Surfactant protein A recruits neutrophils into the lungs of ventilated preterm lambs

Getting Your Neutrophil: Neutrophil Transepithelial Migration in the Lung

Neutrophil transepithelial migration is a fundamental process that facilitates the rapid trafficking of neutrophils to inflammatory foci and occurs across a diverse range of tissues. For decades there has been widespread interest in understanding the mechanisms that drive this migratory process in response to different pathogens and organ systems. This has led to the successful integration of key findings on neutrophil transepithelial migration from the intestines, lungs, liver, genitourinary tract, and other tissues into a single, cohesive model. However, recent studies have identified organ specific differences in neutrophil transepithelial migration. These findings support a model where the tissue in concert with the pro-inflammatory stimuli dictate a unique collection of signals that drive neutrophil trafficking. This review focuses on the mechanisms that drive neutrophil transepithelial migration in response to microbial infection of a single organ, the lung. Herein we provide a detailed analysis of the adhesion molecules and chemoattractants that contribute to the recruitment of neutrophil into the airways. We also highlight important advances in experimental models for studying neutrophil transepithelial migration in the lung over the last decade.

Aspiration and Inspiration: Using Bronchoalveolar Lavage for Toxicity Assessment

Bronchoalveolar lavage (BAL) is a simple procedure that is used to investigate drug efficacy or lung toxicity. It is sensitive to lung changes and less invasive than histological evaluation. It can be performed repeatedly at interim time points or as a terminal procedure. Airborne contaminants and purposely inhaled compounds, resident and inflammatory cells, as well as different cellular soluble products can be harvested in bronchoalveolar fluid (BALF) and measured. Bronchoalveolar lavage can also be an important tool to understand drug exposure and its metabolism in the lung, although it should be rigorously performed and interpreted with caution, especially in the context of regulated toxicology studies. This review focuses on the methods and uses of BAL in animal research, primarily in the pharmaceutical industry, as well as for the assessment of drugs, pollutants, and chemical lung toxicity. Methods of collecting and analyzing BALF and parameters affecting variability are discussed in detail. Improved automated methods for cell counting and analysis of the inflammatory cellular differential using hematology analyzers, common markers of lung injury, and new methodologies are described. Correlation between BALF and histological evaluation should not be considered as repetitive but as complementary assessments in the context of efficacy and toxicity studies.

Overcoming barriers to optimal drug dosing during ECMO in critically ill adult patients

INTRODUCTION

One major challenge to achieving optimal patient outcome in extracorporeal membrane oxygenation (ECMO) is the development of effective dosing strategies in this critically ill patient population. Suboptimal drug dosing impacts on patient outcome as patients on ECMO often require reversal of the underlying pathology with effective pharmacotherapy in order to be liberated of the life-support device. Areas covered: This article provides a concise review of the effective use of antibiotics, analgesics, and sedative by characterizing the specific changes in PK secondary to the introduction of the ECMO support. We also discuss the barriers to achieving optimal pharmacotherapy in patients on ECMO and also the current and potential research that can be undertaken to address these clinical challenges. Expert opinion: Decreased bioavailability due to sequestration of drugs in the ECMO circuit and ECMO induced PK alterations are both significant barriers to optimal drug dosing. Evidence-based drug choices may minimize sequestration in the circuit and would enable safety and efficacy to be maintained. More work to characterize ECMO related pharmacodynamic alterations such as effects of ECMO on hepatic cytochrome system are still needed. Novel techniques to increase target site concentrations should also be explored.

Optimization of Variable Ventilation for Physiology, Immune Response and Surfactant Enhancement in Preterm Lambs

Preterm infants often require mechanical ventilation due to lung immaturity including reduced or abnormal surfactant. Since cyclic stretch with cycle-by-cycle variability is known to augment surfactant release by epithelial cells, we hypothesized that such in vivo mechanotransduction improves surfactant maturation and hence lung physiology in preterm subjects. We thus tested whether breath-by-breath variability in tidal volume (V_T) in variable ventilation (VV) can be tuned for optimal performance in a preterm lamb model. Preterm lambs were ventilated for 3 h with conventional ventilation (CV) or two variants of VV that used a maximum V_T of 1.5 (VV1) or 2.25 (VV2) times the mean V_T. V_T was adjusted during ventilation to a permissive pCO₂ target range. Respiratory mechanics were monitored continuously using the forced oscillation technique, followed by postmortem bronchoalveolar lavage and tissue collection. Both VVs outperformed CV in blood gas parameters (pH, SaO₂, cerebral O₂ saturation). However, only VV2 lowered PaCO₂ and had a higher specific respiratory compliance than CV. VV2 also increased surfactant protein (SP)-B release compared to VV1 and stimulated its production compared to CV. The production and release of proSP-C however, was increased with CV compared to both VVs. There was more SP-A in both VVs than CV in the lung, but VV2 downregulated SP-A in the lavage, whereas SP-D significantly increased in CV in both the lavage and lung. Compared to CV, the cytokines IL-1β, and TNFα decreased with both VVs with less inflammation during VV2. Additionally, VV2 lungs showed the most homogeneous alveolar structure and least inflammatory cell infiltration assessed by histology. CV lungs exhibited over-distension mixed with collapsed and interstitial edematous regions with occasional hemorrhage. Following VV1, some lambs had normal alveolar structure while others were similar to CV. The IgG serum proteins in the lavage, a marker of leakage, were the highest in CV. An overall combined index of performance that included physiological, biochemical and histological markers was the best in VV2 followed by VV1. Thus, VV2 outperformed VV1 by enhancing SP-B metabolism resulting in open alveolar airspaces, less leakage and inflammation and hence better respiratory mechanics.

