Pharmaceutics, Preformulation and Drug Delivery6-Mercaptopurine Transport by Equilibrative Nucleoside Transporters in Conditionally Immortalized Rat Syncytiotrophoblast Cell Lines TR-TBTs
Section snippets
INTRODUCTION
Recently pregnancy rate has risen in women who are 35 years old or more. This late pregnancy is considered a high-risk pregnancy because of increasing occurrence of malignant diseases such as cancer in women of this age.1,2 In addition, it is known that an attack of chronic inflammatory disease such as inflammatory bowel disease (IBD) in women patients begins at their childbearing age.3 6-Mercaptopurine (6-MP) is one of the antineoplastic and immunosuppressive drugs used as maintenance
Materials
[14C]6-Mercaptopurine (54 mCi/mmol) was obtained from Moravek Biochemicals Inc. (Brea, California, USA). All other chemicals and reagents were purchased from Sigma Chemical (St. Louis, Missouri, USA).
Cell Culture
The TR-TBTs were cultured according to the previous report.15 For the functional study, the cells were seeded on rat tail collagen type I-coated 24-well culture plates (IWAKI, Tokyo, Japan) at a density of 1 × 105 cells/well. After incubation for 3 days at 33°C, the cells were cultured confluent.
Time Course of [14C]6-MP Uptake and Efflux by TR-TBTs
We first experimented the uptake of [14C]6-MP for 60 min in TR-TBTs. [14C]6-MP was taken up time dependently and it was linear for 5 min (Fig. 1). [14C]6-MP uptake was significantly decreased by 0.5 mm unlabeled 6-MP (Fig. 1). To investigate the adenosine triphosphate (ATP)-dependent transporter responsible for [14C]6-MP uptake, we measured the accumulation of 6-MP in the presence of sodium azide, an ATPase inhibitor. The accumulation of 6-MP by TR-TBTs enhanced significantly in the presence of 10
DISCUSSION
It has been reported that 6-MP blood concentration in fetus merely represents by 1%–2% of its respective maternal blood level, although 6-MP is supposed to be transported to the human placenta.7 The limited 6-MP blood distribution in fetus may allow the embryo and the fetus will not be exposed to the cytotoxicity of 6-MP. Therefore, the study about the BPB transport mechanism of 6-MP is important to explain the teratogenicity of 6-MP during pregnancy. Our results show that the uptake as well as
CONCLUSION
In present study, we clarify that MRPs, including MRP4 and MRP5, and ENTs expressed at the BPB are involved in the transport of 6-MP. Our findings are important for therapy of ALL and autoimmune diseases of pregnant women, and should provide useful data in elucidating teratogenicity of 6-MP during pregnancy.
Acknowledgements
The authors thank Dr. Terasaki for the valuable discussion. This study was supported in grant from the SRC Research Center for Women's Diseases of Sookmyung Women's University.
REFERENCES (32)
- et al.
The safety of 6-mercaptopurine for childbearing patients with inflammatory bowel disease: A retrospective cohort study
Gastroenterology
(2003) - et al.
Review of the potential effects of three commonly used antineoplastic and immunosuppressive drugs (cyclophosphamide, azathioprine, doxorubicin on the embryo and placenta)
Reprod Toxicol
(2004) - et al.
Immunosuppression during pregnancy: Transmission of azathioprine and its metabolites from the mother to the fetus
Am J Obstet Gynecol
(1973) - et al.
Functional and molecular characterization of nucleobase transport by recombinant human and rat equilibrative nucleoside transporters 1 and 2. Chimeric constructs reveal a role for the ENT2 helix 5-6 region in nucleobase translocation
J Biol Chem
(2002) - et al.
Anticancer nucleobase analogues 6-mercaptopurine and 6-thioguanine are novel substrates for equilibrative nucleoside transporter 2
Int J Pharm
(2007) - et al.
Tissue-specific mRNA expression profiles of human ATP-binding cassette and solute carrier transporter superfamilies
Drug Metab Pharmacokinet
(2005) - et al.
Choline transport via choline transporter-like protein 1 in conditionally immortalized rat syncytiotrophoblast cell lines TR-TBT
Placenta
(2009) - et al.
Potential of various drugs to inhibit nucleoside uptake in rat syncytiotrophoblast cell line, TR-TBT 18d-1
Placenta
(2008) - et al.
Influx mechanism of 2′,3′-dideoxyinosine and uridine at the blood–placenta barrier
Placenta
(2009) - et al.
Kinetic and pharmacological properties of cloned human equilibrative nucleoside transporters, ENT1 and ENT2, stably expressed in nucleoside transporter-deficient PK15 cells. ENT2 exhibits a low affinity for guanosine and cytidine but a high affinity for inosine
J Biol Chem
(2000)