Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.651
Filtrar
1.
Toxicol Lett ; 321: 131-137, 2020 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-31877331

RESUMO

Prior exposures to chemicals/agents may alter epigenome in such a way that subsequent exposure to the same or different xenobiotic would produce different responses. Understanding the mechanism for this "priming" effect is of clinical significance in avoiding adverse drug-drug interactions. Here we reported a dramatic priming effect of dimethyl sulfoxide (DMSO) on pregnane X receptor (PXR)-mediated gene regulations and analyzed the underpinning epigenetic mechanism. We showed that DMSO (1.25-2.5 %) pretreatment has a profound effect in enhancing the expression of PXR target genes. This priming effect persisted up to 48 h. Mechanistically, DMSO pretreatment reduced H4K12 acetylation and therefore enhanced the subsequent rifampicin stimulated histone H4R3 methylation on the regulatory region of PXR target gene CYP3A4. We showed that protein arginine methyltransferase 1 (PRMT1), which methylates H4R3, was important for priming by DMSO. Inhibition of methyltransferase by the pharmacological inhibitor adenosine dialehyde (AdoX), or RNAi knockdown of PRMT1, abolished the DMSO priming effects. On the other hand, Trichostation A (TSA) pretreatment, which increases histone acetylation and therefore suppresses H4R3 methylation, also abolished the DMSO priming effects. Based on the above observation, we proposed a model of sequential order of histone methylation and acetylation on the transcription "relay".


Assuntos
Montagem e Desmontagem da Cromatina/efeitos dos fármacos , Metilação de DNA/efeitos dos fármacos , Dimetil Sulfóxido/toxicidade , Epigênese Genética/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Histonas/metabolismo , Receptor de Pregnano X/agonistas , Acetilação , Pontos de Checagem do Ciclo Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Citocromo P-450 CYP3A/genética , Citocromo P-450 CYP3A/metabolismo , Células Hep G2 , Hepatócitos/metabolismo , Hepatócitos/patologia , Humanos , Metilação , Receptor de Pregnano X/genética , Receptor de Pregnano X/metabolismo , Proteína-Arginina N-Metiltransferases/genética , Proteína-Arginina N-Metiltransferases/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismo , Fatores de Tempo
2.
Chemosphere ; 240: 124789, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31561157

RESUMO

Poly- and perfluorinated compounds (PFCs) may induce potential endocrine-disrupting hormonal effects. However, the molecular mechanism of the toxicology of PFCs remains unclear, and the insufficient information is available on the biological activities of PFCs at present. In this study, the cell-based reporter gene assays were used to determine the agonistic activity of PFCs on the human pregnane X receptor (hPXR). The heuristic method combined with best subset modeling (HM-BSM) based on Dragon descriptors and comparative similarity indices analysis (CoMSIA) were employed to build classical quantitative structure-activity relationship (QSAR) and three-dimensional QSAR models, respectively. The applicability domain (AD) of the classical QSAR model was assessed. Both the HM-BSM and CoMSIA approaches demonstrated good robustness, predictive ability, and mechanistic interpretability. The r2 and leave-one-out cross-validation squared correlated coefficient (q2LOO) values were 0.872 and 0.759 for the HM-BSM, and 0.976 and 0.751 for the CoMSIA model, respectively. The hPXR agonistic activity of the PFCs predicted by the built HM-BSM and CoMSIA agreed well with experimental activity, with root mean square error (RMSE) values of 0.0803 and 0.117, respectively, and external validation squared correlated coefficients (q2EXT) of 0.972 and 0.932, respectively. The hPXR agonistic activity of PFCs was related to their molecular polarizability, charge and atomic mass. Hydrogen bonding and hydrophobic interactions constituted the primary intermolecular forces between PFCs and the hPXR. The developed models were used to screen the PFCs with high hPXR agonistic activity.


Assuntos
Fluorcarbonetos/química , Receptor de Pregnano X/química , Simulação por Computador , Heurística , Humanos , Ligações de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Relação Quantitativa Estrutura-Atividade
3.
J Biochem Mol Toxicol ; 33(12): e22408, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31617658

RESUMO

In this study, gene expression alterations of phase I to III enzymes, transcription factors, and microRNA (miRNA) in embryonic zebrafish fibroblasts (ZF4) cells after the treatment of Pb(NO3 )2 and AgNO3 were investigated, to illustrate the possible detoxification pathway of heavy metal ions. It was observed that both metals caused concentration-dependent death and moderate elevation of oxidative stress in ZF4 cells. In response to such toxicity, upregulation of multidrug resistance protein (mdr)4 and multiresistance-associated protein (mrp)1 were found. However, enhanced expression of glutathione S-transferase (gst) and cytochrome P450 (cyp)1a could only be detected during the exposure of Pb2+ . In addition, both metals induced extensive upregulation of pregnane X receptor (pxr), but only moderate elevation of E2-related factor (nrf2), while they suppressed the expression of miR-122 and miR-126. In conclusion, Pb2+ and Ag+ shared the same detoxification mechanism including ABC transporters, Pxr, and miRNA in ZF4 cells, which needs further investigation.


