Biomedical subjects

Boris W Kramer

Publications and source records attributed to Boris W Kramer.

At least 19 recordsLinked to original sources

PubMed2006

Antenatal inflammation induced TGF-beta1 but suppressed CTGF in preterm lungs.

Chorioamnionitis is frequently associated with preterm birth and increases the risk of adverse outcomes such as bronchopulmonary dysplasia (BPD). Transforming growth factor (TGF)-beta1 is a key regulator of lung development, airway remodeling, lung fibrosis, and regulation of inflammation, and all these processes contribute to the development of BPD. Connective tissue growth factor (CTGF) is a downstream mediator of some of the profibrotic effects of TGF-beta1, vascular remodeling, and angiogenesis. TGF-beta1-induced CTGF expression can be blocked by TNF-alpha. We asked whether chorioamnionitis-associated antenatal inflammation would regulate TGF-beta1, the TGF-beta1 signaling pathway, and CTGF in preterm lamb lungs. Fetal sheep were exposed to 4 mg of intra-amniotic endotoxin or saline for 5 h, 24 h, 72 h, or 7 days before preterm delivery at 125 days gestation (full term = 150 days). Intra-amniotic endotoxin increased lung TGF-beta1 mRNA and protein expression. Elevated TGF-beta1 levels were associated with TGF-beta1-induced phosphorylation of Smad2. CTGF was selectively expressed in lung endothelial cells in control lungs, and intra-amniotic endotoxin caused CTGF expression to decrease to 30% of control values and TNF-alpha protein to increase. The antenatal inflammation-induced TGF-beta1 expression and Smad signaling in the fetal lamb lung may contribute to impaired lung alveolarization and reduced lung inflammation. Decreased CTGF expression may inhibit vascular development or remodeling and limit lung fibrosis during remodeling. These effects may contribute to the impaired alveolar and pulmonary vascular development that is the hallmark of the new form of BPD.

Animals↗

PubMed2006

TGF-beta1 in SP-A preparations influence immune suppressive properties of SP-A on human CD4+ T lymphocytes.

Surfactant protein A (SP-A) and transforming growth factor-beta1 (TGF-beta1) have been shown to modulate the functions of different immune cells and specifically to inhibit T lymphocyte proliferation. The aim of the present study was to elucidate whether the Smad signaling pathway, which is activated by TGF-beta1, also plays a role in SP-A-mediated inhibition of CD4+ T lymphocyte activation. Recombinant human SP-A1 expressed in Chinese hamster ovary cells [rSP-A1m (mammalian)], but not recombinant Baculovirus-derived rSP-A1hyp (hydroxyproline-deficient), suppressed T lymphocyte proliferation and IL-2 mRNA expression. To test whether SP-A induced Smad signaling, a Smad3/4-specific reporter gene was transfected in primary human CD4+ T lymphocytes. Only rSP-A1m, but not rSP-A1hyp, induced Smad-specific reporter genes, Smad2 phosphorylation, and Smad7 mRNA expression. The effect of rSP-A1m was mediated through the TGF-betaRII and could be antagonized by anti-TGF-beta1 neutralizing antibodies and sTGF-betaRII. Western blot and ELISA analysis revealed that rSP-A1m, but not rSP-A1hyp, contained TGF-beta1. TGF-beta1 was responsible for the differences in inhibition of CD4+ T lymphocyte proliferation and activation of the Smad signaling pathway between rSP-A1m and rSP-A1hyp. After acidification, native SP-A, obtained from patients with alveolar proteinosis, also induced Smad signaling in human CD4+ T lymphocytes leading to an increased inhibition of T lymphocyte proliferation, thus indicating the presence of inactive, latent TGF-beta1 in native SP-A samples. Association between SP-A and latent TGF-beta1 provides a possible novel mechanism to regulate TGF-beta1-mediated inflammation and fibrosis reactions in the lung but also leads to possible misinterpretation of immune-modulator functions of SP-A. Monitoring of SP-A preparations for possible TGF-beta1 is essential.

Acids↗

PubMed2006

Chronic exposure to intra-amniotic lipopolysaccharide affects the ovine fetal brain.

