Baicalein inhibits DMBA-DNA adduct formation by modulating CYP1A1 and CYP1B1 activities

Qi Gong Wan ameliorates adipocyte hypertrophy and inflammation in adipose tissue in a PCOS mouse model through the Nrf2/HO-1/Cyp1b1 pathway: Integrating network pharmacology and experimental validation in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Initially recorded in Yifang Jijie (an ancient Chinese text), Qi Gong Wan (QGW) is used to treat obese women with infertility. QGW can help promote follicular development and maturation, regulate the balance of serum hormones between testosterone and estradiol, enhance endometrial receptivity, improve waist circumference, and ameliorate insulin resistance. It contains eight herbs: Pinellia ternata (Thunb.) Makino (Banxia), Citrus maxima (Burm.) (Juhong), Poria cocos (Schw.) Wolf. (Fuling), Atractylodes macrocephala Koidz (Baizhu), Cyperus rotundus L. (Xiangfu), Conioselinum anthriscoides 'Chuanxiong' (Chuanxiong), Massa Medicata Fermentata (Shenqu), and Glycyrrhiza uralensis Fisch. ex DC. (Gancao). However, the underlying mechanism of how QGW affects women with PCOS remains unclear.

AIM OF THE STUDY

QGW has been widely used to treat PCOS patients with obesity clinically. This study was designed to identify its chemical and pharmacological properties.

MATERIALS AND METHODS

Network pharmacology was used to predict the active compounds, potential targets, and pathways of QGW. Female C57BL/6J mice were injected with letrozole and fed a high-fat diet to establish a PCOS-insulin resistance (PCOS-IR) model. Body weight, estrous cycles, ovarian pathology, and serum insulin resistance were measured. qRT-PCR was used to examine the inflammation-related and steroid hormone biosynthesis-related mRNA expression in adipose tissue. Western blotting was used to determine the protein levels of Nrf2, HO-1, and Cyp1b1 in adipose tissue. Molecular docking was used to reveal the key chemical compounds of QGW.

RESULTS

Network pharmacology revealed a total of 91 active ingredients in QGW that were associated with 167 targets. QGW could potentially treat PCOS-IR via nitrogen metabolism, steroid hormone biosynthesis, and ovarian steroidogenesis pathways. In the PCOS-IR mouse model, we found that QGW decreased the mean diameter of adipocytes and the total adipocyte area. Furthermore, QGW was found to significantly lower the expression of inflammation-related genes including Tnfɑ and C4a/b and the steroid hormone biosynthesis-related gene Cyp1b1. QGW showed a tendency to improve cystic follicles, fasting insulin, and HOMA-IR index in the PCOS-IR mouse model. Combining these findings with the results of KEGG analysis, we conclude that QGW promotes the Nrf2/HO-1/Cyp1b1 pathway to protect adipose tissue under conditions of PCOS. Molecular docking revealed that rutin, nicotiflorin, and baicalein may be the key chemical compounds of QGW through which it improves adipocyte hypertrophy and inflammation.

CONCLUSIONS

QGW improved adipocyte hypertrophy and inflammation in the PCOS-IR mouse model by activating the Nrf2/HO-1/Cyp1b1 pathway to protect adipose tissue. Our work thus provides a new research avenue for the study of traditional Chinese medicine in the treatment of PCOS.

Potential of cytochrome P450, a family of xenobiotic metabolizing enzymes, in cancer therapy

SIGNIFICANCE

Targeted cancer therapy with minimal off-target consequences has shown promise for some cancer types. Although cytochrome P450 (CYP) consists of 18 families, CYP1-4 families play key role in metabolizing xenobiotics and cancer drugs. This eventually affects the process of carcinogenesis, treatment outcome, and cancer drug resistance. Differential overexpression of CYPs in transformed cells, together with phenotypic alterations in tumors, presents a potential for therapeutic intervention.

