The presence of platelet-activating factor associated with eosinophil and/or neutrophil accumulations in the pleural fluids

Monocyte chemoattractant protein-1 and 5-lipoxygenase products recruit leukocytes in response to platelet-activating factor-like lipids in oxidized low-density lipoprotein

Oxidized low-density lipoprotein (LDL) contains inflammatory agents, including oxidatively fragmented phospholipids that activate the platelet-activating factor (PAF) receptor, but in vivo events caused by these pathologically generated agents are not well defined. Injection of PAF-like lipids derived from oxidized LDL, or C(4)-PAF that is a major PAF-like lipid in these particles, into the pleural cavity of mice resulted in rapid monocyte, neutrophil, and eosinophil accumulation. Increased numbers of intracellular lipid bodies in these cells show they were in an inflammatory environment. Leukocyte recruitment was abolished by a PAF receptor antagonist, as expected. PAF-like lipids induced 5-lipoxygenase expression in leukocytes, mRNA expression for monocyte chemoattractant protein-1 (MCP-1) and other chemokines, synthesis of MCP-1, and leukotriene B(4). The 5-lipoxygenase inhibitor zileuton impaired neutrophil influx, while MCP-1 had a more global role, as determined with MCP-1(-/-) mice. The lack of MCP-1 abrogated leukocyte accumulation and lipid body formation both in vivo and in vitro and chemokine transcription in vivo, and reduced in vivo leukotriene B(4) production. Thus, PAF-like phospholipids in oxidized LDL induce an inflammatory infiltrate through the PAF receptor, chemokine transcription, lipid body formation, and 5-lipoxygenase expression in leukocytes. MCP-1 has a key role in this inflammatory response, and 5-lipoxygenase products are essential for neutrophil recruitment into the inflamed pleural cavity.

Production of eosinophilic chemokines by normal pleural mesothelial cells

Eosinophilic pleural effusion occurs in many diseases. The mechanisms of eosinophil accumulation are not well understood. We showed previously that eotaxin was readily detectable in most pleural effusions, and its concentration significantly correlated with eosinophil number. To test the hypothesis that pleural eotaxin is produced by resident mesothelial cells, we examined its production by normal pleural mesothelial cells (NPMC). Eotaxin was induced by tumor necrosis factor (TNF)-alpha or interleukin (IL)-4 and was drastically increased by their combination. In contrast, interferon (IFN)-gamma inhibited eotaxin production. Regulated on activation, normal T cells expressed and secreted (RANTES) was also induced by TNF-alpha and was drastically increased by the addition of IFN-gamma. These effects were observed at both protein and mRNA levels. Stabilization of RANTES mRNA was observed with IFN-gamma but not IL-4; neither cytokine stabilized eotaxin mRNA. Eosinophil chemoattractant activity in culture supernatants of NPMC stimulated with TNF-alpha plus IL-4 was diminished by an anti-eotaxin antibody; that induced by TNF-alpha plus IFN-gamma was attenuated by an anti-RANTES antibody. Thus, NPMC can produce eotaxin, and different cytokines act on NPMC to induce different chemokines by different mechanisms. IFN-gamma, a Th1 cytokine, acts at least at the posttranscriptional level to induce RANTES production, but it inhibits eotaxin production. In contrast, IL-4, a Th2 cytokine, acts at the transcriptional level to induce eotaxin.

Analysis of pleural fluid in idiopathic spontaneous pneumothorax; correlation of eosinophil percentage with the duration of air in the pleural space

Pleural fluid analysis was performed in patients with idiopathic spontaneous pneumothorax. The objective of the study was to define the cell differentiation, and part of the cytokine profile, in relation to the duration of pneumothorax. In the 23 consecutive patients (19 men, mean age 34.2 years, 17 smokers), pleural fluid was obtained immediately after chest tube drainage (n = 6), or during thoracoscopy (n = 17). Cytospins were carried out, and supernatant analysis of the different cytokines was performed using sandwich ELISA. All concentrations were corrected for dilution. The duration of the pneumothorax was correlated with the rise in eosinophil percentage (r = 0.81, P < 0.00001) in pleural fluid. RANTES, platelet-activating factor (PAF), and monocyte chemotactic protein-1 (MCP-1) were detectable but no relationship with eosinophils or duration of the pneumothorax was found. Granulocyte-macrophage colony stimulating factor (GM-CSF) and interluekin-8 (IL-8) were not detectable. Interleukin-5 (IL-5) concentration correlated with the eosinophil concentration (r = 0.84, P = 0.037) and the eosinophil percentage (r = 0.68, P = 0.005) in the pleural fluid. Idiopathic spontaneous pneumothorax causes a time-related rise in the eosinophil percentage in the pleural space, which correlates with the level of IL-5.

