Schisandrin B—A novel inhibitor of P-glycoprotein

Bioavailability and interactions of schisandrin B with 5-fluorouracil in a xenograft mouse model of colorectal cancer

Schisandrin B (Sch B) is a predominant bioactive lignan from the fruit of a Chinese medicine food homology plant, Schisandra chinensis. Previously, we observed potent anti-tumor effect of Sch-B in colorectal cancer (CRC) and enhanced chemotherapy efficacy with fluorouracil (5-FU). However, their bioavailability and reciprocal interactions under CRC conditions are unclear. In this study, we first compared the bioavailability, metabolism and tissue distribution of Sch-B between non-tumor-bearing and xenograft CRC tumor-bearing mice. Next, we examined SchB-5-FU interactions via investigating alterations in drug metabolism and multidrug resistance. Using a validated targeted metabolomics approach, five active metabolites, including Sch-B and fluorodeoxyuridine triphosphate, were found tumor-accumulative. Co-treatment resulted in higher levels of Sch-B and 5-FU metabolites, showing improved phytochemical and drug bioavailability. Multidrug resistance gene (MDR1) was significantly downregulated upon co-treatment. Overall, we demonstrated the potential of Sch-B to serve as a promising chemotherapy adjuvant via improving drug bioavailability and metabolism, and attenuating MDR.

Computational evaluation of efflux pump homologues and lignans as potent inhibitors against multidrug-resistant Salmonella typhi

Typhoid fever, caused by Salmonella enterica serovar typhi, presents a substantial global health threat, particularly in regions with limited healthcare infrastructure. The rise of multidrug-resistant strains of S. typhi exacerbates this challenge, severely compromising conventional treatment efficacy due to over activity of efflux pumps. In our study, a comprehensive exploration of two fundamental aspects to combat MDR in S. typhi is carried out; i.e. employing advanced bioinformatics analyses and AlphaFold AI, We successfully identified and characterised a putative homologue, ABC-TPA, reminiscent of the P-glycoprotein (P-gp) known for its role in multidrug resistance in diverse pathogens. This discovery provides a critical foundation for understanding the potential mechanisms driving antibiotic resistance in S. typhi. Furthermore, employing computational methodologies, We meticulously assessed the potential of lignans, specifically Schisandrin A, B, and C, as promising Efflux Pump Inhibitors (EPIs) against the identified P-gp homologue in S. typhi. Noteworthy findings revealed robust binding interactions of Schisandrin A and B with the target protein, indicating substantial inhibitory capabilities. In contrast, Schisandrin C exhibited instability, showing varied effectiveness among the evaluated lignans. Pharmacokinetics and toxicity predictions underscored the favourable attributes of Schisandrin A, including prolonged action duration. Furthermore, high systemic stability and demanished toxicity profile of SA and SB present their therapeutic efficacy against MDR. This comprehensive investigation not only elucidates potential therapeutic strategies against MDR strains of S. typhi but also highlights the relevance of computational approaches in identifying and evaluating promising candidates. These findings lay a robust foundation for future empirical studies to address the formidable challenges antibiotic resistance poses in this clinically significant infectious diseases.

Comprehensive review of dibenzocyclooctadiene lignans from the Schisandra genus: anticancer potential, mechanistic insights and future prospects in oncology

Cancer remains one of the leading causes of mortality worldwide. The search for novel and effective anticancer agents has been a significant area of research. Dibenzocyclooctadiene lignans (DBCLS), derived from the Schisandra genus plants like: S. chinensis, S. sphenanthera, S. henryi, S. rubriflora, S. grandiflora, S. propinqua, and S. glabra, have been traditionally used in various medicinal systems and are known for their myriad health benefits, including anticancer properties. This comprehensive review aimed to collate and critically analyse the recent literature on the anticancer properties of DBCLS, focusing on their mechanistic approaches against different cancer types. An exhaustive literature search was performed using databases like PubMed/MedLine, Scopus, Web of Science, Embase, TRIP database and Google Scholar from 1980 to 2023. Peer-reviewed articles that elucidated the mechanistic approach of these lignans on cancer cell lines, in vivo models and preliminary clinical studies were included. Studies were assessed for their experimental designs, cancer types studied, and the mechanistic insights provided. The studies demonstrate that the anticancer effects of DBCLS compounds are primarily driven by their ability to trigger apoptosis, arrest the cell cycle, induce oxidative stress, modulate autophagy, and disrupt essential signaling pathways, notably MAPK, PI3K/Akt, and NF-κB. Additionally, these lignans have been shown to amplify the impact of traditional chemotherapy treatments, suggesting their potential role as supportive adjuncts in cancer therapy. Notably, several studies also emphasise their capacity to target cancer stem cells and mitigate multi-drug resistance specifically. DBCLS from the Schisandra genus have showcased significant potential as anticancer agents. Their multi-targeted mechanistic approach makes them promising candidates for further research, potentially leading to developing of new therapeutic strategies in cancer management.

A LC-MS/MS Method for Quantifying the Schisandrin B and Exploring Its Intracellular Exposure Correlating Antitumor Effect

Schisandrin B (Sch.B) shows antineoplastic activity in colorectal cancer, but the mechanism is still obscure. The intracellular spatial distribution may be helpful in elucidating the mechanism. To investigate the intracellular drug distribution of Sch.B in cancer cells, a simple, rapid, and sensitive ultra-highperformance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) method was established for the determination of Sch.B in colorectal cancer cells. Warfarin was utilized as an internal standard. The sample pretreatment was carried out with protein precipitation using methanol. The analyte was separated on an Atlantis T3-C₁₈ column (3 μm, 2.1∗100 mm) using gradient elution with a mobile phase comprised of methanol and 0.2% formic acid in water. The flow rate was 0.4 mL/min. The linear range of Sch.B was 20.0-1000.0 ng/mL with a correlation coefficient (R) more than 0.99. The matrix effect and recovery ranged from 88.01% to 94.59% and from 85.25% to 91.71%; the interday and intraday precision and accuracy, stability, specificity, carryover, matrix effect, and recovery all conformed to the requirements of pharmacopoeia. Cell viability and apoptosis assays demonstrated that Sch.B has an inhibitory effect in a dose-dependent way on HCT116 proliferation and achieved significant suppression at 75 μM (IC₅₀). It was found that in HCT116 cell, nucleus, and mitochondria, exposure levels of Sch.B peaked at 36 h and then decreased, and mitochondria possessed more Sch.B than nucleus. These results may help to elucidate the antitumor effect of Sch.B.

Exploration of the Use of Natural Compounds in Combination with Chemotherapy Drugs for Tumor Treatment

Currently, chemotherapy is the main treatment for tumors, but there are still problems such as unsatisfactory chemotherapy results, susceptibility to drug resistance, and serious adverse effects. Natural compounds have numerous pharmacological activities which are important sources of drug discovery for tumor treatment. The combination of chemotherapeutic drugs and natural compounds is gradually becoming an important strategy and development direction for tumor treatment. In this paper, we described the role of natural compounds in combination with chemotherapeutic drugs in synergizing, reducing drug resistance, mitigating adverse effects and related mechanisms, and providing new insights for future oncology research.

