In Vivo Exposure of Kaempferol Is Driven by Phase II Metabolic Enzymes and Efflux Transporters

Kaempferol efficacy in metabolic diseases: Molecular mechanisms of action in diabetes mellitus, obesity, non-alcoholic fatty liver disease, steatohepatitis, and atherosclerosis

The incidence of metabolic diseases has progressively increased, which has a negative impact on human health and life safety globally. Due to the good efficacy and limited side effects, there is growing interest in developing effective drugs to treat metabolic diseases from natural compounds. Kaempferol (KMP), an important flavonoid, exists in many vegetables, fruits, and traditional medicinal plants. Recently, KMP has received widespread attention worldwide due to its good potential in the treatment of metabolic diseases. To promote the basic research and clinical application of KMP, this review provides a timely and comprehensive summary of the pharmacological advances of KMP in the treatment of four metabolic diseases and its potential molecular mechanisms of action, including diabetes mellitus, obesity, non-alcoholic fatty liver disease (NAFLD)/nonalcoholic steatohepatitis (NASH), and atherosclerosis. According to the research, KMP shows remarkable therapeutic effects on metabolic diseases by regulating multiple signaling transduction pathways such as NF-κB, Nrf2, AMPK, PI3K/AKT, TLR4, and ER stress. In addition, the most recent literature on KMP's natural source, pharmacokinetics studies, as well as toxicity and safety are also discussed in this review, thus providing a foundation and evidence for further studies to develop novel and effective drugs from natural compounds. Collectively, our manuscript strongly suggested that KMP could be a promising candidate for the treatment of metabolic diseases.

An acute herb-drug interaction of Magnoliae Officinalis Cortex with methotrexate via inhibiting multidrug resistance-associated protein 2

Magnoliae Officinalis Cortex (MOC), an herbal drug, contains polyphenolic lignans mainly magnolol (MN) and honokiol (HK). Methotrexate (MTX), a critical drug for cancers and autoimmune deseases, is a substrate of multidrug resistance-associated protein 2 (MRP2) and breast cancer resistance protein (BCRP). This study investigated the effect of coadministration of MOC on the pharmacokinetics of MTX and relevant mechanisms. Sprague-Dawley rats were orally administered MTX alone and with single dose (2.0 and 4.0 g/kg) and repeated seven doses of MOC (2.0 g/kg thrice daily for 2 days, the 7th dose given at 0.5 h before MTX). The serum concentrations of MTX were determined by a fluorescence polarization immunoassay. The results showed that a single dose of MOC at 2.0 g/kg significantly increased the AUC0-t and MRT of MTX by 352% and 308%, and a single dose at 4.0 g/kg significantly enhanced the AUC0-t and MRT by 362% and 291%, respectively. Likewise, repeated seven doses of MOC at 2.0 g/kg significantly increased the AUC0-t and MRT of MTX by 461% and 334%, respectively. Mechanism studies indicated that the function of MRP2 was significantly inhibited by MN, HK and the serum metabolites of MOC (MOCM), whereas BCRP was not inhibited by MOCM. In conclusion, coadministration of MOC markedly enhanced the systemic exposure and mean residence time of MTX through inhibiting the MRP2-mediated excretion of MTX.

Kaempferol improves Pb-induced cognitive impairments via inhibiting autophagy

Kaempferol (Kam) is a flavonoid antioxidant found in fruits and vegetables, which was discovered as neuroprotective antioxidants. Lead (Pb), an environmental pollution, could induce learning and memory deficits. Nevertheless, little is known about the mechanisms underlying Kam actions in Pb-induced learning and memory deficits. In this study, we investigated the effects of Kam on Pb-induced cognitive deficits. Pb-exposed rats were treated with 50 mg/kg Kam from postnatal day (PND) 30 to PND 60. Then, Y-maze and Morris water maze have been used to detect the spatial memory in all groups of rats. Hematoxylin and eosin (HE) staining and Nissl staining were used to analyze the neuronal structure damages. The results found Kam treatment improved the learning and memory ability and alleviated hippocampal neuronal pathological damages. Besides, Kam could significantly reverse the synaptic transmission related protein expression including PSD95 and NMDAR2B. Further research found that Kam downregulated autophagy markers, P62, ATG5, Beclin1, and LC3-II. Furthermore, 3-MA, autophagy inhibitor, increased the levels of NMDAR2B and PSD95 in Pb-induced PC12 cells, indicating Kam alleviated Pb-induced neurotoxicity through inhibiting autophagy activation. Our results showed that Kam could ameliorate Pb-induced cognitive impairments and neuronal damages by decreasing Pb-induced excess autophagy accumulation.

Beneficial role of kaempferol and its derivatives from different plant sources on respiratory diseases in experimental models

Respiratory illnesses impose a significant health burden and cause deaths worldwide. Despite many advanced strategies to improve patient outcomes, they are often less effective. There is still considerable room for improvement in the treatment of various respiratory diseases. In recent years, alternative medicinal agents derived from food plants have shown better beneficial effects against a wide variety of disease models, including cancer. In this regard, kaempferol (KMF) and its derivatives are the most commonly found dietary flavonols. They have been found to exhibit protective effects on multiple chronic diseases like diabetes, fibrosis, and so on. A few recent articles have reviewed the pharmacological actions of KMF in cancer, central nervous system diseases, and chronic inflammatory diseases. However, there is no comprehensive review that exists regarding the beneficial effects of KMF and its derivatives on both malignant- and non-malignant respiratory diseases. Many experimental studies reveal that KMF and its derivatives are helpful in managing a wide range of respiratory diseases, including acute lung injury, fibrosis, asthma, cancer, and chronic obstructive pulmonary disease, and their underlying molecular mechanisms. In addition, we also discussed the chemistry and sources, the absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties, methods to enhance bioavailability, as well as our perspective on future research with KMF and its derivatives.

