Lack of the receptor for advanced glycation end-products attenuates E. coli pneumonia in mice

Background

The receptor for advanced glycation end-products (RAGE) has been suggested to modulate lung injury in models of acute pulmonary inflammation. To study this further, model systems utilizing wild type and RAGE knockout (KO) mice were used to determine the role of RAGE signaling in lipopolysaccharide (LPS) and E. coli induced acute pulmonary inflammation. The effect of intraperitoneal (i.p.) and intratracheal (i.t.) administration of mouse soluble RAGE on E. coli injury was also investigated.

Methodology/Principal Findings

C57BL/6 wild type and RAGE KO mice received an i.t. instillation of LPS, E. coli, or vehicle control. Some groups also received i.p. or i.t. administration of mouse soluble RAGE. After 24 hours, the role of RAGE expression on inflammation was assessed by comparing responses in wild type and RAGE KO. RAGE protein levels decreased in wild type lung homogenates after treatment with either LPS or bacteria. In addition, soluble RAGE and HMGB1 increased in the BALF after E. coli instillation. RAGE KO mice challenged with LPS had the same degree of inflammation as wild type mice. However, when challenged with E. coli, RAGE KO mice had significantly less inflammation when compared to wild type mice. Most cytokine levels were lower in the BALF of RAGE KO mice compared to wild type mice after E. coli injury, while only monocyte chemotactic protein-1, MCP-1, was lower after LPS challenge. Neither i.p. nor i.t. administration of mouse soluble RAGE attenuated the severity of E. coli injury in wild type mice.

Conclusions/Significance

Lack of RAGE in the lung does not protect against LPS induced acute pulmonary inflammation, but attenuates injury following live E. coli challenge. These findings suggest that RAGE mediates responses to E. coli-associated pathogen-associated molecular pattern molecules other than LPS or other bacterial specific signaling responses. Soluble RAGE treatment had no effect on inflammation.     

Pulmonary gemcitabine delivery for treating lung cancer: pharmacokinetics and acute lung injury aspects in animals

Gemcitabine, a nucleoside analogue for treating lung cancer, is clinically administered as an intravenous infusion. To achieve better patient compliance and more direct effect on the lung, we explored a new gemcitabine pulmonary delivery route and evaluated the pharmacokinetics and acute lung injury aspects in animals. Pharmacokinetics of gemcitabine were measured in Sprague-Dawley rats after intravenous (i.v.), intratracheal instillation by tracheotomy (i.t.t.), intratracheal instillation via orotrachea (i.t.o.), and intragastric (i.g.) administration of gemcitabine. Acute lung injury effects of the pulmonary delivery of gemcitabine were performed in Sprague-Dawley rats after i.t.o. and i.v. administration of gemcitabine and i.t.o. administration of lipopolysaccharide (LPS) as a positive control and physiological saline as a blank control. Indicators for acute lung injury that were evaluated included lung morphology, lung histopathology, lung coefficient, lung wet/dry weight ratio, total cell and classification counts in bronchoalveolar lavage cells (BALC), and total protein and TNF-alpha levels in bronchoalveolar lavage fluids (BALF). After i.t.t. or i.t.o. administration, gemcitabine was quickly absorbed, but i.g. administration led to an undetectable plasma gemcitabine concentration. Absolute bioavailability of gemcitabine after i.t.t. and i.t.o. administration was 91% and 65%, respectively. Gemcitabine given as i.t.o. administration did not cause any overt acute lung injury. All indicators for acute lung injury in the i.t.o. group were similar to those in the i.v. group or in the blank control, but significantly different from those in the positive control. In conclusion, the pharmacokinetics and acute lung injury studies suggest that pulmonary gemcitabine delivery would be a new and promising administration route.     

