Study on mechanism of action of Chinese medicine Chan Su: dose-dependent biphasic production of nitric oxide in trophoblastic BeWo cells

Background: Chan Su, a traditional Chinese medicine, is used for treating the heart diseases and other systemic illnesses. Our studies with animal model have revealed its role in increasing intracellular calcium concentration in cardiomyocytes. Nitric oxide (NO), a second messenger molecule, and its metabolites have been demonstrated to maintain and modulate multiple physiologic functions including the cardiovascular and reproductive systems. In order to explore the mechanism of action of Chan Su, we studied the ability of Chan Su to stimulate NO production in cultured trophoblastic BeWo cells. Materials and methods: BeWo cell is a cloned established cell line purified from human choriocarcinoma. These cells have some similarities in biological behavior with endothelial cells. Therefore, BeWo cell line may act as a model system for production of nitric oxide by Chan Su both in placenta and in cardiovascular tissue, and the results can easily be extrapolated to cardiomyocytes. Very small amount of ethanol extract of Chan Su was added to the cultured cells in KBNI buffer and a chemiluminescence system was used for the measurement of nitric oxide. The amounts of Chan Su extract added to cultured cells were comparable to expected level of Chan So in human serum after ingestion. We also repeated these experiments with bufalin, the active component of Chan Su. Results: The ethanol extract of Chan Su (5 and 10 mug/ml) significantly increased NO production up to 110% of basal control value, but higher concentrations (40 and 80 mug/ml) of Chan Su (as expected in an overdose) resulted in decreased NO production below the control level. This biphasic effect on nitric oxide production was also observed with bufalin, the active component of Chan Su responsible for its digoxin-like immunoreactivity. The presence of bufalin in Chan Su preparation was confirmed by thin layer chromatography (TLC) analysis. Conclusions: Chan Su as well as bufalin is able to modulate the production of NO in BeWo cell line. (C) 2003 Elsevier Science B.V. All rights reserved.