Inhibition of human cytochrome P450 enzymes by the natural hepatotoxin safrole

Piper auritum ethanol extract is a potent antimutagen against food-borne aromatic amines: mechanisms of action and chemical composition

An ethanol extract of Piper auritum leaves (PAEE) inhibits the mutagenic effect of three food-borne aromatic amines (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP); 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx); 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx)) in the TA98 Salmonella typhimurium strain. Preincubation with MeIQx demonstrated in mutagenesis experiments that inhibition of Cytochrome P450 (CYP), as well as direct interaction between component(s) of the plant extract with mutagens, might account for the antimutagenic observed effect. Gas chromatography/mass spectrometry analysis revealed that safrole (50.7%), α-copaene (7.7%), caryophyllene (7.2%), β-pinene (4.2%), γ-terpinene (4.1%), and pentadecane (4.1%) as the main components (PAEE). Piper extract and safrole were able to inhibit the rat liver microsomal CYP1A1 activity that participates in the amines metabolism, leading to the formation of the ultimate mutagenic/ molecules. According to this, safrole and PAEE-inhibited MeIQx mutagenicity but not that of the direct mutagen 2-nitrofluorene. No mutagenicity of plant extract or safrole was detected. This study shows that PAEE and its main component safrole are associated with the inhibition of heterocyclic amines activation due in part to the inhibition of CYP1A subfamily activity.

Apiole, an important constituent of parsley, is a mixed-type inhibitor of the CYP1A subfamily

Apiole (1-allyl-2,5-dimethoxy-3,4-methylenedioxybenzene) and parsley leaves ethanolic extract containing it inhibit the rat liver microsomal ethoxy- and methoxyresorufin-O-deacetylase activities associated with cytochrome P450 (CYP) 1A1 and 1A2, respectively. Cytochrome P4501A subfamily metabolizes environmental mutagens and several drugs, leading to the formation of mutagenic metabolites. Docking analysis showed that residue Phe123 within the active site of the CYP1A1 enzyme is bound to apiole through a π/π stacking of its benzene ring. In the case of 1A2, its Phe226 interacts with the dioxolane ring of apiole. Furthermore, apiole behaves as a mixed-type inhibitor of bacterial human recombinant CYP1A1. To explore one of the possible biological implications of this inhibitory effect, we tested the capacity of apiole and the parsley ethanolic extract to interfere with the mutagenicity of the promutagen 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) metabolized by CYP1A subfamily. As expected, both apiole and the plant extract reduced the number of revertant colonies of Salmonella typhimurium TA98 Ames strain after exposure to MeIQx, reaching a 78 % and 100 % reduction, respectively. Neither apiol nor parsley extract were mutagenic to the TA98 strain. We speculate that consuming apiole, a constituent of edible herbs, in conjunction with the utilization of pharmaceuticals metabolized by the CYP1A subfamily, may result in herb-drug interactions. Furthermore, the consumption of apiole by individuals who regularly ingest fresh vegetables may contribute to the low incidence of cancer observed in those who adhere to such a dietary regimen.

Systematic Review of Naturally Derived Substances That Act as Inhibitors of the Nicotine Metabolizing Enzyme Cytochrome P450 2A6

Tobacco smoking has been highlighted as a major health challenge in modern societies. Despite not causing death directly, smoking has been associated with several health issues, such as cardiovascular diseases, respiratory disorders, and several cancer types. Moreover, exposure to nicotine during pregnancy has been associated with adverse neurological disorders in babies. Nicotine Replacement Therapy (NRT) is the most common strategy employed for smoking cessation, but despite its widespread use, NRT presents with low success and adherence rates. This is attributed partially to the rate of nicotine metabolism by cytochrome P450 2A6 (CYP2A6) in each individual. Nicotine addiction is correlated with the high rate of its metabolism, and thus, novel strategies need to be implemented in NRT protocols. Naturally derived products are a cost-efficient and rich source for potential inhibitors, with the main advantages being their abundance and ease of isolation. This systematic review aims to summarize the natural products that have been identified as CYP2A6 inhibitors, validated through in vitro and/or in vivo assays, and could be implemented as nicotine metabolism inhibitors. The scope is to present the different compounds and highlight their possible implementation in NRT strategies. Additionally, this information would provide valuable insight regarding CYP2A6 inhibitors, that can be utilized in drug development via the use of in silico methodologies and machine-learning models to identify new potential lead compounds for optimization and implementation in NRT regimes.

