Subchronic Toxicity Studies of Cortex Dictamni Extracts in Mice and Its Potential Hepatotoxicity Mechanisms in Vitro

Obacunone, a Promising Phytochemical Triterpenoid: Research Progress on Its Pharmacological Activity and Mechanism

Obacunone, a natural triterpenoid, is an active component of the herbs Dictamnus dasycarpus Turcz. and Phellodendron amurense Rupr, and an indicator of the herbs' quality. Owing to its multiple health benefits, several studies have investigated the multi-targeting potential action mechanisms of obacunone. To summarize recent developments on the pharmacological actions of obacunone and focus on the underlying molecular mechanisms and signaling networks, we searched PubMed, Europe PMC, Wiley Online Library, Web of Science, Google Scholar, Wanfang Medical Network, and China National Knowledge Infrastructure for articles published prior to March 2024. Existing research indicates obacunone has great potential to become a promising therapeutic option against tumors, fibrotic diseases, bone and cholesterol metabolism diseases, and infections of pathogenic microorganisms, among others. The paper contributes to providing up-to-date references for further research and clinical applications of obacunone.

Protection of schisantherin A against dictamnine-induced hepatotoxicity: Pharmacokinetic insights

Dictamnine (DIC), as the most abundant furoquinoline alkaloid ingredient of the herbal medicine Cortex Dictamni (CD), can induce severe liver injury. A previous study found that DIC-induced liver injury was initiated by cytochrome P4503A (CYP3A)-mediated metabolic activation and subsequent formation of adducts with cellular proteins. Schisantherin A (SchA) is the major lignan component of the herbal medicine Schisandra chinensis (SC). SC is frequently combined with CD used in numerous Chinese medicinal formulas for the treatment of eczema and urticaria. Furthermore, SC could protect against CD-induced hepatotoxicity. The objective of the study was to investigate the protective effect of SchA on DIC-induced hepatotoxicity based on pharmacokinetic interactions. The studies found that SchA exerted a protective effect on DIC-induced hepatotoxicity in a dose-dependent manner. Pharmacokinetic studies showed that pretreatment with SchA enhanced the area under concentration-time curve (AUC) and maximal concentration (Cmax ) values of DIC in the serum and liver tissue of mice, indicating that SchA could augment the accumulation of DIC in the circulation. In vitro metabolism assays with mouse liver microsomes (MLMs) showed that SchA reduced the production of DIC-glutathione (GSH) conjugate. In addition, SchA significantly reduced the excretion of DIC-GSH conjugate in the urine of mice and relieved hepatic GSH depletion induced by DIC. These results suggested that SchA could inhibit the metabolic activation of DIC in vitro and in vivo. In summary, our findings showed that the observed pharmacokinetic interactions might be attributable to the inhibition of the metabolism of DIC by SchA, which might be responsible for the protection of SchA against DIC-induced hepatotoxicity. Therefore, the development of a standardized combination of DIC and SchA may protect patients from DIC-induced liver injury.

Isomaculosidine facilitates NLRP3 inflammasome activation by promoting mitochondrial reactive oxygen species production and causes idiosyncratic liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Dictamnus dasycarpus Turcz. (Dictamni Cortex, DC), a Chinese herbal medicine, is commonly used for treating chronic dermatosis and rheumatism, but can also cause herb-induced liver injury (HILI). Our study has demonstrated that DC can induce idiosyncratic HILI, but the mechanism remains unknown. The NLRP3 inflammasome has become a major target for addressing many diseases. The activation of NLRP3 inflammasome is responsible for many liver-related inflammatory diseases, including idiosyncratic HILI.

AIM OF THE STUDY

The objective of our study was to demonstrate the mechanism underlying the idiosyncratic HILI induced by DC and clarify the susceptible component in DC.

MATERIALS AND METHODS

Bone marrow-derived macrophages (BMDMs) and THP1 cells were selected to assess the effect of isomaculosidine (IMD) on NLRP3 inflammasome activation in vitro. Western blot, ELISA and Caspase-Glo® 1 Inflammasome Assay, flow cytometry and Immunofluorescence were employed to detect the mechanism of IMD on NLRP3 inflammasome activation. To assess the efficacy of IMD in vivo, mice were intravenously administrated with LPS and then IMD were injected intraperitoneally for 6 h.

