Xenobiotic-metabolizing Enzymes Research Articles

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.

Time of Day-Specific Changes in Metabolic Detoxification and Insecticide Tolerance in the House Fly, Musca domestica L.

Both insects and mammals all exhibit a daily fluctuation of susceptibility to chemicals at different times of the day. However, this phenomenon has not been further studied in the house fly (Musca domestica L.) and a better understanding of the house fly on chronobiology should be useful for controlling this widespread disease vector. Here we explored diel time-of-day variations in insecticide susceptibility, enzyme activities, and xenobiotic-metabolizing enzyme gene expressions. The house fly was most tolerant to beta-cypermethrin in the late photophase at Zeitgeber time (ZT) 8 and 12 [i.e., 8 and 12 h after light is present in the light-dark cycle (LD)]. The activities of cytochrome P450, GST, and CarE enzymes were determined in the house flies collected at various time, indicating that rhythms occur in P450 and CarE activities. Subsequently, we observed diel rhythmic expression levels of detoxifying genes, and CYP6D1 and MdαE7 displayed similar expression patterns with enzyme activities in LD conditions, respectively. No diel rhythm was observed for CYP6D3 expression. These data demonstrated a diel rhythm of metabolic detoxification enzymes and insecticide susceptibility in M. domestica. In the future, the time-of-day insecticide efficacy could be considered into the management of the house fly.

Факторы риска формирования хронического полипозного риносинусита у детей с муковисцидозом

The investigation of the pathogenesis of chronic rhinosinusitis in patients with cystic fibrosis (CF) and analysis of molecular biomarkers can promote the development of tailored approaches to its treatment and prevention. Objective. To analyze associations between sinonasal polyposis and genetic polymorphisms of the xenobiotic metabolizing enzymes (XMEs) in CF patients. Patients and methods. We performed a retrospective comparative analysis of 145 CF patients from the Russian Federation (RF) and 82 patients from the Republic of Belarus (RB). Patients provided blood samples that were later used for DNA extraction; clinical information was collected for all study participants. The diagnosis was based on the guidelines of the European and Russian Consensus. This was a case-control study. The XME gene polymorphisms were assessed using polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP) or amplified fragment length polymorphism (AFLP) analysis with special primers. The following genes and polymorphic variants were chosen for the study: phase I (CYP2C9*3 (rs1057910; c.1075A>C; I359L), CYP2C9*2 (rs1799853; c.430C>T; R144C), CYP2C19*2 (rs4244285; c.681G>A), CYP2C19*3 (rs4986893; c.636G>A; W212X), CYP2D6*4 (rs3892097; c.1846G>A), CYP3A4*3 (rs4986910; M445T; c.1334T>C), CYP3A4*1B (rs2740574; c.-392C>T); phase II (deletions in GSTT1 and GSTM1; GSTP1 (c.313A>G); GCLC (TNR(GAG), c.-129C>T); GCLM (c.-588C>T); NAT2 (c.191G>A, c.282C>T, c.341T>C, c.434A>C, c.481C>T, c.590G>A, c.803A>G, c.845A>C, c.857G>A)). Results. Mean patient age was 12.69 ± 6.9 years (5.03–40.36) and did not vary between the RF and RB patients. The male to female ratio was 0.52:0.48 (118:109). Nasal polyposis was diagnosed in 61 patients (26.9%), while 166 children (73.1%) had no nasal polyps. We found that patients with chronic rhinosinusitis and nasal polyps were more likely to have ‘severe’ CFTR genotypes: 95.6% vs 4.4% of patients with a ‘mild’ genotype (р = 0.05). We observed no significant associations between nasal polyposis and analyzed XME gene polymorphisms, as well as glutathione metabolic genes. Conclusion. We found no associations between nasal polyposis and XME gene polymorphisms (phase 1 and 2), which suggests the need for further research aimed to identify other molecular mechanisms underlying the development of nasal polyps in CF patients. Key words: sinonasal polyposis, chronic rhinosinusitis, xenobiotic biotransformation enzymes, cystic fibrosis, glutathione, inflammation

Green sweet potato leaves increase Nrf2-mediated antioxidant activity and facilitate benzo[a]pyrene metabolism in the liver by increasing phase II detoxifying enzyme activities in rats

