Inhalation of toluene diisocyanate vapor induces allergic rhinitis in mice

Supplementation of syringic acid-rich Phrynium pubinerve leaves imparts protection against allergic inflammatory responses by downregulating iNOS, COX-2, and NF-κB expressions

Background

The present study was designed to characterize the role of ethanolic leaf extract of Phrynium pubinerve Blume (EPP) supplement in attenuating allergic inflammation, encouraged by the presence of syringic acid in it, as this phenolic acid is reportedly promising in suppressing serum immunoglobulin E (IgE) and inflammatory cytokine levels.

Materials and methods

HPLC-DAD dereplication analysis was performed to determine the presence of the vital polyphenolic metabolites. The efficacy of EPP against lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 cells was evaluated by measuring its inhibitory effects on NO and ROS/RNS production. The expressions of major inflammation-associated molecules (iNOS, COX-2, NF-κB, IL-6, and TNF-α) in RAW 264.7 cells were assessed through Western blot. Physiological and behavioral changes, BMI, and different biochemical parameters in mice blood serum were investigated in the toxicological assays. Formaldehyde-induced paw edema test in mice was conducted using established animal model. TDI-induced allergic model in mice was carried out to determine different allergy-like symptoms, and differential white blood cell (WBC) counts in blood and bronchoalveolar lavage (BAL) fluid. The intermolecular interaction analysis of the identified major metabolite of EPP with H1R and iNOS was studied by molecular docking.

Results

HPLC-DAD analysis showed the presence of syringic acid (89.19 mg/100 g EPP) and a few other compounds. LPS-induced NO generation was reduced by EPP in a concentration-dependent manner, showing IC₅₀ of 28.20 ± 0.27 μg/mL. EPP exhibited a similar inhibitory effect on ROS/RNS production with IC₅₀ of 29.47 ± 2.19 μg/mL. Western blotting revealed that EPP significantly downregulated the expressions of iNOS, COX-2, NF-κB, IL-6, and TNF-α in RAW 264.7 cells when challenged with LPS. The toxicological assays confirmed the dosage and organ-specific safety of EPP. In the formaldehyde-induced paw edema test, EPP caused a 66.41% reduction in mice paw volume at 500 mg/kg dose. It ameliorated TDI-induced allergy-like symptoms and decreased different inflammatory WBCs in mice's blood and BAL fluid in a dose-dependent manner. Finally, syringic acid demonstrated mentionable intermolecular binding affinity towards H1R (-6.6 Kcal/moL) and iNOS (-6.7 Kcal/moL).

Conclusions

Collectively, considerable scientific reasoning was obtained in favor of the suppressive potential of EPP against allergic inflammatory responses that are proposed to be exerted via the downregulation of iNOS, COX-2, and NF-κB expressions, H1R antagonism and suppression of cytokines, such as IL-6, and TNF-α.

Diisocyanates influence models of atopic dermatitis through direct activation of TRPA1

We recently used EPA databases to identify that isocyanates, most notably toluene diisocyanate (TDI), were the pollutant class with the strongest spatiotemporal and epidemiologic association with atopic dermatitis (AD). Our findings demonstrated that isocyanates like TDI disrupted lipid homeostasis and modeled benefit in commensal bacteria like Roseomonas mucosa through disrupting nitrogen fixation. However, TDI has also been established to activate transient receptor potential ankyrin 1 (TRPA1) in mice and thus could directly contribute to AD through induction of itch, rash, and psychological stress. Using cell culture and mouse models, we now demonstrate that TDI induced skin inflammation in mice as well as calcium influx in human neurons; each of these findings were dependent on TRPA1. Furthermore, TRPA1 blockade synergized with R. mucosa treatment in mice to improve TDI-independent models of AD. Finally, we show that the cellular effects of TRPA1 are related to shifting the balance of the tyrosine metabolites epinephrine and dopamine. This work provides added insight into the potential role, and therapeutic potential, or TRPA1 in the pathogenesis of AD.

Occupational Rhinitis

There is convincing evidence that tight relationships between the upper and lower airways also apply to the workplace context. Most patients with occupational asthma (OA) also suffer from occupational rhinitis (OR), although OR is 2 to 3 times more common than OA. OR most often precedes the development of OA, especially when high-molecular-weight protein agents are involved, and longitudinal cohort studies have confirmed that OR is associated with an increased risk for the development of OA. The level of exposure to sensitizing agents at the workplace is the most important determinant for the development of IgE-mediated sensitization and OR. Atopy is a risk factor for the development of IgE-mediated sensitization only to high-molecular-weight agents. In workers with work-related rhinitis symptoms, documentation of IgE-mediated sensitization to a workplace agent via skin prick testing or serum specific IgE confirms a diagnosis of probable OR, whereas specific nasal provocation testing in the laboratory remains the reference method to establish a definite diagnosis of OR. Complete avoidance of exposure to the causal agent is the most effective therapeutic option for controlling work-related nasal symptoms and preventing the development of OA. If complete elimination of exposure is expected to induce meaningful adverse socioeconomic consequences, reduction of exposure can be considered as an alternative approach, but it is important to consider the individual risk factors for the development of OA to implement a more personalized management of OR.

