The crucial role of metabolic regulation in differential hepatotoxicity induced by furanoids in Dioscorea bulbifera.

Diterpenoid lactones (DLs), a group of furan-containing compounds found in Dioscorea bulbifera L. (DB), have been reported to be associated with hepatotoxicity. Different hepatotoxicities of these DLs have been observed in vitro, but reasonable explanations for the differential hepatotoxicity have not been provided. Herein, the present study aimed to confirm the potential factors that contribute to varied hepatotoxicity of four representative DLs (diosbulbins A, B, C, F). In vitro toxic effects were evaluated in various cell models and the interactions between DLs and CYP3A4 at the atomic level were simulated by molecular docking. Results showed that DLs exhibited varied cytotoxicities, and that CYP3A4 played a modulatory role in this process. Moreover, structural variation may cause different affinities between DLs and CYP3A4, which was positively correlated with the observation of cytotoxicity. In addition, analysis of the glutathione (GSH) conjugates indicated that reactive intermediates were formed by metabolic oxidation that occurred on the furan moiety of DLs, whereas, GSH consumption analysis reflected the consistency between the reactive metabolites and the hepatotoxicity. Collectively, our findings illustrated that the metabolic regulation played a crucial role in generating the varied hepatotoxicity of DLs.

Metabolomic-transcriptomic landscape of 8-epidiosbulbin E acetate -a major diterpenoid lactone from Dioscorea bulbifera tuber induces hepatotoxicity.

Studies have shown that 8-epidiosbulbin E acetate (EEA), a major diterpenoid lactone in the tuber of Dioscorea bulbifera, can induce hepatotoxicity in vivo. However, the underlying mechanisms remain unknown. Using the integrated transcriptomic and metabolomics method, in this study we investigated the global effect of EEA exposure on the transcriptomic and metabolomic profiles in mice. The abundance of 7131 genes and 42 metabolites in the liver, as well as 43 metabolites in the serum were altered. It should be noted that EEA mainly damaged hepatic cells through the aberrant regulation of multiple systems primarily including bile acid metabolism, and taurine and hypotaurine metabolism. In addition, an imbalance of bile acid metabolism was found to play a key pat in response to EEA-triggered hepatotoxicity. In summary, these findings contributed to understanding the underlying mechanisms of EEA hepatotoxicity.

The Modulatory Role of CYP3A4 in Dictamnine-Induced Hepatotoxicity.

Dictamni Cortex (DC) has been reported to be associated with acute hepatitis in clinic and may lead to a selective sub-chronic hepatotoxicity in rats. Nevertheless, the potent toxic ingredient and the underlying mechanism remain unknown. Dictamnine (DTN), the main alkaloid from DC, possesses a furan ring which was suspected of being responsible for hepatotoxicity via metabolic activation primarily by CYP3A4. Herein, the present study aimed to evaluate the role of CYP3A4 in DTN-induced liver injury. The in vitro results showed that the EC50 values in primary human hepatocytes (PHH), L02, HepG2 and NIH3T3 cells were correlated with the CYP3A4 expression levels in corresponding cells. Furthermore, the toxicity was increased in CYP3A4-induced PHH by rifampicin, and CYP3A4 over-expressed (OE) HepG2 and L02 cells. Contrarily, the cytotoxicity was decreased in CYP3A4-inhibited PHH and CYP3A4 OE HepG2 and L02 cells inhibited by ketoconazole (KTZ). In addition, the hepatotoxicity of DTN in enzyme induction/inhibition mice was further investigated in the aspects of biochemistry, histopathology, and pharmacokinetics. Administration of DTN in combination with KTZ resulted in attenuated liver injury, including lower alanine transaminase and aspartate transaminase activities and greater AUC and C max of serum DTN, whereas, pretreatment with dexamethasone aggravated the injury. Collectively, our findings illustrated that DTN-induced hepatotoxicity correlated well with the expression of CYP3A4, namely inhibition of CYP3A4 alleviated the toxicity both in vitro and in vivo, and induction aggravated the toxicity effects.

Liver-specific metabolomics characterizes the hepatotoxicity of Dioscorea bulbifera rhizome in rats by integration of GC-MS and 1H-NMR.

ETHNOPHARMACOLOGICAL RELEVANCE: Dioscorea bulbifera rhizome (DBR), one type of herbal medicine, is extensively used in both Indian and Chinese system of traditional medicine. It has been effective in treating various diseases, such as sore throat, struma, and tumors. However, more and more clinical investigations have suggested that DBR can cause liver injury. AIM OF THE STUDY: In the present study, we aimed to characterize the corresponding molecular changes of liver dysfunction and reveal overall metabolic and physiological mechanisms of the subchronic toxic effect of DBR. MATERIALS AND METHODS: A liver-specific metabolomics approach integrating GC-MS and 1H-NMR was developed to assess the hepatotoxicity in rats after DBR exposure for 12 weeks. Multivariate statistical analysis and pattern recognition were employed to examine different metabolic profiles of liver in DBR-challenged rats. RESULTS: A total of 61 metabolites were screened as significantly altered metabolites, which were distributed in 43 metabolic pathways. The correlation network analysis indicated that the hub metabolites of hepatotoxicity could be mainly linked to amino acid, lipid, purine, pyrimidine, bile acid, gut microflora, and energy metabolisms. Notably, purine, pyrimidine, and gut microflora metabolisms might be novel pathways participating in metabolic abnormalities in rats with DBR-triggered hepatic damage. CONCLUSIONS: Our results primarily showed that the liver-specific metabolic information provided by the different analytical platforms was essential for identifying more biomarkers and metabolic pathways, and our findings provided novel insights into understand the mechanistic complexity of herb-induced liver injury.

