Decreased leukotriene B4 synthesis in smokers' alveolar macrophages in vitro

Altered release of eicosanoids by rat alveolar macrophages during granulomatous pulmonary inflammation

Release of arachidonic acid metabolites (eicosanoids) by alveolar macrophages may be important in regulating pulmonary inflammatory reactions. The purpose of this study was to characterize eicosanoids released by rat alveolar macrophages during the evolution of experimentally induced pulmonary inflammation. Immunization with subcutaneous bacillus Calmette-Guerin (BCG) followed 2 wk later by intravenous BCG challenge resulted in mild granulomatous pulmonary inflammation for up to 30 days. At serial intervals, alveolar macrophages were lavaged from the BCG-treated rats as well as from control normal rats. Lavaged macrophages were cultured in vitro, and culture supernatants were assayed by radioimmunoassay for release of prostaglandin E2 (PGE2), Leukotriene B4 (LTB4), and thromboxane B2 (TXB2). Cells were cultured alone, or with added LPS or calcium ionophore A23187 to stimulate eicosanoid release. During BCG-induced inflammation, spontaneous release of PGE2 and LTB4 was unchanged, while spontaneous release of TXB2 was depressed acutely and then returned to control levels. The capacity of alveolar macrophages to release specific eicosanoids in response to an in vitro stimulus was dramatically altered during the course of BCG-induced inflammation. Stimulated release of PGE2 was transiently increased during acute lung injury, but stimulated release of LTB4 was significantly decreased at all stages of inflammation. Stimulated release of TXB2 was unchanged. These results indicate that during the course of granulomatous pulmonary inflammation there are dynamic changes in the profile of eicosanoids released by alveolar macrophages, both spontaneously and in response to in vitro stimulation. This alteration in the release of eicosanoids by alveolar macrophages may be an important factor in the resolution of pulmonary inflammation.

Inhibition of human alveolar macrophage production of leukotriene B4 by acute in vitro and in vivo exposure to tobacco smoke

The number of neutrophils in the lungs of cigarette smokers is increased. This could be a consequence of the chemotactic mediator synthesis by alveolar macrophages (AM). In order to evaluate the possible role of leukotriene B4 (LTB4) in this condition, we studied the formation of LTB4 by nonsmokers' AM exposed in vitro and in vivo to cigarette smoke and by smokers' AM. In the absence of stimulus or upon stimulation, nonsmokers' AM exposed in vitro to tobacco smoke formed less LTB4 than did nonexposed AM, e.g., the cells incubated with arachidonic acid and ionophore produced, respectively, 241 +/- 132 and 425 +/- 106 pmol LTB4/10(6) cells (mean +/- SEM) (P less than 0.01). In other experiments, smokers' AM were incubated in absence of stimulus and produced less LTB4 than did nonsmokers' AM; during a 3-h incubation, smokers' and nonsmokers' adherent AM released, respectively, 3 +/- 2 and 40 +/- 28 pmol LTB4/10(6) cells (P less than 0.05). Similarly stimulated smokers' AM produced less LTB4 than did nonsmokers' AM, e.g., the cells incubated with arachidonic acid and ionophore formed, respectively, 225 +/- 41 and 573 +/- 150 pmol LTB4/10(6) cells (P less than 0.05). In a group including mild smokers and nonsmokers, in vivo exposure to the smoke of 4 cigarettes produced a decrease in the release of LTB4 by AM, e.g., in the presence of arachidonic acid and ionophore, nonexposed and exposed AM produced, respectively, 198 +/- 38 and 143 +/- 38 pmol LTB4/10(6) cells (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Arachidonic acid metabolism in normal human alveolar macrophages: stimulus specificity for mediator release and phospholipid metabolism, and pharmacologic modulation in vitro and in vivo

