Induction of rat hepatic cytochrome P4501A and P4502B by the methoxsalen

Synthesis, In Vitro Antitumor Activity and Molecular Mechanism of Novel Furan Derivatives and their Precursors

BACKGROUND

Compounds featuring furan nucleus exhibit diverse biological properties. Lots of furan derivatives have been explored as pharmaceutical compounds. Hence it is of great interest to explore furan derivatives and their precursors as antitumor agents.

OBJECTIVE

A series of novel furan derivatives and their precursors (1-36) were synthesized from α-haloketones and β-dicarbonyl compounds.

METHODS

The reactions between β-dicarbonyl compounds and α-haloketones under basic conditions produced tricarbonyls or dihydrofurans, which were then condensed into their corresponding furan products. Their potential antiproliferative activity in vitro against two human tumor cell lines-cervical (HeLa) and colorectal (SW620) was evaluated using CCK-8 assay. Compounds 1 and 24 were selected for Western blot analysis.

RESULTS

Pronounced anti-proliferative effect in the micromolar level was observed for compounds (1, 4, 17, 20, 21, 24, 27, 31 and 32) in HeLa cells, with their IC50 values ranging from 0.08 to 8.79μM. Additionally, furan compounds (24, 26, 32 and 35) had moderate to potent anti-proliferative activity against the SW620 cell line. Furthermore, the possible targets of these compounds were explored by Western blot analysis. The results indicated that the candidates (compounds 1 and 24) exhibited excellent antiproliferative activity, which may be mediated by promoting the activity of PTEN to suppress PI3K/Akt and Wnt/β-catenin signaling.

CONCLUSION

Most of the furan derivatives and their precursors reported herein exhibited moderate to excellent anti-proliferative activity against HeLa cell line and/or SW620 cell line. Compounds 1 and 24, as well as their analogues may be developed as promising anti-cancer agents.

Root extract of water dropwort, Oenanthe javanica (Blume) DC, induces protein and gene expression of phase I carcinogen-metabolizing enzymes in HepG2 cells

Background

Cytochrome P450 (CYP) isoenzymes are an important phase I enzyme system. In the present study, we investigated the effects of Oenanthe javanica (Blume) DC on CYP1A1 and CYP1A2.

Findings

Whole plants were completely dried and then divided into leaves, stems, and roots for extraction. The human liver hepatocellular carcinoma cell line HepG2 was treated with ethanol extracts of these organs for 72 h and mRNA and protein expression levels were assessed. The root extract of O. javanica significantly elevated the expression of both CYP1A1 and CYP1A2 mRNAs (by 68 and 102 %, respectively). Similarly, the CYP1A1 and CYP1A2 protein levels were increased by the root extract (by 112 and 157 %, respectively). The effects of the root extract were much more pronounced than those of leaf and stem extracts. Subsequent GC–MS analysis revealed that the levels of major coumarin derivatives, xanthotoxin, bergapten, and isopimpinellin, were significantly higher in O. javanica root extracts than in leaf or stem extracts. Of note, 5 μM xanthotoxin (the most abundant furanocoumarin in O. javanica) induced the expression of CYP1A1 mRNA as well as CYP1A2 mRNA and protein, albeit the CYP1A1 protein level was elevated only at 10 μM xanthotoxin.

Conclusions

Although it is difficult to extrapolate such effects to metabolic outcomes because of the inherent limitations of in vitro experiments, it is important to note that dietary exposure to O. javanica may modulate phase I enzymes and thereby affect various xenobiotic metabolism.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-2078-8) contains supplementary material, which is available to authorized users.

