Liver is regarded as one of the most important organs for drug clearance in the body, which mediates both the metabolism and biliary excretion of drugs. Transporters are a class of functional membrane proteins and control the movement of substances into or out of cells. Transporters, which are extensively expressed in the liver, play important roles in the drug hepatic disposition by regulating the uptake of drugs from blood into hepatocytes or the efflux of drugs and their metabolites into bile. In this review, the localization, functions and substrate selectivity of the major transporters in the liver will be summarized, and the impacts of these transporters on drug hepatic disposition, the potential drug-drug interactions as well as their genetic polymorphisms will also be reviewed.
ATP Binding Cassette Transporter, Sub-Family G, Member 2 ; ATP-Binding Cassette Transporters ; genetics ; metabolism ; ATP-Binding Cassette, Sub-Family B, Member 1 ; genetics ; metabolism ; Bile ; metabolism ; Biological Transport ; Drug Interactions ; Humans ; Liver ; metabolism ; Membrane Transport Proteins ; genetics ; metabolism ; Metabolic Clearance Rate ; Multidrug Resistance-Associated Proteins ; genetics ; metabolism ; Neoplasm Proteins ; genetics ; metabolism ; Organic Anion Transporters ; genetics ; metabolism ; Organic Anion Transporters, Sodium-Dependent ; metabolism ; Organic Anion Transporters, Sodium-Independent ; genetics ; metabolism ; Organic Cation Transport Proteins ; genetics ; metabolism ; Pharmacokinetics ; Polymorphism, Genetic ; Symporters ; metabolism

Drug transport is an important source of inter-individual variations in drug responses and is also a common site where drug-drug interactions happen. In recent years, more and more novel identified transporters have been added into the transporter super family, and this trend will continue in the future. Among the transporter members of this family, ATP-dependent efflux transporter P-glycoprotein (MDR1) and organic anion transporters (OATP) are the most important proteins involved in drug transport. MDR1 is the most well known transporter. Widely distributed in tissues such as the gastrointestinal tract, liver, kidney and so on, MDR1 plays an important role in drug absorption, distribution and excretion. Its functional genetic polymorphisms have significantly changed the pharmacokinetics of its substrate drugs, which has important clinical implications. OATP expressed in multiple tissues, and it mediated the drug excretion through the bile acid and kidney. Some genetic polymorphism of OATP genes is the cause of some abnormal drug responses.
ATP Binding Cassette Transporter, Subfamily B, Member 1 ; genetics ; Drug Interactions ; genetics ; Humans ; Membrane Transport Proteins ; genetics ; metabolism ; Organic Anion Transporters ; genetics ; Pharmaceutical Preparations ; metabolism ; Polymorphism, Genetic

OBJECTIVETo study organic anion transporting polypeptide (OATP) superfamily member 4a1 (oatp4a1) mRNA expression in the Pi deficiency model rats, thus exploring its mechanism for transporting and transforming the dampness.

METHODSSix SD rats of SPF grade were used to prepare over-fatigue impairing Pi model. Another 12 SD rats were randomly divided into the blank control group and the high fat diets group, 6 in each. The special binding tube was used for the over-fatigue impairing Pi model group on the odd day, 3 h each time. Then the rats were forced to swim in the cold water (10 degrees C +/- 1 degrees C) for 7 min on the even day, for 2 successive weeks. Rats in the model group and the blank control group were granulated feed for 12 weeks, while rats in the high fat group were fed with high fat diet for 12 weeks. All rats were free to take food and drink water. The mRNA and protein expressions of oatp4al were detected in the Fei, Pi, Gan, Shen, Wei, Xiaochang, and Dachang using Real-time fluorescent quantitative polymerase chain reaction (FQ-PCR) and Western blot.

RESULTSRats in the model group were idled together with lousy defecate and coarse skin. They ate and drank less, and lost body weight (P<0.05). They were consistent with clinical manifestations of Pi deficiency syndrome, indicating that the over-fatigue impairing Pi animal model was successfully established. Rats in the high fat group started to have poor appetite and languish spirit, move lazily and addict to sleep, have coarse, dark, and colorless hair 9 weeks later, indicating phlegm dampness syndrome. Compared with the blank control group, the average body weight increased in the high fat group at the 9th week (P<0.05). The oatp4a1 mRNA expressed in the Fei, Pi, Gan, Shen, Wei, Xiaochang, and Dachang. There was no statistical difference in the oatp4al mRNA expression among all tissues (P>0.05). The oatp4al mRNA expressions were higher in the Fei and Shen of the high fat group than in the Gan (P<0.05).

CONCLUSIONSoatp4al might be one of the basic substances in the transportation and transformation of phlegm dampness. Of them, Fei, Shen, and Dachang might play important roles in the transportation and transformation of phlegm dampness.

