2,3,5,4′- tetrahydroxystilbene-2-O-β-D- glucopyranoside (TSG)-Driven immune response in the hepatotoxicity of Polygonum multiflorum

Ethnopharmacological relevance: 2,3,5,4 '-tetrahydroxystilbene-2-O-beta-D-glucopyranoside (TSG) as the primary constituent of Polygonum multiflorum Thumb. (PM) possesses anti-oxidative, antihypercholesterolemic, antitumor and many more biological activities. The root of PM has been used as a tonic medicine for thousands of years. However, cases of PM-induced liver injury are occasionally reported, and considered to be related to the host immune status. Aim of the study: The primary toxic elements and specific mechanisms PM causing liver damage are still not thoroughly clear. Our study aimed to investigate the influences of TSG on the immune response in idiosyncratic hepatotoxicity of PM. Materials and methods: The male C57BL/6 mice were treated with different doses of TSG and the alterations in liver histology, serum liver enzyme levels, proportions of T cells and cytokines secretion were evaluated by hematoxylin and eosin (HE), RNA sequencing, quantitative real time polymerase chain reaction (qRT-PCR), Flow cytometry (FCM), and enzyme-linked immunosorbent assay (ELISA), respectively. Then, primary spleen cells from drug-naive mice were isolated and cultured with TSG in vitro. T cell subsets proliferation and cytokines secretion after treated with TSG were assessed by CCK8, FCM and ELISA. In addition, mice were pre-treated with anti-CD25 for depleting regulatory T cells (Tregs), and then administered with TSG. Liver functions and immunological alterations were analyzed to evaluate liver injury. Results: Data showed that TSG induced liver damage, and immune cells infiltration in the liver tissues. FCM results showed that TSG could activate CD4+T and CD8+T in the liver. Results further confirmed that TSG notably up-regulated the levels of inflammatory cytokines including TNF-alpha, IFN-gamma, IL-18, perforin and granzyme B in the liver tissues. Furthermore, based on transcriptomics profiles, some immune system-related pathways including leukocyte activation involved in inflammatory response, leukocyte cell-cell adhesion, regulation of interleukin-1 beta production, mononuclear cell migration, antigen processing and presentation were altered in TSG treated mice. CD8+T/CD4+T cells were also stimulated by TSG in vitro. Interestingly, increased proportion of Tregs was observed after TSG treatment in vitro and in vivo. Foxp3 and TGF-beta 1 mRNA expressions were up-regulated in the liver tissues. Depletion of Tregs moderately enhanced TSG induced the secretion of inflammatory cytokines in serum. Conclusions: Our findings showed that TSG could trigger CD4+T and CD8+T cells proliferation, promote cytokines secretion, which revealed that adaptive immune response associated with the mild liver injury cause by TSG administration. Regulatory T cells (Tregs) mainly sustain immunological tolerance, and in this study, the progression of TSG induced liver injury was limited by Tregs. The results of our investigations allow us to preliminarily understand the mechanisms of PM related idiosyncratic hepatotoxicity.