RESULTS

The results of our in vitro studies demonstrate that IMD, the major constituent of DC, specifically promoted ATP- and nigericin-induced activation of NLRP3 inflammasome, but not NLRC4 and AIM2 inflammasomes. Additionally, IMD promoted nigericin-induced ASC oligomerization. Notably, synergistic induction of mtROS played a key role on the activation of NLRP3 inflammasome. IMD increased the mtROS production in the activation of NLRP3 inflammasome induced by nigericin. In addition, the results of our in vivo study showed that the combination of nonhepatotoxic doses of LPS and IMD can increase the levels of ALT, AST, and DBIL, leading to liver injury.

CONCLUSIONS

IMD specifically facilitated the activation of NLRP3 inflammasome induced by nigericin and ATP, which is responsible for DC-induced idiosyncratic HILI.

Cinobufotalin prevents bone loss induced by ovariectomy in mice through the BMPs/SMAD and Wnt/β-catenin signaling pathways

BACKGROUND

Osteoporosis is a chronic bone disease characterized by bone loss and decreased bone strength. However, current anti-resorptive drugs carry a risk of various complications. The deep learning-based efficacy prediction system (DLEPS) is a forecasting tool that can effectively compete in drug screening and prediction based on gene expression changes. This study aimed to explore the protective effect and potential mechanisms of cinobufotalin (CB), a traditional Chinese medicine (TCM), on bone loss.

METHODS

DLEPS was employed for screening anti-osteoporotic agents according to gene profile changes in primary osteoporosis. Micro-CT, histological and morphological analysis were applied for the bone protective detection of CB, and the osteogenic differentiation/function in human bone marrow mesenchymal stem cells (hBMMSCs) were also investigated. The underlying mechanism was verified using qRT-PCR, Western blot (WB), immunofluorescence (IF), etc. RESULTS: A safe concentration (0.25 mg/kg in vivo, 0.05 μM in vitro) of CB could effectively preserve bone mass in estrogen deficiency-induced bone loss and promote osteogenic differentiation/function of hBMMSCs. Both BMPs/SMAD and Wnt/β-catenin signaling pathways participated in CB-induced osteogenic differentiation, further regulating the expression of osteogenesis-associated factors, and ultimately promoting osteogenesis.

CONCLUSION

Our study demonstrated that CB could significantly reverse estrogen deficiency-induced bone loss, further promoting osteogenic differentiation/function of hBMMSCs, with BMPs/SMAD and Wnt/β-catenin signaling pathways involved.

The pharmacological and pharmacokinetic properties of obacunone from citrus fruits: A comprehensive narrative review

Limonoids are a class of oxygenated terpenoids that exist mainly in citrus fruits. As a kind of limonoid, obacunone has attracted more and more researchers' attention because of its extensive pharmacological activities. The purpose of the narrative review is to systematically review relevant studies on the pharmacological effects and pharmacokinetic characteristics of obacunone to provide researchers with the latest and useful information. Pharmacological studies have shown that obacunone has a variety of pharmacological activities, such as anticancer, antioxidant, anti-inflammatory, anti-diabetes, neuroprotection, antibiosis, and antivirus. Among them, the anticancer effect is the most prominent. Pharmacokinetic studies have shown that the oral bioavailability of obacunone is low. This indicates the presence of high first-pass metabolism. We hope that this paper can help relevant scholars understand the progress in pharmacological and pharmacokinetic research of obacunone and help the further development of obacunone as a functional food.

