Toluene Diisocyanate-induced Asthma Research Articles

Inhibition of TAK1 aggravates airway inflammation by increasing RIPK1 activity and promoting macrophage death in a mouse model of toluene diisocyanate-induced asthma

To explore the effect of transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1) on toluene diisocyanate (TDI)-induced allergic airway inflammation in mice. Thirty-two mice were randomly divided into AOO group, AOO+5Z-7-Oxozeaenol group, TDI group, and TDI+5Z-7-Oxozeaenol group. Another 32 mice were randomly divided into AOO group, TDI group, TDI +5Z-7-Oxozeaenol group, and TDI +5Z-7-Oxozeaenol + Necrostatin-1 group. TAK1 inhibitor (5Z-7-Oxozeaenol, 5 mg/kg) and/or RIPK1 inhibitor (Necrostatin-1, 5 mg/kg) were used before each challenge. Airway responsiveness, airway inflammation and airway remodeling were assessed after the treatments. We also examined the effect of TDI-human serum albumin (TDI-HSA) conjugate combined with TAK1 inhibitor on the viability of mouse mononuclear macrophages (RAW264.7) using CCK8 assay. The expressions of TAK1, mitogen-activated protein kinase (MAPK) and receptor interacting serine/threonine protease 1 (RIPK1) signal pathway in the treated cells were detected with Western blotting. The effects of RIPK1 inhibitor on the viability of RAW264.7 cells and airway inflammation of the mouse models of TDI-induced asthma were evaluated. TAK1 inhibitor aggravated TDI-induced airway inflammation, airway hyper responsiveness and airway remodeling in the mouse models (P < 0.05). Treatment with TAK1 inhibitor significantly decreased the viability of RAW264.7 cells, which was further decreased by co-treatment with TDI-HSA (P < 0.05). TAK1 inhibitor significantly decreased the level of TAK1 phosphorylation and activation of MAPK signal pathway induced by TDI-HSA (P < 0.05). Co-treatment with TAK1 inhibitor and TDI-HSA obviously increased the level of RIPK1 phosphorylation and caused persistent activation of caspase 8 (P < 0.05). RIPK1 inhibitor significantly inhibited the reduction of cell viability caused by TAK1 inhibitor and TDI-HSA (P < 0.05) and alleviated the aggravation of airway inflammation induced by TAK1 inhibitors in TDI-induced mouse models (P < 0.05). Inhibition of TAK1 aggravates TDI-induced airway inflammation and hyperresponsiveness and may increase the death of macrophages by enhancing the activity of RIPK1 and causing persistent activation of caspase 8.

Association of GSTM1 and GSTT1 Null Genotypes with Toluene Diisocyanate-Induced Asthma.

Background Toluene diisocyanate (TDI) causes occupational asthma by generating oxidative stress, leading to tissue injury and inflammation. Glutathione transferases (GSTs) are detoxifying enzymes that eliminate oxidative stress. We examined whether the genotypes of the GSTM1 and GSTT1 genes are associated with TDI-induced occupational asthma (TDI-OA). Methods The study population consisted of 26 asthmatics with a positive response to the TDI challenge (TDI-PA) and 27 asthmatics with negative responses (TDI-NA). GSTM1 and GSTT1 null and wild-type genotypes were determined using multiplex PCR. The plasma GSTM1 and GSTT1 protein concentrations were determined using ELISA. Results The GSTM1 null genotype was more frequent in the TDI-PA than in the TDI-NA (77.8 vs. 50.0%, OR = 3.5, p=0.03), while the frequency of the GSTT1 null genotype tended to be higher in the TDI-PA than in the TDI-NA (59.3 vs. 42.3%, OR = 1.98, p=0.21). When analyzed together, the GSTM1/GSTT1 null genotype was more frequent in the TDI-PA than in the TDI-NA (48.2 vs. 15.3%, OR = 6.5, p=0.04). The decline in the FEV in 1 s after TDI challenge was higher with the GSTM1/GSTT1 null than the GSTM1 wild-type/GSTT1 null genotypes (24.29% vs. 7.47%, p=0.02). The plasma GSTM1 level was lower with the GSTM1 null than with the GSTM1 wild-type genotypes both before (13.7 vs. 16.6 ng/mg, p=0.04) and after (12.9 vs. 17.1 ng/mg, p=0.007) the TDI challenge, while the GSTT1 level was not changed with either the GSTT1 null or wild-type genotype. Conclusions The GSTM1 null genotype, but not GSTT1 alone, may confer susceptibility to TDI-OA. However, the genetic effect of the GSTM1 null genotype may be enhanced synergistically by the GSTT1 null genotype. The genetic effect of GSTM1 was validated in the plasma as the GSTM1 protein level. Therefore, the GSTM1 and GSTT1 genotypes may be useful diagnostic markers for TDI-OA.

