Bronchoalveolar neutrophilia during late asthmatic reactions induced by toluene diisocyanate

In vitro modulation of the eosinophil-dependent enhancement of the permeability of the bronchial mucosa

1. Basolateral to apical albumin flux has been measured in sheets of bovine bronchial and tracheal mucosa mounted in vitro. 2. Addition of guinea-pig peritoneal eosinophils or neutrophils to the basolateral side of such tissues had no significant influence on the transmucosal flux of albumin in either the bronchial or tracheal mucosa. 3. Stimulation of eosinophils or neutrophils by the calcium ionophore A23187, or by their presentation to an opsonized airways mucosa, resulted in a significant increase in the transbronchial flux of albumin. This effect was seen after only 60 min incubation of the leucocytes with the bronchial mucosa, and was no greater when the contact time was extended to 180 min. Incubation of bronchial mucosal tissues with 1 mg ml-1 polyarginine for 3 h produced a significant increase in albumin flux, but was ineffective at 0.5 mg ml-1. 4. In contrast to the bronchial mucosa, the tracheal mucosa appeared resistant to the effects of stimulated eosinophils and neutrophils. 5. The lipoxygenase inhibitor AA-861 failed to influence the ability of eosinophils to augment the transmembrane flux of albumin. However, insertion of a Millipore filter mask between the eosinophils and the bronchial mucosa significantly inhibited the eosinophil-dependent enhancement of mucosal permeability. 6. The broad spectrum antiproteinase alpha 2-macroglobulin achieved almost total ablation of the action of stimulated eosinophils in the bronchial mucosa. These results suggest that proteinases may make a significant contribution to the genesis of epithelial injury, whereas leukotrienes do not.

Bronchial smooth muscle responses evoked by toluene diisocyanate are inhibited by ruthenium red and by indomethacin

We have investigated the ability of ruthenium red, an inorganic dye with Ca2+ entry-blocking properties and a selective antagonist of capsaicin, and of indomethacin, a cyclooxygenase inhibitor, to inhibit bronchial smooth muscle responses evoked by toluene diisocyanate in guinea pigs. Previous exposure of isolated guinea pig bronchi to ruthenium red significantly decreased the response produced by toluene diisocyanate. Further, the response to toluene diisocyanate was significantly decreased by pretreatment with indomethacin. These findings provide evidence that toluene diisocyanate-induced contractions of guinea pig bronchi are produced indirectly by generation of a prostanoid that activates capsaicin-sensitive afferents via a ruthenium red-sensitive mechanism.

The roles of inflammatory cells in the pathogenesis of asthma and of chronic obstructive pulmonary disease

Studies of the inflammatory processes in asthma and in COPD have been hindered by the imprecise definitions of these diseases, the uncertainty as to the location of the relevant inflammatory sites for these diseases within the lungs, and the difficulties in relating observed histopathologic changes to the effects of particular proinflammatory leukocytes or their products. Circumstantial evidence exists implicating neutrophils, eosinophils, mast cells, and monocytes in asthma pathogenesis based on increased numbers and activation of these cells in blood, BAL fluid, or biopsy material, and the propensity of these cells to release products causing tissue damage. There is increasing evidence that the accumulation and activation of these cells is orchestrated by lymphokines elaborated by sensitized T lymphocytes. In COPD, attention has been focused on the secretion of proteases by infiltrating neutrophils and macrophages, although there is no incontrovertible evidence that these are relevant to the disease pathogenesis in the majority of patients with normal serum concentrations of protease inhibitors. In the future, studies of the functions of inflammatory cells actually at the sites of inflammation using the techniques of immunocytochemistry and molecular biology may provide further information as to the role of these cells in the inflammatory processes associated with asthma and COPD.

Isocyanate-induced asthma: results of inhalation tests with TDI, MDI and methacholine

We performed diisocyanate inhalation tests (maximal concentration, 20 ppb; exposure time, 1-2 h) using toluene diisocyanate (TDI, n = 15) and diphenylmethane diisocyanate (MDI, n = 7) as well as methacholine challenges in 19 workers who had a clinical history of TDI/MDI-induced asthma. Additionally we tested volunteers who had no previous contact with diisocyanates: 10 healthy individuals with a negative methacholine test and 14 patients with asthma and a positive methacholine test were exposed to TDI. In all, 1 of the normal volunteers and 3 of the patients with asthma unrelated to diisocyanates showed a positive airway reaction to TDI, and 13 of the 19 diisocyanate workers displayed a positive result in the TDI/MDI inhalation test; however, only 6 of these 13 individuals reacted to methacholine. Furthermore, 3 of the 6 patients with a negative TDI/MDI challenge test demonstrated a significant response to methacholine. We conclude that bronchial hyperreactivity as evaluated by the methacholine challenge test is not closely related to isocyanate-induced bronchoconstriction and, therefore, the metacholine challenge is only of limited diagnostic value in patients with suspected isocyanate-induced asthma.

A bradykinin antagonist modifies allergen-induced mediator release and late bronchial responses in sheep

