Tenacigenin B derivatives reverse P-glycoprotein-mediated multidrug resistance inHepG2/Dox cells

Comprehensive insights into herbal P-glycoprotein inhibitors and nanoformulations for improving anti-retroviral therapy efficacy

The worldwide HIV cases were 39.0 million (33.1-45.7 million) in 2022. Due to genetic variations, HIV-1 is more easily transmitted than HIV-2 and favours CD4 + T cells and macrophages, producing AIDS. Conventional HIV drug therapy has many drawbacks, including adherence issues leading to resistance, side effects that lower life quality, drug interactions, high costs limiting global access, inability to eliminate viral reservoirs, chronicity requiring lifelong treatment, emerging toxicities, and a focus on managing infections. Conventional dosage forms have bioavailability issues due to intestinal P-glycoprotein (P-gp) efflux, which can reduce anti-retroviral drug efficacy and lead to resistance. Use of phyto-constituents with P-gp regulating actions has great benefits for semi-synthetic modification to create formulations with greater bioavailability and reduced toxicity, which improves drug effectiveness. Lipid-based nanocarriers, solid lipid nanoparticles, nanostructured lipid carriers, polymer-based nanocarriers, and inorganic nanoparticles may inhibit P-gp efflux. Employing potent P-gp inhibitors within nanocarriers as a Trojan horse approach can enhance the intracellular accumulation of anti-retroviral drugs (ARDs), which are substrates for efflux transporters. This technique increases oral bioavailability and offers lower-dose options, boosting HIV patient compliance and lowering costs. Molecular docking of the inhibitor with P-gp may anticipate optimum binding and function, allowing drug efflux to be minimised.

Investigating the Effect of Satureja khuzestanica Essential oil on MDR1 Gene Expression in Leishmania major

BACKGROUND

Cutaneous leishmaniasis is among the neglected diseases in the world. Pentavalent antimonial compounds are considered the first-line treatment for this disease. However, using alternative natural products has received great attention due to the side effects of chemical drugs and drug resistance of the Leishmania parasite. The present study aims to investigate the effect of Satureja khuzestanica essential oil (SKEO) on MDR1 gene expression.

METHODS

In this study, standard strains of Leishmania major promastigotes were exposed to 5, 10, 15, and 20 µg/ml of SKEO. MDR1 gene expression of parasites exposed to essential oil was evaluated using real-time PCR. GAPDH was employed as the housekeeping gene for internal control.

RESULTS

Despite the increase, no statistically significant difference was observed in the relative expression of the MDR1 gene between the control group and the groups containing 5, 10, and 20 µg/ml of SKEO (P > 0.05). The relative expression of the MDR1 gene significantly increased in the group containing 15 μg/ml of essential oil compared to the control one (P < 0.05).

CONCLUSION

This study showed that the use of essential oil of Satureja khuzestanica plant can have an increasing effect on the expression of MDR1 gene of Leishmania promastigotes, which is the best case if Satureja khuzestanica essential oil reduces the expression of MDR1 gene. So it seems that the use of essential oil of Satoria plant is effective in controlling Leishmania parasite, but its concentrations induce drug resistance. As a result, concentrations of essential oil should be used that have a controlling effect on the growth and proliferation of Leishmania parasite and also have the least effect on the induction of MDR1 gene expression.

Xiaoaiping injection combined with chemotherapy for advanced gastric cancer: An updated systematic review and meta-analysis

Aim: To evaluate the clinical efficacy and safety of Xiaoaiping injection combined with chemotherapy in the treatment of advanced gastric cancer by meta-analysis.

Methods: Seven databases, including China National Knowledge Infrastructure (CNKI), Wanfang Database, VIP Database, Cochrane Library, PubMed, Embase, and Web of Science, were searched by computer for randomized controlled clinical trials of Xiaoaiping injection combined with chemotherapy in the treatment of gastric cancer. Risk of bias assessment and meta-analysis were performed by Review Manager 5.3 software.

Results: There were 16 articles that met the inclusion criteria, with a total of 1,236 patients, 617 in the observation group and 619 in the control group. The results of meta-analysis showed that the observation group was better than chemotherapy alone control group in RR [OR = 1.86, p < 0.00001]; disease control rate (DCR) [OR = 2.45, p < 0.00001]; Karnofsky performance status (KPS) score [OR = 3.21, p < 0.00001] or [MD = 7.73, p = 0.001]. In terms of biochemical indicators, Xiaoaiping significantly reduced inflammation factors level, including tumor necrosis factor alpha (TNF-α) [MD = −15.00, p < 0.00001]; interleukin-6 (IL-6) [MD = −13.00, p < 0.00001]; C-reaction protein (CRP) [MD = −5.80, p < 0.00001]. Xiaoaiping could enhance immune function, significantly reducing myeloid-derived suppressor cells (MDSCs) [MD = −6.20, p < 0.00001] and Treg [MD = −1.70, p < 0.00001]. Xiaoaiping injection combined with chemotherapy could significantly decrease tumor markers, including carcinoembryonic antigen (CEA) [MD = −11.64, p < 0.00001]; CA199 [MD = −33.57, p = 0.02]; CA242 [MD = −20.66, p < 0.00001]; CA125 [MD = −12.50, p = 0.0005]. In the comparison of adverse reactions, the incidence rate of Xiaoaiping injection group was significantly lower than that of control group. The funnel plot showed that the left and right sides are basically symmetrical, and it can be considered that there is no obvious publication bias.

Conclusion: Xiaoaiping injection combined with chemotherapy has better curative effect and less adverse reactions in the treatment of gastric cancer. However, limited by the quality of the included studies, more high-quality studies are still needed to be verified.

Systematic Review Registration: [https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022353842], identifier [CRD42022353842].

