Taraxacum officinale restores inhibition of nitric oxide production by cadmium in mouse peritoneal macrophages

Nitric oxide (NO) produced at high concentrations by the inducible NO synthase is an important effector molecule involved in immune regulation and defense. The involvement of NO in the toxicity of cadmium (Cd) has been proposed. We have established that Cd inhibits the production of NO by recombinant IFN-gamma (rIFN-gamma) and lipopolysaccharide-stimulated mouse peritoneal macrophages. In the present study, we searched restoration drug against the inhibition of NO production by Cd in Oriental medicine. An aqueous extract of Taraxacum officinale (Compositae) (TOAE) restored the inhibition of NO production by mouse peritoneal macrophages pretreated with Cd in a dose-dependent manner. The effect of TOAE was mainly dependent on TOAE-induced tumor necrosis factor-alpha (TNF-alpha) secretion. These results suggest that the capacity of TOAE to restore NO production from interferon-gamma (IFN-gamma)-primed mouse peritoneal macrophages is the result of TOAE-induced TNF-alpha secretion.