Toluene diisocyanate exposure induces oxidative stress injury in rat lung / 公共卫生与预防医学

Objective To investigate the effect of subchronic inhalation of toluene diisocyanate (TDI) on oxidative stress damage in rat lung tissue. Methods SPF-grade Sprague-Dawley male rats were randomly divided into 4 groups,the rats were placed in a HOPE-MED 8050A movable poison cabinet in a cage.To observe the ultrastructural and histopathology changes of lung tissue in rats.The levels of reduced glutathione (GSH), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) in lung tissue were detected. The ultrastructural and histopathological changes were examined. The expression levels of HO-1 mRNA and protein were detected by Real-time PCR and Western Blot, respectively. Results The body mass, lung tissue mass, and lung organ coefficient of rats in each dose group were lower than those in the control group (P0.05). Conclusion Subchronic inhalation of TDI can cause changes in the pathology and ultrastructure of rat lung tissue, leading to abnormal levels of metabolic enzymes in lung function, thereby inducing oxidative stress damage to the lungs. However, but HO-1 is involved in oxidative stress damage in the lungs induced by TDI.

Toluene diisocyanate induces liver injury and affects HO-1 expression in rats / 公共卫生与预防医学

Objective To investigate the effect of subchronic inhalation of toluene diisocyanate (TDI) on the pathological changes, oxidative stress damage, and HO-1 expression levels in rat liver tissues. Methods Forty healthy 3-week-old SPF-grade Sprague-Dawley male rats were randomly divided into 4 groups (control group, low-dose group, medium-dose group, and high-dose group), each with 10 rats. The rats were placed in a HOPE-MED 8050A movable poison cabinet in a cage. TDI was administered to animals by inhalation at doses of 0, 3.06 mg/m3, 12.25 mg/m3, and 49.00 mg/m3, respectively, for 6 hours a day and 5 days a week, and continuously for 13 weeks. The control group was exposed to fresh air. The effect of TDI on pathological changes, oxidative stress damage and HO-1 expression in rat liver tissues was examined. Results Compared with the control group, the rats in the medium and high-dose TDI-exposed groups exhibited vacuolar changes, hepatocyte swelling, steatosis and other pathological changes. With the increase of the TDI dose, the gap between hepatocytes was widened, mitochondria were swollen and vacuolated, and mitochondrial cristae disappeared. The expression levels of HO-1 gene and protein in the liver tissues of the low, medium, and high dose groups were significantly higher than those in the control group (P<0.05). Compared with the control group, the number of HO-1 positive cells in the low, medium and high dose groups increased and the staining increased gradually, and the difference was statistically significant (P<0.05). Conclusion TDI exposure can cause oxidative damage to rat liver tissues and induce the expression levels of HO-1 gene and protein expression.

Inhibition of TAK1 aggravates airway inflammation by increasing RIPK1 activity and promoting macrophage death in a mouse model of toluene diisocyanate-induced asthma / 南方医科大学学报

OBJECTIVE@#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.@*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.

The role of high mobility group protein 1 in toluene diisocyanate-induced NLPR3 inflammasome activation in human bronchial epithelial cells / 中国职业医学

