Kristina Bry

Inositol Supplementation in Premature Infants with Respiratory Distress Syndrome

Abstract Background. Inositol influences cellular function and organ maturation. Feeding premature infants inositol-rich breast milk increases their serum inositol concentrations. Whether inositol supplementation benefits infants receiving fluids for parenteral nutrition, which are inositol-free, is not known. Methods. We carried out a placebo-controlled, randomized, double-blind trial to determine the effects of administering inositol (80 mg per kilogram of body weight per day) during the first five days of life to 221 infants with respiratory distress syndrome who were receiving parenteral nutrition (gestational age, 24 to 32 weeks; birth weight, <2000 g). All the infants were treated with mechanical ventilation and some with surfactant as well. The primary end point was survival at 28 days without bronchopulmonary dysplasia. Results. The 114 patients given inositol had significantly lower mean requirements for inspiratory oxygen (P<0.01) and mean airway pressure (P<0.05) from the 12th through the 144th...

Transforming growth factor-β2 prevents preterm delivery induced by interleukin-α and tumor necrosis factor-α the rabbit

Objectives: The purpose of the study was to determine whether preterm parturition in the rabbit can be induced by intraamniotic injection of proinflammatory cytokines, interleukin-α and tumor necrosis factor-β2, and whether transforming growth factor-p2, an inhibitor of the cytokine-induced prostaglandin synthesis, modifies the effect of these cytokines. Study Design: New Zealand White rabbits were injected in each amniotic cavity on day 24 of gestation with one of the following: a combination of interleukin-α (150 µg) and tumor necrosis factor-α (1.25 µg), 50 ng of transforming growth factor-β2 concomitantly with interleukin-α and tumor necrosis factor-α, or vehicle. In the first study the animals were observed for signs of delivery until day 29 of gestation. In the second study the effect of transforming growth factor-β2 (50 ng/fetus) on the rate of premature delivery was evaluated. In the third study the concentrations of prostaglandin E 2 and 13,14-dihydro-15-keto-prostaglandin F2α. were measured in the amniotic fluid on day 27 of gestation. The statistics used were Fishers exact test, the X 2 test, and the Mann-Whitney U test. Results: Altogether 61 of 191 fetuses (32%) were born prematurely in the interleukin-1 α-tumor necrosis factor-a group, whereas only two of 161 fetuses (1.2%) ( p = 0.0001) and one of 159 (0.6%) ( p = 0.0001) were born prematurely in the interleukin-1a tumor necrosis factor-α-transforming growth factor-β2 group and in the control group, respectively. Of the 23 animals injected with interleukin-1 α and tumor necrosis factor-α, six (26%) delivered all of their fetuses prematurely versus none in the other groups ( p = 0.02). None of the 88 fetuses in the transforming growth factor-α group were born prematurely. The prostaglandin E 2 concentrations in the amniotic fluids were higher in the interleukin-1a-tumor necrosis factor-α group than in the interleukin-lα-tumor necrosis factor-α-transforming growth factor-β2 group ( p = 0.05) or in the control group ( p = 0.02). Conclusions: Preterm parturition can be provoked in the rabbit by intraamniotic injections of interleukin-la and tumor necrosis factor-a. Transforming growth factor-P2 prevents the cytokine-induced increase in premature delivery.

Transforming growth factor-β opposes the stimulatory effects of interleukin-1 and tumor necrosis factor on amnion cell prostaglandin E2 production: Implication for preterm labor

