Comparison of tissue factor pathway in human umbilical vein and adult saphenous vein endothelial cells: implications for newborn hemostasis and for laboratory models of endothelial cell function

Endothelial Akt activation by hyperoxia: role in cell survival

High oxygen concentrations (hyperoxia), often required in the treatment of preterm infants and critically ill patients, cause lung injury, targeting especially the endothelium. Exposure of primary human lung microvascular endothelial cells (HLMVEC) to hyperoxia caused transient Akt activation after 60 min, as determined by Western blot analysis of phosphorylated Ser 473 of Akt. Akt phosphorylation was also increased after 24 h of hyperoxic exposure, which declined at 48 h. Adenoviral (Ad)-mediated expression of constitutively active myrAkt protected HLMVEC against hyperoxic injury. Cell death due to hyperoxia (95% O2, 8 days), which was primarily necrotic, was substantial in control and Ad-LacZ-transduced cells, but was diminished by almost half in myrAkt-transduced cells. Hyperoxia caused increased cellular glucose consumption, an effect that was amplified in cells transduced with myrAkt compared to the LacZ-transduced or the nontransduced controls. Increased glucose consumption in myrAkt-expressing cells was accompanied by increased phosphorylation of mTOR and p70 S6-kinase. Rapamycin treatment decreased glucose consumption in myrAkt-transduced cells to levels comparable to those in control and LacZ-transduced cells exposed to hyperoxia. Ultrastructural morphometric analyses demonstrated that mitochondria and endoplasmic reticulum were less swollen in myrAkt cells relative to controls exposed to hyperoxia. These studies demonstrate that early activation of Akt occurs in hyperoxia in HLMVEC. That this event is a beneficial response is suggested by the finding that constitutive activation of Akt protects against hyperoxic stress, at least in part, by maintaining mitochondrial integrity.

Voltage-gated calcium channels mediate hypoxic vasoconstriction in the human placenta

Unlike all vascular beds with the exception of the pulmonary circulation, fetoplacental vessels respond to acute hypoxia with vasoconstriction. While this hypoxic fetoplacental vasoconstriction (HFPV) is considered essential in the pathogenesis of intrauterine growth retardation, its mechanism is largely unknown. Hypoxia inhibits potassium channels and thus causes depolarization in fetoplacental vascular smooth muscle. We propose that this hypoxia-induced depolarization leads to vasoconstriction by activating voltage-dependent calcium (Ca) channels and Ca influx. We compared HFPV between isolated perfused human cotyledons treated with an inhibitor of L-type channels, nifedipine, and preparations receiving only vehicle. While the solvent (diluted DMSO) had no inhibitory effect on HFPV, the hypoxic responses were completely abolished even by a relatively low dose of nifedipine (1 nM). We conclude that activation of L-type Ca channels is an essential part of HFPV.

Comparative Efficacy of Intratracheal Adeno-Associated Virus Administration to Newborn Rats

Transient local overexpression of genes that promote lung defense or repair may help to protect or promote alveolar development in premature neonates. We showed that the use of adenoviral vectors in neonates was limited by the induction of lung growth disorders. In the present work we compare the efficiency of gene transfer to the neonatal lung by three adeno-associated viral vectors: rAAV1, rAAV2, and rAAV5. Transduction efficiency was first measured in vitro, by infecting A549 immortalized human lung epithelial cells, and primary epithelial and mesenchymal cells isolated from human fetal lung. AAV vectors yielded similar low levels of luciferase gene expression in the different cell types. In vivo transduction efficiency was evaluated in newborn rats, with AAV-LacZ vectors being intratracheally instilled at 3 days of age. Both rAAV5 and rAAV1, but not rAAV2, induced significant lung beta-galactosidase expression, which persisted on day 35. Highest beta- galactosidase levels were measured with rAAV5, but remained far lower than those obtained with adenoviral vectors. A transient increase in alveolar macrophages was observed on day 6, but not on day 8, after rAAV5-LacZ instillation. Morphometric evaluation of lung structures was performed on day 21, and showed no altered lung growth. We conclude that rAAV1 or rAAV5 was more efficient at mediating gene transfer in the neonatal lung than was rAAV2, without adversely affecting lung development. However, in vivo transgene expression was relatively low, and needs to be improved for future therapeutic use of these adeno-associated vectors.