Assuntos
Fibroblastos/efeitos dos fármacos , Fibroblastos/metabolismo , Chumbo/toxicidade , Nitratos/toxicidade , Nitrato de Prata/toxicidade , Peixe-Zebra/embriologia , Animais , Morte Celular/efeitos dos fármacos , Linhagem Celular , Proliferação de Células/efeitos dos fármacos , Sistema Enzimático do Citocromo P-450/metabolismo , Regulação da Expressão Gênica , Glutationa Transferase/metabolismo , MicroRNAs/genética , MicroRNAs/metabolismo , Proteínas Associadas à Resistência a Múltiplos Medicamentos/metabolismo , Fator 2 Relacionado a NF-E2/genética , Fator 2 Relacionado a NF-E2/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Receptor de Pregnano X/genética , Receptor de Pregnano X/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Transdução de Sinais/efeitos dos fármacos , Proteínas de Peixe-Zebra/genética , Proteínas de Peixe-Zebra/metabolismo
4.
Environ Pollut ; 255(Pt 2): 113329, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31600704

RESUMO

Transcription factors including pregnane X receptor (Pxr) and nuclear factor-erythroid 2-related factor-2 (Nrf2) are important modulators of Adenosine triphosphate-binding cassette (ABC) transporters in mammalian cells. However, whether such modulation is conserved in zebrafish embryos remains largely unknown. In this manuscript, pxr- and nrf2-deficient models were constructed with CRISPR/Cas9 system, to evaluate the individual function of Pxr and Nrf2 in the regulation of ABC transporters and detoxification of heavy metal ions like Cd2+ and Ag+. As a result, both Cd2+ and Ag+ conferred extensive interactions with ABC transporters in wild type (WT) embryos: their accumulation and toxicity were affected by the activity of ABC transporters, and they significantly induced the mRNA expressions of ABC transporters. These induction effects were reduced by the mutation of pxr and nrf2, but elevations in the basal expression of ABC transporters compensated for the loss of their inducibility. This could be an explanation for remaining transporter function in both mutant models as well as the unaltered toxicity of metal ions in pxr-deficient embryos. However, mutation of nrf2 disrupted the production of glutathione (GSH), resulting in the enhanced toxicity of Cd2+/Ag+ in zebrafish embryos. In addition, elevated expressions of other transcription factors like aryl hydrocarbon receptor (ahr) 1b, peroxisome proliferator-activated receptor (ppar)-ß, and nrf2 were found in pxr-deficient models without any treatment, while enhanced induction of ahr1b, ppar-ß and pxr could only be seen in nrf2-deficient embryos after the treatment of metal ions, indicating different compensation phenomena for the absence of transcription factors. After all, pxr-deficient and nrf2-deficient zebrafish embryos are useful tools in the functional investigation of Pxr and Nrf2 in the early life stages of aquatic organisms. However, the compensatory mechanisms should be taken into consideration when interpreting the results and need in-depth investigations.


Assuntos
Transportadores de Cassetes de Ligação de ATP/metabolismo , Metais Pesados/toxicidade , Fator 2 Relacionado a NF-E2/genética , Receptor de Pregnano X/genética , Peixe-Zebra/embriologia , Animais , Glutationa/metabolismo , Inativação Metabólica , Receptores de Hidrocarboneto Arílico/metabolismo , Receptores de Esteroides/genética , Fatores de Transcrição/metabolismo , Proteínas de Peixe-Zebra/metabolismo
5.
Anticancer Res ; 39(9): 4749-4755, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31519575

RESUMO

BACKGROUND: Cisplatin is a platinum compound capable of inducing apoptosis of cancer cells. However, cancer cells can become cisplatin-resistant. A recent study showed that a pregnane X receptor (PXR) antagonist, leflunomide, can enhance the antitumor activity of cisplatin and overcome such resistance. This study determined whether PXR antagonists ketoconazole and phenethyl isothiocyanate (PEITC) enhance the antitumor activity of platinum compounds and by which mechanism(s) of action. MATERIALS AND METHODS: Caspase-3 activity, intracellular platinum level, and expression of ATP-binding cassette subfamily C member 2 (ABCC2; previously named multidrug resistance-associated protein 2) were assessed in HepG2 human hepatocellular carcinoma cells exposed to carboplatin or cisplatin with and without PXR antagonist. RESULTS: In combination with platinum compounds, PEITC increased the intracellular platinum level, while ketoconazole induced higher caspase-3 activity. Additionally, PEITC suppressed ABCC2 protein expression. CONCLUSION: These results suggested that ketoconazole and PEITC enhance the antitumor activity of platinum compounds by different and complex mechanisms.


