CD11b/CD18 expression, adherence, and chemotaxis of granulocyte in adult respiratory distress syndrome

Release of neutrophil extracellular traps in response to Candida albicans yeast, as a secondary defense mechanism activated by phagocytosis

Candida albicans is one of the main pathogens responsible for the development of difficult-to-fight fungal infections called candidiasis. Neutrophils are the major effector cells involved in the eradication of fungal pathogens. This group of immune cells uses several mechanisms that enable the rapid neutralization of pathogens. The most frequently identified mechanisms are phagocytosis and the release of neutrophil extracellular traps (NETs). The mechanism for selecting the type of neutrophil immune response is still unknown. In our study, we analyzed the relationship between the activation of phagocytosis and netosis. We detected the presence of two neutrophil populations characterized by different response patterns to contact with C. albicans blastospores. The first neutrophil population showed an increased ability to rapidly release NETs without prior internalization of the pathogen. In the second population, the netosis process was inherently associated with phagocytosis. Differences between populations also referred to the production of reactive oxygen species. Our results suggest that neutrophils use different strategies to fight C. albicans and, contrary to previous reports, these mechanisms are not mutually exclusive.

Effect of inhaled endotoxin on airway and circulating inflammatory cell phagocytosis and CD11b expression in atopic asthmatic subjects

BACKGROUND

In a cohort of 8 normal and 10 allergic asthmatic volunteers, we previously reported that inhalation of 5 microg of endotoxin (LPS) induced airway inflammation that correlated with CD14 expression that was, in turn, correlated with eosinophil numbers in the airway. Macrophage and neutrophil functions have been reported to be modified by endotoxin in vitro and in vivo, and response to endotoxin is mediated largely by airway phagocytes and related to allergic inflammation.

OBJECTIVE

We sought to examine functional and cell-surface phenotype changes in phagocytes recovered from atopic asthmatic subjects after endotoxin challenge.

METHODS

Sputum and peripheral blood from 10 allergic asthmatic subjects was recovered after saline and LPS challenge. Assessment of phagocytosis and cell-surface phenotype (CD11b, CD14, and CD64) was performed on phagocytes obtained from sputum (n = 7) and blood samples (n = 10).

RESULTS

Phagocytosis of blood and sputum phagocytes was blunted after LPS challenge in a fashion that correlated with the increase in airway neutrophils after LPS challenge. Cell-surface expression of CD14 (membrane-bound CD14) was increased in sputum cells, whereas CD11b was decreased in sputum and circulating phagocytes. Baseline expression of CD11b in blood correlated with the magnitude of the neutrophil response after LPS inhalation, as well as (inversely) with baseline airway eosinophil levels.

CONCLUSIONS

Inhalation of endotoxin at levels adequate to induce a neutrophil influx to the airways (but not systemic symptoms) results in decreased phagocytosis in both airway and circulating cells and modifies CD11b expression in a way that implicates its involvement in phagocyte responsiveness to inhaled LPS.

Effect of endogenous nitric oxide on hyperoxia and tumor necrosis factor-alpha-induced leukosequestration and proinflammatory cytokine release in rat airways

OBJECTIVE

To investigate the effects of endogenous nitric oxide on hyperoxia and tumor necrosis factor-alpha-induced leukosequestration and proinflammatory cytokine release in rat airways.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Experimental laboratory.

SUBJECTS

Male Sprague-Dawley rats weighing 350-500 g.

INTERVENTIONS

The rats were pretreated with N(G)-nitro-L-arginine methyl ester (L-NAME; 10 mg/kg) or saline intravenously 4-6 mins before intratracheal administration of tumor necrosis factor-alpha, 95% oxygen, or both, when the vasopressor effect of L-NAME had reached a plateau.

