Comparison of in vivo bioluminescence imaging and lavage biomarkers to assess pulmonary inflammation

Gram-negative bacterial endotoxin triggers innate immunity via TLR-4 and NF-kB signal activation. The aim of this study was to evaluate the use of transgenic mice expressing luciferase as a marker of NF-kB activation for exploring innate immune responses to pulmonary endotoxin exposure over time thus obviating the need for serial necropsies. Transgenic rNF-kB-Luc BALB/c mice were exposed to two different types of endotoxin (Neisseria meningitidis lipooligosaccharide, and Escherichia coli lipopolysaccharide) at multiple doses by nasal instillation. Bioluminescence was quantified in vivo at five time points in three separate experiments. In the fourth experiment lungs were imaged ex vivo 8h post exposure and tissue was analyzed for luciferase activity. Non-transgenic BALB/c mice were similarly exposed to lipooligosaccharide and bronchoalveolar lavage was assessed for neutrophil recruitment and IL-6. Non-transgenic BALB/c mice exhibited highly significant increases of IL-6 and neutrophils in bronchoalveolar lavage 4h after the exposure to instilled doses as low as 30EU/mouse. In contrast, luciferase imaging of NF-kB signal activation in vivo in transgenic rNF-kB-Luc mice did not show significant changes over time or over doses from 30EU to 300,000EU/mouse of nasally-instilled endotoxin. Ex vivo lung imaging 8h after endotoxin exposure to 3000EU demonstrated a strong signal. An intravenous LPS dose of 300,000EU/mouse produced a measurable luminescence signal in vivo. This non-terminal assessment method is useful only with extremely high doses of endotoxin that induce systemic injury and cannot be applied to research of occupational and environmental exposures at relevant levels of endotoxin.

Targeting inflammation to prevent bronchopulmonary dysplasia: can new insights be translated into therapies?

Bronchopulmonary dysplasia (BPD) frequently complicates preterm birth and leads to significant long-term morbidity. Unfortunately, few therapies are known to effectively prevent or treat BPD. Ongoing research has been focusing on potential therapies to limit inflammation in the preterm lung. In this review we highlight recent bench and clinical research aimed at understanding the role of inflammation in the pathogenesis of BPD. We also critically assess currently used therapies and promising developments in the field.

Effect of inhibition of the ubiquitin-proteasome-system and IκB kinase on airway inflammation and hyperresponsiveness in a murine model of asthma

The current treatment of asthma is far from optimal and there is a need for novel therapeutic approaches. NFkB has recently been highlighted as an important pro-inflammatory transcriptional factor and its blockade is believed to represent a new therapeutic approach for asthma. The purpose of this study is to investigate the effects of blocking the actions of NFkB, through inhibition of the ubiquitin-proteasome system (UPS) or IkB kinase (IKK), in a murine model of asthma. Treatment with the UPS inhibitor, MG-132 (0.03 and 0.1 mg/kg), did not significantly affect the ovalbumin-induced increase in total and differential cell numbers, histological changes such as perivascular and peribronchial inflammatory cell infiltration, perivascular and peribronchial fibrosis or the increased Penh to methacholine. In contrast, treatment of mice with the IKK inhibitor, BAY 11-7085, (3 and 10 mg/kg) dose-dependently inhibited the ovalbumin-induced increase in airway leukocyte influx and decreased the percentage of airway lymphocytes, neutrophils and eosinophils. Also, BAY 11-7085-treated (10 mg/kg) mice showed a significant decrease in the histologically assessed inflammatory indices as well as a significant reduction in the ovalbumin-induced increase in Penh to inhaled methacholine. Furthermore, BAY 11-7085 significantly inhibited the ovalbumin-induced increase in the level of phosphorylation of IkBalpha and extracellular regulated kinases (ERK) 1/2, whilst MG-132 significantly increased the phosphorylation of (ERK) 1/2. These findings confirm the critical role that NFkB plays in airway inflammation, highlight the importance of IKK in regulating the pro-inflammatory activity of NFkB and also suggest that UPS may not be a useful drug target for asthma treatment.

Silencing hyperoxia-induced C/EBPα in neonatal mice improves lung architecture via enhanced proliferation of alveolar epithelial cells

Postnatal lung development requires proliferation and differentiation of specific cell types at precise times to promote proper alveolar formation. Hyperoxic exposure can disrupt alveolarization by inhibiting cell growth; however, it is not fully understood how this is mediated. The transcription factor CCAAT/enhancer binding protein-α (C/EBPα) is highly expressed in the lung and plays a role in cell proliferation and differentiation in many tissues. After 72 h of hyperoxia, C/EBPα expression was significantly enhanced in the lungs of newborn mice. The increased C/EBPα protein was predominantly located in alveolar type II cells. Silencing of C/EBPα with a transpulmonary injection of C/EBPα small interfering RNA (siRNA) prior to hyperoxic exposure reduced expression of markers of type I cell and differentiation typically observed after hyperoxia but did not rescue the altered lung morphology at 72 h. Nevertheless, when C/EBPα hyperoxia-exposed siRNA-injected mice were allowed to recover for 2 wk in room air, lung epithelial cell proliferation was increased and lung morphology was restored compared with hyperoxia-exposed control siRNA-injected mice. These data suggest that C/EBPα is an important regulator of postnatal alveolar epithelial cell proliferation and differentiation during injury and repair.

Hydrogen inhalation reduced epithelial apoptosis in ventilator-induced lung injury via a mechanism involving nuclear factor-kappa B activation

We recently demonstrated the inhalation of hydrogen gas, a novel medical therapeutic gas, ameliorates ventilator-induced lung injury (VILI); however, the molecular mechanisms by which hydrogen ameliorates VILI remain unclear. Therefore, we investigated whether inhaled hydrogen gas modulates the nuclear factor-kappa B (NFκB) signaling pathway. VILI was generated in male C57BL6 mice by performing a tracheostomy and placing the mice on a mechanical ventilator (tidal volume of 30 ml/kg or 10 ml/kg without positive end-expiratory pressure). The ventilator delivered either 2% nitrogen or 2% hydrogen in balanced air. NFκB activation, as indicated by NFκB DNA binding, was detected by electrophoretic mobility shift assays and enzyme-linked immunosorbent assay. Hydrogen gas inhalation increased NFκB DNA binding after 1h of ventilation and decreased NFκB DNA binding after 2h of ventilation, as compared with controls. The early activation of NFκB during hydrogen treatment was correlated with elevated levels of the antiapoptotic protein Bcl-2 and decreased levels of Bax. Hydrogen inhalation increased oxygen tension, decreased lung edema, and decreased the expression of proinflammatory mediators. Chemical inhibition of early NFκB activation using SN50 reversed these protective effects. NFκB activation and an associated increase in the expression of Bcl-2 may contribute, in part, to the cytoprotective effects of hydrogen against apoptotic and inflammatory signaling pathway activation during VILI.

