Inhibitory effects of flavonoids on organic cation transporter 1: Implications for food/herb-drug interactions and hepatoprotective effects

Organic cation transporter 1 (OCT1, gene symbol: SLC22A1) is mainly responsible for the hepatic uptake of various cationic drugs, closely associated with drug-induced liver injury (DILI). Screening and identifying potent OCT1 inhibitors with little toxicity in natural products is of great value in alleviating OCT1-mediated liver injury. Flavonoids, a group of polyphenols commonly found in foodstuffs and herbal products, have been reported to cause transporter-mediated food/herb-drug interactions (FDIs). Our objective was to investigate potential inhibitors of OCT1 from 96 flavonoids, evaluate the hepatoprotective effects on retrorsine-induced liver injury, and clarify the structure-activity relationships of flavonoids with OCT1. Thirteen flavonoids exhibited significant inhibition (>50%) on OCT1 in OCT1-HEK293 cells. Among them, the five strongest flavonoid inhibitors (IC50 < 10 μM), including α-naphthoflavone, apigenin, 6-hydroxyflavone, luteolin, and isosilybin markedly decreased oxaliplatin-induced cytotoxicity. In retrorsine-induced liver injury models, they also reduced alanine aminotransferase (ALT) and aspartate aminotransferase (AST) to different levels, the best of which was 6-hydroxyflavone. The pharmacophore model clarified that hydrogen bond acceptors at the 4,8,5' position might play a vital role in the inhibitory effect of flavonoids on OCT1. Taken together, our findings would pave the way to predicting the potential risks of flavonoid-related FDIs in humans and optimizing flavonoid structure to alleviate OCT1-mediated liver injury.

Dual mass spectrometry imaging and spatial metabolomics to investigate the metabolism and nephrotoxicity of nitidine chloride

Evaluating toxicity and decoding the underlying mechanisms of active compounds are crucial for drug development. In this study, we present an innovative, integrated approach that combines air flow-assisted desorption electrospray ionization mass spectrometry imaging (AFADESI-MSI), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and spatial metabolomics to comprehensively investigate the nephrotoxicity and underlying mechanisms of nitidine chloride (NC), a promising anti-tumor drug candidate. Our quantitive AFADESI-MSI analysis unveiled the region specific of accumulation of NC in the kidney, particularly within the inner cortex (IC) region, following single and repeated dose of NC. High spatial resolution ToF-SIMS analysis further allowed us to precisely map the localization of NC within the renal tubule. Employing spatial metabolomics based on AFADESI-MSI, we identified over 70 discriminating endogenous metabolites associated with chronic NC exposure. These findings suggest the renal tubule as the primary target of NC toxicity and implicate renal transporters (organic cation transporters, multidrug and toxin extrusion, and organic cation transporter 2 (OCT2)), metabolic enzymes (protein arginine N-methyltransferase (PRMT) and nitric oxide synthase), mitochondria, oxidative stress, and inflammation in NC-induced nephrotoxicity. This study offers novel insights into NC-induced renal damage, representing a crucial step towards devising strategies to mitigate renal damage caused by this compound.

Nitidine chloride induces cardiac hypertrophy in mice by targeting autophagy-related 4B cysteine peptidase

Nitidine chloride (NC) is a standard active component from the traditional Chinese medicine Zanthoxylum nitidum (Roxb.) DC. (ZN). NC has shown a variety of pharmacological activities including anti-tumor activity. As a number of anti-tumor drugs cause cardiotoxicity, herein we investigated whether NC exerted a cardiotoxic effect and the underlying mechanism. Aqueous extract of ZN (ZNE) was intraperitoneally injected into rats, while NC was injected into beagles and mice once daily for 4 weeks. Cardiac function was assessed using echocardiography. We showed that both ZNE administered in rats and NC administered in mice induced dose-dependent cardiac hypertrophy and dysfunction, whereas administration of NC at the middle and high dose caused death in Beagles. Consistently, we observed a reduction of cardiac autophagy levels in NC-treated mice and neonatal mouse cardiomyocytes. Furthermore, we demonstrated that autophagy-related 4B cysteine peptidase (ATG4B) may be a potential target of NC, since overexpression of ATG4B reversed the cardiac hypertrophy and reduced autophagy levels observed in NC-treated mice. We conclude that NC induces cardiac hypertrophy via ATG4B-mediated downregulation of autophagy in mice. Thus, this study provides guidance for the safe clinical application of ZN and the use of NC as an anti-tumor drug.

