P450 3A Enzymes Research Articles

Genetic variation of CYP3A and its influence on the pharmacokinetics of tacrolimus, a calcineurin inhibitor

Background: Tacrolimus (Tac) a calcineurin inhibitor (CNI), is a potent immunosuppressive drug which is widely used in organ transplant recipients. The drug has a narrow therapeutic window and high inter-individual pharmacokinetic variability. Tac is metabolized by cytochrome P450 3A (CYP3A) enzymes. The CYP3A5 activity is largely determined by the single nucleotide variant (SNV) CYP3A5*3 (c.219-237A>G; rs776746), which results in alternate mRNA splicing and a non-functional protein.Methods: An observational prospective study was carried out at nephrology centre of army hospital where the consenting patients were enrolled in the study. The whole blood sample drawn was utilized to analyze for plasma drug concentration of Tac and genotyping for the CYP3A*5 polymorphism by the method as described by Cheung et al.Results: 100 patients participated with an average of 98±8 days after transplantation. Recipients having heterozygous CYP3A5*1 genotype manifested 70% lower mean steady state concentration of Tac (C0/D ratio) 1.67±0.43 μg*l-1/mg in comparison to homozygote carriers of CYP3A5*3 5.60±1.94 μg*l-1/mg p<0.001.Conclusions: Study suggested that Indian sub population closely mimics Caucasian population in terms of genotype expression for CYP3A5*3, who are expressing a non-functional enzyme for metabolism. Also, this study reinforces that population genotype CYP3A5*1 is significantly associated with lower C0/D ratio for Tac than the ones expressing homozygous CYP3A5*3 genotype. It also established the importance of pre-transplant genotyping, for better individualization of Tac doses. Further studies are suggested for population pharmacokinetic modelling study in future to derive starting dosage of Tac based on profiling of CYP3 genetics in recipients.

Effects of dexamethasone to reverse decreased hepatic midazolam metabolism in rats with acute renal failure

The inductive effects of dexamethasone on hepatic midazolam metabolism were examined in Wistar rats with acute renal failure (ARF) to clarify whether the ARF-related decrease in the hepatic expression of drug-metabolizing enzymes is caused by an impairment in the translation/polypeptide formation process.ARF was induced with intramuscular glycerol injection. Dexamethasone was orally administered. Pooled liver microsomes from five rats were prepared with ultracentrifugation for each of four groups, namely, control and ARF rats, control rats with dexamethasone treatment and ARF rats with dexamethasone treatment.Hepatic drug-metabolizing activity was examined in an incubation study with the microsomes, where midazolam was employed as a substrate of cytochrome P450 (CYP) 3A enzymes. The hepatic protein and mRNA expressions of CYP3A23/3A1 and 3A2 enzymes were also evaluated.With dexamethasone treatment, the hepatic metabolic rate of midazolam increased 1.4 times in control rats, while it increased 19.6 times in ARF rats, reflecting the greater induction of hepatic protein expressions of CYP3A enzymes in ARF rats than in control rats.The hepatic protein expression process for CYP3A23/3A1 and 3A2 responds well to dexamethasone treatment in ARF rats, indicating that the translation/polypeptide formation process is not impaired in the presence of ARF.

Clinical Pharmacodynamics, Pharmacokinetics, and Drug Interaction Profile of Doravirine.

