Effects of vitamin C on intracytoplasmic cytokine production in human whole blood monocytes and lymphocytes

Background: Vitamin C (ascorbic acid) is an essential water-soluble nutrient which primarily exerts its effect on immune homeostasis as physiological antioxidant. However, conflicting data exist regarding the effect of vitamin C on the expression of proinflammatory cytokines. Methods: It vas the aim of this study to investigate the impact of vitamin C on intracytoplasmic production of pro-inflammatory cytokines in monocytes and lymphocytes by flow cytometry after human whole blood assay. Results: Vitamin C dose dependently inhibited the LPS-induced number of monocytes producing IL-6 (e.g., 41.0% reduction, p < 0.001: 20 mM vitamin C) and TNF-alpha (e.g., 26.0% reduction, P < 0.005, 20 mM vitamin C). Simultaneously, the number of lymphocytes producing IL-2 after PMA/ionomycin stimulation was dose dependently reduced (e.g., 24.2% inhibition, p < 0.005, 20 mM vitamin C). Notably, the number of IL-1 and IL-8 producing monocytes as well as TNF-alpha and IFN-gamma producing lymphocytes were not significantly affected by 20 mM vitamin C. Conclusions: These data suggest that vitamin C selectively influences intracytoplasmic cytokine production and therefore, further studies are needed to elucidate the underlying mechanisms of immunomodulation, i.e. regulation of NFkappaB activation which is mandatory for the induction of pro-inflammatory cytokines. (C) 2004 Published by Elsevier Ltd.