Interleukin-8 is a potent mediator of eosinophil chemotaxis through endothelium and epithelium

Interleukin-8 (IL-8), a potent pro-inflammatory cytokine, has been shown to have chemotactic activity for neutrophils, lymphocytes, and basophils. Effects of IL-8 on eosinophil chemotaxis are unresolved. Because eosinophils accumulate at the site of allergic inflammation and may play a role in the pathogenesis of asthma, we investigated the eosinophilotactic capacity of IL-8. We examined the ability of IL-8 to induce human eosinophil migration across 3-microns pore naked filters, and human umbilical vein endothelial cell and human pulmonary type II-like epithelial cell (A549) monolayers cultured on these filters. IL-8 induced similar dose-related eosinophil migration through all three barriers. Kinetic experiments indicated more rapid migration through noncellular barriers but equivalent migration through all barriers by 3 h. Chemotactic/chemokinetic data show that IL-8-induced eosinophil migration is chemotactic. We also determined that the ability of IL-8 to induce transcellular migration was unique in comparison with other cytokines and was not dependent on the use of fresh vs. passaged monolayer cells as barriers. Therefore our data indicate that IL-8 may play a significant role in tissue eosinophilia observed in allergic respiratory diseases.

Comparative studies indicate that platelet-activating factor is a relatively weak eosinophilotactic mediator

Eosinophils are important immune effector cells in a variety of allergic responses and inflammatory lung diseases. Bacterial products and inflammatory mediators have been implicated in inducing an influx of eosinophils into the respiratory tract subsequent to an acute inflammatory response. Therefore, to better understand the role of eosinophils in lung inflammation, we compared the ability of three known chemoattractants, formylmethionylleucylphenylalanine (FMLP), leukotriene B4 (LTB4), and platelet-activating factor (PAF), to induce human eosinophils to migrate across 3.0-microns-pore naked filters and human umbilical vein endothelial cells (HUVEC) and A549 human pulmonary type II-like epithelial (A549) cells cultured in monolayers on these filters. Kinetic experiments indicated that eosinophil migration through all three barriers occurred by 60 min and plateaued by 2 h. Each of these chemoattractants induced eosinophil migration in dose-responsive fashion across all three barriers. Although similar maximal eosinophil migration was observed, the doses at which this occurred varied, indicating that the rank order of potency through naked filters is FMLP > PAF > or = LTB4. However, their relative chemotactic potency through cellular barriers was different, with FMLP > LTB4 > PAF. In contrast to previous studies with neutrophils, the rank order of potency of the three chemoattractants was not influenced by the barrier through which the eosinophil migrated. Thus, these and previous data show that FMLP, LTB4, and PAF are eosinophil and neutrophil chemoattractants. Therefore, it is likely that these three agents are important mediators of granulocytic inflammatory responses in the lung, albeit with different potency profiles.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergic models and cytokines

Cytokines are proinflammatory protein mediators produced by many cells, including mast cells, T lymphocytes, eosinophils, airway epithelial cells, and macrophages. There are numerous in vitro and in vivo animal and human studies showing that cytokines are released as a result of allergic reactions. Cytokines mediate allergic inflammation by activating eosinophils, promoting mast cell development, regulating immunoglobulin isotype switching to immunoglobulin E, modulating adhesion molecule regulation, and promoting both neutrophil and eosinophil chemotaxis. Furthermore, there are data that show the pro-inflammatory effects of cytokines may be blocked by cytokine antagonists. This report reviews the in vitro and in vivo animal and human studies of allergic models of cytokine production and regulation. It also discusses the specific roles of cytokines in the allergic inflammatory response and asthma.