Inflammatory-induced hibernation in the fetus: priming of fetal sheep metabolism correlates with developmental brain injury

Prenatal inflammation is considered an important factor contributing to preterm birth and neonatal mortality and morbidity. The impact of prenatal inflammation on fetal bioenergetic status and the correlation of specific metabolites to inflammatory-induced developmental brain injury are unknown. We used a global metabolomics approach to examine plasma metabolites differentially regulated by intrauterine inflammation. Preterm-equivalent sheep fetuses were randomized to i.v. bolus infusion of either saline-vehicle or LPS. Blood samples were collected at baseline 2 h, 6 h and daily up to 10 days for metabolite quantification. Animals were killed at 10 days after LPS injection, and brain injury was assessed by histopathology. We detected both acute and delayed effects of LPS on fetal metabolism, with a long-term down-regulation of fetal energy metabolism. Within the first 3 days after LPS, 121 metabolites were up-regulated or down-regulated. A transient phase (4-6 days), in which metabolite levels recovered to baseline, was followed by a second phase marked by an opposing down-regulation of energy metabolites, increased pO(2) and increased markers of inflammation and ADMA. The characteristics of the metabolite response to LPS in these two phases, defined as 2 h to 2 days and at 6-9 days, respectively, were strongly correlated with white and grey matter volumes at 10 days recovery. Based on these results we propose a novel concept of inflammatory-induced hibernation of the fetus. Inflammatory priming of fetal metabolism correlated with measures of brain injury, suggesting potential for future biomarker research and the identification of therapeutic targets.     

Adrenomedullin ameliorates lipopolysaccharide-induced acute lung injury in rats

Adrenomedullin (AM), an endogenous peptide, has been shown to have a variety of protective effects on the cardiovascular system. However, the effect of AM on acute lung injury remains unknown. Accordingly, we investigated whether AM infusion ameliorates lipopolysaccharide (LPS)-induced acute lung injury in rats. Rats were randomized to receive continuous intravenous infusion of AM (0.1 microg x kg(-1) x min(-1)) or vehicle through a microosmotic pump. The animals were intratracheally injected with either LPS (1 mg/kg) or saline. At 6 and 18 h after intratracheal instillation, we performed histological examination and bronchoalveolar lavage and assessed the lung wet/dry weight ratio as an index of acute lung injury. Then we measured the numbers of total cells and neutrophils and the levels of tumor necrosis factor (TNF)-alpha and cytokine-induced neutrophil chemoattractant (CINC) in bronchoalveolar lavage fluid (BALF). In addition, we evaluated BALF total protein and albumin levels as indexes of lung permeability. LPS instillation caused severe acute lung injury, as indicated by the histological findings and the lung wet/dry weight ratio. However, AM infusion attenuated these LPS-induced abnormalities. AM decreased the numbers of total cells and neutrophils and the levels of TNF-alpha and CINC in BALF. AM also reduced BALF total protein and albumin levels. In addition, AM significantly suppressed apoptosis of alveolar wall cells as indicated by cleaved caspase-3 staining. In conclusion, continuous infusion of AM ameliorated LPS-induced acute lung injury in rats. This beneficial effect of AM on acute lung injury may be mediated by inhibition of inflammation, hyperpermeability, and alveolar wall cell apoptosis.     

Interaction of P-selectin and PSGL-1 generates microparticles that correct hemostasis in a mouse model of hemophilia A

High plasma levels of soluble P-selectin are associated with thrombotic disorders and may predict future cardiovascular events. Mice with high levels of soluble P-selectin have more microparticles in their plasma than do normal mice. Here we show that chimeras of P-selectin and immunoglobulin (P-sel-Ig) induced formation of procoagulant microparticles in human blood through P-selectin glycoprotein ligand-1 (PSGL-1; encoded by the Psgl1 gene, officially known as Selpl). In addition, Psgl1-/- mice produced fewer microparticles after P-sel-Ig infusion and did not spontaneously increase their microparticle count in old age as do wild-type mice. Injected microparticles specifically bound to thrombi and thus could be involved in thrombin generation at sites of injury. Infusion of P-sel-Ig into hemophilia A mice produced a 20-fold increase over control immunoglobulin in microparticles containing tissue factor. This significantly improved the kinetics of fibrin formation in the hemophilia A mice and normalized their tail-bleeding time. P-sel-Ig treatment could become a new approach to sustained control of bleeding in hemophilia.     