Astragalus Polysaccharides/Chitosan Microspheres for Nasal Delivery: Preparation, Optimization, Characterization, and Pharmacodynamics

Chitosan (CTS) constitutes a promising area in treatment of nose-related diseases as a nasal drug delivery carrier. Astragalus polysaccharide (APS) significantly attenuates eosinophils and neutrophil-dominant airway inflammation, and it has a potential pharmaceutical application in the treatment of severe asthma. The purpose of this work was to prepare APS/CTS microspheres intended for nasal drug delivery by the spray-drying method. The characteristics of APS/CTS microspheres were evaluated by a scanning electron microscope, Fourier transform infrared spectroscopy, differential scanning calorimetry, and in vitro drug release. The effect of APS/CTS microspheres on rats with allergic rhinitis (AR) was investigated by eosinophil and neutrophil counts in nasal lavage fluid. Results of SEM showed that microspheres were spherical and wrinkled. In vitro release showed that 67.48-93.76% APS was released from APS/CTS microspheres at pH 6.8 within 24 h. The effects showed that APS/CTS microspheres alleviated allergic symptoms and reduced eosinophils infiltration and the expression of interleukin-4 in the nasal mucosa tissue of rats that had no liver and kidney toxicity by hematoxylin-eosin staining observation. In conclusion, these results indicated that APS/CTS microspheres had excellent characteristics for the treatment of AR.

Isolation and Culture of Primary Mouse Middle Ear Epithelial Cells

Epithelial abnormalities underpin the development of the middle ear disease, otitis media (OM). Until now, a well-characterized in vitro model of the middle ear (ME) epithelium that replicates the complex cellular composition of the middle ear has not been available. This chapter describes the development of a novel in vitro model of mouse middle ear epithelial cells (mMECs), cultured at the air-liquid interface (ALI). This system enables recapitulation of the characteristics of the native murine ME epithelium. We demonstrate that mMECs undergo differentiation into the varied cell populations seen within the native middle ear. Overall, our mMEC culture system can help better understand the cell biology of the middle ear and improve our understanding of the pathophysiology of OM. The model also has the potential to serve as a platform for validation of treatments designed to reverse aspects of epithelial remodeling underpinning OM development.

Effects of irradiation with narrowband-ultraviolet B on up-regulation of histamine H1 receptor mRNA and induction of apoptosis in HeLa cells and nasal mucosa of rats

Narrowband-ultraviolet B (NB-UVB) phototherapy is used for the treatment of atopic dermatitis. Previously, we reported that irradiation with 200 mJ/cm² of 310 nm NB-UVB suppressed phorbol-12-myristate-13-acetate (PMA)-induced up-regulation of histamine H₁ receptor (H1R) gene expression without induction of apoptosis in HeLa cells. However, the effect of NB-UVB irradiation on nasal symptoms is still unclear. Here, we show that low dose irradiation with 310 nm NB-UVB alleviates nasal symptoms in toluene 2,4-diisocyanate (TDI)-sensitized allergy model rats. Irradiation with 310 nm NB-UVB suppressed PMA-induced H1R mRNA up-regulation in HeLa cells dose-dependently at doses of 75-200 mJ/cm² and reversibly at a dose of 150 mJ/cm² without induction of apoptosis. While, at doses of more than 200 mJ/cm², irradiation with 310 nm NB-UVB induced apoptosis. Western blot analysis showed that the suppressive effect of NB-UVB irradiation on H1R gene expression was through the inhibition of ERK phosphorylation. In TDI-sensitized rat, intranasal irradiation with 310 nm NB-UVB at an estimated dose of 100 mJ/cm² once a day for three days suppressed TDI-induced sneezes and up-regulation of H1R mRNA in nasal mucosa without induction of apoptosis. These findings suggest that repeated intranasal irradiation with low dose of NB-UVB could be clinically used as phototherapy of AR.

FGFR3-TACC3 is an oncogenic fusion protein in respiratory epithelium

Structural rearrangements of the genome can drive lung tumorigenesis through the generation of fusion genes with oncogenic properties. Advanced genomic approaches have identified the presence of a genetic fusion between fibroblast growth factor receptor 3 (FGFR3) and transforming acidic coiled-coil 3 (TACC3) in non-small cell lung cancer (NSCLC), providing a novel target for FGFR inhibition. To interrogate the functional consequences of the FGFR3-TACC3 fusion in the transformation of lung epithelial cells, we generated a novel transgenic mouse model that expresses FGFR3-TACC3 concomitant with loss of the p53 tumor suppressor gene. Intra-nasal delivery of an Ad5-CMV-Cre virus promoted seromucinous glandular transformation of olfactory cells lining the nasal cavities of FGFR3-TACC3 (LSL-F3T3) mice, which was further accelerated upon loss of p53 (LSL-F3T3/p53). Surprisingly, lung tumors failed to develop in intra-nasally infected LSL-F3T3 and LSL-F3T3/p53 mice. In line with these observations, we demonstrated that intra-nasal delivery of Ad5-CMV-Cre induces widespread Cre-mediated recombination in the olfactory epithelium. Intra-tracheal delivery of Ad5-CMV-Cre into the lungs of LSL-F3T3 and LSL-F3T3/p53 mice however, resulted in the development of lung adenocarcinomas. Taken together, these findings provide in vivo evidence for an oncogenic function of FGFR3-TACC3 in respiratory epithelium.

