Effects of UV- pretreated riboflavin on lymphocyte viability and apoptosis rate

Background  As an essential vitamin, riboflavin has been extensively investigated for its role in boosting immune function. However, the effect of riboflavin on immune cell function after pretreatment by ultraviolet remains underreported.

Objective  To investigate the impact of UV-pretreated riboflavin on lymphocyte viability and apoptosis rate, aiming to offer novel insights for the clinical application of riboflavin.

Methods  The UV-pretreated riboflavin was co-cultured with lymphocytes in vitro to investigate the impact of UV-pretreated riboflavin concentration (0, 50, 100, 200, 400 μmol/L), cell concentration (2.5 × 10⁶/mL, 5.0 × 10⁶/mL, 1.0 × 10⁶/mL), and storage time of UV-pretreated riboflavin (1 d, 3 d, 7 d) on the apoptosis rate of lymphocytes. Different concentrations of UV-pretreated riboflavin (0, 25, 50, 75, 100, 150, 200 μmol/L) were co-cultured with lymphocyte CD4⁺ T and CD8⁺ T for 24 h, and the cell viability was assessed using CCK-8 proliferation assay. The apoptosis rate of CD4 ⁺ T and CD8⁺ T cells was evaluated by flow cytometry after treatment with UV-pretreated riboflavin at various concentrations (0, 10, 25, 200, 400 μmol/L), the disparity in tolerance between the two kinds of cells was investigated.

Results Compared to the control group, UV-pretreated riboflavin could induce lymphocyte apoptosis, with the rate of apoptosis showing a positive correlation with the concentration of UV-pretreated riboflavin (P<0.01). However, there was a negative correlation in the apoptosis rate and the concentration of treated cells (P<0.01) and the storage time of UV-pretreated riboflavin (P<0.05). When the concentration of riboflavin was less than 50 μmol/L, there was minimal impact on the activity of CD4 ⁺T and CD8 ⁺ T cells; however, once it exceeded 50 μmol/L, a noticeable decline in overall cell viability could be seen (P<0.05). Additionally, when comparing equivalent riboflavin concentrations, a significantly lower apoptosis rate was observed in CD8 ⁺ T cells compared to CD4 ⁺ T cells (P<0.01).

Conclusion The UV-pretreated riboflavin can induce apoptosis in lymphocytes and suppress the activity of CD4 ⁺ T and CD8 ⁺ T cells. Notably, CD8 ⁺ T cells exhibit higher tolerance compared to CD4 ⁺ T cells.