A role for matrix metalloproteinase 9 in IFNγ-mediated injury in developing lungs: relevance to bronchopulmonary dysplasia

We noted a marked increase in IFNγ mRNA in newborn (NB) murine lungs after exposure to hyperoxia. We sought to evaluate the role of IFNγ in lung injury in newborns. Using a unique triple-transgenic (TTG), IFNγ-overexpressing, lung-targeted, externally regulatable NB murine model, we describe a lung phenotype of impaired alveolarization, resembling human bronchopulmonary dysplasia (BPD). IFNγ-mediated abnormal lung architecture was associated with increased cell death and the upregulation of cell death pathway mediators caspases 3, 6, 8, and 9, and angiopoietin 2. Moreover, an increase was evident in cathepsins B, H, K, L, and S, and in matrix metalloproteinases (MMPs) 2, 9, 12, and 14. The IFNγ-mediated abnormal lung architecture was found to be MMP9-dependent, as indicated by the rescue of the IFNγ-induced pulmonary phenotype and survival during hyperoxia with a concomitant partial deficiency of MMP9. This result was concomitant with a decrease in caspases 3, 6, 8, and 9 and angiopoietin 2, but an increase in the expression of angiopoietin 1. In addition, NB IFNγ TTG mice exhibited significantly decreased survival during hyperoxia, compared with littermate controls. Furthermore, as evidence of clinical relevance, we show increased concentrations of the downstream targets of IFNγ chemokine (C-X-C motif) ligands (CXCL10 and CXCL11) in baboon and human lungs with BPD. IFNγ and its downstream targets may contribute significantly to the final common pathway of hyperoxia-induced injury in the developing lung and in human BPD.

NO inhibits hyperoxia-induced NF-κB activation in neonatal pulmonary microvascular endothelial cells

Inhaled NO (iNO) may be protective against hyperoxic injury in the premature lung, but the mechanism is unknown. We hypothesized that NO would prevent hyperoxia-induced nuclear factor kappa B (NF-κB) activation in neonatal pulmonary microvascular endothelial cells [human pulmonary microvascular endothelial cell (HPMEC)] and prevent the up-regulation of target genes. After hyperoxic exposure (O2 >95%), nuclear NF-κB consensus sequence binding increased and was associated with IκBα degradation. Both of these findings were prevented by exposure to NO. Furthermore, intracellular adhesion molecule (ICAM)-1 mRNA and protein levels increased in cells exposed to hyperoxia, an effect abrogated by NO. To evaluate the potentially toxic effect of NO plus hyperoxia, cell viability and proliferation were assessed. Cells exposed to NO plus hyperoxia demonstrated improved survival as measured by trypan blue exclusion when compared with cells exposed to hyperoxia alone. These differences in cell death could not be attributed to apoptosis measured by caspase-3 activity. Finally, cellular proliferation inhibited by hyperoxia was rescued by concurrent exposure to NO. These data demonstrate that NO prevents hyperoxia-induced NF-κB activation in HPMEC and results in decreased expression of adhesion molecules and decreased cellular toxicity. This may help to explain the protective effects of NO on hyperoxic injury in the developing lung vasculature.

The protective effect of overexpression of extracellular superoxide dismutase on nitric oxide bioavailability in the lung after exposure to hyperoxia stress

The objective of this study was to determine whether overexpression of human extracellular superoxide dismutase (hEC-SOD) can preserve nitric oxide (NO) bioavailability. In vitro studies examined the transient expression of hEC-SOD in mouse epithelial (C10) cells and its effect on extracellular accumulation of NO, intracellular cyclic guanosine monophosphate (cGMP), and nuclear factor kappa B (NF-κB) activation under normal and oxidative stress conditions. In vivo, newborn rabbits were treated with a plasmid containing hEC-SOD cDNA or vehicle plasmid alone, followed by exposure to hyperoxia (Fio₂ = 95% for 7 days). A third group was raised under normoxic conditions. cGMP and NF-κB activation were studied. There was significantly higher NO accumulation in cells expressing hEC-SOD exposed to oxidative stress compared with nontransfected cells. Accumulation of cGMP was significantly higher in cells expressing hEC-SOD. Oxidative stress induced NF-κB activation, which was abrogated by hEC-SOD expression. In vivo, there was significantly higher cGMP accumulation in transfected neonatal rabbit lung tissue at 3 and 7 days of hyperoxic exposure. Immunostaining for NF-κB, showed a marked increase in NF-κB concentration in nontreated neonatal rabbit lung tissue compared to transfected neonatal lung with hEC-SOD and the control air group. These results show that transient EC-SOD overexpression maintains NO bioavailability, which directly leads to maintenance of cGMP activity and reduction of NF-κB activation under oxidative stress.

Bcl-2 overexpression in type II epithelial cells does not prevent hyperoxia-induced acute lung injury in mice

Bcl-2 is an anti-apoptotic molecule preventing oxidative stress damage and cell death. We have previously shown that Bcl-2 is able to prevent hyperoxia-induced cell death when overexpressed in a murine fibrosarcoma cell line L929. We hypothesized that its specific overexpression in pulmonary epithelial type II cells could prevent hyperoxia-induced lung injury by protecting the epithelial side of the alveolo-capillary barrier. In the present work, we first showed that in vitro Bcl-2 can rescue murine pulmonary epithelial cells (MLE12) from oxygen-induced cell apoptosis, as shown by analysis of LDH release, annexin V/propidium staining, and caspase-3 activity. We then generated transgenic mice overexpressing specifically Bcl-2 in lung epithelial type II cells under surfactant protein C (SP-C) promoter (Tg-Bcl-2) and exposed them to hyperoxia. Bcl-2 did not hinder hyperoxia-induced mitochondria and DNA oxidative damage of type II cell in vivo. Accordingly, lung damage was identical in both Tg-Bcl-2 and littermate mice strains, as measured by lung weight, bronchoalveolar lavage, and protein content. Nevertheless, we observed a significant lower number of TUNEL-positive cells in type II cells isolated from Tg-Bcl-2 mice exposed to hyperoxia compared with cells isolated from littermate mice. In summary, these results show that although Bcl-2 overexpression is able to prevent hyperoxia-induced cell death at single cell level in vitro and ex vivo, it is not sufficient to prevent cell death of parenchymal cells and to protect the lung from acute damage in mice.

Moderate postnatal hyperoxia accelerates lung growth and attenuates pulmonary hypertension in infant rats after exposure to intra-amniotic endotoxin

To determine the separate and interactive effects of fetal inflammation and neonatal hyperoxia on the developing lung, we hypothesized that: 1) antenatal endotoxin (ETX) causes sustained abnormalities of infant lung structure; and 2) postnatal hyperoxia augments the adverse effects of antenatal ETX on infant lung growth. Escherichia coli ETX or saline (SA) was injected into amniotic sacs in pregnant Sprague-Dawley rats at 20 days of gestation. Pups were delivered 2 days later and raised in room air (RA) or moderate hyperoxia (O₂, 80% O₂ at Denver's altitude, ∼65% O₂ at sea level) from birth through 14 days of age. Heart and lung tissues were harvested for measurements. Intra-amniotic ETX caused right ventricular hypertrophy (RVH) and decreased lung vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR-2) protein contents at birth. In ETX-exposed rats (ETX-RA), alveolarization and vessel density were decreased, pulmonary vascular wall thickness percentage was increased, and RVH was persistent throughout the study period compared with controls (SA-RA). After antenatal ETX, moderate hyperoxia increased lung VEGF and VEGFR-2 protein contents in ETX-O₂ rats and improved their alveolar and vascular structure and RVH compared with ETX-RA rats. In contrast, severe hyperoxia (≥95% O₂ at Denver's altitude) further reduced lung vessel density after intra-amniotic ETX exposure. We conclude that intra-amniotic ETX induces fetal pulmonary hypertension and causes persistent abnormalities of lung structure with sustained pulmonary hypertension in infant rats. Moreover, moderate postnatal hyperoxia after antenatal ETX restores lung growth and prevents pulmonary hypertension during infancy.