The Role of Selective Flavonoids on Triple-Negative Breast Cancer: An Update

Among the many types of breast cancer (BC), Triple-Negative Breast Cancer (TNBC) is the most alarming. It lacks receptors for the three main biomarkers: estrogen, progesterone, and human epidermal growth factor, hence the name TNBC. This makes its treatment a challenge. Surgical procedures and chemotherapy, performed either alone or in combination, seem to be the primary therapeutic possibilities; however, they are accompanied by severe complications. Currently, the formulation of drugs using natural products has been playing an important role in the pharmaceutical industries, owing to the drugs’ increased efficacies and significantly lessened side effects. Hence, treating TNBC with chemotherapeutic drugs developed using natural products such as flavonoids in the near future is much warranted. Flavonoids are metabolic compounds largely present in all plants, vegetables, and fruits, such as blueberries, onions, (which are widely used to make red wine,) chocolates, etc. Flavonoids are known to have enormous health benefits, such as anticancer, antiviral, anti-inflammatory, and antiallergic properties. They are known to arrest the cell cycle of the tumor cells and induces apoptosis by modulating Bcl-2, Bax, and Caspase activity. They show a considerable effect on cell proliferation and viability and angiogenesis. Various studies were performed at both the biochemical and molecular levels. The importance of flavonoids in cancer treatment and its methods of extraction and purification to date have been reported as individual publications. However, this review article explains the potentiality of flavonoids against TNBC in the preclinical levels and also emphasizes their molecular mechanism of action, along with a brief introduction to its methods of extraction, isolation, and purification in general, emphasizing the fact that its quantum of yield if enhanced and its possible synergistic effects with existing chemotherapeutics may pave the way for better anticancer agents of natural origin and significantly lessened side-effects.

Pharmacokinetics and pharmacokinetic interactions of orally administered oxfendazole and oxyclozanide tablet formulation to sheep

The combination of oxfendazole and oxyclozanide is used to provide activity against fluke and gastrointestinal nematodes. This study aimed to determine both the pharmacokinetics of oxfendazole (7.5 mg/kg) and oxyclozanide (15 mg/kg) tablet formulation administered orally to sheep and whether there is a pharmacokinetic interaction between these two drugs. The study was conducted in a three-period, crossover pharmacokinetic design and on six healthy Awassi sheep 1-3 years of age. The plasma concentrations of oxfendazole and its metabolites (fenbendazole and fenbendazole sulphone) and oxyclozanide were determined by high-performance liquid chromatography using an ultraviolet detector. Compounds recovered in plasma when oxfendazole was administered alone or combined with oxyclozanide were oxfendazole, fenbendazole sulphone, and fenbendazole, respectively. When oxfendazole was administered alone and co-administered with oxyclozanide, the AUC_FBZ /AUC_OFZ was 0.26 and 0.23, respectively, and the AUC_FBZSO2 /AUC_OFZ was 0.35 and 0.32, respectively. The volume of distribution (Vz/F) of oxfendazole was large in both groups. Oxyclozanide did not change the plasma disposition of oxfendazole. When the oxyclozanide tablet formulation was administered alone, the elimination half-life (21.35 h) and the Vz/F (940.17 ml/kg) were long and large, respectively. The area under the curve (AUC) and the maximum plasma concentration of oxyclozanide were significantly larger and higher, respectively, in the oxyclozanide plus oxfendazole group (1146.61 h × μg/ml and 29.80 μg/ml) compared with the oxyclozanide group (491.44 h × μg/ml and 14.24 μg/ml) while a significant decrease in apparent Vz/F (940.17 vs 379.14 ml/kg) and total clearance (30.52 vs 13.08 ml/h/kg) was detected. In conclusion, co-administration with oxfendazole causing an increase in the plasma profile of oxyclozanide may increase the antiparasitic activity of oxyclozanide.

Natural Blockers of PD-1/PD-L1 Interaction for the Immunotherapy of Triple-Negative Breast Cancer-Brain Metastasis

The limited treatment options for triple-negative breast cancer with brain metastasis (TNBC-BM) have left the door of further drug development for these patients wide open. Although immunotherapy via monoclonal antibodies has shown some promising results in several cancers including TNBC, it cannot be considered the most effective treatment for brain metastasis. This is due to the protective role of the blood-brain barrier (BBB) which limits the entrance of most drugs, especially the bulky ones such as antibodies, to the brain. For a drug to traverse the BBB via passive diffusion, various physicochemical properties should be considered. Since natural medicine has been a key inspiration for the development of the majority of current medicines, in this paper, we review several naturally-derived molecules which have the potential for immunotherapy via blocking the interaction of programmed cell death protein-1 (PD-1) and its ligand, PD-L1. The mechanism of action, physicochemical properties and pharmacokinetics of these molecules and their theoretical potential to be used for the treatment of TNBC-BM are discussed.