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavage fluid was recovered from the airway of rats after exposure to 95% oxygen and tumor necrosis factor-alpha for 6 hrs under ventilator support. Neutrophils in lavage fluid were isolated and examined for the inducible nitric oxide synthase expression by flow-cytometric assay. Tumor necrosis factor-alpha and interleukin-1 beta in lavage fluid were measured by enzyme-linked immunosorbent assay. The percentage of neutrophils in bronchoalveolar fluid was significantly higher in rats exposed to hyperoxia + tumor necrosis factor-alpha (29.7 +/- 12.5%) compared with rats with hyperoxia (16.3 +/- 1.2%), tumor necrosis factor-alpha (4.2 +/- 1.1%), or room air (5.0 +/- 1.8%) alone (p <.05). Rats exposed to hyperoxia + tumor necrosis factor-alpha had significantly higher concentrations of inducible nitric oxide synthase of neutrophils (350.1 +/- 75.7 mean fluorescence intensity), compared with rats with hyperoxia (64.9 +/- 1.6 mean fluorescence intensity), tumor necrosis factor-alpha (102.6 +/- 15.3 mean fluorescence intensity), or room air (111.2 +/- 25.8 mean fluorescence intensity) alone (p <.05). Rats exposed to hyperoxia + tumor necrosis factor-alpha significantly produced higher concentrations of tumor necrosis factor-alpha and interleukin-1 beta, compared with rats with tumor necrosis factor-alpha, hyperoxia, or room air alone. Hyperoxia + tumor necrosis factor-alpha also significantly increased growth-related oncogene/cytokine-induced neutrophil chemoattractant (GRO/CINC)-1 in bronchoalveolar fluid, compared with those receiving tumor necrosis factor-alpha alone, hyperoxia alone, or room air alone. L-NAME significantly enhanced the percentage of neutrophil recovery and the production of tumor necrosis factor-alpha, interleukin-1 beta, and GRO/CINC-1 in airways compared with the corresponding hyperoxia + tumor necrosis factor-alpha treatment alone.

CONCLUSIONS

Endogenous nitric oxide may be an important endogenous inhibitor of hyperoxia + tumor necrosis factor-alpha-induced leukocyte recruitment and subsequently tumor necrosis factor-alpha, interleukin-1 beta, and GRO/CINC-1 release.

Glucocorticoid suppresses neutrophil activation in ventilator-induced lung injury

OBJECTIVE

To investigate, in a rat model, the role of the Mac-1/ICAM-1 pathway and the anti-inflammatory activity of steroid in ventilator-induced lung injury.

DESIGN

Prospective, randomized controlled study.

SETTING

Animal investigation using Wistar rats.

INTERVENTION

Rats in three randomly assigned groups of 18, a total of 54 animals, were subject to the following: Two groups received high peak inspiratory pressure (35 cm H2O) ventilation after pretreatment with methylprednisolone (high-methylprednisolone group) or pretreatment with methylprednisolone vehicle (high-vehicle group). The third group of animals received low peak inspiratory pressure (7 cm H2O) ventilation after pretreatment with methylprednisolone vehicle (low-vehicle group). Except for animals previously killed to establish baseline values, after 40 mins of mechanical ventilation, the animals in each group were killed. Some animals provided histological samples, and the rest received total lung lavage.

MEASUREMENT

We measured flow cytometry of lavage fluid, cell counts of tissue samples, and pressure-volume curves before and after mechanical ventilation.

RESULTS

In the groups that received high peak inspiratory pressure ventilation, both the number of neutrophils that infiltrated the lungs and the expression of Mac-1 and ICAM-1 on neutrophils and macrophages increased significantly more than in the low-vehicle group. Static lung compliance was reduced in the high peak inspiratory pressure groups. In the high peak inspiratory pressure groups, there were significantly fewer neutrophils in samples from the high-methylprednisolone group (0.412 +/- 0.1 x 10(5)) than from the high-vehicle group (1.10 +/- 0.1 x 10(5); p < .05). The high-vehicle group showed greater expression of CD11b on neutrophils, but this was significantly decreased by methylprednisolone (mean fluorescence intensity: high-vehicle, 118.4 +/- 34.3; high-methylprednisolone, 25.8 +/- 4.2; p < .05). The lung mechanics measured by pressure-volume curve analysis were deteriorated less in the high-methylprednisolone group.

CONCLUSION

Our study suggests that a neutrophil-endothelium interaction via the Mac-1/ICAM-1 pathway is involved in the activation and recruitment of neutrophils in ventilator-induced lung injury. Activation and recruitment of neutrophils were lessened by pretreatment with methylprednisolone, which might have contributed to the improvement of lung dysfunction after mechanical ventilation.