Arachidonic acid (AA) metabolism in normal human alveolar macrophages including phospholipid turnover, stimulus specificity for mediator release including trigger synergy, and the pharmacologic control of the release of AA metabolites was explored. Macrophages labeled overnight with [3H]AA, then activated, released three major AA metabolites, thromboxane B2 (TxB2), leukotriene B4 (LTB4), and 5-hydroxyeicosatetraenoic acid (5-HETE), as characterized by thin layer chromatography, high performance liquid chromatography, and radioimmunoassay. Although all triggers (phorbol myristate acetate [PMA], serum-activated zymosan, and ionophore A23187) resulted in the release of TxB2 and free AA, efficient synthesis of lipoxygenase products, particularly LTB4, required A23187. A23187 was the most effective single agent in producing LTB4 synthesis, was synergistic with PMA in causing LTB4 release, and was associated with significant turnover of phosphatidylcholine and phosphatidylinositol. Incubation of macrophages in vitro with cyclooxygenase inhibitors resulted in an inhibition of the formation of cyclooxygenase products; however, no shunting of metabolites into products of the lipoxygenase pathway was observed. Although overnight incubation of macrophages in vitro with dexamethasone (1 microM) resulted in an inhibition of both the spontaneous and A23187/PMA-triggered release of all AA metabolites, treatment of 5 volunteers with dexamethasone (4 mg po bid x 7 doses, in a single-blind, placebo-controlled, crossover protocol) resulted in no significant inhibition of the release of AA metabolites from macrophages triggered ex vivo. We conclude that activation of normal human alveolar macrophages results in phospholipid turnover (phosphatidylcholine and phosphatidylinositol) and the release of three major AA metabolites (TxB2, LTB4, and 5-HETE); that optimal synthesis of lipoxygenase product requires the presence of a calcium signal (A23187), although PMA can synergize with A23187 in the production of lipoxygenase products; and that glucocorticoids may have a different effect on the release of AA metabolites from alveolar macrophages when administered in vitro versus in vivo.

Airway hyperreactivity induced by active cigarette smoke exposure in guinea-pigs: possible role of sensory neuropeptides

Exposure to cigarette smoke is associated with increased airway responsiveness to different stimuli, both in human and animal studies. However, the mechanisms involved in the pathogenesis of smoke-induced airway hyperreactivity are less clear. We investigated the development of airway hyperreactivity induced by active cigarette smoke exposure in anaesthetised guinea-pigs and the possible mechanisms involved. Active inhalation of cigarette smoke (15 s/min for 10 min) potentiated the broncho-contractile effect of acetylcholine (Ach), indicating the occurrence of airway hyperreactivity. This phenomenon appeared within 5 min and lasted up to 50 min after smoke exposure. Smoke induced airway hyperreactivity was a non-specific phenomenon, involving an enhanced responsiveness to both Ach and histamine (Hist). Recruitment of proinflammatory cells into the airway lumen, as revealed by the analysis of bronchoalveolar lavage fluid, paralleled the development of the hyperreactive phenomenon, suggesting a relationship between the inflammatory reaction and the genesis of smoke-induced airway hyperreactivity. Cervical bilateral vagotomy did not modify either the degree and the time-course of smoke induced airway hyperreactivity. Moreover, atropine treatment did not affect the increase in Hist response due to smoke inhalation. On the other hand, depletion of substance P due to capsaicin pretreatment almost completely prevented the capacity of cigarette smoke to potentiate Ach induced bronchoconstriction. Cyclo-oxygenase inhibition, by indomethacin pretreatment, reduced the time course of the hyperreactivity induced by smoke inhalation. Our results clearly demonstrate the occurrence of airway hyperreactivity triggered by active cigarette smoke exposure. Moreover, the data obtained suggest a predominant role for substance P and related peptides in the pathogenesis of smoke induced increase in airway responsiveness.

Seasonal variation in the phagocytic activity and arachidonic-acid metabolism of human blood monocytes in healthy non-smokers, smokers and chronic bronchitics

Peripheral blood monocytes are precursor cells to alveolar macrophages (AMs). Many studies have been performed with a view to assessing the differences, in respect of morphology and function, between the AMs of smokers and those of non-smokers. Disturbed host-defence activity of smokers' AMs is reflected by, for instance, decreased phagocytic activity and impaired arachidonic acid metabolism. However, very little attention has been paid to the question what effects cigarette smoking and chronic bronchitis may have on the function of the precursors of these cells--the blood monocytes. The collection of blood monocytes is much less laborious than the sampling of AMs. Therefore, it would be a great advance if the deteriorated host defence in chronic bronchitis could be detected and followed by studies of blood monocytes. However, a seasonal variation in monocyte function, discussed in this paper, may counteract the advantage inherent in repeated sampling. This seasonal variation in cellular host-defence mechanisms should be taken into account when designing longitudinal intervention trials in chronic bronchitis.