Peripheral inflammation increases seizure susceptibility via the induction of neuroinflammation and oxidative stress in the hippocampus

Background

Neuroinflammation with activation of microglia and production of proinflammatory cytokines in the brain plays an active role in epileptic disorders. Brain oxidative stress has also been implicated in the pathogenesis of epilepsy. Damage in the hippocampus is associated with temporal lobe epilepsy, a common form of epilepsy in human. Peripheral inflammation may exacerbate neuroinflammation and brain oxidative stress. This study examined the impact of peripheral inflammation on seizure susceptibility and the involvement of neuroinflammation and oxidative stress in the hippocampus.

Results

In male, adult Sprague-Dawley rats, peripheral inflammation was induced by the infusion of Escherichia coli lipopolysaccharide (LPS, 2.5 mg/kg/day) into the peritoneal cavity for 7 days via an osmotic minipump. Pharmacological agents were delivered via intracerebroventricular (i.c.v.) infusion with an osmotic minipump. The level of cytokine in plasma or hippocampus was analyzed by ELISA. Redox-related protein expression in hippocampus was evaluated by Western blot. Seizure susceptibility was tested by intraperitoneal (i.p.)  injection of kainic acid (KA, 10 mg/kg). We found that i.p. infusion of LPS for 7 days induced peripheral inflammation characterized by the increases in plasma levels of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). This is associated with a significant increase in number of the activated microglia (Iba-1⁺ cells), enhanced production of proinflammatory cytokines (including IL-1β, IL-6 and TNF-α), and tissue oxidative stress (upregulations of the NADPH oxidase subunits) in the hippocampus. These cellular and molecular responses to peripheral inflammation were notably blunted by i.c.v. infusion of a cycloxygenase-2 inhibitor, NS398 (5 μg/μl/h). The i.c.v. infusion of tempol (2.5 μg/μl/h), a reactive oxygen species scavenger, protected the hippocampus from oxidative damage with no apparent effect on microglia activation or cytokine production after peripheral inflammation. In the KA-induced seizure model, i.c.v. infusion of both NS398 and tempol ameliorated the increase in seizure susceptibility in animals succumbed to the LPS-induced peripheral inflammation.

Conclusions

Together these results indicated that LPS-induced peripheral inflammation evoked neuroinflammation and the subsequent oxidative stress in the hippocampus, resulting in the increase in KA-induced seizure susceptibility. Moreover, protection from neuroinflammation and oxidative stress in the hippocampus exerted beneficial effect on seizure susceptibility following peripheral inflammation.     

Effect of lipopolysaccharide on C3 and C5 production by human lung cells

Although studies to date have demonstrated the ability of the monocyte/macrophage to produce C components in vitro, very few studies on C production by nonhepatic tissue cells have been reported. Recently, using 35S-methionine incorporation and immunoprecipitation techniques our laboratory has demonstrated the ability of tissue cells, i.e., the human lung type II pneumocyte (A549) and human lung fibroblast (WI-38), to synthesize and secrete a variety of early and terminal complement components, as well as several regulatory proteins in vitro, i.e., C1r, C1s, C4, C3, C5, C6, C7, C8, C9, factor B, factor H, factor I, and C1s inactivator. In our studies, we extended these observations by demonstrating the capability of LPS to modulate C3 production by A549 pneumocytes. Specifically, using a sensitive ELISA we demonstrated that A549 pneumocytes exposed to LPS induced an 80 to 180% increase in C3 levels when compared to untreated A549 cells. Interestingly, LPS had no effect on C5 production or total protein synthesis by A549 pneumocytes. In the case of the WI-38 fibroblast, LPS had no effect on 1) C3 production, 2) C5 production, or 3) total protein synthesis in vitro. These studies demonstrate that agents such as LPS have the potential to selectively regulate C production (i.e., C3) in individual lung cells in vitro, and suggests that in vivo LPS may alter the local tissue reservoir of C components during infection and lung injury, thus impacting on pulmonary inflammation and host defense.     

Systemic complement activation and acute lung injury

Experimental studies of rats have provided significant evidence that intravascular complement activation after i.v. injection of cobra venom factor (CVF) or thermal injury of skin can result in acute lung injury. This has been determined by morphological changes in lung and increases in lung vascular permeability. Systemic complement activation is associated with an early appearance of C5-derived chemotactic activity in the circulation coincident with the development of transient neutropenia, followed by extensive granulocytosis and sequestration of neutrophils in lung interstitial capillaries. The acute pulmonary injury depends on availability of complement and neutrophils. Depletion of either complement or blood neutrophils before CVF injection or thermal injury will prevent development of lung injury. Interventional studies with catalase, scavengers of hydroxyl radical OH., and iron chelators have revealed that the acute pulmonary injury is related to production of oxygen-derived free radicals by activated neutrophils. OH. appears to be the key mediator involved in the acute lung microvascular injury.     

