[Production of innervated bronchial epithelium from a blood sample]

Asthma is a frequent respiratory disease, with severe asthma occurring in 3 to 5% of cases. Chronic inflammation of the bronchial epithelium is essential to its pathophysiology. When activated by the bronchial environment, the peripheral sensory nervous system contributes to inflammation of the airways. However, due to a lack of reliable models, the mechanisms of action remain largely unknown. Using induced pluripotent stem cells reprogrammed from blood cells, we have set up a model of bronchial epithelium innervated by sensory neurons. This model will ensure better understanding of the mechanisms of action underlying neurogenic inflammation.

Activation of the lung S1P(1) receptor reduces allergen-induced plasma leakage in mice

BACKGROUND AND PURPOSE

It has been suggested that intratracheal administration of the immunomodulator, FTY720, could have anti-inflammatory effects without causing a decrease in blood lymphocyte counts. However, the receptor responsible for this effect has not been defined.

EXPERIMENTAL APPROACH

We have described, in a mouse model of allergen-induced inflammation, the use of proton magnetic resonance imaging to non-invasively assess lung fluid accumulation and inflammation. Here, we used this model to investigate the sphingosine-1-phosphate (S1P) receptor responsible for the anti-inflammatory effect of FTY720.

KEY RESULTS

When given intranasally, FTY720 (3 and 10 microg.kg(-1)) inhibited by approximately 50% the allergen-induced accumulation of fluid in the lung detected by magnetic resonance imaging, but had no effect on the cellular inflammation in the airway space or on circulating blood lymphocytes. Inhibition of the infiltration of inflammatory cells into the airways was only observed at a dose of FTY720 that induced lymphopenia (100 microg.kg(-1)). Similar results were observed in S1P(3)-deficient mice. The effect of FTY720 was mimicked by intranasal treatment of wild-type mice with a S1P(1)-specific agonist, AUY954.

CONCLUSIONS AND IMPLICATIONS

Thus, in contrast to previously published work, our results suggest that systemic exposure of FTY720 is necessary to obtain an airway anti-inflammatory effect. On the contrary, inhibition of the allergen-induced accumulation of fluid in the lung, via activation of the S1P(1) receptor, is obtainable without systemic effects.

The nerve growth factor and its receptors in airway inflammatory diseases

The nerve growth factor (NGF) belongs to the neurotrophin family and induces its effects through activation of 2 distinct receptor types: the tropomyosin-related kinase A (TrkA) receptor, carrying an intrinsic tyrosine kinase activity in its intracellular domain, and the receptor p75 for neurotrophins (p75NTR), belonging to the death receptor family. Through activation of its TrkA receptor, NGF activates signalling pathways, including phospholipase Cgamma (PLCgamma), phosphatidyl-inositol 3-kinase (PI3K), the small G protein Ras, and mitogen-activated protein kinases (MAPK). Through its p75NTR receptor, NGF activates proapoptotic signalling pathways including the MAPK c-Jun N-terminal kinase (JNK), ceramides, and the small G protein Rac, but also activates pathways promoting cell survival through the transcription factor nuclear factor-kappaB (NF-kappaB). NGF was first described by Rita Levi-Montalcini and collaborators as an important factor involved in nerve differentiation and survival. Another role for NGF has since been established in inflammation, in particular of the airways, with increased NGF levels in chronic inflammatory diseases. In this review, we will first describe NGF structure and synthesis and NGF receptors and their signalling pathways. We will then provide information about NGF in the airways, describing its expression and regulation, as well as pointing out its potential role in inflammation, hyperresponsiveness, and remodelling process observed in airway inflammatory diseases, in particular in asthma.

Anti-proliferative effect of Euphorbia stenoclada in human airway smooth muscle cells in culture

The ethanolic extract of a Malagasy species Euphorbia stenoclada (ES) (Euphorbiaceae), traditionally used as a herbal remedy against asthma and acute bronchitis, was tested to evaluate possible anti-proliferative activity on human airway smooth muscle cells (HASMC). The ES ethanolic extract totally abolished the interleukin-1beta (IL-1beta) induced proliferation of HASMC (IC(50)=0.73+/-0.08 microg/mL). No cytotoxic effect was observed up to 20 microg/mL. A bioassay-guided fractionation of the ethanolic extract was performed by reversed-phase (RP) flash chromatography, giving five fractions (FA to FE) where fraction FE was the only active one (IC(50)=0.38+/-0.02 microg/mL). The purification of this bioactive fraction FE was carried out by RP-HPLC affording six sub-fractions 1-6, and only sub-fraction 5 kept the anti-proliferative activity. Its major constituent was identified as quercetin (IC(50)=0.49+/-0.12 microg/mL) by means of HPLC/UV/MS and co-elution with the authentic standard. Quercitrin was also identified in the fraction FE but was inactive. A structure-activity relationship with flavonols determined that methylation reduced the anti-proliferative activity whereas glycosylation abolished it. The present study shows that the anti-proliferative properties of Euphorbia stenoclada are mediated through the presence of quercetin that may explain the traditional use of this plant as a remedy against asthma.

Effect of glucocorticoids on stem cell factor expression in human asthmatic bronchi

BACKGROUND

Stem cell factor (SCF) is a major mast cell growth factor promoting differentiation, chemotaxis as well as inhibition of apoptosis of mast cells. Regulation of SCF expression by glucocorticoids has not yet been reported in human asthmatic bronchi.

OBJECTIVE

To evaluate SCF mRNA and protein expression in biopsy specimen and bronchoalveolar lavage fluid, respectively, and to determine the mast cell numbers in biopsy sections from control and asthmatic subjects treated or not with glucocorticoids.

METHODS

Volunteers were recruited out of pollen season. Asthmatic patients were allergic to common allergen extracts including grass and tree pollen, cat, dog or mite; three volunteers had non-allergic asthma. Mast cell numbers were counted after anti-human tryptase immunolabelling. SCF mRNA was quantified by real-time fluorescent PCR (LightCycler) after reverse transcription, and SCF protein was measured by ELISA.

RESULTS

Asthmatic patients not treated with glucocorticoids showed a 5.8-, 1.8- and 3.1-fold significant increase in SCF mRNA, protein levels and mast cell numbers, respectively, compared with healthy volunteers of the control group (7.8 and 1.3 pg/mug SCF mRNA/GAPDH; 99.8+/-11.5 and 56.0+/-11.0 pg/mL SCF protein; 103+/-21 and 33+/-8 mast cells/mm(2), respectively; P<0.05). In asthmatic patients treated with glucocorticoids, a significant decrease of SCF mRNA, protein levels and mast cell numbers was observed as compared with untreated asthmatic patients (1.1 pg/microg mRNA; 62.0+/-10.3 pg/mL SCF protein and 39+/-13 mast cells/mm(2); P<0.05), reaching levels comparable to those of the control group.