Interleukin 1 production by alveolar macrophages is decreased in smokers

To evaluate the mechanism by which cigarette smoking suppresses pulmonary immune responses, we determined the capacity of alveolar macrophages (AM) to produce interleukin 1 (IL-1 in 32 normal subjects and in 40 patients with pulmonary sarcoidosis. The amount of IL-1 released from LPS-stimulated AM from smokers was significantly decreased compared with that in nonsmokers in both normal and sarcoid groups. The addition of indomethacin to the cultures in 18 normal subjects and in 22 patients with pulmonary sarcoidosis yielded similar results, thus excluding the possibility that this difference resulted from a difference in the amount of cyclooxygenase metabolites released in the culture supernatants. Similar results were obtained by enzyme-linked immunosolvent assay. Because IL-1 is thought to induce the accumulation of T cells at the site of disease and contribute to local cellular and humoral immunity of the lung, our data suggest that the reduced capacity of AM to release IL-1 in smokers affords partial protection against the initiation of immune responses in the lung and the development of granulomatous lung diseases.

Quantitation of leukotriene B4 in human serum by negative ion gas chromatography-mass spectrometry

Leukotriene B4 (LTB4) is a potent chemotactic agent formed via the 5-lipoxygenase pathway from arachidonic acid. To understand the role LTB4 plays in several pathological processes it is essential that endogenous concentrations of LTB4 be accurately quantitated. We have developed a method based on electron capture negative ion mass spectrometry for the analysis of LTB4 in serum at low picogram per milliliter concentrations. Blood is collected into the 5-lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) to suppress ex vivo formation. Serum is isolated, equilibrated with the internal standard [2H4]LTB4, and extracted using octadecyl-silica (C-18) cartridges. After conversion of the carboxylic acids to their pentafluorobenzyl esters the extract is purified by straight-phase HPLC. Gas chromatographic-mass spectrometric analysis is accomplished on the tert-butyldimethylsilyl ether derivatives using dual-selected ion monitoring of m/z 431 and 435. These ions correspond to loss of tert-butyldimethylsilanol from the (M-PFB)- ion of endogenous and [2H4]LTB4, respectively. The concentration of LTB4 in human serum samples was 10.0 +/- 4.0 pg/ml (n = 5). The assay exhibited satisfactory precision, with an intraassay coefficient of variation of 17% and a high degree of accuracy. The concentration of LTB4 in serum collected with (NDGA) was less than 10% of that observed in blood collected without the lipoxygenase inhibitor. Ex vivo formation can therefore be a major obstacle in assessing circulating levels of LTB4.

Alveolar macrophages from patients with asbestos exposure release increased levels of leukotriene B4

The alveolar influx and subsequent activation of inflammatory cells such as neutrophils and eosinophils are believed to be important in the pathogenesis of many interstitial lung disorders, including asbestosis. Indices of lower respiratory tract abnormalities detected by bronchoalveolar lavage (BAL) were investigated in 93 asbestos-exposed workers as well as in smoking (n = 12) and nonsmoking (n = 10) control subjects. Patients with clinical asbestosis (n = 12) exhibited increases in both BAL neutrophils and BAL eosinophils, expressed as both percentage of total cells and total numbers, when compared to asbestos-exposed workers without asbestosis (n = 81) and control subjects. Significantly greater numbers of BAL neutrophils were also found in asbestos-exposed workers without asbestosis than in either smoking or nonsmoking control subjects. These abnormalities correlated significantly with in vitro BAL alveolar macrophage production of the potent leukocyte chemotaxin, leukotriene B4 (LTB4). For example, basal, unstimulated LTB4 production was 3.1 +/- 0.8 ng/10(6) alveolar macrophages for patients with asbestosis, 1.05 +/- 0.2 ng/10(6) cells in asbestos workers without asbestosis, 0.9 +/- 0.2 ng/10(6) cells in control nonsmokers, and 0.2 +/- 0.05 ng/10(6) cells in control smokers. Stimulated LTB4 release from BAL alveolar macrophages (A23187 or arachidonate) was even more pronounced in asbestos workers with or without asbestosis, suggesting an in vivo priming effect on alveolar macrophage synthesis of LTB4. Cell-free BAL supernatants from asbestos-exposed patients with or without asbestosis also contained significantly greater amounts of LTB4 than did those from control subjects, indicating enhanced in vivo production of this inflammatory mediator.(ABSTRACT TRUNCATED AT 250 WORDS)

