Analysis of gene expression changes of drug metabolizing enzymes in the livers of F344 rats following oral treatment with kava extract

The sub-acute toxicity of kavalactone in rats: a study of the effect of oral doses and the mechanism of toxicity in combination with ethanol

Kava is a herbal supplement and beverage made from the Piper methysticum plant, which is known for its recreational use as a mood enhancer, relaxation, as well as pain relief for centuries. Kava is widely used among alcoholics, but it is dangerous and potentially fatal. The objectives of this study were to examine the sub-acute toxicity effects of different doses of 70% kavalactone (KL) in rats by oral application, as well as to elucidate the mechanisms of toxicity alone and in combination with ethanol (EtOH). The most common side effects observed were abnormal breathing, ataxia, lethargy, loss of appetite, indigestion, and loss of coordination, especially in the 800 mg/kg bw, po bodyweight dosage of kava treatment group alone, and in combination with EtOH. In the sub-acute study, there were dose-related decreases in body weight, feed intake, and water consumption rates. Gross and histopathological findings revealed that the liver was abnormal in color, size, consistency, and the weight significantly increased at a dose of 800 mg/kg bw, po, with KL alone and a greater increase in combination with EtOH. Hepatocellular hypertrophy (HP) and necrosis with Kupffer cells hyperplasia were observed in the periacinar zone of all rats dosed with KL (800 mg/kg bw, po) alone, and extensive changes were observed in combination with EtOH. The periportal (Z1) and mid-zonal (Z2) areas of hepatocytes were less affected as compared to the periacinar zone. These results demonstrate that EtOH exacerbated the sedative and hypnotic activity of KL, and markedly increased toxicity. The histopathological results supported the clinical and biochemical findings and the severity of hepatic damage in a dose-dependent manner.

An Updated Review on the Psychoactive, Toxic and Anticancer Properties of Kava

Kava (Piper methysticum) has been widely consumed for many years in the South Pacific Islands and displays psychoactive properties, especially soothing and calming effects. This plant has been used in Western countries as a natural anxiolytic in recent decades. Kava has also been used to treat symptoms associated with depression, menopause, insomnia, and convulsions, among others. Along with its putative beneficial health effects, kava has been associated with liver injury and other toxic effects, including skin toxicity in heavy consumers, possibly related to its metabolic profile or interference in the metabolism of other xenobiotics. Kava extracts and kavalactones generally displayed negative results in genetic toxicology assays although there is sufficient evidence for carcinogenicity in experimental animals, most likely through a non-genotoxic mode of action. Nevertheless, the chemotherapeutic/chemopreventive potential of kava against cancer has also been suggested. Both in vitro and in vivo studies have evaluated the effects of flavokavains, kavalactones and/or kava extracts in different cancer models, showing the induction of apoptosis, cell cycle arrest and other antiproliferative effects in several types of cancer, including breast, prostate, bladder, and lung. Overall, in this scoping review, several aspects of kava efficacy and safety are discussed and some pertinent issues related to kava consumption are identified.

Characterization of cytochrome P450s (CYP)-overexpressing HepG2 cells for assessing drug and chemical-induced liver toxicity

Hepatic metabolism catalyzed by the cytochrome P450 (CYP) superfamily affects liver toxicity associated with exposures to natural compounds and xenobiotic agents. Previously we generated a battery of HepG2-derived stable cell lines that individually express 14 CYPs (1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7). In this study, we comprehensively characterized each cell line for its CYP expression and enzyme activity. Specifically, we measured the mRNA expression, protein expression, and metabolite formation. Using CYP3A4, 2D6, and 2C9-overexpressing cells as representatives, we examined the stability of these cells in long-term cultures for up to 10 passages. The results showed that CYPs can be stably overexpressed for up to 10 cell culture passages without losing their activities. The robustness of responses to stimuli among the cells at different passages was also investigated in CYP3A4-overexpressing cells and the response to amiodarone and dronedarone showed no difference between the cells at the passage 2 and 10. Moreover, the mRNA expression level of most CYPs was higher in CYP-overexpressing HepG2 cells than that in HepaRG cells and primary human hepatocytes. This study confirmed the stability of CYP-overexpressing HepG2 cell lines and provided useful information for a broader use of these cells in pharmacologic and toxicologic research.

The role of hepatic cytochrome P450s in the cytotoxicity of sertraline

Sertraline, an antidepressant, is commonly used to manage mental health symptoms related to depression, anxiety disorders, and obsessive-compulsive disorder. The use of sertraline has been associated with rare but severe hepatotoxicity. Previous research demonstrated that mitochondrial dysfunction, apoptosis, and endoplasmic reticulum stress were involved in sertraline-associated cytotoxicity. In this study, we reported that after a 24-h treatment in HepG2 cells, sertraline caused cytotoxicity, suppressed topoisomerase I and IIα, and damaged DNA in a concentration-dependent manner. We also investigated the role of cytochrome P450 (CYP)-mediated metabolism in sertraline-induced toxicity using our previously established HepG2 cell lines individually expressing 14 CYPs (1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7). We demonstrated that CYP2D6, 2C19, 2B6, and 2C9 metabolize sertraline, and sertraline-induced cytotoxicity was significantly decreased in the cells expressing these CYPs. Western blot analysis demonstrated that the induction of ɣH2A.X (a hallmark of DNA damage) and topoisomerase inhibition were partially reversed in CYP2D6-, 2C19-, 2B6-, and 2C9-overexpressing HepG2 cells. These data indicate that DNA damage and topoisomerase inhibition are involved in sertraline-induced cytotoxicity and that CYPs-mediated metabolism plays a role in decreasing the toxicity of sertraline.