OBJECTIVE: Fetal brain injury is associated with chorioamnionitis, which is often present without signs of overt infection or fetal compromise. We aimed to determine if prolonged exposure to intrauterine inflammation caused by intra-amniotic infusion of lipopolysaccharide (LPS) would affect the fetal brain. METHODS: At 80 days of pregnancy ewes bearing singletons had osmotic pumps implanted intra-amniotically to infuse Escherichia coli LPS (055:B5; n = 8) or saline (n = 7) for 28 days. At delivery (110 days), umbilical arterial blood and chorioamnion were assessed for inflammation; cytokine concentrations (interleukin [IL]-6 and IL-8) in amniotic fluid and fetal and maternal plasma were measured. The fetal cerebral hemispheres were examined for gross anatomical changes and the number of activated microglia/macrophages, astrocytes, and oligodendrocytes estimated after immunohistochemical staining. RESULTS: Intra-amniotic administration of LPS caused chorioamnionitis, fetal leucocytosis, and a moderate to extensive infiltration of activated microglia/macrophages in the subcortical white matter in six of eight fetuses; the remaining two fetuses were less affected. Within these focal regions of damage there was an attenuation of astrocytic processes, axonal injury, and a reduction in the number of 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) immunoreactive oligodendrocytes in areas of extensive focal damage. In control fetuses there was mild (3/7) or no infiltration of activated microglia/macrophages in the subcortical white matter. Overall the infiltration of activated microglia/macrophages in the white matter was significantly greater in LPS-exposed fetuses compared to controls. In regions devoid of injury, the number of oligodendrocytes and astrocytes was not different between groups, nor was there a difference in the volume of cerebral white matter or density of blood vessels within the white matter. Amniotic fluid IL-6 and IL-8, and maternal plasma IL-8 concentrations were significantly increased by LPS infusion. CONCLUSIONS: An increase in inflammatory cells and axonal disruption in the subcortical white matter of the fetal brain can accompany chorioamnionitis induced by intra-amniotic administration of LPS, but cystic lesions do not occur. Thus, the effect on the fetal brain is milder than that reported from animal models of acute fetal/intrauterine infection.

Amniotic Fluid↗

PubMed2005

Chronic endotoxin exposure does not cause sustained structural abnormalities in the fetal sheep lungs.

Chronic early gestational chorioamnionitis is associated with development of bronchopulmonary dysplasia in preterm infants. A single intra-amniotic exposure to endotoxin decreased alveolarization and reduced expression of endothelial proteins in 125-day gestational age preterm lambs. We hypothesized that prolonged exposure to intra-amniotic endotoxin would cause progressive lung inflammation and inhibit alveolar and pulmonary vascular development. Endotoxin (1 mg/day) or saline was administered via an intra-amniotic osmotic pump from 80 to 108 days of gestational age (continuous pump) or by four weekly 10-mg intra-amniotic endotoxin injections starting at 100 days of gestational age (multiple dose). Lung morphometry, lung inflammation, vascular effects, and lung maturation were measured at delivery. The continuous pump lambs delivered at 100 days (approximately 70% of total endotoxin exposure) had lung inflammation, fewer saccules, and decreased endothelial proteins endothelial nitric oxide synthase and VEGF receptor 2 expression compared with controls. The continuous pump (delivered at 138 days) and multiple dose lambs (delivered at 130 and 145 days) had mild persistent lung inflammation and no significant differences in lung morphometry or expression of endothelial proteins compared with controls. Surfactant saturated phosphatidylcholine pool sizes were increased in all endotoxin-exposed groups, but lung function was not changed relative to controls. Contrary to our hypothesis, a prolonged fetal exposure to intra-amniotic endotoxin caused mild persistent inflammation but did not lead to progressive structural abnormalities in lungs of near-term gestation lambs.

Amniotic Fluid↗

PubMed2005

The clever fetus: responding to inflammation to minimize lung injury.

Clinical and experimental information indicate that fetal exposure to inflammation can induce lung maturation. This inflammation may be chronic and indolent. We present clinical and experimental information that challenge assumptions about chorioamnionitis associated infection/inflammatory exposures to the fetus. We question the assumption that the fetal compartment is sterile, and that delivery is inevitable if chronic infection/inflammation is present. We demonstrate that the preterm fetus can develop a brisk and adequate inflammatory response, and the fetus also can quickly modulate and downregulate inflammation to prevent injury. The fetus at risk of early preterm delivery may be exposed to both chorioamnionitis and glucocorticoids. Both exposures can either increase or decrease fetal inflammatory responses depending on the timing of the exposures. The immunomodulatory ability of the fetus to fetal exposures remains an unexplored research field.