Lung vascular development: implications for the pathogenesis of bronchopulmonary dysplasia

Past studies have primarily focused on how altered lung vascular growth and development contribute to pulmonary hypertension. Recently, basic studies of vascular growth have led to novel insights into mechanisms underlying development of the normal pulmonary circulation and the essential relationship of vascular growth to lung alveolar development. These observations have led to new concepts underlying the pathobiology of developmental lung disease, especially the inhibition of lung growth that characterizes bronchopulmonary dysplasia (BPD). We speculate that understanding basic mechanisms that regulate and determine vascular growth will lead to new clinical strategies to improve the long-term outcome of premature babies with BPD.

Stimulation of HIF-1alpha, HIF-2alpha, and VEGF by prolyl 4-hydroxylase inhibition in human lung endothelial and epithelial cells

Diminished alveolar and vascular development is characteristic of bronchopulmonary dysplasia (BPD) affecting many preterm newborns. Hypoxia promotes angiogenic responses in developing lung via, for example, vascular endothelial growth factor (VEGF). To determine if prolyl 4-hydroxylase (PHD) inhibition could augment hypoxia-inducible factors (HIFs) and expression of angiogenic proteins essential for lung development, HIF-1alpha and -2alpha proteins were assessed in human developing and adult lung microvascular endothelial cells and alveolar epithelial-like cells treated with either the HIF-PHD-selective inhibitor PHI-1 or the nonselective PHD inhibitors dimethyloxaloylglycine (DMOG) and deferoxamine (DFO). PHI-1 stimulated HIF-1alpha and -2alpha equally or more effectively than did DMOG or DFO, enhanced VEGF release, and elevated glucose consumption, whereas it was considerably less cytotoxic than DMOG or DFO. Moreover, VEGF receptor Flt-1 levels increased, whereas KDR/Flk-1 decreased. PHI-1 treatment also increased PHD-2, but not PHD-1 or -3, protein. These results provide proof of principle that HIF stimulation and modulation of HIF-regulated angiogenic proteins through PHI-1 treatment are feasible, effective, and nontoxic in human lung cells, suggesting the use of PHI-1 to enhance angiogenesis and lung growth in evolving BPD.

Developmental biology of the pulmonary circulation

From the earliest stage of lung development, there is an accompanying blood circulation. In the adult lung, the pulmonary arteries are closely associated with the airways. During early fetal development, the airways act as a template for pulmonary blood vessel development in that the vessels form by vasculogenesis around the branching airways. In later lung development, as the alveoli multiply, new capillaries form by angiogenesis. As blood vessels increase in size, they develop a muscle wall that is relatively thick during fetal life and shows a rapid reduction after birth. The control of development by growth factors and the physiological changes immediately after birth are described in this review. Abnormal pulmonary vascular development leading to pulmonary arterial hypertension and strategies for treatment are also discussed.

Gene expression profile and histopathology of experimental bronchopulmonary dysplasia induced by prolonged oxidative stress

Oxidative stress is an important factor in the pathogenesis of bronchopulmonary dysplasia (BPD), a chronic lung disease of premature infants characterized by arrested alveolar and vascular development of the immature lung. We investigated differential gene expression with DNA microarray analysis in premature rat lungs exposed to prolonged hyperoxia during the saccular stage of development, which closely resembles the development of the lungs of premature infants receiving neonatal intensive care. Expression profiles were largely confirmed by real-time RT-PCR (27 genes) and in line with histopathology and fibrin deposition studied by Western blotting. Oxidative stress affected a complex orchestra of genes involved in inflammation, coagulation, fibrinolysis, extracellular matrix turnover, cell cycle, signal transduction, and alveolar enlargement and explains, at least in part, the pathological alterations that occur in lungs developing BPD. Exciting findings were the magnitude of fibrin deposition; the upregulation of chemokine-induced neutrophilic chemoattractant-1 (CINC-1), monocyte chemoattractant protein-1 (MCP-1), amphiregulin, plasminogen activator inhibitor-1 (PAI-1), secretory leukocyte proteinase inhibitor (SLPI), matrix metalloproteinase-12 (MMP12), p21, metallothionein, and heme oxygenase (HO); and the downregulation of fibroblast growth factor receptor-4 (FGFR4) and vascular endothelial growth factor (VEGF) receptor-2 (Flk-1). These findings are not only of fundamental importance in the understanding of the pathophysiology of BPD, but also essential for the development of new therapeutic strategies.