The role of hepatic cytochrome P450s in the cytotoxicity of dronedarone

Dronedarone is used to treat patients with cardiac arrhythmias and has been reported to be associated with liver injury. Our previous mechanistic work demonstrated that DNA damage-induced apoptosis contributes to the cytotoxicity of dronedarone. In this study, we examined further the underlying mechanisms and found that after a 24-h treatment of HepG2 cells, dronedarone caused cytotoxicity, G1-phase cell cycle arrest, suppression of topoisomerase II, and DNA damage in a concentration-dependent manner. We also investigated the role of cytochrome P450s (CYPs)-mediated metabolism in the dronedarone-induced toxicity using our previously established HepG2 cell lines expressing individually 14 human CYPs (1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C18, 2C19, 2D6, 2E1, 3A4, 3A5, and 3A7). We demonstrated that CYP3A4, 3A5, and 2D6 were the major enzymes that metabolize dronedarone, and that CYP3A7, 2E1, 2C19, 2C18, 1A1, and 2B6 also metabolize dronedarone, but to a lesser extent. Our data showed that the cytotoxicity of dronedarone was decreased in CYP3A4-, 3A5-, or 2D6-overexpressing cells compared to the control HepG2 cells, indicating that the parent dronedarone has higher potency than the metabolites to induce cytotoxicity in these cells. In contrast, cytotoxicity was increased in CYP1A1-overexpressing cells, demonstrating that CYP1A1 exerts an opposite effect in dronedarone's toxicity, comparing to CYP3A4, 3A5, or 2D6. We also studied the involvement of topoisomerase II in dronedarone-induced toxicity, and demonstrated that the overexpression of topoisomerase II caused an increase in cell viability and a decrease in γ-H2A.X induction, suggesting that suppression of topoisomerase II may be one of the mechanisms involved in dronedarone-induced liver toxicity.

DNA Microarray-Based Screening and Characterization of Traditional Chinese Medicine

The application of DNA microarray assay (DMA) has entered a new era owing to recent innovations in omics technologies. This review summarizes recent applications of DMA-based gene expression profiling by focusing on the screening and characterizationof traditional Chinese medicine. First, herbs, mushrooms, and dietary plants analyzed by DMA along with their effective components and their biological/physiological effects are summarized and discussed by examining their comprehensive list and a list of representative effective chemicals. Second, the mechanisms of action of traditional Chinese medicine are summarized by examining the genes and pathways responsible for the action, the cell functions involved in the action, and the activities found by DMA (silent estrogens). Third, applications of DMA for traditional Chinese medicine are discussed by examining reported examples and new protocols for its use in quality control. Further innovations in the signaling pathway based evaluation of beneficial effects and the assessment of potential risks of traditional Chinese medicine are expected, just as are observed in other closely related fields, such as the therapeutic, environmental, nutritional, and pharmacological fields.

The role of CYP 3A4 and 1A1 in amiodarone-induced hepatocellular toxicity

Amiodarone is a widely used potent antiarrhythmic for the treatment of cardiac disease; however, its use is often discontinued due to numerous adverse effects, including hepatotoxicity. To investigate the role of drug metabolism in this liver toxicity, amiodarone and its major metabolite desethylamiodarone were incubated with HepG2 cells overexpressing a series of cytochrome P450 (CYP) isoforms. Significantly higher cytotoxicity of amiodarone was observed in HepG2 cells overexpressing CYP3A4 or CYP1A1, compared with that observed in empty vector transduced control cells. Further, higher levels of the more potent hepatotoxic metabolite desethylamiodarone were detected in CYP3A4 or CYP1A1 expressed cells. The CYP3A4 inhibitor ketoconazole and the CYP1A1 inhibitor α-naphthoflavone drastically inhibited the metabolism of amiodarone to desethylamiodarone. Along with the inhibition of CYP1A1 or CYP3A4, the cytotoxicity of amiodarone was significantly reduced. These data indicate that the metabolism of amiodarone to desethylamiodarone by CYP1A1 or CYP3A4 plays an important role in the hepatocellular toxicity of amiodarone.

Hepatotoxicity Induced by "the 3Ks": Kava, Kratom and Khat

The 3Ks (kava, kratom and khat) are herbals that can potentially induce liver injuries. On the one hand, growing controversial data have been reported about the hepatotoxicity of kratom, while, on the other hand, even though kava and khat hepatotoxicity has been investigated, the hepatotoxic effects are still not clear. Chronic recreational use of kratom has been associated with rare instances of acute liver injury. Several studies and case reports have suggested that khat is hepatotoxic, leading to deranged liver enzymes and also histopathological evidence of acute hepatocellular degeneration. Numerous reports of severe hepatotoxicity potentially induced by kava have also been highlighted, both in the USA and Europe. The aim of this review is to focus on the different patterns and the mechanisms of hepatotoxicity induced by “the 3Ks”, while trying to clarify the numerous aspects that still need to be addressed.