CONCLUSION

Our study shows that SCF is expressed in the bronchus in humans in vivo. This expression is increased in asthma, and is parallel to the increased mast cell numbers in the airways. Both increases were normalized in glucocorticoid-treated patients, strongly suggesting an involvement of SCF in the mast cell-associated asthmatic disease.

Nerve growth factor is released by IL-1beta and induces hyperresponsiveness of the human isolated bronchus

Nerve growth factor (NGF) is a neurotrophic factor essential for the development and survival of neurons, and is also an important mediator of inflammation. It is released by airway cells stimulated by interleukin (IL)-1beta. As IL-1beta induces airway hyperresponsiveness (AHR) to the tachykinin NK-1 receptor agonist [Sar9,Met(O2)11]-substance P in human isolated bronchi, the aim of this study was to determine whether IL-1beta was able to induce NGF release from isolated bronchi, and whether NGF might participate into IL-1beta-induced AHR. IL-1beta (10 ng x mL(-1); 21 degrees C; 15 h) increased the release of NGF from human isolated bronchi in vitro, and, in organ bath studies, the response of human bronchi to [Sar9,Met(O2)11]-substance P (0.1 microm). A significant correlation was found between these responses. AHR induced by IL-1beta was abolished by a blocking anti-human NGF antibody. Finally, NGF (1 ng x mL(-1); 37 degrees C; 0.5 h) by itself induced a significant increase in [Sar9,Met(O2)11]-substance P responsiveness. By contrast, it did not change the maximal contraction to acetylcholine. In conclusion, the present study clearly demonstrated that nerve growth factor may participate in the airway hyperresponsiveness induced by interleukin-1beta, which supports the neuro-immune cross-talk that may be active in the development of hyperresponsiveness in the human airways, and suggests nerve growth factor is active in the airways in asthma.

Dose-dependent effects of endotoxins on allergen sensitization and challenge in the mouse

BACKGROUND

Levels of endotoxins greatly differ according to environmental settings.

OBJECTIVE

To study the effect of lipopolysaccharide (LPS) at increasing doses (0.1-1000 ng) on allergen sensitization and challenge in the mouse.

METHODS

Mice were sensitized systemically and challenged locally with ovalbumin (OVA) in the presence or absence of LPS. Inflammation was assessed by determining total and differential cell counts and T-helper type 2 (Th)2 cytokine (IL-4 and IL-5) levels in bronchoalveolar lavage fluid (BALF). Total and OVA-specific IgE levels were quantified in serum. Airway hyper-responsiveness (AHR) was assessed by whole-body barometric plethysmography.

RESULTS

Administered prior to sensitization, LPS at 100 or 1000 ng dose-dependently decreased allergen- induced total and OVA-specific IgE, airway eosinophilia and Th2 cytokines in BALF, without changing AHR. Administered during OVA challenge, LPS at 1 ng (an infra-clinical dose) or 100 ng (a dose triggering neutrophilia) enhanced airway eosinophilia, without affecting IgE levels or AHR.

CONCLUSION

Our data clearly demonstrate that exposure to LPS influences allergen-induced IgE production and airway eosinophilia in a time and dose-dependent manner, preventing IgE production and development of eosinophilia when administered during allergen sensitization at high doses, and inducing exacerbation of eosinophilia when administered upon allergen challenge at low doses, including infra-clinical doses.

Expression of tyrosine hydroxylase and neuropeptide tyrosine in mouse sympathetic airway-specific neurons under normal situation and allergic airway inflammation

BACKGROUND

The traditional neurotransmitter catecholamine and the neuropeptide tyrosine in sympathetic airway nerves have been proposed to be involved in the pathogenesis of airway diseases.

OBJECTIVE

The aim of the present study was to investigate the effect of allergic airway inflammation on the expression of catecholamine enzyme tyrosine hydroxylase (TH), neuropeptide tyrosine (NPY) and tachykinins in mouse sympathetic airway ganglia.

METHODS

Using neuronal tracing in combination with immunohistochemistry, the present study was designed to characterize TH, NPY and tachykinin profiles of superior cervical (SCG) and stellate ganglia after allergen challenge.

RESULTS

The vast majority of fast blue-labelled SCG neurons (allergen: 97.5+/-1.22% (mean+/-SEM) vs. controls: 94.5+/-1.48%, P=0.18) and stellate neurons (allergen: 95.3+/-1.01% vs. controls: 93.6+/-1.33%, P=0.34) were immunoreactive for TH. Of the TH immunoreactive and fast blue-labelled SCG neurons, 52.0+/-1.01% allergen vs. 51.2+/-3.58% controls (P=0.83) and stellate neurons, 57.3%+/-0.97 allergen vs. 56.4+/-1.65% controls (P=0.64) were positive for TH only but not NPY, whereas 45.3+/-1.05% allergen vs. 43.3+/-1.18% controls (P=0.47) of fast blue-labelled SCG neurons and 37.9+/-0.86% allergen vs. 37.1+/-1.24% controls (P=0.62) of fast blue-labelled stellate neurons were immunoreactive for both TH and NPY immunoreactivities. There was a trend of an increase, but not significant one, in the percentage of TH-/NPY-immunoreactive and fast blue-labelled neurons in allergen-treated animals in comparison with the controls. Tachykinins, however, were not expressed by sympathetic neurons and were also not induced in sympathetic neurons after allergen challenge.

CONCLUSION

The present study indicates that allergic airway inflammation does not alter the expression of noradrenalin and NPY in sympathetic ganglia and also shows that sympathetic neurons do not respond to allergic airway inflammation with tachykinins induction. However, a participation of catecholamine and NPY in the pathogenesis of allergic airway inflammation cannot be excluded in the present study as a higher neurotransmitter output per neuron following allergen challenge could be possible.

In vivo evaluation of a reverse water-in-fluorocarbon emulsion stabilized with a semifluorinated amphiphile as a drug delivery system through the pulmonary route

The potential of a reverse water-in-fluorocarbon (w-in-FC) emulsion stabilized with a semifluorinated amphiphile, namely C8F17(CH2)11OP(O)[N(CH2CH2)2O]2 (F8H11DMP) for drug delivery through intrapulmonary administration was investigated in the mouse. This study involved assessment of the effect of single or repeated intranasal instillations of a plain emulsion on lung tissue integrity, and evaluation of blood glucose levels in mice treated with an insulin-loaded emulsion. When instilled intranasally to mice, the plain emulsion did not alter lung tissue integrity, as demonstrated by histological staining, and did not induce any airway inflammatory reaction. Treated mice exhibited decreased body weight within the 3-4 days that followed the first emulsion administration, but this decrease was reversible within few days. Mice instilled intranasally with the insulin-loaded emulsion displayed decreased blood glucose levels within the 20 min that followed the administration, thus demonstrating the potential of the reverse w-in-FC emulsion stabilized with F8H11DMP to systemically deliver drugs, including peptides, upon lung administration.