Effect of sulfatide on acute lung injury during endotoxemia in rats

Experimental studies have shown that intrapulmonary leukocyte sequestration and activation is implicated in the pathogenesis of acute lung injury during endotoxemia. Selectins are involved in the adhesion of leukocyte to the endothelium. Sulfatide is recognized by P selectin and blocks this adhesion molecule. We studied the effects of sulfatide on endotoxin-induced lung damage in rats. Endotoxin shock was produced in male rats by a single intravenous (i.v.) injection of 20 mg/kg of Salmonella enteritidis lipopolysaccharide (LPS). LPS administration reduced survival rate (0%, 72 h after endotoxin challenge) decreased mean arterial blood pressure (MAP), produced leukopenia (Controls = 11,234+/-231 cells/mL, LPS = 4,567+/-123 cells/mL) and increased lung myeloperoxidase activity (MPO; a marker of leukocyte accumulation) in the lung (Controls = 0.35+/-0.1 U/g/tissue; LPS = 10+/-1.2 U/g/tissue). Furthermore LPS administration markedly impaired the concentration-response curves for acetylcholine and sodium nitroprusside in isolated pulmonary arterial rings. There was also an increased staining for P-selectin in the pulmonary arteries. Sulfatide treatment (10 mg/kg, 30 min. after LPS challenge), significantly protected against LPS-induced lethality (90% survival rate and 70% survival rate 24 h and 72 h after LPS injection), reduced LPS induced hypotension, reverted leukopenia (8,895+/-234 cells/ml) and lowered lung MPO activity (1.7+/-0.9 U/g/tissue). Furthermore sulfatide restored to control values the LPS-induced impairment in arterial pulmonary vasorelaxation and reduced P-selectin immunostaining. Our data indicate that sulfatide attenuates LPS-induced lung injury and protects against endotoxin shock.     

Duration and intensity of NF-kappaB activity determine the severity of endotoxin-induced acute lung injury

Activation of innate immunity in the lungs can lead to a self-limited inflammatory response or progress to severe lung injury. We investigated whether specific parameters of NF-kappaB pathway activation determine the outcome of acute lung inflammation using a novel line of transgenic reporter mice. Following a single i.p. injection of Escherichia coli LPS, transient NF-kappaB activation was identified in a variety of lung cell types, and neutrophilic inflammation resolved without substantial tissue injury. However, administration of LPS over 24 h by osmotic pump (LPS pump) implanted into the peritoneum resulted in sustained, widespread NF-kappaB activation and neutrophilic inflammation that culminated in lung injury at 48 h. To determine whether intervention in the NF-kappaB pathway could prevent progression to lung injury in the LPS pump model, we administered a specific IkappaB kinase inhibitor (BMS-345541) to down-regulate NF-kappaB activation following the onset of inflammation. Treatment with BMS-345541 beginning at 20 h after osmotic pump implantation reduced lung NF-kappaB activation, concentration of KC and MIP-2 in lung lavage, neutrophil influx, and lung edema measured at 48 h. Therefore, sustained NF-kappaB activation correlates with severity of lung injury, and interdiction in the NF-kappaB pathway is beneficial even after the onset of lung inflammation.     

Cutting edge: expression patterns of surface and soluble triggering receptor expressed on myeloid cells-1 in human endotoxemia

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a recently identified molecule involved in the amplification of inflammation. To determine the regulation of TREM-1, we studied TREM-1 expression and soluble TREM-1 plasma levels upon i.v. LPS challenge in healthy humans in vivo and in vitro. Granulocyte TREM-1 expression was high at baseline and immediately down-regulated upon LPS exposure along with an increase in soluble TREM-1. Monocytes displayed a gradual up-regulation of TREM-1 upon LPS in vivo and in vitro. In vitro studies extended these findings to highly purified lipoteichoic acid and Streptococcus pneumoniae. Nonbacterial TLR ligands such as polyinosine-polycytidylic acid and imidazoquinoline, as well as the TLR9 ligand CpG, did not impact TREM-1 expression. The LPS-induced alterations in TREM-1 surface expression were not a result of increased TNF-alpha or IL-10. Inhibitor studies disclosed a PI3K-dependent pathway in LPS-induced up-regulation of TREM-1 on monocytes, whereas MAPK played a limited role.     