OBJECTIVE In preterm labor increased concentrations of interleukin-1 and tumor necrosis factor are present in amniotic fluid. These cytokines may promote labor by stimulating the production of prostaglandins by intrauterine tissues. In many biologic processes, transforming growth factor-beta modifies the actions of cytokines. We studied the effect of transforming growth factor-beta on the cytokine-induced prostaglandin E2 production by amnion cells. STUDY DESIGN Human amnion cells in monolayer culture were treated with interleukin-1, tumor necrosis factor, or vehicle in the presence or absence of transforming growth factor-beta. The prostaglandin E2 production was measured. RESULTS Transforming growth factor-beta decreased the interleukin-1- or tumor necrosis factor-induced prostaglandin E2 production by 70% to 80% and the basal prostaglandin E2 synthesis by 27%. The synergistic stimulation of prostaglandin E2 production by the combination of interleukin-1 with tumor necrosis factor was inhibited by 80% in cells treated with transforming growth factor-beta. Transforming growth factor-beta 1, -beta 2, and -beta 1,2 were equipotent. CONCLUSION Transforming growth factor-beta suppresses the cytokine-induced prostaglandin E2 production by amnion cells and may be an important factor in maintaining pregnancy in the face of labor-promoting cytokines.

The Fate of Exogenous Surfactant in Neonates with Respiratory Distress Syndrome

SummaryRespiratory distress syndrome (RDS) in newborn neonates is characterised by deficient secretion of surfactant from type III alveolar cells. Administration of surfactant to airways acutely decreases the degree of respiratory failure and increases the survival rate in neonates with RDS. Clinically available surfactants are lipid extracts derived from animal lung lavage or from whole lung. Synthetic surfactants contain phospholipids or additional spreading agents. An optimal exogenous surfactant would be efficacious, nontoxic and nonimmunogenic, resistant to oxidants and proteolytic agents, widely available at reasonable cost and manufactured with little batch-to-batch variability.Surfactant has been instilled into the airways as a bolus infusion through the endotracheal tube. In addition, surfactant may be given by aerosolisation or continuous infusion into the airways. Suggested dosages range from 50 to 200 mg/kg. Exogenous surfactant is cleared from the epithelial lining fluid (ELF) mainly by alveolar epithelial cells, although alveolar macrophages and the central airways may also contribute to clearance of the drug. Only small quantities of surfactant actually enter the blood stream. A significant fraction of surfactant is taken up, processed, and secreted back into the alveolar space by type II alveolar cells. This process is termed recycling.Phosphatidylglycerol, given to small premature neonates as a component of exogenous human surfactant, has an apparent pulmonary half-life of 31 ± 3 hours (n=11). The apparent pulmonary half-life of the main surfactant component dipalmitoyl phosphatidylcholine is 45 hours (n=3) and that of surfactant protein A is about 9 hours (n=4). A relationship between the dose of exogenous surfactant and its concentration in the ELF has been demonstrated.Some neonates with RDS respond poorly to surfactant therapy. The reasons for this include insufficient levels of surfactant in the ELF, uneven distribution of exogenous surfactant, inability of exogenous surfactant to enter the metabolic pathways, inhibition of surface activity by plasma-derived proteins, or inactivation of surfactant as a result of proteases, phospholipases, or oxygen free radicals. In addition, surfactant therapy may be ineffective in neonates with respiratory failure caused by factors other than surfactant deficiency. The efficacy of exogenous surfactant can be improved by increasing the dosage of surfactant and by administration of surfactant very early in respiratory failure.

Nitric oxide and lung surfactant

Inhalation of nitric oxide (NO) is an experimental treatment for severe pulmonary hypertension. Being rapidly metabolized by hemoglobin, inhaled NO causes selective vasodilation in the pulmonary vascular bed. In addition to the vascular smooth muscle, other pulmonary structures are exposed to inhaled NO, resulting in suppression of NO synthesis in a variety of pulmonary cells and in potential toxicity. NO is a free radical that interacts with a number of proteins, particularly metalloproteins. Together with superoxide radical, it rapidly forms highly toxic peroxynitrite. Peroxynitrite is involved in the killing of microbes by activated phagocytosing macrophages. In severe inflammation, peroxynitrite may be responsible for damaging proteins, lipids, and DNA. Peroxynitrite added to surfactant in vitro is capable of decreasing the surface activity, inducing lipid peroxidation, decreasing the function of surfactant proteins, SP-A and SP-B, and inducing protein-associated nitro-tyrosine. Exposure of animals for prolonged periods (48 to 72 hours) to inhaled NO (80 to 120 ppm) has been associated with a decrease in surface activity. This is caused by binding of surfactant to iron-proteins that are modified by NO (particularly methemoglobin), or by peroxynitrite induced damage of surfactant. In contrast, exposure of isolated surfactant complex to NO during surface cycling strikingly decreases the inactivation of surfactant, preventing the conversion of surfactant to small vesicles that are no longer surface-active, and preventing lipid peroxidation. This finding is consistent with the function of NO as a lipid-soluble chain-braking antioxidant. It is possible that this lipophilic gas has as yet undefined roles in regulation of surfactant metabolism and maintenance of surface activity. Deficiency in pulmonary NO may be present during the early neonatal period in respiratory distress syndrome and in persistent fetal circulation. The premature lung is likely to be sensitive to NO toxicity that may include lung damage, abnormal alveolarization, and mutagenicity. Defining of the indications, the dosage, and the toxicity of inhaled NO therapy remains the challenge for experimental and clinical research.

