Metabolic alterations in triptolide-induced acute hepatotoxicity

Triptolide, a major active constitute of Tripterygium wilfordii Hook. F, is prescribed for the treatment of autoimmune diseases in China. One of its most severe adverse effects observed in the clinical use is hepatotoxicity, but the mechanism is still unknown. Therefore, the present study applied an LC/MS-based metabolomic analysis to characterize the metabolomic changes in serum and liver induced by triptolide in mice. Mice were administered triptolide by gavage to establish the acute liver injury model, and serum biochemical and liver histological analyses were applied to assess the degree of toxicity. Multivariate data analyses were performed to investigate the metabolic alterations. Potential metabolites were identified using variable importance in the projection values and Student's t-test. A total of 30 metabolites were observed that were significantly changed by triptolide treatment and the abundance of 29 metabolites was correlated with the severity of toxicity. Pathway analysis indicated that the mechanism of triptolide-induced hepatotoxicity was related to alterations in multiple metabolic pathways, including glutathione metabolism, tricarboxylic acid cycle, purine metabolism, glycerophospholipid metabolism, taurine and hypotaurine metabolism, pantothenate and CoA biosynthesis, pyrimidine metabolism and amino acid metabolism. The current study provides new mechanistic insights into the metabolic alterations that lead to triptolide-induced hepatotoxicity.

Metabolic profiling of dehydrodiisoeugenol using xenobiotic metabolomics

Dehydrodiisoeugenol (DDIE), a representative and major benzofuran-type neolignan in Myristica fragrans Houtt., shows anti-inflammatory and anti-bacterial actions. In order to better understand its pharmacological properties, xenobiotic metabolomics was used to determine the metabolic map of DDIE and its influence on endogenous metabolites. Total thirteen metabolites of DDIE were identified through in vivo and in vitro metabolism, and seven of them were reported for the first time in the present study. The identity of DDIE metabolites was achieved by comparison of the MS/MS fragmentation pattern with DDIE using ultra-performance chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (UPLC-ESI- QTOFMS). Demethylation and ring-opening reaction were the major metabolic pathways for in vivo metabolism of DDIE. Recombinant cytochrome P450s (CYPs) screening revealed that CYP1A1 is a primary enzyme contributing to the formation of metabolites D1-D4. More importantly, the levels of two endogenous metabolites 2,8-dihydroxyquinoline and its glucuronide were significantly elevated in mouse urine after DDIE exposure, which explains in part its modulatory effects on gut microbiota. Taken together, these data contribute to the understanding of the disposition and pharmacological activities of DDIE in vivo.

Transgenic mice and metabolomics for study of hepatic xenobiotic metabolism and toxicity

INTRODUCTION

The study of xenobiotic metabolism and toxicity has been greatly aided by the use of genetically modified mouse models and metabolomics.

AREAS COVERED

Gene knockout mice can be used to determine the enzymes responsible for the metabolism of xenobiotics in vivo and to examine the mechanisms of xenobiotic-induced toxicity. Humanized mouse models are especially important because there exist marked species differences in the xenobiotic-metabolizing enzymes and the nuclear receptors that regulate these enzymes. Humanized mice expressing CYPs and nuclear receptors including the pregnane X receptor, the major regulator of xenobiotic metabolism and transport were produced. With genetically modified mouse models, metabolomics can determine the metabolic map of many xenobiotics with a level of sensitivity that allows the discovery of even minor metabolites. This technology can be used for determining the mechanism of xenobiotic toxicity and to find early biomarkers for toxicity.

EXPERT OPINION

Metabolomics and genetically modified mouse models can be used for the study of xenobiotic metabolism and toxicity by: i) comparison of the metabolomics profiles between wild-type and genetically modified mice, and searching for genotype-dependent endogenous metabolites; ii) searching for and elucidating metabolites derived from xenobiotics; and iii) discovery of specific alterations of endogenous compounds induced by xenobiotics-induced toxicity.