Hyperoxia sensing: from molecular mechanisms to significance in disease

Oxygen therapy using mechanical ventilation with hyperoxia is necessary to treat patients with respiratory failure and distress. However, prolonged exposure to hyperoxia leads to the generation of excessive reactive oxygen species (ROS), causing cellular damage and multiple organ dysfunctions. As the lungs are directly exposed, hyperoxia can cause both acute and chronic inflammatory lung injury and compromise innate immunity. ROS may contribute to pulmonary oxygen toxicity by overwhelming redox homeostasis, altering signaling cascades that affect cell fate, ultimately leading to hyperoxia-induced acute lung injury (HALI). HALI is characterized by pronounced inflammatory responses with leukocyte infiltration, injury, and death of pulmonary cells, including epithelia, endothelia, and macrophages. Under hyperoxic conditions, ROS mediate both direct and indirect modulation of signaling molecules such as protein kinases, transcription factors, receptors, and pro- and anti-apoptotic factors. The focus of this review is to elaborate on hyperoxia-activated key sensing molecules and current understanding of their signaling mechanisms in HALI. A better understanding of the signaling pathways leading to HALI may provide valuable insights on its pathogenesis and may help in designing more effective therapeutic approaches.

NADPH oxidase-1 plays a crucial role in hyperoxia-induced acute lung injury in mice

RATIONALE

Hyperoxia-induced acute lung injury has been used for many years as a model of oxidative stress mimicking clinical acute lung injury and the acute respiratory distress syndrome. Excess quantities of reactive oxygen species (ROS) are responsible for oxidative stress-induced lung injury. ROS are produced by mitochondrial chain transport, but also by NADPH oxidase (NOX) family members. Although NOX1 and NOX2 are expressed in the lungs, their precise function has not been determined until now.

OBJECTIVES

To determine whether NOX1 and NOX2 contribute in vivo to hyperoxia-induced acute lung injury.

METHODS

Wild-type and NOX1- and NOX2-deficient mice, as well as primary lung epithelial and endothelial cells, were exposed to room air or 100% O(2) for 72 hours.

MEASUREMENTS AND MAIN RESULTS

Lung injury was significantly prevented in NOX1-deficient mice, but not in NOX2-deficient mice. Hyperoxia-dependent ROS production was strongly reduced in lung sections, in isolated epithelial type II cells, and lung endothelial cells from NOX1-deficient mice. Concomitantly, lung cell death in situ and in primary cells was markedly decreased in NOX1-deficient mice. In wild-type mice, hyperoxia led to phosphorylation of c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK), two mitogen-activated protein kinases involved in cell death signaling, and to caspase-3 activation. In NOX1-deficient mice, JNK phosphorylation was blunted, and ERK phosphorylation and caspase-3 activation were decreased.

CONCLUSIONS

NOX1 is an important contributor to ROS production and cell death of the alveolocapillary barrier during hyperoxia and is an upstream actor in oxidative stress-induced acute lung injury involving JNK and ERK pathways in mice.

Manipulation of gene expression by oxygen: a primer from bedside to bench

For nearly 100 y, pediatricians have regularly used oxygen to treat neonatal and childhood diseases. During this time, it has become clear that oxygen is toxic and that overzealous use can lead to significant morbidity. As we have learned more about the appropriate clinical indications for oxygen therapy, studies at the bench have begun to elucidate the molecular mechanisms by which cells respond to hyperoxia. In this review, we discuss transcription factors whose activity is regulated by oxygen, including nuclear factor, erythroid 2-related factor 2 (Nrf2), activator protein 1 (AP-1), p53, nuclear factor kappaB (NF-kappaB), signal transducers and activators of transcription protein (STAT), and ccat/enhancer binding protein (CEBP). Special attention is paid to the mechanisms by which hyperoxia affects these transcription factors in the lung. Finally, we identify downstream targets of these transcription factors, with a focus on heme oxygenase-1. A better understanding of how oxygen affects various signaling pathways could lead to interventions aimed at preventing hyperoxic injury.

Hyperoxia-induced NF-kappaB activation occurs via a maturationally sensitive atypical pathway

NF-kappaB activation is exaggerated in neonatal organisms after oxidant and inflammatory insults, but the reason for this and the downstream effects are unclear. We hypothesized that specific phosphorylation patterns of IkappaBalpha could account for differences in NF-kappaB activation in hyperoxia-exposed fetal and adult lung fibroblasts. After exposure to hyperoxia (>95% O(2)), nuclear NF-kappaB binding increased in fetal, but not adult, lung fibroblasts. Unique to fetal cells, phosphorylation of IkappaBalpha on tyrosine 42, rather than serine 32/36 as seen in TNF-alpha-exposed cells, preceded NF-kappaB nuclear translocation. In fetal cells stably transfected with an NF-kappaB-driven luciferase reporter, hyperoxia significantly suppressed reporter activity, in contrast to increased reporter activity after TNF-alpha incubation. Targeted gene profiling analysis showed that hyperoxia resulted in decreased expression of multiple genes, including proapoptotic factors. Transfection with a dominant-negative IkappaBalpha (Y42F), which cannot be phosphorylated on tyrosine 42, resulted in upregulation of multiple proapoptotic genes. In support of this finding, caspase-3 activity and DNA laddering were specifically increased in fetal lung fibroblasts expressing Y42F after exposure to hyperoxia. These data demonstrate a unique pathway of NF-kappaB activation in fetal lung fibroblasts after exposure to hyperoxia, whereby these cells are protected against apoptosis. Activation of this pathway in fetal cells may prevent the normal pattern of fibroblast apoptosis necessary for normal lung development, resulting in aberrant lung morphology in vivo.

IL-6 cytoprotection in hyperoxic acute lung injury occurs via suppressor of cytokine signaling-1-induced apoptosis signal-regulating kinase-1 degradation

Hyperoxic acute lung injury (HALI) is characterized by a cell death response that is inhibited by IL-6. Suppressor of cytokine signaling-1 (SOCS-1) is an antiapoptotic negative regulator of the IL-6-mediated Janus kinase-signal transducer and activator of transcription signaling pathway. We hypothesized that SOCS-1 is a critical regulator and key mediator of IL-6-induced cytoprotection in HALI. To test this hypothesis, we characterized the expression of SOCS-1 and downstream apoptosis signal-regulating kinase (ASK)-1-Jun N-terminal kinase signaling molecules in small airway epithelial cells in the presence of H(2)O(2), which induces oxidative stress. We also examined these molecules in wild-type and lung-specific IL-6 transgenic (Tg(+)) mice exposed to 100% oxygen for 72 hours. In control small airway epithelial cells exposed to H(2)O(2) or in wild-type mice exposed to 100% oxygen, a marked induction of ASK-1 and pJun N-terminal kinase was observed. Both IL-6-stimulated endogenous SOCS-1 and SOCS-1 overexpression abolished H(2)O(2)-induced ASK-1 activation. In addition, IL-6 Tg(+) mice exposed to 100% oxygen exhibited reduced ASK-1 levels and enhanced SOCS-1 expression compared with wild-type mice. Interestingly, no significant changes in activation of the key ASK-1 activator, tumor necrosis factor receptor-1/tumor necrosis factor receptor-associated factor-2 were observed between wild-type and IL-6 Tg(+) mice. Furthermore, the interaction between SOCS-1 and ASK-1 promotes ubiquitin-mediated degradation both in vivo and in vitro. These studies demonstrate that SOCS-1 is an important regulator in IL-6-induced cytoprotection against HALI.