RAGE mediates airway inflammation via the HDAC1 pathway in a toluene diisocyanate-induced murine asthma model

BackgroundExposure to toluene diisocyanate (TDI) is a significant pathogenic factor for asthma. We previously reported that the receptor for advanced glycation end products (RAGE) plays a key role in TDI-induced asthma. Histone deacetylase (HDAC) has been reported to be important in asthmatic pathogenesis. However, its effect on TDI-induced asthma is not known. The aim of this study was to determine the role of RAGE and HDAC in regulating airway inflammation using a TDI-induced murine asthma model.MethodsBALB/c mice were sensitized and challenged with TDI to establish an asthma model. FPS-ZM1 (RAGE inhibitor), JNJ-26482585 and romidepsin (HDAC inhibitors) were administered intraperitoneally before each challenge. In vitro, the human bronchial epithelial cell line 16HBE was stimulated with TDI-human serum albumin (TDI-HSA). RAGE knockdown cells were constructed and evaluated, and MK2006 (AKT inhibitor) was also used in the experiments.ResultsIn TDI-induced asthmatic mice, the expression of RAGE, HDAC1, and p-AKT/t-AKT was upregulated, and these expressions were attenuated by FPS-ZM1. Airway reactivity, Th2 cytokine levels in lymph supernatant, IgE, airway inflammation, and goblet cell metaplasia were significantly increased in the TDI-induced asthmatic mice. These increases were suppressed by JNJ-26482585 and romidepsin. In addition, JNJ-26482585 and romidepsin ameliorated the redistribution of E-cadherin and β-catenin in TDI-induced asthma. In TDI-HSA-stimulated 16HBE cells, knockdown of RAGE attenuated the upregulation of HDAC1 and phospho-AKT (p-AKT). Treatment with the AKT inhibitor MK2006 suppressed TDI-induced HDAC1 expression.ConclusionsThese findings indicate that RAGE modulates HDAC1 expression via the PI3K/AKT pathway, and that inhibition of HDAC prevents TDI-induced airway inflammation.

Bronchial epithelial pyroptosis promotes airway inflammation in a murine model of toluene diisocyanate-induced asthma

Airway epithelial injury in response to allergens such as toluene diisocyanate (TDI) leads to persistent airway inflammation. Pyroptosis is recognized as a strong proinflammatory cell death process. However, the role of pyroptosis in bronchial epithelial injury and airway inflammation in TDI-induced asthma remains unknown.In this study, cytotoxic effect of TDI on 16HBE cells (a human bronchial epithelial cell line) was detected. Then a TDI-induced experimental asthma mouse model was established for in vivo study.Here we found that TDI induced pyroptosis in 16HBE cells, as evidenced by enhanced expressions of caspase-1 and elevated levels of LDH, IL-1β and HMGB1. As expected, TDI-induced inflammatory cell death was significantly blocked by a specific NLRP3 inflammasome inhibitor. Intriguingly, in asthmatic mice, the increased cleavages of caspase-1 and pyroptotic executioner gasdermin D (GSDMD) in bronchial epithelial cells were decreased by NLRP3 inflammasome inhibitor. Furthermore, inhibition of NLRP3 inflammasome attenuated airway hyper-responsiveness and airway inflammation, accompanied by lower levels of IL-1β, IgE and Th2-related cytokines.Our data suggest that bronchial epithelial pyroptosis exacerbates airway inflammation and hyper-responsiveness in TDI-induced asthma via NLRP3 inflammasome activation and GSDND cleavage. Therefore, NLRP3 inflammasome-mediated pyroptosis may be a potential treatment target for TDI-induced asthma.

