P450 1A2 Research Articles

Tris (2,3-Dibromopropyl) Isocyanurate (TDBP-TAZTO or TBC) Shows Different Toxicity Depending on the Degree of Differentiation of the Human Neuroblastoma (SH-SY5Y) Cell Line

Tris (2,3-dibromopropyl) isocyanurate (TDBP-TAZTO or TBC) is a heterocyclic hexabromated flame retardant. It is widely used during the production of many synthetic compounds. High concentrations of TDBP-TAZTO were found in river water, surface sediments, soil, earthworms, and carp tissues. Moreover, it has been shown that this compound can cross the blood–brain barrier and accumulate in the gut and brain of carp. The aryl hydrocarbon receptor (AhR) has been characterized as a multifunctional intracellular sensor and receptor. AhR is an activator of cytochrome P450 1A1 and 1A2, which metabolize various toxic compounds. The aim of the study was to explain how/whether TDBP-TAZTO increases the expression and/or activity of the CYP1A1 enzyme and the AhR and TUBB3 expression during SH-SY5Y cell differentiation. SH-SY5Y cells were differentiated for 7 and 14 days using retinoic acid. Cell viability, ethoxyresorufin-O-deethylase (EROD) activity, and mRNA expression of CYP1A1, AhR, and TUBB3 were assessed. Our experiment showed that, during the differentiation process, the ability of TDBP-TAZTO to induce EROD activity in SH-SY5Y cells subsequently decreased, which may have been an effect of cell differentiation into neurons. Moreover, the results suggest that TDBP-TAZTO can affect the differentiation process. Since no CYP2B6 mRNA expression was detected, the CAR receptor may not be involved in the TDBP-TAZTO mechanism of action. However, more research is needed in this field to elucidate this mechanism precisely.

Functional Characterization of 21 Rare Allelic CYP1A2 Variants Identified in a Population of 4773 Japanese Individuals by Assessing Phenacetin O-Deethylation.

Cytochrome P450 1A2 (CYP1A2), which accounts for approximately 13% of the total hepatic cytochrome content, catalyzes the metabolic reactions of approximately 9% of frequently used drugs, including theophylline and olanzapine. Substantial inter-individual differences in enzymatic activity have been observed among patients, which could be caused by genetic polymorphisms. Therefore, we functionally characterized 21 novel CYP1A2 variants identified in 4773 Japanese individuals by determining the kinetic parameters of phenacetin O-deethylation. Our results showed that most of the evaluated variants exhibited decreased or no enzymatic activity, which may be attributed to potential structural alterations. Notably, the Leu98Gln, Gly233Arg, Ser380del Gly454Asp, and Arg457Trp variants did not exhibit quantifiable enzymatic activity. Additionally, three-dimensional (3D) docking analyses were performed to further understand the underlying mechanisms behind variant pharmacokinetics. Our data further suggest that despite mutations occurring on the protein surface, accumulating interactions could result in the impairment of protein function through the destabilization of binding regions and changes in protein folding. Therefore, our findings provide additional information regarding rare CYP1A2 genetic variants and how their underlying effects could clarify discrepancies noted in previous phenotypical studies. This would allow the improvement of personalized therapeutics and highlight the importance of identifying and characterizing rare variants.

Simultaneous quantitation of serum caffeine and its metabolites by ultra-high-performance liquid chromatography-tandem mass spectrometry for CYP1A2 activity prediction in premature infants.