Interactions of Betel Quid Constituents with Drug Disposition Pathways: An Overview

Global estimates indicate that over 600 million individuals worldwide consume the areca (betel) nut in some form. Nonetheless, its consumption is associated with a myriad of oral and systemic ailments, such as precancerous oral lesions, oropharyngeal cancers, liver toxicity and hepatic carcinoma, cardiovascular distress, and addiction. Users commonly chew slivers of areca nut in a complex consumable preparation called betel quid (BQ). Consequently, the user is exposed to a wide array of chemicals with diverse pharmacokinetic behavior in the body. However, a comprehensive understanding of the metabolic pathways significant to BQ chemicals is lacking. Henceforth, we performed a literature search to identify prominent BQ constituents and examine each chemical's interplay with drug disposition proteins. In total, we uncovered over 20 major chemicals (e.g., arecoline, nicotine, menthol, quercetin, tannic acid) present in the BQ mixture that were substrates, inhibitors, and/or inducers of various phase I (e.g., CYP, FMO, hydrolases) and phase II (e.g., GST, UGT, SULT) drug metabolizing enzymes, along with several transporters (e.g., P-gp, BCRP, MRP). Altogether, over 80 potential interactivities were found. Utilizing this new information, we generated theoretical predictions of drug interactions precipitated by BQ consumption. Data suggests that BQ consumers are at risk for drug interactions (and possible adverse effects) when co-ingesting other substances (multiple therapeutic classes) with overlapping elimination mechanisms. Until now, prediction about interactions is not widely known among BQ consumers and their clinicians. Further research is necessary based on our speculations to elucidate the biological ramifications of specific BQ-induced interactions and to take measures that improve the health of BQ consumers.

Refined CYP2E1∗ Template∗∗ system to decipher the ligand-interactions

A Template system for a prediction of human CYP2E1-mediated reactions (Drug Metab Rev 2011) has been refined with the introduction of ideas of Trigger-residue and the residue-initiated movement of ligands in the active site. The refined system also includes ideas of bi-molecule binding and angled-placement, which allow to sit diverse types of ligands on Template. With the use of these ideas in common with other Template systems for human CYP1A1, CYP1A2 and CYP3A4 (Drug Metab Pharmacokinet 2016, 2017, 2019, and 2020), 349 reactions of 192 distinct chemicals published as CYP2E1 ligands were examined in the refined system. Verifications of good and poor substrates, regioselectivity and also inhibitory interaction were available faithfully for these ligands from their placements on the refined Template and rules for interaction modes, accompanied with their deciphering information to lead to the judgements. The refined CYP2E1 Template system will thus offer more reliable estimations of human CYP2E1 catalysis toward ligands of diverse structures.

Betel quid containing safrole enhances metabolic activation of tobacco specific 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)

Cigarette smoking (CS) and betel quid (BQ) chewing are two known risk factors that have synergistic potential for the enhancing the development of oral squamous cell carcinoma (OSCC) in Taiwan. Most mutagens and carcinogens are metabolically activated by cytochrome P450 (CYP450) to exert their mutagenicity or carcinogenicity. Previous studies have shown that metabolic activation of the tobacco-specific nitrosamine, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), by CYP2A6 activity determines NNK-induced carcinogenesis. In addition, safrole affects cytochrome P450 activity in rodents. However, the effect of BQ safrole on the metabolism of tobacco-specific NNK and its carcinogenicity remains elusive. This study demonstrates that safrole (1 mg/kg/d) induced CYP2A6 activity, reduced urinary 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) levels, and increased NNK-induced DNA damage, including N7-methylguanine, 8-OH-deoxyguanosine and DNA strand breaks in a Syrian golden hamster model. Furthermore, altered NNK metabolism and increased NNK-induced DNA damage were also observed in healthy subjects with CS and BQ chewing histories compared to healthy subjects with CS histories. In conclusion, BQ containing safrole induced tobacco-specific NNK metabolic activation, resulting in higher NNK-induced genotoxicity. This study provides valuable insight into the synergistic mechanisms of CS- and BQ-induced OSCC.

