PLoS ONE (Jan 2013)

The Immunosuppressant Protosappanin A Promotes Dendritic Cell-Mediated Expansion of Alloantigen-Specific Tregs and Prolongs Allograft Survival in Rats.

  • Maomao Zhang,
  • Shuo Zhang,
  • Jian Wu,
  • Yong Sun,
  • Lili Li,
  • Wenjuan Du,
  • Jingjin Liu,
  • Jingbo Hou,
  • Bo Yu

DOI
https://doi.org/10.1371/journal.pone.0066336
Journal volume & issue
Vol. 8, no. 6
p. e66336

Abstract

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Protosappanin A (PrA), an immunosuppressive ingredient of the medicinal herb Caesalpinia sappan L, prolongs heart allograft survival in rats, possibly by impairing the function of antigen-presenting cells (APCs). We examined the effects of PrA on the maturation and function of dendritic cells (DCs), a potent class of APCs, and the downstream cell-cell and intracellular signaling pathways mediating the immunosuppressive activity of PrA. PrA inhibited LPS-stimulated maturation of Wistar rat DCs in vitro as reflected by reduced expression of costimulatory molecules (CD80 and CD86) and reduced expression of TLR4 and NF-κB, two critical signaling components for antigen recognition. PrA also enhanced the release of IL-10 and decreased the release of IL-12 from DCs, but had no effect on the production of TGF-ß. In mixed cultures, Wistar DCs pretreated with PrA impaired the proliferation of Sprague Dawley (SD) rat T cells while promoting the expansion of SD rat CD4(+)CD25(+) regulatory T cells (Tregs). Both oral PrA treatment and infusion of PrA-pretreated Wistar DCs prolonged cardiac allograft survival (Wistar donor, SD recipient) and expanded recipient CD4(+)CD25(+)Foxp3(+) Tregs. Donor spleen cells, but not spleen cells from a third rat strain (DA), supported the expansion of recipient CD4(+)CD25(+)Foxp3(+) Tregs and suppressed recipient T cell proliferation. We conclude that PrA triggers a tolerogenic state in DCs that allows for the induction of alloantigen-specific Tregs and the suppression of allograft rejection in vivo.