Genotoxicity of pyrrolizidine alkaloids in metabolically inactive human cervical cancer HeLa cells co-cultured with human hepatoma HepG2 cells

Pyrrolizidine alkaloids (PAs) are secondary plant metabolites, which can be found as contaminant in various foods and herbal products. Several PAs can cause hepatotoxicity and liver cancer via damaging hepatic sinusoidal endothelial cells (HSECs) after hepatic metabolization. HSECs themselves do not express the required metabolic enzymes for activation of PAs. Here we applied a co-culture model to mimic the in vivo hepatic environment and to study PA-induced effects on not metabolically active neighbour cells. In this co-culture model, bioactivation of PA was enabled by metabolically capable human hepatoma cells HepG2, which excrete the toxic and mutagenic pyrrole metabolites. The human cervical epithelial HeLa cells tagged with H2B-GFP were utilized as non-metabolically active neighbours because they can be identified easily based on their green fluorescence in the co-culture. The PAs europine, riddelliine and lasiocarpine induced micronuclei in HepG2 cells, and in HeLa H2B-GFP cells co-cultured with HepG2 cells, but not in HeLa H2B-GFP cells cultured alone. Metabolic inhibition of cytochrome P450 enzymes with ketoconazole abrogated micronucleus formation. The efflux transporter inhibitors verapamil and benzbromarone reduced micronucleus formation in the co-culture model. Furthermore, mitotic disturbances as an additional genotoxic mechanism of action were observed in HepG2 cells and in HeLa H2B-GFP cells co-cultured with HepG2 cells, but not in HeLa H2B-GFP cells cultured alone. Overall, we were able to show that PAs were activated by HepG2 cells and the metabolites induced genomic damage in co-cultured HeLa cells.

Nitidine chloride, a benzophenanthridine alkaloid from Zanthoxylum nitidum (Roxb.) DC., exerts multiple beneficial properties, especially in tumors and inflammation-related diseases

Plant-derived alkaloids are a kind of very important natural organic compounds. Nitidine chloride is one of the main active ingredients in Zanthoxylum nitidum (Roxb.) DC. which is a frequently-used Chinese herbal medicine. Z. nitidum has many kinds of efficacy, such as activating blood circulation and removing stasis, promoting qi circulation and relieving pain, and detoxication and detumescence. In China, Z. nitidum is usually used for the treatment of gastrointestinal diseases, toothache, and traumatic injury. At present, there are numerous studies of nitidine chloride with regard to its pharmacology, pharmacokinetics, toxicology, etc. However, a systematic, cutting-edge review of nitidine-related studies is extremely lacking. The present paper aimed at comprehensively summarizing the information on the extraction, separation and purification, pharmacology, pharmacokinetics, toxicology and formulation of nitidine chloride. The knowledge included in the present study were searched from the following academic databases involving Web of Science, PubMed, Google scholar, Elsevier, CNKI and Wanfang Data, till July 2022. In terms of nitidine chloride extraction, enzymatic method and ultrasonic method are recommended. Resin adsorption and chromatography were usually used for the separation and purification of nitidine chloride. Nitidine chloride possesses diversified therapeutical effects, such as anti-tumor, anti-inflammation, anti-colitis, anti-malaria, anti-osteoporosis, anti-rheumatoid and so on. According to pharmacokinetics, the intestinal absorption of nitidine chloride is passive diffusion, and it is rarely excreted with urine and feces in the form of prototype drug. Nitidine chloride has a moderate binding to plasma protein, which is independent of the drug concentration. As to toxicology, nitidine chloride showed certain toxicity on liver, kidney and heart. Certain new formulations, such as nanoparticle, microsphere and nano-micelle, could increase the therapeutic effect and decrease the toxicity of nitidine chloride. Despite limitations such as poor solubility, low bioavailability and certain toxicity, nitidine chloride is still a promising natural alkaloid for drug candidates. Extensive and intensive exploration on nitidine chloride is essential to promote the usage of nitidine-based drugs in the clinic practice.

Nitidine Chloride Alleviates Inflammation and Cellular Senescence in Murine Osteoarthritis Through Scavenging ROS

Osteoarthritis (OA) is one of the most common chronic musculoskeletal disorder worldwide, representing a major source of disability, pain and socioeconomic burden. Yet the effective pharmaceutical treatments applied in the clinical works are merely symptomatic management with uncertainty around their long-term safety and efficacy, namely no drugs currently are capable of modulating the biological progression of OA. Here, we identified the potent anti-inflammatory as well as anti-oxidative properties of Nitidine Chloride (NitC), a bioactive phytochemical alkaloid extracted from natural herbs, in IL-1β-treated rat articular chondrocytes (RACs), LPS-stimulated RAW 264.7 and rat osteoarthritic models in vivo. We demonstrated NitC remarkably inhibited the production of inflammatory mediators including COX2 and iNOS, suppressed the activation of MAPK and NF-κB cell signaling pathway and reduced the expression of extracellular matrix (ECM) degrading enzymes including MMP3, MMP9 and MMP13 in IL-1β-treated RACs. Several emerging bioinformatics tools were performed to predict the underlying mechanism, the result of which indicated the potential reactive oxygen species (ROS) clearance potential of NitC. Further, NitC exhibited its anti-oxidative potential through ameliorating cellular senescence in IL-1β-treated RACs and decreasing NLRP3 inflammasomes activation in LPS-stimulated RAW 264.7 via scavenging ROS. Additionally, X-ray, micro-CT and other experiments in vivo demonstrated that intra-articular injection of NitC significantly alleviated the cartilage erosion, ECM degradation and subchondral alterations in OA progression. In conclusion, the present study reported the potent anti-inflammatory and anti-oxidative potential of NitC in OA biological process, providing a promising therapeutic agent for OA management.