We assessed the role of bradykinin (BK) in allergen-induced early and late bronchial responses, airway inflammation, mediator release, and antigen-induced airway hyperresponsiveness in allergic sheep by studying the effects of the BK B2 receptor antagonist, NPC-567 (D-Arg-[Hyp3, D-Phe7]-BK), on these parameters. Antigen challenge was performed on two occasions greater than 3 wk apart, once with placebo (control) and once after high-dose (10 mg/ml) and low-dose (5 mg/ml) treatments with aerosol NPC-567. In the control trials (n = 14) antigen challenge resulted in an early and late increase in specific lung resistance (SRL). The early response was associated with increases (p less than 0.05) in prostaglandin (PG) D2, immunoreactive kinin, tosyl-L-arginine methyl ester (TAME)-esterase, and PGE2 in bronchoalveolar lavage (BAL) fluid. The late response was associated with increases (p less than 0.05) in leukotrienes (LT) B4 and C4, thromboxane (TX) B2, 6-keto-PGF10, and PGE2. There was a significant influx of neutrophils in the BAL fluid during the late response, and airway hyperresponsiveness to carbachol aerosol was apparent 4 h after challenge. In six sheep the high-dose NPC-567 treatment (given before, during, and 4 h after antigen challenge) did not attenuate the early bronchoconstrictor response or the early release of mediators but caused a significant reduction in the late response (p less than 0.05). This protective effect was accompanied by reductions (p less than 0.05) in both the concentrations of all the mediators associated with the late response and the severity of the BAL neutrophilia. High-dose NPC-567 did not attenuate the airway hyperresponsiveness or the cellular inflammatory response seen 24 h after challenge. In eight sheep treated with the low dose of NPC-567 (given before, during, and 4, 8, and 24 h after challenge) the early response was not blocked but the late response was again inhibited, as were the mediators associated with the late response. At the low dose the drug did not prevent the airway inflammation at 8 or 24 h. The additional treatments did, however, prevent the 24 h hyperresponsiveness. These data suggest that kinin generation during antigen-induced airway anaphylaxis may be important for controlling the release of arachidonic acid metabolites from airway inflammatory cells that contribute to the development of the late response in the allergic sheep model.

Comparison of peak expiratory flow rate and FEV1 in assessing bronchomotor tone after challenges with occupational sensitizers

Bronchial responses to occupational sensitizers measured by peak expiratory flow rate (PEFR) and forced expiratory volume in 1 s (FEV1) during late reactions (between 90 minutes and 8 hours after exposure) were compared in two groups of 88 subjects who had undergone specific inhalation challenges in the laboratory. The first group had what was considered a positive reaction (a fall of at least 15 percent in FEV1) whereas the second group's reaction was interpreted as negative (fall in FEV1 less than 15 percent). Although the correlation in terms of percentage of change from baseline values was statistically significant, the correspondence was poor. PEFR proved far less sensitive than FEV1 in detecting a reaction. Whereas the mean maximum change in FEV1 overall was 27 percent, the mean maximum change in PEFR at the same time interval was only 16 percent. Moreover, individual correlations between the percentage of change in FEV1 and PEFR were satisfactory (r2 greater than 0.80) in only 32/88 subjects (36 percent). No subject who was considered to have a negative challenge according to FEV1 had a change in PEFR greater than 20 percent. We therefore conclude that changes in PEFR are far less sensitive than changes in FEV1 in detecting responses during late reactions to occupational sensitizers.

Interdependence of polymorphonuclear neutrophils and macrophages stained for N-acetyl-beta-glucosaminidase in lavage effluents from toluene diisocyanate-exposed rat lungs

Male Sprague-Dawley rats were exposed to toluene diisocyanate (TDI) concentrations between 0.082 and 1.087 ppm for 4 h, and pulmonary lavage was carried out 24 h after initiation of the exposure. Cells recovered from the lavage effluents of TDI-exposed rat lungs were identified and counted, then pulmonary macrophages (PMs) resulting from cytocentrifuged preparations were examined for N-acetyl-beta-glucosaminidase (NAG) cytochemical staining. Exposure to TDI led to a parallel and concentration-dependent increase in the number of polymorphonuclear neutrophils (PMNs) and the proportion of PMs stained for NAG, suggesting that the same primary event initiates the two cell responses.

In vitro incubation with influenza virus primes human polymorphonuclear leukocyte generation of superoxide

Viral respiratory illnesses exacerbate asthma, increase airway responsiveness, and enhance the frequency of late asthmatic reactions. A number of mechanisms have been identified to explain how respiratory viral illnesses provoke wheezing, including enhanced inflammatory activity of leukocytes. To further understand how respiratory virus-caused illnesses promote leukocyte-dependent airway injury, the following study evaluated the effect of an in vitro incubation of influenza A virus on human polymorphonuclear leukocyte (PMN) generation of superoxide (O2-). PMNs were isolated from anticoagulated human blood following density gradient centrifugation; purified PMNs were then incubated (37 degrees C x 30 min) with influenza virus (PMN:virus ratio of 5:1 [egg-infective dose 50%] and 10:1) in the presence of 10% autologous serum. After incubation, the viable PMNs (greater than 95% exclusion of trypan blue) were activated, by the chemotactic peptide formyl-methionine-leucine-phenylalanine (fMLP), calcium ionophore A23187, or phorbol myristate acetate (PMA), and O2- generation was then measured. Generation of O2- to fMLP and A23187 was significantly enhanced from PMNs that had been incubated with influenza virus. Although influenza virus itself did not generate O2-, it caused a transient increase in intracellular calcium ([Ca2+]i), when measured with Indo-1-loaded cells. These results suggest that influenza virus primes PMNs to generate increased amounts of O2- and that the priming effect is associated with a transient increase in [Ca2+]. Consequently, we postulate that influenza virus priming produces PMNs of enhanced inflammatory potential to cause greater airway injury, obstruction, and responsiveness during a viral respiratory infection.