OBJECTIVE: To investigate the role of high mobility group protein 1(HMGB1) in toluene diisocyanate(TDI) induced nucleotide-binding oligomerization domain like receptor family pyrin domain-containing 3(NLRP3) inflammasome activation in human bronchial epithelial cells(HBECs). METHODS: i) The TDI-human serum albumin(HSA) stimulation experiment: the HBECs in logarithmic growth phase were randomly divided into control group, low-, medium-and high-dose groups that were pretreated with TDI-HSA with the final concentration of 0.00, 40.00, 80.00 and 120.00 mg/L for 12 hours. ii) The HMGB1 expression inhibition experiment: the HBECs in logarithmic growth phase were divided into control group, TDI-HSA group, TDI-HAS+negative-siRNA group, and TDI-HAS+HMGB1-siRNA group. The cells in TDI-HAS+negative-siRNA group and TDI-HAS+HMGB1-siRNA group were infected with HBECs with negative-siRNA lentivirus and HMGB1-siRNA lentivirus, respectively. Cells in these two groups and the TDI-HSA group were treated with 120.00 mg/L of TDI-HSA for 12 hours. The cells in the control group were not treated with TDI-HAS. iii) The expression of HMGB1, NLRP3, apoptosis-associated speck-like protein containing CARD(ASC), pro-caspase-1 and caspase-1 p20 proteins in all groups were detected by Western blot. The number of NLRP3 and caspase-1 inflammasome in TDI-HSA stimulation experiment was observed by immunofluorescence method. RESULTS: i) TDI-HSA stimulation experiment: the relative protein expression of HMGB1 and ASC was higher in HBECs of medium-and high-dose groups than that of control group(all P values were <0.01). The relative protein expression of NLRP3 and casepase-1 p20 and the number of NLRP3-caspase-1 inflammasome were higher in HBECs of 3 dose groups than that of control group(all P values were <0.01). The number of NLRP3-caspase-1 inflammasome in HBECs increased obviously in low-, medium-and high-dose groups as compared to the control group(all P values were <0.05). The number of NLRP3-caspase-1 inflammasome in HBECs increased with the increase of TDI-HSA dose(all P values were <0.01). ii) The HMGB1 expression inhibition experiment: the relative protein expression of HMGB1, NLRP3, ASC, pro caspase-1 and caspase-1 p20 in HBECs were higher in the TDI-HSA group and TDI-HSA + negative-siRNA group than those of the control group(all P values were <0.01). The above indexes of HBECs were lower in the TDI-HAS + HMGB1-siRNA group than those in the TDI-HSA group and TDI-HSA + negative-siRNA group(all P values were <0.01).CONCLUSION: TDI treatment in HBECS can induce the increase of HMGB1 protein expression and activate NLPR3 inflammasome. Inhibition of HMGB1 expression can down-regulate the expression of NLPR3 and its related proteins.

Determination of diphenylmethane diisocyanate in workplace air by HPLC with impregnated filter membrane / 中华劳动卫生职业病杂志

Objective@#To develop a method for determining diphenylmethane diisocyanate in workplace air by HPLC with impregnated filter membrane.@*Methods@#MDI in workplace air reacted with 1- (2-pyridyl) piperazine on impregnated filter membrane to form MDI-urea derivatives, after elution and filtration, it was detected by HPLC-UV.@*Results@#Limit of detection was 0.003 8 μg/ml and limit of quantification was 0.013 μg/ml. Good linearity was obtained in the range of 0.013~2.000 μg/ml (r=0.999 7) . The precision was 3.10%~8.03% (n=6) , while the recovery was 96.3%~101.9%. Asorption capacity of the membrane was 40.8 μg MDI, and could be stored for 14 days in the light-proof environment of 2~8 ℃.@*Conclusion@#The method optimized testing steps for MDI's standard curve, and provided good guidance for determination of MDI in workplace air with impregnated fiter membrane.

Toluene diisocyanate induces inflammatory response and autophagy in human bronchial epithelial cells / 中国职业医学