RECENT ADVANCES

Recent advances in molecular tools and information technology have helped utilize CYPs as cancer targets. The precise expression in various tumors, X-ray crystal structures, improved understanding of the structure-activity relationship, and new approaches in the development of prodrugs have supported the ongoing efforts to develop CYPs-based drugs with a better therapeutic index.

CRITICAL ISSUES

Narrow therapeutic index, off-target effects, drug resistance, and tumor heterogeneity limit the benefits of CYP-based conventional cancer therapies. In this review, we address the CYP1-4 families as druggable targets in cancer. An emphasis is given to the CYP expression, function, and the possible mechanisms that drive expression and activity in normal and transformed tissues. The strategies that inhibit or activate CYPs for therapeutic benefits are also discussed.

FUTURE DIRECTIONS

Efforts are needed to develop more selective tools that will help comprehend molecular and metabolic alterations in tumor tissues with biological end-points in relation to CYPs. This will eventually translate to developing more specific CYP inhibitors/inducers.

Baicalein Inhibits Benzo[a]pyrene-Induced Toxic Response by Downregulating Src Phosphorylation and by Upregulating NRF2-HMOX1 System

Benzo[a]pyrene (BaP), a major environmental pollutant, activates aryl hydrocarbon receptor (AHR), induces its cytoplasmic-to-nuclear translocation and upregulates the production of cytochrome P450 1A1 (CYP1A1), a xenobiotic metabolizing enzyme which metabolize BaP. The BaP-AHR-CYP1A1 axis generates reactive oxygen species (ROS) and induces proinflammatory cytokines. Although the anti-inflammatory phytochemical baicalein (BAI) is known to inhibit the BaP-AHR-mediated CYP1A1 expression, its subcellular signaling remains elusive. In this study, normal human epidermal keratinocytes and HaCaT keratinocytes were treated with BAI, BaP, or BAI + BaP, and assessed for the CYP1A1 expression, antioxidative pathways, ROS generation, and proinflammatory cytokine expressions. BAI and BAI-containing herbal medicine Wogon and Oren-gedoku-to could inhibit the BaP-induced CYP1A1 expression. In addition, BAI activated antioxidative system nuclear factor-erythroid 2-related factor-2 (NRF2) and heme oxygenase 1 (HMOX1), leading the reduction of BaP-induced ROS production. The BaP-induced IL1A and IL1B was also downregulated by BAI. BAI inhibited the phosphorylation of Src, a component of AHR cytoplasmic complex, which eventually interfered with the cytoplasmic-to-nuclear translocation of AHR. These results indicate that BAI and BAI-containing herbal drugs may be useful for inhibiting the toxic effects of BaP via dual AHR-CYP1A1-inhibiting and NRF2-HMOX1-activating activities.

Oroxylin A, a methylated metabolite of baicalein, exhibits a stronger inhibitory effect than baicalein on the CYP1B1-mediated carcinogenic estradiol metabolite formation

Human cytochrome P450 1B1 (CYP1B1)-mediated formation of 4-hydroxyestradiol (4-OHE2) from 17β-estradiol plays an important role in the progression of human breast cancer, while the biotransformation of 17β-estradiol to 2-hydroxyestradiol mediated by cytochrome P450 1A1 (CYP1A1) is considered as a less harmful pathway. In this study, inhibitory effects of flavonoids baicalein and oroxylin A, a metabolite of baicalein in human body, on CYP1A1 and 1B1 activities were investigated in vitro. The inhibition intensities of baicalein and oroxylin A towards CYP1B1 were greater than towards CYP1A1 with a mixed mechanism. In addition, oroxylin A showed a stronger inhibitory effect than baicalein towards the CYP1B1-mediated 17β-estradiol 4-hydroxylation, with the IC₅₀ values of 0.0146 and 2.27 μM, respectively. Docking studies elucidated that oroxylin A had a stronger binding affinity than baicalein for CYP1B1. In MCF-7 cells, compared with baicalein-treated groups, oroxylin A with lower doses decreased and increased the formation of 4-OHE2 and 2-hydroxyestradiol, respectively, with a preferential induction of mRNA of CYP1A1 over CYP1B1. In conclusion, this study demonstrated that oroxylin A showed a stronger inhibitory effect than baicalein on CYP1B1-mediated 4-OHE2 formation in MCF-7 cells, providing crucial implications for their possibly preventive/therapeutic potential against breast cancer via inhibition of CYP1B1, particularly of oroxylin A.