Sweet potato leaves (SPL) are a valuable source of phytonutrients with nutritional and various health-promoting benefits. This study evaluated the effects of green and purple SPL supplementation on hepatic xenobiotic-metabolizing enzymes (XME) and membrane transporters, and benzo[a]pyrene (B[a]P) metabolism and B[a]P accumulation in rats. The experiments were conducted in standard and B[a]P-treated rat models. The first experiment showed that rats fed a diet containing 5% (w/w) green or purple SPL for two weeks showed increased hepatic activity of cytochrome P-450 (CYP)1A1/1A2 and glutathione S-transferase. Green SPL supplementation also increased the CYP2C, CYP2D and CYP3A and multidrug resistance-associated protein 2 levels in the liver. Notably, green and purple SPL induced nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 protein expression and reduced oxidative stress in the liver. The second experiment was to evaluate the effects of green and purple SPL supplementation on B[a]P metabolism and B[a]P accumulation in rats. Rats were fed SPL diets (the same as experiment I) for two weeks. When rats were exposed to a single dose (25 mg per kg BW) of B[a]P, green SPL had no effect on B[a]P-induced elevation of CYP1A1 activity but induced GST activity in the intestinal mucosa and the liver. Green SPL also increased hepatic UDP-glucuronosyltransferase activity and reduced B[a]P levels in the plasma, liver, and intestinal mucosa. A lower plasma 8-hydroxy-2'-deoxyguanosine level was found after B[a]P treatment only in the green SPL group. This study suggests that, in the standard rat model, green and purple SPL may increase Nrf2-mediated antioxidant activity and facilitate the xenobiotic detoxification process by increasing hepatic XME and transporters. When exposed to B[a]P, however, only green SPL consumption may increase hepatic B[a]P metabolism and lower the B[a]P level in the liver by increasing phase II detoxifying enzyme activities.

MicroRNA target-based network predicts androgen receptor-linked mycotoxin stress

Stress-responsive microRNAs (miRNAs) contribute to the regulation of cellular homeostasis or pathological processes, including carcinogenesis, by reprogramming target gene expression following human exposure to environmental or dietary xenobiotics. Herein, we predicted the targets of carcinogenic mycotoxin-responsive miRNAs and analyzed their association with disease and functionality. miRNA target-derived prediction indicated potent associations of oncogenic mycotoxin exposure with metabolism- or hormone-related diseases, including sex hormone-linked cancers. Mechanistically, the signaling network evaluation suggested androgen receptor (AR)-linked signaling as a common pivotal cluster associated with metabolism- or hormone-related tumorigenesis in response to aflatoxin B1 and ochratoxin A co-exposure. Particularly, high levels of AR and AR-linked genes for the retinol and xenobiotic metabolic enzymes were positively associated with attenuated disease biomarkers and good prognosis in patients with liver or kidney cancers. Moreover, AR-linked signaling was protective against OTA-induced genetic insults in human hepatocytes whereas it was positively involved in AFB1-induced genotoxic actions. Collectively, miRNA target network-based predictions provide novel clinical insights into the progression or intervention against malignant adverse outcomes of human exposure to environmental oncogenic insults.

Nuclear hormone receptors promote gut and glia detoxifying enzyme induction and protect C.elegans from the mold P.brevicompactum.

SUMMARYAnimals encounter microorganisms in their habitats, adapting physiology and behavior accordingly. The nematode Caenorhabditis elegans is found in microbe-rich environments; however, its responses to fungi are not extensively studied. Here, we describe interactions of C. elegans and Penicillium brevicompactum, an ecologically relevant mold. Transcriptome studies reveal that co-culture upregulates stress response genes, including xenobiotic-metabolizing enzymes (XMEs), in C. elegans intestine and AMsh glial cells. The nuclear hormone receptors (NHRs) NHR-45 and NHR-156 are induction regulators, and mutants that cannot induce XMEs in the intestine when exposed to P. brevicompactum experience mitochondrial stress and exhibit developmental defects. Different C. elegans wild isolates harbor sequence polymorphisms in nhr-156, resulting in phenotypic diversity in AMsh glia responses to microbe exposure. We propose that P. brevicompactum mitochondria-targeting mycotoxins are deactivated by intestinal detoxification, allowing tolerance to moldy environments. Our studies support the idea that C. elegans NHRs may be regulated by environmental cues.