An ester derivative of tenacigenin B from Marsdenia tenacissima (Roxb.) Wight et Arn reversed paclitaxel-induced MDR in vitro and in vivo by inhibiting both P-gp and MRP2

ETHNOPHARMACOLOGICAL RELEVANCE

Marsdenia tenacissima is a medicinal plant, used as a raw material for cancer treatment in China. In our previous studies, 11α-O-2-methylbutanoyl-12β-O-tigloyl-tenacigenin B (MT2), the main steroid aglycone isolated from M. tenacissima, was found to significantly enhance the antitumor activity of paclitaxel (PTX) in vivo. However, it is unclear whether MT2 reverses multidrug resistance (MDR) in tumors.

AIM OF THE STUDY

To determine the role and mechanism of MT2 in reversing tumor MDR.

MATERIALS AND METHODS

MDR cell line HeLa/Tax was established from the human cervical carcinoma cell line HeLa by long-term exposure to subtoxic concentrations of PTX and was used to evaluate the ability of MT2 to restore chemosensitivity of cells both in vitro and in a nude mouse model. The expression of P-glycoprotein (P-gp) and multidrug resistance-associated protein 2 (MRP2) was determined using western blotting and immunohistochemistry. The substrate transport function was assessed using an MDR function assay kit. The binding modes of MT2 and P-gp were determined using the conformation-sensitive anti-P-gp antibodies. The permeability and transport properties of MT2 were analyzed in Caco-2 cell monolayers.

RESULTS

Compared to parental cells, HeLa/Tax cells overexpress P-gp and MRP2 and are approximately 100-360 fold more resistant to the anticancer drugs PTX, docetaxel, and vinblastine. MT2 at 5 or 10 μmol/L significantly increased the sensitivity of HeLa/Tax to these three anticancer drugs (18-56-fold decrease in IC₅₀ value) and suppressed the expression of P-gp and MRP2. Knockdown of P-gp with small interfering RNA partially reversed MT2-induced sensitivity to PTX in HeLa/Tax cells. Moreover, MT2 directly inhibited P-gp-mediated substrate transport while interacting with membrane P-gp in non-substrate ways. MT2 was highly permeable and could not be transported in the Caco-2 cell monolayers. In nude mice bearing HeLa/Tax xenografts, the combination treatment with MT2 and PTX exerted a synergistic inhibitory effect on the growth of tumors and the expression of P-gp and MRP2 without increasing toxicity.

CONCLUSION

MT2 is a potential agent for reversing MDR. It impedes membrane drug efflux pumps by suppressing P-gp and MRP2 expression, and directly inhibiting the transport function of P-gp.

Polyoxypregnanes as safe, potent, and specific ABCB1-inhibitory pro-drugs to overcome multidrug resistance in cancer chemotherapy in vitro and in vivo

Multidrug resistance (MDR) mediated by ATP binding cassette subfamily B member 1 (ABCB1) is significantly hindering effective cancer chemotherapy. However, currently, no ABCB1-inhibitory drugs have been approved to treat MDR cancer clinically, mainly due to the inhibitor specificity, toxicity, and drug interactions. Here, we reported that three polyoxypregnanes (POPs) as the most abundant constituents of Marsdenia tenacissima (M. tenacissima) were novel ABCB1-modulatory pro-drugs, which underwent intestinal microbiota-mediated biotransformation in vivo to generate active metabolites. The metabolites at non-toxic concentrations restored chemosensitivity in ABCB1-overexpressing cancer cells via inhibiting ABCB1 efflux activity without changing ABCB1 protein expression, which were further identified as specific non-competitive inhibitors of ABCB1 showing multiple binding sites within ABCB1 drug cavity. These POPs did not exhibit ABCB1/drug metabolizing enzymes interplay, and their repeated administration generated predictable pharmacokinetic interaction with paclitaxel without obvious toxicity in vivo. We further showed that these POPs enhanced the accumulation of paclitaxel in tumors and overcame ABCB1-mediated chemoresistance. The results suggested that these POPs had the potential to be developed as safe, potent, and specific pro-drugs to reverse ABCB1-mediated MDR. Our work also provided scientific evidence for the use of M. tenacissima in combinational chemotherapy.

Distributions of eight bioactive components in rat tissues administered Marsdenia tenacissima extract orally detected through UPLC-MS/MS

Marsdenia tenacissima (Roxb.) Wight et Arn. (M. tenacissima) is considered an anticancer medicine in traditional Chinese medicine, which is extensively used in clinical application since it has great therapeutic effects. Currently, although a number of articles have examined M. tenacissima in terms of its pharmacology and quality control, few have investigated the in vivo mechanism of M. tenacissima active ingredients. Previously, we have studied the pharmacokinetics of eight active ingredients after oral administration of M. tenacissima extracts in rat plasma. This study constructed a new scientific ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) approach to simultaneously quantify the contents of tenacissosides B, G, H and I, cryptochlorogenic acid, chlorogenic acid, neochlorogenic acid and caffeic acid in rats orally administered M. tenacissima extract. The proposed approach was successfully used for investigating the distributions of those eight analytes in rat tissues, with digoxin being used as an internal control. The Eclipse Plus C₁₈ RRHD column was used for determination at a column temperature of 30°C. The mobile phase system consisted of acetonitrile and water (supplemented with 0.1% formic acid) under optimal gradient elution conditions. Afterwards, this approach was validated according to the requirements for the analysis of biological samples developed by the US Food and Drug Administration, including precision, accuracy, stability and matrix effects. Based on tissue distribution analysis, those eight analytes showed rapid distribution within all the tested tissues. With regard to organic acid distribution, it followed the order stomach > liver > kidney > small intestine > lung > spleen > heart, whereas the four steroids followed the order stomach > lung > spleen > small intestine > liver > kidney > heart. The present study lays the theoretical foundation for the use and development of M. tenacissima in clinical practice.

