基于毒理学软件和细菌回复突变试验的大黄素型蒽醌基因突变风险评价

目的 使用毒理学软件和细菌回复突变（Ames）试验评价大黄素型蒽醌类化合物的致突变风险，分析不同取代基及所在位置对大黄素型蒽醌致突变风险的影响。方法 使用Toxtree、Derek Nexus和Sarah Nexus毒性预测软件对大黄素、羟基大黄素、芦荟大黄素、大黄素甲醚、大黄酚、大黄酸、大黄素-8-O-β-D-葡萄糖苷、芦荟大黄素-8-O-β-D-葡萄糖苷、大黄素-1-O-β-D-葡萄糖苷、大黄素甲醚-8-O-β-D-葡萄糖苷的致突变风险进行预测，并使用鼠伤寒沙门氏菌TA97、TA98、TA100、TA102、TA1535和TA1537及大肠杆菌WP2 uvrA开展基于6孔板的Ames试验，评价10种大黄素型蒽醌的致突变性。结果 基于蒽醌母核结构，Toxtree、Derek Nexus和Sarah Nexus毒性预测软件提示所有大黄素型蒽醌均存在致突变风险。在非S9代谢活化状态下，芦荟大黄素导致TA98和WP2 uvrA Ames菌落数增加，大黄酚、大黄酸导致WP2 uvrA Ames菌落数增加。在大鼠肝S9代谢活化状态下，大黄素和大黄酸导致TA98和TA1537 Ames菌落数增加，羟基大黄素导致TA97、TA98、TA1537和WP2 uvrA Ames菌落数增加，芦荟大黄素导致TA98、TA1537和WP2 uvrA Ames菌落数增加，大黄素甲醚导致TA1537 Ames菌落数增加，大黄酚导致TA1537和WP2 uvrA回复菌落突变数增加，大黄素-8-O-β-D-葡萄糖苷可引起TA1537回复突变菌落数增加。结论 大黄素型蒽醌类化合物在大黄素母核的基础引入羟基后其诱变能力显著升高，较大葡萄糖苷基团的引入反而使受试物诱变能力降低。     

基于体外Pig-a基因突变试验的大黄素型蒽醌致突变风险评价

目的 对相同母核结构的8种大黄素型蒽醌类化合物开展体外Pig-a基因突变试验，分析不同大黄素型蒽醌结构与致突变性的关联。方法 L1578Y细胞分别与系列浓度的大黄素、芦荟大黄素、大黄素甲醚、大黄酚、大黄酸、羟基大黄素、大黄素-8-O-β-D-葡萄糖苷和芦荟大黄素-8-O-β-D-葡萄糖苷作用4 h（有S9）或24 h（无S9），给药24 h后应用细胞计数板进行计数，计算细胞相对倍增速率（RPD）评价受试物细胞毒性；细胞表达8 d后经APC-anti-CD45和PE-anti-CD90.2标定后，使用流式细胞仪检测突变细胞（CD45^＋CD90^－）发生率。结果 所有受试物在有或无S9代谢活化条件下所设浓度组RPD均大于50%，未见明显细胞毒性作用，可排除试验中假阳性结果。在非S9代谢活化条件下芦荟大黄素25 μg·mL^-1组Pig-a基因突变率与溶媒对照组比较显著升高（P<0.001）； S9代谢活化条件下，与溶剂对照组比较，大黄素50 μg·mL^-1组，羟基大黄素6.25、12.5、25 μg·mL^-1组，大黄酚25、50、100 μg·mL^-1组和大黄酸12.5、25、50 μg·mL^-1组Pig-a基因突变率显著升高（P<0.05、0.01、0.001）。结论 羟基取代基的多寡及所在位点是蒽醌类化合物致突变性强弱的决定性因素，其体内致突变性及致癌性作用仍需进行大量体内研究证实。     