Cultured peripheral blood mononuclear cells derived from patients with acute severe asthma ("status asthmaticus") spontaneously elaborate a neutrophil chemotactic activity distinct from interleukin-8

Peripheral blood mononuclear cells (PBMC) isolated from patients with acute severe asthma on the day of admission to hospital were cultured in vitro in serum-free medium in the absence of mitogenic stimulants for as long as 72 h. PBMC isolated from control groups (mild asthma, chronic obstructive airway disease, normal subjects) were cultured in a similar fashion. After incubation, the culture supernatants were tested for neutrophil chemotactic activity (NCA) using a modified Boyden chamber technique. PBMC from patients with acute severe asthma elaborated significantly greater amounts of NCA into the culture supernatants as compared with all three control groups (p less than 0.01). The amounts of PBMC-derived NCA from the same patients after 7 days of hospital therapy and clinical improvement were reduced (p less than 0.01). A correlation was observed between the extent of reduction in spontaneous release of NCA by PBMC derived from patients with acute severe asthma and the degree of clinical improvement of their asthma (p less than 0.02). Both monocytes and lymphocytes, when cultured separately, released NCA in amounts sufficient to account for the total activity released by unfractionated PBMC. NCA in PBMC culture supernatants accumulated progressively with time, a process inhibited in a dose-dependent fashion by cycloheximide. The amounts of NCA in culture supernatants did not correlate with the concentrations of histamine in lysates of the PBMC prepared just prior to culture.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway inflammation during late asthmatic reactions induced by toluene diisocyanate

To determine the importance of airway inflammation for the development of late asthmatic reactions, we examined sensitized subjects during late asthmatic reactions induced by exposure to toluene diisocyanate (TDI) in the laboratory. Late asthmatic reactions are associated with a transient increase of bronchial responsiveness and, at the same time, with an increase of neutrophils followed by eosinophils, and of LTB4 and albumin in bronchoalveolar lavage fluid. Late asthmatic reactions, increased bronchial responsiveness, and increase of neutrophils, eosinophils, LTB4, and albumin concentration in bronchoalveolar lavage induced by exposure to TDI are all prevented by pretreatment with prednisone but not with the nonsteroidal anti-inflammatory agent indomethacin. Aerosolized steroids (beclomethasone and dexamethasone isonicotinate) completely inhibit late asthmatic reactions induced by TDI, whereas theophylline has a partial, and verapamil, ketotifen, and cromolyn have no protective effect. These results suggest that late asthmatic reactions induced by TDI may be caused by airway inflammation, and that anti-inflammatory steroids should be recommended in the prophylaxis of TDI asthma.

Eosinophilic airway inflammation during exacerbation of asthma and its treatment with inhaled corticosteroid

We have compared the inflammatory changes in the bronchial mucosa and the increase in the airway hyperresponsiveness in an asthmatic patient during the deterioration of symptoms. A striking increase in the number of bronchial epithelial eosinophils was associated with an increase in both airway hyperresponsiveness and asthma symptoms. During 16 wk of treatment with the inhaled corticosteroid, budesonide, the patient's clinical status and airway hyperresponsiveness improved. This was accompanied by an improvement in the ultrastructure of bronchial mucosa and a decrease in the number of epithelial eosinophils.

Bronchial responsiveness is not increased by bronchoalveolar and bronchial lavage performed after allergen challenge

Nonspecific bronchial responsiveness was studied in 23 allergic patients with a history of rhinitis and/or bronchial asthma who underwent fiberoptic bronchoscopy with bronchoalveolar and bronchial lavage (BAL-BL) 4h (Group A) or 24 h (Group B) after an allergen inhalation challenge. In all patients, the dose of methacholine causing an FEV1 fall of 15% (PD15) was determined at baseline, 24 h before allergen challenge. Methacholine bronchial challenge was repeated 1 h before BAL-BL in patients of both groups and again 12 to 14 h after BAL-BL in Group A and 24 h after BAL-BL in Group B. In patients of Group A, the values of methacholine PD15 after BAL-BL were not significantly different from those determined before BAL-BL. This was also the case in patients in whom bronchial responsiveness was increased after allergen challenge. In patients of Group B, methacholine PD15 was significantly decreased after allergen challenge, and this decrease was correlated with the occurrence and the severity of the late asthmatic reaction. Even in patients who showed dual asthmatic reactions and an increased responsiveness after allergen challenge, methacholine PD15 was not further decreased after BAL-BL. These data support the safety of a procedure combining bronchial allergen challenge with BAL-BL, which can be used for studies on the pathophysiology of bronchial asthma.

New aspects of isocyanate asthma

Air concentration of isocyanates are associated with the frequency of induced diseases. Asthma, bronchitis and rhinitis, chronic obstructive lung disease, and allergic alveolitis, respectively, were observed in exposed workers. Inhalation challenge tests with isocyanates found some 14% of symptomatic persons immunologically sensitized. At and above current threshold limit values (10 ppb) there is a risk of lung function deterioration also in asymptomatic workers.

Effect of antiasthma drugs on asthmatic reactions induced by toluene diisocyanate in sensitized subjects

To determine the effect of antiasthma drugs on asthmatic reactions and airway inflammation, we studied several groups of sensitized subjects treated with active drugs or placebo before and after exposure to toluene diisocyanate in the laboratory. We observed that the steroidal anti-inflammatory agent prednisone, but not the nonsteroidal anti-inflammatory agent indomethacin, inhibits the late (but not the early) asthmatic reactions induced by TDI. Prednisone also inhibits the increase of bronchial responsiveness and the increase of neutrophils, eosinophils, and albumin in bronchoalveolar lavage fluid that are associated with late asthmatic reactions induced by exposure to TDI. Beclomethasone has a dose-dependent inhibitory effect on TDI-induced late asthmatic reactions, whereas theophylline has a partial inhibitory effect on both early and late asthmatic reactions, and verapamil, ketotifen, cromolyn. Beta 2-adrenergic agonists have variable effects: salbutamol has no effect on early and late asthmatic reactions by itself, but it potentiates the inhibitory effect of low doses of beclomethasone. Broxaterol inhibits early asthmatic reactions, but has no effect on the late asthmatic reactions and the associated inflammatory response. These results suggest that, in sensitized subjects, late asthmatic reactions induced by toluene diisocyanate can be prevented by steroidal anti-inflammatory agents, whereas early asthmatic reactions may be prevented either by an association of inhaled steroids and beta-adrenergic agonists, or by beta-adrenergic agonists (e.g., broxaterol) with more complex mechanisms of action.