Effects of aqueous extract of Ruta graveolens and its ingredients on cytochrome P450, uridine diphosphate (UDP)-glucuronosyltransferase, and reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H)-quinone oxidoreductase in mice

Ruta graveolens (the common rue) has been used for various therapeutic purposes, including relief of rheumatism and treatment of circulatory disorder. To elucidate the effects of rue on main drug-metabolizing enzymes, effects of an aqueous extract of the aerial part of rue and its ingredients on cytochrome P450 (P450/CYP), uridine diphosphate (UDP)-glucuronosyltransferase, and reduced nicotinamide adenine dinucleotide (phosphate) (NAD(P)H):quinone oxidoreductase were studied in C57BL/6JNarl mice. Oral administration of rue extract to males increased hepatic Cyp1a and Cyp2b activities in a dose-dependent manner. Under a 7-day treatment regimen, rue extract (0.5 g/kg) induced hepatic Cyp1a and Cyp2b activities and protein levels in males and females. This treatment increased hepatic UDP-glucuronosyltransferase activity only in males. However, NAD(P)H:quinone oxidoreductase activity remained unchanged. Based on the contents of rutin and furanocoumarins of mouse dose of rue extract, rutin increased hepatic Cyp1a activity and the mixture of furanocoumarins (F_mix) increased Cyp2b activities in males. The mixture of rutin and F_mix increased Cyp1a and Cyp2b activities. These results revealed that rutin and F_mix contributed at least in part to the P450 induction by rue.

Apiaceous vegetable consumption decreases PhIP-induced DNA adducts and increases methylated PhIP metabolites in the urine metabolome in rats

BACKGROUND

Heterocyclic aromatic amines, such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), are carcinogenic compounds produced during heating of protein-containing foods. Apiaceous vegetables inhibit PhIP-activating enzymes, whereas cruciferous vegetables induce both PhIP-activating and -detoxifying enzymes.

OBJECTIVE

We investigated the effects of these vegetables, either alone or combined, on PhIP metabolism and colonic DNA adduct formation in rats.

METHODS

Male Wistar rats were fed cruciferous vegetables (21%, wt:wt), apiaceous vegetables (21%, wt:wt), or a combination of both vegetables (10.5% wt:wt of each). Negative and positive control groups were fed an AIN-93G diet. After 6 d, all groups received an intraperitoneal injection of PhIP (10 mg · kg body weight(-1)) except for the negative control group, which received only vehicle. Urine was collected for 24 h after the injection for LC-tandem mass spectrometry metabolomic analyses. On day 7, rats were killed and tissues processed.

RESULTS

Compared with the positive control, cruciferous vegetables increased the activity of hepatic PhIP-activating enzymes [39.5% and 45.1% for cytochrome P450 (CYP) 1A1 (P = 0.0006) and CYP1A2 (P < 0.0001), respectively] and of uridine 5'-diphospho-glucuronosyltransferase 1A (PhIP-detoxifying) by 24.5% (P = 0.0267). Apiaceous vegetables did not inhibit PhIP-activating enzymes, yet reduced colonic PhIP-DNA adducts by 20.4% (P = 0.0496). Metabolomic analyses indicated that apiaceous vegetables increased the relative abundance of urinary methylated PhIP metabolites. The sum of these methylated metabolites inversely correlated with colonic PhIP-DNA adducts (r = -0.43, P = 0.01). We detected a novel methylated urinary PhIP metabolite and demonstrated that methylated metabolites are produced in the human liver S9 fraction.

CONCLUSIONS

Apiaceous vegetables did not inhibit the activity of PhIP-activating enzymes in rats, suggesting that the reduction in PhIP-DNA adducts may involve other pathways. Further investigation of the importance of PhIP methylation in carcinogen metabolism is warranted, given the inverse correlation of methylated PhIP metabolites with a biomarker of carcinogenesis and the detection of a novel methylated PhIP metabolite.

A dual function of the furanocoumarin chalepensin in inhibiting Cyp2a and inducing Cyp2b in mice: the protein stabilization and receptor-mediated activation