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

Mechanisms and therapeutic prospects of polyphenols as modulators of the aryl hydrocarbon receptor

Polyphenolic AhR modulators displayed concentration-, XRE-, gene-, species- and cell-specific agonistic/antagonistic activity.

The role of mid-chain hydroxyeicosatetraenoic acids in the pathogenesis of hypertension and cardiac hypertrophy

The incidence, prevalence, and hospitalization rates associated with cardiovascular diseases (CVDs) are projected to increase substantially in the world. Understanding of the biological and pathophysiological mechanisms of survival can help the researchers to develop new management modalities. Numerous experimental studies have demonstrated that mid-chain HETEs are strongly involved in the pathogenesis of the CVDs. Mid-chain HETEs are biologically active eicosanoids that result from the metabolism of arachidonic acid (AA) by both lipoxygenase and CYP1B1 (lipoxygenase-like reaction). Therefore, identifying the localizations and expressions of the lipoxygenase and CYP1B1 and their associated AA metabolites in the cardiovascular system is of major importance in understanding their pathological roles. Generally, the expression of these enzymes is shown to be induced during several CVDs, including hypertension and cardiac hypertrophy. The induction of these enzymes is associated with the generation of mid-chain HETEs and subsequently causation of cardiovascular events. Of interest, inhibiting the formation of mid-chain HETEs has been reported to confer a protection against different cardiac hypertrophy and hypertension models such as angiotensin II, Goldblatt, spontaneously hypertensive rat and deoxycorticosterone acetate (DOCA)-salt-induced models. Although the exact mechanisms of mid-chain HETEs-mediated cardiovascular dysfunction are not fully understood, the present review proposes several mechanisms which include activating G-protein-coupled receptor, protein kinase C, mitogen-activated protein kinases, and nuclear factor kappa B. This review provides a clear understanding of the role of mid-chain HETEs in the pathogenesis of cardiovascular diseases and their importance as novel targets in the treatment for hypertension and cardiac hypertrophy.

Characterization of the antioxidant activity of aglycone and glycosylated derivatives of hesperetin: an in vitro and in vivo study

The flavonoids are mainly present in Citrus fruits as their glycosyl derivatives. This study was conducted comparing in vitro xanthine oxidase inhibitory activity of the aglycone hesperetin and its glycosylated forms (hesperidin and G-hesperidin) and their effects on the plasma lipid profile and the oxidative-antioxidative system (TBARS and antioxidant enzymes) in rats. The concentrations of the major conjugated metabolites in rat plasma after oral administration of these compounds were also determined. Wistar male rats were randomly assigned to three groups (n=6) supplemented for 30 days with 1 mmol/kg body mass of hesperetin, hesperidin or G-hesperidin. Hesperetin was a stronger xanthine oxidase inhibitor (IC50=53 μM and Ki=17.3 μM) than the glycosylate derivatives. Supplementation with the three compounds led to a lower (more favorable) atherogenic index, and an antioxidant preventive effect from the increase of hepatic superoxide dismutase was observed associated to HT supplementation, possibly because of the higher level of hesperetin-glucuronide in rat plasma.

Cytochrome P450 family 1 inhibitors and structure-activity relationships

With the widespread use of O-alkoxyresorufin dealkylation assays since the 1990s, thousands of inhibitors of cytochrome P450 family 1 enzymes (P450s 1A1, 1A2, and 1B1) have been identified and studied. Generally, planar polycyclic molecules such as polycyclic aromatic hydrocarbons, stilbenoids, and flavonoids are considered to potentially be effective inhibitors of these enzymes, however, the details of the structure-activity relationships and selectivity of these inhibitors are still ambiguous. In this review, we thoroughly discuss the selectivity of many representative P450 family 1 inhibitors reported in the past 20 years through a meta-analysis.

