Down-regulation of LPS-induced nitric oxide synthesis of murine macrophages by oral administration of Sho-saiko-to

Abstract

The effect of oral administration of a traditional Chinese herbal medicine, Sho-saiko-to (SST), on nitric oxide (NO) synthesis by murine macrophages was examined. SST was orally administered to mice, and NO synthesis of peritoneal exudate cells (PEC) cultured in the presence or absence of lipopolysaccharide (LPS) was measured. NO synthesis of PEC in response to LPS was reduced by oral administration of SST, whereas alkaline phosphatase (ALP) activity expressed by splenic B cells in response to LPS was enhanced. This finding suggests that augmented ALP activity possibly resulted from a decrease in macrophage functions, including NO synthesis. These activities were observed when SST or a low molecular weight fraction of SST was orally administered to mice, suggesting that down-regulation of macrophage functions depend on low molecular weight substances in SST.