title: P-glycoprotein functions as an immunomodulator in healthy human primary nasal epithelial cells.
abstract: BACKGROUND
  P-glycoprotein (P-gp) is an adenosine triphosphate (ATP)-dependent efflux pump that confers chemotherapeutic resistance in cancer cells. Recent studies suggest that P-gp may also function as an immunomodulator through regulation of cytokine transport. Sinonasal epithelial cells have been recognized as drivers of local innate and adaptive immunity and are known to overexpress P-gp in the setting of inflammation. The objective of this study is to therefore determine whether P-gp participates in the regulation of cytokine secretion in sinonasal epithelial cells.
  
  
  METHODS
  Primary nasal epithelial cell cultures (PNECCs) were cultivated from 5 healthy patients. Membranous P-gp was quantified through quantitative fluorescent immunohistochemistry (Q-FIHC) and confirmed by enzyme-linked immunosorbent assay (ELISA). Sensitivity to inhibition was determined using a rhodamine 123 accumulation assay. Baseline and lipopolysaccharide (LPS)-stimulated cytokine secretion of interleukin 6 (IL-6), IL-8, granulocyte macrophage colony stimulating factor (GM-CSF), and thymic stromal lymphopoietin (TSLP) were quantified by ELISA and compared to LPS stimulated secretion in the setting of P-gp-specific inhibition. Differences in P-gp expression and cytokine secretion were compared using 2-tailed Student t tests with post hoc testing using the Bonferroni procedure.
  
  
  RESULTS
  Membranous P-gp is detectable in PNECCs and upregulated following LPS exposure. P-gp is sensitive to inhibition by both PSC 833 and verapamil in a dose-dependent fashion. LPS stimulated secretion of normalized IL-6 (mean, 95% confidence interval [CI]) (79.67, 42.26-117.07), GM-CSF (39.92, 7.90-71.94), and TSLP (6.65, 5.35-7.96) was significantly reduced following P-gp inhibition (37.60, 11.54-63.65, p = 0.023; 7.64, 2.25-13.03, p = 0.044; and 5.13, 4.44-5.82, p = 0.038; respectively).
  
  
  CONCLUSIONS
  P-gp is functionally active in PNECCs. P-gp participates in modulation of epithelial secretion of LPS stimulated IL-6, GM-CSF, and TSLP.
authors.affiliation: Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA. benjamin_bleier@meei.harvard.edu
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: 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*; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000378:metabolism*; D005456:Fluorescent Dyes; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000378:metabolism; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D009296:Nasal Cavity / Q000378:metabolism*; D020112:Rhodamine 123; D014700:Verapamil / Q000494:pharmacology; D000094632:Thymic Stromal Lymphopoietin
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D016207:Cytokines; D005456:Fluorescent Dyes; D015850:Interleukin-6; D016209:Interleukin-8; D008070:Lipopolysaccharides; D020112:Rhodamine 123; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D014700:Verapamil; D000094632:Thymic Stromal Lymphopoietin