Number Of Neutrophils In Lung Research Articles

Local immune dysregulation and subsequent inflammatory response contribute to pulmonary edema caused by Enterovirus infection in mice.

Pulmonary edema that comes on suddenly is the leading cause of mortality in hand-foot-and-mouth disease (HFMD) patients; however, its pathogenesis is still largely unclear. A range of research suggest immunopathogenesis during the occurrence of pulmonary edema in severe HFMD patients. Herein, to investigate the potential mechanism of immune dysregulation in the development of pulmonary edema upon Enterovirus (EV) infection, we established mouse infection models for Enteroviruses (EVs) including Coxsackievirus (CV) A6, Enterovirus A71 (EVA71), and CVA2 exhibiting a high incidence of pulmonary edema. We found that EVs infection induced an immune system disorder by reducing the numbers of pulmonary and circulatory T cells, B cells, macrophages, and monocytes and increasing the numbers of lung neutrophils, myeloid-derived suppressor cells (MDSCs), and activated T cells. In addition, the concentrations of C-X-C motif chemokine ligand 1 (CXCL-1), tumor necrosis factor-alpha, monocyte chemoattractant protein-1, and interleukin 6 were increased in EV-infected lungs. Moreover, we found that EVs replication in mice lungs lead to apoptosis of lung cells and degradation of tight junction proteins. In conclusion, EVs infection likely triggered a complexed immune defense mechanism and caused dysregulation of innate immune cells (MDSCs, neutrophils, monocytes, and macrophages) and adaptive cellular immunity (B cells, T cells). This dysregulation increased the release of cytokines and other inflammatory factors from activated immune-related cells and caused lung barrier damage and pulmonary edema.

Evaluation of IL-1 Blockade as an Adjunct to Linezolid Therapy for Tuberculosis in Mice and Macaques.

In 2017 over 550,000 estimated new cases of multi-drug/rifampicin resistant tuberculosis (MDR/RR-TB) occurred, emphasizing a need for new treatment strategies. Linezolid (LZD) is a potent antibiotic for drug-resistant Gram-positive infections and is an effective treatment for TB. However, extended LZD use can lead to LZD-associated host toxicities, most commonly bone marrow suppression. LZD toxicities may be mediated by IL-1, an inflammatory pathway important for early immunity during M. tuberculosis infection. However, IL-1 can contribute to pathology and disease severity late in TB progression. Since IL-1 may contribute to LZD toxicity and does influence TB pathology, we targeted this pathway with a potential host-directed therapy (HDT). We hypothesized LZD efficacy could be enhanced by modulation of IL-1 pathway to reduce bone marrow toxicity and TB associated-inflammation. We used two animal models of TB to test our hypothesis, a TB-susceptible mouse model and clinically relevant cynomolgus macaques. Antagonizing IL-1 in mice with established infection reduced lung neutrophil numbers and partially restored the erythroid progenitor populations that are depleted by LZD. In macaques, we found no conclusive evidence of bone marrow suppression associated with LZD, indicating our treatment time may have been short enough to avoid the toxicities observed in humans. Though treatment was only 4 weeks (the FDA approved regimen at the time of study), we observed sterilization of the majority of granulomas regardless of co-administration of the FDA-approved IL-1 receptor antagonist (IL-1Rn), also known as Anakinra. However, total lung inflammation was significantly reduced in macaques treated with IL-1Rn and LZD compared to LZD alone. Importantly, IL-1Rn administration did not impair the host response against Mtb or LZD efficacy in either animal model. Together, our data support that inhibition of IL-1 in combination with LZD has potential to be an effective HDT for TB and the need for further research in this area.

Cigarette Smoke Increases CD8α+ Dendritic Cells in an Ovalbumin-Induced Airway Inflammation.