New surfactant with SP-B and C analogs gives survival benefit after inactivation in preterm lambs

BACKGROUND

Respiratory distress syndrome in preterm babies is caused by a pulmonary surfactant deficiency, but also by its inactivation due to various conditions, including plasma protein leakage. Surfactant replacement therapy is well established, but clinical observations and in vitro experiments suggested that its efficacy may be impaired by inactivation. A new synthetic surfactant (CHF 5633), containing synthetic surfactant protein B and C analogs, has shown comparable effects on oxygenation in ventilated preterm rabbits versus Poractant alfa, but superior resistance against inactivation in vitro. We hypothesized that CHF 5633 is also resistant to inactivation by serum albumin in vivo.

METHODOLOGY/PRINCIPAL FINDINGS

Nineteen preterm lambs of 127 days gestational age (term = 150 days) received CHF 5633 or Poractant alfa and were ventilated for 48 hours. Ninety minutes after birth, the animals received albumin with CHF 5633 or Poractant alfa. Animals received additional surfactant if P(a)O(2) dropped below 100 mmHg. A pressure volume curve was done post mortem and markers of pulmonary inflammation, surfactant content and biophysiology, and lung histology were assessed. CHF 5633 treatment resulted in improved arterial pH, oxygenation and ventilation efficiency index. The survival rate was significantly higher after CHF 5633 treatment (5/7) than after Poractant alfa (1/8) after 48 hours of ventilation. Biophysical examination of the surfactant recovered from bronchoalveolar lavages revealed that films formed by CHF 5633-treated animals reached low surface tensions in a wider range of compression rates than films from Poractant alfa-treated animals.

CONCLUSIONS

For the first time a synthetic surfactant containing both surfactant protein B and C analogs showed significant benefit over animal derived surfactant in an in vivo model of surfactant inactivation in premature lambs.

Toll-like receptor 2 (TLR2), transforming growth factor-β, hyaluronan (HA), and receptor for HA-mediated motility (RHAMM) are required for surfactant protein A-stimulated macrophage chemotaxis

The innate immune system protects the host from bacterial and viral invasion. Surfactant protein A (SPA), a lung-specific collectin, stimulates macrophage chemotaxis. However, the mechanisms regulating this function are unknown. Hyaluronan (HA) and its receptors RHAMM (receptor for HA-mediated motility, CD168) and CD44 also regulate cell migration and inflammation. We therefore examined the role of HA, RHAMM, and CD44 in SPA-stimulated macrophage chemotaxis. Using antibody blockade and murine macrophages, SPA-stimulated macrophage chemotaxis was dependent on TLR2 but not the other SPA receptors examined. Anti-TLR2 blocked SPA-induced production of TGFβ. In turn, TGFβ1-stimulated chemotaxis was inhibited by HA-binding peptide and anti-RHAMM antibody but not anti-TLR2 antibody. Macrophages from TLR2(-/-) mice failed to migrate in response to SPA but responded normally to TGFβ1 and HA, effects that were blocked by anti-RHAMM antibody. Macrophages from WT and CD44(-/-) mice had similar responses to SPA, whereas those from RHAMM(-/-) mice had decreased chemotaxis to SPA, TGFβ1, and HA. In primary macrophages, SPA-stimulated TGFβ production was dependent on TLR2, JNK, and ERK but not p38. Pam3Cys, a specific TLR2 agonist, stimulated phosphorylation of JNK, ERK, and p38, but only JNK and ERK inhibition blocked Pam3Cys-stimulated chemotaxis. We have uncovered a novel pathway for SPA-stimulated macrophage chemotaxis where SPA stimulation via TLR2 drives JNK- and ERK-dependent TGFβ production. TGFβ1, in turn, stimulates macrophage chemotaxis in a RHAMM and HA-dependent manner. These findings are highly relevant to the regulation of innate immune responses by SPA with key roles for specific components of the extracellular matrix.

Human amnion epithelial cells as a treatment for inflammation-induced fetal lung injury in sheep

OBJECTIVE

The purpose of this study was to determine whether human amnion epithelial cells (hAECs) can modulate the pulmonary developmental consequences of intrauterine inflammation in fetal sheep that are exposed to intraamniotic lipopolysaccharide (LPS) injection.