Adrenal suppression and extubation rate after moderately early low-dose dexamethasone therapy in very preterm infants

OBJECTIVE

A short course of moderately early dexamethasone therapy with a starting dose of 0.5 mg/kg/day improves lung compliance and shortens the duration of ventilatory support in preterm infants with respiratory distress syndrome (RDS). We conducted a double-blind, randomized study to evaluate whether a moderately early 14-day weaning course of low-dose dexamethasone affects adrenal function and facilitates weaning from the ventilator.

PATIENTS AND METHODS

Thirty-six preterm infants with a gestational age < or =32 weeks who required ventilatory support for RDS on days 7-14 were randomized to a 14-day treatment course with dexamethasone (0.2 mg/kg/day start, tapering doses) or placebo (equivalent amounts of normal saline). Prior to the first study treatment and the day after completion of the treatment course, adrenal function was assessed from serum cortisol levels drawn before and 30 min after intravenous administration of 0.1 mg Cortrosyn. Extubation rate during treatment in both groups was compared.

RESULTS

In both groups baseline serum cortisol levels decreased significantly during treatment, but stimulated cortisol levels did not change. After the 14-day treatment course, stimulated cortisol levels increased significantly from baseline levels in both groups (p<0.001), following Cortrosyn administration. More infants in the dexamethasone group were extubated within 7-14 days of study entry than in the placebo group (p<0.05). Hyperglycemia was more frequently diagnosed in the dexamethasone group and open-label dexamethasone treatment was given more frequently in the control group.

CONCLUSIONS

A moderately early 14-day weaning course of low-dose dexamethasone does not significantly suppress the adrenal function of very preterm infants with RDS, but accelerates weaning from the ventilator.

Effects of childhood respiratory diseases on the anatomical and functional development of the respiratory system

The anatomical and functional development of the lung appears especially vulnerable to a whole range of insults during gestation and the first few years of life. A significant proportion of adult lung disease originates in utero or early infancy. Most publications on this topic are descriptive retrospective studies. An important limitation of these is that structural changes may precede abnormalities in lung function and development of symptoms. Little is known with certainty with respect to the long-term effects of early insults to the respiratory system. Furthermore, the reversibility of the functional and/or structural defects is hardly ever adequately investigated and it is probably not correct to extrapolate findings from adult studies to paediatric pulmonary diseases. Promoting or facilitating optimal lung growth in fetuses and infants and reducing the incidence of lower respiratory tract infection in infancy may reduce the incidence of adult chronic lung disease in generations to come.

Populations at risk for developing respiratory syncytial virus and risk factors for respiratory syncytial virus severity: infants with predisposing conditions