Preconditioning by inhaled nitric oxide prevents hyperoxic and ischemia/reperfusion injury in rat lungs

Since the generation of nitric oxide (NO) is an essential step in the trigger phase of ischemic preconditioning, short-term inhalation of NO before ischemia should ameliorate ischemia/reperfusion (I/R) injury of the lung. We tested this hypothesis in high oxygen (>99%) ventilated rats in order to additionally evaluate compatibility of NO and exposure to hyperoxia. Male adult Sprague-Dawley rats inhaled NO (15 ppm, 10 min) before the left lung hilum was clamped for 1 h, and the reperfusion phase was observed for 4 h (NO group). Animals in the I/R group underwent the same treatment, but without NO inhalation. A third group without I/R served as time-matched controls. Animals in the I/R group showed severe I/R injury in terms of arterial pO2 (apO2), which was reduced to 22% of surgical controls (SCs) at time point 30 min reperfusion, and increased endothelial permeability (Evans blue procedure). The pretreatment with NO attenuated these effects. The pO2 after 4 h reperfusion was still 3.0-fold higher in the NO group compared to I/R. In contrast, the I/R- and hyperoxia-induced invasion of leukocytes, as determined by measuring myeloperoxidase (MPO) activity, was not affected by NO. These data were correlated with the activity of major cellular signaling pathways by measuring the phosphorylation at activating and inhibitory sites of extracellular-signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), p38, protein kinase B (AKT), and glycogen synthase kinase 3beta (GSK-3beta), and by determination of cGMP in plasma and lung tissue. Inhalation of NO partly prevented the loss of activation by I/R and hyperoxic ventilation of ERK, JNK, and AKT, and it reduced the I/R-induced activation of GSK-3beta. The level of cGMP in plasma and lung tissue was increased in the NO group after 4 h reperfusion. In conclusion, application of inhaled NO in the preconditioning mode prevented I/R injury in the rat lung without interfering effects of hyperoxic ventilation. The effects of NO on cellular signaling pathways resemble mechanisms of ischemic preconditioning, but further studies have to evaluate the physiological relevance of these results.

Selective blockade of NF-kappaB by novel mutated IkappaBalpha suppresses CD3/CD28-induced activation of memory CD4+ T cells in asthma

BACKGROUND

Nuclear factor kappaB (NF-kappaB) overactivation plays a crucial role in T-helper 2 (Th2)-biased allergic airway inflammation by increased activation and decreased apoptosis of CD4(+) T cells. We have shown that targeted NF-kappaB suppression in dendritic cells by adenoviral gene transfer of a novel mutated inhibitor of NF-kappaB (IkappaBalpha) (AdIkappaBalphaM) contributes to T-cell tolerance, but the immunosuppressive action of AdIkappaBalphaM on memory (CD45RO(+)) CD4(+) T cells remains enigmatic.

METHODS

CD45RO(+) T cells from Dermatophagoides farinaei-sensitized asthmatic patients, untransfected or transfected with AdIkappaBalphaM or AdLacZ (beta-galactosidase) for 24 h, were stimulated with anti-CD3 (1.0 microg/ml) plus anti-CD28 (0.5 microg/ml) monoclonal antibody for an additional 24 h. IkappaBalphaM transgene expression and NF-kappaB activation were detected by polymerase chain reaction (PCR), reverse transcription-PCR (RT-PCR), Western blot analysis, and electrophoretic mobility shift assay. Phenotype and apoptosis were measured by flow cytometry, annexin V binding, and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling analyses. Cytokine production and cell proliferation were determined using enzyme-linked immunosorbent assay and [(3)H] thymidine incorporation.

RESULTS

A unique 801-bp IkappaBalphaM cDNA and a dose-dependent increase in IkappaBalphaM transgene expression were observed in AdIkappaBalphaM-transfected CD45RO(+) T cells. Significantly, AdIkappaBalphaM inhibited CD3/CD28-mediated NF-kappaB activation in CD45RO(+) T cells, leading to evident apoptosis, reduction of eotaxin, RANTES, Th1 [interferon (IFN)-gamma and interleukin (IL)-2], and Th2 (IL-4, IL-5, and IL-13 despite a slight decrease in IL-10) cytokines and secondary proliferative response. AdIkappaBalphaM also upregulated cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) and downregulated CD69 besides no change in CD28.

CONCLUSION

IkappaBalphaM might be beneficial to augment memory CD4(+) T-cell tolerance through modulating B7-CD28/CTLA-4 co-stimulatory pathways and NF-kappaB-dependent cytokine profiles in allergic inflammatory diseases including asthma.

Developmental regulation of NO-mediated VEGF-induced effects in the lung

Vascular endothelial growth factor (VEGF) is known to have a pivotal role in lung development and in a variety of pathologic conditions in the adult lung. Our earlier studies have shown that NO is a critical mediator of VEGF-induced vascular and extravascular effects in the adult murine lung. As significant differences have been reported in the cytokine responses in the adult versus the neonatal lung, we hypothesized that there may be significant differences in VEGF-induced alterations in the developing as opposed to the mature lung. Furthermore, nitric oxide (NO) mediation of these VEGF-induced effects may be developmentally regulated. Using a novel externally regulatable lung-targeted transgenic murine model, we found that VEGF-induced pulmonary hemorrhage was mediated by NO-dependent mechanisms in adults and newborns. VEGF enhanced surfactant production in adults as well as increased surfactant and lung development in newborns, via an NO-independent mechanism. While the enhanced survival in hyperoxia in the adult was partly NO-dependent, there was enhanced hyperoxia-induced lung injury in the newborn. In addition, human amniotic fluid VEGF levels correlated positively with surfactant phospholipids. Tracheal aspirate VEGF levels had an initial spike, followed by a decline, and then a subsequent rise, in human neonates with an outcome of bronchopulmonary dysplasia or death. Our data show that VEGF can have injurious as well as potentially beneficial developmental effects, of which some are NO dependent, others NO independent. This opens up the possibility of selective manipulation of any VEGF-based intervention using NO inhibitors for maximal potential clinical benefit.

Cystic fibrosis transmembrane conductance regulator controls lung proteasomal degradation and nuclear factor-kappaB activity in conditions of oxidative stress

Cystic fibrosis is a lethal inherited disorder caused by mutations in a single gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR) protein, resulting in progressive oxidative lung damage. In this study, we evaluated the role of CFTR in the control of ubiquitin-proteasome activity and nuclear factor (NF)-kappaB/IkappaB-alpha signaling after lung oxidative stress. After a 64-hour exposure to hyperoxia-mediated oxidative stress, CFTR-deficient (cftr(-/-)) mice exhibited significantly elevated lung proteasomal activity compared with wild-type (cftr(+/+)) animals. This was accompanied by reduced lung caspase-3 activity and defective degradation of NF-kappaB inhibitor IkappaB-alpha. In vitro, human CFTR-deficient lung cells exposed to oxidative stress exhibited increased proteasomal activity and decreased NF-kappaB-dependent transcriptional activity compared with CFTR-sufficient lung cells. Inhibition of the CFTR Cl(-) channel by CFTR(inh-172) in the normal bronchial immortalized cell line 16HBE14o- increased proteasomal degradation after exposure to oxidative stress. Caspase-3 inhibition by Z-DQMD in CFTR-sufficient lung cells mimicked the response profile of increased proteasomal degradation and reduced NF-kappaB activity observed in CFTR-deficient lung cells exposed to oxidative stress. Taken together, these results suggest that functional CFTR Cl(-) channel activity is crucial for regulation of lung proteasomal degradation and NF-kappaB activity in conditions of oxidative stress.

