CYP1A1 Is a Major Enzyme Responsible for the Metabolism of Granisetron in Human Liver Microsomes

DeepP450: Predicting Human P450 Activities of Small Molecules by Integrating Pretrained Protein Language Model and Molecular Representation

Cytochrome P450 enzymes (CYPs) play a crucial role in Phase I drug metabolism in the human body, and CYP activity toward compounds can significantly affect druggability, making early prediction of CYP activity and substrate identification essential for therapeutic development. Here, we established a deep learning model for assessing potential CYP substrates, DeepP450, by fine-tuning protein and molecule pretrained models through feature integration with cross-attention and self-attention layers. This model exhibited high prediction accuracy (0.92) on the test set, with area under the receiver operating characteristic curve (AUROC) values ranging from 0.89 to 0.98 in substrate/nonsubstrate predictions across the nine major human CYPs, surpassing current benchmarks for CYP activity prediction. Notably, DeepP450 uses only one model to predict substrates/nonsubstrates for any of the nine CYPs and exhibits certain generalizability on novel compounds and different categories of human CYPs, which could greatly facilitate early stage drug design by avoiding CYP-reactive compounds.

Dimethylmonothioarsinic acid (DMMTAV) differentially modulates the expression of AHR-regulated cytochrome P450 1A enzymes in vivo and in vitro

Dimethylmonothioarsinic acid (DMMTAV), a pentavalent thio-arsenic derivative, has been found in bodily fluids and tissues including urine, liver, kidney homogenates, plasma, and red blood cells. Although DMMTAV is a minor metabolite in humans and animals, its substantial toxicity raises concerns about potential carcinogenic effects. This toxicity could be attributed to arsenicals' ability to regulate cytochrome P450 1 A (CYP1A) enzymes, pivotal in procarcinogen activation or detoxification. The current study investigates DMMTAV's impact on CYP1A1/2 expression, individually and in conjunction with its inducer, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). C57BL/6 mice were intraperitoneally injected with 6 mg/kg DMMTAV, alone or with 15 μg/kg TCDD, for 6 and 24 h. Similarly, Hepa-1c1c7 cells were exposed to DMMTAV (0.5, 1, and 2 μM) with or without 1 nM TCDD for 6 and 24 h. DMMTAV hindered TCDD-induced elevation of Cyp1a1 mRNA, both in vivo (at 6 h) and in vitro, associated with reduced CYP1A regulatory element activation. Interestingly, in C57BL/6 mice, DMMTAV boosted TCDD-induced CYP1A1/2 protein and activity, unlike Hepa-1c1c7 cells where it suppressed both. DMMTAV co-exposure increased TCDD-induced Cyp1a2 mRNA. While Cyp1a1 mRNA stability remained unchanged, DMMTAV negatively affected protein stability, indicated by shortened half-life. Baseline levels of CYP1A1/2 mRNA, protein, and catalytic activities showed no significant alterations in DMMTAV-treated C57BL/6 mice and Hepa-1c1c7 cells. Taken together, these findings indicate, for the first time, that DMMTAV differentially modulates the TCDD-mediated induction of AHR-regulated enzymes in both liver of C57BL/6 mice and murine Hepa-1c1c7 cells suggesting that thio-arsenic pentavalent metabolites are extremely reactive and could play a role in the toxicity of arsenic.

Quantitative Translation of Substrate Intrinsic Clearance from Recombinant CYP1A1 to Humans

CYP1A1 is a cytochrome P450 family 1 enzyme that is mostly expressed in the extrahepatic tissues. To understand the CYP1A1 contribution to drug clearance in humans, we examined the in vitro-in vivo extrapolation (IVIVE) of intrinsic clearance (CLint) for a set of drugs that are in vitro CYP1A1 substrates. Despite being strong in vitro CYP1A1 substrates, 82% of drugs gave good IVIVE with predicted CLint within 2-3-fold of the observed values using human liver microsomes and hepatocytes, suggesting they were not in vivo CYP1A1 substrates due to the lack of extrahepatic contribution to CLint. Only three drugs (riluzole, melatonin and ramelteon) that are CYP1A2 substrates yielded significant underprediction of in vivo CLint up to 11-fold. The fold of CLint underprediction was linearly proportional to human recombinant CYP1A1 (rCYP1A1) CLint, indicating they were likely to be in vivo CYP1A1 substrates. Using these three substrates, a calibration curve can be developed to enable direct translation from in vitro rCYP1A1 CLint to in vivo extrahepatic contributions in humans. In vivo CYP1A1 substrates are planar and small, which is consistent with the structure of the active site. This is in contrast to the in vitro substrates, which include large and nonplanar molecules, suggesting rCYP1A1 is more accessible than what is in vivo. The impact of CYP1A1 on first-pass intestinal metabolism was also evaluated and shown to be minimal. This is the first study providing new insights on in vivo translation of CYP1A1 contributions to human clearance using in vitro rCYP1A1 data.

