Highlights:
Abstract :
Objective:To determine the therapeutic effects of silybin (SBI) and its synergistic effects with mesenchymal stem cells (MSCs) in a lupus mouse model and to explore the therapeutic mechanisms.
Methods: TLR7/8 agonist resiquimod (R848) was applied for the induction of lupus mice. R848-induced B6 mice were randomly divided into normal saline control group, SBI group, MSCs group and SBI plus MSCs group, and treated with daily SBI by gavage or received MSCs injection once via the tail vein. Mice were sacrificed at week 12, with urine, serum, kidney and spleen collected. The proportion of cell subsets was detected by flow cytometry using splenocytes. Quantitative PCR and western blot were used to detect mRNA and protein levels. The regulatory mechanism of SBI on follicular helper T (Tfh) cells was explored throughin vitro splenocyte experiments.
Results : SBI treatment significantly decreased total IgG, anti-dsDNA antibody and urinary protein levels, as well as renal IgG and C3 deposition in R848-induced mice. It also increased the ability of MSCs to suppress splenomegaly and serum antinuclear antibody levels. In vivo and in vitrostudies showed a decrease in the percentage of Tfh cells and an increase in the percentage of regulatory T (Treg) cells after SBI treatment, which was most pronounced when combined with MSC therapy. SBI inhibited Tfh cell production in a dose-dependent manner. When splenocytes of R848-induced mice were treated with SBI and MSCs in vitro , the expression of genes related to Tfh cell differentiation, includingIcos, Stat3 and Bcl-6 , was reduced, and the phosphorylation of AKT, S6, and STAT3 proteins in Tfh cells was decreased. Correspondingly, addition of IL-6 or STAT3/mTOR agonists to the culture system completely or partially blocked the inhibitory effect of SBI on Tfh cells.
Conclusion: SBI acts synergistically with MSCs to ameliorate lupus-like features in R848-induced mice. It may enhance the ability of MSCs to inhibit Tfh cell production by counteracting the activation of IL-6 and its downstream pathways.