Phosphorylation of low density lipoprotein receptor-related protein 6 is involved in receptor for advanced glycation end product-mediated β-catenin stabilization in a toluene diisocyanate-induced asthma model

BackgroundWe have previously demonstrated that the receptor for advanced glycation end products (RAGE)/β-catenin axis plays a vital role in regulating airway inflammation and airway remodeling in a toluene diisocyanate (TDI)-induced murine asthma model. However, the exact mechanism of β-catenin activation remains unclear. Given that phosphorylation of the low-density lipoprotein receptor-related protein 6 (Lrp6) is a key step in mediating β-catenin stabilization in canonical wnt/β-catenin signaling, we explored the possible relationship between RAGE and Lrp6 in regulating β-catenin stabilization in TDI-induced asthma. MethodsIn this study, a TDI-induced murine asthma model was generated, and mice were treated with a specific inhibitor of RAGE. In vitro, the human bronchial epithelial cell line 16HBE was treated with TDI-human serum albumin (TDI-HSA). RAGE overexpression or knockdown cells were also constructed and assessed. ResultsThe results showed that RAGE inhibition or RAGE knockdown decreased β-catenin nuclear accumulation and the expression of relevant β-catenin targeted genes (VEGF, MMP9, TGF-β1) in the TDI-induced murine asthma model and TDI-HSA-treated 16HBE cells, respectively. Silencing of RAGE reversed the TDI-induced increase in phospho-ERK1/2 (p-ERK) and phospho-Lrp6 (p-Lrp6) in 16HBE cells. Pretreatment with the extracellular signal-regulated kinase (ERK)1/2 inhibitor U0126 suppressed TDI-induced Lrp6 phosphorylation. Furthermore, knockdown of Lrp6 in 16HBE cells decreased β-catenin nuclear translocation and the expression of VEGF, MMP9, and TGF-β1. ConclusionThese data suggested that the RAGE/ERK axis modulates Lrp6 phosphorylation, contributing to β-catenin stabilization in a TDI-induced murine model.

Vitamin E effect in a rat model of toluene diisocyanate-induced asthma.

Background and aimThe aim of the study was to evaluate vitamin E effect upon oxidative stress associated with toluene −2, 4-diisocyanate (TDI)-induced asthma in rats.MethodsThe five study groups were: control, vehicle, TDI, vehicle+E, TDI+E. TDI animals were sensitized by nasal administration of TDI 10% (5μl/nostril) between days 1–7 and 15–21. Between days 22–28 groups TDI+E and vehicle+E rats received vitamin E (50 mg/kg, i. v.), and control, vehicle and TDI groups received saline solution. On day 29 the rats were challenged by intranasal application of 5% TDI (5 μl/nostril). On day 30 blood, BALF and lung biopsy were harvested. Oxidative stress tests were malondialdehyde (MDA), protein carbonyls (PC), total thiols (tSH), 1,1-diphenyl-2-picryl hydrazyl (DPPH) and reduced glutathione (GSH).ResultsTDI sensitization increased oxidative stress systemically, but also locally in the respiratory airways and lung tissue. There was an increase of MDA and PC formation associated with a deficiency of the antioxidant defense reflected by DPPH decreases. There were no differences between systemic and local lung concentrations of oxidized molecules.After vitamin E treatment oxidative stress was reduced mostly due to serum, BALF and lung tissue GSH and DPPH increase.ConclusionThe study showed that in rat TDI-induced asthma there was oxidative stress caused by increased ROS production and antioxidants deficiency, and vitamin E reduced ROS production and improved antioxidant defense.

Mild Improvement in Symptoms and Pulmonary Function in a Long-Term Follow-Up of Patients with Toluene Diisocyanate-Induced Asthma

Background: Long-term follow-up of diisocyanate-induced occupational asthma has been occasionally reported. Methods: We studied the outcome of toluene diisocyanate (TDI)-induced asthma in 46 patients at diagnosis and after a follow-up of 11 ± 3.6 years. Symptoms, anti-asthma therapy, forced expiratory volume in 1 s (FEV₁) and bronchial hyperresponsiveness to methacholine were assessed. Results: A significant improvement in FEV₁ (% predicted) and PD20FEV₁ methacholine was observed at follow-up in comparison with diagnosis. Anti-asthma treatment was performed by 42% of patients at diagnosis and by 70% at follow-up. At the time of follow-up, 32 subjects had been removed from exposure for 6.0 ± 6.9 years, whereas 14 subjects continued to work with reduced exposure to TDI. There was a significant reduction in the prevalence of attacks of shortness of breath and dyspnoea at follow-up, but only in unexposed patients. PD20FEV₁ was significantly improved only in patients with a lower FEV₁ at diagnosis and in those who have ceased work. Logistic regression analysis, using different models with some independent variables, showed that there were no significant determinants of improvement in FEV₁ at follow-up, while a shorter duration of symptoms before diagnosis was a significant predictor of improvement in PD20FEV₁ at follow-up. Conclusions: Asthma-like symptoms, bronchial hyperresponsiveness and airway obstruction improved, but did not normalize, after a long-term follow-up with cessation or reduction in TDI exposure, mainly in subjects with an early diagnosis of occupational asthma and in patients with a lower baseline FEV₁ no longer exposed to TDI.

