Increase In Bronchoalveolar Lavage Protein Research Articles

Farnesoid X receptor regulates macrophage activation and recruitment to the lung following exposure of mice to nitrogen mustard.

Abstract Nitrogen mustard (NM) is a toxic vesicant known to cause acute lung injury which progresses to fibrosis. This is accompanied by the accumulation of pro-inflammatory/cytotoxic M1 macrophages and anti-inflammatory/pro-fibrotic M2 macrophages in the lung. Farnesoid X receptor (FXR) is a bile-acid activated nuclear receptor involved in lipid homeostasis; it has also been shown to exert anti-inflammatory activity. In these studies, we analyzed the role of FXR in regulating macrophage accumulation and activation in the lung following NM exposure. Male and female wild type (WT) and FXR−/− mice were treated with PBS (control) or NM (0.08 mg/kg) via intratracheal instillation. Lung tissue and bronchoalveolar lavage (BAL) fluid were collected 3, 14, and 28 days later. NM caused histopathologic alterations in the lung including inflammatory cell infiltration, septal damage, and epithelial thickening, which were more prominent in FXR−/− mice relative to WT mice at all post exposure time points. This correlated with aggravated increases in BAL protein and cell content. Flow cytometric analysis revealed pro-inflammatory macrophages were most abundant in BAL 3 days post NM, a response more pronounced in FXR−/− mice. In male but not female mice, increases in proinflammatory macrophages persisted in the lung for at least 28 d post NM. In contrast, while anti-inflammatory macrophages also increased in the lung following NM administration, no differences were observed between WT and FXR−/− mice. These findings demonstrate that FXR modulates proinflammatory macrophage responses to NM in a sex-dependent manner and suggest a potential new target for the development of therapeutics to blunt mustard vesicant induced lung inflammation and injury.

Farnesoid X Receptor Regulates Immune Cell Activation and Recruitment to the Lung following Exposure of Mice to Nitrogen Mustard

Nitrogen mustard (NM) is a cytotoxic vesicant known to cause acute lung injury which progresses to fibrosis. This is accompanied by a robust inflammatory cell response, including activation of resident alveolar macrophages and an accumulation of bone marrow-derived monocytes in the lung, which develop into pro-inflammatory/cytotoxic M1 macrophages and anti-inflammatory/pro-fibrotic M2 macrophages. Farnesoid X receptor (FXR) is a bile-acid activated nuclear receptor involved in lipid homeostasis; it has also been shown to exert anti-inflammatory activity. In previous studies we showed that expression of FXR, along with two of its targets, ApoA and ApoE, were upregulated in lung macrophages following NM exposure. In these studies, we analyzed the role of FXR in regulating macrophage accumulation and activation in the lung following NM exposure. Male and female wild type (WT) and FXR-/- mice were treated with PBS (control) or NM (0.08 mg/kg) via intratracheal instillation. Lung tissue and bronchoalveolar lavage (BAL) fluid were collected 3, 14, and 28 days later. NM caused histopathologic alterations in the lung including inflammatory cell infiltration, septal damage, and epithelial thickening, which were more prominent in FXR-/- mice relative to WT mice at all post exposure time points. This correlated with aggravated increases in BAL protein and cell content. Flow cytometric analysis revealed that both pro- and anti-inflammatory macrophages accumulate in the lung following NM exposure. Pro-inflammatory macrophages were most abundant in BAL 3 days post NM, a response more pronounced in FXR-/- mice. In male but not female mice, increases in proinflammatory macrophages persisted in the lung for at least 28 d post NM. In contrast, while anti-inflammatory macrophages also increased in the lung following NM administration, no differences were observed between WT and FXR-/- mice. These findings demonstrate that FXR modulates proinflammatory macrophage responses to NM in a sex-dependent manner and suggest a potential new target for the development of therapeutics to blunt mustard vesicant induced lung inflammation and injury.

P38 Inhibition Ameliorates Inspiratory Resistive Breathing-Induced Pulmonary Inflammation.