Animals↗

PubMed2005

Decreased expression of angiogenic factors in placentas with chorioamnionitis after preterm birth.

Chorioamnionitis and funisitis are associated with neonatal morbidity and mortality. We hypothesized that chorioamnionitis may stress fetal endothelium, activate proinflammatory gene transcription. and affect angiogenic homeostasis in fetal capillaries. Placentas from preterm infants were stained for heat-shock protein 70, nuclear factor-kappaB, hypoxia-inducible factor-1alpha, and vascular endothelial growth factor (VEGF). VEGF receptors (VEGF-R) 1 and 2 as well as the receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (TIE-2), which is involved in vascular remodeling, were quantified. Immunohistochemistry was analyzed by counting positive capillaries in placental terminal villi. Staining intensity was quantified by a three-step semiquantitative scale. The samples were divided into three matched groups according to histology: chorioamnionitis with funisitis ("funisitis"), chorioamnionitis without funisitis ("chorioamnionitis"), and control group with no inflammation. In tissues from the funisitis or chorioamnionitis group, heat-shock protein 70 expression was increased over the control group. More nuclear factor-kappaB-positive nuclei of endothelial cells in capillaries were counted in the funisitis and chorioamnionitis groups. Expression of VEGF and VEGF-R1 and -R2 were reduced in cases of funisitis or chorioamnionitis in comparison with controls. Hypoxia-inducible factor-1alpha expression tended to be slightly lower in the funisitis and chorioamnionitis groups but did not reach statistical significance. We speculate that cellular stress and changes in angiogenic homeostasis induced by proinflammatory activation of fetal endothelium in chorioamnionitis may not be limited to the placenta but may also involve other fetal organs.

Angiogenesis Inducing Agents↗

PubMed2004

Activation of umbilical cord endothelial cells and fetal inflammatory response in preterm infants with chorioamnionitis and funisitis.

Chorioamnionitis and funisitis are associated with preterm labor and postnatal morbidity. Activation of endothelium resulting in up-regulation of adhesion molecules seems to be a key mechanism in development of organ damage. We investigated whether chorioamnionitis with or without funisitis in preterm infants induced expression and shedding of adhesion molecules in the umbilical cord and resulted in increased concentrations of E-selectin, intercellular adhesion molecule (ICAM)-1, IL-1beta, IL-6, and IL-8 in the cord blood. Data were obtained by using immunohistochemistry and ELISA. Thirty-two preterm infants were divided into three groups according to histology: chorioamnionitis with funisitis, chorioamnionitis without funisitis, and controls without signs of inflammation. ICAM-1 expression on arterial endothelium was higher with funisitis compared with chorioamnionitis alone or with the control group. Similar results for ICAM-1 expression were found in venous endothelium, vascular walls, Wharton's jelly, and amnion epithelium. Endothelial E-selectin and vascular cell adhesion molecule (VCAM)-1 expression was only induced significantly with funisitis. Serum-concentrations of soluble ICAM-1 were higher with funisitis compared with chorioamnionitis alone or control group. Similarly, concentrations of soluble E-selectin, IL-1beta, IL-6, and IL-8 were increased exclusively with funisitis. In conclusion, only chorioamnionitis with funisitis was associated with systemic inflammation and endothelial activation with up-regulation and shedding of umbilical cord adhesion molecules. We speculate that this activation of endothelium may not be limited to the umbilical cord but may also involve other organs resulting in neonatal morbidity. This underlines the importance of funisitis as a risk factor for adverse outcome.

Cell Adhesion↗

PubMed2004

BAG-1 haplo-insufficiency impairs lung tumorigenesis.

