Investigation of the chemical-induced selective type II (TH2) allergic response in mice: Effect of the length of the sensitizing phase

Exacerbating effects of trimellitic anhydride in ovalbumin-induced asthmatic mice and the gene and protein expressions of TRPA1, TRPV1, TRPV2 in lung tissue

With the increasing morbidity and mortality of asthma, asthma aggravated by environmental pollution has drawn more attention. This study investigated the exacerbating effects of trimellitic anhydride (TMA), a typical pollutant, in ovalbumin (OVA)-induced asthmatic mice and the gene and protein expressions of TRPA1, V1, V2 in lung tissue. Female BALB/c mice were respectively administered for 42 days as follow: sensitized and challenged with OVA, sensitized and challenged with TMA, sensitized with OVA and challenged with OVA plus TMA, as well as sensitized and challenged with OVA plus TMA. 24 h after the last challenge, the changes in airway resistance (RI) and lung dynamic compliance (Cdyn) were tested. The levels of the inflammatory cells in blood and bronchoalveolar lavage fluid (BALF) were determined. The gene and protein expressions of TRPA1, V1, V2 in lung tissue were examined, and levels of interleukin (IL)-4, -13, substance P (SP), prostaglandin D₂ (PGD₂), nerve growth factor (NGF) in BALF and the supernatant of lung homogenate were measured. The results indicated that OVA plus TMA significantly increased the amount of inflammatory cells in blood and BALF, enhanced RI while decreased Cdyn, and aggravated lung injury. Increased gene and protein expressions of TRPA1, V1, V2 in lung tissue, level of IL-4 in the supernatant of lung homogenate, levels of IL-13, SP, PGD₂, NGF in BALF and the supernatant of lung homogenate were observed. It was suggested that exacerbating effects of TMA in OVA-induced asthma might be related to the regulation of TRPA1, V1, V2 and relevant neurokines.

Effect of mouse strain in a model of chemical-induced respiratory allergy

The inhalation of many types of chemicals is a leading cause of allergic respiratory diseases, and effective protocols are needed for the detection of environmental chemical–related respiratory allergies. In our previous studies, we developed a method for detecting environmental chemical–related respiratory allergens by using a long-term sensitization–challenge protocol involving BALB/c mice. In the current study, we sought to improve our model by characterizing strain-associated differences in respiratory allergic reactions to the well-known chemical respiratory allergen glutaraldehyde (GA). According to our protocol, BALB/c, NC/Nga, C3H/HeN, C57BL/6N, and CBA/J mice were sensitized dermally with GA for 3 weeks and then challenged with intratracheal or inhaled GA at 2 weeks after the last sensitization. The day after the final challenge, all mice were euthanized, and total serum IgE levels were assayed. In addition, immunocyte counts, cytokine production, and chemokine levels in the hilar lymph nodes (LNs) and bronchoalveolar lavage fluids (BALF) were also assessed. In conclusion, BALB/c and NC/Nga mice demonstrated markedly increased IgE reactions. Inflammatory cell counts in BALF were increased in the treated groups of all strains, especially BALB/c, NC/Nga, and CBA/J strains. Cytokine levels in LNs were increased in all treated groups except for C3H/HeN and were particularly high in BALB/c and NC/Nga mice. According to our results, we suggest that BALB/c and NC/Nga are highly susceptible to respiratory allergic responses and therefore are good candidates for use in our model for detecting environmental chemical respiratory allergens.

Beneficial autoimmunity at body surfaces - immune surveillance and rapid type 2 immunity regulate tissue homeostasis and cancer

Epithelial cells (ECs) line body surface tissues and provide a physicochemical barrier to the external environment. Frequent microbial and non-microbial challenges such as those imposed by mechanical disruption, injury or exposure to noxious environmental substances including chemicals, carcinogens, ultraviolet-irradiation, or toxins cause activation of ECs with release of cytokines and chemokines as well as alterations in the expression of cell-surface ligands. Such display of epithelial stress is rapidly sensed by tissue-resident immunocytes, which can directly interact with self-moieties on ECs and initiate both local and systemic immune responses. ECs are thus key drivers of immune surveillance at body surface tissues. However, ECs have a propensity to drive type 2 immunity (rather than type 1) upon non-invasive challenge or stress – a type of immunity whose regulation and function still remain enigmatic. Here, we review the induction and possible role of type 2 immunity in epithelial tissues and propose that rapid immune surveillance and type 2 immunity are key regulators of tissue homeostasis and carcinogenesis.

Chemical allergen induced perturbations of the mouse lymph node DNA methylome

Epigenetic regulation of gene expression plays a pivotal role in the orchestration of immune responses and may determine the vigor, quality, or longevity of such responses. Chemical allergens can be divided into two categories: skin sensitizing chemicals associated with allergic contact dermatitis, and chemicals that cause sensitization of the respiratory tract and occupational asthma. In mice, these are characterized by different T helper cell responses. To explore the regulation and maintenance of these divergent responses, mice were exposed to 2,4-dinitrochlorobenzene (DNCB, a contact allergen) or trimellitic anhydride (TMA, a respiratory allergen). DNA from draining lymph nodes was processed for methylated DNA immunoprecipitation followed by hybridization to a whole-genome DNA promoter array. 6319 differently methylated regions (DMRs) were identified following DNCB treatment, whereas 2178 DMRs were measured following TMA treatment, with approximately half of the TMA DMRs common to DNCB. When limited to promoter region-associated DMRs, 637 genes were uniquely associated with DNCB-induced DMRs but only 164 genes were unique to TMA DMRs. Promoter-associated DMRs unique to either DNCB or TMA were generally hypomethylated whereas DMRs common to both allergens tended to be hypermethylated. Pathway analyses highlighted a number of immune-related pathways, including chemokine and cytokine signaling. These data demonstrate that chemical allergen exposure results in characteristic patterns of DNA methylation indicative of epigenetic regulation of the allergic response.

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.