A novel nitidine chloride nanoparticle overcomes the stemness of CD133+EPCAM+ Huh7 hepatocellular carcinoma cells for liver cancer therapy

Background

Stemness of CD133⁺EPCAM⁺ hepatocellular carcinoma cells ensures cancer resistance to apoptosis,which is a challenge to current liver cancer treatments. In this study, we evaluated the tumorcidal activity of a novel nanoparticle of nitidine chloride (TPGS-FA/NC, TPGS-FA: folic acid modified D-α-tocopheryl polyethylene glycol 1000 succinate, NC: nitidine chloride), against human hepatocellular carcinoma (HCC) cell line Huh7 growth in vitro and in vivo.

Methods

Huh7 cells were treated with TPGS-FA/NC. Cell proliferation was assessed using MTT and colony assays. The expression of cell markers and signaling proteins was detected using western blot analyses. A sphere culture technique was used to enrich cancer stem cells (CSC) in Huh7 cells. TPGS-FA/NC (7.5, 15, 30, 60, 120 μg/mL) dose-dependently inhibited the proliferation of HCC cells, which associated with a reduction in AQP3 and STAT3 expression. Importantly,TPGS-FA/NC (10, 20, and 40 μg/mL) significantly reduced the EpCAM⁺/CD133⁺cell numbers, suppressed the sphere formation. The in vivo antitumor efficacy of TPGS-FA/NC was proved in Huh7 cell xenograft model in BALB/c nude mice, which were administered TPGS-FA/NC(4 mg· kg − 1· d − 1, ig) for 2 weeks.

Results

TPGS-FA/NC dose-dependently suppressed the AQP3/STAT3/CD133 axis in Huh7 cells. In Huh7 xenograft bearing nude mice, TPGS-FA/NC administration markedly inhibited Huh7 xenograft tumor growth .

Conclusions

TPGS-FA/NC inhibit HCC tumor growth through multiple mechanisms, and it may be a promising candidate drug for the clinical therapy of hepatocellular carcinoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-022-00589-z.

A Comprehensive Review on the Chemical Properties, Plant Sources, Pharmacological Activities, Pharmacokinetic and Toxicological Characteristics of Tetrahydropalmatine

Tetrahydropalmatine (THP), a tetrahydroproberine isoquinoline alkaloid, is widely present in some botanical drugs, such as Stephania epigaea H.S. Lo (Menispermaceae; Radix stephaniae epigaeae), Corydalis yanhusuo (Y.H.Chou & Chun C.Hsu) W.T. Wang ex Z.Y. Su and C.Y. Wu (Papaveraceae; Corydalis rhizoma), and Phellodendron chinense C.K.Schneid (Berberidaceae; Phellodendri chinensis cortex). THP has attracted considerable attention because of its diverse pharmacological activities. In this review, the chemical properties, plant sources, pharmacological activities, pharmacokinetic and toxicological characteristics of THP were systematically summarized for the first time. The results indicated that THP mainly existed in Papaveraceae and Menispermaceae families. Its pharmacological activities include anti-addiction, anti-inflammatory, analgesic, neuroprotective, and antitumor effects. Pharmacokinetic studies showed that THP was inadequately absorbed in the intestine and had rapid clearance and low bioavailability in vivo, as well as self-microemulsifying drug delivery systems, which could increase the absorption level and absorption rate of THP and improve its bioavailability. In addition, THP may have potential cardiac and neurological toxicity, but toxicity studies of THP are limited, especially its long-duration and acute toxicity tests. In summary, THP, as a natural alkaloid, has application prospects and potential development value, which is promising to be a novel drug for the treatment of pain, inflammation, and other related diseases. Further research on its potential target, molecular mechanism, toxicity, and oral utilization should need to be strengthened in the future.

Natural products targeting cancer cell dependency

Precision cancer medicine is a tailored treatment approach for individual cancer patients with different genomic characteristics. Mutated or hyperactive oncogenes have served as main drug targets in current precision cancer medicine, while defective or inactivated tumor suppressors in general have not been considered as druggable targets. Synthetic lethality is one of very few approaches that enable to target defective tumor suppressors with pharmacological agents. Synthetic lethality exploits cancer cell dependency on a protein or pathway, which arises when the function of a tumor suppressor is defective. This approach has been proven to be effective in clinical settings since the successful clinical introduction of BRCA-PARP synthetic lethality for the treatment of breast and ovarian cancer with defective BRCA. Subsequently, large-scale screenings with RNAi, CRISPR/Cas9-sgRNAs, and chemical libraries have been applied to identify synthetic lethal partners of tumor suppressors. Natural products are an important source for the discovery of pharmacologically active small molecules. However, little effort has been made in the discovery of synthetic lethal small molecules from natural products. This review introduces recent advances in the discovery of natural products targeting cancer cell dependency and discusses potentials of natural products in the precision cancer medicine.

mPEG2k-PCLx Polymeric Micelles Influence Pharmacokinetics and Hypoglycemic Efficacy of Metformin through Inhibition of Organic Cation Transporters in Rats