BACKGROUND: BAG-1 is a multifunctional co-chaperone of heat shock proteins (Hsc70/Hsp70) that is expressed in most cells. It interacts with Bcl-2 and Raf indicating that it might connect protein folding with other signaling pathways. Evidence that BAG-1 expression is frequently altered in human cancers, in particular in breast cancer, relative to normal cells has been put forward but the notion that overexpression of BAG-1 contributes to poor prognosis in tumorigenesis remains controversial. METHODS: We have evaluated the effect of BAG-1 heterozygosity in mice in a model of non-small-cell lung tumorigenesis with histological and molecular methods. We have generated mice heterozygous for BAG-1, carrying a BAG-1 null allele, that in addition express oncogenic, constitutively active C-Raf kinase (SP-C C-Raf BxB) in type II pneumocytes. SP-C C-Raf BxB mice develop multifocal adenomas early in adulthood. RESULTS: We show that BAG-1 heterozygosity in mice impairs C-Raf oncogene-induced lung adenoma growth. Lung tumor initiation was reduced by half in BAG-1 heterozygous SP-C C-Raf BxB mice compared to their littermates. Tumor area was reduced by 75% in 4 month lungs of BAG-1 haploinsufficient mice compared to mice with two BAG-1 copies. Whereas BAG-1 heterozygosity did not affect the rate of cell proliferation or signaling through the mitogenic cascade in adenoma cells, it increased the rate of apoptosis. CONCLUSION: Reduced BAG-1 expression specifically targets tumor cells to apoptosis and impairs tumorigenesis. Our data implicate BAG-1 as a key player in oncogenic transformation by Raf and identify it as a potential molecular target for cancer treatment.

Adenoma↗

PubMed2004

Endotoxin-induced chorioamnionitis modulates innate immunity of monocytes in preterm sheep.

The preterm fetus is immune naive and has immature innate immune function. Although the preterm fetus is frequently exposed to chorioamnionitis, the effects of exposure of the fetal lung to inflammation on innate immune responses are unknown. Using the fetal sheep model of chorioamnionitis, cord blood monocytes were isolated from preterm lambs 1 to 14 days after intra-amniotic endotoxin injection, cultured for approximately 16 hours, and challenged with endotoxin in vitro. Compared with monocytes from adult sheep, the preterm monocytes produced less H(2)O(2) and interleukin-6, and toll-like receptor 4 expression was decreased. Three days after intra-amniotic endotoxin exposure, preterm monocyte responses to in vitro endotoxin challenge demonstrated decreased H(2)O(2) and interleukin-6 production and decreased CD14 and major histocompatibility complex class II expression. Preterm monocyte responses 7 to 14 days after endotoxin tended to exceed those of adults and preterm control animals indicating augmented function. In contrast, a second intra-amniotic endotoxin injection 7 days after the initial endotoxin exposure suppressed monocyte function at 14 days. The fetal monocytes demonstrated patterns of responses consistent with endotoxin tolerance (immune paralysis) as well as maturation of function. Modulation of fetal innate immune responses by exposure to inflammation may alter subsequent immune adaptation after birth.

Amnion↗

PubMed2004

Use of mitogenic cascade blockers for treatment of C-Raf induced lung adenoma in vivo: CI-1040 strongly reduces growth and improves lung structure.

BACKGROUND: Signaling networks promoting cell growth and proliferation are frequently deregulated in cancer. Tumors often are highly dependent on such signaling pathways and may become hypersensitive to downregulation of key components within these signaling cascades. The classical mitogenic cascade transmits stimuli from growth factor receptors via Ras, Raf, MEK and ERK to the cell nucleus and provides attractive molecular targets for cancer treatment. For example, Ras and Raf kinase inhibitors are already in a number of ongoing phase II and phase III clinical trials. In this study the effect of the Raf kinase inhibitor BAY 43-9006 and of the MEK inhibitor CI-1040 (PD184352) on a Raf dependent lung tumor mouse model was analyzed in detail. METHODS: We have generated a lung cancer mouse model by targeting constitutively active C-Raf kinase to the lung. These mice develop adenomas within 4 months of life. At this time-point they received daily intraperitoneal injections of either 100 mg/kg BAY 43-9006 or CI-1040 for additional 21 days. Thereafter, lungs were isolated and the following parameters were analyzed using histology and immunohistochemistry: overall lung structure, frequency of adenoma foci, proliferation rate, ERK activity, caspase-3 activation, and lung differentiation. RESULTS: Both inhibitors were equally effective in vitro using a sensitive Raf/MEK/ERK ELISA. In vivo, the systemic administration of the MEK inhibitor CI-1040 reduced adenoma formation to a third and significantly restored lung structure. The proliferation rate of lung cells of mice treated with CL-1040 was decreased without any obvious effects on differentiation of pneumocytes. In contrast, the Raf inhibitor BAY 43-9006 did not influence adenoma formation in vivo. CONCLUSION: The MEK inhibitor CI-1040 may be used for the treatment of Ras and/or Raf-dependent human malignancies.

