Huidi Jiang

Metabolism of flavonoids in human: a comprehensive review.

Flavonoids are naturally occurring polyphenols, which are widely taken in diets, supplements and herbal medicines. Epidemiological studies have shown a flavonoid-rich diet is associated with the decrease in incidence of a range of diseases. Pharmacological evidences also reveal flavonoids display anti-oxidant, anti-allergic, anti-cancer, anti-inflammatory, anti-microbial and anti-diarrheal activities. Therefore, it is critical to study the biotransformation and disposition of flavonoids in human. This review summarizes the major metabolism pathways of flavonoids in human. First, lactase-phlorizin hydrolase (LPH) and human intestinal microflora mediate the hydrolysis of flavonoid glycosides, which is recognized as the first and determinant step in the absorption of flavonoids. Second, phase II metabolic enzymes (UGTs, SULTs and COMT) dominate the metabolism of flavonoids in vivo. UGTs are the most major contributors, followed by SULTs and COMT. By contrast, phase I metabolism pathway mediated by CYPs only plays a minor role. Third, the coupling of transporters (such as BCRP and MRPs) and phase II enzymes (UGTs and SULTs) plays an important role in the disposition of flavonoids, especially in the enteroenteric and enterohepatic circulations. Thus, all the above factors should be taken into consideration when studying pharmacokinetics of flavonoids. Here we describe a comprehensive metabolism profile of flavonoids, which will enhance our understanding of the mechanisms underlying the disposition and pharmacological effects of flavonoids in vivo.

Pulsatile protein release from a laminated device comprising of polyanhydrides and pH-sensitive complexes

A laminated device comprising of polyanhydrides as isolating layers and pH-sensitive complexes as protein-loaded layers was designed to deliver proteins in a pulsatile manner. Poly(sebacic anhydride)-b-polyethylene glycol (PSA-b-PEG) and poly(trimellitylimidoglycine-co-sebacic anhydride)-b-polyethylene glycol (P(TMA-gly-co-SA)-b-PEG) were synthesized as isolating layers for their good processing properties at room temperature and suitable erosion duration. During the erosion period, pH of the dissolution fluid decreases to a low value (3.8-5.8). Poly(methacrylic acid)/polyethoxazoline (PMAA/PEOx) complex was used as protein-loaded layers, which could dissociate and release model proteins, Myoglobin (Mb) and Bovine Serum Albumin (BSA), at pH 7.4 while become stable and retained the drugs below pH 5.0. The protein release from the device showed a typical pulsatile fashion. The lag time prior to the pulsatile protein release correlated with the hydrolytic duration of the polyanhydrides, which varied from 30 to 165 h by selecting polyanhydride type and isolating layer thickness. In addition, the pulse duration could be adjusted from 18.5 to 40 h by varying the mass of the complex. The results can be attributed to the synergistic effects between the degrading polyanhydrides, pH-sensitive complexes and proteins.

Kidney Transplantation from Hepatitis B Surface Antigen Positive Donors into Hepatitis B Surface Antibody Positive Recipients: A Prospective Nonrandomized Controlled Study from a Single Center

The number of patients on renal transplant waiting list is increasing rapidly in many countries, exacerbating the shortage of organs. We conducted a study to evaluate the safety and efficacy of deceased‐donor kidney transplantation from hepatitis B surface antigen (HBsAg)‐positive (+) donors into hepatitis B surface antibody (anti‐HBs)‐positive (+) recipients. Sixty‐five patients received grafts from HBsAg(+) donors, and 308 subjects received grafts from HBsAg‐negative(−) donors. Posttransplantation, recipients with HBsAg(−) grafts or HBsAg(+) grafts received 400 U of hepatitis B immunoglobulin once and twice, respectively. The seven recipients who received grafts from hepatitis B virus (HBV) DNA(+) donors were treated with hepatitis B immunoglobulin 400 U weekly for 3 months and lamivudine 100 mg daily for 6 months. All patients were monitored for liver function and hepatitis B viral status. The follow‐up period was 38.7 ± 15.4 months. Although two recipients developed de novo HBV infection, neither patient developed severe liver dysfunction nor died. The incidence of liver injury (39/65 vs. 207/308, chi‐square test, p > 0.05) and survival (log‐rank test, p > 0.05) did not differ between the groups. We conclude that anti‐HBs(+) recipients receiving HBsAg(+) grafts did as well as those receiving HBsAg(−) grafts.

Role of catechol-O-methyltransferase in the disposition of luteolin in rats.