Catalytic inactive heme oxygenase-1 protein regulates its own expression in oxidative stress

Heme oxygenase-1 (HO-1) catalyzes the degradation of heme and forms antioxidant bile pigments as well as the signaling molecule carbon monoxide. HO-1 is inducible in response to a variety of chemical and physical stress conditions to function as a cytoprotective molecule. Therefore, it is important to maintain the basal level of HO-1 expression even when substrate availability is limited. We hypothesized that the HO-1 protein itself could regulate its own expression in a positive feedback manner, and that this positive feedback was important in the HO-1 gene induction in response to oxidative stress. In cultured NIH 3T3 cells, transfection of HO-1 cDNA or intracellular delivery of pure HO-1 protein resulted in activation of a 15-kb HO-1 promoter upstream of luciferase as visualized by bioluminescent technology and increased HO-1 mRNA and protein levels. These effects were independent of HO activity because an enzymatically inactive mutant form of HO-1 similarly activated the HO-1 promoter and incubation with HO inhibitor metalloporphyrin SnPP did not affect the promoter activation. In addition, HO-1-specific siRNA significantly reduced hemin and cadmium chloride-mediated HO-1 induction. Furthermore, deletion analyses demonstrated that the E1 and E2 distal enhancers of the HO-1 promoter are required for this HO-1 autoregulation. These experiments document feed-forward autoregulation of HO-1 in oxidative stress and suggest that HO-1 protein has a role in the induction process. We speculate that this mechanism may be useful for maintaining HO-1 expression when substrate is limited and may also serve to up-regulate other genes to promote cytoprotection and to modulate cell proliferation.

Effects of oxidative stress on embryonic development

Oxygen radicals, or reactive oxygen species (ROS) act as primary or secondary messengers to promote cell growth or death. Many instances demonstrate an important direct role of ROS in development because redox status regulates key transcription factors that influence cell signaling pathways involved in proliferation, differentiation, and apoptosis. Therefore, oxidative stress can alter many important reactions that affect embryonic development both positively and negatively. During particular periods in development, the embryo is more or less susceptible to oxidative stress, and teratogens, which can modify redox status, such as thalidomide, phenytoin, and ethanol, will disrupt fetal development. Various events in pregnancy such as diabetes also alter the redox state. Fortunately, antioxidants can obviate these effects through modification of gene expression, transcription factor signaling, and cell cycle alterations. A better understanding of ROS-mediated reactions and their impact on embryonic development is important to ensure optimal outcomes.

Oxidative stress induces extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase in cystic fibrosis lung epithelial cells: Potential mechanism for excessive IL-8 expression

Cystic fibrosis (CF) is a lethal disease caused by defective function of the cftr gene product, the CF transmembrane conductance regulator (CFTR) that leads to oxidative damage and excessive inflammatory response in lungs of CF patients. We here report the effects of oxidative stress (hyperoxia, 95% O(2)) on the expression of pro-inflammatory interleukin (IL)-8 and CXCR1/2 receptors in two human CF lung epithelial cell lines (IB3-1, with the heterozygous F508del/W1282X mutation and CFBE41o- with the homozygous F508del/F508del mutation) and two control non-CF lung epithelial cell lines (S9 cell line derived from IB3-1 after correction with wtCFTR and the normal bronchial cell line 16HBE14o-). Under oxidative stress, the expression of IL-8 and CXCR1/2 receptors was increased in CF, corrected and normal lung cell lines. The effects of oxidative stress were also investigated by measuring the transcription nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1) activities. Under oxidative stress, no increase of NF-kappaB activation was observed in CF lung cells in contrast to that observed in normal and corrected CF lung cells. The signalling of mitogen-activated protein (MAP) kinases was further studied. We demonstrated that extracellular signal-regulated kinase (ERK1/2) and AP-1 activity was markedly enhanced in CF but not non-CF lung cells under oxidative stress. Consistently, inhibition of ERK1/2 in oxidative stress-exposed CF lung cells strongly decreased both the IL-8 production and CXCR1/2 expression. Therefore, targeting of ERK1/2 MAP kinase may be critical to reduce oxidative stress-mediated inflammation in lungs of CF patients.

Heme oxygenase-1 protein localizes to the nucleus and activates transcription factors important in oxidative stress

Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme degradation, is an integral membrane protein of the smooth endoplasmic reticulum. However, we detected an HO-1 immunoreactive signal in the nucleus of cultured cells after exposure to hypoxia and heme or heme/hemopexin. Under these conditions, a faster migrating HO-1 immunoreactive band was enriched in nuclear extracts, suggesting that HO-1 was cleaved to allow nuclear entry. This was confirmed by the absence of immunoreactive signal with an antibody against the C terminus and the lack of a C-terminal sequence by gas chromatographymass spectrometry. Incubation with leptomycin B prior to hypoxia abolished nuclear HO-1 and the faster migrating band on Western analysis, suggesting that this process was facilitated by CRM1. Furthermore, preincubation with a cysteine protease inhibitor prevented nuclear entry of green fluorescent protein-labeled HO-1, demonstrating that protease-mediated C-terminal cleavage was also necessary for nuclear transport of HO-1. Nuclear localization was also associated with reduction of HO activity. HO-1 protein, whether it was enzymatically active or not, mediated activation of oxidant-responsive transcription factors, including activator protein-1. Nevertheless, nuclear HO-1 protected cells against hydrogen peroxide-mediated injury equally as well as cytoplasmic HO-1. We speculate that nuclear localization of HO-1 protein may serve to up-regulate genes that promote cytoprotection against oxidative stress.

The impact of hyperoxia on the neonatal and adult developing dendritic cell

Oxygen is essential therapy for neonates with acute respiratory failure, including those with infections. However, high oxygen levels may be counterproductive for overcoming infections because hyperoxia may kill cells, including dendritic cells that are essential to the emergence of the pulmonary immune system and pivotal in mounting immune responses to infections. We studied the impact of hyperoxia on developing dendritic cells from neonatal cord blood and adult blood monocytes, comparing viability, development of maturation, and endocytic function. Our data suggest that cord blood-derived dendritic cells may be more resistant to hyperoxic-induced cell death than adult blood-derived cells. Moreover, the surviving cells in either group are those that maintain an immature phenotype. This may impair their ability to perform optimal immune function.

Poly(ADP-ribose) polymerase-1 (PARP-1) controls lung cell proliferation and repair after hyperoxia-induced lung damage

Oxygen-based therapies expose lung to elevated levels of ROS and induce lung cell damage and inflammation. Injured cells are replaced through increased proliferation and differentiation of epithelial cells and fibroblasts. Failure to modulate these processes leads to excessive cell proliferation, collagen deposition, fibrosis, and chronic lung disease. Poly(ADP-ribose) polymerase-1 (PARP-1) is activated in response to DNA damage and participates in DNA repair, genomic integrity, and cell death. In this study, we evaluated the role of PARP-1 in lung repair during recovery after acute hyperoxia exposure. We exposed PARP-1 -/- and wild-type mice for 64 h to 100% hyperoxia and let them recover in air for 5-21 days. PARP-1-deficient mice exhibited significantly higher lung cell hyperplasia and proliferation than PARP-1 +/+ animals after 5 and 10 days of recovery. This was accompanied by an increased inflammatory response in PARP-1 -/- compared with wild-type animals, characterized by neutrophil infiltration and increased IL-6 levels in bronchoalveolar lavages. These lesions were reversible, since the extent of the hyperplastic regions was reduced after 21 days of recovery and did not result in fibrosis. In vitro, lung primary fibroblasts derived from PARP-1 -/- mice showed a higher proliferative response than PARP-1 +/+ cells during air recovery after hyperoxia-induced growth arrest. Altogether, these results reveal an essential role of PARP-1 in the control of cell repair and tissue remodeling after hyperoxia-induced lung injury.