Neurogenic mechanisms in bronchial inflammatory diseases

Neurogenic inflammation encompasses the release of neuropeptides from airway nerves leading to inflammatory effects. This neurogenic inflammatory response of the airways can be initiated by exogenous irritants such as cigarette smoke or gases and is characterized by a bi-directional linkage between airway nerves and airway inflammation. The event of neurogenic inflammation may participate in the development and progression of chronic inflammatory airway diseases such as allergic asthma or chronic obstructive pulmonary disease (COPD). The molecular mechanisms underlying neurogenic inflammation are orchestrated by a large number of neuropeptides including tachykinins such as substance P and neurokinin A, or calcitonin gene-related peptide. Also, other biologically active peptides such as neuropeptide tyrosine, vasoactive intestinal polypeptide or endogenous opioids may modulate the inflammatory response and recently, novel tachykinins such as virokinin and hemokinins were identified. Whereas the different aspects of neurogenic inflammation have been studied in detail in laboratory animal models, only little is known about the role of airway neurogenic inflammation in human diseases. However, different functional properties of airway nerves may be used as targets for future therapeutic strategies and recent clinical data indicates that novel dual receptor antagonists may be relevant new drugs for bronchial asthma or COPD.

[Nerve growth factor (NGF) in inflammation and asthma]

INTRODUCTION

The nerve growth factor (NGF) is known as a factor involved in neuronal growth and survival. From recent studies it may also be considered as a mediator of inflammation, in particular in the airways.

STATE OF ART

Several animal studies have shown that NGF may increase the sensory innervation, and participate in the bronchial hyperresponsiveness and inflammation observed in the airways of asthmatic patients. Different cell types are capable of secreting NGF: inflammatory cells that infiltrate the bronchial mucosa, and structural cells such as epithelial cells, smooth muscle cells and pulmonary fibroblasts. Furthermore, increased NGF levels have been detected in the bronchoalveolar lavage fluid from asthmatic patients.

PERSPECTIVES AND CONCLUSION

Altogether, these results suggest that NGF may play a role in inflammation, bronchial hyperresponsiveness and airway remodelling in asthma, and may lead to a better understanding of the mechanisms occurring in chronic inflammatory diseases, in particular asthma.

Evaluation of cytotoxicity of new semi-fluorinated amphiphiles derived from dimorpholinophosphate

Water-in-fluorocarbon reverse emulsions and microemulsions stabilized by semi-fluorinated amphiphiles derived from the dimorpholinophosphate polar head group, C(n)F(2n+1)(CH(2))(m)OP(O)[N(CH(2)CH(2))(2)O](2) (FnHmDMP), are being investigated as new delivery systems for drugs or genetic materials into the lung. Since information related to the toxicity of fluorinated surfactants is still very limited, we evaluated herein the cytotoxicity of a series of FnHmDMP (n=4, 6, 8 and 10 and m=2, 5, and 11). Both solutions of FnHmDMP in fluorocarbons, and reverse water-in-fluorocarbon emulsions stabilized by FnHmDMP were assessed in order to determine the relation between surfactant structure and cell toxicity, and select the most innocuous emulsifier. A first short-term evaluation on mouse fibroblasts using a viability/cytotoxicity assay indicated that amphiphiles (in solution) with a chain length longer than C12 exhibit less toxicity than amphiphiles with shorter chain. Moreover cytotoxicity decreased also with length of the fluorinated segment. The protective effect of the fluorinated chain was strongly supported by the fact that the hydrogenated analog, C(15)H(31)OP(O)[N(CH(2)CH(2))(2)O](2) (H15DMP), was highly toxic. Qualitative evaluation on human lung epithelial cells (HLEC) using a colorimetric method (Mayer's hematoxylin) confirmed that amphiphiles (in solution) with longer chain were the least cytotoxic. The protective effect of the fluorinated chain appeared, however, to be significant only at low amphiphile concentrations (0.1% w/v). In contrast, at higher concentrations (1% and 5% w/v), the total chain length was the determining factor. Quantitative evaluation of the least cytotoxic amphiphiles using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method then showed that F10H11DMP (in solution) was harmless until its solubility limit (1% w/v); cell growth was even enhanced due to improved oxygenation provided by the fluorocarbon phase. F8H11DMP exhibited some cytotoxicity at both 1% and 5% w/v, but the toxicity appeared to level off with concentration. Reverse water-in-perfluorooctyl bromide (PFOB) emulsions stabilized by either F10H11DMP or F8H11DMP were found to be non-cytotoxic. In conclusion, the present evaluation indicates that the cytotoxicity of FnHmDMP depends on both total and fluorinated amphiphile chain length, and leads us to select F8H11DMP and F10H11DMP as the less cytotoxic amphiphiles among a series of FnHmDMP compounds. Furthermore, water-in-fluorocarbon emulsions stabilized with F8H11DMP and F10H11DMP appeared to be non-cytotoxic towards HLEC in culture.

Nerve growth factor levels and localisation in human asthmatic bronchi

Nerve growth factor (NGF) has recently been suggested to be an important mediator of inflammation. In support of this, serum levels of NGF have been shown to be enhanced in asthmatics. However, it has not yet been shown whether the levels of NGF are also altered locally in asthmatic airways, when compared with healthy subjects, and the localisation of potential sources of NGF in the human bronchus have not yet been described. The aim of the present study was to assess NGF levels in bronchoalveolar lavage fluid (BALF) from asthmatics and to compare them to those of control subjects. Furthermore, the authors wanted to localise potential sources of NGF in bronchial tissue, and to number NGF-immunopositive infiltrating cells in the bronchial submucosa. BALF and bronchial biopsies were obtained from seven control subjects and seven asthmatic patients by fibreoptic bronchoscopy. NGF protein levels were quantified by enzyme-linked immunosorbent assay in BALF. NGF localisation was examined by immunohistochemistry on bronchial biopsy sections. The asthmatics exhibited significantly enhanced NGF levels in BALF. Intense NGF-immunoreactivity was observed in bronchial epithelium, smooth muscle cells and infiltrating inflammatory cells in the submucosa, and to a lesser extent in the connective tissue. The asthmatics exhibited a higher number of NGF-immunoreactive infiltrating cells in the bronchial submucosa than control subjects. This study provides evidence that nerve growth factor is locally produced in the airways, and shows that this production is enhanced in asthmatics. These findings suggest that nerve growth factor is produced by both structural cells and infiltrating inflammatory cells in human bronchus in vivo, and the authors suggest that the increase in nerve growth factor protein in bronchoalveolar lavage fluid observed in asthmatic patients may originate both from structural cells, producing increased nerve growth factor levels in inflammatory conditons, and from the increase in nerve growth factor-immunopositive cells determined in the bronchial submucosa.