Nitro-oxidative stress in a mice model of toluene diisocyanate-induced asthma.

Toluene-2,4-diisocyanate (TDI) induced occupational asthma mechanisms are not completelyknown. The aim of the study was to evaluate the nitro-oxidative stress associated to experimental miceTDI induced asthma. It was used a model of mice experimental exposure to TDI for 10 days. The studygroups (n = 12) were: a negative control group with skin sensitization and intranasal challenge, performedwith saline; group with sensitization and challenge with the solvent; group withsensitization and challenge with TDI; groups with TDI and aminoguanidine (AG) (50 mg/kg/d i.p.) orNG-nitro-L-arginine methyl ester (NAME), (5 mg/kg/d i.p.) or arginine (ARG) (100 mg/kg/d i.p.) ortrolox (20 mg / kg / day ip). On the 11th day blood was collected by cardiac puncture, and nitro-oxidativestress was assessed by total oxidative status (TOS), total antioxidative capacity (TAC), oxidative stressindex (OSI) and serum nitrates and nitrites (NOx). TDI increased TOS, OSI and NOx andreduced TAC. The solvent did not influence any parameter. AG, NAME and Trolox reduced NOx, TOSand OSI. Experimental exposure of mice to TDI caused systemic nitro-oxidative stress, and NOxreduction and Trolox lowered the systemic nitro-oxidative stress.

AMPK activation reduces vascular permeability and airway inflammation by regulating HIF/VEGFA pathway in a murine model of toluene diisocyanate-induced asthma

Occupational asthma is characterized by airway inflammation and hyperresponsiveness associated with increased vascular permeability. AMP-activated protein kinase (AMPK) has been suggested to be a novel signaling molecule modulating inflammatory responses. We sought to evaluate the involvement of AMPK in pathogenesis of occupational asthma and more specifically investigate the effect and molecular mechanisms of AMPK activation in regulating vascular permeability. The mechanisms of action and therapeutic potential of an AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) were tested in a murine model of toluene diisocyanate (TDI)-induced asthma. AICAR attenuated airway inflammation and hyperresponsiveness increased by TDI inhalation. Moreover, TDI-induced increases in levels of hypoxia-inducible factor (HIF)-1α, HIF-2α, vascular endothelial growth factor A (VEGFA), and plasma exudation were substantially decreased by treatment with AICAR. Our results also showed that VEGFA expression was remarkably reduced by inhibition of HIF-1α and HIF-2α with 2-methoxyestradiol (2ME2) and that an inhibitor of VEGFA activity, CBO-P11 as well as 2ME2 significantly suppressed vascular permeability, airway infiltration of inflammatory cells, and airway hyperresponsiveness induced by TDI. In addition, AICAR reduced reactive oxygen species (ROS) generation and levels of malondialdehyde and T-helper type 2 cytokines (IL-4, IL-5, and IL-13), while this agent enhanced expression of an anti-inflammatory cytokine, IL-10. These results suggest that AMPK activation ameliorates airway inflammatory responses by reducing vascular permeability via HIF/VEGFA pathway as well as by inhibiting ROS production and thus may be a possible therapeutic strategy for TDI-induced asthma and other airway inflammatory diseases.