Comparative Efficacy of Chinese Herbal Injections Combined with Paclitaxel Plus Cisplatin for Non-Small-Cell Lung Cancer: A Multidimensional Bayesian Network Meta-Analysis

Introduction

Considering the limitations of pure paclitaxel plus cisplatin chemotherapy in the treatment of non-small-cell lung cancer and the extensive exploration of Chinese herbal injections, this study performed a multidimensional network meta-analysis to systematically evaluate the clinical efficacy and safety of 12 Chinese herbal injections in the treatment of non-small-cell lung cancer.

Methods

Randomized controlled trials were obtained from several databases according to the eligibility criteria, and the study quality was assessed by the Cochrane risk of bias tool. Data analysis was performed by Stata 13.1 software and WinBUGS 14.0 software. Multidimensional cluster analysis was performed with the "scatterplot3d" package in R 3.6.1 software (PROSPERO ID: CRD42020163503).

Results

A total of 58 eligible randomized controlled trials involving 4578 patients and 12 Chinese herbal injections were included. Combined with paclitaxel plus cisplatin chemotherapy, Xiaoaiping injection exhibited a better impact on the clinical effective rate than paclitaxel plus cisplatin alone. Shenqifuzheng injection was associated with a preferable response in performance status and reduced leukopenia and gastrointestinal reactions. Kangai injection was dominant in the comprehensive results of the cluster analysis.

Conclusions

Chinese herbal injections combined with paclitaxel plus cisplatin chemotherapy have a certain adjuvant effect in treating non-small-cell lung cancer, but the results of this study need to be verified by more well-designed, large-sample, multicenter randomized controlled trials.

Simultaneous determination of eight bioactive components in Marsdenia tenacissima extract in rat plasma by LC-MS/MS and its application in a pharmacokinetic study

As a traditional Chinese medicine, Marsdenia tenacissima (Roxb.) Wight et Arn. plays an indispensable role in clinical practice owing to its specific efficacy in treating malignant tumors, leukocythemia, cystitis and asthma. This study aimed to establish a novel and scientific LC-MS/MS approach to simultaneously determine tenacissoside B, H, G and I, caffeic acid, cryptochlorogenic acid, chlorogenic acid and neochlorogenic acid from M. tenacissima extract within the rat plasma samples. Digoxin was used as the internal reference. All determinations were carried out using the Eclipse Plus C₁₈ column, and water (containing 0.1% formic acid) was used as the mobile phase A, while acetonitrile was the mobile phase B for gradient elution. The UPLC methods were validated, including calibration curves, accuracy, precision, stability and recovery of the total eight analytes, in accordance with the requirements for biopharmaceutical analysis. Moreover, the proposed approach was also used in comprehensive pharmacokinetic research on those eight analytes in rats following M. tenacissima extract gavage. According to the pharmacokinetic parameters, tenacissoside B, I, H and G are the long-acting and primary bioactive constituents in M. tenacissima extract, with long mean residence times and high concentrations. Our findings shed light on the absorption mechanism and provide significant information for the clinical application of M. tenacissima.

Phytochemicals: Potential Lead Molecules for MDR Reversal

Multidrug resistance (MDR) is one of the main impediments in the treatment of cancers. MDR cancer cells are resistant to multiple anticancer drugs. One of the major mechanisms of MDR is the efflux of anticancer drugs by ABC transporters. Increased activity and overexpression of these transporters are important causes of drug efflux and, therefore, resistance to cancer chemotherapy. Overcoming MDR is a fundamental prerequisite for developing an efficient treatment of cancer. To date, various types of ABC transporter inhibitors have been employed but no effective anticancer drug is available at present, which can completely overcome MDR. Phytochemicals can reverse MDR in cancer cells via affecting the expression or activity of ABC transporters, and also through exerting synergistic interactions with anticancer drugs by addressing additional molecular targets. We have listed numerous phytochemicals which can affect the expression and activity of ABC transporters in MDR cancer cell lines. Phytochemicals in the groups of flavonoids, alkaloids, terpenes, carotenoids, stilbenoids, lignans, polyketides, and curcuminoids have been examined for MDR-reversing activity. The use of MDR-reversing phytochemicals with low toxicity to human in combination with effective anticancer agents may result in successful treatment of chemotherapy-resistant cancer. In this review, we summarize and discuss published evidence for natural products with MDR modulation abilities.

Medicinal chemistry strategies to discover P-glycoprotein inhibitors: An update

The presence of multidrug resistance (MDR) in malignant tumors is one of the primary causes of treatment failure in cancer chemotherapy. The overexpression of the ATP binding cassette (ABC) transporter, P-glycoprotein (P-gp), which significantly increases the efflux of certain anticancer drugs from tumor cells, produces MDR. Therefore, inhibition of P-gp may represent a viable therapeutic strategy to overcome cancer MDR. Over the past 4 decades, many compounds with P-gp inhibitory efficacy (referred to as first- and second-generation P-gp inhibitors) have been identified or synthesized. However, these compounds were not successful in clinical trials due to a lack of efficacy and/or untoward toxicity. Subsequently, third- and fourth-generation P-gp inhibitors were developed but dedicated clinical trials did not indicate a significant therapeutic effect. In recent years, an extraordinary array of highly potent, selective, and low-toxicity P-gp inhibitors have been reported. Herein, we provide a comprehensive review of the synthetic and natural products that have specific inhibitory activity on P-gp drug efflux as well as promising chemosensitizing efficacy in MDR cancer cells. The present review focuses primarily on the structural features, design strategies, and structure-activity relationships (SAR) of these compounds.

