Discovery and characterization of amentoflavone as a naturally occurring inhibitor against the bile salt hydrolase produced by Lactobacillus salivarius.

Bile salt hydrolases (BSHs), a group of cysteine-hydrolases produced by gut microbes, play a crucial role in the hydrolysis of glycine- or taurine-conjugated bile acids and have been validated as key targets to modulate bile acid metabolism. This study aims to discover one or more efficacious inhibitors against a BSH produced by Lactobacillus salivarius (lsBSH) from natural products and to characterize the mechanism of the newly identified BSH inhibitor(s). Following screening of the inhibition potentials of more than 100 natural compounds against lsBSH, amentoflavone (AMF), a naturally occurring biflavone isolated from various medicinal plants, was discovered to be an efficacious BSH inhibitor (IC50 = 0.34 µM). Further investigation showed that AMF could strongly inhibit the lsBSH-catalyzed hydrolytic reaction in living gut microbes. Inhibition kinetic analyses demonstrated that AMF reversibly inhibited the lsBSH-catalyzed hydrolytic reaction in a mixed-inhibition manner, with an apparent Ki value of 0.65 µM. Fluorescence quenching assays suggested that AMF could quench the fluorescence of lsBSH via a static quenching procedure. Docking simulations suggested that AMF could be fitted into lsBSH at two distinct ligand-binding sites, mainly via hydrophobic interactions and hydrogen bonding, which explained well the mixed inhibition mode of this agent. Animal tests showed that the hydrolytic activities of BSHs in mice feces could be significantly blocked by AMF. In summary, this study reports that AMF is a strong, naturally occurring inhibitor of lsBSH, which offers a promising lead compound to develop novel agents for modulating bile acid metabolism in the host via targeting BSHs.

A fluorescence-based microplate assay for high-throughput screening and evaluation of human UGT inhibitors.

Human UDP-glucuronosyltransferase enzymes (hUGTs), one of the most important classes of conjugative enzymes, are responsible for the glucuronidation and detoxification of a variety of endogenous substances and xenobiotics. Inhibition of hUGTs may cause undesirable effects or adverse drug-drug interactions (DDI) via modulating the glucuronidation rates of endogenous toxins or the drugs that are primarily conjugated by the inhibited hUGTs. Herein, to screen hUGTs inhibitors in a more efficient way, a novel fluorescence-based microplate assay has been developed by utilizing a fluorogenic substrate. Following screening of series of 4-hydroxy-1,8-naphthalimide derivatives, we found that 4-HN-335 is a particularly good substrate for a panel of hUGTs. Under physiological conditions, 4-HN-335 can be readily O-glucuronidated by ten hUGTs, such reactions generate a single O-glucuronide with a high quantum yield (Ф = 0.79) and bring remarkable changes in fluorescence emission. Subsequently, a fluorescence-based microplate assay is developed to simultaneously measure the inhibitory effects of selected compound(s) on ten hUGTs. The newly developed fluorescence-based microplate assay is time- and cost-saving, easy to manage and can be adapted for 96-well microplate format with the Z-factor of 0.92. We further demonstrate the utility of the fluorescence-based assay for high-throughput screening of two compound libraries, resulting in the identification of several potent UGT inhibitors, including natural products and FDA-approved drugs. Collectively, this study reports a novel fluorescence-based microplate assay for simultaneously sensing the residual activities of ten hUGTs, which strongly facilitates the identification and characterization of UGT inhibitors from drugs or herbal constituents and the investigations on UGT-mediated DDI.

Dual-modal imaging-guided theranostic nanocarriers based on 2-methoxyestradiol and indocyanine green.

Drug toxicity and insufficient drug dosing place a limit on the effect of chemotherapy. Optimal efficacy is achieved by exposing tumor cells to the maximum tolerated dose of a chemotherapeutic drug. In this study, we developed a strategy (graphic summary) for enhancing the therapeutic and diagnostic capabilities of known chemotherapeutics. We used a dual-mode near-infrared (NIR) fluorescence/photoacoustic imaging technology to achieve actively guided tumor targeting of the photothermal therapeutic agent indocyanine green (ICG) and the chemotherapeutic drug 2-methoxyestradiol (2-ME), which were loaded into thermosensitive liposomes (TSLs) with surface-grafted tumor-targeting peptide cRGDyk (cRGDyk-2-ME@ICG-TSLs). In vitro studies demonstrated that cRGDyk-2-ME@ICG-TSLs effectively induced drug accumulation and cytotoxicity in NIR laser-irradiated B16-F10 melanoma cells using dual targeting based on the cRGDyk peptide and temperature sensitivity. An in vivo study showed that 24 h after intravenously injecting cRGDyk-2-ME@ICG-TSLs into melanoma tumor-bearing mice, the dual-mode NIR fluorescence/photoacoustic imaging could accurately identify tumors and normal tissues. In addition, the combination of cRGDyk-2-ME@ICG-TSLs and NIR radiation suppressed tumor growth in tumor-bearing nude mice and was associated with a low risk of side effects on normal organs. Our results indicate that TSLs are a suitable drug delivery system for diagnostic and chemotherapeutic agents guided by dual-mode imaging.

