Anti-inflammatory and anti-remodelling effects of ISU201, a modified form of the extracellular domain of human BST2, in experimental models of asthma: association with inhibition of histone acetylation.

There are few alternatives to glucocorticosteroids for treatment of asthma. We assessed the activity of a novel protein drug designated ISU201, the extracellular domain of the human cell surface protein BST2, stabilised by fusion with the Fc region of IgG, in mouse models of mild chronic asthma and an acute exacerbation of asthma. The ability of ISU201 to suppress airway inflammation and remodelling was compared with that of dexamethasone. Female BALB/c mice were systemically sensitised with ovalbumin, then received controlled low-level challenge with aerosolised ovalbumin for 6 weeks, which induced lesions of mild chronic asthma, and were treated with drugs during the final 2 weeks. Alternatively, sensitised mice received 4 weeks of chronic low-level challenge and were treated 24 and 2 hours before a final single moderate-level challenge, which triggered acute airway inflammation simulating an asthmatic exacerbation. Inflammation and remodelling were quantified, as was the expression of pro-inflammatory cytokines in bronchoalveolar lavage fluid and tissues. To identify cellular targets of ISU201, we assessed the effects of the drug on activated lymphocytes, macrophages and airway epithelial cells. In the model of mild chronic asthma, ISU201 was as effective as dexamethasone in suppressing airway inflammation and most changes of remodelling. In the model of an allergen-induced acute exacerbation of chronic asthma, ISU201 was also an effective anti-inflammatory agent, although it was less active than dexamethasone. The drug acted on multiple cellular targets, suppressing production of pro-inflammatory cytokines by lymphocytes and macrophages. ISU201 significantly reduced acetylation of histone H4 in airway epithelial cells, suggesting at least one potential mechanism of action. We conclude that in these models of asthma, ISU201 is a broad-spectrum inhibitor of both airway inflammation and remodelling. Thus, unlike drugs which target specific mediators, it could potentially be an alternative or an adjunct to glucocorticoids for the treatment of asthma

Development of asthmatic inflammation in mice following early-life exposure to ambient environmental particulates and chronic allergen challenge

Childhood exposure to environmental particulates increases the risk of development of asthma. The underlying mechanisms might include oxidant injury to airway epithelial cells (AEC). We investigated the ability of ambient environmental particulates to contribute to sensitization via the airways, and thus to the pathogenesis of childhood asthma. To do so, we devised a novel model in which weanling BALB/c mice were exposed to both ambient particulate pollutants and ovalbumin for sensitization via the respiratory tract, followed by chronic inhalational challenge with a low mass concentration of the antigen. We also examined whether these particulates caused oxidant injury and activation of AEC in vitro. Furthermore, we assessed the potential benefit of minimizing oxidative stress to AEC through the period of sensitization and challenge by dietary intervention. We found that characteristic features of asthmatic inflammation developed only in animals that received particulates at the same time as respiratory sensitization, and were then chronically challenged with allergen. However, these animals did not develop airway hyper-responsiveness. Ambient particulates induced epithelial injury in vitro, with evidence of oxidative stress and production of both pro-inflammatory cytokines and Th2-promoting cytokines such as IL-33. Treatment of AEC with an antioxidant in vitro inhibited the pro-inflammatory cytokine response to these particulates. Ambient particulates also induced pro-inflammatory cytokine expression following administration to weanling mice. However, early-life dietary supplementation with antioxidants did not prevent the development of an asthmatic inflammatory response in animals that were exposed to particulates, sensitized and challenged. We conclude that injury to airway epithelium by ambient environmental particulates in early life is capable of promoting the development of an asthmatic inflammatory response in sensitized and antigen-challenged mice. These findings are likely to be relevant to the induction of childhood asthma

Immunoreactivity for acetylated histone H4 in nuclei of airway epithelial cells.

<p>(A) Photomicrograph of immunopositive nuclei (brown) in epithelial cells lining the trachea, original magnification ×400. (B) Percent positive cells in the trachea in the model of an allergen-induced acute exacerbation of chronic asthma. OVA-exposed animals treated with vehicle alone are compared to unexposed animals or to animals treated with ISU201 or dexamethasone. Data are mean ± SEM (<i>n</i> = 6 samples per group). Significant differences relative to the naïve group are shown as **(p<0.01); relative to the vehicle-treated group are shown as #(p<0.05).</p

Effects of drug treatment in-S cells.

<p>Values are fold expression relative to medium alone, shown as mean ± SEM (<i>n</i> = 6). Significant differences compared to cells cultured in medium alone are shown as *** (p<0.001), compared to IL-33-treated cells as ^#(p<0.05) and ^###(p<0.001).</p

Effects of drug treatment on expression of cytokine mRNA by AM from the acute exacerbation model.

<p>Values are fold expression relative to naïve animals, shown as mean ± SEM (<i>n</i> = 6). Significant differences compared to naïve animals are shown as ***(p<0.001); compared to the vehicle-treated group as ^#(p<0.05), ^##(p<0.01) and ^###(p<0.001).</p

Models of asthma.

<p>Timelines for sensitisation, inhalational challenges and drug treatment for the models of chronic asthma and an allergen-induced acute exacerbation of asthma.</p

Relative expression of mRNA for IL-13 by primed CD4⁺ T cells co-cultured with MH-S cells.

<p>Cells were either untreated or stimulated with IL-33 in the absence or presence of ISU201 or dexamethasone. Data are mean ± SEM (<i>n</i> = 3 samples per group). Significant differences relative to unstimulated cells are shown as *** (p<0.001); relative to IL-33-stimulated cells in medium alone are shown as ##(p<0.01) and ###(p<0.001).</p

Effects of drug treatment on cytokine concentrations in supernatants of restimulated PBLN cells from the acute exacerbation model.

<p>Values are pg/mL, shown as mean ± SEM (<i>n</i> = 3 samples per group, pooled pairs from 6 animals). Significant differences compared to naïve animals are shown as *(p<0.05), **(p<0.01) and ***(p<0.001); compared to the vehicle-treated group as ^#(p<0.05) and ^##(p<0.01). For technical reasons, sufficient numbers of cells could not be collected from animals treated with 20 mg/kg of ISU201.</p

Airway inflammation in the model of mild chronic asthma.

<p>(A) Intraepithelial eosinophils (B) Inflammatory cells in the lamina propria of the trachea. OVA-exposed animals treated with vehicle alone are compared to unexposed animals or to animals treated with 4 or 20 mg/kg/day of ISU201, or of 1 mg/kg/day dexamethasone. Data are mean ± SEM (<i>n</i> = 6 samples per group). Significant differences relative to the naïve group are shown as **(p<0.01) and ***(p<0.001); relative to the vehicle-treated group are shown as #(p<0.05) and ##(p<0.01).</p

Airway remodelling in the model of mild chronic asthma.

<p>(A) Subepithelial accumulation of collagen (B) Epithelial thickening (C) Mucous cell change. OVA-exposed animals treated with vehicle alone are compared to unexposed animals or to animals treated with ISU201 or dexamethasone. Data are mean ± SEM (<i>n</i> = 6 samples per group) (A,B) or median ± interquartile range (C). Significant differences relative to the naïve group are shown as ***(p<0.001); relative to the vehicle-treated group are shown as #(p<0.05), ##(p<0.01) and ###(p<0.001).</p