P-glycoprotein activity in human Caucasian male lymphocytes does not follow its increased expression during aging

Authors

  • Vânia Vilas-Boas,

    Corresponding author
    1. REQUIMTE—Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal, Cunha, 164, 4099-030 Porto, Portugal
    • REQUIMTE—Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal, Cunha, 164, 4099-030 Porto, Portugal
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  • Renata Silva,

    1. REQUIMTE—Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal, Cunha, 164, 4099-030 Porto, Portugal
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  • A. Rita Gaio,

    1. Departamento de Matemática, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 687, 4169-007 Porto, Portugal
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  • Ana Margarida Martins,

    1. REQUIMTE—Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal, Cunha, 164, 4099-030 Porto, Portugal
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  • Sofia Costa Lima,

    1. IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto Portugal
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  • Anabela Cordeiro-da-Silva,

    1. IBMC—Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre, 823, 4150-180 Porto Portugal
    2. Departamento de Ciências Biológicas, Laboratório de Bioquímica, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal Cunha, 164, 4099-030 Porto, Portugal
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  • Maria de Lourdes Bastos,

    1. REQUIMTE—Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal, Cunha, 164, 4099-030 Porto, Portugal
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  • Fernando Remião

    Corresponding author
    1. REQUIMTE—Laboratório de Toxicologia, Departamento de Ciências Biológicas, Faculdade de Farmácia, Universidade do Porto, Rua Aníbal, Cunha, 164, 4099-030 Porto, Portugal
    • REQUIMTE, Toxicology Department, Faculty of Pharmacy, University of Porto Rua Anibal Cunha 164, 4099-030 Porto, Portugal
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Abstract

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

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