Uncovering the pharmacological mechanism and the main herbal medicine contributing to the efficacy of Xiaoyanlidan Tablet (XYLDT) in treating cholestatic liver injury.

ETHNOPHARMACOLOGICAL RELEVANCE: Xiaoyanlidan Tablet (XYLDT) is a Chinese patent medicine consisted of three traditional Chinese medicines (TCMs) including Andrographis Herba (AH), Linearstripe Rabdosia Herba (LRH) and Picrasmae Ramulus et Folium (PRF). In Chinese traditional medicine theory, XYLDT has the "heat-clearing, dampness-dispelling and gallbladder function promoting" properties, and was widely used in the clinic for decades to treat pain in the subcostal region or bitter taste in the mouth, which were induced by liver-gallbladder dampness-heat. Meanwhile, it was also used for the therapy of acute cholecystitis and cholangitis.

AIM OF THE STUDY: To explore the mechanism of XYLDT in alleviating the alpha-naphthylisothiocyanate (ANIT)-induced cholestatic liver injury (CLI), and to find out which TCM consisted in XYLDT contributed the most to the therapeutic efficacy of XYLDT.

METHODS: ANIT was orally given to mice to induce CLI in vivo. Each TCM in XYLDT alone, XYLDT-without one TCM or XYLDT was orally given to mice before or after ANIT administration. Serum biochemical indicators were measured by using commercial kits. Liver histopathology was observed. Clinical data analysis was used to predict molecules and signal pathways involved in the XYLDT-provided improvement on CLI, which was further verified by using RT-PCR and Western-blot assay.

RESULTS: The alleviation of XYLDT on ANIT-induced CLI was proved by the data of serum biochemical indicators and liver histological observation. Results from clinical data analysis indicated that XYLDT improved CLI via improving mitochondrial function, oxidative phosphorylation, oxidative stress. XYLDT reduced the ROS level, MDA content, and increased GSH content. Meanwhile XYLDT improved the level of Nrf2 into the nucleus and mRNA expression of Nqo1, Gclc, Gclm. Andrographis Herba was proved to be the most crucial for the XYLDT-provided therapeutic efficacy on CLI. Moreover, andrographolide and neoandrographolide, two main active compounds in Andrographis Herba, had the apparent anti-inflammatory ability in LPS-stimulated RAW264.7 cells. Andrographolide also promoted nuclear translocation activation of Nrf2 in antioxidant response elements (ARE)-luciferin transfected L-02 cells.

CONCLUSION: XYLDT alleviated the ANIT-induced CLI via improving oxidative stress and activated Nrf2-related signaling pathways. Andrographis Herba was important for the XYLDT-provided alleviation on CLI.