Doravirine is a novel non-nucleoside reverse transcriptase inhibitor(NNRTI) that has demonstrated good efficacy, tolerability, and safety for the treatment of patients with human immunodeficiency virus (HIV)-1 infection in phase III clinical trials. Doravirine achieved non-inferiority when compared with efavirenz- and darunavir/ritonavir-based regimens. Fewer adverse effects, including neuropsychiatric effects were observed with doravirine compared with efavirenz. Key pharmacodynamic and pharmacokinetic characteristics as well as drug-drug interactions and the resistance profile were assessed in this clinical review. Doravirine is a pyridinone NNRTI with potent antiviral activity against wild-type HIV-1 virus and common NNRTI variants. Studies in healthy volunteers and HIV-infected individuals have shown that doravirine has a favorable pharmacokinetic profile for once-daily dosing, with an elimination half-life of around 15h, median time to maximum plasma concentrations of 1-4h, and time to steady-state concentration of 7days. The pharmacokinetics of doravirine arenot greatly influenced by sex, age, race, or hepatic impairment. Although no dose adjustment is required for doravirine in renal impairment when given as a single tablet, the fixed-dose combination tablet of doravirine/lamivudine/tenofovir disoproxil fumarate is not recommended in patients with a creatinine clearance of < 50mL/min. Doravirine has a low potential for drug-drug interactions and does not impact on the pharmacokinetics of other drugs. However, it is metabolized via cytochrome P450 (CYP) 3A enzymes and is thus susceptible to interactions with CYP3A inhibitors and inducers. Strong CYP3A inhibitors can significantly increase doravirine exposure; however, this is not considered to be clinically relevant. Conversely, strong CYP3A inducers, such as rifampin, are contraindicated with doravirine owing to a significant reduction in exposure with potential for impaired virological efficacy. Moderate CYP3A inducers, such as rifabutin, may be co-administered if the doravirine dose is increased to 100mg twice daily. Doravirine has a unique resistance profile and has demonstrated in vitro activity against some of the most common, clinically relevant NNRTI-resistant mutations. Prevalence of baseline NNRTI resistance to doravirine appears to be low in treatment-naïve cohorts. Further data on the efficacy of doravirine in patients with previous treatment experience and/or transmitted NNRTI resistance are required to further inform its place in the current armamentarium of drugs for the treatment of HIV infection.

SUN-115 Personalised Pharmacogenomics of Tacrolimus in Renal Transplantation- Indian Experience

Tacrolimus has a narrow therapeutic index with high intra and inter individual pharmacokinetic variability. Tacrolimus is metabolized by Cytochrome P450 (CYP) 3A enzymes specifically 3A4 and 3A5 in small intestine, liver and in kidney. Single Nucleotide Polymorphisms of CYP3A5 can result in changes to the activity of CYP3A5 . Caucasians commonly have a Non Expressor status of CYP3A5 (CYP3A5 GG) and have vastly reduced dosing requirements compared to Expressor status (CYP3A5 AA/AG). We studied the CYPA4 Expression status in Indian Patients.

Regioselective hydroxylation of an antiarrhythmic drug, propafenone, mediated by rat liver cytochrome P450 2D2 differs from that catalyzed by human P450 2D6

1. Propafenone, an antiarrhythmic drug, is a typical human cytochrome P450 (P450) 2D6 substrate used in preclinical studies. Here, propafenone oxidation by mammalian liver microsomes was investigated in vitro.2. Liver microsomes from humans and marmosets preferentially mediated propafenone 5-hydroxylation, minipig, rat and mouse livers primarily mediated 4′-hydroxylation, but cynomolgus monkey and dog liver microsomes differently mediated N-despropylation.3. Quinine, ketoconazole or anti-P450 2D antibodies suppressed propafenone 4′/5-hydroxylation in human and rat liver microsomes. Pretreatments with β-naphthoflavone or dexamethasone increased N-despropylation in rat livers.4. Recombinant rat P450 2D2 efficiently catalysed propafenone 4′-hydroxylation in a substrate inhibition manner, comparable to rat liver microsomes, while human P450 2D6 displayed propafenone 5-hydroxylation. Human and rat P450 1A, 2C and 3A enzymes mediated propafenone N-despropylation with high capacities.5. Carbon-4′ of propafenone docked favourably into the active site of P450 2D2 based on an in silico model; in contrast, carbon-5 of propafenone docked into human P450 2D6.6. These results suggest that the major roles of individual P450 2D enzymes in regioselective hydroxylations of propafenone differ between human and rat livers, while the minor roles of P450 1A, 2C and 3A enzymes for propafenone N-despropylation are similar in livers of both species.

Enzymatic Activities of CYP3A4 Allelic Variants on Quinine 3-Hydroxylation In Vitro.