Arsenic trioxide (ATO) up-regulates cytochrome P450 1A (CYP1A) enzymes in murine hepatoma Hepa-1c1c7 cell line

Arsenic trioxide (ATO) is a highly toxic arsenical which has been successfully exploited for treating acute promyelocytic leukemia (APL). Unfortunately, its therapeutic efficacy is accompanied by serious toxicities with undeciphered mechanisms. Cytochrome P450 1A (CYP1A) enzymes undergo modulation by arsenicals, with ensuing critical consequences regarding drug clearance or procarcinogen activation. Here, we investigated the potential of ATO to alter basal and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1/1A2 expressions. Mouse-derived hepatoma Hepa-1c1c7 cells were exposed to 0.63, 1.25, and 2.5μM ATO with or without 1nM TCDD. ATO increased TCDD-induced CYP1A1/1A2 mRNA, protein, and activity. Constitutively, ATO induced Cyp1a1/1a2 transcripts and CYP1A2 protein. ATO increased AHR nuclear accumulation and subsequently increased XRE-luciferase reporter activity. ATO enhanced CYP1A1 mRNA and protein stabilities. In conclusion, ATO up-regulates CYP1A in Hepa-1c1c7 cells transcriptionally, post-transcriptionally, and post-translationally. Therefore, ATO can be implicated in clearance-related interactions with CYP1A1/1A2 substrates, or in excessive activation of environmental procarcinogens.

Genic-intergenic polymorphisms of CYP1A genes and their clinical impact

The humancytochrome P450 1A (CYP1A) subfamily genes, CYP1A1 and CYP1A2, encoding monooxygenases are critically involved in biotransformation of key endogenous substrates (estradiol, arachidonic acid, cholesterol) and exogenous compounds (smoke constituents, carcinogens, caffeine, therapeutic drugs). This suggests their significant involvement in multiple biological pathways with a primary role of maintaining endogenous homeostasis and xenobiotic detoxification. Large interindividual variability exist in CYP1A gene expression and/or catalytic activity of the enzyme, which is primarily due to the existence of polymorphic alleles which encode them. These polymorphisms (mainly single nucleotide polymorphisms, SNPs) have been extensively studied as susceptibility factors in a spectrum of clinical phenotypes. An in-depth understanding of the effects of polymorphic CYP1A genes on the differential metabolic activity and the resulting biological pathways is needed to explain the clinical implications of CYP1A polymorphisms. The present review is intended to provide an integrated understanding of CYP1A metabolic activity with unique substrate specificity and their involvement in physiological and pathophysiological roles. The article further emphasizes on the impact of widely studied CYP1A1 and CYP1A2 SNPs and their complex interaction with non-genetic factors like smoking and caffeine intake on multiple clinical phenotypes. Finally, we attempted to discuss the alterations in metabolism/physiology concerning the polymorphic CYP1A genes, which may underlie the reported clinical associations. This knowledge may provide insights into the disease pathogenesis, risk stratification, response to therapy and potential drug targets for individuals with certain CYP1A genotypes.

