May the reduction of exposure to specific sensitizers be an alternative to work cessation in occupational asthma? Results from a follow-up study.

BACKGROUND: Few data are reported on the effects of a reduction of exposure to specific sensitizers in occupational asthma (OA). The objective of this study was to evaluate the clinical outcome of subjects with OA, comparing the effect of a reduction with that of the persistence or cessation of occupational exposure to the specific sensitizer. SUBJECTS AND METHODS: Forty-one subjects with OA due to different sensitizers were diagnosed via a specific inhalation challenge. After a follow-up interval of 3.5 years, subjects were reexamined by clinical assessment, bronchial hyperresponsiveness (BH) and induced sputum. RESULTS: At follow-up, subjects who had reduced occupational exposure (n = 22) showed a significant improvement in BH and a nonsignificant improvement in sputum eosinophilia (from 5.3 to 1.1%, n.s.), while subjects still exposed (n = 10) showed a significant decrease in FEV(1). Subjects who ceased work (n = 9) showed a trend of improvement in BH and sputum eosinophilia. Logistic analysis showed that the major determinant of improvement in BH at follow-up was the severity of BH at diagnosis, with a minimal contribution from the duration of exposure and treatment with inhaled corticosteroids during follow-up; reduction of work exposure did not enter into any model. CONCLUSION: The reduction of occupational exposure could not be considered to be as effective as work cessation, which remained the best treatment for OA. However, it was not associated with a deterioration of FEV(1) as observed in subjects with persistent exposure.

Leukocyte counts in hypertonic saline-induced sputum in subjects with occupational asthma.

We measured markers of eosinophilic inflammation in the blood and in the sputum induced by hypertonic saline (HS) inhalation of 24 subjects with occupational asthma who were still exposed to high molecular weight compounds (HMWCs, n = 8) or to low molecular weight compounds (LMWCs, n = 16); all subjects were symptomatic and showed bronchial hyperresponsiveness to methacholine at the time of study. Sputum cell counts were also measured in 14 normal subjects and in 24 subjects with non-occupational asthma with asthma severity similar to that of occupational asthmatics. Both occupational and non-occupational asthmatic subjects showed higher neutrophil percentages in HS-induced sputum than normal subjects, asthmatics with LMWC-induced asthma showing the highest values. Eosinophil percentages in HS-induced sputum were higher in non-occupational asthmatics and in asthmatics with HMWC-induced asthma than in normal subjects and in subjects with occupational asthma due to LMWCs. No difference in bronchial responsiveness, peak expiratory flow variability and serum eosinophil cationic protein (ECP) levels were observed among the different asthma groups. Although sputum eosinophil percentages significantly correlated with blood eosinophil percentages, sputum allowed the detection of a higher number of subjects with eosinophilic inflammation than blood. Serum ECP levels were normal in most asthmatic subjects. A significant correlation between sputum eosinophil percentages and bronchial hyperresponsiveness to HS was observed. Despite a similar degree of functional abnormalities, subjects with asthma due to LMWCs and still exposed to the occupational sensitizer showed a lower degree of eosinophilic inflammation and a higher degree of neutrophilic inflammation in the airways than subjects with occupational asthma due to HMWCs or non-occupational asthmatics. Furthermore, sputum eosinophil counts detect, better than blood indices, the degree of airway inflammation in both occupational and non-occupational asthma.

Sister chromatid exchange and micronucleus frequency in human lymphocytes of 1,650 subjects in an Italian population: I. Contribution of methodological factors.

The influence of several methodological factors on mean values of sister chromatid exchanges (SCEs) and micronuclei (MN) in peripheral lymphocytes of 1,650 subjects was analyzed. Donors belonged to a general healthy population living in Pisa and in two nearby small cities: Cascina and Navacchio (Ca-Na). Blood samples were collected over a period of 29 months and processed in three different laboratories of the some institute. Slides were analyzed by several scorers. Our data showed that lymphocyte proliferation indexes (PIs) and baseline mean values of SCEs were affected mainly by sampling period. This factor accounted for a percentage ranging from roughly 10% (Pisa) to 20% (Ca-Na) of total SCE variance and from roughly 10% (Pisa) to 13% (Ca-Na) of total PIs variance. A marginal effect was attributable to the different laboratories involved (maximum 3% for SCEs and 7% for PIs). The sampling period variable included many sources of variability such as culture media batches, fetal calf serum, PHA, BrdUrd, and seasonality. MN counts revealed a more marked dependence on processing laboratories. This factor accounted for a percentage of roughly 10% (Pisa and Ca-Na) of total variance, while the sampling period was marginally effective (about 1-4% of total variability). Because laboratories were equipped and supplied with the same materials and consumables and technicians were rotated constantly, the only variable ascertained was represented by the three different models of CO2 incubators used for lymphocyte culturing. When "month" and "incubator" variables were considered jointly, experimental variability accounted for 15-20% of total variance, both for PIs and mean values SCEs and MN. The variability due to slide scoring was reduced by assigning each slide to five different scorers and matching low with high scorers in each group. Present data show that when the study is performed under these controlled conditions, about 20% of total interdonor variability can be explained by experimental or seasonal factors.