Caffeine (CA) is accepted as a probe of cytochrome P450 1A2 enzyme (CYP1A2) activity and is commonly used in premature infants with great inter-individual variability of metabolism. To evaluate the change characteristics of CYP1A2 activity in premature infants, an ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed and optimized for the simultaneous quantitation of serum CA and its major metabolites, including paraxanthine (PX), theophylline (TP) and theobromine (TB), in premature infants. A C18 column and gradient elution with 0.1% formic acid in methanol and 0.1% formic acid in water at a flow rate of 0.3 mL/min were used for compound separation. The mass spectrometer monitored the transitions of CA (m/z 195.0 → 138.0), CA-d9 (m/z 204.0 → 144.1), PX (m/z 181.0 → 124.1), TP (m/z 181.0 → 123.9) and TB (m/z 181.0 → 138.0) using multiple reaction monitoring in positive ion mode. CYP1A2 activity was evaluated by serum molar concentration ratios of CA and its metabolites. The results showed that CYP1A2 has a significant positive correlation with the clearance of CA, and was affected by current weight and CYP1A2*1C. The results suggested that the serum concentration ratios of CA metabolites could be used to predict the changes in CYP1A2 enzyme activity in premature infants.

Characterization of the metabolites of irisflorentin by using ultra-high performance liquid chromatography combined with quadrupole/orbitrap tandem mass spectrometry

Irisflorentin is one of the bioactive constituents from the root of Belamcanda chinensis (L.) DC, which displayed anti-inflammatory and anti-tumor activities. In this work, the in vitro metabolism of irisflorentin was investigated using liver microsomes and hepatocytes. The metabolites were identified by ultra-high performance liquid chromatography combined with quadrupole/orbitrap tandem mass spectrometry. Under the current conditions, a total of 11 metabolites were detected and structurally identified according to accurate masses, fragment ions and retention times. Metabolite M10, identified as 6,7-dihydroxy-5,3′,4′,5′-tetramethoxy isoflavone, was biosynthesized and unambiguously characterized by nuclear magnetic resonance spectroscopy. The metabolic pathways of irisflorentin included oxidation, demethylation and glucuronidation. M10 was the most abundant metabolite in all tested species. Further phenotyping studies revealed that α-naphthoflavone and ketoconazole displayed significant inhibitory effect on the formation of M10. Cytochrome P450 (CYP) 1A2 and 3A4 were the major enzymes responsible for the formation of M10 by using individual recombinant human CYP450 enzymes. For the first time the current study provides an overview of the in vitro metabolic fates of irisflorentin, which is helpful for us to predict the human metabolism and the potential drug-drug interactions caused by irisflorentin.

Identification of the contact region responsible for the formation of the homomeric CYP1A2•CYP1A2 complex.

Previous studies showed that cytochrome P450 1A2 (CYP1A2) forms a homomeric complex that influences its metabolic characteristics. Specifically, CYP1A2 activity exhibits a sigmoidal response as a function of NADPH-cytochrome P450 reductase (POR) concentration and is consistent with an inhibitory CYP1A2•CYP1A2 complex that is disrupted by increasing [POR] (Reed et al. (2012) Biochem. J. 446, 489-497). The goal of this study was to identify the CYP1A2 contact regions involved in homomeric complex formation. Examination of X-ray structure of CYP1A2 implicated the proximal face in homomeric complex formation. Consequently, the involvement of residues L91-K106 (P1 region) located on the proximal face of CYP1A2 was investigated. This region was replaced with the homologous region of CYP2B4 (T81-S96) and the protein was expressed in HEK293T/17 cells. Complex formation and its disruption was observed using bioluminescence resonance energy transfer (BRET). The P1-CYP1A2 (CYP1A2 with the modified P1 region) exhibited a decreased BRET signal as compared with wild-type CYP1A2 (WT-CYP1A2). On further examination, P1-CYP1A2 was much less effective at disrupting the CYP1A2•CYP1A2 homomeric complex, when compared with WT-CYP1A2, thereby demonstrating impaired binding of P1-CYP1A2 to WT-CYP1A2 protein. In contrast, the P1 substitution did not affect its ability to form a heteromeric complex with CYP2B4. P1-CYP1A2 also showed decreased activity as compared with WT-CYP1A2, which was consistent with a decrease in the ability of P1-CYP1A2 to associate with WT-POR, again implicating the P1 region in POR binding. These results indicate that the contact region responsible for the CYP1A2•CYP1A2 homomeric complex resides in the proximal region of the protein.