Natural products as multidrug resistance modulators in cancer

Cancer is a prominent cause of death globally. Currently, many drugs that are in clinical practice are having a high prevalence of side effect and multidrug resistance. Risk of tumors acquiring resistance to chemotherapy (multidrug resistance) remains a significant hurdle to the successful treatment of various types of cancer. Membrane-embedded drug transporters, generally overexpressed in cancer, are the leading cause among multiple mechanisms of multidrug resistance (MDR). P-glycoprotein (P-gp) also MDR1/ABCB1, multidrug resistance associated protein 1 (MRP1/ABCC1), MRP2 and breast cancer resistance protein (BCRP/ABCG2) are considered to be a prime factor for induction of MDR. To date, several chemical substances have been tested in a number of clinical trials for their MDR modulatory activity which are not having devoid of any side effects that necessitates to find newer and safer way to tackle the current problem of multidrug resistance in cancer. The present study systematically discusses the various classes of natural products i.e flavonoids, alkaloids, terpenoids, coumarins (from plants, marine, and microorganisms) as potential MDR modulators and/or as a source of promising lead compounds. Recently a bisbenzyl isoquinoline alkaloid namely tetrandrine, isolated from Chinese herb Stephania tetrandra (Han-Fang-Chi) is in clinical trials for its MDR reversal activity.

Tenacigenin B ester derivatives from Marsdenia tenacissima actively inhibited CYP3A4 and enhanced in vivo antitumor activity of paclitaxel

ETHNOPHARMACOLOGICAL RELEVANCE

Marsdenia tenacissima (Roxb.) Wight et Arn is a vine distributed in southwest area of China and used in folk medicine for treatment of tumors. Recent decades of studies on this plant reveal its synergistic effects with certain anticancer drugs in cancer therapy. In our previous study, an extract ETA which contains total aglycones made from M. tenacissima significantly enhanced antitumor activity of paclitaxel in tumor-bearing mice. However, the effective constituents in ETA and the underlying mechanisms remain unclear.

AIM OF THE STUDY

Reveal the active components in ETA as well as the molecular mechanism in enhancing antitumor efficacy of paclitaxel.

MATERIAL AND METHODS

Main constituents in ETA were purified by chemical methods. Effects of the purified constituents on metabolic activity of CYP450 enzymes were evaluated in human liver microsomes. Ability of the constituents to enhance antitumor activity of paclitaxel were investigated in nude mice bearing HeLa tumors. Pharmacokinetic study was performed in SD rats. Molecular docking was carried out for investigation of drug-protein interactions.

RESULTS

Three main C₂₁ steroidal aglycones, 11α-O-tigloyl-12β-O-acetyl-tenacigenin B (MT1), 11α-O-2-methylbutanoyl-12β-O-tigloyl-tenacigenin B (MT2) and 11α-O-2-methylbutanoyl-12β-O-acetyl-tenacigenin B (MT3), together with tenacigenin B (MT4) was prepared from ETA. Among them, MT1, MT2 and MT3 strongly inhibit the metabolic activity of CYP3A4. MT2 also showed inhibitory effects on CYP2C8, CYP2B6 and CYP2C19. In HeLa tumor xenografts, MT1, MT2 and MT3 (30 mg/kg) did not affect tumor growth themselves, but significantly enhanced paclitaxel-induced growth inhibition. In addition, coadministration of MT2 with paclitaxel resulted in significant reduction of liver CYP2C8. In pharmacokinetic study, MT2 significantly increased the blood concentration of paclitaxel with increased AUC value by 2.2-5.3 folds. Molecular docking analysis suggested hydrophobic interaction modes of tenacigenin B derivatives with CYP3A4, and also the essential roles of the C-11 and C-12 ester groups for effective interaction with CYP3A4.

CONCLUSION

Our study proves that, 11α-O-tigloyl-12β-O-acetyl-tenacigenin B, 11α-O-2-methylbutanoyl-12β-O-tigloyl-tenacigenin B and 11α-O-2-methylbutanoyl-12β-O-acetyl-tenacigenin B, which are the main constituents of ETA, are active inhibitors of CYP3A4 with potential to increase therapeutic efficacy of anticancer drugs that are substrates of CYP3A4. Tenacigenin B derivatives with C-11 and C-12 ester group substitutions, or at least a large part of them, are active components in ETA and M. tenacissima to enhance in vivo antitumor efficacies of paclitaxel.

The Antitumor Activities of Marsdenia tenacissima

Marsdenia tenacissima (MT), a traditional Chinese herbal medicine, has long been used for thousands of years to treat asthma, tracheitis, rheumatism, etc. An increasing number of recent studies have focused on the antitumor effects of MT. The effects of MT on cancer are the result of various activated signaling pathways and inhibiting factors and the high expression levels of regulatory proteins. MT can inhibit different cancer types including non-small cell lung cancer (NSCLC), malignant tumors, hepatic carcinoma, and so on. This article mainly focuses on the activities and mechanisms of MT. In addition, the efficacy and toxicity of MT are also discussed. Further studies of MT are required for improved medicinal utilization.

Marsdenia tenacissima: A Review of Traditional Uses, Phytochemistry and Pharmacology

The stems and roots of Marsdenia tenacissima (Roxb.) Wight et Arn., a traditional Chinese medicine and Dai herbal medicine, have been widely used for the treatment of asthma, trachitis, tonsillitis, pharyngitis, cystitis, pneumonia and drug or food poisoning. Nowadays, the extract of Marsdenia tenacissima, under the trademark of "Xiao-ai-ping", is widely used in clinic for the treatment of different cancers in China. To date, approximately 196 chemical ingredients covering steroids, triterpenes and organic acids have been identified from different parts of this plant. Steroids are the major characteristic and bioactive constituents of this plant. Modern pharmacology has demonstrated that the crude extracts and steroids have various in vitro and in vivo pharmacological activities, such as multidrug resistance reversal, antitumor, anti-angiogenic, immunomodulation and anti-HIV activities. The multidrug resistance reversal of steroids provided evidence for the use of this herb in clinic. However, despite wide clinical application, clinical trials, quality control method, pharmacokinetic and toxicity research on Marsdenia tenacissima were seldom reported and deserved further efforts. The present review aimed to achieve a comprehensive and up-to-date investigation in ethnopharmacology, phytochemistry, pharmacology, clinical study, pharmacokinetics, toxicology and quality control of Marsdenia tenacissima. In addition, the possible perspectives and trends for future studies of Marsdenia tenacissima have also been put forward. It is believed that this review would provide a theoretical basis and valuable data for future in-depth studies and applications.