Asthma is an allergic lung disease and, when associated to cigarette smoke exposition, some patients show controversial signs about lung function and other inflammatory mediators. Epidemiologic and experimental studies have shown both increasing and decreasing inflammation in lungs of subjects with asthma and exposed to cigarette smoke. Therefore, in this study, we analyzed how cigarette smoke affects pro-inflammatory and anti-inflammatory mediators in a murine model of allergic pulmonary inflammation. We sensitized Balb/c mice to ovalbumin (OVA) with two intraperitoneal injections. After sensitization, the animals were exposed to cigarette smoke twice a day, 30 min per exposition, for 12 consecutive days. In order to drive the cell to the lungs, four aerosol challenges were performed every 48 h with the same allergen of sensitization. OVA sensitization and challenge developed pulmonary Th2 characteristic response with increased airway responsiveness, remodeling, increased levels of IgE, interleukin (IL)-4, and IL-13. Cigarette smoke, unexpectedly, reduced the levels of IL-4 and IL-13 and simultaneously decreased anti-inflammatory cytokines as IL-10 and transforming growth factor (TGF)-β in sensitized and challenged animals. OVA combined with cigarette smoke exposition decreased the number of eosinophils in bronchoalveolar lavage and increased the number of neutrophils in lung. The combination of cigarette smoke and lung allergy increased recruitment of lymphoid dendritic cells (DCs) into lymph nodes, which may be the leading cause to an increase in number and activation of CD8+ T cells in lungs. In addition, lung allergy and cigarette smoke exposure decreased an important regulatory subtype of DC such as plasmacytoid DC as well as its activation by expression of CD86, PDL2, and ICOSL, and it was sufficient to decrease T regs influx and anti-inflammatory cytokines release such as IL-10 and TGF-β but not enough to diminish the structural changes. In conclusion, we observed, in this model, that OVA sensitization and challenge combined with cigarette smoke exposure leads to mischaracterization of the Th2 response of asthma by decreasing the number of eosinophils, IL-4, and IL-13 and increasing number of neutrophils, which is related to the increased number of CD8ɑ+ DCs and CD8+ T cells as well as reduction of the regulatory cells and its released cytokines.

Granulocyte colony-stimulating factor blockade enables dexamethasone to inhibit lipopolysaccharide-induced murine lung neutrophils.

Glucocorticoids promote neutrophilic inflammation, the mechanisms of which are poorly characterized. Using a lipopolysaccharide (LPS)-induced acute murine lung injury model, we determined the role of granulocyte colony-stimulating factor (G-CSF) in mouse lung neutrophil numbers in the absence and presence of dexamethasone, a potent glucocorticoid. G-CSF was blocked using a neutralizing antibody. Airway neutrophil numbers, cytokine levels, and lung injury parameters were measured. Glucocorticoid treatment maintained LPS-induced airway G-CSF while suppressing TNF and IL-6. The addition of anti-G-CSF antibodies enabled dexamethasone to decrease airway G-CSF, neutrophils, and lung injury scores. In LPS-challenged murine lungs, structural cells and infiltrating leukocytes produced G-CSF. In vitro using BEAS 2B bronchial epithelial cells, A549 lung epithelial cells, human monocyte-derived macrophages, and human neutrophils, we found that dexamethasone and proinflammatory cytokines synergistically induced G-CSF. Blocking G-CSF production in BEAS 2B cells using shRNAs diminished the ability of BEAS 2B cells to protect neutrophils from undergoing spontaneous apoptosis. These data support that G-CSF plays a role in upregulation of airway neutrophil numbers by dexamethasone in the LPS-induced acute lung injury model.

Chronic Obstructive Pulmonary Disease, Neutrophils and Bacterial Infection: A Complex Web Involving IL-17 and IL-22 Unravels

Neutrophils provide innate immune defence against microbes such as bacteria. Neutrophilic airway inflammation is a characteristic feature of chronic obstructive pulmonary disease (COPD) (Hogg et al., 2004), a condition that is commonly caused by cigarette smoking. Neutrophils activated by the inhalation of toxic particles contribute to the pathophysiology of COPD by secreting proteases that cause tissue destruction and by releasing mediators that promote airway inflammation. On the one hand, it could be therapeutically beneficial to reduce neutrophil activity in COPD lungs. On the other hand, one has to be careful about preserving anti-bacterial defence. This is particularly relevant for the subset of COPD patients who have persistent bacterial colonisation and/or acute bacterial exacerbations, often caused by nontypeable Haemophilus influenzae (NTHi) or Streptococcus pneumoniae (Desai et al., 2014).

