Integrated targeted sphingolipidomics and transcriptomics reveal abnormal sphingolipid metabolism as a novel mechanism of the hepatotoxicity and nephrotoxicity of triptolide.

ETHNOPHARMACOLOGICAL RELEVANCE: Tripterygium wilfordii Hook F (TWHF) is a traditional herbal medicine in China. Triptolide (TP), the primary bioactive compound of TWHF, is an anti-inflammatory and immunosuppressive compound that can also injure the liver and kidney. Unfortunately, the toxicity mechanism remains unknown.

AIM OF THE STUDY: The aim of this study is to understand the regulatory role of sphingolipid (SPL) pathways in the TP-induced toxic mechanism in the liver and kidney in delayed-type hypersensitivity (DTH) Balb\c mouse.

MATERIAL AND METHODS: 76 core sphingolipids and 29 species of related metabolic enzymes in liver, kidney and plasma were analyzed with previous HPLC-MS/MS and real time qPCR method, respectively. Furthermore, the data generated from these two omics underwent integrated analysis to describe TP-induced abnormal sphingolipid metabolism and identify the specific biomarkers of TP toxicity using bioinformation method.

RESULTS: High-dose (LD50) TP could induce severe liver and kidney injuries. Moreover, TP comprehensively influenced the enzymes involved in the sphingolipids metabolism in the liver and kidney at the mRNA expression level. Furthermore, the total levels of ceramides (Cers), sphingomyelins (SMs) and sphingosine (Sph) were all elevated, while dihydroceramides (dhCers) and hexosylceramides (HexCers) were all down-regulated. Several enzymes, including kdsr, CerS2, CerS4, CerS5 and CerS6 in the liver and Cerk in the kidney were probably responsible for the TP-induced toxic effect, identifying them as possible novel therapeutic targets. Besides, fractions of long chain SPL (C16-C20) exhibited significant increase, and fractions of unsaturated dhCer and Cer were significantly changed, both of which above may be due to the change of mRNA expression level of CerSs. Moreover, several biomarkers for the diagnosis of TP poisoning were discovered.

CONCLUSION: In summary, the regulation of SPL metabolism uncovered a novel mechanism underlying TP poisoning in the liver and kidney. In addition, key biomarkers and enzymes may play an important role in reducing the clinical risk associated with the use of TP.