Modulation of cytochrome P450 1A (CYP1A) enzymes by monomethylmonothioarsonic acid (MMMTAV) in vivo and in vitro

Inorganic arsenic (iAs) is a natural toxicant which, upon entering the biosphere, undergoes extensive biotransformation and becomes a portal for generating various organic intermediates/products. The chemical diversity of iAs-derived organoarsenicals (oAs) is accompanied by varying degree of toxicity that can be held responsible, at least partly, for the overall health outcome of the originally encountered parent inorganic molecule. Such toxicity may originate from arsenicals ability to modulate cytochrome P450 1A (CYP1A) enzymes, whose activity is critical in activating/detoxifying procarcinogens. In this study, we evaluated the effect of monomethylmonothioarsonic acid (MMMTA^V) on CYP1A1 and CYP1A2 in absence and presence of their inducer; 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Therefore, C57BL/6 mice were intraperitoneally injected with 12.5 mg/kg MMMTA^V, with or without 15 μg/kg TCDD for 6 and 24 h. Moreover, murine Hepa-1c1c7 and human HepG2 cells were treated with MMMTA^V (1, 5, and 10 μM), with or without 1 nM TCDD for 6 and 24 h. MMMTA^V significantly inhibited TCDD-mediated induction of CYP1A1 mRNA, both in vivo and in vitro. This effect was attributed to decreased transcriptional activation of CYP1A regulatory element. Interestingly, MMMTA^V significantly increased TCDD-induced CYP1A1 protein and activity in C57BL/6 mice and Hepa-1c1c7 cells, while both were significantly inhibited by MMMTA^V treatment in HepG2 cells. CYP1A2 mRNA, protein and activity induced by TCDD were significantly increased by MMMTA^V co-exposure. MMMTA^V had no effect on CYP1A1 mRNA stability or protein stability and did not alter their half-lives. At basal level, only CYP1A1 mRNA was significantly decreased in MMMTA^V-treated Hepa-1c1c7 cells. Our findings show that MMMTA^V exposure potentiates procarcinogen-induced catalytic activity of both CYP1A1 and CYP1A2 in vivo. This effect entails excessive activation of such procarcinogens upon co-exposure, with potentially negative health-related outcomes.

Down-regulation of hepatic cytochromes P450 1A1 and 1A2 by arsenic trioxide (ATO) in vivo and in vitro: A role of heme oxygenase 1

Arsenic trioxide (ATO) has evolved from an environmental threat to a successful therapy for acute promyelocytic leukemia (APL) and probably for solid tumors in the future. However, its efficacy comes at a cost of multi-organ toxicity whose mechanism remains unresolved. Arsenicals have been reported to modulate cytochrome P450 1A (CYP1A) enzymes, thus modifying activation/detoxification of drugs/procarcinogens. Therefore, this study aimed to investigate the possible effects of ATO on CYP1A1 and CYP1A2, in absence and presence of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) using in vivo and in vitro models. For this purpose, C57BL/6 mice were intraperitoneally injected with 8 mg/kg ATO with or without 15 μg/kg TCDD for 6 and 24 h. Furthermore, HepG2 cells were treated with ATO (1, 5, and 10 μM) with or without 1 nM TCDD for 6 and 24 h. ATO significantly inhibited TCDD-mediated induction of CYP1A1/1A2 mRNA, protein, and activity in both models. ATO differentially modulated CYP1A1/1A2 basal levels in vivo. We also demonstrated that ATO downregulates CYP1A through inhibiting the transcriptional activation of its regulatory element at both basal and inducible levels. Additionally, ATO significantly induced mRNA and protein of heme oxygenase 1 (HMOX1) in vivo and in vitro. In HepG2 cells, inhibition of HMOX1 by tin (IV) mesoporphyrin (IX) (SnMP) resulted in a partial restoration of the TCDD-mediated induction of CYP1A1 activity that was inhibited by ATO co-exposure. Our findings show that ATO alters both constitutive and inducible CYP1A1/1A2 expressions through transcriptional and HMOX1-mediated post-translational mechanisms. This implies the possible involvement of ATO in clearance-related consequences for the substrates of these enzymes such as drug-drug interactions or suboptimal toxicant elimination.