Late engagement of CD86 after influenza virus clearance promotes recovery in a FoxP3+ regulatory T cell dependent manner.

Influenza A virus (IAV) infection in the respiratory tract triggers robust innate and adaptive immune responses, resulting in both virus clearance and lung inflammation and injury. After virus clearance, resolution of ongoing inflammation and tissue repair occur during a distinct recovery period. B7 family co-stimulatory molecules such as CD80 and CD86 have important roles in modulating T cell activity during the initiation and effector stages of the host response to IAV infection, but their potential role during recovery and resolution of inflammation is unknown. We found that antibody-mediated CD86 blockade in vivo after virus clearance led to a delay in recovery, characterized by increased numbers of lung neutrophils and inflammatory cytokines in airways and lung interstitium, but no change in conventional IAV-specific T cell responses. However, CD86 blockade led to decreased numbers of FoxP3+ regulatory T cells (Tregs), and adoptive transfer of Tregs into αCD86 treated mice rescued the effect of the blockade, supporting a role for Tregs in promoting recovery after virus clearance. Specific depletion of Tregs late after infection mimicked the CD86 blockade phenotype, confirming a role for Tregs during recovery after virus clearance. Furthermore, we identified neutrophils as a target of Treg suppression since neutrophil depletion in Treg-depleted mice reduced excess inflammatory cytokines in the airways. These results demonstrate that Tregs, in a CD86 dependent mechanism, contribute to the resolution of disease after IAV infection, in part by suppressing neutrophil-driven cytokine release into the airways.

β2-Adrenoreceptor blockade improves early posttrauma hyperglycemia and pulmonary injury in obese rats

Early hyperglycemia after trauma increases morbidity and mortality. Insulin is widely used to control posttrauma glucose, but this treatment increases the risk of hypoglycemia. We tested a novel method for early posttrauma hyperglycemia control by suppressing hepatic glycogenolysis via β2-adrenoreceptor blockade [ICI-118551 (ICI)]. We have shown that, after severe trauma, obese Zucker (OZ) rats, similar to obese patients, exhibit increased acute lung injury compared with lean Zucker (LZ) rats. We hypothesized that OZ rats exhibit a greater increase in early posttrauma glucose compared with LZ rats, with the increased posttrauma hyperglycemia suppressed by ICI treatment. Orthopedic trauma was applied to both hindlimbs in LZ and OZ rats. Fasting plasma glucose was then monitored for 6 h with or without ICI (0.2 mg·kg(-1)·h(-1) iv.) treatment. One day after trauma, plasma IL-6 levels, lung neutrophil numbers, myeloperoxidase (MPO) activity, and wet-to-dry weight ratios were measured. Trauma induced rapid hepatic glycogenolysis, as evidenced by decreased liver glycogen levels, and this was inhibited by ICI treatment. Compared with LZ rats, OZ rats exhibited higher posttrauma glucose, IL-6, lung neutrophil infiltration, and MPO activity. Lung wet-to-dry weight ratios were increased in OZ rats but not in LZ rats. ICI treatment reduced the early hyperglycemia, lung neutrophil retention, MPO activity, and wet-to-dry weight ratio in OZ rats to levels comparable with those seen in LZ rats, with no effect on blood pressure or heart rate. These results demonstrate that β2-adrenoreceptor blockade effectively reduces the early posttrauma hyperglycemia, which is associated with decreased lung injury in OZ rats.