Pulmonary epithelial cells facilitate TNF-alpha-induced neutrophil chemotaxis. A role for cytokine networking

TNF-alpha and neutrophils are postulated to play important roles in several inflammatory lung diseases. Thus, we examined TNF-alpha-induced neutrophil migration through polycarbonate filters and human pulmonary type II-like epithelial (A549) cells cultured as monolayers on these filters. TNF-alpha induced both dose- and time-dependent migration of neutrophils across both barriers, but migration across A549 cells was much greater than that across naked filters. Migration of neutrophils across both barriers was completely inhibited by anti-TNF-alpha. Furthermore, supernatants of TNF-alpha (10(-9) M)-stimulated A549 monolayers induced threefold greater migration of neutrophils across naked filters than 10(-9) M TNF-alpha itself, suggesting release of soluble chemotactic factor(s). Pretreatment of A549 monolayers with actinomycin D inhibited both the production of soluble chemotactic factors and TNF-alpha-induced transcellular migration. Supernatants from TNF-alpha-stimulated A549 cells contained significant concentrations of IL-8, and coincubation of these supernatants with anti-IL-8 decreased supernatant-induced chemotaxis. Finally, coincubation of TNF-alpha with anti-IL-8 during transmigration experiments partially inhibited neutrophil migration through A549 monolayers. Therefore, pulmonary type II epithelial cells facilitate TNF-alpha-induced transcellular migration of neutrophils through the production of soluble protein synthesis-dependent chemotactic factors, including IL-8. These data support the concepts of cytokine networking in inflammatory cell recruitment and an active role for pulmonary epithelium in lung inflammation.

Pulmonary epithelial cells facilitate TNF-alpha-induced neutrophil chemotaxis. A role for cytokine networking

TNF-alpha and neutrophils are postulated to play important roles in several inflammatory lung diseases. Thus, we examined TNF-alpha-induced neutrophil migration through polycarbonate filters and human pulmonary type II-like epithelial (A549) cells cultured as monolayers on these filters. TNF-alpha induced both dose- and time-dependent migration of neutrophils across both barriers, but migration across A549 cells was much greater than that across naked filters. Migration of neutrophils across both barriers was completely inhibited by anti-TNF-alpha. Furthermore, supernatants of TNF-alpha (10(-9) M)-stimulated A549 monolayers induced threefold greater migration of neutrophils across naked filters than 10(-9) M TNF-alpha itself, suggesting release of soluble chemotactic factor(s). Pretreatment of A549 monolayers with actinomycin D inhibited both the production of soluble chemotactic factors and TNF-alpha-induced transcellular migration. Supernatants from TNF-alpha-stimulated A549 cells contained significant concentrations of IL-8, and coincubation of these supernatants with anti-IL-8 decreased supernatant-induced chemotaxis. Finally, coincubation of TNF-alpha with anti-IL-8 during transmigration experiments partially inhibited neutrophil migration through A549 monolayers. Therefore, pulmonary type II epithelial cells facilitate TNF-alpha-induced transcellular migration of neutrophils through the production of soluble protein synthesis-dependent chemotactic factors, including IL-8. These data support the concepts of cytokine networking in inflammatory cell recruitment and an active role for pulmonary epithelium in lung inflammation.

TNF-alpha-induced transendothelial neutrophil migration is IL-8 dependent

The early phases of airway inflammation include complex interactions between leukocytes, vascular endothelium, and inflammatory cytokines. Therefore, we examined tumor necrosis factor-alpha (TNF-alpha)-induced neutrophil migration through polycarbonate filters and human umbilical vein endothelial (HUVE) cells cultured as monolayers on these filters. TNF-alpha induced both dose- and time-dependent migration of neutrophils across both barriers. At 10(-11)-10(-9) M TNF-alpha, neutrophil migration across HUVE monolayers was more than twofold greater than that observed across naked filters. Modified checkerboard experiments indicated that neutrophils crossed naked filters as a chemokinetic rather than chemotactic response. Supernatants of TNF-alpha (10(-9) M)-stimulated HUVE monolayers induced threefold greater migration of neutrophils across naked filters than 10(-9) M TNF-alpha itself, suggesting release of soluble chemotactic factor(s). Pretreatment of HUVE monolayers with actinomycin D inhibited both TNF-alpha-induced production of soluble chemotactic factors and transendothelial neutrophil migration by > 90%. Supernatants from TNF-alpha-treated HUVE cells contained significant concentrations of interleukin 8 (IL-8), and coincubation of these supernatants with anti-IL-8 decreased supernatant-induced chemotaxis. Finally, coincubation of TNF-alpha with anti-IL-8 during transmigration experiments nearly completely inhibited the increase in neutrophil migration measured across HUVE monolayers. In contrast, WEB 2086, a platelet-activating factor receptor antagonist, had no effect. Therefore, endothelial cells greatly facilitate TNF-alpha-induced transcellular migration of neutrophils. This facilitation is dependent on TNF-alpha-stimulated production of IL-8. These data further support the active role of vascular endothelium in recruiting leukocytes to sites of inflammation.