Inhibition of CD11-CD18 complex prevents acute lung injury and reduces mortality after peritonitis in rabbits

Acute lung injury is frequent after severe peritonitis. The aim of this study was to investigate whether inhibition of the adhesion molecule CD11-CD18 on polymorphonuclear leukocytes (PMNs) would have any beneficial effects on pulmonary function and mortality in an animal model reproducing these clinical conditions. Acute peritonitis was induced in 36 rabbits by intraperitoneal injection of zymosan (0.6 g/kg) suspended in mineral oil; 20 were pretreated with a murine-specific IgG2a anti-CD18 monoclonal antibody, 16 (controls) with nonspecific purified murine IgG (1 mg/kg). The animals were followed for 10 d, then killed for histologic examination of the lungs. Blood samples were taken on Days 0, 1, 3, 7, and 10 for red blood cell (RBC), white blood cell (WBC), and platelet counts, pH, PO(2), PCO(2), carbon dioxide content (HCO(3)(-)) measurements, and renal and liver tests. Treatment with the anti-CD18 monoclonal antibody reduced mortality by approximately 40% (p < 0.05). PO(2) was higher in these treated animals than in the control animals throughout the study (p < 0.05 on Day 1, 3, and 10). On Day 1 control animals had significant leukopenia, whereas anti-CD18-treated animals had a moderate increase of the number of circulating WBC compared with baseline values (p < 0.05 between groups). The lungs of the anti-CD18-treated animals showed minor signs of inflammation and PMN infiltration whereas controls had interstitial and intra-alveolar edema and a large number of granulocytes. Quantification of PMNs by morphometry showed that there were constantly less granulocytes in the lungs of the animals treated with the anti-CD18 antibody (p < 0.001). PMN infiltration correlated with the levels of PO(2) (p < 0.001). Lung tissue of anti-CD18-treated rabbits contained less malonyldialdehyde, a by-product of membrane lipid peroxidation by PMN oxygen radicals (950 +/- 120 versus 1,710 +/- 450 pM/mg of protein) and, conversely, more of the antioxidant alpha-tocopherol (136 +/- 22 versus 40 +/- 9 ng/mg of protein), than the control rabbits (p < 0.01). In this particular model of ARDS the monoclonal antibody against the CD11-CD18 complex had a beneficial effect, reducing PMN infiltration and oxygen radical release in the lungs, preventing alveolocapillary membrane damage, improving gas exchange and, finally, significantly reducing mortality.

Estudo de crianças com síndrome do desconforto respiratório agudo: correlação anatomoclínica radiológica

Estudo retrospectivo com revisão dos casos clínicos de Síndrome do Desconforto Respiratório Agudo, realizado no período de out/88 a dez/90 na Unidade de Pacientes Graves do Instituto Fernandes Figueira. Os autores estudaram as características clínicas, radiológicas e histopatológicas de acordo com o estágio evolutivo da doença. Dentre 459 casos estudados, foram selecionados 49 (11%). Onze casos tiveram exame anatomopatologico [biopsia (4), necropsia (8)] e foram classificados de acordo com o estágio evolutivo em: fase exsudativa inicial, fase proliferativa celular e fase proliferativa fibrótica. Houve correlação clínica radiológica e anatomopatológica nos casos confirmados com exame histológico. Os autores consideram importante estudos futuros em que a interação entre a pesquisa clínica e experimental permita o melhor conhecimento desta Síndrome na população pediátrica.

A systemic fetal inflammatory response and the development of bronchopulmonary dysplasia

OBJECTIVE

The purpose of this study was to test the hypothesis that a systemic fetal inflammatory response is a risk factor for the subsequent development of bronchopulmonary dysplasia in preterm neonates.

STUDY DESIGN

The relationship between interleukin 6 concentrations in umbilical cord plasma at birth and the occurrence of bronchopulmonary dysplasia was examined in 203 preterm births (25-34 weeks). Ninety-six patients underwent transabdominal amniocentesis within 5 days of birth. The relationship between umbilical cord plasma interleukin 6 concentration and bronchopulmonary dysplasia was compared with the relationship between amniotic fluid interleukin 6 concentration and bronchopulmonary dysplasia. Interleukin 6 was measured by specific immunoassay. Logistic regression was used for statistical analysis.

RESULTS

Bronchopulmonary dysplasia was diagnosed in 17% (34/203) of the infants. Neonates in whom bronchopulmonary dysplasia developed had a significantly higher median interleukin 6 concentration in umbilical cord plasma at birth than did those in whom bronchopulmonary dysplasia did not develop (median, 68.3 pg/mL and range, 0.3-6150.0 pg/mL vs median, 6.9 pg/mL and range 0-19,230.0 pg/mL; P <.001). This difference remained significant after adjustment for gestational age at birth (odds ratio, 4.2; 95% confidence interval, 1.6-11.2). Logistic regression analysis indicated that an elevated umbilical cord plasma interleukin 6 concentration was a better predictor of the development of bronchopulmonary dysplasia than was an elevated amniotic fluid interleukin 6 concentration (P <.005).

