Inflammatory mechanisms and T-cell function in occupationally related lung diseases with special reference to isocyanates
Prosjekt
- Prosjektnummer
- 911455
- Ansvarlig person
- Lizhi Sun
- Institusjon
- Helse Bergen HF
- Prosjektkategori
- Forskerutdanning - dr.grad
- Helsekategori
- Inflammatory and Immune System
- Forskningsaktivitet
- 4. Detection and Diagnosis
Rapporter
Toluene diisocyanate (TDI) is one of the leading causes of occupational asthma. We compared dermal sensitization producing IgE-mediated pathophysiology in TDI and ovalbumin (OVA) murine models of asthma. Mice were randomly divided into four groups: TDI, acetone olive oil (AOO), OVA and saline (sal). The mice were epicutaneously sensitized and then were challenged intranasally with same reagent once daily.TDI-exposed mice exhibited neutrophil-dominant pulmonary inflammation, instead of the eosinophil-dominant inflammation presented in OVA mice. Similar results were also observed in bronchoalveolar lavage fluid (BALF) differential cell counts. TDI and OVA mice had a significant increased airway hyper-responsiveness when evaluated by Penh, compared to respective controls. Augmented serum levels of IgG1 and IgE antibodies were observed. Moreover, from a large panel of cytokines, both groups displayed elevated serum protein interleukin-5 (IL-5) levels, and the only difference was found in OVA group showing significantly increased IL-1ß protein. In our epicutaneous mouse model, the neutrophil-dominant airway response to TDI differs from the eosinophil-dominant response to OVA, and inhaled allergen challenge will not increase Penh unlike in OVA mice. Our results suggest that dermal sensitization on its own could initiate pathophysiology of altered airway functions questioning the importance of intranasal challenge in TDI-induced bronchial hyperreactivity.
So far, the pathogenic mechanism of TDI-induced asthma is still far from clear. It has been commonly accepted that TDI sensitization involves binding of TDI to carrier molecules. Specific IgE to diisocyanate has been regarded to be helpful in the diagnosis of occupational asthma. Increased immunoglobulin IgG1 was suggested to be associated to TDI exposure and the protein-conjugated TDI can be a useful marker for progress of TDI-asthma.We established a TDI BALB/c mouse model by subcutaneous sensitization and intranasal challenge to investigate the inflammatory and immune responses that occurred in the development of TDI-induced asthma.The Th2 mode was involved since the TDI mice demonstrated Th2-like immune responses with significantly increased serum total IgE, IL-4 and decreased IFN-?. Airway remodeling was initiated in the early phase of the development of the TDI asthma. However, neutrophil-dominant pulmonary inflammation in TDI-induced mouse model of asthma suggested a different inflammatory phenotype from the eosinophil-dominant allergic responses induced by OVA and OVA 323-339.The skin might function as one of most possible initiative site for sensitization, later on airways became hyper-sensitive and asthma occurred.Followed by exposure to TDI, increased airway hypersensitivity was observed when indicated by Penh. It seems that IgG1 may not be ignored as well as IgE in the development of TDI-induced asthma, at least in mouse model of asthma.
Inflammatory and immunological responses to TDI, ovalbumin (OVA) and ovalbumin peptide OVA 323-339 in mouse modelsAmong three major diisocyanates: toluene diisocyanate (TDI), diphenyl diisocyanate (MDI) and hexamethylene diisocyanate (HDI), TDI has been regarded as the leading cause of diisocyanate-induced asthma. The principal feature of TDI-induced asthma is the airway inflammation with influx of neutrophils, lymphocytes and eosinophils. This in turn leads to the variable airway hyper-responsiveness. TDI-induced asthma can share many similar features with allergic asthma, such as increased total and specific IgE serum levels, activated CD4+ T cells, eosinophils and mast cells, increased levels of IL-4 and IL-5 and airway remodeling.
So far, the pathogenic mechanism of TDI-induced asthma is still far from clear. It has been commonly accepted that TDI sensitization involves binding of TDI to carrier molecules. Specific IgE to diisocyanate has been regarded to be helpful in the diagnosis of occupational asthma. Particularly, increased immunoglobulin IgG1 was suggested to be associated to TDI exposure and the protein-conjugated TDI can be a useful marker for progress of TDI-asthma. In the past decades, the reports on the phenotype of immune response to TDI have been quite controversial. Maestrelli et al. reported that increased levels of Th2 cytokines were detected in the airways and bronchial mucosa of TDI asthmatics. However, some authors such as Lummus et al. observed Th1-like response characterized by an increase in the number of neutrophils and the levels of IFN-? and IL-8.
In order to better address those issues, we established a TDI BALB/c mouse model by subcutaneous sensitization and intranasal challenge to investigate the inflammatory and immune responses that occurred in the development of TDI-induced asthma. In this model, the Th2 mode was involved in the murine model of asthma induced by TDI since the TDI mice demonstrated Th2-like immune responses with significantly increased serum total IgE, IL-4 and decreased IFN-?. Airway remodeling was initiated in the early phase of the development of the TDI asthma. However, neutrophil-dominant pulmonary inflammation in TDI-induced mouse model asthma suggested a different inflammatory phenotype from the eosinophil-dominant allergic responses induced by high molecular weight chemicals, such as OVA and OVA 323-339.