Exploring the Mechanism of Hepatotoxicity Induced by Dictamnus dasycarpus Based on Network Pharmacology, Molecular Docking and Experimental Pharmacology

The root bark of Dictamnus dasycarpus Turcz is a traditional Chinese medicine, Dictamni Cortex (DC), which is mainly used in the clinical treatment of skin inflammation, eczema, rubella, rheumatism, and gynecological inflammation. Unexpectedly, there are some cases of liver injury after the administration of DC. However, the mechanism of hepatotoxicity remains ambiguous. The aim of this study was to explore the mechanism and substance bases of DC hepatotoxicity based on network pharmacology and molecular docking, verified through pharmacological experiments. Partial prototype components and metabolites in vivo of quinoline alkaloids from DC were selected as candidate compounds, whose targets were collected from databases. Network pharmacology was applied to study the potential hepatotoxic mechanism after correlating the targets of candidate compounds with the targets of hepatotoxicity. Molecular docking was simulated to uncover the molecular mechanism. Furthermore, the hepatotoxicity of the extract and its constituents from DC was evaluated in vivo and in vitro. We constructed the "potential toxic components-toxic target-toxic pathway" network. Our results showed that the targets of DC included CYP1A2 and GSR, participating in heterologous steroid metabolism, REDOX metabolism, drug metabolism, heterocyclic metabolic processes, the synthesis of steroid hormone, cytochrome P450 metabolism, chemical carcinogens and bile secretion pathways. In vitro and in vivo experiments displayed that DC could result in a decrease in GSH-Px and oxidative stress, simultaneously inhibiting the expression of CYP1A2 and inducing hepatotoxicity. These results further indicated the mechanism of hepatotoxicity induced by Dictamnus dasycarpus, providing a basic theory to explore and prevent hepatotoxicity in the clinical usage of Dictamnus dasycarpus.

Unveiling hepatotoxicity distinction of coumarin-related compounds from glycosides to aglycones in Fructus Psoraleae by integrating UPLC-Q-TOF-MS and high content analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Fructus Psoraleae (FP), the dried and ripe fruit of Cullen corylifolium (L.) Medik., is widely used due to its various clinical pharmacological effects, but its hepatotoxicity restricts its clinical application. So far, its hepatotoxic components and their underlying mechanism have not been systematically elucidated.

AIM OF THE STUDY

This study was undertaken to reveal the hepatotoxicity distinction of coumarin-related compounds from glycosides to aglycones in FP and elucidate their potential mechanism.

METHODS

Rats were administrated with the aqueous extract of Fructus Psoraleae (AEFP), in which eight coumarin-related compounds were focused. Subsequently, compounds exposed in rats' livers were detected by UPLC-Q-TOF-MS, and the identified hepatotoxic compounds were evaluated to elaborate their possible mechanism by the aid of high content analysis (HCA).

RESULTS

Eight coumarin-related compounds were identified, among which psoralenoside (PO), isopsoralenoside (IPO), psoralen (P), and isopsoralen (IP) were the principally exposed compounds in rats' livers. Furocoumarinic acid glucoside (FAG), (E)-3-(4-(((2S, 3R, 4S, 5S, 6R)-3,4,5-trihydroxy-6-(hydroxymethyl) tetrahydro-2H-pyran-2-yl) oxy) benzofuran-5-yl) acrylic acid (isofurocoumarinic acid glucoside, IFAG), furocoumarinic acid (FA), and (E)-3-(4-hydroxybenzofuran-5-yl) acrylic acid (isofurocoumarinic acid, IFA) were also detected in low abundance. P, IP, FA, and IFA were identified as the hepatotoxic compounds, while their glycosides were almost non-hepatotoxic. The HCA's results showed that hepatotoxic compounds disrupted the balance in reactive oxygen species (ROS), nuclear area, and mitochondrial membrane potential of HepG2 cells, leading to the occurrence of hepatotoxicity.

CONCLUSIONS

P, IP, FA, and IFA were identified as hepatotoxic compounds, from which P and IP were proposed as the important risk components for hepatotoxicity. The conversion from glycosides to aglycones played an essential role in FP-induced hepatotoxicity.