Therapeutic Importance of Kaempferol in the Treatment of Cancer through the Modulation of Cell Signalling Pathways

Plant-derived flavonoids are considered natural nontoxic chemo-preventers and have been widely studied for cancer treatment in recent decades. Mostly all flavonoid compounds show significant anti-inflammatory, anticancer and antioxidant properties. Kaempferol (Kmp) is a well-studied compound and exhibits remarkable anticancer and antioxidant potential. Kmp can regulate various cancer-related processes and activities such as cell cycle, oxidative stress, apoptosis, proliferation, metastasis, and angiogenesis. The anti-cancer properties of Kmp primarily occur via modulation of apoptosis, MAPK/ERK1/2, P13K/Akt/mTOR, vascular endothelial growth factor (VEGF) signalling pathways. The anti-cancer property of Kmp has been recognized in several in-vivo and in-vitro studies which also includes numerous cell lines and animal models. This flavonoid possesses toxic activities against only cancer cells and have restricted toxicity on healthy cells. In this review, we present extensive research investigations about the therapeutic potential of Kmp in the management of different types of cancers. The anti-cancer properties of Kmp are discussed by concentration on its capability to target molecular-signalling pathway such as VEGF, STAT, p53, NF-κB and PI3K-AKT signalling pathways. The anti-cancer property of Kmf has gained a lot of attention, but the accurate action mechanism remains unclear. However, this natural compound has a great pharmacological capability and is now considered to be an alternative cancer treatment.

Systematically Exploring the Chemical Ingredients and Absorbed Constituents of Polygonum capitatum in Hyperuricemia Rat Plasma Using UHPLC-Q-Orbitrap HRMS

Polygonum capitatum as an ethnic medicine has been used to treat urinary tract infections, pyelonephritis and urinary calculi. In our previous study, P. capitatum was found to have anti-hyperuricemia effects. Nevertheless, the active constituents of P. capitatum for treating hyperuricemia were still unclear. In this study, an ultra-high-performance liquid chromatography coupled to quadrupole/orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) was used to comprehensively detect the chemical ingredients of P. capitatum and its absorbed constituents in the plasma of hyperuricemia rats for the first time. Xcalibur 3.0 and Compound Discoverer 2.0 software coupled to mzCloud and ChemSpider databases were utilized for qualitative analysis. A total of 114 chemical components including phenolics, flavonoids, tannins, phenylpropanoids, amino acids, amides and others were identified or tentatively characterized based on the exact mass, retention time and structural information. Compared to the previous P. capitatum study, an additional 66 different components were detected. Moreover, 68 related xenobiotics including 16 prototype components and 52 metabolites were found in the plasma of hyperuricemia rats. The metabolic pathways included ring fission, hydrolysis, decarboxylation, dehydroxylation, methylation, glucuronidation and sulfation. This work may provide important information for further investigation on the active constituents of P. capitatum and their action mechanisms for anti-hyperuricemia effects.

The anti-hyperuricemic effect of flavonoid extract of saffron by-product and its pharmacokinetics in rats after oral administration

Only the dried stigma of the saffron, a flower deemed as the most valuable spice globally, is utilized for industrial production. Hence, there exists a growing interest in utilizing saffron floral bio-residues. The anti-hyperuricemic activity of a flavonoid extract from saffron floral bio-residues was assessed in potassium oxonate-induced hyperuricemia mice. In addition, an ultra-high performance liquid chromatography-triple quadrupole mass spectrometry method was established and validated to determine the pharmacokinetics of five main flavonoids and three phase-II metabolites in rat plasma after oral administration of the flavonoid extract for the first time. Compared with pharmacokinetic parameters of kaempferol-3-O-sophoroside, the most abundant flavonoid in the extract, and its aglycone kaempferol, we observed that coexisting compounds significantly reduced the absorption, accelerated the excretion of kaempferol-3-O-sophoroside, while significantly increasing the absorption and prolonging the residence time of kaempferol in the flavonoid extract. These results suggest the promising potential of the flavonoid extract from saffron floral bio-residues as an anti-hyperuricemic agent. Kaempferol was absorbed in plasma at high concentrations owing to the biotransformation of kaempferol glycosides in vivo.

Pharmacokinetic herb-disease-drug interactions: Effect of ginkgo biloba extract on the pharmacokinetics of pitavastatin, a substrate of Oatp1b2, in rats with non-alcoholic fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. is a traditional Chinese medicine for hyper lipaemia. Ginkgo flavonols and terpene lactones are responsible for the lipid-lowering effect in non-alcoholic fatty liver disease (NAFLD). However, the pharmacokinetics of ginkgo flavonols and terpene lactones in NAFLD was not clarified.

AIM OF THE STUDY

To investigate the effects of Ginkgo biloba L. leaves extracts (EGB) and NAFLD on hepatocyte organic anion transporting polypeptide (Oatp)1b2, and to assess the pharmacokinetics of EGB active ingredients in NAFLD rats.

MATERIALS AND METHODS

Male rats were fed with a high-fat diet to induce NAFLD models. The pharmacokinetic characteristics of EGB active ingredients were studied in NAFLD rats after two or four weeks of treatment with 3.6, 10.8, and 32.4 mg/kg EGB. The effects of NAFLD and EGB were investigated on the systemic exposure of pitavastatin, a probe substrate of Oatp1b2. The inhibitory effects of ginkgo flavonols and terpene lactones on OATP1B1-mediated uptake of ³H-ES were tested in hOATP1B1-HEK293 cells.

