Inhibitory interaction of flavonoids with organic anion transporter 3 and their structure-activity relationships for predicting nephroprotective effects.

The organic anion transporter 3 (OAT3), an important renal uptake transporter, is associated with drug-induced acute kidney injury (AKI). Screening and identifying potent OAT3 inhibitors with little toxicity in natural products, especially flavonoids, in reducing OAT3-mediated AKI is of great value. The five strongest OAT3 inhibitors from the 97 flavonoids markedly decreased aristolochic acid I-induced cytotoxicity and alleviated methotrexate-induced nephrotoxicity. The pharmacophore model clarified hydrogen bond acceptors and hydrophobic groups are the critical pharmacophores. These findings would provide valuable information in predicting the potential risks of flavonoid-containing food/herb-drug interactions and optimizing flavonoid structure to alleviate OAT3-related AKI.

Caffeic acid phenethyl ester alleviated hypouricemia in hyperuricemic mice through inhibiting XOD and up-regulating OAT3.

BACKGROUND: Hyperuricemia is characterized with high serum uric acids (SUAs) and directly causes suffering gout. Caffeic acid phenethyl ester (CAPE) is widely included in dietary plants and especially propolis of honey hives. HYPOTHESIS/PURPOSE: Since CAPE exerts a property resembling a redox shuttle, the hypothesis is that it may suppress xanthine oxidase (XOD) and alleviate hyperuricemia. The aim is to unveil the hypouricemic effect of CAPE and the underlying mechanisms. METHODS: By establishing a hyperuricemic model with potassium oxonate (PO) and hypoxanthine (HX) together, we investigated the hypouricecmic effect of CAPE. On this model, the expressions of key mRNAs and proteins, including glucose transporter 9 (GLUT9) and urate transporter 1 (URAT1), and the activity of XOD were assayed in vivo. Also, the inhibitory effect of CAPE against XOD was assayed in vitro through enzymatic activity tests and by molecular docking. RESULTS: CAPE demonstrated a remarkable hypouricemic effect, which reduced the SUAs of hyperuricemic mice (401 ± 111 µmol/l) to 209 ± 56, 204 ± 65 and 154 ± 40 µmol/l (p < 0.01) at the doses of 15, 30 and 60 mg/kg respectively, depicting efficacies between 48 and 62% and approaching allopurinol's efficacy (52%). Serum parameters, body weights, inner organ coefficients, and H&E staining suggested that CAPE displayed no general toxicity and it alleviated the liver and kidney injuries caused by hyperuricemia. Mechanistically, CAPE decreased XOD activities significantly in vivo, presented an IC50 at 214.57 µM in vitro and depicted a favorable binding to XOD in molecular simulation, indicating that inhibiting XOD may be an underlying mechanism of CAPE against hyperuricemia. CAPE did decreased GLUT9 protein and down-regulated URAT1 mRNA and protein. In addition, CAPE up-regulated ATP binding cassette subfamily G member 2 (ABCG2) and organic anion transporter 3 (OAT3) mRNA and proteins in comparison with that of the hyperuricemic control. All above, CAPE may alleviate hyperuricmia through inhibiting XOD, decreasing GLUT9 and URAT1 and increasing ABCG2 and OAT3. CONCLUSION: CAPE presented potent hypouricemic effect in hyperuricemic mice through inhibiting XOD activity and up-regulating OAT3. CAPE may be a promising treatment against hyperuricemia.

Oral epigallocatechin gallate reduces intestinal nadolol absorption via modulation of Oatp1a5 and Oct1 transcriptional levels in spontaneously hypertensive rats.