Involvement of aldehyde oxidase in the metabolism of aromatic and aliphatic aldehyde-odorants in the mouse olfactory epithelium

Xenobiotic-metabolizing enzymes (XMEs) expressed in the olfactory epithelium (OE) are known to metabolize odorants. Aldehyde oxidase (AOX) recognizes a wide range of substrates among which are substrates with aldehyde groups. Some of these AOX substrates are odorants, such as benzaldehyde and n-octanal. One of the mouse AOX isoforms, namely AOX2 (mAOX2), was shown to be specifically expressed in mouse OE but its role to metabolize odorants in this tissue remains unexplored. In this study, we investigated the involvement of mouse AOX isoforms in the oxidative metabolism of aldehyde-odorants in the OE. Mouse OE extracts effectively metabolized aromatic and aliphatic aldehyde-odorants. Gene expression analysis revealed that not only mAOX2 but also the mAOX3 isoform is expressed in the OE. Furthermore, evaluation of inhibitory effects using the purified recombinant enzymes led us to identify specific inhibitors of each isoform, namely chlorpromazine, 17β-estradiol, menadione, norharmane, and raloxifene. Using these specific inhibitors, we defined the contribution of mAOX2 and mAOX3 to the metabolism of aldehyde-odorants in the mouse OE. Taken together, these findings demonstrate that mAOX2 and mAOX3 are responsible for the oxidation of aromatic and aliphatic aldehyde-odorants in the mouse OE, implying their involvement in odor perception.

DOSE-DEPENDENT PROTECTIVE FEATURES OF LOBOPHORA VARIEGATA METHANOLIC EXTRACT (LVME) IN N-NITROSODIETHYLAMINE INDUCED EXPERIMENTAL HEPATOCARCINOGENESIS IN RATS

Objective: This study explores the anti-cancer property of Lobophora variegata, also an effective dose to treat hepatocarcinoma in Male Albino Wistar rats in N-nitrosodiethylamine induced hepatocarcinoma paradigm and its possible mechanism of action.
 Methods: In this study, rats were segregated into five groups; group-1 (control), group-2 treated with 0.01% NDEA through drinking water for 15 w, group-3 NDEA+treated with Lobophora variegata methanolic extract (LVME) (100 mg/kg b.w.), group-4 NDEA+treated with (LVME) (200 mg/kg b.w.) and group-5 NDEA+treated with (LVME) (400 mg/kg b.w.).
 Results: After the experimental period, functional and morphological changes in the liver were observed both macro and microscopically, the activities of liver marker enzymes, alkaline phosphatase (ALP), aspartate and alanine transaminases (AST and ALT) were analyzed. Administration of LVME as 200 mg/kg b.w. (to NDEA treated rats) significantly (i) reduced the preneoplastic lesions alleviated lipid peroxidation through scavenging free radicals, (ii) enhanced antioxidant status and reverted liver/disease marker enzymes plausibly by modulating xenobiotics metabolizing enzymes (XMEs) and by exhibiting antiproliferative and cytoprotective effects.
 Conclusion: LVME doses higher than 200 mg/kg b.w. are not effective in quenching the free radicals and restoring the liver functions as saturation level could have been reached; also, doses lower than 200 mg/kg b.w. could not be effective as they are below the optimum dose required to exhibit the pharmacological effects.

DMSO-free highly differentiated HepaRG spheroids for chronic toxicity, liver functions and genotoxicity studies.