Recombinant interferon-gamma primes alveolar macrophages cultured in vitro for the release of leukotriene B4 in response to IgG stimulation

The capacity of interferon-gamma to regulate the generation and release of leukotriene B4 (LTB4) from human alveolar macrophages of normal nonsmoking individuals was evaluated. When alveolar macrophages were incubated for 60 min with heat aggregated IgG (HAIgG), they generated and released 5.7 +/- 1.7 ng of LT B4 per 10(6) cells compared to 1.9 +/- 0.4 ng from cells incubated with buffer alone, P = 0.02. When alveolar macrophages were preincubated with interferon-gamma for 24 h before activation for 60 min with heat-aggregated IgG, the soluble IgG aggregates became a significantly more effective stimulus for LTB4 release, 17.0 +/- 3.9 ng/10(6) cells, P = 0.001, compared to cells incubated in the absence of interferon-gamma and challenged with HAIgG. Interferon-gamma did not alter the response to A23187. This effect of interferon-gamma was both time and dose dependent; it also was specific since neither interferon-alpha nor interferon-beta had a regulatory effect on the release of LTB4 from cells in response to challenge with HAIgG. Preincubation of the alveolar macrophages with interferon-gamma augmented the density of IgG1 receptors by 81.5 +/- 17.3%; neither interferon-alpha nor interferon-beta effected this parameter. Furthermore, monomeric IgG1 blocked HAIgG induced LTB4 release from alveolar macrophages primed with interferon-gamma. Therefore, at least one of the mechanisms by which interferon-gamma primes alveolar macrophages for the production and release of LTB4 in response to stimulation by aggregates of IgG is that of increasing the number of receptors for this stimulus.

The contribution of alveolar macrophages to hyperreactive airway disease

Thus, there is substantial evidence that favors a role for macrophages in subjects with atopic asthma. The precise manner in which these cells participate and the relative degree to which these cells contribute to, or orchestrate, events remains to be delineated. Research on the potential role of macrophages in asthma syndromes remains in its infancy. In time we will discover new roles for mononuclear phagocyte-derived mediators and many more new mediators that will play a role in the complex immunologic events ongoing in the airways of patients with asthma. Also, future research will continue to explore what promises to be a productive area of research, namely, cell-cell interactions and the manner in which many cells participate together in the pathophysiology of asthma. If macrophages can be demonstrated to influence airway inflammation associated with atopic disease, they may be appropriate targets for therapeutic intervention.

Cigarette smoking decreases interleukin 1 release by human alveolar macrophages

To determine whether alveolar macrophages from smokers have an abnormal interleukin 1 beta (IL-1) release, we obtained macrophages by bronchoalveolar lavage (BAL) of otherwise healthy volunteers in three groups: nonsmokers (NS; n = 11), light smokers (LS, less than 10 pack-yr smoking history; n = 4) and heavy smokers (HS, greater than 10 pack-yr smoking history; n = 9). After 24 h in culture, unstimulated macrophages (from each group) released negligible amounts of IL-1. Lipopolysaccharide (LPS) (1 micrograms/ml) caused release of 21.77 +/- 4.33 ng IL-1/10(6) cells at 24 h from NS macrophages; IL-1 release from HS macrophages was significantly decreased (5.52 +/- 1.66 ng/10(6) cells; P less than 0.05), whereas LS macrophages released intermediate amounts (15.07 +/- 6.15 ng/10(6) cells). Release of IL-1 from HS macrophages was also decreased after 48 and 72 h in culture and was observed over a wide range of concentrations of LPS. The decreased amount of IL-1 in HS macrophage supernatants appeared to be due to a defect in release of IL-1 from the cells and not due to a defect in production of the mediator, since total IL-1 (IL-1 present in the cell lysates plus that in the cell supernatants) was similar in the NS and HS groups. In addition, after 24 h in culture, LPS-stimulated HS macrophages released significantly less prostaglandin E2 (PGE2) (which can suppress IL-1 production) than did NS macrophages; in the presence of indomethacin, which abolished macrophage PGE2 release, no augmentation of LPS-stimulated IL-1 release was observed. Cell viability, as measured by lactate dehydrogenase release, was not different between HS and NS macrophages under any conditions. We conclude that there is a defect in release but not production of IL-1 from the alveolar macrophages of chronic smokers.