Tolerance to the protective effect of salmeterol on allergen challenge.

Long-term treatment with inhaled beta 2-agonists may be associated with a deterioration in asthma control, potentially due to tolerance. Regular use of short-acting beta 2-agonists has been shown to induce tolerance to allergen or adenosine 5'-monophosphate challenge. The aim of the study was to detect the efficacy of a single dose and a short-term treatment with salmeterol, a long-acting beta 2-agonist, to protect against early asthmatic reaction (EAR) to allergen. Eight subjects with mild allergic asthma underwent two treatment periods in which subjects performed an allergen challenge (specific bronchial provocation test) protected by a single dose (50 micrograms) of salmeterol (Salm-1) followed by a second specific bronchial provocation test after regular treatment with salmeterol for 1 week (Salm-2), or a single dose of placebo (Plac-1) and regular treatment (1 week) with placebo (Plac-2). Each subject performed both treatments in a randomized order. Each time allergen challenge was performed 1 h after last drug inhalation and it was stopped when the same provocative dose of allergen of a previous screening allergen challenge was achieved. The maximum decrease in FEV1 and area under curve in the first hour after allergen inhalation were significantly lower in Salm-1 (max delta FEV1 %, median [range]: 4%[0 to 9]) with respect to Salm-2, Plac-1, Plac-2 (24%[13 to 38], 31%[19 to 50], 30%[6 to 44], respectively, p < 0.001); there was no difference among Salm-2, Plac-1 and Plac-2. In Salm-1, all subjects were protected against EAR, whereas in Salm-2 only 2 subjects showed a partial protection. In conclusion the protective effect of a single dose of salmeterol against allergen-induced EAR was lost after regular treatment with salmeterol for 1 week. The clinical relevance of this mechanism remains to be elucidated.

Prognosis of occupational asthma.

Several studies on the prognosis of occupational asthma have shown that a significant proportion of patients continue to experience asthmatic symptoms and nonspecific bronchial hyperresponsiveness after cessation of work. The determinants of this unfavourable prognosis of asthma are: long duration of exposure before the onset of asthma; long duration of symptoms before diagnosis; baseline airway obstruction; dual response after specific challenge test; and the persistence of markers of airway inflammation in bronchoalveolar lavage fluid and bronchial biopsy. The relevance of immunological markers in the outcome of occupational asthma has not yet been assessed. Further occupational exposure in sensitized subjects leads to persistence and sometimes to progressive deterioration of asthma, irrespective of the reduction of exposure to the specific sensitizer, and only the use of particular protective devices effectively prevents the progression of the disease. A long-term follow-up study of toluene diisocyanate (TDI)-induced asthma showed that the improvement in bronchial hyperresponsiveness to methacholine occurred in a small percentage of subjects and only a long time after work cessation. Bronchial sensitivity to TDI may disappear, but non-specific bronchial hyperresponsiveness often persists unchanged, suggesting a permanent deregulation of airway tone. Steroid treatment significantly reduces nonspecific bronchial hyperresponsiveness only when started immediately after diagnosis.

Pesticides and groundwater quality protection : Calibrating a simple model for ranking the contamination potential.

A simple approach for ranking the leaching of pesticides from surface soil is presented and tentatively calibrated with field data from an agricultural area. The approach is based on the calculation of a leaching index indicating the proportion of active ingredient, with respect to the quantity applied, leaching from a soil model in a given time interval (one year). In the selected area, 85 wells tapping an unconfined aquifer were sampled for groundwater pesticide residue analysis, in order to explore the index region between leachers and nonleachers.

Monitoring human exposure to urban air pollutants.

