Hydroxytyrosol, a phenolic compound from virgin olive oil, prevents macrophage activation.

We investigated the effect of hydroxytyrosol (HT), a phenolic compound from virgin olive oil, on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in J774 murine macrophages stimulated with lipopolysaccharide (LPS). Incubation of cells with LPS caused an increase in iNOS and COX-2 mRNA and protein level as well as ROS generation, which was prevented by HT. In addition, HT blocked the activation of nuclear factor-kappaB (NF-kappaB), signal transducer and activator of transcription-1alpha (STAT-1alpha) and interferon regulatory factor-1 (IRF-1). These results, showing that HT down-regulates iNOS and COX-2 gene expression by preventing NF-kappaB, STAT-1alpha and IRF-1 activation mediated through LPS-induced ROS generation, suggest that it may represent a non-toxic agent for the control of pro-inflammatory genes.