Inspiratory resistive breathing (IRB), a hallmark of obstructive airway diseases, is associated with strenuous contractions of the inspiratory muscles and increased negative intrathoracic pressures that act as an injurious stimulus to the lung. We have shown that IRB induces pulmonary inflammation in healthy animals. p38 kinase is activated in the lung under stress. We hypothesized that p38 is activated during IRB and contributes to IRB-induced pulmonary inflammation. Anesthetized, tracheostomized rats breathed spontaneously through a two-way valve. Resistance was connected to the inspiratory port to provoke a peak tidal inspiratory pressure 50% of maximum. Following 3 and 6h of IRB, respiratory system mechanics were measured and bronchoalveolar lavage (BAL) was performed. Phosphorylated p38, TNF-α, and MIP-2α were detected in lung tissue. Lung injury was estimated histologically. SB203580 (p38 inhibitor) was administered prior to IRB (1mgkg-1). Six hours of IRB increased phosphorylated p38 in the lung, compared with quietly breathing controls (p = 0.001). Six hours of IRB increased the numbers of macrophages and neutrophils (p = 0.01 and p = 0.005) in BAL fluid. BAL protein levels and lung elasticity increased after both 3 and 6h IRB. TNF-α and MIP-2α increased after 6h of IRB (p = 0.01 and p < 0.001, respectively). Increased lung injury score was detected at 6h IRB. SB203580 administration blocked the increase of neutrophils and macrophages at 6h IRB (p = 0.01 and p = 0.005 to 6h IRB) but not the increase in BAL protein and elasticity. TNF-α, MIP-2α, and injury score at 6h IRB returned to control. p38 activation contributes to IRB-induced pulmonary inflammation.

Prophylactic efficacy of S-2(2-aminoethylamino)ethyl phenyl sulfide (DRDE-07) against sulfur mustard induced lung toxicity in mice

Objective: The present study was planned to investigate the prophylactic efficacy of S-2(2-aminoethylamino)ethyl phenyl sulfide (DRDE-07), against topically applied SM induced pulmonary toxicity in mouse. Materials and methods: Animals were pretreated with S-2(2-aminoethylamino)ethyl phenyl sulfide (DRDE-07) (249.4 mg/kg by oral gavage) 30 minutes before SM exposure. The SM (6.48 mg/kg) was applied on hair clipped dorsocaudal region (percutaneous) of the animal. The animals were sacrificed on day 1, 3, 5 and 7. The biochemical changes those were observed in the bronchoalveolar lavage (BAL) fluid and lung tissue included protein, LDH, MPO, β-glucuronidase, MMP-2, MMP-9, activated macrophages, reduced glutathione and lipid peroxidation level. Results and discussion: Pretreatment with DRDE-07 (0.2 LD50) attenuated SM-induced changes at all time point tested. BAL fluid biochemical endpoints indicated epithelial and endothelial cell damages as evidenced by increase in BAL protein, LDH level and increased number of activated macrophages. The increased myeloperoxidase activity and β-glucuronidase level exhibited the degranulation of neutrophils due to SM toxicity in lung. The zymogrphy analysis of BAL fluid showed a significant increase in matrix metalloproteases (MMP) activity due to inflammatory cells accumulation. Conclusion: Thirty minutes pretreatment with DRDE-07 decreased vascular permeability reduced the inflammation and oxidative stress, hence may be recommended as a potential prophylactic agent for SM intoxication.

Endothelial CD74 mediates macrophage migration inhibitory factor protection in hyperoxic lung injury.

Exposure to hyperoxia results in acute lung injury. A pathogenic consequence of hyperoxia is endothelial injury. Macrophage migration inhibitory factor (MIF) has a cytoprotective effect on lung endothelial cells; however, the mechanism is uncertain. We postulate that the MIF receptor CD74 mediates this protective effect. Using adult wild-type (WT), MIF-deficient (Mif(-/-)), CD74-deficient (Cd74(-/-)) mice and MIF receptor inhibitor treated mice, we report that MIF deficiency or inhibition of MIF receptor binding results in increased sensitivity to hyperoxia. Mif(-/-) and Cd74(-/-) mice demonstrated decreased median survival following hyperoxia compared to WT mice. Mif(-/-) mice demonstrated an increase in bronchoalveolar protein (48%) and lactate dehydrogenase (LDH) (68%) following 72 hours of hyperoxia. Similarly, treatment with MIF receptor antagonist resulted in a 59% and 91% increase in bronchoalveolar lavage protein and LDH, respectively. Inhibition of CD74 in primary murine lung endothelial cells (MLECs) abrogated the protective effect of MIF, including decreased hyperoxia-mediated AKT phosphorylation and a 20% reduction in the antiapoptotic effect of exogenous MIF. Treatment with MIF decreased hyperoxia-mediated H2AX phosphorylation in a CD74-dependent manner. These data suggest that therapeutic manipulation of the MIF-CD74 axis in lung endothelial cells may be a novel approach to protect against acute oxidative stress.

