Dietary lutein but not astaxanthin or beta-carotene increases pim-1 gene expression in murine lymphocytes

This study investigates the effect of dietary carotenoids on pim-1 gene exp ression in mouse splenocytes Female BALB/c mice were fed 0%, 0.02%, or 0.4% astaxanthin, beta-carotene, and lutein for two weeks. Plasma and liver wer e obtained for the analysis of carotenoids. Splenocytes were isolated and c ultured in the presence of concanavalin A, and the level of pim-1 mRNA was determined by Northern blot analysis. None of the carotenoids were detectab le in the plasma and liver of unsupplemented mice. In plasma the concentrat ion of astaxanthin (4.9-54.7 mu mol/l) was dramatically higher than that of lutein (1.4-2.0 mu mol/l) and beta-carotene (0.1-0.7 mu mol/l). Carotenoid uptake by the spleen but nor the liver reflected that observed in plasma. In mice fed 0.4% of each carotenoid, the absolute concentration of the caro tenoid in the liver was highest for astaxanthin (24 nmol/g) followed by bet a-carotene (7.5 nmol/g) and lutein (1.58 nmol/g), Mice fed lutein showed a dose-related increase in pim-1 mRNA expression. The steady-state level of p im-1 mRNA in mice fed 0.4% lutein was sixfold higher than in mice fed 0.02% lutein. In contrast, dietary astaxanthin and beta-carotene did nor affect pim-1 expression. Therefore, an increase in pim-1 mRNA was observed in sple nocytes stimulated with concanavalin A in lutein-fed mice. This appears to be a unique effect of lutein and may be associated with its antitumor activ ity observed in vivo.