CD86-dependent FoxP3+ regulatory T cells promote resolution of disease after influenza virus infection (IRC4P.492)

Abstract Influenza A virus (IAV) infection in the respiratory tract triggers a robust immune response, resulting in both virus clearance and lung inflammation and injury. After virus clearance, resolution of lung disease occurs during a distinct recovery period. The costimulatory molecule CD86 can modulate T cell activity during the initiation and effector stages of the host response to IAV infection, but the role of CD86 during recovery is unknown. We found that antibody-mediated CD86 blockade after virus clearance led to a delay in recovery, characterized by increased numbers of lung neutrophils and innate cytokines in the bronchial alveolar lavage fluid (BAL), but no change in conventional IAV-specific T cell responses. However, CD86 blockade led to decreased numbers of FoxP3+ regulatory T cells (Tregs), and adoptive transfer of Tregs into α-CD86 treated mice rescued the effect of the blockade, supporting a role for Tregs in promoting recovery after virus clearance. Direct depletion of Tregs late after infection using DEREG mice mimicked the CD86 blockade phenotype, confirming a role for Tregs during recovery after virus clearance. Finally, we identified neutrophils as a target of Treg suppression, since neutrophil depletion in Treg-depleted DEREG mice reduced excess BAL cytokines. These results show that CD86-dependent Tregs contribute to the resolution of disease after IAV infection, in part by suppressing neutrophil-driven cytokine release into the airways.

Aquaporin 5 regulates cigarette smoke induced emphysema by modulating barrier and immune properties of the epithelium

Chronic obstructive pulmonary disease (COPD) causes significant morbidity and mortality. Cigarette smoke, the most common risk factor for COPD, induces airway and alveolar epithelial barrier permeability and initiates an innate immune response. Changes in abundance of aquaporin 5 (AQP5), a water channel, can affect epithelial permeability and immune response after cigarette smoke exposure. To determine how AQP5-derived epithelial barrier modulation affects epithelial immune response to cigarette smoke and development of emphysema, WT and AQP5−/− mice were exposed to cigarette smoke (CS). We measured alveolar cell counts and differentials, and assessed histology, mean-linear intercept (MLI), and surface-to-volume ratio (S/V) to determine severity of emphysema. We quantified epithelial-derived signaling proteins for neutrophil trafficking, and manipulated AQP5 levels in an alveolar epithelial cell line to determine specific effects on neutrophil transmigration after CS exposure. We assessed paracellular permeability and epithelial turnover in response to CS. In contrast to WT mice, AQP5−/− mice exposed to 6 months of CS did not demonstrate a significant increase in MLI or a significant decrease in S/V compared with air-exposed mice, conferring protection against emphysema. After sub-acute (4 weeks) and chronic (6 mo) CS exposure, AQP5−/− mice had fewer alveolar neutrophil but similar lung neutrophil numbers as WT mice. The presence of AQP5 in A549 cells, an alveolar epithelial cell line, was associated with increase neutrophil migration after CS exposure. Compared with CS-exposed WT mice, neutrophil ligand (CD11b) and epithelial receptor (ICAM-1) expression were reduced in CS-exposed AQP5−/− mice, as was secreted LPS-induced chemokine (LIX), an epithelial-derived neutrophil chemoattractant. CS-exposed AQP5−/− mice demonstrated decreased type I pneumocytes and increased type II pneumocytes compared with CS-exposed WT mice suggestive of enhanced epithelial repair. Absence of AQP5 protected against CS-induced emphysema with reduced epithelial permeability, neutrophil migration, and altered epithelial cell turnover which may enhance repair.

IL-5 produced by natural helper cells suppresses neutrophil function during influenza infection. (P4239)

Abstract Interleukin (IL)-5 is a prototypical type II cytokine that is essential for eosinophil maturation and egress out of the bone marrow. We observed that eosinophil numbers progressively increase in the lungs during the course of experimental influenza A virus (IAV) infection in mice as a result of high level production of IL-5 by natural helper cells recruited to the infected lungs. Mice genetically deficient in IL-5 (IL-5 KO) demonstrate increased lung neutrophil numbers and decreased viral titers during the acute phase of IAV infection. However, this phenotype is not recapitulated in mice deficient in eosinophils (PHIL mice) suggesting an eosinophil independent function of IL-5 during infection. Unexpectedly, we found that like eosinophils, >98% of neutrophils express the IL-5 receptor alpha subunit (CD125) in the lung throughout infection. Unlike eosinophils, where ligation of the IL-5R by IL-5 induces phosphorylation of STAT1 and STAT5, engagement of the IL-5R on activated neutrophils results in suppressed pSTAT5 and pSTAT1 signalling as well as decreased expression of the activation marker CD11b. Furthermore, neutrophils treated with IL-5 undergo accelerated cell death in vitro suggesting a potential mechanism for the enhanced neutrophil numbers seen in the IAV infected IL-5 KO. Overall these data suggest that IL-5 may serve a regulatory role during the acute phase of IAV infection by controlling the number (viability) and activation state of recruited neutrophils.