Assuntos
Antineoplásicos/farmacologia , Cisplatino/farmacologia , Receptor de Pregnano X/antagonistas & inibidores , Apoptose/efeitos dos fármacos , Biomarcadores , Caspase 3/metabolismo , Linhagem Celular Tumoral , Sinergismo Farmacológico , Humanos , Proteínas Associadas à Resistência a Múltiplos Medicamentos/genética , RNA Mensageiro/genética
6.
Food Chem Toxicol ; 133: 110792, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31472229

RESUMO

Parabens are widely used as preservatives in personal care products, medicines and foods, resulting in substantial human exposures, even though some harmful effects, such as endocrine-disrupting activity, have been reported. Pregnane X receptor (PXR), constitutive androstane receptor (CAR) and peroxisome proliferator-activated receptor α (PPARα), which are members of the nuclear receptor superfamily, regulate the metabolism of endogenous substrates including hormones. Therefore, we hypothesized that parabens may alter hormone-metabolizing activities by acting on these receptors, and such changes could contribute to the endocrine-disrupting activity. To test this idea, we systematically examined the effects of 17 parabens on these receptors using reporter gene assays. Nine parabens significantly activated human and rat PXR. Parabens with C2-C5 (linear and branched) side chains were most active. Butylparaben and isobutylparaben also significantly activated rat CAR. We found that long-side-chain (C7-C12) parabens showed up to 2-fold activation of PPARα at 10 µM. Furthermore, pentylparaben and hexylparaben showed rat PXR antagonistic activity and rat CAR inverse agonistic activity. The activity of butylparaben towards PXR and CAR was lost after carboxylesterase-mediated metabolism. These findings confirm that parabens influence the activities of PXR, CAR and PPARα, and thus have the potential to contribute to endocrine disruption by altering hormone metabolism.


Assuntos
PPAR alfa/metabolismo , Parabenos/farmacologia , Receptor de Pregnano X/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Ativação Transcricional/efeitos dos fármacos , Animais , Agonismo Inverso de Drogas , Humanos , Masculino , Microssomos Hepáticos/metabolismo , PPAR alfa/agonistas , PPAR alfa/genética , Parabenos/metabolismo , Receptor de Pregnano X/antagonistas & inibidores , Receptor de Pregnano X/genética , Ratos Sprague-Dawley , Receptores Citoplasmáticos e Nucleares/agonistas , Receptores Citoplasmáticos e Nucleares/genética
7.
Mol Pharmacol ; 96(3): 345-354, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31436536

RESUMO

Phenobarbital (PB), a broadly used antiseizure drug, was the first to be characterized as an inducer of cytochrome P450 by activation of the constitutive androstane receptor (CAR). Although PB is recognized as a conserved CAR activator among species via a well-documented indirect activation mechanism, conflicting results have been reported regarding PB regulation of the pregnane X receptor (PXR), a sister receptor of CAR, and the underlying mechanisms remain elusive. Here, we show that in a human CAR (hCAR)-knockout (KO) HepaRG cell line, PB significantly induces the expression of CYP2B6 and CYP3A4, two shared target genes of hCAR and human PXR (hPXR). In human primary hepatocytes and hCAR-KO HepaRG cells, PB-induced expression of CYP3A4 was markedly repressed by genetic knockdown or pharmacological inhibition of hPXR. Mechanistically, PB concentration dependently activates hPXR but not its mouse counterpart in cell-based luciferase assays. Mammalian two-hybrid assays demonstrated that PB selectively increases the functional interaction between the steroid receptor coactivator-1 and hPXR but not mouse PXR. Moreover, surface plasmon resonance binding affinity assay showed that PB directly binds to the ligand binding domain of hPXR (KD = 1.42 × 10-05). Structure-activity analysis further revealed that the amino acid tryptophan-299 within the ligand binding pocket of hPXR plays a key role in the agonistic binding of PB and mutation of tryptophan-299 disrupts PB activation of hPXR. Collectively, these data reveal that PB, a selective mouse CAR activator, activates both hCAR and hPXR, and provide novel mechanistic insights for PB-mediated activation of hPXR.


