CYP2E1 Inhibitor Research Articles

Environmentally Persistent Free Radicals stimulate CYP2E1-mediated generation of reactive oxygen species at the expense of substrate metabolism.

Environmentally persistent free radicals (EPFRs) are a recently recognized component of particulate matter that cause respiratory and cardiovascular toxicity. The mechanism of EPFR toxicity appears to be related to their ability to generate reactive oxygen species (ROS), causing oxidative damage. EPFRs were shown to affect P450 function, inducing the expression of some forms through the Ah receptor. However, another characteristic of EPFRs lies in their ability to inhibit P450 activities. CYP2E1 is one of the P450s that is inhibited by EPFR (MCP230) exposure. As CYP2E1 is also known to generate ROS, it is important to understand the ability of EPFRs to influence the function of this enzyme and to identify the mechanisms involved. CYP2E1 was shown to be inhibited by EPFRs, and to a lesser extent by non-EPFR particles. As EPFR-mediated inhibition was more robust at subsaturating NADPH-cytochrome P450 reductase (POR) concentrations, disruption of POR·CYP2E1 complex formation and electron transfer were examined. Surprisingly, neither complex formation nor electron transfer between POR and CYP2E1 were inhibited by EPFRs. Examination of ROS production showed that MCP230 generated a greater amount of ROS than the non-EPFR CuO-Si. When a POR/CYP2E1-containing reconstituted system was added to the pollutant-particle systems there was a synergistic stimulation of ROS production. The results indicate that EPFRs cause inhibition of CYP2E1-mediated substrate metabolism, yet do not alter electron transfer and actually stimulate ROS generation. Taken together, the results are consistent with EPFRs affecting CYP2E1 function by inhibiting substrate metabolism and increasing the generation of ROS. Significance Statement Environmentally persistent free radicals affect CYP2E1 function by inhibition of monooxygenase activity. This inhibition is not due to disruption of the POR·CYP2E1 complex or inhibition of electron transfer, but due to uncoupling of NADPH and oxygen consumption from substrate metabolism to the generation of ROS. These results show that EPFRs block the metabolism of foreign compounds, and also synergistically stimulate the formation of reactive oxygen species that lead to oxidative damage within the organism.

Ameliorative effects of Monascus-fermented hawthorn extract on a high-fat diet-induced rat model of non-alcoholic fatty liver disease

ObjectiveThe aim of this study was to elucidate the effects of fermented hawthorn extract on high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) in rats, and explore the possible underlying mechanisms. MethodsA total of 42 male adult Sprague-Dawley rats were randomly divided into five groups: normal control group (given a normal feed diet and distilled water by gavage), NAFLD model (given HFD and distilled water by gavage), low-, medium-, and high-dose fermented hawthorn extract treatment groups (given HFD and different doses of fermented hawthorn extract by gavage). After 12 weeks of gavage administration, changes in body weight, liver/body weight ratio, serum liver enzymes, as well as triglyceride (TG) content and oxidative stress levels in rat liver tissueswere detected. Histological evaluation was performed to observe the degree of fat accumulation (steatosis). qRT-PCR and western blotting were performed to detect the mRNA and protein expression of cytochrome P4502E1 (CYP2E1, a key enzyme associated with lipid peroxidation), and lipogenic factors (sterol regulatory element-binding protein 1c (SREBP-1c) and fatty acid synthase (FAS)) in rat liver tissues. ResultsFermented hawthorn extract significantly reduced the body weight, decreased the levels of liver enzymes, improved hepatic steatosis, and exhibited obvious antioxidant effects. Fermented hawthorn extract also significantly down-regulated the mRNA and protein expression levels of CYP2E1, SREBP-1c and FAS. ConclusionOur findings suggested that fermented hawthorn extract can markedly reduce body weight, ameliorate HFD-induced NAFLD in rats, and exhibits significant antioxidant effects. Its underlying mechanism may depend on the inhibition of CYP2E1, SREBP-1c, and FAS expression.

