Inhibitory effects of Schizandrae Fructus on eotaxin secretion in A549 human epithelial cells and eosinophil migration

Abstract 

Eosinophilia have been implicated in a broad range of diseases, most notably allergic conditions (e.g. asthma, rhinitis and atopic dermatitis) and inflammatory diseases. These diseases are characterized by an accumulation of eosinophils in the affected tissue. Defining the mechanisms that control the recruitment of eosinophil is fundamental to understanding how these diseases progress and identifying a novel target for drug therapy. Accordingly, this study was conducted to evaluate the regulatory effect of Schizandrae Fructus (SF) on the expression of eotaxin, an eosinophil-specific chemokine released in respiratory epithelium following allergic stimulation, as well as its effects on eosinophil migration.

To accomplish this, human epithelial lung cells (A549 cell) were stimulated with a combination of TNF-α (100ng/ml) and IL-4 (100ng/ml) for 24h. The cells were then restimulated with TNF-α (100ng/ml) and IL-1β (10ng/ml) to induce the expression of chemokines and adhesion molecules involved in eosinophil chemotaxis for another 24h. Next, the samples were treated with various concentrations of Schizandrae Fructus (SF) (1, 10, 100, 1000μg/ml) or one of the major constituents of SF, schizandrin (0.1, 1, 10, 100μg/ml), after which following inhibition effect assay was performed triplicates in three independence.

The levels of eotaxin in secreted proteins were suppressed significantly by SF (100 and 1000μg/ml, p<0.01) and schizandrin (10 and 100μg/ml, p<0.01). In addition, SF (1, 10, 100 and 1000μg/ml) decreased mRNA expression levels in A549 cells significantly (p<0.01). Eosinophil recruitment to lung epithelial cells was also reduced by SF, which indicates that eotaxin plays a role in eosinophil recruitment. Furthermore, treatment with SF suppressed the expression of another chemokine, IL-8 (0.1 and 1μg/ml SF, p<0.01), as well as intercellular adhesion molecule-1 (10 and 100μg/ml SF, p<0.01) and vascular cell adhesion molecule-1 (0.1 and 1μg/ml SF, p<0.05), which are all related to eosinophil migration. Taken together, these findings indicate that SF may be a desirable medicinal plant for the treatment of allergic diseases.

Abbreviations: ERK, extracellular signal-regulated kinases p42/p44, HOG, p38/MAPK, HPLC, high-performance liquid chromatography, ICAM-1, intercellular adhesion molecule-1, IL-4, interleukin-4, JNK/SAPK, c-Jun N-terminal kinase/stress-activated protein kinase, MAPK, mitogen-activated protein kinases, MTS, [3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt, SF, Schizandrae Fructus, TNF-α, tumor necrosis factor-α, VCAM-1, vascular cell adhesion molecule-1

Keywords: Schizandrae Fructus, Eosinophil migration, Eotaxin, Allergic diseases