Identification of Potential Lead Molecules against Dibenzo[a,l]pyrene-induced Mammary Cancer through Targeting Cytochrome P450 1A1, 1A2, and 1B1 Isozymes

Cytochrome P450 (CYP) isozymes are promising therapeutic targets against dibenzo[a,l]pyrene-induced mammary cancer. Current research aims to identify potential lead molecules against mammary cancer targetting CYP1A1, 1A2, and 1B1 using ligand-based virtual screening (LBVS), molecular interactions, MD simulation, and in vitro studies. The LBVS predicted 30,500 hits, which were reduced to 400 when sifted through Lipinski RO5, and ADMET parameters. These 400 compounds were carried forward for molecular docking with the selected CYP isozymes. The ligand CHEMBL224064 (CHEMBL1), CHEMBL2420083 (CHEMBL2), and CHEMBL61745 (CHEMBL3) depicted stronger binding respectively in CYP1A1 (-10-52 kcal/mol), 1A2 (-10.82 kcal/mol), and 1B1 (-10.78 kcal/mol) in comparison to known inhibitor alpha-naphthoflavone (ANF) (-9.13 kcal/mol, -9.66 kcal/mole, and -9.67 kcal/mol respectively in CYP1A1, 1A2, and 1B1). These compounds were found stable with their respective targets during MD studies of 50 ns duration. Furthermore, (3-(4, 5-dimethylthiazolyl-2)-2, 5-diphenyltetrazolium bromide) (MTT) and enzyme inhibition assay elucidated and validated the inhibitory potential of identified ligands against mammary carcinomas. The study reveals a significant understanding of PAH-mediated mammary cancer and its prevention.

The inhibition of CYP1A2, CYP2C9, and CYP2D6 by pterostilbene in human liver microsomes.

This study used human liver microsomes to assess pterostilbene's effect on the metabolic activity of cytochrome P450 (CYP) 1A2, CYP2C9, and CYP2D6. The metabolism of their substrates (phenacetin, tolbutamide, and dextromethorphan) was assayed by quantifying their relevant metabolites by HPLC. The IC50 value was used to express the strength of inhibition, and the value of a volume per dose index (VDI) was used to indicate the metabolic ability of the enzyme. In this study, pterostilbene inhibited CYP1A2, CYP2C9, and CYP2D6's metabolic activities in vitro. CYP2C9's activity was most significantly inhibited by pterostilbene; its IC50 value was 0.12±0.04 μM. The IC50 value of CYP1A2 and CYP2D6 was 56.3±10.4 μM and 62.33±11.4 μM, respectively. The finding that suggests that pterostilbene has the potential to interact with CYP2C9 substrates in vivo. These results warrant clinical studies to assess the in vivo significance of these interactions.

Immobilization stress increased cytochrome P450 1A2 (CYP1A2) expression in the ovary of rat

Jong-Chan Hwang, Hwan-Deuk Kim, Byung-Joon Park, Ryoung-Hoon Jeon, Su-Min Baek, Seoung-Woo Lee, Min Jang, Seul-Gi Bae, Sung-Ho Yun, Jin-Kyu Park, Young-Sam Kwon, Seung-Joon Kim and Won-Jae Lee. Journal of Animal Reproduction and Biotechnology 2021;36:9-16. https://doi.org/10.12750/JARB.36.1.9

In silico screening and analysis of nonsynonymous SNPs in human CYP1A2 to assess possible associations with pathogenicity and cancer susceptibility