According to National Vital Statistics Reports, premature infants (< 36 weeks gestation) account for approximately 7.4% of all births. During the 8 years from 1989 to 1997, multiple births steadily increased across all categories from twin to quintuplet and higher orders. During that same period low birth weight (< 2500 g) births increased almost 12%, and very low birth weight (< 1500 g) births increased approximately 20%.Attendant to these national trends in multiple and preterm births, overall gestation-specific survival rates have improved substantially. This improved outcome can be attributed in large measure to advances in neonatal care and technology. Despite the encouraging statistics on survival, infants born prematurely, at low or very low birth weights and/or with chronic conditions that predispose to lower respiratory tract illness, continue to incur serious risk of long term morbidity and the consumption of inpatient hospital services. In a recent 2-year study of US children, low and very low birth weights were found to be independent risk factors for bronchiolitis-associated mortality. In the past 14 years what defines bronchopulmonary dysplasia (BPD)/chronic lung disease (CLD) has shifted away from clinical, radiographic and pathologic findings in the preterm infant toward the pathophysiology of arrested lung development and the need for supportive care beyond 36 weeks corrected gestational age. The incidence of BPD/CLD ranges from 14 to 43%, with higher rates observed among infants of lower gestational age and birth weight. The health care team approach to the management of BPD directs its efforts toward minimizing pulmonary vascular resistance, alleviating airway obstruction and improving short term lung mechanics. Measures to prevent BPD/CLD attempt to forestall both acute and chronic lung function abnormalities. To that end researchers have investigated the early use of continuous positive airway pressure, vitamin supplementation and recombinant human copper/zinc superoxide dismutase. Despite significant gains in the survival of infants born at lower gestational ages, prematurity, low birth weight and/or underlying chronic pulmonary disease put the pediatric patient at risk for increased frequency and severity of respiratory syncytial virus lower respiratory tract illness and the potential for its long term sequelae.

Neonatal respiratory failure

The classic entity of neonatal distress syndrome, as a lung disease expressing predominant surfactant deficiency, is currently changing to a more complex disease of the developing lung as a result of the number of extremely immature preterm infants. Prenatal factors, such as the fetal inflammatory response syndrome influence short- and long-term outcome in these premature infants presenting with respiratory distress syndrome at birth. Therefore, various previously dismissed treatment strategies, such as surfactant prophylaxis or newer anti-inflammatory approaches have to be reinvestigated in this emerging population. Despite the resurrection of a new picture of bronchopulmonary dysplasia, lung injury induced by mechanical ventilation remains a major issue in neonatal intensive care. With the advance in understanding of mechanical ventilation, it is becoming evident, that improvement in outcome can not be achieved by restoring normal lung physiology in the diseased lung using sophisticated ventilators and ventilation modes. A more disease specific ventilator strategy that will target as early as possible homogenous lung opening while at the same time avoiding overdistention of the lung, has the potential to affect outcome. The possible antiinflammatory properties of surfactant-proteins, nitric oxide and corticosteroids, despite some drawbacks, may show to have a synergistic effect. However, this needs further exploration.

Profile of eicosanoids produced by human saphenous vein endothelial cells and the effect of dietary fatty acids

Human saphenous vein endothelial cells (HSVECs) derived from primary cultures of adult human veins constitute an excellent in vitro model for studying human endothelial metabolism. In this study we report the (14)C-labelled prostanoid profile of HSVECs under resting and stimulated conditions and the effect of the n-3 polyunsaturated fatty acids eicosapentaenoic acid and docosahexaenoic acid on them. Results indicate that HSVECs while under resting conditions produce mainly prostaglandin F(2alpha)(PGF(2alpha)). After stimulation with calcium ionophore A23187, the cells were found to synthesise PGI(2), PGE(2)and PGF(2alpha) as major products and thromboxane B(2)and PGD(2)as minor products. Production of (14)C-labelled hydroxyeicosatetraenoic acids was not detected. Eicosapentaenoic acid was found to inhibit basal and stimulated prostanoid production whereas docosahexaenoic acid inhibited basal but strongly increased stimulated prostanoid production. These results may offer the basis for further studies aiming to investigate targets for pharmacological intervention in inflammatory conditions.

Prevention of bronchopulmonary dysplasia

The clinical syndrome of bronchopulmonary dysplasia (BPD) in preterm infants results primarily from an arrest of lung vascular and alveolar development. The most likely mediators are proinflammatory cytokines that are induced by antenatal exposure to infection, postnatal ventilation, and oxygen exposure. New epidemiologic data suggest that attempts to avoid intubation and ventilation are the best ways to avoid severe BPD. The claim that one ventilation technique is better than another remains unconvincing, and any strategy that maintains the lung open and minimizes tidal volumes probably will be helpful. More adverse effects of postnatal steroids are being recognized. New insights into the pathophysiology of BPD and a new emphasis on minimizing ventilation and ventilator-mediated injury should improve outcomes for very preterm infants.

