Biotin deficiency enhances the inflammatory response of human dendritic cells

Abstract

The water-soluble biotin (vitamin B7) is indispensable for normal human health. The vitamin acts as a cofactor for five carboxylases that are critical for fatty acid, glucose, and amino acid metabolism. Biotin deficiency is associated with various diseases, and mice deficient in this vitamin display enhanced inflammation. Previous studies have shown that biotin affects the functions of adaptive immune T and NK cells, but its effect(s) on innate immune cells is not known. Because of that and because vitamins such as vitamins A and D have a profound effect on dendritic cell (DC) function, we investigated the effect of biotin levels on the functions of human monocyte-derived DCs. Culture of DCs in a biotin-deficient medium (BDM) and subsequent activation with LPS resulted in enhanced secretion of the proinflammatory cytokines TNF-α, IL-12p40, IL-23, and IL-1β compared with LPS-activated DCs cultured in biotin-sufficient (control) and biotin-oversupplemented media. Furthermore, LPS-activated DCs cultured in BDM displayed a significantly higher induction of IFN-γ and IL-17 indicating Th1/Th17 bias in T cells compared with cells maintained in biotin control or biotin-oversupplemented media. Investigations into the mechanisms suggested that impaired activation of AMP kinase in DCs cultured in BDM may be responsible for the observed increase in inflammatory responses. In summary, these results demonstrate for the first time that biotin deficiency enhances the inflammatory responses of DCs. This may therefore be one of the mechanism(s) that mediates the observed inflammation that occurs in biotin deficiency.

Keywords: biotin; dendritic cells; human; inflammation.

Fig. 1.

Biotin deficiency has no significant effect on dendritic cell (DC) phenotype. DCs were cultured in biotin-deficient (0 μM), control (10 μM), and biotin-oversupplemented (100 μM) media for 48 and subsequently stimulated with LPS for another 24 h. Bar graphs depict the mean fluorescence intensity (MFI) and %positive DCs of the expression of activation molecules on LPS-stimulated aged and young DCs. A: CD80; B: CD86; C: HLADR. Data are mean ± SE of 3 experiments.

Fig. 2.

Biotin deficiency enhances proinflammatory cytokine secretion from LPS-stimulated DCs. Bar graphs depict the levels of cytokine and chemokines secreted by LPS-stimulated biotin-deficient, control, and biotin-oversupplemented DCs. A: TNF-α, IL-1β, IL-23, and IL-12p40; B: IL-1α, IL-6, IL-10, and CXCL-10; C: CCL-3, CCL-4, CCL-2, and CXCL-8. Data are mean ± SE of 8 experiments.

Fig. 3.

Biotin-deficient DCs bias the Th-cell response towards Th1/Th17. Bar graphs depict the level of cytokines secreted by T cells after 5 days of coculture with LPS-stimulated biotin-deficient, control, and biotin-oversupplemented DCs. IFN-γ, IL-17, IL-22, and IL-10. Data are mean ± SE of 8 experiments.

Fig. 4.

Biotin deficiency impairs the activation of AMPK signaling pathway in DCs. phospho (p)AMPK and total AMPK levels were determined in biotin-deficient, control, and biotin-oversupplemented DCs before and after AICAR stimulation by ELISA. Bar graphs depict the levels of pAMPK (A) and AMPK (B) in DCs. Data are mean ± SE of 6 experiments.