BACKGROUND: Concurrent use of epigallocatechin-3-gallate (EGCG) and medication may lead to botanical-drug interactions, subsequently therapeutic failure or drug toxicity. It has been reported that EGCG reduces plasma nadolol bioavailability in normotensive models. Nevertheless, evidence on the effects of EGCG on hypertensive model, and the possible underlying mechanism have not been elucidated. OBJECTIVES: This study aims (i) to investigate the effects of EGCG on nadolol pharmacokinetics (maximum plasma concentration, time to achieve maximum concentration, area under the time-plasma concentration curve, plasma half-life and total clearance) and subsequently its impact on blood pressure control; and (ii) to identify transcriptional regulatory roles of EGCG on the nadolol intestinal and hepatic drug-transporters in SHR. METHODS: Male SHR were pre-treated with a daily dose of EGCG (10 mg/kg body weight, i.g.) for 13 days. On day-14, a single dose of nadolol (10 mg/kg body weight) was given to the rats 30 min after the last dose of EGCG administration. Systolic blood pressure (SBP) was measured at 6-h and 22-h post-nadolol administration. Plasma and urinary nadolol concentrations were quantified using high-performance liquid chromatography, and pharmacokinetic parameters were analyzed by using non-compartmental analysis. Hepatic and ileal Oatp1a5, P-gp, and Oct1 mRNA expressions were determined by real-time PCR. RESULTS: SBP of SHR pre-treated with EGCG and received nadolol was significantly higher than those which were not pre-treated with EGCG but received nadolol. Pre-treatment of EGCG resulted in a marked reduction of plasma nadolol maximum concentration (Cmax) and area under the time-plasma concentration curve (AUC) by 53% and 51% compared to its control. The 14-day treatment with oral EGCG led to a significant downregulation of mRNA levels of ileal Oatp1a5, P-gp, and Oct1 genes by 4.03-, 8.01- and 4.03-fold; and hepatic P-gp, and Oct1 genes by 2.61- and 2.66-fold. CONCLUSION: These data concluded that exposure to EGCG could lead to reduced nadolol bioavailability and therefore, uncontrolled raised blood pressure and higher risks of cardiovascular events. Our data suggest that the reduced nadolol bioavailability is associated with the downregulation of ileal Oatp1a5 and Oct1 mRNA levels that subsequently lead to poor absorption of nadolol to the systemic circulation.

Pharmacokinetics of gallic acid and protocatechuic acid in humans after dosing with Relinqing (RLQ) and the potential for RLQ-perpetrated drug-drug interactions on organic anion transporter (OAT) 1/3.

CONTEXT: Relinqing granules (RLQ) are being used alone or in combination with antibacterial drugs to treat urological disorders. OBJECTIVE: This study investigates the pharmacokinetics of RLQ in humans and the potential for RLQ-perpetrated interactions on transporters. MATERIALS AND METHODS: Twelve healthy subjects (six women and six men) participated to compare single- and multiple-dose pharmacokinetics of RLQ. In the single-dose study, all 12 subjects received 8 g of RLQ orally. After a 7-d washout period, the subjects received 8 g of RLQ for seven consecutive days (t.i.d.) and then a single dose. Gallic acid (GA) and protocatechuic acid (PCA) in plasma and urine samples were analysed using LC-MS/MS. The transfected cells were used to study the inhibitory effect of GA (50-5000 µg/L) and PCA (10-1000 µg/L) on transporters OAT1, OAT3, OCT2, OATP1B1, P-gp and BCRP. RESULTS: GA and PCA were absorbed into the blood within 1 h after administration and rapidly eliminated with a half-life of less than 2 h. The mean peak concentrations of GA (102 and 176 µg/L) and PCA (4.54 and 7.58 µg/L) were lower in males than females, respectively. The 24 h urine recovery rates of GA and PCA were about 10% and 5%, respectively. The steady-state was reached in 7 d without accumulation. GA was a potent inhibitor of OAT1 (IC50 = 3.73 µM) and OAT3 (IC50 = 29.41 µM), but not OCT2, OATP1B1, P-gp or BCRP. DISCUSSION AND CONCLUSIONS: GA and PCA are recommended as PK-markers in RLQ-related pharmacokinetic and drug interaction studies. We should pay more attention to the potential for RLQ-perpetrated interactions on transporters.

Effects of rhein and Rheum palmatum L. extract on the pharmacokinetics and tissue distribution of aristolochic acid I and its demethylated metabolite in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Aristolochic acid nephropathy (AAN) is a kidney disease caused by the administration of plants containing aristolochic acids (AAs). Aristolochic acid I (AAI) is the main toxic component in AAs. Organic anion transporters (OATs) 1 and 3 mediate the renal uptake of AAI, which is related to AAN. In our previous study, we found that anthraquinones derived from the herbal medicine Rheum palmatum L. (RP) inhibited both OAT1 and OAT3, with rhein exhibiting the greatest potency among the components. AIM OF THE STUDY: This study aimed to investigate the effects of rhein and RP extract on the pharmacokinetics and tissue distribution of AAI and its demethylated metabolite (8-hydroxy-aristolochic acid I [AAIa]) in rats. MATERIALS AND METHODS: Rhein and RP extract were used as OAT inhibitors, and AAI was used as the toxic substrate. The pharmacokinetics and tissue distribution of AAI and AAIa in rats following the intravenous injection of AAI (10 mg/kg) in the presence and absence of rhein (100 mg/kg) or RP extract (5 g crude drug/kg) were investigated. RESULTS: Co-administration with rhein increased AUC0-∞ of AAI and AAIa by 39 and 44%, respectively. However, the renal level of AAI was decreased to 50, 42, and 58% of those in rats treated with AAI alone at 5, 10, and 20 min after treatment, respectively, and the renal level of AAIa was decreased to 58, 57, and 61% of the level in rats treated with AAI alone, respectively, at these time points. In the RP extract co-administration group, AAI and AAIa plasma exposure was not significantly increased, but renal accumulation of AAI was decreased to 63, 58, and 68% of that in rats treated with AAI alone at 5, 10, and 20 min after treatment, respectively. In addition, renal accumulation of AAIa was decreased to 74, 70, and 70% of that in rats treated with AAI alone at 5, 10, and 20 min after treatment, respectively. CONCLUSIONS: This study indicated that co-administration with rhein significantly increased the plasma exposure of AAI and AAIa while decreased their renal accumulation in rats. RP extract reduced the renal accumulation of AAI and AAIa, but have no significant effect on their plasma exposure levels in rats.