Animals ; Antiporters ; metabolism ; Diet, High-Fat ; Eye Proteins ; metabolism ; Fatigue ; metabolism ; Male ; Organic Anion Transporters ; metabolism ; RNA, Messenger ; genetics ; Rats ; Yin Deficiency ; metabolism

OBJECTIVETo assess the feasibility of high-resolution melting (HRM) analysis for screening patients with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD).

METHODSBased on previous studies on SLC25A13 gene in Chinese patients with NICCD, four hotspot mutations (851del4, 1638ins23, IVS6+5G>A and IVS16ins3kb) were selected. Results of the HRM analysis was validated using 50 negative controls and 20 patients with NICCD whose genotypes were confirmed previously by direct sequencing. With the established protocol, 171 suspected patients were enrolled. Samples with abnormal melting curves were further validated by DNA sequencing.

RESULTSHRM analysis can accurately determine the genotypes of all negative controls and patients. The sensitivity and specificity of the technique reached 100% (70/70). The melting curves of samples with the same genotype were highly reproducible. In 171 suspected patients, seven NICCD patients were detected by HRM. Identified mutations have included one case of 851del4 homozygote, one case of IVS6+5G>A heterozygote, 3 cases of 851del4 heterozygotes, one case of [IVS6+5G>A]+[ 851del4] and one case of [1638ins23+IVS16ins3kb]+[1638ins23]. All mutations were subsequently confirmed by DNA sequencing.

CONCLUSIONHRM analysis is a convenient, high-throughput and rapid technique for the screening of NICCD patients.

Anion Transport Proteins ; genetics ; Base Sequence ; Calcium-Binding Proteins ; deficiency ; China ; Citrullinemia ; diagnosis ; genetics ; metabolism ; DNA ; chemistry ; genetics ; Genetic Predisposition to Disease ; Genotype ; Humans ; Mitochondrial Proteins ; genetics ; Molecular Sequence Data ; Mutation ; Nucleic Acid Denaturation ; Organic Anion Transporters ; deficiency ; Sensitivity and Specificity

AIM: The present study was undertaken to characterize the effects of Wuling San on urate excretion and renal function, and explore its possible mechanisms of action in hyperuricemic mice. METHODS: Mice were administered with 250 mg·kg(-1) potassium oxonate by gavage once daily (10 animals/group) for seven consecutive days to develop a hyperuricemia model. Different doses of Wuling powder were orally initiated on the day 1 h after oxonate was given, separately. Allopurinol was used as a positive control. Serum and urine levels of uric acid and creatinine, and fractional excretion of uric acid (FEUA) were measured in hyperuricemic mice treated with Wuling San and allopurinol. Simultaneously, renal mRNA and protein levels of urate transporter 1 (mURAT1), glucose transporter 9 (mGLUT9), organic anion transporter 1 (mOAT1), as well as organic cation/carnitine transporters mOCT1, mOCT2 and mOCTN2, were assayed by semi-quantitative RT-PCR and Western blot methods, respectively. RESULTS AND CONCLUSION Compared to the hyperuricemia control group, Wuling San significantly reduced serum uric acid and creatinine levels, increased 24 h urate and creatinine excretion, and FEUA in hyperuricemic mice, exhibiting its ability to enhance urate excretion and improve kidney function. Wuling San was found to down-regulate mRNA and protein levels of mURAT1 and mGLUT9, as well as up-regulate mOAT1 in the kidney of hyperuricemic mice. Moreover, Wuling San up-regulated renal mRNA and protein levels of mOCT1, mOCT2 and mOCTN2, leading to kidney protection in this model.
Animals ; Drugs, Chinese Herbal ; administration & dosage ; Glucose Transport Proteins, Facilitative ; genetics ; metabolism ; Humans ; Hyperuricemia ; drug therapy ; genetics ; metabolism ; Kidney ; drug effects ; metabolism ; Male ; Mice ; Organic Anion Transport Protein 1 ; genetics ; metabolism ; Organic Anion Transporters ; genetics ; metabolism ; Up-Regulation ; drug effects ; Uric Acid ; metabolism

OBJECTIVETo investigate the diagnostic value of histopathological changes in the liver of patients with neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD).

METHODSLiver specimens from 10 cases of NICCD were evaluated by hematoxylin-eosin stain, histochemistry and immunohistochemistry (EnVision method). SLC25A13 mutation analysis was performed to correlate with histopathology.

RESULTSMost specimens showed varying degrees of fat deposition in hepatocytes, necrotic inflammation, cholestasis and fibrosis (so-called tetralogy). The combination of the above four histological changes was highly characteristic for NICCD. With the progression of the disease, hepatic fibrosis deteriorated and ultimately led to cirrhosis.

