Prostaglandin I2 promotes recruitment of endothelial progenitor cells and limits vascular remodeling

Prostacyclin in trauma patients with hemorrhagic shock: A randomized clinical trial

BACKGROUND

A main cause of trauma morbidity and mortality is multiple-organ failure, and endotheliopathy has been implicated. Pilot studies indicate that low-dose prostacyclin improves endothelial functionality in critically ill patients, suggesting that this intervention may improve trauma patient outcome.

METHODS

We conducted a multicenter, randomized, blinded, clinical investigator-initiated trial in 229 trauma patients with hemorrhagic shock who were randomized 1:1 to 72 hours infusion of the prostacyclin analog iloprost (1 ng/kg/min) or placebo. The primary outcome was the number of intensive care unit (ICU)-free days alive within 28 days of admission. Secondary outcomes included 28-day all-cause mortality and hospital length of stay.

RESULTS

The mean number of ICU-free days alive within 28 days was 15.64 days in the iloprost group versus 13.99 days in the placebo group (adjusted mean difference, -1.63 days [95% confidence interval (CI), -4.64 to 1.38 days]; p = 0.28). The 28-day mortality was 18.8% in the iloprost group versus 19.6% in the placebo group (odds ratio, 1.01 [95% CI, 0.51-2.0]; p = 0.97). The mean hospital length of stay was 19.96 days in the iloprost group versus 27.32 days in the placebo group (adjusted mean difference, 7.84 days [95% CI, 1.66-14.02 days], p = 0.01).

CONCLUSION

Iloprost did not result in a statistically significant increase in the number of ICU-free days alive within 28 days of admission, whereas it was safe and a statistically significant reduction in hospital length of stay was observed. Further research on prostacyclin in shocked trauma patients is warranted.

LEVEL OF EVIDENCE

Therapeutic/Care Management; Level II.

Small molecules in the treatment of COVID-19

The outbreak of COVID-19 has become a global crisis, and brought severe disruptions to societies and economies. Until now, effective therapeutics against COVID-19 are in high demand. Along with our improved understanding of the structure, function, and pathogenic process of SARS-CoV-2, many small molecules with potential anti-COVID-19 effects have been developed. So far, several antiviral strategies were explored. Besides directly inhibition of viral proteins such as RdRp and Mpro, interference of host enzymes including ACE2 and proteases, and blocking relevant immunoregulatory pathways represented by JAK/STAT, BTK, NF-κB, and NLRP3 pathways, are regarded feasible in drug development. The development of small molecules to treat COVID-19 has been achieved by several strategies, including computer-aided lead compound design and screening, natural product discovery, drug repurposing, and combination therapy. Several small molecules representative by remdesivir and paxlovid have been proved or authorized emergency use in many countries. And many candidates have entered clinical-trial stage. Nevertheless, due to the epidemiological features and variability issues of SARS-CoV-2, it is necessary to continue exploring novel strategies against COVID-19. This review discusses the current findings in the development of small molecules for COVID-19 treatment. Moreover, their detailed mechanism of action, chemical structures, and preclinical and clinical efficacies are discussed.

The effect of prostacyclin infusion on markers of endothelial activation and damage in mechanically ventilated patients with SARS-CoV-2 infection

Background

In a pilot study, we found a significant reduction in mean daily sequential organ failure assessment score in mechanically ventilated patients with COVID-19 who received prostacyclin, compared to placebo. We here investigate the effect on biomarkers of endothelial activation and damage.

Methods

Post-hoc study of a randomized controlled trial in adult patients with confirmed SARS-CoV-2 infection, mechanically ventilated, with soluble thrombomodulin (sTM) plasma levels >4 ng/mL. Patients received prostacyclin infusion (1 ng/kg/min) or placebo. Blood samples were collected at baseline and 24 h.

Results

Eighty patients were randomized (41 prostacyclin, 39 placebo). The median changes in syndecan-1 plasma levels at 24 h were −3.95 (IQR: −21.1 to 2.71) ng/mL in the prostacyclin group vs. 3.06 (IQR: −8.73 to 20.5) ng/mL in the placebo group (difference of the medians: -7.01 [95% CI: −22.3 to −0.231] ng/mL, corresponding to −3% [95% CI: −11% to 0%], p = 0.04). Changes in plasma levels of sTM, PECAM-1, p-selectin, and CD40L did not differ significantly between groups.

Conclusions

Prostacyclin infusion, compared to placebo, resulted in a measurable decrease in endothelial glycocalyx shedding (syndecan-1) at 24 h, suggesting a protective effect on the endothelium, which may be related to the observed reduction in organ failure.

The Endothelium and COVID-19: An Increasingly Clear Link Brief Title: Endotheliopathy in COVID-19

The endothelium has a fundamental role in the cardiovascular complications of coronavirus disease 2019 (COVID-19). Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) particularly affects endothelial cells. The virus binds to the angiotensin-converting enzyme 2 (ACE-2) receptor (present on type 2 alveolar cells, bronchial epithelial cells, and endothelial cells), and induces a cytokine storm. The cytokines tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 have particular effects on endothelial cells-leading to endothelial dysfunction, endothelial cell death, changes in tight junctions, and vascular hyperpermeability. Under normal conditions, apoptotic endothelial cells are removed into the bloodstream. During COVID-19, however, endothelial cells are detached more rapidly, and do not regenerate as effectively as usual. The loss of the endothelium on the luminal surface abolishes all of the vascular responses mediated by the endothelium and nitric oxide production in particular, which results in greater contractility. Moreover, circulating endothelial cells infected with SARS-CoV-2 act as vectors for viral dissemination by forming clusters that migrate into the circulation and reach distant organs. The cell clusters and the endothelial dysfunction might contribute to the various thromboembolic pathologies observed in COVID-19 by inducing the formation of intravascular microthrombi, as well as by triggering disseminated intravascular coagulation. Here, we review the contributions of endotheliopathy and endothelial-cell-derived extracellular vesicles to the pathogenesis of COVID-19, and discuss therapeutic strategies that target the endothelium in patients with COVID-19.

Prostacyclin in Mechanically Ventilated Patients with COVID-19 and Severe Endotheliopathy: A Multicenter, Randomized, Clinical Trial

Rationale

The mortality in patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who require mechanical ventilation remains high, and endotheliopathy has been implicated.

Objectives

To determine the effect of prostacyclin infusion in mechanically ventilated patients infected with SARS-CoV-2 with severe endotheliopathy.

Methods

We conducted a multicenter, randomized clinical trial in adults infected with coronavirus disease (COVID-19) who required mechanical ventilation and had a plasma level of thrombomodulin >4 ng/ml; patients were randomized to 72-hour infusion of prostacyclin 1 ng/kg/min or placebo.

Measurements and Main Results

The main outcome was the number of days alive and without mechanical ventilation within 28 days. Key secondary outcomes were 28-day mortality and serious adverse events within 7 days. Eighty patients were randomized (41 prostacyclin and 39 placebo). The median number of days alive without mechanical ventilation at 28 days was 16.0 days (SD, 12) versus 5.0 days (SD, 10) (difference of the medians, 10.96 days; 95% confidence interval [CI], −5 to 21; P = 0.07) in the prostacyclin and the placebo groups, respectively. The 28-day mortality was 21.9% versus 43.6% in the prostacyclin and the placebo groups, respectively (risk ratio, 0.50; 95% CI, 0.24 to 0.96; P = 0.06). The incidence of serious adverse events within 7 days was 2.4% versus 12.8% (risk ratio, 0.19; 95% CI, 0.001 to 1.11; P = 0.10) in the prostacyclin and the placebo groups, respectively.

Conclusions

Prostacyclin was not associated with a significant reduction in the number of days alive and without mechanical ventilation within 28 days. The point estimates, however, favored the prostacyclin group in all analyses, including 28-day mortality, warranting further investigation in larger trials.

Clinical trial registered with www.clinicaltrials.gov (NCT 04420741); EudraCT Identifier: 2020-001296-33.

