Highlights:
- Silybin relieved lupus-like disease in
TLR7/8 agonist (R848)-induced mice.
- Silybin increased the efficacy of mesenchymal stem cells (MSCs) in the
treatment of lupus mice.
- Silybin synergized with MSCs to inhibit Tfh cell production, which was
mostly achieved by suppressing the expression of Tfh differentiation
genes such as IL-6 and STAT3.
- The effects of silybin on Tfh cells could be counteracted by the
activation of IL-6 and its downstream pathways.
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.