Breast Cancer Resistance Protein Knockout Research Articles

Age-related changes in hepatic expression and activity of drug metabolizing enzymes in male wild-type and breast cancer resistance protein knockout mice.

This study aimed to reveal age-related changes in the expression and activity of seven hepatic drug metabolizing enzymes (DMEs) in male wild-type and breast cancer resistance protein knockout (Bcrp1-/- ) FVB mice. The protein expression of four cytochrome P450 (Cyps) (Cyp3a11, 2d22, 2e1, and 1a2), and three UDP-glucuronosyltransferases (Ugts) (Ugt1a1, 1a6a, and 1a9) in liver microsomes of wild-type and Bcrp1-/- FVB mice at different ages were determined using a validated ultra high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method. The activities and mRNA levels of these DMEs were measured using the probe substrates method and real-time PCR, respectively. In the liver of wild-type FVB mice, Cyp3a11, 2d22, 2e1, 1a2, Ugt1a1, and 1a6a displayed maximum protein levels at 6-9weeks of age. Cyp1a2, Ugt1a1, 1a6a, and 1a9 showed maximum activities at 6-9weeks of age, whereas Cyp3a11, 2d22, and 2e1 showed maximum activities in 1-3-week-old mice. Additionally, most of the DMEs showed maximum mRNA levels in 17-week-old mice liver. Compared with wild-type FVB mice, the protein levels of these DMEs showed no significant changes in Bcrp1-/- FVB mice liver. However, the activity of Cyp2e1 was increased and that of Cyp2d22 was decreased. In conclusion, the seven hepatic DMEs in FVB mice liver showed significant alterations in an isoform-specific manner with increased age. Although the protein levels of these DMEs showed no significant changes, the activities of Cyp2e1 and 2d22 were changed in Bcrp1-/- mice.

Simultaneous determination of tilianin and its metabolites in mice using ultra-high-performance liquid chromatography with tandem mass spectrometry and its application to a pharmacokinetic study.

Tilianin is an active flavonoid glycoside found in many medical plants. Data are lacking regarding its pharmacokinetics and disposition in vivo. The objective of this study was to develop a sensitive, reliable and validated ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method to simultaneously quantify tilianin and its main metabolites and to determine its pharmacokinetics in wild-type and breast cancer resistance protein knockout (Bcrp1-/-) FVB mice. Chromatographic separation was accomplished on a C18 column by utilizing acetonitrile and 0.5 mm ammonium acetate as the mobile phase. Mass spectrometric detection was performed using electrospray ionization in both positive and negative modes. The results showed that the precision, accuracy and recovery, as well as the stability of tilianin and its metabolites in mouse plasma, were all within acceptable limits. Acacetin-7-glucuronide and acacetin-7-sulfate were the major metabolites of tilianin in mouse plasma. Moreover, systemic exposure of acacetin-7-sulfate was significantly higher in Bcrp1 (-/-) FVB mice compared with wild-type FVB mice. In conclusion, the fully validated UHPLC-MS/MS method was sensitive, reliable, and was successfully applied to assess the pharmacokinetics of tilianin in wild-type and Bcrp1 (-/-) FVB mice. Breast cancer resistance protein had a significant impact on the elimination of the sulfated metabolite of tilianin in vivo.

Sulfonation Disposition of Acacetin: In Vitro and in Vivo.

Acacetin, an important component of acacia honey, exerts extensive therapeutic effects on many cancers. However, the sulfonation disposition of acacetin has rarely been reported. Therefore, this study aimed to investigate the sulfonation disposition of acacetin systematically. The results showed that acacetin-7-sulfate was the main metabolite mediated primarily by sulfotransferases (SULT) 1A1. Dog liver S9 presented the highest formation rate of acacetin-7-sulfate. Compared with that in wild-type Friend Virus B (FVB) mice, plasma exposure of acacetin-7-sulfate decreased significantly in multidrug resistance protein 1 knockout (Mrp1-/-) mice vut increased clearly in breast cancer resistance protein knockout (Bcrp-/-) mice. In Caco-2 monolayers, the efflux and clearance of acacetin-7-sulfate was reduced distinctly by the BCRP inhibitor Ko143 on the apical side and by the MRP1 inhibitor MK571 on the basolateral side. In conclusion, acacetin sulfonation was mediated mostly by SULT1A1. Acacetin-7-sulfate was found to be transported mainly by BCRP and MRP1. Hence, SULT1A1, BCRP, and MRP1 are responsible for acacetin-7-sulfate exposure in vivo.

Impact of genetic deficiencies of P-glycoprotein and breast cancer resistance protein on pharmacokinetics of aripiprazole and dehydroaripiprazole