Co-administration of paclitaxel and 2-methoxyestradiol using folate-conjugated human serum albumin nanoparticles for improving drug resistance and antitumor efficacy.

The use of chemotherapeutic drug paclitaxel (PTX) for the treatment of tumors has several limitations, including multidrug resistance (MDR) and serious adverse reactions. This research aims to co-encapsulate PTX and the chemosensitizer 2-methoxyestradiol (2-ME) into folate-conjugated human serum albumin nanoparticles (FA-HSANPs) to reduce multiple drug resistance and improve antitumor efficiency. The results show PTX/2-ME@FA-HSANPs had uniform particle size (180 ± 12.31 nm) and high encapsulation efficacy. It also exhibited highly potent cytotoxicity and apoptosis-inducing activities in the G2/M phase of PTX-resistant EC109/Taxol cells. Moreover, PTX/2-ME@FA-HSANPs not only displayed better inhibition of tumor growth in S-180 tumor-bearing mice than PTX alone but also reduced pathological damage to normal tissues. In summary, PTX/2-ME@FA-HSANPs could be a promising vehicle for tumor therapy and reducing drug resistance. This research will also provide references for other MDR treatment.

Design, synthesis and biological evaluation of novel chalcone-like compounds as potent and reversible pancreatic lipase inhibitors.

Pancreatic lipase (PL), a crucial enzyme responsible for hydrolysis of dietary lipids, has been validated as a key therapeutic target to prevent and treat obesity-associated metabolic disorders. Herein, we report the design, synthesis and biological evaluation of a series of chalcone-like compounds as potent and reversible PL inhibitors. Following two rounds of structural modifications at both A and B rings of a chalcone-like skeleton, structure-PL inhibition relationships of the chalcone-like compounds were studied, while the key substituents that would be beneficial for PL inhibition were revealed. Among all tested chalcone-like compounds, compound B13 (a novel chalcone-like compound bearing two long carbon chains) displayed the most potent PL inhibition activity, with an IC50 value of 0.33 µM. Inhibition kinetic analyses demonstrated that B13 could potently inhibit PL-mediated 4-MUO hydrolysis in a mixed inhibition manner, with the Ki value of 0.12 µM. Molecular docking simulations suggested that B13 could tightly bind on PL at both the catalytic site and a non-catalytic site that was located on the surface of PL, which was consistent with the mixed inhibition mode of this agent. In addition, B13 displayed excellent stability in artificial gastrointestinal fluids and good metabolic stability in human liver preparations. Collectively, our findings suggested that chalcone-like compounds were good choices for design and development of orally administrated PL inhibitors, while B13 could be served as a promising lead compound to develop novel anti-obesity agents via targeting on PL.

Design, synthesis and biological evaluation of indanone-chalcone hybrids as potent and selective hCES2A inhibitors.

Human carboxylesterase 2 (hCES2A), one of the major serine hydrolases distributed in the small intestine, plays a crucial role in hydrolysis of ester-bearing drugs. Accumulating evidence has indicated that hCES2A inhibitor therapy can modulate the pharmacokinetic and toxicological profiles of some important hCES2A-substrate drugs, such as the anticancer agent CPT-11. Herein, a series of indanone-chalcone hybrids are designed and synthesized to find potent and highly selective hCES2A inhibitors. Inhibition assays demonstrated that most indanone-chalcone hybrids displayed strong to moderate hCES2A inhibition activities. Structure-hCES2A inhibition activity relationship studies showed that introduction of a hydroxyl at the C4' site and introduction of an N-alkyl group at the C6 site were beneficial for hCES2A inhibition. Particularly, B7 (an N-alkylated 1-indanone-chalcone hybrid) exhibited the most potent inhibition on hCES2A and excellent specificity (this agent could not inhibit other human esterases including hCES1A and butyrylcholinesterase). Inhibition kinetic analyses demonstrated that B7 potently inhibited hCES2A-mediated FD hydrolysis in a mixed inhibition manner, with a calculated Ki value of 0.068 µM. Furthermore, B7 was capable of inhibiting intracellular hCES2A in living cells and displayed good metabolic stability. Collectively, our findings show that indanone-chalcone hybrids are good choices for the development of hCES2A inhibitors, while B7 is a promising candidate for the development of novel anti-diarrhea agents to ameliorate irinotecan-induced intestinal toxicity.