Ozone-induced lung injury and sterile inflammation. Role of toll-like receptor 4

Inhalation of toxic doses of ozone is associated with a sterile inflammatory response characterized by an accumulation of macrophages in the lower lung which are activated to release cytotoxic/proinflammatory mediators that contribute to tissue injury. Toll-like receptor 4 (TLR4) is a pattern recognition receptor present on macrophages that has been implicated in sterile inflammatory responses. In the present studies we used TLR4 mutant C3H/HeJ mice to analyze the role of TLR4 in ozone-induced lung injury, oxidative stress and inflammation. Acute exposure of control C3H/HeOuJ mice to ozone (0.8ppm for 3h) resulted in increases in bronchoalveolar lavage (BAL) lipocalin 24p3 and 4-hydroxynonenal modified protein, markers of oxidative stress and lipid peroxidation. This was correlated with increases in BAL protein, as well as numbers of alveolar macrophages. Levels of surfactant protein-D, a pulmonary collectin known to regulate macrophage inflammatory responses, also increased in BAL following ozone inhalation. Ozone inhalation was associated with classical macrophage activation, as measured by increased NF-κB binding activity and expression of TNFα mRNA. The observation that these responses to ozone were not evident in TLR4 mutant C3H/HeJ mice demonstrates that functional TLR4 contributes to ozone-induced sterile inflammation and macrophage activation.

Role of TNFR1 in lung injury and altered lung function induced by the model sulfur mustard vesicant, 2-chloroethyl ethyl sulfide

Lung toxicity induced by sulfur mustard is associated with inflammation and oxidative stress. To elucidate mechanisms mediating pulmonary damage, we used 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant. Male mice (B6129) were treated intratracheally with CEES (3 or 6mg/kg) or control. Animals were sacrificed 3, 7 or 14days later and bronchoalveolar lavage (BAL) fluid and lung tissue collected. Treatment of mice with CEES resulted in an increase in BAL protein, an indication of alveolar epithelial damage, within 3days. Expression of Ym1, an oxidative stress marker also increased in the lung, along with inducible nitric oxide synthase, and at 14days, cyclooxygenase-2 and monocyte chemotactic protein-1, inflammatory proteins implicated in tissue injury. These responses were attenuated in mice lacking the p55 receptor for TNFα (TNFR1−/−), demonstrating that signaling via TNFR1 is key to CEES-induced injury, oxidative stress, and inflammation. CEES-induced upregulation of CuZn−superoxide dismutase (SOD) and MnSOD was delayed or absent in TNFR1−/− mice, relative to WT mice, suggesting that TNFα mediates early antioxidant responses to lung toxicants. Treatment of WT mice with CEES also resulted in functional alterations in the lung including decreases in compliance and increases in elastance. Additionally, methacholine-induced alterations in total lung resistance and central airway resistance were dampened by CEES. Loss of TNFR1 resulted in blunted functional responses to CEES. These effects were most notable in the airways. These data suggest that targeting TNFα signaling may be useful in mitigating lung injury, inflammation and functional alterations induced by vesicants.

Functional and inflammatory alterations in the lung following exposure of rats to nitrogen mustard

Nitrogen mustard is a vesicant that causes damage to the respiratory tract. In these studies, we characterized the acute effects of nitrogen mustard on lung structure, inflammatory mediator expression, and pulmonary function, with the goal of identifying mediators potentially involved in toxicity. Treatment of rats (male Wistar, 200–225 g) with nitrogen mustard (mechlorethamine hydrochloride, i.t., 0.25 mg/kg) resulted in marked histological changes in the respiratory tract, including necrotizing bronchiolitis, thickening of alveolar septa, and inflammation which was evident within 24 h. This was associated with increases in bronchoalveolar lavage protein and cells, confirming injury to alveolar epithelial regions of the lung. Nitrogen mustard administration also resulted in increased expression of inducible nitric oxide synthase and cyclooxygenase-2, pro-inflammatory proteins implicated in lung injury, in alveolar macrophages and alveolar and bronchial epithelial cells. Expression of connective tissue growth factor and matrix metalloproteinase-9, mediators regulating extracellular matrix turnover was also increased, suggesting that pathways leading to chronic lung disease are initiated early in the pathogenic process. Following nitrogen mustard exposure, alterations in lung mechanics and function were also observed. These included decreases in baseline static compliance, end-tidal volume and airway resistance, and a pronounced loss of methacholine responsiveness in resistance, tissue damping and elastance. Taken together, these data demonstrate that nitrogen mustard induces rapid structural and inflammatory changes in the lung which are associated with altered lung functioning. Understanding the nature of the injury induced by nitrogen mustard and related analogs may aid in the development of efficacious therapies for treatment of pulmonary injury resulting from exposure to vesicants.