The Effect of Yokukansan, a Traditional Herbal Preparation Used for the Behavioral and Psychological Symptoms of Dementia, on the Drug-Metabolizing Enzyme Activities in Healthy Male Volunteers

The concomitant use of herb and prescription medications is increasing globally. Herb-drug interactions are therefore a clinically important problem. Yokukansan (YKS), a Japanese traditional herbal medicine, is one of the most frequently used herbal medicines. It is effective for treating the behavioral and psychological symptoms of dementia. We investigated the potential effects of YKS on drug-metabolizing enzyme activities in humans. An open-label repeat-dose study was conducted in 26 healthy Japanese male volunteers (age: 22.7±2.3 years) with no history of smoking. An 8-h urine sample was collected after a 150-mg dose of caffeine and a 30-mg dose of dextromethorphan before and after the administration of YKS (2.5 g, twice a day for 1 week). The activities of cytochrome P450 (CYP) 1A2, CYP2D6, CYP3A, xanthine oxidase (XO) and N-acetyltransferase 2 (NAT2) were assessed based on the urinary metabolic indices of caffeine and dextromethorphan, and the urinary excretion ratio of 6β-hydroxycortisol to cortisol. There were no statistically significant differences in the activities of the examined enzymes before or after the 7-d administration of YKS. Although further studies assessing the influence of YKS on the pharmacokinetics and pharmacodynamics of the substrates of the drug-metabolizing enzymes are needed to verify the present results, YKS is unlikely that a pharmacokinetic interaction will occur with concomitantly administered medications that are predominantly metabolized by the CYP1A2, CYP2D6, CYP3A, XO and NAT2.

Review of Scientific Evidence of Medicinal Convoy Plants in Traditional Persian Medicine

One concept used in traditional Persian medicine (TPM) for multidrug therapy is that of the convoy drug (Mobadregh). According to TPM texts, convoy drugs are substances (or drugs), which facilitate the access of drugs or foods to the whole body or to specific organs. This study reviewed some convoy drugs presented in TPM, their biological effects, and their probable interactions with main drugs, considering the increased absorption through inhibition of P-glycoprotein (P-gp) efflux function, bioavailability-enhancing effects, and decreased metabolism of the main drug using electronic databases including PubMed, Scopus, ScienceDirect, and Google Scholar in November and December, 2013. Recent studies have proven the beneficial effects of Crocus sativus L. (saffron) and camphor on the heart and brain, the cerebral therapeutic effects of Asarum europaeum (hazelwort), the hepatoprotective effects of Cichorium intybus (chicory), and Apium graveolens (celery) seeds, and the diuretic effects of Cinnamomum zeylanicum (cinnamon), and Cucumis melo (melon) seeds. The effects of vinegar in targeting the liver and brain have also been demonstrated. An evaluation of the results demonstrated that the suggested convoy drugs, including Piper nigrum (black pepper), Piper longum (long pepper), red wine, Camellia sinensis (tea), hazelwort, Mentha longifolia (pennyroyal), Anethum graveolens (dill), Foeniculum vulgare (fennel), cinnamon, and Sassafras albidum (sassafras) can increase the bioavailability of coadministered drugs by inhibition of P-gp or cytochrome P450s (CYP450s) or both of them. This evidence could be a good basis for the use of these agents as convoys in TPM.

Stimulatory effect of sesamin on hepatic cytochrome P450 activities in Atlantic salmon (Salmo salar L.) is not directly associated with expression of genes related to xenobiotic metabolism

1. This study examined hepatic cytochrome P450 (CYP450) response to dietary sesamin in combination with different n-6/n-3 fatty acid ratios in fish diet. Over a period of 4 months, fish were fed seven different experimental diets an n-6/n-3 FA ratio of either 0.5 or 1.0 in combination with two sesamin levels: low sesamin = 1.16 g/kg feed and high sesamin = 5.8 g/kg feed. Control diets did not contain sesamin. 2. The CYP450-associated activities of ethoxyresorufin O-deethylase (EROD), 7-benzyloxy-4-trifluoromethylcoumarin O-debenzylation (BFCOD), pentoxyresorufin O-depentylase (PROD), coumarin hydroxylase (COH), methoxyresorufin O-deethylase (MROD) and p-nitrophenol hydroxylase (PNPH) were significantly induced by dietary sesamin in a dose-related manner. 3. Expressions of the genes CYP1A1, CYP1A3, CYP3A, AhR1α, AhR2β, AhR2δ and PXR involved in the regulation of CYP450 activities, was not the primary source of this induction.

