title: Upregulation of P-glycoprotein expression by ophthalmic drugs in different corneal in-vitro models.
abstract: OBJECTIVE
  The purpose of this study was to analyse P-glycoprotein (P-gp) expression in different human in-vitro cornea models (HCE-T epithelial model and Hemicornea construct) after stimulation with P-gp substrates (rhodamine 123, levofloxacin and acebutolol).
  
  
  METHODS
  The influence of P-gp substrates on mRNA expression was analysed using reverse transcriptase polymerase chain reaction (PCR) and real-time PCR. The effect of stimulation on the transporter functionality was estimated with a digoxin efflux assay. The Caco-2 cell line was used as positive control.
  
  
  RESULTS
  The reverse transcriptase PCR results showed an increase in band intensity compared with the control medium for all substrates. The real-time PCR for the Caco-2 and HCE-T epithelial model yielded a similar outcome, in which all tested substrates upregulated P-gp. In contrast, the Hemicornea construct showed no significant increase in the mRNA expression after stimulation. Both in-vitro models possessed similar drug transport profiles after stimulation. A significantly increased efflux of digoxin was measured after 24 and 72 h of stimulation with levofloxacin and acebutolol.
  
  
  CONCLUSIONS
  The expression and functionality of the P-gp in corneal tissue can be influenced through time exposure with specific substrates. However, the exact mechanism still requires further elucidation.
authors: Institut für Pharmazeutische Technologie, Technische Universität Braunschweig, Braunschweig, Germany.
authors: Jessica
authors: J
authors: Verstraelen
authors: Stephan
authors: S
authors: Reichl
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000070:Acebutolol / Q000494:pharmacology*; D002478:Cells, Cultured; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D064704:Levofloxacin / Q000494:pharmacology*; D009883:Ophthalmic Solutions / Q000494:pharmacology*; D020112:Rhodamine 123 / Q000494:pharmacology; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D009883:Ophthalmic Solutions; D020112:Rhodamine 123; D000070:Acebutolol; D064704:Levofloxacin
keywords: biopharmaceutics and drug disposition; cellular drug uptake and absorption; other topics