Naturally occurring coumarins inhibit human cytochromes P450 and block benzo[a]pyrene and 7,12-dimethylbenz[a]anthracene DNA adduct formation in MCF-7 cells

CYP1A inhibitors: Recent progress, current challenges, and future perspectives

Mammalian cytochrome P450 1A (CYP1A) are key phase I xenobiotic-metabolizing enzymes that play a distinctive role in metabolic activation or metabolic clearance of a variety of procarcinogens, drugs, and endogenous substances. Human CYP1A subfamily contains two members (hCYP1A1 and hCYP1A2), which are known to catalyze the oxidative activation of some environmental procarcinogens into carcinogenic species. Increasing evidence has demonstrated that CYP1A inhibitor therapies are promising strategies for cancer chemoprevention or overcoming CYP1A-associated drug toxicity and resistance. Herein, we reviewed recent advances in the discovery and characterization of hCYP1A inhibitors, from the discovery approaches to structural features and biomedical applications of hCYP1A inhibitors. The inhibition potentials, inhibition modes, and inhibition constants of all reported hCYP1A inhibitors are comprehensively summarized. Meanwhile, the structural features and structure-activity relationships of different classes of hCYP1A1 and hCYP1A2 inhibitors are analyzed and discussed in depth. Furthermore, the major challenges and future directions for this field are presented and highlighted. Collectively, the information and knowledge presented here will strongly facilitate the researchers to discover and develop more efficacious CYP1A inhibitors for specific purposes, such as chemo-preventive agents or as tool molecules in hCYP1A-related fundamental studies.

Effects of xenobiotics on CYP1 enzyme-mediated biotransformation and bioactivation of estradiol

Endogenous estradiol (E2) exerts diverse physiological and pharmacological activities, commonly used for hormone replacement therapy. However, prolonged and excessive exposure to E2 potentially increases estrogenic cancer risk. Reportedly, CYP1 enzyme-mediated biotransformation of E2 is largely concerned with its balance between detoxification and carcinogenic pathways. Among the three key CYP1 enzymes (CYP1A1, CYP1A2, and CYP1B1), CYP1A1 and CYP1A2 mainly catalyze the formation of nontoxic 2-hydroxyestradiol (2-OH-E2), while CYP1B1 specifically catalyzes the formation of genotoxic 4-hydroxyestradiol (4-OH-E2). 4-OH-E2 can be further metabolized to electrophilic quinone intermediates accompanied by the generation of reactive oxygen species (ROS), triggering DNA damage. Since abnormal alterations in CYP1 activities can greatly affect the bioactivation process of E2, regulatory effects of xenobiotics on CYP1s are essential for E2-associated cancer development. To date, thousands of natural and synthetic compounds have been found to show potential inhibition and/or induction actions on the three CYP1 members. Generally, these chemicals share similar planar polycyclic skeletons, the structural motifs and substituent groups of which are important for their inhibitory/inductive efficiency and selectivity toward CYP1 enzymes. This review comprehensively summarizes these known inhibitors and/or inductors of E2-metabolizing CYP1s based on chemical categories and discusses their structure-activity relationships, which would contribute to better understanding of the correlation between xenobiotic-regulated CYP1 activities and estrogenic cancer susceptibility.

Osthole inhibits the migration and invasion of highly metastatic breast cancer cells by suppressing ITGα3/ITGβ5 signaling

Metastasis is the leading cause of death in breast cancer patients. Osthole, as an active compound detected in the traditional Chinese medicine Wenshen Zhuanggu Formula, has shown a promising anti-metastatic activity in human breast cancer cells, but the underlying mechanisms remain ambiguous. In this study we elucidated the anti-metastatic mechanisms of osthole in highly metastatic breast cancer cells and a zebrafish xenograft model. We showed that the expression of integrin α3 (ITGα3) and integrin β5 (ITGβ5) was upregulated in highly metastatic MDA-MB-231, MDA-MB-231BO breast cancer cell lines but was downregulated in poorly metastatic MCF-7 breast cancer cell line, which might be the key targets of osthole's anti-metastatic action. Furthermore, we showed that knockdown of ITGα3 and ITGβ5 attenuated breast cancer cell migration and invasion possibly via suppression of FAK/Src/Rac1 pathway, whereas overexpression of ITGα3 and ITGβ5 caused the opposite effects. Consistently, osthole significantly inhibited breast cancer metastasis by downregulating ITGα3/ITGβ5 signaling in vitro and in vivo. These results provide new evidence that osthole may be developed as a candidate therapeutic drug for metastatic breast cancer.

Coumarins and Gastrointestinal Cancer: A New Therapeutic Option?

Cancers of the gastrointestinal (GI) tract are often life-threatening malignancies, which can be a severe burden to the health care system. Globally, the mortality rate from gastrointestinal tumors has been increasing due to the lack of adequate diagnostic, prognostic, and therapeutic measures to combat these tumors. Coumarin is a natural product with remarkable antitumor activity, and it is widely found in various natural plant sources. Researchers have explored coumarin and its related derivatives to investigate their antitumor activity, and the potential molecular mechanisms involved. These mechanisms include hormone antagonists, alkylating agents, inhibitors of angiogenesis, inhibitors of topoisomerase, inducers of apoptosis, agents with antimitotic activity, telomerase inhibitors, inhibitors of human carbonic anhydrase, as well as other potential mechanisms. Consequently, drug design and discovery scientists and medicinal chemists have collaborated to identify new coumarin-related agents in order to produce more effective antitumor drugs against GI cancers. Herein, we summarize the therapeutic effects of coumarin and its derivatives against GI cancer.

Isopimpinellin extends antiangiogenic effect through overexpression of miR-15b-5p and downregulating angiogenic stimulators

BACKGROUND

Angiogenesis is the formation of new blood vessels from an existing vasculature through a series of processes such as activation, proliferation, and directed migration of endothelial cells. Angiogenesis is instrumental in the metastatic spread of tumors. Isopimpinellin, a furanocoumarin group of phytochemicals, is an anticarcinogenic agent. However, no studies have proven its antiangiogenic effects. The current study thus aimed to screen the antiangiogenic effect of isopimpinellin.

METHODS AND RESULTS

Human Umblical Vein Endothelial Cell (HUVEC) as an in vitro model and zebrafish embryos as an in vivo model was used in this study. The experimental results showed that isopimpinellin effectively inhibited HUVEC proliferation, invasion, migration, and tube formation, which are the key steps in angiogenesis by markedly suppressing the expression of pro-angiogenic genes VEGF, AKT, and HIF-1α. In addition, isopimpinellin exerts its anti-angiogenic effect through the regulation of miR-15b-5p and miR-542-3p. Furthermore, in zebrafish embryos, isopimpinellin inhibited the development of intersegmental vessels (ISVs) through the significant downregulation of all pro-angiogenic genes vegf, vegfr2, survivin, angpt-1, angpt-2, and tie-2.

CONCLUSION

Collectively, these experimental findings offer novel insights into the antiangiogenic nature of isopimpinellin and open new avenues for therapeutic approaches.