RESULTS

The plasma exposure of ginkgolides and flavonols in NAFLD rats increased in a dose-dependent manner following oral administration of EGB at 3.6-32.4 mg/kg. The half-lives of ginkgolides A, B, C, and bilobalide (2-3 h) were shorter than quercetin, kaempferol, and isorhamnetin (approximately 20 h). NAFLD reduced the plasma pitavastatin exposure by about 50 % due to the increased Oatp1b2 expression in rat liver. Increased EGB (from 3.6 to 32.4 mg/kg) substantially increased the C_max and AUC_0-t of pitavastatin by 1.8-3.2 and 1.3-3.0 folds, respectively. In hOATP1B1-HEK293 cells, kaempferol and isorhamnetin contributed to the inhibition of OATP1B1-mediated uptake of ³H-ES with IC₅₀ values of 3.28 ± 1.08 μM and 46.12 ± 5.25 μM, respectively.

CONCLUSIONS

NAFLD and EGB can alter the activity of hepatic uptake transporter Oatp1b2 individually or in combination. The pharmacokinetic herb-disease-drug interaction found in this research will help inform the clinical administration of EGB or Oatp1b2 substrates.

Extensive metabolism of flavonoids relevant to their potential efficacy on Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disorder, the incidence of which is climbing with ever-growing aged population, but no cure is hitherto available. The epidemiological studies unveiled that chronic intake of flavonoids was negatively associated with AD risk. Flavonoids, a family of natural polyphenols widely distributed in human daily diets, were readily conjugated by phase II drug metabolizing enzymes after absorption in vivo, and glucuronidation could occur in 1 min following intravenous administration. Recently, as many as 191 metabolites were obtained after intragastric administration of a single flavonoid, indicating that other bioactive metabolites, besides conjugates, might be formed and account for the contradiction between efficacy of flavonoids in human or animal models and low systematic exposure of flavonoid glycosides or aglycones. In this review, metabolism of complete 68 flavonoid monomers potential for AD treatment, grouped in flavonoid O-glycosides, flavonoid aglycones, flavonoid C-glycosides, flavonoid dimers, flavonolignans and prenylated flavonoids according to their common structural elements, respectively, has been systematically retrospected, summarized and discussed, including their unequivocally identified metabolites, metabolic interconversions, metabolic locations, metabolic sites (regio- or stereo-selectivity), primarily involved metabolic enzymes or intestinal bacteria, and interspecies correlations or differences in metabolism, and their bioactive metabolites and the underlying mechanism to reverse AD pathology were also reviewed, providing whole perspective about advances on extensive metabolism of diverse potent flavonoids in vivo and in vitro up to date and aiming at elucidation of mechanism of actions of flavonoids on AD or other central nervous system (CNS) disorders.

Bioactive Compounds and Metabolites from Grapes and Red Wine in Breast Cancer Chemoprevention and Therapy

Phytochemicals and their metabolites are not considered essential nutrients in humans, although an increasing number of well-conducted studies are linking their higher intake with a lower incidence of non-communicable diseases, including cancer. This review summarizes the current findings concerning the molecular mechanisms of bioactive compounds from grapes and red wine and their metabolites on breast cancer—the most commonly occurring cancer in women—chemoprevention and treatment. Flavonoid compounds like flavonols, monomeric catechins, proanthocyanidins, anthocyanins, anthocyanidins and non-flavonoid phenolic compounds, such as resveratrol, as well as their metabolites, are discussed with respect to structure and metabolism/bioavailability. In addition, a broad discussion regarding in vitro, in vivo and clinical trials about the chemoprevention and therapy using these molecules is presented.

Dihydromyricetin: A review on identification and quantification methods, biological activities, chemical stability, metabolism and approaches to enhance its bioavailability

BACKGROUND

Dihydromyricetin (DMY) is an important plant flavonoid, which has received great attention due to its health-benefiting activities, including antioxidant, antimicrobial, anti-inflammatory, anticancer, antidiabetic and neuroprotective activities. DMY capsules have been sold in US as a nutraceutical supplement to prevent alcoholic hangovers. The major disadvantage associated with DMY is its chemical instability and poor bioavailability caused by the combined effects of its low solubility and poor membrane permeability. This limits its practical use in the food and pharmaceutical fields.

SCOPE AND APPROACH

The present paper gives an overview of the current methods for the identification and quantification of DMY. Furthermore, recent findings regarding the main biological properties and chemical stability of DMY, the metabolism of DMY as well as different approaches to increase DMY bioavailability in both aqueous and lipid phases are discussed.

KEY FINDINGS AND CONCLUSIONS

Current trends on identification and quantification of DMY have been focused on spectral and chromatographic techniques. Many factors such as heat, pH, metal ions, could affect the chemical stability of DMY. Despite the diverse biological effects of DMY, DMY faces with the problem of poor bioavailability. Utilization of different delivery systems including solid dispersion, nanocapsule, microemuslion, cyclodextrin inclusion complexes, co-crystallization, phospholipid complexes, and chemical or enzymatic acylation has the potential to improve both the solubility and bioavailability. DMY digested in laboratory animals undergoes reduction, dehydroxylation, methylation, glucuronidation, and sulfation. Novel DMY delivery systems and basic pharmacokinetic studies of encapsulated DMY on higher animals and humans might be required in the future.

