Toluene diisocyanate occupational exposure data in the polyurethane industry (2005-2020): A descriptive summary from an industrial hygiene perspective.

This article provides an overview of toluene diisocyanate (TDI) workplace air concentration data. Data were collected between 2005-2020 in workplaces across the United States, Canada, and the European Union by a number of different organizations, primarily using the sampling procedures published in OSHA Methods 42 and 5002. The data were then collated and organized by the International Isocyanate Institute. Air samples were collected from several market segments, with a large portion of the data (87%) from the flexible foam industry. The air samples (2534 in total) were categorized into "area" or "personal," and the personal samples were subcategorized into "task," "short term," and "long term." Most of the air sample concentrations (87%) were less than 5 ppb. However, the presence of airborne TDI greater than 5 ppb indicated the importance of respiratory protection in some situations; therefore, respirator use patterns were studied and summarized. Additionally, this article provides a summary of air sample concentrations at different flexible foam manufacturing job roles. The information on air sampling concentrations and respiratory protection during TDI applications collected in this paper could be useful for product stewardship and industrial hygiene purposes in the industries studied.

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

OBJECTIVE: To explore the effect of transforming growth factor-ß (TGF-ß)-activated kinase 1 (TAK1) on toluene diisocyanate (TDI)-induced allergic airway inflammation in mice. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

Exposure of Toluene Diisocyanate Induces DUSP6 and p53 through Activation of TRPA1 Receptor.

Toluene diisocyanate (TDI), a major intermediate agent used in the manufacturing industry, causes respiratory symptoms when exposed to the human body. In this study, we aimed to determine the molecular mechanism of TDI toxicity. To investigate the impact of TDI exposure on global gene expression, we performed transcriptomic analysis of human bronchial epithelial cells (BEAS-2B) after TDI treatment. Differentially expressed genes (DEGs) were sorted and used for clustering and network analysis. Among DEGs, dual-specificity phosphatase 6 (DUSP6) was one of the genes significantly changed by TDI exposure. To verify the expression level of DUSP6 and its effect on lung cells, the mRNA and protein levels of DUSP6 were analyzed. Our results showed that DUSP6 was dose-dependently upregulated by TDI treatment. Thereby, the phosphorylation of ERK1/2, one of the direct inhibitory targets of DUSP6, was decreased. TDI exposure also increased the mRNA level of p53 along with its protein and activity which trans-activates DUSP6. Since TRPA1 is known as a signal integrator activated by TDI, we analyzed the relevance of TRPA1 receptor in DUSP6 regulation. Our data revealed that up-regulation of DUSP6 mediated by TDI was blocked by a specific antagonist against TRPA1. TDI exposure attenuated the apoptotic response, which suggests that it promotes the survival of cancerous cells. In conclusion, our results suggest that TDI induces DUSP6 and p53, but attenuates ERK1/2 activity through TRPA1 receptor activation, leading to cytotoxicity.

Occupational Exposure to Diisocyanates in the European Union.

OBJECTIVES: Diisocyanates are a chemical group that are widely used at workplaces in many sectors. They are also potent skin- and respiratory sensitizers. Exposure to diisocyanates is a main cause of occupational asthma in the European Union. To reduce occupational exposure to diisocyanates and consequently the cases of diisocyanate-induced asthma, a restriction on diisocyanates was recently adopted under the REACH Regulation in the European Union. METHODS: A comprehensive evaluation of the data on occupational exposure to the most important diisocyanates at workplaces was made and is reported here. The diisocyanates considered are methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), and hexamethylene diisocyanate (HDI), accounting for more than 95% of the market volume in the EU. The exposure assessment is based on data from Chemical Safety Reports (CSRs) of REACH Registration Dossiers, workplace air monitoring data from Germany, from the UK Health and Safety Executive (HSE), and literature data relevant for the EU, and the USA. RESULTS: Occupational exposure to diisocyanates is particularly relevant in: (i) C.A.S.E. applications (Coatings, Adhesives, Sealants, Elastomers), (ii) production of polyurethanes (PUs) (e.g. slab-stock foam), (iii) handling of partly uncured PU products (e.g. cutting, demoulding, spray application of foam), and (iv) when diisocyanates/PUs are heated (e.g. hot lamination, foundry applications/casting forms). Ranking of the reported data on inhalation to diisocyanate exposure at workplaces (maximum values) leads to following order: (i) HDI and its oligomers in coatings, (ii) MDI in spray foam applications, (iii) TDI in manufacture of foam, (iv) TDI in manufacture of PUs and PU composite materials, (v) TDI in adhesives, (vi) MDI in adhesives, (vii) MDI in manufacture of PUs and PU composite materials, (viii) TDI in coatings, (ix) MDI in manufacture of foam, and (x) HDI in adhesives.