Lung injury and complement activation: Role of neutrophils and xanthine oxidase

Evidence is presented that oxygen products generated from xanthine oxidase (XO) may also be involved in the pathogenesis of neutrophil-mediate lung injury following intravascular activation of complement with cobra venom factor (CVF). CVF injection in rats resulted a rapid increase in plasma of both XO activity (but not xanthine dehydrogenase) and its reaction product, uric acid. These changes were greatly attenuated in allopurinol-treated animals. The apperance of XO activity was paralleled by a raise in plasma of histamine. Prevention of histamine release by pretreatment of rats withy cromolyn abolished both the rise in plasma histamine and the increase in XO activity. Since we have previously shown that histamine can enhance XO activity in vitro and in vivo (Am. J. Pathol. 135:203, 1989), these observations suggest that the increase in plasma XO activity following CVF injection is related to the appearance in plasma of histamine. Accordingly, pretreatment of rats with xanthine oxidase inhibitors (allopurinol, lodoxamine) or prevention of histamine release by pretreatment with cromolyn significantly attenuated development of lung injury following injection of CVF. Our data support the concept that oxygen radicals derived from both neutrophils and XO are playing a role in the CVF-induced acute lung injury.     

Development of an immunopredictor for the evaluation of the risk of cardiovascular diseases based on the level of soluble P-selectin

Due to its physiologic role in modulating adhesive interactions between blood cells and the endothelium during inflammatory processes or at injury sites, the adhesion molecule P-selectin is of great interest. The level of soluble P-selectin in plasma or serum can be detected and used as a clinical predictor for adverse cardiovascular events, leading to the presumption that it is secreted, shed or cleaved from the cell membrane during the process of diseases. Increased levels of soluble P-selectin in the plasma have been shown to be associated with a range of cardiovascular disorders, including coronary artery disease, hypertension and atrial fibrillation. Therefore, it is of huge significance to develop simple, rapid and sensitive methods for the detection of such pathological predictors, not only for facilitating the surveillance of cardiovascular mortality/sudden cardiac death, but also for effectively monitoring the drug potency on platelets based on measurement of P-selectin performed on fixed blood samples following platelet stimulation in whole blood in a remote setting. We herein developed a simple, yet novel and sensitive electrochemical sandwich immunosensor for the detection of P-selectin; it operates through covalent linkage of anti-P-selectin antibody on CNT@GNB nanocomposites-modified disposable screen-printed electrode as the detection platform, with the potassium ferrocyanide-encapsulated, anti-P-selectin-tagged liposomal biolabels as the electrochemical signal probes. The immunorecognition of the sample P-selectin by the liposomal biolabels occurred on the surface of the electrodes; the release of potassium ferrocyanide from the bound liposomal biolabels extensively contributed to the increase in electrochemical signal, which was acquired in HCl solution at +0.32V in square wave voltammetry mode. The resulting sigmoidally shaped dose-response curves possessed a linear dynamic working range from 1×10(-13) to 1×10(-5)g/mL. This liposome-based electrochemical immunoassay provides an amplification approach for detecting P-selectin at trace levels, leading to a detection limit as low as 4.3fg (equivalent to 5μL of 0.85pg/mL solution). A commercially available ELISA kit was used as a reference method to validate the newly-developed assay through the analysis of mouse serum samples. A strong correlation was observed between the two data sets as the R-squared value of 0.997 from the linear regression line. This electrochemical immunosensor will be useful for the detection of P-selectin in biological fluids and tissue extracts.     