Interleukin-8-induced transcellular neutrophil migration is facilitated by endothelial and pulmonary epithelial cells

Interleukin-8 (IL-8) is an 8,000 D protein produced by many cells and has potent neutrophil chemoattractant and activating properties. Indeed, there is substantial data supporting a role for IL-8 in neutrophilic lung inflammatory responses. In vivo, neutrophils must adhere to and then migrate across endothelial and epithelial cell barriers in order to reach inflammatory foci. Therefore, we examined IL-8-induced neutrophil migration through naked filters and through human umbilical vein endothelial (HUVE) cells and human pulmonary type II-like epithelial cells (A549) cultured on these filters. IL-8 induced both dose- and time-dependent migration of neutrophils across all three barriers. At IL-8 concentrations greater than 10(-8) M, neutrophil migration across both endothelial and epithelial cell barriers was significantly greater than that observed across naked filters. In addition, time-course experiments indicated that neutrophil migration continued to occur for up to 3 h across both cellular barriers while neutrophil migration across naked filters plateaued by approximately 60 to 90 min. Migration of neutrophils through all barriers was completely inhibited by anti-IL-8 neutralizing antibody. The increased migration observed through both cellular barriers was not due to either changes in chemotactic gradients or the production of other soluble chemotactic factors by IL-8-stimulated HUVE and A549 cells versus naked filters. Furthermore, pretreatment of monolayers with actinomycin-D had no effect on the degree of transcellular migration. Thus, the facilitation of neutrophil migration through HUVE and A549 monolayers is not dependent upon new protein synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of neuropeptides on neutrophil migration through noncellular and endothelial barriers

BACKGROUND

Neuropeptides and neutrophils are postulated to be important immune effector molecules and cells, respectively, in a variety of lung inflammatory conditions.

METHODS

We examined the effects of three lung neuropeptides, substance P, vasoactive intestinal peptide (VIP), and somatostatin and two relatively protease-resistant peptides, helodermin and sandostatin, on human neutrophil migration across 3 microns pore filters and human endothelial monolayers cultured on these filters.

RESULTS

At concentrations of 1 to 10 mumol/L, substance P induced significant neutrophil migration that was dose-responsive and equivalent through endothelium and filters. Neither VIP, helodermin, somatostatin, nor sandostatin induced significant neutrophil migration through either barrier at doses of 10(-14) to 10(-5) mol/L. Because VIP and somatostatin have been reported to inhibit some inflammatory cell functions, we also examined their effects on chemoattractant-induced neutrophil migration. Pretreatment of neutrophils and/or endothelium with VIP or somatostatin at either 10(-5) or 10(-10) mol/L did not significantly inhibit formyl-methionyl-leucyl-phenylalanine-, leukotriene B4-, or platelet activating factor-induced neutrophil migration through naked filters or endothelium. Thus only substance P had significant effects on neutrophil chemotaxis.

CONCLUSIONS

Substance P, but not VIP or somatostatin, may be important in directly influencing neutrophil migration across endothelium towards lung inflammatory sites. However, all three neuropeptides might still modulate neutrophil functions and lung inflammatory responses through effects on other lung cells.