Lycium barbarum polysaccharides protect mice from hyperuricaemia through promoting kidney excretion of uric acid and inhibiting liver xanthine oxidase.

CONTEXT: Lycium barbarum L. (Solanaceae) polysaccharides (LBPs) are important active constituents that have demonstrated kidney protection. OBJECTIVE: This study investigated the effect of LBPs on hyperuricaemia and explored the underlying mechanism in mice. MATERIALS AND METHODS: Thirty-six C57BL/6 mice were randomly divided into the control group, hyperuricaemia group, allopurinol group (5 mg/kg) and three LBP groups (n = 6). The LBP groups were treated orally with LBPs at 50, 100 and 200 mg/kg body weight for 7 days. We examined the levels of serum uric acid (SUA) and urinary uric acid (UUA), as well as xanthine oxidase (XOD) activities. mRNA and protein were quantified by quantitative real-time PCR and Western blotting, respectively. RESULTS: LBPs treatment (100 and 200 mg/kg) significantly reduced the SUA levels to 4.83 and 4.48 mg/dL, and markedly elevated the UUA levels to 4.68 and 5.18 mg/dL (p < 0.05), respectively, while significantly increased the mRNA and protein expression levels of renal organic anti-transporter 1 (OAT1) and organic anti-transporter 3 (OAT3), and markedly decreased the levels of glucose transporter 9 (GLUT9) (p < 0.05). Additionally, the serum XOD activities were reduced to 31.5 and 31.1 mU/mL, and the liver XOD activities were reduced to 80.6 and 75.6 mU/mL after treatment with 100 and 200 mg/kg LBPs (p < 0.01), respectively. DISCUSSION AND CONCLUSIONS: This study demonstrated the potential role of LBPs in reducing the uric acid level in hyperuricemic mice. A border study population should be evaluated. These results are valuable for the development of new anti-hyperuricaemia agents from LBPs.

Organic anion transporter 1 and 3 contribute to traditional Chinese medicine-induced nephrotoxicity.

With the internationally growing popularity of traditional Chinese medicine (TCM), TCM-induced nephropathy has attracted public attention. Minimizing this toxicity is an important issue for future research. Typical nephrotoxic TCM drugs such as Aristolochic acid, Tripterygium wilfordii Hook. f, Rheum officinale Baill, and cinnabar mainly damage renal proximal tubules or cause interstitial nephritis. Transporters in renal proximal tubule are believed to be critical in the disposition of xenobiotics. In this review, we provide information on the alteration of renal transporters by nephrotoxic TCMs, which may be helpful for understanding the nephrotoxic mechanism of TCMs and reducing adverse effects. Studies have proven that when administering nephrotoxic TCMs, the expression or function of renal transporters is altered, especially organic anion transporter 1 and 3. The alteration of these transporters may enhance the accumulation of toxic drugs or the dysfunction of endogenous toxins and subsequently sensitize the kidney to injury. Transporters-related drug combination and clinical biomarkers supervision to avoid the risk of future toxicity are proposed.

Epigallocatechin gallate reduces uric acid levels by regulating xanthine oxidase activity and uric acid excretion in vitro and in vivo.

