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P‐glycoprotein activity in human Caucasian male lymphocytes does not follow its increased expression during aging
Author(s) -
VilasBoas Vânia,
Silva Renata,
Gaio A. Rita,
Martins Ana Margarida,
Lima Sofia Costa,
CordeirodaSilva Anabela,
de Lourdes Bastos Maria,
Remião Fernando
Publication year - 2011
Publication title -
cytometry part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.316
H-Index - 90
eISSN - 1552-4930
pISSN - 1552-4922
DOI - 10.1002/cyto.a.21135
Subject(s) - p glycoprotein , efflux , rhodamine 123 , flow cytometry , vinblastine , monoclonal antibody , transporter , biology , microbiology and biotechnology , atp binding cassette transporter , gene expression , immunology , antibody , multiple drug resistance , gene , biochemistry , drug resistance , genetics , chemotherapy
P‐glycoprotein (P‐gp) is a transmembrane protein that mediates the efflux of innumerous structurally unrelated compounds. It was initially found over‐expressed in tumor cells, associated to a multidrug resistance phenotype (MDR). Then, P‐gp was found constitutively expressed in excretory cells/tissues and in circulating cells, such as lymphocytes. Considering the importance of this transporter in the establishment of therapeutic protocols and the existence of contradictory results, this study aimed at evaluating the influence of aging in the expression and function of P‐gp in human lymphocytes, comparing two different methodologies to assess both parameters. P‐gp activity and expression were evaluated in lymphocytes isolated from whole blood samples of 65 healthy caucasian male donors, divided into two groups according to age (group 1: under 30‐years old; group 2: above 60‐years old). P‐gp expression was assessed using the anti‐P‐gp monoclonal antibody, UIC2, in the presence and in absence of vinblastine (Vbl). P‐gp activity was evaluated measuring the efflux rate of the fluorescent P‐gp substrate rhodamine 123 (Rho 123) and also using UIC2 shift assay. Flow cytometric analysis was performed to assess all the proceedings. Furthermore, P‐gp expression and each of the P‐gp activity determination methods were compared, through correlation analysis and linear regression models. We observed a significant age‐dependent increase in mean P‐gp expression ( p = 0.029), which was not reflected in the transporter's activity ( p > 0.050). Statistical analysis allowed selection of UIC2 shift assay over Rho 123 efflux assay as a more selective method to assess P‐gp activity. Despite the significant correlation between P‐gp expression and P‐gp activity found in lymphocytes (Gp1(group 1)— r = 0.609, p < 0.001; Gp2— r = 0.461, p = 0.012), using UIC2 shift assay, these data reinforce the need for P‐gp activity assessment, rather than P‐gp expression determination alone, when starting new therapeutic regimens with P‐gp substrates, especially in men older than 60 years of age. © 2011 International Society for Advancement of Cytometry