There are several different routes of exposure from which the professional workers finally could develop asthma. The skin might function as one of most possible initiative site for sensitization and later on, the final target tissue, airways became hyper-sensitive and asthma occurred. In this context, the improved mouse model by repeated epicutaneous sensitization and intranasal challenge was established. Similar inflammatory and immune responses were triggered as in the mice by subcutaneous sensitization. Furthermore, followed exposure to TDI, increased airway hypersensitivity indicated by Penh using plethysmography was observed. It seems that IgG1 may not be ignored as well as IgE in the development of TDI-induced asthma, at least in mouse model of asthma.
Compared to the response against OVA, the observed lower total IgE production to OVA323-339 stimulation implied OVA 323-339 might not function as OVA in vivo. In addition to the differential in vitro proliferative response, we can come to the conclusion that OVA 323-339 could not be taken as a substitute of OVA neither in vivo nor in vitro due to their differential immune response.
Toluene diisocyanate-induced bronchial hyper-reactivity and neutrophilic inflammation deviates from the eosinophil-dominant response to ovalbuminBackground: Toluene diisocyanate (TDI) is one of the leading causes of occupational asthma in industrialized countries. However, the pathogenesis of TDI-induced asthma still remains poorly understood. Methods: Thirty two mice were randomly divided into four groups (n=8): TDI, acetone olive oil (AOO), ovalbumin (OVA) and saline (sal). On days 0, 7 and 14, the mice were epicutaneously sensitized with 1% TDI, AOO, 0.1% OVA and sal respectively. On days 21, 23 and 25, mice were challenged intranasally with same reagent once daily. On day 26, pulmonary functions were tested for evaluating bronchial hyper-reactivity (Penh). All mice were sacrificed on day 27. Serum TDI- and OVA-specific IgG1, IgG2A and IgE levels were measured by ELISA. Several serum cytokines selected for delayed hypersensitivity profile were analyzed with Multiplex sandwich immunoassay. Results: TDI-exposed mice exhibited peri-bronchial and peri-vascular neutrophil-dominant pulmonary inflammation, instead of the eosinophil-dominant inflammation presented in OVA mice. Similar results were also observed in bronchoalveolar lavage fluid (BALF) differential cell counts. TDI and OVA mice had a significant increased airway hyper-responsiveness when evaluated by Penh, compared to respective controls. Augmented serum level of IgG1 and IgE antibodies were observed in the respective groups. Moreover, both groups displayed elevated serum IL-5 protein levels. Conclusions: In our epicutaneous mouse model, the neutrophil-dominant airway response to TDI differs from the eosinophil-dominant response to OVA. The role of IgE and IL-5 in the development of TDI-induced asthma remains unclear.
OVA 323-339 induced a Th2-like response in the mouse model as did OVA, OVA 323-339 has clearly limited immunogenic potency to activate OVA-sensitized and challenged mice splenocytes, unlike OVA.Ovalbumin (OVA) is widely used in allergy research. OVA peptide 323-339 has been reported to be responsible for 25-35% of isolated BALB/c mouse T cell response to intact OVA. Objectives: An investigation of whether OVA and OVA 323-339 molecules can induce equivalent in vivo and in vitro immune responses was conducted. Methods: Eight-week BALB/c mice were randomly divided into 3 groups: OVA, OVA 323-339 and saline. On days 0, 7, 14, mice were intraperitoneally injected with 25 µg OVA or OVA 323-339 absorbed on 300 µg Alum, or saline; on days 21-23 all groups were challenged intranasally with either 20 µl of 1% OVA, 1% OVA 323-339 or saline. On day 28, after sacrifice, splenocytes were isolated and cultured under stimulus of each allergen or medium. Results: Evaluated by hematoxylin/eosin and major basic protein immunohistochemical stainings, OVA and OVA 323-339 induced similar lung inflammation. Interestingly, significant serum total IgE and OVA-specific IgE were observed in OVA mice when compared to saline control. OVA 323-339 mice showed higher serum OVA-specific IgE, OVA 323-339-specific IgE, IL-4 and lower IFN-? similar to OVA mice. The proliferative response to OVA was found in cultured splenocytes of both OVA and OVA 323-339 mice, while the similar proliferative response to OVA 323-339 was only observed in the splenocytes of OVA 323-339-sensitized and challenged mice. Conclusion: Although OVA 323-339 induced a Th2-like response in the mouse model as did OVA, OVA 323-339 has clearly limited immunogenic potency to activate OVA-sensitized and challenged mice splenocytes, unlike OVA.
Vitenskapelige artikler
Sun L-Z, Elsayed S, Aasen T B, Van Do T, Aardal N P, Florvaag E, Vaali K
Comparison between ovalbumin and ovalbumin peptide 323-339 responses in allergic mice: humoral and cellular aspects.
Scand J Immunol 2010 May;71(5):329-35.
PMID: 20500683 - Inngår i doktorgradsavhandlingen
Doktorgrader
Lizhi Sun
PhD
- Disputert:
- juni 2012
- Hovedveileder:
- Erik Florvaag
eRapport er utarbeidet av Sølvi Lerfald og Reidar Thorstensen, Regionalt kompetansesenter for klinisk forskning, Helse Vest RHF, og videreutvikles av de fire RHF-ene i fellesskap, med støtte fra Helse Vest IKT
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