Network pharmacology-based analysis to explore the therapeutic mechanism of Cortex Dictamni on atopic dermatitis

ETHNOPHARMACOLOGICAL RELEVANCE

Dermatitis is a common clinical chronic inflammatory skin disease, which incidence has been on the rise in recent years. It not only seriously affects the physical and mental health of patients but also increase economic burden. Currently, commonly used drugs such as corticosteroids, anti-histamines have certain side effects or are expensive. Therefore, the search for an alternative therapy for dermatitis has important clinical significance. Cortex Dictamni is a commonly used traditional Chinese medicine for expelling wind and itching, but its mechanism for treating dermatitis is still unclear.

MATERIALS AND METHODS

Network pharmacological analysis was performed to predict the potential targets and pathways of Cortex Dictamni against dermatitis. Molecular docking was used to assess the binding affinity of active compounds and core targets. By repeatedly stimulating the ears with 1-fluoro-2,4-dinitrobenzene (DNFB), an atopic dermatitis (AD) mouse model was established in order to study the anti-dermatitis effect of Cortex Dictamni. The skin thickness and inflammatory cell infiltration in mouse ears were assessed by tissue staining and flow cytometric. The levels of inflammatory factors were detected by enzyme-linked immunosorbent assay (ELISA), and the total protein and phosphorylation levels of related pathways were analyzed by western blotting.

RESULTS

In this study, 11 active ingredients, 122 Cortex Dictamni and dermatitis intersection targets were identified. The results from Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the core targets were mainly enriched in immune response and inflammatory signaling pathways. AD mice treated with ethanol extract of Cortex Dictamni (ECD) improved the symptoms of ear skin lesions, alleviated epidermis and dermis thickening of the AD mice ears, decreased pathological immune cell infiltration and attenuated the levels of inflammatory cytokines (TLR4, IL-6, IL-17), and inhibited the hyperactivation of the PI3K-AKT, JAK1-STAT3/STAT6 signal pathways.

CONCLUSIONS

Cortex Dictamni can improve the symptoms of skin lesions and the degree of inflammation caused by AD, and may inhibit AD through multiple pathways, such as regulating PI3K-AKT and JAK1-STAT3/STAT6 pathways. These results not only provide experimental evidence for the clinical application of Cortex Dictamni but also provide some help for the research and development of dermatitis drugs.

Molecular mechanisms of hepatotoxicity induced by compounds occurring in Evodiae Fructus

Evodiae Fructus (EF) is a common herbal medicine with thousands of years of medicinal history in China, which has been demonstrated with many promising pharmacological effects on cancer, cardiovascular diseases and Alzheimer's disease. However, there have been increasing reports of hepatotoxicity associated with EF consumption. Unfortunately, in a long term, many implicit constituents of EF as well as their toxic mechanisms remain poorly understood. Recently, metabolic activation of hepatotoxic compounds of EF to generate reactive metabolites (RMs) has been implicated. Herein, we capture metabolic reactions relevant to hepatotoxicity of these compounds. Initially, catalyzed by the hepatic cytochrome P450 enzymes (CYP450s), the hepatotoxic compounds of EF are oxidized to generate RMs. Subsequently, the highly electrophilic RMs could react with nucleophilic groups contained in biomolecules, such as hepatic proteins, enzymes, and nucleic acids to form conjugates and/or adducts, leading to a sequence of toxicological consequences. In addition, currently proposed biological pathogenesis, including oxidative stress, mitochondrial damage and dysfunction, endoplasmic reticulum (ER) stress, hepatic metabolism disorder, and cell apoptosis are represented. In short, this review updates the knowledge on the pathways of metabolic activation of seven hepatotoxic compounds of EF and provides considerable insights into the relevance of proposed molecular hepatotoxicity mechanisms from a biochemical standpoint, for the purpose of providing a theoretical guideline for the rational application of EF in clinics.

Integrating pharmacokinetics and network pharmacology to identify and validate targets of Guben Xiaozhen prescription for the treatment of chronic urticaria

ETHNOPHARMACOLOGICAL RELEVANCE

Guben Xiaozhen prescription (GXP), a prescription of traditional Chinese medicine, has been used to treat skin diseases for a long history and achieved satisfactory therapeutic effects. However, its active ingredients and targets remain to be further elucidated.