Nedocromil sodium is rapidly effective in the therapy of seasonal allergic rhinitis

BACKGROUND

Nedocromil sodium has proven to be efficacious in prophylactic and long-term therapy for the treatment of seasonal allergic rhinitis. We examined the speed of onset of intranasal nedocromil sodium (1%) for relief of symptoms due to ragweed allergic rhinitis.

METHODS

In a double-blind, placebo-controlled trial, 104 patients received either nedocromil sodium or placebo four times daily. Patients spent 10 hours per day for 2 consecutive days in Iowa City Park during the peak of ragweed season. Only patients who had significant symptoms during 3 hourly baseline assessments received drug. Symptom scores for stuffy nose, runny nose, itchy nose, and sneezing and global symptom summary scores were recorded at 19 hourly time points during the 2 days. In the evening patients recorded symptom scores for the postexposure period.

RESULTS

In comparison with placebo, nedocromil significantly improved rhinitis symptoms as evidenced by lower symptom summary scores within 2 hours (p = 0.016). Further, this reduction in rhinitis symptoms was maintained throughout the 2-day pollen exposure period. After patients left the study site, postexposure symptom summary scores were also significantly lower in patients treated with nedocromil compared with those treated with placebo (p < 0.007).

CONCLUSIONS

Nedocromil significantly relieved preexisting seasonal allergic rhinitis symptoms during peak pollen exposures within 2 hours of the first dose, and the therapeutic benefits were maintained on a dosing regimen of four times a day.

Acute effects of in vitro mast cell degranulation on human lung muscarinic receptors

Allergic asthmatic patients have baseline airway cholinergic hyperresponsiveness that rapidly increases after antigen inhalation and mediator release. We therefore examined whether anaphylaxis of human lung tissue (exposure to mast cell mediators) acutely modulated the human lung muscarinic receptor system in ways that might account for these increased in vivo cholinergic airway responses. Fresh thoracotomy peripheral lung samples from 24 patients were incubated with (anaphylaxis) or without (control) anti-IgE (1:100) for up to 90 min. The average percentage of histamine released ranged from 20 to 30% in anaphylaxis and 3 to 5% in control samples, with > 80% of total histamine released by 15 to 30 min. Lung fragments were quick frozen at various times after anti-IgE for analyses of muscarinic receptor binding parameters. Antagonist Kd (dissociation constant) and receptor concentration values were determined using [3H]quinuclidinyl benzilate, and agonist IC50 values were determined using carbachol. In comparison with time 0, neither anaphylaxis nor control samples had differences in receptor binding parameters with time. There were also no differences between anaphylaxis and control lung samples at any time point, and ratios of log control binding parameter/log anaphylaxis binding parameter ranged from 0.96 to 1.04. Thus, anaphylaxis of lung does not lead to acute changes in antagonist or agonist affinity for muscarinic receptors or changes in receptor concentration. Therefore, under the conditions studied, lung mast cell degranulation does not appear to acutely alter the human lung muscarinic receptor system in ways that might account for the increased in vivo lung cholinergic hyperresponsiveness found in allergic asthmatic patients.

Platelet-activating factor-induced human eosinophil transendothelial migration: evidence for a dynamic role of the endothelium

Stimulated migration of eosinophils out of the bloodstream and into the lung is key in the development of tissue eosinophilia and inflammation in asthma. Platelet-activating factor (PAF) has been implicated as an important inflammatory mediator in asthma pathogenesis in part because of its chemotactic capacity. We therefore studied the ability of PAF to induce human peripheral blood eosinophil migration through naked filters and human umbilical vein endothelial cells (HUVECs) cultured on these filters. PAF induced eosinophil migration through both barriers in a time-dependent fashion, with maximal eosinophil migration occurring at 180 min. Significant eosinophil migration was observed at PAF concentration > or = 0.1 microM and was dose dependent up to 10.0 microM. No significant differences in eosinophil chemotactic responses were noted between naked filter and HUVEC barriers. The PAF receptor antagonist, WEB 2086, inhibited (> 85%) eosinophil transendothelial migration when co-incubated with PAF or when used as a pretreatment of either the eosinophils or HUVECs. However, WEB 2086 pretreatment of HUVECs did not inhibit PAF-induced neutrophil transendothelial migration, nor did it affect leukotriene B4-induced neutrophil or eosinophil transendothelial migration. Thus, the data indicate that the endothelial cell plays an important role in PAF-induced eosinophil inflammatory processes. Moreover, these data suggest that PAF's pathogenic role in asthma may in part be due to its ability to stimulate eosinophil migration across endothelial barriers and into the airways.