STUDY DESIGN

At 117 days' gestation, fetal sheep (n=16) received intraamniotic LPS (20 mg). hAECs were delivered at 0, 6, and 12 hours into the fetal jugular vein (n=4), trachea (n=4), or both (n=4). Controls (n=6) received equivalent administration of saline solution. Lungs were collected at 124 days.

RESULTS

Intraamniotic LPS caused pulmonary inflammation and altered lung structure and function. hAECs attenuated changes in lung function and structure that had been induced by LPS: lung volume, 40 cm H2O (P<.05, intravenous+intratracheal hAECs vs LPS), tissue-to-airspace ratio (P<.05, intravenous+intratracheal hAECs vs LPS), and septal crest density (P<.001, all hAEC groups vs LPS). Leukocyte infiltration of the lungs was not reduced by hAECs; however, inflammatory cytokines were reduced (tumor necrosis factor-α, P<.01, vs LPS; interleukin-1b, P<.01, vs LPS; interleukin-6, P<.01 vs LPS). Surfactant protein A and C messenger RNA was increased by LPS, although this was not statistically significant (P>.05 vs control); there were significant increases in all hAEC-treated animals (surfactant protein-A, P<.05 vs LPS; surfactant protein-C, P<.01 vs LPS).

CONCLUSION

Human amnion epithelial cells attenuate the fetal pulmonary inflammatory response to experimental intrauterine inflammation and reduce, but (as administered in our study) do not prevent, consequent alterations in lung development.

Surfactant protein-A as an anti-inflammatory component in the amnion: implications for human pregnancy

The mechanism of mouse parturition is thought to involve myometrial infiltration by amniotic fluid (AF) macrophages, activated by surfactant protein-A (SP-A). In humans, the concentration of AF SP-A decreases during labor, and no fetal macrophages are found in the myometrium after labor. Therefore, it appears that the mechanisms of labor in mice and humans are different. We investigated a potential role for SP-A in human pregnancy and parturition by examining SP-A expression patterns in AF and amnion. High molecular mass (>250 kDa) oligomeric SP-A was increased in AF with advancing gestation. Interestingly, these oligomers were more abundant in placental amnion before labor at term, while they increased primarily in reflected amnion during labor (p < 0.05). Immunoblotting showed a binding of high molecular mass SP-A in AF to amnion. In C57BL/6 mice, oligomeric SP-A was also readily detected in AF from E15 onwards, but not in amnion. Macrophage density in mice myometrium did not change with advancing gestational age. Microarray analysis of human amnion explants incubated with SP-A revealed a molecular signature of inhibited cytokine-cytokine receptor interaction with downregulation of IL-1beta, CXCL2, and CXCL5 mRNA expression. The findings in this study strongly suggest that SP-A signals amniotic anti-inflammatory response via AF during pregnancy. We propose that an SP-A interaction among AF, placental amnion, and reflected amnion is a unique mechanism for immunoregulation in human pregnancy akin to that established in lung biology. However, AF SP-A and fetal macrophages by themselves do not seem to be exclusive effectors of parturition in humans.

Surfactant protein-d inhibits lung inflammation caused by ventilation in premature newborn lambs

RATIONALE

Premature newborns frequently require manual ventilation for resuscitation during which lung injury occurs. Although surfactant protein (SP)-D regulates pulmonary inflammation, SP-D levels are low in the preterm lung. Commercial surfactants for treatment of respiratory distress syndrome do not contain SP-D.

OBJECTIVES

To determine whether addition of recombinant human SP-D (rhSP-D) to commercial surfactant influences lung inflammation in ventilated premature newborn lambs.

METHODS

Prematurely delivered lambs (130 d gestation age) were resuscitated with 100% O(2) and peak inspiratory pressure 40 cm H(2)O for 20 minutes and then treated with Survanta or Survanta containing rhSP-D. Ventilation was then changed to regulate tidal volume at 8 to 9 ml/kg. At 5 hours of age lambs were killed for sample collection.

MEASUREMENTS AND MAIN RESULTS

Sequential blood gas and tidal volume were similar in lambs treated with or without rhSP-D, indicating that lung immaturity and ventilatory stress used to support premature lambs were comparable between the two groups. Ventilation caused pulmonary inflammation in lambs treated with surfactant alone. In contrast, surfactant containing rhSP-D decreased neutrophil numbers in bronchoalveolar lavage fluid and decreased neutrophil elastase activity in lung tissue. IL-8 mRNA and IL-8 protein were significantly decreased in the +rhSP-D group lamb lungs, to 20% of those in controls. The addition of rhSP-D also rendered Survanta more resistant to plasma protein inhibition of surfactant function.

CONCLUSIONS

Treatment with rhSP-D-containing surfactant inhibited lung inflammation and enhanced the resistance of surfactant to inhibition, supporting its potential usefulness for prevention of lung injury in the preterm newborn.