LC-MS-based assay of granisetron 7-hydroxylation activity for the evaluation of CYP1A1 induction from diesel particulate matter-exposed hepatic and respiratory cell lines

Particulate matter (PM) generally consists of aggregated particles containing trace metals and polycyclic aromatic hydrocarbons (PAHs). Cytochrome P450 (CYP) 1A1, one of the extensively investigated biomarkers, is highly inducible when PAHs activate the aryl hydrocarbon receptor (AhR). The present study focused on developing a LC-MS/MS-based assay to evaluate CYP1A1 induction potential following PM exposure. This assay adapted a CYP1A1 selective reaction of granisetron 7-hydroxylation in response to an AhR inducer, 6-formylindolo[3,2-b]carbazole (FICZ), in HepaRG and A549 cell lines. Exposure to FICZ (10 nM) increased the levels of granisetron 7-hydroxylation significantly, whereas no elevation of ethoxyresorufin-O-deethylation (EROD) activity was found in HepaRG cells. In A549 cells, granisetron 7-hydroxylation showed a better dose-response from 0 to 10000 nM FICZ treatment than EROD. EROD Additionally, the application of the assay with diesel PM exposure showed a concentration-dependent induction of CYP1A1 in HepaRG, A549, and human nasal epithelial cells. The granisetron assay has better selectivity for CYP1A1 than the conventional EROD assay, which is overlapped reaction with CYP1A2 and CYP1B1, with high correlations between AhR activation and CYP1A1 mRNA levels. Accompanying the great application potential to different organs and cell culture systems, future studies will implement the granisetron assay for the respiratory toxicity evaluation.

Recent advances in computational metabolite structure predictions and altered metabolic pathways assessment to inform drug development processes

Many drug candidates fail during preclinical and clinical trials due to variable or unexpected metabolism which may lead to variability in drug efficacy or adverse drug reactions. The drug metabolism field aims to address this important issue from many angles which range from the study of drug-drug interactions, pharmacogenomics, computational metabolic modeling, and others. This manuscript aims to provide brief but comprehensive manuscript summaries highlighting the conclusions and scientific importance of seven exceptional manuscripts published in recent years within the field of drug metabolism. Two main topics within the field are reviewed: novel computational metabolic modeling approaches which provide complex outputs beyond site of metabolism predictions, and experimental approaches designed to discern the impacts of interindividual variability and species differences on drug metabolism. The computational approaches discussed provide novel outputs in metabolite structure and formation likelihood and/or extend beyond the saturated field of drug phase I metabolism, while the experimental metabolic pathways assessments aim to highlight the impacts of genetic polymorphisms and clinical animal model metabolic differences on human metabolism and subsequent health outcomes.

Drug-Drug Interactions Involving Intestinal and Hepatic CYP1A Enzymes

Cytochrome P450 (CYP) 1A enzymes are considerably expressed in the human intestine and liver and involved in the biotransformation of about 10% of marketed drugs. Despite this doubtless clinical relevance, CYP1A1 and CYP1A2 are still somewhat underestimated in terms of unwanted side effects and drug–drug interactions of their respective substrates. In contrast to this, many frequently prescribed drugs that are subjected to extensive CYP1A-mediated metabolism show a narrow therapeutic index and serious adverse drug reactions. Consequently, those drugs are vulnerable to any kind of inhibition or induction in the expression and function of CYP1A. However, available in vitro data are not necessarily predictive for the occurrence of clinically relevant drug–drug interactions. Thus, this review aims to provide an up-to-date summary on the expression, regulation, function, and drug–drug interactions of CYP1A enzymes in humans.

In vitro-in vivo correlation of the drug-drug interaction potential of antiretroviral HIV treatment regimens on CYP1A1 substrate riociguat

Objectives: Riociguat is a soluble guanylate cyclase stimulator licensed for the treatment of pulmonary arterial hypertension (PAH), a potentially fatal complication of human immunodeficiency virus infection. This study investigated the inhibitory potency of selected antiretroviral regimens on the metabolic clearance of riociguat.Methods: The inhibitory potential of the components of six antiretroviral combinations (ATRIPLA® (efavirenz/emtricitabine/tenofovir disoproxil), COMPLERA® (rilpivirine/emtricitabine/tenofovir disoproxil), STRIBILD® (elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil), TRIUMEQ® (abacavir/dolutegravir/lamivudine), and two ritonavir-boosted regimens) on riociguat metabolism were evaluated in recombinant human CYP1A1 and CYP3A4 as well as in human hepatocytes exhibiting both CYP1A1 and CYP3A4 activity. In vitro-in vivo correlation was performed between calculated and observed increases in riociguat exposure in vivo.Results: Using both in vitro systems, the predicted increase in exposure of riociguat was highest with components of TRIUMEQ® followed by COMPLERA®, ATRIPLA®, STRIBILD®, and the ritonavir-boosted regimens. Further experiments in human hepatocytes confirmed CYP1A1 to be the predominant enzyme in the metabolic clearance of riociguat.Conclusion: Antiretroviral treatment containing the potent CYP1A1 inhibitor abacavir had the greatest impact on riociguat metabolic clearance. The impact of comedications containing only strong CYP3A4 inhibitors e.g. ritonavir was less pronounced, suggesting a benefit of riociguat over PAH-targeting medications with contraindications for use with strong CYP3A4 inhibitors.