Analyzing Cytotoxic and Apoptogenic Properties of Scutellaria litwinowii Root Extract on Cancer Cell Lines

The Scutellaria species (Lamiaceae) is used as a source of flavonoids to treat a variety of diseases in traditional medicine. In spite of many reports about the cytotoxic and antitumor effects of some species of this genus, anticancer researches on one of the Iranian species S. litwinowii have not yet been conducted. The cytotoxic properties of total methanol extract of S. litwinowii and its fractions were investigated on different cancer cell lines including AGS, HeLa, MCF-7, PC12 and NIH 3T3. Meanwhile, the role of apoptosis in this toxicity was explored. The cells were cultured in DMEM medium and incubated with different concentrations of herb plant extracts. Cell viability was quantitated by MTT assay. Apoptotic cells were determined using propidium iodide staining of DNA fragmentation by flow cytometry (sub-G1 peak). Scutellaria litwinowii inhibited the growth of malignant cells in a dose-dependent manner. Among solvent fractions of S. litwinowii, the methylene chloride fraction was found to be more toxic compared to other fractions. The IC₅₀ values of this fraction against AGS, HeLa, MCF-7 and PC12 cell lines after 24 h were determined, 121.2 ± 3.1, 40.9 ± 2.5, 115.9 ± 3.5 and 64.5 ± 3.4 μg/ml, respectively. Scutellaria litwinowii induced a sub-G1 peak in the flow cytometry histogram of treated cells compared to control cells indicating that apoptotic cell death is involved in S. litwinowii toxicity. Scutellaria litwinowii exerts cytotoxic and proapototic effects in a variety of malignant cell lines and could be considered as a potential chemotherapeutic agent in cancer treatment.

The genus Scutellaria an ethnopharmacological and phytochemical review

Scutellaria (HUANG QIN) (Lamiaceae), which includes about 350 species commonly known as skullcaps, is widespread in Europe, the United States and East Asia. Some species are taken to clear away the heat-evil and expel superficial evils in traditional Chinese medicine (TCM). The present paper reviews the ethnopharmacology, the biological activities and the correlated chemical compounds of Scutellaria species. More than 295 compounds have been isolated, among them flavonoids and diterpenes. Studies show that Scutellaria and its active principles possess wide pharmacological actions, such as antitumor, anti-angiogenesis, hepatoprotective, antioxidant, anticonvulsant, antibacterial and antiviral activities. Currently, effective monomeric compounds or active parts have been screened for pharmacological activity from Scutellaria in vivo and in vitro. Increasing data supports application and exploitation for new drug development.

Flavonoids as anti-inflammatory agents: implications in cancer and cardiovascular disease

Chronic inflammation is being shown to be increasingly involved in the onset and development of several pathological disturbances such as arteriosclerosis, obesity, diabetes, neurodegenerative diseases and even cancer. Treatment for chronic inflammatory disorders has not been solved, and there is an urgent need to find new and safe anti-inflammatory compounds. Flavonoids belong to a group of natural substances occurring normally in the diet that exhibit a variety of beneficial effects on health. The anti-inflammatory properties of flavonoids have been studied recently, in order to establish and characterize their potential utility as therapeutic agents in the treatment of inflammatory diseases. Several mechanisms of action have been proposed to explain in vivo flavonoid anti-inflammatory actions, such as antioxidant activity, inhibition of eicosanoid generating enzymes or the modulation of the production of proinflammatory molecules. Recent studies have also shown that some flavonoids are modulators of proinflammatory gene expression, thus leading to the attenuation of the inflammatory response. However, much work remains to be done in order to achieve definitive conclusions about their potential usefulness. This review summarizes the known mechanisms involved in the anti-inflammatory activity of flavonoids and the implications of these effects on the protection against cancer and cardiovascular disease.