Differential Effects of Sphingosine 1–Phosphate Receptors on Airway and Vascular Barrier Function in the Murine Lung

The therapeutic options for ameliorating the profound vascular permeability, alveolar flooding, and organ dysfunction that accompanies acute inflammatory lung injury (ALI) remain limited. Extending our previous finding that the intravenous administration of the sphingolipid angiogenic factor, sphingosine 1-phosphate (S1P), attenuates inflammatory lung injury and vascular permeability via ligation of S1PR(1), we determine that a direct intratracheal or intravenous administration of S1P, or a selective S1P receptor (S1PR(1)) agonist (SEW-2871), produces highly concentration-dependent barrier-regulatory responses in the murine lung. The intratracheal or intravenous administration of S1P or SEW-2871 at < 0.3 mg/kg was protective against LPS-induced murine lung inflammation and permeability. However, intratracheal delivery of S1P at 0.5 mg/kg (for 2 h) resulted in significant alveolar-capillary barrier disruption (with a 42% increase in bronchoalveolar lavage protein), and produced rapid lethality when delivered at 2 mg/kg. Despite the greater selectivity for S1PR(1), intratracheally delivered SEW-2871 at 0.5 mg/kg also resulted in significant alveolar-capillary barrier disruption, but was not lethal at 2 mg/kg. Consistent with the S1PR(1) regulation of alveolar/vascular barrier function, wild-type mice pretreated with the S1PR(1) inverse agonist, SB-649146, or S1PR(1)(+/-) mice exhibited reduced S1P/SEW-2871-mediated barrier protection after challenge with LPS. In contrast, S1PR(2)(-/-) knockout mice as well as mice with reduced S1PR(3) expression (via silencing S1PR3-containing nanocarriers) were protected against LPS-induced barrier disruption compared with control mice. These studies underscore the potential therapeutic effects of highly selective S1PR(1) receptor agonists in reducing inflammatory lung injury, and highlight the critical role of the S1P delivery route, S1PR(1) agonist concentration, and S1PR(1) expression in target tissues.

Activated protein C protects against ventilator-induced pulmonary capillary leak

The coagulation system is central to the pathophysiology of acute lung injury. We have previously demonstrated that the anticoagulant activated protein C (APC) prevents increased endothelial permeability in response to edemagenic agonists in endothelial cells and that this protection is dependent on the endothelial protein C receptor (EPCR). We currently investigate the effect of APC in a mouse model of ventilator-induced lung injury (VILI). C57BL/6J mice received spontaneous ventilation (control) or mechanical ventilation (MV) with high (HV(T); 20 ml/kg) or low (LV(T); 7 ml/kg) tidal volumes for 2 h and were pretreated with APC or vehicle via jugular vein 1 h before MV. In separate experiments, mice were ventilated for 4 h and received APC 30 and 150 min after starting MV. Indices of capillary leakage included bronchoalveolar lavage (BAL) total protein and Evans blue dye (EBD) assay. Changes in pulmonary EPCR protein and Rho-associated kinase (ROCK) were assessed using SDS-PAGE. Thrombin generation was measured via plasma thrombin-antithrombin complexes. HV(T) induced pulmonary capillary leakage, as evidenced by significant increases in BAL protein and EBD extravasation, without significantly increasing thrombin production. HV(T) also caused significant decreases in pulmonary, membrane-bound EPCR protein levels and increases in pulmonary ROCK-1. APC treatment significantly decreased pulmonary leakage induced by MV when given either before or after initiation of MV. Protection from capillary leakage was associated with restoration of EPCR protein expression and attenuation of ROCK-1 expression. In addition, mice overexpressing EPCR on the pulmonary endothelium were protected from HV(T)-mediated injury. Finally, gene microarray analysis demonstrated that APC significantly altered the expression of genes relevant to vascular permeability at the ontology (e.g., blood vessel development) and specific gene (e.g., MAPK-associated kinase 2 and integrin-beta(6)) levels. These findings indicate that APC is barrier-protective in VILI and that EPCR is a critical participant in APC-mediated protection.

The peroxisome proliferator‐activated gamma (PPARγ) ligand, rosiglitazone, attenuates lung barrier dysfunction following chronic alcohol ingestion

Chronic alcohol consumption increases the incidence of the Acute Respiratory Distress Syndrome in part through alcohol‐induced, NADPH oxidase‐mediated increases in oxidative stress in the lung. We hypothesized that rosiglitazone, a PPAR‐γ ligand that attenuates NADPH oxidase expression, would attenuate alcohol‐induced oxidative stress and alveolar capillary barrier dysfunction in the lung. To explore this hypothesis, C57Bl/6 mice consumed standard chow ± ethanol (EtOH, 20% w/v) in drinking water for 12 weeks. After 11 weeks, selected mice were gavaged daily with rosiglitazone (10 mg/kg) for 1 week. Mice were then treated ± lipopolysaccahride (LPS, 2mg/kg IP) 6 h prior to sacrifice. LPS treatment stimulated lung barrier dysfunction evidenced by increases in bronchoalveolar lavage (BAL) protein levels. Chronic EtOH ingestion enhanced LPS‐mediated increases in BAL protein, whereas rosiglitazone attenuated BAL protein levels in EtOH and EtOH + LPS‐treated mice. In vitro studies employing HUVEC monolayers on transwell filters confirmed that EtOH (0.1% for 72 h)‐induced endothelial barrier dysfunction was attenuated by rosiglitazone. These findings indicate that PPARγ may represent a novel therapeutic target that can reduce the barrier disruptive effects of alcohol on the lung despite continued EtOH ingestion. This work is supported by grants from NIAAA and the VA Research Service.