Bergamottin a CYP3A inhibitor found in grapefruit juice inhibits prostate cancer cell growth by downregulating androgen receptor signaling and promoting G0/G1 cell cycle block and apoptosis

Prostate cancer is the second leading cause of cancer related death in American men. Several therapies have been developed to treat advanced prostate cancer, but these therapies often have severe side effects. To improve the outcome with fewer side effects we focused on the furanocoumarin bergamottin, a natural product found in grapefruit juice and a potent CYP3A inhibitor. Our recent studies have shown that CYP3A5 inhibition can block androgen receptor (AR) signaling, critical for prostate cancer growth. We observed that bergamottin reduces prostate cancer (PC) cell growth by decreasing both total and nuclear AR (AR activation) reducing downstream AR signaling. Bergamottin’s role in reducing AR activation was confirmed by confocal microscopy studies and reduction in prostate specific antigen (PSA) levels, which is a marker for prostate cancer. Further studies revealed that bergamottin promotes cell cycle block and accumulates G0/G1 cells. The cell cycle block was accompanied with reduction in cyclin D, cyclin B, CDK4, P-cdc2 (Y15) and P-wee1 (S642). We also observed that bergamottin triggers apoptosis in prostate cancer cell lines as evident by TUNEL staining and PARP cleavage. Our data suggests that bergamottin may suppress prostate cancer growth, especially in African American (AA) patients carrying wild type CYP3A5 often presenting aggressive disease.

Anticancer Potential of Furanocoumarins: Mechanistic and Therapeutic Aspects

Cancer is one of the most extreme medical conditions in both developing and developed countries around the world, causing millions of deaths each year. Chemotherapy and/or radiotherapy are key for treatment approaches, but both have numerous adverse health effects. Furthermore, the resistance of cancerous cells to anticancer medication leads to treatment failure. The rising burden of cancer overall requires novel efficacious treatment modalities. Natural medications offer feasible alternative options against malignancy in contrast to western medication. Furanocoumarins' defensive and restorative impacts have been observed in leukemia, glioma, breast, lung, renal, liver, colon, cervical, ovarian, and prostate malignancies. Experimental findings have shown that furanocoumarins activate multiple signaling pathways, leading to apoptosis, autophagy, antioxidant, antimetastatic, and cell cycle arrest in malignant cells. Additionally, furanocoumarins have been shown to have chemo preventive and chemotherapeutic synergistic potential when used in combination with other anticancer drugs. Here, we address different pathways which are activated by furanocoumarins and their therapeutic efficacy in various tumors. Ideally, this review will trigger interest in furanocoumarins and their potential efficacy and safety as a cancer lessening agents.

In vitro modulation of cytochrome P450 isozymes and pharmacokinetics of caffeine by extracts of Hibiscus sabdariffa Linn calyx

Background Hibiscus sabdariffa beverage (HSB) is widely consumed as a medicinal herb and sometimes used concomitantly with drugs. This study evaluated the in vitro inhibitory potential of the aqueous extract of H. sabdariffa calyces (AEHS) on selected cytochrome P450 (CYP) isozymes and the effect of HSB on the pharmacokinetics of caffeine in vivo. Methods In vitro inhibitions of eight major CYP isozymes by AEHS were estimated by monitoring CYP-specific model reactions of 10 CYP probe substrates using N-in-one assay method. Subsequently, an open, randomized, two-period crossover design was used to evaluate the effect of HSB on the pharmacokinetics of single-dose 200 mg caffeine in six healthy human volunteers. Blood samples were obtained at specific times over a 24 h period. Probe drugs and metabolites were analyzed in their respective matrices with ultra-performance liquid chromatography/mass spectrometer/mass spectrometer and reversed-phase high-performance liquid chromatography/ultraviolet detection. Results The H. sabdariffa aqueous extract weakly inhibited the selected CYP isozymes in vitro, with IC50 of >100 μgmL-1 in the order of CYP1A2 > CYP2C8 > CYP2B6 >> CYP2D6 > CYP2C19 > CYP3A4 > CYP2A6 > CYP2C9. HSB decreased terminal t1/2 and Tmax of caffeine by 13.6% and 13.0%, respectively, and increased Cmax by 10.3%. Point estimates of primary pharmacokinetic endpoints, Cmax = 1.142 (90% confidence interval (CI) = 0.882, 1.480) and AUC0-∞ = 0.992 (90% CI = 0.745, 1.320), were outside the 90% CI of 0.8-1.25 bioequivalence limits. Conclusion The aqueous extract of H. sabdariffa weakly inhibited eight CYP isozymes in vitro, but HSB modified the exposure to caffeine in human. Caution should be exercised in administering HSB with caffeine or similar substrates of CYP1A2 until more clinical data are available.

Medicinal properties of Angelica archangelica root extract: Cytotoxicity in breast cancer cells and its protective effects against in vivo tumor development

OBJECTIVE

Although Angelica archangelica is a medicinal and aromatic plant with a long history of use for both medicinal and food purposes, there are no studies regarding the antineoplastic activity of its root. This study aimed to evaluate the cytotoxicity and antitumor effects of the crude extract of A. archangelica root (CEAA) on breast cancer.

METHODS

The cytotoxicity of CEAA against breast adenocarcinoma cells (4T1 and MCF-7) was evaluated by a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Morphological and biochemical changes were detected by Hoechst 33342/propidium iodide (PI) and annexin V/PI staining. Cytosolic calcium mobilization was evaluated in cells staining with FURA-4NW. Immunoblotting was used to determine the effect of CEAA on anti- and pro-apoptotic proteins (Bcl-2 and Bax, respectively). The 4T1 cell-challenged mice were used for in vivo assay.

RESULTS

Using ultra-high-performance liquid chromatography-mass spectrometry analysis, angelicin, a constituent of the roots and leaves of A. archangelica, was found to be the major constituent of the CEAA evaluated in this study (73 µg/mL). The CEAA was cytotoxic for both breast cancer cell lines studied but not for human fibroblasts. Treatment of 4T1 cells with the CEAA increased Bax protein levels accompanied by decreased Bcl-2 expression, in the presence of cleaved caspase-3 and cytosolic calcium mobilization, suggesting mitochondrial involvement in breast cancer cell death induced by the CEAA in this cell line. No changes on the Bcl-2/Bax ratio were observed in CEAA-treated MCF7 cells. Gavage administration of the CEAA (500 mg/kg) to 4T1 cell-challenged mice significantly decreased tumor growth when compared with untreated animals.

CONCLUSION

Altogether, our data show the antitumor potential of the CEAA against breast cancer cells in vitro and in vivo. Further research is necessary to better elucidate the pharmacological application of the CEAA in breast cancer therapy.

Biomolecular Targets of Oxyprenylated Phenylpropanoids and Polyketides

Oxyprenylated secondary metabolites (e.g. phenylpropanoids and polyketides) represent a rare class of natural compounds. Over the past two decades, this group of phytochemicals has become a topic of intense research activity by several teams worldwide due to their in vitro and in vivo pharmacological activities, and to their great therapeutic and nutraceutical potential for the chemoprevention of acute and chronic diseases affecting humans. Such investigations have provided evidence that oxyprenylated secondary metabolites are able to interact with several biological targets at different levels accounting for their observed anticarcinogenic, anti-inflammatory, neuroprotective, immunomodulatory, antihypertensive, and metabolic effects. The aim of the present contribution is to provide a detailed survey of the so far reported data on the capacities of selected oxyprenylated phenylpropanoids and polyketides to trigger receptors, enzymes, and other types of cellular factors for which they exhibit a high degree of affinity and therefore evoke specific responses. With respect to the rather small amounts of these compounds available from natural sources, their chemical synthesis is also highlighted.