Effects of nedocromil sodium and WEB 2086 on chemoattractant-stimulated neutrophil migration through cellular and noncellular barriers

Nedocromil sodium (Tilade) is an effective therapeutic agent against asthma and has been shown to exhibit antiinflammatory activity in vitro; however, its mode of action is yet to be described fully. Using an in vitro assay designed to mimic the extravasation of neutrophils from the peripheral circulation through cellular barriers to sites of inflammation, the effect of nedocromil sodium on chemoattractant-stimulated neutrophil migration was examined. We also examined the effects of WEB 2086, a platelet-activating factor (PAF) receptor antagonist, in parallel. Neutrophils and the cellular barrier were pretreated and/or co-incubated with nedocromil or WEB 2086 and the effects on neutrophil chemotaxis measured. In all treatments, nedocromil did not significantly affect chemotaxis through cellular or noncellular barriers to N-formyl-methionyl-leucyl-phenylalanine (FMLP), leukotriene B4 (LTB4), or PAF. In contrast, WEB 2086 inhibited PAF-induced neutrophil migration through both naked filters and endothelial and epithelial monolayers cultured on these filters. We conclude that while nedocromil has been shown to have inhibitory effects on neutrophils and is an effective therapeutic agent for asthma and inflammatory conditions, its activity is not primarily mediated by inhibition of neutrophil chemotaxis. Platelet-activating factor antagonists may partially be effective in asthma through inhibitory effects on neutrophil chemotaxis.

Comparison of methodologies to measure human lung histamine

The measurement of histamine in samples obtained from human lung is important in determining the roles of histamine and mast cells in normal and disease states. We, therefore, compared different assays for the measurement of histamine in human lung samples. Both a single isotope enzymatic assay and a radioimmunoassay (RIA) were capable of accurately measuring the low concentrations of histamine (0.05-2.0 ng/ml) normally found in bronchoalveolar lavage fluid. The RIA was also able to measure histamine levels up to 1500 ng/ml in human lung tissue samples. Moreover, the RIA measurement of high levels of histamine in lung samples compared favorably to an automated spectrofluorometric method. Unlike either the single isotope enzymatic assay or the automated spectrofluorometric assay which have effective capabilities at less than and greater than 2 ng/ml, respectively, the RIA can accurately measure histamine levels from 0.05 to 1500 ng/ml. Since the RIA is easier to perform, less costly, and has a wider range of effectiveness, this assay should prove valuable in assessing histamine levels from a variety of human lung samples, thereby, providing an avenue to elucidate the roles of histamine and mast cells in lung functions.

Degree of neutrophil chemotaxis is dependent upon the chemoattractant and barrier

Stimulated neutrophil migration across lung endothelial and epithelial barriers is important in lung inflammatory processes. To better understand the interaction between chemoattractants, neutrophils, and endothelium and epithelium, we compared the ability of leukotriene B4 (LTB4), formylmethionylleucylphenylalanine (FMLP), and platelet-activating factor (PAF) to induce human neutrophil migration across 3-microns-pore filters alone and human umbilical vein endothelial (HUVE) cells and two different epithelial cell types, Madin-Darby canine kidney (MDCK) cells and human lung A549 cells, cultured in monolayers on these filters. LTB4, FMLP, and PAF induced neutrophil migration through naked filters, endothelial cells, and epithelial cells in a dose-related fashion. At optimal chemoattractant doses, LTB4, FMLP, and PAF induced relatively equivalent neutrophil migration through filters and endothelial and epithelial monolayers. However, the doses at which optimal neutrophil migration was observed to occur as well as the degree of neutrophil migration through the three barriers varied depending upon the chemoattractant. Based on dose-response experiments, the relative rank order of potency for the three chemoattractants was: LTB4 = FMLP greater than PAF for filter alone barrier; LTB4 greater than FMLP greater than PAF for HUVE cell barrier; and FMLP greater than LTB4 greater than PAF for MDCK and A549 epithelial cell barriers. Our data suggest that neutrophil chemotactic and subsequent lung inflammatory responses are interrelatedly influenced by both the quantity and type of chemoattractant present and the barrier through which the neutrophil must migrate.