Prostacyclin is an endosteal bone marrow niche component and its clinical analog iloprost protects hematopoietic stem cell potential during stress

Hematopoietic stem cells (HSCs) with superior reconstitution potential are reported to be enriched in the endosteal compared to central bone marrow (BM) region. To investigate whether specific factors at the endosteum may contribute to HSC potency, we screened for candidate HSC niche factors enriched in the endosteal compared to central BM regions. Together with key known HSC supporting factors Kitl and Cxcl12, we report that prostacyclin/prostaglandin I₂ (PGI₂ ) synthase (Ptgis) was one of the most highly enriched mRNAs (>10-fold) in endosteal compared to central BM. As PGI₂ signals through receptors distinct from prostaglandin E₂ (PGE₂ ), we investigated functional roles for PGI₂ at the endosteal niche using therapeutic PGI₂ analogs, iloprost, and cicaprost. We found PGI₂ analogs strongly reduced HSC differentiation in vitro. Ex vivo iloprost pulse treatment also significantly boosted long-term competitive repopulation (LT-CR) potential of HSCs upon transplantation. This was associated with increased tyrosine-phosphorylation of transducer and activator of transcription-3 (STAT3) signaling in HSCs but not altered cell cycling. In vivo, iloprost administration protected BM HSC potential from radiation or granulocyte colony-stimulating factor-induced exhaustion, and restored HSC homing potential with increased Kitl and Cxcl12 transcription in the BM. In conclusion, we propose that PGI₂ is a novel HSC regulator enriched in the endosteum that promotes HSC regenerative potential following stress.

Factors Affecting the Re-Endothelialization of Endothelial Progenitor Cell

The vascular endothelium, which plays an essential role in maintaining the normal shape and function of blood vessels, is a natural barrier between the circulating blood and the vascular wall tissue. The endothelial damage can cause vascular lesions, such as atherosclerosis and restenosis. After the vascular intima injury, the body starts the endothelial repair (re-endothelialization) to inhibit the neointimal hyperplasia. Endothelial progenitor cell is the precursor of endothelial cells and plays an important role in the vascular re-endothelialization. However, re-endothelialization is inevitably affected in vivo and in vitro by factors, which can be divided into two types, namely, promotion and inhibition, and act on different links of the vascular re-endothelialization. This article reviews these factors and related mechanisms.

Pericyte-specific deletion of ninjurin-1 induces fragile vasa vasorum formation and enhances intimal hyperplasia of injured vasculature

Adventitial abnormalities including enhanced vasa vasorum malformation are associated with development and vulnerability of atherosclerotic plaque. However, the mechanisms of vasa vasorum malformation and its role in vascular remodeling have not been fully clarified. We recently reported that ninjurin-1 (Ninj1) is a crucial adhesion molecule for pericytes to form matured neovessels. The purpose is to examine if Ninj1 regulates adventitial angiogenesis and affects the vascular remodeling of injured vessels using pericyte-specific Ninj1 deletion mouse model. Mouse femoral arteries were injured by insertion of coiled wire. Four weeks after vascular injury, fixed arteries were decolorized. Vascular remodeling, including intimal hyperplasia and adventitial microvessel formation were estimated in a three-dimensional view. Vascular fragility, including blood leakiness was estimated by extravasation of fluorescein isothiocyanate (FITC)-lectin or FITC-dextran from microvessels. Ninj1 expression was increased in pericytes in response to vascular injury. NG2-CreER/Ninj1^loxp mice were treated with tamoxifen (Tam) to induce deletion of Ninj1 in pericyte (Ninj1 KO). Tam-treated NG2-CreER or Tam-nontreated NG2-CreER/Ninj1^loxp mice were used as controls. Intimal hyperplasia was significantly enhanced in Ninj1 KO compared with controls. Vascular leakiness was significantly enhanced in Ninj1 KO. In Ninj1 KO, the number of infiltrated macrophages in adventitia was increased, along with the expression of inflammatory cytokines. In conclusion, deletion of Ninj1 in pericytes induces the immature vasa vasorum formation of injured vasculature and exacerbates adventitial inflammation and intimal hyperplasia. Thus, Ninj1 contributes to the vasa vasorum maturation in response to vascular injury and to reduction of vascular remodeling.NEW & NOTEWORTHY Although abnormalities of adventitial vasa vasorum are associated with vascular remodeling such as atherosclerosis, the mechanisms of vasa vasorum malformation and its role in vascular remodeling have not been fully clarified. The present study provides a line of novel evidence that ninjurin-1 contributes to adventitial microvascular maturation during vascular injury and regulates vascular remodeling.

Efficacy and safety of iloprost in trauma patients with haemorrhagic shock-induced endotheliopathy-Protocol for the multicentre randomized, placebo-controlled, blinded, investigator-initiated shine-trauma trial

BACKGROUND

Traumatic injury accounts for 800 000 deaths in the European Union annually. The main causes of deaths in trauma patients are exsanguination and multiple organ failure (MOF). We have studied >1000 trauma patients and identified shock-induced endotheliopathy (SHINE), the pathophysiological mechanism responsible for MOF and high mortality. Pilot studies indicate that low-dose iloprost (1 ng/kg/min) improves endothelial functionality in critically ill patients suggesting this intervention may improve patient outcome in traumatic SHINE.

MATERIAL AND METHODS

This is a multicentre, randomized, blinded clinical investigator-initiated phase 2B trial in trauma patients with haemorrhagic shock-induced endotheliopathy. Patients are randomized 1:1 to 72 hours infusion of iloprost 1 ng/kg/min or Placebo (equal volume of saline). A total of 220 trauma patients will be included. The primary endpoint is the number of intensive care unit (ICU)-free days, within 28 days of admission. Secondary endpoints include 28- and 90-day all-cause mortality, hospital length of stay, vasopressor-free days in the intensive care unit (ICU) within 28 days, ventilator-free days in the ICU within 28 days, renal replacement-free days in the ICU within 28 days, number of serious adverse reactions and serious adverse events within the first 4 days of admission.

DISCUSSION

This trial will test the safety and efficacy of administration of iloprost vs placebo for 72 hours in trauma patients with haemorrhagic shock-induced endotheliopathy. Trial endpoints focus on the potential effect of iloprost to reduce the need for ICU stay secondary to mitigation of organ failure.

TRIAL REGISTRATION

SHINE-TRAUMA trial-EudraCT no. 2019-000936-24-Clinicaltrials.gov: NCT03903939 Ethics Committee no. H-19014482.

Efficacy and safety of iloprost in patients with septic shock-induced endotheliopathy-Protocol for the multicenter randomized, placebo-controlled, blinded, investigator-initiated trial

BACKGROUND

In Europe 700.000 new cases of sepsis occur annually and more than 100.000 of these patients die due to multiorgan failure (MOF). We have identified shock-induced endotheliopathy (SHINE) to be associated with development of MOF and mortality. Furthermore, in patients with septic shock those with circulating levels of thrombomodulin (TM) above 10 ng/mL have twice the mortality (56% vs 28%) than those with levels below this level. Pilot studies indicate that infusion of iloprost (1 ng/kg/min) is associated with improved endothelial function in patients with septic shock.

MATERIAL AND METHODS

This is a multicenter, randomized, blinded, investigator-initiated, adaptive phase 2B trial in up to 384 patients with septic shock-induced endotheliopathy defined by TM > 10 ng/mL who are allocated 1:1 to 72 hours continuous infusion of iloprost 1 ng/kg/min or placebo (equal volume of saline). The primary outcome is the mean daily modified Sequential Organ Failure Assessment (SOFA) score in the ICU up to day 90. Secondary outcomes include 28- and 90-day all-cause mortality, days alive without vasopressor in the ICU within 90 days, days alive without mechanical ventilation in the ICU within 90 days, days alive without renal replacement therapy in the ICU within 90 days, numbers of serious adverse reactions, and the number of serious adverse events within the first 7 days.

DISCUSSION

This trial tests the safety and efficacy of iloprost vs placebo for 72 hours in patients with septic shock and SHINE. The outcome measures focus on the potential effect of the intervention to mitigate organ failure.

TRIAL REGISTRATION

COMBAT-SHINE trial-EudraCT no. 2019-001131-31-Clinicaltrials.gov: NCT04123444-Ethics Committee no. H-19018258.

"Endothelial Dysfunction in Resuscitated Cardiac Arrest (ENDO-RCA): Safety and efficacy of low-dose Iloprost, a prostacyclin analogue, in addition to standard therapy, as compared to standard therapy alone, in post-cardiac-arrest-syndrome patients."

OBJECTIVE

An increasingly recognized prognostic factor for out-of-hospital-cardiac-arrest (OHCA) patients is the ischemia-reperfusion injury after restored blood circulation. Endothelial injury is common in patients resuscitated from cardiac arrest and is associated with poor outcome. This study was designed to investigate if iloprost infusion, a prostacyclin analogue, reduces endothelial damage in OHCA patients.

