Chemico-Biological Interactions 186 (2010) 287–294 Contents lists available at ScienceDirect Chemico-Biological Interactions journal homepage: www.elsevier.com/locate/chembioint In vitro modulation of ABCB1/P-glycoprotein expression by polyphenols from Mangifera indica Elisabetta Chieli a,∗ , Nadia Romiti a , Idania Rodeiro b , Gabino Garrido c a Dipartimento di Patologia Sperimentale e Biotecnologie Mediche, Facoltà di Medicina e Chirurgia, Università degli Studi di Pisa, via Roma 55, 56126 Pisa, Italy b Laboratorio de Farmacología, Centro de Química Farmacéutica, 200 y 21, Atabey, Playa, Ciudad de La Habana, Cuba c Departamento de Química y Farmacia, Facultad de Ciencias, Universidad Católica del Norte, Angamos 0610, Antofagasta, Chile article info Article history: Received 14 February 2010 Received in revised form 19 May 2010 Accepted 20 May 2010 Available online 1 June 2010 Keywords: ABCB1 expression HK-2 cells Mangifera indica Mangiferin P-glycoprotein abstract Many plant compounds are able to modulate the activity and/or the expression of the major mul- tidrug transporter ABCB1/P-glycoprotein (P-gp). In this study, mango (Mangifera indica L.) stem bark extract (MSBE), its main polyphenol mangiferin and the mangiferin aglycone derivative norathyriol, as well as catechin, gallic acid and quercetin, were investigated for their potential ability to influence ABCB1 gene and P-gp expression in HK-2 cells, a proximal tubule line constitutively expressing this transporter. Western blot analysis demonstrated a concentration-dependent decrease in P-gp in cells cultured in the presence of MSBE for 72 h. Gallic acid and quercetin also decreased the levels of P-gp at all studied concentrations, whereas catechin was almost ineffective. However, in cells exposed to mangiferin (10–200 М), the P-gp amount showed a concentration- and time-dependent increase, being 2-fold higher than the controls after 72 h. Norathyriol (5 M) induced P-gp, but the effect decreased at higher concentrations. The changes in the P-gp protein amount were correlated with relative changes in the ABCB1 mRNA content and with the efflux activity of the transporter. The transcriptional inhibitor 1-d-ribofuranosylbenzimidazole (DRB) contrasted the increased expression of ABCB1 by mangiferin, suggesting that the increase could be due to transcriptional up-regulation of ABCB1 mRNA. Mangiferin- treated cells overexpressing the transporter were protected against the cytotoxicity of the known P-gp substrate cyclosporine A. However, the opposite effect was not observed in cells pretreated with MSBE. These results demonstrate that MSBE and mango polyphenols, already shown in our previous studies to influence P-gp activity, may also interact with ABCB1/P-gp at the expression level. In particular, we show for the first time that the main mango polyphenol mangiferin up-regulates this multidrug transporter. The molecular mechanisms and the consequences of these effects, including the possibility of interactions with conventional drugs or other herbal constituents, remain to be elucidated. © 2010 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Drug–drug or herb–drug interactions based on the alteration of important absorption, distribution, metabolism and excretion (ADME) processes are currently a hot topic in pharmacology. These interactions may arise from modulation of cytochrome P450 (CYP) isoenzymes, multidrug transporters like P-glycoprotein (P-gp), or a combination of the two [1–5]. ABCB1/P-gp, an efflux transporter member of the ABC trans- porter superfamily [6], has long been known for its contribution Abbreviations: Calcein-AM, calcein acetoxymethylester; CsA, cyclosporine A; CYP, cytochrome P-450; CTCH, catechin; DRB, 1-d-ribofuranosylbenzimidazole; GA, gallic acid; MG, mangiferin; MSBE, mango stem bark extract; NTR, norathyriol; P-gp, P-glycoprotein; QCT, quercetin; SQRT-PCR, semiquantitative RT-PCR; VP, verapamil. ∗ Corresponding author. Tel.: +39 050 2218553; fax: +39 050 2218557. E-mail addresses: chieli@biomed.unipi.it, elibetachi@yahoo.com (E. Chieli). to the acquisition of multidrug resistance by cancer cells dur- ing antitumor treatments, which often jeopardizes the success of chemotherapy [7–8]. However, in recent years, interest in this transporter has gradually and intensively focused on its physiological role in normal cells. Presently, P-gp is acknowledged as being largely distributed among several normal body tissues and particularly highly expressed in organs involved in the handling of chemi- cals, such as the liver, intestine and kidney. At these anatomical sites, P-gp localization within the biliary pole of hepatocytes, as well as within the polarized apical membranes of enterocytes or the brush border of renal proximal tubule cells, is consistent with its putative role in unidirectional transport and efflux of endoge- nous and exogenous substances, contributing to their clearance [9–13]. Activity and expression of P-gp have been reported to be influenced by a variety of chemical factors, including hormones, 0009-2797/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.cbi.2010.05.012