A multidisciplinary study on a general population exposed to vehicle exhaust was undertaken in Pisa in 1991. Environmental factors such as air pollution and those associated with lifestyle were studied. Meanwhile, biological and medical indicators of health condition were investigated. Chromosomal aberrations, sister chromatid exchanges (SCEs), and micronuclei in lymphocytes were included for the assessment of the genotoxic risk. Because of the large number (3800) of subjects being investigated, standardization of protocols was compulsory. The results on data reproducibility are reported. To assess the reliability of the protocol on a large scale, the population of Porto Tolle, a village located in northeast Italy, was studied and compared to a subset of the Pisa population. Preliminary results showed that probable differences between the two populations and individuals were present in terms of SCE frequencies. The study was potentially able to detect the effects of several factors such as age, smoking, genetics, and environment. The in vitro treatment of lymphocytes with diepoxybutane confirmed the presence of more responsive individuals and permitted us to investigate the genetic predisposition to genetic damage. The possible influence of environmental factors was studied by correlation analyses with external exposure to air pollutants as well as with several lifestyle factors.

Characterization of tachykinin receptors in ferret trachea by peptide agonists and nonpeptide antagonists.

The tachykinin receptors mediating mucus secretion and smooth muscle contraction were studied in the ferret trachea in vitro. Substance P (SP) and the selective agonist for NK1 receptor ([Sar9,Met(O2)11]SP), but not selective agonists for NK2 ([Ala5,beta-Ala8]neurokinin A-(4-10)) and NK3 ([MePhe7]neurokinin B) receptors, induced secretion of macromolecules in a concentration-dependent fashion. The nonpeptide NK1 receptor antagonist, CP-96,345, but not the nonpeptide NK2 receptor antagonist, SR-48968, inhibited SP-induced secretion. Both neurokinin A (NKA) and [Ala5,beta-Ala8]NKA-(4-10), but not NK1 and NK3 selective agonists, evoked a concentration-dependent smooth muscle contraction. SR-48968, but not CP-96,345, inhibited in a concentration-dependent manner the response to NKA. CP-96,345 and SR-48968 did not affect the concentration-dependent increase in macromolecule secretion or smooth muscle contraction by carbachol. These findings indicate that NK1 receptors mediate secretion of macromolecules and NK2 receptors mediate smooth muscle contraction, in response to tachykinins in the ferret trachea in vitro.

Bis(5-amidino-2-benzimidazolyl)methane and related amidines are potent, reversible inhibitors of mast cell tryptases.

Tryptase is the major secretory protease of human mast cells and is proposed to be involved in neuropeptide processing and tissue inflammation. Exploration of the biology of tryptase has been hindered by the lack of potent, selective inhibitors. The current study explores the properties of aromatic diamidines as inhibitors of dog and human tryptase. The strongest inhibitors of tryptase in this series are bis(5-amidino-2-benzimidazolyl)methane (BABIM) and (5-amidino-2-benzimidazolyl)-(5-(N,N'-dimethylamidino)-2- benzimidazolyl)methane, which exhibit K(i) values of 1.8 and 1.4 nM, respectively, in blocking the hydrolysis of tosyl-L-Gly-Pro-Lys-4-nitroanilide by human tryptase. These compounds are approximately 10,000-fold more potent than benzamidine, and are the strongest reversible inhibitors of tryptase described to date. Other aromatic mono- and diamidines, including amiloride and pentamidine, are less potent. Nonetheless, they abolish tryptase activity at high inhibitor concentrations. The rank order of tryptase inhibitor potency parallels that of inhibitors tested against trypsin. BABIM, the only highly active member of this series whose potency against other targets has been examined previously, is a far stronger inhibitor of tryptase than of other trypsin-like serine proteases, including those involved with hemostasis, fibrinolysis and the complement system. Therefore, BABIM appears to have selective affinity for tryptase. In addition to inhibiting tryptase-induced hydrolysis of peptide-based chromogenic substrates, BABIM blocks completely the reversal of vasoactive intestinal peptide-induced relaxation of isolated trachea by dog tryptase. Thus, BABIM and related amidines are potent inhibitors of mast cell tryptases that may be useful in exploring mast cell protease biology.

[A cross-sectional epidemiological study of symptoms and respiratory physiology in a sample of workers in shoe manufacture]. / Indagine epidemiologica trasversale sui sintomi e la funzione respiratoria in un campione di lavoratori del settore calzaturiero.

