CYP3A4 inducer aggravates big flower Evodiae Fructus-induced hepatotoxicity whereas limonin attenuates its hepatotoxicity

The inhibitory effect of licorice on the hepatotoxicity induced by the metabolic activation of Euodiae Fructus

ETHNOPHARMACOLOGICAL RELEVANCE

Euodiae Fructus (EF), the dried, unripe, scented fruit of Tetradium ruticarpum (A. Juss, T.G.Hartley), is a traditional food and herb with mild toxicity. In Asia, it is processed with licorice (EFP), which has been used for centuries to alleviate pain and suppress cough. Pharmacological studies have reported that this herb could cause liver injury by activating the P450 3A enzyme, thus carrying the risk of clinical application. Processing with licorice is an effective method to reduce EF toxicity. It is urgent to explore the toxic components of EF and the attenuation mechanism of licorice.

AIM OF THE STUDY

This study aimed to indicate the specific pathway of EF-induced damage and identify the mechanism of action of licorice in reducing P450 activation and resulting in reduced liver damage.

MATERIALS AND METHODS

Male C57BL-6 mice were used to investigate the toxicity of EF to the liver and determine the attenuation effect on P450 from licorice ingestion. Glutathione (GSH) was used to capture the metabolic activation intermediates of EF. The key component reducing the EF toxicity of licorice was investigated by comparing the differences in chemical components and inhibition on the EF metabolism of licorice from different habitats.

RESULTS

The intermediate product of evodiamine (EVO) in EF was found to be activated by the P450 enzyme during metabolism, causing liver injury and inflammation. Isoliquiritigenin and liquiritigenin in licorice produced by intestinal bacterial metabolism and glycyrrhizin inhibited the metabolic activation of EF. Glycosides in licorice are metabolized into aglycones by intestinal bacteria, inhibiting the metabolic activation of EF and alleviating hepatotoxicity.

CONCLUSIONS

By combining with GSH, the electrophilic intermediates produced by the P450 enzyme's metabolic activation of the indole ring of EVO might cause hepatotoxicity. Glycyrrhizin from licorice and the liquiritigenin and isoliquiritigenin generated by intestinal bacterial metabolism play an attenuated function by inhibiting the P450 enzyme and preventing the metabolic activation of EF.

Selection of Reference Genes in Evodia rutaecarpa var. officinalis and Expression Patterns of Genes Involved in Its Limonin Biosynthesis

E. rutaecarpa var. officinalis is a traditional Chinese medicinal plant known for its therapeutic effects, which encompass the promotion of digestion, the dispelling of cold, the alleviation of pain, and the exhibition of anti-inflammatory and antibacterial properties. The principal active component of this plant, limonin, is a potent triterpene compound with notable pharmacological activities. Despite its significance, the complete biosynthesis pathway of limonin in E. rutaecarpa var. officinalis remains incompletely understood, and the underlying molecular mechanisms remain unexplored. The main purpose of this study was to screen the reference genes suitable for expression analysis in E. rutaecarpa var. officinalis, calculate the expression patterns of the genes in the limonin biosynthesis pathway, and identify the relevant enzyme genes related to limonin biosynthesis. The reference genes play a pivotal role in establishing reliable reference standards for normalizing the gene expression data, thereby ensuring precision and credibility in the biological research outcomes. In order to identify the optimal reference genes and gene expression patterns across the diverse tissues (e.g., roots, stems, leaves, and flower buds) and developmental stages (i.e., 17 July, 24 August, 1 September, and 24 October) of E. rutaecarpa var. officinalis, LC-MS was used to analyze the limonin contents in distinct tissue samples and developmental stages, and qRT-PCR technology was employed to investigate the expression patterns of the ten reference genes and eighteen genes involved in limonin biosynthesis. Utilizing a comprehensive analysis that integrated three software tools (GeNorm ver. 3.5, NormFinder ver. 0.953 and BestKeeper ver. 1.0) and Delta Ct method alongside the RefFinder website, the best reference genes were selected. Through the research, we determined that Act1 and UBQ served as the preferred reference genes for normalizing gene expression during various fruit developmental stages, while Act1 and His3 were optimal for different tissues. Using Act1 and UBQ as the reference genes, and based on the different fruit developmental stages, qRT-PCR analysis was performed on the pathway genes selected from the "full-length transcriptome + expression profile + metabolome" data in the limonin biosynthesis pathway of E. rutaecarpa var. officinalis. The findings indicated that there were consistent expression patterns of HMGCR, SQE, and CYP450 with fluctuations in the limonin contents, suggesting their potential involvement in the limonin biosynthesis of E. rutaecarpa var. officinalis. This study lays the foundation for further research on the metabolic pathway of limonin in E. rutaecarpa var. officinalis and provides reliable reference genes for other researchers to use for conducting expression analyses.

Elucidation of the relationship between evodiamine-induced liver injury and CYP3A4-mediated metabolic activation by UPLC-MS/MS analysis

Evodiamine (EVD), which has been reported to cause liver damage, is the main constituent of Evodia rutaecarpa (Juss.) Benth and may be bioactivated into reactive metabolites mediated by cytochrome P450. However, the relationships between bioactivation and EVD-induced hepatotoxicity remain unknown. In this study, comprehensive hepatotoxicity evaluation was explored, which demonstrated that EVD caused hepatotoxicity in both time- and dose-dependent manners in mice. By application of UPLC-Q/TOF-MS/MS, two GSH conjugates (GM1 and GM2) derived from reactive metabolites of EVD were identified, in microsomal incubation systems exposed to EVD with glutathione (GSH) as trapping agents. CYP3A4 was proved to be the main metabolic enzyme. Correspondingly, the N-acetyl-L-cysteine conjugate derived from the degradation of GM2 was detected in the urine of mice after exposure to EVD. For the first time, the iminoquinone intermediate was found in EVD-pretreated rat bile by the high-resolution MS platform. Pretreatment with ketoconazole protected the animals from hepatotoxicity, decreased the protein expression of cleaved caspase-1 and -3, but increased the area under the serum-concentration-time curve of EVD in blood determined by UPLC-QQQ-MS/MS. Depletion of GSH by buthionine sulfoximine exacerbated EVD-induced hepatotoxicity. These results implicated that the CYP3A4-mediated metabolic activation was responsible for the observed hepatotoxicity induced by EVD.