Natural products targeting the ATR-CHK1 signaling pathway in cancer therapy

Cancer is one of the most severe medical conditions in the world, causing millions of deaths each year. Chemotherapy and radiotherapy are critical for treatment approaches, but both have numerous adverse health effects. Furthermore, the resistance of cancerous cells to anticancer medication leads to treatment failure. The rising burden of cancer requires novel efficacious treatment modalities. Natural remedies offer feasible alternative options against malignancy in contrast to available synthetic medication. Selective killing of cancer cells is privileged mainstream in cancer treatment, and targeted therapy represents the new tool with the potential to pursue this aim. The discovery of innovative therapies targeting essential components of DNA damage signaling and repair pathways such as ataxia telangiectasia mutated and Rad3 related Checkpoint kinase 1 (ATR-CHK1)has offered a possibility of significant therapeutic improvement in oncology. The activation and inhibition of this pathway account for chemopreventive and chemotherapeutic activity, respectively. Targeting this pathway can also aid to overcome the resistance of conventional chemo- or radiotherapy. This review enlightens the anticancer role of natural products by ATR-CHK1 activation and inhibition. Additionally, these compounds have been shown to have chemotherapeutic synergistic potential when used in combination with other anticancer drugs. Ideally, this review will trigger interest in natural products targeting ATR-CHK1 and their potential efficacy and safety as cancer lessening agents.

Effect of hepar-protecting Wuzhi capsule on Pharmacokinetics and Dose-effect Character of Tacrolimus in Healthy Volunteers

Wuzhi capsule (WZC), a preparation of Fructus Schisandra sphenanthera extract, has been widely used for the treatment of viral and drug-induced hepatitis in China. This study aimed to determine the pharmacokinetic parameters of tacrolimus (TAC) when co-administered with WZC and its dose-effect of WZC on TAC in healthy volunteers. We assessed the effect of increased dosage of WZC (1, 2, 6, and 8 capsules once daily) on the relative oral exposure of TAC to explore the dose-response relationship between WZC and TAC using bioanalysis, pharmacokinetic, genotypical analyses. We elucidate the influence of CYP3A5 and MDR1 genetic polymorphisms on the WZC dose by maintaining C_trough of TAC in Chinese healthy volunteers. When co-administered with WZC, the T_max of TAC was increased significantly while the apparent oral clearance was decreased. The plasma TAC level in volunteers with high CYP3A5 expression was greatly lower than that in those with mutant CYP3A5. However, polymorphisms of MDR1 exon26 C3435T, exon21 G2677T/A and exon12 C1236T were not associated with plasma TAC levels. Our findings provide important information on interactions between modern medications and herbal products, thus facilitating a better usage of TAC in patients receiving WZC. This article is protected by copyright. All rights reserved.

Ellagic Acid and Schisandrins: Natural Biaryl Polyphenols with Therapeutic Potential to Overcome Multidrug Resistance in Cancer

Multidrug resistance (MDR) is one of the major clinical challenges in cancer treatment and compromises the effectiveness of conventional anticancer chemotherapeutics. Among known mechanisms of drug resistance, drug efflux via ATP binding cassette (ABC) transporters, namely P-glycoprotein (P-gp) has been characterized as a major mechanism of MDR. The primary function of ABC transporters is to regulate the transport of endogenous and exogenous small molecules across the membrane barrier in various tissues. P-gp and similar efflux pumps are associated with MDR because of their overexpression in many cancer types. One of the intensively studied approaches to overcome this mode of MDR involves development of small molecules to modulate P-gp activity. This strategy improves the sensitivity of cancer cells to anticancer drugs that are otherwise ineffective. Although multiple generations of P-gp inhibitors have been identified to date, reported compounds have demonstrated low clinical efficacy and adverse effects. More recently, natural polyphenols have emerged as a promising class of compounds to address P-gp linked MDR. This review highlights the chemical structure and anticancer activities of selected members of a structurally unique class of 'biaryl' polyphenols. The discussion focuses on the anticancer properties of ellagic acid, ellagic acid derivatives, and schisandrins. Research reports regarding their inherent anticancer activities and their ability to sensitize MDR cell lines towards conventional anticancer drugs are highlighted here. Additionally, a brief discussion about the axial chirality (i.e., atropisomerism) that may be introduced into these natural products for medicinal chemistry studies is also provided.

Potential Herb-Drug Interactions in the Management of Age-Related Cognitive Dysfunction

Late-life mild cognitive impairment and dementia represent a significant burden on healthcare systems and a unique challenge to medicine due to the currently limited treatment options. Plant phytochemicals have been considered in alternative, or complementary, prevention and treatment strategies. Herbals are consumed as such, or as food supplements, whose consumption has recently increased. However, these products are not exempt from adverse effects and pharmacological interactions, presenting a special risk in aged, polymedicated individuals. Understanding pharmacokinetic and pharmacodynamic interactions is warranted to avoid undesirable adverse drug reactions, which may result in unwanted side-effects or therapeutic failure. The present study reviews the potential interactions between selected bioactive compounds (170) used by seniors for cognitive enhancement and representative drugs of 10 pharmacotherapeutic classes commonly prescribed to the middle-aged adults, often multimorbid and polymedicated, to anticipate and prevent risks arising from their co-administration. A literature review was conducted to identify mutual targets affected (inhibition/induction/substrate), the frequency of which was taken as a measure of potential interaction. Although a limited number of drugs were studied, from this work, interaction with other drugs affecting the same targets may be anticipated and prevented, constituting a valuable tool for healthcare professionals in clinical practice.

Isolation of enantiomeric furolactones and furofurans from Rubus idaeus L. with neuroprotective activities

A phytochemical study on the fruits of Rubus idaeus L. (Rosaceae) yielded eight pairs of enantiomeric lignans, including one undescribed furolactone named (-)-idaeusinol A and six undescribed furofuran derivatives named (+/-)-idaeusinol B-D. The structures of these isolated compounds were elucidated by spectroscopic analyses and a combination of computational techniques including gauge-independent atomic orbital (GIAO) calculation of 1D NMR data and TD-DFT calculation of electronic circular dichroism (ECD) spectra. Bioactivity screenings suggested that (+)-idaeusinol D exhibited the most significant protective effect against H₂O₂-induced neurotoxicity at the concentration of 25 μM. In contrast, (-)-idaeusinol D, as the enantiomer of (+)-idaeusinol D, showed no effect against H₂O₂-induced neurotoxicity at both 25 and 50 μM concentration.

Schisandrin B prevents ulcerative colitis and colitis-associated-cancer by activating focal adhesion kinase and influence on gut microbiota in an in vivo and in vitro model

Colitis-associated cancer (CAC) has a close relationship with ulcerative colitis (UC). Therapeutic effect of Schisandrin B (SchB) on UC and CAC remains largely unknown. We investigated the preventative effect of SchB on the dextran sulphate sodium (DSS) model of UC and azoxymethane (AOM)/DSS model of CAC. Furthermore, focal adhesion kinase (FAK) activation and influence on commensal microbiota are important for UC treatment. Impact on FAK activation by SchB in UC development was evaluated in vivo and vitro. We also conducted 16S rRNA sequencing to detect regulation of gut microbiota by SchB. Enhanced protection of intestinal epithelial barrier by SchB through activating FAK contributed to protective effect on colon for the fact that protection of SchB can be reversed by inhibition of FAK phosphorylation. Furthermore, influence on gut microbiota by SchB also played a significant role in UC prevention. Our results revealed that SchB was potent to prevent UC by enhancing protection of intestinal epithelial barrier and influence on gut microbiota, which led to inhibition of CAC. SchB was potential to become a new treatment for UC and prevention of CAC.

