Curcuminoids distinctly exhibit antioxidant activities and regulate expression of scavenger receptors and heme oxygenase-1.

Scope: Curcumin (CUR), demethoxycurcumin (DMC), and bisdemethoxycurcumin (BDMC) have been demonstrated as having antioxidant, anticarcinogenic, and hypocholesterolemic activities. We report the diverse antiatherogenic effects and mechanisms of curcuminoids.

Methods And Results: We found that CUR was the most potent antioxidant against copper-mediated LDL oxidation as measured by thiobarbituric acid-reactive substances assay, oxidized LDL (oxLDL) ELISA, and electrophoretic mobility. CUR upregulated heme oxygenase-1, modifier subunit of glutamate-cysteine ligase (GCLM), and CD36 expression in undifferentiated THP-1 cells, supporting the possible involvement of Nrf2 pathway in CD36 expression. Monocyte-to-macrophage differentiation plays a vital role in early atherogenesis. BDMC reduced oxLDL uptake most effectively, while CUR was the best inhibitor for CD36, scavenger receptor A, and lectin-like oxidized LDL receptor-1 expression during phorbol 12-myristate 13-acetate (PMA)-induced THP-1 differentiation. In PMA-differentiated THP-1 macrophages, CUR and DMC effectively induced heme oxygenase-1 expression, but attenuated oxLDL-induced CD36 expression, leading to decreased oxLDL uptake.

Conclusion: This result indicates curcuminoids, despite structural similarities, exert different atheroprotective effects. Curcuminoids, especially CUR and DMC, are hormetic compounds, which induce Phase II enzyme expression and confer resistance to PMA- and oxLDL-induced scavenger receptor expression and activity.