Surfactant protein-A limits Ureaplasma-mediated lung inflammation in a murine pneumonia model

Ureaplasma respiratory tract colonization stimulates prolonged, dysregulated inflammation in the lungs of preterm infants, contributing to bronchopulmonary dysplasia (BPD) pathogenesis. Surfactant protein-A (SP-A), a lung collectin critical for bacterial clearance and regulating inflammation, is deficient in the preterm lung. To analyze the role of SP-A in modulating Ureaplasma-mediated lung inflammation, SP-A deficient (SP-A-/-) and WT mice were inoculated intratracheally with a mouse-adapted U. parvum isolate and indices of inflammation were sequentially assessed up to 28 d postinoculation. Compared with infected WT and noninfected controls, Ureaplasma-infected SP-A-/- mice exhibited an exaggerated inflammatory response evidenced by rapid influx of neutrophils and macrophages into the lung, and higher bronchoalveolar lavage TNF-alpha, mouse analogue of human growth-related protein alpha (KC), and monocyte chemotactic factor (MCP-1) concentrations. However, nitrite generation in response to Ureaplasma infection was blunted at 24 h and Ureaplasma clearance was delayed in SP-A-/- mice compared with WT mice. Coadministration of human SP-A with the Ureaplasma inoculum to SP-A-/- mice reduced the inflammatory response, but did not improve the bacterial clearance rate. SP-A deficiency may contribute to the prolonged inflammatory response in the Ureaplasma-infected preterm lung, but other factors may contribute to the impaired Ureaplasma clearance.

Intravenous lipopolysaccharide-induced pulmonary maturation and structural changes in fetal sheep

BACKGROUND

Antenatal pulmonary inflammation is associated with reduced risk for respiratory distress syndrome but with an increased risk for bronchopulmonary dysplasia (BPD) with impaired alveogenesis.

OBJECTIVE

We hypothesized that fetal systemic inflammation induced by intravenous (IV) lipopolysaccharide (LPS) would affect lung development in utero.

STUDY DESIGN

Twenty-one fetal sheep were instrumented (107 days gestational age). Control fetuses received saline (N = 12) and 9 in the study group received 100 ng of LPS IV 3 days after surgery. Animals were assessed for lung maturation and structure after 3 (N = 5) and 7 (N = 4) days.

RESULTS

Interleukin-6 concentration increased in the bronchoalveolar lavage more than 40-fold 3 days after LPS IV. Processing of pro-surfactant protein (SP)-B to mature SP-B and increased SP-B concentrations were shown 7 days after LPS IV. Deposition of elastin fibers at sites of septation was disturbed within 3 days after LPS IV.

CONCLUSION

Lung maturation and disturbed lung structure occurred after short-term exposure to fetal inflammation and suggests new targeted therapies for BPD.

Effects of oxygen concentration and exposure time on cultured human airway epithelial cells

OBJECTIVES

To distinguish the direct effects of oxygen dose and exposure time on human airway epithelial cells. We hypothesized that progressive oxygen exposure would induce cell dysfunction and inflammation in a dose-dependent manner.

DESIGN

Interventional laboratory study.

SETTING

An academic medical research facility in the northeastern United States.

SUBJECTS

Calu-3 human airway epithelial cell culture.

INTERVENTIONS

Cells were cultured at a gas-liquid interface with the cells fed basolaterally with medium and grown to full confluence. The apical surfaces were then exposed to gas containing 21%, 40%, 60%, or 80% oxygen, 5% CO2, and balance nitrogen for 24 or 72 hrs.

MEASUREMENTS AND MAIN RESULTS

The effects of oxygen concentration and time-induced cellular change were examined by measuring transepithelial resistance of monolayers, cell viability by trypan blue exclusion, basolateral lactate concentration, histology of monolayer cross-sections, and cytospin slides, plus interleukin (IL)-6 and IL-8 secretion in apical surface fluid. Transepithelial resistance decreased in a dose- and time-dependent manner (p < .001), whereas cell viability was reduced only at 72 hrs and in all hyperoxic groups (p < .05). IL-6 secretion was elevated in all hyperoxic groups at 24 hrs (p < .001), and both IL-6 and IL-8 levels were greater in the 40% FiO2 group compared with all other groups at 72 hrs (p < .01).

CONCLUSIONS

In this model, airway epithelial cells demonstrate profound concentration and time-dependent responses to hyperoxic exposure with respect to cell physiology, viability, histology, and secretion of inflammatory mediators. This model might be a valuable tool for preliminary analysis of potentially protective therapies against hyperoxia-induced airway epithelial injury.