Potential Inhibitory Influence of miRNA 210 on Regulatory T Cells during Epicutaneous Chemical Sensitization

Toluene diisocyanate (TDI) is a potent low molecular weight chemical sensitizer and a leading cause of chemical-induced occupational asthma. The regulatory potential of microRNAs (miRNAs) has been recognized in a variety of disease states, including allergic disease; however, the roles of miRNAs in chemical sensitization are largely unknown. In a previous work, increased expression of multiple miRNAs during TDI sensitization was observed and several putative mRNA targets identified for these miRNAs were directly related to regulatory T-cell (T_reg) differentiation and function including Foxp3 and Runx3. In this work, we show that miR-210 expression is increased in the mouse draining lymph node (dLN) and T_reg subsets following dermal TDI sensitization. Alterations in dLN mRNA and protein expression of T_reg related genes/putative miR-210 targets (foxp3, runx3, ctla4, and cd25) were observed at multiple time points following TDI exposure and in ex vivo systems. A T_reg suppression assay, including a miR-210 mimic, was utilized to investigate the suppressive ability of T_regs. Cells derived from TDI sensitized mice treated with miR-210 mimic had less expression of miR-210 compared to the acetone control suggesting other factors, such as additional miRNAs, might be involved in the regulation of the functional capabilities of these cells. These novel findings indicate that miR-210 may have an inhibitory role in T_reg function during TDI sensitization. Because the functional roles of miRNAs have not been previously elucidated in a model of chemical sensitization, these data contribute to the understanding of the potential immunologic mechanisms of chemical induced allergic disease.

Blocking TRPA1 in Respiratory Disorders: Does It Hold a Promise?

Transient Receptor Potential Ankyrin 1 (TRPA1) ion channel is expressed abundantly on the C fibers that innervate almost entire respiratory tract starting from oral cavity and oropharynx, conducting airways in the trachea, bronchi, terminal bronchioles, respiratory bronchioles and upto alveolar ducts and alveoli. Functional presence of TRPA1 on non-neuronal cells got recognized recently. TRPA1 plays a well-recognized role of “chemosensor”, detecting presence of exogenous irritants and endogenous pro-inflammatory mediators that are implicated in airway inflammation and sensory symptoms like chronic cough, asthma, chronic obstructive pulmonary disease (COPD), allergic rhinitis and cystic fibrosis. TRPA1 can remain activated chronically due to elevated levels and continued presence of such endogenous ligands and pro-inflammatory mediators. Several selective TRPA1 antagonists have been tested in animal models of respiratory disease and their performance is very promising. Although there is no TRPA1 antagonist in advanced clinical trials or approved on market yet to treat respiratory diseases, however, limited but promising evidences available so far indicate likelihood that targeting TRPA1 may present a new therapy in treatment of respiratory diseases in near future. This review will focus on in vitro, animal and human evidences that strengthen the proposed role of TRPA1 in modulation of specific airway sensory responses and also on preclinical and clinical progress of selected TRPA1 antagonists.

Antihistamines suppress upregulation of histidine decarboxylase gene expression with potencies different from their binding affinities for histamine H1 receptor in toluene 2,4-diisocyanate-sensitized rats

Antihistamines inhibit histamine signaling by blocking histamine H1 receptor (H1R) or suppressing H1R signaling as inverse agonists. The H1R gene is upregulated in patients with pollinosis, and its expression level is correlated with the severity of nasal symptoms. Here, we show that antihistamine suppressed upregulation of histidine decarboxylase (HDC) mRNA expression in patients with pollinosis, and its expression level was correlated with that of H1R mRNA. Certain antihistamines, including mepyramine and diphenhydramine, suppress toluene-2,4-diisocyanate (TDI)-induced upregulation of HDC gene expression and increase HDC activity in TDI-sensitized rats. However, d-chlorpheniramine did not demonstrate any effect. The potencies of antihistamine suppressive effects on HDC mRNA elevation were different from their H1R receptor binding affinities. In TDI-sensitized rats, the potencies of antihistamine inhibitory effects on sneezing in the early phase were related to H1R binding. In contrast, the potencies of their inhibitory effects on sneezing in the late phase were correlated with those of suppressive effects on HDC mRNA elevation. Data suggest that in addition to the antihistaminic and inverse agonistic activities, certain antihistamines possess additional properties unrelated to receptor binding and alleviate nasal symptoms in the late phase by inhibiting synthesis and release of histamine by suppressing HDC gene transcription.

Occupational asthma in a cable manufacturing company

Background:

During the past decade, incidence of asthma has increased, which might have been due to environmental exposures.

Objectives:

Considering the expansion of cable manufacturing industry in Iran, the present study was conducted to evaluate the prevalence of occupational asthma in a cable manufacturing company in Iran as well as its related factors.

Patients and Methods:

This study was conducted on employees of a cable manufacturing company in Yazd, Iran, in 2012. The workers were divided into two groups of exposure (to toluene diisocyanate, polyvinyl chloride, polyethylene or polypropylene) and without exposure. Diagnosis of occupational asthma was made based on the subjects’ medical history, spirometry and peak flowmetry, and its frequency was compared between the two groups.

Results:

The overall prevalence of occupational asthma was 9.7%. This rate was 13.8% in the exposed group. Logistic regression analysis showed that even after adjustment for confounding factors, a significant correlation existed between the frequency of occupational asthma and exposure to the produced dust particles (P < 0.05). In addition, age, work experience, body mass index, cigarette smoking and shift work had significant correlations with the prevalence of occupational asthma (P < 0.05).

Conclusions:

Considering the high prevalence of occupational asthma among cable manufacturing company workers in Iran, this issue needs to be addressed immediately in addition to reduction of exposure among subjects. Reduction in work shift duration, implementation of tobacco control and cessation programs for the personnel, and performing spirometry tests and respiratory examinations in shorter periods may be among effective measures for reducing the incidence of occupational asthma in this industry.

