Host-microbial co-mediated C-sulfonation attenuates celastrol hepatotoxicity while preserving anti-rheumatic efficacy

Tripterygium wilfordii (Thunder God Vine, T. wilfordii) is a well-documented traditional medicinal herb widely used for the treatment of rheumatoid arthritis (RA). Celastrol (CEL) is one of its principal bioactive constituents responsible for anti-RA efficacy; however, its clinical translation is restricted by dose-dependent hepatotoxicity. Clarifying the metabolic basis underlying both its toxicity attenuation and efficacy preservation is essential for the safe modernization and rational development of this ethnomedicine.

This study aimed to determine whether C-sulfonation represents a metabolic detoxification pathway for CEL and to elucidate the host-microbial mechanisms regulating this process.

The C-sulfonated metabolite of CEL was identified by ultra-high performance liquid chromatography-Orbitrap mass spectrometry (UHPLC-Orbitrap MS) and nuclear magnetic resonance (NMR) spectroscopy. Mechanistic investigations were performed using a microbial colonization model combined with pharmacological interventions. Hepatotoxicity and anti-RA efficacy were evaluated in mice, hepatocytes, and a collagen-induced arthritis (CIA) model.

CEL underwent extensive intestinal C-sulfonation in vivo to form 2-phenolic-6-sulfo-celastrol (CELS), driven by a coordinated host-microbiota metabolic network. In this process, host cysteine metabolism via cysteine dioxygenase contributes to sulfate (SO₄^2-) production, while gut microbial adenosine-5'-phosphosulfate reductase from Desulfovibrio piger (D. piger) reduces SO₄^2- to sulfite (HSO₃^-), thereby enabling C-sulfonation of CEL. Compared with CEL, CELS showed markedly reduced hepatotoxicity, as indicated by a 15.4-fold increase in half maximal inhibitory concentration (IC₅₀) value in L02 cells (30.38 μM for CELS vs. 1.85 μM for CEL) and 100% survival in mice at 60 mg/kg for 7 days, whereas CEL caused 80% mortality at the same dose. Importantly, CELS maintained anti-RA efficacy, producing improvements in joint swelling, arthritis scores, and histopathological damage comparable to those of CEL in CIA mice.

Host-microbial co-mediated C-sulfonation constitutes a key metabolic detoxification pathway for CEL, markedly improving its safety profile while maintaining therapeutic efficacy against RA, thereby providing mechanistic support for the safer clinical application and modernization of T. wilfordii-derived ethnomedicines.