Impaired recruitment of inflammatory cells to aged lungs following influenza infection contributes to delayed virus clearance (168.24)

Abstract Elderly people are very susceptible to influenza virus and often exhibit complications following infection including secondary bacterial infections and exacerbation of lung diseases. Using mouse models, it has been well established that, much like humans, aged animals exhibit a delay in clearing sublethal influenza virus infection compared to young. However, the mechanisms responsible for this delay are not well understood. In this study, we have determined that following influenza infection, the levels of early IFNg production (days 3-6) are significantly lower in aged lungs. Reduced IFNg levels lead to the reduced production of important IFNg-dependent chemokines by innate lung cells, including CCL3, CCL4 and CXCL10, which are necessary for the proper recruitment of inflammatory cells such as neutrophils. This observation is important since it is now appreciated that neutrophils are critical for efficient viral clearance. Reduced lung neutrophil numbers and reduced lung immunopathology were observed in aged flu-infected animals, indicating an overall less vigorous immune response. This diminished initial response plays an important role in the delay in virus clearance. In addition, it also subsequently contributes to lingering inflammation in aged lungs, including high levels of inflammatory cytokines and chemokines, which can contribute to exacerbating pre-existing lung disease.

Cyclophilin A synergizes with MIP-2 to augment pro-inflammatory leukocyte recruitment (140.5)

Abstract Chemokines contribute to inflammatory responses by inducing leukocyte migration and extravasation. Extracellular cyclophilins are a group of alternative chemokines that can be elevated during inflammation, and we have previously shown that their inhibition reduces neutrophil infiltration by >40% in a mouse model of LPS-induced acute lung inflammation. Given the presence of many other chemokines during this inflammatory response, the observed potent contribution of cyclophilins led us to investigate whether they might function in a synergistic partnership with concurrent chemokines. To test whether cyclophilin A (CypA) can work with other chemokines in vivo, recombinant extracellular CypA was co-delivered with intranasal LPS and lung neutrophil numbers were examined at a time point when two classical chemokines, MIP-2 and KC, but not CypA, are present. The addition of CypA induced a significant increase in early neutrophil recruitment that was greater than the additive recruitment induced by LPS and CypA alone. Boyden chamber chemotaxis assays in which purified mouse neutrophils were incubated with various combinations of CypA plus MIP-2 or KC were used to show that CypA had the capacity to synergize with MIP-2, but not KC, to induce augmented neutrophil migration. These findings provide a potential explanation for why the inhibition of cyclophilin activity in vivo has such a great impact on cell recruitment.

β2-Agonists Potentiate Corticosteroid-Induced Neutrophil Survival

Neutrophils are considered to play a role in the pathogenesis of chronic obstructive pulmonary disease (COPD) and severe asthma. Recent guidelines recommend the use of a combination of inhaled corticosteroids (ICS) and long-acting β2-agonists (LABA) in the treatment of COPD with exacerbations and asthma not adequately controlled by ICS alone. LABA have been proposed to have a synergistic effect with corticosteroids by activating glucocorticoid receptors. The aim of this study was to investigate the effect of β2-agonists on the inhibitory effects of corticosteroids on human neutrophil apoptosis. In addition, the effects of β2-agonists on spontaneous neutrophil apoptosis and on GM-CSF- and LTB4-afforded survival were also evaluated. Neutrophils were isolated from human blood under sterile conditions and cultured for 16 hours. Apoptosis was assessed by relative DNA fragmentation assay. Morphological analysis was used as a control method to confirm the occurrence of apoptosis. Salbutamol, formoterol and salmeterol prolonged the lifespan of budesonide- and fluticasone propionate-treated neutrophils by inhibiting apoptosis. Formoterol and salbutamol partly reversed the inhibitory effect of GM-CSF on neutrophil apoptosis. In contrast, the effects of β2-agonists on spontaneous neutrophil apoptosis and on LTB4-afforded survival were negligible. β2-agonists potentiate corticosteroid-induced neutrophil survival at clinically relevant drug concentrations. Whether these effects translate into clinically relevant changes in lung neutrophil numbers remains to be demonstrated.