BACKGROUND: This study investigates the effect of epigallocatechin gallate (EGCG) from tea leaves on hyperuricemia and explores the underlying mechanisms in vitro and in vivo. METHODS: The effects of EGCG on proliferation of BRL 3A rat liver cells were evaluated by CCK8 and after stimulation by xanthine the uric acid and xanthine oxidase (XOD) levels were evaluated by a kit; In an in vivo experiment, rats were treated with oxonic acid potassium salt combined with ethylamine pyrimidine to induce high uric acid hematic disease (7 days), The serum uric acid levels and XOD levels were evaluated by a kit, The expressions of OTA1 and GLUT9 were detected by RT-qPCR and Immunohistochemical. RESULTS: EGCG had no effect on proliferation, and significantly reduced serum uric acid levels and inhibited XOD activity (P<0.05). The rat model exhibited a significant rise in blood uric acid levels (54.59 mg/dL), and EGCG significantly reduced the high level of serum uric acid and inhibited XOD activity in the serum and liver tissues (P<0.05). RT-PCR showed that EGCG significantly increased mOAT1 expression in the kidney tissues and reduced mGLUT9 expression (P<0.05). Immunohistochemical results showed that EGCG significantly increased OAT1 expression in the kidney tissues and decreased GLUT9 expression (P<0.05). CONCLUSIONS: These results demonstrate that EGCG has obvious anti-hyperuricemia effects in vitro and in vivo via the inhibition of XOD activity and GLUT9 expression and the promotion of OAT1 expression.

Spirogyra neglecta Aqueous Extract Attenuates LPS-Induced Renal Inflammation.

Spirogyra neglecta (SN), commonly named "Tao" in Thai, is a genus of filamentous green macroalgae. SN contains polyphenols such as isoquercetin, catechin, hydroquinone and kaempferol. These constituents exhibit beneficial effects including anti-oxidant, anti-gastric ulcer, anti-hyperglycaemia and anti-hyperlipidaemia in both in vitro and in vivo models. Whether SN extract (SNE) has an anti-inflammatory effect in vivo remains unclear. This study examined the effect of SNE on renal function and renal organic transport in lipopolysaccharide (LPS)-induced renal inflammation in rats. Rats were randomised and divided into normal saline (NS), NS supplemented with 1000 mg/kg body weight (BW) of SNE (NS + SNE), intraperitoneally injected with 12 mg/kg BW of LPS and LPS treated with 1000 mg/kg BW of SNE (LPS + SNE). Biochemical parameters in serum and urine, lipid peroxidation concentration, kidney function and renal organic anion and cation transports were determined. LPS-injected rats developed renal injury and inflammation by increasing urine microalbumin, total malondialdehyde (MDA) and inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-1ß protein expression, respectively. In addition, uptake of renal organic anion, [3H]-oestrone sulphate (ES), was reduced in LPS-injected rats together with increased expression of organic anion transporter 3 (Oat3). However, the renal injury and inflammation, as well as impaired Oat3 function and protein expression, were restored in LPS + SNE rats. Accordingly, SNE could be developed as nutraceutical product to prevent inflammation-induced nephrotoxicity.

Pharmacological Evaluation of Dotinurad, a Selective Urate Reabsorption Inhibitor.

The effect of dotinurad [(3,5-dichloro-4-hydroxyphenyl)(1,1-dioxo-1,2-dihydro-3H-1λ 6-1,3-benzothiazol-3-yl)methanone] was compared with that of commercially available uricosuric agents-namely, benzbromarone, lesinurad, and probenecid. Its effect on urate secretion transporters was evaluated using probe substrates for respective transporters. Dotinurad, benzbromarone, lesinurad, and probenecid inhibited urate transporter 1 (URAT1) with IC50 values of 0.0372, 0.190, 30.0, and 165 µM, respectively. Dotinurad weakly inhibited ATP-binding cassette subfamily G member 2 (ABCG2), organic anion transporter 1 (OAT1), and OAT3, with IC50 values of 4.16, 4.08, and 1.32 µM, respectively, indicating higher selectivity for URAT1. The hypouricemic effects of dotinurad and benzbromarone were evaluated in Cebus monkeys. Dotinurad, at doses of 1-30 mg/kg, concomitantly decreased plasma urate levels and increased fractional excretion of urate (FEUA) in a dose-dependent manner. On the contrary, benzbromarone, at a dose of 30 mg/kg, showed a modest effect on plasma urate levels. The inhibitory effect of dotinurad on urate secretion transporters was evaluated in Sprague-Dawley rats, with sulfasalazine and adefovir as probe substrates of ABCG2 and OAT1, respectively. Drugs, including febuxostat as a reference ABCG2 inhibitor, were administered orally before sulfasalazine or adefovir administration. Dotinurad had no effect on urate secretion transporters in vivo, whereas benzbromarone, lesinurad, probenecid, and febuxostat increased the plasma concentrations of probe substrates. These results suggested dotinurad is characterized as a selective urate reabsorption inhibitor (SURI), which is defined as a potent URAT1 inhibitor with minimal effect on urate secretion transporters, including ABCG2 and OAT1/3, because of its high efficacy in decreasing plasma urate levels compared with that of other uricosuric agents. SIGNIFICANCE STATEMENT: Our study on the inhibitory effects on urate transport showed that dotinurad had higher selectivity for urate transporter 1 (URAT1) versus ATP-binding cassette subfamily G member 2 (ABCG2) and organic anion transporter (OAT) 1/3 compared to other uricosuric agents. In Cebus monkeys, dotinurad decreased plasma urate levels and increased fractional excretion of urate in a dose-dependent manner. To determine the inhibitory effect of dotinurad on urate secretion transporters, we studied the movement of substrates of ABCG2 and OAT1 in rats. Dotinurad had no effect on these transporters, whereas the other uricosuric agents increased the plasma concentrations of the substrates. These results suggested dotinurad as a potent and selective urate reabsorption inhibitor is characterized by increased efficacy with decreasing plasma urate levels.