Immunological determinants in a murine model of toluene diisocyanate-induced asthma

Diisocyanates (DIC) are highly reactive, low-molecular-weight chemicals which are the leading cause of occupational asthma (OA). The aim of the study was to analyze certain aspects of the pathogenesis of allergic inflammation in the airways induced by toluene diisocyanate (TDI) in an experimental model in mice. The experiment was carried out on 50 female BALB/cJ/Han/IMP mice, which were exposed by inhalation (intranasal and in the inhalation chamber) to toluene diisocyanate (2,4-TDI). After the experiment, the bronchoalveolar lavage fluid (BALF) was collected from the animals, and the composition of the induced inflammatory cells, and the concentrations of certain cytokines (IL-4, IL-5, TNF-α) were evaluated. The total number of cells in BALF of the examined group of mice was significantly higher compared to the control mice. There was also a significant increase in neutrophils and eosinophils in the study group compared to the controls. The number of lymphocytes and macrophages did not differ significantly between the two groups. A statistically significant increase in the level of TNF-α was shown to occur in the group exposed to toluene diisocyanate in comparison to the control group. The concentration of IL-4 increased in the study group, compared to the control one, but the differences did not reach the level of significance, p > 0.05. Such difference was not observed for IL-5. We developed a murine model of TDI-induced asthma which caused the influx of inflammatory cells like eosinophils and neutrophils in the bronchoalveolar lavage fluid (BALF) in the TDI-treated mice. The increase of the concentration of some proinflammatory cytokines (TNF-α, IL-4) in BALF from the exposed mice was also observed.

Serum cytokines markers in toluene diisocyanate-induced asthma

Toluene diisocyante-induced occupational asthma (TDI-OA) is an inflammatory disease of airway, composing inflammatory cells and cytokines associated with airway remodeling. Majority of the patients with TDI-OA presented persistent asthma. Therefore, early diagnosis is essential for the favorable prognosis. We investigated to identify serologic markers for early diagnosis of TDI-OA. We enrolled 69 patients with TDI-OA and 95 asymptomatic exposed controls (AECs). Neutrophil-related cytokines, including myeloperoxidase (MPO) and interleukin-8 (IL-8), as well as airway remodeling-related cytokines, including transforming growth factor-β1 (TGF-β1), metalloproteinase-9 (MMP-9), tissue inhibitor of metalloproteinase-1 (TIMP-1), and vascular endothelial growth factor (VEGF), were measured by ELISA in the sera of each subject. To evaluate the validity of the each cytokine and combined cytokines for discriminating between TDI-OA and AEC, Receiver operating characteristic (ROC) curve was used. There were significant differences in the serum levels of MMP-9 and VEGF between two groups (p < 0.05). Using the optimal cutoff value of MMP-9 (182.96 ng/mL), the sensitivity and specificity were 79.7% and 80.0%, respectively, with the area under the curve (AUC) of 0.815. When the cytokines were combined to improve sensitivity, the combined values of MMP-9, VEGF, and IL-8 comprised the best set, for which the AUC increased to 0.822 and the sensitivity increased to 82.6% but specificity decreased to 75.8%. The single serum cytokine MMP-9 level or the combined cytokines MMP-9, VEGF, and IL-8 can be used as meaningful serologic markers for identifying patients with TDI-OA among exposed workers.

Serum Cytokine Levels as Serologic Markers of Toluene Diisocyanate-induced Occupational Asthma

Serum Cytokine Levels as Serologic Markers of Toluene Diisocyanate-induced Occupational Asthma

Tissue Transglutaminase Can Be Involved in Airway Inflammation of Toluene Diisocyanate-Induced Occupational Asthma

This study was conducted to evaluate whether tissue transglutaminase (tTG) may be involved in airway inflammation of toluene diisocyanate-induced occupational asthma (TDI-OA). We enrolled 93 patients with TDI-OA, 177 asymptomatic exposed subjects, 43 patients with allergic asthma, and 70 unexposed normal controls. The prevalence of serum immunoglobulin G (IgG) to tTG in the TDI-OA group (20.2%) was significantly higher than that in the three other groups (P < 0.001). TDI-OA patients with serum IgG to tTG had significantly lower methacholine PC(20) values (P < 0.02) and significantly higher prevalence of specific immunoglobulin E to vapor type TDI-human serum albumin conjugate (P < 0.01; r(2) = 0.411, P < 0.05). TDI exposure could increase tTG activity via reactive oxygen species (ROS) production, which was found to cross-link with cytokeratin 19 on immunoblot analysis. Therefore, TDI exposure may activate tTG via ROS-mediated mechanism in the airway epithelium leading to persistent airway inflammation in TDI-OA patients.