Flavokawains a and B in kava, not dihydromethysticin, potentiate acetaminophen-induced hepatotoxicity in C57BL/6 mice

Anxiolytic kava products have been associated with rare but severe hepatotoxicity in humans. This adverse potential has never been captured in animal models, and the responsible compound(s) remains to be determined. The lack of such knowledge greatly hinders the preparation of a safer kava product and limits its beneficial applications. In this study we evaluated the toxicity of kava as a single entity or in combination with acetaminophen (APAP) in C57BL/6 mice. Kava alone revealed no adverse effects for long-term usage even at a dose of 500 mg/kg bodyweight. On the contrary a three-day kava pretreatment potentiated APAP-induced hepatotoxicity, resulted in an increase in serum ALT and AST, and increased severity of liver lesions. Chalcone-based flavokawains A (FKA) and B (FKB) in kava recapitulated its hepatotoxic synergism with APAP while dihydromethysticin (DHM, a representative kavalactone and a potential lung cancer chemopreventive agent) had no such effect. These results, for the first time, demonstrate the hepatotoxic risk of kava and its chalcone-based FKA and FKB in vivo and suggest that herb–drug interaction may account for the rare hepatotoxicity associated with anxiolytic kava usage in humans.

Sertraline induces endoplasmic reticulum stress in hepatic cells

Sertraline is used for the treatment of depression, and is also used for the treatment of panic, obsessive-compulsive, and post-traumatic stress disorders. Previously, we have demonstrated that sertraline caused hepatic cytotoxicity, with mitochondrial dysfunction and apoptosis being underlying mechanisms. In this study, we used microarray and other biochemical and molecular analyses to identify endoplasmic reticulum (ER) stress as a novel molecular mechanism. HepG2 cells were exposed to sertraline and subjected to whole genome gene expression microarray analysis. Pathway analysis revealed that ER stress is among the significantly affected biological changes. We confirmed the increased expression of ER stress makers by real-time PCR and Western blots. The expression of typical ER stress markers such as PERK, IRE1α, and CHOP was significantly increased. To study better ER stress-mediated drug-induced liver toxicity; we established in vitro systems for monitoring ER stress quantitatively and efficiently, using Gaussia luciferase (Gluc) and secreted alkaline phosphatase (SEAP) as ER stress reporters. These in vitro systems were validated using well-known ER stress inducers. In these two reporter assays, sertraline inhibited the secretion of Gluc and SEAP. Moreover, we demonstrated that sertraline-induced apoptosis was coupled to ER stress and that the apoptotic effect was attenuated by 4-phenylbutyrate, a potent ER stress inhibitor. In addition, we showed that the MAP4K4-JNK signaling pathway contributed to the process of sertraline-induced ER stress. In summary, we demonstrated that ER stress is a mechanism of sertraline-induced liver toxicity.

Endoplasmic reticulum stress in drug- and environmental toxicant-induced liver toxicity

Liver injury resulting from exposure to drugs and environmental chemicals is a major health problem. Endoplasmic reticulum stress (ER stress) is considered to be an important factor in a wide range of diseases, such as cancer, neurological and cardiovascular disease, diabetes, and inflammatory diseases. The role of ER stress in drug-induced and environmental toxicant-induced liver toxicity has been underestimated in the past; emerging evidence indicates that ER stress makes a substantial contribution to the pathogenesis of drug-induced liver toxicity. In this review, we summarize current knowledge on drugs and environmental toxicants that trigger ER stress in liver and on the underlying molecular mechanisms. We also discuss experimental approaches for ER stress studies.

Sertraline, an antidepressant, induces apoptosis in hepatic cells through the mitogen-activated protein kinase pathway

Sertraline is generally used for the treatment of depression and is also approved for the treatment of panic, obsessive-compulsive, and posttraumatic stress disorders. Previously, using rat primary hepatocytes and isolated mitochondria, we demonstrated that sertraline caused hepatic cytotoxicity and mitochondrial impairment. In the current study, we investigated and characterized molecular mechanisms of sertraline toxicity in human hepatoma HepG2 cells. Sertraline decreased cell viability and induced apoptosis in a dose- and time-dependent manner. Sertraline activated the intrinsic checkpoint protein caspase-9 and caused the release of cytochrome c from mitochondria to cytosol; this process was Bcl-2 family dependent because antiapoptotic Bcl-2 family proteins were decreased. Pretreatment of the HepG2 cells with caspase-3, caspase-8, and caspase-9 inhibitors partially but significantly reduced the release of lactate dehydrogenase, indicating that sertraline-induced apoptosis is mediated by both intrinsic and extrinsic apoptotic pathways. Moreover, sertraline markedly increased the expression of tumor necrosis factor (TNF) and the phosphorylation of JNK, extracellular signal-regulated kinase (ERK1/2), and p38. In sertraline-treated cells, the induction of apoptosis and cell death was shown to be the result of activation of JNK, but not ERK1/2 or p38 in the mitogen-activated protein kinase (MAPK) pathway. Furthermore, silencing MAP4K4, the upstream kinase of JNK, attenuated both apoptosis and cell death caused by sertraline. Taken together, our findings suggest that sertraline induced apoptosis in HepG2 cells at least partially via activation of the TNF-MAP4K4-JNK cascade signaling pathway.

