Curcumin enhances non-inflammatory phagocytic activity of RAW264.7 cells

Present study was performed to assess the effect of curcumin treatment on macrophage functions using RAW264.7 cells, a murine macrophage cell line. Phagocytic activity of RAW264.7 cells was enhanced by the treatment with curcumin for 48 hours while the nitric oxide synthesis from RAW264.7 cells following lipopolysaccharide exposure was blocked. The incubation of RAW264.7 cells with curcumin dose-dependently inhibited the stimulatory responses of macrophage triggered by lipopolysaccharide; the enhanced secretion of inflammatory cytokines such as TNF-alpha and IL-1beta and the up-regulated expression of surface antigens like CD14 and CD40. Curcumin alone, however, was able to increase the basal level of TNF-alpha secretion and elevated markedly the expression of CD14 and slightly CD40. The marked enhancement of both phagocytic activity and CD14 was detectable as early as 75min after curcumin treatment which is the minimum time period required for the phagocytosis and CD14 measurement, suggesting a signaling pathway distinct from that triggered by apoptotic cells. In conclusion, this study elucidates that curcumin treatment enhances the phagocytic activity with blocking nitric oxide synthesis, a scavenger function of macrophages in non-inflammatory condition. In addition, this enhancement of phagocytic activity is triggered directly by the signals from curcumin itself not by apoptotic cells.