A Physiologically Based Pharmacokinetic Model for Pregnant Women to Predict the Pharmacokinetics of Drugs Metabolized Via Several Enzymatic Pathways

BACKGROUND

Physiologically based pharmacokinetic modeling is considered a valuable tool for predicting pharmacokinetic changes in pregnancy to subsequently guide in-vivo pharmacokinetic trials in pregnant women. The objective of this study was to extend and verify a previously developed physiologically based pharmacokinetic model for pregnant women for the prediction of pharmacokinetics of drugs metabolized via several cytochrome P450 enzymes.

METHODS

Quantitative information on gestation-specific changes in enzyme activity available in the literature was incorporated in a pregnancy physiologically based pharmacokinetic model and the pharmacokinetics of eight drugs metabolized via one or multiple cytochrome P450 enzymes was predicted. The tested drugs were caffeine, midazolam, nifedipine, metoprolol, ondansetron, granisetron, diazepam, and metronidazole. Pharmacokinetic predictions were evaluated by comparison with in-vivo pharmacokinetic data obtained from the literature.

RESULTS

The pregnancy physiologically based pharmacokinetic model successfully predicted the pharmacokinetics of all tested drugs. The observed pregnancy-induced pharmacokinetic changes were qualitatively and quantitatively reasonably well predicted for all drugs. Ninety-seven percent of the mean plasma concentrations predicted in pregnant women fell within a twofold error range and 63% within a 1.25-fold error range. For all drugs, the predicted area under the concentration-time curve was within a 1.25-fold error range.

CONCLUSION

The presented pregnancy physiologically based pharmacokinetic model can quantitatively predict the pharmacokinetics of drugs that are metabolized via one or multiple cytochrome P450 enzymes by integrating prior knowledge of the pregnancy-related effect on these enzymes. This pregnancy physiologically based pharmacokinetic model may thus be used to identify potential exposure changes in pregnant women a priori and to eventually support informed decision making when clinical trials are designed in this special population.

Defining the Contribution of CYP1A1 and CYP1A2 to Drug Metabolism Using Humanized CYP1A1/1A2 and Cyp1a1/Cyp1a2 Knockout Mice

Cytochrome P450s CYP1A1 and CYP1A2 can metabolize a broad range of foreign compounds and drugs. However, these enzymes have significantly overlapping substrate specificities. To establish their relative contribution to drug metabolism in vivo, we used a combination of mice humanized for CYP1A1 and CYP1A2 together with mice nulled at the Cyp1a1 and Cyp1a2 gene loci. CYP1A2 was constitutively expressed in the liver, and both proteins were highly inducible by 2,3,7,8-tetrachlorodibenzodioxin (TCDD) in a number of tissues, including the liver, lung, kidney, and small intestine. Using the differential inhibition of the human enzymes by quinidine, we developed a method to distinguish the relative contribution of CYP1A1 or CYP1A2 in the metabolism of drugs and foreign compounds. Both enzymes made a significant contribution to the hepatic metabolism of the probe compounds 7-methoxy and 7-ehthoxyresorufin in microsomal fractions from animals treated with TCDD. This enzyme kinetic approach allows modeling of the CYP1A1, CYP1A2, and non-CYP1A contribution to the metabolism of any substrate at any substrate, inhibitor, or enzyme concentration and, as a consequence, can be integrated into a physiologically based pharmacokinetics model. The validity of the model can then be tested in humanized mice in vivo. SIGNIFICANCE STATEMENT: Human CYP1A1 and CYP1A2 are important in defining the efficacy and toxicity/carcinogenicity of drugs and foreign compounds. In light of differences in substrate specificity and sensitivity to inhibitors, it is of central importance to understand their relative role in foreign compound metabolism. To address this issue, we have generated mice humanized or nulled at the Cyp1a gene locus and, through the use of these mouse lines and selective inhibitors, developed an enzyme kinetic-based model to enable more accurate prediction of the fate of new chemicals in humans and which can be validated in vivo using mice humanized for cytochrome P450-mediated metabolism.