Assuntos
Fenobarbital/farmacologia , Receptor de Pregnano X/química , Receptor de Pregnano X/genética , Receptores Citoplasmáticos e Nucleares/genética , Animais , Células Cultivadas , Citocromo P-450 CYP2B6/metabolismo , Citocromo P-450 CYP3A/metabolismo , Técnicas de Inativação de Genes , Humanos , Camundongos , Receptor de Pregnano X/metabolismo , Ligação Proteica , Receptores Citoplasmáticos e Nucleares/metabolismo , Especificidade da Espécie , Ressonância de Plasmônio de Superfície , Triptofano/metabolismo
8.
Int J Mol Sci ; 20(15)2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31374856

RESUMO

The pregnane X receptor (PXR) is the main nuclear receptor regulating the expression of xenobiotic-metabolizing enzymes and is highly expressed in the liver and intestine. Recent studies have highlighted its additional role in lipid homeostasis, however, the mechanisms of these regulations are not fully elucidated. We investigated the transcriptomic signature of PXR activation in the liver of adult wild-type vs. Pxr-/- C57Bl6/J male mice treated with the rodent specific ligand pregnenolone 16α-carbonitrile (PCN). PXR activation increased liver triglyceride accumulation and significantly regulated the expression of 1215 genes, mostly xenobiotic-metabolizing enzymes. Among the down-regulated genes, we identified a strong peroxisome proliferator-activated receptor α (PPARα) signature. Comparison of this signature with a list of fasting-induced PPARα target genes confirmed that PXR activation decreased the expression of more than 25 PPARα target genes, among which was the hepatokine fibroblast growth factor 21 (Fgf21). PXR activation abolished plasmatic levels of FGF21. We provide a comprehensive signature of PXR activation in the liver and identify new PXR target genes that might be involved in the steatogenic effect of PXR. Moreover, we show that PXR activation down-regulates hepatic PPARα activity and FGF21 circulation, which could participate in the pleiotropic role of PXR in energy homeostasis.


Assuntos
Fatores de Crescimento de Fibroblastos/metabolismo , Fígado/metabolismo , PPAR alfa/metabolismo , Receptor de Pregnano X/metabolismo , Animais , Fatores de Crescimento de Fibroblastos/genética , Deleção de Genes , Perfilação da Expressão Gênica , Masculino , Camundongos Endogâmicos C57BL , Receptor de Pregnano X/genética , Ativação Transcricional , Transcriptoma
9.
Biol Pharm Bull ; 42(8): 1243-1252, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31366862

RESUMO

Nuclear receptors pregnane X receptor (PXR) and constitutive active/androstane receptor (CAR) are xenobiotic-responsible transcriptional factors that belong to the same subfamily and are expressed abundantly in the liver. They play crucial roles in various liver functions including xenobiotic disposition and energy metabolism. CAR is also involved in xenobiotic-induced hepatocyte proliferation and hepatocarcinogenesis in rodents. However, there are some open questions on the association between chemical carcinogenesis and these nuclear receptors. These include the molecular mechanism for CAR-mediated hepatocyte proliferation and hepatocarcinogenesis. Another important question is whether PXR is associated with hepatocyte proliferation. We have recently reported a novel and unique function of PXR associated with murine hepatocyte proliferation: PXR activation alone does not induce hepatocyte proliferation but accelerates hepatocyte proliferation induced by various types of stimuli including CAR- or peroxisome proliferator-activated receptor alpha activating compounds, liver injury, and growth factors. We have also reported a role of yes-associated protein (YAP), a transcriptional cofactor controlling organ size and cell growth under the Hippo pathway, in CAR-mediated hepatocyte proliferation in mice. In this review, I will introduce our recent results as well as related studies on the roles of PXR and CAR in xenobiotic-induced hepatocyte proliferation and their molecular mechanisms.


Assuntos
Carcinogênese/metabolismo , Hepatócitos/metabolismo , Neoplasias Hepáticas/metabolismo , Receptor de Pregnano X/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Carcinogênese/induzido quimicamente , Proliferação de Células/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Humanos , Neoplasias Hepáticas/induzido quimicamente , Xenobióticos/toxicidade
10.
Nat Commun ; 10(1): 2514, 2019 06 07.
Artigo em Inglês | MEDLINE | ID: mdl-31175293

RESUMO

The type II nuclear receptors (NRs) function as heterodimeric transcription factors with the retinoid X receptor (RXR) to regulate diverse biological processes in response to endogenous ligands and therapeutic drugs. DNA-binding specificity has been proposed as a primary mechanism for NR gene regulatory specificity. Here we use protein-binding microarrays (PBMs) to comprehensively analyze the DNA binding of 12 NR:RXRα dimers. We find more promiscuous NR-DNA binding than has been reported, challenging the view that NR binding specificity is defined by half-site spacing. We show that NRs bind DNA using two distinct modes, explaining widespread NR binding to half-sites in vivo. Finally, we show that the current models of NR specificity better reflect binding-site activity rather than binding-site affinity. Our rich dataset and revised NR binding models provide a framework for understanding NR regulatory specificity and will facilitate more accurate analyses of genomic datasets.