HPLC法测定通乐颗粒中2, 3, 5, 4′-四羟基二苯乙烯-2-O-β-D-葡萄糖苷

目的 建立测定通乐颗粒中2, 3, 5, 4′-四羟基二苯乙烯-2-O-β-D-葡萄糖苷的方法。方法 采用HPLC法,色谱柱为Phenomenex C₁₈柱,检测波长为320 nm,流动相为乙腈-水（20∶80）,体积流量为1.0 mL/min。结果 2, 3, 5, 4′-四羟基二苯乙烯-2-O-β-D-葡萄糖苷在10～100 μg/mL与峰面积呈良好线性关系（r＝0.999 7）,平均回收率为99.74%。结论 本方法准确、简便、重复性好,可用于通乐颗粒中2, 3, 5, 4′-四羟基二苯乙烯-2-O-β-D-葡萄糖苷的含量测定。     

HPLC测定安尔眠胶囊中2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷

目的 建立安尔眠胶囊中2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷（C₂₀H₂₂0₉）的含量测定方法。方法 采用高效液相色谱（HPLC）法,以Dionex Acclaim 120^® C₁₈色谱柱（150 mm×4.6 mm,5 μm）为分离柱,以乙腈-1%甲酸溶液（23：77）为流动相,体积流量1.0 mL/min,检测波长320 nm,柱温25 ℃。结果 2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷在0.010～0.200 μg呈现良好的线性关系（r=0.999 6）,平均回收率为97.35%,RSD为2.07%。结论 该方法<准确可靠,适用于安尔眠胶囊中2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷的含量测定。     

平消胶囊联合左甲状腺素钠治疗结节性甲状腺肿的临床研究

目的 对狭叶薰衣草Lavandula angustifolia中的木脂素类化合物进行研究。方法 运用RP-HPLC、TLC、硅胶、凝胶、MCI-gel树脂等方法进行分离纯化,并根据理化性质和波谱数据鉴定化合物的结构。结果 从狭叶薰衣草中分离得到11个木脂素类化合物,分别鉴定为松脂醇（1）、丁香树脂醇（2）、fraxiresinol-4''-O-β-D-glucopyranoside（3）、syringaresinol-4''-O-β-D-glucopyranoside（4）、8-hydroxypinoresinol-4-O-β-D-glucopyranoside（5）、rel-（2α,3β）-7-O-methylcedrusin（6）、落叶松脂醇-4''-O-β-D-葡萄糖苷（7）、（2S,3R）-2,3-dihydro-2-（4-hydroxy-3-methoxyphenyl）-3-hydroxymethyl-7-methoxybenzofuran-5-（trans） propen-1-ol-3-O-β-glucoside（8）、（7S,8R）-dihydrodehydrodiconiferyl alcohol-9-β-D-glucopyranoside（9）、（7R,8R）-7,8-dihydro-9''-hydroxyl-3''-methoxyl-8-hydroxymethyl-7-（4-hydroxy-3-methoxyphenyl）-1''-benzofuranpropanol-9''-O-β-D-glucopyranoside（10）、（E）-3-（（2S,3S）-2-（4-hydroxy-3-methoxyphenyl）-3-hydroxymethyl-7-methoxy-2,3-dihydrobenzofuran-5-yl） allyl-2-hydroxyacetate（11）。结论 11个化合物均首次从狭叶薰衣草中分离得到。     

银杏叶中的黄酮醇苷类成分

目的　对银杏（Ginkgo biloba L.）叶的化学成分进行分离、鉴定。方法　采用各种色谱技术进行分离,用IR,UV,MS,¹HNMR,¹³CNMR和2DNMR光谱技术确定化合物的结构。结果　分得8个黄酮醇苷类成分：槲皮素-3-O-β-D-葡糖苷（1）,山奈酚-3-O-β-D-葡糖苷（2）,芦丁（3）,山奈酚-3-O-β-D-芸香糖苷（4）,异鼠李素-3-O-β-D-芸香糖苷（5）,槲皮素-3-O-β-D-葡萄糖基(1-2)-α-L-鼠李糖苷（6）,山奈酚-3-O-β-D-葡萄糖基(1-2)-α-L-鼠李糖苷（7）,异鼠李素-3-O-β-D-葡萄糖基(1-2)-α-L-鼠李糖苷（8）。结论　化合物8为新化合物。     