Schisandrin B inhibits the proliferation and invasion of glioma cells by regulating the HOTAIR-micoRNA-125a-mTOR pathway

Glioma is one of the most common malignant central nervous system tumors in humans. Schisandrin B (Sch B) has been confirmed to cause the proliferation and invasion of glioma cells. In the present study, the potential mechanism underlying the antitumor effect of Sch B on glioma cells was investigated. The glioma cell lines, U251 and U87, were exposed to Sch B, and the cell viability, apoptosis, migration, and invasion were determined using the MTT assay, flow cytometry, and transwell assay, respectively. Then, the effects of HOTAIR and miR-125a on tumor biology and the mammalian target of rapamycin (mTOR) protein expression in cell lines exposed to Sch B were investigated. The results showed that Sch B decreased HOTAIR expression and increased miR-125a-5p expression. HOTAIR overexpression decreased miR-125a expression and increased mTOR expression in cells with the treatment of Sch B. The miR-125a inhibitor reversed the effects of HOTAIR downregulation on cell proliferation and migration. On co-incubation with rapamycin, a specific mTOR inhibitor, the cell viability, migration, and invasion were decreased and cell apoptosis was increased in two cell lines exposed to Sch B after the treatment of pcDNA-HOTAIR. In conclusion, Sch B played an inhibitory role in the proliferation and invasion of glioma cells by regulating the HOTAIR-micoRNA-125a-mTOR pathway.

Schisandrin B reverses doxorubicin resistance through inhibiting P-glycoprotein and promoting proteasome-mediated degradation of survivin

Acquired drug resistance poses a great challenge in cancer therapy. Drug efflux and anti-apoptotic processes are the most two common mechanisms that confer cancer drug resistance. In this study, we found that Schisandrin B (Sch B), one of the major dibenzocyclooctadiene derivatives extracted from Chinese herbal medicine Schisandrae Chinensis Fructus, could significantly enhance the sensitivity of doxorubicin (DOX)-resistant breast cancer and ovarian cancer cells to DOX. Our results showed that Sch B increased the intracellular accumulation of DOX through inhibiting expression and activity of P-glycoprotein (P-gp). Meanwhile, Sch B could markedly downregulate the expression of anti-apoptotic protein survivin. Overexpression of survivin attenuated the sensitizing effects of Sch B, while silencing of survivin enhanced Sch B-mediated sensitizing effects. Furthermore, Sch B preferentially promoted chymotryptic activity of the proteasome in a concentration-dependent manner, and the proteasome inhibitor MG-132 prevented Sch B-induced survivin downregulation. Taken together, our findings suggest that Sch B could be a potential candidate for combating drug resistant cancer via modulating two key factors that responsible for cancer resistance.

WITHDRAWN: The anti-growth and anti-metastasis effects of Schisandrin B on hepatocarcinoma cells in vitro and in vivo

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Mechanism Underlying the Reversal of Drug Resistance in P-Glycoprotein-Expressing Leukemia Cells by Pinoresinol and the Study of a Derivative

P-glycoprotein (P-gp) is a membrane protein associated with multidrug resistance (MDR) due to its key role in mediating the traffic of chemotherapeutic drugs outside cancer cells, leading to a cellular response that hinders efforts toward successful therapy. With the aim of finding agents that circumvent the MDR phenotype mediated by P-gp, 15 compounds isolated from native and naturalized plants of Argentina were screened. Among these, the non-cytotoxic lignan (±) pinoresinol successfully restored sensitivity to doxorubicin from 7 μM in the P-gp overexpressed human myelogenous leukemia cells, Lucena 1. This resistance-reversing effect was confirmed by competitively increasing the intracellular doxorubicin accumulation and by significantly inhibiting the efflux of doxorubicin and, to a lesser extent, that of rhodamine 123. The activity obtained was similar to that observed with verapamil. No such results were observed in the sensitive parental K562 cell line. To gain deeper insight into the mode of action of pinoresinol, its effect on P-gp function and expression was examined. The docking simulations indicated that the lignan bound to P-gp at the apex of the V-shaped transmembrane cavity, involving transmembrane helices 4, 5, and 6, and partially overlapped the binding region of tariquidar, which was used as a positive control. These results would shed some light on the nature of its interaction with P-gp at molecular level and merit further mechanistic and kinetic studies. In addition, it showed a maximum 29% activation of ATP hydrolysis and antagonized verapamil-stimulated ATPase activity with an IC₅₀ of 20.9 μM. On the other hand, pinoresinol decreased the presence of P-gp in the cell surface. Derivatives of pinoresinol with improved activity were identified by docking studies. The most promising one, the non-cytotoxic 1-acetoxypinoresinol, caused a reversion of doxorubicin resistance from 0.11 μM and thus higher activity than the lead compound. It also caused a significant increase in doxorubicin accumulation. Results were similar to those observed with verapamil. The results obtained positioned these compounds as potential candidates for effective agents to overcome P-gp-mediated MDR, leading to better outcomes for leukemia chemotherapy.

Effect of traditional Chinese medicine components on multidrug resistance in tumors mediated by P-glycoprotein

Multidrug resistance (MDR) is a major cause of chemotherapy failure. It occurs when an organism is resistant to one type of drug, but also develops resistance to other drugs with different structures and targets. There is a high incidence of MDR in cancer chemotherapy, therefore, finding an effective and non-toxic MDR reversal agent is an important goal, particularly for P-glycoprotein-mediated MDR in cancer. Improvements continue to be made to the status and understanding of traditional Chinese medicine (TCM), due to the advantages of low toxicity and relatively minor side effects. Therefore TCM is currently being used in the treatment of various types of diseases. In recent years, numerous components of TCM have been identified to be effective in reversing MDR by downregulating expression of the drug transporter membrane protein, recovering changes in enzymes involved in detoxification and metabolism and repairing the cell apoptosis pathway. The present study summarizes the anticancerous properties and MDR reversing components of traditional medicinal plants commonly used in the treatment of cancer.