Interleukin-1 binding and prostaglandin E2 synthesis by amnion cells in culture: regulation by tumor necrosis factor-α, transforming growth factor-β, and interleukin-1 receptor antagonist

Proinflammatory cytokines may promote preterm labor in the setting of intrauterine infection. Tumor necrosis factor (TNF) and interleukin-1 (IL-1) synergistically stimulate the production of prostaglandin E2 (PGE2) by amnion cells. Transforming growth factor-beta (TGF-beta) inhibits the cytokine-stimulated PGE2 production. In the present study, we investigated the binding of IL-1 beta on human amnion cells in culture. Untreated amnion cells possessed 540 +/- 60 IL-1 receptors per cell, with a dissociation constant of 1.4 +/- 0.4 nM. Cells treated with TGF-beta 1 (10 ng/ml) had 570 +/- 110 receptors per cell. TNF-alpha (50 ng/ml) increased the number of IL-1 receptors to 2930 +/- 590. TGF-beta 1 inhibited the receptor upregulation by TNF-alpha. Cells treated with TGF-beta 1 and TNF-alpha expressed 1140 +/- 590 receptors per cell. The binding affinity was not changed by the cytokines. IL-1 receptor antagonist (IL-1ra) inhibited the stimulation of amnion cell PGE2 production by IL-1 beta, but not by TNF-alpha. Amnion cells secreted large amounts of IL-1ra (1.1 +/- 0.3 ng/10(5) cells). Treatment of the cells with TGF-beta 1 or TNF-alpha did not affect the release of IL-1ra. We conclude that IL-1 receptor expression is an important step in the regulation of the effects of cytokines on amnion cell PGE2 production.

Cytokines and production of surfactant components

The production of pulmonary surfactant, a complex of lipids and proteins that reduces surface tension at the alveolar air-liquid interface, is developmentally regulated. Several hormones, most notably glucocorticoids, are known to accelerate maturation of the surfactant system. Cytokines are polypeptides that act mostly in a paracrine fashion and possess a wide spectrum of activities on multiple types of cells. Many cytokines are produced by different lung cells a various stages of fetal development or under pathological conditions affecting the fetus. In addition, cytokines present in amniotic fluid or in the blood stream may reach the fetal lungs. Some cytokines, including epidermal growth factor, transforming growth factor-alpha, and interferon-gamma have been shown to stimulate the production of surfactant components. On the other hand, tumor necrosis factor and transforming growth factor-beta downregulate the production of surfactant lipids and proteins. We have recently shown that the proinflammatory cytokine interleukin-1 (IL-I) enhances the expression of surfactant protein A (SP-A) in fetal rabbit lung explants. In addition, injection of IL-I into the amniotic fluid of fetal rabbits enhances the expression of surfactant proteins and improves the lung compliance of preterm animals. Preterm delivery is often associated with subclinical intraamniotic infection. In these cases, amniotic fluid concentrations of IL-I are often elevated. We propose that this cytokine accelerates maturation of the surfactant system in fetal lungs and thus prepares the fetus for extrauterine life.

Interleukin-1 receptor antagonist in the fetomaternal compartment.

