Anti-inflammatory abilities of Imupret ® : Inhibition of IL-8 and human β -defensin 2 induced by LPS and IL-1 β in lung epithelial A549 cells

Background The respiratory epithelium is a major portal of entry for pathogens and applies various defense mechanisms. Recruitment of neutrophils in airway inflammation may account for the generation of interleukin 8 (IL-8), which is also generated by tissue cells after stimulation by endotoxin (LPS) or proinflammatory cytokines. This study was designed to evaluate the effectiveness of the commercial herbal medicinal product (Imupret®, Bionorica AG) in the modulation of airway inflammation. For the production of IL-8 and human β-defensin 2 (hBD-2), LPS and interleukin-1β (IL-1β) activated A549 bronchial epithelial cells were analyzed. Materials and methods A549 cells, which express toll-like receptor 4 (TLR4), were used. The cytotoxicity and antiproliferative effect of Imupret® (50–2000 μg/ml) were investigated (propidium iodide uptake, WST-1 assay). LPS from Pseudomonas aeruginosa (100 μg/ml) or IL-1β (50 ng/ml) were used as stimulating agents. Dexamethasone (10−7 M) served as positive anti-inflammatory control. IL-8 and hBD-2 production were detected in the supernatants of A549 cells after 18 h with commercially available ELISA test kits (Bender MedSystems, CA; Phoenix Pharmaceuticals, CA). Imupret® dissolved in single solvents (bidest H2O, cell culture medium, 70% (v/v) ethanol and DMSO) was investigated at nontoxic concentrations in the range between 0.01 and 100 μg/ml. Results Imupret® (50–2000 μg/ml) in different solvents showed dose-dependent growth inhibitory effect on A549 cells. Comparative studies indicate quantitative differences concerning 50% growth inhibitory (GI50) concentrations ranging between 122–823 μg/ml. Viability of cells was not affected. The growth inhibitory effect of water and DMSO extracts was significantly diminished in LPS-primed cells at concentrations above 100 μg/ml in contrast to medium and ethanol preparations. Production of IL-8 after stimulation by LPS or IL-1β in A549 cells was significantly inhibited by pre-treatment with Imupret®. IL-8 level of LPS-stimulated cells was decreased about 20–40% by Imupret® (1–100 μg/ml ) treatment; however in Il-1β-primed cells 30% (100 μg/ml) and 20% (10 μg/ml) decreases were detected. IL-1β up-regulated level of hBD-2 was inhibited by Imupret® at concentrations between 0.1 and 100 μg/ml. Conclusion Imupret® may help to suppress airway inflammation by inhibiting IL-8 production and down-regulation of hBD-2 (increased level in chronic inflammatory diseases) in epithelial cells.