Role of breast cancer resistance protein in the adaptive response to cholestasis - PubMed (original) (raw)

Role of breast cancer resistance protein in the adaptive response to cholestasis

Albert Mennone et al. Drug Metab Dispos. 2010 Oct.

Abstract

Breast cancer resistance protein (Bcrp) is a member of the ATP-binding cassette membrane transporter family, which is expressed apically in liver, kidney, and intestine epithelium. Recent reports suggest that in addition to xenobiotics, porphyrins, and food toxins, Bcrp can also transport bile acids and, therefore, may participate in the adaptive response to cholestasis. Bile duct ligation (BDL), an experimental model of obstructive cholestasis, was performed in male wild-type (WT) and Bcrp knockout (KO) mice. An initial time course of 3, 7, and 14 days of BDL in WT mice revealed that Bcrp expression was significantly reduced in liver but increased in ileum by 7 days. Subsequent experiments using 7-day BDL in WT and Bcrp KO mice demonstrated that there was no difference in liver necrosis, serum glutamic pyruvate aminotransferase, bilirubin, or bile acid levels in serum, hepatic tissue, bile, urine, or feces between the two groups. Protein expression levels for liver organic solute transporter (Ost) α and multidrug resistance protein 1 and kidney multidrug resistance-associated protein (Mrp) 2, Mrp3, and Mrp4 were significantly greater in the sham Bcrp KO versus sham WT mice. The expression of Mrp2 and Mrp4 in KO kidneys was further increased after BDL. In contrast, the adaptive response of transporters to BDL in the liver was similar in KO and WT BDL mice, including Ostα and Ostβ expression, which increased in liver and kidney but decreased in the ileum. These findings suggest that Bcrp does not have a significant role in the adaptive response to cholestasis in the liver but may be more important for solute export in the kidney and intestine.

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Figures

Fig. 1.

Time course of Bcrp protein expression after BDL in C57BL/6 mice. Densitometry of Western blot analysis of Bcrp expression at 3, 7, and 14 days after BDL showed that liver Bcrp was significantly decreased by 3 days and maintained over 14 days. Kidney levels gradually declined over the time course and were significantly decreased by 14 days. In contrast, Bcrp in the ileum was significantly increased at all time points. *, p < 0.05.

Fig. 2.

Transporter expression in liver and kidney of Bcrp-deficient mice. A, in the liver (□) mRNA expression for Mrp2 is increased and that for Ostα is decreased in Bcrp KO mice compared with expression in WT controls. In the kidney (■), both Mrp4 and Ostβ were slightly decreased compared with those in WT controls. n = 6 for all groups. B, in the liver, protein expression of both Mdr1a and Ostα is increased in the Bcrp KO mice compared with that in WT controls. In the kidney, protein expression of Mrp2, Mrp3, and Mrp4 is increased and that of Mdr1a is decreased in Bcrp KO mice compared with expression in WT controls. n = 6 for all groups. ND, non detectable.

Fig. 3.

A and B, liver necrosis is the same in WT and Bcrp KO mice. Necrotic regions (arrows) were easily distinguished from healthy parenchyma. The extent of necrosis in WT and KO livers was comparable. C, the serum liver enzyme alanine aminotransferase [glutamic pyruvate aminotransferase (SGPT)] level was significantly (p < 0.005) increased in both WT and Bcrp KO animals after BDL. This increase was the same in both (n = 6) groups of animals.

Fig. 4.

Serum bilirubin and bile acid levels are increased in both WT and Bcrp KO mice after BDL. A, bilirubin was below detection levels in sham mice (S, n = 6) but rose to similar levels after BDL (B, n = 6). B, there was no difference in the increase in serum bile acids after BDL in WT and KO animals. However, there was a significantly (*, p < 0.05) lower concentration of serum bile acids in the KO sham compared with the WT group. n = 6 for both groups.

Fig. 5.

Western blot and densitometric analysis of transporter protein expression in total liver membrane of WT and Bcrp KO mice. Representative blots (n = 3) are shown, and densitometry values for all six mice are shown below the blots. Expression of apical Mrp2 is down equally in WT and KO mice after BDL. There was no difference in Bsep expression levels after BDL in either group. However, Mrp4 and Mdr1a were up-regulated after BDL in WT and KO mice. The increase in Mrp4 in the KO mice was only half that seen in the WT BDL mice, whereas the increase in Mdr1a was twice as great in the KO mice compared with that in the WT mice. Oatp1, Ntcp, and Oct1 protein expression was significantly decreased after BDL in the livers of both WT and KO animals, although the decrease for Oct1 was significantly less in the Bcrp KO mice than that seen in the WT mice. *, p < 0.05, sham versus BDL; #, p < 0.05, WT BDL versus KO BDL; +, p < 0.05, WT sham versus KO sham.

Fig. 6.

Western blot and densitometric analysis of transporter protein expression in total kidney membrane of WT and Bcrp KO mice. Representative blots (n = 3) are shown, and densitometry values for all six mice are shown below the blots. As shown in Fig. 2, the basal levels of Mrp2, Mrp3, and Mrp4 protein were significantly higher than those in the WT mice. After BDL, Mrp2 and Mrp4 were further increased in the KO mice and remained significantly higher than those in the WT BDL mice. *, p < 0.05, sham versus BDL; #, p < 0.05, WT BDL versus KO BDL; +, p < 0.05, WT sham versus KO sham.

Fig. 7.

Representative Western blots and densitometry values of ileum transporters in Bcrp WT and KO sham and BDL mice. n = 6 for each group. Ostα: WT BDL, *, p < 0.05 versus WT sham; *, p < 0.0005 for KO BDL versus KO sham. Ostβ: * p < 0.05 versus respective sham.

References

1. Abbott BL. (2006) ABCG2 (BCRP): a cytoprotectant in normal and malignant stem cells. Clin Adv Hematol Oncol 4:63–72 - PubMed
1. Allen JD, Brinkhuis RF, Wijnholds J, Schinkel AH. (1999) The mouse Bcrp1/Mxr/Abcp gene: amplification and overexpression in cell lines selected for resistance to topotecan, mitoxantrone, or doxorubicin. Cancer Res 59:4237–4241 - PubMed
1. Beilke LD, Besselsen DG, Cheng Q, Kulkarni S, Slitt AL, Cherrington NJ. (2008) Minimal role of hepatic transporters in the hepatoprotection against LCA-induced intrahepatic cholestasis. Toxicol Sci 102:196–204 - PubMed
1. Boyer JL. (2007) New perspectives for the treatment of cholestasis: lessons from basic science applied clinically. J Hepatol 46:365–371 - PMC - PubMed
1. Boyer JL, Trauner M, Mennone A, Soroka CJ, Cai SY, Moustafa T, Zollner G, Lee JY, Ballatori N. (2006) Upregulation of a basolateral FXR-dependent bile acid efflux transporter OSTα-OSTβ in cholestasis in humans and rodents. Am J Physiol Gastrointest Liver Physiol 290:G1124–G1130 - PubMed

Role of breast cancer resistance protein in the adaptive response to cholestasis - PubMed (original) (raw)