Pharmacological Utilization of Bergamottin, Derived from Grapefruits, in Cancer Prevention and Therapy

Cancer still remains one of the leading causes of death worldwide. In spite of significant advances in treatment options and the advent of novel targeted therapies, there still remains an unmet need for the identification of novel pharmacological agents for cancer therapy. This has led to several studies evaluating the possible application of natural agents found in vegetables, fruits, or plant-derived products that may be useful for cancer treatment. Bergamottin is a furanocoumarin derived from grapefruits and is also a well-known cytochrome P450 inhibitor. Recent studies have demonstrated potent anti-oxidative, anti-inflammatory, and anti-cancer properties of grapefruit furanocoumarin both in vitro and in vivo. The present review focuses on the potential anti-neoplastic effects of bergamottin in different tumor models and briefly describes the molecular targets affected by this agent.

Hesperidin exhibits in vitro and in vivo antitumor effects in human osteosarcoma MG-63 cells and xenograft mice models via inhibition of cell migration and invasion, cell cycle arrest and induction of mitochondrial-mediated apoptosis

The objective of the present study was to investigate the anticancer properties of hesperidin against human osteosarcoma MG-63 cells. Its effects on apoptosis, cell migration, cell invasion and cell cycle arrest, and its effects on tumor volume and weight were also evaluated in the present study. MTS assay was used to study the cytotoxic effects of the compound on cell viability. Effects on apoptosis and cell cycle arrest were evaluated by flow cytometry. In vitro wound healing assay and Matrigel assay were performed to study the effects of hesperidin on cell migration and cell invasion, respectively. Hesperidin exerted dose-dependent and time-dependent growth inhibitory effects on cervical cancer cells with IC50 values of 33.5, 23.8 and 17.6 µM, respectively, at 24, 48 and 72 h time intervals. Hesperidin led to early and late apoptosis induction in these cells. Hesperidin-treated cells also led to G2/M phase cell cycle arrest, which exhibited strong dose-dependence. Hesperidin treatment also led to inhibition of cell migration and invasion.

Effects of isoimperatorin on proliferation and apoptosis of human gastric carcinoma cells

Resistance to apoptosis is an characteristic of cancer cells that serves a critical function in tumor development and represents a target for antitumor therapy. Isoimperatorin (ISOIM), a coumarin compound, exhibits antitumor functions in multiple types of tumor cells. However, its antitumor effects and molecular mechanisms with respect to gastric cancer have not been elucidated. The present study assessed the anti-proliferative and apoptotic effects of ISOIM on human BGC-823 gastric cancer cells and elucidated its underlying molecular mechanisms. Cell proliferation was evaluated using MTT assays. Analysis of cell morphology was performed by hematoxylin and eosin, Hoechst 33258 and acridine orange/ethidium bromide staining. In addition, cell cycle and apoptosis was evaluated using flow cytometry analysis; expression of apoptosis-associated proteins was studied by western blotting. The results of the present study revealed that ISOIM significantly inhibited cell proliferation by arresting the cell cycle at the G₂/M phase and induced apoptosis by increasing Bcl-2-associated X (Bax) expression with a concomitant decrease in Bcl-2 expression, resulting in a decreased Bcl-2/Bax ratio compared with the control. In addition, ISOIM treatment also resulted in cytochrome c translocating from the mitochondria to the cytosol. Furthermore, caspase-3 was significantly activated in response to treatment with ISOIM, suggesting that apoptosis in BGC-823 cells is induced in the mitochondrial pathway. Taken together, the results of the present study indicate that ISOIM may significantly induce apoptosis in BGC-823 cells and that the pro-apoptotic mechanisms of ISOIM could be associated with the mitochondrial pathway.

Bergamottin, a natural furanocoumarin abundantly present in grapefruit juice, suppresses the invasiveness of human glioma cells via inactivation of Rac1 signaling

The aim of the present study was to explore the effect of bergamottin, a natural furanocoumarin obtained from grapefruit juice, on the invasiveness of human glioma cells. The results revealed that treatment with bergamottin for 48 h significantly inhibited wound-healing migration and Matrigel invasion of human glioma cells, compared with untreated cells (P<0.05). Bergamottin treatment caused a significant decrease in the expression and secretion of matrix metalloproteinase (MMP)-9 in glioma cells compared with untreated cells (P<0.05). A Rac1-GTP pull-down assay demonstrated that bergamottin-treated glioma cells had a significantly decreased level of active Rac1-GTP compared with untreated cells (P<0.05). However, bergamottin had no significant effect on cell division cycle 42 activity. Expression of constitutively activated Rac1 almost completely restored the migration and invasion of bergamottin-treated glioma cells. In addition, bergamottin-induced downregulation of MMP-9 was prevented by exogenous activated Rac1. The results of the present study demonstrated that bergamottin exhibits anti-invasive activity in human glioma cells through the inactivation of Rac1 and downregulation of MMP-9.

Effect of Naringenin, Quercetin, and Sesamin on Xenobiotica-Metabolizing CYP1A and CYP3A in Mice Offspring after Maternal Exposure to Persistent Organic Pollutants

The aim of the present study was to evaluate in vitro effects of dietary phytochemicals naringenin, quercetin, and sesamin on the activities of ethoxy- (EROD; CYP1A) and benzyloxy- (BROD; CYP3A) resorufin O-dealkylases after the exposure to the cocktail of persistent organic pollutants (POPs). CD-1 mice were exposed from weaning, through gestation and lactation to a defined mixture of POPs. Hepatic microsomes were prepared from their female offspring at postnatal day 42. Hepatic EROD and BROD activity were evaluated in the presence of quercetin, naringenin, and sesamin at nine concentrations from 5 to 100000 nM. EROD activity was strongly inhibited by quercetin with Ki values from 1.7 to 2.6 μM. BROD activity was inhibited by quercetin with Ki values from 64.9 to 75.3 μM and naringenin with Ki values from 39.3 to 45.8 μM. The IC₅₀ and Ki values did not differ between the groups of mice with different levels of POPs exposure in any of the experimental sets. Sesamin did not inhibit either EROD or BROD. We concluded that the interactions of quercetin and naringenin with CYP1A and CYP3A in mice liver were not affected by the levels of POPs exposure.

Anthelmintic effect of 2H-chromen-2-one isolated from Gliricidia sepium against Cooperia punctata

Gliricidia sepium is a tropical legume with known anthelmintic-like properties. The aim of this study was to: (1) perform a bio-guided fractionation of an acetonic extract of G. sepium leaves using the egg hatch assay (EHA); (2) elucidate the anthelmintic (AH)-like phytochemical using nuclear magnetic resonance (NMR); and (3) assess the ultrastructural damage of the Cooperia punctata treated eggs. The anthelmintic activity of G. sepium was traced from an acetonic extract using the EHA. Phytochemicals were isolated through silica gel columns and elucidated through spectroscopic measurements (1H and 13C). Final fraction was evaluated with EHA at decreasing concentrations of: 1.100; 0.500, 0.250, 0.125, 0.060, 0.001 and 0.00001 mg mL-1. Egg hatching inhibition was calculated using the formula: 100*(1-HT/HC). The maximal half of effective concentration (EC₅₀) was calculated with GraphPad. Bio-guided isolation procedures lead to the elucidation of 2H-chromen-2-one, which inhibited both hatching and embryo development of C. punctata (EC₅₀ of 0.024 ± 0.082 mg mL-1) (P < 0.05). Scanning and Transmission Electron Microscopy (SEM and TEM) revealed electrodensity alterations and fractures in the eggshell layers. After toxicity evaluations and in vivo assessment, 2H-chromen-2-one can be suggested as a novel AH-phytochemical for reducing larval density in pastures and worm burdens inside the host.