Neutrophil inhibition with L-selectin-directed MAb improves or worsens survival dependent on the route but not severity of infection in a rat sepsis model

Both route and severity of infection may influence immunomodulator agents in sepsis. We studied the effect of each variable on HRL-3, an L-selectin-directed MAb that inhibits neutrophil function, in a rat sepsis model. Animals (n = 800) were randomized to be treated with either HRL-3 or placebo and to receive Escherichia coli either intravenously (IV) or intrabronchially (IB) in doses producing low or high mortality rates. Animals received antibiotics and were observed for 168 h. Route but not dose of E. coli altered the effects HRL-3 on mortality rate (mean hazards ratio +/- SE). With IV E. coli, compared with control, HRL-3 was beneficial and reduced the hazards ratio both early (0 to 6 h; -0.75 +/- 0.23) and late (6 to 168 h; -0.72 +/- 0.36) (P = 0.001 and 0.04, respectively, over all E. coli doses). In contrast, with IB E. coli HRL-3 reduced the hazards ratio early (-1.1 +/- 0.36) but worsened it late (0.87 +/- 0.23) (P = 0.002 for both effects over all E. coli doses) in patterns significantly different from IV E. coli (P < 0.0001). Compared with control, although HRL-3 did not alter lung neutrophil numbers or injury score at 6 or 168 h with IV E. coli (P = ns for all), it reduced both early and increased them late with IB E. coli (P </= 0.05 for all comparing 6 with 168 h). Thus immunomodulators inhibiting neutrophil function, although potentially beneficial with sepsis due to intravascular infection, may be harmful with extravascular infection regardless of severity.

Role of stromelysin 1 and gelatinase B in experimental acute lung injury.

Matrix metalloproteinases (MMPs) are upregulated locally in sites of inflammation, including the lung. Several MMP activities are upregulated in acute lung injury models but the exact role that these MMPs play in the development of the lung injury is unclear due to the absence of specific inhibitors. To determine the involvement of individual MMPs in the development of lung injury, mice genetically deficient in gelatinase B (MMP-9) and stromelysin 1 (MMP-3) were acutely injured with immunoglobulin G immune complexes and the intensity of the lung injury was compared with genetically identical wild-type (WT) mice with normal MMP activities. In the WT mice there was upregulation of gelatinase B and stromelysin 1 in the injured lungs which, as expected, was absent in the genetically deficient gelatinase B- and stromelysin 1-deficient mice, respectively. In the deficient mice there was little in the way of compensatory upregulation of other MMPs. The gelatinase B- and the stromelysin 1-deficient mice had less severe lung injury than did the WT controls, suggesting that both MMPs are involved in the pathogenesis of the lung injury. Further, the mechanism of their involvement in the lung injury appears to be different, with the stromelysin 1-deficient mice having a reduction in the numbers of neutrophils recruited into the lung whereas the gelatinase B-deficient mice had the same numbers of lung neutrophils as did the injured WT controls. These studies indicate, first, that both gelatinase B and stromelysin 1 are involved in the development of experimental acute lung injury, and second, that the mechanisms by which these individual MMPs function appear to differ.

Antigen-specific immunoglobulin-A prevents increased airway responsiveness and lung eosinophilia after airway challenge in sensitized mice.