Cytochrome P450 1A2 (CYP1A2) is one of the main hepatic CYPs involved in metabolism of carcinogens and clinically used drugs. Nonsynonymous single nucleotide polymorphisms (nsSNPs) of this enzyme could affect cancer susceptibility and drug efficiency. Hence, identification of human CYP1A2 pathogenic nsSNPs could be of great importance in personalized medicine and pharmacogenetics. Here, 176 nsSNPs of human CYP1A2 were evaluated using a variety of computational tools, of which 18 nsSNPs were found to be associated with pathogenicity. Further analysis suggested possible association of 9 nsSNPs (G73R, G73W, R108Q, R108W, E168K, E346K, R431W, F432S and R456H) with the risk of hepatocellular carcinoma. Molecular dynamics simulations revealed higher overall flexibility, decreased intramolecular hydrogen bonds and lower content of regular secondary structures for both cancer driver variants G73W and F432S when compared to the wild-type structure. In case of F432S, loss of the conserved hydrogen bond between Arg137 and heme propionate oxygen may affect heme stability and the observed significant rise in fluctuation of the CD loop could modify CYP1A2 interactions with its redox partners. Together, these findings propose CYP1A2 as a possible candidate for hepatocellular carcinoma and provide structural insights into how cancer driver nsSNPs could affect protein structure, heme stability and interaction network.

Detoxification gene expression, genotoxicity, and hepatorenal damage induced by subacute exposure to the new pyrethroid, imiprothrin, in rats.

The pyrethroid imiprothrin is widely used worldwide for control of insects in the agriculture and public health sectors. No sufficient information is however available concerning detoxification gene expression, i.e., cytochrome P450 1A2 (CYP1A2) and metallothionein 1a gene, oxidative stress, lipid peroxidation, DNA damage, cytotoxicity, genotoxicity, and organ injury induced by imiprothrin in mammals. This study is designed to explain the mechanism of imiprothrin induced detoxification gene expression, DNA damage, cytotoxicity, genotoxicity, and organ toxicity in male rats. The benchmark dose (BMD) was calculated to find the best sensitive markers to imiprothrin toxicity. Imiprothrin was injected intraperitoneally (i.p.) into male rats once a day for 5 days with doses of 19, 38, and 75 mg/kg body weight (b.wt.). Imiprothrin caused a significant increase in lipid peroxidation and changes in oxidative stress biomarkers in treated rats. Significant dose-dependent changes in the liver and kidney biomarkers were observed. Histopathological alterations were seen in the liver and kidney tissue of male rats. Imiprothrin also significantly increased chromosomal aberrations (CA) and micronuclei in bone-marrow cells, and induced lipid peroxidation, oxidative stress, cytotoxicity, and liver and kidney dysfunction, and damage. Imiprothrin induced DNA damage and over detoxification gene expression of CYP1A2 and metallothionein 1a gene in hepatocytes of male rats. Imiprothrin thus shows clastogenic and genotoxic potential. The mechanism for hepatorenal toxicity and injury, genotoxicity/cytotoxicity of imiprothrin might be due to enhanced lipid peroxidation, and oxidative stress associated with overproduction of free radicals, especially reactive oxygen species, and an imbalance in redox status. From the BMD models, aspartate aminotransferase (AST), total protein, uric acid, superoxide dismutase (SOD), and micronuclei (MPEs) were very sensitive markers to imiprothrin toxicity.

Electrochemical Activity of Cytochrome P450 1A2: The Relevance of O2 Control and the Natural Electron Donor

AbstractInvited for this month's cover picture is the Group of Biomarkers and Biosensors – GB2 (https://gb29.webnode.pt) at Universidade NOVA de Lisboa (Portugal) and CiiEM (Portugal). The cover picture shows the electrochemical response of the human monooxygenase enzyme, cytochrome P450 1A2 (CYP1A2), in the presence of its natural electron donor partner, cytochrome P450 oxidoreductase (CPR), highlighting the role of the interaction with the latter in the stabilization of CYP1A2 and attaining the electrochemically driven activity towards O2. The picture also emphasizes the protein entrapment matrix, a biocompatible sol‐gel film, which proved to be crucial for the achievement of interfacial electron transfer. Read the full text of the Article at 10.1002/celc.202001255.

