Suppressive Activity of Quercetin on Periostin Functions In Vitro

Periostin, a 90-kDa extracellular matrix protein, has been attracting attention as a novel biomarker of airway inflammatory diseases such as allergic rhinitis (AR) and asthma. Although oral administration of quercetin to patients with AR can favorably modify the clinical condition of this disease, the influence of quercetin on periostin functions is not well understood. The present study was, therefore, undertaken to examine the influence of quercetin on the production of both periostin and periostin-induced eosinophil chemoattractants from human nasal epithelial cells (HNEpC) in vitro. HNEpC were stimulated with 15.0 ng/ml interleukin (IL)-4 in the absence or presence of quercetin for 72 h. Periostin levels in the culture supernatants were measured using enzyme-linked immunosorbent assay (ELISA). Addition of 4.0 μM quercetin into cell cultures suppressed periostin production from HNEpC that was induced by IL-4 stimulation through inhibitation of signal transducer and activator of transcription 6 (STAT6) activation. We then examined whether quercetin could inhibit production of the periostin-induced eosinophil chemoattractants, regulated on activation, normal T-cell expressed and secreted (RANTES) and eotaxin, from HNEpC. HNEpC were stimulated with 2.0 ng/ml periostin in the absence or presence of quercetin for 72 h. RANTES and eotaxin levels in culture supernatants were examined using ELISA. Treatment of HNEpC with quercetin at a concentration of 4.0 μM suppressed the ability of cells to produce RANTES and eotaxin. This suppression was mediated through suppression of activation of the transcription factor nuclear factor-kappa B (NF-κB) p65, as measured using ELISA, and of chemokine mRNA expression, as measured using reverse transcriptase-polymerase chain reaction (RT-PCR). These results strongly suggest that quercetin suppresses the production of both periostin and periostin-induced eosinophil chemoattractants from HNEpC and results in improvement of the clinical condition of AR.