Surfactant protein A regulates IgG-mediated phagocytosis in inflammatory neutrophils

Surfactant proteins (SP)-A and SP-D have been shown to affect the functions of a variety of innate immune cells and to interact with various immune proteins such as complement and immunoglobulins. The goal of the current study is to test the hypothesis that SP-A regulates IgG-mediated phagocytosis by neutrophils, which are major effector cells of the innate immune response that remove invading pathogens by phagocytosis and by extracellular killing mediated by reactive oxygen and nitrogen. We have previously shown that SP-A stimulates chemotaxis by inflammatory, but not peripheral, neutrophils. To evaluate the ability of SP-A to modulate IgG-mediated phagocytosis, polystyrene beads were coated with BSA and treated with anti-BSA IgG. SP-A significantly and specifically enhanced IgG-mediated phagocytosis by inflammatory neutrophils, but it had no effect on beads not treated with IgG. SP-A bound to IgG-coated beads and enhanced their uptake via direct interactions with the beads as well as direct interactions with the neutrophils. SP-A did not affect reactive oxygen production or binding of IgG to neutrophils and had modest effects on polymerization of actin. These data suggest that SP-A plays an important role in mediating the phagocytic response of neutrophils to IgG-opsonized particles.

Intratracheal recombinant surfactant protein d prevents endotoxin shock in the newborn preterm lamb

RATIONALE

The susceptibility of neonates to pulmonary and systemic infection has been associated with the immaturity of both lung structure and the immune system. Surfactant protein (SP) D is a member of the collectin family of innate immune molecules that plays an important role in innate host defense of the lung.

OBJECTIVES

We tested whether treatment with recombinant human SP-D influenced the response of the lung and systemic circulation to intratracheally administered Escherichia coli lipopolysaccharides.

METHODS

After intratracheal lipopolysaccharide instillation, preterm newborn lambs were treated with surfactant and ventilated for 5 h.

MEASUREMENT

Survival rate, physiologic lung function, lung and systemic inflammation, and endotoxin level in plasma were evaluated.

MAIN RESULTS

In control lambs, intratracheal lipopolysaccharides caused septic shock and death associated with increased endotoxin in plasma. In contrast, all lambs treated with recombinant human SP-D were physiologically stable and survived. Leakage of lipopolysaccharides from the lungs to the systemic circulation was prevented by intratracheal recombinant human SP-D. Recombinant human SP-D prevented systemic inflammation and decreased the expression of IL-1beta, IL-8, and IL-6 in the spleen and liver. Likewise, recombinant human SP-D decreased IL-1beta and IL-6 in the lung and IL-8 in the plasma. Recombinant human SP-D did not alter pulmonary mechanics following endotoxin exposure. Recombinant human SP-D was readily detected in the lung 5 h after intratracheal instillation.

CONCLUSIONS

Intratracheal recombinant human SP-D prevented shock caused by endotoxin released from the lung during ventilation in the premature newborn.

Identification of the surfactant protein A receptor 210 as the unconventional myosin 18A

Mass spectrometric characterization of the surfactant protein A (SP-A) receptor 210 (SP-R210) led to the identification of myosin (Myo) XVIIIA and nonmuscle myosin IIA. Antibodies generated against the unique C-terminal tail of MyoXVIIIA revealed that MyoXVIIIA, MyoIIA, and SP-R210 have overlapping tissue distribution, all being highly expressed in myeloid cells, bone marrow, spleen, lymph nodes, and lung. Western blot analysis of COS-1 cells stably transfected with either MyoXVIIIA or MyoIIA indicated that SP-R210 antibodies recognize MyoXVIIIA. Furthermore, MyoXVIIIA but not MyoIIA localized to the surface of COS-1 cells, and most importantly, expression of MyoXVIIIA in COS-1 cells conferred SP-A binding. Western analysis of recombinant MyoXVIIIA domains expressed in bacteria mapped the epitopes of previously derived SP-R210 antibodies to the neck region of MyoXVIIIA. Antibodies raised against the neck domain of MyoXVIIIA blocked the binding of SP-A to macrophages. Together, these findings indicate that MyoXVIIIA constitutes a novel receptor for SP-A.

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.

Angiotensin II receptor inhibition prevents pneumocyte apoptosis in surfactant-depleted rat lungs

Pneumocyte apoptosis is implicated in the pathophysiology of acute inflammatory lung injuries in newborns and adults. Pulmonary angiotensin (ANG) II contributes to lung epithelial apoptosis in vitro, but its role in acute lung injury in vivo is unclear. We therefore studied the effects of ANG II receptor action on the pulmonary inflammatory and apoptotic changes in surfactant-depleted lungs in rats. Lung injury was induced by repeated lung lavage with saline, and the rats were then ventilated with 60% oxygen for 1, 3, or 5 hr. Separate groups of rats were pretreated with a nonspecific ANG II receptor inhibitor saralasin, the specific ANG II type 1 receptor antagonist losartan, or ANG II type 2 receptor inhibitor PD123319, and were similarly studied. Lungs were studied histologically for tissue injury, and with terminal deoxynucleodityl transferase-mediated dUTP nick end-labeling (TUNEL) and cleaved caspase 3 antibody staining, and by electron microscopy for apoptotic cell death. Surfactant-depleted lungs showed an increased number of TUNEL-positive epithelial cells throughout the study, and intrapulmonary leukocyte migration and histological tissue injury scores were similarly elevated, compared to controls, from 1-5 hr of ventilation. Pretreatment with saralasin or losartan significantly prevented the increase of TUNEL positivity in pneumocytes, but had no effect on the amount of neutrophil influx or total injury score in lavaged lungs. In contrast, administration of PD123319 did not affect the number of TUNEL-positive epithelial cells or histological injury . The results suggest that increased epithelial apoptosis in surfactant-deficient lungs is mediated by ANG II receptor (specifically, subtype 1) action.