Evaluation of tissue-factor production by human endothelial cells incubated with three acrylic bone cements

The effect of three methacrylate-based cements used for the fixation of joint prostheses on tissue-factor production by human umbilical vein endothelial cells was evaluated in vitro. The extracts in the culture medium of the cements were tested after 1-h and 7-day curing. The endothelial cells were incubated with the cement extracts for 4 h, and then the tissue factor was determined in cell lysates with both the recalcification time and enzyme immuno assay. The cements did not induce significant production of tissue factor and, therefore, did not activate the extrinsic pathway of coagulation within the limits of the mechanism considered.

Multiple courses of antenatal glucocorticoid treatment and fetal outcome

Thanks to the US National Institutes of Health Consensus Conference, the odds of antenatal use of glucocorticoids for preventing severe neonatal complications of premature delivery have significantly increased these last years. The belief that neonatal benefits last up to 7 days after the first course and administration of further courses is safe has led many obstetricians to prescribe multiple antenatal glucocorticoid courses. Whether multiple courses offer an advantage over a single course has not been demonstrated. In contrast, there are accumulating evidence suggesting that this practice may have short and long-term side effects. The potential benefits and side effects of multiple antenatal courses of glucocorticoids, extrapolated from experimental data and observational studies, are detailed in this review. Until the results of ongoing randomized trials with long term follow-up are available, the practice of giving multiple courses of glucocorticoids to women should be considered with the greatest caution.

Shear stress decreases endothelial cell tissue factor activity by augmenting secretion of tissue factor pathway inhibitor

Monolayers of human umbilical vein endothelial cells were activated with 50 U/mL interleukin-1alpha (IL-1alpha) for 3 hours and simultaneously conditioned with shear stresses of 0, 0.68, or 13.2 dyne/cm(2) in a parallel-plate flow chamber. In the presence of an inflow buffer containing 100 nmol/L factor X and 10 nmol/L factor VII, production of factor Xa, a measure of functional tissue factor (TF), was determined as the product of outflow concentration of factor Xa (chromogenic assay performed under quasi-static flow conditions after the shear period) and flow rate. Similarly, production of TF pathway inhibitor (TFPI) was estimated as the product of antigenic TFPI (by enzyme-linked immunosorbent assay) in the supernatant and flow rate. In parallel experiments, total RNA was isolated for determination of amplification products of TF mRNA by reverse transcription-polymerase chain reaction. We found that shear stress reduced factor Xa production (mean+/-SE; n=number of experiments) from 13.33+/-1.14 (n=16) fmol/minxcm(2) at 0 shear stress to 5.70+/-2.51 (n=5) and 0.54+/-0.54 (n=4) fmol/minxcm(2) at shear stresses of 0.68 and 13.2 dyne/cm(2), respectively. At the same time, immunogold labeling showed that TF antigen on the endothelial surface increased >5-fold with shear stress, whereas TFPI antigen on the surface increased 2-fold. The secretion of TFPI (appearance of new supernatant TFPI) rose from 7.4+/-2.4 (n=12) x10(-)(3) fmol/minxcm(2) at 0 shear stress to 23.7+/-7.3 (n=9) and 50.2+/-14.3 (n=4) x10(-)(3) fmol/minxcm(2) at 0.68 and 13.2 dyne/cm(2), respectively. TF mRNA amplification products were not markedly changed by shear stress. We conclude that acute application of shear stress reduces functional, but not antigenic, expression of TF by intact, activated endothelial cell monolayers in a manner associated with shear stress-augmented endothelial cell secretion of TFPI.