METHODS

50 patients were randomized in a placebo controlled double-blinded trial and allocated 1:2 to 48-hours iloprost infusion, (1 ng/kg/min) or placebo (saline infusion). Endothelial biomarkers (soluble thrombomodulin (sTM), sE-selectin, syndecan-1, soluble vascular endothelial growth factor (sVEGF), vascular endothelial cadherine (VEcad), nucleosomes) and sympathoadrenal activation (epinephrine/norepinephrine) from baseline to 48 and 96-hours were evaluated.

RESULTS

Iloprost infusion did not influence endothelial biomarkers by the 48-hour endpoint. A rebound effect was observed with higher biomarker plasma values in the iloprost group (sTM p=0.02; Syndecan p=0.004; nucleosomes p<0.001; VEcad p<0.03) after 96-hours. There was a significant difference in 180-day mortality in favor of placebo. There was no difference regarding total adverse events between groups (p=0.73). Two patients were withdrawn in the iloprost group due to hypotension.

CONCLUSIONS

The administration of low-dose iloprost (1ng/kg/min) to OHCA patients did not significantly influence endothelial biomarkers as measured by the 48- hour endpoint. A rebound effect was however observed in the 96-hour statistical model, with increasing endothelial biomarker levels after cessation of the iloprost-infusion.

Pericyte-Specific Ninjurin1 Deletion Attenuates Vessel Maturation and Blood Flow Recovery in Hind Limb Ischemia

Supplemental Digital Content is available in the text.

Objective—

Angiogenesis, entire step from endothelial cells (ECs) sprouts to vascular maturation, is a critical response to ischemia. To form functional mature vessels, interactions between ECs and pericytes are essential. Ninj1 (ninjurin1) is an adhesion molecule that contributes to the pathogenesis of neuroinflammation. We recently demonstrated that Ninj1 is expressed in pericytes during angiogenesis. However, the role of Ninj1 in angiogenesis under pathophysiological ischemic conditions has not yet been elucidated.

Approach and Results—

Ninj1 was detected in microvessels, and its expression was enhanced in ischemic tissues after mouse hindlimb ischemia. Knockdown of Ninj1 was performed by injection of biodegradable microspheres releasing Ninj1-small interfering RNA into muscle tissues. Alternatively, pericyte-specific Ninj1 knockout was induced by tamoxifen treatment of NG2-CreERT/Ninj1-flox mice. Ninj1 knockdown/knockout reduced the formation of blood-circulating functional vessels among total CD31⁺ microvessels within ischemic tissues and subsequently attenuated color Doppler–assessed blood flow recovery. Ninj1 overexpression enhanced expression of Anpt (angiopoietin) 1, whereas Ninj1 knockdown enhanced the endogenous Anpt1 antagonist, Anpt2 expression in pericytes and inhibited the association of pericytes with ECs and subsequent formation of capillary-like structure, that is, EC tube surrounded with pericytes in 3-dimensional gel culture.

Conclusions—

Our data demonstrate that Ninj1 is involved in the formation of functional matured vessels through the association between pericytes and ECs, resulting in blood flow recovery from ischemia. These findings further the current our understanding of vascular maturation and may support the development of therapeutics for ischemic diseases.

Protective Effects of Total Flavones of Elaeagnus rhamnoides (L.) A. Nelson against Vascular Endothelial Injury in Blood Stasis Model Rats

The aim was to evaluate the protective effects of total flavones of Elaeagnus rhamnoides (L.) A. Nelson (TFE) against vascular endothelial injury in blood stasis model rats and explore the potential mechanisms preliminarily. The model of blood stasis rat model with vascular endothelial injury was induced by subcutaneous injection of adrenaline combined with ice-water bath. Whole blood viscosity (WBV), histological examination, and prothrombin time (PT), activated partial thromboplastin time (APTT), and fibrinogen (FIB) were measured. Meanwhile, the levels of Thromboxane B2 (TXB2), 6-keto-PGF1α , von Willebrand factor (vWF), and thrombomodulin (TM) were detected. In addition, Quantitative Real-Time PCR (qPCR) was performed to identify PI3K, Erk2, Bcl-2, and caspase-3 gene expression. The results showed that TFE can relieve WBV, increase PT and APTT, and decrease FIB content obviously. Moreover, TFE might significantly downregulate the levels of TXB2, vWF, and TM in plasma and upregulate the level of 6-keto-PGF1α in plasma. Expressions of PI3K and Bcl-2 were increased and the expression of caspase-3 was decreased by TFE pretreatment in the rat model. Consequently, the study suggested that TFE may have the potential against vascular endothelial injury in blood stasis model rats induced by a high dose of adrenaline with ice-water bath.

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin promotes endothelial cell apoptosis through activation of EP3/p38MAPK/Bcl-2 pathway

Endothelial injury or dysfunction is an early event in the pathogenesis of atherosclerosis. Epidemiological and animal studies have shown that 2, 3, 7, 8‐tetrachlorodibenzo‐p‐dioxin (TCDD) exposure increases morbidity and mortality from chronic cardiovascular diseases, including atherosclerosis. However, whether or how TCDD exposure causes endothelial injury or dysfunction remains largely unknown. Cultured human umbilical vein endothelial cells (HUVECs) were exposed to different doses of TCDD, and cell apoptosis was examined. We found that TCDD treatment increased caspase 3 activity and apoptosis in HUVECs in a dose‐dependent manner,at doses from 10 to 40 nM. TCDD increased cyclooxygenase enzymes (COX)‐2 expression and its downstream prostaglandin (PG) production (mainly PGE₂ and 6‐keto‐PGF_1α) in HUVECs. Interestingly, inhibition of COX‐2, but not COX‐1, markedly attenuated TCDD‐triggered apoptosis in HUVECs. Pharmacological inhibition or gene silencing of the PGE₂ receptor subtype 3 (EP3) suppressed the augmented apoptosis in TCDD‐treated HUVECs. Activation of the EP3 receptor enhanced p38 MAPK phosphorylation and decreased Bcl‐2 expression following TCDD treatment. Both p38 MAPK suppression and Bcl‐2 overexpression attenuated the apoptosis in TCDD‐treated HUVECs. TCDD increased EP3‐dependent Rho activity and subsequently promoted p38MAPK/Bcl‐2 pathway‐mediated apoptosis in HUVECs. In addition, TCDD promoted apoptosis in vascular endothelium and delayed re‐endothelialization after femoral artery injury in wild‐type (WT) mice, but not in EP3^−/− mice. In summary, TCDD promotes endothelial apoptosis through the COX‐2/PGE₂/EP3/p38MAPK/Bcl‐2 pathway. Given the cardiovascular hazard of a COX‐2 inhibitor, our findings indicate that the EP3 receptor and its downstream pathways may be potential targets for prevention of TCDD‐associated cardiovascular diseases.

The effect of intraoperative and 6-h postoperative intravenous administration of low-dose prostacyclin on the endothelium, hemostasis, and hemodynamics in patients undergoing a pancreaticoduodenoctemy: a randomized-controlled pilot study

BACKGROUND

Capillary leakage, secondary to endothelial breakdown, is common in patients undergoing major surgical procedures with extensive tissue injury and this is associated with increased morbidity and mortality. Prostacyclin has been ascribed cytoprotective properties together with its vasodilatory and antiplatelet effects. The present pilot study investigated the safety and endothelial protective effects of low-dose prostacyclin infusion.

PATIENTS AND METHODS

A randomized placebo-controlled pilot study evaluating the effect of prostacyclin (iloprost) infusion (1.0 ng/kg/min) versus placebo (saline infusion) intraoperatively and 6 h postoperatively in patients undergoing a pancreaticoduodenoctemy was carried out. Hemodynamics were evaluated by Nexfin, hemostasis was evaluated by thrombelastography, and transfusion requirements were registered. Endothelial damage was evaluated by circulating sE-selectin, soluble thrombomodulin, and nucleosomes.

RESULTS

Comparable baseline demography and surgical time were found. Hemodynamics were comparable between groups. The placebo group received more red blood cells, median 115 ml [interquartile range (IQR): 0-296 ml] versus 0 ml (IQR: 0-0 ml), P=0.027, at the postoperative ward and after 6 h. Thrombelastography maximum clot firmness decreased intraoperatively only in the placebo group (P=0.034)). Soluble thrombomodulin increased more in the placebo group postoperatively [1.63 ng/ml (IQR: 0.65-2.55 ng/ml) versus 0.40 ng/ml (IQR: 0.21-0.63 ng/ml), P=0.027] and 6 h postoperatively [1.83 (1.1-2.36) versus 0.67 (0.42-0.91), P=0.027]. Nucleosomes increased intraoperatively and postoperatively only in the placebo group; thus, the overall level of nucleosomes was higher in the placebo group (P=0.019).