Pentacyclic triterpenoid acids in Styrax as potent and highly specific inhibitors against human carboxylesterase 1A.

Human carboxylesterase 1A1 (hCES1A) is a promising target for the treatment of hyperlipidemia and obesity-associated metabolic diseases. To date, the highly specific and efficacious hCES1A inhibitors are rarely reported. This study aims to find potent and highly specific hCES1A inhibitors from herbs, and to investigate their inhibitory mechanisms. Following large-scale screening of herbal products, Styrax was found to have the most potent hCES1A inhibition activity. After that, a practical bioactivity-guided fractionation coupling with a chemical profiling strategy was used to identify the fractions from Styrax with strong hCES1A inhibition activity and the major constituents in these bioactive fractions were characterized by LC-TOF-MS/MS. The results demonstrated that seven pentacyclic triterpenoid acids (PTAs) in two bioactive fractions from Styrax potently inhibit hCES1A, with IC50 values ranging from 41 nM to 478 nM. Among all the identified PTAs, epibetulinic acid showed the most potent inhibition activity and excellent specificity towards hCES1A. Both inhibition kinetic analyses and in silico analysis suggested that epibetulinic acid potently inhibited hCES1A in a mixed inhibition manner. Collectively, our findings demonstrate that some PTAs in Styrax are potent and highly specific inhibitors of hCES1A and these constituents can be used as promising lead compounds for the development of more efficacious hCES1A inhibitors.

Herb-drug interaction between Styrax and warfarin: Molecular basis and mechanism.

BACKGROUND: Styrax, one of the most famous folk medicines, has been frequently used for the treatment of cardiovascular diseases and skin problems in Asia and Africa. It is unclear whether Styrax or Styrax-related herbal medicines may trigger clinically relevant herb-drug interactions. PURPOSE: This study was carried out to investigate the inhibitory effects of Styrax on human cytochrome P450 enzymes (CYPs) and to clarify whether this herb may modulate the pharmacokinetic behavior of the CYP-substrate drug warfarin when co-administered. STUDY DESIGN: The inhibitory effects of Styrax on CYPs were assayed in human liver microsomes (HLM), while the pharmacokinetic interactions between Styrax and warfarin were investigated in rats. The bioactive constituents in Styrax with strong CYP3A inhibitory activity were identified and their inhibitory mechanisms were carefully investigated. METHODS: The inhibitory effects of Styrax on human CYPs were assayed in vitro, while the pharmacokinetic interactions between Styrax and warfarin were studied in rats. Fingerprinting analysis of Styrax coupled with LC-TOF-MS/MS profiling and CYP inhibition assays were used to identify the constituents with strong CYP3A inhibitory activity. The inhibitory mechanism of oleanonic acid (the most potent CYP3A inhibitor occurring in Styrax) against CYP3A4 was investigated by a panel of inhibition kinetics analyses and in silico analysis. RESULTS: In vitro assays demonstrated that Styrax extract strongly inhibited human CYP3A and moderately inhibited six other tested human CYPs, as well as potently inhibited warfarin 10-hydroxylation in liver microsomes from both humans and rats. In vivo assays demonstrated that compared with warfarin given individually in rats, Styrax (100 mg/kg) significantly prolonged the plasma half-life of warfarin by 2.3-fold and increased the AUC(0-inf) of warfarin by 2.7-fold when this herb was co-administrated with warfarin (2 mg/kg) in rats. Two LC fractions were found with strong CYP3A inhibitory activity and the major constituents in these fractions were characterized by LC-TOF-MS/MS. Five pentacyclic triterpenoid acids (including epibetulinic acid, betulinic acid, betulonic acid, oleanonic acid and maslinic acid) present in Styrax were potent CYP3A inhibitors, and oleanonic acid was a competitive inhibitor against CYP3A-mediated testosterone 6ß-hydroxylation. CONCLUSION: Styrax and the pentacyclic triterpenoid acids occurring in this herb strongly modulate the pharmacokinetic behavior of warfarin via inhibition of CYP3A.

Construction and antitumor effects of antitumor micelles with cyclic RGD-modified anlotinib.

Anlotinib is a new type of small-molecule multi-target tyrosine kinase inhibitor with inhibitory effects against angiogenesis and tumor growth. An effective targeted nano-delivery system is urgently needed to effectively utilize anlotinib for the treatment of melanoma and lung metastases. In this study, an anlotinib-loaded reduction-sensitive nanomicelle, cyclic RGD peptide (cRGDyk)-anlotinib-reduction sensitive micelles (cARM), was developed as a tumor microenvironment-responsive delivery platform. The micelle carrier was formed by the self-assembly of reduction-sensitive amphiphilic copolymers DSPE-SS-PEG2k and DSPE-PEG2k-cRGDyk. The disulfide bonds in the amphiphilic block of micelles are responsive to elevated GSH in tumor cells for controlled drug release. In a B16F10 tumor-bearing mouse model, cRGDyk-anlotinib-RM (cARM) showed better tumor tissue accumulation and internalization than those for non-reduction-sensitive micelles. Therefore, this reduction-sensitive drug delivery system benefits from its specificity, prolonged blood circulation time, effective absorption by tumor cells, and rapid release of intracellular drugs and is therefore a promising strategy.

