Anthocyanins are natural colorant belonging to the
flavonoid family, widely distributed among flowers, fruits, and vegetables. Some
flavonoids have been found to possess anticarcinogenic, cytotoxic,
cytostatic,
antioxidant, and anti-inflammatory properties. Since increased
nitric oxide (NO) plays a role in
inflammation, we have investigated whether the pharmacological activity of the
anthocyanin fraction of a blackberry extract (
cyanidin-3-O-
glucoside representing about 88% of the total
anthocyanin content) was due to the suppression of NO synthesis. The markedly increased production of
nitrites by stimulation of J774 cells with
lipopolysaccharide (LPS) for 24 h was concentration-dependently inhibited by the
anthocyanin fraction (11, 22, 45, and 90 microg/ml) of the extract. Moreover, this inhibition was dependent on a dual mechanism, since the extract attenuated iNOS
protein expression and decreased the iNOS activity in lungs from LPS-stimulated rats. Inhibition of iNOS
protein expression appeared to be at the transcriptional level, since the extract and similarly cyanidin-3-O-glucoside (10, 20, 40, and 80 microg/ml, amounts corresponding to the concentrations present in the extract) decreased LPS-induced
NF-kappaB activation, through inhibition of
IkappaBalpha degradation, and reduced ERK-1/2 phosphorylation in a concentration-dependent manner. In conclusion, our study demonstrates that at least some part of the anti-inflammatory activity of blackberry extract is due to the suppression of NO production by cyanidin-3-O-glucoside, which is the main
anthocyanin present in the extract. The mechanism of this inhibition seems to be due to an action on the expression/activity of the
enzyme. In particular, the
protein expression was inhibited through the attenuation of
NF-kappaB and/or MAPK activation.