The prevalence of respiratory symptoms and functional abnormalities has been evaluated in a sample of 350 workers (186 males and 164 females, mean age: 35.1 and 36.6 years respectively) employed in 24 factories of the shoes industry in the area of Pisa, exposed to airway irritants (solvent vapours, leather dusts and fumes). Each subject performed C.N.R. questionnaire of respiratory symptoms and diseases, and measurement of Forced Vital Capacity and derived indices. A mild prevalence of respiratory symptoms (chronic cough: 9.3% and 8.5% in males and females respectively; chronic phlegm: 14.6% and 6.8%; persistent wheeze: 2.1% and 1.7%; dyspnea of 1st degree: 23.3% and 39.0%) was reported, more frequently in smokers than in non smokers. Subjects with longer job duration in the shoe industry showed a trend to have a higher prevalence of chronic phlegm than subjects with shorter job duration; on the contrary, the last ones had a higher prevalence of rhino-conjunctivitis. A higher prevalence of attacks of shortness of breath and dyspnea of 2nd degree in males, and dyspnea of 1st degree in females was observed in workers to high risk job (to shear, to use adhesive, etc.) with respect to workers employed in low risk job (to assembly, to store etc). Mean spirometric values where in the normal range. Subdividing the subjects in groups with different smoking habit and job duration, a mild effect of the occupational exposure in groups with the same smoking habit could be observed for FEV1 and MEF50 particularly.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurogenic plasma extravasation in the rat nasal mucosa is potentiated by peptidase inhibitors.

The increase in vascular permeability associated with neurogenic inflammation in the nasal mucosa is mediated by neuropeptides such as substance P released from sensory nerves. Substance P is degraded by the peptidases neutral endopeptidase-24.11 (NEP-24.11) and angiotensin converting enzyme (ACE). In the present study, we used capsaicin to produce neurogenic inflammation in the nasal mucosa of rats, and we examined the effect of inhibition of NEP-24.11 by phosphoramidon, inhibition of ACE by captopril or inhibition of both enzymes by giving both inhibitors. Using as tracers intravenous Evans blue dye to quantify the extravasation and Monastral blue pigment to localize the sites of leakage, we examined the magnitude and distribution of capsaicin-induced plasma extravasation in the nasoturbinates, maxilloturbinates, ethmoidal turbinates and septum. Capsaicin caused a dose-dependent increase in Evans blue extravasation in the naso- and maxilloturbinates but had only a slight effect in the septum. The leaky blood vessels responsible for this plasma extravasation, as manifested by Monastral blue labeling, were most numerous in the naso- and maxilloturbinates, particularly near the front and free borders. After phosphoramidon, the leakage of Monastral blue was more widespread and extended in a more caudal direction. The response to capsaicin was augmented by phosphoramidon alone but not by captopril alone. However, in the presence of phosphoramidon, captopril further augmented the capsaicin-induced extravasation. We conclude that neurogenic inflammation in the rat nasal mucosa is greatest in the naso- and maxilloturbinates and can be modulated by NEP-24.11 and, to a lesser extent, by ACE.

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.

Specific bronchial reactivity to toluene diisocyanate: dose-response relationship.

20 patients with toluene diisocyanate (TDI)-induced asthma were examined in order to assess their threshold of response to TDI during specific bronchial provocative tests (BPT). Specific bronchial hyperresponsiveness was evaluated by performing, on different days, specific BPT with increasing concentrations of TDI until a positive response was obtained; the threshold of response to TDI (low: 0.02-0.05 ppm; moderate: 0.1 ppm; high: 0.2-0.25 ppm) and the pattern of positive response were evaluated in comparison with some clinical features of the disease. The threshold of airway response to TDI was low in 9, moderate in 7 and high in 4 patients. No evident relationship was observed between the threshold of response to TDI and the pattern of positive response to the lower TDI concentration (immediate in 5, late in 8 and dual in 7 subjects) or other clinical features (duration of asthmatic symptoms, smoking habits, cessation of work, nonspecific bronchial hyperresponsiveness to methacholine); however, 6 out of 9 patients with low threshold had nonspecific bronchial hyperreactivity in comparison with 6 out of 11 patients with moderate or high threshold. In 10 out of 13 patients who performed two positive BPT with different TDI concentrations, the pattern of response was the same either at lower and at higher TDI concentrations; 3 subjects who had a late reaction at the lower concentration showed a dual reaction to the higher TDI concentration. A relationship between the degree of the specific bronchial reaction (% fall in FEV1 from baseline value) and TDI concentration during BPT was observed for the immediate reaction but not for the late reaction.