Leukotriene B4 and late asthmatic reactions induced by toluene diisocyanate.

We investigated whether leukotriene B4 (LTB4) is released from the lungs of sensitized subjects during asthmatic reactions induced by toluene diisocyanate (TDI). We examined three groups of TDI-sensitized subjects, one after no exposure to TDI, the second 8 h after an exposure to TDI that caused an early asthmatic reaction, and the third 8 h after an exposure to TDI that caused a late asthmatic reaction. We analyzed bronchoalveolar lavage (BAL) fluid by reverse-phase high-performance liquid chromatography and by specific radioimmunoassay. The mean concentration of LTB4 was higher [0.31 +/- 0.09 (SE) ng/ml, range 0.15-0.51] in BAL fluid of sensitized subjects who developed a late asthmatic reaction than in BAL fluid of subjects who developed an early asthmatic reaction (0.05 +/- 0.04 ng/ml, range 0-0.224), and no LTB4 was detectable in the control subjects. We also performed BAL 8 h after TDI exposure on four TDI-sensitized late-dual reactors who were on steroid treatment. In this group of subjects no LTB4 was detectable. These results suggest that LTB4 may be involved in late asthmatic reactions induced by TDI.

Theophylline serum levels unmodified by postprandial administration of a sustained-release preparation (Teonova).

The authors studied serum theophylline levels after administration of new single-dose capsules: Teonova. Special attention was paid to possible fluctuations of serum theophylline after administration of the drug following a standardized meal. For this purpose a test was carried out on eight male patients with intrinsic asthma. The patients were given a dose able to produce a serum concentration of theophylline of between 10 mcg and 20 mcg at the tenth hour after the administration. This dose was found to be 400 mg (2 tablets of 200 mg) for one patient and 600 mg (2 tablets of 300 mg) for the remaining seven. The capsules of Teonova were administered to each patient for two subsequent days at 07h00. On the first day the patients had their capsules after fasting, and on the second day after a standardized meal. The test proved that Teonova assured a satisfactory serum theophylline level throughout the 24 hours in all patients; food in no way affected the absorption kinetics of the drug. Such features make Teonova suitable for long-term theophylline therapy.

Pathogenesis of late asthmatic reactions induced by exposure to isocyanates.

The importance of airways inflammation for the development of bronchial hyperresponsiveness and for exacerbation of asthma was investigated in subjects with occupational asthma. We examined subjects sensitized to isocyanates, a small molecular weight compound that causes occupational asthma. Studies in asthmatic subjects sensitized to toluene diisocyanate (TDI) demonstrated that late, but not early, asthmatic reactions induced by TDI were associated with an acute increase in bronchial responsiveness, and with a marked infiltration of neutrophils and a slight infiltration of eosinophils into the airways, both prevented by steroids. As the late asthmatic reactions and the increase in responsiveness induced by TDI were prevented by steroids, but not by indomethacin, we speculated that cell membrane phospholipid metabolites, which are inhibited by steroids but not by indomethacin, may be involved in TDI induced hyperresponsiveness. The results of these studies suggest that bronchial hyperresponsiveness and exacerbation of asthma may be related to inflammation of the airways and that cell membrane phospholipid metabolites may be involved.

Importance of airway inflammation for late asthmatic reactions induced by toluene diisocyanate in sensitized subjects.

To determine the importance of airway inflammation for late asthmatic reactions and increased airway responsiveness induced by TDI, we investigated whether late asthmatic reactions and increased responsiveness induced by TDI are associated with airway inflammation and whether steroids prevent them by modifying the inflammatory response within the airways. We measured FEV1 before and at regular intervals after exposure to TDI and performed dose-response curves to methacholine and bronchoalveolar lavage 8 hr after TDI in two subjects with previously documented late asthmatic reaction; then we repeated the same procedure a few weeks after treatment with steroids. Airway responsiveness and polymorphonuclear cells were increased in both subjects after the late asthmatic reaction; treatment with steroids prevented late asthmatic reaction and the increase in airway responsiveness and polymorphonuclear cells in bronchoalveolar lavage. These results suggest that late asthmatic reaction induced by TDI may be caused by airway inflammation.

Airway mucosal inflammation in occupational asthma induced by toluene diisocyanate.