Mechanism study of goldenseal-associated DNA damage

Goldenseal has been used for the treatment of a wide variety of ailments including gastrointestinal disturbances, urinary tract disorders, and inflammation. The five major alkaloid constituents in goldenseal are berberine, palmatine, hydrastine, hydrastinine, and canadine. When goldenseal was evaluated by the National Toxicology Program (NTP) in the standard 2-year bioassay, goldenseal induced an increase in liver tumors in rats and mice; however, the mechanism of goldenseal-associated liver carcinogenicity remains unknown. In this study, the toxicity of the five goldenseal alkaloid constituents was characterized, and their toxic potencies were compared. As measured by the Comet assay and the expression of γ-H2A.X, berberine, followed by palmatine, appeared to be the most potent DNA damage inducer in human hepatoma HepG2 cells. Berberine and palmatine suppressed the activities of both topoisomerase (Topo) I and II. In berberine-treated cells, DNA damage was shown to be directly associated with the inhibitory effect of Topo II, but not Topo I by silencing gene of Topo I or Topo II. In addition, DNA damage was also observed when cells were treated with commercially available goldenseal extracts and the extent of DNA damage was positively correlated to the berberine content. Our findings suggest that the Topo II inhibitory effect may contribute to berberine- and goldenseal-induced genotoxicity and tumorigenicity.

Genome-wide analysis of hepatic gene silencing in hepatoma cell variants

Genome-wide gene expression profiling was carried out on rat hepatoma cells and compared to profiles of hepatoma "variant" cell lines derived via a stringent selection protocol that enriches for rare cells (<1 in 100,000 cells) that fail to drive liver function. Results show 132 genes that are strongly (>5-fold) repressed in each of the four variant cell lines tested. An additional 68 genes were repressed in 3 of 4 variant cell lines. Importantly, several of the repressed genes are members of transcriptional activation pathways, suggesting that they may contribute to maintaining the hepatic phenotype. Ectopic expression of the HNF1A gene in a variant cell line resulted in activation of 56 genes, 37 of which were included in the repressed data set. These data suggest that a high level of reprogramming occurs when hepatoma cells convert to a non-differentiated phenotype, a process that can be partially reversed by the introduction of transcription factors.

Omics and its potential impact on R&D and regulation of complex herbal products

In traditional Chinese medicine (TCM), multicomponent and principally plant-derived drugs are used for disease prevention, symptom amelioration and treatment in a personalized manner. Because of their complex composition and consequent multiple targets and treatment objectives, the application of omics techniques and other integrative approaches seems inherently appropriate and even necessary for the demonstration of their potential preclinical and clinical safety and efficacy. This perspectives article provides proposals for the application of omics methods to the investigation of complex herbal products (CHP),(1) including Chinese herbal medicines (CHM), both in vitro and in vivo, for preclinical and clinical toxicity, pharmacokinetics, pharmacodynamics and efficacy tests. Ultimately, such approaches could aid regulatory scrutiny and potential acceptance, although currently there is no regulatory requirement of omics-based data in any submitted dossier to any regulatory agency, including for conventional drugs and CHP. However, it has been acknowledged that such studies are being increasingly performed, and almost surely will eventually be included into regulatory submission dossiers, possibly initially as supplementary materials. Specifically for CHM and CHP, omics can play a role both in determining product composition and its variability and in monitoring biological effects in carefully selected platforms. Predicting the future is difficult, but it seems possible that regulatory acceptance of omics techniques and a systems biology approach for the study of TCM, CHM and CHP will not be long delayed. It is expected that current studies and plans employing omics techniques and other integrative approaches will prove to be positive and informative.

Two-Year Toxicity and Carcinogenicity Studies of Panax ginseng in Fischer 344 Rats and B6C3F1 Mice

Ginseng is one of the most popular herbal supplements on the US market. Numerous reports of adverse effects from products containing ginseng have been filed with the US Food and Drug Administration (FDA) and the literature documents a "ginseng abuse syndrome" among regular users. However, the chronic toxic effects of ginseng are not well characterized. Because of its significant human exposure and the fact that little information on its toxicity is available, Panax ginseng was nominated by the US National Institutes of Health (NIH) to the US National Toxicology Program (NTP) to assess its carcinogenic potential. In this paper, we reported the results of NTP chronic toxicity and tumorigenicity bioassay. It shows that, under these experimental conditions, Panax ginseng is not toxic or tumorigenic.