Bronchoalveolar lavage and morphology of the airways after cessation of exposure in asthmatic subjects sensitized to toluene diisocyanate

To evaluate the morphologic basis of the different outcomes of toluene diisocyanate (TDI) asthma after quitting occupational exposure, we examined ten patients with TDI asthma who showed, at diagnosis, a positive TDI challenge test and nonspecific bronchial hyperresponsiveness (NSBH) to methacholine. After diagnosis, all patients ceased work and a 4- to 40-month follow-up was obtained with three to eight determinations of the cumulative dose producing a 15 percent fall in FEV1 (PD15FEV1) methacholine in each patient. Bronchoalveolar lavage (BAL) and biopsy of bronchial muscosa were performed 3 to 39 months after cessation of work, in the absence of acute exacerbations of the disease. Total cell count in BAL fluid was moderately increased in four of ten patients, eosinophils were increased in five of ten patients, and neutrophils were increased in eight of ten patients. Mucosal biopsy specimens of main or lobar bronchi were available in eight of ten patients; epithelial damage and thickening of basement membrane was observed in almost all patients, as well as a mild-to-moderate inflammatory reaction in the submucosa, mainly represented by lymphocytes, eosinophils, and neutrophils. No relationship was observed between the cellularity of BAL and the degree of NSBH at the time of BAL; mean values of total cells and differential count were not different between patients with presence or absence of the different histologic findings. Mucosal biopsy and BAL were performed also in four subjects exposed to dusts without respiratory symptoms or NSBH; similar findings were obtained except for the absence of eosinophils in BAL and a lesser degree of basement membrane thickening and inflammatory reaction in the submucosa. The study of the changes in NSBH after quitting exposure showed that five of ten patients had a significant improvement in NSBH to methacholine, as evaluated by a positive significant linear regression between months of work cessation and PD15FEV1 methacholine; only one of these five patients had an increased number of eosinophils in BAL fluid. By contrast, four of the five patients with persistent NSBH after quitting exposure had an increased number of eosinophils in BAL. We suggest that persistent NSBH in TDI asthma after cessation of work may be related to an inflammatory reaction in which eosinophil infiltration seems to be a major determinant.

Mucosal inflammation in asthma

Over the past decade, it has become increasingly recognized that airways inflammation is one of the major components of asthma. Until recently, measurements of bronchial responsiveness and mediators of allergic reactions were the only methods of studying pathogenetic mechanisms in asthma. With improved diagnostic procedures such as fiberoptic bronchoscopy, it has become possible to investigate these mechanisms and the resulting inflammatory changes in situ. BAL has highlighted the presence of mast cells and eosinophils and has given proof of their mediator participation in airways inflammation and hyperresponsiveness. Endobronchial biopsies have so far yielded results that are similar to those obtained from postmortem studies, although it appears that there are varying degrees of inflammation in living asthmatics. Even in mild disease, the histopathologic features of bronchial asthma are consistent with chronic inflammation. Indirect evidence obtained from allergen challenge leading to increased bronchial hyperresponsiveness during LAR, and direct evidence of inflammatory cells and their mediators in the airway mucosa and lumen after allergen challenge argue for an active role of cells in bringing about inflammatory changes. At present, however, it is not possible to relate precisely the findings obtained by bronchoscopy to the clinical presentation and progression of asthma. Cell activation with production of potent mediators of inflammation may be more relevant to inflammation than the simple presence of these cells in the airways. Almost all the inflammatory cells present in the bronchial wall and lumen have been implicated in the pathogenesis of mucosal inflammation in asthma, but with our current state of knowledge, none can be singled out as the most important contributor. The mast cell was the first to be investigated in depth, and despite the accumulation of large amounts of data concerning its ultrastructure and function, it remains uncertain to what extent this cell is involved in inflammatory responses. Thus, while its main role appears to be that of initiator of allergen-induced responses, the eosinophil has attracted more attention as a proinflammatory cell rather than as an antiinflammatory cell with a capacity to be selectively recruited from the circulation in response to IgE-dependent signals. The eosinophil secretes potent mediators that cause damage to the bronchial epithelium and lead to bronchoconstriction. The role of other cells is at present not as well defined.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacological modulation of the contractile response to toluene diisocyanate in the rat isolated urinary bladder

1. Toluene diisocyanate produced concentration-dependent contractions of the rat isolated urinary bladder. 2. The contractions were tetrodotoxin-resistant and were abolished by previous exposure of the strips to capsaicin. 3. Indomethacin (5 microM) and ruthenium red (30 microM) inhibited toluene diisocyanate-induced contractions. Responses expressed as a percentage of the response obtained with substance P, 30 nM, were respectively 141.6 +/- 24.8% and 20.1 +/- 5.1% in control and indomethacin-treated strips (P less than 0.005); 123.0 +/- 30.2% and 14.0 +/- 6.5% in control and ruthenium red-treated strips (0.01 less than P less than 0.05). 4. These results suggest that toluene diisocyanate-induced contractions of the rat isolated bladder are the result of the release of cyclo-oxygenase products which may act by activating the capsaicin receptor.

Bronchoalveolar lavage in stable asthmatics does not cause pulmonary inflammation

Bronchoalveolar lavage (BAL) has become an important tool for evaluating changes in airway cells and fluid in asthma, and it may give insights into mechanisms of bronchial inflammation. Many factors contribute to airway inflammation in asthma including, possibly, airway instrumentation. To establish whether BAL leads to diffuse airway inflammation in stable asthmatics, we performed paired BAL studies (24 h apart) in eight subjects with mild asthma whose prebronchoscopy spirometric results were similar on both days. Airflow limitation did not occur in any subject after bronchoscopy. We observed no significant changes in BAL volume return, cell differential, lymphocyte subsets, reactive oxygen species metabolism by air-space cells, or BAL total protein. There was a slight increase in second-day BAL total cell return. We conclude that bronchoscopy and BAL in stable asthmatics with mild disease is not associated with evidence of diffuse airway inflammation.