HPLC法测定软脉灵口服液中毛蕊花糖苷、焦地黄苯乙醇苷B1、迷迭香酸、紫草酸、丹酚酸B、2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷和虎杖苷

目的 建立HPLC法测定软脉灵口服液中毛蕊花糖苷、焦地黄苯乙醇苷B1、迷迭香酸、紫草酸、丹酚酸B、2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷和虎杖苷。方法 采用Venusil XBP C₁₈色谱柱（250 mm×4.6 mm,5μm）;以乙腈–0.1%甲酸水溶液为流动相,梯度洗脱;检测波长分别为330 nm（0～17 min检测毛蕊花糖苷和焦地黄苯乙醇苷B1）、280 nm（17～50 min检测迷迭香酸、紫草酸、丹酚酸B、2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷和虎杖苷）;体积流量1.0 mL/min;柱温30℃;进样量10μL。结果 毛蕊花糖苷、焦地黄苯乙醇苷B1、迷迭香酸、紫草酸、丹酚酸B、2,3,5,4’-四羟基二苯乙烯-2-O-β-D-葡萄糖苷和虎杖苷分别在1.23～30.75、0.59～14.75、0.71～17.75、1.47～36.75、9.78～244.50、6.57～164.25、1.19～29.75 μg/mL线性关系良好（r≥0.999 1）;平均回收率分别为99.14%、97.62%、96.84%、98.96%、100.11%、99.46%、98.92%,RSD值分别为1.15%、1.27%、1.02%、0.96%、0.65%、1.41%、0.87%。结论 该方法操作简便、重复性好,为软脉灵口服液中多指标质量评价和临床应用提供参考依据。     

红芽大戟化学成分研究

目的研究茜草科植物红芽大戟(Knoxia corymbosa Willd．)的化学成分。方法利用硅胶、聚酰胺等色谱技术分离纯化,根据化合物的理化性质和光谱数据进行鉴定。结果从红芽大戟的正丁醇萃取部分分离得到4个黄酮醇苷成分,分别鉴定为:槲皮素-7-O-α-L-阿拉伯糖-3-O-β-D-6″-乙酰基吡喃葡糖苷(quercetin-7- O-α-L-arabinosyl-3-O-β-D-6″-acetylglucopyranoside,1);山奈酚-7-O-α-L-阿拉伯糖-3-O-β-D-吡喃葡糖苷(kaempferol-7-O-α-L-arabinosyl-3-O-β-D-glucopyranoside,2);槲皮素-3-O-β-D-吡喃葡糖苷(quercetin-3-O-β-D-glucopyranoside,3); 槲皮素-3-O-β-D-6″-乙酰基吡喃葡糖苷(quercetin-3-O-β-D-6″-acetylglucopyranoside,4)。结论化合物1为新化合物,其余均为首次从该种植物分到。     

UHPLC-FLD法测定不同产地大黄中6种大黄蒽醌

目的 建立超高效液相色谱荧光（UHPLC-FLD）法同时测定大黄中大黄素、芦荟大黄素、大黄酸、大黄酚、大黄素甲醚和大黄素-8-O-β-D-葡萄糖苷的含量,并应用于10个不同产地大黄饮片的分析。方法 大黄粉末经甲醇提取制备供试品溶液,采用Agilent Poroshell 120 EC-C₁₈柱（50 mm×4.6 mm,2.7 μm）;流动相为0.1%甲酸水溶液（A）-0.1%甲酸甲醇（B）,梯度洗脱;体积流量0.6 mL·min^-1;柱温30℃;荧光检测器激发波长435 nm,发射波长515 nm。进行专属性、线性关系、定量限及检出限、精密度、稳定性、重复性、加样回收率考察。应用已建立的方法分析10个不同产地大黄饮片中6种大黄蒽醌含量。结果 6种成分在各自范围内线性关系良好,精密度、稳定性、重复性均良好;平均加样回收率为97.86%～103.2%,RSD为1.27%～2.15%。10个不同产地大黄饮片中蒽醌总量均符合《中国药典》要求;但不同产地的大黄中蒽醌单体的含量差别较大。结论 建立的UHPLC-FLD法灵敏、快速、准确、稳定且重复性好,可用于大黄中6种大黄蒽醌的含量测定。     