Assuntos
DNA/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores X Retinoide/metabolismo , Proteínas de Ligação a DNA , Humanos , Receptores X do Fígado , Mutagênese Sítio-Dirigida , Receptores Ativados por Proliferador de Peroxissomo , Receptor de Pregnano X , Receptores de Calcitriol , Receptores do Ácido Retinoico , Receptores dos Hormônios Tireóideos
11.
Toxicol In Vitro ; 60: 347-358, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31233785

RESUMO

Pregnane & Xenobiotic Receptor (PXR), one of the members of nuclear receptor superfamily, acts as a 'master-regulator' of drug metabolism and disposition machinery (DMD). Activation of PXR enables detoxification and elimination of toxic xenobiotics/endobiotics, and defends our body against chemical insults. On the contrary, PXR activation also imposes a serious concern for drug-drug interactions (DDIs). Such DDIs could either decrease the efficacy or lead to accumulation of co-administered drugs at toxic level. Therefore, it is desirable that during drug development process the small drug molecules are screened on PXR-platform prior to their clinical trial and prevent late stage failures. In view of this, we have selected a group of anti-diabetic drug molecules to examine if the success and potential failure of small molecule modulators can be pre-assessed and judiciously correlated on PXR platform. For this purpose, we have examined the PXR activation potential of the selected anti-diabetic drugs. Subsequent to screening of these anti-diabetic drugs, we elaborated the study further with rosiglitazone and pioglitazone (thiazolidinediones, TZDs) which are oral anti-diabetic formulations and have been in controversy owing to their association with cardiotoxicity and bladder cancer respectively. Our study revealed that some of the selected anti-diabetic drugs possess PXR activation potential, implying that these can up-regulate the expression of CYP3A4, UGT1A1, MDR1 and thereby can be predicted to inflict undesirable consequences.


Assuntos
Hipoglicemiantes/farmacologia , Receptor de Pregnano X/metabolismo , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Animais , Linhagem Celular , Citocromo P-450 CYP3A/genética , Citocromo P-450 CYP3A/metabolismo , Interações de Medicamentos , Glucuronosiltransferase/genética , Humanos , Pioglitazona/farmacologia , Receptor de Pregnano X/genética , RNA Interferente Pequeno/genética , Rosiglitazona/farmacologia
12.
Int J Mol Sci ; 20(11)2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-31212662

RESUMO

Vitamin K is a fat-soluble vitamin that was originally found as an essential factor for blood coagulation. With the discovery of its role as a co-factor for γ-glutamyl carboxylase (GGCX), its function for blood coagulation was understood as the activation of several blood coagulation factors by their γ-carboxylation. Over the last two decades, other modes of vitamin K actions have been discovered, such as the regulation of transcription by activating the steroid and xenobiotic receptor (SXR), physical association to 17ß-Hydroxysteroid dehydrogenase type 4 (17ß-HSD4), covalent modification of Bcl-2 antagonist killer 1 (Bak), and the modulation of protein kinase A (PKA) activity. In addition, several epidemiological studies have revealed that vitamin K status is associated with some aging-related diseases including osteoporosis, osteoarthritis, and sarcopenia. Clinical studies on single nucleotide polymorphisms of GGCX suggested an association between higher GGCX activity and bone protective effect, while recent findings using conditional knockout mice implied that a contribution in protective effect for bone loss by GGCX in osteoblastic lineage was unclear. GGCX in other cell lineages or in other tissues might play a protective role for osteoporosis. Meanwhile, animal experiments by our groups among others revealed that SXR, a putative receptor for vitamin K, could be important in the bone metabolism. In terms of the cartilage protective effect of vitamin K, both GGCX- and SXR-dependent mechanisms have been suggested. In clinical studies on osteoarthritis, the γ-carboxylation of matrix Gla protein (MGP) and gla-rich protein (GRP) may have a protective role for the disease. It is also suggested that SXR signaling has protective role for cartilage by inducing family with sequence similarity 20a (Fam20a) expression in chondrocytes. In the case of sarcopenia, a high vitamin K status in plasma was associated with muscle strength, large muscle mass, and high physical performance in some observational studies. However, the basic studies explaining the effects of vitamin K on muscular tissue are limited. Further research on vitamin K will clarify new biological mechanisms which contribute to human longevity and health through the prevention and treatment of aging-related musculoskeletal disorders.


