Yazhuo Li

Herb-drug Interactions Involving Drug Metabolizing Enzymes and Transporters

Herbal medicines and their active ingredients are widely used worldwide, and they have become an important part of clinical medicine. The combined use of herbs and drugs has increased the possibility of pharmacokinetic and pharmacodynamic interactions. Clinical studies have demonstrated that the combined use of herbs and drugs can enhance or attenuate the drug efficacy and toxicity. The herb-drug combinations may reduce a drug efficacy and lead to treatment failure when long-term administration. Case reports detailing serious clinical adverse reactions have promoted studies on the interactions between herbs and drugs. This review highlights recent knowledge to discuss herb-drug interactions involving metabolizing enzymes and drug transporters. Drug transporters are widely present in body and play an important role in the absorption, distribution, excretion and metabolism, efficacy, and toxicity of drugs. Investigation of transporters has developed rapidly since 1990s, the effects of many transporters on the pharmacokinetics of drugs and herb-drug interactions have been reported. Some concepts on drug transporters issued experimentally and clinically drug-drug and herb-drug interactions have applied in many studies. Methodology studies are very important for understanding the mechanism, considerations and evaluation of experiments and clinical studies on drug metabolizing enzymes and transporters in drug-drug interactions.

Aspartate‐modified doxorubicin on its N‐terminal increases drug accumulation in LAT1‐overexpressing tumors

L‐type amino acid transporter 1 (LAT1), overexpressed on the membrane of various tumor cells, is a potential target for tumor‐targeting therapy. This study aimed to develop a LAT1‐mediated chemotherapeutic agent. We screened doxorubicin modified by seven different large neutral amino acids. The aspartate‐modified doxorubicin (Asp‐DOX) showed the highest affinity (Km = 41.423 μmol/L) to LAT1. Aspartate was attached to the N‐terminal of DOX by the amide bond with a free carboxyl and a free amino group on the α‐carbon atom of the Asp residue. The product Asp‐DOX was characterized by HPLC/MS. In vitro, Asp‐DOX exerted stronger inhibition on the cancer cells overexpressing LAT1 and the uptake of Asp‐DOX was approximately 3.5‐fold higher than that of DOX in HepG2 cells. Pharmacokinetic data also showed that Asp‐DOX was expressed over a longer circulation time (t1/2 = 49.14 min) in the blood compared to DOX alone (t1/2 = 15.12 min). In HepG2 and HCT116 tumor‐bearing mice, Asp‐DOX achieved 3.1‐fold and 6.4‐fold accumulation of drugs in tumor tissue, respectively, than those of the unmodified DOX. More importantly, treatment of tumor‐bearing mice with Asp‐DOX showed a significantly stronger inhibition of tumor growth than mice treated with free DOX in HepG2 tumor models. Furthermore, after Asp modification, Asp‐DOX avoided MDR mediated by P‐glycoprotein. These results suggested that the Asp‐DOX modified drug may provide a new treatment strategy for tumors that overexpress LAT1 and MDR1.

Research Advances on Hepatotoxicity of Herbal Medicines in China.

In general, herbal medicines have been considered as safe by the general public, since they are naturally occurring and have been applied in treatment for over thousands of years. As the use of herbal medicine is rapidly increasing globally, the potential toxicity of herbal drugs, in particular drug-induced liver injury (DILI), has now become a serious medical issue. According to the literature, the authors analyzed and discussed the hepatotoxicity problem of Chinese herbal medicines (CHM), including global overview on herbal-induced liver injury (HILI), current research progress on toxic CHM, diagnosis and treatment of HILI, and modern approaches and technologies of study of hepatotoxicity. As to promote the recognition of HILI and tackle the issue, a guideline for the diagnosis and treatment of HILI has recently been drafted by Chinese scientists. As suggested by the guideline, the hepatotoxicity issue of CHM, as a matter of fact, is overestimated. Up to date, the investigation of hepatotoxicity of CHM is now booming with worldwide application of CHM. This review therefore provides useful information for investigating hepatotoxicity of herbal medicine and characterizing DILI caused by CHM. In addition, authors describe in which way further efforts should be made to study the rationale of CHM and liver injury.

The Targeted-liposome Delivery System of Antitumor Drugs

The liposome delivery system has been intensively explored as novel drug delivery system (DDS) for antitumor drugs, due to its safety, selective cytotoxicity, long circulation and slow elimination in blood, which is favorable for cancer therapy. The liposome-based chemotherapeutics are used to treat a variety of cancers to enhance the therapeutic index of antitumor drugs. Here, the author reviewed the important targets for cancer therapy and the pharmacokinetic behavior of liposomal drugs in vivo, as well as the application of the targeting liposomal system in cancer therapy. Considering further application for clinical use, the great challenges of the liposome-based delivery system were also proposed as follows: 1) prepare stealth liposome with steric stabilization and further enhance the therapeutic effects and safety; 2) explore more safe clinical targets and complementary or different types of targeting liposome; 3) thirdly, more investment is needed on the research of pharmacokinetics of the elements such as the ligands (antibody), PEG and lipids of liposome delivery system as well as safety evaluation. Considering the complex process of the liposomal encapsulation drugs in vivo, the author inferred that there are maybe different forms of the encapsulation drug to be internalized by the tumor tissues at the same time and space, although there are little reports on it.