消乳散结胶囊联合他莫昔芬治疗乳腺增生症的疗效观察

目的 研究瑞香狼毒Stellera chamaejasme花中黄酮和木脂素类化学成分及其抗氧化活性,分析构效关系。方法 利用大孔吸附树脂、正反相硅胶、Sephadex LH-20等色谱分离材料,通过柱色谱和高效液相色谱等分离方法进行分离纯化,运用核磁共振（NMR）、质谱（MS）等波谱技术鉴定化合物结构,并采用FRAP法、DPPH法和ABTS法对分离得到的化合物进行体外抗氧化活性测试。结果 从瑞香狼毒花甲醇提取物中分离鉴定了12个化合物,分别鉴定为艾黄素（1）、槲皮素（2）、isoscutellarein-8-O-β-D-glucuronopyranoside（3）、槲皮素-3-O-β-D-葡萄糖苷（4）、紫云英苷（5）、hypolaetin-8-O-β-D-glucuronopyranoside（6）、kaempferol 3-O-β-D-glucopyranosyl-（1→2）-O-α-L-xylopyranoside（7）、rel-（3R,3''S,4R,4''S）-3,3'',4,4''-tetrahydro-6,6''-dimethoxy[3,3''-bi-2H-benzopyran]-4,4''-diol（8）、马台树脂醇（9）、乌拉尔醇（10）、环黄芪醇（11）、松脂醇（12）。抗氧化活性实验表明,黄酮和木脂素类化合物均显示了较强的抗氧化活性。结论 化合物1、3、5～7和10为首次从该植物中分离得到;化合物2、4、5和10表现出显著的抗氧化活性,其中黄酮类化合物C-3或C-8位连有糖链会降低其抗氧化活性。     

Clinical importance of OATP1B1 and OATP1B3 in drug-drug interactions

OATP1B1 and OATP1B3 are transporters that are expressed on the sinusoidal membrane of hepatocytes; they accept a number of therapeutic reagents as their substrates. In vitro and in vivo studies have shown that some drugs inhibit these transporters and cause clinically relevant drug-drug interactions (DDIs). Among these drugs, cyclosporin A markedly increases the plasma concentrations of OATP1B1 substrates. In such cases, the area under the plasma concentration-time curve and the maximum concentration of the affected drugs are increased to a similar degree. Even for OATP1B1 substrates that are metabolized in the liver, the hepatic uptake rate is a determinant of overall hepatic clearance, and the DDIs are partly caused by the inhibition of OATP1B1. Gemfibrozil displays DDIs with some OATP1B1 substrates, although their extent is small. Rifampicin and some HIV protease inhibitors are also OATP1B1 inhibitors. Rifampicin is also an inducer of metabolic enzymes, and although its single coadministration produces an increase in the plasma concentration of the affected drugs, multiple coadministrations may result in reductions in the plasma concentrations of OATP1B1 and CYP3A4 bisubstrates. As a large number of therapeutic reagents are substrates and/or inhibitors of OATP1B1 and OATP1B3, we should be aware of DDIs caused by the inhibition of these transporters.     