CONCLUSION

Intraoperative and postoperative low-dose prostacyclin infusion is safe and associated with reduced endothelial cell damage in patients undergoing a pancreaticoduodenoctemy compared with those receiving placebo.

Eicosanoids: Emerging contributors in stem cell-mediated wound healing

Eicosanoids are bioactive lipid products primarily derived from the oxidation of arachidonic acid (AA). The individual contributions of eicosanoids and stem cells to wound healing have been of great interest. This review focuses on how stem cells work in concert with eicosanoids to create a beneficial environment in the wound bed and in the promotion of wound healing. Stem cells contribute to wound healing through modulating inflammation, differentiating into skin cells or endothelial cells, and exerting paracrine effects by releasing various potent growth factors. Eicosanoids have been shown to stimulate proliferation, migration, homing, and differentiation of stem cells, all of which contribute to the process of wound healing. Increasing evidence has shown that eicosanoids improve wound healing through increasing stem cell densities, stimulating differentiation, and enhancing the angiogenic properties of stem cells. Chronic wounds have become a major problem in health care. Therefore, research regarding the effects of stem cells and eicosanoids in the promotion wound healing is of great importance.

Inhibition of intimal thickening after vascular injury with a cocktail of vascular endothelial growth factor and cyclic Arg-Gly-Asp peptide

BACKGROUND

Percutaneous coronary intervention is widely used for the treatment of coronary artery disease; however, significant challenges such as restenosis remain. Key to solving these problems is to inhibit smooth muscle cell activation while enhancing re-endothelialization. Early growth response-1 (Egr-1) is a transcription factor that regulates vascular smooth muscle cell (SMC) proliferation and migration through its control of an array of downstream genes.

METHODS

A "cocktail" of vascular endothelial growth factor (VEGF)-A, VEGF-D and cyclic RGD was tested for its ability to inhibit neointima formation and accelerate re-endothelialization following balloon injury to carotid arteries of rats.

RESULTS

In vitro, the cocktail stimulated endothelial cell growth yet inhibited smooth muscle cell growth. In vivo, cocktail-treated injured arteries exhibited reduced intimal thickening by >50% (P<0.05). It increased both re-endothelialization and endothelial nitric oxide synthase (NOS) expression. Cocktail reduced Egr-1 expression, an effect blocked by the NOS inhibitor L-N(G)-nitroarginine methyl ester (L-NAME) that also prevented cocktail inhibition of neointima inhibition.

CONCLUSIONS

This combination may potentially be useful for the treatment of restenosis with concomitant stimulation of revascularization.

Regulated expression of the prostacyclin receptor (IP) gene by androgens within the vasculature: Combined role for androgens and serum cholesterol

The prostanoid prostacyclin plays a key cardioprotective role within the vasculature. There is increasing evidence that androgens may also confer cardioprotection but through unknown mechanisms. This study investigated whether the androgen dihydrotestosterone (DHT) may regulate expression of the prostacyclin/I prostanoid receptor or, in short, the IP in platelet-progenitor megakaryoblastic and vascular endothelial cells. DHT significantly increased IP mRNA and protein expression, IP-induced cAMP generation and promoter (PrmIP)-directed gene expression in all cell types examined. The androgen-responsive region was localised to a cis-acting androgen response element (ARE), which lies in close proximity to a functional sterol response element (SRE) within the core promoter. In normal serum conditions, DHT increased IP expression through classic androgen receptor (AR) binding to the functional ARE within the PrmIP. However, under conditions of low-cholesterol, DHT led to further increases in IP expression through an indirect mechanism involving AR-dependent upregulation of SCAP expression and enhanced SREBP1 processing & binding to the SRE within the PrmIP. Chromatin immunoprecipitation assays confirmed DHT-induced AR binding to the ARE in vivo in cells cultured in normal serum while, in conditions of low cholesterol, DHT led to increased AR and SREBP1 binding to the functional ARE and SRE cis-acting elements, respectively, within the core PrmIP resulting in further increases in IP expression. Collectively, these data establish that the human IP gene is under the transcriptional regulation of DHT, where this regulation is further influenced by serum-cholesterol levels. This may explain, in part, some of the protective actions of androgens within the vasculature.

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.

Human mesenchymal stem cells (hMSC) expressing paracrine factors may enhance therapeutic benefits when transplanted. Here, the authors show that hMSCs stably expressing prostacyclin enhance host regeneration and muscle mass gain in a mouse hindlimb ischaemia model, mediated by the long noncoding RNA H19.

Increased prostacyclin levels inhibit the aggregation and activation of platelets via the PI3K-AKT pathway in prolonged isolated thrombocytopenia after allogeneic hematopoietic stem cell transplantation

OBJECTIVES

The aim of this study was to investigate the role of prostacyclin (PGI2) in prolonged isolated thrombocytopenia (PT) following allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the effect of PGI2 on the activation and aggregation of platelets in PT.

METHODS

We enrolled 37 patients with PT and 36 controls following allo-HSCT in this study. Platelet aggregation and activation and PGI2 levels were measured. Endothelial progenitor cells (EPCs) from either PT or control patients were cultured ex vivo with serum from either PT or control patients. PGI2 secretions were then measured. PGI2 was added to the platelets ex vivo, and platelet aggregation and activation and PI3K/Akt phosphorylation were analyzed.

RESULTS

A higher PGI2 level was observed in the PT patients. The activation and aggregation of platelets were significantly lower in the PT patients. EPCs from PT patients cultured in PT serum secreted higher levels of PGI2, and PGI2 inhibited platelet activation and aggregation in a concentration-dependent manner ex vivo. PI3K/Akt phosphorylation of platelets was regulated by PGI2 after allo-HSCT. Disease status, serum PGI2 level and platelet aggregation were independent risk factors in patients with PT after allo-HSCT.

CONCLUSIONS

Higher PGI2 levels and lower platelet activation and aggregation occurred simultaneously in PT patients. PGI2 inhibited platelet activation and aggregation, probably by regulating the phosphorylation of PI3K/Akt.

Treprostinil indirectly regulates endothelial colony forming cell angiogenic properties by increasing VEGF-A produced by mesenchymal stem cells

Pulmonary vasodilators and prostacyclin therapy in particular, have markedly improved the outcome of patients with pulmonary hypertension (PH). Endothelial dysfunction is a key feature of PH, and we previously reported that treprostinil therapy increases number and proliferative potential of endothelial colony forming cells (ECFC) isolated from PH patients' blood. In the present study, the objective was to determine how treprostinil contributes to the proangiogenic functions of ECFC. We examined the effect of treprostinil on ECFC obtained from cord blood in terms of colony numbers, proliferative and clonogenic properties in vitro, as well as in vivo vasculogenic properties. Surprisingly, treprostinil inhibited viability of cultured ECFC but did not modify their clonogenic properties or the endothelial differentiation potential from cord blood stem cells. Treprostinil treatment significantly increased the vessel-forming ability of ECFC combined with mesenchymal stem cells (MSC) in Matrigel implanted in nude mice. In vitro, ECFC proliferation was stimulated by conditioned media from treprostinil-pretreated MSC, and this effect was inhibited either by the use of VEGF-A blocking antibodies or siRNA VEGF-A in MSC. Silencing VEGF-A gene in MSC also blocked the pro-angiogenic effect of treprostinil in vivo. In conclusion, increased VEGF-A produced by MSC can account for the increased vessel formation observed during treprostinil treatment. The clinical relevance of these data was confirmed by the high level of VEGF-A detected in plasma from patients with paediatric PH who had been treated with treprostinil. Moreover, our results suggest that VEGF-A level in patients could be a surrogate biomarker of treprostinil efficacy.

