Total glucosides of paeony attenuated functional maturation of dendritic cells via blocking TLR4/5 signaling in vivo.

It is well known that dendritic cells (DCs) play a critical role in the initiation and development of an immune response. Inhibitory effect on DC maturation alters immune-mediated inflammatory reaction in vivo. Total glucosides of paeony (TGP) are active compounds extracted from the roots of Paeonia lactiflora and have been widely used to ameliorate inflammation in therapy for autoimmune diseases. However, whether TGP act on DC maturation remains unknown. In this study, we investigated the effect of TGP on DC maturation in ovalbumin (OVA) immunized mice. Ear inflammation was inhibited by TGP (150 mgkg(-1), i.p.×11 days) obviously. The antigen presenting capacity of DC derived from TGP-treated mice was arrested. Meanwhile, OVA specific T cell proliferation was inhibited. In addition, we found that maturation of DCs was decreased by TGP treatment. Furthermore, OVA specific T cell proliferation was rescued by the adoptive transfer of mature DCs (mDCs) into TGP treated OVA-challenged mice. The research on the mechanism showed that TGP significantly inhibited activation of TLR4/5 singling. All these results demonstrated that TGP inhibited DC maturation and function by selectively blocking TLR4/5 activation in vivo, which in turn leads to reduce immune-mediated inflammation in vivo, adding a novel mechanism and therapeutic target of TGP for inflammatory and autoimmune disease treatment.