Assuntos
Envelhecimento/metabolismo , Doenças Musculoesqueléticas/metabolismo , Vitamina K/metabolismo , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Humanos , Osteoporose/metabolismo , Receptor de Pregnano X/metabolismo , Proteínas/metabolismo
13.
Int J Mol Sci ; 20(12)2019 Jun 20.
Artigo em Inglês | MEDLINE | ID: mdl-31226734

RESUMO

Vitamin K is classified into three homologs depending on the side-chain structure, with 2-methyl-1,4-naphthoqumone as the basic skeleton. These homologs are vitamin K1 (phylloquinone: PK), derived from plants with a phythyl side chain; vitamin K2 (menaquinone-n: MK-n), derived from intestinal bacteria with an isoprene side chain; and vitamin K3 (menadione: MD), a synthetic product without a side chain. Vitamin K homologs have physiological effects, including in blood coagulation and in osteogenic activity via γ-glutamyl carboxylase and are used clinically. Recent studies have revealed that vitamin K homologs are converted to MK-4 by the UbiA prenyltransferase domain-containing protein 1 (UBIAD1) in vivo and accumulate in all tissues. Although vitamin K is considered to have important physiological effects, its precise activities and mechanisms largely remain unclear. Recent research on vitamin K has suggested various new roles, such as transcriptional activity as an agonist of steroid and xenobiotic nuclear receptor and differentiation-inducing activity in neural stem cells. In this review, we describe synthetic ligands based on vitamin K and exhibit that the strength of biological activity can be controlled by modification of the side chain part.


Assuntos
Neurogênese/efeitos dos fármacos , Ativação Transcricional/efeitos dos fármacos , Vitamina K/análogos & derivados , Vitamina K/farmacologia , Vitaminas/química , Vitaminas/farmacologia , Animais , Humanos , Células-Tronco Neurais/citologia , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/metabolismo , Receptor de Pregnano X/metabolismo
14.
Chem Biol Interact ; 308: 185-193, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31132328

RESUMO

Cytochrome P450 3A (CYP3A) activity is inhibited, and its expression is suppressed during many diseases, including nonalcoholic fatty liver disease (NAFLD). However, the mechanism is controversial. Here, we report that PXR may not take part in the downregulation of CYP3A during NAFLD. Hepatic CYP3A11 (major subtype of mouse CYP3A) mRNA and protein expression was significantly decreased in both mice fed a high-fat diet (HFD) for 8 weeks and palmitate (PA)-treated mouse primary hepatocytes. Similarly, in HepG2 cells, PA treatment significantly suppressed the CYP3A4 (major subtype of human CYP3A) mRNA level and promoter transcription activity. However, Western blotting analysis found an induction of PXR nuclear translocation during NAFLD in both in vivo and in vitro models. Moreover, immunofluorescence determination also found nuclear translocation effect of PXR by PA stimulation in HepG2 cells. In addition, the siRNA knockdown of PXR did not affect the suppressive effects of PA on the CYP3A4 promoter transcription activity and mRNA levels in HepG2 cells. Similarly, PXR knockdown also did not affect the suppressive effects of PA on CYP3A11 mRNA and protein expression levels in mouse primary hepatoctyes. Taken together, the results showed that the suppressive effect of CYP3A transcription was independent of PXR regulation.


Assuntos
Citocromo P-450 CYP3A/metabolismo , Dieta Hiperlipídica , Hepatopatia Gordurosa não Alcoólica/patologia , Receptor de Pregnano X/metabolismo , Animais , Citocromo P-450 CYP3A/genética , Regulação para Baixo/efeitos dos fármacos , Células Hep G2 , Hepatócitos/citologia , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Hepatopatia Gordurosa não Alcoólica/metabolismo , Hepatopatia Gordurosa não Alcoólica/veterinária , Palmitatos/farmacologia , Receptor de Pregnano X/antagonistas & inibidores , Receptor de Pregnano X/genética , Interferência de RNA , RNA Mensageiro/metabolismo , RNA Interferente Pequeno/metabolismo , Transcrição Genética/efeitos dos fármacos
15.
Methods Mol Biol ; 1966: 163-173, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31041746

RESUMO

Reporter assays are useful to study nuclear receptor activation and for example to evaluate the propensity of novel drug candidates to cause induction of drug-metabolizing cytochrome P450 enzymes. Here, we describe a protocol for a reverse transfection system to study the activation of human nuclear receptors constitutive androstane receptor and pregnane X receptor. The system provides long-term stability and uniformity of DNA-carrier complexes, thus avoiding the inherent variation in conventional transfection methods. Further, the system is easily adaptable for different studies. It offers reproducible and reliable results for early drug development and mechanistic studies related to nuclear receptor activation and resulting changes in gene expression.


