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Conflicting data exist on the effect of ginsenosides on transactivation of human glucocorticoid receptor α (herein referred to as glucocorticoid receptor), and relatively little is known regarding the effect of these chemicals on transrepression of this receptor. We investigated the effect of 20(S)-protopanaxadiol (PPD), PPD-type ginsenosides (Rb1, Rb2, Rc, Rd, Rh2, and Compound K), 20(S)-protopanaxatriol (PPT), and PPT-type ginsenosides (Re, Rf, Rg1, and Rh1) on glucocorticoid receptor binding, transactivation, and transrepression. Each ginsenoside was less efficacious than dexamethasone (positive control) in binding to the ligand-binding domain of glucocorticoid receptor. Among the ginsenosides investigated, Rh2 had the smallest IC 50 value (15 ± 1µM), whereas it was 0.02 ± 0.01µM for dexamethasone. In contrast to dexamethasone, none of the ginsenosides influenced glucocorticoid receptor transactivation or transrepression in LS180 human colorectal adenocarcinoma cells, as assessed in a dual-luciferase reporter gene assay. Rh2 did not affect the endogenous mRNA level of tyrosine aminotransferase (marker for glucocorticoid receptor transactivation) or corticosteroid-binding globulin (marker for glucocorticoid receptor transrepression) in HepG2 human hepatocellular carcinoma cells. This chemical also did not alter the response by a glucocorticoid receptor agonist (dexamethasone or Compound A) in the dual-luciferase reporter gene assay or target gene expression assay. In conclusion, ginsenosides were less efficacious and less potent than dexamethasone in binding to the ligand-binding domain of glucocorticoid receptor. The number of glycosylated groups was associated with a decrease in receptor binding potency. PPD-type and PPT-type ginsenosides are not modulators of glucocorticoid receptor transactivation or transrepression in LS180 and HepG2 cells., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Sulfotransferase 2A1 (SULT2A1) is a major catalyst of the sulfation of dehydroepiandrosterone (DHEA) to dehydroepiandrosterone sulfate (DHEA-S) in human liver cytosol. However, there is a lack of a sensitive and fast analytical method for the human liver cytosolic SULT2A1-dependent DHEA sulfation assay. Therefore, we developed and validated an ultra-high performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method to quantify DHEA-S and used it to optimize the human liver cytosolic SULT2A1-dependent DHEA sulfation assay. DHEA-S and cortisol (internal standard) eluted at 2.95 and 2.75min, respectively. Negative multiple reaction monitoring was used to quantify DHEA-S (m/z 367.3→97.0) and cortisol (m/z 407.2→331.3). No interfering peaks were observed in blank samples. The lower limit of quantification was 0.2pmol DHEA-S and the calibration curve was linear from 0.2 to 200pmol. The intra-day and inter-day accuracy and precision was <11.7%. DHEA-S in the quality control samples was stable at room temperature, 4°C, and -20°C. The cytosolic matrix (20-100μg cytosolic protein) did not affect DHEA-S quantification. Our UPLC-MS/MS method was applied to optimize the human liver cytosolic SULT2A1-dependent DHEA sulfation assay. The optimal levels of MgCl2 and 3'-phosphoadenosine 5'-phosphosulfate (PAPS) cofactor were 2.5mM and 20μM, respectively. Reducing agents, including 2-mercaptoethanol and DL-dithiothreitol, did not affect the enzyme activity. A linear relationship existed between DHEA sulfation and amount of human liver cytosol (20-200μg cytosolic protein) or incubation time (5-30min). This UPLC-MS/MS approach is safer, easier, and faster than existing radiometric-based sulfotransferase enzyme assays, and it is the first UPLC-MS/MS method for determining SULT2A1-dependent DHEA sulfation in human liver cytosol., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Meclizine is an agonist of human pregnane X receptor (PXR). It increases CYP3A4 mRNA expression, but decreases CYP3A-catalyzed testosterone 6β-hydroxylation in primary cultures of human hepatocytes, as assessed at 24h after the last dose of meclizine. Therefore, the hypothesis to be tested is that meclizine inactivates human CYP3A enzymes. Our findings indicated that meclizine directly inhibited testosterone 6β-hydroxylation catalyzed by human liver microsomes, recombinant CYP3A4, and recombinant CYP3A5. The inhibition of human liver microsomal testosterone 6β-hydroxylation by meclizine occurred