Modulation of hepatic ABC transporters by Eruca vesicaria intake: Potential diet-drug interactions

The aim of this work was to evaluate whether oral administration of Eruca vesicaria, a species of rocket cultivated in Argentina, could modify cyclophosphamide (CP)-induced genotoxicity through modulation of hepatic ABC transporters. Daily oral administration of E. vesicaria fresh leaves juice (1.0, 1.4 and 2.0  g/kg) for 14 days did not alter genotoxicity biomarkers -alkaline comet assay and micronucleus test -in neither male nor female mice. Instead, repeated intake of this cruciferous decreased CP-induced DNA damage dose-dependently and it caused hepatic overexpression of P-glycoprotein (P-gp; 1.4 and 2.0  g/kg) and multidrug resistance protein 2 (MRP2; 2.0  g/kg), but not breast cancer resistance protein (Bcrp). The antigenotoxic effect of E. vesicaria was prevented by 50 mg/kg verapamil (P-gp inhibitor) or 10 mg/kg indomethacin (MRP2 inhibitor). In turn, CP-induced cytotoxicity (10 mM, 24 h) on human hepatoma cells (HepG2/C3A) was significantly reduced by preincubation with E. vesicaria (1.4 mg/ml; 48 h); this effect was absent when CP was coincubated with 35 μM verapamil, 80 μM indomethacin or 10 μM KO-143 (BCRP inhibitor). Altogether, these results allow us to demonstrate that repeated intake of E. vesicaria exhibited antigenotoxicity, at least in part, by induction of hepatic ABC transporters in vivo in mice as well as in vitro in human liver cells. This could account for other diet-drug interactions.

Kaempferol: A Key Emphasis to Its Anticancer Potential

A marked decrease in human cancers, including breast cancer, bone cancer, and cervical cancer, has been linked to the consumption of vegetable and fruit, and the corresponding chemoprotective effect has been associated with the presence of several active molecules, such as kaempferol. Kaempferol is a major flavonoid aglycone found in many natural products, such as beans, bee pollen, broccoli, cabbage, capers, cauliflower, chia seeds, chives, cumin, moringa leaves, endive, fennel, and garlic. Kaempferol displays several pharmacological properties, among them antimicrobial, anti-inflammatory, antioxidant, antitumor, cardioprotective, neuroprotective, and antidiabetic activities, and is being applied in cancer chemotherapy. Specifically, kaempferol-rich food has been linked to a decrease in the risk of developing some types of cancers, including skin, liver, and colon. The mechanisms of action include apoptosis, cell cycle arrest at the G2/M phase, downregulation of epithelial-mesenchymal transition (EMT)-related markers, and phosphoinositide 3-kinase/protein kinase B signaling pathways. In this sense, this article reviews data from experimental studies that investigated the links between kaempferol and kaempferol-rich food intake and cancer prevention. Even though growing evidence supports the use of kaempferol for cancer prevention, further preclinical and clinical investigations using kaempferol or kaempferol-rich foods are of pivotal importance before any public health recommendation or formulation using kaempferol.

Breast Cancer Resistance Protein and Multidrug Resistance Protein 2 Determine the Disposition of Esculetin-7-O-Glucuronide and 4-Methylesculetin-7-O-Glucuronide

Esculetin (ET)-7-O-glucuronide (ET-G) and 4-methylesculetin (4-ME)-7-O-glucuronide (4-ME-G) are the main glucuronide of ET and 4-ME, respectively. The disposition mediated by efflux transporters for glucuronide has significant influence on the pharmacokinetic profile and efficacy of bioactive compounds. In the current study, transporter gene knockout mice and Caco-2 cells were used to explore the effects of breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 2 (MRP2) on the disposition of ET-G and 4-ME-G. After oral or i.v. administration of ET and 4-ME, the area under the plasma concentration-time curve from time 0 to the last data point or infinity values of ET, 4-ME, and their glucuronides (ET-G and 4-ME-G) were remarkably and significantly increased in most Bcrp1^-/- and Mrp2^-/- mice compared with those in wild-type FVB mice (P < 0.05). These results were accompanied with a significant increase of maximum plasma concentration values (P < 0.05). In Caco-2 monolayers, the efflux and clearance rates of ET-G and 4-ME-G were markedly reduced by the BCRP inhibitor Ko143 and MRP2 inhibitor MK571 on the apical side (P < 0.05). In an intestinal perfusion study, the excretion of ET-G was significantly decreased in perfusate and increased in plasma in Bcrp1^-/- mice compared with those in wild-type FVB mice (P < 0.05). The 4-ME-G concentration was also decreased in the bile in transporter gene knockout mice. ET and 4-ME showed good permeability in both Caco-2 monolayers [apparent permeability (P_app ) ≥ 0.59 × 10^-5 cm/s] and duodenum (P_app ≥ 1.81). In conclusion, BCRP and MRP2 are involved in excreting ET-G and 4-ME-G. ET and 4-ME are most likely absorbed via passive diffusion in the intestines.

An update on polyphenol disposition via coupled metabolic pathways

INTRODUCTION

Polyphenols, which are widely distributed in plants and the human diets, are known to have numerous biological activities. However, the low bioavailability of polyphenols is mediated by coupled metabolic pathways. Areas covered: The key role of the interplay between drug metabolic enzymes (DMEs) and efflux transporters (ETs), nuclear receptors (NRs), and intestinal microflora in the disposition of polyphenols is summarized. Expert opinion: ETs are shown to act as a 'revolving door', facilitating and/or controlling cellular polyphenol glucuronide/sulfate excretion. Elucidating the mechanisms underlying the glucuronidation/sulfation-transport interplay and structure-activity relationships (SAR) of glucuronide/sulfate efflux by an ET is important. Some new physiologically based pharmacokinetic (PBPK) models could be developed to predict the interplay between glucuronides/sulfates and ETs. Additionally, the combined actions of uridine-5'-diphosphate glucuronosyltransferases, ETs, and intestinal microflora/enterocyte-derived β-glucuronidase enable triple recycling (local, enteric, and enterohepatic recycling), thereby increasing the residence time of polyphenols and their glucuronides in the local intestine and liver. Further studies are necessary to explore these recycling mechanisms and interactions between polyphenols and the intestinal microbiota. Since NRs govern the inducible expression of target genes that encode DMEs and ETs. Determination of the regulation mechanism mediated by NRs using transgenic and knockout animals is still needed.