Workers' compensation for occupational respiratory diseases

The respiratory system is one of the most important body systems particularly from the viewpoint of occupational medicine because it is the major route of occupational exposure. In 2013, there were significant changes in the specific criteria for the recognition of occupational diseases, which were established by the Enforcement Decree of the Industrial Accident Compensation Insurance Act (IACIA). In this article, the authors deal with the former criteria, implications of the revision, and changes in the specific criteria in Korea by focusing on the 2013 amendment to the IACIA. Before the 2013 amendment to the IACIA, occupational respiratory disease was not a category because the previous criteria were based on specific hazardous agents and their health effects. Workers as well as clinicians were not familiar with the agent-based criteria. To improve these criteria, a system-based structure was added. Through these changes, in the current criteria, 33 types of agents and 11 types of respiratory diseases are listed under diseases of the respiratory system. In the current criteria, there are no concrete guidelines for evaluating work-relatedness, such as estimating the exposure level, latent period, and detailed examination methods. The results of further studies can support the formulation of detailed criteria.

Toluene diisocyanate (TDI) disposition and co-localization of immune cells in hair follicles

Diisocyanates (dNCOs) are potent chemical allergens utilized in various industries. It has been proposed that skin exposure to dNCOs produces immune sensitization leading to work-related asthma and allergic disease. We examined dNCOs sensitization by using a dermal murine model of toluene diisocyanate (TDI) exposure to characterize the disposition of TDI in the skin, identify the predominant haptenated proteins, and discern the associated antigen uptake by dendritic cells. Ears of BALB/c mice were dosed once with TDI (0.1% or 4% v/v acetone). Ears and draining lymph nodes (DLNs) were excised at selected time points between 1 h and 15 days post-exposure and were processed for histological, immunohistochemical, and proteomic analyses. Monoclonal antibodies specific for TDI-haptenated protein (TDI-hp) and antibodies to various cell markers were utilized with confocal microscopy to determine co-localization patterns. Histopathological changes were observed following exposure in ear tissue of mice dosed with 4% TDI/acetone. Immunohistochemical staining demonstrated TDI-hp localization in the stratum corneum, hair follicles, and sebaceous glands. TDI-hp were co-localized with CD11b(+) (integrin αM/Mac-1), CD207(+) (langerin), and CD103(+) (integrin αE) cells in the hair follicles and in sebaceous glands. TDI-hp were also identified in the DLN 1 h post-exposure. Cytoskeletal and cuticular keratins along with mouse serum albumin were identified as major haptenated species in the skin. The results of this study demonstrate that the stratum corneum, hair follicles, and associated sebaceous glands in mice are dendritic cell accessible reservoirs for TDI-hp and thus identify a mechanism for immune recognition following epicutaneous exposure to TDI.

Does diisocyanate exposure result in neurotoxicity?

CONTEXT

Diisocyanates have been associated with respiratory and dermal sensitization. Limited number of case reports, and a few case studies, media, and other references suggest potential neurotoxic effects from exposures to toluene diisocyanate (TDI), 1,6 hexamethylene diisocyanate (HDI), and methylene diisocyanate (MDI). However, a systematic review of the literature evaluating the causal association on humans does not exist to support this alleged association.

OBJECTIVE

To perform systematic review examining the body of epidemiologic evidence and provide assessment of causal association based on principles of the Sir Austin Bradford Hill criteria or considerations for causal analysis.

METHODS

A comprehensive search of public databases for published abstracts, case reports, cross-sectional surveys, and cohort studies using key search terms was conducted. Additional searches included regulatory reviews, EU IUCLID and EU Risk Assessment databases, and unpublished reports in the International Isocyanate Institute database. An expert panel consisting of physicians, toxicologists, and an epidemiologist critically reviewed accepted papers, providing examination of epidemiologic evidence of each report. Finally, the Hill criteria for causation were applied to the summative analysis of identified reports to estimate probability of causal association.

RESULTS

Twelve papers reporting exposed populations with a variety of neurological symptoms or findings suitable for analysis were identified, including eleven case or case series reports, and one cross-sectional study. Three papers reported on the same population. Each of the papers was limited by paucity of diisocyanate exposure estimates, the presence of confounding exposures to known or suspected neurotoxicants, a lack of objective biological measures of exposure or neurotoxic effects, and lack of relative strength of association measures. Additionally, reported health symptoms and syndromes lacked consistency or specificity. No plausible mechanism of toxicity was found. Application of a predictive mathematical model for determining probability of causal association for neurotoxicity was calculated to be 21%.

CONCLUSION

There is insufficient evidence for a causal association of neurotoxic effects and diisocyanate exposure based on lack of evidence in all categories of the Hill criteria for causality except for temporal association of reported symptoms and alleged exposure. Future reports should attempt to address more rigorous exposure assessment and control for confounding exposures.