AIM OF THIS STUDY

Identify activity ingredients of GXP for the treatment of chronic urticaria (CU) and further validate the efficacy and targets of the selected component.

MATERIALS AND METHODS

Firstly, the pharmacokinetics of different disassemble groups of GXP was investigated to screen for active ingredients with improved bioavailability. Then, shared targets between active ingredients and CU were performed by network pharmacology. Finally, the ovalbumin (OVA) induced CU model was used to verify the efficacy and targets of the screened active ingredient.

RESULTS

Pharmacokinetic results showed that, compared with sub-division groups, the maximum concentration (C_max) and blood concentration-time curve (AUC_0-t) of eight ingredients, including 6-shogaol, 6-gingerol, calycosin, dictamnine, fraxinellone, schizandrin, cimifugin, and sec-o-glucosylhamaudol were increased in the GXP group. Then, 218 CU-related targets and 20 shared targets with six potential active compounds were screened by network pharmacology. Further analysis found that fraxinellone was not reported to be associated with CU in the literature. Therefore, the present study employed an OVA-induced CU model and found that fraxinellone could dose-dependently inhibit the locus coeruleus reaction, mast cell degranulation, and pathological skin damage. Moreover, we further verified the ADRB2 and its downstream target caspase3 predicted by network pharmacology, and fraxinellone inhibited the expression of ADRB2 and caspase3 in high dose group, suggesting that fraxinellone may play an anti-CU role by inhibiting inflammation and cell apoptosis.

CONCLUSION

In this study, integrated pharmacokinetics and network pharmacology methods were established to screen out six effective active ingredients in GXP for the treatment of CU. This study provides a new idea for screening active substances in traditional Chinese medicine.

Probing the biological toxicity of pyrene to the earthworm Eisenia fetida and the toxicity pathways of oxidative damage: A systematic study at the animal and molecular levels

Pyrene (Pyr), a widely used tetracyclic aromatic hydrocarbon, enters soil in large quantities and causes environmental pollution due to its production and mining. In order to systematically study the biotoxicity of pyrene to model organisms Eisenia fetida in soil, experiments were carried out from four dimensions: animal, tissue, cell and molecule. Experimental results proved that the mortality rate increased with increasing concentration and time of exposure to pyrene, while the mean body weight and spawning rate decreased. Meanwhile, when the pyrene concentration reached 900 mg/kg, the seminal vesicle and longitudinal muscle of the earthworm showed obvious atrophy. Experimental results at the cellular level showed that pyrene induced cell membrane damage and Ca²⁺ influx triggered mitochondrial membrane depolarization and a surge in ROS levels. Oxidative stress causes damage to proteins and lipids and DNA inside cells. When the mortality rate was 91.67 %, the Olive Tail Movement (OTM) of the comet experiment reached 15. The results of molecular level tests showed that pyrene inhibited the activity of Cu/Zn-superoxide dismutase (Cu/Zn-SOD) mainly by changing the microenvironment and secondary structure of amino acid Tyr 108. The weakened function of direct antioxidant enzymes may be the root cause of the excessive increase of reactive oxygen species (ROS) in cells. The systematic approach used in this study enriches the network of toxic pathways in toxicological studies, and basic data on the biological toxicity of pyrene can provide support for future soil contamination detection.

The Potential Application of Chinese Medicine in Liver Diseases: A New Opportunity

Liver diseases have been a common challenge for people all over the world, which threatens the quality of life and safety of hundreds of millions of patients. China is a major country with liver diseases. Metabolic associated fatty liver disease, hepatitis B virus and alcoholic liver disease are the three most common liver diseases in our country, and the number of patients with liver cancer is increasing. Therefore, finding effective drugs to treat liver disease has become an urgent task. Chinese medicine (CM) has the advantages of low cost, high safety, and various biological activities, which is an important factor for the prevention and treatment of liver diseases. This review systematically summarizes the potential of CM in the treatment of liver diseases, showing that CM can alleviate liver diseases by regulating lipid metabolism, bile acid metabolism, immune function, and gut microbiota, as well as exerting anti-liver injury, anti-oxidation, and anti-hepatitis virus effects. Among them, Keap1/Nrf2, TGF-β/SMADS, p38 MAPK, NF-κB/IκBα, NF-κB-NLRP3, PI3K/Akt, TLR4-MyD88-NF-κB and IL-6/STAT3 signaling pathways are mainly involved. In conclusion, CM is very likely to be a potential candidate for liver disease treatment based on modern phytochemistry, pharmacology, and genomeproteomics, which needs more clinical trials to further clarify its importance in the treatment of liver diseases.