OBJECTIVE: To investigate the effect of toluene diisocyanate(TDI) on the activation of autophagy and expression of inflammatory cytokines interleukin(IL)-4 and IL-6 in normal human bronchial epithelial cells(16 HBE). METHODS: i) We prepared TDI-human serum albumin(HSA) and determined the mass concentration of TDI in TDI-HSA. ii) The cells were treated with TDI-HSA and HSA at concentrations of 0.00-400.00 mg/L for 12 hours. CCK-8 assay was used to determinate the cell viability, and TDI-HSA and HSA doses were selected for subsequent experiments. iii) The cells were treated with TDI-HSA and HSA at doses of 0.00-120.00 mg/L for 12 hours, and the levels of reactive oxygen species(ROS) in the cells were detected by flow cytometry. The levels of IL-4 and IL-6 in the cell supernatant were measured by enzyme-linked immunosorbent assay. iv) The cells were treated with TDI-HSA at doses of 0.00-120.00 mg/L for 12 hours, and the autophagy activity was observed under transmission electron microscope. Western blot was utilized to detect the expression of Beclin1, microtubule-associated protein 1 light chain(LC3β) and P62. RESULTS: i) The mass concentrations of TDI in 40.00, 80.00 and 120.00 mg/L TDI-HSA groups were 0.44, 0.89 and 1.33 mg/L respectively. ii) The results of CCK-8 showed that TDI-HSA and HSA at doses below 120.00 mg/L did not affect cell viability, and 0.00-120.00 mg/L was selected as the TDI-HSA and HSA treatment doses for subsequent experiments. iii) The level of ROS in cells and the levels of IL-4 and IL-6 in the supernatant of 16 HBE cells in the TDI-HSA group at 40.00, 80.00, and 120.00 mg/L were higher than that in HSA group at the same dose(P<0.01). The level of ROS in cells and the levels of IL-4 and IL-6 in the supernatant of 16 HBE cells increased with the increase of TDI-HSA doses(P<0.01). iv) Transmission electron microscopy showed that the number of autophagic lysosomes in 16 HBE cells increased significantly, and the number of mitochondrial vacuoles increased in 40.00, 80.00, 120.00 mg/L TDI-HSA group compared with 0.00 mg/L group. With the increase of TDI-HSA dose, the relative expression of Beclin1 protein and LC3β-Ⅱ/Ⅰ ratio in 16 HBE cell supernatant increased(P<0.05), and the relative expression of P62 protein decreased(P<0.05). CONCLUSION: TDI-HSA induces increased expression of ROS and inflammatory factors and induces autophagy activation in 16 HBE cells. Autophagy may be an important factor for the development of airway inflammation in TDI-induced occupational asthma.

Serum Periostin Levels: A Potential Serologic Marker for Toluene Diisocyanate-Induced Occupational Asthma

PURPOSE: Toluene diisocyanate (TDI) is a leading cause of occupational asthma (OA). Periostin is a matricellular protein implicated in type 2 immunity-driven asthma. Its pathogenic role in TDI-OA has not been completely elucidated. The present study was performed to investigate the role of periostin in TDI-OA. MATERIALS AND METHODS: Serum periostin levels were measured in subjects with TDI-OA, asymptomatic TDI-exposure controls (AECs), non-occupational asthmatics (NAs), and unexposed normal controls (NCs). To understand the mechanism by which TDI induces periostin production, primary small airway epithelial cells (SAECs) were cultured under stimulation of TDI and neutrophils from asthmatic patients. RESULTS: Fifty-three subjects with TDI-OA, 71 AECs, 67 NAs, and 83 NCs were enrolled. Serum periostin levels were significantly higher in TDI-OA subjects than in AECs (p=0.001), NAs (p < 0.001), and NCs (p < 0.001). In TDI-exposed subjects (TDI-OA and AEC), the PC20 methacholine levels were significantly lower in subjects with a higher periostin level than in those with a lower periostin level. TDI exposure did not increase periostin production directly by SAECs; however, periostin production increased significantly after co-culture with TDI and neutrophils, which was suppressed by an antioxidant. In addition, increased release of TGF-β1 was noted from SAECs when exposed to TDI and neutrophils, which was also suppressed by an antioxidant. CONCLUSION: These results suggest that an increased periostin level may contribute to the progression of airway inflammation to remodeling in TDI-exposed workers. A high serum periostin level is a potential serologic marker of the phenotype of TDI-OA.

Determination of methylenedianiline in urine by high performance liquid chromatography-tandemmass spectrometry / 中华劳动卫生职业病杂志

Objective@#To develop a method for determination of metabolites of diphenylmethane diisocyanate (MDI) in urine, i.e. methylenedianiline (MDA) by high performance liquid chromatography-tandem mass (LC-MS-MS) . @*Methods@#Urine samples were prepared by hydrolyzation with sulfuric acid and extraction by acetonitrile, and then separated on a Shim-pack XR-ODS column, analyzed with high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) . The external solvent standard calibration were tested. @*Results@#The linearity ranges were 0.05~20.00 μg/L, The related coefficients were 0.999 5. The limit of detection was 0.02 μg/L. The rats of recovery were 91.0%~103.4%. The relative standard deviations were between 2.7%~7.3%. @*Conclusion@#The method was sensitive, accurate and suitable for the MDA determination in urine of MDI exposed population.