The AKT inhibitor MK2206 suppresses airway inflammation and the pro­remodeling pathway in a TDI­induced asthma mouse model.

The cellular and molecular mechanisms via which MK2206, an AKT inhibitor, prevents the activation of AKT in toluene diisocyanate (TDI)­induced asthma remain unclear. Thus, the present study aimed to evaluate the potential effects of MK2206 on airway AKT activation, inflammation and remodeling in a TDI­induced mouse model of asthma. A total of 24 BALB/c mice were selected and randomly divided into untreated (AOO), asthma (TDI), MK2206 (TDI + MK2206), and dexamethasone (TDI + DEX) groups. Phosphorylated AKT (p­AKT), total AKT, airway remodeling indices, α­smooth muscle actin (α­SMA) and collagen I levels in pulmonary tissue were measured using western blotting. Airway inflammation factors, including interleukin (IL)­4, ­5, ­6, and ­13 in bronchoalveolar lavage fluid (BALF) and IgE in serum, were determined using ELISA. Additionally, the airway hyperresponsiveness (AHR) and pulmonary pathology of all groups were evaluated. The results of the present study demonstrated that p­AKT levels in lung protein lysate were upregulated, and neutrophil, eosinophil and lymphocyte counts were increased in the lungs obtained from the asthma group compared with the AOO group. Both MK2206 and DEX treatment in TDI­induced mice resulted not only in the attenuation of AKT phosphorylation, but also reductions in neutrophil, eosinophil and lymphocyte counts in the lungs of mice in the asthma group. Consistently, increases in the levels of the inflammatory cytokines IL­4, ­5, ­6 and ­13 analyzed in BALF, and serum IgE in the TDI group were demonstrated to be attenuated in the TDI + MK2206 and TDI + DEX groups. Furthermore, α­SMA and AHR were significantly attenuated in the TDI + MK2206 group compared with the TDI group. These results revealed that MK2206 not only inhibited AKT activation, but also served a role in downregulating airway inflammation and airway remodeling in chemical­induced asthma. Therefore, the findings of the present study may provide important insight into further combination therapy.

Biomonitoring for Occupational Exposure to Diisocyanates: A Systematic Review.

Diisocyanates are a group of chemicals that are widely used in occupational settings. They are known to induce various health effects, including skin- and respiratory tract sensitization resulting in allergic dermatitis and asthma. Exposure to diisocyanates has been studied in the past decades by using different types of biomonitoring markers and matrices. The aim of this review as part of the HBM4EU project was to assess: (i) which biomarkers and matrices have been used for biomonitoring diisocyanates and what are their strengths and limitations; (ii) what are (current) biomonitoring levels of the major diisocyanates (and metabolites) in workers; and (iii) to characterize potential research gaps. For this purpose we conducted a systematic literature search for the time period 2000-end 2018, thereby focussing on three types of diisocyanates which account for the vast majority of the total isocyanate market volume: hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and 4,4'-methylenediphenyl diisocyanate (MDI). A total of 28 publications were identified which fulfilled the review inclusion criteria. The majority of these studies (93%) investigated the corresponding diamines in either urine or plasma, but adducts have also been investigated by several research groups. Studies on HDI were mostly in the motor vehicle repair industry [with urinary hexamethylene diamine result ranging from 0.03 to 146.5 µmol mol-1 creatinine]. For TDI, there is mostly data on foam production [results for urinary toluene diamine ranging from ~0.01 to 97 µmol mol-1 creatinine] whereas the available MDI data are mainly from the polyurethane industry (results for methylenediphenyl diamine range from 0.01 to 32.7 µmol mol-1 creatinine). About half of the studies published were prior to 2010 hence might not reflect current workplace exposure. There is large variability within and between studies and across sectors which could be potentially explained by several factors including worker or workplace variability, short half-lives of biomarkers, and differences in sampling strategies and analytical techniques. We identified several research gaps which could further be taken into account when studying diisocyanates biomonitoring levels: (i) the development of specific biomarkers is promising (e.g. to study oligomers of HDI which have been largely neglected to date) but needs more research before they can be widely applied, (ii) since analytical methods differ between studies a more uniform approach would make comparisons between studies easier, and (iii) dermal absorption seems a possible exposure route and needs to be further investigated. The use of MDI, TDI, and HDI has been recently proposed to be restricted in the European Union unless specific conditions for workers' training and risk management measures apply. This review has highlighted the need for a harmonized approach to establishing a baseline against which the success of the restriction can be evaluated.