Important Role of Platelets in Modulating Endotoxin-Induced Lung Inflammation in CFTR-Deficient Mice

Mutation of CFTR (cystic fibrosis transmembrane conductance regulator) leads to cystic fibrosis (CF). Patients with CF develop abnormalities of blood platelets and recurrent lung inflammation. However, whether CFTR-mutated platelets play a role in the development of lung inflammation is elusive. Therefore, we intratracheally challenged wildtype and F508del (a common type of CFTR mutation) mice with LPS to observe changes of F508del platelets in the peripheral blood and indexes of lung inflammation (BAL neutrophils and protein levels). Furthermore, we investigated whether or not and how F508del platelets modulate the LPS-induced acute lung inflammation by targeting anti-platelet aggregation, depletion of neutrophils, reconstitution of bone marrow or neutrophils, blockade of P-selectin glycoprotein ligand-1 (PSGL-1), platelet activating factor (PAF), and correction of mutated CFTR trafficking. We found that LPS-challenged F508del mice developed severe thrombocytopenia and had higher levels of plasma TXB2 coincided with neutrophilic lung inflammation relative to wildtype control. Inhibition of F508del platelet aggregation or depletion of F508del neutrophils diminished the LPS-induced lung inflammation in the F508del mice. Moreover, wildtype mice reconstituted with either F508del bone marrow or neutrophils developed worse thrombocytopenia. Blocking PSGL-1, platelet activating factor (PAF), or rectifying trafficking of mutated CFTR in F508del mice diminished and alveolar neutrophil transmigration in the LPS-challenged F508del mice. These findings suggest that F508del platelets and their interaction with neutrophils are requisite for the development of LPS-induced lung inflammation and injury. As such, targeting platelets might be an emerging strategy for dampening recurrent lung inflammation in cystic fibrosis patients.     

Comparison between effects of dantrolene and nifedipine on lipopolysaccharide-induced endotoxemia in the anesthetized rats

Intracellular calcium is an important mediator for regulating the cellular response in endotoxemia. In this study, we investigated the effects of dantrolene and nifedipine, two agents of reducing intracellular calcium levels, on bacterial endotoxin (lipopolysaccharide, LPS; 10 mg/kg i.v.)-induced production of tumor necrosis factor-alpha (TNF-alpha) and nitric oxide (NO) as well as hemodynamic changes in the anesthetized rat. Injection of LPS (i) induced biphasic changes of blood glucose and rectal temperature: an initial increased phase (<180 min after injection of LPS) followed by a decreased phase (at 240 or 360 min), (ii) caused a significant fall in mean arterial blood pressure from 119+/-3 mmHg (at time 0) to 73+/-67 mmHg (at 360 min) with a concomitant increase of heart rate, (iii) resulted in a substantial hyporeactivity to norepinephrine (NE) (1 microg/kg i.v.), (iv) increased plasma nitrate (an indicator of NO formation) in a time-dependent manner, and (v) induced bell-shape changes in plasma TNF-alpha levels which reached a peak at 60 min. Pretreatment of animals with dantrolene (1 mg/kg i.v. at 20 min prior to LPS) or nifedipine (20 microg/kg i.v. infusion for 20 min at 20 min prior to LPS) not only attenuated the delayed circulatory failure (e.g. delayed hypotension and vascular hyporeactivity to NE), but also prevented the overproduction of NO caused by LPS in the rat. However, the prevention of NO overproduction by dantrolene, but not by nifedipine, was associated with an inhibition of TNF-alpha production elicited by LPS. Thus, both dantrolene and nifedipine have beneficial hemodynamic effects, although through different mechanisms, in animals with endotoxic shock.     

Pulmonary exposure to diesel exhaust particles enhances coagulatory disturbance with endothelial damage and systemic inflammation related to lung inflammation