CONCLUSIONSNICCD should be suspected in the presence of cholestasis during infancy. A liver biopsy must be performed to rule out other liver diseases. The tetralogy of the hepatic histopathological changes has a highly diagnostic value for NICCD, which is also practical for accurately assessing the degree of inflammation and fibrosis, and similarly the progression of hepatic cirrhosis.

Biopsy ; Calcium-Binding Proteins ; deficiency ; genetics ; metabolism ; Cholestasis, Intrahepatic ; etiology ; genetics ; pathology ; Disease Progression ; Female ; Hepatocytes ; pathology ; Humans ; Infant ; Liver ; pathology ; Liver Cirrhosis ; pathology ; Male ; Mitochondrial Membrane Transport Proteins ; genetics ; Mutation ; Organic Anion Transporters ; deficiency ; genetics ; metabolism

The human organic anion transporter 4 (hOAT4) has been identified as the fourth isoform of OAT family. hOAT4 contributes to move several negatively charged organic compounds between cells and their extracellular milieu. The functional characteristics and regulatory mechanisms of hOAT4 remain to be elucidated. It is well known that caveolin plays a role in modulating proteins having some biological functions. To address this issue, we investigated the co-localization and interaction between hOAT4 and caveolin-1. hOAT4 and caveolin-1 (mRNA and protein expression) were observed in cultured human placental trophoblasts isolated from placenta. The confocal microscopy of immuno-cytochemistry using primary cultured human trophoblasts showed hOAT4 and caveolin-1 were co-localized at the plasma membrane of the cell. This finding was confirmed by Western blot analysis using isolated caveolae-enriched membrane fractions and immune-precipitates from the trophoblasts. When synthesized cRNA of hOAT4 along with scrambled- or antisense-oligodeoxynucleotide (ODN) of Xenopus caveolin-1 were co-injected to Xenopus oocytes, the [3H]estrone sulfate uptake was significantly decreased by the co-injection of antisense ODN but not by scrambled ODN. These findings suggest that hOAT4 and caveolin-1 share a cellular expression in the plasma membrane and caveolin-1 up-regulates the organic anionic compound uptake by hOAT4 under the normal physiological condition.
Animals ; Caveolin 1/genetics/*metabolism ; Cells, Cultured ; Female ; Humans ; Immunohistochemistry ; Immunoprecipitation ; Microscopy, Confocal ; Models, Biological ; Oocytes/metabolism ; Organic Anion Transporters/genetics/*metabolism ; Placenta/cytology ; Protein Binding ; Reverse Transcriptase Polymerase Chain Reaction ; Trophoblasts/cytology/*metabolism ; Xenopus

OATP1B3, a member of SLC superfamily, is specifically expressed on the sinusoidal membrane of hepatocytes and is considered to be important in hepatic drug elimination. The overexpression of OATP1B3 was found recently in tumor tissues such as prostate, colon, and pancreatic tumors. Sequence variations in SLCO1B3 gene, such as SNPs, have been described and a common haplotype consisting of 334T>G and 699G>A SNPs is related to altered transport characteristics of OATP1B3. OATP1B3 is of relevance to drug metabolism through affecting alteration of hepatic concentration of endo- and xenobiotic compounds that interact with nuclear receptors such as PXR and CAR, and thereby directly alter the extent of target gene transcription, including major CYP isoenzymes such as CYP3A4. This review will provide an overview of substrates and inhibitors of OATP1B3 and subsequently to assess the effect of genetic mutation on transport activity. The studies linking OATP1B3 with cancer clinical outcomes are also discussed in this review.
Animals ; Biological Transport ; Cytochrome P-450 CYP3A ; metabolism ; Drug Interactions ; Gene Expression Regulation, Neoplastic ; Gene Frequency ; Hepatocytes ; metabolism ; Humans ; Liver ; metabolism ; Neoplasms ; metabolism ; Organic Anion Transporters, Sodium-Independent ; antagonists & inhibitors ; chemistry ; genetics ; Polymorphism, Single Nucleotide ; RNA, Messenger ; metabolism ; Receptors, Cytoplasmic and Nuclear ; metabolism ; Receptors, Steroid ; metabolism ; Solute Carrier Organic Anion Transporter Family Member 1B3