Multi-Omics Integration to Reveal the Mechanism of Hepatotoxicity Induced by Dictamnine

Herb-induced liver injury (HILI) has become a great concern worldwide due to the widespread usage of herbal products. Among these products is Dictamni Cortex (DC), a well-known Traditional Chinese Medicine (TCM), widely used to treat chronic dermatosis. Dictamni Cortex has drawn increasing attention because of its hepatotoxicity caused by the hepatotoxic component, dictamnine. However, the potential hepatotoxicity mechanism of dictamnine remains unclear. Therefore, this study aimed to use the multi-omics approach (transcriptomic, metabolomic, and proteomic analyses) to identify genes, metabolites, and proteins expressions associated with dictamnine-induced hepatotoxicity. A study on mice revealed that a high dose of dictamnine significantly increases serum aspartate aminotransferase (AST) activity, total bilirubin (TBIL), and direct bilirubin (DBIL) levels, the relative liver weight and liver/brain weight ratio in female mice (P < 0.05 and P < 0.01), compared to the normal control group. Liver histologic analysis further revealed a high dose of dictamnine on female mice caused hepatocyte vesicular steatosis characterized by hepatocyte microvesicles around the liver lobules. The expressed genes, proteins, and metabolites exhibited strong associations with lipid metabolism disorder and oxidative stress. Dictamnine caused increased oxidative stress and early hepatic apoptosis via up-regulation of glutathione S transferase a1 (GSTA1) and Bax/Bcl-2 ratio and down-regulation of the antioxidative enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase 1 (GPx-1). Besides, the up-regulation of Acyl-CoA synthetase long-chain family member 4 (ACSL4) and down-regulation of acetyl-coa acetyltransferase 1 (ACAT1) and fatty acid binding protein 1 (FABP-1) proteins were linked to lipid metabolism disorder. In summary, dictamnine induces dose-dependent hepatotoxicity in mice, which impairs lipid metabolism and aggravates oxidative stress.

Biotransformation patterns of dictamnine in vitro/in vivo and its relative molecular mechanism of dictamnine-induced acute liver injury in mice

Dictamnine (DIC), a typical furan-quinoline alkaloid, has a wide range of pharmacological and toxicological effects, such as anti-bacterial, antifungal, anti-cancer, and hepatoxicity. But the molecular mechanism of DIC-induced hepatoxicity in mice remains unclear. This study aimed to clarify the biotransformation patterns of DIC in vitro/in vivo and the relative molecular mechanism of DIC-induced hepatoxicity in mice. All metabolites of DIC were identified by comparing the blank and drug-containing urine, feces, plasma, and liver samples. The structure of epoxide intermediate derived from DIC was confirmed by trapping assay. Oxidative stress injury and inflammation have been confirmed to be involved in the toxicological process of DIC-induced hepatoxicity in mice by detecting the relative biochemical indexes. The results will help to develop a deeper understanding about the biotransformation patterns of DIC, structure of the epoxide intermediate, and the molecular mechanism of DIC-induced hepatoxicity in mice.