Influence of organic anion transporter 1/3 on the pharmacokinetics and renal excretion of ginkgolides and bilobalide.

ETHNOPHARMACOLOGICAL RELEVANCE: The major terpene lactones of ginkgo biloba extract (GBE) include ginkgolide A, B, C and bilobalide are used for the protection of cardiovascular, cerebrovascular and neurodegenerative diseases. Terpene lactones are orally bioavailable and predominantly eliminated via the renal pathway. However, information on the transporters involved in the pharmacokinetics (PK) and renal excretion of terpene lactones is limited. AIM OF THE STUDY: The objective of this study is to assess the role of OAT1/3 which are important transporters in the human kidney in the PK and renal excretion ginkgolide A, B, C and bilobalide. MATERIALS AND METHODS: Uptake of ginkgolide A, B, C and bilobalide in Madin-Darby Canine Kidney (MDCK) and human embryonic kidney 293 (HEK293) cells overexpressing OAT1 or OAT3, respectively were studied. To verify the result from in vitro cell models, the studies on PK, kidney accumulation and urinary excretion of ginkgolide A, B, C and bilobalide were carried out in rats. RESULTS: The result showed that ginkgolide A, B, C and bilobalide are low-affinity substrates of OAT1/3. Following co-administration with probenecid, a typical inhibitor of OAT1/3, the rat plasma concentrations of ginkgolide A, B, C and bilobalide increased significantly. AUC showed a significant increase in the probenecid-treated rats compared to control rats (893.48 vs. 1123.85, 314.91 vs. 505.74, and 2724.97 vs. 3096.40 µg/L*h for ginkgolide A, B and bilobalide, respectively), while the clearance of these compounds significantly decreased. The accumulation of ginkgolide A, B and bilobalide in the kidney of the probenecid-treated rats was reduced by 1.8, 2.4, and 1.5-fold, respectively; further reducing the cumulative urinary recovery of these compounds. CONCLUSION: The findings indicated that ginkgolide A, B and bilobalide are excreted via OAT1/3-mediated transport in the kidney and OAT1/3 inhibitor significantly influence the PK ginkgolides and bilobalide.

Zebrafish (Danio rerio) Oat1 and Oat3 transporters and their interaction with physiological compounds.

Organic anion transporters (OATs) are membrane proteins within the Solute carrier family 22 (SLC22). They play important roles in cellular uptake of various organic compounds, and due to their expression in barrier tissues of major excretory and non-excretory organs are considered as crucial elements in absorption and distribution of a wide range of endobiotic and xenobiotic compounds. Based on our previous work and initial insights on SLC22 members in zebrafish (Danio rerio), in this study we aimed at in vitro characterization of Oat1 and Oat3 transporters and understanding of their interaction with potential physiological substrates. We first performed synteny analysis to describe in more detail orthological relationship of zebrafish oat1 and oat3 genes. We then developed stable cell lines overexpressing Oat1 and Oat3, and identified Lucifer yellow as Oat1 model fluorescent substrate (Km = 11.4 µM) and 6-carboxyfluorescein as Oat3 model substrate (Km = 5.8 µM). Initial identification performed using the developed assays revealed Kreb's cycle intermediates, bilirubin, bile salts and steroid hormones as the most potent of Oat1 and Oat3 interactors, with IC50 values in micromolar range. Finally, we showed that bilirubin, deoxycholic acid, α-ketoglutarate, pregnenolone, estrone-3-sulfate and corticosterone are in vitro substrates of zebrafish Oat1, and bilirubin and deoxycholic acid are Oat3 substrates. In conclusion, using the approach described, structural and functional similarities of both transporters to human and mammalian orthologs are revealed, their broad ligand selectivity confirmed, potent interactors among endobiotic compounds identified, and first indications of their potential physiological role(s) in zebrafish obtained.