By analyzing the related indicators [hepatic CYP450 subtype and renal organic anion and cation transporters (OATs and OCTs)], the present study investigated the effects of formula Banxia Houpo decoction principal drug pinellia, assistant drug magnolia, their compatibility and the principle of the whole decoction on the metabolism ability in the liver and the transport change in the kidney of mice. Biochemical and molecular (RT-PCR and western blotting) results indicated that pinellia increased activity and expression of hepatic Cyp2e1 and Cyp3a11 in mice, respectively. Pinellia and magnolia increased expression of renal OAT1, OAT3, OCT1 and OCT2 in mice, respectively. The compatibility of pinellia and magnolia, as well as Banxia Houpo decoction synergistically restrained the activated effect of pinellia on hepatic Cyp2e1, therefore avoiding liver peroxidation and reducing toxicity potential. The compatibility of this drug pair and Banxia Houpo decoction not only reduced activity and expression of hepatic Cyp3a11 to control drug metabolism speed, but also balanced the expression of renal OAT1/3 and OCT1/2 to enhance drug efficacy. The effect of compatibility of Banxia Houpo decoction was better than that of pinellia and magnolia pair, and the normal dosage was better than the high dosage. The present study proved the advantage of the compatibility of pinellia combined with magnolia and the principle of Banxia Houpo decoction, which related to hepatic CYP450 and renal organic ion transporters, and guided the clinical use of Banxia Houpo decoction to exert its toxicity reduction and efficacy enhancement.
Animals ; Cytochrome P-450 Enzyme System ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; Gene Expression ; drug effects ; Kidney ; drug effects ; metabolism ; Liver ; drug effects ; enzymology ; metabolism ; Male ; Mice ; Organic Anion Transporters ; genetics ; metabolism

OBJECTIVETo explore roles of mRNA and protein expressions of organic anion transporting polypeptide (oatp2b1) of rats with high fat diet and overstrain induced Pi deficiency syndrome in the transporting of damp turbidity.

METHODSTotally 24 SD rats were randomly divided into three groups, i.e., the normal group, the overstrain group, and the high fat diet group, 8 in each group. After successful modeling, one piece of tissues such as spleen, kidney, liver, lung, stomach, small intestine, and large intestine was taken from each rat. Rats of the overstrain group were bonded by specially made bondage cylinder, 3 h each time on odd days, and forced to swim in cold water (10 +/- 1) degrees C for 7 min on even days alternatively for twelve weeks. Rats in the model group and the normal group were fed with standard routine granular forage for 12 weeks. Rats in the high fat diet group were fed with high fat forage for twelve weeks. All rats drank and ate freely. The mRNA and protein expressions of oatp2b1 were detected in the seven tissues using RT-PCR and Western blot.

RESULTSThe mRNA expression of oatp2b1 in liver and kidney tissues of rats in the high fat diet group was higher when compared with that of the normal group and the overstrain group (P < 0.01, P < 0.05). The oatp2b1 mRNA expression in the normal group was sequenced from high to low as liver > lung > spleen > larger intestine > small intestine > kidney > stomach. The oatp2b1 mRNA expression in the overstrain group was sequenced from high to low as liver > lung > larger intestine > spleen > kidney > stomach > small intestine. The oatp2b1 mRNA expression in the high fat diet group was sequenced from high to low as liver > lung > spleen > small intestine > kidney > larger intestine > stomach. The oatp2b1 protein expression in the lung tissue was sequenced from high to low as the overstrain group > the normal group > the high fat diet group (P > 0.05). The oatp2b1 protein expression in the spleen tissue was sequenced from high to low as the high fat diet group > the normal group > the overstrain group (P > 0.05). The oatp2b1 protein expression in the kidney tissue was sequenced from high to low as the normal group > the overstrain group > the high fat diet group (P > 0.05). The oatp2b1 protein expression in the liver tissue was sequenced from high to low as the normal group > the high fat diet group > the overstrain group (P > 0.05). Of them, the oatp2b1 protein expressed extremely less in the stomach, large intestine, and small intestine. The oatp2b1 protein expression in the normal group was sequenced from high to low as lung >spleen > liver, kidney > stomach, larger intestine, and small intestine. The oatp2b1 protein expression in the overstrain group was sequenced from high to low as lung > spleen > kidney > liver > stomach, larger intestine, and small intestine. The oatp2b1 protein expression in the high fat diet group was sequenced from high to low as spleen > lung > kidney > liver > stomach, larger intestine, and small intestine. However, there was no statistical significance among the three groups by pair-wise comparison (P > 0.05).

CONCLUSIONSKidney and liver might play important roles in the transportation and transformation of damp under the state of Pi deficiency syndrome. Oatp2b1 may be one of the material bases involved in the transportation and transformation of damp turbidity. Pi's function of governing transportation and transformation of damp might not only include the functions of the gastrointestinal tract, but also include partial liver and kidney functions.

Animals ; Diet, High-Fat ; Disease Models, Animal ; Fatigue ; diagnosis ; metabolism ; Kidney ; metabolism ; Liver ; metabolism ; Male ; Medicine, Chinese Traditional ; Organic Anion Transporters ; metabolism ; RNA, Messenger ; genetics ; Rats ; Rats, Sprague-Dawley