypersensitivity (CHS) to mPGES-1 and PGIS knockout (KO) mice as a model of acquired immune responses. Mice were treated with 1-fluoro-2,4-dinitrobenzene (DNFB) and evaluated for ear thickness and histopathological features. The results showed that the severity of ear swelling in both gene-deficient mice was much lower than that in wild-type (WT) mice. Histological examination of DNFB-treated ears showed that inflammatory cell infiltration and edema in the dermis were also less apparent in both genotypic mice. LC-MS analysis further showed that the increment in PGE2 levels in DNFB-treated ear tissue was reduced in mPGES-1 KO mice, and that 6-keto PGF1α (a stable metabolite of PGI2) was not detected in PGIS KO mice. Furthermore, we made bone marrow (BM) chimera and found that transplantation of WT mouse-derived BM cells restored the impaired CHS response in mPGES-1 KO mice but did not restore the response in PGIS KO mice. These results indicated that mPGES-1 in BM-derived cells and PGIS in non-BM-derived cells might play critical roles in DNFB-induced CHS. mPGES-1-derived PGE2 and PGIS-derived PGI2 might coordinately promote acquired cutaneous immune responses.

Involvement of prostacyclin synthase in high-fat-diet-induced obesity

Prostacyclin (PGI2) synthase (PGIS) functions downstream of inducible cyclooxygenase COX-2 in the PGI2 biosynthetic pathway. Although COX-2 and PGI2 receptor (IP) are known to be involved in adipogenesis and obesity, the involvement of PGIS has not been fully elucidated. In this study, we examined the role of PGIS in adiposity by using PGIS-deficient mice. Although PGIS deficiency did not affect in vitro adipocyte differentiation, when fed a high-fat diet (HFD), PGIS knockout (KO) mice showed reductions in both body weight gain and epididymal fat mass relative to wild-type (WT) mice. PGIS deficiency might reduce HFD-induced obesity by suppressing PGI2 production. We further found that additional gene deletion of microsomal prostaglandin (PG) E synthase-1 (mPGES-1), one of the other PG terminal synthases that also functions downstream of COX-2, emphasized the metabolic phenotypes of PGIS-deficient mice. More marked reduction in obesity and improved insulin resistance were observed in PGIS/mPGES-1 double KO (DKO) mice. Since an additive increase in PGF2α level in epididymal fat was observed in DKO mice, mPGES-1 deficiency might affect adiposity by enhancing the production of PGF2α. Our immunohistochemical analysis further revealed that in adipose tissues, PGIS was expressed in vascular and stromal cells but not in adipocytes. These results suggested that PGI2 produced from PGIS-expressed stromal tissues might enhance HFD-induced obesity by acting on IP expressed in adipocytes. The balance of expressions of PG terminal synthases and the subsequent production of prostanoids might be critical for adiposity.

Generation of an induced pluripotent stem cell line (PUMCHi006-A) derived from a patient with pulmonary arterial hypertension carrying heterozygous c.1339 G>A mutation in PTGIS gene.

Our previous study found that mutations in the PTGIS gene contributed high susceptibility to pulmonary arterial hypertension (PAH). We have generated disease-specific induced pluripotent stem cell (iPSC) lines from a PAH patient carrying the heterozygous c.1339 G>A mutation in PTGIS gene. The generated iPSC lines can be differentiated into endothelial cells to investigate the pathogenesis of PAH associated with PTGIS gene, which could provide valuable resources for personalized medicine.

Derivation of an induced pluripotent stem cell line (PUMCHi003-A) from a patient with pulmonary arterial hypertension carrying heterozygous mutation in PTGIS gene

Pulmonary arterial hypertension (PAH) is a rare but severe illness associated with mutations in the PTGIS gene. The single nucleotide variants may lead to the impairment of the endothelial cells functions, resulting in proliferation of the smooth muscle cells and occlusion of the pulmonary arterioles. We derived an induced pluripotent cell line from a PAH patient with heterozygous PTGIS c.755 G>A, which could serve as a unique model to understand the pathogenesis of PAH.