Luteolin is mainly metabolized by phase II enzymes in animals and humans with glucuronidation and sulfation as the two known metabolic pathways. Although methylation of luteolin was reported previously, the structure of the methylated metabolites and the enzymes involved in the process have not been clarified. In our study, two methylated metabolites, M1 (chrysoeriol) and M2 (diosmetin), were identified in the urine after intravenous administration of luteolin to rats, and the data suggested that the methylation was mediated by catechol-O-methyltransferase (COMT). When luteolin was coadministered with a specific COMT inhibitor, entacapone, the formation of M1 and M2 was significantly reduced, whereas the plasma concentration of luteolin increased. Methylation of luteolin was also studied in vitro using rat tissue homogenates. The apparent kinetic parameters associated with the formation of M1 and M2 in vitro were estimated, and regioselectivity of methylation of luteolin was observed. In the in vitro experiment, there was a preference for the formation of M2 over M1. In contrast, accumulation of M1 was preferred in vivo in both rat plasma and urine after an intravenous dose of luteolin. In conclusion, COMT played a crucial role in the disposition of luteolin in rats. Our results indicated that the methylation pathway in rats was significantly reduced when luteolin was coadministered with a specific COMT inhibitor. Therefore, COMT-associated drug-drug interactions need be considered in the future in luteolin clinical trials because the plasma concentrations and related therapeutic effects may be altered in vivo in the presence of a COMT inhibitor.

Pharmacokinetic study of luteolin, apigenin, chrysoeriol and diosmetin after oral administration of Flos Chrysanthemi extract in rats

Abstract Flos Chrysanthemi (the flower of Chrysanthemum morifolium Ramat.) is widely used in China as a food and traditional Chinese medicine for many diseases. Luteolin and apigenin are two main bioactive components in Flos Chrysanthemi, and chrysoeriol and diosmetin are two methylated metabolites of luteolin in vivo by cathechol-O-methyltransferase (COMT). However, there was lack of pharmacokinetic information of chrysoeriol and diosmetin after oral administration of Flos Chrysanthemi extract (FCE). The present study aimed to develop an HPLC-UV method for simultaneous determination of rat plasma concentration of luteolin, apigenin, chrysoeriol and diosmetin and utilize it in pharmacokinetic study of the four compounds after orally giving FCE to rats. The method was successfully validated and applied to the pharmacokinetic study when oral administration of FCE to rats with or without co-giving a COMT inhibitor, entacapone. Chrysoeriol and diosmetin were detected in rat plasma after oral administration of FCE and their concentrations were significantly decreased after co-giving entacapone. Furthermore, AUC of luteolin was significantly increased by entacapone, while that of chrysoeriol was decreased by entacapone, which revealed COMT might play an important role in the disposition of luteolin in rats after dosing of FCE. In conclusion, a sensitive, accurate and reproducible HPLC-UV method for simultaneous determination of luteolin, apigenin, chrysoeriol and diosmetin in rat plasma were developed, pharmacokinetics of chrysoeriol and diosmetin combined with luteolin and apigenin were characterized after oral administration of FCE to rats, which gave us more information on pharmacokinetics and potential pharmacological effects of FCE in vivo.

Stereoselective binding of chiral drugs to plasma proteins.

Chiral drugs show distinct biochemical and pharmacological behaviors in the human body. The binding of chiral drugs to plasma proteins usually exhibits stereoselectivity, which has a far-reaching influence on their pharmacological activities and pharmacokinetic profiles. In this review, the stereoselective binding of chiral drugs to human serum albumin (HSA), α1-acid glycoprotein (AGP) and lipoprotein, three most important proteins in human plasma, are detailed. Furthermore, the application of AGP variants and recombinant fragments of HSA for studying enantiomer binding properties is also discussed. Apart from the stereoselectivity of enantiomer-protein binding, enantiomer-enantiomer interactions that may induce allosteric effects are also described. Additionally, the techniques and methods used to determine drug-protein binding parameters are briefly reviewed.

Relative contribution of small and large intestine to deglycosylation and absorption of flavonoids from Chrysanthemun morifolium extract.

The flower of Chrysanthemum morifolium Ramat (CM) is an established part of traditional Chinese medicine (TCM). Luteolin and apigenin flavonoids are the effective components of the CM extract (CME); however, they exist in the orally consumed CME as glycosides. The present study was carried out to determine the relative contribution of the small and large intestine to the deglycosylation and absorption of flavonoids from CME using a rat model system. The distribution of luteolin and apigenin in rat gastrointestinal (GI) luminal contents, tissues, and plasmas was assessed after the oral administration of CME. The hydrolysis and absorption of CME flavonoids in different rat GI segments were further evaluated by using in situ ligated models and cell-free extracts prepared from rat GI segments. The results demonstrated that after the oral administration of CME, the magnitude of deglycosylation in rats was surprisingly high (about 30%) in the stomach and upper intestine within the first 5 min after ingestion, and early absorption in the plasma was detected. The results from site-limited administration revealed that the stomach was the initial hydrolysis site, while the duodenum was the first effective absorption site for CME flavonoids. Diminishing microbial flora in the jejunum had no significant effect on the hydrolysis of the flavonoids from CME, but the cell-free extracts prepared from rat GI segments demonstrated a strong ability to hydrolyze. Taken together, our findings suggest that enteric disposition contributes to the pharmacokinetics of luteolin and apigenin after oral administration of CME. Moreover, the upper digestive tract plays a key role in the hydrolysis and absorption of flavonoids in CME.

