Inhibition of substance P-induced cytokine synthesis by St. John's wort extracts

We tested the hypothesis that extracts from St. John's wort interfere with protein synthesis induced by substance P (SP), a neuropeptide which has bee n implicated in the etiopathology of depression and anxiety. Using human as trocytoma cells, which express functional neurokinin (NK)-1-receptors, we i nvestigated whether extracts from St. John's wort are able to inhibit SP-in duced synthesis of the cytokine interleukin-6 (IL-6). We found a potent and dose-dependent inhibition of SP-induced IL-6 synthesis by various extracts from St. John's wort. These results do not only give further evidence of t he anti-inflammatory effects of St. John's wort, but also lend support to t he hypothesis that the antidepressant effect of St. John's wort is, at leas t in part, a result of its inhibitory effects on SP-induced protein synthes is.