Effect of obesity on pulmonary inflammation induced by acute ozone exposure: role of interleukin-6

To determine the role of interleukin (IL)-6 in the increased ozone (O3)-induced inflammation and injury observed in obese vs. lean mice, lean wild-type and leptin-deficient obese (ob/ob) mice were injected with anti-IL-6 antibody (Ab) or isotype control Ab 24 h before exposure to either O3 (2 ppm for 3 h) or room air. Four or 24 h after O3 exposure, bronchoalveolar lavage (BAL) was performed, and the lungs were harvested for Western blotting. Anti-IL-6 Ab caused substantial reductions in O3-induced increases in BAL IL-6 in mice of both genotypes. Four hours following O3, ob/ob mice had increased BAL neutrophils compared with controls, and anti-IL-6-Ab virtually abolished this difference. At 24 h, O3-induced increases in BAL protein and BAL serum albumin were augmented in ob/ob vs. wild-type mice, and anti-IL-6 Ab ablated these obesity-related differences in epithelial barrier injury. O3 increased tyrosine phosphorylation of STAT-3 and STAT-1. There was no effect of obesity on STAT-3 phosphorylation, whereas obesity decreased STAT-1 expression, resulting in reduced STAT-1 phosphorylation. IL-6 neutralization did not alter STAT-3 or STAT-1 phosphorylation in ob/ob or wild-type mice. O3 increased BAL leukemia inhibitory factor (LIF) to a greater extent in obese than in lean mice, and LIF may account for effects on STAT phosphorylation. Our results suggest that IL-6 plays a complex role in pulmonary responses to O3, a role that differs between wild-type and ob/ob mice. Moreover, obesity-related differences in activation of STAT proteins may contribute to some of the differences in the response of obese vs. lean mice.

Dietary Flaxseed is Protective in a Murine Model of Lung Ischemia/Reperfusion Injury

Flaxseed (FS), rich in omega-3 fatty acids and lignans with known anti-inflammatory and anti-oxidant properties, is protective in experimental Acute Lung Injury (ALI). In this study FS was evaluated in a murine model of ischemia/reperfusion injury (IRI), a common complication of lung transplantation. Animals fed either 10% FS-supplemented or control diets (0% FS) for several weeks were anesthetized for tracheostomy and mechanical ventilation, and the entire left hilum was clamped (60 min) and unclamped to allow reperfusion (60 min). IRI was evaluated using real time arterial blood gases (ABG), histology, and bronchoalveolar lavage (BAL) protein and white blood cell (WBC) content measurements. Compared to sham operated mice, mice fed 0% FS before IRI had significant decreases in PaO2 (100 vs. 54.5 mmHg), O2 saturation (96 vs. 70%), and pH (7.28 vs. 7.02), an increase in BAL protein (0.27 vs. 1.0 mg/ml), and marked perivascular and alveolar edema, intra-alveolar hemorrhage, and WBC accumulation seen histologically. In contrast, as compared to 0% FS fed mice before IRI, mice fed 10% FS before IRI had significant increases in PaO2 (54.5 vs. 81.4 mmHg), O2 saturation (70 vs. 91%), and pH (7.02 vs. 7.15), a significant decrease in lung BAL protein (1.0 vs. 0.8 mg/ml), and no histological evidence of IRI (all groups p<0.05). We conclude that dietary FS is protective in experimental IRI as demonstrated by an improvement in physiologic, histologic, and biologic parameters. Funded by: NIH/NCI, AICR and U. Penn Research Foundation (MCS).

Ozone-induced production of nitric oxide and TNF-alpha and tissue injury are dependent on NF-kappaB p50.