The Toll-like receptor agonist imiquimod is metabolized by aryl hydrocarbon receptor-regulated cytochrome P450 enzymes in human keratinocytes and mouse liver

The Toll-like receptor 7 agonist imiquimod (IMQ) is an approved drug for the topical treatment of various skin diseases that, in addition, is currently tested in multiple clinical trials for the immunotherapy of various types of cancers. As all of these trials include application of IMQ to the skin and evidence exists that exposure to environmental pollutants, i.e., tobacco smoke, affects its therapeutic efficacy, the current study aims to elucidate the cutaneous metabolism of the drug. Treatment of human keratinocytes with 2.5 µM benzo[a]pyrene (BaP), a tobacco smoke constituent and aryl hydrocarbon receptor (AHR) agonist, for 24 h induced cytochrome P450 (CYP) 1A enzyme activity. The addition of IMQ 30 min prior measurement resulted in a dose-dependent inhibition of CYP1A activity, indicating that IMQ is either a substrate or inhibitor of CYP1A isoforms. Incubation of 21 recombinant human CYP enzymes with 0.5 µM IMQ and subsequent LC-MS analyses, in fact, identified CYP1A1 and CYP1A2 as being predominantly responsible for IMQ metabolism. Accordingly, treatment of keratinocytes with BaP accelerated IMQ clearance and the associated formation of monohydroxylated IMQ metabolites. A co-incubation with 5 µM 7-hydroxyflavone, a potent inhibitor of human CYP1A isoforms, abolished basal as well as BaP-induced IMQ metabolism. Further studies with hepatic microsomes from CD-1 as well as solvent- and β-naphthoflavone-treated CYP1A1/CYP1A2 double knock-out and respective control mice confirmed the critical contribution of CYP1A isoforms to IMQ metabolism. Hence, an exposure to life style-related, dietary, and environmental AHR ligands may affect the pharmacokinetics and, thus, treatment efficacy of IMQ.

Intestinal Microbiota Mediates the Susceptibility to Polymicrobial Sepsis-Induced Liver Injury by Granisetron Generation in Mice

Sepsis-induced liver injury is recognized as a key problem in intensive care units. The gut microbiota has been touted as an important mediator of liver disease development; however, the precise roles of gut microbiota in regulating sepsis-induced liver injury are unknown. Here, we aimed to investigate the role of the gut microbiota in sepsis-induced liver injury and the underlying mechanism. Cecal ligation and puncture (CLP) was used to induce polymicrobial sepsis and related liver injury. Fecal microbiota transplantation (FMT) was used to validate the roles of gut microbiota in these pathologies. Metabolomics analysis was performed to characterize the metabolic profile differences between sepsis-resistant (Res; survived to 7 days after CLP) and sepsis-sensitive (Sen; moribund before or approximately 24 hours after CLP) mice. Mice gavaged with feces from Sen mice displayed more-severe liver damage than did mice gavaged with feces from Res mice. The gut microbial metabolic profile between Sen and Res mice was different. In particular, the microbiota from Res mice generated more granisetron, a 5-hydroxytryptamine 3 (5-HT₃ ) receptor antagonist, than the microbiota from Sen mice. Granisetron protected mice against CLP-induced death and liver injury. Moreover, proinflammatory cytokine expression by macrophages after lipopolysaccharide (LPS) challenge was markedly reduced in the presence of granisetron. Both treatment with granisetron and genetic knockdown of the 5-HT_3A receptor in cells suppressed nuclear factor kappa B (NF-кB) transactivation and phosphorylated p38 (p-p38) accumulation in macrophages. Gut microbial granisetron levels showed a significantly negative correlation with plasma alanine aminotransferase (ALT)/aspartate aminotransferase (AST) levels in septic patients. Conclusion: Our study indicated that gut microbiota plays a key role in the sensitization of sepsis-induced liver injury and associates granisetron as a hepatoprotective compound during sepsis development.