Results of the National Institute of Allergy and Infectious Diseases Collaborative Clinical Trial to test the predictive value of skin testing with major and minor penicillin derivatives in hospitalized adults

BACKGROUND

A history (or lack thereof) of penicillin allergy is known to be unreliable in predicting reactions on subsequent administration of the drug. This study tests the usefulness of four penicillin allergen skin tests in the prediction of IgE-mediated reactions subsequent to administration of penicillin.

METHODS

Eight centers cooperated in the National Institute of Allergy and Infectious Diseases trial of the predictive value of skin testing with major and minor penicillin derivatives. Hospitalized adults were tested with a major determinant (octa-benzylpenicilloyl-ocytalysine) and a minor determinant mixture and its components (potassium benzylpenicillin, benzylpenicilloate, and benzylpenicilloyl-N-propylamine). Patients then received a therapeutic course of penicillin and were observed, for 48 hours, for adverse reactions compatible with an IgE-mediated immediate or accelerated allergy.

RESULTS

Among 726 history-positive patients, 566 with negative skin tests received penicillin and only seven (1.2%) had possibly IgE-mediated reactions. Among 600 history-negative patients, 568 with negative skin tests received penicillin and none had a reaction. Only nine of the 167 positive skin test reactors received a penicillin agent and then usually by cautious incremental dosing. Two (22%) of these nine patients had reactions compatible with IgE-mediated immediate or accelerated penicillin allergy; both were positive to the two determinants.

CONCLUSIONS

These data corroborate previous data about the negative predictive value of negative skin tests to these materials. The reaction rate in skin test-positive patients was significantly higher than in those with negative skin tests, demonstrating the positive predictive value of positive tests to both major and minor determinants. The number of patients positive only to the major determinant or only to the minor determinant mix was too small to draw conclusions about the positive predictive value of either reagent alone.

Comparison of platelet-activating factor-induced chemotaxis of normodense and hypodense eosinophils

Platelet-activating factor (PAF)-induced eosinophil (EOS) migration is an important event in the development of tissue eosinophilia and allergic inflammation. EOSs are heterogeneous cells in that different states of activation have been ascribed to EOSs of varying densities. We therefore studied the ability of PAF to induce hypodense and normodense EOS chemotaxis. Both hypodense and normodense EOSs were isolated in pure form from seven subjects and studied concurrently. Dose-response and time-course experiments indicated no significant differences in PAF-induced hypodense versus normodense EOS chemotactic responses. Hypodense and normodense cells achieved maximal chemotaxis in response to 1 mumol/L of PAF, and maximal chemotaxis was achieved at 2 hours. However, marked differences in PAF-induced EOS chemotactic responses existed between patients. We conclude that PAF is a potent EOS chemoattractant, and despite reported differences in metabolic activity, normodense and hypodense EOSs exhibit similar chemotactic responsiveness to PAF.