Leukotriene generation and metabolism in isolated human lung macrophages

We studied the generation and metabolism of leukotrienes (LTs) in human lung macrophages obtained from lung tissue of patients with central bronchial carcinoma. By counterflow centrifugation macrophages were enriched with a purity of more than 95-100%. A time and dose dependent generation of LTB4 and LTC4 was determined by specific radioimmunoassays after stimulation with the Ca-ionophore and anti-IgE. The amount of LTB4 exceeded the amount of LTC4. The concentrations of leukotrienes in the macrophage fraction amounted to 4.3 +/- 2.2 ng LTB4 and 0.6 +/- 0.05 ng LTC4/1 x 10(7) cells after 5 min of incubation with the Ca-ionophore. The LTB4 levels decreased to 3.0 +/- 0.6 ng after 60 min indicating the metabolism of the generated LTB4 by human lung macrophages. This was confirmed by incubation of the cells with exogenously added [3H]LTB4. LTB4 was converted into unpolar products as was identified by thin-layer chromatography and high-performance liquid chromatography; a comparison with the fibroblast cell line L929 which is known to convert LTB4 into the dihydro-LTB4 metabolite (5,12-dihydroxyeicosatrienoic acid) indicates that human lung macrophages use the same pathway of metabolization. Biological inactivation as determined by chemotaxis and cross-reaction with the LTB4 antiserum correlates with the degree of LTB4 metabolism. Moreover, the macrophages convert LTC4 into LTD4 and LTE4 by the enzymatic activity of the gamma-glutamyltranspeptidase and dipeptidase. Our data emphasize that the human alveolar macrophage not only produces arachidonic acid metabolites but modulates the local inflammatory potential by its metabolizing capacity for leukotrienes.

Arachidonic acid metabolism in cultured alveolar macrophages from normal, atopic, and asthmatic subjects

In order to test the hypothesis that alveolar macrophages (AM) from asthmatics might manifest abnormalities in the amounts, spectrum, or glucocorticoid regulation of eicosanoid synthesis, we compared arachidonic acid (AA) metabolism under resting and ionophore A23187-stimulated conditions in cultured AM obtained by bronchoalveolar lavage from 10 asthmatic, nine atopic, and 10 nonatopic normal subjects. [14C]AA-prelabeled AM constitutively released free [14C]AA and release increased significantly with A23187 incubation. Under resting conditions, unlabeled cells produced small amounts of immunoreactive thromboxane B2 (TxB2), prostaglandin D2 (PGD2), prostaglandin E2 (PGE2), and leukotriene B4 (LTB4). With A23187 stimulation there were significant increases in the synthesis of all immunoreactive metabolites, which were produced in the following relative amounts: LTB4 much greater than TxB2 greater than PGD2 greater than leukotriene C4 greater than PGE2. High performance liquid chromatographic separation of radiolabeled eicosanoids produced by prelabeled cells confirmed the radioimmunoassay results and further indicated the production of relatively large amounts of 5-hydroxyeicosatetraenoic acid and 12-hydroxyheptadecatrienoic acid. Pretreatment (16 h) with 1 microM methylprednisolone inhibited A23187-induced synthesis of immunoreactive cyclooxygenase products to a greater extent than immunoreactive leukotrienes. We identified no significant differences among the three study groups in the quantities or profiles of eicosanoids synthesized either constitutively or with A23187 stimulation, nor in their regulation by methylprednisolone.