The liver is essential in the elimination of environmental and food contaminants. Given the interspecies differences between rodents and humans, the development of relevant in vitro human models is crucial to investigate liver functions and toxicity in cells that better reflect pathophysiological processes. Classically, the differentiation of the hepatic HepaRG cell line requires high concentration of dimethyl sulfoxide (DMSO), which restricts its usefulness for drug-metabolism studies. Herein, we describe undifferentiated HepaRG cells embedded in a collagen matrix in DMSO-free conditions that rapidly organize into polarized hollow spheroids of differentiated hepatocyte-like cells (Hepoid-HepaRG). Our conditions allow concomitant proliferation with high levels of liver-specific functions and xenobiotic metabolism enzymes expression and activities after a few days of culture and for at least 4weeks. By studying the toxicity of well-known injury-inducing drugs by treating cells with 1- to 100-fold of their plasmatic concentrations, we showed appropriate responses and demonstrate the sensitivity to drugs known to induce various degrees of liver injury. Our results also demonstrated that the model is well suited to estimate cholestasis and steatosis effects of drugs following chronic treatment. Additionally, DNA alterations caused by four genotoxic compounds (Aflatoxin B1 (AFB1), Benzo[a]Pyrene (B[a]P), Cyclophosphamide (CPA) and Methyl methanesulfonate (MMS)) were quantified in a dose-dependent manner by the comet and micronucleus assays. Their genotoxic effects were significantly increased after either an acute 24h treatment (AFB1: 1.5-6μM, CPA: 2.5-10μM, B[a]P: 12.5-50μM, MMS: 90-450μM) or after a 14-day treatment at much lower concentrations (AFB1: 0.05-0.2μM, CPA: 0.125-0.5μM, B[a]P: 0.125-0.5μM) representative to human exposure. Altogether, the DMSO-free 3D culture of Hepoid-HepaRG provides highly differentiated and proliferating cells relevant for various toxicological in vitro assays, especially for drug-preclinical studies and environmental chemicals risk assessment.

Investigating the interaction between organic anion transporter 1 and ochratoxin A: An in silico structural study to depict early molecular events of substrate recruitment and the impact of single point mutations

Organic anion transporters (OATs) belong to a subgroup of the solute carrier 22 transporter family. OATs have a central role in xenobiotic disposition affecting the toxicokinetics of its substrates and inter-individual differences in their expression, activity and function impact both toxicokinetics and toxicodynamics. Amongst OATs, OAT1 (solute carrier family 22 member 6) is involved in the urinary excretion of many xenobiotics bringing substrates into renal proximal tubular cells which can then be secreted across the apical membrane into the tubule lumen. The mycotoxin ochratoxin A has been shown to have a high affinity for OAT1, which is an important renal transporter involved in its urinary excretion. Nowadays, molecular modeling techniques are widely applied to assess protein-ligand interactions and may provide a tool to depict the mechanic of xenobiotic action be it toxicokinetics or toxicodynamics. This work provides a structured pipeline consisting of docking and molecular dynamic simulations to study OAT1-ligand interactions and the impact of OAT1 polymorphisms on such interactions. Such a computational structure-based analytical framework allowed to: i) model OAT1-substrate complex formation and depict the features correlating its sequence, structure and its capability to recruit substrates; and ii) investigate the impact of OAT1 missense mutations on substrate recruitment. Perspectives on applying such a structured pipeline to xenobiotic-metabolising enzymes are discussed.

Oral enzymatic detoxification system: Insights obtained from proteome analysis to understand its potential impact on aroma metabolization.

The oral cavity is an entry path into the body, enabling the intake of nutrients but also leading to the ingestion of harmful substances. Thus, saliva and oral tissues contain enzyme systems that enable the early neutralization of xenobiotics as soon as they enter the body. Based on recently published oral proteomic data from several research groups, this review identifies and compiles the primary detoxification enzymes (also known as xenobiotic-metabolizing enzymes) present in saliva and the oral epithelium. The functions and the metabolic activity of these enzymes are presented. Then, the activity of these enzymes in saliva, which is an extracellular fluid, is discussed with regard to the salivary parameters. The next part of the review presents research evidencing oral metabolization of aroma compounds and the putative involved enzymes. The last part discusses the potential role of these enzymatic reactions on the perception of aroma compounds in light of recent pieces of evidence of in vivo oral metabolization of aroma compounds affecting their release in mouth and their perception. Thus, this review highlights different enzymes appearing as relevant to explain aroma metabolism in the oral cavity. It also points out that further works are needed to unravel the effect of the oral enzymatic detoxification system on the perception of food flavor in the context of the consumption of complex food matrices, while considering the impact of food oral processing. Thus, it constitutes a basis to explore these biochemical mechanisms and their impact on flavor perception.