Assuntos
Hepatócitos/metabolismo , Receptor de Pregnano X/genética , Receptores Citoplasmáticos e Nucleares/genética , Transfecção/métodos , Linhagem Celular Tumoral , Sistema Enzimático do Citocromo P-450/metabolismo , Genes Reporter , Humanos , Receptor de Pregnano X/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo
16.
Int J Mol Sci ; 20(9)2019 May 10.
Artigo em Inglês | MEDLINE | ID: mdl-31083458

RESUMO

To appraise how evolutionary processes, such as gene duplication and loss, influence an organism's xenobiotic sensitivity is a critical question in toxicology. Of particular importance are gene families involved in the mediation of detoxification responses, such as members of the nuclear receptor subfamily 1 group I (NR1I), the pregnane X receptor (PXR), and the constitutive androstane receptor (CAR). While documented in multiple vertebrate genomes, PXR and CAR display an intriguing gene distribution. PXR is absent in birds and reptiles, while CAR shows a tetrapod-specific occurrence. More elusive is the presence of PXR and CAR gene orthologs in early branching and ecologically-important Chondrichthyes (chimaeras, sharks and rays). Therefore, we investigated various genome projects and use them to provide the first identification and functional characterization of a Chondrichthyan PXR from the chimaera elephant shark (Callorhinchus milii, Holocephali). Additionally, we substantiate the targeted PXR gene loss in Elasmobranchii (sharks and rays). Compared to other vertebrate groups, the chimaera PXR ortholog displays a diverse expression pattern (skin and gills) and a unique activation profile by classical xenobiotic ligands. Our findings provide insights into the molecular landscape of detoxification mechanisms and suggest lineage-specific adaptations in response to xenobiotics in gnathostome evolution.


Assuntos
Elasmobrânquios/classificação , Elasmobrânquios/genética , Evolução Molecular , Redes Reguladoras de Genes , Filogenia , Receptor de Pregnano X/genética , Animais , Células COS , Genes Reporter , Inativação Metabólica/genética , Luciferases/metabolismo , Receptor de Pregnano X/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Sintenia/genética , Ativação Transcricional/genética
17.
Drug Metab Pharmacokinet ; 34(3): 172-180, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31101589

RESUMO

Rifamycin SV (rifamycin), is a member of the ansamycin family of antimicrobial compounds which kills bacteria commonly associated with infectious diarrhea and other enteric infections. Rifamycin has been found to be effective in experimental animal models of gut inflammation and its efficacy in these settings has been attributed partially to immunomodulatory non-bactericidal activities. This study aimed to further evaluate the anti-inflammatory activities of rifamycin by analyzing its effect on two key regulators of inflammation: PXR and NFκB. Rifamycin stimulated PXR transcriptional activity in two PXR reporter cell lines and induced expression of two genes known to be regulated by PXR and are directly involved in cellular detoxification: CYP3A4 and PgP. Moreover, CYP3A4 metabolic activity was induced by rifamycin in HepG2 cells. Rifamycin also antagonized TNFα and LPS-induced NFκB activities and inhibited IL1ß-induced synthesis of inflammatory chemokine, IL8. Although reciprocal regulation of PXR and NFkB by rifamycin was not directly addressed, the data suggest that in the absence of PXR, inhibition of NFκB by rifamycin is not dependent on PXR stimulation. Thus, rifamycin exhibits potent anti-inflammatory activities, characterized by in vitro PXR activation and concomitant CYP3A4 and PgP induction, in parallel with potent NFκB inhibition and concomitant IL8 inhibition.


Assuntos
Anti-Inflamatórios/farmacologia , NF-kappa B/antagonistas & inibidores , Receptor de Pregnano X/genética , Rifamicinas/farmacologia , Ativação Transcricional/efeitos dos fármacos , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Células CACO-2 , Técnicas de Cultura de Células , Citocromo P-450 CYP3A/genética , Células HT29 , Células Hep G2 , Humanos , NF-kappa B/genética , Transdução de Sinais
18.
Mol Genet Genomic Med ; 7(5): e574, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30955239