A Naturally-Derived Compound Schisandrin B Enhanced Light Sensation in the pde6c Zebrafish Model of Retinal Degeneration

Retinal degeneration is often progressive. This feature has provided a therapeutic window for intervention that may extend functional vision in patients. Even though this approach is feasible, few promising drug candidates are available. The scarcity of new drugs has motivated research to discover novel compounds through different sources. One such example is Schisandrin B (SchB), an active component isolated from the five-flavor fruit (Fructus Schisandrae) that is postulated in traditional Chinese medicines to exert prophylactic visual benefit. This SchB benefit was investigated in this study in pde6c^w59, a zebrafish retinal-degeneration model. In this model, the pde6c gene (phosphodiesterase 6C, cGMP-specific, cone, alpha prime) carried a mutation which caused cone degeneration. This altered the local environment and caused the bystander rods to degenerate too. To test SchB on the pde6c^w59 mutants, a treatment concentration was first determined that would not cause morphological defects, and would initiate known physiological response. Then, the mutants were treated with the optimized SchB concentration before the appearance of retinal degeneration at 3 days postfertilization (dpf). The light sensation of animals was evaluated at 6 dpf by the visual motor response (VMR), a visual startle that could be initiated by drastic light onset and offset. The results show that the VMR of pde6c^w59 mutants towards light onset was enhanced by the SchB treatment, and that the initial phase of the enhancement was primarily mediated through the mutants’ eyes. Further immunostaining analysis indicates that the treatment specifically reduced the size of the abnormally large rods. These observations implicate an interesting hypothesis: that the morphologically-improved rods drive the observed VMR enhancement. Together, these investigations have identified a possible visual benefit of SchB on retinal degeneration, a benefit that can potentially be further developed to extend functional vision in patients.

Validation of an LC-MS/MS method for quantitative analysis of the 5 bioactive components of Wuzhi capsule in human plasma samples

BACKGROUND

Wuzhi capsule (WZC) is an ethanol extract from the ripe fruit of Schisandra sphenanthera in traditional Chinese medicine that has long been used to treat viral and drug-induced hepatitis in China. The principal active components in WZC are Schisandra lignans. The clinical pharmacokinetics of these components in the form of an oral WZC preparation is unknown. To optimize the WZC dosage and develop WZC-related combination therapies, it is necessary to conduct a comprehensive pharmacokinetic study of the Schisandra lignans.

METHODS

A method was developed for simultaneous quantification of multiple bioactive lignans in WZC in human plasma through liquid-liquid extraction followed by multiple reaction monitoring liquid chromatography/tandem mass spectrometry with positive-mode electrospray ionization. The 5 bioactive constituents were separated by isocratic elution using a mobile phase consisting of acetonitrile, methanol, and 0.1% aqueous formic acid at a flow rate of 0.3 mL/min. The total run time was 3.5 minutes.

RESULTS

All analytes showed good linearity over a wide concentration range with a lower limit of quantification at 0.5 ng/mL. Using this method, we determined the 5 bioactive lignans in WZC from human plasma simultaneously and performed a pharmacokinetic study on the Schisandra lignans in healthy volunteers.

CONCLUSIONS

Owing to simplicity, quickness, high sensitivity, and selectivity, and a sufficient lower limit of detection of the new liquid chromatography/tandem mass spectrometry method, it may be used as a routine technique for clinical monitoring of WZC, and for understanding interactions between herbal and conventional drug therapies.

Schisandra chinensis regulates drug metabolizing enzymes and drug transporters via activation of Nrf2-mediated signaling pathway

Drug metabolizing enzymes (DMEs) and drug transporters are regulated via epigenetic, transcriptional, posttranscriptional, and translational and posttranslational modifications. Phase I and II DMEs and drug transporters play an important role in the disposition and detoxification of a large number of endogenous and exogenous compounds. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a critical regulator of a variety of important cytoprotective genes that are involved in disposition and detoxification of xenobiotics. Schisandra chinensis (SC) is a commonly used traditional Chinese herbal medicine that has been primarily used to protect the liver because of its potent antioxidative and anti-inflammatory activities. SC can modulate some DMEs and drug transporters, but the underlying mechanisms are unclear. In this study, we aimed to explore the role of Nrf2 in the regulatory effect of SC extract (SCE) on selected DMEs and drug transporters in human hepatocellular liver carcinoma cell line (HepG2) cells. The results showed that SCE, schisandrin A, and schisandrin B significantly increased the expression of NAD(P)H: Nicotinamide Adenine Dinucleotide Phosphate-oxidase or:quinone oxidoreductase 1, heme oxygenase-1, glutamate–cysteine ligase, and glutathione S-transferase A4 at both transcriptional and posttranscriptional levels. Incubation of HepG2 cells with SCE resulted in a significant increase in the intracellular level of glutathione and total glutathione S-transferase content. SCE significantly elevated the messenger ribonucleic acid and protein levels of P-glycoprotein and multidrug resistance-associated protein 2 and 4, whereas the expression of organic anion transporting peptide 1A2 and 1B1 was significantly downregulated by SCE. Knockdown of Nrf2 by small interfering ribonucleic acid attenuated the regulatory effect of SCE on these DMEs and drug transporters. SCE significantly upregulated Nrf2 and promoted the translocation of Nrf2 from cytoplasm to the nuclei. Additionally, SCE significantly suppressed the expression of cytosolic Kelch-like ECH-associated protein 1 (the repressor of Nrf2) and remarkably increased Nrf2 stability in HepG2 cells. Taken together, our findings suggest that the hepatoprotective effects of SCE may be partially ascribed to the modulation of DMEs and drug transporters via Nrf2-mediated signaling pathway. SCE may alter the pharmacokinetics of other coadministered drugs that are substrates of these DMEs and transporters and thus cause unfavorable herb–drug interactions.

Gene expression profiling of sesaminol triglucoside and its tetrahydrofuranoid metabolites in primary rat hepatocytes

Sesaminol triglucoside is a major lignin in sesame meal and has a methylenedioxyphenyl group and multiple functions in vivo. As a tetrahydrofurofuran type lignan, sesaminol triglucoside is metabolized to mammalian lignans. This investigation studies the effect of sesaminol triglucoside and its tetrahydrofuranoid metabolites (sesaminol, 2-episesaminol, hydroxymethyl sesaminol-tetrahydrofuran, enterolactone, and enterodiol) on gene expression in primary rat hepatocytes using a DNA microarray. Sesame lignans significantly affected the expression of xenobiotic-induced transcripts of cytochrome P450, solute carrier (SLC), and ATP-binding cassette (ABC) transporters. Changes in gene expression were generally greater in response to metabolites with methylenedioxyphenyl moieties (sesaminol triglucoside, sesaminol, and 2-episesaminol) than to the tetrahydrofuranoid metabolites (hydroxymethyl sesaminol-tetrahydrofuran, enterolactone, and enterodiol). Tetrahydrofuran lignans, such as sesaminol triglucoside, sesamin, hydroxymethyl sesaminol-tetrahydrofuran, and sesaminol changed the expression of ABC transporters.

Schisandrin B induces apoptosis and cell cycle arrest of gallbladder cancer cells

Gallbladder cancer, with high aggressivity and extremely poor prognosis, is the most common malignancy of the bile duct. The main objective of the paper was to investigate the effects of schisandrin B (Sch B) on gallbladder cancer cells and identify the mechanisms underlying its potential anticancer effects. We showed that Sch B inhibited the viability and proliferation of human gallbladder cancer cells in a dose-, time -dependent manner through MTT and colony formation assays, and decrease mitochondrial membrane potential (ΔΨm) at a dose-dependent manner through flow cytometry. Flow cytometry assays also revealed G0/G1 phase arrest and apoptosis in GBC-SD and NOZ cells. Western blot analysis of Sch B-treated cells revealed the upregulation of Bax, cleaved caspase-9, cleaved caspase-3, cleaved PARP and downregulation of Bcl-2, NF-κB, cyclin D1 and CDK-4. Moreover, this drug also inhibited the tumor growth in nude mice carrying subcutaneous NOZ tumor xenografts. These data demonstrated that Sch B induced apoptosis in gallbladder cancer cells by regulating apoptosis-related protein expression, and suggests that Sch B may be a promising drug for the treatment of gallbladder cancer.