The changes of ROR-γt,IL-17A and Foxp3 mRNA expression and promoter methylation in TDI-induced mouse asthma / 中国职业医学

OBJECTIVE: To explore the changes of retinoic acid related orphan receptor-γt( ROR-γt),interleukin( IL)-17 A and forkhead / winged helix protein 3( Foxp3) mRNA expression and promoter methylation in the process of asthma induced by toluene-diisocyanate( TDI). METHODS: Specific pathogens free grade healthy male BALB / c mice were randomly assigned into asthma group and control group with 18 animals in each group. In the asthma group,the mice were sensitized with 0. 30% TDI( mass-volume concentration) dropped on the dorsum of both ears( 20 μL / ear) on day 1 and day 8. On day 15,the mice were challenged with 20 μL 0. 01% TDI( mass-volume concentration) by the trachea. The control group mice were sensitized and challenged by the same procedures with the same amount of solvent( acetone / olive oil). The mice were challenged 24 hours,the pathological changes of trachea and lung tissues were observed. The bronchoalveolar lavage fluid( BALF) from each group was collected,and the inflammatory cells in BALF were counted and classified. IL-4and Interferon-γ( IFN-γ) levels in BALF supernatant were measured by enzyme-linked immunosorbent assay. ROR-γt,IL-17 A and Foxp3 mRNA expression in the lung tissue were measured by real-time fluorescent quantitative polymease chain reaction. The degree of ROR-γt,IL-17 A and Foxp3 promoter methylation in lung issue were detected by Mass Array system.RESULTS: The asthmatic group demonstrated the symptoms of acute asthma,such as breathing deeply and fastly,bowing the back,lifting the forelimbs,et al. But the control group had no such symptoms in mice. Hematoxylin-Eosin staining showed obvious inflammatory lesions in the trachea and lung tissue of asthmatic mice. Compared with the control group,the white blood cell count,the neutrophil and eosinophil percentages in BALF,the IL-4,IFN-γ levels in BALF supernatant in asthma group were all significantly increased( P < 0. 01),meanwhile the lymphocyte and monocyte percentages in BALF were reduced( P < 0. 01); ROR-γt mRNA expression was significantly increased( P < 0. 01),and the degree of promoter methylation from sites 3,4,5,6,8,11 and 12 was significantly reduced( P < 0. 05); IL-17 A mRNA expression was significantly increased( P < 0. 01),and the degree of promoter methylation from sites 6 and 7 was significantly reduced( P < 0. 01); Foxp3 mRNA expression was significantly reduced( P < 0. 01),and the degree of promoter methylation from sites 1 and 10 was significantly increased( P < 0. 01). CONCLUSION: Th17 / Treg cell immune imbalance occurs in asthma induced by TDI. ROR-γt,IL-17 A and Foxp3 gene promoter methylation abnormalities may be involved in Th17 / Treg cell immune imbalance.

Therapeutic effects of recombinant human interleukin-1 receptor antagonist on toluene-2, 4-diisocyanate-induced guinea pig allergic rhinitis model / 国际药学研究杂志

Objective To evaluate the effects of the recombinant human interleukin-1 receptor antagonist(rhIL-1ra)on a toluene-2, 4-diisocyanate (TDI)-induced guinea pig allergic rhinitis (AR)model. Methods An AR model was established via sensitization and challenge of two-step procedure using TDI in guinea pigs. Normal animals were treated only with the olive oil(TDI vehicle). Sixty adult guinea pigs were randomly divided into six groups (n=10): normal group, model group (rhIL-1ra vehicle), positive control group (budesonide, 25.6 µg/kg), rhIL-1ra treated groups (rhIL-1ra 50, 100 and 200 µg/kg, respectively). From day 8 after sensitization, animals of all the groups were treated respectively with the agents or vehicle once a day for 14 days. During the observation period, the index of clinic score was recorded for every animal. At day 14 of the dosing, guinea pigs were sacrificed 30 min after the last TDI challenge and observation. Blood samples were taken from the abdominal aorta to prepare the serum for detection of histamine, and the nasal mucosase were dissected for histamine detection and histopathological observation. Results Compared with the guinea pigs in normal group, those in the model group exerted the typical symptoms of AR. It was shown that rhIL-1ra could improve nasal symptoms and cause a significant decrease in the instances of nasal sneezing as well. In addition, rhIL-1ra significantly reduced the concentrations of histamine in the nasal mucosa and IgE in the blood compared with those in the model group (P<0.05). Moreover, the pathological results showed that less edema, vasodilation and inflammatory cell infiltration were found in the nasal mucosa after rhIL-1ra application. Budesonide also showed the above effects with no significant difference compared with rhIL-1ra. Conclusion A guinea pig allergic rhinitis model is successfully induced by TDI. The results indicated that rhIL-1ra(50-200 µg/kg)is effective in improving allergic rhinitis. Our findings indicated that rhIL-1ra might serve as a potential new drug for allergic rhinitis therapy.