Incidence of Occupational Asthma and Exposure to Toluene Diisocyanate in the United States Toluene Diisocyanate Production Industry.

OBJECTIVE: This study examines asthma risk in facilities producing toluene diisocyanate (TDI). METHODS: A total of 197 workers were monitored from 2007 to 2012. TDI air concentrations were used to estimate exposures. RESULTS: The incidence of cases consistent with TDI-induced asthma was 0.009 per person-years (seven cases) or consistent with TDI-induced asthma or asthma indeterminate regarding work-relatedness was 0.012 (nine cases). Increased risk of cases consistent with TDI asthma was observed for cumulative (odds ratio [OR] = 2.08, 95% confidence interval [CI] 1.07 to 4.05) per logarithm parts per billion-years and peak TDI exposures (OR = 1.18, 95% CI 1.06 to 1.32) (logarithm parts per billion). There was a weak association with cumulative and peak exposures for decline of short-term forced expiratory volume in one second (FEV1). Asthma symptoms were associated with workers noticing an odor of TDI (OR 6.02; 95% CI 1.36 to 26.68). CONCLUSIONS: There is evidence that cumulative and peak exposures are associated with TDI-induced asthma.

Blockade of ß-catenin signaling attenuates toluene diisocyanate-induced experimental asthma.

BACKGROUND: Aberrant activation of ß-catenin signaling by both WNT-dependent and WNT-independent pathways has been demonstrated in asthmatic airways, which is thought to contribute critically in remodeling of the airways. Yet, the exact role of ß-catenin in asthma is very poorly defined. As we have previously reported abnormal expression of ß-catenin in a toluene diisocyanate (TDI)-induced asthma model, in this study, we evaluated the therapeutic efficacy of two small molecules XAV-939 and ICG-001 in TDI-asthmatic male BALB/c mice, which selectively block ß-catenin-mediated transcription. METHODS: Male BALB/c mice were sensitized and challenged with TDI to generate a chemically induced asthma model. Inhibitors of ß-catenin, XAV-939, and ICG-001 were respectively given to the mice through intraperitoneally injection. RESULTS: TDI exposure led to a significantly increased activity of ß-catenin, which was then confirmed by a luciferase assay in 16HBE transfected with the TOPFlash reporter plasmid. Treatment with either XAV-939 or ICG-001 effectively inhibited activation of ß-catenin and downregulated mRNA expression of ß-catenin-targeted genes in TDI-asthmatic mice, paralleled by dramatically attenuated TDI-induced hyperresponsiveness and inflammation of the airway, alleviated airway goblet cell metaplasia and collagen deposition, decreased Th2 inflammation, as well as lower levels of TGFß1, VEGF, HMGB1, and IL-1ß. CONCLUSION: The results showed that ß-catenin is a principal mediator of TDI-induced asthma, proposing ß-catenin as a promising therapeutic target in asthma.

[Analysis of correlation between pulmonary function and expression levels of matrix metalloproteinases-9 and tissue inhibitor of metalloproteinase-1 among toluene diisocyanate exposed workers].

