Baohuoside-1 inhibits activated T cell proliferation at G(1)-S phase transition

BACKGROUND: The effect of baohuoside-1 (B1), a novel flavonoid, on cell proliferation and the cell cycle was evaluated in this study. METHODS: The antiproliferative properties of B1 were evaluated by proliferation assay. Western blotting and flow cytometric analysis were employed to investigate the expression of cyclins and cyclin-dependent kinase proteins. RESULTS: The major findings were (1) B1 effectively inhibited the cell proliferation activated by mitogenic antigen, with a 50% inhibitory concentration in low muM and in a dose- and time-dependent manner. (2) B1 resulted in G(1)-S phase cells arrest. (3) It down-regulated the expression of cyclin A, D and p33 cyclin-dependent kinase-2 (p33cdk2) proteins. (4) B1 suppressed the growth of several tumor cell lines. (5) B1 prevented rat heart allograft rejection in vivo. CONCLUSIONS: B1 immunosuppression of mitogen-activated T cell proliferation occurs in G(1)-S transition. It may be associated with the expression of cyclin A, D and p33cdk2 proteins. B1 prevents rat heart allograft rejection in vivo. The mechanism of B1 is different from tacrolimus and sirolimus.