Therapeutic effects of recombinant human interleukin-1 receptor antagonist on toluene-2,4-diisocyanate-induced guinea pig allergic rhinitis model / 国际药学研究杂志

Objective To evaluate the effects of the recombinant human interleukin-1 receptor antagonist(rhIL-1ra)on a tol?uene-2,4-diisocyanate(TDI)-induced guinea pig allergic rhinitis (AR)model. Methods An AR model was established via sensiti?zation and challenge of two-step procedure using TDI in guinea pigs. Normal animals were treated only with the olive oil(TDI vehicle). Sixty adult guinea pigs were randomly divided into six groups(n=10):normal group,model group(rhIL-1ra vehicle),positive con?trol group(budesonide,25.6μg/kg),rhIL-1ra treated groups(rhIL-1ra 50,100 and 200μg/kg,respectively). From day 8 after sensi?tization,animals of all the groups were treated respectively with the agents or vehicle once a day for 14 days. During the observation pe?riod,the index of clinic score was recorded for every animal. At day 14 of the dosing,guinea pigs were sacrificed 30 min after the last TDI challenge and observation. Blood samples were taken from the abdominal aorta to prepare the serum for detection of histamine , and the nasal mucosase were dissected for histamine detection and histopathological observation. Results Compared with the guinea pigs in normal group,those in the model group exerted the typical symptoms of AR. It was shown that rhIL-1ra could improve nasal symptoms and cause a significant decrease in the instances of nasal sneezing as well. In addition,rhIL-1ra significantly reduced the concentrations of histamine in the nasal mucosa and IgE in the blood compared with those in the model group(P<0.05). Moreover, the pathological results showed that less edema,vasodilation and inflammatory cell infiltration were found in the nasal mucosa after rhIL-1ra application. Budesonide also showed the above effects with no significant difference compared with rhIL-1ra. Conclusion A guinea pig allergic rhinitis model is successfully induced by TDI. The results indicated that rhIL-1ra(50-200μg/kg)is effective in im?proving allergic rhinitis. Our findings indicated that rhIL-1ra might serve as a potential new drug for allergic rhinitis therapy.

Analysis of adverse events with use of orthodontic sequential aligners as reported in the manufacturer and user facility device experience database.

Background: Sequential aligners (SAs) introduced about a decade ago, changed the practice of orthodontics as we knew it but the adverse events and reactions (AER) associated with SA is not known. The Food and Drug Administration’s Manufacturer and User Facility Device Experience (MAUDE) database is a reliable database that has AERs reported. The manuscript attempts to review the AER associated with SA using the MAUDE database. Materials and Methods: The authors downloaded and reviewed the SA‑related AER from MAUDE for a period of 5 years. In‑depth analysis of the site and nature of intraoral and extraoral AERs were performed. We attempted to calculate the probability of pathologies being directly related to SA use, using Bayes’ theorem. Results: In the study period of 5 years, 175 cases of AER registered with MAUDE database owing to use of SA. Of the 175 cases, 129 (73.71%) instances were mandatory reports filed by the manufacturer. Of all AERs, 32 (18.29%) cases had been diagnosed/suspected to have an allergic reaction, 20 (11.43%) of them with anaphylactic reaction and 4 (2.29%) of them with angioedema. Lesions involving tongue, throat, and lip such as soreness, inflammation, and hives were more commonly reported. In addition, 12 cases (6.86%) reported of nausea, 11 (6.29%) of gastrointestinal issues (stomach upset, diarrhea, and vomiting), 13 (7.43%) of neuromuscular issues (muscle cramps, spasm, and pain), 13 (7.43%) of cough, 10 (5.71%) of persistent headache, 3 (1.71%) of fever, and 12 (6.86%) of cardiac‑related issues were identified. Conclusions: The AERs associated with SA has been described. Though the MAUDE database is not an exact, wholesome and reliable source to identify the potential AER, currently, it is the only available source of AERs associated with SA use. The nature of AERs with the use of SA and its potential pathogenesis and implications has been discussed.