Increasing evidence has shown that nanocarriers have effects on several efflux drug transporters. To date, little is known about whether influx transporters are also modulated. Herein, we investigated the impact of amphiphilic polymer micelles on the uptake function of organic cation transporters (OCTs) and the influence on the pharmacokinetics and pharmacodynamics of metformin, a well-characterized substrate of OCTs. Five types of polymeric micelles (mPEG_2k-PCL_2k, mPEG_2k-PCL_3.5k, mPEG_2k-PCL_5k, mPEG_2k-PCL_7.5k, and mPEG_2k-PCL_10k) were prepared to evaluate the inhibition of hOCT1-3-overexpressing Madin-Darby canine kidney cells. The mPEG_2k-PCL_x micelles played an inhibitory role above the critical micelle concentration. The inhibitory potency could be ranked as mPEG_2k-PCL_2k > mPEG_2k-PCL_3.5k > mPEG_2k-PCL_5k > mPEG_2k-PCL_7.5k > mPEG_2k-PCL_10k, which negatively declined with the increase of molecular weight of the hydrophobic segment. The inhibitory effects of polymeric micelles on the hOCT1 isoform were the most pronounced, with the lowest IC₅₀ values ranging from 0.106 to 0.280 mg/mL. The mPEG_2k-PCL_2k micelles distinctly increased the plasma concentration of metformin and significantly decreased V_ss by 35.6% (p < 0.05) after seven consecutive treatments in rats, which was interrelated with the restrained metformin distribution in the liver and kidney. The uptake inhibition of micelles on hepatic and renal rOcts also diminished the glucose-lowering effect of metformin and fasting insulin levels in the oral glucose tolerance test. Consistent with the inhibitory effects, the mRNA and protein levels of rOct1 and rOct2 were decreased in the liver, kidney, and small intestine. The present study demonstrated that mPEG_2k-PCL_x micelles could inhibit the transport function of OCTs, indicating a potential risk of drug-drug interactions during concomitant medication of nanomedicine with organic cationic drugs.

Transport of Drugs and Endogenous Compounds Mediated by Human OCT1: Studies in Single- and Double-Transfected Cell Models

Organic Cation Transporter 1 (OCT1, gene symbol: SLC22A1) is predominately expressed in human liver, localized in the basolateral membrane of hepatocytes and facilitates the uptake of endogenous compounds (e.g. serotonin, acetylcholine, thiamine), and widely prescribed drugs (e.g. metformin, fenoterol, morphine). Furthermore, exogenous compounds such as MPP⁺, ASP⁺ and Tetraethylammonium can be used as prototypic substrates to study the OCT1-mediated transport in vitro. Single-transfected cell lines recombinantly overexpressing OCT1 (e.g., HEK-OCT1) were established to study OCT1-mediated uptake and to evaluate transporter-mediated drug-drug interactions in vitro. Furthermore, double-transfected cell models simultaneously overexpressing basolaterally localized OCT1 together with an apically localized export protein have been established. Most of these cell models are based on polarized grown MDCK cells and can be used to analyze transcellular transport, mimicking the transport processes e.g. during the hepatobiliary elimination of drugs. Multidrug and toxin extrusion protein 1 (MATE1, gene symbol: SLC47A1) and the ATP-driven efflux pump P-glycoprotein (P-gp, gene symbol: ABCB1) are both expressed in the canalicular membrane of human hepatocytes and are described as transporters of organic cations. OCT1 and MATE1 have an overlapping substrate spectrum, indicating an important interplay of both transport proteins during the hepatobiliary elimination of drugs. Due to the important role of OCT1 for the transport of endogenous compounds and drugs, in vitro cell systems are important for the determination of the substrate spectrum of OCT1, the understanding of the molecular mechanisms of polarized transport, and the investigation of potential drug-drug interactions. Therefore, the aim of this review article is to summarize the current knowledge on cell systems recombinantly overexpressing human OCT1.

Drug-Drug Interactions at Organic Cation Transporter 1

The interaction between drugs and various transporters is one of the decisive factors that affect the pharmacokinetics and pharmacodynamics of drugs. The organic cation transporter 1 (OCT1) is a member of the Solute Carrier 22A (SLC22A) family that plays a vital role in the membrane transport of organic cations including endogenous substances and xenobiotics. This article mainly discusses the drug-drug interactions (DDIs) mediated by OCT1 and their clinical significance.

The Toxicity and Attenuation Methods of Toxic Chinese Materia Medica for its Reasonable Application: A Review

Over a millennia, traditional Chinese medicine (TCM) has been used to treat various diseases in China. In recent years, more and more Chinese materia medica (CMM) have been studied in scientific research projects, applied in clinical practice, and their extracts have even appeared in some health products. However, the toxicity of some CMM is often overlooked, including hepatotoxicity, nephrotoxicity, neurotoxicity, cardiotoxicity, etc. In this review, the toxic components and their toxicological mechanisms of some toxic CMM were listed according to the chemical structure classification of toxic components. Afterwards, the traditional methods (processing and compatibility) and modern methods (structural modification, biotransformation, etc.) of attenuation of CMM were discussed. Since ancient times, it has been said that "fight fire with fire, fight poison with poison," and toxic CMM are of great significance in the treatment of difficult and severe diseases. The rational application of toxic CMM and their components in clinical practice was also exemplified in this review. While the pharmacological effects of TCMs have been emphasized, the scientific attenuation and rational application of toxic components should be concerned. We hope this review can provide a reference for future related research.