Cutaneous responses to anticholinergics: evidence for muscarinic receptor subtype participation

We conducted a series of experiments to determine if anticholinergics induce immediate cutaneous wheal-and-flare responses in normal volunteers. We performed intradermal skin testing in seven healthy volunteers (three atopic and four nonatopic) with 20 nmol of atropine. All subjects had an immediate wheal-and-flare response to atropine. To determine if this cutaneous response was due to anticholinergics in general, skin testing was also performed to scopolamine and ipratropium. These agents also produced immediate wheal-and-flare responses in all subjects, but they less potent than atropine. Pretreatment with antihistamines equivalently inhibited wheal-and-flare responses to both histamine and atropine, indicating a possible mast cell role. The potential role of M1, M2, and M3 muscarinic receptor subtypes was evaluated by use of the selective antagonists, pirenzepine (M1), 11[[2-1[(diethylamino)methyl]-1-piperidinyl]-acetyl]-5, 11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one (AFDX-116) (M2), and 4-diphenylacetoxy-N-methylpiperidine (4-DAMP) (M3). Cutaneous wheal responses induced by pirenzepine and 4-DAMP were relatively equivalent and larger than responses induced by AFDX-116 at doses less than 200 nmol. At 200 nmol, all three muscarinic receptor subtype antagonists induced equivalent wheal formation. We then compared the cutaneous wheal responses to these specific muscarinic receptor antagonists based on their relative affinity for their respective muscarinic receptor subtype. This comparison suggested that M1 or M2, but not M3, muscarinic receptor subtypes may be important in anticholinergic-induced cutaneous wheal-and-flare responses. We propose that there may be an M1 or M2 muscarinic autoreceptor that inhibits the release of acetylcholine and other neurotransmitters.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of various barriers on platelet-activating factor-induced neutrophil chemotaxis

Platelet-activating factor (PAF)-induced neutrophil migration across endothelial and epithelial barriers is an important event in inflammation. We compared the effects of PAF on human neutrophil migration through filters alone, and human umbilical vein endothelial and Madin-Darby canine kidney epithelial cells cultured on these filters. We found that the amount of PAF-induced neutrophil migration was barrier dependent. At low PAF concentrations, neutrophil migration through filters exceeded migration measured through either cellular barrier. As PAF concentrations increased to greater than or equal to 1 mumol/L, neutrophil migration through human umbilical vein endothelial cells often equaled or exceeded migration measured through filters alone. In contrast, significant neutrophil migration through Madin-Darby canine kidney cells was not observed until PAF concentrations exceeded 50 mumol/L. Thus, the intensity of PAF-induced neutrophil inflammatory processes is, in part, dependent on the barrier through which the neutrophils must migrate.

Mast cell hyperplasia in experimental hypersensitivity pneumonitis

We investigated the presence of mast cells in a model of experimental hypersensitivity pneumonitis (EPH). Guinea pigs exposed to 8 weekly intratracheal challenges with Micropolyspora faeni exhibited significant increases in the number of mast cells within the lung as compared to controls and animals challenged only 2 or 4 times. The number of cells in M. faeni-challenged animals were increased around bronchi, bronchioles, blood vessels and in alveolar septa. There appeared to be contraction of peribronchial, peribronchiolar and vascular smooth muscle. Ultrastructural examination of lung tissue revealed the presence of degranulating mast cells. Bronchoalveolar lavage histamine levels were increased after 8 but not after 2 or 4 weekly challenges. Serum anti-M. faeni antibody was present in all M. faeni-exposed animals but not in control animals. We conclude that mast cells and histamine levels in bronchoalveolar lavage fluid are increased in a model of EHP caused by repetitive, intratracheal injection of M. faeni particulate antigen.

Degree of platelet activating factor-induced neutrophil migration is dependent upon the molecular species

