Eriobotrya japonica Leaf and Its Triterpenes Inhibited Lipopolysaccharide-Induced Cytokines and Inducible Enzyme Production via the Nuclear Factor-kappa B Signaling Pathway in Lung Epithelial Cells

Pulmonary inflammation is a characteristic of many lung diseases. Increased levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and proinflammatory cytokines, such as interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) and IL-8, have been correlated with lung inflammation. In this study, we used lipopolysaccharide (LPS) to induce iNOS, COX-2, and cytokines (TNF-alpha, IL-1 beta, and IL-8) productions in human lung epithelial cells (A-549). Leaf of Eriobotrya japonica (Pi-Pa-Ye, PPY), a traditional Chinese medicine for the treatment of pulmonary inflammatory diseases, was capable of suppressing LPS-induced cytokine productions in a dose-dependent manner. Moreover, the suppression of PPY on the cytokine productions resulted from the inhibition of inhibitory kappa B-alpha phosphorylation and nuclear factor-kappa B (NF-kappa B) activation. Analysis of the anti-inflammatory effects of ursolic acid and oleanolic acid, the triterpene compounds present in PPY, showed that ursolic acid significantly inhibited LPS-induced IL-8 production, NF-kappa B activation, and iNOS mRNA expression, whereas oleanolic acid did not have these effects. In conclusion, our findings suggested the potential mechanisms of PPY and its active component, ursolic acid, in the treatment of pulmonary inflammation.