Integrated Metabolomics and Proteomics Approach To Identify Metabolic Abnormalities in Rats with Dioscorea bulbifera Rhizome-Induced Hepatotoxicity.

Previous studies have shown that Dioscorea bulbifera rhizome (DBR) can induce hepatotoxicity in clinical practice. However, its underlying mechanisms remain largely unexplored. In the present study, we investigated the global effect of DBR exposure on the proteomic and metabolomic profiles in rats over a 12-week administration using an integrated proteomics and metabolomics approach. The abundance of 1366 proteins and 58 metabolites in the liver of rats after subchronic exposure to DBR was dose-dependently altered. The results indicated that DBR mainly damaged hepatic cells through the aberrant regulation of multiple systems mainly including purine metabolism, pyrimidine metabolism, taurine and hypotaurine metabolism, and bile acid metabolism. Notably, the deregulated proteins including Pnp, Dpyd, Upp1, and Tymp and the differential metabolites including uridine, uracil, cytidine, thymine, adenine, adenosine, adenosine 3'-monophosphate, and deoxycytidine were well correlated to purine and pyrimidine metabolism, which might be novel pathways involved in metabolic abnormalities in rats with DBR-induced liver damage. Collectively, these findings not only contributed to understanding the mechanisms underlying the hepatotoxicity of DBR, but also illustrated the power of integrated proteomics and metabolomics approaches to improve the identification of metabolic pathways and biomarkers indicative of herb-induced liver injury.

Metabolism of five diterpenoid lactones from Dioscorea bulbifera tubers in zebrafish.

Diterpenoid lactones (DLs) have been reported to be the main hepatotoxic constituents in Dioscorea bulbifera tubers (DBT), a traditional Chinese medicinal herb. The acquisition of early information regarding its metabolism is critical for evaluating the potential hepatotoxicity of DLs. We investigated, for the first time, the main metabolites of diosbulbin A (DIOA), diosbulbin C (DIOC), diosbulbin (DIOG), diosbulbin (DIOM) and diosbulbin (DIOF) in adult zebrafish. By using ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF MS), 6, 2, 7, 5 and 4 metabolites of DIOA, DIOC, DIOF, DIOM and DIOG were identified in the zebrafish body and the aqueous solution, respectively. Both phase-I and phase-II metabolites were observed in the metabolic profiles and the metabolic pathways involved in hydroxyl reduction, glucuronidation, glutathione conjugation and sulfation. The above results indicated that hepatocytic metabolism might be the major route of clearance for DLs. This study provided important information for the understanding of the metabolism of DLs in DBT.

Describing the holistic toxicokinetics of hepatotoxic Chinese herbal medicines by a novel integrated strategy: Dioscorea bulbifera rhizome as a case study.

It is vital to monitor the holistic toxicokinetics of toxic Chinese herbal medicines (CHMs) for safety. Although an integrated strategy based on the area under the curve (AUC) has been proposed to characterize the pharmacokinetic/toxicokinetic properties of CHMs, improvement is still needed. This study attempted to use 50% inhibitory concentration (IC50) as weighting coefficient to investigate holistic toxicokinetics of the major diosbulbins i.e. diosbulbin A (DA), diosbulbin B (DB), and diosbulbin C (DC) after oral administration of Dioscorea bulbifera rhizome (DBR) extract. Firstly, the cytotoxicities of the three diosbulbins on human hepatic L02 cells were evaluated and the IC50 values were calculated. Then, integrated toxicokinetics of multiple diosbulbins based on AUC and IC50 were determined. Finally, correlations between integrated plasma concentrations and hepatic injury biomarkers including alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and total bile acid (TBA) were analyzed. As a result, integrated plasma concentrations were correlated well with TBA and the correlation between TBA and IC50-weighting integrated plasma concentrations was better than that of AUC-weighting integrated plasma concentrations. In conclusion, the newly developed IC50-weighting method is expected to generate more reasonable integrated toxicokinetic parameters, which will help to guide the safe usage of DBR in clinical settings.

Rapid discovery of cyclopamine analogs from Fritillaria and Veratrum plants using LC-Q-TOF-MS and LC-QqQ-MS.

Cyclopamine, an inhibitor of the Hedgehog (Hh) signaling pathway, has been paid much attention in treating a wide variety of tumors. However, isolation and purification of cyclopamine analogs from medicinal plants remain challengeable. We herein proposed an efficient strategy using liquid chromatography quadrupole-time-of-flight mass spectrometry (LC-Q-TOF-MS) and liquid chromatography triple-quadrupole mass spectrometry (LC-QqQ-MS) for rapid screening and targeted isolation of cyclopamine analogs in Fritillaria and Veratrum plants. Firstly, fifteen reference compounds were characterized by LC-Q-TOF-MS and their characteristic fragment ions were summarized. Secondly, according to the characteristic fragment ions at m/z 67.1, 84.1, 109.1 and 114.1, rapid chemical screening of plant extracts was carried out by LC-QqQ-MS using precursor ion scan mode and 69 pre-target compounds were screened out. Thirdly, 24 real target compounds were verified by LC-Q-TOF-MS based on relative abundances (over 20%) of characteristic fragment ions. Fourthly, the targeted isolation of Fritillaria ussuriensis bulb and Veratrum dahuricum rhizome afforded a novel cyclopamine analog namely 15ß-hydroxy-23-isopengbeisine B as well as four known ones, whose structures were determined by nuclear magnetic resonance (NMR) analysis. Additionally, these five analogs were evaluated for the inhibitory activity of Hh signaling pathway in NIH/3T3 cell and cytotoxicity in PANC-1 and HepG2 cells. These results indicated that the proposed strategy was reliable for rapid discovery and targeted isolation of important natural products from chemically complex plant matrices.