Expression kinetics of miRNA involved in dermal toluene 2,4-diisocyanate sensitization

Allergic disease is an important occupational health concern, with work-related asthma and allergic contact dermatitis being the most frequently diagnosed occupational illnesses. Diisocyanates, particularly toluene 2,4-diisocyanate (TDI), have been the leading cause of occupational asthma for many years. Understanding the mechanisms behind allergic disease is critical for treatment and prevention. Recently, the study of post-transcriptional regulation by microRNAs (miRNA) has shed light on mechanisms of allergic disease. The present studies report the expression of miRNA during the sensitization phase of an allergic response to TDI in a murine model. Female BALB/c mice were dermally exposed to TDI (0.1-15% [v/v]) or vehicle. RNA was isolated from superficial parotid lymph nodes at timepoints between 1 h and 15 days post-exposure and then miRNA expression was analyzed using array and real-time quantitative PCR analysis. Consistent changes in miRNA expression were identified for miR-21, miR-22, miR-27b, miR-31, miR-126, miR-155, miR-210, and miR-301a. Following TDI exposure, peak expression was observed by Day 4 for the majority of miRNA evaluated with trends in expression correlated to exposure concentration. Confirmed and predicted targets were identified using Diana-microT, miRanda, miRwalk, and Targetscan algorithms. Evaluation of mRNA expression of cytokine and transcription factor targets suggests that miRNA may have a central role early in TDI sensitization. Understanding the role of these miRNA and their specific mechanism of action in sensitization to TDI may provide pertinent information for the identification of other chemical sensitizers while also contributing to the treatment and prevention of allergic disease.

Evaluation of furfuryl alcohol sensitization potential following dermal and pulmonary exposure: enhancement of airway responsiveness

Furfuryl alcohol is considered by the U.S. Environmental Protection Agency to be a high volume production chemical, with over 1 million pounds produced annually. Due to its high production volume and its numerous industrial and consumer uses, there is considerable potential for work-related exposure, as well as exposure to the general population, through pulmonary, oral, and dermal routes of exposure. Human exposure data report a high incidence of asthma in foundry mold workers exposed to furan resins, suggesting potential immunologic effects. Although furfuryl alcohol was nominated and evaluated for its carcinogenic potential by the National Toxicology Program, studies evaluating its immunotoxicity are lacking. The studies presented here evaluated the immunotoxic potential of furfuryl alcohol following exposure by the dermal and pulmonary routes using a murine model. When tested in a combined irritancy local lymph node assay, furfuryl alcohol was identified to be an irritant and mild sensitizer (EC3 = 25.6%). Pulmonary exposure to 2% furfuryl alcohol resulted in enhanced airway hyperreactivity, eosinophilic infiltration into the lungs, and enhanced cytokine production (IL-4, IL-5, and interferon-γ) by ex vivo stimulated lung-associated draining lymphoid cells. Airway hyperreactivity and eosinophilic lung infiltration were augmented by prior dermal exposure to furfuryl alcohol. These results suggest that furfuryl alcohol may play a role in the development of allergic airway disease and encourage the need for additional investigation.

Environmental isocyanate-induced asthma: morphologic and pathogenetic aspects of an increasing occupational disease

Occupational diseases affect more and more people every year. According to the International Labour Organization (ILO), in 2000 an estimated amount of at least 160 million people became ill as a result of occupational-related hazards or injuries. Globally, occupational deaths, diseases and injuries account for an estimated loss of 4% of the Gross Domestic Product. Important substances that are related to occupational diseases are isocyanates and their products. These substances, which are used in a lot of different industrial processes, are not only toxic and irritant, but also allergenic. Although the exposure to higher concentrations could be monitored and restricted by technical means, very low concentrations are difficult to monitor and may, over time, lead to allergic reactions in some workers, ending in an occupational disease. In order to prevent the people from sickening, the mechanisms underlying the disease, by patho-physiological and genetical means, have to be known and understood so that high risk groups and early signs in the development of an allergic reaction could be detected before the exposure to isocyanates leads to an occupational disease. Therefore, this paper reviews the so far known facts concerning the patho-physiologic appearance and mechanisms of isocyanate-associated toxic reactions and possible genetic involvement that might trigger the allergic reactions.

Production, characterization and utility of a panel of monoclonal antibodies for the detection of toluene diisocyanate haptenated proteins

Diisocyanates (dNCOs) are highly reactive low molecular weight chemicals used in the manufacture of polyurethane products and are the most commonly reported cause of occupational asthma. Mechanistic disease studies and development of biomonitoring and research tools, such as monoclonal antibodies (mAbs) have been hampered by dNCOs' ability to self-polymerize and to cross-link biomolecules. Toluene diisocyanate (TDI)-specific monoclonal antibodies (mAbs), with potential use in immunoassays for exposure and biomarker assessments, were produced and reactivities characterized against mono- and diisocyanate and dithioisocyanate protein conjugates. In general, TDI reactive mAbs displayed stronger recognition of isocyanate haptenated proteins when the NCO was in the ortho position relative to the tolyl group, and were capable of discriminating between isocyanate and isothiocyanate conjugates and between aromatic and aliphatic dNCOs. Preliminary studies using TDI vapor exposed cells suggest potential utility of these mAbs for both research and biomonitoring.

Inhalation of ortho-phthalaldehyde vapor causes respiratory sensitization in mice

Ortho-Phthalaldehyde (OPA) has been approved for high-level sterilization of heat-sensitive medical instruments and is increasingly being used as a replacement in the healthcare industry for glutaraldehyde, a known sensitizer. Numerous case reports have been published indicating workers and patients experiencing respiratory problems, anaphylaxis, skin reactivity, and systemic antibody production. Our laboratory previously demonstrated that OPA is a dermal sensitizer in mice. The goal of the present study was to determine if OPA is a respiratory sensitizer following inhalation exposure. Mice were exposed to OPA vapor and airway and lymph nodes were examined for cytokine gene expression and alterations in lymphocyte populations. Inhalation of OPA for 3 days resulted in a concentration-dependent increase in lymphocyte proliferation, mainly B lymphocytes, in the draining lymph nodes. A secondary challenge of mice with OPA resulted in a dramatic increase in the population of B lymphocytes expressing IgE. Expression of Th2 (IL-4, IL-5, and IL-13) and anti/proinflammatory (IL-10, TNFα, and IL-1β) cytokine genes was upregulated in the lymph nodes and the nasal mucosa. Mice exposed to the higher concentrations of OPA-produced OPA-specific IgG₁ antibodies indicating systemic sensitization. These findings provide evidence that OPA has the potential to cause respiratory sensitization in mice.