Adenovirus-mediated gene therapy enhances parainfluenza virus 3 infection in neonatal lambs

Parainfluenza viruses are a common cause of seasonal respiratory disease, but in high-risk individuals (e.g., young children) these viruses can cause severe clinical manifestations that require hospitalization. Beta-defensins are a subclass of antimicrobial peptides with antiviral activity. Use of adenovirus-mediated beta-defensin gene expression has been proposed as therapy for chronic bacterial infections commonly seen in cystic fibrosis patients; however, its use during parainfluenza virus 3 (PIV3) infection has not been evaluated. The hypothesis in this experiment was that adenovirus expression of human beta-defensin 6 (HBD6) would diminish concurrent PIV3 infection in neonatal lambs. The group infected with adenovirus HBD6 and PIV3 had increased levels of pulmonary neutrophil recruitment compared to those for the group infected with PIV3 or PIV3 and adenovirus, with an increased respiration rate and body temperature late in the course of the PIV3-adenovirus HBD6 infection. Interestingly, the adenovirus-treated groups had higher levels of immunohistochemical staining for PIV3 and syncytial cell formation than the group infected with PIV3, suggesting that treatment with the adenovirus vector, regardless of whether it was carrying a target gene, exacerbated the PIV3 infection. The levels of expression of mRNA for antimicrobial surfactant proteins A and D and sheep beta-defensin 1 were increased by PIV3 and adenovirus treatment, and the increased levels of expression roughly corresponded to the degree of inflammation. While pulmonary administration of a high-dose adenovirus vector has been associated with undesirable inflammation, this is the first study to show that it can exacerbate concurrent viral infection, a concern that needs to be addressed for future studies of adenovirus in the lung. Additionally, this study showed that adenovirus-mediated HBD6 expression increases neutrophil recruitment, a recently described attribute of beta-defensins, with mild accentuation of PIV3 activity and inflammation.

Effect of pulmonary surfactant on TNF-α-activated endothelial cells and neutrophil adhesion in vitro

Pulmonary surfactant given to infants and adults with respiratory failure is metabolized and recycled to a large extent. A small proportion also enters the circulation in cases of increased permeability of the alveolar-capillary membrane. We therefore investigated whether exogenous surfactants such as a natural bovine (natSF) or a synthetic (synSF) preparation had an impact on inflammatory conditions involving the adhesion of neutrophils to endothelial cells. Human umbilical cord vein endothelial cells (HUVEC) were plated on coverslips until confluence, activated by tumor necrosis factor-alpha and incubated with or without surfactant in the media. Human neutrophils passed the HUVEC layer in a flow chamber and interactions were visualized using a video microscope. To test if surfactant affected the expression of cell adhesion molecules, RT-PCR analyses were performed for E-selectin, vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1). Using concentrations between 50 and 300 microg/ml of surfactant in the pre-incubation media the number of adherent neutrophils increased by 10-20% at the higher concentration of the natSF (*P < 0.05) whereas the synSF had no effect. Increased neutrophil adhesion was associated with a significant up-regulation of mRNA levels for E-selectin and VCAM-1; mRNA levels for ICAM-1, however, were not affected by the presence of surfactant. These observations indicate that natSF but not synSF might have pro-inflammatory effects when higher amounts of the exogenous dose reach the circulation. This might be explained by different fatty acid profiles, e.g. the presence of arachidonic acid in the natSF or higher concentrations of surfactant-associated protein-C in the synSF.

Glucocorticoid regulation of the inflammatory response to injury

During the first half of the 20th century, physiologists were interested in the adrenal glands primarily because adrenalectomized animals failed to survive even mild degrees of systemic stress. It eventually became clear that hormones secreted by the adrenal cortex were critical for survival and, in this context, adrenal cortical hormones were widely considered to support or stimulate important responses to stress or injury. With the purification and manufacture of adrenal cortical hormones in the 1930s and 1940s, clinicians suddenly discovered the potent anti-inflammatory actions of glucocorticoids (GCs). This dramatic, and unexpected, discovery has dominated clinical and laboratory research into GC actions throughout the second half of the 20th century. More recent research is again reporting GC-induced stimulatory effects on a variety of inflammatory response components. These effects are usually observed at low GC concentrations, close to concentrations that are observed in vivo during basal, unstimulated states. For example, GC-mediated stimulation has been reported for the hepatic acute-phase response, for cytokine secretion, expression of cytokine/chemokine receptors, and for the pro-inflammatory mediator, macrophage migration inhibition factor. It seems clear that the long-held clinical view that GCs act solely as anti-inflammatory agents needs to be re-assessed. Varying doses of GCs do not lead simply to varying degrees of inflammation suppression, but rather GCs can exert a full range of effects from permissive to stimulatory to suppressive.