Adduct ion-targeted qualitative and quantitative analysis of polyoxypregnanes by ultra-high pressure liquid chromatography coupled with triple quadrupole mass spectrometry

Polyoxypregnane and its glycosides (POPs) are frequently present in plants of Asclepiadaceae family, and have a variety of biological activities. There is a great need to comprehensively profile these phytochemicals and to quantify them for monitoring their contents in the herbs and the biological samples. However, POPs undergo extensive adduct ion formation in ESI-MS, which has posed a challenge for qualitative and quantitative analysis of POPs. In the present study, we took the advantage of such extensive adduct ion formation to investigate the suitability of adduct ion-targeted analysis of POPs. For the qualitative analysis, we firstly demonstrated that the sodium and ammonium adduct ion-targeted product ion scans (PIS) provided adequate MS/MS fragmentations for structural characterization of POPs. Aided with precursor ion (PI) scans, which showed high selectivity and sensitivity and improved peak assignment confidence in conjunction with full scan (FS), the informative adduct ion-targeted PIS enabled rapid POPs profiling. For the quantification, we used formic acid rather than ammonium acetate as an additive in the mobile phase to avoid simultaneous formation of sodium and ammonium adduct ions, and greatly improved reproducibility of MS response of POPs. By monitoring the solely formed sodium adduct ions [M+Na]⁺, a method for simultaneous quantification of 25 POPs in the dynamic multiple reaction monitoring mode was then developed and validated. Finally, the aforementioned methods were applied to qualitative and quantitative analysis of POPs in the extract of a traditional Chinses medicinal herb, Marsdenia tenacissima (Roxb.) Wight et Arn., and in the plasma obtained from the rats treated with this herb. The results demonstrated that adduct ion formation could be optimized for the qualitative and quantitative analysis of POPs, and our developed PI/FS-PIS scanning and sole [M+Na]⁺ ion monitoring significantly improved the analysis of POPs in both herbal and biological samples. This study also provides implications for the analysis of other compounds which undergo extensive adduct ion formation in ESI-MS.

Natural Products as Alternative Choices for P-Glycoprotein (P-gp) Inhibition

Multidrug resistance (MDR) is regarded as one of the bottlenecks of successful clinical treatment for numerous chemotherapeutic agents. Multiple key regulators are alleged to be responsible for MDR and making the treatment regimens ineffective. In this review, we discuss MDR in relation to P-glycoprotein (P-gp) and its down-regulation by natural bioactive molecules. P-gp, a unique ATP-dependent membrane transport protein, is one of those key regulators which are present in the lining of the colon, endothelial cells of the blood brain barrier (BBB), bile duct, adrenal gland, kidney tubules, small intestine, pancreatic ducts and in many other tissues like heart, lungs, spleen, skeletal muscles, etc. Due to its diverse tissue distribution, P-gp is a novel protective barrier to stop the intake of xenobiotics into the human body. Over-expression of P-gp leads to decreased intracellular accretion of many chemotherapeutic agents thus assisting in the development of MDR. Eventually, the effectiveness of these drugs is decreased. P-gp inhibitors act by altering intracellular ATP levels which are the source of energy and/or by affecting membrane contours to increase permeability. However, the use of synthetic inhibitors is known to cause serious toxicities. For this reason, the search for more potent and less toxic P-gp inhibitors of natural origin is underway. The present review aims to recapitulate the research findings on bioactive constituents of natural origin with P-gp inhibition characteristics. Natural bioactive constituents with P-gp modulating effects offer great potential for semi-synthetic modification to produce new scaffolds which could serve as valuable investigative tools to recognize the function of complex ABC transporters apart from evading the systemic toxicities shown by synthetic counterparts. Despite the many published scientific findings encompassing P-gp inhibitors, however, this article stand alones because it provides a vivid picture to the readers pertaining to Pgp inhibitors obtained from natural sources coupled with their mode of action and structures. It provides first-hand information to the scientists working in the field of drug discovery to further synthesise and discover new P-gp inhibitors with less toxicity and more efficacies.

Reversal of multidrug resistance by Marsdenia tenacissima and its main active ingredients polyoxypregnanes

ETHNOPHARMACOLOGICAL RELEVANCE

Multidrug resistance (MDR) of cancer is often associated with the overexpression of ATP-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), multidrug resistance-associated protein-1 (MRP-1) and breast cancer resistance protein (BCRP or ABCG2), in cancer cells, which facilitates the active efflux of a wide variety of chemotherapeutic drugs out of the cells. Marsdenia tenacissima is a traditional Chinese medicinal herb that has long been clinically used for treatment of cancers, particularly in combinational use with anticancer drugs. Polyoxypregnanes (POPs) are identified as main constituents of this herb, and three of them have been reported to exhibit P-gp modulatory effect and thus reverse MDR. Therefore, it is of great necessity to investigate more POPs that have potential to reverse transporters-mediated MDR.

AIM OF THE STUDY

We aimed to identify POPs as the chemical basis responsible for circumventing ABC transporters-mediated MDR by M. tenacissima.

MATERIALS AND METHODS

The MDR reversal effects of M. tenacissima crude extract together with a series of isolated POPs were evaluated on several MDR cancer cell lines that overexpress P-gp, MRP1 or ABCG2. The activities of P-gp, MRP1 and ABCG2 were determined by the flow cytometry-based substrate efflux assay. Molecular docking of POPs to a three-dimensional human P-gp homology structure was also performed.