Ozone-induced lung injury is associated with increased production of reactive nitrogen intermediates and TNF-alpha, which have been implicated in the pathogenic process. Generation of these mediators is regulated in part by transcription factors, e.g., NF-kappaB and CCAAT/enhancer-binding protein (C/EBP). The present studies used NF-kappaB p50 knockout mice to assess the role of this transcription factor protein in ozone-induced inflammatory mediator production and toxicity. Treatment of wild-type (WT) mice with ozone (0.8 ppm, 3 h) resulted in a rapid increase in NF-kappaB binding activity in alveolar macrophages that peaked after 6-12 h. This response was attenuated in NF-kappaB p50(-)/(-) mice. In WT mice, but not NF-kappaB p50(-)/(-) mice, C/EBP was also markedly increased in macrophages following ozone inhalation. Ozone also induced changes in the mobility of C/EBP in gel shift assays, suggesting alterations in the transcription factor complex that may be important in controlling inflammatory gene expression. Whereas macrophages from WT mice produced increased quantities of nitric oxide and TNF-alpha following ozone inhalation, this was not observed in cells from NF-kappaB p50(-)/(-) mice. Ozone-induced decreases in expression of the anti-inflammatory cytokine IL-10 were also prevented in NF-kappaB p50(-)/(-) mice. In WT mice, ozone inhalation caused an increase in bronchoalveolar lavage protein, a marker of tissue damage. This was not evident in NF-kappaB p50(-)/(-) mice. There was also no evidence of peroxynitrite-mediated lung injury in these mice. These findings demonstrate that NF-kappaB and possibly C/EBP signaling are important in ozone-induced production of reactive nitrogen intermediates and TNF-alpha and in tissue injury.

Heat stress attenuates air bubble-induced acute lung injury: a novel mechanism of diving acclimatization.

Diving acclimatization refers to a reduced susceptibility to acute decompression sickness (DCS) in individuals undergoing repeated compression-decompression cycles. We postulated that mechanisms responsible for the acclimatization are similar to that of a stress preconditioning. In this study, we investigated the protective effect of prior heat shock treatment on air embolism-induced lung injury and on the incidence of DCS in rats. We exposed rats (n = 31) to a pressure cycle that induced signs of severe DCS in 48% of the rats, greater wet-to-dry ratio (W/D) of lung weight compared with the control group (5.48 +/- 0.69 vs. 4.70 +/- 0.17), and higher protein concentration in bronchoalveolar lavage (BAL) fluid (362 +/- 184 vs. 209 +/- 78 mg/l) compared with the control group. Rats with DCS expressed more heat shock protein 70 (HSP70) in the lungs than those without signs of disease. Prior heat shock (n = 12) increased the expression of HSP70 in the lung and attenuated the elevation of W/D of lung weight (5.03 +/- 0.17) after the identical decompression protocol. Prior heat shock reduced the incidence of severe DCS by 23%, but this failed to reach statistical significant (chi(2) = 1.94, P = 0.163). Venous air infusion (1.0 ml/40 min) caused profound hypoxemia (54.5 +/- 3.8 vs. 83.8 +/- 3.2 Torr at baseline; n = 6), greater W/D of lung weight (5.98 +/- 0.45), and high protein concentration in BAL fluid (595 +/- 129 mg/l). Prior heat shock (n = 6) did not alter the level of hypoxemia caused by air embolism, but it accelerated the recovery to normoxemia after air infusion was stopped. Prior heat shock also attenuated the elevation of W/D of lung weight (5.19 +/- 0.40) and the increase in BAL protein (371 +/- 69 mg/l) in air embolism group. Our results showed that the occurrence of DCS after rapid decompression is associated with increased expression of a stress protein (HSP70) and that prior heat shock exposure attenuates the air bubble-induced lung injury. These results suggest that bubble formation in tissues activates a stress response and that stress preconditioning attenuates lung injury on subsequent stress, which may be the mechanism responsible for diving acclimatization.

Fas (CD95) Induces Alveolar Epithelial Cell Apoptosis in Vivo: Implications for Acute Pulmonary Inflammation

Activation of the Fas/FasL system induces apoptosis of susceptible cells, but may also lead to nuclear factor kappaB activation. Our goal was to determine whether local Fas activation produces acute lung injury by inducing alveolar epithelial cell apoptosis and by generating local inflammatory responses. Normal mice (C57BL/6) and mice deficient in Fas (lpr) were treated by intranasal instillation of the Fas-activating monoclonal antibody (mAb) Jo2 or an irrelevant control mAb, and studied 6 or 24 hours later using bronchoalveolar lavage (BAL), histopathology, DNA nick-end-labeling assays, and electron microscopy. Normal mice treated with mAb Jo2 had significant increases in BAL protein at 6 hours, and BAL neutrophils at 24 hours, as compared to lpr mice and to mice treated with the irrelevant mAb. Neutrophil recruitment was preceded by increased mRNA expression for tumor necrosis factor-alpha, macrophage inflammatory protein-1alpha, macrophage inflammatory protein-2, macrophage chemotactic protein-1, and interleukin-6, but not interferon-gamma, transforming growth factor-ss, RANTES, eotaxin, or IP-10. Lung sections from Jo2-treated normal mice showed neutrophilic infiltrates, alveolar septal thickening, hemorrhage, and terminal dUTP nick-end-labeling-positive cells in the alveolar septae and airspaces. Type II pneumocyte apoptosis was confirmed by electron microscopy. Fas activation in vivo results in acute alveolar epithelial injury and lung inflammation, and may be important in the pathogenesis of acute lung injury.