OBJECTIVE: To investigate the effect of occupational toluene diisocyanate(TDI) exposure on matrix metalloproteinases-9 (MMP-9) and tissue inhibitor of metalloproteinase-1(TIMP-1), and analysis of the correlation of MMP-9,TIMP-1,MMP-9/TIMP-1 and lung function. METHODS: In October 2014, based on cluster sampling, we conducted a cross-sectional study in a TDI production factory located in China's western region. 61 exposed workers were recruited from workers engaged in packing, operating and checking. Based on different levels of the external exposure, the packers were classified as high exposed group, while operators and checkers as low exposed group. 58 factory managers, matching age and agent, were selected as controls, having same work intense and not contacting the TDI or other allergens. The questionnaire surveys were used to obtain the agent, age, work age, smoking and drinking, personal and family allergic history, occupational history, and the recent health conditions. The levels of MMP-9 and TIMP-1 in serum of subjects were determind by ELISA. The time weighted average concentrations (8h-TWA) were used to describe the levels of TDI air exposure in working environment. Spearman correlation assay was used to investigate the correlation of MMP-9, TIMP-1, MMP-9/TIMP-1 and lung function, exposure time. RESULTS: 8-hour TWA means of TDI air levels in exposed group, packers, operators and checkers were 0.39, 0.76, 0.25 mg/m(3), respectively . According to the external exposure concentration, the packers were classified as high exposed group, and the operators and checkers were classified as low exposed group. In controls, low exposed group and high exposed group, the levels of MMP-9, respectively, were (807.21±347.70),(586.91±317.50),(388.94±312.01) ng/ml (χ(2)=16.69, P<0.001), respectively, and the P50(P25-P75) of MMP-9/TIMP-1 were 4.67(2.87-6.68), 2.3(1.44-3.48), 1.11(0.59-1.48) (χ(2)=39.42, P<0.001), respectively, and the concentrations of TIMP-1, were (173.44±72.67), (236.12±51.98), (302.81±44.39) ng/ml (F=20.09, P< 0.001), respectively. The levels P50(P25-P75) of FVC, FEV1.0 and FEV1.0/FVC in exposed group were, 92.8% (86.0%-101.8%), 85.5%(76.7%-92.8%), 112.5(108.2-118.5), respectively, which were lower than that in control group (124.3%(107.9%-144.2%), 142.7%(119.1%-155.7%), 129.2(123.5-134))(Z values were 7.70, 8.97, 8.62, and all P<0.001). Spearman rank correlation analysis showed that levels of MMP-9 were positively associated with FEV1.0, and FEV1.0/FVC (r values were 0.27, 0.25, respectively, all P<0.05), and The levels of TIMP-1 were negatively associated with FVC, FEV1.0, and FEV1.0/FVC (r valuse were -0.33, -0.39, -0.39, all P<0.05).The levels of MMP-9 were negatively correlated with exposure time(r=-0.26, P=0.040). The positive correlations of MMP-9/TIMP-1 with FVC, FEV1.0, and FEV1.0/FVC were also found (r valuse were 0.34, 0.44, 0.40, all P<0.05). CONCLUSION: TDI exposure could induce the downs of MMP-9 and MMP-9/TIMP-1 associated with lung functions. The MMP-9 and MMP-9/TIMP-1,in a way, could reflect the respiratory inflammatory injury caused by TDI exposure.

[Effect of occupational exposure to toluene diisocyanate on workers' health].

OBJECTIVE: To investigate the effect of occupational exposure to toluene diisocyanate (TDI) on the workers' health. METHODS: A total of 76 workers exposed to TDI (exposure group) and 64 management staff members (control group) were selected from a factory as the study subjects. Area sampling was performed for the place with exposure to TDI according to the method in GBZ 159-2004 Specifications of air sampling for hazardous substances monitoring in the workplace, and gas chromatography was applied to measure the concentration of TDI in workplace air. The workers' personal information was collected with questionnaire, pulmonary ventilation function was determined with a portable spirometer, hematological parameters were analyzed by automatic blood analyzer and blood chemistry analyzer, and the indicators of oxidative damage and energy metabolism were measured by the reagent kit provided by Nanjing Jiancheng Bioengineering Institute. SPSS 17 software was applied for statistical analysis. RESULTS: The exposure group had significantly lower forced vital capacity (FVC), forced expiratory volume in 1 second(FEV1.0), and FEV1.0/FVC ratio than the control group (P <0.05). Compared with the control group, the exposure group had significantly higher red blood cell count, platelet distribution width, mean platelet volume, lymphocyte count, and neutrophil count(P<0.01), and significantly lower activities of lactate dehydrogenase(LDH), superoxide dismutase, and succinodehydrogenase (SDH)(P <0.01). In the exposure group, the length of exposure was negatively correlated with the activities of SDH and LDH in the serum (r=-0.319, P <0.05; r=-0.239, P <0.05), and the length of exposure was not found to be correlated with the activity of SOD and pulmonary function indices. CONCLUSION: TDI can induce inflammatory response and lung ventilation function impairment in workers exposed to TDI, as well as oxidative stress and imbalance of energy metabolism. Therefore, it can cause damage to workers' health, and protective measures should be enhanced.