Gene expression profiling and pathway network analysis of hepatic metabolic enzymes targeted by baicalein

ETHNOPHARMACOLOGICAL RELEVANCE

Baicalein is a flavone originally isolated from the roots of traditional Chinese medicinal herb, Scutellaria baicalensis, which has been proved as a promising chemopreventive compound for many chronic human diseases.

AIM OF THE STUDY

The present study aimed to clarify the molecular mechanism targeted by baicalein.

MATERIALS AND METHODS

Gene expression profiling of HepG2 cells treated with baicalein was carried out, using the Affymetrix 42K oligonucleotide microarray in the present study. Microarray data analyzed by Ingenuity Pathway Analysis (IPA), further study performed by real time PCR, reporter gene assay, and Western blot.

RESULTS

Among total 42K gene probes, baicalein treatment up-regulated the signals of 440 gene probes (1.04% of total gene probes) and down-regulated signals of 254 gene probes (0.6% of total gene probes) by ≥2-fold. These genes were categorized into 35 groups and hit for biological processes, molecular functions, and signaling pathways. The network and pathway analyses of these data further revealed that an Nrf2 (nuclear factor-erythroid 2 p45-related factor 2)-mediated ARE (antioxidant response element) pathway is involved in baicalein-induced gene expression of hepatic metabolic enzymes. The representative enzymes involved in Nrf2/ARE pathway were further confirmed at mRNA level by real time PCR and at protein level by Western blot analysis. Moreover, the ARE-reporter gene assay demonstrated that baicalein stimulated Nrf2-mediated ARE transactivation.

CONCLUSIONS

Our results provide a comprehensive data for understanding the hepatic metabolism, bioactive role and the molecular mechanisms of baicalein.

Toxicological actions of plant-derived and anthropogenic methylenedioxyphenyl-substituted chemicals in mammals and insects

The methylenedioxyphenyl (MDP) substituent is a structural feature present in many plant chemicals that deter foraging by predatory insects and herbivores. With increasing use of herbal extracts in alternative medicine, human exposure to MDP-derived plant chemicals may also be significant. Early studies found that most MDP agents themselves possess relatively low intrinsic toxicity, but strongly influence the actions of other xenobiotics in mammals and insects by modulating cytochrome P-450 (CYP)-dependent biotransformation. Thus, after exposure to MDP chemicals an initial phase of CYP inhibition is followed by a sustained phase of CYP induction. In insects CYP inhibition by MDP agents underlies their use as pesticide synergists, but analogous inhibition of mammalian CYP impairs the clearance of drugs and foreign compounds. Conversely, induction of mammalian CYP by MDP agents increases xenobiotic oxidation capacity. Exposure of insects to MDP-containing synergists in the environment, in the absence of coadministered pesticides, may also enhance xenobiotic detoxication. Finally, although most MDP agents are well tolerated, several, typified by safrole, aristolochic acid, and MDP-kavalactones, are associated with significant toxicities, including the risk of hepatotoxicity or tumorigenesis. Thus, the presence of MDP-substituted chemicals in the environment may produce a range of direct and indirect toxicities in target and nontarget species.

Methysticin and 7,8-dihydromethysticin are two major kavalactones in kava extract to induce CYP1A1

Kava is a plant traditionally used for making beverages in Pacific Basin countries and has been used for the treatment of nervous disorders in the United States. The pharmacological activity of kava is achieved through kavalactones in kava extract, which include kawain, 7,8-dihydrokawain, yangonin, 5,6-dehydrokawain, methysticin, and 7,8-dihydromethysticin. Recent studies have shown that kava extract induces hepatic CYP1A1 enzyme; however, the mechanisms of CYP1A1 induction have not been elucidated, and the kavalactones responsible for CYP1A1 induction have not yet been identified. Using a combination of biochemical assays and molecular docking tools, we determined the functions of kava extract and kavalactones and delineated the underlying mechanisms involved in CYP1A1 induction. The results showed that kava extract displayed a concentration-dependent effect on CYP1A1 induction. Among the six major kavalactones, methysticin triggered the most profound inducing effect on CYP1A1 followed by 7,8-dihydromethysticin. The other four kavalactones (yangonin, 5,6-dehydrokawain, kawain, and 7,8-dihydrokawain) did not show significant effects on CYP1A1. Consistent with the experimental results, in silico molecular docking studies based on the aryl hydrocarbon receptor (AhR)-ligand binding domain homology model also revealed favorable binding to AhR for methysticin and 7,8-dihydromethysticin compared with the remaining kavalactones. Additionally, results from a luciferase gene reporter assay suggested that kava extract, methysticin, and 7,8-dihydromethysticin were able to activate the AhR signaling pathway. Moreover, kava extract-, methysticin-, and 7,8-dihydromethysticin-mediated CYP1A1 induction was blocked by an AhR antagonist and abolished in AhR-deficient cells. These findings suggest that kava extract induces the expression of CYP1A1 via an AhR-dependent mechanism and that methysticin and 7,8-dihydromethysticin contribute to CYP1A1 induction. The induction of CYP1A1 indicates a potential interaction between kava or kavalactones and CYP1A1-mediated chemical carcinogenesis.

