Effects of rapamycin on DC-SIGN expression and biological functions in DC

Rapamycin, a macrolide antibiotic, has potent immunosuppressive properties as an antirejection therapy in organ transplantation. Studies show that dendritic cells (DC) are important targets for rapamycin, which can inhibit DC maturation and DC-induced allogeneic T cell proliferation. In this study, we investigated the effects of rapamycin on the expressions of DC-SIGN and transcription factor PU.1 and the function of DC. Treatment with rapamycin significantly reduced the expression of DC-SIGN in a dose-dependent manner associated with suppression of PU.1 gene expression and the ability of DC to migrate and stimulate T cell proliferation. The expression of DC-SIGN was significantly suppressed using PU.1 siRNA. Intriguingly, rapamycin treatment largely decreased the expressions of PU.1 and DC-SIGN in THP-1 cells. In addition, treatment with rapamycin down-regulated the promoter activity of DC-SIGN. In conclusion, rapamycin inhibits DC-SIGN expression and suppresses the ability of DC to migrate and stimulate T cell proliferation through the PU.1 gene transcription pathway.