CONCLUSION

An elevated interleukin 6 concentration in umbilical cord plasma at birth is an independent risk factor for the development of bronchopulmonary dysplasia. These data support the concept that the injury responsible for bronchopulmonary dysplasia in a subset of neonates may begin before birth and is associated with the development of a fetal systemic inflammatory response, as determined by plasma concentrations of interleukin 6.

Attenuation of ventilator-induced acute lung injury in an animal model by inhibition of neutrophil adhesion by leumedins (NPC 15669)

OBJECTIVES

Beta2-integrin (CD11b/CD18) expression, an indicator of neutrophil activation, has been associated with the development of acute respiratory distress syndrome. Leumedins act directly on leukocytes to inhibit the up-regulated expression of beta2-integrins involved in leukocyte adhesion. We examined the effect of such a new anti-inflammatory agent, NPC 15669 (N-[9H-(2,7-dimethylfluorenyl-9-methoxy)-carbonyl]-L-leucine), on neutrophil-mediated acute lung injury in an animal model.

DESIGN

Prospective, randomized, blinded, controlled animal study.

SETTING

An animal laboratory in a university setting.

SUBJECTS

Adult New Zealand rabbits.

INTERVENTIONS

After repeated lung lavages with normal saline to induce acute lung injury, anesthetized rabbits were randomly assigned to one of two groups (n = 6 per group): a) treatment group (pretreated with NPC 15669 [10 mg/kg i.v. bolus] 30 mins before lavage, followed by a continuous infusion [5 mg/kg/hr] for the duration [4 hrs] of the experiment); or b) control group (pretreatment and continuous infusion with placebo). All animals were mechanically ventilated with identical pressure settings over 4 hrs and were killed at the end of the experiment.

MEASUREMENTS AND MAIN RESULTS

PaO2, PaCO2, and tidal volumes were repeatedly measured and airway pressure settings were noted every 30 mins. At the end of the experiment, lungs were taken out for measurements of the myeloperoxidase content, for conventional histology (hematoxylin and eosin staining), and for intracellular adhesion molecule-1 immunohistostaining. Pretreatment with NPC 15669 profoundly improved oxygenation from a PaO2 of 52 +/- 5 torr (6.9 +/- 0.7 kPa) to 250 +/- 161 torr (33.3 +/- 21.5 kPa) within 60 mins after lung lavage (p < .05). Oxygenation continued to improve throughout the study, reaching a maximal PaO2 value of 395 +/- 98 torr (52.7 +/- 13.1 kPa) at 4 hrs. In the control group, oxygenation remained poor throughout the observation period. PaO2 values differed significantly (51 +/- 20 torr [6.8 +/- 2.7 kPa] vs. 306 +/- 126 torr [40.8 +/- 16.8 kPa], p < .005) at 90 mins and at all subsequent measurements from those values in the NPC 15669 group. Dynamic lung compliance improved significantly 60 to 90 mins after repeated lung lavage. Histology demonstrated markedly less lung damage (hyaline membrane formation and leukocyte infiltration) in treated animals (p < .05) than in controls.

CONCLUSIONS

NPC 15669 seems to block inflammatory reactions by inhibiting the sequestration of neutrophils in acute, ventilator-associated lung injury. As a result, gas exchange and total lung compliance improve. Application of this and similar compounds affecting neutrophil adhesion warrants further investigation as a treatment modality for acute lung injury.

Effect of endogenous nitric oxide on tumour necrosis factor-alpha-induced leukosequestration and IL-8 release in guinea-pigs airways in vivo