Cytochrome P450 3A4 (CYP3A4) enzyme activity is known to show considerable ethnic heterogeneity and inter-individual differences, affecting the outcome of drug treatment. CYP3A4 genetic polymorphisms are believed to be one of the important causes, leading to inter-individual variability in drug metabolism. Quinine is an antipyretic drug with antimalarial properties that is metabolized primarily by CYP3A4. Quinine 3-hydroxylation has been proven as a biomarker reaction for evaluating CYP3A4 ability. Quinine has frequent adverse effects and there are distinct inter-individual differences in quinine sensitivity. The open reading frame for 30 CYP3A4 allelic variants were constructed from wild-type CYP3A4*1A by an overlap extension polymerase chain reaction. Recombinant CYP3A4 variants were expressed using baculovirus-insect cell expression system, and their catalytic activities towards quinine hydroxylation were determined and evaluated. Of the 30 CYP3A4 allelic variants, 23 variants exhibited significantly reduced intrinsic clearance towards quinine, 2 variants showed increased intrinsic clearance for quinine, 2 variants possessed no significant differences towards quinine, compared with CYP3A4*1A, and 3 variants had no detected expression and enzyme activity. Our assessment on the enzymatic activities of CYP3A4 variants towards quinine may contribute to laying an experimental foundation for further clinical studies so as to accelerate the process of determining the associations between genetic variations and clinical phenotypes.

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 2.5µM benzo[a]pyrene (BaP), a tobacco smoke constituent and aryl hydrocarbon receptor (AHR) agonist, for 24h induced cytochrome P450 (CYP) 1A enzyme activity. The addition of IMQ 30min 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 0.5µM 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 5µM 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.

Evaluation of Maternal Drug Exposure Following the Administration of Antenatal Corticosteroids During Late Pregnancy Using Physiologically-Based Pharmacokinetic Modeling.

Betamethasone and dexamethasone are the most widely studied antenatal corticosteroids (ACS) administered to pregnant women, just prior to the birth of a preterm neonate, to accelerate fetal lung maturation. Although betamethasone, predominantly used in developed countries, has been shown to be an effective and safe intervention for reducing neonatal mortality, the choice of ACS and optimal dosing in low and middle income countries (LMICs) remains unclear. This is primarily because the exposure-response relationships have not been established for ACS despite the long history of use. As the first step toward the optimal use of ACS in LMICs, we developed physiologically-based pharmacokinetic (PBPK) models to describe the kinetics of ACS following i.v., p.o., or i.m. dosing. In vitro data describing the cytochrome P450 3A4 enzyme contribution were incorporated and this was refined using clinical data. The models can be applied prospectively to predict kinetics of ACS in pregnant women receiving various dosing regimens.

Ultrasensitive near-infrared fluorescent probe with large stokes shift for real-time tracing of CYP1A1 in living cells and zebrafish model

Human cytochrome P450 1A1 (CYP1A1) enzyme is involved in the oxidation of various procarcinogenes into active carcinogenic metabolites in the phase I of biotransformation and initiates the carcinogenic process. Here, a novel ultrasensitive CYP1A1-specific fluorescent probe (DPCl) was investigated deeply which has O-chloroethyl group as a trigger for CYP1A1 activity and a dicyanoisophorone derivative fluorophore with a 673 nm emission. The size of the O-chloroethyl group is suitable for the cavity volume of the active sites of CYP1A1 and the lipophilicity and polarity of the group make the probe suitable for oriented at the actives sites. Hence, this near-infrared fluorescent probe reveals ultrasensitive sensitivity (minimum detectable limit is 0.026 nM), excellent specificity, and low toxicity in the process of target enzyme monitoring under simulated physiological condition, living cells and zebrafish. The success of this strategy is rely on intermediate product (DPOH) after dechloroethylation of DPCl is NIR-illuminant platform with a prominent Stokes Shift (118 nm), which is the first report of a NIR fluorescent probe for detecting CYP1A1. Anyhow, this probe provides support for clinical studies of CYP1A1 cell screening inhibitors and real-time tracking of enzyme activity in vivo.