Interplay of Efflux Transporters with Glucuronidation and Its Impact on Subcellular Aglycone and Glucuronide Disposition: A Case Study with Kaempferol

Glucuronidation is a major process of drug metabolism and elimination that generally governs drug efficacy and toxicity. Publications have demonstrated that efflux transporters control intracellular glucuronidation metabolism. However, it is still unclear whether and how efflux transporters interact with UDP-glucuronosyltransferases (UGTs) in subcellular organelles. In this study, kaempferol, a model fluorescent flavonoid, was used to investigate the interplay of glucuronidation with transport at the subcellular level. Human recombinant UGTs and microsomes were utilized to characterize the in vitro glucuronidation kinetics of kaempferol. The inhibition of UGTs and efflux transporters on the subcellular disposition of kaempferol were determined visually and quantitatively in Caco-2/TC7 cells. The knockout of transporters on the subcellular accumulation of kaempferol in liver and intestine were evaluated visually. ROS and Nrf2 were assayed to evaluate the pharmacological activities of kaempferol. The results showed that UGT1A9 is the primary enzyme responsible for kaempferol glucuronidation. Visual and quantitative data showed that the UGT1A9 inhibitor carvacrol caused a significant rise in subcellular aglycone and reduction in subcellular glucuronides of kaempferol. The inhibition and knockout of transporters, such as P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance-associated proteins (MRPs), exhibited a marked increase in subcellular kaempferol and decrease in its subcellular glucuronides. Correspondingly, inhibition of UGT1A9 and transporters led to increased kaempferol and, consequently, a significantly enhanced ROS scavenging efficiency and nuclear translocation of Nrf2. In conclusion, the interplay of efflux transporters (P-gp, BCRP, and MRPs) and UGTs govern the subcellular exposure and corresponding pharmacological activity of kaempferol.

The roles of breast cancer resistance protein (BCRP/ABCG2) and multidrug resistance-associated proteins (MRPs/ABCCs) in the excretion of cycloicaritin-3-O-glucoronide in UGT1A1-overexpressing HeLa cells

Cycloicaritin is a bioactive natural phenolic compound from Epimedium species. However, the glucuronidation and excretion which would influence oral bioavailability and pharmacokinetics of cycloicaritin still remain unknown. Here we aimed to establish UGT1A1 stably transfected HeLa cells, and to determine the contributions of BCRP and MRPs transporters to excretion of cycloicaritin-3-O-glucuronide. First, β-estradiol was used to validate the expression of active UGT1A1 protein in engineered HeLa1A1 cells. Furthermore, Ko143 (5 and 20 μM) led to a significant decrease (42.4%-63.8%, p < 0.01) in CICT-3-G excretion and obvious accumulation (19.7%-54.2%, p < 0.05) of intracellular CICT-3-G, while MK571 (5 and 20 μM) caused a significant reduction (46.8%-64.8%, p < 0.05) in the excretion and obvious elevation (50.7%-85.2%, p < 0.01) of intracellular level of CICT-3-G. Furthermore, BCRP knocked-down brought marked reduction in excretion rates of CICT-3-G (26.0%-42.2%, p < 0.01), whereas MRP1 and MRP4-mediated silencing led to significant decrease in the excretion of CICT-3-G (23.8%-35.4%, p < 0.05 for MRP1 and 11.9%-16.0%, p < 0.05 for MRP4). By contrast, neither CICT-3-G excretion nor CICT-3-G accumulation altered in MRP3 knocked-down cells as compared to scramble cells. Taken together, BCRP, MRP1 and MRP4 were identified as the most important contributors for CICT-3-G excretion. Meanwhile, the UGT1A1 modified HeLa cells were a simple and practical tool to study UGT1A1-mediated glucuronidation and to characterize BCRP and MRPs-mediated glucuronide transport at a cellular level.

Intestinal phase-II metabolism of quercetin in HT29 cells, 3D human intestinal tissues and in healthy volunteers: a qualitative comparison using LC-IMS-MS and LC-HRMS

Flavonoids are a large class of dietary molecules, among which quercetin is the most ubiquitous, which undergo an extensive intestinal phase-II metabolism. We compared the in vivo metabolism of quercetin in healthy volunteers with two in vitro models, HT29 cells and 3 D human intestinal tissues. Supernatants of the in vitro experiments and the human intestinal fluids (HIF) were analyzed by LC-IMS-MS and LC-HRMS in a qualitative way. Quercetin glucuronides, sulfates and their methyl conjugates were detected in all three systems. The metabolic profiles were found to be different, both in terms of the metabolites produced and their relative proportions. In particular, quercetin sulfates were almost absent in supernatants from HT29 cells incubations while they were a major metabolite in HIF and also found in 3 D intestinal tissues incubations. IMS provided structural information as well as a third dimension of characterization, while HRMS brought increased sensitivity and MS/MS confirmation. HT29 cells are a useful tool to generate phase-II metabolites but do not represent the in vivo situation. 3 D intestinal tissues appear as a more relevant tool to study the intestinal phase-II metabolism of flavonoids.