Interaction of Sulfonylureas with Liver Uptake Transporters OATP1B1 and OATP1B3

Sulfonylureas (SUs) such as glibenclamide, gliclazide, glimepiride, glipizide and gliquidone are one of the first oral medicines available for the treatment of type 2 diabetes and are widely used for the treatment of hyperglycaemia. The hepatic transporters, organic anion transporting polypeptide 1B1 (OATP1B1) and organic anion transporting polypeptide 1B3 (OATP1B3), play an important role in the disposition of a variety of drugs by mediating their uptake from blood into hepatocytes. Drug–drug interactions mediated by OATP1B1/1B3 may result in the hepatic transporting change for drug substrates. The inhibitory effects of glibenclamide and glimepiride on sulfobromophthalein (BSP) uptake have been previously studied, and glibenclamide has been reported as the substrate of OATP1B3, but it remains unclear whether other SUs such as gliclazide, glipizide and gliquidone are substrates of OATP1B1 and OATP1B3. Here, we investigated the relationship between the five most commonly applied SUs (glibenclamide, gliclazide, glimepiride, glipizide, gliquidone) and OATP1B1 and OATP1B3. We performed uptake and inhibition assays in HEK293T cells stably expressing OATP1B1 or OATP1B3, respectively, and established a liquid chromatography–mass spectrometry (LC‐MS) method for the simultaneous measurement of five SUs. We demonstrated that gliclazide and glimepiride are substrates of OATP1B1 and glibenclamide and glipizide are substrates of OATP1B3. We also confirmed the interaction between these SUs and rosuvastatin. No transporting was observed for gliquidone, suggesting that it is not a substrate of either transporter.     

Interactions of crizotinib and gefitinib with organic anion-transporting polypeptides (OATP)1B1, OATP1B3 and OATP2B1: gefitinib shows contradictory interaction with OATP1B3

1.?The drug–drug interaction (DDI) mediated by organic anion-transporting polypeptide (OATP)1B1, OATP1B3 and OATP2B1 has a major impact on the hepatic clearance of drugs. The effects of tyrosine kinase inhibitors (TKIs) on OATPs have not been well studied. In the present study, we evaluated the contribution of OATPs to the hepatic uptake of crizotinib and gefitinib and the interaction of those TKIs with OATPs to estimate DDIs.

2.?To clarify whether crizotinib and gefitinib were substrates for OATPs, we performed uptake studies. We examined the effects of the TKIs on uptake of typical substrates and fluvastatin via OATPs. IC₅₀ and EC₅₀ values of the TKIs were calculated.

3.?OATP1B3- and OATP2B1-mediated crizotinib uptake and OATP2B1-mediated gefitinib uptake were observed. Gefitinib accelerated OATP1B3-mediated [³H]TCA uptake and inhibited OATP2B1-mediated [³H]E₃S uptake. On the other hand, gefitinib inhibited OATP1B1- and OATP2B1-mediated fluvastatin uptake.

4.?We provided basic information to estimate the DDI on OATPs caused by TKIs. The DDI on OATPs caused by gefitinib could occur in a normal clinical situation. And the uptake of crizotinib into the intrahepatocellular environment via OATPs may induce DDI and liver damage. We therefore emphasize the necessity of careful use of TKIs.     

Substrate-dependent drug-drug interactions between gemfibrozil, fluvastatin and other organic anion-transporting peptide (OATP) substrates on OATP1B1, OATP2B1, and OATP1B3.

Hepatic uptake carriers of the organic anion-transporting peptide (OATP) family of solute carriers are more and more recognized as being involved in hepatic elimination of many drugs and potentially associated drug-drug interactions. The gemfibrozil-statin interaction was studied at the level of active hepatic uptake as a model for such drug-drug interactions. Active, temperature-dependent uptake of fluvastatin into primary human hepatocytes was shown. Multiple transporters are involved in this uptake as Chinese hamster ovary or HEK293 cells expressing either OATP1B1 (K(m) = 1.4-3.5 microM), OATP2B1 (K(m) = 0.7-0.8 microM), or OATP1B3 showed significant fluvastatin uptake relative to control cells. For OATP1B1 the inhibition by gemfibrozil was substrate-dependent as the transport of fluvastatin (IC(50) of 63 microM), pravastatin, simvastatin, and taurocholate was inhibited by gemfibrozil, whereas the transport of estrone-3-sulfate and troglitazone sulfate (both used at 3 microM) was not affected. The OATP1B1- but not OATP2B1-mediated transport of estrone-3-sulfate displayed biphasic saturation kinetics, with two distinct affinity components for estrone-3-sulfate (0.23 and 45 microM). Only the high-affinity component was inhibited by gemfibrozil. Recombinant OATP1B1-, OATP2B1-, and OATP1B3-mediated fluvastatin transport was inhibited to 97, 70, and 62% by gemfibrozil (200 microM), respectively, whereas only a small inhibitory effect by gemfibrozil (200 microM) on fluvastatin uptake into primary human hepatocytes was observed (27% inhibition). The results indicate that the in vitro engineered systems can not always predict the behavior in more complex systems such as freshly isolated primary hepatocytes. Therefore, selection of substrate, substrate concentration, and in vitro transport system are critical for the conduct of in vitro interaction studies involving individual liver OATP carriers.     