Genetics of occupational asthma

PURPOSE OF REVIEW

To discuss gene association studies conducted in workers diagnosed with occupational asthma.

RECENT FINDINGS

Human leukocyte antigen studies conducted in European workers have defined major histocompatibility complex class II alleles and haplotypes associated with diisocyanate asthma. Recently, certain glutathione S-transferase genotypes (e.g. the GSTM1 null genotype) and N-acetyltransferase genotypes associated with slow acetylation phenotypes have been reported to be associated with diisocyanate asthma. Genotype combinations of IL-4 receptor-α and CD14 single nucleotide polymorphisms (SNPs) were significantly associated with diisocyanate asthma, but only in workers exposed to hexamethylene diisocyanate. A recent genome-wide association study (GWAS) conducted in Korea identified several SNPs of the α-T-catenin gene that were significantly associated with diisocyanate asthma.

SUMMARY

Although candidate gene association studies have yet to identify reliable predictors of occupational asthma, future investigations including GWAS studies may identify high-risk genotypes allowing identification of workers at risk.

Immune sensitization to methylene diphenyl diisocyanate (MDI) resulting from skin exposure: albumin as a carrier protein connecting skin exposure to subsequent respiratory responses

Background

Methylene diphenyl diisocyanate (MDI), a reactive chemical used for commercial polyurethane production, is a well-recognized cause of occupational asthma. The major focus of disease prevention efforts to date has been respiratory tract exposure; however, skin exposure may also be an important route for inducing immune sensitization, which may promote subsequent airway inflammatory responses. We developed a murine model to investigate pathogenic mechanisms by which MDI skin exposure might promote subsequent immune responses, including respiratory tract inflammation.

Methods

Mice exposed via the skin to varying doses (0.1-10% w/v) of MDI diluted in acetone/olive oil were subsequently evaluated for MDI immune sensitization. Serum levels of MDI-specific IgG and IgE were measured by enzyme-linked immunosorbant assay (ELISA), while respiratory tract inflammation, induced by intranasal delivery of MDI-mouse albumin conjugates, was evaluated based on bronchoalveolar lavage (BAL). Autologous serum IgG from "skin only" exposed mice was used to detect and guide the purification/identification of skin proteins antigenically modified by MDI exposure in vivo.

Results

Skin exposure to MDI resulted in specific antibody production and promoted subsequent respiratory tract inflammation in animals challenged intranasally with MDI-mouse albumin conjugates. The degree of (secondary) respiratory tract inflammation and eosinophilia depended upon the (primary) skin exposure dose, and was maximal in mice exposed to 1% MDI, but paradoxically limited in mice receiving 10-fold higher doses (e.g. 10% MDI). The major antigenically-modified protein at the local MDI skin exposure site was identified as albumin, and demonstrated biophysical changes consistent with MDI conjugation.

Conclusions

MDI skin exposure can induce MDI-specific immune sensitivity and promote subsequent respiratory tract inflammatory responses and thus, may play an important role in MDI asthma pathogenesis. MDI conjugation and antigenic modification of albumin at local (skin/respiratory tract) exposure sites may represent the common antigenic link connecting skin exposure to subsequent respiratory tract inflammation.

Monoclonal antibodies against toluene diisocyanate haptenated proteins from vapor-exposed mice

Toluene diisocyanate (TDI) is an industrially important polymer cross-linker used in the production of polyurethane. Workplace exposure to TDI and other diisocyanates is reported to be a leading cause of low molecular weight-induced occupational asthma (OA). Currently we have a limited understanding of the pathogenesis of OA. Monoclonal antibodies (MAbs) that recognize TDI bound proteins would be valuable tools/reagents, both in exposure monitoring and in TDI-induced asthma research. We sought to develop toluene diisocyanate (TDI)-specific MAbs for potential use in the development of standardized immunoassays for exposure and biomarker assessments. Mice were exposed 4 h/day for 12 consecutive weekdays to 50 ppb, 2,4;2,6 TDI vapor (80/20 mixture). Splenocytes were isolated 24 h after the last exposure for hybridoma production. Hybridomas were screened in a solid-phase indirect enzyme-linked immunosorbent assay (ELISA) against a 2,4 TDI-human serum albumin (2,4 TDI-HSA) protein conjugate. Three hybridomas producing 2,4 TDI-HSA reactive IgM MAbs were obtained. The properties of these MAbs (isotype and reactivity to various protein-isocyanate conjugate epitopes) were characterized using ELISA, dot blot, and Western blot analyses. Western blot analyses demonstrated that some TDI conjugates form inter- and intra-molecular links, resulting in multimers and a change in the electrophoretic mobility of the conjugate. These antibodies may be useful tools for the isolation of endogenous diisocyanate-modified proteins after natural or experimental exposures and for characterization of the toxicity of specific dNCOs.

Occupational rhinitis and asthma: where do we stand, where do we go?