Effect of Tacrolimus on the pharmacokinetics of bioactive lignans of Wuzhi tablet (Schisandra sphenanthera extract) and the potential roles of CYP3A and P-gp

We recently reported that Wuzhi tablet (WZ), a preparation of the ethanol extract of Wuweizi (Schisandra sphenanthera), had significant effects on blood concentrations of Tacrolimus (FK506) in renal transplant recipients and rats. The active lignans in WZ are schisandrin A, schisandrin B, schisandrin C, schisandrol A, schisandrol B, schisantherin A, and schisantherin B. Until now, whether the pharmacokinetics of these lignans in WZ would be affected by FK506 remained unknown. Therefore, this study aimed to investigate whether and how FK506 affected pharmacokinetics of lignans in WZ in rats and the potential roles of CYP3A and P-gp. After a single oral co-administration of FK506 and WZ, the blood concentration of lignans in WZ was decreased by FK506; furthermore, the AUC of schisantherin A, schisandrin A, schisandrol A and schisandrol B was only 64.5%, 47.2%, 55.1% and 57.4% of that of WZ alone group, respectively. Transport study in Caco-2 cells showed that these lignans were not substrates of P-gp, suggesting decreased blood concentration of lignans by FK506 was not via P-gp pathway. Metabolism study in the human recombinant CYP 3A showed that these lignans had higher affinity to CYP3A than that of FK506, and thus had a stronger CYP3A-mediated metabolism. It was concluded that the blood concentrations of these lignans were decreased and their CYP3A-mediated metabolisms were increased in the presence of FK506 since these lignans had higher affinity to CYP3A.

In vivo effect of Schisandrin B on cytochrome P450 enzyme activity

To investigate the possible drug interaction, this study is designed to evaluate the ability of Schisandrin B (Sch B) to modulate cytochrome P450 3A activity (CYP3A) in vivo and to alter the pharmacokinetic profiles of CYP3A substrate (midazolam) in treated rats. Rats were repeated administered with physiological saline (negative control group), ketoconazole (75 mg/kg, positive control group) or varied doses of Sch B (experimental groups) for three consecutive days. Subsequently, changes in hepatic microsomal CYP3A activity and the pharmacokinetic profiles of midazolam and 1'-hydroxy midazolam in plasma were studied to evaluate CYP3A activity. The results indicated that Sch B significantly dose-dependently inhibited rat hepatic microsomal CYP3A activity with Ki value of 16.64 mg/kg and showed the characteristic of a noncompetitive inhibitor. Oral administration of Sch B for 3 days in rats produced significant effect on the pharmacokinetics of oral midazolam. Sch B resulted in a significant, dose-dependent increase in midazolam AUC0-∞ except at the dose of 2 mg/kg, while AUC0-∞ increased by 26.1% (8 mg/kg) and 60.6% (16 mg/kg), respectively. In the pharmacokinetic profiles of 1'-hydroxy midazolam, the significant, dose-dependent decrease in AUC0-∞ was observed except at the dose of 2 mg/kg, while AUC0-∞ reduced by 44.5% (8 mg/kg) and 49.2% (16 mg/kg), respectively. These results suggested that 3-day treatment of Sch B could increase concentration and oral bioavailability of drug metabolized by CYP3A. When the drug, consisting of Sch B, is used in the clinic for more than 3 days, the possible drug-drug interactions should be taken into consideration.

Effect of long-term co-administration of Wuzhi tablet (Schisandra sphenanthera extract) and prednisone on the pharmacokinetics of tacrolimus

Tacrolimus (TAC) is an immunosuppressant that has been widely used alone or in combination with prednisone (PRED) to prevent acute rejection after organ transplantation. Wuzhi tablet (WZ, Schisandra sphenanthera extract) is often prescribed with TAC to prevent drug-induced hepatitis. We recently reported that WZ could significantly increase TAC blood exposure by inhibiting P-gp-mediated efflux and CYP3A-mediated metabolism of TAC. PRED is also a substrate of P-gp and is a weak inducer of CYP3A, and drug-drug interactions within this combination therapy might occur. Therefore, the purpose of this study was to investigate the effect of long-term treatment of WZ and PRED on the pharmacokinetics of TAC in rats. After 14 days of co-administration of WZ and PRED, the AUC(0-24h) of oral TAC was increased (from 59.6±37.3 to 95.3±39.4 ng h/ml, p=0.18) and the clearance was decreased (from 38.4±28.4 to 17.7±6.4 l/h/kg, p=0.15). When only co-administered with WZ, AUC(0-24h) of TAC was demonstrated a significantly increase (from 59.6±37.3 to 135.9±34.8 ng h/ml, p<0.05). The concomitant administration of PRED resulted in a reduction in the systemic exposure of TAC and an increase in its clearance, though neither was statistically significant. Thus, our study suggested that the presence of WZ and PRED still could increase the systemic exposure of TAC in rats. The drug-drug interactions among this combination therapy should still be taken into consideration in clinical practice.

Anticancer agent shikonin is an incompetent inducer of cancer drug resistance

PURPOSE

Cancer drug resistance is a major obstacle for the success of chemotherapy. Since most clinical anticancer drugs could induce drug resistance, it is desired to develop candidate drugs that are highly efficacious but incompetent to induce drug resistance. Numerous previous studies have proven that shikonin and its analogs not only are highly tumoricidal but also can bypass drug-transporter and apoptotic defect mediated drug resistance. The purpose of this study is to investigate if or not shikonin is a weak inducer of cancer drug resistance.

EXPERIMENTAL DESIGN

Different cell lines (K562, MCF-7, and a MDR cell line K562/Adr), after repeatedly treated with shikonin for 18 months, were assayed for drug resistance and gene expression profiling.

RESULTS

After 18-month treatment, cells only developed a mere 2-fold resistance to shikonin and a marginal resistance to cisplatin and paclitaxel, without cross resistance to shikonin analogs and other anticancer agents. Gene expression profiles demonstrated that cancer cells did strongly respond to shikonin treatment but failed to effectively mobilize drug resistant machineries. Shikonin-induced weak resistance was associated with the up-regulation of βII-tubulin, which physically interacted with shikonin.

CONCLUSION

Taken together, apart from potent anticancer activity, shikonin and its analogs are weak inducers of cancer drug resistance and can circumvent cancer drug resistance. These merits make shikonin and its analogs potential candidates for cancer therapy with advantages of avoiding induction of drug resistance and bypassing existing drug resistance.