Human Family 1-4 cytochrome P450 enzymes involved in the metabolic activation of xenobiotic and physiological chemicals: an update.

This is an overview of the metabolic activation of drugs, natural products, physiological compounds, and general chemicals by the catalytic activity of cytochrome P450 enzymes belonging to Families 1-4. The data were collected from > 5152 references. The total number of data entries of reactions catalyzed by P450s Families 1-4 was 7696 of which 1121 (~ 15%) were defined as bioactivation reactions of different degrees. The data were divided into groups of General Chemicals, Drugs, Natural Products, and Physiological Compounds, presented in tabular form. The metabolism and bioactivation of selected examples of each group are discussed. In most of the cases, the metabolites are directly toxic chemicals reacting with cell macromolecules, but in some cases the metabolites formed are not direct toxicants but participate as substrates in succeeding metabolic reactions (e.g., conjugation reactions), the products of which are final toxicants. We identified a high level of activation for three groups of compounds (General Chemicals, Drugs, and Natural Products) yielding activated metabolites and the generally low participation of Physiological Compounds in bioactivation reactions. In the group of General Chemicals, P450 enzymes 1A1, 1A2, and 1B1 dominate in the formation of activated metabolites.Drugs are mostly activated by the enzyme P450 3A4, and Natural Products by P450s 1A2, 2E1, and 3A4. Physiological Compounds showed no clearly dominant enzyme, but the highest numbers of activations are attributed to P450 1A, 1B1, and 3A enzymes. The results thus show, perhaps not surprisingly, that Physiological Compounds are infrequent substrates in bioactivation reactions catalyzed by P450 enzyme Families 1-4, with the exception of estrogens and arachidonic acid. The results thus provide information on the enzymes that activate specific groups of chemicals to toxic metabolites.

Coadministration of tizanidine and ciprofloxacin: a retrospective analysis of the WHO pharmacovigilance database

PurposeTizanidine, an alpha-adrenergic substance with antinociceptive and antihypertensive effects, is extensively metabolized via cytochrome P450 (CYP) 1A2. Therefore, coadministration with potent CYP1A2 inhibitors, such as ciprofloxacin, is contraindicated. However, both drugs are broadly utilized in various countries. Their concomitant use bears an inherent high risk for clinically significant symptoms, especially in multimorbid patients experiencing polypharmacy. This study aims to investigate the impact of coadministration of tizanidine and ciprofloxacin using real-world pharmacovigilance data and to raise awareness of this potentially underestimated safety issue.MethodsWe conducted a retrospective study including Individual Case Safety Reports (ICSR) registered until March 1, 2017, in the World Health Organization (WHO) global database. Demographic data, drug administration information, the course of the adverse drug reaction (ADR), its severity, and outcomes were analyzed for cases reporting ciprofloxacin comedication.ResultsIn 91 (2.0%) of the identified 4192 worldwide ICSR on tizanidine, coadministration of ciprofloxacin was reported. Most of the patients were female (n = 59, 64.8%) with a median age of 54 years (range 13–85 years). The countries contributing most reports were the USA (n = 54, 59.3%) and Switzerland (n = 16, 17.6%). ADRs reported most often affected the nervous system and the cardiac function, especially with large tizanidine doses or drugs with CNS and cardiovascular depressant effects. In two cases, a fatal outcome was reported.ConclusionDespite the existing formal contraindication, the concomitant use of tizanidine and ciprofloxacin can be observed in real-world clinical practice. Reactions mainly affected the central nervous and the cardiovascular system resulting in potentially severe adverse effects. The concomitant use of tizanidine and ciprofloxacin should absolutely be avoided.

Metabolic activation and deactivation of dietary-derived coumarin mediated by cytochrome P450 enzymes in rat and human liver preparations.