Chalepensin, a furanocoumarin, is present in several medicinal Rutaceae plants and causes a mechanism-based inhibition of human and mouse cytochrome P450 (P450, CYP) 2A in vitro. To address the in vivo effect, we investigated the effects of chalepensin on multiple hepatic P450 enzymes in C57BL/6JNarl mice. Oral administration of 10 mg/kg chalepensin to mice for 7 days significantly decreased hepatic coumarin 7-hydroxylation (Cyp2a) and increased 7-pentoxyresorufin O-dealkylation (Cyp2b) activities, whereas activities of Cyp1a, Cyp2c, Cyp2e1, and Cyp3a were not affected. Without affecting its mRNA level, the decreased Cyp2a activity was accompanied by an increase in the immunodetected Cyp2a5 protein level. In chalepensin-treated mice, microsomal Cyp2a5 was less susceptible to ATP-fortified cytosolic degradation than that in control mice, resulting in the elevated protein level. The in vitro inactivation through NADPH-fortified pre-incubation with chalepensin also protected microsomal Cyp2a5 against protein degradation. Using cell-based reporter systems, chalepensin at a concentration near unbound plasma concentration activated mouse constitutive androstane receptor (CAR), in agreement with the observed induction of Cyp2b. These findings revealed that suicidal inhibition of Cyp2a5 and the CAR-mediated Cyp2b9/10 induction concurrently occurred in chalepensin-treated mice.

The aryl hydrocarbon receptor and light

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that has been intensively studied with respect to the toxicity of xenobiotics. However, its function in response to light has never been summarized. Here, we provide an overview of AhR activation by light with a focus on the role of tryptophan in light-induced AhR activation. We discuss the involvement of the AhR in different biological rhythms and speculate on the possible role of the AhR in UV-induced responses in skin. Furthermore, this review points out future research needs in this field.

Natural furocoumarins as inducers and inhibitors of cytochrome P450 1A1 in rat hepatocytes

Furocoumarins are natural plant constituents present in medicinal plants and in a variety of foods such as grapefruit juice. They are phototoxic and act as potent inhibitors of drug metabolism. We have investigated the interaction of four furocoumarins angelicin, bergamottin, isopimpinellin, and 8-methoxypsoralen with the expression and activity of aryl hydrocarbon receptor (AhR)-regulated CYP1A1 in rat hepatocytes in primary culture, both in the presence and absence of light. In intact hepatocytes pretreated with 2,3,7,8-tetrachlorodibenzo-p-dioxin and in microsomes isolated thereof, all furocoumarins tested acted as potent inhibitors of CYP1A1 activity bergamottin being the most potent inhibitor in microsomes with an IC(50) of 10 nM in the presence and 60 nM in the absence of light. 8-Methoxypsoralen and angelicin led to a significant induction of CYP1A1 mRNA in hepatocytes, while all furocoumarins except bergamottin increased xenobiotic-responsive element-driven reporter gene expression in transfected H4IIE rat hepatoma cells when light was excluded. Furthermore, all furocoumarins tested induced the expression of endogenous, immunoreactive CYP1A1 protein, primarily in the dark. In conclusion, our results demonstrate that individual furocoumarins present in food and medicinal plants can interfere with AhR-regulated CYP1A1 expression and activity in at least three major ways, i.e., (i) act as highly potent inhibitors of the catalytic activity of CYP1A1 both in the presence and absence of light, (ii) induce CYP1A1 gene expression in the absence of light via activation of the AhR, and (iii) induce CYP1A1 gene expression without activation of the AhR.

Transcriptional response elements in the promoter of CYP6B1, an insect P450 gene regulated by plant chemicals

Papilio polyxenes, a lepidopteran continually exposed to toxic furanocoumarins in its hostplants, owes its tolerance to these compounds to the transcriptional induction of the CYP6B1 gene encoding a P450 capable of metabolizing linear furanocoumarins, such as xanthotoxin, at high rates. Transient expression of various lengths of wild-type and mutant CYP6B1v3 promoter in lepidopteran Sf9 cells defines a positive element (XRE-xan) from -136 to -119 required for both basal and xanthotoxin-inducible transcription and a negative element from -228 to -146 that represses basal transcription. Fusion of the CYP6B1v3 XRE-xan element to the Drosophila melanogaster Eip28/29 core promoter indicates that the XRE-xan functions in conjunction with its own core promoter but not with a heterologous core promoter. Sequence searches of the CYP6B1v3 proximal promoter region revealed a number of putative elements (XRE-AhR, ARE, OCT-1, EcRE, C/EBP, Inr) sharing sequence similarity with those in other regulated vertebrate and insect promoters. Mutation of TGAC nucleotides shared by the overlapping EcRE/ARE/XRE-xan indicates that this sequence is essential for basal and regulated transcription of this gene. Mutagenesis in the non-overlapping region of the EcRE indicates it modulates basal transcription. These findings are incorporated into a working model for regulation of this toxin-inducible promoter.