RESULTS

The crude extract of M. tenacissima was firstly found to circumvent P-gp-mediated MDR. Then, 11 polyoxypregnane compounds (POPs) isolated from this herb were found to overcome P-gp-, MRP1- and/or ABCG2-mediated MDR. Further mechanistic study delineated that the reversal of MDR by these POPs was due to significant increase in the intracellular concentrations of the substrate anticancer drugs via their inhibition of different ABC transporter-mediated efflux activities. Furthermore, molecular docking revealed that POPs with P-gp modulatory effect bound to P-gp and fitted well into the cavity between the alpha and beta subunit of P-gp via forming hydrogen bonds. In addition, several key structural determinants for inhibition of P-gp, MRP1 or ABCG2 by POPs were illustrated.

CONCLUSIONS

Our findings advocated the rational use of M. tenacissima to enhance efficacies of conventional anticancer drugs in tumors with ABC drug transporters-mediated MDR. Furthermore, 11 POPs were found to contribute to MDR reversal effect of M. tenacissima via inhibition of different ABC efflux transporters.

Marsdenia tenacissima extract suppresses tumor growth and angiogenesis in A20 mouse lymphoma

Marsdenia tenacissima (MT), a traditional Chinese medicine, has been utilized in the treatment of a variety of malignant conditions for decades, but the underlying mechanism remains unclear. Angiogenesis, new blood vessel formation by nearby endothelial cells (ECs) from pre-existing vessels, plays a key role in cancer growth. In the present study, the effects of MT extract (MTE) on EC proliferation and apoptosis in vitro, and on A20 mouse lymphoma growth and angiogenesis in vivo were investigated. MTE exhibited an anti-proliferative effect on the ECs, with a half maximal inhibitory concentration of 11.91±0.24 µl/ml. Acridine orange/propidium iodide staining indicated that cell apoptosis increased with MTE concentration. Flow cytometry revealed that the EC apoptosis rates induced by 0, 6.25, 12.5 and 25 µl/ml MTE were 4.8, 23.3, 49.8 and 92.3%, respectively. In vivo, the volume and weight of the A20 solid tumors were significantly inhibited following administration of 300 µl MTE per day for 14 days (P<0.05). MTE showed extended survivability and a satisfactory security. Subsequent to treatment with MTE, peritumorous angiogenesis was significantly reduced, with lower microvessel density (P<0.05) was quantified by hemotoxylin and eosin staining. Moreover, serum vascular endothelial growth factor, matrix metalloproteinase (MMP)-2 and MMP-9 expression at the protein level in the MTE-treated group, quantified using an ELISA, was significantly lower than that of the control (P<0.05). In a chick chorioallantoic membrane assay, 12.5 and 25 µl/ml MTE distinctly decreased the level of angiogenesis (P<0.05). In conclusion, MTE exhibited potent anti-lymphoma efficacy in vitro and this may be associated with its effects against tumor angiogenesis.

[Clinical value of Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract combined with chemotherapy in the treatment of advanced non-small cell lung cancer: a Meta-analysis]

OBJECTIVE

To investigate the clinical efficacy and safety of Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract combined with chemotherapy in the treatment of advanced non-small cell lung cancer (NCSLC) compared with chemotherapy alone.

METHODS

Databases including Chinese National Knowledge Infrastructure, China Biology Medicine Disc, Wanfang, and MEDLINE were searched until April 1, 2014. Two assessors independently reviewed each trial. The primary outcome was the effective rate (ER) of Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract combined with chemotherapy. The secondary outcomes included quality of life improvement rate (QOLIR) and adverse reactions. Statistical calculations were performed by using Cochrane Collaboration Review Manager 5.2.

RESULTS

A total of 888 patients from 15 studies, 13 randomized controlled trials (RCT) and two controlled clinical trials, were included. Compared with chemotherapy alone, Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract plus chemotherapy significantly improved ER [Risk ratio (RR) = 1.32, 95% CI, (1.14, 1.54)] (based on 15 studies) and QOLIR [RR = 2.04, 95% CI, (1.69, 2.47)] (based on 13 studies). Compared with chemotherapy alone, Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract plus chemotherapy significantly inhibited chemotherapy-induced white blood cell decline [RR = 0.79, 95% CI, (0.70, 0.90) (based on 10 studies), chemotherapy-induced platelet decline [RR = 0.77, 95% CI, (0.60, 0.98)] (based on 8 studies), and significantly alleviated nausea and vomiting (NV) [RR = 0.83, 95% CI, (0.71, 0.97)] (based on 7 studies). There was no significant difference in hemoglobin decline between the two therapies [RR = 0.88, 95% CI, (0.70, 1.09)] (based on 6 studies).

CONCLUSION

This Meta-analysis suggests that Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract combined with chemotherapy may be more efficacious in the treatment of advanced NSCLC than chemotherapy alone. This effect includes enhancing ER and QOLIR, and weakening chemotherapy toxicity. However, large-scale RCTs are required to further investigate the short- and long-term effects of Tongguanteng (Radix seu Herba Marsdeniae Tenacissimae) extract.

Polyoxypregnane steroids with an open-chain sugar moiety from Marsdenia tenacissima and their chemoresistance reversal activity

A polyoxypregnane aglycone, 12β-O-acetyl-11α-O-isobutyryltenacigenin B, and four polyoxypregnane glycosides with a pachybionic acid ester moiety, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandronyl)-11α-O-isobutyryltenacigenin B, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandronyl)-11α-O-tigloyltenacigenin B, 12β-O-acetyl-3-O-(6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-β-D-oleandronyl)-11α-O-2-methylbutyryltenacigenin B, and 12β-O-acetyl-3-O-(β-D-glucopyranosyl-(1→4)-6-deoxy-3-O-methyl-β-D-allopyranosyl-(1→4)-D-oleandronyl)-11α-O-tigloyltenacigenin B, were isolated from the canes of Marsdenia tenacissima, together with a disaccharide derivative. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configurations were further determined by X-ray crystallographic analysis. With the exception of the disaccharide derivative, all five compounds are unusual naturally occurring polyoxypregnane glycosides bearing an open-chain sugar moiety. Two of these exhibit a wide spectrum of chemoresistance reversal activity, and potential mechanisms were studied accordingly.