The mechanistic basis of prostacyclin and its stable analogues in pulmonary arterial hypertension: Role of membrane versus nuclear receptors

Pulmonary arterial hypertension (PAH) is a progressive disease of distal pulmonary arteries in which patients suffer from elevated pulmonary arterial pressure, extensive vascular remodelling and right ventricular failure. To date prostacyclin (PGI2) therapy remains the most efficacious treatment for PAH and is the only approved monotherapy to have a positive impact on long-term survival. A key thing to note is that improvement exceeds that predicted from vasodilator testing strongly suggesting that additional mechanisms contribute to the therapeutic benefit of prostacyclins in PAH. Given these agents have potent antiproliferative, anti-inflammatory and endothelial regenerating properties suggests therapeutic benefit might result from a slowing, stabilization or even some reversal of vascular remodelling in vivo. This review discusses evidence that the pharmacology of each prostacyclin (IP) receptor agonist so far developed is distinct, with non-IP receptor targets clearly contributing to the therapeutic and side effect profile of PGI2 (EP3), iloprost (EP1), treprostinil (EP2, DP1) along with a family of nuclear receptors known as peroxisome proliferator-activated receptors (PPARs), to which PGI2 and some analogues directly bind. These targets are functionally expressed to varying degrees in arteries, veins, platelets, fibroblasts and inflammatory cells and are likely to be involved in the biological actions of prostacylins. Recently, a highly selective IP agonist, selexipag has been developed for PAH. This agent should prove useful in distinguishing IP from other prostanoid receptors or PPAR binding effects in human tissue. It remains to be determined whether selectivity for the IP receptor gives rise to a superior or inferior clinical benefit in PAH.

N-3 PUFA increase bioavailability and function of endothelial progenitor cells

BACKGROUND AND AIMS

Recent data suggest that n-3 PUFA exert beneficial effects on endothelial progenitor cell (EPC) biology. We sought to investigate whether these effects might be mediated by enhanced EPC in vitro function and/or in vivo bioavailability.

METHODS AND RESULTS

CACs and late-outgrowth EPCs were isolated from peripheral blood mononuclear cells obtained from 12 donor buffy-coats. The effect of n-3 PUFA (EPA:DHA = 0.9:1.5; 9 μM EPA plus 15 μM DHA) was tested on CAC/EPC viability, function (tube-formation) and pro-inflammatory molecule expression. Circulating EPC (cells positive for CD34, CD133 and kinase insert domain receptor - KDR cell-surface antigens by flow cytometry) number was evaluated in 20 healthy subjects (10 F/10 M, 32 ± 5 years), randomized to receive 4 mackerel or sardine portions per week for 6 weeks followed by a 6 week free-diet period. N-3 PUFA improved CAC and late-outgrowth EPC viability (p < 0.05) and the capacity to form tube-like structures in CACs (+38%; p < 0.05) and late-outgrowth EPCs (+15%; p < 0.05). ICAM-1 expression was reduced in both CACs (p < 0.05) and late-outgrowth EPCs (p < 0.05) and VCAM-1 in late-outgrowth EPCs (p < 0.005). N-3 PUFA significantly decreased TNF-α and MCP-1 expression in CACs and IL-8, TNF-α and MCP-1 in late-outgrowth EPCs (p < 0.05). Circulating EPC number significantly improved after 6 weeks of a fish-enriched diet (p < 0.01) and returned to baseline levels after a 6 week free-diet period (p < 0.01). Plasma EPA levels were independently and positively associated with EPC levels (p < 0.005).

CONCLUSION

Our findings support the case of a beneficiary role played by n-3 PUFA in EPC function and bioavailability.

Immortalized multipotent pericytes derived from the vasa vasorum in the injured vasculature. A cellular tool for studies of vascular remodeling and regeneration

Adventitial microvessels, vasa vasorum in the vessel walls, have an active role in the vascular remodeling, although its mechanisms are still unclear. It has been reported that microvascular pericytes (PCs) possess mesenchymal plasticity. Therefore, microvessels would serve as a systemic reservoir of stem cells and contribute to the tissues remodeling. However, most aspects of the biology of multipotent PCs (mPCs), in particular of pathological microvessels are still obscure because of the lack of appropriate methods to detect and isolate these cells. In order to examine the characteristics of mPCs, we established immortalized cells residing in adventitial capillary growing at the injured vascular walls. We recently developed in vivo angiogenesis to observe adventitial microvessels using collagen-coated tube (CCT), which also can be used as an adventitial microvessel-rich tissue. By using the CCT, CD146- or NG2-positive cells were isolated from the adventitial microvessels in the injured arteries of mice harboring a temperature-sensitive SV40 T-antigen gene. Several capillary-derived endothelial cells (cECs) and PCs (cPCs) cell lines were established. cECs and cPCs maintain a number of key endothelial and PC features. Co-incubation of cPCs with cECs formed capillary-like structure in Matrigel. Three out of six cPC lines, termed capillary mPCs demonstrated both mesenchymal stem cell- and neuronal stem cell-like phenotypes, differentiating effectively into adipocytes, osteoblasts, as well as schwann cells. mPCs differentiated to ECs and PCs, and formed capillary-like structure on their own. Transplanted DsRed-expressing mPCs were resident in the capillary and muscle fibers and promoted angiogenesis and myogenesis in damaged skeletal muscle. Adventitial mPCs possess transdifferentiation potential with unique phenotypes, including the reconstitution of capillary-like structures. Their phenotype would contribute to the pathological angiogenesis associated with vascular remodeling. These cell lines also provide a reproducible cellular tool for high-throughput studies on angiogenesis, vascular remodeling, and regeneration as well.

Prostacyclin signaling boosts NADPH oxidase 4 in the endothelium promoting cytoprotection and angiogenesis

AIMS

Prostacyclin (PGI2) that is released from the vascular endothelium plays an important role in vasodilatation and thrombo-resistance, and it has long been suspected to protect cell survival. How it does so has never been clear. Recently, it has been shown that the NADPH oxidase 4 (Nox4) improves endothelial cell functions and promotes angiogenesis in vivo, but it was not known how to boost Nox4 therapeutically to exploit its protective functions in the vasculature. Here, we identified such a stimulus.

RESULTS

The selective and stable prostacyclin receptor (IP-R) agonist cicaprost increases the expression of Nox4 in human endothelial cells of several types, including endothelial progenitor cells. The elevation of cellular cyclic-AMP increased Nox4 expression and H2O2 production and prevented endothelial cell apoptosis. We delineate the intracellular signaling that promotes cytoprotection: Cicaprost acts via the IP-R/protein kinase A (PKA)/cyclic adenosine monophosphate (cAMP) response element binding (CREB) protein pathway. Importantly, the up-regulation of Nox4 by cicaprost also enhanced endothelial cell proliferation, migration, and angiogenesis, with all effects being substantially decreased by Nox4 gene silencing. Finally, cicaprost enhanced the growth of blood vessels into subcutaneous sponges implanted in mice, an effect that was also blocked by Nox4 gene silencing.

INNOVATION

The prostacyclin analogue cicaprost induces Nox4 via IP receptor-cAMP/PKA/CREB pathway. The activation of this pathway protects endothelial cells and enhances pro-angiogenic activity both in vitro and in vivo.

CONCLUSION

Prostacyclin promotes the up-regulation of Nox4 in endothelial cells, which opens up a novel strategy that protects and enhances endothelial cell functions in cardiovascular disease, such as repair after myocardial infarction or other ischemic conditions.

Nerve growth factor stimulates regeneration of perivascular nerve, and induces the maturation of microvessels around the injured artery

An immature vasa vasorum in the adventitia of arteries has been implicated in induction of the formation of unstable atherosclerotic plaques. Normalization/maturation of the vasa vasorum may be an attractive therapeutic approach for arteriosclerotic diseases. Nerve growth factor (NGF) is a pleotropic molecule with angiogenic activity in addition to neural growth effects. However, whether NGF affects the formation of microvessels in addition to innervation during pathological angiogenesis is unclear. In the present study, we show a new role for NGF in neovessels around injured arterial walls using a novel in vivo angiogenesis assay. The vasa vasorum around arterial walls was induced to grow using wire-mediated mouse femoral arterial injury. When collagen-coated tube (CCT) was placed beside the injured artery for 7-14 days, microvessels grew two-dimensionally in a thin layer on the CCT (CCT-membrane) in accordance with the development of the vasa vasorum. The perivascular nerve was found at not only arterioles but also capillaries in the CCT-membrane. Biodegradable hydrogels containing VEGF and NGF were applied around the injured artery/CCT. VEGF significantly increased the total length and instability of microvessels within the CCT-membrane. In contrast, NGF induced regeneration of the peripheral nerve around the microvessels and induced the maturation and stabilization of microvessels. In an ex vivo nerve-free angiogenesis assay, although NGF potentially stimulated vascular sprouting from aorta tissues, no effects of NGF on vascular maturation were observed. These data demonstrated that NGF had potent angiogenic effects on the microvessels around the injured artery, and especially induced the maturation/stabilization of microvessels in accordance with the regeneration of perivascular nerves.