Toluene diisocyanate: Induction of the autotaxin-lysophosphatidic acid axis and its association with airways symptoms.

Diisocyanates are industrial chemicals which have a wide range of applications in developed and developing countries. They are notorious lung toxicants and respiratory sensitizers. However, the mechanisms behind their adverse effects are not adequately characterized. Autotaxin (ATX) is an enzyme producing lysophosphatidic acid (LPA), and the ATX-LPA axis has been implicated in lung related inflammatory conditions and diseases, including allergic asthma, but not to toxicity of environmental low-molecular-weight chemicals. We investigated effects of toluene diisocyanate (TDI) on ATX induction in human lung epithelial cell models, and we correlated LPA-levels in plasma to biomarkers of TDI exposure in urine collected from workers exposed to <5ppb (parts per billion). Information on workers' symptoms was collected through interviews. One nanomolar TDI robustly induced ATX release within 10min in vitro. A P2X7- and P2X4-dependent microvesicle formation was implicated in a rapid ATX release and a subsequent protein synthesis. Co-localization between purinergic receptors and ATX was documented by immunofluorescence and confocal microscopy. The release was modulated by monocyte chemoattractant protein-1 (MCP-1) and by extracellular ATP. In workers, we found a dose-response relationship between TDI exposure biomarkers in urine and LPA levels in plasma. Among symptomatic workers reporting "sneezing", the LPA levels were higher than among non-symptomatic workers. This is the first report indicating induction of the ATX-LPA axis by an environmental low-molecular-weight chemical, and our data suggest a role for the ATX-LPA axis in TDI toxicity.

Serum specific IgG response to toluene diisocyanate-tissue transglutaminase conjugate in toluene diisocyanate-induced occupational asthmatics.

BACKGROUND: Tissue transglutaminase (tTG) is a post-translational modifying enzyme located in airway epithelial cells. A potential contribution of serum specific IgG (sIgG) to tTG in airway inflammation of toluene diisocyanate (TDI)-induced occupational asthma (OA) has been suggested. OBJECTIVE: To prepare a TDI-tTG conjugate and detect serum specific antibodies in sera of patients with TDI-OA to understand this mechanism. METHODS: Ninety-nine patients with TDI-OA, 76 asymptomatic exposed controls, 208 patients with non-OA, and 74 unexposed controls were enrolled for this study. The TDI-tTG conjugate was prepared and confirmed by a native gel. Serum sIgG and/or sIgE antibodies to tTG, TDI-tTG, TDI conjugated to human serum albumin, cytokeratin 19, and serum cytokine levels, such as interleukin-8, transforming growth factor-ß1, and tissue inhibitor of metalloproteinase-1, were measured by enzyme-linked immunosorbent assay. The level of interleukin-8 produced from airway epithelial cells (A549) treated with tTG was evaluated to investigate the inflammatory effect of tTG and TDI-tTG. RESULTS: In the TDI-OA group, the prevalence of serum sIgG to TDI-tTG (17.2%) was higher than that of sIgG to tTG (11.1%), which were significantly higher than those of the 3 control groups (P < .05 for all groups). TDI-exposed subjects with high levels of serum sIgG to TDI-tTG had a high prevalence of sIgG to cytokeratin 19 and higher serum levels of transforming growth factor-ß1 and tissue inhibitor of metalloproteinase-1. The tTG and TDI-tTG dose-dependently increased interleukin-8 production from A549 cells. CONCLUSION: These findings suggest that TDI exposure in the workplace binds to tTG to form a conjugate that can induce serum sIgG antibody production, airway inflammation, and airway remodeling in patients with TDI-OA.

Combination of leukotoriene receptor antagonist with antihistamine has an additive suppressive effect on the up-regulation of H1-receptor mRNA in the nasal mucosa of toluene 2,4-diisocyanate-sensitized rat.