Interleukin‐1 (IL‐1) is a major mediator in infections and inflammation. Interleukin‐1 receptor antagonist (IL‐1ra) opposes the actions of IL‐1. IL‐1ra is present in exceptionally high concentrations in third trimester amniotic fluid. We studied IL‐1ra in amniotic fluid, fetal serum and newborn urine. The concentrations of IL‐1ra in amniotic fluid at mid‐trimester and at 25‐41 gestational weeks were 6.6 ± 0.5ng/ml (n = 30) and 100 ± 4ng/ml (n = 202), respectively. At mid‐trimester, amniotic fluid IL‐1ra was not dependent on fetal gender, whereas during the third trimester IL‐1ra was higher in female‐ than in male‐bearing gestations. Urine of normal term newborns during the first day of life contained a very high concentration of IL‐1ra (125 ± 16ng/ml, n= 50). Urinary concentration in female newborns was significantly higher than that in male newborns (202 ± 19ng/ml, n = 25 versus 49 ± 14ng/ml, n = 25). IL‐1ra concentration in fetal serum at 22‐36 gestational weeks was 0.50 ± 0.07ng/ml (n= 31) and at term 1.5 ± 0.3ng/ml (n= 17). Serum concentrations were not gender‐dependent. The gender differences in IL‐1ra concentrations may in part explain the lower susceptibility of female fetuses to infection.

Protective effect of exogenous transferrin against hyperoxia: A study on premature rabbits

We hypothesized that an increase in plasma iron binding capacity would decrease the generation of oxygen radicals and of lipid peroxides. To test this hypothesis, we studied whether supplementation of transferrin (TF) in premature rabbits would modify the degree of hyperoxic lung injury. Animals, delivered prematurely at 29 days of gestation (term 31 days), were randomized and given either 0.5 g/kg of albumin (Alb) (n = 116) or 0.5 g/kg of iron‐free TF (n = 132) intravenously within 2 hours after birth. Another group was randomized to receive saline (n = 15), or either 0.35 g/kg (n = 12) or 0.70 g/kg of iron‐free TF (n = 8). After exposure to a 100% oxygen environment for 2 or 4 days, the animals were killed, and plasma and bronchoalveolar lavage (BAL) fluid was recovered.

Transferrin modifies surfactant responsiveness in acute respiratory failure : Role of iron-free transferrin as an antioxidant

In respiratory failure, transferrin (TF) with variable iron saturation accumulates in the alveolar space. Binding free iron to TF may inhibit metal‐catalyzed formation of free radicals. The aim of this study was to evaluate whether the degree of the iron‐saturation of TF influences the severity of respiratory failure and surfactant responsiveness. Surfactant deficiency and lung edema was induced in 42 paralyzed and ventilated young rabbits by bronchoalveolar lavage (BAL); 19 of these animals were preexposed to 100% O2 for 40 hours. The animals received (1) exogenous surfactant intratracheally (100 mg/kg in 4 ml/kg saline); (2) surfactant and Fe3+‐TF (50 or 25 mg/kg); or (3) surfactant and iron‐free TF (50 mg/kg). One hour after administration of TF, 13–25% of exogenous TF was recovered by BAL. Administration of iron‐free TF significantly decreased the iron saturation of TF in BAL. In acute respiratory failure induced by BAL, Fe3+‐TF decreased the efficacy of exogenous surfactant in improving the gas exchange, and increased surfactant inhibition, while iron‐free TF had no effect. By contrast, in respiratory failure induced by hyperoxia and BAL, iron‐free TF improved the efficacy of exogenous surfactant, but Fe3+‐TF had no effect. After administration of iron‐free TF, surfactant isolated from BAL was more surface‐active than surfactant from BAL of the other hyperoxia‐treated animals. In animals exposed to hyperoxia, treatment with iron‐free TF decreased malondialdehyde content of BAL. We propose that low iron saturation of TF decreases oxidant stress and favors the recovery from respiratory failure. Pediatr Pulmonol. 1996;22:14–22.