Uptake and Transport Mechanism of Dihydromyricetin Across Human Intestinal Caco-2 Cells

A variety of beneficial pharmacological activities have been reported for dihydromyricetin (DMY), however, its oral bioavailability is poor and the intestinal absorption profiles of DMY remains unknown. The aim of this study was to investigate the uptake and transport mechanism of DMY in human intestinal Caco-2 cells. DMY was detected using a liquid chromatography-tandem mass spectrometry method. Several factors including time, concentration, pH, temperature and efflux transporters were systematically evaluated. DMY was poorly absorbed by a passive diffusion mechanism. The uptake and transport of DMY were time and concentration dependent. Interestingly, decreasing the pH from 8.0 to 6.0 markedly enhanced the DMY uptake, but didn't significantly affect its bidirectional transport. Efflux transporters, multidrug resistance protein 2 and breast cancer resistance protein also influenced the DMY uptake and transport processes. This work details the uptake and transport characteristics of DMY and provides basis for future study.

PRACTICAL APPLICATION

This study elucidated the uptake and transport characteristics of dihydromyricetin (DMY). DMY was poorly absorbed by a passive diffusion mechanism. The uptake and transport of DMY were time and concentration dependent. Interestingly, pH affected DMY uptake but not its bidirectional transport. MRP2 and BCRP were involved in the uptake and transport of DMY, which hindered the absorption of DMY in the intestinal. Thus, the present study may provide useful information for designing DMY delivery systems and avoiding DMY-drug interactions.

UGT-mediated metabolism plays a dominant role in the pharmacokinetic behavior and the disposition of morusin in vivo and in vitro

Morusin is a prenylated flavone isolated from mulberry, the branch and root bark of various Morus species, which possesses diverse pharmacological activities. However, it lacks extensive studies about its absorption and disposition. This study investigated the pharmacokinetic behavior of morusin in rat, and its first-pass metabolism in situ. The metabolic pathway of morusin was further investigated by 12 human recombinant UDP-glucuronosyltransferases (UGTs), 9 CYP450s, as well as liver and intestinal microsomes. Four mono-glucuronide metabolites (M-5-G, M-4'-G, M-2'-G, and M_II-2) were identified in rat intestine and bile by LC-MS/MS, while three of them were also detected in plasma (M-5-G, M-4'-G, and M_II-2). M-4'-G was the principal conjugate. However, few CYP450 metabolites were found in rat intestine and bile. Only a small amount of M_I-1 could be detected in rat plasma. UGT1A1, 1A3, 1A7, and 2B7 were the major contributors to morusin glucuronidation. Morusin exhibited substrate inhibition kinetic characteristics in all UGTs. Clearance rates of M-4'-G in HLM, RLM, UGT1A1, UGT1A3, and UGT2B7 were 137.02, 127.55, 32.54, 41.18, and 35.07 ml/min/mg, respectively. Besides, CYP3A5, 3A4, and 2C19 primarily contributed to the oxidative metabolism of morusin. The pharmacokinetic curves of morusin and its conjugates presented double peaks, showing that an enterohepatic recycling may exist. In conclusion, glucuronidation was confirmed to be the crucial metabolic pathway for morusin in vivo, and M-4'-G was the main metabolite.

DACT2 Epigenetic Stimulator Exerts Dual Efficacy for Colorectal Cancer Prevention and Treatment

DACT2, a tumor suppressor gene in various tumors, is frequently down-regulated via hypermethylation. We found DACT2 gene expressions were dramatically silenced (P = 0.002, n = 8) in our clinical colorectal cancer (CRC) tissues, and TCGA data revealed DACT2 hypermethylation correlated to CRC poor prognosis (P = 0.0129, HR = 0.2153, n = 248). Thus, by screening twelve nutritional compounds, we aimed to find out an effective DACT2 epigenetic stimulator to determine whether DACT2 epigenetic restoration could reverse CRC tumorigenesis. We found that kaempferol significantly increased DACT2 expressions up to 3.47-fold in three CRC cells (HCT116, HT29, and YB5). Furthermore, kaempferol remarkably decreased DACT2 methylation (range: 19.58%-67.00%, P < 0.01), while increased unmethylated DACT2 by 13.72-fold (P < 0.01) via directly binding to DNA methyltransferases DNMT1. By epigenetic reactivating DACT2 transcription, kaempferol notably inhibited nuclear β-catenin expression to inactivate Wnt/β-catenin pathway, which consequently restricted CRC cells proliferation and migration. Moreover, in AOM/DSS-induced CRC tumorigenesis, kaempferol-demethylated DACT2 effectively decreased tumor load (range: 50.00%-73.52%, P < 0.05). By determining the chemopreventive and chemotherapeutic efficacy of a novel DACT2 demethylating stimulator, we demonstrated that DACT2 epigenetic restoration could successfully slow down and reverse CRC tumorigenesis.

Non-digestible stachyose promotes bioavailability of genistein through inhibiting intestinal degradation and first-pass metabolism of genistein in mice

This study was designed to explore the molecular mechanism of stachyose in enhancing the gastrointestinal stability and absorption of soybean genistein in mice. Male Kunming mice in each group (n = 8) were administered by intragastric gavage with saline, stachyose (250 mg/kg·bw), genistein (100 mg/kg·bw), and stachyose (50, 250, and 500 mg/kg·bw) together with genistein (100 mg/kg·bw) for 4 consecutive weeks, respectively, and then their urine, feces, blood, gut, and liver were collected. UPLC-qTOF/MS analysis showed that levels of genistein and its metabolites (dihydrogenistein, genistein 7-sulfate sodium salt, genistein 4'-β-D-glucuronide, and genistein 7-β-D-glucuronide) in serum and urine were increased with an increase in stachyose dosages in mice. Furthermore, the feces level of genistein aglycone was also elevated by co-treatment of stachyose with genistein. However, the feces concentration of dihydrogenistein, a characteristic metabolite of genistein by gut microorganism, was decreased by stachyose administration in a dose-dependent manner. Additionally, the simultaneous administration with stachyose and genistein in mice could decrease intestinal SULT, UGT, P-gp, and MRP1 expression, relative to the treatment with individual stachyose or genistein. These results demonstrate that stachyose-mediated inhibition against the intestinal degradation of genistein and expression of phase II enzymes and efflux transporters can largely contribute to the elevated bioavailability of soybean genistein.