Transcriptional Responses of Flavin-Containing Monooxygenase Genes in Scallops Exposed to PST-Producing Dinoflagellates Implying Their Involvements in Detoxification

Flavin-containing monooxygenase (FMO) is one of the most prominent xenobiotic metabolic enzymes. It can catalyze the conversion of heteroatom-containing chemicals to polar, readily excretable metabolites and is considered an efficient detoxification system for xenobiotics. Bivalves can accumulate paralytic shellfish toxins (PSTs) produced by dinoflagellates, especially during outbreaks of harmful algal blooms. Exploring FMO genes in bivalves may contribute to a better understanding of the adaptation of these species and the mechanisms of PSTs bioavailability. Therefore, through genome screening, we examined the expansion of FMO genes in two scallops (Patinopecten yessoensis and Chlamys farreri) and found a new subfamily (FMO_like). Our expression analyses revealed that, in both scallops, members of the FMO_N-oxide and FMO_like subfamilies were mainly expressed from the D-stage larvae to juveniles, whereas the FMO_GS-OX subfamily genes were mainly expressed at and prior to the trochophore stage. In adult organs, higher expressions of FMOs were observed in the kidney and hepatopancreas than in other organs. After exposure to PST-producing algae, expression changes in FMOs occurred in hepatopancreas and kidney of both scallops, with more members being up-regulated in hepatopancreas than in kidney for Alexandrium catenella exposure, while more up-regulated FMOs were found in kidney than in hepatopancreas of C. farreri exposed to A. minutum. Our findings suggest the adaptive functional diversity of scallop FMO genes in coping with the toxicity of PST-producing algae.

Okadaic acid-induced changes in xenobiotic-metabolizing enzyme and cytokine expression

Okadaic acid-induced changes in xenobiotic-metabolizing enzyme and cytokine expression

Amelioration of oxidative stress by trans-Anethole via modulating phase I and phase II enzymes against hepatic damage induced by CCl4 in male Wistar rats.

The current study was designed to assess the in vivo hepatoprotective properties of trans-Anethole, which is a principal aromatic component of star anise. The hepatoprotective effects of trans-Anethole were evaluated at three doses [40, 80, and 160 mg/kg body weight (b.wt.)] against carbon tetrachloride (CCl4)-induced hepatic damage in male Wistar rats for 4 weeks. Forty-two male Wistar rats were equally divided into seven groups; the control (group I) received only distilled water. Rats of group II received CCl4 (1 ml/kg b.wt.) in a 1:1 ratio of CCl4 and olive oil via intraperitoneal doses, while rats of group III received silymarin (50 mg/kg b.wt.), followed by CCl4 intraperitoneal doses, 3 days in a week. Rats of group IV received trans-anethole (160 mg/kg b.wt.) for 28 days as a negative control. Trans-anethole at the doses of 40, 80, and 160 mg/kg b.wt. was administered to groups V, VI, and VII, respectively, for 28 days, followed by CCl4 (i.p). Results showed that CCl4 treatment (group II) elevated the levels of different serum markers like aspartate aminotransferase (AST) by 4.74 fold, alanine aminotransferase (ALT) by 3.47 fold, aspartate alkaline phosphatase (ALP) by 3.55 fold, direct bilirubin by 3.48 fold, and total bilirubin by 2.38 fold in contrast to control. Furthermore, it was found that the decreased levels of liver antioxidant enzymes viz. catalase (CAT) and glutathione reductase (GR) were significantly modulated by the pre-administration of rats with different doses (40, 80, and 160 mg/kg b.wt.) of trans-anethole. Furthermore, pre-treatment of trans-anethole reduced the level of phase I enzymes and elevated the level of phase II detoxifying enzymes. Histopathological investigations showed that the treatment with trans-anethole was effective in ameliorating CCl4-induced liver injury and restored the normal hepatic architecture. Moreover, trans-anethole restored p53 and cyclin D levels in liver tissue relative to group II. Western blot analysis revealed that the trans-anethole treatment downregulated the expression of Bax and caspase-3 while upregulated the expression of Bcl-xL. Collectively, the findings of the study showed the strong efficacy of trans-anethole in ameliorating the hepatic damage caused by CCl4 through the modulation of antioxidants and xenobiotic-metabolizing enzymes.