Eicosapentaenoic acid (EPA) reduces cardiovascular events: relationship with the EPA/arachidonic acid ratio

The clinical efficacy of fish oil and high-purity eicosapentaenoic acid ethyl ester (hp-EPA-E) for treating cardiovascular disease (CVD) has been reported. Fish oil contains saturated and monounsaturated fatty acids that have pharmacological effects opposite to those of ω3 fatty acids (ω3). Moreover, ω3, such as EPA and docosahexaenoic acid (DHA), do not necessarily have the same metabolic and biological actions. This has obscured the clinical efficacy of ω3. Recently, the Japan EPA Lipid Intervention Study (JELIS) of hp-EPA-E established the clinical efficacy of EPA for CVD, and higher levels of blood EPA, not DHA, were found to be associated with a lower incidence of major coronary events. A significant reduction in the risk of coronary events was observed when the ratio of EPA to arachidonic acid (AA) (EPA/AA) was > 0.75. Furthermore, the ratio of prostaglandin (PG) I3 and PGI2 to thromboxane A2 (TXA2) ([PGI2 + PGI3]/TXA2) was determined to have a linear relationship with the EPA/AA ratio as follows: (PGI2 + PGI3)/TXA2 =λ + π＊ (EPA/AA). Like PGI2, PGI3 not only inhibits platelet aggregation and vasoconstriction, but also is assumed to reduce cardiac ischemic injury and arteriosclerosis and promote angiogenesis. Thus, the effects of EPA in reducing the risk of CVD could be mediated by biological action of PGI3 in addition to hypotriglyceridemic action of EPA. Compared with DHA, EPA administration increases the EPA/AA ratio and the (PGI2 + PGI3)/TXA2 balance to a state that inhibits the onset and/or progression of CVD.

Apurinic/apyrimidinic endonucelase 1 maintains adhesion of endothelial progenitor cells and reduces neointima formation

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional protein that processes DNA-repair function and controls cellular response to oxidative stress. Endothelial progenitor cells (EPCs) are recruited to oxidative stress-rich injured vascular walls and positively contribute to vascular repair and endothelialization. We hypothesized that APE1 functions for EPCs-mediated inhibition of neointima formation in injured vasculature. EPCs isolated from bone marrow cells of C57BL6 mice (12-16 wk old) were able to survive in the presence of hydrogen peroxide (H2O2; up to 1,000 μM) due to the highly expressed reactive oxygen species (ROS) scavengers. However, adhesion capacity of EPCs was significantly inhibited by H2O2 (100 μM) even though an intracellular ROS was retained at small level. An APE1-selective inhibitor or RNA interference-mediated knockdown of endogenous APE1 in EPCs aggravated the H2O2-mediated inhibition of EPCs-adhesion. In contrast, when APE1 was overexpressed in EPCs using an adenovirus harboring the APE1 gene (APE-EPCs), adhesion was significantly improved during oxidative stress. To examine in vivo effects of APE1 in EPCs, APE-EPCs were transplanted via the tail vein after wire-mediated injury of the mouse femoral artery. The number of adherent EPCs at injured vascular walls and the vascular repair effect of EPCs were enhanced in APE-EPCs compared with control EPCs. Among the cellular functions of EPCs, adhesion is especially sensitive to oxidative stress. APE1 enhances in vivo vascular repair effects of EPCs in part through the maintenance of adhesion properties of EPCs. APE1 may be a novel and useful target gene for effective cellular transplantation therapy.

Sustained-release delivery of prostacyclin analogue enhances bone marrow-cell recruitment and yields functional benefits for acute myocardial infarction in mice

Background

A prostacyclin analogue, ONO-1301, is reported to upregulate beneficial proteins, including stromal cell derived factor-1 (SDF-1). We hypothesized that the sustained-release delivery of ONO-1301 would enhance SDF-1 expression in the acute myocardial infarction (MI) heart and induce bone marrow cells (BMCs) to home to the myocardium, leading to improved cardiac function in mice.

Methods and Results

ONO-1301 significantly upregulated SDF-1 secretion by fibroblasts. BMC migration was greater to ONO-1301-stimulated than unstimulated conditioned medium. This increase was diminished by treating the BMCs with a CXCR4-neutralizing antibody or CXCR4 antagonist (AMD3100). Atelocollagen sheets containing a sustained-release form of ONO-1301 (n = 33) or ONO-1301-free vehicle (n = 48) were implanted on the left ventricular (LV) anterior wall immediately after permanent left-anterior descending artery occlusion in C57BL6/N mice (male, 8-weeks-old). The SDF-1 expression in the infarct border zone was significantly elevated for 1 month in the ONO-1301-treated group. BMC accumulation in the infarcted hearts, detected by in vivo imaging after intravenous injection of labeled BMCs, was enhanced in the ONO-1301-treated hearts. This increase was inhibited by AMD3100. The accumulated BMCs differentiated into capillary structures. The survival rates and cardiac function were significantly improved in the ONO-1301-treated group (fractional area change 23±1%; n = 22) compared to the vehicle group (19±1%; n = 20; P = 0.004). LV anterior wall thinning, expansion of infarction, and fibrosis were lower in the ONO-1301-treated group.

Conclusions

Sustained-release delivery of ONO-1301 promoted BMC recruitment to the acute MI heart via SDF-1/CXCR4 signaling and restored cardiac performance, suggesting a novel mechanism for ONO-1301-mediated acute-MI heart repair.

Effects of nitric oxide on cell proliferation: novel insights

Nitric oxide (NO) has been suggested to be a pathophysiological modulator of cell proliferation, cell cycle arrest, and apoptosis. In this context, NO can exert opposite effects under diverse conditions. Indeed, several studies have indicated that low relative concentrations of NO seem to favor cell proliferation and antiapoptotic responses and higher levels of NO favor pathways inducing cell cycle arrest, mitochondria respiration, senescence, or apoptosis. Here we report the effects of NO on both promotion and inhibition of cell proliferation, in particular in regard to cardiovascular disease, diabetes, and stem cells. Moreover, we focus on molecular mechanisms of action involved in the control of cell cycle progression, which include both cyclic guanosine monophosphate-dependent and -independent pathways. This growing field may lead to broad and novel targeted therapies against cardiovascular diseases, especially concomitant type 2 diabetes, as well as novel bioimaging NO-based diagnostic tools.

Exposure to diesel exhaust upregulates COX-2 expression in ApoE knockout mice

INTRODUCTION

We have shown that diesel exhaust (DE) inhalation caused progression of atherosclerosis; however, the mechanisms are not fully understood. We hypothesize that exposure to DE upregulates cyclooxygenase (COX) expression and activity, which could play a role in DE-induced atherosclerosis.

METHODS

ApoE knockout mice (30-week old) fed with regular chow were exposed to DE (at 200 µg/m(3) of particulate matter) or filtered air (control) for 7 weeks (6 h/day, 5 days/week). The protein and mRNA expression of COX-1 and COX-2 were evaluated by immunohistochemistry analysis and quantitative real-time PCR, respectively. To examine COX activity, thoracic aortae were mounted in a wire myograph, and phenylephrine (PE)-stimulated vasoconstriction was measured with and without the presence of COX antagonists (indomethacin). COX-2 activity was further assessed by urine 2,3-dinor-6-keto PGF(1α) level, a major metabolite of prostacyclin I(2) (PGI(2)).

RESULTS

Immunohistochemistry analysis demonstrates that DE exposure enhanced COX-2 expression in both thoracic aorta (p < 0.01) and aortic root (p < 0.03), with no modification of COX-1 expression. The increased COX-2 expression was positively correlated with smooth muscle cell content in aortic lesions (R(2) = 0.4081, p < 0.008). The fractional changes of maximal vasoconstriction in the presence of indomethacin was attenuated by 3-fold after DE exposure (p < 0.02). Urine 2,3-dinor-6-keto PGF(1α) level was 15-fold higher in DE group than the control (p < 0.007). The mRNA expression of COX-2 (p < 0.006) and PGI synthase (p < 0.02), but not COX-1, was significantly augmented after DE exposure.