Geographical traceability of Marsdenia tenacissima by Fourier transform infrared spectroscopy and chemometrics

A combination of Fourier transform infrared spectroscopy with chemometrics tools provided an approach for studying Marsdenia tenacissima according to its geographical origin. A total of 128 M. tenacissima samples from four provinces in China were analyzed with FTIR spectroscopy. Six pattern recognition methods were used to construct the discrimination models: support vector machine-genetic algorithms, support vector machine-particle swarm optimization, K-nearest neighbors, radial basis function neural network, random forest and support vector machine-grid search. Experimental results showed that K-nearest neighbors was superior to other mathematical algorithms after data were preprocessed with wavelet de-noising, with a discrimination rate of 100% in both the training and prediction sets. This study demonstrated that FTIR spectroscopy coupled with K-nearest neighbors could be successfully applied to determine the geographical origins of M. tenacissima samples, thereby providing reliable authentication in a rapid, cheap and noninvasive way.

Hedyotis diffusa Willd overcomes 5-fluorouracil resistance in human colorectal cancer HCT-8/5-FU cells by downregulating the expression of P-glycoprotein and ATP-binding casette subfamily G member 2

Previous studies have demonstrated that Hedyotis diffusa Willd (HDW), a traditional Chinese herbal medicine, exhibits potent anticancer activity in models of colorectal cancer (CRC). Aggressive forms of CRC exhibit resistance to widely used chemotherapeutic drugs, including the antimetabolite, 5-fluorouracil (5-FU); however, less is known with regard to the activity of HDW against 5-FU-resistant cancer. In the present study, the mechanism of action and the potency of ethanol extracts of HDW (EEHDW) were investigated on a multidrug-resistant CRC HCT-8/5-FU cell line. Using an MTT cell proliferation assay, EEHDW treatment was shown to significantly reduce the cell viability of HCT-8/5-FU cells in a dose- and time-dependent manner. Furthermore, EEHDW significantly increased the retention of the ATP-binding cassette (ABC) transporter substrate, rhodamine-123, as compared with the untreated controls. To further investigate the molecular mechanisms targeted by EEHDW in the resistant cells, the expression levels of the ABC drug transporter protein, P-glycoprotein (P-gp), and ABC subfamily G member 2 (ABCG2), were analyzed using reverse-transcription polymerase chain reaction and western blot analysis. The mRNA and protein expression levels of P-gp and ABCG2 were reduced in the HCT-8/5-FU cells following EEHDW treatment, indicating that EEHDW inhibits ABCG2-mediated drug resistance by downregulating the expression of ABCG2 and P-gp. Therefore, the potential application of EEHDW as a chemotherapeutic adjuvant represents a promising alternative approach to the treatment of drug-resistant CRC.

Marsdenia tenacssima extract and its functional components inhibits proliferation and induces apoptosis of human Burkitt leukemia/lymphoma cells in vitro and in vivo

Burkitt lymphoma is a fast growing non-Hodgkin lymphoma that occurs primarily in young males. The causes of Burkitt lymphoma include chromosome rearrangement and virus infection, but accurate and complete reasons remain to be discovered. The available treatment for Burkitt lymphoma is chemotherapy and radiation therapy. It is a highly aggressive B-cell neoplasm with not all patients cured, in spite of current therapies. This study evaluated the effects of traditional Chinese medicine Marsdenia tenacssima (MTE) and its component compound Tenacigenoside A (TGTA) and 11α-O-benzoyl-12β-O-acetyltenacigenin B (TGTB) on human Burkitt lymphoma growth. It was observed that MTE, TGTA or TGTB inhibited cell growth and induced apoptosis of Burkitt lymphoma cells in culture. In lymphoma bearing NOD/SCID nude mice, both TGTA and TGTB inhibited tumor growth and improved animal survival. TGTA and TGTB significantly increased tumor cell apoptosis on lymphoma bearing mice, primarily through down-regulation of BCL2 and BCL-XL and up-regulation of BID.

Synthesis of new steroidal inhibitors of P-glycoprotein-mediated multidrug resistance and biological evaluation on K562/R7 erythroleukemia cells

A simple route for improving the potency of progesterone as a modulator of P-gp-mediated multidrug resistance was established by esterification or etherification of hydroxylated 5α/β-pregnane-3,20-dione or 5β-cholan-3-one precursors. X-ray crystallography of representative 7α-, 11α-, and 17α-(2'R/S)-O-tetrahydropyranyl ether diastereoisomers revealed different combinations of axial-equatorial configurations of the anomeric oxygen. Substantial stimulation of accumulation and chemosensitization was observed on K562/R7 erythroleukemia cells resistant to doxorubicin, especially using 7α,11α-O-disubstituted derivatives of 5α/β-pregnane-3,20-dione, among which the 5β-H-7α-benzoyloxy-11α-(2'R)-O-tetrahydropyranyl ether 22a revealed promising properties (accumulation index 2.9, IC50 0.5 μM versus 1.2 and 10.6 μM for progesterone), slightly overcoming those of verapamil and cyclosporin A. Several 7α,12α-O-disubstituted derivatives of 5β-cholan-3-one proved even more active, especially the 7α-O-methoxymethyl-12α-benzoate 56 (accumulation index 3.8, IC50 0.2 μM). The panel of modulating effects from different O-substitutions at a same position suggests a structural influence of the substituent completing a simple protection against stimulating effects of hydroxyl groups on P-gp-mediated transport.