Genetic Polymorphisms and Pesticide-Induced DNA Damage: A Review

The drastic increase in pesticide applications makes human exposure inevitable either through environment or occupation. Pesticide toxicity causes many adverse health effects through a number of pathways leading to DNA damage, mutations and cancers. Nevertheless, there is heterogeneity in the degree of toxicity among individuals due to the influence of genetic polymorphisms on xenobiotic metabolizing enzymes (XMEs) that modulate the biological process. Thus, study of the most common polymorphic genes coding for the enzymes involved in pesticide metabolism (such as cytochrome P450, Glutathione S-transferases, N-acetyltransferase and paraoxonase) may help determine individual’s susceptibility to pesticide toxicity. In this review, we give an overview of some recent developments in the field of genetic polymorphism and pesticide-related DNA damage, including probable biomarkers that may uncover genome susceptibility to pesticide toxicity. We have tried to create a connection between DNA polymorphism and cancer onslaught globally. It is envisaged that knowledge on this line would improve our understanding of facilitating the association between genotype and phenotype in cancer biology.

Influence of Bisphenol Compounds at Nanomolar Concentrations on Chromosome Damage Induced by Metabolically Activated Carcinogens in HepG2 Cells

Bisphenol (BP) compounds are endocrine-disrupting organic pollutants. BPs may increase the messenger RNA (mRNA) transcripts of nuclear receptors (NRs) regulating the expression of xenobiotic-metabolizing cytochrome P450 (CYP) enzymes. Their impact on the genotoxicity of metabolically activated carcinogens, however, remains unknown. In this study, effects of the bisphenols A, F, S, and AF on the expression of the aryl hydrocarbon receptor (AhR), the pregnane X receptor (PXR), the constitutive androstane receptor, and individual xenobiotic-metabolizing CYP enzymes in a human hepatoma (HepG2) cell line were investigated, along with in silico binding studies of BPs to each receptor. The results indicated that each BP at 1 to 100 nM concentrations increased the mRNA transcripts and protein levels of AhR, PXR, CYP1A1, 1A2, 1B1, 2E1, and 3A4. The predicted affinities of the BPs for binding AhR were comparable to those of potent agonists. Pretreatment of HepG2 cells with each BP potentiated the induction of micronuclei by benzo[a]pyrene, aflatoxin B1, benzene, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone; this effect was abolished/reduced by inhibitors of NRs and/or CYPs. Our study suggests that BPs at human exposure levels may aggravate chromosome damage by several impactful carcinogens in human cells by inducing relevant CYP enzymes, mostly via NR modulation.

Mitochondrial Biotransformation of Drugs and other Xenobiotics.

In vivo biotransformation of exposed chemicals is one of the major factors that determine the concentration and the duration of a substance at the systemic site of effect. Given that toxicity is expressed as a function of two factors, namely dose and time, the type and intensity of the toxicity are directly dependent on the chemical transformation of the exposed parent substance. This dependency involves two different situations. The amount of the chemical reaching the target will be decreased with the extent of metabolism if the parent chemical is toxic, and the opposite is true if the metabolite(s) is toxic instead. To date, the liver microsomal fraction in mammals has been justifiably considered as the center of biotransformation reactions because the liver and microsomes (i.e., endoplasmic reticulum component of the cell) possess the most abundant types and quantities of xenobiotic-metabolizing enzymes, especially the cytochrome P450 supergene enzyme family. These enzymes are common in all kingdoms of life, which strongly suggests that the origin of life is common. It is already known that various drugs enter mitochondria by different mechanisms, and this translocation is believed to be responsible for mitochondrial effects that are part of the therapeutic actions of various drugs such as lipid-lowering statins or antidiabetogenic thiazolidindiones. However, the discovery of mitochondrial forms of the xenobiotic-metabolizing enzymes provoked discussions about whether mitochondria metabolize drugs and other chemicals to some extent. This possibility may particularly be important as mitochondria have various critical cellular structures and functions. In the case of in situ generated metabolite(s), when there are adverse interactions with either these structures or functions, various toxic outcomes may appear. In this review, we compiled studies in the literature regarding biotransformation of drugs and other chemicals catalyzed by mitochondria where it is both an initiator and target of toxicity.

