Multidrug transporter p‐glycoprotein 170 as a differentiation antigen on normal human lymphocytes and thymocytes: Modulation with differentiation stage and during aging

Abstract

P-glycoprotein 170 (P-gp), the multidrug transport pump, excludes drugs from the interior of cells and is inhibited by agents such as cyclosporin A (CsA), verapamil, and FK-506, which are also substrates for the P-gp pump. This work documents the age- and differentiation-related changes in P-gp on T and B lymphocytes from human blood or spleen, and its absence on most thymus and bone marrow cells. Analysis of rhodamine 123 (Rh123) dye efflux, and its inhibition by cyclosporin A, was used as a quantitative measure of functional P-gp, and reactivity with MRK-16 was used as a measure of P-gp surface expression. The dye efflux and phenotypic expression of P-gp+ PBMC appeared equivalent to that of a moderately drug-resistant cell line, although efflux is prolonged. The sensitivity to inhibition by CsA, cyclosporin G (CsG), and PSC833 of P-gp on PBMC, thymocytes, or T-cell lines varied with apparent cell-type specificity. Normal blood and splenic T- or B-cells included 50-80% of cells with surface P-gp (MRK-16+), which mediated CsA-sensitive dye export. The proportion of P-gp+ T- and B-cells was lowest among children under age 10 years, increased in adulthood, and decreased after age 60. Thymus included 30% of P-gp+ cells mediating CsA-sensitive dye export, including CD3-4-8- progenitors and mature CD3hi CD4+8- or CD4-8+ thymocytes. Mature T-cells in cord or adult blood, spleen, and bone marrow included a large proportion (50-60%) with efficient CsA-sensitive dye export, preferentially among the CD45RA+ subset. Monocytes from all tissue sources, and most bone marrow cells, expressed surface P-gp but retained Rh123, suggesting the absence of a functional dye export mechanism. In vitro mitogen-stimulated PBMC T and B lymphocytes lost P-gp function within 4-24 hr, consistent with the observation that P-gp was reduced on antigen-experienced CD45R0+ T-cells in vivo. Drug export by P-gp may protect lymphocytes from toxic effects of CsA, and may contribute to the immunosuppressive effects of such drugs. The developmentally regulated expression of P-gp function on lymphocytes, and its modulation on activated T- or B-cells, suggest an important role in normal immune development.

P-glycoprotein targeting: a unique strategy to selectively eliminate immunoreactive T cells

“…Activated T lymphocytes demonstrated preferential accumulation and retention of the TH9402 rhodamine derivative over resting T cells. Indeed, we found that resting T lymphocytes, which express MDR1, 29 extruded TH9402 through this channel transporter, whereas the cellular activation process led to an impairment in MDR1-mediated TH9402 efflux. These kinetics of accumulation of TH9402 have resulted in the photodynamic eradication of responder cells immunized ex vivo against stimulator cells, in conditions simulating MHC-mismatched transplantation.…”

“…26 Pgp, the product of the multidrug-resistance-1 (MDR1) gene, is a protein expressed not only in normal stem cells, but also in T lymphocytes. [27][28][29][30] Investigators have proposed that T-cell activation may actually lead to the inactivation of Pgp. 29 Thus, activated T cells should fail to extrude rhodamine.…”

“…[27][28][29][30] Investigators have proposed that T-cell activation may actually lead to the inactivation of Pgp. 29 Thus, activated T cells should fail to extrude rhodamine. Although rhodamine is not cytotoxic, 4,5-dibromorhodamine methyl ester (TH9402), a rhodamine derivative, was found to harbor important photosensitizing potential.…”

Evidence for the Involvement of Carbon-centered Radicals in the Induction of Apoptotic Cell Death by Artemisinin Compounds

“…No toxicity was seen at concentrations up to 250 M, and PBMC were at least 500-fold less susceptible to the endoperoxides, thus demonstrating the selective cytotoxic properties of endoperoxide compounds against rapidly dividing cell lines. An IC 50 value for doxorubicin in PBMC could not be determined because of large inter-individual variations in IC 50 values, possibly arising from polymorphic expression of the efflux pump p-glycoprotein in PBMC (50), of which doxorubicin is known to be a substrate (51). The deoxygenated counterpart of PFDHA, dPFDHA, which has an ether linkage in place of the endoperoxide bridge, displayed low levels of cytotoxicity; IC 50 values were 50-and 130-fold higher in HL-60 and Jurkat cells, respectively, than for the parent compound, thus confirming that high levels of cytotoxic activity are dependent upon the presence of the endoperoxide bridge.…”

Expression of c‐kit and Sca‐1 and their relationship with multidrug resistance protein 1 in mouse bone marrow mononuclear cells

“…These transport proteins play a critical role in the absorption, distribution, metabolism and excretion of drugs and toxins. 4 Moreover, these proteins were described in thymocytes, [5][6][7] mature lymphocytes, 8,9 dendritic cells, 10,11 monocytes 12 and macrophages. 13 It has been suggested that multidrug transporters may play a role in the cells of the immune system, mediating the efflux of xenobiotics 14,15 and regulating cell activation [16][17][18] and migration.…”