Isocratic determination of arachidonic acid 5-lipoxygenase products in human neutrophils by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed to determine arachidonic 5-lipoxygenase products in calcium ionophore-stimulated neutrophils. This procedure allows the simultaneous measurement of leukotriene B4 (LTB4) and its omega-oxidation products without using a gradient elution system. 20-Carboxy-LTB4, 20-hydroxy-LTB4, 6-trans-LTB4, 12-epi-6-trans-LTB4, LTB4 and 5s,12s-dihydroxyeicosatetraenoic acid can be separated and quantitated by reversed-phase chromatography using isocratic elution. The generation and degradation of 5-lipoxygenase products by human neutrophils following stimulation with calcium ionophore have been examined by this method.

Human alveolar macrophage arachidonic acid metabolism

Metabolites of arachidonic acid are potent modulators of many biological events, and their release from macrophages appears to play an important role in immune and inflammatory processes. In addition, metabolites of the cyclooxygenase or lipoxygenase pathway exhibit distinct biological effects. We used a method to determine if human alveolar macrophages (HAM) could be selectively activated to release products of cyclooxygenase or lipoxygenase pathway of arachidonic acid. HAM obtained by bronchoalveolar lavage from individuals were [3H]arachidonic acid labeled and then stimulated with lipopolysaccharide (LPS) or Ca ionophore A23187. Essentially no arachidonate metabolites were released by unstimulated cells. LPS caused dose- and time-dependent release of arachidonate and only cyclooxygenase products; no lipoxygenase products were detected, even in presence of cyclooxygenase inhibition. Metabolites released in response to LPS included thromboxane B2, prostaglandins D2, F2a, E2, and hydroxyheptadecatrienoic acid. A23187 caused a rapid release of arachidonate and 5-lipoxygenase products, leukotriene B4 and 5-hydroxyeicosatetraenoic acid; no cyclooxygenase inhibition. This demonstrates that HAM are specifically activated to release metabolites derived from cyclooxygenase or lipoxygenase pathway of arachidonic acid. Additionally, shunting down an alternate pathway is not induced by use of inhibitors of either pathway. This suggests alveolar macrophages may enhance or suppress various inflammatory or immune processes in lung, in part, by selective release of various derivatives of arachidonic acid.

In vivo effects of 1,25-dihydroxyvitamin D3 and minerals on synthesis of leukotriene B4 and 5-hydroxyeicosatetraenoic acid by rat peritoneal neutrophils

We investigated the in vivo effects of 1,25-dihydroxyvitamin D3, and serum calcium and inorganic phosphorus concentrations on productions of leukotriene B4 and 5-hydroxyeicosatetraenoic acid by glycogen stimulated peritoneal neutrophils of the rat. Neutrophils were incubated with ionophore A23187 for 5 min and the incubation medium was subjected to a reverse-phase high performance liquid chromatography for quantitation. Productions of these lipoxygenase metabolites by neutrophils from vitamin D depleted rats were decreased compared to the vitamin D sufficient levels. This difference was not observed when arachidonic acid was added to the incubation medium. When serum calcium concentrations of rats were altered by dietary calcium levels but 1,25-dihydroxyvitamin D3 was administered to those rats, the difference in serum calcium concentration did not show any effect on the production of leukotriene B4. In contrast, neutrophils from 1,25-dihydroxyvitamin D3 sufficient but phosphorus deficient rats still demonstrated decreased leukotriene B4 production. This reduction was corrected by exogenous arachidonic acid. The data suggest that 1,25-dihydroxyvitamin D3 or cellular calcium translocation mediated by the hormone, and serum inorganic phosphorus independent of 1,25-dihydroxyvitamin D3 affect arachidonic acid release, thus productions of leukotriene B4 and 5-hydroxyeicosatetraenoic acid.

Arachidonic acid metabolism in alveolar macrophages. A comparison of cells from healthy subjects, allergic asthmatics, and chronic bronchitis patients