CONCLUSION

We show that DE inhalation enhanced COX-2 expression, which is also associated with phenotypic changes of aortic lesion.

Adipose-derived factor CTRP9 attenuates vascular smooth muscle cell proliferation and neointimal formation

Obesity is closely associated with the progression of vascular disorders, including atherosclerosis and postangioplasty restenosis. C1q/TNF-related protein (CTRP) 9 is an adipocytokine that is down-regulated in obese mice. Here we investigated whether CTRP9 modulates neointimal hyperplasia and vascular smooth muscle cell (VSMC) proliferation in vivo and in vitro. Left femoral arteries of wild-type (WT) mice were injured by a steel wire. An adenoviral vector expressing CTRP9 (Ad-CTRP9) or β-galactosidase as a control was intravenously injected into WT mice 3 d before vascular injury. Delivery of Ad-CTRP9 significantly attenuated the neointimal thickening and the number of bromodeoxyuridine-positive proliferating cells in the injured arteries compared with that of control. Treatment of VSMCs with CTRP9 protein attenuated the proliferative and chemotactic activities induced by growth factors including platelet-derived growth factor (PDGF)-BB, and suppressed PDGF-BB-stimulated phosphorylation of ERK. CTRP9 treatment dose-dependently increased cAMP levels in VSMCs. Blockade of cAMP-PKA pathway reversed the inhibitory effect of CTRP9 on DNA synthesis and ERK phosphorylation in response to PDGF-BB. The present data indicate that CTRP9 functions to attenuate neointimal formation following vascular injury through its ability to inhibit VSMC growth via cAMP-dependent mechanism, suggesting that the therapeutic approaches to enhance CTRP9 production could be valuable for prevention of vascular restenosis after angioplasty.

Regulation of the human prostacyclin receptor gene by the cholesterol-responsive SREBP1

Prostacyclin and its prostacyclin receptor, the I Prostanoid (IP), play essential roles in regulating hemostasis and vascular tone and have been implicated in a range cardio-protective effects but through largely unknown mechanisms. In this study, the influence of cholesterol on human IP [(h)IP] gene expression was investigated in cultured vascular endothelial and platelet-progenitor megakaryocytic cells. Cholesterol depletion increased human prostacyclin receptor (hIP) mRNA, hIP promoter-directed reporter gene expression, and hIP-induced cAMP generation in all cell types. Furthermore, the constitutively active sterol-response element binding protein (SREBP)1a, but not SREBP2, increased hIP mRNA and promoter-directed gene expression, and deletional and mutational analysis uncovered an evolutionary conserved sterol-response element (SRE), adjacent to a known functional Sp1 element, within the core hIP promoter. Moreover, chromatin immunoprecipitation assays confirmed direct cholesterol-regulated binding of SREBP1a to this hIP promoter region in vivo, and immunofluorescence microscopy corroborated that cholesterol depletion significantly increases hIP expression levels. In conclusion, the hIP gene is directly regulated by cholesterol depletion, which occurs through binding of SREBP1a to a functional SRE within its core promoter. Mechanistically, these data establish that cholesterol can regulate hIP expression, which may, at least in part, account for the combined cardio-protective actions of low serum cholesterol through its regulation of IP expression within the human vasculature.

Protective Effects of Mesenchymal Stem Cells with Transient Overexpression of Hmgb1 on Balloon-Induced Carotid Artery Injury

Mesenchymal stem cells (MSC) play a crucial role in endothelial repair after artery injury. The high mobility group box 1 (HMGB1) is a key modulator of the homing of MSC to impaired artery and endothelialization. This study was aimed to determine whether balloon-induced carotid artery injury could be improved by transplantation with MSC modified by HMGB1. MSC were infected by adenoviral serotype 5 encoding recombinant green fluorescent protein (GFP) gene and HMGB1 (ad5GFP-HMGB1). The expression of HMGB1, vascular endothelial growth factor (VEGF) and proliferating cell nuclear antigen (PCNA) was detected in MSC using Real-time PCR, Western blot and semi-quantitative immunohistochemical assays. In vivo, reendothelialization was examined in rats subjected to carotid artery injury. The homing of MSC was observed under fluorescence microscopy, and the levels of serum tumor necrosis factor-α (TNF-α) and C-reactive protein (CRP) was assessed by ELISA assay. As a result, compared with the MSC group, the expression of HMGB1, VEGF and PCNA was markedly increased, vascular reendothelialization was accelerated, and the levels of serum TNF-α and CRP were decreased in group ad5GFP and ad5GFP-HMGB1. Transplantation of MSC infected with adGFP-HMGB1 strengthened the MSC effect. Taken together, modification of HMGB1 can enhance the protective effects of MSC on balloon-induced carotid artery injury through up-regulation of VEGF and PCNA expression and inhibition of the inflammatory response. HMGB1 in MSC may represent a novel therapeutic target for the treatment of endothelial repair.

Engineered endothelial progenitor cells that overexpress prostacyclin protect vascular cells

Prostacyclin (PGI2) is a potent vasodilator and important mediator of vascular homeostasis; however, its clinical use is limited because of its short (<2-min) half-life. Thus, we hypothesize that the use of engineered endothelial progenitor cells (EPCs) that constitutively secrete high levels of PGI2 may overcome this limitation of PGI2 therapy. A cDNA encoding COX-1-10aa-PGIS, which links human cyclooxygenase-1 (COX-1) to prostacyclin synthase (PGIS), was delivered via nucleofection into outgrowth EPCs derived from rat bone marrow mononuclear cells. PGI2-secreting strains (PGI2-EPCs) were established by continuous subculturing of transfected cells under G418 selection. Genomic PCR, RT-PCR, and Western blot analyses confirmed the overexpression of COX-1-10aa-PGIS in PGI2-EPCs. PGI2-EPCs secreted significantly higher levels of PGI2 in vitro than native EPCs (P < 0.05) and showed higher intrinsic angiogenic capability; conditioned medium (CM) from PGI2-EPCs promoted better tube formation than CM from native EPCs (P < 0.05). Cell- and paracrine-mediated in vitro angiogenesis was attenuated when COX-1-10aa-PGIS protein expression was knocked down. Whole-cell patch-clamp studies showed that 4-aminopyridine-sensitive K(+) current density was increased significantly in rat smooth muscle cells (rSMCs) cocultured under hypoxia with PGI2-EPCs (7.50 ± 1.59 pA/pF; P < 0.05) compared with rSMCs cocultured with native EPCs (3.99 ± 1.26 pA/pF). In conclusion, we successfully created EPC strains that overexpress an active novel enzyme resulting in consistent secretion of PGI2. PGI2-EPCs showed enhanced intrinsic proangiogenic properties and provided favorable paracrine-mediated cellular protections, including promoting in vitro angiogenesis of native EPCs and hyperpolarization of SMCs under hypoxia.

Vascular effects of prostacyclin: does activation of PPARδ play a role?

Prostacyclin (PGI(2)) is a potent vasodilator that exerts multiple vasoprotective effects in the cardiovascular system. The effects of PGI(2) are mediated by activation of the cell membrane G-protein-coupled PGI(2) receptor (IP receptor). More recently, however, it has been suggested that PGI(2) might also serve as an endogenous ligand and activator of nuclear peroxisome proliferator-activated receptorδ (PPARδ). Consistent with this concept, studies designed to define pharmacological properties of stable PGI(2) analogs revealed that beneficial effects of these compounds appear to be mediated, in part, by activation of PPARδ. This review discusses emerging evidence regarding the contribution of PPARδ activation to vasoprotective and regenerative functions of PGI(2) and stable analogs of PGI(2).

Advanced glycation end products impair the migration, adhesion and secretion potentials of late endothelial progenitor cells

Background

Endothelial progenitor cells (EPCs), especially late EPCs, play a critical role in endothelial maintenance and repair, and postnatal vasculogenesis. Advanced glycation end products (AGEs) have been shown to impair EPC functions, such as proliferation, migration and adhesion. However, their role in the regulation of the production of vasoactive substances in late EPCs is less well defined.

Methods

Passages of 3~5 EPCs, namely late EPCs, were cultured with different concentrations (0~500 μg/ml) of AGEs, and the apoptosis, adhesion and migration were subsequently determined. The release of vasoactive substances, such as stromal cell-derived factor-1 (SDF-1), nitric oxide (NO), prostaglandin I₂ (PGI₂), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA), and in addition the activity of superoxide dismutase (SOD), were evaluated by ELISA. At the same time, the gene and protein expressions of CXCR4 were assayed by real-time RT-PCR and western-blot.