Pulmonary exposure to diesel exhaust particles (DEP) enhances lung inflammation related to bacterial endotoxin (lipopolysaccharide [LPS]) in mice. Severe lung inflammation can reportedly induce coagulatory abnormalities and systemic inflammation. This study examined the effects of components of DEP on lung inflammation, pulmonary permeability, coagulatory changes, systemic inflammatory response, and lung-to-systemic translocation of LPS in a murine model of lung inflammation. ICR mice were divided into six experimental groups that intratracheally received vehicle, LPS (2.5 mg/kg), organic chemicals in DEP (DEP-OC; 4 mg/kg) extracted with dicloromethane), residual carbonaceous nuclei of DEP (washed DEP: 4 mg/kg), DEP-OC + LPS, or washed DEP + LPS. Both DEP components exacerbated lung inflammation, vascular permeability, and the increased fibrinogen and E-selectin levels induced by LPS. With overall trends, the exacerbation was more prominent with washed DEP than with DEP-OC. Washed DEP + LPS significantly decreased activated protein C and antithrombin-III and elevated circulatory levels of interleukin (IL)-6, keratinocyte chemoattractant (KC), and LPS as compared with LPS alone, whereas DEP-OC + LPS elevated IL-6, KC, and LPS without significance. These results show that DEP components, especially washed DEP, amplify the effects if LPS on the respiratory system and suggest that they contribute to the adverse health effects of particulate air pollution on the sensitive populations with predisposing vascular and/or pulmonary diseases, including ischemic vascular diseases and respiratory infection.     

Prostaglandins mediate the fetal pulmonary response to intrauterine inflammation

Intra-amniotic (IA) lipopolysaccharide (LPS) induces intrauterine and fetal lung inflammation and increases lung surfactant and compliance in preterm sheep; however, the mechanisms are unknown. Prostaglandins (PGs) are inflammatory mediators, and PGE(2) has established roles in fetal lung surfactant production. The aim of our first study was to determine PGE(2) concentrations in response to IA LPS and pulmonary gene expression for PG synthetic [prostaglandin H synthase-2 (PGHS-2) and PGE synthase (PGES)] and PG-metabolizing [prostaglandin dehydrogenase (PGDH)] enzymes and PGE(2) receptors. Our second study aimed to block LPS-induced increases in PGE(2) with a PGHS-2 inhibitor (nimesulide) and determine lung inflammation and surfactant protein mRNA expression. Pregnant ewes received an IA saline or LPS injection at 118 days of gestation. In study 1, fetal plasma and amniotic fluid were sampled before and at 2, 4, 6, 12, and 24 h after injection and then daily, and fetuses were delivered 2 or 7 days later. Amniotic fluid PGE(2) concentrations increased (P < 0.05) 12 h and 3-6 days after LPS. Fetal lung PGHS-2 mRNA and PGES mRNA increased 2 (P = 0.0084) and 7 (P = 0.014) days after LPS, respectively. In study 2, maternal intravenous nimesulide or vehicle infusion began immediately before LPS or saline injection and continued until delivery 2 days later. Nimesulide inhibited LPS-induced increases in PGE(2) and decreased fetal lung IL-1β and IL-8 mRNA (P ≤ 0.002) without altering lung inflammatory cell infiltration. Nimesulide decreased surfactant protein (SP)-A (P = 0.05), -B (P = 0.05), and -D (P = 0.0015) but increased SP-C mRNA (P = 0.023). Thus PGHS-2 mediates, at least in part, fetal pulmonary responses to inflammation.     

Angiogenic growth factors in the pathophysiology of a murine model of acute lung injury

Capillary leakage and alveolar edema are hallmarks of acute lung injury (ALI). Neutrophils and serum macromolecules enter alveoli, promoting inflammation. Vascular endothelial growth factor (VEGF) causes plasma leakage in extrapulmonary vessels. Angiopoietin (Ang)-1 and -4 stabilize vessels, attenuating capillary leakage. We hypothesized that VEGF and Ang-1 and -4 modulate vessel leakage in the lung, contributing to the pathogenesis of ALI. We examined a murine model of lipopolysaccharide (LPS)-induced ALI. C57BL/6 and 129/J mice were studied at baseline and 24, 48, and 96 h after single or multiple doses of aerosolized LPS. Both strains exhibited time- and dose-dependent increases in inflammation and a deterioration of lung mechanics. Bronchoalveolar lavage (BAL) protein levels increased significantly, suggesting capillary leakage. Increased BAL neutrophil and total protein content correlated with time-dependent increased tissue VEGF and decreased Ang-1 and -4 levels, with peak VEGF and minimum Ang-1 and -4 expression after 96 h of LPS challenge. These data suggest that changes in the balance between VEGF and Ang-1 and -4 after LPS exposure may modulate neutrophil influx, protein leakage, and alveolar flooding during early ALI.