β-Carotene Modulates the Immunological Function of RAW264, a Murine Macrophage Cell Line, by Enhancing the Level of Intracellular Glutathione

The activities of beta-carotene on redox status and the immune functions of RAW264 cells, a murine macrophage cell line, were investigated. Supplementation with beta-carotene for RAW264 cells resulted in apparently inconsistent redox indices: lipid peroxidation was enhanced but intracellular oxidation was moderately attenuated. Attenuated intracellular oxidation was endorsed by an increase in glutathione accompanied by up-regulated transcription of a subunit of gamma-glutamylcysteine synthetase, the rate-limiting enzyme for glutathione synthesis. alpha-Tocopherol, which can quench lipid peroxidation by free radical, neither inhibited that by beta-carotene nor influenced the intracellular redox status. Lipopolysaccharide-stimulated transcriptions of IL-1beta and IL-12 p40 in RAW264 were inhibited by beta-carotene but not by alpha-tocopherol. These results indicate that beta-carotene, which can modulate the intracellular redox status of macrophages by enhancing the level of intracellular glutathione, is related to the immune functions of macrophages.