Lutein acted as anti-inflammatory agent by decreasing the expression of inducible NO synthase at the mRNA and protein levels. This was the conclusion study conducted at The State University of New Jersey by M Rafi and Y Shafaie . They investigated the anti-oxidant capacity of lutein in cultured mouse macrophage cells which were stimulated with lipopolysaccharides. They found that lutein treatment reduced lipopolysaccharides-stimulated nitric oxide by 50% and inhibited the expression of inducible NO synthase by 72.5%.
A Korean study conducted at the Kangwon National University, led by J Kim and co-workers also demonstrated the anti-inflammatory action of lutein . They studied the effect of lutein on the activation of NF-kappaB, which plays an important role in inflammation and cell survival. They found that lutein decreased intracellular hydroxyl peroxide accumulation in macrophages exposed to lipopolysaccharide and that the phytochemical inhibited the expression of NF-kappaB-regulated inflammatory genes.
 Dietary lutein modulates inducible nitric oxide synthase (iNOS) gene and protein expression in mouse macrophage cells (RAW 264.7). Mol Nutr Food Res. 2007 Mar;51(3):333-40.
Rafi MM, Shafaie Y.
 The non-provitamin A carotenoid, lutein, inhibits NF-kappaB-dependent gene expression through redox-based regulation of the phosphatidylinositol 3-kinase/PTEN/Akt and NF-kappaB-inducing kinase pathways: role of H(2)O(2) in NF-kappaB activation. Free Radic Biol Med. 2008 Sep 15;45(6):885-96.