Adenoma↗

PubMed2004

Antenatal betamethasone changes cord blood monocyte responses to endotoxin in preterm lambs.

Corticosteroids are routinely administered to women at risk for preterm delivery to induce fetal lung maturation. Antenatal corticosteroids have immunomodulatory effects on fetal immune cells that are poorly understood. We hypothesized that maternal betamethasone would alter in fetal monocytes both the initiation of inflammation in response to pro-inflammatory stimuli and the resolution of inflammation by phagocytosis of apoptotic neutrophils. Preterm lambs at 124 d gestation were delivered 15 h, 1 d, 2 d, or 7 d after 0.5 mg/kg maternal intramuscular betamethasone. Monocytes from cord blood were isolated and cultured and results were compared with monocytes from preterm lambs exposed to maternal saline or monocytes from adult sheep. Phagocytosis of Escherichia coli was not changed, however, phagocytosis of apoptotic neutrophils was low in fetal monocytes but increased after 7 d exposure to maternal betamethasone to the level found in adult monocytes. Hydrogen peroxide production after endotoxin stimulus was significantly reduced to 7.1 +/- 2.2 micromol at 5 h, 8.7 +/- 2.9 micromol at 24 h, and 4.1 +/- 1.9 micromol at 48 h versus 16.4 +/- 3.6 micromol in control animals; at 7 d, the hydrogen peroxide production increased to 74.3 +/- 19.7 micromol (p < 0.05, per 10(6) monocytes). IL-6 production was reduced at 15 h after maternal betamethasone but at no other time point. Maternal betamethasone initially suppressed several fetal monocyte functions, however, at 7 d, measurements of initiation and resolution of inflammation were increased to levels similar to monocytes from adult sheep. The time-dependent changes in maternal betamethasone modulation of the responses of fetal monocytes may influence immune function of the preterm lamb after delivery.

Adrenal Cortex Hormones↗

PubMed2003

Monocyte function in preterm, term, and adult sheep.

The preterm infant has functionally immature monocytes. The effects of common clinical interventions and exposures that might modulate inflammation were evaluated using monocytes isolated from blood of preterm lambs [130 d gestational age (GA)], near-term lambs (141 d GA), and adult sheep. Endotoxin stimulated hydrogen peroxide production by adult monocytes, but monocytes from 130-d and 141-d GA lambs had a reduced and delayed hydrogen peroxide production. Endotoxin did not decrease apoptosis of monocytes from 130-d and 141-d GA lambs but decreased apoptosis of adult monocytes. Dexamethasone increased the phagocytosis of bacteria and apoptotic cells by adult monocytes by 35% but not by monocytes from 130-d and 141-d GA lambs. Synthetic and natural surfactants and dipalmitoylphosphatidylcholine increased phagocytosis of apoptotic cells by monocytes from preterm, term, and adult sheep. Monocytes from preterm and term lambs differ from adult monocytes in tests of both the initiation and the resolution of inflammation. The reduced phagocytosis of apoptotic cells by monocytes from the preterm may contribute to prolonged inflammation in diseases such as bronchopulmonary dysplasia.

Age Factors↗

PubMed2003

Minimal lung and systemic responses to TNF-alpha in preterm sheep.

TNF-alpha has been associated with chorioamnionitis and the subsequent development of bronchopulmonary dysplasia in preterm infants. We asked whether bioactive recombinant ovine TNF-alpha could induce chorioamnionitis, lung inflammation, lung maturation, and systemic effects in fetal sheep. We compared the responses to IL-1alpha, a cytokine known to induce these responses in preterm sheep. Intra-amniotic TNF-alpha caused no chorioamnionitis, no lung maturation, and a very small increase in inflammatory cells in the fetal lung after 5 h, 2 days (d), and 7 d. In contrast, IL-1alpha induced inflammation and lung maturation. TNF-alpha given into the airways at birth increased granulocytes in the bronchoalveolar lavage fluid of ventilated preterm lungs and decreased the mRNA for surfactant protein C but did not adversely effect postnatal lung function. An intravascular injection of IL-1alpha caused a systemic inflammatory response in fetal sheep, whereas there was no fetal response to intravascular TNF-alpha. Fetal and newborn preterm sheep are minimally responsive to TNF-alpha. Therefore, the presence of a mediator such as TNF-alpha in a developing animal does not necessarily mean that it is causing the responses anticipated from previous results in adult animals.

