Immune stimulatory effects of Loranthi ramulus on macrophages through the increase of NO and TNF-α

The activation of macrophages by microorganisms plays an important role in host defense and immunopathology. Loranthi ramulus (LR) is commonly used as a traditional drug and health food in Korea. Here, we investigated the regulatory effects of LR on macrophage-mediated immune responses. Treatment of macrophages with LR resulted in the enhanced cell-surface expression of CD80, CD86 and major histocompatibility complex (MHC) class II, as well as the enhanced production of nitric oxide (NO) and tumor necrosis factor (TNF)-α, and also iNOS and TNF-α mRNA expression. These alterations of LR-treated cells were associated with the activation of NF-κB and mitogen-activated protein kinases (MAPKs). LR increased the phosphorylation of MAPKs (JNK, ERK1/2, p38 MAPK) and the activation of NF-κB in Raw 264.7 cells. These results suggest that LR has increased NO and TNF-α production through phosphorylation of all three MAPKs following IκBα degradation and NF-κB activation. In conclusion, our results demonstrate that LR can effectively promote the activation of macrophages, suggesting that LR may possess the potential to regulate immune responses.