Upregulation of nerve growth factor expression by human airway smooth muscle cells in inflammatory conditions

Recent studies have suggested that nerve growth factor (NGF) may play a role in inflammation and bronchial hyperresponsiveness in asthma. Neither the types of cells that produce NGF in the human airways nor the effect of inflammation on NGF expression are clear. The two-fold aim of the present study was to determine whether airway smooth muscle produces NGF in vitro, and, if so, whether the pro-inflammatory cytokine interleukin-1beta (IL-1beta) affects this expression. Human airway smooth muscle cells in culture were incubated in the presence or absence of IL-1beta. NGF production was measured by enzyme-linked immunosorbent assay. NGF messenger ribonucleic acid (mRNA) was measured using a specific real-time fluorescent polymerase chain reaction technique, and expressed in relation to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels. Human airway smooth muscle cells in vitro expressed NGF constitutively (21.4+/-7.8 pg x mL(-1); 14.6+/-5.4 pg NGF complementary deoxyribonucleic acid (cDNA) x pg GAPDH cDNA(-1) (mean+/-SEM)). Stimulation with IL-1beta (0.1-30 U x mL(-1)) for 24 h induced a dose-dependent increase in NGF production (22.1 pg x mL(-1) at 10 U x mL(-1); p<0.05). The IL-1beta (10 U x mL(-1))-induced increase in NGF expression was time-dependent. It was highest for NGF protein at 10 h (1.6-fold increase over control; p<0.001) and for NGF mRNA at 2.5 h (2.4-fold increase over control; p<0.05). In conclusion, the present study clearly shows that the human airway smooth muscle cell is a source of nerve growth factor, the expression of which is upregulated in inflammatory conditions, mimicked in vitro by the addition of interleukin-1beta.

Comparative activity of cetirizine and mizolastine on histamine-induced skin wheal and flare responses at 24 h

AIMS

The aim of our study was to compare the activity of cetirizine 10 mg with that of mizolastine 10 mg vs placebo at 24 h after intake in healthy volunteers.

METHODS

This was a double-blind, randomized, placebo controlled, three-way cross-over study with a wash-out period of 7 +/- 2 days between each period. The study included 36 healthy volunteers (18--50 years, mean age = 32 years; 9 males). The objective measurement was the cutaneous reactivity to increasing concentrations of histamine (0, 5, 10, 20, 40, 80, 160 mg ml(-1)) administered by prick tests. The reactivity was evaluated by the wheal and flare areas (mm2). The AUC (area under curves) values of the wheal and flare areas as a function of the log2 transformed histamine concentration were calculated for each subject and treatment, and compared.

RESULTS

A highly significant treatment effect was evidenced both for wheal and flare responses (P = 0.0001). This indicates the good activity of both cetirizine 10 mg and mizolastine 10 mg in inhibiting skin wheal and flare reactions to histamine. In addition, the mean AUC values significantly differed between cetirizine and mizolastine (64.8 and 117.8 log2 (mg ml(-1)) x mm2 for wheal, and 939.4 and 2340.8 for flare, respectively; P = 0.0001), with a superior activity of cetirizine than mizolastine at 24 h after intake both on wheal and flare responses. The tolerance of cetirizine and mizolastine was good. The severity of the adverse events was never more than 'moderate', 'fatigue' being the most frequent reported symptom [cetirizine (6 subjects), placebo (3), mizolastine (5)], followed by 'somnolence' [cetirizine (0), placebo (1), mizolastine (3)]. There was no serious adverse event.

CONCLUSIONS

This study shows that cetirizine (10 mg) suppresses skin reactivity to histamine more effectively than mizolastine (10 mg) 24 h after intake in healthy volunteers.

Nerve growth factor secretion by human lung epithelial A549 cells in pro- and anti-inflammatory conditions

Nerve growth factor (NGF) has recently been presented as a possible effector of inflammation and bronchial hyperresponsiveness. However, the production of NGF in human airways as well as the regulation of its expression by inflammatory cytokines and glucocorticoids have received little attention. A549 epithelial cells were cultured in Dulbecco's modified Eagle's medium supplemented with 10% foetal bovine serum, and starved for 24 h. The effect of the pro-inflammatory cytokine interleukin-1beta (1-30 U/ml), and of the glucocorticoid dexamethasone (1 microM) on NGF secretion was studied and quantified by enzyme-linked immunosorbent assay (ELISA). In addition, NGF production within the cells was visualized by immunocytochemistry. Under basal conditions, A549 cells produced and secreted NGF (12.6+/-2.0 pg/ml). Stimulation by interleukin-1beta for 24 h induced a dose-dependent increase in NGF production (maximal at 10 U/ml with 59.6+/-3.5% increase, P<0.05). Dexamethasone (1 microM) markedly reduced the constitute NGF secretion by 44.9% (7.0+/-2.1 pg/ml, P<0.001). In addition, the interleukin-1beta-stimulated NGF secretion was inhibited to approximately the same low level (8.5+/-2.5 pg/ml, P<0.001). In conclusion, we here report that human airway A549 epithelial cells are capable of producing NGF. This production is positively regulated by the pro-inflammatory interleukin-1beta, and negatively regulated by dexamethasone.

Local increase in the number of mast cells and expression of nerve growth factor in the bronchus of asthmatic patients after repeated inhalation of allergen at low-dose

BACKGROUND

Repeated inhalation of allergen at low-dose induces an increase in bronchial hyper-responsiveness, without any associated symptom. The concomitant events in the bronchus have not been described.

OBJECTIVE

We have studied the dynamic number of mast cells in the airways of patients with mild asthma before and after repeated inhalation of allergen at low-dose and the expression of nerve growth factor (NGF), which is reported to promote growth and survival of mast cells.

METHODS

Twelve patients with mild asthma to cat allergen were enrolled at random in a blind placebo-controlled study, and submitted to repeated low-dose allergen exposure (1/5 of the provocative dose). Mast cells were immunolocalized using an antibody against mast cell tryptase. NGF and its high affinity receptor, TrkA, were immunolocalized using anti-NGF and anti-TrkA antibodies, respectively. NGF mRNA was quantified by competitive polymerase chain reaction (PCR) after reverse transcription of total RNA extracted from bronchial biopsy. NGF protein levels were measured by ELISA in bronchoalveolar lavage (BAL) fluid.

RESULTS

Bronchial mast cell number was increased significantly after allergen exposure as compared with before. NGF expression in the bronchus was immunolocalized mainly to epithelial cells, but also to fibroblasts, blood vessels, and a few infiltrated cells. NGF mRNA levels in bronchial biopsies were increased significantly after allergen exposure. The high affinity receptor for NGF, TrkA, was immunolocalized to the infiltrated mast cell membrane.

CONCLUSION

Our study shows that the increase in the number of mast cells and in the expression of NGF induced by allergen exposure in the bronchus of asthmatic patients is occurring before the onset of symptoms. In addition, our finding of the presence of the TrkA receptor on the membrane of the infiltrated mast cell in situ brings evidence of the mast cell as a target cell for the growth factor activity of NGF in the airways in asthma.