Preparation, characterization and in vitro release properties of ibuprofen-loaded microspheres based on polylactide, poly(epsilon-caprolactone) and their copolymers

In this paper, ibuprofen was encapsulated into microspheres by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymers with certain compositions and characteristics such as polylactide (PLA), poly(ϵ-caprolactone) (PCL) and their block copolymer were used to prepare the microspheres. The results indicate that, under the same processing conditions, the drug entrapment efficiency was similar (∼80%) for microspheres prepared with PLA and P(LA-b-CL) (78.7/21.3 by mole), but it was only 25.4% for PCL microspheres. The in vitro drug release rate decreased in the order of PCL, P(LA-b-CL) (78.7/21.3 by mole) and PLA microspheres. PCL microspheres showed more serious burst release during the first day (almost 80%) than P(LA-b-CL) (50%) and PLA microspheres (18%). The complete ibuprofen release duration from the last two kinds of microspheres exceeded 1 month. Characterization of the microspheres by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and polarized optical microscope (POM) revealed that ibuprofen was amorphous in PCL microspheres and partially crystalline in P(LA-b-CL) and PLA microspheres. The different release behaviour of ibuprofen from the three kinds of microspheres could be attributed to the different crystallinity of the studied polymers and drug dispersion state in polymer matrices. All the above results suggest that the copolymer with a certain ratio of lactide to ϵ-caprolactone could have potential applications for long-term ibuprofen release.

Inhibition of organic cation transporter 2 and 3 may be involved in the mechanism of the antidepressant-like action of berberine.

Organic cation transporter 2 (OCT2) and 3 (OCT3) are low-affinity, high-capacity transporters (uptake-2) expressed in the central nervous system (CNS) and other major organs. Proven to be essential components in the CNS functions, OCT2 and OCT3 are suggested as potential targets of antidepressant therapeutics recently. Berberine, an active constituent derived from many medicinal plants, such as Coptis chinensis, has been reported to possess antidepressant-like action in the tail suspension test and forced swim test with elevated serotonin/norepinephrine/dopamine (5-HT/NE/DA) level in mouse brain; however the mechanism has not been elucidated. In consideration of the relation between OCT2/3 and antidepressant action, and the characteristic of berberine as an organic cation, we investigated the potential involvement of OCT2 and OCT3 in the antidepressant-like action of berberine in the present study. The results in mouse brain synaptosomes demonstrated that uptake-2 inhibition might play a notable role in enhanced serotonergic and noradrenergic effects induced by berberine. The inhibitory study in transfected MDCK cells displayed that berberine is a potent inhibitor of human OCT2 and OCT3, and its IC50 values for inhibition of transporter-mediated 5-HT/NE uptake are between 0.1 and 1μM. In addition, berberine was identified as a substrate of hOCT2 and hOCT3. In conclusion, berberine is a substrate and an inhibitor of hOCT2 and hOCT3, and its inhibition on OCT2- and OCT3-mediated 5-HT and NE uptake may contribute to the enhanced monoamine neurotransmission in mouse brain. It was deduced that the inhibition of OCT2 and OCT3 probably be implicated in the mechanism of antidepressant-like action.

MicroRNA-195 targets ADP-ribosylation factor-like protein 2 to induce apoptosis in human embryonic stem cell-derived neural progenitor cells

Neural progenitor cells (NPCs) derived from human embryonic stem cells (hESCs) have great potential in cell therapy, drug screening and toxicity testing of neural degenerative diseases. However, the molecular regulation of their proliferation and apoptosis, which needs to be revealed before clinical application, is largely unknown. MicroRNA miR-195 is known to be expressed in the brain and is involved in a variety of proapoptosis or antiapoptosis processes in cancer cells. Here, we defined the proapoptotic role of miR-195 in NPCs derived from two independent hESC lines (human embryonic stem cell-derived neural progenitor cells, hESC-NPCs). Overexpression of miR-195 in hESC-NPCs induced extensive apoptotic cell death. Consistently, global transcriptional microarray analyses indicated that miR-195 primarily regulated genes associated with apoptosis in hESC-NPCs. Mechanistically, a small GTP-binding protein ADP-ribosylation factor-like protein 2 (ARL2) was identified as a direct target of miR-195. Silencing ARL2 in hESC-NPCs provoked an apoptotic phenotype resembling that of miR-195 overexpression, revealing for the first time an essential role of ARL2 for the survival of human NPCs. Moreover, forced expression of ALR2 could abolish the cell number reduction caused by miR-195 overexpression. Interestingly, we found that paraquat, a neurotoxin, not only induced apoptosis but also increased miR-195 and reduced ARL2 expression in hESC-NPCs, indicating the possible involvement of miR-195 and ARL2 in neurotoxin-induced NPC apoptosis. Notably, inhibition of miR-195 family members could block neurotoxin-induced NPC apoptosis. Collectively, miR-195 regulates cell apoptosis in a context-dependent manner through directly targeting ARL2. The finding of the critical role of ARL2 for the survival of human NPCs and association of miR-195 and ARL2 with neurotoxin-induced apoptosis have important implications for understanding molecular mechanisms that control NPC survival and would facilitate our manipulation of the neurological pathogenesis.