Effect of Ginkgo biloba extract on procarcinogen-bioactivating human CYP1 enzymes: Identification of isorhamnetin, kaempferol, and quercetin as potent inhibitors of CYP1B1

In the present study, we investigated the effect of Ginkgo biloba extracts and some of its individual constituents on the catalytic activity of human cytochrome P450 enzymes CYP1B1, CYP1A1, and CYP1A2. G. biloba extract of known abundance of terpene trilactones and flavonol glycosides inhibited 7-ethoxyresorufin O-dealkylation catalyzed by human recombinant CYP1B1, CYP1A1, and CYP1A2, and human liver microsomes, with apparent Ki values of 2 +/- 0.3, 5 +/- 0.5, 16 +/- 1.4, and 39 +/- 1.2 microg/ml (mean +/- SE), respectively. In each case, the mode of inhibition was of the mixed type. Bilobalide, ginkgolides A, B, C, and J, quercetin 3-O-rutinoside, kaempferol 3-O-rutinoside, and isorhamentin 3-O-rutinoside were not responsible for the inhibition of CYP1 enzymes by G. biloba extract, as determined by experiments with these individual chemicals at the levels present in the extract. In contrast, the aglycones of quercetin, kaempferol, and isorhamentin inhibited CYP1B1, CYP1A1, and CYP1A2. Among the three flavonol aglycones, isorhamentin was the most potent in inhibiting CYP1B1 (apparent Ki = 3 +/- 0.1 nM), whereas quercetin was the least potent in inhibiting CYP1A2 (apparent Ki = 418 +/- 50 nM). The mode of inhibition was competitive, noncompetitive, or mixed, depending on the enzyme and the flavonol. G. biloba extract also reduced benzo[a]pyrene hydroxylation, and the effect was greater with CYP1B1 than with CYP1A1 as the catalyst. Overall, our novel findings indicate that G. biloba extract and the flavonol aglycones isorhamnetin, kaempferol, and quercetin preferentially inhibit the in vitro catalytic activity of human CYP1B1.

Dietary flavonoids: effects on xenobiotic and carcinogen metabolism

Flavonoids are present in fruits, vegetables and beverages derived from plants (tea, red wine), and in many dietary supplements or herbal remedies including Ginkgo Biloba, Soy Isoflavones, and Milk Thistle. Flavonoids have been described as health-promoting, disease-preventing dietary supplements, and have activity as cancer preventive agents. Additionally, they are extremely safe and associated with low toxicity, making them excellent candidates for chemopreventive agents. The cancer protective effects of flavonoids have been attributed to a wide variety of mechanisms, including modulating enzyme activities resulting in the decreased carcinogenicity of xenobiotics. This review focuses on the flavonoid effects on cytochrome P450 (CYP) enzymes involved in the activation of procarcinogens and phase II enzymes, largely responsible for the detoxification of carcinogens. A number of naturally occurring flavonoids have been shown to modulate the CYP450 system, including the induction of specific CYP isozymes, and the activation or inhibition of these enzymes. Some flavonoids alter CYPs through binding to the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, acting as either AhR agonists or antagonists. Inhibition of CYP enzymes, including CYP 1A1, 1A2, 2E1 and 3A4 by competitive or mechanism-based mechanisms also occurs. Flavones (chrysin, baicalein, and galangin), flavanones (naringenin) and isoflavones (genistein, biochanin A) inhibit the activity of aromatase (CYP19), thus decreasing estrogen biosynthesis and producing antiestrogenic effects, important in breast and prostate cancers. Activation of phase II detoxifying enzymes, such as UDP-glucuronyl transferase, glutathione S-transferase, and quinone reductase by flavonoids results in the detoxification of carcinogens and represents one mechanism of their anticarcinogenic effects. A number of flavonoids including fisetin, galangin, quercetin, kaempferol, and genistein represent potent non-competitive inhibitors of sulfotransferase 1A1 (or P-PST); this may represent an important mechanism for the chemoprevention of sulfation-induced carcinogenesis. Importantly, the effects of flavonoids on enzymes are generally dependent on the concentrations of flavonoids present, and the different flavonoids ingested. Due to the low oral bioavailability of many flavonoids, the concentrations achieved in vivo following dietary administration tend to be low, and may not reflect the concentrations tested under in vitro conditions; however, this may not be true following the ingestion of herbal preparations when much higher plasma concentrations may be obtained. Effects will also vary with the tissue distribution of enzymes, and with the species used in testing since differences between species in enzyme activities also can be substantial. Additionally, in humans, marked interindividual variability in drug-metabolizing enzymes occurs as a result of genetic and environmental factors. This variability in xenobiotic metabolizing enzymes and the effect of flavonoid ingestion on enzyme expression and activity can contribute to the varying susceptibility different individuals have to diseases such as cancer. As well, flavonoids may also interact with chemotherapeutic drugs used in cancer treatment through the induction or inhibition of their metabolism.