This review provides an overview of current and emerging issues regarding occupational rhinitis (OR) and occupational asthma (OA), focusing on studies discussing concepts and results that are relevant to both diseases. OA and OR are conditions that affect the upper and lower airways, are characterized by reduced airway caliber and hyperresponsiveness and by inflammation, and are caused by agents present in the workplace. To explain disease expression, research is moving from the T-helper type 1/type 2 cells paradigm to consider the contribution of diverse alternative pathways such as neural inflammation, a dysfunctional epithelial barrier, and autoimmune mechanisms, among others. Objective assessment of OR and OA has been improved and tested for research and, currently, clinical application. Further developments in the field of OR are expected to lead to more generalized clinical applications, following the example of what has been achieved for OA.

Toluene diisocyanate (TDI) induces calcium elevation and interleukine-4 (IL-4) release - early responses upon TDI stimulation

Occupational exposure to toluene diisocyanats (TDI) may cause asthma. In asthma patients, the allergic syndromes correlate cytokine production with the elevation in cytosolic calcium concentration [Ca(2+)](c) of lymphocytes in airway. We previously found TDI induces calcium signaling in neuronal cells. TDI mainly gets into human body via inhalation; therefore this study investigated the possibility of TDI inducing the changes in [Ca(2+)](c) in airway. We used human lung epithelial cell line H1355, human T-cell line Jurkat, and human neuroblastoma SH-SY5Y cells to present the kinds of cells existing in airway. The changes of [Ca(2+)](c) were measured by Fura-2 fluorescent dye. Results show that TDI induced an elevation in [Ca(2+)](c )in those cell lines and two primary isolated cells, bovine adrenal chromaffin cells and human white blood cells. Cytokine release and their gene expressions of Jurkat cells and human white blood cells were measured by ELISA and reverse transcription polymerase chain reaction. TDI acutely promoted the interleukine-4 (IL-4) release significantly in both Jurkat cells and human white blood cells. TDI-induced IL-4 release was suppressed in the presence of 1,2-bis- (O-aminophenoxy)ethane-N,N,N',N'- tetraacetic acid (BAPTA), an intracellular Ca(2+) chelator, in Jurkat cells. In the hand of gene expression, TDI induced an increase in the mRNA level of TNF-alpha and IL-4 in Jurkat cells. We conclude that the release of IL-4 were coupled with the elevation in [Ca(2+)](c) induced by TDI. Further studies are required to clarify the roles of TDI-induced IL-4 secretion in acute inflammation.

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.

Suplatast tosilate inhibits histamine signaling by direct and indirect down-regulation of histamine H1 receptor gene expression through suppression of histidine decarboxylase and IL-4 gene transcriptions

Allergic rhinitis (AR) is an inflammatory disorder typified by symptoms such as sneezing, congestion, and rhinorrhea. Histamine plays important roles in eliciting AR symptoms. Up-regulation of the histamine H(1) receptor (H1R) and histidine decarboxylase (HDC) mRNAs was observed in AR patients. Th2 cytokines are also involved in the pathogenesis of AR. We examined the effect of suplatast tosilate on nasal symptoms, and H1R, HDC, and IL-4 gene expression using toluene-2,4-diisocyanate (TDI)-sensitized rats and HeLa cells expressing endogenous H1R. Provocation with TDI increased nasal symptoms, HDC activity, the histamine content of nasal lavage fluid, and the expression of H1R, HDC, and IL-4 mRNAs in TDI-sensitized rats. Pretreatment with suplatast for 2 wk significantly suppressed TDI-induced nasal symptoms and elevation of H1R, HDC, and IL-4 mRNAs. Suplatast also suppressed HDC activity in the nasal mucosa and the histamine content of the nasal lavage fluid. Bilateral injection of IL-4 into the nasal cavity of normal rats up-regulated H1R mRNA, while intranasal application of histamine up-regulated IL-4 mRNA. Suplatast suppressed IL-4-induced up-regulation of H1R mRNA in HeLa cells. However, it did not inhibit histamine-induced H1R mRNA elevation. These results suggest that suplatast alleviates nasal symptoms by inhibiting histamine signaling in TDI-sensitized rats through the suppression of histamine- and IL-4-induced H1R gene expression by the inhibitions of HDC and IL-4 gene transcriptions, respectively.

Kujin suppresses histamine signaling at the transcriptional level in toluene 2,4-diisocyanate-sensitized rats

Kujin, the dried root of Sophorae flavescensis, has been used in Chinese folklore medicine against allergy. Evaluation of its anti-allergic potential as well as its mechanism of action has rarely been established. We investigated the effect of Kujin on toluene-2,4-diisocyanate (TDI)-induced allergic behavior and related histamine signaling including mRNA levels of histamine H(1) receptor (H1R) and histidine decarboxylase (HDC), H1R and HDC activities, and histamine content in rat nasal mucosa. We also investigated the effect of Kujin on the mRNA levels of helper T cell type 2 (Th2)-cytokine genes closely related to histamine signaling. TDI provocation caused acute allergic symptoms accompanied with up-regulations of H1R and HDC mRNAs and increases in HDC activity, histamine content, and [(3)H]mepyramine binding activity in the nasal mucosa, all of which were significantly suppressed by pretreatment with Kujin for 3 weeks. Kujin also suppressed the TDI-induced IL-4 and IL-5 mRNA elevations. These data suggest that oral administration of Kujin showed anti-allergic activity through suppression of histamine signaling by the inhibition of TDI-induced H1R and HDC mRNA elevations followed by decrease in H1R, HDC protein level, and histamine content in the nasal mucosa of TDI-sensitized rats. Suppression of Th2-cytokine signaling by Kujin also suggests that it could affect the histamine-cytokine network.