Endogenous adenosine and secondary injury after chest trauma.

No previous studies have examined actions of adenosine or related compounds after blunt chest trauma, but we have shown that the prototype adenosine-regulating agent, acadesine (aminoimidazole carboxamide ribonucleotide [AICAR]), has multiple favorable anti-inflammatory actions after other forms of trauma, ischemia, hemorrhage, and sepsis; and that a progressive inflammatory response in the contralateral (uninjured) lung after unilateral blunt chest trauma is caused (in part) by activation and sequestration of circulating leukocytes (white blood cells [WBCs]). Thus, we hypothesized that AICAR would ameliorate WBC-dependent, secondary pathophysiologic changes after blunt chest trauma. Mongrel pigs (28+/-1 kg, n = 21) were anesthetized, mechanically ventilated, and injured on the right chest (pulmonary contusion) with a captive bolt gun. Either AICAR (1 mg/kg + 0.2 mg/kg/min) or its saline vehicle were administered for a 12-hour period, beginning 15 minutes before injury. Injury caused a three- to fourfold increase in bronchoalveolar lavage (BAL) WBC counts, 10- to 20-fold increases in BAL protein, and 200% increases in lung edema as measured by wet-dry ratio (all p < 0.05), in both the injured (right) and the noninjured (left) lungs. With AICAR versus saline, BAL WBC counts, lung myeloperoxidase levels, and systemic hemodynamics were similar. However, the increases in BAL protein were attenuated by 30% to 50% (p < 0.14, NS) and edema was reduced (p < 0.05) in both lungs. Furthermore, oxygenation, hypercapnia, acidosis (all p < 0.05), and survival were improved (9 of 10 vs. 4 of 11, p < 0.04). Pretreatment with AICAR before experimental pulmonary contusion ameliorates the trauma-induced destruction of the alveolar capillary membrane, and attenuates the delayed secondary injury in the contralateral uninjured lung, by a mechanism that may be independent of leukocytes. Endogenous adenosine could have a role in the pathophysiologic response after blunt chest injury, with potential sites of action including the endothelium and alveolar macrophage. Adenosine-regulating agents may have therapeutic potential after blunt chest injury, but further studies are needed in clinically relevant models, with administration begun at the time of resuscitation.

Acute inhalation toxicity of polymeric diphenyl-methane 4,4'-diisocyanate in rats: time course of changes in bronchoalveolar lavage.

The early acute pulmonary response of Wistar rats exposed nose-only to respirable polymeric diphenylmethane 4,4'-diisocyanate (MDI) aerosol was examined. This study investigated the time course of the relationship between acute pulmonary irritation and ensuing disturbances of the air/blood barrier in rats exposed to concentrations of 0.7, 2.4, 8, or 20 mg MDI/m3. The duration of exposure was 6 h. The time-response relationship of MDI-induced acute lung injury was examined 0 h (directly after cessation of exposure), 3 h, 1 day, 3 days, and 7 days after exposure. Bronchoalveolar lavage (BAL) fluid was analyzed for markers indicative of injury of the bronchoalveolar region, i.e., angiotensin-converting enzyme, protein, alkaline phosphatase, lactate dehydrogenase, gamma-glutamyltranspeptidase, and sialic acid. Phosphatidylcholine and acid phosphatase were determined in BAL fluid and cells. Glutathione was determined in BAL fluid and lung tissue. This analysis revealed no latent period of effects except a transiently delayed influx of cells and increased lung weights on postexposure days 1 and 3. Markedly loaded BAL cells with phosphatidylcholine were observed on day 1 only. In most instances, changes returned to the level of the air exposed control on day 7, except increased glutathione in lung tissue. The findings suggest that the most sensitive markers of dysfunction of the air/blood barrier are angiotensin-converting enzyme and protein, including alkaline phosphatase. The statistically significant increase in intracellular phosphatidylcholine and decreased intracellular acid phosphatase on the exposure day suggest that increased amounts of phospholipids are phagocytized by alveolar macrophages, associated with protracted lysosomal catabolism. Partially glutathione-depleted rats exposed to 20 mg/m3 experienced a more pronounced increase in BAL protein than normal rats. In summary, this study suggests that respirable polymeric MDI aerosol interacts directly with the air/blood barrier causing increased extravasation of plasma constituents as a result of increased permeability of capillary endothelial cells. Overall, a transient dysfunction of the pulmonary epithelial barrier occurred at level as low as 0.7 mg/m3 and appears to be related a dysfunction of pulmonary surfactant. Nonprotein sulfhydryl constituents appear to play a role as portal-of-entry specific modifying factors.

