Vitamin K2 is suggested to have a suppressive effect on the peripheral blood mononuclear cells (PBMCs) of pediatric atopic dermatitis patients. We examined the molecular targets of vitamin K2 to suppress proliferation and cytokine production in T-cell mitogen-activated PBMCs of atopic dermatitis patients from the viewpoint of mitogen-activated protein kinase signaling molecules. The study population included 16 pediatric vitamin K2 patients and 21 healthy subjects. The effect of vitamin K2 on concanavalin A-activated PBMC proliferation was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and cell counting assays. T-helper (Th)1/Th2/Th17 cytokine profiles in plasma and PBMC-culture supernatants were analyzed by a cytometric beads array assay. Mitogen-activated protein kinase signaling molecules in concanavalin A-activated PBMCs were examined by enzyme-linked immunosorbent assay (ELISA) assays. At 10-100 µM, vitamin K2 significantly suppressed the proliferation of mitogen-activated PBMCs derived from atopic dermatitis patients and healthy subjects (p < 0.05). The interleukin (IL)-10 concentrations in plasma and the PBMC culture supernatants of atopic dermatitis patients were significantly higher than those of healthy subjects (p < 0.05). The IL-2 concentrations in the culture supernatants of atopic dermatitis PBMCs were significantly lower than those of healthy PBMCs (p < 0.05). Vitamin K2 significantly inhibited the IL-17A, IL-10, and tumor necrosis factor α (TNF-α) production (p < 0.05), and increased the IL-2 production (p < 0.01) in the culture supernatant of atopic dermatitis PBMCs. At 10-100 µM, vitamin K2 markedly decreased the of Mek1, extracellular signal-regulated kinases (ERK)1/2 mitogen-activated protein kinase, and SAPK/c-Jun N-terminal kinase (JNK) expression in atopic dermatitis PBMCs (p < 0.05). Vitamin K2 is suggested to attenuate activated T-cell immunity in atopic dermatitis patients through the inhibition of mitogen-activated protein kinase-Mek1-ERK1/2 and SAPK/JNK signaling pathways.
Keywords: atopic dermatitis; cytokine; mitogen-activated protein kinase signaling pathway; vitamin K2.