Aeroallergens such as Amb a I from short ragweed are important in the development of allergic airway disease. We tested the ability of a human monoclonal immunoglobulin-A (IgA) antibody specific for Amb a I (A-IgA) to modulate airway responsiveness and lung eosinophilia after airway challenge with nebulized Amb a I or ragweed extract in mice sensitized to Amb a I or ragweed extract, respectively. A-IgA or nonspecific IgA (C-IgA) were given intranasally up to 8 h before each challenge. Allergen challenge resulted in increases in airway responsiveness, in numbers of lung eosinophils, and in Amb a I-specific IgE levels. These were prevented by pretreatment with A-IgA but not with C-IgA. Decreases in IFN-gamma and increases in IL-4 and IL-5 production following challenge with Amb a I were also reduced by A-IgA treatment. In contrast, increases in total IgE and total IgG and in numbers of lung neutrophils after challenge were not significantly affected by A-IgA, which additionally induced increased levels of Amb a I-specific IgG2a antibodies. In mice sensitized and challenged with ovalbumin (OVA), A-IgA did not affect airway responsiveness, lung eosinophilia, cytokine production, or immunoglobulin levels. These data indicate that allergen-specific IgA can prevent airway hyperresponsiveness and reduce eosinophil influx into the lungs following allergen challenge via the airways in sensitized mice, and these effects are allergen-specific. Neutralization of allergen may contribute to the effects of IgA, but the induction of allergen-specific IgG2a in A-IgA-treated mice suggests an immunomodulatory action for A-IgA.

Initiation of and tolerance to neutrophil - mediated acute lung injury (ARDS): A yin-yang mechanism involving interleukin-1

The significance of the increased interleukin 1 (IL-l) levels in lungs of ARDS patients is unknown. Our results indicate that IL-I can not only cause acute lung injury but also produce tolerance to acute lung injury. We found that lungs in rats given IL-I (50 ng) intratracheally promptly became edematous and that leak was associated with increases in NFKB activity, lung neutrophils, TNF, cytokine induced neutrophil chemoattractant (CINC) levels and oxidative stress. Paradoxically, we also found that rats pretreated with IL-1 had the same numbers of lung neutrophils, but developed less lung leak, compared to saline-pretreated rats following a subsequent instillation of IL-l intratracheally. Similarly, lungs isolated from rats pretreated with IL-l also developed less leak than saline-perfused isolated lungs that were subsequently perfused with neutrophils and given IL-I intratracheally. Likewise, rat lung microvascular endothelial cells (RLMEC,) pretreated with IL-1 in vitro resisted injury by stimulated neutrophils better than saline-pretreated RLMEC. IL-I pretreatment increased NFKB activation in RLMEC and overexpression of the mutant forms of IKB~ (S32136A) or IKBB (S19123A) decreased both NFKB activation and tolerance in IL-I pretreated RLMEC. Identification of these “yin yang” responses is relevant to the design and interpretation of approaches that increase or decrease IL-I in ARDS and other inflammatory disorders.

Effect of granulocyte colony-stimulating factor on acute lung injury in the rat.

The effect of G-CSF pretreatment on experimental acute lung injury was studied in Sprague-Dawley rats receiving one of the following treatments: (1) G-CSF 50 micrograms/kg subcutaneously twice daily beginning 2 d prior to being killed; (2) ANTU 50 mg/kg intraperitoneally; (3) ANTU+G-CSF 50, 25, or 12.5 micrograms/kg; (4) HCl 0.6 ml of a 0.1 N solution intratracheally; (5) HCl+G-CSF 50 or 25 micrograms/kg; (6) control solutions. Lung injury was quantified by measurement of lung wet/dry weights, by histopathologic scoring, and by measurement of fluid flux during ex vivo perfusion. G-CSF pretreatment elevated the baseline blood neutrophil counts as much as 6-fold compared with Control, and it increased the numbers of lung neutrophils and caused a mild histologic lung injury, but it did not significantly alter wet/dry weight ratios or fluid flux. ANTU alone and HCl alone caused a moderate histologic lung injury, increased wet/dry weight ratio, and resulted in a small increase in flux. The combination injuries, ANTU+G-CSF and HCl+G-CSF, caused a more severe lung injury manifested by increased wet/dry weight ratios and increase in flux when compared with ANTU alone and HCl alone, respectively. We conclude that pretreatment with G-CSF potentiates ANTU- and HCl-induced lung injury in non-neutropenic rats. The potential for G-CSF to aggravate acute lung injury in patients remains speculative.

