Fien Devos

Crucial role of transient receptor potential ankyrin 1 and mast cells in induction of nonallergic airway hyperreactivity in mice.

RATIONALE Airway hyperreactivity (AHR) is a key feature of bronchial asthma, and inhalation of irritants may facilitate development of nonallergic AHR. Swimmers exposed to hypochlorite (ClO(-))-containing water show a higher risk of developing AHR. We developed a mouse model in which instillation of ClO(-) before ovalbumin (OVA) induces AHR without bronchial inflammatory cells. OBJECTIVES To investigate the mechanisms of ClO(-)-OVA-induced nonallergic AHR. METHODS The involvement of the transient receptor potential ankyrin (TRPA)1 channel was checked in vivo by the use of TRPA1(-/-) mice and in vitro by Ca(2+) imaging experiments. The role of substance P (SP) was investigated by pretreating animals with the receptor antagonist RP67580, by replacing ClO(-) with SP in vivo, and by immunofluorescent staining of large airways of exposed mice. The role of mast cells was evaluated by exposing mast cell-deficient Kit(Wh)/Kit(Wsh) mice to ClO(-)-OVA with or without mast cell reconstitution. MEASUREMENTS AND MAIN RESULTS ClO(-)-OVA did not induce AHR in TRPA1(-/-) mice, and ClO(-) generates a Ca(2+) influx in TRPA1-transfected cells. Pretreatment with RP67580 reduces ClO(-)-OVA-induced AHR, although no increased SP expression was shown in the airways. SP-OVA exposure resulted in the same AHR as induced by ClO(-)-OVA. Kit(Wsh)/Kit(Wsh) mice did not develop AHR in response to ClO(-)-OVA unless they were reconstituted with bone marrow-derived mast cells. CONCLUSIONS Induction of AHR by exposure to ClO(-)-OVA depends on a neuroimmune interaction that involves TRPA1-dependent stimulation of sensory neurons and mast cell activation.

Neuro-immune interactions in chemical-induced airway hyperreactivity

Asthma may be induced by chemical sensitisers, via mechanisms that are still poorly understood. This type of asthma is characterised by airway hyperreactivity (AHR) and little airway inflammation. Since potent chemical sensitisers, such as toluene-2,4-diisocyanate (TDI), are also sensory irritants, it is suggested that chemical-induced asthma relies on neuro-immune mechanisms. We investigated the involvement of transient receptor potential channels (TRP) A1 and V1, major chemosensors in the airways, and mast cells, known for their ability to communicate with sensory nerves, in chemical-induced AHR. In vitro intracellular calcium imaging and patch-clamp recordings in TRPA1- and TRPV1-expressing Chinese hamster ovarian cells showed that TDI activates murine TRPA1, but not TRPV1. Using an in vivo model, in which an airway challenge with TDI induces AHR in TDI-sensitised C57Bl/6 mice, we demonstrated that AHR does not develop, despite successful sensitisation, in Trpa1 and Trpv1 knockout mice, and wild-type mice pretreated with a TRPA1 blocker or a substance P receptor antagonist. TDI-induced AHR was also abolished in mast cell deficient KitWsh/Wsh mice, and in wild-type mice pretreated with the mast cell stabiliser ketotifen, without changes in immunological parameters. These data demonstrate that TRPA1, TRPV1 and mast cells play an indispensable role in the development of TDI-elicited AHR. Chemical-induced AHR relies on neuro-immune interactions, involving lymphocytes, TRP channels and mast cells http://ow.ly/Z4LtH

B-lymphocytes as Key Players in Chemical-Induced Asthma

T-lymphocytes and B-lymphocytes are key players in allergic asthma, with B-lymphocytes producing antigen-specific immunoglobulins E (IgE). We used a mouse model of chemical-induced asthma and transferred B-lymphocytes from sensitized animals into naïve wild type mice, B-lymphocyte knock-out (B-KO) mice or severe combined immunodeficiency (SCID) mice. On days 1 and 8, BALB/c mice were dermally sensitized with 0.3% toluene diisocyanate (TDI) (20µl/ear). On day 15, mice were euthanized and the auricular lymph nodes isolated. B-lymphocytes (CD19+) were separated from the whole cell suspension and 175,000 cells were injected in the tail vein of naïve wild type, B-KO or SCID mice. Three days later, the mice received a single oropharyngeal challenge with 0.01% TDI (20µl) or vehicle (acetone/olive oil (AOO)) (controls). Airway reactivity to methacholine and total and differential cell counts in the bronchoalveolar lavage (BAL) fluid were measured 24 hours after challenge. B-lymphocytes of AOO or TDI-sensitized mice were characterized for the expression of surface markers and production of cytokines. We found that transfer of B-cells obtained from mice dermally sensitized to toluene diisocyanate (TDI) into naïve wild type mice, B-KO mice or SCID mice led, within three days, to an acute asthma-like phenotype after an airway challenge with TDI. This response was specific and independent of IgE. These B-lymphocytes showed antigen presenting capacities (CD80/CD86 and CD40) and consisted of B effector (Be)2- (IL-4) and Be1-lymphocytes (IFN-γ). The transferred B-lymphocytes were visualized near large airways, 24 hours after TDI challenge. Thus, B-lymphocytes can provoke an asthmatic response without the action of T-lymphocytes and without major involvement of IgE.