Screening of chemopreventive tea polyphenols against PAH genotoxicity in breast cancer cells by a XRE-luciferase reporter construct

Polycyclic aromatic hydrocarbons (PAHs) are established cancer initiators that can be found in our food and environment. Some dietary plant polyphenols are strong inhibitors to PAH-induced mutagenesis, whereas others may not be as effective. To identify the chemopreventive compounds from a huge volume of dietary components, the development of an efficient screening method is required. In this study, a xenobiotic response element (XRE)-luciferase reporter plasmid was constructed to screen for some potential chemopreventive agents in tea against PAH-induced DNA damage. Tea is one of the most consumed beverages worldwide, and its beneficial effects on health have been documented. Previous studies have claimed that tea polyphenols could be protective against various cancers, and the rich database can be a source for comparison. Among the green and black tea polyphenols, the XRE-luciferase reporter assays suggested that only epigallocatechin gallate (EGCG) was effective in reducing XRE-driven luciferase assay in MCF-7 cells at the concentrations tested. Further study indicated EGCG could reduce CYP1A1 and CYP1B1 mRNA abundances and decrease the DMBA-DNA lesions. The results of DNA covalent binding of all tea polyphenols tested were consistent with the XRE-reporter assays. This study illustrated that the XRE-reporter assay was a viable screening test for dietary chemopreventive agents against PAH-initiated breast mutagenesis. It has the advantages of shorter sample processing time and producing no radioactive waste over directly measuring the CYP1A1/1B1 expressions, DNA lesion, or gel mobility shift assay.

The red clover (Trifolium pratense) isoflavone biochanin A modulates the biotransformation pathways of 7,12-dimethylbenz[a]anthracene

Several flavonoids have shown their anti-carcinogenic effects in various models. The soyabean isoflavone genistein was demonstrated earlier in our laboratory to be an effective inhibitor of dimethylbenz[a]anthracene (DMBA)-induced DNA damage in MCF-7 cells by curbing cytochrome P450 (CYP) 1 enzymes. The red clover (Trifolium pratense) isoflavone biochanin A is a methylated derivative of genistein, and its anti-mutagenic effect in bacterial cells has been shown previously. Because of its protection against chemical carcinogenesis in an animal model, biochanin A was selected for testing in our established MCF-7 cell system. From the results obtained in the semi-quantitative reverse transcription-polymerase chain reaction and xenobiotic response element (XRE)-luciferase reporter assays, biochanin A could reduce xenobiotic-induced CYP1A1 and -1B1 mRNA abundances through the interference of XRE-dependent transactivation. Enzyme kinetic studies also indicated that biochanin A inhibited both CYP1A1 and -1B1 enzymes with inhibition constant (Ki) values 4.00 and 0.59 microm respectively. Since the biotransformation of DMBA was dependent on CYP1 enzyme activities, biochanin A was able to decrease the DMBA-DNA lesions. The present study illustrated that the red clover isoflavone could protect against polycylic aromatic hydrocarbon-induced DNA damage.