Effect of Ipomea carnea Jacq. flowers on hematological changes in toluene diisocyanate-induced inflammation in Wistar rats / 中国天然药物

AIM@#To investigate the active chloroform fraction of the ethanol extract of Ipomoea carnea flowers on hematological changes in toluene diisocyanate-induced inflammation in Wistar rats.@*METHOD@#Except for the control group, all of the rats were sensitized with intranasal application of 5 μL of 10% toluene diisocyanate (TDI) for 7 days. One week after second sensitization, all of the rats were provoked with 5 μL of 5% TDI to induce airway hypersensitivity. After the last challenge, blood and bronchoalvelor lavage (BAL) fluid were collected and subjected to total and differential leucocytes count. Flash chromatography was performed on the most active chloroform fraction to isolate an individual component.@*RESULTS@#Treatment with the ethanolic extract and its chloroform fraction at an oral dose of 200 mg·kg⁻¹ showed a significant decrease in circulating neutrophil and eosinophil in blood and BAL as compared with standard dexamethasone (DEXA). The structure of the compound obtained from chloroform fraction of Ipomea carnea was elucidated as stigmast-5, 22-dien-3β-ol on the basis of spectral data analysis.@*CONCLUSION@#The chloroform fraction was found to be more effective to suppress airway hyper reactivity symptoms, and decreased count of both total and differential inflammatory cells.

IL-4 and IL-5 Secretions Predominate in the Airways of Wistar Rats Exposed to Toluene Diisocyanate Vapor / 예방의학회지

OBJECTIVES: We established a Wistar rat model of asthma caused by toluene diisocyanate (TDI) exposure, and investigated the relationship between TDI exposure concentrations and respiratory hypersensitivity, airway inflammation, and cytokine secretions in animals, to better understand the mechanism of TDI induced occupational asthma. METHODS: Wistar rats were exposed to two different concentrations of TDI vapor four hours a day for five consecutive days. Bronchoalveolar lavage (BAL) was performed, and differential leucocytes from the BAL fluid were analyzed. Lung histopathological examination was carried out to investigate the inflammatory status in the airways. Production of cytokines interleukin (IL)-4 and IL-5 productions in the BAL fluid in vivo was determined with enzyme-linked immunosorbent assay kits. RESULTS: The TDI-exposed rats exhibited greater airway hypersensitivity symptoms than the control rats. The BAL differential cell count and lung histopathological examination demonstrated that inflammation reactions were present in both the central and peripheral airways, characterized with marked infiltration of eosinophils in the TDI-exposed rats. The cytokine assay showed that IL-4 and IL-5 were predominantly produced in the BAL fluid in vivo. CONCLUSIONS: These findings imply that TDI exposure concentrations may greatly affect the occurrence and extent of inflammatory events and that Th2 type cytokines may play an important role in the immunopathogenesis of TDI-induced occupational respiratory hypersensitivity.