Collectins

Collectins are a family of collagenous calcium-dependent defense lectins in animals. Their polypeptide chains consist of four regions: a cysteine-rich N-terminal domain, a collagen-like region, an alpha-helical coiled-coil neck domain and a C-terminal lectin or carbohydrate-recognition domain. These polypeptide chains form trimers that may assemble into larger oligomers. The best studied family members are the mannan-binding lectin, which is secreted into the blood by the liver, and the surfactant proteins A and D, which are secreted into the pulmonary alveolar and airway lining fluid. The collectins represent an important group of pattern recognition molecules, which bind to oligosaccharide structures and/or lipid moities on the surface of microorganisms. They bind preferentially to monosaccharide units of the mannose type, which present two vicinal hydroxyl groups in an equatorial position. High-affinity interactions between collectins and microorganisms depend, on the one hand, on the high density of the carbohydrate ligands on the microbial surface, and on the other, on the degree of oligomerization of the collectin. Apart from binding to microorganisms, the collectins can interact with receptors on host cells. Binding of collectins to microorganisms may facilitate microbial clearance through aggregation, complement activation, opsonization and activation of phagocytosis, and inhibition of microbial growth. In addition, the collectins can modulate inflammatory and allergic responses, affect apoptotic cell clearance and modulate the adaptive immune system.

Human SP-A genetic variants and bleomycin-induced cytokine production by THP-1 cells: effect of ozone-induced SP-A oxidation

Surfactant protein A (SP-A) plays a role in innate host defense. Human SP-A is encoded by two functional genes (SP-A1 and SP-A2), and several alleles have been characterized for each gene. We assessed the effect of in vitro expressed human SP-A genetic variants, on TNF-alpha and IL-8 production by THP-1 cells in the presence of bleomycin, either before or after ozone-induced oxidation of the variants. The oligomerization of SP-A variants was also examined. We found 1) cytokine levels induced by SP-A2 (1A, 1A(0)) were significantly higher than those by SP-A1 (6A(2), 6A(4)) in the presence of bleomycin. 2) In the presence of bleomycin, ozone-induced oxidation significantly decreased the ability of 1A and 1A/6A(4), but not of 6A(4), to stimulate TNF-alpha production. 3) The synergistic effect of bleomycin/SP-A, either before or after oxidation, can be inhibited to the level of bleomycin alone by surfactant lipids. 4) Differences in oligomerization were also observed between SP-A1 and SP-A2. The results indicate that differences among SP-A variants may partly explain the individual variability of pulmonary complications observed during bleomycin chemotherapy and/or in an environment that may promote protein oxidation.

Donor lung pretreatment with surfactant in experimental transplantation preserves graft hemodynamics and alveolar morphology

In experimental lung transplantation, the reduction of endogenous surfactant properties occurs after graft preservation and transplant reperfusion. The aim of this study was to evaluate the efficacy of donor lung pretreatment with exogenous surfactant on graft damage after ischemia and reperfusion. Fourteen (control group A, n = 8; study group B, n= 6) young female white pigs (mean weight 27 +/- 3.5 kg) were used in a newly developed autotransplantation model within situcold ischemia. In study group B, before thoracotomy, 1.5 ml/kg surfactant apoprotein-A-free surfactant was administrated into the left main bronchus via flexible bronchoscopy. Belzer UW solution was used for lung preservation. Cold ischemia was achieved for 3 hr with interlobar lung parenchyma temperature at 8 +/- 1.3 degrees C, and central temperature maintained at 37.20 +/- 0.5 degrees C. Animals were sacrificed after 3 hr of graft reperfusion. At the end of reperfusion, pulmonary vascular resistance index (was 447.80 dyn/sec.cm(5).m(2)(+/-66.8) in group A vs 249.51 in group B (P< 0.001) and serum nitric oxide was adequately preserved. The mean alveolar surface area estimated by computerized morphometry was 5280.84 (4991.1) microm(2)(group A) vs 3997.89 (3284.70) microm(2)(group B;P< 0.005). Histology revealed milder macrophage and lymphocyte infiltration in group B at the end of reperfusion. Pretreatment of donor lung with an surfactant apoprotein-A -free surfactant agent appears to be beneficial in terms of maintaining serum NO and reducing hemodynamic disturbances. Furthermore, alveolar histology and stereomorphology are better preserved.

