BackgroundVesnarinone, a quinolinone derivative, is a recently synthesized positive inotropic agent that has been shown to dramatically improve the survival of patients with heart failure. However, the mechanism of action of vesnarinone remains unknown. Reversible neutropenia complicated with vesnarinone therapy suggests that vesnarinone may modulate the production of cytokines. Because tumor necrosis factor (TNF)-α and other cytokines have been shown to depress myocardial contractility, we investigated the effects of vesnarinone on the production of various cytokines.Methods and ResultsWe studied the effects of vesnarinone on cytokine production by lipopolysaccharide (LPS)-stimulated whole blood from seven patients with heart failure and from five healthy volunteers. Heparinized blood was diluted in RPMI and stimulated with LPS. Vesnarinone was added in a range of 1 to 30 μg/mL, the blood was incubated for 24 hours, and interleukin (IL)-1α, IL-1β, IL-6, TNF-α, interferon (IFN)-γ, and granulocyte colony-stimulating factor (G-CSF) were measured by an enzyme-linked immunosorbent assay. LPS stimulation induced a more prominent increase in TNF-α in patients with heart failure than in healthy volunteers. Vesnarinone inhibited the production of TNF-α and IFN-γ both in healthy volunteers and in patients with heart failure. IL-la and IL-1β were also suppressed in healthy volunteers, but this response was variable, and a significant reduction was not seen in patients with heart failure. Marked inhibition of G-CSF and other cytokines by vesnarinone was observed in one patient who had developed neutropenia as a result of vesnarinone therapy.ConclusionsAlthough the number of study patients was small and the results are preliminary, these findings provide evidence that vesnarinone plays an important role in the regulation of cytokines and suggest that the reduction of cytokine release may contribute to the beneficial effects of the drug in the treatment of heart failure. Furthermore, the measurement of cytokines may be useful in predicting the occurrence of neutropenia, which has been occasionally reported in patients treated with vesnarinone.