Chemical activation of estrogen and aryl hydrocarbon receptor signaling pathways and their interaction in toxicology and metabolism

INTRODUCTION

Estrogen receptors (ERs) and the arylhydrocarbon receptor (AHR) are ligand-activated transcription factors that regulate the expression of genes involved in many physiological processes. With both receptors binding a broad range of natural and anthropogenic ligands, they are molecular targets for many substances, raising concerns for possible health effects. Areas covered: This review shall give a brief overview on the physiological functions of both receptors including their underlying molecular mechanisms. It summarizes the interaction of the respective signaling pathways including impacts on metabolism of endogenous estrogens, transcriptional interference, inhibitory crosstalk, and proteasomal degradation. Also addressed are the AHR dependent formation of estrogenic metabolites from polycyclic aromatic hydrocarbons and the possible impact of the ER/AHR crosstalk in the context of drug metabolism. Expert opinion: Despite decade-long research, the physiological role of the AHR and ER as well as the implications of their complex mutual crosstalk remain to be determined as do resulting potential impacts on human health. With more and more endogenous AHR ligands being discovered, future research should hence systematically address the potential impact of such substances on estrogen signaling. The intimate link between these two pathways and the genes regulated therein bears the potential for impacts on drug metabolism and human health.

In situ polymerization and FT-IR characterization of poly-glycine on pencil graphite electrode for sensitive determination of anti-emetic drug, granisetron in injections and human plasma

In situ polymerization is a simple and efficient technique for modification and fabrication of modified electrodes in voltammetry. An efficient and highly sensitive square wave voltammetric (SWV) method was developed for analysis of a 5-HT₃ antagonist granisetron (GRN) using in situ polymerized glycine on pencil graphite electrode surface. It was found that the fabricated polymer enhanced the sensitivity by more than two times and enhanced the surface activity by more than three times. Surface area measurements showed that poly-Gly/PGE have large surface area of 44.3 mm², when compared to that of bare PEG (12.1 mm²). Several methods as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) techniques were used to characterize the modified surface. Further, FT-IR spectroscopic study was used to predict the way of glycine polymerization on electrode surface and the possible interaction mechanism with GRN. After optimization, the proposed method showed a linear response of GRN concentrations in the range from 0.08 to 3.00 μmol L⁻¹ with a limit of detection (LOD) of 26.2 nmol L⁻¹ (9.14 ng mL⁻¹). The method was utilized for GRN determination in ampoules and in real human plasma samples.

In situ polymerization is a simple and efficient technique for modification and fabrication of modified electrodes in voltammetry.

Recent advances in antiemetics: new formulations of 5HT3-receptor antagonists

Purpose

To discuss new therapeutic strategies for chemotherapy-induced nausea and vomiting (CINV) involving 5-hydroxytryptamine type 3 (5HT₃)-receptor antagonists (RAs).

Summary

CINV remains poorly controlled in patients receiving moderately emetogenic chemotherapy (MEC) or highly emetogenic chemotherapy (HEC); nausea and delayed-phase CINV (24-120 hours after chemotherapy) are the most difficult to control. National Comprehensive Cancer Network (NCCN) and American Society of Clinical Oncology (ASCO) antiemesis-guideline recommendations for HEC include a four-drug regimen (5HT₃ RA, neurokinin 1 [NK₁] RA, dexamethasone, and olanzapine). For some MEC regimens, a three-drug regimen (5HT₃ RA, NK₁ RA, and dexamethasone) is recommended. While 5HT₃ RAs have dramatically improved CINV in the acute phase (0-24 hours after chemotherapy), their efficacy declines in the delayed phase. Newer formulations have been developed to extend 5HT₃-RA efficacy into the delayed phase. Granisetron extended-release subcutaneous (GERSC), the most recently approved 5HT₃ RA, provides slow, controlled release of therapeutic granisetron concentrations for ≥5 days. GERSC is included in the NCCN and ASCO guidelines for MEC and HEC, with NCCN-preferred status for MEC in the absence of an NK₁ RA. Efficacy and safety of 5HT₃ RAs in the context of guideline-recommended antiemetic therapy are reviewed.