Dual actions on gout flare and acute kidney injury along with enhanced renal transporter activities by Yokuininto, a Kampo medicine.

BACKGROUND: Prolonged hyperuricemia is associated with kidney disease or gouty arthritis. Whether Yokuininto, a commercially available Kampo medicine that has been used for osteoarthritis or rheumatoid arthritis, can exhibit anti-hyperuricemic and inflammatory effects remains elusive. In the present study, Yokuininto exerts multiple homeostatic action on serum uric acid (sUA) levels by blocking pro-inflammatory cytokine activities and inducing uricosuric function with anti-renal injury functions. METHODS: The sUA was measured in potassium oxonate (PO)-administered mice. Renal transporter uptake assays were performed using HEK293 cells overexpressing OAT1, OCT2 or OAT3, MDCKII cells overexpressing BCRP, and Xenopus oocytes overexpressing OAT3 or URAT1. Immunoblot and ELISA assays were performed to detect the molecules (OAT3, GLUT9, XO, NGAL, KIM-1 and IL-1α) in various human kidney cell lines. Cell viability analysis was performed to evaluate the cytotoxicity of Yokuininto [Ephedrine + pseudoephedrine 21.94%; Paeoniflorin 35.40% and Liquiritin 16.21% relatively measured by the ratios (HR-MS2 intensity / HR-MS1 intensity)]. RESULTS: Yokuininto (300 mg/kg) significantly reduced sUA by approximately 44% compared to that of PO-induced mice. The OAT3 levels were decreased in PO-induced hyperuricemic condition, whereas the GLUT9 transporter levels were markedly increased. However, PO did not alter the levels of URAT1. Yokuininto significantly inhibited the lipopolysaccharide (LPS)-induced secretion of IL-1α by approximately 63.2% compared to the LPS-treated macrophages. In addition, Yokuininto inhibited nitric oxide synthesis by approximately 33.7 (500 µg/mL) and 64.6% (1000 µg/mL), compared to that of LPS-treated macrophages. Yokuininto markedly increased xanthine oxidase inhibition activity. Furthermore, interleukin-1α (IL-1α), a pro-inflammatory cytokine, elevated neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) activities in LLC-PK1 cells. Expression of renal inflammatory biomarkers, NGAL and KIM-1, was reduced under the Yokuininto treatment by 36.9 and 72.1%, respectively. CONCLUSIONS: Those results suggest that Yokuininto may suppress inflammation and protect against kidney dysfunction in hyperuricemia. The present findings demonstrated that Yokuininto lowered sUA through both increased uric acid excretion and decreased uric acid production. Our results may provide a basis for the protection of prolonged hyperuricemia-associated kidney injury with uric acid-lowering agents such as Yokuininto.

Modulation of blood-brain barrier function by a heteroduplex oligonucleotide in vivo.

The blood-brain barrier (BBB) is increasingly regarded as a dynamic interface that adapts to the needs of the brain, responds to physiological changes, and gets affected by and can even promote diseases. Modulation of BBB function at the molecular level in vivo is beneficial for a variety of basic and clinical studies. Here we show that our heteroduplex oligonucleotide (HDO), composed of an antisense oligonucleotide and its complementary RNA, conjugated to α-tocopherol as a delivery ligand, efficiently reduced the expression of organic anion transporter 3 (OAT3) gene in brain microvascular endothelial cells in mice. This proof-of-concept study demonstrates that intravenous administration of chemically synthesized HDO can remarkably silence OAT3 at the mRNA and protein levels. We also demonstrated modulation of the efflux transport function of OAT3 at the BBB in vivo. HDO will serve as a novel platform technology to advance the biology and pathophysiology of the BBB in vivo, and will also open a new therapeutic field of gene silencing at the BBB for the treatment of various intractable neurological disorders.

[Study on mechanism of hepatotoxicity of Ploygoni Multiflori Caulis based on function inhibition of bilirubin-associated transporters in idiosyncratic rat].

