Hydroxytyrosol Is the Major Anti-Inflammatory Compound in Aqueous Olive Extracts and Impairs Cytokine and Chemokine Production in Macrophages

Substances in olive products contribute to im- proved health as suggested by epidemiological data. In this study we assessed the effects of hy- droxytyrosol (HT) on inflammatory mediators, cytokines and chemokines, and identified anti-in- flammatory constituents of aqueous olive ex- tracts, i.e., olive vegetation water (OVW). Murine macrophages (RAW264.7 cells) were stimulated with lipopolysaccharide (LPS) in the absence or presence of substances; inflammatory mediators (nitric oxide (NO), prostaglandin E2 (PGE2), cyto- kines, interleukins, chemokines) were deter- mined by the Griess reaction, EIA, or multiplex ELISA (Luminex technology). Expression of in- flammatory genes was determined by RT‑PCR. Aqueous olive extracts were fractionated by pre- parative HPLC and the fractions investigated for their effects on NO and PGE2 production. Results were further analyzed by principal component analysis. HT inhibited production of NO and PGE2 with an IC50 of 11.4 and 19.5 µM, respectively, re- flecting strong anti-inflammatory activity. HT and OVW diminished secretion of cytokines (IL- 1α, IL-1β, IL-6, IL-12, TNF-α), and chemokines (CXCL10/IP-10, CCL2/MCP-1). HT and OVW con- centration-dependently reduced the expression of genes of inducible nitric oxide synthase (iNOS), IL-1α, CXCL10/IP-10, MIP-1β, matrix metallopro- teinase-9, and prostaglandin E2 synthase (PGES). The effects of HT were partly mediated via the NF-κB pathway, as shown by RT‑PCR analysis. HT was identified as the main bioactive compound of OVW. The data provide a molecular basis for elu- cidating the effects of HT on inflammatory pro- cesses. The effects of HT on NO and chemokine production point to their impact on chronic in- flammatory processes in endothelium or arthritis. " polyphenols l " hydroxytyrosol l " olive