Liver toxicity and carcinogenicity in F344/N rats and B6C3F1 mice exposed to Kava Kava

Kava Kava is an herbal supplement used as an alternative to antianxiety drugs. Although some reports suggest an association of Kava Kava with hepatotoxicity , it continues to be used in the United States due to lack of toxicity characterization. In these studies F344/N rats and B6C3F1 mice were administered Kava Kava extract orally by gavage in corn oil for two weeks, thirteen weeks or two years. Results from prechronic studies administered Kava Kava at 0.125 to 2g/kg body weight revealed dose-related increases in liver weights and incidences of hepatocellular hypertrophy. In the chronic studies, there were dose-related increases in the incidences of hepatocellular hypertrophy in rats and mice administered Kava Kava for up to 1g/kg body weight. This was accompanied by significant increases in incidences of centrilobular fatty change. There was no treatment- related increase in carcinogenic activity in the livers of male or female rats in the chronic studies. Male mice showed a significant dose-related increase in the incidence of hepatoblastomas. In female mice, there was a significant increase in the combined incidence of hepatocellular adenoma and carcinoma in the low and mid dose groups but not in the high dose group. These findings were accompanied by several nonneoplastic hepatic lesions.

Kava extract, an herbal alternative for anxiety relief, potentiates acetaminophen-induced cytotoxicity in rat hepatic cells

The widely used over-the-counter analgesic acetaminophen (APAP) is the leading cause of acute liver failure in the United States and due to this high incidence, a recent FDA Advisory Board recommended lowering the maximum dose of APAP. Kava herbal dietary supplements have been implicated in several human liver failure cases leading to the ban of kava-containing products in several Western countries. In the US, the FDA has issued warnings about the potential adverse effects of kava, but kava dietary supplements are still available to consumers. In this study, we tested the potential of kava extract to potentiate APAP-induced hepatocyte cytotoxicity. In rat primary hepatocytes, co-treatment with kava and APAP caused 100% loss of cell viability, while the treatment of kava or APAP alone caused ∼50% and ∼30% loss of cell viability, respectively. APAP-induced glutathione (GSH) depletion was also potentiated by kava. Co-exposure to kava decreased cellular ATP concentrations, increased the formation of reactive oxygen species, and caused mitochondrial damage as indicated by a decrease in mitochondrial membrane potential. In addition, similar findings were obtained from a cultured rat liver cell line, clone-9. These observations indicate that kava potentiates APAP-induced cytotoxicity by increasing the magnitude of GSH depletion, resulting in oxidative stress and mitochondrial dysfunction, ultimately leading to cell death. These results highlight the potential for drug-dietary supplement interactions even with widely used over-the-counter drugs.

Constituents in kava extracts potentially involved in hepatotoxicity: a review

Aqueous kava root preparations have been consumed in the South Pacific as an apparently safe ceremonial and cultural drink for centuries. However, several reports of hepatotoxicity have been linked to the consumption of kava extracts in Western countries, where mainly ethanolic or acetonic extracts are used. The mechanism of toxicity has not been established, although several theories have been put forward. The composition of the major constituents, the kava lactones, varies according to preparation method and species of kava plant, and thus, the toxicity of the individual lactones has been tested in order to establish whether a single lactone or a certain composition of lactones may be responsible for the increased prevalence of kava-induced hepatotoxicity in Western countries. However, no such conclusion has been made on the basis of current data. Inhibition or induction of the major metabolizing enzymes, which might result in drug interactions, has also gained attention, but ambiguous results have been reported. On the basis of the chemical structures of kava constituents, the formation of reactive metabolites has also been suggested as an explanation of toxicity. Furthermore, skin rash is a side effect in kava consumers, which may be indicative of the formation of reactive metabolites and covalent binding to skin proteins leading to immune-mediated responses. Reactive metabolites of kava lactones have been identified in vitro as glutathione (GSH) conjugates and in vivo as mercapturates excreted in urine. Addition of GSH to kava extracts has been shown to reduce cytotoxicity in vitro, which suggests the presence of inherently reactive constituents. Only a few studies have investigated the toxicity of the minor constituents present in kava extract, such as pipermethystine and the flavokavains, where some have been shown to display higher in vitro cytotoxicity than the lactones. To date, there remains no indisputable reason for the increased prevalence of kava-induced hepatotoxicity in Western countries.

Kava hepatotoxicity: pathogenetic aspects and prospective considerations

Kava hepatotoxicity is a well-defined herb-induced liver injury, caused by the use of commercial anxyolytic ethanolic and acetonic kava extracts, and of traditional recreational aqueous kava extracts. The aim of this review is to elucidate possible pathogenetic factors for the development of kava-induced liver injury, considering also confounding variables. In patients with liver disease in a causal relation to kava ± comedication, confounding factors include non-adherence to therapy recommendations and comedication consisting of synthetic and herbal drugs and dietary supplements including herbal ones and herbs-kava mixtures. Various possible pathogenetic factors have to be discussed and comprise metabolic interactions with exogenous compounds at the hepatic microsomal cytochrome P450 level; genetic enzyme deficiencies; toxic constituents and metabolites derived from the kava extract including impurities and adulterations; cyclooxygenase inhibition; P-glycoprotein alterations; hepatic glutathione depletion; solvents and solubilizers of the extracts; and kava raw material of poor quality. In particular, inappropriate kava plant parts and unsuitable kava cultivars may have been used sometimes for manufacturing the kava extracts instead of the rhizome of a noble cultivar of the kava plant (Piper methysticum G. Forster). In conclusion, kava hepatotoxicity occurred independently of the extraction medium used for the kava extracts and may primarily be attributed to daily overdose, prolonged treatment and to a few kava extract batches of poor quality; by improving kava quality and adherence to therapy recommendation under avoidance of comedication, liver injury by kava should be a preventable disease, at least to a major extent.