1. Tumour necrosis factor-alpha (TNF-alpha) is implicated in the pathogenesis of many pulmonary and airway diseases. TNF-alpha stimulation may release interleukin-8 (IL-8) in airways mediated via an increase in intracellular oxidant stress. In the present study, we have assessed leukosequestration and IL-8 release in the airways in response to intratracheal administration of human recombinant TNF-alpha, and examined the modulatory role of endogenous NO by pretreatment with a NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME). 2. TNF-alpha (10(2)-10(-4) u) was administered intratracheally in male guinea-pigs which were anaesthetized with urethane and were ventilated artificially. TNF-alpha induced a time- and dose-related increase in neutrophil numbers and a concomitant increase in human IL-8 equivalent level retrieved from bronchoalveolar lavage (BAL) with the peak effect at 10(3) u at 6 h of TNF-alpha injection (late phase). Intratracheal administration of recombinant human (rh)IL-8 (0.025, 0.25, 2.5 ng) producing a similar range of human IL-8 equivalent levels in BAL as measured in our results induced neutrophil recovery in BAL fluid to a similar extent. Administration of anti-IL-8 antibody prevented the late phase of neutrophil recruitment induced by TNF-alpha or rhIL-8. 3. Pretreatment with L-NAME significantly enhanced the TNF-alpha (10(3) u)-induced neutrophil recruitment and human IL-8 equivalents production at 6 h, but not at 1 h of TNF-alpha administration (early phase). L-Arginine reversed the responses to L-NAME. Pretreatment with 0.2% DMSO (i.v.) significantly inhibited TNF-alpha-induced neutrophil recruitment and human IL-8 equivalents release both in the early and late phase of the responses. Pretreatment with DMSO also inhibited the enhancement effect of L-NAME on the late phase of TNF-alpha-induced responses. DMSO failed to modify exogenous rhIL-8-induced neutrophil recruitment. Neither L-NAME nor DMSO alone induced any significant change in neutrophil numbers or human IL-8 equivalent level in BAL fluid. 4. Neutrophil depletion by cyclophosphamide pretreatment failed to modify TNF-alpha-induced human IL-8 equivalent release. 5. The expression of beta 2-integrin, CD11b/CD18 on neutrophils was increased only in the late but not early phase of TNF-alpha stimulation. L-NAME failed to modify these responses. 6. In conclusion, we demonstrated that NO may be an important endogenous inhibitor of TNF-alpha-induced leukocyte chemotaxis via inhibition of IL-8 production. Thus, the production of NO in airway inflammatory diseases may play a negative feedback role in self-limiting the magnitude of inflammatory responses.

XO increases neutrophil adherence to endothelial cells by a dual ICAM-1 and P-selectin-mediated mechanism

Circulating xanthine oxidase (XO) can modify adhesive interactions between neutrophils and the vascular endothelium, although the mechanism underlying this effect are not clear. We found that treatment with XO of bovine pulmonary artery endothelial cells (EC), but not neutrophils or plasma, increased adherence, suggesting that XO had its primary effect on EC. The mechanism by which XO increased neutrophil adherence to EC involved binding of XO to EC and production of H2O2. XO also increased platelet-activating factor production by EC by a H2O2-dependent mechanism. Similarly, the platelet-activating factor-receptor antagonist WEB-2086 completely blocked XO-mediated neutrophil EC adherence. In addition, neutrophil adherence was dependent on the beta 2-integrin Mac-1 (CD11b/CD18) but not on leukocyte functional antigen-1 (CD11a/CD18). Treatment of EC with XO for 30 min did not alter intercellular adhesion molecule-1 surface expression but increased expression of P-selectin and release of von Willibrand factor. Antibodies against P-selectin (CD62) did not affect XO-mediated neutrophil adherence under static conditions but decreased both rolling and firm adhesive interactions under conditions of shear. We conclude that extracellular XO associates with the endothelium and promotes neutrophil-endothelial cell interactions through dual intercellular adhesion molecule-1 and P-selectin ligation, by a mechanism that involves platelet-activating factor and H2O2 as intermediates.

Alteration of alveolar macrophage chemotaxis, cell adhesion, and cell adhesion molecules following ozone exposure of rats

Ozone (O3) exposure of humans and animals induces an inflammatory response in the lung, which is associated with macrophage stimulation, release of chemotactic agents, and recruitment of polymorphonuclear leukocytes (PMNs). This study was designed to investigate the functional aspects of the macrophages that impact inflammatory processes in the lung. Macrophages recovered by bronchoalveolar lavage (BAL) from rats exposed to purified air or 0.8 ppm O3 were studied for their chemotactic activity, adhesive interactions with alveolar epithelial cells in culture, surface morphology, and surface expression of cell adhesion molecules. The macrophages isolated from O3-exposed rats exhibited a greater motility in response to a chemotactic stimulus than the macrophages isolated from rats exposed to purified air. The macrophages from O3-exposed animals also displayed greater adhesion when placed in culture with epithelial cells isolated from adult rat lung (ARL-14) than the macrophages from control rats. Both chemotactic motility and cell adhesion stimulated by O3 exposure were attenuated when the macrophages were incubated in the presence of monoclonal antibodies to leukocyte adhesion molecules, CD11b, or epithelial cell adhesion molecules, ICAM-1. Flow cytometry revealed a modest increase in the surface expression of CD11b but no change in ICAM-1 expression in macrophages from O3-exposed rats when compared to those from the air-exposed controls. The results demonstrate an alteration of macrophage functions following O3 exposure and suggest the dependence of these functions on the biologic characteristics, rather than the absolute expression, of the cell adhesion molecules.