Effect of Wuzhi tablet (Schisandra sphenanthera extract) on the pharmacokinetics of cyclosporin A in rats

In our previous reports, Wuzhi tablet (an herbal preparation of ethanol extract of Wuweizi (Schisandra sphenanthera)) can significantly increase the blood concentration of tacrolimus and paclitaxel in rats by inhibiting the CYP3A-mediated metabolism and the P-gp-mediated efflux. Cyclosporin A (CsA), a well-known immunosuppressant agent, is also a substrate of CYP3A and P-gp. Therefore, this study aimed to investigate whether and how WZ affects pharmacokinetics of CsA in rats. The AUC0-48 h and Cmax of CsA were increased by 40.1% and 13.1%, respectively, with a single oral co-administration of WZ and high dose of CsA (37.8 mg/kg). Interestingly, after a single oral co-administration of WZ and low dose of CsA (1.89 mg/kg), the AUC0-36 h and Cmax of CsA were dramatically increased by 293.1% (from 1103.2 ± 293.0 to 4336.5 ± 1728.3 ng.h/mL; p < 0.05) and 84.1% (from 208.5 ± 67.9 to 383.1 ± 92.5 ng/mL; p < 0.05), respectively. The CL/F was decreased from 1.7 L/h/kg to 0.5 L/h/kg. Thus, the effect of WZ on high dose of CsA was not significant, but pharmacokinetic parameters of CsA at low dose were significantly influenced by co-administration of WZ. The herb-drug interaction should be taken into consideration at this situation.

Tissue distribution and cytochrome P450 inhibition of sesaminol and its tetrahydrofuranoid metabolites

Sesame lignans such as sesamin, sesaminol, and sesamolin are major constituents of sesame oil, and all have a methylenedioxyphenyl group and multiple functions in vivo. It was previously reported that sesaminol, a tetrahydrofurofuran type lignin, was metabolized to mammalian lignans. The present study examined the tissue distribution of sesaminol in Sprague-Dawley (SD) rats. Changes in the concentration of sesaminol and its metabolites (sesaminol glucuronide/sulfate, hydroxymethylsesaminol-tetrahydrofuran, enterolactone, and enterodiol) were determined in tissues within a 24 h period after tube feeding (po 220 mg/kg) to SD rats. The concentrations of enterodiol and enterolactone were significantly higher than those of sesaminol and its tetrahydrofuranoid metabolites in the organs (liver, heart, brain, and kidney). This study demonstrates that sesaminol has potent inhibition of cytochrome P450 (CYPs), compared to tetrahydrofuranoid metabolites. The IC(50) values of CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 for sesaminol were determined as 3.57, 3.93, 0.69, 1.33, and 0.86 μM, respectively. In addition, hydroxymethylsesaminol-tetrahydrofuran and enterodiol were weak inhibitors of CYP2C9 and CYP1A2, respectively.

Schisandrin B attenuates cancer invasion and metastasis via inhibiting epithelial-mesenchymal transition

Background

Metastasis is the major cause of cancer related death and targeting the process of metastasis has been proposed as a strategy to combat cancer. Therefore, to develop candidate drugs that target the process of metastasis is very important. In the preliminary studies, we found that schisandrin B (Sch B), a naturally-occurring dibenzocyclooctadiene lignan with very low toxicity, could suppress cancer metastasis.

Methodology

BALB/c mice were inoculated subcutaneously or injected via tail vein with murine breast cancer 4T1 cells. Mice were divided into Sch B-treated and control groups. The primary tumor growth, local invasion, lung and bone metastasis, and survival time were monitored. Tumor biopsies were examined immuno- and histo-pathologically. The inhibitory activity of Sch B on TGF-β induced epithelial-mesenchymal transition (EMT) of 4T1 and primary human breast cancer cells was assayed.

Principal Findings

Sch B significantly suppressed the spontaneous lung and bone metastasis of 4T1 cells inoculated s.c. without significant effect on primary tumor growth and significantly extended the survival time of these mice. Sch B did not inhibit lung metastasis of 4T1 cells that were injected via tail vein. Delayed start of treatment with Sch B in mice with pre-existing tumors did not reduce lung metastasis. These results suggested that Sch B acted at the step of local invasion. Histopathological evidences demonstrated that the primary tumors in Sch B group were significantly less locally invasive than control tumors. In vitro assays demonstrated that Sch B could inhibit TGF-β induced EMT of 4T1 cells and of primary human breast cancer cells.

Conclusions

Sch B significantly suppresses the lung and bone metastasis of 4T1 cells via inhibiting EMT, suggesting its potential application in targeting the process of cancer metastasis.

Antitumor agents. 293. Nontoxic dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB) analogues chemosensitize multidrug-resistant cancer cells to clinical anticancer drugs

Novel dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB) analogues were designed and synthesized to improve their chemosensitizing action on KBvin (vincristine-resistant nasopharyngeal carcinoma) cells, a multidrug resistant cell line overexpressing P-glycoprotein (P-gp). Structure-activity relationship analysis showed that aromatic and bulky aliphatic side chains at the 2,2'-positions effectively and significantly sensitized P-gp overexpressing multidrug resistant (MDR) cells to anticancer drugs, such as paclitaxel (TAX), vincristine (VCR), and doxorubicin (DOX). DDB derivatives 16 and 23 showed 5-10 times more effective reversal ability than verapamil (VRP) for TAX and VCR. Analogue 6 also exhibited five times greater chemosensitizing effect against DOX than VRP. Importantly, no cytotoxicity was observed by the active DDB analogues against both non-MDR and MDR cells, suggesting that DDB analogues serve as novel lead compounds for the development of chemosensitizers to overcome the MDR phenotype. The mechanism of action studies demonstrated that effective inhibition of P-glycoprotein by DDB analogues dramatically elevated the cellular concentration of anticancer drugs.

Schisandrin B prevents doxorubicin-induced chronic cardiotoxicity and enhances its anticancer activity in vivo

Background

To mitigate the cardiotoxicity of anthracycline antibiotics without compromising their anticancer activities is still an issue to be solved. We previously demonstrated that schisandrin B (Sch B) could protect against doxorubicin (Dox)-induced acute cardiotoxicity via enhancing cardiomyocytic glutathione redox cycling that could attenuate oxidative stress generated from Dox. In this study, we attempted to prove if Sch B could also protect against Dox-induced chronic cardiotoxicity, a more clinically relevant issue, without compromising its anticancer activity.

Methodology

Rat was given intragastrically either vehicle or Sch B (50 mg/kg) two hours prior to i.p. Dox (2.5 mg/kg) weekly over a 5-week period with a cumulative dose of Dox 12.5 mg/kg. At the 6th and 12th week after last dosing, rats were subjected to cardiac function measurement, and left ventricles were processed for histological and ultrastructural examination. Dox anticancer activity enhanced by Sch B was evaluated by growth inhibition of 4T1, a breast cancer cell line, and S180, a sarcoma cell line, in vitro and in vivo.

Principal Findings

Pretreatment with Sch B significantly attenuated Dox-induced loss of cardiac function and damage of cardiomyocytic structure. Sch B substantially enhanced Dox cytotoxicities toward S180 in vitro and in vivo in mice, and increased Dox cytotoxcity against 4T1 in vitro. Although we did not observe this enhancement against the implanted 4T1 primary tumor, the spontaneous metastasis to lung was significantly reduced in combined treatment group than Dox alone group.