Antioxidants improve antibacterial function in hyperoxia-exposed macrophages

Hyperoxia and pulmonary infections are well known to increase the risk of acute and chronic lung injury in newborn infants, but it is not clear whether hyperoxia directly increases the risk of pneumonia. The purpose of this study was to examine: (1) the effects of hyperoxia and antioxidant enzymes on inflammation and bacterial clearance in mononuclear cells and (2) developmental differences between adult and neonatal mononuclear cells in response to hyperoxia. Mouse macrophages were exposed to either room air or 95% O2 for 24 h and then incubated with Pseudomonas aeruginosa. After 1 h, bacterial adherence, phagocytosis, and macrophage inflammatory protein (MIP)-1alpha production were analyzed. Bacterial adherence increased 5.8-fold (p < 0.0001), phagocytosis decreased 60% (p < 0.05), and MIP-1alpha production increased 49% (p < 0.05) in response to hyperoxia. Overexpression of MnSOD or catalase significantly decreased bacterial adherence by 30.5%, but only MnSOD significantly improved bacterial phagocytosis and attenuated MIP-1alpha production. When monocytes from newborns and adults were exposed to hyperoxia, phagocytosis was impaired in both groups. However, adult monocytes were significantly more impaired than neonatal monocytes. Data indicate that hyperoxia significantly increases bacterial adherence while impairing function of mononuclear cells, with adult cells being more impaired than neonatal cells. MnSOD reduces bacterial adherence and inflammation and improves bacterial phagocytosis in mononuclear cells in response to hyperoxia, which should minimize the development of oxidant-induced lung injury as well as reducing nosocomial infections.

Inhaled ethyl nitrite prevents hyperoxia-impaired postnatal alveolar development in newborn rats

RATIONALE

Inhaled nitric oxide (NO) has been used to prevent bronchopulmonary dysplasia, but with variable results. Ethyl nitrite (ENO) forms S-nitrosothiols more readily than does NO, and resists higher-order nitrogen oxide formation. Because S-nitrosylation is a key pathway mediating many NO biological effects, treatment with inhaled ENO may better protect postnatal lung development from oxidative stress than NO.

OBJECTIVES

To compare inhaled NO and ENO on hyperoxia-impaired postnatal lung development.

METHODS

We treated newborn rats beginning at birth to air or 95% O(2) +/- 0.2-20.0 ppm ENO for 8 days, or to 10 ppm NO for 8 days. Pups treated with the optimum ENO dose, 10 ppm, and pups treated with 10 ppm NO were recovered in room air for 6 more days.

MEASUREMENTS AND MAIN RESULTS

ENO and NO partly prevented 95% O(2)-induced airway neutrophil influx in lavage, but ENO had a greater effect than did NO in prevention of lung myeloperoxidase accumulation, and in expression of cytokine-induced neutrophil chemoattractant-1. Treatment with 10 ppm ENO, but not NO, for 8 days followed by recovery in air for 6 days prevented 95% O(2)-induced impairments of body weight, lung compliance, and alveolar development.

CONCLUSIONS

Inhaled ENO conferred protection superior to inhaled NO against hyperoxia-induced inflammation. ENO prevented hyperoxia impairments of lung compliance and postnatal alveolar development in newborn rats.

Developmental differences in the responses of IL-6 and IL-13 transgenic mice exposed to hyperoxia

Our previous work has shown that adult mice with overexpression of IL-6 and IL-13 in the lung have enhanced survival in hyperoxia associated with reduced hyperoxia-induced lung injury and cell death. We hypothesized that there are developmental differences in these responses in the adult vs. the newborn (NB) animal, and these responses have clinical relevance in the human NB. We compared the responses to 100% O(2) of NB IL-6 and IL-13 transgenic mice with wild-type littermate controls by evaluating mortality, lung tissue TUNEL staining, and mRNA expression using RT-PCR. We used ELISA to measure IL-6 levels in tracheal aspirates from human neonates. Our results show that, in contrast to the cytoprotective effects in mature mice, IL-6 caused significantly increased mortality, DNA injury, caspases, cell death regulator and angiogenic factor expression in hyperoxia in the NB. Furthermore, tracheal aspirate levels of IL-6 were significantly increased in premature neonates with respiratory distress syndrome who had an adverse outcome (bronchopulmonary dysplasia/death). In contrast to the protective effects in adults, there was no survival advantage to the NB IL-13 mice in hyperoxia. These findings imply that caution should be exercised in extrapolating results from the adult to the NB.

Developmental expression of the receptor for advanced glycation end-products (RAGE) and its response to hyperoxia in the neonatal rat lung

Background

The receptor for advanced glycation end products (mRAGE) is associated with pathology in most tissues, while its soluble form (sRAGE) acts as a decoy receptor. The adult lung is unique in that it expresses high amounts of RAGE under normal conditions while other tissues express low amounts normally and up-regulate RAGE during pathologic processes. We sought to determine the regulation of the soluble and membrane isoforms of RAGE in the developing lung, and its expression under hyperoxic conditions in the neonatal lung.

Results

Fetal (E19), term, 4 day, 8 day and adult rat lung protein and mRNA were analyzed, as well as lungs from neonatal (0–24 hrs) 2 day and 8 day hyperoxic (95% O₂) exposed animals. mRAGE transcripts in the adult rat lung were 23% greater than in neonatal (0–24 hrs) lungs. On the protein level, rat adult mRAGE expression was 2.2-fold higher relative to neonatal mRAGE expression, and adult sRAGE protein expression was 2-fold higher compared to neonatal sRAGE. Fetal, term, 4 day and 8 day old rats had a steady increase in both membrane and sRAGE protein expression evaluated by Western Blot and immunohistochemistry. Newborn rats exposed to chronic hyperoxia showed significantly decreased total RAGE expression compared to room air controls.

Conclusion

Taken together, these data show that rat pulmonary RAGE expression increases with age beginning from birth, and interestingly, this increase is counteracted under hyperoxic conditions. These results support the emerging concept that RAGE plays a novel and homeostatic role in lung physiology.

Modulation of airway remodeling and airway inflammation by peroxisome proliferator-activated receptor gamma in a murine model of toluene diisocyanate-induced asthma

Toluene diisocyanate (TDI) is a leading cause of occupational asthma. Although considerable controversy remains regarding its pathogenesis, TDI-induced asthma is an inflammatory disease of the airways characterized by airway remodeling. Peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to play a critical role in the control of airway inflammatory responses. However, no data are available on the role of PPARgamma in TDI-induced asthma. We have used a mouse model for TDI-induced asthma to determine the effect of PPARgamma agonist, rosiglitazone, or pioglitazone, and PPARgamma on TDI-induced bronchial inflammation and airway remodeling. This study with the TDI-induced model of asthma revealed the following typical pathophysiological features: increased numbers of inflammatory cells of the airways, airway hyperresponsiveness, increased levels of Th2 cytokines (IL-4, IL-5, and IL-13), adhesion molecules (ICAM-1 and VCAM-1), chemokines (RANTES and eotaxin), TGF-beta1, and NF-kappaB in nuclear protein extracts. In addition, the mice exposed to TDI developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer, subepithelial collagen deposition, and increased airway mucus production. Administration of PPARgamma agonists or adenovirus carrying PPARgamma2 cDNA reduced the pathophysiological symptoms of asthma and decreased the increased levels of Th2 cytokines, adhesion molecules, chemokines, TGF-beta1, and NF-kappaB in nuclear protein extracts after TDI inhalation. In addition, inhibition of NF-kappaB activation decreased the increased levels of Th2 cytokines, adhesion molecules, chemokines, and TGF-beta1 after TDI inhalation. These findings demonstrate a protective role of PPARgamma in the pathogenesis of the TDI-induced asthma phenotype.