Tissue‐resident macrophages actively suppress IL‐1beta release via a reactive prostanoid/IL‐10 pathway

The alarm cytokine interleukin‐1β (IL‐1β) is a potent activator of the inflammatory cascade following pathogen recognition. IL‐1β production typically requires two signals: first, priming by recognition of pathogen‐associated molecular patterns leads to the production of immature pro‐IL‐1β; subsequently, inflammasome activation by a secondary signal allows cleavage and maturation of IL‐1β from its pro‐form. However, despite the important role of IL‐1β in controlling local and systemic inflammation, its overall regulation is still not fully understood. Here we demonstrate that peritoneal tissue‐resident macrophages use an active inhibitory pathway, to suppress IL‐1β processing, which can otherwise occur in the absence of a second signal. Programming by the transcription factor Gata6 controls the expression of prostacyclin synthase, which is required for prostacyclin production after lipopolysaccharide stimulation and optimal induction of IL‐10. In the absence of secondary signal, IL‐10 potently inhibits IL‐1β processing, providing a previously unrecognized control of IL‐1β in tissue‐resident macrophages.

Association of Rare PTGIS Variants With Susceptibility and Pulmonary Vascular Response in Patients With Idiopathic Pulmonary Arterial Hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is a fatal disease with high heritability; however, the bone morphogenetic protein receptor 2 (BMPR2) gene only accounts for 17% of IPAH. The genetic basis of IPAH needs further investigation. To identify novel IPAH susceptibility genes other than BMPR2. This 2-stage, case-control genetic association study enrolled 230 patients with IPAH from 2 referral pulmonary hypertension centers in China. Eligible patients had no BMPR2 variants and were compared with 968 healthy control participants. Data were collected from January 1, 2000, to July 31, 2015, and analyzed from August 1, 2015, to May 30, 2018. PTGIS rare variants. Whole-genome sequencing was performed to identify putative IPAH genes in a discovery cohort, with validation in an independent referral cohort. Correlation of genotype and hemodynamic characteristics was then evaluated at baseline and after pulmonary vasodilator testing. Functional assessments were conducted to analyze the effects of identified genetic variants on transcript splicing, enzymatic activity, and endothelial cell phenotypes. Among 230 patients with IPAH (164 female [71.3%]; mean [SD] age, 34 [18] years), an enrichment of rare variants in a gene encoding prostacyclin synthase (PTGIS) was identified in the discovery cohort. The association of PTGIS rare variants with IPAH was confirmed in the replication cohort. In the combined data set, PTGIS rare variants were found in 14 of 230 cases (6.1%) and 8 of 968 controls (0.8%) (odds ratio, 7.8; 95% CI, 3.2-18.8; P = 5 × 10-6, logistic regression). Compared with patients without PTGIS variants, inhaled iloprost induced a more significant decrease of pulmonary vascular resistance (difference in the least square mean, -21.7%; 95% CI, -31.4% to -12.0%; P < .001, linear regression model) and an increase of cardiac index (difference in the least square mean, 18.3%; 95% CI, 8.8%-27.8%; P < .001, linear regression model) in patients with PTGIS variants. The minigene assay indicated that the c.521 + 1G>A variant resulted in aberrant messenger RNA transcripts. The functional studies showed that the 2 missense rare variants (R252Q and A447T) resulted in a decrease in prostacyclin production and increased cell death of pulmonary microvascular endothelial cells. This study identified 3 rare loss-of-function variants in the PTGIS gene from 2 independent cohorts with IPAH. The genetic variants of PTGIS predispose pulmonary vascular responses to the iloprost stimulation. These findings suggest that PTGIS variants may be involved in the pathogenesis of IPAH.