Photoelectrochemically driven bioconversion and determination of nifedipine based on a double photoelectrode system

In the present work, a double photoelectrode system has been constructed for photoelectrochemically driven enzymatic bioconversion and determination of nifedipine. In which, the TiO2 nanotube arrays in-situ assembled with g-C3N4 (TNA/g-C3N4) was used as a photoanode, and a cytochrome P450 3A4 (CYP3A4) enzyme was immobilized in the porous ITO/CuO films to fabricate an ITO/CuO/CYP3A4 photocathode. The constructed double photoelectrode system had a significant photocurrent response compared to the single ITO/CuO/CYP3A4 or TNA/g-C3N4 under visible light irradiation. Under optimal conditions, the photocurrent of the double photoelectrode system had a high catalytic activity toward substrate nifedipine with kcat of 5.62 s−1 and catalytic efficiency with kcat/kmapp of 0.94 μM−1 s−1, and the bioconversion yield of nifedipine reached 22.1%. Furthermore, the constructed double photoelectrode system could be used to determine the nifedipine concentration with a high sensitivity of 2.46 μA μM−1 and a low detection limit of 0.015 μM. Therefore, the proposed double photoelectrode system can be used well for study enzyme biocatalysis for target bioconversion, and also has a potential application for toxicity analysis.

Characterization of the Effect of Hepatic Impairment on Upadacitinib Pharmacokinetics.

Upadacitinib is a selective Janus kinase 1 inhibitor being developed for the treatment of several inflammatory autoimmune diseases, including rheumatoid arthritis. Upadacitinib is a nonsensitive substrate for metabolism by cytochrome P450 3A enzymes. This open‐label, single‐dose, multicenter study assessed the pharmacokinetics of upadacitinib following oral administration of a single 15‐mg dose of the upadacitinib extended‐release formulation in subjects with mild (n = 6) and moderate (n = 6) hepatic impairment relative to demographically matched healthy subjects (n = 6). Subjects were assigned to 1 of the 3 groups according to the Child‐Pugh classification. Relative to subjects with normal hepatic function, the ratios (90% confidence intervals) of upadacitinib area under the plasma concentration‐versus‐time profile from time 0 to infinity (AUCinf) for subjects with mild and moderate hepatic impairment were 1.28 (0.91‐1.79) and 1.24 (0.87‐1.76), respectively. The central ratios of upadacitinib maximum observed concentration (Cmax) were 1.04 (0.77‐1.39) and 1.43 (1.05‐1.95) in subjects with mild and moderate hepatic impairment, respectively, compared with subjects with normal hepatic function. No clinically significant changes in vital signs or hematology measurements were observed, and no new safety events were identified in this study. These results indicate that mild and moderate hepatic impairment has no clinically relevant effect on upadacitinib pharmacokinetics.

Interakcje wybranych leków kardiologicznych ze składnikami diety

The ageing society and the growing problem of fragility syndrome necessitate the long-term use of cardiac drugs, thereby increasing the risk from drug/food interactions. The aim of this study was to present the interaction between foods and those drugs used in the clinical practice of cardiologists. The effect of vitamin K antagonists is intensified by food and drink such as sage, camomile, parsley, aniseed, liquorice, ginger, ginseng, cranberry juice, and grapefruit juice, among others. However, products rich in vitamin K inhibit the therapeutic effect of coumarin derivatives. Due to the increased risk of bleeding, antiplatelet drugs should not be combined with dietary supplements containing Ginkgo biloba which inhibits platelet activating factor. The literature indicates the occurrence of a similar risk when combining antiplatelet drugs with garlic-containing supplements. Numerous scientific studies have looked at the impact of food on the absorption of antihypertensive drugs. The best known of these is grapefruit/grapefruit juice. It was recently found that grapefruit acts by interfering in the activity of cytochrome P450 3A4 (CYP3A4) enzyme. People who regularly take cardiac drugs are exposed to food/drug interactions, and should be aware of the possible complications. There is an urgent need to educate patients in the area of food/drug interactions. Therefore, a therapeutic team should be created consisting of a general practitioner, a cardiologist, a psychologist, a nurse and a dietician.

DNA elements for constitutive androstane receptor- and pregnane X receptor-mediated regulation of bovine CYP3A28 gene.

The regulation of cytochrome P450 3A (CYP3A) enzymes is established in humans, but molecular mechanisms of its basal and xenobiotic-mediated regulation in cattle are still unknown. Here, ~10 kbp of the bovine CYP3A28 gene promoter were cloned and sequenced, and putative transcription factor binding sites were predicted. The CYP3A28 proximal promoter (PP; -284/+71 bp) contained DNA elements conserved among species. Co-transfection of bovine nuclear receptors (NRs) pregnane X and constitutive androstane receptor (bPXR and bCAR) with various CYP3A28 promoter constructs into hepatoma cell lines identified two main regions, the PP and the distal fragment F3 (-6899/-4937 bp), that were responsive to bPXR (both) and bCAR (F3 fragment only). Site-directed mutagenesis and deletion of NR motif ER6, hepatocyte nuclear factor 1 (HNF-1) and HNF-4 binding sites in the PP suggested either the involvement of ER6 element in bPXR-mediated activation or the cooperation between bPXR and liver-enriched transcription factors (LETFs) in PP transactivation. A putative DR5 element within the F3 fragment was involved in bCAR-mediated PP+F3 transactivation. Although DNA enrichment by anti-human NR antibodies was quite low, ChIP investigations in control and RU486-treated BFH12 cells, suggested that retinoid X receptor α (RXRα) bound to ER6 and DR5 motifs and its recruitment was enhanced by RU486 treatment. The DR5 element seemed to be recognized mainly by bCAR, while no clear-cut results were obtained for bPXR. Present results point to species-differences in CYP3A regulation and the complexity of bovine CYP3A28 regulatory elements, but further confirmatory studies are needed.

Interindividual variation in the cytochrome P4501A response to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin in herring gull embryo hepatocytes

Exposure to dioxin-like compounds is consistently associated with concentration-dependent induction of cytochrome P4501A (CYP1A) enzymes in primary cultures of avian hepatocytes. We have previously demonstrated that the median effective concentration (EC50) for induction of this response is predictive of in vivo sensitivity to dioxin-like compounds in birds. We investigated sources of interindividual variation in the CYP1A response to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in wild herring gulls and considered how this variation may complicate dioxin sensitivity estimates based on the CYP1A bioassay. Concentration-dependent effects of TCDD on CYP1A mRNA expression were characterized in 55 hepatocyte cultures prepared from individual herring gull embryos. A large degree of variability was observed among the hepatocyte culture preparations. For example, 1) basal CYP1A4 and CYP1A5 mRNA expression varied by 20- and 126-fold, respectively, among individuals, and 2) exposure to TCDD induced CYP1A4 mRNA expression by 57-fold in the most responsive sample but did not significantly induce CYP1A4 mRNA expression above baseline values in 42% of hepatocyte culture preparations. Environmental and genetic factors contributing to the observed variability are discussed. Despite the large amount of interindividual variation, we conclude that reproducible EC50-based estimates of species sensitivity can be obtained from the CYP1A cell culture bioassay when samples are collected from relatively uncontaminated colonies. Environ Toxicol Chem 2019;38:660-670. © 2019 SETAC.

Influence of Amlodipine on Haemostatic Measurements during Clopidogrel Treatment in Patients with Coronary Artery Disease.

Amlodipine has a potential to reduce clopidogrel bioactivation through the cytochrome P450 3A4 enzyme in vivo, but the clinical impact of this interaction remains controversial. This randomized, open-label, two-period, crossover study was performed to evaluate the influence of amlodipine on the haemostatic profiles of high-risk patients during clopidogrel treatment. We recruited 40 Asian patients (Male/Female: n = 36/4) receiving clopidogrel (75 mg/day), aspirin (100 mg/day) and rosuvastatin for at least 6 months following percutaneous coronary intervention. Patients were randomly assigned to receive either 5 mg daily amlodipine or not for 2 weeks, and then were crossed over to the other treatment for 2 weeks. Haemostatic measurements were conducted with the VerifyNow assay and thromboelastography (TEG). Primary endpoint was P2Y12 Reaction Units (PRU) during on- versus off-amlodipine treatment. The on-amlodipine strategy showed higher level of PRU compared with the off-amlodipine strategy (176.8 ± 75.4 vs. 150.7 ± 65.5 PRU; ∆mean: 26.1 PRU; ∆95% confidence interval [CI]: 4.5-47.7 PRU; p = 0.019). Platelet-fibrin clot strength measured by TEG was lower during on- versus off-amlodipine treatment (7,712 ± 1,889 vs. 8,559 ± 2,174 dyne/cm2; ∆mean: -847 dyne/cm2; ∆95% CI: -1,632 to -62 dyne/cm2; p = 0.035). After amlodipine discontinuation, 27 patients (67.5%) showed a decrease in PRU, which was associated with 'PRU ≥ 160 on-amlodipine' in multivariate analysis (odds ratio: 62.014; 95% CI: 2.302-1670.328; p = 0.014). In conclusion, amlodipine increases platelet reactivity and decreases platelet-fibrin clot strength during clopidogrel treatment. In addition, the effect of amlodipine discontinuation on clopidogrel responsiveness is associated with on-amlodipine platelet reactivity.

Efficacy, Tolerability and Pharmacokinetic Impact of Aprepitant in Sarcoma Patients Receiving Ifosfamide and Doxorubicin Chemotherapy: A Randomized Controlled Trial.

Aprepitant, a selective neurokinin-1 receptor antagonist approved for prevention of chemotherapy-induced nausea and vomiting (CINV), is an inhibitor of the cytochrome P450 3A4 (CYP3A4) enzyme, which is involved in the clearance of several chemotherapeutic agents. Here we evaluated the efficacy and toxicity of a combination of aprepitant, palonosetron, and dexamethasone as antiemetic prophylaxis in sarcoma patients receiving ifosfamide and doxorubicin chemotherapy, and examined the potential of aprepitant to affect the pharmacokinetics of ifosfamide, which is primarily metabolized by CYP3A4. A total of 108 sarcoma patients were randomly assigned to either the aprepitant group (antiemetic regimen: aprepitant, palonosetron, and dexamethasone) or the control group (antiemetic regimen: palonosetron and dexamethasone). Data on nausea, vomiting, and use of rescue medication were collected, and the primary efficacy end point was the proportion of patients with complete response (CR), defined as no vomiting and no use of rescue therapy during 120h after initiation of chemotherapy. Tolerability was evaluated on the basis of reported adverse events and laboratory assessments. Blood samples for ifosfamide pharmacokinetic analysis were collected in ten patients. The percentage of patients achieving CR was significantly higher in the aprepitant group compared with that in the control group in the acute, delay, and overall phase (78.4% vs. 59.3%, 74.5% vs. 48.1%, and 68.6% vs. 37.0%, p < 0.05, respectively). No significant differences of adverse events or hematological toxicity were detected between the two groups. Concomitant administration of aprepitant did not cause any statistically significant changes in ifosfamide pharmacokinetics. Values for aprepitant group vs. control group were as follows: geometric mean of Cmax was 119 vs. 120ng/mL, AUC0-last was 648 vs. 635ngh/mL, AUC0-inf was 681 vs. 668ngh/mL, plasma clearance was 4.40 vs. 4.49 (L/h/m2), respectively; harmonic means of t1/2 was 2.11 vs. 2.25h. This study showed that aprepitant in combination with palonosetron and dexamethasone was safe and effectively controlled CINV in sarcoma patients receiving ifosfamide and doxorubicin chemotherapy. Aprepitant may have a low potential to affect the pharmacokinetics of chemotherapeutic agents metabolized by CYP3A4.

Inflammatory marker and aryl hydrocarbon receptor-dependent responses in human macrophages exposed to emissions from biodiesel fuels

Biodiesel or renewable diesel fuels are alternative fuels produced from vegetable oil and animal tallow that are being considered to help reduce the use of petroleum-based fuels and emissions of air pollutants including greenhouse gases. Here, we analyzed the gene expression of inflammatory marker responses and the cytochrome P450 1A1 (CYP1A1) enzyme after exposure to diesel and biodiesel emission samples generated from an in-use heavy-duty diesel vehicle. Particulate emission samples from petroleum-based California Air Resource Board (CARB)-certified ultralow sulfur diesel (CARB ULSD), biodiesel, and renewable hydro-treated diesel all induced inflammatory markers such as cyclooxygenase-2 (COX)-2 and interleukin (IL)-8 in human U937-derived macrophages and the expression of the xenobiotic metabolizing enzyme CYP1A1. Furthermore, the results indicate that the particle emissions from CARB ULSD and the alternative diesel fuel blends activate the aryl hydrocarbon receptor (AhR) and induce CYP1A1 in a dose- and AhR-dependent manner which was supported by the AhR luciferase reporter assay and gel shift analysis. Based on a per mile emissions with the model year 2000 heavy duty vehicle tested, the effects of the alternative diesel fuel blends emissions on the expression on inflammatory markers like IL-8 and COX-2 tend to be lower than emission samples derived from CARB ULSD fuel. The results will help to assess the potential benefits and toxicity from biofuel use as alternative fuels in modern technology diesel engines.

Long-term clinical safety of clindamycin and rifampicin combination for the treatment of hidradenitis suppurativa. A Critically Appraised Topic.

Can therapy with clindamycin and rifampicin be safely continued long term beyond the recommended 10-week course? Clindamycin and rifampicin are used in combination to treat hidradenitis suppurativa (HS). There is no data on the efficacy and safety of clindamycin/rifampicin combination therapy for HS beyond 10 weeks. We identified the following major concerns that still lack a proper evidenced-based analysis: for rifampicin, drug-induced liver injury, interstitial nephritis, drug interaction and hepatic p450 3A4 enzyme induction; for clindamycin, the concern was community-acquired Clostridium difficile infection (CA-CDI); and experience with long-term treatment. Data sources were used as appropriate to answer the question. Systematic searches were used to assess the risk of CA-CDI and experience with long-term treatment with clindamycin. The risk for rifampicin-induced liver injury is highest in the first 6 weeks of treatment, whereas interstitial nephritis is primarily observed during intermittent treatment. Enzyme induction due to rifampicin is usually complete after about 2 weeks of treatment and reduces clindamycin blood levels by about 90%. Three meta-analyses identified antibiotic use as a risk factor for CA-CDI. Two of them assigned the highest risk to clindamycin. None of them stratified by length of treatment. There is extensive experience with rifampicin, primarily for the treatment of tuberculosis. Long-term experience with clindamycin is limited. The analysed risks associated with a combination of clindamycin and rifampicin for hidradenitis suppurative cluster within the first 10 weeks. Treatment can be continued beyond 10 weeks, if clinically necessary.

Enhanced Metabolic Activity of Cytochrome P450 via Carbon Nanocage-Based Photochemical Bionanoreactor.

Recently, the early screening of the genotoxicity of new chemicals and drugs calls for the envelope of micro-/nanoreactors for metabolic study. Herein, a novel light-driven enzymatic bionanoreactor is designed with the gold nanoparticle (NP)-modified carbon nanocage (Au@CNC) as a nanoreactor and meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) as a photosensitizer for cytochrome P450-mediated drug metabolism. By confining the cytochrome P450 3A4 (CYP3A4) enzyme and TCPP inside the pores of Au@CNC, a high metabolic activity is achieved by using 7-ethoxytrifluoromethyl coumarin as the substrate because of the three-dimensional hierarchical porous structure, large surface area, and fast electron transfer capacity of Au@CNC. It is noted that owing to the presence of AuNPs inside CNC, the surface hydrophilicity of CNC is much improved, which further promotes the catalytic activity of the CYP3A4 enzyme. To our knowledge, this is the first attempt to apply CNC as a bionanoreactor for NADPH-free and light-driven in vitro drug metabolism. In addition, the presented bionanoreactor exhibits a variety of advantages in terms of fast response, short assay time (10 min), high sensitivity, and good selectivity, which are expected to expedite drug screening and render potential advances in drug discovery and development.

Bioelectrochemical Systems as Technologies for Studying Drug Interactions Related to Cytochrome P450

The electrocatalytic activity of cytochrome P450 3A4 as the main enzyme of drug metabolism was studied. Cytochrome P450 electrodes allowed to register 10−11–10−12 mol of enzyme/electrode. The study has shown that the developed electrochemical systems based on cytochromes P450 are effective non-invasive models for the analysis of drug–drug interactions at the level of biotransformation of xenobiotics. The effect of clinically significant drug combinations on the activity of cytochrome P450 3A4 was studied. The electroanalytical response of cytochrome P450 3A4 enzyme was interpreted in terms of its impact on drug interference and assessment of heme protein activity. The results can be used for modulation of cytochrome P450 activity in case of comorbid patients with polypharmacy.