An attempt was made to clarify the additive suppressive effects of pranlukast, a cysteinyl leukotriene-receptor (LTR) antagonist, in combination with chlorpheniramine, an antihistamine, on the up-regulation of histamine H1-receptor (H1R) mRNA in toluene 2,4-diisocyanate (TDI)-sensitized rats. Although pre-treatment with pranlukast partially, but significantly, suppressed TDI-induced up-regulation of H1R mRNA and nasal symptoms, pre-treatment with the combination of pranlukast and chlorpheniramine significantly suppressed them in a manner greater than either drug alone. These findings suggest that the additive therapeutic effect of the combination of LTR antagonist and antihistamine is due to their additive suppression of H1R up-regulation.

Interferon-γ promoter is hypermethylated in blood DNA from workers with confirmed diisocyanate asthma.

Risk factors have not been identified that determine susceptibility for development of diisocyanate-induced occupational asthma (DA). We hypothesized that diisocyanate (DI) exposure could modify gene promoter regions regulating transcription of cytokine mediators and thereby influence expression of DA. A cross-sectional study was designed to investigate the promoter methylation status of candidate genes in DI-exposed workers. Subjects consisted of 131 workers in three groups: 40 cases with DA confirmed by a positive specific inhalation challenge (SIC) (DA+), 41 exposed workers with lower respiratory symptoms and negative SIC (DA-), and 50 asymptomatic exposed workers (AWs). We studied four candidate genes (GSTM1, DUSP22, IFN-γ, and IL-4) for which altered promoter methylation has been previously investigated for relationships with a variety of other environmental exposures. Methylation status was determined using methylation-specific quantitative PCR performed on genomic DNA extracted from whole blood. Results showed that relative methylation of IFN-γ promoter was significantly increased in DA+ in comparison with both comparator groups (DA- and AW), and it exhibited good sensitivity (77.5%) and specificity (80%) for identifying DA workers in a multivariate predictive model after adjusting for type of DI exposure, smoking status, methacholine PC20, and gender. IL-4 promoter was slightly less methylated only in DA+ compared with AW among nonsmoking workers. Both GSTM1 and DUSP22 promoter methylations were found not associated with DA. Our finding suggests that exposure to occupational chemicals could play a heretofore undefined mechanistic role via epigenetic modification of specific genes in the promoter region.

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

OBJECTIVES: 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. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

PTEN as a unique promising therapeutic target for occupational asthma.

The tumor suppressor phosphatase and tensin homologue deleted on chromosome ten (PTEN) dephophorylates phosphatidylinositol 3,4,5-triphosphate (PIP3) and is a key negative regulator of phosphoinositide kinase-3 (PI3K) signaling pathway. PTEN also suppresses cellular motility through mechanisms that may be partially independent of phosphatase activity. PTEN is one of the most commonly lost tumor suppressors in human cancers, and its down-regulation is also implicated in several other diseases including airway inflammatory diseases. There is increasing evidence regarding the protective effects of PTEN on the bronchial asthma which is induced by complex signaling networks. Very recently, as for the occupational asthma (OA) with considerable controversy for its pathobiologic mechanisms, PTEN has been considered as a key molecule which is capable of protecting toluene diisocyanate (TDI)-induced asthma, suggesting that PTEN is located at switching point of various molecular signals in OA. Knowledge of the mechanisms of PTEN regulation/function could direct to the pharmacological manipulation of PTEN. This article reviews the latest knowledge and studies on the roles and mechanisms of PTEN in OA.

Inflammation and functional outcome in diisocyanate-induced asthma after cessation of exposure.

BACKGROUND: The clinical outcome of diisocyanate-induced asthma has been found to be poor despite cessation of exposure. Our aim was to study the outcome of diisocyanate-induced asthma after initiation of inhaled steroid treatment at a mean period of 7 months (range 2-60 months) after cessation of exposure by following up lung function and bronchial inflammation. METHODS: Bronchoscopy was performed on 17 patients 2 days after a positive inhalation challenge test, after which budesonide 1600 mug a day was started. Bronchoscopy, spirometry, and histamine challenge tests were repeated at 6 months and on average 3 years. The results were also compared with those obtained from 15 healthy control subjects. RESULTS: Nonspecific bronchial hyperreactivity diminished significantly (P = 0.006); however, forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) values decreased, with a median yearly reduction of FEV1 of 79 ml. The count of mast cells in bronchial mucosa decreased (P = 0.012) and that of macrophages increased (P = 0.001). Interleukin-4 level in mucosa was during the first year significantly higher than in controls but its level decreased in the follow-up. Interleukin-6, interleukin-15, and tumour necrosis factor alpha messenger-RNA levels were significantly higher in hyperreactive patients than in nonhyperreactive patients at the end of the follow-up. CONCLUSION: Our results indicate that inflammation may persist in diisocyanate-induced asthma despite inhaled steroid medication. However, TH2-type inflammation diminished. Persistent nonspecific bronchial hyperreactivity was associated with proinflammatory acting cytokines produced mainly by macrophages. Considering the poor prognosis of the disease the findings could be utilized to develop the follow-up and treatment of diisocyanate-induced asthma.