Biomarkers Predicting Isocyanate-Induced Asthma

Three diisocyanates can cause occupational asthma (OA): toluene diisocyanate (TDI), 4,4 diphenylmethane diisocyanate (MDI), and 1,6-hexamethylene diisocyanate (HDI). We analyzed potential biomarkers of isocyanate-induced OA, based on investigated immunologic, genetic, neurogenic, and protein markers, because there is no serological testing method. The prevalence of serum IgG to cytokeratin (CK)18 and CK19 in TDI-OA was significantly higher than in controls, although the prevalence of these antibodies was too low for them to be used as biomarkers. Another candidate biomarker was serum IgG to tissue transglutaminase (tTG), because the prevalence of serum specific IgG to tTG was significantly higher in patients with TDI-OA than in controls. The human leukocyte antigen (HLA) DRB1*1501-DQB1*0602-DPB1*0501 haplotype may be used as a genetic marker for TDI-OA in Koreans via enhanced specific IgE sensitization in exposed subjects. The genetic polymorphisms of catenin alpha 3, alpha-T catenin (CTNNA3) were significantly associated with TDI-OA. Additionally, examining the neurokinin 2 receptor (NK2R) 7853G>A and 11424 G>A polymorphisms, the NK2R 7853GG genotype had higher serum vascular endothelial growth factor (VEGF) levels than the GA or AA genotypes among Korean workers exposed to TDI. To identify new serologic markers using a proteomic approach, differentially expressed proteins between subjects with MDI-OA and asymptomatic exposed controls in a Korean population showed that the optimal serum cutoff levels were 69.8 ng/mL for ferritin and 2.5 microg/mL for transferrin. When these two parameters were combined, the sensitivity was 71.4% and the specificity was 85.7%. The serum cytokine matrix metalloproteinase-9 (MMP-9) level is a useful biomarker for identifying cases of TDI-OA among exposed workers. Despite these possible biomarkers, more effort should be focused on developing early diagnostic biomarkers using a comprehensive approach based on the pathogenic mechanisms of isocyanate-induced OA.

Antiallergic activity of Aristolochia bracteolata Lank in animal model.

Antiallergic activity of Aristolochia bracteolata was evaluated by using compound 48/80 induced anaphylaxis, dermatitis rhinitis and pruritis, as a preclinical model for acute phase of hypersensitivity reactions. The late phase hypersensitivity was evidenced by considering toluidine diisocyanate induced volume of bronchoalveolar fluid secretion and its inhibition. The possible antiallergic mechanism was evaluated by using compound 48/80 induced mast cell activation and estimated serum nitric oxide (NO), rat peritoneal fluid NO, bronchoalveolar fluid NO and blood histamine levels. The present study implied that the chloroform extract of Aristolochia bracteolata had potent and significant inhibitory effect on compound 48/80 induced pruritis and dermatitis activity in Swiss albino mice. It showed significant effect in toluidine diisocyanate induced rhinitis in swiss albino mice. Mast cell membrane stabilization activity was also observed in compound 48/80 induced mast cell activation. A significant reduction was observed in serum nitrate levels, rat peritoneal fluid nitrate levels and BAL nitrate levels. The extract was also found to possess significant inhibitory effect on blood histamine levels. It could be concluded that chloroform extract of A. bracteata possess potent antiallergic activity, possibly through mast cell membrane stabilization, inhibiting NO and histamine pathway.

Acute and Chronic Changes of Vascular Endothelial Growth Factor (VEGF)in Induced Sputum of Toluene Diisocyanate (TDI)-induced Asthma Patients

Vascular endothelial growth factor (VEGF) is a multi-functional cytokine involved in inflammation, repair and angiogenesis in asthmatic airway. This study aimed to evaluate the role of VEGF in immediate bronchoconstriction induced by TDI inhalation, and in chronic TDI-asthma patients. 11 newly diagnosed TDI-asthma patients (group I), 12 chronic TDI-asthma patients with persistent asthma symptoms followed for >4 yr and 15 unexposed healthy controls were enrolled. In group I, induced sputum and serum were collected before and 7 hr after placebo- and TDI-bronchoprovocation test (BPT). In group II, induced sputum and serum were collected every 2 yr. VEGF levels were measured by ELISA. There were no significant differences in sputum and serum VEGF levels between patients and controls. Before and after placebo and TDI-BPT, no significant changes were noted in sputum and serum VEGF levels of group I. In group II patients, sputum VEGF showed variable changes at 1-yr, then decreased significantly at 2-yr (p<0.05), while serum VEGF showed variable changes at 2-yr, which decreased significantly at 4-yr (p<0.05). These results suggest that VEGF may play a minor role in immediate bronchoconstriction after TDI-BPT. In chronic TDI-asthma, VEGF may be involved to 2 yr after the diagnosis and the contribution may decrease after then.