RESUMO

BACKGROUND: Genetic polymorphisms in numerous pharmacogenetics studies were regarded as the essential factors involved in the response to or metabolism of drugs. These genetic variants called very important pharmacogenetic (VIP) variants played a role in drugs metabolism, which have been summarized in the PharmGKB database. In this study, we genotyped 80 VIP variants from the PharmGKB in 100 members of Blang volunteers from Yunnan province. METHODS: Based on the PharmGKB database, we genotyped 80 VIP variants loci located in 47 genes. We used χ2 tests to evaluate the significant loci between Blang and the other populations, including ASW, CEU, CHB, CHD, GIH, JPT, LWK, MEX, MKK, TSI, and YRI. The global variation distribution of the significant variants was observed from the ALlele FREquency Database. And then, we used F-statistics (Fst), genetic structure, and phylogenetic tree analyses to ascertain the genetic affinity among 12 populations. RESULTS: Comparing the Blang with the other 11 populations from the HapMap Project, the statistical results revealed that rs3814055 (NC_000003.12:g.119781188C>T) of nuclear receptor subfamily 1 group I member 2 (NR1I2, OMIM# 603,065) was the most significant variant, followed by rs1540339 (NC_000012.12:g.47863543C>T) of vitamin D receptor (VDR, OMIM#601,769). Furthermore, we found that genotype frequency of rs3814055 in the Blang was closer to the populations distributed in Miao. And genetic structure and F-statistics indicated that the Blangs had a relatively closer affinity with CHD, CHB, and JPT populations. In addition, the Han nationality in Shaanxi was closer to it. CONCLUSIONS: Our results will complement the pharmacogenomics information of the Blang ethnic group and provide a theoretical basis for safer drug administration for Blang.


Assuntos
Variantes Farmacogenômicos , China , Frequência do Gene , Humanos , Receptor de Pregnano X/genética , Receptores de Calcitriol/genética
19.
J Agric Food Chem ; 67(17): 4967-4975, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-30955332

RESUMO

Rooibos tea ( Aspalathus linearis) is a well-known South African herbal tea enjoyed worldwide. Limited reports indicate the potential of rooibos tea to alter the activity of certain cytochrome P450 (CYP450) isozymes. In this study, the phytochemical investigation of MeOH extract of A. linearis (leaves and stems) resulted in the isolation and characterization of 11 phenolic compounds. The MeOH extract exhibited significant inhibition of the major human CYP450 isozymes (CYP3A4, CYP1A2, CYP2D6, CYP2C9, and CYP2C19). The strongest inhibition was observed by the extract for CYP3A4 (IC50 1.7 ± 0.1 µg/mL) followed by CYP2C19 (IC50 4.0 ± 0.3 µg/mL). Among the tested phytochemicals, the most potent inhibitors were isovitexin on CYP3A4 (IC50 3.4 ± 0.2 µM), vitexin on CYP2C9 (IC50 8.0 ± 0.2 µM), and thermopsoside on CYP2C19 (IC50 9.5 ± 0.2 µM). The two major, structurally related compounds aspalathin and nothofagin exhibited a moderate pregnane-X receptor (PXR) activation, which was associated with increased mRNA expression of CYP3A4 and CYP1A2, respectively. These results indicate that a high intake of nutraceuticals containing rooibos extracts may pose a risk of herb-drug interactions when consumed concomitantly with clinical drugs that are substrates of CYP enzymes.


Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/química , Aspalathus/química , Sistema Enzimático do Citocromo P-450/química , Preparações de Plantas/química , Receptor de Pregnano X/química , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Aspalathus/metabolismo , Linhagem Celular , Sistema Enzimático do Citocromo P-450/genética , Sistema Enzimático do Citocromo P-450/metabolismo , Inocuidade dos Alimentos , Humanos , Folhas de Planta/química , Preparações de Plantas/metabolismo , Receptor de Pregnano X/genética , Receptor de Pregnano X/metabolismo , Chás de Ervas/análise
20.
Sheng Li Xue Bao ; 71(2): 311-318, 2019 Apr 25.
Artigo em Chinês | MEDLINE | ID: mdl-31008491

RESUMO

As a member of the nuclear receptor superfamily, the pregnane X receptor (PXR) is a ligand-activated transcription factor. PXR is highly expressed in liver and intestinal tissues, and also found in other tissues and organs, such as stomach and kidney. After heterodimerization with retinoid X receptor (RXR), PXR recruits numerous co-activating factors, and binds to specific DNA response elements to perform transcriptional regulation of the downstream target genes. As an acknowledged receptor for xenobiotics, PXR was initially considered as a nuclear receptor regulating drug metabolizing enzymes and transporters. However, nowadays, PXR has also been recognized as an important endobiotic receptor. Recent studies have shown that PXR activation can regulate glucose metabolism, lipid metabolism, steroid endocrine homeostasis, detoxification of cholic acid and bilirubin, bone mineral balance, and immune inflammation in vivo. This review focuses on the role of PXR in metabolism of endogenous substances.


Assuntos
Receptor de Pregnano X/metabolismo , Xenobióticos/metabolismo , Animais , Regulação da Expressão Gênica , Humanos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA