Dual regulatory effect of plant extracts of Forsythia suspense on RANTES and MCP-1 secretion in influenza A virus-infected human bronchial epithelial cells

In this study, we investigated the effects of 95% ethanol (FS-t1), 50% ethanol (FS-t2) and water (FS-w) extracts of Forsythia suspense Vahl (Oleaceae) on the production of regulated on activation, normal T cell expressed and secreted (RANTES) and macrophage chemotactic protein-1 (MCP-1) by influenza A virus (H1N1)-infected human bronchial epithelial cell line A549. Virus infection evoked a markedly enhanced production of RANTES from basal 16 +/- 4 to 1307 +/- 294 pg/ml after 72 h inoculation. At the non-cytotoxic doses (20, 100 and 200 microg/ml), FS-t1, FS-t2 and FS-w exhibited a consistent inhibitory effect on virus-stimulated RANTES secretion in a dose-dependent manner wilh IC(50) of 42 +/- 6, 117 +/- 15 and 232 +/- 28 microg/ml, respectively. H1N1 also stimulated MCP-1 production in A549 cells, however to a less degree, from basal 133 +/- 21 to 391 +/- 98 pg/ml after 72 h viral inoculation. The effects of three extracts on MCP-1 secretion were more complex. FS-t1 displayed both positive and negative effect on virus-stimulated MCP-1 production dependent on the concentrations used. On the other hand, FS-t2 increased virus-induced MCP-1 secretion by 1.4-3.3 times while the third fraction FO-w increased by 2.6-3.7 times. These results suggested that Forsythia suspense consisted of both negative and positive regulatory components on RANTES and MCP-1 secretion in H1N1-infected A549 cells, respectively.