HLA-B*35:01-mediated activation of emodin-specific T cells contributes to Polygonum multiflorum thunb. -induced liver injury in mice.

ABSTRACT

ETHNOPHARMACOLOGICAL RELEVANCE HLA-B*3501 has been identified as a risk allele for Polygonum multiflorum Thunb.-induced liver injury (PMLI). However, the immune mechanism underlying HLA-B*3501-mediated PMLI remains unknown. AIM OF THE STUDY To characterize the immune mechanism of HLA-B*3501-mediated PMLI. MATERIALS AND METHODS: Components of P. multiflorum (PM) bound to the HLA-B*3501 molecule was screened by immunoaffinity chromatography. Both wild-type mice and HLA-B*3501 transgenic (TG) mice were treated with emodin. The levels of transaminases, histological changes and T-cell response were assessed. Splenocytes from emodin-treated mice were isolated and cultured in vitro. Phenotypes and functions of T cells were characterized upon drug restimulation using flow cytometry or ELISA. Emodin-pulsed antigen-presenting cells (APCs) or glutaraldehyde-fixed APCs were co-cultured with splenocytes from emodin-treated transgenic mice to detect their effect on T-cell activation. RESULTS: Emodin, the main component of PM, could non-covalently bind to the HLA-B*3501-peptide complexes. TG mice were more sensitive to emodin-induced immune hepatic injury, as manifested by elevated aminotransferase levels, infiltration of inflammatory cells, increased percentage of CD8+T cells and release of effector molecules in the liver. However, these effects were not observed in wild-type mice. An increase in percentage of T cells and the levels of interferon-γ, granzyme B, and perforin was detected in emodin-restimulated splenocytes from TG mice. Anti-HLA-I antibodies inhibited the secretion of these effector molecules induced by emodin. Mechanistically, emodin-pulsed APCs failed to stimulate T cells, while fixed APCs in the presence of emodin could elicit the secretion of T cell effector molecules. CONCLUSION: The HLA-B*3501-mediated CD8+ T cell reaction to emodin through the P-I mechanism may contribute to P. multiflorum-induced liver injury.