Inhibition of Carcinogen-Activating Cytochrome P450 Enzymes by Xenobiotic Chemicals in Relation to Antimutagenicity and Anticarcinogenicity

A variety of xenobiotic chemicals, such as polycyclic aromatic hydrocarbons (PAHs), aryl- and heterocyclic amines and tobacco related nitrosamines, are ubiquitous environmental carcinogens and are required to be activated to chemically reactive metabolites by xenobiotic-metabolizing enzymes, including cytochrome P450 (P450 or CYP), in order to initiate cell transformation. Of various human P450 enzymes determined to date, CYP1A1, 1A2, 1B1, 2A13, 2A6, 2E1, and 3A4 are reported to play critical roles in the bioactivation of these carcinogenic chemicals. In vivo studies have shown that disruption of Cyp1b1 and Cyp2a5 genes in mice resulted in suppression of tumor formation caused by 7,12-dimethylbenz[a]anthracene and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone, respectively. In addition, specific inhibitors for CYP1 and 2A enzymes are able to suppress tumor formation caused by several carcinogens in experimental animals in vivo, when these inhibitors are applied before or just after the administration of carcinogens. In this review, we describe recent progress, including our own studies done during past decade, on the nature of inhibitors of human CYP1 and CYP2A enzymes that have been shown to activate carcinogenic PAHs and tobacco-related nitrosamines, respectively, in humans. The inhibitors considered here include a variety of carcinogenic and/or non-carcinogenic PAHs and acethylenic PAHs, many flavonoid derivatives, derivatives of naphthalene, phenanthrene, biphenyl, and pyrene and chemopreventive organoselenium compounds, such as benzyl selenocyanate and benzyl selenocyanate; o-XSC, 1,2-, 1,3-, and 1,4-phenylenebis( methylene)selenocyanate.

Modulation of benzo[a]pyrene-DNA adduct formation by CYP1 inducer and inhibitor

Benzo[a]pyrene (BaP) is a well-studied pro-carcinogen that is metabolically activated by cytochrome P450 enzymes. Cytochrome P4501A1 (CYP1A1) has been considered to play a central role in the activation step, which is essential for the formation of DNA adducts. This enzyme is strongly induced by many different chemical agents, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which binds to the aryl hydrocarbon receptor (AhR). Therefore, AhR activators are suspected to have the potential to aggravate the toxicity of BaP through the induction of CYP1A1. Besides, CYP1A1 inhibitors, including its substrates, are estimated to have preventive effects against BaP toxicity. However, strangely, increased hepatic BaP–DNA adduct levels have been reported in Cyp1a1 knockout mice. Moreover, numerous reports describe that concomitant treatment of AhR activators reduced BaP–DNA adduct formation. In an experiment using several human cell lines, TCDD had diverse modulatory effects on BaP–DNA adducts, both enhancing and inhibiting their formation. In this review, we focus on the factors that could influence the BaP–DNA adduct formation. To interpret these complicated outcomes, we propose a hypothesis that CYP1A1 is a key enzyme for both generation and reduction of (±)-anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), the major carcinogenic intermediate of BaP. Conversely, CYP1B1 is thought to contribute only to the metabolic activation of BaP related to carcinogenesis.

Purification, characterization and procoagulant activity of polysaccharides from Angelica dahurice roots

Five polysaccharides, namely ADPs-1a, ADPs-1b, ADPs-2, ADPs-3a and ADPs-3b, were extracted from Angelicae dahuricae Radix, purified, and identified by high performance gel permeation chromatography (HPSEC), gas chromatography (GC), Fourier transform infrared (FT-IR) spectrometer and nuclear magnetic resonance spectra (NMR), including the determination of procoagulant activity in vitro. The average molecular weight (Mw) of the polysaccharides was 153,800, 8312, 111,700, 3766 and 96,680 g/mol, respectively. Coagulation assays indicated that ADPs-1b, ADPs-2, ADPs-3a and ADPs-3b had procoagulant activities. ADPs-1b exerted the procoagulant activities through intrinsic pathway, extrinsic pathway and increased the content of FIB in vitro. ADPs-2 exerted the procoagulant activities through intrinsic pathway and extrinsic pathway. ADPs-3a had procoagulant activities and the activity was associated with the intrinsic pathway and increased the content of FIB. ADPs-3b exerted the activities through extrinsic pathway and increased the content of FIB.

Imperatorin-pharmacological meaning and analytical clues: profound investigation

Imperatorin, a furanocoumarin derivative, has many documented pharmacological properties which make it a candidate for possible drug development. In this review, the activity on the central nervous system, the anticancer and antiviral properties and the influence on the cardiovascular system are described. The aim of this review is also to present an overview of the techniques used for the analysis, isolation, and separation of imperatorin from plant material from the practical perspective.

A Ligand-Based Drug Design. Discovery of 4-Trifluoromethyl-7,8-pyranocoumarin as a Selective Inhibitor of Human Cytochrome P450 1A2

In humans, cytochrome P450 1A2 is the major enzyme metabolizing environmental arylamines or heterocyclic amines into carcinogens. Since evidence shows that planar triangle-shaped molecules are capable of selectively inhibiting P450 1A2, 16 triangular flavone, and coumarin derivatives were designed and synthesized for these studies. Among these compounds, 7,8-furanoflavone time-dependently inhibits P450 1A2 with a K(I) value of 0.44 μM. With a 5 min preincubation in the presence of NADPH, 0.01 μM 7,8-furanoflavone completely inactivates P450 1A2 but does not influence the activities of P450s 1A1 and 1B1. Another target compound, 7,8-pyrano-4-trifluoromethylcoumarin, is found to be a competitive inhibitor, showing high selectivity for the inhibition of P450 1A2 with a K(i) of 0.39 μM, 155- and 52-fold lower than its K(i) values against P450s 1A1 and 1B1, respectively. In yeast AhR activation assays, 7,8-pyrano-4-trifluoromethylcoumarin does not activate aryl hydrocarbon receptor when the concentration is lower than 1 μM, suggesting that this compound would not up-regulate AhR-caused P450 enzyme expression. In-cell P450 1A2 inhibition assays show that 7,8-pyrano-4-trifluoromethylcoumarin decreases the MROD activity in HepG2 cells at concentrations higher than 1 μM. Thus, using 7,8-pyrano-4-trifluoromethylcoumarin, a selective and specific P450 1A2 action suppression could be achieved, indicating the potential for the development of P450 1A2-targeting cancer preventive agents.

Cytotoxic activity and composition of petroleum ether extract from Magydaris tomentosa (Desf.) W. D. J. Koch (Apiaceae)

The petroleum ether extract of Magydaris tomentosa flowers (Desf.) W. D. J. Koch has been analyzed by GC-MS. It is mainly constituted by furanocoumarins such as xanthotoxin, xanthotoxol, isopimpinellin, and bergaptene. Other coumarins such as 7-methoxy-8-(2-formyl-2-methylpropyl) coumarin and osthole also occurred. The antiproliferative activity of Magydaris tomentosa flower extract has been evaluated in vitro on murine monocye/macrophages (J774A.1), human melanoma (A375) and human breast cancer (MCF-7) tumor cell lines, showing a major activity against the latter.

Effects of psoralens as anti-tumoral agents in breast cancer cells

This review examines the biological properties of coumarins, widely distributed at the highest levels in the fruit, followed by the roots, stems and leaves, by considering their beneficial effects in the prevention of some diseases and as anti-cancer agents. These compounds are well known photosensitizing drugs which have been used as pharmaceuticals for a broad number of therapeutic applications requiring cell division inhibitors. Despite this, even in the absence of ultraviolet rays they are active. The current paper mainly focuses on the effects of psoralens on human breast cancer as they are able to influence many aspects of cell behavior, such as cell growth, survival and apoptosis. In addition, analytical and pharmacological data have demonstrated that psoralens antagonize some metabolizing enzymes, affect estrogen receptor stability and counteract cell invasiveness as well as cancer drug resistance. The scientific findings summarized highlight the pleiotropic functions of phytochemical drugs, given that recently their target signals and how these are modified in the cells have been identified. The encouraging results in this field suggest that multiple modulating strategies based on coumarin drugs in combination with canonical chemotherapeutic agents or radiotherapy could be a useful approach to address the treatment of many types of cancer.