Ventilator pattern influences neutrophil influx and activation in atelectasis-prone rabbit lung

Both ventilator pattern and neutrophil activation influence lung injury in adult respiratory distress syndrome (ARDS). We therefore questioned whether ventilator pattern independently affects neutrophil accumulation and function in early ARDS. Thirty-five New Zealand White rabbits were anesthetized, paralyzed, and prepared using sterile techniques. Fifteen surfactant-depleted animals were randomized and ventilated for 4 h using high-frequency oscillatory ventilation (HFO) at 15 Hz with an inspired O2 fraction = 1.0 and arterial PO2 (PaO2) > 400 Torr (a pattern known to reverse atelectasis) or conventional mechanical ventilation (CMV) with PaO2 = 80-100 Torr (a pattern with some atelectasis despite positive end-expiratory pressure). Eight normal animals on CMV with PaO2 > 400 Torr served as a reference group (NorCMV). NorCMV animals progressively increased circulating polymorphonuclear neutrophil (PMN) numbers and had minor pressure-volume curve alterations but no other significant changes. Lavaged CMV animals developed the characteristic gas exchange and marked pressure-volume curve abnormalities of ARDS. Circulating PMNs remained constant but developed decreased chemotactic activity, whereas lung neutrophil numbers increased significantly (P = 0.0002) and had substantially enhanced chemiluminescence (P = 0.0003 vs. NorCMV animals). Although lavaged HFO animals accumulated an intermediate number of lung neutrophils (lung myeloperoxidase > NorCMV animals; P = 0.003), the chemiluminescence and chemotaxis of these PMNs were the same as in cells from NorCMV animals. We concluded that both the degree of neutrophil activation and lung injury can be minimized by preventing cyclic alveolar/airway expansion and collapse in the surfactant-deficient lung by use of appropriate ventilator patterns.

Lung neutrophils in the adult respiratory distress syndrome. Clinical and pathophysiologic significance.

Although neutrophils are of pathogenetic importance in various animal models of acute lung injury, their role in the adult respiratory distress syndrome (ARDS) is unclear. To study the significance of lung neutrophils in this disorder, patients with ARDS (n = 11) were evaluated by bronchoalveolar lavage within 24 h of admission to the intensive care unit. Patients with non-ARDS respiratory failure requiring mechanical ventilation (n = 4) and normal volunteers (n = 12) were also studied. Neutrophils constituted 67.6 +/- 9.8% of recovered lavage cells in patients with ARDS compared with only 4.0 +/- 2.4% of cells in mechanically ventilated control patients and 0.8 +/- 0.2% in normal volunteers (p less than 0.005, both comparisons). Furthermore, in patients with ARDS (n = 6) evaluated serially by bronchoalveolar lavage at 72-h intervals, neutrophil percentages decreased from 91 +/- 3.2% (initial lavage) to 42.8 +/- 12% (final lavage) (p less than 0.005). Lung neutrophils also predicted the severity of abnormalities in gas exchange and lung protein permeability. That is, the percentage of neutrophils correlated directly with the alveolar-arterial Po2 difference (r = 0.69, p less than 0.01) and lavage fluid total protein concentrations (r = 0.62, p less than 0.01). Because large numbers of lung neutrophils were present in these patients, ARDS lavage fluid was assayed for neutrophil mediators relevant to the pathogenesis of acute lung injury. Neutrophil elastase activity was not detected in any ARDS lavages, although elastase was antigenically present in most samples and appeared to be complexed to alpha-1-antitrypsin. In contrast to elastase, neutrophil collagenase was readily detectable in ARDS fluid.(ABSTRACT TRUNCATED AT 250 WORDS)