Amniotic Fluid↗

PubMed2003

Betamethasone effects on chorioamnionitis induced by intra-amniotic endotoxin in sheep.

OBJECTIVE: Intra-amniotic administration of endotoxin in sheep is a model of subclinical chorioamnionitis. Intrauterine inflammation alters lung development to improve postnatal lung function and may predispose the infant to lung and brain injury. We describe the effects of intra-amniotic endotoxin on cytokines and white cell responses in the membranes and amniotic fluid and investigate the hypothesis that betamethasone treatment suppresses these responses. STUDY DESIGN: Pregnant ewes were allocated at random to receive either intra-amniotic saline solution (control animals), maternal intramuscular betamethasone, intra-amniotic endotoxin by ultrasound guidance (10 mg Escherichia coli 055:B5), or a combination of the betamethasone and endotoxin treatments. Lambs were delivered abdominally at 110 to 125 days of gestation at time points that ranged from 2 hours to 15 days after treatment. RESULTS: When compared with saline solution-injected control animals, the intra-amniotic injection of endotoxin increased white cell counts in amniotic fluid. Levels of interleukin-8, but not interleukin-6, were significantly increased in amniotic fluid from 5 hours to 15 days after intra-amniotic endotoxin injection, and interleukin-8 levels were not decreased by concurrent treatment with betamethasone. After endotoxin treatment, interleukin-1beta and interleukin-8 messenger RNA were expressed in chorion, and interleukin-6 messenger RNA expression was localized to chorionic blood vessel epithelium. The half-life of endotoxin in the amniotic fluid was 1.7 days, and levels remained measurable 15 days after injection. CONCLUSION: These findings confirm that the fetus can survive within amniotic fluid that contains endotoxin, white cells, and cytokines for periods of weeks or more. Betamethasone treatment can suppress the initial inflammation in the amnion-chorion, but interleukin-8 levels and inflammatory cells in amniotic fluid were not suppressed 5 and 15 days after betamethasone treatment, presumably because of the slow clearance of bioactive endotoxin from the amniotic fluid.

Amnion↗

PubMed2002

Maternal glucocorticoids increase endotoxin-induced lung inflammation in preterm lambs.

Antenatal betamethasone (Beta) is widely used in women with asymptomatic chorioamnionitis at risk for preterm delivery, but its effects on fetal inflammation are unstudied. Groups of ewes at 109 +/- 1 days of gestation received the following treatments: intra-amniotic (IA) saline (control), 0.5 mg/kg intramuscular Beta, 10 mg IA endotoxin (Endo), and Beta + 2 h later Endo (Beta + Endo). Beta suppressed Endo-induced lung inflammation at 1 day. However, compared with Endo 5 days after treatment, Beta + Endo lambs had increased alveolar neutrophils, proinflammatory cytokine mRNA expression, and serum amyloid A3 (SAA3) mRNA expression. IL-1beta mRNA expression was localized to the inflammatory cells, whereas SAA3 mRNA expression was induced in the bronchial epithelium and the inflammatory cells. Compared with Endo, Beta + Endo lambs had increased lung inflammation but equivalent lung volumes 15 days after treatment. The late increase in inflammation in the Beta + Endo animals suggests that glucocorticoids impair the ability of the preterm lung to downregulate Endo-induced inflammation after fetal clearance of the glucocorticoids. These results have implications for lung inflammation and bronchopulmonary dysplasia in preterm infants exposed to chorioamnionitis and maternal glucocorticoids.

Acute-Phase Reaction↗

PubMed2002

Early gestational intra-amniotic endotoxin: lung function, surfactant, and morphometry.