Ethynylflavones, highly potent, and selective inhibitors of cytochrome P450 1A1

The flavone backbone is a well-known pharmacophore present in a number of substrates and inhibitors of various P450 enzymes. In order to find highly potent and novel P450 family I enzyme inhibitors, an acetylene group was incorporated into six different positions of flavone. The introduction of an acetylene group at certain locations of the flavone backbone lead to time-dependent inhibitors of P450 1A1. 3′-Ethynylflavone, 4′-ethynylflavone, 6-ethynylflavone, and 7-ethynylflavone (K_I values of 0.035–0.056 μM) show strong time-dependent inhibition of P450 1A1, while 5-ethynylflavone (K_I value of 0.51 μM) is a moderate time-dependent inhibitor of this enzyme. Meanwhile, 4′-ethynylflavone and 6-ethynylflavone are highly selective inhibitors toward this enzyme. Especially, 6-ethynylflavone possesses a K_i value of 0.035 μM for P450 1A1 177- and 15-fold lower than those for P450s 1A2 and 1B1, respectively. The docking postures observed in the computational simulations show that the orientation of the acetylene group determines its capability to react with P450s 1A1 and 1A2. Meanwhile, conformational analysis indicates that the shape of an inhibitor determines its inhibitory selectivity toward these enzymes.

Grapefruit (Citrus paradisi Macfad) phytochemicals composition is modulated by household processing techniques

Grapefruits (Citrus paradisi Macfad) contain several phytochemicals known to have health maintaining properties. Due to the consumer's interest in obtaining high levels of these phytochemicals, it is important to understand the changes in their levels by common household processing techniques. Therefore, mature Texas "Rio Red" grapefruits were processed by some of the common household processing practices such as blending, juicing, and hand squeezing techniques and analyzed for their phytochemical content by high performance liquid chromatography (HPLC). Results suggest that grapefruit juice processed by blending had significantly (P < 0.05) higher levels of flavonoids (narirutin, naringin, hesperidin, neohesperidin, didymin, and poncirin) and limonin compared to juicing and hand squeezing. No significant variation in their content was noticed in the juice processed by juicing and hand squeezing. Ascorbic acid and citric acid were significantly (P < 0.05) higher in juice processed by juicing and blending, respectively. Furthermore, hand squeezed fruit juice had significantly higher contents of dihydroxybergamottin (DHB) than juice processed by juicing and blending. Bergamottin and 5-methoxy-7 gernoxycoumarin (5-M-7-GC) were significantly higher in blended juice compared to juicing and hand squeezing. Therefore, consuming grapefruit juice processed by blending may provide higher levels of health beneficial phytochemicals such as naringin, narirutin, and poncirin. In contrast, juice processed by hand squeezing and juicing provides lower levels of limonin, bergamottin, and 5-M-7-GC. These results suggest that, processing techniques significantly influence the levels of phytochemicals and blending is a better technique for obtaining higher levels of health beneficial phytochemicals from grapefruits. Practical Application:  Blending, squeezing, and juicing are common household processing techniques used for obtaining fresh grapefruit juice. Understanding the levels of health beneficial phytochemicals present in the juice processed by these techniques would enable the consumers to make a better choice to obtain high level of these compounds.

Effects of furanocoumarins from apiaceous vegetables on the catalytic activity of recombinant human cytochrome P-450 1A2

Inhibition of cytochrome P-450 1A2 (CYP1A2)-mediated activation of procarcinogens may be an important chemopreventive mechanism. Consumption of apiaceous vegetables (rich in furanocoumarins) inhibits CYP1A2 in humans. Because many furanocoumarins are potent inhibitors of several CYPs, we characterized the effects of three furanocoumarins from apiaceous vegetables on human CYP1A2 (hCYP1A2). We assessed hCYP1A2 methoxyresorufin O-demethylase (MROD) activity using microsomes from Saccharomyces cerevisiae expressing hCYP1A2. Isopimpinellin exhibited mechanism-based inactivation (MBI) of hCYP1A2 (K(i) = 1.2 μM, k (inact) = 0.34 min⁻¹, and partition ratio = 8). Imperatorin and trioxsalen were characterized as mixed inhibitors with K(i) values of 0.007 and 0.10 μM, respectively. These results indicate that even if present at low levels in apiaceous vegetables, imperatorin, trioxsalen and isopimpinellin may contribute significantly to CYP1A2 inhibition and potentially decreased procarcinogen activation. Moreover, the in vivo effect of isopimpinellin on CYP1A2 may be longer lasting compared to reversible inhibitors.

Suppressive Effects of Selected Food Phytochemicals on CD74 Expression in NCI-N87 Gastric Carcinoma Cells

Helicobacter pylori (H. pylori) is one of the most widespread human pathogens, and plays major roles in chronic gastritis and gastric cancer. CD74 of gastric epithelial cells has recently been identified as an adhesion molecule to urease in H. pylori. In this study, we found that CD74 is highly expressed in a constitutive manner in NCI-N87 human gastric carcinoma cells at both the protein and mRNA levels as compared with Hs738St./Int fetal gastric cells. Subsequently, a novel cell-based ELISA able to rapidly screen the suppressive agents of CD74 expression was established. NCI-N87 cells were treated separately with 25 different food phytochemicals (4–100 µM) for 48 h and subjected to our novel assay. From those results, a citrus coumarin, bergamottin, was indicated to be the most promising compound with an LC₅₀/IC₅₀ value greater than 7.1, followed by luteolin (>5.4), nobiletin (>5.3), and quercetin (>5.1). Our findings suggest that these CD74 suppressants are unique candidates for preventing H. pylori adhesion and subsequent infection with reasonable action mechanisms.

The Fanconi anemia pathway and ICL repair: implications for cancer therapy

Fanconi anemia (FA) is an inherited disease caused by mutations in at least 13 genes and characterized by genomic instability. In addition to displaying strikingly heterogenous clinical phenotypes, FA patients are exquisitely sensitive to treatments with crosslinking agents that create interstrand crosslinks (ICL). In contrast to bacteria and yeast, in which ICLs are repaired through replication-dependent and -independent mechanisms, it is thought that ICLs are repaired primarily during DNA replication in vertebrates. However, recent data indicate that replication-independent ICL repair also operates in vertebrates. While the precise role of the FA pathway in ICL repair remains elusive, increasing evidence suggests that FA proteins function at different steps in the sensing, recognition and processing of ICLs, as well as in signaling from these very toxic lesions, which can be generated by a wide variety of cancer chemotherapeutic drugs. Here, we discuss some of the recent findings that have shed light on the role of the FA pathway in ICL repair, with special emphasis on the implications of these findings for cancer therapy since disruption of FA genes have been associated with cancer predisposition.