Folic acid modified TPGS as a novel nano-micelle for delivery of nitidine chloride to improve apoptosis induction in Huh7 human hepatocellular carcinoma

Background

The development of novel and effective drugs for targeted human hepatocellular carcinoma still remains a great challenge. The alkaloid nitidine chloride (NC), a component of a traditional Chinese medicine, has been shown to have anticancer properties, but doses at therapeutic levels have unacceptable side effects. Here we investigate folic acid modified D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS-FA) as a potential carrier for controlled delivery of the drug.

Methods

Synthesized TPGS-FA was characterized by FTIR, UV-visible and ¹H NMR spectroscopy, and TPGS loaded with NC was evaluated for its ability to induce apoptosis in Huh7 cells by Annexin V/PI and MTT assays, and observed by laser scanning confocal microscopy and inverted phase contrast microscopy.

Results

TPGS-FA/NC complexes were prepared successfully, and were homogenious with a uniform size of ~ 14 nm diameter. NC was released from the TPGS-FA/NC complexes in a controlled and sustained manner under physiological conditions (pH 7.4). Furthermore, its cytotoxicity to hepatocarcinoma cells was greater than that of free NC.

Conclusions

TPGS-FA is shown to be useful carrier for drugs such as NC, and TPGS-FA/NC could potentially be a potent and safe drug for the treatment of hepatocellular carcinoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40360-020-00461-y.

Organic Cation Transporters in Health and Disease

The organic cation transporters (OCTs) OCT1, OCT2, OCT3, novel OCT (OCTN)1, OCTN2, multidrug and toxin exclusion (MATE)1, and MATE kidney-specific 2 are polyspecific transporters exhibiting broadly overlapping substrate selectivities. They transport organic cations, zwitterions, and some uncharged compounds and operate as facilitated diffusion systems and/or antiporters. OCTs are critically involved in intestinal absorption, hepatic uptake, and renal excretion of hydrophilic drugs. They modulate the distribution of endogenous compounds such as thiamine, L-carnitine, and neurotransmitters. Sites of expression and functions of OCTs have important impact on energy metabolism, pharmacokinetics, and toxicity of drugs, and on drug-drug interactions. In this work, an overview about the human OCTs is presented. Functional properties of human OCTs, including identified substrates and inhibitors of the individual transporters, are described. Sites of expression are compiled, and data on regulation of OCTs are presented. In addition, genetic variations of OCTs are listed, and data on their impact on transport, drug treatment, and diseases are reported. Moreover, recent data are summarized that indicate complex drug-drug interaction at OCTs, such as allosteric high-affinity inhibition of transport and substrate dependence of inhibitor efficacies. A hypothesis about the molecular mechanism of polyspecific substrate recognition by OCTs is presented that is based on functional studies and mutagenesis experiments in OCT1 and OCT2. This hypothesis provides a framework to imagine how observed complex drug-drug interactions at OCTs arise. Finally, preclinical in vitro tests that are performed by pharmaceutical companies to identify interaction of novel drugs with OCTs are discussed. Optimized experimental procedures are proposed that allow a gapless detection of inhibitory and transported drugs.

Organic Cation Transporter 1 and 3 Contribute to the High Accumulation of Dehydrocorydaline in the Heart

Dehydrocorydaline (DHC), one of the main active components of Corydalis yanhusuo, is an important remedy for the treatment of coronary heart disease. Our previous study revealed a higher unbound concentration of DHC in the heart than plasma of mice after oral administration of C. yanhusuo extract or DHC, but the underlying uptake mechanism remains unelucidated. In our investigations, we studied the transport mechanism of DHC in transgenic cells, primary neonatal rat cardiomyocytes, and animal experiments. Using quantitative real-time polymerase chain reaction and Western blotting, we found that uptake transporters expressed in the mouse heart include organic cation transporter 1/3 (OCT1/3) and carnitine/organic cation transporter 1/2 (OCTN1/2). The accumulation experiments in transfected cells showed that DHC was a substrate of OCT1 and OCT3, with K _m of 11.29 ± 3.3 and 8.96 ± 3.7 μM, respectively, but not a substrate of OCTN1/2. Additionally, a higher efflux level (1.71-fold of MDCK-mock) of DHC was observed in MDCK-MDR1 cells than in MDCK-mock cells. Therefore, DHC is a weak substrate for MDR1. Studies using primary neonatal rat cardiomyocytes showed that OCT1/3 inhibitors (quinidine, decynium-22, and levo-tetrahydropalmatine) prevented the accumulation of DHC, whereas OCTN2 inhibitors (mildronate and l-carnitine) did not affect its accumulation. Moreover, the coadministration of OCT1/3 inhibitors (levo-tetrahydropalmatine, THP) decreased the concentration of DHC in the mouse heart. Based on these findings, DHC may be accumulated partly by OCT1/3 transporters and excreted by MDR1 in the heart. THP could alter the distribution of DHC in the mouse heart. SIGNIFICANCE STATEMENT: We reported the cardiac transport mechanism of dehydrocorydaline, highly distributed to the heart after oral administration of Corydalis yanhusuo extract or dehydrocorydaline only. Dehydrocorydaline (an OCT1/3 and MDR1 substrate) accumulation in primary cardiomyocytes may be related to the transport activity of OCT1/3. This ability, hampered by selective inhibitors (levo-tetrahydropalmatine, an inhibitor of OCT1/3), causes a nearly 40% reduction in exposure of the heart to dehydrocorydaline. These results suggest that OCT1/3 may contribute to the uptake of dehydrocorydaline in the heart.