Discovery of CYP2E1 as a novel target in rheumatoid arthritis and validation by a new specific CYP2E1 inhibitor

Considerable evidence indicates that CYP2E1 is associated with a variety of inflammatory diseases. Here we evaluated CYP2E1 as a potential therapeutic target for rheumatoid arthritis (RA) and established the protective effect of a new CYP2E1 inhibitor. Gene-expression datasets were used to analyze the change in expression of CYP2E1 in RA patients; CYP2E1 activity in collagen-induced arthritis (CIA) rats was determined by HPLC. We further evaluated the protective effects of Cyp2e1 knockout and a CYP2E1-specific inhibitor, Q11, synthesized by our group, in CIA and adjuvant-induced arthritis (AIA) rats. The expression of CYP2E1 in synovial tissue was elevated in RA patients and in CIA rats and the activity of CYP2E1 in vivo and in vitro in CIA rats was greater than that of controls. Cyp2e1 knockout significantly reduced the incidence of CIA and alleviated the severity of symptoms. Treatment with different doses of Q11 decreased paw thickness, volume and arthritis scores and reduced the serum levels of IL‐6, TNF‐α, IL‐1β and MDA, and increased the level of GSH in CIA rats. A similar inhibitory effect was exhibited for Q11 in the AIA rats. Moreover, Q11 significantly impeded proliferation, migration, and invasion of human rheumatoid arthritis synovial fibroblasts cells. Q11 decreased the release of ROS and enhanced Nrf2 nuclear translocation and HO-1 expression in the cell nucleus. Overall, our results indicated that CYP2E1 may be a new target for RA and Q11 has potential protective effects against RA by reducing oxidative stress and opposing the inflammatory response via the ROS/Nrf2/HO-1 signaling pathway.

Metabolism-dependent inhibition of CYP2E1 by isoniazid, a mediator of idiosyncratic liver injury

Liver injury is a well-known adverse effect of the anti-tuberculosis drug isoniazid (INH); however, animal models that accurately replicate this effect as seen in humans have not been constructed, and the mechanism of its pathogenesis remains unclear. Recently, an immune-mediated mechanism have been proposed based on clinical studies, suggesting the involvement of cytochrome P450-mediated formation of reactive metabolites and covalent adducts in severe cases. In the present study, we investigated the role of CYP2E1 in this mechanism. Liver microsomes from humans, rats, and mice were preincubated with INH and NADPH; thereafter, residual CYP2E1 activity was measured. The inhibition of CYP2E1 by INH was potentiated by preincubation, indicating time-dependent inhibition. There were no major species-based differences in inhibition among humans, rats, and mice. Further to our findings on the inhibition kinetics, resistance of the inhibition to glutathione and catalase indicated that the reactive metabolites of INH covalently bonded to CYP2E1 in a suicidal manner. A similar time-dependent inhibition was also observed for the known metabolites acetylhydrazine and hydrazine; however, the conditions that inhibited the hydrolysis or activated the acetylation of INH did not affect inhibition by INH, suggesting that the reactive metabolites contributing to the inhibition were generated via alternative pathways. This indicates that CYP2E1 alone generates reactive INH metabolites and that haptenized CYP2E1 may be involved in immune-mediated liver injury.

Inhibitory Effect of Two Carbonic Anhydrases Inhibitors on the Activity of Major Cytochrome P450 Enzymes.

Both AW-9A (coumarin derivative) and WES-1 (sulfonamide derivative) were designed and synthesized as potential selective carbonic anhydrase inhibitors and were tested for anticancer activity. This study was undertaken to investigate their potential inhibitory effects on the major human cytochrome P450 (CYP) drug-metabolizing enzymes. Specific CYP probe substrates and validated analytical methods were used to measure the activity of the tested CYP enzymes. Furthermore, in silico simulations were conducted to understand how AW-9A and WES-1 bind to CYP2A6 at a molecular level. Molecular docking experiments were performed using the high-resolution X-ray structure, Protein Data Bank (PDB) ID: 2FDV for CYP2A6. CYP2E1-catalyzed chlorzoxazone-6'-hydroxylation was strongly inhibited by AW-9A and WES-1 with IC50 values of 0.084 µM and 0.101 µM, respectively. CYP2A6-catalyzed coumarin-7'-hydroxylation was moderately inhibited by AW-9A (IC50 = 4.2 µM). CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 enzymes were weakly or negligibly inhibited by both agents. Docking studies suggest elevated potential to block the catalytic activity of CYP2A6. These findings point to the feasibility of utilizing these agents as promising chemopreventive agents (owing to inhibition of CYP2E1), and AW-9A as a smoking cessation aid (owing to inhibition of CYP2A6). Additional in-vivo studies should be conducted to examine the impact of CYP2A6 and CYP2E1 inhibition on drug interactions with probe substrates of these enzymes.