Suppression of phorbol-12-myristate-13-acetate-induced tumor cell invasion by bergamottin via the inhibition of protein kinase Cdelta/p38 mitogen-activated protein kinase and JNK/nuclear factor-kappaB-dependent matrix metalloproteinase-9 expression

Matrix metalloproteinase (MMP) plays an important role in the invasion and metastasis of cancer cells. The inhibitory effects of bergamottin, a cytochrome P450 inhibitor from Citrus paradis (grapefruit), on tumor invasion and migration and the possible mechanisms involved in this inhibition were investigated in human fibrosarcoma HT-1080 cells. Bergamottin reduced phorbol-12-myristate-13-acetate (PMA)-induced activation of MMP-9 and MMP-2 and further inhibited cell invasion and migration. Bergamottin suppressed PMA-enhanced expression of MMP-9 protein, mRNA and transcription activity levels through suppression of nuclear factor-kappaB (NF-kappaB) activation without changing the tissue inhibitor of metalloproteinase 1 level. Bergamottin also reduced PMA-enhanced MMP-2 expression through suppression of membrane-type 1 MMP, but did not alter tissue inhibitor of metalloproteinase 2 levels. Bergamottin inhibited PMA-induced NF-kappaB nuclear translocation and IkappaBalpha degradation, which are upstream of PMA-induced MMP-9 expression and invasion. Furthermore, bergamottin strongly repressed the PMA-induced phosphorylation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase (JNK), which are dependent on the protein kinase C-delta pathway. In conclusion, we demonstrated that the anti-invasive effects of bergamottin might occur through inhibition of protein kinase C-delta, p38 mitogen-activated protein kinase, and JNK phosphorylation and reduction of NF-kappaB activation, leading to downregulation of MMP-9 expression. These results suggest that the suppression of MMP expression contributes, at least in part, to the antitumor activity of bergamottin.

Selenitetriglicerydes affect CYP1A1 and QR activity by involvement of reactive oxygen species and Nrf2 transcription factor

Selenitetriglycerides are a group of compounds that contain selenium (Se) (IV). In this paper, we present the results of examinations of three structurally-related selenitetriglicerydes that contain various Se concentrations: 2%, 5% and 7% Selol. The present study concentrates on the effect of Selol on phase 1 and 2 enzyme activity and the implications of free radicals and the nuclear erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway in the activity of this compound. The cytotoxic and cytostatic activities of the three kinds of Selol were evaluated; however, the cytotoxic effect was observed only for 7% Selol. Our results show that 2% Selol acts as a monofunctional inducer of phase 2 enzyme activity, and the induction is mediated by the Nrf2 transcription factor. Selol 7% acts in an opposite manner and induces phase 1 with simultaneous inhibition of phase 2 enzyme activity. The differential effect can be associated with the increase in Se content, leading to a change in the structure of the compound.

Thymoquinone and cisplatin as a therapeutic combination in lung cancer: In vitro and in vivo

Background

Thymoquinone (TQ) is a compound extracted from Black Caraway seeds of Nigella Sativa and is active against various cancers. Cisplatin (CDDP) is the most active chemotherapeutic agent in Lung Cancer. Here we report activity of TQ against non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) cell lines alone and in combination with Cisplatin (CDDP).

Methods

For proliferation MTT assay, cell viability trypan blue assay and for apoptosis Annexin-V FITC assay were used in NCI-H460 and NCI-H146 cell lines. Inhibition of invasion by TQ was assessed using Matrigel assay and its affect on release of various cytokines was determined using RayBio Human Cytokine detection kit. Mouse xenograft model using NCI-H460 was used to determine in vivo activity of TQ and CDDP. Inhibition of LPS induced NF-κB expression by TQ was determined using transgenic mice expressing a luciferase reporter.

Results

TQ was able to inhibit cell proliferation, reduce cell viability and induce apoptosis. TQ at 100 μM and CDDP at 5 μM inhibited cell proliferation by nearly 90% and the combination showed synergism. TQ was able to induced apoptosis in both NCI-H460 and NCI-H146 cell lines. TQ also appears to affect the extracellular environment inhibiting invasion and reducing the production of two cytokines ENA-78 and Gro-alpha which are involved in neo-angiogenesis. Using a mouse xenograft model we were able to demonstrate that combination of TQ and CDDP was well tolerated and significantly reduced tumor volume and tumor weight without additional toxicity to the mice. In the combination arms (TQ5 mg/kg/Cis 2.5 mg/kg) tumor volume was reduced by 59% and (TQ20 mg/kg/Cis 2.5 mg/kg) by 79% as compared to control which is consistent with in vitro data. TQ down regulated NF-κB expression which may explain its various cellular activities and this activity may prove useful in overcoming CDDP resistance from over expression of NF-κB.

Conclusions

Thus TQ and CDDP appear to be an active therapeutic combination in lung cancer.

QSAR of cytochrome inhibitors

Cytochrome P450 (CYP450) enzymes are predominantly involved in the Phase I metabolism of xenobiotics. Metabolic inhibition and induction can give rise to clinically important drug-drug interactions. Metabolic stability is a prerequisite for sustaining the therapeutically relevant concentrations, and very often drug candidates are sacrificed due to poor metabolic profiles. Computational tools such as quantitative structure-activity relationships are widely used to study different metabolic end points successfully to accelerate the drug discovery process. There are a lot of computational studies on clinically important CYPs already reported in recent years. But other clinically significant families are to yet be explored computationally. Powerfulness of quantitative structure-activity relationship will drive computational chemists to develop new potent and selective inhibitors of different classes of CYPs for the treatment of different diseases with least drug-drug interactions. Furthermore, there is a need to enhance the accuracy, interpretability and confidence in the computational models in accelerating the drug discovery pathways.

Sulforaphane and its analogues inhibit CYP1A1 and CYP1A2 activity induced by benzo[a]pyrene

CYP1A1 and CYP1A2 enzymes metabolize polycyclic aromatic hydrocarbons (PAHs) to the reactive oxyderivatives. PAHs can induce the activity of both enzymes, which increases its conversion and enhances risk of carcinogenesis. Thus, the inhibition of CYP enzymes is recognized as a cancer chemoprevention strategy. A well-known group of chemopreventive agents is isothiocyanates, which occur naturally in Brassica vegetables. In this paper, a naturally occurring sulforaphane and its two synthetic analogues isothiocyanate-2-oxohexyl and alyssin were investigated. The aim of the study was to determine whether the differences in the isothiocyanate structure change its ability to inhibit CYP1A1 and CYP1A2 activity induced by benzo[a]pyrene in HepG2 and Mcf7 cells. Also a mechanistic study was performed including isothiocyanates' influence on CYP1A1 and CYP1A2 catalytic activity, enzymatic protein level, and AhR translocation. It was shown that both enzymes were significantly induced by benzo[a]pyrene, and isothiocyanates were capable of decreasing the induced activity. The inhibitory properties depend on the types of isothiocyanate and enzyme. In general, CYP1A2 was altered in the more meaningful way than CYP1A1 by isothiocyanates. Sulforaphane exhibited weak inhibitory properties, whereas both analogues were capable of inhibiting BaP-induced activity with the similar efficacy. The mechanistic study revealed that analogues decreased the CYP1A2 activity via the protein-level reduction and CYP1A1 directly. The results indicate that isothiocyanates can be considered as potent chemopreventive substances and the change in the sulforaphane structure increases its chemopreventive potency.