Difference in exposure to airborne major rat allergen (Rat n 1) and to endotoxin in rat quarters according to tasks

Endotoxins found in occupational settings constitute a risk factor in the severity of respiratory allergic symptoms.

OBJECTIVES

To assess the airborne concentrations of major rat allergen (Rat n 1) and endotoxin under various circumstances.

METHODS

We took 483 airborne samples from 12 sites: 114 individual samples for endotoxin measurements and 113 for Rat n 1, from 38 workers (nine animal technicians, nine laboratory technicians, nine scientists and 11 students); and 256 static samples in rat rooms and experimental rooms, with or without disturbance, for simultaneous endotoxin and Rat n 1 measurements. Rat n 1 was measured with a two-site monoclonal ELISA and endotoxins with the Limulus method.

RESULTS

Airborne Rat n 1 and endotoxin were significantly higher in rat rooms than in experimental rooms. Animal technicians had the greatest exposure to both Rat n 1 and endotoxin. Cage cleaning and rat feeding induced the highest exposure to Rat n 1 and endotoxin. Furthermore, we observed no significant difference in endotoxin exposure between researchers with or without rat contact during the sample period. There was no correlation between the number of rats present and airborne endotoxin concentrations.

CONCLUSIONS

Exposure to airborne Rat n 1 and endotoxin is higher during cleaning and feeding tasks than during any other task, we feel that a major source of both is contaminated bedding that becomes airborne during disturbance.

Human lung fibroblasts secrete nerve growth factor: effect of inflammatory cytokines and glucocorticoids

Nerve growth factor (NGF) has recently been suggested to contribute to inflammation and bronchial hyperresponsiveness in asthma. However, the cell types capable of NGF production in the human lung and airways, as well as the regulatory role of pro-inflammatory cytokines and of glucocorticoids on NGF secretion in pulmonary cells, have not been described. Human pulmonary fibroblasts were cultured in the presence or absence of either interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNF-alpha) and/or glucocorticoids. NGF secretion was measured by enzyme-linked immunosorbent assay. The human pulmonary fibroblasts constitutively secreted NGF in vitro. The rate of NGF secretion was shown to be cell density-dependent, since higher NGF secretion was detected in preconfluent cells, i.e. ones with less established cell-to-cell contact (41.0+/-5.0 pg x 10(-6) cells at 80% confluence), than cells in higher densities (8.2 +/- 3.4 pg x 10(-6) cells at 100% confluence). Stimulation with the pro-inflammatory cytokines IL-1beta (0.3-30 U x mL(-1)) or TNF-alpha (0.1-30 ng x mL(-1)) dose- and time-dependently (8-72 h) elevated the NGF secretion (effective concentration causing 50% of the maximum response (EC50)=2.9 U x mL(-1) and 1.0 ng x mL(-1), respectively). Treatment with the glucocorticoid budesonide (10(-7) M) markedly reduced the constitutive secretion of NGF by 42%, and attenuated the cytokine-stimulated NGF secretion to the same level. In conclusion, human lung fibroblasts may serve as a source of nerve growth factor in the lung, positively regulated by the asthma-associated and pro-inflammatory cytokines interleukin-1beta and tumour necrosis factor-alpha, and negatively regulated by the anti-inflammatory glucocorticoids.

Duration of the antihistaminic effect after discontinuation of ebastine

BACKGROUND

The inhibitory effect of antihistamines on allergen-induced skin reactions can impair the results of allergen skin testing, which are necessary for the diagnosis of atopic diseases. This study was designed to determine the time period required for the inhibitory effect of ebastine on allergen-induced skin reactivity to disappear completely.

METHODS

This was a double-blind, placebo-controlled, parallel-group study including 23 out of 27 randomized patients. They received either ebastine 20 mg or placebo once daily for 7 days. At the end of treatment, allergen challenge was performed daily for 7 days. Histamine challenge was performed on day 1 (6 and 24 h) and day 5 after treatment. The wheal and flare surface areas were measured and analyzed.

RESULTS

Highly significant inhibition of the wheal and flare response induced by allergen was observed after ebastine treatment on days 1 and 2 as compared with placebo (P < 0.01 for both). The inhibition was reduced, although still significant, by day 3 (P < 0.05). No significant difference was observed by day 4 between the ebastine and the placebo groups. The effects of histamine challenge were significantly reduced in the ebastine compared with the placebo group at day 1 (6 and 24 h), and were similar at day 5 after treatment.

CONCLUSION

Our results show that the wheal and flare response to allergen after ebastine discontinuation returns to placebo values after 4 days. Therefore, patients using ebastine need to be antihistamine-free for 4 days before the skin prick test. This is valuable information for the allergologist seeking to diagnose allergen sensitivity.

New insights into the second generation antihistamines

Second generation antihistamines are recognised as being highly effective treatments for allergy-based disease and are among the most frequently prescribed and safest drugs in the world. However, consideration of the therapeutic index or the benefit/risk ratio of the H1 receptor antagonists is of paramount importance when prescribing this class of compounds as they are used to treat non-life threatening conditions. There are many second generation antihistamines available and at first examination these appear to be comparable in terms of safety and efficacy. However, the newer antihistamines in fact represent a heterogeneous group of compounds, having markedly differing chemical structures, adverse effects, half-life, tissue distribution and metabolism, spectrum of antihistaminic properties, and varying degrees of anti-inflammatory effects. With regard to the latter, there is growing awareness that some of these compounds might represent useful adjunct medications in asthma therapy. In terms of safety issues, the current second generation grouping includes compounds with proven cardiotoxic effects and others with the potential for adverse drug interactions. Moreover, some of the second generation H1 antagonists have given cause for concern regarding their potential to cause a degree of somnolence in some individuals. It can be argued, therefore, that the present second generation grouping is too large and indistinct since this was based primarily on the concept of separating the first generation sedating compounds from nonsedating H1 antagonists. Although it is too early to talk about a third generation grouping of antihistamines, future membership of such a classification could be based on a low volume of distribution coupled with a lack of sedating effects, drug interactions and cardiotoxicity.

Twenty-four hours of activity of cetirizine and fexofenadine in the skin

BACKGROUND

Cetirizine and fexofenadine, the active metabolite of terfenadine, are powerful and well-tolerated H1 receptor antagonists effective in the treatment of skin and nose atopic diseases.

OBJECTIVE

We have compared the pharmacodynamic activity of the two antihistamines at therapeutic dosages, cetirizine at 10 mg and fexofenadine at 120 mg and 180 mg, on histamine-induced skin reactivity during a 24-hour period after single intake.

METHODS

Twenty-six healthy volunteers participated in a randomized, double-blind, crossover, placebo-controlled study. The areas of wheal and flare induced by histamine (100 mg/mL) administered by prick test were measured at 0, 0.5, 1, 2, 4, 6, 8, 10, 12, and 24 hours postdose. Statistical analysis of the areas under the time-response curves was performed by a Friedman's ANOVA followed by a Wilcoxon test and Bonferroni's correction.

