Progress in the understanding of the pathology of allergic asthma and the potential of fruit proanthocyanidins as modulators of airway inflammation.

Allergic asthma is a chronic inflammatory lung disease characterized by sensitization of the airways, and the development of immunoglobulin E antibodies, to benign antigens. The established pathophysiology of asthma includes recurrent lung epithelial inflammation, excessive mucus production, bronchial smooth muscle hyperreactivity, and chronic lung tissue remodeling, resulting in reversible airflow restriction. Immune cells, including eosinophils and the recently characterized type 2 innate lymphoid cells, infiltrate into the lung tissue as part of the inflammatory response in allergic asthma. It is well established that a diet high in fruits and vegetables results in a reduction of the risk of developing inflammatory diseases. Secondary plant metabolites, such as proanthocyanidins which are found in apples, blackcurrants, boysenberries, cranberries, and grapes, have shown promising results in reducing or preventing allergic asthma airway inflammation. Recent evidence has also highlighted the importance of microbiome-mediated metabolism of plant polyphenols in modulating the immune system. In this review, we will discuss advances in our understanding of the pathophysiology of allergic asthma, including the role of the microbiome in lung immune function, and how proanthocyanidins modulate the airway inflammation. We will highlight the potential of dietary proanthocyanidins to impact on allergic asthma and the immune system.

Blackcurrant anthocyanins modulate CCL11 secretion and suppress allergic airway inflammation.

CCL11, a chemokine, is linked to the early development of airways eosinophilia in allergic asthma. Therefore, CCL11 production is a target for abrogating eosinophilic-driven airway inflammation. Blackcurrants are high in compounds that regulate inflammation, particularly anthocyanins. In this study, we investigated the effect of oral blackcurrant supplementation on allergen-induced eosinophilia and CCL11 production; we also profiled key compounds in blackcurrants that were linked to this effect. Ten milligram per kilogram (total anthocyanins) of a commercially available, anthocyanin-rich New Zealand "Ben Ard" blackcurrant extract ("Currantex 30") attenuated ovalbumin-induced inflammation, eosinophilia (by 52.45 ± 38.50%), and CCL11 production (by 48.55 ± 28.56%) in a mouse model of acute allergic lung inflammation. Ten blackcurrant polyphenolic extracts were also found to suppress CCL11 secretion by stimulated human lung epithelial cells in vitro. Correlation analysis identified potential blackcurrant polyphenolic anthocyanin constituents specifically delphinidins and cyanidins, involved in CCL11 suppression. Our findings show oral supplementation with New Zealand blackcurrant is effective in reducing lung inflammation, and highlight the potential benefit of developing cultivars with specific polyphenolic profiles for the creation of functional foods with desirable biological activity.

Blackcurrant cultivar polyphenolic extracts suppress CCL26 secretion from alveolar epithelial cells.

Eosinophil recruitment to the airways is a characteristic feature of allergic asthma. Eotaxins are potent chemokines that regulate the recruitment of eosinophils to sites of inflammation. Of these, CCL26 is linked to persistent eosinophil recruitment in the later phase of an allergic response. We evaluated the effectiveness of 10 different blackcurrant cultivar polyphenolic extracts in suppressing CCL26 secretion in stimulated human alveolar epithelial cells. Correlation analysis to identify the potential blackcurrant composition constituent(s) involved in CCL26 suppression and the effects of the four major anthocyanins present in blackcurrants to validate results was conducted. All blackcurrant polyphenolic extracts suppressed CCL26 secretion by lung alveolar cells; however, differential efficacy was observed, which was attributed to their cultivar-specific polyphenolic composition profiles. We identified that the ratio of concentrations of delphinidin glycosides to cyanidin glycosides in the blackcurrant cultivars was an important determinant in influencing CCL26 suppression in lung cells. Our findings support the potential use of blackcurrants or blackcurrant-derived foods/ingredients in managing lung inflammation and the development of specific cultivars as functional foods/ingredients with beneficial biological activities.