The effect of isothiocyanates on CYP1A1 and CYP1A2 activities induced by polycyclic aromatic hydrocarbons in Mcf7 cells

Polycyclic aromatic hydrocarbons (PAHs)--environmental carcinogens--are metabolized by CYP1A1 and CYP1A2 enzymes to oxy-derivatives, which are able to bind to DNA and initiate carcinogenesis. PAHs induce CYP1A1 and CYP1A2 activity, which increases the risk of development of carcinogenesis. Isothiocyanates (ITCs), naturally occurring in Brassica vegetables, possess chemopreventive properties and are able to reduce the CYP1A enzyme activity. In this paper we report our study of the ability of ITCs: sulforaphane and its analogues: isothiocyanate-2-oxohexyl and alyssin, to inhibit CYP1A1 and CYP1A2 enzyme activity induced by the PAHs, anthracene (ANT) and dibenzo[a,h]anthracene (DBA) in human breast cancer cell line Mcf7. The aim was to determine whether the differences in structure of ITCs change their inhibitory properties, and whether these properties depend on the type of inducer. The results indicate that the properties of ITCs depend on the type of PAH: ITCs are more potent in inhibiting activity induced by the weaker inducer. It was also found that the change in ITCs' structure influences their activities. ITC 2-oxohexyl was the weakest inhibitor, whereas sulforaphane and alyssin exhibited similar potency. The study revealed that inhibition of CYP1A1 activity is direct whereas inhibition of CYP1A2 activity is not only direct but is also caused by the level of protein disturbance.

Comparison of citrus coumarins on carcinogen-detoxifying enzymes in Nrf2 knockout mice

Naturally occurring coumarins possess anti-carcinogenic activities in part by inducing carcinogen-detoxifying enzymes glutathione S-transferase (GST) and/or NAD(P)H quinone oxidoreductase (NQO1). Our goal was to determine whether citrus coumarins induce hepatic GST and/or NQO1 via activation of Nrf2 and the antioxidant response element (ARE). First, HepG2 cells stably transfected with the ARE and a green fluorescent protein (GFP) reporter were treated with increasing concentrations of coumarins and compared to positive controls. tert-Butylhydroquinone (TBHQ) and oltipraz increased GFP fluorescence, as did coumarin, limettin, auraptene, imperatorin, and 7,8-benzoflavone, suggesting that they activate the ARE, whereas isopimpinellin did not increase GFP fluorescence. Next, the effects of orally administered coumarins and oltipraz on hepatic GST and NQO1 activities were compared in Nrf2 knockout mice or Nrf2 heterozygous mice exhibiting the wild-type phenotype. Oltipraz, auraptene, imperatorin, isopimpinellin, and auraptene all significantly increased liver cytosolic GST activities in Nrf2 heterozygous mice. This effect was abrogated in Nrf2(-/-) mice dosed with oltipraz, attenuated in mice Nrf2(-/-) mice treated with auraptene and imperatorin, and still significant in Nrf2(-/-) mice treated with isopimpinellin. Of these compounds, only isopimpinellin significantly increased liver cytosolic NQO1 activities, and this effect was not attenuated in Nrf2(-/-) mice. These results strongly suggest that imperatorin and auraptene induce murine liver cytosolic GST activities via the Nrf2/ARE mechanism. Although structurally similar, isopimpinellin did not appear to activate HepG2-ARE-GFP and the Nrf2 knockout mouse study suggests that isopimpinellin may induce GST and NQO1 via additional mechanisms.

Effects of naturally occurring coumarins on hepatic drug-metabolizing enzymes in mice

Cytochromes P450 (P450s) and glutathione S-transferases (GSTs) constitute two important enzyme families involved in carcinogen metabolism. Generally, P450s play activation or detoxifying roles while GSTs act primarily as detoxifying enzymes. We previously demonstrated that oral administration of the linear furanocoumarins, isopimpinellin and imperatorin, modulated P450 and GST activities in various tissues of mice. The purpose of the present study was to compare a broader range of naturally occurring coumarins (simple coumarins, and furanocoumarins of the linear and angular type) for their abilities to modulate hepatic drug-metabolizing enzymes when administered orally to mice. We now report that all of the different coumarins tested (coumarin, limettin, auraptene, angelicin, bergamottin, imperatorin and isopimpinellin) induced hepatic GST activities, whereas the linear furanocoumarins possessed the greatest abilities to induce hepatic P450 activities, in particular P450 2B and 3A. In both cases, this corresponded to an increase in protein expression of the enzymes. Induction of P4502B10, 3A11, and 2C9 by xenobiotics often is a result of activation of the pregnane X receptor (PXR) and/or constitutive androstane receptor (CAR). Using a pregnane X receptor reporter system, our results demonstrated that isopimpinellin activated both PXR and its human ortholog SXR by recruiting coactivator SRC-1 in transfected cells. In CAR transfection assays, isopimpinellin counteracted the inhibitory effect of androstanol on full-length mCAR, a Gal4-mCAR ligand-binding domain fusion, and restored coactivator binding. Orally administered isopimpinellin induced hepatic mRNA expression of Cyp2b10, Cyp3a11, and GSTain CAR(+/+) wild-type mice. In contrast, the induction of Cyp2b10 mRNA by isopimpinellin was attenuated in the CAR(-/-) mice, suggesting that isopimpinellin induces Cyp2b10 via the CAR receptor. Overall, the current data indicate that naturally occurring coumarins have diverse activities in terms of inducing various xenobiotic metabolizing enzymes based on their chemical structure.

Time–course and dose–response relationships of imperatorin in the mouse maximal electroshock seizure threshold model

This study was designed to evaluate the anticonvulsant effects of imperatorin (a furanocoumarin isolated from fruits of Angelica archangelica) in the mouse maximal electroshock seizure threshold model. The threshold for electroconvulsions in mice was determined at several times: 15, 30, 60 and 120 min after i.p. administration of imperatorin at increasing doses of 10, 20, 30, 40, 50 and 100 mg/kg. The evaluation of time-course relationship for imperatorin in the maximal electroshock seizure threshold test revealed that the agent produced its maximum antielectroshock action at 30 min after its i.p. administration. In this case, imperatorin at doses of 50 and 100 mg/kg significantly raised the threshold for electroconvulsions in mice by 38 and 68% (P<0.05 and P<0.001), respectively. The antiseizure effects produced by imperatorin at 15, 60 and 120 min after its systemic (i.p.) administration were less expressed than those observed for imperatorin injected 30 min before the maximal electroshock seizure threshold test. Based on this study, one can conclude that imperatorin produces the anticonvulsant effect in the maximal electroshock seizure threshold test in a dose-dependent manner.

Pro-apoptotic effects of 1'-acetoxychavicol acetate in human breast carcinoma cells

The tropical ginger compound, 1'-acetoxychavicol acetate (ACA) possesses cancer chemopreventive properties in several models but its effects on breast cancer have not been fully evaluated. In this study, the effects of ACA on human breast carcinoma-derived MCF-7 and MDA-MB-231 cell viability were assessed using trypan blue exclusion analysis. ACA significantly decreased cell viability in a time- and dose-dependent manner, with effective concentrations 10-50 microM. Apoptosis was confirmed by morphological examination of cells through light microscopy, 4,6-diamidino-2-phenylindole dihydrochloride staining, and annexin V/Alexa Fluor 488 staining visualized using flow cytometry. ACA also increased protein expression of the activated form of caspase-3 in MDA-MB-231 cells. Addition of antioxidants N-acetylcysteine, ascorbic acid, or trolox prevented the loss of viability caused by ACA using trypan blue uptake as a marker. These results suggest ACA may have potential anticancer effects against breast carcinoma cells by inducing apoptosis.

