Induction of nitric oxide synthase by Oldenlandia diffusa in mouse peritoneal macrophages.

Oldenlandia diffusa (OD) has been used to treat malignant tumors. In this study using mouse peritoneal macrophages, we have examined the mechanism by which OD regulates nitric oxide (NO) production. When OD (1 mg/ml) was used in combination with 10 U/ml of recombinant interferon-γ (rIFN-γ), there was a marked cooperative induction of NO production (36.13±7.12 μM) by the Griess method (nitrite). Treatment of macrophages with rIFN-γ plus OD (1 mg/ml) caused a significant increase in tumor necrosis factor-α (TNF-α) production (4.49±1.43 ng/ml) by enzyme-linked immunosorbent assay. The increased production of NO and TNF-α from rIFN-γ-plus OD-stimulated cells was almost completely inhibited by pretreatment with 100 μM of pyrrolidine dithiocarbamate (PDTC), an inhibitor of nuclear factor kappa B (NF-κB). PDTC also inhibited phosphorylation of IκB in rIFN-γ-plus OD-stimulated cells. These findings demonstrate that OD increases the production of NO and TNF-α by rIFN-γ-primed macrophages and suggest that NF-κB plays a critical role in mediating these effects of OD.