Nuclear factor-kappaB activation in neonatal mouse lung protects against lipopolysaccharide-induced inflammation

RATIONALE

Injurious agents often cause less severe injury in neonates as compared with adults.

OBJECTIVE

We hypothesized that maturational differences in lung inflammation induced by lipopolysaccharide (LPS) may be related to the nature of the nuclear factor (NF)-kappaB complex activated, and the profile of target genes expressed.

METHODS

Neonatal and adult mice were injected with intraperitoneal LPS. Lung inflammation was assessed by histology, and apoptosis was determined by TUNEL (terminal deoxynucleotidyl transferase UTP nick-end labeling). The expression of candidate inflammatory and apoptotic mediators was evaluated by quantitative real-time polymerase chain reaction and Western immunoblot.

RESULTS

Neonates demonstrated reduced inflammation and apoptosis, 24 hours after LPS exposure, as compared with adults. This difference was associated with persistent activation of NF-kappaB p65p50 heterodimers in the neonates in contrast to early, transient activation of p65p50 followed by sustained activation of p50p50 in the adults. Adults had increased expression of a panel of inflammatory and proapoptotic genes, and repression of antiapoptotic targets, whereas no significant changes in these mediators were observed in the neonates. Inhibition of NF-kappaB activity in the neonates decreased apoptosis, but heightened inflammation, with increased expression of the same inflammatory genes elevated in the adults. In contrast, inhibition of NF-kappaB in the adults resulted in partial suppression of the inflammatory response.

CONCLUSIONS

NF-kappaB activation in the neonatal lung is antiinflammatory, protecting against LPS-mediated lung inflammation by repressing similar inflammatory genes induced in the adult.

Single nucleotide polymorphisms of tumor necrosis factor-alpha and the susceptibility to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of infancy. A "New" BPD has been characterized in preterm infants that may begin in utero, and then progress post-natally, resulting in arrested lung development and alveolar hypoplasia. Foundations for this "New" BPD may be derived from pro-inflammatory genes including tumor necrosis factor-alpha (TNFalpha). The hypothesis of the current study is that single nucleotide polymorphisms (SNPs) of the pro-inflammatory TNFalpha gene place preterm infants at increased risk for BPD. Preterm infants (105 in number) with birthweights <or=1 kg, who survived to at least 36 weeks postmenstrual age (PMA) or discharge were enrolled into this study. They were stratified for BPD according to their need for supplemental oxygen at 28 days and at 36 weeks PMA (non-, mild-, moderate-, or severe-BPD). DNA was extracted from these infants and subjected to analyses for the TNFalpha SNPs: -1,031, -863, -857, -308, and -238. The PHASE software (version 2.1) was used to reconstruct haplotypes and estimate their frequencies within the study population. Differences in birth weight (P < 0.001) and gestational age (P < 0.001), but not in racial distribution between the groups were found. Haplotype-specific analysis revealed no significant association between BPD severity and any of the 5-marker common haplotypes with 10 or more copies in this study population. Additionally, no significant association was observed in any three SNP haplotypes at -1,031, -863, and -857, and two SNP haplotypes at -308 and -238. We observed no association between BPD severity and the five TNFalpha SNPs investigated.

Arsenic trioxide, a potent inhibitor of NF-kappaB, abrogates allergen-induced airway hyperresponsiveness and inflammation

Background

Overactivation of nuclear factor κB (NF-κB) orchestrates airway eosinophilia, but does not dampen airway hyperresponsiveness in asthma. NF-κB repression by arsenic trioxide (As₂O₃) contributes to apoptosis of eosinophils (EOS) in airways. Here we provide evidence that As₂O₃ abrogates allergen (OVA)-induced airway eosinophilia by modulating the expression of IκBα, an NF-κB inhibitory protein, and decreases the airway hyperresponsiveness.

Methods

Using a murine model of asthma, the airway hyperresponsiveness was conducted by barometric whole-body plethysmography. Airway eosinophilia, OVA-specific IgE in serum, and chemokine eotaxin and RANTES (regulated upon activation, normal T cell expressed and secreted) in bronchoalveolar lavage fluid were measured by lung histology, Diff-Quick staining, and ELISA. Chemokine-induced EOS chemotactic activity was evaluated using EOS chemotaxis assay. Electrophoretic mobility shift assay and Western blot analysis were performed to assess pulmonary NF-κB activation and IκBα expression, respectively.

Results

As₂O₃ attenuated the allergen-induced serum IgE, chemokine expression of eotaxin and RANTES, and the EOS recruitment in bronchoalveolar lavage fluid, which is associated with an increased IκBα expression as well as a decreased NF-κB activation. Also, As₂O₃ suppressed the chemotaxis of EOS dose-dependently in vitro. Additionally, As₂O₃ significantly ameliorated the allergen-driven airway hyperresponsiveness, the cardinal feature underlying asthma.

Conclusion

These findings demonstrate an essential role of NF-κB in airway eosinophilia, and illustrate a potential dissociation between airway inflammation and hyperresponsiveness. As₂O₃ likely exerts its broad anti-inflammatory effects by suppression of NF-κB activation through augmentation of IκBα expression in asthma.

S100A9-positive granulocytes and monocytes in lipopolysaccharide-induced anterior ocular inflammation

S100A9 is a pro-inflammatory protein expressed in infiltrating granulocytes and monocytes. We determined role of S100A9 in endotoxin (LPS)-induced uveitis (EIU) and keratitis in Wistar rats. Anti-S100A9 antibody decreased partially clinical scores, protein, and cells in the aqueous humor at 18-36 h, compared with the LPS group. S100A9-positive cells were expressed in the iris-ciliary body (ICB) and cornea at 24-48 h. Activated caspase-3 (related to apoptosis) and S100A9 co-expressed in ICB at 18-48 h after LPS injection. S100A9 was not expressed in ED2-positive cells in ICB. Dexamethasone (DEX) increased S100A9 mRNA and protein levels in the circulating blood leukocytes, but reduced S100A9 mRNA and protein levels in ICB after LPS injection. BAY 11-7085 (an inhibitor of I-kappaB phosphorylation) suppressed S100A9 mRNA in leukocytes (43.5%) and ICB (68.5%), respectively, after LPS injection. It is possible that S100A9-positive granulocytes and monocyte/macrophages may play a role in the late phase of EIU and keratitis that DEX may inhibit the migration of S100A9-positive granulocytes and monocytes from the blood into the extravascular tissues, and that nuclear factor (NF)-kappaB pathway may be involved in S100A9 expression. S100A9 could play a role in the clearance of inflammatory cells at the late phase of EIU.

Cysteinyl leukotriene upregulates IL-11 expression in allergic airway disease of mice

BACKGROUND

Chronic airway inflammation and airway remodeling are important features of bronchial asthma. IL-11 is one of the important mediators involved in the process of airway inflammation and remodeling. Cysteinyl leukotrienes (cysLTs) play roles in recruitment of inflammatory cells, airway smooth muscle contraction, vascular leakage, increased mucus secretion, decreased mucociliary clearance, and airway fibrosis.