Rapid identification and pharmacokinetic studies of multiple active alkaloids in rat plasma through UPLC-Q-TOF-MS and UPLC-MS/MS after the oral administration of Zanthoxylum nitidum extract

Zanthoxylum nitidum (Roxb.) DC. (ZN) belongs to the genus Zanthoxylum of Rutaceae and has various chemical ingredients and pharmacologic effects. Alkaloids are its main active constituents responsible for diverse pharmacologic effects, such as anti-tumor, anti-bacterial, anti-inflammatory, and analgesic activities. The chemical and pharmacological effects of ZN are well reported, but the in vivo pharmacokinetic profiles of its main active alkaloids are poorly investigated. This study aims to elucidate the absorbed constituents and pharmacokinetic behavior of main active ingredients in rat plasma after the oral administration of ZN extract. The absorbed constituents in rat plasma were qualitatively analyzed using ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination and pharmacokinetic studies of dihydrochelerythrine (DHCHE), nitidine chloride (NIT), chelerythrine (CHE), sanguinarine (SAN), liriodenine (LIR), skimmianine (SKI), γ-fagarine (FAG), and dictamnine (DIC) in rat plasma. Eighteen prototypes and metabolites were identified according to exact mass, characteristic diagnostic fragment ions, and reference standards. The established UPLC-MS/MS quantitative method met the requirements of FDA for biological analysis methods. Method validation showed that this method has good linearity (r ≥ 0.9910), precision (RSD ≤ 18.63 %), accuracy (88.11 %-117.50 %), and stability. The limit of detection (LOD) could reach 1 ng/mL, and the limit of quantitation could reach 2 ng/mL. The plasma drug concentration of benzophenanthridine alkaloids, such as NIT, CHE, and DHCHE, were still low even after dose differences were deducted. For the furan quinoline alkaloids (such as SKI, FAG, and DIC), only SKI showed high plasma drug concentration, although SKI content comprised only approximately 1/6 of benzophenanthridine alkaloids. This study is the first to simultaneously determine the above-mentioned active alkaloids in rat plasma and would contribute to the comprehensive understanding of in vivo pharmacokinetic behavior on active alkaloids in ZN extract.

Antitumor functions and mechanisms of nitidine chloride in human cancers

Nitidine chloride (NC), a quaternary ammonium alkaloid, exhibits multiple biological activities, including antimalarial, antifungal, and antiangiogenesis. Recently, NC has been characterized to perform antitumor activity in a variety of malignancies. NC has been identified to suppress cell proliferation, stimulate apoptosis, and induce cell cycle arrest, retard migration, invasion and metastasis. Moreover, NC is reported to sensitize cancer cells to chemotherapeutic drugs. In this review article, we describe the functions of NC in human cancers and discuss the molecular insight into NC-involved antitumor feature. This review article will stimulate the deeper investigation for using NC as a potent agent for the management of cancer patients.

Roles of Hepatic Drug Transporters in Drug Disposition and Liver Toxicity

Hepatic drug transporters are mainly distributed in parenchymal liver cells (hepatocytes), contributing to drug's liver disposition and elimination. According to their functions, hepatic transporters can be roughly divided into influx and efflux transporters, translocating specific molecules from blood into hepatic cytosol and mediating the excretion of drugs and metabolites from hepatic cytosol to blood or bile, respectively. The function of hepatic transport systems can be affected by interspecies differences and inter-individual variability (polymorphism). In addition, some drugs and disease can redistribute transporters from the cell surface to the intracellular compartments, leading to the changes in the expression and function of transporters. Hepatic drug transporters have been associated with the hepatic toxicity of drugs. Gene polymorphism of transporters and altered transporter expressions and functions due to diseases are found to be susceptible factors for drug-induced liver injury (DILI). In this chapter, the localization of hepatic drug transporters, their regulatory factors, physiological roles, and their roles in drug's liver disposition and DILI are reviewed.

Herb-Induced Liver Injury: Phylogenetic Relationship, Structure-Toxicity Relationship, and Herb-Ingredient Network Analysis

Currently, hundreds of herbal products with potential hepatotoxicity were available in the literature. A comprehensive summary and analysis focused on these potential hepatotoxic herbal products may assist in understanding herb-induced liver injury (HILI). In this work, we collected 335 hepatotoxic medicinal plants, 296 hepatotoxic ingredients, and 584 hepatoprotective ingredients through a systematic literature retrieval. Then we analyzed these data from the perspectives of phylogenetic relationship and structure-toxicity relationship. Phylogenetic analysis indicated that hepatotoxic medicinal plants tended to have a closer taxonomic relationship. By investigating the structures of the hepatotoxic ingredients, we found that alkaloids and terpenoids were the two major groups of hepatotoxicity. We also identified eight major skeletons of hepatotoxicity and reviewed their hepatotoxic mechanisms. Additionally, 15 structural alerts (SAs) for hepatotoxicity were identified based on SARpy software. These SAs will help to estimate the hepatotoxic risk of ingredients from herbs. Finally, a herb-ingredient network was constructed by integrating multiple datasets, which will assist to identify the hepatotoxic ingredients of herb/herb-formula quickly. In summary, a systemic analysis focused on HILI was conducted which will not only assist to identify the toxic molecular basis of hepatotoxic herbs but also contribute to decipher the mechanisms of HILI.