Arachidonic acid (AA) metabolism was studied in preparations of purified human alveolar macrophages (AM) from healthy subjects (HS = 5), allergic asthmatics (ABA = 9) and chronic bronchitis patients (CB = 7). AM incubated for 6 to 24 h in the presence of labeled AA and for an additional 5 h without labeled AA, released cyclooxygenase and lipoxygenase products into the medium. The study of the metabolites showed that the most abundant sulfidopeptide-leukotriene, was LTD4 as analyzed by TLC and identified by reversed phase HPLC. The release of LTD4 was time-dependent but it was shown to be significantly higher (p less than 0.01) in AM from ABA or CB than in those from HS. TLC analysis of radioactivity distributed between the different lipid classes at 24 h revealed more labeling in AM phospholipids from ABA and CB than in those from HS, and was reflected in phosphatidylethanolamine and phosphatidylinositol species. After 5 h without labeled AA the distribution was marked, by different in triglycerides, with a greater proportion of radioactivity in the control cells than in the pathological macrophages. Thus, the pathological lung state is an important factor affecting the release of LTD4 and the distribution of AA into cellular phospholipids. The differences observed between HS and ABA or CB phospholipid distribution suggests the existence of 2 different sources of AA release, one for inflammatory macrophages and another for quiescent cells.

Spectrum of immunoregulatory functions and properties of human alveolar macrophages

In health, pulmonary alveoli are maintained free of inflammatory responses to inhaled foreign antigens. The specific role of alveolar macrophages (AM) in modulating the local cellular immune response to antigens is controversial. Immunoregulatory function and properties of AM and blood monocytes (MN) were compared. The AM were obtained by bronchoalveolar lavage of healthy volunteers, MN by adherence of peripheral blood mononuclear cells to plastic. These accessory cells were added in increasing ratios to a responder population rendered rigorously accessory cell-dependent by nylon wool adherence and depletion of cells bearing the surface Class II MHC determinant, HLA-DR. At low ratios of mononuclear phagocytes to lymphocytes (less than or equal to 1:10), MN and AM supported significant and comparable blastogenic responses to tetanus toxoid (3H-thymidine incorporation at a 1:10 ratio was 9,697 +/- 2,508 for MN and 8,969 +/- 1,454 for AM, mean cpm +/- SE, n = 9, p = NS) and other antigens. Interleukin-1 (IL-1) activity in supernatants of MN stimulated with lipopolysaccharide (LPS), 10 micrograms/ml, was 115 +/- 28 versus 67 +/- 21 U/ml in supernatants of AM (n = 9, p greater than 0.2). At suboptimal concentrations of LPS, however, MN expressed more IL-1 activity than did AM. The specific mean fluorescence intensity of surface expression of HLA-DR determinants as assessed by flow cytometry was similar for MN and AM. At the higher ratio of 1:2, MN supported 32% increased responses to tetanus toxoid compared with that at 1:5 (p less than 0.05). In contrast, AM at a ratio of 1:2 suppressed lymphocyte response by 69% (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Selective inhibition of 5-lipoxygenase pathway in rat pulmonary alveolar macrophages by cigarette smoking

Pulmonary alveolar macrophages from sham or cigarette-smoke-exposed rats were examined for their ability to transform exogenously added arachidonate to metabolites of lipoxygenase and cyclooxygenase pathways. Synthesis of 5-HETE and leukotriene B4 was selectively inhibited by cigarette smoke exposure, whereas the formation of prostaglandin E2 and thromboxane B2 remained unchanged. Selective inhibition of the lipoxygenase pathway was further reflected by the reduced content of leukotriene B4 in bronchoalveolar fluid of smoke-exposed rats. These results suggest that lipoxygenase-derived products may play a unique role in smoking-induced pulmonary diseases.

Arachidonic acid metabolism is altered in sarcoid alveolar macrophages

Macrophages produce various arachidonic acid (AA) metabolites which may either enhance or suppress inflammatory processes. We investigated AA metabolite production by alveolar macrophages (AMs) from 11 patients with pulmonary sarcoidosis and 9 normal volunteers. We assessed the production of both cyclooxygenase products (prostaglandin (PG) E2, thromboxane B2 (TXB2), PGF2 alpha, and 6-keto-PGF1 alpha) and lipoxygenase products (leukotrienes (LT) and hydroxyeicosatetraenoic acids (HETEs] in AM cultures. We found that sarcoid AMs produced less PGE2, TXB2, 6-keto-PGF1 alpha, and HETEs in both the unstimulated and the calcium ionophore-stimulated states compared with normal AMs. Sarcoid AMs also produced less PGF2 alpha and LTs in the unstimulated state after 1 hr of incubation, but following calcium ionophore stimulation, these differences did not achieve statistical significance. We conclude that sarcoid AMs have a reduced capacity to produce AA metabolites compared with that of normal AMs.