by a mixed mode and with an apparent Ki of 31±6μM. Preincubation of meclizine with human liver microsomes and NADPH resulted in a time- and concentration-dependent decrease in testosterone 6β-hydroxylation. The extent of inactivation required the presence of NADPH, was unaffected by nucleophilic trapping agents or reactive oxygen species scavengers, attenuated by a CYP3A substrate, and not reversed by dialysis. Meclizine selectively inactivated CYP3A4, but not CYP3A5. In contrast to meclizine, which has a di-substituted piperazine ring, norchlorcyclizine, which is a N-debenzylated meclizine metabolite with a mono-substituted piperazine ring, did not inactivate but directly inhibited hepatic microsomal CYP3A activity. In conclusion, meclizine inhibited human CYP3A enzymes by both direct inhibition and mechanism-based inactivation. In contrast, norchlorcyclizine is a direct inhibitor but not a mechanism-based inactivator. Furthermore, a PXR agonist may also be an inhibitor of a PXR-regulated enzyme, thereby giving rise to opposing effects on the functional activity of the enzyme and indicating the importance of measuring the catalytic activity of nuclear receptor-regulated enzymes., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Rilpivirine and etravirine are second generation non-nucleoside reverse transcriptase inhibitors approved recently by the United States Food and Drug Administration for the treatment of human immunodeficiency virus-1 infection. Pregnane X receptor (PXR) is a member of the superfamily of nuclear receptors that regulate the expression of various genes controlling diverse biological functions. The present study investigated the effects of rilpivirine and etravirine on the activity of human PXR (hPXR), including the mode of activation, and compared them to those of efavirenz, nevirapine, and delavirdine, which are first generation non-nucleoside reverse transcriptase inhibitors. In transiently transfected HepG2 cells, rilpivirine, etravirine, and efavirenz, but not nevirapine or delavirdine, activated human, mouse, and rat PXR. Results from mechanistic studies indicated that rilpivirine, etravirine, and efavirenz, but not nevirapine or delavirdine, bound to the ligand-binding domain of hPXR, as assessed by a transactivation assay and by a competitive ligand-binding assay using time-resolved fluorescence resonance energy transfer; triggered nuclear translocation of a green fluorescence protein-tagged hPXR, as visualized by confocal imaging; and recruited steroid receptor coactivator-1 (SRC-1), SRC-2, and SRC-3 to hPXR, as demonstrated by mammalian two-hybrid assays. Rilpivirine, etravirine, and efavirenz, but not nevirapine or delavirdine, increased hPXR target gene (CYP3A4) expression in primary cultures of human hepatocytes. In summary, select non-nucleoside reverse transcriptase inhibitors activated human and rodent PXR. Rilpivirine, etravirine, and efavirenz, but not nevirapine or delavirdine, were identified as agonists of hPXR, as assessed in mechanistic experiments, and inducers of CYP3A4, as determined in primary cultures of human hepatocytes., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Adulterations with synthetic drugs are common problems with herbal medicine and this can potentially cause serious adverse effects. It is therefore important to determine the presence of synthetic drugs in herbal medicine to ensure patients' safety. The objective of this study was to develop sensitive and specific methods to analyse phenylbutazone, caffeine and oxyphenbutazone present in a traditional Indonesian herbal product. Liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS) methods in the selected reaction-monitoring (SRM) mode were developed. It was found that the sample contained 0.53% w/w (n=3, RSD=7.56%) phenylbutazone and 0.04% w/w (n=3, RSD=8.39%) caffeine. This corresponded to 43.17 mg phenylbutazone and 3.23 mg caffeine in each sachet of powder. The methods were validated for linearity, precision, accuracy, LOD and LOQ. LOD and LOQ were found to be 3.69 and 12.29 ng/ml, respectively for phenylbutazone. For caffeine, the LOD and LOQ were 0.84 and 2.80 ng/ml, respectively. Oxyphenbutazone in the sample was found to be present at a level below the quantification level of 10.2 ng/ml. With better methods developed for analysis of adulterants in herbal medicine, the quality and safety of these medicines can be better controlled and regulated to ensure patients' safety.