Evidence that toluene diisocyanate activates the efferent function of capsaicin-sensitive primary afferents

Isocyanates are an important cause of occupational asthma. The mechanism of isocyanate-induced asthma is still unknown. To determine whether toluene diisocyanate stimulates the 'efferent' function of peripheral endings of capsaicin-sensitive sensory nerves, we investigated the effect of toluene diisocyanate in the rat isolated urinary bladder, a preparation in which the action of capsaicin has been well characterized. Toluene diisocyanate (0.03-3 mM) produced a concentration-dependent contraction of the bladder strips. Its maximal effect was about 50% of the response to capsaicin (1 microM). Previous exposure of the strips to capsaicin followed by washing out produced complete unresponsiveness, both to the first exposure to toluene diisocyanate and to a second exposure of capsaicin. Further, the response to both toluene diisocyanate and capsaicin was completely prevented by extrinsic bladder denervation, achieved by bilateral removal of pelvic ganglia (72 h before). Repeated exposure of the rat bladder to toluene diisocyanate reduced the capsaicin-evoked release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI), taken as biochemical marker of activation of these sensory nerves. These experiments provide the first evidence that toluene diisocyanate activates directly or indirectly the efferent function of capsaicin-sensitive primary sensory nerves.

Assessment of bronchial responsiveness as a guide to prognosis and therapy in asthma

The severity of airway inflammation in patients with asthma is best assessed by combining several tests of bronchial responsiveness. The prognostic significance of bronchial responsiveness is unknown, but indirect evidence suggests that those with moderate and severe asthma rarely remit spontaneously and permanently. Assessment of severity is crucial to the rational management of all patients with asthma. Severity can be used as a guide to both short- and long-term management.

Outpatient management of bronchial asthma

The current approach to asthma treatment centers around the recognition that asthma is primarily an inflammatory condition; airway hyperresponsiveness and bronchospasm are secondary phenomena. Anti-inflammatory treatments that produce sustained improvement in airway hyperresponsiveness (environmental control, cromolyn, inhaled and ingested corticosteroids) are the mainstay of treatment to keep symptoms and bronchodilator use to a minimum. Adequate control of chronic asthma with clearly defined treatment goals, accompanied by early recognition and patient-initiated treatment of worsened asthma, generally with inhaled/ingested corticosteroid, can successfully reduce the high morbidity and the low, but significant, mortality from this common condition.

Late asthmatic reactions to occupational sensitizing agents: frequency of changes in nonspecific bronchial responsiveness and of response to inhaled beta 2-adrenergic agent

Late asthmatic reactions have been demonstrated, generally, to increase bronchial responsiveness and are believed to respond poorly to inhaled bronchodilator. To assess the frequency of changes in bronchial responsiveness, we reviewed the records of 101 subjects with late asthmatic reactions and of 63 subjects with isolated immediate reactions after specific inhalation challenges to various occupational agents. These subjects had undergone nonspecific inhalation challenges to histamine or methacholine on a control day and after the late reaction when FEV1 had returned to +/- 10% baseline. We also reviewed 99 cases of subjects with late reactions who were administered an inhaled beta 2-agent (albuterol, 200 micrograms) during the late reaction. Fifty-seven/101 (56%) subjects with late reactions and 24/63 (38%) subjects with isolated immediate reactions demonstrated a twofold or greater change in provocative concentration of histamine or methacholine causing a 20% change in FEV1 (PC20) from baseline (p = 0.02; odds for the presence of significant changes in PC20 in subjects with late reactions, 56%; odds for the absence of significant changes in PC20 in subjects with immediate reactions, 62%). Changes in FEV1 greater than 20% after administering albuterol at the time of the late reactions occurred in 78% of the subjects tested; in 66%, FEV1 returned to greater than 90% baseline. This retrospective study demonstrates that changes in bronchial responsiveness after late reactions are not constant and do not appear to distinguish satisfactorily late from immediate reactions. Furthermore, late reactions respond well to beta 2-agonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Eicosanoid release from human bronchial epithelial cells upon exposure to toluene diisocyanate in vitro

Epithelial injury and inflammation are involved in airway hyperresponsiveness and asthma induced by toluene diisocyanate. In that isocyanates are insoluble and highly reactive compounds, bronchial epithelial cells may represent the most important target cells of their toxic effect. We hypothesized that damage to airway epithelium by toluene diisocyanate may result in the release of metabolites of arachidonic acid, which are known to promote inflammation and to alter epithelial cell function and airway smooth muscle responsiveness. To test this hypothesis we examined eicosanoid products in the culture media of bronchial epithelial cells exposed in vitro to 8 and 18 ppb toluene diisocyanate. Epithelial cells derived from human bronchi obtained at surgery were cultured to confluency on collagen-coated microporous membranes. Those cells, which expressed differentiated characteristics of epithelial cells (they showed keratin-containing filaments and had a cobblestone appearance), were alternatively exposed to toluene diisocyanate or air for 30 min in a specially designed in vitro chamber. The production of metabolites of arachidonic acid was assessed by measuring the release of immunoreactive products into the cell medium at the end of the exposure and during a 2 hr period after exposure. This method revealed a predominant isocyanate-induced release of immunoreactive 15-hydroxyeicosatetraenoic acid. Release rate of this compound tended to be dose-related and was associated with cell damage as assessed by the release of lactate dehydrogenase in the medium.