Fraxinellone: From pesticidal control to cancer treatment

Fraxinellone (FRA) is a degraded limonoid isolated from the root bark of Dictamnus plants. The potent insecticidal activity of FRA has led to the synthesis of numerous derivatives (presented here with the structure-activity relationships) active against the oriental armyworm Mythimna separata Walker. In addition to its pesticidal activity, the natural product displays potent anti-inflammatory and immuno-modulatory effects at the origin of hepatoprotective and anticancer properties. This mini-review provides an update of the mechanism of action of FRA to highlight the recently discovered capacity of the compound to deactivate cancer-associated fibroblasts and thus to limit the immunosuppressive tumor microenvironment. The anticancer mode of action of FRA raises new ideas to better understand its primary insecticidal activity. The relationship between drug-induced cancer cell death and insect cell death is discussed. A drug interaction with the insect cytokine growth-blocking peptide (GBP), a member of the large EGF family, is proposed, supported by preliminary molecular modeling data. Altogether, the review shed light on the pharmacological properties of fraxinellone as an antitumor agent and a natural insecticide.

Cytochrome P450-Mediated Bioactivation: Implication for the Liver Injury Induced by Fraxinellone, A Bioactive Constituent from Dictamni Cortex

Fraxinellone, a furanoid, is one of the bioactive and potentially hepatotoxic constituents from Dictamnus dasycarpus Turcz, which is extensively spread throughout Asian countries. This herb was reported to cause liver injury in clinical application. However, the mechanism behind is still not fully understood. This study mainly focused on the hepatotoxicity of fraxinellone and the underlying mechanism. The current study demonstrated that fraxinellone resulted in a significant elevation of serum alanine aminotransferase and aspartate aminotransferase in a dose-dependent manner in mice after oral administration. Pretreatment with ketoconazole for three successive days could significantly alleviate the hepatotoxicity of fraxinellone. Considering that fraxinellone has a structural alert of furan ring, it is believed that the hepatotoxicity caused by fraxinellone required cytochrome P450-mediated bioactivation. Bioactivation studies were subsequently carried out in vitro and in vivo. Fraxinellone was metabolized into cis-enedial intermediate, an electrophile that was prone to react with glutathione or N-acetyl-lysine through 1,2- or 1,4-addition to form stable conjugates. Ketoconazole significantly inhibited the formation of the glutathione conjugates (M1 and M2) in microsomal incubation and similar finding was obtained in vivo. Phenotyping study indicated that CYP3A4 was the principal enzyme responsible for the bioactivation of fraxinellone. This study suggested that CYP3A4-mediated bioactivation plays an indispensable role in fraxinellone-induced hepatotoxicity. The work performed herein enables us to better understand the hepatotoxicity of fraxinellone as well as the mechanism behind.

Cortex dictamni-induced liver injury in mice: The role of P450-mediated metabolic activation of furanoids

Many furan containing compounds have been reported to be toxic resulted from the metabolic activation of the furan ring to reactive metabolite (RM). Cortex Dictamni (CD), a widely used herbal medicine, has been reported to cause severe even fatal hepatotoxicity. The injurious components and mechanism of CD-induced liver injury remain unclear. Our preliminary study showed that dictamnine, one major furanoid in CD, caused mouse liver injury via its reactive epoxide metabolite. Besides dictamnine, the major components of CD are series of bioactivation-alerting furanoids. Thus, we hypothesize that series of furanoids in CD may undergo metabolic activation and play a key role in CD-induced liver injury. Here, a single oral dose of 60 g/kg ethanol extract of CD (ECD) caused severe hepatocellular necrosis in mice at 24 h post-dose. ECD-induced liver injury showed a dose- and time-dependent manner. The hepatotoxic effects could be completely abolished by P450 nonselective inhibitor 1-aminobenzotriazole (ABT) and strongly modulated by other P450 modulators. The furanoids-concentrated fraction of ECD was responsible for the hepatotoxicity. At least ten furanoids with high abundance in ECD, such as obakunone, dictamnine, fraxinellone, limonin, were found to be metabolized to reactive epoxide or cis-enedione. The RM levels were consistent with the liver injury degree. Multiple furanoids, rather than single one, cooperatively contributed to the hepatotoxicity. ECD-induced liver injury could be reproduced by a mixture of pure furanoids. In summary, this study provides toxic component profiles of CD and demonstrates that P450-mediated bioactivation of multiple furanoids is responsible for CD-induced liver injury.