Nicotine causes genotoxic damage but is not metabolized during long-term exposure of human nasal miniorgan cultures

Human nasal miniorgan cultures (MOC) are a useful tool in ecogenotoxicology. Repetitive exposure to nicotine showed reversible DNA damage, and stable CYP2A6 expression was demonstrated in nasal MOC in previous investigations. The aim of the present study was to evaluate the genotoxic effect of nicotine in nasal MOC after chronic nicotine exposure, and to monitor possible metabolism capacities. MOC were dissected from human nasal mucosa and cultured under standard cell culture conditions. MOC were exposed to nicotine for 3 weeks at concentrations of 1 μM and 1 mM. The concentrations were chosen based on nicotine plasma levels in heavy smokers, and possible concentrations used in topical application of nicotine nasal spray. DNA damage was assessed by the comet assay at days 7, 14 and 21. Concentrations of nicotine and cotinine were analyzed in cell culture medium by gas chromatography/mass spectrometry to determine a possible metabolism of nicotine by MOC. Distinct DNA damage in MOC could be demonstrated after 1 week of exposure to 1 μM and 1 mM nicotine. This effect decreased after 2 and 3 weeks with no statistically relevant DNA migration. No nicotine metabolism could be detected by changes in nicotine and cotinine concentrations in the supernatants. This is the first time genotoxic effects have been evaluated in nasal MOC after chronic nicotine exposure for up to 3 weeks. Genotoxic effects were present after 1 week of culture with a decrease over time. Down-regulation of nicotinic acetylcholine receptors, which are expressed in nasal mucosa, may be a possible explanation. The lack of nicotine metabolism in this model could be explained by the functional loss of CYP2A6 during chronic nicotine exposure. Further investigations are necessary to provide a more detailed description of the underlying mechanisms involved in DNA damage by nicotine.

Construction of a CYP2E1-template system for prediction of the metabolism on both site and preference order

We have constructed an in silico system for the prediction of CYP2E1-mediated reaction using a two-dimensional template derived from substrate structures. Although CYP2E1 prefers small-size molecules for the substrates, the enzyme mediates oxidations of large-size molecules, such as benzo[a]pyrene. Overlays of these substrates, to assemble their sites of oxidation into a specific area, suggested a range of regions frequently occupied. The region, having a benzo[a]pyrene-like shape, was thus used as a CYP2E1 template. In this system, atoms in substrates, except for hydrogen atoms, were placed on corners of honeycomb structures of the template after having expanded the structures. Using published data for the metabolism on more than 80 substrates of CYP2E1, the core template was further refined to verify the adjacent area and to define the relative contribution of template positions for the catalysis. The positions on the template were classified into four different point (0-3) groups, depending on relative usage. In addition, we set independent points (-5 to 3) for specific positions to incorporate three-dimensional or functional information. Total scores from both position-occupancy and -function points were calculated for all the orientations of possible conformers of test substrates, and the scores were found to predict the relative abundance (i.e., order) as well as the regioselectivity of human CYP2E1 reactions with high fidelities.

Toxicological actions of plant-derived and anthropogenic methylenedioxyphenyl-substituted chemicals in mammals and insects

The methylenedioxyphenyl (MDP) substituent is a structural feature present in many plant chemicals that deter foraging by predatory insects and herbivores. With increasing use of herbal extracts in alternative medicine, human exposure to MDP-derived plant chemicals may also be significant. Early studies found that most MDP agents themselves possess relatively low intrinsic toxicity, but strongly influence the actions of other xenobiotics in mammals and insects by modulating cytochrome P-450 (CYP)-dependent biotransformation. Thus, after exposure to MDP chemicals an initial phase of CYP inhibition is followed by a sustained phase of CYP induction. In insects CYP inhibition by MDP agents underlies their use as pesticide synergists, but analogous inhibition of mammalian CYP impairs the clearance of drugs and foreign compounds. Conversely, induction of mammalian CYP by MDP agents increases xenobiotic oxidation capacity. Exposure of insects to MDP-containing synergists in the environment, in the absence of coadministered pesticides, may also enhance xenobiotic detoxication. Finally, although most MDP agents are well tolerated, several, typified by safrole, aristolochic acid, and MDP-kavalactones, are associated with significant toxicities, including the risk of hepatotoxicity or tumorigenesis. Thus, the presence of MDP-substituted chemicals in the environment may produce a range of direct and indirect toxicities in target and nontarget species.