Co-administration of nuciferine reduces the concentration of metformin in liver via differential inhibition of hepatic drug transporter OCT1 and MATE1

Nuciferine (NF), one of the main and effective components in Nelumbo nucifera Gaertn. leaf extracts, is a promising drug candidate for the treatment of obesity-related diseases, while metformin is a first line therapeutic drug for type 2 diabetes mellitus. Since nuciferine and metformin are likely to be co-administered, the aim of the present study was to evaluate whether co-administration of nuciferine would influence the liver (target tissue) distribution and the anti-diabetic effect of metformin by inhibiting hepatic organic cation transporter 1 (OCT1) and multidrug and toxin extrusion 1 (MATE1). The data demonstrated that nuciferine significantly reduced metformin accumulation in MDCK cells stably expressing human OCT1 (MDCK-hOCT1) or hMATE1 (MDCK-hMATE1), and primary cultured mouse hepatocytes. Furthermore, the presence of nuciferine in the basal compartment caused a concentration-dependent reduction of intracellular metformin accumulation in MDCK-hOCT1/hMATE1 cell monolayers. Compared with the metformin treatment-alone group, co-administration of nuciferine (40 mg/kg) markedly reduced the metformin concentration in mouse livers at 30 and 60 min after a single oral dose of metformin (200 mg/kg), and subsequently impaired the glucose-lowering effect of metformin (200 mg/kg), but the glucose-lowering effect became no different at 90 and 120 min. Therefore, nuciferine influenced the liver concentration and glucose-lowering effect of metformin only for a period of time after dose, administration of nuciferine and metformin with an interval might prevent the drug-drug interaction mediated by OCT1 and MATE1.

Inter-Subject Variability in OCT1 Activity in 27 Batches of Cryopreserved Human Hepatocytes and Association with OCT1 mRNA Expression and Genotype

PURPOSE

OCT1/3 (Organic Cation Transporter-1 and -3; SLC22A1/3) are transmembrane proteins localized at the basolateral membrane of hepatocytes. They mediate the uptake of cationic endogenous compounds and/or xenobiotics. The present study was set up to verify whether the previously observed variability in OCT activity in hepatocytes may be explained by inter-individual differences in OCT1/3 mRNA levels or OCT1 genotype.

METHODS

Twenty-seven batches of cryopreserved human hepatocytes (male and female, age 24-88 y) were characterized for OCT activity, normalized OCT1/3 mRNA expression, and OCT1 genetic mutation. ASP⁺ (4-[4-(dimethylamino)styryl]-N-methylpyridinium iodide) was used as probe substrate.

RESULTS

ASP⁺ uptake ranged between 75 ± 61 and 2531 ± 202 pmol/(min × million cells). The relative OCT1 and OCT3 mRNA expression ranged between 0.007-0.46 and 0.0002-0.005, respectively. The presence of one or two nonfunctional SLC22A1 alleles was observed in 13 batches and these exhibited significant (p = 0.04) association with OCT1 and OCT3 mRNA expression. However, direct association between genotype and OCT activity could not be established.

CONCLUSION

mRNA levels and genotype of OCT only partially explain inter-individual variability in OCT-mediated transport. Our findings illustrate the necessity of in vitro transporter activity profiling for better understanding of inter-individual drug disposition behavior.

Role of Cytochrome P450 2C8 in Drug Metabolism and Interactions

During the last 10-15 years, cytochrome P450 (CYP) 2C8 has emerged as an important drug-metabolizing enzyme. CYP2C8 is highly expressed in human liver and is known to metabolize more than 100 drugs. CYP2C8 substrate drugs include amodiaquine, cerivastatin, dasabuvir, enzalutamide, imatinib, loperamide, montelukast, paclitaxel, pioglitazone, repaglinide, and rosiglitazone, and the number is increasing. Similarly, many drugs have been identified as CYP2C8 inhibitors or inducers. In vivo, already a small dose of gemfibrozil, i.e., 10% of its therapeutic dose, is a strong, irreversible inhibitor of CYP2C8. Interestingly, recent findings indicate that the acyl-β-glucuronides of gemfibrozil and clopidogrel cause metabolism-dependent inactivation of CYP2C8, leading to a strong potential for drug interactions. Also several other glucuronide metabolites interact with CYP2C8 as substrates or inhibitors, suggesting that an interplay between CYP2C8 and glucuronides is common. Lack of fully selective and safe probe substrates, inhibitors, and inducers challenges execution and interpretation of drug-drug interaction studies in humans. Apart from drug-drug interactions, some CYP2C8 genetic variants are associated with altered CYP2C8 activity and exhibit significant interethnic frequency differences. Herein, we review the current knowledge on substrates, inhibitors, inducers, and pharmacogenetics of CYP2C8, as well as its role in clinically relevant drug interactions. In addition, implications for selection of CYP2C8 marker and perpetrator drugs to investigate CYP2C8-mediated drug metabolism and interactions in preclinical and clinical studies are discussed.