Multiple molecular species of platelet activating factor (PAF) are produced as a result of inflammatory processes. PAF-induced neutrophil migration across endothelium is intrinsic to inflammatory responses. We therefore compared the ability of three naturally occurring PAF species (C16:0, C18:0, and C18:1), which only varied at carbon 1, to induce 51Cr-labeled human neutrophil migration across a naked 3-microns pore filter and human umbilical vein endothelial (HUVE) monolayers cultured on these filters. Time-course experiments indicated that all species of PAF tested induced significant neutrophil migration between 15 and 45 min. PAF-induced neutrophil migration through both filters alone and HUVE monolayers occurred at lower doses with C16:0 PAF. The rank order of chemotactic potency for the PAF species was C16:0 greater than C18:0 greater than C18:1 with both filters and endothelium coated filters as barriers. Intrinsic differences in the potency of these PAF molecular species to induce neutrophil chemotaxis were greater when HUVE cells were the barriers vs when filters alone were the barriers. Regardless of the molecular species used, at optimal PAF doses the degree of neutrophil migration through HUVE cells was often greater than that through filters alone. The specific PAF antagonist WEB 2086 inhibited neutrophil migration induced by all three PAF species equally. WEB 2086 pretreatment of the neutrophil or WEB 2086 coincubation with PAF, but not WEB 2086 pretreatment of the HUVE cell monolayers, significantly inhibited (65 to 80%) neutrophil migration. We conclude that the degree of PAF-induced neutrophil migration is dependent upon the molecular species of PAF. Moreover, the barrier through which the neutrophil must migrate appears to be important in influencing the overall chemotactic response to the various PAF species.

Degree of platelet activating factor-induced neutrophil migration is dependent upon the molecular species

Multiple molecular species of platelet activating factor (PAF) are produced as a result of inflammatory processes. PAF-induced neutrophil migration across endothelium is intrinsic to inflammatory responses. We therefore compared the ability of three naturally occurring PAF species (C16:0, C18:0, and C18:1), which only varied at carbon 1, to induce 51Cr-labeled human neutrophil migration across a naked 3-microns pore filter and human umbilical vein endothelial (HUVE) monolayers cultured on these filters. Time-course experiments indicated that all species of PAF tested induced significant neutrophil migration between 15 and 45 min. PAF-induced neutrophil migration through both filters alone and HUVE monolayers occurred at lower doses with C16:0 PAF. The rank order of chemotactic potency for the PAF species was C16:0 greater than C18:0 greater than C18:1 with both filters and endothelium coated filters as barriers. Intrinsic differences in the potency of these PAF molecular species to induce neutrophil chemotaxis were greater when HUVE cells were the barriers vs when filters alone were the barriers. Regardless of the molecular species used, at optimal PAF doses the degree of neutrophil migration through HUVE cells was often greater than that through filters alone. The specific PAF antagonist WEB 2086 inhibited neutrophil migration induced by all three PAF species equally. WEB 2086 pretreatment of the neutrophil or WEB 2086 coincubation with PAF, but not WEB 2086 pretreatment of the HUVE cell monolayers, significantly inhibited (65 to 80%) neutrophil migration. We conclude that the degree of PAF-induced neutrophil migration is dependent upon the molecular species of PAF. Moreover, the barrier through which the neutrophil must migrate appears to be important in influencing the overall chemotactic response to the various PAF species.

Comparison of leukotriene B4-induced neutrophil migration through different cellular barriers

Migration of neutrophils across epithelial or endothelial barriers in response to chemotactic stimuli occurs in inflammation and host defense. Leukotriene B4 (LTB4) may be synthesized by and certainly induces chemotaxis of neutrophils. To better understand the interaction between LTB4, neutrophils, and endothelium and epithelium, we compared the effects of LTB4 on human peripheral blood neutrophil migration through filters alone and on human umbilical vein endothelial (HUVE) cells and three different epithelial cell types, Madin-Darby canine kidney (MDCK) cells, human colon carcinoma (T84) cells, and rat type II alveolar cells, cultured on these filters. Significant LTB4-stimulated neutrophil migration occurred at the lowest (1 nM) dose and in the shortest period of time (15 min) across endothelial cells vs. all three epithelial cell types, and interestingly, vs. filters alone. Dose-response experiments (1-100 nM) indicated that at equimolar LTB4 concentrations neutrophil migration across endothelium was two- to threefold greater than that observed across filters alone and the three epithelial barriers. At higher LTB4 concentrations (100 nM), the degree of neutrophil migration through the three epithelial barriers was equivalent to that observed for filters alone. Overall, the data indicate that the various cellular barriers play an active role in inflammatory processes by regulating the transmigration of neutrophils in response to certain inflammatory chemotactic stimuli.