Drug Metabolism and Pharmacokinetics of Nanodrugs from Chinese Medicines and Natural Products

Over the past few years, nanoscale Chinese medicine has become one of focuses in modern Chinese medicine research. There is an increasing need for a more systematic study on the basic issues involved in traditional Chinese medicine and a more active participation of researchers in the application area of nanoscale traditional Chinese drugs. In this review, author analyzed the current applications of nanotechnology in research and development of drugs from natural products and herbal medicines involving traditional Chinese medicines, and also discussed the bio-medicinal evaluation issues on ADME including bio-distribution and metabolism of nanodrugs. Author noted that great challenges faced in nanodrugs from herb drugs and natural products are the follows: (1) the first challenge is to prepare nanodrug delivery system and quantitatively evaluate the therapeutic effects and safety; (2) the second challenge is to clarify the concrete metabolism course; and (3) the third challenge is to study the pharmacokinetics of nanodrugs.

LC-MS/MS Method for Quantification of Liquiritigenin in Rat Plasma： Application to Pharmacokinetic Study of Liquiritin

Objective A simple, sensitive, and rapid LC-MS/MS method has been established and validated for the determination of liquiritigenin (LG) in rat plasma.

Development and Application of Network Toxicology in Safety Research of Chinese Materia Medica

Abstract Network toxicology that is an important branch of the network pharmacology emerges on the basis of network biology. It refers to study on the toxicological features of a constructed network model which is used to analyze toxic substances and their interaction and regulation in biological systems, particularly investigate the toxic effects of drugs and/or compatibility of medicines on body, and clarify the mechanism of toxicity. Network toxicology currently develops rapidly in safety prediction of Chinese materia medica (CMM). The application of network toxicology to safety and toxicology study on CMM is extremely beneficial to identify the toxic components and potential incompatibility of CMM. Since CMM is a complex system with multi-components, multi-targets, and multi-interactions, the network toxicology in safety prediction of CMM faces three great challenges, including integration studies of bioinformatics, innovation of methods, and tools and risk assessment in future development of the network toxicology in CMM research. In this paper, relevant database, approaches and tools that network toxicology utilized in the safety study of CMM were carefully reviewed. Based on the progress made, the scientific development and modernization of CMM will be greatly enhanced.

Pharmacokinetics, tissue distribution, and excretion of FGF-21 following subcutaneous administration in rats

As one of the fibroblast growth factor (FGF) superfamily, FGF-21 has been extensively investigated for its functions and roles since its discovery. It has been demonstrated to be one of the key regulators for glucose and lipid metabolism, and exhibits beneficial effects on cardiovascular disease. However, studies focusing on its pharmacokinetic behavior in vivo as a novel therapeutic agent have not been reported. In the present study, rapid and sensitive analytical approaches including radioactivity assay and assay after precipitation/separation by high performance liquid chromatography (HPLC) were established to determine the content of FGF-21 tagged with 125 I in plasma, tissue, and excrement. The results indicated that FGF-21 were quickly absorbed into systematic circulation and slowly eliminated; Cmax and exposure increased in a dose-dependent manner, exhibiting a typical linear pharmacokinetic pattern. Tissue distribution also confirmed that the kidney is the primary organ for FGF-21 to be distributed, even though radioactivity of FGF-21 was recovered in all tissues examined. In addition, the results also supported that urinary excretion was the critical route for FGF-21 to be eliminated. The study fully clarifies the pharmacokinetic behavior of FGF-21 and can provide valuable information and support further safety and toxicology development.

HPV16 E6 Promotes Breast Cancer Proliferation via Upregulation of COX-2 Expression

Background. Breast cancer remains the leading cause of cancer-related mortality worldwide. It has been indicated that human papillomaviruses 16 (HPV16) might participate in the pathogenesis and development of breast cancer. However, the detected rate of HPV16 varies with region. We will investigate HPV16 E6 expression in North China and explore the effects and mechanism of HPV16 E6 on breast cancer proliferation in this study. Methods. The expressions of HPV16 E6 and COX-2 in paraffin-embedded tissues of the invasive ductal breast cancer were detected by qPCR and IHC. The effects of HPV16 E6 on breast cancer proliferation were determined by function studies. The mechanism of HPV16 E6 in promoting breast cancer proliferation was explored by Western blot and Dual-Luciferase Reporter Assay. Results. HPV16 E6 was positive in 28% invasive ductal breast carcinoma in North China; HPV16 E6 promoted breast cancer proliferation. Inhibition of COX-2 by siCOX-2 or Celecoxib attenuated the proliferation of breast cancer cells with HPV16 E6 expression; and the upregulation of COX-2 could be suppressed by the inhibition of NF-κB activity. Conclusion. HPV16 E6 promotes breast cancer proliferation by activation of NF-κB signaling pathway and increase of COX-2 expression. COX-2 will be a potential target for HPV16 E6-associated breast cancer.

Molecular Simulation Study on Bentysrepinine Metabolites Improving Binding Affinity of HBV DNA Polymerase

Abstract Objective To study the effect of bentysrepinine (Y101) metabolites on improving binding affinity of HBV DNA polymerase. Methods The binding mode of Y101 and its metabolites with DNA polymerase has been driven by hydrophobic interaction. Results Two compounds, T2 and T4, exhibited the improvement of the binding affinity to HBV DNA polymerase protein, which suggests that the inhibitory activity against HBV DNA polymerase protein can be enhanced. Conclusion The variant docking poses of T2 and T4 might imply the novel recognition of inhibitory effects of T2 and T4, in comparison with Y101.