Gene expression in nasal lavage from hairdressers exposed to persulphate

OBJECTIVES

Many hairdressers experience work-related symptoms from the airways caused by bleaching powder. This contains persulphates, which could be irritating to the mucous membrane and also may evoke an allergic reaction. However, specific IgE antibodies are difficult to detect. We found earlier that hairdressers with work-related bleaching powder-associated nasal symptoms reacted to persulphate, but that atopics also did and that the mechanism appeared to be similar in the two groups. In this study, we analysed gene expression of cytokines in the nose in order to further investigate the mechanism for work-related bleaching powder-associated nasal symptoms.

METHODS

The study subjects belonged to either hairdressers with work-related bleaching powder-associated nasal symptoms (S; n = 6), hairdressers without work-related bleaching powder-associated symptoms (WS; n = 7) or atopics (A; n = 6). Nasal lavage was performed before and during (up to 4 h after the last challenge) provocation with potassium persulphate. Expression of two genes involved in allergic inflammation [interleukin 5 (IL5) and IL13] and one involved in cell-mediated immunity (interferon-gamma; IFNG) were analysed in nasal lavage with quantitative PCR.

RESULTS

The change of IL5 in the S group differed when compared to the WS group (P = 0.0051), in the A group when compared to the WS group (P = 0.014), but not in the S group when compared to the A group (P = 0.82). The change of IL13 in the A group differed when compared to the S (P = 0.041) and WS (P = 0.014) groups, but no difference was noticed between the S and WS groups (P = 0.30). The relative level of IFNG increased from before challenge to during challenge in the S group (P = 0.031).

CONCLUSIONS

Symptomatic hairdressers showed increased expression of IL5 and IFNG, but not IL13, during challenge. Hairdressers without work-related bleaching powder-associated nasal symptoms showed no markedly changed reaction. Atopics showed increased expression of IL5 and IL13. Thus, this may indicate a difference in the mechanism of symptoms between symptomatic hairdressers and atopics. However, due to the low number of participants, further studies are needed to elucidate the mechanism for persulphate-associated nasal symptoms.

Sho-seiryu-to suppresses histamine signaling at the transcriptional level in TDI-sensitized nasal allergy model rats

BACKGROUND

The therapeutic use of Kampo medicine, Sho-seiryu-to (SST) in allergic disorders is well known. As histamine plays a central role in allergic diseases, it is possible that SST affects the allergy-related histamine signaling. In this study, we investigated the effect of SST on allergy-related histamine signaling in the nasal mucosa of toluene 2, 4-diisocyanate (TDI)-sensitized nasal allergy model rats.

METHODS

Six-week-old male, Brown Norway rats were sensitized for 2 weeks with 10 microl of 10% TDI, and after a 1 week interval, provocation was initiated with the same amount of TDI. SST (0.6g/rat) was given orally 1 hour before TDI treatment began for a period of 3 weeks. Nasal symptoms were scored for 10 minutes immediately after TDI-provocation. The genes expression in nasal mucosa was determined using real-time quantitative RT-PCR.

RESULTS

SST significantly suppressed TDI-induced nasal allergy-like symptoms. TDI provocation showed a significant up-regulation of histamine H(1) receptor (H1R) and histidine decarboxylase (HDC) gene expressions. Prolonged pre-treatment of SST significantly suppressed the mRNA levels of H1R and HDC that was up-regulated by TDI. SST also suppressed TDI-induced interleukin (IL)-4 and IL-5 mRNA elevation. However, SST showed no significant effect for TDI-induced mRNA elevation of IL-13.

CONCLUSIONS

These results demonstrate that SST alleviates nasal symptoms by the inhibition of histamine signaling through suppression of TDI-induced H1R and HDC gene up-regulation. SST also suppresses cytokine signaling through suppression of IL-4 and IL-5 gene expression. Suppression of histamine signaling may be a novel mechanism of SST in preventing allergic diseases.

Transient receptor potential ankyrin 1 mediates toluene diisocyanate-evoked respiratory irritation

Toluene diisocyanate (TDI), a reactive, hazardous irritant, causes respiratory symptoms such as cough, rhinitis, dyspnea, and chest tightness in exposed workers. Although previous animal studies have shown that TDI causes respiratory reflexes that are abolished by desensitization of capsaicin-sensitive sensory nerves, the specific molecular identity of the transducer(s) responsible for sensing this noxious stimulus has, to date, remained elusive. Recent studies have demonstrated that transient receptor potential ankyrin 1 (TRPA1), an ion channel largely restricted to a subset of capsaicin-sensitive sensory nerves, functions as a transducer capable of initiating reflex responses to many reactive chemical stimuli. We therefore hypothesized that TRPA1 is the primary molecular transducer through which TDI causes sensory nerve activation and respiratory reflexes. Consistent with this hypothesis, TDI activated TRPA1, but not the capsaicin-sensitive transient receptor potential vanilloid 1 channel, in heterologous expression systems. TDI also activated a subset of dissociated trigeminal sensory neurons from wild-type but not TRPA1-deficient mice. In vivo, TDI mimicked known TRPA1 agonists by causing a pronounced decrease in breathing rate, indicative of respiratory sensory irritation, and this reflex was abolished in TRPA1-deficient mice. Together, our data suggest that TDI causes sensory nerve activation and airway sensory irritation via the activation of the ion channel, TRPA1.