Role of OCT2 and MATE1 in renal disposition and toxicity of nitidine chloride

BACKGROUND AND PURPOSE

Nitidine chloride (NC), a benzophenanthridine alkaloid, has various biological properties including anticancer and analgesic activities. The aim of the present study was to evaluate the role of organic cation transporter 2 (OCT2) and multidrug and toxin extrusion 1 (MATE1) in the renal disposition and nephrotoxicity of NC.

EXPERIMENTAL APPROACH

MDCK cells stably expressing human OCT2 and/or hMATE1 were used to investigate the OCT2- and MATE1-mediated transport of NC. In addition, the accumulation of NC and its potential toxicity were studied in rat primary-cultured proximal tubular (rPCPT) cells and in rats in vivo.

KEY RESULTS

NC was found to be a high-affinity substrate of both OCT2 and MATE1 with high cytotoxicity in MDCK-hOCT2/hMATE1 and MDCK-hOCT2 compared to mock cells. The OCT2 inhibitors, cimetidine and (+)-tetrahydropalmatine ((+)-THP), significantly reduced NC accumulation and cytotoxicity in MDCK-hOCT2, MDCK-hOCT2/hMATE1 and rPCPT cells. Severe kidney damage with high levels of blood urea nitrogen and lactate dehydrogenase (LDH), reduced levels of alkaline phosphatase (ALP) and pathological changes were found in rats after 20 days of successive i.v. doses of NC (5 mg·kg(-1) ·day(-1) ). Concomitantly, the concentration of NC in the kidney reached similar high levels at 2 h after the last dose of the 20 day treatment as those observed at 0.5 h after a single i.v. dose of 5 mg·kg(-1) .

CONCLUSIONS AND IMPLICATIONS

Our data indicate that NC-induced nephrotoxicity might be mainly attributed to OCT2-mediated extensive renal uptake and weak tubular secretion by MATE1.

Structure and function of multidrug and toxin extrusion proteins (MATEs) and their relevance to drug therapy and personalized medicine

Multidrug and toxin extrusion (MATE; SLC47A) proteins are membrane transporters mediating the excretion of organic cations and zwitterions into bile and urine and thereby contributing to the hepatic and renal elimination of many xenobiotics. Transported substrates include creatinine as endogenous substrate, the vitamin thiamine and a number of drug agents with in part chemically different structures such as the antidiabetic metformin, the antiviral agents acyclovir and ganciclovir as well as the antibiotics cephalexin and cephradine. This review summarizes current knowledge on the structural and molecular features of human MATE transporters including data on expression and localization in different tissues, important aspects on regulation and their functional role in drug transport. The role of genetic variation of MATE proteins for drug pharmacokinetics and drug response will be discussed with consequences for personalized medicine.

Global genetic analyses reveal strong inter-ethnic variability in the loss of activity of the organic cation transporter OCT1

BACKGROUND

The organic cation transporter OCT1 (SLC22A1) mediates the uptake of vitamin B1, cationic drugs, and xenobiotics into hepatocytes. Nine percent of Caucasians lack or have very low OCT1 activity due to loss-of-function polymorphisms in OCT1 gene. Here we analyzed the global genetic variability in OCT1 to estimate the therapeutic relevance of OCT1 polymorphisms in populations beyond Caucasians and to identify evolutionary patterns of the common loss of OCT1 activity in humans.

METHODS

We applied massively parallel sequencing to screen for coding polymorphisms in 1,079 unrelated individuals from 53 populations worldwide. The obtained data was combined with the existing 1000 Genomes data comprising an additional 1,092 individuals from 14 populations. The identified OCT1 variants were characterized in vitro regarding their cellular localization and their ability to transport 10 known OCT1 substrates. Both the population genetics data and transport data were used in tandem to generate a world map of loss of OCT1 activity.

RESULTS

We identified 16 amino acid substitutions potentially causing loss of OCT1 function and analyzed them together with five amino acid substitutions that were not expected to affect OCT1 function. The variants constituted 16 major alleles and 14 sub-alleles. Six major alleles showed improper subcellular localization leading to substrate-wide loss in activity. Five major alleles showed correct subcellular localization, but substrate-specific loss of activity. Striking differences were observed in the frequency of loss of OCT1 activity worldwide. While most East Asian and Oceanian individuals had completely functional OCT1, 80 % of native South American Indians lacked functional OCT1 alleles. In East Asia and Oceania the average nucleotide diversity of the loss-of-function variants was much lower than that of the variants that do not affect OCT1 function (ratio of 0.03) and was significantly lower than the theoretically expected heterozygosity (Tajima's D = -1.64, P < 0.01).

CONCLUSIONS

Comprehensive genetic analyses showed strong global variations in the frequency of loss of OCT1 activity with selection pressure for maintaining OCT1 activity in East Asia and Oceania. These results not only enable pharmacogenetically-based optimization of drug treatment worldwide, but may help elucidate the functional role of human OCT1.