RESULTS

The three active treatments clearly inhibited the wheal and flare areas throughout the 24-hour period compared with placebo. Maximal inhibition occurred at 4 hours postdose. Between 4 and 24 hours postdose, the time course of inhibition by cetirizine differed significantly (P < 0.001) from that by fexofenadine at either dose, which did not differ from each other. At 24 hours, fexofenadine inhibited <40% of the skin reaction, whereas cetirizine reduced 60% of the wheal. The duration of effect, considered as the time for wheal to be inhibited by at least 70%, also significantly favored cetirizine (19 hours) compared with fexofenadine (9.3 and 8.5 hours for 180 and 120 mg, respectively; P < 0.001). Consistency of activity was evaluated by the frequency of total inhibition of the wheal (> or =95%). Consistency was observed in 26 of 26 participants for cetirizine, 21 of 26 for fexofenadine, 180 mg, and 10 of 26 for fexofenadine, 120 mg (P < 0.001), suggesting better consistency for cetirizine. There was no serious adverse event.

CONCLUSIONS

Our study clearly shows better duration of action and consistency of the antihistaminic activity of cetirizine compared with fexofenadine (120 and 180 mg) in the histamine-induced skin reaction during a 24-hour period.

Altered expression of lung cytochrome P450 3A1 in rat after exposure to sulfur mustard

Expression of cytochromes P450 (CYP) and glutathione S-transferases in the lung may be affected by inhaled pollutants. We have investigated the effect of sulfur mustard on the expression of CYP 1A1, 2B1, 2E1 and 3A1, as well as of alpha-, micro- and pi-glutathione S-transferases in rat lung. Sulfur mustard (0.025, 0.05 or 0.1 mg/kg) or its vehicle was administered to anaesthetized animals by intratracheal injection. Expression of CYP and glutathione S-transferases was analysed 24 hr after administration of the vesicant warfare using western blotting. Preservation of airway epithelium integrity after animal exposure to sulfur mustard was confirmed by histological examination of tracheal and lung tissues from control and treated animals. Constitutive levels of CYP 2B1 and 3A1 proteins were found in lung tissue from control rats, whereas CYP 1A1 and 2E1 proteins were not detected. Animal exposure to sulfur mustard enhanced CYP 3A1 protein levels by 80 to 103%. In contrast, exposure to sulfur mustard neither modified CYP 2B1 expression, nor led to detectable expression of CYP 1A1 or 2E1. Constitutive levels of alpha-, micro- and pi-glutathione S-transferase proteins were found in lung tissue from control rats. Exposure to sulfur mustard had no effect on expression of either of the glutathione S-transferases. Our results show that intratracheal exposure to sulfur mustard selectively increases CYP 3A1 expression in rat lung. Taking into account the major role of CYP of the 3A family in the metabolism of drugs, up-regulation of CYP 3A1 by sulfur mustard might have important therapeutic consequences.

Inhalation of toluene diisocyanate affects cytochrome P450 2B1 expression in rat lung

In the lung the expression of xenobiotic-metabolizing enzymes such as cytochromes P450 (CYP) and glutathione S-transferases (GST) may be affected by inhaled pollutants. Toluene diisocyanate (TDI) is a highly volatile chemical compound known to induce a wide array of diseases in workers exposed to vapors or sprays, including respiratory allergy and asthma. We investigated the effect of inhaled TDI on expression of CYP 1A1, 2B1, 2E1, and 3A1 and of alpha-, mu-, and pi-GST in rat lung. Animals were exposed to targeted concentrations of 0.01, 0.1, or 1 ppm TDI vapors or to cleaned filtered air for 8 h. Expression of CYP and GST was analyzed 18 24 h after the end of exposure using western blotting, northern blotting, and immunohistochemistry. Constitutive levels of CYP 2B1 and 3A1 proteins were found in lung tissue from control rats, whereas CYP 1A1 and 2E1 proteins were not detectable. Animal exposure to TDI vapors neither modified CYP 3A1 protein expression, nor led to any detectable expression of CYP 1A1 or 2E1. In contrast, exposure to 1 ppm TDI induced a 40% reduction in CYP 2B1 protein levels. This decrease was associated with a 33% decrease in CYP 2B1 mRNA levels. Additionally, CYP 2B1 immunolabeling localized to ciliated epithelial cells, Clara cells, and type II alveolar cells in the lung tissue of control rats was markedly decreased in animals exposed to 1 ppm TDI. Constitutive levels of alpha-, mu-, and pi-GST proteins were found in lung tissue from control rats. Exposure to TDI had no effect on lung expression of either of the GST. In conclusion, this study clearly shows a selective decrease in CYP 2B1 expression by TDI vapors in rat lung. The contribution of CYP 2B1 to metabolize further xenobiotics is therefore altered.

Activity of ebastine (10 and 20 mg) and cetirizine at 24 hours of a steady state treatment in the skin of healthy volunteers

We have compared the inhibitory effects of ebastine (10 mg), ebastine (20 mg) and cetirizine (10 mg) on histamine-induced wheal and flare skin reactions 24 h following a 6-day-long treatment. This was a double-blind, randomised, crossover, placebo-controlled study involving 24 healthy volunteers (18-65 years) with negative skin prick tests and the absence of specific IgEs to common allergens. Subjects were randomised to receive each of the following treatments once daily for 6 days: ebastine (10 mg), ebastine (20 mg), cetirizine (10 mg) or placebo with a washout period of 5 days. Twenty-four hours after the last dose of each treatment, histamine skin prick tests were performed (0, 0.5, 1, 2.5, 5, 10, 20, 50, 100 and 200 mg/mL), and wheal and flare responses were measured. All active treatments produced significant inhibition of the wheal responses compared to placebo (P < 0.001). Wheal response inhibition was significantly better with 20 mg of ebastine compared with 10 mg of ebastine and 10 mg of cetirizine. In a comparison to histamine concentrations required to produce a wheal surface area of 10 mm2, 20 mg of ebastine was also significantly better than ebastine 10 mg and cetirizine (P < 0.001), and 10 mg ebastine was significantly better than cetirizine (P < 0.05). Highly significant (P < 0.001) effects on the flare response were observed with each active treatment compared to placebo, with no difference between groups. The frequency of adverse events, primarily somnolence, was similar among the four treatment groups. Our results clearly indicate that ebastine, at either recommended dosage of 10 and 20 mg, and cetirizine produced significant inhibition of the histamine-induced wheal and flare reaction compared to placebo for up to 24 h. A superior efficacy of 20 mg of ebastine is observed compared with 10 mg of ebastine and 10 mg of cetirizine on the skin wheal response 24 h after the last dose of a 6-day-long treatment. This study clearly proves ebastine to be an effective, truly once-daily antihistamine.