Dietary-derived coumarin is of clinical interest for its potential hepatotoxicity in humans because such toxicity is especially evident in rats. In this study, the oxidative metabolism of coumarin to active coumarin 3,4-epoxide (as judged by the formation rates of o-hydroxyphenylacetic acid) and excretable 7-hydroxycoumarin was investigated in liver fractions from rats and humans. In rat liver microsomes, the formation rate of o-hydroxyphenylacetic acid (~6 pmol/min/mg microsomal protein) from coumarin at 10 μM was dependent on the presence of liver cytosolic fractions. Rat hepatocytes mediated similar formation rates of o-hydroxyphenylacetic acid and 7-hydroxycoumarin (~0.1 nmol/hr/106 cells) at 0.20-20 μM coumarin. Human hepatocytes mediated the biotransformation of coumarin to o-hydroxyphenylacetic acid at roughly similar rates to those of rat hepatocytes. In contrast, the formation rates of 7-hydroxycoumarin by human hepatocytes were around 10-fold higher at ~1 nmol/hr/106 cells. In the presence of human liver cytosolic fractions, the oxidative formation rate of o-hydroxyphenylacetic acid was relatively high in cytochrome P450 (P450) 1A2-rich human liver microsomes. The inhibitory effects of furafylline/α-naphthoflavone and 8-methoxypsoralen, P450 1A2 and 2A6 inhibitors, respectively, were seen on the rates of o-hydroxyphenylacetic and 7-hydroxylation formations, respectively, in pooled human liver microsomes. Human liver microsomes selectively inactivated for P450 1A2 and 2A6 showed low rates of o-hydroxyphenylacetic acid and 7-hydroxylation formation (~20-30% of control), respectively. Among the P450 isoforms tested, recombinant human P450 1A2 predominantly mediated o-hydroxyphenylacetic formation. These results suggested that the metabolic activation and deactivation of coumarin were mediated mainly by P450 1A2 and 2A6 enzymes, respectively. The metabolic oxidation of coumarin via 3,4-epoxidation forming o-hydroxyphenylacetic acid could inform individual human risk assessments of dietary-derived coumarin, for which hepatotoxicity is especially evident in rats.

Roles of human cytochrome P450 1A2 in coumarin 3,4-epoxidation mediated by untreated hepatocytes and by those metabolically inactivated with furafylline in previously transplanted chimeric mice.

Coumarin is a naturally occurring component of food products but is of clinical interest for its potential hepatotoxicity in humans. In the current study, the pharmacokinetics of coumarin in humanized-liver mice after oral and intravenous administrations (30 mg/kg) were investigated for its transformations to metabolically active coumarin 3,4-epoxide (as estimated by the levels of o-hydroxyphenylacetic acid) and to excretable 7-hydroxycoumarin. After oral administration, control mice metabolized coumarin to o-hydroxyphenylacetic acid at roughly the same rate as that to 7-hydroxycoumarin (total of unconjugated and conjugated forms). In contrast, the in vivo biotransformation of coumarin to o-hydroxyphenylacetic acid by humanized-liver mice was around two orders of magnitude less than that to conjugated and unconjugated 7-hydroxycoumarin. After intravenous administrations of coumarin, differences were observed in the plasma concentrations of o-hydroxyphenylacetic acid between humanized-liver mice treated with furafylline (daily oral doses of 13 mg/kg for 3 days) and untreated humanized-liver mice. The mean values of the areas under the plasma concentration versus time curves and the maximum concentrations for o-hydroxyphenylacetic acid were significantly lower in the group treated with furafylline (45% and 57% of the untreated values, respectively). These results suggested that the metabolic activation of coumarin in humans was mediated mainly by P450 1A2, which was suppressed by furafylline, and that humanized-liver mice orally treated with furafylline might constitute an in vivo model for metabolically inactivated P450 1A2 in human hepatocytes transplanted into chimeric mice.

Biological roles of cytochrome P450 1A1, 1A2, and 1B1 enzymes.