A novel murine model of toluene diisocyanate-induced asthma

A novel murine model of toluene diisocyanate-induced asthma

Modulation of Airway Remodeling and Airway Inflammation by Peroxisome Proliferator-Activated Receptor γ in a Murine Model of Toluene Diisocyanate-Induced Asthma

Toluene diisocyanate (TDI) is a leading cause of occupational asthma. Although considerable controversy remains regarding its pathogenesis, TDI-induced asthma is an inflammatory disease of the airways characterized by airway remodeling. Peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to play a critical role in the control of airway inflammatory responses. However, no data are available on the role of PPARgamma in TDI-induced asthma. We have used a mouse model for TDI-induced asthma to determine the effect of PPARgamma agonist, rosiglitazone, or pioglitazone, and PPARgamma on TDI-induced bronchial inflammation and airway remodeling. This study with the TDI-induced model of asthma revealed the following typical pathophysiological features: increased numbers of inflammatory cells of the airways, airway hyperresponsiveness, increased levels of Th2 cytokines (IL-4, IL-5, and IL-13), adhesion molecules (ICAM-1 and VCAM-1), chemokines (RANTES and eotaxin), TGF-beta1, and NF-kappaB in nuclear protein extracts. In addition, the mice exposed to TDI developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer, subepithelial collagen deposition, and increased airway mucus production. Administration of PPARgamma agonists or adenovirus carrying PPARgamma2 cDNA reduced the pathophysiological symptoms of asthma and decreased the increased levels of Th2 cytokines, adhesion molecules, chemokines, TGF-beta1, and NF-kappaB in nuclear protein extracts after TDI inhalation. In addition, inhibition of NF-kappaB activation decreased the increased levels of Th2 cytokines, adhesion molecules, chemokines, and TGF-beta1 after TDI inhalation. These findings demonstrate a protective role of PPARgamma in the pathogenesis of the TDI-induced asthma phenotype.

Serum specific IgG to cytokeratin may be a diagnostic marker for toluene diisocyanate-induced asthma

Serum specific IgG to cytokeratin may be a diagnostic marker for toluene diisocyanate-induced asthma

Increased levels of IgG to cytokeratin 19 in sera of patients with toluene diisocyanate-induced asthma

Inhaled isocyanate binds with cytokeratin (CK) of the epithelial cells, which could induce immune responses. To elucidate the possible existence of an isocyanate-induced, asthma-associated autoantigen from the bronchial epithelial cells, which may be associated with toluene diisocyanate (TDI)-induced asthma development. We cultured bronchial epithelial cells with incubation of TDI-human serum albumin (HSA) conjugate. Gene expression profiles of cultured epithelial cells were analyzed using a microarray technique. CK19 protein expression within the epithelial cells was confirmed by IgG immunoblot using monoclonal antibody to CK19. Serum IgG to CK19 and specific IgG and IgE antibodies to TDI-HSA conjugate were detected by enzyme-linked immunosorbent assay in 68 TDI asthma patients (group 1) and compared with 40 allergic asthma patients (group 2) and 80 unexposed healthy controls (group 3). After TDI exposure, increased expression of CK19 and CK14 genes from the culture bronchial epithelial cells was noted using microarray analysis. IgG immunoblot analysis confirmed increased expression of CK19 after the TDI exposure. The levels of serum IgG to CK19 were significantly higher in the TDI asthma group than in groups 2 and 3 (P=.008). The prevalence of IgG to CK19 was significantly higher in group 1 (38.2%) than group 2 (22.5%) or group 3 (1.3%) (P=.008). Significant associations were noted between IgG to CK19 and specific IgG to TDI-HSA conjugate and transglutaminase (P=.02) but not with specific IgE to TDI-HSA conjugate. We suggest that TDI exposure can augment CK19 expression from the bronchial epithelial cell, which may involve immune responses as an autoantigen to induce airway inflammation in TDI-induced asthma.