MMP-2-responsive gelatin nanoparticles for synergistic tumor therapy.

Purpose: The aim of this study was to develop a new type of nanoparticle that enables concentrated drug release and synergistic therapy. Methods: To this end, we synthesized Ge-DOX-5-ALA/NPs, which can enter tumor tissue by the enhanced permeability and retention (EPR) effect and release drugs by utilizing matrix metalloproteinase-2 (MMP-2). Results: The Ge-DOX-5-ALA/NPs were synthesized by a single-phase coacervation method, and the hydrodynamic diameters of all nanoparticles were under 200 nm. The drug encapsulation and loading efficiency were 92%±1.13% and 6.02% ± 0.48%, respectively. Gelatin zymography was performed to detect the expression of MMP-2 in MCF-7 and Hs578Bst cells. The nanoparticle sensitivity to MMP-2 was examined by comparing the release behavior and cellular uptake in MCF-7 and Hs578Bst cells. In vitro cytotoxicity of the nanoparticles was measured by an MTT assay. An in vivo anticancer efficacy study in S180-bearing mice demonstrated that Ge-DOX-5-ALA/NPs provide a substantial curative effect. A pharmacokinetics experiment demonstrated that the nanoparticles have a sustained release effect. Conclusions: The MMP-2-triggered nanoparticles can transport drugs successfully into the tumor site and enable combined chemotherapy and photodynamic therapy.

Ultrasound-Triggered Gas-Generating Doxorubicin Poly(lactic-co-glycolic acid)-Nanoparticles for Cancer Therapy.

The purpose of current research is to develop ultrasound-triggered gas-generating Doxorubicin PLGA nanoparticle for cancer therapy. Method: pH-sensitive PLGA nanoparticles (PLGANPs) was fabricated to deliver doxorubicin (DOX) and sodium bicarbonate (NaHCO3) using the water-in-oil-in-water (w/o/w) double emulsion method. Result: The nanoparticle with the size (650 nm) and high drug loading (15.8±2.3%) were successfully prepared and showed pH-responsive release characteristics. In vitro results indicate that DOX/NaHCO3@PLGANPs with ultrasound had higher inhibition and cell uptake on MCF-7 cells than free DOX and other formulation. In vivo animal experiments showed that after treatment of DOX/NaHCO3@PLGANPs with ultrasound, the relative tumor volume (0.63) of S180-tumor-bearing mice was lower than that of without ultrasound (0.81), DOX@PLGANPs (1.00) and Free DOX (1.12). Moreover, safety evaluation result indicated that DOX/NaHCO3@PLGANPs was safer than free DOX. In conclusion, the DOX/NaHCO3@PLGANPs was successfully developed and evaluated In vitro and In vivo. This drug delivery system will be a promising strategy for cancer therapy and diagnosis.

Investigation of an antitumor drug-delivery system based on anti-HER2 antibody-conjugated BSA nanoparticles.

Conjugation of a monoclonal antibody with a nanoparticle often improves its specificity and drug loading in cancer therapy. In this study, we prepared a novel targeting nanodrug-delivery system using 2-methoxy-estradiol (2-ME) based on anti-human epidermal growth factor receptor 2 (HER2) antibody-modified BSA to improve the clinical application and antitumor effect of 2-ME. 2-ME-loaded albumin nanoparticles (2-ME-BSANPs) were prepared using a desolvation method and the anti-HER2 antibodies were conjugated to 2-ME-BSANPs (HER2-2-ME-BSANPs) using the coupling agent, succinimidyl 3-(2-pyridyldithio)propionate. HER2-2-ME-BSANPs were characterized using SDS-polyacrylamide gel electrophoresis, an agglutination test, and an immunofluorescence assay. We found that mouse anti-human anti-HER2 monoclonal antibody was successfully conjugated to the 2-ME-BSANPs. Thereafter, the in-vitro and in-vivo toxicities were evaluated using two cancer cell lines, SK-BR-3 (HER2-overexpressing) and MCF-7 (HER2-underexpressing), using classic pharmacological methods and in-vivo imaging technology. We found that the HER2-2-ME-BSANPs retained the immunospecificity of the anti-HER2 monoclonal antibody, rapidly localized to HER2 receptors, and could be used for targeted cancer therapy.