Human cytochrome P450 enzymes (CYPs) play a critical role in various biological processes and human diseases. CYP1 family members, including CYP1A1, CYP1A2, and CYP1B1, are induced by aryl hydrocarbon receptors (AhRs). The binding of ligands such as polycyclic aromatic hydrocarbons activates the AhRs, which are involved in the metabolism (including oxidation) of various endogenous or exogenous substrates. The ligands that induce CYP1 expression are reported to be carcinogenic xenobiotics. Hence, CYP1 enzymes are correlated with the pathogenesis of cancers. Various endogenous substrates are involved in the metabolism of steroid hormones, eicosanoids, and other biological molecules that mediate the pathogenesis of several human diseases. Additionally, CYP1s metabolize and activate/inactivate therapeutic drugs, especially, anti-cancer agents. As the metabolism of drugs determines their therapeutic efficacy, CYP1s can determine the susceptibility of patients to some drugs. Thus, understanding the role of CYP1s in diseases and establishing novel and efficient therapeutic strategies based on CYP1s have piqued the interest of the scientific community.

Determination of benchmark doses for linear furanocoumarin consumption associated with inhibition of cytochrome P450 1A2 isoenzyme activity in healthy human adults.

Millions of individuals globally consume traditional herbal medicines (THMs), which contain abundant amounts of linear furanocoumarins. Linear furanocoumarins (i.e., 8-methoxypsoralen, 5-methoxypsoralen, and isopimpinellin) are inhibitors of cytochrome P450 (CYP) isoenzymes including 1A2, a major enzyme involved in drug metabolism and carcinogen bioactivation. Despite the high consumption of furanocoumarin-containing THMs, no studies have measured the furanocoumarin consumption level that triggers an inhibition to CYP1A2 activity in humans. The first objective was to verify if the potencies of the three furanocoumarins are additive towards the inhibition of CYP1A2 activity in vitro using concentration-addition and whole-mixture chemical-mixture-assessment models. A second objective was to determine the benchmark dose (BMD) with the mixtures of furanocoumarin oral doses, expressed as 8-MOP equivalents, and to assess the in vivo CYP1A2 activity, expressed as inhibition percentages. The in vitro results indicated that the three furanocoumarin inhibitory potencies were additive in the THM extracts, validating the use of the concentration-addition model in total furanocoumarin dose-equivalent calculations. Using the USEPA BMD software, the BMD was 18.9 μg 8-MOP equivalent/kg body weight. This information is crucial for furanocoumarin-related health-assessment studies and the regulation of THMs. Further studies should be performed for the remaining major metabolic enzymes to complete the safety profile of furanocoumarin-containing THMs and to provide accurate warning labelling.

CYP1A2 suppresses hepatocellular carcinoma through antagonizing HGF/MET signaling.

Rationale: Hyperactivation of HGF/MET signaling pathway is a critical driver in liver tumorigenesis. Cytochrome P450 1A2 (CYP1A2) was significantly down-regulated in hepatocellular carcinoma (HCC). However, little is explored about its tumor suppressive role in HCC. In this study, we examined the functional mechanisms and clinical implication of CYP1A2 in HCC.Methods: The clinical impact of CYP1A2 was evaluated in HCC patients in Hong Kong cohort. The biological functions of CYP1A2 were investigated in vitro and in vivo. A series of biochemical experiments including Western blot assay, immunohistochemistry, quantitative reverse transcription-polymerase chain reaction, and Co-immunoprecipitation assay were conducted.Results: CYP1A2 expression was prominently silenced in HCC tumor tissues and the high expression of CYP1A2 was significantly correlated with lower AFP level, less vascular invasion, and better tumor-free survival in local cohort of HCC patients. The overexpression of CYP1A2 inhibited HCC cell viability and clonogenicity, reduced cell migration and invasion abilities in vitro, and suppressed tumorigenicity in vivo, whereas CYP1A2 knockdown exhibited the opposite effects. CYP1A2 significantly hindered HGF/MET signaling and Matrix metalloproteinases (MMPs) expression in HCC cells. Mechanically, CYP1A2 decreased HGF level and diminished HIF-1α expression, both of which are recognized as key regulators of MET activation. As the transcriptional activator of MET, HIF-1α was identified as a binding partner of CYP1A2. Direct binding of CYP1A2 with HIF-1α induced ubiquitin-mediated degradation of HIF-1α, inhibiting HIF-1α-mediated transcriptions.Conclusions: In conclusion, our results have identified CYP1A2 as a novel antagonist of HGF/MET signaling, and CYP1A2 may serve as an independent new biomarker for the prognosis of HCC patients.