Fractional processing of sequential bronchoalveolar lavage to separate bronchial and alveolar samples

Bronchoalveolar lavage has been widely used to sample the lower respiratory tract. Most of the material recovered with this technique represents alveolar contents. A number of modifications have been suggested in order to obtain samples relatively enriched for bronchial material. In order to be able to use a standard technique for bronchoalveolar lavage to sample both airways and "routine" alveolar material, a simple modification of the technique as described by Reynolds and Newball was used: five sequential 20-ml aliquots were infused into the lower respiratory tract, and each aliquot was immediately aspirated. The return from the first aliquot was processed separately from the return from the subsequent four aliquots. These last four aliquots were pooled. Analysis of the first aliquot revealed it to be enriched for ciliated epithelial cells when compared with the subsequent aliquots. There were also differences in inflammatory cell composition with the bronchial sample containing relatively more neutrophils and relatively less lymphocytes. Aspiration during transoral bronchoscopy was documented by quantifying salivary amylase in the bronchial and alveolar lavage fluids. It was estimated, however, that the aspiration was not of quantitative significance in the vast majority of subjects studied. Finally, with the technique of fractional processing of bronchoalveolar lavage samples, it was possible to compare the protein concentrations in bronchial and alveolar lavages. Most prominent among the differences was a marked relative enrichment in the bronchial samples for immunoglobulin A. The technique of fractional processing of bronchoalveolar lavage samples provides a simple means to obtain samples enriched for bronchial and alveolar components. This should facilitate analysis of lower respiratory tract specimens in airway disease.

In vivo and in vitro methods for evaluating airways inflammation: implications for respiratory toxicology

The lung is frequently the target of injury for toxic exposures. Often these exposures lead to significant disease. Assessment of toxic exposures to the lung, however, may be made using both in vitro and in vivo methods. Recent advances in respiratory cell biology have made possible in vitro analyses of the interactions between airway cells and potential toxins. In addition, the lung can be sampled in vivo using bronchoscopy and bronchoalveolar lavage. This opens up the possibility of assessing potential toxins prior to the development of clinically significant disease. Together, these advancing methodologies promise new potential for the assessment and evaluation of toxic exposures to the lung.

Occurrence and specificity of IgE antibodies to isocyanates in occupationally exposed workers

The levels of IgE antibodies specific for toluene-diisocyanate (TDI), diphenylmethane-diisocyanate (MDI) and hexamethylene-diisocyanate (HDI) were determined in eight workers with an unequivocal history of professional asthma, all having been exposed to isocyanates in the working atmosphere. Five workers were examined at the clinical onset of asthma. They had serum IgE antibodies specific for TDI, MDI and HDI, and depressed pulmonary ventilation parameters. In contrast, three workers, who had only a mild bronchial obstruction at the time of testing, had no anti-isocyanate IgE antibodies. The results indicated that asthma was induced by type I allergic reaction, but other pathogenetic mechanisms of bronchoobstruction could not be completely ruled out.

Ketotifen does not inhibit asthmatic reactions induced by toluene di-isocyanate in sensitized subjects

In order to determine whether treatment with ketotifen inhibits asthmatic reactions induced by toluene di-isocyanate (TDI), we studied six sensitized subjects with previously demonstrated dual or late asthmatic reaction after inhalation challenge with TDI. Ketotifen (1 mg b.i.d., orally) or placebo was administered for 7 days to the examined subjects, according to a double-blind, cross-over, placebo-controlled study design. When the subjects were treated with either ketotifen or placebo, FEV1 markedly decreased after exposure to TDI. These results suggest that the anti-asthmatic agent ketotifen is not effective in TDI-induced asthma and suggest that it should not be used in the prophylaxis of asthmatic reactions induced by TDI in sensitized subjects.

Lymphocyte subsets in bronchoalveolar lavage fluid obtained from stable asthmatics, and their correlations with bronchial responsiveness

Bronchial responsiveness to methacholine (PD20 FEV1) was assessed in 22 asthmatic subjects approximately 5 days prior to bronchoalveolar lavage (BAL). A PD20 FEV1 could not be attained in 20 matched controls with normal pulmonary function. BAL was performed in all subjects, 3 x 60 ml aliquots of buffered saline being introduced into a segment of the middle lobe and immediately aspirated into siliconized glassware at 4 degrees C. After filtration, cells were counted, and the cell pellet resuspended in medium 199. Cytospin slides were prepared and a differential cell count performed. Lymphocyte subsets were identified by labelling further cytospin preparations with specific monoclonal antibodies (Leu series) against T3, T4, T8 and B cell markers, followed by a fluorescent antibody marker. The slides were coded, and 100 lymphocytes were then randomly scanned for fluorescence on each cytospin preparation. The median total lymphocyte counts were significantly greater in the asthmatic subjects, but this increase was confined to the T cell subgroups. The mean T4/T8 ratio was similar in asthmatic (1.51) and control (1.45) subjects. Log PD20 FEV1 correlated positively with total lymphocyte counts (r = 0.42, P less than 0.05), and with total T8 counts (r = 0.60, P less than 0.05). Correlations between bronchial responsiveness and T3, T4 and B lymphocyte numbers all failed to reach significance, and there was no correlation with T4/T8 ratios. The increase in BAL lymphocyte counts in asthma appears to be due to an absolute increase in T cell subsets, especially the T8 lymphocyte subgroup, and is most marked in mild asthmatics.

Pharmacology of allergen-induced early and late airway responses and antigen-induced airway hyperresponsiveness in allergic sheep

The pharmacology of antigen-induced early and late phase airway responses and the associated antigen-induced airway hyperresponsiveness was studied in allergic sheep. Data from studies with anti-allergic agents and specific receptor antagonists, especially leukotriene antagonists and antagonists of platelet activating factor (PAF), have led to the hypothesis that allergen-induced late responses in allergic sheep are linked to a heightened metabolism of arachidonic acid via the 5-lipoxygenase pathway. This increases leukotriene production during the acute allergic reaction, which results in a more prolonged acute bronchoconstriction and subsequently a more severe airway inflammation. These recruited inflammatory cells can then release mediators and other cell products which contribute to the late response and airway hyperresponsiveness.