1. We investigated how deficiencies in P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) affect the pharmacokinetics of atypical antipsychotics aripiprazole and its active metabolite (dehydroaripiprazole) using normal Friend leukemia virus strain B (FVB) mice, BCRP knockout (Bcrp[−/−]) mice, and P-gp and BCRP triple knockout (Mdr1a/1b[−/−]Bcrp[−/−]) mice.2. While plasma concentrations of aripiprazole and dehydroaripiprazole after oral administration were slightly higher in both Bcrp(−/−) and Mdr1a/1b(−/−)/Bcrp(−/−) mice than in normal FVB mice, the difference was not marked. The increase in absolute bioavailability (F) compared with normal mice (approximately 1.3-fold increase) was comparable between Bcrp(−/−) and Mdr1a/1b(−/−)/Bcrp(−/−) mice. This finding suggests that BCRP may be involved in the intestinal absorption of aripiprazole in mice, albeit with minimal contribution to absorption at best.3. In contrast, the brain-to-plasma concentration ratio (Kp,brain) for aripiprazole and dehydroaripiprazole after oral administration was significantly higher in Mdr1a/1b(−/−)/Bcrp(−/−) mice than in normal mice, whereas Bcrp(−/−) mice exhibited Kp,brain values similar to those in normal mice. In addition, the Kp,brain values in Mdr1a/1b(−/−)/Bcrp(−/−) mice were not drastically different from those previously reported in Mdr1a/1b(−/−) mice, suggesting that brain penetration of aripiprazole and dehydroaripiprazole can be affected by P-gp, but with little synergistic effect of BCRP.

Enhanced Brain Disposition and Effects of Δ9-Tetrahydrocannabinol in P-Glycoprotein and Breast Cancer Resistance Protein Knockout Mice

The ABC transporters P-glycoprotein (P-gp, Abcb1) and breast cancer resistance protein (Bcrp, Abcg2) regulate the CNS disposition of many drugs. The main psychoactive constituent of cannabis Δ9-tetrahydrocannabinol (THC) has affinity for P-gp and Bcrp, however it is unknown whether these transporters modulate the brain accumulation of THC and its functional effects on the CNS. Here we aim to show that mice devoid of Abcb1 and Abcg2 retain higher brain THC levels and are more sensitive to cannabinoid-induced hypothermia than wild-type (WT) mice. Abcb1a/b (−/−), Abcg2 (−/−) and wild-type (WT) mice were injected with THC before brain and blood were collected and THC concentrations determined. Another cohort of mice was examined for THC-induced hypothermia by measuring rectal body temperature. Brain THC concentrations were higher in both Abcb1a/b (−/−) and Abcg2 (−/−) mice than WT mice. ABC transporter knockout mice exhibited delayed elimination of THC from the brain with the effect being more prominent in Abcg2 (−/−) mice. ABC transporter knockout mice were more sensitive to THC-induced hypothermia compared to WT mice. These results show P-gp and Bcrp prolong the brain disposition and hypothermic effects of THC and offer a novel mechanism for both genetic vulnerability to the psychoactive effects of cannabis and drug interactions between CNS therapies and cannabis.

Breast Cancer Resistance Protein (BCRP) and Sulfotransferases Contribute Significantly to the Disposition of Genistein in Mouse Intestine

The low bioavailability of genistein has impeded its development into a therapeutic agent. Our earlier studies indicate that glucuronidation is one of the major barriers to genistein oral bioavailability. This study will determine how sulfotransferases and efflux transporters affect its intestinal disposition. A rodent intestinal perfusion model and S9 fractions were used. Sulfate excretion rates were comparable to glucuronide excretion in mouse small intestine but significantly higher than glucuronide excretion in mouse colon, which is different from rat intestinal disposition but similar to disposition in Caco-2 cells. To define efflux transporter(s) involved in sulfate excretion, two organic anion inhibitors (estrone sulfate and dihydroepiandrosterone sulfate) or a multidrug resistance protein inhibitor (MK-571) were used but neither was able to decrease the excretion of genistein sulfates. In contrast, the excretion of genistein sulfate decreased substantially (>90%) in small intestine of breast cancer resistance protein (BCRP) knockout mice and became undetectable in colon of the knockout mice. The excretion rates of genistein glucuronide in the small intestine of BCRP knockout mice were also significant decreased (78%). This study shows clearly that BCRP facilitates the cellular genistein sulfate excretion by removing sulfates to prevent their backward hydrolysis and to limit substrate inhibition, indicating that BCRP plays a dominant role in genistein sulfate excretion and a significant role in genistein glucuronide excretion in the mouse intestine.

The effect of P-gp (Mdr1a/1b), BCRP (Bcrp1) and P-gp/BCRP inhibitors on the in vivo absorption, distribution, metabolism and excretion of imatinib

Imatinib is transported by P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP), however, the exact impact of these transporters on absorption, distribution, metabolism and excretion (ADME) of imatinib is not fully understood due to incomplete data. We have performed a comprehensive ADME study of imatinib given as single agent or in combination with the well known BCRP/P-gp inhibitors, elacridar and pantoprazole, in wild-type and P-gp and/or BCRP knockout mice. The absence of P-gp and BCRP together resulted in a significantly higher area under the plasma concentration-time curve (AUC) after i.v. administration, whereas the AUC after oral dosing was unaltered. Both elacridar and pantoprazole significantly increased the AUC of orally administered imatinib in wild-type but also in P-gp/BCRP knockout mice. This lower clearance was not due to a (further) reduction in biliary excretion. Fecal excretion was significantly reduced in P-gp and P-gp/BCRP knockout but not in BCRP knockout mice, whereas the brain penetration was significantly higher in P-gp/BCRP knockout mice compared to single P-gp or BCRP knockout or wild-type mice. In conclusion, P-gp and BCRP have only a modest effect on the ADME of imatinib in comparison to metabolic elimination. P-gp is the most prevalent factor for systemic clearance and limiting the brain penetration. The considerable drug-drug interaction observed with elacridar or pantoprazole is only partly mediated by inhibition of P-gp and BCRP and far more by the inhibition of other elimination pathways.