Profiles and Gender-Specifics of UDP-Glucuronosyltransferases and Sulfotransferases Expressions in the Major Metabolic Organs of Wild-Type and Efflux Transporter Knockout FVB Mice

Hepatic and extrahepatic tissues participate in xenobiotic detoxication, carcinogen activation, prodrug processing, and estrogen regulation through UDP-glucuronosyltransferases (UGTs/Ugts) and sulfotransferases (SULTs/Sults). Wild-type (WT) and efflux transporter knockout (KO) FVB mice have been commonly used to perform the studies of pharmacokinetics, metabolism, and toxicity. We employed the developed UHPLC-MS/MS approach to gain systematic insight on gender-specific of Ugts and Sults in major metabolic organs. Results showed that the liver was the most abundant with Ugts/Sults, followed by the small intestine and the kidney. In the liver, Ugt2b5, Ugt2b1, Ugt1a6a, Ugt1a1, Sult1a1, and Sult1d1 were the major isoforms. The protein amounts of Ugt1a9 were significantly higher in male efflux transporter KO mice than in WT mice, whereas Ugt1a5 and Sult1a1 severely decreased in female efflux transporter KO mice. In WT and efflux transporter KO mice, the expression levels of Ugt1a1, Ugt1a5, Sult1a1, Sult1d1, and Sult3a1 were female-specific, whereas those of Ugt2b1, Ugt2b5, and Ugt2b36 were male-specific. In the small intestine, Ugt1a1, Sult1b1, and Sult2b1 were the major isoforms. The protein levels and gender differences of Ugts/Sults were obviously affected when KO of Mdr1a, and Bcrp1, Mrp1, Mrp2, and Mdr1a, respectively. The KO of efflux transporter affected the protein amounts of Ugts/Sults in the kidney, heart, and spleen. Therefore, a better understanding of the expression profiles and gender-specific of Ugts and Sults in major metabolic organs of WT and efflux transporter KO mice is useful for the evaluation of potential efficacy, and toxicity of corresponding substrates.

Breast Cancer Resistance Protein and Multidrug Resistance Protein 2 Regulate the Disposition of Acacetin Glucuronides

PURPOSE

To determine the mechanism responsible for acacetin glucuronide transport and the bioavailability of acacetin.

METHODS

Area under the curve (AUC), clearance (CL), half-life (T1/2) and other pharmacokinetic parameters were determined by the pharmacokinetic model. The excretion of acacetin glucuronides was evaluated by the mouse intestinal perfusion model and the Caco-2 cell model.

RESULTS

In pharmacokinetic studies, the bioavailability of acacetin in FVB mice was 1.3%. Acacetin was mostly exposed as acacetin glucuronides in plasma. AUC of acacetin-7-glucuronide (Aca-7-Glu) was 2-fold and 6-fold higher in Bcrp1 (-/-) mice and Mrp2 (-/-) mice, respectively. AUC of acacetin-5-glucuronide (Aca-5-Glu) was 2-fold higher in Bcrp1 (-/-) mice. In mouse intestinal perfusion, the excretion of Aca-7-Glu was decreased by 1-fold and 2-fold in Bcrp1 (-/-) and Mrp2 (-/-) mice, respectively. In Caco-2 cells, the efflux rates of Aca-7-Glu and Aca-5-Glu were significantly decreased by breast cancer resistance protein (BCRP) inhibitor Ko143 and multidrug resistance protein 2 (MRP2) inhibitor LTC4. The use of these inhibitors markedly increased the intracellular acacetin glucuronide content.

CONCLUSIONS

BCRP and MRP2 regulated the in vivo disposition of acacetin glucuronides. The coupling of glucuronidation and efflux transport was probably the primary reason for the low bioavailability of acacetin.

Sulfonation Disposition of Acacetin: In Vitro and in Vivo

Acacetin, an important component of acacia honey, exerts extensive therapeutic effects on many cancers. However, the sulfonation disposition of acacetin has rarely been reported. Therefore, this study aimed to investigate the sulfonation disposition of acacetin systematically. The results showed that acacetin-7-sulfate was the main metabolite mediated primarily by sulfotransferases (SULT) 1A1. Dog liver S9 presented the highest formation rate of acacetin-7-sulfate. Compared with that in wild-type Friend Virus B (FVB) mice, plasma exposure of acacetin-7-sulfate decreased significantly in multidrug resistance protein 1 knockout (Mrp1^-/-) mice vut increased clearly in breast cancer resistance protein knockout (Bcrp^-/-) mice. In Caco-2 monolayers, the efflux and clearance of acacetin-7-sulfate was reduced distinctly by the BCRP inhibitor Ko143 on the apical side and by the MRP1 inhibitor MK571 on the basolateral side. In conclusion, acacetin sulfonation was mediated mostly by SULT1A1. Acacetin-7-sulfate was found to be transported mainly by BCRP and MRP1. Hence, SULT1A1, BCRP, and MRP1 are responsible for acacetin-7-sulfate exposure in vivo.