OLEUROPEIN, THE BITTER PRINCIPLE OF OLIVES, ENHANCES NITRIC-OXIDE PRODUCTION BY MOUSE MACROPHAGES

The Mediterranean diet, rich in fresh fruits and vegetables, has been associated with a lower incidence of cardiovascular disease and cancer , partly because of its high proportion of bioactive compounds such as vitamins, flavonoids and polyphenols. The major lipid component of su ch diet is the drupe-derived olive oil, that can be distinguished from other seed oils for the peculiar composition of its non-triglyceride fraction. In fact, several minor components, including polyphenols, gr ant the oil its particular taste and aroma, Oleuropein, the most abund ant among these components, has been shown to be a potent antioxidant endowed with antiinflammatory properties. We investigated the effects of oleuropein on NO release in cell culture and its activity toward ni tric oxide synthase (iNOS) expression. The results show that oleuropei n dose-dependently enhance nitrite production in LPS-challenged mouse macrophages. This effect was blocked by the iNOS inhibitor L-NAME, ind icating increased iNOS activity. Also, Western blot analysis of cell h omogenates show that oleuropein increases iNOS expression in such cell s. Taken together, our data suggest that, during endotoxin challenge, oleuropein potentiates the macrophage-mediated response, resulting in higher NO production, currently believed to be beneficial for cellular and organismal protection.