Increased expression and catalytic activity of prostacyclin synthase after simvastatin application to human umbilical vein endothelial cells

In addition to lowering blood cholesterol levels, statins are known to exert antiplatelet effects. One of the key factors contributing to the antiplatelet effects of statins includes the upregulation of prostacyclin (PGI2) level. The present study was undertaken to determine the effects of statins on prostacyclin synthase (PGIS, CYP8A1) and PGI2 synthesis at the molecular level. Human umbilical vein endothelial cells (HUVEC) were exposed to five structurally different statins (atorvastatin, simvastatin, pravastatin, lovastatin, and rosuvastatin) and changes in CYP8A1 expression levels and the metabolic activities of CYP8A1 were investigated. Among the tested statins, simvastatin induced significant PGIS expression at both transcriptional (2.9-fold, P&lt;0.05) and translational (1.8-fold, P&lt;0.05) levels. Treatment with a constitutive androstane receptor (CAR) agonist, phenobarbital, significantly increased CYP8A1 mRNA expression (3-fold, P&lt;0.01). A metabolite of prostacyclin, 6-keto prostaglandin F1?, was significantly increased by treatment with simvastatin (P&lt;0.01) and markedly repressed by the CYP8A1 inhibitor tranylcypromine (P&lt;0.01) and the CAR antagonist clotrimazole (P&lt;0.01) in HUVEC. The results of this study improve our understanding of the inter-individual variations in PGI2 levels. Clinical studies in humans are necessary to confirm the present in vitro results.

Identification of Novel Prognosis and Prediction Markers in Advanced Prostate Cancer Tissues Based on Quantitative Proteomics.

Prostate cancer (PCa) is the most frequent cancer found in males worldwide, and its mortality rate is increasing every year. However, there are no known molecular markers for advanced or aggressive PCa, and there is an urgent clinical need for biomarkers that can be used for prognosis and prediction of PCa. Mass spectrometry-based proteomics was used to identify new biomarkers in tissues obtained from patients with PCa who were diagnosed with T2, T3, or metastatic PCa in regional lymph nodes. Among 1,904 proteins identified in the prostate tissues, 344 differentially expressed proteins were defined, of which 124 were up-regulated and 216 were down-regulated. Subsequently, based on the results of partial least squares discriminant analysis and Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analyses, we proposed that spermidine synthase (SRM), nucleolar and coiled-body phosphoprotein 1 (NOLC1), and prostacyclin synthase (PTGIS) represent new protein biomarkers for diagnosis of advanced PCa. These proteomics results were verified by immunoblot assays in metastatic PCa cell lines and by indirect enzyme-linked immunosorbent assay in prostate specimens. SRM was significantly increased depending on the cancer stage, confirming the possibility of using SRM as a biomarker for prognosis and prediction of advanced PCa.

Nitric Oxide in Life and Death of Neutrophils.

Nitric Oxide (NO) is a key signalling molecule that has an important role in inflammation. It can be secreted by endothelial cells, neutrophils, and other cells, and once in circulation, NO plays important roles in regulating various neutrophil cellular activities and fate. To describe neutrophil cellular responses influenced by NO and its concomitant compound peroxynitrite and signalling mechanisms for neutrophil apoptosis. Literature was reviewed to assess the effects of NO on neutrophils. NO plays an important role in various neutrophil cellular activities and interaction with other cells. The characteristic cellular activities of neutrophils are adhesion and phagocytosis. NO plays a protective role in neutrophil-endothelial interaction by preventing neutrophil adhesion and endothelial cell damage by activated neutrophils. NO suppresses neutrophil phagocytic activity but stimulates longdistance contact interactions through tubulovesicular extensions or cytonemes. Neutrophils are the main source of superoxide, but NO flow results in the formation of peroxynitrite, a compound with high biological activity. Peroxynitrite is involved in the regulation of eicosanoid biosynthesis and inhibits endothelial prostacyclin synthase. NO and peroxynitrite modulate cellular 5-lipoxygenase activity and leukotriene synthesis. Long-term exposure of neutrophils to NO results in the activation of cell death mechanisms and neutrophil apoptosis. Nitric oxide and the NO/superoxide interplay fine-tune mechanisms regulating life and death in neutrophils.