P-glycoprotein inhibitors of natural origin as potential tumor chemo-sensitizers: A review

Resistance of solid tumors to treatment is significantly attributed to pharmacokinetic reasons at both cellular and multi-cellular levels. Anticancer agent must be bio-available at the site of action in a cytotoxic concentration to exert its proposed activity. P-glycoprotein (P-gp) is a member of the ATP-dependent membrane transport proteins; it is known to pump substrates out of cells in ATP-dependent mechanism. The over-expression of P-gp in tumor cells reduces the intracellular drug concentrations, which decreases the cytotoxicity of a broad spectrum of antitumor drugs. Accordingly, P-gp inhibitors/blockers are potential enhancer for the cellular bioavailability of several clinically important anticancer drugs such as, anthracyclines, taxanes, vinca alkaloids, and podophyllotoxins. Besides several chemically synthesized P-gp inhibitors/blockers, some naturally occurring compounds and plant extracts were reported for their modulation of multidrug resistance; however, this review will focus only on major classes of naturally occurring inhibitors viz., flavonoids, coumarins, terpenoids, alkaloids and saponins.

Polyoxypregnane steroids from the stems of Marsdenia tenacissima

A new polyoxypregnane aglycone, tenacigenin D (1), and seven new C21 steroid glycosides, tenacissimosides D-J (2-8), were isolated from the stems of Marsdenia tenacissima. Their structures were determined by interpretation of their 1D and 2D NMR and other spectroscopic data, as well as by comparison with published values for related known compounds. Compound 1 was found to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance through an inhibitory effect on P-gp with a similar potency to verapamil. In addition, compound 1 potentiated the activity of erlotinib and gefitinib in epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI)-resistant non-small-cell lung cancer cells.

Total aglycones from Marsdenia tenacissima increases antitumor efficacy of paclitaxel in nude mice

Marsdeniae tenacissimae Caulis (MTC) is a Chinese herbal medicine used mainly for treatment of cancer, whose pharmacologically active constituents responsible for its in vivo activity and clinical efficacy have not been clearly elucidated. In this study, total aglycones of MTC (ETA) showed the ability to sensitize KB-3-1, HeLa, HepG2 and K562 cells to paclitaxel treatment. More inspiringly, ETA markedly enhanced the antitumor activity of paclitaxel in nude mice bearing HeLa or KB-3-1 xenografts. Compared to treatment with paclitaxel alone, treatment with combination of paclitaxel and ETA achieved significant reduction in volume and weight of HeLa tumors (p<0.05), and remarkable inhibition to the growth of KB-3-1 tumors (p<10⁻⁶). ETA was characterized by the presence of a group of tenacigenin B ester derivatives, among which four reference compounds, 11α-O-tigloyl-12β-O-acetyltenacigenin B, 11α,12β-di-O-tigloyltenacigenin B, 11α-O-2-methylbutanoyl-12β-O-tigloyltenacigenin B, and 11α-O-(2-methylbutanoyl)-12β-O-benzoyltenacigenin B, accounted for 42.14% of the total peak area of 19 detectable components assayed by HPLC. Our study has identified ETA as a promising sensitizer for cancer chemotherapy.

P-glycoprotein and its inhibition in tumors by phytochemicals derived from Chinese herbs

P-glycoprotein belongs to the family of ATP-binding cassette (ABC) transporters. It functions in cellular detoxification, pumping a wide range of xenobiotic compounds, including anticancer drugs out of the cell. In cancerous cells, P-glycoprotein confers resistance to a broad spectrum of anticancer agents, a phenomenon termed multidrug resistance. An attractive strategy for overcoming multidrug resistance is to block the transport function of P-glycoprotein and thus increase intracellular concentrations of anticancer drugs to lethal levels. Efforts to identify P-glycoprotein inhibitors have led to numerous candidates, none of which have passed clinical trials with cancer patients due to their high toxicity. The search for naturally inhibitory products from traditional Chinese medicine may be more promising because natural products are frequently less toxic than chemically synthesized substances. In this review, we give an overview of molecular and clinical aspects of P-glycoprotein and multidrug resistance in the context of cancer as well as Chinese herbs and phytochemicals showing inhibitory activity towards P-glycoprotein.

Marsdenia tenacissima extract restored gefitinib sensitivity in resistant non-small cell lung cancer cells

Most non-small cell lung cancer (NSCLC) patients responding to gefitinib harbor activating mutations in the epidermal growth factor receptor (EGFR). However, the responsive cases eventually develop the resistance to gefitinib. Besides, K-ras mutations were identified as the primary resistance to gefitinib. We investigated whether Marsdenia tenacissima extract (MTE, trade name: Xiao-Ai-Ping injection) combined with gefitinib could overcome the resistance of NSCLC cells to gefitinib. NSCLC cell lines with different sensitivities to gefitinib were studied. Cell growth and apoptosis were evaluated by MTT assay and flow cytometry, respectively. The EGFR-related signaling molecule phosphorylation was assessed by Western blotting. We found that MTE inhibited cell growth in gefitinib-sensitive and -resistant cells. In gefitinib-resistant cells, the MTE→MTE+gefitinib (M→M+G) treatment was most potent over the concurrent administration of MTE and gefitinib (M+G) or gefitinib→gefitinib+MTE (G→G+M) treatment in cell growth inhibition and apoptosis induction. The M→M+G treatment significantly reduced the phosphorylation of EGFR downstream signaling molecules PI3K/Akt/mTOR and ERK, on which MTE and gefitinib alone had no obvious effects on the resistant cells. The M→M+G treatment attenuated c-Met phosphorylation in H460 and H1975 as well. Thus, we found that the M→M+G treatment improved the sensitivity of resistant NSCLC cells carrying T790M or K-ras mutations to gefitinib, suggesting that the M→M+G treatment may be a promising therapeutic strategy to overcome gefitinib resistance in NSCLC.