Common anesthetic used in preclinical PET imaging inhibits metabolism of the PET tracer [18F]3F4AP.

Positron emission tomography (PET) imaging studies in laboratory animals are almost always performed under isoflurane anesthesia to ensure that the subject stays still during the image acquisition. Isoflurane is effective, safe, and easy to use, and it is generally assumed to not have an impact on the imaging results. Motivated by marked differences observed in the brain uptake and metabolism of the PET tracer 3-[18F]fluoro-4-aminopyridine [(18F]3F4AP) between human and nonhuman primate studies, this study investigates the possible effect of isoflurane on this process. Mice received [18F]3F4AP injection while awake or under anesthesia and the tracer brain uptake and metabolism was compared between groups. A separate group of mice received the known cytochrome P450 2E1 inhibitor disulfiram prior to tracer administration. Isoflurane was found to largely abolish tracer metabolism in mice (74.8 ± 1.6 vs. 17.7 ± 1.7% plasma parent fraction, % PF) resulting in a 4.0-fold higher brain uptake in anesthetized mice at 35 min post-radiotracer administration. Similar to anesthetized mice, animals that received disulfiram showed reduced metabolism (50.0 ± 6.9% PF) and a 2.2-fold higher brain signal than control mice. The higher brain uptake and lower metabolism of [18F]3F4AP observed in anesthetized mice compared to awake mice are attributed to isoflurane's interference in the CYP2E1-mediated breakdown of the tracer, which was confirmed by reproducing the effect upon treatment with the known CYP2E1 inhibitor disulfiram. These findings underscore the critical need to examine the effect of isoflurane in PET imaging studies before translating tracers to humans that will be scanned without anesthesia.

Comparative In Vitro Study of the Cytotoxic Effects of Doxorubicin’s Main Metabolites on Cardiac AC16 Cells Versus the Parent Drug

Doxorubicin (DOX; also known as adriamycin) serves as a crucial antineoplastic agent in cancer treatment; however, its clinical utility is hampered by its’ intrinsic cardiotoxicity. Although most DOX biotransformation occurs in the liver, a comprehensive understanding of the impact of DOX biotransformation and its’ metabolites on its induced cardiotoxicity remains to be fully elucidated. This study aimed to explore the role of biotransformation and DOX's main metabolites in its induced cardiotoxicity in human differentiated cardiac AC16 cells. A key discovery from our study is that modulating metabolism had minimal effects on DOX-induced cytotoxicity: even so, metyrapone (a non-specific inhibitor of cytochrome P450) increased DOX-induced cytotoxicity at 2 µM, while diallyl sulphide (a CYP2E1 inhibitor) decreased the 1 µM DOX-triggered cytotoxicity. Then, the toxicity of the main DOX metabolites, doxorubicinol [(DOXol, 0.5 to 10 µM), doxorubicinone (DOXone, 1 to 10 µM), and 7-deoxydoxorubicinone (7-DeoxyDOX, 1 to 10 µM)] was compared to DOX (0.5 to 10 µM) following a 48-h exposure. All metabolites evaluated, DOXol, DOXone, and 7-DeoxyDOX caused mitochondrial dysfunction in differentiated AC16 cells, but only at 2 µM. In contrast, DOX elicited comparable cytotoxicity, but at half the concentration. Similarly, all metabolites, except 7-DeoxyDOX impacted on lysosomal ability to uptake neutral red. Therefore, the present study showed that the modulation of DOX metabolism demonstrated minimal impact on its cytotoxicity, with the main metabolites exhibiting lower toxicity to AC16 cardiac cells compared to DOX. In conclusion, our findings suggest that metabolism may not be a pivotal factor in mediating DOX's cardiotoxic effects.Graphical

Translocation of Adenosine A2B Receptor to Mitochondria Influences Cytochrome P450 2E1 Activity after Acetaminophen Overdose.

