title: Transport mechanisms and their pathology-induced regulation govern tyrosine kinase inhibitor delivery in rheumatoid arthritis.
abstract: BACKGROUND
  Tyrosine kinase inhibitors (TKIs) are effective in treating malignant disorders and were lately suggested to have an impact on non-malignant diseases. However, in some inflammatory conditions like rheumatoid arthritis (RA) the in vivo effect seemed to be moderate. As most TKIs are taken up actively into cells by cell membrane transporters, this study aimed to evaluate the role of such transporters for the accumulation of the TKI Imatinib mesylates in RA synovial fibroblasts as well as their regulation under inflammatory conditions.
  
  
  RESULTS
  The transport and accumulation of Imatinib was investigated in transporter-transfected HEK293 cells and human RA synovial fibroblasts (hRASF). Transporter expression was quantified by qRT-PCR. In transfection experiments, hMATE1 showed the highest apparent affinity for Imatinib among all known Imatinib transporters. Experiments quantifying the Imatinib uptake in the presence of specific transporter inhibitors and after siRNA knockdown of hMATE1 indeed identified hMATE1 to mediate Imatinib transport in hRASF. The anti-proliferative effect of Imatinib on PDGF stimulated hRASF was quantified by cell counting and directly correlated with the uptake activity of hMATE1. Expression of hMATE1 was investigated by Western blot and immuno-fluorescence. Imatinib transport under disease-relevant conditions, such as an altered pH and following stimulation with different cytokines, was also investigated by HPLC. The uptake was significantly reduced by an acidic extracellular pH as well as by the cytokines TNFα, IL-1β and IL-6, which all decreased the expression of hMATE1-mRNA and protein.
  
  
  CONCLUSIONS
  The regulation of Imatinib uptake via hMATE1 in hRASF and resulting effects on their proliferation may explain moderate in vivo effects on RA. Moreover, our results suggest that investigating transporter mediated drug processing under normal and pathological conditions is important for developing intracellular acting drugs used in inflammatory diseases.
authors.affiliation: Experimental Nephrology, Department of Internal Medicine D, University Hospital Münster, Münster, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schmidt-Lauber
authors.forename: Saliha
authors.initials: S
authors.lastname: Harrach
authors.forename: Thomas
authors.initials: T
authors.lastname: Pap
authors.forename: Meike
authors.initials: M
authors.lastname: Fischer
authors.forename: Marion
authors.initials: M
authors.lastname: Victor
authors.forename: Marianne
authors.initials: M
authors.lastname: Heitzmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Hansen
authors.forename: Manfred
authors.initials: M
authors.lastname: Fobker
authors.forename: Stefan-Martin
authors.initials: SM
authors.lastname: Brand
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Sindic
authors.forename: Hermann
authors.initials: H
authors.lastname: Pavenstädt
authors.forename: Bayram
authors.initials: B
authors.lastname: Edemir
authors.forename: Eberhard
authors.initials: E
authors.lastname: Schlatter
authors.forename: Jessica
authors.initials: J
authors.lastname: Bertrand
authors.forename: Giuliano
authors.initials: G
authors.lastname: Ciarimboli
mesh_terms: D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000378:metabolism*; D001549:Benzamides / Q000494:pharmacology; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D016207:Cytokines / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D000068877:Imatinib Mesylate; D053583:Interleukin-1beta / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism; D010879:Piperazines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011743:Pyrimidines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D001549:Benzamides; D016207:Cytokines; D053583:Interleukin-1beta; D015850:Interleukin-6; D027701:Organic Cation Transport Proteins; D010879:Piperazines; D047428:Protein Kinase Inhibitors; D011743:Pyrimidines; C521869:SLC47A1 protein, human; D014409:Tumor Necrosis Factor-alpha; D000068877:Imatinib Mesylate; D011505:Protein-Tyrosine Kinases