Eye and airway symptoms in low occupational exposure to toluene diisocyanate.

OBJECTIVES: Exposure to diisocyanates is a well known occupational hazard. The objective of this study was to determine the possibility of an association between low exposure to toluene diisocyanate (TDI) (airborne isocyanates and biomarkers of isocyanates in plasma and urine) and symptoms of the eyes and upper and lower airways. METHODS: Altogether 136 workers occupationally exposed to TDI and 118 unexposed employees were studied. A physician compiled thorough medical and occupational histories and registered symptoms, total and work-related, of the eyes, nose, and lower airways. The exposure was assessed with personal air measurements and with biomarkers of exposure in plasma and urine. The average exposure in the ambient air at the workplace of the exposed participants was below 1 ppb. RESULTS: Compared with the unexposed group, the exposed workers reported more total symptoms of the eyes and lower airways, as well as nose bleeding. A similar pattern, with even higher odds ratios, was observed for work-related symptoms. However, only eye symptoms proved to be significantly associated with the exposure, notably with all of the exposure measures. The risk was more pronounced for exposure to 2,4-TDI than for exposure to 2,6-TDI. CONCLUSIONS: Even very low exposure to TDI is related to negative health effects on exposed workers. Clear dose-response relationships were observed between three different measures of exposure and symptoms of the eyes.

Rechallenging subjects with occupational asthma due to toluene diisocyanate (TDI), after long-term removal from exposure.

OBJECTIVES: Aims of this study were to define (1) whether toluene diisocyanate (TDI) bronchial hyper-responsiveness persists in subjects with occupational asthma after long-term cessation of exposure; (2) whether evolution of specific bronchial TDI sensitization and symptoms and functional abnormalities of asthma were coincident, and (3) the determinants at the time of diagnosis of patients' outcome. METHODS: Twenty-five nonatopic spray painters with occupational asthma due to TDI were re-examined 58 +/- 7 (46-73) months after removal from exposure. On both examinations, the severity of asthmatic symptoms and the need for antiasthma treatment over the past 12 months were graded and lung function tests, measurement of airway responsiveness to methacholine (PD(20)), circulating total IgE and TDI-HSA specific IgE, skin tests with common inhalant allergens and specific bronchial challenge with TDI were carried out. RESULTS: Seven subjects were still TDI-reactors and 18 lost reactivity to it. All persistent reactors had still asthma and their symptom score, medication score, FEV(1), PD(20) and serum IgE were unchanged between assessments. In the 18 subjects no longer responsive to TDI, 8 had still features of asthma: their symptom and medication score had improved significantly, but FEV(1), PD(20) and serum IgE had not significantly changed; the other ten patients no longer reactors to TDI were also asymptomatic and their PD(20) had become normal. The duration of symptomatic exposure to TDI was the only feature at diagnosis that differentiated patients with persistent TDI airway hyper-responsiveness and asthma from those who were no longer responsive to TDI but still asthmatic and those who were no longer responsive to TDI and no longer asthmatic (4 +/- 1.6; 2.1 +/- 0.8; 0.6 +/- 0.3 years, respectively; p < 0.001). CONCLUSION: our study demonstrates that airway sensitization to TDI and symptoms and functional airway abnormalities of asthma can persist for years after cessation of exposure and may have different outcome. If avoidance of the offending agent takes place within few months after the development of symptoms, remission of asthma and of TDI bronchial hyper-responsiveness can occur, whereas waiting for years makes it too late to cure asthma and, in the end, to reverse specific sensitization.