title: P-glycoprotein promotes epithelial T helper 2-associated cytokine secretion in chronic sinusitis with nasal polyps.
abstract: BACKGROUND
  Sinonasal epithelial cells are recognized as drivers of inflammation in chronic sinusitis with nasal polyps (CRSwNP) through secretion of T helper 2 (Th2)-promoting cytokines. P-glycoprotein (P-gp) is overexpressed in nasal polyps and modulates epithelial cytokine secretion in healthy mucosa. The objective of this study is to determine whether P-gp overactivity promotes Th2-associated cytokine secretion in CRSwNP.
  
  
  METHODS
  Polyp explants (n = 4) and primary epithelial cell cultures (n = 5) were cultivated from patients with CRSwNP. Explant P-gp activity was determined using a calcein assay. In culture, P-gp was quantified by enzyme-linked immunosorbent assay (ELISA) and sensitivity to PSC-833 inhibition was determined using a calcein assay. Lipopolysaccharide (LPS)-stimulated cytokine secretion of interleukin 6 (IL-6), IL-8, IL-25, and granulocyte macrophage colony stimulating factor (GM-CSF) were quantified by ELISA and compared to secretion following P-gp inhibition. Differences in P-gp expression and cytokine secretion were compared using a Mann-Whitney U test. Secretion was correlated with P-gp expression using a Pearson correlation coefficient.
  
  
  RESULTS
  Calcein retention is increased in P-gp inhibited vs uninhibited polyp explants (mean ± standard deviation [SD]; 5.17 ± 1.76 vs 2.55 ± 0.62; p < 0.05) but not in controls, indicating increased nasal polyp P-gp activity. P-gp is sensitive to dose-dependent P-gp inhibition with PSC-833 in vitro. LPS-stimulated secretion of normalized GM-CSF (45.21 ± 41.39) and IL-6 (63.16 ± 36.37) were significantly reduced following P-gp inhibition (8.47 ± 3.28; p < 0.01, and 39.94 ± 31.07; p < 0.05; respectively) and secretion was highly correlated with P-gp expression(r = 0.824, p < 0.05, and r = 0.833, p < 0.05; respectively).
  
  
  CONCLUSIONS
  P-gp overactivity promotes Th2-associated epithelial cytokine secretion in nasal polyps, suggesting a novel mechanism for maintaining chronic inflammation in CRSwNP.
authors.affiliation: Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA.
authors.forename: Benjamin S
authors.initials: BS
authors.lastname: Bleier
authors.forename: Angela L
authors.initials: AL
authors.lastname: Nocera
authors.forename: Hufsa
authors.initials: H
authors.lastname: Iqbal
authors.forename: John D
authors.initials: JD
authors.lastname: Hoang
authors.forename: Ulises
authors.initials: U
authors.lastname: Alvarez
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Feldman
authors.forename: Xue
authors.initials: X
authors.lastname: Han
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002478:Cells, Cultured; D002908:Chronic Disease; D003524:Cyclosporins / Q000494:pharmacology; D016207:Cytokines / Q000378:metabolism; D004847:Epithelial Cells / Q000187:drug effects / Q000276:immunology*; D005452:Fluoresceins / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006801:Humans; D008070:Lipopolysaccharides / Q000276:immunology; D009298:Nasal Polyps / Q000276:immunology*; D061251:Primary Cell Culture; D012852:Sinusitis / Q000276:immunology*; D018418:Th2 Cells / Q000276:immunology*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D003524:Cyclosporins; D016207:Cytokines; D005452:Fluoresceins; D008070:Lipopolysaccharides; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; C070272:valspodar; C007740:fluorexon
keywords: P-glycoprotein; Th2 inflammation; chronic sinusitis with nasal polyps; immunomodulator; nasal epithelium