Celastrol as an intestinal FXR inhibitor triggers tripolide-induced intestinal bleeding: Underlying mechanism of gastrointestinal injury induced by Tripterygium wilfordii.

BACKGROUND: Tripterygium wilfordii has been widely used for the treatment of rheumatoid arthritis, which is frequently accompanied by severe gastrointestinal damage. The molecular mechanism underlying the gastrointestinal injury of Tripterygium wilfordii are yet to be elucidated. METHODS: Transmission electron microscopy, and pathological and biochemical analyses were applied to assess intestinal bleeding. Metabolic changes in the serum and intestine were determined by metabolomics. In vivo (time-dependent effect and dose-response) and in vitro (double luciferase reporter gene system, DRATs, molecular docking, HepG2 cells and small intestinal organoids) studies were used to identify the inhibitory role of celastrol on intestinal farnesoid X receptor (FXR) signaling. Fxr-knockout mice and FXR inhibitors and agonists were used to evaluate the role of FXR in the intestinal bleeding induced by Tripterygium wilfordii. RESULTS: Co-treatment with triptolide + celastrol (from Tripterygium wilfordii) induced intestinal bleeding in mice. Metabolomic analysis indicated that celastrol suppressed intestinal FXR signaling, and further molecular studies revealed that celastrol was a novel intestinal FXR antagonist. In Fxr-knockout mice or the wild-type mice pre-treated with pharmacological inhibitors of FXR, triptolide alone could activate the duodenal JNK pathway and induce intestinal bleeding, which recapitulated the pathogenic features obtained by co-treatment with triptolide and celastrol. Lastly, intestinal bleeding induced by co-treatment with triptolide and celastrol could be effectively attenuated by the FXR or gut-restricted FXR agonist through downregulation of the duodenal JNK pathway. CONCLUSIONS: The synergistic effect between triptolide and celastrol contributed to the gastrointestinal injury induced by Tripterygium wilfordii via dysregulation of the FXR-JNK axis, suggesting that celastrol should be included in the quality standards system for evaluation of Tripterygium wilfordii preparations. Determining the mechanism of the FXR-JNK axis in intestinal bleeding could aid in the identification of additional therapeutic targets for the treatment of gastrointestinal hemorrhage diseases. This study also provides a new standard for the quality assessment of Tripterygium wilfordii used in the treatment of gastrointestinal disorders.

Tripterygium wilfordii protects against an animal model of autoimmune hepatitis.

ETHNOPHARMACOLOGICAL RELEVANCE: Tripterygium wilfordii tablets (TWT) is widely used to treat autoimmune diseases such as rheumatoid arthritis. Celastrol, one main active ingredient in TWT, has been shown to produce a variety of beneficial effects, including anti-inflammatory, anti-obesity, anti-cancer, and immunomodulatory. However, whether TWT could protect against Concanavalin A (Con A)-induced hepatitis remains unclear. THE AIM OF THE STUDY: This study aims to investigate the protective effect of TWT against Con A-induced hepatitis and elucidate the underlying mechanism. MATERIALS AND METHODS: Metabolomic analysis, pathological analysis, biochemical analysis, qPCR and Western blot analysis and the Pxr-null mice were used in this study. RESULTS: The results indicated that TWT and its active ingredient celastrol could protect against Con A-induced acute hepatitis. Plasma metabolomics analysis revealed that metabolic perturbations related to bile acid and fatty acid metabolism induced by Con A were reversed by celastrol. The level of itaconate in the liver was increased by celastrol and speculated as an active endogenous compound mediating the protective effect of celastrol. Administration of 4-octanyl itaconate (4-OI) as a cell-permeable itaconate mimicker was found to attenuate Con A-induced liver injury through activation of the pregnane X receptor (PXR) and enhancement of the transcription factor EB (TFEB)-mediated autophagy. CONCLUSIONS: Celastrol increased itaconate and 4-OI promoted activation of TFEB-mediated lysosomal autophagy to protect against Con A-induced liver injury in a PXR-dependent manner. Our study reported a protective effect of celastrol against Con A-induced AIH via an increased production of itaconate and upregulation of TFEB. The results highlighted that PXR and TFEB-mediated lysosomal autophagic pathway may offer promising therapeutic target for the treatment of autoimmune hepatitis.

Recent advances in metabolism and toxicity of tyrosine kinase inhibitors.

Small molecule tyrosine kinase inhibitors (TKIs) are widely used as anticancer drugs approved by U.S. FDA. However, the toxicities of TKIs to multiple organs have greatly limited their clinical applications. The metabolism of TKIs generates several potentially toxic metabolites in vivo, that can disturb the endogenous metabolism as well as cellular function, leading to organ damage. Therefore, it is essential to identify the toxic metabolites and elucidate the underlying mechanism of TKI-induced toxicity. Metabolomics is a powerful tool for the identification of the xenobiotic metabolites and metabolic derangement associated with xenobiotic exposure, that is helpful to understand the toxicity of TKIs. The study using metabolomics approach has revealed that the reactive metabolites/intermediates (e.g., N-oxide metabolite, primary amine metabolite, 1,4-benzoquinone intermediate) and adducts with glutathione, cysteine and mercapturic acid can be derived from TKIs. Fourteen metabolic pathways could be affected following the TKI treatment, including lipid metabolism, bile acid metabolism, and gut microbiota-related pathway. Modulation of xenobiotic receptor signaling, inhibition of xenobiotic metabolism, and supplementation of endogenous metabolites are potential strategies to protect against TKI-induced toxicity. In this review, studies on the metabolism of TKIs and the alterations of endogenous metabolism are discussed, and the potential preventions against TKI-induced toxicity are summarized.