Bioactivities of Piper aduncum L. and Piper obliquum Ruiz & Pavon (Piperaceae) essential oils from Eastern Ecuador

Essential oils from aerial parts of Piper aduncum (Matico) and Piper obliquum (Anis del Oriente) of ecuadorian origin were analyzed by GC-FID, GC-MS, (13)C NMR and their biological and pharmacological activities were assessed. Chemical composition proved to be unusually different from previous reports for safrole-rich P. obliquum (45.8%), while P. aduncum main constituent was dillapiol (45.9%). No genotoxic activity was found in the Ames/Salmonella typhimurium (TA98 and TA100) assay, either with or without S9 activation. Mutagen-protective properties, evaluated using sodium azide, 2-nitrofluorene and 2-aminoanthracene as mutagens/promutagens, was observed against promutagen 2-aminoanthracene, likely in consequence of microsomial deactivation. Antimicrobial assays have been performed on Gram+/Gram- bacteria, dermatophyte and phytopathogenic fungi and best results were provided by P. aduncum against fungal strains with complete inhibition at 500μg/ml. Preliminary analgesic and antithrombotic activities evidenced the absence of the former in hot plate and edema assays and a limited antiplatelet action against three different agonists (ADP, AA and U46619). Both oils have a very limited antioxidant capacity.

Ethnogenetic layering (EL): an alternative to the traditional race model in human variation and health disparity studies

BACKGROUND

Traditionally, studies in human biodiversity, disease risk, and health disparities have defined populations in the context of typological racial models. However, such racial models are often imprecise generalizations that fail to capture important local patterns of human biodiversity.

AIM

More explicit, detailed, and integrated information on relevant geographic, environmental, cultural, genetic, historical, and demographic variables are needed to understand local group expressions of disease inequities. This paper details the methods used in ethnogenetic layering (EL), a non-typological alternative to the current reliance of the biological racial paradigm in public health, epidemiology, and biomedicine.

SUBJECTS AND METHODS

EL is focused on geographically identified microethnic groups or MEGs, a more nuanced and sensitive level of analysis than race. Using the MEG level of analysis, EL reveals clinical variations, details the causes of health disparities, and provides a foundation for bioculturally effective intervention strategies. EL relies on computational approaches by using GIS-facilitated maps to produce horizontally stratified geographical regional profiles which are then stacked and evaluated vertically. Each horizontal digital map details local geographic variation in the attributes of a particular database; usually this includes data on local historical demography, genetic diversity, cultural patterns, and specific chronic disease risks (e.g. dietary and toxicological exposures). Horizontal visual display of these layered maps permits vertical analysis at various geographic hot spots.

RESULTS AND CONCLUSIONS

From these analyses, geographical areas and their associated MEGs with highly correlated chronic disease risk factors can be identified and targeted for further study.

Illuminating cancer health disparities using ethnogenetic layering (EL) and phenotype segregation network analysis (PSNA)

BACKGROUND

Resolving cancer health disparities continues to befuddle simplistic racial models. The racial groups alluded to in biomedicine, public health, and epidemiology are often profoundly substructured.

METHODS

EL and PSNA are computational assisted techniques that focus on microethnic group (MEG) substructure.

RESULTS

Geographical variations in cancer may be due to differences in MEG ancestry or similar environmental exposures to a recognized carcinogen. Examples include breast and prostate cancers in the Chesapeake Bay region and Bight of Biafra biological ancestry, hypertension and stroke in the Carolina Coast region and Central African biological ancestry, and pancreatic cancer in the Mississippi Delta region and dietary/medicinal exposure to safrol from Sassafras albidum.