We determined the effects in preterm lambs of endotoxin-induced inflammation at early gestational ages on lung function and structure and on the surfactant system. Pregnant ewes were randomized to one of five intra-amniotic endotoxin (Escherichia coli 055:B5) groups: 1 mg injected at 60 days of gestation, 1 mg at 80 days, 1 mg at 100 days, 1 mg at 60 days plus 100 days, or 0.6 mg/ day infused from Day 80 to Day 108. Control lambs received saline treatments. At 125 days, lung function was improved in all endotoxin groups. Marked increases in saturated phosphatidylcholine in lung tissue but not alveolar lavage samples were seen in all endotoxin groups except the 60- plus 100-day group. Surfactant protein mRNA and protein pool sizes were affected differently according to the timing of endotoxin treatment, but a large increase in the amount of mature surfactant protein B in alveolar lavage samples was observed in all endotoxin groups. Lung-to-body weight ratio, alveolar number, total surface area, and alveolar wall thickness were reduced by 80- to 108-day endotoxin. Intra-amniotic inflammatory stimuli in early gestation can alter pulmonary development, with the net effect of improving preterm lung function, despite changes in surfactant and lung growth that are similar to changes in the lungs of ventilated animals developing bronchopulmonary dysplasia.

Analysis of Variance↗

PubMed2002

Intratracheal endotoxin causes systemic inflammation in ventilated preterm lambs.

Intratracheal endotoxin causes acute inflammation in the adult lung, and injurious styles of mechanical ventilation can result in systemic inflammation derived from the lungs. We asked how ventilated premature and near-term lungs responded to intratracheal endotoxin and if systemic inflammation occurred. Lambs delivered at 130 d gestational age (GA) were treated with surfactant or surfactant plus endotoxin (0.1 mg/kg or 10 mg/kg) (Escherichia coli, serotype O55:B5) and were ventilated for 6 h. Both endotoxin doses resulted in impaired gas exchange and systemic inflammation in the preterm lambs. Lambs at 141 d GA (term 146 d) were given either 10 mg/kg intratracheal endotoxin, 10 mg/kg endotoxin plus high tidal volume ventilation for the first 30 min of life, or 5 microg/kg endotoxin given intravenously. Endotoxin alone (10 mg/kg) caused lung inflammation but no systemic effects after 6 h of ventilation. Lambs given 10 mg/kg endotoxin plus high tidal volume ventilation or 5 microg/kg endotoxin intravenously had decreased gas exchange and systemic inflammation. Endotoxin was detected in the plasma of lambs at 130 d GA but not at 141 d GA. Inflammation in the lungs was more severe in preterm animals. Mechanical ventilation of the endotoxin-exposed preterm lung resulted in systemic effects at a low endotoxin dose and without high tidal volume ventilation.

Animals↗

PubMed2002

The fetal maturational and inflammatory responses to different routes of endotoxin infusion in sheep.

OBJECTIVES: In clinical practice, chorioamnionitis has been observed to enhance fetal lung maturation in the short term but may predispose to chronic lung disease thereafter. Using the sheep model, we have previously shown that injection of endotoxin into the amniotic cavity results in inflammatory responses and profoundly enhances newborn lung function after preterm birth. The fetus tolerates intra-amniotic doses of endotoxin considerably greater than those that are lethal if given intramuscularly. This study aimed to explore the mechanisms by which endotoxin matures the lungs by determining whether the route of administration influenced the maturational responses of the fetus. STUDY DESIGN: Date-mated ewes at 118 days of pregnancy were allocated at random to receive endotoxin (Escherichia coli lipopolysaccharide 055;B5) directly into the trachea (n = 7), stomach (n = 6), amniotic cavity (n = 7), or peritoneal cavity (n = 4) of the fetal lamb by surgical implantation of an osmotic pump delivering 1 mg of endotoxin over a 24-hour period. Results were compared with those obtained in saline solution-infused controls (n = 9). The lambs were delivered by cesarean section at 125 days' gestation (term is 150 days). RESULTS: Endotoxin infusion into the trachea, stomach, and amniotic cavity each resulted in inflammatory responses in lung fluid and improved postnatal lung function, and effects were similar for each route of administration. These effects occurred with minimal features of systemic inflammation. Intraperitoneal infusion resulted in severe fetal acidosis or death. CONCLUSION: These findings provide further evidence that the lung-maturing effects of intra-amniotic endotoxin are mediated by local factors in the respiratory system rather than by systemic inflammatory responses. Chorioamnionitis may alter lung function and possibly lead to chronic injury without clinical features of systemic inflammation or compromise.

Acidosis↗