Effect of nedocromil sodium on antigen-induced airway responses in allergic sheep

We studied the effects of nedocromil sodium and sodium cromoglycate on early and late bronchial responses, the airway inflammation associated with the late response to inhaled Ascaris suum antigen in allergic sheep in vivo, and the antigen-induced contractile responses of sheep tracheal smooth muscle in vitro. In addition, we examined the effect of nedocromil sodium on the development of antigen-induced airway hyper-responsiveness in this model. Pretreatment with either nedocromil sodium or sodium cromoglycate was effective in blocking antigen-induced early and late responses in allergic sheep. Both drugs also prevented the influx of eosinophils into the airways as assessed by bronchoalveolar lavage, observed during the late response in this model. No difference in drug potency was observed in vivo, but in vitro nedocromil sodium was 10-fold more potent than sodium cromoglycate against antigen-induced contractions of sheep tracheal smooth muscle. Nedocromil sodium was effective in blocking antigen-induced late responses and the subsequent development of airway hyper-responsiveness irrespective of whether the drug was given before antigen challenge or after the immediate response to antigen but before the late response. These findings indicate that nedocromil sodium is effective in the sheep model of asthma and therefore may be beneficial in the treatment of reversible obstructive airway disease in man.

Inflammatory passage of plasma macromolecules into airway wall and lumen

Anaesthetised guinea-pigs received tracer macromolecules 70-340 kDa intravenously and their erythrocytes were labelled in vivo with 99mTc. Superfusion of tracheal mucosa (via oral catheter) with control solutions and inflammatory agents, was followed by sampling of tracheal surface liquids and tracheal tissue. Under baseline conditions no 125I-fibrinogen (340 kDa) and minimal amounts of erythrocytes, 131I-albumin (70 kDa), and FITC-D (150 kDa) were found in tracheal lavage fluids. Undisturbed baseline conditions with negligible leakage of plasma into airway tissue and lumen were thus obtained with the present provocation and sampling techniques. Superfusion during 2 min with bradykinin 2-10 nmol, histamine 2-8 nmol, capsaicin 0.1-0.4 nmol, PAF 4-8 nmol, ovalbumin 3-6 pmol (in sensitised animals) produced, within 1-10 min, a significant and dose-dependent accumulation of plasma in tracheal tissue and lavage fluids. PAF also induced a late phase plasma leakage response at 5 h. At 10 min PAF given intra-arterially produced a similar leakage into the tissue but less into the lumen compared to topical PAF. Intravenous PAF produced additional effects such as pulmonary oedema. Carbachol 8-16 nmol had only minimal effects on 'leakage' but produced severe bronchoconstriction. Toluene diisocyanate (0.003-0.03 microliter) produced dose-dependent and very sustained (17 h) plasma leakage. Recovery of plasma tracers in airway tissue and surface liquids, respectively, was significantly correlated. As examined with capsaicin, absorption of luminal macromolecules increased only slightly during the exudation process. It is suggested that the consistent inflammatory stimulus-induced passage of plasma into the lumen is a consequence of a load on the basal side of the epithelium induced by the extravasated plasma and its derived peptides. An increased interstitial pressure may transiently separate many epithelial cells allowing a mainly uni-directional almost unrestricted flow of large solutes into the lumen.

Leukocyte count and bronchial hyperresponsiveness

The relationship of total and differential blood leukocyte counts with bronchial methacholine response was studied in a population-based sample of 324 men. Geometric mean total leukocyte counts were significantly higher in reactors (6567 cells/mm3) than in nonreactors (5732 cells/mm3; p = 0.003). After adjusting for smoking habits, a factor contributing to both an elevation in peripheral leukocyte count and an increased level of airway responsiveness, reactor status remained significantly associated with leukocyte count. This association also persisted after controlling, with a logistic model, for atopy and common cold (marker of infection) and after excluding men with a history of asthma, chronic bronchitis, or low FEV1. Study of the differential leukocyte counts has shown that an increase was present for almost every type of leukocyte, and particularly evident for neutrophils. Whether these findings reflect an association between bronchial hyperresponsiveness and cellular inflammation needs more investigation.

Cellular markers of inflammation in the airways of allergic sheep with and without allergen-induced late responses

Allergic sheep respond to inhaled Ascaris suum antigen either with an acute bronchoconstriction alone (acute responders, AR) or both an acute and late bronchoconstriction (dual responders, DR). In this study, we determined if: (1) inflammatory cell composition of bronchoalveolar lavage (BAL) obtained during the late response differs between DR and AR; (2) the difference in inflammatory cells is dependent on the prechallenge BAL cell composition; and (3) drugs that block late airway responses also modify this airway inflammation. Antigen challenge caused significant immediate mean increases in specific lung resistance (SRL) both in DR (n = 28) and in AR (n = 14), but only DR had a late increase in SRL. There were no differences between the two groups in total cell returns or in the percentage of neutrophils in BAL 7.5 to 8 h after challenge, but DR had a 3.5-fold increase (p less than 0.05) in the percentage of eosinophils. Methylprednisolone succinate (15 mg/kg intravenously) given to DR (n = 7) 3 h after antigen challenge blocked the late airway response and the eosinophil response. When BAL was performed both before and after (i.e., 7.5 to 8 h) antigen challenge, similar results were observed: AR (n = 7) and DR (n = 14) exhibited characteristic airway responses. No significant differences in prechallenge BAL cell composition were observed between AR and DR; after challenge both groups showed increases in neutrophils, but only the DR showed an increase (p less than 0.05) in eosinophils. Pretreatment of DR with the antiallergic agents (cromolyn sodium or nedocromil sodium aerosol, 20 mg) blocked the immediate and late responses and the late increase in BAL eosinophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Number and activity of inflammatory cells in bronchoalveolar lavage fluid in asthma and their relation to airway responsiveness