OBJECTIVE

An aim of the present study was to determine the effect of the cysLTs on the regulation of IL-11 expression.

METHODS

We used a C57BL/6 mouse model of allergic airway disease and murine tracheal epithelial cells to examine the effects of cysLTs on the regulation of IL-11 expression.

RESULTS

Our present study with an ovalbumin-induced murine model of allergic airway disease revealed that levels of leukotriene C(4) (LTC(4)) in bronchoalveolar lavage fluids were increased and that administration of montelukast or pranlukast reduced the increased levels of LTC(4); the increased expression of IL-11 protein and mRNA in lung tissues; airway inflammation, bronchial hyperresponsiveness; the increased levels of TGF-beta(1), IL-4, and IL-13 in bronchoalveolar lavage fluids and lung tissues; and airway fibrosis. In addition, LTC(4) stimulates epithelial cells to produce IL-11. Our results also showed that cysLT type 1 receptor antagonists downregulated the activity of a transcription factor, nuclear factor kappaB, and BAY 11-7085 substantially reduced the increased levels of IL-11 after ovalbumin inhalation.

CONCLUSION

These results suggest that cysLTs regulate the IL-11 expression in allergic airway disease.

CLINICAL IMPLICATIONS

These findings provide one of the molecular mechanisms for the effects of cysLTs on airway inflammation and fibrosis in allergic airway diseases.

Antioxidant down-regulates interleukin-18 expression in asthma

An alteration in the balance between a T-helper type 2 cell (Th2) response and a Th1 response may predispose to the development of bronchial asthma. Interleukin-18 (IL-18) has an ability to promote both Th1 and Th2 responses, depending on the surrounding cytokine environment. Reactive oxygen species (ROS) play a crucial role in the pathogenesis of airway inflammation and hyperresponsiveness. Recent studies have demonstrated that antioxidants are able to reduce airway inflammation and hyperreactivity in animal models of asthma. In this study, we used a C57BL/6 mouse model of allergic asthma to examine the effects of antioxidants on the regulation of IL-18 expression. Our present study with ovalbumin-induced murine model of asthma revealed that ROS production in cells from bronchoalveolar lavage fluids was increased and that administration of L-2-oxothiazolidine-4-carboxylic acid or alpha-lipoic acid reduced the increased levels of ROS, the increased expression of IL-18 protein and mRNA, airway inflammation, and bronchial hyperresponsiveness. Our results also showed that antioxidants down-regulated a transcription factor, nuclear factor-kappaB (NF-kappaB), activity. These results indicate that antioxidants may reduce IL-18 expression in asthma by inhibiting the activity of NF-kappaB and suggest that ROS regulate the IL-18 expression.

An osteopontin-NADPH oxidase signaling cascade promotes pro-matrix metalloproteinase 9 activation in aortic mesenchymal cells

Osteopontin (OPN) is a cytokine upregulated in diabetic vascular disease. To better understand its role in vascular remodeling, we assessed how OPN controls metalloproteinase (MMP) activation in aortic adventitial myofibroblasts (AMFs) and A7r5 vascular smooth muscle cells (VSMCs). By zymography, OPN and tumor necrosis factor (TNF)-alpha preferentially upregulate pro-matrix metalloproteinase 9 (pro-MMP9) activity. TNF-alpha upregulated pro-MMP9 in AMFs isolated from wild-type (OPN(+/+)) mice, but pro-MMP9 induction was abrogated in AMFs from OPN(-/-) mice. OPN treatment of VSMCs enhanced pro-MMP9 activity, and TNF-alpha induction of pro-MMP9 was inhibited by anti-OPN antibody and apocynin. Superoxide and the oxylipid product 8-isoprostaglandin F(2) alpha-isoprostane (8-IsoP) were increased by OPN treatment, and anti-OPN antibody suppressed 8-IsoP production. Like OPN and TNF-alpha, 8-IsoP preferentially activated pro-MMP9. Superoxide, 8-IsoP, and NADPH oxidase 2 (Nox2) subunits were reduced in OPN(-/-) AMFs. Treatment of A7r5 VSMCs with OPN upregulated NADPH oxidase subunit accumulation. OPN structure/function studies mapped these activities to the SVVYGLR heptapeptide motif in the thrombin-liberated human OPN N-terminal domain (SLAYGLR in mouse OPN). Treatment of aortic VSMCs with SVVYGLR upregulated pro-MMP9 activity and restored TNF-alpha activation of pro-MMP9 in OPN(-/-) AMFs. Injection of OPN-deficient OPN(+/-) mice with SVVYGLR peptide upregulated pro-MMP9 activity, 8-IsoP levels, and Nox2 protein levels in aorta and increased panmural superoxide production (dihydroethidium staining). At equivalent hyperglycemia and dyslipidemia, 8-IsoP levels and aortic pro-MMP9 were reduced with complete OPN deficiency in a model of diet-induced diabetes, achieved by comparing OPN(-/-)/LDLR(-/-) versus OPN(+/-)/LDLR(-/-) siblings. Thus, OPN provides a paracrine signal that augments vascular pro-MMP9 activity, mediated in part via superoxide generation and oxylipid formation.

Oxidative stress response results in increased p21WAF1/CIP1 degradation in cystic fibrosis lung epithelial cells

Lung epithelium in cystic fibrosis (CF) patients is characterized by structural damage and altered repair due to oxidative stress. To gain insight into the oxidative stress-related damage in CF, we studied the effects of hyperoxia in CF and normal lung epithelial cell lines. In response to a 95% O2 exposure, both cell lines exhibited increased reactive oxygen species. Unexpectedly, the cyclin-dependent kinase inhibitor p21WAF1/CIP1 protein was undetectable in CF cells under hyperoxia, contrasting with increased levels of p21WAF1/CIP1 in normal cells. In both cell lines, exposure to hyperoxia led to S-phase arrest. Apoptotic features including nuclear condensation, DNA laddering, Annexin V incorporation, and elevated caspase-3 activity were not readily observed in CF cells in contrast to normal cells. Interestingly, treatment of hyperoxia-exposed CF cells with two proteasome inhibitors, MG132 and lactacystin, restored p21WAF1/CIP1 protein and was associated with an increase of caspase-3 activity. Moreover, transfection of p21WAF1/CIP1 protein in CF cells led to increased caspase-3 activity and was associated with increased apoptotic cell death, specifically under hyperoxia. Taken together, our data suggest that modulating p21WAF1/CIP1 degradation may have the therapeutic potential of reducing lung epithelial damage related to oxidative stress in CF patients.

Cutting edge: TLR4 deficiency confers susceptibility to lethal oxidant lung injury

TLRs have been studied extensively in pathogen-mediated host responses. We use a murine model of lethal oxidant-mediated injury to demonstrate for the first time that mammalian TLR4 is required for survival and lung integrity. Administering high levels of inspired oxygen, or hyperoxia, is commonly used as a life-sustaining measure in critically ill patients. However, prolonged exposures can lead to respiratory failure and death. TLR4-deficient mice exhibited increased mortality and lung injury during hyperoxia. The enhanced susceptibility of TLR4-deficient mice to hyperoxia was associated with an inability to up-regulate Bcl-2 and phospho-Akt. Restoration of Bcl-2 and phospho-Akt levels by the exogenous transfer of the antioxidant gene heme oxygenase-1 markedly attenuated hyperoxia-induced injury, apoptosis, and mortality in TLR4-deficient mice. Taken together, our results suggest a protective role of TLR4 in oxidant-mediated injury, providing novel mechanistic links among innate immunity, oxidant stress, and apoptosis.