A Murine Model of Toluene Diisocyanate-induced Contact Hypersensitivity

BACKGROUND: Toluene diisocyanate (TDI) can cause contact allergy and occupational asthma, but the mechanism underlying sensitization to this chemical compound remains controversal. Also the correlation of mast cell with contact hypersensitivity (CHS) and the role of mast cell in the TDI-induced CHS is unknown. This issue was investigated by administrating TDI on the skin of genetically mast cell-deficient WBB6F1/J-Kit(W)/ Kit(W-v) (W/W(V)) and congenic normal WBB6F1/J-Kit +/+ (+/+) mice. METHODS: To development of animal model of TDI-induced CHS and to investigate the correlation of mast cell with CHS and the role of mast cell in the TDI-induced CHS, W/W(V) and +/+ mice were sensitized with TDI on the back skin at day 1 and day 8, and then challenged with 1% TDI on the ear at day 15. At 1, 2, 4, 8, and 24 hours after 1% TDI challenge, the ear thicknesses were measured. It was investigated the histologic changes of dermis in the ear of W/W(V) and +/+ mice at 24 hours after 1% TDI challenge. RESULTS: TDI induced a significant ear swelling response in W/W(V) and +/+ mice. TDI induced the significant infiltrations of polymorphonuclear leukocytes and eosinophils in W/W(V) and +/+ mice, but not of mast cells in normal mice. And TDI increased a characteristic extent of mast cell degranulation in normal mice. There were no significant differences in the ear swelling and the infiltrations of polymorphonuclear leukocytes and eosinophils of normal versus W/W(V) mice, either at baseline or after TDI-induced CHS. CONCLUSION: From the above results, TDI can be used as a murine CHS model, and the mast cells may not be essential in TDI-induced CHS.

A Murine Model of Toluene Diisocyanate-induced Contact Hypersensitivity

BACKGROUND: Toluene diisocyanate (TDI) can cause contact allergy and occupational asthma, but the mechanism underlying sensitization to this chemical compound remains controversal. Also the correlation of mast cell with contact hypersensitivity (CHS) and the role of mast cell in the TDI-induced CHS is unknown. This issue was investigated by administrating TDI on the skin of genetically mast cell-deficient WBB6F1/J-Kit(W)/ Kit(W-v) (W/W(V)) and congenic normal WBB6F1/J-Kit +/+ (+/+) mice. METHODS: To development of animal model of TDI-induced CHS and to investigate the correlation of mast cell with CHS and the role of mast cell in the TDI-induced CHS, W/W(V) and +/+ mice were sensitized with TDI on the back skin at day 1 and day 8, and then challenged with 1% TDI on the ear at day 15. At 1, 2, 4, 8, and 24 hours after 1% TDI challenge, the ear thicknesses were measured. It was investigated the histologic changes of dermis in the ear of W/W(V) and +/+ mice at 24 hours after 1% TDI challenge. RESULTS: TDI induced a significant ear swelling response in W/W(V) and +/+ mice. TDI induced the significant infiltrations of polymorphonuclear leukocytes and eosinophils in W/W(V) and +/+ mice, but not of mast cells in normal mice. And TDI increased a characteristic extent of mast cell degranulation in normal mice. There were no significant differences in the ear swelling and the infiltrations of polymorphonuclear leukocytes and eosinophils of normal versus W/W(V) mice, either at baseline or after TDI-induced CHS. CONCLUSION: From the above results, TDI can be used as a murine CHS model, and the mast cells may not be essential in TDI-induced CHS.

Review of the occupational exposure to isocyanates: Mechanisms of action

Polyurethanes are useful polymers in a large variety of technical and consumer products that are generally made from diisocyanates and polyols or similar compounds. Toluene diisocyanate (TDI), 4,4'-methylenediphenyl diisocyanate (MDI) and 1,6'-hexamethylene diisocyanate (HDI) are useful for polyurethane products. Isocyanates are reactive chemicals that can be handled without problems in manufacturing or technical environments. In general, consumers may only have contact with these chemicals on rare occasions. The objective of this study was to review the mechanisms of action of inhalation of isocyanates. This paper describes, in summary, the potential occupational exposure to isocyanates, the chemistry and reactivity of isocyanates, the results from genotoxicity studies, investigative toxicity studies, metabolism and results from epidemiology studies on isocyanate-exposed workers. The overall conclusion is that because humans are not exposed to high levels of respiratory isocyanate particles, concerns over the possible development of lung tumors should not be relevant. There are many mechanisms of action induced by isocyanates, but those entities are unclear. This is because these mechanisms act simultaneously and are complex.