Regulation of BCRP (ABCG2) and P-glycoprotein (ABCB1) by cytokines in a model of the human blood-brain barrier

Abstract

Brain capillary endothelial cells form the blood-brain barrier (BBB), a highly selective permeability membrane between the blood and the brain. Besides tight junctions that prevent small hydrophilic compounds from passive diffusion into the brain tissue, the endothelial cells express different families of drug efflux transport proteins that limit the amount of substances penetrating the brain. Two prominent efflux transporters are the breast cancer resistance protein and P-glycoprotein (P-gp). During inflammatory reactions, which can be associated with an altered BBB, pro-inflammatory cytokines are present in the systemic circulation. We, therefore, investigated the effect of the pro-inflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) on the expression and activity of BCRP and P-gp in the human hCMEC/D3 cell line. BCRP mRNA levels were significantly reduced by IL-1beta, IL-6 and TNF-alpha. The strongest BCRP suppression at the protein level was observed after IL-1beta treatment. IL-1beta, IL-6 and TNF-alpha also significantly reduced the BCRP activity as assessed by mitoxantrone uptake experiments. P-gp mRNA levels were slightly reduced by IL-6, but significantly increased after TNF-alpha treatment. TNF-alpha also increased protein expression of P-gp but the uptake of the P-gp substrate rhodamine 123 was not affected by any of the cytokines. This in vitro study indicates that expression levels and activity of BCRP, and P-gp at the BBB may be altered by acute inflammation, possibly affecting the penetration of their substrates into the brain.

Fig. 1

Relative expression of BCRP mRNA normalized to GAPDH in hCMEC/D3 cells. Data are given as means ± SEM of n = 3 individual experiments (***P < 0.0005 vs. control values)

Fig. 2

Relative expression of P-gp mRNA normalized to GAPDH in hCMEC/D3 cells. Data are given as means ± SEM of n = 3 individual experiments (*P < 0.05, ***P < 0.0005 vs. control values)

Fig. 3

Protein expressions of P-gp and P-gp in hCMEC/D3 cells under and after treatment with IL-6 (b), IL-1β (c) or TNF-α (d). Lane (a) represents control experiments (cells grown in assay medium)

Fig. 4

Accumulation of MX in hCMEC/D3 cells after 72-h pre-treatment with IL-1β (0.2, 2 ng/ml), IL-6 (2, 20 ng/ml) or TNF-α (2, 20 ng/ml) in percent of control. Prazosin was used as a positive control in untreated cells. Data are given as means ± SEM of n = 3 individual experiments (*P < 0.05; **P < 0.005; ***P < 0.0005 vs. control values)

Fig. 5

Accumulation of R123 in hCMEC/D3 cells after 72-h pre-treatment with IL-1β (0.2, 2 ng/ml), IL-6 (2, 20 ng/ml) or TNF-α (2, 20 ng/ml) in percent of control. Verapamil was used as a positive control in untreated cells. Data are given as means ± SEM of n = 3 individual experiments (***P <0.0005 vs. control values)