Dietary 5-demethylnobiletin modulates xenobiotic-metabolizing enzymes and ameliorates colon carcinogenesis in benzo[a]pyrene-induced mice

The intake of common polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (BaP), is strongly correlated to the initiation of colon cancer. BaP is a well-known pro-carcinogen that is metabolically activated by xenobiotic-metabolizing enzymes. Studies indicate that polymethoxyflavones, including 5-demethylnobiletin (5-DMNB), exhibit anti-inflammatory and anti-carcinogenic properties. However, the effects of 5-DMNB on xenobiotic-metabolizing enzymes and BaP-induced carcinogenesis remain unclear. The combination of BaP and a promoting agent—dextran sulfate sodium (DSS)—has been demonstrated to induce tumors in mouse models. Thus, this study aimed to determine the protective effect of 5-DMNB on carcinogen biotransformation and BaP/DSS-induced colon carcinogenesis. Our results showed that 5-DMNB had a substantial inhibitory effect on CYP1B1 induced by BaP and upregulated the detoxification enzymes UDP-glucuronosyltransferases (UGTs) and glutathione S-transferases (GSTs). Furthermore, subsequent analyses confirmed that the dietary administration of 5-DMNB markedly ameliorated tumor formation in BaP/DSS-treated mice. Exposure to BaP/DSS also significantly elevated TNF-α levels, and the administration of 5-DMNB reversed this increase. Taken together, we determined that 5-DMNB attenuates BaP/DSS-induced colon cancer through the regulation of inflammation and xenobiotic-metabolizing enzymes. These results indicate that 5-DMNB has significant potential as a novel chemopreventive agent for preventing carcinogen activation and inflammation-associated carcinogenesis.

Content of total aflatoxin, lead, and cadmium in the bovine meat and edible offal: study of their human dietary intake, health risk assessment, and molecular biomarkers.

The objectives of the present study were first to determine the residual contents of total aflatoxins (AFTs), lead (Pb), and cadmium (Cd) in the edible tissues of the cattle reared in Al-Ahsa, Saudi Arabia. Al-Ahsa is the largest governorate in the Eastern Province of Saudi Arabia. The two main economic activities of Al-Ahsa are oil production (industrial) and agriculture. Besides, dietary intake and possible health risks for Saudi population were further calculated. In order to establish potential molecular biomarkers for xenobiotic exposure in cattle, the mRNA expression of xenobiotic-metabolizing enzymes (XMEs) including cytochrome P450 (CYP) 1A1, NAD(P)H dehydrogenase [quinone] 1 (NQO1), metallothionein (MT) 1A, and heat shock protein (HSP) 70 was investigated in the different tissues of the cattle. The tested XMEs were selected because of their specific roles in the metabolism and detoxification of AFTs, Pb, and Cd. The obtained results revealed that the liver had significantly the highest AFT content, while all examined muscle samples had no AFT residues. Consumption of the bovine liver and kidneys represents the highest source for the dietary exposure to total AFTs (0.05-0.98μg/kg/day), Pb (0.06-0.19mg/kg/day), and Cd (0.08-0.19mg/kg/day) among the examined tissues. Therefore, excessive intake of such organs might pose a public health concern, particularly among children. Significant upregulation of mRNA expressions of CYP1A1, NQO1, MT1A, and HSP70 was observed in the different tissues of the cattle in comparison with the muscle. This upregulation had significant positive correlation with the accumulated AFTs, Pb, and Cd. This indicates the possible use of CYP1A1, NQO1, MT1A, and HSP70 as potential biomarkers for the exposure of the cattle to AFTs, Pb, and Cd.

Organoids for toxicology and genetic toxicology: applications with drugs and prospects for environmental carcinogenesis.

Advances in three-dimensional (3D) cell culture technology have led to the development of more biologically and physiologically relevant models to study organ development, disease, toxicology and drug screening. Organoids have been derived from many mammalian tissues, both normal and tumour, from adult stem cells and from pluripotent stem cells. Tissue organoids can retain many of the cell types and much of the structure and function of the organ of origin. Organoids derived from pluripotent stem cells display increased complexity compared with organoids derived from adult stem cells. It has been shown that organoids express many functional xenobiotic-metabolising enzymes including cytochrome P450s (CYPs). This has benefitted the drug development field in facilitating pre-clinical testing of more personalised treatments and in developing large toxicity and efficacy screens for a range of compounds. In the field of environmental and genetic toxicology, treatment of organoids with various compounds has generated responses that are close to those obtained in primary tissues and in vivo models, demonstrating the biological relevance of these in vitro multicellular 3D systems. Toxicological investigations of compounds in different tissue organoids have produced promising results indicating that organoids will refine future studies on the effects of environmental exposures and carcinogenic risk to humans. With further development and standardised procedures, advancing our understanding on the metabolic capabilities of organoids will help to validate their use to investigate the modes of action of environmental carcinogens.