Xenobiotic-metabolizing enzymes involved in activation and detoxification of carcinogenic polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental carcinogens and metabolized by a variety of xenobiotic-metabolizing enzymes such as cytochrome P450 (P450 or CYP), epoxide hydrolase, glutathione transferase, UDP-glucuronosyltransferase, sulfotransferase, NAD(P)H quinone oxidoreductase 1, and aldo-keto reductase. These enzymes mainly participate in the conversion of PAHs to more polar and water-soluble metabolites, and the resultant metabolites are readily excreted from the body. However, during the course of metabolism, a variety of unstable and reactive intermediates of PAHs are formed, and these metabolites attack DNA, causing cell toxicity and transformation. P450s and epoxide hydrolase convert PAHs to proximate carcinogenic metabolites, PAH-diols, and these products are further metabolized by P450s to ultimate carcinogenic metabolites, PAH diol-epoxides, or by aldo-keto reductase to reactive PAH o-quinones. PAHs are also activated by P450 and peroxidases to reactive radical cations that bind covalently to DNA. The oxygenated and reactive metabolites of PAHs are usually converted to more polar and detoxified products by phase II enzymes. Inter-individual differences exist in levels of expression and catalytic activities of a variety of enzymes that activate and/or detoxify PAHs in various organs of humans and these phenomena are thought to be critical in understanding the basis of individual differences in response to PAHs. Factors affecting such variations include induction and inhibition of enzymes by diverse chemicals and, more importantly, genetic polymorphisms of enzymes in humans.

Naturally occurring coumarins inhibit 7,12-dimethylbenz[a]anthracene DNA adduct formation in mouse mammary gland

Naturally occurring coumarins (NOCs) are anti-carcinogenic in the mouse skin model. To characterize the chemopreventive potential of NOCs against breast cancer, we first examined their effects on 7,12-dimethylbenz[a]anthracene (DMBA)-DNA adduct formation in mouse mammary gland. We hypothesized that those NOCs that both inhibited cytochrome P450 1A1/1B1 and induced hepatic glutathione S-transferases (GSTs) would be the most effective in blocking DMBA-DNA adduct formation in mouse mammary gland. To address this hypothesis, simple coumarins (e.g. coumarin and limettin, which induced mouse hepatic GSTs but had little effect on P4501A1/1B1) and linear furanocoumarins (e.g. imperatorin and isopimpinellin, which induced hepatic GSTs and were potent inhibitors of P4501A1/1B1) were compared. Mice were pretreated with NOCs (150 mg/kg body wt, by gavage) prior to either a single dose of DMBA (50 microg) or multiple doses of DMBA (20 microg daily for 3 and 6 weeks). Mammary DMBA-DNA adduct formation was quantitated by the nuclease P1-enhanced 32P-postlabeling assay. With the single dose of DMBA, coumarin, limettin, imperatorin and isopimpinellin inhibited DMBA-DNA adduct formation by 50, 41, 79 and 88%, respectively. Coumarin, limettin and imperatorin blocked DMBA-DNA adduct formation by 36, 60, and 66% at 3 weeks, and by 0, 49 and 55% at 6 weeks of DMBA dosing, respectively. In a 6 week dose-response study of select NOCs and 7,8-benzoflavone (a potent P4501 inhibitor that had little effect on GSTs), DMBA-DNA adduct formation was inhibited by 0, 43 and 24% in the limettin groups; by 26, 26 and 69% in the isopimpinellin groups; and by 80, 96 and 97% in the 7,8- benzoflavone groups at 35, 70 and 150 mg/kg, respectively. Taken together, these results suggest that linear furanocoumarins had a greater inhibitory effect on DMBA-DNA adduct formation in mouse mammary glands compared with simple coumarins, and that the predominant effect may be P4501 inhibition.

Transcriptional signatures of environmentally relevant exposures in normal human mammary epithelial cells: benzo[a]pyrene

Changes in gene expression in a panel of primary normal human mammary epithelial cell strains, developed from healthy breast tissue obtained at reduction mammoplasty from different donors, in response to benzo[a]pyrene exposure have been investigated. It was expected that both gene expression changes common to cell strains derived from different donors as well as inter-individual variation would be observed. Therefore, the strategy that has been adopted is to identify potentially important changes, or useful changes from a biomonitoring perspective, using gene-array technology and a small number of donors; then investigate selected transcription responses using a large number of tissue donors and a cheaper method of transcript detection (real-time polymerase chain reaction). Here we report results from four primary normal human mammary epithelial cell strains that were treated with benzo[a]pyrene in vitro for either 6 or 24 h. Transcription was monitored using high-density oligonucleotide arrays (Affymetrix HuGeneFL). Total RNA was used for the preparation of labeled targets that were hybridized to microarrays containing probes representing more than 6800 human genes and expressed sequence tags. Gene expression data were analyzed using the GeneChip software (MAS 5.0). Altered gene expression patterns were observed in response to benzo[a]pyrene in human mammary epithelial cell strains from different donors. Specifically, the dioxin inducible cytochrome P450 CYP1B1 was consistently induced in response to 6 and 24 h exposure to benzo[a]pyrene in cell strains from all four donors. Two other genes that were relatively consistently induced were IL1beta and MMP1. Less consistent changes in other metabolism genes (CYP1A1, CYP11B2, and NQO1) and certain cell cycle control genes GOS2 and AF1Q were also induced, while EGR1 was suppressed. Although no change in p53 transcription was observed, an accumulation of p53 protein was detected using antibodies. A similar accumulation of Waf1 (p21) was also observed using immunohistochemistry, this was expected since p53 is p21's transcription factor. Significant inter-individual variations in both the levels and patterns of gene expression were observed, in response to benzo[a]pyrene exposure. These studies provide a complementary approach to molecular epidemiology for the investigation of differential susceptibility to chemical carcinogens, and specifically polycyclic aromatic hydrocarbons.

Hypoxia inducible factor pathways as targets for functional foods

The etiology of most chronic angiogenic diseases such as rheumatoid arthritis, atherosclerosis, diabetes complications, and cancer includes the presence of pockets of hypoxic cells growing behind aerobic cells and away from blood vessels. Hypoxic cells are the result of uncontrolled growth and insufficient vascularization and have undergone a shift from aerobic to anaerobic metabolism. Cells respond to hypoxia by stimulating the expression of hypoxia inducible factor (HIF), which is critical for survival under hypoxic conditions and in embryogenesis. HIF is a heterodimer consisting of the O2-regulated subunit, HIF-1alpha, and the constitutively expressed aryl hydrocarbon receptor nuclear translocator, HIF-1beta. Under hypoxic conditions, HIF-1alpha is stable, accumulates, and migrates to the nucleus where it binds to HIF-1beta to form the complex (HIF-1alpha + HIF-1beta). Transcription is initiated by the binding of the complex (HIF-1alpha + HIF-1beta) to hypoxia responsive elements (HREs). The complex [(HIF-1alpha + HIF-1beta) + HREs] stimulates the expression of genes involved in angiogenesis, anaerobic metabolism, vascular permeability, and inflammation. Experimental and clinical evidence show that these hypoxic cells are the most aggressive and difficult angiogenic disease cells to treat and are a major reason for antiangiogenic and conventional treatment failure. Hypoxia occurs in early stages of disease development (before metastasis), activates angiogenesis, and stimulates vascular remodeling. HIF-1alpha has also been identified under aerobic conditions in certain types of cancer. This review summarizes the role of hypoxia in some chronic degenerative angiogenic diseases and discusses potential functional foods to target the HIF-1alpha pathways under hypoxic and normoxic conditions. It is reported that dietary quinones, semiquinones, phenolics, vitamins, amino acids, isoprenoids, and vasoactive compounds can down-regulate the HIF-1 pathways and therefore the expression of several proangiogenic factors. Considering the lack of efficiency or the side effects of synthetic antiangiogenic drugs at clinical trials, down-regulation of hypoxia-induced angiogenesis by use of naturally occurring functional foods may provide an effective means of prevention.