Inhibition of matrix metalloproteinase-9 by doxycycline reduces airway inflammation and hyperresponsiveness in a murine model of toluene diisocyanate-induced asthma

Rationale Toluene diisocyanate (TDI) is a leading cause of occupational asthma. Although considerable controversy remains regarding its pathogenesis, TDI-induced asthma is an inflammatory disease of the airways characterized by airway remodeling due, at least in part, to an excess of extracellular matrix deposition in the airway wall. Matrix metalloproteinases (MMPs) are major proteolytic enzymes that are involved in extracellular matrix (ECM) turnover because of their ability to cleave all proteins constituting ECM. Previous studies have reported that MMP-9 might play a role in chronic airway inflammation and remodeling in asthma. Methods We used a BALB/c mouse model for TDI-induced asthma to determine the effect of a MMP-inhibiting antibiotic agent, doxycycline and MMP inhibitors on bronchial inflammation and airway hyperresponsiveness. Results The following typical pathophysiologic features are observed in the lungs of the mice: airway inflammation, airway hyperresponsiveness, and increased expression of MMP-9 mRNA and protein. Administration of doxycycline and MMP inhibitors reduced all these pathophysiologic findings. In addition, the increased phosphorylated-Akt but not Akt protein levels in lung tissues after TDI inhalation were significantly reduced by the administration of doxycycline and MMP inhibitors. Conclusions These findings suggest that doxycycline may reduce airway inflammation and hyperresponsiveness through phosphatidylinositol 3-kinase pathway in a murine model of TDI-induced asthma.

Matrix metalloproteinase inhibitor regulates inflammatory cell migration by reducing ICAM-1 and VCAM-1 expression in a murine model of toluene diisocyanate-induced asthma

Background: Matrix metalloproteinase-9 (MMP-9) has been reported to play a crucial role in the transmigration of neutrophils, lymphocytes, and eosinophils. Neutrophils, eosinophils, and lymphocytes migrate from the blood to the lungs in response to inflammatory mediators produced in the airways and are subsequently released into the circulation. This traffic is mediated by adhesion molecules. However, little is known about the migration of inflammatory cells through the endothelial and epithelial basement membranes in toluene diisocyanate (TDI)-induced asthma. Objectives: An aim of this study was to evaluate the effect of MMP inhibitors on the expression of ICAM-1 and VCAM-1 in the migration of inflammatory cells in a murine model of TDI-induced asthma. Methods: We used a murine model to investigate TDI-induced asthma to examine the possible involvement of ICAM-1 and VCAM-1 in the pathogenesis of that disease and the effect of MMP inhibitors on the expression of ICAM-1 and VCAM-1. Results: In mice, the following typical pathophysiologic features develop in the lungs: increased numbers of inflammatory cells and increased expression of MMP-9, ICAM-1, and VCAM-1 mRNA and protein. Administration of MMP inhibitors reduced the increased numbers of inflammatory cells and the increased expression of ICAM-1 and VCAM-1 mRNA expression and protein. In addition, MMP inhibitors significantly abrogated the increased expression of IL-1β, IL-4, and TNF-α mRNA in lung tissues and levels of IL-1β, IL-4, and TNF-α in bronchoalveolar lavage fluids after TDI inhalation. Conclusions: These results suggest that MMP inhibitors regulate inflammatory cell migration by reducing ICAM-1 and VCAM-1 expression and possibly also by suppressing IL-1β, IL-4, and TNF-α expression. (J Allergy Clin Immunol 2003;111:1278-84.)

Long-term follow-up of toluene diisocyanate-induced asthma.

Eighty-seven cases of occupational asthma induced by toluene diisocyanate (TDI) were diagnosed by an inhalation challenge with TDI and methacholine. After an average follow-up interval of 11 yrs, all subjects were re-examined. Of the 87 subjects examined, 13 (15%) had remained in the same job, 44 (50.5%) had been removed from exposure for <10 yrs and 30 (34.5%) had been removed for >10 yrs. The proportion of subjects who experienced symptoms of asthma and those who were hyperresponsive to methacholine was significantly lower. Of the patients, 59% used short-acting bronchodilators, 8% long-acting bronchodilators and 18% were on regular inhaled glucocorticoids. Thus, multiple regression analysis showed a positive correlation between forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) at follow-up and FVC and FEV1 at diagnosis, and a negative correlation with smoking and with therapy with bronchodilators. Stepwise logistic regression showed that the follow-up provocative dose causing a 20% fall in the FEV1 (PD20) could be predicted from baseline PD20. These results indicate that respiratory symptoms and airway hyperresponsiveness to methacholine persist in subjects removed from exposure to TDI for >10 yrs. A more favourable prognosis was associated with a better lung function and a lower degree of airway hyperresponsiveness to methacholine at diagnosis.