Interaction of deoxyschizandrin and schizandrin B with liver uptake transporters OATP1B1 and OATP1B3

1. Deoxyschizandrin and schizandrin B have diverse pharmacological effects, including hepatoprotective activity. We aim to study their hepatic uptake and their effects on the hepatic uptake of other clinical drugs mediated by OATP1B1 and OATP1B3.

2. Deoxyschizandrin exhibited a high affinity for OATP1B1 with K_m of 17.61?±?0.43?μM but a low affinity for OATP1B3. Similarly, schizandrin B also showed a strong affinity for OATP1B1 with K_m of 18.45?±?1.23?μM but a weak affinity for OATP1B3.

3. Atorvastatin and rifampicin could inhibit the uptake of deoxyschizandrin and schizandrin B mediated by OATP1B1.

4. Intriguingly, both deoxyschizandrin and schizandrin B significantly promoted the uptake of atorvastatin (with EC₅₀ of 50.58?±?8.08 and 24.70?±?5.82 µM, respectively) and rosuvastatin (with EC₅₀ of 13.46?±?2.70 and 8.99?±?4.73 µM, respectively) mediated by OATP1B1. Deoxyschizandrin could markedly promote the uptake of fluvastatin but inhibit the uptake of sodium taurocholate (TCNa) mediated by OATP1B1.

5. The promotion on hepatic uptake of statins mediated by OATP1B1 might lead to enhanced efficacy of cholesterol lowering and reduced risk of myopathy for hyperlipidemia patients when given statins together with deoxyschizandrin or schizandrin B.     

Role of the liver-specific transporters OATP1B1 and OATP1B3 in governing drug elimination

Members of the organic anion transporting polypeptide (OATP) family are responsible for the cellular uptake of a broad range of endogenous compounds and xenobiotics in multiple tissues. This review focuses on OATP1B1 and -1B3, which are specifically expressed in the liver and considered to be of particular importance for hepatic drug elimination and drug pharmacokinetics. Recent literature has indicated that inhibition of these transporters may result in drug-drug interactions. Furthermore, genetic polymorphisms in the genes encoding OATP1B1 and -1B3 have been described that increase or decrease transport in vitro and in vivo. Alteration of transporter function by either of these mechanisms may contribute to interindividual variability in drug disposition and response. In this review an update of this rapidly emerging field is provided.     

Characterization of ursodeoxycholic and norursodeoxycholic acid as substrates of the hepatic uptake transporters OATP1B1, OATP1B3, OATP2B1 and NTCP

Ursodeoxycholic acid (UDCA) is the only approved treatment for primary biliary cirrhosis, and norursodeoxycholic acid (norUDCA) is currently tested in clinical trials for future treatment of primary sclerosing cholangitis because of beneficial effects in cholestatic Mdr2 knock‐out mice. Uptake of UDCA and norUDCA into hepatocytes is believed to be a prerequisite for subsequent metabolism and therapeutic action. However, the molecular determinants of hepatocellular uptake of UDCA and norUDCA are poorly understood. We therefore investigated whether UDCA and norUDCA are substrates of the hepatic uptake transporters OATP1B1, OATP1B3, OATP2B1 and Na⁺‐taurocholate co‐transporting polypeptide (NTCP), which are localized in the basolateral membrane of hepatocytes. Uptake of [³H]UDCA and [¹⁴C]norUDCA into Human embryonic kidney (HEK) cells stably expressing OATP1B1, OATP1B3, OATP2B1 or NTCP was investigated and compared with uptake into vector control cells. Uptake ratios were calculated by dividing uptake into transporter‐transfected cells by uptake into respective control cells. Uptake ratios of OATP1B1‐, OATP1B3‐ and OATP2B1‐mediated UDCA and norUDCA uptake were at maximum 1.23 and 1.49, respectively. Uptake of UDCA was significantly higher into HEK‐NTCP cells only at the lowest tested concentration (1 μM, p < 0.001) compared with the control cells with an uptake ratio of 1.34‐fold. NorUDCA was not significantly transported by NTCP. The low uptake rates suggest that OATP1B1, OATP1B3, OATP2B1 and NTCP are not relevant for hepatocellular uptake and effects of UDCA and norUDCA in human beings.     