To explore the possible mechanism of liver injury, the effects of Ploygoni Multiflori Caulis and its extractive on the function of bilirubin-associated transporters were investigated in normal (N) and idiosyncratic (LPS) rats (M). The normal and LPS rats were respectively administrated powder of Ploygoni Multiflori Caulis, its extractive and same volume of 0.5% CMC-Na solution for 7 d. BSP, a substrate of the transporters of Oatp1a1 and Oatp1b2 was selected, and its pharmacokinetic parameters of intravenous injection were determined to examined the activity these transporters. Meanwhile the mRNA expressions of transporters were detected. Compared with N-blank control group, besides M-powder group, the Cmax has no significantly different from other groups, t1/2, AUC0-t and AUC0-∞ were significantly increased, and CL were significantly decreased. However, compared with N- blank control group, AST and ALT decreased significantly. The expression of Oatp1a1, Oatp1b2 and MRP2 mRNA was significantly decreased (P<0.05), but there was no act synergistically when Ploygoni Multiflori Caulis and extractive were combined with LPS. The function of Oatp1a1, Oatp1b2 and MRP2 in rats were significantly inhibited by Ploygoni Multiflori Caulis and extractive, which may be an important cause of hepatotoxicity.

Interaction between rhein acyl glucuronide and methotrexate based on human organic anion transporters.

Rhein, a major bioactive compound of many medicinal herbs and the prodrug of diacerein, is often used with low dose of methotrexate as drug combination to treat rheumatoid arthritis. In this study, potential drug-drug interaction between methotrexate and rhein was investigated based on organic anion transporters (OAT). Our study demonstrated that rhein acyl glucuronide (RAG), the major metabolite of rhein in the human blood circulation, significantly inhibited the uptake of p-aminohippurate in hOAT1 transfected cells with IC50 value of 691 nM and estrone sulfate uptake in hOAT3 transfected cells with IC50 value of 78.5 nM. As the substrate of both hOAT1 and hOAT3, the methotrexate transport was significantly inhibited by RAG in hOAT1 transfected cells at 50 µM and hOAT3 transfected cells at 1 µM by 69% and 87%, respectively. Further in vivo study showed that after co-administrated with RAG in rats the AUC0-24 values of methotrexate increased from 3109 to 5370 ng/mL*hr and the t1/2 was prolonged by 40.5% (from 7.4 to 10.4 h), demonstrating the inhibitory effect of RAG on methotrexate excretion. In conclusion, rhein acyl glucuronide could significantly decrease the transport of methotrexate by both hOAT1 and hOAT3. The combination use of rhein, diacerein or other rhein-containing herbs with methotrexate may cause obvious drug-drug interaction and require close monitoring for potential drug interaction in clinical practice.

Smilax glabra Rhizoma affects the pharmacokinetics and tissue distribution of methotrexate by increasing the P­glycoprotein mRNA expression in rats after oral administration.

Methotrexate (MTX) is a widely used immunosuppressant and anticancer agent with high toxicity. Smilax glabra Rhizoma (SGR) has the effect of detoxification and immunoregulation, and has been used as both food and folk medicine in many countries. Co­administration of MTX and SGR occurs in several diseases. However, whether they work synergistically or are incompatible remains unknown. In the present study, MTX was administrated to rats alone or combined with SGR. Blood and tissue samples were collected at designated times. The concentrations of MTX were determined by high­performance liquid chromatography. Reverse transcription­quantitative polymerase chain reaction (RT­qPCR) was used to detected the gene expression. SGR decreased the AUC0­t and Cmax of MTX by 44.5 and 48.2%, but in a tissue­dependent manner. The total exposure of MTX was significantly decreased in the small intestine, stomach, plasma, and kidney by 61.6, 34.7, 63.3 and 46.1%, respectively, but was increased in the lung and spleen by 82.9 and 21.0%, respectively. RT­qPCR demonstrated that SGR increased the mean P­glycoprotein (gp) mRNA expression in the small intestine 2.54 times, but had a marginal effect on the expression of organic anion transporting polypeptide 2, and organic anion transporter (OAT)1 and OAT2. These results suggested that SGR affects the pharmacokinetics of MTX in a tissue­dependent manner by affecting P­gp, and the clinical effect of co­administration depended on the disease site.

Saponins extracted from Dioscorea collettii rhizomes regulate the expression of urate transporters in chronic hyperuricemia rats.