Borneol influences the pharmacokinetics of florfenicol through regulation of cytochrome P450 1A2 (CYP1A2), CYP2C11, CYP3A1, and multidrug resistance 1 (MDR1) mRNA expression levels in rats.

Borneol is a traditional Chinese medicine. In Chinese veterinary clinics, borneol and its related compounds are often used in combination with florfenicol to treat respiratory infections. This study investigated whether the pharmacokinetics of florfenicol in rats was affected by its concomitant use with borneol. Sprague-Dawley rats were intragastrically administered borneol (50 mg/kg body weight (BW)) or 0.5% carboxymethyl-cellulose sodium for 7 consecutive days, and then intragastrically administered florfenicol (25 mg/kg BW) on the eighth day. Pharmacokinetic studies showed that borneol significantly decreased the area under the concentration-time curve from zero to infinity (AUC(0-t)), time to reach peak concentration (Tmax), and the peak concentration (Cmax) values of florfenicol, whereas the values of mean residence time from zero to infinity (MRT(0-t)), elimination half-life (t1/2z), apparent volume of distribution fraction of the dose absorbed (Vz), and plasma clearance fraction of the dose absorbed (CLz) were increased significantly. Furthermore, the mRNA expression levels of multidrug resistance 1 (MDR1) and cytochrome P450 3A1 (CYP3A1) in the jejunum and of CYP1A2 and CYP2C11 in the liver were significantly upregulated by borneol. In conclusion, borneol decreased absorption, increased clearance, improved distribution, and increased the mean residence time of florfenicol in rats, possibly through regulating the mRNA expression levels of drug-metabolizing enzymes and efflux transporters.

Immunohistological expression of cytochrome P450 1A2 (CYP1A2) in the ovarian follicles of prepubertal and pubertal rat

Cytochrome P450 1A2 (CYP1A2) is a member of the cytochrome P450 superfamily enzymes in mammals and plays a major role in metabolizing endogenous hormones in the liver. In recent days, CYP1A2 expression has been found in not only the liver but also other tissues including the pancreas and lung. However, little information is available regarding the expression of CYP1A2 in the ovary, in spite of the facts that the ovarian follicle growth and atresia are tightly associated with controls of endocrine hormonal networks. Therefore, the expression of CYP1A2 in the ovaries of prepubertal and pubertal rats was investigated to assess its expression pattern and puberty-related alteration. It was demonstrated that the expression level of CYP1A2 was significantly (p < 0.01) higher in the pubertal ovaries than prepubertal counterparts. At the ovarian follicle level in both groups, whereas CYP1A2 expression was less detectable in the primordial, primary and secondary follicles, the strongly positive expression of CYP1A2 was localized in the granulosa cell layers in the antral and pre-ovulatory follicles. However, the ratio of CYP1A2-positive ovarian follicle was significantly (p < 0.01) higher in the ovary of pubertal group (73.1 ± 3.1%) than prepubertal one (41.0 ± 10.5%). During the Immunofluorescence, expression of CYP1A2 was mainly localized in Fas-positive follicles, indicating the atretic follicles. In conclusion, these results suggested that CYP1A2 expression was mainly localized at the atretic follicular cells and affected by the onset of puberty. Further study is still necessary but we hypothesize that CYP1A2 expresses in the atretic follicles to metabolize residue of the reproductive hormones. These findings may have important implications for the fields of reproductive biology of animals.