Conclusion

Sch B is capable of protecting Dox-induced chronic cardiotoxicity and enhancing its anticancer activity. To the best of our knowledge, Sch B is the only molecule ever proved to function as a cardioprotective agent as well as a chemotherapeutic sensitizer, which is potentially applicable for cancer treatment.

Interactions of dietary phytochemicals with ABC transporters: possible implications for drug disposition and multidrug resistance in cancer

Common foods, such as fruits and vegetables, contain a large variety of secondary metabolites known as phytochemicals, many of which have been associated with health benefits. However, there is a limited knowledge of the processes by which these, mainly charged, phytochemicals (and/or their metabolites) are absorbed into the body, reach their biological target, and how they are eliminated. Recent studies have indicated that some of these phytochemicals are substrates and modulators of specific members of the superfamily of ABC transporting proteins. In this review, we present the reported interactions between the different classes of phytochemicals and ABC transporters and the mechanism by which they modulate the activity of these transporters. We also discuss the implications that such interactions may have on the pharmacokinetics of xenobiotics and the possible role of phytochemicals in the reversal of multidrug resistance in cancer chemotherapy.

Effect of Wuzhi tablet (Schisandra sphenanthera extract) on the pharmacokinetics of paclitaxel in rats

Wuzhi tablet (WZ, registration no. in China: Z20025766) is a preparation of an ethanol herb extract of Wuweizi (Schisandra sphenanthera) containing 7.5 mg Schisantherin A per tablet. It was reported recently that WZ could significantly increase the blood concentrations of tacrolimus, which might be due to the inhibitory effect of WZ and its ingredients on P-gp and/or CYP450 activity. Paclitaxel is a substrate of the efflux transporter P-gp, and is mainly metabolized by CYP450 enzymes in the liver. Therefore, the purpose of this study was to investigate whether and how WZ affects the pharmacokinetics of paclitaxel in rats. After pretreatment with WZ, there were significant increases in the AUC(0-24h) of oral paclitaxel (from 280.8 ± 97.3 to 543.5 ± 115.2 h ng/mL; p < 0.05) and C(max) (from 44.6 ± 16.4 to 86.8 ± 16.1 ng/mL; p < 0.05). The pharmacokinetic data for i.v. paclitaxel with WZ showed a relatively small (when compared against oral paclitaxel) but still significant increase in AUC(0-24h) (from 163.6 ± 22.1 to 212.7 ± 17.7 h ng/mL; p < 0.05) and a decrease in clearance (from 3.2 ± 0.6 to 2.2 ± 0.3 L/h/kg; p < 0.05). Thus, the presence of WZ improved the systemic exposure of paclitaxel in rats. The herb-drug interaction between WZ and paclitaxel should be taken into consideration in clinical use.

Dibenzocyclooctadiene lignans overcome drug resistance in lung cancer cells--study of structure-activity relationship

A panel of nine dibenzo[a,c]cyclooctadiene lignans, schizandrin, gomisin A, gomisin N, gomisin J, angeloylgomisin H, tigloylgomisin P, deoxyschizandrin, gamma-schizandrin and wuweizisu C was examined for their effect on multidrug resistance, as well as their anti-proliferative activities. COR-L23/R, a multidrug resistant sub-line, which has been reported to over-express multidrug resistance-associated protein (MRP1), was used for the experiments together with its parent cell line COR-L23 (human lung cell carcinoma). We found that lignans deoxyschizandrin and gamma-schizandrin at relatively non-toxic concentrations restored the cytotoxic action of doxorubicin to COR-L23/R cells. Deoxyschizandrin and gamma-schizandrin also significantly enhanced the accumulation of doxorubicin in drug resistant cells. Both lignans alone had no effect on the cell cycle; however, when combined with sub-toxic doses of doxorubicin, they induced cell cycle arrest in the G2/M phase, which is typical for toxic doses of doxorubicin. Our results suggest that deoxyschizandrin and gamma-schizandrin potentiate the cytotoxic effect of doxorubicin in doxorubicin resistant lung cancer cells COR-L23/R by increasing the accumulation of doxorubicin inside the cells. The common structural feature of both active lignans is the R-biaryl configuration and the absence of a hydroxy group at C-8. Unlike the reversal effect, the cytotoxicity of lignans with the R-biaryl configuration was similar to that observed for lignans with the S-biaryl configuration.

Wuweizisu C from Schisandra chinensis decreases membrane potential in C6 glioma cells

AIM

To study the effects of dibenzocyclooctadiene lignans isolated from Schisandra chinensis, such as wuweizisu C, gomisin N, gomisin A, and schisandrin, on the membrane potential in C6 glioma cells.

METHODS

The membrane potential was estimated by measuring the fluorescence change in DiBAC-loaded glioma cells.

RESULTS

Wuweizisu C decreased the membrane potential in a concentration-dependent manner. Gomisin N and gomisin A, however, showed differential modulation and no change was induced by schisandrin or dimethyl- 4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate, a synthetic drug derived from dibenzocyclooctadiene lignans. We found no involvement of G(i/o ) proteins, phospholipase C, and extracellular Na(+) on the wuweizisu C-induced decrease of the membrane potential. Wuweizisu C by itself did not change the intracellular Ca(2+)[Ca(2+)](i) concentration, but decreased the ATP-induced Ca(2+) increase in C6 glioma cells. The 4 lignans at all concentrations used in this study did not induce any effect on cell viability. Furthermore, we found a similar decrease of the membrane potential by wuweizisu C in PC12 neuronal cells.

CONCLUSION

Our results suggest that the decrease in the membrane potential and the modulation of [Ca(2+)](i) concentration by wuweizisu C could be important action mechanisms of wuweizisu C.

Schisandrin B prevents doxorubicin-induced cardiotoxicity via enhancing glutathione redox cycling

PURPOSE

The dose-cumulative cardiotoxicities and the emerging cancerous apoptotic/drug resistance are two major obstacles limiting the efficacy of anthracycline antibiotics, notably doxorubicin. We attempted to prove if schisandrin B (Sch B), a dual inhibitor of P-glycoprotein and multidrug resistance-associated protein 1, could protect against doxorubicin-induced cardiotoxicity, on the premise that Sch B is an enhancer of glutathione redox cycling that may attenuate doxorubicin-induced oxidative stress in the cardiomyocytes.

EXPERIMENTAL DESIGN

Mice or rat were dosed with a single injection of doxorubicin (25 mg/kg, i.p.) with or without pretreatment of Sch B. The protective roles of Sch B against doxorubicin-induced cardiac damage were evaluated on the aspects of the release of cardiac enzymes into serum, the formation of malondialdehyde, the activation of matrix metalloproteinase, the structural damage in the left ventricles, the mortality rates, and the cardiac functions.

RESULTS

Pretreatment of Sch B significantly attenuated doxorubicin-induced cardiotoxicities on all the aspects listed above. The underlying mechanism was associated with the effect of Sch B on maintaining the cardiomyocytic glutathione and the activities of superoxide dismutase, and the key enzymes (glutathione peroxidase, glutathione reductase, and glutathione transferase) responsible for glutathione redox cycling, which neutralized doxorubicin-induced oxidative stress.