Methylisothiazolinone: Dermal and respiratory immune responses in mice

Methylisothiazolinone (MI), a widely used chemical preservative in industrial and household products, and cosmetics, has been associated with allergic contact dermatitis. However, the asthmogenic capacity of MI is currently unknown. In this study, we investigated the capacity of MI to elicit asthma-like responses in a validated mouse model. On days 1 and 8, mice (C57Bl/6 and BALB/c) were dermally treated with MI or vehicle on each ear. On day 15, mice received a single intranasal challenge with MI or vehicle. Immediately after the challenge, the early ventilatory response was measured using a double chamber plethysmograph. One day later, airway hyperreactivity, pulmonary inflammation and immune-related parameters were assessed. Dermal treatment with MI in both C57Bl/6 and BALB/c mice induced increased T- and B-cell proliferation in the auricular lymph nodes, along with IFN-γ production and limited increases in total serum IgE, confirming dermal sensitization. An airway challenge with MI led to an early ventilatory response (decreased breathing frequency), indicative for acute sensory irritation. However, 24h later no allergic respiratory response (no airway hyperreactivity (AHR) nor pulmonary inflammation) was found in either mouse strains. Our study indicates that MI can be classified as a strong dermal sensitizer and irritant, but not an asthmogen after initial dermal sensitization, followed by an airway challenge.

Forced expiration measurements in mouse models of obstructive and restrictive lung diseases

BackgroundPulmonary function measurements are important when studying respiratory disease models. Both resistance and compliance have been used to assess lung function in mice. Yet, it is not always clear how these parameters relate to forced expiration (FE)-related parameters, most commonly used in humans. We aimed to characterize FE measurements in four well-established mouse models of lung diseases.MethodDetailed respiratory mechanics and FE measurements were assessed concurrently in Balb/c mice, using the forced oscillation and negative pressure-driven forced expiration techniques, respectively. Measurements were performed at baseline and following increasing methacholine challenges in control Balb/c mice as well as in four disease models: bleomycin-induced fibrosis, elastase-induced emphysema, LPS-induced acute lung injury and house dust mite-induced asthma.ResultsRespiratory mechanics parameters (airway resistance, tissue damping and tissue elastance) confirmed disease-specific phenotypes either at baseline or following methacholine challenge. Similarly, lung function defects could be detected in each disease model by at least one FE-related parameter (FEV0.1, FEF0.1, FVC, FEV0.1/FVC ratio and PEF) at baseline or during the methacholine provocation assay.ConclusionsFE-derived outcomes in four mouse disease models behaved similarly to changes found in human spirometry. Routine combined lung function assessments could increase the translational utility of mouse models.

Mucosal expression of DEC-205 targeted allergen alleviates an asthmatic phenotype in mice.

Considering the rising incidence of allergic asthma, the symptomatic treatments that are currently applied in most cases are less than ideal. Specific immunotherapy is currently the only treatment that is able to change the course of the disease, but suffers from a long treatment duration. A gene based immunization that elicits the targeting of allergens towards dendritic cells in a steady-state environment might have the potential to amend these difficulties. Here we used a replication deficient adenovirus to induce the mucosal expression of OVA coupled to a single-chain antibody against DEC-205. A single intranasal vaccination was sufficient to mitigate an OVA-dependent asthmatic phenotype in a murine model. Invasive airway measurements demonstrated improved lung function after Ad-Dec-OVA treatment, which was in line with a marked reduction of goblet cell hyperplasia and lung eosinophilia. Furthermore OVA-specific IgE titers and production of type 2 cytokines were significantly reduced. Together, the here presented data demonstrate the feasibility of mucosal expression of DEC-targeted allergens as a treatment of allergic asthma.

IL-13 is a central mediator of chemical-induced airway hyperreactivity in mice

Background While the importance of the Th2 cytokine IL-13 as a central mediator of airway hyperreactivity (AHR) has been described in allergic protein-induced asthma, this has never been investigated in chemical-induced asthma. Objective We examined the importance of IL-13 in a mouse model of chemical-induced AHR, using toluene-2,4-diisocyanate (TDI). Methods In a first set-up, wild type (WT) and IL-13 knockout (KO) C57Bl/6 mice were dermally treated on days 1 and 8 with 1% TDI or vehicle (acetone/olive oil) on both ears. On day 15, mice received an intranasal instillation with 0.1% TDI or vehicle. In a second set-up, WT mice sensitized with 1% TDI or vehicle, received i.v. either anti-IL-13 or control antibody prior to the intranasal challenge. Results TDI-sensitized and TDI-challenged WT mice showed AHR to methacholine, in contrast to TDI-sensitized and TDI-challenged IL-13 KO mice, which also showed lower levels of total serum IgE. TDI-sensitized and TDI-challenged IL-13 KO mice had lower numbers of T-cells in the auricular lymph nodes. TDI-treated WT mice, receiving anti-IL-13, showed no AHR, in contrast to those receiving control antibody, despite increased levels of IgE. Anti-IL-13 treatment in TDI-treated WT mice resulted in lower levels of serum IL-13, but did not induce changes in T- and B-cell numbers, and in the cytokine production profile. Conclusion and clinical relevance We conclude that IL-13 plays a critical role in the effector phase of chemical-induced, immune-mediated AHR. This implicates that anti-IL-13 treatment could have a beneficial effect in patients with this asthma phenotype.

The role of mast cells, interleukin-13 and transient receptor potential channels in a mouse model of chemical-induced airway hyperresponsiveness

Method On days 1 and 8, wild type C57Bl/6 mice, IL-13, TRP (Transient Receptor Potential) A1, TRPV1 and mast cell deficient mice were dermally sensitized with 1% TDI (toluene-2.4-diisocyanate) or vehicle (acetone/olive oil) on both ears. On day 15, the mice received a single intranasal challenge with 0.1% TDI or vehicle. In a second experiment TDI or vehicle sensitized wild type C57Bl/6 mice received an intraperitoneal injection of the NK1R antagonist RP67580 (1μg/μl) prior to the challenge. Airway reactivity to methacholine, lung inflammation, lymphocyte subpopulations in the draining auricular lymph nodes and total serum IgE were assessed 24h after the challenge.