Conclusion

Recent updates in antiemetic guidelines and the development of newer antiemet-ics should help mitigate CINV, this dreaded side effect of chemotherapy. GERSC, the most recently approved 5HT₃-RA formulation, is indicated for use with other antiemetics to prevent acute and delayed nausea and vomiting associated with initial and repeat courses of MEC and anthracycline-cyclophosphamide combination-chemotherapy regimens.

Polymorphisms in CYP1A1 and CYP3A5 Genes Contribute to the Variability in Granisetron Clearance and Exposure in Pregnant Women with Nausea and Vomiting

BACKGROUND

Nausea and vomiting affect up to 90% of pregnant women. Granisetron is a potent and highly selective serotonin receptor antagonist and is an effective antiemetic. Findings from a prior study in pregnant women demonstrated a large interindividual variability in granisetron exposure. Granisetron is primarily metabolized by the cytochrome P450 (CYP) enzymes CYP1A1 and CYP3A and is likely a substrate of the ABCB1 transporter. Single-nucleotide polymorphisms (SNPs) in CYP3A, CYP1A1, and ABCB1 can alter drug metabolism.

OBJECTIVE

This study evaluated the influence of polymorphisms in CYP3A4, CYP3A5, CYP1A1, and ABCB1 on the pharmacokinetic properties of granisetron in pregnant women.

METHODS

The study enrolled 16 pregnant women (gestational age of 12-19 wks). All patients had nausea and vomiting and were treated with granisetron 1 mg. Granisetron plasma concentrations were determined using liquid chromatography tandem-mass spectrometry. The patients' genotype was determined using TaqMan SNP Genotyping Assays. The Hardy-Weinberg equilibrium was assessed by comparing observed and expected genotype frequencies, using the exact test. Intravenous granisetron clearance was used as the dependent variable for analysis of associations.

RESULTS

Of 16 patients, 25% were homozygous for the allele variant CYP3A5*3 and had a significantly lower granisetron clearance and increased area under the plasma concentration-versus-time curve (AUC) compared with nonhomozygous patients. Approximately one-third of patients (n=5) were carriers for the allele variant CYP1A1*2A and had a significantly higher granisetron clearance and decreased AUC. We did not find significant differences in the AUC or clearance for any SNPs in CYP3A4 and ABCB1 genes.

CONCLUSIONS

Polymorphisms in CYP3A5 and CYP1A1 account for some of the variability in systemic clearance and exposure of granisetron in pregnant women.

Effect of casopitant, a novel NK-1 antagonist, on the pharmacokinetics of dolasetron and granisetron

OBJECTIVE

The objective of this study was to characterize the impact of casopitant, a novel neurokinin-1 receptor antagonist under investigation for the prevention of postoperative and chemotherapy-induced nausea and vomiting, on the pharmacokinetics of the commonly prescribed 5-hydroxytryptamine receptor 3 receptor antagonists, dolasetron or granisetron.

MATERIALS AND METHODS

In a phase I, open-label, two-part, two-period, single-sequence study, two cohorts of healthy subjects received either oral dolasetron (100 mg once daily for 3 days) or oral granisetron (2 mg once daily for 3 days) alone (period 1) and combined with oral casopitant, 150 mg day 1, 50 mg days 2 and 3 (period 2). Pharmacokinetics of hydrodolasetron and granisetron were assessed on days 1 and 3 of each period. Log-transformed area under the curve (AUC) and Cmax were statistically analyzed by performing an analysis of variance. Eighteen subjects were enrolled in the dolasetron cohort; nine subjects were CYP2D6 extensive metabolizers (EMs) and nine subjects were CYP2D6 poor metabolizers. Nineteen subjects were enrolled in the granisetron cohort.

RESULTS

The largest changes in hydrodolasetron exposure after coadministration with casopitant were seen in CYP2D6 EMs, with a 24% increase in hydrodolasetron AUC on day 1 and 30% increase in Cmax on days 1 and 3. All other changes in hydrodolasetron exposure were <20%, and granisetron exposure was not altered to any relevant extent (<11%).

CONCLUSION

None of the changes observed are considered clinically meaningful, and coadministration of casopitant with dolasetron or granisetron was well tolerated.