title: Efflux protein expression in human retinal pigment epithelium cell lines.
abstract: OBJECTIVE
  The objective of this study was to characterize efflux proteins (P-glycoprotein (P-gp), multidrug resistance proteins (MRP1-6) and breast cancer resistance protein (BCRP)) of retinal pigment epithelium (RPE) cell lines.
  
  
  METHODS
  Expression of efflux proteins in two secondary (ARPE-19, D407) and two primary (HRPEpiC and bovine) RPE cell lines was measured by quantitative RT-PCR and western blotting. Furthermore, activity of MRP1 and MRP5 of ARPE-19 cell line was assessed with calcein-AM and carboxydichlorofluorescein (CDCF) probes.
  
  
  RESULTS
  Similar efflux protein profile was shared between ARPE-19 and primary RPE cells, whereas D407 cell line was notably different. D407 cells expressed MRP2 and BCRP, which were absent in other cell lines and furthermore higher MRP3 transcript expression was found. MRP1, MRP4 and MRP5 were identified from all human RPE cell lines and MRP6 was not expressed in any cell lines. The pattern of efflux protein expression did not change when ARPE-19 cells were differentiated on filters. The calcein-AM and CDCF efflux tests provided evidence supporting MRP1 and MRP5 activity in ARPE-19 cells.
  
  
  CONCLUSIONS
  MRP1, MRP4 and MRP5 are the main efflux transporters in RPE cell lines. There are differences in efflux protein expression between RPE cell lines.
authors.affiliation: Department of Pharmaceutics, University of Kuopio, Yliopistonranta 1C, 70210 Kuopio, Finland. Eliisa.Mannermaa@uku.fi
authors.forename: Eliisa
authors.initials: E
authors.lastname: Mannermaa
authors.forename: Kati-Sisko
authors.initials: KS
authors.lastname: Vellonen
authors.forename: Tuomas
authors.initials: T
authors.lastname: Ryhänen
authors.forename: Katriina
authors.initials: K
authors.lastname: Kokkonen
authors.forename: Veli-Pekka
authors.initials: VP
authors.lastname: Ranta
authors.forename: Kai
authors.initials: K
authors.lastname: Kaarniranta
authors.forename: Arto
authors.initials: A
authors.lastname: Urtti
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002460:Cell Line; D005452:Fluoresceins; D005456:Fluorescent Dyes; D015870:Gene Expression; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics* / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D055213:Retinal Pigment Epithelium / Q000166:cytology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D005452:Fluoresceins; D005456:Fluorescent Dyes; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D012333:RNA, Messenger; C116614:ABCG2 protein, human; C053897:5(6)-carboxy-2',7'-dichlorofluorescein; C085925:calcein AM