Bronchial responsiveness to inhaled methacholine was measured four to six days before fibreoptic bronchoscopy in 22 asthmatic patients (10 smokers) and 20 control subjects (12 smokers). The asthmatic patients had a baseline FEV1 greater than 60% predicted and a PD20FEV1 (provocative dose of methacholine causing a 20% fall in FEV1) of 0.006-3.7 mg. The 20 control subjects had normal pulmonary function and a PD20FEV1 above the maximum cumulative dose of methacholine of 6.4 mg. Bronchoalveolar lavage of a middle lobe segment (lingula in four subjects) was performed with three sequential 60 ml aliquots of sterile saline. Cellular metabolic activity was stimulated with latex in aliquots of resuspended cells, and measured by means of luminol enhanced chemiluminescence to assess neutrophil activity and lucigenin enhanced chemiluminescence to assess macrophage activity. Mean absolute total cell counts were similar in the asthmatic and control groups but there were differences in differential cell counts, with a significant increase in eosinophil (p less than 0.05) and lymphocyte (p less than 0.005) counts in asthma. PD20FEV1 was negatively correlated with percentage neutrophil counts (p less than 0.005). Luminol enhanced chemiluminescence/1000 neutrophils was increased about twofold in asthmatic subjects (p less than 0.001), but was not correlated with PD20FEV1 Lucigenin enhanced chemiluminescence/1000 macrophages was increased nearly fourfold in asthmatic patients (p less than 0.001) and showed a negative correlation with PD20FEV1 (p less than 0.01). The macrophage count was increased twofold in current smokers in both groups, but other cell numbers were not altered significantly. Smoking did not affect cellular metabolic activity in either group. This study supports the idea that an inflammatory process is present in the airways of those with asthma, and suggests a relation between bronchial responsiveness and both neutrophil numbers and macrophage activity.

Comparison of cellular and protein changes in bronchial lavage fluid of symptomatic and asymptomatic patients with red cedar asthma on follow-up examination

Seventeen patients with occupational asthma due to western red cedar had bronchial lavage during follow-up examination after removal from exposure for at least 1 year. Seven patients were asymptomatic while ten continued to have symptoms of asthma requiring treatment. Symptomatic patients had evidence of airway inflammation, as reflected by a significantly higher total cell count, neutrophils and eosinophils, as well as an increase in protein and albumin in their bronchial lavage fluid compared to those without symptoms. Asymptomatic patients had no evidence of airway inflammation in the lavage fluid. There was no correlation between the degree of non-specific bronchial hyperresponsiveness and the number or percentage of inflammatory cells to suggest that cellular infiltration is the sole cause of persistent bronchial hyperresponsiveness.

Dose-dependent inhibitory effect of inhaled beclomethasone on late asthmatic reactions and increased responsiveness to methacholine induced by toluene diisocyanate in sensitised subjects

To determine whether inhaled beclomethasone, both at low and at high doses, inhibits late asthmatic reactions and the associated increase in airway responsiveness induced by toluene diisocyanate (TDI), we studied 9 sensitised subjects. Low dose beclomethasone (200 micrograms bid), high dose beclomethasone aerosol (1000 micrograms bid), and placebo were administered for 7 days before TDI inhalation challenge to each subject, according to a double-blind, crossover study design. The washout period between the treatments was at least 1 week. When the subjects were treated with placebo, forced expiratory volume in 1 sec (FEV1) markedly decreased after exposure to TDI. By contrast, high dose beclomethasone prevented the late asthmatic reaction and the low dose partially inhibited the reaction. With placebo the mean (+/- SE) value of FEV1 4 h after exposure to TDI was 2.6 +/- 0.17 L, which went to 3.3 +/- 0.12 after low dose beclomethasone, and to 3.5 +/- 0.15 L after high dose of beclomethasone (significant difference in the decrease of FEV1 in the 8 h after exposure to TDI, between treatments: F = 9.87, (P less than 0.001), After treatment with placebo or with low dose beclomethasone, airway responsiveness to methacholine increased 8 h after exposure to TDI. With placebo, the PD20 decreased from 0.66 mg (Geometric Standard Error of the Mean [GSEM], 1.38) to 0.18 mg (GSEM, 1.46); with low dose inhaled beclomethasone, the PD20 decreased from 0.93 mg (GSEM, 1.42) to 0.36 mg (GSEM, 1.63).(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma exudation and asthma

Several pieces of evidence support the view that exudation of plasma into the airway wall and into the airway lumen occurs in asthma. Vascular leakage of plasma results from inflammatory mediator-induced separation of endothelial cells in postcapillary venules belonging to the tracheobronchial circulation. Whereas proposed mediators of asthma induce reversible leakage, several antiasthma drugs exhibit antileakage effects in animals and humans. Potential consequences of plasma exudation are many. Mucosal/submucosal edema might contribute to airway hyperresponsiveness. Plasma exudate in the airway lumen in asthma may contribute to sloughing of epithelium, impairment of mucociliary transport, narrowing of small airways, and mucus plug formation. Exuded plasma may cause airway inflammation and constriction because of its content of powerful mediators, and chemoattractant factors and plasma proteins may condition the inflammatory cells abundant in asthmatic airways to release mediators in response to stimuli that otherwise would be innocuous to the cells. It is concluded that inflammatory stimulus-induced increase in macromolecular permeability of the tracheobronchial microvasculature and mucosa may be a significant pathogenetic mechanism in asthma and that the postcapillary venular endothelium and airway epithelium that regulate leakage of plasma are important effector cells in this disease.