Involvement of P-glycoprotein in the transmembrane transport of interleukin-2 (IL-2), IL-4, and interferon-gamma in normal human T lymphocytes.
The physiological role of the multidrug resistance P-glycoprotein (P-gp), which is expressed by normal human T lymphocytes, is still largely unknown. To investigate whether or not P-gp is involved in the transport of cytokines, peripheral blood lymphocytes were stimulated with phytohemagglutinin (PHA) in the absence or presence of P-gp inhibitors, and concentrations of cytokines (interleukin-2 [IL-2], IL-4, IL-6, interferon-gamma [IFN-gamma]) in the supernatants of these cultures were quantitated by enzyme-linked immunosorbent assay. P-gp inhibitors included verapamil (Ver), tamoxifen (Tmx), and the P-gp specific monoclonal antibody UIC2. Release of IL-2 was significantly suppressed by these inhibitors at concentrations that were also effective in blocking efflux of Rhodamine-123 from normal T lymphocytes. IL-2 mRNA expression in lymphocytes was not different between PHA control and the cultures with P-gp inhibitors. Ver and Tmx did not interfere with T-cell activation as determined by CD25 and CD69 expression. In a nonhematological model, the P-gp expressing HCT-8 adenocarcinoma cell line, exogenously added IL-2 was shown to exert an inhibitory effect on P-gp mediated Rhodamine-123 efflux. In addition, transepithelial transport of IL-2 by electrophysiologically tight and polarized HCT-8 monolayers was examined. A time-dependent flux of IL-2 across dense monolayers, which was partially inhibited by Ver, was observed. We also investigated whether or not P-gp inhibitors suppressed release of other cytokines produced by activated T cells (IL-4, IL-6, IFN-gamma). Release of IL-4 and IFN-gamma was significantly inhibited by Ver, Tmx, and UIC2; however, release of IL-6 remained unaffected. These data show P-gp mediated transmembrane flux of IL-2 in T lymphocytes and HCT-8 cells. We conclude that P-gp participates in the transport of cytokines (IL-2, IL-4, and IFN-gamma) in normal peripheral T lymphocytes.
Drach
J
J
University of Vienna, First Department of Internal Medicine, Austria.
Gsur
A
A
Hamilton
G
G
Zhao
S
S
Angerler
J
J
Fiegl
M
M
Zojer
N
N
Raderer
M
M
Haberl
I
I
Andreeff
M
M
Huber
H
H
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000502:physiology*; D000230:Adenocarcinoma / Q000473:pathology; D001692:Biological Transport; D016572:Cyclosporine / Q000494:pharmacology; D004705:Endocytosis; D006801:Humans; D007078:Ileal Neoplasms / Q000473:pathology; D007080:Ileocecal Valve; D007371:Interferon-gamma / Q000378:metabolism*; D007376:Interleukin-2 / Q000378:metabolism*; D015847:Interleukin-4 / Q000378:metabolism*; D008213:Lymphocyte Activation; D010835:Phytohemagglutinins / Q000494:pharmacology; D011994:Recombinant Proteins; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D013629:Tamoxifen / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007376:Interleukin-2; D010835:Phytohemagglutinins; D011994:Recombinant Proteins; D013629:Tamoxifen; D015847:Interleukin-4; D007371:Interferon-gamma; D016572:Cyclosporine; D014700:Verapamil