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.

Detoxification technology and mechanism of processing with Angelicae sinensis radix in reducing the hepatotoxicity induced by rhizoma Dioscoreae bulbiferae in vivo

Rhizoma Dioscoreae Bulbiferae (RDB) was effective on relieving cough and expectorant but accompanied by severe toxicity, especially in hepatotoxicity. A previous study found that processing with Angelicae Sinensis Radix (ASR) reduced RDB-induced hepatotoxicity. However, up to now, the optimized processing process of ASR-processed RDB has not been explored or optimized, and the detoxification mechanism is still unknown. This study evaluated the detoxification technology and possible mechanism of processing with ASR on RDB-induced hepatotoxicity. The optimized processing process of ASR-processed RDB was optimized by the content of diosbulbin B (DB), the levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and histopathological analysis. The processing detoxification mechanism was evaluated by detecting the antioxidant levels of nuclear factor E2 related factor 2 (Nrf2) and its downstream heme oxygenase 1 (HO-1), quinone oxidoreductase 1 (NQO1), glutamylcysteine ligase catalytic subunit (GCLM), and the levels of downstream antioxidant factors of Nrf2. Besides, the antitussive and expectorant efficacy of RDB was also investigated. This work found that processing with ASR attenuated RDB-induced hepatotoxicity, which can be verified by reducing the levels of ALT, AST, and ALP, and reversing the pathological changes of liver histomorphology. And the optimized processing process of ASR-processed RDB is “processing at a mass ratio of 100:20 (RDB:ASR) and a temperature of 140°C for 10 min.” Further results corroborated that the intervention of processed products of ASR-processed RDB remarkably upregulated the Nrf2/HO-1/NQO1/GCLM protein expression levels in liver, and conserved antitussive and expectorant efficacy of RDB. The above findings comprehensively indicated that the optimized processing process of ASR-processed RDB was “processing at a mass ratio of 100:20 (RDB:ASR) and a temperature of 140°C for 10 min,” and the processing detoxification mechanism involved enhancing the level of Nrf2-mediated antioxidant defense in liver as a key target organ.

Limonin relieves TGF-β-induced hepatocyte EMT and hepatic stellate cell activation in vitro and CCl4-induced liver fibrosis in mice via upregulating Smad7 and subsequent suppression of TGF-β/Smad cascade

Liver fibrosis is a pathological process as a result of intrahepatic deposition of excessive extracellular matrix. Epithelial-mesenchymal transition (EMT) of hepatocytes and activation of hepatic stellate cells (HSCs) both play important roles in the etiology of liver fibrosis. Here, we found that limonin repressed transforming growth factor-β1 (TGF-β)-induced EMT in AML-12 hepatocytes and activation of LX-2 HSCs. In both kinds of cells, limonin suppressed TGF-β-provoked Smad2/3 C-terminal phosphorylation and subsequent nuclear translocation. Transcription of Smad2/3-downstream genes was in turn reduced. However, limonin exerted few effects on Smad2/3 phosphorylation at linker region. Mechanistically, limonin increased Smad7 at mRNA level in both AML-12 and LX-2 cells. Knockdown of Smad7 abrogated inhibitory effects of limonin on TGF-β-induced EMT in AML-12 cells and activation of LX-2 cells. Further studies revealed that limonin alleviated mouse liver fibrosis induced by CCl₄. In livers of model mice, limonin upregulated Smad7 and declined C-terminal phosphorylation and nuclear translocation of Smad2/3. Transcription of Smad2/3-responsive genes was also attenuated. Our findings indicated that limonin inhibits TGF-β-induced EMT of hepatocytes and activation of HSCs in vitro and CCl₄-induced liver fibrosis in mice. Upregulated Smad7 which suppresses Smad2/3-dependent gene transcription is implicated in the hepatoprotective activity of limonin.

Cytotoxicity evaluation and metabolism of hepatotoxicity components of Euodiae Fructus in L02 cells

Euodiae Fructus (EF), the dried unripe scented fruit of Euodia rutaecarpa (Juss.) Benth., was reported to show anti-hypertensive, antitumor, and anti-obesity effects. The main alkaloids of EF were reported as the reason for toxicity of EF by metabolic activation majority through CYP3A. Up till the present moment, the cytotoxicity mechanisms of EF have not yet to be fully clarified. For the purposes of this article, the influence of CYP3A inducer and inhibitor on cytotoxicity of EF and metabolism in L02 cells of five alkaloids related to toxicity of EF were evaluated. The results indicated that CYP3A inducer aggravated the toxicity and CYP3A inhibitor alleviated the toxicity. UPLC-Q-Exactive-MS was used for the identification of five alkaloids of EF in L02 cells. A total of 13 metabolites were detected in L02 cells. In general, five alkaloids were widely metabolized in L02 cells such as oxygenation, demethylation, dehydrogenation, and etc. In addition, oxygenation was the main metabolic pathway. It was inferred that the toxicity of EF was closely related to the CYP3A and the metabolic intermediate might be one of the reasons for the toxicity of EF. Hence, the choice of optimal dose might be critical to avoid the adverse reactions owing to combination of EF and CYP3A inducer.