Induction of nitric oxide & tumour necrosis factor-alpha by Psoralea corylifolia.

BACKGROUND & OBJECTIVES: Psoralea corylifolia (PC) is an herb widely used in medicine for the treatment of a variety of ailment. PC is also known to have immunomodulatory activity. However, its mechanism of action is not known. In the present study we investigated effect of PC on nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha) production in mouse peritoneal macrophages and also examined the mechanism by which PC regulates NO production. METHODS: MTT assay performed for cell viability test and nitrite concentration was measured by using Griess reagent. The amount of TNF-alpha secreted by the cells was measured by a modified enzyme-linked immunosorbent assay (ELISA). Expression of iNOS was investigated by western blot analysis. RESULTS: PC in combination with recombinant interferon-gamma (rIFN-gamma) showed a marked co-operative induction of NO production, with no effect on NO production by itself. The increased production of NO from rIFN-gamma plus PC-stimulated cells was almost completely inhibited by pre-treatment with pyrrolidine dithiocarbamate (PDTC), an inhibitor of nuclear factor kappa B (NF-kappaB). Furthermore, treatment of peritoneal macrophages with rIFN-gamma plus PC caused a significant increase in tumour necrosis factor-alpha (TNF-alpha) production. PDTC also decreased the effect of PC on TNF-alpha production significantly. INTERPRETATION & CONCLUSION: As NO and TNF-alpha play an important role in immune function and host defense, PC treatment could modulate several aspects of host defense mechanisms due to stimulation of the inducible nitric oxide synthase.

Activation of inducible nitric oxide synthase by Kagamjuaguiem in peritoneal macrophages in mice.

BACKGROUND & OBJECTIVE: A Korean herbal formula Kagamjuaguiem (KJE) has been used for the purpose of the tumour therapy. However, its mechanism of action is not clear. Nitric oxide (NO) as a potent macrophage-derived effector molecule against a variety of tumours has received increasing attention. In this study, using mouse peritoneal macrophages, we have examined the mechanism by which KJE regulates NO production. METHODS: Peritoneal macrophages were cultured with recombinant interferon-gamma (gammaIFN-gamma) for 6 h. The cells were then stimulated with various concentrations of KJE. NO synthesis in cell cultures was measured by Griess method, and inducible NOS expression was measured by western blotting. The amount of tumour necrosis factor-alpha (TNF-alpha) secreted by the cell was measured by a modified enzymelinked immunosorbent assay. RESULTS: When KJE was used in combination with gammaIFN-gamma there was a marked co-operative induction of NO production. However, KJE had no effect on NO production by itself. The increased production of NO from rIFN-gamma plus KJE-stimulated cells was almost completely inhibited by pre-treatment with pyrrolidine dithiocarbamate, an inhibitor of nuclear factor kappa B (NF-kappaB). Further, treatment of peritoneal macrophages with rIFN-gamma plus KJE caused a significant increase in TNF-alpha production. INTERPRETATION & CONCLUSION: Our findings demonstrate that KJE increases the production of NO and TNF-alpha by rIFN-gamma-primed macrophages and suggest that NF-kappaB plays a critical role in mediating these effects of KJE.