Tanshinlactone A from Salvia miltiorrhiza modulates interleukin-2 and interferon-gamma gene expression

Salvia miltiorrhiza Bunge (Tanshen), a traditional Chinese herbal medicine, is popularly used to treat cardiovascular disorders. In the present study, effects of tanshinlactone A (C(16)H(12)O(4); M.W. 268), newly discovered from Salvia miltiorrhiza, on phytohemagglutinin (PHA)-stimulated cell proliferation were investigated in human peripheral blood mononuclear cells (PBMC). The results indicated that tanshinlactone A inhibited PBMC proliferation activated with PHA with an IC(50) of 15.6+/-1.9 microM. Cell viability test indicated that inhibitory effects of tanshinlactone A on PBMC proliferation were not through direct cytotoxicity. Furthermore, tanshinlactone A significantly decreased the interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) gene expression in PHA-activated PBMC. It reduced the phosphorylation of mitogen-activated protein kinases (MAPK) involving extracellular signal-regulated protein kinase (ERK), P38, and c-Jun NH(2)-terminal kinase (JNK) in PHA-treated PBMC. We suggested that the inhibitory effects of tanshinlactone A on PHA-induced PBMC proliferation, appeared to be mediated, at least in part, through reduction of MAPK activation and IL-2 and IFN-gamma production. Therefore, data demonstrate for the first time that tanshinlactone A is likely an immunomodulatory agent for PBMC.