OBJECTIVE: The current study aimed to investigate whether the saponins, bioactive component of effects of D. collettii, could reduce the serum uric acid level in a hyperuricemic mouse via regulation of urate transporters. METHODS: Chronic hyperuricemia model was established by combine administration of adenine (100mg/kg) and ethambutol (250mg/kg). In the model group, the serum uric acid (SUA), urine uric acid (UUA) volume, and 24-h UUA values increased significantly, while the uric acid clearance rate (CUr) and creatinine clearance rate (CCr) values decreased. Further, the model groups showed significantly lower expression of organic anion transporter 1 (OAT1) and organic anion transporter 3 (OAT3) and significantly higher expression of renal tubular urate transporter 1 (URAT1), glucose transporter 9 (GLUT9) and URAT1 mRNA than the normal control group. RESULTS: Saponins administration was found to have a dose-dependent effect, as evidenced by the increase in the 24-h UUA, CUr and CCr values; the decrease in SUA; the decrease in the renal expression of URAT1 mRNA and URAT1 and GLUT9 proteins; and the increase in the renal expression of the OAT1 and OAT3 proteins. CONCLUSION: The saponins extracted from D. collettii rhizomes had an obvious anti-hyperuricemic effect through downregulation of the URAT1 mRNA and the URAT1 and GLUT9 proteins and upregulation of the OAT1 and OAT3 proteins.

Effect of Garlic, Gingko, and St. John's Wort Extracts on the Pharmacokinetics of Fexofenadine: A Mechanistic Study.

The aim of this study was to determine the effects of garlic and ginkgo herbal extracts on the pharmacokinetics of the P-glycoprotein (P-gp)/organic anion-transporting polypeptides (Oatps) substrate fexofenadine. Male rats were dosed orally with garlic (120 mg/kg), ginkgo (17 mg/kg), St. John's wort (SJW; 1000 mg/kg; positive control), or Milli-Q water for 14 days. On day 15, rats either were administered fexofenadine (orally or i.v.), had their livers isolated and perfused with fexofenadine, or had their small intestines divided into four segments (SI-SIV) and analyzed for P-gp and Oatp1a5. In vivo, SJW increased the clearance of i.v. administered fexofenadine by 28%. Garlic increased the area under the curve0-∞ and maximum plasma concentration of orally administered fexofenadine by 47% and 85%, respectively. Ginkgo and SJW had no effect on the oral absorption of fexofenadine. In the perfused liver, garlic, ginkgo, and SJW increased the biliary clearance of fexofenadine with respect to perfusate by 71%, 121%, and 234%, respectively. SJW increased the biliary clearance relative to the liver concentration by 64%. The ratio of liver to perfusate concentrations significantly increased in all treated groups. The expression of Oatp1a5 in SI was increased by garlic (88%) and SJW (63%). There were no significant changes in the expression of P-gp. Induction of intestinal Oatp1a5 by garlic may explain the increased absorption of orally administered fexofenadine. Ginkgo had no effect on the expression of intestinal P-gp or Oatp1a5. A dual inductive effect by SJW on opposing intestinal epithelial transport by Oatp1a5 and P-gp remains a possibility.

Both cholestatic and steatotic drugs trigger extensive alterations in the mRNA level of biliary transporters in rat hepatocytes: Application to develop new predictive biomarkers for early drug development.

Disruption of the vectorial bile acid transport in the liver is a key feature of cholestatic drugs, although many causal and mechanistic aspects are still unknown. The aim of the present study was to explore if cholestatic drugs can repress or induce the expression of hepatic transporters. To this end, sandwich-cultured rat hepatocytes were treated with cholestatic and non-cholestatic (steatotic, non-hepatotoxic, etc.) drugs and the mRNA expression of 10 uptake and efflux biliary transporters was measured. Results evidenced that all cholestatic drugs cause extensive alterations in the mRNA expression of most biliary transporters. Surprisingly, nearly all steatotic drugs also affected the expression of these genes. The most frequent alterations triggered by both types of drugs were the repression of OATP1A1, NTCP and BSEP, and the induction of MRP2/3/4, MDR2 and ABCG5/8. The majority of these alterations were also observed in vivo, in the livers of treated rats. The common signature of cholestatic and steatotic drugs was the repression of OATP1A1. Indeed, ROC curve analysis indicated that OATP1A1 mRNA is a very sensitive marker to identify drugs with cholestatic or steatotic potential, with a maximal sensitivity and specificity of 0.917 and 0.941, respectively. We conclude that alteration of expression of hepatobiliary transporters is a hallmark of both cholestatic and steatotic drugs, lending support to a connection between these two mechanisms of hepatotoxicity. Moreover, OATP1A1 mRNA is proposed as a very simple and useful screening biomarker for the prediction of new cholestatic or steatotic drugs in early drug development.