Effects of high PCO2 on ventilated preterm lamb lungs

High PCO(2) levels attenuate reperfusion injury and ventilation-induced injury in isolated and perfused lungs. We asked whether premature lambs could tolerate 6 h of ventilation with a PCO(2) >80 mm Hg and whether the high PCO(2) modulated the ventilator-induced injury. Preterm surfactant-treated lambs were ventilated for 30 min with a high tidal volume (V(T)) to induce lung injury. The lambs then were ventilated for 5.5 h with a V(T) of 6-9 mL/kg to achieve a PCO(2) of 40-50 mm Hg in the control group. CO(2) was added to the ventilator circuit of a high PCO(2) group to maintain an average PCO(2) of 95 +/- 5 mm Hg. The high PCO(2) lambs had heart rates, blood pressures, plasma cortisol values, and oxygenation equivalent to the control lambs. The lungs of the high PCO(2) group had significantly higher gas volumes and had less lung injury by histopathology. Indicators of inflammation (white blood cells, hydrogen peroxide production, and IL-1beta and IL-8 cytokine mRNA expression in cells from the alveolar wash) qualitatively indicated less injury in the high PCO(2) group, although the differences were not significant. Preterm lambs tolerated a very high PCO(2) without physiologic compromise for 6 h. The high PCO(2) may attenuate ventilator-induced lung injury in the preterm.

Combined SP-A-bleomycin effect on cytokines by THP-1 cells: impact of surfactant lipids on this effect

Surfactant protein A (SP-A) plays a role in host defense and inflammation in the lung. In the present study, we investigated the hypothesis that SP-A is involved in bleomycin-induced pulmonary fibrosis. We studied the effects of human SP-A on bleomycin-induced cytokine production and mRNA expression in THP-1 macrophage-like cells and obtained the following results. 1) Bleomycin-treated THP-1 cells increased tumor necrosis factor (TNF)-alpha, interleukin (IL)-8, and IL-1beta production in dose- and time-dependent patterns, as we have observed with SP-A. TNF-alpha levels were unaffected by treatment with cytosine arabinoside. 2) The combined bleomycin-SP-A effect on cytokine production is additive by RNase protection assay and synergistic by enzyme-linked immunosorbent assay. 3) Although the bleomycin effect on cytokine production was not significantly affected by the presence of surfactant lipid, the additive and synergistic effect of SP-A-bleomycin on cytokine production was significantly reduced. We speculate that the elevated cytokine levels resulting from the bleomycin-SP-A synergism are responsible for bleomycin-induced pulmonary fibrosis and that surfactant lipids can help ameliorate pulmonary complications observed during bleomycin chemotherapy.

Injury responses to different surfactants in ventilated premature lamb lungs

The lung of the preterm infant is easily injured and an initial indication of the injury is an inflammatory response. Surfactant treatment and gentle ventilation will minimize the initiation and progression of injury. We asked if the initial lung injury response differed when preterm ventilated lambs were treated with complete natural sheep surfactant, a lipid extract of sheep surfactant, a surfactant used to treat RDS (Survanta), or a synthetic surfactant containing recombinant SP-C (Venticute). We used a gentle style of ventilation and a positive end expiratory pressure of 4 cmH(2)0 to minimize injury. The surfactants were not distinguishable based on gas exchange, compliance or lung gas volumes over the 6h ventilation period. When compared with unventilated controls the ventilated lambs had increased protein and inflammatory cells in alveolar lavages. The cells from the alveolar lavages produced more H(2)0(2), expressed more surface adhesion antigens and CD-14 receptors, and expressed more mRNA for the pro-inflammatory cytokines IL-1 beta and IL-8 than did cells from unventilated lungs. Lung tissue expressed primarily increased IL-6 mRNA relative to unventilated controls. However, there were no consistent differences in any of the inflammatory indicators between the different surfactant treated groups. Because endotoxin free natural surfactant containing SP-A was not superior to three other surfactants containing differing amounts of the surfactant proteins, additions of these proteins to clinical surfactants may not decrease the indicators of lung inflammation that accompany the initiation of ventilation of the preterm lung.

Dose and time response after intraamniotic endotoxin in preterm lambs

Intraamniotic endotoxin causes chorioamnionitis, which is followed by improved fetal lung function after 4 d in fetal sheep. We evaluated 0.1 mg, 1 mg, 4 mg, and 10 mg endotoxin for inflammation and lung maturation effects after 7 d. Four and 10 mg endotoxin caused similar lung maturation and inflammation in the lung and chorioamnion. The number of neutrophils in cord blood and the inflammatory cells in alveolar lavage and fetal lung tissue increased in a dose-dependent manner. Lower endotoxin doses induced indicators of chorioamnionitis, lung and systemic inflammation without inducing lung maturation. Therefore, some degree of inflammation can occur without subsequent lung maturation. The inflammatory changes caused by 4 mg endotoxin were assessed after 5 h, 24 h, 72 h, and 7 d to discern local versus systemic inflammation after intraamniotic endotoxin. At 5 h active inflammatory cells were in the airways producing hydrogen peroxide, and interleukin-6 and -8 were increased in the cord blood indicating both lung and systemic responses. Cells recruited into the amniotic fluid produced proinflammatory cytokine mRNA for 7 d with no cytokine mRNA in chorioamnion, lung, or spleen after 72 h. The cells in the amniotic fluid may be a source of prolonged fetal exposure to proinflammatory cytokines.