Effect of toluene diisocyanate and its corresponding amines on viability and growth of human lung fibroblasts in culture

Toluene diisocyanate (TDI) is a highly volatile chemical known to cause occupational asthma in exposed workers. TDI-induced asthma is associated with airway epithelium injury and repair, and subepithelial fibrosis. We investigated the effect of TDI and its hydrolysis products, the 2,4- and 2,6-toluenediamines (TDA), on viability and growth of human lung fibroblasts (HLFs) in culture, using a tetrazolium-based cell viability assay. The effects of increasing concentrations of each of these chemicals were evaluated on quiescent cells seeded at two densities (2500 and 5000 cells/well) and treated for 24 or 48 h. TDI (10(-4)-10(-5) mol/L, as a mixture of 80% 2,4-TDI and 20% 2,6-TDI) exhibited a partial but significant cytotoxic effect (10-24%, p<0.05) on HLFs. This effect was observed at both cell densities, and was time- and concentration-dependent. 2,4-TDA, at lower concentrations (10(-8)-10(-6) mol/L) applied for 48 h, also partially reduced HLF viability (10-15%, p<0.05), whereas it tended to trigger cell growth at concentrations higher than 10(-5) mol/L. 2,6-TDA exhibited both a cytotoxic and a proliferative effect on HLFs that depended on concentration, time of exposure and cell culture density. Significant cytotoxicity was only observed after 24 h of treatment with 10(-7)-10(-6) mol/L 2,6-TDA, and reached greater intensity in cells cultured at the highest density. In contrast, 2,6-TDA stimulated HLF growth only after 48 h of incubation at 10(-4) mol/L on cells cultured at the lowest density. Taken together, our results showed that TDI and 2,4-TDA somewhat decreased HLF viability, whereas 2,6-TDA appeared to exhibit both a cytotoxic and a growth stimulatory effect on these cells. TDI and 2,4-TDA are thus suggested to contribute to airway epithelium damage associated with TDI-induced asthma, whereas 2,6-TDA might either trigger epithelial damage or induce cell proliferation that could contribute to epithelium repair or subepithelial fibrosis.

[Role of bronchial smooth muscle in inflammation]

We now have to consider the airway smooth muscle as an actor of the bronchial inflammation in asthma. In addition to its bronchoconstricting role in response to mediators secreted by the adjacent cells and tissues, that may be considered as to be passive regarding the airway inflammation, the airway smooth muscle may now be considered as pro-inflammatory, since it has the potential of synthesizing and secreting a variety of chemokines and growth factors that will favor cell proliferation, and attraction of inflammatory cells. The airway smooth muscle may modify its phenotype from a contractile to a secretory or a proliferative phenotype. These differentiation states of the bronchial smooth muscle may be studied experimentally by culturing the airway smooth muscle. The demonstration of the occurrence and/or coexistence of such differentiation states in vivo will help understand the exact role of the bronchial smooth muscle in the airway inflammation in asthma.

Repeated inhalation of low doses of cat allergen that do not induce clinical symptoms increases bronchial hyperresponsiveness and eosinophil cationic protein levels

The aim of this study was to investigate whether repeated exposure to subclinical doses of cat allergens, not inducing asthma symptoms, could affect eosinophil cationic protein (ECP) levels in bronchoalveolar lavage (BAL) or in peripheral blood, without the appearance of clinical symptoms. Twelve patients with mild asthma, all sensitized to cats and not exposed to cat allergen at home, underwent a series of inhalations of cat allergen or placebo for 8 days over 2 weeks. A methacholine challenge was performed before and after the allergen and saline exposures, and BAL and blood were sampled for ECP measurements and eosinophil counts. No patients experienced asthma symptoms. However, PD20 methacholine (geometric mean) decreased significantly from 263 microg before to 126 microg after inhalation of allergen. Inhalation of saline did not induce any significant change in PD20. The change in log PD20 before and after cat allergen exposure was statistically different from the change in log PD20 before and after saline. Median ECP levels in BAL and serum increased significantly after allergen exposure, from 0.8 to 3.1 microg/l (p<0.02) and from 15.9 to 31.4 microg/l (p<0.05), respectively. No change was observed after saline inhalations. The change in BAL and serum ECP levels was statistically significant compared to that in the control group. The number of eosinophils did not change, however, nor did IL-5 and RANTES levels in BAL and serum. In conclusion, our results show that (1) exposure of asthma patients to repeated low doses of allergen, which did not provoke any clinical symptoms, is capable of inducing a local eosinophil activation associated with an increase in nonspecific bronchial hyperresponsiveness and (2) the increase in serum ECP levels due to eosinophil activation precedes the occurrence of asthma symptoms and may thus be a marker of allergen exposure in allergic asthma.

Consistency and efficacy of cetirizine (10 mg) versus ebastine (20 mg) at 4 h on skin reactivity

OBJECTIVE

We compared the consistency and efficacy of the two antihistamines, cetirizine (10 mg) and ebastine (20 mg) on histamine skin reactivity 4 h after treatment.

METHODS

Twenty-four healthy volunteers participated in a randomised double-blind cross-over study. The areas of wheals and flares induced by increasing (0, 5, 10, 50, 100, 200, 300 mg/ml) histamine concentrations, administered by prick tests, were measured before and 4 h after intake of cetirizine or ebastine.

RESULTS

Before treatment, concentration-response curves were similar and threshold concentrations identical (0.57 mg/ml and 0.57 mg/ml for cetirizine and ebastine, respectively). Both treatments exerted a significant effect. However, cetirizine was significantly more efficient than ebastine 20 mg (P < 0.01 both for wheals and flares). After cetirizine, the threshold concentration inducing a 3-mm(2 )wheal was significantly higher (266 mg/ml) than after ebastine (77 mg/ml) (P < 0.01), and total inhibition of the wheal was obtained in 18 of 24 patients for cetirizine and in 4 of 24 for ebastine (P < 0.001). The variation coefficient for the wheal reaction was 31% for cetirizine and 159% for ebastine, indicating a much lower variability after cetirizine.

CONCLUSION

Our study shows clearly that the efficacy of a single therapeutic dosage of cetirizine is greater and consistently better than that of ebastine for suppression of cutaneous reactivity to histamine 4 h after treatment in healthy volunteers. The need for ebastine to metabolise into the active carebastine might explain this difference.