CONCLUSION

To the best of our knowledge, Sch B is the only molecule ever proved to function as a cardioprotective agent as well as a dual inhibitor of P-glycoprotein and multidrug resistance-associated protein 1, which is potentially applicable to treat cancers, especially the multidrug-resistant cancers involving doxorubicin or its kin.

Shikonin circumvents cancer drug resistance by induction of a necroptotic death

Defect in apoptotic signaling and up-regulation of drug transporters in cancer cells significantly limits the effectiveness of cancer chemotherapy. We propose that an agent inducing non-apoptotic cell death may overcome cancer drug resistance and showed that shikonin, a naturally occurring naphthoquinone, induced a cell death in MCF-7 and HEK293 distinct from apoptosis and characterized with (a) a morphology of necrotic cell death; (b) loss of plasma membrane integrity; (c) loss of mitochondrial membrane potentials; (d) activation of autophagy as a downstream consequence of cell death, but not a contributing factor; (e) elevation of reactive oxygen species with no critical roles contributing to cell death; and (f) that the cell death was prevented by a small molecule, necrostatin-1, that specifically prevents cells from necroptosis. The characteristics fully comply with those of necroptosis, a basic cell-death pathway recently identified by Degterev et al. with potential relevance to human pathology. Furthermore, we proved that shikonin showed a similar potency toward drug-sensitive cancer cell lines (MCF-7 and HEK293) and their drug-resistant lines overexpressing P-glycoprotein, Bcl-2, or Bcl-x(L), which account for most of the clinical cancer drug resistance. To our best knowledge, this is the first report to document the induction of necroptosis by a small molecular compound to circumvent cancer drug resistance.

Effects of Schisandra sphenanthera extract on the pharmacokinetics of tacrolimus in healthy volunteers

AIM

To assess the effect of Schisandra sphenanthera extract (SchE) on the pharmacokinetics of tacrolimus in healthy volunteers.

METHODS

Twelve healthy male volunteers were orally treated with SchE, three capsules twice daily for 13 days. Pharmacokinetic investigations of oral tacrolimus administration at 2 mg were performed both before and at the end of the SchE treatment period. Whole blood tacrolimus concentrations were determined by enzyme-linked immunosorbent assay. Estimated pharmacokinetic parameters before and with SchE were calculated with noncompartmental techniques.

RESULTS

Following administration of SchE, the average percentage increases of individual increases in AUC, AUMC and C(max) of tacrolimus were 164.2% [95% confidence interval (CI) 70.1, 258.4], 133.1% (95% CI 49.5, 261.3) and 227.1% (95% CI 155.8, 298.4), respectively (P < 0.01 or 0.05). On average, there was a 36.8% (95% CI 13.4, 60.2) increase in tacrolimus t(max) (P < 0.01). The average percentage decreases in CL/F and V/F were 49.0% (95% CI 31.1, 66.9) and 53.7% (95% CI 40.1, 67.4), respectively (P < 0.01).

CONCLUSIONS

SchE can increase the oral bioavailability of tacrolimus. The results of this study will add important information to the interaction area between drugs and herbal products.

Dibenzocyclooctadiene lignans — A class of novel inhibitors of multidrug resistance-associated protein 1

We recently reported that dibenzocyclooctadiene lignans were a novel class of P-glycoprotein (P-gp) inhibitors. In this study, we demonstrated that the lignans of this class were also effective inhibitors of multidrug resistance-associated protein 1 (MRP1). The activities of 5 dibenzocyclooctadiene lignans (schisandrin A, schisandrin B, schisantherin A, schisandrol A, and schisandrol B) to reverse MRP1-mediated drug resistance were tested using HL60/Adriamycin (ADR) and HL60/Multidrug resistance-associated protein (MRP), two human promyelocytic leukemia cell lines with overexpression of MRP1 but not P-gp. The five lignans could effectively reverse drug resistance of the two cell lines to vincristine, daunorubicin, and VP-16. This study, together with our previous reports, proves that dibenzocyclooctadiene lignans have multiple activities against cancer multidrug resistance, including inhibition of P-gp and MRP1, and enhancement of apoptosis. Considering that cancer multidrug resistance (MDR) is multifactorial, agents with broad activities are preferable to the use of combination of several specific modulators to prevent drug-drug interaction and cumulative toxicity.

Phenylobacterium zucineum sp. nov., a facultative intracellular bacterium isolated from a human erythroleukemia cell line K562

A bacterial strain HLK1(T) was isolated from the human erythroleukemia cell line K562. This bacterium is a Gram-negative rod, motile with a polar flagellum. It is strictly aerobic, nonfermentative, and oxidase and catalase positive. Its optimal growth occurs at 37 degrees C at pH between 6.5 and 7.5. Phylogenetically, although it shares 98% similarity with the 16S rRNA of Phenylobacterium lituiforme, the DNA-DNA hybridization value between the two species is only 43%. HLK1(T) has a DNA G+C content of 71.2+/-0.2 mol%. It is a facultative intracellular organism and may have pathogenic relevance with humans and mammals. On the basis of the phylogenetic and phenotypic characterization, strain HLK1(T) is proposed to be classified in the genus Phenylobacterium, as P. zucineum sp. nov. The type strain is HLK1(T) (=CGMCC 1.3786(T), DSM=18354).

Gomisin A alters substrate interaction and reverses P-glycoprotein-mediated multidrug resistance in HepG2-DR cells

Through an extensive herbal drug screening program, we found that gomisin A, a dibenzocyclooctadiene compound isolated from Schisandra chinensis, reversed multidrug resistance (MDR) in Pgp-overexpressing HepG2-DR cells. Gomisin A was relatively non-toxic but without altering Pgp expression, it restored the cytotoxic actions of anticancer drugs such as vinblastine and doxorubicin that are Pgp substrates but may act by different mechanisms. Several lines of evidence suggest that gomisin A alters Pgp-substrate interaction but itself is neither a Pgp substrate nor competitive inhibitor. (1) First unlike Pgp substrates gomisin A inhibited the basal Pgp-associated ATPase (Pgp-ATPase) activity. (2) The cytotoxicity of gomisin A was not affected by Pgp competitive inhibitors such as verapamil. (3) Gomisin A acted as an uncompetitive inhibitor for Pgp-ATPase activity stimulated by the transport substrates verapamil and progesterone. (4) On the inhibition of rhodamine-123 efflux the effects of gomisin A and the competitive inhibitor verapamil were additive, so were the effects of gomisin A and the ATPase inhibitor vanadate. (5) Binding of transport substrates with Pgp would result in a Pgp conformational change favoring UIC-2 antibody reactivity but gomisin A impeded UIC-2 binding. (6) Photocrosslinking of Pgp with its transport substrate [125I]iodoarylazidoprazosin was inhibited by gomisin A in a concentration-dependent manner. Taken together our results suggest that gomisin A may bind to Pgp simultaneously with substrates and alters Pgp-substrate interaction.