Activated monocytes in sickle cell disease: potential role in the activation of vascular endothelium and vaso-occlusion

Sickle cell anemia is characterized by painful vaso-occlusive crises. It is hypothesized that monocytes are activated in sickle cell disease and can enhance vaso-occlusion by activating endothelium. To test this hypothesis, human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (MVEC) with sickle and normal mononuclear leukocytes were incubated, and endothelial activation was measured. Endothelial cells incubated with sickle mononuclear leukocytes were more activated than those incubated with normal mononuclear leukocytes, as judged by the increased endothelial expression of adhesion molecules and tissue factor and the adhesion of polymorphonuclear leukocytes (PMNL). Monocytes, not lymphocytes or platelets, were the mononuclear cells responsible for activating endothelial cells. Sickle monocytes triggered endothelial nuclear factor-kappa B (NF-κB) nuclear translocation. Cell-to-cell contact of monocytes and endothelium enhanced, but was not required for, activation. Antibodies to tumor necrosis factor-alpha (TNF-α) and interleukin-1-beta (IL-1β) blocked activation of the endothelium by monocytes. Peripheral blood monocytes from patients with sickle cell disease had 34% more IL-1β (P = .002) and 139% more TNF-α (P = .002) per cell than normal monocytes. Sixty percent of sickle monocytes expressed the adhesion molecule ligand CD11b on their surfaces compared with only 20% of normal monocytes (P = .002). Serum C-reactive protein, a marker of systemic inflammation, was increased 12-fold in sickle serum than in normal serum (P = .003). These results demonstrate that sickle monocytes are activated and can, in turn, activate endothelial cells. It is speculated that vascular inflammation, marked by activated monocytes and endothelium, plays a significant role in the pathophysiology of vaso-occlusion in sickle cell anemia.

Activated monocytes in sickle cell disease: potential role in the activation of vascular endothelium and vaso-occlusion

Sickle cell anemia is characterized by painful vaso-occlusive crises. It is hypothesized that monocytes are activated in sickle cell disease and can enhance vaso-occlusion by activating endothelium. To test this hypothesis, human umbilical vein endothelial cells (HUVEC) and human microvascular endothelial cells (MVEC) with sickle and normal mononuclear leukocytes were incubated, and endothelial activation was measured. Endothelial cells incubated with sickle mononuclear leukocytes were more activated than those incubated with normal mononuclear leukocytes, as judged by the increased endothelial expression of adhesion molecules and tissue factor and the adhesion of polymorphonuclear leukocytes (PMNL). Monocytes, not lymphocytes or platelets, were the mononuclear cells responsible for activating endothelial cells. Sickle monocytes triggered endothelial nuclear factor-kappa B (NF-κB) nuclear translocation. Cell-to-cell contact of monocytes and endothelium enhanced, but was not required for, activation. Antibodies to tumor necrosis factor-alpha (TNF-α) and interleukin-1-beta (IL-1β) blocked activation of the endothelium by monocytes. Peripheral blood monocytes from patients with sickle cell disease had 34% more IL-1β (P = .002) and 139% more TNF-α (P = .002) per cell than normal monocytes. Sixty percent of sickle monocytes expressed the adhesion molecule ligand CD11b on their surfaces compared with only 20% of normal monocytes (P = .002). Serum C-reactive protein, a marker of systemic inflammation, was increased 12-fold in sickle serum than in normal serum (P = .003). These results demonstrate that sickle monocytes are activated and can, in turn, activate endothelial cells. It is speculated that vascular inflammation, marked by activated monocytes and endothelium, plays a significant role in the pathophysiology of vaso-occlusion in sickle cell anemia.

Special communicationthe critical role of mechanical forces in blood vessel development, physiology and pathology

The following extended abstracts were presented at the Research Initiatives in Vascular Disease Conference, Movers and Shakers in the Vascular Tree-Hemodynamic and Biomechanical Factors in Blood Vessel Pathology, sponsored by The Lifeline Foundation and the Cardiovascular & Interventional Radiology Research and Educational Foundation; jointly sponsored by the International Society for Cardiovascular Surgery, North American Chapter, The Society for Vascular Surgery, and The Society of Cardiovascular and Interventional Radiology; in cooperation with the National Institutes of Health-National Heart, Lung &Blood Institute on Mar 11-12, 1999, in Bethesda, Md.