Calcitonin gene-related peptide-immunoreactive nerves and neuroendocrine cells after lung transplantation in the rat

Bronchial innervation is interrupted at lung transplantation. Nerve fibers with cell bodies above the section, such as sensory C fibers, should degenerate. Using histofluorescence, we evaluated calcitonin gene-related peptide (CGRP) immunoreactivity in syngeneic Lewis rats 1 and 5 mo after unilateral lung transplantation and in controls. CGRP-immunoreactive (IR) neuroendocrine cells were located within the epithelium of large and small bronchi. At 1 mo after transplantation, their number had significantly increased in large bronchi and had normalized 5 mo after transplantation. The density of CGRP-IR fibers in control lungs gradually decreased from large (0. 35 +/- 0.02 micron/micron basal lamina) to small (0.23 +/- 0.02) and peripheral bronchi (0.12 +/- 0.01). At 1 mo after lung transplantation, few CGRP-IR fibers were observed in large bronchi (0.17 +/- 0.02), fewer in small bronchi (0.04 +/- 0.01) (P < 0.01), and none in peripheral bronchi. At 5 mo after lung transplantation, transplanted lungs still had fewer CGRP-IR fibers in large (0.22 +/- 0.02) and small (0.11 +/- 0.02) bronchi (P < 0.02) than did controls, but there were, nonetheless, more in the small bronchi than at 1 mo after transplantation (P < 0.01). Additionally, few CGRP fibers were present in the peripheral bronchi (0.03 +/- 0.01) (P < 0.01). These results clearly demonstrate the occurrence of denervation followed by partial reinnervation with CGRP-IR fibers after transplantation in rat lung.

Human bronchial smooth muscle cells in culture produce stem cell factor

A mast cell infiltration of the bronchial smooth muscle layer has been reported in patients sensitized to common allergens. Stem cell factor (SCF) is a chemotactic and survival factor for mast cells. SCF is expressed as a soluble (sSCF) and a membrane-bound (mSCF) form, after alternative splicing of the exon encoding the proteolytic cleavage site. SCF expression by human bronchial smooth muscle cells in culture was evaluated, comparing it to that of human lung fibroblasts in culture. sSCF released in the culture supernatant was assessed by an enzyme-linked immunosorbent assay. Total SCF messenger ribonucleic acid (mRNA) was measured by competitive polymerase chain reaction (PCR) after reverse transcription. Expression of the two forms of SCF mRNA was assessed by PCR, with primers spanning the alternatively spliced exon. Smooth muscle cells produced sSCF (21.9+/-2.6 pg x mL(-1)), although at lower levels than fibroblasts (35.9+/-3.5 pg x mL(-1)); the expression of total SCF mRNA was also at lower levels than in fibroblasts (8.6+/-0.2 and 19.0+/-2.0 amol x fmol glyceraldehyde 3-phosphate dehydrogenase complementary deoxyribonucleic acid(-1), respectively). However, smooth muscle cells expressed proportionally more (1.7-fold) mSCF mRNA than did fibroblasts. In conclusion, this study shows that bronchial smooth muscle cells express stem cell factor, with a relatively high expression of membrane-bound stem cell factor. This might be related to the presence of mast cells within the bronchial smooth muscle layer, i.e. at the site of bronchoconstriction, with possible implications in the pathophysiology of asthma.

[The bronchorelaxant effect of helicidine, a Helix pomatia extract, interferes with prostaglandin E2]

Helicidine is a biological extract prepared from the snail Helix pomatia L. and used in man as an anti-tussive agent. However, its mechanisms of action are not fully defined. In this study, we have investigated a possible relaxant effect of helicidine on guinea-pig airway smooth muscle and evaluated the role of prostanoids and airway epithelium in this relaxation. H. pomatia extract (0.001-1 mg/ml) induced a dose-dependent relaxation of guinea-pig trachea pre-contracted with histamine both in the presence and absence of tracheal epithelium. No significant difference in dose-dependency or magnitude of the relaxation was observed between tracheal segments with or without epithelium (maximal relaxant response of 35 +/- 7 and 25 +/- 7.5%, respectively). Relaxation of the trachea induced by H. pomatia extract (0.001-1 mg/ml) was inhibited by pre-treatment with the cyclooxygenase inhibitor, indomethacin, both in the presence or absence of tracheal epithelium. H. pomatia extract (1 mg/ml) induced a marked and significant increase in prostaglandin E2 release in tracheal segments with and without epithelium. These results indicate that helicidine possesses a broncho-relaxant activity which is independent of epithelium integrity and which is partly mediated by the release of the relaxant prostanoid, prostaglandin E2. The origin of prostaglandin E2 production in the airways remains to be defined.

Up- and down-regulation by glucocorticoids of the constitutive expression of the mast cell growth factor stem cell factor by human lung fibroblasts in culture

Stem cell factor (SCF) is a major mast cell growth factor that promotes differentiation and chemotaxis of mast cells and inhibits their apoptosis. SCF therefore may be involved in diseases associated with an increased number of tissue mast cells such as asthma, for which the major treatment is glucocorticoids. In this study, we evaluated the effect of the glucocorticoid budesonide on the constitutive expression of SCF by human lung fibroblasts in primary culture. Budesonide (0.1 microM) induced a time-dependent biphasic effect on SCF mRNA and protein production. A short treatment (2.5-10 hr) induced an inhibition of SCF protein accumulation (-58% at 2.5 hr) and mRNA expression (-69% at 2.5 hr), associated with an accelerated decay of SCF mRNA and with a decrease in SCF gene transcription observed by nuclear run-on assay. Longer treatment (24-72 hr) led to increases in SCF protein accumulation (+64% at 48 hr) and mRNA expression (+125% at 24 hr) as a consequence of transcriptional activation. Similar effects of a decrease followed by an increase in SCF production were observed using another glucocorticoid, dexamethasone. Overall, our results show that glucocorticoids potently regulate SCF expression in human lung fibroblasts, successively decreasing and increasing SCF mRNA levels according to treatment duration. Such time-dependent modulation of SCF levels may explain some current discrepant findings about the effects of glucocorticoids on SCF production and may have functional consequences during glucocorticoid treatment, such as asthma therapy.

Increase in non-specific bronchial hyperresponsiveness without specific response to isocyanate in isocyanate-induced asthma: a pilot study

Increased non-specific bronchial hyperresponsiveness (BHR) has been reported after positive reaction to isocyanates in patients with isocyanate-sensitive asthma. The increased responsiveness may, however, also precede the asthma attack. We therefore compared non-specific BHR to a cholinergic agent before and after exposure to toluene-diisocyanate (TDI) that induced no asthma symptoms in 11 workers with isocyanate-related asthma. Patients were exposed for 3 consecutive days to progressively increasing doses of TDI (5, 10, and 20 ppb min-1 for 20 min) in an exposure chamber with continuous TDI monitoring. No immediate nor late asthmatic bronchial reaction was observed in any patient after any dose of TDI during or after challenge. A significant increase in non-specific BHR was noted 24 h after the last dose of TDI challenge, however. This increase was at least one doubling dose for seven of 11 patients. In conclusion, our study shows that, in patients with isocyanate-induced asthma, exposure to TDI induces a slight but significant increase in non-specific BHR in the absence of any immediate or late bronchial response to isocyanate. This result, which requires further confirmation, may justify a proposal to measure non-specific BHR, even after a negative specific inhalation test to TDI, as an additional diagnostic element for TDI-induced occupational asthma, to help lower the percentage of the undetected occupational asthma cases.