Kavalactones Yangonin and Methysticin induce apoptosis in human hepatocytes (HepG2) in vitro

While cases of severe kava hepatotoxicity have been reported, studies examining the toxicity of individual kavalactones are limited. The present study examined the in vitro hepatotoxicity of kavain, methysticin and yangonin on human hepatocytes (HepG2) and the possible mechanism(s) involved. Cytotoxicity was assessed using lactate dehydrogenase (LDH) and ethidium bromide (EB) assays. The mode of cell death was analysed with acridine orange/ethidium bromide dual staining with fluorescence microscopy. Glutathione oxidation was measured using the ortho-phthalaldehyde (OPT) fluorescence assay. Kavain had minimal cytotoxicity, methysticin showed moderate concentration-dependent toxicity and yangonin displayed marked toxicity with ~ 40% reduction in viability in the EB assay. Acridine orange/ethidium bromide staining showed the predominant mode of cell death was apoptosis rather than necrosis. No significant changes were observed in glutathione levels, excluding this as the primary mechanism of cell death in this model. Further studies may elucidate the precise apoptotic pathways responsible and whether toxic kavalactone metabolites are involved.

Validation of reference gene stability for APAP hepatotoxicity studies in different in vitro systems and identification of novel potential toxicity biomarkers

Liver cell lines and primary hepatocytes are becoming increasingly valuable for in vitro toxicogenomic studies, with RT-qPCR enabling the analysis of gene expression profiles following exposure to potential hepatotoxicants. Supporting the accurate normalisation of RT-qPCR data requires the identification of reference genes which have stable expression during in vitro toxicology studies. Therefore, we performed a comprehensive analysis of reference gene stability in two routinely used cell types, (HepG2 cells and primary rat hepatocytes), and two in vitro culture systems, (2D monolayer and 3D scaffolds). A robust reference gene validation strategy was performed, consisting of geNorm analysis, to test for pair wise variation in gene expression, and statistical analysis using analysis of variance. This strategy identified stable reference genes with respect to acetaminophen treatment and time in HepG2 cells (GAPDH and PPIA), and with respect to acetaminophen treatment and culture condition in primary hepatocytes (18S rRNA and α-tubulin). Following the selection of reference genes, the novel target genes E2F7 and IL-11RA were identified as potential toxicity biomarkers for acetaminophen treatment. We conclude that accurate quantification of gene expression requires the use of a validated normalisation strategy for each species and experimental system employed.

Role of ethanol in kava hepatotoxicity

Kava is known for its recreational, ceremonial and medicinal use in the Pacific. The aqueous non-alcoholic drink of kava rhizome produces intoxicating, relaxing and soothing effects. While kava's medicinal effects receive worldwide recognition, kava-containing products came under scrutiny after over 100 reports of spontaneous adverse hepatic effects. Many mechanisms have been postulated to explain the unexpected toxicity, one being pharmacokinetic interactions between kavalactones and co-administered drugs involving cytochrome P450 enzyme system. Alcohol is often co-injested in kava hepatotoxicity cases. This review evaluates the possible hepatotoxicity mechanisms involving alcohol and kava.

Ginkgo biloba extract induces gene expression changes in xenobiotics metabolism and the Myc-centered network

The use of herbal dietary supplements in the United States is rapidly growing, and it is crucial that the quality and safety of these preparations be ensured. To date, it is still a challenge to determine the mechanisms of toxicity induced by mixtures containing many chemical components, such as herbal dietary supplements. We previously proposed that analyses of the gene expression profiles using microarrays in the livers of rodents treated with herbal dietary supplements is a potentially practical approach for understanding the mechanism of toxicity. In this study, we utilized microarrays to analyze gene expression changes in the livers of male B6C3F1 mice administered Ginkgo biloba leaf extract (GBE) by gavage for 2 years, and to determine pathways and mechanisms associated with GBE treatments. Analysis of 31,802 genes revealed that there were 129, 289, and 2,011 genes significantly changed in the 200, 600, and 2,000 mg/kg treatment groups, respectively, when compared with control animals. Drug metabolizing genes were significantly altered in response to GBE treatments. Pathway and network analyses were applied to investigate the gene relationships, functional clustering, and mechanisms involved in GBE exposure. These analyses indicate alteration in the expression of genes coding for drug metabolizing enzymes, the NRF2-mediated oxidative stress response pathway, and the Myc gene-centered network named "cell cycle, cellular movement, and cancer" were found. These results indicate that Ginkgo biloba-related drug metabolizing enzymes may cause herb-drug interactions and contribute to hepatotoxicity. In addition, the outcomes of pathway and network analysis may be used to elucidate the toxic mechanisms of Ginkgo biloba.