Postural changes in pleural fluid constituents

Measurement of pleural fluid constituents (pH, PCO2, protein, lactic dehydrogenase [LDH], glucose, red blood cells [RBC], and white blood cells [WBC]) are of value in the diagnosis of pleural effusions and in the separation of exudates from transudates. The position of the patient (sitting or lying) prior to thoracentesis may result in differences in the measurement of these constituents. We found significant postural changes (p < 0.05) in the measurement of pH, protein, LDH, and RBCs in all exudative effusions (n = 12) in the upright sitting position compared with the supine position. No postural changes were noted in the transudative effusions (n = 6). The location of basal pleural tumors and the molecular weight of certain constituents may explain this postural sedimentary effect. Repeated thoracentesis after 30 min in the sitting position may result in exudative values when borderline transudates are found in a patient previously in a supine position.

Interleukin-8 is a major neutrophil chemotactic factor in pleural liquid of patients with empyema

Interleukin-8 (IL-8), a potent neutrophil chemotactic peptide, has been found in association with human disease, but its contribution to chemotactic activity in humans is not yet known. We asked whether IL-8 is present in inflammatory human pleural effusions, and to what extent it contributes to pleural liquid neutrophil chemotactic activity. Because tumor necrosis factor alpha (TNF-alpha) is a strong inducer of IL-8, we also asked whether TNF-alpha was present. For this prospective study, we collected pleural liquid from 51 patients (empyema, 14; parapneumonic, four; tuberculous, eight; malignant, nine; miscellaneous exudative, seven; and transudative, nine), counted pleural neutrophils, and measured IL-8 and TNF-alpha concentrations in the supernatant. To determine the contribution of IL-8 to chemotactic activity in empyema, we measured the neutrophil migration induced by empyemic liquids before and after addition of anti-IL-8 F(ab')2 antibody fragments or control anti-IL-6 F(ab')2. We found that IL-8 concentrations were higher in empyema (61.3 +/- 21.0 ng/ml [SEM]) than in all other effusions (1.1 +/- 0.5 ng/ml) (p = 0.0001). All empyema liquids had IL-8 concentrations above 2.5 ng/ml, which was true for only three of the other 37 effusions (two parapneumonic, one tuberculous). IL-8 levels correlated with the pleural neutrophil count (r = 0.46; p = 0.007) and the neutrophil chemotactic activity of pleural liquid (r = 0.43; p = 0.008). Anti-IL-8 antibodies decreased chemotactic activity in empyema liquids by 65 +/- 5%, whereas the control antibody had no effect (0 +/- 5% decrease) (p = 0.0005).(ABSTRACT TRUNCATED AT 250 WORDS)

Interactions between airway epithelium and mediators of inflammation

Epithelial cells lining the respiratory airways classically are considered to be "target" cells, responding to exposure to a variety of inflammatory mediators by altering one or several of their functions, such as mucin secretion, ion transport, or ciliary beating. Specific responses of epithelial cells in vivo or in vitro to many of these inflammatory mediators are discussed. Recent studies have indicated that airway epithelial cells also can act as "effector" cells, responding to a variety of exogenous and/or endogenous stimuli by generating and releasing additional mediators of inflammation, such as eicosanoids, reactive oxygen species, and cytokines. Many of these epithelial-derived substances can diffuse away and affect neighboring cells and tissues, or can act, via autocrine or paracrine mechanisms, to affect structure and function of epithelial cells themselves. Studies dealing with airway epithelium as a source of inflammatory mediators and related compounds also are discussed.

Platelet-activating factor detected in bronchoalveolar lavage fluids from an asthmatic patient

It recently has been recognized that platelet-activating factor (PAF) may be a mediator of asthma exacerbation. We had the opportunity to analyze bronchoalveolar lavage fluids from an asthmatic infant, which were characterized by neutrophil infiltration. The patient's lungs were washed on three occasions with saline during asthmatic attacks. PAF was found in each case on the basis of its ability to cause the immediate aggregation of washed rabbit platelets. The PAF detected was equivalent to 1-1.4 pmol of 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine, three quarters of which were recovered in cell-associated form. By contrast, we did not detect PAF in bronchoalveolar exudates from patients with laryngeal stenosis or with respiratory distress syndrome. LysoPAF, the direct precursor as well as initial metabolite of PAF, was also analyzed after being converted to PAF by acetylation. There was a wide variation in the amount of lysoPAF present in individual patients, suggesting that lysoPAF levels cannot be taken as an indicator for the presence of PAF.

Presence of platelet-activating factor in pyuria in humans

The relationship between the occurrence of platelet-activating factor (PAF) and neutrophils in urine from patients with urinary tract infection was examined. PAF was detected in human pyuria, when leukocyte levels reached at least 300 cells/microL (n = 45), but not in normal urine (n = 12). The amount of PAF found in pyuria, measured by platelet aggregation assay, was 0.01 to 13.3 pmol/mL. A close correlation was seen between the amount of PAF present and the number of urinary leukocytes (p less than 0.01, r = 0.70). The leukocytes in pyuria consisted almost entirely of neutrophils (96 +/- 4%, mean +/- S.D.). Our findings suggest that the occurrence of PAF is associated with the accumulation of neutrophils in urine.