We examined the light and electron microscopic structure of lobar bronchial biopsies of nine subjects with occupational asthma induced by toluene diisocyanate (TDI) and of four control nonasthmatic subjects who had never been exposed to TDI. Inflammatory cell numbers were separately assessed in the intact epithelium, in the more superficial layer of the submucosa, and in the total submucosa. Asthmatic subjects had an increased number of inflammatory cells in the airway mucosa compared with control subjects. Eosinophils were significantly increased in all compartments, CD45-positive cells were significantly increased in the epithelium and in the more superficial layer of the submucosa, and mast cells were significantly increased only in epithelium. By electron microscopy eosinophils and mast cells appeared degranulated only in asthmatic patients. In the areas of epithelium that appeared intact by light microscopy, electron microscopy showed that, although the intercellular spaces between columnar cells were similar in asthmatic and control groups, the intercellular spaces between basal cells were significantly wider in patients with asthma. Patients with TDI-induced asthma also had a thicker subepithelial reticular layer, where immunohistochemistry showed the presence of collagen III. In conclusion, in patients with asthma induced by TDI, the airway mucosa shows pathologic features, such as inflammatory cell infiltrate and thickening of subepithelial collagen, similar to those described in atopic asthma.

Effect of cessation of exposure to toluene diisocyanate (TDI) on bronchial mucosa of subjects with TDI-induced asthma.

The effect of cessation of exposure to toluene diisocyanate (TDI) was studied in six patients with TDI-induced asthma, proved by a positive inhalation challenge with TDI. Bronchial challenges with TDI and methacholine were performed, and lobar bronchial biopsies were taken at diagnosis and 6 months later, after cessation of exposure. Biopsies from four nonasthmatic control subjects were also examined. At diagnosis, asthmatic subjects had thickened reticular basement membrane (p less than 0.05) and increased numbers of mononuclear cells (p less than 0.05) and eosinophils (p less than 0.05) in the lamina propria when compared with control subjects. Electron microscopy showed degranulation of eosinophils and mast cells in asthmatics. Six months after cessation of exposure, the thickness of reticular basement membrane was significantly reduced compared with that at diagnosis (p less than 0.05), and it decreased to values similar to those of control biopsies. Inflammatory cell numbers in bronchial mucosa of asthmatic subjects did not change significantly 6 months after removal from exposure, and degranulation of eosinophils and mast cells was still present. At the end of the study, airway hyperresponsiveness to methacholine and/or sensitivity to TDI persisted in most of the asthmatic patients despite the cessation of exposure and the disappearance of asthmatic symptoms. In conclusion, in patients with occupational asthma induced by TDI, the avoidance of exposure to the sensitizing agent for 6 months is able to reverse the reticular basement membrane thickening in the bronchial mucosa, but the inflammatory cell infiltrate, the specific sensitivity to TDI, and the nonspecific airway hyperreactivity may persist.

Expression of interleukin (IL)-4 and IL-5 proteins in asthma induced by toluene diisocyanate (TDI).

BACKGROUND: TDI-induced asthma exhibits clinical, functional and morphological similarities with allergen-induced asthma, suggesting that an immunological mechanism is involved in the sensitization to TDI. In vitro studies using the technique of cloning lymphocytes demonstrated that a great proportion of T-cell clones derived from bronchial mucosa of subjects with TDI-induced asthma produced IL-5 and interferon-gamma, but not IL-4, upon in vitro stimulation. OBJECTIVES: To investigate in vivo the role of IL-4 and IL-5 on the inflammatory response of the bronchial mucosa to TDI in sensitized subjects, we performed a quantitative analysis of bronchial biopsies. METHODS: We obtained bronchial biopsies from six subjects with TDI asthma 48 h after an asthmatic reaction induced by TDI challenge (challenged group), in six subjects with TDI asthma 1-4 weeks after the last exposure to TDI (chronic group), and in six non-asthmatic controls. The number of eosinophils, mast cells, T-lymphocytes, and IL-4 and IL-5 protein positive cells was determined by immunohistochemistry in the area 100 microm beneath the epithelial basement membrane. RESULTS: The characteristic increase of submucosal eosinophils, but not of mast cells and T-lymphocytes, was observed in the subjects with TDI-induced asthma when compared with controls. No differences were detected between the two groups of asthmatics. In the subjects with TDI-induced asthma, cell immunoreactivity for IL-5 was increased when compared with normal controls. There was no difference in the expression of IL-5 protein between challenged and chronic asthmatics. In contrast, the expression of IL-4 protein was increased only in the asthmatic subjects tested after recent exposure to TDI. CONCLUSIONS: We demonstrated that TDI asthma 48 h after specific bronchial challenge was associated with increased numbers of cells expressing IL-4 and IL-5, whereas chronic TDI asthma was associated with increased expression of IL-5, but not of IL-4. The results suggest that subjects who developed TDI asthma exhibit increased production of IL-5 even in the absence of a recent trigger by the exogenous sensitizer and that production of TH2-like cytokines in TDI-induced asthma may not always be co-ordinately regulated in vivo.