Liver cytochrome P450 CYP1A2 is markedly inhibited by systemic but not by bath PUVA in dermatological patients

BACKGROUND

Methoxsalen (8-MOP) may cause important pharmacokinetic drug interactions as it has been shown to inhibit and/or induce several drug-metabolizing enzymes in vitro, in animal models and in humans.

OBJECTIVES

In order to assess the clinical importance of acute and chronic 8-MOP effects on the liver cytochrome P-450 enzyme CYP1A2 in vivo, we measured caffeine clearance in dermatological patients before the onset of systemic or bath psoralen + ultraviolet A radiation (PUVA) (8-MOP + UVA) therapy, on the first day and after 1 week of treatment.

METHODS

Data from four patients with systemic PUVA and seven patients with bath PUVA were available (age range 23-71 years, five women and six men).

RESULTS

For all of the patients, individual pre-PUVA caffeine clearance values were above the lower limit of previously assessed reference ranges. Systemic PUVA markedly decreased caffeine clearance by factors of 0.17 [90% confidence interval (CI) 0.07-0.42] on the first day and 0.14 (90% CI 0.05-0.36) after 1 week of treatment, respectively, and values thus dropped below the reference ranges. In contrast, bath PUVA had no obvious effect on pre-PUVA clearance values as the latter changed by factors of 1.00 (90% CI 0.81-1.23) and 1.05 (90% CI 0.75-1.49) on the first day and after 1 week of treatment, respectively.

CONCLUSIONS

Systemic PUVA causes pronounced inhibition of liver CYP1A2, while bath PUVA has no such effect. The extent of interaction makes a dose adjustment for most CYP1A2 substrates such as theophylline mandatory in patients undergoing systemic PUVA.

The psoralens adversely affect reproductive function in male wistar rats

The psoralens occur naturally in produce and are widely used in skin therapy. Studies show that 5-methoxypsoralen and 8-methoxypsoralen reduced birth rates in rats. We determined the effect of psoralens on reproductive function in male rats. Male Wistar rats were dosed daily with 5-methoxypsoralen or 8-methoxypsoralen (75 or 150 mg/kg, p.o.), or vehicle control. Treated males had significantly smaller pituitary glands, fewer sperm per ejaculate, and fewer sperm in the vasa defferentia and epididymides than controls. Dosing significantly elevated levels of testosterone and increased relative testis weight, but did not directly affect testicular weight. Females bred to dosed males required more time to become pregnant, and these males required more breeding attempts. The findings demonstrate the importance of determining the potential risk for infertility and/or birth defects in humans who are exposed to therapeutic, dietary, or occupational psoralens.

A novel group of ovarian toxicants: the psoralens

The psoralens are naturally occurring metabolites found in many crop plants; synthetic forms of 5-methoxypsoralen (bergapten) and 8-methoxypsoralen (xanthotoxin) are widely used in skin photochemotherapy. Our previous research documented that dietary bergapten and xanthotoxin reduced birthrates in female rats when males and females were exposed to these chemicals. The present study was designed to determine the cause of this reduced birthrate and whether this resulted from direct impact on the females. The study demonstrates that bergapten and xanthotoxin administered, either alone or in combination to female rats (mated to undosed males), significantly reduced the number of implantation sites, pups, and corpora lutea in dosed females compared with control animals. Additionally, full uterine weight and empty uterine weight were significantly reduced. These compounds also significantly reduced circulating estrogen levels in a dose-dependent manner. Interestingly, the psoralens significantly induced mRNAs of liver enzymes typically induced by polycyclic aromatic hydrocarbons, CYP1A1 and UGT1A6; the higher the dose, the greater the induction. UGT 2B1 mRNA, typically induced by phenobarbital-like compounds, was not significantly affected. Thus, enhanced oxidative metabolism and conjugation of estrogens in psoralen-treated animals may provide a partial explanation for the effects observed. These findings are also consistent with psoralen-induced reduction in ovarian follicular function and ovulation.