The adenosine A2B receptor (A2BAR) is a member of a family of G-protein coupled receptors (GPCRs), which has a low affinity for adenosine and is now implicated in several pathophysiological conditions. We have demonstrated the beneficial effects of A2BAR activation in enhancing recovery after acute liver injury induced by an acetaminophen (APAP) overdose. While receptor trafficking within the cell is recognized to play a role in GPCR signaling, its role in the mediation of A2BAR effects in the context of APAP-induced liver injury is not well understood. This was investigated here, where C57BL/6J mice were subjected to an APAP overdose (300 mg/kg), and the temporal course of A2BAR intracellular localization was examined. The impact of A2BAR activation or inhibition on trafficking was examined by utilizing the A2BAR agonist BAY 60-6583 or antagonist PSB 603. The modulation of A2BAR trafficking via APAP-induced cell signaling was explored by using 4-methylpyrazole (4MP), an inhibitor of Cyp2E1 and JNK activation. Our results indicate that APAP overdose induced the translocation of A2BAR to mitochondria, which was prevented via 4MP treatment. Furthermore, we demonstrated that A2BAR is localized on the mitochondrial outer membrane and interacts with progesterone receptor membrane component 1 (PGRMC1). While the activation of A2BAR enhanced mitochondrial localization, its inhibition decreased PGRMC1 mitochondria levels and blunted mitochondrial Cyp2E1 activity. Thus, our data reveal a hitherto unrecognized consequence of A2BAR trafficking to mitochondria and its interaction with PGRMC1, which regulates mitochondrial Cyp2E1 activity and modulates APAP-induced liver injury.

High-Dose Acetaminophen with Concurrent CYP2E1 Inhibition Has Profound Anticancer Activity without Liver Toxicity.

Acetaminophen (AAP) is metabolized by a variety of pathways such as sulfation, glucuronidation, and fatty acid amide hydrolase-mediated conversion to the active analgesic metabolite AM404. CYP2E1-mediated metabolism to the hepatotoxic reactive metabolite NAPQI (N-acetyl-p-benzoquinone imine) is a minor metabolic pathway that has not been linked to AAP therapeutic benefits yet clearly leads to AAP liver toxicity. N-acetylcysteine (NAC) (an antioxidant) and fomepizole (a CYP2E1 inhibitor) are clinically used for the treatment of AAP toxicity. Mice treated with AAP in combination with fomepizole (plus or minus NAC) were assessed for liver toxicity by histology and serum chemistry. The anticancer activity of AAP with NAC and fomepizole rescue was assessed in vitro and in vivo. Fomepizole with or without NAC completely prevented AAP-induced liver toxicity. In vivo, high-dose AAP with NAC/fomepizole rescue had profound antitumor activity against commonly used 4T1 breast tumor and lewis lung carcinoma lung tumor models, and no liver toxicity was detected. The antitumor efficacy was reduced in immune-compromised NOD-scid IL2Rgammanull mice, suggesting an immune-mediated mechanism of action. In conclusion, using fomepizole-based rescue, we were able to treat mice with 100-fold higher than standard dosing of AAP (650 mg/kg) without any detected liver toxicity and substantial antitumor activity. SIGNIFICANCE STATEMENT: High-dose acetaminophen can be given concurrently with CYP2E1 inhibition to allow for safe dose escalation to levels needed for anticancer activity without detected evidence of toxicity.

Functionalized selenium nanoparticles ameliorated acetaminophen-induced hepatotoxicity through synergistically triggering PKCδ/Nrf2 signaling pathway and inhibiting CYP 2E1

Selenium nanoparticles (SeNPs) have been demonstrated potential for use in diseases associated with oxidative stress. Functionalized SeNPs with lower toxicity and higher biocompatibility could bring better therapeutic activity and clinical application value. Herein, this work was conducted to investigate the protective effect of Pleurotus tuber-regium polysaccharide-protein complex funtionnalized SeNPs (PTR-SeNPs) against acetaminophen (APAP)-induced oxidative injure in HepG2 cells and C57BL/6J mouse liver. Further elucidation of the underlying molecular mechanism, in particular their modulation of Nrf2 signaling pathway was also performed. The results showed that PTR-SeNPs could significantly ameliorate APAP-induced oxidative injury as evidenced by a range of biochemical analysis, histopathological examination and immunoblotting study. PTR-SeNPs could hosphorylate and activate PKCδ, depress Keap1, and increase nuclear accumulation of Nrf2, resulting in upregulation of GCLC, GCLM, HO-1 and NQO-1 expression. Besides, PTR-SeNPs suppressed the biotransformation of APAP to generate intracellular ROS through CYP 2E1 inhibition, restoring the mitochondrial morphology. Furthermore, the protective effect of PTR-SeNPs against APAP induced hepatotoxicity was weakened as Nrf2 was depleted in vivo, indicating the pivotal role of Nrf2 signaling pathway in PTR-SeNPs mediated hepatoprotective efficacy. Being a potential hepatic protectant, PTR-SeNPs could serve as a new source of selenium supplement for health-promoting and biomedical applications.

Amelioration of ethanol-induced oxidative stress and alcoholic liver disease by invivo RNAi targeting Cyp2e1.

Alcoholic liver disease (ALD) results from continuous and heavy alcohol consumption. The current treatment strategy for ALD is based on alcohol withdrawal coupled with antioxidant drug intervention, which is a long process with poor efficacy and low patient compliance. Alcohol-induced CYP2E1 upregulation has been demonstrated as a key regulator of ALD, but CYP2E1 knockdown in humans was impractical, and pharmacological inhibition of CYP2E1 by a clinically relevant approach for treating ALD was not shown. In this study, we developed a RNAi therapeutics delivered by lipid nanoparticle, and treated mice fed on Lieber-DeCarli ethanol liquid diet weekly for up to 12 weeks. This RNAi-based inhibition of Cyp2e1 expression reduced reactive oxygen species and oxidative stress in mouse livers, and contributed to improved ALD symptoms in mice. The liver fat accumulation, hepatocyte inflammation, and fibrosis were reduced in ALD models. Therefore, this study suggested the feasibility of RNAi targeting to CYP2E1 as a potential therapeutic tool to the development of ALD.

Calotropis gigantea stem bark extract activates HepG2 cell apoptosis through ROS and its effect on cytochrome P450

The 95% ethanolic extract of the dry powder of Calotropis gigantea (C. gigantea) stem bark was separated by fractionation with different solutions to yield 4 fractions: dichloromethane (CGDCM), ethyl acetate (CGEtOAc), and water (CGW). This research focused on CGDCM-induced apoptosis in HepG2 cells with IC50 and above-IC50 values, which provide useful information for future anticancer applications. CGDCM had lower cytotoxicity on normal lung fibroblast IMR-90 cells than on HepG2 cells. Apoptotic induction of CGDCM was mediated by decreased fatty acid and ATP synthesis while increasing reactive oxygen species production. The effects of the four extracts on the activity of the four major CYP450 isoforms (CYP1A2, CYP2C9, CYP2E1 and CYP3A4) were determined using the CYP-specific model activity of each isoform. All four fractions of the extract were shown to be poor inhibitors of CYP1A2 and CYP2E1 (IC50 > 1000 μg/mL) and moderate inhibitors of CYP3A4 (IC50 = 56.54–296.9 μg/mL). CGDCM and CGW exerted moderate inhibition activities on CYP2C9 (IC50 = 59.56 and 46.38 μg/mL, respectively), but CGEtOH and CGEtOAc exhibited strong inhibition activities (IC50 = 12.11 and 20.43 μg/mL, respectively). It is proposed that C. gigantea extracts at high doses have potential for further studies to develop alternative anticancer applications. Inhibiting CYP2C9 activity may also lead to drug-herb interactions.

Study on the liver Drug's dominant metabolic enzymes for six effective components of the Huang qi Liuyi decoction.

Objective: To investigate the dominant metabolic enzymes of six effective components (astragaloside IV, glycyrrhizic acid, calycosin-glucuronide, formononetin, ononin, calycosin-7-O-β-D- glucoside) of Huangqi Liuyi decoction extract (HQD). Methods: Mouse liver microsomes were prepared. The effects of specific inhibitors of CYP450 enzymes on the metabolism of six effective components of HQD were studied using liver microsomal incubation in vitro. Results: The chemical inhibitors of CYP2C37 inhibit the metabolism of glycyrrhizic acid and astragaloside IV. Formononetin and astragaloside IV metabolism is inhibited by the chemical inhibitors of CYP2C11. The chemical inhibitors of CYP2E1 and CYP1A2 inhibit the metabolism of calycosin-glucuronide. Chemical CYP3A11 inhibitors prevent formononetin and glycyrrhizic acid from being metabolized. However, no inhibitor significantly affected the metabolism of ononin and calycosin-7-O-β-D-glucoside. Conclusion: CYP2C37 may be involved in the metabolism of astragaloside IV and glycyrrhizic acid, the metabolism of astragaloside IV and formononetin may be related to CYP2C11, the metabolism of calycosin-glucuronide may be related to CYP1A2 and CYP2E1, and CYP3A11 may be involved in the metabolism of glycyrrhizic acid and formononetin. This research provides an experimental basis for exploring the pharmacokinetic differences caused by metabolic enzymes.

Amelioration of Hepatic Steatosis by the Androgen Receptor Inhibitor EPI-001 in Mice and Human Hepatic Cells Is Associated with the Inhibition of CYP2E1.

Nonalcoholic fatty liver disease (NAFLD) is recognized as a metabolic disease characterized by hepatic steatosis. Despite the growing burden of NAFLD, approved pharmacological treatment is lacking. As an inhibitor of androgen receptor (AR), EPI-001 is being explored for the treatment of prostate cancer. This study aimed to investigate the potential of EPI-001 for treating NAFLD in free fatty acids (FFAs)-induced human hepatic cells and high-fat-high-sugar (HFHS)-feeding mice. Our results showed that EPI-001 reduced lipid accumulation in hepatic cells and ameliorated hepatic steatosis in mouse livers. Further exploration suggested that the effect of EPI-001 was associated with CYP2E1-mediated reduction of reactive oxygen species (ROS). This provides encouraging evidence for further studies on EPI-001 therapy for NAFLD.

Endoplasmic reticulum-targeted inhibition of CYP2E1 with vitamin E nanoemulsions alleviates hepatocyte oxidative stress and reverses alcoholic liver disease

Alcoholic liver disease (ALD) is a global healthcare problem and socioeconomic issue that is primarily driven by chronic and/or excessive alcohol consumption. Upon alcohol exposure, parenchymal hepatocytes (HCs) up-regulate endoplasmic reticulum (ER)-localized monooxygenase Cytochrome P450 family 2 subfamily E member 1 (CYP2E1) to accelerate the metabolism of ethanol (EtOH), which concurrently exacerbates the production and accumulation of toxic metabolic intermediates, especially reactive oxygen species (ROS), playing a decisive role in the initiation and perpetuation of alcohol-induced liver injury. ALD patients without timely intervention may develop a spectrum of metabolic and functional disorders in the liver, including hepatic steatosis, hepatitis, fibrosis, and even cirrhosis. However, up to now, there have been no FDA-approved pharmacological or nutritional therapeutics for treating patients with ALD, and an effective amelioration of alcohol-induced hepatotoxicity with satisfactory biosafety is still demanding. In this study, antioxidant Vitamin E-incorporating nanoemulsions modified with ER-targetable small molecule p-dodecylbenzene sulfonamide (p-DBSN) was constructed to load and deliver CYP2E1 inhibitor Clomethiazole (CMZ) to the ER of HCs for site-specific inhibition, which displayed remarkable hepatoprotective effects against chronic alcohol exposure without off-target toxicity, both intravenously injected and orally administrated. Generally, our work may provide a promising nanoplatform for reversing ALD.

An experimental and theoretical study of ROS scavenging by organosulfur compounds from garlic: In silico analysis of metabolic pathways and interactions on CYP2E1

Using experimental and computational methodologies, we analyzed the possible interactions of two organosulfur compounds (OSC), Allyl methyl sulfide (AMS) and Diallyl sulfide (DAS), with different reactive oxygen species (ROS), which cause oxidative stress. Additionally, we study both OSC as inhibitors of CYP2E1, an enzyme involved in the generation of ROS. Effective quantitative interaction of both OSC with H2O2, O2 • - and O2(1Δg) was found by experimental methods. The experimental k values at 288 K of H2O2 scavenging reaction for AMS (5.43 × 10−20 cm3 molecule−1 s−1) and DAS (1.65 × 10−21 cm3 molecule−1 s−1) indicate the reaction is more quick when AMS is the reactant. This trend was maintained when the HO• scavenging reactions were analyzed with computational methodologies using IRC calculations with M06-2x/6-311++G(3df, 2p) level of theory and gaseous, aqueous and no-polar phases. An in silico analysis of OSC and their metabolites derived from epoxidation and sulfoxidation reactions showed that these compounds present a high probability of being inhibitors of the CYP2E1 enzyme. The molecular docking showed an effective binding in the complexes enzyme-OSC and enzyme-metabolites, with a major interaction between the sulfur and oxygen atoms and the heme iron ion.

Crosstalk between CYP2E1 and PPARα substrates and agonists modulate adipose browning and obesity

Although the functions of metabolic enzymes and nuclear receptors in controlling physiological homeostasis have been established, their crosstalk in modulating metabolic disease has not been explored. Genetic ablation of the xenobiotic-metabolizing cytochrome P450 enzyme CYP2E1 in mice markedly induced adipose browning and increased energy expenditure to improve obesity. CYP2E1 deficiency activated the expression of hepatic peroxisome proliferator-activated receptor alpha (PPARα) target genes, including fibroblast growth factor (FGF) 21, that upon release from the liver, enhanced adipose browning and energy expenditure to decrease obesity. Nineteen metabolites were increased in Cyp2e1-null mice as revealed by global untargeted metabolomics, among which four compounds, lysophosphatidylcholine and three polyunsaturated fatty acids were found to be directly metabolized by CYP2E1 and to serve as PPARα agonists, thus explaining how CYP2E1 deficiency causes hepatic PPARα activation through increasing cellular levels of endogenous PPARα agonists. Translationally, a CYP2E1 inhibitor was found to activate the PPARα–FGF21–beige adipose axis and decrease obesity in wild-type mice, but not in liver-specific Ppara-null mice. The present results establish a metabolic crosstalk between PPARα and CYP2E1 that supports the potential for a novel anti-obesity strategy of activating adipose tissue browning by targeting the CYP2E1 to modulate endogenous metabolites beyond its canonical role in xenobiotic-metabolism.

Large paracetamol overdose - Higher dose NAC is NOT required.

Paracetamol overdose is common in developed countries but less than 10% involve large ingestions exceeding 30 g or 500 mg/kg. High dose acetylcysteine (NAC) has been proposed in patients taking large paracetamol overdoses based on reports of hepatotoxicity despite early initiation of NAC treatment with the commonly used 300 mg/kg intravenous acetylcysteine regimen. The evidence from cohorts of patients treated with the standard NAC regimen after large paracetamol overdoses shows that it is effective in most patients. A small study in patients with paracetamol overdoses of 40 g or more and paracetamol concentrations above the 300 mg/L nomogram line showed that modification of the standard NAC regimen to provide a total of 400-500 mg/kg NAC over 21-22 h may reduce the risk of hepatotoxicity (peak ALT > 1000 IU/L) but the impact on development of hepatic failure, liver transplantation and mortality with this approach is presently unknown. Better risk stratification of patients taking paracetamol overdose may allow higher dose NAC and adjunctive treatments such as CYP2E1 inhibition and extracorporeal removal of paracetamol to be targeted to those patients at the highest risk of hepatotoxicity after a large paracetamol overdose.

Triptolide regulates oxidative stress and inflammation leading to hepatotoxicity via inducing CYP2E1.

Triptolide (TP), the main active compound extracted from medicine-tripterygium wilfordii Hook f. (TWHF). It has anti-tumor and immunomodulatory properties. Our study aimed to investigate the mechanisms of hepatotoxicity treated with TP in vivo and in vitro, as well as their relationship with the NF-κB (p65) signal pathway; and to assess TP-induced hepatotoxicity after CYP2E1 modulation by the known inhibitor, clomethiazole, and the known inducer, pyrazole. Mice were given TP to cause liver injury and IHHA-1 cells were given TP to cause hepatocyte injury. The enzyme activity and hepatotoxicity changed dramatically when the CYP2E1 inhibitor and inducer were added. In comparison to the control group, the enzyme inducer increased the activity of CYP2E1, whereas the enzyme inhibitor had the opposite effect. Our findings suggest that TP is an inducer of CYP2E1 via a time-dependent activation mechanism. In addition, TP can promote oxidative stress, inflammatory and involving the NF-κB (p65) signal pathway. Therefore, we used triptolide to stimulate C57 mice and IHHA-1 cells to determine whether TP can promote oxidative stress and inflammation by activating CYP2E1 in response to exacerbated liver damage and participate in NF-κB (p65) signaling pathway.

Human CYP enzyme-activated genotoxicity of 2,2′,4,4′-tetrabromobiphenyl ether in mammalian cells

Polybrominated biphenyl ethers (PBDEs) are a group of persistent organic pollutants with endocrine-disrupting, neurotoxic, tumorigenic and DNA-damaging activities. They are hydroxylated by human liver microsomal CYP enzymes, however, their mutagenicity remains unknown. In this study, 2,2′,4,4′-tetrabromobiphenyl ether (BDE-47, relatively abundant in human tissues) was investigated for micronuclei induction and DNA damage in mammalian cells. The results indicated that BDE-47 up to 80 μM under a 6 h/18 h (exposure/recovery, covering 2 cell cycles) regime did not induce micronuclei in V79-Mz and V79-derived cell lines expressing human CYP1A1 or 1A2, while it was moderately positive in human CYP2B6-, 2E1-and 3A4-expressing cell lines (V79-hCYP2B6, V79-hCYP2E1-hSULT1A1 and V79-hCYP3A4-hOR, respectively). Following 24 h exposure, BDE-47 induced micronuclei in V79-hCYP2E1-hSULT1A1 and V79-hCYP3A4 cells at increased potencies. In the human hepatoma (HepG2) cells BDE-47 (48 h exposure) was inactive up to 40 μM, however, pretreatment of the cells with ethanol (0.2%, v:v, inducer of CYP2E1) or rifampicin (10 μM, inducer of CYP3A4) led to significant micronuclei formation by BDE-47; pretreatment with bisphenol AF (100 nM) also potentiated BDE-47-induced micronuclei formation (which was blocked by a CYP2E1 inhibitor trans-1,2-dichloroethylene or a CYP3A inhibitor (ketoconazole). Immunofluorescent staining of centromere protein B with the micronuclei formed by BDE-47 in HepG2 cells pretreated with ethanol or rifampicin demonstrated selective formation of centromere-containing micronuclei. The increased phosphorylation of both histones H2AX and H3 in HepG2 by BDE-47 also indicated an aneugenic potential. Therefore, this study suggests that BDE-47 is an aneugen activated by several human CYP enzymes.