Cytokine mRNA profiles for isocyanates with known and unknown potential to induce respiratory sensitization

Identification of contact and respiratory sensitizers according to IL-4 receptor α expression and IL-2 production

Identification of allergenic chemicals is an important occupational safety issue. While several methods exist to identify contact sensitizers, there is currently no validated model to predict the potential of chemicals to act as respiratory sensitizers. Previously, we reported that cytometry analysis of the local immune responses induced in mice dermally exposed to the respiratory sensitizer trimellitic anhydride (TMA 10%) and contact sensitizer dinitrochlorobenzene (DNCB 1%) could identify divergent expression of several immune parameters. The present study confirms, first, that IgE-positive B cells, MHC class II molecules, interleukin (IL)-2, IL-4 and IL-4Rα can differentiate the allergic reactions caused by high doses of strong respiratory (TMA, phthalic anhydride and toluene diisocyanate) and contact sensitizers (DNCB, dinitrofluorobenzene and oxazolone). The second part of the study was designed to test the robustness of these markers when classing the weakly immunogenic chemicals most often encountered. Six respiratory allergens, including TMA (2.5%), five contact allergens, including DNCB (0.25%), and two irritants were compared at doses of equivalent immunogenicity. The results indicated that IL-4Rα and IL-2 can be reliably used to discriminate sensitizers. Respiratory sensitizers induced markedly higher IL-4Rα levels than contact allergens, while irritants had no effect on this parameter. Inversely, contact allergens tended to induce higher percentages of IL-2⁺CD8⁺ cells than respiratory allergens. In contrast, the markers MHC-II, IgE and IL-4 were not able to classify chemicals with low immunogenic potential. In conclusion, IL-4Rα and IL-2 have the potential to be used in classifying a variety of chemical allergens.

Effect of Moringa oleifera Lam. seed extract on toluene diisocyanate-induced immune-mediated inflammatory responses in rats

Moringa oleifera Lam. is a small tree cultivated throughout India. We have investigated the effect of ethanolic extract of seeds of Moringa oleifera (MOEE, an herbal remedy) on the potential prevention of immune-mediated inflammatory responses in toluene diisocyanate (TDI as antigen)-induced asthma in Wistar rats. Rats were divided into five different groups (n = 8/group): Group-I = unsensitized control; Group-II = TDI control/vehicle; Group-III = dexamethasone (DXM) 2.5 mg/kg; and, Groups IV and V = 100 mg/kg and 200 mg/kg body weight [BW] of MOEE, respectively. All rats (except unsensitized controls) were sensitized by intranasal application of 10% TDI to induce airway hypersensitivity. Animals in Groups II-V were given their respective drug treatment per os from 1 wk prior to initiation of sensitization until the day of final provocation with 5% TDI. After this last challenge, all rats were examined for hyperreactivity symptoms and then sacrificed to determine their total and differential leucocytes in blood and bronchoalveolar (BAL) fluid and levels of TNF proportional, variant, IL-4, and IL-6 in their BAL and serum. Homogenates of one lung lobe from each animal were utilized to assess oxidative stress; a separate lobe underwent histologic examination to assess airway inflammatory status. The results suggest that asthmatic symptoms were found in TDI control rats only, while both MOEE- and DXM-treated rats did not manifest any airway abnormality. In MOEE- and DXM-treated rats, neutrophil and eosinophil levels in the blood were decreased significantly; levels of total cells and each different cell in their BAL fluid were markedly decreased as compared to those in TDI controls. TNF alpha, IL-4, and IL-6 were predominant in serum as well as in BAL fluids in TDI controls, but these levels were reduced significantly by MOEE treatment. The antioxidant activity in relation to antiinflammatory activity of the extract and histopathological observations also reflected a protective effect. Based on the above findings and observations, it can be concluded that Moringa oleifera may possess some beneficial properties that act against chemically stimulated immune-mediated inflammatory responses that are characteristic of asthma in the rat.

Gene expression profiling of in vitro cultured macrophages after exposure to the respiratory sensitizer hexamethylene diisocyanate

Occupational exposure to chemicals is one of the main causes of respiratory allergy and asthma. Identification of chemicals that trigger allergic asthma is difficult as underlying processes and specific markers have not yet been clearly defined. Moreover, adequate classification of the respiratory toxicity of chemicals is hampered due to the lack of validated in vivo and in vitro test methods. The study of differential gene expression profiles in appropriate human in vitro cell systems is a promising approach to identify selective markers for respiratory allergy. As alveolar macrophages display important immunological and inflammatory properties in response to foreign substances in the lung, we aimed at gaining more insight in changes of human macrophages transcriptome and to identify selective genetic markers for respiratory sensitization in response to hexamethylene diisocyanate (HDI). In vitro cultures of human THP-1 cells were differentiated into macrophages and exposed to 55 microg/ml HDI for 6 and 10h. Using human oligonucleotide microarrays, changes were observed in the expression of genes that are involved in diverse biological and molecular processes, including detoxification, oxidative stress, cytokine signaling, and apoptosis, which can lead to the development of asthma. These genes are possible markers for respiratory sensitization caused by isocyanates.

Brown Norway rat asthma model of diphenylmethane-4,4'-diisocyanate (MDI): impact of vehicle for topical induction

The development of this Brown Norway (BN) rat asthma model was focused on the duplication of at least some hallmarks of human diisocyanate asthma using the skin as the initial priming route of exposure. Equal total doses of polymeric diphenylmethane-diisocyanate (MDI) were applied to similar surface areas either dissolved in di-n-octyl sebacic acid ester (20%) (SEBA), in acetone:olive oil (20%) (AOO) or undiluted. The elicitation of respiratory allergy utilized four repeated nose-only inhalation challenges of 30 min with 39 mg/m(3) MDI-aerosol approximately every 2 weeks. Emphasis was directed towards the analysis of respiratory responses delayed in onset. Endpoints suggestive of an allergic inflammatory response were examined by bronchoalveolar lavage (BAL) 1 day after the last inhalation challenge and comprised protein, LDH, cytodifferentiation of BAL cells, MCP-1, and some Th1 and Th2 cytokines. MCP-1 and cytokines were comparatively determined in three compartments: BAL fluid, BAL cells, and lung-associated lymph nodes (LALN). In all groups sensitized topically to MDI typical delayed-onset respiratory responses occurred. The lung and LALN weights, BAL-protein and -LDH were significantly increased as compared to the naïve control group challenged identically. There was compelling evidence of a neutrophilic rather than an eosinophilic inflammatory response. The patterns of interleukin (IL) IL-1alpha, TNF-alpha, IFN-gamma, GM-CSF, and IL-4 differed appreciably from one compartment to another and were essentially maximal in BAL cells. In contrast, MCP-1 was increased to the same extent in all compartments measured. Collectively, changes were slightly, although consistently more pronounced when using SEBA as vehicle when compared with the vehicle AOO or undiluted MDI. Notable was a discordance of cytokine profiles and respiratory responses. In conclusion, the priming potency of topically administered MDI and subsequent asthma-like responses following repeated inhalation exposures appear to be dependent on multiple factors, one of them appears to be associated with the type of matrix used to dissolve MDI. This animal model provides a versatile and robust experimental tool to evaluate and assess at least some features of MDI-related asthma.