(P01-004-25) Xanthophylls and Carotenes Differentially Influence Regulatory T Cell Differentiation

Objectives: Regulatory T cells (Tregs) are critical in maintaining immune homeostasis and function. Dietary carotenoids possess antioxidant properties and may influence immune cell differentiation. Thus, we investigated whether carotenoids differentially impact naïve CD4+ T cell differentiation to Tregs.

Methods: Naïve CD4+ T cells were differentiated to Tregs in the presence of 0 μM, and 4 μM xanthophylls astaxanthin (ASTX) and fucoxanthin (FX), and carotenes beta-carotene (BC) and lycopene (LYCO) for 4 days, then restimulated via the T cell receptor for 24 hrs. Cells were collected to assess cellular expansion, mRNA expression of Treg (FOXP3, IL10), Th17 (IL17A, IL22), antioxidant (SOD1, NRF1) and activation (IL2, STAT5A, STAT5B, CD69) markers by qPCR, and characterization of CD4+ T cell subpopulations by flow cytometry.

Results: Following differentiation, cell counts were increased by ASTX and FX, while no carotenoid-specific effects on cellular expansion were observed following Treg restimulation. A trend toward increased cell viability following differentiation was observed in ASTX-treated cells. ASTX significantly enhanced FOXP3 mRNA expression at both 2 μM and 4 μM concentrations, with lower dose ASTX inducing the highest FOXP3 expression. Higher dose FX increased FOXP3 expression to a lesser degree, whereas BC suppressed FOXP3 expression and LYCO had no effect. Accordingly, %FOXP3+ cells detected by flow cytometry across carotenoid treatments followed similar patterns. Additionally, lower dose ASTX increased IL10 expression compared to controls and other carotenoid treatments, whereas robust reductions in IL17A and IL22 mRNA expression were observed in differentiated controls and carotenoid-treated cells. Notably, ASTX-treated cells exhibited higher mRNA expression of CD69 and IL2, whereas LYCO-treated cells had the highest mRNA expression of STAT5A and STAT5B and antioxidant genes SOD1 and NRF1.

Conclusions: These findings demonstrate that xanthophylls and carotenes differentially regulate Treg differentiation and markers of activation, with ASTX having the greatest Treg-differentiating effects. Further study is warranted to evaluate whether these effects are attributable to antioxidant or other properties.

Funding Sources: USDA Hatch/Multistate