Inhaled nitric oxide primes lung macrophages to produce reactive oxygen and nitrogen intermediates.

Inhaled nitric oxide is a selective pulmonary vasodilator used for the treatment of pulmonary hypertension. The potential adverse effects of inhaled nitric oxide are unknown and represent the focus of the present studies. Whereas inhalation of nitric oxide (10 to 100 ppm, 5 h) by Balb/c mice had no effect on the number or type of cells recovered from the lung, a dose-related increase in bronchoalveolar lavage protein was observed, suggesting that nitric oxide induces alveolar epithelial injury. To determine if this was associated with altered alveolar macrophage activity, we quantified production of reactive oxygen and nitrogen intermediates by these cells. Interferon-gamma, alone or in combination with lipopolysaccharide (LPS), induced expression of inducible nitric oxide synthase (iNOS) protein and nitric oxide production by alveolar macrophages. Cells from mice exposed to 20 to 100 ppm nitric oxide produced significantly more nitric oxide and expressed greater quantities of iNOS than cells from control animals. Superoxide anion production and peroxynitrite generation by alveolar macrophages were also increased after exposure of mice to nitric oxide. This was correlated with increased antinitrotyrosine antibody binding to macrophages in histologic sections. Taken together, these data demonstrate that inhaled nitric oxide primes lung macrophages to release reactive oxygen and nitrogen intermediates. Increased production of these mediators by macrophages following inhalation of nitric oxide may contribute to tissue injury.

Pretreatment with inhaled nitric oxide inhibits neutrophil migration and oxidative activity resulting in attenuated sepsis-induced acute lung injury

To determine if, and by what mechanisms, inhaled nitric oxide attenuates acute lung injury in a porcine model of adult respiratory distress syndrome induced by Gram-negative sepsis. Nonrandomized, controlled study. Laboratory at a university medical center. Thirty pathogen-free Yorkshire swine (15 to 20 kg). Four groups of swine were anesthetized, mechanically ventilated, and studied for 5 hrs. Both control-nitric oxide and septic-nitric oxide animals received inhaled nitric oxide at 20 parts per million throughout the study. Control (n = 10) and control-nitric oxide (n = 5) animals received a 1-hr infusion of sterile saline. Sepsis was induced in septic (n = 10) and septic-nitric oxide (n = 5) animals with a 1-hr intravenous infusion of live Pseudomonas aeruginosa. Untreated septic animals developed a progressive decrease in Pao2 that was prevented in septic-nitric oxide animals (73 +/- 4 vs. 214 +/- 23 torr [9.7 +/- 0.5 vs. 28.5 +/- 3.1 kPa], respectively, at 5 hrs, p < .05). Untreated septic animals showed a significant increase in bronchoalveolar lavage protein and neutrophil count at 5 hrs, compared with the baseline value, indicating acute lung injury. Septic-nitric oxide animals showed no significant increase in these parameters. Peripheral blood neutrophils from untreated septic animals and septic-nitric oxide animals exhibited significant (p < .05) up-regulation of CD18 receptor expression and oxidant activity (10.5 +/- 0.9 and 5.0 +/- 0.9 nmol of superoxide anion/10(6) neutrophils/10 mins, respectively) compared with both control and control-nitric oxide animals (3.0 +/- 0.6 and 2.6 +/- 0.2 nmol of superoxide anion/10(6) neutrophils/10 mins, respectively). Also, priming for the oxidant burst at 5 hrs was decreased by 50% in septic-nitric oxide animals compared with untreated septic animals. Both untreated septic and septic-nitric oxide animals showed a significant increase in pulmonary arterial pressure at 30 mins (47.5 +/- 2.4 and 51.0 +/- 3.0 mm Hg, respectively), followed by a progressive decrease (32.8 +/- 2.6 and 31.3 +/- 5.4 mm Hg, respectively, at 5 hrs). Both of these changes were significant (p < .05) compared with baseline values and compared with the control groups. There was no significant difference in pulmonary arterial pressure or systemic arterial pressure at any time between untreated septic and septic-nitric oxide animals. These results demonstrate that inhaled nitric oxide attenuates alveolar-capillary membrane injury in this porcine model of Gram-negative sepsis but does not adversely affect systemic hemodynamics. The data suggest that inhaled nitric oxide preserves alveolar-capillary membrane integrity by the following means: a) inhibiting transendothelial migration of activated, tightly adherent neutrophils; and b) possibly by attenuating the neutrophil oxidant burst.