Dual kinetics of OATP2B1: Inhibitory potency and pH-dependence of OATP2B1 inhibitors

Organic anion transporting polypeptide (OATP) 2B1 is expressed in the intestine and liver, and OATP2B1-mediated transport of estrone 3-sulfate is pH-dependent and consists of: the high-affinity component (Hc) and low-affinity component (Lc). This study aimed to evaluate the influence of pH on the transport kinetics of each component, along with the inhibitory nature of ten OATP2B1 inhibitors. The Michaelis constants (K_m) were 4-fold and 1.5-fold lower at pH 6.3 than at pH 7.4, for Hc and Lc respectively. The inhibitory potencies of diclofenac, indomethacin, and ibuprofen towards Hc were 1.5–4.3 fold lower at pH 6.3 than at pH 7.4. Contrastingly, inhibitory potencies towards Lc were 9.0–52 fold lower at pH 7.4. Similarly, the inhibitory effect of naproxen was stronger towards Hc at pH 6.3 and towards Lc at pH 7.4. On the other hand, celecoxib selectively inhibited Lc transport at pH 7.4. Rifampicin inhibited both components at pH 6.3 and 7.4 to a similar extent, while bromosulphophthalein, naringin, and gefitinib selectively inhibited Hc irrespective of pH. Fexofenadine inhibited neither component. In conclusion, the transport affinities of both Hc and Lc were enhanced under acidic conditions. The influence of pH on the inhibitory potency towards each component varied among the inhibitors.     

Nostocyclopeptide-M1: a potent, nontoxic inhibitor of the hepatocyte drug transporters OATP1B3 and OATP1B1

We have isolated a novel cyanobacterial cyclic peptide (nostocyclopeptide M1; Ncp-M1) that blocks the hepatotoxic action of microcystin (MC) and nodularin (Nod). We show here that Ncp-M1 is nontoxic to primary hepatocytes in long-term culture. Ncp-M1 does not affect any known intracellular targets or pathways involved in MC action, like protein phosphatases, CaM-KII, or ROS-dependent cell death effectors. In support of this conclusion Ncp-M1 had no protective effect when microinjected into cells. Rather, the antitoxin effect was solely due to blocked hepatocyte uptake of MC and Nod. The hepatic uptake of MC and Nod is mainly via the closely related organic anion transporters OATP1B1 and OATP1B3, which also mediate hepatic transport of endogenous metabolites and hormones as well as drugs. OATP1B3 is also expressed in some aggressive cancers, where it confers apoptosis resistance. We show that Ncp-M1 inhibits transport through OATP1B3 and OATP1B1 expressed in HEK293 cells. The Ncp-M1 molecule has several nonproteinogenic amino acids and an imino bond, which hamper its synthesis. Moreover, a cyclic all L-amino acid heptapeptide analogue of Ncp-M1 also inhibits the OATP1B1/1B3 transporters, and with higher OATP1B3 preference than Ncp-M1 itself. The nontoxic Ncp-M1 and its synthetic cyclic peptide analogues thus provide new tools to probe the role of OATB1B1/1B3 mediated drug and metabolite transport in liver and cancer cells. They can also serve as scaffolds to design new, exopeptidase resistant OATP1B3-specific modulators.