Results

AGEs promoted late EPC apoptosis. Moreover, AGEs impaired late EPC migration and adhesion in a concentration-dependent manner. Accordingly, the production of SDF-1 was decreased by AGEs. Although the CXCR4 expressions of late EPCs were up-regulated for AGE concentrations of 50, 100 or 200 μg/ml, a marked decrease was observed for the higher concentration of 500 μg/ml. Furthermore, co-culturing with AGEs decreased the levels of NO, t-PA, PGI_2, and the activity of SOD but up-regulated the production of PAI-1.

Conclusion

Our data provide evidence that AGEs play an important role in impairing late EPC functions, which could contribute to the development of vascular diseases in diabetes.

Prostacyclin receptor in tumor endothelial cells promotes angiogenesis in an autocrine manner

Molecules highly expressed in tumor endothelial cells (TEC) are important for specific targeting of these cells. Previously, using DNA microarray analysis, we found that the prostacyclin receptor (IP receptor) gene was upregulated in TEC compared with normal endothelial cells (NEC). Although prostacyclin is implicated in re-endothelialization and angiogenesis, its role remains largely unknown in TEC. Moreover, the effect of the IP receptor on TEC has not been reported. In the present study we investigated the function of the IP receptor in TEC. The TEC were isolated from two types of human tumor xenografts in nude mice, while NEC were isolated from normal counterparts. Prostacyclin secretion levels in TEC were significantly higher than those in NEC, as shown using ELISA. Real-time RT-PCR showed that the IP receptor was upregulated in TEC compared with NEC. Furthermore, migration and tube formation of TEC were suppressed by the IP receptor antagonist RO1138452. Immunohistostaining showed that the IP receptor was specifically expressed in blood vessels of renal cell carcinoma specimens, but not in glomerular vessels of normal renal tissue. These findings suggest that the IP receptor is a TEC-specific marker and might be a useful therapeutic target.

Inflammation-related gene expression by lipid oxidation-derived products in the progression of atherosclerosis

Vascular areas of atherosclerotic development persist in a state of inflammation, and any further inflammatory stimulus in the subintimal area elicits a proatherogenic response; this alters the behavior of the artery wall cells and recruits further inflammatory cells. In association with the inflammatory response, oxidative events are also involved in the development of atherosclerotic plaques. It is now unanimously recognized that lipid oxidation-derived products are key players in the initiation and progression of atherosclerotic lesions. Oxidized lipids, derived from oxidatively modified low-density lipoproteins (LDLs), which accumulate in the intima, strongly modulate inflammation-related gene expression, through involvement of various signaling pathways. In addition, considerable evidence supports a proatherogenic role of a large group of potent bioactive lipids called eicosanoids, which derive from oxidation of arachidonic acid, a component of membrane phospholipids. Of note, LDL lipid oxidation products might regulate eicosanoid production, modulating the enzymatic degradation of arachidonic acid by cyclooxygenases and lipoxygenases; these enzymes might also directly contribute to LDL oxidation. This review provides a comprehensive overview of current knowledge on signal transduction pathways and inflammatory gene expression, modulated by lipid oxidation-derived products, in the progression of atherosclerosis.

Interaction of the human prostacyclin receptor with the PDZ adapter protein PDZK1: role in endothelial cell migration and angiogenesis

Prostacyclin is widely implicated in re-endothelialization and angiogenesis but through unknown mechanisms. Herein the HDL scavenger receptor class B, type 1 adapter PDZK1 was identified as a direct, functional interactant of the human prostacyclin receptor and was found to influence prostacyclin-mediated endothelial migration and in vitro angiogenesis.

Prostacyclin is increasingly implicated in re-endothelialization and angiogenesis but through largely unknown mechanisms. Herein the high-density lipoprotein (HDL) scavenger receptor class B, type 1 (SR-B1) adapter protein PDZ domain-containing protein 1 (PDZK1) was identified as an interactant of the human prostacyclin receptor (hIP) involving a Class I PDZ ligand at its carboxyl terminus and PDZ domains 1, 3, and 4 of PDZK1. Although the interaction is constitutive, it may be dynamically regulated following cicaprost activation of the hIP through a mechanism involving cAMP-dependent protein kinase (PK)A-phosphorylation of PDZK1 at Ser-505. Although PDZK1 did not increase overall levels of the hIP, it increased its functional expression at the cell surface, enhancing ligand binding and cicaprost-induced cAMP generation. Consistent with its role in re-endothelialization and angiogenesis, cicaprost activation of the hIP increased endothelial cell migration and tube formation/in vitro angiogenesis, effects completely abrogated by the specific IP antagonist RO1138452. Furthermore, similar to HDL/SR-B1, small interfering RNA (siRNA)-targeted disruption of PDZK1 abolished cicaprost-mediated endothelial responses but did not affect VEGF responses. Considering the essential role played by prostacyclin throughout the cardiovascular system, identification of PDZK1 as a functional interactant of the hIP sheds significant mechanistic insights into the protective roles of these key players, and potentially HDL/SR-B1, within the vascular endothelium.

Identification of a novel endoplasmic reticulum export motif within the eighth α-helical domain (α-H8) of the human prostacyclin receptor

The human prostacyclin receptor (hIP) undergoes agonist-dependent trafficking involving a direct interaction with Rab11a GTPase. The region of interaction was localised to a 14 residue Rab11a binding domain (RBD) within the proximal carboxyl-terminal (C)-tail domain of the hIP, consisting of Val(299)-Val(307) within the eighth helical domain (α-H8) adjacent to the palmitoylated residues at Cys(308)-Cys(311). However, the factors determining the anterograde transport of the newly synthesised hIP from the endoplasmic reticulum (ER) to the plasma membrane (PM) have not been identified. The aim of the current study was to identify the major ER export motif(s) within the hIP initially by investigating the role of Lys residues in its maturation and processing. Through site-directed and Ala-scanning mutational studies in combination with analyses of protein expression and maturation, functional analyses of ligand binding, agonist-induced intracellular signalling and confocal image analyses, it was determined that Lys(297), Arg(302) and Lys(304) located within α-H8 represent the critical determinants of a novel ER export motif of the hIP. Furthermore, while substitution of those critical residues significantly impaired maturation and processing of the hIP, replacement of the positively charged Lys with Arg residues, and vice versa, was functionally permissible. Hence, this study has identified a novel 8 residue ER export motif within the functionally important α-H8 of the hIP. This ER export motif, defined by "K/R(X)(4)K/R(X)K/R," has a strict requirement for positively charged, basic Lys/Arg residues at the 1st, 6th and 8th positions and appears to be evolutionarily conserved within IP sequences from mouse to man.

Activation of vascular BK channels by docosahexaenoic acid is dependent on cytochrome P450 epoxygenase activity

AIMS

n-3 Polyunsaturated fatty acids (PUFAs) are known to protect the cardiovascular system and improve blood pressure control. These important dietary constituents are converted into bioactive metabolites, but their role in regulation of the cardiovascular system is unclear. In particular, the functions of the cytochrome P450 (CYP) metabolites of n-3 PUFAs remain virtually unexplored. In this study, we examined the effects of docosahexaenoic acid (DHA) on the regulation of large-conductance calcium-activated potassium (BK) channel activities in coronary arterial smooth muscle cells.

METHODS AND RESULTS

Using whole-cell patch-clamp techniques, we found that DHA is a potent activator of BK currents in rat coronary arterial smooth muscle cells with an EC(50) of 0.23 ± 0.03 µM. This effect was abolished by pre-incubation with the CYP epoxygenase inhibitor, SKF525A (10 µM). The effects of DHA on the BK channels were reproduced by 16,17-epoxydocosapentaenoic acid (16,17-EpDPE) with an EC(50) of 19.7 ± 2.8 nM. The physiological role of the CYP metabolites of DHA was confirmed by measuring DHA-mediated vasodilatation in isolated rat coronary arteries. DHA dilated pressurized isolated coronary arteries in a dose-dependent manner, and the DHA effects were abolished after pre-treatment with SKF525A (10 µM) or with iberiotoxin (100 nM). In addition, 16,17-EpDPE directly produced coronary vasodilatation that was iberiotoxin sensitive.

CONCLUSION

These results suggest that DHA-mediated vasodilatation is mediated through CYP epoxygenase metabolites by activation of vascular BK channels.