Drug-botanical interactions: a review of the laboratory, animal, and human data for 8 common botanicals

Many Americans use complementary and alternative medicine (CAM) to prevent or alleviate common illnesses, and these medicines are commonly used by individuals with cancer.These medicines or botanicals share the same metabolic and transport proteins, including cytochrome P450 enzymes (CYP), glucuronosyltransferases (UGTs), and P-glycoprotein (Pgp), with over-the-counter and prescription medicines increasing the likelihood of drug-botanical interactions.This review provides a brief description of the different proteins, such as CYPs, UGTs, and Pgp.The potential effects of drug-botanical interactions on the pharmacokinetics and pharmacodynamics of the drug or botanical and a summary of the more common models used to study drug metabolism are described.The remaining portion of this review summarizes the data extracted from several laboratory, animal, and clinical studies that describe the metabolism, transport, and potential interactions of 8 selected botanicals. The 8 botanicals include black cohosh, Echinacea, garlic, Gingko biloba, green tea, kava, milk thistle, and St John's wort; these botanicals are among some of the more common botanicals taken by individuals with cancer.These examples are included to demonstrate how to interpret the different studies and how to use these data to predict the likelihood of a clinically significant drug-botanical interaction.

Abnormal gene expression in cerebellum of Npc1-/- mice during postnatal development

Niemann-Pick Type C (NPC) disease is an autosomal recessive neurodegenerative disorder with abnormal lipid storage as the major cellular pathologic hallmark. Genetic analyses have identified mutations in NPC1 gene in the great majority of cases, while mutations in NPC2 account for the remainders. Yet little is known regarding the cellular mechanisms responsible for NPC pathogenesis, especially for neurodegeneration, which is the usual cause of death. To identify critical steps that could account for the pathological manifestations of the disease in one of the most affected brain structures, we performed global gene expression analysis in the cerebellum from 3-week old Npc1+/+ and Npc1-/- mice with two different microarray platforms (Agilent and Illumina). Differentially expressed genes identified by both microarray platforms were then subjected to KEGG pathway analysis. Expression of genes in six pathways was significantly altered in Npc1-/- mice; functionally, these signaling pathways belong to the following three categories: (1) steroid and terpenoid biosynthesis, (2) immune response, and (3) cell adhesion/motility. In addition, the expression of several proteins involved in lipid transport was significantly altered in Npc1-/- mice. Our results provide novel molecular insight regarding the mechanisms of pathogenesis in NPC disease and reveal potential new therapeutic targets.

Gene expression profiling as an initial approach for mechanistic studies of toxicity and tumorigenicity of herbal plants and herbal dietary supplements

Dietary supplements are consumed by more than 300 million people worldwide, and herbal dietary supplements represent the most rapidly growing portion of this industry. Even though adverse health effects of many herbal dietary supplements have been reported, safety assurances are not being addressed adequately. Toxicological data on the identification of genotoxic and tumorigenic ingredients in many raw herbs are also lacking. Currently, more than 30 herbal dietary supplements and active ingredients have been selected by the National Toxicology Program (NTP) for toxicity and tumorigenicity studies. Due to the complexity of the chemical components present in plant extracts, there are no established methodologies for determining the mechanisms of toxicity (particularly tumorigenicity) induced by herbs, such as Gingko biloba leaf extract (GBE) and other herbal plant extracts. Consequently, the understanding of toxicity of herbal dietary supplements remains limited. We have proposed that application of DNA microarrays could be a highly practical initial approach for revealing biological pathways and networks associated with toxicity induced by herbal dietary supplements and the generation of hypotheses to address likely mechanisms. The changes in expression of subsets of genes of interest, such as the modulation of drug metabolizing genes, can be analyzed after treatment with an herbal dietary supplement. Although levels of gene expression do not represent fully the levels of protein activities, we propose that subsequent biochemical and genomic experiments based on these initial observations will enable elucidation of the mechanisms leading to toxicity, including tumorigenicity. This review summarizes the current practices of microarray analysis of gene expressions in animals treated with herbal dietary supplements and discusses perspectives for the proposed strategy.

Gene expression profiling in male B6C3F1 mouse livers exposed to kava identifies--changes in drug metabolizing genes and potential mechanisms linked to kava toxicity

The association of kava products with liver-related health risks has prompted regulatory action in many countries. We used a genome-wide gene expression approach to generate global gene expression profiles from the livers of male B6C3F1 mice administered kava extract by gavage for 14 weeks, and identified the differentially expressed drug metabolizing genes in response to kava treatments. Analyses of gene functions and pathways reveal that the levels of significant numbers of genes involving drug metabolism were changed and that the pathways involving xenobiotics metabolism, Nrf2-mediated oxidative stress response, mitochondrial functions and others, were altered. Our results indicate that kava extract can significantly modulate drug metabolizing enzymes, potentially leading to herb-drug interactions and hepatotoxicity.